JP7079829B2 - A method for producing a rubber composition and a method for improving the yield ratio of silica in the rubber composition. - Google Patents

Description

The present invention relates to a method for producing a rubber composition having a high silica yield ratio. The present invention also relates to a rubber composition obtained by the production method, a formulation containing the rubber composition, and a method for improving the yield ratio of silica in the rubber composition.

For the purpose of improving the strength and wear resistance of various rubber materials, a rubber composition (hereinafter referred to as carbon dry masterbatch, abbreviated as C-DMB) in which solid rubber and carbon black particles are kneaded has been used for a long time. It has been used in various fields. Further, a rubber composition obtained by kneading solid rubber and silica particles (hereinafter referred to as silica dry masterbatch and abbreviated as Si-DMB) has long been widely known as a material having similar performance to C-DMB. It was.

In the early 1990s, tire manufacturers found that using Si-DMB for tire tread rubber had the effect of reducing energy loss and saving fuel, and since then Si-DMB has been used for energy. As a rubber composition with little loss, it has come to be widely used for tire tread rubber and power transmission rubber products that are repeatedly deformed.

However, since the silica particles have a lower chemical affinity for solid rubber than the carbon black particles, Si-DMB requires a large amount of time and power energy in the step of uniformly dispersing the silica particles in the solid rubber, that is, the kneading step. It has been needed and a significant reduction in it has been strongly desired.

As one of the means, instead of solid rubber, water-dispersible rubber latex such as synthetic rubber latex or natural rubber latex and water-dispersed slurry of silica particles are uniformly mixed in a liquid state in advance, and then acid or inorganic metal. A method has been proposed in which a rubber composition is produced by coagulating with a salt or the like and sequentially undergoing precipitation, dehydration, washing, and drying steps. The rubber composition produced by this method (hereinafter referred to as silica wet masterbatch and abbreviated as Si-WMB) is a technical concept well known by many prior arts since the 1970s.

For example, Patent Documents 1 to 11 describe multifaceted techniques for Si-WMB, such as the properties of silica particles, a method for stirring an aqueous dispersion slurry of silica particles, the use of a silane coupling agent, and the types and methods of salting out agents. Information is disclosed.

Special Table No. 11-507981 Japanese Unexamined Patent Publication No. 2006-169292 Special Table 2007-508961 Special Table 2009-533495 Special Table 2010-510342A Japanese Unexamined Patent Publication No. 2013-185102 Japanese Unexamined Patent Publication No. 53-71147 Special Table No. 10-512323 Gazette Japanese Unexamined Patent Publication No. 2006-96906 Japanese Unexamined Patent Publication No. 2008-56860 Japanese Unexamined Patent Publication No. 2012-57074

An object of the present invention is to provide a rubber composition having a high silica yield ratio and a method for producing the same. Another object of the present invention is to provide a formulation containing the rubber composition. Further, an object of the present invention is to provide a method for improving the yield ratio of silica in a rubber composition.

The present invention provides a rubber composition containing a rubber latex (A), silica particles (B) and a water-soluble polymer compound (C), and having a total content of chloride ions and sulfate ions of 26000 ppm or less.

The rubber composition preferably contains 20 to 200 parts by weight of the silica particles (B) with respect to 100 parts by weight of the rubber latex (A). Further, it is preferable that the rubber latex (A) contains an emulsion polymerization conjugated diene-based rubber. The water-soluble polymer compound (C) preferably contains a polyalkylene oxide.

The present invention also provides a tread rubber compound containing the above rubber composition.

Further, the present invention is a method for producing a rubber composition containing a rubber latex (A) and silica particles (B), wherein the rubber composition is 100 parts by weight (solid content equivalent) of the rubber latex (A). On the other hand, the amount of the silica particles (B) used is 20 to 200 parts by weight (solid content equivalent), and the amount of the water-soluble polymer compound (C) used is 0.05 to 10 parts by weight (solid content equivalent). Yes, the amount of the coagulant (D) used is less than 10 parts by weight (in terms of solid content), and the rubber latex (A) and the silica particles (B) are used as the water-soluble polymer compound (C) or the water-soluble polymer. Provided is a method comprising a co-coagulation step of contacting a compound (C) with a coagulant (D) to co-coagulate the compound (C), wherein the co-coagulation step includes any of the following conditions (1) to (6).
(1) Part or all of the water-soluble polymer compound (C) is added at the same time as or before the time when the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated. throw into.
(2) The water-soluble polymer compound (2) at the same time as or before the time when the total amount of the rubber latex (A), the total amount of the silica particles (B), and the total amount of the coagulant (D) are added to the raw material system to be co-coagulated. Add a part or all of C).
(3) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is charged.
(4) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are added to the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is added, and then the coagulant (D) is added. ) Is added.
(5) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) and the total amount of the coagulant (D) are simultaneously charged. do.
(6) After adding the total amount of the rubber latex (A) and the total amount of the silica particles (B) to the raw material system to be co-coagulated, the total amount of the coagulant (D) is added, and then the water-soluble polymer compound (C) is added. ) Is added.

