JP5524810B2 - Composite, production method thereof, rubber composition and pneumatic tire - Google Patents

Description

The present invention relates to a composite and a method for producing the same, a rubber composition containing the composite, and a pneumatic tire using the rubber composition.

Conventionally, the fuel consumption of a vehicle has been reduced by reducing tire rolling resistance and suppressing heat generation. In recent years, the demand for lower fuel consumption has increased, and the demand for lower fuel consumption by improving treads with a high occupation ratio in tires is particularly large. In recent years, a reduction in fuel consumption is required not only for passenger car tires but also for heavy duty tires for trucks and buses, and at the same time, it is important to improve wear resistance. In addition to the tread, there is an increasing demand for lower fuel consumption for other members such as sidewalls.

Known methods for satisfying the low heat build-up of the rubber composition include a method using a low reinforcing filler, a method for reducing the content of the reinforcing filler, and the like. However, such low fuel consumption has the problem that the rubber composition's reinforcing properties are reduced, resulting in a decrease in wear resistance and fracture performance, and high fuel efficiency (low rolling resistance) and high wear resistance. It has been difficult to achieve both compatibility and fracture performance.

Moreover, rolling resistance is reduced by using silica (filler) to reduce fuel consumption. Here, a kneading method in which solid rubber and dry silica (particle size of about 20 to 60 nm) are kneaded with a Banbury mixer or the like is widely used for the production of a rubber composition containing silica. However, since silica has a silanol group on the surface and is hydrophilic, it generally has low affinity with rubber that exhibits hydrophobicity and strong self-aggregation properties. Therefore, it is difficult to disperse uniformly in rubber. Absent. In particular, fine particle silica having a particle size of less than 20 nm tends to increase the surface area of the particles and further facilitate aggregation.

Patent Document 1 discloses a method for producing a composite by mixing rubber latex with fine particle silica produced from water glass in a liquid state. However, here, only a production method using a normal natural rubber latex is disclosed, and there is still room for improvement in fuel efficiency. Also, with normal natural rubber latex, it is difficult to finely and uniformly disperse the fine particle silica in the rubber.

Furthermore, when natural rubber is used as a rubber component, Mooney viscosity is high and processability is poor compared to other synthetic rubbers, so usually after adding mastication agent and masticating, and reducing Mooney viscosity used. Therefore, productivity is reduced when natural rubber is used. Moreover, since the molecular chain of natural rubber is cleaved by mastication, there is also a problem that the characteristics (for example, high wear performance, low fuel consumption, and rubber strength) of the high molecular weight polymer inherently lost.

JP 2009-51955 A

An object of the present invention is to solve the above-mentioned problems and to provide a composite in which fine particle silica is uniformly dispersed in a rubber component and a method for producing the same. Another object of the present invention is to provide a rubber composition containing the composite that has both excellent fuel economy, wear resistance, and fracture performance while having excellent processability, and a pneumatic tire using the rubber composition. .

The present invention cleans the coagulate of a compounded latex in which a modified natural rubber latex and a fine particle silica dispersion having an average particle size of 100 nm or less produced from water glass are mixed, and adjusts the phosphorus content in the rubber to 200 ppm or less. It relates to the composite obtained.

The composite preferably has a nitrogen content in the rubber of 0.3% by mass or less. Moreover, it is preferable that the said composite body is 20 mass% or less of the gel content rate measured as a toluene insoluble content in rubber | gum. Further, the modified natural rubber latex is preferably obtained by saponifying natural rubber latex.

The average particle diameter of silica in the fine particle silica dispersion is preferably 20 nm or less. The fine particle silica dispersion is prepared by adjusting the pH of a water glass aqueous solution to 9 to 11 using an ion exchange resin, and the average particle diameter of silica in the dispersion is 20 nm or less. Is preferred.

The present invention includes a step (I) of preparing the compounded latex by mixing the modified natural rubber latex and the fine particle silica dispersion, a step (II) of coagulating the compounded latex obtained in the step (I), And a method for producing the above composite comprising the step (III) of washing the coagulated product obtained in the step (II) and adjusting the phosphorus content in the rubber to 200 ppm or less.

The present invention relates to a rubber composition containing the composite.
The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, a mixture of a modified natural rubber latex subjected to a modification treatment such as a saponification treatment and a fine particle silica dispersion produced from water glass is washed, and the phosphorus content in the rubber Therefore, fine particle silica can be uniformly dispersed in the composite. Therefore, by using the rubber composition containing the composite for a tire member such as a tread, it is possible to provide a pneumatic tire that achieves both good fuel economy, wear resistance, and fracture performance.

Moreover, since the said composite body is excellent also in workability, in the manufacture of the rubber composition using this composite body, favorable workability is obtained even if it does not perform a mastication process beforehand. Therefore, when mastication is not performed, the molecular chain of natural rubber is not cleaved by mastication, so that the characteristics of the high molecular weight polymer that is inherently maintained are maintained, and the fine particle silica is uniformly dispersed. Fuel efficiency, wear resistance, and breaking performance can be obtained.

