JP2008063364A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

[PROBLEMS] To maintain a grip property without impairing processability, and to achieve a high compatibility between low rolling resistance and wear resistance, and to improve the above-described performance using the rubber composition for a tire member. To provide an improved pneumatic tire.
(A) Gel permeation chromatography before modification having at least one functional group for a high molecular weight rubber component having a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography of 200,000 or more. A rubber composition containing a low molecular weight conjugated diene polymer having a polystyrene-reduced weight average molecular weight of 2,000 to less than 200,000 and (C) a filler.
[Selection figure] None

Description

  The present invention relates to a rubber composition for tires, and more specifically, a rubber composition having both low rolling resistance and low temperature flexibility at a high level, and improvement of the above performance using the rubber composition for a tire member. Related to pneumatic tires.

In recent years, demands for lower fuel consumption and safety of automobiles are intensifying in connection with the movement of global carbon dioxide emission regulations accompanying the growing interest in environmental problems. In order to meet such demands, the tire performance is also required to be reduced in rolling resistance and improved in grip performance such as wet performance and dry performance.
Here, as a technique for reducing the rolling resistance of the tire, it is effective to use a low heat-generating rubber composition having a lower loss tangent (tan δ) as a rubber composition applied to the tread portion of the tire. Conventionally used butadiene rubber for tire treads, or styrene-butadiene copolymer rubber with low styrene and low vinyl content has a lower glass transition temperature (Tg) than other synthetic rubbers. It is known that it is excellent in flexibility.

  However, when a butadiene rubber or a styrene-butadiene copolymer rubber having a low styrene and low vinyl content is used in the tread, the loss tangent (tan δ) of these rubber compositions is low, so that it is difficult to obtain sufficient grip performance. There is.

As a method for obtaining such a rubber composition having low exothermicity, it is conceivable to reduce the amount of filler such as carbon black or silica, or to use carbon black having a large particle diameter. Decrease in reinforcement, wear resistance and grip on wet roads is inevitable.
Further, as a method for obtaining a rubber composition having low exothermic property, many technical developments have been made to improve the dispersibility of the filler in the rubber composition. Among them, the method of modifying the polymerization active site of a conjugated diene polymer obtained by anionic polymerization using alkyllithium with a functional group capable of interacting with a filler is most effective (see Patent Documents 1 to 3). ).
However, when the above modified conjugated diene polymer is used as a rubber component, when a large amount of softener, especially aroma oil, is added, the effect of improving the dispersibility of the filler is not sufficiently exhibited, and the rubber composition There was a problem that workability, low heat generation, fracture characteristics and wear resistance could not be sufficiently improved.
Moreover, although the technique excellent in low temperature flexibility is known, maintaining workability, the effect is not enough and rolling resistance was not able to be improved simultaneously (refer patent document 4).

  On the other hand, as a rubber composition applied to the tread portion of a tire, a rubber composition having a high storage elastic modulus (G ′) is suitable for securing a grip, so that the loss tangent (tan δ) is low and the storage elasticity A rubber composition having a high rate (G ′) is demanded. On the other hand, as a means for improving the storage elastic modulus (G ′) of the rubber composition, there is a method of increasing the amount of carbon black compounded in the rubber composition. When the amount is increased, the storage elastic modulus (G ′) of the rubber composition can be improved, but at the same time, the loss tangent (tan δ) of the rubber composition is increased, and the low exothermic property of the rubber composition is decreased. Furthermore, there is a problem that the Mooney viscosity of the rubber composition increases and the processability decreases. Although there is a method of adding a softening agent to improve workability, the wear resistance and rolling resistance are reduced as described above. Accordingly, there is an increasing demand for development of a rubber composition having both the above-mentioned conflicting performances.

Japanese Patent Publication No. 5-87530 JP-A-6-49279 JP 62-207342 A JP-A-10-53671

  Under such circumstances, the present invention provides a rubber composition that is highly compatible with low temperature flexibility and low rolling resistance, and a pneumatic tire with improved performance using the rubber composition as a tire member. Is intended to provide.