In the method for producing the rubber composition, when the amount of the coagulant (D) used exceeds 0, the water-soluble polymer is used before the rubber latex (A) and the silica particles (B) are brought into contact with the coagulant (D). The compound (C) and the coagulant (D) can be mixed in advance, and the rubber latex (A) and the silica particles (B) can be brought into contact with the coagulant (D) in the presence of the water-soluble polymer compound (C). preferable.

Further, it is preferable that the pH of the filtrate when the co-coagulated product co-coagulated in the co-coagulation step is filtered is 6.5 to 10.0.

Further, the present invention is a method for improving the yield ratio of silica in a rubber composition, wherein the rubber composition has silica particles (B) with respect to 100 parts by weight (solid content equivalent) of the rubber latex (A). The amount of the water-soluble polymer compound (C) used is 0.05 to 10 parts by weight (solid content equivalent), and the amount of the coagulant (D) is 20 to 200 parts by weight (solid content equivalent). The amount used is less than 10 parts by weight (in terms of solid content), and the rubber latex (A) and the silica particles (B) are mixed with the water-soluble polymer compound (C) or the water-soluble polymer compound (C) and the coagulant (D). ) Is included, and the coagulation step includes any of the following conditions (1) to (6).
(1) Part or all of the water-soluble polymer compound (C) is added at the same time as or before the time when the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated. throw into.
(2) The water-soluble polymer compound (2) at the same time as or before the time when the total amount of the rubber latex (A), the total amount of the silica particles (B), and the total amount of the coagulant (D) are added to the raw material system to be co-coagulated. Add a part or all of C).
(3) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is charged.
(4) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are added to the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is added, and then the coagulant (D) is added. ) Is added.
(5) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) and the total amount of the coagulant (D) are simultaneously charged. do.
(6) After adding the total amount of the rubber latex (A) and the total amount of the silica particles (B) to the raw material system to be co-coagulated, the total amount of the coagulant (D) is added, and then the water-soluble polymer compound (C) is added. ) Is added.

Further, the present invention comprises a rubber composition containing a rubber latex (A), silica particles (B) and a water-soluble polymer compound (C), wherein the total content of chloride ions and sulfate ions is 26000 ppm or less. Provided is a method for producing a compound for tread rubber, in which a vulcanizing agent is kneaded. In this method, it is preferable to further knead the vulcanization accelerator.

According to the present invention, it is possible to provide a rubber composition having a high silica yield ratio and a method for producing the rubber composition. Further, according to the present invention, it is also possible to provide a formulation containing a rubber composition having a high silica yield ratio. Further, according to the present invention, it is possible to provide a method for improving the yield ratio of silica in the rubber composition.

It is a photograph which shows the silica dispersibility of the formulation of Production Example 1. FIG. It is a photograph which shows the silica dispersibility of the formulation of Production Example 2.

The rubber composition according to one embodiment of the present invention contains a rubber latex (A), silica particles (B) and a water-soluble polymer compound (C), and contains chloride ion (Cl ⁻ ) and sulfate ion ₍ SO ⁴² ). ^- ) The total content is 26000 ppm or less.

The rubber latex (A) may be an emulsion in which fine particles of a rubber-based polymer are stably dispersed in a solvent, and may further contain an emulsifier, if necessary. Examples of the rubber latex (A) include emulsion polymerization conjugated diene rubber latex, natural rubber latex and modified latex thereof. Furthermore, solid rubber such as solution-polymerized styrene-butadiene copolymer rubber, solution-polymerized polybutadiene rubber, and solution-polymerized acrylonitrile-butadiene copolymer rubber is dissolved in a good solvent for each rubber, and this is dissolved with an emulsifier or a surfactant. Examples include rubber latex obtained as a forced emulsion in water, and one or more of these can be used. Above all, the rubber latex (A) preferably contains an emulsion polymerization conjugated diene rubber latex.

Examples of the emulsified polymerization conjugated diene rubber latex include known polybutadiene emulsified polymer latex, styrene-butadiene emulsified copolymer latex, acrylonitrile-butadiene emulsified copolymer latex, and styrene-butadiene-vinylpyridine emulsified copolymer latex. One kind or two or more kinds can be used. As the emulsion polymerization conjugated diene rubber latex, a styrene-butadiene emulsified copolymer latex is particularly preferable.

Further, in obtaining the emulsified copolymer latex, it is also possible to copolymerize a known copolymerizable monomer having a functional group in addition to styrene, butadiene, acrylonitrile and vinyl pyridine. Specifically, as such a monomer, an unsaturated carboxylic acid monomer such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid, and an unsaturated epoxy-based single amount such as an anhydride thereof, glycidyl methacrylate, and allyl glycidyl ether. Examples thereof include a hydroxyl group-containing unsaturated monomer such as a body, hydroxyethyl acrylate, and hydroxyethyl methacrylate, and one or more of them can be used, respectively.

