Silicone rubber sponge-forming emulsion composition and method for producing silicone rubber sponge

Abstract

Provided is a silicone rubber sponge-forming emulsion composition for which the emulsion stability does not drop when the amount of reinforcing silica filler is increased, for which the cell shape of a sponge does not become defective, and for which the hardness is not too high; and further provided is a method for manufacturing a silicone rubber sponge from the aforementioned composition. This silicone rubber sponge-forming emulsion composition is comprised of: (A) 100 parts by weight of a liquid diorganopolysiloxane having at least two silicon atom-bonding alkenyl groups within one molecule; (B) 1-50 parts by weight of a reinforcing silica filler comprised of (b1) fumed silica and (b2) precipitation method silica (with the (b1) / (b2) weight ratio being 0.01 / 1-30 / 1); (C) 50-250 parts by weight of water containing (c) smectite clay; (D) 0.1-7 parts by weight of sorbitan fatty acid ester; (E) 0-10 parts by weight of isononanoic acid ester; (F) 0-10 parts by weight of Guerbet alcohol; and (G) an amount of curing agent sufficient to cross-link and harden component (A). This method manufactures a silicone rubber sponge by hardening said composition while heating and dehydrating the same, or by heating and hardening the same and then dehydrating the resulting silicone rubber-like hardened object in the wet state.

Description

technical field [0001] The present invention relates to a silicone rubber sponge-forming emulsion composition and a method for producing a silicone rubber sponge. Background technique [0002] Silicone rubber sponge has excellent heat resistance and weather resistance, is lightweight, and has low thermal conductivity, so it has been used as parts and components of electrical equipment, electronic equipment, construction, machinery, etc. Silicone rubber sponges are usually prepared by combining a silicone rubber base material composed of a diorganopolysiloxane raw rubber and a reinforcing silica filler, a foaming agent and an organic peroxide, or a liquid containing ethylene It is produced by heating liquid silicone rubber compositions such as diorganopolysiloxane based, reinforced silica filler, organohydrogenpolysiloxane, organosiloxane containing silanol group, platinum catalyst, etc. [0003] Japanese Patent Application Laid-Open No. 2004-346248 and International Publica...

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Problems solved by technology

However, the present inventors found that none of the publications described the combined use of fumed silica and precipitated silica, and did not describe the improvement of the emulsifying properties and the strength of the silicone rubber sponge through the combined use.

[0005] Generally, in order to obtain a high-strength silicone rubber sponge from an emulsion composition for silicone rubber sponge, it is necessary to mix a reinforcing silica filler. The more unstable the emulsion composition for sponges, the problem that a silicone rubber sponge with good cells cannot be formed when the emulsion composition is cured, dehydrated, or dried

In addition, as the amount of reinforcing silica filler increases, the hardness of the silicone rubber sponge increases, making it difficult to obtain a low-hardness silicone rubber sponge.

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