JP2006328555A - Meta type wholly aromatic polyamide fiber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method capable of producing a meta type wholly aromatic polyamide fiber without having close adhesion among fibers and having good dynamic characteristics and thermal properties efficiently in an industrial production level. <P>SOLUTION: This method for producing the wholly aromatic polyamide fiber is provided by wet spinning the meta type wholly aromatic polyamide polymer solution obtained by dissolving the meta type wholly aromatic polyamide having a metaphenyleneisophthalamide skeleton as a main component in an amide-based solvent, under a specific condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a meta-type wholly aromatic polyamide fiber and a method for producing the same. More specifically, the present invention relates to a meta-type wholly aromatic polyamide fiber having a metaphenylene isophthalamide skeleton as a main component by a wet spinning method. And an aromatic polyamide fiber having excellent mechanical properties obtained by the method.

  It has been well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dichlorides are excellent in heat resistance and flame retardancy, and these aromatic polyamides can be used as amide solvents. It is also well known that these polymers can be made into fibers from these polymer solutions by methods such as dry spinning, wet spinning, and semi-dry semi-wet spinning.

  Among such aromatic polyamides, meta-type wholly aromatic polyamides (hereinafter sometimes abbreviated as “meta-aramid”) represented by polymetaphenylene isophthalamide are particularly useful as heat-resistant and flame-retardant fibers. -It is said that such meta-aramid fibers are currently being produced industrially mainly by the following two methods (a) and (b). Furthermore, as other methods for producing meta-aramid fibers, The following methods (ha) to (e) have been proposed.

  (A) A polymetaphenylene isophthalamide solution is prepared by subjecting metaphenylenediamine and isophthalic acid chloride to low-temperature solution polymerization in N, N-dimethylacetamide, and then, by-product hydrochloric acid is hydroxylated. A method of producing polymetaphenylene isophthalamide fiber by dry spinning a polymer solution containing calcium chloride obtained by neutralization with calcium (Japanese Patent Publication No. 35-14399, US Pat. No. 3,360,595).

  (B) By contacting an organic solvent (for example, tetrahydrofuran) that is not a good solvent for the resulting polyamide containing metaphenylenediamine salt and isophthalic acid chloride with an aqueous solution containing an inorganic acid acceptor and a soluble neutral salt, A method of isolating a metaphenylene isophthalamide polymer powder (Japanese Patent Publication No. 47-10863), re-dissolving the polymer powder in an amide solvent, and then wet spinning in an inorganic salt-containing aqueous coagulation bath (Japanese Patent Publication) 48-17551).

  (C) A wet molding method from a meta-aramid solution prepared by dissolving and isolating a meta-aramid synthesized in a solution polymerization method in an amide solvent and containing no inorganic salt or a small amount (2 to 3%) of lithium chloride. A method for producing a molded product such as a fiber (Japanese Patent Laid-Open No. 50-52167).

  (D) A meta-aramid polymer solution containing calcium chloride and water produced by solution polymerization in an amide solvent and neutralized with calcium hydroxide, calcium oxide or the like is extruded from the orifice into the gas, A method of passing through an aqueous coagulation bath and then passing through an aqueous solution of an inorganic salt such as calcium chloride to form cedar into a yarn (Japanese Patent Laid-Open No. 56-31009).

  (E) A meta-aramid polymer solution containing calcium chloride and water produced by solution polymerization in an amide solvent and neutralized with calcium hydroxide, calcium oxide, etc. A method of spinning in a coagulation bath to form a yarn (JP-A-8-74121, JP-A-10-88421).

  The above method (a) has the advantage that a polymer solution for spinning (spinning stock solution) can be prepared without isolating the polymer, but it is an energy cost for production due to dry spinning using an amide solvent having a high boiling point. However, when the number of holes per spinneret is increased, the spinning stability rapidly decreases. In addition, even when this polymer solution is wet-spun into an aqueous coagulation bath, only weak fibers with high devitrification can often be obtained. Therefore, a meta-aramid polymer solution obtained by solution polymerization is still wet-spun using an aqueous coagulation bath. The method is believed to have many difficulties and has not been implemented industrially.

