JP2005314841A - Acrylic synthetic fiber improved with dyeing and discharging property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic synthetic fiber having a soft touch feeling, exhibiting a short steam-treating time required for discharge, excellent in processability and having a good whiteness after the discharge. <P>SOLUTION: This acrylic fiber obtained from a spinning stock solution obtained by mixing a polymer obtained by copolymerizing acrylonitrile and a halogen-containing monomer with a polymer having relatively high hydrophilicity and consisting of a monomer having ≥1% solubility to water at 20°C is significantly improved in dyeing and discharging properties, and also keeps the soft touch feeling. Therefore, it is possible to produce a pile cloth having both various designs treated with discharge processes and the soft touch feeling jointly, and it is possible to develop the pile cloth widely for uses in clothes, stuffed toys, interior materials, etc. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acrylic synthetic fiber having improved dyeability and dischargeability, which is suitable mainly for pile applications.

Acrylic synthetic fibers are widely used in fields such as bores, seals, fleeces, and high piles because of their soft feel, texture such as bulkiness, and ease of processing. The required quality of acrylic synthetic fibers for piles has a soft texture and at the same time excellent dyeability, that is, fast dye exhaustion speed, high color development, and discharge processing. Is easy. However, an acrylic synthetic fiber copolymerized with a highly hydrophobic halogen-containing monomer is excellent in soft texture, but does not have sufficient performance in dyeability, particularly in discharging. As a method for improving this dischargeability, an acrylic synthetic fiber containing 0.2 to 5% by weight of acrylic acid, methacrylic acid and alkyl esters thereof has been proposed (Patent Document 1), and discharge to some extent is performed by this method. Although the later whiteness was improved, the steam heat treatment time required for discharging was still long, and problems were left in workability, and the performance was not always sufficient in practice.
JP2003-183931A

  An object of the present invention is to obtain an acrylic synthetic fiber that has a soft texture, has a short steaming heat treatment time required for discharging, has excellent workability, and has good whiteness after discharging.

  As a result of diligent research to achieve the above objective, it was found that the hydrophilicity of the polymer constituting the fiber has a great correlation with the dyeing and discharging properties, and the dyeing and discharging properties are greatly improved by improving the hydrophilicity. I found out that In order to improve hydrophilicity, it is preferable to use a polymer having 80% by weight or more of acrylonitrile. However, when acrylonitrile is 80% by weight or more, the soft texture peculiar to the fiber copolymerized with the halogen-containing monomer is lost. There are drawbacks. The present invention is intended to obtain a fiber excellent in dyeing and discharging properties as much as or more than 80% by weight of acrylonitrile while maintaining the unique soft texture of the fiber copolymerized with a halogen-containing monomer. Is. For this purpose, a polymer obtained by copolymerizing a halogen-containing monomer with a polymer having a relatively high hydrophilicity, the fibers obtained from the spinning dope are dramatically improved in dyeing and discharging properties, and soft. It turns out that the texture is not lost. That is, a polymer (A) comprising 40 to 60% by weight of acrylonitrile, 40 to 60% by weight of a halogen-containing monomer copolymerizable with acrylonitrile, and 0 to 5% by weight of a sulfonic acid group-containing monomer is added to a polymer having a relatively high hydrophilicity. By mixing the coalesced, an improvement in dyeing and discharging properties is achieved. The polymer having a relatively high hydrophilicity herein is a polymer composed of a monomer having a solubility in water at 20 ° C. of 1% or more, and further includes a polymer obtained by copolymerizing a sulfonic acid group-containing monomer. A polymer obtained by copolymerizing a sulfonic acid group-containing monomer is divided into a polymer and a polymer that does not contain the polymer, and the effect of improving dyeing and dischargeability is seen with a smaller amount of mixing. Specifically, the polymer (A) is composed of 50 to 99% by weight, 60 to 99 parts by weight of a monomer having a solubility in water at 20 ° C. of 1% or more, and 1 to 40% by weight of a sulfonic acid group-containing monomer. Polymer (C) comprising acrylic synthetic fiber consisting of 1 to 50% by weight of union (B) or 50 to 95% by weight of polymer (A) and a monomer having a solubility in water at 20 ° C. of 1% or more By the acrylic synthetic fiber comprising 5 to 50% by weight, excellent dyeing and discharging properties which are the object of the present invention can be obtained.

