JP5092344B2 - Silica-containing rubber composition, process for producing the same, and crosslinked molded article thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica-containing rubber composition that is excellent in processability, reinforcing properties and abrasion resistance and is suitably employable as a rubber for a tire, and its manufacturing method, and to provide a crosslinkable silica-containing rubber composition and a crosslinked molded item thereof. <P>SOLUTION: The manufacturing method of the silica-containing rubber composition comprises a step for kneading a conjugated diene rubber-silica co-coagulate with a silane coupling agent, where kneading of the conjugated diene rubber-silica co-coagulate is started at 5-90&deg;C and, after the kneading temperature is reached 120&deg;C or higher, the silane coupling agent is added to the kneadate of the conjugated diene rubber-silica co-coagulate followed by further kneading. The crosslinkable rubber composition is obtained from the silica-containing rubber composition. The crosslinked molded item is also provided. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a silica-containing rubber composition. More specifically, the present invention relates to a silica-containing rubber composition excellent in processability, reinforcement and abrasion resistance suitable as a tire rubber, a method for producing the same, and a crosslinked molded article obtained by crosslinking the silica-containing rubber composition.

Conventionally, in rubber compositions for tires, silica and carbon black have been widely used as reinforcing agents, and in general, a dry method of blending into rubber using a kneader such as a Banbury mixer or a kneader has been widely adopted. ing.
A rubber composition for tires in which silica or silica and carbon black are blended has been found to be compatible with low fuel consumption and wet grip, and has attracted attention as a rubber material for tire treads.

However, when silica is used, the hardness tends to decrease compared to a tire tread containing carbon black, which is insufficient in terms of tire handling stability and wear resistance. It is necessary to increase the hardness of the rubber composition.
Thus, it has been proposed to obtain a rubber composition excellent in processability, low heat build-up, fracture characteristics and wear resistance by setting the particle diameter (surface area) of silica within a specific range (Patent Document 1). .
However, in this method, although the above properties are improved, there is a problem that the viscosity of the compound is very high and kneading becomes difficult, and furthermore, the effect of improving the wear resistance is still insufficient.

Silica is usually covered with silanol groups and has a strong self-aggregation property, so it has poor affinity with rubber and is difficult to disperse uniformly in rubber.
Therefore, in order to improve the dispersibility of silica in rubber, conjugated diene rubber latex and silica dispersion are mixed, and then the rubber in conjugated diene rubber latex is replaced with a cationic resin or cationic polymer. A method of obtaining a silica-containing rubber composition by so-called “co-coagulation”, in which silica is uniformly taken into the coagulated rubber by coagulation, is proposed.
According to this method, it has been shown that even when silica having a CTAB specific surface area higher than that of general silica is used, it can be dispersed well in rubber (Patent Document 2 and Patent Document 3). .

  However, when kneading compounding agents such as silane coupling agents, zinc oxide, and anti-aging agents, using a kneading machine such as a Banbury mixer or kneader to the silica-containing rubber composition obtained by these methods, There was a problem that kneading became difficult. Furthermore, when sulfur is contained in the silane coupling agent to be blended, the sulfur atom of the silane coupling agent is cleaved and partially causes a crosslinking reaction with the rubber, so that later molding cannot be performed, so-called “scorch” There was a problem that it is easy to cause.

JP 2003-238739 A JP 2001-213971 A International Publication No. 2004/067625 Pamphlet

  Accordingly, an object of the present invention is to provide a silica-containing rubber composition that is excellent in processability, reinforcement and wear resistance. Another object of the present invention is to provide a method for producing the silica-containing rubber composition. Still another object of the present invention is to provide a crosslinkable silica-containing rubber composition and a crosslinked molded product thereof.

  As a result of intensive studies to achieve the above object, the inventors of the present invention, in the step of preparing a silica-containing rubber composition by blending a silane coupling agent or the like with a conjugated diene rubber-silica co-coagulated product, It has been found that a silica-containing rubber composition that is excellent in processability, reinforcement and abrasion resistance and can be suitably used as a rubber for tires can be obtained by blending the agent by a specific method. The invention has been completed.

Thus, according to the present invention, there is provided a process for producing a silica-containing rubber composition comprising a step of kneading a conjugated diene rubber-silica co-coagulated product and a silane coupling agent, wherein the conjugated diene rubber-silica co-coagulated product The kneading is started at 5 to 90 ° C., and after the kneading temperature reaches 120 ° C. or higher, the silane coupling agent is added to the diene rubber-silica co-coagulated product kneaded product and kneaded. A method for producing a silica-containing rubber composition is provided.
In the method for producing a silica-containing rubber composition, it is preferable that the temperature at the time of discharging the kneaded product of the conjugated diene rubber-silica co-coagulated product and the silane coupling agent in the kneading step is 130 to 180 ° C.
Moreover, in the manufacturing method of the said silica containing rubber composition, it is preferable that the cetyl trimethyl ammonium bromide adsorption | suction specific surface area (CTAB specific surface area) of a silica is 40-400 m < ² > / g.
In the method for producing a silica-containing rubber composition, the conjugated diene rubber-silica co-coagulated product is obtained by co-coagulating rubber and silica by mixing a solution or aqueous dispersion of a conjugated diene rubber and silica. It is preferable that it is what was obtained.
In the method for producing a silica-containing rubber composition, the conjugated diene rubber-silica co-coagulated product contains 100 parts by weight of a conjugated diene rubber, 20 to 200 parts by weight of silica, and 5 to 100 parts by weight of an extending oil. It is preferable that

Furthermore, according to this invention, the silica containing rubber composition obtained by the manufacturing method of the silica containing rubber composition of the said invention is provided.
Furthermore, according to this invention, the crosslinkable silica containing rubber composition formed by containing the said silica containing rubber composition and a crosslinking agent is provided.
Furthermore, according to the present invention, there is provided a crosslinked molded article obtained by crosslinking and molding the above-mentioned crosslinkable silica-containing rubber composition.

According to the method for producing a silica-containing rubber composition of the present invention, the viscosity of the kneaded product is reduced and the scorch is suppressed in the step of blending and kneading various compounding agents with the conjugated diene rubber-silica co-coagulated product. Can do.
Moreover, the resulting silica-containing rubber composition is excellent in reinforcement and wear resistance. Therefore, the silica-containing rubber composition and the molded product obtained by crosslinking the silica-containing rubber composition are used in various applications utilizing the characteristics, for example, tire members such as treads, undertreads, carcass, sidewalls, and bead parts; hoses, windows. Useful for rubber members such as frames, belts, shoe soles, anti-vibration rubber, automobile parts, seismic isolation rubber; resin-reinforced rubber members such as impact-resistant polystyrene and ABS resin; It is.

In the method for producing a silica-containing rubber composition of the present invention, first, a conjugated diene rubber-silica co-coagulated product is kneaded.
The conjugated diene rubber-silica co-coagulated product is obtained by dispersing silica in the conjugated diene rubber by coagulating the conjugated diene rubber from a mixture of the conjugated diene rubber and silica.

The conjugated diene rubber used in the present invention is a conjugated diene monomer homopolymer or copolymer, or a copolymer of a conjugated diene monomer and a monomer copolymerizable therewith.
Examples of the conjugated diene include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and 1,3-pentadiene. Etc. Among these, 1,3-butadiene, 2-methyl-1,3-butadiene and the like are preferable, and 1,3-butadiene is more preferable.
A conjugated diene monomer may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the monomer copolymerizable with the conjugated diene monomer include aromatic vinyl monomers and α, β-ethylenically unsaturated nitrile monomers.
The aromatic vinyl monomer is not particularly limited, but styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4 -T-butylstyrene, 5-t-butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene and the like are preferable, and styrene is more preferable.
An aromatic vinyl monomer may be used individually by 1 type, and may be used in combination of 2 or more type.
Specific examples of the α, β-ethylenically unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, vinylidene cyanide and the like.
One α, β-ethylenically unsaturated nitrile monomer may be used alone, or two or more may be used in combination.

Specific examples of the conjugated diene rubber include conjugated diene homopolymers such as natural rubber, isoprene rubber, butadiene rubber and chloroprene rubber; conjugated diene copolymers such as butadiene-isoprene copolymer rubber; styrene-butadiene copolymer rubber, Copolymers of conjugated diene monomers such as acrylonitrile-butadiene copolymer rubber, styrene-butadiene-isoprene copolymer rubber, acrylonitrile-styrene-butadiene copolymer rubber, and monomers copolymerizable therewith; It is done.
These rubbers may be used alone or in combination of two or more.