As a result of intensive studies to achieve the above object, the present inventors have at least one functional group having a weight average molecular weight in a specific range with respect to a high molecular weight rubber component having a specific weight average molecular weight. It has been found that the purpose can be achieved by using a low molecular weight conjugated diene polymer in place of a part of the softening agent. The present invention has been completed based on such findings.
That is, the present invention
(1) (A) Gel permeation chromatography before modification having at least one functional group on a high molecular weight rubber component having a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography of 200,000 or more. A rubber composition comprising a low molecular weight conjugated diene polymer having a polystyrene-reduced weight average molecular weight of 2,000 to less than 200,000, and (C) a filler,
(2) The rubber composition according to (1) above, containing 1 to 60 parts by mass of the component (B) with respect to 100 parts by mass of the rubber component (A),
(3) The above (1) or (B) wherein the vinyl bond content of the component (B) is 5 to 80% by mass of the polymerized unit of the conjugated diene, and the content of the aromatic vinyl compound in the component (B) is 5% by mass or less. 2) rubber composition,
(4) The rubber composition according to any one of the above (1) to (3), wherein the component (B) is a butadiene homopolymer or a butadiene / styrene copolymer,
(5) The rubber composition according to any one of the above (1) to (4), wherein the functional group of the component (B) is a functional group containing tin, silicon, and a nitrogen atom,
(6) The rubber composition according to any one of (1) to (5) above, wherein the polystyrene-converted weight average molecular weight measured by gel permeation chromatography of the component (B) before modification is 20,000 to less than 200,000.
(7) The rubber composition according to (6), wherein the polystyrene-converted weight average molecular weight measured by gel permeation chromatography of the component (B) before modification is 50,000 to 150,000,
(8) (A) The rubber composition according to any one of (1) to (7) above, containing 30 to 90 parts by mass of a filler with respect to 100 parts by mass of the rubber component.
(9) The rubber composition according to (8), wherein the filler (C) is carbon black and / or silica,
(10) Any of (1) to (9) above, wherein (A) the rubber component comprises at least one (D) aromatic vinyl compound-conjugated diene compound copolymer, (E) conjugated diene polymer, and natural rubber Any rubber composition,
(11) The rubber composition according to (10), wherein the component (D) is a styrene-butadiene copolymer,
(12) The rubber composition according to (11), wherein the component (E) is a butadiene homopolymer,
(13) The rubber composition according to any one of the above (10) to (12), wherein the component (D) and the component (E) have at least one functional group,
(14) The rubber composition according to (13) above, wherein the functional groups of the component (D) and the component (E) are tin and a functional group containing a nitrogen atom,
(15) The rubber composition according to any one of (1) to (14) above, wherein the total amount of the component (B) and the softening agent is 5 to 80 parts by mass with respect to 100 parts by mass of the (A) rubber component,
(16) The rubber composition according to (15), wherein the total amount of the component (B) and the softening agent is 5 to 60 parts by mass with respect to 100 parts by mass of the (A) rubber component,
(17) The rubber composition according to any one of (1) to (16) above, wherein the component (B) is 20% by mass or more of the total amount of the softener and the component (B).
(18) (C) The rubber composition according to any one of (1) to (17), wherein the filler is carbon and / or silica.
(19) A rubber composition for tires, wherein the rubber composition according to any one of (1) to (18) is for tires,
(20) A pneumatic tire characterized by using the tire rubber composition of (19) as a tire member, and (21) a tire tread, sidewall, and bead filler of (19) above. , Pneumatic tire applied to body price kim and run-flat tire reinforcement rubber.
Is to provide.

According to the present invention, by applying a low molecular weight conjugated diene polymer having a functional group within a weight average molecular weight range of 2,000 to less than 200,000, low temperature flexibility and low rolling resistance are enhanced. It is possible to provide a rubber composition having improved performance as described above, and a rubber composition using the rubber composition as a tire member.
In particular, when a low molecular weight conjugated diene polymer having a functional group having a weight average molecular weight of 2,000 to 150,000 is applied, the wet performance is maintained at a high level, and the weight average molecular weight is less than 20,000 to 200,000. When the low molecular weight conjugated diene polymer is applied, the storage elastic modulus and the low rolling resistance at high temperature are improved.

First, the rubber composition for tires of the present invention comprises (A) a high molecular weight rubber component having a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography of 200,000 or more, and (B) at least one functional group. A low molecular weight conjugated diene polymer having a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography before modification having a molecular weight of 2,000 to less than 200,000 and (C) a filler is required.
Here, the term “before modification” refers to an unmodified state before the modification reaction is performed by adding a modifying agent after the completion of the polymerization reaction. However, when polymerization is carried out using a polymerization initiator having a functional group such as a lithium amide compound, it is distinguished from a modification reaction. In such a case, the polymer has a functional group, so that it is within the scope of the present invention. It is.
The rubber composition of the present invention comprises (A) a high molecular weight rubber containing, as a rubber component, at least one (D) aromatic vinyl compound-conjugated diene compound copolymer, (E) a conjugated diene polymer, and natural rubber. The polystyrene-reduced weight average molecular weight selected from the group of components and measured by gel permeation chromatography must be 200,000 or more. The preferred weight average molecular weight of the high molecular weight rubber component is in the range of 200,000 to 1,000,000.
By making the weight average molecular weight of the high molecular weight rubber component in the above range, when the low molecular weight conjugated diene polymer of the component (B) is blended, the decrease in Mooney viscosity, the degradation property and the wear resistance are suppressed, Excellent processability can be obtained.

  On the other hand, the polystyrene equivalent weight average molecular weight measured by gel permeation chromatography before modification of the low molecular weight conjugated diene polymer having at least one functional group of the component (B) is less than 2,000 to less than 200,000. is required. By making the weight average molecular weight of the component (B) within the above range, a rubber composition that maintains wet grip properties without impairing workability, and is highly compatible with storage modulus at low temperatures and low rolling resistance. You can get things. Further, in addition to the above-mentioned various performances, a range of 20,000 to 150,000 is preferable, and a range of 50,000 to 100,000 is more preferable from the viewpoint of improving grip properties in a wide temperature range from low temperature to high temperature. is there.

