JP6328532B2 - Manufacturing method of rubber wet masterbatch - Google Patents

Description

  The present invention was obtained by using a rubber wet masterbatch obtained by using at least a filler, a dispersion solvent, and a rubber latex solution as a raw material and a production method thereof, a rubber composition containing the rubber wet masterbatch, and a rubber composition. Related to pneumatic tires.

  Conventionally, in the rubber industry, it is known to use a rubber wet masterbatch in order to improve the processability and dispersibility of fillers when producing rubber compositions containing fillers such as carbon black. Yes. This is because the filler and the dispersion solvent are mixed in advance at a certain ratio, and the filler-containing slurry solution in which the filler is dispersed in the dispersion solvent by mechanical force and the rubber latex solution are mixed in the liquid phase. Thereafter, the solidified product obtained by adding a coagulant such as an acid is recovered and dried. When using a rubber wet masterbatch, compared to using a rubber dry masterbatch obtained by mixing the filler and rubber in a solid phase, the dispersibility of the filler is excellent, and rubber properties such as workability and reinforcement A rubber composition having excellent resistance is obtained. By using such a rubber composition as a raw material, for example, a rubber product such as a pneumatic tire with reduced rolling resistance and excellent fatigue resistance can be manufactured.

  As described above, in the method for producing a rubber wet masterbatch, it is common to use an acid in order to coagulate the rubber latex solution. For example, in Patent Document 1 below, a mixing step of mixing a slurry solution containing a filler and a natural rubber latex that has undergone a deproteinization treatment step, a coagulation step of coagulating by adding an acid to the mixed solution obtained in the mixing step In a rubber wet masterbatch production method comprising a solid-liquid separation step for obtaining a coagulated product from a coagulated solution obtained in the coagulation step, and a drying step for drying the coagulated product, in 1 ml of serum of natural rubber latex after the deproteinization treatment step A specific relationship between the amount of protein E (mg / ml) contained in and the amount C (g) of filler contained in a slurry solution mixed with 1 g of natural rubber latex after the deproteinization treatment step; The technology to do is described. However, as a result of investigation by the present inventor, the above-mentioned technique in which no particular treatment is performed with respect to the acid added in the coagulation step indicates that the viscosity of the rubber wet masterbatch obtained after the drying step is not stable, and further, Vulcanized rubber has been found to have room for further improvement in terms of heat generation.

  In the field of recycled plastics, for example, when the raw material contains polyvinyl chloride, there is a known problem that hydrochloric acid is generated during molding, which adversely affects production machines including molds. In order to solve this problem, in Patent Document 2 below, when waste plastic is used as a recycled plastic material, 0.1% by mass or more of an acid acceptor is mixed with the recycled plastic material and mixed with the base resin. A technique for suppressing hydrochloric acid generated during recycling of waste plastic mixed as a master batch is described. However, there is little technical relevance in the fields of waste plastics and rubber, and there is no motivation to combine the technology described in Patent Document 2 below with the technology of rubber wet masterbatch.

JP 2013-203811 A International Publication No. 2006-085400

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a rubber wet masterbatch having a stable viscosity and a method for producing the same, and a rubber composition containing such a rubber wet masterbatch as a raw material. Another object of the present invention is to provide a rubber composition that can be a raw material of rubber having excellent heat generation after vulcanization, and a pneumatic tire using such a rubber composition as a raw material.

  The above object can be achieved by the present invention as described below. That is, the present invention is a method for producing a rubber wet masterbatch obtained using at least a filler, a dispersion solvent, and a rubber latex solution as raw materials, and the filler is dispersed in the dispersion solvent to obtain a filler-containing slurry solution. Step (I) for producing, Step (II) for producing a filler-containing rubber latex solution by mixing the filler-containing slurry solution and the rubber latex solution, and the filler-containing rubber latex solution as a coagulant Step (III) for coagulating the filler-containing rubber latex solution by adding an acid, and addition of an acid acceptor to the filler-containing rubber latex solution containing the coagulum obtained in the step (III) And a method for producing a rubber wet masterbatch, which comprises a step (IV) of performing a deoxidation treatment.

