JP2019112542A - Method of producing rubber composition for tire - Google Patents

Abstract

To provide a method of producing a rubber composition for a tire, capable of giving a vulcanized rubber having excellent wear resistance and tear resistance.SOLUTION: The method of producing a rubber composition for a tire, which contains a rubber wet master batch obtained by using at least carbon black, a dispersion solvent, and a rubber latex solution as raw materials, includes: a step (I) of mixing the carbon black, the dispersion solvent, and the rubber latex solution to produce a carbon black-containing rubber latex solution; a step (II) of coagulating the obtained carbon black-containing rubber latex solution to produce a carbon black-containing rubber coagulum; and a step (III) of dehydrating/drying the obtained carbon black-containing rubber coagulum to produce the rubber wet master batch. In the step (I), the mechanical stability of the rubber latex solution measured according to ASTM D1076-59 is 300 seconds or more. In the step (II), the pH of the carbon black-containing latex solution before coagulation is 6.0-8.5.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a rubber composition for a tire including at least carbon black, a dispersion solvent, and a rubber wet masterbatch obtained using a rubber latex solution as a raw material.

  Conventionally, in the rubber industry, it is known to use a rubber wet masterbatch in order to improve the processability at the time of producing a rubber composition containing carbon black and the dispersibility of carbon black. In this method, a carbon black-containing slurry solution in which carbon black and a dispersion solvent are mixed in advance at a constant ratio, and carbon black is dispersed in the dispersion solvent by mechanical force, and a rubber latex solution are mixed in a liquid phase, Thereafter, a coagulant such as an acid is added and solidified (carbon black-containing rubber coagulated material) is recovered and dried.

  When a rubber wet masterbatch is used, it has excellent carbon black dispersibility and rubber physical properties such as processability and reinforcement, as compared with a rubber dry masterbatch obtained by mixing carbon black and rubber in a solid phase. The rubber composition which is excellent in is obtained. By using such a rubber composition as a raw material, for example, rolling resistance can be reduced, and a rubber product (vulcanized rubber) such as a pneumatic tire having excellent fatigue resistance can be manufactured.

  In the method for producing a rubber wet masterbatch, the abrasion resistance and low heat buildup can be achieved by adjusting the pH in the preparation step of the above-mentioned carbon black-containing slurry solution or the above-mentioned preparation step of the carbon black-containing rubber coagulated material to a predetermined range. It is known that a rubber product (vulcanized rubber) having improved rubber properties such as is obtained (Patent Documents 1 to 4).

  Moreover, rubber products (vulcanized rubber) such as pneumatic tires obtained from a rubber composition containing a rubber wet masterbatch have the above-mentioned reduction in rolling resistance, fatigue resistance, low heat buildup, wear resistance, and resistance What is excellent in tear resistance such as cracking is required (Patent Documents 5 and 6).

Unexamined-Japanese-Patent No. 2006-328135 JP 2007-197549 JP, 2015-48416, A JP, 2017-39881, A WO 2010/123072 JP 2017-88747 A

  However, it has been found that vulcanized rubber obtained from a rubber composition containing a rubber wet masterbatch as in the above-mentioned patent documents has room for improvement in the abrasion resistance and tear resistance.

  The present invention has been made in view of the above situation, and provides a method for producing a rubber composition for a tire from which a vulcanized rubber having excellent abrasion resistance and tear resistance can be obtained.

  The present invention is a method for producing a rubber composition for a tire comprising at least carbon black, a dispersion solvent, and a rubber wet masterbatch obtained using a rubber latex solution as a raw material, wherein the carbon black, the dispersion solvent, and the rubber latex Mixing the solution to produce a carbon black-containing rubber latex solution (I), and coagulating the obtained carbon black-containing rubber latex solution to produce a carbon black-containing rubber coagulated product (II); The rubber latex solution, which includes the step (III) of dehydrating and drying the obtained carbon black-containing rubber coagulated material to produce a rubber wet masterbatch, and measuring according to ASTM D1076-59 in the step (I). Mechanical stability of 300 seconds or more, In), pH of the carbon black-containing latex solution before solidification, a method of manufacturing a tire rubber composition, which is a 6.0 to 8.5, related.

