Patent GB-1049009-A (GB)
Title: Alkali-soluble cellulose acetate textile material and process for producing same
IPC: D06Q1/00
Filed: 1965-08-13
Abstract: Alkali soluble cellulose acetate textile material that is at least 90% soluble in an alkaline solution at room temperature, but possesses the necessary physical properties for effective use as textile fibre, yarn or fabric and may be dissolved and easily removed from textile material containing this treated cellulose acetate as one component and other textile components that are not alkali soluble, is made by treating non-alkali soluble cellulose acetate textile material with a composition comprising (1) either chromic acid or a dichromate salt in combination with (2) either a mineral acid or certain organic acids, e.g. oxalic acid, for sufficient length of time to render the cellulose acetate material soluble in alkali, washing the material free of the treating chemical and drying the material. The treated material is preferably substantially completely soluble in 0.01% to 3.0% sodium hydroxide.  The alkali soluble property may be obtained by treating the cellulose acetate textile material with a dichromate and a mineral acid; e.g. sodium dichromate of 0.7 to 4.0% concentration and nitric acid of approximately 1.0 to 18% by weight concentration. Alternatively the alkali soluble property may be obtained by treating the cellulose acetate material with chromic acid and oxalic acid. In an example a cellulose acetate cloth is treated for 60 minutes at 170 DEG  F. at a liquid to fibre ratio of 20:1 with a solution containing 0.8% sodium dichromate expressed as the dihydrate, and 2.4% nitric acid expressed as 100% nitric acid.ALSO:Alkali soluble cellulose acetate textile material that is at least 90% soluble in an alkaline solution at room temperature, but possesses the necessary physical properties for effective use as textile fibre, yarn or fabric and may be dissolved and easily removed from textile material containing this treated cellulose acetate as one component and other textile components that are not alkali soluble, is made by treating non-alkali soluble cellulose acetate textile material with a composition comprising (1) either chromic acid or a dichromate salt in combination with (2) either a mineral acid or certain organic acids e.g. oxalic acid for sufficient length of time to render the cellulose acetate material soluble in alkali washing the material free of the treating chemical and drying the material.  The treated material is preferably substantially completely soluble in 0.01% to 3.0% sodium hydroxide. The alkali soluble property may be obtained by treating the cellulose acetate textile material with a dichromate and a mineral acid; e.g. sodium dichromate of 0.7% to 4.0% concentration and nitric acid of approximately 1.0% to 18% by weight concentration.  Alternatively the alkali soluble property may be obtained by treating the cellulose acetate material with chromic acid and oxalic acid.  In an example a cellulose acetate cloth is treated for 60 minutes at 170 DEG F. at a liquid to fibre ratio of 20:1 with a solution containing 0.8% sodium dichromate expressed as the dihydrate, and 2.4% nitric acid expressed as 100% nitric acid.  The alkali soluble cellulose acetate of the invention may be used for the production of non-puckering fabrics. Differences in contraction of adjacent portions of fabrics, e.g. the main body portion and the decorative border portion respectively of a water absorbent towel, may be avoided by using a special fabric yarn in the border portion.  This yarn is purposely spiralled or coiled to provide excess length which becomes useful when effective upon wetting of the yarns and straightening out of the coils or spirals. To enable the coiled or spiralled yarn, usually the filling yarn in the woven fabric to be woven satisfactorily in the decorative border using conventional weaving equipment, a temporary core yarn is employed around which the filling yarn is coiled or spiralled, the core yarn acting as a carrying medium for the spiralled or coiled yarn.  It is necessary for this core yarn to be easily removed and preferably by the use of liquid or solutions commonly employed in towel or fabric finishing.  One of the important commercial advantages of the cellulose acetate yarn of the present invention is that it is relatively inexpensive and is a readily available commodity in fibre, yarn or fabric form, and its processing in accordance with the present invention to render it alkali soluble, is relatively inexpensive.  The alkali soluble material of the present invention may also be used in the manufacture of lace.  The alkali soluble portion of the lace fabric is removed by scouring or the like to produce the desired lace design.