JP2012246331A - Silica-containing rubber master batch and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the incorporability of silica into a rubber component when making a wet master batch.SOLUTION: Silica is heat-treated at 400-1,000°C to reduce the amount of silanol groups on the silica surface, the heat-treated silica is dispersed in water to prepare a silica slurry, and the silica slurry is mixed with a rubber solution to produce a silica-containing rubber master batch. In regard to the heat-treated silica, ((Sears titration amount)/(BET specific surface area))×100, that is, the ratio of Sears titration amount (ml) to BET specific surface area (m/g) is preferably ≤9. Also, the Sears titration amount (ml) of silica is preferably reduced by the heat treatment to ≤70% of that before the heat treatment.

Description

  The present invention relates to a rubber masterbatch containing silica, a method for producing the same, and a rubber composition containing the silica-containing rubber masterbatch.

  In rubber compositions used for tires and the like, fillers such as carbon black and silica are blended as a reinforcing material. Such a filler is generally added to a rubber component and mixed together with other additives at the time of kneading the rubber composition (this method is called dry kneading or dry kneading). However, in dry kneading, it is not always easy to uniformly disperse the filler in the rubber component, so that it is possible to improve the dispersibility in the rubber component or to simplify the kneading process of the rubber composition. Therefore, a filler slurry and a rubber solution such as latex may be mixed to prepare a filler-containing master batch (so-called wet master batch).

  Among the fillers described above, silica has been used in recent years in order to reduce fuel consumption in tires, for example, because it can reduce the hysteresis loss of the rubber composition and reduce heat generation. However, since silica has a silanol group (Si-OH) on the particle surface and is hydrophilic, the incorporation into rubber is very easy when forming a wet masterbatch for simplification of the process as described above. There is a problem of being bad. This problem can be improved, for example, by adding a surfactant or the like to the silica slurry, but these additives may adversely affect the physical properties of the rubber composition.

  In Patent Document 1 below, in order to improve the affinity between rubber molecules and silica, it has been proposed to produce a wet masterbatch using silica surface-treated with a specific polysiloxane compound. In addition, since the polysiloxane compound applied to the silica surface may affect the physical properties of the rubber composition, it is required to improve the incorporation into rubber without using such a compound. .

  The following Patent Documents 2 and 3 disclose rubber compositions containing precipitated silica heat-treated within a temperature range of 180 to 1000 ° C., and the pores on the surface of the precipitated silica are reduced by the heat treatment. Thus, it is described that low hysteresis loss is exhibited while improving wear resistance. Patent Document 4 below discloses that silica is treated with heat at 250 to 500 ° C. to reduce OH-containing components such as silanol groups and suppress silica aggregation. However, these documents only disclosed that the reduction of pores and the reduction of OH-containing components due to heat treatment lead to improvement of physical properties such as dispersibility of silica in rubber components and wear resistance during dry kneading. It does not show the ability of silica to be incorporated into the rubber component when producing a wet masterbatch.

JP 2006-213858 A JP-A-9-156307 JP-A-9-157441 Japanese Patent Laid-Open No. 10-251455

  The present invention has been made in view of the above points, and an object of the present invention is to provide a method for producing a silica-containing rubber masterbatch that can improve silica incorporation into a rubber component during wet masterbatch formation. And

  In the method for producing a silica-containing rubber masterbatch according to the present invention, silica is heat-treated at 400 to 1000 ° C. to reduce the amount of silanol groups on the silica surface, and the heat-treated silica is dispersed in water to prepare a silica slurry. The silica slurry and the rubber solution are mixed to produce a silica-containing rubber master batch.

  The silica-containing rubber master batch according to the present invention is produced by the above method. The rubber composition according to the present invention is obtained by blending the silica-containing rubber master batch.

  According to the present invention, the compatibility between silica and the rubber component is improved by controlling the amount of silanol groups of the silica by heat treatment, thereby improving the silica incorporation into the rubber component during wet master batching. it can.

  Hereinafter, embodiments of the present invention will be described.

  In the present embodiment, first, the amount of silanol groups on the particle surface is controlled by treating silica at a high temperature. That is, by heat-treating silica, the amount of silanol groups on the surface can be reduced to achieve hydrophobicity, and the ability to incorporate silica into the rubber component can be improved when forming a wet masterbatch in a subsequent step.