  The details of the action mechanism of the effect in the method for producing a rubber composition for a tire according to the present invention are unclear, but are presumed as follows. However, the present invention may not be interpreted as being limited to this mechanism of action.

  In the method for producing a rubber composition for a tire according to the present invention, mechanical stability of the rubber latex solution measured according to ASTM D1076-59 in the step (I) of producing the carbon black-containing rubber latex solution is The pH of the carbon black-containing latex solution before coagulation is 6.0 to 8.5 in the step (II) of producing a carbon black-containing rubber coagulated product for 300 seconds or more. The mechanical stability is an index showing colloidal stability, and in the case of the small mechanical stability, rubber latex particles are aggregated by a small stimulus. When coagulating a carbon black-containing rubber latex solution using a rubber latex solution having such small mechanical stability, coagulation occurs by the reaction between the latex particles and the carbon black before the carbon black is uniformly dispersed in the latex solution. As a result, the dispersibility (homogeneity) of the carbon black in the obtained rubber wet masterbatch becomes insufficient. Therefore, from the viewpoint of enhancing the storage stability of the rubber latex solution, or from the viewpoint of stably mixing the rubber latex solution and the carbon black-containing slurry solution containing carbon black and the dispersion solvent, the mechanical stability is high. A rubber latex solution is considered advantageous.

  However, since the carbon black-containing rubber latex solution obtained by using the rubber latex solution having high mechanical stability has high stability of latex particles, the reactivity between the rubber latex particles and carbon black is low. It is estimated that the dispersibility of carbon black in the medium is insufficient. When such a carbon black-containing rubber latex solution is coagulated, coagulation due to shearing or heat during mixing occurs more dominantly than coagulation due to reaction between latex particles and carbon black, and the obtained rubber wet masterbatch The dispersibility (homogeneity) of carbon black will become inadequate.

  On the other hand, even when using a rubber latex solution having high mechanical stability as described above, the pH of the carbon black-containing rubber latex solution is adjusted to a range of 6.0 to 8.5 before coagulation with a coagulant. Thus, the reactivity between the rubber latex particles and the carbon black can be kept optimum, and the dispersibility of the carbon black can be improved. Furthermore, since rapid solidification can be prevented in the subsequent solidification step, it is presumed that carbon black is uniformly incorporated into the coagulated body of the rubber latex particles while maintaining its dispersibility. As a result, it is considered that a rubber wet masterbatch having good carbon black dispersibility (homogeneity) can be obtained.

  The rubber composition containing such a rubber wet masterbatch is presumed to have good dispersibility (homogeneity) of carbon black in the rubber composition, so that the resulting vulcanized rubber has excellent abrasion resistance and resistance. It is excellent in tearability.

  The method for producing a rubber composition for a tire according to the present invention includes the step of producing a rubber wet masterbatch obtained using at least carbon black, a dispersion solvent, and a rubber latex solution as raw materials.

  As said carbon black, conductive carbon blacks, such as acetylene black and ketjen black, can be used besides carbon black used by usual rubber industry, such as SAF, ISAF, HAF, FEF, GPF, for example. . The carbon black may be granulated carbon black or non-granulated carbon black which is granulated in consideration of its handling property in ordinary rubber industry. The carbon black may be used alone or in combination of two or more.

The carbon black, from the viewpoint of improving the wear resistance of the vulcanized rubber, the nitrogen adsorption specific surface area, is preferably ^{50 m} 2 / g or more, more preferably ^{60 m} 2 / g or more, ^70m 2 / more preferably g or more, and is preferably at 200 meters ² / g or less, more preferably 190 m ² / g or less, and more preferably not more than 180 m ² / g.

  The content of the carbon black is preferably 20 to 100 parts by weight, preferably 30 to 90 parts by weight, with respect to 100 parts by weight of the rubber component contained in the rubber composition, from the viewpoint of improving the reinforcing property of the vulcanized rubber. It is more preferable that it is a part, and it is further more preferable that it is 40 to 80 parts by weight. In addition, the content of the carbon black is preferably 10 to 100 parts by weight with respect to 100 parts by weight of the rubber component contained in the rubber wet master batch, from the viewpoint of improving the reinforcing property of the vulcanized rubber. It is more preferable that it is -90 weight part, and it is further more preferable that it is 20-80 weight part.