<Composite>
The composite of the present invention cleans a coagulated product of a compounded latex in which a modified natural rubber latex and a fine particle silica dispersion having an average particle size of 100 nm or less produced from water glass are mixed, and the phosphorus content in the rubber is 200 ppm. It is obtained by adjusting to the following. That is, first, a natural rubber latex subjected to a modification treatment such as a saponification treatment and a dispersion of fine particle silica having an average particle diameter of 100 nm or less are prepared from water glass, and then the latex and the dispersion are in a liquid state. After the blended latex (mixed solution) produced by mixing in step 1 was prepared and coagulated, the obtained coagulated product was washed to reduce the amount of phosphorus in natural rubber, thereby improving the phosphorus amount to 200 ppm or less. A composite containing high quality natural rubber (HPNR) is produced. For this reason, a composite in which silica is finely dispersed in a modified natural rubber (HPNR) can be produced.

The composite of the present invention includes, for example, a step (I) of preparing a blended latex by mixing a modified natural rubber latex and a fine particle silica dispersion, and a step of coagulating the blended latex obtained in the step (I) ( II) and the step (III) of washing the coagulated product obtained in the step (II) and adjusting the phosphorus content in the rubber to 200 ppm or less, wherein the fine particle silica dispersion is produced from water glass It is suitably obtained by a production method which is a dispersion containing fine particle silica having an average particle diameter of 100 nm or less.

(Process (I))
The modified natural rubber latex used in step (I) can be prepared, for example, by saponifying natural rubber latex with an alkali. The saponification treatment can be performed by adding an alkali and, if necessary, a surfactant to natural rubber latex and allowing to stand at a predetermined temperature for a predetermined time. In addition, you may perform stirring etc. as needed. When the saponification treatment is performed, the phosphorus compound separated by saponification in the step (III) described later is washed and removed, so that the phosphorus content in the natural rubber contained in the prepared composite can be suppressed. Moreover, since the protein in the natural rubber is decomposed by the saponification treatment, the nitrogen content of the natural rubber can be suppressed. In the present invention, alkali can be added to natural rubber latex for saponification, but by adding it to natural rubber latex, there is an effect that saponification can be efficiently performed.

Natural rubber latex is collected as sap of heavy trees and contains rubber, water, proteins, lipids, inorganic salts, etc., and the gel content in rubber is thought to be based on the complex presence of various impurities. . In the present invention, raw latex produced by tapping a heavy tree or purified latex concentrated by centrifugation can be used. Furthermore, high ammonia latex to which ammonia is added by a conventional method may be used to prevent the progress of decay due to bacteria present in the raw rubber latex and to avoid coagulation of the latex.

Examples of the alkali used for the saponification treatment include sodium hydroxide, potassium hydroxide, calcium hydroxide, and an amine compound. From the viewpoint of the effect of the saponification treatment and the influence on the stability of the natural rubber latex, it is particularly hydroxylated. Sodium or potassium hydroxide is preferably used.

The amount of alkali added is not particularly limited, but the lower limit is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and the upper limit is 12 parts by mass or less with respect to 100 parts by mass of the solid content of natural rubber latex. Is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and particularly preferably 5 parts by mass or less. If the amount of alkali added is less than 0.1 parts by mass, saponification may take time. Conversely, if the amount of alkali added exceeds 12 parts by mass, the natural rubber latex may be destabilized.

As the surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant can be used. Examples of the anionic surfactant include carboxylic acid-based, sulfonic acid-based, sulfate ester-based and phosphate ester-based anionic surfactants. Examples of nonionic surfactants include nonionic surfactants such as polyoxyalkylene ethers, polyoxyalkylene esters, polyhydric alcohol fatty acid esters, sugar fatty acid esters, and alkyl polyglycosides. Examples of amphoteric surfactants include amphoteric surfactants such as amino acid type, betaine type, and amine oxide type. Among these, an anionic surfactant is preferable, and a sulfonic acid anionic surfactant is more preferable.

The addition amount of the surfactant is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and still more preferably 1.1 parts by mass or more with respect to 100 parts by mass of the solid content of the natural rubber latex. The amount added is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 3.5 parts by mass or less, and particularly preferably 3.0 parts by mass or less. If the addition amount of the surfactant is less than 0.01 parts by mass, the natural rubber latex may become unstable during the saponification treatment. On the other hand, if the amount of the surfactant added exceeds 6.0 parts by mass, the natural rubber latex may be overstabilized and coagulation may be difficult.

