JP2001348726A - Method for producing dense poly(metaphenyleneisophthalamide)-based fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a meta-type aromatic polyamide fiber having good mechanical characteristics, heat resistance and the like in high productivity. SOLUTION: This method for producing the dense meta-type aromatic polyamide fiber by wet-spinning a solution of a meta-type aromatic polyamide polymer, comprising an amide-based solvent containing the meta-type aromatic polyamide consisting essentially of a metaphenylenediamineisophthalamide skeleton comprises (1) coagulating the polymer solution as a porous filament by extruding the solution into a coagulation bath holding a coagulation liquid comprising the amide-based solvent and water, (2) heating and drawing the resultant filament in air while including the coagulation liquid in the pores or allowing the pores to include a plasticizing liquid, (3) heating the resultant filament to 100-200 deg.C while including the coagulation liquid in the pores, and (4) heat- treating the heated filament at 250-400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a dense meta-type aromatic polyamide fiber. More specifically, the present invention relates to a method for producing a meta-type aromatic polyamide fiber having a meta-phenylenediamine skeleton as a main component having good mechanical properties and heat resistance with high productivity.

[0002]

2. Description of the Related Art It has been well known that an aromatic polyamide (hereinafter sometimes referred to as aramid) produced from an aromatic diamine and an aromatic dicarboxylic acid dichloride has excellent heat resistance and flame retardancy. It is also well known that this aramid is soluble in an amide-based solvent and can be formed into fibers by a method such as dry spinning, wet spinning, and semi-dry semi-wet spinning.

Among such aramids, fibers of meta-type aromatic polyamide (hereinafter sometimes referred to as meta-type aramid) represented by polymetaphenyleneisophthalamide are particularly useful as heat-resistant and flame-retardant fibers. Yes,
At present, it is said that industrial production is mainly performed by the following two methods (a) and (b). In addition, the following methods (c) to (f) have been proposed as methods for producing meta-type aramid fibers.

(A) A polymetaphenylene isophthalamide solution is prepared by low-temperature solution polymerization of metaphenylenediamine and isophthalic chloride in N, N-dimethylacetamide, and then hydrochloric acid by-produced in the solution is prepared. A method in which a polymer solution containing calcium chloride obtained by neutralization with calcium hydroxide is dry-spun to produce fibers (Japanese Patent Publication No. 35-14399, US Pat. No. 3,360,595).

(B) contacting an organic solvent system (eg, tetrahydrofuran) which is not a good solvent for the resulting polyamide containing a metaphenylenediamine salt and isophthalic chloride with an aqueous system containing an inorganic acid acceptor and a soluble neutral salt; Thus, a powder of the polymetaphenylene isophthalamide polymer was isolated (see Japanese Patent Publication No. 47-10863), and the polymer powder was redissolved in an amide-based solvent and then wet-spun in an aqueous coagulation bath containing an inorganic salt. (Japanese Patent Publication No. 48-17551).

(C) A meta-type aramid solution prepared by dissolving a meta-type aramid synthesized by a solution polymerization method in an amide-based solvent and containing no or a small amount (2 to 3%) of lithium chloride from an inorganic salt, A method of producing a molded article such as a fiber by a wet molding method (JP-A-50-52167).

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

(E) A solution of a meta-type aramid polymer containing calcium chloride and water produced by solution polymerization in an amide solvent and neutralization with calcium hydroxide, calcium oxide, or the like,
A method of spinning an orifice into an aqueous coagulation bath containing a high concentration of calcium chloride to form a yarn (Japanese Patent Application Laid-Open No. Hei 8-
074121, JP-A-10-88421).

(F) The polymer solution of the amide-based solvent is discharged to a high-temperature spinning tower, and is cooled with a low-temperature aqueous solution at the time of exiting the spinning tower, and is stretched in a plastic bath. A method of molding as a porous fiber having a density of 1.3 or less. (JP-A-52-43930)

The method (a) has the advantage that a spinning solution can be prepared without isolating the polymer, but the dry spinning using an amide-based solvent having a high boiling point has a high energy cost in production and has a high energy cost. Increasing the number of holes per spinneret rapidly reduces spinning stability. In addition, even if the polymer solution is wet-spun in an aqueous coagulation bath, only weak fibers with much devitrification can be obtained in many cases. Therefore, the meta-aramid solution by solution polymerization is still wet-spun using the aqueous coagulation bath. The method is believed to have many difficulties and has not yet been implemented industrially. On the other hand, the methods (b) and (c) avoid the above-mentioned problem of the dry spinning, however, the solvent is different between the polymerization system and the spinning system, and a step for re-dissolving the once isolated polymer. And special considerations and meticulous process control are required to obtain a stable solution upon re-dissolution (Japanese Patent Publication No. 48-4661).

In the method (d), when the yarn is spun from the spinneret into the air, if the number of holes per spinneret is increased, the spinning stability is remarkably reduced.

Although the method (e) gives a yarn having good physical properties, it is considered that since a solution containing a salt and a solvent having a relatively high concentration is used, the coagulation is slow and it is difficult to increase the spinning speed.

Further, in the method (f), by coagulating with a low-temperature aqueous solution and stretching it in a plastic bath, very dense porous fibers can be obtained, and finally the density becomes 1.3. This is a method for producing a porous meta-aramid fiber having a particle size of less than. However, this is an applied technique of the dry spinning method, and has the same problems as the dry spinning method. Furthermore, in this method, after the dry spinning, a step of swelling again in a low-temperature aqueous solution containing a solvent is required, so that it is difficult to obtain fibers with high productivity by increasing the number of holes. Also, the density of the fibers obtained under the conditions described here is less than 1.3,
It is an extremely porous fiber.