The silica to be treated may be wet silica (hydrous silicic acid) or dry silica (anhydrous silicic acid), but is preferably wet silica that has good effects of improving fracture characteristics and low heat generation. Since wet silica has a large amount of silanol groups on the particle surface, the effect of controlling the amount of silanol groups by the heat treatment is high, and a more excellent improvement effect is obtained. Nitrogen adsorption specific surface area of the silica to be processed (BET specific surface area) is not particularly limited, is preferably 80~300m ² / g, more preferably from 100 to 250 m ² / g, more preferably 100 -200 m < ² > / g. The BET specific surface area of silica is measured by a single point value of the BET method described in ISO 5794.

  The heat treatment temperature for heat treating silica is set within a range of 400 to 1000 ° C. In general, in silica, bound water is released up to about 400 ° C., and silanol groups are released by heating to about 400 ° C., and silanol groups can be efficiently released at about 800 ° C. Therefore, in order to reduce the amount of silanol groups on the silica surface by heat treatment, it is necessary to perform heat treatment at 400 ° C. or more, more preferably heat treatment at 600 ° C. or more, and further preferably heat treatment at 800 ° C. or more. It is. On the other hand, if the heat treatment temperature exceeds 1000 ° C., the particle size may increase due to crystallization and the original performance may be impaired, so the heat treatment temperature is set to 1000 ° C. or less, more preferably 900 ° C. or less. It is.

  The heat treatment time is not particularly limited because it varies depending on the heat treatment temperature. That is, the purpose of the heat treatment is to reduce the amount of silanol groups on the silica surface, but the amount of silanol groups decreases in a shorter time as the heat treatment temperature is higher, and the lower the heat treatment temperature, the longer the time for reduction. Cost. Therefore, the heat treatment time may be appropriately set according to the temperature.

  Preferably, it is preferable to reduce the Sears titer of silica to 70% or less before heat treatment by heat treatment. The Sears titration is an index of how many silanol groups are present on the silica surface, and the larger the Sears titration, the greater the amount of silanol groups on the silica surface. For this reason, silica is effectively hydrophobized by reducing the amount of silanol groups by heat treatment so that the Sears titration amount of silica after heat treatment is 70% or less of the Sears titration amount before heat treatment. Can be significantly improved. The ratio of the Sears titration amount after the heat treatment to that before the heat treatment is preferably 65% or less, more preferably 50% or less. On the other hand, if this ratio is too low, the reaction with the silane coupling agent decreases when blended in the rubber composition, and the physical properties may be impaired. Therefore, the ratio is preferably 20% or more, more preferably. Is 25% or more. Here, the Sears titration is a value measured by G. W. Sears, Analytical Chemistry, Vol. 28, No. 12, 1982-83 (1956).

In the present embodiment, the silica after the heat treatment is preferably a ratio of the Sears titration amount (ml) to the BET specific surface area (m ² / g) (Sears titration / BET specific surface area) × 100 is 9 or less. . In general, the larger the specific surface area (ie, the smaller the silica particle), the larger the value of the Sears titration value, and the smaller the specific surface area (ie, the larger the particle size silica), the greater the Sears titration value. The value of is small. Therefore, by setting the ratio of the Sears titration amount and the BET specific surface area as an index of the amount of silanol groups per surface area, silica hydrophobized by heat treatment can be defined regardless of the particle size. That is, by performing heat treatment so that the ratio is 9 or less, silica uptake with respect to the rubber component can be improved, and by further heat treatment to be 6 or less, the uptake is remarkably improved. can do. The lower limit of the ratio is not particularly limited, but is preferably 2 or more.

  In this embodiment, the silica heat-treated in this manner is dispersed in water to prepare a silica slurry. The preparation of the silica slurry can be performed using a known method, and is not particularly limited. For example, the heat-treated silica can be dispersed in water using a known disperser such as an ultrasonic homogenizer, a high-pressure homogenizer, a high shear mixer, or a colloid mill. The density | concentration of the silica in a silica slurry is not specifically limited, For example, it can be set as 1-20 mass%.

  In this embodiment, the silica slurry and the rubber solution are then mixed to produce a silica-containing rubber master batch. As the rubber solution, natural rubber latex or synthetic rubber latex is preferably used, but an organic solvent solution of synthetic rubber by solution polymerization may be used.

  The natural rubber latex may be a field latex, or may be a concentrated latex obtained by concentrating the field latex by removing a protein by a known concentration method such as centrifugation. Synthetic rubber latex includes isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), diene rubber such as nitrile rubber (NBR), butyl rubber, halogenated butyl rubber, ethylene propylene rubber, etc. These latex polymers are latexes obtained by dispersing them in an aqueous solvent such as water or a hydrocarbon solvent. These can be used alone or in combination of two or more. Of these, diene rubber latex is preferably used. The content of the rubber component (rubber polymer) in the rubber solution is not particularly limited, but is generally 10 to 70% by mass.

