Title of Invention	A MODIFIED POLYPROPYLENE AND PROCESS FOR INCREASING THE MELT STRENGHT AND/OR THE EXTENSIONAL MELT VISCOSITY OF A POLYPROPYLENE (CO) POLYMER.
Abstract	A process for increasing the melt strength and/or the extensional melt viscosity of,a polypropylene (co)polymer wherein said process comprises melt mixing the polypropylene (co)polymer in the presence of an initiator and ordinary a mondene mononer wvherein said initiator is selected from the group defined by formula 1: Formula 1 wherein R is selected from the group consisting of optionally substituted C1 ro C18 aryl, optionally substituted C1 to C18 alkyl, aroyl defined by formula 2,

Title of Invention

A MODIFIED POLYPROPYLENE AND PROCESS FOR INCREASING THE MELT STRENGHT AND/OR THE EXTENSIONAL MELT VISCOSITY OF A POLYPROPYLENE (CO) POLYMER.

Abstract

A process for increasing the melt strength and/or the extensional melt viscosity of,a polypropylene (co)polymer wherein said process comprises melt mixing the polypropylene (co)polymer in the presence of an initiator and ordinary a mondene mononer wvherein said initiator is selected from the group defined by formula 1: Formula 1 wherein R is selected from the group consisting of optionally substituted C1 ro C18 aryl, optionally substituted C1 to C18 alkyl, aroyl defined by formula 2,

