Title of Invention	A PROCESS FOR THE PREPARATION OF REPROCESSABLE, REUSABLE AND REVULCANIZABLE RUBBER COMPOSITIONS FROM WASTE/USED AND VIRGIN RUBBER VULCANIZATES
Abstract	The present invention relates to a process for the preparation or reprocessable, reusable and revulcanizable rubber compositions from waste/used and virgin rubber Vulcani/ates. The present invention particularly relatres to a processes for the preparation of reqprocessable, revulcanizable and reusable rubber compositions from waste/used and virgin rubber vulcanizates by modification with oligomeric resins of renewable natural resources.The novelty of our invention is that either waste/used tire tread rubber or virgin rubber on mixing with 5 to 10% of oligomers such as PCNSL at 160-180°C in a Brabender Plasticorder at a rotor speed of 20-40 rpm for 20-60 min gives compostions which are easily processable and revulcanizsable with conventional curatives at 140 160°C at cure time ranging from 5-20 minutes.

Title of Invention

A PROCESS FOR THE PREPARATION OF REPROCESSABLE, REUSABLE AND REVULCANIZABLE RUBBER COMPOSITIONS FROM WASTE/USED AND VIRGIN RUBBER VULCANIZATES

Abstract

The present invention relates to a process for the preparation or reprocessable, reusable and revulcanizable rubber compositions from waste/used and virgin rubber Vulcani/ates. The present invention particularly relatres to a processes for the preparation of reqprocessable, revulcanizable and reusable rubber compositions from waste/used and virgin rubber vulcanizates by modification with oligomeric resins of renewable natural resources.The novelty of our invention is that either waste/used tire tread rubber or virgin rubber on mixing with 5 to 10% of oligomers such as PCNSL at 160-180°C in a Brabender Plasticorder at a rotor speed of 20-40 rpm for 20-60 min gives compostions which are easily processable and revulcanizsable with conventional curatives at 140 160°C at cure time ranging from 5-20 minutes.