  Water is particularly preferably used as the dispersion solvent, but it may be, for example, water containing an organic solvent. The dispersion solvents may be used alone or in combination of two or more.

  As the rubber latex solution, a natural rubber latex solution and a synthetic rubber latex solution can be used.

  The natural rubber latex solution is a natural product produced by the metabolism of plants, and a natural rubber / water system in which the dispersion solvent is water is particularly preferable. The number average molecular weight of the natural rubber contained in the natural rubber latex is preferably 2,000,000 or more, and more preferably 2,500,000 or more. As the natural rubber latex solution, concentrated latex, fresh latex called field latex, etc. can be used without distinction. Examples of the synthetic rubber latex solution include those produced by emulsion polymerization of styrene-butadiene rubber, butadiene rubber, nitrile rubber and chloroprene rubber. The rubber latex solution may be used alone or in combination of two or more. In addition, when using two or more latex solutions having largely different pH when coagulation occurs, the rubber latex solution may be used alone, from the viewpoint of fear that the dispersibility of carbon black may be poor. It is preferable to use, and it is more preferable to use a natural rubber latex solution alone.

  The rubber latex solution has a mechanical stability (also referred to as mechanical stability) of 300 seconds or more, which is measured according to ASTM D1076-59. The mechanical stability is preferably 300 seconds or more, more preferably 400 seconds or more, from the viewpoint of improving the storage stability and the viewpoint of improving the homogeneity of carbon black in the rubber wet masterbatch. . The mechanical stability is determined according to ASTM D1076-59 by the time until a coagulated substance is found in the latex when the rotating plate is agitated at a predetermined rotation speed. The mechanical stability is exemplified by, for example, 3600 seconds or less and 2400 seconds or less as the upper limit value.

  The above-mentioned mechanical stability includes basic compounds such as ammonia, sodium hydroxide and potassium hydroxide; aromatic carboxylic acid salts such as sodium salicylate; long-chain fatty acid salts such as ammonium laurate; formic acid, acetic acid, propionic acid and the like Adjustment agents such as short-chain fatty acids; and the like can be adjusted to the above range by adding them to the raw material rubber latex solution. Among these, it is preferable to use ammonia. When these modifiers are used, the concentration of the rubber latex solution is not limited, but from the viewpoint of stabilization of the rubber latex solution, it is preferable to use the latex solution 12 hours or more after preparation.

  Below, the manufacturing method of the rubber composition for tires of this invention is demonstrated concretely. The production method comprises the step (I) of mixing the carbon black, the dispersion solvent, and the rubber latex solution to produce a carbon black-containing rubber latex solution, and coagulating the obtained carbon black-containing rubber latex solution And a step (II) of producing a carbon black-containing rubber coagulated product, and a step (III) of dehydrating and drying the obtained carbon black-containing rubber coagulated product to produce a rubber wet masterbatch. Further, in the step (I), the mechanical stability of the rubber latex solution measured according to ASTM D1076-59 is 300 seconds or more, and in the step (II), the carbon black containing before coagulation is contained. The pH of the latex solution is 6.0 to 8.5.

<Step (I)>
In step (I) of the present invention, the carbon black, the dispersion solvent, and the rubber latex solution are mixed to produce a carbon black-containing rubber latex solution. In particular, in the present invention, the step (I) disperses the carbon black in the dispersion solvent to produce a carbon black-containing slurry solution (hereinafter also referred to as a slurry solution) (I-a1) and It is preferable to include the process (I-b1) of mixing the obtained carbon black containing slurry solution and the said rubber latex solution, and manufacturing a carbon black containing rubber latex solution. In the present invention, the carbon black to which the rubber latex particles are attached by adding at least a part of the rubber latex solution when the carbon black is dispersed in the dispersion solvent in the step (I). A step (I-a2) of producing a containing slurry solution, a carbon black containing slurry solution to which the obtained rubber latex particles are attached, and the remaining rubber latex solution are mixed, and carbon black to which rubber latex particles are attached It is preferable to include the process (I-b2) of manufacturing a containing rubber latex solution.

