JP2014208937A - White anti-pilling acrylic fiber and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white anti-pilling acrylic fiber which has excellent whiteness, feeling and anti-pilling property, provides a fiber product having good quality and performance, and substantially does not harm productivity of fiber production; and a method for producing the same.SOLUTION: Provided is a white anti-pilling acrylic fiber comprising an acrylonitrile copolymer containing 91 to 95 mass% of acrylonitrile, 3 to 8 mass% of an ethylenic vinyl monomer having copolymerizability with the acrylonitrile, and 1 to 6 mass% of a sulfonic acid-containing vinyl monomer. The fiber has a color such that a b value in the Hunter color system is +1.5 to +4.7, single fiber fineness of 0.3 to 1.3 dtex, tensile strength of 2.0 cN/dtex or more, knot strength of 1.3 to 2.2 cN/dtex, knot elongation of 10 to 20%, and an anti-pilling property of Class 3.5 or more. Also provided is a method for producing the same.

Description

  The present invention relates to an anti-pill acrylic fiber and a method for producing the same, which have excellent whiteness, texture and anti-pill property, and can provide a fiber product having good quality and performance.

  Acrylic fibers have a soft texture, heat retention, bulkiness and excellent dyeability that are most similar to wool compared to other synthetic fibers, and are widely used in the clothing and interior fields. However, the fiber product made of acrylic fibers has a problem that pilling (a state where the pills are not dropped off and are attached to the surface of the fabric) is likely to occur during wearing. Since this pilling impairs the appearance and texture of the fiber product, there has been a need for an improvement in so-called anti-pilling, in which pilling hardly occurs in acrylic fibers.

  In recent years, there has been an increasing demand for whitening of fibers in order to produce a clearer color in white or light color dyeing of inner products. In addition, whitening of fibers is required at present in response to demands for simplification of work in white dyeing processing and reduction of processing costs.

  Conventionally, various proposals have been made for improving the anti-pill performance of acrylic fibers. For example, a method has been proposed in which stretching at a low draw ratio is employed in a fiber production process to reduce the strength of the fiber to obtain an anti-pill acrylic resin (see Patent Document 1). In addition, a method has been proposed in which a local defect is imparted to an acrylic fiber to reduce the strength of the fiber (see Patent Document 2). Although these methods can provide practically desirable anti-pill acrylic fibers, these anti-pill acrylic fibers can be mixed with other fibers that do not have anti-pill properties such as natural fibers. When used, the anti-pill properties were still insufficient.

JP-A-57-121610 JP-A-56-128324

  Accordingly, an object of the present invention is to provide a white anti-pill acrylic fiber which has excellent whiteness, texture and anti-pill property and from which a fiber product of good quality and performance can be obtained.

  Another object of the present invention is to provide a method for producing the above white anti-pill acrylic fiber without substantially impairing the productivity of the fiber production.

  The present invention is to solve the above problems, and the white anti-pyracrylic fiber of the present invention comprises 91 to 95% by mass of acrylonitrile and an ethylenic vinyl monomer copolymerizable with the acrylonitrile. It is a fiber made of an acrylonitrile-based copolymer containing 3 to 8% by mass and 1 to 6% by mass of a sulfonic acid-containing vinyl monomer, and the color of the fiber is +1.5 to +4. 7, the single fiber fineness of the fiber is 0.3 to 1.3 dtex, the tensile strength is 2.0 cN / dtex or more, the nodule strength is 1.3 to 2.2 cN / dtex, and the nodule elongation is 10 to 10. A white anti-pill acrylic fiber having 20% and an anti-pill property of 3.5 or higher.

  Further, the method for producing the white anti-pyracrylic fiber of the present invention comprises 91 to 95% by mass of acrylonitrile, 3 to 8% by mass of an ethylenic vinyl monomer copolymerizable with the acrylonitrile, and a sulfonic acid-containing vinyl monomer. A spinning dope comprising 20 to 25% by mass of an acrylonitrile-based copolymer containing 1 to 6% by mass and 75 to 80% by mass of an organic solvent has a solvent concentration in the coagulation bath of 60 to 70% by mass and a temperature of 30 to 50%. After coagulation greed at ℃, spinning under conditions of spinning stock solution temperature of 60-80 ℃ spinning draft 1.5-2.2, and then stretched at a draw ratio of 3.5-5 times, and then shrinkage during drying densification This is a method for producing a white anti-pill acrylic fiber, which is densified to a rate of 5% or less and then subjected to tension heat treatment at a temperature of 160 to 180 ° C. for 10 to 30 seconds.

