Rubber composition

Abstract

Provided is a rubber composition comprising a rubber component and a polyester, the rubber component comprising natural rubber, the polyester being a polycondensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having 2-16 carbon atoms in the alcohol component being 85% by mass or more, and the content of an aliphatic diol having 2-16 carbon atoms in the carboxylic acid component being 85% by mass or more. The content of an aliphatic dicarboxylic acid compound having 2-16 carbon atoms in the carboxylic acid component is 50 mass% or more; also provided are: a rubber molded article obtained by vulcanizing the rubber composition; a tire member comprising the rubber molded article; a use of the rubber composition for improving wear resistance; and a method for improving wear resistance of a rubber molded article comprising a rubber component and a polyester.

Description

Technical Field

[0001] This invention relates to rubber compositions, rubber molded articles, tire components, methods for manufacturing rubber compositions, methods for manufacturing rubber molded articles, and methods for improving the wear resistance of rubber molded articles. Background Technology

[0002] Rubber is an amorphous and soft polymer, a material with high elastic limit and low elastic modulus, mainly composed of organic polymers such as natural rubber and synthetic rubber. Utilizing these properties, rubber-containing compositions are used in various fields such as tires, sealing materials, and vibration damping materials.

[0003] In rubber compositions used in tire applications, inorganic fillers are often incorporated to increase the elastic modulus. Furthermore, techniques for incorporating polyesters have been proposed to fully utilize the properties of rubber and meet various required physical properties.

[0004] For example, in Japanese Patent Application Publication No. 2020-94113 (Patent Document 1), a rubber composition was disclosed as a rubber composition that highly balances SNOW performance, WET performance, low rolling resistance and handling stability. The rubber composition contains, in a specific proportion, a rubber component, a filler, a thermoplastic resin (C) comprising at least one of styrene-olefin block copolymers and polyester polyol resins having aromatic rings, and a polymeric material (D) that does not have a diene skeleton in its molecular backbone.

[0005] In Japanese Patent Application Publication No. 2012-136586 (Patent Document 2), a rubber composition containing a specific low-polarity diene rubber, a specific thermoplastic polyester resin, and a specific high-polarity diene rubber in a specific ratio was disclosed as a rubber composition that can suppress a significant decrease in tensile elongation while ensuring processability and achieving high elasticity.

[0006] In International Publication No. 2021 / 193795 (Patent Document 3), as a rubber additive and rubber composition capable of obtaining a rubber molded body that is not easily deformed and has low heat generation even when deformed, a rubber additive comprising a polyester as a condensation polymer of a specific alcohol component and a specific carboxylic acid component and a rubber composition containing the rubber additive were disclosed. Summary of the Invention

[0007] This invention relates to a rubber composition comprising a rubber component and a polyester. The rubber component comprises natural rubber, and the polyester is a condensation polymer of an alcohol component and a carboxylic acid component. The alcohol component contains at least 85% by mass of aliphatic diols with 2 or more carbon atoms and less than 16 carbon atoms, and the carboxylic acid component contains at least 50% by mass of aliphatic dicarboxylic acid compounds with 2 or more carbon atoms and less than 16 carbon atoms. DETAILED DESCRIPTION

[0008] In the rubber compositions of Patent Literatures 1 and 2, mainly the blending of aromatic polyester is investigated, however, the abrasion resistance of a tire molded body containing natural rubber using aliphatic polyester is not investigated, and the balance between the abrasion resistance and the storage modulus is not sufficient.

[0009] Further, the present inventors found that, as described in Patent Literature 3, by using aliphatic polyester as a rubber additive, a rubber molded body which is not easily deformed and which has low heat generation even when deformed can be obtained, however, the abrasion resistance of a tire molded body containing natural rubber is not sufficiently investigated.

[0010] The present application relates to a rubber composition capable of obtaining a rubber molded body which is excellent in abrasion resistance and which has a high storage modulus, a rubber molded body using the rubber composition, a tire member, a method for producing a rubber composition, a method for producing a rubber molded body, and a method for improving the abrasion resistance of a rubber molded body.

[0011] The present application relates to the following [1] to [6].

[0012] [1] A rubber composition comprising a rubber component and a polyester, the rubber component comprising natural rubber, the polyester being a condensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component being 85% by mass or more, and the content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component being 50% by mass or more.

[0013] [2] A rubber molded body obtained by vulcanizing the rubber composition described in the above [1].

[0014] [3] A tire member comprising the rubber molded body described in the above [2].

[0015] [4] A method for producing the rubber composition described in the above [1], the method comprising the following steps (1) and (2).

[0016] (1) a step of mixing a composition, the composition comprising a rubber component and a polyester, the rubber component comprising natural rubber, the polyester being a condensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component being 85% by mass or more, and the content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component being 50% by mass or more;

[0017] (2) a step of further adding mixed sulfur.

[0018] [5] A method for producing a rubber molded article, the method comprising vulcanizing the rubber composition described in the above [1].

[0019] [6] A method for improving the wear resistance of a rubber molded article, the method being a method for improving the wear resistance of a rubber molded article containing a rubber component and a polyester, the rubber component containing natural rubber, the polyester being a condensate of an alcohol component containing an aliphatic diol having 2 or more and 16 or less carbon atoms and a carboxylic acid component containing an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms, the content of the aliphatic diol in the alcohol component being 85% by mass or more, and the content of the aliphatic dicarboxylic acid compound in the carboxylic acid component being 50% by mass or more.

[0020] According to the present application, it is possible to provide a rubber composition which can obtain a rubber molded article having excellent wear resistance and a high storage modulus, a rubber molded article using the rubber composition, a tire member, a method for producing a rubber composition, a method for producing a rubber molded article, and a method for improving the wear resistance of a rubber molded article.

[0021] Further, according to the present application, it is possible to further reduce the loss tangent of a rubber molded article and reduce the heat generation property of a rubber molded article.

[0022] [Rubber composition]

[0023] The rubber composition of the present application is a rubber composition containing a rubber component and a polyester, the rubber component containing natural rubber, the polyester being a condensate of an alcohol component containing an aliphatic diol having 2 or more and 16 or less carbon atoms and a carboxylic acid component containing an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms, the content of the aliphatic diol in the alcohol component being 85% by mass or more, and the content of the aliphatic dicarboxylic acid compound in the carboxylic acid component being 50% by mass or more.

[0024] According to the rubber composition of the present application, it is possible to obtain a rubber molded article having excellent wear resistance and a high storage modulus. The reason for this is not necessarily clear, but can be considered as follows.

[0025] The natural rubber contained as the rubber component of the present application exhibits so-called elongation crystallization in which molecules are oriented and crystallized due to elongation. The natural rubber has a tendency for stress relaxation to become significant due to this elongation crystallization.

[0026] On the other hand, the polyester of the present application is a condensate of an alcohol component containing an aliphatic diol having 2 or more and 16 or less carbon atoms and a carboxylic acid component containing an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms. It is considered that, here, since the alcohol component and the carboxylic acid component of the above-described polyester are both aliphatic compounds having 2 or more and 16 or less carbon atoms, the polyester does not compatibilize with the rubber component containing natural rubber in the rubber composition and the rubber molded article, but forms fine crystals and forms a network of the polyester in the rubber component. It is thus considered that the polyester becomes a nucleus of the elongation crystals of the natural rubber contained in the rubber component.

[0027] As such, since the rubber composition of the present application contains the natural rubber and the above polyester, elongation crystallization of the obtained rubber molded body is promoted, and thus it is considered that the abrasion resistance is excellent. Furthermore, since the rubber molded body of the present application has the network of the polyester as described above, the obtained rubber molded body can exhibit a high storage modulus, and when used for a tire member or the like, it is expected that the handling stability is excellent.

[0028] In addition, since the rubber composition of the present application has the network of the polyester as described above, the obtained rubber molded body does not easily become large in the loss tangent (tan δ) even when deformed, and the heat generation property can be reduced, and when used for a tire member or the like, it is expected that the low fuel consumption property is excellent.

[0029] <Rubber component>

[0030] The rubber composition of the present application contains the natural rubber. By making the rubber component contain the natural rubber, elongation crystallization can be promoted with the polyester described later as a nucleus, and thus the abrasion resistance of the obtained rubber molded body is excellent, and a higher storage modulus can be exhibited.

[0031] As the natural rubber, SMR, SIR, STR, RSS, or the like can be given, and it is preferably selected from one or more of SMR20, STR20, RSS#3, and RSS#4, more preferably one or more of RSS#3 and RSS#4, and further preferably RSS#3.

[0032] In addition, the natural rubber can be used after modification, and as the modified natural rubber, epoxidized natural rubber, hydrogenated natural rubber, or the like can be given.