<Step (I-a1)>
Examples of the method of mixing the carbon black and the dispersion solvent in the step (I-a1) include general methods such as high shear mixer, high shear mixer, homo mixer, homo mixer, ball mill, bead mill, high pressure homogenizer, ultrasonic homogenizer, colloid mill, etc. Of dispersing carbon black using a conventional dispersing machine.

  The "high shear mixer" is a mixer including a rotor and a stator, and the rotor rotates in a state where a precise clearance is provided between the rotor capable of high speed rotation and the fixed stator. Means a mixer with high shear action. In order to produce such high shear action, it is preferable to set the clearance between the rotor and the stator to 0.8 mm or less and to set the circumferential speed of the rotor to 5 m / s or more. A commercial item can be used for such a high shear mixer, For example, the "high shear mixer" by SILVERSON can be mentioned.

<Step (I-a2)>
In the step (I-a2), when the carbon black is dispersed in the dispersion solvent, at least a part of the rubber latex solution is added to produce a carbon black-containing slurry solution to which the rubber latex particles adhere. The 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 the carbon black may be dispersed in the dispersion solvent while adding the rubber latex solution at a predetermined addition rate, or carbon black may be added to the dispersion solvent. Then, the carbon black may be dispersed in the dispersing solvent while adding a constant amount of rubber latex solution in several divided portions. By dispersing carbon black in the dispersion solvent in the presence of the rubber latex solution, it is possible to produce a carbon black-containing slurry solution to which rubber latex particles adhere. The addition amount of the rubber latex solution in the step (I-a2) is 0.075 to the total amount of the rubber latex solution to be used (the total amount added in the step (I-a2) and the step (I-b2)). 12% by weight is exemplified.

  In the step (I-a2), the rubber solid content of the rubber latex solution to be added is preferably 0.25 to 15% by weight ratio to carbon black, and is 0.5 to 6%. Is preferred. In addition, the concentration of the rubber solids in the rubber latex solution to be added is preferably 0.2 to 5% by weight, and more preferably 0.5 to 1.5% by weight. In these cases, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of carbon black is increased while the rubber latex particles are reliably attached to carbon black.

  As the method of mixing the carbon black and the dispersion solvent in the presence of the rubber latex solution in the step (I-a2), the same method as the method of mixing the carbon black and the dispersion solvent described above can be mentioned.

<Step (I-b1)>
At the process (I-b1) of this invention, the said slurry solution and rubber latex solution are mixed, and a carbon black containing rubber latex solution is manufactured. The method of mixing the slurry solution and the rubber latex solution in the liquid phase is not particularly limited, and the slurry solution and the rubber latex solution may be mixed, for example, with a high shear mixer, high shear mixer, homo mixer, homo mixer, ball mill, bead mill, Examples of the mixing method include a common disperser such as a high pressure homogenizer, an ultrasonic homogenizer, and a colloid mill, and a mixer using a mixer whose blades rotate in a cylindrical container. If necessary, the entire mixing system such as a dispersing machine may be heated during mixing.

  The rubber latex solution preferably has a concentration of rubber solids of preferably 10 to 60% by weight, taking into account the dehydration time and labor in step (III) described later, and specifically 20 to 30% by weight. It is more preferable that

<Step (I-b2)>
In the step (I-b2), the carbon black-containing slurry solution to which the rubber latex particles are attached and the remaining rubber latex solution are mixed to produce a carbon black-containing rubber latex solution to which the rubber latex particles are attached. The method of mixing the carbon black-containing slurry solution to which the rubber latex particles adhere and the remaining rubber latex solution in the liquid phase is the same as the method of mixing the slurry solution and the rubber latex solution in the liquid phase described above. The method is mentioned.

  The remaining rubber latex solution preferably has a higher rubber solids concentration than the rubber latex solution added in step (I-a2), considering the dehydration time and labor in step (III) described later, Specifically, the concentration of the rubber solid content is preferably 10 to 60% by weight, and more preferably 20 to 30% by weight.

  In the step (I), a surfactant may be added to improve the dispersibility of carbon black. As the surfactant, surfactants known in the rubber industry can be used. For example, nonionic surfactants, anionic surfactants, cationic surfactants, zwitterionic surfactants, etc. Can be mentioned. Also, instead of the surfactant or in addition to the surfactant, an alcohol such as ethanol may be used. However, when the surfactant is used, there is a concern that the final rubber physical properties of the vulcanized rubber may be reduced. Therefore, the blending amount of the surfactant is 100 parts by weight of the rubber solid content of the rubber latex solution. The amount is preferably 2 parts by weight or less, more preferably 1 part by weight or less, and it is preferable that the surfactant is not used substantially.