  On the other hand, in the methods (b) and (c), the above-mentioned problem of dry spinning is avoided, but the solvent is different between the polymerization system and the spinning system, and the polymer once isolated is redissolved. The problem is that it requires a process, and special consideration and meticulous process control are required to re-dissolve and obtain a stable solution. (Japanese Patent Publication No. 48-4661).

Further, in the method (2), when spinning from a spinneret into the air, increasing the number of holes per die results in a significant decrease in spinning stability, resulting in low productivity and inefficiency.
Furthermore, although the method (e) gives fibers with good physical properties, there is a problem in productivity because it is difficult to increase the spinning speed.

  As means for improving such a problem, Japanese Patent Application Laid-Open No. 2001-348726 discloses that a meta type wholly aromatic polyamide mainly composed of a metaphenylene isophthalamide skeleton obtained by the same method as (b) is used as an amide solvent. The polymer solution dissolved in the solution is discharged into a coagulation bath composed of an amide solvent and water to coagulate as a porous linear body, and then in the air as it is or after impregnation with a plastic liquid. There has been proposed a method in which a heat treatment is performed at a low temperature of 100 to 200 ° C., followed by heat treatment at a high temperature of 250 to 400 ° C.

  In addition, in Japanese Patent Application Laid-Open Nos. 2003-342832 and 2003-301326, a meta type wholly aromatic polyamide mainly composed of a metaphenylene isophthalamide skeleton obtained by the same method as (b) is used as an amide solvent. The dissolved polymer solution is discharged into a coagulation bath composed of an amide solvent and water to be coagulated as a porous linear body, and then this is a plastic stretching bath composed of an aqueous solution of the amide solvent. There has been proposed a method of producing a dense meta-type wholly aromatic polyamide fiber by drawing in, washing with water, and heat-treating.

Certainly, this method is excellent as a method for obtaining meta-aramid fibers having excellent mechanical properties, but depending on the solvent remaining rate in the fibers, adhesion between the fibers may occur in the heat treatment step. If the solvent is removed over time to eliminate this problem, a new problem arises that the apparatus for that purpose becomes larger, which is insufficient for industrial production. In addition, when the number of holes in the spinneret increases, there arises a problem that the mechanical properties are deteriorated. Therefore, from this point, it is not useful as an industrial production method. When the number of holes in the spinneret increases, sufficient fiber properties cannot be obtained. The increase in the concentration of the amide solvent, which is a dope solvent, in the vicinity of the discharge part becomes larger in the interior. This is probably because the washing of the thread does not proceed sufficiently.
As described above, the actual situation is that no method has yet been proposed for producing meta-dried amide having excellent adhesion characteristics between fibers and having excellent chemistry characteristics at an industrial production level.

JP 2001-348726 A JP 2003-342832 A JP 2003-301326 A

  The present invention has been made against the background of the above-described prior art, and its purpose is to efficiently produce meta-type wholly aromatic polyamide fibers having good mechanical properties and thermal properties without adhesion between fibers at an industrial production level. And a meta type wholly aromatic polyamide fiber produced by the method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a desired meta-type wholly aromatic polyamide fiber can be obtained when the production method shown below is adopted, and have reached the present invention. did.

