JP2008179718A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire in which a rubber composition useful for the belt cushion of a pneumatic tire has reduced heat generation and which has an improved fatigue resistance and processability. <P>SOLUTION: The pneumatic tire is obtained by using a rubber composition comprising (A) 100 pts.wt. of a rubber component containing 5-30 pts.wt. of a vinyl-cis-polybutadiene rubber obtained by (1) adjusting the water concentration of a mixture of 1,3-butadiene and an inert organic solvent composed of a 4C fraction as a main component, (2) then adding a cis-1,4 polymerization catalyst to the mixture and subjecting 1,3-butadiene to cis-1,4 polymerization and (3) then adding a 1,2 polymerization catalyst to the obtained polymerization reaction mixture and subjecting 1,3-butadiene to 1,2 polymerization and (B) 10-40 pts.wt. of carbon black and/or silica in a belt cushion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire useful for heavy loads, in which a rubber composition excellent in low heat generation and processability is used for a belt cushion rubber.

  The belt cushion of pneumatic tires, especially heavy duty tires, acts to relieve stress between the belt and the carcass, and the belt cushion rubber has low heat buildup, high fatigue resistance, and excellent workability. It is necessary to be. Patent Document 1 is known as a proposal for improving the separation resistance of a belt cushion of a pneumatic tire. However, there is a need for a belt cushion rubber having further low heat generation and excellent workability.

JP-A-6-92108

  Accordingly, it is an object of the present invention to develop a rubber composition suitable for use in a pneumatic tire belt cushion having improved low heat build-up, fatigue resistance and processability.

According to the present invention, the concentration of water in the mixture of (A) (1) 1,3-butadiene and an inert organic solvent mainly composed of C ₄ fraction is adjusted. , 4-polymerization catalyst is added to the mixture to polymerize 1,3-butadiene in cis-1,4 polymerization. (3) Then, a 1,2-polymerization catalyst is present in the resulting polymerization reaction mixture, and 1 100 parts by weight of a rubber component containing 5 to 30 parts by weight of vinyl cis-polybutadiene rubber obtained by 1,2 polymerization of 1,3-butadiene and (B) 10 to 40 parts by weight of carbon black and / or silica There is provided a pneumatic tire using a rubber composition comprising the belt composition as a belt cushion.

  According to the present invention, by blending the above-mentioned specific vinyl cis-polybutadiene rubber (hereinafter referred to as a modified VCR), low heat generation suitable for use as a belt cushion and improvement in fatigue resistance can be ensured. Furthermore, the rubber composition which improves workability was discovered.

  As a result of researches to solve the above problems, the present inventors can ensure further lower heat generation and improved fatigue resistance by blending with the rubber composition for the modified VCR belt cushion, and further improve workability. Found to improve.

In the present invention, the modified VCR compounded in the rubber composition used for the belt cushion of the pneumatic tire can be produced by, for example, a method described in JP-A-2005-247899. Specifically, (1) an inert organic solvent (for example, n-butane, cis-2-butene, trans-2-butene, butene-1) containing 1,3-butadiene and a C ₄ fraction as main components The water concentration of the mixture is adjusted (specifically, the water content is preferably 0.1 to 1.0 mol, particularly preferably 0.2 to 1.0 mol per mol of the halogen-containing organoaluminum compound in the medium. Outside this range, the catalytic activity decreases, the cis-1,4 structure content decreases, the molecular weight decreases abnormally or increases, and the generation of gel during polymerization is suppressed. This is not preferable because the gel may adhere to the polymerization tank and the continuous polymerization time may not be extended. Known methods The method is applicable. Porous method (JP-A-4-85304 JP) of adding and dispersing throughout the filtering material is also effective.), (2) Then, as a catalyst for cis-1,4 polymerization, the general formula AlR _n X _{3 -n} (wherein R is an alkyl group having 1 to 6 carbon atoms, phenyl group or cycloalkyl group, X is a halogen element, and n is 1.5 to 2) An organoaluminum compound and a soluble cobalt compound (for example, a β-diketone complex of cobalt, a β-keto acid ester complex of cobalt, a cobalt salt of an organic carboxylic acid of C ₆ or more, a cobalt halide complex) are added to the mixture, and 1 , 3-butadiene cis-1,4 polymerization, (3) then, the soluble cobalt compound in the resulting polymerization reaction mixture with the general formula AlR ₃ (where, R represents an alkyl group having 1 to 6 carbon atoms, It can be obtained by subjecting 1,3-butadiene to 1,2 polymerization in the presence of a 1,2-polymerization catalyst obtained from an organoaluminum compound represented by the following formula: it can. Further details are as described in JP-A-2005-247899.

