JP2012251086A - Silica-containing rubber master batch and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silica-containing rubber master batch capable of excellently satisfying both of rolling resistance performance and wet performance.SOLUTION: There is provided a silica-containing rubber master batch provided by drying a mixture liquid provided by mixing a latex of a diene-based resin (A) having ≥-80°C but ≤-55°C glass transition point, a latex of a diene-based rubber (B) having >-55°C but ≤-30°C glass transition point, an oil, and a silica slurry provided by dispersing silica in water, wherein the content of the diene based rubber (A) is 5-30 mass% based on the dry mass ratio to the whole rubber components, the content of the diene-based rubber (B) is 70-95 mass% based on the dry mass ratio to the whole rubber components, the content of the oil is 3-20 pts.mass based on 100 pts.mass whole rubber components and the content of the silica is 20-200 pts.mass based on 100 pts.mass whole rubber components.

Description

  The present invention relates to a rubber masterbatch containing silica, a rubber composition using the rubber masterbatch, and a pneumatic tire using the rubber composition.

  In recent pneumatic tires, there is an increasing demand for achieving both rolling resistance performance that contributes to low fuel consumption and wet performance related to grip performance on wet road surfaces. However, since rolling resistance performance and wet performance are in a trade-off relationship, it is generally not easy to achieve both of these performances. In order to achieve both performances, it is known to use silica as a filler instead of or in combination with conventional carbon black, but silica has a silanol group (Si-OH) on the particle surface. Since it is easy to agglomerate, it is not easy to uniformly disperse it in the rubber composition in dry kneading (dry kneading). For this reason, it has been proposed to use a silica-containing rubber masterbatch (so-called wet masterbatch) in which a diene rubber and silica are dispersed in an aqueous medium and then solidified and dried.

  For example, in Patent Document 1 below, silica and a cationic polymer are mixed in water to obtain an aqueous dispersion, and then the aqueous dispersion and diene rubber latex are mixed to co-solidify silica and rubber. A silica-containing rubber masterbatch that is dehydrated and dried is disclosed, and it has excellent tensile strength and wear resistance while achieving both low fuel consumption and high grip, and has excellent workability. It is stated that Patent Document 2 below uses a silica-containing rubber master batch obtained by co-coagulating an aqueous dispersion of a conjugated diene rubber having a glass transition point of −120 to 0 ° C. and an aqueous dispersion of silica. A rubber composition obtained by adding and kneading a conjugated diene rubber having a difference in glass transition point from the conjugated diene rubber of 3 to 100 ° C. to the rubber master batch is disclosed. It is described that the fuel economy, wet grip, mechanical strength, wear resistance, and low temperature embrittlement resistance are highly balanced.

International Publication No. 2004/067625 International Publication No. 2005/042632

  In the above-described prior art, although the effect of improving the rolling resistance performance and the wet performance is recognized, it is required to make both performances more compatible with each other, and it is not possible to sufficiently meet such demands. Moreover, the processability at the time of preparing a rubber composition may be inferior.

  The present invention has been made in view of the above points, and is capable of highly achieving both rolling resistance performance and wet performance as compared with the prior art, and has excellent workability when preparing a rubber composition. The object is to provide a silica-containing rubber masterbatch.

  The present inventor is intensively studying in view of the above problems, and uses a silica-containing rubber masterbatch obtained by adding oil to a specific rubber latex blend, mixing silica in an aqueous medium, and drying. As a result, it has been found that a rubber composition having high rolling resistance performance and wet performance can be obtained at the same time and having excellent processability, and the present invention has been completed.

   The silica-containing rubber masterbatch according to the present invention includes a latex of a diene rubber (A) having a glass transition point of −80 ° C. or higher and −55 ° C. or lower, and a diene having a glass transition point of −55 ° C. or higher and −30 ° C. or lower. A silica-containing rubber masterbatch obtained by drying a mixed solution obtained by mixing a latex of a base rubber (B), an oil, and a silica slurry in which silica is dispersed in water, the diene rubber (A ) In the dry mass ratio with respect to the total rubber component is 5 to 30 mass%, the content of the diene rubber (B) is 70 to 95 mass% in the dry mass ratio with respect to the total rubber component, and the oil The content of is 3 to 20 parts by mass with respect to 100 parts by mass of all rubber components, and the content of silica is 20 to 200 parts by mass with respect to 100 parts by mass of all rubber components.

  The rubber composition according to the present invention is formed by blending the silica-containing rubber master batch. Moreover, the pneumatic tire which concerns on the preferable aspect of this invention uses this rubber composition for tread rubber.

