Indian Patents. 270335:NOVEL POLYMERIC TACKIFIER, PROCESS FOR PREPARING THE SAME AND USE THEREOF

Title of Invention	NOVEL POLYMERIC TACKIFIER, PROCESS FOR PREPARING THE SAME AND USE THEREOF
Abstract	Disclosed herein a novel polymeric tackifier suitable for use with natural rubber and various synthetic rubbers wherein the said tackifier consists of a coagulated emulsion polymer in dry solid particulate form, which is prepared by employing emulsion polymerization process followed by coagulation and drying.

Full Text	Field of the Invention This invention, in general, relates to the field of tackifiers and in particular to a novel polymeric tackifier. More specifically, but without restriction to the preferred embodiments hereinafter described in accordance with the best mode of practice, the present invention provides a coagulated emulsion polymer in dry solid particulate form suitable as a tackifier in synthetic rubbers and natural rubber compounding process. Background of the Invention Tackifiers are generally used to impart or enhance surface tack properties and find widespread application in diverse fields e.g. in hot melt adhesive (HMA), pressure sensitive adhesive (PSA), lamination adhesive and variety of rubber compounds etc. In elastomeric compositions, such tackifiers are used to enhance or control various physical and mechanical properties such as stiffness and tack. It also improves adhesion and sometimes cohesion without excessive stiffening or softening of elastomeric composition and prevents bleeding or blooming of the additives to the surface of the elastomeric compounds. US patent no. 3,970,623 issued to Feeney et al. on July 20,1976 reveals an adhesive composition comprising of an admixture of 100 parts by wt. of the copolymer of butadiene (92-97%), styrene (3-8%) and acrylonitrile (1-4%) with 50-150 parts by weight of a tackifier based on rosin ester and diolefin or olefin coplymers containing about 5-35 wt % of aromatic units prepared through the emulsion polymerization with the help of a primary and tertiary mercaptan as chain modifier. US patent no. 4,038,346 issued to Feeney on July 26,1977 discloses a tackifying resin composition prepared by mixing about 75-98% of tackifying resin having softening point in the range of 80-130°C with about 2-25% oily polymer having a boiling point of 190-250°C. The tackifying resin is prepared by step wise method of polymerizing at a temperature range of about 0-50°C in presence of the catalyst selected from aluminum chloride, ethyl aluminum dichloride, a monomer mixture of 20-80% of piperylene and 80-20% of a monoolefin containing 4-6 carbon atoms comprised of at least one olefin selected from the group consisting of 2-methyl-2-butene, 2-methyl-l-butene, 2-methyl- 1-pentene, 2-methyl-2-butene and 0-30%of a monomer selected from dicyclopentadiene and a-methyl styrene. The adhesive composition is prepared by mixing the copolymer and tackifier in presence of a hydrocarbon solvent. The composition finds application in pressure sensitive adhesives and hot melt adhesives. US patent no. 4,073,776 issued to Galkiewicz et al. on February 14,1978 discloses the reaction product of oxirane bearing materials with alkyl phenol novolacs. These reaction products act as excellent tackifiers for various synthetic and natural rubbers requiring good green tack. Generally oxirane-bearing materials contains an epoxy group and is based on glycidyl ethers, glycidyl esters, aliphatic oxiranes, cycloaliphatic oxiranes etc. These oxirane bearing materials reacts with alkyl phenol novolacs, wherein the alkyl group of the alkyl phenol novolacs contains 4-16 carbon atoms. This invention is directed to tackifiers utilized as tire stock tackifiers, cement tackifiers etc. When compounded with elastomers, this tackifier can comprise 0.5-20 parts per hundred parts of rubber (phr). In carcass compounds, it is used about 3-12 phr. US patent no. 4,130,701 issued to Lepert on December 19,1978 reveals the preparation of a suitable tackifier resin which is prepared by polymerization using a Friedel-Crafts catalyst, a petroleum resin feed comprising C5 olefins and diolefins, C6 olefins and diolefins or a mixture of above. The feed is obtained from cracking of petroleum feedstock and an additive, comprising a nonaromatic cyclic compound selected from vinyl norbornene or tetrahydroindene. These resins exhibits better compatibility with thermoplastic elastomers such as styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS) block copolymers and are mainly used in pressure sensitive adhesives or hot melt adhesives. These resins are successfully used as tackifiers in carpet backing, hot melts, book binding, paper sizing with natural rubber and synthetic rubbers like polyisoprene, ethylene propylene diene (EPDM), butyl, chlorobutyl, bromobutyl, neoprene rubber and also with SIS block copolymers. US patent no. 4,157,319 issued to Feeney et al. on June 5,1979 reveals an adhesive composition comprising of a rubbery copolymer of butadiene, styrene and acrylonitrile in combination with a tackifier. A pressure sensitive adhesive composition, which comprises an admixture of 100 parts by weight of the above rubbery copolymer and about 50-150 parts by weight of tackifying resin. The adhesive composition is prepared by mixing the copolymer and the tackifier in the presence of at least one solvent selected from toluene, benzene, xylene, pentane, hexane, heptane and octane, wherein the tackifier resin is selected from fully hydrogenated rosin esters and from diolefin or olefin copolymers prepared by polymerization of a mixture comprising piperylene, olefins selected primarily from 2-methyl-l-butene and 2-methyl-2-butene and at least one monomer selected from styrene and a-methyl styrene and about 0-10% dicyclopentadiene in the presence of aluminum chloride. US patent no. 4,230,842 issued to Bullard et al. on October 28,1980 reveals the preparation of a hydrocarbon based tackifier specifically to be applied with SIS block copolymer. This diolefin or olefin backbone resin is prepared, by reacting in the presence of an aliphatic hydrocarbon solvent and a selected catalyst, a monomer mixture comprised primarily of a diolefin/olefin mixture of the piperylene/olefin type and about 2-12% alpha-methyl styrene. The product is characterized with a softening point of 85-100°C and is prepared by the method which consists essentially of reacting at a temperature range of 10-50°C in presence of a solvent e.g. hexane or heptane and a catalyst selected from aluminum chloride or ethyl aluminum dichloride. US patent no. 4,324,710 issued to Davis et al. on April 13,1982 reveals a thermoplastic resin used as a substitute of process oils or hydrocarbon resins as well as