Full Text	PROCESS FOR INCREASING THE MELT STRENGTH OF POLYPROPYLENE The present invention relates to polypropylene homopolymers and copolymers. In particular, the present invention relates to a process for increasing the melt strength and/or the extensional melt viscosity of said polymers by melt phase processing. The melt strength and extensional viscosity of linear or straight chain polymers, such as polypropylene, decreases rapidly with temperature. By contrast, polymers such as low density polyethylene which are highly branched retain relatively high melt strengths and extensional viscosities. It is generally understood that the difference In melt strengths and extensional viscosities is attributable to the presence of long chain branching in polymers such as low density polyethylene. Long chain branching allows a greater degree of chain entanglement. A number of methods for increasing the melt strength/extensional viscosity of polypropylene and related polymers through the introduction of branching or a limited degree of crosslinking in a process involving reactive extrusion have been proposed and are summarised in a recent paper by Wang et al. (Wang, X., Tzoganakis, C., and Rempel, G.L., J. Appl. Polym. Sci, 1996, 61, 1395). One such process involves the reactive extrusion of polypropylene with a White (US 5578682) has disclosed the use of various polyunsamrated crosslinking agents (for example, bismeleimide derivatives) in combination with free radical initiators to achieve an increase in the melt strength various polymers. It is well known that the melt phase processing of polypropylene leads to mechanochemical degradation. The processing of polypropylene in the presence of free radical initiators SUBSTITUTE SHEET (Rule 26) (RO/AU) provides an increased rate of degradation. This controlled degradation of polypropylene is used commercially for the production of controlled rheology resins having reduced polydispersity and reduced die swell (Lambla, M. in Comprehensive Polymer Science, Pergamon, New York 1992, vol Suppl. 1, p 619; Hogt, A.H., Meijer, J., Jelinic, J. in Reactive Modifiers for Polymers, Al-Malaika, S Ed., Chapman & Hall, London, 1996, p 84.). The degradation of polypropylene as described therein results in a lowering of melt strength. The batch modification of polypropylene to produce crosslinked (insoluble) polypropylene by treatment with peroxides is described by Borsig et al. (Borsig, E., Fiedlerova, A., Lazar, M. J., Macromol. Sci. Chem. 1981, A16, 513). Initiators which produce benzoyloxy radicals or phenyl ladicals are described as being more efficient in inducing crosslinking or grafting than those which produce t-butoxy or alkyl radicals. The process requires the use of high levels of peroxide. The use of polyfunctional monomers as coagents to retard degradation and enhance crosslinking is described by Chodak, I.; Fabianova, K.; Borsig, E.; Lazar, M. Agnew. Makromol. Chem., 1978, 69, 107. DeNicola (EP 384; 31A2) has disclosed a means :o produce a branched propylene polymer material showing a net increase in the weight average molecular weight by solid state modification of predominantly isotactic semi-crystalline linear polypropylene. The process described in EP384331A2 involves blending peroxides with short half lives (eg peroxy dicarbonates) with linear propylene polymer in a mixing vessel at temperatures from 23°C to 120°C in an in;rt atmosphere and continuing to mix for a period of time until the peroxide decompos es and polymer fragmentation and branching occurs without significant gelation of the pclymer. DeNicola states that at temperatures greater than 120°C no branching or melt strength enhancement is achieved. U.S. 5,464,907 teathes that certain unsaturated itaconale derived peroxides may be used to induce grafting in polypropylene and a-olefm copolymers. They report that use of other peroxides generally results in chain degradation Polypropylene is also known to undergo substantial degradation during melt phase grafting of monofunctional monomers, for example maleic anhydride and glycidyl methacrylate. It has also been reported that the degradation that accompanies grafting of these monomers to polypropylene may be reduced by the addition of relatively high concentrations of certain comonomers including styrene (see, for example Sun, Y.J., Hu, G.-H., and Lambla, M., Angew. Makromol. Chem. 1995, 229, 1; Chen, L-F., Wong, B. and Baker, W.E. Polym, Eng. Sci. 1996, 36, 1594.) Sun et al. report that there is degradation (as indicated by an overall decrease in molecular weight) when styrene alone is grafted onto polypropylene even when a relatively high concentration is used (4 moles/lOOg PP). Either 2,5-dimethyl-2,5-(t- butylperoxy)hex-3-yne or 2,5-dimethyl-2,5(t-butylpcroxy-hexane(DHBP) was used as the initiator in these experiments. We have found that melt mixing polypropylene homopolymer or ethylene-polypropylene copolymer in the presence of a suitable initiator provides one or more of the following: increased melt strength; increased extensional viscosity; increased molecular weight; and broadened molecular weight distribution. According to the present invention there is provided a process for modifying a polypropylene (co)polymer wherein said process comprises melt mixing the polypropylene (co)polymer in the presence of an initiator wherein said initiator is selected from the group defined by formula 1: Formula 1 wherein R is selected from the group consisting of optionally substituted C, to Qg acyl, optionally substituted-C1 to C18 alkyl, aroyl defined by formula 2, Formula 2 and groups of formula 3, wherein U, V, X, Y, Z, U' V, X', Y' and Z' are independently selected from the group consisting hydrogei, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl. carboxy, alkoxycarbonyl, aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4, Formula 4 and wherein T is alkylene. Advantageously the thus formed modified polypropylene may be obtained without the associated production of significant and detrimental amounts of gels. Polymers suitable for use in the present invention include a wide variety of polypropylene homopolyraers, opolymers and blends containing one or more polypropylene homopolyiners and/or copolymers. Suitable polypropylene homopolymers include isotactic polypropylene, atactic polypropylene ami syndintactic polypropylene. Commercial isotactic polypropylene having a proportion of meso/dyads of greater than 90% is preferably used in the process of the present invention. Isotactic polypropylene is a semi-crystalline polymer having a number of properties which have made it one of the most widely used commercial polymers. These properties include heat resistance, stress cracking resistance, chemical resistance, toughness, and low manufacturing costs. However, the melt strength of isotactic polypropylene as measured directly by extensional viscosity or use of a commercial melt strength tester or indirectly by more qualitative measures such as drop time or die swell ratio is relatively low. This relatively low melt strength limits the use of polypropylene in applications such as foam extrusion, thermoforming and film blowing. In order to use polypropylene in such applications it is necessary to employ sophisticated processing equipment. The present invention now permits this already widely used commercial polymer to be used in an even wider range of applications. Polypropylene copolymers include copolymers of propylene and other monomers with such other monomers being present preferably in amounts of up to 10%wt/wt. A preferred comonomer is ethylene. The present invention is also applicable to other polvmers cornnrisinp a-olefin monomers. The initiators for use in the present invention may be selected from the group defined by formula 1. Formula 1 wherein R is selected from the group consisting of optionally substituted C1 to C18 acyl, optionally substituted C1 to C18 alkyl, aroyl defined by formula 2, Formula 2 and groups of formula 3, Formula 3 wherein U, V, X, Y, Z, U', V', X', Y' and Z' are independently selected from the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarboxyl aryovycarboxyl, trialkyl silyl ht\ydroxy, or a moiety of formula 4, Formula 4 and wherein T is alkylene. The alkyl, including acyl and alkoxy, groups included in the initiators of formula 1 may include hetero atoms within the carbon chain (eg polyalkylene oxide) and may be branched or unbranched and may be substituted with one or more groups such as with alkyl, aryl, alkoxy or halogen substituents. Without wishing to be bound by theory, it is believed that the aroyloxy radical of formula 5 Formula 5 ,where U, V, X, Y and Z are as hereinabove defined, provide the surprising increase in melt strength. Other compounds which generate these aroyloxy radicals may also be used in the present invention. A preferred class of initiators of formula 1 are diaroyl peroxides of formula 6. Formula 6 where X, Y, Z, U, V, X', Y' Z' U' V are independently selected from the group consisting of hydrogen and C1 - C18 alkyl where at least one of X, Y, Z, U, V and X', Y', Z', U', V' are not hydrogen. Diaryl peroxides of formula 6 include Dibenzoyi peroxide, o,o'-Bis(mcthylbenzoyI) peroxide, p,p'-Bis(inethylbcnzoyl) peroxide, M,M'-Bis(mcthylbenzoyl) peroxide, o,m'-Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyI)peroxide, m,p-Bis(methylbeozoyl) peroxide, Bis(ethylbenzoyl) peroxide (all isomers), Bis(propyibenzoyl) peroxide (all isomers), Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isomers), Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzoyl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl) peroxide (all isomers), Bis(propoxybenzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide (all isomers), Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybenzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(cblorobenzoyl) peroxide (all isomers), Bis(fiuorobenzoyl) peroxide (all isomers), Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide (all isomers), Bis(trimetfaylbenzoyl) peroxide (all isomers), Bis(tert-butylbenzoyl)peroxide (all isomers), Bis(di- tert-butylbenzoyl)peroxide (all isomers), Bis(tertbutoxybenzoyl)peroxide (all isomers), Bis(dhrimethylsilylbenzoyl) peroxide (all isomers), Bis(heptafluoropropylbenzoyl) peroxide (all isomers), Bis(2,6-dimethyI-4- trimethylsilyl benzoyl) peroxide and isomers, 2,2'(dioxydicarbonyl) bis - Benzoic acid dibutyl ester where the term "all isomers" refers to any variation in the position of the ring substituent as well as the structure of the substituent itself i.e. for propyl; n-propyi and isopropyl. Examples of aromatic peresters of formula 1 include the following: tert-butyl perbcnzoate, tert- butyl (methyl)perbenzoate (all isomers), tert-butyl (ethyl)perbenzoate (all isomers), tert-butyl (octyl)perbenzoate (all isomers), tert-butyl (nonyl)perbenzoate (all isomers), tert-arnyl perbenzoate, tert-amyl (methy)perbenzoate (all isomers), tert-amyl (ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoatc (all isomers), tert-amyl (nonyl)perbcnzoate (all isomers), tert-amyl (methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoatc (all isomers), tert- amyl (nonyioxy)perbenzoate (all isomers), 2-ethylhexyl perbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers),, 2-ethylhexyl (ethyl)perbenzoate (all isomers), 2-ethylhexyl (octyl)perbenzoate (all isomers),, 2-ethylhexyl (nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbcnzoate (all isomers), 2-ethyihexyl (ethoxy)perbcnzoate (all isomers), 2- ethylhexyi (octyloxy)perbcnzoate(all isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers) The initiators for use in the present invention also include compounds of formula 1 where at least one of U, V, X, Y, Z, U', V', X' Y' and Z' is a moiety of formula 4 where R is as defined above. Preferably there is no more than one moiety of formula 4 per aromatic ring. Such initiators are di or higher functional peroxides and may include polymeric peroxides such as Bis (tertbutylmonoperoxy phthaloyl) diperoxy terephthalate, Bis (tertamylmonoperoxy phthaloyl) diperoxy terephthalate diacetyl phthaloyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4 methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide, dibenzoyl terephthaloyl diperoxide, Poly[ dioxycarbonyldioxy(l,l,4,4-tetramethyl-1,4-butanediyl)] peroxide. It is described that the initiators are selected such that it has an appropriate decomposition temperature (half life), solubility, and reactivity and such that the groups R, T, X, Y, Z, U, V, X', Y', Z',, U', V' give no adverse reaction under the conditions of the process. Preferred peroxides will have a 0.1 hour half life in the range 100 - 170°C The amount of initiator used in the process of the present invention should be an effective amount to achieve the desired increase in melt strength. Melt strength is considered in the art to be an indication of long-chain branching in polyolefins. It is preferable in the process of the present invention that long-chain branching predominates over crosslinking in the reaction between the initiator and the polypropylene (co)polymer. Crosslinking of the polypropylene (co)polymcr may result in the formation of gels which disrupt the appearance of the polypropylene (co)polymer. In the process of the present invention it is desirable to control Die degree and distribution of crosslinking and keep the level of crosslinking as uniform and as low as necessary to produce the desired effects. The amount of crosslinking which occurs in the polypropylene (co)potymer is dependant upon the amount of initiator melt mixed with the polypropylene (co)polymer. The amount of crosslinking is also dependent upon the degree of mixing as any regions high in initiator concentration will result in excessive localised crosslinking and the formation of gels. It is desirable that good distributive and dispersive mixing be employed to promote even distribution of the initiator in the polypropylene (co)polymer so as to minimise the variation in initiator concentration throughout the polypropylene (co)polymer and reduce the likelihood of the formation of gels. Preferably the initiator will be present in the range of from 0.004 to 0.25 moles of initiator per kg of the polypropylene homopolymer or copoiymer (polypropylene (co)polymer). The more preferred range being from 0.006 to 0.10 moles of initiator per kg. of the polypropylene (co)polymer and even more preferred range being from 0.01 to 0.05 moles of initiator per kg of the polypropylene (co)polymer. The initiator is preferably introduced into the polymer melt directly, either neat (as a powder or a liquid), dispersed or dissolved in a suitable medium (for example, dissolved in 2- butanone) or adsorbed on polymer pellets or powder which are added as a masterbatch. It is desirable that the initiator is rapidly mixed with the polymer melt at a raie in keeping with the half life of the initiator at the processing temperature of the polypropylene (co)porymer. The initiator may be added either alone, or along with the polypropylene (co)polymcr, or with any other polymer, additive or filler, so that the polymer melts and mixes with the initiator as it is decomposing. When the initiator is fed to the main feed throat of the extruder it is preferred to have a barrel temperature which is relatively low in the region adjacent to the main feed throat and increases towards the die to prevent premature decomposition of the peroxide. Preferably the initiators for use in the present invention are selected from the group consisting ofDibenzoylperoxide, o,o'-Bis(njethylbeozoyl)peroxide, p,p'-Bis(niethyIbenzoyl)peroxide, o,o- Bis(methylbenzoyl) peroxide, o,m'-Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenz:oyl) peroxide, tn,p'-Bis(methylberaoyl) peroxide, Bis(ethyibenzoyl) peroxide (all isomers), Bis(propylbenzoyl) peroxide (all isomers), Bis(butylbenzoyl) peroxide (all isomers), Bis(pcntylbenzoyl) peroxide (all isomers), Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzoyl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (aU isomers), Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl) peroxide (all isoraers), Bis(propoxybenzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide (all isomers), Bis;(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybenzoyl) peroxide (all isomers), Bi Bis(octyloxybenzoyl) peroxide (all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyr peroxide (all isomers), Bis(fluorobenzoyl) peroxide (all isomers), Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzojl) peroxide (all isomers), Bis(trimethylbenzcyl) peroxide (all isomers), Bis(tert-butylbenzoyl)peroxide (all isomers), Bis(di-tert-butylbenzoyl)peroxide (all isomers), Bis(tertbutoxybenzoyl)peroxide (all isomers), Bis(ditririethylsilylbenzoyl) peroxide (all isomers), Bis(heptafluoropropylbenzoyJ) peroxide (all isomers), Bis(2,4-dimethyl-6- trirr.ethylsilyl benzoyl) peroxide and isomers tert-amyl perbcnzoate, tert-amyl (methyl)i?erbenzoate (all isomers), tert-amyl (ethyl)perbcnzoate (all isomers), tert-amyl (o;tyl)perbenzoate (all isomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all isoraers), tert-amyl (octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate (all isomers), Bis (tertamylmonopercxy phthaloyl) diperoxy terephthalate, diacetyl phthaloyl diperoxide, dibenzoyl phthakyl diperoxide, bis(4-methybenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide and dibenzoyl terephthaloyl diperoxide. More preferably the initiators are selected from the group consisting of dibenzoyl peroxide, o,o'-Bis(methylbenzoyl) peroxide, p,p'-B:s(methylbenzoyI) peroxide, M,M'- Bis(methylbenzoyl) peroxide. o,m'-Bis(rnethylbenzoyI) peroxide. o.p'-Bis(methylbenzoyl) peroxide, m,p'-Bis(methylben2oyI) peroxide. The initiators may optionally be used in combination with one or more monoene monomers. It will be understood by those skilled in the art that by the term "monoene monomer'1 it is meant a monomer having a single reactive double bond. The preferred menoene monomer(s) or mixtures thereof include vinyl monomers of structure CH2 = CHX where X is chosen so as to confer the desired reactivity and solubility. More preferred monomers include styrene. The amount of monomer will preferably be up to 5 times the total moles of initiator added to the polypropylene (co)polymer. The most preferred range being 1 to 4 times the total moles of initiator added to the polypropylene (co)polymer. The monomer may be added with the polypropylene (co)polymer or it can be added prior to the initiator, with the initiator or subsequent to the initiator. However it is preferred to have the monomer mixed and dispersed into the polymer melt before the initiator has substantially decomposed. The monomer is preferably introduced into the polymer melt directly, either neat (as a powder or a liquid), dispersed or dissolved in a suitable medium (for example, dissolved in 2-butanone) or adsorbed on polymer pellets or powder which are added as a mastprbatch. Preferred initiators for use in combination with monomers include Dibenzoyl peroxide, o,o'- Bis(methylbenzoyl) peroxide, p,p'-Bis(methyibenzoyl) peroxide, M,M-Bis(inethylbenzoyl) peroxide, o,m'-Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl) peroxide, m,p'- Bis(metbylbenzoyl) peroxide, Bis(ethyibenzoyl) peroxide (all isomers), Bis(propylbeozoyl) peroxide (all isomers), Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isomers), Bis(hexylbenzoyl) peroxide (all isoxners), Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzoyl) peroxide (all isomers), Bis(nonytbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl) peroxide (all isomers), Bis(propoxybcnzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide (all isomers), Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybcnzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide (all isomers), Bis(fluorobcnzoyl) peroxide (all isomers), Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide (all isomers), Bis(trimethyibenzoyl) peroxide (all isomers), Bis(tert-butylbcnzoyi)peroxide (all isomers), Bis(di-tert-butylbenzoyl)pcroxide (all isomers), Bis(tcrt-butoxybenzoyl)peroxide(all isomers), Bis(ditrimethylsilyibcnzoyl) peroxide (all isomers), ' Bis(heptaftuoropropylbenzoyl) peroxide (all isomers), Bis(2,4-dimethyl-6- trimethylsilyl benzoyl) peroxide and isomers, 2,2'(dioxydicarbonyl) bis - Benzoic acid dibutyl ester, tert-butyl perbenzoate, tert-butyl (methyl)perbenzoate (all isomers), lert-butyl (etbyl)perbenioate (all isomers), tert-butyl (octyl)perbenzoate (all isomers), tertbutyl (nonyl)perbenzoate (all isomers), tert-amyl perbenzoate, tert-amyl (methyl)perbenzoate (all isomers), tert-arnyl (ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate (all isomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perberizcate (all isomers), tert-amyl (nonyloxy)perbenzoate (all isomers), 2- ethylhexyl perbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers), 2-ethylhexyl (ethyl)perbenzoate (all isomers), 2-ethylhexyl (octyl)perbenzoate (all isomers), 2-ethylhexyl (nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (all isomers), 2- ethylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl (octyloxy)perbenzoate (all isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers), Bis (tertbutylmonoperoxy phthaloyl) diperoxy terephthalate, Bis (tertamylmonoperoxy phthaloyl) diperoxy terephthalate diacetyl phthaloyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4 methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide, diben2oyl terephthaloyl diperoxide and Poly[ dioxycarbonyldiox/(1,1,4,4-tetramethyl-1,4-butariediyl)] peroxide. Advantageously iratiators may be selected to avoid undesirable by-products. In certair applications. it may be desirable to avoid the use of initiators which generate benzene. For example di toluoyl peroxides (bis methyl benzoyl peroxides) may be used in preference to dibenzoyl peroxide. The processability and other properties of the product may be improved by a chain scissior. step following the initial polymer modification step This may be carried out by: a) adding one or more additional initiators with or subsequent to the first initiator addition; b) the use of high shear mixing; c) the use of high temperatures; d) the use combina ion is of one or more of (a) - (c) above. This additional step in the production of a polymer enables tailoring the properties of the product to meet the requirements of the desired application. For example, by this two stage process it is possitle to produce materials with similar melt viscosity to the base polymer but a substantially increased melt strength. Use of the single stage process generally provides both an. ir crease in melt strength and an increase in melt viscosity (see examples) One or more additional initiators may be added to the polypropylene (co)polymer during the modification process either with or subsequent to the initiator and monomer addition. The additional ;:ni iator is typically added to give chain scission of the polypropylene (co)polymer so as to decrease the melt viscosity and improve the processability of the modified polypropylene (co)polymer. The additional initiator should be introduced to the polymer melt after the first initiator or have a sufficiently long half-life relative to the first initiator such that its decomposition can be staged to occur after the initial polymer modification process. In some instances a polypropylene (co)polymer modified in accordance with the present invention may have a MFK1 g/10 min. With use of the additional initiator an MFI >1 g/10 min may be achieved. The additional initiator may be selected from the group consisting of 2.5-dimethyl-2,5-di(t-butylperoxy)hexane (DHBP), dicumyl peroxide DCP), t-butyl peroxy-2-ethylhexonate(TBEH), and dilauryl peroxide (DLP) or any other peroxide which may result in the overall chain scission of the polypropylene (co)polymer during melt processing. For example in the absence of the monoene monomers, t-butyl peroxybenzoate or other non-preferred initiators for use in the presence of the monomer may be preferably added as the additional initiator. While the improvement in processability through chain scission normally results in some decrease in the melt strength/extensional viscosity of the modified polypropylene (co)polymer, the melt strength/extensional viscosity may still be acceptable, and improved over the unmodified polypropylene (co)polymer. It is possible to combine the process of the present invention with other processes of polymer modification or witi, for example, the addition of fillers, additives or stabilisers, or blending with other polymers. In the process of th; present invention the polypropylene (co)polymer is melt mixed in the presence of initiato and optionally a monoene monomer. Melt mixing may be carried out by any convenient means capable of mixing the polypropylene (co)polymer at temperatures above the melting point of the polypropylene (co)polymer. Suitable apparatus for melt mixing the polypropylene (co)polymer include continuous and batch mixers. Suitable mixing equipment include:; extruders such as single screw and twin screw extruders, static mixers, cavity transfer mixers and combinations of two or more thereof. It is preferred that the melt mixing is conducted in either a co or counter- rotating twin screw extrude]. The barrel set temperatures are preferably in the range 80-280 °C. Typical melt temperatures are in the range 170-290 °C. In order to optimise the melt strength/extensional viscosity, the preferred melt temperatures are in the range 160 °C to 220 °C. This range provides optimal properties whilst minimising the amount of chain scission which occurs during processing. However, in some cases it may be desirable to use higher temperatures such as in the venting/discharge sections of single screw or twin screw extruders or to induce some chain scission in order to decrease the molecular weight of the modified polypropylene (co)polymer and irr prove the processability of the modified polypropylene (co)polymer. Typically, the die temperatures are in the range 180-290 °C. Preferably the extrusion conditions are adjusted so that the polypropylene (co)poiymer. initiator/monomer mixture are conveyed as quickly as possible into the melting/mixing zone to maximise the melt phase reaction (eg for twin screw extruders - high throughput rates. higher screw speeds under starve fed conditions). It is more prefeired that the additives arc added to and mixed with molten polypropylene (co)polyrner to further enhance the melt phase reaction. Preferably residence times in the range of from 10 seconds to 5 minutes are selected depending upon the temperature profile, throughput rate and initiator levels. More preferred residence times axe in the range of from 15 seconds to 120 seconds. Vacuum venting can be applied to remove volatile by-products, solvents and/or excess monomer. While not wishing to be limited by theory, it is believed that the effectiveness of the present invention is determined by three factors: (a) The rate and specificity of the reaction of the aroyloxy or the derived phenyl radicals or substituted phenyl radicals with polypropylene, and the monomer if present. It is believed that the aroyloxy, phenyl or substituted aroyloxy or phenyl radicals show less specificity for abstraction of tertiary vs. secondary or primary hydrogens than do, for example, alkoxy or alkyl radicals. (b) The initiator half-life. Use of an initiator with a short initiator half-life will generate a locally high concentration of radicals thus increasing the likelihood of radical combination events. (c) The solubility characteristics of the initiator in the polymer melt. Without wishing to be bound by theory, peroxides that generate aroyloxy or aryl radicals (for example benzoyloxy, p-toluouloxy) are preferred over those that generate alkoxy radicals (for example, t-butoxy radical, cumyloxy radical). It is believed and supported in the literature that the latter class of peroxides promote chain scission under the melt mixing conditions. While not wishing to be bound by the mechanism, it is believed that this effect is due to the specificity shown by the alkoxy radicals as opposed to the aroyloxy or aryl radicals generated by the peroxides of structure 1. Furthermore we believe that peroxides which generate both alkoxy and aroyloxy or aryl radicals (for example, t-butyl perbenzoate) show intermediate behaviour. It is believed that they promote less chain scission than peroxides which generate only alkoxy radicals (for example, dialkyl peroxides) when used alone and can be used to advantage in systems where a monomer coagent is employed. Preferred peresters are thus those which generate alkoxy radicals which are not active in hydrogen abstraction (for example t-amyl perbenzoate). Similarly, it is believed, without wishing to be bound by theory, that the effectiveness of the monomer is determined by: (a) The solubility of the monomer in the polymer melt. For example, sryrene is known to be soluble in molten polypropylene. (b) The reactivity of the monomer towards polypropylene derived radicals. (c) The propensity for the radical formed by addition of monomer to give combination or addition (which leads to branch or crosslink formation) vs. disproportionabon or hydrogen abstraction. It is known mat the benzylic radicals give predominantly combination and have low (with relation to other radicals) tendency to abstract hydrogen. Other initiators and monomers that meet the above criteria may also be used to advantage in the present invention. Surprisingly, the process of the present invention results in a polypropylene (co)polymer with substantially increased melt strength. We have found that it is possible with the present invention to obtain a polypropylene (co)polymer which has a melt strength at least 25% greater than the melt strength of the base polymer. We have also found that it is possible to obtain an increase in melt strength of greater than 100% for a number of the polypropylene (co)polymers produced in accordance with the process of the present invention. Increases in melt strength were assessed using a Gottfert-Rheotens melt strength tester operated with a roller acceleration of 1.2 cm/sec3 measuring the melt strength of a 2 mm strand of molten polypropylene (co)porymer (melt temperature of 210°C) which is fed to the Gottfert tester at ~4 g/min. In a further aspect of the present invention there is provided a modified polypropylene: (co)polymer produced according to the process described herein, wherein said modifier! polypropylene (co)polymer preferably has a melt strength at least 25%, and more preferably at least 100%, grerier than the unmodified polypropylene (co)polymer. The polypropylene (co)porymers produced according to the process of the present invention also may provide a significant increase in long-chain branching. Long-chain branching may be assessed by the Dow Rheology Index. Advantageously, the modified polypropylene (co)polymers may demonstrate a Dow Rheology Index (DRI) of greater than 1, preferably at least 2 and most preferably greater than 60. The process of the present invention may also be used to increase the melt elasticity of a polypropylene (co)polymer. Advantageously, the process of the. present invention also provides a means to alter the molecular weight, molecular weight distribution and/or degree and length of branching of polypropylene, ethylene-propylene copolyners, and analogous a-olefin copolymers with or without altering the melt strength of said polymers by melt processing The