Rubber composition having a resistant ozonization

Abstract

A rubber composition having improved anti-ozonization properties, the rubber composition comprising an anti-ozonization system, the anti-ozonization system comprising an antiozonant and a coupling agent. Such compositions are particularly useful in rubber articles. The improved rubber composition has long-lasting anti-ozonization performance, mitigates migration through the rubber article and reduces outflow of the antiozonant. Such rubber articles may include rubber pneumatic tires, solid tires, non-pneumatic tires, belts, hoses, cables, automobile mounts, sleeves, and general mechanical products exposed to continuous and intermittent dynamic operating conditions and requiring prevention of ozonization.

Description

Technical Field

[0001] The present invention generally relates to rubber compositions, and more particularly to tire rubber compositions having improved ozone resistance, and in particular good ozone resistance without the use of 6PPD. Such compositions are particularly suitable for use in rubber products. Such rubber products may include rubber pneumatic tires, solid tires, non-pneumatic tires, belts, hoses, cables, automotive mountings, casings, and general mechanical products that are exposed to continuous and intermittent dynamic operating conditions and require protection from ozone. Background Art

[0002] Tires and other articles made of rubber are manufactured from rubber compositions that include rubber (e.g., natural rubber, synthetic rubber, or combinations thereof), reinforcing fillers, vulcanizing agents, and other components that improve the physical and mechanical properties of both the uncured and cured rubber compositions.

[0003] It is well known that if left unprotected, ozone in the environment will attack the surface of rubber, which is typically formulated with highly unsaturated elastomers, particularly if the rubber is under strain during use. This ozone attack will cause small cracks on the rubber surface that can develop into deep, large cracks. Small cracks reduce aesthetics, while deep, large cracks can shorten the service life of rubber products such as tires.

[0004] In order to resist ozone attack, various antiozonants have been developed and commercialized to slow down the formation of ozone cracks under static and dynamic conditions. For example, waxes of various properties have been developed and used in rubbers that resist static ozone attack by forming a film barrier on the surface, although such films will break and lose ozone protection under dynamic conditions. For dynamic protection, various chemical antiozonants have been developed and are commercially available, one of which is well-known and widely used. substituted phenyl-p-phenylenediamine or PPD. These PPDs may include N-isopropyl-N'-phenyl-p-phenylene (IPPD), N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis-(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N-cyclohexyl-N'-phenyl-p-phenylenediamine (CHPPD) and N,N'-diphenyl-p-phenylenediamine (DPPD). Although not well understood, it is generally accepted that the amino groups on the PPD molecules protect rubber by reacting with ozone molecules and thereby reducing the ozone concentration at the surface of the rubber article. Note that these PPDs can also act as primary and secondary antioxidants by scavenging free radicals and converting hydroperoxides into less harmful intermediates.

[0005] During the useful life of the rubber composition, the antiozonant must migrate to the surface in order to react with and provide protection against ozone in the environment, such as in the case of tire sidewalls and treads. The rate of migration determines the useful life of the rubber article; the faster the migration to the surface, the better the initial protection. However, at a fixed antiozonant loading, too rapid migration to the surface will not only negatively impact long-term protection due to surface leaching and / or volatilization, but also cause "staining" of the article due to excessive surface concentrations. Therefore, some longer-lasting antiozonants of larger molecular size have been proposed and developed. For example, US Pat. No. 6,444,759 discloses a rubber composition having a protective agent in the form of a salt of p-phenylenediamine and an acid; the composition does not contain an elastomeric copolymer having glycidyl groups. US Pat. No. 5,047,530 proposes the preparation and use of larger molecular substituted triazines for longer-lasting and non-staining ozone protection.

[0006] Antiozonant molecules with lower migration rates than 6PPD, such as hydroxylated forms of substituted phenyl-p-phenylenediamines (sPPD-OH) and quinoneimines of substituted (hydroxy)anilines (sPAQI), have shown promise as alternatives to 6PPD, as noted in PCT publications WO 2022 / 146,441 and WO 2022 / 146,442. Although the environmental impact of their degradation products remains incompletely understood, these molecules show promise. Further improvements to this class of antiozonants would be desirable.

[0007] Another group of chemicals, hindered phenols, such as 2,2'-methylenebis(4-methyl-6-tert-butylphenol), are often used as antioxidants in rubber compositions, although they do not provide protection against ozone attack. Since these hindered phenols are generally non-staining, they are often compounded into light-colored articles where staining should be minimized, such as white sidewalls and pigmented treads in tires. Although the exact mechanism is still not well known, it is generally accepted that the hydroxyl group acts as a primary antioxidant by donating hydrogen atoms to free radicals, scavenging free radicals generated during oxidation or aging.

[0008] Another group of chemicals selected from quinone (Q), quinone imine (QI) and quinone diamine (QDI) has been reported in rubber formulations. For example, US6,533,859 discloses a method for pretreating the surface of carbon black with such chemicals to improve the dispersibility of carbon black and the dynamic properties of rubber formulations. EP1,025,155 proposes a method for improving the processability of uncured rubber by mixing quinone diamine, natural rubber and carbon black at high temperature. US8,207,247 proposes a method for mixing a rubber composition comprising natural rubber and an additive selected from the aforementioned chemicals, preferably quinone diamine.

