Cellulose acetate fibers in nonwoven fabrics

Abstract

Staple fibers and filament yarns formed from cellulose esters, such as cellulose acetate, are described herein, along with methods of making the fibers and their use in nonwoven fabrics and articles. The filament yarns and fibers described herein may be coated with at least one finish and, in some cases, may be coated with two or more finishes selected to enhance the properties of the fibers. Staple fibers as described herein may be used to produce nonwoven webs that are strong, soft, absorbent, and biodegradable, and may be used in wet or dry nonwoven articles for a variety personal care, medical, industrial, and commercial applications.

1 . A staple fiber formed from cellulose acetate, wherein said fiber is at least partially coated with at least one finish, wherein said fiber has a denier per filament of less than about 3.0 and a crimp frequency of less than 22 crimps per inch (CPI), and wherein a plurality of said fibers exhibit a fiber-to-fiber staple pad coefficient of friction of not more than about 0.70. 
     
     
         2 . The staple fiber of  claim 1 , wherein said fiber has a static half-life of not more than about 12 minutes and wherein a plurality of said fibers exhibit a fiber-to-fiber staple pad coefficient of friction of at least about 0.1. 
     
     
         3 . The staple fiber of  claim 1 , wherein a plurality of said fibers exhibit a fiber-to-fiber staple pad coefficient of friction of at least about 0.1 and wherein said fiber has a surface resistivity, expressed as log R, of not more than about 11. 
     
     
         4 . The staple fiber of  claim 1 , wherein said fiber is at least partially coated with a spinning finish and a top-coat finish, wherein said spinning finish is present on said fiber in an amount of at least about 0.5% FOY and wherein said top-coat finish is present on said fiber in an amount of not more than about 0.5% FOY, and wherein each of said spinning finish and said top-coat finish have been applied prior to cutting a filament yarn to form said fiber. 
     
     
         5 . The staple fiber of  claim 1 , wherein said fiber has a crimp frequency in the range of from about 8 to about 22 CPI, a denier per filament of about 0.5 to about 2.75, a Y-shaped or round cross-sectional shape, and a length of about 3 to about 75 mm. 
     
     
         6 . The staple fiber of  claim 1 , wherein said fiber is a biodegradable fiber, wherein the total amount of all finishes on said fiber is not more than about 1% FOY, and wherein said fiber exhibits at least one of the following biodegradability characteristics (i) through (iii) below—
 (i) a biodegradation of at least 90% within a period of not more than 180 days, measured according to ISO 14855-1 (2012) under industrial composting conditions; 
 (ii) biodegradation of at least 90% within a period of not more than 2 years, measured according to ISO 17556 (2012) under soil compositing conditions; and 
 (iii) biodegradation of at least 90% within a period of not more than 1 year measured according to ISO 14855-1 (2012) under home composting conditions. 
 
     
     
         7 . A nonwoven web comprising the staple fiber of  claim 1 . 
     
     
         8 . A crimped staple fiber formed from cellulose acetate and having a crimp frequency in the range of from about 4 to about 22 crimps per inch (CPI) and a denier per filament of less than about 3.0, and wherein the average tenacity of said fiber is at least about 85 percent of the average tenacity of an identical but uncrimped fiber. 
     
     
         9 . The staple fiber of  claim 8 , wherein said fiber is not coated with a spinning finish and is coated with at least one ionic finish in an amount of not more than about 0.4% FOY, and wherein said fiber has a crimp frequency in the range of from about 10 to about 16 crimps per inch (CPI). 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . A nonwoven web comprising the staple fiber of  claim 8 . 
     
     
         13 . A process for producing crimped, coated cellulose acetate staple fibers, said process comprising:
 (a) forming a cellulose acetate filament yarn comprising plurality of individual cellulose acetate filaments, wherein said individual cellulose acetate filaments have an average denier per filament of not more than 15, wherein said forming includes applying at least one spinning finish to at least a portion of said filament yarn;   (b) crimping at least a portion of said cellulose acetate filament yarn to provide a crimped filament yarn, wherein said crimped filament yarn has an average crimping frequency, measured in at least 5 different locations of said crimped filament yarn, of not more than 22 crimps per inch (CPI); and   (c) cutting said crimped filament yarn to form a plurality of crimped cellulose acetate staple fibers,   wherein the average tenacity of the filaments of said crimped filament yarn is at least 90 percent of the average tenacity of the filaments of said filament yarn prior to said crimping.   
     