  The silica-containing rubber masterbatch according to the present invention is a wet masterbatch using oil together with two or more kinds of specific rubber latexes having different glass transition points. Can be achieved at a high level, and a rubber composition excellent in processability can be obtained.

  Hereinafter, embodiments of the present invention will be described.

  The silica-containing rubber masterbatch according to this embodiment includes a latex of a diene rubber (A) having a glass transition point of −80 ° C. to −55 ° C., and a diene system having a glass transition point of −55 ° C. to −30 ° C. It is a wet masterbatch obtained by drying a mixed solution formed by mixing latex of rubber (B), oil, and silica slurry, and is a composite of silica and diene rubber. In this way, the above-mentioned patent document is not limited to the case of blending rubbers having different glass transition points by dry kneading by blending the above-mentioned specific rubber latex and further adding oil during wet master batching. Compared with the case where one diene rubber is made into a wet masterbatch and the other diene rubber is dry-kneaded with the other diene rubber as shown in Fig. 2, the mixing uniformity of the silica with the rubber component is improved, and the rolling resistance performance and wetness are improved. A higher effect can be obtained in balance with performance.

  Here, the glass transition point of the diene rubber is determined by the differential scanning calorimetry (DSC) method according to JIS K7121 at a rate of temperature increase of 20 ° C./minute (measurement temperature range: −150 ° C. to 50 ° C.). The value to be measured.

  As the diene rubber (A), those having a glass transition point (Tg) of −80 ° C. or more and −55 ° C. or less are used. By using such a rubber having a relatively low glass transition point, it is possible to improve the rolling resistance performance. If the glass transition point is less than −80 ° C., the wet performance is deteriorated. Conversely, if it exceeds −55 ° C., the effect of improving the rolling resistance performance is impaired. The glass transition point of the diene rubber (A) is more preferably −70 to −60 ° C. Specific examples of the diene rubber (A) include natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), and nitrile rubber (NBR). Among these, SBR, NR Is preferred. These diene rubbers may have a functional group such as an epoxy group, hydroxyl group, amino group, carboxyl group or alkoxysilyl group introduced into the molecule.

  The amount of the diene rubber (A) is 5 to 30% by mass with respect to the total mass of rubber components contained in the silica-containing rubber masterbatch. That is, 5 to 30 parts by mass of the diene rubber (A) is contained in 100 parts by mass of all the rubber components after drying. If the content of the diene rubber (A) is too small, the effect of improving the rolling resistance performance is reduced. Conversely, if the content is too large, the wet performance may be deteriorated. The more preferable content of the diene rubber (A) is 10 to 30% by mass, and further preferably 15 to 25% by mass.

  As the diene rubber (B), one having a glass transition point higher than −55 ° C. and not higher than −30 ° C. is used. Wet performance can be improved by using such a rubber having a relatively high glass transition point. If the glass transition point is −55 ° C. or lower, the effect of using the high-Tg diene rubber (B) cannot be obtained. Conversely, if it is higher than −30 ° C., the rolling resistance performance may be deteriorated. The glass transition point of the diene rubber (B) is more preferably -50 to -30 ° C. Specific examples of the diene rubber (B) include, for example, styrene butadiene rubber (SBR), epoxidized natural rubber (ENR), nitrile rubber (NBR), chloroprene rubber (CR), and among these, SBR ENR is preferred. These diene rubbers may have a functional group such as an epoxy group, hydroxyl group, amino group, carboxyl group or alkoxysilyl group introduced into the molecule. Specific examples of preferable combinations with the diene rubber (A) include, for example, an example of SBR in both (A) and (B), an example in which (A) is NR and (B) is SBR, and (A) is NR. (B) is an example of ENR, etc.

  The amount of the diene rubber (B) is 70 to 95% by mass with respect to the total mass of rubber components contained in the silica-containing rubber master batch. That is, 70 to 95 parts by mass of the diene rubber (A) is contained in 100 parts by mass of all the rubber components after drying. If the content of the diene rubber (B) is too small, the wet performance may be deteriorated. Conversely, if the content is too large, the effect of improving the rolling resistance performance becomes insufficient. The more preferable content of the diene rubber (B) is 70 to 90% by mass, and further preferably 75 to 85% by mass.

  The diene rubber (B) preferably has an absolute value of the difference in glass transition point from that of the diene rubber (A) of 10 ° C. or more. By providing such a difference, the rolling resistance performance and the wet performance are improved. Balance can be achieved more effectively. The absolute value of this difference is preferably 15 to 40 ° C, more preferably 20 to 35 ° C.