[0033] In the rubber composition of the present application, it is preferable that the rubber component further contain a synthetic rubber. By making the rubber component further contain the synthetic rubber, the abrasion resistance of the obtained rubber molded body can be improved, and the storage modulus can be further increased.

[0034] As the synthetic rubber, a diene-based synthetic rubber is preferable. As the diene-based synthetic rubber, from the viewpoint of improving the abrasion resistance and the storage modulus of the obtained rubber molded body, it is preferably selected from one or more of polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and polyisobutylene, and more preferably styrene-butadiene copolymer rubber (SBR).

[0035] Among the above diene-based synthetic rubbers, the copolymer rubber can be a block copolymer or a random copolymer, but from the viewpoint of improving the abrasion resistance and the storage modulus of the obtained rubber molded body, a random copolymer is preferable.

[0036] The rubber component can be used alone or in combination with two or more kinds.

[0037] The styrene-butadiene copolymer rubber (SBR) is a rubber that does not show elongation crystallization, however, even if the styrene-butadiene copolymer rubber (SBR) is contained in the rubber component in the present application, the wear resistance and the storage modulus of the obtained rubber molded body can be improved.

[0038] In the present application, in the case where the rubber component further contains a synthetic rubber, the mass ratio (natural rubber / synthetic rubber) of the contents of the natural rubber and the synthetic rubber is preferably 50 / 50 or more, more preferably 60 / 40 or more, further preferably 80 / 20 or more, and more further preferably 90 / 10 or more, from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber molded body and the viewpoint of reducing the tangent of the loss angle of the obtained rubber molded body.

[0039] In addition, the content of the natural rubber in the rubber component is preferably 100 mass% from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber molded body and the viewpoint of reducing the tangent of the loss angle of the obtained rubber molded body.

[0040] < Polyester >

[0041] In the present application, the polyester is a condensate of an alcohol component and a carboxylic acid component, the content of the aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component is 85 mass% or more, and the content of the aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms in the carboxylic acid component is 50 mass% or more.

[0042] (Alcohol component)

[0043] In the present application, with respect to the alcohol component of the polyester, the content of the aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component is 85 mass% or more from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber molded body. If the content of the aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component is less than 85 mass%, the wear resistance cannot be improved, and in addition, the storage modulus cannot be sufficiently increased, and thus it is not preferable. In addition, by making the content of the aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component 85 mass% or more, the tangent of the loss angle of the obtained rubber molded body can be reduced, and thus it is also preferable from this point of view.

[0044] With respect to the content of the aliphatic diol having 2 or more and 16 or less carbon atoms, the content in the alcohol component is preferably 90 mass% or more, more preferably 92 mass% or more, further preferably 95 mass% or more, and more further preferably substantially 100 mass%.

[0045] The chain hydrocarbon group in the above-mentioned aliphatic diol can be either straight-chain or branched, but from the viewpoint of improving the wear resistance and storage modulus of the resulting rubber molded article and reducing the loss tangent of the resulting rubber molded article, a straight-chain hydrocarbon group is preferred, and preferably the hydroxyl group is at the end of the hydrocarbon chain.

[0046] That is, the aliphatic diol is more preferably an α,ω-straight-chain alkanediol having 2 or more and 16 or less carbon atoms.

[0047] The number of carbon atoms of the aliphatic diol is 2 or more, preferably 4 or more, more preferably 6 or more, and further preferably 8 or more, from the same viewpoint as described above, and is 14 or less, more preferably 12 or less, from the viewpoint of improving the crystallinity of the polyester in the rubber composition and rubber molded article.

[0048] As the aliphatic diol having 2 or more and 16 or less carbon atoms, and particularly the α,ω-straight-chain alkanediol having 2 or more and 16 or less carbon atoms, there can be mentioned ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, and the like. Among them, one or more selected from the group consisting of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, and 1,12-dodecanediol is preferred, and one or more selected from the group consisting of ethylene glycol, 1,4-butanediol, 1,10-decanediol, and 1,12-dodecanediol is more preferred.

[0049] In the alcohol component, an alcohol other than the aliphatic diol having 2 or more and 16 or less carbon atoms can be contained within a range not interfering with the object of the present application. As the alcohol component other than the aliphatic diol having 2 or more and 16 or less carbon atoms, there can be mentioned an aromatic diol such as an alkylene oxide adduct of bisphenol A, glycerol, pentaerythritol, trimethylolpropane, a polyhydric alcohol having 3 or more valences, a monovalent alcohol, and the like.

[0050] The above-mentioned alcohol component can be used alone or in combination with two or more.

[0051] (Carboxylic Acid Component)

[0052] In the present application, in the carboxylic acid component of the polyester, 50% by mass or more of an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms is contained, from the viewpoint of improving the wear resistance and storage modulus of the resulting rubber molded article.

[0053] If the content of the aliphatic dicarboxylic compound having 2 or more and 16 or less carbon atoms in the carboxylic acid component is less than 50% by mass, the wear resistance of the obtained rubber molded article cannot be improved, and the storage modulus cannot be sufficiently increased. Since the storage modulus cannot be improved, this is not preferred. In addition, by making the content of the aliphatic dicarboxylic compound having 2 or more and 16 or less carbon atoms in the alcohol component 50% by mass or more, the tangent of the loss angle of the obtained rubber molded article decreases, and this is also preferred from this viewpoint.

[0054] The content of the aliphatic dicarboxylic compound having 2 or more and 16 or less carbon atoms is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and more further preferably 90% by mass or more in the carboxylic acid component, and more further preferably substantially 100% by mass.

[0055] The chain hydrocarbon group in the above aliphatic dicarboxylic compound can be a straight chain or a branched chain, but from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber molded article and the viewpoint of decreasing the tangent of the loss angle of the obtained rubber molded article, a straight chain hydrocarbon group is preferred, and the carboxyl group is preferably at the end of the hydrocarbon chain.

[0056] That is, the aliphatic dicarboxylic compound is more preferably an α,ω-straight chain aliphatic dicarboxylic acid having 2 or more and 16 or less carbon atoms.

[0057] The carbon number of the aliphatic dicarboxylic compound is preferably 4 or more and preferably 14 or less from the same viewpoint as above.

[0058] As the aliphatic dicarboxylic compound having 2 or more and 16 or less carbon atoms, and particularly the α,ω-straight chain aliphatic dicarboxylic acid having 2 or more and 16 or less carbon atoms, there are succinic acid (carbon number: 4), fumaric acid (carbon number: 4), sebacic acid (carbon number: 10), dodecanedioic acid (carbon number: 12), tetradecanedioic acid (carbon number: 14), hexadecanedioic acid (carbon number: 16), succinic acid having an alkyl group or an alkenyl group in the side chain, and the like, and among the aliphatic dicarboxylic compounds, anhydrides thereof, alkyl esters thereof having 1 or more and 3 or less carbon atoms, and the like are also included. Among them, one or more selected from the group consisting of succinic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid are preferred, one or more selected from the group consisting of succinic acid, sebacic acid, dodecanedioic acid, and tetradecanedioic acid are more preferred, and one or more selected from the group consisting of succinic acid, sebacic acid, and dodecanedioic acid are further preferred.

[0059] Note that in the present application, the carboxylic acid component includes not only free acids but also anhydrides that are decomposed to generate acids in the reaction and alkyl esters having 1 or more and 3 or less carbon atoms. However, the carbon number of the alkyl group of the alkyl ester part is not included in the carbon number of the aliphatic dicarboxylic compound.

[0060] In the carboxylic acid component, other carboxylic acid compounds than the aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms can be contained within a range not impeding the object of the present application. As the other carboxylic acid compounds, aromatic dicarboxylic acid compounds such as terephthalic acid, isophthalic acid, and the like, 3 or more polybasic carboxylic acid compounds such as trimellitic acid, pyromellitic acid, and the like, and 1 -membered carboxylic acid compounds can be mentioned.

[0061] The total amount of the content of the aliphatic diol having 2 or more and 16 or less carbon atoms and the content of the aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms is preferably 85% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and still further preferably substantially 100% by mass in the raw monomers of the polyester.

[0062] Further, the content of the aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms with respect to 100 parts by mole of the aliphatic diol having 2 or more and 16 or less carbon atoms is preferably 75 parts by mole or more, more preferably 85 parts by mole or more, and preferably 115 parts by mole or less, more preferably 110 parts by mole or less, and further preferably 105 parts by mole or less.

[0063] (Production of the polyester)

[0064] In the present application, the polyester can be produced by a publicly known method. For example, the polycondensation reaction of the alcohol component and the carboxylic acid component can be performed in a non-active gas atmosphere, and as necessary, in the presence of an esterification catalyst, an esterification cocatalyst, a polymerization inhibitor, or the like, preferably at a temperature of 160°C or higher and 240°C or lower, and more preferably at a temperature of 190°C or higher and 230°C or lower.