tackifiers, softeners, extenders, processing aids and cure retarders. This is basically a crude wood rosin of high melting point having carboxylic acid groups and is insoluble in aliphatic hydrocarbons. The above-mentioned thermoplastic resin contains a major phenolic fraction, a neutral fraction and a minor rosin derived fraction. The phenolic resin fraction is derived as phlobaphenes, carboxylated phlobaphenes, substituted stilbenes, lignan hydroxy lactones, neutral fraction includes a wax, polymerized terpenes and the rosin derived fraction includes resin acids and polymerized resin acids. US patent no. 4,968,740 issued to Makati et al. on November 6,1990 discloses a latex based adhesive prepared by emulsion polymerization process. The adhesive consists of two components, an adhesive part prepared from at least one hard monomer, one soft monomer and optionally a copolymerizable carboxylic acid monomer having glass transition temperature (Tg) of -70 to -5°C and tackifier part compatible with adhesive having a number average molecular weight (M„) less than 5000 and Tg of -10 to 50°C. Both the adhesive and tackifier part is synthesized separately by emulsion polymerization process. The adhesive comprises of 20-95% of the latex and tackifier comprises 5-80% of the latex based on dry weight. Both the adhesive and tackifier components comprise interpolymers of styrene, butadiene and itaconic acid. US patent no. 6,710,147 issued to Cottman on March 24,2004 discloses that the reactivity of the most important monomers commonly used in synthesizing tackifier resins with aluminum halide catalysts can be enhanced by conducting the polymerization in the presence of an allylic halide. Increased monomer conversion is of great commercial importance because it leads to an increased level of efficiency and reactor capacity. This invention discloses a process for synthesizing a tackifier resin by polymerization of an unsaturated hydrocarbon monomer mixture in presence of aluminum halide and an allylic halide, wherein the unsaturated hydrocarbon monomer mixture is comprised of unsaturated hyrdocarbon monomers containing from about 4 to about 18 carbon atoms, and wherein the said process is conducted in the absence of tantalum compounds. Previously used tackifiers for rubber include hydrocarbon resins, coumarone-indene resins, polyterpenes, phenol formaldehyde resins etc. Hydrocarbon tackifiers provide good initial tack but low long term tack while the phenolic tackifiers provide good initial and long term tack but are relatively expensive. Some of these tackifiers also do not provide sufficient tack in certain rubbers e.g. in styrene butadiene rubber (SBR) and polybutadiene rubber, unless high levels are used which adversely affects the physical properties of the rubbers. Further, during manufacturing of molded goods like pneumatic tires, inner tubes, belts, hoses, rubberized fabrics and rolls etc., it is very important to have a good green strength for assembling different components together without bleeding and blooming of various ingredients from the cured and uncured material. Mostly petroleum based resins and wood rosins are used for this purpose. Due to the resinous and viscous nature, these resins cause various processing problem during handling. For instance, quite often the stock sticks to the roll during mixing and sometimes due to compatibility problems it causes bleeding and leaches out on to the surface. Being a natural product, natural rubber possesses good tack property and bond strength; however, inherited properties of natural rubber alone are often inadequate for many applications, while on the other hand synthetic rubbers have relatively lower tack. Hence tackifiers in the form of resins are added to the system to increase the tack and adhesion during compounding. Therefore, there is a need to develop a novel tackifier to improve upon the limitations in the prior art for the application in rubber compounding. Accordingly, the present invention provides a novel polymeric tackifier, which is coagulated emulsion polymer in dry solid particulate form suitable as a tackifier in synthetic rubbers and natural rubber compounding process. Summary of the Invention In accordance with the principal aspect of the present invention, there is provided a novel polymeric tackifier, wherein the said tackifier consists of a coagulated emulsion polymer in dry solid particulate form, suitable for use in rubber compounding. In accordance with another aspect of the invention, there is provided a novel polymeric tackifier, wherein the said tackifier consists of a coagulated emulsion polymer in dry solid particulate form comprising a mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier. In accordance with one other aspect of the invention, there is provided a process for preparation of polymeric tackifier, wherein the process comprising employing emulsion polymerization followed by coagulation and drying using a system comprising mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier. In accordance with yet another aspect of the invention, there is provided a process for preparation of polymeric tackifier, wherein this process comprises employing emulsion polymerization followed by coagulation and drying using a system comprising vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine as monomers, rosin acid soap as base emulsifier and tertiary dodecyl mercaptan as a chain modifier along with other ingredients. In accordance with a further aspect of the present invention, an application of the said polymeric tackifier is provided, wherein said polymeric tackifier is used with natural rubber and various synthetic rubbers like styrene butadiene rubber, polybutadiene rubber etc. Detailed Description of the Invention The present invention provides a novel polymeric tackifier and its application in conventional rubber compounding. It also describes the process for preparation of the polymeric tackifier. Tackifiers are mainly used to impart and improve the surface tack properties of the base polymer and also to improve cohesion without excess stiffening, softening of the polymer and bleeding & blooming of various other compounding ingredients to the surface of the finished product. Tackifier resins are mainly classified into two major groups. These are rosin resin and its derivatives and hydrocarbon resins. The rosin resins, as the name implies, consists of rosins, hydrogenated rosins and their various derivatives such as esters while the hydrocarbon resin group consists of polyterpenes, synthetic hydrocarbon resin, and a collection of modified or special resins primarily phenolics. Besides these resins, some low molecular weight polymers are also used to improve