JP2012207088A - Rubber wet master batch and method of producing the same, rubber composition, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a rubber wet master batch, which prevents a filler from aggregating again with time by dispersing the filler uniformly, thereby reducing the amount of coagulants used such as a strong acid.SOLUTION: In the method of producing the rubber wet master batch, at least the filler, a dispersing solvent, and a rubber latex solution are used as raw materials. The method includes: a step (I) of dispersing the filler in the dispersing solvent to produce a filler-containing slurry solution; a step (II) of mixing the filler-containing slurry solution with the rubber latex solution to produce a filler-containing rubber latex solution; and a step (III) of adding tannin to the filler-containing rubber latex solution, then coagulating the rubber latex solution having the tannin added thereto, and drying the resultant coagulation.

Description

  The present invention relates to a rubber wet masterbatch using at least a filler, a dispersion solvent, and a rubber latex solution, a method for producing the same, a rubber composition, and a pneumatic tire.

  Conventionally, in the rubber industry, it is known to use a natural rubber wet masterbatch in order to improve the processability and dispersibility of fillers when producing rubber compositions containing fillers such as carbon black. (For example, Patent Document 1 below). This is because the filler and the dispersion solvent are mixed in advance at a certain ratio, and the slurry solution containing filler in which the filler is dispersed in the dispersion solvent by mechanical force and the natural rubber latex are mixed in the liquid phase. Thereafter, a coagulant made of a strong acid such as formic acid or sulfuric acid or a salt such as aluminum chloride is used, and finally a dehydration and drying is performed through a coagulation step of coagulating the natural rubber latex. In such a coagulation step, the natural rubber latex is generally coagulated in the natural rubber latex by neutralizing ammonia acting as a latex stabilizer with the coagulant and precipitating it as an ammonium salt. Since the obtained natural rubber coagulated product contains precipitated ammonium salt, it is necessary to remove the ammonium salt by repeatedly washing the natural rubber coagulated product. If such washing is insufficient, it has been a problem that it adversely affects the adhesiveness, heat build-up and reinforcing properties of vulcanized rubber made from natural rubber coagulum. On the other hand, it is preferable to perform sufficient washing in consideration of the physical properties of the vulcanized rubber. However, since much time and labor are consumed, the productivity is deteriorated. Moreover, since the waste liquid after washing contains a strong acid, there has been a concern about adverse environmental effects during disposal.

  The following Patent Documents 2 to 5 describe a method of blending a tea extract with a tire rubber composition for the purpose of improving anti-aging performance. Patent Document 6 below describes a method of blending a calcium compound or tannic acid with a rubber composition containing an organic acid cobalt for the purpose of maintaining initial adhesive strength and improving wet heat stability. . However, the tea extract or tannic acid blended in these documents is not used as a coagulant for rubber latex solutions.

  By the way, when manufacturing a natural rubber wet rubber masterbatch, paying attention to the dispersion state of the carbon black slurry solution that is the raw material, and optimizing the particle size distribution of the carbon black, the physical properties of the final vulcanized rubber can be improved. Techniques to try have been reported. For example, in Patent Document 7 below, a method for producing a natural rubber wet masterbatch comprising a step of mixing a slurry solution in which a filler such as carbon black is dispersed in water in advance and a natural rubber latex, Describes a method for producing a natural rubber masterbatch in which the particle size distribution of the filler is adjusted to 90 volume% (D90) to 30 μm or less. In addition, as a natural rubber wet masterbatch rubber composition, in Patent Document 8 below, a natural rubber wet masterbatch obtained by a production method in which a slurry solution in which carbon black is previously dispersed in water and a natural rubber latex is mixed is used. A rubber composition is described.