  The acrylic synthetic fiber of the present invention has a short steaming heat treatment time required for discharging, excellent workability, good whiteness after discharging, and maintains a soft texture. As a result, pile fabrics that combine a variety of designs that have undergone discharge printing and a soft texture can be produced, and can be widely deployed in clothing, stuffed animals, interior use, and the like.

  The polymer (A) in the present invention comprises 40 to 60% by weight of acrylonitrile, 40 to 60% by weight of a halogen-containing monomer copolymerizable with acrylonitrile, and 0 to 5% by weight of a sulfonic acid group-containing monomer, but is copolymerized with acrylonitrile. Possible halogen-containing monomers include vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide and the like. Among these, vinyl chloride and vinylidene chloride are preferable, and these may be used alone or in combination. Examples of the sulfonic acid group-containing monomer include allyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, isoprene sulfonic acid, and alkali metal salts thereof.

  The polymer (B) in the present invention comprises 60 to 99 parts by weight of a monomer having a solubility in water at 20 ° C. of 1% or more and 1 to 40% by weight of a sulfonic acid group-containing monomer. Examples of monomers having a solubility of 1% or more include acrylonitrile, acids such as (meth) acrylic acid and their salts, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, hexyl (meth) acrylate, etc. (Meth) acrylic acid esters, (meth) acrylamide, vinyl acetate and the like. Examples of the sulfonic acid group-containing monomer include allyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, isoprene sulfonic acid, and alkali metal salts thereof. These may be used alone or in combination.

  The polymer (C) in the present invention comprises a monomer having a solubility in water at 20 ° C. of 1% or more, and like the polymer (B), the monomer having a solubility in water at 20 ° C. of 1% or more. , Acrylonitrile, acids such as (meth) acrylic acid and salts thereof, (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, hexyl (meth) acrylate, ( And meth) acrylamide, vinyl acetate, vinyl pyrrolidone and the like. These may be used alone or in combination.

  The polymers (A), (B), and (C) of the present invention are known as suspension polymerizations using known compounds such as peroxide compounds, azo diameter compounds, or various redox compounds. It can be obtained by a general vinyl polymerization method such as emulsion polymerization or solution polymerization.

  Polymers (A) and (B) or (A) and (C) are mixed within the predetermined ratio described above, and organic solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetone, rhodan salts, nitric acid Then, it is dissolved in an inorganic solvent such as zinc chloride to obtain a spinning dope. Using this spinning dope, after spinning from the nozzle by a method similar to that of normal acrylic synthetic fiber wet spinning, it may be stretched, washed with water, dried, and heat-treated in succession. Is preferably carried out in a saturated steam or heated steam atmosphere.

  The acrylic synthetic fiber obtained in the present invention can be dyed with a commonly used cationic dye, and is excellent in dye exhaustion performance as compared with an acrylic synthetic fiber consisting only of the polymer (A). In addition, when used for discharging, cationic dyes that are reduced by various reducing discharging agents are preferable, and in general, a cation having at least one azo group (—N═N—) as a chromophore in the dye structure. A dye is used.

  When discharging, after using a fiber dyed with a reducible cationic dye to create a pile fabric by a general pile processing process, zinc-based discharging agent such as zinc formaldehyde sulfoxylate or stannous chloride Discharge using a commonly used discharge paste containing a tin-based discharge agent. After printing the discharging paste on the surface of the pile, steaming is performed for 10 to 30 minutes in a saturated steam atmosphere or a heated steam atmosphere at 90 ° C. or higher to perform discharging. Furthermore, the final pile is completed after washing with water, drying and finishing.

  When the acrylic synthetic fiber of the present invention is used, the time for steaming at the time of discharging is sufficient within 10 to 15 minutes, the whiteness after discharging is excellent, and the soft texture is maintained. .