the tack property, which are known as polymeric tackifier. In the present invention a polymeric tackifier is synthesized via emulsion polymerization route, which is not only ecofriendly insofar as in avoidance of solvent use but also avoids the hazards of solution polymerization. Full conversion of monomers without any undesirable by-product formation yields the maximum output as well makes the process most cost effective. Due to the presence of styrene butadiene backbone in the tackifier, the molecular level compatibility of the tackifier with styrene butadiene and polybutadiene rubber increases and in turn enhances various physicomechanical properties that generally does not occur with petroleum based or natural rosin based tackifiers. The polymerization process disclosed herein is extended and the resultant latex obtained from the process is further coagulated and dried. This dried latex is used as a tackifier with natural rubber and also with various synthetic rubbers like styrene butadiene rubber, polybutadiene rubber etc., which requires a good green tack without sacrificing its virgin mechanical and physical properties. The polymeric tackifier disclosed herein comprising vinyl benzene derivative, 1,3 butadiene and 2- vinyl pyridine as monomers, rosin acid soap as base emulsifier and tertiary dodecyl mercaptan as a chain modifier along with other ingredients. It is prepared via emulsion polymerization route and the ratio of the monomers e.g. vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine varied from 2:68:30 to 15:70:15. The vinyl benzene derivative is selected from a class comprising of styrene, a-methyl styrene, para-methyl styrene and vinyl toluene. The reaction is controlled in the temperature range of 45-70°C during different stages of polymerization and a time span of 3-30 hours is required. The initiator used for the reaction is a thermally decomposable initiator selected from sodium, potassium or ammonium peroxodisulphate. The base emulsifier used in the reaction is sodium or potassium soap of rosin acid and is used up to 7.0 parts per hundred parts of monomer herein after referred as phm. The chain modifier is selected from primary, secondary or tertiary dodecyl mercaptan and is used up to 2 phm level. The polymeric tackifier disclosed herein provides optimized property combination when used with natural and some synthetic rubbers in terms of tensile strength, modulus at 300 % elongation, elongation at break, tear strength, heat build up and abrasion resistance. Conventional sulfur cure characteristic are also improved with compared to normally used tackifiers like coumarone-indene (CI), phenol formaldehyde (PF) resin tackifier. The subject invention also reveals the performance of the polymeric tackifier in styrene butadiene rubber and polybutadiene rubber. For determination of tack strength, rubber sheets of 2.5 + 0.05 mm thickness has been prepared by pressing the sheets in between smooth aluminum foil under 5 mPa pressure and 100 C temperature for two minutes in an electrically heated hydraulic press. One side of the rubber is backed by canvas cloth. Specimens of 146 mm x 25 mm size has been taken from the sheet so as to fit into the mould of the same width and 4 mm depth. Two such specimens has been kept one over the other on an aluminum foil of 25 mm length such that, rest portion of the rubber should be in contact with each other and then again pressed for 1 minute in the same press with a pressure of 5 mPa. Self-adhesion strength is measured by peel adhesion test and peel strength at 180 is also measured. From the molded sheets, narrow strips of 146 mm x 25 mm has been prepared. Just before the test, the aluminum foil is removed and the strips are allowed to come into intimate contact with each other quickly by pressing them in the hydraulic press under a pressure of 5 mPa and at temperature of 100 C. The test is carried out at a crosshead speed of 50 mm/minute. The tack strength (Ga) (N/mm) is calculated by using the formula; (Formula Removed) wherein, F= force of separation(N) and W= width of strips(mm) The rubber sheets has been prepared by the method described earlier and sheets of specified dimension has been taken out from the sheet and laid on a clean cellophane paper to avoid any contamination of the rubber surface. The cellophane film is removed just before molding. This test is performed by following BS 903 specification (part A 12). Specimens have been prepared in the same mould, which is used for self-adhesion tests. Canvas fabric of specified dimension (146mm x 25mm) has been placed inside the mould cavity along with an aluminum foil of 25 mm length to prevent bonding with the rubber matrix. The assembly is cured at 150 C in a hydraulic press. 180° peel test have been performed by using a universal testing machine at a crosshead speed of 50 mm/minute at room temperature. Adhesion of rubber matrix with nylon cord is determined using H-pull test by following the standard BS 903 (Part A48) specification. The samples have been prepared in a special mould with some weight attached to both the ends of the nylon cord to keep it in a stretched condition. The H-shaped samples (i.e. both ends of the cords are embedded in the rubber matrix) are then used for this test. The test has been performed by using a universal testing machine (Hounsfield) at a crosshead speed of 50 mm/minute. Four different samples have been tested and the mean values are reported as the maximum load in Newton (N) required for separation of embedded cord from the rubber matrix. In the present invention, the tensile strength has been determined by following ASTM D 412-1980 test method. The dumbbell shaped test pieces are prepared by using a C-type die along the mill grain direction of sheets. The thickness of the narrow portion of the specimen is measured by using a bench thickness gauge. The specimens have been tested in a universal testing machine at 25 ± 2 C at a crosshead speed of 500 mm/minute. The tear strength of the samples has been determined by following ASTM D 624-81 standard. Using un-nicked 90 angle test specimens has been punched out from the vulcanized sheets along the mill grain direction and tested in a universal testing machine at a crosshead speed of 500 mm/minute at room temperature. The tear strength values are reported in Newton/mm(N/mm). The abrasion resistance of the samples has been tested by using a Dupont abrader. In this apparatus, two test pieces, each having 4cm2 (2cmx2cm) surface area are simultaneously held against an abrasive paper disc, which rotates at a speed of 40 rpm. The normal load on the samples is 3.26 kg and the silicon carbide abrasive paper of grain size 320 is used. The samples have been abraded for 