JP2009029961A - Masterbatch for rubber composition and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a masterbatch capable of reducing heat build-up of a rubber composition and of improving processability, tensile strength and flexural fatigue resistance. <P>SOLUTION: This masterbatch for the rubber composition comprises (A1) a diene rubber of 100 pts.wt. and (B) silica of 10-30 pts.wt., wherein ≥60 and ≤100 pts.wt of the diene rubber (A1) of 100 pts.wt. is composed of (A1-i) polybutadiene rubber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a masterbatch for a rubber composition containing polybutadiene rubber and silica and a method for producing the same, and more particularly to improve processability before vulcanization, reduce exothermicity after vulcanization, The present invention relates to a masterbatch for a rubber composition capable of improving strength and bending fatigue resistance, a method for producing the same, and a method for producing a rubber composition for a tire using the masterbatch.

  In recent years, demands for lower fuel consumption and less maintenance for tires have been increasing. The most effective way to reduce the fuel consumption of tires is to reduce the rolling resistance of the tread that contacts the road surface due to its volume, but the particle size of carbon black used as a reinforcing filler to reduce heat generation The larger the amount and the larger the blending amount, the lower the wear resistance required for the tire tread. Therefore, for the rubber composition constituting the sidewall, silica can be blended, for example, in Patent Document 1 below. And 2 are proposed. Further, as a technique for dispersing silica in a rubber composition, it is proposed in Patent Document 3 below to use a silica-containing master batch under specific conditions for a diene rubber. Although these prior arts have achieved certain effects, they can improve fuel economy (low heat generation), tensile strength, and bending fatigue resistance at a high level in a well-balanced manner while maintaining good processability. It has been demanded.

JP 2006-124487 A JP 2005-126556 A JP 2005-350595 A

  As a result of intensive studies to solve the above problems, the present inventors have improved the dispersibility of silica by using a diene rubber containing 60% by weight or more of polybutadiene rubber as a rubber component used in a silica-containing masterbatch. Further, the inventors have found that the heat generation is further reduced and the bending fatigue resistance is improved, and the present invention has been completed.

That is, according to the present invention, in the first aspect,
(A1) 100 parts by weight of a diene rubber,
(B) 10 to 30 parts by weight of silica;
A master batch for a rubber composition, wherein 60 parts by weight or more and 100 parts by weight or less of 100 parts by weight of the diene rubber (A1) is composed of (A1-i) polybutadiene rubber. A masterbatch for a rubber composition is provided.

  According to the second aspect of the present invention, a method for producing a masterbatch for a rubber composition comprising adding (B1) 10 to 30 parts by weight of silica to 100 parts by weight of (A1) diene rubber and mixing them. A method for producing a masterbatch for a rubber composition, wherein 60 parts by weight or more and 100 parts by weight or less of 100 parts by weight of diene rubber (A1) is composed of (A1-i) polybutadiene rubber. Is provided.

  According to the third aspect of the present invention, the rubber composition masterbatch according to the first aspect of the present invention is prepared by adding (D) to 100 parts by weight of the diene rubber (A1) in the rubber composition masterbatch. And 10) to 100 parts by weight of carbon black are added and mixed. A method for producing a rubber composition for tires is provided.

The diene rubber (component (A1)) used in the master batch for a rubber composition according to the first aspect of the present invention is composed of 60 parts by weight or more and 100 parts by weight or less of the total amount of 100 parts by weight. It is composed of rubber (BR) (component (A1-i)). Of the polybutadiene rubber (A1-i) contained in the masterbatch of the present invention, 5 to 30 parts by weight are composed of a low molecular weight polybutadiene rubber having a weight average molecular weight of 5.0 × 10 ^{3 to} 3.0 × 10 ^4. It is preferable. By using a low molecular weight polybutadiene rubber having a weight average molecular weight of 5.0 × 10 ^{3 to} 3.0 × 10 ⁴ , while maintaining the workability at a good level by the plasticizing action of the low molecular weight polybutadiene rubber, The exothermic property can be further reduced. The polybutadiene rubber (A1-i) is a low molecular weight polybutadiene rubber having a weight average molecular weight of 5.0 × 10 ^{3 to} 3.0 × 10 ⁴ of 5 to 30 parts by weight per 100 parts by weight of the total amount of the polybutadiene rubber (A1-i). And 75 to 95 parts by weight of polybutadiene rubber having a weight average molecular weight of 3.5 × 10 ^{5 to} 7.0 × 10 ⁵ . Low molecular weight polybutadiene rubber having a weight average molecular weight of 5.0 × 10 ^{3 to} 3.0 × 10 ⁴ is, for example, trade name poly-bd R-45HT (polybutadiene rubber having a weight average molecular weight of about 10,000) from Idemitsu Chemical Co., Ltd. It is available. A polybutadiene rubber (A1-i) containing a low molecular weight polybutadiene rubber having a weight average molecular weight of 5.0 × 10 ^{3 to} 3.0 × 10 ⁴ is, for example, trade name BRX5000 (weight average molecular weight of about 20,000 from Nippon Zeon Co., Ltd.). A mixture of a low molecular weight component and a high molecular weight component having a weight average molecular weight of about 570,000).

  The diene rubber (A1) contains other diene rubber (component (A1-ii)) in addition to the polybutadiene rubber (A1-i) as long as the polybutane diene rubber (A1-i) is contained in the above amount. But you can. Examples of other diene rubbers (A1-ii) include natural rubber (NR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), Examples include chloroprene rubber (CR), ethylene-propylene-diene copolymer rubber (EPDM), styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber (SIBR), and isoprene-butadiene copolymer rubber. It is done. One or more selected from these diene rubbers can be used in combination with the polybutadiene rubber (A1-i).

The silica can be used in the preparation of the masterbatch of the present invention phosphite (Component (B)), for example, nitrogen adsorption specific surface area (N ₂ SA) of 100m ² / g~250m ² / g wet - by precipitation The generated one can be used. Silica (B) is blended in an amount of 10 to 30 parts by weight with respect to 100 parts by weight of diene rubber (A1). When the silica (B) is less than 10 parts by weight with respect to 100 parts by weight of the diene rubber (A1), the resulting masterbatch contains a compounding agent such as carbon black (component (D)) described later, and further diene The heat build-up after vulcanization of the rubber composition for tires obtained by blending rubber (component (A-2)) cannot be sufficiently reduced, and silica (100 parts by weight with respect to 100 parts by weight of diene rubber (A1)). When B) exceeds 30 parts by weight, the processability when compounding agents such as diene rubber (A2) and carbon black (D) are blended with the masterbatch decreases.

  In order to improve the dispersibility of the silica (B) in the diene rubber (A1), the master batch of the present invention contains 3 to 15% by weight of a silane coupling agent (component (component ( C)) is preferably blended. As the silane coupling agent (C), those generally used in the rubber industry can be used. Examples of the silane coupling agent (C) include 3,3′-bis (trimethoxysilylpropyl) disulfide, 3,3′-bis (triethoxysilylpropyl) disulfide, and 3,3′-bis (triethoxysilyl). Propyl) tetrasulfide.

  The method for producing a masterbatch according to the second aspect of the present invention includes adding (B1) 10 to 30 parts by weight of silica to (A1) 100 parts by weight of a diene rubber, and mixing the diene rubber. (A1) 60 parts by weight or more and 100 parts by weight or less of 100 parts by weight are composed of (A1-i) polybutadiene rubber. In order to improve the dispersibility of the silica (B) in the diene rubber (A-1), 3 to 15% by weight of the silane coupling agent (C) based on the total amount of the silica (B) is mixed to obtain a master batch. Is preferably formed. The mixing temperature for producing the master batch is preferably 90 to 160 ° C.

The manufacturing method of the rubber composition for tires concerning the 3rd mode of the present invention is the master batch for the rubber composition according to the 1st mode of the present invention. (D) 10 to 100 parts by weight of carbon black is added to 100 parts by weight of the diene rubber (A1) and mixed. In the present invention, examples of the carbon black (D) that can be added to the master batch include SAF to HAF grades. When the carbon black (D) is blended, the carbon black (D) preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 60 to 120 m ² / g. When N ₂ SA is less than 60 m ² / g, the filling amount can be increased, but the reinforcing effect is insufficient, and the flexural fatigue resistance after vulcanization of the obtained rubber composition is lowered. Carbon black (D) with N ₂ SA exceeding 120 m ² / g is difficult to disperse in the rubber component because of its high cohesiveness. When the compounding amount of carbon black (D) exceeds the above range with respect to 100 parts by weight of the master batch, the workability when mixing the carbon black (D) into the master batch is lowered.

  In the method for producing a tire rubber composition according to the third aspect of the present invention, a diene rubber (component (A2)) may be further added in addition to the carbon black (D). When the diene rubber (A2) is added in the method for producing a tire rubber composition according to the third aspect of the present invention, the blending amount of the diene rubber (A2) is the diene type contained in the masterbatch. It is preferable that it is 5-100 weight part with respect to 100 weight part of rubber | gum (A1). The diene rubber (A2) that can be added to the masterbatch in this method for producing a rubber composition for tires is one of those described above for the diene rubber (A1) contained in the masterbatch or Two or more types can be used. That is, examples of the diene rubber (A2) that can be added to the masterbatch in the method for producing a tire rubber composition according to the third aspect of the present invention include natural rubber (NR) and polybutadiene rubber (BR). , Styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), ethylene-propylene-diene copolymer rubber (EPDM), styrene -Isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber (SIBR), isoprene-butadiene copolymer rubber and the like. One or two or more selected from these diene rubbers can be used, and the diene rubber (A2) has no conditions regarding the polybutadiene rubber content as described above for the diene rubber (A1). When the diene rubber (A2) is added, the rubber composition obtained by containing 30-80 parts by weight of polybutadiene rubber in the combination of the diene rubber (A1) and the diene rubber (A2) It is preferable from the viewpoint of reducing the exothermic property of the vulcanizate.

  In the method for producing a rubber composition for a tire according to the third aspect of the present invention, as described above, carbon black (D) and, if necessary, diene rubber (A2) are added to the master batch of the present invention. And preferably mixed at a temperature of 120 to 170 ° C. After this mixing, a vulcanizing agent and a vulcanization accelerator are preferably mixed at a temperature of 130 ° C. or lower to obtain an unvulcanized tire rubber composition. The blending amount of the above components in the method for producing a rubber composition for a tire of the present invention is a tire rubber composition in which the exothermic property after vulcanization is further reduced and the tensile strength and the bending fatigue resistance are further improved. In order to obtain 100 parts by weight of the diene rubber, the proportion of the polybutadiene rubber is 30 to 80 parts by weight, and the silica content is 5 to 30 parts by weight with respect to 100 parts by weight of the total diene rubber. The black content is preferably selected so as to be 10 to 50 parts by weight with respect to 100 parts by weight of the total diene rubber content.

  In the method for producing a tire rubber composition according to the third aspect of the present invention, if necessary, in addition to the above components, any compounding agent generally used in the technical field, for example, silica and Other fillers other than carbon black, processing aids, anti-aging agents, oils, and the like can be added in general amounts. As a mixing method used for blending the additive, a general method can be used. Generally, a lump, pellet or powder compound is mixed with an appropriate mixer such as a kneader, an internal mixer, It can mix using a Banbury mixer, a roll, etc. After preparing an unvulcanized rubber composition by mixing various compounding agents, for example, a pneumatic tire can be formed by a general pressure molding or vulcanization method.

  The rubber composition for tires obtained by the production method of the third aspect of the present invention can be used for various rubber members of tires, but has high processability before vulcanization, low exothermicity after vulcanization, and high tensile strength. In addition, the rubber composition is preferably used as a rubber composition for applications requiring bending fatigue resistance, for example, tire sidewalls.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but it goes without saying that the technical scope of the present invention is not limited by these examples.

Preparation of rubber compositions of standard examples, comparative examples 1 to 4 and examples 1 to 6 In accordance with the blending in Table 1 below, blended in the first mixing step at a rotation speed of 60 rpm using a 1.7 liter sealed Banbury mixer. The ingredients were mixed for about 5 minutes and released at about 150 ° C. to form a masterbatch (first mixture). In the next second mixing step, a compounding agent such as carbon black is added to the master batch, mixed at a mixer rotation speed of 60 rpm for about 5 minutes, and discharged at about 160 ° C. to form a second mixture. The two mixtures were cooled to room temperature. Then, as a 3rd mixing process, a vulcanization accelerator and sulfur were added using an open roll, and each unvulcanized rubber composition of a standard example, comparative examples 1-4, and examples 1-6 was obtained.

Table 1 Note:
(1) RSS # 4
(2) Nipol 1220 manufactured by Nippon Zeon Co., Ltd.
(3) BRX5000 manufactured by Nippon Zeon Co., Ltd. (a pre-blend polybutadiene rubber consisting of a low molecular weight component having a weight average molecular weight of about 20,000 and a high molecular weight component having a weight average molecular weight of about 570,000 (weight ratio (low molecular weight component: high molecular weight component) = 40: 100)))
(4) poly-bd R-45HT polybutadiene rubber manufactured by Idemitsu Chemical Co., Ltd. (weight average molecular weight about 10,000)
(5) Nip seal AQ (N ₂ SA = approx. 210 m ² / g) manufactured by Tosoh Silica Co., Ltd.
(6) SI69 manufactured by Degussa
(7) Seast 3 made by Tokai Carbon Co., Ltd. (N ₂ SA = approx. 75 m ² / g)
(8) Idemitsu Kosan Co., Ltd. Diana Process Oil AH-20
(9) Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
(10) Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.
(11) Bead stearic acid manufactured by NOF Corporation
(12) SANTOCURE TBBS made by FLEXSYS
(13) Fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd.

Test Method Each unvulcanized rubber composition obtained as described above was subjected to the following test.
(1) Workability Samples were taken from each of the unvulcanized rubber compositions of the standard examples, comparative examples 1 to 4 and examples 1 to 6, and each sample was subjected to an L-shaped rotor (testing machine) according to JIS K6300. : SMV300J manufactured by Shimadzu Corporation), Mooney viscosity was measured at a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a temperature of 100 ° C. The measured Mooney viscosity was expressed as an index with the Mooney viscosity determined for a sample collected from the unvulcanized rubber composition of the standard example as 100. The smaller the value, the lower the Mooney viscosity. The Mooney viscosity is an index of processability before vulcanization of the rubber composition, and a small Mooney viscosity value means that the viscosity before vulcanization is low and the processability is excellent.
(2) Elongation at break The unvulcanized rubber compositions of the standard examples, comparative examples 1 to 4 and examples 1 to 6 were press vulcanized at 150 ° C. for 30 minutes to vulcanize 15 cm long, 15 cm wide and 2 mm thick. A rubber sheet was prepared. A JIS No. 3 dumbbell specimen was punched from the vulcanized rubber sheet, and the elongation at break was measured at a temperature of 23 ° C. in accordance with JIS K6251. The measurement results were expressed as an index with the elongation at break of Standard Example 1 as 100. It shows that breaking elongation is so large that a numerical value is large.
(3) Exothermic property (tan δ (60 ° C))
The unvulcanized rubber compositions of the standard example, comparative examples 1 to 4 and examples 1 to 6 were press vulcanized at 150 ° C. for 30 minutes to prepare vulcanized rubber sheets having a length of 15 cm, a width of 15 cm and a thickness of 2 mm. . A test piece was prepared from this vulcanized rubber sheet, and tan δ was determined under the conditions of strain 10 ± 2%, frequency 20 Hz, and ambient temperature 60 ° C. according to JIS K6394 using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho. . The test results were expressed as an index with the value of tan δ (60 ° C.) obtained for the standard example being 100. It shows that exothermic property was reduced, so that the numerical value of an index | exponent is small.
(4) Bending fatigue resistance Each of the unvulcanized rubber compositions of the standard examples, comparative examples 1 to 4 and examples 1 to 6 was press vulcanized at 150 ° C. for 30 minutes using a predetermined mold to prepare test pieces. . Using this test piece, a flex crack test was performed according to JIS K6260. The crack length after bending a total of 100,000 times at a room temperature at a stroke of 40 mm and a bending speed of 300 ± 10 times per minute was measured. The measurement result is a value of 100 × L ₀ / L ₁ when the crack length of the standard example is L ₀ and the crack length of the example to be compared with the standard example is L ₁ . Expressed as an index, with L ₀ being 100. The larger the value, the better the bending fatigue resistance.

  From the results shown in Table 2, the viscosity of the rubber composition obtained when silica is added in the second mixing step is higher than that of the standard example (Comparative Example 1), and a masterbatch containing only natural rubber as a rubber component is obtained. When prepared, the exothermic property is increased (Comparative Example 2). When the amount of silica is less than the amount specified in the present invention, the elongation at break is reduced (Comparative Example 3), and the amount of silica is specified in the present invention. It can be seen that the exothermicity increases when the amount is larger than the amount (Comparative Example 4). On the other hand, in Examples 1 to 6 included in the scope of the present invention, the elongation at break, exothermic property and bending fatigue resistance were improved while improving the workability. Further, the addition of a low molecular weight polybutadiene rubber further improved the workability. It can be seen that it can be further improved and the exothermicity can be further reduced.

Claims (8)

(A1) 100 parts by weight of a diene rubber,
(B) 10 to 30 parts by weight of silica;
A master batch for a rubber composition, wherein 60 parts by weight or more and 100 parts by weight or less of 100 parts by weight of the diene rubber (A1) is composed of (A1-i) polybutadiene rubber. Masterbatch for rubber composition. 5 to 30 parts by weight of the polybutadiene rubber (A1-i) is composed of a low molecular weight polybutadiene rubber having a weight average molecular weight of 5.0 × 10 ^{3 to} 3.0 × 10 ⁴ , The masterbatch for rubber compositions according to claim 1.   The rubber according to claim 1 or 2, wherein the master batch for rubber composition further comprises (C) 3 to 15% by weight of a silane coupling agent based on the total amount of silica (B). A master batch for the composition.   (A1) A method for producing a masterbatch for a rubber composition, comprising adding (B) 10 to 30 parts by weight of silica to 100 parts by weight of a diene rubber and mixing, the diene rubber (A1) A method for producing a masterbatch for a rubber composition, wherein 60 parts by weight or more and 100 parts by weight or less of 100 parts by weight is composed of (A1-i) polybutadiene rubber. 5 to 30 parts by weight of the polybutadiene rubber (A1-i) is composed of a low molecular weight polybutadiene rubber having a weight average molecular weight of 5.0 × 10 ^{3 to} 3.0 × 10 ⁴ , The manufacturing method of the masterbatch for rubber compositions of Claim 4.   The method further comprises adding (C) 3 to 15% by weight of a silane coupling agent to the diene rubber (A1) based on the total amount of silica (B) and mixing. A method for producing a masterbatch for a rubber composition according to 4 or 5.   The rubber composition masterbatch according to any one of claims 1 to 3, wherein (D) is 10 to 100 parts by weight with respect to 100 parts by weight of the diene rubber (A1) in the rubber composition masterbatch. A method for producing a rubber composition for a tire, comprising adding and mixing the carbon black.   Adding 100 parts by weight of diene rubber (A1) in the master batch for rubber composition to (A2) 5 to 100 parts by weight of diene rubber to the master batch for rubber composition and mixing. Furthermore, the manufacturing method of the rubber composition for tires of Claim 7 characterized by the above-mentioned.