Dry spinning of cellulose acetate fiber

Abstract

A dry spinning system and process are used to produce cellulose ester fibers. The process utilizes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or mixtures thereof as the dissolution solvent. The process minimizes or avoids discoloration of the fibers.

1 . A process for producing a cellulose ester fiber, said process comprising dry spinning a cellulose ester dope through a spinneret to make one or more of said fibers, wherein said cellulose ester dope comprises dissolved and/or dispersed solids (hereinafter “solids”) and solvent, at least 35 wt. % of said solids comprises cellulose ester, and said solvent comprises N,N-dimethylformamide, N,N-dimethylacetamide, or dimethyl sulfoxide, or mixtures thereof, provided that if said solvent comprises N,N-dimethylacetamide:
 (i) said cellulose ester dope comprises not more than 50% by weight acetone, based on the total weight of the cellulose ester dope; or 
 (ii) said cellulose ester dope comprises 0% by weight cellulose nanocrystals based on the total weight of the cellulose ester dope; or 
 (iii) both (i) and (ii), wherein the combined weight of a polyurethane, polyolefin, nylon, polyester, and/or polyurethaneurea, if present in said cellulose ester dope, is not more than 60% by weight, based on the total solids in said cellulose ester dope. 
 
     
     
         2 . The process of  claim 1 , wherein said cellulose ester dope comprises not more than 10% by weight polyurethanes or polyurethaneureas, based on the total solids in the cellulose ester dope. 
     
     
         3 . The process of claim  11 , wherein said cellulose ester dope comprises not more than 50% by weight acrylonitrile-vinyl acetate copolymer, based on the total solids in the cellulose ester dope. 
     
     
         4 . The process according to,  claim 1 , wherein said cellulose ester fiber comprises at least 50% by weight cellulose ester obtained from said cellulose ester dope. 
     
     
         5 . The process according to,  claim 1 , wherein said cellulose ester has a DS acetyl  of at least 1.5 and/or not more than 2.95. 
     
     
         6 . The process according to  claim 1 , wherein said cellulose ester has a glass transition temperature of at least 120° C. and/or not more than 250° C. 
     
     
         7 . The process according to  claim 1 , wherein said dry spinning comprises:
 spinning said cellulose ester dope so as to produce spun fibers containing said solvent; and   evaporating said solvent from said spun fibers.   
     
     
         8 . The process according to  claim 1 , wherein said cellulose ester dope comprises a polyfunctional acid. 
     
     
         9 . The process according to  claim 1 , wherein said cellulose ester dope has a moisture content of not more than 4% by weight, based on the total weight of the cellulose ester dope. 
     
     
         10 . The process according to  claim 1 , further comprising preparing said cellulose ester dope by slurrying the cellulose ester and said solvent and subsequently cooling said dope to a temperature of at least −100° C. and/or not more than 5° C. and storing at one of the foregoing temperatures for at least 1 hour. 
     
     
         11 . The process according to  claim 1 , wherein said cellulose ester dope has a b* value is of not more than 0.75. 
     
     
         12 . A cellulose ester fiber formed according to  claim 1 . 
     
     
         13 . A yarn comprising said cellulose ester fiber formed according to  claim 12 . 
     
     
         14 . An article comprising said cellulose ester fiber formed according to  claim 12 . 
     
     
         15 . A woven article comprising said cellulose ester fiber formed according to  claim 12 . 
     
     
         16 . A nonwoven article comprising said cellulose ester fiber formed according to  claim 12 . 
     
     
         17 . A staple fiber comprising said cellulose ester fiber formed according to  claim 12 . 
     
     
         18 . A knitted textile comprising said cellulose ester fiber formed according to  claim 12 . 
     
     
         19 . The process of  claim 7 , wherein evaporating said solvent from said spun fibers takes place in a spinning cabinet. 
     
     
         20 . The process of  claim 19 , wherein said spun fibers in said spinning cabinet are drawn to a draw ratio of no more than 2×.