GB760004A - Improvements in and relating to reclaimed silicone rubber - Google Patents

Abstract

Silicone rubber is made by (1) mixing a reclaimed, vulcanizable, solid, elastic organopolysiloxane which has been obtained by subjecting to steam pressure a comminuted solid elastic organopolysiloxane in a wholly or partially cured state, with an uncured organopolysiloxane convertible by heat to the solid, elastic, cured state, and (2) moulding the mixture under heat and pressure until an infusible and insoluble product is obtained. The silicone rubber, constituting the material which is reclaimed, may be that made in known manner from the siloxanes described in Specifications 592,018, 594,481, [both in Group IV], and 618,453, fillers such as lithopone, ferric oxide, titania, talc, zinc oxide, silica aerogel, asbestos and glass fibres, and curing catalysts, such as benzoyl peroxide, t.-butyl perbenzoate, 2-azo-bis-isobutyronitrile and boron hydrides. In the reclaimation, the cured rubber is disintegrated, e.g. on a heavy two-roll mill, placed in a pressure vessel, e.g. an autoclave, and subjected to steam at pressures ranging from 5 to 1000 p.s.i. Alternatively water may be added to the comminuted rubber in the pressure vessel in amount sufficient to produce adequate steam pressure. The steamtreated rubber is then preferably dried and plasticized and may be freed from fibrous fillers if used in the initial rubber. The reclaimed rubber may then be mixed with further curing catalyst, if it is to be used alone, or be mixed with uncured siloxane and curing catalyst and moulded under heat and pressure. Examples are given. The use of the reclaimed rubber with the uncured siloxane is stated to improve the shrinkage and compression set of the moulded products. Reference has been directed by the Comptroller to Specification 716,024.