JP 2000-507892 A JP 2010-31260 A JP 2010-31261 A JP 2010-31262 A JP 2010-242072 A JP-A-57-98532 JP 2004-99625 A JP 2006-213804 A

  However, as a result of intensive studies by the present inventors, in the vulcanized rubber of the natural rubber wet masterbatch rubber composition obtained by the production method described in the above-mentioned patent document, in terms of heat generation, strength, and fatigue resistance It turns out that there is room for further improvement. In addition, the manufacturing methods described in these patent documents have a step of mixing a slurry solution in which carbon black is previously dispersed in water with a natural rubber latex. When time is required, re-aggregation of filler such as carbon black is likely to proceed in the slurry solution, and re-aggregation of the filler is likely to proceed even after making a natural rubber wet masterbatch. It has been found that local carbon black dispersion failure may occur. When the filler reagglomerates in the slurry solution and also in the natural rubber wet masterbatch and local carbon black dispersion occurs, the physical properties deteriorate in terms of heat generation, strength, and fatigue resistance. Is seen. Therefore, the rubber wet masterbatch production method has room for further improvement in view of the physical properties of the final vulcanized rubber.

  The present invention has been made in view of the above circumstances, and its purpose is to uniformly disperse the filler, suppress reaggregation of the filler over time, and reduce the amount of coagulant such as strong acid used. Another object of the present invention is to provide a method for producing a rubber wet masterbatch. Further, the present invention is a rubber wet masterbatch in which the filler is uniformly dispersed, re-aggregation of the filler over time is suppressed, and has excellent anti-aging properties and storage stability. Another object of the present invention is to provide a rubber wet masterbatch that is a raw material for vulcanized rubber having excellent rubber strength.

  The above object can be achieved by the present invention as described below. That is, the method for producing a rubber wet masterbatch according to the present invention is a method for producing a rubber wet masterbatch using at least a filler, a dispersion solvent, and a rubber latex solution as raw materials, and the filler is contained in the dispersion solvent. Step (I) for producing a filler-containing slurry solution by dispersing, Step (II) for producing a filler-containing rubber latex solution by mixing the filler-containing slurry solution and the rubber latex solution, Adding tannin to the filler-containing rubber latex solution, coagulating it, and then drying (III).

  According to the above production method, the rubber composition containing the rubber wet masterbatch is produced via each step (I) to step (III), so that the dispersibility of the filler in the rubber composition is improved. Excellent and exothermic.

  Furthermore, in the manufacturing method described above, since tannin is used as a coagulant in the solidification / drying step (III), compared to a coagulant composed of a strong acid such as formic acid or sulfuric acid or a salt such as aluminum chloride, In addition, the rubber solidified washing step can be omitted or simplified. Furthermore, since the rubber wet masterbatch containing tannin is excellent in anti-aging properties, an increase in rubber viscosity during storage can be suppressed. For this reason, the rubber wet masterbatch obtained by the said manufacturing method is excellent in anti-aging property and storage stability.

  In the manufacturing method, when the step (I) disperses the filler in the dispersion solvent, the filler to which rubber latex particles are adhered is added by adding at least a part of the rubber latex solution. This is a step (I- (a)) for producing a slurry solution containing the slurry solution, and the step (II) mixes the slurry solution containing the filler to which rubber latex particles are adhered and the remaining rubber latex solution. And it is preferable that it is the process (II- (a)) which manufactures the said filler containing rubber latex solution to which the rubber latex particle adhered.

  According to the above production method, when the filler is dispersed in the dispersion solvent, a slurry solution containing the filler to which the rubber latex particles are adhered is produced by adding at least a part of the rubber latex solution (step) (I- (a))). As a result, a very thin latex phase is formed on a part or all of the surface of the filler, and re-aggregation of the filler is prevented when mixing with the remaining rubber latex solution in the step (II- (a)). In addition, in the step (III) of solidifying and drying the filler-containing rubber latex solution to which the rubber latex particles are adhered, reaggregation of the filler can be suppressed. As a result, it is possible to produce a rubber wet masterbatch in which the filler is uniformly dispersed and the filler has excellent dispersion stability over time. In such a wet masterbatch, the filler is uniformly dispersed and the re-aggregation of the dispersing material over time is also suppressed. Therefore, in the vulcanized rubber obtained using this as a raw material, the exothermic property, durability and rubber strength are remarkably increased. improves.

