JP2005112918A - Rubber composition - Google Patents

Abstract

Disclosed is a rubber composition and a vulcanized rubber having excellent vulcanization productivity, improved dispersibility of silica, improved scorch stability capable of imparting excellent tensile strength and abrasion resistance.
(A) a co-coagulated product comprising a conjugated diene rubber, silica and a cationic substance; (b) sulfur and a specific vulcanization accelerator; (c) Nt-butyl-2-benzothiazin Selected from the group consisting of amide, N-oxydiethylene-2-benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, N, N-diisopropyl-2-benzothiazylsulfenamide And a vulcanized rubber obtained by vulcanizing the rubber composition.
[Selection figure] None

Description

  The present invention relates to a novel rubber composition and its vulcanized rubber. Specifically, it is possible to obtain a vulcanized rubber excellent in tensile strength and wear resistance, including a system in which sulfur and a vulcanization accelerator are added to a co-coagulated product composed of a conjugated diene rubber, silica and a cationic substance. The present invention also provides a rubber composition excellent in vulcanization productivity and molding processability, and a vulcanized rubber obtained by vulcanizing the rubber composition.

  In recent years, rubber compositions filled with silica can be freely colored compared to rubber compositions filled with carbon black, have less environmental pollution, have excellent tear resistance, and have low fuel consumption and high grip. It has been found that it is possible to achieve both, and has attracted attention as a rubber material for tire treads.

  However, since the surface of silica is covered with silanol groups and has strong self-aggregation properties, it has been difficult to disperse it well in rubber.

  Therefore, in order to improve the dispersibility and processability of silica in rubber, after mixing rubber latex and silica in an appropriate ratio, the rubber in rubber latex is coagulated using a coagulant such as acid or salt. Thus, a method of obtaining a silica composition containing silica by so-called “co-coagulation” in which silica is uniformly taken into the coagulated rubber has been studied. For example, a method in which silica is treated with an alkyltrimethylammonium salt and then mixed with a rubber latex and co-coagulated using a salt such as sodium chloride and an inorganic acid such as sulfuric acid (Patent Document 1). A method of co-coagulation with a salt such as sodium chloride after being dispersed in (Patent Document 2), an aqueous suspension of silica containing a cationic polymer and a rubber latex are mixed simultaneously or after mixing. A method of co-coagulation (Patent Document 3) has been proposed.

  However, among the co-coagulated products obtained by the above production method, organic co-cured materials such as cationic surfactants and cationic polymers, particularly co-coagulated products obtained by a method using a cationic polymer are used. However, a rubber composition to which sulfur and a vulcanization accelerator are added can shorten the vulcanization time and is excellent in vulcanization productivity. However, depending on the processing conditions, the rubber composition may be vulcanized due to an increase in temperature during the processing step before vulcanization. It has been clarified by experiments by the present inventors that the rubber compounded with the vulcanizing agent is partially crosslinked and is likely to cause a phenomenon in which later molding cannot be performed, so-called “scorch”. That is, it has been found that a rubber composition using a co-coagulated product obtained from the organic cationic substance has a problem in that a stable vulcanization treatment cannot be performed due to scorching depending on the member during kneading or molding. did.

  Usually, when a rubber composition containing silica is vulcanized, a composition containing sulfur and a vulcanization accelerator is used for the composition, but the vulcanization accelerator is adsorbed on the surface of silica. It is easy to vulcanize the rubber composition, and it has been pointed out that the vulcanization speed is slow and the cycle time of the vulcanization process must be lengthened. In this case, the occurrence of scorch was unexpected.

U.S. Pat. No. 4,482,657 Japanese Patent Application Laid-Open No. 11-285677 JP 2003-113250 A

  Accordingly, an object of the present invention is to effectively prevent the occurrence of scorch in a rubber composition using a co-coagulated product obtained by a method using an organic cationic substance and adding sulfur and a vulcanization accelerator thereto. An object of the present invention is to provide a rubber composition capable of stably performing vulcanization.

  The present inventors have conducted intensive research to solve the above technical problems. As a result, in the rubber composition containing a co-coagulated product, sulfur and a vulcanization accelerator obtained by a method using an organic cationic substance, the above problem can be solved by using a specific vulcanization accelerator. The headline and the present invention were completed.

  That is, according to the present invention, (a) a co-coagulated product comprising a conjugated diene rubber, silica and a cationic substance, (b) sulfur and (c) Nt-butyl-2-benzothiazylsulfenamide, Selected from the group consisting of N-oxydiethylene-2-benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, N, N-diisopropyl-2-benzothiazylsulfenamide There is provided a rubber composition comprising at least one vulcanization accelerator.

  Moreover, according to this invention, the vulcanized rubber obtained by vulcanizing said rubber composition is also provided.

  The rubber composition of the present invention is a rubber composition containing a co-coagulated product, sulfur and a vulcanization accelerator obtained by a method using an organic cationic substance, and vulcanizes while effectively preventing the occurrence of scorch. As a result, it exhibits high vulcanization productivity and molding processability, and can be vulcanized while maintaining the properties of the co-coagulated product. In addition, it is possible to obtain a vulcanized rubber having excellent wear resistance.

  Therefore, the rubber composition of the present invention can be used as a material before vulcanization of molded articles in various fields including tire applications.

