Title of Invention	FINELY DIVIDED RUBBER POWDER.
Abstract	TITLE: FINELY DIVIDED RUBBER POWDER THIS INVENTION RELATES TO FINELY DIVIDED, PULVERULENT RUBBERS CONTAINING FILLER WHICH CONTAIN FURTHER PROCESSING AND VULCANISATION AUXILIARIES NECESSARY FOR THE PRODUCTION OF VULCANISABLE RUBBER MIXTURES, WHICH RUBBERS ARE POURABLE EVEN AFTER EXPOSURE TO MECHANICAL STRESS,AND TO A PROCESS FOR THE PRODUCTION THEREOF, IN WHICH THE RUBBER POWDER IS OBTAINED WITHIN TWO PRECIPITATION STEPS, AND TO THE USE OF THESE POWDERS FOR THE PRODUCTION OF VULCANISABLE RUBBER MIXTURES. THE FILLERS USED, WHICH COMPRISE NOT ONLY PRECIPITATED SILICAS BUT ALSO CARBON BLACKS KNOWN IN THE RUBBER SECTOR, ARE OPTIONALLY SURFACE MODIFIED WITH ORGANOSILICON COMPOUNDS, ESPECIALLY WITH REGARD TO THE SILICAS.

Title of Invention

FINELY DIVIDED RUBBER POWDER.

Abstract

TITLE: FINELY DIVIDED RUBBER POWDER THIS INVENTION RELATES TO FINELY DIVIDED, PULVERULENT RUBBERS CONTAINING FILLER WHICH CONTAIN FURTHER PROCESSING AND VULCANISATION AUXILIARIES NECESSARY FOR THE PRODUCTION OF VULCANISABLE RUBBER MIXTURES, WHICH RUBBERS ARE POURABLE EVEN AFTER EXPOSURE TO MECHANICAL STRESS,AND TO A PROCESS FOR THE PRODUCTION THEREOF, IN WHICH THE RUBBER POWDER IS OBTAINED WITHIN TWO PRECIPITATION STEPS, AND TO THE USE OF THESE POWDERS FOR THE PRODUCTION OF VULCANISABLE RUBBER MIXTURES. THE FILLERS USED, WHICH COMPRISE NOT ONLY PRECIPITATED SILICAS BUT ALSO CARBON BLACKS KNOWN IN THE RUBBER SECTOR, ARE OPTIONALLY SURFACE MODIFIED WITH ORGANOSILICON COMPOUNDS, ESPECIALLY WITH REGARD TO THE SILICAS.