These conjugated diene rubbers may be appropriately selected depending on the application.
Particularly for tires, a copolymer of a conjugated diene monomer and an aromatic vinyl monomer is preferred. The ratio of each monomer unit in the conjugated diene-aromatic vinyl copolymer is not particularly limited, but the conjugated diene monomer unit content is preferably 50 to 85% by weight, more preferably 55 to 82% by weight. The content of the aromatic vinyl monomer unit is preferably 15 to 50% by weight, more preferably 18 to 45% by weight, and particularly preferably 20 to 40% by weight. .
In the conjugated diene-α, β-ethylenically unsaturated nitrile copolymer, the conjugated diene monomer unit content is preferably 40% by weight or more, more preferably 45% by weight or more, and α, β- The amount of the ethylenically unsaturated nitrile monomer is preferably 60% by weight or less, more preferably 55% by weight or less.
In the conjugated diene rubber, if the amount of monomers other than the conjugated diene monomer is too large, the exothermic property increases and the low temperature brittleness is also inferior.

The conjugated diene rubber used in the present invention may have a polar group such as hydroxyl group, carboxyl group, alkoxysilyl group, amino group, and epoxy group.
The conjugated diene rubber having a polar group can be obtained, for example, by copolymerizing a vinyl monomer having these polar groups with a conjugated diene monomer.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the conjugated diene rubber used in the present invention is preferably 10 to 250, and more preferably 30 to 200. If the Mooney viscosity is small, the processability is excellent, but it may be difficult to obtain sufficient heat generation characteristics and wear resistance. On the contrary, if it is large, it is excellent in abrasion resistance and the like, but the compound Mooney viscosity becomes too high, and the workability may be lowered.

  The conjugated diene rubber may be in any form such as latex, organic solvent solution, slurry, dispersion, etc., but in order to make the dispersion of silica uniform in the conjugated diene rubber-silica co-coagulated product, It is preferably used in the state of a solution or an aqueous dispersion, and particularly preferably used in a latex state.

The organic solvent solution of the conjugated diene rubber can be usually obtained by solution polymerization, but it can also be obtained by making a solid rubber obtained by another polymerization method and dissolving it in a solvent.
The latex of the conjugated diene rubber can be usually obtained by emulsion polymerization, but can also be obtained by phase inversion of an organic solvent solution of the conjugated diene rubber.

In order to obtain a latex of a conjugated diene rubber, a known emulsion polymerization method may be used, and known materials such as an emulsifier, a polymerization initiator, a molecular weight regulator, and a polymerization terminator may be used.
As the molecular weight modifier, for example, thiol compounds such as t-dodecyl mercaptan, n-dodecyl mercaptan, thioglycolic acid; halides such as carbon tetrachloride; Can do.
Although the temperature of emulsion polymerization can be suitably selected according to the kind of polymerization initiator to be used, it is 0-100 degreeC normally, Preferably it is 0-60 degreeC. The polymerization mode may be any mode such as continuous polymerization or batch polymerization.

The polymerization conversion rate at the time of stopping the polymerization reaction is preferably 85% by weight or less, and more preferably in the range of 50 to 80% by weight, from the viewpoint of preventing gelation of the polymer. The polymerization reaction is usually stopped by adding a polymerization terminator to the polymerization system when a predetermined polymerization conversion rate is reached. Examples of the polymerization terminator include amine compounds such as diethylhydroxylamine and hydroxylamine; quinone compounds such as hydroquinone and benzoquinone; sodium nitrite; sodium dithiocarbamate;
After the emulsion polymerization reaction is stopped, unreacted monomers are removed from the obtained emulsion polymerization reaction liquid (latex) as necessary, and then an acid such as nitric acid and sulfuric acid is added and mixed as necessary to adjust the pH of the latex. Is adjusted to a predetermined value to prepare a conjugated diene rubber latex.

The conjugated diene rubber preferably contains an antiaging agent.
Specific examples of the antioxidant include 2,6-di-t-butyl-4-methylphenol, octadecyl-3- (3 ′, 3′-di-t-butyl-4-hydroxyphenyl) propionate, Phenol-based anti-aging agents such as styrenated phenol; Sulfur-based anti-aging agents such as 2,4-bis (octylthiomethyl) -6-methylphenol; N- (1,3-dimethylbutyl) -N′-phenyl- Examples include amine-based anti-aging agents such as p-phenylenediamine; quinoline-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline; hydroquinone-based anti-aging agents; and phosphorus-based anti-aging agents. Among these, a phenol type anti-aging agent and a sulfur type anti-aging agent are preferable.
These anti-aging agents may be used alone or in combination of two or more.
The anti-aging agent may be added to the conjugated diene rubber at any time after the completion of the polymerization. The anti-aging agent can also be kneaded simultaneously when kneading the conjugated diene rubber-silica co-coagulated product and the silane coupling agent.
The addition amount of the anti-aging agent is usually 0.05 to 10.0 parts by weight, preferably 0.08 to 6.0 parts by weight, and more preferably 0.1 to 4 parts per 100 parts by weight of the conjugated diene rubber. 0.0 part by weight.

In the present invention, a conjugated diene rubber mixed with an extending oil can be used.
As the extender oil, those commonly used in the rubber industry can be used, and specific examples thereof include paraffinic, aromatic and naphthenic petroleum softeners; plant softeners; fatty acids and the like. . In the case of petroleum softeners, the polycyclic aromatic content is preferably less than 3%. This content is measured by the method of IP346 (the testing method of THE INSTITUTE PETROLEUM, UK).
The amount of the extender oil is generally 5 to 100 parts by weight, preferably 15 to 60 parts by weight, and particularly preferably 30 to 50 parts by weight with respect to 100 parts by weight of the conjugated diene rubber.
The addition timing of the extender oil is not particularly limited, but it is preferably dissolved or dispersed in a conjugated diene rubber solution or an aqueous dispersion.
The extender oil can also be kneaded simultaneously when kneading the conjugated diene rubber-silica co-coagulated product and the silane coupling agent.

The silica used in the present invention is not particularly limited by its production method. Specifically, dry silica generally obtained by burning silicon tetrachloride in an oxyhydrogen flame, wet silica obtained by neutralizing an alkali silicate with an acid, tetramethoxysilane, tetraethoxysilane, etc. Sol-gel silica obtained by hydrolyzing silicon alkoxide in an acidic or alkaline water-containing organic solvent, colloidal silica obtained by dealkalizing an alkali silicate aqueous solution by electrodialysis, and the like can be used.
These silicas may be used individually by 1 type, and may be used in combination of 2 or more type. In the present invention, wet silica excellent in productivity is preferable, and precipitated silica obtained without going through gel is particularly preferable.

Silica measured specific surface area by adsorption of cetyltrimethylammonium bromide _{(CTAB) (S} CTAB) is preferably has a 40 to 400 ² / g, more preferably those which are 100 to 350 m ² / g, 150 to Most preferred is 300 m ² / g.
Further, the silica, preferably has a specific surface area measured by a nitrogen adsorption method _{(S BET)} is 50 to 300 m ² / g, more preferably those which are 130~280m ² / g, in 170~280m ² / g Some are most preferred.
Further, the silica preferably has a dibutyl phthalate oil absorption (hereinafter simply referred to as “oil absorption”) of 100 to 400 ml / 100 g, more preferably 110 to 350 ml / 100 g, and 120 to 300 ml / 100 g. Is most preferred.
When silica having the above specific surface area and oil absorption is used, a silica-containing rubber composition that gives a crosslinked molded article having excellent strength, wear resistance, etc. is obtained, and a fuel-efficient tire excellent in reinforcing effect by silica is obtained. be able to.

The average particle diameter of silica is not particularly limited, and may be appropriately determined in consideration of the intended use. Generally, the range of 0.1-50 micrometers is preferable.
By setting the average particle size to 0.1 μm or more, poor dispersion due to self-aggregation of silica can be prevented, and a silica-containing rubber composition excellent in physical property balance can be obtained. On the other hand, when the average particle size is 50 μm or less, the reinforcing effect and low fuel consumption by silica are improved.
In particular, when used for a tire, the average particle diameter of silica is preferably 1 to 30 μm.

