JP2018154943A - Meta-type wholly aromatic polyamide fiber having excellent flame retardancy and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white meta-type wholly aromatic polyamide fiber that is safe and shows high flame retardancy friendly to the environment.SOLUTION: An organic phosphorus compound, which is dissolved in an organic solvent by 5% or more but is insoluble in a 60% aqueous solution of the organic solvent, is added to a spinning dope so that a phosphorus atom content is 0.2-5.0 wt.%, and after that, spinning is performed.SELECTED DRAWING: None

Description

  The present invention relates to a white meta-type wholly aromatic polyamide fiber. More specifically, the present invention relates to a white meta-type wholly aromatic having flame retardancy that gives the obtained fiber a limiting oxygen index LOI of at least 33 or more. It relates to polyamide fibers.

  Conventionally, it is well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides are excellent in heat resistance and flame retardancy, and these wholly aromatic polyamides are amide polar It is also well known that it is soluble in a solvent and can be formed into a fiber from a polymer solution in which a wholly aromatic polyamide is dissolved in the solvent by a method such as dry spinning, wet spinning, semi-dry semi-wet spinning, or the like. Among these wholly aromatic polyamides, fibers of meta-type wholly aromatic polyamides (sometimes referred to as “meta-aramid”) represented by polymetaphenylene isophthalamide are particularly useful as heat-resistant and flame-retardant fibers. It is used in fields that exhibit these characteristics, for example, 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 meta-type wholly aromatic polyamide fibers is required to be higher and more stable from the viewpoints of fire prevention and human life protection.

  Therefore, in order to improve the flame retardancy of the meta-type wholly 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. A method for improving flame retardancy by blending has been proposed (see Patent Document 1 below). However, since these agents added so as not to hinder the stable processing of the fibers are low molecular weight organic compounds, some of them tend to be discharged and dropped during the fiber forming process. Is against the recent trend of dehalogenation, which is concerned about environmental problems due to the halogen content.

  On the other hand, meta-type wholly aromatic polyamide fibers generally use an amide-based organic solvent in the production process, and this is known to leave amide-based solvents in the fibers. Thus, the flame retardancy inherently possessed by the meta-type wholly aromatic polyamide cannot be sufficiently exhibited, and only the inferior flame retardancy can be obtained (see Patent Documents 2 to 10 below). .

  In order to improve the flame retardant performance of the meta-type wholly aromatic polyamide fiber, it is desirable to reduce the amount of the residual solvent, and the layered form is 0.1 to 10% by weight based on the weight of the meta-type wholly aromatic polyamide. Contains clay minerals, makes the amount of solvent remaining in this fiber 1.0% or less, effectively develops the flame retardancy inherent in meta-type wholly aromatic polyamides, and does not contain flame retardants Has proposed a method for obtaining a meta-type wholly aromatic polyamide fiber having a good flame retardant effect. However, there is a limit to the flame retardancy in this method, and the addition of a flame retardant is indispensable to give more performance, and the original problem has not been sufficiently solved.

  Furthermore, many of the inexpensive flame retardants that are easy to add into the fiber are thermally decomposed at 160 ° C. to 300 ° C., so that the decomposition starts at the fiber production stage and turns yellow. I couldn't get it.

  On the other hand, in the readily dyeable meta-type aromatic polyamide fiber, it can be easily dyed with a cationic dye by containing a non-halogenated aromatic condensed-type phosphate ester, and also has flame retardancy and washing durability. It is disclosed that excellent dyed fibers can be obtained (Document 12 below).

  However, the fiber obtained by this method is yellowish and there is no problem when coloring the fiber by dyeing, but it is insufficient as a white meta-type aromatic polyamide fiber.

