CN116940723A

CN116940723A - Meta-type wholly aromatic polyamide fiber colored with stock solution and method for producing same

Info

Publication number: CN116940723A
Application number: CN202180095127.4A
Authority: CN
Inventors: 竹山直彦; 山口顺久
Original assignee: Teijin Ltd
Current assignee: Teijin Ltd
Priority date: 2021-03-02
Filing date: 2021-12-23
Publication date: 2023-10-24
Also published as: JP7466054B2; KR20230151002A; JPWO2022185683A1; WO2022185683A1

Abstract

The invention provides a method for producing a meta-type wholly aromatic polyamide fiber by coloring a raw liquid, which minimizes the loss generated during color replacement. In the method for producing a dope-dyed meta-type wholly aromatic polyamide fiber of the present invention, 1 or more pigments are dispersed in an amide-based solvent in an amount of 5 to 50 mass%, at least 3 kinds or more of the mother pigment dispersions having a specific color tone are not mixed in advance, and the mixture is sequentially mixed with a spinning dope so that the total pigment concentration in the fiber is 0.1 to 5.0 mass%, and then spun and drawn to obtain a dope-dyed meta-type wholly aromatic polyamide fiber.

Description

Meta-type wholly aromatic polyamide fiber colored with stock solution and method for producing same

Technical Field

The present invention relates to a colored dope-dyed meta-type wholly aromatic polyamide fiber, and more particularly, to a dope-dyed meta-type wholly aromatic polyamide fiber which can efficiently produce desired various colors and can minimize an increase in cost.

Background

Wholly aromatic polyamide fibers produced from aromatic diamines and aromatic dicarboxylic acid dihalides are known to be excellent in heat resistance and flame retardancy, and among such wholly aromatic polyamide fibers, meta-type wholly aromatic polyamide fibers typified by polymetaphenylene diamine are known to be particularly useful as heat resistant and flame retardant fibers. In addition, by utilizing these characteristics, the meta-type wholly aromatic polyamide fiber is preferably used in the field of protective clothing such as firefighters and heat-resistant work clothes (see patent document 1).

In the use of such clothing fields, colored fibers are generally used. As a method for obtaining a colored fiber, a post-dyeing method in which a dye is used for dyeing after the fiber is formed, or a dope-dyeing method in which a pigment is added to a dope and the fiber is formed is known.

However, meta-type wholly aromatic polyamide fibers colored by post-dyeing using dye after fiberization have disadvantages of discoloration and fading due to light irradiation and discoloration and fading due to abscission of washed pigment.

In contrast, in protective clothing such as firefighters and heat-resistant work clothes used outdoors for a long period of time, coloring by a stock solution coloring method in which a pigment is added to a spinning stock solution and then fibrillated is performed. In this stock solution coloring method, as shown in fig. 1, for example, a method of mixing a meta-type wholly aromatic polyamide and a pigment, a method of mixing a pigment and stirring to prepare a mixed pigment dispersion uniformly dispersed in an amide-based solvent, a method of adding the amide-based solvent slurry to a solution (polymer stock solution) in which a meta-type wholly aromatic polyamide is dissolved in an amide-based solvent, a method of directly adding pigment powder to a solution (polymer stock solution) in which a meta-type wholly aromatic polyamide is dissolved in an amide-based solvent, and the like are mentioned (see patent document 2).

As a method for mixing the meta-type wholly aromatic polyamide and the pigment, there is also a method for preparing a meta-type wholly aromatic polyamide-pigment mixture in which the pigment is dispersed in a polymer stock solution of a low-concentration meta-type wholly aromatic polyamide diluted with an amide-based solvent, and mixing and stirring the mixture with a stock solution of a high-concentration meta-type wholly aromatic polyamide (see patent document 3).

However, in these methods, since the stock solution of the meta-type wholly aromatic polyamide is mixed with the pigment in a tank and then spun, there is a problem that each time the pigment is replaced, the following is involved: it takes time to extract the pigment remaining in the pigment tank and the pipe, clean the pigment tank and the pipe, and input new pigment, and a large amount of the raw liquid of the meta-type wholly aromatic polyamide, the pigment, and the amide solvent must be discarded.

In view of this, a method has been proposed in which a method for mixing a meta-type wholly aromatic polyamide with a pigment is a method in which an amide-based solvent slurry (pigment dispersion) in which a pigment is uniformly dispersed in an amide-based solvent and a raw liquid of the meta-type wholly aromatic polyamide are simultaneously supplied to a head of a split type biaxial extruder, and the process of the pigment slurry is short and the screw can be easily taken out, so that the cleaning time at the time of color replacement can be shortened and the waste amount of the raw liquid of the meta-type wholly aromatic polyamide, the pigment and the amide-based solvent can be reduced (see patent document 4).

However, even in this method, it is necessary to clean a tank, piping, and a split type twin-screw extruder in which the amide-based solvent slurry of the pigment to be supplied is uniformly dispersed at the time of color replacement, and this method has not been sufficiently solved.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2006-016709

Patent document 2: japanese patent No. 5852127

Patent document 3: korean patent No. 101961189

Patent document 4: chinese patent publication No. 102400242

Disclosure of Invention

The present invention addresses the problems of the prior art as described above and provides a method for producing a meta-type wholly aromatic polyamide fiber by coloring a raw liquid, which minimizes the loss generated during color conversion.

The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found a method for producing meta-type wholly aromatic polyamide fiber by coloring a raw liquid using the following steps, thereby completing the present invention. That is to say,

(A) A process for producing a liquid-dyed meta-type wholly aromatic polyamide fiber, characterized by comprising the steps of (1) to (7) below,

(1) A step of polymerizing a meta-type aromatic diamine and a meta-type aromatic dicarboxylic acid to obtain a meta-type wholly aromatic polyamide, and preparing a stock solution of an amide solvent,

(2) A step of producing a master pigment dispersion in which, when at least 3 or more kinds of pigments other than black pigments are dispersed in an amide-based solvent used in (1) in an amount of 5 to 50 mass%, points of the respective fibers containing the respective master pigment dispersions, each of which is drawn with a color a value (hereinafter, may be abbreviated as "a value") as a horizontal axis and a color b value (hereinafter, may be abbreviated as "b value") as a vertical axis, are connected by straight lines that do not intersect each other so that the pigment concentration in the fibers becomes 1 mass%, the area enclosed by the straight lines is 1500 or more,