A known method can be used for adjusting the particle diameter of silica without any particular limitation.
Specifically, using a jet mill, a ball mill, a Nara mill, a micro mill, etc., a dry pulverization method appropriately adjusted to obtain the desired particle size; using a disper, a homogenizer, a high pressure homogenizer, a colloid mill, etc. And a wet pulverization method which is appropriately adjusted so as to obtain a target particle diameter. Moreover, when adjusting the particle diameter of a silica by a wet grinding method, it can adjust in water, an organic solvent, rubber latex, or these mixed solutions.

  The silica used in the conjugated diene rubber-silica co-coagulated product of the present invention is usually used in the form of an aqueous dispersion. The silica aqueous dispersion is prepared by, for example, using a silica wet cake obtained by filtering and washing silica obtained by neutralization reaction between an alkali silicate and an acid, and water using a stirring mixer such as a homogenizer. It can be obtained by mixing while grinding.

  In the mixture of the conjugated diene rubber and the silica, the ratio of the two is preferably 20 to 200 parts by weight of silica, more preferably 30 to 150 parts by weight with respect to 100 parts by weight of the conjugated diene rubber. 40 to 120 parts by weight is most preferable. When the amount of silica is less than 20 parts by weight, in the resulting rubber composition, the effect of improving the wear resistance and reinforcing property is small, and when it exceeds 200 parts by weight, the rubber composition becomes too hard and the workability tends to deteriorate. It is in.

  The method for preparing the mixture of the conjugated diene rubber and silica is not particularly limited, but it is preferable to mix the conjugated diene rubber latex and the silica aqueous dispersion. The mixture obtained in this way is preferable because the dispersion of silica in the conjugated diene rubber becomes uniform when co-coagulated.

A cationic substance may be contained in the mixture of the conjugated diene rubber and silica. In the co-coagulation, the presence of the cationic substance makes the silica dispersed more uniformly in the co-coagulated product.
Specific examples of the cationic substance include a cationic surfactant and a cationic polymer.

The cationic surfactant can be used without any limitation as long as it is a surfactant that dissociates into ions when dissolved in water and positively ionizes the hydrophilic group portion.
Specific examples of the cationic surfactant include alkylamine acetates such as stearylamine acetate; alkylamine hydrochlorides such as cetylamine hydrochloride and stearylamine hydrochloride; alkylammonium halides such as lauryltrimethylammonium bromide and cetyltrimethylammonium bromide. Alkylamine oxides; alkylarylammonium halides; alkylbetaines; and the like.
A cationic surfactant may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these, alkylammonium halides are preferable, and cetyltrimethylammonium bromide is particularly preferable.

  The cationic surfactant is preferably used in the form of an extending oil emulsion using the cationic surfactant as an emulsifier.

  In order to contain a cationic surfactant in a mixture of conjugated diene rubber and silica, (1) a method of simultaneously mixing a conjugated diene rubber latex, an aqueous silica dispersion and a cationic surfactant, (2) a cation A method in which an extending oil emulsion having a surfactant as an emulsifier and an aqueous silica dispersion are mixed in advance, and then mixed with a conjugated diene rubber latex, (3) a conjugated diene rubber latex and an aqueous silica dispersion And then mixing this with an extending oil emulsion using a cationic surfactant as an emulsifier. (4) After mixing a conjugated diene rubber latex and an aqueous silica dispersion, the cationic surfactant is mixed. (5) An aqueous solution of a cationic surfactant with an aqueous solution of a conjugated diene rubber latex and an aqueous silica dispersion. A method of mixing a slip solution, (6) silica and a cationic surfactant are mixed in water to form an aqueous suspension, a method of mixing conjugated diene rubber latex thereto, etc. can show.

  The cationic surfactant is added as an extending oil emulsion containing 1 to 4.5 parts by weight, more preferably 1.5 to 4 parts by weight of the cationic surfactant with respect to 100 parts by weight of silica. Is preferred. By making the addition amount of the cationic surfactant within this range, it is excellent in reinforcement and wear resistance in the case of a cross-linked molded article, and there is no problem of scorch, and it is in the direction of excellent kneadability and extrusion processability. .

The cationic polymer can be used without limitation as long as it is ionized when dissolved in water and exhibits cationic properties. Specific examples thereof include those obtained by polymerizing a monomer having a primary to tertiary amino group, an ammonium base thereof, or a quaternary ammonium base, optionally together with other monomers.
Specific examples of the cationic polymer include polydiallylmethylamine; dicyandiamide / formalin condensate and their ammonium salts; epichlorohydrin such as epichlorohydrin / polyamine condensate and epichlorohydrin / dimethylamine condensate. -Amine condensates; polymers having a quaternary ammonium base such as polydiallyldimethylammonium chloride and polymethacrylate methyl chloride; Of these, polydiallyldimethylammonium chloride and epichlorohydrin-amine condensate are preferred.

The weight average molecular weight of the cationic polymer is preferably 1,000 to 1,000,000, more preferably 2,000 to 900,000, and most preferably 3,000 to 800,000.
If the weight average molecular weight is less than 1,000, the reinforcing properties such as the strength and abrasion resistance of the vulcanized rubber may be deteriorated. If the weight average molecular weight exceeds 1,000,000, silica in the rubber Dispersion may be poor.
The value of the cation equivalent molecular weight of the cationic polymer is preferably 250 or less, more preferably 220 or less, and most preferably 200 or less by colloid titration.
A cationic polymer may be used individually by 1 type, and may be used in combination of 2 or more type.
The cationic polymer may be used as an aqueous solution or as it is.

  In order to contain a cationic polymer in the mixture of conjugated diene rubber and silica, (1) conjugated diene rubber latex, silica aqueous dispersion and cationic polymer are mixed simultaneously, (2) cationic polymer A method of mixing an aqueous dispersion of silica and silica in advance and then mixing it with a conjugated diene rubber latex, (3) pre-mixing a conjugated diene rubber latex and an aqueous silica dispersion, The method of mixing with a functional polymer can be shown.

The cationic polymer is added so as to have a ratio of 0.1 to 7.5 parts by weight, preferably 0.5 to 7 parts by weight, more preferably 1 to 6 parts by weight with respect to 100 parts by weight of silica. Is preferred.
By making the addition amount of the above cationic polymer within this range, it is excellent in reinforcing property and wear resistance in the case of a cross-linked molded article, and there is no problem of scorching, and it is in the direction of excellent kneadability and extrusion processability. .

In order to obtain a conjugated diene rubber-silica co-coagulated product by coagulating the conjugated diene rubber from the mixture of the conjugated diene rubber and silica, sulfuric acid, hydrochloric acid, etc. are added to the mixture of the conjugated diene rubber and silica. An inorganic acid such as formic acid, acetic acid and butyric acid; an inorganic salt such as aluminum sulfate, sodium chloride and calcium chloride; and the like may be added.
When a cationic substance such as a cationic surfactant or a cationic polymer is contained in the mixture of conjugated diene rubber and silica, coagulation may be caused by blending this cationic substance. it can.

By co-coagulating a mixture of a conjugated diene rubber latex and an aqueous silica dispersion, an aqueous dispersion (slurry) of a mixture of conjugated diene rubber and silica (hereinafter referred to as “crumb”) is produced. Filtration, water washing, dehydration, drying, etc. of crumb are not particularly limited, and a method generally used for rubber may be used as appropriate.
The crumb produced by co-coagulation and the liquid component (hereinafter referred to as “serum”) are separated, and the resulting crumb is washed with water, filtered, and then squeezed with a squeezer, centrifugal dehydration, filter press, etc. to dehydrate. . Next, the crumb is pulverized into granules and then dried by an extrusion dryer, a hot air dryer, an indirect heating dryer having a stirring blade, or the like, and formed into a pellet shape or a block shape. Moreover, a crumb can be shape | molded by powder-drying, without isolate | separating a crumb and a serum.
As described above, a conjugated diene rubber-silica co-coagulated product is obtained.