The temperature of the saponification treatment can be appropriately set within a range where the saponification reaction with alkali can proceed at a sufficient reaction rate and within a range where the natural rubber latex does not undergo alteration such as coagulation, but is usually 20 to 70 ° C. Preferably, 30-70 degreeC is more preferable. Further, the treatment time is 3 to 48 hours in consideration of both sufficient treatment and productivity improvement, depending on the treatment temperature when the treatment is performed with natural rubber latex standing. Is preferable, and 3 to 24 hours is more preferable.

In step (I), a fine particle silica dispersion having an average particle diameter of 100 nm or less produced from water glass is used. That is, silica is used by growing it as spherical fine particles, instead of using the raw water glass as it is. In this growth, it is more preferable to take a long ripening time and to make it spherical. When the spherical shape is obtained, the contact between the silica particles is minimized, the cohesive force is reduced, and the silica is easily dispersed.

The fine particle silica dispersion is preferably prepared by adjusting the pH of the aqueous water glass solution to 9-11.
The water glass is usually represented by a composition represented by the following formula.
Na ₂ O · nSiO ₂ · mH ₂ O
The coefficient n is a value represented by a molecular ratio of SiO ₂ / Na ₂ O, and is a range defined in JIS K 1408-1966 generally called a molar ratio. Although this coefficient n is not specifically limited, Preferably it is 2.1-3.3, More preferably, it is 3.1-3.3. When the coefficient n is 3.1 to 3.3, the silica component (in terms of SiO ₂ ) in the water glass increases, so that the efficiency of the composite treatment with rubber is improved.

In general, the water glass having the coefficient n of 3.1 to 3.3 is commercially available as Water Glass No. 3. The water glass which can be used for this invention is not limited to this, For example, No. 1-3 water glass prescribed | regulated to JISK1408, and other various grade products can be used.

By preparing an aqueous solution of water glass and adjusting the pH of the aqueous solution in the range of 9 to 11, a fine particle silica dispersion in which fine particle silica having an average particle diameter of 100 nm or less is dispersed can be prepared. When the pH is less than 9, gelation tends to occur, and when the pH exceeds 11, the fine particle silica tends to dissolve. More preferably, the pH is adjusted to a range of 9.5 to 10.5. The method for adjusting the pH to the range of 9 to 11 is not particularly limited, and can be carried out by a conventionally known method such as addition of an acid or alkali, use of an ion exchange resin, etc. Among them, a dispersion in which fine particle silica is more dispersed From the point that can be obtained, it is preferable to use an ion exchange resin.

Examples of the pH adjustment method using an ion exchange resin include a method of bringing an aqueous solution of water glass into contact with a cation exchange resin. Specifically, an aqueous solution of water glass diluted to a predetermined concentration is brought into contact with a cation exchange resin to be dealkalized, and if necessary, brought into contact with an OH type strongly basic anion exchange resin to deanion. Can be done by. Examples of the contacting method include a batch method in which a cation exchange resin is directly put into an aqueous solution of water glass and stirred and contacted, and a method in which an aqueous solution of water glass is passed through a column filled with the cation exchange resin. . As the cation exchange resin, an H-type strong acid cation exchange resin, a weak acid cation exchange resin, or the like can be used, and commercially available products include Amberlite IR120B, IR124, 200CT, IRC76, and FPC3500 manufactured by Organo Corporation. It is done. By the above method, sodium ions and the like in the water glass can be removed, so that silica particles in a more atomized state can be generated.

When adjusting the pH, the temperature of the aqueous solution of water glass is preferably adjusted to 10 to 90 ° C. If the temperature is less than 10 ° C., the production rate of fine-particle silica is slow, and if the temperature exceeds 90 ° C., water in the aqueous solution evaporates, and the concentration of water glass in the aqueous solution tends to become unstable. What is necessary is just to adjust the temperature of the said aqueous solution suitably, and 15-40 degreeC and 60-80 degreeC are mentioned as a preferable range, for example.

The reaction time is preferably in the range of 1 to 72 hours. If it is less than 1 hour, the production of fine-particle silica is not sufficient, and even if it exceeds 72 hours, the reaction has already ended, and there is a tendency that there is no further change. When making it react at room temperature, it is suitable to carry out for 6 to 24 hours on stirring conditions. Further, in order to be as close to a true sphere as possible, aging at a high temperature and a long time is good, and a temperature of 60 to 80 ° C. for 24 hours or more is preferable.

The concentration of the silica component (SiO ₂ ) contained in the aqueous water glass solution is preferably in the range of 1 to 30% by mass. When the concentration is less than 1% by mass, a large amount of water glass aqueous solution is required for complexing with the rubber latex, and when it exceeds 30% by mass, silica aggregation tends to occur. The concentration of the silica component is more preferably in the range of 1.5 to 20% by mass, still more preferably 2 to 8% by mass. However, when water glass that has been subjected to desalting treatment is used, the upper limit is not particularly limited because silica aggregation is unlikely to occur.