  The rubber composition of the present invention is used in various applications that make use of the above characteristics, for example, for molding each part of the tire tread, carcass, sidewall, bead, etc., or for a hose, window frame, belt, shoe sole, It can be used for molding rubber products such as vibration rubber and automobile parts, and further for adding resin-reinforced rubber such as impact-resistant polystyrene and ABS resin.

  Especially, it is suitable as a member for tires, and is particularly suitable as a tire tread of a low fuel consumption tire.

(Conjugated diene rubber)
In the rubber composition of the present invention, the conjugated diene rubber constituting the co-coagulated product can be produced by a known emulsion polymerization method or solution polymerization method without any particular limitation. In the present invention, it is preferable to use a conjugated diene rubber produced by emulsion polymerization of a conjugated diene monomer or a conjugated diene monomer and a monomer copolymerizable with the conjugated diene monomer. Such emulsion polymerization methods can employ known conditions.

  As the extender oil used when recovering the polymer latex as rubber, those usually used in the rubber industry can be used, including paraffinic, aromatic and naphthenic petroleum softeners, plant softeners, fatty acids. Etc. 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 extending 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 rubber in the polymer latex.

  Examples of the conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1 , 3-pentadiene. Among these, 1,3-butadiene and 2-methyl-1,3-butadiene are preferable, and 1,3-butadiene is more preferable. These conjugated diene monomers can be used alone or in combination of two kinds.

  Moreover, the monomer copolymerizable with the conjugated diene monomer is not particularly limited. For example, amino group-containing vinyl monomers, pyridyl group-containing vinyl monomers, hydroxyl group-containing vinyl monomers, alkoxyl group-containing vinyl monomers, aromatic vinyl monomers and the like can be mentioned. A monomer is preferred. Examples of the aromatic vinyl monomer include 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, N, N-dimethylaminoethylstyrene, N, N-diethylaminoethylstyrene and the like can be mentioned. Among these, styrene is particularly preferable. These copolymerizable monomers may be used alone or in combination of two or more.

Specific examples of conjugated diene rubbers that can be suitably used in the present invention include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene copolymer rubber, chloroprene rubber, butyl rubber, acrylonitrile butadiene copolymer rubber, Examples thereof include styrene butadiene isoprene copolymer rubber, butadiene isoprene copolymer rubber, acrylonitrile styrene butadiene copolymer rubber, and acrylic rubber. Further, a modified rubber into which a functional group such as a hydroxyl group, a carboxyl group, an alkoxysilyl group, an amino group, or an epoxy group is introduced can be used.
These conjugated diene rubbers can be used alone or in combination of two or more.

  In the present invention, in particular, a styrene butadiene copolymer rubber containing 1 to 60% by weight of styrene units, preferably 10 to 55% by weight, more preferably 20 to 50% by weight is used as the rubber composition of the present invention. A vulcanized rubber obtained by vulcanization is preferable because of its excellent balance between wear resistance and gripping property.

  The Mooney viscosity (ML1 + 4, 100 ° C.) of the conjugated diene rubber is preferably in the range of 10 to 200, preferably 30 to 150.

(silica)
In the rubber composition of the present invention, as the silica constituting the co-coagulated product, silica added as a filler to rubber is used without particular limitation. For example, the so-called wet silica produced by neutralization reaction between alkali silicate and mineral acid, dry silica obtained by burning silicon tetrachloride in an oxyhydrogen flame, tetraemexylsilane and tetraethoxysilane Examples thereof include sol-gel silica obtained by hydrolyzing silicon alkoxide such as in an acidic or alkaline water-containing organic solvent. In addition, in the precipitated silica, a precipitated silica containing a large amount of a metal salt neutralized with a part of a mineral acid or using aluminum sulfate in place of the mineral acid by a wet method can also be used. In the present invention, precipitated silica that is excellent in rubber reinforcement and productivity is preferred.

For the silica, In detail, the measured specific surface area by the adsorption method of nitrogen _{(S BET)} is preferably from 70~300m ² / g, more preferably from 80~280m ² / g 90 to 260 m ² / g is most preferable.

Further, the measured specific surface area by adsorption of cetyltrimethylammonium bromide of the silica _{(CTAB) (S} CTAB) is preferably from 60~300m ² / g, more preferably from 70~280m ² / g, Most preferably, it is 80-260 m < ² > / g.

  Furthermore, the silica dibutyl phthalate oil absorption (hereinafter also referred to simply as oil absorption) is preferably 100 to 400 ml / 100 g, more preferably 110 to 350 ml / 100 g, and most preferably 120 to 300 ml / 100 g. preferable.

  In the present invention, when silica having a specific surface area and oil absorption in the above-described ranges is used, the reinforcing properties such as tensile strength and wear resistance of the vulcanized rubber are particularly good.

(Organic cationic substance)
The rubber composition of the present invention uses an organic cationic substance for the formation of a co-coagulated product, and the addition of a scorch inhibitor is very effective as will be described in detail later for those containing it. Such an organic cationic substance is suitably used to obtain a co-coagulated product uniformly filled with silica by appropriately adjusting the function of co-coagulating rubber latex and silica and the affinity between silica and rubber. .

  Specific examples of the organic cationic substance include a cationic surfactant and a cationic polymer.