[0065] As the esterification catalyst, metal compounds such as tin catalysts, titanium catalysts, antimony trioxide, zinc acetate, germanium dioxide, and the like can be mentioned, however, from the viewpoint of the reaction efficiency of esterification, tin compounds such as dibutyltin oxide, tin (II) 2-ethylhexanoate, titanium compounds such as diisopropyltin bis(triethanolamine) titanate, and the like are preferred.

[0066] The amount of use of the esterification catalyst is preferably 0.01 parts by mass or more and 1.5 parts by mass or less, and more preferably 0.1 parts by mass or more and 1.0 parts by mass or less, with respect to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0067] As the esterification cocatalyst, a pyrogallol compound is preferred, and specifically, pyrogallol, gallic acid, gallate, benzophenone derivatives, catechin derivatives, and the like can be mentioned, however, from the viewpoint of the reactivity, gallic acid is preferred.

[0068] The amount of use of the esterification cocatalyst is preferably 0.001 parts by mass or more and 0.5 parts by mass or less, more preferably 0.01 parts by mass or more and 0.1 parts by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0069] As the polymerization inhibitor, tertiary butyl catechol and the like can be given.

[0070] The amount of use of the polymerization inhibitor is preferably 0.001 parts by mass or more and 0.5 parts by mass or less, more preferably 0.01 parts by mass or more and 0.1 parts by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0071] In the present application, the weight average molecular weight of the polyester is preferably 3000 or more, more preferably 5000 or more, further preferably 6000 or more, more further preferably 7000 or more, and more further preferably 10000 or more, and is preferably 100000 or less, more preferably 50000 or less, further preferably 40000 or less, and more further preferably 35000 or less, from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber molded body and the viewpoint of reducing the tangent of the loss angle of the obtained rubber molded body.

[0072] The weight average molecular weight of the polyester can be measured by the method described in the Examples.

[0073] The polyester of the present application is preferably a crystalline polyester from the viewpoint of improving the wear resistance of the rubber molded body. When a polyester in a solid state is heated, the crystalline polyester sharply changes from a solid state to a molten state at the melting point. On the other hand, an amorphous polyester slowly changes from a solid state to a molten state at the glass transition temperature. In the present application, a polyester in which a melting point is observed is defined as a crystalline polyester.

[0074] In the present application, the melting point of the polyester is preferably 60°C or more, more preferably 70°C or more, and further preferably 75°C or more, and is preferably 150°C or less, more preferably 130°C or less, and further preferably 120°C or less, from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber molded body and the viewpoint of reducing the tangent of the loss angle of the obtained rubber molded body.

[0075] The melting point of the polyester can be measured by the method described in the Examples.

[0076] In the present application, the larger the heat absorption amount ΔH of the melting endothermic peak based on DSC of the polyester is, the higher the crystallinity of the polyester tends to be. Therefore, the larger the heat absorption amount ΔH of the melting endothermic peak based on DSC of the polyester is, the more easily the polyester becomes a nucleus of the elongation crystal of the natural rubber, the more easily the polyester promotes the elongation crystallization of the obtained rubber molded body, and in particular, the more easily the polyester improves the wear resistance.

[0077] In the present application, the heat absorption amount ΔH of the melting endothermic peak based on DSC of the polyester is preferably 50 J / g or greater, more preferably 70 J / g or greater, further preferably 80 J / g or greater, more further preferably 90 J / g or greater, and preferably 180 J / g or less, more preferably 170 J / g or less, further preferably 160 J / g or less, more further preferably 150 J / g or less, from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber molded body, and from the viewpoint of reducing the loss tangent of the obtained rubber molded body.

[0078] The heat absorption amount ΔH of the polyester can be adjusted to the above range by adjusting the monomer composition, the molecular weight of the polyester, and the like.

[0079] The heat absorption amount ΔH of the polyester can be measured using the method described in the examples.

[0080] The Hansen solubility parameter (SP value) of the polyester of the present application is preferably 16 (MPa) 1 / 2 or more, more preferably 17.0 (MPa) 1 / 2 or more, further preferably 17.5 (MPa) 1 / 2 or more, more further preferably 18.0 (MPa) 1 / 2 or more, more further preferably 18.5 (MPa) 1 / 2 or more, and preferably 24.0 (MPa) 1 / 2 or less, more preferably 23.5 (MPa) 1 / 2 or less, further preferably 23.0 (MPa) 1 / 2 or less. By controlling the SP value of the polyester to be within the above range, the polyester is easily formed into fine crystals without being compatible with the rubber component in the rubber composition and the rubber molded body, and is easily formed into the nucleus of the elongated crystal, and thus the wear resistance can be improved. In addition, the network of the polyester is easily formed in the rubber component, and the storage modulus can be improved.

[0081] The above SP value can be calculated using solubility parameter calculation software (Hansen Solubility Parameters in Practice 4th Edition 4.1.03). Note that in the present specification, the SP value uses the solubility parameter of Hansen. The solubility parameter of Hansen is a parameter calculated based on the chemical structure by classifying the types of interaction energy acting between the molecules of a substance into three types. Specifically, the SP value δ is calculated using the following formula in which the solubility parameter of Hildebrand is classified into three components. δ = (δ d 2 + δp 2 + δ h 2 1 / 2

[0082] Here, δ d is a London dispersion term, δ p is a molecular polarization term, and δ h is a hydrogen bond term. Each of δ d , δ p , and δ h is described in detail in "HANSEN SOLUBILITY PARAMETERS" A User's Handbook Second Edition.

[0083] In addition, in a case where the SP value cannot be calculated using the above method, the value described in "Solubility Parameter Values" in Polymer Handbook Fourth Edition (Wiley, 1999), pp. 675-714, etc. can be used.

[0084] The polyester of the present application can also be a modified polyester modified to an extent that does not substantially impair its properties. As the modified polyester, for example, a urethane-modified polyester in which the polyester is modified by a urethane bond, an epoxy-modified polyester in which the polyester is modified by an epoxy bond, and a composite resin having two or more resin components including a polyester component and an addition polymer-based resin component, etc. can be given.

[0085] The polyester of the present application preferably has a polyester portion of 98 mass% or more, more preferably consists substantially of a polyester portion, and further preferably consists of a polyester portion only.

[0086] <Inorganic Filler>

[0087] The rubber composition of the present application preferably further contains an inorganic filler. By containing an inorganic filler, the wear resistance and the storage modulus of the obtained rubber molded body can be improved.

[0088] As the inorganic filler, there is no particular limitation, and silica, carbon black, etc. can be given. In addition, as needed, alumina, calcium carbonate, clay, talc, zeolite, diatomaceous earth, etc. can be used. Among them, the inorganic filler is preferably one or more selected from the group consisting of silica and carbon black.

[0089] The inorganic filler can be used alone or in combination with two or more.

[0090] (Silica) ​

[0091] The silica used is not particularly limited, and examples that can be given include wet-process silica, dry-process silica, colloidal silica, and the like. Among these, wet-process silica in which aqueous silicic acid is used as the main component is preferred. The wet-process silica can be a precipitated silica, a gel silica, a sol-gel silica, and more preferably a precipitated silica.

[0092] The BET specific surface area of the silica (determined in accordance with ISO 5794 / 1) is preferably 50 m 2 / g or more, more preferably 100 m 2 / g or more, further preferably 150 m 2 / g or more, and preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, further preferably 250 m 2 / g or less.

[0093] The average secondary particle diameter of the silica is preferably 10 μm or more, more preferably 15 μm or more, further preferably 18 μm or more, and preferably 100 μm or less, more preferably 80 μm or less, further preferably 50 μm or less, from the viewpoint of the dispersibility of the silica in the rubber composition and rubber molded article and the rubber reinforcing properties.

[0094] Examples of commercially available products of silica that can be given include those manufactured by TOSOH SILICA Co., Ltd., trade name: Nipsil AQ (BET specific surface area: 205 m 2 / g), Nipsil KQ (BET specific surface area: 240 m 2 / g), and the like, and those manufactured by EVONIK Co., Ltd., trade name: Ultrasil VN3 (BET specific surface area: 175 m 2 / g), and the like.

[0095] (Carbon Black)

[0096] The carbon black used is not particularly limited, and examples that can be given include carbon black of the SAF, ISAF, IISAF, N339, HAF, FEF, GPF, SRF, and the like grades, and the like, and in addition, examples that can be given include carbon and silica two-phase fillers in which silica is supported on the surface of the carbon black, and the like. Among these, carbon black of the SAF, ISAF, IISAF, N339, HAF, and FEF grades is preferred.