10 minutes after an initial conditioning period of 5 minutes. Separate abrasive discs are used for each sample. The abrasion loss of the samples then calculated and expressed as volume loss in cm3/hour. The heat build up of the samples has been tested by using Goodrich flexometer following ASTM D 623-67 (method A) specification. A cylindrical sample of 2.54 cm height and 1.95 cm diameter have been prepared. The stroke is adjusted to 0.445 cm and the load to 10.9 kg. The sample is pre-conditioned by keeping it at a temperature of 50°C in the oven for 20 minutes. The heat development at the base of the sample is sensed by a thermocouple and relayed to a digital temperature indicator. The temperature rise ( T) at the end of 20 minutes is recorded as the heat build-up. The cure characteristics of different compounds has been studied at 150 C using the chart motor of 30 minutes. The oscillation of the rotor is maintained at 3°. The optimum cure time (T%) of the compounds are calculated from the rheograph corresponding to a torque (M90). Table-1 illustrates comparative study of properties of filled and unfilled natural rubber using different dose of three different tackifier systems e.g. coumarone-indene tackifier, phenol formaldehyde tackifier and styrene butadiene vinyl pyridine based tackifier. Similar set of experiments using styrene butadiene rubber and polybutadiene rubber are conducted and tabulated in Table-2 and table-3. Further, the present invention is illustrated in greater detail by way of the following examples. The examples are given herein for illustration of the invention and are not intended to be limiting thereof. Example 1 Preparation of vinyl pyridine styrene butadiene polymer Vinyl pyridine styrene butadiene latex is prepared by conventional emulsion polymerization route. Initially a solution of dehydroabitic rosin acid in sodium or potassium hydroxide solution is prepared and aspirated to the pressure reactor fitted with a variable drive agitator. Desired dose of tertiary dodecyl mercaptan used as a chain modifier is also aspirated to the reactor followed by thermally decomposable initiator potassium peroxodisulphate. The three monomers styrene, 1,3 butadiene and 2-vinyl pyridine in the weight ratio of 5:75:20 are then aspirated into the reactor and the reactor temperature is then increased to 45°C and it is controlled in the range of 45-50 °C. After completion of feeding, the reactants are held for certain duration and the progress of reaction is monitored by measuring the non-volatile matter on a hourly basis. The reaction is continued until two constant solids are obtained. The total batch cycle time usually takes 22-30 hours. After completion of the reaction, the mass is cooled, filtered and the filtrate is coagulated with 2 % alum solution until a clear separation between solid and aqueous phase has occurred. Solid polymers are then filtered out and washed thoroughly with water till the pH of water is neutral and then it is dried at 100-120°C for four hours in a vacuum oven. The dry powders thus obtained are ready for use as tackifier. Example 2 Application of vinyl pyridine styrene butadiene polymer as tackifier Three experiments are conducted with three different tackifier, vinyl pyridine styrene butadiene polymer (exp.A), coumarone-indene (CI) resin (exp.B), phenol formaldehyde (PF) resin (exp.C) with the base polymer of styrene butadiene rubber, polybutadiene rubber and natural rubber as described in table-l,table-2 & table-3. The different unfilled and filled rubber compounds are prepared in a laboratory internal mixer. Out of three experiments exp.B and exp.C are considered as comparative controlled sample as they are very commonly used in tire industries. Various filled and unfilled rubber samples are prepared by keeping the amount of other ingredients constant and varying the tackifier. For each tackifier-elastomer combination, three sets of experiments are conducted with specified elastomer by varying the doses (e.g. 2,5,8 parts per hundred parts of rubber hereafter referred as phr). In the filled sample, the other ingredients used are carbon black (N 330)-30 phr, zinc oxide - 5 phr, stearic acid - 1.5 phr, antioxidant TQ - 1.0 phr, accelerator (CBS) - 1.2 phr, secondary accelerator (TMTD) - 0.2 phr and sulphur -2.1 phr. Certain modifications and improvements of the disclosed invention will occur to those skilled in the art without departing from the scope of invention, which is limited only by the appended claims. Table 1 (Table Removed) We Claim: 1. A novel polymeric tackifier, wherein the tackifier consists of a coagulated emulsion polymer in dry solid particulate form comprising a mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier. 2. The tackifier according to claim 1, wherein the mixture of monomers consists of straight chain or branched chain aliphatic or aromatic compounds with or without heteroatom. 3. The tackifier according to claim 1, wherein the mixture of monomers consists of a vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine. 4. The tackifier according to claim 3, wherein ratio of vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine varies from 2:68:30 to 15:70:15. 5. The tackifier according to claim 3, wherein said vinyl benzene derivative is selected from the group consisting of styrene, alpha-methyl styrene, para-methyl styrene, vinyl toluene or any combination thereof. 6. The tackifier according to claim 1, wherein said initiator is selected from any of the group consisting of sodium, potassium or ammonium peroxodisulphate. 7. The tackifier according to claim 1, wherein said chain modifier is selected from primary, secondary or tertiary dodecyl mercaptan. 8. The tackifier according to claim 7, wherein said dodecyl marcaptan is used in the range of 0.5-3.0 phm. 9. The tackifier according to claim 1, wherein said emulsifier is a salt of rosin acid soap. 10. The tackifier according to claim 9, wherein said salt of rosin acid soap is used in the range of 1.0 to 7.0 phm. 11. A process for preparing polymeric tackifier comprising employing emulsion polymerization followed by coagulation and drying using a system comprising mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier, wherein said polymeric tackifier consists of a coagulated emulsion polymer in dry solid particulate form. 12. The process according to claim 11, wherein the coagulation is carried out in the presence of an alum. 13. The process according to claim 12, wherein the alum is used in the range of 0.1-2 phm. 14. The process according to claim 11, wherein the drying is carried out at a temperature range of 100-120°C. 15. A novel polymeric tackifier as substantially herein described with reference to the examples.