Full Text	Rubber powders (compounds) and process for the production The present invention relates to rubber powders which also contain, in addition to the rubber components, further constituents important for the production of the vulcanisable rubber mixture. If, in addition to the constituents of the basic batch, the rubber powder also contains crosslinking chemicals (accelerator, sulfur), it is known as a full compound. If the rubber powder in particular consists of the constituents of the basic batch, it is known as a semi- compound. Intermediate forms between these stages are also suitable. Numerous documents have been published relating to the aim and purpose of using rubber powders (powdered rubbers) and relating to processes for the production thereof. The interest in pulverulent rubbers is explained by the processing methods used in the rubber industry, where rubber mixtures are produced with a considerable input of time, energy and labour. The main reason for this is that the raw material, crude rubber, is in the form of bales. The bale is comminuted and intimately mixed over several processing stages with fillers, mineral oil plasticisers and vulcanisation auxiliaries in roll mills or internal mixers. The mixture is generally stored between the stages. Extruder/pelletisers or extruder/roller dies are generally arranged downstream from the internal mixers or roll mills. The only way forward from this highly complex method of rubber processing is to develop an entirely new processing technology. The use of pourable rubber powders has thus been discussed for some time as this approach makes it possible to process rubbers mixtures simply and rapidly in the same way as powdered thermoplastics. DE-PS 2822 148 discloses a process for the production of a pulverulent rubber containing filler. According to the said patent, an aqueous filler emulsion is added to a rubber latex, rubber solution or the aqueous emulsion of a rubber and the desired rubber powder is precipitated. In order to avoid the grain size dependent filler contents obtained from this process, variants have been filed under numbers DE-PS 3723 213 and DE-PS 3723 214 and are part of the prior art. According to DE-PS 3723 213, in a two-stage process, a quantity of >50% of the filler is initially incorporated into the particles of rubber powder. In the second stage, the remainder of the filler is applied onto the so-called basic rubber grain. This may be considered a variant of dusting, as no bond is created between the filler and rubber. However, as E.T. Italiaander has pointed out (presentation 151, technical conference of the Rubber Division of the ACS, Anaheim, California, 6-9 May 1997 (GAK 6/1997 (50) 456-464)), despite the bright future predicted in the Delphi Report (Delphi Report, "Kiinftige Herstellverfahren in der Gummiindustrie", Rubber Journal, volume 154, no. 11, 20-34 (1972)) for pulverulent and pelletised rubbers and numerous attempts made by well-known polymer manufacturers from the mid 1970"s until the early 1980"s to produce pulverulent NBR, SBR/carbon black masterbatches and pelletised NR, the rubber bale remains the standard form in which polymers are supplied. One disadvantage of known processes is firstly that a grinding operation is necessary in order to achieve a grain diameter of the filler particles of 10 µm, which is considered essential to the quality of the final product. However, this requires not only elevated energy input but also results in damage to the filler structure which, together with the active surface area, is a significant parameter for its efficacy in rubber applications. Secondly, the handling properties of prior art products suffer in that the particles stick together during storage. The object of the invention is accordingly to provide a pulverulent rubber containing filler which is easily processed, together with a process for the production thereof. The present invention provides a finely divided rubber powder (powdered rubber), which a) contains a rubber matrix and additionally b) one or more white and/or black fillers known from the rubber industry optionally modified with one or more of the organosilicon compounds of the formulae (I), (II) or (III), c) one of more of the additions known for the production of rubber vulcanisates. All or part of the filler(s) may be used in premodified form or may have been modified during the present process. Depending upon the extent of processing (nature of the added mixture components), the product may be designated a semi-compound or full compound. The rubber powder in particular contains the organosilicon compounds in a form which has reacted with the filler if a silicate filler, in particular a precipitated silica, is used. The grain size range of the rubber powders according to the invention is generally between 0.05 and 10 mm, in particular between 0.5 and 2 mm. The powders according to the invention exhibit a narrower size distribution which is shifted towards smaller particle sizes than is known from the prior art (Kautschuk + Gummi + Kunststoffe ,7, 28 (1975) 397-402). This fact facilitates processing of the powders. Moreover, due to the production process, the filler content of the individual particles is not determined by grain size. The pulverulent rubbers contain from 20 to 250 phr, in particular from 50 to 100 phr (phr: parts per hundred parts of rubber) , of filler, part or all of which has optionally been surface modified before the process according to the invention using the organosilicon compounds of the formulae (I), (II) or (III) known in the rubber sector. The following, individually or as mixtures, have proved to be suitable types of rubber: natural rubber, emulsion SBR having a styrene fraction of 10 to 50%, butyl/acrylonitrile rubber. Butyl rubbers, terpolymers prepared from ethylene, propylene (EPM) and unconjugated dienes (EPDM), butadiene rubbers, SBR, produced using the solution polymerisation process, having styrene contents of 10 to 25%, as well as 1,2-vinyl constituent contents of 20 to 55% and isoprene rubbers, in particular 3,4-polyisoprene. In addition to the stated rubbers, the following elastomers may be considered, individually or as mixtures: carboxyl rubbers, epoxy rubbers, trans-polypentenamer, halogenated butyl rubbers, rubbers prepared from 2- chlorobutadiene, ethylene/vinyl acetate copolymers, epichlorohydrins, optionally also chemically modified natural rubber, such as for example epoxidised grades. Fillers which are generally used are the carbon blacks known from rubber processing and white fillers of a synthetic nature, such as for example precipitated silicas or natural fillers, such as for example siliceous chalk, clays etc. are additionally used. Carbon blacks, as are generally used in rubber processing, are particularly suitable. Such carbon blacks include furnace blacks, gas blacks and lamp backs having an iodine absorption value of 5 to 1000 mVg, a CTAB value of 15 to 600 m2/g, a DBP adsorption of 30 to 400 ml/100 g and a 24 M4 DBP value of 50 to 370 ml/100 g in a quantity of 5 to 250 parts, in particular of 20 to 150 parts, per 100 parts of rubber, in particular of 40 to 100 parts. Silicate fillers of synthetic or natural origin known from the rubber sector, in particular precipitated silicas, are also suitable. These generally have an N2 surface area, determined using the known BET method, of 35 to 700 m2/g, a CTAB surface area of 30 to 500 m2/g, a DBP value of 150 to 400 ml/100 g. The product according to the invention contains these silicas in a quantity of 5 to 250 parts, in particular of 20 to 100 parts, relative to 100 parts of rubber. If the fillers comprise white natural fillers, such as clays or siliceous chalks having an N2 surface area of 2 to 35 m2/g, these are used in a quantity of 5 to 350 parts, relative to 100 parts of rubber. Powders containing one or more of the above-stated fillers in the mixture are also suitable. Apart from the unmodified fillers of the stated type, modified fillers are optionally additionally used in the production of the rubber powders claimed in the present document. The proportion of unmodified fillers depends upon the specific mixture to be produced. In any event, the total quantity of filler amounts to 20 to 250 phr. 100%, in particular of 30 to 100%, preferably of 60 to 100% of this quantity consists of the unmodified fillers: silica and/or carbon black. Surface modification is generally performed using organosilicon compounds of the general formulae [R1n(RO)3-n Si-(Alk)m -(Ar)p] q [B] (I) R1n, (RO)3-n Si-(Alk) (II), or R1n (R0)3-n Si- (Alkenyl) (III) in which B: means -SCN, -SH, -Cl, -NH2 (if q=1) or -Sx- (if q = 2) R and R1: mean an alkyl group having 1 to 4 carbon atoms, branched or unbranched, the phenyl residue, wherein all residues R and R1 may each have the same or a different meaning, preferably an alkyl group, R: means a C1-C4, alkyl, C1-C4 alkoxy group, branched or unbranched, n: means 0; 1 or 2, Alk: means a divalent linear or branched carbon residue having 1 to 6 carbon atoms, m: means 0 or 1 Ar: means an arylene residue having 6 to 12 C atoms p: means 0 or 1, providing that p and m do not simultaneously mean 0, x: means a number from 2 to 8, Alkyl: means a monovalent linear or branched unsaturated hydrocarbon residue having 1 to 2 0 carbon atoms, preferably 2 to 8 carbon atoms, Alkenyl: means a monovalent linear or branched, unsaturated hydrocarbon residue having 2 to 2 0 carbon atoms, preferably 2 to 8 carbon atoms. Modified fillers which are used according to the invention are described, for example, in EP-B 0442 143, EP-B 0177 674 and, in particular in pellet form, in EP-A 0795 579 (white fillers) or in EP-B 0519 188 (carbon black). Bis(alkoxysilylalkyl)oligosulfanes of the bis(trialkoxy- silylpropyl)tetrasulfane and -disulfane types have in particular proved suitable for premodification or for addition to the filler suspension. The modified fillers known from the stated applications or patents or the organosilicon compounds stated therein are explicitly included in the present application as a constituent of the claimed compositions. Apart from the above-stated fillers, the rubber powders according to the invention in particular contain known processing or vulcanisation auxiliaries such as zinc oxide, zinc stearate, stearic acid, polyalcohols, polyamines, resins, waxes, plasticising oils, anti-ageing agents to counter the action of heat, light or oxygen and ozone, reinforcing resins, flame retardants, such as for example A1(OH)3 and Mg(OH)2, pigments, various crosslinking chemicals and accelerators and optionally sulfur in concentrations conventional in rubber processing, preferably sulfur modified by combination with surface active substances, as is commercially available. Grain size is determined from the filler suspension. In a particularly preferred embodiment of the process according to the invention, all the solids used are present in a grain size of rubber particles are precipitated from the suspension. Agglomeration may optionally occur as a result of the production process, but this has no negative influence on processing behaviour. The present invention also provides a process for the production of finely divided rubber powders containing filler by precipitation from mixtures containing water, which mixtures contain finely divided filler(s) (carbon black and/or silicate filler) optionally modified with organosilicon compounds, water-soluble salts of a metal of groups IIa, IIb, IIIa and VIII of the periodic system of elements and a rubber latex or the aqueous emulsion of a rubber solution, optionally in the presence of an organic solvent, which process is characterised in that a) =50 wt.%, but less than 100 wt.%, of the intended quantity of finely divided filler, preferably in the form of an aqueous suspension containing 2 to 15 wt.% of water, optionally with a of the (sic) quantity intended for modification of the filler surface of one or more organosilicon compounds according to the formulae (I), (II) or (III) in a quantity of 0.1 to 20 wt.%, relative to the filler, in particular if the filler is a silicate filler, preferably precipitated silica, and/or =50 wt.%, but less than 100 wt.%, of a filler at least partially surface modified with one or more of the organosilicon compounds (formulae (I), (II) or III) (sic), in particular in the presence of an emulsifier, are mixed with a rubber latex or an aqueous emulsion of a rubber solution and the pH value of the mixture is reduced to a value in the range from 7.5 to 6.5, in particular by addition of a Lewis acid (first stage), b) the remaining proportion (splitting proportion) of the above-stated finely divided fillers, optionally together with the residual quantity intended for modification of the filler surface of organosilicon compounds of the formulae (I), (II) or (III), is added in the form of a suspension, the pH value is reduced to a value in the range from in particular by addition of a Lewis acid, such that the rubber present in the mixture completely precipitates together with the filler (second stage), c) the precipitated solids are separated using measures known per se, d) are optionally washed and e) dried. The organosilicon compounds are in particular used when silicate fillers, preferably silicas, are used. The precipitation process is generally performed at room temperature, in particular at 20 to 80 °C. The quantities of filler and rubber are adjusted depending upon the application in accordance with the desired filler content of the resultant rubber. At a total content of =80 parts of filler phr, 1 to 10 wt.