Full Text	The present invention relates to a process for the preparation of reprocessable, reusable and revulcanizable rubber compositions from waste/used and virgin rubber Vulcanizates. The present invention particularly relates to a processes for the preparation of reprocessable, revulcanizable and reusable rubber compositions from waste/used and virgin rubber vulcanizates by modification with oligomeric resins of renewable natural resources./- The disposal of defective and used rubber products poses a major threat to the environment globally and is a matter of great concern. At present, the US generates 270 million scrap tires annually (1) ((1). M.H. Blumenthal, History and status of scrap tire management in the US, Muanyag Gumi, 36(6) 177 (1999) (Hung.)). The various options for recycling rubber such as (i) fuel source, (ii) pyrolysis, (iii) depolymerized scrap rubber (iv) in asphalt, (v) reclaiming, (vi) tire retreading, (vii) grinding and (viii) other uses has been dealt with in a review by John Paul (2) ((2). John Paul in Kirk-Othmer Encyclopedia of Chemical Technology, vol. 19, 3rd edn., (Eds.) H.F. Mark, D.F. Othmer, C.G. Overberger and G.T. Seaborg, John Wiley & Sons Inc., New York, 1982, pp 1002 -1010. Three major markets for scrap tires are (1) tire derived fuel (2) products and (3) civil engineering applications. Pyrolysis of waste rubber has been considered as an emerging, potential technology for the recovery of value added energy, fuel and chemicals in addition to its capability for solving at least in part the environmental threat mentioned above (3"4) ((3). M.J. Kawser and N.A. Farid, Plastics Rubber and Composites, 29(2), 100 (2000); (4). M.J. Kawser and N.A. Farid, Plastics Rubber and Composites, 29(8), 427 (2000)). The manufacture of new products from used tires and the use of scrap tires for civil engineering applications are technically and economically viable options, keeping into consideration the cleanliness of the environment. A number of patents, publications and research reports are coming out on reclaiming and reuse of vulcanized rubber thrown out as scrap rubber. In an exhaustive review Schnecko has summarized the present situation on elastomer recycling with emphasis on tires (5) ((5).H. Schnecko, Rubber Recycling, Macromol. Symp. 135, 327 (1998)). He has specified the various areas and possibilities of recycling, viz., reduction, reuse (retreading), rubber crumb manufacture and use, reclaim, recovery ie. Pyrolysis, hydrogenation and conversion to energy, apart from landfills and biodegradation. Another recent review by Elias and Spirk^ describes various methods for devulcanization of cured rubber ((6) O. Elias and E. Spirk, Recycling of cured rubber - methods of modification of rubber scrap, Polym. RecycL, 4(1) 27 (1999)). This includes the use of mechanical stress, partial dissolution, chemical, flame, ultrasound, microwave and micro-organisms. Use of a variety of proprietory additives as devulcanization agents (eg. Delink) is also reported (6"9)( (7).U.S.Ishiaku, C.S.Chong and H.Ismail, Cure characteristics and vulcanizate properties of blends of a rubber compound and its recycled DE-VULC, Polymers & polymer Composites, 6(6), 399 (1998),(8).R. Singleton, Ground vulcanized rubber and reclaimed rubber, in 'Rubber Technology and Manufacture1 , 2nd Edn., C.M. Blow and C.Hepburn (Eds.), Butterworth Scientific, London, 1982, pp 237-243.,(9). E.F.Sverdrup and B.R.Wendrow, Rubber Reclaiming, in 'Encyclopedia of Polymer Science and Technology', Vol. 12, Interscience Pub., New York, 1970, pp 341-355). A recent patent describes a recycling technique for tires as well as various other mechanical rubber products (10) ((10) E.V. Danschikov, I.N. Luchnik, A.V. Ryazanov, S.V. Chuiko and V.D. Feldman, Rubber waste surface modified with oxygen containing groups and a method for manufacturing of composite materials, PCT Int. Appl. WO 00 09, 598 (Cl. C 08J11/04) 24 Feb 2000). This invention relates to composite materials obtained from recycled rubbers. The modified rubber is obtained from a ground vulcanizate by treatment with ozone and subsequent chemical modification of the surface. The surface of the modified rubber particles is enriched with O- containing functional groups, such as carboxy, hydroxy, carbonyl and peroxy groups which are obtained from the original material. Surface layer of particles is depolymerized and contains monomers, oligomers and adsorbed active O. The modified rubber vulcanizate powder and binder are mixed to obtain a homogeneous mixture which then is molded and vulcanized. Recycling of waste tires to produce high valued products without producing secondary pollutants involves producing of crumb rubber by grinding the tires (11)((11) S.G. Kim, D.H.Shin, D.C.Kim, S.H.Chung and O.C.Kwon, Recycling technology of crumb rubber produced from waste tire, Chawon Rissaikuring, 8(1) 3 (1999) (Korean)). To maximize crumb rubber utilization, research was carried out to investigate domestic and foreign crumb rubber production and utilization technologies and the properties of rubber compounds prepared using crumb rubber was evaluated. Sulfur vulcanized rubbers are reclaimed by mixing with nucleophilic agents and heating in supercritical COa in CO: atmosphere (12)((12). H. Mizoshima, K.Ogawa and K.Todo, Reclaiming of vulcanized rubbers using nucleophilic agents, Jpn. Kokai Tokkyo Koho JP 2000, 95 895 (C1.C08 Jll/28), 4 Apr 2000 ( Japan)). Thus, mixing vulcanized isoprene rubber (IR 2000) with 6.4 phr thiophenol in autoclave, filling the autoclave with COa under pressure, heating at 180°C for 60 min and feeding supercritical CO2 continuously for 60 min gave reclaimed rubber containing 45% sol fraction with no. av.mol.wt. 35000. A method for the regeneration of rubbers from production wastes and tires has been patented (13)((13). I.F. Runcan et. al., Rom. RO 108,568 (Cl. COS Jll/18), 30 June, 1994 (Rom)). Some of the recent patents describe procedures for the manufacture of rubber materials having excellent mechanical properties from recycled rubbers (14'15)((14). Y. Ichiba, Manufacture of rubber materials from recycled rubbers, Jpn. Kokai Tokkyo Koho JP 10310, 661 (C1.C08 Jll/04), 24 Nov. 1998 ( Japan). (15).Y. Ichiba, Manufacture of rubber materials from rubber wastes, Jpn. Kokai Tokkyo Koho JP 10316, 766(98316.766), 