  Specific examples of the cationic surfactant include alkylamine acetates such as stearylamine acetate, alkylamine hydrochlorides such as cetylamine hydrochloride and stearylamine hydrochloride, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, Cetyltrimethylammonium chloride, distearyldimethylammonium chloride, alkylammonium halides such as didecyldimethylammonium chloride, alkylamine oxides such as lauryldimethylamine oxide, alkylarylammonium halides such as alkylbenzyldimethylammonium chloride, lauryl betaine, Examples include alkylbetaines such as stearyl betaine.

  In addition, as the cationic polymer, a polymer that becomes cationic when ionized when dissolved in water is used without any limitation. For example, those obtained by polymerizing monomers having a primary to tertiary amino group or an ammonium base thereof and a quaternary ammonium base are preferably used. Further, it may be copolymerized with other monomers as long as the above effects are not impaired.

  Specific examples of suitable cationic polymers include polyethyleneimine, polyvinylamine, polyvinylpyridine, polyaminesulfone, polyallylamine, polydiallylmethylamine, polyamidoamine, polyaminoalkyl acrylate, polyaminoalkyl methacrylate, polyaminoalkylacrylamide, poly Epoxy amine, polyamide polyamine, polyester polyamine, dicyandiamide / formalin condensate, polyalkylene polyamine / dicyandiamide condensate and their ammonium salts, and quaternary ammonium bases such as polydiallyldimethylammonium chloride and polymethacrylate methyl chloride The polymer which it has can be mentioned.

  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.

  When the weight average molecular weight is 1,000 or more, the effect of improving the reinforcing properties such as tensile strength and wear resistance of the vulcanized rubber is enhanced, and the weight average molecular weight is 1,000,000 or less. As a result, silica dispersion in the rubber is improved. In the present invention, it is preferable to use a cationic polymer because the rubber composition has high vulcanization productivity and the vulcanized rubber obtained by vulcanization has excellent tensile strength and wear resistance.

  The cationic surfactant and the cationic polymer can be used alone or in combination of two or more.

(Co-coagulated product)
In the rubber composition of the present invention, the co-coagulated product comprising a conjugated diene rubber, silica and an organic cationic substance is a latex of the above conjugated diene rubber (hereinafter also simply referred to as rubber latex), silica or an organic cationic substance. Were mixed and dispersed at an appropriate ratio to coagulate the conjugated diene rubber in the conjugated diene rubber latex, and at the same time, the silica conjugated organic organic substance incorporated into the coagulated conjugated diene rubber was dried. Is.
The silica filling amount in the co-coagulated product is preferably 20 to 200 parts by weight, more preferably 30 to 150 parts by weight, and most preferably 40 to 120 parts by weight with respect to 100 parts by weight of the conjugated diene rubber. When the silica filling amount is less than 20 parts by weight, the resulting rubber composition and vulcanized rubber have a small effect of improving the reinforcing properties such as tensile strength and wear resistance. It becomes too hard and the kneadability tends to deteriorate.

  The filling amount of the organic cationic substance in the co-coagulated product is 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. It is preferable to determine the ratio of parts.

  When the amount of the organic cationic substance used is less than 0.1 parts by weight, not only the effect of improving the vulcanization rate is reduced, but also a co-coagulated product in which silica is uniformly dispersed is difficult to obtain, Reinforcing properties such as wear resistance tend to decrease. Moreover, when the usage-amount of an organic cationic substance exceeds 7.5 weight part, it will become easy to scorch and there exists a tendency for kneading workability and extrusion processability to deteriorate.

(Method for producing co-coagulated product)
In the present invention, the method for producing a co-coagulated product comprising a conjugated diene rubber, silica and an organic cationic substance is not limited in any way, but can be obtained by a neutralization reaction between rubber latex, alkali silicate and acid. Silica is mixed with an aqueous suspension and organic cationic substance prepared by dispersing it in water in the form of a slurry or wet cake without drying, and the silica and rubber are co-coagulated, dehydrated and dried. The co-coagulated product obtained by doing so is particularly preferable because of good silica dispersion.

  The average particle diameter of silica used in the co-coagulation is in the range of 0.1 to 50 μm, more preferably 1 to 40 μm, and most preferably 10 to 30 μm.

  The step of adjusting the particle diameter of the silica used for co-coagulation to the above range may be performed anywhere before co-coagulation. Moreover, the adjustment method can use a well-known method without a restriction | limiting in particular. For example, using a jet mill, a ball mill, a Nara mill, a micro mill, etc., using a dry pulverization method that adjusts appropriately so as to obtain the desired particle diameter, or using a disper, a homogenizer, a high-pressure homogenizer, a colloid mill, etc. It can be obtained by a wet pulverization method that is appropriately adjusted so as to obtain a target particle size. Moreover, when adjusting the particle diameter of a silica by a wet grinding method, it can also adjust in water, an organic solvent, rubber latex, or these mixed solutions.

  In the method for producing a co-coagulated product, the method for mixing rubber latex, silica and organic cationic substance is not particularly limited, but the following methods can be mentioned as examples of typical adjustment methods.

  (1) A method in which a rubber latex and silica are mixed, and then the organic cationic substance is mixed as it is or as an aqueous solution, or a mixture of a rubber latex and silica is mixed in an aqueous solution of the organic cationic substance.

  (2) A method in which silica and an organic cationic substance are mixed in water, and then a rubber latex is mixed therewith, or a rubber latex is mixed in an aqueous solution in which silica and an organic cationic substance are mixed in water.