That is, according to the present invention, a meta-type wholly aromatic polyamide polymer solution in which a meta-type wholly aromatic polyamide having a metaphenylene isophthalamide skeleton as a main component is dissolved in an amide solvent is wet-spun so that the meta-type is obtained. A method for producing a wholly aromatic polyamide fiber, which comprises the following steps (1) to (6):
(1) After discharging the meta-type wholly aromatic polyamide polymer solution from the spinneret into a coagulation bath composed of an amide solvent and water to coagulate as a porous linear body,
(2) First-stage stretching in a plastic stretching bath comprising an aqueous solution of water or an amide solvent,
(3) After heat washing with water or an aqueous solution of an amide solvent, heat treatment is performed at a temperature of 100 to 250 ° C.
(4) Next, the content of the meta-type wholly aromatic polyamide polymer in the fiber (P) and the content of the amide solvent (N) in water or an aqueous solution of the amide solvent are expressed by the following formula (I): After adjusting so as to add a groove, the composition ratio of the amide solvent and water is 30/70 / -80 / 20 by weight, and the temperature is 40-100 ° C. Second-stage stretching in a plastic stretching bath at a stretching ratio of 0.9 to 1.4 times,
(5) Further, after washing with water or an aqueous solution of an amide solvent and then heat treating at a temperature of 100 to 250 ° C.,
(6) Heat treatment at a temperature of 270 to 400 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the method which can produce efficiently the meta-type wholly aromatic polyamide fiber with favorable mechanical characteristics and a thermal property without the contact | adherence between fibers at an industrial production level is provided.

  The present invention is a method for producing a meta type wholly aromatic polyamide fiber by wet spinning a polymer solution comprising an amide solvent containing a meta type wholly aromatic polyamide mainly comprising a metaphenylene isophthalamide skeleton. By adopting the steps (1) to (6) above, it is possible to produce meta-type wholly aromatic polyamide fibers that have no adhesion between fibers and are excellent in mechanical properties and thermal properties.

  The aromatic polyamide used in the present invention has metaphenylene isophthalamide as a main skeleton, and its production method is not particularly limited. For example, a meta-type aromatic diamine and an aromatic dicarboxylic acid chloride are used as raw materials. Can be produced by solution polymerization or interfacial polymerization.

As the meta-type aromatic diamine which is one of such raw materials, diamines represented by the following formula are mainly used.

  Specific examples of such meta-type aromatic diamines include metaphenylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene and the like. It is done. Examples of other meta-type aromatic diamines include 3,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl sulfone, and the like.

  In the present invention, it is particularly preferable to use metaphenylenediamine or mixed diamine mainly composed of metaphenylenediamine. Other aromatic diamines used in combination with metaphenylenediamine include paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene, aminoanisidine, etc. in addition to the above-mentioned meta-type aromatic diamine. Benzene derivatives, 1,5-naphthylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylketone, bis (aminophenyl) phenylamine, bis (paraaminophenyl) methane and the like are used.

  When a polymer with good solubility is desired, such other aromatic diamines can be used up to about 20 mol% of the whole. However, when a highly crystalline polymer is desired, metaphenylene can be used. It is preferable that diamine is contained at 90 mol% or more, particularly 95 mol% or more.

  On the other hand, the aromatic dicarboxylic acid chloride used in the present invention is isophthalic acid chloride or an aromatic dicarboxylic acid chloride mainly composed thereof. Other aromatic dicarboxylic acid chlorides that can be used in combination with isophthalic acid chloride include terephthalic acid chloride, 1,4-naphthalenedicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, 4,4′-biphenyldicarboxylic acid chloride, 5 -Chlorisophthalic acid chloride, 5-methoxyisophthalic acid chloride, bis (chlorocarbonylphenyl) ether and the like.

In the practice of the present invention, when a polymer having good solubility is desired, these other aromatic dicarboxylic acids can be mixed up to a ratio of about 20 mol%. Is desired, isophthalic acid chloride is preferably contained in an amount of 90 mol% or more, particularly 95 mol% or more.
Among the meta-type wholly aromatic polyamides, a polymer in which 90 to 100 mol% of all polymer repeating units are metaphenylene isophthalamide units is preferably used.

  In the present invention, a polymer solution in which the meta-type wholly aromatic polyamide is dissolved in an amide solvent is supplied to the process described later. As such a polymer solution, an amide solvent solution containing a meta type wholly aromatic polyamide obtained by the above solution polymerization or the like, or a meta type wholly aromatic polyamide obtained by the above solution polymerization or interfacial polymerization or the like may be used. The meta-type wholly aromatic polyamide may be isolated from a solution containing, and dissolved in an amide solvent.

