Heat-bondable composite fiber, process for producing the same, and fibrous mass

Abstract

A POM/POM thermoadhesive conjugate fiber is produced by providing two kinds of POM-based polymers A and B which satisfy 30<MI A wherein MI A is a before-spinning melt index (g/10 min) of the POM-based polymer A (conditions: 190° C., load: 21.18N (2.16 kg)), and T B >T A +10 wherein T A and T B are before-spinning fusion peak temperatures of the POM-based polymers A and B respectively, compositely spinning a first component containing the POM-based polymer A and a second component containing the POM-based polymer B such that the first component is exposed with an exposed length of not less than 20% relative to a peripheral length of the fiber, subjecting the spun fiber to a drawing treatment, and subjecting the drawn fiber to an annealing treatment at a temperature of from 60° C. to 110° C.

1 . A thermoadhesive conjugate fiber comprising a first component as a thermoadhesive component which comprises a polyoxymethylene-based polymer A and a second component which comprises a polyoxymethylene-based polymer B, wherein the first component is exposed with an exposed length of not less than 20% relative to a peripheral length of the fiber,
 which fiber satisfies:   30<MI A  wherein MI A  is a before-spinning melt index (g/10 min) of the polyoxymethylene-based polymer A, which is determined according to JIS K 7210 (conditions: 190° C., load: 21.18N (2.16 kg)),   a before-spinning 150° C. ½ crystallization time of the polyoxymethylene-based polymer B is not less than 10 seconds and less than 30 seconds, and   Tf B >Tf A +10 wherein Tf A  and Tf B  are after-spinning fusion peak temperatures of the polyoxymethylene-based polymers A and B respectively, which are determined according to JIS K 7121.   
   
   
       2 . (canceled) 
   
   
       3 . The thermoadhesive conjugate fiber according to  claim 1 , wherein an after-spinning 150° C. ½ crystallization time of the polyoxymethylene-based polymer B is from 10 seconds to 100 seconds. 
   
   
       4 . A thermoadhesive conjugate fiber comprising a first component as a thermoadhesive component which comprises a polyoxymethylene-based polymer A and a second component which comprises a polyoxymethylene-based polymer B, wherein:
 the first component is exposed with an exposed length of not less than 20% relative to a peripheral length of the fiber,   a before-spinning 150° C. ½ crystallization time of the polyoxymethylene-based polymer B is not less than 10 seconds and less than 30 seconds, and   Tf B >Tf A +10 wherein Tf A  and Tf B  are after-spinning fusion peak temperatures of the polyoxymethylene-based polymers A and B respectively, which are determined according to JIS K 7121.   
   
   
       5 . A thermoadhesive conjugate fiber comprising a first component as a thermoadhesive component which comprises a polyoxymethylene-based polymer A and a second component which comprises a polyoxymethylene-based polymer B, wherein:
 the first component is exposed with an exposed length of not less than 20% relative to a peripheral length of the fiber,   an after-spinning 150° C. ½ crystallization time of the polyoxymethylene-based polymer B is from 10 seconds to 100 seconds, and   Tf B >Tf A +10 wherein Tf A  and Tf B  are after-spinning fusion peak temperatures of the polyoxymethylene-based polymers A and B respectively, which are determined according to JIS K 7121.   
   
   
       6 . The thermoadhesive conjugate fiber according to  claim 4 , wherein a before-spinning Z-average molecular weight of the polyoxymethylene-based polymer B is 500,000 or less. 
   
   
       7 . The thermoadhesive conjugate fiber according to  claim 5 , wherein an after-spinning Z-average molecular weight of the conjugate fiber is 350,000 or less. 
   
   
       8 . The thermoadhesive conjugate fiber according to  claim 4 , which is a sheath-core conjugate fiber consisting of the first component and the second component, the first component being a sheath component and the second component being a core component. 
   
   
       9 . The thermoadhesive conjugate fiber according to  claim 8 , which has an eccentric sheath-core cross section in which a center position of the second component is shifted from the center position of the fiber. 
   
   
       10 . A method for producing a thermoadhesive conjugate fiber which comprises:
 providing two kinds of polyoxymethylene-based polymers A and B which satisfy:   30<MI A  wherein MI A  is a before-spinning melt index (g/10 min) of the polyoxymethylene-based polymer A, which is determined according to JIS K 7210 (conditions: 190° C., load: 21.18N (2.16 kg)),   a before-spinning 150° C. ½ crystallization time of the polyoxymethylene-based polymer B is not less than 10 seconds and less than 30 seconds, and   T B >T A +10 wherein T A  and T B  are before-spinning fusion peak temperatures of the polyoxymethylene-based polymers A and B respectively, which are determined according to JIS K 7121,   compositely spinning a first component comprising the polyoxymethylene-based polymer A and a second component comprising the polyoxymethylene-based polymer B such that the first component is exposed with an exposed length of not less than 20% relative to a peripheral length of the fiber,   subjecting the spun fiber to a drawing treatment, and   subjecting the drawn fiber to an annealing treatment at a temperature of from 60° C. to 110° C.   
   
   
       11 . (canceled) 
   
   
       12 . A method for producing a thermoadhesive conjugate fiber, which comprises:
 providing two kinds of polyoxymethylene-based polymers A and B, the polymer B having a before-spinning 150° C. ½ crystallization time of not less than 10 seconds and less than 30 seconds, and the polymers satisfying T B >T A +10 wherein T A  and T B  are before-spinning fusion peak temperatures of the polyoxymethylene-based polymers A and B respectively which temperatures are determined according to JIS K 7121,   compositely spinning a first component comprising the polyoxymethylene-based polymer   A and a second component comprising the polyoxymethylene-based polymer B such that the first component is exposed with an exposed length of not less than 20% relative to a peripheral length of the fiber,   subjecting the spun fiber to a drawing treatment, and   subjecting the drawn fiber to an annealing treatment at a temperature of from 60° C. to 110° C.   
   
   
       13 . The method for producing a thermoadhesive conjugate fiber according to  claim 12 , wherein the annealing is conducted at a temperature of from 60° C. to 90° C. 
   
   
       14 . The method for producing a thermoadhesive conjugate fiber according to  claim 12 , wherein spinning is conducted at a draft ratio of from 100 times to 1000 times and the drawing is conducted at a draw ratio of from 4 times to 10 times. 
   
   
       15 . A fiber assembly comprising the thermoadhesive conjugate fiber according to  claim 4  in an amount of 10 mass % or more. 
   
   
       16 . The fiber assembly according to  claim 15 , wherein the fibers are thermally bonded to each other. 
   
   
       17 . The fiber assembly according to  claim 15 , which is a nonwoven. 
   
   
       18 . A wiper which comprises the nonwoven according to  claim 17 . 
   
   
       19 . The fiber assembly according to  claim 15 , which is a molded article.