Patent GB-592210-A (GB)
Title: Improvements in the manufacture of cellulose and other carbohydrate ethers and of materials made of or containing them
IPC: C08B15/00
Filed: 1941-11-05
Abstract: A water-soluble ether of a carbohydrate particularly of cellulose, starch, or other polyose, is converted into a form insoluble in water and in the common organic solvents by mixing an aqueous solution of such ether with a water-soluble aldehyde of the general formula R-CO-CHO wherein R represents hydrogen or an alkyl radical, and removing water from the ensuing reaction mixture during the course of the reaction.  The mixture of carbohydrate ether solution and aldehyde may be used as a coating, impregnating, or adhesive composition, or as a solution for the production of shaped articles such as filaments or films. Conversion of the ether to the insoluble form is effected during or after the shaping of the solution to form a filament, film, or other article, or during or after its application as a coating, impregnation, or adhesive, to a fabric, paper, or other article. The treatment renders such materials resistant to linting and imparts high wet and dry strength.  It renders them resistant to penetration by oils and greases. Impregnated paper articles may still retain a high degree of moisture absorption and permeability to air.  Paper comprising wood fibres mixed with cotton or linen fibres may be treated.  A water-soluble cellulose ether such as a hydroxy alkyl cellulose ether or a water-soluble methyl or ethyl cellulose may be dissolved in water and then the aldehyde, e.g. glyoxal or pyruvic aldehyde, is dissolved in the aqueous solution.  The solution is used to form, coat, or impregnate an article, and is then heated to eliminate water and facilitate the reaction between the cellulose ether and the aldehyde, thereby forming an insoluble filament, film or other shaped mass, or coating or impregnation.  The treated cellulose ether materials are insoluble in water, acetone, methyl ethyl ketone, methanol, ethanol, butanol, chlorinated hydrocarbons, toluene, petroleum ether, acetic acid, glycol ethers, fatty oils, and dilute aqueous solutions of caustic soda.  The aqueous solutions of the cellulose ethers may be subjected to dialysis in order to ensure uniformity in the films or other products produced.  Mineral acids or other substances acting as catalysts for the acetaltype of reaction may be present in the solutions.  Small amounts of organic liquids such as ketones, alcohols, and ethers may be present.  The solutions may also contain glycerol, propylene glycol or other polyhydric alcohol and these substances may react with some of the aldehyde which is present so as to form a mixed acetal of the cellulose ether and polyhydric alcohol. In an example, glyoxal is added to an aqueous solution of water soluble methyl cellulose. After standing for some days, the solution is spread in a thin layer on a glass plate and the film is dried. The plate is wetted with water and the film is stripped.  In another example, a water soluble hydroxy ethyl cellulose is produced by treating alkali cellulose with ethylene oxide vapour.  The product is dissolved in water and neutralized with acetic acid.  The sodium salts are removed by dialysis using a seamless tube of regenerated cellulose as the semi-permeable membrane.  Glyoxal is added to an aqueous solution of the product.  A film is cast from the solution and dried at 105 DEG  C.  Fabrics of cellulose and cellulose derivatives, paper, and other fibrous structures may be impregnated or laminated with the cellulose ether compositions.  The films or other products may be used as wrapping materials, e.g. as water-proof wrappings for stick dynamite.  In another example, a watersoluble hydroxypropyl starch ether is made by heating a mixture of tapioca starch, dimethyl dibenzyl ammonium hydroxide, water, and propylene oxide.  The product is extracted with methanol and dried.  Glyoxal is added to a solution of the product in water and the solution is formed into films.  The process may be applied to the production of paper towelling of high wet and dry strength.  The cellulosic fibres may be treated with the aqueous aldehyde cellulose ether solution in the pulp beaters but preferably the solntion is applied to the felted sheet.  The solution may be applied uniformly or in local areas.  In an example, unbleached paper towelling made from sulphate wood pulp is treated with a solution containing about 5 parts of hydroxyethyl cellulose, about 5 parts of glycerine, and about 2 parts by glyoxal per 1000 parts by weight of the solution.  Excess of solution is removed by pressing and the towel is dried. Several impregnations and dryings may be performed.  Provided the treatment is such that the increase in weight does not greatly p  exceed 1.5 per cent of the dry weight of the untreated material, a satisfactory increase in strength is obtained without appreciable decrease in the moisture absorption capacity.ALSO:A water-soluble ether of a carbohydrate, e.g., of starch, or other polyose, is converted into a form insoluble in water and in the common organic solvents by mixing an aqueous solution of such ether with a water-soluble aldehyde of the formula R.CO. CHO wherein R is hydrogen or an alkyl radical, e.g., glyoxal or pyruvic aldehyde, and removing water from the ensuing reaction mixture during the course of the reaction, conversion to the insoluble form being effected during or after shaping or during or after application to a fabric, paper, or other article as a coating, impregnation, or adhesive.  Water may be eliminated and the reaction may be facilitated by heating.  Mineral acids or other catalysts may be present and the solution may also contain small amounts of organic liquids such as acetone, alcohols, or ethers.  The solution may contain glycerol or other polyhydric alcohol, such substance reacting with the aldehyde so as to form a mixed acetal of the carbohydrate ether and the polyhydric alcohol.