Full Text

Field of the Invention
This invention, in general, relates to the field of tackifiers and in particular to a novel polymeric tackifier. More specifically, but without restriction to the preferred embodiments hereinafter described in accordance with the best mode of practice, the present invention provides a coagulated emulsion polymer in dry solid particulate form suitable as a tackifier in synthetic rubbers and natural rubber compounding process.
Background of the Invention
Tackifiers are generally used to impart or enhance surface tack properties and find widespread application in diverse fields e.g. in hot melt adhesive (HMA), pressure sensitive adhesive (PSA), lamination adhesive and variety of rubber compounds etc. In elastomeric compositions, such tackifiers are used to enhance or control various physical and mechanical properties such as stiffness and tack. It also improves adhesion and sometimes cohesion without excessive stiffening or softening of elastomeric composition and prevents bleeding or blooming of the additives to the surface of the elastomeric compounds.
US patent no. 3,970,623 issued to Feeney et al. on July 20,1976 reveals an adhesive composition comprising of an admixture of 100 parts by wt. of the copolymer of butadiene (92-97%), styrene (3-8%) and acrylonitrile (1-4%) with 50-150 parts by weight of a tackifier based on rosin ester and diolefin or olefin coplymers containing about 5-35 wt % of aromatic units prepared through the emulsion polymerization with the help of a primary and tertiary mercaptan as chain modifier.
US patent no. 4,038,346 issued to Feeney on July 26,1977 discloses a tackifying resin composition prepared by mixing about 75-98% of tackifying resin having softening point in the range of 80-130°C with about 2-25% oily polymer having a boiling point of 190-250°C. The tackifying resin is prepared by step wise method of polymerizing at a temperature range of about 0-50°C in presence of the catalyst selected from aluminum chloride, ethyl aluminum dichloride, a monomer mixture of 20-80% of piperylene and 80-20% of a monoolefin containing 4-6 carbon atoms comprised of at least one olefin selected from the group consisting of 2-methyl-2-butene, 2-methyl-l-butene, 2-methyl-
1-pentene, 2-methyl-2-butene and 0-30%of a monomer selected from dicyclopentadiene and a-methyl styrene. The adhesive composition is prepared by mixing the copolymer and tackifier in presence of a hydrocarbon solvent. The composition finds application in pressure sensitive adhesives and hot melt adhesives.
US patent no. 4,073,776 issued to Galkiewicz et al. on February 14,1978 discloses the reaction product of oxirane bearing materials with alkyl phenol novolacs. These reaction products act as excellent tackifiers for various synthetic and natural rubbers requiring good green tack. Generally oxirane-bearing materials contains an epoxy group and is based on glycidyl ethers, glycidyl esters, aliphatic oxiranes, cycloaliphatic oxiranes etc. These oxirane bearing materials reacts with alkyl phenol novolacs, wherein the alkyl group of the alkyl phenol novolacs contains 4-16 carbon atoms. This invention is directed to tackifiers utilized as tire stock tackifiers, cement tackifiers etc. When compounded with elastomers, this tackifier can comprise 0.5-20 parts per hundred parts of rubber (phr). In carcass compounds, it is used about 3-12 phr.
US patent no. 4,130,701 issued to Lepert on December 19,1978 reveals the preparation of a suitable tackifier resin which is prepared by polymerization using a Friedel-Crafts catalyst, a petroleum resin feed comprising C5 olefins and diolefins, C6 olefins and diolefins or a mixture of above. The feed is obtained from cracking of petroleum feedstock and an additive, comprising a nonaromatic cyclic compound selected from vinyl norbornene or tetrahydroindene. These resins exhibits better compatibility with thermoplastic elastomers such as styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS) block copolymers and are mainly used in pressure sensitive adhesives or hot melt adhesives. These resins are successfully used as tackifiers in carpet backing, hot melts, book binding, paper sizing with natural rubber and synthetic rubbers like polyisoprene, ethylene propylene diene (EPDM), butyl, chlorobutyl, bromobutyl, neoprene rubber and also with SIS block copolymers.
US patent no. 4,157,319 issued to Feeney et al. on June 5,1979 reveals an adhesive composition comprising of a rubbery copolymer of butadiene, styrene and acrylonitrile in combination with a tackifier. A pressure sensitive adhesive composition, which
comprises an admixture of 100 parts by weight of the above rubbery copolymer and about 50-150 parts by weight of tackifying resin. The adhesive composition is prepared by mixing the copolymer and the tackifier in the presence of at least one solvent selected from toluene, benzene, xylene, pentane, hexane, heptane and octane, wherein the tackifier resin is selected from fully hydrogenated rosin esters and from diolefin or olefin copolymers prepared by polymerization of a mixture comprising piperylene, olefins selected primarily from 2-methyl-l-butene and 2-methyl-2-butene and at least one monomer selected from styrene and a-methyl styrene and about 0-10% dicyclopentadiene in the presence of aluminum chloride.
US patent no. 4,230,842 issued to Bullard et al. on October 28,1980 reveals the preparation of a hydrocarbon based tackifier specifically to be applied with SIS block copolymer. This diolefin or olefin backbone resin is prepared, by reacting in the presence of an aliphatic hydrocarbon solvent and a selected catalyst, a monomer mixture comprised primarily of a diolefin/olefin mixture of the piperylene/olefin type and about 2-12% alpha-methyl styrene. The product is characterized with a softening point of 85-100°C and is prepared by the method which consists essentially of reacting at a temperature range of 10-50°C in presence of a solvent e.g. hexane or heptane and a catalyst selected from aluminum chloride or ethyl aluminum dichloride.
US patent no. 4,324,710 issued to Davis et al. on April 13,1982 reveals a thermoplastic resin used as a substitute of process oils or hydrocarbon resins as well as tackifiers, softeners, extenders, processing aids and cure retarders. This is basically a crude wood rosin of high melting point having carboxylic acid groups and is insoluble in aliphatic hydrocarbons. The above-mentioned thermoplastic resin contains a major phenolic fraction, a neutral fraction and a minor rosin derived fraction. The phenolic resin fraction is derived as phlobaphenes, carboxylated phlobaphenes, substituted stilbenes, lignan hydroxy lactones, neutral fraction includes a wax, polymerized terpenes and the rosin derived fraction includes resin acids and polymerized resin acids.
US patent no. 4,968,740 issued to Makati et al. on November 6,1990 discloses a latex based adhesive prepared by emulsion polymerization process. The adhesive consists of
two components, an adhesive part prepared from at least one hard monomer, one soft monomer and optionally a copolymerizable carboxylic acid monomer having glass transition temperature (Tg) of -70 to -5°C and tackifier part compatible with adhesive having a number average molecular weight (M„) less than 5000 and Tg of -10 to 50°C. Both the adhesive and tackifier part is synthesized separately by emulsion polymerization process. The adhesive comprises of 20-95% of the latex and tackifier comprises 5-80% of the latex based on dry weight. Both the adhesive and tackifier components comprise interpolymers of styrene, butadiene and itaconic acid.
US patent no. 6,710,147 issued to Cottman on March 24,2004 discloses that the reactivity of the most important monomers commonly used in synthesizing tackifier resins with aluminum halide catalysts can be enhanced by conducting the polymerization in the presence of an allylic halide. Increased monomer conversion is of great commercial importance because it leads to an increased level of efficiency and reactor capacity. This invention discloses a process for synthesizing a tackifier resin by polymerization of an unsaturated hydrocarbon monomer mixture in presence of aluminum halide and an allylic halide, wherein the unsaturated hydrocarbon monomer mixture is comprised of unsaturated hyrdocarbon monomers containing from about 4 to about 18 carbon atoms, and wherein the said process is conducted in the absence of tantalum compounds.
