JP7028682B2 - Original meta-type all-aromatic polyamide fiber and its manufacturing method, and flame-retardant spun yarn and flame-retardant cut-off spun yarn made of the fiber. - Google Patents

Description

The present invention relates to a raw meta-type total aromatic polyamide fiber, and more specifically, after the obtained fiber has a combustion limit oxygen index LOI of at least 33 or more and is subjected to a wet heat treatment at 130 ° C. for 2 hours. Related to the highly durable original meta-type total aromatic polyamide fiber having a strength retention rate of 90% or more, a method for producing the same, and a flame-retardant spun yarn and a flame-retardant cut-off spun fiber made of the fiber. Is.

It has been well known that all aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides have excellent heat resistance and flame retardancy, and these all aromatic polyamides are amide-based polarities. It is also well known that it is soluble in a solvent and can be made into a fiber by a method such as dry spinning, wet spinning, semi-dry semi-wet spinning, etc. from a polymer solution in which total aromatic polyamide is dissolved in the solvent. Among these total aromatic polyamides, the fibers of the meta-type total aromatic polyamide represented by polymethaphenylene isophthalamide (sometimes referred to as "meta aramid") are particularly useful as heat-resistant and flame-retardant fibers. It is used in fields that exhibit these characteristics, such as industrial applications such as filters and electronic parts, and disaster prevention and safety clothing applications such as protective clothing where heat resistance, flame resistance, and flame resistance are important. ..

In these fields, the flame retardancy of the meta-type all-aromatic polyamide fiber is required to be higher and more stable from the viewpoint of fire prevention and protection of human life.

Therefore, in order to improve the flame retardancy of the meta-type total aromatic polyamide fiber, a method of adding an organic phosphorus compound, a phosphorus-containing phenol resin, a halogen compound, etc. to the polymer has been proposed, and an organic phosphorus compound containing a halogen atom has been proposed. A method of blending to improve flame retardancy has been proposed (see Patent Document 1 below). However, since the compound used here is a low molecular weight organic compound from the viewpoint of performing stable fiber molding, a part of the compound tends to be discharged or dropped during the fiber molding. In the case of halogen compounds, is facing the recent movement toward dehalogenation, which is concerned about environmental problems.

On the other hand, for meta-type total aromatic polyamide fibers, it is common to use an amide-based organic solvent in the production process, and in this case, it is known that the amide-based solvent remains in the fibers. Therefore, the flame retardancy originally possessed by the meta-type all-aromatic polyamide cannot be sufficiently exhibited, and only those having inferior flame retardancy can be obtained (see Patent Documents 2 to 10 below). ..

Further, in order to improve the flame retardant performance of the meta-type total aromatic polyamide fiber, it is desirable to reduce the amount of this residual solvent, and based on the weight of the meta-type total aromatic polyamide fiber, 0.1 to It contains 10% by weight of layered clay mineral, the amount of solvent remaining in this fiber is 1.0% or less, and the flame retardancy originally possessed by the meta-type total aromatic polyamide is effectively expressed, and the flame retardant is used. A method for obtaining a meta-type total aromatic polyamide fiber having a good flame retardant effect has been proposed without blending. (Reference 11 below) However, there is a limit to the improvement of flame retardancy by this method, and the addition of a flame retardant is indispensable to give more performance, and the initial problem has not been sufficiently solved. Is the reality.

Among the uses of these meta-type total aromatic polyamide fibers, spun yarns obtained by crimping the fibers, cutting them into short pieces, and subsequently performing cotton carding, cotton carding, roving, and rewinding processes are used in the industrial materials field and clothing. It is useful in various fields such as fields, and is suitably used in the field of protective clothing such as firefighting clothes and heat-resistant work clothes.

Here, as a method for producing a spun yarn made of a meta-type total aromatic polyamide, a method by a normal spinning method, for example, a method of a cut-out spinning method can be mentioned (see Patent Document 12). According to the cut-off spinning method, it is necessary to go through complicated processes such as crimping, cutting, cotton carding, cotton carding, kneading, rough spinning, and rewinding, which are necessary processes in the conventional method for manufacturing spun yarn. do not have. Further, according to this method, since the influence of crimping and the disorder of the orientation of the single yarn fiber are small, unlike the conventional spun yarn, it has extremely low elongation, high strength, low crimping degree, and high creep resistance. Heat resistant spun yarn can be obtained.

In the field of clothing, which is the main use of these spun yarns, it is common to use colored fibers because of the demand for design. As a method for obtaining colored fibers, a post-dyeing method in which the fibers are dyed with a dye after fiberization, or a dyeing method in which a pigment is added to a spinning stock solution to form fibers is known.

For example, in Patent Document 13, the easily dyeable meta-aromatic polyamide fiber can be easily dyed with a cationic dye by containing a non-halogenated aromatic condensed phosphoric acid ester, and is flame-retardant. And it is disclosed that a dyed fiber having excellent washing durability can be obtained.

However, there is a limit to the dyeing rate of the dye by this method, and in order to perform dyeing more effectively and sufficiently absorb the dye to the inside of the fiber, the molecular chain of the meta-aromatic polyamide fiber is generally used. Staining with a carrier agent is used. In this case, sufficient residual flame retardant could not be obtained after staining, and the effect was insufficient.

Further, it is known that most of the inexpensive flame retardants, which are easy to add to the fiber, are thermally decomposed at 160 ° C to 300 ° C, so that the decomposition starts at the manufacturing stage of the fiber and a phosphoric acid component is generated. ing. Therefore, there is a problem that the amide-bonded portion of the meta-type total aromatic polyamide fiber is hydrolyzed in a moist heat state to reduce the strength.

Japanese Unexamined Patent Publication No. 53-12281 Special Publication No. 35-14399 Special Publication No. 47-10863 Special Publication No. 48-17551 Japanese Unexamined Patent Publication No. 50-52167 Japanese Unexamined Patent Publication No. 56-31009 Japanese Unexamined Patent Publication No. 8-74121 Japanese Unexamined Patent Publication No. 10-88421 Japanese Patent Application Laid-Open No. 2000-303365 Japanese Unexamined Patent Publication No. 2001-348726 JP-A-2007-254915 Japanese Unexamined Patent Publication No. 02-234932 Japanese Unexamined Patent Publication No. 2004-52166

The problem of the present invention is to solve the problems in the prior art, to show safer and more environmentally friendly flame retardancy, and to provide safer flame retardant performance for a long period of time, especially in protective clothing. It is an object of the present invention to provide a raw meta-type total aromatic polyamide fiber having excellent durability, a method for producing the same, and a flame-retardant spun yarn and a flame-retardant cut-off spun yarn made of the fiber.