[0009] However, another group of chemicals, hydroxyphenyl-aniline in combination with methylene donors, has been reported to improve the ozone resistance and / or fatigue resistance of rubber. For example, US 9,518,165 discloses a tire rubber component and method thereof, comprising a diene elastomer, a reinforcing filler, a methylene donor, a methylene acceptor selected from 3-hydroxydiphenylamine, 4-hydroxydiphenylamine, and combinations thereof, wherein the ratio of methylene acceptor to methylene donor is at least 15:1. US 9,708,459 discloses a tire rubber component comprising a methylene donor and a hydroxydiphenylamine having the following structure,

[0010]

[0011] However, although not related to rubber formulations, US Pat. No. 10,723,969 discloses the use of alkylated hydroxy-phenyl-aniline (see structure below) in automotive engine lubricating oils to provide antioxidant and deposit control properties. US Pat. No. 10,723,969 suggests the use of a single amine structure and does not suggest that the engine oil additive would be useful as a tire antidegradant.

[0012]

[0013] Concerns have recently been raised about the potential toxic effects of 6PPD-quinone (a chemical formed by the interaction of 6PPD with ozone) on coho salmon, as described in a recent study, “A ubiquitous tire rubber–derived chemical induces acute mortality in coho salmon”, Zhenyu Tian et al., Science, 371(6525), 185-189 (2020). If so, it would be useful to identify suitable antiozonants that can reduce or eliminate the amount of 6PPD required to protect rubber products, including tires. Specifically useful would be antiozonants that do not form 6PPD-quinone, due to its function of protecting rubber products from the effects of ozone.

[0014] Consumers expect long-lasting rubber products that maintain their aesthetic appearance throughout their useful life. There is a need for an improved rubber compound having longer-lasting ozone resistance and reduced migration rates. Summary of the Invention

[0015] Specific embodiments of the present invention include rubber compositions with longer-lasting antiozonants. Embodiments of the present invention can be used in finished rubber products, including non-pneumatic tires, solid tires, pneumatic tires, and tire components. Aspects and advantages of the present invention will be set forth in part in the following description, or will be apparent from the specific embodiments, or will be learned through the practice of the invention. Specific embodiments of the present invention include rubber compositions, articles made from such rubber compositions, and methods of making the same. Such embodiments include tire components; the tire components include a rubber composition based on a crosslinkable elastomeric composition; the crosslinkable elastomeric composition includes, per 100 parts by weight of rubber (phr), a highly unsaturated diene elastomer, a reinforcing filler, a cure package, and an antiozonation system consisting of an antiozonant and a reactive linker for the antiozonant; wherein the antiozonant is selected from molecules having the structures in (I) and (II), respectively,

[0016]

[0017] and wherein the linking agent is selected from the group consisting of methylene donors and epoxides; wherein the linking agent in the antiozonant system increases the size of the antiozonant by reacting with the antiozonant molecule under appropriate conditions of downstream curing such as in a tire article.

[0018] Referring to the above antiozonant structures (I) and (II), Z is selected from carbon, nitrogen and sulfur; X is selected from oxygen, carbon, nitrogen and sulfur; A is selected from nitrogen and sulfur. m is 1 or 2, n is 0, 1 or 2; p is 0, 1, 2, 3 or 4; q is 0, 1, 2, 3 or 4; the sum of m and p is less than 6; the sum of n and q is less than 5. For each structure, R', R", R 1 and R 2 Each of the can be the same or different and is selected from hydrogen, an alkyl moiety, a cycloalkyl moiety, an aryl moiety, an amine moiety, an amide moiety, an alcohol moiety, an aldehyde moiety, a ketone moiety, a carboxylic acid moiety, an ether moiety, an ester moiety and a thiol moiety, or a combination thereof.

[0019] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the detailed description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A complete and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, wherein:

[0021] Figure 1 A schematic diagram of a "composite" ozone coupon is provided to determine antiozonant migration.

[0022] The use of the same or similar reference numbers in different drawings denotes the same or similar features. DETAILED DESCRIPTION

[0023] The present invention relates to a rubber with a more durable anti-ozonation system. For the purpose of describing the present invention, reference will now be made in detail to embodiments and / or methods of the present invention, one or more examples of which are shown in or with the accompanying drawings. Each example is provided as an explanation of the present invention and not as a limitation of the present invention. Indeed, it will be clear to those skilled in the art that various modifications and changes can be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature or step illustrated or described as part of one embodiment can be used together with another embodiment or step to produce yet another embodiment or method. Therefore, it is intended that the present invention covers such modifications and variations as if they were within the scope of the appended claims and their equivalents.

[0024] As the method for an embodiment of the present invention, the method includes a method for manufacturing tire components, such method includes mixing the components of the rubber composition together into a non-productive mixture, these components include a highly unsaturated diene elastomer, a reinforcing filler and an antiozonant of the structure selected from (I) and (II). Such method may also include cooling the non-productive mixture and mixing a vulcanization bag and a connector for the antiozonant into the non-productive mixture to convert the non-productive mixture into a productive mixture. Alternatively, the aforementioned antiozonant can be added to the non-productive mixture to form a productive mixture simultaneously with the vulcanization bag. In a specific embodiment, the method may also include forming a tire component by the productive mixture.

[0025] Surprisingly, it was discovered that the model molecule of structure (I), dPPD-OH representing 4-{[4-(dimethylamino)phenyl]amino}phenol, and the model molecule of structure (II), dPAQI representing 4-{[4-(dimethylamino)phenyl]imino}cyclohexa-2,5-dien-1-one, when combined with hexamethylenetetramine, not only provide comparable initial ozone resistance but also significantly improve the longevity of the ozone resistance in rubber formulations compared to the widely used 6PPD.

[0026] Provided is a rubber composition comprising rubber, a reinforcing filler, a vulcanization system, and an antiozonation system consisting of an antiozonant and a linker for the antiozonant; wherein the antiozonant is selected from molecules having the structures of (I) and (II), respectively,

[0027]

[0028] And wherein the linking agent is selected from methylene donors and epoxides. The linking agent in the antiozonant system amplifies the size of the antiozonant by reacting with the antiozonant molecule under appropriate conditions of downstream curing, such as in a tire product. Suitable linking agents include epoxides and methylene donors.

