WO2024201114A1

WO2024201114A1 - Environment-friendly tire rubber composition

Info

Publication number: WO2024201114A1
Application number: PCT/IB2023/053254
Authority: WO
Inventors: Marymol PUTHUSSERY JOHNSON; Neeraj PALERI KUNDATHIL; Rajitha RAMAKRISHNAN; Ramakrishnan Subramanian
Original assignee: Apollo Tyres Ltd.
Priority date: 2023-03-31
Filing date: 2023-03-31
Publication date: 2024-10-03

Abstract

The present disclosure relates to a tire rubber composition comprising turmeric oleoresin as antioxidant. The bio-based turmeric oleoresincan be used as partial or total replacement of conventional antioxidants, such as 6PPD, used in tire applications.

Description

ENVIRONMENT-FRIENDLY TIRE RUBBER COMPOSITION

FIELD OF THE INVENTION

[0001] The present disclosure relates to environment-friendly rubber compositions intended in particular for the manufacture of tires or tire components, such as tire treads.

BACKGROUND OF THE INVENTION

[0002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Automotive tires are known to deteriorate due to radicals generated in rubber when exposed to oxygen, ozone, or heat. These radicals react with double bonds in rubber molecule, causing polymer chain scission and subsequent formation of cracks. For this reason, conventionally, an antioxidant is added to rubber compositions to prevent the degradation and cracking of rubber. N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is currently the most prevalent chemical used for this purpose and is known to produce 6PPD- quinone (6PPD-q) through interaction with ozone. The 6PPD and 6PPD-q enter environment via tire fragments and particles on road that eventually enters larger waterways and aquatic environments through runoff. In December 2020, researchers identified 6PPD-q as the second most toxic aquatic contaminant currently known. In November2022, The Department of Ecology for the State of Washington published “6PPD in Road Runoff: Assessment and Mitigation Strategies”, which identifies watersheds in the state that are particularly vulnerable to 6PPD-q pollution. The report also summarizes research on actions to reduce the toxicity of 6PPD-q.The threat of 6PPD and 6PPD-q is an urgent problem that needs dynamic solutions. Furthermore, most of antioxidants used in tire rubber compositions are made of raw materials derived from petroleum resources. However, there is a limit for using raw materials derived from the petroleum resources considering environmental constraints, as well as forecasted rising of petroleum price caused by limited reserve and declining production of petroleum.

[0004] In view of the above problems in the conventional art, there is a high desire to provide a new, more environmentally acceptable antioxidant from renewable sources as partial or total replacement of 6PPD and/or other petroleum-based antioxidants. The present disclosure satisfies these needs and provides further related advantages.

SUMMARY OF THE INVENTION

[0005] Aspects of the present disclosure relate to the use of turmeric oleoresin as antioxidant for rubber compositions usable for the manufacture of tires or tire components such as tire treads. The bio-based turmeric oleoresin mitigates or resolves the ecological problems resulting from the pollution caused by the use of conventional antioxidants such as 6PPD andother petroleum-based antioxidants, and may be used to replace a part of the conventional antioxidant or to replace itcompletely in vulcanizable or vulcanized rubber compositions specifically designed for tire applications. The use of turmeric oleoresin as antioxidant enables a tire rubber to have oxidation resistance equivalent to or better than that of the conventionaltire rubber.

[0006] Accordingly, one aspect of the present disclosure is directed to a rubber composition comprising an elastomer, a filler, and a turmeric oleoresin. According to embodiments of the present disclosure, the turmeric oleoresin can be a curcumin-removed turmeric oleoresin (CRTO) or a maleic anhydride-grafted curcumin removed turmeric oleoresin (MAH grafted CRTO). In various embodiments, the turmeric oleoresincan be used in the rubber composition in an amount of from 1 to 20 phr.The elastomer can be a natural rubber or a synthetic rubber usable for the manufacture of tires or tire components. In some embodiments, the elastomer can be a blend of natural rubber with a synthetic rubber. In some embodiments, the elastomer can be a blend of two or more synthetic rubbers. In one exemplary embodiment, the elastomer is a blend of natural rubber with a polybutadiene rubber.

[0007] As indicated above, the rubber composition comprises a filler. The filler can be selected from the group consisting of carbon black, silica, aluminosilicates, chalk, titanium dioxide, magnesium oxide, zinc oxide, clay, calcium carbonate, and a mixture thereof. Preferably, filler(s) are present in the tirerubber composition in an amount of from 30 to 90 phr.