% of the filler is/are added as the remaining proportion in the second stage. The resultant particles do not stick together, even under pressure, such as when several sacks are stacked. This "inertisation" of the surface should not be confused with the known technique of dusting tacky powders with fillers. These only superficially adhering fillers are rapidly detached when exposed to mechanical stress, for example in conveying plant or on transfer into silos. The sticking and agglomeration of the finely divided powders, which it is the intention to avoid, then occurs despite the dusting. Unlike the tacky particles superficially coated with fillers as flow auxiliaries as are known from the prior art, according to the invention, filler particles are incorporated into the surface during the precipitation process for the production of the pulverulent rubber. Depending upon the filler loading with one or more of the above-stated fillers, the advisable distribution between the interior of the particles and an outer zone associated therewith is established. In a product having an elevated filler loading (>80 parts of filler per hundred parts of rubber), only 1 to 10 parts of this quantity of filler are incorporated in the outer grain zone. However, if the pulverulent rubber contains a total of parts of filler per hundred parts of rubber, 10 to 20 parts thereof are preferably incorporated in the outer grain zone (peripheral zone), i.e. do not merely adhere by less effective adhesive forces. The distributions of the filler within the particles and in the so-called peripheral zone generally vary between these contents. The greater is the total filler content, the less is the need to suppress the tackiness of the powder by an increased concentration of filler in the peripheral zone. According to the invention, these proportions of the filler are not applied externally onto the individual rubber particles (c.f. DE-PS 37 23213), but are instead incorporated into the rubber surface. This distribution of the filler and the manner in which the fillers are bonded to the rubber composition bring about the elevated flowability of the powders according to the invention and prevent sticking during storage of the powder, without these properties being lost on exposure to mechanical stresses during conveying, transfer into silos etc . The above-stated carbon blacks are used as fillers in finely divided (fluffy) form, the carbon blacks generally having an average grain diameter of 1 to 9 µm, preferably of 1 to 8 µm, before they are suspended. This facilitates dispersion, such that aqueous suspensions containing filler particles of an average particle diameter of distinctly less than 10 µm are obtained without elevated energy input. Precipitated silica may advantageously be used in the form of a filter cake which has been washed until salt-free. Metal salts which may be considered are those originating from elements of groups IIa, IIb, IIIa and VIII of the periodic system of elements. This division into groups corresponds to the former IUPAC recommendation (Periodisches System der Elemente, Verlag Chemie, Weinheim, 1985). Typical representatives are magnesium chloride, zinc sulfate, aluminium chloride, aluminium sulfate, iron chloride, iron sulfate, cobalt nitrate and nickel sulfate, wherein the salts of aluminium are preferred. Aluminium sulfate is particularly preferred. The salts are used in a quantity of 0.1 to 6.5 parts by weight, preferably in the form of an aqueous solution, per 100 parts by weight of rubber. Acids suitable for establishing the defined pH values are primarily mineral acids, such as for example sulfuric acid, phosphoric acid and hydrochloric acid, wherein sulfuric acid is particularly preferred. However, carboxylic acids, such as for example formic and acetic acid, may also be used. The quantity of acid is determined by the nature and quantity of the water-soluble metal salt, the filler, the rubber and the optionally present alkali metal silicate. This quantity may readily be determined by initial investigatory testing. According to a preferred embodiment of the process according to the invention, up to 5 parts by weight per 100 parts by weight of rubber of silica (SiO2) are additionally used in the form of an alkali metal silicate solution, preferably as water glass having an Na2O:SiO2 molar ratio of 2:1 to 1:4. The alkali metal silicate solution may here be added both to the rubber component and to the filler suspension. It is preferably added to the rubber component, especially when the process is performed continuously. The process according to the invention is generally performed as follows: first of all, a filler suspension is produced by dispersing a proportion, preferably >50%, of the filler present in the final product, which filler is optionally in part surface modified with compounds according to the formulae (I), (II) or (III), in water together with the metal salt and optionally the alkali metal silicate solution. The overall quantity of water is determined by the nature of the filler and the degree of digestion. In general, the water- insoluble constituents of the filler amount to approx. 6 wt.%. This value is not a binding restriction and both lower and higher quantities may be encountered. The maximum content is limited by the pumpability of the suspension. The filler suspension produced in this manner is then intimately mixed with the rubber latex optionally containing alkali metal silicate solution or the aqueous emulsion of a rubber solution optionally containing alkali metal silicate solution. Known stirrers, such as for example propeller stirrers, are suitable for this purpose. After mixing, a pH value in the range from 7.5 to 6.5 is established in the first stage using an acid while stirring is continued. This results in basic rubber grains having a homogeneous filler content. The size of these basic grains is controlled by the selected quantity of metal salt in the range from 0.1 to 6.5 phr. Control is effected by the largest grain size being obtained with the lowest quantity of metal salt. The solids content of the latex used generally amounts to 20 to 25 wt.%. The solids content of the rubber solutions is generally 3 to 35 wt.%, that of the rubber emulsions generally from 5 to 30 wt.%. The process according to the invention may be performed both discontinuously and continuously. The precipitated rubber powder is advantageously separated by means of a centrifuge and then dried to a residual water content of generally drier. During the production process according to the invention, in addition to the preferably used known emulsifiers, such as for example fatty alcohol polyethylene glycol ethers, in a preferred embodiment further processing and optionally vulcanisation auxiliaries are generally added to the suspension in a quantity as is conventional for vulcanisable rubber mixtures or also in a smaller quantity. Such auxiliaries comprise known a) activators, such as for example stearic acid, b) antioxidants c) processing auxiliaries such as resins and/or waxes, which are generally added in quantities of 0.5 to 10 wt.%, relative to the rubber content, directly to the filler suspension or with the latex emulsion/solution. Vulcanisation accelerators are further important additions. These are in particular selected from among the classes of sulfenamides, mercapto and sulfide accelerators, as well as thiurams, thiocarbamates and amines, and are generally added in a quantity of 0.1 to 8 wt.%, relative to the rubber content, directly to the filler suspension or with the latex emulsion/solution in finely divided form or in a known oil compatible with the rubber. In a preferred embodiment, the rubber powder containing the above-stated constituents is mixed with the accelerator substances or these are sprayed, for example dissolved in an oil, onto the rubber powder. The sulfur necessary for vulcanisation, in particular in a finely divided (5 to 45 µm) modification combined with surface-active substances, is optionally mixed into the suspension or rubber powder in a quantity of 0.2 to 8 wt.%, relative to the rubber content. Nonionic, cationic or anionic surfactants are optionally also added as surface-active substances, especially when organosilicon compounds are added to the filler suspension. The use of finely divided solid compounds is particularly suitable. The grain size range of the above-stated substances is generally below 50 µm, in particular 10 µm. This facilitates the best possible distribution in the rubber powders according to the invention which are obtained using the process described in the present document. Incorporating generally known zinc salts, in particular zinc oxide, in a quantity of 0.5 to 8 wt.%, relative to the rubber content, is also of particular significance to subsequent use. A zinc oxide having a specific surface area of between 2 0 and 50 m2/g is preferably used. This property is associated with the above-stated grain size range of particular of However, if all or some of the available additions have a grain size range greater than this, it is possible according to the prior art to pass the aqueous suspensions obtained before addition of the rubber content through known, suitable grinding units. Suspensions are then obtained having solids contents of the desired particle size distribution. In one particular embodiment, the suspension from which the rubber powder according to the invention is precipitated additionally contains a plasticising oil known as a processing auxiliary in the rubber industry. The purpose of this oil is, inter alia, to improve the processing characteristics of the plasticised crude mixture (injection behaviour, extrusion behaviour) and it is added either with the rubber latex/emulsion/solution or separately to the suspension. The rubber powders according to the invention are used for the production of vulcanisable rubber mixtures. The constituents necessary for producing the mixture are all preferably present in the rubber powder. They may, however, also additionally be mixed with other conventional rubbers, vulcanisation auxiliaries and fillers, if this is necessary for the properties of the desired vulcanisate. It is possible according to the invention directly to produce finely divided rubber powders containing optionally modified fillers and further constituents necessary for vulcanisation, which powders are free-flowing and also remain free-flowing after exposure to mechanical stresses (for example conveying, packaging). By virtue of the finely divided nature thereof, no grinding or other comminution measures are required to obtain finely divided products. The resultant finely divided rubber powders (semi-compounds and full compounds) are readily processable and give rise to vulcanisates having improved properties. Production Examples Example I Production of a semi-compound in powder form based on E- SBR, N234 and additions A stable dispersion is produced by stirring together 5.6 kg of N234, 1 kg of active ZnO, 2.2 kg of oil, 96 g of Marlipal 1618/25, 0.2 kg each of stearic acid, 6PPD and TMQ, 0.6 kg of Rhenosin C 90 in 134.4 L of water. The dispersion is mixed together with 95.69 kg of a 20.9% E-SBR latex emulsion with vigorous stirring. The pH value of the complete mixture is reduced to 6.5 by addition of an approx. 10% Al2(SO4)3 solution, so initiating precipitation. At this pH value, another stable dispersion prepared from 4 kg of N234 and 96.0 L of completely deionised water is added and the pH value is then reduced to 6.0 by addition of further Al2(SO4)3. After the precipitation process, the great majority of the water is separated mechanically and a drying stage then reduces the residual moisture content to E-SBR and 48 parts of N234 and all added substances.(H-EPB I) Example II Production of a full compound in powder form based on E- SBR, N234 and additions A stable dispersion is produced by initially stirring together 5.6 kg of N234, 1 kg of active ZnO, 96 g of Marlipal 1618/25, 0.32 kg of sulfur and 0.04 kg of MBTS in 126.6 L of completely deionised water. An oil solution is also produced from 2.2 kg of oil with 0.2 kg each of stearic acid, 6PPD and TMQ, 0.6 kg of Rhenosin C90, 0.32 kg of TBBS and heated to 75 °C. The oil solution is mixed together with 95.69 kg of a 20.9% E-SBR latex emulsion with vigorous stirring. The above-stated stable dispersion is then added to the latex/oil mixture. The pH value of the mixture is then reduced to 6.5 by addition of an approx. 10% Al2(SO4)3 solution (beginning of precipitation). At this pH value, precipitation is interrupted and another stable dispersion prepared from 4 kg of N234 and 96.0 L of completely deionised water is added to the reaction mixture. After this process step, the pH value is further reduced to 5.5 by addition of further quantities of Al2(SO4)3. After the precipitation process, the great majority of the water is separated mechanically and a drying stage then reduces the residual moisture content to E-SBR and 48 parts of N234 and all added substances. (F-EPB II) Example III Production of a semi-compound in powder form based on E- SBR, silica and additions A stable dispersion is produced by stirring together 12 kg of Ultrasil 7000, 0.98 kg of Si 69, 0.6 kg of active ZnO, 120 g of Marlipal 1618/25 in 108 L of completely deionised water. An oil solution is also produced from 5 kg of oil, 0.2 kg of stearic acid, 0.3 kg of 6PPD, 0.2 kg of Protector G 35 and heated to 75 °C. The oil solution is mixed together with 95.69 kg of a 20.9% E-SBR latex emulsion with vigorous stirring. The above-stated stable dispersion is then added to the latex/oil mixture. The pH value is reduced to 7 by addition of an approx. 10% Al2(SO4)3 solution. Once the pH value has been reduced to 7, another stable dispersion prepared from 3 kg of Ultrasil 7000, 240 g of Si 69, 40 g of Marlipal and 27 L of completely deionised water is added. Once the dispersion has been added, the pH value is further reduced to 5.5 by means of Al2(SO4)3. After the precipitation process, the great majority of the water is separated mechanically and a drying stage then reduces the residual moisture content to E-SBR and 75 parts of Ultrasil 7000 and all added substances. (H-EPB III) Example IV Production of a full compound in powder form based on E- SBR, silica and additions A stable dispersion is produced by stirring together 12 kg of Ultrasil 7000, 0.98 kg of Si 69, 0.6 kg of active ZnO, 120 g of Marlipal 1618/25, 0.3 kg of sulfur in 108 L of completely deionised water. An oil solution is also produced from 5 kg of oil, 0.2 kg of stearic acid, 0.3 kg of 6PPD, 0.2 kg of Protector G 35, 0.3 kg of CBS and 0.4 kg of DPG and heated to 75 °C. The oil solution is mixed together with 95.69 kg of a 20.9% E-SBR latex emulsion with vigorous stirring. The above-stated stable dispersion is then added to the latex/oil mixture. The pH value is reduced to 7 by addition of an approx. 