[0029] In antiozonant structures (I) and (II), Z is selected from carbon, nitrogen, and sulfur. X is selected from oxygen, carbon, nitrogen, and sulfur. A is selected from nitrogen and sulfur. m is 1 or 2, n is 0, 1, or 2; typically m is 1 and n is 0 or 1, and in many embodiments, m is 1 and n is 0. In addition, p is 0, 1, 2, 3, or 4; q is 0, 1, 2, 3, or 4; typically p is 0 or 1 and q is 0 or 1, and in many embodiments, both p and q are 0. The sum of m and p is less than 6; the sum of n and q is less than 5. For either structure, R', R", R 1 and R 2 Each of R', R", R" can be the same or different and is selected from hydrogen, an alkyl moiety, a cycloalkyl moiety, an aryl moiety, an amine moiety, an amide moiety, an alcohol moiety, an aldehyde moiety, a ketone moiety, a carboxylic acid moiety, an ether moiety, an ester moiety, and a thiol moiety, or a combination thereof. 1 and R 2 Each of is selected from hydrogen, an alkyl moiety, a cycloalkyl moiety and an aryl moiety, or a combination thereof.

[0030] In many embodiments, the values of m, n, p, q, X, Z, A, R 1 and R 2 The combination of the form of R, the form and position of R' and R", and the type of linker will result in different antiozonation systems with various antiozonation properties and lifespans.

[0031] Specifically, m is 1 or 2; in many embodiments, m is 1. When m is 1, there will be one hydroxyl group on the phenyl ring in (I), but no hydroxyl group in (II) will be present on the 6-membered ring in (II); and the hydroxyl group in (I) may be located at any position available for substitution on the phenyl ring, preferably in the para position relative to the Z group. When m is 2, there will be two hydroxyl groups on the phenyl ring in (I) and one hydroxyl group on the 6-membered ring in (II), and the hydroxyl groups may be located at any position available for substitution; preferably, one of the two hydroxyl groups in (I) is located in the para position relative to the Z group on the phenyl ring, and the hydroxyl group in (II) is adjacent to the double bond Z on the 6-membered ring.

[0032] For the structures (I) and (II) discussed, n is 0, 1, or 2; in many embodiments, n is 0 or 1. When n is 0, there will be no hydroxyl groups on the phenyl rings in (I) and (II). When n is 1, there will be only one hydroxyl group on the phenyl ring, and it can be located at any position available for substitution. When n is 2, there will be two hydroxyl groups on the phenyl ring, which can be located at any position available for substitution.

[0033] For both structures, p is 0, 1, 2, 3, or 4, as long as the sum of p and m is less than 6. In many embodiments, p is 0, 1, or 2. When p is 0, there will be no R' substitution.

[0034] For the structure in question, q is 0, 1, 2, 3, or 4, as long as the sum of q and n is less than 5. In many embodiments, q is 0, 1, or 2. When q is 0, there will be no R" substitution.

[0035] In antiozonant structures (I) and (II), Z is selected from carbon, nitrogen, and sulfur; typically, Z is carbon or nitrogen. In structure (II), X is selected from oxygen, carbon, nitrogen, and sulfur; typically, X is oxygen or nitrogen. In (I) and (II), A is selected from nitrogen and sulfur; typically, A is nitrogen.

[0036] Each R' can be located anywhere on the 6-membered ring; preferably, at least one R' is adjacent to a hydroxyl group in (I) or adjacent to X in (II). The R" can be located anywhere on the phenyl ring in both (I) and (II).

[0037] For specific implementation schemes, R 1 、R 2 Each of the R' and R" moieties can be characterized as follows. The alkyl moiety can be in the range of, for example, 1 to 24 carbons, or alternatively any range of combinations of such numbers, including, for example, 1 to 18 carbons, 1 to 7 carbons, 3 to 18 carbons, 4 to 9 carbons, and the alkyl moiety can be straight or branched. The cycloalkyl moiety and the aryl moiety can be formed from 3 to 7 members, or alternatively 3 to 6 members, or 5 to 6 members, that make up the ring. These members are typically carbon, but in some embodiments, the cycloalkyl and aryl moieties can be heterocyclic, such that one of the members that make up the ring can be oxygen, nitrogen, sulfur, or a combination thereof, and the remaining members are carbon. Each of the other moieties, including amines, amides, alcohols, aldehydes, ketones, carboxylic acids, ethers, esters, and thiols, can be characterized as having a number of carbon atoms in the range of 1 to 24, straight or branched.

[0038] Examples of useful antiozonants according to structure (I) include, but are not limited to: 4-{[4-(dimethylamino)phenyl]amino}phenol in (I-1); 4-({4-[(4-methylpentan-2-yl)amino]phenyl}amino)phenol in (I-2); 4-({3-methyl-4-[(4-methylpentan-2-yl)amino]phenyl}amino)phenol in (I-3); 2,6-di-tert-butyl-4-({4-[(4-methylpentan-2-yl)amino]phenyl}amino)phenol in (I-4); 5-[(4-hydroxyphenyl)amino]-2-[(4-methylpentan-2-yl)amino]phenol in (I-5); 4-({4-[(3,5-dinitrothiophen-2-yl)amino]phenyl}amino)phenol in (I-6); and 4-{[4-(dimethylamino)phenyl]methyl}phenol in (I-7).