  In the method for producing a rubber wet masterbatch according to the present invention, in step (III), by adding an acid as a coagulant to the filler-containing rubber latex solution, the filler-containing rubber latex solution is coagulated to obtain a coagulated product. A filler-containing rubber latex solution is produced. Here, the filler-containing rubber latex solution containing the coagulated product can be dehydrated and dried as it is, and the coagulated product can be taken out as a rubber wet masterbatch. However, in the present invention, in the step (IV), an acid acceptor is added to the filler-containing rubber latex solution containing a coagulated product to perform a deoxidation treatment. By carrying out such deoxidation treatment, the rubber wet solution obtained by shifting the pH of the filler-containing rubber latex solution that was acidic at the end of step (III) to the neutral side, dehydrating it, and then drying it The viscosity of the master batch is stabilized. Furthermore, the vulcanized rubber of the rubber composition using the rubber wet masterbatch obtained through the deoxidation treatment as a raw material has excellent exothermic properties.

  In the method for producing a rubber wet masterbatch, the step (IV) is preferably a step of dehydrating the filler-containing rubber latex solution containing the coagulum while performing the deoxidation treatment. According to such a configuration, a rubber wet masterbatch having a stable viscosity can be efficiently produced.

  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)). Can do. 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 this 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 a rubber composition containing the filler as a raw material, exothermic and durable Property and rubber strength are remarkably improved.

  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 method for producing a rubber wet masterbatch, the acid acceptor is at least one selected from the group consisting of magnesium oxide, calcium hydroxide, magnesium carbonate, calcium carbonate, and magnesium silicate. The deoxidation treatment of the filler-containing rubber latex solution can be effectively performed.

  Moreover, this invention relates to the rubber composition containing the rubber wet masterbatch manufactured with the manufacturing method in any one of the said, and this rubber wet masterbatch. Such a rubber wet masterbatch and a vulcanized rubber of a rubber composition containing this as a raw material are excellent in exothermic properties. Therefore, a pneumatic tire having at least a member obtained using such a rubber composition, in particular, the member is at least one selected from the group consisting of a tread, a sidewall, a ply, a belt-covered rubber, and a bead filler. A pneumatic tire as a seed is excellent in exothermic property, for example, in characteristics such as rolling resistance.

  The present invention relates to a method for producing a rubber wet masterbatch obtained using 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 natural rubber latex solution can be used without distinction such as concentrated latex and fresh latex called 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.

  Below, the manufacturing method of the rubber wet masterbatch which concerns on this invention is demonstrated. In this production method, the filler is dispersed in a dispersion solvent to produce a filler-containing slurry solution (I), the filler-containing slurry solution and the rubber latex solution are mixed, and the filler-containing rubber latex solution is mixed. The coagulation obtained in the step (II) of producing, the step (III) of coagulating the rubber latex solution containing filler by adding an acid as a coagulant to the rubber latex solution containing filler, and the step (III) A step (IV) of adding an acid acceptor to the filler-containing rubber latex solution containing the product and performing a deoxidation treatment.

  In particular, in the present invention, when the step (I) disperses the filler in the dispersion solvent, by adding at least a part of the rubber latex solution, the packing to which rubber latex particles are adhered is added. A slurry solution containing a material (I- (a)), wherein the step (II) includes a slurry solution containing the filler to which rubber latex particles are adhered, and the remaining rubber latex solution. Is preferably a step (II- (a)) for producing the filler-containing rubber latex solution to which the rubber latex particles are 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 rubber latex particles are adhered is manufactured by adding at least a part of the rubber latex solution. To do. 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 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, carbon black may be dispersed in a dispersion solvent while adding a certain amount of rubber latex solution in several times. By dispersing carbon black in a dispersion solvent in the state where the rubber latex solution is present, a slurry solution containing carbon black with rubber latex particles attached thereto can be produced. The amount of rubber latex solution added in the step (I- (a)) is based on the total amount of rubber latex solution used (total amount added in the step (I- (a)) and step (II- (a))). 0.075-12 mass% is illustrated.

  In the step (I- (a)), the solid content (rubber) amount of the rubber latex solution to be added is preferably 0.25 to 15% by mass ratio to carbon black, and 0.5 to 6%. Preferably there is. Moreover, it is preferable that the solid content (rubber) density | concentration in the 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 rubber latex particles to carbon black.

