JP2009035655A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition exhibiting excellent processability, reinforcing property, fracture elongation and heat ageing resistance as well as decreased heat generating property. <P>SOLUTION: A rubber composition that can be subjected to sulfur vulcanization is obtained, by compounding zinc acetylacetonate and copper acetylacetonate into diene rubber, in such a manner that the weight ratio of zinc included in the zinc acetylacetonate to copper included in the copper acetylacetonate ranges from 5:95 to 95:5 and the total amount of zinc included in the zinc acetylacetonate and copper included in the copper acetylacetonate is 0.01 to 0.3 part by weight based on 100 parts by weight of the diene rubber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to rubber compositions and, more particularly, is a balanced and superior material useful for forming rubber members, such as belt cushions and upper bead fillers, disposed adjacent to a coated rubber of a steel member. The present invention relates to a rubber composition exhibiting processability, reinforcing property, elongation at break and heat aging resistance and having reduced heat build-up, and a pneumatic tire using the same.

  In heavy-duty tires, steel cords are used as reinforcements for belts and carcass to support the load, and the rubber members used to directly coat steel cords are highly rigid and A rubber composition having high adhesiveness is generally used. In addition to the rubber member used to directly coat the steel cord, the rubber member disposed adjacent to the rubber member also has a great influence on the durability of the tire. The rubber members disposed adjacent to each other are also required to improve their characteristics in order to improve the durability of the tire. Examples of the rubber member disposed adjacent to the rubber member that directly covers the steel cord include a belt cushion and an upper bead filler that play a role of absorbing the movement of the steel cord and relaxing the stress to prevent separation. These rubber members are required to exhibit high elongation at break, low exothermic property, and high heat aging resistance because large tensile and compressive stresses are applied during tire running.

  Generally, as a technique for improving adhesiveness, a technique of blending a large amount of sulfur (Patent Document 1), a technique of blending a specific adhesion promoter (Patent Document 2), etc. are known. There is a problem that the performance is lowered. In order to increase the heat aging resistance, it is known to increase the blending amount of the vulcanization accelerator with respect to sulfur (Patent Document 3), but the workability and elongation at break when unaged are lowered, and the exothermic property is reduced. There is a problem of increasing. As a technique for suppressing heat generation, generally, (1) a technique of blending large particle size carbon (Patent Document 4), (2) a technique of blending S-SBR (Patent Document 5), (3) silica A method of blending (Patent Document 6) and the like are known, but the method (1) has a problem that the reinforcing property is lowered, and the methods (2) and (3) have a problem that the workability is lowered.

JP 2000-338734 A JP-A-57-165431 JP 2005-225985 A JP-A-8-176345 JP-A-6-248113 JP-A-8-245838

  As a result of diligent studies to solve the above problems, the present inventors have used a specific amount of zinc acetylacetonate and copper acetylacetonate in combination with a diene rubber so as to be adjacent to the coated rubber of the steel member. The present invention has been completed by finding that a rubber composition that exhibits excellent processability, reinforcement, elongation at break and heat aging resistance and has reduced heat buildup can be obtained that is useful as a rubber member to be installed. It was.

  According to the present invention, zinc acetylacetonate and copper acetylacetonate are added to the diene rubber, and the weight ratio of zinc contained in zinc acetylacetonate to copper contained in copper acetylacetonate is 5:95 to 95. 5: the amount of zinc contained in the zinc acetylacetonate and the copper contained in the copper acetylacetonate is 0.01 to 0.3 parts by weight with respect to 100 parts by weight of the diene rubber. A sulfur vulcanizable rubber composition is provided.

  As the diene rubber used in the rubber composition of the present invention, natural rubber or diene synthetic rubber can be used alone or in combination of two or more thereof. Examples of the diene-based synthetic rubber that can be used include various types of butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), butyl rubber (IIR), and acrylonitrile-butadiene copolymer. Combined rubber (NBR), chloroprene rubber (CR), ethylene-propylene-diene copolymer rubber (EPDM), styrene-isoprene copolymer rubber, chloroprene rubber (CR), styrene-isoprene-butadiene copolymer rubber (SIBR) ) And isoprene-butadiene copolymer rubber.

In the rubber composition of the present invention, zinc acetylacetonate and copper acetylacetonate are contained in zinc acetylacetonate and copper contained in copper acetylacetonate with respect to 100 parts by weight of the diene rubber. The weight ratio was 5:95 to 95: 5, and the total amount of zinc contained in zinc acetylacetonate and copper contained in copper acetylacetonate was 0.01 to 0 with respect to 100 parts by weight of the diene rubber. The amount is 3 parts by weight. Zinc acetylacetonate and copper acetylacetonate are commercially available, for example “Narsem zinc” (molecular formula: Zn (C ₅ H ₇ O ₂ ) ₂ .H ₂ O) and “Narsem copper” from Nippon Chemical Industry Co., Ltd. (Molecular formula: Cu (C ₅ H ₇ O ₂ ) ₂ ). The combination of zinc acetylacetonate and copper acetylacetonate improves the workability, reinforcement, break elongation, heat aging resistance and heat buildup in a well-balanced manner.

According to a preferred embodiment of the present invention, from the viewpoints of reinforcing property, elongation at break and processability, the rubber composition is a total of carbon black and / or silica as a reinforcing filler with respect to 100 parts by weight of the diene rubber. Contains 20-60 parts by weight. As for carbon black and silica, conventional ones can be used, but carbon black has an iodine adsorption amount required in accordance with JIS K6217-1 of 70 to 100 g / kg, and is determined in accordance with JIS K6217-4. It is preferable that the absorbed amount of dibutyl phthalate (DBP) is 60 to 160 ml / 100 g, and silica has a nitrogen adsorption specific surface area (N ₂ SA) determined in accordance with JIS K6217-2 of 200 to 400 m ^2. It is preferable that the cetyltrimethylammonium bromide (CTAB) adsorption specific surface area calculated | required based on JISK6217-3 is 170-270 m < ² > / g.

  Further, when silica is blended, in order to enhance the dispersibility of the silica in the rubber and enhance the reinforcing effect on the rubber, 3 to 30% by weight of a silane coupling agent is blended with respect to the weight of the silica. preferable. A conventional silane coupling agent can be used. Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide.

  In the rubber composition of the present invention, typically, 1 to 5 parts by weight of sulfur is blended with 100 parts by weight of the diene rubber. If the amount of sulfur is less than 1 part by weight relative to 100 parts by weight of the diene rubber, the reinforcing property is reduced, and if it exceeds 5 parts by weight relative to 100 parts by weight of the diene rubber, the elongation at break is preferably reduced. Absent. Sulfur may be any of those commercially available.

  In the rubber composition according to the present invention, in addition to the above components, if necessary, any compounding agent generally used in the technical field, for example, a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator. , Processing aids, reinforcing agents and fillers other than carbon black and silica, various oils, anti-aging agents, and other compounding agents generally blended in rubber for tires. , And can be added in a general blending amount. 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, the obtained unvulcanized rubber composition is used as a member such as a cushion rubber and a bead filler disposed adjacent to the steel rubber coat rubber. A pneumatic tire can be formed by a general pressure molding or vulcanization method.

  Next, with reference to FIG. 1, the pneumatic tire which used the said rubber composition for the belt cushion, the upper bead filler, or those both parts is demonstrated. FIG. 1 is a partial cross-sectional view taken along a direction (a meridian direction) along a rotation axis direction of a pneumatic tire. The pneumatic tire includes a carcass 1, and an end portion of the carcass 1 is wound up from the inner side to the outer side by a bead core 2, and is fixed to the bead core 2 by an upper bead filler 3 and a lower bead filler 4. Here, the upper bead filler has a role of absorbing and relaxing the compressive strain caused by deformation generated in the running tire, and the lower bead filler has a role of suppressing deformation generated in the running tire. Further, in the bead portion, a rim cushion 10 is provided on the inner peripheral side of the tire, and a chafer 5 is provided as a reinforcing layer on the rim cushion 10 side of the carcass 1. A belt layer 6 is provided on the tire outer peripheral side of the carcass 1, and a belt cushion 7 is provided at an end of the belt layer 6. Further, an under tread 8 and a cap tread 9 are provided in this order on the tire outer peripheral side of the belt layer 6. Sidewalls 11 that serve to protect the carcass are provided on the side surface of the tire.

  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 to these examples.

Preparation of rubber compositions of standard examples, comparative examples 1 to 5 and examples 1 to 3 According to the formulation shown in the following Table 1, 1.7 liters of compounding agents such as rubber and carbon black excluding sulfur and a vulcanization accelerator were sealed. The banbury mixer was charged and mixed for about 5 minutes. The resulting mixture was discharged from the mixer at 150 ° C. and then cooled to room temperature. Next, sulfur and a vulcanization accelerator are blended into this cooled mixture using a roll and mixed for about 3 minutes, and each unvulcanized rubber of the standard examples, comparative examples 1 to 5 and examples 1 to 3 A composition was obtained.

Test Method Each of the unvulcanized rubber compositions of the standard examples, Comparative Examples 1 to 5 and Examples 1 to 3 obtained as described above was subjected to the following test.
(1) Workability Samples were taken from the unvulcanized rubber compositions of the standard examples, comparative examples 1 to 5 and examples 1 to 3, and each sample was subjected to an L-shaped rotor (testing machine) in accordance with JIS K6300. : SMV300J manufactured by Shimadzu Corporation), Mooney viscosity (MV) 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 is expressed as an index using the Mooney viscosity of the standard example as 100, that is, the following formula: (Mooney viscosity of the standard example) / (Mooney viscosity of other comparative examples or examples) × 100. It was. A larger index value means a lower Mooney viscosity and better workability before vulcanization.

(2) Reinforcing property Unvulcanized rubber compositions of the standard examples, comparative examples 1 to 5 and examples 1 to 3 were press vulcanized at 150 ° C. for 30 minutes to produce a vulcanized rubber sheet having a thickness of 2.0 mm. Then, a JIS No. 3 dumbbell-shaped test piece was punched out from the obtained vulcanized rubber sheet. Next, the test piece of each example was stretched at a tensile speed of 500 mm / min in accordance with JIS K6251 and the tensile stress (M100) at 100% elongation at a temperature of 20 ° C. was measured. The measurement results were expressed as an index with the measured value of the standard example being 100. The larger the index value, the greater the tensile stress and the higher the reinforcement.

(3) Elongation at break The unvulcanized rubber compositions of the standard example, comparative examples 1 to 5 and examples 1 to 3 were press vulcanized at 150 ° C. for 30 minutes to produce a vulcanized rubber sheet having a thickness of 2.0 mm. Then, a JIS No. 3 dumbbell-shaped test piece was punched out from the obtained vulcanized rubber sheet. Next, about the test piece of each example, the elongation at break (EB) was measured at a tensile speed of 500 mm / min and a temperature of 20 ° C. according to JIS K6251. The measurement results were expressed as an index with the elongation at break of the standard example as 100. The larger the index value, the greater the elongation at break.

(4) Heat aging resistance Each of the unvulcanized rubber compositions of the standard examples, Comparative Examples 1 to 5 and Examples 1 to 3 was press vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized rubber sheet having a thickness of 2.0 mm. Produced. For each example, a JIS No. 3 dumbbell-shaped test piece was punched out from the vulcanized rubber sheet, and the test piece was hung in a thermostat at 80 ° C. for 96 hours and aged according to JIS K6257. Next, the breaking elongation (EB) was measured at a temperature of 20 ° C. and a tensile speed of 500 mm / min. The measurement results were expressed as an index with the measured value of the standard example as 100. It shows that it is excellent in heat aging resistance, so that the value of an index | exponent is large.

(5) Exothermic property (tan δ (20 ° C))
The unvulcanized rubber compositions of the standard example, comparative examples 1 to 5 and examples 1 to 3 were press vulcanized at 150 ° C. for 30 minutes to prepare a vulcanized rubber sheet having a thickness of 2.0 mm. A test piece is prepared from this vulcanized rubber sheet, and using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho, in accordance with JIS K6394, under conditions of initial strain 10%, amplitude 2%, frequency 20 Hz and temperature 20 ° C. Loss tangent tan δ (20 ° C.) was determined. The test results were obtained by setting the value of tan δ (20 ° C.) obtained for the standard example to 100, that is, the following formula: (tan δ of standard example (20 ° C.)) / (Tan δ of other comparative examples or examples (20 ° C.) )) X100 and expressed as an index. The larger the index value, the more the exothermic property is reduced.

Table 1 Note:
(1) TSR-20
(2) Nipol 1502 manufactured by Nippon Zeon Co., Ltd.
(3) Show Black N330 manufactured by Showa Cabot Co., Ltd. (iodine adsorption amount 82 g / kg, DBP oil absorption amount 102 ml / 100 g)
(4) Nippon Steel & Carbon Co., Ltd. HTC # SL (iodine adsorption 20 g / kg, DBP oil absorption 55 ml / 100 g)
(5) ULTRASIL VN-3G manufactured by UNITED SILICA INDUSTRIAL
(6) Si-69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
(7) Extract 4 made by Showa Shell Co., Ltd.
(8) FLECTOL TMQ manufactured by FLEXSYS
(9) Toho Zinc Co., Ltd.
(10) Nursem zinc (zinc acetylacetonate) manufactured by Nippon Chemical Industry Co., Ltd.
(11) Nursem copper (copper acetylacetonate) manufactured by Nippon Chemical Industry Co., Ltd.
(12) Fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd.
(13) Noxeller NS-P manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
(14) SANTOGARD PVI made by FLEXSYS

  From the results in Table 1, the rubber composition according to the present invention contains a specific amount of zinc acetylacetonate and copper acetylacetonate with respect to the diene rubber, thereby providing excellent workability, reinforcement, and breakage that are balanced. It can be seen that it exhibits elongation and heat aging resistance, and the exothermicity is reduced.

FIG. 1 is a partial cross-sectional view taken along a direction (a meridian direction) along a rotation axis direction of a pneumatic tire.

Explanation of symbols

1 Carcass 2 Bead Core 3 Upper Bead Filler 4 Lower Bead Filler 5 Chafer 6 Belt Layer 7 Belt Cushion 8 Undertread 9 Cap Tread 10 Rim Cushion 11 Side Wall

Claims (2)

  Zinc acetylacetonate and copper acetylacetonate are added to the diene rubber, and the weight ratio of zinc contained in zinc acetylacetonate to copper contained in copper acetylacetonate becomes 5:95 to 95: 5. Sulfur vulcanization comprising a total amount of zinc contained in acetonate and copper contained in copper acetylacetonate in an amount of 0.01 to 0.3 parts by weight per 100 parts by weight of the diene rubber. Possible rubber composition.   A pneumatic tire using the rubber composition according to claim 1 for a belt cushion, an upper bead filler, or both.

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