  The rubber component contained in the silica-containing rubber masterbatch is a rubber other than the diene rubber (A) and the diene rubber (B) as a third component within a range that does not impair the advantageous effects of the present embodiment. It may contain.

  As latexes of these diene rubbers (A) and (B), in addition to synthetic rubber latex synthesized by emulsion polymerization method, natural rubber latex (for example, field latex, concentrated latex, etc.), or solution polymerization method Various rubber latexes such as a latex obtained by emulsifying and dispersing the rubber synthesized by the above can be used. The content of the rubber component (rubber polymer) in the latex is not particularly limited, but generally 10 to 70% by mass can be used.

  As the oil, a hydrophilic oil is preferably used, that is, an oil having an ester bond and / or a hydroxyl group as a part of the structure is preferable. The hydroxyl group includes a case where it exists as a part of a carboxyl group. By adding oil, the rubber viscosity after drying can be lowered and the processability can be improved. In particular, by containing an ester bond and / or a hydroxyl group, it becomes weakly hydrophilic and is in a state where the mixing uniformity of latex and silica is excellent. Specific examples of the oil having such an ester bond and / or hydroxyl group as a part of the structure include castor oil, rapeseed oil, soybean oil, sesame oil, tall oil (tall oil fatty acid), coconut oil, palm oil, olive oil, Examples thereof include vegetable oils such as corn oil, safflower oil, tung oil, and rice oil, and unsaturated fatty acids having 10 to 24 carbon atoms such as oleic acid, linoleic acid, linolenic acid, and pinolenic acid. , Or a combination of two or more.

  The amount of oil added to the mixed solution is preferably 3 to 20 parts by mass with respect to 100 parts by mass of the rubber component (dry mass). If the amount of oil is too small, there will be no effect of lowering viscosity when kneading the rubber composition using the obtained rubber master batch, and processability cannot be improved. Conversely, if the amount of oil is too large, the strength of the rubber composition is reduced. The amount of oil is more preferably 5 to 15 parts by mass.

The silica slurry is an aqueous dispersion of silica obtained by dispersing silica in water. The silica may be wet silica (hydrous silicic acid) or dry silica (anhydrous silicic acid), but is preferably wet silica having good effect of improving fracture characteristics and improving effect of low heat generation. The nitrogen adsorption specific surface area of the silica (BET specific surface area) is not particularly limited, is preferably 80~300m ² / g, more preferably 100 to 250 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 preparation of the silica slurry can be performed using a known method, and is not particularly limited. For example, 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%.

  The amount of silica added to the mixed solution is preferably 20 to 200 parts by mass with respect to 100 parts by mass of the rubber component (dry mass). When the amount of silica is too small, when preparing a rubber composition using the obtained silica-containing rubber masterbatch, the amount of silica derived from the masterbatch is reduced, which is advantageous for improving dispersibility by making a wet masterbatch. The effect is insufficient. On the other hand, when the amount of silica is too large, the rubber component is reduced to form a powdery master batch, and the processability is deteriorated in dry mixing. The amount of silica is more preferably 20 to 100 parts by mass, still more preferably 30 to 80 parts by mass.

  In addition to the above, the mixed solution may contain a silane coupling agent or a surfactant. As the silane coupling agent, various known silane coupling agents described later can be used. Examples of the surfactant include various surfactants such as an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

  In preparing the mixed solution, silica slurry may be mixed with a rubber-containing solution obtained by mixing (1) latex of diene rubber (A), latex of diene rubber (B) and oil, and (2 ) The silica slurry may be mixed with the rubber-containing liquid composed of the latex of the diene rubber (A) and the latex of the diene rubber (B), and then the oil may be added. Alternatively, (3) the oil is added to the silica slurry in advance. In addition, the silica slurry may be mixed with a rubber-containing liquid comprising a latex of diene rubber (A) and a latex of diene rubber (B). Further, (4) oil may be added in advance to both the rubber-containing liquid composed of the latex of the diene rubber (A) and the latex of the diene rubber (B) and the silica slurry, and the both may be mixed. Among these, from the viewpoint of uniform dispersion of the silica particles in the rubber, oil is previously added to the latex of the diene rubber (A) and the diene rubber (B) as described in (1) above. It is preferable to add and mix the silica slurry.