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Prior to describing the examples, various analyzes and evaluation methods will be described.
(Measurement method of resin composition)
(1) Measuring method of resin composition of polymer (A) (1-1) Acrylonitrile content The nitrogen content in the resin is measured using a CHN coder manufactured by Yanaco, and this nitrogen content is regarded as the nitrogen content derived from acrylonitrile. The acrylonitrile content was calculated.
(1-2) Content of sulfonic acid group-containing monomer Using a sample combustion apparatus QF-02 manufactured by Mitsubishi Chemical, the combustion gas was reduced to 0 under the conditions of argon / O ₂ = 100/100, heating temperature 900 ° C., and heating time 35 minutes. .3 is absorbed in weight% aqueous H ₂ O ₂ solution, using ion chromatography IC-7000 manufactured by Yokogawa to determine the sulfur content. From this sulfur content, the content of the sulfonic acid group-containing monomer was calculated.
(1-3) Content of Halogen-Containing Monomer The amount obtained by subtracting the acrylonitrile content and the sulfonic acid group-containing monomer content was taken as the halogen-containing monomer content.
(2) Method for measuring resin composition of polymer (B) (2-1) Content of sulfonic acid group-containing monomer The content of the sulfonic acid group-containing monomer was calculated in the same manner as in (1-2) above.
(2-2) Content of monomer having a solubility in water at 20 ° C of 1% or more Subtracting the content of the sulfonic acid group-containing monomer from the monomer having a solubility in water at 20 ° C of 1% or more It was set as the content.
(Dyeing exhaustion rate evaluation)
The malachite green (MG) dye, which is a standard for dyeability of acrylic fibers, was exhausted and converted to a relative saturation value SF value of the following formula to evaluate exhaustion power. Dyeing was performed in boiling water for 60 minutes.

SF = M. G. Dyeing amount × 400/463 (M.G. molecular weight)
(Color development evaluation)
(1) Dyeing method Fibers are set in a dyeing machine (Over Meyer), and a dyeing bath adjusted to pH about 3.5 with ultraphosphoric acid (Ultra MT-110: manufactured by Gokajima Chemical) is used. The temperature was raised to 50 ° C. while operating. Furthermore, a cationic dye formulated to be gray with a total dye concentration of 0.36% owf (Maxilon Yellow / Maxilon Red / Maxilon Blue = 11.5 / 10.3 / 10.7: weight ratio, all manufactured by Ciba-Geigy ) Was dissolved in acetic acid and diluted with hot water. Next, the temperature was raised to 90 ° C. at a rate of 1 ° C. per minute and kept for 15 minutes, and then heated to 0.5 ° C./min until boiling, followed by boiling dyeing for 30 minutes. Thereafter, it was cooled to 50 ° C. at a rate of 5 ° C./min, and dyed yarn was obtained through ordinary water washing and drying.

(2) Color development measurement Similar to the whiteness measurement, the fiber dyed in gray is fully opened, weighed a certain amount, placed in a sample table with a diameter of 30 mm, and a color difference meter under the standard light source C The L value was measured using a type Σ90 (manufactured by Nippon Denshoku Industries Co., Ltd.).

(Dischargeability evaluation)
(1) Pre-dyeing method Fibers are set in a dyeing machine (Over Meyer), and a dyeing bath adjusted to pH about 3.5 with ultraphosphoric acid (Ultra MT-110: manufactured by Gogashima Chemical) is used. The temperature was raised to 50 ° C. while operating. Furthermore, the dye measured according to the following dye formulation was dissolved in acetic acid, diluted with hot water, and added. Next, the temperature was raised to 90 ° C. at a rate of 1 ° C. per minute and maintained for 15 minutes, and then heated to 0.5 ° C./min until boiling, and then boiled for 60 minutes. Thereafter, it was cooled to 50 ° C. at a rate of 5 ° C./min, and dyed yarn was obtained through ordinary water washing and drying.