(3) A step of mixing the stock solution prepared in (1) in this order so that the total pigment concentration in the fiber is 0.1 to 5.0 mass% (99.9 to 95.0 mass% of the polymer+the total pigment concentration is 0.1 to 5.0 mass%) without pre-mixing 3 or more kinds of the master pigment dispersions of (2),

(4) Spinning the stock solution mixed with the mother pigment dispersion in (3) from a spinning head into a coagulating liquid to coagulate the stock solution to obtain a fiber,

(5) A step of stretching the fiber in a plastic stretching bath when the fiber obtained by coagulation in the coagulation bath is in a plastic state,

(6) A step of sufficiently cleaning the drawn fiber in the plastic drawing bath,

(7) A step of drying and heat-treating the fiber subjected to the washing step,

(B) The method for producing a meta-type wholly aromatic polyamide fiber colored with a stock solution as described in (A) above, wherein the method comprises dispersing a black pigment in an amide-based solvent used in (1) in an amount of 5 to 50 mass%, wherein the fiber has a color L value (hereinafter, may be simply referred to as L value) of 40 or less when the black pigment is contained in an amount of 1 mass%,

(C) The process for producing a liquid-colored meta-wholly aromatic polyamide fiber as described in (A) or (B) above, wherein each of the mother pigment dispersions has an L value of 35 to 85, an a value of-30 to 60 and a B value of-30 to 60,

the method comprises the steps of,

(D) A meta-type wholly aromatic polyamide fiber is colored with a mother pigment dispersion, wherein the mother pigment dispersion is at least 3 kinds of mother pigment dispersions other than black pigment, and when the mother pigment dispersion is connected to a point of the fiber containing each mother pigment dispersion in a 1 mass% manner by straight lines which do not intersect each other, the area surrounded by the straight lines is at least 1500.

According to the present invention, since the meta-type wholly aromatic polyamide fiber can be continuously obtained by mixing and spinning the mother pigment dispersions of at least 3 kinds with the spinning dope in sequence while adjusting the ratio of the target color, the color can be changed by changing the addition ratio of each mother pigment dispersion while spinning, and the loss of the spinning dope during this period can be reduced, and further, the loss of the amide-based solvent after the cleaning, which occurs with the discarding of the mother pigment dispersion remaining in the pigment tank, the cleaning of the equipment such as the pigment tank and piping, etc., can be eliminated, and the load on the environment can be reduced. In addition, in this case, by using 3 or more kinds of parent pigment dispersions having specific hues, the range of hues as target colors can be widened as much as possible.

Drawings

Fig. 1 is a flowchart showing an example of a method of mixing a polymer stock solution and a pigment in a conventional stock solution coloring method.

Fig. 2 is a graph showing an example of points drawn on the horizontal axis of the a value and the vertical axis of the b value of each raw cotton containing pigment so that the pigment concentration in the fiber becomes 1 mass% by using the mother pigment dispersion and connecting the raw cotton with straight lines not intersecting each other.

FIG. 3 is a flowchart showing an example of a method of mixing a polymer stock solution with a mother pigment dispersion in the stock solution coloring method of the present invention.

Fig. 4 is a graph showing the positions of triangles of points plotted on the horizontal axis of the a value and the vertical axis of the b value of each raw cotton containing pigment so that the pigment concentration in the fiber becomes 1 mass% and the target color of the second color are connected by straight lines that do not intersect each other using the mother pigment dispersion in comparative example 1.

Detailed Description

The present invention will be described in detail below in the order of the production steps.

(1) Step of producing stock solution of amide-based solvent

In this step, the polyamide is produced by, for example, solution polymerization or interfacial polymerization using a meta-type aromatic diamine and a meta-type aromatic dicarboxylic acid halide as raw materials, but the polyamide may be produced by copolymerizing other copolymerization components such as a para-type component within a range that does not hinder the object of the present invention.

As the meta-type aromatic diamine, m-phenylenediamine, 3,4 '-diaminodiphenyl ether, 3,4' -diaminodiphenyl sulfone, and the like, and derivatives thereof having a substituent such as halogen, alkyl group having 1 to 3 carbon atoms in the aromatic ring, for example, 2, 4-toluenediamine, 2, 6-toluenediamine, 2, 4-diaminochlorobenzene, 2, 6-diaminochlorobenzene, and the like can be used. Among them, m-phenylenediamine or the above mixed diamine containing 70 mol% or more of m-phenylenediamine is preferable.

As the meta-type aromatic dicarboxylic acid halide, isophthaloyl halide such as isophthaloyl chloride and isophthaloyl bromide, and derivatives thereof having substituents such as halogen, alkoxy group having 1 to 3 carbon atoms and the like on the aromatic ring, for example, 3-chloroisophthaloyl chloride and 3-methoxyisophthaloyl chloride, can be used. Among them, isophthaloyl chloride or the above-mentioned mixed carboxylic acid halide containing 70 mol% or more of isophthaloyl chloride is preferable.

The copolymerization component obtained by using the above-mentioned meta-type aromatic diamine and the above-mentioned meta-type aromatic dicarboxylic acid halide may be exemplified by benzene derivatives such as p-phenylenediamine, 2, 5-diaminochlorobenzene, 2, 5-diaminobromobenzene and aminoaniline, benzene derivatives such as 1, 5-naphthalenediamine, 4 '-diaminodiphenyl ether, 4' -diaminobenzophenone, 4 '-diaminodiphenylamine and 4,4' -diaminodiphenylmethane, and the aromatic dicarboxylic acid halide may be exemplified by terephthaloyl chloride, 1, 4-naphthalenedicarboxylic acid chloride, 2, 6-naphthalenedicarboxylic acid chloride, 4 '-biphenyldicarboxylic acid chloride and 4,4' -diphenylether dicarboxylic acid chloride.

If the copolymerization ratio of these copolymerization components becomes too large, the meta-type wholly aromatic polyamide tends to be deteriorated in properties, and therefore, it is preferably 20 mol% or less based on the total acid component of the polyamide. In particular, the meta-type wholly aromatic polyamide is preferably a polyamide comprising m-xylylenediamine units in an amount of 80 mol% or more based on the total repeating units, and among these, poly-m-xylylenediamine is preferred. The meta-type wholly aromatic polyamide has a polymerization degree in a range of 1.3 to 3.0 as measured at 30℃with 97% concentrated sulfuric acid as a solvent.

The meta-type wholly aromatic polyamide obtained as described above is dissolved in a solvent to prepare a spinning dope, but after polymerization, the meta-type wholly aromatic polyamide may be directly used as a spinning dope without separation. As the solvent used herein, an amide-based solvent can be generally used. Examples of the main amide solvents include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc). Among these amide solvents, NMP or DMAc is preferably used from the viewpoints of solubility and handling safety.