JP-A-53-122817 Japanese Patent Publication No. 35-14399 Japanese Patent Publication No.47-10863 Japanese Patent Publication No. 48-17551 JP 50-52167 A Japanese Patent Laid-Open No. 56-31209 JP-A-8-74121 JP-A-10-88421 JP 2000-303365 A JP 2001-348726 A JP 2007-254915 A JP 2004-52166 A

  An object of the present invention is to provide a white meta-type wholly aromatic polyamide fiber that eliminates the problems in the prior art and exhibits higher flame retardancy that is safer and more environmentally friendly.

  As a result of intensive studies to solve the above problems, the present inventor has obtained a flame retardant comprising an organic phosphorus compound exhibiting a specific dissolution behavior with respect to an organic solvent used in the production of a meta-type wholly aromatic polyamide fiber. Investigate that white meta-type wholly aromatic polyamide fiber with high flame retardancy can be obtained when the phosphorus atom content in the meta-type wholly aromatic polyamide fiber is 0.2 wt% or more. The present invention has been reached.

That is, according to the present invention, there is provided a meta-type wholly aromatic polyamide fiber containing an organic phosphorus compound so that the phosphorus atom content in the meta-type wholly aromatic polyamide fiber is 0.2 wt% or more, When dissolved in an organic solvent, 5% or more of a white meta-type wholly aromatic polyamide fiber excellent in flame retardancy with a flame critical oxygen index LOI of 33 or more and a lightness L value of 85 or more. A white meta-type wholly aromatic compound, characterized in that an organophosphorus compound that is insoluble in an aqueous solution is added to the spinning dope so that the phosphorus atom content is 0.2 to 5.0 wt%, and then spun. A method for producing a polyamide fiber is provided.

  According to the present invention, since the flame retardant composed of an organophosphorus compound is uniformly mixed, there is little decrease in productivity such as yarn breakage in the fiber forming process, and the flame retardant remains efficiently in the fiber, so that it is small. A flame retardant effect can be obtained with the added amount, and white meta-type wholly aromatic polyamide fibers that do not affect the corrosion of the apparatus when the coagulating liquid is reused can be obtained.

  Hereinafter, the present invention will be described in detail.

  The meta-type wholly aromatic polyamide in the present invention is a polyamide 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. For example, other copolymer components such as the para type may be copolymerized within a range that does not inhibit the above.

  Examples of the meta-type aromatic diamine include metaphenylene diamine, 3,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl sulfone and the like, and substitution of halogens, alkyl groups having 1 to 3 carbon atoms, etc. on these aromatic rings. A derivative having a group such as 2,4-toluylenediamine, 2,6-toluylenediamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene and the like can be used. Especially, said mixed diamine containing 70 mol% or more of metaphenylenediamine or metaphenylenediamine is preferable.

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

  Examples of copolymer components that can be used other than the above diamine and dicarboxylic acid halide include aromatic diamines such as paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene, and aminoanisidine. 1,5-naphthylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ketone, 4,4′-diaminodiphenylamine, 4,4′-diaminodiphenylmethane, etc., while aromatic 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′-diphenyl ether dicarboxylic acid chloride, and the like. .

  The copolymerization ratio of these copolymer components is preferably 20 mol% or less based on the total acid component of the polyamide, since the properties of the meta-type wholly aromatic polyamide are liable to deteriorate if it is too large. In particular, a suitable meta-type wholly aromatic polyamide is a polyamide in which 80 mol% or more of all repeating units are composed of metaphenylene isophthalamide units, and among them, polymetaphenylene isophthalamide is preferable.

  The degree of polymerization of such a meta-type wholly aromatic polyamide is suitably in the range of 1.3 to 3.0 in terms of intrinsic viscosity (IV) measured at 97C using 97% concentrated sulfuric acid as a solvent.

  Next, the spinning dope is prepared by dissolving in a solvent that dissolves the meta-type wholly aromatic polyamide obtained here, but it is also possible to make the spinning dope as it is without isolating the meta-type wholly aromatic polyamide after polymerization. . An amide solvent can be generally used as the solvent used here, and examples of the main amide solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like. can do. Of these, NMP or DMAc is preferably used from the viewpoints of solubility and handling safety.