  According to the present invention, the white resistance, which has excellent whiteness, texture, anti-pill property, and soft knitted fabric texture, and can obtain a product fiber with clearer and better quality and performance with white or light dyeing. A pill acrylic fiber is obtained. The white anti-pill acrylic fiber obtained by the present invention is excellent in soft texture when spinning alone or mixed with cotton, rayon, wool, etc. and other fibers in clothing such as sweaters, underwear, jerseys and socks. In addition, it is possible to provide an anti-pill fiber product having a clearer and better quality with white and light dyeing.

  In addition, according to the method for producing a white anti-pill acrylic fiber of the present invention, a white fiber that has excellent texture and anti-pill property while having a white or light-colored color, and has a clearer and better quality and performance. The white anti-pill acrylic fiber from which the product can be obtained can be stably produced without substantially impairing the productivity of fiber production.

  The white anti-pyrogenic acrylic fiber of the present invention comprises 91 to 95% by mass of acrylonitrile, 3 to 8% by mass of an ethylenic vinyl monomer copolymerizable with the acrylonitrile, and 1 to 6% by mass of a sulfonic acid-containing vinyl monomer. In which the color of the fiber is b +1.5 to +4.7 in the Hunter color system, and the single fiber fineness of the fiber is 0.3 to White resistance of 1.3 dtex, tensile strength of 2.0 cN / dtex or more, nodule strength of 1.3 to 2.2 cN / dtex, nodular elongation of 10 to 20%, and anti-pill property of 3.5 grade or more Pill acrylic fiber.

  The acrylonitrile-based copolymer used in the present invention is a copolymer composed of 91 to 95% by mass of acrylonitrile, and other copolymerizable unsaturated vinyl compounds copolymerizable with acrylonitrile within 4 to 9% by mass. Copolymerized. When the content of acrylonitrile is less than 91% by mass, the heat setability in a tension state applied in advance in the yarn production process is remarkably deteriorated by dyeing or steam heat treatment in a higher processing step, and when it is greater than 95% by mass. , Stretchability is significantly reduced, and productivity is impaired.

  Moreover, the copolymerization rate of said ethylenic vinyl monomer needs to be 3-8 mass%, Preferably it is 3.2-7.5 mass%. When the copolymerization ratio of the ethylenic vinyl monomer is less than 3% by mass, the stretchability is poor and stable production becomes difficult. On the other hand, when the copolymerization rate of the ethylenic vinyl monomer is more than 8% by mass, the anti-pill performance is lowered.

  Furthermore, the copolymerization rate of the sulfonic acid-containing vinyl monomer is required to be 1 to 6% by mass, and preferably 1.2 to 5.0% by mass. If the copolymerization ratio of the sulfonic acid-containing vinyl monomer is less than 1% by mass, sufficient dyeing performance cannot be obtained. If it exceeds 6% by mass, the dyeing performance increases, but the coagulation is slow, and the fibers are bonded to each other in the spinning process. Is likely to occur. Moreover, the obtained fiber also causes staining spots such as ring staining.

  Examples of the ethylenic vinyl monomer contained in the acrylonitrile copolymer used in the present invention include acrylic acid, methacrylic acid or esters thereof, acrylamide, methacrylamide, vinyl acetate, vinyl chloride, and vinylidene chloride. In particular, methyl acrylate is preferably used.

  Examples of the sulfonic acid-containing vinyl monomer include acidic monomers such as vinyl sulfonic acid, acrylic sulfonic acid, methallyl sulfonic acid and unsaturated sulfonic acid such as P-styrene sulfonic acid or salts thereof. Sodium sulfonate is preferably used.

  A polymerization initiator, a pH adjuster, a molecular weight adjuster, etc. can be mix | blended with the acrylonitrile-type copolymer used by this invention as an additive as needed.