The concentration of the solution of the spinning dope may be appropriately selected from the viewpoints of the coagulation rate in the spinning/coagulation step in the subsequent step and the solubility of the polymer, and for example, when the polymer is polymetallic amide and the solvent is NMP, the concentration of the solution is preferably in the range of 10 to 30 mass% (90 to 70 mass% of the solvent+10 to 30 mass% of the polymer).

(2) A step of producing a master pigment dispersion containing 3 or more pigments dispersed therein

In order to produce a dope-dyed meta-type wholly aromatic polyamide fiber having a desired color tone, it is necessary to add a mother pigment dispersion to the spinning dope.

Here, the master pigment dispersion is a pigment dispersion in which a pigment is dispersed in a solvent and adjusted to a predetermined color tone, and generally, 1 pigment is dispersed in many cases, and it may be produced by mixing 2 or more pigments, or a commercially available pigment dispersion may be purchased.

Examples of pigments used in the selected master pigment dispersion include organic pigments such as azo pigments, phthalocyanine pigments, pyrenone pigments, perylene pigments, and anthraquinone pigments, and inorganic pigments such as carbon black, ultramarine pigments, iron oxide red, titanium oxide, and iron oxide pigments, but are not limited thereto.

Then, a master pigment dispersion obtained by dispersing 5 to 50 mass% of the selected pigment (95 to 50 mass% of the amide-based solvent+5 to 50 mass% of the pigment) in the amide-based solvent used in (1) above was prepared, or a master pigment dispersion was selected from commercially available products. When the pigment concentration of the master pigment dispersion is less than 5 mass%, the amount of the master pigment dispersion added increases in the case of producing a dark color, the concentration of the meta-type wholly aromatic polyamide in the spinning solution decreases, and filaments are likely to be broken and unstable in the spinning step. In addition, when the pigment concentration of the master pigment dispersion exceeds 50 mass%, the amount of pigment added becomes very small in the case of producing a light color, and it may be difficult to stably add the pigment.

As described above, at least 3 or more types of master pigment dispersions used in the present application are prepared by using respective master pigment dispersions so that the pigment concentration in the fibers is 1% by mass (99% by mass of polymer+1% by mass of pigment), fully opening the fibers containing the pigment in the above manner in a carding machine, taking out 1.3 g of the fibers, placing the fibers in a circular measuring cell having a diameter of 30mm, and connecting points drawn by using a value a as a horizontal axis and a value b as a vertical axis measured by a spectrocolorimeter SD7000 (manufactured by japan electric color industry) with straight lines not intersecting each other, and it is necessary to select a master pigment dispersion having an area of 1500 or more surrounded by the straight lines. (refer to FIG. 2)

For example, in the case of using 3 types of master pigment dispersions, if the pigment concentration in the fibers is 1% by mass using 3 types of respective master pigment dispersions, points drawn by straight lines not intersecting each other and having the a value of each fiber containing a pigment as described above as the horizontal axis and the b value as the vertical axis are connected, the color becomes triangular as shown in fig. 2, but the color tone a and b values obtained by mixing these 3 types of master pigment dispersions at any ratio are contained in the triangle, and therefore, if the area surrounded by the points drawn by the a value and the b value is large, the larger the range of colors that can be expressed becomes wider. Therefore, in the present application, the area is required to be at least 1500 or more, preferably 1800 or more. When the area is smaller than 1500, the color tone range which can be expressed by the pigment selected is narrowed, the color tone which cannot be expressed is increased, and when the color is changed, the result is obtained that the characteristic of the present application that the color change can be performed by changing the addition ratio of each pigment while spinning cannot be sufficiently exhibited.

In order to expand the range of colors that can be adjusted, it is necessary to select a minimum 3-color master pigment dispersion, and it is desirable to select a master pigment dispersion close to cyan, magenta, yellow, langong, yellow, or the like, which are called three primary colors, in order to maximize the features of the present application. In other words, the preferable ranges of the respective L values of the master pigment dispersion are 35 to 85, a values of-30 to 60, and b values of-30 to 60. Further, in order to further expand the range of adjustable colors, it is more effective to additionally select 4 colors and 5 colors such as green and violet, but if the types of pigments are increased, a lot of pigment boxes need to be provided on the manufacturing line, and there is a possibility that limitation may occur in securing space and the like.

Further, even if another mother pigment dispersion having a value a and b within a range surrounded by a value a and b values of 3 or more mother pigment dispersions is further added, the area surrounded by a curve of a and b values does not change, but may be used when judged to be necessary due to other factors.

On the other hand, in order to effectively produce a dark color, it is also effective to contain a black pigment in the fiber when the content of the pigment is 1 mass%, and the L value of the fiber is 40 or less. That is, in addition to the parent pigment dispersion of (2), a black pigment having an L value of 40 or less of the fiber contained so that the pigment content in the fiber is 1 mass% may be further selected and added to (2).

The black pigment used here is usually 1 pigment, but may be used by mixing 2 or more pigments, and commercially available black pigments may be used. Examples of the black pigment to be mainly selected include iron oxide, carbon black, titanium-based black pigment, and the like, but are not limited thereto.

(3) Adjusting the ratio of the master pigment dispersion to the target color while mixing the master pigment dispersion with the stock solution in order

Next, these 3 or more types of master pigment dispersions were put into the pigment box separately without being mixed in advance, and mixed in the stock solution prepared in (1) in this order while adjusting the addition amounts of the respective dispersions to achieve the target color ratio.

In this case, it is important to mix the fibers to which 3 or more types of the master pigment dispersion are added so that the total of the pigment concentrations is 0.1 to 5.0 mass% (99.9 to 95.0 mass% of the polymer+the total of the pigment concentrations is 0.1 to 5.0 mass%). When the sum of the pigment concentrations is less than 0.1 mass%, stable addition is difficult because the respective addition amounts of the parent pigment dispersions become very small. On the other hand, when the sum of the pigment concentrations exceeds 5.0 mass%, a decrease in the fiber strength can be seen, and the standards in the field of protective clothing become difficult.

As a method of mixing 3 or more types of master pigment dispersions with a stock solution in sequence, for example, as shown in fig. 3, various methods such as a method of continuously feeding the respective pigment tanks together with a spinning stock solution to a head part of a twin-screw extruder by using a constant delivery pump and a method of directly injecting and mixing the respective pigment tanks into a spinning stock solution in a pipe by using a constant delivery pump can be cited.