10% Al2(SO4)3 solution. Once the pH value has been reduced to 7, another stable dispersion prepared from 3 kg of Ultrasil 7000, 240 g of Si 69, 40 g of Marlipal and 27 L of completely deionised water is added. Once the dispersion has been added, the pH value is further reduced to 5.5 by means of Al2(SO4)3. After the precipitation process, the great majority of the water is separated mechanically and a drying stage then reduces the residual moisture content to E-SBR and 75 parts of Ultrasil 7000 and all added substances. (F-EBP IV) Example V Production of a full compound in powder form based on NR/E- SBR, N234 and additions A stable dispersion is produced by initially stirring together 6.0 kg of N234, 0.6 kg of active ZnO, 100 g of Marlipal 1618/25, 0.4 kg of sulfur and 0.06 kg of MBTS in 126.6 L of completely deionised water. An oil solution is also produced from 2.4 kg of oil with 0.4 kg each of stearic acid and 6PPD, 0.2 kg of TMQ, 0.2 kg of Protector G 35, 0.24 kg of TBBS and heated to 75 °C. The oil solution is mixed together with 47.85 kg each of a 20.9% NR and a 20.9% E-SBR latex emulsion with vigorous stirring. The above-stated stable dispersion is then added to the latex/oil mixture. The pH value of the mixture is then reduced to 7.0 by addition of an approx. 10% Al2(SO4)3 solution (beginning of precipitation). At this pH value, precipitation is interrupted and another stable dispersion prepared from 4 kg of N234 and 96.0 L of completely deionised water is added to the reaction mixture. After this process step, the pH value is further reduced to 6.0 by addition of further quantities of Al2(SO4)3. After the precipitation process, the great majority of the water is separated mechanically and a drying stage then reduces the residual moisture content to product contains 100 parts of E-SBR and 50 parts of N234 and all added substances. (F-EPB V) Products according to the invention in rubber applications Europrene 1552 Styrene/butadiene rubber having a styrene content of 19% (Enichem) Europrene N 5564 Bale masterbatch consisting of Europrene 1552/N234/oil in a 100:52:10 ratio (Enichem) RSS1 Natural rubber (ribbed smoked sheet) H-EPB I Semi-compound according to the invention (powdered rubber) consisting of 100 parts of SBR 1552, 48 parts of N234, 11 parts of oil, 5 parts of ZnO, 1 part of stearic acid, 1 part of 6PPD, 1 part of TMQ, 3 parts of resin F-EPB II Full compound according to the invention, composition as H-EPB I and additionally 1.6 parts of TBBS, 0.2 parts of MBTS, 1.6 parts of sulfur H-EPB III Semi-compound according to the invention (powdered rubber) consisting of 100 parts of E-SBR, 75 parts of Ultrasil 7000, 6.1 parts of Si 69, 3 parts of ZnO, 25 parts of oil, 1 part of stearic acid, 1.5 parts of 6PPD, 1 part of wax F-EPB IV Full compound according to the invention, composition as H-EPB III and additionally 1.5 parts of CBS, 2 parts of DPG, 1.5 parts of sulfur F-EPB V Full compound according to the invention Powdered rubber consisting of 50 parts of NR, 50 parts of SBR, 50 parts of N234, 12 parts of oil, 3 parts of zinc oxide, 2 parts of stearic acid, 2 parts of 6PPD, 1 part of TMQ, 1 part of wax, 1.2 parts of TBBS, 0.3 parts of MBTS, 2 parts of sulfur 6PPD N-(1,3-dimethylbutyl)-N-phenyl-p- phenylenediamine Ultrasil 7000 Gr Enhanced dispersion tyre silica (N2 surface area approx. 180m2/g) (Degussa AG) TMQ 2,2,4-Trimethyl-l,2-dihydroquinoline Si69 Bis(triethoxysilylpropyl)tetrasulfane TBBS N-tert-butyl-2-benzthiazylsulfenamide MBTS Dibenzothiazyl disulfide Enerthene 1849-1 Aromatic plasticiser (BP) DPG Diphenylguanidine CBS Benzothiazyl-2-cyclohexylsulfenamide E-SBR 1500 Emulsion styrene/butadiene latex having a styrene content of 23.4% Active ZnO Zinc oxide: having a surface area of 4 5 mVg Marlipal Emulsifier: fatty alcohol polyethylene 1618/25 glycol ether (Hüls AG) Rhenosin C 90 Reinforcing resin Protector G 35 Ozone protection wax N234 Carbon black, N2 surface area 125 m2/g Rubber test methods Tensile bar test DIN 53 504 Shore hardness DIN 53 505 100% modulus DIN 53 504 300% modulus DIN 53 504 Elongation at break DIN 53 504 Fracture energy DIN 53 504 Ball rebound ASTM D5308 Dmax-Dmin DIN 53 52 9 Example A Comparison of technical rubber properties of a semi-compound (H-EPB I) with a conventionally produced standard mixture a) Formulation * The constituents of the basic batch are present in the powdered rubber c) Vulcanisate data Vulcanisation temperature: 165 °C Vulcanisation time: 15 min The results demonstrate that it is possible, without loss of subsequent technical rubber performance, to add further mixture constituents, in addition to the polymer and filler, during production of the powdered rubber. In this manner, it is possible inter alia to dispense with the energy-intensive 1st mixing stage. Example B Comparison of the technical rubber properties of a full compound (F-EPB II) with a conventionally produced standard mixture (bale masterbatch, carbon black filled) a) Formulation * All constituents of the mixture are present in the powdered rubber b) Mixing process 1st stage c) Vulcanisate data Vulcanisation temperature: 165°C Vulcanisation time: 15 min It is evident from the overall properties of the full compound that chemicals which must otherwise be incorporated into the polymer in an energy-intensive mixing process may be added, without loss of efficacy, during production of the product. In this manner, finished, extrudable mixtures are obtained without having to use a conventional mixing unit (for example internal mixer, roll mill) . Example C Comparison of the technical rubber properties of a silica-filled semi-compound (H-EPB III) with a conventionally produced standard mixture a) Formulation * All the ingredients of the basic compound were added to the powdered rubber during the production thereof. c) Vulcanisate data Vulcanisation temperature: 165°C Vulcanisation time: 15 min In the case of silica-filled mixtures too, it is feasible to add further mixture constituents during the powdered rubber process without loss of efficacy. Example D Comparison of the technical rubber properties of a silica-filled full compound (F-EPB IV) with a conventionally produced standard mixture a) Formulation c) Vulcanisate data Vulcanisation temperature: 165°C Vulcanisation time: 15 min A white, silica-filled full compound may be produced in the powdered rubber production process without impairing technical rubber performance. Example E Comparison of the data for a full compound based on NR/SBR with a conventionally produced standard mixture a) Formulation * The full compound contains all the constituents from mixture 1. c) Vulcanisate data Vulcanisation temperature: 155°C Vulcanisation time: 20 min It is evident from the overall properties of the full compound that all the chemicals of the overall properties of the (sic) full compound standard mixture 1 may be added to the product as early as during the powdered rubber process. No impairment of technical rubber properties is observed. WE CLAIM 1. Finely divided rubber powder, which a) contain a rubber matrix and additionally b) one or more white and/or black fillers such as herein described, optionally modified with one or more of the organosilicon compounds of the formulae (I), (II) or (III), c) one or more of the additives known for the production of rubber vulcanisates. / 2. Rubber powder according to claim 1, wherein it contains one or more of the following among the additives in the quantities conventional for processing to yield a vulcanisate : zinc oxide and/or zinc stearate, stearic acid, polyalcohols, polyamines, resins, waxes, plasticising oils, antioxidants such as herein described, optionally flame retardants, vulcanisation accelerators and sulfur, in particular modified with a surface-active substance, such as herein described, wherein the solids in the rubber powder are preferably present in a grain size of = 50 mm. 3. Rubber powder according to claim 2. wherein they contain fillers, which are modified with organosilicon compounds of the general formulae (I), (II) or (III) (R1n(RO)3-n Si-(Alk)m -(Ar)p] q [B] (I), (R1n(RO)3-n Si-(Alk) (II), or (R1n(RO)3-n Si-(Alkenyl) (III) in which B: means -SCN, -SH, -Cl, -NH2 (if q=1) or -Sx- (if q = 2) R and R1: mean an alkyl group having 1 to 4 carbon atoms, branched or unbranched, the phenyl residue, wherein all residues R and R1 may each have the same or a different meaning, preferably an alkyl group, R: means a C1-C4 alkyl, C1-C4 alkoxy group, branched or unbranched, n: means 0; 1 or 2, Alk: means a divalent linear or branched carbon residue having 1 to 6 carbon atoms, m: means 0 or 1 Ar: means an arylene residue having 6 co 12 C atoms p: means 0 or 1, providing that p and m do not simultaneously mean 0, x: means a number from 2 to 8, Alkyl: means a monovalent linear or branched, unsaturated hydrocarbon residue having X to 20 carbon atoms, preferably 2 to 8 carbon atoms, Alkenyl: means a monovalent linear or branched, unsaturated hydrocarbon residue having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms. 4. Process for the production of finely divided rubber powders containing filler by precipitation from mixtures containing water, which mixtures contain finely divided filler(s), (carbon black and/or silicate filler) optionally modified with organosilicon compounds, water-soluble salts of a metal of groups IIa, IIb, IIIa and VIII of the periodic table of elements and a rubber latex or the aqueous emulsion of a rubber solution, optionally in the presence of an organic solvent, which process is characterised in that a) =50 wt.%, but less than 100 wt.%, of the finely divided filler, preferably in the form of an aqueous suspension containing 2 to 15 wt.% of water, optionally with a of the (sic) quantity intended for modification of the filler surface of one or more organosilicon compounds according to the formulae (I), (II) or (III) in a quantity of 0.1 to 20 wt.%, relative to the filler, and/or >50 wt.%, but less than 100 wt.%, of a filler at lease partially surface modified with one or more of the organosilicon compounds (formulae (I), (II) or (III) (sic), in particular in the presence of an emulsifier, are mixed with a rubber latex or an. aqueous emulsion of a rubber solution and the pH value of the mixture is reduced to a value in the range from 7.5 to 6.5, in particular by addition of a Lewis acid (first stage). b) the remaining proportion (splitting proportion) of the above-stated finely divided fillers, optionally together with the residual quantity intended for modification of the filler surface of organosilieon compounds of the formulae (I), II or (III), is added in the form of a suspension, the pH value is reduced to a value in the range from present in the mixture completely precipitates together with the filler (second stage), c) the precipitated solids are separated in a known manner, d) are optionally washed and e) (sic) dried. 5. Process as claimed in claim 4, wherein of a total content of = 80 parts of filler phr, 1 to 10 parts of this quantity is/are added as the remaining proportion in the second stage. 6. Process as claimed in claim 5, wherein of a total content of =. 80 parts of filler phr, 10 to 20 parts of this quantity are added as the remaining proportion in the second stage. 7. Process as claimed in one or more of the preceding claims, wherein a carbon black having an average particle size of 1 to 9 ~um is used. 8. Process as claimed in one or more of the preceding claims, wherein the white filler (precipitated silica) is used at least in part in the form of a filter cake which has been washed until salt-free. 9. Process or more of the preceding claims, before precipitating the rubber powder, further of the conventional processing and/or vulcanization auxiliaries, a) to i), as stated in claim 2, are added to the suspension/emulsion, providing that the particle size of the added solid constituents is = 50 mm. Preferably 10. Process claim 9, the filler suspension containing one or more of the stated processing and/or vulcanization auxiliaries is passed through a grinder before addition of the rubber components. 11. Process claim 9, zinc oxide having a surface area of between 20 and 50 m2/g is premixed with the filler suspension and added in the first stage. 12. Process one or more of the preceding claims, one or more of the constituents a) to i) from claim 2 is/are premixed with the latex emulsion or rubber solution or the filler suspension and then the latex emulsion or rubber solution produced in this manner is mixed in the first stage with the filler suspension produced in this manner. 13. Process one or more of the preceding claim, the vulcanisation accelerator (s) is/are mixed with the rubber powder containing the above-stated additions (a to g) or is/are sprayed, in suspended or dissolved form in an oil compatible with the rubber, onto the rubber powder. 14. Process claim 13, sulfur is additionally used with the vulcanisation accelerator. 15. Use of the pulverulent rubber powders containing filler according to claims 1 to 7 for the production of vulcanisable rubber mixtures. This invention relates to finely divided, pulverulent rubbers containing filler which contain further processing and vulcanisation auxiliaries necessary for the production of vulcanisable rubber mixtures, which rubbers are pourable even after exposure to mechanical stress, and to a process for the production thereof, in which the rubber powder is obtained within two precipitation steps, and to the use of these powders for the production of vulcanisable rubber mixtures. The fillers used, which comprise not only precipitated silicas but also carbon blacks known in the rubber sector, are optionally surface modified with organosilicon compounds, especially with regard to the silicas.