The average particle size of the rubber-based polymer contained in the rubber latex (A) by the photon correlation method is preferably 10 nm to 200 nm, more preferably 20 nm to 100 nm. The average particle size of rubber latex by the photon correlation method shall be prepared by appropriately adjusting various emulsifiers used in the polymerization of rubber latex, the types of polymerization initiators and their amounts and addition methods, the proportion of polymerized water used, and the like. Is possible.

The silica particles (B) may be silica prepared by a wet method. As the silica particles (B), a wet method silica aqueous dispersion slurry produced by precipitating silica particles by adding an acid to an aqueous solution of sodium silicate, that is, water glass, or by blowing carbon dioxide gas, and a wet method silica. Examples thereof include a silica aqueous dispersion slurry in which silica powder obtained by drying from an aqueous dispersion slurry is dispersed in water again, and a silica aqueous dispersion slurry in which dry silica powder produced by a dry method is dispersed in water. One kind or two or more kinds can be used.

The water-soluble polymer compound (C) is a compound having a viscosity average molecular weight of 100,000 to 20 million. The viscosity average molecular weight of the water-soluble polymer compound (C) is more preferably 500,000 to 15 million. Examples of the water-soluble polymer compound (C) include polyalkylene oxide, polyacrylamide, acrylamide-unsaturated carboxylate copolymer, alkali-soluble acrylic emulsion, and modified products thereof, and one of them is used. , Or two or more types can be used. The water-soluble polymer compound (C) is preferably a polyalkylene oxide, polyacrylamide, or acrylamide-unsaturated carboxylate copolymer. The water-soluble polymer compound (C) preferably contains a polyalkylene oxide. The water-soluble polymer compound (C) is more preferably polyethylene oxide.

The total content of chloride ion and sulfate ion is preferably 26000 ppm or less, more preferably 20000 ppm or less, and further preferably 5000 ppm or less. The content of sulfate ion is preferably 800 ppm or more, more preferably 1000 ppm or more.

Another embodiment of the present invention is a method for producing a rubber composition containing a rubber latex (A) and silica particles (B), wherein the rubber composition is 100 parts by weight (solid content) of the rubber latex (A). The amount of the silica particles (B) used is 20 to 200 parts by weight (solid content equivalent), and the amount of the water-soluble polymer compound (C) used is 0.05 to 10 parts by weight (solid content). The amount of the coagulant (D) used is less than 10 parts by weight (in terms of solid content), and the rubber latex (A) and the silica particles (B) are mixed with the water-soluble polymer compound (C) or water-soluble. A method comprising a co-coagulation step of contacting the sex polymer compound (C) with the coagulant (D) to co-coagulate, wherein the co-coagulation step includes any of the following conditions (1) to (6). be.
(1) Part or all of the water-soluble polymer compound (C) is added at the same time as or before the time when the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated. throw into.
(2) The water-soluble polymer compound (2) at the same time as or before the time when the total amount of the rubber latex (A), the total amount of the silica particles (B), and the total amount of the coagulant (D) are added to the raw material system to be co-coagulated. Add a part or all of C).
(3) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is charged.
(4) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are added to the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is added, and then the coagulant (D) is added. ) Is added.
(5) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) and the total amount of the coagulant (D) are simultaneously charged. do.
(6) After adding the total amount of the rubber latex (A) and the total amount of the silica particles (B) to the raw material system to be co-coagulated, the total amount of the coagulant (D) is added, and then the water-soluble polymer compound (C) is added. ) Is added.
Here, the raw material system to be co-coagulated is when the rubber latex (A), the silica particles (B) and the water-soluble polymer compound (C), and if necessary, the coagulant (D) are mixed in the container. , Means the mixed solution (reaction system) present in the container.

The amount of the rubber latex (A) used is preferably 30 to 90 parts by mass (in terms of solid content) and preferably 40 to 80 parts by mass (in terms of solid content) with respect to 100 parts by mass of the total mass of the rubber composition. , 40 to 70 parts by mass (in terms of solid content) is more preferable.

The amount of the silica particles (B) used is preferably 20 to 200 parts by mass (in terms of solid content) and preferably 30 to 150 parts by mass (in terms of solid content) with respect to 100 parts by mass of the rubber latex (A). , 50 to 150 parts by mass (in terms of solid content) is more preferable.

The amount of the water-soluble polymer compound (C) used is 0.05 to 10 parts by mass (in terms of solid content) and 0.1 to 5 parts by mass (solid content) with respect to 100 parts by mass of the rubber latex (A). (Conversion) is preferable, and 0.1 to 3 parts by mass (solid content conversion) is more preferable.