  The mixing of the rubber-containing liquid and the silica slurry can be performed using a known mixer, and is not particularly limited. For example, a method of dropping a rubber-containing liquid while stirring a silica slurry in a homomixer, a method of dropping a silica slurry while stirring a rubber-containing liquid in a homomixer, a silica slurry flow having a predetermined flow rate and a rubber-containing liquid For example, a method in which the flow is mixed and mixed can be used.

  As a technique for drying the mixed solution thus obtained to obtain a silica-containing rubber master batch, (i) the mixed solution may be solidified and dried according to a normal wet master batch, or alternatively, (Ii) The mixed solution may be spray-dried. Preferably, the latter is spray drying, in which case the oil can be more effectively incorporated into the rubber masterbatch.

  In the above (i), a known method can be used to coagulate (co-coagulate) the rubber together with silica, for example, coagulation using an acid such as formic acid or sulfuric acid or a salt coagulant such as sodium chloride. Alternatively, the coagulation may be performed without adding a coagulant. 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.

  The spray drying in the above (ii) can be performed using a known spray dryer. Examples of the spray drying method include a nozzle type and a disk type, and a nozzle type spray dryer is preferable. Spray drying is preferably carried out without coagulating the mixed liquid. For this reason, for example, the rubber-containing liquid and the silica slurry are separately supplied from the respective raw material supply paths and merged into one path. It is preferable that the liquid mixture is immediately sprayed from the spray nozzle into the drying chamber and spray-dried. Although the temperature in this drying chamber is not specifically limited, It is suitable that it is about 50-170 degreeC. Thereby, it is made to dry instantaneously and a silica containing rubber masterbatch is obtained.

  In the silica-containing rubber master batch of the present embodiment obtained as described above, the content of silica is 20 to 200 parts by weight, more preferably 20 to 100 parts by weight, and more preferably 100 parts by weight of the rubber component. Preferably it is 30-80 mass parts. The oil content is 3 to 20 parts by mass, more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the rubber component.

  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, a sulfur-containing compound, and the like, and are not particularly limited. However, the blending amount is 0.1 to 10 parts by mass with respect to 100 parts by mass of all rubber components in the rubber composition. It is preferable that 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 all the rubber components in a rubber composition, More preferably, it is 0.5-5 mass parts. is there. 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 an ordinary Banbury mixer, kneader, or roll. The rubber composition thus obtained can be used for various applications such as treads and sidewalls, belts and ply topping rubbers, bead fillers, tires such as rim strips, conveyor belts, and anti-vibration rubbers. Preferably, it is used for a pneumatic tire. In particular, it is suitably used for a tread rubber constituting the ground contact surface of a pneumatic tire, and the tread portion can be formed by vulcanization molding at, for example, 140 to 200 ° C. according to a conventional method. In the tread portion of the pneumatic tire, there are a two-layer structure of a cap rubber and a base rubber, and a single-layer structure in which both are integrated. In the case of a single layer structure, the entire tread portion is preferably made of the rubber composition, and in the case of a double layer structure, the cap rubber is preferably made of the rubber composition.

  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]
Master batches of Examples and Comparative Examples were prepared as follows. The composition of each master batch is as shown in Table 1. In addition, phr in Table 1 shows the mass part of each component in 100 mass parts or 100 mass parts of rubber components.

Master batch a (Example):
As the diene rubber (A), natural rubber latex (Tg = −64 ° C., “LA Latex” manufactured by Regex Corp.) is used, and as the diene rubber (B), SBR latex (Tg = −31 ° C., “SB latex 0545” manufactured by JSR Corporation is used, “Ultrasil VN3” (BET = 175 m ² / g) manufactured by Degussa is used as silica, and tall oil fatty acid (“Hartol” manufactured by Harima Chemicals Co., Ltd.) is used as the oil. FA-1 ").

  Water was added so that the silica became a 5% by mass silica slurry, and the mixture was processed using a colloid mill under the condition of 8000 rotations × 30 minutes to obtain a uniform silica slurry S1. On the other hand, after blending both diene rubber (A) and diene rubber (B) latex so that the dry mass ratio is A / B = 20/80, the total rubber concentration is 20% by mass. After diluting in this manner, the oil was added to 5 parts by mass with respect to 100 parts by mass of the rubber component and stirred to prepare a rubber-containing liquid R1. The obtained rubber-containing liquid R1 and the silica slurry S1 are mixed at a ratio of 50 parts by mass of silica with respect to 100 parts by mass of the rubber component, and the resulting mixture is spray-dried (a spray dryer manufactured by Yamato Scientific Co., Ltd.). Using “ADL311-A”), spray drying (chamber temperature = 160 ° C.) was performed to obtain a silica-containing rubber masterbatch a.