  Examples of the amide solvent used here include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone and the like. N-methyl-2-pyrrolidone and N, N-dimethylacetamide are preferred from the viewpoint of the stability of the polymer solution up to the wet spinning process.

  In the present invention, the polymer solution used for the spinning dope may contain water. Such water may be added as necessary, but it may be inevitably produced in the solution preparation process. The concentration may be any concentration as long as the solution exists stably, but it is preferably added and contained, for example, usually in the range of 0 to 60% by weight with respect to the polymer weight, particularly 15% by weight. % Or less is preferable. If the concentration exceeds this, the stability of the polymer solution is impaired, and the spinnability may be significantly impaired by the precipitation and gelation of the polymer.

  In the present invention, when the polymer solution is discharged into the coagulation bath, a multi-hole spinneret can be used. In practice, the upper limit of the number of holes is about 50,000 holes, preferably 300 to 30000 holes, particularly 3000 to 20000 holes.

The coagulation bath used in the present invention is composed of an aqueous solution substantially consisting of two components of an amide solvent and water (H ₂ O). In this coagulation bath composition, the amide solvent can be suitably used as long as it dissolves meta-aramid and is miscible with water. In particular, N-methyl-2-pyrrolidone, N, N-dimethylacetamide , Dimethylformamide, dimethylimidazolidinone, and the like can be preferably used. In consideration of recovery of the solvent and the like, it is preferable to use the same type of amide-based solvent in the spinning dope.

  The optimum mixing ratio of the amide solvent and water varies slightly depending on the conditions of the polymer solution, but the concentration of the amide solvent in the coagulation bath liquid is 40 to 70% by weight, particularly 50 to 65%. Preferably there is. When the concentration of the amide solvent is less than 40% by weight, very large voids are likely to be generated in the yarn, which is liable to cause subsequent yarn breakage. On the other hand, under the condition where the concentration of the amide solvent exceeds 70% by weight, solidification does not proceed and the yarns tend to adhere to each other (welding, gluing, fusing, etc.).

  The temperature of the coagulation bath is closely related to the composition of the coagulation solution, but generally a higher temperature is preferable because coarse bubble-like pores called fingers are hardly formed in the formed yarn. However, when the concentration of the coagulation liquid is high, if the temperature is too high, the yarns are closely adhered to each other, so that the suitable temperature of the coagulation bath is 20 to 90 ° C, more preferably 30 to 80 ° C.

The coagulation liquid is preferably substantially composed of only an amide solvent and water, but may contain a small amount of salts other than this. In particular, salts such as calcium chloride and calcium hydroxide may be extracted from the polymer solution, but this does not inhibit the porous coagulation at all, for example, 10% by weight based on the coagulation liquid. In the following, there is no problem even if salts are contained as long as the concentration is 5% by weight or less. Therefore, the preferred concentration of the salt is in the range of 0 to 10% by weight with respect to the coagulating liquid.
The immersion time of the yarn in the coagulation bath is preferably 0.1 to 30 seconds. If the soaking time is too short, the formation of the yarn is insufficient and there is a possibility that the yarn breaks.

  In the present invention, the yarn solidified as the porous linear body needs to be subjected to plastic stretching in at least two stages in water or an aqueous solution of an amide solvent. As the amide solvent used here, any swellable meta-type wholly aromatic polyamide can be used as long as it is well mixed with water. Particularly, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethyl Formamide, dimethylimidazolidinone and the like can be preferably used. More preferably, the same solvent as that used in the coagulation bath is preferably used. If the same kind of solvent as the coagulation bath is used, the recovery process is simplified, which is economically beneficial.

  That is, it is preferable to use the same type of amide solvents in the polymer solution, the coagulation bath, and the plastic drawing bath, and N-methyl-2-pyrrolidone, N, N-dimethyl, It is convenient to use acetamide or dimethylformamide alone or in combination of two or more.