[0097] The DBP absorption amount of the carbon black (determined in accordance with ASTM D2414-65T) is preferably 70 cm 3more preferably 80 cm 3 more preferably 90 cm 3 more preferably 90 cm

[0098] In addition, the nitrogen adsorption specific surface area (N2AS, measured in accordance with JIS K 6217-2:2017) of the carbon black is preferably 50 m 2 more preferably 60 m 2 more preferably 70 m 2 more preferably 70 m

[0099] (Sulfur)

[0100] The rubber composition of the present application preferably contains sulfur as a vulcanizing agent in order to form a rubber molded body by vulcanization.

[0101] As the sulfur, powder sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, and the like, which are generally used in the rubber industry, can be mentioned.

[0102] The sulfur can be used alone or in combination of two or more.

[0103] <Other Components>

[0104] The rubber composition of the present application can contain, in addition to the above components, various additives generally used in the rubber industry, such as a silane coupling agent, an anti-aging agent, a scorch retarder, a softening agent, stearic acid, a processing oil, zinc oxide, a vulcanization accelerator, and the like, as needed, within a range not impairing the object of the present application.

[0105] (Processing Oil)

[0106] As the processing oil, a processing oil having a flow point of 40°C or lower is preferred.

[0107] As the processing oil, from the viewpoint of improving the processability of the rubber composition, one or more selected from the group consisting of aromatic processing oils, naphthenic processing oils, and paraffinic processing oils is preferred, and a naphthenic processing oil is more preferred.

[0108] <Contents of Each Component in the Rubber Composition>

[0109] In the rubber composition of the present application, regarding the content of the polyester, relative to 100 parts by mass of the rubber component, it is preferably 1.0 part by mass or more, more preferably 1.2 parts by mass or more, and further preferably 1.4 parts by mass or more, from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber shaped body, and from the viewpoint of reducing the tangent of the loss angle of the obtained rubber shaped body, and it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, further preferably 20 parts by mass or less, and more further preferably 15 parts by mass or less, and more further preferably 12 parts by mass or less, from the viewpoint of maintaining the properties of the rubber component.

[0110] In addition, in the rubber composition of the present application, regarding the mass ratio of the content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]), it is preferably 0.01 or more, and more preferably 0.02 or more, from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber shaped body, and it is preferably 0.20 or less, more preferably 0.10 or less, and further preferably 0.05 or less, from the viewpoint of reducing the tangent of the loss angle of the obtained rubber shaped body.

[0111] Regarding the content of the rubber component, it is preferably 30% by mass or more, more preferably 35% by mass or more, further preferably 40% by mass or more, and more further preferably 45% by mass or more, and it is preferably 80% by mass or less, more preferably 75% by mass or less, further preferably 70% by mass or less, and more further preferably 65% by mass or less, in the rubber composition, from the viewpoint of maintaining the properties of the rubber component.

[0112] Regarding the content of the inorganic filler, relative to 100 parts by mass of the rubber component, it is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, further preferably 40 parts by mass or more, and more further preferably 45 parts by mass or more, from the viewpoint of improving the wear resistance and the storage modulus of the obtained rubber shaped body, and it is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, further preferably 150 parts by mass or less, more further preferably 100 parts by mass or less, and more further preferably 80 parts by mass or less, from the viewpoint of reducing the heat generation property of the rubber shaped body.

[0113] Regarding the content of the sulfur, relative to 100 parts by mass of the uncrosslinked rubber component, it is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 0.8 parts by mass or more, from the viewpoint of sufficiently vulcanizing the uncrosslinked rubber composition, and it is preferably 3 parts by mass or less, more preferably 2.5 parts by mass or less, and further preferably 2 parts by mass or less.

[0114] In the case where the rubber composition of the present application further contains a processing oil, the content of the processing oil is preferably 4 parts by mass or more and 16 parts by mass or less, more preferably 6 parts by mass or more and 14 parts by mass or less, further preferably 8 parts by mass or more and 12 parts by mass or less, with respect to 100 parts by mass of the rubber component, from the viewpoint of improving the processability of the rubber composition.

[0115] <Manufacture of Rubber Composition>

[0116] The manufacturing method of the rubber composition of the present application has the following steps (1) and (2).

[0117] Step (1): a step of mixing a composition containing a rubber component and a polyester, the rubber component containing natural rubber, the polyester being a condensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component being 85% by mass or more, the content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component being 50% by mass or more;

[0118] Step (2): a step of further adding a mixed sulfur.

[0119] In step (1), more specifically, the rubber component, the polyester, and inorganic filler, silane coupling agent, anti-aging agent, scorch retarder, softener, stearic acid, processing oil, and the like, which are used as needed, are mixed using a mixer, whereby a rubber mix is obtained.

[0120] As the mixer, for example, a Banbury mixer, a roll mixer, a powerful mixer, and the like can be given.

[0121] Regarding the mixing temperature, from the viewpoint of improving the dispersibility of the polyester in the rubber composition, improving the wear resistance and the storage modulus of the obtained rubber shaped body, it is preferably 140°C or higher, more preferably 143°C or higher, further preferably 145°C or higher, and it is preferably 165°C or lower, more preferably 160°C or lower, further preferably 155°C or lower.

[0122] Step (2) is a step of further adding a mixed sulfur after step (1).

[0123] In step (2), more specifically, a mixed sulfur, and zinc oxide, vulcanization accelerator, and the like (sulfenamide-based, guanidine-based, and the like), which are used as needed, are preferably added.

[0124] Regarding the mixing temperature in step (2), from the viewpoint of not causing a vulcanization reaction, it is preferably less than 140°C, more preferably 130°C or lower, further preferably 125°C or lower, and more further preferably 120°C or lower.

[0125] [Rubber Shaped Body]

[0126] The rubber molded body of the present application is obtained by vulcanizing the above-mentioned rubber composition of the present application, i.e., unvulcanized rubber composition.

[0127] The unvulcanized rubber composition is subjected to molding processing by a known method, preferably heated or heated and pressurized at 140°C or higher, more preferably 145°C or higher, and preferably 200°C or lower, more preferably 180°C or lower, to produce a vulcanized rubber molded body.

[0128] The content of the rubber component, the polyester, and the additive such as inorganic filler in the rubber molded body of the present application, and the suitable range thereof are the same as those of the above-mentioned rubber composition.

[0129] The rubber molded body of the present application is obtained by vulcanizing the above-mentioned rubber composition of the present application, i.e., unvulcanized rubber composition, and therefore has excellent wear resistance and storage modulus, and is therefore suitably used as a tire member such as inner liner, tread, tread base, carcass, sidewall, and bead portion of a tire, and also as a rubber molded body such as various rubber conveyor belts, various sealing materials, vibration isolation and vibration prevention materials, and shoe soles.

[0130] <Method for producing rubber molded body>

[0131] The method for producing a rubber molded body of the present application has a step of vulcanizing the above-mentioned rubber composition of the present application.

[0132] As the step of vulcanizing the rubber composition, specifically, it is a step of molding the above-mentioned rubber composition of the present application into a desired shape, and heating or heating and pressurizing at 140°C or higher, more preferably 145°C or higher, and preferably 200°C or lower, more preferably 180°C or lower, to obtain a rubber molded body.

[0133] The content of the rubber component, the polyester, and the additive such as inorganic filler in the rubber molded body obtained, and the suitable range thereof are the same as those of the above-mentioned rubber composition.

[0134] [Tire member]

[0135] The tire member of the present application contains the above-mentioned rubber molded body of the present application. The tire member of the present application has excellent wear resistance and storage modulus because it contains the above-mentioned rubber molded body of the present application.

[0136] As the tire member of the present application, there can be mentioned inner liner, tread, tread base, carcass, sidewall, and bead portion of a tire.

[0137] [Method for improving wear resistance]

[0138] The method for improving the wear resistance of a rubber molded body according to the present application is a method for improving the wear resistance of a rubber molded body containing a rubber component and a polyester, the rubber component containing natural rubber, and the polyester being a condensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component being 85% by mass or more, and the content of an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms in the carboxylic acid component being 50% by mass or more.

[0139] The method for improving the wear resistance according to the present application is considered to be able to improve the wear resistance of a rubber molded body because the rubber molded body contains natural rubber as the above-described rubber component, and because the elongation crystallization of the rubber molded body is promoted by containing the above-described polyester.

[0140] In the method for improving the wear resistance of a rubber molded body according to the present application, the contents of the rubber component, the polyester, the inorganic filler, sulfur, and other additives in the rubber molded body, and the appropriate ranges thereof, are the same as in the above-described rubber composition.

[0141] The present application further includes the following modes.

[0142] <1> A rubber composition containing a rubber component and a polyester,

[0143] The rubber component contains natural rubber,

[0144] The polyester is a condensate of an alcohol component and a carboxylic acid component,

[0145] The content of an aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component is 85% by mass or more,

[0146] The content of an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms in the carboxylic acid component is 50% by mass or more.