As a result of diligent studies to solve the above problems, the present inventor has obtained a flame retardant composed of an organic phosphorus compound that exhibits a specific dissolution behavior with respect to the organic solvent used for producing the meta-type all-aromatic polyamide fiber. , It was clarified that when the phosphorus atom content in the meta-type total aromatic polyamide fiber is 0.2 wt% or more, the original meta-type total aromatic polyamide fiber having high flame retardant performance can be obtained. And reached the present invention.

That is, according to the present invention, the meta-type total aromatic polyamide fiber contains an organic phosphorus compound so that the phosphorus raw yarn content in the meta-type total aromatic polyamide fiber is 0.2 wt% or more. The fiber contains 0.1 to 10.0 wt% of a pigment, has a combustion limit oxygen index LOI of 33 or more, and has a strength retention rate of 90% or more after being subjected to wet heat treatment at 130 ° C. for 2 hours. A certain original meta-type total aromatic polyamide fiber, and
Dissolve 5% or more in N-methyl -2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) and dissolve in N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide. It is characterized by adding an organic phosphorus compound insoluble in a 60% aqueous solution of (DMAc) so that the phosphorus atom content is 0.2 to 5.0 wt% with respect to a spinning dope containing a pigment, and then spinning. The method for producing the original meta-type total aromatic polyamide fiber, and
A flame-retardant spun yarn characterized by containing the above-mentioned original meta-type total aromatic polyamide fiber as a constituent component, and a flame-retardant spun yarn, and
A flame-retardant check-cut spun yarn, which comprises the above-mentioned original meta-type total aromatic polyamide fiber as a constituent component thereof.
Is provided.

According to the present invention, since the flame retardant composed of the organic phosphorus compound is uniformly mixed, there is little decrease in productivity such as thread breakage in the fiber molding process, and the flame retardant remains efficiently in the fiber, so that the amount is small. A flame retardant effect can be obtained depending on the amount added, and an organophosphorus meta-type total aromatic polyamide fiber that does not affect the corrosion of the apparatus when the coagulating liquid is reused can be obtained.

Furthermore, by using the organic phosphorus compound having a thermal decomposition start temperature of 300 ° C. or higher, the generation of components such as phosphoric acid in the fiber can be suppressed, so that the strength retention rate after moist heat treatment at 130 ° C. for 2 hours is 90. % Or more, it is possible to obtain a highly durable original meta-type total aromatic polyamide fiber.

Further, if a spun yarn or a pruned spun yarn containing the above-mentioned uncoated meta-type total aromatic polyamide fiber as a constituent component thereof, the spun yarn or the plucked yarn having excellent flame retardancy and preventing deterioration of moist heat strength is produced. You can get the thread.

Hereinafter, the present invention will be described in detail.

The meta-type total aromatic polyamide in the present invention is a polyamide produced by, for example, solution polymerization or interfacial polymerization using a meta-aromatic diamine and a meta-aromatic dicarboxylic acid halide as raw materials. As long as it does not inhibit the above, it may be a copolymer of other copolymerization components such as para-type.

Examples of the meta-aromatic diamine include metaphenylenediamine, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfone and the like, and halogens in these aromatic rings and substituents such as alkyl groups having 1 to 3 carbon atoms. For example, 2,4-toluylene diamine, 2,6-toluylene diamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene and the like can be used. Among them, the above-mentioned mixed diamine containing 70 mol% or more of meta-phenylenediamine or meta-phenylenediamine is preferable.

Examples of the meta-aromatic dicarboxylic acid halide include isophthalic acid halides such as isophthalic acid chloride and isophthalic acid bromide, and derivatives having a substituent such as a halogen or an alkoxy group having 1 to 3 carbon atoms in these aromatic rings. For example, 3-chlorisophthalic acid chloride and 3-methoxyisophthalic acid chloride can be used. Among them, the above-mentioned mixed carboxylic acid halide containing 70 mol% or more of isophthalic acid chloride or isophthalic acid chloride is preferable.

Examples of the copolymerization component that can be used other than the above diamine and dicarboxylic acid halide include benzene derivatives such as paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobrombenzene, and aminoanisidine as aromatic diamines. , 1,5-naphthylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylketone, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenylmethane and the like, while aromatics. Examples of the dicarboxylic acid halide include terephthalic acid chloride, 1,4-naphthalenedicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, 4,4'-biphenyldicarboxylic acid chloride, 4,4'-diphenylether dicarboxylic acid chloride and the like. ..

If the copolymerization ratio of these copolymerization components is too large, the characteristics of the meta-type total aromatic polyamide tend to deteriorate. Therefore, the copolymerization ratio is preferably 20 mol% or less based on the total acid component of the polyamide. In particular, a suitable meta-type total aromatic polyamide is a polyamide in which 80 mol% or more of all repeating units are composed of metaphenylene isophthalamide units, and polymethphenylene isophthalamide is particularly preferable.
The degree of polymerization of such a meta-type total aromatic polyamide is appropriately in the range of 1.3 to 3.0 in intrinsic viscosity (IV) measured at 30 ° C. using 97% concentrated sulfuric acid as a solvent.

Next, the spinning dope is adjusted by dissolving the meta-type total aromatic polyamide obtained here in a solvent that dissolves it. However, it is also possible to use the meta-type total aromatic polyamide as it is without isolation after polymerization. .. An amide-based solvent can be generally used as the solvent used here, and examples of the main amide-based solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc). can do. Among these, it is preferable to use NMP or DMAc from the viewpoint of solubility and handling safety.

As the solution concentration, an appropriate concentration may be appropriately selected from the viewpoint of the coagulation rate in the spinning / coagulation step, which is the next step, and the solubility of the polymer. For example, the polymer is polymetaphenylene isophthalamide and the solvent is NMP. In the case of, it is usually preferably in the range of 10 to 30% by mass.