  The polymerization method of the acrylonitrile-based copolymer used in the present invention may be any of suspension polymerization method, emulsion polymerization method, solution polymerization method and the like. Examples of the organic solvent to be used include organic solvents such as dimethyl sulfoxide (hereinafter sometimes referred to as DMSO), dimethylacetamide and dimethylformamide, and the effect is particularly remarkable in DMSO wet spinning. Therefore, it is desirable to use a solution polymerization method using DMSO as the polymerization method.

  The proportion of the acrylonitrile copolymer is 20 to 25% by mass as the spinning dope, and the proportion of the organic solvent needs to be 75 to 80% by mass. The proportion of the acrylonitrile copolymer is preferably 21 to 24% by mass, and the proportion of the organic solvent is preferably 76 to 79% by mass.

  If the proportion of the acrylonitrile copolymer is less than 20% by mass in the spinning dope, the resulting fiber is devitrified and gloss is lost, and the color developability is lowered. On the other hand, if the ratio of the acrylonitrile copolymer exceeds 25% by mass, the spinnability is remarkably deteriorated.

  The spinning dope thus prepared is spun using a normal wet spinning apparatus.

  Examples of the coagulation bath include organic solvents such as DMSO, dimethylformamide, and dimethylacetamide, and a DMSO aqueous solution is particularly preferably used. When spinning the stock solution into a DMSO aqueous solution in a coagulation bath, the temperature of the stock solution is 60 to 80 ° C., preferably 65 to 75 ° C., and the spinning draft is 1.5 to 2.2, preferably 1.6 to 2. A condition in the range of .1 is used.

  When the spinning dope temperature is lower than 60 ° C., not only the spinning property of the spinning dope is insufficient, but also the viscosity is high, which causes equipment damage such as an increase in nozzle pressure. On the other hand, when the temperature of the stock solution for spinning is higher than 80 ° C., it often causes modification such as gelation of the stock solution for spinning, and stable spinning cannot be expected.

  Also, if the spinning draft is less than 1.5, the yarn from the die to the take-up roller is loosened, the yarn is shaken by the turbulent flow of the coagulation bath liquid, and the yarn is cut at the die surface, and if the spinning draft exceeds 2.2, the yarn Is too tight and the thread breaks at the base.

  The single fiber fineness of the white anti-pill acrylic fiber of the present invention is 0.3 to 1.3 dtex, preferably 0.5 to 1.1 dtex. In a general acrylic fiber manufacturing method, it is necessary to reduce the spinning solution discharge rate in order to make the fiber thin. By reducing the discharge amount of the spinning dope, thread breakage or the like occurs on the spinneret surface, and the productivity tends to decrease.However, by using the method for producing the white anti-pill acrylic fiber of the present invention, As an ultrafine fiber having a fiber fineness of 0.3 to 1.3 dtex, it is possible to stably produce a fiber expressing a remarkable soft texture and anti-pill performance without substantially impairing productivity.

  In addition, the tensile strength of the white anti-pill acrylic fiber of the present invention needs to be 2.0 cN / dtex or more. When the tensile strength is lower than 2.0 cN / dtex, it is not preferable because the process processability such as the spinning process is deteriorated and the productivity is remarkably lowered.

  Furthermore, in the white anti-pill acrylic fiber of the present invention, the knot strength is 1.3 to 2.2 cN / dtex, preferably 1.4 to 2.1 cN / dtex, and the knot elongation is 10 to 10. It is necessary to satisfy two conditions of 20%, preferably 12 to 18%. When the nodule strength is higher than 2.2 cN / dtex, and when the nodule elongation is higher than 20%, the anti-pill property is remarkably lowered in any case.

  In the white anti-pill acrylic fiber of the present invention, the anti-pill property should be 3.5 or higher, preferably 4 to 5.

  Here, the anti-pill property is a value measured in a test with an operation time of 5 hours in accordance with JIS L 1076 A method: (2012).