By applying a low molecular weight conjugated diene polymer having at least one functional group having a weight average molecular weight of 2,000 to less than 200,000 as component (B), low rolling properties, wear resistance and grip performance are Although both are improved, especially when the component (B) having a weight average molecular weight of 2,000 to 50,000, preferably 2,000 to 30,000 is applied, the flexibility and wet performance at a low temperature are enhanced to a high degree. When the (B) component having a weight average molecular weight of 20,000 to less than 200,000, preferably 50,000 to 150,000 is applied, the storage elastic modulus and low rolling resistance at high temperatures are improved. To do.
Therefore, in the case where importance is placed on any of wet performance, dry performance and intermediate performance as tire performance, the range of the weight average molecular weight of the component (B) can be selected according to the performance emphasized.

  It is preferable to contain 1-60 mass parts of said (B) component with respect to 100 mass parts of said (A) component. More preferably, it is 3-50 mass parts. By replacing part of the softener with the component (B) and making the content of the component (B) in the above range, the wet performance is maintained and the low rolling resistance and the dry performance are improved without impairing the workability. be able to.

The high molecular weight rubber component (A) used in the rubber composition of the present invention is not particularly limited, and is a natural rubber or a synthetic diene rubber (D) aromatic vinyl compound-conjugated diene compound copolymer. (E) It can be selected from the group of highly divided quantum rubber components containing a conjugated diene polymer. As the high molecular weight rubber component (A), any of unmodified rubber and modified rubber may be used.
The natural rubber or isoprene rubber (IR) is not particularly limited, and any natural rubber or isoprene rubber that is generally available can be used.
The aromatic vinyl compound-conjugated diene compound copolymer (D) is particularly preferably a styrene-butadiene copolymer.
Here, examples of the conjugated diene monomer include 1,3-butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene and the like, and among these, 1,3-butadiene is preferable. Examples of the aromatic vinyl monomer used for copolymerization with the conjugated diene monomer include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4- Examples thereof include cyclohexyl styrene and 2,2,6-tolyl styrene, among which styrene is preferable.
Examples of the conjugated diene polymer of component (E) include conjugated diene homopolymers and copolymers of conjugated dienes, and polybutadienes of conjugated diene homopolymers are preferred.
Natural rubber and component (D) (E) may be used alone or in combination of two or more.

The conjugated diene polymer can be produced by various methods such as emulsion polymerization or solution polymerization, and the polymerization method may be either a batch polymerization method or a continuous polymerization method. A preferable production method is as follows.
That is, it is obtained by polymerizing a monomer containing a conjugated diene in an inert solvent, preferably a hydrocarbon solvent, in the presence of an initiator such as an organic metal, preferably an organic lithium compound initiator. Although there is no restriction | limiting in particular as said hydrocarbon solvent, For example, n-pentane, n-hexane, n-heptane, a cyclohexane, benzene, toluene etc. are raised, A preferable solvent is a cyclohexane and n-hexane. These hydrocarbon solvents may be used alone or in combination of two or more.
The organic lithium used as the initiator is preferably a hydrocarbon lithium compound having at least one lithium atom bonded thereto and having 2 to 20 carbon atoms, such as n-butyl lithium, ethyl lithium, n-propyl lithium, tert. -Octyllithium, phenyllithium, etc., with n-butyllithium being preferred. These organolithium initiators may be used alone or in combination of two or more.

Furthermore, as the conjugated diene polymer of the component (D) and the component (E) used in the present invention, a modified polymer containing tin or silicon or a modified polymer containing a nitrogen atom may be used in the molecule or terminal. preferable.
Such a modified polymer suppresses a decrease in elastic modulus due to a temperature rise, and when a tin atom or a nitrogen atom is introduced, a carbon black compounded rubber composition, and when a silicon atom is introduced, a reinforcing property such as silica. In the rubber composition which mix | blended the inorganic filler, since heat_generation | fever can also be suppressed, it is preferable.
In addition, the content of the polymer containing at least one of a tin atom, a nitrogen atom and a silicon atom in the molecule or terminal of the component (D) or the component (E) is preferably 50% or more. It is preferable that 80% by mass or more of the component or component (E) is a modified polymer containing at least one of a tin atom, a nitrogen atom and a silicon atom in the molecule.

In addition, the component (D) and the component (E) preferably have a branched structure. The branched structure can be introduced by using a trifunctional or higher functional initiator, a trifunctional or higher functional modifier, a monomer having two or more polymerization active groups, and a trifunctional or higher functional modifier is preferably used. .
The modified polymer is produced by a known method. Usually, polymerization is initiated by an organolithium initiator, and then various modifiers are added to a polymer solution having an active lithium end (JP-B-6-89183, JP-A-11-29659). Such). It is preferable that the modifier is introduced after the completion of the polymerization.
The coupling agent is a halide such as tin halide or silicon halide. The halogen in the coupling agent is generally fluorine, chlorine, bromine or iodine, with chlorine being particularly preferred. Further, tin and silicon of Group VIa atom are preferable, and tin is particularly preferable.
For example, tin atoms can be introduced by tin compounds such as tin tetrachloride, tributyltin, dioctyltin dichloride, dibutyltin dichloride, triphenyltin chloride. In addition, when a bifunctional or higher functional tin modifier is used, the polymer having a lithium active terminal is coupled by the modifier, the tin atom is incorporated into the molecule, and the monofunctional modification such as triphenyltin chloride is performed. When the agent is used, lithium atoms are taken into the polymer ends.