In this case, since the dope can be continuously added from the tank to the dope, the color can be changed by adjusting the ratio thereof, and the dope in the color changing process is lost, and the loss required for cleaning the apparatus such as the dope tank and the piping is eliminated, thereby enabling efficient production.

(4) Spinning the stock solution mixed with the mother pigment dispersion from the spinning head into a coagulating liquid, and coagulating the obtained stock solution to obtain a fiber

In the step (3), the continuously colored spinning dope is spun into a coagulation liquid and coagulated. The spinning device is not particularly limited, and a conventionally known wet spinning device can be used. In addition, if the wet spinning can be stably performed, the number of spinning holes, the arrangement state, the hole shape, and the like of the spinneret are not particularly limited, and for example, a porous spinning head for a short fiber having 500 to 30000 holes and a spinning hole diameter of 0.05 to 0.2mm may be used. The temperature of the spinning dope at the time of spinning from the spinneret is preferably in the range of 10 to 90 ℃.

For example, an aqueous solution (45 to 60 mass% of an amide solvent+55 to 40 mass% of water) having a concentration of 45 to 60 mass% of an amide solvent free of an inorganic salt is used in a range of 10 to 35 ℃ in the bath to obtain the coagulation bath used for the fiber of the present application. When the concentration of the amide-based solvent is less than 45 mass%, the surface layer becomes thick, and the cleaning efficiency in the cleaning step is lowered, and the solvent may remain in the final fiber. In addition, when the concentration of the amide-based solvent exceeds 60 mass%, uniform coagulation cannot be performed until the inside of the fiber, and therefore, many defects such as monofilament cutting may occur during the fiber forming process. It is preferable that the time for immersing the fiber in the coagulation bath is in the range of 0.1 to 30 seconds.

(5) A step of stretching the fiber in a plastic stretching bath while the coagulated fiber is in a plastic state

Then, the fiber obtained by solidification in the coagulation bath is subjected to a stretching treatment in a plastic stretching bath while the fiber is in a plastic state. The plastic stretching bath is not particularly limited, and a known bath may be used, for example, an aqueous amide solvent solution having an amide solvent content of 0 to 60% by mass and 100 to 40% by mass of water.

In order to obtain the fiber of the present application, the draw ratio in the plastic draw bath is required to be in the range of 3.5 to 5.0 times, and more preferably in the range of 3.7 to 4.5 times. In the production of the fiber of the present application, the solvent can be accelerated to be removed from the coagulated filaments by plastic stretching in a plastic stretching bath at a specific rate in a range.

In the case where the draw ratio in the plastic draw bath is less than 3.5 times, the removal of the solvent from the coagulated filaments is insufficient. In addition, the breaking strength is insufficient, and handling in a processing step such as a spinning step becomes difficult. On the other hand, when the stretch ratio exceeds 5.0 times, the monofilament is broken, and the process stability may be deteriorated.

If the temperature of the plastic stretching bath is preferably in the range of 10 to 90 ℃, more preferably in the range of 20 to 90 ℃, the process stability is good.

(6) A step of sufficiently cleaning the drawn fiber in the plastic drawing bath

Next, the solvent remaining in the fiber was washed. In this step, the fibers stretched in the plastic stretching bath are sufficiently washed. The cleaning is preferably performed in a plurality of stages because of the influence on the quality of the obtained fiber. In particular, the temperature of the cleaning bath in the cleaning process and the concentration of the amide-based solvent in the cleaning bath affect the extraction state of the amide-based solvent from the fibers and the state of water immersed in the fibers from the cleaning bath. Therefore, in order to optimize these conditions, it is preferable that the washing step be divided into a plurality of stages, and the temperature conditions and the concentration conditions of the amide-based solvent be controlled.

The temperature conditions of the cleaning bath and the concentration conditions of the amide-based solvent are not particularly limited as long as the quality of the finally obtained fiber can be satisfied. However, if the initial cleaning bath is set to a high temperature of 60 ℃ or higher, water is immersed in the fibers at once, and thus, large voids are generated in the fibers, resulting in deterioration of quality. Therefore, the initial cleaning bath is preferably set at a low temperature of 30 ℃ or lower.

When the amide-based solvent remains in the fiber, the flame retardancy of the fiber is lowered, and it is not preferable in terms of the processing of a product using the fiber and the environmental safety in use of a product formed using the fiber. Accordingly, the amount of the amide-based solvent contained in the fiber used in the present application is 0.2 mass% or less, more preferably 0.15 mass% or less, and particularly preferably 0.1 mass% or less.

(7) Drying and heat-treating the fiber subjected to the washing step

Next, in the drying treatment step, the fibers subjected to the above-described washing step are required to be subjected to drying and heat treatment (also referred to as dry heat treatment). The method of the dry heat treatment is not particularly limited, and examples thereof include a method using a heat roller, a hot plate, and the like. The meta-type wholly aromatic polyamide fiber used in the present application can be finally obtained by dry heat treatment.

In order to obtain the fiber used in the present application, the heat treatment temperature in the dry heat treatment step is preferably in the range of 260 to 350 ℃, more preferably in the range of 270 to 340 ℃. When the dry heat treatment temperature is less than 260 ℃, the crystallization of the fiber is insufficient, and the shrinkage of the fiber may be high. On the other hand, when the dry heat treatment temperature exceeds 350 ℃, the elongation at break may be significantly reduced. Further, when the dry heat treatment temperature is in the range of 270 to 340 ℃, the breaking strength of the obtained fiber tends to be improved, and thus it is preferable.

If necessary, the meta-type wholly aromatic polyamide fiber subjected to the above-mentioned dry heat treatment may be further subjected to crimping. Further, after the crimping process, the fiber is cut into an appropriate fiber length and supplied to the subsequent process. In addition, the yarn may be wound as a multifilament yarn, as the case may be.

Examples

The present application will be described in detail with reference to examples and comparative examples, but the scope of the present application is not limited to the examples and comparative examples.

In the examples, "part" and "%" are values based on mass unless otherwise specified, and unless otherwise specified, the quantitative ratio indicates the mass ratio. The physical properties of the examples and comparative examples were measured by the following methods.

< Intrinsic Viscosity (IV) >, of

The polymer was dissolved in 97% concentrated sulfuric acid and measured at 30℃using an Oryzer viscometer.

< titre >

The measurement was carried out according to the method A of the metric denier based on JIS L1015, and the apparent denier is expressed.

< tensile Strength, tensile elongation >

The tensile strength and tensile elongation at break measured under the following conditions were set as the tensile strength and tensile elongation of the fiber, based on JIS L1015, model 5565 manufactured by Instron.

(measurement conditions)

Chuck spacing: 20mm of

Initial load: 0.044cN (1/20 g)/dtex

Stretching speed: 20 mm/min

< L value, a value, b value >)

The obtained fibers were sufficiently opened in a carding machine, 1.3 g of the fibers were taken out and put into a measuring circular unit having a diameter of 30mm, and the fibers were measured by using a spectrocolorimeter SD7000 (manufactured by Nippon electric color industry).

Example 1

In a reaction vessel under a dry nitrogen atmosphere, 721.5 parts by mass of N, N-dimethylacetamide (DMAc) having a water content of 100ppm or less was weighed, 97.2 parts by mass (50.18 mol%) of m-phenylenediamine was dissolved in the DMAc, and cooled to 0 ℃. Further, 181.3 parts by mass (49.82 mol%) of isophthaloyl dichloride (hereinafter abbreviated as IPC) was added to the cooled DMAc solution while stirring slowly, and polymerization was performed.

Then, 66.6 parts by mass of calcium hydroxide powder having an average particle diameter of 10 μm or less was weighed and gradually added to the polymer solution after completion of the polymerization reaction, followed by neutralization reaction. After the calcium hydroxide was added, the mixture was stirred for 40 minutes to obtain a transparent polymer stock solution.

From the obtained polymer stock solution, polymetaphenylene diamine was separated, and the IV was found to be 1.65. The polymer concentration in the polymer dope was 17 mass%.

Pigment blue 15 as a blue pigment: 1 (PB15:1), pigment Red 254 (PR 254) as a red pigment, and pigment yellow 138 (PY 138) as a yellow pigment were added to the polymer stock solution so as to be 1% by mass (99% by mass of polymer+1% by mass of pigment) relative to the total mass of the polymer and the pigment, and the resulting spinning stock solution was subjected to spinning, washing, drawing and heat treatment to obtain 3 kinds of colored fibers. After these fibers were crimped and cut into 50mm raw cotton, the L value, the a value and the b value were measured. Points plotted with the a value of the line and the b value of the line plotted on the horizontal axis and the vertical axis are connected by non-intersecting straight lines, and the area of the triangle surrounded by the straight lines is obtained, resulting in 1815.

In a vessel capable of stirring at high speed under a dry nitrogen atmosphere, 90 mass% of N, N-dimethylacetamide (DMAc) having a water content of 100ppm or less was weighed and cooled to 0 ℃. To this DMAc, 10 mass% of the above-selected pigment was added while stirring at a high speed, and then the mixture was stirred for 1 hour to prepare 3 kinds of mother pigment dispersions in which the pigment was uniformly dispersed in DMAc, and the 3 kinds of mother pigment dispersions were stored in a pigment tank.

Using the apparatus shown in fig. 3, the master pigment dispersion was mixed into the polymer stock solution in sequence via a stock solution pipe without pre-mixing, so that PB15: 1=0.31 mass%, pr254=0.35 mass%, and py138=0.54 mass%, and then, the resultant yarn was discharged from a spinneret having a pore diameter of 0.07mm and a pore number of 500 into a coagulation bath having a bath temperature of 30 ℃ to spin the yarn. The composition of the coagulation liquid was water/dmac=45/55 (mass%), and was discharged into the coagulation bath at a yarn speed of 7 m/min, whereby spinning of the first color was performed. The target color of the obtained raw cotton was L value=41.9, a value= -3.0, b value=3.4.

Next, while spinning was continuously performed, color replacement of the second color was performed, and the ratio of the parent pigment dispersion was changed to PB15 with respect to the weight of the polymer in the polymer stock solution: 1=0.05 mass%, pr254=0.17 mass%, PY 138=0.48 mass%. The target color of the raw cotton obtained was L value=53.5, a value=3.9, b value=14.5.

Next, stretching at a stretching ratio of 3.7 times was performed in a plastic stretching bath having a composition of water/dmac=45/55 at a temperature of 40 ℃.

After stretching, the sheet was washed with a bath of water/dmac=70/30 (immersion length 1.8 m) at 20 ℃ followed by a water bath (immersion length 3.6 m) at 20 ℃ and further thoroughly washed by a water bath (warm water) at 60 ℃ (immersion length 5.4 m).

The washed fibers were subjected to a dry heat treatment with a hot roll having a surface temperature of 300 ℃, and then, the fibers were bundled, crimped by a crimping machine, and cut into short fibers of 51mm by a cutter, to obtain raw cotton colored with a pigment-colored stock solution.

The fineness of the raw cotton of the first color was 1.67dtex, the tensile strength was 3.25cN/dtex, and the tensile elongation was 32.3%. The fineness of the raw cotton of the second color was 1.67dtex, the tensile strength was 3.37cN/dtex, and the tensile elongation was 34.3%. These have sufficient strength for protective clothing and the like.

The L value, a value, and b value of the raw cotton obtained were measured using a spectrocolorimeter SD7000 (manufactured by japan electric color industry), and as a result, it was confirmed that the first color was L value=42.1, a value= -3.1, b value=3.3, and the second color was L value=53.3, a value=3.9, and b value=14.9, respectively, which were close to the target color.

In the case of changing the color from the first color to the second color, the color can be changed by continuously spinning the yarn and changing the yarn without cleaning the yarn box and piping, and by slightly wearing the spinning dope and the mother pigment dispersion.

Comparative example 1

A polymer solution was prepared in the same manner as in example 1. IV was 1.65, and the polymer concentration in the polymer stock solution was 17 mass%.

Pigment blue 15 selected as a blue pigment: 1 (PB15:1), pigment Red 254 (PR 254) as a red pigment, and pigment Green 7 (PG 7) as a yellow pigment were added to the polymer dope so as to be 1 mass% with respect to the total mass of the polymer and the pigment, and spinning, washing, drawing and heat treatment were performed using the dope to obtain colored fibers. After the fibers were crimped and cut into 50mm raw cotton, the L value, the a value and the b value were measured. The area surrounded by the straight line was obtained by connecting points plotted with the a value as the horizontal axis and the b value as the vertical axis with the straight line not intersecting with each other, and the result was 683.

Next, each of the mother pigment dispersions was prepared by the same method as in example 1, and stored in a pigment box.

Using the apparatus shown in fig. 3, the master pigment dispersion was mixed into the polymer stock solution in sequence via a stock solution pipe without pre-mixing, so that PB15: 1=0.17 mass%, pr254=0.48 mass%, and pg7=0.35 mass%, and then, the spinning was performed by ejecting the spinning yarn from a spinneret having a pore diameter of 0.07mm and a pore number of 500 into a coagulation bath having a bath temperature of 30 ℃. The composition of the coagulation liquid was water/dmac=45/55 (parts by mass), and was discharged into the coagulation bath at a yarn speed of 7 m/min, whereby spinning of the first color was performed. The target color of the obtained raw cotton was L value=41.9, a value= -3.0, and b value=3.4 as in example 1.

Next, while spinning was continuously performed, the ratio of the mother pigment dispersion was changed as shown in table 2, and the color was changed to the second color so that the target color of the obtained raw cotton was L value=53.5, a value=3.9, and b value=14.5, but as shown in fig. 4, in the range surrounded by the triangle obtained by the combination of these mother pigment dispersions, the maximum b value was only 11.3, and the target color was not in this range, and therefore, only raw cotton having different colors from the target color was obtained.

After stretching, the sheet was washed with a water/dmac=70/30 bath (immersion length 1.8 m) at 20 ℃ followed by a water bath (immersion length 3.6 m) at 20 ℃ and further thoroughly washed with a warm water bath (immersion length 5.4 m) at 60 ℃.

The fineness of the raw cotton of the first color was 1.66dtex, the tensile strength was 3.40cN/dtex, and the tensile elongation was 29.9%. The fineness of the raw cotton of the second color was 1.67dtex, the tensile strength was 3.39cN/dtex, and the tensile elongation was 34.2%, which were sufficient for protective clothing and the like.

As a result of measurement of the L value, a value, and b value of the raw cotton obtained by the measurement with the spectrocolorimeter SD7000 (manufactured by japan electric color industry system), it was confirmed that the first color was L value=41.8, a value= -3.2, and b value=3.6, which were close to the target color, but the second color was L value=53.7, a value=3.0, and b value=6.1, as described above, and only raw cotton of a color different from the target color was obtained.

In addition, when the color is changed from the first color to the second color, the color can be changed without cleaning the paint tank or piping because the color is changed while spinning is continuously performed, and the color can be changed by only slightly consuming the spinning dope and the paint, and the points drawn by the selected mother pigment dispersion on the horizontal axis and the vertical axis are connected by the straight line which does not intersect, and the area surrounded by the straight line is smaller than 1500, so that the target raw cotton color cannot be expressed.

Comparative example 2

A pigment dispersion was prepared in the same manner as in comparative example 1, and pigment blue 15 as a blue pigment used in comparative example 1 was prepared by: 1 (PB15:1) was 0.17 mass%, pigment Red 254 (PR 254) was 0.48 mass%, and pigment Green 7 (PG 7) was 0.35 mass%, both of which were pigments, and stored in a pigment tank. The target color of the first color of the obtained raw cotton was L value=41.9, a value= -3.0, and b value=3.4 as in example 1.

Next, a pigment dispersion was prepared by mixing in advance in the same manner as in comparative example 1, and pigment blue 15 as a blue pigment was prepared: 1 (PB15:1) was 0.03 mass%, pigment Red 254 (PR 254) was 0.17 mass%, and pigment yellow 138 (PY 138) was 0.51 mass%, both of which were pigments, and stored in an iron drum. The target color of the second color of the obtained raw cotton was L value=53.5, a value=3.9, and b value=14.5 as in example 1.

The pre-mixed pigment dispersion of the first color was mixed into the polymer dope so as to be 1.0 mass% with respect to the total mass of the polymer and the pigment by using the apparatus shown in fig. 1, and then was discharged from a spinneret having a pore diameter of 0.07mm and a pore number of 500 into a coagulation bath having a bath temperature of 30 ℃ to be spun. The composition of the coagulation liquid was water/dmac=45/55 (parts by mass), and was discharged into the coagulation bath at a yarn speed of 7 m/min, whereby spinning of the first color was performed.

Next, in order to spin the fibers of the second color, the remaining pigment was extracted from the pigment tank, the tank and surrounding piping were washed 4 times with an uncolored amide-based solvent, after confirming that no pigment remained, the pre-mixed pigment dispersion of the second color stored in the iron barrel was added to the pigment tank, and then, the mixture was mixed into the polymer dope so as to be 1.0 mass% with respect to the weight of the polymer, and the mixture was spun under the same conditions as the first color, thereby performing color change to the second color.

After stretching, the sheet was washed with a water/dac=70/30 bath (immersion length 1.8 m) at 20℃followed by a water bath (immersion length 3.6 m) at 20℃and further thoroughly washed with a warm water bath (immersion length 5.4 m) at 60 ℃.

The fiber of the first color had a fineness of 1.67dtex, a tensile strength of 3.30cN/dtex and a tensile elongation of 34.2%. The second color fiber had a fineness of 1.67dtex, a tensile strength of 3.42cN/dtex, and a tensile elongation of 33.2%. These have sufficient strength for protective clothing and the like.

The L value, a value, and b value of the raw cotton obtained were measured using a spectrocolorimeter SD7000 (manufactured by japan electric color industry), and as a result, it was confirmed that the first color was L value=41.9, a value= -3.1, b value=3.5, and the second color was L value=54.2, a value=4.0, and b value=14.3, respectively, near the target color.

However, when the color is changed from the first color to the second color, the pigment dispersion in the pigment tank needs to be changed, and therefore, the tank, piping, and the like must be cleaned, and the cleaning takes a lot of labor and time, and a lot of amide-based solvent for cleaning is used, resulting in a large loss.

Example 2

The polymer solution was prepared in the same manner as in example. IV was 1.65, and the polymer concentration in the polymer stock solution was 17 mass%.

Pigment blue 15 as a blue pigment: 1 (PB15:1), pigment Red 254 (PR 254) as a red pigment, pigment yellow 93 (PY 93) as a yellow pigment, and pigment Violet 29 (PV 29) as a violet pigment were added to the polymer dope so as to be 1 mass% relative to the total mass of the polymer and the pigment, and spinning, washing, stretching and heat treatment were performed using the obtained spinning dope to obtain 4 kinds of colored fibers. After the fibers were crimped and cut into 50mm raw cotton, the L value, the a value and the b value were measured. Points plotted on the horizontal axis of the a value and the b value are connected by non-intersecting straight lines, and the area of the quadrangle surrounded by the straight lines is obtained, as a result, 2629.

Using the apparatus shown in fig. 3, the master pigment dispersion was mixed into the polymer stock solution in sequence via a stock solution pipe without pre-mixing, so that PB15: 1=0.72 mass%, pr254=0.45 mass%, py93=0.27 mass%, and pv29=0.36 mass%, and then, the resultant yarn was discharged from a spinneret having a pore diameter of 0.07mm and a pore number of 500 into a coagulation bath having a bath temperature of 30 ℃ to spin the yarn. The composition of the coagulation liquid was water/dmac=45/55 (parts by mass), and was discharged into the coagulation bath at a yarn speed of 7 m/min, whereby spinning of the first color was performed. The target color of the obtained raw cotton is L value=36.0, a value=3.4, b value= -24.9.

Next, while spinning was continuously performed, color replacement of the second color was performed, and the ratio of the parent pigment dispersion was changed to PB15 with respect to the total mass of the polymer and the pigment in the polymer stock solution: 1=0.04 mass%, pr254=0.18 mass%, py93=0.58 mass%. The target color of the raw cotton obtained was L value=53.5, a value=3.9, b value=14.5.

The fiber of the first color had a fineness of 1.66dtex, a tensile strength of 3.52cN/dtex and a tensile elongation of 35.2. The second color fiber had a fineness of 1.68dtex, a tensile strength of 3.38cN/dtex, and a tensile elongation of 32.7%. These have sufficient strength for protective clothing and the like.

The L value, a value, and b value of the raw cotton obtained were measured using a spectrocolorimeter SD7000 (manufactured by japan electric color industry system), and as a result, it was confirmed that the first color was L value=36.3, a value=3.4, and b value= -25.2, and the second color was L value=53.9, a value=3.7, and b value=15.0, respectively, near the target color.

In addition, when the color is changed from the first color to the second color, the color can be changed by continuously spinning the yarn and changing the yarn without cleaning the yarn box and the piping, and by slightly wearing the spinning dope and the mother pigment dispersion.

Comparative example 3

A pre-mixed pigment dispersion was prepared in the same manner as in example 1, and pigment blue 15 as a blue pigment used in example 2 was prepared: 1 (PB15:1) was 0.72 mass%, pigment Red 254 (PR 254) was 0.45 mass%, pigment yellow 93 (PY 93) was 0.27 mass%, and pigment Violet 29 (PV 29) was 0.36 mass%, each of which was a red pigment, and the resulting mixture was stored in a pigment box. The target color of the first color of the obtained raw cotton is L value=36.0, a value=3.4, b value= -24.9.

Next, a pigment dispersion was prepared by mixing in advance in the same manner as in example 1, and pigment blue 15 as a blue pigment was prepared: 1 (PB15:1) was 0.04 mass%, pigment Red 254 (PR 254) was 0.18 mass%, and pigment yellow 93 (PY 93) was 0.58 mass%, both of which were pigments, and stored in an iron drum. The target color of the second color of the obtained raw cotton was L value=53.5, a value=3.9, b value=14.5.

The pre-mixed pigment dispersion of the first color was mixed into the polymer dope so as to be 1.8 mass% with respect to the total mass of the polymer and the pigment by using the apparatus shown in fig. 1, and then was discharged from a spinneret having a pore diameter of 0.07mm and a pore number of 500 into a coagulation bath having a bath temperature of 30 ℃ to be spun. The composition of the coagulation liquid was water/dmac=45/55 (parts by mass), and was discharged into the coagulation bath at a yarn speed of 7 m/min, whereby spinning of the first color was performed.

Next, in order to spin the fibers of the second color, the remaining pigment was extracted from the pigment tank, the tank and surrounding piping were washed 4 times with an uncolored amide-based solvent, after confirming that no pigment remained, the pre-mixed pigment dispersion of the second color stored in the iron tank was added to the pigment tank, and then, the mixture was mixed into the polymer dope so that the total mass of the polymer and the pigment was 0.8 mass%, using the apparatus shown in fig. 1, and the fibers were spun under the same conditions as the first color, thereby changing the color to the second color.

Next, stretching at a stretching ratio of 3.7 times was performed in a plastic stretching bath having a composition of water/dmac=45/55 at a temperature of 40 ℃. After stretching, the sheet was washed with a water/dmac=70/30 bath (immersion length 1.8 m) at 20 ℃ followed by a water bath (immersion length 3.6 m) at 20 ℃ and further thoroughly washed with a warm water bath (immersion length 5.4 m) at 60 ℃.

The fiber of the first color had a fineness of 1.65dtex, a tensile strength of 3.30cN/dtex and a tensile elongation of 32.4%. The second color fiber had a fineness of 1.67dtex, a tensile strength of 3.31cN/dtex, and a tensile elongation of 33.2%. These have sufficient strength for protective clothing and the like.

The L value, a value, and b value of the raw cotton obtained were measured using a spectrocolorimeter SD7000 (manufactured by japan electric color industry), and as a result, it was confirmed that the first color was L value=35.7, a value=3.6, and b value= -24.8, and the second color was L value=53.8, a value=3.8, and b value=14.8, respectively, near the target color.

However, when the color is changed from the first color to the second color, the pigment in the pigment tank needs to be changed, and therefore, the tank, piping, and the like must be cleaned, and the cleaning takes a lot of labor and time, and a lot of amide-based solvent for cleaning is used, resulting in a large loss.

Example 3

Pigment blue 15 as a blue pigment: 1 (PB15:1), pigment Red 254 (PR 254) as a red pigment, and pigment yellow 138 (PY 138) as a yellow pigment were added to the polymer dope so as to be 1 mass% with respect to the total mass of the polymer and the pigment, and spinning, washing, drawing and heat treatment were performed with the obtained dope to obtain 3 kinds of colored fibers. After these fibers were crimped and cut into 50mm raw cotton, the L value, the a value and the b value were measured. Points plotted with the a value of the line and the b value of the line plotted on the horizontal axis and the vertical axis are connected by non-intersecting straight lines, and the area of the triangle surrounded by the straight lines is obtained, resulting in 1815.

Further, pigment black 7 (PB 7) as a black pigment was added to the polymer dope so that the total mass of the polymer and the pigment was 1 mass%, and the obtained spinning dope was spun, washed, drawn, and heat-treated to obtain a colored fiber. After the fibers were crimped and cut into 50mm raw cotton, the L value, the a value and the b value were measured. The L value of the obtained fiber was 36.6.

The master pigment dispersion was mixed into the polymer stock solution in this order via stock solution piping without pre-mixing using the apparatus shown in fig. 3, so that PB15: 1=0.02 mass%, pr254=0.15 mass%, py138=0.31 mass%, and pb7=1.72 mass%, and then, the resultant yarn was discharged from a spinneret having a pore diameter of 0.07mm and a pore number of 500 into a coagulation bath having a bath temperature of 30 ℃ to spin the yarn. The composition of the coagulation liquid was water/dmac=45/55 (mass%), and was discharged into the coagulation bath at a yarn speed of 7 m/min, whereby spinning of the first color was performed. The target color of the obtained raw cotton is L value=31.1, a value=0.3, and b value= -3.6.

Next, while spinning was continuously performed, color replacement of the second color was performed, and the ratio of the parent pigment dispersion was changed to PB15 with respect to the total mass of the polymer and the pigment in the polymer stock solution: 1=0.62 mass%, pr254=1.01 mass%, PY 138=0.13 mass%, pb7=0.55 mass%. The target color of the obtained raw cotton is L value=31.6, a value=0.5, b value= -2.1.

The fiber of the first color had a fineness of 1.67dtex, a tensile strength of 3.12cN/dtex and a tensile elongation of 30.7%. The second color fiber had a fineness of 1.67dtex, a tensile strength of 3.21cN/dtex, and a tensile elongation of 30.7%. These have sufficient strength for protective clothing and the like.

As a result of measurement of the L value, a value, and b value of the raw cotton using a spectrocolorimeter SD7000 (manufactured by japan electric color industry), raw liquid colored raw cotton approaching a very dark target color can be produced by using black pigment, with the first color being L value=31.2, a value=0.3, and b value= -3.7, and the second color being L value=31.6, a value=0.6, and b value= -1.7.

When the color is changed from the first color to the second color, the color can be changed by continuously spinning the yarn and changing the yarn without cleaning the yarn box and piping, and by slightly wearing the spinning dope and the mother pigment dispersion.

Comparative example 4

Using the apparatus shown in fig. 3, the master pigment dispersion was mixed into the polymer stock solution in sequence via a stock solution pipe without pre-mixing, so that PB15: 1=0.26 mass%, pr254=1.70 mass%, and py138=3.34 mass%, and then, the resultant yarn was discharged from a spinneret having a pore diameter of 0.07mm and a pore number of 500 into a coagulation bath having a bath temperature of 30 ℃ to spin the yarn. The composition of the coagulation liquid was water/dmac=45/55 (parts by mass), and was discharged into the coagulation bath at a yarn speed of 7 m/min, whereby spinning of the first color was performed. The target color of the obtained raw cotton is L value=31.1, a value=0.3, and b value= -3.6.

As a result of measurement of the L value, a value, and b value of the raw cotton using a spectrocolorimeter SD7000 (manufactured by japan electric color industry), L value=31.4, a value=0.3, and b value= -3.9, a very deep target color can be approached without using a black pigment, but the total pigment concentration is high, and many filament breakage and the like occur in the spinning, drawing, or cleaning steps, and a large amount of loss occurs.

The fiber had a fineness of 1.68dtex, a tensile strength of 1.98cN/dtex, and a tensile elongation of 19.3%, and was not changed to the second color, but only a strength which was not usable for protective clothing or the like.

Physical properties of the dope-dyed meta-type wholly aromatic polyamide fibers obtained in example 1 and comparative examples 1 to 2 are shown in tables 1 and 2, and physical properties of the dope-dyed meta-type wholly aromatic polyamide fibers obtained in example 2 to 3 and comparative examples 3 to 4 are shown in tables 3 and 4.

TABLE 1

TABLE 2

TABLE 3

TABLE 4

Industrial applicability

The present invention relates to a method for efficiently producing a meta-type wholly aromatic polyamide fiber colored with a stock solution for use in protective clothing and the like, which can greatly reduce the loss of waste pigments, amide solvents and the like, and which is environmentally friendly.

Claims

1. A process for producing a liquid-dyed meta-type wholly aromatic polyamide fiber, characterized by comprising the steps of (1) to (7) below,

(1) A step of polymerizing a meta-type aromatic diamine and a meta-type aromatic dicarboxylic acid to obtain a meta-type wholly aromatic polyamide, and preparing a stock solution of an amide solvent;

(2) A step of producing a master pigment dispersion in which at least 3 or more kinds of pigments other than black pigments are dispersed in an amide-based solvent used in (1) in an amount of 5 to 50 mass%, and points drawn by a horizontal axis and a vertical axis of a value of a and b of each fiber containing each of the master pigment dispersions so that the pigment concentration in the fiber becomes 1 mass% are connected by straight lines that do not intersect each other, wherein the area surrounded by the straight lines is 1500 or more;

(3) A step of mixing the stock solution prepared in (1) in sequence so that the sum of pigment concentrations in the fibers is 0.1 to 5.0 mass% without pre-mixing 3 or more types of the master pigment dispersion of (2);

(4) Spinning the stock solution mixed with the mother pigment dispersion in (3) from a spinning head into a coagulating liquid to coagulate the stock solution, thereby obtaining a fiber;

(5) A step of stretching the fiber in a plastic stretching bath when the fiber obtained by solidification in the coagulation bath is in a plastic state;

(6) A step of sufficiently cleaning the drawn fiber in the plastic drawing bath;

(7) And a step of drying and heat-treating the fiber subjected to the washing step.

2. The method for producing a liquid-in-liquid colored meta-type wholly aromatic polyamide fiber as claimed in claim 1, wherein the fiber contains a black pigment dispersion obtained by dispersing a black pigment in an amide-based solvent used in (1) in an amount of 5 to 50 mass%, and the fiber has an L value of 40 or less when the black pigment is contained in the fiber so as to be 1 mass%.

3. The method for producing a liquid-colored meta-type wholly aromatic polyamide fiber as claimed in claim 1 or 2, wherein the parent pigment dispersion has an L value of 35 to 85, an a value of-30 to 60, and a b value of-30 to 60.

4. A meta-type wholly aromatic polyamide fiber is colored with a mother pigment dispersion, wherein the mother pigment dispersion is at least 3 kinds of mother pigment dispersions other than black pigment, and when the mother pigment dispersion is connected to a point of the fiber containing each mother pigment dispersion in a 1 mass% manner by straight lines which do not intersect each other, the area surrounded by the straight lines is at least 1500.