15 May. 1997 ( Japan)). Kim has reported a cost effective method of recycling used automobile tires (16)((16). J.K. Kim, Utilization of recycled crumb rubber as a compounding tool, Int. Polym. Process, 13(4), 358 (1998)). Other patents report methods for using granulated tire waste for making shaped products(17) and composites tl8)((17). J. Kozakiewicz et. al., Pol. PL 175,891 (C1.C08 Jll/04), 31 Mar. 1999 (Pol.). (18). T.Shinkura, Bridgestone Sports Co. Ltd., Japan, JP 2000 191,838, 11 Jul. 2000). A few innovative and novel techniques for the devulcanization of rubbers have also been reported recently09'20^ 19) M.Mauri, N. Sato, H.Okamoto, M. Matsushita, K.Fukumori, K.Takeuchi, N.Suzuki and M.Owaki, Nippon Gomu Kyo Kaishi, 73(3), 138 (2000). (20). D.L.Wertz and C.D.Deaton, Improved WOMBAT method for processing scrap tires into useful materials, Prepr. Symp. Am. Chem. Soc. Div. Fuel Chem., 45(3) 458 (2000)). One of these involves continuous devulcanisation of rubber by shear flow stage reaction control technology (I9). The other one involves a sequence of redox reactions which degrades a tire into four recoverable component parts such as steel, rubber backings, fibers and particulates(20). An overview of the works carried out so far on reclaiming and recycling of waste rubber products as outlined above clearly indicates that most of the procedures involve either expensive processing routes, conditions or chemicals. Considering the colossal nature of the environmental problem posed by rubber wastes, it is of utmost importance to develop environmentally friendly processes for reclaiming/recycling of used rubber products. In this respect, if the reclaimed rubber made out of such a process can be used for the manufacture of second generation rubber products, the twin objectives of cost effective utilization of otherwise expensive resources and solution of a grave environmental problem can be met. Recently, it has been reported that additives based on renewable natural resources can be used as reclaiming agents for vulcanized rubber(21"24 )((21). D.De, B.Adhikari and S.Maiti , Reclaiming of rubber by a renewable resource material. Part -I. Reclaiming of NR vulcanizates, J. Polym.Mater., 14(4), 333 (1997).(22). D.De, S.Maiti and B.Adhikari, Reclaiming of rubber by a renewable resource material (RRM) -II. Comparative evaluation of reclaiming process of NR vulcanizate by RRM and diallyl disulfide, J.Appl.Polym.Sci., 73 (14), 2951 (1999).(23). D.De, S.Maiti and B.Adhikari, Reclaiming of rubber by a renewable resource material (RRM) -HI. Evaluation of properties of NR reclaim, J.Appl.Polym.Sci., 75 (12), 1493 (2000).(24) D.De, S.Maiti and B.Adhikari, Reclaiming of rubber by a renewable resource material. Assessment of vulcanized SBR reclaiming process, Kauts. Gummi Kunsts., 53(6), 346 (2000)). Since these are based on renewable natural resources, it may be possible that a reclaiming technology based on such materials can be made cost effective as well. Recently, the use of oligomeric resins for physical and/or chemical modification of polymers has been resorted to with considerable interest. This is mainly because of the multifunctional nature of such additives in improving the processability of the base polymer and imparting a host of desirable properties to the final products based on such compositions. Phosphorylated Cashew Nut Shell Liquid (PCNSL) prepolymer - a derivative of Cashew Nut Shell Liquid is one such material, on which considerable information with application potential has been generated by extensive work carried out recently characteristics of natural rubber modified with a bromo derivative of phosphorylated cashew nut shell liquid, J.Fire Sci,, 15(1), 3 (1997).(31). A.R.R.Menon, Stress-relaxation characteristics of natural rubber modified with phosphorylated cashew nut shell liquid prepolymer, J.Appl.Polym.ScL, 65(11), 2183 (1997).(32). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Modification of natural rubber with phosphatic plasticizers - a comparison of phosphorylated cashew nut shell liquid prepolymer with 2-ethyl hexyl diphenyl phosphate, Eur. Polym. J., 34 (7), 923 (1998). (33). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Vulcanization of natural rubber modified with cashew nut shell liquid and its phosphorylated derivative - a comparative study, Polymer, 39(17), 4033 (1998). (34). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Physicomechanical properties of filled natural rubber vulcanizates modified with phosphorylated cashew nut shell liquid, J. Appl. Polym. Sci., 68(8), 1303(1998). (35). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Cure characteristics and physicomechanical properties of natural rubber modified with phosphorylated cashew nut shell liquid prepolymer - a comparison with aromatic oil, J. Appl. Polym. Sci., 73, 813 (1999).(36). A.R.R.Menon, Melt rheology of Natural Rubber modified with Phosphorylated Cashew Nut Shell Liquid prepolymer - A comparative study with spindle oil, Iran. Polym.J., 8(3), 167 (1999).(37).A.R.R. Menon, C.K.S.Pillai, G.B.Nando, A.K.Bhattacharya and B.R.Gupta, Melt rheology of phosphorylated cashew nut shell liquid prepolymer modified natural rubber - a capillary rheometric study, Kauts Gummi Kunsts., 53(1-2), 35 (2000)). Thus, it has been shown that at low dosages PCNSL can serve as a multifunctional additive in natural rubber in various roles as a crosslinkable plasticizer, tackifier, improver of filler dispersion, thermal stability and cure reversion, improver of tensile strength, tear strength and fatigue resistance. It has also been found that low dosages of PCNSL can form self crosslinkable blends with polychloroprene rubber and epoxidised natural rubber. Further study on the multifunctional role of PCNSL in elastomers and its application in vulcanized rubbers led to the present invention. The main object of the invention is, therefore, to develop a novel and cost-effective process for the preparation of reclaimed rubber from waste, used / virgin rubber products which can be translated easily to a production scale in an industry. Accordingly the present invention provides a process for preparation of reprocessable and revulcanizable rubber compositions by physicochemical modification of used, vulcanized, waste rubber products or virgin rubber vulcanizates