  The method for producing a silica-containing rubber composition according to the present invention is a method for producing a silica-containing rubber composition having a step of kneading a conjugated diene rubber-silica co-coagulated product and a silane coupling agent, wherein the conjugated diene rubber -The kneading of the silica co-coagulated product was started at 5 to 90 ° C, and after the kneading temperature reached 120 ° C or higher, the silane coupling agent was added to the diene rubber-silica co-coagulated product kneaded material and kneaded. It is characterized by doing.

In the method for producing a silica-containing rubber composition of the present invention, it is necessary to start kneading of the conjugated diene rubber-silica co-coagulated product at 5 to 90 ° C. The kneading start temperature is preferably 20 ° C to 85 ° C, and more preferably 40 ° C to 85 ° C.
When the kneading of the conjugated diene rubber-silica co-coagulated product is started at a temperature exceeding 90 ° C., the temperature rapidly rises due to kneading heat generation, and it becomes difficult to control to a predetermined temperature range in which the silane coupling agent is added, As a result, when the silane coupling agent receives an excessive heat history, the viscosity of the compound is increased, and the processability such as extrusion molding is remarkably deteriorated.
On the other hand, when the kneading start temperature is less than 5 ° C., the torque increases and a load is applied to the machine.

At the same time that the conjugated diene rubber-silica co-coagulated product is kneaded, various compounding agents described later except for the silane coupling agent, the crosslinking agent and the crosslinking accelerator may be added thereto and kneaded.
The method for kneading the conjugated diene rubber-silica co-coagulated product is not particularly limited, and a known method can be adopted. As the kneader, a conventionally-used closed kneader such as a kneader, a brand bender, a Banbury mixer, an open roll, a biaxial extruder, or the like can be used.

  In the method for producing a silica-containing rubber composition of the present invention, after the start of kneading of the conjugated diene rubber-silica co-coagulated product, as described above, the conjugated diene rubber-silica co-coagulated product (and various types of kneading simultaneously if desired) Heat generation occurs due to mechanical shearing due to the kneading of the compounding agent, and the temperature of the kneaded product rises.

In the present invention, it is necessary to add a silane coupling agent and knead the kneaded product after the temperature of the kneaded product has risen to 120 ° C. or higher.
The temperature of the kneaded product of the conjugated diene rubber-silica co-coagulated product when the silane coupling agent is added is preferably 120 to 180 ° C, and more preferably 140 to 175 ° C.

If the temperature when the silane coupling agent is added to the kneaded product of the conjugated diene rubber-silica co-coagulated product is less than 120 ° C., the kneaded product of the conjugated diene rubber-silica co-coagulated product and the silane coupling agent It takes a long time to knead, the silane coupling agent receives an excessive heat history, and the effect of improving workability cannot be obtained.
That is, by adding and kneading the silane coupling agent to the conjugated diene rubber-silica co-coagulated product within the above temperature range, the silane coupling agent does not receive an excessive heat history. The conjugated diene rubber-silica co-coagulated product kneaded product and the silane coupling agent kneaded product can be kneaded without increasing the viscosity. When such a kneaded material is used, a silica-containing rubber composition having excellent molding processability can be obtained.
In addition, the upper limit of the temperature when the silane coupling agent is added to the kneaded conjugated diene rubber-silica co-coagulated product is 180 ° C. or less, which is better in terms of improving workability.

In kneading the conjugated diene rubber-silica co-coagulated product and the silane coupling agent, the kneading torque S2 when adding the silane coupling agent was added as required and the conjugated diene rubber-silica co-coagulated product. It is preferable that the following formula (1) is satisfied with respect to the maximum kneading torque S1 after adding the compounding agent.
0.4 ≦ S2 / S1 ≦ 0.7 (1)
That is, when the conjugated diene rubber-silica co-coagulated product and the compounding agent added as desired are kneaded, the kneading torque rapidly rises to S1. Thereafter, when the rubber has plasticity, and when a compounding agent is added, the kneading torque decreases due to the uniform dispersion. It is preferable to add a silane coupling agent when the reduction in kneading torque is within a certain range. If S2 / S1 exceeds 0.7, the viscosity and scorch effect of the resulting rubber compound may not be sufficiently obtained, and the processability may be inferior. And the effect of improving the wear resistance may be reduced.

The kneading of the conjugated diene rubber-silica co-coagulated product and the silane coupling agent is preferably performed in the range of 130 to 180 ° C, more preferably in the range of 140 to 170 ° C.
The temperature during the kneading of the conjugated diene rubber-silica co-coagulated product and the silane coupling agent is not particularly limited as long as it is within the above range, and need not be constant. For example, the kneading temperature may be raised or lowered so as to reach the target discharging temperature at the end of kneading, or the target discharging temperature may be reached before the kneading is finished, and the kneading temperature is kept constant until the kneading is finished. You may make it maintain.

  By maintaining the temperature during the kneading within the above range, the reaction between the silane coupling agent and the silanol groups on the silica surface can be sufficiently advanced. When the temperature during the kneading is lower than the above, there is a risk that the reinforcing property and low fuel consumption by the silica of the resulting rubber composition may be deteriorated. Conversely, when the temperature is higher than the above range, the conjugated diene rubber- There is a possibility that the kneaded product of the silica co-coagulated product / the silane coupling agent will be deteriorated.

The time for maintaining the kneaded conjugated diene rubber-silica co-coagulated product and the silane coupling agent at the kneading temperature is preferably 30 seconds or more, more preferably 1 minute or more, preferably 30 minutes or less, more preferably Is 25 minutes or less.
If the kneading time is shorter than the above range, the silane coupling agent and silica cannot be sufficiently reacted, and the reinforcing effect, wear resistance, and fuel efficiency may be impaired. Moreover, when longer than said range, there exists a possibility that the improvement effect to the reinforcement property or abrasion resistance of the rubber composition obtained may fall.
After kneading for a predetermined time, the kneaded product is discharged from the kneader. The temperature during discharge of the kneaded product of the conjugated diene rubber-silica co-coagulated product and the silane coupling agent is preferably in the range of 130 to 180 ° C, more preferably 140 to 170 ° C.

Examples of the silane coupling agent include vinyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, 3-octathio- 1-propyltriethoxysilane, γ-mercaptopropyl-di (tridecyl-oligooxyalkylene) ethoxysilane, bis (3- (triethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) propyl) disulfide, etc. , Tetrasulfides such as γ-trimethoxysilylpropyldimethylthiocarbamyl tetrasulfide, γ-trimethoxysilylpropylbenzothiazyl tetrasulfide, and the like. Among them, the silane coupling agent is preferably one having 4 or less sulfur contained in one molecule because scorch during kneading can be avoided.
These silane coupling agents may be used individually by 1 type, and may be used in combination of 2 or more type.
The compounding quantity of the silane coupling agent with respect to 100 weight part of silica is 0.1-20 weight part normally, Preferably it is 0.5-15 weight part, More preferably, it is 1-10 weight part.

In the method for producing a silica-containing rubber composition of the present invention, the silica-containing rubber composition may contain a silylating agent.
The amount of the silylating agent is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, and most preferably 1 to 10 parts by weight with respect to 100 parts by weight of silica.
By adding a silylating agent, the silica-containing rubber composition is further improved in reinforcement and fuel efficiency.

Examples of the silylating agent include chlorosilane compounds such as phenyltrichlorosilane, diphenyldichlorosilane, trimethylchlorosilane, and t-butyldimethylchlorosilane; phenyltrimethoxysilane, phenyltriethoxysilane, isobutyltrimethoxysilane, diphenyldimethoxysilane, vinyltris ( alkoxysilane compounds such as β-methoxy) silane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane; silazane compounds such as hexamethyldisilazane; N-trimethylsilylacetamide, N, N- (bistrimethylsilyl) acetamide And the like; and ureas such as N, N- (bistrimethylsilyl) urea; and the like.
Of these silylating agents, chlorosilane compounds, alkoxysilane compounds, and silazane compounds are particularly preferably used.
These silylating agents may be used alone or in combination of any two or more.
The blending amount of the silylating agent with respect to 100 parts by weight of silica is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, and most preferably 1 to 10 parts by weight.