The average particle diameter of silica contained in the fine particle silica dispersion is 100 nm or less, preferably 30 nm or less, more preferably 20 nm or less, still more preferably 15 nm or less, and particularly preferably 10 nm or less. Here, the size of the average particle diameter can be arbitrarily adjusted by adjusting the pH of the aqueous solution, the concentration of the silica component, the reaction temperature, the reaction time, and the like. In the present invention, by using a dispersion of modified natural rubber latex and spherical silica fine particles, a composite in which silica is finely dispersed can be obtained even if it is fine particle silica.

In this specification, transmission electron microscope (TEM) observation is used as a method for measuring the average particle size of the fine particle silica. Specifically, the microparticles are photographed with a transmission electron microscope. If the shape of the microparticles is spherical, the diameter of the sphere is the particle diameter, and if it is needle-shaped or rod-shaped, the minor diameter is the particle diameter. In this case, the average particle diameter from the center is defined as the particle diameter, and the average value of the particle diameters of 100 fine particles is defined as the average particle diameter.

In the step (I), the modified natural rubber latex and the fine particle silica dispersion obtained by the above-mentioned production method are mixed by a known method, and then sufficiently stirred until the compounded latex becomes a uniform solution. A blended latex (mixed solution) is prepared. The modified natural rubber latex preferably has a rubber solid content of 10 to 70% by mass.

Further, in the mixing step, the modified natural rubber 100 parts by weight with respect to (the solid content), silica it is preferable to mix a fine particle silica dispersion such that 5 to 150 parts by weight (SiO ₂ conversion). If the amount is less than 5 parts by mass, the amount of silica may be reduced when used as a master batch. When it exceeds 150 parts by mass, it is difficult to obtain uniform dispersion of silica in the rubber latex, and the uniform dispersion of silica in the rubber composition after coagulating the compounded latex tends to decrease. More preferably, it is 5-120 mass parts, More preferably, it is 10-100 mass parts.

(Process (II))
In step (II), the compounded latex obtained in step (I) is coagulated (aggregated) to produce a composite in which fine particle silica is uniformly dispersed in rubber. Solidification of compounded latex includes acid coagulation, salt coagulation, methanol coagulation, coagulation with polymer coagulant, etc. In order to coagulate rubber latex and silica by uniform dispersion, acid coagulation, salt coagulation, polymer coagulation Coagulation with an agent or a combination thereof is preferred.

Examples of the acid for coagulation include sulfuric acid, hydrochloric acid, formic acid, acetic acid and the like.

Examples of the salt include monovalent to trivalent metal salts (such as calcium salts such as sodium chloride, magnesium chloride, calcium nitrate, and calcium chloride). When the amount of silica is small relative to the rubber latex, the type of metal salt is not limited, but when the amount of silica is large, monovalent and divalent metal salts such as sodium chloride and magnesium chloride are preferred. Here, when a trivalent metal salt is used, the cohesive force between silicas is too strong, and finally it is difficult to be finely dispersed.

Further, as the polymer flocculant, any of anionic, cationic and nonionic polymer flocculants can be used. Examples of the anionic polymer flocculant include sodium alginate, CMC-Na, sodium polyacrylate, acrylamide-sodium acrylate copolymer, polyacrylamide partial hydrolyzate, and the like. Examples of the cationic polymer flocculant include polymethacrylate ester polymer flocculant, water-soluble aniline resin hydrochloride, polyethyleneimine, polyamine, polydiallyldimethylammonium chloride, chitosan, hexamethylenediamine-epichlorohydrin condensate, polyvinyl Examples include imidazoline, polyalkylamino (meth) acrylate, polyacrylamide Mannich modified product, dimethylaminoethyl acrylate-acrylamide copolymer, and the like. Examples of nonionic polymer flocculants include starch, guar gum, gelatin, polyacrylamide, and polyethylene oxide.

Especially, coagulation | solidification of mixing | blending latex adjusts the pH of mixing | blending latex to 5-9 (preferably 6-8, more preferably 6.5-7.5) by addition of an acid or a salt, and solidifies solid content. It is preferable to be implemented. Thereby, a composite in which silica is finely dispersed can be suitably produced.

(Step (III))
In step (III), the coagulated product (aggregate containing aggregated rubber and silica) obtained in step (II) is washed, and the phosphorus content in the rubber (natural rubber) is adjusted (reduced) to 200 ppm or less. By performing the washing treatment after the saponification treatment, the amount of phosphorus in the natural rubber in the coagulated product can be reduced to 200 ppm or less. As the washing method in step (III), for example, a method of repeatedly washing with water until the phosphorus content relative to the rubber content is 200 ppm or less, a method of centrifuging after diluting the rubber content with water, or standing still. One method is to lift the rubber and discharge only the water phase. When centrifuging, it may be first diluted with water so that the rubber content of the natural rubber latex is 5 to 40% by mass, preferably 10 to 30% by mass, and then centrifuged at 5000 to 10000 rpm for 1 to 60 minutes. The washing may be repeated until the desired phosphorus content is reached. Also, when the rubber is floated by standing, the addition of water and stirring may be repeated until the desired phosphorus content is obtained.

