JP2002201306A - Compounding agent for studless tire and rubber composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performances on ice of studless tire while maintaining processability by compounding a rubber composition for studless tire with a hollow polymer. SOLUTION: This master batch for studless tire is obtained by compounding 100 pts.wt. of a natural rubber and/or a polyisoprene rubber with 1-30 pts.wt. of an unexpanded acrylonitrile-based hollow polymer and 10-50 pts.wt. of carbon black and kneading the mixture at the expansion starting temperature of the hollow polymer or above. This rubber composition for studless tire comprises the master batch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compounding agent for studless tires and a rubber composition containing the same. More specifically, the present invention relates to a rubber compound containing a hollow polymer to enhance the performance of the rubber on ice and improve the processability of the rubber composition. And a rubber composition for a studless tire containing the same.

[0002]

2. Description of the Related Art In recent years, it has been proposed to incorporate hollow particles or a foaming agent into rubber in order to reduce the weight and impart cushioning properties of tires (for example, JP-A-2-170840 and 4-246440). No. 10-202768
Reference). However, according to the findings of the present inventors,
When the expandable polymer particles are blended with the rubber composition and expanded during vulcanization, the rubber composition does not expand sufficiently (for example, about 40 μm), and a desired effect on ice performance cannot be sufficiently obtained. In addition, when an acrylonitrile-based hollow polymer that has been expanded to a size of 50 μm or more in advance is blended with a rubber composition, the unvulcanized rubber strength is significantly reduced, and the rubber composition cannot be used in a normal rubber processing step. Becomes

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a compounding agent for studless tires having excellent performance on ice and good processability in a manufacturing process, and a rubber composition containing the compounding agent. .

[0004]

According to the present invention, 1 to 30 parts by weight of an unexpanded acrylonitrile-based hollow polymer and 10 to 50 parts by weight of carbon black are blended with 100 parts by weight of natural rubber and / or polyisoprene rubber. And a master batch for studless tires mixed at a temperature not lower than the expansion start temperature of the hollow polymer, and a rubber composition for studless tires containing the master batch.

[0005]

According to the present invention, 1 to 30 phr (parts by weight per 100 parts by weight of rubber) of unexpanded acrylonitrile-based hollow polymer, preferably 20 to 30 phr, and 10 to 50 phr, preferably 10 to 10 phr, of carbon black are used. ~ 30
A master batch is produced by blending with natural rubber (NR) and / or polyisobrene rubber (IR) together with phr, and mixing so as to raise the temperature to the expansion start temperature of the hollow polymer or higher. This masterbatch is an appropriate amount in the rubber composition,
Preferably 30-100 phr, more preferably 50-7
By blending at 5 phr, a rubber composition for a studless tire having improved performance on ice can be obtained.

It is necessary to use an acrylonitrile-based hollow polymer in order to form a necessary hollow particle diameter without crushing even after a rubber processing step. Examples of the acrylonitrile-based hollow polymer particles that can be used in the present invention include Microsphere manufactured by Matsumoto Yushi-Seiyaku Co., Ltd. Such an expandable hollow polymer contains a liquid hydrocarbon inside and has a structure that foams when heated.

According to the findings of the present inventors, it is necessary to form a porous state having a diameter of 50 μm or more in a product tire in order to sufficiently improve performance on ice by blending hollow polymer particles. is there. However, on the other hand, if foreign matter such as hollow particles having a diameter of 30 μm or more is mixed into the rubber, the strength of the green rubber is reduced, and handling in a normal rubber processing step becomes difficult.

As described above, according to the present invention, since the expandable hollow polymer is expanded in the mixing step with NR and / or IR, the expandable hollow polymer can be expanded into a hollow polymer having a diameter of 50 μm or more. High intensity NR and / or I
By making a master batch with R as a matrix,
When the rubber composition for a studless tire is manufactured by mixing with other compounding components, a decrease in the strength of the green rubber can be suppressed. In addition, a small amount (for example, 20% by weight of the total weight of the rubber)
A diene rubber such as polybutadiene rubber (BR) and styrene butadiene copolymer rubber (SBR) described below can be compounded.

As the acrylonitrile-based hollow polymer, it is necessary to use a polymer having a diameter after expansion of 50 μm or more. Although the expansion start temperature is not particularly limited, a material that expands at 100 to 150 ° C. is preferable in consideration of expanding during mixing of the master batch.

The masterbatch for a studless tire according to the present invention may contain, in addition to the matrix rubber and the intumescent polymer described above, a compounding agent such as carbon black which has been generally used in a conventional manner. Can be.

The masterbatch for studless tires according to the present invention may further comprise other compounding agents other than the vulcanization system (for example, polymers other than the masterbatch, carbon black, zinc oxide, processing aids, antioxidants, etc.) according to the manufacturing method. Mixed with
After processing, a vulcanizing system such as a vulcanizing agent and a vulcanization accelerator is blended and heated and vulcanized to produce a studless tire.

[0012]

EXAMPLES The present invention will be further described with reference to the following examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Standard Example 1, Example 1 and Comparative Examples 1 and 2 100 parts by weight of natural rubber (STR20), 20 parts by weight of carbon black (HAF), and expandable hollow polymer (Microsphere F-100D manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) 20 The parts by weight were mixed in advance with a Banbury mixer and discharged at 150 ° C. to produce a master batch. This master batch was blended so that the hollow polymer content in the particle size composition was 10 parts by weight.

Other ingredients are as follows. 50 parts by weight of Nipol 1220 manufactured by Nippon Zeon Co., Ltd. 40 parts by weight of HAF-grade carbon black 40 parts by weight of antioxidant 2 parts by weight of Santoflex 13 manufactured by Flexis Oil 30 parts by weight of Desolex 3 manufactured by Showa Shell Sekiyu KK Zinc oxide Co., Ltd. 5 parts by weight Stearic acid Kao Corporation Beads stearic acid 1 part by weight

Next, 2 parts by weight of sulfur (manufactured by Karuizawa Refinery) and a vulcanization accelerator (Noxeller CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) are blended with the rubber composition obtained above as a vulcanization system. Then, it was vulcanized at a temperature of 110 ° C. for 2 minutes to produce a test material. The results are shown in Table I.

[0016]

[Table 1]

[0017] The hollow polymer diameter products of the cross-section in the footnote product Table I was observed 50-fold with SEM, it is measured. The maximum diameter is indicated (the hole cut in a state not including the center because it is spherical has a smaller diameter, so the maximum diameter was regarded as the diameter of the hollow polymer in the product).

Performance index on ice The braking distance from 40 km / h was actually measured on an ice- snow road. The index of the test sample when the value of Standard Example 1 was set to 100 was calculated by the following formula (average value of N = 5). Index value = braking distance of standard example 1 / test product braking distance

[0019] At workability in a 2.5 liter laboratory-Banbury mixer, a blend of Comparative Example 1 or 2 or Example 1 were mixed each 1.2 kg, the mixture was sheeted at 10 inch Rabororu. At the time of this roll operation, the amount of rubber that was not dropped into a series of sheets but became rubber was displayed. The smaller the value, the better the workability.

[0020]

As is clear from the results of Table I, in Comparative Example 1 in which an expandable hollow polymer was blended and expanded during vulcanization, the workability was good because the hollow polymer diameter in the product was as small as 35 μm. Yes, but poor on ice. On the other hand, in Comparative Example 2 in which the expandable hollow polymer was expanded at the time of mixing before vulcanization, the performance on ice was improved because the hollow polymer diameter in the product was as large as 83 μm, but the strength of the unvulcanized rubber was reduced and it was united. And the workability is poor. On the other hand, in Example 1 expanded at the time of mixing the master batch, the hollow polymer diameter was as large as 81 μm, so that the performance on ice was excellent and the workability was also good.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 33/20 C08L 33/20 (72) Inventor Kinya Kawakami 2-1 Oiwake, Hiratsuka-shi, Kanagawa Prefecture Yokohama Rubber Co., Ltd. F-term in Hiratsuka Works (reference) 4F070 AA05 AA06 AB09 AB16 AC04 AC83 AD03 FB04 FC07 4J002 AC01W AC06W AC06X BG10Y DA036 FA10Y GN01

Claims (2)

[Claims] 1. An unexpanded acrylonitrile-based hollow polymer (1 to 30 parts by weight) and carbon black (10 to 50 parts by weight) are blended with natural rubber and / or polyisoprene rubber (100 parts by weight), and the expansion start temperature of the hollow polymer is exceeded. Masterbatch for studless tires mixed at different temperatures. 2. A rubber composition for a studless tire, comprising the master batch according to claim 1.