[0039]

[0040]

[0041] Examples of useful antiozonants according to structure (II) include, but are not limited to: 4-{[4-(dimethylamino)phenyl]imino}cyclohexa-2,5-dien-1-one in (II-1); 4-({4-[(4-methylpentan-2-yl)amino]phenyl}imino)cyclohexa-2,5-dien-1-one in (II-2); 4-({3-methyl-4-[(4-methylpentan-2-yl)amino]phenyl}imino)cyclohexa-2,5-dien-1-one in (II-3). ; 2,6-di-tert-butyl-4-({3-methyl-4-[(4-methylpentan-2-yl)amino]phenyl}imino)cyclohexa-2,5-dien-1-one in (II-4); 4-({3-hydroxy-4-[(4-methylpentan-2-yl)amino]phenyl}imino)cyclohexa-2,5-dien-1-one in (II-5); 4-({4-[(4-methylpentan-2-yl)amino]phenyl}imino)cyclohexa-2,5-diene-1-thione in (II-6).

[0042]

[0043]

[0044] Another aspect of the antiozonant system of the present invention comprises a linking agent selected from the group consisting of methylene donors and epoxides; wherein the linking agent reacts with the antiozonant molecule under appropriate conditions of downstream curing, such as in a tire article.

[0045] Suitable methylene donors can be selected from, for example, hexamethylenetetramine (HMT); hexamethoxymethylmelamine (HMMM); formaldehyde; paraformaldehyde; trioxane; 2-methyl-2-nitro-1-propionaldehyde; substituted melamine resins, such as N-substituted oxymethylmelamine resins; glycoluril compounds, such as tetramethoxymethyl glycoluril; urea-formaldehyde resins, such as butylated urea-formaldehyde resins; or mixtures thereof. In particular embodiments, hexamethylenetetramine (HMT), hexamethoxymethylmelamine (HMMM) or mixtures thereof are preferred methylene donors. Any combination of these methylene donors and other suitable methylene donors can be used in particular embodiments.

[0046] Suitable epoxides may be of the form shown in structure (III) below,

[0047]

[0048] wherein R3 can be a single or repeated substituent and is selected from an alkyl moiety, an alkenyl moiety, an aryl moiety, a phenol moiety, a phenolic epoxide moiety, a halogen moiety, a halohydrin moiety, or a combination thereof.

[0049] More useful epoxides are phenolic epoxides having the structure (IV) below,

[0050]

[0051] wherein G is selected from an alkyl moiety, an alkenyl moiety, an aryl moiety, a phenolic moiety, a phenolic epoxide moiety, or a combination thereof; R 4 and R 5 Each of can be the same or different and is selected from hydrogen, an alkyl moiety, an alkenyl moiety, an aryl moiety, a phenolic moiety, a phenolic epoxide moiety, or a combination thereof. The following are some phenolic epoxides that can be used in rubber compositions such as tire applications.

[0052]

[0053]

[0054]

[0055] wherein in (IV-6), k represents the total number of phenolic epoxide groups, wherein k has a range of 3 to 13, and R 6 Able to work with R 4 and R 5 are the same or different and are selected from hydrogen, an alkyl moiety, an alkenyl moiety, an aryl moiety, a phenolic moiety, a phenolic epoxide moiety, or a combination thereof.

[0056] Other examples of antiozonation systems may include those with different antiozonants and different linkers having various types of X, Z, A, and G, various values of m, n, p, and q, and specific forms and positions of R. 1 、R 2 , R3, R 4 、R 5 、R 6 , R' and R", so that the obtained compound still has effective anti-ozonation effect in rubber formulations.

[0057] The typical loading of the antiozonant and its linker in the antiozonation system can vary depending on the needs of the rubber application, severity of use, environmental factors and other factors. For several disclosed embodiments, the loading of the above-disclosed antiozonant in structure (I) or (II) is between 0.2 phr and 15 phr, alternatively between 0.5 phr and 10 phr, and between 1 phr and 5 phr; wherein the loading of the antiozonant linker is between 0.02 phr and 15 phr, alternatively between 0.05 phr and 10 phr, and between 0.1 phr and 5 phr, respectively.

[0058] In the rubber composition comprising the above anti-ozonation system, other components such as elastomers, fillers, plasticizers and vulcanizing agents will be further described below.

[0059] Elastomers: Suitable diene elastomers for use with embodiments of the present invention include highly unsaturated diene rubbers such as polybutadiene rubber (BR), polyisoprene rubber (IR), natural rubber (NR), styrene-butadiene rubber (SBR), isobutylene-isoprene rubber (IIR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers. Polyisoprene includes synthetic cis-1,4-polyisoprene, which can be characterized as having greater than 90 mol%, or alternatively, greater than 98 mol%, of cis-1,4 bonds. Embodiments of the rubber compositions disclosed herein include only natural rubber.

[0060] Also suitable for use in embodiments of the present invention are rubber elastomers which are copolymers and include, for example, butadiene-styrene copolymers (SBR), butadiene-isoprene copolymers (BIR), isoprene-styrene copolymers (SIR), and isoprene-butadiene-styrene copolymers (SBIR), and mixtures thereof.

[0061] The elastomeric system may be a blend of various elastomers totaling 100 phr.

[0062] Reinforcement fillers: Reinforcing fillers include carbon black, silica (and associated silane chemistries).