  (3) A method of simultaneously mixing rubber latex, silica and an organic cationic substance.

The rubber latex is not limited in any way, and rubber latex stabilized with an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier, or the like can be used. Among these, it is preferable to use a rubber latex stabilized with an anionic emulsifier. That is, due to the reaction between the organic cationic substance and the anionic emulsifier, part or all of the rubber coagulates with the silica, and the silica is uniformly filled.
The concentration of rubber in the rubber latex is not particularly limited, and may be set as appropriate according to the purpose and application. Usually, the range of 5 to 80% by weight is preferable.

  The co-coagulation of the conjugated diene rubber and silica may be carried out, if necessary, to complete the coagulation of the rubber, such as inorganic acids such as sulfuric acid, phosphoric acid and hydrochloric acid; organic acids such as formic acid, acetic acid and butyric acid; sulfuric acid Acids such as Lewis acids such as aluminum; salts such as sodium chloride and calcium chloride can be used.

  Also, there is no particular limitation on each step such as filtration, water washing, dehydration and drying of the co-coagulated product of conjugated diene rubber and silica obtained by co-coagulation, and a generally used method can be used appropriately. It ’s fine. Separate the co-coagulated product and liquid components, wash the resulting co-coagulated product with water, filter, dehydrate with a screen, centrifuge, decanter, filter press, squeezer, etc. A method of drying into a granule, a pellet, a sheet, or a block by drying in a machine, a hot air dryer, an indirect heating container having a stirring blade, or the like is employed. Further, the co-coagulated product can be formed into a powder form by spray drying without solid-liquid separation.

  In the rubber composition of the present invention, sulfur, a vulcanization accelerator, and a scorch inhibitor are blended with the co-coagulated product of the conjugated diene rubber and silica. Hereinafter, each component will be described in detail.

(sulfur)
As sulfur used in the rubber composition of the present invention, sulfur added as a rubber vulcanizing agent is usually used without particular limitation. Examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, sulfur such as highly dispersed sulfur, and halogenated sulfur such as sulfur monochloride and sulfur dichloride. Among these, powdered sulfur is particularly preferred. These sulfurs are used alone or in combination of two or more.

  In the rubber composition of the present invention, the amount of sulfur is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight, and most preferably 1.5 to 6 parts by weight based on 100 parts by weight of the total rubber component. Parts by weight. If the amount of sulfur is less than 0.5, the breaking strength and wear resistance of the vulcanized rubber obtained by vulcanizing the rubber composition of the present invention are reduced, and the amount of sulfur exceeds 10 parts by weight. And rubber elasticity tends to be impaired.

(Vulcanization accelerator)
The vulcanization accelerator used in the rubber composition of the present invention includes Nt-butyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, N, N-dicyclohexyl- Examples thereof include 2-benzothiazylsulfenamide and N, N-diisopropyl-2-benzothiazylsulfenamide, and these vulcanization accelerators are used alone or in combination of two or more.

  In the vulcanized rubber obtained in the present invention, Nt-butyl-2-benzothiazylsulfenamide is used when importance is attached to fuel efficiency and hardness dependence, and N-oxydiethylene is used when importance is attached to tensile strength. 2-Benzothiazylsulfenamide is preferably used.

  The amount of the vulcanization accelerator is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 8 parts by weight, and particularly preferably 0.5 to 6 parts by weight with respect to 100 parts by weight of the rubber component. It is. When the blending amount of the vulcanization accelerator is less than 0.1 parts by weight, vulcanization does not proceed sufficiently, and the effect of improving tensile strength and wear resistance is small. Further, when the blending amount of the vulcanization accelerator exceeds 10 parts by weight, scorch is likely to occur.

  Conventionally, as a vulcanization accelerator used for dry kneading silica, N-cyclohexyl-2-benzothiazylsulfenamide, which can shorten the scorch time and vulcanization speed, is generally used. there were. According to the present invention, by causing the vulcanization accelerator of the present invention to co-coagulate comprising a conjugated diene rubber, silica and a cationic substance, vulcanization that could not be achieved in the past while appropriately suppressing the generation of scorch. Productivity can be imparted.

  Further, guanidine-based vulcanization accelerators such as diphenylguanidine, triphenylguanidine, diortolylguanidine, orthotolylbiguanidine, diethylthiourea, trimethylthiourea, diortolylthiourea, ethylenethiourea, as long as the effects of the present invention are not impaired. Thiocarbanides, di-n-butylthiourea, thiourea vulcanization accelerators such as di-n-laurylthiourea, 2-mercaptobenzothiazole, dibenzothiazyl disulfide, 2-mercaptobenzothiazole zinc salt, 2-mercapto Thiazole vulcanization accelerators such as benzothiazolecyclohexylamine salt, 2-mercaptobenzothiazole sodium salt, 2-benzothiazyl-N, N-diethylthiocarbamoyl sulfide, tetramethylthiurammo Thiuram vulcanization accelerators such as sulfide, tetramethylthiouram disulfide, tetraethylthiouram disulfide, tetrabutylthiouram disulfide, dipentamethylene thiuram tetrasulfide, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, zinc dimethyldithiocarbamate, diethyldithiocarbamine It can be used in combination with vulcanization accelerators such as diethyldithiocarbamate vulcanization accelerators such as zinc acid, and xanthone acid vulcanization accelerators such as zinc isopropylxanthate and zinc butylxanthate.