After washing, it is usually dried by a known method (such as an oven). When the rubber is kneaded with a biaxial roll or Banbury after drying, a composite containing modified natural rubber (HPNR) having a phosphorus content of 200 ppm or less and silica is obtained. In the above composite, silica is uniformly dispersed in a rubber matrix and can be used as a master batch. In addition, the said composite_body | complex may contain another component in the range which does not inhibit the effect of this invention.

The modified natural rubber contained in the composite has a phosphorus content of 200 ppm or less. If it exceeds 200 ppm, the Mooney viscosity will increase during storage and the processability will deteriorate, and excellent fuel efficiency will not be obtained, and there will be a tendency that the performance, wear resistance and fracture performance cannot be improved in a well-balanced manner. The phosphorus content is preferably 150 ppm or less, and more preferably 120 ppm or less. Here, the phosphorus content can be measured by a conventional method such as ICP emission analysis. Phosphorus is derived from phospholipids (phosphorus compounds).

The nitrogen content of the modified natural rubber contained in the composite is preferably 0.3% by mass or less, more preferably 0.15% by mass or less. If it exceeds 0.3% by mass, the Mooney viscosity will increase during storage and the processability will deteriorate, and excellent fuel efficiency will not be obtained, and the performance and wear resistance and fracture performance tend not to be improved in a well-balanced manner. There is. Nitrogen is derived from proteins. The nitrogen content can be measured by a conventional method such as Kjeldahl method.

The modified natural rubber contained in the composite preferably has a gel content measured as a toluene insoluble content of 20% by mass or less, and more preferably 15% by mass or less. If it exceeds 20% by mass, the Mooney viscosity tends to increase and the processability tends to deteriorate. The gel content means a value measured as an insoluble content with respect to toluene which is a nonpolar solvent, and may be simply referred to as “gel content” or “gel content” below. The measuring method of the content rate of a gel part is as follows. First, a natural rubber sample is soaked in dehydrated toluene, light-shielded in the dark and left for 1 week, and then the toluene solution is centrifuged at 1.3 × 10 ⁵ rpm for 30 minutes to obtain an insoluble gel content and a toluene soluble content. Isolate. Methanol is added to the insoluble gel and solidified, and then dried, and the gel content is determined from the ratio between the mass of the gel and the original mass of the sample.

<Rubber composition>
The rubber composition of the present invention contains the above composite. Thereby, the excellent reinforcement property is exhibited. The composite can be used as a master batch. Since the composite has the silica uniformly dispersed in the rubber, the silica can be uniformly dispersed in the rubber composition of the present invention obtained when mixed with other rubber components and a rubber compounding agent. Therefore, fuel economy, wear resistance, and breaking performance are improved in a well-balanced manner.

The silica content (in terms of SiO ₂ ) of the composite contained in the rubber composition is preferably 10 parts by mass or more, more preferably 100 parts by mass (solid content) relative to 100 parts by mass (solid content) of the modified natural rubber in the composite. 20 parts by mass or more, more preferably 30 parts by mass or more. If the amount is less than 10 parts by mass, sufficient reinforcement may not be obtained. The silica content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less. When it exceeds 120 parts by mass, there is a possibility that sufficient low fuel consumption and wear resistance may not be obtained.

The rubber composition of the present invention may contain a rubber component other than the modified natural rubber. Examples of other rubber components include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), Examples include chloroprene rubber (CR) and acrylonitrile butadiene rubber (NBR).

About the rubber component (modified natural rubber and other rubber components in the composite) contained in the rubber composition, the content of the modified natural rubber (solid content) contained in the composite in 100% by mass of the rubber component The amount is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. If the amount is less than 60% by mass, sufficient fuel economy and wear resistance may not be obtained.

In addition to the above materials, the rubber composition of the present invention includes carbon black, silica, silane coupling agent, zinc oxide, stearic acid, anti-aging agent, sulfur, vulcanization, which are generally used in the tire industry. Various materials such as an accelerator may be appropriately blended.

In addition to the composite silica, general silica may be added during kneading. Examples of the silica include silica produced by a dry method or a wet method, but the method for producing silica is not particularly limited.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 30 m ² / g or more, more preferably 50 m ² / g or more, and still more preferably 100 m ² / g or more. If it is less than 30 m ² / g, the reinforcing effect tends to be small. The _N 2 SA of the silica is 500m or less preferably ² / g, more preferably not more than 400 meters ² / g, more preferably not more than 250m ² / g. When the N ₂ SA of silica exceeds 500 m ² / g, the dispersibility tends to decrease and the exothermic property of the rubber composition tends to increase. In addition, the nitrogen adsorption specific surface area by the BET method of a silica can be measured by the method based on ASTM-D-4820-93.