[0147] <2> The rubber composition described in <1>, wherein the mass ratio of the content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]) is 0.01 or more and 0.20 or less.

[0148] <3> A rubber composition containing a rubber component and a polyester,

[0149] The rubber component contains natural rubber,

[0150] The polyester is a condensate of an alcohol component and a carboxylic acid component,

[0151] The content of an aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component is 85% by mass or more,

[0152] The content of an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms in the carboxylic acid component is 50% by mass or more,

[0153] The mass ratio of the content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]) is 0.01 or more and 0.20 or less.

[0154] <4> The rubber composition according to any one of <1> to <3>, wherein the rubber component further comprises a synthetic rubber.

[0155] <5> The rubber composition according to <4>, wherein the mass ratio of the content of the natural rubber to the content of the synthetic rubber (natural rubber / synthetic rubber) is 50 / 50 or more.

[0156] <6> A rubber composition comprising a rubber component and a polyester,

[0157] The rubber component comprises a natural rubber and a synthetic rubber,

[0158] The polyester is a polycondensate of an alcohol component and a carboxylic acid component,

[0159] The content of the aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component is 85% by mass or more,

[0160] The content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component is 50% by mass or more, and the mass ratio of the content of the natural rubber to the content of the synthetic rubber (natural rubber / synthetic rubber) is 50 / 50 or more,

[0161] The mass ratio of the content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]) is 0.01 or more and 0.20 or less.

[0162] <7> The rubber composition according to any one of <1> to <6>, wherein the aliphatic diol is an α,ω-linear alkane diol having a carbon number of 2 or more and 16 or less.

[0163] <8> The rubber composition according to any one of <1> to <7>, wherein the aliphatic dicarboxylic acid compound is an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 2 or more and 16 or less, preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 4 or more and 14 or less, more preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 6 or more and 14 or less, and further preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 6 or more and 14 or less.

[0164] <9> The rubber composition according to any one of <1> to <8>, wherein the content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less is 60% by mass or more in the carboxylic acid component, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more, and still further preferably substantially 100% by mass.

[0165] <10> The rubber composition according to any one of <1> to <9>, wherein the aliphatic dicarboxylic acid compound has a carbon number of 4 or more and 14 or less.

[0166] <11> The rubber composition according to any one of <1> to <10>, wherein the total amount of the content of the aliphatic diol having a carbon number of 2 or more and 16 or less and the content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less is 85% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably substantially 100% by mass, in the raw monomers of the polyester.

[0167] <12> The rubber composition according to any one of <1> to <11>, wherein the content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less is 75 moles or more and 115 moles or less, preferably 85 moles or more and 110 moles or less, more preferably 85 moles or more and 115 moles or less, further preferably 85 moles or more and 110 moles or less, and more further preferably 85 moles or more and 105 moles or less, per 100 moles of the aliphatic diol having a carbon number of 2 or more and 16 or less.

[0168] <13> The rubber composition according to any one of <1> to <12>, wherein the weight average molecular weight of the polyester is 3000 or more and 100000 or less, preferably 5000 or more and 50000 or less, more preferably 6000 or more and 40000 or less, further preferably 7000 or more and 35000 or less, and more further preferably 10000 or more and 35000 or less.

[0169] <14> The rubber composition according to any one of <1> to <13>, wherein the melting point of the polyester is 60°C or more and 150°C or less, preferably 70°C or more and 130°C or less, and more preferably 75°C or more and 120°C or less.

[0170] <15> The rubber composition according to any one of <4> to <14>, wherein the synthetic rubber is a diene-based synthetic rubber.

[0171] <16> The rubber composition according to any one of <4> to <15>, wherein the synthetic rubber comprises a diene-based synthetic rubber, and preferably comprises one or more selected from the group consisting of polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chlorobutyl rubber (CR), butyl rubber (IIR), and polyisobutylene, and more preferably comprises styrene-butadiene copolymer rubber (SBR).

[0172] <17> The rubber composition according to any one of <4> to <16>, wherein the mass ratio of the content of the natural rubber to the content of the synthetic rubber (natural rubber / synthetic rubber) is 60 / 40 or more, preferably 80 / 20 or more, further preferably 90 / 10 or more.

[0173] <18> The rubber composition according to any one of <1> to <17>, wherein the mass ratio of the content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]) is 0.02 or more and 0.10 or less, preferably 0.02 or more and 0.05 or less.

[0174] <19> The rubber composition according to any one of <1> to <18>, further comprising an inorganic filler.

[0175] <20> The rubber composition according to any one of <1> to <19>, further comprising a processing oil, the content of the processing oil being 4 parts by mass or more and 16 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0176] <21> The rubber composition according to any one of <1> to <20>, wherein the content of the polyester is 1.0 parts by mass or more and 30 parts by mass or less, preferably 1.2 parts by mass or more and 25 parts by mass or less, more preferably 1.4 parts by mass or more and 20 parts by mass or less, further preferably 1.4 parts by mass or more and 15 parts by mass or less, and still further preferably 1.4 parts by mass or more and 12 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0177] <22> The rubber composition according to any one of <1> to <21>, wherein the content of the rubber component in the rubber composition is 30% by mass or more and 80% by mass or less, preferably 35% by mass or more and 75% by mass or less, more preferably 40% by mass or more and 70% by mass or less, and further preferably 45% by mass or more and 65% by mass or less.

[0178] <23> A rubber molded body obtained by vulcanizing the rubber composition according to any one of <1> to <22>.

[0179] <24> A tire member comprising the rubber molded body according to <23>.

[0180] <25> A method for producing the rubber composition according to any one of <1> to <22>, the method comprising the following steps (1) and (2).

[0181] Process (1): a process of mixing a composition containing a rubber component and a polyester, the rubber component containing natural rubber, the polyester being a condensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component being 85% by mass or more, the content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component being 50% by mass or more;

[0182] Process (2): a process of further adding mixed sulfur.

[0183] <26> A method for producing a rubber molded body, the method comprising a step of vulcanizing the rubber composition described in any one of <1> to <22>.

[0184] <27> A method for producing a rubber composition, the method comprising the following steps (1) and (2).

[0185] Process (1): a process of mixing a composition containing a rubber component and a polyester, the rubber component containing natural rubber, the polyester being a condensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component being 85% by mass or more, the content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component being 50% by mass or more;

[0186] Process (2): a process of further adding mixed sulfur.

[0187] <28> The method for producing a rubber composition described in <27>, wherein the mass ratio of the content of the polyester to the content of the natural rubber in the composition of step (1) ([content of the polyester] / [content of the natural rubber]) is 0.01 or more and 0.20 or less.

[0188] <29> A method for producing a rubber composition, the method comprising the following steps (1) and (2).

[0189] Process (1): a process of mixing a composition containing a rubber component and a polyester, the rubber component containing natural rubber, the polyester being a condensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component being 85% by mass or more, the content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component being 50% by mass or more, the mass ratio of the content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]) being 0.01 or more and 0.20 or less;

[0190] Process (2): a process of further adding mixed sulfur.

[0191] The method for producing a rubber composition according to any one of <27> to <29>, wherein the rubber component further contains a synthetic rubber.

[0192] The method for producing a rubber composition according to <30>, wherein the mass ratio of the content of the natural rubber to the content of the synthetic rubber (natural rubber / synthetic rubber) in the composition of step (1) is 50 / 50 or more.

[0193] The method for producing a rubber composition according to <30>, wherein the mass ratio of the content of the natural rubber to the content of the synthetic rubber (natural rubber / synthetic rubber) in the composition of step (1) is 50 / 50 or more.

[0194] Step (1): a step of mixing a composition containing a rubber component and a polyester, the rubber component containing a natural rubber, the polyester being a polycondensate of an alcohol component and a carboxylic acid component, the content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component being 85% by mass or more, the content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component being 50% by mass or more, the mass ratio of the content of the natural rubber to the content of the synthetic rubber (natural rubber / synthetic rubber) being 50 / 50 or more, and the mass ratio of the content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]) being 0.01 or more and 0.20 or less;

[0195] Step (2): a step of further adding a sulfuric agent.

[0196] The method for producing a rubber composition according to any one of <27> to <32>, wherein the aliphatic diol is an α,ω-linear aliphatic diol having a carbon number of 2 or more and 16 or less.

[0197] The method for producing a rubber composition according to any one of <27> to <33>, wherein the aliphatic dicarboxylic acid compound is an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 2 or more and 16 or less, preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 4 or more and 14 or less, more preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 6 or more and 14 or less, and further preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 6 or more and 14 or less.