The method for adding a silylating agent to the silica-containing rubber composition is not particularly limited, and a conjugated diene rubber-a method of kneading a silica co-coagulated product and a silane coupling agent simultaneously, conjugated diene rubber- A method of adding to a silica co-coagulated product, a method of adding a conjugated diene rubber-silica co-coagulated product from a mixture of a conjugated diene rubber and silica, a mixture of a conjugated diene rubber and silica before co-coagulation And a method of mixing with a solution or dispersion of a conjugated diene rubber or silica before preparing the conjugated diene rubber-silica mixture.
Among these, a method of mixing with silica before preparing a mixture of conjugated diene rubber and silica is preferable. As a result, the hydrophilic portion of the silica surface is hydrophobized, the dispersion of the silica in the conjugated diene rubber-silica co-coagulated product is improved, and the reaction efficiency between the silanol group on the silica surface and the silane coupling agent is improved. To improve.

In the method for producing a silica-containing rubber composition of the present invention, the silica-containing rubber composition may contain an organopolysiloxane or a polyether polymer.
By blending these polymers, the reinforcing property and fuel efficiency of the crosslinkable rubber composition obtained from the silica-containing rubber composition are further improved.
The organopolysiloxane preferably has a polymerization degree of 3 to 10,000, and has a functional group such as a methoxy group, a hydroxyl group, an amino group, an alkoxy group, an epoxy group, a carbonyl group, a sulfide group, a sulfonyl group, and a nitrile group. It is preferable.
The polyether polymer is a polymer having an ether bond in the main chain obtained by polymerizing an oxirane compound such as alkylene oxide, epihalohydrin or unsaturated epoxide. The polyether polymer preferably has a molecular weight of 100 to 10,000,000.

The compounding amount of the organopolysiloxane or the polyether polymer is not particularly limited, but is preferably in the range of 0.1 to 50 parts by weight with respect to 100 parts by weight of silica.
One of these organopolysiloxanes and polyether polymers may be used alone, or two or more thereof may be used in combination.
The method for adding the organopolysiloxane and the polyether polymer is not particularly limited, and a method similar to the method for adding the silylating agent can be shown.

  In the present invention, the silica-containing rubber composition includes a filler such as carbon black, talc, clay, calcium carbonate, aluminum hydroxide, corn starch, and additional silica as long as the effects of the present invention are not impaired; Oil, plasticizer, lubricant, etc. can be blended. Moreover, rubbers other than the conjugated diene rubber used in the present invention can be blended as required.

As carbon black, furnace black, acetylene black, thermal black, channel black, graphite, etc. can be used, for example. Among these, furnace black is particularly preferable.
Further, a carbon-silica dual phase filler in which silica is supported on the surface of carbon black may be used.
The compounding amount of carbon black with respect to 100 parts by weight of all rubber components is usually 150 parts by weight or less, and the total of carbon black and silica is preferably 20 to 200 parts by weight.
The blending time of these carbon blacks is not particularly limited.

Specific examples of the activator include diethylene glycol, polyethylene glycol, and silicone oil.
Specific examples of the plasticizer include phthalic acid monoester and phthalic acid diester.
Specific examples of the lubricant include wax.
These compounding amounts are preferably 1 to 5 parts by weight with respect to 100 parts by weight of all rubber components.
The blending time of these additives is not particularly limited.

Other rubbers other than the conjugated diene rubber used in the present invention include conjugated diene rubbers other than the conjugated diene rubber used in the conjugated diene rubber-silica co-coagulated product; polyethers such as acrylic rubber and epichlorohydrin rubber Examples thereof include rubber, fluorine rubber, silicon rubber, ethylene-propylene-diene rubber, urethane rubber, and the like.
The blending method of other rubbers other than the conjugated diene rubber used in the present invention is not particularly limited, and even if added and kneaded during the kneading of the conjugated diene rubber-silica co-coagulated product, the diene rubber-silica co-coagulated material kneaded. It may be added and kneaded at the time of kneading the product and the silane coupling agent, or may be added and kneaded to the silica-containing rubber composition. Further, depending on the type of other rubber, it may be used in combination with the conjugated diene rubber when preparing the conjugated diene rubber-silica co-coagulated product.

  The crosslinkable silica-containing rubber composition of the present invention comprises the silica-containing rubber composition of the present invention and a crosslinking agent.

A crosslinking agent will not be specifically limited if it is normally used for bridge | crosslinking of conjugated diene type rubber | gum.
Specific examples of the crosslinking agent include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur; sulfur halides such as sulfur monochloride and sulfur dichloride; dicumyl peroxide, di-t- Organic peroxides such as butyl peroxide; quinone dioximes such as p-quinone dioxime and p, p'-dibenzoylquinone dioxime; triethylenetetramine, hexamethylenediamine carbamate, 4,4'-methylenebis-o- Organic polyamine compounds such as chloroaniline; alkylphenol resins having a methylol group; and the like.
Among these, sulfur is preferable.
These crosslinking agents may be used individually by 1 type, and may be used in combination of 2 or more type.
The compounding amount of the crosslinking agent is preferably 0.3 to 10 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the total rubber component.

Moreover, a crosslinking accelerator or a crosslinking activator can be used in combination with the crosslinking agent.
Specific examples of the crosslinking accelerator include N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N- Sulfenamide-based crosslinking accelerators such as oxyethylene-2-benzothiazole sulfenamide and N, N′-diisopropyl-2-benzothiazole sulfenamide; guanidines such as diphenylguanidine, diortolylguanidine, orthotolylbiguanidine Thiourea crosslinking accelerators such as diethylthiourea; thiazole crosslinking accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, 2-mercaptobenzothiazole zinc salt; tetramethylthiuram monosulfide, tetrame Thiuram-based cross-linking accelerators such as tilthiuram disulfide; Dithiocarbamic acid-based cross-linking accelerators such as sodium dimethyldithiocarbamate and zinc diethyldithiocarbamate; Agents; and the like.
These crosslinking accelerators may be used alone or in combination of two or more.
Among these crosslinking accelerators, those containing a sulfenamide-based crosslinking accelerator are preferable.
The amount of the crosslinking accelerator is preferably 0.3 to 10 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the total rubber component.

Specific examples of the crosslinking activator include metal oxides, fatty acids and derivatives thereof, metal oxides other than zinc, metal hydroxides, metal carbonates, amines and the like.
Specific examples of the metal oxide include zinc oxide, magnesium oxide, lead monoxide and the like.
Specific examples of fatty acids include stearic acid, oleic acid, lauric acid and the like, and derivatives thereof include metal salts such as zinc stearate and ammonium salts such as dibutylammonium oleate.
Specific examples of the metal hydroxide include calcium hydroxide and activated calcium hydroxide.
Specific examples of the metal carbonate include zinc carbonate and basic lead carbonate.
Among these, zinc oxide and fatty acid are preferable.
As zinc oxide, those having a high surface activity particle size of 5 μm or less are preferably used, and examples thereof include activated zinc white having a particle size of 0.05 to 0.2 μm and zinc white having a particle size of 0.3 to 1 μm. Zinc oxide may be surface-treated with an amine-based dispersant or wetting agent.
These crosslinking activators may be used individually by 1 type, and can also use 2 or more types together.

The blending ratio of the crosslinking activator may be appropriately selected depending on the type of the crosslinking activator, but in the case of zinc oxide, it is preferably 0.1 to 5 parts by weight, more preferably 100 parts by weight of the total rubber component. Is 0.5 to 2 parts by weight. Moreover, in the case of a higher fatty acid, it is preferably 0.3 to 10 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the total rubber component.
The crosslinking activator is preferably contained in the silica-containing rubber composition before the crosslinking agent and the crosslinking accelerator are added to the silica-containing rubber composition. The conjugated diene rubber-silica co-coagulated product and the silane cup It is more preferable to mix | blend with a kneaded material with a ring agent. At this time, the kneading time is preferably 30 seconds or longer, more preferably 60 seconds or longer, preferably 30 minutes or shorter, more preferably 25 minutes or shorter.

  The compounding of the silica-containing rubber composition, the crosslinking agent and the crosslinking accelerator is usually carried out by kneading them at 100 ° C. or lower, preferably 80 ° C. or lower. Thus, by making temperature low, it can prevent that a crosslinkable rubber composition will bridge | crosslink before shaping | molding. The kneader is not particularly limited, and a closed kneader such as a kneader, a brabender, or a Banbury mixer, an open roll, a twin screw extruder, or the like can be used.

