GB682685A - Improvements in and relating to casein plastics - Google Patents

Abstract

A casein plastic showing improved resistance to water and moisture is obtained by forming a mixture containing casein, melamine and water and/or a water-miscible alcohol, said mixture containing between 2.5 and 25 per cent by weight of melamine (calculated on the weight of the casein) into a mass or article, subjecting the mass or article to a treatment with formaldehyde, drying the thus treated product and heating the dried product. Preferably the forming of the mixture into a mass or article is effected by extrusion. The term melamine includes mixtures of substances containing melamine, e.g. the mixture obtained by heating melamine which in addition to unchanged melamine includes melon and melan. The concentration of the formaldehyde bath is usually about 5 to 6 per cent by weight of formaldehyde. The formalization may be effected in a similar manner to that employed for compositions not containing melamine. A suitable plasticizer may be added to the initial mixture. In examples: (1) a mixture of water, finely-melamine, and glycerine, is added slowly to rennet casein in a mixing machine and after mixing until the mass is homogeneous the mixture is allowed to stand and then extruded to form a rod. The rod is cut into suitable lengths and immersed in a solution of formalin and left for 3 days at 65 DEG F. The rods are then removed from the bath, dried at 100-120 DEG F., and then placed in an oven and heated for 16 hours at 158 DEG F. The rods are then allowed to remain ina humid atmosphere to regain normal moisture content; (2) a mixture of water, glycerine, dyestuffs, titanium dioxide and finely-ground melamine is added to rennet casein as in (1) and the moist mass extruded to yield a rod which is then cut into lengths and treated with formaldehyde solution for 7 days at 65 DEG F. The rods are then removed from the bath, dried at 100 DEG to 120 DEG F., and then heated at 210 DEG F. for 16 hours p and the normal moisture content restored as in (1); (3) the ingredients used in (1) are mixed in the same way but after standing the mixture is worked on a two-roll mill with rolls heated to 60 DEG to 80 DEG C. until a homogeneous mass free from unplasticized particles of casein is obtained. The rough sheet formed on the mill is then removed and pressed into a thin sheet in a steam heated hydraulic press and the sheet is cooled, formalized for a period of about 4 days, dried, and then heated as in (1).