[0063] Carbon black as an organic filler is well known to those of ordinary skill in the art of rubber compounding. In a specific embodiment, the amount of carbon black included in the rubber composition prepared by the method disclosed herein can be, for example, between 30 phr and 150 phr, or alternatively between 40 phr and 100 phr, or between 40 phr and 80 phr. Suitable carbon black is any carbon black known in the art and suitable for a given purpose, for example, any carbon black having a BET surface area and a specific CTAB surface area both less than 400 m2 / g, or alternatively between 20 m2 / g and 200 m2 / g can be suitable for a specific embodiment based on the desired properties of the cured rubber composition. The CTAB specific surface area is the surface area measured according to the standard AFNOR-NFT-45007 of November 1987. Suitable carbon blacks such as types HAF, ISAF and SAF are commonly used in tire treads. Non-limiting examples of carbon black include, for example, N115, N134, N234, N299, N326, N330, N339, N343, N347, N375, and the 600 series of carbon blacks including, but not limited to, N630, N650, and N660 carbon blacks.

[0064] As mentioned above, silicon dioxide also can be suitable for use as reinforcing filler.Silicon dioxide can be any reinforcing silicon dioxide known to those of ordinary skill in the art, including for example, BET surface area and specific CTAB surface area both less than 450m / g or alternatively between 20m / g and 400m / g any precipitation or pyrolytic silica can be applicable to specific embodiments based on the desired characteristic of the vulcanized rubber composition.The specific embodiments of rubber composition disclosed herein can include CTAB between 80m / g and 200m / g, between 100m / g and 190m / g, between 120m / g and 190m / g or between 140m / g and 180m / g silicon dioxide.

[0065] When silica is added to the rubber composition, a proportional amount of a silane coupling agent is also added to the rubber composition. Silane coupling agents are sulfur-containing organosilicon compounds that react with the silanol groups of silica during mixing and with the elastomer during vulcanization to provide improved properties of the cured rubber composition. Suitable coupling agents are those capable of establishing sufficient chemical and / or physical bonds between the inorganic filler and the diene elastomer; they are at least bifunctional, having, for example, the simplified general formula "YTX", wherein: Y represents a functional group capable of physical and / or chemical bonding with the inorganic filler ("Y" functional group), such bonds being able to be established, for example, between a silicon atom of the coupling agent and a surface hydroxyl (OH) group of the inorganic filler (for example, a surface silanol in the case of silica); X represents a functional group capable of physical and / or chemical bonding with the diene elastomer, for example, via a sulfur atom ("X" functional group); and T represents a divalent organic group that allows for the connection between Y and X.

[0066] Other fillers may also be included as reinforcing fillers for the elastomeric system, for example, graphene, graphite, zeolites, and the like.

[0067] plasticizers : plasticizer comprises oil, resin (from petroleum or other natural renewable resources, for example sunflower seed, citrus orange peel).Processing oil is well known to those of ordinary skill in the art, is usually extracted from petroleum and is classified as paraffin, aromatic or naphthenic type processing oil, comprises MES and TDAE oil.Also known processing oil comprises, especially based on plant oil, such as sunflower oil, rapeseed oil and vegetable oil.Some rubber compositions disclosed herein may comprise elastomer, such as styrene-butadiene rubber, it has been increased with one or more such processing oils, but such oil is limited to 40phr of the total elastomer content of this rubber composition in the rubber composition of a specific embodiment and is no more than.

[0068] Vulcanization systemFor specific embodiments, the vulcanization system is preferably a vulcanization system based on sulfur and an accelerator, but other vulcanizing agents well known to those skilled in the art may also be available, such as elemental sulfur, sulfur donors, and peroxides. As used herein, a vulcanizing agent is one that causes rubber crosslinking and can therefore only be added to a productive mixture so that premature curing does not occur, and such agents include, for example, elemental sulfur, sulfur donor agents, and peroxides. Any compound that can serve as an accelerator for elastomer vulcanization in the presence of sulfur can be used, specifically those compounds selected from the group consisting of: 2-mercaptobenzothiazolyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazole sulfonamide (abbreviated as "CBS"), N,N-dicyclohexyl-2-benzothiazole sulfonamide (abbreviated as "DCBS"), N-tert-butyl-2-benzothiazole sulfonamide (abbreviated as "TBBS"), N-tert-butyl-2-benzothiazole-sulfinyl imide (abbreviated as "TBSI"), and a mixture of these compounds. Preferably, a primary accelerator of the sulfenamide type is used.

[0069] The rubber composition may further include a vulcanization retarder, a vulcanization system based on, for example, sulfur or peroxide, a vulcanization accelerator, a vulcanization activator, etc. The vulcanization system may also include various known auxiliary accelerators or vulcanization activators, such as zinc oxide, stearic acid, and guanidine derivatives (specifically diphenylguanidine or "DPG").

[0070] Other components In addition to the compounds already described, the rubber compositions disclosed herein may also include all or part of the components commonly used in diene rubber compositions intended for tire manufacture, such as additional protective agents of the type including antioxidants and / or antiozonants, such as 6PPD, 77PD, TMQ, hindered phenols, and waxes. If desired, one or more conventional non-reinforcing fillers, such as clay, bentonite, talc, chalk kaolin, aluminosilicates, fibers, or coal, may also be added.

[0071] The rubber composition as an embodiment of the present invention can be prepared in a suitable mixer in a manner known to those skilled in the art. Typically, mixing can be carried out using two consecutive preparation stages, the first stage being a thermomechanical work at a high temperature, followed by a second stage being a mechanical work at a lower temperature.

[0072] The first stage (sometimes called the "non-productive" stage) involves thoroughly mixing the various ingredients of the composition, excluding some of the vulcanization system, such as the vulcanizing agent, accelerator, retardant, and linker for the antiozonant, usually by kneading. The first stage is carried out in a suitable kneading device, such as a Banbury-type internal mixer, until a maximum temperature, generally between 120° C. and 190° C., is reached under the action of mechanical work and high shear applied to the mixture, indicating that the components are fully dispersed.