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

  In the present invention, a flame retardant composed of an organophosphorus compound is added to the spinning dope so that the phosphorus atom content in the meta-type wholly aromatic polyamide fiber is 0.2 wt% or more. It is possible to dissolve in the spinning dope and mix evenly by selecting and adding a material that dissolves above and does not dissolve in a 60% aqueous solution of this solvent. The residual rate is high and the processing is efficient.

  Here, when an organic phosphorus compound that dissolves less than 5% in the solvent is used, it becomes difficult to dissolve the flame retardant in an amount necessary for the spinning dope. Further, in this case, in order to add to the spinning dope, it is necessary to disperse uniformly, but this is a very difficult process. Even if the particles can be uniformly dispersed, the presence of particles or agglomerates of particles often causes problems such as a single yarn being cut during fiber forming processing, and even if fibers are formed, the strength of the fibers decreases.

  In addition, those that dissolve 5% or more in the solvent of the spinning dope and sufficiently dissolve in the 60% aqueous solution of this solvent will also cause the flame retardant to fall off together with this solvent during fiber forming processing, and add many agents in advance. Otherwise, the performance cannot be realized, and the processing becomes inefficient and inappropriate.

  The thermal decomposition starting temperature of the organophosphorus compound is preferably 300 ° C. or higher, and more preferably 330 ° C. or higher. If this thermal decomposition start temperature is high, not only the flame retardancy performance by the organic phosphoric acid compound will be high, but also the discoloration and flame retardancy caused by the decomposition will be suppressed during the heat treatment performed during the fiber molding process of the meta-type wholly aromatic polyamide. It can prevent a decline in sex.

  Furthermore, it is possible to cope with environmental problems by selecting the organic phosphorus compound that does not contain halogen.

  The flame retardant comprising the organic phosphorus compound used here has the above characteristics among aromatic phosphate esters, aromatic condensed phosphate esters, halogen-containing phosphate esters, and halogen-containing condensed phosphate esters. You can choose one. In particular, those having the property of being dissolved in a solvent of spinning dope by 5% or more and not dissolving in a 60% aqueous solution of this solvent are mostly aromatic condensed phosphate esters, mainly resorcinol bis- Diphenyl phosphate (RDP), resorcinol bis-dixylenyl phosphate (RDX), and the like can be used.

  However, many of the aromatic condensed phosphate esters having the following structures are mostly liquid at room temperature, and are easily used in a 60% aqueous solution of a spinning dope solvent and may be dissolved by 5% or more. It is not preferable.

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。

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 phosphate represented by the following structural formula is solid at room temperature and is preferable as a flame retardant for 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.

  The organophosphorus compound dissolves in an organic solvent used for the production of the meta-type wholly aromatic polyamide fiber by 5% or more, so that it can be easily added to the spinning dope. Since the fibers are uniformly mixed in a dissolved state, problems such as single yarn breakage are less likely to occur during fiber forming processing, and stable fibers can be produced.

  Further, since the organophosphorus compound has a characteristic that it becomes insoluble in the 60% aqueous solution of the organic solvent, there is no elution into the aqueous organic solvent solution that becomes a coagulation liquid during fiber forming processing, and the efficiency in the fiber. Since it remains well, the rate of contribution to the development of flame retardancy increases.

  Furthermore, when the thermal decomposition start temperature of the organophosphorus compound is 300 ° C. or higher, decomposition due to heat treatment carried out during fiber forming processing hardly occurs, discoloration and strength decrease are reduced, and a white color having an L value of 85 or higher. Fibers can be obtained. Furthermore, it is possible to cope with environmental problems by selecting an organic phosphorus compound that does not contain halogen.