Full Text

Rubber powders (compounds) and process for the production
The present invention relates to rubber powders which also
contain, in addition to the rubber components, further
constituents important for the production of the
vulcanisable rubber mixture.
If, in addition to the constituents of the basic batch,
the rubber powder also contains crosslinking chemicals
(accelerator, sulfur), it is known as a full compound. If
the rubber powder in particular consists of the
constituents of the basic batch, it is known as a semi-
compound. Intermediate forms between these stages are also
suitable.
Numerous documents have been published relating to the aim
and purpose of using rubber powders (powdered rubbers) and
relating to processes for the production thereof.
The interest in pulverulent rubbers is explained by the
processing methods used in the rubber industry, where
rubber mixtures are produced with a considerable input of
time, energy and labour. The main reason for this is that
the raw material, crude rubber, is in the form of bales.
The bale is comminuted and intimately mixed over several
processing stages with fillers, mineral oil plasticisers
and vulcanisation auxiliaries in roll mills or internal
mixers. The mixture is generally stored between the stages.
Extruder/pelletisers or extruder/roller dies are generally
arranged downstream from the internal mixers or roll mills.
The only way forward from this highly complex method of
rubber processing is to develop an entirely new processing
technology.
The use of pourable rubber powders has thus been discussed
for some time as this approach makes it possible to process
rubbers mixtures simply and rapidly in the same way as
powdered thermoplastics.
DE-PS 2822 148 discloses a process for the production of a
pulverulent rubber containing filler.
According to the said patent, an aqueous filler emulsion is
added to a rubber latex, rubber solution or the aqueous
emulsion of a rubber and the desired rubber powder is
precipitated.
In order to avoid the grain size dependent filler contents
obtained from this process, variants have been filed under
numbers DE-PS 3723 213 and DE-PS 3723 214 and are part of
the prior art.
According to DE-PS 3723 213, in a two-stage process, a
quantity of >50% of the filler is initially incorporated
into the particles of rubber powder. In the second stage,
the remainder of the filler is applied onto the so-called
basic rubber grain.
This may be considered a variant of dusting, as no bond is
created between the filler and rubber.
However, as E.T. Italiaander has pointed out (presentation
151, technical conference of the Rubber Division of the
ACS, Anaheim, California, 6-9 May 1997 (GAK 6/1997 (50)
456-464)), despite the bright future predicted in the
Delphi Report (Delphi Report, "Kiinftige Herstellverfahren
in der Gummiindustrie", Rubber Journal, volume 154, no. 11,
20-34 (1972)) for pulverulent and pelletised rubbers and
numerous attempts made by well-known polymer manufacturers
from the mid 1970"s until the early 1980"s to produce
pulverulent NBR, SBR/carbon black masterbatches and
pelletised NR, the rubber bale remains the standard form in
which polymers are supplied.
One disadvantage of known processes is firstly that a
grinding operation is necessary in order to achieve a grain
diameter of the filler particles of 10 µm, which is
considered essential to the quality of the final product.
However, this requires not only elevated energy input but
also results in damage to the filler structure which,
together with the active surface area, is a significant
parameter for its efficacy in rubber applications.
Secondly, the handling properties of prior art products
suffer in that the particles stick together during storage.
The object of the invention is accordingly to provide a
pulverulent rubber containing filler which is easily
processed, together with a process for the production
thereof.
The present invention provides a finely divided rubber
powder (powdered rubber), which
a) contains a rubber matrix and additionally
b) one or more white and/or black fillers known from the
rubber industry optionally modified with one or more of
the organosilicon compounds of the formulae (I), (II)
or (III),
c) one of more of the additions known for the production
of rubber vulcanisates.
All or part of the filler(s) may be used in premodified
form or may have been modified during the present process.
Depending upon the extent of processing (nature of the
added mixture components), the product may be designated a
semi-compound or full compound.
The rubber powder in particular contains the organosilicon
compounds in a form which has reacted with the filler if a
silicate filler, in particular a precipitated silica, is
used.
The grain size range of the rubber powders according to the
invention is generally between 0.05 and 10 mm, in
particular between 0.5 and 2 mm.
The powders according to the invention exhibit a narrower
size distribution which is shifted towards smaller particle
sizes than is known from the prior art (Kautschuk + Gummi
+ Kunststoffe ,7, 28 (1975) 397-402).
This fact facilitates processing of the powders.
Moreover, due to the production process, the filler content
of the individual particles is not determined by grain
size.
The pulverulent rubbers contain from 20 to 250 phr, in
particular from 50 to 100 phr (phr: parts per hundred parts
of rubber) , of filler, part or all of which has optionally
been surface modified before the process according to the
invention using the organosilicon compounds of the formulae
(I), (II) or (III) known in the rubber sector.
The following, individually or as mixtures, have proved to
be suitable types of rubber:
natural rubber, emulsion SBR having a styrene fraction of
10 to 50%, butyl/acrylonitrile rubber.
Butyl rubbers, terpolymers prepared from ethylene,
propylene (EPM) and unconjugated dienes (EPDM), butadiene
rubbers, SBR, produced using the solution polymerisation
process, having styrene contents of 10 to 25%, as well as
1,2-vinyl constituent contents of 20 to 55% and isoprene
rubbers, in particular 3,4-polyisoprene.
In addition to the stated rubbers, the following elastomers
may be considered, individually or as mixtures:
carboxyl rubbers, epoxy rubbers, trans-polypentenamer,
halogenated butyl rubbers, rubbers prepared from 2-
chlorobutadiene, ethylene/vinyl acetate copolymers,
epichlorohydrins, optionally also chemically modified
natural rubber, such as for example epoxidised grades.
Fillers which are generally used are the carbon blacks
known from rubber processing and white fillers of a
synthetic nature, such as for example precipitated silicas
or natural fillers, such as for example siliceous chalk,
clays etc. are additionally used.
Carbon blacks, as are generally used in rubber processing,
are particularly suitable.
Such carbon blacks include furnace blacks, gas blacks and
lamp backs having an iodine absorption value of 5 to
1000 mVg, a CTAB value of 15 to 600 m2/g, a DBP adsorption
of 30 to 400 ml/100 g and a 24 M4 DBP value of 50 to
370 ml/100 g in a quantity of 5 to 250 parts, in particular
of 20 to 150 parts, per 100 parts of rubber, in particular
of 40 to 100 parts.
Silicate fillers of synthetic or natural origin known from
the rubber sector, in particular precipitated silicas, are
also suitable.
These generally have an N2 surface area, determined using
the known BET method, of 35 to 700 m2/g, a CTAB surface
area of 30 to 500 m2/g, a DBP value of 150 to 400 ml/100 g.
The product according to the invention contains these
silicas in a quantity of 5 to 250 parts, in particular of
20 to 100 parts, relative to 100 parts of rubber.
If the fillers comprise white natural fillers, such as
clays or siliceous chalks having an N2 surface area of 2 to
35 m2/g, these are used in a quantity of 5 to 350 parts,
relative to 100 parts of rubber.
Powders containing one or more of the above-stated fillers
in the mixture are also suitable.
Apart from the unmodified fillers of the stated type,
modified fillers are optionally additionally used in the
production of the rubber powders claimed in the present
document.
The proportion of unmodified fillers depends upon the
specific mixture to be produced.
In any event, the total quantity of filler amounts to 20 to
250 phr.
100%, in particular of 30 to 100%, preferably of 60 to 100%
of this quantity consists of the unmodified fillers: silica
and/or carbon black.
Surface modification is generally performed using
organosilicon compounds of the general formulae
[R1n(RO)3-n Si-(Alk)m -(Ar)p] q [B] (I)
R1n, (RO)3-n Si-(Alk) (II),
or
R1n (R0)3-n Si- (Alkenyl) (III)
in which
B: means -SCN, -SH, -Cl, -NH2 (if q=1) or
-Sx- (if q = 2)
R and R1: mean an alkyl group having 1 to 4 carbon atoms,
branched or unbranched, the phenyl residue,
wherein all residues R and R1 may each have the
same or a different meaning,
preferably an alkyl group,
R: means a C1-C4, alkyl, C1-C4 alkoxy group,
branched or unbranched,
n: means 0; 1 or 2,
Alk: means a divalent linear or branched carbon
residue having 1 to 6 carbon atoms,
m: means 0 or 1
Ar: means an arylene residue having 6 to 12 C atoms
p: means 0 or 1, providing that p and m do not
simultaneously mean 0,
x: means a number from 2 to 8,
Alkyl: means a monovalent linear or branched
unsaturated hydrocarbon residue having 1 to 2 0
carbon atoms, preferably 2 to 8 carbon atoms,
Alkenyl: means a monovalent linear or branched,
unsaturated hydrocarbon residue having 2 to 2 0
carbon atoms, preferably 2 to 8 carbon atoms.
Modified fillers which are used according to the invention
are described, for example, in EP-B 0442 143, EP-B 0177 674
and, in particular in pellet form, in EP-A 0795 579 (white
fillers) or in EP-B 0519 188 (carbon black).
Bis(alkoxysilylalkyl)oligosulfanes of the bis(trialkoxy-
silylpropyl)tetrasulfane and -disulfane types have in
particular proved suitable for premodification or for
addition to the filler suspension.
The modified fillers known from the stated applications or
patents or the organosilicon compounds stated therein are
explicitly included in the present application as a
constituent of the claimed compositions.
Apart from the above-stated fillers, the rubber powders
according to the invention in particular contain known
processing or vulcanisation auxiliaries such as zinc oxide,
zinc stearate, stearic acid, polyalcohols, polyamines,
resins, waxes, plasticising oils, anti-ageing agents to
counter the action of heat, light or oxygen and ozone,
reinforcing resins, flame retardants, such as for example
A1(OH)3 and Mg(OH)2, pigments, various crosslinking
chemicals and accelerators and optionally sulfur in
concentrations conventional in rubber processing,
preferably sulfur modified by combination with surface
active substances, as is commercially available.
Grain size is determined from the filler suspension.
In a particularly preferred embodiment of the process
according to the invention, all the solids used are present
in a grain size of rubber particles are precipitated from the suspension.
Agglomeration may optionally occur as a result of the
production process, but this has no negative influence on
processing behaviour.
The present invention also provides a process for the
production of finely divided rubber powders containing
filler by precipitation from mixtures containing water,
which mixtures contain finely divided filler(s) (carbon
black and/or silicate filler) optionally modified with
organosilicon compounds, water-soluble salts of a metal of
groups IIa, IIb, IIIa and VIII of the periodic system of
elements and a rubber latex or the aqueous emulsion of a
rubber solution, optionally in the presence of an organic
solvent, which process is characterised in that
a) =50 wt.%, but less than 100 wt.%, of the intended
quantity of finely divided filler, preferably in the
form of an aqueous suspension containing 2 to 15 wt.%
of water, optionally with a of the (sic) quantity
intended for modification of the filler surface of one
or more organosilicon compounds according to the
formulae (I), (II) or (III) in a quantity of 0.1 to 20
wt.%, relative to the filler, in particular if the
filler is a silicate filler, preferably precipitated
silica, and/or =50 wt.%, but less than 100 wt.%, of a
filler at least partially surface modified with one or
more of the organosilicon compounds (formulae (I), (II)
or III) (sic), in particular in the presence of an
emulsifier, are mixed with a rubber latex or an aqueous
emulsion of a rubber solution and the pH value of the
mixture is reduced to a value in the range from 7.5 to
6.5, in particular by addition of a Lewis acid (first
stage),
b) the remaining proportion (splitting proportion) of the
above-stated finely divided fillers, optionally
together with the residual quantity intended for
modification of the filler surface of organosilicon
compounds of the formulae (I), (II) or (III), is added
in the form of a suspension, the pH value is reduced to
a value in the range from in particular by addition of a Lewis acid, such that
the rubber present in the mixture completely
precipitates together with the filler (second stage),
c) the precipitated solids are separated using measures
known per se,
d) are optionally washed and
e) dried.
The organosilicon compounds are in particular used when
silicate fillers, preferably silicas, are used.
The precipitation process is generally performed at room
temperature, in particular at 20 to 80 °C.
The quantities of filler and rubber are adjusted depending
upon the application in accordance with the desired filler
content of the resultant rubber.
At a total content of =80 parts of filler phr, 1 to 10 wt.%
of the filler is/are added as the remaining proportion in
the second stage.
The resultant particles do not stick together, even under
pressure, such as when several sacks are stacked.
This "inertisation" of the surface should not be confused
with the known technique of dusting tacky powders with
fillers. These only superficially adhering fillers are
rapidly detached when exposed to mechanical stress, for
example in conveying plant or on transfer into silos.
The sticking and agglomeration of the finely divided
