Patent GB-573768-A (GB)
Title: Improvements in or relating to the coating and impregnating of textile materials with cellulose
IPC: D06M15/05
Filed: 1943-04-07
Abstract: Textile material is impregnated or coated with a solution of cellulose in a liquid obtained by dissolving zinc oxide, zinc hydroxide, or metallic zinc, in an aqueous solution of an alkali metal hydroxide, and is then treated so as to cause precipitation of cellulose on the material.  Preferably, the cellulose is used in substantially undegraded condition and the alkali metal hydroxide is in excess of the amount theoretically required to convert the zinc or zinc oxide into alkali metal zincate.  Caustic soda or potash may be used, e.g. a solution of caustic soda of 8-15 per cent strength. Fabric or thread may be passed through the cellulose solution and then between squeeze rolls, or it may be passed over a roll which is moistened with the solution.  The material may be passed through a bath of dilute acid, e.g. sulphuric, hydrochloric, or acetic acid to precipitate the cellulose.  Alternatively, the treated material may be heated to at least 50 DEG  C. by steam, air, or quick immersion in hot water, or it may be dried in air at atmospheric temperature, the cellulose precipitating as the water is evaporated.  Precipitation of cellulose may also be effected by addition of electrolytes such as soluble salts or additional alkali such as sodium, potassium, or lithium hydroxide, or by addition of alcohol, acetone, glycerine, glycol, or other dehydrating substance to the solution adhering to the textile material.  After the cellulose has been precipitated, the material is washed, if acid has been used, and then dried.  The cellulose solution may contain dyes, pigments, starch, oils, waxes, alkyd resins, soft urea-formaldehyde resins, methacrylate resins, or wetting agents, e.g. sulphonated hydrocarbons, or sulphated higher aliphatic alcohols.  Preferably, the cellulose is dissolved in the zincate solution at a temperature below 0 DEG  C.  The treatment stiffens the fabric or yarn, decreases the shrinkage of a shrinkable fabric on washing with water, increases the tensile strength, and in the case of woven or knitted fabrics, the individual strands adhere at their crossings and are prevented from slipping.  The textile material may be composed of fibres of cotton, flax, silk, viscose rayon, cellulose acetate rayon, or glass.  The alkalinity of the solution modifies the surface of glass fibres so as to give a satisfactory adherence of the cellulose coating.  When starch and a filler are included in the cellulose solution, the application of the solution and suspended material may produce a back-filling of the textile fabric.  In an example, powdered viscose rayon is stirred into a mixture of water and chopped ice.  Sodium zincate solution is added and the mixture is stirred till the cellulose is dissolved. The solution is applied to a fabric, e.g. a spun rayon fabric, and precipitation of cellulose is effected by treatment with sulphuric acid.  A mosquito netting is padded with the cellulose solution and dried and then treated with dilute sulphuric acid.  A fabric of woven glass wool fibres is padded with the cellulose solution and then treated with sulphuric acid. The glass fabric may then be dyed. Specification 573,767 is referred to.