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. Moreover, the number of spinning holes, the arrangement state, the hole shape and the like 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 spinning hole diameter is 0.05. A multi-hole spinneret for ˜0.2 mm sufu may be used.
The spinning dope temperature when spinning from the spinneret is suitably 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 an amide solvent concentration of 45 to 60% by mass not containing an inorganic salt is used in a bath liquid temperature range of 10 to 35 ° C. If the amide solvent concentration is less than 45% by mass, the skin has a thick structure, the washing efficiency in the washing step is lowered, and the solvent remains in the final fiber. Further, when the amide solvent concentration exceeds 60% by mass, uniform coagulation cannot be performed until reaching the inside of the fiber, and thus there are many problems such as a single yarn being cut during fiber forming processing. . In addition, the range of 0.1-30 seconds is suitable for the immersion time of the fiber in a coagulation bath.

  Next, while the fiber obtained by coagulation in the coagulation bath is in a plastic state, the fiber is drawn in the plastic drawing bath. It does not specifically limit as a plastic drawing bath liquid, A conventionally well-known bath liquid can be employ | adopted.

  In order to obtain the fiber of the present invention, the draw ratio in the plastic drawing 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 solvent removal from the coagulated yarn can be promoted by plastic drawing in a range of a specific magnification in a plastic drawing bath.

  When the draw ratio in the plastic drawing bath is less than 3.5 times, the solvent removal from the coagulated yarn becomes insufficient. Further, 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 stretching bath is preferably in the range of 10 to 90 ° C. Preferably process stability is good in the range of 20-90 degreeC of temperature.

  Next, the solvent remaining in the fiber is washed. In this step, the fiber drawn in the plastic drawing bath is thoroughly washed. Washing is preferably performed in multiple stages because it affects the quality of the resulting fiber. In particular, the temperature of the cleaning bath in the cleaning step and the concentration of the amide solvent in the cleaning bath liquid affect the state of extraction of the amide solvent from the fibers and the state of penetration of water from the cleaning bath into the fibers. For this reason, it is preferable to control the temperature condition and the concentration condition of the amide solvent by setting the washing process in multiple stages for the purpose of bringing them into an optimum state.

  The temperature condition and the amide solvent concentration condition 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 ° C. or higher, water enters the fiber at a stretch, and a huge void is generated in the fiber, resulting in deterioration of quality. For this reason, it is preferable that the first washing bath has a low temperature of 30 ° C. or lower.

  When the solvent remains in the fiber, in addition to reducing the flame retardancy of the fiber, the processing of the product using the fiber and the environmental safety in the use of the product formed using the fiber Is also not preferred. For this reason, the amount of 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 fiber that has undergone the washing step is dried and heat treated. Although it does not specifically limit as a method of dry heat processing, For example, the method of using a hot roller, a hot plate, etc. can be mentioned. By performing the dry heat treatment, finally, the meta type wholly aromatic polyamide fiber used in the present invention can be obtained.

  In order to obtain the fiber used for this invention, it is necessary to make the heat processing temperature in a dry heat treatment process into the range of 260-350 degreeC, and it is more preferable to set it as the range of 270-340 degreeC. When the heat treatment temperature is less than 260 ° C., the fiber is insufficiently crystallized and the shrinkage of the fiber is increased. On the other hand, when it exceeds 350 ° C., the crystallization of the fiber becomes too large, and the elongation at break is significantly reduced. Moreover, making the dry heat processing temperature into the range of 270-340 degreeC contributes to the improvement of the breaking strength of the fiber obtained.