The crosslinkable silica-containing rubber composition of the present invention can be made into a cross-linked molded article by cross-linking molding. The crosslinked molded product of the present invention is particularly suitable for tires.
The crosslinking method is not particularly limited, and may be selected according to the properties and size of the crosslinked molded body. The mold may be filled with a crosslinkable rubber composition and heated to crosslink simultaneously with molding, or a previously molded unvulcanized rubber composition may be heated to crosslink. The crosslinking temperature is preferably 120 to 200 ° C, more preferably 100 to 190 ° C, and most preferably 120 to 180 ° C.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but it goes without saying that the scope of the present invention is not limited to these examples. In addition, the part and% in an Example and a comparative example are mass references | standards unless there is particular notice. Various physical properties in Examples and Comparative Examples were measured by the following methods.

(1) Average particle diameter of silica The value of the volume-based median diameter measured using a light scattering diffraction type particle size distribution measuring apparatus (trade name “LS-230” manufactured by Coulter, Inc.) is adopted.

(2) Specific surface area of silica (S _CTAB ) by adsorption of cetyltrimethylammonium bromide ( _CTAB )
After the silica wet cake is put in a drier (120 ° C.) and dried, the value obtained by improving the method described in ASTM D3765-92 as follows is adopted.
That is, in place of IRTB (83.0 m ² / g), which is a standard product of carbon black, a CTAB standard solution is prepared separately, whereby the aerosol OT solution is standardized, and the adsorption of CTAB per molecule on the silica surface is blocked. The specific surface area is calculated from the amount of CTAB adsorbed with an area of 35 square angstroms. This is because carbon black and silica have different surface states, and it is considered that there is a difference in the amount of CTAB adsorbed even with the same specific surface area.

(3) Specific surface area of silica based on nitrogen adsorption (S _BET )
After the silica wet cake was put in a dryer (120 ° C.) and dried, the nitrogen adsorption amount was measured using a measuring device (trade name “ASAP 2010”) manufactured by Micromeritics, and the relative pressure was 0.2. The value of the one-point method is adopted.
(4) Oil absorption amount of silica Determined according to JIS K6220.

(5) Moisture content of silica The moisture content is measured according to JIS K-6220.

(6) Amount of styrene unit in conjugated diene copolymer Measured according to JIS K6383 (refractive index method).
(7) Mooney viscosity of the conjugated diene polymer (ML _{1 + 4} , 100 ° C.)
Measurement is performed according to JIS K6300 using a Mooney viscometer (manufactured by Shimadzu Corporation).

(8) Silica content of conjugated diene rubber-silica co-coagulated product Thermal decomposition of dried sample in air using thermal analyzer TG / DSC (trade name “TG / DTA320” manufactured by Seiko Denshi Kogyo Co., Ltd.) The subsequent combustion residue rate (%) and the weight reduction rate (%) up to 150 ° C. are measured, calculated using the following formula, and converted into an amount (parts) relative to 100 parts of the conjugated diene rubber.
The measurement conditions are a heating rate of 20 ° C./min in air and a holding time of 20 minutes at an ultimate temperature of 600 ° C.
Silica content (%) = combusted residue ratio / (100− (weight reduction rate up to 150 ° C.)) × 100

(9) Moisture content of conjugated diene rubber-silica co-coagulated product After measuring the weight of the sample of the conjugated diene rubber-silica co-coagulated product, it is vacuum-dried at 120 ° C. for 3 hours, and the weight is measured again. The percentage of the weight loss due to drying to the weight before vacuum drying is determined.
(10) Formulation viscosity of the crosslinkable silica-containing composition (ML _{1 + 4} , 130 ° C.)
Measurement was performed according to JIS K6300 using a Mooney viscometer (manufactured by Shimadzu Corporation). About a measurement result, it represents with the index | exponent which makes the measured value of the comparative example 1 100. FIG. A low value indicates excellent workability.

(11) Scorch Time of Crosslinkable Silica-Containing Composition According to JIS K6300, scorch time t ₅ (min) at a measuring temperature of 130 ° C. by Mooney scorch test using Mooney viscometer (manufactured by Shimadzu Corporation) with L-shaped rotor. taking measurement. About a measurement result, it represents with the index | exponent which makes the measured value of the comparative example 1 100. FIG. A high value indicates excellent workability.

(12) Hardness of cross-linked molded article According to JIS K6253, the hardness at room temperature is measured using a Duro-A hardness meter (manufactured by Kobunshi Keiki Co., Ltd.). About a measurement result, it represents with the index | exponent which makes the measured value of the comparative example 1 100. FIG. Higher values indicate better tire handling stability and wear resistance.
(13) Tensile strength of the cross-linked molded article According to JIS K6251, the rupture stress and the rupture elongation were measured using Strograph AE-CT (manufactured by Toyo Seiki Seisakusho). About a measurement result, it represents with the index | exponent which makes the measured value of the comparative example 1 100. FIG. Higher numerical values indicate better silica dispersibility and better mechanical strength and reinforcement.

(14) Abrasion resistance of the crosslinked molded body Using a Ramborn abrasion tester (manufactured by Ueshima Seisakusho Co., Ltd.), measurement is performed under conditions of a slip ratio of 10% and a load of 1.0 kg. About a measurement result, it represents with the index | exponent which makes the measured value of the comparative example 1 100. FIG. Higher values indicate better wear resistance.
(15) Kneading torque S1 and S2
Using a Banbury mixer (labor plast mill model 100C mixer type B-250; manufactured by Toyo Seiki Seisakusho Co., Ltd.), measurement is performed at a kneading start temperature of 80 ° C. and a rotor rotational speed of 70 rpm.

(Example of production of conjugated diene rubber latex)
200 parts deionized water, 1.5 parts rosin acid soap, 2.1 parts fatty acid soap, 57.5 parts 1,3-butadiene and 42.5 parts styrene as monomers, and t- 0.09 part of dodecyl mercaptan was charged. The reactor temperature was 10 ° C., 0.1 parts of diisopropylbenzene hydroperoxide as a polymerization initiator and 0.06 parts of sodium formaldehyde sulfoxylate, 0.014 parts of sodium ethylenediaminetetraacetate and 0 of ferric sulfate. .02 parts were added to the reactor to initiate the polymerization. When the polymerization conversion reached 45%, 0.05 part of t-dodecyl mercaptan was added to continue the reaction. When the polymerization conversion reached 70%, 0.05 part of diethylhydroxylamine was added to stop the reaction.
After removing the unreacted monomer by steam distillation, 0.45 parts of styrenated phenol and 2,4-bis (n-octylthiomethyl) -6-methyl are used as an antioxidant for 100 parts of the polymer. 0.15 parts of phenol was added to obtain a styrene-butadiene copolymer rubber latex having a solid content concentration of 20%.

  A part of the styrene-butadiene copolymer rubber latex was taken out, and with respect to 100 parts of the styrene-butadiene copolymer rubber, Enthertine 1849A (manufactured by British Petroleum Co., Ltd.) was used as an extender oil, and 37.5 emulsified aqueous solution with a fatty acid soap as 37.5% by weight. Part was added. Thereafter, the styrene-butadiene copolymer rubber latex containing the extending oil was coagulated with sodium chloride at 60 ° C. while adjusting the pH to 3 to 5 with sulfuric acid to obtain a crumb-like styrene-butadiene copolymer rubber. This crumb was dried with a hot air dryer at 80 ° C. to obtain a solid styrene-butadiene copolymer rubber (SBR1). The resulting styrene-butadiene copolymer rubber (SBR1) had a styrene content of 35% and a Mooney viscosity of 70. The obtained solid styrene-butadiene copolymer rubber (SBR1) was used in Comparative Examples 1 and 2.

(Silica production example)
A sodium silicate aqueous solution (SiO ₂ concentration: 10 g / L, molar ratio: SiO ₂ / Na ₂ O = 3.41) 230 L was charged into a 1 m ³ stainless steel reaction vessel equipped with a temperature controller, and the temperature was raised to 85 ° C. . Next, 73 L of 22% sulfuric acid and 440 L of an aqueous sodium silicate solution (SiO ₂ concentration: 90 g / L, molar ratio: SiO ₂ / Na ₂ O = 3.41) were added simultaneously over 120 minutes. After aging for 10 minutes, 16 L of 22% sulfuric acid was added over 15 minutes. The above reaction was performed while maintaining the reaction liquid temperature at 85 ° C. and constantly stirring the reaction liquid, and finally a silica slurry having a reaction liquid pH of 3.2 was obtained.
The obtained silica slurry was washed with a filter press and filtered to obtain a silica B wet cake having a silica solid content of 25%.
Here, a part of the obtained silica B wet cake was dried to obtain silica B powder. The BET specific surface area (S _BET ), CTAB specific surface area (S _CTAB ), oil absorption and water content of the silica B powder were measured. As a result, the BET specific surface area (S _BET ) was 201 m ² / g, the CTAB specific surface area (S _CTAB ) was 190 m ² / g, the oil absorption was 210 ml / 100 g, and the water content was 7.1%. The obtained silica B powder was used in Comparative Example 2.

