JPH0156095B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to tires used for vehicles and other purposes, and particularly to tires whose tread portions are made of foam. Tires widely used for automobiles, bicycles, motorcycles, motorbikes, other vehicles, and transportation equipment such as agricultural machinery and transporters have conventionally been made of non-foamed rubber, and their specific gravity is generally low.
It was about 1.15. It is clear that if some of these tires, especially the tread parts, were made of foam, the wear of the tires that were constantly in contact with the road surface would be significant.
For this reason, foam tires have never been used experimentally. Tires are classified into many types depending on their use, but all are required to have tensile strength, elongation, hardness, and abrasion resistance. When this is considered in relation to a tire whose tread portion is made of a foam, which is the object of the present invention, it is found that the hardness and abrasion resistance, which are the most important characteristics of a tire, are immediately reduced if the tread is made of a foam. It is clear that it is confirmed that In other words, if the tread part of a rubber tire is made of foam,
Since the volume inevitably increases, the amount of raw materials used is reduced in order to obtain a tire with a predetermined shape, but on the other hand, such foamed tires are faced with the contradictory fact that they suffer from a decrease in hardness and wear resistance.
The inventors of the present application have made various efforts to resolve these contradictions, and as a result, regardless of the foamed tires, non-foamed tires made using the same and same amount of raw rubber as the foamed tires. This is a new foam tire that has the same hardness and wear resistance as rubber tires. In the process of completing the claimed invention, the inventors carried out careful experiments on the combination of various additives in the raw materials, the use of fillers, and even the vulcanization process, but none of them worked as expected. No results were obtained. The inventors conducted further research and discovered the surprising fact that only when an azo-based organic blowing agent was used, the hardness and abrasion resistance of the foam obtained did not decrease in the slightest. This invention was completed based on this fact. In other words, the present invention provides raw material rubber made of natural or synthetic rubber, or a blend of both, with a cross-curing agent, a cross-sulfur accelerator, and other conventional additives, as well as an azo organic blowing agent, in an amount of not more than 15 parts by weight per 100 parts by weight of raw rubber. This is a foamed tire characterized in that a foam made by heating and pressurizing blended raw materials is used at least in the tread portion. The details of this invention will be explained below. A tire normally consists of a tread portion, which serves as a ground contact surface, a cushion portion, a carcass portion, a bead portion, etc., but in the present invention, at least the tread portion of the tire is made of a foamed material. The tread portion includes the sidewall, shoulder, and lower reinforcing portion that are integrally connected, and in the present invention, all of these may be referred to as the tread portion and made of the above-mentioned foam. As the rubber raw material for the foam used here, natural rubber or a blend of both can be used. After thoroughly kneading these,
Sulfur and other usual cross-curing agents, cross-curing accelerators, anti-aging agents, etc. are added, but in the present invention, a blowing agent is further added to these. The specification of the blowing agent here is particularly important in this invention, and is limited to azo organic blowing agents. Examples of the azo organic blowing agent include azodicarbonamide, azobisisobutylnitrile,
These include azocyclohexylnitrile and diazoaminobenzene. The amount of these azo organic blowing agents used is 15 parts by weight or less per 100 parts by weight of raw rubber. If the amount exceeds 15 parts, excessive foaming will occur, resulting in a decrease in hardness and wear resistance, making it impossible to obtain a good tire. The cushion part and carcass part other than the tread part may be the same as those of conventional tires, but depending on the type of tire, the same foam rubber with a different expansion ratio may be used. Note that other constituent members such as the tire cord, bead wire, and bead hill are the same as those of conventional tires. As shown in the examples below, the tire of the present invention as described above, although it uses foam rubber, has a hardness and abrasion resistance that is comparable to tires using non-foam rubber. It turns out that there is no difference. Therefore, the tire of the present invention can be said to be a product that uses fewer raw materials in proportion to the expansion ratio, and is also lighter in weight. Experimental examples using test pieces prepared under the same conditions as those for forming the tread of a tire component will be described below. Experimental Example 1 Raw materials A to G were kneaded for 30 minutes using rolls with a surface temperature of 70° C. to form a sheet according to the formulation shown in Table 1 below. Thereafter, this was filled into a mold of 20 cm x 20 cm x 20 cm, heated and pressurized at 150 Kg/cm ² and 145° C. for 20 minutes, and then demolded.

【table】 The results were as shown in Table 2.

[Table] Experimental Example 2 Test pieces were obtained in the same manner as in Experimental Example 1 using the same formulation as in Experimental Example 1 and varying the type of blowing agent. The amount of blowing agent used here was 8.0 parts by weight per 100 parts by weight of the raw materials. The results were as shown in Table 3.

[Table] As can be seen from Experiments 1 and 2 above, when the azo organic foam specified in the present invention is used, the hardness and abrasion resistance are superior to non-foamed rubber, even though it is a foam. Therefore, tires using this in the tread portion use less raw material and can sufficiently withstand harsh operating conditions like conventional tires.

Claims (1)

[Claims] 1. Adding not more than 15 parts by weight of a vulcanizing agent, a vulcanization accelerator, other usual additives, and an azo organic blowing agent to 100 parts by weight of raw rubber to raw rubber made from a blend of natural rubber, synthetic rubber, or both. A foam tire characterized in that at least the tread is made of a foam obtained by heating and pressurizing raw materials.