Examples of the coagulant (D) include alkali metals, alkaline earth metals, and aluminum sulfates or chlorides. As the coagulant (D), sodium chloride, calcium chloride or aluminum sulfate is preferable, and sodium chloride is more preferable.

The amount of the coagulant (D) used is less than 10 parts by mass, preferably 0.1 to 5 parts by mass (in terms of solid content), with respect to 100 parts by mass of the rubber latex (A), preferably 0.1. It is more preferable that the amount is up to 3 parts by mass (in terms of solid content). In the present invention, when the amount of the coagulant (D) used is in the above range, the total content of chloride ions and sulfate ions in the rubber composition can be 26000 ppm or less. In this embodiment, the coagulant (D) may not be used.

Further, in the method for producing the rubber composition, the use of the coagulant (D) is not essential. Usually, in order to reduce the ion content in the rubber composition, it is necessary to add a step such as washing with water. However, performing a step such as washing with water may cause a decrease in the yield ratio of silica in the rubber composition. In the present embodiment, by reducing the amount of the coagulant (D) used, the step of washing the rubber composition with water can be omitted. Further, by omitting the washing step of the rubber composition, not only the productivity can be further improved, but also the yield ratio of silica in the rubber composition can be further increased. Further, by omitting the washing step, the outflow of uniformly dispersed silica particles can be suppressed, and a rubber composition in which silica particles are uniformly dispersed can be obtained with better reproducibility. As the coagulant (D), an acid such as mineral acid or acetic acid, an alkali metal, an alkaline earth or a metal hydroxide such as aluminum may be used in combination.

In addition, the rubber composition usually may be deteriorated by heat (deterioration of thermal oxidation), light (deterioration of photooxidation), ozone, residual chlorine, metal ions, solvent swelling and the like. When the amount of the coagulant (D) used is large, the content of metal ions contained in the rubber composition tends to increase. Reducing the amount of acid used as the coagulant (D) can further reduce the possibility of quality deterioration during heating. Further, when the amount of the metal hydroxide used as the coagulant (D) is reduced, the hydrolysis of the rubber can be further suppressed and the durability is further improved. In this embodiment, the preferred coagulant (D) is an alkali metal, alkaline earth metal or aluminum sulfate or chloride.

In the method for producing a rubber composition of the present embodiment, a rubber latex (A), silica particles (B), a water-soluble polymer compound (C), and a coagulant (D), if necessary, are mixed and co-coagulated. After that, for example, the rubber composition can be obtained by filtering the obtained cocoagulated product. The pH of the filtrate when the rubber composition is filtered is preferably 6.0 to 11.0, more preferably 6.5 to 10.0. When the pH is in the above range, the yield ratio of silica can be improved.

In the method for producing the rubber composition, when the amount of the coagulant (D) used exceeds 0, the water-soluble polymer is used before the rubber latex (A) and the silica particles (B) are brought into contact with the coagulant (D). The compound (C) and the coagulant (D) can be mixed in advance, and the rubber latex (A) and the silica particles (B) can be brought into contact with the coagulant (D) in the presence of the water-soluble polymer compound (C). preferable.

In the method for producing a rubber composition of the present embodiment, after the co-coagulation step, further steps such as washing with water, dehydration, and drying may be performed. There are no particular restrictions on these steps, and methods common in the art can be used. Further, since the yield ratio of silica can be further increased, the method of the present embodiment does not require washing with water because the amount of metal ions contained in the rubber composition is small. By producing the rubber composition without performing the washing step, the content of silica in the obtained rubber composition tends to be higher.

The rubber composition of the present embodiment may contain a known additive. Known additives include vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, fillers, silane coupling agents, plasticizers, anti-aging agents and the like. These additives can be used alone or as a mixture of two or more.

Examples of the vulcanizing agent include organic sulfur-containing compounds such as sulfur, trimethylthiourea, N, N'-diethylthiourea, and 4,4'-dithiodimorpholine.

Examples of the vulcanization accelerator include di-2-benzothiazolyl disulfide, zinc N-phenyl-N-ethyl-dithiocarbamate, zinc N, N-dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and the like. Examples include bis (benzothiazole-2-ylthio) zinc and the like. Specifically, as the vulture accelerator, the product name "Soxinol DM" (MBTS) manufactured by Sumitomo Chemical Co., Ltd., the product name "Soxinol PX" (ZnEPDC) manufactured by Sumitomo Chemical Co., Ltd., and the product name "Soxinol PZ" manufactured by the same company. (ZnMDC), the company's product name "Soxinol EZ" (ZnEDC), the company's product name "Soxinol BZ" (ZnBDC), the company's product name "Soxinol MZ" (ZnMBT), the company's product name "ZnMBT". Soxinol TT "(TMTD), product name" Noxeller DM-P "(MBTS) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., product name" Noxeller PX "(ZnEPDC) manufactured by the company, product name" Noxeller PZ "manufactured by the company. (ZnMDC), the company's product name "Noxeller EZ" (ZnEDC), the company's "Noxeller BZ-P" (ZnBDC), the company's product name "Noxeller MZ" (ZnMBT), the company's product name "ZnMBT" There are Noxeller TT-P "(TMTD), product name" Sunseller DM-G "(MBTS) manufactured by Sanshin Chemical Industry Co., Ltd., and product name" Sunseller MZ "(ZnMBT) manufactured by Sanshin Chemical Industry Co., Ltd.