・ Master batch (comparative example):
The same diene rubber (B), silica and oil as those used in the master batch a were used. After diluting the diene rubber (B) latex so that the rubber concentration is 20% by mass, the oil is added to 5 parts by mass with respect to 100 parts by mass of the diene rubber (B) and stirred. A rubber-containing liquid R2 was prepared. The obtained rubber-containing liquid R2 and the silica slurry S1 are mixed at a ratio that the amount of silica is 50 parts by mass with respect to 100 parts by mass of the diene rubber (B). The silica-containing rubber master batch b was obtained by spray drying.

Master batch c (Example):
As the oil, castor oil (“LAV” manufactured by Ito Oil Co., Ltd.) was used.

Master batch d (comparative example), e (example), f (comparative example):
The blending ratio of oil was changed as shown in Table 1, and the others were the same as in the master batch a to obtain master batches d, e, and f.

Master batch g (Example):
The rubber-containing liquid R1 and the silica slurry S1 are mixed in such a ratio that the silica amount is 50 parts by mass with respect to 100 parts by mass of the rubber component, and after mixing, formic acid is added as a coagulant to solidify, and solid-liquid separation is performed. Then, the coagulated product was washed and dehydrated. Furthermore, it was dried in an oven at 80 ° C. for 150 minutes to obtain a master batch g.

Master batch h (comparative example), i (example), j (example), k (comparative example), l (comparative example):
The compounding ratio of the diene rubber (A) and the diene rubber (B) was changed as shown in Table 1, and the others were the same as in the master batch a to obtain master batches h, i, j, k, and l. .

・ Masterbatch m (comparative example):
SBR latex (Tg = −15 ° C., “Nipol LX206” manufactured by Nippon Zeon Co., Ltd.) was used as the diene rubber (B), and the others were the same as in the master batch a to obtain a master batch m.

Master batch n (Example):
SBR latex (Tg = −66 ° C., “SB Latex 2108” manufactured by JSR Corporation) as the diene rubber (A), and SBR latex (Tg = −31 ° C., manufactured by JSR Corporation) as the diene rubber (B) SB latex 0545 ") was used, and the others were the same as in master batch a to obtain master batch n.

・ Masterbatch o (Example):
SBR latex (Tg = −66 ° C., “SB Latex 2108” manufactured by JSR Corporation) as the diene rubber (A), and SBR latex (Tg = −47 ° C., manufactured by Nippon Zeon Co., Ltd.) as the diene rubber (B). The master batch o was obtained in the same manner as the master batch a except that “Nipol Lx110”) was used.

[Preparation of rubber composition]
Using the master batches a to o obtained above, a rubber composition was prepared using a Banbury mixer according to a conventional method according to the formulation (parts by mass) shown in Table 2 below. 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 parenthesis about the compounding quantity of each masterbatch in Table 2 is the quantity of oil. The rubber component is 100 parts by mass in total for each rubber composition, and the silica is 50 parts by mass in total for each rubber composition. Details of each component in Table 2 are as follows.

SBR1502: “JSR1502” manufactured by JSR Corporation (Tg = −66 ° C.)
・ Natural rubber: natural rubber latex (Tg = −64 ° C., “LA latex” manufactured by Regex Corp.) coagulated and dried using formic acid SBR0545: SBR latex (Tg = −31 ° C., JSR stock) Dry rubber / silica obtained by coagulating and drying “SB Latex 0545” manufactured by the company using formic acid: “Ultrasil VN3” manufactured by Degussa
Silane coupling agent: bis (3-triethoxysilylpropyl) disulfide, “Si75” manufactured by Evonik Degussa
・ Oil: Tall oil fatty acid, “Hartor FA-1” manufactured by Harima Kasei Co., Ltd.
・ Zinc flower: "Zinc flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Sulfur: “5% oil-filled fine powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator: “Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd.

  About each obtained rubber composition, abrasion resistance, rolling resistance performance, and wet performance were measured and evaluated using the test piece of the predetermined shape vulcanized at 160 degreeC * 20 minutes. The results are shown in Table 2. In addition, each measuring method is as follows.

Abrasion resistance: In accordance with JIS K6264, wear loss was measured under the conditions of a load of 40 N and a slip rate of 30% using a lambone wear tester manufactured by Iwamoto Seisakusho, and the value of Comparative Example 1 was taken as 100. Expressed as an index. It shows that it is excellent in abrasion resistance, so that an index | exponent is large.

Rolling resistance performance: Using a viscoelasticity testing machine manufactured by Ueshima Seisakusho, the loss coefficient tan δ at a frequency of 50 Hz, a static strain of 10%, a dynamic strain of ± 1%, and a temperature of 60 ° C. was measured. Expressed as an index. The smaller the index, the smaller the tan δ and the better the rolling resistance performance (ie, low fuel consumption).

Wet performance: Using a viscoelasticity tester manufactured by Ueshima Seisakusho, the loss factor tan δ at a frequency of 50 Hz, a static strain of 10%, a dynamic strain of ± 0.2%, and a temperature of 0 ° C. was measured. The index was displayed. The larger the index, the larger the tan δ, indicating that the wet performance is excellent.

  As shown in Table 2, in Examples 1 to 8 using master batches obtained by adding oil to a blend of a specific diene rubber latex and mixing with a silica slurry to form a wet master batch, abrasion resistance The rolling resistance performance and the wet performance can be made highly compatible without impairing the hardness, and the workability when preparing the rubber composition was also excellent. In particular, as can be seen from a comparison between Example 1 and Example 4, by making a masterbatch by spray drying, the dispersibility of silica was excellent, and the rolling resistance performance was more effective.

  On the other hand, although the diene rubber (A) and the diene rubber (B) are blended and oil is added, in Comparative Example 2 in which normal dry mixing was performed using a Banbury mixer, rolling resistance performance was improved. The improvement effect was insufficient, and the improvement effect was hardly obtained with respect to wear resistance. Further, even in Comparative Example 3 in which the diene rubber (B) was made into a wet masterbatch with silica alone and the diene rubber (A) was dry mixed therewith, the effect of improving rolling resistance performance and wear resistance was insufficient. It was.

  In Comparative Example 4, the oil was added by dry mixing without adding the oil during wet masterbatch formation. In this case, the obtained master batch was dried and unresolved, so that the mixing time of the rubber composition using a Banbury mixer was twice as long as that in Example 3, and the processability was poor. Moreover, the improvement effect of rolling resistance performance was inadequate. In Comparative Example 5, since the amount of oil in forming the wet masterbatch was too large, the strength of the vulcanized rubber was lowered, and the rubber pieces were detached during the wear test, and the wear resistance was greatly deteriorated. In Comparative Example 6, the ratio of the diene rubber (A) was too small, and the effect of improving the rolling resistance performance was insufficient. In Comparative Example 7, the ratio of the diene rubber (A) was too large, and the effect of improving the wet performance was insufficient. In Comparative Example 8, since the low Tg diene rubber (A) was used alone, the wet performance was poor. In Comparative Example 9, the glass transition point of the diene rubber (B) was too high, and the rolling resistance performance was inferior.

  The silica-containing rubber masterbatch according to the present invention can be suitably used for blending in various rubber compositions, and can be preferably used particularly for tire rubber compositions.

Claims (7)

  A latex of a diene rubber (A) having a glass transition point of −80 ° C. or higher and −55 ° C. or lower, a latex of a diene rubber (B) having a glass transition point of −55 ° C. or higher and −30 ° C. or lower, an oil, A silica-containing rubber masterbatch obtained by drying a mixed solution obtained by mixing silica slurry in which silica is dispersed in water, wherein the content of the diene rubber (A) is a dry mass relative to all rubber components 5 to 30% by mass, the content of the diene rubber (B) is 70 to 95% by mass with respect to the total rubber components, and the oil content is 100 parts by mass of the total rubber components. On the other hand, the silica containing rubber masterbatch which is 3-20 mass parts and whose silica content is 20-200 mass parts with respect to 100 mass parts of all rubber components.   The silica-containing rubber according to claim 1, wherein the silica slurry is mixed and dried in a rubber-containing liquid obtained by mixing the latex of the diene rubber (A), the latex of the diene rubber (B) and oil. Master Badge.   The silica-containing rubber masterbatch according to claim 1 or 2, wherein the diene rubber (B) is a styrene butadiene rubber.   The silica-containing rubber masterbatch according to any one of claims 1 to 3, wherein the oil is an oil having an ester bond and / or a hydroxyl group as a part of its structure.   The silica-containing rubber master batch according to any one of claims 1 to 4, wherein the mixed liquid is spray-dried.   The rubber composition formed by mix | blending the silica containing rubber masterbatch of any one of Claims 1-5.   A pneumatic tire using the rubber composition according to claim 6 as a tread rubber.