process of the preheat invention may provide a means to generally increase the molecular weight and broadea the molecular weight distribution and/or introduce branching of the polypropylene (co)polymer. This will not always equate to significant increases in the melt strength or extensions] viscosity of the polymer that is being modified eg modification of a lower molecular weight polymer to broaden the molecular weight and/or induce shorter branches. Such a product may not necessarily demonstrate a high melt strength, but may demonstrate other desireable properties, for example improved filler uptake, mechanical properties, surface properties, thermal and morphological properties. The modified polypropylene (co)polymer produced by the process of the present invention may be used either neat or blended with another polymer or other additives to provide the desired balance of properties in the polymer blend. The modified polypropylene (co)polymers and blends may be used in a wide variety of applications including thermoforming, blow moulding, tube or pipe extrusion, blown films, foams and extrusion coating. The present invention may also be used in the recycling of waste polypropylene or materials containing waste polypropylene. The increased melt strength of the modified polypropylene (co)polymers renders these (co)polymers more suitable for use in thermoforming applications. The modified polypropylene (co)polymers may be used to thermofonn containers such as margarine tubs. The benefits of this invention include that the polypropylene (co)polymers and blends containing same provide a wider temperature processing window than conventional isotactic polypropylene. The modified polypropylene (co)polymers may also be used in large pan thermoforming such as in the production of refrigerator liners and the like where conventional isotactic polypropylene is unsuitable. The modified polypropylene (co)polymers produced in accordance with the present invention are suitable for blow moulding and we have found that they can be more readily blow moulded into containers. Furthermore, the increased melt strength makes it possible to produce large blow moulded parts through the use of the high melt strength modified polypropylene (co)polymer. Thus components currently made by rotational moulding may now be produced by blow moulding using the modified polypropylene (co)polymer of the present invention. Profile extrusion for example tube or pipe extrusion, using the modified polypropylene (co)polymer has been found to produce a more consistent product than conventional isotactic polypropylene. Blown films made of polypropylene are generally blown downwards using relatively expensive equipment. The modified polypropylene (co)polymers of the present invention have sufficient melt strength for them to be able them to be blown upwardly using conventional polyethylene type film blowing equipment which is less expensive and generally more convenient to operate. Advantageously the modified polypropylene (co)polymcrs of the present invention may be used in the production of blown films. The modified polypropylene (co)polymers of the present invention may also be foamed with a wider processing window than for conventional polypropylene. Either a physical or chemical blowing agent may be used. It is preferred to use carbon dioxide as a physical blowing agent to produce foams having a fine closed cell structure. Foamed pellets may be subsequently moulded to form components for use in a variety of applications such as automotive door trims, roofttnings, dash boards, bumpers and the like. Applications such as in foamed packaging arc also possible, including thermoformed containers, insulating cups and the like. Waste polypropylene or waste streams containing a significant proportion of polypropylene are presently difficult to recycle as conventionally a high degree of chain scission results from die recycling process. The process of the present invention may be used to upgrade recycled streams containing polypropylene by increasing the overall mechanical properties of the recycled polypropylene by the addition of initiator and monomer in accordance with the present invention. The present invention will now be described with reference to the following non-limiting examples. Described hereunder are the measurement techniques used in the examples and a full description of the process conditions employed. Comparative Examples are labelled CE- n. Melt Strength Measurement Melt strengths were measured on a "Rheotens" Melt Strength Tester, Type 010.1, supplied by Gottfert Werkstoff-Pruftnaschinen Gmbh of Buchen, Germany. This test involves drawing an extruded strand of polymer vertically into the nip between two counter-rotating nip rollers. The strand was extruded using a Brabender Plasticord single screw extruder of screw diameter 19mm and length to diameter ratio (L/D) of 25. The extrudatc exited via a right angle capillary die (2mm diameter). The temperature profile used was uniform along the length of the barrel of the extruder and the die and was set at 190°C. The nip rollers are mounted on a balance arm which allows the force in the drawing strand to be measured. The velocity of the nip rolls is increased at a uniform acceleration rate. As the test proceeds, the force increases until eventually the strand breaks. The force at breakage is termed the "melt strength". While there is no internationally-established standard set of test requirements for melt strength testing, comparative melt strength values obtained under the given set of test conditions provide a quantitative determination of the increase in melt strength used in the patent. The test conditions used were: die temperature 190°C, extruder output rate -4 g/min, acceleration rate 1.2 cm/sec2, draw distance 210 mm, matt finish steel rollers. Dow Rheotogy Index The Dow Rheology Index (DRI) is believed in the art to be a measure of the long chain branching in a polymer. It is expressed as the deviation of a viscosity parameter obtained from shear rheology measurements on a "branched" polymer compared with that for a linear polymer. The branched polymers have lower values of the viscosity parameter than the linear polymers (for a given relaxation parameter). The parameters are obtained by fitting the Cross model to the shear viscosity flow curves. The DRI method has been described by Lai, Plumley, Butler, Knight and Kao in a paper in SPE ANTEC '94 Conference Proceedings (ppl814-1818) - "Dow Rheology Index (DRI) for Insite Technology Polyolefins (ITP): Unique Structure-Processing Relationships". Dynamic Rheology Tests The dynamic rheology tests were performed on a Rheometrics Dynamic Stress Rheometer SR200. Test conditions were: parallel plates, temperature 190°C, frequency range 0.01 to 100 rad/sec, and 3-4% strain, in a nitrogen atmosphere to prevent degradation. G' is the storage modulus representing the elasticity of the polymer melt, G"is the loss modulus which represents the viscous component of the deformation. The polydispersity index is 10 to power 5 divided by the crossover modulus, which is the value of G1 = G" when the G' and G" curves crossover - it is believed to be a measure of MWD. The higher G' the greater elasticity in the polymer and the higher the MW. MFI Melt flow indexes (MFI) were measured a 230°C with a 2.16 kg load according to ASTM 1238. Drop Times The drop times were determined by measuring the time taken for the polypropylene strand (cut at the die face) to drop from the die of the extruder to the floor. The die of the JSW twin screw extruder was 1140 mm above the floor. The drop time test combines the effects of melt viscosity, extensional viscosity, chain entanglement (as shown by die swell), and elasticity (as shown by the tendency resist neck formation). Higher melt viscosity polypropylene polymers had drop times which incorporated some additional effect due to prolonged cooling of the slower moving (falling) molten strand. GPC GPC molecular weights were determined using a Waters 150C high temperature GPC unit. 1,2,4-trichlorobenzene was used as the solvent, eluting through two Styragel HT6E linear columns. The oven temperature was set at 140oC and the pump flow rate was l.0ml/min. Calibration was performed using narrow polydispersity polystyrene standards. AH molecular weights quoted as polystyrene equivalents. Mn= number average molecular weight Mw= weight average molecular weight Mz= viscosity average molecular weight Mp= peak molecular weight Twin Screw Extruder The twin screw extruder used in the examples was a JSW TEX-30 with a 30 mm screw diameter and an overall L/D of 42 [comprising ten temperature controlled barrel sections (L/D 3.5, temperatures between 120 and 230°C as specified in Table 1), three unheated sampling/monitoring blocks (L/D 1.167) and a cooled feed block (L/D 3-5)) equipped with two JSW TTF20 gravimetric feeders, one K-Tron KQx gravimetric additives feeder and a volumetric liquid addition pump (Fuji Techno Industries model HYM-03-08)]. The extruder was operated in either co-rotating (intermeshing self wiping) or counter rotating (intermeshing non-self wiping) modes with a throughput rate of between 5 and 20 kg/hr and screw speeds of between 100 and 400 rpm as specified in Table 1. The melt temperature and pressures were monitored at three points along the barrel and in the die. The overall extruder configuration and modifier conditions may be recited, for example, as condition: A16. Solvent Addition of Modifiers The initiator, and monomer if present, was introduced as a solution in 2-butanone or xylene. The concentration of the initiator varied from 5.6% wt/wt to 8.5% wt/wt. The benzoyl peroxide and the di-toluol peroxides were both powders wetted with 25% (wt/wt) water. The monomer was present in an amount between 4 to 10% wt/wt solvent. Increased levels of initiator were generally added by increasing the amount of solution added to the polymer melt. The additional peroxides (if any) were added with the initiator in the carrier solvent. Solventless Addition of Modifiers t-Butyl peroxybenzoate is a liquid. The solventless modification of the polymer was achieved by absorbing the initiator onto powdered polymer or blending it with powdered polymer at concentrations ranging from 5% wt/wt to 10% wt/wt to form a masterbatch. The masterbatch was added to the extruder in varying feed rates to alter the amount of additives. The amount of polymer feed was adjusted accordingly to give constant overall feed rate. The stabilisers were also added as a masterbatch. The amount of stabiliser was generally kept constant at 0.33%wt/wt Irganox 1010 and 0.17%wt/wt Irgaphos 168 in the total composition. The main polymer feed was added as either powder or pellets. Single Screw Extruders Killion The Killion single screw extruder used in the examples was a segmented single screw extruder of L/D=40 (11 barrel sections , 10 heated) and screw diameter of 31.75 mm. Polypropylene powder, stabilisers (0-33%wt/wt Irganox 1010, 0.17%wt/wt Irgaphos 168 in total) and initiator were added to the feed throat of the single screw extruder via a twin screw K-Tron volumetric feeder. Alternatively, the polypropylene powder and stabilisers were added via the K-Tron feeder and polypropylene powder, stabilisers and the modifiers were added as a master batch via a single screw APV Accurate volumetric feeder. The masterbatch contained 7.5%wt/wt benzoyl peroxide (prepared using a dispersion of benzoyl peroxide containing 25%wt/wt water). The output of the extruder was ~ 1.5 kg/hr using a screw speed of 30rpm. The set barrel temperature was either (I) a flat 220°C with each barrel section and the die set at a temperature of 220°C or (ii) 230oC/190oC with the first six melting sections of the barrel set at 230oC and the next four metering sections of the barrel and the die set at 190°C. The melt temperature varied from 220 to 260°C. Brabender 5 The Brabender single screw extruder used was a single screw extruder of L/D = 25 (4 Barrel sections), compression ratio 2.5:1 and screw diameter of 19 mm. The die was a 4 mm rod die. The screw speed of the extruder was 20 ipm. The set barrel temperature was 140oC, 170°C, 180°C, 180°C. Residences time: Start 3 min 40 sec; Middle 4 min 35 sec; and End 7 min 30 sec. Polypropylene powder either as cryoground pellets or ex-reactor powder was mixed with the modifiers and added to the feed throat, either flood feed or by a Brabender single screw volumetric feeder. The following commercial polypropylene (co)polymers were used in the examples. The properties of the (co)polymers are shown in Table 4 below. 1 Melt strength and MFI were measured for a particular batch and we have found actual values vary up to 20% of these values. Examples 1 to 5 GYM45 was modified in accordance with Table 5 below. GYM45 is a low molecular weighc/higher MFI injection moulding grade of polypropylene homopolymer. Examples 6 to 18 GWM22 was modified in accordance with Table 6. GWM22 is an intermediate molecular weight/medium MFI extrusion grade of polypropylene homopolymer. The increase in complex viscosity of examples 14, 16, 17 and 18 is shown in Figure l.G' has been plotted against frequency in Figure 2. The modified polypropylene's of examples 14, 16, 17 and 18 were tested for additional physical properties and it was found that the modified polypropylene's had: Examples 19 to 26 PXCA6152 was modified in accordance with Table 7 below. PXCA6152 is a high molecular weight/low MFI thermoforming grade of polypropylene homopolymer. iii) Polydispersity Index 3.9 Mw/Mn iv) Dow Rheology Index 10 Long Chain Branching The DRI of the base polypropylene material, PXCA 6152 (an unbranched polypropylene) was expected to be 0. The DRI of the modified polypropylene demonstrates a significant degree of long chain branching. Examples 27 to 33 LYM120 was modified in accordance with Table 8 below. LYM120 is a low molecular weight/higher MFI injection moulding grade of PP copolymer. Examples 34 to 42 Ex-reactor GYM45 powder was modified according to Table 9 below. GYM45 is a low molecular weight/higher MFI injection moulding grade of polypropylene homopolymer. The polypropylene was stabilized with Irganox 1010 (0.33 wt%) and Irgaphos (0.17 wt%). The modifiers and stabilizers were added to the twin-screw extruder at the feed throat. LYM120 was modified in accordance with Table 12 below. LYM120 is a low molecular weight/higher MFI injection moulding grade of polypropylene copolymer. Examples 62 to 73 LYM120 was modified in accordance with Table 13 below. LYM120 is a low molecular weight/higher MFI injection moulding grade of polypropylene copolymer. Examples 74 to 77 GYM45 was modified in accordance with Table 13 below. GYM45 is a low molecular weight/higher MFI injection moulding grade of polypropylene homopotymer. Examples 78 to 82 LYM120 was modified in accordance with Table 14 below. LYM120 is a low molecular weight/higher MFI injection moulding grade of polypropylene copolymer. Examples 83 to 92 LYM120 was modified in accordance with Table 15 below. LYM120 is a low molecular weight/higher MFI injection moulding grade of polypropylene copoiymer. Examples 93 to 97 GYM45 was modified in accordance with Table 16 below. GYM45 is a low molecular weight/higher MFI injection moulding grade of polypropylene homopolymer. Example 98 to 105 LYM120 was modified in accordance with Table 17 below. LYM120 is a low molecular weight/higher MFI injection moulding grade of polypropylene copolymer. Examples 108 and 109 Montell 6501 was modified in accordance with Table 19 below on the Killion screw extruder described above. Examples 40, 41, 7, 12, 28, 29, 31 and 14 GPC molecular weights were determined using a Waters 150C high temperature GPC unit. 1,2,4-trichlorobenzene was used as the solvent, eluting through two Ultrastyragel linear columns. The oven temperature was set at 140°C and the pump[ flow rate was 1.0 ml/min. Calibration was performed using narrow polydispersity polystyrene standards. AH molecular weights quoted as linear polystyrene equivalents. Mn=number average molecular weight Mw mc weight average molecular weight Mz mcviscosity average molecular weight Examples 118 to 121 KM6l00u was modified with para-toluoyl peroxide (FTP) and BPO in accordance with Table 23 below. The KM6100u was stabilized with Irganox 1010 (0.33wt%) and Irgaphos 168 (0.17 wt%) which were added to the main feed throat of the extruder. Examples 122 to 128 PXCA6152 was modified with mixed initiator systems in accordance with Table 24 below. Table 24: Example Conditions Init #l Init # 2 Mole Motor Drop Die MFI Melt Str. wt% wt% ratio Current Time Temp (g/10 (cN) Init#l/ln (amps) (sec) °C min.) Control 0.8 6 5 CE-88 B3a 0 0 - 22 14 255 0.9 5.1 122 B3a 0.87 0 24 20 257 1.28 14.2 Initiator #1 = BPO, Initiator # 2 = DHBP 123 B3a 0.87 0.045 23.2 22 19 251 40 80 124 B3a 0.87 0.064 16.3 20 16 250 5.4 Examples 129 to 132 Cryoground PXCA6152 to the fonn in the form of a powder was modified with mixed initiator systems according to Table 25 below. Examples 129 to 132 Table 15; Effect of Mixed Initiators on the Modification of PXCA6 152 Powder a (cryoground pellets) Examples 134 to 137 Cryoground KM6100 in the form of a powder was modified on a Brabender single screw extruder in accordance with the general description of the Brabender SSE above and Table 28 below. The initiator was added at the feed throat of the SSE along with the stabilizers (0.33 wt% Irganox 1010 and 0.17 wt% Irgaphos 168). Examples of Carbon Dioxide Foaming of Modified PP The equipment used for foaming the polypropylene (from earlier examples) was a tandem extrusion line made up of an Leitritz twin screw extruder (34 mm screw diameter, co- rotating, with 11 barrel sections) connected via a melt pipe to a single screw extruder (43 mm screw diameter). CO2 was introduced into barrel six of the twin screw extruder. The gassed polymer was then cooled slowly in the single screw extruder. Non high melt strength grades of polypropylene have foam temperature processing windows of less than 1°C. Foamed examples 13 and 17 both has a fine closed cell structure. Examples of thermoforming The modified polypropylene produced in Example 69 was extruded on a Welex single screw extruder through a sheet die to produce a sheet 78cm wide and "1.25 mm thick. The sheet was fed to a Gabler F702 continuous thermoformer to produce margarine tubs. Tubs produced from the modified PP sample had a crush strength of 25 kg after 1 hour. No appreciable sag was noticed of the PP sheet during the process. The modified polypropylene of Example 5 was blow moulded on Bekum blow moulder fitted with a general puipose polyolefin screw using a 750 ml screw top bottle mould, (radially non symmetrical bottle with waist). The mould temperature was 0C. The blow mouldabiuty of the modified injection moulding grade of PP was compared against that of a commercial low melt flow index PP homopolymer (ICI GWM110 of MFI = 1.5). It was found that the modified PP homopolymer (MFI = 9.1 and Melt Strength = 6.9 cN) i could be easily blow moulded into 750 ml bottles. Conventional PP of similar MFI could not be-successfully blow moulded. The modified PP gave similar performance to an extrusion grade PP of low MFI. The results are very promising where a higher MFI PP could be used to blow bottles. This possibly opens up the opportunity to produce large blow moulded parts through use of a high melt strength modified PP which has been tailored to have an MFI acceptable to blow moulding (ie 1-2 MFI) Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and ail combinations of any two or more of said steps or features. WE CLAIM 1. A process for increasing the melt strength and/or the extensional melt viscosity of a polypropylene (co) polymer wherein, said process comprises melt mixing the polypropylene (co)polymer in the presence of an initiator and oxlionally a mondene mononer vherein said initiator is selected from the group defined by formula 1 : Formula 1 wherein R is selecied from the group consisting of optionally substituted C1 to C18 acyl, optionally substituted C1 to C18 alkyl, aroyl defined by formula 2, and groups of formula 3, Formula 3 wherein U, V, X, Y, Z, U', V', X', Y' and Z' are independently selected from the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxycarbonyl, aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4, Formula 4 and wherein T is a ikylene, and wherein the melt strength and/or the extensional melt viscosity of the polypropylene (co)polyroer is incuased during the melt mixing step. 2. A process according to claim 1 wherein the initiator is selected from compounds of formula 6. Formula 6 where X, Y, Z, U, V, X', Y', Z', U', V' are independently selected from the group consisting of hydrogen and C - C18 alkyl where at least one of X, Y, Z, U, V and X', Y', Z', U', V are not hydrogen. 3. A process according to claim I wherein the initiator is selected from the group consisting of Dibenzoyl peroxide, o,o'-Bis(methylbe;nzoyl) peroxide, p,p'- Bis(methylbenzoyl) peroxide, M,M'-Bis(methylbenzoyl) peroxide, o,m'- Bis(methylbenzoyl) peroxide, o,p'-Bis(methylber.zoyl) peroxide. m,p'-Bis(methylbenzoyl) peroxide, Bis(ethylbenzoyl) peroxide (all isomers), Bis(propylbenzoyl) peroxide (all isomers), Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isomers), Bis(hexylbenzoyl) peroxide (all isoomers), Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzoyl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (all isomers), Bis(methyoxybenzoyl) peroxide (all isomers), Bis(eihoxybenzoyl) peroxide (all isomers), Bis(propoxybcnzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide (all isomers), Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybenzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide (all isomers), Bis(iluorobcnzoyl) peroxide (all isomers), Bis(bro:nobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide (all isoners), Bis(trimethylbenzoyl) peroxide (all isomers), Bis(tert-butylbenzoyl)peroxide (all isomers). Bis(di- tert-butylbenzoyl)peroxide (all isomers), Bis(tertbutoxybenzoyl)peroxide (all isomers), Bis(ditrimethylsily benzoyl) peroxide (all isomers), Bis(heptafluoropropylbenzoyl) peroxide (all isonurs), Bis(2,6-dimethyl-4- trimethylsilyl benzoyl) peroxide and isomers, 2,2'(dioxydicarbonyl) bis - Benzoic acid dibutyl ester where the term "all isomers" refers to any variation in the position of the ring substituent as well as the structure of the substituent itself i.e.. for propyl; n-propyl and isopropyl. 4. A process according to claim 1 wherein the initiator is selected from the group consisting of tert-butyl perbenzoate, tert-butyl (methyl)perbenzoate (all isomers), tert- butyl (ethyl)perbenzoate (all isomers), tert-butyl (Octyl)perbenzoate (all isomers), tert-butyl (nonyl)perbenzoate (all isomers), tert-amyl perbenzoate, tert-amyl (raethyl)perbenzoate (al) isomers), tert-amyl (ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate (all isomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate (all isomers). 2-ethylhexyl perbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers), 2- ethylhexyl (ethyil)p2rbenzoate (all isomers), 2-ethylhexyl (octyl)perbenzoate (all isomers), 2-ethylhexyl (nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (all isomers), 2-elhylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl (octyloxy)perberizcate (all isomers), and 2-ethylhexyl (nonyloxy)perbenzoate (all isomers). 5. A process according to claim 1 wherein the initiator is selected from the group consisting of Bis (tertbutylmonoperoxy phthaloyl) diperoxy terephthalate. Bis (tertamylmonoperoy phthaloyl) diperoxy terephthalate diacetyl phthaloyl diperoxide, dibenzoyl phthaloyl diperoxide. bis(4 methyltenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide, dibenzoyl terephthaJoyl diperoxide. Poly[ dioxycarbonyldioxy(l,l,4,4-tetramethyl-l,4-butanediyl)] peroxide. 6. A process according to claim 1 wherein the initiator has a 0.1 hour half life in the range 100- 170°C. 7. A process according to claim 1 wherein the initiator is present in the range of from 0.004 to 0.25 moles of initiator per kg of the polypropylene homopolymer or copolymer. 8. A process jccording to claim 7 wherein the initiator is present in the range of from 0.006 to 0.10 mole 3 of initiator per kg of the polypropylene homopolymer or copolymer. 9. A process according to claim 8 wherein the initiator is present in the range of from 0.01 to 0.05 moles of initiator per kg of the polypropylene homopolymer or copolymer. 10. A process according to claim 1 wherein there is no added monoene monomer and the initiator is selected from the group consisting of Dibenzoyl peroxide, o,o'-Bis(methylbenzoyl peroxide, p,p'-Bis(methylbenzoyl) peroxide. o,o'-Bis(methylbenzoyl) peroxide, o,m' Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl) peroxide, m?p'-Bis(methylbenzoyl peroxide, Bis(ethylbcnzoyl) peroxide (all isomers), Bis(propylbenzcyl) peroxide (all isomers) Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isoroers) Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide (all isomers) Bis(octylbenzoyl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (all isomers) Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl) peroxide (all isomers) Bis(propoxybenzoyl) peroxide (ail isomers). Bis(butoxybenzoyl) peroxide (all isomers) Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybenzoyl) peroxide (all isomers) Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers) Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide (all isomers) Bis(fluorobenzoyl) peroxide (all isomers), Bis(bromobenzoyl) peroxide (all isomers) Bis(dimethylbenzcyl) peroxide (all isomers). B.is(trimethylbenzoyl) peroxide (all isomers) Bis(tert-butylbenzc'yl)peroxide (all isomers). Bis(di-tert-butylbenzoyl)peroxide (all isomers) Bis(tertbutoxybenzoyl)peroxide (all isomers), Bis(ditrimethylsilylbenzoyl) peroxide (al isomers), Bis(heptafluoropropylbenzoyl) peroxide (all isomers). Bis(2.4-dimethyl-6 trimethylsilyl beizoyl) peroxide and isomers tert-amyl perbenzoate, tert-amy (methyl)perbenzoate (all isoraers), tert-amvl (ethyl)perbenzoate (all isomers), tert-amy (octyl)perbenzoate (all isomers). len-arnyl (nonyl)perbenzoate (all isomers), tert-amy (methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoate (all isomers), tert- amyl (nonyloxy)perbenzoate (all isomers). Bis (tertamylmonoperoxy phthaloyl) diperoxy terephthalate, diacetyl phthaioyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4- methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide and dibenzoyl terephthaloyl diperoxide. 11. A process according to claim 10 wherein the initiator is more preferably the initiators are selected from the group consisting of dibenzoyl peroxide, 0,0'- Bis(methylbenzoyl) peroxide, p,p'-Bis(methylbenzoyl) peroxide, M,M'- Bis(methylbenzoyl) peroxide, o,m'-Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl) peroxide, and m,p-Bis(methylbenzoyl) peroxide. 12. A process according to claim 1 wherein the initiator is used in combination with a monoene monomer. 13. A process according to claim 12 wherein i:he amount of monoene monomer is up to 5 times the total moles of initiator. 14. A process according to claim 12 or claim 13 wherein the monoene monomer is tyrene. 15. A process iccording to claim 1- wherein the initiator is selected from the group consisting of Dibenzoyl peroxide, o,o'-Bis(methylbenzoyl) peroxide, p,p'- Bis(methylbenzoyl) peroxide, M,M'-Bis(methylbenzoyl) peroxide, o,m'~ Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl) peroxide, m,p'-Bis(methylbenzoyl) peroxide, Bis(ethylbenzoyl) peroxide (all isomers). Bis(propylbenzoyl) peroxide (all isomers), Bis(butyl) lbenzoyl) peroxide (all isomers), Bi$(pentylbenzoyl) peroxide (all isomers). Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzovl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl peroxide (all isomers), Bis(propoxybenzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide (all isomers), Bis(pentoxybenzoyi) peroxide (all isomers), Bis(hexyloxybernzcyl) peroxide (all isomers), Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octylxybenzoyl) peroxide (all isomers), Bis(nonyloxybenoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide (all isomers), Bis(fluorobenzoyl) peroxide (all isomers), Bis(brarrobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide (all isoraers), Bis(trimethylbenzoyl) peroxide (all isorners), Bis(tert-butylbenzoyl)peroxide (all isomers), Bis(di-teit-butylbenzoyl)peroxide (all isomers), Bis(tert-butoxybenzoyl)peroxide (all isomers), Bis(ditrimethylsilylbenzoyl) peroxide (all isomers). Bis(heptafluoropropylbenzoyl) peroxide (all isomers), Bis(2,4-dimethyl-6- trimethylsilyl benzoyl) peroxide itnd isomers, 2,2'(dioxydicarboiyl) bis - Benzoic acid dibutyl ester, tert- butyl perbenzoat;, lert-butyl (methyl)perbenzoate (al! isomers), ten-butyl (ethyl)perbenzoate (all isomers), tert-butyl (ociyl)perbenzoate (all isomers), tert-butyl (nonyl)perbenzoate (all isomers), tert-amyl perberizoate, tert-amyl (methyl)perbenzoate (all isomers), tert-any, (ethyl)perbenzoate (all isorners), tert-amyl (octyl)perbenzoate (all isomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all isomers), tert-aml (octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate (all isomers), 2-ethylhexyl perbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers), 2- ethylhexyl (ethyl)perbenzoate (all isomers), 2-ethylhexyl (octyl)perbenzoate (all isomers), 2-ethylhexyl (nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (all isomers), 2-ethylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl (octyloxy)perbenzoate (all isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers), Bis (tertbutylmonoperoxy phathloyl) diperoxy te-rephihalare. Bis (tertamylmonopenoxy phthaloyl) diperoxy terephthalate diacetyl phthaloyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4 rrethylbenzoyl) phthaloyl diperoxide, diacetyl terephthaioyl di peroxide, dibenzoyl terephthaloyl diperoxide and Poly[ dioxycarbonyldioxy(l,1.4,4-tetramethyl-l,4- butanediyl)] peroxide. 16. A modified polypropylene produced according to the process of any one of claims 1 to 15. 17, A process wherein the modified polypropylene of claim 16 is melt mixed with ar unmodified polypropylene to produce a modified polypropylene. 18. A process for modifying an a-olefin polymer wherein said process comprises melt mixing the a-olefin polymer in the presence of an initiator and optionally a monoene monomer wherein s aid initiator is selected from the group defined by formula 1. Formula 1 wherein R is selected from the group consisting of optionally substituted C1 to C18 acyl, optionally substituted C1 to C18 alkyl aroyl defined by formula 2, and groups of foraiula 3, Formula 3 wherein U, V, X, Y, Z, U', V', X', Y' and Z' ars independently selected from the group consisting hydrogen, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl, carboxy, alkoxy carbony1, aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula 4, Formula 4 wherein T is alkylene; and wherein the amount of monomer is 0 to 3 times the total moles of initiator. A process for increasing the melt strength and/or the extensional melt viscosity of,a polypropylene (co)polymer wherein said process comprises melt mixing the polypropylene (co)polymer in the presence of an initiator and ordinary a mondene mononer wvherein said initiator is selected from the group defined by formula 1: Formula 1 wherein R is selected from the group consisting of optionally substituted C1 ro C18 aryl, optionally substituted C1 to C18 alkyl, aroyl defined by formula 2,