  The composition and temperature of the plastic stretching bath are closely related to the method for producing the meta-type wholly aromatic polyamide fiber of the present invention. First, in the first-stage plastic stretching, the concentration of the amide solvent in the plastic stretching bath Is preferably 20 to 70% by weight, and the temperature is preferably 20 to 90 ° C. In a region lower than this range, plasticization does not proceed sufficiently, and it becomes difficult to obtain a sufficient draw ratio. On the other hand, in a range exceeding this range, the surface of the yarn is dissolved and tends to adhere, and good spinning is often difficult.

  The first stage of plastic stretching is usually 1.5 to 10 times, preferably 2 to 10 times, and more preferably 2.1 to 6.0 times. By stretching at a high magnification in this way, the strength and elastic modulus of the meta-aramid fiber are improved, and good physical properties are exhibited. At the same time, pores in the porous structure are collapsed, and the densification is performed by heat treatment performed after plastic stretching. Will progress well. However, when the film is stretched at an extremely high magnification, the condition of the process is deteriorated and it becomes difficult to produce a good yarn.

The thread after the plastic stretching bath is washed with water or an aqueous solution of an amide solvent. At that time, the meta-type wholly aromatic polyamide polymer content (P) in the fiber, It is preferable to adjust the amide solvent content (N) and water content (W) so as to satisfy the following formulas (II) and (III).

  By adjusting the content and moisture content of the amide solvent within the above ranges, in the subsequent heat treatment, the fluidity of the polymer is moderately improved, the orientation proceeds but the crystallization is suppressed, and the fiber It is thought that densification of the material is promoted.

  The range of the preferable value of N / (P + N) in the formula (II) is 0.15 to 0.25, and the range of the preferable value of W / (P + W) in the formula (III) is 0.45 to 0.00. 65.

  In addition, as a method for adjusting the content and water content of the amide solvent within the above ranges, a 10 to 70 ° C. water bath or a 10 to 40 ° C. amide solvent / water mixed bath after the first stage of plastic stretching. Etc., and a method of adjusting the immersion length by the number of threading turns is exemplified.

  Thus, the yarn in which the content of the amide solvent in the fiber is adjusted is once heat-treated in a temperature range of 100 to 250 ° C., preferably 100 to 200 ° C. by a heating roller, a heating plate, hot air, or the like. The The heat treatment step in the temperature range of 100 to 200 ° C. is an important step for promoting the orientation and crystallization of the polymer of the porous linear body and expressing the heat shrinkage stability of the fiber. If the heat treatment temperature is less than 100 ° C., the evaporation of water and amide solvents is remarkably slow, which not only reduces productivity but also hinders the promotion of orientation, which is not preferable. On the other hand, when the heat treatment temperature exceeds 250 ° C., decomposition of the amide solvent occurs at once and the fibers are colored, which is not preferable.

In the present invention, it is important that the fibers subjected to the first stage drawing and heat treatment as described above are further subjected to the second stage drawing in a plastic drawing bath in order to improve the mechanical properties. The second-stage stretching needs to be performed after the content of the amide solvent in the fiber is adjusted with water or an aqueous solution of the amide solvent. In this case, the following formula (I) is satisfied. It needs to be adjusted.

The range of a preferable value of N / P in the above formula (I) is 0.10 to 0.17.
If the value of N / P is less than 0.05, the effect of improving the polymer fluidity during heat treatment becomes insufficient, the fiber is not sufficiently densified, and it becomes difficult to obtain good fiber properties. On the other hand, if the value of N / P exceeds 0.2, repair crystallization at the time of heat treatment is likely to proceed, and at the same time, the close contact of fibers is likely to occur, so that it is difficult to obtain good fiber properties.

  As a method for adjusting the content of the amide solvent in the fiber to the above range, after the heat treatment step, it is passed through a 10-70 ° C. water bath or a 10-40 ° C. amide solvent / water mixed bath, etc. Examples thereof include a method of adjusting the length by the number of yarn hooking turns.

