GB594966A - Improvements in or relating to manufacture of articles from rubber or the like - Google Patents

Abstract

In making a balloon &c. having a neck less than one half the greatest dimension of the mould which must pass through the neck, the following steps are performed:-(1) A coagulant-coated mould is dipped into a liquid dispersion of rubber. If a dispersion of natural rubber is used it must contain less than 0.45 per cent. combined sulphur based on the dry weight of the rubber hydrocarbon. (2) The gel-coated mould is withdrawn from the dispersion. (3) The wet gel is removed from the mould by stretching the neck. (4) The gel is dried. Before drying, the gel may be distended to thin it and give it its required size with uniform wall thickness. After drying and deflation it is vulcanized. During removal of the gel from the mould, the net form of the gel may be conserved by keeping the interstices filled or distended with an "intervenor," as described in U.S.A. Specification 1,745,657. A dispersion of synthetic rubber may comprise polymerized chloroprene 1 : 3 dispersion, dibutyl sebacate emulsion (this emulsion is a plasticiser and comprises dibutyl sebacate, oleic acid, wetting agent and ammonia), clay, ammonia, formaldehyde condensation product of naphthalene sulphonic acid (dispersing agent), zinc oxide, phenyl beta naphthylamine, and a solution of casein in water. The coagulant for this dispersion comprises calcium nitrate tetra hydrate, acetone, glycerine, bentonite and water. A dispersion of natural rubber may comprise rubber latex, potassium hydroxide, zinc stearate, zinc dibutyl dithiocarbamate, symmetrical dibeta-naphthyl-para-phenylene diamine, formaldehyde condensation product of naphthalene sulphonic acid, titanium dioxide, wetting agent and sulphur. The coagulant for this dispersion comprises calcium nitrate tetra hydrate, acetone, glacial acetic acid, glycerine, bentonite and water. The Specification as open to inspection under Sect. 91 contains drawings illustrating the invention. These drawings are not present in the Specification as accepted.