The nitrogen atom is an isocyanate compound such as 2,4-tolylene diisocyanate or diisocyanate diphenylmethane; an aminobenzophenone compound such as 4,4′bis (diethylamino) -benzophenone or 4- (dimethylamino) benzophenone; -Urea derivatives such as dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydropyrimidine, and other 4-dimethylaminobenzylideneanilines , Dimethylimidazolidinone, N-methylpyrrolidone, and other nitrogen-containing compounds.
In addition, when a lithium amide compound is used as a polymerization initiator, the nitrogen atom has a (co) polymer having a nitrogen-containing functional group at the polymerization initiation terminal and the other terminal being a polymerization active site. The polymer can be used as a high molecular weight (co) polymer of the component (A) having one functional group without being modified with a modifier.
Examples of the lithium amide compound include lithium hexamethylene imide, lithium pyrrolidide, lithium piperidide, lithium heptamethylene imide, lithium dodecamethylene imide, lithium dimethyl amide, lithium diethyl amide, lithium dipropyl amide, lithium dibutyl amide, lithium dihexyl amide. Lithium diheptylamide, Lithium dioctylamide, Lithymdi-2-ethylhexylamide, Lithium didecylamide, Lithium-N-methylpiperazide, Lithium ethylpropylamide, Lithium ethylbutyramide, Lithium methylbutyramide, Lithium ethylbenzylamide, Lithium methyl Phenethyl amide, etc., among these, lithium hexamethylene imide, lithium pyrrolidide, lithium piperi Cyclic lithium amide compounds such as zide, lithium heptamethylene imide and lithium dodecamethylene imide are preferred, and lithium hexamethylene imide and lithium pyrrolidide are particularly preferred.

Silicon atoms can be introduced by a terminal modifier such as alkoxysilane or aminoalkoxysilane.
Specifically, as the epoxy group-containing alkoxysilane compound, as the hydrocarbyloxysilane compound, for example, 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl) ) Methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl) methyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Silane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl (methyl) dimethoxysilane and the like can be mentioned.

  Examples of the amino group-containing alkoxysilane compound include 3-dimethylaminopropyl (triethoxy) silane, 3-dimethylaminopropyl (trimethoxy) silane; 3-diethylaminopropyl (triethoxy) silane, 3-diethylaminopropyl (trimethoxy) silane, 2 -Dicarbyloxy group-containing hydrocarbyloxysilane compounds such as dimethylaminoethyl (triethoxy) silane, 2-dimethylaminoethyl (trimethoxy) silane, 3-dimethylaminopropyl (diethoxy) methylsilane, 3-dibutylaminopropyl (triethoxy) silane, 3- (1-hexamethyleneimino) propyl (triethoxy) silane, 3- (1-hexamethyleneimino) propyl (trimethoxy) silane, (1-hexamethyleneimino) Ru (trimethoxy) silane, (1-hexamethyleneimino) methyl (triethoxy) silane, 2- (1-hexamethyleneimino) ethyl (triethoxy) silane, 2- (1-hexamethyleneimino) ethyl (trimethoxy) silane, 3 -(1-pyrrolidinyl) propyl (triethoxy) silane, 3- (1-pyrrolidinyl) propyl (trimethoxy) silane, 3- (1-heptamethyleneimino) propyl (triethoxy) silane, 3- (1-dodecamethyleneimino) propyl (Triethoxy) silane, 3- (1-hexamethyleneimino) propyl (diethoxy) methylsilane, 3- (1-hexamethyleneimino) propyl (diethoxy) ethylsilane, 1- [3- (triethoxysilyl) propyl] -4, 5-dihydroimidazole, 1- [ - (trimethoxysilyl) propyl] -4,5-dihydroimidazole, 3- [10- (triethoxysilyl) decyl] -4-oxazoline cyclic amino group-containing hydrocarbyloxy silane compound, and the like.

  Further, as imino group-containing alkoxysilane compounds, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine, N- (1-methylethylidene) -3- (triethoxy Silyl) -1-propanamine, N-ethylidene-3- (triethoxysilyl) -1-propanamine, N- (1-methylpropylidene) -3- (triethoxysilyl) -1-propanamine, N- (4-N, N-dimethylaminobenzylidene) -3- (triethoxysilyl) -1-propanamine, N- (cyclohexylidene) -3- (triethoxysilyl) -1-propanamine and the like can be mentioned.

Further, for example, by using a lithium amide initiator obtained from a secondary amino compound such as diethylamine or an imine compound such as hexamethyleneimine and an organolithium compound, or the lithium activity obtained by the polymerization. The modified polymer can also be obtained by adding the modifying agent to a polymer solution having a terminal.
This modified polymer with functional groups introduced into the molecular chain also suppresses the decrease in elastic modulus due to temperature rise and effectively improves the low heat buildup in rubber compositions containing reinforcing inorganic fillers such as silica. In particular, those having a branched structure obtained by using a polyfunctional modifier are preferred. In addition, a modified polymer in which an amino group, an imino group, an epoxy group or a tin atom is introduced together with an alkoxysilyl group can be applied particularly effectively when carbon black is used together with the inorganic filler as a reinforcing filler.