  In the above production method, the dispersibility of the filler in the slurry solution is excellent and the reaggregation of the filler is prevented as compared with the case where the slurry solution is produced simply by dispersing the filler in the dispersion solvent. Therefore, an effect that the storage stability of the slurry solution is excellent is also achieved.

  In the said manufacturing method, it is preferable in the said process (I- (a)) that the 90% volume particle diameter (D90) of the said filler to which the rubber latex particle adhered in the said slurry solution is 31 micrometers or more. According to such a configuration, the dispersibility of the filler in the slurry solution is excellent, and re-aggregation of the filler can be prevented, so that the slurry solution is excellent in storage stability and the final vulcanized rubber generates heat. An unvulcanized rubber composition having excellent properties, durability and rubber strength can be produced. In the present invention, D90 of the filler to which the rubber latex particles are attached means a value measured in addition to the filler and the rubber latex particles to which the rubber latex particles are attached.

  In the said rubber wet masterbatch manufacturing method, in the said process (I- (a)), solid content (rubber) amount of the said rubber latex solution to add is 0.25-15% by mass ratio with the said filler. It is preferable that Moreover, in the said process (I- (a)), it is preferable that solid content (rubber) density | concentration in the said rubber latex solution to add is 0.2-5 mass%. In these cases, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of the filler is increased while reliably attaching the rubber latex particles to the filler.

  In the method for producing a rubber wet masterbatch, the step (I- (a)) previously mixes at least a part of the rubber latex solution and the dispersion solvent, and then adds and disperses the filler. Preferably, this is a step of producing the slurry solution containing the filler to which rubber latex particles are attached. According to this production method, the rubber latex particles adhere to the filler more reliably and more uniformly in the step (I- (a)). Thereby, in the whole process which manufactures a rubber wet masterbatch, reaggregation of a filler can be suppressed more reliably.

  The rubber wet masterbatch according to the present invention is manufactured by any one of the manufacturing methods described above. In such a rubber wet masterbatch, the contained filler is uniformly dispersed, and the dispersion stability of the filler over time is excellent. Therefore, for example, a pneumatic tire obtained using such a rubber composition has a good balance of heat generation, strength, and fatigue resistance, and is excellent in tear resistance and adhesion.

  The rubber composition according to the present invention is obtained using the rubber wet masterbatch described above. In such a rubber composition, the filler is uniformly dispersed, re-aggregation of the filler over time is suppressed, and the anti-aging property and the storage stability are excellent. Therefore, for example, a pneumatic tire obtained using such a rubber composition is excellent in heat generation, durability and rubber strength.

  The rubber wet masterbatch according to the present invention contains at least a filler, a dispersion solvent, and a rubber latex solution as raw materials.

  In the present invention, the filler means an inorganic filler usually used in the rubber industry, such as carbon black, silica, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide. Among the inorganic fillers, carbon black can be particularly preferably used in the present invention.

  As carbon black, for example, conductive carbon black such as acetylene black and ketjen black can be used in addition to carbon black used in ordinary rubber industry such as SAF, ISAF, HAF, FEF, and GPF. The carbon black may be a granulated carbon black or a non-granulated carbon black granulated in the normal rubber industry in consideration of its handleability.

  As the dispersion solvent, it is particularly preferable to use water, but for example, water containing an organic solvent may be used.

  Natural rubber latex solution and synthetic rubber latex solution can be used as the rubber latex solution.

  The natural rubber latex solution is a natural product produced by the metabolic action of plants, and a natural rubber / water system is particularly preferred in which the dispersion solvent is water. The number average molecular weight of the natural rubber in the natural rubber latex used in the present invention is preferably 2 million or more, and more preferably 2.5 million or more. In addition, about natural rubber latex, it can be used without distinction, such as fresh latex called concentrated latex and field latex. Examples of the synthetic rubber latex solution include those produced by emulsion polymerization of styrene-butadiene rubber, butadiene rubber, nitrile rubber, and chloroprene rubber.

  Tannin is a generic name for water-soluble compounds derived from plants and reacting with proteins, alkaloids, and metal ions to form sparingly soluble salts. Tannins are roughly classified into condensed tannins belonging to catechol groups such as mimosa, quebracho, gambia, and strawberry, and pyrogallols such as chestnuts, oak, tea, milabram, cod, and gallic ( It can be classified into hydrolyzable tannin belonging to Pyrogallol group.