(Other ingredients)
In the rubber composition of the present invention, silane coupling agent, carbon black, talc, clay, calcium carbonate, aluminum hydroxide, corn starch and other fillers, zinc oxide, anti-aging agent, as long as the effects of the present invention are not impaired. Activators, process oils, plasticizers, lubricants, fillers and the like can be blended. Moreover, rubbers, such as diene rubber for dilution, can also be mix | blended as needed.

  As the rubber for dilution, for example, natural rubber, polyisoprene rubber, emulsion polymerization diene rubber, solution polymerization random styrene butadiene copolymer rubber (bonded styrene 1 to 50% by weight, 1,2-bond content 8 of butadiene part) ~ 80%), high trans styrene butadiene copolymer rubber (trans bond content of butadiene part 70-95%), low cis polybutadiene rubber, high cis butadiene rubber, high trans butadiene rubber (trans bond content of butadiene part 70 ~ 95%), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-butadiene-isoprene copolymer rubber, styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, etc. It is appropriately selected and used accordingly. These rubbers can be used alone or in combination of two or more. The rubber component may include polyether rubber such as acrylic rubber and epichlorohydrin rubber, fluorine rubber, silicon rubber, ethylene-propylene-diene rubber, urethane rubber, and the like.

  In the rubber composition of the present invention, the inclusion of a silane coupling agent is preferable because the fuel efficiency and wear resistance of the vulcanized rubber obtained by vulcanization are further improved.

  Examples of the silane coupling agent include vinyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, bis (3- (Triethoxysilyl) propyl) tetrasulfide, bis (3- (trimethoxysilyl) propyl) tetrasulfide, bis (3- (methyldimethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) ethyl) tetra Sulfide, bis (3- (triethoxysilyl) propyl) disulfide, bis (3- (trimethoxysilyl) propyl) disulfide, bis (3- (triethoxysilyl) propyl) trisulfide and the like, and JP-A-6-248116 Gamma-trimethoxysilane described in the publication Can be exemplified Le dimethyl tetrasulfide, tetrasulfide such as γ- trimethoxysilylpropyl benzothiazyl tetrasulfide and the like. Since scorch during kneading can be avoided, the silane coupling agent preferably has an average of 4 or less sulfur in one molecule, and particularly preferably an average of 2 or less. These silane coupling agents can be used alone or in combination of two or more.

  These silane coupling agents can be used alone or in combination of two or more. The amount of the silane coupling agent based on 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.

  As carbon black, carbon black such as furnace black, acetylene black, thermal black, channel black, and graphite may be blended. Among these, furnace black is preferable, and specific examples include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, and FEF. The carbon blacks can be used alone or in combination of two or more. The compounding amount of carbon black with respect to 100 parts by weight of the total rubber component 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 BET specific surface area of the carbon black is not particularly limited, but is preferably 30 to 200 m ² / g, more preferably 50 to 150 m ² / g, and most preferably 70 to 140 m ² / g. The oil absorption of the carbon black is preferably 30 to 300 m ² / g, more preferably 50 to ²⁰⁰ m ² / g, and most preferably 80 to 160 m ² / g.

  By containing zinc oxide in the rubber composition of the present invention, vulcanization proceeds more completely, and the fuel efficiency and wear resistance of the resulting vulcanized rubber are further improved, which is preferable. As zinc oxide, those having a high surface activity particle size of 5 μm or less are preferably used, and examples thereof include active 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. In addition, zinc oxide that has been surface-treated with an amine-based dispersant or wetting agent can be used.

  The compounding ratio of zinc oxide is 0.1 to 10 parts by weight, preferably 0.3 to 8 parts by weight, particularly preferably 0.5 to 7 parts by weight, based on 100 parts by weight of the total rubber component.

(Method for adjusting rubber composition)
The rubber composition of the present invention can be obtained by kneading each component according to a conventional method. For example, a rubber composition can be obtained by kneading a compounding ingredient excluding sulfur, a vulcanization accelerator, and a scorch inhibitor and a rubber component, and then mixing sulfur and a vulcanization accelerator in the kneaded product. The kneading time of the compounding agent excluding sulfur and the vulcanization accelerator and the rubber composition is preferably 30 seconds to 30 minutes. The kneading temperature is preferably in the range of 80 to 200 ° C, more preferably 100 to 190 ° C, and particularly preferably 140 to 180 ° C. Mixing of the vulcanizing agent and the vulcanization accelerator is usually performed after cooling to 100 ° C. or lower, preferably 80 ° C. or lower.
The scorch inhibitor may be added in any step before mixing the vulcanizing agent, at the time of mixing the vulcanizing agent, or after mixing the vulcanizing agent. From the viewpoint of the effect on the number of added parts and the shortening of the process, it is preferable to mix simultaneously with the vulcanizing agent.

(Vulcanized rubber)
The rubber composition of the present invention is usually vulcanized and used as a vulcanized rubber. The vulcanization method is not particularly limited, and may be selected according to the properties and size of the vulcanizate. The mold may be vulcanized at the same time as molding by filling the mold with a vulcanizable rubber composition and heating, or by heating and vulcanizing a previously molded unvulcanized rubber composition. good. The vulcanization temperature is preferably 120 to 200 ° C, more preferably 140 to 180 ° C, and the vulcanization time is usually about 1 to 120 minutes.