  The composition and temperature of the second-stage plastic drawing bath are also closely related to the method for producing the meta-type wholly aromatic polyamide fiber of the present invention, as in the first-stage plastic drawing, and the concentration of the amide solvent The composition ratio of the amide solvent and water is preferably 30/70 to 80/20 by weight, and the temperature is preferably 40 to 100 ° C. When the composition and temperature of the plastic stretching bath are lower than this range, plasticization does not proceed sufficiently, it is difficult to perform stretching, and the mechanical properties become insufficient. Moreover, since the surface of a thread | yarn melt | dissolves and it becomes easy to adhere | attach closely, the range exceeding this is not preferable. A particularly preferred concentration of the amide solvent is such that the composition ratio of the amide solvent and water is 50/50 to 70/30 by weight, and the temperature is 60 to 95 ° C.

  In the second stage plastic drawing, it is preferable to draw at a draw ratio of 0.9 to 1.4 times. In a region lower than this range, the stretching effect is small and the mechanical properties are insufficient. Here, under the above-described conditions of the plastic stretching bath concentration and temperature, the stretching effect can be obtained because the shrinkage stress acts on the fiber even at a draw ratio of 0.9. Moreover, in the range exceeding this, since generation | occurrence | production of a fluff and single thread breakage will increase and a process tone will fall, it is unpreferable.

  The reason why the second stage plastic drawing can provide a fiber having excellent mechanical properties even if the number of holes in the die increases is not clear, but the second stage plastic drawing uses the shrinkage stress of the fiber. Since the effect of stretching is obtained, the effect of stretching is exerted on low-strength fibers that are not sufficiently advanced in orientation and crystallization in the previous steps, so the spots between holes are reduced, It is considered that excellent mechanical properties can be obtained even if the number of holes in the die increases.

  Thus, after the second stage plastic stretched yarn is further washed with water or an aqueous solution of an amide solvent, it is once heated to 100 to 250 ° C., preferably 100 to 200 ° C. with a heating roller, a heating plate, hot air or the like. Heat treatment, preferably dry heat treatment, is performed in the temperature range of ° C.

  In the heat treatment at a temperature of 270 to 400, which is performed following the above treatment, the treatment temperature and the fiber density are closely related, and the treatment is preferably performed at a temperature of 300 to 370 ° C. At this time, the yarn may be severely deteriorated and colored by treatment at a high temperature exceeding 400 ° C., and in some cases, the yarn may be broken. On the other hand, if the treatment temperature is lower than 270 ° C., it cannot be sufficiently densified, resulting in insufficient mechanical properties. In addition, the treatment temperature here means the set temperature of a heating means such as a hot plate or a heating roller, and dry heat treatment is particularly preferable.

  The draw ratio at this time is closely related to the development of the elastic modulus and strength, and can take any ratio as necessary, but is usually 0.7 to 3.0 times, particularly 1.0. By setting it in a range of ˜2.7 times, good heat stretchability is obtained, and strength and elastic modulus are exhibited.

Here, the draw ratio of 0.7 times means that the yarn shrinks by 30% with respect to the length before the treatment by heat treatment, and the heat treatment of the present invention is a limited shrink heat treatment within a certain range during the treatment. It means that you can. The draw ratio at the time of heat treatment is preferably selected in consideration of the above-mentioned plastic draw ratio. From the viewpoints of densification of the yarn, manifestation of physical properties, and stable yarn forming properties, plastic drawing and hot drawing are performed. It is more preferable that the total draw ratio is 3.0 to 12 times, more preferably 2.5 to 6 times. The meta-type wholly aromatic polyamide fiber in the present invention has good stretchability, and can be smoothly stretched to a high magnification without causing yarn breakage or fluff during plastic stretching or heat stretching.
Further, the fiber thus produced may be crimped as necessary, cut into an appropriate fiber length, and provided to spinning or other processes.

  Hereinafter, the present invention will be described more specifically with reference to examples. Further, “parts” and “%” are all based on weight unless otherwise specified, and the ratio of amounts indicates a weight ratio unless otherwise specified. Further, the polymer concentration in the polymer solution (spinning stock solution) used for spinning is the polymer weight% with respect to the total weight of the solution, that is, (polymer weight) / [(polymer weight) + (solvent weight) + (other weight). )] × 100. In addition, each characteristic in an Example was evaluated in accordance with the following method.