  Below, the manufacturing method of the rubber composition which concerns on this invention is demonstrated. Such a production method includes a step (I) of producing a filler-containing slurry solution by dispersing a filler in a dispersion solvent, and mixing the filler-containing slurry solution and the rubber latex solution to obtain a filler-containing rubber latex solution. And a step (III) of adding tannin to the filler-containing rubber latex solution and coagulating it, followed by drying (III).

  In particular, in the present invention, when the step (I) disperses the filler in the dispersion solvent, the slurry containing the filler to which the rubber latex particles are adhered by adding at least a part of the rubber latex solution. A process for producing a solution (I- (a)), in which the process (II) is performed by mixing a slurry solution containing a filler to which rubber latex particles are adhered and the remaining rubber latex solution, thereby producing rubber latex particles. It is preferable to be a step (II- (a)) for producing a filler-containing rubber latex solution to which is adhered. The step (I- (a)) and the step (II- (a)) will be described below. In particular, in this embodiment, an example in which carbon black is used as a filler will be described.

(1) Step (I- (a))
In the step (I- (a)), when carbon black is dispersed in a dispersion solvent, a slurry solution containing carbon black to which natural rubber latex particles are adhered by adding at least a part of the natural rubber latex solution. Manufacturing. The natural rubber latex solution may be mixed with a dispersion solvent in advance, and then carbon black may be added and dispersed. Alternatively, carbon black may be added to the dispersion solvent, and then carbon black may be dispersed in the dispersion solvent while adding the natural rubber latex solution at a predetermined addition rate, or carbon black may be added to the dispersion solvent. Then, carbon black may be dispersed in a dispersion solvent while adding a certain amount of natural rubber latex solution in several times. By dispersing carbon black in the dispersion solvent in the presence of the natural rubber latex solution, a slurry solution containing carbon black with natural rubber latex particles attached thereto can be produced. As the addition amount of the rubber component in the natural rubber latex solution in the step (I- (a)), the total amount of the rubber component in the natural rubber latex solution to be used (step (I- (a)) and step (II- ( Examples are 0.075 to 12% by mass with respect to the total amount added in a)).

  In the step (I- (a)), the amount of solid content (rubber) of the natural rubber latex solution to be added is preferably 0.25 to 15% by mass ratio with respect to carbon black, 0.5 to 6% It is preferable that Moreover, it is preferable that the solid content (rubber) density | concentration in the natural rubber latex solution to add is 0.2-5 mass%, and it is more preferable that it is 0.25-1.5 mass%. In these cases, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of carbon black is increased while reliably attaching the natural rubber latex particles to the carbon black.

  In the step (I- (a)), carbon black and a dispersion solvent are mixed in the presence of a natural rubber latex solution. And a method of dispersing carbon black using a general dispersing machine such as a colloid mill.

  The "high shear mixer" is a mixer having a rotor and a stator, and the rotor rotates with a precise clearance between a rotor capable of high-speed rotation and a fixed stator. Means a mixer with a high shearing action. In order to produce such a high shearing action, it is preferable that the clearance between the rotor and the stator is 0.8 mm or less and the circumferential speed of the rotor is 5 m / s or more. A commercial item can be used for such a high shear mixer, for example, “High Shear Mixer” manufactured by SILVERSON.

  In the present invention, carbon black and a dispersion solvent are mixed in the presence of a natural rubber latex solution to produce a slurry solution containing carbon black to which natural rubber latex particles are adhered, in order to improve the dispersibility of the carbon black. An activator may be added. As the surfactant, known surfactants in the rubber industry can be used, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. It is done. Further, alcohol such as ethanol may be used instead of or in addition to the surfactant. However, when a surfactant is used, there is a concern that the rubber properties of the final vulcanized rubber will be lowered. Therefore, the amount of the surfactant to be blended is 100 mass of solid content (rubber) of the natural rubber latex solution. The amount is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and substantially no surfactant is used.