[0008] In various embodiments, the rubber composition can further include a vulcanization system to cause dynamic vulcanization (cross-linking) of the unvulcanised elastomer(s). The vulcanization system can include at least one vulcanizing agent, at least one vulcanization accelerator, at least one vulcanization activator, or a mixture thereof. In one embodiment, the vulcanization system is present in the rubber composition in an amount of from 0.5 to 20 phr.

[0009] In one particularly preferred embodiment, the tire rubber composition comprises 100 phr of at least one elastomer, 30 to 90 phr of at least filler, and 1 to 20 phr of a turmeric oleoresin.

[00010] In another preferred embodiment, the tire rubber composition comprises 100 phr of at least one elastomer, 30 to 90 phr of at least one filler, 1 to 20 phr of a turmeric oleoresin, 3 to 30 phr of at least one process oil, 1 to 30 phr of at least one resin, 0.1 to 3 phr of at least one antiozonant, 0.1 to 5 phr of at least one vulcanizing agent, 0.1 to 6 phr of at least one vulcanization accelerator, and 1 to 8 phr of at least one vulcanization activator.

[00011] Another aspect of the present disclosure relates to a vulcanizedrubber composition, obtained by vulcanizing the rubber composition disclosed herein.

[00012] Another aspect of the present disclosure relates to a process for preparing a vulcanized rubber compositionusable for the manufacture of tires or tire components. The process can include the steps of: combining at least one elastomer, at least one filler, a turmeric oleoresin and, optionally, one or more additives, to form a master batch rubber composition; and blending the master batch rubber composition with a vulcanization system, and vulcanizing the resulting composition to form the vulcanized rubber composition.

[00013] In various embodiments, the process further includes the step of forming a tire component from the vulcanized rubber composition.

[00014] Another aspect of the present disclosure relates to a tire, comprising the vulcanizedrubber composition disclosed herein.

[00015] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[00016] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[00017] FIG. 1 shows a comparison of the FTIR spectrum of the CRTO to the FTIR spectrum of the MAH grafted CRTO produced according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[00018] The following is a detailed description of embodiments of the present disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[00019] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

[00020] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[00021] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. [00022] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, process conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.

[00023] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.

[00024] All methods described herein can be performed in suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[00025] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[00026] Various terms are used herein. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[00027] As used herein, the term "phr" refers to parts by weight of the referenced component per 100 parts by weight of total rubber or elastomer in the composition. Such term is commonly used in the rubber compounding art. [00028] The present disclosure relates to the use of turmeric oleoresin as antioxidant for rubber compositions usable for the manufacture of tires or tire components such as tire treads. The bio-based turmeric oleoresin mitigates or resolves the ecological problems resulting from the pollution caused by the use of conventional antioxidants such as 6PPD and other petroleum-based antioxidants, and may be used to replace a part of the conventional antioxidant or to replace it completely in vulcanizable or vulcanized rubber compositions specifically designed for tire applications. Further, rubber compositions containing turmeric oleoresin as antioxidant can achieve oxidation resistance equivalent or superior to those containing the conventional antioxidants.

[00029] Accordingly, one aspect of the present disclosure is directed to a rubber composition comprising an elastomer, a filler, and a turmeric oleoresin. The rubber composition is useful for the manufacture of tires or tire components such as tire treads, and includes at least one elastomer.Thus, it is considered that the elastomer is a cross-linkable (curable), e.g., vulcanizable, elastomer. The term "elastomer" is often used interchangeably with the term “rubber” or more professional "un-vulcanized rubber". The elastomer can be a natural rubber, a synthetic rubber, a blend of synthetic and natural rubber, or a blend of various synthetic rubbers.