Previously used tackifiers for rubber include hydrocarbon resins, coumarone-indene resins, polyterpenes, phenol formaldehyde resins etc. Hydrocarbon tackifiers provide good initial tack but low long term tack while the phenolic tackifiers provide good initial and long term tack but are relatively expensive. Some of these tackifiers also do not provide sufficient tack in certain rubbers e.g. in styrene butadiene rubber (SBR) and polybutadiene rubber, unless high levels are used which adversely affects the physical properties of the rubbers.
Further, during manufacturing of molded goods like pneumatic tires, inner tubes, belts, hoses, rubberized fabrics and rolls etc., it is very important to have a good green strength for assembling different components together without bleeding and blooming
of various ingredients from the cured and uncured material. Mostly petroleum based resins and wood rosins are used for this purpose. Due to the resinous and viscous nature, these resins cause various processing problem during handling. For instance, quite often the stock sticks to the roll during mixing and sometimes due to compatibility problems it causes bleeding and leaches out on to the surface. Being a natural product, natural rubber possesses good tack property and bond strength; however, inherited properties of natural rubber alone are often inadequate for many applications, while on the other hand synthetic rubbers have relatively lower tack. Hence tackifiers in the form of resins are added to the system to increase the tack and adhesion during compounding.
Therefore, there is a need to develop a novel tackifier to improve upon the limitations in the prior art for the application in rubber compounding.
Accordingly, the present invention provides a novel polymeric tackifier, which is coagulated emulsion polymer in dry solid particulate form suitable as a tackifier in synthetic rubbers and natural rubber compounding process.
Summary of the Invention
In accordance with the principal aspect of the present invention, there is provided a novel polymeric tackifier, wherein the said tackifier consists of a coagulated emulsion polymer in dry solid particulate form, suitable for use in rubber compounding.
In accordance with another aspect of the invention, there is provided a novel polymeric tackifier, wherein the said tackifier consists of a coagulated emulsion polymer in dry solid particulate form comprising a mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier.
In accordance with one other aspect of the invention, there is provided a process for preparation of polymeric tackifier, wherein the process comprising employing emulsion polymerization followed by coagulation and drying using a system comprising mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier.
In accordance with yet another aspect of the invention, there is provided a process for preparation of polymeric tackifier, wherein this process comprises employing emulsion polymerization followed by coagulation and drying using a system comprising vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine as monomers, rosin acid soap as base emulsifier and tertiary dodecyl mercaptan as a chain modifier along with other ingredients.
In accordance with a further aspect of the present invention, an application of the said polymeric tackifier is provided, wherein said polymeric tackifier is used with natural rubber and various synthetic rubbers like styrene butadiene rubber, polybutadiene rubber etc.
Detailed Description of the Invention The present invention provides a novel polymeric tackifier and its application in conventional rubber compounding. It also describes the process for preparation of the polymeric tackifier.
Tackifiers are mainly used to impart and improve the surface tack properties of the base polymer and also to improve cohesion without excess stiffening, softening of the polymer and bleeding & blooming of various other compounding ingredients to the surface of the finished product.
Tackifier resins are mainly classified into two major groups. These are rosin resin and its derivatives and hydrocarbon resins. The rosin resins, as the name implies, consists of rosins, hydrogenated rosins and their various derivatives such as esters while the hydrocarbon resin group consists of polyterpenes, synthetic hydrocarbon resin, and a collection of modified or special resins primarily phenolics. Besides these resins, some low molecular weight polymers are also used to improve the tack property, which are known as polymeric tackifier.
In the present invention a polymeric tackifier is synthesized via emulsion polymerization route, which is not only ecofriendly insofar as in avoidance of solvent
use but also avoids the hazards of solution polymerization. Full conversion of monomers without any undesirable by-product formation yields the maximum output as well makes the process most cost effective. Due to the presence of styrene butadiene backbone in the tackifier, the molecular level compatibility of the tackifier with styrene butadiene and polybutadiene rubber increases and in turn enhances various physicomechanical properties that generally does not occur with petroleum based or natural rosin based tackifiers.
The polymerization process disclosed herein is extended and the resultant latex obtained from the process is further coagulated and dried. This dried latex is used as a tackifier with natural rubber and also with various synthetic rubbers like styrene butadiene rubber, polybutadiene rubber etc., which requires a good green tack without sacrificing its virgin mechanical and physical properties.
The polymeric tackifier disclosed herein comprising vinyl benzene derivative, 1,3 butadiene and 2- vinyl pyridine as monomers, rosin acid soap as base emulsifier and tertiary dodecyl mercaptan as a chain modifier along with other ingredients. It is prepared via emulsion polymerization route and the ratio of the monomers e.g. vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine varied from 2:68:30 to 15:70:15. The vinyl benzene derivative is selected from a class comprising of styrene, a-methyl styrene, para-methyl styrene and vinyl toluene. The reaction is controlled in the temperature range of 45-70°C during different stages of polymerization and a time span of 3-30 hours is required. The initiator used for the reaction is a thermally decomposable initiator selected from sodium, potassium or ammonium peroxodisulphate. The base emulsifier used in the reaction is sodium or potassium soap of rosin acid and is used up to 7.0 parts per hundred parts of monomer herein after referred as phm. The chain modifier is selected from primary, secondary or tertiary dodecyl mercaptan and is used up to 2 phm level.
The polymeric tackifier disclosed herein provides optimized property combination when used with natural and some synthetic rubbers in terms of tensile strength, modulus at 300 % elongation, elongation at break, tear strength, heat build up and
abrasion resistance. Conventional sulfur cure characteristic are also improved with compared to normally used tackifiers like coumarone-indene (CI), phenol formaldehyde (PF) resin tackifier. The subject invention also reveals the performance of the polymeric tackifier in styrene butadiene rubber and polybutadiene rubber.