[0198] The method for producing a rubber composition according to any one of <27> to <34>, wherein the content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the composition of step (1) is 60% by mass or more in the carboxylic acid component, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more, and still further preferably substantially 100% by mass.

[0199] The method for producing a rubber composition according to any one of <27> to <36>, wherein the aliphatic dicarboxylic acid compound has a carbon number of 4 or more and 14 or less.

[0200] The method for producing a rubber composition according to any one of <27> to <36>, wherein the content of the aliphatic diol having a carbon number of 2 or more and 16 or less and the content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the composition of step (1) are 85% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably substantially 100% by mass, in the raw monomers of the polyester.

[0201] The method for producing a rubber composition according to any one of <27> to <36>, wherein the content of the aliphatic diol having a carbon number of 2 or more and 16 or less and the content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the composition of step (1) are 85% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably substantially 100% by mass, in the raw monomers of the polyester.

[0202] The method for producing a rubber composition according to any one of <27> to <36>, wherein the weight average molecular weight of the polyester is 3000 or more and 100000 or less, preferably 5000 or more and 50000 or less, more preferably 6000 or more and 40000 or less, further preferably 7000 or more and 35000 or less, and more further preferably 10000 or more and 35000 or less.

[0203] The method for producing a rubber composition according to any one of <27> to <36>, wherein the melting point of the polyester is 60°C or more and 150°C or less, preferably 70°C or more and 130°C or less, and more preferably 75°C or more and 120°C or less.

[0204] The method for producing a rubber composition according to any one of <27> to <36>, wherein the aliphatic diol having a carbon number of 2 or more and 16 or less and the content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the composition of step (1) are 85% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably substantially 100% by mass, in the raw monomers of the polyester.

[0205] The method for producing a rubber composition according to any one of <30> to <41>, wherein the synthetic rubber comprises a diene synthetic rubber, preferably comprises one or more selected from the group consisting of polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chlorobutyl rubber (CR), butyl rubber (IIR), polyisobutylene, more preferably comprises styrene-butadiene copolymer rubber (SBR).

[0206] The method for producing a rubber composition according to any one of <30> to <42>, wherein the mass ratio of the content of natural rubber to the content of synthetic rubber in the composition of step (1) (natural rubber / synthetic rubber) is 60 / 40 or more, preferably 80 / 20 or more, further preferably 90 / 10 or more.

[0207] The method for producing a rubber composition according to any one of <27> to <43>, wherein the mass ratio of the content of the polyester to the content of the natural rubber in the composition of step (1) ([content of the polyester] / [content of the natural rubber]) is 0.02 or more and 0.10 or less, preferably 0.02 or more and 0.05 or less.

[0208] The method for producing a rubber composition according to any one of <27> to <44>, wherein the composition of step (1) further contains an inorganic filler.

[0209] The method for producing a rubber composition according to any one of <27> to <45>, wherein the composition of step (1) further contains a processing oil, and the content of the processing oil is 4 parts by mass or more and 16 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0210] The method for producing a rubber composition according to any one of <27> to <47>, wherein the content of the polyester in the composition of step (1) is 1.0 parts by mass or more and 30 parts by mass or less, preferably 1.2 parts by mass or more and 25 parts by mass or less, more preferably 1.4 parts by mass or more and 20 parts by mass or less, further preferably 1.4 parts by mass or more and 15 parts by mass or less, and more further preferably 1.4 parts by mass or more and 12 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0211] The method for producing a rubber composition according to any one of <27> to <47>, wherein the content of the rubber component in the composition of step (1) is 30% by mass or more and 80% by mass or less, preferably 35% by mass or more and 75% by mass or less, more preferably 40% by mass or more and 70% by mass or less, and further preferably 45% by mass or more and 65% by mass or less.

[0212] Use of the rubber composition described in any one of <1> to <22> for improving wear resistance.

[0213] <50> A method for improving wear resistance of a rubber molded body, which is a method for improving wear resistance of a rubber molded body containing a rubber component and a polyester,

[0214] The rubber component contains natural rubber,

[0215] The polyester is a condensation polymer of an alcohol component and a carboxylic acid component,

[0216] The content of an aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component is 85% by mass or more, and the content of an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms in the carboxylic acid component is 50% by mass or more.

[0217] <51> The method for improving wear resistance of a rubber molded body described in <50>, wherein the mass ratio of the content of the polyester to the content of the natural rubber in the rubber molded body ([content of the polyester] / [content of the natural rubber]) is 0.01 or more and 0.20 or less.

[0218] <52> A method for improving wear resistance of a rubber molded body, which is a method for improving wear resistance of a rubber molded body containing a rubber component and a polyester,

[0219] The rubber component contains natural rubber,

[0220] The polyester is a condensation polymer of an alcohol component and a carboxylic acid component,

[0221] The content of an aliphatic diol having 2 or more and 16 or less carbon atoms in the alcohol component is 85% by mass or more, and the content of an aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon atoms in the carboxylic acid component is 50% by mass or more,

[0222] The content of the polyester to the content of the natural rubber ([content of the polyester] / [content of the natural rubber]) is 0.01 or more and 0.20 or less.

[0223] <53> The method for improving wear resistance of a rubber molded body described in any one of <50> to <52>, wherein the rubber component further contains a synthetic rubber.

[0224] <54> The method for improving wear resistance of a rubber molded body described in <53>, wherein the mass ratio of the content of the natural rubber to the content of the synthetic rubber in the rubber molded body (natural rubber / synthetic rubber) is 50 / 50 or more.

[0225] <55> A method for improving wear resistance of a rubber molded body,

[0226] a method for improving wear resistance of a rubber molded body containing a rubber component and a polyester,

[0227] the rubber component contains natural rubber,

[0228] the polyester is a condensation polymer of an alcohol component and a carboxylic acid component,

[0229] a content of an aliphatic diol having a carbon number of 2 or more and 16 or less in the alcohol component is 85% by mass or more, and a content of an aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the carboxylic acid component is 50% by mass or more,

[0230] a mass ratio of contents of the natural rubber and the synthetic rubber (natural rubber / synthetic rubber) is 50 / 50 or more,

[0231] a mass ratio of a content of the polyester to a content of the natural rubber ([content of the polyester] / [content of the natural rubber]) is 0.01 or more and 0.20 or less.

[0232] <56> The method for improving wear resistance of a rubber molded body according to any one of <50> to <55>, wherein the aliphatic diol is an α,ω-linear alkanediol having a carbon number of 2 or more and 16 or less.

[0233] <57> The method for improving wear resistance of a rubber molded body according to any one of <50> to <56>, wherein the aliphatic dicarboxylic acid compound is an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 2 or more and 16 or less, preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 4 or more and 14 or less, more preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 6 or more and 14 or less, and further preferably an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 6 or more and 14 or less.

[0234] <58> The method for improving wear resistance of a rubber molded body according to any one of <50> to <57>, wherein a content of the aliphatic dicarboxylic acid compound having a carbon number of 2 or more and 16 or less in the rubber molded body is 60% by mass or more in the carboxylic acid component, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more, and still further preferably substantially 100% by mass.

[0235] <59> The method for improving wear resistance of a rubber molded body according to any one of <50> to <58>, wherein the aliphatic dicarboxylic acid compound has a carbon number of 4 or more and 14 or less.

[0236] The wear resistance improvement method of the rubber molded body according to any one of <50> to <59>, wherein the total amount of the content of the aliphatic diol having 2 or more and 16 or less carbon number and the content of the aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon number in the raw material monomers of the polyester is 85% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably substantially 100% by mass.

[0237] The wear resistance improvement method of the rubber molded body according to any one of <50> to <60>, wherein the content of the aliphatic dicarboxylic acid compound having 2 or more and 16 or less carbon number with respect to 100 mol of the aliphatic diol having 2 or more and 16 or less carbon number in the rubber molded body is 75 mol or more and 115 mol or less, preferably 85 mol or more and 110 mol or less, more preferably 85 mol or more and 115 mol or less, further preferably 85 mol or more and 110 mol or less, and more further preferably 85 mol or more and 105 mol or less.

[0238] The wear resistance improvement method of the rubber molded body according to any one of <50> to <61>, wherein the weight average molecular weight of the polyester is 3000 or more and 100000 or less, preferably 5000 or more and 50000 or less, more preferably 6000 or more and 40000 or less, further preferably 7000 or more and 35000 or less, and more further preferably 10000 or more and 35000 or less.

[0239] The wear resistance improvement method of the rubber molded body according to any one of <50> to <62>, wherein the melting point of the polyester is 60°C or more and 150°C or less, preferably 70°C or more and 130°C or less, and more preferably 75°C or more and 120°C or less.

[0240] The wear resistance improvement method of the rubber molded body according to any one of <53> to <63>, wherein the synthetic rubber is a diene-based synthetic rubber.