which comprises; mixing reclaiming vulcanized rubber with low dosages of phosphorylated cashew nut shell liquid prepolymer (PCNSL) ranging from 5 to 10 phr, at a temperature ranging from 160 to 180 °C at a rotor speed ranging from 20-40 rpm to get PCNSL modified rubber , mixing the above said modified rubber with stearic acid , sulphur and mercaptobenzothiazole and curing at a temperature ranging between 140-160 °C for a period between 5-30 minutes to yield cured products . In an embodiment of the invention Zinc oxide used may be 5 parts per hundered rubber (phr). In another embodiment of the invention the stearic acid used may be 2 parts per hundered rubber (phr). In yet another embodiment of the invention sulphur used is 2 parts per hundered rubber (phr). In yet another embodiment of the invention mercaptobenzothiazole used may be 2 parts per hundered rubber (phr). The novelty of our invention is that either waste / used tire tread rubber or virgin rubber on mixing with 5 to 10 % of oligomers such as PCNSL at 160 - 180°C in a Brabender Plasticorder at a rotor speed of 20 - 40 rpm for 20 - 60 min gives compositions which are easily processable and revulcanisable with conventional curatives at 140-160 °C at cure time ranging from 5-20 min. Molded samples having very good finish have been obtained. The present invention provides a process for the preparation of reprocessable and revulcanizable rubber compositions by appropriate physicochemical treatment of vulcanized .waste / virgin rubber products with oligomeric resins, specifically by modification with PCNSL, a derivative of a renewable natural resource such as cashew nut shell liquid (CNSL). The invention is described in detail in the following examples which are provided by way of illustration only and should not be construed to limit the scope of the invention. Example 1: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 3.5 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 160 °C and at a rotor speed of 30 rpm for approximately 24 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 parts per hundred rubber (phr)), stearic acid (2 phr), sulphur (2 phr) and mercaptobenzothiazole (2 phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak. Another batch of uncured mix containing curatives as above was compression molded in a hydraulic press at 150 °C for the optimum cure time as determined above. A uniform, homogeneous cured sample having good surface finish and strength was obtained. A similar mix of the unmodified tread rubber containing the curatives could not be cured to a single, homogeneous sample as above. Example 2: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 3.5 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 170 °C and at a rotor speed of 30 rpm for approximately 20 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak. Example 3: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 1.75 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 160 °C and at a rotor speed of 30 rpm for approximately 30 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2phr), sulphur (2 phr) and rnercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak. Example 4: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 1.75 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 170 °C and at a rotor speed of 30 rpm for approximately 26 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak. Example 5: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 1.75 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 180 °C and at a rotor speed of 30 rpm for approximately 36 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2 phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak. Example 6: A virgin natural rubber compound was cured in the measuring mixer of a Brabender Plasticorder set at 150 °C at a rotor speed of 30 rpm. The mixing was continued till the vulcanizate was broken down to fine crumbs. 30 g of this rubber crumbs was mixed with lOg of PCNSL in the measuring mixer (W50) of the Plasticorder set at 180 °C and at a rotor speed of 30 rpm for approximately 16 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2 phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak, which was found to be 5 minutes. The main advantages of the present invention are the following: 1. The reclaiming agent used herein viz. PCNSL is based on CNSL - a low cost renewable natural resource. Also, the dosage requirement of PCNSL to achieve adequate reclamation and improved processability is low (5 to 10 phr). Besides, the processing conditions such as temperature and shear rate needed are comparatively low. Hence, it is expected that a process based on this observation can be made cost effective . 2. Since the reclamation process is very simple, involving only a mixing operation in a conventional internal mixer under mild conditions, this process may be made popular thereby leading to novel solution of a critical environmental problem and simultaneously generating new industrial applications for waste products from rubber. We Claim: 1. A process for preparation of reprocessable and revulcanizable rubbci compositions by physicochemical modification from waste/used and virgin rubbci vulcanizates which comprises; mixing reclaiming vulcanized rubber with 5 to 10 % of phosphorylated cashew nut shell liquid prepolymer (PCNSL) at a temperature ranging from 160 to 180 C at a rotor speed ranging from 20-40 rpm to get PCNSL modified rubber, mixing the above said modified rubber with zinc oxide, stearic acid, sulphur and mercaptobenzothiazole and curing at a temperature ranging between 140-160 C for a period between 5-30 minutes to obtain desired product. 2. A process as claimed in claim 1, wherein the zinc oxide used is 5 parts per hundered rubber (phr). 3. A process as claimed in claims 1-2, wherein stearic acid used is 2 parts per hundered rubber (phr). 4. A process as claimed in claims 1-3, wherein the sulphur used is 2 parts per hundered rubber (phr). 5. A process as calimed in claims 1-4, wherein mercaptobenzothiazole used is 2 parts per hundered rubber (phr). 6. A process for preparation of reprocessable and revulcanizable rubber compositions by physicochemical modification from waste/used and virgin rubber vulcanizates substantially as herein described with reference to the examples.