powders, which it is the intention to avoid, then occurs
despite the dusting.
Unlike the tacky particles superficially coated with
fillers as flow auxiliaries as are known from the prior
art, according to the invention, filler particles are
incorporated into the surface during the precipitation
process for the production of the pulverulent rubber.
Depending upon the filler loading with one or more of the
above-stated fillers, the advisable distribution between
the interior of the particles and an outer zone associated
therewith is established.
In a product having an elevated filler loading (>80 parts
of filler per hundred parts of rubber), only 1 to 10 parts
of this quantity of filler are incorporated in the outer
grain zone.
However, if the pulverulent rubber contains a total of parts of filler per hundred parts of rubber, 10 to 20 parts
thereof are preferably incorporated in the outer grain zone
(peripheral zone), i.e. do not merely adhere by less
effective adhesive forces.
The distributions of the filler within the particles and in
the so-called peripheral zone generally vary between these
contents.
The greater is the total filler content, the less is the
need to suppress the tackiness of the powder by an
increased concentration of filler in the peripheral zone.
According to the invention, these proportions of the filler
are not applied externally onto the individual rubber
particles (c.f. DE-PS 37 23213), but are instead
incorporated into the rubber surface.
This distribution of the filler and the manner in which the
fillers are bonded to the rubber composition bring about
the elevated flowability of the powders according to the
invention and prevent sticking during storage of the
powder, without these properties being lost on exposure to
mechanical stresses during conveying, transfer into silos
etc .
The above-stated carbon blacks are used as fillers in
finely divided (fluffy) form, the carbon blacks generally
having an average grain diameter of 1 to 9 µm, preferably
of 1 to 8 µm, before they are suspended.
This facilitates dispersion, such that aqueous suspensions
containing filler particles of an average particle diameter
of distinctly less than 10 µm are obtained without elevated
energy input.
Precipitated silica may advantageously be used in the form
of a filter cake which has been washed until salt-free.
Metal salts which may be considered are those originating
from elements of groups IIa, IIb, IIIa and VIII of the
periodic system of elements. This division into groups
corresponds to the former IUPAC recommendation
(Periodisches System der Elemente, Verlag Chemie, Weinheim,
1985).
Typical representatives are magnesium chloride, zinc
sulfate, aluminium chloride, aluminium sulfate, iron
chloride, iron sulfate, cobalt nitrate and nickel sulfate,
wherein the salts of aluminium are preferred. Aluminium
sulfate is particularly preferred.
The salts are used in a quantity of 0.1 to 6.5 parts by
weight, preferably in the form of an aqueous solution, per
100 parts by weight of rubber. Acids suitable for
establishing the defined pH values are primarily mineral
acids, such as for example sulfuric acid, phosphoric acid
and hydrochloric acid, wherein sulfuric acid is
particularly preferred. However, carboxylic acids, such as
for example formic and acetic acid, may also be used.
The quantity of acid is determined by the nature and
quantity of the water-soluble metal salt, the filler, the
rubber and the optionally present alkali metal silicate.
This quantity may readily be determined by initial
investigatory testing.
According to a preferred embodiment of the process
according to the invention, up to 5 parts by weight per 100
parts by weight of rubber of silica (SiO2) are additionally
used in the form of an alkali metal silicate solution,
preferably as water glass having an Na2O:SiO2 molar ratio
of 2:1 to 1:4. The alkali metal silicate solution may here
be added both to the rubber component and to the filler
suspension. It is preferably added to the rubber component,
especially when the process is performed continuously.
The process according to the invention is generally
performed as follows:
first of all, a filler suspension is produced by dispersing
a proportion, preferably >50%, of the filler present in the
final product, which filler is optionally in part surface
modified with compounds according to the formulae (I), (II)
or (III), in water together with the metal salt and
optionally the alkali metal silicate solution. The overall
quantity of water is determined by the nature of the filler
and the degree of digestion. In general, the water-
insoluble constituents of the filler amount to approx.
6 wt.%. This value is not a binding restriction and both
lower and higher quantities may be encountered. The maximum
content is limited by the pumpability of the suspension.
The filler suspension produced in this manner is then
intimately mixed with the rubber latex optionally
containing alkali metal silicate solution or the aqueous
emulsion of a rubber solution optionally containing alkali
metal silicate solution. Known stirrers, such as for
example propeller stirrers, are suitable for this purpose.
After mixing, a pH value in the range from 7.5 to 6.5 is
established in the first stage using an acid while stirring
is continued. This results in basic rubber grains having a
homogeneous filler content. The size of these basic grains
is controlled by the selected quantity of metal salt in the
range from 0.1 to 6.5 phr. Control is effected by the
largest grain size being obtained with the lowest quantity
of metal salt.
The solids content of the latex used generally amounts to
20 to 25 wt.%. The solids content of the rubber solutions
is generally 3 to 35 wt.%, that of the rubber emulsions
generally from 5 to 30 wt.%.
The process according to the invention may be performed
both discontinuously and continuously.
The precipitated rubber powder is advantageously separated
by means of a centrifuge and then dried to a residual water
content of generally drier.
During the production process according to the invention,
in addition to the preferably used known emulsifiers, such
as for example fatty alcohol polyethylene glycol ethers, in
a preferred embodiment further processing and optionally
vulcanisation auxiliaries are generally added to the
suspension in a quantity as is conventional for
vulcanisable rubber mixtures or also in a smaller quantity.
Such auxiliaries comprise known
a) activators, such as for example stearic acid,
b) antioxidants
c) processing auxiliaries such as resins and/or waxes,
which are generally added in quantities of 0.5 to 10 wt.%,
relative to the rubber content, directly to the filler
suspension or with the latex emulsion/solution.
Vulcanisation accelerators are further important additions.
These are in particular selected from among the classes of
sulfenamides, mercapto and sulfide accelerators, as well as
thiurams, thiocarbamates and amines, and are generally
added in a quantity of 0.1 to 8 wt.%, relative to the
rubber content, directly to the filler suspension or with
the latex emulsion/solution in finely divided form or in a
known oil compatible with the rubber.
In a preferred embodiment, the rubber powder containing the
above-stated constituents is mixed with the accelerator
substances or these are sprayed, for example dissolved in
an oil, onto the rubber powder.
The sulfur necessary for vulcanisation, in particular in a
finely divided (5 to 45 µm) modification combined with
surface-active substances, is optionally mixed into the
suspension or rubber powder in a quantity of 0.2 to 8 wt.%,
relative to the rubber content.
Nonionic, cationic or anionic surfactants are optionally
also added as surface-active substances, especially when
organosilicon compounds are added to the filler suspension.
The use of finely divided solid compounds is particularly
suitable. The grain size range of the above-stated
substances is generally below 50 µm, in particular 10 µm.
This facilitates the best possible distribution in the
rubber powders according to the invention which are
obtained using the process described in the present
document.
Incorporating generally known zinc salts, in particular
zinc oxide, in a quantity of 0.5 to 8 wt.%, relative to the
rubber content, is also of particular significance to
subsequent use.
A zinc oxide having a specific surface area of between 2 0
and 50 m2/g is preferably used. This property is associated
with the above-stated grain size range of particular of However, if all or some of the available additions have a
grain size range greater than this, it is possible
according to the prior art to pass the aqueous suspensions
obtained before addition of the rubber content through
known, suitable grinding units.
Suspensions are then obtained having solids contents of the
desired particle size distribution.
In one particular embodiment, the suspension from which the
rubber powder according to the invention is precipitated
additionally contains a plasticising oil known as a
processing auxiliary in the rubber industry.
The purpose of this oil is, inter alia, to improve the
processing characteristics of the plasticised crude mixture
(injection behaviour, extrusion behaviour) and it is added
either with the rubber latex/emulsion/solution or
separately to the suspension.
The rubber powders according to the invention are used for
the production of vulcanisable rubber mixtures.
The constituents necessary for producing the mixture are
all preferably present in the rubber powder.
They may, however, also additionally be mixed with other
conventional rubbers, vulcanisation auxiliaries and
fillers, if this is necessary for the properties of the
desired vulcanisate.
It is possible according to the invention directly to
produce finely divided rubber powders containing optionally
modified fillers and further constituents necessary for
vulcanisation, which powders are free-flowing and also
remain free-flowing after exposure to mechanical stresses
(for example conveying, packaging).
By virtue of the finely divided nature thereof, no grinding
or other comminution measures are required to obtain finely
divided products.
The resultant finely divided rubber powders (semi-compounds
and full compounds) are readily processable and give rise
to vulcanisates having improved properties.
Production Examples
Example I
Production of a semi-compound in powder form based on E-
SBR, N234 and additions
A stable dispersion is produced by stirring together 5.6 kg
of N234, 1 kg of active ZnO, 2.2 kg of oil, 96 g of
Marlipal 1618/25, 0.2 kg each of stearic acid, 6PPD and
TMQ, 0.6 kg of Rhenosin C 90 in 134.4 L of water. The
dispersion is mixed together with 95.69 kg of a 20.9% E-SBR
latex emulsion with vigorous stirring. The pH value of the
complete mixture is reduced to 6.5 by addition of an
approx. 10% Al2(SO4)3 solution, so initiating precipitation.
At this pH value, another stable dispersion prepared from 4
kg of N234 and 96.0 L of completely deionised water is
added and the pH value is then reduced to 6.0 by addition
of further Al2(SO4)3. After the precipitation process, the
great majority of the water is separated mechanically and a
drying stage then reduces the residual moisture content to
E-SBR and 48 parts of N234 and all added substances.(H-EPB
I)
Example II
Production of a full compound in powder form based on E-
SBR, N234 and additions
A stable dispersion is produced by initially stirring
together 5.6 kg of N234, 1 kg of active ZnO, 96 g of
Marlipal 1618/25, 0.32 kg of sulfur and 0.04 kg of MBTS in
126.6 L of completely deionised water. An oil solution is
also produced from 2.2 kg of oil with 0.2 kg each of
stearic acid, 6PPD and TMQ, 0.6 kg of Rhenosin C90, 0.32 kg
of TBBS and heated to 75 °C. The oil solution is mixed
together with 95.69 kg of a 20.9% E-SBR latex emulsion with
vigorous stirring. The above-stated stable dispersion is
then added to the latex/oil mixture. The pH value of the
mixture is then reduced to 6.5 by addition of an approx.
10% Al2(SO4)3 solution (beginning of precipitation). At this
pH value, precipitation is interrupted and another stable
dispersion prepared from 4 kg of N234 and 96.0 L of
completely deionised water is added to the reaction
mixture. After this process step, the pH value is further
reduced to 5.5 by addition of further quantities of
Al2(SO4)3. After the precipitation process, the great
majority of the water is separated mechanically and a
drying stage then reduces the residual moisture content to
E-SBR and 48 parts of N234 and all added substances. (F-EPB
II)
Example III
Production of a semi-compound in powder form based on E-
SBR, silica and additions
A stable dispersion is produced by stirring together 12 kg
of Ultrasil 7000, 0.98 kg of Si 69, 0.6 kg of active ZnO,
120 g of Marlipal 1618/25 in 108 L of completely deionised
water. An oil solution is also produced from 5 kg of oil,
0.2 kg of stearic acid, 0.3 kg of 6PPD, 0.2 kg of Protector
G 35 and heated to 75 °C. The oil solution is mixed
together with 95.69 kg of a 20.9% E-SBR latex emulsion with
vigorous stirring. The above-stated stable dispersion is
then added to the latex/oil mixture. The pH value is
reduced to 7 by addition of an approx. 10% Al2(SO4)3
solution. Once the pH value has been reduced to 7, another
stable dispersion prepared from 3 kg of Ultrasil 7000,
240 g of Si 69, 40 g of Marlipal and 27 L of completely
deionised water is added. Once the dispersion has been
added, the pH value is further reduced to 5.5 by means of
Al2(SO4)3. After the precipitation process, the great
majority of the water is separated mechanically and a
drying stage then reduces the residual moisture content to
E-SBR and 75 parts of Ultrasil 7000 and all added
substances. (H-EPB III)
Example IV
Production of a full compound in powder form based on E-
SBR, silica and additions
A stable dispersion is produced by stirring together 12 kg
of Ultrasil 7000, 0.98 kg of Si 69, 0.6 kg of active ZnO,
120 g of Marlipal 1618/25, 0.3 kg of sulfur in 108 L of
completely deionised water. An oil solution is also
produced from 5 kg of oil, 0.2 kg of stearic acid, 0.3 kg
