Silicon rubber composition for sponge

Abstract

The invention provides a silicone rubber composition for sponge comprising (A) 100 pts.mass of an organopolysiloxane having a degree of polymerization of 100 or greater and at least two alkenyl groups bound to a silicon atom in the molecule; (B) 3-100 pts.mass of wet silica dioxide having the properties as follows: specific surface area (BET method) is 50m2 / g or greater, the ratio of BET specific surface area / CTAB specific surface area is 1.0-1.3, and moisture content is 4% or less; (C) 0.5-50 pts.mass of a foaming agent that generates gas at 50-250[deg.]C and (D) an effective amount of a curing agent. The invention can suppress abnormal foaming and effectively mold sponge even if undergoing hot-air curing at high temperatures and ordinary pressure using wet silica dioxide, andgiving a silicone rubber composition for sponge of good touch feeling with uniform and soft sponge cells.

Description

technical field The present invention relates to a silicone rubber composition for sponge containing wet silica. Background technique Since silicone rubber has excellent weather resistance, electrical properties, low compression set, heat resistance, and cold resistance, it is widely used in various fields such as electrical appliances, automobiles, construction, medical care, and food. For example, rubber contacts used for rubber contacts of remote controls, typewriters, word processors, computer terminals, musical instruments, etc., construction gaskets, fixing rollers, developing rollers, transfer rollers, charging rollers, paper feed rollers, etc. Rollers for machines, anti-vibration rubber for audio equipment, packaging packing for CDs, wire covering materials, etc. The silicone rubber composition that cures to become silicone rubber is usually obtained by mixing a curing agent with a reinforcing filler represented by organopolysiloxane as a base polymer and silica. ...

AI Technical Summary

Problems solved by technology

That is, moisture is easily absorbed in the fine pores inside the wet silica. When the sponge material using it is foamed and cross-linked under normal pressure at high temperature, the adsorbed moisture on the surface of the material will instantly change due to the sharp rise in the surface temperature of the polysiloxane material. It is a gas, so there is a problem that the pores of the sponge become huge in the range of about 10 mm from the surface of the sponge molded product, or an abnormal foam layer is formed such as the pores are closely bonded to each other.

Therefore, when using wet-type silica-based polysiloxane sponge materials, the foaming temperature must be lowered, or the molding time must be prolonged, so it cannot be practically used.

In addition, in JP-A-3-9932 (Patent Document 1), JP-A-5-59207 (Patent Document 2), JP-A-7-18110 (Patent Document 3), and JP-A-8-176333 (Patent Document 4) , JP-10-87865 (Patent Document 5), JP-10-182972 (Patent Document 6), JP-2000-160017 (Patent Document 7), JP-2001-164116 (Patent Document 8) Various silicone rubber compositions for sponges have been proposed, but no silicone rubber compositions for sponges using wet silica have been proposed

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