  The modified VCR used in the present invention is blended in an amount of 5 to 30 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of the rubber component. If this amount is too small, improvement in processability cannot be found, which is not preferable. Other diene rubbers used in the present invention may be any diene rubber that can be used in a belt cushion, such as natural rubber (NR), polyisoprene rubber (IR), various polybutadiene rubbers (BR), and various styrene-butadienes. Examples thereof include copolymer rubber.

  In the rubber composition of the present invention, 10 to 40 parts by weight, preferably 25 to 35 parts by weight of carbon black and / or silica are mixed with 100 parts by weight of the rubber component. If the blending amount is too small, the reinforcing effect cannot be obtained and the strength is lowered, so that it is not preferred.

  The carbon black used in the present invention can be any carbon black that can be blended in a rubber composition for tires, particularly for belt cushions, but has an iodine adsorption amount of 60 to 100 g from the viewpoint of reinforcing effect and heat generation. It is preferred to use / kg of carbon black.

  The silica used in the present invention may be any silica that can be used for tires, particularly belt cushion rubber, such as natural silica, synthetic silica, more specifically dry silica, wet silica, and the like. In addition, it is preferable to use the silane coupling agent generally mix | blended conventionally with a silica, and it is preferable that the compounding quantity is 5 to 20 weight% of a silica weight.

  The ratio (weight ratio) of carbon black and silica used in the present invention is not particularly limited, but is preferably carbon black / silica = 100/0 to 60/40.

  FIG. 1 shows a half sectional view with designations of parts of a typical pneumatic tire. In FIG. 1, in the present invention, the rubber composition is used for the belt cushion of the belt portion and the carcass portion, and has an action of relieving the stress between the belt portion and the carcass portion. The rubber composition according to the present invention can be used for a belt cushion in a conventional pneumatic tire production line.

  In addition to the components described above, the rubber composition according to the present invention includes reinforcing agents (fillers) other than carbon black and silica, vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, vulcanization retarders, various oils, Various additives that are generally blended for tires such as anti-aging agents and plasticizers and other rubber compositions can be blended, and such additives are kneaded by a general method to form a composition. Can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Standard Example 1, Examples 1-2 and Comparative Examples 1-4
Sample preparation In the formulation shown in Table I, the components other than the vulcanization accelerator and sulfur were kneaded in a 1.7 liter closed mixer for 5 minutes and released when the temperature reached 160 ° C to obtain a master batch. A vulcanization accelerator and sulfur were kneaded with this masterbatch with an open roll to obtain a rubber composition. Using this rubber composition, unvulcanized physical properties were evaluated by the following test methods. The results are shown in Table I.

  Next, the resulting rubber composition was vulcanized in a 15 × 15 × 0.2 cm mold at 150 ° C. for 30 minutes to prepare a vulcanized rubber sheet, and the physical properties of the vulcanized rubber were measured by the following test methods. It was measured. The results are shown in Table I.

Rubber physical property evaluation test method Workability: Extrusion workability was measured using a garbage die according to ASTM D-2230-70. The swell, surface skin, and edge of the extruded product were evaluated, and based on the standard example 1, a good one was indicated by ◎, a slightly good one was indicated by ◯, a slightly inferior one was indicated by △, and a bad one was indicated by ×.
Exothermic property: Tan δ was measured at 60 ° C. according to JIS K6394. The results were expressed as an index with the value of standard example 1 being 100. The larger this value, the better the result.

Table I footnote * 1: STR20
* 2: VCR412 (manufactured by Ube Industries)

* 3: Modified VCR
It was manufactured by the following method.
A mixed medium (water content; 2.09 mmol / L) of C ₄ fraction (68 wt%) containing cis-2-butene as a main component at a concentration of 32% by weight of 1,3-butadiene dissolved in a predetermined amount of water 12.5 liters per hour (containing 20 mg / L of carbon disulfide) was fed into a stainless steel aging tank with a capacity of 2 liters maintained at 20 ° C. and diethylaluminum chloride (10% by weight n-hexane solution, 3.13 mmol / L) is fed and the diethylaluminum chloride / water molar ratio in this reactor solution is adjusted to 1.5. The obtained ripening liquid is supplied to a stainless cis polymerization tank with a stirrer having a capacity of 5 liters maintained at 40 ° C. This cis polymerization tank has cobalt octoate (cobalt octoate 0.0117 mmol / L, n-hexane solution) and a molecular weight regulator 1,2-butadiene (1,2-butadiene 8.2 mmol / L; 1.535 mol / L). N-hexane solution). The obtained cis polymerization liquid was supplied to a stainless steel 1,2 polymerization tank with a ribbon stirrer having a content of 5 liters and continuously polymerized at 35 ° C. for 10 hours. Triethylaluminum (10 wt% n-hexane solution, 4.09 mmol / L) was continuously supplied to the 1,2 polymerization tanks. The obtained polymerization solution was supplied to a mixing tank equipped with a stirrer, and 1 PHR of 2,6-di-t-butyl-p-cresol was added to the rubber, and a small amount of methanol was added to stop the polymerization. 1,3-Butadiene and C ₄ fraction were removed by evaporation and vacuum dried at room temperature to obtain 8.3 kg of VCR. ML of this VCR = 57, H.V. l = 11.1%, H.I. l melting point = 204.1 ° C., H.I. l η _sp /c=1.84, boiling n-hexane soluble part ML = 30, boiling n-hexane soluble part T-cp = 62, boiling n-hexane soluble part cis-1,4 Structure = 98.5%, Mw = 465,000, Mn = 188,000, Mw / Mn = 2.47. The distribution of the major axis length of the short fiber crystal obtained from the transmission electron microscope observation photograph is that 98% or more of the fiber length is less than 0.6 μm, and 70% or more of the fiber length is less than 0.2 μm. there were.

* 4: N330T (manufactured by Cabot Japan)
* 5: Dia Black E (Mitsubishi Chemical Corporation)
* 6: Nipsil AQ (Tosoh Silica Co., Ltd.)
* 7: Si69 (Degussa)
* 8: Three types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
* 9: LUNAC S-25 (manufactured by Kao Corporation)
* 10: Fine powder sulfur with Jinhua seal oil (manufactured by Tsurumi Chemical Co., Ltd.)
* 11: Noxeller NS (made by Ouchi Shinsei Chemical Co., Ltd.)

  As is clear from the results in Table I, compared to standard example 1 which is a typical example of the prior art, comparative example 1 has a reduced amount of carbon and improved low heat buildup compared to standard example 1. However, workability deteriorates. In Comparative Example 2, compared with Standard Example 1, the type of carbon is changed and the low heat build-up is improved, but the processability is inferior. Comparative Example 3 is a blend of VCR compared to Standard Example 1 and improves the workability but deteriorates the low heat build-up. In Example 1, a modified VCR is blended, and durability and workability are improved while maintaining low heat generation. Comparative Example 4 is a blend of VCR and silica as compared with Standard Example 1, and can maintain low exothermic properties but is inferior in workability. In Example 2, a modified VCR is blended according to the present invention, and further silica is blended, and both processability and low heat build-up are improved.

  As described above, in the present invention, by adding the modified VCR to the rubber composition, further reduction in heat generation and improvement in fatigue resistance can be ensured, and further workability can be improved. It is suitable for use in the belt cushion of heavy duty tires.

It is a half sectional view of a pneumatic tire showing the belt cushion of the pneumatic tire of the present invention together with other parts.

Claims (2)

(A) (1) adjusting the concentration of water in a mixture of 1,3-butadiene and an inert organic solvent mainly composed of a C ₄ fraction; (2) Next, a catalyst for cis-1,4 polymerization 1,3-butadiene is added to the mixture to polymerize cis-1,4. (3) Then, a 1,2-polymerization catalyst is present in the resulting polymerization reaction mixture, and 1,3-butadiene is added to 1 , 100 parts by weight of a rubber component containing 5-30 parts by weight of vinyl cis-polybutadiene rubber obtained by polymerization, and (B) a rubber composition comprising 10-40 parts by weight of carbon black and / or silica. Pneumatic tire using a belt cushion.   The pneumatic tire according to claim 1, wherein an iodine adsorption amount of the carbon black is 60 to 100 g / kg.

Images