(Preparation Example of Silica Aqueous Suspension (sd1))
The silica B wet cake and pure water obtained in the silica production example were mixed while pulverizing the silica B wet cake using a homogenizer so that the silica B solid content concentration in the aqueous suspension was 15%. An aqueous silica suspension (sd1) was obtained. The particle diameter of silica B in the aqueous silica suspension (sd1) was 15 μm.

(Example of preparation of an extended oil emulsion)
Extending oil Energy 1849A (manufactured by British Petroleum) 66.0 parts, 2.5 parts of surfactant cetyltrimethylammonium bromide and 31.5 parts of pure water were mixed using a homogenizer to obtain an extending oil emulsion. In addition, the pure water and the extension oil used what was heated at 60 degreeC.

(Preparation example of silica-containing extending oil emulsion (se1))
462 parts of the above aqueous suspension of silica (sd1), 56.8 parts of an extended oil emulsion and 300 parts of pure water were mixed using a homogenizer, and the silica-containing extended oil emulsion (se1) (silica content 69.3 parts) was mixed. , Extending oil content 37.5 parts).

(Production of conjugated diene rubber-silica co-coagulated product (a1))
500 parts of the styrene-butadiene copolymer rubber latex obtained in the above conjugated diene rubber latex production example was diluted with 1,000 parts of pure water and heated to 50 ° C. Next, 824 parts of a silica-containing extending oil emulsion (se1) was added to the styrene-butadiene copolymer rubber latex diluted above with stirring. The pH at this time was 8.5.
Next, 10% sulfuric acid was added to the mixed solution to lower the pH, and co-coagulation proceeded. When the pH was reduced to 7 or less, the supernatant liquid began to become transparent, and 10% sulfuric acid was further added to finally adjust the pH to about 6. The temperature of the mixed solution was maintained at 50 ° C.
The obtained coagulated product was filtered and vacuum dried at 70 ° C. to obtain a styrene-butadiene copolymer rubber-silica cocoagulated product (a1). The silica content of the styrene-butadiene copolymer rubber-silica co-coagulated product (a1) is 69.3 parts with respect to 100 parts of the rubber solid content, and the water content of the styrene-butadiene copolymer rubber-silica co-coagulated product (a1). The rate was 0.2%. The obtained styrene-butadiene copolymer rubber-silica co-coagulated product (a1) was used in Example 1 and Example 3.

(Preparation example of silica aqueous suspension (sd2))
While pulverizing the silica B wet cake and the pure water obtained in the silica production example using a homogenizer so that the silica solid content concentration in the aqueous suspension is 15.7 wt%, Next, a cationic polymer (10% aqueous solution of epichlorohydrin / dimethylamine copolycondensate (weight average molecular weight 240,000, cation equivalent molecular weight 138)) was mixed with 3 parts of silica solid content of 100 parts. The resulting mixture was mixed to obtain an aqueous silica-containing suspension (sd2) containing a cationic surfactant. The average particle diameter of silica in the aqueous silica suspension (sd2) was 15 μm.

(Production of conjugated diene rubber-silica co-coagulated product (a2))
500 parts of the rubber latex obtained in the production example of the conjugated diene rubber latex and 57 parts of an extending oil (trade name “Ethergene 1849A” manufactured by British Petroleum Co., Ltd.) made into a 66% emulsified aqueous solution with fatty acid soap were mixed.
The obtained mixed solution was diluted with 1,000 parts of pure water and heated to 50 ° C. Next, 467 parts of the silica aqueous suspension (sd2) obtained in the above silica aqueous suspension (sd2) production example are added to the mixture under stirring to add a conjugated diene rubber-silica co-coagulated product. Got. The pH of the mixed solution at this time was 7.4.
Next, 10% sulfuric acid was added to the mixed solution to lower the pH. The pH was set to 6.5 or less to complete the coagulation. The temperature of the mixed solution was maintained at 50 ° C.
The obtained co-coagulated product was filtered and vacuum-dried at 70 ° C. to obtain a conjugated diene rubber-silica co-coagulated product (a2). The content of silica in the conjugated diene rubber-silica co-coagulated product (a2) is 69.3 parts with respect to 100 parts of rubber solids, and the water content of the conjugated diene rubber-silica co-coagulated product (a2) is 0. 2%. The obtained conjugated diene rubber-silica co-coagulated product (a2) was used in Example 2, Comparative Example 3 and Comparative Example 4.

Using the formulation and kneading method shown in Table 1, a crosslinkable silica-containing rubber composition and a crosslinked molded body were obtained.
Various rubber components and compounding agents shown in Table 1 are as follows.
Conjugated diene rubber-silica co-coagulated product (a1): (conjugated diene rubber (SBR1) 100 parts / silica B 69.3 parts / extension oil 37.5 parts)
Conjugated diene rubber-silica co-coagulated product (a2): (conjugated diene rubber (SBR1) 100 parts / silica B 69.3 parts / extension oil 37.5 parts)
Styrene-butadiene rubber (SBR1): (styrene-butadiene rubber: 100 parts / extended oil: 37.5 parts)
Silica A: Zeosil 165GR (manufactured by Rhodia) (BET specific surface area (S _BET ): 163 m ² / g, CTAB specific surface area (S _CTAB ): 157 m ² / g, oil absorption: 215 ml / 100 g), water content: 7 .1%
Silica B: Silica powder obtained by silica production example (BET specific surface area (S _BET ): 201 m ² / g, CTAB specific surface area (S _CTAB ): 190 m ² / g, oil absorption: 200 ml / 100 g), water content Rate: 7.1%
Silane coupling agent: bis- (3-triethoxysilylpropyl) tetrasulfide (manufactured by Degussa, trade name “Si69”)
Process oil: Energy 1849A (British Petroleum)
・ Carbon black: Tokai Carbon Co., Ltd., trade name “SEAST 7HM”
Anti-aging agent: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”)
・ Vulcanization accelerator CBS: N-cyclohexyl-2-benzothiazolylsulfenamide (Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ”)
・ Vulcanization accelerator DPG: 1,3-diphenylguanidine (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller D”)

Example 1
(Silica-containing rubber composition)
The styrene-butadiene copolymer rubber-silica co-coagulated product (a1) was kneaded with a Banbury mixer (manufactured by Toyo Seiki Co., Ltd., Laboplast Mill, model 100C mixer type B-250) at a kneading start temperature of 80 ° C. and a rotor rotation speed of 70 rpm. After 2 minutes, silane coupling agent, process oil, carbon black and stearic acid were added. The kneading temperature at this time was 150 ° C., and S2 / S1 was 0.597. Further, when the temperature of the kneader reached 150 ° C., the rotor rotation speed was set to 50 rpm so that the temperature became constant. The kneading was further continued, and after 5 minutes, the kneaded product (silica-containing rubber composition 1A) was discharged. The discharge temperature of the kneaded product was 151 ° C.
Next, the above kneaded product (silica-containing rubber composition 1A), zinc oxide and anti-aging agent were added to a Banbury mixer and kneaded at a kneading start temperature of 80 ° C. and a rotor rotational speed of 70 rpm. After 3 minutes, the kneaded product (silica-containing rubber composition 1) was discharged. Further, when the temperature of the kneader reached 145 ° C., the rotor rotation speed was set to 50 rpm so that the temperature became constant.

(Crosslinkable silica-containing rubber composition)
Next, the kneaded product (silica-containing rubber composition 1) was kneaded by adding sulfur and a vulcanization accelerator on an open roll at 50 ° C., and then a crosslinkable silica-containing rubber composition 1 was obtained.