[0073] After cooling the mixture, the second stage of mechanical work is implemented at a lower temperature. Sometimes referred to as the "productivity" stage, this finishing stage comprises using suitable device (such as an open mill) to mix some (including vulcanizing agent, accelerator, retarder and antiozonant linker) in the aforementioned vulcanization system that is not added in the "non-productivity" stage into the rubber composition. It performs appropriate time (usually, for example, between 1 minute and 30 minutes or between 2 minutes and 10 minutes) under enough low temperatures (i.e., lower than the vulcanization temperature of the mixture), to prevent premature vulcanization.

[0074] The rubber composition can be formed into usable articles, including tire components. The tire tread, for example, can be formed as a tread band and subsequently made into a tire, or it can be formed directly onto the tire carcass, for example by extrusion, and then cured in a mold. Other components, such as those located in the bead area or sidewalls of the tire, can be formed and assembled into a green tire and then cured as the tire cures.

[0075] The characterization of the novel antiozonant molecules and linkers disclosed in the examples and the properties of the rubber compositions were evaluated as follows.

[0076] NMR Analysis: Structural analysis and molar purity determination of sPPD-OH and sPAQI were performed by NMR analysis. Spectra were acquired on an Avance 3, 400 MHz BRUKER spectrometer equipped with a "big band" BBFO-zgrad 5 mm probe. Quantitative NMR 1 H was empirically measured using a 30° simple pulse and a 3 second repetition period between every 64 acquisitions. The sample was dissolved in deuterated dimethyl sulfoxide (DMSO). This solvent was also used to lock the signal. Calibration was done on the deuterated DMSO proton signal at 2.44 ppm with a TMS reference at 0 ppm. 1 H Experience and 2D HSQC 1 H / 13 C and HMBC 1 H / 13 C empirically combined to determine the structure of the molecules given in the assignment table. Molar quantification of purity was performed by NMR 1D 1 H spectrum is given.

[0077] Rheometer : Curing and curing properties of the rubber composition were carried out by using MDR (Moving Die Rheometer) according to ASTM D 2084. The test was carried out at 150°C.

[0078] Static ozone cracking test: Static ozone surface cracking is evaluated using a test closely related to the ASTM 1149-99 standard test method for rubber degradation, which is called surface ozone cracking in a chamber. The test used in the subsequent examples differs in the construction of the sample holder, which is a rod rather than the wooden block holder required under the ASTM test method. Rectangular samples are prepared as follows: the raw rubber is sheeted, molded into a specific mold, cured at a specific curing temperature and time, cooled, cut with a die, then folded in half and sewn so that the curvature of the ring has a maximum local strain of 18%. These samples are hung on the rod for 2 days under ambient conditions and then placed in an ozone chamber. The ozone chamber conditions are set to 50 parts per billion of ozone (pphm) and a temperature of 40°C for a specific time. The cracks in the samples are periodically evaluated. The surface cracks of the samples are then evaluated using a rubber degradation test scale consisting of three numbers. The first number indicates the number of cracks in the sample, the second number indicates the crack width, and the third number is the crack depth. The higher these numbers, the more severe the ozone cracking. Zero indicates that no cracks were observed. The ozone cracking index is the product of three numbers determined from the rubber degradation test rating. A normalized index is used by normalizing the index of the "control formulation" to the index of the "witness formulation."

[0079] Dynamic ozone cracking test : Sample preparation and ozone cracking index were the same as those for the static ozone cracking test described above, except that the samples were subjected to cyclic strains up to 25% at 30 RPM for 2 days in an ozone chamber.

[0080] Antiozonant migration and ozone resistance life test : The migration of antiozonants in rubber to the surrounding rubber was conducted in the “composite” ozone samples, and the antiozonation lifetime was evaluated by grading the surface ozone cracks on the “composite” ozone samples after exposure to an ozone environment.

[0081] First, according to the above and Figure 1 The "base formulation" 30 without any antiozonant and the "control formulation" 20 with specific loadings of specific antiozonants 40, 42 were prepared according to the protocol shown in FIG. Figure 1As shown in , a "composite" ozone sample 10 is prepared as follows: the "base formulation" 30 (which does not have an antiozonant) is sheeted into a 2.5 mm thick skin layer 32, and the "comparative formulation" 20 (which contains an antiozonant) is sheeted into a 0.5 mm thick skin layer 22, and the "comparative formulation" skin layer is stacked on top of the "base formulation" skin layer to prepare a "composite". The "composite" sample is then cured under specific conditions and deliberately left under ambient conditions for 14 days. The sample is then nailed / wrapped around a rod, ensuring that the "comparative formulation" faces outward on the ring. The sample is then exposed to ozone in an ozone chamber for a specific duration. The surface ozone cracks of the "comparative formulation" are then graded and the normalized cracking index is calculated in exactly the same manner as described in the "static ozone cracking test".

[0082] Note that once the "comparative preparation" containing antiozonant 40 and the "base preparation" without any antiozonant are in close contact, some of the antiozonant molecules 42 in the "comparative preparation" surface layer 20 will begin to migrate into the "base preparation" surface layer 30 until concentration equilibrium is reached, which in theory should take infinite time. The migration rate in this process depends on various factors, such as the molecular size of the antiozonant, the solubility and affinity of the antiozonant in the preparation matrix, and environmental conditions. The faster migration of the antiozonant from the "comparative preparation" surface layer will result in a lower antiozonant residual concentration in the "comparative preparation", and therefore result in more severe ozone cracking after exposure to an ozone environment. Therefore, a smaller ozone cracking index indicates a slower migration and a more lasting protective agent.

[0083] The present invention is further illustrated by the following examples, which are to be regarded as illustrative only and not limiting of the invention in any way.