  The composition of the coagulation bath for maintaining spinnability needs to have an organic solvent concentration of 60 to 70% by mass, and preferably contains 30 to 40% by mass of water. When the organic solvent concentration is less than 60% by mass, the tension of the yarn in the coagulation bath increases, and the yarn breakage on the die surface increases. When the organic solvent concentration is higher than 70% by mass, adhesion at the take-up roller portion occurs due to insufficient solidification of the yarn.

  In addition to the above coagulation bath conditions, in the present invention, by setting the coagulation bath temperature in the range of 30 to 50 ° C., preferably in the range of 35 to 45 ° C., it is possible to produce white acrylic fibers having excellent anti-pill properties. Become. When the coagulation bath temperature is less than 35 ° C., the yarn tension in the coagulation bath becomes high, and yarn breakage at the spinneret surface increases. On the other hand, when the coagulation bath temperature is higher than 40 ° C., Adhesion occurs at the take-up roller due to insufficient solidification.

  The coagulated yarn thus produced is preferably stretched 3.5 to 5.0 times in a DMSO aqueous solution having a concentration of 30% or less, for example. When the draw ratio is less than 3.5 times, the fiber passing through the spinning process may be lowered, and when the draw ratio exceeds 5.0 times, the anti-pill property may be lowered.

  The drawn acrylic fiber yarn is preferably heated at a heat treatment temperature of 160 to 180 ° C. after removing the solvent contained in the acrylic fiber yarn in warm water, for example, warm water at a temperature of 40 to 60 ° C. Preferably, the heat treatment time is preferably 10 to 30 seconds, more preferably 15 to 25 seconds under a dry heat at a temperature of 165 to 175 ° C., and the shrinkage rate is preferably 5% or less, more preferably 1 to 3%. By performing drying and densifying tension heat treatment while maintaining the shrinkage rate, the color of the fiber is obtained as white in which b in the Hunter color system is +1.5 to +4.7.

  When the shrinkage ratio exceeds 5%, or when the heat treatment temperature is lower than 165 ° C. and the heat treatment time is shorter than 10 seconds, the spinning draft is set to 1.5 to 2.2, and the fiber orientation of the acrylic fiber is increased. May not be sufficiently maintained, and orientational relaxation may remarkably occur in a high-order processing step, and the anti-pill property may deteriorate. In addition, when the heat treatment temperature is higher than 180 ° C. and the heat treatment time is longer than 30 seconds, although the anti-pill property is obtained, the color of the fiber is b higher than +4.7 in the Hunter color system and yellowish. It becomes a strong fiber, and this yellowness is harmful, and it is difficult to produce a clear color in white or light dyeing.

  With conventional acrylic fibers, even if they are dried in a tension state, the orientation given there is easily relaxed by a subsequent heat treatment, for example, a heat treatment such as dyeing, and finally settles into a certain relaxed state. Although the anti-pill performance is poor, the white anti-pill acrylic fiber obtained in the present invention has suitable physical properties such as a tensile strength of 2.0 cN / dtex or more and a knot strength of 1.3 to 2.2 cN / dtex. Fiber can be obtained.

  According to the present invention, by optimizing the manufacturing conditions and maximizing the synergistic effect, not only whiteness and anti-pill properties, but also sliminess, gloss and color developability, etc., rich in versatility, Fibers with high commercial value can be stably obtained with high productivity.

  Further, the white anti-pill acrylic fiber of the present invention is spun after being cut into short fibers. The composition of the spun yarn may be 100% by mass of the white anti-pill acrylic fiber of the present invention, and other fibers, for example, synthetic fibers such as polyester fibers, nylon fibers, rayon fibers or the like, chemical fibers, cotton, It is also possible to make a spun yarn by blending with natural fibers such as wool and silk. Furthermore, the use of the white anti-pill acrylic fiber obtained in the present invention has an excellent soft texture and a clearer and better quality with white and light-colored dyeing in apparel applications such as sweaters, underwear, jerseys and socks. It makes it possible to provide an anti-pill textile product.

  Further, the white anti-pill acrylic fiber of the present invention has a white resistance with a flatness ratio A / B of 1.5 to 5 when the length of the long side of the fiber cross section is A and the length of the short side is B. It is preferably a pill acrylic fiber. Hereinafter, this flat white anti-pill acrylic fiber may be referred to as a white anti-pill flat acrylic fiber.