Full Text

PROCESS
FOR INCREASING THE MELT STRENGTH OF POLYPROPYLENE
The present invention relates to polypropylene homopolymers and copolymers. In particular,
the present invention relates to a process for increasing the melt strength and/or the
extensional melt viscosity of said polymers by melt phase processing.
The melt strength and extensional viscosity of linear or straight chain polymers, such as
polypropylene, decreases rapidly with temperature. By contrast, polymers such as low
density polyethylene which are highly branched retain relatively high melt strengths and
extensional viscosities. It is generally understood that the difference In melt strengths and
extensional viscosities is attributable to the presence of long chain branching in polymers such
as low density polyethylene. Long chain branching allows a greater degree of chain
entanglement.
A number of methods for increasing the melt strength/extensional viscosity of polypropylene
and related polymers through the introduction of branching or a limited degree of crosslinking
in a process involving reactive extrusion have been proposed and are summarised in a recent
paper by Wang et al. (Wang, X., Tzoganakis, C., and Rempel, G.L., J. Appl. Polym. Sci,
1996, 61, 1395). One such process involves the reactive extrusion of polypropylene with a
White (US 5578682) has disclosed the use of various polyunsamrated crosslinking agents (for
example, bismeleimide derivatives) in combination with free radical initiators to achieve an
increase in the melt strength various polymers.
It is well known that the melt phase processing of polypropylene leads to mechanochemical
degradation. The processing of polypropylene in the presence of free radical initiators
SUBSTITUTE SHEET (Rule 26) (RO/AU)
provides an increased rate of degradation. This controlled degradation of polypropylene is
used commercially for the production of controlled rheology resins having reduced
polydispersity and reduced die swell (Lambla, M. in Comprehensive Polymer Science,
Pergamon, New York 1992, vol Suppl. 1, p 619; Hogt, A.H., Meijer, J., Jelinic, J. in
Reactive Modifiers for Polymers, Al-Malaika, S Ed., Chapman & Hall, London, 1996, p
84.). The degradation of polypropylene as described therein results in a lowering of melt
strength.
The batch modification of polypropylene to produce crosslinked (insoluble) polypropylene
by treatment with peroxides is described by Borsig et al. (Borsig, E., Fiedlerova, A., Lazar,
M. J., Macromol. Sci. Chem. 1981, A16, 513). Initiators which produce benzoyloxy
radicals or phenyl ladicals are described as being more efficient in inducing crosslinking or
grafting than those which produce t-butoxy or alkyl radicals. The process requires the use
of high levels of peroxide. The use of polyfunctional monomers as coagents to retard
degradation and enhance crosslinking is described by Chodak, I.; Fabianova, K.; Borsig,
E.; Lazar, M. Agnew. Makromol. Chem., 1978, 69, 107.
DeNicola (EP 384; 31A2) has disclosed a means :o produce a branched propylene polymer
material showing a net increase in the weight average molecular weight by solid state
modification of predominantly isotactic semi-crystalline linear polypropylene. The process
described in EP384331A2 involves blending peroxides with short half lives (eg peroxy
dicarbonates) with linear propylene polymer in a mixing vessel at temperatures from 23°C
to 120°C in an in;rt atmosphere and continuing to mix for a period of time until the
peroxide decompos es and polymer fragmentation and branching occurs without significant
gelation of the pclymer. DeNicola states that at temperatures greater than 120°C no
branching or melt strength enhancement is achieved.
U.S. 5,464,907 teathes that certain unsaturated itaconale derived peroxides may
be used to induce grafting in polypropylene and a-olefm copolymers. They report that use
of other peroxides generally results in chain degradation
Polypropylene is also known to undergo substantial degradation during melt phase grafting
of monofunctional monomers, for example maleic anhydride and glycidyl methacrylate. It
has also been reported that the degradation that accompanies grafting of these monomers to
polypropylene may be reduced by the addition of relatively high concentrations of certain
comonomers including styrene (see, for example Sun, Y.J., Hu, G.-H., and Lambla, M.,
Angew. Makromol. Chem. 1995, 229, 1; Chen, L-F., Wong, B. and Baker, W.E. Polym,
Eng. Sci. 1996, 36, 1594.) Sun et al. report that there is degradation (as indicated by an
overall decrease in molecular weight) when styrene alone is grafted onto polypropylene even
when a relatively high concentration is used (4 moles/lOOg PP). Either 2,5-dimethyl-2,5-(t-
butylperoxy)hex-3-yne or 2,5-dimethyl-2,5(t-butylpcroxy-hexane(DHBP) was used as the
initiator in these experiments.
We have found that melt mixing polypropylene homopolymer or ethylene-polypropylene
copolymer in the presence of a suitable initiator provides one or more of the following:
increased melt strength; increased extensional viscosity; increased molecular weight; and
broadened molecular weight distribution.
According to the present invention there is provided a process for modifying a polypropylene
(co)polymer wherein said process comprises melt mixing the polypropylene (co)polymer in
the presence of an initiator wherein said initiator is selected from the group defined by
formula 1:
Formula 1
wherein R is selected from the group consisting of optionally substituted C, to Qg acyl,
optionally substituted-C1 to C18 alkyl, aroyl defined by formula 2,
Formula 2
and groups of formula 3,
wherein U, V, X, Y, Z, U' V, X', Y' and Z' are independently selected from the group
consisting hydrogei, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl.
carboxy, alkoxycarbonyl, aryloxycarbonyl, trialkyl silyl, hydroxy,
or a moiety of formula 4,