In the rubber composition of the present invention, it is preferable to use a silane coupling agent in combination. Thereby, reinforcement can be further improved.
The silane coupling agent is not particularly limited, and those conventionally used in combination with silica in the tire industry can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) Tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide Bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3- Trimet Such as sulfides such as silyl (propyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, mercapto such as 3-mercaptopropyltrimethoxysilane, vinyltriethoxysilane, etc. Vinyl-based, amino-based such as 3-aminopropyltriethoxysilane, glycidoxy-based such as γ-glycidoxypropyltriethoxysilane, nitro-based such as 3-nitropropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, etc. A chloro system etc. are mentioned.

In the rubber composition, the content of the silane coupling agent is preferably 4 parts by mass or more, and more preferably 6 parts by mass or more with respect to 100 parts by mass of the total amount of the composite and the silica contained therein. If it is less than 4 parts by mass, it does not sufficiently react with silica and the reinforcing property tends not to be improved. Further, the content of the silane coupling agent is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less. If it exceeds 20 parts by mass, the effect of improving the rubber strength and wear resistance due to the blending of the silane coupling agent is not seen, and the cost tends to increase.

As a method for producing the rubber composition of the present invention, known methods can be used. For example, the above components are kneaded using a rubber kneader such as an open roll, a Banbury mixer, a closed kneader, and then added. It can be manufactured by a method of sulfurating. Usually, when natural rubber is used, the mastication step is first performed. However, in the present invention, since the above composite is used, the processability of the rubber composition is good even without mastication.

The rubber composition can be applied to each member of a tire, and among them, it can be suitably used for a tread and a sidewall.

<Pneumatic tire>
The rubber composition of the present invention is suitably applied to a pneumatic tire. Since a composite in which silica is finely dispersed is used, excellent reinforcing properties are exhibited, and low heat build-up, wear resistance, and fracture performance can be satisfactorily achieved.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of each member of the tire at an unvulcanized stage and molded by a normal method on a tire molding machine. After forming an unvulcanized tire by heating, the tire can be manufactured by heating and pressing in a vulcanizer.

Moreover, the pneumatic tire of the present invention can be suitably used for passenger cars, trucks and buses, and low-pollution vehicles (eco-cars) compatible with global environmental conservation.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.
The various chemicals used in the examples are described below.
Natural rubber latex: Field latex obtained from Taitex Co., Ltd. Surfactant: Emal-E manufactured by Kao Corporation
NaOH: NaOH manufactured by Wako Pure Chemical Industries, Ltd.
Water glass: Water glass No. 3 manufactured by Fuji Chemical Co., Ltd. (Na ₂ O.nSiO ₂ .mH ₂ O, n = 3.2, silica component (SiO ₂ equivalent) content: 28% by mass)
Natural rubber: TSR
Silica (1): Ultrasil VN3 (N ₂ SA: 175 m ² / g) manufactured by EVONIK-DEGUSSA
Silica (2): Premium 200MP (N ₂ SA: 200 m ² / g) manufactured by Rhodia
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by EVONIK-DEGUSSA
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Anti-aging agent manufactured by NOF Corporation: Nocrack 6C (N- (1,3- Dimethylbutyl) -N′-phenyl-p-phenylenediamine)
Sulfur: powder sulfur vulcanization accelerator NS manufactured by Tsurumi Chemical Co., Ltd. NS: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator D: Noxeller D (N, N′-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Preparation of saponified natural rubber latex with alkali)
After adjusting the solid rubber latex solids concentration (DRC) to 30% (w / v), 1000 g of natural rubber latex was added with 10 g of Emal-E and 20 g of NaOH, followed by saponification at room temperature for 48 hours. Natural rubber latex was obtained.

(Production of saponified natural rubber (solid rubber))
After adding water to the saponified natural rubber latex obtained above to adjust the solid content concentration (DRC) to 15% (w / v), formic acid is added while slowly stirring to adjust the pH to 4.0-4. .5 and agglomerated. The agglomerated rubber was pulverized, washed repeatedly with 1000 ml of water, and then dried at 110 ° C. for 2 hours to obtain a saponified natural rubber (solid rubber).

(Preparation of fine particle silica dispersions (1) and (2))
A water glass aqueous solution having a silica component content (concentration) of 2% by mass is prepared using water glass, adjusted to pH 10 and stirred at 25 ° C. for 10 to 24 hours to obtain a fine particle silica dispersion (1) and (2) was obtained. The pH was adjusted with sulfuric acid.
Observation of the TEM photograph confirmed that silica having an average particle size of about 20 nm (fine particle silica dispersion (1)) and silica having an average particle size of about 15 nm (fine particle silica dispersion (2)) were obtained.