  Here, the length A of the long side of the fiber cross section is the distance when the distance between the straight lines becomes the maximum when the fiber cross section is sandwiched between two parallel straight lines, and the length B of the short side is This is the minimum interval.

  If the flatness of the cross section of the fiber is less than 1.5, the single fiber is difficult to bend and good flexibility cannot be obtained, and if the flatness exceeds 5, the flexibility is improved easily, but the contact area between the fibers increases. However, the spinnability deteriorates.

  The white anti-pill flat acrylic fiber of the present invention has a long side length of 0.065 to 0.145 mm, preferably 0.080 to 0.120 mm, and a short side length of 0.015 to 0.15 mm. If it is a rectangular hole of 0.035 mm, preferably 0.020 to 0.030 mm, and the hole depth / hole area value is 12 to 32, preferably 16 to 28, the thread breakage on the die surface Is generated, and the white anti-pill flat acrylic fiber of the present invention in which the flatness A / B of the fiber cross section is 1.5 to 5 cannot be obtained.

  Here, the length of the long side of the hole is the long side of the rectangular hole, and the length of the short side is the short side of the rectangular hole. In addition, the value of the depth of the hole represents the length in the vertical direction of the hole portion perpendicularly formed from the base surface, and the value of the area of the hole is represented by the length of the long side × the length of the short side. .

  Next, although an Example demonstrates concretely the white anti-pill acrylic fiber of this invention, and its manufacturing method, this invention is not limited to these.

(1) "Evaluation of spinnability and stretchability"
Table 1 shows the evaluation criteria for spinnability and stretchability. With respect to spinnability, “○” indicates that there is no yarn breakage on the die surface, and the spinnability was accepted. Further, “△” indicates that there is a slight yarn breakage on the base, and “×” indicates that there is frequent breakage. Furthermore, about the drawability, the thing without the single fiber winding to a roller was set as "(circle)", and it was set as the pass as a drawability. In addition, “Δ” indicates that the single fiber is slightly wound around the roller, and “X” indicates that the single fiber is frequently wound.

(2) “Measuring method of fineness, tensile strength, knot strength, knot elongation”
JIS L1015: (2010) Measured by chemical fiber staple test method.

(3) “Measurement method of anti-pill property”
The fiber is cut into 38 mm, the spun yarn is 1/52 spun yarn by short spinning, the spun yarn is knitted with a smooth knitting and 18 gauge, and the resulting knitted fabric is 1.0% owf A knitted fabric made by dyeing with a click white TK dye solution manufactured by Kagaku Co. under the conditions of a bath ratio of 1:15, a temperature of 97 ° C., and a time of 30 minutes, exhibits anti-pilling properties by a JIS L 1076 A method operating time 5 hour test. evaluated.

(4) “Measurement method of Hunter color system b”
A sample 2.5 g is filled in a colorimetric cell (16 cm ³ square cell), and is set on a sample stand and colorimetrically measured using an SM color computer SM-3 manufactured by Suga Test Instruments Co., Ltd. For the measurement, the average value of the two times when setting and when the colorimetric cell was rotated by 90 ° was obtained.

(5) "Evaluation method of texture of knitted fabric"
The evaluation method for the texture of the knitted fabric is “○” when five judges judge that the knitted fabric for the texture evaluation is tactile and is judged to have sufficient softness. “×” is added to the items that are judged to be sharp. Judgment result when all five people put a circle is ◎, judgment result when ○ is 3 or more is ○, “◎, ○” is a soft pass, and x is 3 or more The evaluation result of x was evaluated as x, and “x” was evaluated as a soft failure.

(6) “Method of measuring flatness”
Two to three fibers are taken from 20 or more of the sample 3g, and a fiber bundle is made by drawing them through a small hole in a metal plate, both sides are cut at right angles, and a cross-sectional photograph is taken using a microscope. The maximum short side and the maximum long side of 30 fiber cross sections are measured from the cross-sectional photograph, and the flatness is calculated.

[Example 1]
92% by mass of acrylonitrile, 7% by mass of methyl acrylate and 1% by mass of sodium methallyl sulfonate were copolymerized in DMSO to obtain an acrylonitrile-based copolymer, and the spinning dope concentration was 22% by mass.

