JP5269370B2 - Rubber composition for racing tire and racing tire having tread using the same - Google Patents

Description

  The present invention relates to a rubber composition for a racing tire and a racing tire having a tread using the rubber composition.

  High grip performance is required for the tread portion of high-performance tires, particularly for racing tires.

  In order to improve the grip performance of the tread portion, for example, (1) a method using a rubber component having a high glass transition temperature (see, for example, Patent Document 1), (2) a method using carbon black having a large surface area, ( 3) A method of filling a large amount of softener is known. When these techniques are used, sulfur vulcanization is generally used as the vulcanization system, and zinc oxide or stearic acid is used as the vulcanization aid. Here, as the zinc oxide, one having a large average primary particle diameter of 200 nm or more is usually used.

  However, if zinc oxide having a large average primary particle size is used, it is difficult to disperse zinc oxide in the rubber, regardless of which method (1) to (3) is used. It becomes the core of out, the crosslink density changes, and the rubber physical properties change. For this reason, blowout or rubber physical properties deteriorate due to thermal deterioration during traveling, resulting in a decrease in grip performance.

JP 2003-213044 A

  An object of the present invention is to provide a rubber composition for a racing tire that is excellent in grip performance and can suppress a decrease in grip performance, and a racing tire having a tread using the same.

  In the present invention, zinc oxide having an average primary particle size of 200 nm or less is 0.5 to 4.0 with respect to 100 parts by weight of a rubber component containing styrene butadiene rubber having a styrene content of 25 to 50% by weight. The present invention relates to a rubber composition for racing tires containing parts by weight.

  The present invention also relates to a racing tire having a tread using the rubber composition for a racing tire.

  According to the present invention, by containing a predetermined amount of a predetermined rubber component and a predetermined zinc oxide, a rubber composition for a racing tire that is excellent in grip performance and can suppress a decrease in grip performance, and the same are used. A racing tire having a tread can be provided.

  The rubber composition for racing tires of the present invention contains a rubber component and zinc oxide.

  The rubber component contains styrene butadiene rubber (SBR).

  Examples of SBR include emulsion polymerization SBR (E-SBR) and solution polymerization SBR (S-SBR). S-SBR is preferred because blowout is unlikely to occur.

  The SBR has a styrene content of 25% by weight or more, preferably 30% by weight or more. When the styrene content of SBR is less than 25% by weight, grip performance is insufficient. The SBR has a styrene content of 50% by weight or less, preferably 45% by weight or less. When the styrene content of SBR exceeds 50% by weight, heat generation tends to occur and blowout tends to occur.

  The content of SBR in the rubber component is preferably 80% by weight or more, and more preferably 90% by weight or more. When the SBR content is less than 80% by weight, grip performance tends to be insufficient. In particular, the content of SBR is most preferably 100% by weight.

  As the rubber component, in addition to SBR, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), acrylonitrile butadiene rubber (NBR) , Ethylene propylene diene rubber (EPDM), and halides of copolymers of isomonoolefin and paraalkyl styrene. As rubber components, one or more of these can be selected and used in combination with SBR, but grip performance, wear resistance, blowout resistance, and vulcanization adhesion to members inside the tire It is preferable to use SBR alone because it is excellent in properties.

  The average primary particle diameter of zinc oxide is 200 nm or less, preferably 150 nm or less. When the average primary particle diameter of zinc oxide exceeds 200 nm, it becomes difficult to disperse zinc oxide in the rubber, so that it becomes a starting point of cracks and blows out. Moreover, the average primary particle diameter of zinc oxide is preferably 20 nm or more, and more preferably 30 nm or more. If the average primary particle diameter of zinc oxide is less than 20 nm, there is a tendency that it is difficult to disperse due to aggregation of zinc oxide particles.

  The content of zinc oxide is 0.5 parts by weight or more, preferably 1 part by weight or more with respect to 100 parts by weight of the rubber component. When the content of zinc oxide is less than 0.5 parts by weight, the vulcanization reaction is insufficient. The zinc oxide content is 4.0 parts by weight or less, preferably 3.0 parts by weight or less. When the content of zinc oxide exceeds 4.0 parts by weight, it tends to be a starting point of cracks and blowout is likely to occur.

  The rubber composition for high-performance tires of the present invention can further contain carbon black.

  There is no restriction | limiting in particular as carbon black, SAF, ISAF, HAF, FEF, GPF etc. which are conventionally used in the tire industry can be used.

  The content of carbon black is preferably 50 parts by weight or more and more preferably 65 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of carbon black is less than 50 parts by weight, the wear resistance tends to decrease. The carbon black content is preferably 150 parts by weight or less, and more preferably 135 parts by weight or less. When the content of carbon black exceeds 150 parts by weight, processability tends to be lowered.

  The rubber composition for a racing tire of the present invention may further contain a softening agent.

  The softening agent is not particularly limited, and plasticizers for improving low temperature characteristics such as aroma oil, naphthene oil, paraffin oil and the like conventionally used in the tire industry can be used.

  The content of the softening agent is preferably 30 parts by weight or more and more preferably 50 parts by weight or more with respect to 100 parts by weight of the rubber component. If the content of the softening agent is less than 30 parts by weight, there is a tendency that the predetermined grip performance cannot be exhibited. The softener content is preferably 200 parts by weight or less, and more preferably 150 parts by weight or less. When the content of the softening agent exceeds 200 parts by weight, the workability tends to decrease due to adhesion. In addition, content of a softening agent means content including the oil component contained in an oil-extended rubber | gum.

  In addition to the rubber component, zinc oxide, carbon black and softener, the rubber composition for competition tires of the present invention includes a compounding agent conventionally used in the tire industry, such as various anti-aging agents, stearic acid, Vulcanizing agents such as sulfur, various vulcanization accelerators and the like can be appropriately blended as necessary.

  The rubber composition for racing tires of the present invention is produced by a general method. That is, the rubber composition for racing tires of the present invention is obtained by kneading the diene rubber, alkylphenol / sulfur chloride condensate and, if necessary, the compounding agent with a Banbury mixer, kneader, open roll, etc., and then vulcanizing. Can be manufactured.

  The rubber composition for a racing tire of the present invention is suitably used for a tread because it has excellent grip performance and durability.

  The tire of this invention can be manufactured by a normal method using the rubber composition for racing tires of this invention. That is, if necessary, the rubber composition for a racing tire of the present invention blended with the above-mentioned compounding agent is extruded in accordance with the shape of the tread of the tire at an unvulcanized stage, and another tire on a tire molding machine. The unvulcanized tire is formed by bonding together with the members and molding by a normal method. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain the tire of the present invention.

  The tire of the present invention is suitably used as a racing tire for a cart or the like because of its excellent high grip performance and durability, and particularly excellent initial grip performance.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Styrene butadiene rubber (SBR): Toughden 4350 manufactured by Asahi Kasei Co., Ltd. (styrene content: 40% by weight, containing 50 parts by weight of oil with respect to 100 parts by weight of rubber solid content)
Carbon black: Dia Black A (N110) manufactured by Mitsubishi Chemical Corporation
Aroma oil: X-140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Santoflex 13 (N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine) manufactured by Flexis
Stearic acid: Stearic acid “paulownia” manufactured by NOF Corporation
Zinc oxide (1): Zincox Super F-2 (average primary particle size: 65 nm) manufactured by Hakusuitec Co., Ltd.
Zinc oxide (2): Two types of zinc oxide (average primary particle diameter: 400 nm) manufactured by Mitsui Mining & Smelting Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-2 and Comparative Examples 1-3
According to the formulation shown in Table 1, using a 1.7 L Banbury mixer manufactured by Kobe Steel, chemicals other than sulfur and vulcanization accelerator were kneaded at a discharge temperature of 160 ° C. to obtain a kneaded product. . Next, using an open roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 4 minutes at 80 ° C. to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition is formed into a tread shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire. By vulcanizing, cart tires (size: 11 / 7.00-5) of Examples 1-2 and Comparative Examples 1-3 were manufactured.

(Grip performance)
The manufactured cart tire was mounted on the cart, and the circuit of 1 lap 500 m was run 10 laps, and the grip performance of the 1st to 5th laps was used as the initial grip performance index, and sensory evaluation was performed with a perfect score of 100 points. The grip performance is preferably 70 points or more.

  Further, the grip performance on the 6th to 10th laps is also sensorially evaluated as the second half grip performance index, similar to the initial grip performance index, and the ratio of the second half grip performance index to the initial grip performance index (the grip performance degradation index, the second half grip performance index / The initial grip performance index × 100) was calculated. In addition, it shows that 70% or more of a grip performance fall index | exponent is preferable.

  The evaluation results are shown in Table 1.

Claims (3)

For 100 parts by weight of a rubber component containing a styrene butadiene rubber having a styrene content of 30 to 50% by weight,
0.5 to 4.0 parts by weight of zinc oxide having an average primary particle size of 200 nm or less , and
A rubber composition for a tread for a racing tire containing 50 to 150 parts by weight of carbon black . The rubber composition for a tread for a competition tire according to claim 1, further comprising 30 to 200 parts by weight of a softening agent. Racing tire having a tread with claim 1 or 2 for a tread rubber composition competition tire according.