(Preparation of fine particle silica dispersion (3))
A water glass aqueous solution having a silica component content (concentration) of 2% by mass was prepared using water glass, adjusted to pH 10 and stirred at 80 ° C. for 24 hours to obtain a fine particle silica dispersion (3). . The pH was adjusted using an H-type strongly acidic cation exchange resin (IR120B manufactured by Organo Corporation).
It was confirmed by observation of the TEM photograph that silica having an average particle diameter of about 10 nm was obtained.

(Preparation of compounded latex, coagulation, preparation of composite)
Saponified natural rubber latex or natural rubber latex was mixed with the fine particle silica dispersions (1) to (3) in a blending amount as shown in Table 1 to prepare a blended latex. After sufficiently stirring until the blended latex became uniform, the blended latex was adjusted to pH 7 with sulfuric acid and coagulated. The obtained solid was filtered to recover the rubber, washed with pure water and dried to obtain composites (A) to (G).

The modified natural rubber contained in the composites (A) to (D), the natural rubber contained in the composites (E) to (G), the saponified natural rubber (solid rubber), and the TSR are as follows. , Nitrogen content, phosphorus content, gel content were measured.
The results are shown in Table 2.

(Measurement of nitrogen content)
The nitrogen content was measured using CHN CORDER MT-5 (manufactured by Yanaco Analytical Industries). For the measurement, first, a calibration curve for determining the nitrogen content was prepared using antipyrine as a standard substance. Next, about 10 mg of each composite, saponified natural rubber or TSR sample was weighed, and an average value was obtained from the measurement results of three times to obtain the nitrogen content of the sample.

(Measurement of phosphorus content)
The phosphorus content was determined using an ICP emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation).

(Measurement of gel content)
A raw rubber sample 70.00 mg cut to 1 mm × 1 mm was weighed, 35 mL of toluene was added thereto, and the mixture was allowed to stand in a cool dark place for 1 week. Subsequently, centrifugation was performed to precipitate a gel component insoluble in toluene, the soluble component of the supernatant was removed, and only the gel component was solidified with methanol, and then dried and the mass was measured. The gel content (%) was determined by the following formula.
Gel content (mass%) = [mass mg after drying / mg of initial sample] × 100

As shown in Table 2, in the HPNR forming the composites (A) to (D), compared to the composites (E) to (G), saponified natural rubber, TSR, phosphorus content, nitrogen content, The gel content was reduced.

(Production of rubber test piece)
According to the formulation shown in Tables 3 to 4, chemicals other than sulfur and a vulcanization accelerator were kneaded using a 1.7 L Banbury mixer. Next, using a roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized product.
In Comparative Examples 4, 5, and 8 using TSR, 0.4 part by mass of a peptizer was added to 100 parts by mass of the rubber component of TSR, and kneaded in advance using a 1.7 L Banbury mixer. Went. On the other hand, in Examples 1 to 3 and Comparative Examples 1 to 3, 6, 7, and 9, natural rubber was not masticated.
Each obtained unvulcanized rubber composition and vulcanizate were evaluated as follows, and the results are shown in Tables 3-4.

(Measurement of Mooney viscosity)
About the obtained unvulcanized rubber composition, it measured at 130 degreeC according to the measuring method of the Mooney viscosity based on JISK6300. The Mooney viscosity (ML _{1 + 4} ) of Comparative Example 4 or 8 was set to 100, and the index was expressed by the following formula (Mooney viscosity index). The larger the index, the lower the Mooney viscosity and the better the processability.
_{(ML 1 +} 4 of Comparative Example 4) (Mooney viscosity index) = / _{(ML 1 + 4} of Examples 1 to 3 and Comparative Examples 1 to 7) × 100
/ _{(ML 1 + 4} of Example 4 and Comparative Example 8 to 9) _{(ML 1 +} 4 of Comparative Example 8) (Mooney viscosity index) = × 100

(Rolling resistance)
Loss tangent (tan δ) of each compound (vulcanized product) using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of a temperature of 50 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. Was measured, and the loss coefficient tan δ of Comparative Example 4 or 8 was taken as 100, and an index was expressed by the following formula (rolling resistance index). The larger the index, the better the rolling resistance characteristics (low fuel consumption).
(Rolling resistance index) = (tan δ of Comparative Example 4) / (tan δ of Examples 1 to 3 and Comparative Examples 1 to 7) × 100
(Rolling resistance index) = (tan δ of Comparative Example 8) / (tan δ of Example 4 and Comparative Examples 8 to 9) × 100