  In the step (I- (a)), as a method of mixing carbon black and a dispersion solvent in the presence of a rubber latex solution, a high shear mixer, a high shear mixer, a homomixer, a ball mill, a bead mill, a high pressure homogenizer, an ultrasonic homogenizer, Examples thereof include 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, when a slurry solution containing carbon black to which rubber latex particles are adhered is produced by mixing carbon black and a dispersion solvent in the presence of a rubber latex solution, a surfactant is used to improve the dispersibility of the carbon black. 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 deteriorate. Therefore, the amount of the surfactant added is 100 parts by mass of the solid content (rubber) of the rubber latex solution. On the other hand, it is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and substantially no surfactant is preferably used.

  In the slurry solution produced in the step (I- (a)), the carbon black to which rubber latex particles are attached preferably has a 90% volume particle size (μm) (“D90”) of 31 μm or more, and 35 μm. More preferably. 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.

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

  The remaining rubber latex solution preferably has a higher solid content (rubber) concentration than the rubber latex solution added in the step (I- (a)) in consideration of dehydration / drying time and labor in the subsequent step. 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 step (III), the filler-containing rubber latex solution is coagulated by adding an acid as a coagulant to the filler-containing rubber latex solution. Examples of the acid include formic acid and sulfuric acid which are usually used for coagulating rubber latex solutions.

(4) Step (IV)
In step (IV), an acid acceptor is added to the filler-containing rubber latex solution containing the coagulated product obtained in step (III) to perform deoxidation treatment. As the acid acceptor, those known to those skilled in the art can be used, and in the present invention, at least selected from the group consisting of magnesium oxide, calcium hydroxide, magnesium carbonate, calcium carbonate, and magnesium silicate. When using 1 type, since the deoxidation process of the filler containing rubber latex solution containing a coagulum can be performed effectively, it is preferable. From the viewpoint of stabilizing the viscosity of the resulting rubber wet masterbatch and improving the heat build-up of the vulcanized rubber of the finally obtained rubber composition, the amount of the acid acceptor used is determined by the solid content of the rubber latex solution (rubber ) The amount is preferably 2 to 50 parts by mass, more preferably 5 to 25 parts by mass with respect to 100 parts by mass.

  In the present invention, the step (IV) may be a step of dehydrating the filler-containing rubber latex solution containing a coagulum while performing a deoxidation treatment. Moreover, you may provide the solid-liquid separation stage which isolate | separates (solid-liquid separation) the solidified material obtained at process (III) from the solution before process (IV). In the solid-liquid separation step, if necessary, a flocculant may be contained in the carbon black-containing rubber latex solution, and then the obtained agglomerates may be collected and dried. As the flocculant, known rubber flocculant flocculants can be used without limitation, and specific examples thereof include cationic flocculants. Solid-liquid separation can be carried out by methods known to those skilled in the art, such as centrifugation and filtration.

  As a method for dewatering the solidified product, various drying apparatuses such as an oven, a vacuum dryer, and an air dryer can be used. As a dehydration temperature, 150-200 degreeC can be illustrated, for example.

  Further, the rubber wet masterbatch after dehydration may be further dried using various drying devices such as an oven, a vacuum dryer, and an air dryer. As a drying temperature, 170-230 degreeC can be illustrated, for example.

  The rubber wet masterbatch obtained after the step (IV), and further the rubber wet masterbatch subjected to dehydration and / or drying treatment as necessary contains 40 to 120 parts by mass of a filler with respect to 100 parts by mass of rubber. It is preferable to do. In this case, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of the filler and the heat generation and durability when used as a vulcanized rubber are improved in a well-balanced manner.

  After the step (IV) is carried out, or after the dehydration and / or drying treatment is carried out as necessary, the obtained rubber wet masterbatch and various compounding agents are dry-mixed. Examples of usable compounding agents include sulfur vulcanizing agents, vulcanization accelerators, silica, silane coupling agents, zinc oxide, methylene acceptors and methylene donors, stearic acid, vulcanization accelerators, vulcanization Examples of the additives generally used in the rubber industry include retarders, organic peroxides, antioxidants, softeners such as wax and oil, and processing aids.

  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 according to the present invention is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the rubber component. If the sulfur content is less than 0.1 parts by mass, the crosslinking density of the vulcanized rubber will be insufficient and the rubber strength will decrease, and if it exceeds 20 parts by mass, both heat resistance and durability will be deteriorated. . In order to ensure good rubber strength of the vulcanized rubber and to further improve heat resistance and durability, the sulfur content is more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. Preferably, it is 0.5-5 mass parts.

