Water-disintegrable composite fiber and method for producing the same

Abstract

A water-disintegrable composite fiber comprising a phase containing a polyglycolic acid resin and a phase containing a polylactic acid resin with a D-lactic acid unit ratio of at least 1.0%; the two phases extending continuously in a lengthwise direction; and the composite fiber having a cross sectional area formed by the phase containing the polyglycolic acid resin having an area ration of at most 50%; and the content of the polyglycolic acid resin being from 2 to 100 parts by mass per 1 part by mass of the D-lactic acid units in the polylactic acid resin.

1 . A water-disintegrable composite fiber comprising a phase containing a polyglycolic acid resin and a phase containing a polylactic acid resin with a D-lactic acid unit ratio of at least 1.0%;
 the two phases extending continuously in a lengthwise direction respectively; and   the composite fiber having a cross-sectional area formed by the phase containing the polyglycolic acid resin having an area ratio of at most 50%; and   the content of the polyglycolic acid resin being from 2 to 100 parts by mass per 1 part by mass of the D-lactic acid units in the polylactic acid resin.   
     
     
         2 . The water-disintegrable composite fiber according to  claim 1 , wherein the water-disintegrable composite fiber has a side surface in which a surface area formed by the phase containing the polyglycolic acid resin has an area ratio of at most 50%. 
     
     
         3 . The water-disintegrable composite fiber according to  claim 1 , wherein the water-disintegrable composite fiber has at least one type of structure selected from a core-sheath type, a multicore type, a side-by-side type, a multiple-division type, a multilayer type, and a radial type. 
     
     
         4 . The water-disintegrable composite fiber according to  claim 1 , wherein the fiber is an undrawn fiber. 
     
     
         5 . The water-disintegrable composite fiber according to  claim 1 , wherein the fiber is a drawn fiber. 
     
     
         6 . The water-disintegrable composite fiber according to  claim 5 , wherein a single fiber fineness is 3.0 denier or less. 
     
     
         7 . A fiber obtained by removing either the polyglycolic acid resin or the polylactic acid resin from the water-disintegrable composite fiber described in  claim 5 . 
     
     
         8 . A water-disintegrable composite staple fiber obtained by cutting the water-disintegrable composite fiber described in  claim 5 . 
     
     
         9 . The water-disintegrable composite staple fiber according to  claim 8 , wherein the staple fiber is used as an additive at a time of drilling or sompletion of oil or gas recovery. 
     
     
         10 . A method for producing a water-disintegrable composite fiber, the method comprising the steps of:
 forming a fibrous composite by continuously discharging a polylactic acid resin having a D-lactic acid unit ratio of at least 1.0% and from 2 to 100 parts by mass of a polyglycolic acid resin per 1 part by mass of D-lactic acid units in the polylactic acid resin from a spinneret for composite fibers, each of the resins being discharged in a molten state; and   cooling the fibrous composite to obtain an undrawn yarn comprising a phase containing the polyglycolic acid resin and a phase containing the polylactic acid resin, the undrawn yarn having a cross section in which an area formed by the phase containing the polyglycolic acid resin has an area ratio of at most 50%.   
     
     
         11 . A method for producing a water-disintegrable composite fiber, the method comprising the step of:
 drawing an undrawn yarn obtained by the production method described in  claim 10  so as to obtain a drawn yarn comprising the phase containing the polyglycolic acid resin and the phase containing the polylactic acid resin, the drawn yarn having a cross section in which an area formed by the phase containing the polyglycolic acid resin has an area ratio of at most 50%, and the drawn yarn containing from 2 to 100 parts by mass of the polyglycolic acid resin per 1 part by mass of the D-lactic acid units in the polylactic acid resin.   
     
     
         12 . A method of producing a water-disintegrable composite fiber, the method comprising the step of cutting a drawn yarn obtained by the production method described in  claim 11  to obtain a water-disintegrable composite fiber staple fiber.