[00030] In one embodiment, the elastomer can be selected from the group consisting of natural rubber (NR), synthetic polyisoprene rubber (IR), polybutadiene rubber (PBD), polyvinyl-butadiene rubber, styrene -butadiene rubber (SBR), solution-polymerized styrenebutadiene rubber (SSBR), emulsion-polymerized styrene -butadiene rubber (ESBR), nitrile rubber (NBR), hydrogenated nitrile rubber, butyl rubber, halogenated butyl rubbers, liquid rubbers, polynorbornene copolymer, isoprene-isobutylene copolymer, chloroprene rubber, ethylene propylene diene monomer rubber (EPDM), acrylate rubber, fluorine rubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, a terpolymer formed from ethylene monomers, propylene monomers, and/or ethylene propylene diene monomer (EPDM), styrene-isoprene-butadiene terpolymer, hydrated acrylonitrile butadiene rubber, isoprenebutadiene copolymer, hydrogenated styrene -butadiene rubber, butadiene acrylonitrile rubber, styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene/butylene-styrene block copolymer (SEBS), styrene-[ethylene-(ethylene/propylene)]-styrene block copolymer (SEEPS), styrene-isoprene- styrene block copolymer (SIS), isoprene-based block copolymers, butadiene-based block copolymers, styrenic block copolymers, hydrogenated styrenic block copolymers, styrene butadiene copolymers, polyisobutylene, ethylene vinyl acetate (EVA) polymers, polyolefins, metallocene-catalyzed polyolefin polymers and elastomers, reactor- made thermoplastic polyolefin elastomers, olefin block copolymer, polyurethane block copolymer, polyamide block copolymer, thermoplastic polyolefins, thermoplastic vulcanizates, ethylene vinyl acetate copolymer, ethylene n-butyl acrylate copolymer, ethylene methyl acrylate copolymer, neoprene, urethane, ethylene acrylic acid copolymer, ethylenepropylene polymers, propylene -hexene polymers, ethylene-butene polymers, ethylene octene polymers, propylene-butene polymers, ethylene-propylene-butylene terpolymers, and a mixture thereof.

[00031] In some embodiments, the elastomer is a blend of natural rubber with a polybutadiene rubber.In an embodiment, the rubber composition comprises from 10 to 60 phr of natural rubber as a blend with from 40 to 90 phr of a polybutadiene rubber.In one particularly preferred embodiment, the rubber composition comprises 50 phr of natural rubber as a blend with 50 phr of a polybutadiene rubber.

[00032] As indicated above, the tire rubber composition comprises a turmeric oleoresin as antioxidant. The turmeric oleoresin can be used to replace a part of the conventional antioxidant or to replace it completely in vulcanizable or vulcanized rubber compositions specifically designed for tire applications. The use of turmeric oleoresin as an antioxidant enables a tire rubber to have oxidation resistance equivalent or superior to that of the conventional tire rubber.In one embodiment, the turmeric oleoresin is a curcumin-removed turmeric oleoresin (CRTO). In another embodiment, the turmeric oleoresin is a maleic anhydride-grafted curcuminremoved turmeric oleoresin (MAH grafted CRTO). According to embodiments of the present disclosure, the turmeric oleoresin described above can be prepared by any method known in the art. In one exemplary embodiment, the turmeric oleoresin is prepared by cutting fresh rhizomes of turmeric (Curcuma longa L.) into slices, followed by drying and grinding the dry tissue into a powder. The powder is then extracted by way of organic solvent extraction. Solvents like acetone, ethylene dichloride and ethanol are suitable solvents for extraction of turmeric oleoresin. After extraction, the miscella is subjected to desolventation (e.g. by performing a standard solvent evaporation step), thereby delivering a product commonly known as turmeric oleoresin. Turmeric oleoresin typically contains 5-55% of curcuminoids. After curcumin is crystallized and separated off from the turmeric oleoresin, the mother liquor named “curcumin-removed turmeric oleoresin” (CRTO) is collected as a by-product. CRTO typically contains volatile oils and uncrystallisable curcuminoids. The major constituent of CRTO isar-Turmerone (-35%). In various embodiments, MAH grafted CRTO can be prepared by reacting CRTO with maleic anhydride. The turmeric oleoresin, CRTO and MAH grafted CRTO all function as an antioxidant which can provide oxidation resistanceto tire rubber that is equal or superior to that provided by conventional antioxidants. The bio-based turmeric oleoresin mitigates or resolves the ecological problems resulting from the pollution caused by the use of conventional antioxidants such as 6PPD and other petroleum-based antioxidants, and may be used to replace a part of the conventional antioxidant or to replace it completely in vulcanizable or vulcanized rubber compositions specifically designed for tire applications. In various embodiments, the turmeric oleoresin can be used in the rubber composition in an amount of from 1 to 20 phr.