Full Text

The present invention relates to a process for the preparation of reprocessable, reusable and revulcanizable rubber compositions from waste/used and virgin rubber Vulcanizates. The present invention particularly relates to a processes for the preparation of reprocessable, revulcanizable and reusable rubber compositions from waste/used and virgin rubber vulcanizates by modification with oligomeric resins of renewable natural resources./-
The disposal of defective and used rubber products poses a major threat to the environment globally and is a matter of great concern. At present, the US generates 270 million scrap tires annually (1) ((1). M.H. Blumenthal, History and status of scrap tire management in the US, Muanyag Gumi, 36(6) 177 (1999) (Hung.)). The various options for recycling rubber such as (i) fuel source, (ii) pyrolysis, (iii) depolymerized scrap rubber (iv) in asphalt, (v) reclaiming, (vi) tire retreading, (vii) grinding and (viii) other uses has been dealt with in a review by John Paul (2) ((2). John Paul in Kirk-Othmer Encyclopedia of Chemical Technology, vol. 19, 3rd edn., (Eds.) H.F. Mark, D.F. Othmer, C.G. Overberger and G.T. Seaborg, John Wiley & Sons Inc., New York, 1982, pp 1002 -1010.
Three major markets for scrap tires are (1) tire derived fuel (2) products and (3) civil engineering applications. Pyrolysis of waste rubber has been considered as an emerging, potential technology for the recovery of value added energy, fuel and chemicals in addition to its capability for solving at least in part the environmental threat mentioned above (3"4) ((3). M.J. Kawser and N.A. Farid, Plastics Rubber and Composites, 29(2), 100 (2000); (4). M.J. Kawser and N.A. Farid, Plastics Rubber and Composites, 29(8), 427 (2000)). The manufacture of new products from used tires and the use of scrap

tires for civil engineering applications are technically and economically viable options, keeping into consideration the cleanliness of the environment.
A number of patents, publications and research reports are coming out on reclaiming and reuse of vulcanized rubber thrown out as scrap rubber.
In an exhaustive review Schnecko has summarized the present situation on elastomer recycling with emphasis on tires (5) ((5).H. Schnecko, Rubber Recycling, Macromol. Symp. 135, 327 (1998)). He has specified the various areas and possibilities of recycling, viz., reduction, reuse (retreading), rubber crumb manufacture and use, reclaim, recovery ie. Pyrolysis, hydrogenation and conversion to energy, apart from landfills and biodegradation. Another recent review by Elias and Spirk^ describes various methods for devulcanization of cured rubber ((6) O. Elias and E. Spirk, Recycling of cured rubber - methods of modification of rubber scrap, Polym. RecycL, 4(1) 27 (1999)). This includes the use of mechanical stress, partial dissolution, chemical, flame, ultrasound, microwave and micro-organisms. Use of a variety of proprietory additives as devulcanization agents (eg. Delink) is also reported (6"9)( (7).U.S.Ishiaku, C.S.Chong and H.Ismail, Cure characteristics and vulcanizate properties of blends of a rubber compound and its recycled DE-VULC, Polymers & polymer Composites, 6(6), 399 (1998),(8).R. Singleton, Ground vulcanized rubber and reclaimed rubber, in 'Rubber Technology and Manufacture1 , 2nd Edn., C.M. Blow and C.Hepburn (Eds.), Butterworth Scientific, London, 1982, pp 237-243.,(9). E.F.Sverdrup and B.R.Wendrow, Rubber Reclaiming, in 'Encyclopedia of Polymer Science and Technology', Vol. 12, Interscience Pub., New York, 1970, pp 341-355).

A recent patent describes a recycling technique for tires as well as various other mechanical rubber products (10) ((10) E.V. Danschikov, I.N. Luchnik, A.V. Ryazanov, S.V. Chuiko and V.D. Feldman, Rubber waste surface modified with oxygen containing groups and a method for manufacturing of composite materials, PCT Int. Appl. WO 00 09, 598 (Cl. C 08J11/04) 24 Feb 2000). This invention relates to composite materials obtained from recycled rubbers. The modified rubber is obtained from a ground vulcanizate by treatment with ozone and subsequent chemical modification of the surface. The surface of the modified rubber particles is enriched with O- containing functional groups, such as carboxy, hydroxy, carbonyl and peroxy groups which are obtained from the original material. Surface layer of particles is depolymerized and contains monomers, oligomers and adsorbed active O. The modified rubber vulcanizate powder and binder are mixed to obtain a homogeneous mixture which then is molded and vulcanized.
Recycling of waste tires to produce high valued products without producing secondary pollutants involves producing of crumb rubber by grinding the tires (11)((11) S.G. Kim, D.H.Shin, D.C.Kim, S.H.Chung and O.C.Kwon, Recycling technology of crumb rubber produced from waste tire, Chawon Rissaikuring, 8(1) 3 (1999) (Korean)). To maximize crumb rubber utilization, research was carried out to investigate domestic and foreign crumb rubber production and utilization technologies and the properties of rubber compounds prepared using crumb rubber was evaluated.
Sulfur vulcanized rubbers are reclaimed by mixing with nucleophilic agents and heating in supercritical COa in CO: atmosphere (12)((12). H. Mizoshima, K.Ogawa and K.Todo, Reclaiming of vulcanized rubbers using nucleophilic agents, Jpn. Kokai Tokkyo