Next, the rubber composition of the present invention has a polystyrene equivalent weight average molecular weight of 2,000 to 200, measured by gel permeation chromatography before modification having at least one functional group as the component (B) as described above. It is necessary to include a low molecular weight conjugated diene polymer of less than 000.
The low molecular weight conjugated diene polymer of the component (B) is not particularly limited as long as it has at least one functional group and satisfies the above weight average molecular weight. As the conjugated diene polymer, a butadiene homopolymer is used. However, as the aromatic vinyl compound-conjugated diene compound copolymer, a styrene-butadiene copolymer containing 5% by mass or less of the aromatic vinyl compound is preferable. By substituting a part of a softening agent such as aroma oil and blending the butadiene-based low molecular weight polymer into the composition of the present invention, there is no increase in Mooney viscosity, and storage modulus (G ′ ), Storage modulus (G ′) in the high temperature range and tan δ in the high temperature range, which leads to low rolling resistance, and improved wear resistance due to improved fracture characteristics. Further, by setting the styrene content to 5% or less, the elastic modulus at a low temperature can be kept low, and the low glass transition temperature (Tg) polymer can improve the wear resistance.

  Moreover, it is preferable that the low molecular weight butadiene-based polymer of the component (B) has a vinyl bond content in the conjugated diene compound portion of 5 to 80% by mass. By setting the vinyl bond amount of the conjugated diene compound portion within the above range, it is possible to achieve both improvement in storage elastic modulus (G ′) and reduction in loss tangent (tan δ) of the rubber composition.

  The low molecular weight conjugated diene polymer of component (B) is a polymerization initiator comprising (1) monomeric aromatic vinyl compound and conjugated diene compound as described in detail in (A) high molecular weight rubber component. And a method of modifying the polymerization active site with various modifiers, and (2) an aromatic vinyl compound as a monomer, and a conjugated diene polymer having a polymerization active site. It can be obtained by copolymerizing a conjugated diene compound with a polymerization initiator having a functional group.

  As a polymerization initiator used for the synthesis | combination of the conjugated diene type polymer of the said (B) component, an organolithium compound is preferable and hydrocarbyl lithium and a lithium amide compound are still more preferable. When an organic lithium compound is used as the polymerization initiator, the aromatic vinyl compound and the conjugated diene compound are copolymerized by anionic polymerization. When hydrocarbyl lithium is used as the polymerization initiator, a conjugated diene polymer having a hydrocarbyl group at the polymerization initiation terminal and the other terminal being a polymerization active site is obtained. On the other hand, when a lithium amide compound is used as the polymerization initiator, a conjugated diene polymer having a nitrogen-containing functional group at the polymerization start terminal and the other terminal being a polymerization active site is obtained, and the conjugated diene polymer is The low molecular weight conjugated diene polymer having at least one functional group of the component (B) in the present invention can be used without being modified with a modifier. In addition, the usage-amount of a polymerization initiator has the preferable range of 0.2-20 mmol per 100g of monomers.

Examples of the hydrocarbyl lithium include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, and 2-butyl-phenyl. Examples include lithium, 4-phenyl-butyllithium, cyclohexyllithium, cyclopentyllithium, reaction products of diisopropenylbenzene and butyllithium, and among these, ethyllithium, n-propyllithium, isopropyllithium, n-butyl Alkyl lithium such as lithium, sec-butyl lithium, tert-octyl lithium and n-decyl lithium is preferable, and n-butyl lithium is particularly preferable.
The lithium amide compound is as described in (A) High molecular weight rubber component.

  The above polymerization reaction may be carried out in the presence of a randomizer. The randomizer can control the microstructure of the conjugated diene compound portion of the conjugated diene polymer, more specifically, control the vinyl bond amount of the conjugated diene compound portion of the conjugated diene polymer, It has effects such as randomizing the conjugated diene compound unit and the aromatic vinyl compound unit of the conjugated diene polymer. Examples of the randomizer include dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, bistetrahydrofurylpropane, triethylamine, pyridine, N-methylmorpholine, N, N, N ′, N′-tetramethylethylenediamine, 1 , 2-dipiperidinoethane, potassium-t-amylate, potassium-t-butoxide, sodium-t-amylate and the like. The amount of these randomizers used is preferably in the range of 0.01 to 100 molar equivalents per mole of polymerization initiator.

  The polymerization reaction is preferably carried out by solution polymerization, and the concentration of the monomer in the polymerization reaction solution is preferably in the range of 5 to 50% by mass, and more preferably in the range of 10 to 30% by mass. The content of the aromatic vinyl compound in the mixture of the conjugated diene compound and the aromatic vinyl compound is preferably in the range of 5% by mass or less, more preferably 0%.

  The polymerization temperature of the polymerization reaction is preferably in the range of 0 to 150 ° C, more preferably in the range of 20 to 130 ° C. The polymerization can be carried out under generated pressure, but it is usually preferable to carry out the polymerization under a pressure sufficient to keep the monomer used in a substantially liquid phase. Here, when the polymerization reaction is carried out under a pressure higher than the generated pressure, it is preferable to pressurize the reaction system with an inert gas. Moreover, it is preferable to use what removed reaction-inhibiting substances, such as water, oxygen, a carbon dioxide, and a protic compound, as raw materials, such as a monomer used for superposition | polymerization, a polymerization initiator, and a solvent.