(1) Reduced viscosity (IV)
The reduced viscosity was measured at 30 ° C. with a polymer concentration of 100 mg / 100 ml sulfuric acid in concentrated sulfuric acid after the aromatic polyamide polymer was isolated from the polymer solution and dried.

(2) Fineness The fineness of the obtained fiber was measured according to JIS-L-1015.

(3) Toughness factor According to JIS-L-1015, the toughness factor of the obtained fiber was determined by measuring the strength and elongation at a sample length of 20 mm, an initial load of 1/20 g / dtex, and an elongation rate of 20 mm / min. It was expressed as the product of the value obtained by multiplying the value of tensile strength expressed in dtex by 0.9 and the square root of tensile elongation (%).

(4) Total aromatic polyamide polymer content (P) and amide solvent content (N)
The fiber subjected to the first-stage plastic drawing is subjected to a centrifuge (rotation speed: 5000 rpm) for 10 minutes, and the fiber weight M1 at this time is measured. The fiber is boiled in methanol for 4 hours, the amide solvent and water in the fiber are extracted, and the methanol solution weight M2 after extraction is measured.
After the extraction, the fiber is dried in an atmosphere of 105 ° C., and the weight of the fiber after drying is measured. The weight concentration C (%) of the amide solvent in the extract is obtained by gas chromatography, and N1 = C / 100 × M2 and W1 = M1-P1-N1 are obtained from these, and then P and N are calculated by the following formulas. To do.

(5) Adhesiveness of fiber About 30 g of fiber cut to a length of 5 cm was sampled, and its weight (Wa) was precisely weighed after drying. Further, this was mixed with 30 liters of water and stirred for 15 minutes, and then passed through a filter having 400 slits having a width of 0.15 mm and a length of 50 mm. At this time, the weight (Wb) after drying of the fiber remaining without passing through the slit was precisely weighed, and the adhesion rate (%) was calculated from Wb / Wa × 100. Here, the case where the adhesion rate is less than 0.1% is indicated by ◯, the case where the adhesion rate is 0.1% or more and less than 1.0% is indicated by Δ, and the case where the adhesion rate is 1.0% or more is indicated by ×.

[Example 1]
N, N-dimethyl obtained by cooling 21.5 parts by weight of polymetaphenylene isophthalamide powder of IV = 1.9 produced by an interfacial polymerization method according to the method described in Japanese Patent Publication No. 47-10863, to -10 ° C. After suspending in 78.5 parts by weight of acetamide (hereinafter referred to as DMAc) to form a slurry, the solution was heated to 60 ° C. and dissolved to obtain a transparent polymer solution A. The polymer concentration of the polymer solution was 21.5%.

  Using the polymer solution A as a spinning solution, spinning was carried out from a spinning nozzle having a pore diameter of 0.07 mm and a pore number of 15000 into a coagulation bath having a bath temperature of 50 ° C. As this coagulation bath, a bath having a composition of water / DMAc = 40/60 was used. The immersion length (effective coagulation bath length) was 40 cm, and the yarn was allowed to pass at a yarn speed of 7 m / min.

  Subsequently, the film was stretched at a stretching ratio of 3.6 times in a plastic stretching bath. The plastic stretching bath at this time was a bath having a composition of water / DMAc = 40/60, and the temperature was 20 ° C. After stretching, it was passed through a 20 ° C. water bath (immersion length 9.0 m). At this time, it was N / (P + N) = 0.20. Then, it was wound on a roller having a surface temperature of 120 ° C. and subjected to dry heat treatment.

  Subsequently, after passing through a 20 ° C. water bath (immersion length: 2.0 m) and adjusting to N / P = 0.15, the film was stretched at a stretch ratio of 1.1 times in the second-stage plastic stretching bath. It was. The plastic stretching bath at this time was a bath having a composition of water / DMAc = 40/60, and the temperature was 90 ° C. After stretching, the film was passed through a 90 ° C. water bath (immersion length 3.6 m). Thereafter, the film was wound on a roller having a surface temperature of 120 ° C. and subjected to dry heat treatment, and subsequently wound on a roller having a surface temperature of 160 ° C. to be subjected to dry heat treatment.