  In order to describe the present invention more specifically, examples and comparative examples will be described below, but the present invention is not limited to these examples. Various physical properties in Examples and Comparative Examples were measured by the following methods.

(1) Average particle diameter of silica The volume-based median diameter was measured using a light scattering diffraction type particle size distribution analyzer (Coulter LS-230, manufactured by Coulter, Inc.), and this value was adopted as the average particle diameter.

(2) Specific surface area ・ Measurement of specific surface area (S _BET ) by nitrogen adsorption method After putting a silica wet cake in a drier (120 ° C.) and drying it, using Asap 2010 made by Micromeritics, nitrogen adsorption The quantity was measured and the value of the one-point method at a relative pressure of 0.2 was adopted.

Measurement of specific surface area (S _CTAB ) by adsorption of cetyltrimethylammonium bromide (CTAB) A silica wet cake was placed in a drier (120 ° C.) and dried, and then carried out according to the method described in ASTM D3765-92. However, the method of ASTM D3765-92 described, since the method of measuring the _{S CTAB} of carbon black, and the method with minor modifications. That is, the carbon black standard ITRB (83.0 m ² / g) is not used, but a CTAB standard solution is prepared separately, whereby the aerosol OT solution is standardized, and the adsorption per CTAB molecule on the silica surface. The specific surface area was calculated from the amount of CTAB adsorbed with a cross-sectional 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) Oil absorption amount Determined according to JIS K6220.

(4) Amount of styrene unit in copolymer: Measured according to JIS K6383 (refractive index method).
(5) Silica content in the co-coagulated product Using a thermal analyzer TG / DTA (TG / DTA320 manufactured by Seiko Denshi Kogyo Co., Ltd.), the residual fraction after pyrolysis in air of the dried sample and the weight up to 150 ° C. The reduction rate was measured and calculated using the following formula. In the examples, it is described in terms of the amount (parts by weight) relative to 100 parts by weight of rubber. The measurement conditions were as follows: a temperature rising rate of 20 ° C./min in air, an ultimate temperature of 600 ° C., and a holding time of 20 minutes at 600 ° C.
Silica content (% by weight) = combustion residue rate / [100− (weight reduction rate up to 150 ° C.)] × 100
(6) Mooney viscosity Measured according to JIS K6300 at ML (1 + 4) 130 ° C. Comparative example 1 is index 100, and the smaller one indicates better kneading and extrusion processability.

(7) Mooney scorch time It measured at 130 degreeC with the L-type rotor according to JISK6300.
The Mooney scorch time t5 (minutes) indicates that the comparative example 1 is indexed 100, and the larger one than the comparative example 2 is superior in scorch stability.

(8) Tensile strength, 300% modulus Measured according to the tensile stress test method of JIS K6253.

(9) Low fuel consumption RDA-II manufactured by Rheometrics was used, and measurement was performed under the conditions of 1 Hz, 60 ° C., and 5% twist. Comparative example 1 is index 100, and a small value indicates excellent fuel efficiency.

(10) Abrasion resistance Abrasion resistance was measured according to JIS K6264 using a Lambourn abrasion tester. This characteristic was expressed as an index (abrasion resistance index). Comparative example 1 is index 100, and the larger this value, the better the wear resistance.

(Example of rubber latex production)
200 parts deionized water, 1.5 parts rosin acid soap, 2.1 parts fatty acid soap, 72 parts 1,3-butadiene, 28 parts styrene, and t-dodecyl mercaptan 20 copies were prepared. The reactor temperature was 10 ° C., 0.03 part of diisopropylbenzene hydroperoxide, 0.04 part of sodium formaldehyde sulfoxylate as polymerization initiator, 0.01 part of sodium ethylenediaminetetraacetate and ferric sulfate 0.03 part was 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, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate 0.8 is used as an anti-aging agent with respect to 100 parts of the polymer. And 0.12 part of 2,4-bis (n-octylthiomethyl) -6-methylphenol are added as a 30% by weight emulsified aqueous solution to obtain a polymer latex (rubber latex 1) having a solid content concentration of 24%. It was.

  A part of the polymer latex was taken out and adjusted to pH 3 to 5 with sulfuric acid, and the polymer latex was coagulated with sodium chloride at 50 ° C. to obtain a crumb-like polymer. This crumb was dried with a hot air dryer at 80 ° C. to obtain a solid rubber (SBR1). The obtained rubber had a styrene content of 23.6% by weight and a Mooney viscosity of 52. This solid rubber (SBR1) was used in a comparative example.

(Production example of silica aqueous suspension)
200 L of an aqueous sodium silicate solution (SiO ₂ concentration: 10 g / L, molar ratio: SiO ₂ / Na ₂ O = 3.41) was charged into a 1 m ³ stainless steel reaction vessel equipped with a temperature controller, and the temperature was raised to 95 ° C. Subsequently, 77 L of 22% sulfuric acid and 455 L of an aqueous sodium silicate solution (SiO ₂ concentration: 90 g / L, molar ratio: SiO ₂ / Na ₂ O = 3.41) were simultaneously added over 140 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 95 ° C. and constantly stirring the reaction liquid, and finally a silica slurry having a reaction liquid pH of 3.2 was obtained. This was washed with a filter press and filtered to obtain a silica wet cake having a silica solid content of 25%.