  In the slurry solution produced in the step (I- (a)), the carbon black to which the natural rubber latex particles are attached preferably has a 90% volume particle size (μm) (“D90”) of 31 μm or more, More preferably, it is 35 μm or more. In this case, the dispersibility of the carbon black in the slurry solution is excellent and the reaggregation of the carbon black can be prevented, so that the storage stability of the slurry solution is excellent and the exothermic property and durability of the final vulcanized rubber are excellent. Excellent in properties and rubber strength. In the present invention, D90 of the carbon black to which the natural rubber latex particles are attached means a value measured in addition to the carbon black and including the attached natural rubber latex particles.

(2) Step (II- (a))
In the step (II- (a)), the slurry solution and the remaining natural rubber latex solution are mixed to produce a carbon black-containing rubber latex solution to which the natural rubber latex particles are adhered. The method of mixing the slurry solution and the remaining natural rubber latex solution in a liquid phase is not particularly limited, and the slurry solution and the remaining natural rubber latex solution are mixed with a high shear mixer, a high shear mixer, a homomixer, and a ball mill. And a mixing method using a general disperser such as a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer, and a colloid mill. If necessary, the entire mixing system such as a disperser may be heated during mixing.

  The remaining natural rubber latex solution has a higher solid content (rubber) concentration than the natural rubber latex solution added in step (I- (a)), considering the drying time and labor in the next step (III). Specifically, the solid content (rubber) concentration is preferably 10 to 60% by mass, and more preferably 20 to 30% by mass.

(3) Step (III)
In the step (III), tannin is added to the filler-containing natural rubber latex solution or the filler-containing natural rubber latex solution to which the natural rubber latex particles are adhered, solidified, and then dried. Improves the anti-aging and storage stability of the resulting natural rubber wet masterbatch in a well-balanced manner while reliably coagulating the natural rubber latex solution containing filler or the carbon black-containing natural rubber latex solution to which the natural rubber latex particles are adhered. For this purpose, it is preferable that the amount of tannin added to 100 parts by mass of the rubber component is 1.0 to 10 parts by mass. In the present invention, in addition to tannin, a coagulant comprising a strong acid such as formic acid or sulfuric acid or a salt such as aluminum chloride may be used in combination. By using in combination with tannin, even when these coagulants are used in combination, the amount added can be reduced. When a coagulant other than tannin is used in combination, the amount added is preferably 2 parts by mass or less with respect to 100 parts by mass of the rubber component.

  As a method for drying the carbon black-containing natural rubber latex solution to which the natural rubber latex particles are adhered, various drying devices such as an oven, a vacuum dryer, and an air dryer can be used.

  The natural rubber wet masterbatch obtained after step (III) preferably contains 40 to 80 parts by mass of carbon black with respect to 100 parts by mass of rubber. In this case, it is possible to produce a natural rubber wet masterbatch in which the degree of carbon black dispersion and the heat generation and durability when vulcanized rubber is improved in a well-balanced manner.

  In the natural rubber wet masterbatch obtained after step (III), the contained carbon black is uniformly dispersed, and the dispersion stability of carbon black over time is excellent.

  In the rubber wet masterbatch obtained by the method for producing a rubber wet masterbatch according to the present invention, a sulfur vulcanizing agent, a vulcanization accelerator, silica, a silane coupling agent, zinc oxide, stearic acid, By adding compounding agents usually used in the rubber industry such as vulcanization accelerators, vulcanization retarders, organic peroxides, anti-aging agents, softeners such as waxes and oils, and processing aids. Such a rubber composition can be produced.

