GB601374A - Manufacture of ethers and esters of polysaccharides - Google Patents

Abstract

Ethers, esters, or mixed ether-esters soluble in cold and/or hot water from polysaccharides which swell or dissolve in hot water and are adapted to be made into a solution or paste with a small proportion of water, wherein a mixture of the polysaccharide with a proportion of water not substantially exceeding twice the weight of the polysaccharide, an etherifying agent and/or an esterifying agent and an alkaline substance, either after the etherification or esterification process or in any desired stage of the said process, is heated to a temperature adapted to remove the water and to gelatinise gelatinisable polysaccharides while the mixture is pressed under mechanical pressure into a thin layer on a rotary drum, and the said layer is simultaneously or immediately thereafter dried and subsequently comminuted. Alternatively, the etherifying and/or esterifying agent may be reacted with the dry powder after the drum treatment. A solvent for the said agent, e.g. chloroform, may be employed. Polysaccharides specified are starch, soluble starch, dextrin, insulin and gums such as gum arabic, but not gum tragacanth or locust bean gum. Etherifying agents specified are alkyl sulphates and epoxy-alkanes, in which the alkyl groups may be substituted by hydroxy, mercapto, sulphocyano, halogen, amino, carboxy, arylcarboxy (or salts or amides thereof) sulphonic, or arylsulphonic (or salts thereof) or may be straight or branched, or interrupted by oxygen, nitrogen, or sulphur. Mixtures of etherifying agents may be used. The products may be used as sizing and finishing agents, thickening agents for printing processes, adhesives and binding agents for paper, paints, and granular, pulverous, and fibrous materials. In examples, potato starch is (1) mixed with water, sodium hydroxide, and dimethyl sulphate, the mixture is stirred, and then dried on a heated rotating cylinder, and ground, and (2) mixed with water and caustic soda, dried as in 1, and the dry product treated with chlorsulphonic acid in chloroform. The Specification as open to inspection under Sect. 91 has further examples describing: (1) the mixing of tapioca starch with sodium hydroxide, water, and bromethane sulphonic acid sodium salt or a mixture of chloracetic sodium salt and trichloracetic acid, followed by drum drying and comminution; the mixing of (2) potato flour, water, sodium hydroxide, and acetyl chloride in chloroform, or (3) potato starch, water, sodium hydroxide, and ethylene oxide, followed by drum drying and comminution. This subject-matter does not appear in the Specification as accepted.ALSO:Adhesives and sizing and finishing agents for paper and fibrous materials comprise products obtained by etherification and/or esterification of polysaccharides which swell or dissolve in hot water and are adapted to be made into a solution or paste with a small proportion of water, e.g. starch, soluble starch, dextrin, inulin, gum arabic. A mixture of the polysaccharide with water and alkali is treated with an etherifying and/or esterifying agent, the addition of the agent being followed or preceded by drying of the mixture on heated rolls (see Group IV(b)).