Cathilon Discharge Yellow NLH: 1.65% omf
Cathilon Red CD-FGLH: 0.737% omf
Cathilon Blue GLH (200): 1.007% omf
(Both manufactured by Hodogaya Chemical Co., Ltd.)
(2) White discharge prescription and dischargeability evaluation (2-1) White fiber discharge prescription and discharge speed, whiteness evaluation As a discharge agent, 10 parts of stannous chloride (manufactured by Kishida Chemical) and 90 parts of water are mixed. A discharge agent solution was prepared. 200 ml of this discharging agent solution was set in a pot dyeing machine and heated, and after boiling, 2 g of pre-dyed short fibers were added to perform discharging. In order to evaluate the discharging speed of the short fibers, those after 5, 10, 15, 20, 25, 30, and 40 minutes were obtained after the short fibers were added, and each was washed with water and dried. This fiber is fully opened and weighed 2 g, put on a sample table with a diameter of 30 mm, and using a color difference meter type Σ90 (manufactured by Nippon Denshoku Industries Co., Ltd.) under a standard light source C, the whiteness after discharge processing is measured. It was measured. In this example / comparative example, the Hunter whiteness W value of 70 or higher was regarded as acceptable, the elapsed time after the short fiber was fed when the W value was 70 or higher was defined as the discharge time, and the shorter the time, the better the discharge performance. It was evaluated.
(2-2) Pile raw fabric white discharge prescription and discharge evaluation 10 parts of stannous chloride (manufactured by Kishida Chemical) as discharge agent, locust bean paste Meypro Gum NP-25 (30% concentration: Mayhall) as paste 40 parts), tartaric acid 0.1 part, and water 49.9 parts were used, and the viscosity of the printing paste for discharging was adjusted to 8000 to 10,000 cp with a B-type viscometer. This printing paste for printing is stamped on the pile surface of the high-pile raw fabric at a printing amount of 200 to 300 g / m 2 using a roller printing machine, steamed for 15 minutes in a steamer at about 98 ° C., and then washed with water. -Dried. Next, in order to improve the pile disturbance and texture of the high-pile raw fabric, a polishing-shearing process was performed to arrange the high-pile dough into a final product form. The discharge products thus obtained were evaluated using a color scale for contamination (best in grade 5 and worst in grade 1).
(Pile texture evaluation)
The feeling of the pile after discharging was conducted by sensory evaluation of five experts. The evaluation criteria are as follows.
[○] Soft and smooth texture [△] Texture with a slight roughness [X] Texture with a large roughness (Example 1)
In a pressure-resistant polymerization reactor having an internal volume of 20 L, 200 parts of ion exchange water, 0.9 part of sodium lauryl sulfate, 0.43 part of sodium sulfite, 0.22 part of sodium hydrogen sulfite, 0.001 part of iron sulfate, 4.9 parts of acrylonitrile, 52.5 parts of vinyl chloride was added and replaced with nitrogen. The internal temperature of the polymerization machine was adjusted to 50 ° C., 0.035 part of ammonium persulfate was added as an initiator, and polymerization was started. In the middle of the polymerization, polymerization was performed for 5 hours and 10 minutes while adding 42.1 parts of acrylonitrile, 0.5 part of sodium styrenesulfonate, and 0.23 part of ammonium persulfate. Then, unreacted VC was collect | recovered, latex was discharged | emitted from the polymerizer, salting-out, heat processing, filtration, water washing, dehydration, and drying were performed, and the polymer 1 applicable to the polymer (A) of this invention was obtained. The composition of the obtained copolymer was 49% by weight of acrylonitrile, 0.5% by weight of sodium styrenesulfonate, and 50.5% by weight of vinyl chloride.