     
         14 . The process of  claim 13 , wherein said filaments exhibit an average fiber-to-fiber coefficient of friction of at least about 0.30 measured with a continuous tension tester electronic device according to ASTM D3412 with the specified yarn parameters, a speed of 20 m/min, an input tension of 10 grams, and a single twist applied to the yarn, and an average fiber-to-metal coefficient of friction of at least about 0.20 measured using a continuous tension tester electronic device according to ASTM D3108 with the specified yarn parameters, a speed of 100 m/min, and an input tension of 10 grams, wherein said filament yarn has a crimp frequency in the range of from about 8 CPI to about 24 CPI, wherein said filaments have a round or Y-shaped cross-section, and wherein said filaments have an average tenacity of at least about 1.2 g/denier. 
     
     
         15 . (canceled) 
     
     
         16 . The process of  claim 13 , wherein said staple fibers have a crimp frequency in the range of from about 6 CPI to about 22 CPI, wherein said staple fibers have a denier per filament in the range of from about 0.5 to about 2.75, and wherein said staple fibers have a round or Y-shaped cross-section. 
     
     
         17 . The process of  claim 13 , further comprising applying a top-coat finish to at least a portion of said crimped filament yarn prior to said cutting, wherein the total amount of spinning finish and top-coat finish on said staple fibers is at least about 0.60% FOY. 
     
     
         18 . The process of  claim 13 , wherein said fibers are biodegradable fibers, wherein the total amount of finish on said fibers is not more than about 1% FOY, and wherein said fibers exhibit at least one of the following biodegradability characteristics (i) through (iii) below—
 (i) a biodegradation of at least 90% within a period of not more than 180 days, measured according to ISO 14855-1 (2012) under industrial composting conditions; 
 (ii) biodegradation of at least 90% within a period of not more than 2 years, measured according to ISO 17556 (2012) under soil compositing conditions; and 
 (iii) biodegradation of at least 90% within a period of not more than 1 year measured according to ISO 14855-1 (2012) under home composting conditions. 
 
     
     
         19 . A process for producing crimped, coated cellulose acetate staple fibers, said process comprising:
 (a) forming a cellulose acetate filament yarn comprising plurality of individual cellulose acetate filaments, wherein said filaments have an average denier per filament of not more than 15;   (b) crimping at least a portion of said cellulose acetate filament yarn to provide a crimped filament yarn, wherein said crimped filament yarn has an average crimping frequency, measured in at least 5 different locations of said filament yarn, of not more than 22 crimps per inch (CPI);   (c) coating at least a portion of said crimped filament yarn with at least one finish to provide a coated crimped cellulose acetate filament yarn; and   (d) cutting said coated crimped cellulose acetate filament yarn to form a plurality of crimped cellulose acetate staple fibers.   
     
     
         20 . The process of  claim 19 , further comprising, prior to said crimping, applying at least one spinning finish to at least a portion of said filament yarn to provide a spin-coated filament yarn and wherein said spin-coated filament yarn is crimped in step (b), wherein said spinning finish is present on said staple fibers in an amount of at least about 0.5% FOY, and said top-coat finish is present on said staple fibers in an amount of not more than about 0.5% FOY. 
     
     
         21 . The process of  claim 19 , wherein no spinning finish is applied to said filament yarn prior to said crimping. 
     
     
         22 . The process of  claim 19 , wherein said staple fibers have a fiber-to-fiber staple pad coefficient of friction of at least about 0.10 and a static half-life of not more than about 30 seconds, wherein said staple fibers have an average denier per filament in the range of from about 0.5 to about 3, wherein said crimped filament yarn comprises a plurality of individual crimped filaments, wherein the average tenacity of said crimped filaments is at least about 50 percent of the average tenacity of said individual filaments of said filament yarn prior to said crimping of step (b), wherein said crimped filaments have a crimping frequency in the range of from about 8 to about 24 CPI, and wherein said individual filaments have a round or Y-shaped cross-sectional shape. 
     
     
         23 . The process of  claim 19 , wherein said staple fibers are biodegradable fibers, wherein the total amount of finish on said fibers is not more than about 1% FOY, and wherein said fibers exhibit at least one of the following biodegradability characteristics (i) through (iii) below—
 (i) a biodegradation of at least 90% within not more than 180 days, measured according to ISO 14855-1 (2012) under industrial composting conditions; 
 (ii) biodegradation of at least 90% within not more than 2 years, measured according to ISO 17556 (2012) at ambient temperature; and 
 (iii) biodegradation of at least 90% within not more than 1 year measured according to ISO 14855-1 (2012) under industrial composting conditions.