  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 0.1-7 mass parts with respect to 100 mass parts of rubber components, and it is further more preferable that it is 0.3-5 mass parts.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a monophenol-based anti-aging agent, a bisphenol-based anti-aging agent, a polyphenol-based 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 0.3 to 10 parts by mass, and further preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

  In the rubber composition according to the present invention, for example, when used for tires, a methylene acceptor and a methylene donor may be blended in order to improve the adhesion to the tire belt. In the vulcanized rubber of the rubber composition containing a methylene acceptor and a methylene donor, the hydroxyl group of the methylene acceptor and the methylene group of the methylene donor undergo a curing reaction, thereby improving the adhesion to other members. it can.

  As the methylene acceptor, a phenolic compound or a phenolic resin obtained by condensing a phenolic compound with formaldehyde is used. Such phenolic compounds include phenol, resorcin or alkyl derivatives thereof. Alkyl derivatives include methyl group derivatives such as cresol and xylenol, and derivatives with long chain alkyl groups such as nonylphenol and octylphenol. The phenol compound may contain an acyl group such as an acetyl group as a substituent.

  In addition, phenol-based resins obtained by condensing phenolic compounds with formaldehyde include resorcin-formaldehyde resin, phenolic resin (phenol-formaldehyde resin), cresol resin (cresol-formaldehyde resin), etc. and formaldehyde composed of a plurality of phenolic compounds. Resin etc. are included. These are uncured resins that have liquid or heat fluidity.

  Among these, from the viewpoint of compatibility with the rubber component and other components, the density of the resin after curing, and the reliability, the methylene acceptor is preferably resorcin or a resorcin derivative, and in particular, resorcin or resorcin Alkylphenol-formalin resins are preferred.

  As the methylene donor, hexamethylenetetramine or melamine resin is used. As such a melamine resin, for example, methylol melamine, a partially etherified product of methylol melamine, a condensate of melamine, formaldehyde, and methanol is used, and among them, hexamethoxymethyl melamine is particularly preferable.

  As described above, the rubber wet masterbatch produced by the production method according to the present invention and the vulcanized rubber of the rubber composition containing this as a raw material are excellent in exothermic properties. Therefore, a pneumatic tire provided with at least one selected from the group consisting of a tread, a sidewall, a ply, a belt-covered rubber, and a bead filler obtained using such a rubber composition is excellent in heat generation, for example, rolling. Excellent resistance and other characteristics.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Raw materials used)
a) Carbon black “N330”; “Seast 3” (manufactured by Tokai Carbon Co., Ltd.)
b) Dispersion solvent Water c) Rubber latex solution Natural rubber latex solution (NR concentrated latex); (manufactured by Regex Corp.) (DRC (Dry Rubber Content) = 60%, adjusted so that the rubber concentration is 25% by mass, (Mass average molecular weight Mw = 23.6 million)
d) Coagulant formic acid (primary 85%, 10% solution diluted to pH 1.2), “Nacalai Tesque”
e) Acid acceptor (A) Magnesium oxide (MgO), “Nacalai Tesque”
(B) Calcium hydroxide (Ca (OH) ₂ ), “manufactured by Nacalai Tesque”
(C) Magnesium carbonate (MgCO ₃ ), “Nacalai Tesque”
f) Zinc Hana Zinc Hana 3 (Mitsui Metals)
g) Stearic acid, “Lunac S-20” (manufactured by Kao Corporation)
h) Anti-aging agent “NOCRACK 6C” (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
i) Sulfur, “powder sulfur” (manufactured by Tsurumi Chemical Co., Ltd.)
j) Vulcanization accelerator “Noxeller D” (Ouchi Shinsei Chemical Co., Ltd.)
k) Oil “Process NC140” (manufactured by JOMO)
l) Wax “OZOACE0355” (Nippon Seiki Co., Ltd.)
m) Styrene butadiene rubber (SBR) “SBR1502” (manufactured by JSR)

Example 1
80 parts by mass of carbon black is added to a dilute latex aqueous solution adjusted to 0.5% by mass when the rubber component in the finally produced rubber wet masterbatch is 100 parts by mass, and a high shear mixer manufactured by SILVERSON Was used to disperse carbon black (conditions of the mixer: 9000 rpm, 30 minutes)) to produce a carbon black-containing slurry solution with natural rubber latex particles attached (step (I- (a))) .