  In modifying the polymerization active site of the conjugated diene polymer having the polymerization active site with a modifier, the modifier used preferably includes a modifier compound containing tin, silicon, or a nitrogen atom. Among them, a modifier compound containing tin and a compound containing nitrogen are preferable. Specific examples of the modifying agent are as described in the modification of the high molecular weight rubber component (A).

  The modification reaction of the polymerization active site by the modifying agent is preferably performed by a solution reaction, and the solution may contain a monomer used at the time of polymerization. The reaction mode of the modification reaction is not particularly limited, and may be a batch type or a continuous type. Furthermore, the reaction temperature of the modification reaction is not particularly limited as long as the reaction proceeds, and the reaction temperature of the polymerization reaction may be employed as it is. In addition, the usage-amount of modifier | denaturant has the preferable range of 0.25-3.0 mol with respect to 1 mol of polymerization initiators used for manufacture of a copolymer, and the range of 0.5-1.5 mol is further more preferable.

  In this invention, after drying the reaction solution containing the said (B) component and isolate | separating (B) component, you may mix | blend the obtained (B) component with the said (A) component, (B The reaction solution containing the component (A) may be mixed with the rubber cement of the component (A) in a solution state and then dried to obtain a mixture of the component (A) and the component (B).

The rubber composition of the present invention needs to further contain a filler of the component (C), and is preferably contained in an amount of 30 to 90 parts by mass with respect to 100 parts by mass of the component (A). By making the blending amount of the filler in the above range, workability deterioration can be suppressed, and excellent vulcanized rubber fracture characteristics and wear resistance can be obtained.
Here, as the filler, carbon black and silica are preferable. The carbon black is preferably FEF, SRF, HAF, ISAF, or SAF grade, and more preferably HAF, ISAF, or SAF grade. On the other hand, as silica, wet silica and dry silica are preferable, and wet silica is more preferable. These reinforcing fillers may be used alone or in a combination of two or more.

  The rubber composition of the present invention may further contain a softening agent. Here, examples of the softening agent include process oils such as paraffin oil, naphthenic oil, and aroma oil. Aromatic oil is preferable from the viewpoint of fracture characteristics and wear resistance, and from the viewpoint of low heat generation and low temperature characteristics. Are preferably naphthenic oils and paraffin oils. The blending amount of the softening agent is not particularly limited, but the total blending amount of the low molecular weight conjugated diene polymer and the softening agent of the component (B) is 100 parts by mass of the component (A). It is preferable to mix | blend so that it may become 5-80 mass parts, More preferably, it is 5-60 mass parts. By making the total blending amount of the component (B) and the softening agent within the above range, it is possible to suppress the deterioration of the fracture characteristics of the vulcanized rubber.

  In the rubber composition of the present invention, in addition to the filler (A), the component (B), the component (C), and a softener, a compounding agent usually used in the rubber industry, for example, an anti-aging agent A silane coupling agent, a vulcanization accelerator, a vulcanization acceleration aid, a vulcanizing agent, and the like can be appropriately selected and blended within a range that does not impair the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition can be produced by blending the component (A) with the component (B) and various compounding agents appropriately selected as necessary, kneading, heating, extruding, and the like. .

The pneumatic tire of the present invention is characterized in that the rubber composition is used as a tire member for a tread, a sidewall, a bead filler, and a body price kim.
A tire using the rubber composition in at least the ground contact portion of the tread portion is excellent in fuel efficiency and steering stability. The pneumatic tire of the present invention is not particularly limited with respect to the tire member that also disperses the above rubber composition, 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.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. Various measurement methods were performed based on the following methods.
<Physical properties of unvulcanized rubber>
(1) Weight average molecular weight (Mw)
Gel permeation chromatography [GPC: Tosoh HLC-8020, column: Tosoh GMH-XL (two in series), detector: differential refractometer (RI)], based on monodisperse polystyrene, The weight average molecular weight (Mw) in terms of polystyrene was determined.

(2) Microstructure and bound styrene content The microstructure of the polymer was determined by the infrared method (Morero method), and the bound styrene content of the polymer was determined from the integral ratio of the ¹ H-NMR spectrum.

<Physical properties of vulcanized rubber>
(3) Storage elastic modulus (G ′) and loss tangent (tan δ)
Storage elastic modulus (G ′) at a temperature of −20 ° C., a frequency of 15 Hz, and a strain of 1%, and a storage elastic modulus (G ′) at a temperature of 50 ° C., a frequency of 15 Hz, and a strain of 1%. ), Loss tangent (tan δ), temperature 0 ° C., frequency 15 Hz, loss tangent (tan δ) was measured at 1% strain, and the storage elastic modulus (G ′) and loss tangent (tan δ) of Comparative Example 1 were each expressed as an index. did. As for the storage elastic modulus (G ′) at 50 ° C., the larger the index value, the higher the storage elastic modulus. The −20 ° C. storage elastic modulus (G ′) indicates that the lower the index value, the lower the value. Shows excellent flexibility.
On the other hand, regarding the loss tangent (tan δ) at 50 ° C., the smaller the index value, the better the low heat build-up. Further, the loss tangent (tan δ) at 0 ° C. indicates that the larger the value, the better the wet performance.

