JP2005263916A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which shows both high elasticity and low generation of heat and can be extruded into an article having good shape. <P>SOLUTION: The rubber composition comprises (i) 100 pts. wt. of a rubber component consisting of (a) 30 pts. wt. or more of a highly-crystalline syndiotactic polybutadiene-containing polybutadiene and (b) 70 pts. wt. or less of natural rubber and/or polyisoprene rubber, and (ii) 1-7 pts. wt. of a curing accelerator consisting of (a) a thiuram curing accelerator and (b) a sulfenamide curing accelerator in a weight ratio of (a)/(b) of 0.05-0.50. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition having a good extrusion shape while having both a high elastic modulus and low heat build-up, and a run flat tire using the rubber composition as a side reinforcing layer of a sidewall portion.

  Conventionally, in order to improve the run flat durability of a rubber composition used as a side reinforcing rubber of a run flat tire, for example, compounding by fiber blending has been studied, but under severe conditions such as run flat running There is a problem that sufficient durability cannot be obtained because the matrix rubber itself undergoes molecular breakage or crosslinking breakage. In addition, it has been studied to change the composition of the matrix rubber to increase the elastic modulus of the rubber composition or to reduce the heat generation, but conventionally it has been difficult to balance these performances at a high level, and at the same time It was difficult to obtain a good extruded shape.

Japanese Patent Laid-Open No. 11-302458

  Accordingly, an object of the present invention is to provide a rubber composition having a high elastic modulus and low heat build-up and having a good extrusion shape, and a run flat tire using the rubber composition as a side reinforcing layer of a sidewall portion. .

  According to the present invention, (i) 100 parts by weight of a rubber component comprising (a) 30 parts by weight or more of highly crystalline syndiotactic polybutadiene-containing polybutadiene and (b) 70 parts by weight or less of natural rubber and / or polyisoprene rubber; (Ii) (a) a thiuram vulcanization accelerator and (b) a sulfenamide vulcanization accelerator as a vulcanization accelerator, and a blending amount of the thiuram vulcanization accelerator (a) and a sulfenamide A rubber composition comprising 1 to 7 parts by weight of a total amount in a ratio (weight ratio) (a) / (b) of the blending amount of the vulcanization accelerator (b) being 0.05 to 0.50; A run flat tire using the same as a side reinforcing layer of the sidewall portion is provided.

  As described above, according to the present invention, it is possible to obtain a rubber composition having a high elastic modulus and low heat build-up by limiting the blending ratio of a specific vulcanization accelerator and having a good extrusion shape, For example, it is suitable for use as a side reinforcing layer of a run flat tire.

  In order to solve the above-mentioned problems, the present inventors in 100 parts by weight of a rubber component composed of polybutadiene (VCR) containing highly crystalline syndiotactic polybutadiene and natural rubber (NR) and / or polyisoprene rubber (IR). 30 parts by weight or more of highly crystalline syndiotactic polybutadiene-containing polybutadiene (VCR), a specific thiuram vulcanization accelerator (a) as a vulcanization accelerator, and a sulfenamide vulcanization accelerator (b) The ratio (weight ratio) (a) / (b) of the blending amount (a) of the thiuram vulcanization accelerator (a) / the blending amount (b) of the sulfenamide vulcanization accelerator is 0.05 to 0.50. It was found that a rubber composition having both a high elastic modulus and low heat build-up and having a good extrusion shape can be obtained by blending at a ratio of preferably 0.05 to 0.30.

  In the rubber composition of the present invention, if the blending amount of the highly crystalline syndiotactic polybutadiene-containing polybutadiene is less than 30 parts by weight, the performance balance cannot be obtained, and the vulcanization accelerators (a) and (b) are the above (a). If the ratio is less than the lower limit of the ratio of / (b), the performance change of the rubber composition during run-flat running is large, and if the upper limit of the ratio of (a) / (b) is exceeded, the vulcanization rate of the rubber composition increases. This is not preferable because processability deteriorates.

  Examples of polybutadiene (VCR) containing highly crystalline syndiotactic polybutadiene blended in the rubber composition according to the present invention include Japanese Patent Publication Nos. 53-39917, 54-5436, and 56-18005. Can be polymerized according to the method described in 1., for example, those commercially available as “UBEPOL VCR412” from Ube Industries, Ltd. can be used.

  The NR and / or IR compounded in the rubber composition according to the present invention can be any NR and IR that can be used for the rubber composition, and they can be used alone or blended in any proportion. Can be used.

  The thiuram vulcanization accelerator that can be used in the rubber composition of the present invention is represented by the formula (I):

(In the formula, R ¹ represents a C ₁ -C ₃ alkylene group, which may be linear or branched, and may be the same or different. R ₂ and R ₃ are independently a phenyl group. An aromatic hydrocarbon group such as C ₁ -C ₁₀ alkyl group or hydrogen, etc. The alkyl group may be linear or branched, and may be the same or different. Specific examples of the vulcanization accelerator include tetrabenzyl thiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, and the like, which are conventionally known compounds such as PERKACIT TB _z TD manufactured by FLEXSYS, Ouchi Commercial products such as Shinsei Chemical's Noxeller TOTN can be used.

  Examples of the sulfenamide vulcanization accelerator that can be used in the rubber composition of the present invention include N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, And N-oxydiethylene-2-benzothiazole sulfenamide, N, N′-diisopropyl-2-benzothiazole sulfenamide, N, N′-dicyclohexyl-2-benzothiazole sulfenamide, and the like. Is a conventionally known compound. For example, commercially available products such as Noxeller CZ-G and Noxeller NS-F manufactured by Ouchi Shinsei Chemical Industry can be used.

  FIG. 1 shows an example of a tire portion of the run-flat tire of the present invention, where 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. The left and right sidewall portions 3 are connected to the left and right bead portions 2 on the tire outer diameter side, and the tread portion 1 extending in the tire circumferential direction is provided between the left and right sidewall portions 3. Two carcass layers 4 are disposed on the inner side of the tire, and both ends of the carcass layer 4 are embedded in the left and right bead portions 2, respectively, and the inside of the tire is surrounded by a bead core 6 with bead fillers 5 disposed on the outer periphery. It is folded back from the outside. The outer carcass layer 4 extends only to the vicinity of the boundary where the bead core 6 and the bead filler 5 are in contact with each other, whereas the both ends of the inner carcass layer 4 are connected to the bead filler 5. It extends beyond the outer periphery of the bead filler 5 to the outside of the tire so as to be sandwiched. A plurality of belt layers 7 are embedded in the tread portion 1 on the outer peripheral side of the carcass layer 4.

  An annular side reinforcing layer 8 having a crescent-shaped cross section is disposed inside the carcass layer 4 located in the sidewall portion 3. The outer peripheral end of the side reinforcing layer 8 on the tire outer diameter side extends so as to overlap the end portion of the belt layer 7 in a plan view, and the inner peripheral end on the tire inner diameter side is a bead filler 5 in a side view. It is extended so as to overlap. Reference numeral 9 denotes an inner liner disposed inside the tire, and a side reinforcing layer 8 is disposed between the inner liner 9 and the inner carcass layer 4.

  In the rubber composition according to the present invention, any compounding agent usually used in a tire or other rubber composition can be blended as necessary. Examples of such compounding agents include reinforcing fillers, process oils, vulcanizing agents, vulcanization accelerators other than those mentioned above, anti-aging agents, activators, plasticizers, and the like, and the compounding amount is also the object of the present invention. As long as the above is not impaired, the conventional blending amount can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these examples.

Examples 1-4 and Comparative Examples 1-4
Sample preparation In the formulation (parts by weight) shown in Table I, the ingredients other than the vulcanization accelerator and sulfur were kneaded for 3 to 5 minutes in a 1.8 liter closed mixer and released when the temperature reached 160 ± 5 ° C. To obtain a master batch. This master batch was kneaded with an vulcanization accelerator and sulfur in an 8-inch open roll to obtain a rubber composition. Next, the obtained rubber composition was press vulcanized at 160 ° C. for 20 minutes in a 15 × 15 × 0.2 cm mold to prepare a target test piece. Aging condition: after being left in a 70 ° C. oven for 168 hours, the change in hardness was evaluated. The results are shown in Table I. The unvulcanized product was used as it was for evaluation of extrusion processability.

Table 1 footnote * 1: UBEPOL VCR412 manufactured by Ube Industries, Ltd.
* 2: Seest F manufactured by Tokai Carbon Co., Ltd.
* 3: Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. * 4: Bead stearic acid manufactured by Nippon Oil & Fats Co., Ltd. * 5: Nocrack 6C manufactured by Ouchi Shinsei Chemical Co., Ltd.
* 6: Sumitomo Bakelite Co., Ltd. Sumilite Resin PR-YR-150
* 7: Tetrabenzylthiuram disulfide FLEXSYS Co., Ltd. PERKACIT TB _z TD
* 8: Tetrakis (2-ethylhexyl) thiuram disulfide Ouchi Shinsei Chemical Co., Ltd. Noxeller TOTN
* 9: N-cyclohexyl-2-benzothiazyl-sulfenamide Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
* 10: Cristox HS OT 20 manufactured by Akzo Nobel

Evaluation test method * 11: Using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho, E '(storage modulus) at 100 ° C and 60 under conditions of dynamic strain ± 2%, initial strain 10%, deformation frequency 20Hz The tan δ at 0 ° C. was measured.
* 12: Extrusion workability: The shape of the sample after the garbage die extrusion test was subjected to sensory evaluation. ○ is good skin and edge shape, × is not.
* 13: Hardness difference before and after heat aging: JIS hardness difference at 20 ° C before and after aging test at 70 ° C x 168 hours.

  The rubber composition according to the present invention is suitable for use as, for example, a rubber for side reinforcement of a run-flat tire because it has a high elastic modulus, low heat build-up, and good extrudability.

It is a meridian half sectional view showing an example of a tire portion of a run flat tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Tread part 2 ... Bead part 3 ... Side wall part 4 ... Carcass layer 5 ... Bead filler 6 ... Bead core 7 ... Belt layer 8 ... Side reinforcement layer

Claims (3)

  (I) (a) 100 parts by weight of a rubber component comprising 30 parts by weight or more of a highly crystalline syndiotactic polybutadiene-containing polybutadiene and (b) 70 parts by weight or less of natural rubber and / or polyisoprene rubber, and (ii) vulcanization acceleration (A) a thiuram vulcanization accelerator and (b) a sulfenamide vulcanization accelerator, and a blending amount of the thiuram vulcanization accelerator (a) and a sulfenamide vulcanization accelerator (b ) In the ratio (weight ratio) (a) / (b) of 0.05 to 0.50, the rubber composition comprising 1 to 7 parts by weight in total. The rubber composition according to claim 1, wherein the thiuram vulcanization accelerator (a) is a compound represented by the formula (I).

(In the formula, R ¹ independently represents a C ₁ -C ₃ alkylene group, R ² represents an aromatic hydrocarbon group, and R ³ represents an aromatic hydrocarbon group, a hydrocarbon group, or hydrogen.)   The run flat tire which used the rubber composition of Claim 1 or 2 as a side reinforcement layer of a side wall part.

Images