[0084] Example

[0085] Example 1

[0086] This example illustrates the synthesis and characterization of a model compound of structure (II), 4-{[4-(dimethylamino)phenyl]imino}cyclohexa-2,5-dien-1-one denoted as dPAQI, where the synthetic route is shown in the formula below and the NMR characterization is shown in Table 1.

[0087]

[0088] A solution of phenol (10.0 g, 0.106 mol), sodium hydroxide (5.53 g, 0.138 mol), and sodium acetate (6.97 g, 0.085 mol) in water (400 mL) was mechanically stirred at -5°C. Two dropping funnels were placed in place, one containing an aqueous solution of NaOCl (4% active chloride, 201 mL, 0.138 mol) and the other containing a solution of N,N-dimethyl-p-phenylenediamine sulfate (17.43 g, 0.074 mol) in water (200 mL). These two solutions were then added simultaneously to the phenol solution over a period of 1 hour. The temperature was maintained at -5°C during the addition. Stirring was continued at -5°C for 1 hour, and the blue precipitate was filtered, washed several times with water (600 mL), and air-dried for 10-15 hours.

[0089] A dark blue solid (14.35 g, 0.063 mol) was obtained with a yield of 85%. 1 The purity of H was 95% mol. The crude solid was crystallized from ethyl acetate (80°C to -18°C) to give dark blue crystals (12.98 g, 0.057 mol) in 77% yield. The melting point was 153°C. NMR 1 The H purity was 97% mol.

[0090] Table 1. NMR 1 H and 13 C Characterization of dPAQI in DMSO .

[0091]

[0092] It is noteworthy that the ring of the dimethyl-p-phenylamine-quinone imine to which the oxygen is double-bonded is no longer aromatic. It is expected that the ozonation product of this molecule should be different from 6PPD-quinone and therefore may have different toxic effects than the above-mentioned salmon.

[0093] Example 2

[0094] This example illustrates the synthesis and characterization of a model compound of structure (I), 4-{[4-(dimethylamino)phenyl]amino}phenol, denoted as dPPD-OH, where the synthetic route is shown in the formula below and the NMR characterization is shown in Table 2.

[0095]

[0096] A solution of phenol (4.44 g, 47.2 mmol), sodium hydroxide (2.45 g, 61.4 mmol) and sodium acetate (3.10 g, 37.8 mmol) in water (200 mL) was mechanically stirred at -5°C. Two dropping funnels were placed in place, one containing an aqueous solution of NaOCl (active chloride 4%, 101 mL, 0.69 mol) and the other containing a solution of N,N-dimethyl-p-phenylenediamine sulfate (4.50 g, 23.1 mmol) and sulfuric acid (2.3 mL, 43.1 mmol) in water (100 mL). The two solutions were then added simultaneously over a period of 1 hour. The temperature was maintained at 0°C during the addition. Stirring was continued at 0°C for 2 hours and the blue precipitate was filtered and washed several times with water (300 mL). A dark blue solid (5.5 g) was obtained. NMR 1 The H purity was 59 mol% dPAQI and 12 mol% dPPD-OH.

[0097] The crude solid was used directly in the next step. A solution of sodium hydroxide (6.0 g, 0.15 mol) and the crude product (5.5 g) was stirred in water (250 mL) at room temperature for 1 hour. Sodium hydrosulfide (25 g) was added and the dark suspension was stirred for 30 minutes. The solid was filtered and washed with water (three times, 25 mL each time) and dried in vacuo at 50 ° C. A gray solid (1.80 g, 7.85 mmol) was obtained with a yield of 34%. The melting point was 155-158 ° C. NMR 1 The H purity was 94% mol.

[0098] Table 2. NMR 1 H and 13 C Characterization of dPPD-OH in DMSO .

[0099]

[0100] Example 3

[0101] This example demonstrates the ozone resistance of the novel antiozonation system of the present invention under static and dynamic conditions. Table 3 shows the static and dynamic ozone cracking indices of formulations with 1.2 phr 6PPD (with and without 0.06 phr HMT), dPPD-OH (with 0.06 phr HMT), and dPAQI (with 0.06 phr HMT), respectively, where the ozone rubber samples were cured at 150°C for 15 minutes before the cracking test. Note that the higher the cracking index, the more severe the cracking and the lower the antiozonation performance. It can be seen that compared to the widely used antiozonant 6PPD in W1-1 and 6PPD with HMT in W1-2, dPPD-OH with HMT in F1-1 and dPAQI with HMT in F1-2 showed equivalent initial antiozonation performance under both static and dynamic conditions, as represented by their corresponding ozone cracking indices.

[0102] Table 3. Static and dynamic ozone cracking indices in non-oil formulations

[0103] Example W1-1 W1-2 F1-1 F1-2 Element natural rubber 100 100 100 100 Carbon black N347 50 50 50 50 SAD 2 2 2 2 ZnO 4 4 4 4 S 3 3 3 3 CBS 1 1 1 1 6PPD 1.2 1.2 dPPDOH 1.2 dPAQI 1.2 HMT 0.06 0.06 0.06 nature MDR maximum torque, dNm 24.7 25.6 27.2 26.9 MDR minimum torque, dNm 2.2 2.3 2.5 2.4 Static ozone cracking index 100 100 100 100 Dynamic Ozone Cracking Index 100 100 100 100

[0104] Example 4

[0105] This example demonstrates the excellent ozone longevity of the present invention using the aforementioned composite migration test. Table 4 shows the formulation of the "base formulation" without any antiozonant or linker. Table 5 shows the formulation and test results of the "comparative formulation," where the composite ozone sample was cured at 150°C for 20 minutes. It can be seen that the addition of HMT to the widely used 6PPD did not significantly change the composite ozone cracking index of 6PPD, which was 94 and 100 for W2-2 and W2-1, respectively. On the other hand, the cracking indices of the HMT-containing dPPH-OH in F2-1 and the HMT-containing dPAQI in F2-2 of the present invention were 8 and 10, respectively, significantly lower than the 100 for the widely used 6PPD formulation. These relative values of the composite ozone cracking index indicate that the antiozonation system from the present invention will provide longer-lasting ozone protection for rubber compared to the widely used 6PPD.

