Process for the acetylation of regenerated cellulose fibers and product resulting therefrom

Claim 2

A PROCESS FOR THE ACETYLATION OF REGENERATED CELLULOSE FIBERS WITH RETENTION OF THEIR FIBROUS STRUCTURE COMPRISING SUCCESSIVELY IMPREGNATING REGENERATED CELLULOSE FIBERS IN THEIR SWOLLEN, WET GEL STATE AND CONTAINING BETWEEN 35% AND 60% BY WEIGHT OF WATER WITH (1) GLACIAL ACETIC ACID AND (2) A MIXTURE CONTAINING BETWEEN ABOUT 2% AND 10% BY WEIGHT OF ACETIC ANHYDRIDE, A SMALL AMOUNT BY WEIGHT OF AN ACETYLATION CATLYST AND THE BALANCE GLACIAL ACETIC ACID, SAID SUCCESSIVE IMPREGNATIONS EFFECTING THE SUBSTITUTION OF ACETIC ACID FOR SUBSTANTIALLY ALL OF THE WATER CONTAINED BY THE WET GEL FIBERS WHILE MAINTAINING THE FIBERS IN A SWOLLEN STATE, REMOVING THE EXCESS ACETIC ACID SOLUTION TO PROVIDE THE FIBERS WITH AN ACETIC ACID CONTENT BETWEEN 35% AND 60% BY WEIGHT, THEN IMMERSING THE SWOLLEN FIBERS FOR FROM 15 SECONDS TO 150 SECONDS IN AN ACETYLATING BATH MAINTAINED AT A TEMPERATURE BETWEEN 35* C. AND 60* C., SAID BATH COMPRISING BY WEIGHT BETWEEN 5% AND 25% ACETIC ANHYDRIDE, BETWEEN 0.05% AND 0.1% OF AN ACETYLATION CATALYST AND BETWEEN 75% AND 95% OF AN ORGANIC DILUENT FOR THE ACETIC ANHYDRIDE, THE ORGANIC DILUENT BEING SUBSTANTIALLY INERT TO CELLULOSE ACETATE WASHING THE ACETYLATED FIBERS AND FINALLY DRYING THE ACETYLATED FIBERS.

Claim 3

AS AN ARTICLE OF MANUFACTURE, A REGENERATED CELLULOSE FIBER ACETYLATED ONLY AT ITS SURFACE AND OUTER PERIPHERAL ZONE FORMED, BY SUCCESSIVELY IMPREGNATING A SWOLLEN WET GEL REGENERATED CELLULOSE FIBER CONTAINING BETWEEN 35% AND 60% BY WEIGHT OF WATER WITH (1) GLACIAL ACETIC ACID AND (2) A MIXTURE CONTAINING BETWEEN ABOUT 2% AND 10% BY WEIGHT OF ACETIC ANHYDRIDE, A SMALL AMOUNT BY WEIGHT OF AN ACETYLATION CATALYST AND THE BALANCE GLACIAL ACETIC ACID, SAID SUCCESSIVE IMPREGNATIONS EFFECTING THE SUBSTITUTION OF ACETIC ACID FOR SUBSTANTIALLY ALL OF THE WATER CONTAINED BY THE WET GEL FIBERS WHILE MAINTAINING THE FIBERS IN A SWOLLEN STATE, REMOVING THE EXCESS ACETIC ACID SOLUTION TO PROVIDE THE FIBERS WITH AN ACETIC ACID CONTENT BETWEEN 35% AND 60% BY WEIGTH AND THEN IMMERSING THE SWOLLEN FIBERS IN AN ACETYLATING BATH MAINTAINED AT A TEMPERATURE BETWEEN 35* C. AND 65* C., SAID BATH COMPRISING BY WEIGHT, BETWEEN 5% AND 25% OF ACETIC ANHYDRIDE, BETWEEN 0.05% AND 0.1% OF AN ACETYLATION CATALYST AND BETWEEN 75% AND 95% OF AN ORGANIC DILUENT FOR THE ACETIC ANHYDRIDE, THE ORGANIC DILUENT BEING SUBSTANTIALLY INERT TO CELLULOSE ACETATE, AND WASHING AND FINALLY DRYING THE ACETYLATED FIBER, SAID FIBER HAVING AN ACETYL CONTENT OF BETWEEN 6% AND 22%, A DRY TENACITY OF AT LEAST 2.5 GRAMS PER DENIER, A WET TENACITY OF 1.45 GRAMS PER DENIER AND A WET AND DRY EXTENSIBILITY OF AT LEAST 15%

Claim 4

AS AN ARTICLE OF MANUFACTURE, A REGENERATED CELLULOSE FIBER ACETYLATED ONLY AT ITS SURFACE AND OUTER PERIPHERAL ZONE FORMED, BY SUCCESSIVELY IMPREGNATING A SWOLLEN WET GEL REGENERATED CELLULOSE FIBER CONTAINING BETWEEN 35% AND 60% BY WEIGHT OF WATER WITH (1) GLACIAL ACETIC ACID AND (2) A MIXTURE CONTAINING BETWEEN ABOUT 2% AND 10% BY WEIGHT OF ACETIC ANHYDRIDE, A SMALL AMOUNT BY WEIGHT OF AN ACETYLATION CATALYST AND THE BALANCE GLACIAL ACETIC ACID, SAID SUCCESSIVE IMPREGNATIONS EFFECTING THE SUBSTITUTION OF ACETIC ACID FOR SUBSTANTIALLY ALL OF THE WATER CONTAINED BY THE WET GEL FIBERS WHILE MAINTAINING THE FIBERS IN A SWOLLEN STATE, REMOVING THE EXCESS ACETIC ACID SOLUTION TO PROVIDE THE FIBERS WITH AN ACETIC ACID CONTENT BETWEEN 35% AND 60% BY WEIGTH AND THEN IMMERSING THE SWOLLEN FIBERS IN AN ACETYLATING BATH MAINTAINED AT A TEMPERATURE BETWEEN 35* C. AND 65* C., SAID BATH COMPRISING BY WEIGHT, BETWEEN 5% AND 25% OF ACETIC ANHYDRIDE, BETWEEN 0.05% AND 0.1% OF AN ACETYLATION CATALYST AND BETWEEN 75% AND 95% OF AN ORGANIC DILUENT FOR THE ACETIC ANHYDRIDE, THE ORGANIC DILUENT BEING SUBSTANTIALLY INERT TO CELLULOSE ACETATE, AND WASHING AND FINALLY DRYING THE ACETYLATED FIBER, SAID FIBER HAVING AN ACETYL CONTENT OF BETWEEN 6% AND 22%, A DRY TENACITY OF AT LEAST 2.5 GRAMS PER DENIER, A WET TENACITY OF 1.45 GRAMS PER DENIER AND A WET AND DRY EXTENSIBILITY OF AT LEAST 15%