<Step (II)>
In step (II) of the present invention, the carbon black-containing rubber latex solution obtained above is coagulated to produce a carbon black-containing rubber coagulated product. In the present invention, in the step (II), the pH of the carbon black-containing latex solution before coagulation is 6.0 to 8.5. The pH of the carbon black-containing latex solution before coagulation is preferably 6.2 or more, more preferably 6.5 or more, from the viewpoint of improving the dispersibility of carbon black, and improving the dispersibility of carbon black From the viewpoint, 8.0 or less is preferable, and 7.4 or less is more preferable.

  In the carbon black-containing latex solution before coagulation, as a method of adjusting the pH of the solution to 6.0 to 8.5, when producing the carbon black-containing rubber latex solution in the step (I), Methods of heating, methods of vacuum degassing, methods of adding an acid such as formic acid, sulfuric acid, boric acid, citric acid, lactic acid and the like, and the like can be mentioned.

  Examples of the method of coagulation include a method of incorporating a coagulant in the carbon black-containing rubber latex solution. As the coagulant, an acid such as formic acid or sulfuric acid, a salt such as sodium chloride or the like that is usually used for coagulating a rubber latex solution can be used.

<Step (III)>
In step (III) of the present invention, the carbon black-containing rubber coagulated material obtained above is dewatered and dried to produce a rubber wet masterbatch. As the method of the said dehydration and drying, various dehydration and drying apparatuses, such as a single screw extruder, a twin screw extruder, a screw press, an oven, a conveyor type dryer, a vacuum dryer, an air dryer, can be used, for example . Before the step (III), for the purpose of appropriately reducing the amount of water contained in the carbon black-containing rubber coagulated material, for example, a centrifugal separation step or a solid-liquid separation step using a vibrating screen is provided. A washing process such as a water washing method may be provided for the purpose of washing.

<Step (IV)>
The method for producing a rubber composition for a tire according to the present invention preferably includes the step (IV) of dry mixing using the rubber wet masterbatch obtained above.

  In the step (IV), various compounding agents can be further used. Examples of usable compounding agents include rubber, carbon black, sulfur-based vulcanizing agent, vulcanization accelerator, anti-aging agent, silica, silane coupling agent, zinc oxide, methylene acceptor and methylene donor, stearic acid Examples of such additives include vulcanization accelerators, vulcanization retarders, organic peroxides, softeners such as waxes and oils, and processing aids and the like, which are commonly used in the rubber industry.

  The rubber is used separately from the rubber component derived from the rubber wet masterbatch. Examples of the rubber include synthetic dienes such as natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR) and nitrile rubber (NBR). Rubber is mentioned. The rubber may be used alone or in combination of two or more.

  From the viewpoint of imparting tear resistance to the vulcanized rubber, it is preferable to use a synthetic diene rubber, and as the synthetic diene rubber, it is preferable to use SBR or BR.

  In the step (IV), when using the rubber, the weight ratio of the rubber component of the rubber latex solution in the wet master batch to the rubber (rubber component of the rubber latex solution / rubber) is the resistance of the vulcanized rubber From the viewpoint of improving physical properties such as abrasion, it is preferably 60/40 or more, more preferably 65/35 or more, and from the viewpoint of improving physical properties such as the abrasion resistance of vulcanized rubber, It is preferably 90/10 or less, more preferably 80/20 or less.

  The sulfur as the sulfur-based vulcanizing agent may be any conventional sulfur for rubber, and for example, powder sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. The sulfur-based vulcanizing agent may be used alone or in combination of two or more.

  The content of sulfur is preferably 0.3 to 6.5 parts by weight with respect to 100 parts by weight of the rubber component in the rubber composition. If the content of sulfur is less than 0.3 parts by weight, the crosslink density of the vulcanized rubber will be insufficient to lower the rubber strength, etc. If it exceeds 6.5 parts by weight, both the heat resistance and the durability will be particularly good. Getting worse. In order to ensure the rubber strength of the vulcanized rubber favorably and to further improve the heat resistance and durability, the sulfur content is 1.0 to 5.5 with respect to 100 parts by weight of the rubber component in the rubber composition. It is more preferable that it is a weight part.