In the present invention, a flame retardant composed of an organic phosphorus compound is added to the spinning dope so that the phosphorus atom content in the meta-type total aromatic polyamide fiber is 0.2 wt% or more, and the hue required by the market is further added. In order to obtain the original fiber of the above, a pigment is added to this spun dope in an amount of 0.1 to 10.0 wt% per polymer component. Examples of the pigment used here include organic pigments such as azo-based, phthalocyanine-based, perinone-based, perylene-based, and anthraquinone-based pigments, and inorganic pigments such as carbon black, ultramarine, red iron oxide, titanium oxide, and iron oxide. , Not limited to these.

In the present invention, a flame retardant composed of an organic phosphorus compound is added to this spinning dope, and in particular, 5% or more is dissolved in N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) . Further, by selecting and adding a substance having a property of not dissolving in a 60% aqueous solution of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) , spinning dope It can be dissolved in and mixed uniformly, and the residual rate in the fiber after the fiber molding process is high, resulting in efficient processing.

Here, when an organophosphorus compound that dissolves less than 5% in N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) is used, the amount of flame retardant required for spinning dope is used. Becomes difficult to dissolve. Further, in this case, less than 5% of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) is required to be uniformly dispersed for addition to the spinning dope. If it only dissolves, it will be a very difficult process. Further, even if the particles can be uniformly dispersed, the presence of particles or aggregates of the particles causes many problems such as cutting of the single yarn during the fiber molding process, and even if the fibers can be made into fibers, the strength of the fibers is lowered.

In addition, 5% or more is dissolved in N-methyl-2 -pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) , and N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or Those that are sufficiently soluble in a 60% aqueous solution of dimethylacetamide (DMAc) will lose their flame retardant agent together with this solvent during the fiber molding process, and will exhibit their performance unless a large number of agents are added in advance. It cannot be done, and it is inefficient and improper processing.

The thermal decomposition start temperature of the organic phosphorus compound is preferably 300 ° C. or higher, more preferably 330 ° C. or higher. When this thermal decomposition start temperature is high, not only the flame retardant performance of the organic phosphoric acid compound becomes high, but also the decomposition is suppressed during the heat treatment process performed during the fiber forming process of the meta-type all-aromatic polyamide, and the temperature is kept at 130 ° C. for 2 hours. It is possible to obtain a highly durable original meta-type total aromatic polyamide fiber having a strength retention rate of 90% or more after heat treatment.
Furthermore, by selecting an organic phosphorus compound that does not contain a halogen, it is possible to deal with environmental problems.

The flame retardant made of the organic phosphorus compound used here has the above-mentioned characteristics from among aromatic phosphoric acid esters, aromatic condensed phosphoric acid esters, halogen-containing phosphoric acid esters, and halogen-containing condensed phosphoric acid esters. You can select the one. In particular, aromatic condensed phosphoric acid esters have the property of being 5% or more soluble in a spinning-doped solvent and not soluble in a 60% aqueous solution of this solvent, and are mainly resorcinol bis-. Diphenyl phosphate (RDP) resorcinol bis-dixylenyl phosphate (RDX) and the like can be used.

However, most of the aromatic condensed phosphates having the following structure are liquid at room temperature, and are N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) 60. It is generally not preferable to use it because it easily blends with the aqueous solution and may dissolve 5% or more.

式中、Ｒは非ハロゲン化フェニル基、ＸはビスフェノールＡ残基、ｎは１～３の整数を表す。
一方、下記構造式であらわされる芳香族縮合リン酸エステルは、常温で固体であり、本願の難燃剤として好ましい。

In the formula, R represents a non-halogenated phenyl group, X represents a bisphenol A residue, and n represents an integer of 1 to 3.
On the other hand, the aromatic condensed phosphoric acid ester represented by the following structural formula is solid at room temperature and is preferable as the flame retardant of the present application.

式中、Ｒは非ハロゲン化フェニル基、Ｘは芳香環を有する構造で主に下記のものが好ましい。

In the formula, R is a non-halogenated phenyl group and X is a structure having an aromatic ring, and the following are mainly preferable.

Since the organic phosphorus compound dissolves in N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) in an amount of 5% or more, it can be easily added to the spinning dope, and the organic phosphorus can be easily added. Since both the compound and the meta-type total aromatic polyamide are uniformly mixed in the dissolved state, problems such as single yarn breakage are less likely to occur during the fiber molding process, and stable fiber can be produced.

Further, since the organic phosphorus compound has a property of being insoluble in a 60% aqueous solution of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc), it is insoluble during fiber molding. In the above, there is no elution into the organic solvent aqueous solution which is the coagulating liquid, and it remains efficiently in the fiber, so that the contribution rate to the development of flame retardant performance is high.

Further, when the thermal decomposition start temperature of the organic phosphorus compound is 300 ° C. or higher, decomposition by heat treatment performed during the fiber molding process hardly occurs, and it becomes possible to obtain fibers with less discoloration and reduced strength. Furthermore, by selecting an organic phosphorus compound that does not contain a halogen, it is possible to deal with environmental problems.

Next, the spinning dope prepared as described above is spun into a coagulating liquid and coagulated. The spinning device is not particularly limited, and a conventionally known wet spinning device can be used. Further, the number of spinning holes, the arrangement state, the hole shape, etc. of the spinneret are not particularly limited as long as they can be stably wet-spun. For example, the number of holes is 500 to 30,000 and the diameter of the spinning holes is 0.05. A multi-hole spinneret or the like for a rayon of ~ 0.2 mm may be used.
Further, the temperature of the spinning dope when spinning from the spinneret is appropriately in the range of 10 to 90 ° C.

As an example of the coagulation bath used to obtain the fibers used in the present invention, an aqueous solution containing no inorganic salt and having an amide solvent concentration of 45 to 60% by mass is used in a bath solution temperature range of 10 to 35 ° C.
If the concentration of the amide-based solvent is less than 45% by mass, the skin has a thick structure, the cleaning efficiency in the cleaning step is lowered, and the solvent remains in the final fiber. Further, when the concentration of the amide-based solvent exceeds 60% by mass, uniform coagulation cannot be performed up to the inside of the fiber, which causes many problems such as cutting of the single yarn during the fiber molding process. .. The time for immersing the fiber in the coagulation bath is appropriately in the range of 0.1 to 30 seconds.

Next, while the fibers obtained by coagulation in the coagulation bath are in the plastic state, the fibers are drawn in the plastic drawing bath. The plastic stretched bath liquid is not particularly limited, and conventionally known bath liquids can be adopted.

In order to obtain the fiber of the present invention, the draw ratio in the plastic stretching bath needs to be in the range of 3.5 to 5.0 times, more preferably in the range of 3.7 to 4.5 times. .. In the production of the fiber of the present invention, the removal of solvent from the coagulated yarn can be promoted by performing plastic stretching in a plastic stretching bath within a range of a specific magnification.

When the draw ratio in the plastic drawing bath is less than 3.5 times, the solvent removal from the coagulated yarn becomes insufficient. In addition, the breaking strength becomes insufficient, and handling in a processing process such as a spinning process becomes difficult. On the other hand, when the draw ratio exceeds 5.0 times, single yarn breakage occurs, resulting in poor process stability.
The temperature of the plastic stretch bath is preferably in the range of 10 to 90 ° C. When the temperature is preferably in the range of 20 to 90 ° C., the process stability is good.

Next, the solvent remaining in the fiber is washed. In this step, the fibers stretched in the plastic stretching bath are thoroughly washed. Cleaning is preferably performed in multiple stages because it affects the quality of the obtained fibers. In particular, the temperature of the washing bath and the concentration of the amide-based solvent in the washing bath liquid in the washing step affect the extraction state of the amide-based solvent from the fibers and the infiltration state of water from the washing bath into the fibers. For this reason, it is preferable to control the temperature condition and the concentration condition of the amide-based solvent by having a multi-stage cleaning step also for the purpose of optimizing these states.

The temperature condition and the concentration condition of the amide-based solvent are not particularly limited as long as they can satisfy the quality of the finally obtained fiber. However, when the temperature of the first washing bath is as high as 60 ° C. or higher, water infiltrates into the fibers at once, so that huge voids are generated in the fibers, which causes deterioration of quality. Therefore, it is preferable that the first washing bath has a low temperature of 30 ° C. or lower.

When the solvent remains in the fiber, it is preferable not only to reduce the flame retardancy of the fiber but also to the environmental safety in the processing of the product using the fiber and the use of the product formed by using the fiber. do not have. Therefore, the amount of the solvent contained in the fiber used in the present invention is 0.2% or less, more preferably 0.15% or less, and particularly preferably 0.1% or less.

Next, in the dry heat treatment step, the fibers that have undergone the washing step are dried and heat-treated. The method of dry heat treatment is not particularly limited, and examples thereof include a method using a hot roller, a hot plate, and the like. By undergoing a dry heat treatment, the meta-type total aromatic polyamide fiber used in the present invention can be finally obtained.

In order to obtain the fibers used in the present invention, the heat treatment temperature in the dry heat treatment step needs to be in the range of 260 to 350 ° C., more preferably in the range of 270 to 340 ° C. When the heat treatment temperature is less than 260 ° C., the crystallization of the fiber becomes insufficient and the shrinkage of the fiber becomes high. On the other hand, when the temperature exceeds 350 ° C., the crystallization of the fiber becomes too large, so that the elongation at break is significantly reduced. Further, setting the dry heat treatment temperature in the range of 270 to 340 ° C. contributes to the improvement of the breaking strength of the obtained fiber.

If necessary, the meta-type total aromatic polyamide fiber that has been subjected to the dry heat treatment may be further subjected to a crimping process. Further, after the crimping process, the fiber may be cut to an appropriate fiber length and provided to the next step. In some cases, it may be wound as a multifilament yarn.

In the case of producing a spun yarn containing the meta-type total aromatic polyamide fiber as a constituent component, the meta-type total aromatic polyamide fiber that has been subjected to a dry heat treatment is crimped. The method of performing crimping is not particularly limited, and a known method can be adopted. The number of crimps to be given may be, for example, 5 to 20 T / in, and the degree of crimps may be, for example, 5 to 20 (%), but the number is not particularly limited.

Subsequently, the crimped fibers are cut to obtain short fibers to be subjected to the spinning process. The cutting method is not particularly limited, and a known method can be adopted. For example, a method of cutting long fibers to a predetermined fiber length using a guillotine cutter can be mentioned. Further, the cut length is not particularly limited, and examples thereof include about 10 to 500 mm.

Next, cotton carding, cotton carding, kneading, roving, spinning, finishing and the like can be performed to obtain spun yarn. These steps are not particularly limited, and known methods can be adopted.

Further, in the case of producing a plucked spun yarn containing the above-mentioned meta-type all-aromatic polyamide fiber as a constituent component, crimping is not performed by indentation crimping or the like, and continuous yarn (toe) having no crimping is pulled. Cut off. When the toe has crimps, a part of the crimps tends to remain even if the tow is crimped, which is an obstacle to lowering the elongation of the obtained spun yarn.
When the tow is cut off, it can be cut off in one stage between the pair of supply rollers and the cut-off roller, or it can be cut out in multiple stages by dividing it into a plurality of times.

Further, in order to obtain the cut-out spun yarn of the present invention, conjugation is imparted to the cut-off yarn. In conjugation, it is necessary to continuously conjugate after being cut off, and as means for imparting conjugation, for example, interlacing treatment, fluff wrapping treatment by swirling flow, plying, etc. are used alone. Or it can be used in combination. The overfeed rate when imparting conjugation is preferably 4% or less to maintain a tense state, and more preferably 3% or less. If conjugation is imparted in excess of 4%, the elongation of the obtained spun yarn becomes too high, and creep deformation becomes large, which is not preferable.

Further, in the production of the cut-out spun yarn of the present invention, heat treatment may be performed after winding, a method of causing the heating roller to make a plurality of turns after imparting conjugation, running on a heat plate, and the like. The heat treatment may be continuously performed by the above method or the like.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.
In addition, "part" and "%" in an Example are all based on a mass standard unless otherwise specified, and a mass ratio indicates a mass ratio unless otherwise specified. Each physical property value in Examples and Comparative Examples was measured by the following method.

<Intrinsic viscosity (IV)>
The polymer was dissolved in 97% concentrated sulfuric acid and measured at 30 ° C. using an Ostwald viscometer.
<Solubility evaluation>
The solubility evaluation was carried out with two kinds of evaluation solutions.
(i) 100% organic solvent used in the production of meta-type total aromatic polyamide fibers,
(ii) 60% aqueous solution of the organic solvent (organic solvent 60 / water 40)
The measurement was carried out according to the following procedure.
(1) Add 5 g of the compound to be measured to a flask in which 100 g of the evaluation solution is weighed in advance, stir at 20 ° C. for 2 hours, and then dissolve all of the compound to make the solubility:> 5%.
(2) When undissolved residue is confirmed, the solubility is set to> 5% even when all the undissolved residue is dissolved after standing at 20 ° C. for 12 hours or more.
(3) If undissolved residue is confirmed at this stage, the supernatant liquid is taken out into a 50 g weighing bottle, and the dissolved concentration is determined by weight% by an absolute drying method.

<Fineness>
Based on JIS L1015, the measurement was carried out in accordance with the method A of the positive amount fineness, and it was expressed by the apparent fineness.
<Breaking strength, breaking elongation>
Based on JIS L1015, measurement was performed under the following conditions using model number 5565 manufactured by Instron.
(Measurement condition)
Grab interval: 20 mm
Initial load: 0.044cN (1 / 20g) / dtex
Tensile speed: 20 mm / min <flame retardant LOI value>
The LOI value was determined according to the LOI measurement method of JIS K7201.
<Pyrolysis start temperature>
Thermogravimetric analysis was carried out with Pyris1 TGA (manufactured by PerkinElmer) at a rate of 10 ° C./min, and the temperature at which the sample weight was reduced by 5% was defined as the thermal decomposition start temperature.

[Examples 1 and 2]
(Manufacturing of polymer)
721.5 parts by mass of N, N-dimethylacetamide (DMAc) having a water content of 100 ppm or less was weighed in a reaction vessel under a dry nitrogen atmosphere, and 97.2 parts by mass (50.18 mol) of metaphenylenediamine was contained in the DMAc. %) Was dissolved and cooled to 0 ° C. To this cooled DMAc solution, 181.3 parts by mass (49.82 mol%) of isophthalic acid chloride (hereinafter abbreviated as IPC) was gradually added with stirring to carry out a polymerization reaction.
Next, 66.6 parts by mass of calcium hydroxide powder having an average particle size of 10 μm or less was weighed and slowly added to the polymer solution in which the polymerization reaction was completed to carry out a neutralization reaction. After the addition of calcium hydroxide was completed, the mixture was further stirred for 40 minutes to obtain a transparent polymer solution.
When polymethaphenylene isophthalamide was isolated from the obtained polymer solution and IV was measured, it was 1.65. The polymer concentration in the polymer solution was 17%.

(Manufacturing of spinning dope)
Pigment Blue 15 powder was added to the obtained polymer solution so as to be 2.0 wt% with respect to the polymer component, and the powder was uniformly dispersed. The solubility of resorcinol bis-dixylenyl phosphate, which is an aromatic condensed phosphoric acid ester, in DMAc was measured. The solubility was> 5%, and the solubility was 0% in a 60% DMAc aqueous solution. The thermal decomposition start temperature of this compound was 320 ° C.
This compound was added to the polymer solution as a flame retardant so that the phosphorus content in the fiber was 0.25 wt% and 0.50 wt%, respectively, and defoamed under reduced pressure to obtain a spin dope.

(spinning)
The spinning dope was discharged from a spinning spout having a hole diameter of 0.07 mm and a hole number of 500 into a coagulation bath having a bath temperature of 30 ° C. for spinning. The composition of the coagulating liquid was water / DMAc = 45/55 (parts by mass), and the coagulating liquid was spun by discharging it into a coagulating bath at a yarn speed of 7 m / min.
Subsequently, stretching was carried out at a stretching ratio of 3.7 times in a plastic stretching bath having a composition of water / DMAc = 45/55 at a temperature of 40 ° C.
After stretching, the cells are washed in a water bath at 20 ° C./DMAc=70/30 (immersion length 1.8 m), then in a water bath at 20 ° C. (immersion length 3.6 m), and further in a warm water bath at 60 ° C. (immersion length 5). It was thoroughly washed by passing it through 0.4 m).
The washed fibers were subjected to dry heat treatment with a hot roller having a surface temperature of 300 ° C., and meta-type total aromatic polyamide fibers were sampled in the tow state to measure the breaking strength and breaking elongation.

Further, the obtained towed fibers were bundled, passed through a crimper, crimped, and then cut with a cutter to obtain 51 mm short fibers to obtain raw cotton. The flame-retardant LOI value was measured using the obtained raw cotton. Further, a wet heat treatment was carried out at 130 ° C. for 2 hours under saturated steam, and the breaking strength retention rate before and after that was determined. These results are shown in Table 1.

[Comparative Example 1]
To the spinning dope produced in Example 2, a benzotriazole ultraviolet absorber, tinubin 234, was further added as a light-resistant stabilizer so as to be 3.0 wt% with respect to the polymer component, and defoamed under reduced pressure to obtain a spinning dope. Was carried out in the same manner as in Example 2.

[Example 3]
In Comparative Example 1, resorcinol bis-dixylenyl phosphate, which is an aromatic condensed phosphoric acid ester, was added so that the phosphorus content in the fiber was 0.75 wt%, and the fiber was defoamed under reduced pressure to form a spinning dope. It was carried out in the same manner as in Comparative Example 1.

[Comparative Example 2]
The same procedure as in Example 1 was carried out except that Pigment Blue 15 powder was added to the above polymer solution so as to be 2.0 wt% with respect to the polymer component, dispersed uniformly, and then defoamed under reduced pressure to form a spinning dope. did.

[Comparative Example 3]
After isolating polymethaphenylene isophthalamide from the above polymer solution, it was dissolved in N-methyl-2-pyrrolidone (NMP), which is an amide solvent, so that the polymer concentration was 18%, and Pigment Blue 15 was added to the obtained polymer solution. The powder was added in an amount of 2.0 wt% with respect to the polymer component, dispersed uniformly, and then defoamed under reduced pressure to form a spinning dope, and the same procedure as in Example 1 was carried out.

[Comparative Example 4]
A benzotriazole ultraviolet absorber, tinubin 234, was further added to the spinning dope produced in Comparative Example 3 so as to be 3.0 wt% with respect to the polymer component, and defoamed under reduced pressure to obtain a spinning dope. Was carried out in the same manner as in Comparative Example 3.

[Comparative Examples 5 to 8]
Tris (chloropropyl) phosphate (thermal decomposition start temperature: 160 ° C.), which has a solubility of the organic phosphorus compound in NMP of 5% or more in the polymer solution obtained in Comparative Example 3 but is well dissolved in a DMAc 60% aqueous solution. Was added to the polymer component so that the phosphorus content was 0.39 wt%, 0.47 wt%, 0.59 wt%, 0.68 wt%, and the mixture was defoamed under reduced pressure to form a spinning dope, which was the same as in Comparative Example 3. It was carried out in. The chlorine content for the polymer components in these dope was 2.13%, 2.53%, 2.79%, 3.15%.

The washed fibers were subjected to dry heat treatment with a hot roller having a surface temperature of 300 ° C., and meta-type total aromatic polyamide fibers were sampled in the tow state to measure the breaking strength and breaking elongation.

Further, the obtained towed fibers were bundled, passed through a crimper, crimped, and then cut with a cutter to obtain 51 mm short fibers to obtain raw cotton. The flame-retardant LOI value was measured using the obtained raw cotton. Further, a wet heat treatment was carried out at 130 ° C. for 2 hours under saturated steam, and the breaking strength retention rate before and after that was determined. These results are also shown in Table 1.

The original fibers obtained in Comparative Examples 2 and 3 had low LOI values of 29 and 26 due to the addition of the pigment. Further, in Comparative Example 4 in which the light-resistant stabilizer was added to Comparative Example 3, the LOI value was further lowered to 24.

In order to improve Comparative Example 4, tris (chloropropyl) phosphate, which is a halogen-containing phosphoric acid ester, was added in Comparative Examples 5 to 8. The LOI value improved with the increase in the amount added, but the strength retention rate after the wet heat treatment at 130 ° C. for 2 hours decreased. In Comparative Example 6, the LOI value was 33, but the strength retention rate. However, the durability was 90% or less, which was a low-durability raw fiber.

On the other hand, in Examples 1 and 2, a LOI value of 33 or more and a strength retention rate of 95 after wet heat treatment were used using resorcinol bis-dixylenyl phosphate, which is an aromatic condensed phosphoric acid ester having a thermal decomposition start temperature of 320 ° C. We were able to obtain a highly durable raw fiber with a percentage of% or more.

In Comparative Example 1 in which the light-resistant stabilizer was used in Example 2, a decrease in the LOI value was observed, but as in Example 3, the addition amount of the aromatic condensed phosphoric acid ester was increased to maintain the light resistance. The LOI value could be improved. Further, it was possible to obtain an uncoated fiber having a strength retention rate of 93% after the wet heat treatment at this time and maintaining durability.

[Example 4]
(Manufacturing of polymer)
721.5 parts by mass of N, N-dimethylacetamide (DMAc) having a water content of 100 ppm or less was weighed in a reaction vessel under a dry nitrogen atmosphere, and 97.2 parts by mass (50.18 mol) of metaphenylenediamine was contained in the DMAc. %) Was dissolved and cooled to 0 ° C. To this cooled DMAc solution, 181.3 parts by mass (49.82 mol%) of isophthalic acid chloride (hereinafter abbreviated as IPC) was gradually added with stirring to carry out a polymerization reaction.
Next, 66.6 parts by mass of calcium hydroxide powder having an average particle size of 10 μm or less was weighed and slowly added to the polymer solution in which the polymerization reaction was completed to carry out a neutralization reaction. After the addition of calcium hydroxide was completed, the mixture was further stirred for 40 minutes to obtain a transparent polymer solution.
When polymethaphenylene isophthalamide was isolated from the obtained polymer solution and IV was measured, it was 1.65. The polymer concentration in the polymer solution was 17%.

(Manufacturing of spinning dope)
Pigment Blue 15 powder was added to the obtained polymer solution so as to be 2.0 wt% with respect to the polymer component, and the powder was uniformly dispersed. The solubility of resorcinol bis-dixylenyl phosphate, which is an aromatic condensed phosphoric acid ester, in DMAc was measured. The solubility was> 5%, and the solubility was 0% in a 60% DMAc aqueous solution. The thermal decomposition start temperature of this compound was 320 ° C.
This compound was added to the polymer solution as a flame retardant so as to have a phosphorus content of 0.50 wt% with respect to the polymer component, and defoamed under reduced pressure to obtain a spin dope.

(spinning)
The spinning dope was discharged from a spinning spout having a hole diameter of 0.07 mm and a hole number of 500 into a coagulation bath having a bath temperature of 30 ° C. for spinning. The composition of the coagulating liquid was water / DMAc = 45/55 (parts by mass), and the coagulating liquid was spun by discharging it into a coagulating bath at a yarn speed of 7 m / min.
Subsequently, stretching was carried out at a stretching ratio of 3.7 times in a plastic stretching bath having a composition of water / DMAc = 45/55 at a temperature of 40 ° C.
After stretching, the cells are washed in a water bath at 20 ° C./DMAc=70/30 (immersion length 1.8 m), then in a water bath at 20 ° C. (immersion length 3.6 m), and further in a warm water bath at 60 ° C. (immersion length 5). It was thoroughly washed by passing it through 0.4 m).
After washing, dry heat treatment is performed with a hot roller having a surface temperature of 300 ° C., the fibers are bundled and passed through a crimper to give crimping, and then cut with a cutter to make 51 mm short fibers. Obtained. The flame retardant LOI value was measured using the obtained raw cotton, and the flame retardancy was as high as 36. Further, a wet heat treatment was carried out at 130 ° C. for 2 hours under saturated steam, and the breaking strength retention rate before and after that was determined. As a result, no decrease in strength was observed at 96%. These results are shown in Table 2.

(Making spun yarn)
Further, the obtained uncoated raw cotton was used in a normal spinning process to produce a 20-count spun yarn. The spun yarn was also subjected to wet heat treatment at 130 ° C. for 2 hours under saturated steam, and the breaking strength retention rate before and after that was determined. As a result, the strength was maintained at 94% even in a harsh environment under high temperature saturated steam like raw cotton. It has been shown to be durable in hot, humid and harsh environments where protective clothing such as firefighting clothing and heat-resistant workwear may be used. These results are shown in Table 2.

[Example 5]
To the spinning dope produced in Example 4, a benzotriazole ultraviolet absorber, tinubin 234, was further added as a light-resistant stabilizer so as to be 3.0 wt% with respect to the polymer component, and further, an aromatic condensed phosphoric acid ester was added. The same procedure as in Example 4 was carried out except that resorcinol bis-dixylenyl phosphate was added so that the phosphorus content was 0.75 wt% with respect to the polymer component, and the mixture was defoamed under reduced pressure to form a spinning dope. The LOI value of the raw cotton tended to decrease due to the addition of the ultraviolet absorber, but maintained a high value of 33 because the flame retardant of the present invention was added. Further, when the breaking strength retention rates of the raw cotton and the spun yarn in the wet heat treatment under saturated steam at 130 ° C. for 2 hours were obtained, they were 93% and 91%, respectively, and no decrease in strength was observed. It had the durability required for protective clothing such as heat-resistant work clothes. These results are shown in Table 2.

[Comparative Example 9]
Polymethaphenylene isophthalamide was isolated from the polymer solution obtained according to the production of the polymer described in Example 4, and then dissolved in N-methyl-2-pyrrolidone (NMP), which is an amide-based solvent, so that the polymer concentration was 18%. Then, the powder of Pigment Blue 15 was added to the obtained polymer solution so as to be 2.0 wt% with respect to the polymer component, and the benzotriazole ultraviolet absorber chinubin 234 as a light-resistant stabilizer was added to the polymer component. It was added so as to be 0 wt%, dispersed uniformly, and then defoamed under reduced pressure to obtain a spinning dope. Further, the same procedure as in Example 4 was carried out except that the composition of the coagulating liquid was water / NMP = 70/30 (parts by mass). When the breaking strength retention rates of this raw cotton and spun yarn in moist heat treatment under saturated steam at 130 ° C for 2 hours were determined, they were 97% and 95%, respectively, and no decrease in strength was observed, and firefighting clothes and heat-resistant work were performed. Although it had the durability required for protective clothing such as clothes, the LOI value of raw cotton became as low as 24 due to the addition of ultraviolet absorbers and organic pigments, and the human body was used as protective clothing for firefighting clothing and heat-resistant work clothing. It became insufficient for the purpose of protecting. These results are shown in Table 2.

[Comparative Examples 10 and 11]
In the polymer solution obtained in Comparative Example 9, the solubility of the organic phosphorus compound in NMP is 5% or more, but the tris (chloropropyl) phosphate (thermal decomposition start temperature: 160 ° C.) is well dissolved in a 60% NMP aqueous solution. Was added to the polymer component so that the phosphorus content was 0.47 wt% and 0.68%, and the mixture was defoamed under reduced pressure to form a spinning dope, but the same procedure as in Comparative Example 9 was carried out. The chlorine content with respect to the polymer component in each spinning dope was 2.53% and 3.15%. The LOI value of these raw cottons was improved from Comparative Example 1 by the addition of a flame retardant and showed high flame retardancy of 33 and 37. When the breaking strength retention rate was determined, it was 89% and 79% for raw cotton and 87% and 76% for spun yarn, showing a decrease in strength, and protective clothing such as firefighting clothes and heat-resistant work clothes could be used. Durability is weak in a harsh environment with high temperature and humidity. These results are shown in Table 2.

[Example 6]
(Manufacturing of polymer)
721.5 parts by mass of N, N-dimethylacetamide (DMAc) having a water content of 100 ppm or less was weighed in a reaction vessel under a dry nitrogen atmosphere, and 97.2 parts by mass (50.18 mol) of metaphenylenediamine was contained in the DMAc. %) Was dissolved and cooled to 0 ° C. To this cooled DMAc solution, 181.3 parts by mass (49.82 mol%) of isophthalic acid chloride (hereinafter abbreviated as IPC) was gradually added with stirring to carry out a polymerization reaction.
Next, 66.6 parts by mass of calcium hydroxide powder having an average particle size of 10 μm or less was weighed and slowly added to the polymer solution in which the polymerization reaction was completed to carry out a neutralization reaction. After the addition of calcium hydroxide was completed, the mixture was further stirred for 40 minutes to obtain a transparent polymer solution.
When polymethaphenylene isophthalamide was isolated from the obtained polymer solution and IV was measured, it was 1.65. The polymer concentration in the polymer solution was 17%.

(Manufacturing of spinning dope)
Pigment Blue 15 powder was added to the obtained polymer solution so as to be 2.0 wt% with respect to the polymer component, and the powder was uniformly dispersed. The solubility of resorcinol bis-dixylenyl phosphate, which is an aromatic condensed phosphoric acid ester, in DMAc was measured. The solubility was> 5%, and the solubility was 0% in a 60% DMAc aqueous solution. The thermal decomposition start temperature of this compound was 320 ° C.
This compound was added to the polymer solution as a flame retardant so as to have a phosphorus content of 0.50 wt% with respect to the polymer component, and defoamed under reduced pressure to obtain a spin dope.

(spinning)
The spinning dope was discharged from a spinning spout having a hole diameter of 0.07 mm and a hole number of 500 into a coagulation bath having a bath temperature of 30 ° C. for spinning. The composition of the coagulating liquid was water / DMAc = 45/55 (parts by mass), and the coagulating liquid was spun by discharging it into a coagulating bath at a yarn speed of 7 m / min.
Subsequently, stretching was carried out at a stretching ratio of 3.7 times in a plastic stretching bath having a composition of water / DMAc = 45/55 at a temperature of 40 ° C.
After stretching, the cells are washed in a water bath at 20 ° C./DMAc=70/30 (immersion length 1.8 m), then in a water bath at 20 ° C. (immersion length 3.6 m), and further in a warm water bath at 60 ° C. (immersion length 5). It was thoroughly washed by passing it through 0.4 m).
After washing, a dry heat treatment was performed with a hot roller having a surface temperature of 300 ° C. to obtain continuous yarns (tows) having no crimping without applying crimping by indentation and crimping. The flame-retardant LOI value was measured using the obtained continuous yarn (tow) having no crimp, and showed high flame retardancy of 36. Further, a wet heat treatment was carried out at 130 ° C. for 2 hours under saturated steam, and the breaking strength retention rate before and after that was determined. As a result, no decrease in strength was observed at 96%. These results are shown in Table 3.

(Making cut-out spun yarn)
The tow of the obtained polymethaphenylene isophthalamide fiber is towed between a pair of rollers at intervals of 600 mm at a check-off ratio of 21 times, and subsequently, by continuously imparting conjugation under the following conditions, the check-off is performed. Obtained cut-spun yarn. The cut-out spun yarn was also subjected to wet heat treatment at 130 ° C. for 2 hours under saturated steam, and the breaking strength retention rate before and after that was determined. Similar to (Tow), its strength is maintained even in a harsh environment under high temperature saturated steam, and it is durable in a hot and humid harsh environment where protective clothing such as firefighting clothes and heat-resistant work clothes may be used. Was seen. These results are shown in Table 3.

[Example 7]
To the spinning dope produced in Example 6, a benzotriazole ultraviolet absorber, tinubin 234, was further added as a light-resistant stabilizer so as to be 3.0 wt% with respect to the polymer component, and further, an aromatic condensed phosphoric acid ester was added. The same procedure as in Example 6 was carried out except that resorcinol bis-dixylenyl phosphate was added so that the phosphorus content was 0.75 wt% with respect to the polymer component, and the mixture was defoamed under reduced pressure to form a spinning dope. The LOI value of the continuous yarn (tow) having no crimping before the cut-off process tends to decrease due to the addition of the ultraviolet absorber, but it is as high as 33 because the flame retardant of the present invention is added. I was keeping it. Further, when the breaking strength retention rates of the tow and the cut-out spun yarn in the wet heat treatment under saturated steam at 130 ° C. for 2 hours were obtained, they were 93% and 91%, respectively, and no decrease in strength was observed. It had the durability required for protective clothing such as clothes and heat-resistant work clothes. These results are shown in Table 3.

[Comparative Example 12]
Polymethaphenylene isophthalamide was isolated from the polymer solution obtained according to the production of the polymer described in Example 6, and then dissolved in N-methyl-2-pyrrolidone (NMP), which is an amide-based solvent, so that the polymer concentration was 18%. Then, the powder of Pigment Blue 15 was added to the obtained polymer solution so as to be 2.0 wt% with respect to the polymer component, and the benzotriazole ultraviolet absorber chinubin 234 as a light-resistant stabilizer was added to the polymer component. It was added so as to be 0 wt%, dispersed uniformly, and then defoamed under reduced pressure to obtain a spinning dope. Further, the same procedure as in Example 6 was carried out except that the composition of the coagulating liquid was water / NMP = 70/30 (parts by mass). The breaking strength retention rates of the continuous yarn (toe) without crimping before the cut-off process and the cut-off spun yarn in the wet heat treatment under saturated steam at 130 ° C. for 2 hours were determined and found to be 97% and 93, respectively. %, No decrease in strength was observed, and it had the durability required for protective clothing such as firefighting clothing and heat-resistant workwear, but the LOI value of tow was 24 due to the addition of ultraviolet absorbers and organic pigments. It became a low value, and it became insufficient for the purpose of protecting the human body as protective clothing such as firefighting clothes and heat-resistant work clothes. These results are shown in Table 3.

[Comparative Examples 13 and 14]
Tris (chloropropyl) phosphate (thermal decomposition start temperature: 160 ° C.), which has a solubility of the organic phosphorus compound in NMP of 5% or more in the polymer solution obtained in Comparative Example 12 but is well dissolved in a 60% aqueous solution of NMP. Was added to the polymer component so that the phosphorus content was 0.47 wt% and 0.68%, and the mixture was defoamed under reduced pressure to form a spinning dope, but the same procedure as in Comparative Example 12 was carried out. The chlorine content with respect to the polymer component in each spinning dope was 2.53% and 3.15%. The LOI value of the continuous yarn (toe) having no crimping before the cut-off process was improved from Comparative Example 1 by the addition of the flame retardant, and showed high flame retardancy of 33 and 37. When the breaking strength retention rate in the wet heat treatment under saturated steam at 130 ° C. for 2 hours was obtained for the cut-out spun yarn, it was 89% and 79% for the tow and 86% and 74% for the cut-off spun yarn, resulting in a decrease in strength. However, the durability was weak in the harsh environment of high temperature and humidity where protective clothing such as firefighting clothes and heat-resistant work clothes may be used. These results are shown in Table 3.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to impart high light resistance to high durability of the original meta-type total aromatic polyamide fiber used for protective clothing, and even if the protective clothing is worn for a long period of time, discoloration and deterioration are less likely to occur. It is possible to provide a textile material as a product.

Claims (8)

A meta-type total aromatic polyamide fiber containing an organic phosphorus compound so that the phosphorus atom content in the meta-type total aromatic polyamide fiber is 0.2 wt% or more, and the fiber contains 0.1 pigment. It contains ~ 10.0 wt%, has a combustion limit oxygen index LOI of 33 or more, and has a strength retention rate of 90% or more after moist heat treatment at 130 ° C. for 2 hours. fiber. The original meta-type total aromatic polyamide fiber according to claim 1, wherein the organic phosphorus compound contained in the fiber has a thermal decomposition start temperature of 300 ° C. or higher. The organic phosphorus compound is dissolved in N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) in an amount of 5% or more, and N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) is dissolved. ), Or the original meta-type total aromatic polyamide fiber according to claim 1 or 2, which is insoluble in a 60% aqueous solution of dimethylacetamide (DMAc) . The original meta-type total aromatic polyamide fiber according to any one of claims 1 to 3, wherein the halogen content in the fiber is 0.2 wt% or less. The original meta-type total aromatic polyamide fiber according to any one of claims 1 to 4, wherein the color difference ΔE before and after the dry heat treatment when the fiber is dry heat treated at 180 ° C. for 30 seconds is 0.75 or less. Dissolve 5% or more in N-methyl -2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide (DMAc) and dissolve in N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or dimethylacetamide. It is characterized by adding an organic phosphorus compound insoluble in a 60% aqueous solution of (DMAc) so that the phosphorus atom content is 0.2 to 5.0 wt% with respect to a spinning dope containing a pigment, and then spinning. A method for producing a fully aromatic polyamide fiber of the original meta-type. A flame-retardant spun yarn comprising the original meta-type total aromatic polyamide fiber according to any one of claims 1 to 5 as a constituent component thereof. A flame-retardant cut-off spun yarn comprising the original meta-type total aromatic polyamide fiber according to any one of claims 1 to 5 as a constituent component thereof.