<(B) component: Production Example 1 of low molecular weight polybutadiene>
According to the modification | denaturation conditions of B component shown in Table 2-Table 6, the low molecular weight polybutadiene used for each Example (1-25) and Comparative Example (1-6) except Example 3 and 6 was manufactured.
Into a dried and nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane and 50 g of 1,3-butadiene are injected, and ditetrahydrofuryl so that the ratio of ditetrahydrofurylpropane / n-butyllithium is 0.03. Propane was injected. Further, 3.6 ml of n-butyllithium (n-BuLi) was added, followed by polymerization at 50 ° C. for 5 hours to obtain an unmodified low molecular weight butadiene having a weight average molecular weight of 25,000 and a vinyl content of 20%. Other molecular weights were synthesized by changing the amount of n-butyllithium by a conventional method.
The polymerization conversion rate at this time was almost 100%. Next, in the case of tin tetrachloride as a modifier, tin tetrachloride / n-butyllithium = 0.22, tetraethoxysilane / n-butyllithium = 0.9, crude MDI / n-butyl in the polymerization reaction system. A denaturant was quickly added so that lithium = 0.9, and a denaturation reaction was further performed at 50 ° C. for 30 minutes. Thereafter, 0.5 mL of an isopropanol solution (BHT concentration: 5% by mass) of 2,6-di-t-butyl-p-cresol (BHT) was added to the polymerization reaction system to stop the polymerization reaction. And then each modified low molecular weight polybutadiene was obtained.
When the modification reaction was not performed, the same treatment was performed except for the reaction to obtain each low molecular weight polybutadiene.

<(B) component: Production Example 2 of low molecular weight polybutadiene>
A polymerization reaction was carried out in the same manner as in Production Example 1 except that the polymerization catalyst of Production Example 1 was changed from n-butyllithium (n-BuLi) to 3.6 mmol of lithium hexamethyleneimide (HMI-Li). Without performing the modification reaction, 5 mL of an isopropanol solution (BHT concentration: 5 mass%) of 2,6-di-t-butyl-p-cresol (BHT) was added to the polymerization reaction system to stop the polymerization reaction. Dry low molecular weight polybutadiene was obtained according to a conventional method.

<(A) component: Production Example 3 of high molecular weight styrene-butadiene copolymer>
Pour butadiene cyclohexane solution (16%) and styrene cyclohexane solution (21%) into an 800 mL pressure-resistant glass container that has been dried and purged with nitrogen so as to be 40 g of butadiene monomer and 10 g of styrene monomer. Inject 0.12 mmol of 2,2-ditetrahydrofurylpropane, add 0.4 mmol of n-butyllithium (BuLi), and then polymerize in a hot water bath at 50 ° C. for 1.5 hours. The polymerization conversion is almost 100%. Thereafter, 0.5 mL of a 5% by weight solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol is further added to the polymerization system to stop the reaction. Then, S-SBR is obtained by drying according to a conventional method. The obtained high molecular weight styrene-butadiene copolymer had a bound styrene content of 20% by mass, a vinyl bond content of 58%, and a weight average molecular weight of 290.000.

<(A) Component: Production Example 4 of Modified High Molecular Weight Styrene-Butadiene Copolymer>
To the above polymerization reaction system, 0.1 mmol of tin tetrachloride was added as a modifier, and a modification reaction was further performed at 50 ° C. for 30 minutes. Thereafter, 0.5 mL of an isopropanol solution (BHT concentration: 5% by mass) of 2,6-di-t-butyl-p-cresol (BHT) was added to the polymerization reaction system to stop the polymerization reaction. The respective high molecular weight styrene-butadiene copolymers were obtained.

「注」
＊１．東海カーボン(株)製, 商標：シーストＫＨ（Ｎ３３９）
＊２．東・ソーシリカ (株)製, 商標：ニプシルＡＱ.
＊３．デグサ社製, 商標Ｓｉ６９, ビス(３-トリエトキシシリルプロピル)テトラスルフィド
＊４．Ｎ-(１,３-ジメチルブチル)-Ｎ'-フェニル-ｐ-フェニレンジアミン
＊５．ジフェニルグアニジン
＊６．ジベンゾチアジルジスルフィド
＊７．Ｎ-ｔ-ブチル-２-ベンゾチアジルスルフェンアミド

"note"
* 1. Tokai Carbon Co., Ltd. Trademark: Seast KH (N339)
* 2. Made by Tohsoh Silica Co., Ltd. Trademark: Nipsil AQ.
* 3. Degussa, trademark Si69, bis (3-triethoxysilylpropyl) tetrasulfide
* 4. N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine * 5. Diphenylguanidine * 6. Dibenzothiazyl disulfide * 7. Nt-butyl-2-benzothiazylsulfenamide

「注」
＊８．リチウムヘキサメチレンイミド
＊９．四塩化スズ
＊１０．クルードＭＤＩ、日本ウレタン社製「ＭＲ４００」
＊１１．テトラエトキシシラン

"note"
* 8. Lithium hexamethylene imide * 9. Tin tetrachloride * 10. Crude MDI, "MR400" manufactured by Nippon Urethane Co., Ltd.
* 11. Tetraethoxysilane

  The weight average molecular weight (Mw), microstructure, and bound styrene content of the low molecular weight polybutadiene and high molecular weight styrene-butadiene copolymer produced in Production Examples 1 to 4 were measured by the above methods. The results are shown in Table 2.