  As the vulcanization accelerator, any conventional vulcanization accelerator for rubber may be used, and a sulfenamide-based vulcanization accelerator, a thiuram-based vulcanization accelerator, a thiazole-based vulcanization accelerator, a thiourea-based vulcanization accelerator And guanidine-based vulcanization accelerators and dithiocarbamate-based vulcanization accelerators. The vulcanization accelerators may be used alone or in combination of two or more.

  The content of the vulcanization accelerator is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the rubber component in the rubber composition.

  The anti-aging agent may be any conventional anti-aging agent for rubber, such as aromatic amine based anti-aging agent, amine-ketone based anti-aging agent, monophenol based anti-aging agent, bisphenol based anti-aging agent, polyphenol based Antiaging agents, dithiocarbamate antiaging agents, thiourea antiaging agents, etc. may be mentioned. The antioxidant may be used alone or in combination of two or more.

  The content of the anti-aging agent is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the rubber component in the rubber composition.

  In the step (IV), the method of blending (adding) the rubber wet masterbatch and the various compounding agents is, for example, using a kneader used in a usual rubber industry such as a Banbury mixer, a kneader, or a roll. The method of knead | mixing is mentioned.

  Although the method of kneading is not particularly limited, for example, a method of adding and kneading components other than a vulcanizing component such as a sulfur-based vulcanizing agent and a vulcanization accelerator in any order, and a method of simultaneously adding and kneading Also, a method of simultaneously adding and kneading all the components may be mentioned. The number of times of kneading may be one or more. The time for kneading varies depending on the size of the kneader used, etc., but may usually be about 2 to 5 minutes. Moreover, it is preferable to set it as 120-170 degreeC, and, as for the discharge temperature of a kneading machine, it is more preferable to set it as 120-150 degreeC. In addition, when the discharge temperature of a kneading machine contains the said vulcanization system component, it is preferable to set it as 80-110 degreeC, and it is more preferable to set it as 80-100 degreeC.

  According to the method for producing a rubber composition for a tire of the present invention, a vulcanized rubber having excellent abrasion resistance and tear resistance can be obtained. The rubber composition for a tire of the present invention can be used for each part of a pneumatic tire, but is particularly suitable for a tire tread.

  EXAMPLES The present invention will be described by way of examples, but the present invention is not limited by these examples.

(Raw material used)
a) Carbon black:
Carbon black "N234 (Seat 7HM)" (made by Tokai Carbon Co., Ltd.)
Carbon black "N110 (Seat 9)" (made by Tokai Carbon Co., Ltd.)
Carbon black "N339 (Seat KH)" (made by Tokai Carbon Co., Ltd.)
b) dispersion solvent: water c) rubber latex solution:
Natural rubber concentrated latex solution (60% by weight of Dry Rubber Content), (made by Redex)
d) Coagulant: Formic acid (diluted to a primary grade 85%, 10% solution and adjusted to pH 1.2), (Nacalai Tesque)
e) Diene rubber: "BR150B" (made by Ube Industries, Ltd.)
f) Zinc flower: "No. 3 zinc flower" (made by Mitsui Metal Mining Co., Ltd.)
g) Stearic acid: "Beads stearic acid" (manufactured by NOF Corporation)
h) Wax: "OZOACE 0355" (manufactured by Nippon Seiwa Co., Ltd.)
i) Anti-aging agent (A): N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine, "6PPD" (manufactured by Monsanto)
j) Anti-aging agent (B): 2,2,4-trimethyl-1,2-dihydroquinoline polymer, "RD", (made by Ouchi New Chemical Co., Ltd.)
k) Sulfur: "5% oil-filled fine powder sulfur" (made by Tsurumi Chemical Industry Co., Ltd.)
l) Vulcanization accelerator (A): N-cyclohexyl-2-benzothiazolesulfenamide, "Sunseller CM", (manufactured by Sanshin Chemical Industry Co., Ltd.)
m) Vulcanization accelerator (B): 1,3-diphenylguanidine, "Noxceler D", (made by Ouchi New Chemical Co., Ltd.)

