GB364684A - Improvements in method for making shaped rubber articles - Google Patents

Abstract

Rubber goods are manufactured by dipping a coated former into latex &c. dispersions. The former is coated with a solution of a coagulant in a volatile organic solvent part of which is evaporated before dipping. A mixture of a volatile organic solvent and a less volatile solvent may be used. The solvent may be evaporated until a viscous or even a solid film of coagulant remains on the former. If the solution is very fluid a viscous liquid such as glycerine or syrup or colloids such as gum arabic, a cellulose ester polymerized vinyl acetate, &c, may be added to increase the viscosity after evaporation, but in amounts insufficient to produce a solid coagulant film. As examples of coagulants are a non-volatile acid, a coagulating salt or a mixture of the two. As examples of salts are the salts of bivalent metals such as magnesium, the alkaline earths, zinc, copper, cobalt, cadmium, ferrous iron, lead, nickel, and manganese, of tri- and tetravalent metals such as aluminium, ferric iron, antimony, chromium, molybdenum, tin, thorium, vanadium, and zirconium. In general the chlorides and nitrates are preferable but many other acid radicles may be used. As volatile organic solvents are used methyl, ethyl or amyl alcohol, acetone, glycol or glycerine, ether, carbon disulphide, chloroform, ethyl formate or ethyl acetate. As less volatile solvents are used water, higher monohydric alcohols, water soluble esters, glycol or glycerine. Where a coagulant is used such that it may form an insoluble hydroxide or oxide in an alkaline latex, an acid may be added to the coagulant to assist coagulation. In examples the coagulant solution consists of (1) 100 parts of hydrated calcium nitrate in 200 parts of acetone; (2) 100 parts anhydrous commercial calcium nitrate in 200 parts of acetone; (3) 40 parts of calcium chloride, 10 parts of lactic acid in 80 parts of methyl alcohol. Further examples of coagulant solutions are 10 parts citric acid, 1 part glucose (corn syrup), 100 parts acetone; 10 parts zinc chloride or basic lead acetate, 40 parts methyl alcohol and either 10 parts isopropyl alcohol, 5 parts normal butyl alcohol or 2 parts ethylene glycol. Specification 299,737, [Class 70, India-rubber &c.], is referred to.