of 6PPD, 0.2 kg of Protector G 35, 0.3 kg of CBS and 0.4 kg
of DPG and heated to 75 °C. The oil solution is mixed
together with 95.69 kg of a 20.9% E-SBR latex emulsion with
vigorous stirring. The above-stated stable dispersion is
then added to the latex/oil mixture. The pH value is
reduced to 7 by addition of an approx. 10% Al2(SO4)3
solution. Once the pH value has been reduced to 7, another
stable dispersion prepared from 3 kg of Ultrasil 7000,
240 g of Si 69, 40 g of Marlipal and 27 L of completely
deionised water is added. Once the dispersion has been
added, the pH value is further reduced to 5.5 by means of
Al2(SO4)3. After the precipitation process, the great
majority of the water is separated mechanically and a
drying stage then reduces the residual moisture content to
E-SBR and 75 parts of Ultrasil 7000 and all added
substances. (F-EBP IV)
Example V
Production of a full compound in powder form based on NR/E-
SBR, N234 and additions
A stable dispersion is produced by initially stirring
together 6.0 kg of N234, 0.6 kg of active ZnO, 100 g of
Marlipal 1618/25, 0.4 kg of sulfur and 0.06 kg of MBTS in
126.6 L of completely deionised water. An oil solution is
also produced from 2.4 kg of oil with 0.4 kg each of
stearic acid and 6PPD, 0.2 kg of TMQ, 0.2 kg of Protector G
35, 0.24 kg of TBBS and heated to 75 °C. The oil solution
is mixed together with 47.85 kg each of a 20.9% NR and a
20.9% E-SBR latex emulsion with vigorous stirring. The
above-stated stable dispersion is then added to the
latex/oil mixture. The pH value of the mixture is then
reduced to 7.0 by addition of an approx. 10% Al2(SO4)3
solution (beginning of precipitation). At this pH value,
precipitation is interrupted and another stable dispersion
prepared from 4 kg of N234 and 96.0 L of completely
deionised water is added to the reaction mixture. After
this process step, the pH value is further reduced to 6.0
by addition of further quantities of Al2(SO4)3. After the
precipitation process, the great majority of the water is
separated mechanically and a drying stage then reduces the
residual moisture content to product contains 100 parts of E-SBR and 50 parts of N234
and all added substances. (F-EPB V)
Products according to the invention in rubber applications
Europrene 1552 Styrene/butadiene rubber having a
styrene content of 19% (Enichem)
Europrene N 5564 Bale masterbatch consisting of
Europrene 1552/N234/oil in a
100:52:10 ratio (Enichem)
RSS1 Natural rubber (ribbed smoked sheet)
H-EPB I Semi-compound according to the
invention (powdered rubber) consisting
of 100 parts of SBR 1552, 48 parts of
N234, 11 parts of oil, 5 parts of ZnO,
1 part of stearic acid, 1 part of 6PPD,
1 part of TMQ, 3 parts of resin
F-EPB II Full compound according to the
invention, composition as H-EPB I and
additionally 1.6 parts of TBBS, 0.2
parts of MBTS, 1.6 parts of sulfur
H-EPB III Semi-compound according to the
invention (powdered rubber) consisting
of 100 parts of E-SBR, 75 parts of
Ultrasil 7000, 6.1 parts of Si 69, 3
parts of ZnO, 25 parts of oil, 1 part
of stearic acid, 1.5 parts of 6PPD, 1
part of wax
F-EPB IV Full compound according to the
invention, composition as H-EPB III and
additionally 1.5 parts of CBS, 2 parts
of DPG, 1.5 parts of sulfur
F-EPB V Full compound according to the
invention
Powdered rubber consisting of 50 parts
of NR, 50 parts of SBR, 50 parts of
N234, 12 parts of oil, 3 parts of zinc
oxide, 2 parts of stearic acid, 2 parts
of 6PPD, 1 part of TMQ, 1 part of wax,
1.2 parts of TBBS, 0.3 parts of MBTS,
2 parts of sulfur
6PPD N-(1,3-dimethylbutyl)-N-phenyl-p-
phenylenediamine
Ultrasil 7000 Gr Enhanced dispersion tyre silica (N2
surface area approx. 180m2/g)
(Degussa AG)
TMQ 2,2,4-Trimethyl-l,2-dihydroquinoline
Si69 Bis(triethoxysilylpropyl)tetrasulfane
TBBS N-tert-butyl-2-benzthiazylsulfenamide
MBTS Dibenzothiazyl disulfide
Enerthene 1849-1 Aromatic plasticiser (BP)
DPG Diphenylguanidine
CBS Benzothiazyl-2-cyclohexylsulfenamide
E-SBR 1500 Emulsion styrene/butadiene latex having
a styrene content of 23.4%
Active ZnO Zinc oxide: having a surface area of
4 5 mVg
Marlipal Emulsifier: fatty alcohol polyethylene
1618/25 glycol ether (Hüls AG)
Rhenosin C 90 Reinforcing resin
Protector G 35 Ozone protection wax
N234 Carbon black, N2 surface area 125 m2/g
Rubber test methods
Tensile bar test DIN 53 504
Shore hardness DIN 53 505
100% modulus DIN 53 504
300% modulus DIN 53 504
Elongation at break DIN 53 504
Fracture energy DIN 53 504
Ball rebound ASTM D5308
Dmax-Dmin DIN 53 52 9
Example A Comparison of technical rubber properties of
a semi-compound (H-EPB I) with a
conventionally produced standard mixture
a) Formulation
* The constituents of the basic batch are present in the
powdered rubber
c) Vulcanisate data
Vulcanisation temperature: 165 °C
Vulcanisation time: 15 min
The results demonstrate that it is possible, without loss
of subsequent technical rubber performance, to add further
mixture constituents, in addition to the polymer and
filler, during production of the powdered rubber. In this
manner, it is possible inter alia to dispense with the
energy-intensive 1st mixing stage.
Example B Comparison of the technical rubber
properties of a full compound (F-EPB II)
with a conventionally produced standard
mixture (bale masterbatch, carbon black
filled)
a) Formulation
* All constituents of the mixture are present in the
powdered rubber
b) Mixing process
1st stage
c) Vulcanisate data
Vulcanisation temperature: 165°C
Vulcanisation time: 15 min
It is evident from the overall properties of the full
compound that chemicals which must otherwise be
incorporated into the polymer in an energy-intensive mixing
process may be added, without loss of efficacy, during
production of the product. In this manner, finished,
extrudable mixtures are obtained without having to use a
conventional mixing unit (for example internal mixer, roll
mill) .
Example C Comparison of the technical rubber
properties of a silica-filled semi-compound
(H-EPB III) with a conventionally produced
standard mixture
a) Formulation
* All the ingredients of the basic compound were added to
the powdered rubber during the production thereof.
c) Vulcanisate data
Vulcanisation temperature: 165°C
Vulcanisation time: 15 min
In the case of silica-filled mixtures too, it is feasible
to add further mixture constituents during the powdered
rubber process without loss of efficacy.
Example D Comparison of the technical rubber
properties of a silica-filled full compound
(F-EPB IV) with a conventionally produced
standard mixture
a) Formulation
c) Vulcanisate data
Vulcanisation temperature: 165°C
Vulcanisation time: 15 min
A white, silica-filled full compound may be produced in the
powdered rubber production process without impairing
technical rubber performance.
Example E Comparison of the data for a full compound
based on NR/SBR with a conventionally
produced standard mixture
a) Formulation
* The full compound contains all the constituents from
mixture 1.
c) Vulcanisate data
Vulcanisation temperature: 155°C
Vulcanisation time: 20 min
It is evident from the overall properties of the full
compound that all the chemicals of the overall properties
of the (sic) full compound standard mixture 1 may be added
to the product as early as during the powdered rubber
process. No impairment of technical rubber properties is
observed.
WE CLAIM
1. Finely divided rubber powder, which
a) contain a rubber matrix and additionally
b) one or more white and/or black fillers such as herein described,
optionally modified with one or more of the organosilicon
compounds of
the formulae (I), (II) or (III),
c) one or more of the additives known for the production of rubber
vulcanisates. /
2. Rubber powder according to claim 1, wherein
it contains one or more of the following among the additives in the
quantities conventional for processing to yield a vulcanisate :
zinc oxide and/or zinc stearate,
stearic acid,
polyalcohols,
polyamines,
resins, waxes, plasticising oils, antioxidants such as herein described,
optionally flame retardants, vulcanisation accelerators and
sulfur, in particular modified with a surface-active substance, such as
herein described,
wherein the solids in the rubber powder are preferably present
in a grain size of = 50 mm.
3. Rubber powder according to claim 2. wherein
they contain fillers, which are modified with
organosilicon compounds of the general formulae (I),
(II) or (III)
(R1n(RO)3-n Si-(Alk)m -(Ar)p] q [B] (I),
(R1n(RO)3-n Si-(Alk) (II),
or
(R1n(RO)3-n Si-(Alkenyl) (III)
in which
B: means -SCN, -SH, -Cl, -NH2 (if q=1) or
-Sx- (if q = 2)
R and R1: mean an alkyl group having 1 to 4 carbon
atoms,
branched or unbranched, the phenyl residue,
wherein all residues R and R1 may each have
the same or a different meaning,
preferably an alkyl group,
R: means a C1-C4 alkyl, C1-C4 alkoxy group,
branched or unbranched,
n: means 0; 1 or 2,
Alk: means a divalent linear or branched carbon
residue having 1 to 6 carbon atoms,
m: means 0 or 1
Ar: means an arylene residue having 6 co 12 C
atoms
p: means 0 or 1, providing that p and m do not
simultaneously mean 0,
x: means a number from 2 to 8,
Alkyl: means a monovalent linear or branched,
unsaturated hydrocarbon residue having X to
20 carbon atoms, preferably 2 to 8 carbon
atoms,
Alkenyl: means a monovalent linear or branched,
unsaturated hydrocarbon residue having 2 to
20 carbon atoms, preferably 2 to 8 carbon
atoms.
4. Process for the production of finely divided rubber
powders containing filler by precipitation from
mixtures containing water, which mixtures contain
finely divided filler(s), (carbon black and/or silicate
filler) optionally modified with organosilicon
compounds, water-soluble salts of a metal of groups
IIa, IIb, IIIa and VIII of the periodic table of
elements and a rubber latex or the aqueous emulsion of
a rubber solution, optionally in the presence of an
organic solvent, which process is characterised in that
a) =50 wt.%, but less than 100 wt.%, of the finely
divided filler, preferably in the form of an
aqueous suspension containing 2 to 15 wt.% of
water, optionally with a of the (sic) quantity
intended for modification of the filler surface of
one or more organosilicon compounds according to
the formulae (I), (II) or (III) in a quantity of
0.1 to 20 wt.%, relative to the filler, and/or >50
wt.%, but less than 100 wt.%, of a filler at lease
partially surface modified with one or more of the
organosilicon compounds (formulae (I), (II) or
(III) (sic), in particular in the presence of an
emulsifier, are mixed with a rubber latex or an.
aqueous emulsion of a rubber solution and the pH
value of the mixture is reduced to a value in the range from 7.5 to
6.5, in particular by addition of a Lewis acid (first stage).
b) the remaining proportion (splitting proportion) of
the above-stated finely divided fillers, optionally together with the
residual quantity intended for modification of the filler surface of
organosilieon compounds of the formulae (I), II or (III), is added
in the form of a suspension, the pH value is reduced to a value in
the range from present in the mixture completely precipitates together with the
filler (second stage),
c) the precipitated solids are separated in a known manner,
d) are optionally washed and
e) (sic) dried.
5. Process as claimed in claim 4, wherein
of a total content of = 80 parts of filler phr, 1 to 10 parts of this
quantity is/are added as the remaining proportion in the second
stage.
6. Process as claimed in claim 5, wherein
of a total content of =. 80 parts of filler phr, 10 to 20 parts of this
quantity are added as the remaining proportion in the second stage.
7. Process as claimed in one or more of the preceding claims, wherein
a carbon black having an average particle size of 1 to 9 ~um is used.
8. Process as claimed in one or more of the preceding claims, wherein
the white filler (precipitated silica) is used at least in part in the form
of a filter cake which has been washed until salt-free.
9. Process or more of the preceding claims,
before precipitating the rubber powder, further of the conventional
processing and/or vulcanization auxiliaries, a) to i), as stated in claim
2, are added to the suspension/emulsion, providing that the particle
size of the added solid constituents is = 50 mm.
Preferably 10. Process claim 9,
the filler suspension containing one or more of the stated processing
and/or vulcanization auxiliaries is passed through a grinder before
addition of the rubber components.
11. Process claim 9,
zinc oxide having a surface area of between 20 and 50 m2/g is
premixed with the filler suspension and added in the first stage.
12. Process one or more of the preceding claims,
one or more of the constituents a) to i) from claim 2 is/are premixed
with the latex emulsion or rubber solution or the filler suspension
and then the latex emulsion or rubber solution produced in this
manner is mixed in the first stage with the filler suspension produced
in this manner.
13. Process one or more of the preceding claim,
the vulcanisation accelerator (s) is/are mixed with the rubber
powder containing the above-stated additions (a to g) or is/are
sprayed, in suspended or dissolved form in an oil compatible with
the rubber, onto the rubber powder.
14. Process claim 13,
sulfur is additionally used with the vulcanisation accelerator.
15. Use of the pulverulent rubber powders containing filler according to
claims 1 to 7 for the production of vulcanisable rubber mixtures.
This invention relates to finely divided, pulverulent
rubbers containing filler which contain further processing
and vulcanisation auxiliaries necessary for the production
of vulcanisable rubber mixtures, which rubbers are pourable
even after exposure to mechanical stress, and to a process
for the production thereof, in which the rubber powder is
obtained within two precipitation steps, and to the use of
these powders for the production of vulcanisable rubber
mixtures.
The fillers used, which comprise not only precipitated
silicas but also carbon blacks known in the rubber sector,
are optionally surface modified with organosilicon
compounds, especially with regard to the silicas.

