Acrylic fibers, method for manufacturing same, and spun yarn and knitted fabric using said fibers

Abstract

Provided are: acrylic fibers having 2-7% boiling water shrinkage and formed by the side-by-side conjugation of a copolymer A, which contains 5-10 mass % of an unsaturated monomer that can form a copolymer with acrylonitrile units, and a copolymer B, which contains 2-5 mass % of unsaturated monomer units that can form a copolymer with acrylonitrile units and 0.2-1.5 mass % of sulfonic acid group-containing monomer units; a method for manufacturing said fibers; a spun yarn containing said fibers; and a knitted fabric obtained from said spun yarn. The single fiber fineness of the heat-treated acrylic fibers is 1.7-6.6 dtex, the bulkiness is at least 380 cm3/g, the percentage of crimp is at least 15%, and the product (DKSDKE) of the knot strength (cN/dtex) and the knot elongation (%) is 10-25. The acrylic fibers have excellent crimp characteristics and anti-pilling properties.

1 . An acrylic fiber, which has a crimp rate measured in accordance with JIS L1015 (2010) of 15% or higher; and
 a bulkiness of 380 cm 3 /g or greater,   wherein the bulkiness is an average value of bulkiness of three samples and each bulkiness of each sample is measured by   collecting approximately 10 grams of the acrylic fiber cut into 51 mm-long pieces, and opening the fiber until almost no fiber adhesion is observed;   collecting 1.5 grams of the opened acrylic fiber;   dividing the collected fiber into batches of approximately 0.15 grams each, and softly dropping each batch into a 1000 mL graduated cylinder with a bottom area of 33.17 cm 2  to fill the cylinder homogenously without creating any gap;   lowering a 6-gram load disc into the cylinder, and measuring volume v, which is a volume in a unit of cm 3 , occupied by the acrylic fiber two minutes later; and   calculating a degree of bulkiness by the following formula:
   degree of bulkiness(cm 3 /g)=v÷1.5
 
   
     
     
         2 . The acrylic fiber according to  claim 1 , wherein
 a single fiber fineness is 1.7 to 6.6 dtex, and   a value obtained by multiplying knot strength in a unit of cN/dtex and knot elongation by % is 10 to 25.   
     
     
         3 . The acrylic fiber according to  claim 1 , wherein a number of crimps is 20 to 50 per 2.54 cm. 
     
     
         4 . The acrylic fiber according to  claim 1 , wherein an acrylonitrile copolymer (A) with an acrylonitrile unit content of 90-95 mass % and an acrylonitrile copolymer (B) with an acrylonitrile unit content of 93.5-97.8 mass % are arranged to form a side-by-side bicomponent structure with an area ratio of 1:3 to 3:1 at a fiber cross-section perpendicular to a fiber axis direction. 
     
     
         5 . The acrylic fiber according to  claim 4 , wherein a difference between the acrylonitrile unit content in the copolymer (A) and the acrylonitrile unit content in the copolymer (B) is 2 mass % or greater. 
     
     
         6 . The acrylic fiber according to  claim 4 , wherein
 the copolymer (A) is formed by copolymerizing 90-95 mass % of an acrylonitrile unit and 5-10 mass % of an unsaturated monomer copolymerizable with the acrylonitrile unit, and   the copolymer (B) is formed by copolymerizing 93.5-97.8 mass % of an acrylonitrile unit, 2-5 mass % of an unsaturated monomer unit copolymerizable with the acrylonitrile unit, and 0.2-1.5 mass % of a sulfonic acid group-containing monomer unit.   
     
     
         7 . The acrylic fiber according to  claim 6 , wherein
 an unsaturated monomer unit in the unsaturated monomer copolymerizable with the acrylonitrile in the copolymers (A) and (B) is a vinyl acetate unit, and   the sulfonic acid group-containing monomer unit is a sodium methallyl sulfonate unit.   
     
     
         8 . The acrylic fiber according to  claim 1 , wherein a shrinkage rate is 2-7%. 
     
     
         9 . A method for manufacturing an acrylic fiber, the method comprising:
 preparing a spinning dope (A′) by dissolving a copolymer (A) with an acrylonitrile unit content of 90-95 mass % in a solvent;   preparing a spinning dope (B′) by dissolving a copolymer (B) with an acrylonitrile unit content of 93.5-97.8 mass % in a solvent; and   forming a side-by-side bicomponent fiber by discharging spinning dopes (A′) and (B′) from a nozzle into a coagulation bath with a solvent concentration of 35-60%,   wherein a difference between the acrylonitrile unit content in the copolymer (A) and the acrylonitrile unit content in the copolymer (B) is 2 mass % or greater.   
     
     
         10 . The method according to  claim 9 , wherein
 the copolymer (A) comprises 90-95 mass % of an acrylonitrile unit and 5-10 mass % of an unsaturated monomer copolymerizable with the acrylonitrile unit, and   the copolymer (B) comprises 93.5-97.8 mass % of an acrylonitrile unit, 2-5 mass % of an unsaturated monomer unit copolymerizable with the acrylonitrile unit, and 0.2-1.5 mass % of a sulfonic acid group-containing monomer unit.   
     
     
         11 . The method according to  claim 9 , wherein
 the unsaturated monomer copolymerizable with the acrylonitrile unit in the copolymers (A) and (B) is a vinyl acetate, and   the sulfonic acid group-containing monomer is a sodium methallyl sulfonate.   
     
     
         12 . The method according to  claim 9 , further comprising:
 forming a side-by-side bicomponent fiber by discharging the spinning dope (A′) and the spinning dope (B′) from a nozzle into a spinning bath;   conducting a primary drawing at a draw ratio of 3.0-5.0 times;   conducting a relaxation heat treatment under saturated steam of 90-230 kPa; and   conducting a secondary drawing at a draw ratio of 1.05-1.20 times.   
     
     
         13 . A spun yarn, comprising:
 the acrylic fiber according to  claim 1  at 30 mass % or greater.   
     
     
         14 . The spun yarn according to  claim 13 , further comprising a conductive acrylic fiber in a range of 3-15 mass %. 
     
     
         15 . A knitted fabric, comprising:
 the spun yarn according to  claim 13  at 50 mass % or greater,   wherein an anti-pill grade is four or higher.   
     
     
         16 . The knitted fabric according to  claim 15 , wherein a dimensional change of the knitted fabric after washing 10 times is ±3% or lower in both vertical and horizontal directions.