The silica powder obtained by drying a part of the obtained silica wet cake has a BET specific surface area (S _BET ) of 121 m ² / g, a CTAB specific surface area (S _CTAB ) of 110 m ² / g, and an oil absorption of 170 ml. / 100g. This silica powder was used in Comparative Example 1 described later.

  The silica wet cake and pure water obtained by the above method were mixed while pulverizing the silica wet cake using a homogenizer so that the silica solid content concentration in the aqueous suspension was 15%, and then cationic Polymer (polydiallylmethylammonium chloride having a molecular weight of 20,000) was mixed so as to be 3 parts by weight with respect to 100 parts by weight of the silica solid content to obtain a cationic polymer-containing silica aqueous suspension I (below Silica aqueous suspension (I)). The particle diameter of silica in (I) in the aqueous silica suspension was 15 μm.

(Production Example 2 of Silica Aqueous Suspension)
The silica wet cake and pure water obtained in Production Example 1 were mixed while pulverizing the silica wet cake using a homogenizer so that the silica solid content concentration in the aqueous suspension was 15%, and then the cation Cationic surfactant (cetyltrimethylammonium chloride) was mixed so as to be 5 parts by weight with respect to 100 parts by weight of the silica solid content to obtain a cationic surfactant-containing silica aqueous suspension II (hereinafter referred to as silica aqueous). Suspension (II)). The particle diameter of silica in (II) silica aqueous suspension was 15 μm.

(Production example 1 of co-coagulated product)
3. 3.6 kg of the above silica aqueous suspension (I) and 11.0 kg of pure water were mixed and stirred, and the polymer latex (rubber latex 1) obtained in rubber latex production example 1 was added to this silica aqueous suspension. 5 kg was mixed and agglomerated under stirring. The final pH of the mixture was 7.5. The temperature of the mixed solution was maintained at 50 ° C.

  The coagulated product was filtered, washed with water, and dried, and then passed through a roll to obtain 1.5 kg of a sheet-like co-coagulated product (A). The silica content in the co-coagulated product was 50 parts by weight.

(Production example 2 of co-coagulated product)
3. 3.6 kg of the silica aqueous suspension (II) and 11.0 kg of pure water were mixed and stirred, and the polymer latex (rubber latex 1) obtained in rubber latex production example 1 was added to the silica aqueous suspension. 5 kg was mixed and agglomerated under stirring. The co-coagulation was performed while maintaining the temperature of the mixed solution at 50 ° C. and maintaining the pH at 6 or less while adding 10% sulfuric acid.

  The coagulated product was filtered, washed with water, and dried, and then passed through a roll to obtain 1.4 kg of a sheet-like co-coagulated product (B). The silica content in the co-coagulated product was 49 parts by weight.

(Production example 3 of co-coagulated product)
2. 6.0 kg of the above silica aqueous suspension (I) and 12.0 kg of pure water were mixed and stirred, and the polymer latex (rubber latex 1) obtained in rubber latex production example 1 was added to this silica aqueous suspension. 8 kg was mixed and co-coagulated with stirring. The final pH of the mixture was 7.5. The temperature of the mixed solution was maintained at 60 ° C.

  The coagulated product was filtered, washed with water, and dried, and then passed through a roll to obtain 1.7 kg of a sheet-like co-coagulated product (C). The silica content in the co-coagulated product was 98 parts by weight.

(Vulcanization accelerator)
The following vulcanization accelerators were used.

・ Vulcanization accelerator A1: N-tert-butyl-2-benzothiazylsulfenamide Trade name Noxeller NS (manufactured by Ouchi Shinsei Chemical Industry)
A2: N-oxydiethylene-2-benzothiazylsulfenamide product name Noxeller MSA (Ouchi Shinsei Chemical Industry)
A3: N, N-diisopropyl-2-benzothiazylsulfenamide trade name Sunseller DIB (manufactured by Sanshin Chemical Industry)
A4: N, N-dicyclohexyl-2-benzothiazylsulfenamide trade name Noxeller DZ (manufactured by Ouchi Shinsei Chemical Industry)
A5: N-cyclohexyl-2-benzothiazylsulfenamide trade name Noxeller CZ (manufactured by Ouchi Shinsei Chemical Industry).

Example 1
In the co-coagulated product (A), a silane coupling agent (KBE-846, manufactured by Shin-Etsu Chemical Co., Ltd.), stearic acid, paraffin wax, zinc oxide, anti-aging agent (Ouchi) so as to have the blending amounts shown in Table 1. Shinoki Chemical Industry Nocrack 6PPD) was added and kneaded for 2 minutes using a Banbury mixer (Toyo Seiki Lab-Plast Mill Model 100C Mixer Type B-250). The temperature at the end of kneading was 145 ° C. Next, vulcanization accelerator A1 and sulfur were added so as to have the blending amounts shown in Table 1, and kneaded at 70 ° C. for 1 minute using a Banbury mixer to obtain a rubber composition (A). The rubber composition (A) was measured for Mooney viscosity, t5, and t35.

  The obtained rubber composition (A) was press vulcanized at 160 ° C. for 15 minutes to produce a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 1.

Example 2
A rubber composition (B) was obtained in the same manner as in Example 1 except that A2 was used instead of A1 as a vulcanization accelerator in Example 1. The Mooney viscosity, t5, and t35 of this rubber composition (B) were measured.
The obtained rubber composition (B) was press vulcanized at 160 ° C. for 15 minutes to prepare a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 1.

