JP2009013266A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in durability while reducing its own rolling resistance through improving the low-exothermic tendency of tire members used, particularly, a pneumatic tire markedly improved in durability by improving moist heat adhesion between steel cords and coating rubber while reducing its own rolling resistance through improving the low-exothermic tendency of the coating rubber on the steel cords. <P>SOLUTION: The pneumatic tire is such that a rubber composition obtained by compounding 100 pts.mass of a rubber component comprising a modified natural rubber containing polar groups in natural rubber molecules with 1-10 pts.mass of sulfur and 0.1-10 pts.mass of a compound comprising a disubstituted or trisubstituted benzene ring having at least one hydroxy group as the substituent is used in either one of tire members. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which low heat generation of a tire member to be used is improved and durability is improved while reducing rolling resistance, and in particular, low heat generation of a coating rubber of a steel cord is improved. The present invention relates to a pneumatic tire in which the damp heat resistance between the steel cord and the coating rubber is improved and the durability is greatly improved while reducing rolling resistance.

  Nowadays, there is an increasing demand for lower fuel consumption of automobiles, and tires with low rolling resistance are required. On the other hand, tire treads are currently being actively reduced in loss, but in order to further reduce rolling resistance, it is expected that the demand for lower loss in case members will increase in the future. Is done.

  On the other hand, further improvement of the durability of the tire is also desired. For example, in a steel cord reinforced pneumatic tire, it is important to ensure the adhesion between the steel cord and the coating rubber covering the cord, It is known that when the adhesion is lowered, the durability of the carcass and the belt is lowered, and as a result, a problem occurs in the durability of the tire. Therefore, various studies have been made so far in order to improve the adhesion between the steel cord and the coating rubber and extend the life of the tire.

  For example, as a study of coating rubber, a technique using an adhesive rubber composition containing resorcin or resorcin-formaldehyde resin (hereinafter referred to as “RF resin”) obtained by condensing resorcin and formaldehyde as coating rubber ( JP, 2001-234140, A) is known, and it is known that moisture-and-heat adhesion nature of a steel cord and coating rubber will improve drastically by blending resorcinol or RF resin.

JP 2001-234140 A

  However, when resorcin or RF resin is blended, there is a problem that the heat generated by the rubber increases and the rolling resistance increases. Further, as the heat generation of the rubber increases, there is a problem that the thermal deterioration of the rubber is promoted and the durability is deteriorated.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, improve the low heat build-up of the tire member to be used, and reduce the rolling resistance while improving the durability. To provide a pneumatic tire that improves the low heat buildup of the coating rubber of the cord and reduces the rolling resistance while improving the wet heat adhesion between the steel cord and the coating rubber and greatly improving the durability. is there.

  As a result of intensive studies to achieve the above object, the present inventors have developed a rubber composition in which a compound having a specific structure is blended with a rubber component containing a modified natural rubber containing a polar group in a natural rubber molecule. By using any of the members, the low exothermic property of the tire member can be improved, the tire member can be reduced in resistance to thermal deterioration while reducing the rolling resistance of the tire, and the durability can be improved. By using the rubber composition as a steel cord coding rubber, it was found that the wet heat adhesion between the steel cord and the coating rubber was improved, and the durability of the tire was greatly improved, thereby completing the present invention. It was.

  That is, the pneumatic tire of the present invention has 1 to 10 parts by mass of sulfur and at least one hydroxyl group as a substituent with respect to 100 parts by mass of a rubber component containing a modified natural rubber containing a polar group in the natural rubber molecule. A rubber composition obtained by blending 0.1 to 10 parts by mass of a compound containing a disubstituted or trisubstituted benzene ring and having any one of the tire members is used.

［式中、Ｘは、水酸基、カルボキシル基又は−ＣＯＯＣ_mＨ_2m+1（ここで、ｍは１〜５のいずれかの整数である）であり；Ｙは、２-位，４-位，５-位又は６-位にあり、水素、水酸基又は下記一般式(II)：

｛式中、Ｚ₁及びＺ₂は、それぞれ独立して水酸基、カルボキシル基又は−ＣＯＯＣ_qＨ_2q+1（ここで、ｑは１〜５のいずれかの整数である）であり；ｐは、１〜７のいずれかの整数である｝で表される置換基である］で表される化合物が好ましい。 In the pneumatic tire of the present invention, the compound containing a substituted benzene ring is represented by the following general formula (I):

[Wherein, X is a hydroxyl group, a carboxyl group or —COOC _m H _{2m + 1} (where m is an integer of 1 to 5); Y is a 2-position, a 4-position, 5- or 6-position, hydrogen, hydroxyl group or the following general formula (II):

{In the formula, Z ₁ and Z ₂ are each independently a hydroxyl group, a carboxyl group or —COOC _q H _{2q + 1} (where q is an integer of 1 to 5); It is a substituent represented by} which is an integer of 1 to 7.] is preferable.

［式中、Ｒは炭素数１〜１２の２価の脂肪族基又は２価の芳香族基を表す］で表される化合物も好ましく、下記一般式(IV)：

［式中、Ｒは炭素数１〜１２の２価の脂肪族基又は２価の芳香族基を表す］で表される化合物が特に好ましい。 In the pneumatic tire of the present invention, the compound containing a substituted benzene ring is represented by the following general formula (III):

[Wherein R represents a divalent aliphatic group having 1 to 12 carbon atoms or a divalent aromatic group] is also preferred, and the following general formula (IV):

[Wherein, R represents a divalent aliphatic group having 1 to 12 carbon atoms or a divalent aromatic group] is particularly preferable.

［式中、Ｒは炭素数１〜１２の２価の脂肪族基又は２価の芳香族基を表し、ｎは２〜６の整数を示す。］ In the pneumatic tire of the present invention, as the compound containing the substituted benzene ring, the compound represented by the general formula (IV) is 60 to 100% by mass, represented by the following general formula (V), and n = 2. The compound is represented by 0 to 20% by mass, represented by the following general formula (V), and the compound represented by n = 3 is represented by 0 to 10% by mass and represented by the following general formula (V) and n = 4 to 6 in total. A composition consisting of 0 to 10% by mass is also preferred.

[In formula, R represents a C1-C12 bivalent aliphatic group or a bivalent aromatic group, and n shows the integer of 2-6. ]

  R in the general formula (IV) is preferably an alkylene group having 2 to 10 carbon atoms or a phenylene group. R in the general formula (V) is also preferably an alkylene group having 2 to 10 carbon atoms or a phenylene group.

  In the pneumatic tire of the present invention, the rubber composition preferably further contains an organic acid cobalt salt in an amount of 0.03 to 1 part by mass as a cobalt amount with respect to 100 parts by mass of the rubber component.

  In a preferable example of the pneumatic tire of the present invention, the polar group of the modified natural rubber is an amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group. , Carboxyl group, carbonyl group, epoxy group, oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, alkoxysilyl group, and tin-containing group Is at least one selected from the group consisting of

  In another preferred embodiment of the pneumatic tire of the present invention, the polar group content of the modified natural rubber is 0.001 to 0.5 mmol / g with respect to the rubber component of the modified natural rubber.

  The pneumatic tire of the present invention includes a carcass made of one or more carcass plies, and a belt made of one or more belt layers disposed on the outer side in the tire radial direction of the carcass, and at least one of the carcass and the belt Includes a layer made of a steel cord coated with a coating rubber, and the rubber composition is preferably used for the coating rubber covering the steel cord on at least one of the carcass and the belt.

  According to the present invention, a rubber composition in which a compound having a specific structure is blended with a rubber component containing a modified natural rubber containing a polar group in a natural rubber molecule is used for any of the tire members. As a result, the tire member can be prevented from thermal deterioration while the durability of the tire member is improved. Furthermore, by using the rubber composition as a coding rubber for a steel cord, the wet heat adhesion between the steel cord and the coating rubber can be improved, and the durability of the tire can be greatly improved.

  The present invention is described in detail below. The pneumatic tire of the present invention has 1 to 10 parts by mass of sulfur and at least one hydroxyl group as a substituent with respect to 100 parts by mass of a rubber component containing a modified natural rubber containing a polar group in a natural rubber molecule. A rubber composition comprising 0.1 to 10 parts by mass of a compound containing a substituted or trisubstituted benzene ring is used for any of tire members. By using a rubber composition containing the above compound containing a substituted benzene ring as a coating rubber, it is possible to improve wet heat resistance between the steel cord and the coating rubber. For this reason, by using the rubber composition as a coding rubber for a steel cord, the wet heat adhesion between the steel cord and the coating rubber can be improved, and the durability of the tire can be greatly improved. However, when the compound containing a substituted benzene ring is blended, the heat generation of the rubber deteriorates, the rolling resistance increases, and the heat generation of the rubber increases, so that the heat deterioration of the rubber is promoted and the durability is increased. Getting worse. On the other hand, since the modified natural rubber has a higher affinity for the filler than the unmodified natural rubber, by using the modified natural rubber, the dispersibility of the filler with respect to the rubber component is improved, and the rubber composition Low exothermic property (low loss property) can be greatly improved. Therefore, by using a rubber composition in which the compound containing the substituted benzene ring is blended with the rubber component containing the modified natural rubber for any of the tire members, the low heat buildup of the tire member is improved, and the tire It is possible to improve durability by suppressing thermal deterioration of the tire member while reducing rolling resistance. In particular, when the rubber composition is used as a steel cord coding rubber, in addition to these effects, the wet heat adhesion between the steel cord and the coating rubber is improved, so that the durability of the tire can be greatly improved. It becomes possible.

  The rubber component of the rubber composition used for any of the tire members of the pneumatic tire of the present invention includes a modified natural rubber containing a polar group in the natural rubber molecule. In the production of the modified natural rubber, natural rubber latex may be used as a raw material, or at least one solid natural rubber raw material selected from the group consisting of natural rubber, natural rubber latex coagulum and natural rubber cup lamp is used. It may be used.

  For example, when natural rubber latex is used as a raw material, a polar group-containing modified natural rubber can be obtained by producing a polar group-containing modified natural rubber latex and further coagulating and drying. Here, the production method of the polar group-containing modified natural rubber latex is not particularly limited. For example, (1) a polar group-containing monomer is added to the natural rubber latex, and the polar group-containing monomer is used as a natural rubber. (2) A method of adding a polar group-containing mercapto compound to natural rubber latex and adding the polar group-containing mercapto compound to the natural rubber molecule in natural rubber latex (3) ) A method in which a polar group-containing olefin and a metathesis catalyst are added to natural rubber latex and the natural rubber molecule in the natural rubber latex is reacted with the polar group-containing olefin by the metathesis catalyst.

  The natural rubber latex used for the production of the modified natural rubber is not particularly limited. For example, field latex, ammonia-treated latex, centrifugal concentrated latex, deproteinized latex treated with a surfactant or an enzyme, and a combination thereof. A thing etc. can be used.

  The polar group-containing monomer added to the natural rubber latex is not particularly limited as long as it has at least one polar group in the molecule and can be graft-polymerized with the natural rubber molecule. Here, the polar group-containing monomer preferably has a carbon-carbon double bond in the molecule for graft polymerization with a natural rubber molecule, and is preferably a polar group-containing vinyl monomer. . Specific examples of the polar group include amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, and oxycarbonyl. Preferred examples include a group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, alkoxysilyl group, and tin-containing group. These monomers containing polar groups may be used alone or in combination of two or more.

  Examples of the monomer containing an amino group include polymerizable monomers containing at least one amino group selected from primary, secondary, and tertiary amino groups in one molecule. , N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dioctylaminoethyl (meth) acrylate, N-methyl N, N-disubstituted aminoalkyl (meth) acrylates such as -N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N N, N-disubstituted aminoalkyl (meth) acrylamides such as, N-dioctylaminopropyl (meth) acrylamide are preferred.

  Examples of the nitrile group-containing monomer include (meth) acrylonitrile, vinylidene cyanide, and the like.

  Examples of the monomer containing a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3- Hydroxyalkyl (meth) acrylates such as hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate; polyalkylene glycols such as polyethylene glycol and polypropylene glycol (the number of alkylene glycol units is, for example, 2 to 23) Mono (meth) acrylates containing hydroxyl groups such as N-hydroxymethyl (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, N, N-bis (2-hydroxymethyl) (meth) acrylamide Unsaturated amides; o-hydroxystyrene Hydroxyl group-containing vinyl aroma such as m-hydroxystyrene, p-hydroxystyrene, o-hydroxy-α-methylstyrene, m-hydroxy-α-methylstyrene, p-hydroxy-α-methylstyrene, p-vinylbenzyl alcohol Group compounds and the like.

  Examples of the monomer containing a carboxyl group include unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, tetraconic acid and cinnamic acid; non-phthalic acids such as phthalic acid, succinic acid and adipic acid. And free carboxyl group-containing esters such as monoesters of polymerizable polycarboxylic acids and hydroxyl-containing unsaturated compounds such as (meth) allyl alcohol and 2-hydroxyethyl (meth) acrylate, and salts thereof. Of these, unsaturated carboxylic acids are particularly preferred.

  Examples of the monomer containing an epoxy group include (meth) allyl glycidyl ether, glycidyl (meth) acrylate, and 3,4-oxycyclohexyl (meth) acrylate.

  In the monomer containing the nitrogen-containing heterocyclic group, the nitrogen-containing heterocyclic ring includes pyrrole, histidine, imidazole, triazolidine, triazole, triazine, pyridine, pyrimidine, pyrazine, indole, quinoline, purine, phenazine, pteridine, Examples include melamine. The nitrogen-containing heterocycle may contain other heteroatoms in the ring. Here, as a monomer containing a pyridyl group as a nitrogen-containing heterocyclic group, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 5-methyl-2-vinylpyridine, 5-ethyl-2- Examples include vinyl compounds containing a pyridyl group such as vinyl pyridine, among which 2-vinyl pyridine, 4-vinyl pyridine and the like are particularly preferable.

  Examples of the monomer containing the alkoxysilyl group include (meth) acryloxymethyltrimethoxysilane, (meth) acryloxymethylmethyldimethoxysilane, (meth) acryloxymethyldimethylmethoxysilane, (meth) acryloxymethyltrimethoxysilane. Ethoxysilane, (meth) acryloxymethylmethyldiethoxysilane, (meth) acryloxymethyldimethylethoxysilane, (meth) acryloxymethyltripropoxysilane, (meth) acryloxymethylmethyldipropoxysilane, (meth) acryloxy Methyldimethylpropoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxypropyltri Ethoxysilane, γ -(Meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, γ- (meth) acryloxypropyltripropoxysilane, γ- (meth) acryloxypropylmethyldipropoxysilane, γ -(Meth) acryloxypropyldimethylpropoxysilane, γ- (meth) acryloxypropylmethyldiphenoxysilane, γ- (meth) acryloxypropyldimethylphenoxysilane, γ- (meth) acryloxypropylmethyldibenzyloxysilane, γ- (meth) acryloxypropyldimethylbenzyloxysilane, trimethoxyvinylsilane, triethoxyvinylsilane, 6-trimethoxysilyl-1,2-hexene, p-trimethoxysilylstyrene and the like can be mentioned.

  Examples of the monomer having a tin-containing group include allyltri-n-butyltin, allyltrimethyltin, allyltriphenyltin, allyltri-n-octyltin, (meth) acryloxy-n-butyltin, and (meth) acryloxytrimethyltin. Listed tin-containing monomers such as (meth) acryloxytriphenyltin, (meth) acryloxy-n-octyltin, vinyltri-n-butyltin, vinyltrimethyltin, vinyltriphenyltin, vinyltri-n-octyltin Can do.

  When the polar group-containing monomer is graft-polymerized to the natural rubber molecule in the natural rubber latex, the graft polymerization of the polar group-containing monomer to the natural rubber molecule is performed by emulsion polymerization. Here, in the emulsion polymerization, generally, the polar group-containing monomer is added to a solution obtained by adding water and, if necessary, an emulsifier to a natural rubber latex, and a polymerization initiator is further added. It is preferable to polymerize the polar group-containing monomer by stirring at the temperature. In addition, in the addition of the polar group-containing monomer to the natural rubber latex, an emulsifier may be added to the natural rubber latex in advance, or after emulsifying the polar group-containing monomer with the emulsifier, May be added. In addition, it does not specifically limit as an emulsifier which can be used for emulsification of a natural rubber latex and / or a polar group containing monomer, Nonionic surfactants, such as polyoxyethylene lauryl ether, are mentioned.

  There is no restriction | limiting in particular as said polymerization initiator, The polymerization initiator for various emulsion polymerization can be used, and there is no restriction | limiting in particular also about the addition method. Examples of commonly used polymerization initiators include benzoyl peroxide, hydrogen peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, 2,2-azobisisobutyronitrile, 2,2-azobis (2-diaminopropane) hydrochloride, 2,2-azobis (2-diaminopropane) dihydrochloride, 2,2-azobis (2,4-dimethylvaleronitrile), potassium persulfate, sodium persulfate And ammonium persulfate. In order to lower the polymerization temperature, it is preferable to use a redox polymerization initiator. Examples of the reducing agent to be combined with the peroxide in the redox polymerization initiator include tetraethylenepentamine, mercaptans, acidic sodium sulfite, reducing metal ions, ascorbic acid and the like. A preferred combination of a peroxide and a reducing agent in the redox polymerization initiator includes a combination of tert-butyl hydroperoxide and tetraethylenepentamine. In order to improve the low loss and wear resistance without lowering the processability of the rubber composition using the modified natural rubber, a small amount of the polar group-containing monomer is uniformly introduced into each natural rubber molecule. Therefore, the amount of the polymerization initiator added is preferably in the range of 1 to 100 mol%, more preferably in the range of 10 to 100 mol% with respect to the polar group-containing monomer.

  Each component described above is charged into a reaction vessel and reacted at 30 to 80 ° C. for 10 minutes to 7 hours, whereby a modified natural rubber latex in which the polar group-containing monomer is graft copolymerized with a natural rubber molecule is obtained. The modified natural rubber latex is coagulated, washed, and then dried using a dryer such as a vacuum dryer, an air dryer, a drum dryer or the like to obtain a modified natural rubber. Here, the coagulant used for coagulating the modified natural rubber latex is not particularly limited, and examples thereof include acids such as formic acid and sulfuric acid, and salts such as sodium chloride.

  The polar group-containing mercapto compound that is added to the natural rubber latex and undergoes an addition reaction with the natural rubber molecule in the natural rubber latex, as long as it has at least one mercapto group and a polar group other than the mercapto group in the molecule. It is not limited. Specific examples of the polar group include amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl Preferred examples include a group, a nitrogen-containing heterocyclic group, a mixed oxygen heterocyclic group, an alkoxysilyl group, and a tin-containing group. These mercapto compounds containing a polar group may be used singly or in combination of two or more.

  Examples of the mercapto compound containing an amino group include mercapto compounds having at least one amino group selected from primary, secondary and tertiary amino groups in one molecule. Among the mercapto compounds having an amino group, a tertiary amino group-containing mercapto compound is particularly preferable. Here, as the primary amino group-containing mercapto compound, 4-mercaptoaniline, 2-mercaptoethylamine, 2-mercaptopropylamine, 3-mercaptopropylamine, 2-mercaptobutylamine, 3-mercaptobutylamine, 4-mercaptobutylamine Etc. The secondary amino group-containing mercapto compounds include N-methylaminoethanethiol, N-ethylaminoethanethiol, N-methylaminopropanethiol, N-ethylaminopropanethiol, N-methylaminobutanethiol, N- And ethylaminobutanethiol. Further, the tertiary amino group-containing mercapto compounds include N, N-dimethylaminoethanethiol, N, N-diethylaminoethanethiol, N, N-dimethylaminopropanethiol, N, N-diethylaminopropanethiol, N, N N, N-disubstituted aminoalkyl mercaptans such as -dimethylaminobutanethiol and N, N-diethylaminobutanethiol. Among these amino group-containing mercapto compounds, 2-mercaptoethylamine, N, N-dimethylaminoethanethiol and the like are preferable.

  Examples of the mercapto compound having a nitrile group include 2-mercaptopropanenitrile, 3-mercaptopropanenitrile, 2-mercaptobutanenitrile, 3-mercaptobutanenitrile, 4-mercaptobutanenitrile, and the like.

  Examples of the mercapto compound containing a hydroxyl group include mercapto compounds having at least one primary, secondary, or tertiary hydroxyl group in one molecule. Specific examples of the hydroxyl group-containing mercapto compound include 2-mercaptoethanol, 3-mercapto-1-propanol, 3-mercapto-2-propanol, 4-mercapto-1-butanol, 4-mercapto-2-butanol, 3 -Mercapto-1-butanol, 3-mercapto-2-butanol, 3-mercapto-1-hexanol, 3-mercapto-1,2-propanediol, 2-mercaptobenzyl alcohol, 2-mercaptophenol, 4-mercaptophenol, etc. Is mentioned.

  Examples of the mercapto compound containing a carboxyl group include mercaptoacetic acid, mercaptopropionic acid, thiosalicylic acid, mercaptomalonic acid, mercaptosuccinic acid, mercaptobenzoic acid and the like. Among these, mercaptoacetic acid is preferred.

  In the mercapto compound containing the nitrogen-containing heterocyclic group, the nitrogen-containing heterocyclic ring includes pyrrole, histidine, imidazole, triazolidine, triazole, triazine, pyridine, pyrimidine, pyrazine, indole, quinoline, purine, phenazine, pteridine, melamine. Etc. The nitrogen-containing heterocycle may contain other heteroatoms in the ring. Here, as a mercapto compound containing a pyridyl group as a nitrogen-containing heterocyclic group, 2-mercaptopyridine, 3-mercaptopyridine, 4-mercaptopyridine, 5-methyl-2-mercaptopyridine, 5-ethyl-2-mercapto Examples of mercapto compounds containing other nitrogen-containing heterocyclic groups include 2-mercaptopyrimidine, 2-mercapto-5-methylbenzimidazole, 2-mercapto-1-methylimidazole, and 2-mercapto. Examples include benzimidazole and 2-mercaptoimidazole. Among these, 2-mercaptopyridine and 4-mercaptopyridine are preferable.

  Examples of the mercapto compound containing an alkoxysilyl group include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, and 2-mercaptoethyltrimethoxysilane. Examples include silane, 2-mercaptoethyltriethoxysilane, mercaptomethylmethyldiethoxysilane, mercaptomethyltrimethoxysilane, and the like. Among these, 3-mercaptopropyltrimethoxysilane is preferable.

  Examples of the mercapto compound having a tin-containing group include 2-mercaptoethyltri-n-butyltin, 2-mercaptoethyltrimethyltin, 2-mercaptoethyltriphenyltin, 3-mercaptopropyltri-n-butyltin, and 3-mercaptopropyl. Mention may be made of tin-containing mercapto compounds such as trimethyltin and 3-mercaptopropyltriphenyltin.

  When adding the polar group-containing mercapto compound to the natural rubber molecule in the natural rubber latex, generally, the polar group-containing mercapto compound is added to a solution obtained by adding water and, if necessary, an emulsifier to the natural rubber latex, By stirring at a predetermined temperature, the polar group-containing mercapto compound is added to the double bond of the main chain of the natural rubber molecule in the natural rubber latex. In addition, in the addition of the polar group-containing mercapto compound to the natural rubber latex, an emulsifier may be added to the natural rubber latex in advance, or the polar group-containing mercapto compound may be added to the natural rubber latex after being emulsified with the emulsifier. Good. Moreover, an organic peroxide can also be added as needed. In addition, it does not specifically limit as an emulsifier which can be used for emulsification of natural rubber latex and / or a polar group containing mercapto compound, Nonionic surfactants, such as polyoxyethylene lauryl ether, are mentioned.

  In order to improve the low loss and wear resistance without reducing the processability of the rubber composition, it is important that the polar group-containing mercapto compound is introduced in a small amount and uniformly into each natural rubber molecule. The modification reaction is preferably performed with stirring. For example, the above components such as natural rubber latex and a polar group-containing mercapto compound are charged into a reaction vessel and reacted at 30 to 80 ° C. for 10 minutes to 24 hours. A modified natural rubber latex in which the polar group-containing mercapto compound is added to rubber molecules is obtained.

  The polar group-containing olefin added to the natural rubber latex has at least one polar group in the molecule, and also has a carbon-carbon double bond for cross-metathesis reaction with the natural rubber molecule. Here, specific examples of the polar group include amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, and epoxy group. Preferable examples include oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, alkoxysilyl group, and tin-containing group. These polar group-containing olefins may be used alone or in combination of two or more. In addition, as a polar group containing olefin, the compound which has a carbon-carbon double bond can be selected suitably from the monomer containing the polar group mentioned above, and can be used.

  When a polar group-containing olefin is reacted with a natural rubber molecule in a natural rubber latex by a metathesis catalyst, the polar group-containing olefin is generally added to a solution obtained by adding water and an emulsifier as necessary to a natural rubber latex, Further, a metathesis catalyst is added and stirred at a predetermined temperature to cause a metathesis reaction between the natural rubber molecule and the polar group-containing olefin. Here, in the addition of the polar group-containing olefin to the natural rubber latex, an emulsifier may be added to the natural rubber latex in advance, or the polar group-containing olefin may be added to the natural rubber latex after emulsification with the emulsifier. Good. In addition, it does not specifically limit as an emulsifier which can be used for emulsification of natural rubber latex and / or a polar group containing olefin, Nonionic surfactants, such as polyoxyethylene lauryl ether, are mentioned.

The metathesis catalyst is not particularly limited as long as it has a catalytic action on the metathesis reaction between the natural rubber molecule and the polar group-containing olefin, and various metathesis catalysts can be used. The metathesis catalyst contains a transition metal, but since it is used in a natural rubber latex, it is preferable that the stability to water is high. Therefore, the transition metal constituting the metathesis catalyst is preferably any one of ruthenium, osmium, and iridium. Specific examples of the metathesis catalyst include bis (tricyclohexylphosphine) benzylideneruthenium dichloride [RuCl ₂ (═CHPh) (PCy ₃ ) ₂ ], and RuCl ₂ (═CH—CH═CPh ₂ ) (PPh ₃ ). ₂ , RuCl ₂ (= CHPh) (PCp ₃ ) ₂ , RuCl ₂ (= CHPh) (PPh ₃ ) ₂ , RuCl ₂ (= CHPh) [Cy ₂ PCH ₂ CH ₂ N (CH ₃ ) ₃ ⁺ Cl] ₂ etc. Can be mentioned. In the chemical formula, Cy represents a cyclohexyl group, and Cp represents a cyclopentyl group. The addition amount of the metathesis catalyst is preferably in the range of 1 to 500 mol%, more preferably in the range of 10 to 100 mol% with respect to the polar group-containing olefin.

  Each component described above is charged into a reaction vessel and reacted at 30 to 80 ° C. for 10 minutes to 24 hours, whereby a modified natural rubber latex in which the polar group is introduced into natural rubber molecules is obtained.

  Further, when using at least one natural rubber raw material selected from the group consisting of natural rubber, natural rubber latex coagulum and natural rubber cup lamp as a raw material, the polar group-containing compound is given a mechanical shearing force, A modified natural rubber can be obtained by graft polymerization or addition to a rubber raw material.

  As the natural rubber raw material, various kinds of solid natural rubber after drying, various natural rubber latex coagulated products (including unsmoked sheets) or natural rubber cup lamps can be used. These natural rubber raw materials are used alone. You may use, and may use it in combination of 2 or more type.

  When the polar group-containing compound is graft-polymerized to a natural rubber molecule in a natural rubber raw material, the polar group-containing compound preferably has a carbon-carbon double bond in the molecule, and the polar group-containing vinyl monomer It is preferable that On the other hand, when a polar group-containing compound is subjected to an addition reaction with a natural rubber molecule in a natural rubber raw material, the polar group-containing compound preferably has a mercapto group in the molecule, and is preferably a polar group-containing mercapto compound.

  As means for imparting mechanical shearing force to the mixture of the natural rubber raw material and the polar group-containing compound, a twin-screw extrusion kneader and a dry prebreaker are preferable. Here, in the case where the polar group-containing compound is graft-polymerized to the natural rubber molecule in the natural rubber raw material, the natural rubber raw material and the polar group-containing compound (preferably, the polar group-containing vinyl are contained in the apparatus to which the mechanical shearing force is applied. By introducing a polymerization initiator together with a system monomer) and applying a mechanical shearing force, a polar group-containing compound can be introduced into the natural rubber molecule in the natural rubber raw material by graft polymerization. In addition, when a polar group-containing compound is subjected to an addition reaction with a natural rubber molecule in a natural rubber raw material, the natural rubber raw material and the polar group-containing compound (preferably, a polar group-containing mercapto compound are contained in the above-described mechanical shear force device. ) And, if necessary, organic peroxides and the like are further added to give mechanical shearing force, so that a polar group-containing compound is added to the double bond of the main chain of the natural rubber molecule in the natural rubber raw material. An addition reaction can be performed. Examples of the polar group-containing compound used here include the above-described polar group-containing monomers, polar group-containing mercapto compounds, polar group-containing olefins, and the like.

  The above-described components are charged into a device that can be given mechanical shearing force, and mechanical shearing force is applied to obtain a modified natural rubber in which the polar group-containing compound is graft-polymerized or added to the natural rubber molecule. In this case, the modification reaction of the natural rubber molecule may be carried out by heating, preferably at a temperature of 30 to 160 ° C., more preferably 50 to 130 ° C., so that the modified natural rubber has sufficient reaction efficiency. Can be obtained.

  The polar group content of the modified natural rubber is preferably in the range of 0.001 to 0.5 mmol / g, more preferably in the range of 0.002 to 0.3 mmol / g, and 0.003 to 0.2 mmol / g with respect to the rubber component in the modified natural rubber. The range of is more preferable. When the polar group content of the modified natural rubber is less than 0.001 mmol / g, the low loss property and wear resistance of the rubber composition may not be sufficiently improved. Moreover, when the polar group content of the modified natural rubber exceeds 0.5 mmol / g, the natural physical properties of natural rubber such as viscoelasticity and SS characteristics (stress-strain curve in a tensile tester) are greatly changed. The natural physical properties inherent to natural rubber are impaired, and the processability of the rubber composition may be greatly deteriorated.

  The rubber component of the rubber composition includes, in addition to the modified natural rubber, natural rubber (NR); vinyl aromatic hydrocarbon / conjugated diene copolymer, polyisoprene rubber (IR), polybutadiene rubber (BR), butyl rubber ( IIR), synthetic rubbers such as halogenated butyl rubber, ethylene-propylene rubber, and the like. The rubber component of the rubber composition preferably contains 10% by mass or more, more preferably 50% by mass or more of the modified natural rubber, from the viewpoint of reducing loss.

  The rubber composition contains 1 to 10 parts by mass, preferably 3 to 8 parts by mass of sulfur as a vulcanizing agent with respect to 100 parts by mass of the rubber component. When the amount of sulfur is less than 1 part by mass, for example, when used for steel cord coating rubber, the adhesion to the steel cord is insufficient, while when it exceeds 10 parts by mass, an excessive adhesive layer is formed. And the adhesiveness is reduced.

  The rubber composition contains 0.1 to 10 parts by mass, and 0.3 to 6 parts by mass of a compound containing a disubstituted or trisubstituted benzene ring having at least one hydroxyl group as a substituent with respect to 100 parts by mass of the rubber component. Is preferred. When the compounding amount of the compound containing the substituted benzene ring is less than 0.1 parts by mass, the effect of improving the wet heat resistance is low. On the other hand, when the compounding amount exceeds 10 parts by mass, the compound blooms and the adhesiveness decreases.

  Examples of the compound containing a di- or tri-substituted benzene ring having at least one hydroxyl group as a substituent compounded in the rubber composition include (1) a compound represented by the above general formula (I), (2) The compound represented by the general formula (III), and (3) the compound represented by the general formula (IV) is 60 to 100% by mass, the compound represented by the following general formula (V) and n = 2. 0 to 20% by mass, a compound represented by the following general formula (V) and n = 3 is 0 to 10% by mass, and a compound represented by the following general formula (V) and n = 4 to 6 is 0 to 6 in total. A composition consisting of 10% by weight is preferred. The said compound containing a substituted benzene ring may be used individually by 1 type, and may mix and use 2 or more types.

In the general formula (I), X is a hydroxyl group, a carboxyl group, or —COOC _m H _{2m + 1} , where m is an integer of 1 to 5. Y may be bonded to any of the 2-position, 4-position, 5-position and 6-position of the benzene ring, and is hydrogen, a hydroxyl group or a substituent represented by the above general formula (II). is there. In the formula (II), Z ₁ and Z ₂ are each independently a hydroxyl group, a carboxyl group or —COOC _q H _{2q + 1} , where q is an integer of 1 to 5, Moreover, p is an integer in any one of 1-7. Specific examples of the compound of the formula (I) include resorcin, resorcin / formaldehyde resin, and the like.

  In the general formula (III), R represents a divalent aliphatic group having 1 to 12 carbon atoms or a divalent aromatic group. Examples of the compound represented by the general formula (III) include a compound represented by the above general formula (IV). R in the general formula (IV) has the same meaning as R in the general formula (III).

  Here, examples of the divalent aliphatic group having 1 to 12 carbon atoms include linear or branched alkylene such as methylene group, ethylene group, butylene group, isobutylene group, octylene group, and 2-ethylhexylene group. Group, vinylene group (ethenylene group), butenylene group, octenylene group or other linear or branched alkenylene group, alkylene group or alkylene group or alkenylene in which the hydrogen atom of alkenylene group is substituted with hydroxyl group or amino group And alicyclic groups such as a cyclohexylene group. Examples of the divalent aromatic group include an optionally substituted phenylene group and an optionally substituted naphthylene group. Among these, in view of availability, an alkylene group having 2 to 10 carbon atoms and a phenylene group are preferable, and an ethylene group, butylene group, octylene group, and phenylene group are particularly preferable.

  Specific examples of the compound of the above general formula (III) include malonic acid bis (3-hydroxyphenyl) ester, succinic acid bis (3-hydroxyphenyl) ester, fumaric acid bis (3-hydroxyphenyl) ester, maleic acid bis (3-hydroxyphenyl) ester, malic acid bis (3-hydroxyphenyl) ester, itaconic acid bis (3-hydroxyphenyl) ester, citraconic acid bis (3-hydroxyphenyl) ester, adipic acid bis (3-hydroxyphenyl) Ester, bis (3-hydroxyphenyl) tartrate, bis (3-hydroxyphenyl) azelaic acid, bis (3-hydroxyphenyl) sebacate, bis (3-hydroxyphenyl) cyclohexanedicarboxylate, bis (terephthalate) ( -Hydroxyphenyl) ester and isophthalic acid bis (4-hydroxyphenyl) ester are preferred, especially succinic acid bis (3-hydroxyphenyl) ester, adipic acid bis (3-hydroxyphenyl) ester, sebacic acid bis (3-hydroxyphenyl) ) Ester, bis (4-hydroxyphenyl) terephthalate, and bis (4-hydroxyphenyl) isophthalate are preferred.

［式中、Ｒは炭素数１〜１２の２価の脂肪族基又は２価の芳香族基を表し、Ｘ'はハロゲン原子を表す］で表されるジカルボン酸ハライドと、下記一般式(VII)：

で表される化合物とを、塩基の存在下または非存在下で反応させて製造される。 Although the manufacturing method of the compound represented by the general formula (III) is not particularly limited, for example, the following general formula (VI):

[Wherein R represents a divalent aliphatic group having 1 to 12 carbon atoms or a divalent aromatic group, and X ′ represents a halogen atom], a dicarboxylic acid halide represented by the following general formula (VII ):

In the presence or absence of a base.

  R in the general formula (VI) has the same meaning as R in the general formula (III), and X ′ represents a halogen atom. As a halogen atom, a chlorine atom or a bromine atom is preferable.

  The compounds represented by the general formula (VI) include malonic acid dichloride, succinic acid dichloride, adipic acid dichloride, azelaic acid dichloride, sebacic acid dichloride, terephthalic acid dichloride, isophthalic acid dichloride, malonic acid dibromide, succinic acid dibromide. Adipic acid dibromide, azelaic acid dibromide, sebacic acid dibromide, terephthalic acid dibromide, isophthalic acid dibromide and the like are preferable. On the other hand, examples of the compound represented by the general formula (VII) include catechol, resorcin, and hydroquinone.

  As the base used when the compound represented by the general formula (VI) and the compound represented by the general formula (VII) are reacted, usually pyridine, β-picoline, N-methylmorpholine, dimethylaniline, diethyl Organic bases such as aniline, trimethylamine, triethylamine, tributylamine are used. In addition, when the compound represented by the general formula (VI) and the compound represented by the general formula (VII) are reacted, the compound represented by the general formula (VI) and the general formula (VII) are usually used. And the compound to be reacted in a molar ratio of 1: 4 to 1:30. In addition, when reacting the compound represented by the general formula (VI) and the compound represented by the general formula (VII), a solvent can be used for the purpose of dissolving the raw materials. As the solvent, the above-described organic base may be used as it is, or another organic solvent that does not inhibit the reaction may be used. Examples of such a solvent include ether solvents such as dimethyl ether and dioxane. The reaction temperature for reacting the compound represented by the general formula (VI) with the compound represented by the general formula (VII) is usually -20 ° C to 120 ° C.

  The compound represented by the general formula (III) obtained by the above reaction can be isolated from the reaction mixture by a known method. That is, an organic base used for the reaction and a compound represented by the general formula (VII) by an operation such as distillation under reduced pressure, and when an organic solvent is used for the reaction, a method of distilling off the organic solvent to dryness, a reaction Examples include a method of reprecipitation by adding a poor solvent of the compound represented by formula (III) to the mixture, a method of adding water and an organic solvent immiscible with water to the reaction mixture, and extracting to the organic layer. . Moreover, you may refine | purify by recrystallization depending on the case. In addition, water is usually used as a poor solvent for the compound represented by the general formula (III). Examples of the organic solvent immiscible with water include esters such as ethyl acetate and butyl acetate, and ketones such as methyl isobutyl ketone and diisobutyl ketone.

  When resorcin is used as the compound represented by the general formula (III), the compound represented by the general formula (IV) containing the compound represented by the general formula (IV) as a main component and the general formula (V ) Is obtained. In addition, R in general formula (V) is synonymous with R in general formula (III), and n shows the integer of 2-6.

  For example, in a composition comprising a compound represented by the general formula (IV) and a compound represented by the general formula (V) obtained when resorcin is used in the above reaction, the general formula (IV ) Is 60 to 100% by mass, n = 2 in the general formula (V) is 0 to 20% by mass, n = 3 in the general formula (V) is 0 to 10% by mass, The compound of n = 4-6 in Formula (V) is contained about 0-10 mass% in total. These ratios can be controlled by changing the molar ratio of the compound represented by the general formula (VI) and resorcin.

  A composition comprising the compound represented by the general formula (IV) and the compound represented by the general formula (V) can also be obtained by a method similar to the method for isolating the compound represented by the general formula (III). Can be isolated from a reaction mixture comprising

  When the compound represented by the general formula (IV) is 60% by mass or more, wet heat adhesiveness is improved when blended with rubber and bonded. Judging from the viewpoint of improving wet heat adhesion, the content of the compound represented by the general formula (IV) is more preferably 70 to 100% by mass, and still more preferably 80 to 100% by mass.

  The rubber composition preferably further comprises 0.03 to 1 part by mass of an organic acid cobalt salt as an adhesion promoter as a cobalt amount with respect to 100 parts by mass of the rubber component. When the amount of the organic acid cobalt salt is less than 0.03 parts by mass as the amount of cobalt, the adhesion between the coating rubber and the steel cord is not sufficient, and when it exceeds 1 part by mass, the aging characteristics of the coating rubber are excessively deteriorated. Examples of the organic acid cobalt salt include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate and cobalt tall oil. The organic acid cobalt salt may be a complex salt in which a part of the organic acid is replaced with boric acid or the like. Specifically, Manobond (trademark: manufactured by OMG) can be mentioned.

  The rubber composition preferably further contains a filler such as carbon black and silica. The blending amount of the filler is not particularly limited, but is preferably in the range of 5 to 100 parts by mass, more preferably in the range of 10 to 70 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount of the filler is less than 5 parts by mass, sufficient reinforcement may not be obtained, and if it exceeds 100 parts by mass, the workability may be deteriorated.

  The rubber composition includes the rubber component, sulfur, a compound containing a substituted benzene ring, an organic acid cobalt salt, a filler, a silane coupling agent for silica, a vulcanization accelerator, a softening agent such as aroma oil, Methylene donors such as methoxymethylated melamine such as hexamethylenetetramine, pentamethoxymethylmelamine, hexamethylenemethylmelamine, zinc oxide, stearic acid, vulcanization accelerator, vulcanization accelerator, aging inhibitor, ozone deterioration inhibitor The compounding agents usually used in the rubber industry such as the above can be appropriately blended within a range not impairing the effects of the present invention.

  The method for preparing the rubber composition is not particularly limited. For example, the rubber composition can be prepared by kneading sulfur, the compound having a substituted benzene ring, and various compounding agents into a rubber component using a Banbury mixer or a roll. .

  Hereinafter, the pneumatic tire of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a cross-sectional view of an example of the pneumatic tire of the present invention. In the figure, 1 indicates a tread portion, 2 indicates a pair of sidewall portions extending radially inward from the side portion of the tread portion 1, and 3 indicates a bead portion connected to the radially inner end of the sidewall portion 2. .

  Here, the carcass 4 that forms the skeleton structure of the tire and reinforces each of the parts 1, 2, and 3 of the tire is constituted by one or more carcass plies, and each bead core disposed in each bead part 3 A main body portion extending in a toroidal manner between 5 and a bend portion wound up radially outward from the inner side in the tire width direction around each bead core 5. The carcass 4 in the figure is composed of one carcass ply. However, in the tire of the present invention, a plurality of carcass plies may be provided.

  In the figure, reference numeral 6 denotes a belt, and the belt 6 is composed of one or more belt layers disposed on the outer side in the tire radial direction of the crown portion of the carcass 4. The belt 6 in the figure is composed of two belt layers. However, in the tire of the present invention, the number of belt layers is not limited to this.

  The pneumatic tire includes a steel cord layer in which at least one of the carcass 4 and the belt 6 is coated with a coating rubber. That is, at least one of the carcass plies of the carcass 4 and / or at least one of the belt layers of the belt 6 may be a steel cord layer, and one or more carcass plies and one or more belt layers may be a layer of steel cord. It may be.

  In this case, at least one of the carcass 4 and the belt 6, sulfur is added to 100 parts by mass of the rubber component including the above-described modified natural rubber containing a polar group in the natural rubber molecule in the coating rubber covering the steel cord. A rubber composition comprising 1 to 10 parts by mass and 0.1 to 10 parts by mass of a compound containing a disubstituted or trisubstituted benzene ring having at least one hydroxyl group as a substituent is used. As a result, it is possible to improve the moisture and heat resistant adhesion between the steel cord and the coating rubber without deteriorating the exothermic property of the coating rubber. For this reason, by using the rubber composition as a coding rubber for a steel cord, the wet heat adhesion between the steel cord and the coating rubber can be improved, and the durability of the tire can be greatly improved.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

<Production Example 1 of Modified Natural Rubber>
(Natural rubber latex modification reaction process)
The field latex was centrifuged at a rotational speed of 7500 rpm using a latex separator (manufactured by Saito Centrifugal Industries) to obtain a concentrated latex having a dry rubber concentration of 60%. 1000 g of this concentrated latex was put into a stainless steel reaction vessel equipped with a stirrer and a temperature control jacket, and 10 mL of water and 90 mg of emulsifier [Emulgen 1108, manufactured by Kao Corporation] were preliminarily added to N, N-diethylaminoethyl. What was emulsified in addition to 3.0 g of methacrylate was added together with 990 mL of water, and these were stirred at room temperature for 30 minutes while purging with nitrogen. Next, 1.2 g of tert-butyl hydroperoxide and 1.2 g of tetraethylenepentamine were added as polymerization initiators and reacted at 40 ° C. for 30 minutes to obtain a modified natural rubber latex.

(Coagulation and drying process)
Formic acid was added to the modified natural rubber latex to adjust the pH to 4.7 to coagulate the modified natural rubber latex. The solid material thus obtained was treated with a creper five times, passed through a shredder and crushed, and then dried at 110 ° C. for 210 minutes with a hot air drier to obtain modified natural rubber A. From the mass of the modified natural rubber A thus obtained, it was confirmed that the conversion rate of N, N-diethylaminoethyl methacrylate added as a monomer was 100%. In addition, the modified natural rubber A was extracted with petroleum ether and further extracted with a 2: 1 mixed solvent of acetone and methanol, but when the extract was analyzed, no homopolymer was detected. It was confirmed that 100% of the added monomer was introduced into the natural rubber molecule. Accordingly, the polar group content of the resulting modified natural rubber A is 0.027 mmol / g with respect to the rubber component in the natural rubber latex.

<Production Example 2 of Modified Natural Rubber>
Modified natural rubber B was obtained in the same manner as in Production Example 1 except that 2.1 g of 2-hydroxyethyl methacrylate was added instead of 3.0 g of N, N-diethylaminoethyl methacrylate as a monomer. Further, when the modified natural rubber B was analyzed in the same manner as the modified natural rubber A, it was confirmed that 100% of the added monomer was introduced into the natural rubber molecule. Therefore, the polar group content of the modified natural rubber B is 0.027 mmol / g with respect to the rubber component in the natural rubber latex.

<Production Example 3 of Modified Natural Rubber>
Modified natural rubber C was obtained in the same manner as in Production Example 1 except that 1.7 g of 4-vinylpyridine was added instead of 3.0 g of N, N-diethylaminoethyl methacrylate as a monomer. Further, when the modified natural rubber C was analyzed in the same manner as the modified natural rubber A, it was confirmed that 100% of the added monomer was introduced into the natural rubber molecule. Therefore, the polar group content of the modified natural rubber C is 0.027 mmol / g with respect to the rubber component in the natural rubber latex.

<Production Example 4 of Modified Natural Rubber>
Water was added to the field latex to obtain a latex having a dry rubber concentration of 30%. 2000 g of this latex is put into a stainless steel reaction vessel equipped with a stirrer and a temperature control jacket, and 10 mL of water and 90 mg of emulsifier [Emulgen 1108, manufactured by Kao Corporation] are added to 1.2 g of 2-mercaptoethylamine in advance. In addition, the emulsified product was added and reacted at 60 ° C. for 8 hours with stirring to obtain a modified natural rubber latex D. Thereafter, a modified natural rubber D was obtained by coagulation and drying in the same manner as in Production Example 1. Moreover, when the polar group content of the obtained modified natural rubber D was analyzed using a pyrolysis gas chromatograph-mass spectrometer, it was 0.021 mmol / g with respect to the rubber component in the natural rubber latex.

<Production Example 5 of Modified Natural Rubber>
Modified natural rubber E was obtained in the same manner as in Production Example 4 except that 1.8 g of 2-mercaptopyridine was added as a polar group-containing mercapto compound instead of 1.2 g of 2-mercaptoethylamine. Moreover, when the polar group content of the obtained modified natural rubber E was analyzed using a pyrolysis gas chromatograph-mass spectrometer, it was 0.022 mmol / g with respect to the rubber component in the natural rubber latex.

<Production Example 6 of Modified Natural Rubber>
1000 g of the above concentrated latex was put into a stainless steel reaction vessel equipped with a stirrer and a temperature control jacket, and 10 mL of water and 90 mg of emulsifier [Emulgen 1108, manufactured by Kao Corporation] were preliminarily added to N, N-diethylaminoethyl. What was emulsified in addition to 3.0 g of methacrylate was added together with 990 mL of water, and these were stirred for 30 minutes while purging with nitrogen. Next, modified natural rubber latex F was obtained by adding 3.0 g of bis (tricyclohexylphosphine) benzylideneruthenium dichloride as a metathesis catalyst and reacting at 40 ° C. for 7 hours. Thereafter, the modified natural rubber F was obtained by coagulation and drying in the same manner as in Production Example 1. From the mass of the modified natural rubber F thus obtained, it was confirmed that the conversion rate of the added N, N-diethylaminoethyl methacrylate was 84%. Further, when the modified natural rubber F was extracted with petroleum ether and further extracted with a 2: 1 mixed solvent of acetone and methanol, an attempt was made to separate a reaction product of olefins not introduced into the natural rubber molecule. A reaction product of olefins not introduced into the rubber molecules was detected and 6% of the amount of olefins charged was detected. Accordingly, the polar group content of the modified natural rubber F is 0.021 mmol / g with respect to the rubber component in the natural rubber latex.

<Production Example 7 of Modified Natural Rubber>
Formic acid was added to the field latex to adjust the pH to 4.7, the latex was coagulated, and the obtained solid was treated 5 times with a creper and crushed through a shredder. Next, the dry rubber content of the obtained coagulum was determined, and 600 g of coagulum, 3.0 g of N, N-diethylaminoethyl methacrylate, tert-butyl hydroperoxide (t-BHPO) in terms of dry rubber 1.2 g was kneaded in a kneader at room temperature for 2 minutes at 30 rpm, and uniformly dispersed. Next, while adding 1.2 g of tetraethylenepentamine (TEPA) uniformly to the obtained mixture, a twin-screw kneading extruder made of Kobe Steel [same direction rotating screw diameter = 30 mm, L / D = 35, vent hole 3 The modified natural rubber G was dried by extruding while applying mechanical shearing force at a barrel temperature of 120 ° C. and a rotational speed of 100 rpm. Further, from the mass of the obtained modified natural rubber G, the conversion rate of N, N-diethylaminoethyl methacrylate added as a monomer was 83%. Furthermore, when the modified natural rubber G was extracted with petroleum ether and further extracted with a 2: 1 mixed solvent of acetone and methanol, the homopolymer was separated, and 7% of the charged monomer amount was detected. . Therefore, the polar group content of the modified natural rubber G is 0.021 mmol / g with respect to the solid rubber component in the natural rubber raw material.

<Examples of natural rubber production>
Natural rubber H was prepared by directly coagulating and drying the natural rubber latex without undergoing a modification reaction step.

<Production example of bis (3-hydroxyphenyl) ester of adipic acid>
A solution of 330.6 g (3.0 mol) of resorcin in 600.0 g of pyridine was kept dropwise at 15 ° C. or lower on an ice bath, and 54.9 g (0.30 mol) of adipoyl chloride was gradually added dropwise thereto. After completion of the dropping, the resulting reaction mixture was warmed to room temperature and allowed to stand overnight to complete the reaction. From the reaction mixture, pyridine was distilled off under reduced pressure, 1200 g of water was added to the residue, and the mixture was cooled with ice to precipitate a precipitate. The deposited precipitate was filtered and washed with water, and the obtained wet body was dried under reduced pressure to obtain 84 g of white to pale yellow powder. This powder was processed under the following conditions by liquid chromatography equipped with a fractionation device, and an eluent containing main components was fractionated. The eluent was concentrated, and the precipitated crystals were collected by filtration and dried under reduced pressure to obtain crystals having a melting point of 140 to 143 ° C. As a result of analysis, the crystals were adipic acid bis (3-hydroxyphenyl) ester.

Preparative HPLC conditions are as follows.
Column: Shim-pack PREP-ODS (manufactured by Shimadzu Corporation)
Column temperature: 25 ° C
Eluent: Methanol / water mixed solvent (85/15 (w / w%))
Eluent flow rate: Flow rate 3 ml / min Detector: UV detector (254 nm)

In addition, the identification data of adipic acid bis (3-hydroxyphenyl) ester are as follows.
MS spectrum data EI (Pos.) M / z = 330
IR spectrum data
3436 cm-1 ： Hydroxyl group
2936 cm-1: Alkyl
1739 cm @ -1: ester NMR spectrum data are shown in Table 1-1 and Table 1-2.

(Examples 1-9 and Comparative Examples 1-5)
Using the above modified natural rubber or natural rubber as a rubber component and using a 2200 mL Banbury mixer with adipic acid bis (3-hydroxyphenyl) ester, resorcin or RF resin as a test compound, rubber compounding formulations shown in Tables 2 and 3 The unvulcanized rubber composition was prepared by kneading and mixing, and the Mooney viscosity, tensile strength, tan δ, adhesion immediately after compounding and adhesion after leaving the compounded rubber were measured and evaluated by the following methods. The results are shown in Tables 2 and 3.

(1) Mooney Viscosity Mooney viscosity ML _{1 + 4} (130 ° C.) was measured according to JIS K6300-1: 2001. The smaller the value, the better the processability of the unvulcanized rubber composition.

(2) Tensile strength The vulcanized rubber obtained by vulcanizing the rubber composition at 160 ° C. for 15 minutes was subjected to a tensile test according to JIS K6301-1995, and the tensile strength (TB) was measured. . It shows that fracture resistance is so favorable that tensile strength is large.

(3) tanδ
Using a viscoelasticity measuring device [Rheometrics Co., Ltd.] for the vulcanized rubber obtained by vulcanizing the above rubber composition at 160 ° C for 15 minutes, loss tangent at a temperature of 50 ° C, a strain of 5%, and a frequency of 15 Hz ( tan δ) was measured. It shows that it is excellent in low-loss property, so that tan-delta is small.

(4) Adhesion test Brass (Cu; 63 mass%, Zn; 37 mass%) plated steel cords (1x5 structure, strand diameter 0.25 mm) are arranged in parallel at 12.5 mm intervals, and the steel cords are arranged on both the upper and lower sides. Then, it was coated with the unvulcanized rubber composition and immediately vulcanized at 160 ° C. for 15 minutes to prepare a sample having a width of 12.5 mm. Next, in accordance with ASTM-D-2229, the steel cord of the sample was pulled out, the state of rubber coating was visually observed, and the coverage was displayed as 0 to 100%, which was used as an index of each adhesive property. It shows that adhesiveness is so high that a numerical value is large. The initial adhesiveness is a result measured immediately after vulcanization, and the wet heat adhesiveness is a result measured after aging and after aging under wet heat conditions of 70 ° C., 100% RH for 4 days.

* 1 N, N'-dicyclohexyl-2-benzothiazylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller DZ.
* 2 N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: NOCRACK 6C.
* 3 Made by OMG, trade name: Manobond C22.5, cobalt content = 22.5% by mass.
* 4 Made by Indspec, trade name: B19S.

  As is apparent from Examples 1 to 9, a rubber composition comprising a modified natural rubber containing a polar group in a natural rubber molecule and a compound containing a disubstituted or trisubstituted benzene ring having at least one hydroxyl group as a substituent. Has low tan δ, improved low loss, and improved wet heat adhesion.

  On the other hand, the rubber composition of Comparative Example 1, which contains a modified natural rubber but does not contain a compound containing a substituted benzene ring, has significantly lower wet heat adhesiveness than the examples, and the modified natural rubber also has a substituted benzene ring. The rubber composition of Comparative Example 2, which does not contain any compound, had lower wet heat adhesion than Comparative Example 1, had a higher tan δ, and had a lower loss. Further, the rubber composition of Comparative Example 3 containing bis (3-hydroxyphenyl) adipate but not containing modified natural rubber has a higher tan δ and lower loss than Examples 1 and 4-9, and resorcinol. The rubber composition of Comparative Example 4 containing no modified natural rubber but having a higher tan δ and lower loss than that of Example 2 and containing an RF resin but no modified natural rubber The product was higher in tan δ than in Example 3 and poor in low loss.

It is sectional drawing of an example of the pneumatic tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5 Bead core 6 Belt

Claims (11)

  1 to 10 parts by mass of sulfur and a di- or tri-substituted benzene ring having at least one hydroxyl group as a substituent for 100 parts by mass of a rubber component containing a modified natural rubber containing a polar group in the natural rubber molecule A pneumatic tire characterized in that a rubber composition comprising 0.1 to 10 parts by mass of a compound is used for any of tire members. The pneumatic tire according to claim 1, wherein the compound containing the substituted benzene ring is represented by the following general formula (I).

[Wherein, X is a hydroxyl group, a carboxyl group or —COOC _m H _{2m + 1} (where m is an integer of 1 to 5); Y is a 2-position, a 4-position, It is a 5- or 6-position, hydrogen, a hydroxyl group or a substituent represented by the following general formula (II). ]

[Wherein, Z ₁ and Z ₂ are each independently a hydroxyl group, a carboxyl group, or —COOC _q H _{2q + 1} (where q is an integer of 1 to 5); It is an integer from 1 to 7. ] The pneumatic tire according to claim 1, wherein the compound containing the substituted benzene ring is represented by the following general formula (III).

[In formula, R represents a C1-C12 bivalent aliphatic group or a bivalent aromatic group. ] The pneumatic tire according to claim 3, wherein the compound represented by the general formula (III) is a compound represented by the following general formula (IV).

[In formula, R represents a C1-C12 bivalent aliphatic group or a bivalent aromatic group. ] In the compound containing the substituted benzene ring, the compound represented by the general formula (IV) is 60 to 100% by mass, the compound represented by the following general formula (V) and n = 2 is 0 to 20% by mass, A composition represented by the general formula (V) and n = 3 is 0 to 10% by mass, and a compound represented by the following general formula (V) and n = 4 to 6 is a total of 0 to 10% by mass. The pneumatic tire according to claim 1, wherein

[In formula, R represents a C1-C12 bivalent aliphatic group or a bivalent aromatic group, and n shows the integer of 2-6. ]   The pneumatic tire according to claim 4 or 5, wherein R in the general formula (IV) is an alkylene group or a phenylene group having 2 to 10 carbon atoms.   The pneumatic tire according to claim 5, wherein R in the general formula (IV) and the general formula (V) is an alkylene group or a phenylene group having 2 to 10 carbon atoms.   The pneumatic tire according to any one of claims 1 to 7, wherein the rubber composition further contains 0.03 to 1 part by mass of an organic acid cobalt salt as a cobalt amount with respect to 100 parts by mass of the rubber component.   The polar group of the modified natural rubber is amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl And at least one selected from the group consisting of a group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, an alkoxysilyl group, and a tin-containing group. The pneumatic tire according to any one of claims 1 to 8.   The pneumatic tire according to any one of claims 1 to 9, wherein the polar group content of the modified natural rubber is 0.001 to 0.5 mmol / g with respect to the rubber component of the modified natural rubber. A steel cord comprising a carcass made of one or more carcass plies and a belt made of one or more belt layers arranged on the outer side in the tire radial direction of the carcass, wherein at least one of the carcass and the belt is coated with a coating rubber In a pneumatic tire including a layer comprising:
The pneumatic tire according to any one of claims 1 to 10, wherein the rubber composition is used as a coating rubber covering a steel cord on at least one of the carcass and the belt.

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