  Mixing of the silica slurry and the rubber solution can be performed using a known mixer, and is not particularly limited. For example, a method of dropping a rubber solution while stirring a silica slurry in a homomixer, a method of dropping a silica slurry while stirring a rubber solution in a homomixer, a silica slurry flow having a predetermined flow rate, and a rubber solution flow A method of mixing and mixing can be used.

  After mixing in this manner, the rubber is coagulated (co-coagulated) with silica and dehydrated and dried to obtain a silica-containing rubber master batch. Coagulation can be performed using a known method. For example, coagulation may be performed using an acid such as formic acid or sulfuric acid, or a salt coagulant such as sodium chloride, or coagulation without adding a coagulant. May be made. After solidification, solid-liquid separation is performed to collect the solidified product, and then the solidified product is washed, dehydrated and then dried. Drying can be performed using a known method, and can be performed using a normal dryer such as a vacuum dryer, an air dryer, a drum dryer or the like, and is performed while applying mechanical shearing force using a kneader. You may let them.

  Although the ratio of the silica and the rubber component in the silica-containing rubber master batch is not particularly limited, for example, the silica can be 5 to 150 parts by mass, more preferably 30 to 100 parts per 100 parts by mass of the rubber component. Part by mass.

  The rubber composition according to the present embodiment includes the silica-containing rubber master batch (that is, the wet master batch) obtained above. In the rubber composition, the rubber component may be composed of only the rubber polymer derived from the silica-containing rubber master batch. And various rubber polymers such as diene-based synthetic rubber (for example, the above IR, BR, SBR, CR, NBR, etc.). The rubber component derived from the silica-containing rubber master batch with respect to the entire rubber component in the rubber composition is preferably 30% by mass or more, and more preferably 50% by mass or more.

  It is preferable that a silane coupling agent is further added to the rubber composition. As the silane coupling agent, various known silane coupling agents can be used and are not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilyl) Propyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide, etc. Sulfide silane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane Protected mercaptosilanes such as mercaptosilane such as 3-octanoylthio-1-propyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, etc., and these may be used alone or in combination of two or more. Can be used. It is preferable that the compounding quantity of a silane coupling agent is 2-20 mass parts with respect to 100 mass parts of silica, More preferably, it is 4-15 mass parts.

  In addition to the above, the rubber composition may contain various additives such as anti-aging agents, zinc white, stearic acid, softeners, plasticizers, activators, lubricants, vulcanizing agents, and vulcanization accelerators as necessary. Can be added. Examples of the vulcanizing agent include sulfur and sulfur-containing compounds, and are not particularly limited. However, the blending amount is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. More preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.5-5 mass parts. In addition, other fillers such as carbon black may be added to the rubber composition, and additional addition is made within the range that does not impair the above-described effect of the present embodiment of using wet masterbatch silica. Silica may be added to.

  The rubber composition is prepared by kneading according to a conventional method using a rubber kneader such as a normal Banbury mixer or kneader. The use of the rubber composition thus obtained is not particularly limited, and can be used for various uses such as tires such as treads and sidewalls, conveyor belts, and anti-vibration rubbers. Preferably, it is used for a tire, and rubber parts (tread rubber, sidewall rubber, etc.) of various pneumatic tires can be constituted by vulcanization molding at 140 to 200 ° C., for example, according to a conventional method.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Preparation of silica-containing rubber masterbatch]
Examples 1-8:
Wet wet silica (“VN3” manufactured by Degussa) having a BET specific surface area of 168 m ² / g and a Sears titration = 15.2 ml in a crucible, and in the electric furnace, the treatment temperatures shown in Table 1 below and Heat treatment was performed for the treatment time. After the heat treatment, it was taken out from the electric furnace and allowed to cool in a desiccator. About the obtained heat-treated silica, the BET specific surface area and the Sears titration amount were measured, and the measurement result was the ratio “(Sears / BET) × 100” of both and the ratio to the Sears titration amount before the heat treatment (silanol group amount) Table 1 shows the change.

  Water was added to the heat-treated silica so as to be a 5% by mass silica slurry, and the mixture was treated using a colloid mill under the condition of 8000 revolutions × 30 minutes to obtain a uniform silica slurry. Styrene butadiene rubber latex (“0561” manufactured by JSR Corporation) was diluted so that the rubber concentration was 20 mass%, and 2000 g of the latex was added to 5600 g of the silica slurry and mixed (100 mass of rubber polymer). 70 parts by mass of silica with respect to parts).