Example 3
In Example 1, except that A3 was used instead of A1 as a vulcanization accelerator, kneading was carried out in the same manner as in Example 1 to obtain a rubber composition (C). The Mooney viscosity, t5, and t35 of this rubber composition (C) were measured.
The obtained rubber composition (C) was press vulcanized at 160 ° C. for 15 minutes to prepare a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 1.

Example 4
In Example 1, except that A4 was used instead of A1 as a vulcanization accelerator, kneading was performed in the same manner as in Example 1 to obtain a rubber composition (D). The Mooney viscosity, t5, and t35 of this rubber composition (D) were measured.
The obtained rubber composition (D) was press vulcanized at 160 ° C. for 15 minutes to produce a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 1.

Example 5
In Example 1, the rubber composition (E) was obtained by kneading in the same manner as in Example 1 except that the co-coagulated product (B) was used instead of the co-coagulated product (A). The Mooney viscosity, t5, and t35 of this rubber composition (E) were measured.

  The obtained rubber composition (E) was press vulcanized at 160 ° C. for 15 minutes to prepare a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 1.

Example 6
Example 1 is the same as Example 1 except that the co-coagulated product (C) was used instead of the co-coagulated product (A), and the co-coagulated product (C) and SBR1 were compounded in the amounts shown in Table 1. Kneading was carried out in the same manner to obtain a rubber composition (F). The Mooney viscosity, t5, and t35 of this rubber composition (F) were measured.

  The obtained rubber composition (F) was press vulcanized at 160 ° C. for 15 minutes to prepare a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 1.

比較例１
表２に示す配合量になるように、ＳＢＲ１、シリカ粉末、シランカップリング剤（ＫＢＥ−８４６、信越化学工業製）、ステアリン酸、パラフィンワックス、酸化亜鉛、老化防止剤（ノクラック６ＰＰＤ、大内新興化学工業社製）を添加し、バンバリーミキサー（東洋精機製ラボプラストミル型式１００Ｃ ミキサータイプＢ−２５０）を用いて２分間混練した。混練終了時の温度は１４５℃であった。次いで加硫促進剤Ａ１、硫黄を表１に示す配合量になるように添加し、バンバリーミキサーを用いて７０℃で１分混練し、ゴム組成物（Ｇ）を得た。このゴム組成物（Ｇ）のムーニー粘度、ｔ５、ｔ３５を測定した。

Comparative Example 1
SBR1, silica powder, silane coupling agent (KBE-846, manufactured by Shin-Etsu Chemical Co., Ltd.), stearic acid, paraffin wax, zinc oxide, anti-aging agent (NOCRACK 6PPD, Ouchi Emerging) Chemical Industry Co., Ltd.) was added and kneaded for 2 minutes using a Banbury mixer (Toyo Seiki Laboplast Mill Model 100C Mixer Type B-250). The temperature at the end of kneading was 145 ° C. Next, vulcanization accelerator A1 and sulfur were added so as to have the blending amounts shown in Table 1, and kneaded at 70 ° C. for 1 minute using a Banbury mixer to obtain a rubber composition (G). The Mooney viscosity, t5, and t35 of this rubber composition (G) were measured.

  The obtained rubber composition (G) was press vulcanized at 160 ° C. for 20 minutes to produce a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 2.

Comparative Example 2
In Example 1, except that A5 was used instead of A1 as a vulcanization accelerator, kneading was performed in the same manner as in Example 1 to obtain a rubber composition (H). The rubber composition (H) was measured for Mooney viscosity, t5 and t35.
The obtained rubber composition (H) was press vulcanized at 160 ° C. for 15 minutes to prepare a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 2.

Comparative Example 3
In Example 5, except that A5 was used instead of A1 as a vulcanization accelerator, kneading was performed in the same manner as in Example 1 to obtain a rubber composition (I). The Mooney viscosity, t5, and t35 of this rubber composition (I) were measured.
The obtained rubber composition (I) was press vulcanized at 160 ° C. for 15 minutes to prepare a test piece, and each physical property was measured. The measured value was expressed as an index with Comparative Example 1 as 100. The results are shown in Table 2.

表１に示すように本発明の実施例のゴム組成物は、スコーチ安定性が高く、加硫生産性に優れることがわかる。一方、比較例１に示すように、シリカをドライ混練したゴム組成物は、加硫生産性に劣り、比較例２、３に示すように、従来の加硫促進剤を配合したゴム組成物は、スコーチ安定性が不十分である。

As shown in Table 1, it can be seen that the rubber compositions of the examples of the present invention have high scorch stability and excellent vulcanization productivity. On the other hand, as shown in Comparative Example 1, the rubber composition obtained by dry kneading silica is inferior in vulcanization productivity, and as shown in Comparative Examples 2 and 3, the rubber composition containing the conventional vulcanization accelerator is Scorch stability is insufficient.

Claims (3)

  (A) conjugated diene rubber, co-coagulated product comprising silica and a cationic substance, (b) sulfur and (c) Nt-butyl-2-benzothiazinamide, N-oxydiethylene-2-benzothia At least one vulcanization accelerator selected from the group consisting of dilsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, N, N-diisopropyl-2-benzothiazylsulfenamide A rubber composition comprising.   The rubber composition according to claim 1 containing a silane coupling agent. A vulcanized rubber obtained by vulcanizing the rubber composition according to claim 1.