  Sulfur as the sulfur-based vulcanizing agent may be normal sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. The sulfur content in the rubber composition for tire rubber according to the present invention is preferably 0.3 to 6 parts by mass with respect to 100 parts by mass of the rubber component. If the sulfur content is less than 0.3 parts by mass, the crosslinking density of the vulcanized rubber will be insufficient and the rubber strength will be reduced. If it exceeds 6.5 parts by mass, both heat resistance and durability will be improved. Getting worse. In order to secure the rubber strength of the vulcanized rubber and improve the heat resistance and durability, the sulfur content should be 1.5 to 5.5 parts by mass with respect to 100 parts by mass of the rubber component. Is more preferably 2 to 4.5 parts by mass.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate. As for content of a vulcanization accelerator, it is more preferable that it is 1-5 mass parts with respect to 100 mass parts of rubber components, and it is further more preferable that it is 1.5-4 mass parts.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone anti-aging agent, a monophenol anti-aging agent, a bisphenol anti-aging agent, a polyphenol anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in an appropriate mixture. The content of the anti-aging agent is more preferably 1 to 5 parts by mass and further preferably 2 to 4.5 parts by mass with respect to 100 parts by mass of the rubber component.

  In addition to the rubber wet masterbatch, the rubber composition according to the present invention includes a sulfur-based vulcanizing agent, a vulcanization accelerator, silica, a silane coupling agent, zinc oxide, stearic acid, and a vulcanization acceleration aid as necessary. Agent, vulcanization retarder, organic peroxide, anti-aging agent, softener such as wax and oil, processing aid, etc., using kneading machines used in normal rubber industry such as Banbury mixer, kneader, roll And kneading.

  In addition, the blending method of each of the above components is not particularly limited, and a blending component other than a vulcanizing component such as a sulfur vulcanizing agent and a vulcanization accelerator is previously kneaded to obtain a master batch, and the remaining components are added. Any of a method of further kneading, a method of adding and kneading each component in an arbitrary order, a method of adding all components simultaneously and kneading may be used.

  As described above, in the rubber wet masterbatch according to the present invention, the filler is uniformly dispersed, re-aggregation of the filler over time is suppressed, and the anti-aging property and the storage stability are excellent. Therefore, the rubber composition produced using the same also has the filler uniformly dispersed, the re-aggregation of the filler over time is suppressed, and the anti-aging property and the storage stability are excellent. In particular, a pneumatic tire manufactured using this rubber composition, specifically a pneumatic tire using the rubber composition according to the present invention for tread rubber, side rubber, ply or belt coating rubber, or bead filler rubber, Since the filler has a rubber portion in which the filler is well dispersed, for example, rolling resistance is reduced, and heat generation, durability and rubber strength are excellent.

  Hereinafter, the present invention will be described in more detail with reference to examples. The raw materials used and the equipment used are as follows.

(Raw materials used)
a) Filler
Carbon black “N110”; “Seast 9” (manufactured by Tokai Carbon Co., Ltd.)
b) Dispersion solvent Water c) Rubber latex solution Natural rubber concentrated latex solution; Reticex (DRC (Dry Rubber Content) = 60% product) diluted to 25% by mass with distilled water d) Coagulant
Tannin 1; condensed tannin (Mimosa) (manufactured by Kawamura Tsusho)
Tannin 2; Hydrolyzed tannin (chestnut) (manufactured by Kawamura Tsusho)
Formic acid (primary 85%, 10% solution diluted to pH 1.2), “manufactured by Nacalai Tesque”
e) Zinc oxide No. 1 zinc white f) Stearic acid made by NOF Corporation g) Wax made by Nippon Seiki Co., Ltd. h) Anti-aging agent 6PPD (made by Monsanto)
i) Sulfur, manufactured by Tsurumi Chemical Co., Ltd. j) Vulcanization accelerator N-cyclohexyl-2-benzothiazolesulfenamide "Sunseller CM" (manufactured by Sanshin Chemical Industry Co., Ltd.)

(Evaluation)
The evaluation was performed on rubber obtained by heating and vulcanizing each rubber composition at 150 ° C. for 30 minutes using a predetermined mold.

(Particle size distribution (90 vol% particle size (D90))
In the slurry solution produced in the step (I), D90 of the filler to which rubber latex particles are adhered is set to an absorbance at the time of measurement of 0.01 to 0.1, and “SALD2200” (refraction of CB) manufactured by Shimadzu Corporation. D90 (μm) was measured using a ratio: 2.0-0.10i).

