JP3534329B2 - Rubber composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition, and more particularly to a rubber composition used for a stiffener of an aircraft tire. 2. Description of the Related Art Conventionally, in an aircraft tire, a rubber composition for a hard stiffener, which is one of the peripheral parts of a bead, is composed of only natural rubber. In order to ensure the durability of a tire, it is necessary to consider hardness (elastic modulus) and heat generation as a rubber member. In that respect, natural rubber has a high elastic modulus, low heat generation, and heat generation. Excellent in terms of sex. In addition, for an aircraft tire, it is necessary to consider a decrease in air temperature during the flight, but natural rubber is also advantageous in that it has a low glass transition temperature. [0004] In recent years, while the weight of tires has been reduced, high durability has also been required, and further improvements in heat generation and heat resistance have been required. Although natural rubber is excellent in terms of heat generation as described above, there is still room for improvement in heat resistance. Also, natural rubber is
There is also room for improvement in terms of workability (factory workability). Accordingly, an object of the present invention is to provide a rubber composition which can be used for a stiffener of an aircraft tire while improving heat resistance and factory workability while maintaining low heat generation. The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, the raw material rubber of the rubber composition is not a natural rubber but a natural rubber and a specific styrene-butadiene. It has been found that the above object can be achieved by using a blend system with rubber, and the present invention has been completed. That is, the rubber composition of the present invention comprises a styrene-butadiene rubber containing 5 to 30 parts by weight of a raw rubber;
A rubber composition comprising 5 to 70 parts by weight of natural rubber, wherein the styrene-butadiene rubber is a polymer rubber obtained by solution polymerization, and the vinyl composition ratio of the polymer rubber is 20 to
40% and a glass transition temperature of −60 ° C. or less. Preferably, the rubber composition is applied to a stiffener of an aircraft tire. The rubber composition of the present invention comprises a reinforcing filler,
Needless to say, compounding agents usually used in the rubber industry, such as a softening agent, an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator, can be appropriately compounded. In the rubber composition of the present invention, the polymerization mode of the styrene-butadiene rubber constituting the blend system with the natural rubber is limited to the solution polymerization because the processability (factory workability) and the low-temperature characteristics are emulsified. This is because it is superior to polymerization. The reason why the vinyl composition ratio of the styrene-butadiene rubber is in the range of 20 to 40% is that 20% or less.
If it is less than 40%, the effect of improving heat resistance is small, while if it exceeds 40%, the glass transition point (Tg) becomes too high, which is not preferable. Preferably it is in the range of 30 to 40%. Here, in the present invention, such a glass transition point is -6.
The temperature is limited to 0 ° C. or less, because if the temperature exceeds −60 ° C., the low-temperature properties lose their advantage over other styrene-butadiene rubbers. That is, the styrene-butadiene rubber according to the present invention is characterized by having a glass transition point comparable to that of natural rubber. Glass transition point is -60 ° C
Below, the lower the better. The ratio of the styrene-butadiene rubber to the raw rubber is 5 to 100 parts by weight of the raw rubber.
30 parts by weight, the rest being all natural rubber. If the styrene-butadiene rubber is less than 5 parts by weight, the effect of improving factory workability (unvulcanized rubber viscosity) is too small, while if it exceeds 30 parts by weight, elongation and breaking strength of the rubber at high temperatures are reduced, which is not preferable. . [0013] The rubber composition of the present invention is suitable for application to a stiffener of an aircraft tire. The lower limit of the internal pressure of currently used aircraft tires is about 12.0 kg.
f / cm ² , in other words, the internal pressure is 12.
It can be said that it is suitable for application to aircraft stiffeners of 0 kgf / cm ² or more. Next, the present invention will be described in detail with reference to examples and comparative examples. Various test rubber compositions having the formulation (parts by weight) shown in Table 2 below were prepared. In addition, S shown in Table 2
BR-A, B, and C are styrene-butadiene rubbers synthesized by a polymerization method shown in Table 1 below and having a vinyl composition ratio (%) and a glass transition point (Tg) shown in the table. . [Table 1] The vinyl composition ratio (%) in Table 1 is determined as follows. ¹³ C-NMR measurement device (GX
400, manufactured by JEOL Ltd., the bound vinyl content (%) in the styrene-butadiene rubber was measured. The measurement conditions are as follows. Solvent: deuterated chloroform Measurement temperature: room temperature Pulse repetition time: 3 seconds Pulse width: 45 ° The following tests were performed on the obtained various rubber compositions. (1) Exothermicity (resilience) British Standard 903: Part A
8: It was calculated from the following equation from a rebound resilience test performed according to 1963. Exothermic index = rebound resilience of test specimen / rebound resilience of test piece of Comparative Example 1 using only natural rubber The larger the exothermic index, the better the exothermic property, that is, the smaller the calorific value. Is shown. (2) Heat resistance load 68 kg (150 LB), rotation speed 300 rpm (1
100 rpm increments every 0 minutes), measurement start temperature 160
Under a condition of ° C., a dynamic shear test was carried out, a time until blow-out was measured, and this was used as an index of heat resistance. The evaluation was performed using an index with Comparative Example 1 being 100.
The larger the index value, the better the heat resistance. (3) Factory workability The factory workability as referred to herein is a matter relating to the viscosity when unvulcanized rubber flows in a factory.
And the index was set as 100. The larger the index value, the better the factory workability. The results obtained are shown in Table 2 below. [Table 2] As described above, in the rubber composition of the present invention, heat generation and factory workability are greatly improved while heat generation is maintained as low as natural rubber. Therefore, the rubber composition of the present invention has an internal pressure of 12.0 kgf / c.
m ² or more is suitable for application to the stiffener of aircraft tires.

Claims (1)

(57) [Claims 1] The raw rubber is 5 to 30 parts by weight of styrene.
A rubber composition comprising butadiene rubber and 95 to 70 parts by weight of a natural rubber, wherein the styrene-butadiene rubber is a polymer rubber obtained by solution polymerization, and the vinyl constituent ratio of the polymer rubber is 20 to 40%. Characterized by having a glass transition temperature of -60 ° C or lower .
A rubber composition used for tire stiffeners .