Examples of the vulcanization accelerating aid include fatty acids such as stearic acid, oleic acid and cottonseed fatty acid, and metal oxides such as zinc oxide.

Examples of the filler include carbon black, kaolin clay, hard clay, calcium carbonate, barium sulfate, diatomaceous earth and the like.

Examples of the silane coupling agent include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, and γ-glycidoxypropyl. Trimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ -Aminopropyltrimethoxysilane, bis- (3- (triethoxysilyl) propyl) tetrasulfide, bis- (3- (triethoxysilyl) propyl) disulfide, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, γ -Trimethoxysilylpropylbenzothiaziltetrasulfide and the like can be mentioned.

Examples of the plasticizer include paraffin-based oils, ester-based oils, olefin-based oils, and the like.

Examples of the antiaging agent include imidazoles such as 2-mercaptobenzoimidazole, for example, phenyl-α-naphthylamine, N, N'-di-β-naphthyl-p-phenylenediamine, N-phenyl-N'-isopropyl. Amines such as -p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl) -p-phenylenediamine, phenols such as di-tert-butyl-p-cresol, styrenated phenol, etc. Can be mentioned. Specifically, as the aging accelerator, the product name "Nocrack PA" (PAN) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., the product name "Nocrack White" (DNPD) manufactured by the same company, and the product name "Nocrack PA" (DNPD) manufactured by the same company. Nocrack 810-NA (IPPD), the company's product name "Nocrack 6C" (6PPD), Kawaguchi Chemical Industry Co., Ltd.'s product name "Antage 3C" (IPPD), the company's product name "Antage 6C" ( 6PPD) and the like.

A formulation in which an additional rubber component is further added to the rubber composition of the present embodiment is suitable for producing a tread rubber. That is, the formulation of the present embodiment contains the above rubber composition and an additional rubber component, and tread rubber can be produced by appropriately molding. The formulation of the present embodiment contains silica particles contained in the rubber composition by kneading the rubber composition (masterbatch) with additional rubber components, optionally a vulcanizing agent, and a vulcanization accelerator. It is evenly distributed throughout. The tread rubber produced by the formulation of the present embodiment can not only uniformly disperse the silica particles, but also can have a higher content of silica particles than the tread rubber produced by the conventional method. In addition, a large amount of time and power energy required in the conventional kneading process can be reduced. Such tread rubber is suitable as a material for tires and has better grip characteristics, wear resistance and rolling resistance.

The additional rubber component may be the same as or different from the rubber component derived from the rubber latex. The additional rubber component is not particularly limited, and is, for example, natural rubber, polyisoprene rubber, emulsified polymerized styrene-butadiene copolymer rubber, solution-polymerized random styrene-butadiene copolymer rubber, high transstyrene-butadiene copolymer rubber, low. Sispolybutadiene rubber, high cispolybutadiene rubber, high transpolybutadiene rubber, styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, solution-polymerized random styrene-butadiene-isoprene copolymer rubber, emulsified polymerized styrene-butadiene-isoprene copolymer Examples thereof include rubber, emulsified polymerized styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, and various diene rubbers such as block copolymers such as polystyrene-polybutadiene-polystyrene block copolymer. These can be used alone or in combination of two or more.

In addition to the silica particles (B), an additional filler may be added to the formulation of the present embodiment. Additional fillers include, for example, carbon black.

The formulation of the present embodiment may contain various additives generally used in the formulation for tread rubber. Examples of such additives include silane coupling agents, softeners, plasticizers, antiaging agents, zinc oxide, stearic acid, vulcanizing agents, vulcanization accelerators and the like. As each additive, a known additive that can be blended in the above-mentioned rubber composition can be used.

The formulation of the present embodiment is obtained by kneading according to a conventional method using a commonly used mixer such as a Banbury mixer, a kneader, or a roll.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples. Unless otherwise specified,% and parts are based on mass.

