Patent GB-828643-A (GB)
Title: Improvements in latex sponge rubber
IPC: C08L21/00
Filed: 1957-05-31
Abstract: Latex sponge rubber particularly for use as a backing for fabrics, e.g. woollen carpets, is obtained by blowing an alkaline rubber latex composition with a blowing agent which on heating liberates nitrogen and forms an acidic decomposition product which reduces the pH of the latex and thus causes the froth to gel. Blowing agents specified are azodicarbonamides or aryl sulphonyl hydrazides.  The latex may be a natural rubber latex or a conjugated diene polymer synthetic rubber latex, e.g. an aqueous emulsion polymer of mixtures of butadienes-1,3, isoprene, 2-chlorobutadiene-1,3 (chloroprene), piperylene, 2,3-dimethyl-butadiene-1,3, or a mixture of butadienes-1,3 with compounds containing a CH2=C group, e.g. styrene, vinylnaphthalene, alpha-olefine-carboxylic acids and their esters, nitriles or amides.  The latex is compounded with the usual vulcanizing agents, e.g. sulphur, zinc oxides and accelerators and with thickening agents, e.g. sodium polyacrylate, methyl cellulose; humectants may be added, e.g. sorbitol, glycerine; and trimene bases, e.g. triethyl trimethylenetriamine as foam stabilizers.  In examples: (1) a synthetic rubber latex copolymer of 75 parts butadiene and 25 parts styrene of 60% solids concentration was compounded to form a mixture comprising 100 parts latex, 3 parts zinc oxide, 2 parts sulphur, 1.5 parts accelerator, 1 part antioxidant, 0.5 parts sodium polyacrylate and 0.38 parts methyl cellulose.  Prior to spreading 8 parts of a 25% aqueous dispersion of p,p1-oxy-bis-(benzenesulphonylhydrazide) were added and the mixture adjusted to a pH of 10-10.5 by addition of ammonia.  The composition was spread on the back of a piece of woollen carpet and the coated carpet heated to 110-115 DEG  C. in an oven with a relative humidity of 95%, the film blowing and gelling in 6 minutes.  The coated carpet was dried and vulcanized giving a sponge coating of 3/16 -\ba4/16 inch.ALSO:Latex sponge rubber particularly for use as a backing for fabrics, e.g. woollen carpets is obtained by blowing an alkaline rubber latex composition with a blowing agent which on heating liberates nitrogen and forms an acidic decomposition product which reduces the pH of the latex and thus causes the froth to gel. Blowing agents specified are azodicarbonamides or aryl sulphonyl hydrazides. The latex may be a natural rubber latex or a conjugated diene polymer synthetic rubber latex, e.g. and aqueous emulsion polymer of mixtures of butadienes-1, 3, isoprene, 2-chlorobutadiene 1, 3 (chloroprene), piperylene, 2, 3-dimethyl butadiene-1, 3 or a mixture of butadienes-1, 3 with compounds containing a CH2=C group, e.g. styrene, vinylnaphthalene, alpha-olefinecarboxylic acids and their esters, nitriles or amides.  The latex is compounded with the usual vulcanising agents, e.g. sulphur, zinc oxides and accelerators and with thickening agents, e.g. sodium polyacrylate, methyl cellulose; humectants may be added, e.g. sorbitol, glycerine; and trimene p bases, e.g. triethyl trimethylenetriamine as foam stabilisers.  In Examples (1) a synthetic rubber latex copolymer of 75 parts butadiene and 25 parts styrene of 60% solids concentration was compounded to form a mixture comprising 100 parts latex, 3 parts zinc oxide, 2 parts sulphur, 1,5 parts accelerator, 1 part antioxidant, 0,5 parts sodium polyacrylate and 0,38 parts methyl cellulose.  Prior to spreading 8 parts of a 25% aqueous dispersion of p,p1,-oxy-bis (benzenesulphonylhydrazide) were added and the mixture adjusted to a pH of 10-10,5 by addition of ammonia.  The composition was spread on the back of a piece of woollen carpet and the coated carpet heated to 110-115 DEG C in an oven with a relative humidity of 95%, the film blowing and gelling in 6 mins.  The coated carpet was dried and vulcanised giving a sponge coating of 3/16-4/16 inches.