  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). In combination with the natural rubber latex solution used in step (I- (a)), and added to a solid content (rubber) amount of 100 parts by mass, and then PRIMIX Using the Robomix manufactured, mixing in a state heated to 60 ° C. (the Robomix condition 11300 rpm, 30 minutes) to produce a carbon black-containing natural rubber latex solution to which the natural rubber latex particles adhered (Step (II -(A))).

  To the carbon black-containing natural rubber latex solution to which the natural rubber latex particles produced in the step (II- (a)) are attached, a 10% by weight aqueous solution of formic acid as a coagulant is added until the pH becomes 4.5, and the mixture is heated to 60 ° C. In a heated state, the carbon black-containing natural rubber latex solution with the natural rubber latex particles adhered thereto was coagulated (step (III)).

  In a state heated to 60 ° C., the coagulated material is separated from the solution (SUS punching metal 2.0φ, filtered with 3.5P), and a squeezer type single-screw extrusion dehydrator (V-02 type) manufactured by Suehiro EPM. In this, while dehydrating while heating to 180 ° C., magnesium oxide as an acid acceptor was added to the dehydrator using an automatic feeder to perform deoxidation treatment (step (IV)). Thereafter, the obtained rubber wet masterbatch was again put into a squeezer type single-screw extrusion dehydrator (model V-02) manufactured by Suehiro EPM, and dried at 200 ° C. to produce a rubber wet masterbatch.

  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. In the table, the filling amount of carbon black was blended so as to be 60 parts by mass with respect to the rubber component. The results are shown in Table 1.

Comparative Example 1
A rubber wet masterbatch was produced under the same conditions as in Example 1 except that a rubber dry masterbatch was used instead of the rubber wet masterbatch.

Examples 2-4, Comparative Examples 2-3
A rubber wet masterbatch was produced under the same conditions as in Example 1 except that the presence or absence of the acid acceptor and the type of the acid acceptor used were changed to those shown in Table 1.

(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.

(Mooney viscosity)
In accordance with JIS K6300, using a rotorless Mooney measuring machine manufactured by Toyo Seiki Co., Ltd., after preheating the unvulcanized rubber at 100 ° C. for 1 minute, the torque value after 4 minutes was measured in Mooney units. It was shown as an index with a value of 100. The lower the measured viscosity value, the lower the INDEX value, which means that the viscosity is stable. The results are shown in Table 1.

(Exothermic)
Using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd., the loss factor tan δ was measured at a frequency of 10 Hz, a static strain of 10%, the same strain of 1%, and a temperature of 60 ° C. Indicated. The lower the exothermicity, the lower the INDEX value, and the better. The results are shown in Table 1.

  From the results in Table 1, it can be seen that the rubber wet masterbatches according to Examples 1 to 4 have a low Mooney viscosity and are stable. Furthermore, it can be seen that the vulcanized rubber of the rubber composition containing the rubber wet masterbatch according to Examples 1 to 3 has a low tan δ and a low exothermic property.

Claims (4)

A method for producing a rubber wet masterbatch obtained using at least a filler, a dispersion solvent, and a rubber latex solution as raw materials,
Step (I) of producing a filler-containing slurry solution by dispersing the filler in the dispersion solvent, and mixing the filler-containing slurry solution and the rubber latex solution to produce a filler-containing rubber latex solution. Obtained by the step (II), the step (III) of coagulating the filler-containing rubber latex solution by adding an acid as a coagulant to the filler-containing rubber latex solution, and the step (III). A method for producing a rubber wet masterbatch, comprising a step (IV) of adding an acid acceptor to the filler-containing rubber latex solution containing a coagulum and performing a deoxidation treatment.   The method for producing a rubber wet masterbatch according to claim 1, wherein the step (IV) is a step of dehydrating the filler-containing rubber latex solution containing the coagulum while performing the deoxidation treatment. 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, wherein the rubber wet masterbatch is a step (II- (a)).   The rubber wet masterbatch according to any one of claims 1 to 3, wherein the acid acceptor is at least one selected from the group consisting of magnesium oxide, calcium hydroxide, magnesium carbonate, calcium carbonate, and magnesium silicate. Manufacturing method.