Formula 4
and wherein T is alkylene.
Advantageously the thus formed modified polypropylene may be obtained without the
associated production of significant and detrimental amounts of gels.
Polymers suitable for use in the present invention include a wide variety of polypropylene
homopolyraers, opolymers and blends containing one or more polypropylene
homopolyiners and/or copolymers.
Suitable polypropylene homopolymers include isotactic polypropylene, atactic
polypropylene ami syndintactic polypropylene. Commercial isotactic polypropylene
having a proportion of
meso/dyads of greater than 90% is preferably used in the process of the present invention.
Isotactic polypropylene is a semi-crystalline polymer having a number of properties which
have made it one of the most widely used commercial polymers. These properties include
heat resistance, stress cracking resistance, chemical resistance, toughness, and low
manufacturing costs. However, the melt strength of isotactic polypropylene as measured
directly by extensional viscosity or use of a commercial melt strength tester or indirectly by
more qualitative measures such as drop time or die swell ratio is relatively low. This
relatively low melt strength limits the use of polypropylene in applications such as foam
extrusion, thermoforming and film blowing. In order to use polypropylene in such
applications it is necessary to employ sophisticated processing equipment. The present
invention now permits this already widely used commercial polymer to be used in an even
wider range of applications.
Polypropylene copolymers include copolymers of propylene and other monomers with such
other monomers being present preferably in amounts of up to 10%wt/wt. A preferred
comonomer is ethylene.
The present invention is also applicable to other polvmers cornnrisinp a-olefin monomers.
The initiators for use in the present invention may be selected from the group defined by
formula 1.
Formula 1
wherein R is selected from the group consisting of optionally substituted C1 to C18 acyl,
optionally substituted C1 to C18 alkyl, aroyl defined by formula 2,
Formula 2
and groups of formula 3,
Formula 3
wherein U, V, X, Y, Z, U', V', X', Y' and Z' are independently selected from the group
consisting hydrogen, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl,
carboxy, alkoxycarboxyl aryovycarboxyl, trialkyl silyl ht\ydroxy,
or a moiety of formula 4,
Formula 4
and wherein T is alkylene.
The alkyl, including acyl and alkoxy, groups included in the initiators of formula 1 may
include hetero atoms within the carbon chain (eg polyalkylene oxide) and may be branched
or unbranched and may be substituted with one or more groups such as with alkyl, aryl,
alkoxy or halogen substituents.
Without wishing to be bound by theory, it is believed that the aroyloxy radical of formula 5
Formula 5
,where U, V, X, Y and Z are as hereinabove defined, provide the surprising increase in melt
strength. Other compounds which generate these aroyloxy radicals may also be used in the
present invention.
A preferred class of initiators of formula 1 are diaroyl peroxides of formula 6.
Formula 6
where X, Y, Z, U, V, X', Y' Z' U' V are independently selected from the group
consisting of hydrogen and C1 - C18 alkyl where at least one of X, Y, Z, U, V and X', Y',
Z', U', V' are not hydrogen.
Diaryl peroxides of formula 6 include Dibenzoyi peroxide, o,o'-Bis(mcthylbenzoyI) peroxide,
p,p'-Bis(inethylbcnzoyl) peroxide, M,M'-Bis(mcthylbenzoyl) peroxide, o,m'-Bis(methylbenzoyl)
peroxide, o,p'-Bis(methylbenzoyI)peroxide, m,p-Bis(methylbeozoyl) peroxide, Bis(ethylbenzoyl)
peroxide (all isomers), Bis(propyibenzoyl) peroxide (all isomers), Bis(butylbenzoyl) peroxide (all
isomers), Bis(pentylbenzoyl) peroxide (all isomers), Bis(hexylbenzoyl) peroxide (all isomers),
Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzoyl) peroxide (all isomers),
Bis(nonylbenzoyl) peroxide (all isomers), Bis(methoxybenzoyl) peroxide (all isomers),
Bis(ethoxybenzoyl) peroxide (all isomers), Bis(propoxybenzoyl) peroxide (all isomers),
Bis(butoxybenzoyl) peroxide (all isomers), Bis(pentoxybenzoyl) peroxide (all isomers),
Bis(hexyloxybenzoyl) peroxide (all isomers), Bis(heptyloxybenzoyl) peroxide (all isomers),
Bis(octyloxybenzoyl) peroxide (all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers),
Bis(cblorobenzoyl) peroxide (all isomers), Bis(fiuorobenzoyl) peroxide (all isomers),
Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide (all isomers),
Bis(trimetfaylbenzoyl) peroxide (all isomers), Bis(tert-butylbenzoyl)peroxide (all isomers), Bis(di-
tert-butylbenzoyl)peroxide (all isomers), Bis(tertbutoxybenzoyl)peroxide (all isomers),
Bis(dhrimethylsilylbenzoyl) peroxide (all isomers), Bis(heptafluoropropylbenzoyl) peroxide (all
isomers), Bis(2,6-dimethyI-4- trimethylsilyl benzoyl) peroxide and isomers, 2,2'(dioxydicarbonyl)
bis - Benzoic acid dibutyl ester where the term "all isomers" refers to any variation in the position
of the ring substituent as well as the structure of the substituent itself i.e. for propyl; n-propyi and
isopropyl.
Examples of aromatic peresters of formula 1 include the following: tert-butyl perbcnzoate, tert-
butyl (methyl)perbenzoate (all isomers), tert-butyl (ethyl)perbenzoate (all isomers), tert-butyl
(octyl)perbenzoate (all isomers), tert-butyl (nonyl)perbenzoate (all isomers), tert-arnyl
perbenzoate, tert-amyl (methy)perbenzoate (all isomers), tert-amyl (ethyl)perbenzoate (all
isomers), tert-amyl (octyl)perbenzoatc (all isomers), tert-amyl (nonyl)perbcnzoate (all isomers),
tert-amyl (methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoatc (all isomers), tert-
amyl (nonyioxy)perbenzoate (all isomers), 2-ethylhexyl perbenzoate, 2-ethylhexyl
(methyl)perbenzoate (all isomers),, 2-ethylhexyl (ethyl)perbenzoate (all isomers), 2-ethylhexyl
(octyl)perbenzoate (all isomers),, 2-ethylhexyl (nonyl)perbenzoate (all isomers), 2-ethylhexyl
(methoxy)perbcnzoate (all isomers), 2-ethyihexyl (ethoxy)perbcnzoate (all isomers), 2-
ethylhexyi (octyloxy)perbcnzoate(all isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers)
The initiators for use in the present invention also include compounds of formula 1 where at
least one of U, V, X, Y, Z, U', V', X' Y' and Z' is a moiety of formula 4 where R is as
defined above. Preferably there is no more than one moiety of formula 4 per aromatic ring.
Such initiators are di or higher functional peroxides and may include polymeric peroxides
such as Bis (tertbutylmonoperoxy phthaloyl) diperoxy terephthalate, Bis (tertamylmonoperoxy
phthaloyl) diperoxy terephthalate diacetyl phthaloyl diperoxide, dibenzoyl phthaloyl diperoxide,
bis(4 methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide, dibenzoyl
terephthaloyl diperoxide, Poly[ dioxycarbonyldioxy(l,l,4,4-tetramethyl-1,4-butanediyl)]
peroxide.
It is described that the initiators are selected such that it has an appropriate decomposition
temperature (half life), solubility, and reactivity and such that the groups R, T, X, Y, Z, U, V,
X', Y', Z',, U', V' give no adverse reaction under the conditions of the process. Preferred
peroxides will have a 0.1 hour half life in the range 100 - 170°C
The amount of initiator used in the process of the present invention should be an effective
amount to achieve the desired increase in melt strength. Melt strength is considered in the
art to be an indication of long-chain branching in polyolefins. It is preferable in the process
of the present invention that long-chain branching predominates over crosslinking in the
reaction between the initiator and the polypropylene (co)polymer. Crosslinking of the
polypropylene (co)polymcr may result in the formation of gels which disrupt the appearance
of the polypropylene (co)polymer. In the process of the present invention it is desirable to
control Die degree and distribution of crosslinking and keep the level of crosslinking as
uniform and as low as necessary to produce the desired effects. The amount of crosslinking
which occurs in the polypropylene (co)potymer is dependant upon the amount of initiator melt
mixed with the polypropylene (co)polymer. The amount of crosslinking is also dependent
upon the degree of mixing as any regions high in initiator concentration will result in
excessive localised crosslinking and the formation of gels. It is desirable that good
distributive and dispersive mixing be employed to promote even distribution of the initiator
in the polypropylene (co)polymer so as to minimise the variation in initiator concentration
throughout the polypropylene (co)polymer and reduce the likelihood of the formation of gels.
Preferably the initiator will be present in the range of from 0.004 to 0.25 moles of initiator
per kg of the polypropylene homopolymer or copoiymer (polypropylene (co)polymer). The
more preferred range being from 0.006 to 0.10 moles of initiator per kg. of the polypropylene
(co)polymer and even more preferred range being from 0.01 to 0.05 moles of initiator per
kg of the polypropylene (co)polymer.
The initiator is preferably introduced into the polymer melt directly, either neat (as a powder
or a liquid), dispersed or dissolved in a suitable medium (for example, dissolved in 2-
butanone) or adsorbed on polymer pellets or powder which are added as a masterbatch. It
is desirable that the initiator is rapidly mixed with the polymer melt at a raie in keeping with
the half life of the initiator at the processing temperature of the polypropylene (co)porymer.
The initiator may be added either alone, or along with the polypropylene (co)polymcr, or with
any other polymer, additive or filler, so that the polymer melts and mixes with the initiator
as it is decomposing. When the initiator is fed to the main feed throat of the extruder it is
preferred to have a barrel temperature which is relatively low in the region adjacent to the
main feed throat and increases towards the die to prevent premature decomposition of the
peroxide.
Preferably the initiators for use in the present invention are selected from the group consisting
ofDibenzoylperoxide, o,o'-Bis(njethylbeozoyl)peroxide, p,p'-Bis(niethyIbenzoyl)peroxide, o,o-
Bis(methylbenzoyl) peroxide, o,m'-Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenz:oyl)
peroxide, tn,p'-Bis(methylberaoyl) peroxide, Bis(ethyibenzoyl) peroxide (all isomers),
Bis(propylbenzoyl) peroxide (all isomers), Bis(butylbenzoyl) peroxide (all isomers),
Bis(pcntylbenzoyl) peroxide (all isomers), Bis(hexylbenzoyl) peroxide (all isomers),
Bis(heptylbenzoyl) peroxide (all isomers), Bis(octylbenzoyl) peroxide (all isomers),
Bis(nonylbenzoyl) peroxide (aU isomers), Bis(methoxybenzoyl) peroxide (all isomers),
Bis(ethoxybenzoyl) peroxide (all isoraers), Bis(propoxybenzoyl) peroxide (all isomers),
Bis(butoxybenzoyl) peroxide (all isomers), Bis;(pentoxybenzoyl) peroxide (all isomers),
Bis(hexyloxybenzoyl) peroxide (all isomers), Bi Bis(octyloxybenzoyl) peroxide (all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers),
Bis(chlorobenzoyr peroxide (all isomers), Bis(fluorobenzoyl) peroxide (all isomers),
Bis(bromobenzoyl) peroxide (all isomers), Bis(dimethylbenzojl) peroxide (all isomers),
Bis(trimethylbenzcyl) peroxide (all isomers), Bis(tert-butylbenzoyl)peroxide (all isomers),
Bis(di-tert-butylbenzoyl)peroxide (all isomers), Bis(tertbutoxybenzoyl)peroxide (all
isomers), Bis(ditririethylsilylbenzoyl) peroxide (all isomers), Bis(heptafluoropropylbenzoyJ)
peroxide (all isomers), Bis(2,4-dimethyl-6- trirr.ethylsilyl benzoyl) peroxide and isomers
tert-amyl perbcnzoate, tert-amyl (methyl)i?erbenzoate (all isomers), tert-amyl
(ethyl)perbcnzoate (all isomers), tert-amyl (o;tyl)perbenzoate (all isomers), tert-amyl
(nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all isoraers), tert-amyl
(octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate (all isomers), Bis
(tertamylmonopercxy phthaloyl) diperoxy terephthalate, diacetyl phthaloyl diperoxide,
dibenzoyl phthakyl diperoxide, bis(4-methybenzoyl) phthaloyl diperoxide, diacetyl
terephthaloyl di peroxide and dibenzoyl terephthaloyl diperoxide.
More preferably the initiators are selected from the group consisting of dibenzoyl peroxide,
o,o'-Bis(methylbenzoyl) peroxide, p,p'-B:s(methylbenzoyI) peroxide, M,M'-
Bis(methylbenzoyl) peroxide. o,m'-Bis(rnethylbenzoyI) peroxide. o.p'-Bis(methylbenzoyl)
peroxide, m,p'-Bis(methylben2oyI) peroxide.
The initiators may optionally be used in combination with one or more monoene monomers.
It will be understood by those skilled in the art that by the term "monoene monomer'1 it is
meant a monomer having a single reactive double bond.
The preferred menoene monomer(s) or mixtures thereof include vinyl monomers of
structure CH2 = CHX where X is chosen so as to confer the desired reactivity and solubility.
More preferred monomers include styrene. The amount of monomer will preferably be up
to 5 times the total moles of initiator added to the polypropylene (co)polymer. The most
preferred range being 1 to 4 times the total moles of initiator added to the polypropylene
(co)polymer.
The monomer may be added with the polypropylene (co)polymer or it can be added prior to
the initiator, with the initiator or subsequent to the initiator. However it is preferred to have
the monomer mixed and dispersed into the polymer melt before the initiator has substantially
decomposed. The monomer is preferably introduced into the polymer melt directly, either
neat (as a powder or a liquid), dispersed or dissolved in a suitable medium (for example,
dissolved in 2-butanone) or adsorbed on polymer pellets or powder which are added as a
mastprbatch.
Preferred initiators for use in combination with monomers include Dibenzoyl peroxide, o,o'-
Bis(methylbenzoyl) peroxide, p,p'-Bis(methyibenzoyl) peroxide, M,M*-Bis(inethylbenzoyl)
peroxide, o,m'-Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl) peroxide, m,p'-
Bis(metbylbenzoyl) peroxide, Bis(ethyibenzoyl) peroxide (all isomers), Bis(propylbeozoyl)
peroxide (all isomers), Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all
isomers), Bis(hexylbenzoyl) peroxide (all isoxners), Bis(heptylbenzoyl) peroxide (all isomers),
Bis(octylbenzoyl) peroxide (all isomers), Bis(nonytbenzoyl) peroxide (all isomers),
Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl) peroxide (all isomers),
Bis(propoxybcnzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide (all isomers),
Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybcnzoyl) peroxide (all isomers),
Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers),
Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide (all isomers),
Bis(fluorobcnzoyl) peroxide (all isomers), Bis(bromobenzoyl) peroxide (all isomers),
Bis(dimethylbenzoyl) peroxide (all isomers), Bis(trimethyibenzoyl) peroxide (all isomers),
Bis(tert-butylbcnzoyi)peroxide (all isomers), Bis(di-tert-butylbenzoyl)pcroxide (all isomers),
Bis(tcrt-butoxybenzoyl)peroxide(all isomers), Bis(ditrimethylsilyibcnzoyl) peroxide (all isomers),
' Bis(heptaftuoropropylbenzoyl) peroxide (all isomers), Bis(2,4-dimethyl-6- trimethylsilyl benzoyl)
peroxide and isomers, 2,2'(dioxydicarbonyl) bis - Benzoic acid dibutyl ester, tert-butyl
perbenzoate, tert-butyl (methyl)perbenzoate (all isomers), lert-butyl (etbyl)perbenioate (all
isomers), tert-butyl (octyl)perbenzoate (all isomers), tertbutyl (nonyl)perbenzoate (all
isomers), tert-amyl perbenzoate, tert-amyl (methyl)perbenzoate (all isomers), tert-arnyl
(ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate (all isomers), tert-amyl
(nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all isomers), tert-amyl
(octyloxy)perberizcate (all isomers), tert-amyl (nonyloxy)perbenzoate (all isomers), 2-
ethylhexyl perbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers), 2-ethylhexyl
(ethyl)perbenzoate (all isomers), 2-ethylhexyl (octyl)perbenzoate (all isomers), 2-ethylhexyl
(nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (all isomers), 2-
ethylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl (octyloxy)perbenzoate (all
isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers), Bis (tertbutylmonoperoxy
phthaloyl) diperoxy terephthalate, Bis (tertamylmonoperoxy phthaloyl) diperoxy terephthalate
diacetyl phthaloyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4 methylbenzoyl) phthaloyl
diperoxide, diacetyl terephthaloyl di peroxide, diben2oyl terephthaloyl diperoxide and Poly[
dioxycarbonyldiox/(1,1,4,4-tetramethyl-1,4-butariediyl)] peroxide.
Advantageously iratiators may be selected to avoid undesirable by-products. In certair
applications. it may be desirable to avoid the use of initiators which generate benzene. For
example di toluoyl peroxides (bis methyl benzoyl peroxides) may be used in preference to
dibenzoyl peroxide.
The processability and other properties of the product may be improved by a chain scissior.
step following the initial polymer modification step This may be carried out by:
a) adding one or more additional initiators with or subsequent to the first initiator addition;
b) the use of high shear mixing;
c) the use of high temperatures;
d) the use combina ion is of one or more of (a) - (c) above.
This additional step in the production of a polymer enables tailoring the properties of the
product to meet the requirements of the desired application. For example, by this two stage
process it is possitle to produce materials with similar melt viscosity to the base polymer
but a substantially increased melt strength. Use of the single stage process generally
provides both an. ir crease in melt strength and an increase in melt viscosity (see examples)
One or more additional initiators may be added to the polypropylene (co)polymer during
the modification process either with or subsequent to the initiator and monomer addition.
The additional ;:ni iator is typically added to give chain scission of the polypropylene
(co)polymer so as to decrease the melt viscosity and improve the processability of the
modified polypropylene (co)polymer. The additional initiator should be introduced to the
polymer melt after the first initiator or have a sufficiently long half-life relative to the first
initiator such that its decomposition can be staged to occur after the initial polymer
modification process. In some instances a polypropylene (co)polymer modified in
accordance with the present invention may have a MFK1 g/10 min. With use of the
additional initiator an MFI >1 g/10 min may be achieved. The additional initiator may be
selected from the group consisting of 2.5-dimethyl-2,5-di(t-butylperoxy)hexane (DHBP),
dicumyl peroxide DCP), t-butyl peroxy-2-ethylhexonate(TBEH), and dilauryl peroxide
(DLP) or any other peroxide which may result in the overall chain scission of the
polypropylene (co)polymer during melt processing. For example in the absence of the
monoene monomers, t-butyl peroxybenzoate or other non-preferred initiators for use in the
presence of the monomer may be preferably added as the additional initiator. While the
improvement in processability through chain scission normally results in some decrease in
the melt strength/extensional viscosity of the modified polypropylene (co)polymer, the
melt strength/extensional viscosity may still be acceptable, and improved over the
unmodified polypropylene (co)polymer.
It is possible to combine the process of the present invention with other processes of polymer