  The spinning stock solution was adjusted to a temperature of 67 ° C., a bath solution of DMSO 65 mass% and water 35 mass% was adjusted to a temperature of 40 ° C., and extruded by a spinning draft 1.85 to perform wet spinning, 4.0 times stretching in water, followed by washing with water, adhering oil, drying with hot air dryer at a temperature of 168 ° C for 23 seconds, and densifying with a relaxation rate of 5% Thus, a white anti-pill acrylic fiber having a single fiber fineness of 0.9 dtex and a Hunter color system b of +3.9 was obtained.

  The obtained white anti-pill acrylic fiber was cut into 38 mm, and was spun into a spun yarn with a count of 1/52. The spun yarn was knitted with a smooth knitting and 18 gauge, and the resulting knitted fabric was The dyeing was carried out with 1.0% owf Aclick White TK dye solution manufactured by Shigensei Chemical Co., Ltd. at a bath ratio of 1:15, a temperature of 97 ° C., and a time of 30 minutes. When the anti-pill property and knitted fabric texture of the produced knitted fabric were evaluated, the anti-pill property was grade 5 and the knitted fabric texture was good (◎). The results are shown in Table 2.

[Examples 2 to 7 and Comparative Examples 1 to 11]
In Example 1, the acrylonitrile-based copolymer, the polymer ratio in the spinning dope, the spinning dope temperature, the coagulation bath conditions, the spinning draft, the draw ratio, the drying conditions, and the target fineness were obtained as shown in Tables 2 and 3. Tables 2 and 3 show the results of spinning the obtained raw cotton to produce knitted fabrics and evaluating their anti-pill properties and knitted fabric texture.

[Examples 8 to 12, Comparative Examples 12 to 17]
The acrylic fiber 38 mm cut obtained in Example 1 and Comparative Example 1 and the rayon 1.7 dtex 38 mm cut were mixed at 60 mass% / 40 mass%, 50 mass% / 50 mass%, and Examples 1, 3, 7 The acrylic fiber obtained in Comparative Examples 1, 2, 6 and 9 and the shrinkable acrylic fiber of 1.15 dtex 38 mm cut having a shrinkage ratio in boiling water of 22% at 60% by mass / 40% by mass. Blended cotton, short-spun to give a spun yarn with a count of 1/52, and the spun yarn was knitted with a smooth knitting and 18 gauge. The click white TK dye solution was used for dyeing at a bath ratio of 1:15, a temperature of 97 ° C., and a time of 30 minutes. Table 4 shows the evaluation results of the anti-pill properties, Hunter color system b and knitted fabric texture of the produced knitted fabric.

  As is clear from the results of Tables 2 to 4, the white anti-pill acrylic fiber produced under the conditions satisfying the process requirements related to the present invention has excellent whiteness, knitted fabric texture and anti-pill performance. It can be seen that it exhibits excellent whiteness, knitted fabric texture and anti-pill performance even after blending with other fibers.

[Example 13]
92% by mass of acrylonitrile, 7% by mass of methyl acrylate and 1% by mass of sodium methallyl sulfonate were copolymerized in DMSO to obtain an acrylonitrile-based copolymer, and the spinning dope concentration was 22% by mass.

  The spinning stock solution was adjusted to a temperature of 67 ° C., and a coagulation bath in which a bath solution of DMSO 65 mass% and water 35 mass% was adjusted to a temperature of 40 ° C. had a spinning draft of 1.75 and a long side length. Extruded from a rectangular hole with 0.085 mm, short side length of 0.030 mm, hole depth / hole area value of 23.5, wet-spun, and stretched 4.0 times in hot water And then washing with water, attaching an oil agent, drying with a hot air dryer at a temperature of 168 ° C., a treatment time of 23 seconds, and drying and densifying with a relaxation rate of 5%, a single fiber fineness of 1.0 dtex, a hunter A white anti-pill flat acrylic fiber having a color system b of +3.8 and a flatness ratio of 2.2 was obtained.