(Mooney viscosity of rubber wet masterbatch)
For Example 1 and Comparative Example 1, index evaluation was performed using the initial Mooney viscosity measurement value of Comparative Example 1 as 100, and for Examples 2 to 5 and Comparative Examples 2 to 3, the initial Mooney viscosity of Comparative Example 2 was used. Index evaluation is performed with the measured value as 100, and the smaller the numerical value, the smaller the Mooney viscosity increase, which means better. The Mooney viscosity of the wet masterbatch was measured according to JIS K6300-1.

(Exothermic property of vulcanized rubber)
According to JIS K6265, the exothermic property of the vulcanized rubber produced was evaluated by loss tangent tan δ. Tan δ was measured using a rheometer E4000 manufactured by UBM in a state of 50 Hz, 80 ° C., and dynamic strain of 2%. For Example 1 and Comparative Example 1, index evaluation was performed with the measured value of Comparative Example 1 being 100, and for Examples 2 to 5 and Comparative Examples 2 to 3, index evaluation was performed with the measured value of Comparative Example 2 being 100. The smaller the numerical value, the lower the exotherm and the better.

(Rubber strength of vulcanized rubber (TB))
A sample produced using a JIS No. 3 dumbbell was measured for tensile strength (TB (MPa)) according to JIS K 6251. For Example 1 and Comparative Example 1, index evaluation was performed with the measured value of Comparative Example 1 being 100, and for Examples 2 to 5 and Comparative Examples 2 to 3, index evaluation was performed with the measured value of Comparative Example 2 being 100. The higher the numerical value, the higher the rubber strength and the better.

(Fatigue resistance of vulcanized rubber)
The fatigue resistance of the manufactured vulcanized rubber was evaluated according to JIS K6260. For Example 1 and Comparative Example 1, index evaluation was performed with the measured value of Comparative Example 1 being 100, and for Examples 2 to 5 and Comparative Examples 2 to 3, index evaluation was performed with the measured value of Comparative Example 2 being 100. The higher the value, the better the fatigue resistance.

(Anti-aging performance)
A No. 3 type dumbbell test piece conforming to JIS K6251 was used, each dumbbell test piece was divided into two groups, and one of them was heated at 80 ° C. for 96 hours (aging treatment). Using dumbbell specimens before and after aging treatment, a tensile test is performed, and breaking strength and breaking elongation are measured. For each, (((physical properties after aging treatment) / (physical properties before aging treatment)) × 100) The rate of change (%) was calculated. For Example 1 and Comparative Example 1, index evaluation was performed with the measured value of Comparative Example 1 being 100, and for Examples 2 to 5 and Comparative Examples 2 to 3, index evaluation was performed with the measured value of Comparative Example 2 being 100. The larger the index, the better the anti-aging performance.

Example 1
Add 50 parts by mass of carbon black to a dilute latex aqueous solution adjusted to 0.5% by mass (the concentration of carbon black in water is 5% by mass), and disperse the carbon black using PRIMIX's Robomix. (Conditions for the robotics: 9000 rpm, 30 minutes) to produce a carbon black-containing slurry solution to which the natural rubber latex particles adhered (step (I- (a))). The D90 of the slurry containing carbon black containing the natural rubber latex particles produced in the step (I- (a)) is 48 μm, and the solid content (rubber) of the natural rubber latex solution in the step (I- (a)) The amount (mass ratio with carbon black) was 1%.

  Next, to the carbon black-containing slurry solution to which the natural rubber latex particles produced in the step (I- (a)) are attached, water is added so that the remaining natural rubber latex solution (solid content (rubber) concentration is 25% by mass). Was added to the natural rubber latex solution used in the step (I- (a)) to a solid content (rubber) amount of 100 parts by mass, and then SANYO Mixing was performed using a home-made mixer SM-L56 type (mixer conditions 11300 rpm, 30 minutes) to produce a carbon black-containing natural rubber latex solution (step (II- (a))).

  By adding tannin and formic acid as coagulants in the addition amount shown in Table 1 to the carbon black-containing natural rubber latex solution produced in the step (II- (a)), coagulating and drying, A natural rubber wet masterbatch was produced (step (III)). Various additives shown in Table 1 were blended with the obtained natural rubber wet masterbatch to obtain a rubber composition, and the physical properties of the vulcanized rubber were measured. The results are shown in Table 1.