[0241] The wear resistance improvement method of the rubber molded body according to any one of <53> to <64>, wherein the synthetic rubber comprises a diene-based synthetic rubber, and preferably comprises one or more selected from the group consisting of polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chlorobutyl rubber (CR), butyl rubber (IIR), and polyisobutylene, and more preferably comprises styrene-butadiene copolymer rubber (SBR).

[0242] The abrasion resistance of the rubber molded body according to any one of <53> to <66> is improved, wherein the mass ratio of the content of natural rubber to the content of synthetic rubber in the rubber molded body (natural rubber / synthetic rubber) is 60 / 40 or more, preferably 80 / 20 or more, and further preferably 90 / 10 or more.

[0243] The abrasion resistance of the rubber molded body according to any one of <50> to <66> is improved, wherein the mass ratio of the content of the polyester to the content of the natural rubber in the composition of step (1) ([content of the polyester] / [content of the natural rubber]) is 0.02 or more and 0.10 or less, and preferably 0.02 or more and 0.05 or less.

[0244] The abrasion resistance of the rubber molded body according to any one of <50> to <67> is improved, wherein the rubber molded body further contains an inorganic filler.

[0245] The abrasion resistance of the rubber molded body according to any one of <50> to <68> is improved, wherein the rubber molded body further contains a processing oil, and the content of the processing oil is 4 parts by mass or more and 16 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0246] The abrasion resistance of the rubber molded body according to any one of <50> to <69> is improved, wherein the content of the polyester in the rubber molded body is 1.0 parts by mass or more and 30 parts by mass or less, preferably 1.2 parts by mass or more and 25 parts by mass or less, more preferably 1.4 parts by mass or more and 20 parts by mass or less, further preferably 1.4 parts by mass or more and 15 parts by mass or less, and more further preferably 1.4 parts by mass or more and 12 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0247] The abrasion resistance of the rubber molded body according to any one of <50> to <70> is improved, wherein the content of the rubber component in the rubber molded body is 30 mass% or more and 80 mass% or less, preferably 35 mass% or more and 75 mass% or less, more preferably 40 mass% or more and 70 mass% or less, and further preferably 45 mass% or more and 65 mass% or less.

[0248] Examples

[0249] Hereinafter, the present application will be specifically described using examples, but the present application is not limited by any of these examples. Each property value was measured and evaluated using the following methods.

[0250] Measurement of the melting point of the polyester and the heat absorption amount ΔH of the melting endothermic peak based on differential scanning calorimetry (DSC)

[0251] A 0.02 g sample of the polyester powder obtained by the freeze drying was weighed in an aluminum pan, and using a differential scanning calorimeter (manufactured by TA Instruments, trade name: Q-100), the sample was cooled from room temperature (20°C) to 0°C at a cooling rate of 10°C / min, and then left still for 1 minute. Thereafter, the melting point was measured while the sample was heated at a heating rate of 10°C / min up to 180°C. The temperature of the peak on the highest temperature side in the observed endothermic peak was taken as the melting point of the polyester.

[0252] In addition, the endothermic amount ΔH (J / g) per 1 g of the polyester was calculated from the area of the melting endothermic peak.

[0253] <Measurement of SP value of polyester>

[0254] The SP value was calculated based on the solubility parameter of Hansen using solubility parameter calculation software (Hansen Solubility Parameters in Practice 4thEdition 4.1.03). Note that, in the calculation of the SP value, the specific gravity of the polyester was set to 1.0.

[0255] <Measurement of weight average molecular weight of polyester>

[0256] The weight average molecular weight (Mw) of the polyester was determined by measuring the molecular weight distribution using the following gel permeation chromatography (GPC) method.

[0257] (1) The polymer was dissolved in chloroform so that the concentration of the sample solution was 0.5 g / 100 mL. Then, the solution was filtered using a fluororesin filter (manufactured by Sumitomo Electric Industries, Ltd., trade name: FP-200) having a pore size of 2 μm to remove insoluble components, and a sample solution was prepared.

[0258] (2) Using a molecular weight measuring device (manufactured by TOSOH Corporation, trade name: CO-8010, analysis column: GMHXL + G3000HXL), a chromatographic column was stabilized in a constant-temperature bath at 40°C using chloroform as an eluent at a flow rate of 1 mL / min. A 100-μl sample solution was injected into the device to perform the measurement. The molecular weight of the sample was calculated based on a standard curve prepared in advance. The standard curve at this time was prepared using several monodisperse polystyrenes (monodisperse polystyrenes manufactured by TOSOH Corporation; 2.63 x 10 3 , 2.06 x 10 4 , 1.02 x 10 5 , monodisperse polystyrenes manufactured by GL Science, Inc.; 2.10 x 10 3 , 7.00 x 10 3 , 5.04 x 104 A standard curve was prepared using the standard curve samples (number average molecular weight) as a standard curve.

[0259] Production Examples 1 to 5 [Production of polyesters A to D and M]

[0260] The raw material monomers and tin (II) 2-ethylhexanoate 20 g shown in Table 1 were added to a 10 L volume four-necked flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and held at 140°C for 6 hours, and then warmed to 200°C over 6 hours, and after reaction at 200°C for 1 hour, reacted at 8.3 kPa for 1 hour, to obtain polyesters A to D and M. The results are shown in Table 1.

[0261] Details of each component shown in Table 1 are shown below.

[0262] [Alcohol component]

[0263] • EG: ethylene glycol

[0264] • 1,2-PD: 1,2-propanediol

[0265] • 1,4-BD: 1,4-butanediol

[0266] • 1,10-DD: 1,10-decanediol

[0267] • 1,12-DD: 1,12-dodecanediol

[0268] [Carboxylic acid component]

[0269] • succinic acid

[0270] • sebacic acid

[0271] • DDA: dodecanedioic acid

[0272] • TPA: terephthalic acid

[0273] • TMA: trimellitic acid

[0274] [Table 1]

[0275]

[0276] Examples 1 to 9, Comparative Examples 1 to 6, and Reference Examples 1 to 4

[0277] The raw material components shown in Tables 2 to 5 were prepared, and the components except for zinc oxide, sulfur, and vulcanization accelerators 1 and 2 were kneaded using a Banbury mixer at a maximum temperature of 150°C for 4 minutes. Then, zinc oxide, sulfur, and vulcanization accelerators 1 or 2 were added, and kneaded at a maximum temperature of 110°C for 2 minutes, to obtain unvulcanized rubber compositions.

[0278] The obtained unvulcanized rubber composition was heated at 160°C for 30 minutes to obtain a sheet-like vulcanized rubber molded body. The thickness of the sheet-like vulcanized rubber molded body was 2 mm.

[0279] Details of each component shown in Tables 2 to 5 are shown below.

[0280] [ Rubber Component ]

[0281] • NR: RSS #3

[0282] • SBR1: Solution polymerized SBR, manufactured by JSR Corporation, trade name: HPR850, styrene content: 27.5 mass%

[0283] • SBR2: Emulsion polymerized SBR, manufactured by ZEON Corporation, trade name: NIPOL 1502, styrene content: 23.5 mass%

[0284] [ Polyester ]

[0285] • Polyesters A to D and M obtained in Production Examples 1 to 5

[0286] [ Inorganic Filler ]

[0287] • Silica: Nipsil AQ, manufactured by TOSOH SILICA Corporation, BET specific surface area: 205 m 2 / g

[0288] • Carbon black: N234, manufactured by Beilum Carbon Chemical, furnace black, DBP absorption: 125 cm 3 / 100 g, N2AS: 117 m 2 / g

[0289] [ Other Additives ]

[0290] • Silane coupling agent: Si75, manufactured by EVONIK Corporation

[0291] • Processing oil: Naphthenic processing oil, manufactured by SUNPO Co., Ltd., trade name: SUNTHENE 410

[0292] • Stearic acid: LUNAC S-70V, manufactured by Kao Corporation

[0293] • Anti-aging agent: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD., trade name: NOCRAC 6C

[0294] • Zinc oxide: Zinc oxide (first grade), manufactured by FUJIFILM Wako Pure Chemical Corporation

[0295] • Sulfur: Fuji Photo Film and Seigyo Kagaku Co., Ltd. Reagent, Sulfur (powder, chemical use)

[0296] • Sulfurization accelerator 1: Sulfenamide-based sulfurization accelerator, N-tert-butyl-2-benzothiazylsulfenamide (TBBS) manufactured by Sanwa Chemical Industry Co., Ltd. "SANCCELER NS"

[0297] • Sulfurization accelerator 2: Sulfenamide-based sulfurization accelerator, N-cyclohexyl-2-benzothiazylsulfenamide, manufactured by Ono Pharmaceutical Co., Ltd., trade name: NOCELER CZ-G

[0298] Evaluation of abrasion resistance

[0299] A test piece having a hole of a size of a dedicated mandrel, with a diameter of 50 mm and a thickness of 10 mm, was prepared from the obtained sheet-like vulcanized rubber molded body, and an FPS abrasion tester (AB-2012) manufactured by Ushio Manufacturing Co., Ltd. was used to measure the FPS abrasion amount under the conditions of METABRIT (grit 240, abrasive A) manufactured by Noritake Coated Abrasive Co., Ltd. as the abrasion road surface, a sample speed of 80 m / minute, a load of 40 N, a talc powder feeder of 0.4 rpm, a set temperature of 35°C, and a slip ratio of 10%. The measurement results are shown in Tables 2 to 5.