[00033] As indicated above, the rubber composition includesa reinforcing filler to improve technical requirements of tires, such as high wear resistance, low rolling resistance, or wet grip. While any filler can be used as long as it is compatible with the elastomer, typical fillers include carbon black, silica, aluminosilicates, chalk, titanium dioxide, magnesium oxide, zinc oxide, clay, calcium carbonate, and a mixture thereof. Preferably, silica or carbon clack is used as the filler. In one embodiment, the filler is a blend of silica and carbon black. Filler(s) are present in the rubber composition in an amount of from 30 to 90 phr, preferably from 40 to 90 phr. In one embodiment, the filler has a BET surface of between 150 and 250 m /g, as measured according to ASTM D6738.

[00034] In various embodiments, the rubber composition of the present disclosure can further include a vulcanization system to cause dynamic vulcanization (cross-linking) of the unvulcanised elastomer(s). The vulcanization system can include at least one vulcanizing agent, at least one vulcanization accelerator, at least one vulcanization activator, or a mixture thereof. In one embodiment, the vulcanization system is present in the rubber composition in an amount of from 0.5 to 20 phr.

[00035] While any vulcanizing agent known in the art may be used, in preferred embodiments of the present disclosure, sulphur is used. The amount of vulcanizing agent is preferably between 0.1 and 5 phr. [00036] While any vulcanization accelerators can be used, typical accelerators include but not limited to n-cyclohexyl-2-benzothiazole sulfenamide (CBS), diphenyl guanidine (DPG),N-Tertiarybutyl-2-benzothiazole sulfennamide (TBBS), N,N-dicyclohexyl-2- benzothiazyl sulfenamide (DCBS), and combination thereof.The vulcanization accelerator can be used in an amount ranging from 0.1 to 6 phr.

[00037] The vulcanization activator can be any activator as would be known to one of skill in the art. Preferably, the activator is selected from zinc oxide, stearic acid, and a combination thereof. In one embodiment, a mixture of zinc oxide and stearic acid is used as the vulcanization activator. The vulcanization activator can be used in an amount ranging from 1 to 8 phr.

[00038] The rubber composition of the present disclosure may also include any suitable additives generally used in tire rubber compositions. In one embodiment, the rubber composition includes one or more additives from the group consisting ofprocess oil, antiozonant, anti-reversion agent, resin, coupling agent, stabilizer, masticating agent, adhesion promoter, colorant, homogenizer, and dispersion agent.

[00039] In various embodiments, the rubber composition of the present disclosure further comprisesa process oil. Process oil may be included in the rubber composition as extending oil typically used to extend elastomers. Process oil may also be included in the rubber composition by addition of the oil directly during rubber compounding. Suitable process oils include various oils as are known in the art, including aromatic, paraffinic, naphthenic, and low polycyclic aromatic (PC A) oils, such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), residual aromatic extract (RAE) oil and heavy naphthenic oils, and vegetable oils such as sunflower, soybean, and safflower oils. Process oil(s) can be used in the range from 3 to 30 phr.

[00040] In one embodiment, the rubber composition can further include at least one antireversion agent to prevent reversion, i.e., an undesirable decrease in crosslink density.While any anti-reversion agents may be used, typical anti-reversion agents include but not limited to zinc salts of aliphatic carboxylic acids, zinc salts of monocyclic aromatic acids, bismaleimides, biscitraconimides, bisitaconimides, aryl bis-citraconamic acids, bissuccinimides, and polymeric bissuccinimide polysulfides (e.g., N,N’- xylenedicitraconamides).The anti-reversion agent can be present in a range of from 0.5 to 5 phr.

[00041] In one embodiment, the rubber composition further comprises at least one antiozonant. The preferred antiozonant is ozone protecting wax. Preferably, the antiozonant is present in an amount of from 0.1 to 3 phr.