For determination of tack strength, rubber sheets of 2.5 + 0.05 mm thickness has been prepared by pressing the sheets in between smooth aluminum foil under 5 mPa pressure and 100 C temperature for two minutes in an electrically heated hydraulic press. One side of the rubber is backed by canvas cloth. Specimens of 146 mm x 25 mm size has been taken from the sheet so as to fit into the mould of the same width and 4 mm depth. Two such specimens has been kept one over the other on an aluminum foil of 25 mm length such that, rest portion of the rubber should be in contact with each other and then again pressed for 1 minute in the same press with a pressure of 5 mPa. Self-adhesion strength is measured by peel adhesion test and peel strength at 180 is also measured. From the molded sheets, narrow strips of 146 mm x 25 mm has been prepared. Just before the test, the aluminum foil is removed and the strips are allowed to come into intimate contact with each other quickly by pressing them in the hydraulic press under a pressure of 5 mPa and at temperature of 100 C. The test is carried out at a crosshead speed of 50 mm/minute. The tack strength (Ga) (N/mm) is calculated by using the formula;
(Formula Removed)
wherein, F= force of separation(N) and W= width of strips(mm) The rubber sheets has been prepared by the method described earlier and sheets of specified dimension has been taken out from the sheet and laid on a clean cellophane paper to avoid any contamination of the rubber surface. The cellophane film is removed just before molding. This test is performed by following BS 903 specification (part A 12). Specimens have been prepared in the same mould, which is used for self-adhesion tests. Canvas fabric of specified dimension (146mm x 25mm) has been placed inside the mould cavity along with an aluminum foil of 25 mm length to prevent bonding with the rubber matrix. The assembly is cured at 150 C in a hydraulic press. 180° peel test
have been performed by using a universal testing machine at a crosshead speed of 50 mm/minute at room temperature.
Adhesion of rubber matrix with nylon cord is determined using H-pull test by following the standard BS 903 (Part A48) specification. The samples have been prepared in a special mould with some weight attached to both the ends of the nylon cord to keep it in a stretched condition. The H-shaped samples (i.e. both ends of the cords are embedded in the rubber matrix) are then used for this test. The test has been performed by using a universal testing machine (Hounsfield) at a crosshead speed of 50 mm/minute. Four different samples have been tested and the mean values are reported as the maximum load in Newton (N) required for separation of embedded cord from the rubber matrix.
In the present invention, the tensile strength has been determined by following ASTM D 412-1980 test method. The dumbbell shaped test pieces are prepared by using a C-type die along the mill grain direction of sheets. The thickness of the narrow portion of the specimen is measured by using a bench thickness gauge. The specimens have been tested in a universal testing machine at 25 ± 2 C at a crosshead speed of 500 mm/minute.
The tear strength of the samples has been determined by following ASTM D 624-81 standard. Using un-nicked 90 angle test specimens has been punched out from the vulcanized sheets along the mill grain direction and tested in a universal testing machine at a crosshead speed of 500 mm/minute at room temperature. The tear strength values are reported in Newton/mm(N/mm).
The abrasion resistance of the samples has been tested by using a Dupont abrader. In this apparatus, two test pieces, each having 4cm2 (2cmx2cm) surface area are simultaneously held against an abrasive paper disc, which rotates at a speed of 40 rpm. The normal load on the samples is 3.26 kg and the silicon carbide abrasive paper of grain size 320 is used. The samples have been abraded for 10 minutes after an initial
conditioning period of 5 minutes. Separate abrasive discs are used for each sample. The abrasion loss of the samples then calculated and expressed as volume loss in cm3/hour.
The heat build up of the samples has been tested by using Goodrich flexometer following ASTM D 623-67 (method A) specification. A cylindrical sample of 2.54 cm height and 1.95 cm diameter have been prepared. The stroke is adjusted to 0.445 cm and the load to 10.9 kg. The sample is pre-conditioned by keeping it at a temperature of 50°C in the oven for 20 minutes. The heat development at the base of the sample is sensed by a thermocouple and relayed to a digital temperature indicator. The temperature rise ( T) at the end of 20 minutes is recorded as the heat build-up.
The cure characteristics of different compounds has been studied at 150 C using the chart motor of 30 minutes. The oscillation of the rotor is maintained at 3°. The optimum cure time (T%) of the compounds are calculated from the rheograph corresponding to a torque (M90).
Table-1 illustrates comparative study of properties of filled and unfilled natural rubber using different dose of three different tackifier systems e.g. coumarone-indene tackifier, phenol formaldehyde tackifier and styrene butadiene vinyl pyridine based tackifier. Similar set of experiments using styrene butadiene rubber and polybutadiene rubber are conducted and tabulated in Table-2 and table-3.
Further, the present invention is illustrated in greater detail by way of the following examples. The examples are given herein for illustration of the invention and are not intended to be limiting thereof.
Example 1
Preparation of vinyl pyridine styrene butadiene polymer
Vinyl pyridine styrene butadiene latex is prepared by conventional emulsion polymerization route. Initially a solution of dehydroabitic rosin acid in sodium or potassium hydroxide solution is prepared and aspirated to the pressure reactor fitted with a variable drive agitator. Desired dose of tertiary dodecyl mercaptan used as a
chain modifier is also aspirated to the reactor followed by thermally decomposable initiator potassium peroxodisulphate. The three monomers styrene, 1,3 butadiene and 2-vinyl pyridine in the weight ratio of 5:75:20 are then aspirated into the reactor and the reactor temperature is then increased to 45°C and it is controlled in the range of 45-50 °C. After completion of feeding, the reactants are held for certain duration and the progress of reaction is monitored by measuring the non-volatile matter on a hourly basis. The reaction is continued until two constant solids are obtained. The total batch cycle time usually takes 22-30 hours. After completion of the reaction, the mass is cooled, filtered and the filtrate is coagulated with 2 % alum solution until a clear separation between solid and aqueous phase has occurred. Solid polymers are then filtered out and washed thoroughly with water till the pH of water is neutral and then it is dried at 100-120°C for four hours in a vacuum oven. The dry powders thus obtained are ready for use as tackifier.
Example 2
Application of vinyl pyridine styrene butadiene polymer as tackifier Three experiments are conducted with three different tackifier, vinyl pyridine styrene butadiene polymer (exp.A), coumarone-indene (CI) resin (exp.B), phenol formaldehyde (PF) resin (exp.C) with the base polymer of styrene butadiene rubber, polybutadiene rubber and natural rubber as described in table-l,table-2 & table-3. The different unfilled and filled rubber compounds are prepared in a laboratory internal mixer. Out of three experiments exp.B and exp.C are considered as comparative controlled sample as they are very commonly used in tire industries. Various filled and unfilled rubber samples are prepared by keeping the amount of other ingredients constant and varying the tackifier. For each tackifier-elastomer combination, three sets of experiments are conducted with specified elastomer by varying the doses (e.g. 2,5,8 parts per hundred parts of rubber hereafter referred as phr).
In the filled sample, the other ingredients used are carbon black (N 330)-30 phr, zinc oxide - 5 phr, stearic acid - 1.5 phr, antioxidant TQ - 1.0 phr, accelerator (CBS) - 1.2 phr, secondary accelerator (TMTD) - 0.2 phr and sulphur -2.1 phr.
Certain modifications and improvements of the disclosed invention will occur to those skilled in the art without departing from the scope of invention, which is limited only by the appended claims.
Table 1
(Table Removed)