Example 1
<Preparation of rubber latex solution>
Ammonia was added to the natural rubber latex-concentrated latex solution at room temperature so that the following mechanical stability was 600 seconds. Subsequently, water was added at normal temperature to prepare a rubber latex solution having a rubber component of 25% by weight.
[Measurement of mechanical stability of rubber latex solution]
The mechanical stability of the rubber latex solution was measured by rotating the rotating plate at 14000 rpm according to ASTM D1076-59, and measuring the time (seconds) until the visible clot was found in the latex visually. . In addition, the density | concentration of rubber | gum solid content in the rubber latex solution in the said measurement is 60 weight%.

<Step (I): Production of Carbon Black-Containing Rubber Latex Solution>
Water was added to the rubber latex solution having the predetermined mechanical stability obtained above to prepare a 0.5 wt% rubber dilute latex aqueous solution. To the obtained rubber dilute latex aqueous solution, 50 parts by weight of carbon black "N234" (the solid content (rubber amount) of the latex solution is 1 part by weight relative to carbon black) is added, and to this ROMIBO manufactured by PRIMIX By dispersing carbon black using the mix (conditions of the robot mix: 9000 rpm, 30 minutes), a carbon black-containing slurry solution to which rubber latex particles were attached was produced (step (I-a2)). Next, the remaining carbon latex-containing slurry solution to which the rubber latex particles produced in the step (I-a2) have been adhered is treated with the remaining rubber latex solution (25% by weight) having the predetermined mechanical stability obtained above. Add together with the rubber dilute latex aqueous solution used in (I-a2) so that the solid content (rubber) amount is 100 parts by weight, and then mix using a SANYO household mixer SM-L56. (Mixer conditions 11300 rpm, 30 minutes) A carbon black-containing rubber latex solution to which rubber latex particles were attached was produced (step (I-b2)).

<Step (II): Production of carbon black-containing rubber coagulated material>
Formic acid (10%) is added to the carbon black-containing rubber latex solution produced in the above step (I) until the whole solution reaches pH 7.2, and it is further added using SANYO's household mixer SM-L56. Mixing was performed (mixer conditions: 11300 rpm, 25 minutes). Then, formic acid (10% solution) is added as a coagulant until the whole solution reaches pH 4, and furthermore, by using SANYO's household mixer SM-L56 type (mixer conditions: 11300 rpm, 2 minutes), carbon A black-containing rubber coagulum was produced (step (II)). The pH was evaluated according to JIS Z8802 using "Portable pH meter HM-30P" manufactured by Toa DKK Co., Ltd.

<Step (III): Production of Rubber Wet Masterbatch>
The carbon black-containing rubber coagulated material produced in the above step (II) is dewatered and dried with a squeezer type single-screw extrusion dehydrator (V-02 type manufactured by Suehiro EPM) until the water content becomes 1.5% or less Thus, a rubber wet masterbatch was produced (step (III)).

<Step (IV): Production of Rubber Composition and Unvulcanized Rubber Composition>
Dry mixing (mixing time: 3 minutes, discharge temperature: 150 ° C.) of the rubber wet masterbatch obtained above and each raw material (components except sulfur and vulcanization accelerator) described in Table 1 using a Banbury mixer The rubber composition was manufactured by carrying out. Next, the sulfur, vulcanization accelerator (A) and vulcanization accelerator (B) described in Table 1 are added to the obtained rubber composition, and dry mixing (kneading time: 1 minute, discharge using a Banbury mixer) The unvulcanized rubber composition was manufactured by carrying out temperature: 90 degreeC. In addition, the compounding ratio in Table 1 is shown by the weight part (phr) when the whole quantity of the rubber component contained in a rubber composition is 100 weight part.

<Examples 2 to 10 and Comparative Examples 1 to 5>
In <Preparation of rubber latex solution> of Example 1, the mechanical stability of the rubber latex was changed to a value shown in Table 1, and <Step (I) of Example 1: Production of carbon black-containing rubber latex solution In <>, the carbon black to be used was changed to the type and blending amount shown in Table 1, and in <Step (II) of Example 1: Production of carbon black-containing rubber coagulant>, carbon black-containing before solidification. The rubber compositions and unvulcanized rubber compositions of Examples 2 to 10 and Comparative Examples 1 to 5 were prepared in the same manner as in Example 1 except that the pH of the rubber latex solution was changed to the values shown in Table 1. Manufactured. In addition, the compounding quantity in Table 1 shows a weight part (phr) when the whole quantity of the rubber component contained in a rubber wet masterbatch is 100 weight part.