  Next, 187 parts of acetone, 47 parts of water, 50 parts of acrylonitrile, 40 parts of methyl acrylate, and 10 parts of sodium 2-acrylamido-2-methylpropanesulfonate (hereinafter referred to as SAM) in a pressure-resistant polymerization reactor having an internal volume of 5 L. Was replaced with nitrogen. The temperature inside the polymerization machine was adjusted to 65 ° C., and 0.5 part of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as an initiator to initiate polymerization. On the way, polymerization was performed for 2 hours while adding 1.0 part of azobis, and then heated to 70 ° C. and polymerized for 2 hours to prepare a solution of polymer 2 corresponding to the polymer (B) of the present invention having a polymer concentration of 30%. Obtained. The composition of the obtained copolymer was 10% by weight of SAM, 50% by weight of acrylonitrile, and 40% by weight of methyl acrylate. A solution of polymer 2 is added to a solution of polymer 1 in which acetone is added and dissolved so that the polymer 1 is 30%, and the weight ratio of the polymer becomes a ratio of polymer 1: polymer 2 = 90: 10. The mixture was used as the spinning dope. The obtained spinning dope was spun into a coagulation bath of acetone / water = 30/70, 25 ° C. through a nozzle having a diameter of 0.1 mm and a hole number of 300, and stretched 3 times in 85 ° C. hot water, Further, after drying, the film was stretched twice at 130 ° C. and further subjected to relaxation heat treatment in steam heated at 145 ° C. to obtain 3 dtex fibers. Subsequently, crimping was applied to the obtained fiber to cut the fiber length to 38 mm. The short fibers were evaluated for the dye exhaustion rate and the color developability by gray dyeing by the above methods. Moreover, after performing pre-dyeing for discharging, short fibers were discharged and the discharging time was evaluated. Further, after the pre-dyed cotton for discharging was opened with a fair note machine, a sliver was formed with a carding machine, and a high pile original fabric having a pile length of 12 mm was prepared by a sliver knitting method. When the high pile fabric was discharged by the above method, it was uniformly discharged at a depth of about 2 mm from the pile hair tip, and the whiteness of the discharged portion and the boundary between the pre-dyed portion and the discharged portion were clear. It was expressed and the texture of the pile was also good. The composition of the polymer of the example is shown in Table 1, and the results of color removal, dischargeability and texture evaluation are shown in Table 2.

（実施例２）
実施例１における重合体１を得た方法と同様の方法により、アクリロニトリル４９重量％、スチレンスルホン酸ナトリウム１重量％，塩化ビニル５０重量％の重合体３を得た。さらに、実施例１における重合体２を得た方法と同様の方法によりＳＡＭ３０重量％，アクリロニトリル３０重量％、アクリル酸メチル４０重量％の重合体４を得た。重合体３：重合体４の重量比が９７：３の比率になるように混合した物を紡糸原液とし、実施例１と同様の方法で短繊維を得、実施例１と同様の方法で染色性、抜染性の評価を行った。

(Example 2)
By a method similar to the method for obtaining the polymer 1 in Example 1, a polymer 3 comprising 49% by weight of acrylonitrile, 1% by weight of sodium styrenesulfonate, and 50% by weight of vinyl chloride was obtained. Further, a polymer 4 having 30% by weight of SAM, 30% by weight of acrylonitrile, and 40% by weight of methyl acrylate was obtained by the same method as that for obtaining the polymer 2 in Example 1. A mixture of polymer 3 and polymer 4 in a weight ratio of 97: 3 is used as a spinning stock solution, and short fibers are obtained in the same manner as in Example 1, and dyeing is performed in the same manner as in Example 1. And dischargeability were evaluated.

(Example 3)
In a pressure-resistant polymerization reactor having an internal volume of 20 L, 200 parts of ion-exchanged water, 1.1 parts of sodium lauryl sulfate, 0.13 parts of sodium sulfite, 0.17 parts of sodium hydrogen sulfate, 0.002 parts of iron sulfate, 10.7 parts of acrylonitrile, 4.4 parts of vinylidene chloride was added and purged with nitrogen. Polymerizer internal temperature was adjusted to 55 ° C., and 0.012 part of ammonium persulfate was added as an initiator to initiate polymerization. On the way, 42.7 parts of acrylonitrile, 41.0 parts of vinylidene chloride, 1 part of sodium styrenesulfonate and 0.135 part of ammonium persulfate were added, and the polymerization was carried out in 6 hours and 10 minutes. Thereafter, the latex was discharged from the polymerizer, salted out, heat treated, filtered, washed with water, dehydrated and dried to obtain a polymer 5 corresponding to the polymer (A) of the present invention. The composition of the obtained copolymer was 50% by weight of acrylonitrile, 1% by weight of sodium styrenesulfonate, and 49% by weight of vinylidene chloride. Further, a polymer 6 having 5% by weight of SAM, 50% by weight of acrylonitrile and 45% by weight of methyl acrylate was obtained by the same method as that for obtaining the polymer 2 in Example 1. A mixture obtained so that the weight ratio of polymer 5: polymer 6 is 85:15 is used as a spinning dope, and short fibers are obtained by the same method as in Example 1, and dyeing is performed by the same method as in Example 1. And dischargeability were evaluated.