Koho JP 2000, 95 895 (C1.C08 Jll/28), 4 Apr 2000 ( Japan)). Thus, mixing vulcanized isoprene rubber (IR 2000) with 6.4 phr thiophenol in autoclave, filling the autoclave with COa under pressure, heating at 180°C for 60 min and feeding supercritical CO2 continuously for 60 min gave reclaimed rubber containing 45% sol fraction with no. av.mol.wt. 35000.
A method for the regeneration of rubbers from production wastes and tires has been patented (13)((13). I.F. Runcan et. al., Rom. RO 108,568 (Cl. COS Jll/18), 30 June, 1994 (Rom)). Some of the recent patents describe procedures for the manufacture of rubber materials having excellent mechanical properties from recycled rubbers (14'15)((14). Y. Ichiba, Manufacture of rubber materials from recycled rubbers, Jpn. Kokai Tokkyo Koho JP 10310, 661 (C1.C08 Jll/04), 24 Nov. 1998 ( Japan). (15).Y. Ichiba, Manufacture of rubber materials from rubber wastes, Jpn. Kokai Tokkyo Koho JP 10316, 766(98316.766), 15 May. 1997 ( Japan)). Kim has reported a cost effective method of recycling used automobile tires (16)((16). J.K. Kim, Utilization of recycled crumb rubber as a compounding tool, Int. Polym. Process, 13(4), 358 (1998)). Other patents report methods for using granulated tire waste for making shaped products(17) and composites tl8)((17). J. Kozakiewicz et. al., Pol. PL 175,891 (C1.C08 Jll/04), 31 Mar. 1999 (Pol.). (18). T.Shinkura, Bridgestone Sports Co. Ltd., Japan, JP 2000 191,838, 11 Jul. 2000).
A few innovative and novel techniques for the devulcanization of rubbers have also been reported recently09'20^ 19) M.Mauri, N. Sato, H.Okamoto, M. Matsushita, K.Fukumori, K.Takeuchi, N.Suzuki and M.Owaki, Nippon Gomu Kyo Kaishi, 73(3), 138 (2000). (20). D.L.Wertz and C.D.Deaton, Improved WOMBAT method for processing scrap tires into useful materials, Prepr. Symp. Am. Chem. Soc. Div. Fuel Chem., 45(3)

458 (2000)). One of these involves continuous devulcanisation of rubber by shear flow stage reaction control technology (I9). The other one involves a sequence of redox reactions which degrades a tire into four recoverable component parts such as steel, rubber backings, fibers and particulates(20).
An overview of the works carried out so far on reclaiming and recycling of waste rubber products as outlined above clearly indicates that most of the procedures involve either expensive processing routes, conditions or chemicals. Considering the colossal nature of the environmental problem posed by rubber wastes, it is of utmost importance to develop environmentally friendly processes for reclaiming/recycling of used rubber products. In this respect, if the reclaimed rubber made out of such a process can be used for the manufacture of second generation rubber products, the twin objectives of cost effective utilization of otherwise expensive resources and solution of a grave environmental problem can be met.
Recently, it has been reported that additives based on renewable natural resources can be used as reclaiming agents for vulcanized rubber(21"24 )((21). D.De, B.Adhikari and S.Maiti , Reclaiming of rubber by a renewable resource material. Part -I. Reclaiming of NR vulcanizates, J. Polym.Mater., 14(4), 333 (1997).(22). D.De, S.Maiti and B.Adhikari, Reclaiming of rubber by a renewable resource material (RRM) -II. Comparative evaluation of reclaiming process of NR vulcanizate by RRM and diallyl disulfide, J.Appl.Polym.Sci., 73 (14), 2951 (1999).(23). D.De, S.Maiti and B.Adhikari, Reclaiming of rubber by a renewable resource material (RRM) -HI. Evaluation of properties of NR reclaim, J.Appl.Polym.Sci., 75 (12), 1493 (2000).(24) D.De, S.Maiti and B.Adhikari, Reclaiming of rubber by a renewable resource material. Assessment of vulcanized SBR