[0106] Table 4. "Base Formulation" containing oil

[0107]

[0108]

[0109] Table 5. Comparative formulations and test performance

[0110] Example W2-1 W2-2 F2-1 F2-2 Ingredients, phr natural rubber 100 100 100 100 Carbon black N347 55 55 55 55 Naphthenic oil 5 5 5 5 stearic acid 1 1 1 1 zinc oxide 3 3 3 3 sulfur 3 3 3 3 Accelerator CBS 1 1 1 1 6PPD 3 3 3 dPPDOH 3 dPAQI 3 HMT 0.15 0.15 0.15 nature MDR maximum torque, dNm 23.2 24.9 28.0 28.4 MDR minimum torque, dNm 2.5 2.6 2.9 2.8 Composite static ozone index 100 94 8 10

[0111] The selected combinations of aspects of the disclosed technology correspond to a variety of different embodiments of the present invention. It should be noted that each of the exemplary embodiments presented and discussed herein should not imply limitations on the present subject matter. Features or steps illustrated or described as part of one embodiment may be used in combination with aspects of another embodiment to produce yet another embodiment. In addition, certain features may be interchangeable with similar devices or features that are not explicitly mentioned but perform the same or similar functions.

[0112] The terms "a", "an" and the singular form of a word should be deemed to include the plural form of the same word, so that these terms mean that one or more of something is provided. The terms "at least one" and "one or more" are used interchangeably. A range described as "between a and b" includes the values of "a" and "b". The terms "preferably", "preferred", "preferably", "optionally", "may" and similar terms are used to indicate that the item, condition or step mentioned is an optional (not required) feature of the present invention.

[0113] It will be understood from the foregoing that various modifications and variations may be made to the embodiments of the present invention without departing from the true spirit of the invention. The foregoing description is provided for illustrative purposes only and should not be construed in a limiting sense. The scope of the present invention is limited only by the language of the appended claims.

Claims

1. A rubber composition comprising: Diene elastomers; reinforcing fillers; vulcanization system; and An antidegradant system, wherein the antidegradant system consists of an antiozonant and a linker, Wherein the antiozonant has the following formula: Where m is 1 or 2; Where n is 0, 1 or 2; where p is 0, 1, 2, 3, or 4; where q is 0, 1, 2, 3, or 4; The sum of m and p is less than 6; The sum of n and q is less than 5; wherein A is selected from nitrogen and sulfur; wherein Z is selected from the group consisting of carbon, nitrogen and sulfur; wherein X is selected from oxygen, carbon, nitrogen and sulfur; Among them, R', R", R 1 and R 2 Each of can be the same or different, and each is selected from hydrogen, an alkyl moiety, a cycloalkyl moiety, an aryl moiety, an amine moiety, an amide moiety, an alcohol moiety, an aldehyde moiety, a ketone moiety, a carboxylic acid moiety, an ether moiety, an ester moiety, and a thiol moiety, or a combination thereof; wherein the linking agent is selected from the group consisting of methylene donors and epoxides.

2. The rubber composition according to claim 1, wherein the linking agent is selected from the group consisting of hexamethylenetetramine and hexamethoxymethylmelamine.

3. The rubber composition according to claim 1, wherein the linking agent is selected from the following structures: The rubber composition according to claim 1 , wherein A is nitrogen. The rubber composition according to claim 1 , wherein Z is nitrogen.

6. The rubber composition according to any one of the preceding claims, wherein m is 1 and n is 0. 7 . The rubber composition according to claim 1 , wherein p is 0, 1 or 2, and q is 0.

8. The rubber composition according to any one of claims 1 to 6, wherein R 1 is a C1-C18 alkyl moiety, R 2 is selected from hydrogen and C1-C18 alkyl moieties.

9. The rubber composition according to any one of claims 1 to 6, wherein the antiozonant consists of 4-{[4-(dimethylamino)phenyl]imino}cyclohexa-2,5-dien-1-one and 4-({4-[(4-methylpentan-2-yl)amino]phenyl}imino)cyclohexa-2,5-dien-1-one.

10. The rubber composition according to any one of claims 1 to 6, wherein the amount of the antiozonant in the antiozonation system is between 0.2 phr and 15 phr.

11. The rubber composition according to any one of claims 1 to 6, wherein the amount of the linker in the anti-ozonation system is between 0.05 phr and 10 phr. 12 . The rubber composition according to claim 1 , wherein the diene elastomer is a highly unsaturated diene elastomer selected from the group consisting of natural rubber, isoprene rubber, styrene-butadiene, polybutadiene, and any combination thereof.

13. The rubber composition according to any one of claims 1 to 6, wherein the reinforcing filler is selected from the group consisting of carbon black, silica, graphene, graphite, and combinations thereof.

14. The rubber composition according to any one of claims 1 to 6, further comprising an antioxidant and / or antiozonant selected from the group consisting of 6PPD, 77PD, TMQ, hindered phenols, waxes, or combinations thereof. 15 . The rubber composition according to claim 1 , comprising a plasticizer selected from the group consisting of oils, resins, and combinations thereof.

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