  A vulcanized rubber was produced by vulcanizing the unvulcanized rubber compositions obtained in the above Examples and Comparative Examples under the conditions of 150 ° C. and 30 minutes. The following evaluation was performed about the obtained vulcanized rubber. The evaluation results are shown in Table 1.

<Evaluation of wear resistance>
The evaluation of the abrasion resistance was carried out on a test piece of the obtained vulcanized rubber according to JIS K6264 using a Rambone abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd., load 40 N, slip ratio 30%, temperature 23 The abrasion loss is measured at 20 ° C and the amount of falling sand is 20 g / min, and Examples 1 to 6, 9 and 10, and Comparative Examples 2 to 3 are indices based on the value of Comparative Example 1 as 100, Example 7 is a Comparative Example The value of 4 was set to 100, and the value of Example 8 was set to 100 as the value of Comparative Example 5. The smaller the index, the smaller the loss on wear and the better the wear resistance.

<Evaluation of tear resistance>
In the evaluation of tear resistance, the vulcanized rubber obtained above was punched out in a crescent form defined in JIS K6252 to obtain a sample in which a cut of 0.50 ± 0.08 mm was inserted in the center of the recess. The tear strength was measured at a tensile speed of 500 mm / min with a Shimadzu tensile tester, and Examples 1 to 6, 9 and 10, and Comparative Examples 2 to 3 were indices with the value of Comparative Example 1 being 100, Example 7 was expressed as an index with the value of Comparative Example 4 being 100, and Example 8 was expressed as an index with the value of Comparative Example 5 being 100. The larger the index, the better the tear resistance.

Claims (7)

A method for producing a rubber composition for a tire comprising at least carbon black, a dispersion solvent, and a rubber wet masterbatch obtained using a rubber latex solution as a raw material,
A step (I) of mixing the carbon black, the dispersion solvent, and the rubber latex solution to produce a carbon black-containing rubber latex solution;
Step (II) of coagulating the obtained carbon black-containing rubber latex solution to produce a carbon black-containing rubber coagulated product,
Including the step (III) of dewatering and drying the obtained carbon black-containing rubber coagulated material to produce a rubber wet masterbatch,
In the step (I), the mechanical stability of the rubber latex solution measured according to ASTM D 1076-59 is 300 seconds or more.
In the step (II), the pH of the carbon black-containing latex solution before coagulation is 6.0 to 8.5.   The method for producing a rubber composition for a tire according to claim 1, wherein in the step (II), the pH of the carbon black-containing latex solution before coagulation is 6.0 to 7.4. A step (I-a1) of producing a carbon black-containing slurry solution by dispersing the carbon black in the dispersion solvent in the step (I);
The tire according to claim 1 or 2, comprising the step (I-b1) of producing a carbon black-containing rubber latex solution by mixing the obtained carbon black-containing slurry solution with the rubber latex solution. Method of producing a rubber composition A step of producing a carbon black-containing slurry solution to which rubber latex particles adhere by adding at least a part of the rubber latex solution when the carbon black is dispersed in the dispersion solvent in the step (I) (I-a2),
A step (I-b2) of manufacturing a carbon black-containing rubber latex solution with rubber latex particles attached by mixing the obtained carbon black-containing slurry solution with the rubber latex particles attached and the remaining rubber latex solution The manufacturing method of the rubber composition for tires in any one of the Claims 1-3 characterized by including.   The method for producing a rubber composition for a tire according to any one of claims 1 to 4, further comprising a step (IV) of dry mixing using the rubber wet masterbatch. In the step (IV), the step of dry mixing using the rubber wet masterbatch and the rubber is included,
The rubber latex solution is a natural rubber latex solution,
The method for producing a rubber composition for a tire according to claim 5, wherein the rubber is a synthetic diene rubber.   The method for producing a rubber composition for a tire according to any one of claims 1 to 6, which is for a tire tread.