reclaiming process, Kauts. Gummi Kunsts., 53(6), 346 (2000)). Since these are based on renewable natural resources, it may be possible that a reclaiming technology based on such materials can be made cost effective as well.
Recently, the use of oligomeric resins for physical and/or chemical modification of polymers has been resorted to with considerable interest. This is mainly because of the multifunctional nature of such additives in improving the processability of the base polymer and imparting a host of desirable properties to the final products based on such compositions. Phosphorylated Cashew Nut Shell Liquid (PCNSL) prepolymer - a derivative of Cashew Nut Shell Liquid is one such material, on which considerable information with application potential has been generated by extensive work carried out recently
characteristics of natural rubber modified with a bromo derivative of phosphorylated cashew nut shell liquid, J.Fire Sci,, 15(1), 3 (1997).(31). A.R.R.Menon, Stress-relaxation characteristics of natural rubber modified with phosphorylated cashew nut shell liquid prepolymer, J.Appl.Polym.ScL, 65(11), 2183 (1997).(32). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Modification of natural rubber with phosphatic plasticizers - a comparison of phosphorylated cashew nut shell liquid prepolymer with 2-ethyl hexyl diphenyl phosphate, Eur. Polym. J., 34 (7), 923 (1998). (33). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Vulcanization of natural rubber modified with cashew nut shell liquid and its phosphorylated derivative - a comparative study, Polymer, 39(17), 4033 (1998). (34). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Physicomechanical properties of filled natural rubber vulcanizates modified with phosphorylated cashew nut shell liquid, J. Appl. Polym. Sci., 68(8), 1303(1998). (35). A.R.R.Menon, C.K.S.Pillai and G.B.Nando, Cure characteristics and physicomechanical properties of natural rubber modified with phosphorylated cashew nut shell liquid prepolymer - a comparison with aromatic oil, J. Appl. Polym. Sci., 73, 813 (1999).(36). A.R.R.Menon, Melt rheology of Natural Rubber modified with Phosphorylated Cashew Nut Shell Liquid prepolymer - A comparative study with spindle oil, Iran. Polym.J., 8(3), 167 (1999).(37).A.R.R. Menon, C.K.S.Pillai, G.B.Nando, A.K.Bhattacharya and B.R.Gupta, Melt rheology of phosphorylated cashew nut shell liquid prepolymer modified natural rubber - a capillary rheometric study, Kauts Gummi Kunsts., 53(1-2), 35 (2000)).
Thus, it has been shown that at low dosages PCNSL can serve as a multifunctional additive in natural rubber in various roles as a crosslinkable plasticizer, tackifier, improver of filler dispersion, thermal stability and cure reversion, improver of tensile

strength, tear strength and fatigue resistance. It has also been found that low dosages of PCNSL can form self crosslinkable blends with polychloroprene rubber and epoxidised natural rubber. Further study on the multifunctional role of PCNSL in elastomers and its application in vulcanized rubbers led to the present invention.
The main object of the invention is, therefore, to develop a novel and cost-effective process for the preparation of reclaimed rubber from waste, used / virgin rubber products which can be translated easily to a production scale in an industry. Accordingly the present invention provides a process for preparation of reprocessable and revulcanizable rubber compositions by physicochemical modification of used, vulcanized, waste rubber products or virgin rubber vulcanizates which comprises; mixing reclaiming vulcanized rubber with low dosages of phosphorylated cashew nut shell liquid prepolymer (PCNSL) ranging from 5 to 10 phr, at a temperature ranging from 160 to 180 °C at a rotor speed ranging from 20-40 rpm to get PCNSL modified rubber , mixing the above said modified rubber with stearic acid , sulphur and mercaptobenzothiazole and curing at a temperature ranging between 140-160 °C for a period between 5-30 minutes to yield cured products .
In an embodiment of the invention Zinc oxide used may be 5 parts per hundered rubber (phr).
In another embodiment of the invention the stearic acid used may be 2 parts per hundered rubber (phr).
In yet another embodiment of the invention sulphur used is 2 parts per hundered rubber (phr).
In yet another embodiment of the invention mercaptobenzothiazole used may be 2 parts per hundered rubber (phr).
The novelty of our invention is that either waste / used tire tread rubber or virgin rubber on mixing with 5 to 10 % of oligomers such as PCNSL at 160 - 180°C in a Brabender Plasticorder at a rotor speed of 20 - 40 rpm for 20 - 60 min gives compositions which are easily processable and revulcanisable with conventional curatives at 140-160 °C at cure time ranging from 5-20 min. Molded samples having very good finish have been obtained.
The present invention provides a process for the preparation of reprocessable and revulcanizable rubber compositions by appropriate physicochemical treatment of vulcanized .waste / virgin rubber products with oligomeric resins, specifically by modification with PCNSL, a derivative of a renewable natural resource such as cashew nut shell liquid (CNSL).
The invention is described in detail in the following examples which are provided by way of illustration only and should not be construed to limit the scope of the invention.
Example 1: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 3.5 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 160 °C and at a rotor speed of 30 rpm for approximately 24 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 parts per hundred rubber (phr)), stearic acid (2 phr), sulphur (2 phr) and mercaptobenzothiazole (2 phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed
of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak. Another batch of uncured mix containing curatives as above was compression molded in a hydraulic press at 150 °C for the optimum cure time as determined above. A uniform, homogeneous cured sample having good surface finish and strength was obtained. A similar mix of the unmodified tread rubber containing the curatives could not be cured to a single, homogeneous sample as above.
Example 2: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 3.5 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 170 °C and at a rotor speed of 30 rpm for approximately 20 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak.
Example 3: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 1.75 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 160 °C and at a rotor speed of 30 rpm for approximately 30 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2phr), sulphur
(2 phr) and rnercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak.
Example 4: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 1.75 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 170 °C and at a rotor speed of 30 rpm for approximately 26 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak.
Example 5: The tread rubber portion of a used tire was cut into small pieces, 35 g of which was mixed with 1.75 g of PCNSL in the measuring mixer (W50) of a Brabender Plasticorder set at 180 °C and at a rotor speed of 30 rpm for approximately 36 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified tread rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2 phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a
rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak.
Example 6: A virgin natural rubber compound was cured in the measuring mixer of a Brabender Plasticorder set at 150 °C at a rotor speed of 30 rpm. The mixing was continued till the vulcanizate was broken down to fine crumbs. 30 g of this rubber crumbs was mixed with lOg of PCNSL in the measuring mixer (W50) of the Plasticorder set at 180 °C and at a rotor speed of 30 rpm for approximately 16 minutes, till a uniform, stable low torque value was obtained. 30 g of the PCNSL modified rubber as obtained above was mixed with zinc oxide (5 phr), stearic acid (2 phr), sulphur (2 phr) and mercaptobenzothiazole (2phr) in the measuring mixer (W50) of the Plasticorder at room temperature and at a rotor speed of 30 rpm till a uniform low torque was obtained. 30 g of the above mix was mixed in the Plasticorder set at 150 °C, at a rotor speed of 30 rpm. Optimum cure time of the mix was calculated as the time to reach a maximum in the cure peak, which was found to be 5 minutes. The main advantages of the present invention are the following:
1. The reclaiming agent used herein viz. PCNSL is based on CNSL - a low cost renewable natural resource. Also, the dosage requirement of PCNSL to achieve adequate reclamation and improved processability is low (5 to 10 phr). Besides, the processing conditions such as temperature and shear rate needed are comparatively low. Hence, it is expected that a process based on this observation can be made cost effective .
2. Since the reclamation process is very simple, involving only a mixing operation in a conventional internal mixer under mild conditions, this process may be made popular thereby leading to novel solution of a critical environmental problem and simultaneously generating new industrial applications for waste products from rubber.

