High population of closed c-shaped fibers

Abstract

A high population density of closed C shaped cellulose acetate filament can now be reliably produced. The closed C filaments are made from a spinneret having a. substantially D shaped orifice under particular processing conditions depending on the dpf of the filament, the theta angle of the D shaped orifice, and dope temperature. The process can make a high population count of closed C shaped fibers in a. tow band, and article are not provided having the high population density of closed C shaped fibers.

1 . A process for making closed C shaped filaments comprising a cross-sectional configuration having a first proximal end, a second proximal end, and a hollow core, the process comprising:
 a. providing a cellulose acetate dope comprising cellulose acetate and solvent;   b. extruding the cellulose acetate dope through at least one spinneret having at least one D-shaped orifice to form wet filaments; and   c. drying the wet filaments in an apparatus adapted for removing solvent from the wet filaments to form the closed C shaped filaments in which—   
       A. at least a portion of the first proximal end is either—
 i. oriented toward at least a portion of the second proximal end, or 
 ii. contacting at least a portion of the second proximal end; and 
 
       B. the first proximal end and the second proximal end form either—
 i. a channel defined by a gap between the first proximal end and the second proximal end having a transverse distance D1, wherein the channel leads from an outer surface of the closed C shaped filaments to the hollow core defined by an inner filament surface and having a diameter D2, and wherein D2/D1>1, or 
 ii. no channel or passageway resulting from at least a portion the first proximal end contacting at least a portion of the second proximal end. 
 
     
     
         2 . The process of  claim 1 , wherein the cellulose acetate dope has a concentration of the cellulose acetate of from 28 weight % to 35 weight %, the cellulose acetate having an average degree of substitution of from 2.2 to 2.8, and the cellulose acetate dope is at a temperature of 45° C. to less than 62° C. as measured from a candle filter water temperature (CFWT). 
     
     
         3 . The process of  claim 1 , wherein the D-shaped orifice comprises a circular annular open portion defined as a space within an inner circumference of the circular annular portion and a chord, wherein the chord intersects a first point and a second point on the inner circumference, wherein θ is the angle determined by and between two radii, (R1) and (R2), extending from an imaginary center and intersecting the first point and the second point, the imaginary center is defined as the center of an imaginary circle drawn along the circular annular portion and continuing until a complete circle is drawn, and wherein the θ is from 90° to 160°. 
     
     
         4 . The process of  claim 1 , wherein at least a portion of the first proximal end and the second proximal end are spaced apart at a distance of less than 1.0 radian and are not touching. 
     
     
         5 . The process of  claim 1 , wherein at least a portion of the closed C shaped filaments have the first proximal end and the second proximal end in contact with each other. 
     
     
         6 . The process of  claim 1 , wherein at least 30% of the closed C shaped filaments are mutually opposed. 
     
     
         7 . The process of  claim 1 , wherein the hollow core has a cross-section area that is at least 25% of the cross-section area of an individual closed C shaped filament. 
     
     
         8 . The process of  claim 1 , wherein the hollow core has an aspect ratio (width:height) of not more than 2:1. 
     
     
         9 . The process of  claim 1 , wherein the first proximal end and the second proximal end are co-extensively oriented to each other in an amount of at least 5%. 
     
     
         10 . The process of  claim 1 , wherein the cellulose acetate dope comprises less than 5 weight % of a delusterant, a plasticizer, and water, based on the total weight of the cellulose acetate dope. 
     
     
         11 . The process of  claim 1 , wherein the cellulose acetate dope contains not more than 4.5 weight % of plasticizer based on the total weight of the cellulose acetate dope. 
     
     
         12 . The process of  claim 1 , further comprising drawing at least a portion of the closed C shaped filaments at a draft ratio from 0.9 to 1.6. 
     
     
         13 . The process of  claim 12 , wherein the dpf of a closed C shaped filament spun through the D-shaped orifice at a fixed θ angle is changed in an amount of 0.35 to 0.7 units for every 0.1 unit change in draft ratio. 
     
     
         14 . The process according to  claim 1 , wherein the dpf can be adjusted within +/−3 full integers for a given D shaped orifice. 
     
     
         15 . An article comprising cellulose acetate fibers, wherein at least 50% of the cellulose acetate fibers are closed C shaped fibers based on:
 a. 150 cellulose acetate fibers, or   b. 150 C shaped cellulose acetate fibers.   
     
     
         16 . The article of  claim 15 , wherein at least 65% of the cellulose acetate fibers are the closed C shaped fibers. 
     
     
         17 . The article of  claim 15 , wherein the cellulose acetate fibers comprise a cellulose acetate having a degree of substitution (DS) of from 2.2 to 2.8. 
     
     
         18 . The article of  claim 15 , wherein the closed C shaped fibers have a first proximal end and a second proximal end that either:
 i. form a channel defined by a gap between the first proximal end and the second proximal end having a transverse distance D1, wherein the channel leads from an outer surface of the closed C shaped fibers to a hollow core defined by an inner fiber surface and having a diameter D2, and wherein D2/D1>1, or   ii. no channel or passageway results from at least a portion the first proximal end contacting at least a portion of the second proximal end.   
     
     
         19 . The article of  claim 15 , wherein at least 30% of the closed C shaped fibers are mutually opposed. 
     
     
         20 . The article of  claim 18 , wherein the first proximal end and the second proximal end are co-extensively oriented to each other in an amount of at least 5%.