Patent GB-616033-A (GB)
Title: Improvements in the purification of cellulose products
IPC: D06M11/05
Filed: 1946-08-21
Abstract: Cellulose, regenerated cellulose, or cellulose ester or ether material containing metallic cations derived from mineral-containing fresh water, is subjected to treatment with mineral-containing fresh water at a pH of about 2-5 to remove metallic cations and is then washed with water substantially free from metallic cations.  The treatment may be applied to filaments, fibres, ribbons, films, or other materials which have been subjected to wet treatments and washed with water containing dissolved salts of calcium, magnesium, or sodium.  Such compounds cause irregularities in the material if they are not removed before the material is dried.  Sulphuric or hydrochloric acid may be used for acidifying the water.  Subsequent washing may be effected with distilled water or water which has been freed from metallic cations by contact with a substance that exchanges hydrogen for those cations.  A small proportion of ammonia may be added to the water in the last stages of washing to hasten the attainment of neutrality.  In an example, bobbins of freshly-spun viscose yarn are subjected to treatment with hot and cold water, then to treatment with a desulphurizing liquid, e.g. ammonium sulphide solution at 40 DEG  C., and then to another washing treatment with hot water.  Hard water is used for all these washing treatments.  The bobbins are then washed with hard water acidified to pH2, and then with de-mineralized water.  The dye affinity of the yarn is improved. In another example, high tenacity cellulose acetate yarn is completely saponified with a solution of caustic soda and sodium acetate.  The yarn is washed thoroughly in hard water, then in hard water acidified with hydrochloric acid to pH2, and finally washed with distilled water.  The treatment may be applied to cotton, linen, or other cellulosic material.  It may be applied to cellulose pulp, and to cellulose esters and ethers in flake or powder form.ALSO:Cellulose, regenerated cellulose, or cellulose ester or ether material containing metallic cations derived from mineral-containing fresh water, is subjected to treatment with mineral-containing fresh water at a pH of about 2-5 to remove metallic cations and is then washed with water substantially free from metallic cations.  The treatment may be applied to filaments, fibres, ribbons, films, or other materials which have been subjected to wet treatments and washed with water containing dissolved salts of calcium, magnesium, or sodium.  Such compounds cause irregularities in the material if they are not removed before the material is dried. Sulphuric or hydrochloric acid may be used for acidifying the water. Subsequent washing may be effected with distilled water or water which has been freed from metallic cations by contact with a substance that exchanges hydrogen for those cations.  A small proportion of ammonia may be added to the water in the last stages of washing to hasten the attainment of neutrality.  In an example, bobbins of freshly spun viscose yarn are subjected to treatment with hot and cold water, then to treatment with a desulphurizing liquid, e.g. ammonium sulphide solution at 40 DEG  C., and then to another washing treatment with hot water.  Hard water is used for all these washing treatments.  The bobbins are then washed with hard water acidified to pH2, and then with de-mineralized water.  The dye affinity of the yarn is improved.  In another example, high tenacity cellulose acetate yarn is completely saponified with a solution of caustic soda and sodium acetate.  The yarn is washed thoroughly in hard water, then in hard water acidified with hydrochloric acid to pH2, and finally washed with distilled water.  The treatment may be applied to cotton, linen, or other cellulosic material.