Examples 2-5
After carbon black is previously dispersed in water (the concentration of carbon black in water is 5% by mass), tannin and formic acid are added in the amounts shown in Table 2 when mixed with the natural rubber latex solution, and coagulated. Then, a natural rubber wet masterbatch was produced by drying. Various additives shown in Table 2 were blended with the obtained natural rubber wet masterbatch to obtain a rubber composition, and the physical properties of the vulcanized rubber were measured. The results are shown in Table 2.

Comparative Example 1
Producing a slurry solution in which carbon black is dispersed in water in advance (the concentration of carbon black in water is 5% by mass), and adding a whole amount of natural rubber latex to this to produce a carbon black-containing natural rubber latex solution. Except for the above, a natural rubber wet masterbatch, a rubber composition, and a vulcanized rubber were produced in the same manner as in Example 1. Table 1 shows the physical properties of the vulcanized rubber.

Comparative Examples 2-3
A natural rubber wet masterbatch, a rubber composition, and a vulcanized rubber were produced in the same manner as in Examples 2 to 5, except that the addition amounts of tannin and formic acid were changed to the amounts shown in Table 1. Table 2 shows the physical properties of the vulcanized rubber.

  From the results of Table 1, it can be seen that the vulcanized rubber of the rubber composition containing the wet masterbatch according to Example 1 has improved low heat buildup, rubber strength, fatigue resistance, and anti-aging performance.

From the results of Table 2, it can be seen that the vulcanized rubber of the rubber composition containing the wet masterbatch according to Examples 2 to 5 improves the low heat buildup, rubber strength, fatigue resistance and anti-aging performance. On the other hand, in the vulcanized rubber of the rubber composition containing the wet masterbatch according to Comparative Example 3, the tannin is less charged, so the low heat build-up, rubber strength, fatigue resistance, and anti-aging performance are hardly improved. Recognize.

Claims (9)

A method for producing a rubber wet masterbatch using at least a filler, a dispersion solvent, and a rubber latex solution as raw materials,
A step (I) of producing a filler-containing slurry solution by dispersing the filler in the dispersion solvent;
Step (II) of mixing the filler-containing slurry solution and the rubber latex solution to produce a filler-containing rubber latex solution;
Adding a tannin to the filler-containing rubber latex solution, coagulating and then drying (III), and a method for producing a rubber wet masterbatch. When the step (I) disperses the filler in the dispersion solvent, a slurry solution containing the filler to which rubber latex particles are adhered is added by adding at least a part of the rubber latex solution. A manufacturing step (I- (a)),
In the step (II), the slurry solution containing the filler to which rubber latex particles are adhered is mixed with the remaining rubber latex solution to produce the filler-containing rubber latex solution to which rubber latex particles are adhered. The method for producing a rubber wet masterbatch according to claim 1, which is a step (II- (a)).   3. The unvulcanized rubber composition according to claim 2, wherein, in the step (I- (a)), a 90% volume particle size (D90) of the filler to which rubber latex particles are adhered is 31 μm or more in the slurry solution. Manufacturing method.   The solid content (rubber) amount of the rubber latex solution to be added in the step (I- (a)) is 0.25 to 15% by mass ratio with the filler. Manufacturing method of rubber wet masterbatch.   The rubber wet master according to any one of claims 2 to 4, wherein in the step (I- (a)), a solid content (rubber) concentration in the rubber latex solution to be added is 0.2 to 5% by mass. Batch manufacturing method.   In the step (I- (a)), at least a part of the rubber latex solution and the dispersion solvent are mixed in advance, and then the filler is added and dispersed to disperse the rubber latex particles. It is a process of manufacturing the said slurry solution containing a material, The manufacturing method of the rubber wet masterbatch in any one of Claims 2-5.   The rubber wet masterbatch manufactured by the manufacturing method in any one of Claims 1-6.   A rubber composition obtained by using the rubber wet masterbatch according to claim 7.   A pneumatic tire obtained using the rubber composition according to claim 8.