(Manufacturing of rubber latex (A))
In a stainless steel pressure resistant polymerization reactor, under reduced pressure, 200 parts by mass of pure water, 4.5 parts by mass of potassium disproportionate, 0.45 parts by mass of sodium phthalene sulfonate formalin condensate, 74 parts by mass of butadiene, and 26 parts by mass of styrene. , T-dodecyl mercaptan 0.2 parts by mass, sodium tertiary phosphate 0.65 parts by mass, ethylenediamine tetraacetic acid 0.07 parts by mass, sodium formaldehyde sulfoxylate 0.15 parts by mass, paramentan hydroperoxide 0.10 A parts by mass and 0.05 parts by mass of ferrous sulfate heptahydrate were mixed, and the polymerization reaction was started at 5 ° C. It was confirmed that the polymerization conversion rate reached 57% 6 hours after the start of the polymerization, and 0.5 part by mass of diethyl hydroxyamine was added 7 hours after the start of the polymerization to stop the polymerization reaction. The polymerization conversion rate when the reaction was stopped was 62%. After removing the unreacted monomer by steam distillation, the solid content concentration was adjusted to 20.0% by mass with pure water to obtain a rubber latex (A). The average particle size of the rubber latex (A) by the photon correlation method was 60 nm.

(Measurement of polymerization conversion rate of rubber latex (A))
The reaction solution collected from the reaction vessel is weighed, dried at 150 ° C. for 1 hour, weighed again, and the solid content is measured, which can be calculated from the following formula.
Polymerization conversion rate (%) = [(solid content (g) -solid content other than the monomer contained in the reaction solution (g)) / amount of monomer component added to the reaction system (g)] × 100

(Measurement of average particle size by photon correlation method of rubber latex (A))
The average particle size of the obtained rubber latex (A) was measured by the photon correlation method. For the measurement, FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.) was used (JIS Z8826).

(Silica particles (B))
Prepare 79 parts by mass of pure water in a stainless steel container with a stirrer, add 21 parts by mass (containing about 5% by mass of water) of Tosoh's "Nipseal VN3" while stirring, and add silica water-dispersed slurry (solid content). The concentration was 20.0% by mass).

(Water-soluble polymer compound (C))
1 part by mass of "PEO-8" manufactured by Sumitomo Seika Chemical Co., Ltd. was dissolved in 99 parts by mass of water to obtain a 1% by mass polyethylene oxide aqueous solution.

(Coagulant (D))
1 part by mass of calcium chloride was dissolved in 99 parts by mass of pure water to obtain a 1% by mass calcium chloride aqueous solution.

(Manufacturing of anti-aging agent emulsified water dispersion)
In a stainless steel container with a jacket set with a stirrer, put 76.3 parts by mass of styrene phenol, 23.7 parts by mass of sodium dodecylbenzene sulfonate, and 160 parts by mass of pure water, and pour warm water through the jacket to heat to 60 ° C. Then, the mixture was stirred for 30 minutes to emulsify and then cooled to room temperature to produce an antioxidant aqueous dispersion having a solid content concentration of 38.5% by mass.

(Manufacturing method of rubber composition)
Example 1
An aqueous dispersion solution in which rubber latex (A), silica particles (B), and an antiaging agent emulsified aqueous dispersion are mixed is added to the co-coagulating raw material system at the ratio shown in Table 1, and the mixture is stirred for 15 minutes. After adding the water-soluble polymer compound (C) and stirring for 5 minutes, the coagulant (D) was added and co-coagulated. Then, the obtained co-coagulated product was filtered through a 100-mesh stainless wire mesh, and the residue remaining on the mesh was dried at 95 ° C. for 4 hours to obtain a rubber composition.

Example 2
An aqueous dispersion containing a mixture of rubber latex (A), silica particles (B), and an antiaging agent emulsified aqueous dispersion was added to the co-coagulating raw material system at the ratio shown in Table 1, and the mixture was stirred for 15 minutes. After adding the water-soluble polymer compound (C), the mixture was stirred for 5 minutes and then co-coagulated. Then, the obtained co-coagulated product was filtered through a 100-mesh stainless wire mesh, and the residue remaining on the mesh was dried at 95 ° C. for 4 hours to obtain a rubber composition.

Examples 3-5
An aqueous dispersion solution in which rubber latex (A), silica particles (B), and an antiaging agent emulsified aqueous dispersion are mixed is added to the co-coagulating raw material system at the ratio shown in Table 1, and the mixture is stirred for 15 minutes. After adding the water-soluble polymer compound (C) and stirring for 5 minutes, the coagulant (D) was added and co-coagulated. Then, the obtained co-coagulated product was filtered through a 100-mesh stainless wire mesh, and the residue remaining on the mesh was dried at 95 ° C. for 4 hours to obtain a rubber composition.

Comparative Examples 1 to 3
After adding an aqueous dispersion solution containing rubber latex (A), silica particles (B), and an antiaging agent emulsified aqueous dispersion to the raw material system to be co-coagulated at the ratio shown in Table 1, and stirring for 15 minutes. , Coagulant (D) was added and co-coagulated. Then, the obtained co-coagulated product was filtered through a 100-mesh stainless wire mesh, and the residue remaining on the mesh was dried at 95 ° C. for 4 hours.