(Crosslinked molded product)
After measuring the blend viscosity and scorch time of the crosslinkable silica-containing rubber composition 1, press vulcanization was performed at 160 ° C. for 15 minutes, and the physical properties of the obtained crosslinked molded body 1 were measured. The results are shown in Table 1.

(Example 2)
The silica-containing rubber composition 2 was prepared in the same manner as in Example 1 except that the conjugated diene rubber-silica co-coagulated product (a2) was used instead of the styrene-butadiene copolymer rubber-silica co-coagulated product (a1). Got. The kneading temperature at the time when the silane coupling agent, carbon black and stearic acid were added after the elapse of 2 minutes from the start of kneading was 150 ° C., S2 / S1 was 0.563, and the discharge temperature of the kneaded product was 152 ° C. .
From this silica-containing rubber composition 2, a crosslinkable silica-containing rubber composition 2 was obtained in the same manner as in Example 1, and a crosslinked molded body 2 was further obtained. The physical properties of the obtained crosslinked molded body 2 were measured. The results are shown in Table 1.

(Example 3)
2/3 of the total weight of the styrene-butadiene copolymer rubber-silica co-coagulated product (a1) is charged into a Banbury mixer, and the remaining styrene-butadiene copolymer rubber-silica co-coagulated product after 1 minute 30 seconds. A silica-containing rubber composition 3 was obtained in the same manner as in Example 1 except that (a1) and the silane coupling agent, process oil, carbon black, and stearic acid were added. The kneading temperature at the time when the remaining styrene-butadiene copolymer rubber-silica co-coagulated product (a1) and the silane coupling agent, process oil, carbon black and stearic acid were added after 1 minute 30 seconds was 140 ° C., S2 / S1 was 0.565, and the discharge temperature of the kneaded material was 150 ° C.
In the same manner as in Example 1, a crosslinkable silica-containing rubber composition 3 was obtained from this silica-containing rubber composition 3, and a crosslinked molded body 3 was further obtained. The physical properties of the obtained crosslinked molded body 3 were measured. The results are shown in Table 1.

(Comparative Example 1)
Styrene-butadiene rubber was kneaded with a Banbury mixer at a kneading start temperature of 80 ° C. and a rotor rotation speed of 70 rpm. After 30 seconds, 50 parts of silica A and a silane coupling agent were added (the temperature at this time was 100 ° C.), and then 19.3 parts of silica A of the remaining compounding agent after 2 minutes. Part, carbon black, and stearic acid were added, kneading was continued, and after 5 minutes, the kneaded product C1A was discharged. Further, when the temperature of the kneader reached 150 ° C., the rotor rotation speed was set to 50 rpm so that the temperature became constant. The torque S2 when the silane coupling agent was added was the same value as the maximum torque S1, S2 / S1 was 1.0, and the discharge temperature of the kneaded product was 151 ° C.

Next, the above kneaded product C1A, zinc oxide and anti-aging agent were added to a Banbury mixer and kneaded at a rotor rotational speed of 70 rpm. After 3 minutes, the kneaded product (silica-containing rubber composition C1) was discharged. Further, when the temperature of the kneader reached 145 ° C., the rotor rotation speed was set to 50 rpm so that the temperature became constant. Next, after adding sulfur and a vulcanization accelerator to a silica-containing rubber composition C1 on an open roll at 50 ° C. and kneading, a crosslinkable silica-containing rubber composition C1 was obtained.
After measuring the blend viscosity and scorch time of the crosslinkable silica-containing rubber composition C1, press vulcanization was carried out at 160 ° C. for 15 minutes, and the physical properties of the obtained crosslinked molded body C1 were measured. The results are shown in Table 1.

(Comparative Example 2)
A silica-containing rubber composition C2 and then a crosslinkable silica-containing rubber composition C2 were obtained in the same manner as in Comparative Example 1, except that silica B was used instead of silica A. Similar to Comparative Example 1, S2 has the same value as the maximum torque S1, and S2 / S1 is 1.0. The discharge temperature of the kneaded product was 150 ° C. From this, a crosslinked molded body C2 was obtained, and the physical properties of the obtained crosslinked molded body C2 were measured. The results are shown in Table 1.

(Comparative Example 3)
A silane coupling agent was added in advance to the conjugated diene rubber-silica co-coagulated product (a2) and then charged into a Banbury mixer. The kneading start temperature at that time is 80 ° C., S2 is the same value as the maximum torque S1, and S2 / S1 is 1.0. A silica-containing rubber composition C3 was obtained in the same manner as in Example 1 except that carbon black, zinc oxide, stearic acid and an antioxidant were added after 2 minutes and 30 seconds from the start of kneading.
From this silica-containing rubber composition C3, a crosslinkable silica-containing rubber composition C3 was obtained in the same manner as in Example 1, and a crosslinked molded product C3 was further obtained. The discharge temperature of the kneaded product was 150 ° C. The physical properties of the obtained crosslinked molded body C3 were measured. The results are shown in Table 1.

(Comparative Example 4)
Kneading of the conjugated diene rubber-silica co-coagulated product (a2) was started at 120 ° C. After 30 seconds from the start of kneading, the silane coupling agent, carbon black and stearic acid were added. The kneading temperature at the time of addition was 150 ° C., S2 / S1 was 0.822, and the discharge temperature of the kneaded product was 150 ° C.
Thereafter, a silica-containing rubber composition C4 was obtained in the same manner as in Example 1.
From this silica-containing rubber composition C4, a crosslinkable silica-containing rubber composition C4 was obtained in the same manner as in Example 1, and a crosslinked molded product C4 was further obtained. The physical properties of the obtained crosslinked molded body C4 were measured. The results are shown in Table 1.

From the results in Table 1, the following can be understood.
As in Comparative Examples 1 and 2, in the kneading and mixing of emulsion-polymerized styrene-butadiene rubber and silica by a dry method, silica dispersibility is insufficient. Abrasion is inferior.
When the silane coupling agent was added to the conjugated diene rubber-silica co-coagulated product at a temperature lower than that of the present invention as in Comparative Example 3, the resulting crosslinked molded product C3 had a tensile strength. Although it has excellent wear resistance, it has a high compound viscosity, a short scorch time, and poor workability.
When the kneading of the conjugated diene rubber-silica co-coagulated product was started at a temperature higher than that of the present invention as in Comparative Example 4, the resulting crosslinked molded product C4 had a tensile strength and abrasion resistance. Although it has excellent properties, the viscosity of the compound is high, the scorch time is short, and the processability is poor.
On the other hand, the cross-linked molded products 1 to 3 (Examples 1 to 3) obtained by the production method defined in the present invention are excellent in the balance of the blend viscosity, scorch time, reinforcement and wear resistance. .

Claims (8)

  A method for producing a silica-containing rubber composition comprising a step of kneading a conjugated diene rubber-silica co-coagulated product and a silane coupling agent, the kneading of the conjugated diene rubber-silica co-coagulated product at 5 to 90 ° C. The production of a silica-containing rubber composition is characterized by adding a silane coupling agent to a diene rubber-silica co-coagulated product kneaded material and kneading after the kneading temperature reaches 120 ° C. or higher. Method.   2. The silica-containing rubber composition according to claim 1, wherein the temperature during discharge of the kneaded product of the conjugated diene rubber-silica co-coagulated product and the silane coupling agent in the kneading step is 130 to 180 ° C. 3. Production method. Cetyl trimethyl ammonium bromide adsorption specific surface area of the silica (CTAB specific surface area) The production method of claim 1 or a silica-containing rubber composition according to 2, characterized in that a 40 to 400 2 / ^g.   The conjugated diene rubber-silica co-coagulated product is obtained by co-coagulating rubber and silica by mixing a solution or aqueous dispersion of a conjugated diene rubber and silica. The manufacturing method of the silica containing rubber composition of any one of -3.   The conjugated diene rubber-silica co-coagulated product contains 100 parts by weight of a conjugated diene rubber, 20 to 200 parts by weight of silica, and 5 to 100 parts by weight of an extending oil. The manufacturing method of the silica-containing rubber composition of any one of Claims 1.   A silica-containing rubber composition obtained by the production method according to any one of claims 1 to 5.   A crosslinkable silica-containing rubber composition comprising the silica-containing rubber composition according to claim 6 and a crosslinking agent.   A crosslinked molded article obtained by crosslinking and molding the crosslinkable silica-containing rubber composition according to claim 7.