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

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
In the examples, “parts” and “%” are all based on the mass standard unless otherwise specified, and the quantitative ratio indicates the 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 performed with two kinds of evaluation solutions.
(i) 100% organic solvent used for the production of meta-type wholly aromatic polyamide fiber,
(ii) 60% aqueous solution of the organic solvent (organic solvent 60 / water 40)
The measurement was performed according to the following procedure.
(1) When 5 g of the compound to be measured is added to a flask in which 100 g of the evaluation liquid has been weighed in advance and stirred at 20 ° C. for 2 hours and then all dissolved, the solubility is set to> 5%.
(2) When the undissolved residue is confirmed, the solubility is set to> 5% even when the undissolved portion is completely dissolved after standing at 20 ° C. for 12 hours or more.
(3) When undissolved residue is confirmed at this stage, the supernatant is taken out into a 50 g weighing bottle, and the dissolution concentration is determined by weight% by the absolutely dry method.
<Fineness>
Based on JIS L1015, the measurement based on the A method of positive fineness was implemented, and it described with the apparent fineness.
<Breaking strength, breaking elongation>
Based on JIS L1015, it measured on condition of the following using model number 5565 by Instron.
(Measurement condition)
Grasp interval: 20mm
Initial load: 0.044 cN (1/20 g) / dtex
Tensile speed: 20 mm / min <flame retardant LOI value>
The LOI value was determined in accordance with the LOI measurement method of JIS K7201.
<Lightness L value and chromaticity b value>
Measurement was performed using a branch color meter SD7000 (manufactured by Nippon Denshoku Industries Co., Ltd.).
<Pyrolysis start temperature>
Thermogravimetry was carried out at a rate of 10 ° C./min using Pyris1 TGA (manufactured by PerkinElmer), and the temperature at which the sample weight decreased by 5% was defined as the thermal decomposition start temperature.

[Examples 1 to 4]
(Manufacture of polymers)
In a reaction vessel under a dry nitrogen atmosphere, 721.5 parts by mass of N, N-dimethylacetamide (DMAc) having a moisture content of 100 ppm or less was weighed, and 97.2 parts by mass (50.18 mol) of metaphenylenediamine was added to 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 added while gradually 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 after completion of the polymerization reaction 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 polymetaphenylene 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%.

(Manufacture of fibers)
When the solubility of resorcinol bis-dixylenyl phosphate, which is an aromatic condensed phosphate ester, in DMAc was measured, it was insoluble at a solubility of> 5% and in a DMAc 60% aqueous solution at a solubility of 0%. Moreover, the thermal decomposition start temperature of this compound was 320 degreeC.
This compound is added as a flame retardant to the polymer solution so that the phosphorus content in the fibers is 0.20%, 0.30%, 0.40%, and 0.50%, respectively, and the spin dope is prepared by depressurization under reduced pressure. It was.

(spinning)
The spinning dope was spun from a spinning nozzle 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. The composition of the coagulation liquid was water / DMAc = 45/55 (parts by mass), and was spun by discharging into a coagulation bath at a yarn speed of 7 m / min.
Subsequently, the film was stretched 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 film was washed with a 20 ° C. water / DMAc = 70/30 bath (immersion length 1.8 m), followed by a 20 ° C. water bath (immersion length 3.6 m), and then a 60 ° C. hot water bath (immersion length 5). 4m) and thoroughly washed.
The washed fiber was subjected to a dry heat treatment with a hot roller having a surface temperature of 300 ° C., and the meta-type wholly aromatic polyamide fiber was sampled in a tow state to measure the breaking strength and breaking elongation. The results are shown in Table 1.

  Further, the obtained tow-like fibers were bundled, passed through a crimper, crimped, and then cut with a cutter to obtain 51 mm short fibers, thereby obtaining raw cotton. Using the obtained raw cotton, the values of lightness L and chromaticity b were measured using a flame retardant LOI value and a color difference meter. The results are shown in Table 1.

[Comparative Example 1]
Tris (chloropropyl) phosphate (pyrolysis onset temperature: 160 ° C.) that dissolves well in a DMAc 60% aqueous solution, although the solubility of the organophosphorus compound in DMAc is 5% or more, contains phosphorus in the fiber. It was carried out in the same manner as in Example 1 except that it was added in an amount of 0.95% and was subjected to vacuum depressurization to obtain a spinning dope. At this time, the chlorine content in the fiber was 3.20%.