  After mixing, formic acid was added as a coagulant for coagulation, solid-liquid separation was performed to recover the coagulum, and the coagulum was washed and dehydrated. Further, it was dried in an oven at 100 ° C. for 60 minutes to obtain a silica-containing rubber master batch. For the obtained silica-containing rubber masterbatch, the amount of silica contained in the masterbatch was measured, and the amount of silica actually taken into the masterbatch (A [phr]) with respect to the amount of silica charged during mixing (A [phr]) B [phr]) ratio (B / A × 100) was determined as the uptake rate and is shown in Table 1. Here, the amount of silica contained in the master batch was measured by TGA (thermogravimetry).

Comparative example 1:
A silica-containing rubber masterbatch was prepared in the same manner as in Examples 1 to 8 except that the above-described wet silica having a small particle size (“VN3” manufactured by Degussa) was used without heat treatment.

Example 9:
As silica, a wet silica having a large particle size (“VN2” manufactured by Degussa) having a BET specific surface area of 106 m ² / g and a Sears titration amount of 10.5 ml was used. A contained rubber masterbatch was prepared.

Comparative example 2:
A silica-containing rubber masterbatch was prepared in the same manner as in Example 9 except that the above-mentioned large silica wet silica (“VN2” manufactured by Degussa) was used without heat treatment.

Comparative Example 3:
As silica, dry silica (“AEROSIL 130” manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 134 m ² / g and a Sears titration amount of 4.2 ml was used without heat treatment. A silica-containing rubber master batch was prepared in the same manner as described above.

[Preparation of rubber composition]
According to the composition (parts by mass) shown in Table 2 below, a rubber composition was prepared using a Banbury mixer according to a conventional method. In detail, first, components excluding sulfur and vulcanization accelerator are kneaded in the first mixing stage, and then sulfur and vulcanization accelerator are added to the obtained mixture and kneaded in the second mixing stage. A composition was prepared. In addition, the numerical value in the parenthesis about the compounding amount of each masterbatch in Table 2 is the amount of silica, and the balance is the amount of the rubber component. In addition, as shown in the said Table 1, since the silica uptake rate of each silica containing rubber masterbatch differs, in each rubber composition, the compounding quantity of the silica with respect to 100 mass parts of rubber components is made constant at 50 mass parts. The rubber component and silica were separately added to the silica-containing rubber master batch. Details of each component in Table 2 are as follows.

Masterbatches E3, 5-8 and 9: Silica-containing rubber masterbatch obtained in Examples 3, 5-8 and 9 respectively Masterbatch C3: Silica-containing rubber masterbatch obtained in Comparative Example 3 SBR: A rubber obtained by coagulating and drying the styrene butadiene rubber latex (“0561” manufactured by JSR Corporation) in the same manner as in Example 1 without mixing with the silica slurry.

・ Small particle size silica: unheat-treated product of small particle size wet silica (“VN3” manufactured by Degussa) used in Example 1 ・ Small particle size heat treated silica: The small particle size silica was subjected to the heat treatment conditions of Example 5. Heat treated silica / large particle size silica: untreated product of large particle size wet silica (Degussa “VN2”) used in Example 9 / large particle size heat treated silica: the large particle size silica of Example 9 Silica silane coupling agent heat-treated under heat treatment conditions: bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik Degussa
・ Carbon black: “Seast KH” manufactured by Tokai Carbon Co., Ltd.
・ Oil: “Process X140” manufactured by Japan Energy Co., Ltd.
・ Zinc flower: "Zinc flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Sulfur: “5% oil-filled fine powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator: “Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd.

  Each rubber composition obtained was vulcanized at 160 ° C. for 30 minutes to prepare a test sample having a predetermined shape, and low exothermic properties, tensile properties, and abrasion resistance were measured and evaluated using the sample. The results are shown in Table 2. In addition, each measuring method is as follows.

Low exothermic property: Using a rheometer E4000 manufactured by UBM, the loss tangent tan δ was measured in a state of 50 Hz, 60 ° C., and dynamic strain 2%, and the value was expressed as an index with the value of Comparative Example 4 being 100. The smaller the index value, the less heat is generated (excellent low heat build-up), and thus the lower the rolling resistance and the better the fuel efficiency when made into a tire.