[00042] In one embodiment, the rubber composition further comprises at least one resin to impart desirable properties to the rubber composition, including hardness, tear strength, and adhesion to reinforcement.Suitable resins include coumarone type resins, including coumarone-indene resins and mixtures of coumarone resins, naphthenic oils, phenol resins, and rosins. Other suitable resins include phenol-terpene resins such as phenol-acetylene resins, phenol-formaldehyde resins, terpene-phenol resins, polyterpene resins, and xyleneformaldehyde resins. Further suitable resins include petroleum hydrocarbon resins such as synthetic polyterpene resins; aromatic hydrocarbon resins; aliphatic hydrocarbon resins; aliphatic cyclic hydrocarbon resins, such as dicyclopentadiene resins; aliphatic aromatic petroleum resins; hydrogenated hydrocarbon resins; hydrocarbon tackified resins; aliphatic alicyclic petroleum resins; rosin derivatives; and terpene resins. In one embodiment, the resin is selected from phenol-formaldehyde (PF) resin, resorcinol-formaldehyde (RF) resin, aliphatic resin, and aliphatic cyclic hydrocarbon resins. The amount of resin which is used in the rubber composition is between 1 and 30 phr, and preferably between 1 and 15 phr.

[00043] In one particularly preferred embodiment, the rubber composition comprises 100 phr of at least one elastomer, 30 to 90 phr of at least filler, and 1 to 20 phr of a turmeric oleoresin.

[00044] In another preferred embodiment, the tire rubber composition comprises 100 phr of at least one elastomer, 30 to 90 phr of at least one filler, 1 to 20 phr of a turmeric oleoresin, 3 to 30 phr of at least one process oil, 1 to 30 phr of at least one resin, 0.1 to 3 phr of at least one antiozonant, 0.1 to 5 phr of at least one vulcanizing agent, 0.1 to 6 phr of at least one vulcanization accelerator, and 1 to 8 phr of at least one vulcanization activator.

[00045] In one exemplary embodiment, the tire rubber composition comprises:

50 phr of natural rubber,

50 phr of polybutadiene rubber, 46 phr of carbon black,

8 phr of silica,

1-20 phr of an antioxidant, which is selected from turmeric oleoresin, curcumin- removed turmeric oleoresin (CRTO), a maleic anhydride-grafted curcumin removed turmeric oleoresin (MAH grafted CRTO), and a mixture thereof, 12 phr of a RAE oil,

2 phr of a PF resin,

1 phr of ozone protecting wax,

0.7phr of sulphur,

0.8 phr of an accelerator, and

3.6 phr of an activator.

[00046] In another aspect, the present disclosure is directed to a process for preparing a vulcanized rubber composition usable for the manufacture of tires or tire components. The process can include the steps of: combining at least one elastomer, at least one filler, a turmeric oleoresin and, optionally, one or more additives, to form a masterbatch rubber composition; and blending the masterbatch rubber composition with a vulcanization system, and vulcanizing the resulting composition to form the vulcanized rubber composition.

[00047] In various embodiments, the masterbatch rubber composition can be produced by mixing the above-mentioned components by using conventional kneaders used in the rubber industry, such as heating rolls, kneaders, Banbury mixers and the like. After the masterbatch is formed, it can be blended with a vulcanization system as described above. The vulcanization can be carried out in the usual way by heating the mixture to the vulcanization temperature for a sufficient time. The vulcanization can be carried out at temperatures of 110 to 200° C.The resulting vulcanized composition (vulcanizate) can be used for tire applications such as tire treads, under treads, carcass, side walls, and bead portions. The vulcanizate can be used particularly as rubber for tire treads.

[00048] In various embodiments, the process further includes the step of forming a tire component from the vulcanized rubber composition.

[00049] In another aspect, the present disclosure is directed to a vulcanizedrubber composition, obtained by vulcanizing the rubber composition disclosed herein. [00050] In another aspect, the present disclosure is directed to atire, comprising the vulcanizedrubber composition disclosed herein.

[00051] While the foregoing description discloses various embodiments of the disclosure, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

EXAMPLES

[00052] The present disclosure is further explained in the form of following examples. However, it is to be understood that the foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

Example 1: Preparation of maleic anhydride grafted curcuminremoved turmeric oleoresin (MAH grafted CRTO)

[00053] MAH grafted CRTO was prepared by reacting CRTO with maleic anhydride (30% by weight based on the total weight of CRTO). The reaction was carried out in a three- neck flask equipped with a magnetic stirrer and a thermometer. CRTO and maleic anhydride (MAH) were added into the three-necked flask and heated to 70°C. Afterbenzoyl peroxide activator wasadded, the reaction was maintained at the same temperature for about 60 minutes under stirring to produce MAH grafted CRTO. FIG. 1 shows a comparison of the FTIR spectrum of the CRTO to the FTIR spectrum of the MAH grafted CRTO. The MAH grafted CRTO has characteristic FTIR peaks at 1848 cm'¹ and 1779 cm'¹.