  The obtained white anti-pill flat acrylic fiber was cut into 38 mm, and spun into a spun yarn with a count of 1/52 by short spinning, and the spun yarn was knitted with a smooth knitting and 18 gauge to obtain the knitted fabric Was dyed with 1.0% owf Aclick White TK dye solution manufactured by Shigensei Chemical Co., Ltd. at a bath ratio of 1:15, a temperature of 97 ° C., and a time of 30 minutes. When the anti-pill property and knitted fabric texture of the produced knitted fabric were evaluated, the anti-pill property was 4.5 grade and the knitted fabric texture was good (◯). The results are shown in Table 5.

[Examples 14 to 19 and Comparative Examples 18 to 23]
In Example 13, the acrylonitrile copolymer, the polymer ratio in the spinning dope, the spinning dope temperature, the coagulation bath conditions, the mouthpiece hole, the draw ratio, the drying conditions, and the target fineness were changed as shown in Tables 5 and 6. The results of the obtained raw cotton are shown in Tables 5 and 6. In Comparative Examples 18 to 23 in which the base holes were changed, both the spinnability and the stretchability were x, and no raw cotton could be obtained.

[Examples 20 to 24]
The acrylic fiber 38 mm cut obtained in Example 13 and the rayon 1.7 dtex 38 mm cut were mixed at 60 mass% / 40 mass% and 50 mass% / 50 mass%, and obtained in Examples 13, 15, and 19. Acrylic fiber and 1.15 dtex 38 mm cut shrinkable acrylic fiber with a shrinkage ratio in boiling water of 22% are blended at 60% / 40% by weight, and the spinning is 1/52 by short spinning. The spun yarn was knitted with a smooth knitting and 18 gauge, and the resulting knitted fabric was bathed with a click white TK dye solution of 1.0% owf by Shigesei Chemical Co., Ltd. at a bath ratio of 1:15 and a temperature of 97. Staining was carried out at 30 ° C. for 30 minutes. Table 7 shows the evaluation results of the anti-pill properties, Hunter color system b and knitted fabric texture of the produced knitted fabric.

As is clear from the results of Tables 5 to 7, the white anti-pill flat acrylic fiber produced under the conditions satisfying the various process requirements related to the present invention is flat and has excellent whiteness itself. It can be seen that the fabric texture and anti-pill performance are exhibited.

Claims (4)

  A fiber comprising 91 to 95% by mass of acrylonitrile, 3 to 8% by mass of an ethylenic vinyl monomer copolymerizable with the acrylonitrile, and 1 to 6% by mass of a sulfonic acid-containing vinyl monomer. In the Hunter color system, b is +1.5 to +4.7, the single fiber fineness of the fiber is 0.3 to 1.3 dtex, and the tensile strength is 2.0 cN / dtex. As described above, a white anti-pill acrylic fiber having a knot strength of 1.3 to 2.2 cN / dtex, a knot elongation of 10 to 20%, and an anti-pill property of 3.5 or higher.   2. The white anti-pill acrylic according to claim 1, wherein the flatness ratio A / B is 1.5 to 5 when the long side length of the fiber cross section is A and the short side length is B. 3. Fiber.   Acrylonitrile copolymer 20 to 25% by mass comprising 91 to 95% by mass of acrylonitrile, 3 to 8% by mass of ethylenic vinyl monomer copolymerizable with acrylonitrile, and 1 to 6% by mass of sulfonic acid-containing vinyl monomer And an organic solvent 75-80% by mass into a coagulation bath having a solvent concentration in the coagulation bath of 60-70% by mass and a temperature of 30-50 ° C., and the spinning dope temperature at 60-80 ° C. and a spinning draft Is stretched at a draw ratio of 3.5 to 5.0, and then is densified with a shrinkage ratio of 5% or less during drying and then 160. A method for producing a white anti-pyracrylic fiber, which is subjected to tension heat treatment at a temperature of ˜180 ° C. for 10 to 30 seconds. A rectangular hole having a long side length of 0.065 to 0.145 mm, a short side length of 0.015 to 0.035 mm, and a hole depth / hole area value of 12 to 32. 4. The method for producing a white anti-pill acrylic fiber according to claim 3, wherein the spinning is performed from