表中の数字は、固形分の質量部を意味する。

The numbers in the table mean the parts by mass of the solid content.

(Measuring method of ion content)
Pressurized extraction / ion chromatograph method Weigh about 0.05 to 0.1 g of the rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 3 into a cylindrical container (inner diameter 2.5 cm) having a volume of 20 ml, and ultrapure water. 10 ml of water was added, and pressure extraction was performed at 230 ° C. for 16 hours. After filtering the obtained liquid, chloride ion (Cl ⁻ ) and sulfate ion ( _SO4-2 ) are ^quantified using the ion chromatograph method under the following detection conditions, and elution per unit mass of the rubber composition is performed. Converted to quantity. The contents of the obtained chloride ion and sulfate ion are shown in Table 2.
<Detection conditions>
Column used: AS9-HC (manufactured by Thermo Fisher Scientific)
Elution solvent: Potassium carbonate Detection method: Electrical conductivity detector

(Number of copies of silica particles in the rubber composition, yield ratio of silica particles)
The rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 3 are placed in an empty platinum crucible and weighed, and then the platinum crucible is placed in an electric furnace set at 800 ° C. and burned for 10 hours. After 10 hours, the platinum crucible is removed from the electric furnace and weighed again. Then, the difference between the mass before combustion and the mass after combustion is defined as the yield of the latex in the rubber composition, and the mass after combustion is defined as the yield of silica particles. The number of copies of the yield (in terms of solid content) was calculated. Table 2 shows the values of the yield of the obtained silica particles.
Number of yields of silica particles (parts by mass) = (silica yield (g) / latex yield (g)) x 100
Next, the yield ratio of the silica particles was calculated from the calculated number of parts of silica particles (in terms of solid content) and the number of parts of silica particles blended with respect to 100 parts by mass of rubber latex (in terms of solid content) from the following equation. The values of the yield ratio of the obtained silica particles are shown in Table 2.
Yield ratio of silica particles = (number of yields of silica particles (parts by mass) / number of parts compounded with silica particles (parts by mass))

In the rubber composition of Comparative Example 1, cocoagulation did not proceed.

シリカ： ＣＡＲＰＬＥＸ＃８０（商品名、ＤＳＬ．ジャパン（株）製）
カーボンブラック： Ｎ３３０（商品名、東海カーボン（株）製）
シランカップリング剤： Ｓｉ７５（商品名、エボニックジャパン（株）製）
環境対応オイル： ＶｉｖａＴｅｃ５００（商品名、Ｈ＆Ｒ社製）
亜鉛華： 酸化亜鉛２種（ハクスイテック（株）製）
ステアリン酸： 日本精化（株）製
老化防止剤： ノクラック６Ｃ（商品名、大内新興化学工業（株）製） (Manufacturing of vulcanized rubber)
The vulcanized rubber was manufactured by the following procedure.
(1) Using a laboplast mill, the materials shown in Table 3 were kneaded at 90 ° C. to obtain a rubber kneaded product. In Table 3, the numerical values mean parts by mass.

Silica: CARPLEX # 80 (trade name, manufactured by DSL. Japan Co., Ltd.)
Carbon black: N330 (trade name, manufactured by Tokai Carbon Co., Ltd.)
Silane coupling agent: Si75 (trade name, manufactured by Evonik Japan Co., Ltd.)
Environmentally friendly oil: VivaTec500 (trade name, manufactured by H & R)
Zinc Oxide: 2 types of zinc oxide (manufactured by Hakusui Tech Co., Ltd.)
Stearic acid: Nippon Fine Chemical Co., Ltd. Anti-aging agent: Nocrack 6C (trade name, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)

加硫促進剤１： ノクセラー ＣＺ（商品名、大内新興化学工業（株）製）
加硫促進剤２： ノクセラー Ｄ（商品名、大内新興化学工業（株）製）
硫黄： オイル硫黄３２５Ｍ（商品名、細井化学工業（株）製） (2) A vulcanized rubber kneaded product was obtained by adding the vulcanization accelerator and sulfur shown in Table 4 to the obtained rubber kneaded product and kneading the rolls. In Table 4, the numerical values mean parts by mass. The obtained vulcanized rubber kneaded product was hot-pressed at 160 ° C. for 12 minutes to produce a vulcanized rubber sheet having a thickness of 2 mm.

Vulcanization accelerator 1: Noxeller CZ (trade name, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
Vulcanization accelerator 2: Noxeller D (trade name, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
Sulfur: Oil sulfur 325M (trade name, manufactured by Hosoi Chemical Industry Co., Ltd.)