Example 2: Rubber compositions

[00054] Rubber compositions were prepared according to the ingredients and amounts indicated in Table 1. Composition production was performed under industry standard conditions in two stages, as shown in Table 2. In the masterbatch mixing step, the elastomers (natural rubber and polybutadiene rubber) were added to an internal rubber mixer and mixed for about 2-5 min. Then, process oil, silica and carbon black were added to the mixer and mixed for 2-6 min. Then, antioxidant, resin, and ozone protecting waxwere added to the mixer. Subsequently, all the ingredients were mixed for 5 min. The masterbatch rubber composition was discharged from the mixer and air cooled to room temperature. In the final batch mixing step, the masterbatch rubber composition, sulphur, accelerator and activator were added into an internal rubber mixer or a two -roll open mill rubber machine and mixed for 3 min. The resulting unvulcanized rubber composition was discharged from the mixer and air cooled. Test pieces were produced from each of the compositions by optimal vulcanization under pressure at 160° C, and these test pieces were used to determine the material properties typical for the tire industry. Testing was performed according to ASTM and ISO test methods.

Table-1

6-PPD - N-phenyl-N'-(l,3-dimethylbutyl)-p-phenylenediamine

CRTO - Curcumin-removed turmeric oleoresin

MAH - Maleic anhydride

Phr - Parts per hundred mass units of rubber RAE - Residual aromatic extract

PF - Phenol-formaldehyde

Table 2

DeMattia crack growth properties

[00055] Unagedandaged test pieces produced from the rubber compositions 1, 2 and3were subjected to theDeMattia rubber crack growth test (ASTM D813)and the results are reported in Table 3. Test pieces produced from compositions 2 and 3 exhibited improved crack growthresistance compared to that of the composition 1.

Table 3

Example 3: Rubber compositions

[00056] Rubber compositions 4 and 5 (containing 2phrof 6PPD and 2 phr of CRTO, respectively) were prepared according to the ingredients and amounts indicated in Table 4. The compositions were produced using the process similar to the one in Example 2. Testing of the rubber compositions was performed according to ASTM and ISO test methods.

Table-4

Mechanical properties

[00057] Unaged and aged test pieces produced from the compositions4and 5 were tested for modulus, tensile strength and elongation at breakand the results are reported in Table 5.

Table-5

[00058] From the data shown in Table-5, it is evident that the rubber composition containing CRTO as antioxidant (Composition 5) exhibits improved modulus, tensile strength and elongation properties compared to the rubber composition containing the conventional antioxidant 6PPD (Composition 4). The data contained in Table-5 show that the rubber composition containing CRTO as antioxidant had a decreased rate of degradation compared to the rubber composition containing the conventional antioxidant 6PPD after aging.

Example 4: Rubber compositions

[00059] Rubber compositions5, 6 and 7 (containing 2 phr, 8 phr and 16 phr of CRTO, respectively) were prepared according to the ingredients and amounts indicated in Table 6. The compositions were produced using the process similar to the one in Example 2. Testing of the rubber compositions was performed according to ASTM and ISO test methods. Table-6

Mechanical properties

[00060] Unaged and aged test pieces produced from the compositions 5, 6 and 7were tested for modulus, tensile strength and elongation at break. The data are reported in Table 7.

Table-7

[00061] The data contained in Table-7indicate that the rubber compositions formulated with CRTO as the antioxidant undergo less degradation after ageing.

[00062] The above examples demonstrate experimentally that the rubber compositions prepared with CRTO or MAH grafted CRTO as the antioxidant in accordance with the present invention result in a rubber product of significantly improved properties as compared to the rubber compositions prepared with the conventional antioxidant 6PPD. In all, data from the above experiments suggest that the bio-based CRTO and MAH grafted CRTO are suitable antioxidants for rubber compositions usable in tire application and are an effective replacement of the conventional antioxidants like 6PPD.

Claims

We Claim:

1. A rubber composition, comprising: an elastomer, a filler, and a turmeric oleoresin.

2. The rubber composition as claimed in claim 1, wherein the turmeric oleoresin is a curcumin removed turmeric oleoresin (CRTO) or a maleic anhydride-grafted curcumin removed turmeric oleoresin.