We Claim:
1. A novel polymeric tackifier, wherein the tackifier consists of a coagulated emulsion polymer in dry solid particulate form comprising a mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier.
2. The tackifier according to claim 1, wherein the mixture of monomers consists of straight chain or branched chain aliphatic or aromatic compounds with or without heteroatom.
3. The tackifier according to claim 1, wherein the mixture of monomers consists of a vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine.
4. The tackifier according to claim 3, wherein ratio of vinyl benzene derivative, 1,3 butadiene and 2-vinyl pyridine varies from 2:68:30 to 15:70:15.
5. The tackifier according to claim 3, wherein said vinyl benzene derivative is selected from the group consisting of styrene, alpha-methyl styrene, para-methyl styrene, vinyl toluene or any combination thereof.
6. The tackifier according to claim 1, wherein said initiator is selected from any of the group consisting of sodium, potassium or ammonium peroxodisulphate.
7. The tackifier according to claim 1, wherein said chain modifier is selected from primary, secondary or tertiary dodecyl mercaptan.
8. The tackifier according to claim 7, wherein said dodecyl marcaptan is used in the range of 0.5-3.0 phm.
9. The tackifier according to claim 1, wherein said emulsifier is a salt of rosin acid soap.
10. The tackifier according to claim 9, wherein said salt of rosin acid soap is used in the range of 1.0 to 7.0 phm.
11. A process for preparing polymeric tackifier comprising employing emulsion polymerization followed by coagulation and drying using a system comprising mixture of monomers having 4-9 carbon atoms, an initiator, a chain modifier and an emulsifier,
wherein said polymeric tackifier consists of a coagulated emulsion polymer in dry solid particulate form.
12. The process according to claim 11, wherein the coagulation is carried out in the presence of an alum.
13. The process according to claim 12, wherein the alum is used in the range of 0.1-2 phm.
14. The process according to claim 11, wherein the drying is carried out at a temperature range of 100-120°C.
15. A novel polymeric tackifier as substantially herein described with
reference to the examples.

Documents:

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Patent Number

270335

Indian Patent Application Number

901/DEL/2005

PG Journal Number

51/2015

Publication Date

18-Dec-2015

Grant Date

12-Dec-2015

Date of Filing

07-Apr-2005

Name of Patentee

JUBILANT ORGANOSTS LIMITED

Applicant Address

PLOT 1A, SECTOR 16 A, NOIDA-201 301, UP, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SANTRA, RABIN	BLOCK 133, VILLAGE: SAMLAYA, TALUKA: SAVLI, VADODARA-391520, INDIA
2	MOHANTY, SUBHRA	BLOCK 133, VILLAGE: SAMLAYA, TALUKA: SAVLI, VADODARA-391520, INDIA

PCT International Classification Number

C09J 201/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA