JP6155086B2 - Modified natural rubber and method for producing the same, rubber composition and tire - Google Patents

Description

  The present invention relates to a modified natural rubber, a method for producing the same, and a rubber composition and a tire using the modified natural rubber. Particularly, the modified natural rubber is excellent in low loss and processability when used as a rubber composition. The present invention relates to rubber and a method for producing the same.

  In recent years, there is an increasing demand for lower fuel consumption of automobiles, and tires with low rolling resistance are required. Therefore, a rubber composition having a low tan δ (hereinafter referred to as “low loss property”) and an excellent low heat generation property is required as a rubber composition used for a tire tread or the like. In addition, a rubber composition for a tread is required to have excellent wear resistance and fracture characteristics in addition to low loss. On the other hand, in order to improve the low loss property, wear resistance and fracture characteristics of the rubber composition, it is necessary to improve the affinity between the rubber component and the filler such as carbon black and silica in the rubber composition. It is valid.

  For example, in order to improve the affinity between the filler and the rubber component in the rubber composition and to improve the reinforcing effect by the filler, synthetic rubber or functional group having improved affinity with the filler by terminal modification Synthetic rubbers and the like have been developed in which the monomers are copolymerized to improve the affinity with the filler.

  On the other hand, although natural rubber is used in large quantities by taking advantage of its excellent physical properties, it is a technology that improves the natural rubber itself to improve the affinity with the filler and greatly enhance the reinforcing effect of the filler. There is no.

  For example, a technology for epoxidizing natural rubber has been proposed. However, since this technology cannot sufficiently improve the affinity between the natural rubber and the filler, the reinforcing effect of the filler can be sufficiently improved. Can not. Further, a technique (see Patent Documents 1 to 3) in which a vinyl monomer is added to natural rubber latex to perform graft polymerization is known, and grafted natural rubber obtained by the technique is MG latex or the like. As already produced. However, in order to achieve high grafting efficiency by this method, it is necessary to use a high-purity latex, so that it is necessary to separately perform an operation such as centrifugation, and there is a problem that the manufacturing cost increases.

Therefore, for the purpose of improving the reinforcing property and affinity with the filler and reducing the production cost, Patent Document 4 includes graft polymerization of a polar group-containing monomer on natural rubber latex, coagulation, A rubber composition obtained by blending a modified natural rubber obtained by drying and carbon black or silica is disclosed.
Further, as a technique for further reducing the manufacturing cost, Patent Document 5 discloses that at least one natural rubber raw material selected from the group consisting of natural rubber, natural rubber latex coagulum, and natural rubber cup lamp is mechanically used. A modified natural rubber obtained by graft-polymerizing or adding a polar group-containing compound by applying a shearing force is disclosed.

  If the technique of patent document 4 and 5 is used, it will become possible to manufacture cheaply the modified natural rubber which can improve the low loss property of a rubber composition, abrasion resistance, and a fracture characteristic. However, in the techniques of Patent Documents 4 and 5, a lot of gel is generated in the obtained modified rubber, and further improvement in processability has been desired.

JP-A-5-287121 JP-A-6-329702 Japanese Patent Laid-Open No. 9-25468 JP 2004-262773 A JP 2006-152171 A

  Accordingly, an object of the present invention is to provide a modified natural rubber excellent in low loss and processability when used as a rubber composition by improving the prior art, and a method for producing the same. Another object of the present invention is to provide a rubber composition using the modified natural rubber and a tire using the rubber composition.

  The present inventor has intensively studied to achieve the above object. And by including a specific tertiary alcohol in the modified natural rubber, the amount of gel in the modified natural rubber can be reduced, and the processability when used as a rubber composition can be improved while maintaining low loss. As a result, the present invention has been completed.

That is, the tire rubber composition of the present invention is obtained by graft-polymerizing a polar group-containing compound to at least one natural rubber raw material selected from the group consisting of a natural rubber latex coagulum and a natural rubber cup lamp. The modified natural rubber containing a tertiary alcohol having a carbon number of 5 to 10 and a graft amount of the group-containing compound in the range of 0.01 to 2.0 parts by mass with respect to 100 parts by mass of the solid rubber component in the natural rubber raw material Ingredients and fillers are included.

In a preferred example of the tire rubber composition of the present invention, the tertiary alcohol is non-conjugated.
In another preferred embodiment, the tertiary alcohol has 6 to 8 carbon atoms.
Furthermore, in another suitable example, content of the said tertiary alcohol is 0.01-1 mass part with respect to 100 mass parts of solid rubber components in the said natural rubber raw material.

In another preferable embodiment of the rubber composition for a tire of the present invention, the polar group is an amino group of the polar group-containing compound, an imino group, a nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo And at least one selected from the group consisting of a group, a hydroxyl group, a carboxyl group, a carbonyl group, an epoxy group, an oxycarbonyl group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, a tin-containing group, and an alkoxysilyl group. More preferred.

Furthermore, the tire according to the present invention is characterized by using the tire rubber composition described above for any of the tire members.

  ADVANTAGE OF THE INVENTION According to this invention, when used as a rubber composition, the modified natural rubber excellent in the low loss property and processability and its manufacturing method can be provided. Moreover, the rubber composition and tire which were excellent in the low loss property, abrasion resistance, and a fracture | rupture characteristic using this modified natural rubber can be provided.

(Modified natural rubber, rubber composition)
Embodiments of the present invention will be specifically described below.
The modified natural rubber of the present invention contains a tertiary alcohol having 5 to 10 carbon atoms.
By containing a tertiary alcohol having 5 to 10 carbon atoms, when used as a rubber composition, the processability can be greatly improved compared to conventional modified natural rubber.

  Here, examples of the tertiary alcohol having 5 to 10 carbon atoms include 1,1,3,3-tetramethylbutanol, 1-t-hexanol and the like, and the carbon number of the tertiary alcohol is 6 to 8 is more preferable.

  Moreover, it is preferable that content of the said tertiary alcohol is 0.01-1 with respect to 100 mass parts of solid rubber components in the said natural rubber raw material. When the content of the tertiary alcohol is less than 0.01 parts by mass, the performance improvement effect of the modified natural rubber is not exhibited. On the other hand, when the content exceeds 1 part by mass, other performance may be affected. It is.

  Furthermore, the tertiary alcohol is preferably a non-conjugated system. This is because a modified natural rubber having better performance in terms of processability and the like can be obtained.

Further, the modified natural rubber of the present invention provides a polar group-containing compound by applying mechanical shearing force to at least one natural rubber raw material selected from the group consisting of natural rubber, natural rubber latex coagulum and natural rubber cup lamp. It is preferable to perform graft polymerization.
Since the polar group of the polar group-containing compound is excellent in affinity to various fillers such as carbon black and silica, the modified natural rubber has higher affinity for various fillers than unmodified natural rubber. . Therefore, the rubber composition of the present invention using the modified natural rubber as a rubber component has high dispersibility of the filler with respect to the rubber component, and the reinforcing effect of the filler is sufficiently exerted, resulting in fracture characteristics and wear resistance. This is because the heat resistance (low loss property) is greatly improved.

Furthermore, as the natural rubber raw material, various solid natural rubbers after drying, various natural rubber latex coagulates (including unsmoked sheets) or natural rubber cup lamps can be used, and these natural rubber raw materials are one kind. They may be used alone or in combination of two or more.
Since the production of the modified natural rubber of the present invention does not require the use of a natural rubber latex having a high purity, the modified natural rubber can be produced at a relatively low cost. Among the natural rubber raw materials, cup lamps and the like can be obtained at a low cost, so that they have a great merit in terms of cost. When a cup lamp or the like is used as a raw material, the modification efficiency of natural rubber may be slightly reduced, but there is an advantage from a comprehensive view of cost and modification efficiency.

  The modified natural rubber of the present invention is obtained by graft-polymerizing a natural rubber raw material with a polar group-containing compound on the natural rubber material, and the polar group-containing compound is a compound having an arbitrary polar group as the name implies. The type can be appropriately selected depending on the type and application of the modified rubber.

  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

  As a means for imparting mechanical shearing force to the mixture of the natural rubber raw material and the polar group-containing compound, it is preferable to use a twin-screw extrusion kneader or a dry prebreaker. 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, 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.

  Specific examples of polar groups of polar group-containing vinyl monomers suitable for graft polymerization to natural rubber molecules in the natural rubber raw material include amino groups, imino groups, nitrile groups, ammonium groups, imide groups, amides. Group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, tin-containing group, alkoxysilyl group, etc. Can be mentioned. These polar group-containing vinyl monomers may be used alone or in combination of two or more.

  Examples of the vinyl 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. . Among the polymerizable monomers having an amino group, a tertiary amino group-containing vinyl monomer such as dialkylaminoalkyl (meth) acrylate is particularly preferable. These amino group-containing vinyl monomers may be used alone or in a combination of two or more.

  Here, the primary amino group-containing vinyl monomers include acrylamide, methacrylamide, 4-vinylaniline, aminomethyl (meth) acrylate, aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, aminobutyl Examples include (meth) acrylate.

  Secondary vinyl group-containing vinyl monomers include (1) anilinostyrene, β-phenyl-p-anilinostyrene, β-cyano-p-anilinostyrene, β-cyano-β-methyl. -p-anilinostyrene, β-chloro-p-anilinostyrene, β-carboxy-p-anilinostyrene, β-methoxycarbonyl-p-anilinostyrene, β- (2-hydroxyethoxy) carbonyl-p- Anilinostyrene such as anilinostyrene, β-formyl-p-anilinostyrene, β-formyl-β-methyl-p-anilinostyrene, α-carboxy-β-carboxy-β-phenyl-p-anilinostyrene (2) 1-anilinophenyl-1,3-butadiene, 1-anilinophenyl-3-methyl-1,3-butadiene, 1-anilinophenyl-3-chloro-1,3-butadiene, 3 -Anilinophenyl-2-methyl-1,3-butadiene, 1-a Linophenyl-2-chloro-1,3-butadiene, 2-anilinophenyl-1,3-butadiene, 2-anilinophenyl-3-methyl-1,3-butadiene, 2-anilinophenyl-3-chloro- Anilinophenylbutadienes such as 1,3-butadiene, (3) N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methylolacrylamide, N- (4-anilinophenyl) methacrylamide, etc. N-mono substituted (meth) acrylamides and the like can be mentioned.

  Furthermore, examples of the tertiary amino group-containing vinyl monomer include N, N-disubstituted aminoalkyl (meth) acrylate and N, N-disubstituted aminoalkyl (meth) acrylamide.

  Examples of the N, N-disubstituted aminoalkyl (meth) acrylate include N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N-diethylaminobutyl (meth) acrylate, N-methyl -N-ethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-dibutylaminopropyl (meth) acrylate, N, N-dibutylaminobutyl (meth) acrylate, N, N-dihexylaminoethyl (meth) acrylate, N, N-dioctyl Aminoethyl (meth) acrylate, esters of acrylic acid or methacrylic acid such as acryloyl morpholine and the like. Among these, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dioctylaminoethyl (meth) Particularly preferred are acrylate, N-methyl-N-ethylaminoethyl (meth) acrylate, and the like.

  Examples of the N, N-disubstituted aminoalkyl (meth) acrylamide include N, N-dimethylaminomethyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl ( (Meth) acrylamide, N, N-dimethylaminobutyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N, N-diethylaminobutyl (meth) acrylamide, N -Methyl-N-ethylaminoethyl (meth) acrylamide, N, N-dipropylaminoethyl (meth) acrylamide, N, N-dibutylaminoethyl (meth) acrylamide, N, N-dibutylaminopropyl (meth) acrylamide, N, N-dibutylaminobutyl (meth) acrylamide, N, N-dihexylaminoethyl ( Data) acrylamide, N, N-dihexyl-aminopropyl (meth) acrylamide, N, N-acrylamide compounds such as dioctyl aminopropyl (meth) acrylamide or methacrylamide compounds and the like. Among these, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N, N-dioctylaminopropyl (meth) acrylamide and the like are particularly preferable.

  Examples of the vinyl monomer containing a nitrile group include (meth) acrylonitrile and vinylidene cyanide. These nitrile group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing a hydroxyl group include polymerizable monomers having at least one primary, secondary or tertiary hydroxyl group in one molecule. Examples of such monomers include hydroxyl group-containing unsaturated carboxylic acid monomers, hydroxyl group-containing vinyl ether monomers, hydroxyl group-containing vinyl ketone monomers, and the like. Here, specific examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meta ) Acrylate, 3-hydroxybutyl (meth) acrylate, hydroxyalkyl (meth) acrylates such as 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; N-hydroxymethyl (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, N, N-bis (2-hydroxymethyl) (meth) acrylamide Hydroxyl group-containing unsaturated amides such as o- Contains hydroxyl groups such as loxystyrene, m-hydroxystyrene, p-hydroxystyrene, o-hydroxy-α-methylstyrene, m-hydroxy-α-methylstyrene, p-hydroxy-α-methylstyrene, p-vinylbenzyl alcohol And vinyl aromatic compounds. Among these, hydroxyl group-containing unsaturated carboxylic acid monomers, hydroxyalkyl (meth) acrylates, and hydroxyl group-containing vinyl aromatic compounds are preferable, and hydroxyl group-containing unsaturated carboxylic acid monomers are particularly preferable. Here, examples of the hydroxyl group-containing unsaturated carboxylic acid-based monomer include esters such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, amides, and anhydrides. Among these, Particularly preferred are esters such as acrylic acid and methacrylic acid. These hydroxyl group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing a carboxyl group include unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, tetraconic acid, cinnamic acid; phthalic acid, succinic acid, adipic acid, etc. Non-polymerizable polyvalent carboxylic acids and free carboxyl group-containing esters such as monoesters of hydroxyl-containing unsaturated compounds such as (meth) allyl alcohol and 2-hydroxyethyl (meth) acrylate, and salts thereof It is done. Of these, unsaturated carboxylic acids are particularly preferred. These carboxyl group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing an epoxy group include (meth) allyl glycidyl ether, glycidyl (meth) acrylate, and 3,4-oxycyclohexyl (meth) acrylate. These epoxy group-containing vinyl monomers may be used alone or in combination of two or more.

  In the vinyl 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, Examples include pteridine and melamine. The nitrogen-containing heterocycle may contain other heteroatoms in the ring. Here, as a vinyl monomer containing a pyridyl group as a nitrogen-containing heterocyclic group, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 5-methyl-2-vinylpyridine, 5-ethyl- 2-vinylpyridine and the like can be mentioned, among which 2-vinylpyridine, 4-vinylpyridine and the like are particularly preferable. These nitrogen-containing heterocyclic group-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer having a tin-containing group include allyltri-n-butyltin, allyltrimethyltin, allyltriphenyltin, allyltri-n-octyltin, (meth) acryloxy-n-butyltin, (meth) acryloxy Tin-containing monomers such as trimethyltin, (meth) acryloxytriphenyltin, (meth) acryloxy-n-octyltin, vinyltri-n-butyltin, vinyltrimethyltin, vinyltriphenyltin, vinyltri-n-octyltin Can be mentioned. These tin-containing vinyl monomers may be used alone or in a combination of two or more.

  Examples of the vinyl monomer containing the alkoxysilyl group include (meth) acryloxymethyltrimethoxysilane, (meth) acryloxymethylmethyldimethoxysilane, (meth) acryloxymethyldimethylmethoxysilane, (meth) acryloxy. Methyltriethoxysilane, (meth) acryloxymethylmethyldiethoxysilane, (meth) acryloxymethyldimethylethoxysilane, (meth) acryloxymethyltripropoxysilane, (meth) acryloxymethylmethyldipropoxysilane, (meth) Acryloxymethyldimethylpropoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxy Propyltriethoxy Lan, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, γ- (meth) acryloxypropyltripropoxysilane, γ- (meth) acryloxypropylmethyldipropoxy Silane, γ- (meth) acryloxypropyldimethylpropoxysilane, γ- (meth) acryloxypropylmethyldiphenoxysilane, γ- (meth) acryloxypropyldimethylphenoxysilane, γ- (meth) acryloxypropylmethyldibenzyl Examples include loxysilane, γ- (meth) acryloxypropyldimethylbenzyloxysilane, trimethoxyvinylsilane, triethoxyvinylsilane, 6-trimethoxysilyl-1,2-hexene, and p-trimethoxysilylstyrene. These alkoxysilyl group-containing vinyl monomers may be used alone or in a combination of two or more.

  In the production of the modified natural rubber of the present invention, a polymerization initiator is added to the natural rubber raw material in order to graft polymerize the polar group-containing compound to the natural rubber molecule in the natural rubber raw material. As the polymerization initiator to be added, from the viewpoint of suppressing the gelation of the modified natural rubber described above, as the polymerization initiator, carbon in the alkyl chain extending from an atom which is radically cleaved at one point and becomes at least one radical. Those having a structure having a number of 5 to 10 are used. When it has a structure that is cleaved at two points, the natural rubber is cross-linked, and thus gelation may be accelerated. In addition, the atom which becomes the radical is an atom in which the covalent bond of the cleaved portion is broken, and the alkyl chain extending from the atom means an alkyl chain extending from the atom before radical cleavage. The reason why the number of carbons in the alkyl chain is limited to 5 to 10 is that when the number of carbons is less than 5, a sufficient gelation-inhibiting effect cannot be achieved. This is because the chain becomes long and the cleavage temperature becomes low, making it difficult to use.

Examples of the polymerization initiator described above include those having the following structure.

  Here, in the modified natural rubber of the present invention, the reason for suppressing the gelation by optimizing the polymerization initiator is that when the gelation exceeds a certain amount, the processability deteriorates.

  In order to improve the low loss and wear resistance without reducing the processability of the rubber composition by adding a filler such as carbon black or silica to the modified natural rubber, the polar group is added to each natural rubber molecule. Since it is important that the contained compound is introduced in a small amount and uniformly, the addition amount of the polymerization initiator 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 compound. preferable.

  About each component mentioned above, the modification | denaturation natural rubber which the said polar group containing compound was graft-copolymerized to the natural rubber molecule | numerator is obtained by charging in the apparatus which gives a mechanical shearing force, and giving a mechanical shearing force. 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.

  In addition to the above-described graft polymerization, a natural rubber raw material and a polar group-containing compound (preferably, a polar group-containing mercapto compound) are introduced into an apparatus capable of applying mechanical shearing force, and an organic peroxide is used as necessary. Further, by adding a mechanical shearing force, etc., a polar group-containing compound can be added to the double bond of the main chain of the natural rubber molecule in the natural rubber raw material.

  Specific examples of polar groups of a polar group-containing mercapto compound suitable for addition reaction with natural rubber molecules in the natural rubber raw material include amino groups, imino groups, nitrile groups, ammonium groups, imide groups, amides. Group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, tin-containing group, alkoxysilyl group, etc. Can be mentioned. These polar group-containing mercapto compounds may be used alone 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. These amino group-containing mercapto compounds may be used alone or in combination of two or more.

  Examples of the mercapto compound having a nitrile group include 2-mercaptopropane nitrile, 3-mercaptopropane nitrile, 2-mercaptobutane nitrile, 3-mercaptobutane nitrile, 4-mercaptobutane nitrile, etc., and these nitrile group-containing mercapto compounds May be used individually by 1 type, and may be used in combination of 2 or more type.

  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. Among these, 2-mercaptoethanol and the like are preferable. These hydroxyl group-containing mercapto compounds may be used alone or in a combination of two or more.

  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. These carboxyl group-containing mercapto compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  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. These nitrogen-containing heterocyclic group-containing mercapto compounds may be used alone or in combination of two or more.

  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. These tin-containing mercapto compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the mercapto compound containing an alkoxysilyl group include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, and 2-mercaptoethyltrimethoxy. Examples include silane, 2-mercaptoethyltriethoxysilane, mercaptomethylmethyldiethoxysilane, mercaptomethyltrimethoxysilane, and the like. Among these, 3-mercaptopropyltrimethoxysilane is preferable. These alkoxysilyl group-containing mercapto compounds may be used alone or in a combination of two or more.

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

  In the modified natural rubber of the present invention, the graft amount or addition amount of the polar group-containing compound is preferably in the range of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the solid rubber component in the natural rubber raw material, and 0.05 to 2.0 parts by weight. The range of parts is more preferable, and the range of 0.10 to 1.0 parts by mass is even more preferable. When the grafting amount or addition amount of the polar group-containing compound is less than 0.01 parts by mass, the low loss and wear resistance of the rubber composition may not be sufficiently improved. Moreover, if the grafting amount or addition amount of the polar group-containing compound exceeds 5.0 parts by mass, the natural physical properties of natural rubber such as viscoelasticity and SS characteristics (stress-strain curve in a tensile testing machine) will be greatly changed. In addition, the physical properties inherent to natural rubber are impaired, and the processability of the rubber composition may be greatly deteriorated.

  The rubber composition of the present invention is characterized by using the modified natural rubber and preferably further contains a filler. Here, 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 modified natural rubber. 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.

Examples of the filler used in the rubber composition of the present invention include carbon black and inorganic filler. Here, as the inorganic filler, silica and the following formula (I):
nM · xSiO _y · zH ₂ O (I)
[Wherein, M is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium and zirconium, an oxide or hydroxide of these metals, and a hydrate thereof, or a carbonate of these metals. And n, x, y, and z are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10]. Is mentioned. These fillers may be used alone or in a combination of two or more.

Examples of the carbon black include GPF, FEF, SRF, HAF, ISAF, and SAF grades, and examples of the silica include wet silica, dry silica, and colloidal silica. Further, the inorganic compound of the formula (I) includes alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina; alumina monohydrate such as boehmite and diaspore (Al ₂ O ₃ .H ₂ O). Aluminum hydroxide [Al (OH) ₃ ] such as gibbsite and bayerite; aluminum carbonate [Al ₂ (CO ₃ ) ₃ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (MgO), magnesium carbonate ( MgCO ₃ ), talc (3MgO · 4SiO ₂ · H ₂ O), attapulgite (5MgO · 8SiO ₂ · 9H ₂ O), titanium white (TiO ₂ ), titanium black (TiO _2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca (OH) _2], magnesium aluminum oxide _{(MgO · Al 2 O 3)} , clay _{(Al 2 O 3 · 2SiO 2} ), kaolin _{(Al 2 O 3 · 2SiO 2} · 2 ₂ O), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite _{(Al 2 O 3 · 4SiO 2} · 2H 2 O), aluminum silicate _{(Al 2 SiO 5, Al 4} · 3SiO 4・ 5H ₂ O etc.), magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ · CaO · 2SiO ₂ etc.), Magnesium calcium oxide (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO (OH) ₂ · nH ₂ O], zirconium carbonate [Zr (CO ₃ ) ₂ ], various zeolites Examples thereof include crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals that correct electric charges.

  In addition to the modified natural rubber and filler, the rubber composition of the present invention includes compounding agents commonly used in the rubber industry, such as anti-aging agents, softeners, silane coupling agents, stearic acid, zinc white. Further, a vulcanization accelerator, a vulcanizing agent, and the like can be appropriately selected and blended within a range not impairing the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition of the present invention can be produced by blending various modified additives appropriately selected as necessary with the modified natural rubber, kneading, heating, extruding and the like.

(tire)
The tire of the present invention is characterized by using the rubber composition, and the rubber composition is preferably used for a tread. A tire using the rubber composition as a tread is excellent in fuel efficiency, fracture characteristics, and wear resistance. The tire of the present invention is not particularly limited except that the rubber composition described above is used for any of the tire members, and can be produced according to a conventional method. Moreover, as gas with which this tire is filled, inert gas, such as nitrogen, argon, helium other than normal or the air which adjusted oxygen partial pressure, can be used.

  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.

<Comparative Example 1>
600 g of the natural rubber shown below, 1.8 g of N, N-diethylaminoethyl methacrylate, and 0.2 parts by mass of the polymerization initiator shown in Table 1 with respect to 100 parts by mass of the rubber component at room temperature in a kneader at 30 rpm for 2 minutes. Kneaded and dispersed uniformly. Next, while adding 0.7 g of tetraethylenepentamine (TEPA) uniformly to the resulting mixture, Kobe Steel made a twin-screw kneading extruder [same-direction rotating screw diameter = 30 mm, L / D = 35, three vent holes The modified natural rubber according to Comparative Example 1 was obtained by extruding while applying mechanical shearing force at a barrel temperature of 120 ° C. and a rotation speed of 100 rpm.
The natural rubber prepared as a natural rubber raw material is a natural rubber latex (CT-1) added with 0.4% by mass of ammonia using a latex separator SLP-3000 (manufactured by Saito Centrifuge Co., Ltd.) at a rotational speed of 7500 rpm. Concentrated by centrifuging for min. The concentrated latex was further centrifuged at 7500 rpm for 15 minutes. A natural rubber obtained by diluting the resulting concentrated latex to about 20% as a solid content, adding formic acid and allowing it to stand overnight, and then coagulating the rubber content obtained at 110 ° C. for 210 minutes. .
The tertiary alcohols contained in the modified natural rubber are shown in Table 1.

<Examples 1 and 2>
Furthermore, instead of the polymerization initiator of Comparative Example 1, 0.2 parts by mass of the polymerization initiator shown in Table 1 was blended with respect to 100 parts by mass of the rubber component, instead of the polymerization initiator of Comparative Example 1, Comparative Example 1 except that 0.2 parts by mass of the polymerization initiator shown in 1 was blended with respect to 100 parts by mass of the rubber component and that the mixture was extruded without adding tetraethylenepentamine (TEPA). Under the same conditions, modified natural rubbers according to Examples 1 and 2 were obtained.
The tertiary alcohols contained in the modified natural rubber are shown in Table 1.

<Comparative example 2>
Moreover, it replaced with the natural rubber raw material of the comparative example 1, and Example was carried out on the conditions similar to the comparative example 1 except having used SIR20 (natural rubber cup lamp (nitrogen amount: 0.38 mass%)) as a natural rubber raw material. A modified natural rubber according to No. 4 was obtained.
The tertiary alcohols contained in the modified natural rubber are shown in Table 1.

<Examples 3 to 5>
Furthermore, in place of the polymerization initiator of Comparative Example 2, 0.2 parts by mass of the polymerization initiator shown in Table 1 was added to 100 parts by mass of the rubber component, and tetraethylenepentamine (TEPA) was added. The modified natural rubber according to Examples 3 to 5 was obtained under the same conditions as in Comparative Example 2 except that the mixture was extruded.
The tertiary alcohol contained in the modified natural rubber is shown in Table 1.

(1) Low loss property Each modified natural rubber obtained was kneaded with a plastmill, and Comparative Examples 1, 2 and 5 and Examples 1 to 5 were combined in Table 2 and Comparative Examples 3 and 6 were combined. 2. For Comparative Example 4, a rubber composition having the formulation shown in Formulation 3 was prepared, and the loss tangent (tan δ) of the rubber composition was measured using a viscoelasticity measuring device (Rheometrics) at a temperature of 50 The measurement was performed under the conditions of ° C., strain 5%, and frequency 15 Hz. The results are shown as an index when the tan δ of Comparative Example 1 is 100, and the results are shown in Table 1. It shows that it is excellent in low-loss property, so that an index value is small.

(2) Processability About each obtained modified natural rubber, according to JIS-K6300-1: 2001, with Mooney viscometer (RPA made by Monsanto Co., Ltd.), using an L-shaped rotor, at 130 ° C, The Mooney viscosity [ML1 + 4 (130 ° C.)] of the unvulcanized rubber composition was measured.
The value of Mooney viscosity of the obtained unvulcanized rubber composition is shown in Table 1 as an index with the value of Comparative Example 1 being 100. In addition, the smaller the index value, the better the flowability of the unvulcanized rubber composition and the better the processability.

* 1 Table 1 shows the types of rubber components used.
* 2 N- (1,3-Dimethylbutyl) -N'-phenyl-p-phenylenediamine
* 3 N, N'-Dicyclohexyl-2-benzothiazolylsulfenamide

  A tire using a rubber composition containing a modified natural rubber according to the present invention is industrially useful in terms of low loss and excellent processability.

Claims (6)

A polar group-containing compound is graft-polymerized to at least one natural rubber raw material selected from the group consisting of a natural rubber latex coagulum and a natural rubber cup lamp, and the amount of the polar group-containing compound grafted is the natural rubber raw material. A modified natural rubber component containing a tertiary alcohol having a carbon number of 5 to 10 in a range of 0.01 to 2.0 parts by mass with respect to 100 parts by mass of the solid rubber component therein ,
A rubber composition for tires , comprising a filler . The tire rubber composition according to claim 1, wherein the tertiary alcohol is a non-conjugated system. The tire rubber composition according to claim 1 or 2, wherein the tertiary alcohol has 6 to 8 carbon atoms. 4. The tire use according to claim 1, wherein a content of the tertiary alcohol is 0.01 to 1 part by mass with respect to 100 parts by mass of the solid rubber component in the natural rubber raw material . Rubber composition. The polar group of the polar group-containing compound 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 It is at least one selected from the group consisting of a group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, a tin-containing group, and an alkoxysilyl group. Rubber composition for tires . A tire, wherein the tire rubber composition according to any one of claims 1 to 5 is used for any tire member.