modification or witi, for example, the addition of fillers, additives or stabilisers, or blending
with other polymers.
In the process of th; present invention the polypropylene (co)polymer is melt mixed in the
presence of initiato and optionally a monoene monomer. Melt mixing may be carried out
by any convenient means capable of mixing the polypropylene (co)polymer at
temperatures above the melting point of the polypropylene (co)polymer.
Suitable apparatus for melt mixing the polypropylene (co)polymer include continuous and
batch mixers. Suitable mixing equipment include:; extruders such as single screw and twin
screw extruders, static mixers, cavity transfer mixers and combinations of two or more
thereof. It is preferred that the melt mixing is conducted in either a co or counter- rotating
twin screw extrude].
The barrel set temperatures are preferably in the range 80-280 °C. Typical melt
temperatures are in the range 170-290 °C.
In order to optimise the melt strength/extensional viscosity, the preferred melt
temperatures are in the range 160 °C to 220 °C. This range provides optimal properties
whilst minimising the amount of chain scission which occurs during processing. However,
in some cases it may be desirable to use higher temperatures such as in the
venting/discharge sections of single screw or twin screw extruders or to induce some chain
scission in order to decrease the molecular weight of the modified polypropylene
(co)polymer and irr prove the processability of the modified polypropylene (co)polymer.
Typically, the die temperatures are in the range 180-290 °C.
Preferably the extrusion conditions are adjusted so that the polypropylene (co)poiymer.
initiator/monomer mixture are conveyed as quickly as possible into the melting/mixing zone
to maximise the melt phase reaction (eg for twin screw extruders - high throughput rates.
higher screw speeds under starve fed conditions). It is more prefeired that the additives arc
added to and mixed with molten polypropylene (co)polyrner to further enhance the melt phase
reaction. Preferably residence times in the range of from 10 seconds to 5 minutes are selected
depending upon the temperature profile, throughput rate and initiator levels. More preferred
residence times axe in the range of from 15 seconds to 120 seconds.
Vacuum venting can be applied to remove volatile by-products, solvents and/or excess
monomer.
While not wishing to be limited by theory, it is believed that the effectiveness of the present
invention is determined by three factors:
(a) The rate and specificity of the reaction of the aroyloxy or the derived phenyl radicals or
substituted phenyl radicals with polypropylene, and the monomer if present. It is believed
that the aroyloxy, phenyl or substituted aroyloxy or phenyl radicals show less specificity for
abstraction of tertiary vs. secondary or primary hydrogens than do, for example, alkoxy or
alkyl radicals.
(b) The initiator half-life. Use of an initiator with a short initiator half-life will generate a
locally high concentration of radicals thus increasing the likelihood of radical combination
events.
(c) The solubility characteristics of the initiator in the polymer melt.
Without wishing to be bound by theory, peroxides that generate aroyloxy or aryl radicals (for
example benzoyloxy, p-toluouloxy) are preferred over those that generate alkoxy radicals (for
example, t-butoxy radical, cumyloxy radical). It is believed and supported in the literature
that the latter class of peroxides promote chain scission under the melt mixing conditions.
While not wishing to be bound by the mechanism, it is believed that this effect is due to the
specificity shown by the alkoxy radicals as opposed to the aroyloxy or aryl radicals generated
by the peroxides of structure 1. Furthermore we believe that peroxides which generate both
alkoxy and aroyloxy or aryl radicals (for example, t-butyl perbenzoate) show intermediate
behaviour. It is believed that they promote less chain scission than peroxides which generate
only alkoxy radicals (for example, dialkyl peroxides) when used alone and can be used to
advantage in systems where a monomer coagent is employed. Preferred peresters are thus
those which generate alkoxy radicals which are not active in hydrogen abstraction (for
example t-amyl perbenzoate).
Similarly, it is believed, without wishing to be bound by theory, that the effectiveness of the
monomer is determined by:
(a) The solubility of the monomer in the polymer melt. For example, sryrene is known to be
soluble in molten polypropylene.
(b) The reactivity of the monomer towards polypropylene derived radicals.
(c) The propensity for the radical formed by addition of monomer to give combination or
addition (which leads to branch or crosslink formation) vs. disproportionabon or hydrogen
abstraction. It is known mat the benzylic radicals give predominantly combination and have
low (with relation to other radicals) tendency to abstract hydrogen.
Other initiators and monomers that meet the above criteria may also be used to advantage in
the present invention.
Surprisingly, the process of the present invention results in a polypropylene (co)polymer with
substantially increased melt strength. We have found that it is possible with the present
invention to obtain a polypropylene (co)polymer which has a melt strength at least 25%
greater than the melt strength of the base polymer. We have also found that it is possible to
obtain an increase in melt strength of greater than 100% for a number of the polypropylene
(co)polymers produced in accordance with the process of the present invention. Increases in
melt strength were assessed using a Gottfert-Rheotens melt strength tester operated with a
roller acceleration of 1.2 cm/sec3 measuring the melt strength of a 2 mm strand of molten
polypropylene (co)porymer (melt temperature of 210°C) which is fed to the Gottfert tester at
~4 g/min.
In a further aspect of the present invention there is provided a modified polypropylene:
(co)polymer produced according to the process described herein, wherein said modifier!
polypropylene (co)polymer preferably has a melt strength at least 25%, and more preferably
at least 100%, grerier than the unmodified polypropylene (co)polymer.
The polypropylene (co)porymers produced according to the process of the present invention
also may provide a significant increase in long-chain branching. Long-chain branching may
be assessed by the Dow Rheology Index. Advantageously, the modified polypropylene
(co)polymers may demonstrate a Dow Rheology Index (DRI) of greater than 1, preferably
at least 2 and most preferably greater than 60.
The process of the present invention may also be used to increase the melt elasticity of a
polypropylene (co)polymer.
Advantageously, the process of the. present invention also provides a means to alter the
molecular weight, molecular weight distribution and/or degree and length of branching of
polypropylene, ethylene-propylene copolyners, and analogous a-olefin copolymers with or
without altering the melt strength of said polymers by melt processing
The process of the preheat invention may provide a means to generally increase the molecular
weight and broadea the molecular weight distribution and/or introduce branching of the
polypropylene (co)polymer. This will not always equate to significant increases in the melt
strength or extensions] viscosity of the polymer that is being modified eg modification of a
lower molecular weight polymer to broaden the molecular weight and/or induce shorter
branches. Such a product may not necessarily demonstrate a high melt strength, but may
demonstrate other desireable properties, for example improved filler uptake, mechanical
properties, surface properties, thermal and morphological properties.
The modified polypropylene (co)polymer produced by the process of the present invention
may be used either neat or blended with another polymer or other additives to provide the
desired balance of properties in the polymer blend.
The modified polypropylene (co)polymers and blends may be used in a wide variety of
applications including thermoforming, blow moulding, tube or pipe extrusion, blown films,
foams and extrusion coating.
The present invention may also be used in the recycling of waste polypropylene or materials
containing waste polypropylene.
The increased melt strength of the modified polypropylene (co)polymers renders these
(co)polymers more suitable for use in thermoforming applications. The modified
polypropylene (co)polymers may be used to thermofonn containers such as margarine tubs.
The benefits of this invention include that the polypropylene (co)polymers and blends
containing same provide a wider temperature processing window than conventional isotactic
polypropylene. The modified polypropylene (co)polymers may also be used in large pan
thermoforming such as in the production of refrigerator liners and the like where conventional
isotactic polypropylene is unsuitable.
The modified polypropylene (co)polymers produced in accordance with the present invention
are suitable for blow moulding and we have found that they can be more readily blow
moulded into containers. Furthermore, the increased melt strength makes it possible to
produce large blow moulded parts through the use of the high melt strength modified
polypropylene (co)polymer. Thus components currently made by rotational moulding may
now be produced by blow moulding using the modified polypropylene (co)polymer of the
present invention.
Profile extrusion for example tube or pipe extrusion, using the modified polypropylene
(co)polymer has been found to produce a more consistent product than conventional isotactic
polypropylene.
Blown films made of polypropylene are generally blown downwards using relatively
expensive equipment. The modified polypropylene (co)polymers of the present invention
have sufficient melt strength for them to be able them to be blown upwardly using
conventional polyethylene type film blowing equipment which is less expensive and generally
more convenient to operate. Advantageously the modified polypropylene (co)polymcrs of the
present invention may be used in the production of blown films.
The modified polypropylene (co)polymers of the present invention may also be foamed with
a wider processing window than for conventional polypropylene. Either a physical or
chemical blowing agent may be used. It is preferred to use carbon dioxide as a physical
blowing agent to produce foams having a fine closed cell structure. Foamed pellets may be
subsequently moulded to form components for use in a variety of applications such as
automotive door trims, roofttnings, dash boards, bumpers and the like. Applications such as
in foamed packaging arc also possible, including thermoformed containers, insulating cups
and the like.
Waste polypropylene or waste streams containing a significant proportion of polypropylene
are presently difficult to recycle as conventionally a high degree of chain scission results from
die recycling process. The process of the present invention may be used to upgrade recycled
streams containing polypropylene by increasing the overall mechanical properties of the
recycled polypropylene by the addition of initiator and monomer in accordance with the
present invention.
The present invention will now be described with reference to the following non-limiting
examples. Described hereunder are the measurement techniques used in the examples and a
full description of the process conditions employed. Comparative Examples are labelled CE-
n.
Melt Strength Measurement
Melt strengths were measured on a "Rheotens" Melt Strength Tester, Type 010.1, supplied
by Gottfert Werkstoff-Pruftnaschinen Gmbh of Buchen, Germany. This test involves drawing
an extruded strand of polymer vertically into the nip between two counter-rotating nip rollers.
The strand was extruded using a Brabender Plasticord single screw extruder of screw diameter
19mm and length to diameter ratio (L/D) of 25. The extrudatc exited via a right angle
capillary die (2mm diameter). The temperature profile used was uniform along the length of
the barrel of the extruder and the die and was set at 190°C. The nip rollers are mounted on
a balance arm which allows the force in the drawing strand to be measured. The velocity of
the nip rolls is increased at a uniform acceleration rate. As the test proceeds, the force
increases until eventually the strand breaks. The force at breakage is termed the "melt
strength".
While there is no internationally-established standard set of test requirements for melt strength
testing, comparative melt strength values obtained under the given set of test conditions
provide a quantitative determination of the increase in melt strength used in the patent. The
test conditions used were: die temperature 190°C, extruder output rate -4 g/min, acceleration
rate 1.2 cm/sec2, draw distance 210 mm, matt finish steel rollers.
Dow Rheotogy Index
The Dow Rheology Index (DRI) is believed in the art to be a measure of the long chain
branching in a polymer. It is expressed as the deviation of a viscosity parameter obtained
from shear rheology measurements on a "branched" polymer compared with that for a linear
polymer. The branched polymers have lower values of the viscosity parameter than the linear
polymers (for a given relaxation parameter). The parameters are obtained by fitting the
Cross model to the shear viscosity flow curves. The DRI method has been described by Lai,
Plumley, Butler, Knight and Kao in a paper in SPE ANTEC '94 Conference Proceedings
(ppl814-1818) - "Dow Rheology Index (DRI) for Insite Technology Polyolefins (ITP):
Unique Structure-Processing Relationships".
Dynamic Rheology Tests
The dynamic rheology tests were performed on a Rheometrics Dynamic Stress Rheometer
SR200. Test conditions were: parallel plates, temperature 190°C, frequency range 0.01 to
100 rad/sec, and 3-4% strain, in a nitrogen atmosphere to prevent degradation. G' is the
storage modulus representing the elasticity of the polymer melt, G"is the loss modulus which
represents the viscous component of the deformation. The polydispersity index is 10 to
power 5 divided by the crossover modulus, which is the value of G1 = G"
when the G' and G" curves crossover - it is believed to be a measure of MWD. The higher
G' the greater elasticity in the polymer and the higher the MW.
MFI
Melt flow indexes (MFI) were measured a 230°C with a 2.16 kg load according to ASTM
1238.
Drop Times
The drop times were determined by measuring the time taken for the polypropylene strand
(cut at the die face) to drop from the die of the extruder to the floor. The die of the JSW twin
screw extruder was 1140 mm above the floor. The drop time test combines the effects of
melt viscosity, extensional viscosity, chain entanglement (as shown by die swell), and
elasticity (as shown by the tendency resist neck formation). Higher melt viscosity
polypropylene polymers had drop times which incorporated some additional effect due to
prolonged cooling of the slower moving (falling) molten strand.
GPC
GPC molecular weights were determined using a Waters 150C high temperature GPC unit.
1,2,4-trichlorobenzene was used as the solvent, eluting through two Styragel HT6E linear
columns. The oven temperature was set at 140oC and the pump flow rate was l.0ml/min.
Calibration was performed using narrow polydispersity polystyrene standards. AH molecular
weights quoted as polystyrene equivalents.
Mn= number average molecular weight
Mw= weight average molecular weight
Mz= viscosity average molecular weight
Mp= peak molecular weight
Twin Screw Extruder
The twin screw extruder used in the examples was a JSW TEX-30 with a 30 mm screw
diameter and an overall L/D of 42 [comprising ten temperature controlled barrel sections
(L/D 3.5, temperatures between 120 and 230°C as specified in Table 1), three unheated
sampling/monitoring blocks (L/D 1.167) and a cooled feed block (L/D 3-5)) equipped with
two JSW TTF20 gravimetric feeders, one K-Tron KQx gravimetric additives feeder and a
volumetric liquid addition pump (Fuji Techno Industries model HYM-03-08)]. The extruder
was operated in either co-rotating (intermeshing self wiping) or counter rotating
(intermeshing non-self wiping) modes with a throughput rate of between 5 and 20 kg/hr and
screw speeds of between 100 and 400 rpm as specified in Table 1. The melt temperature and
pressures were monitored at three points along the barrel and in the die.
The overall extruder configuration and modifier conditions may be recited, for example, as
condition: A16.
Solvent Addition of Modifiers
The initiator, and monomer if present, was introduced as a solution in 2-butanone or xylene.
The concentration of the initiator varied from 5.6% wt/wt to 8.5% wt/wt. The benzoyl
peroxide and the di-toluol peroxides were both powders wetted with 25% (wt/wt) water. The
monomer was present in an amount between 4 to 10% wt/wt solvent.
Increased levels of initiator were generally added by increasing the amount of solution added
to the polymer melt. The additional peroxides (if any) were added with the initiator in the
carrier solvent.
Solventless Addition of Modifiers
t-Butyl peroxybenzoate is a liquid. The solventless modification of the polymer was achieved
by absorbing the initiator onto powdered polymer or blending it with powdered polymer at
concentrations ranging from 5% wt/wt to 10% wt/wt to form a masterbatch. The masterbatch
was added to the extruder in varying feed rates to alter the amount of additives. The amount
of polymer feed was adjusted accordingly to give constant overall feed rate.
The stabilisers were also added as a masterbatch. The amount of stabiliser was generally kept
constant at 0.33%wt/wt Irganox 1010 and 0.17%wt/wt Irgaphos 168 in the total composition.
The main polymer feed was added as either powder or pellets.
Single Screw Extruders
Killion
The Killion single screw extruder used in the examples was a segmented single screw extruder
of L/D=40 (11 barrel sections , 10 heated) and screw diameter of 31.75 mm.
Polypropylene powder, stabilisers (0-33%wt/wt Irganox 1010, 0.17%wt/wt Irgaphos 168 in
total) and initiator were added to the feed throat of the single screw extruder via a twin screw
K-Tron volumetric feeder.
Alternatively, the polypropylene powder and stabilisers were added via the K-Tron feeder and
polypropylene powder, stabilisers and the modifiers were added as a master batch via a single
screw APV Accurate volumetric feeder. The masterbatch contained 7.5%wt/wt benzoyl
peroxide (prepared using a dispersion of benzoyl peroxide containing 25%wt/wt water).
The output of the extruder was ~ 1.5 kg/hr using a screw speed of 30rpm. The set barrel
temperature was either (I) a flat 220°C with each barrel section and the die set at a
temperature of 220°C or (ii) 230oC/190oC with the first six melting sections of the barrel set
at 230oC and the next four metering sections of the barrel and the die set at 190°C. The melt
temperature varied from 220 to 260°C.
Brabender
5 The Brabender single screw extruder used was a single screw extruder of L/D = 25 (4 Barrel
sections), compression ratio 2.5:1 and screw diameter of 19 mm. The die was a 4 mm rod
die.
The screw speed of the extruder was 20 ipm. The set barrel temperature was 140oC, 170°C,