[0300] Regarding the measured FPS abrasion amount, the relative value when the FPS abrasion amount of Reference Example 1 is taken as 100 is shown in Table 2, the relative value when the FPS abrasion amount of Reference Example 2 is taken as 100 is shown in Table 3, the relative value when the FPS abrasion amount of Reference Example 3 is taken as 100 is shown in Table 4, and the relative value when the FPS abrasion amount of Reference Example 4 is taken as 100 is shown in Table 5.

[0301] The smaller the relative value of the FPS abrasion amount, the less the abrasion amount, and the better the abrasion resistance.

[0302] Evaluation of storage modulus (G')

[0303] The storage modulus (G') of the obtained sheet-like vulcanized rubber molded body was measured using a viscoelasticity measuring device (manufactured by TA Instruments, ARES-G2) under the conditions of a temperature of 50°C, a dynamic strain of 5%, and a frequency of 10 Hz. The measurement results are shown in Tables 2 to 5.

[0304] The relative value of the storage modulus (G') when the storage modulus (G') of Reference Example 1 is taken as 100 is shown in Table 2, the relative value of the storage modulus (G') when the storage modulus (G') of Reference Example 2 is taken as 100 is shown in Table 3, the relative value of the storage modulus (G') when the storage modulus (G') of Reference Example 3 is taken as 100 is shown in Table 4, and the relative value of the storage modulus (G') when the storage modulus (G') of Reference Example 4 is taken as 100 is shown in Table 5.

[0305] The greater the relative value of the storage modulus (G'), the greater the storage modulus, the higher the block rigidity when used in a tire or the like, and the more excellent the handling stability of a vehicle when used in a tire member.

[0306] <Evaluation of Loss Tangent (tan δ)>

[0307] The loss tangent (tan δ) of the obtained sheet-like vulcanized rubber molded body was measured using a viscoelasticity measuring device (ARES-G2 manufactured by TA Instruments, Inc.) under conditions of a temperature of 50°C, a dynamic strain of 5%, and a frequency of 10 Hz. The measurement results are shown in Tables 2 to 5.

[0308] The relative value of the loss tangent (tan δ) when the loss tangent (tan δ) of Reference Example 1 is taken as 100 is shown in Table 2, the relative value of the loss tangent (tan δ) when the loss tangent (tan δ) of Reference Example 2 is taken as 100 is shown in Table 3, the relative value of the loss tangent (tan δ) when the loss tangent (tan δ) of Reference Example 3 is taken as 100 is shown in Table 4, and the relative value of the loss tangent (tan δ) when the loss tangent (tan δ) of Reference Example 4 is taken as 100 is shown in Table 5.

[0309] The smaller the relative value of the loss tangent (tan δ), the smaller the rolling resistance of a tire when used in a tire member, the smaller the heat generation, and the more excellent the low fuel consumption.

[0310] [Table 2]

[0311]

[0312] [Table 3]

[0313]

[0314] [Table 4]

[0315]

[0316] [Table 5]

[0317]

[0318] According to Tables 2 to 5, it was confirmed that the rubber molded bodies obtained in Examples 1 to 9 of the present application were excellent in wear resistance and high in storage modulus, as compared with the rubber molded bodies obtained in Comparative Examples 1 to 6. In addition, it was confirmed that the rubber molded bodies obtained in Examples 1 to 5 were reduced in tan δ, as compared with the rubber molded body obtained in Comparative Example 1.

[0319] In addition, Comparative Examples 3 to 6 not containing natural rubber but containing a polyester were compared with Reference Example 1 not containing natural rubber and a polyester, and it was confirmed that the wear resistance was reduced in Comparative Examples 3 to 6, as compared with Reference Example 1. That is, it was confirmed that in the rubber composition and the rubber molded body, even in the case of containing a polyester, if natural rubber is not contained as a rubber component, the wear resistance cannot be improved.

[0320] Industrial applicability

[0321] According to the present application, it is possible to provide a rubber composition excellent in wear resistance and high in storage modulus, a rubber molded body using the rubber composition, a tire member, and a method for improving the wear resistance of a rubber composition. The obtained rubber molded body can be particularly suitably used as a tire member such as various tires, tire treads, and the like for passenger cars, small and medium-sized trucks, and large vehicles (large-sized trucks, buses, construction vehicles, and the like), and the like, and in addition, can be particularly suitably used for various rubber conveyor belts, various sealing materials, vibration isolation and vibration prevention materials, shoe soles, and the like.

Claims

1. A rubber composition comprising a rubber component and a polyester, The rubber component includes natural rubber. Polyester is a condensation polymer of alcohol and carboxylic acid components. The content of aliphatic diols with 2 or more carbon atoms and 16 or fewer in the alcohol component is 85% by mass or more, and the content of aliphatic dicarboxylic acid compounds with 2 or more carbon atoms and 16 or fewer in the carboxylic acid component is 50% by mass or more.

2. The rubber composition according to claim 1, wherein, Aliphatic diols are α,ω-straight-chain alkanediols with 2 or more but less than 16 carbon atoms.

3. The rubber composition according to claim 1 or 2, wherein, Aliphatic dicarboxylic acid compounds are α,ω-linear aliphatic dicarboxylic acids with 2 or more carbon atoms and 16 or fewer carbon atoms.

4. The rubber composition according to any one of claims 1 to 3, wherein, The weight-average molecular weight of polyester is above 3,000 and below 100,000.

5. The rubber composition according to any one of claims 1 to 4, wherein, Polyester has a melting point above 60°C and below 150°C.

6. The rubber composition according to any one of claims 1 to 5, wherein, The rubber component further includes synthetic rubber.

7. The rubber composition according to claim 6, wherein, The synthetic rubber is a diene-based synthetic rubber.

8. The rubber composition according to claim 6 or 7, wherein, The mass ratio of natural rubber to synthetic rubber, i.e., natural rubber / synthetic rubber, is 50 / 50 or higher.

9. The rubber composition according to any one of claims 1 to 8, further comprising an inorganic filler.

10. The rubber composition according to any one of claims 1 to 9, further comprising processing oil, wherein the content of processing oil is 4 parts by mass or more and 16 parts by mass or less relative to 100 parts by mass of the rubber component.

11. The rubber composition according to any one of claims 1 to 10, wherein, The polyester content is more than 1.0 part by weight and less than 30 parts by weight per 100 parts by weight of rubber component.

12. The rubber composition according to any one of claims 1 to 11, wherein, The mass ratio of polyester content to natural rubber content, i.e., [polyester content] / [natural rubber content], is 0.01 or more and 0.20 or less.

13. A rubber molded article, which is formed by vulcanizing the rubber composition according to any one of claims 1 to 12.

14. A tire component comprising the rubber molded body of claim 13.

15. A method for manufacturing the rubber composition according to any one of claims 1 to 12, the method comprising the steps (1) and (2): Step (1): A step of mixing the composition, wherein the composition comprises a rubber component and a polyester, the rubber component comprises natural rubber, the polyester is a condensation polymer of an alcohol component and a carboxylic acid component, the content of aliphatic diols with 2 or more carbon atoms and 16 or less in the alcohol component is 85% by mass or more, and the content of aliphatic dicarboxylic acid compounds with 2 or more carbon atoms and 16 or less in the carboxylic acid component is 50% by mass or more. Process (2): The process of further adding mixed sulfur.

16. A method for manufacturing a rubber molded article, comprising a step of vulcanizing the rubber composition according to any one of claims 1 to 12.

17. Use of the rubber composition according to any one of claims 1 to 12 for improving abrasion resistance.

18. A method for improving the wear resistance of a rubber molded article, wherein the method comprises a rubber component and a polyester. The rubber component includes natural rubber. Polyester is a condensation polymer of alcohol and carboxylic acid components. The content of aliphatic diols with 2 or more carbon atoms and 16 or fewer in the alcohol component is 85% by mass or more, and the content of aliphatic dicarboxylic acid compounds with 2 or more carbon atoms and 16 or fewer in the carboxylic acid component is 50% by mass or more.

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