High dpf cellulose acetate tow and process for making

Abstract

Disclosed are cellulose acetate cellulose acetate tow and processes for making cellulose acetate tow having at least 15 denier per filament, e.g., at least 20 denier per filament, or at least 25 denier per filament. The cellulose acetate tows may have total denier of more than 20,500.

We claim: 
     
         1 . A cellulose acetate tow having at least 15 denier per filament and more than 20,500 total denier. 
     
     
         2 . The tow of  claim 1 , wherein the tow has from 20 to 50 denier per filament. 
     
     
         3 . The tow of  claim 1 , wherein the tow has from 25 to 40 denier per filament. 
     
     
         4 . The tow of  claim 1 , wherein the tow has from 21,000 to 60,000 total denier. 
     
     
         5 . The tow of  claim 1 , wherein the tow has from 20,500 to 40,000 total denier. 
     
     
         6 . The tow of  claim 1 , wherein the tow has a breaking strength between 3.5 kg and 25 kg. 
     
     
         7 . A filter comprising cellulose acetate tow, the tow having at least 15 denier per filament and more than 20,500 total denier. 
     
     
         8 . The filter of  claim 7 , wherein the filter has an encapsulated pressure drop of less than 3 mm water/mm length. 
     
     
         9 . The filter of  claim 7 , wherein the filter has an encapsulated pressure drop of less than 1 mm water/mm length. 
     
     
         10 . The filter of  claim 7 , wherein the encapsulated pressure drop of the filter comprising the cellulose acetate tow has a coefficient of variability of less than 15%. 
     
     
         11 . The filter of  claim 7 , wherein the filter has a circumference from 5 to 30 mm. 
     
     
         12 . A process for producing a cellulose acetate tow bale, comprising:
 dissolving cellulose acetate in a solvent to form a cellulose acetate dope;   spinning the cellulose acetate dope through at least one spinneret with at least one hold diameter from 100 to 300 microns to form filaments having a denier per filament of at least 15, and a total denier of more than 20,500;   bundling the filaments to form a tow;   plasticizing and crimping the tow;   drying the tow; and   packaging the tow into a bale.   
     
     
         13 . The process of  claim 12 , wherein the at least one spinneret comprises at least one hole with a diameter from 100 to 250 microns. 
     
     
         14 . The process of  claim 12 , wherein the filaments undergo an evaporation step prior to bundling to form a tow. 
     
     
         15 . The process of  claim 12 , wherein the evaporation removes at least 90 wt. % of the solvent. 
     
     
         16 . The process of  claim 12 , wherein the evaporation is conducted at a temperature in the range of 90 to 100° C. 
     
     
         17 . The process of  claim 12 , wherein the evaporation is conducted at a pressure in the range of 120 to 180 psi. 
     
     
         18 . The process of  claim 12 , wherein the filaments exit the at least one spinneret at a drawdown ratio ranging from 0.7 to 1.6. 
     
     
         19 . The process of  claim 12 , wherein the residence time for the evaporation step is increased by more than 10% when compared with the residence time for a similar cellulose acetate tow bale made from filaments having a dpf from 2 to 8. 
     
     
         20 . The tow of  claim 1 , wherein the tow has an EPD mm water/per mm length of 0.9 or less.