JPH0478463B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a method for producing a rubber foam by open vulcanization. It is particularly suitable for producing rubber foam whose surface is covered with fibers, leather, etc. (B) Conventional technology Rubber foam is produced by: (1) charging heat-foamable unvulcanized rubber into a mold, press-vulcanizing it, and expanding it to form a foam when the pressure is released during demolding; (2) There is a method in which an unvulcanized rubber molded body is placed in a vulcanizing can or the like and made into a foam by open vulcanization. Here, open vulcanization refers to vulcanization in an open space, such as hot air vulcanization, as opposed to press vulcanization, which applies large pressure in a closed space such as a mold. Other methods include vulcanization using dielectric heating and microwave heating. Open vulcanization is convenient for foams with complex shapes or for continuous vulcanization, and there is little dimensional change in the foam over time. However, on the other hand, foams are prone to a phenomenon called abnormal foaming, in which abnormally large bubbles are generated here and there, making the exterior uneven and creating voids inside, and the dimensions are not stable. (c) Problems to be Solved by the Invention The present invention provides a method for producing a rubber foam with good dimensional stability without abnormal foaming when the rubber foam is produced by open vulcanization. (d) Means for Achieving the Object The present invention covers the outside of vulcanized, foamable unvulcanized rubber with a breathable covering material (e.g., fibers), and then performs open vulcanization to form a rubber foam. At this time, the desired rubber foam is manufactured by regulating the expansion of the foamed rubber by the tension of the outer covering material. Here, the term "enveloping material" refers to any material that can suppress the expansion pressure at that point when a predetermined expansion is achieved in the rubber foaming process, and any material whose tension can withstand the expansion pressure can be used in the present invention. Can be used as outer covering material. Typical breathable jacket materials are textiles, including wovens, nonwovens, and leather. As the vulcanized and foamable rubber compound, a general rubber compound blended with a blowing agent is used. Particularly in open vulcanization, in order to obtain a high-quality rubber foam with excellent cell uniformity and quick elasticity recovery response, the rubber content (100 parts by weight) should be 90-50% natural rubber or/or synthetic rubber. 10 to 50 parts by weight of thermoplastic rubber. Thermoplastic rubbers include styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, hydrogenated versions of these, and other polymers, which melt and flow when heated and exhibit rubber-like elasticity at the operating temperature. It is something. (E) Example Example 1 A wooden palm mold used in manufacturing gloves is made of 30
A number of cotton knitted gloves are covered, and a rubber sheet prepared by kneading each of the formulations shown in Table 1 with a roll and rolling to a thickness of 0.8 to 1 mm is laminated over the entire surface of the knitted gloves. This is removed from the open hand mold, recoated onto a metal curved hand mold, and allowed to fit into the mold.A No. 10 cotton knitted glove is placed over it, and hot air vulcanization is performed at 130°C for 30 minutes. When heated, the rubber sheet adheres and is fixed to the inner 30-knit stockinette glove, and since there is a curved hand shape on the inside, the rubber expands outward and integrates with the outer 10-knit stockinette glove, forming a shape of about 2 mm. The gloves have a thick rubber foam layer. The thickness of the foam layer is regulated by the fact that the outer No. 10 knitted glove stretches under the pressure of rubber foaming, and the expansion of the rubber is stopped at a point where the tension can suppress the foaming pressure. Therefore, the thickness of the foam layer can be controlled by controlling the stress-elongation characteristics of the No. 10 stockinette glove, in other words, by controlling the elongation properties of the stockinette knit. During foaming, the rubber foam is restrained from expanding by using No. 10 knitted gloves, and a slight amount of pressure is applied, so the bubbles do not aggregate and become abnormally foamed, and the bubbles are fairly uniform. If necessary, apply adhesive to the stockinette gloves to improve adhesion to the rubber layer. Alternatively, a starch paste that does not easily adhere to rubber is applied to a 10-count stockinette glove, and after vulcanization and foaming, the stockinette glove is peeled off to expose the foam layer and used as a glove that particularly requires non-slip properties. do.

[Table] Example 2 A cotton material with a thickness of about 0.7 mm is coated with No. 3 blended rubber in Table 1 to a thickness of about 1 mm by extrusion or by wrapping a thin rubber tape. Cut 40 count stockinette cloth and sew it into a tube shape with a folded diameter of 15 mm.
Seven coated wires were bundled into a plum bowl-shaped cross section, a cylindrical body of stockinette cloth was placed on the outside, and the bundle was vulcanized in hot air at 130°C for 30 minutes. The foamed rubber fills the gaps in a cylindrical body made of knitted cloth, making it an integral part.It is covered with knitted cloth, and has a diameter of about 13 cm, with seven wires arranged in a plum bowl-shaped cross section.
Obtain rubber foam wire of mm. Continuous vulcanization yields long products. Example 3 Three edges of a 400mm square woven fabric were sewn together and a front surface was formed inside.
Cut a 5 mm sheet of No. 3 compound rubber from Step 1 into the hole and insert it just enough to fit it, and stitch the remaining edges. When this is vulcanized in hot air at 130℃ for 30 minutes,
Obtain a cushion with a thickness of 14-15 mm. (f) Functions and Effects In the present invention, the outside of the unvulcanized rubber of the vulcanized foam is covered with a breathable outer cover material and open vulcanization is performed. The tension of the covering material suppresses further expansion, and the rubber foam is regulated to a predetermined thickness.The rubber foam is also subjected to some pressure due to the suppression of the outer covering material, and the bubbles are uniform without becoming abnormally foamed. A foam is obtained. The outer cover material has breathability, so when the rubber foams and expands, the air that exists between the rubber and the outer cover material is pushed by the foamed rubber and easily escapes to the outside of the outer cover material, causing the outer cover to expand. Air between material and rubber foam
No traps will occur.

Claims (1)

[Scope of Claims] 1. Expansion of the foamed rubber when heat-foamable unvulcanized rubber is covered with a breathable outer cover material (for example, fibers) and then open vulcanized to form a rubber foam. A method for producing a rubber foam, characterized in that the tension of the outer covering material is regulated by the tension of the outer covering material. 2. Claim 1, in which part or all of the outer covering material is removed after forming a rubber foam by vulcanization foaming.
A method for producing a rubber foam as described in Section 1. 3. The rubber foam according to claim 1 or 2, wherein the unvulcanized rubber comprises 90-50 parts by weight of natural rubber and/or synthetic rubber and 10-50 parts by weight of thermoplastic rubber. manufacturing method.