Documents:

974-CAL-1999-CORRESPONDENCE-1.1.pdf

974-CAL-1999-CORRESPONDENCE.pdf

974-CAL-1999-FORM 27-1.1.pdf

974-CAL-1999-FORM 27.pdf

974-CAL-1999-FORM-27.pdf

974-cal-1999-granted-abstract.pdf

974-cal-1999-granted-claims.pdf

974-cal-1999-granted-correspondence.pdf

974-cal-1999-granted-description (complete).pdf

974-cal-1999-granted-form 1.pdf

974-cal-1999-granted-form 18.pdf

974-cal-1999-granted-form 2.pdf

974-cal-1999-granted-form 3.pdf

974-cal-1999-granted-form 5.pdf

974-cal-1999-granted-gpa.pdf

974-cal-1999-granted-letter patent.pdf

974-cal-1999-granted-priority document.pdf

974-cal-1999-granted-reply to examination report.pdf

974-cal-1999-granted-specification.pdf

974-cal-1999-granted-translated copy of priority document.pdf

974-CAL-1999-PA.pdf

« Previous Patent

Next Patent »

Patent Number

212157

Indian Patent Application Number

974/CAL/1999

PG Journal Number

47/2007

Publication Date

23-Nov-2007

Grant Date

20-Nov-2007

Date of Filing

14-Dec-1999

Name of Patentee

PKU PULVERKAUTSCHUK UNION GMBH

Applicant Address

PAUL-BAUMANN-STRASSE 1 DE-45764 MARL, A GERMAN COMPANY.

Inventors:

#	Inventor's Name	Inventor's Address
1	DR, UDO GORL	DORSTENER STRASSE 15A, DE-45657 RECKLILNGHAUSEN
2	DR. REINHARD STOBER	BORNWIESENWEG 22, DE-63594 HASSELROTH
3	HARTMUT LAUER	ECKARDROTHER-STRASSE2, DE-63628 BAD SODEN SALMUNSTER
4	UWE ERNST	OPHOFFSTRASSE 22B, DE-45768 MARL.

PCT International Classification Number

C08K 3/34

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	198 58 706.6	1998-12-18	Germany