180°C, 180°C. Residences time: Start 3 min 40 sec; Middle 4 min 35 sec; and End 7 min
30 sec.
Polypropylene powder either as cryoground pellets or ex-reactor powder was mixed with the
modifiers and added to the feed throat, either flood feed or by a Brabender single screw
volumetric feeder.
The following commercial polypropylene (co)polymers were used in the examples. The
properties of the (co)polymers are shown in Table 4 below.
1* Melt strength and MFI were measured for a particular batch and we have found actual
values vary up to 20% of these values.
Examples 1 to 5
GYM45 was modified in accordance with Table 5 below. GYM45 is a low molecular
weighc/higher MFI injection moulding grade of polypropylene homopolymer.
Examples 6 to 18
GWM22 was modified in accordance with Table 6. GWM22 is an intermediate molecular
weight/medium MFI extrusion grade of polypropylene homopolymer.
The increase in complex viscosity of examples 14, 16, 17 and 18 is shown in Figure l.G' has
been plotted against frequency in Figure 2.
The modified polypropylene's of examples 14, 16, 17 and 18 were tested for additional
physical properties and it was found that the modified polypropylene's had:
Examples 19 to 26
PXCA6152 was modified in accordance with Table 7 below. PXCA6152 is a high molecular
weight/low MFI thermoforming grade of polypropylene homopolymer.
iii) Polydispersity Index 3.9 Mw/Mn
iv) Dow Rheology Index 10 Long Chain Branching
The DRI of the base polypropylene material, PXCA 6152 (an unbranched polypropylene) was
expected to be 0. The DRI of the modified polypropylene demonstrates a significant degree
of long chain branching.
Examples 27 to 33
LYM120 was modified in accordance with Table 8 below. LYM120 is a low molecular
weight/higher MFI injection moulding grade of PP copolymer.
Examples 34 to 42
Ex-reactor GYM45 powder was modified according to Table 9 below. GYM45 is a low
molecular weight/higher MFI injection moulding grade of polypropylene homopolymer. The
polypropylene was stabilized with Irganox 1010 (0.33 wt%) and Irgaphos (0.17 wt%). The
modifiers and stabilizers were added to the twin-screw extruder at the feed throat.
LYM120 was modified in accordance with Table 12 below. LYM120 is a low molecular
weight/higher MFI injection moulding grade of polypropylene copolymer.
Examples 62 to 73
LYM120 was modified in accordance with Table 13 below. LYM120 is a low molecular
weight/higher MFI injection moulding grade of polypropylene copolymer.
Examples 74 to 77
GYM45 was modified in accordance with Table 13 below. GYM45 is a low molecular
weight/higher MFI injection moulding grade of polypropylene homopotymer.
Examples 78 to 82
LYM120 was modified in accordance with Table 14 below. LYM120 is a low molecular
weight/higher MFI injection moulding grade of polypropylene copolymer.
Examples 83 to 92
LYM120 was modified in accordance with Table 15 below. LYM120 is a low molecular
weight/higher MFI injection moulding grade of polypropylene copoiymer.
Examples 93 to 97
GYM45 was modified in accordance with Table 16 below. GYM45 is a low molecular
weight/higher MFI injection moulding grade of polypropylene homopolymer.
Example 98 to 105
LYM120 was modified in accordance with Table 17 below. LYM120 is a low molecular
weight/higher MFI injection moulding grade of polypropylene copolymer.
Examples 108 and 109
Montell 6501 was modified in accordance with Table 19 below on the Killion screw extruder
described above.
Examples 40, 41, 7, 12, 28, 29, 31 and 14
GPC molecular weights were determined using a Waters 150C high temperature GPC unit.
1,2,4-trichlorobenzene was used as the solvent, eluting through two Ultrastyragel linear
columns. The oven temperature was set at 140°C and the pump[ flow rate was 1.0 ml/min.
Calibration was performed using narrow polydispersity polystyrene standards. AH molecular
weights quoted as linear polystyrene equivalents.
Mn=number average molecular weight
Mw mc weight average molecular weight
Mz mcviscosity average molecular weight
Examples 118 to 121
KM6l00u was modified with para-toluoyl peroxide (FTP) and BPO in accordance with Table
23 below. The KM6100u was stabilized with Irganox 1010 (0.33wt%) and Irgaphos 168
(0.17 wt%) which were added to the main feed throat of the extruder.
Examples 122 to 128
PXCA6152 was modified with mixed initiator systems in accordance with Table 24 below.
Table 24:
Example Conditions Init #l Init # 2 Mole Motor Drop Die MFI Melt Str.
wt% wt% ratio Current Time Temp (g/10 (cN)
Init#l/ln (amps) (sec) °C min.)
Control 0.8 6
5
CE-88 B3a 0 0 - 22 14 255 0.9 5.1
122 B3a 0.87 0 24 20 257 1.28 14.2
Initiator #1 = BPO, Initiator # 2 = DHBP
123 B3a 0.87 0.045 23.2 22 19 251 40 80
124 B3a 0.87 0.064 16.3 20 16 250 5.4
Examples 129 to 132
Cryoground PXCA6152 to the fonn in the form of a powder was modified with mixed initiator systems according to Table 25 below.
Examples 129 to 132
Table 15; Effect of Mixed Initiators on the Modification of PXCA6 152 Powder a (cryoground pellets)
Examples 134 to 137
Cryoground KM6100 in the form of a powder was modified on a Brabender single screw
extruder in accordance with the general description of the Brabender SSE above and Table
28 below. The initiator was added at the feed throat of the SSE along with the stabilizers
(0.33 wt% Irganox 1010 and 0.17 wt% Irgaphos 168).
Examples of Carbon Dioxide Foaming of Modified PP
The equipment used for foaming the polypropylene (from earlier examples) was a tandem
extrusion line made up of an Leitritz twin screw extruder (34 mm screw diameter, co-
rotating, with 11 barrel sections) connected via a melt pipe to a single screw extruder (43 mm
screw diameter). CO2 was introduced into barrel six of the twin screw extruder. The gassed
polymer was then cooled slowly in the single screw extruder.
Non high melt strength grades of polypropylene have foam temperature processing windows
of less than 1°C.
Foamed examples 13 and 17 both has a fine closed cell structure.
Examples of thermoforming
The modified polypropylene produced in Example 69 was extruded on a Welex single screw
extruder through a sheet die to produce a sheet 78cm wide and "1.25 mm thick. The sheet
was fed to a Gabler F702 continuous thermoformer to produce margarine tubs. Tubs
produced from the modified PP sample had a crush strength of 25 kg after 1 hour. No
appreciable sag was noticed of the PP sheet during the process.
The modified polypropylene of Example 5 was blow moulded on Bekum blow moulder fitted
with a general puipose polyolefin screw using a 750 ml screw top bottle mould, (radially non
symmetrical bottle with waist). The mould temperature was 0C.
The blow mouldabiuty of the modified injection moulding grade of PP was compared against
that of a commercial low melt flow index PP homopolymer (ICI GWM110 of MFI = 1.5).
It was found that the modified PP homopolymer (MFI = 9.1 and Melt Strength = 6.9 cN)
i could be easily blow moulded into 750 ml bottles. Conventional PP of similar MFI could not
be-successfully blow moulded. The modified PP gave similar performance to an extrusion
grade PP of low MFI.
The results are very promising where a higher MFI PP could be used to blow bottles. This
possibly opens up the opportunity to produce large blow moulded parts through use of a high
melt strength modified PP which has been tailored to have an MFI acceptable to blow
moulding (ie 1-2 MFI)
Those skilled in the art will appreciate that the invention described herein is susceptible to
variations and modifications other than those specifically described. It is to be understood
that the invention includes all such variations and modifications which fall within its spirit and
scope. The invention also includes all of the steps, features, compositions and compounds
referred to or indicated in this specification, individually or collectively, and any and ail
combinations of any two or more of said steps or features.
WE CLAIM
1. A process for increasing the melt strength and/or the extensional melt viscosity of a
polypropylene (co) polymer wherein, said process comprises melt mixing the polypropylene
(co)polymer in the presence of an initiator and oxlionally a mondene mononer vherein said initiator is selected from the group
defined by formula 1 :
Formula 1
wherein R is selecied from the group consisting of optionally substituted C1 to C18 acyl,
optionally substituted C1 to C18 alkyl, aroyl defined by formula 2,
and groups of formula 3,
Formula 3
wherein U, V, X, Y, Z, U', V', X', Y' and Z' are independently selected from the group
consisting hydrogen, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl,
carboxy, alkoxycarbonyl, aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula
4,
Formula 4
and wherein T is a ikylene,
and wherein the melt strength and/or the extensional melt viscosity of the polypropylene
(co)polyroer is incuased during the melt mixing step.
2. A process according to claim 1 wherein the initiator is selected from compounds of
formula 6.
Formula 6
where X, Y, Z, U, V, X', Y', Z', U', V' are independently selected from the group consisting
of hydrogen and C - C18 alkyl where at least one of X, Y, Z, U, V and X', Y', Z', U', V are
not hydrogen.
3. A process according to claim I wherein the initiator is selected from the group
consisting of Dibenzoyl peroxide, o,o'-Bis(methylbe;nzoyl) peroxide, p,p'-
Bis(methylbenzoyl) peroxide, M,M'-Bis(methylbenzoyl) peroxide, o,m'-
Bis(methylbenzoyl) peroxide, o,p'-Bis(methylber.zoyl) peroxide. m,p'-Bis(methylbenzoyl)
peroxide, Bis(ethylbenzoyl) peroxide (all isomers), Bis(propylbenzoyl) peroxide (all
isomers), Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all
isomers), Bis(hexylbenzoyl) peroxide (all isoomers), Bis(heptylbenzoyl) peroxide (all
isomers), Bis(octylbenzoyl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (all
isomers), Bis(methyoxybenzoyl) peroxide (all isomers), Bis(eihoxybenzoyl) peroxide (all
isomers), Bis(propoxybcnzoyl) peroxide (all isomers), Bis(butoxybenzoyl) peroxide (all
isomers), Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybenzoyl) peroxide (all
isomers), Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl) peroxide
(all isomers), Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide
(all isomers), Bis(iluorobcnzoyl) peroxide (all isomers), Bis(bro:nobenzoyl) peroxide (all
isomers), Bis(dimethylbenzoyl) peroxide (all isoners), Bis(trimethylbenzoyl) peroxide (all
isomers), Bis(tert-butylbenzoyl)peroxide (all isomers). Bis(di-
tert-butylbenzoyl)peroxide (all isomers), Bis(tertbutoxybenzoyl)peroxide (all isomers),
Bis(ditrimethylsily benzoyl) peroxide (all isomers), Bis(heptafluoropropylbenzoyl)
peroxide (all isonurs), Bis(2,6-dimethyl-4- trimethylsilyl benzoyl) peroxide and isomers,
2,2'(dioxydicarbonyl) bis - Benzoic acid dibutyl ester where the term "all isomers" refers to
any variation in the position of the ring substituent as well as the structure of the
substituent itself i.e.. for propyl; n-propyl and isopropyl.
4. A process according to claim 1 wherein the initiator is selected from the group
consisting of tert-butyl perbenzoate, tert-butyl (methyl)perbenzoate (all isomers), tert-
butyl (ethyl)perbenzoate (all isomers), tert-butyl (Octyl)perbenzoate (all isomers), tert-butyl
(nonyl)perbenzoate (all isomers), tert-amyl perbenzoate, tert-amyl (raethyl)perbenzoate (al)
isomers), tert-amyl (ethyl)perbenzoate (all isomers), tert-amyl (octyl)perbenzoate (all
isomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all
isomers), tert-amyl (octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate
(all isomers). 2-ethylhexyl perbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers), 2-
ethylhexyl (ethyil)p2rbenzoate (all isomers), 2-ethylhexyl (octyl)perbenzoate (all isomers),
2-ethylhexyl (nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (all
isomers), 2-elhylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl
(octyloxy)perberizcate (all isomers), and 2-ethylhexyl (nonyloxy)perbenzoate (all isomers).
5. A process according to claim 1 wherein the initiator is selected from the group
consisting of Bis (tertbutylmonoperoxy phthaloyl) diperoxy terephthalate. Bis
(tertamylmonoperoy phthaloyl) diperoxy terephthalate diacetyl phthaloyl diperoxide,
dibenzoyl phthaloyl diperoxide. bis(4 methyltenzoyl) phthaloyl diperoxide, diacetyl
terephthaloyl di peroxide, dibenzoyl terephthaJoyl diperoxide. Poly[
dioxycarbonyldioxy(l,l,4,4-tetramethyl-l,4-butanediyl)] peroxide.
6. A process according to claim 1 wherein the initiator has a 0.1 hour half life in the
range 100- 170°C.
7. A process according to claim 1 wherein the initiator is present in the range of from
0.004 to 0.25 moles of initiator per kg of the polypropylene homopolymer or copolymer.
8. A process jccording to claim 7 wherein the initiator is present in the range of from
0.006 to 0.10 mole 3 of initiator per kg of the polypropylene homopolymer or copolymer.
9. A process according to claim 8 wherein the initiator is present in the range of from
0.01 to 0.05 moles of initiator per kg of the polypropylene homopolymer or copolymer.
10. A process according to claim 1 wherein there is no added monoene monomer and the
initiator is selected from the group consisting of Dibenzoyl peroxide, o,o'-Bis(methylbenzoyl
peroxide, p,p'-Bis(methylbenzoyl) peroxide. o,o'-Bis(methylbenzoyl) peroxide, o,m'
Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl) peroxide, m?p'-Bis(methylbenzoyl
peroxide, Bis(ethylbcnzoyl) peroxide (all isomers), Bis(propylbenzcyl) peroxide (all isomers)
Bis(butylbenzoyl) peroxide (all isomers), Bis(pentylbenzoyl) peroxide (all isoroers)
Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide (all isomers)
Bis(octylbenzoyl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (all isomers)
Bis(methoxybenzoyl) peroxide (all isomers), Bis(ethoxybenzoyl) peroxide (all isomers)
Bis(propoxybenzoyl) peroxide (ail isomers). Bis(butoxybenzoyl) peroxide (all isomers)
Bis(pentoxybenzoyl) peroxide (all isomers), Bis(hexyloxybenzoyl) peroxide (all isomers)
Bis(heptyloxybenzoyl) peroxide (all isomers), Bis(octyloxybenzoyl) peroxide (all isomers)
Bis(nonyloxybenzoyl) peroxide (all isomers), Bis(chlorobenzoyl) peroxide (all isomers)
Bis(fluorobenzoyl) peroxide (all isomers), Bis(bromobenzoyl) peroxide (all isomers)
Bis(dimethylbenzcyl) peroxide (all isomers). B.is(trimethylbenzoyl) peroxide (all isomers)
Bis(tert-butylbenzc'yl)peroxide (all isomers). Bis(di-tert-butylbenzoyl)peroxide (all isomers)
Bis(tertbutoxybenzoyl)peroxide (all isomers), Bis(ditrimethylsilylbenzoyl) peroxide (al
isomers), Bis(heptafluoropropylbenzoyl) peroxide (all isomers). Bis(2.4-dimethyl-6
trimethylsilyl beizoyl) peroxide and isomers tert-amyl perbenzoate, tert-amy
(methyl)perbenzoate (all isoraers), tert-amvl (ethyl)perbenzoate (all isomers), tert-amy
(octyl)perbenzoate (all isomers). len-arnyl (nonyl)perbenzoate (all isomers), tert-amy
(methoxy)perbenzoate (all isomers), tert-amyl (octyloxy)perbenzoate (all isomers), tert-
amyl (nonyloxy)perbenzoate (all isomers). Bis (tertamylmonoperoxy phthaloyl) diperoxy
terephthalate, diacetyl phthaioyl diperoxide, dibenzoyl phthaloyl diperoxide, bis(4-
methylbenzoyl) phthaloyl diperoxide, diacetyl terephthaloyl di peroxide and dibenzoyl
terephthaloyl diperoxide.
11. A process according to claim 10 wherein the initiator is more preferably the
initiators are selected from the group consisting of dibenzoyl peroxide, 0,0'-
Bis(methylbenzoyl) peroxide, p,p'-Bis(methylbenzoyl) peroxide, M,M'-
Bis(methylbenzoyl) peroxide, o,m'-Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl)
peroxide, and m,p-Bis(methylbenzoyl) peroxide.
12. A process according to claim 1 wherein the initiator is used in combination with a
monoene monomer.
13. A process according to claim 12 wherein i:he amount of monoene monomer is up to
5 times the total moles of initiator.
14. A process according to claim 12 or claim 13 wherein the monoene monomer is
tyrene.
15. A process iccording to claim 1- wherein the initiator is selected from the group
consisting of Dibenzoyl peroxide, o,o'-Bis(methylbenzoyl) peroxide, p,p'-
Bis(methylbenzoyl) peroxide, M,M'-Bis(methylbenzoyl) peroxide, o,m'~
Bis(methylbenzoyl) peroxide, o,p'-Bis(methylbenzoyl) peroxide, m,p'-Bis(methylbenzoyl)
peroxide, Bis(ethylbenzoyl) peroxide (all isomers). Bis(propylbenzoyl) peroxide (all
isomers), Bis(butyl) lbenzoyl) peroxide (all isomers), Bi$(pentylbenzoyl) peroxide (all
isomers). Bis(hexylbenzoyl) peroxide (all isomers), Bis(heptylbenzoyl) peroxide (all
isomers), Bis(octylbenzovl) peroxide (all isomers), Bis(nonylbenzoyl) peroxide (all
isomers), Bis(methoxybenzoyl) peroxide (all isomers),
Bis(ethoxybenzoyl peroxide (all isomers), Bis(propoxybenzoyl) peroxide (all isomers),
Bis(butoxybenzoyl) peroxide (all isomers), Bis(pentoxybenzoyi) peroxide (all isomers),
Bis(hexyloxybernzcyl) peroxide (all isomers), Bis(heptyloxybenzoyl) peroxide (all
isomers), Bis(octylxybenzoyl) peroxide (all isomers), Bis(nonyloxybenoyl) peroxide (all
isomers), Bis(chlorobenzoyl) peroxide (all isomers), Bis(fluorobenzoyl) peroxide (all
isomers), Bis(brarrobenzoyl) peroxide (all isomers), Bis(dimethylbenzoyl) peroxide (all
isoraers), Bis(trimethylbenzoyl) peroxide (all isorners), Bis(tert-butylbenzoyl)peroxide (all
isomers), Bis(di-teit-butylbenzoyl)peroxide (all isomers), Bis(tert-butoxybenzoyl)peroxide
(all isomers), Bis(ditrimethylsilylbenzoyl) peroxide (all isomers).
Bis(heptafluoropropylbenzoyl) peroxide (all isomers), Bis(2,4-dimethyl-6- trimethylsilyl
benzoyl) peroxide itnd isomers, 2,2'(dioxydicarboiyl) bis - Benzoic acid dibutyl ester, tert-
butyl perbenzoat;, lert-butyl (methyl)perbenzoate (al! isomers), ten-butyl
(ethyl)perbenzoate (all isomers), tert-butyl (ociyl)perbenzoate (all isomers), tert-butyl
(nonyl)perbenzoate (all isomers), tert-amyl perberizoate, tert-amyl (methyl)perbenzoate (all
isomers), tert-any, (ethyl)perbenzoate (all isorners), tert-amyl (octyl)perbenzoate (all
isomers), tert-amyl (nonyl)perbenzoate (all isomers), tert-amyl (methoxy)perbenzoate (all
isomers), tert-aml (octyloxy)perbenzoate (all isomers), tert-amyl (nonyloxy)perbenzoate
(all isomers), 2-ethylhexyl perbenzoate, 2-ethylhexyl (methyl)perbenzoate (all isomers), 2-
ethylhexyl (ethyl)perbenzoate (all isomers), 2-ethylhexyl (octyl)perbenzoate (all isomers),
2-ethylhexyl (nonyl)perbenzoate (all isomers), 2-ethylhexyl (methoxy)perbenzoate (all
isomers), 2-ethylhexyl (ethoxy)perbenzoate (all isomers), 2-ethylhexyl
(octyloxy)perbenzoate (all isomers), 2-ethylhexyl (nonyloxy)perbenzoate (all isomers), Bis
(tertbutylmonoperoxy phathloyl) diperoxy te-rephihalare. Bis (tertamylmonopenoxy
phthaloyl) diperoxy terephthalate diacetyl phthaloyl diperoxide, dibenzoyl phthaloyl
diperoxide, bis(4 rrethylbenzoyl) phthaloyl diperoxide, diacetyl terephthaioyl di peroxide,
dibenzoyl terephthaloyl diperoxide and Poly[ dioxycarbonyldioxy(l,1.4,4-tetramethyl-l,4-
butanediyl)] peroxide.
16. A modified polypropylene produced according to the process of any one of claims
1 to 15.
17, A process wherein the modified polypropylene of claim 16 is melt mixed with ar
unmodified polypropylene to produce a modified polypropylene.
18. A process for modifying an a-olefin polymer wherein said process comprises melt
mixing the a-olefin polymer in the presence of an initiator and optionally a monoene
monomer wherein s aid initiator is selected from the group defined by formula 1.