(Measurement of silica dispersibility)
A part of the obtained vulcanized rubber sheet was cut out, and the silica dispersibility was evaluated by performing 3D-SEM measurement under the following conditions using a focused ion / electron beam processing device (FIB-SEM device).
FIB-SEM device: FEI Helios 660
FIB processing conditions: Acceleration voltage 30kV
SEM observation conditions: Acceleration voltage 2kV
Processing area: 5 μm x 5 μm
Slice Step: 10 nm
Number of slices: 300 Sample tilt angle: 52 °

A 3D image can be obtained by superimposing the images obtained by observation (300 images in total) and performing three-dimensional reconstruction. 1 and 2 show a plan photograph of the central part of the sample before the three-dimensional reconstruction. In the figure, the black part represents rubber and the white part represents silica. In the vulcanized rubber sheet of Production Example 1 (FIG. 1), the area of the portion where silica was not dispersed was large. On the other hand, in the vulcanized rubber sheet of Production Example 2 (FIG. 2), silica was dispersed substantially uniformly throughout the photograph. That is, by using the rubber composition of the present embodiment, the dispersibility of silica in the vulcanized rubber sheet was improved.

Claims (4)

A method for producing a rubber composition containing a rubber latex (A) and silica particles (B).
The rubber composition uses 20 to 200 parts by mass (solid content equivalent) of the silica particles (B) with respect to 100 parts by mass (solid content equivalent) of the rubber latex (A), and is a water-soluble polymer compound. The amount of (C) used is 0.05 to 10 parts by mass (in terms of solid content), and the amount of coagulant (D) used is less than 10 parts by mass (in terms of solid content).
The coagulant (D) is an alkali metal, an alkaline earth metal or an aluminum sulfate or chloride.
The water-soluble polymer compound (C) contains a polyalkylene oxide and contains.
The coagulation step of contacting the rubber latex (A) and the silica particles (B) with the water-soluble polymer compound (C) or the water-soluble polymer compound (C) with the coagulant (D) is included.
A method in which the coagulation step includes any of the following conditions (1) to (6).
(1) Part or all of the water-soluble polymer compound (C) is added at the same time as or before the time when the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated. throw into.
(2) The water-soluble polymer compound (2) at the same time as or before the time when the total amount of the rubber latex (A), the total amount of the silica particles (B), and the total amount of the coagulant (D) are added to the raw material system to be co-coagulated. Add a part or all of C).
(3) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is charged.
(4) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are added to the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is added, and then the coagulant (D) is added. ) Is added.
(5) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) and the total amount of the coagulant (D) are simultaneously charged. do.
(6) After adding the total amount of the rubber latex (A) and the total amount of the silica particles (B) to the raw material system to be co-coagulated, the total amount of the coagulant (D) is added, and then the water-soluble polymer compound (C) is added. ) Is added. Before the amount of the coagulant (D) used exceeds 0 and the rubber latex (A) and the silica particles (B) are brought into contact with the coagulant (D), the water-soluble polymer compound (C) and the coagulant (D) are used. The method according to claim 1, wherein the rubber latex (A) and the silica particles (B) are brought into contact with the coagulant (D) in the presence of the water-soluble polymer compound (C). The method according to claim 1 or 2, wherein the pH of the filtrate when the co-coagulated product co-coagulated in the co-coagulation step is filtered is 6.5 to 10.0. A method for improving the yield ratio of silica in a rubber composition.
The amount of silica particles (B) used is 20 to 200 parts by mass (in terms of solid content) with respect to 100 parts by mass (in terms of solid content) of the rubber latex (A), and the amount of water-soluble polymer compound (C) used. Is 0.05 to 10 parts by mass (in terms of solid content), and the amount of the coagulant (D) used is less than 10 parts by mass (in terms of solid content).
The coagulant (D) is an alkali metal, an alkaline earth metal or an aluminum sulfate or chloride.
The water-soluble polymer compound (C) contains a polyalkylene oxide and contains.
The coagulation step of contacting the rubber latex (A) and the silica particles (B) with the water-soluble polymer compound (C) or the water-soluble polymer compound (C) with the coagulant (D) is included.
A method in which the coagulation step includes any of the following conditions (1) to (6).
(1) Part or all of the water-soluble polymer compound (C) is added at the same time as or before the time when the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated. throw into.
(2) The water-soluble polymer compound (2) at the same time as or before the time when the total amount of the rubber latex (A), the total amount of the silica particles (B), and the total amount of the coagulant (D) are added to the raw material system to be co-coagulated. Add a part or all of C).
(3) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is charged.
(4) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are added to the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) is added, and then the coagulant (D) is added. ) Is added.
(5) After the total amount of the rubber latex (A) and the total amount of the silica particles (B) are charged into the raw material system to be co-coagulated, the total amount of the water-soluble polymer compound (C) and the total amount of the coagulant (D) are simultaneously charged. do.
(6) After adding the total amount of the rubber latex (A) and the total amount of the silica particles (B) to the raw material system to be co-coagulated, the total amount of the coagulant (D) is added, and then the water-soluble polymer compound (C) is added. ) Is added.

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