Furthermore, dry heat treatment was performed at a constant length on a hot plate having a surface temperature of 330 ° C. to obtain polymetaphenylene isophthalamide fibers.
The obtained fiber had a fineness of 2.22 dtex, a strength of 4.37 cN / dtex (4.46 g / dtex), an elongation of 41.0%, and a toughness factor of 31.7. Further, the adhesion rate was 0.03%.

[Examples 2 to 4, Comparative Examples 1 to 3]
In Example 1, after changing the temperature and immersion length of the water bath after stretching and changing the value of N / P after washing as shown in Table 1, the composition, temperature, and temperature of the second-stage plastic stretching bath, The same procedure as in Example 1 was performed except that the magnification was changed as shown in Table 1.
Table 1 shows the fineness, strength, elongation, toughness factor and adhesion of the obtained fiber.

  According to the present invention, a meta-type wholly aromatic polyamide fiber having no adhesion between fibers and good mechanical properties and thermal properties is provided. Therefore, a fire fighting garment, for example, in the form of woven or knitted fabric, alone or in combination with other fibers. Can be used as heat-resistant and flame-resistant clothing such as protective clothing, flame-resistant bedding and interior materials.

Claims (5)

A meta type wholly aromatic polyamide fiber is produced by wet spinning a meta type wholly aromatic polyamide polymer solution in which a meta type wholly aromatic polyamide mainly composed of a metaphenylene isophthalamide skeleton is dissolved in an amide solvent. A method for producing a meta-type wholly aromatic polyamide fiber having excellent mechanical properties, comprising the following steps (1) to (6).
(1) After discharging the meta-type wholly aromatic polyamide polymer solution from the spinneret into a coagulation bath composed of an amide solvent and water to coagulate as a porous linear body,
(2) First-stage stretching in a plastic stretching bath comprising an aqueous solution of water or an amide solvent,
(3) After heat washing with water or an aqueous solution of an amide solvent, heat treatment is performed at a temperature of 100 to 250 ° C.
(4) Next, the content of the meta-type wholly aromatic polyamide polymer in the fiber (P) and the content of the amide solvent (N) in water or an aqueous solution of the amide solvent are expressed by the following formula (I): After adjusting so as to add a groove, the composition ratio of the amide solvent and water is 30/70 / -80 / 20 by weight, and the temperature is 40-100 ° C. Second-stage stretching in a plastic stretching bath at a stretching ratio of 0.9 to 1.4 times,
(5) Further, after washing with water or an aqueous solution of an amide solvent and then heat treating at a temperature of 100 to 250 ° C.,
(6) Heat treatment at a temperature of 270 to 400 ° C.

  The meta type according to claim 1, wherein in step (1), the composition ratio of the amide solvent and water in the coagulation bath is 40/60 to 70/30 by weight, and the temperature of the coagulation bath is 20 to 90 ° C. A method for producing wholly aromatic polyamide fibers.   In the step (2), the composition ratio of the amide solvent to water is 20/80 to 70/30 by weight, and the temperature is 20 to 90 ° C. The process for producing a meta-type wholly aromatic polyamide fiber according to claim 1 or 2, which is drawn at a draw ratio of.   The process for producing a meta-type wholly aromatic polyamide fiber according to any one of claims 1 to 3, wherein in the step (6), heat treatment is performed under stretching of 0.7 to 4 times.   A meta-type wholly aromatic polyamide fiber manufactured by the method according to any one of claims 1 to 4, wherein the tensile strength of the meta-type wholly aromatic polyamide fiber (the value expressed in g / dtex is 0). A meta type wholly aromatic polyamide fiber, wherein a toughness factor expressed by a product of a product of .9 multiplied by a square root of tensile elongation (%) is 25 or more.