Formula 1
wherein R is selected from the group consisting of optionally substituted C1 to C18 acyl,
optionally substituted C1 to C18 alkyl aroyl defined by formula 2,
and groups of foraiula 3,

Formula 3
wherein U, V, X, Y, Z, U', V', X', Y' and Z' ars independently selected from the group
consisting hydrogen, halogen, C1-C18 alkyl, C1-C18 alkoxy, aryloxy, acyl, acyloxy, aryl,
carboxy, alkoxy carbony1, aryloxycarbonyl, trialkyl silyl, hydroxy, or a moiety of formula
4,

Formula 4
wherein T is alkylene;
and wherein the amount of monomer is 0 to 3 times the total moles of initiator.
A process for increasing the melt strength and/or the extensional melt viscosity of,a
polypropylene (co)polymer wherein said process comprises melt mixing the polypropylene
(co)polymer in the presence of an initiator and ordinary a mondene mononer wvherein said initiator is selected from the group
defined by formula 1:
Formula 1
wherein R is selected from the group consisting of optionally substituted C1 ro C18 aryl,
optionally substituted C1 to C18 alkyl, aroyl defined by formula 2,

Documents:

in-pct-2000-142-kol-granted-abstract.pdf

in-pct-2000-142-kol-granted-claims.pdf

in-pct-2000-142-kol-granted-correspondence.pdf

in-pct-2000-142-kol-granted-description (complete).pdf

in-pct-2000-142-kol-granted-examination report.pdf

in-pct-2000-142-kol-granted-form 1.pdf

in-pct-2000-142-kol-granted-form 18.pdf

in-pct-2000-142-kol-granted-form 2.pdf

in-pct-2000-142-kol-granted-form 3.pdf

in-pct-2000-142-kol-granted-form 5.pdf

in-pct-2000-142-kol-granted-pa.pdf

in-pct-2000-142-kol-granted-reply to examination report.pdf

in-pct-2000-142-kol-granted-specification.pdf

in-pct-2000-142-kol-granted-translated copy of priority document.pdf

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Patent Number

224800

Indian Patent Application Number

IN/PCT/2000/142/KOL

PG Journal Number

43/2008

Publication Date

24-Oct-2008

Grant Date

22-Oct-2008

Date of Filing

18-Jul-2000

Name of Patentee

POLYMERS AUSTRALIA PTY LIMITED

Applicant Address

32 BUSSINESS PARK DRIVE, NOTTING HILL, VISTORIA

Inventors:

#	Inventor's Name	Inventor's Address
1	PEETERS GARY	89 DUFF STREET, CRANBOURNE, VICTORIA 3977
2	O'SHEA MICHAEL SHANE	4 WORTHINGTON COURT, MULGRAVE, VICTORIA 3170
3	MOAD GRAEME	9 CLARKMONT ROAD, SASSAFRAS, VICTORIA 3787

PCT International Classification Number

C08K 5/14

PCT International Application Number

PCT/AU99/00036

PCT International Filing date

1999-01-19

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	1392	1998-01-19	Australia
2	1393	1998-01-19	Australia