Examples 1-15, Comparative Examples 1-4
Next, using the low molecular weight polybutadiene and high molecular weight styrene-butadiene copolymer produced in the above Production Examples 1 to 4, a rubber composition having a formulation shown in Table 1 was prepared. Was vulcanized at 160 ° C. for 15 minutes to obtain a vulcanized rubber, and the storage elastic modulus (G ′) and loss tangent (tan δ) of the vulcanized rubber were measured by the above methods. The results are shown in Table 2.

When the molecular weight before modification is less than 2,000 to 200,000 from Table 2, the storage elastic modulus at −20 ° C. can be reduced without reducing the loss tangent at 0 ° C., and the loss at 50 ° C. It can be seen that the tangent can be lowered.
From Table 2-2, the effect can be seen even if the modifier type is changed to one containing nitrogen and silicon.
Further, even when the high molecular weight polymer is modified, the storage elastic modulus at −20 ° C. can be further lowered, and the loss tangent at 50 ° C. can be lowered.

The rubber composition for tires of the present invention is excellent in low temperature flexibility by applying a low molecular weight conjugated diene polymer having a functional group within a weight average molecular weight in the range of 2,000 to less than 200,000. A rubber composition that maintains grip properties and achieves a high level of both high-temperature storage elastic modulus, low rolling resistance, and wear resistance, and a pneumatic that has improved performance as described above, using the rubber composition for a tire member Tires can be provided.
The tire member can be applied to treads, sidewalls, bead fillers, body price kims, and the like.

Claims (21)

  (A) A high molecular weight rubber component having a polystyrene-reduced weight average molecular weight of 200,000 or more measured by gel permeation chromatography (B) measured by gel permeation chromatography before modification having at least one functional group A rubber composition comprising a low molecular weight conjugated diene polymer having a polystyrene-equivalent weight average molecular weight of 2,000 to less than 200,000 and a filler (C).   The rubber composition according to claim 1, comprising 1 to 60 parts by mass of the component (B) with respect to 100 parts by mass of the rubber component (A).   The rubber according to claim 1 or 2, wherein the component (B) has a vinyl bond content of 5 to 80% by mass of the polymerized unit of the conjugated diene, and the component (B) has an aromatic vinyl compound content of 5% by mass or less. Composition.   The rubber composition according to any one of claims 1 to 3, wherein the component (B) is a butadiene homopolymer or a butadiene / styrene copolymer.   The rubber composition according to claim 1, wherein the functional group of the component (B) is a functional group containing tin, silicon, and a nitrogen atom.   The rubber composition according to any one of claims 1 to 5, wherein the polystyrene-converted weight average molecular weight measured by gel permeation chromatography of the component (B) before modification is 20,000 to less than 200,000.   The rubber composition according to claim 6, wherein the polystyrene-converted weight average molecular weight of the component (B) before modification measured by gel permeation chromatography is 50,000 to 150,000.   (A) The rubber composition according to any one of claims 1 to 7, comprising 30 to 90 parts by mass of a filler with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 8, wherein the (C) filler is carbon black and / or silica.   The rubber according to any one of claims 1 to 9, wherein the rubber component (A) contains at least one (D) aromatic vinyl compound-conjugated diene compound copolymer, (E) conjugated diene polymer, and natural rubber. Composition.   The rubber composition according to claim 10, wherein the component (D) is a styrene-butadiene copolymer.   The rubber composition according to claim 11, wherein the component (E) is a butadiene homopolymer.   The rubber composition according to any one of claims 10 to 12, wherein the component (D) and the component (E) have at least one functional group.   The rubber composition according to claim 13, wherein the functional groups of the component (D) and the component (E) are functional groups containing tin, silicon, and a nitrogen atom.   The rubber composition according to any one of claims 1 to 14, wherein the total amount of the component (B) and the softening agent is 5 to 80 parts by mass with respect to 100 parts by mass of the (A) rubber component.   The rubber composition according to claim 15, wherein the total amount of the component (B) and the softening agent is 5 to 60 parts by mass with respect to 100 parts by mass of the (A) rubber component.   The rubber composition according to any one of claims 1 to 16, wherein the component (B) is 20% by mass or more of the total amount of the softener and the component (B).   (C) The rubber composition according to any one of claims 1 to 17, wherein the filler is carbon and / or silica.   A rubber composition for tires, wherein the rubber composition according to any one of claims 1 to 18 is used for tires. A pneumatic tire comprising the tire rubber composition according to claim 19 as a tire member. A pneumatic tire obtained by applying the tire rubber composition according to claim 19 to a tread, a sidewall, a bead filler, a body price kim, and a reinforcement rubber for a run-flat tire.