We Claim:
1. A process for preparation of reprocessable and revulcanizable rubbci compositions by physicochemical modification from waste/used and virgin rubbci vulcanizates which comprises; mixing reclaiming vulcanized rubber with 5 to 10 % of phosphorylated cashew nut shell liquid prepolymer (PCNSL) at a temperature ranging from 160 to 180 C at a rotor speed ranging from 20-40 rpm to get PCNSL modified rubber, mixing the above said modified rubber with zinc oxide, stearic acid, sulphur and mercaptobenzothiazole and curing at a temperature ranging between 140-160 C for a period between 5-30 minutes to obtain desired product.
2. A process as claimed in claim 1, wherein the zinc oxide used is 5 parts per hundered rubber (phr).
3. A process as claimed in claims 1-2, wherein stearic acid used is 2 parts per hundered rubber (phr).
4. A process as claimed in claims 1-3, wherein the sulphur used is 2 parts per hundered rubber (phr).
5. A process as calimed in claims 1-4, wherein mercaptobenzothiazole used is 2 parts per hundered rubber (phr).
6. A process for preparation of reprocessable and revulcanizable rubber compositions by physicochemical modification from waste/used and virgin rubber vulcanizates substantially as herein described with reference to the examples.

Documents:

571-DEL-2002-Abstract-(04-02-2009).pdf

571-del-2002-abstract.pdf

571-DEL-2002-Claims-(04-02-2009).pdf

571-del-2002-claims.pdf

571-DEL-2002-Correspondence-Others-(04-02-2009).pdf

571-del-2002-correspondence-others.pdf

571-del-2002-correspondence-po.pdf

571-del-2002-description (complete).pdf

571-del-2002-form-1.pdf

571-del-2002-form-18.pdf

571-del-2002-form-2.pdf

571-DEL-2002-Form-3-(04-02-2009).pdf

571-del-2002-form-3.pdf

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Patent Number

233100

Indian Patent Application Number

571/DEL/2002

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

26-Mar-2009

Date of Filing

21-May-2002

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	ARYIAPALLIL RAMANKUTTYMENON RAVINDRANATHA MENON	REGIONAL RESEARCH LABORATORY, COUNCIL OF SCIENTIFIC AND INDUSTRIAL, RESEARCH, THIRUVANANTHAPURAM 695019, INDIA.

PCT International Classification Number

C08L 19/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA