GB681577A - Improvements in and relating to the manufacture of sponge rubber - Google Patents

Abstract

Spongy articles having a cellular texture are made from Hevea latex or from an artificial latex obtained by colloidal dispersion of natural rubber by partially hydrolysing or breaking down the proteins e.g. by an enzyme such as trypsin or heating under pressure with NH3 or by natural ageing or by any other substance which can produce the same result, stirring, shaking or beating violently to produce a non-reversible cream or foam which coagulates in time or on heating without any addition of gelifying or coagulating agent. A foaming agent e.g. soap may be added to the hydrolysed latex prior to the stirring to retard flocculation and accelerate the foaming. Alternatively or in addition the cream may be treated with NH3 water to dilute it and air can be enclosed in the mass by any known means. In an example Hevea latex concentrated to 58 per cent dry rubber content and ammoniated to 0.8 per cent is partially digested in 4 days with dry pancreas of pig powder at the rate of 1.5 grm/litre concentrated latex and then converted in a turboagitator to a non-reversible cream which is diluted with NH3 water followed by the addition of a stock soap make of oil palm and potash at the rate of 0.2 grm of soap per 100 grms dry rubber. The following dispersion is added per 100 grms of dry rubber: S 2 grms, zinc diethyldithiocarbamate 1.0 grm, zinc mercaptobenzothiazole 0.5 grm, water and dispersing agents as needed. Air is incorporated by letting the diluted and compounded cream run down a sloped plate perforated with gauged apertures through which compressed air escapes. The foam is poured into a mould and sets in 20 mins.