Example 4
A mixture of polymer 1 in Example 1 and polyvinyl acetate (manufactured by Kaneka Chemical Co., Ltd.) corresponding to the polymer (C) of the present invention in a weight ratio of 90:10 was used as the spinning dope. Short fibers were obtained in the same manner as in Example 1, and dyeability and dischargeability were evaluated in the same manner as in Example 1.

(Example 5)
A mixture of polymer 1 in Example 1 and polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.) corresponding to the polymer (C) of the present invention in a weight ratio of 90:10 was used as the spinning dope. The short fibers were obtained in the same manner as in Example 1, and the dyeability and dischargeability were evaluated in the same manner as in Example 1.

(Comparative Example 1)
From the spinning dope of the polymer 1 described in Example 1, short fibers were obtained in the same manner as in Example 1, and dyeability and dischargeability were evaluated in the same manner as in Example 1.

(Comparative Example 2)
In a pressure-resistant polymerization reactor having an internal volume of 14 L, ion-exchanged water 200 parts, acrylonitrile 3.8 parts, vinyl chloride 49.5 parts, vinyl acetate 2.5 parts, sodium lauryl sulfate 0.87 parts, sulfurous acid 0.43 parts, 0.22 parts of sodium hydrogen sulfite, 0.001 part of ferrous sulfate and 0.035 part of ammonium persulfate were charged, and emulsion polymerization was carried out at a polymerization temperature of 50 ° C. and a polymerization time of 5 hours. During the polymerization, 43.95 parts of acrylonitrile, 0.75 part of sodium parastyrenesulfonate, and 0.23 part of ammonium persulfate were added. After the polymerization was completed, unreacted vinyl chloride was recovered to obtain a copolymer latex. The composition of the obtained copolymer was 50.0% by weight of acrylonitrile, 47.3% by weight of vinyl chloride, 2% by weight of vinyl acetate, and 0.7% by weight of sodium parastyrenesulfonate. From this polymer spinning dope, short fibers were obtained in the same manner as in Example 1, and the dyeability and dischargeability were evaluated in the same manner as in Example 1.

Claims (5)

  Polymer (A) comprising 40 to 60% by weight of acrylonitrile, 40 to 60% by weight of a halogen-containing monomer copolymerizable with acrylonitrile, and 0 to 5% by weight of a sulfonic acid group-containing monomer, and 20 ° C. An acrylic synthetic fiber comprising 1 to 50% by weight of a polymer (B) comprising 60 to 99 parts by weight of a monomer having a solubility in water of 1% or more and 1 to 40% by weight of a sulfonic acid group-containing monomer.   A polymer (A) comprising 40 to 60% by weight of acrylonitrile, 40 to 60% by weight of a halogen-containing monomer copolymerizable with acrylonitrile, and 0 to 5% by weight of a sulfonic acid group-containing monomer, and 20 ° C. Acrylic synthetic fiber comprising 5 to 50% by weight of polymer (C) comprising a monomer having a solubility in water of 1% or more.   The monomer having a solubility in water at 20 ° C. of 1% or more is at least one selected from acrylonitrile, acrylic acid and methacrylic acid and salts thereof, acrylic ester and methacrylic ester, acrylamide and methacrylamide, and vinyl acetate The acrylic synthetic fiber according to claim 1.   A monomer having a solubility in water at 20 ° C. of 1% or more is selected from acrylonitrile, acrylic acid and methacrylic acid and their salts, acrylic acid ester and methacrylic acid ester, acrylamide and methacrylamide, vinyl acetate, vinylpyrrolidone The acrylic synthetic fiber according to claim 2, which is at least one kind.   The acrylic non-shrinkable synthetic fiber according to claim 1, which has a discharging property such that the whiteness after the deep-dyed dyed fiber is white-discharged is 70 or more in terms of W value.