-Tensile properties: Tensile strength (dumbbell shape No. 3) was measured by a tensile test according to JIS K6251 and displayed as an index with the value of Comparative Example 4 being 100. The larger the index value, the greater the tensile strength and the better the reinforcement.

-Abrasion resistance: A wear loss volume was measured using a Lambone abrasion tester under the conditions of a temperature of 23 ° C and a slip rate of 50%, and the reciprocal of the measured value was displayed as an index with the value of Comparative Example 4 being 100. did. A larger index value indicates better wear resistance.

  As shown in Table 1, in Comparative Example 1 in which a small particle size silica was formed into a wet masterbatch without heat treatment, only about 5% of silica was incorporated into the masterbatch. As in Examples 1 and 2, when the heat treatment temperature was 400 ° C., the silica uptake rate was low, but an improvement effect was observed for Comparative Example 1. When the heat treatment temperature was 400 ° C., no further decrease in the amount of silanol groups was observed even if the treatment time was extended. In Example 3 where the heat treatment temperature was 600 ° C., the amount of silanol groups was remarkably reduced, and silica incorporation was greatly improved during wet master batch formation. Further, in Examples 4 to 7 in which the heat treatment temperature was 800 ° C., the silica uptake during wet master batch formation was greatly improved, and the longer the heat treatment time, the higher the silica uptake rate. In Example 8 in which the heat treatment temperature was 1000 ° C., the improvement in silica uptake due to the decrease in the amount of silanol groups was excellent as in the case of 800 ° C. However, the silica particle size is large, which is probably due to the effect of crystallization due to high temperature.

  As shown in Table 2, the silica dispersibility of Comparative Examples 4 and 5 by dry kneading is that of Examples 10 to 14 using the rubber master batches of the examples with improved silica uptake rate. The improvement effect was recognized in the low exothermic property, the tensile property, and the wear resistance because of the superiority.

  Even in the case of using a large particle size silica, in Comparative Example 2 in which the wet masterbatch was formed without heat treatment, as shown in Table 1, the silica uptake was inferior. In the case of a large particle size silica, the Sears titration amount is seemingly small, but the titer per surface area is as large as Sears / BET × 100 = 9.91, and therefore, the uptake is inferior. On the other hand, in Example 9 in which the large particle size silica was heat-treated, the silica uptake was greatly improved during wet masterbatch formation as in the case of the small particle size silica. Also, in the evaluation of the rubber composition using the rubber master batch, as shown in Table 2, in Example 15, the low exothermic property, the tensile property and the wear resistance were compared with Comparative Examples 6 and 7 by dry kneading. An improvement effect was observed in.

  On the other hand, in Comparative Example 3, since the silica was originally a dry silica with a small amount of silanol groups, there was no problem in silica uptake during wet masterbatch formation, but as shown in Table 2, the particle structure (no pores) ) In the evaluation of the rubber composition, the deterioration of physical properties was remarkable as compared with the examples.

  INDUSTRIAL APPLICATION This invention can be utilized suitably for manufacturing the rubber masterbatch mix | blended and used for various rubber compositions, such as a rubber composition for tires.

Claims (9)

  Silica is heat-treated at 400 to 1000 ° C. to reduce the amount of silanol groups on the silica surface, and the heat-treated silica is dispersed in water to prepare a silica slurry, and the silica slurry and a rubber solution are mixed to produce a silica-containing rubber. A method for producing a silica-containing rubber masterbatch, characterized by producing a masterbatch.   The method for producing a silica-containing rubber masterbatch according to claim 1, wherein the heat treatment temperature of the silica is 600 to 1000 ° C. The heat-treated silica has a ratio of the Sears titration amount (ml) to the BET specific surface area (m ² / g) (Sears titration / BET specific surface area) × 100 is 9 or less. Or the manufacturing method of the silica containing rubber masterbatch of 2 description.   4. The method for producing a silica-containing rubber masterbatch according to claim 3, wherein (the Sears titration / BET specific surface area) × 100 is 6 or less.   The method for producing a silica-containing rubber masterbatch according to any one of claims 1 to 4, wherein the Sears titration (ml) of silica is reduced to 70% or less before the heat treatment by the heat treatment.   The method for producing a silica-containing rubber masterbatch according to any one of claims 1 to 5, wherein the silica to be heat-treated is wet silica.   The method for producing a silica-containing rubber masterbatch according to any one of claims 1 to 6, wherein the rubber solution is a diene rubber latex.   The silica containing rubber masterbatch manufactured by the method of any one of Claims 1-7.   A rubber composition comprising the silica-containing rubber master batch according to claim 8.