[Comparative Example 2]
The same procedure as in Example 1 was carried out except that nothing was added to the polymer solution and the spinning dope was removed under reduced pressure.

[Example 5]
Resorcinol bis-dixylenyl phosphate (thermal decomposition onset temperature: 320 ° C.) having solubility of 0% and insoluble in DMAc 60% aqueous solution of the aromatic condensed phosphate ester in DMAc is 5% or more, and the polymer solution In addition to adding 0.50% in the phosphorus content in the fiber, and further adding tinuvin 234 as a light-resistant stabilizer to 3.0% in the fiber, except that the spin dope was made by depressurization under reduced pressure. The same operation as in Example 1 was performed.

[Comparative Example 3]
The same procedure as in Example 1 was performed except that only tinuvin 234 was added to the polymer solution as a light-resistant stabilizer so as to be 3.0% in the fiber, and the solution was depressurized and depressurized to form a spinning dope.

  After measuring the breaking strength and breaking elongation in the tow state of the obtained fiber to obtain a raw cotton, the lightness L and the chromaticity b were measured using a flame retardant LOI value and a color difference meter. Table 2 shows the results of the evaluation of light resistance.

  In Example 1, the flame retardant LOI value could be improved to 33 by adding a small amount of the flame retardant. Furthermore, in Examples 2-4, the flame retardant LOI value was improved as the amount of flame retardant added increased. At this time, a decrease in strength was not confirmed with respect to Comparative Example 2 in which no flame retardant was added. On the other hand, the flame retardant used in Comparative Example 1 was able to improve the flame retardancy by adding excessively, but the fiber strength decreased, the raw cotton color changed to yellow, and the value as a white product was It became low.

  Discoloration due to exposure to light in white products becomes a problem, but the light resistance of Comparative Example 2 is grade 1 and the discoloration of the part irradiated with light is severe, and a light resistance stabilizer can be added to solve this. . In Comparative Example 3, when only the light-resistant agent was added, the light resistance was improved to a third grade, but the flame-retardant LOI value of the raw cotton was as low as 26 due to the addition of the light-resistant agent having low heat resistance.

  By adding the flame retardant in Example 5, the flame retardant LOI value was improved to 36 while maintaining the light fastness third grade.

  According to the present invention, a white meta-type wholly aromatic polyamide fiber having a high flame retardance performance that does not appear without the addition of a flame retardant composed of an organic phosphorus compound can be obtained, industrial use such as filters and electronic parts, and heat resistance In addition, it is possible to provide a white fiber material that is extremely useful and has never been used in disaster prevention safety clothing applications such as protective clothing where flame resistance and flame resistance are important.

Claims (6)

  Meta-type wholly aromatic polyamide fiber containing an organophosphorus compound so that the phosphorus atom content in the meta-type wholly aromatic polyamide fiber is 0.2 wt% or more, which is a combustion limit oxygen index LOI of the fiber Is a white meta-type wholly aromatic polyamide fiber having an excellent flame retardancy of 33 or more and a lightness L value of 85 or more.   The white meta-type wholly aromatic polyamide fiber according to claim 1, wherein the pyrolysis start temperature of the organophosphorus compound contained in the fiber is 300 ° C or higher.   3. The white meta-type wholly aromatic polyamide fiber according to claim 1, wherein the organic phosphorus compound is dissolved in an organic solvent used in the production of the fiber by 5% or more and insoluble in a 60% aqueous solution of the organic solvent.   The white meta-type wholly 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.   5. The white meta type wholly aromatic polyamide fiber according to any one of claims 1 to 4, wherein the light resistance of the fiber is tertiary or higher. After adding an organic phosphorus compound that is dissolved in an organic solvent by 5% or more and insoluble in a 60% aqueous solution of the organic solvent so that the phosphorus atom content is 0.2 to 5.0 wt% with respect to the spinning dope. A process for producing a white meta-type wholly aromatic polyamide fiber, characterized by spinning.