(Abrasion test)
Using a Lambourn abrasion tester, the Lambourn abrasion amount was measured under the conditions of a temperature of 20 ° C., a slip ratio of 20% and a test time of 2 minutes. Further, the volume loss amount was calculated from the measured lamborn wear amount, the lamborn wear index of Comparative Example 4 or 8 was set to 100, and the volume loss amount of each compound (vulcanized product) was displayed as an index according to the following calculation formula. In addition, it shows that it is excellent in abrasion resistance, so that a Lambourn abrasion index is large.
(Lambourn wear index) = (volume loss amount of comparative example 4) / (volume loss amount of examples 1 to 3 and comparative examples 1 to 7) × 100
(Lambourn wear index) = (volume loss amount of comparative example 8) / (volume loss amount of example 4 and comparative examples 8 to 9) × 100

(Rubber strength)
A vulcanized product was used to prepare a No. 3 dumbbell-shaped rubber test piece, which was subjected to a tensile test according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. The time elongation (EB) was measured, and the product (TB × EB) was calculated. The rubber strength (TB × EB) of each compound (vulcanized product) was indicated by an index according to the following formula. In addition, it shows that it is excellent in fracture performance, so that a rubber | gum strength index is large.
(Rubber strength index) = (TB × EB of Examples 1 to 3 and Comparative Examples 1 to 7) / (TB × EB of Comparative Example 4) × 100
(Rubber strength index) = (TB × EB of Example 4 and Comparative Examples 8 to 9) / (TB × EB of Comparative Example 8) × 100

From the results of Table 3, a rubber composition using a composite containing fine modified silica produced from water glass with a modified natural rubber having a low phosphorus content in Examples 1 to 3 is a rubber having a TSR crushed. Compared to the rubber compositions of Comparative Examples 4 and 5 prepared by a normal kneading process using silica, the processability was excellent and the fuel efficiency was excellent even though it was not broken.

Further, in the examples, since the composite was produced by the above-described production method, the dispersibility of silica was greatly improved, and the wear resistance performance and the fracture performance were remarkably improved. In addition, the wear resistance and fracture performance were greatly improved as compared with the rubber compositions of Comparative Examples 6 and 7 prepared by a normal kneading process using saponified natural rubber and silica. Furthermore, all the performances were compared with the rubber compositions of Comparative Examples 1 to 3 using a composite obtained from a compounded latex obtained by mixing a normal natural rubber latex and a fine particle silica dispersion produced from water glass. Was excellent.
Further, from the results of Table 4, the same tendency was obtained even when the amount of silica was 75 parts by mass.

Claims (12)

It is obtained by washing a coagulated product of a compounded latex obtained by mixing a modified natural rubber latex and a fine particle silica dispersion having an average particle size of 100 nm or less produced from water glass, and adjusting the phosphorus content in the rubber to 200 ppm or less. Complex. The composite according to claim 1, wherein the nitrogen content in the rubber is 0.3 mass% or less. The composite according to claim 1 or 2, wherein the gel content measured as a toluene insoluble matter in the rubber is 20% by mass or less. The composite according to any one of claims 1 to 3, wherein the modified natural rubber latex is obtained by saponifying natural rubber latex. The composite according to any one of claims 1 to 4, wherein the fine particle silica dispersion has an average particle diameter of silica of 20 nm or less. The fine particle silica dispersion is prepared by adjusting the pH of a water glass aqueous solution to 9 to 11 using an ion exchange resin, and the average particle diameter of silica in the dispersion is 20 nm or less. Item 6. The complex according to any one of Items 1 to 5. The complex according to claim 6, wherein the temperature of the aqueous water glass solution at the time of pH adjustment is 10 to 90 ° C and the reaction time is 1 to 72 hours. The step (I) of preparing the compounded latex by mixing the modified natural rubber latex and the fine particle silica dispersion, the step (II) of coagulating the compounded latex obtained in the step (I), and the step ( and washing the obtained coagulum in II), the production method of the complex according to any one of claims 1 to 7 including the step (III) for adjusting the phosphorus content in the rubber 200ppm or less. Rubber composition comprising a complex according to any one of claims 1-7. The step (I) of preparing the compounded latex by mixing the modified natural rubber latex and the fine particle silica dispersion, the step (II) of coagulating the compounded latex obtained in the step (I), and the step (II) The solidified product obtained in step (3) is washed, and the phosphorus content in the rubber is adjusted to 200 ppm or less, and any one of claims 1 to 7 obtained through steps (I) to (III). The method for producing a rubber composition according to claim 9, comprising a step (IV) of kneading the composite according to claim 1. A pneumatic tire produced using the rubber composition according to claim 9 . The step (I) of preparing the compounded latex by mixing the modified natural rubber latex and the fine particle silica dispersion, the step (II) of coagulating the compounded latex obtained in the step (I), and the step (II) The solidified product obtained in step (3) is washed, and the phosphorus content in the rubber is adjusted to 200 ppm or less, and any one of claims 1 to 7 obtained through steps (I) to (III). The manufacturing method of the pneumatic tire of Claim 11 including the process (IV) of kneading the composite_body | complex of crab.