3. The rubber composition as claimed in claim 1 or 2, wherein the turmeric oleoresin is present in an amount of from Ito 20phr.

4. The rubber composition as claimed in claim 1, wherein the elastomer is selected from the group consisting of natural rubber (NR), synthetic polyisoprene rubber (IR), polybutadiene rubber (PBD), polyvinyl-butadiene rubber, styrene-butadiene rubber (SBR), solution-polymerized styrene-butadiene rubber (SSBR), emulsion- polymerized styrene-butadiene rubber (ESBR), nitrile rubber (NBR), hydrogenated nitrile rubber, butyl rubber, halogenated butyl rubbers, liquid rubbers, polynorbornene copolymer, isoprene-isobutylene copolymer, chloroprene rubber, ethylene propylene diene monomer rubber (EPDM), acrylate rubber, fluorine rubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, a terpolymer formed from ethylene monomers, propylene monomers, and/or ethylene propylene diene monomer (EPDM), styrene-isoprene-butadiene terpolymer, hydrated acrylonitrile butadiene rubber, isoprene-butadiene copolymer, hydrogenated styrene-butadiene rubber, butadiene acrylonitrile rubber, styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene/butylene- styrene block copolymer (SEBS), styrene-[ethylene-(ethylene/propylene)]-styrene block copolymer (SEEPS), styrene-isoprene-styrene block copolymer (SIS), isoprene-based block copolymers, butadiene-based block copolymers, styrenic block copolymers, hydrogenated styrenic block copolymers, styrene butadiene copolymers, polyisobutylene, ethylene vinyl acetate (EVA) polymers, polyolefins, metallocene-catalyzed polyolefin polymers and elastomers, reactor-made thermoplastic polyolefin elastomers, olefin block copolymer, polyurethane block copolymer, polyamide block copolymer, thermoplastic polyolefins, thermoplastic vulcanizates, ethylene vinyl acetate copolymer, ethylene n-butyl acrylate copolymer, ethylene methyl acrylate copolymer, neoprene, urethane, ethylene acrylic acid copolymer, ethylene -propylene polymers, propylene-hexene polymers, ethylene-butene polymers, ethylene octene polymers, propylene -butene polymers, ethylene -propylene -butylene terpolymers, and a mixture thereof.

5. The rubber composition as claimed in claim 4, wherein the elastomer is a blend of natural rubber with a polybutadiene rubber.

6. The rubber composition as claimed in claim 1, wherein the filler is selected from the group consisting of carbon black, silica, aluminosilicates, chalk, titanium dioxide, magnesium oxide, zinc oxide, clay, calcium carbonate, and a mixture thereof.

7. The rubber composition as claimed in claim 1, wherein the filler is present in an amount of from 30 to 90 phr.

8. The rubber composition as claimed in any of claims 1 to 7, further comprising a vulcanization system.

9. The rubber composition as claimed in claim 8, wherein the vulcanization system is present in the rubber composition in an amount of from 0.5 to 20 phr.

10. The rubber composition as claimed in claim 8, wherein the vulcanization system comprises at least one vulcanizing agent, at least one vulcanization accelerator, at least one vulcanization activator, or a mixture thereof.

11. The rubber composition as claimed in any of claims 1 to 10, further comprising one or more additives from the group consisting of process oil, antiozonant, antireversion agent, resin, coupling agent, stabilizer, masticating agent, adhesion promoter, colorant, homogenizer, and dispersion agent.

12. The rubber composition as claimed in any of claims 1 to 11, comprising:

100 phr of at least one elastomer;

30 to 90 phr of at least one filler; and 1 to 20 phr of an antioxidant, which is selected from turmeric oleoresin, curcumin- removed turmeric oleoresin (CRTO), a maleic anhydride-grafted curcumin removed turmeric oleoresin, and a mixture thereof.

13. A vulcanized rubber composition, obtained by vulcanizing a rubber composition comprising an elastomer, a filler, and a turmeric oleoresin.

14. A tire, comprising the vulcanized rubber composition as claimed in claim 13.

15. A process for preparing a vulcanized rubber composition, comprising: combining at least one elastomer, at least one filler, a turmeric oleoresin and, optionally, one or more additives, to form a master batch rubber composition; and blending the master batch rubber composition with a vulcanization system, and vulcanizing the resulting composition to form the vulcanized rubber composition.