The meta-aramid fiber is used as an electronic material because of its heat resistance and insulating properties. However, in order to use it as an electronic material, it is required to minimize contamination of ionic substances and the like. It is preferable that no active substance is contained. However, in the methods known so far, it is essential that the spinning process has a very high affinity for polymer dope such as calcium chloride and lithium chloride and contains a very high concentration of easily soluble salts. Therefore, it was difficult to remove salts remaining in the manufactured yarn, and it was necessary to take a large washing step, and it was not possible to completely remove the salts.

JP-A-51-564 describes a method of wet spinning using a coagulation bath containing no salt. Here, it is described that salt-free meta-type aramid fibers can be produced by using polyethylene glycol as a coagulation bath. However, in this method, a polymer that cannot be distilled is used as a solvent, which makes it extremely difficult to recover the solvent and increases the cost.Therefore, it is not a method suitable for industrial production. A spinning method using a commercially available salt-free coagulation bath has not been developed.

Therefore, there is a need for a method for producing a meta-aramid having satisfactory yarn properties and containing no salts at a high productivity.

[0017]

SUMMARY OF THE INVENTION It is an object of the present invention to produce a salt-free meta-type aramid fiber having good mechanical properties and thermal properties in an industrially advantageous manner with good productivity. It is to provide a new method to perform.

The present inventors have proposed a wet spinning method in which a meta-type aromatic polyamide polymer solution comprising an amide-based solvent containing a meta-type aromatic polyamide having a metaphenylenediamine isophthalamide skeleton as a main component is directly spun into a coagulation bath. In producing the meta-type aromatic polyamide fiber by the method, the specific spinning of porous coagulation and post-densification, by sequentially performing the spinning process, to know that dense meta-type aromatic polyamide fiber is provided, The present invention has been reached.

[0019]

That is, the present invention provides a method for wet spinning a meta-type aromatic polyamide polymer solution comprising an amide solvent containing a meta-type aromatic polyamide having a meta-phenylenediamine isophthalamide skeleton as a main component. (1) discharging the polymer solution into a coagulation bath which holds a coagulation liquid comprising an amide solvent and water to obtain a porous linear body. (2) Subsequently, the linear body is heated and stretched in the air while the coagulating liquid is contained or the plastic liquid is contained in the pores, and (3) the coagulating liquid is contained in the pores. While keeping the linear body at 100 ° C. or more and 200 ° C.
Heat at the following temperature, and then (4)
This is a method for producing a dense meta-type aromatic polyamide fiber, which is heat-treated at 0 to 400 ° C.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The meta-type aromatic polyamide used in the present invention has a meta-phenylenediamine isophthalamide skeleton as a main component. The production method is not particularly limited. For example, it can be produced by solution polymerization or interfacial polymerization using a meta-type aromatic diamine and an aromatic dicarboxylic acid chloride as raw materials.

As the meta-type aromatic diamine which is one of such raw materials, a diamine represented by the following formula (1) is mainly used.

[0022]

Embedded image

Wherein R is a halogen atom or a carbon atom
And n represents 0 or 1. ]

Here, the halogen atom is a chlorine atom,
A bromine atom and the like can be mentioned, and examples of the alkyl group having 1 to 3 carbon atoms include a linear or branched alkyl group such as a methyl group and an ethyl group. Specific examples of such meta-type aromatic diamines include metaphenylenediamine, 2,4-toluenediamine, 2,6-toluenediamine, 2,4-diaminochlorobenzene, and 2,6-diaminochlorobenzene. Other meta-type aromatic diamines include 3,4′-diaminodiphenyl ether,
4'-diaminodiphenyl sulfone and the like.

In the present invention, particularly, metaphenylenediamine or a mixed diamine containing the same as the main component is preferred. Other aromatic diamines used in combination with metaphenylenediamine, in addition to the above meta-type aromatic diamine, paraphenylenediamine, 2,5-diaminochlorobenzene,
Benzene derivatives such as 2,5-diaminobromobenzene and aminoanisidine, 1,5-paranaphthylenediamine,
4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylketone, bis (aminophenyl) phenylamine, bis (paraaminophenyl) methane and the like are used.

When a polymer having good solubility is desired,
Such other aromatic diamines can be used up to about 20 mol% of the entire diamine component. However, when a polymer having high crystallinity is desired, metaphenylenediamine may be used in an amount of 90%.
It is preferably contained in an amount of at least 95 mol%, especially at least 95 mol%.

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 of isophthalic acid chloride. Other aromatic dicarboxylic acid chlorides that can be used in combination with isophthalic acid chloride include terephthalic acid chloride and 1,4-
Naphthalenedicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, 4,4′-biphenyldicarboxylic acid chloride, 3-chloroisophthalic acid chloride, 3-methoxyisophthalic acid chloride, bis (chlorocarbonylphenyl) ether and the like can be mentioned.

In the practice of the present invention, when a polymer having good solubility is desired, a high ratio (up to about 20 mol%) of these other aromatic dicarboxylic acids is mixed with the entire dicarboxylic acid chloride component. However, when a polymer having high crystallinity is desired, it is preferable that isophthalic acid chloride be contained in an amount of 90 mol% or more, particularly 95 mol% or more.

As the polymer solution used in the present invention, any solution may be used as long as it is a solution containing a meta-type aromatic polyamide as a main component which can be synthesized from the above-mentioned raw materials. For example, a solution in which a polymer obtained by reacting the above-described raw materials in THF and adding an aqueous alkali solution to neutralize hydrogen chloride generated at the interface between THF and the aqueous solution and dissolving the polymer in an amide solvent may be used. Alternatively, a polymer solution produced by a solution polymerization method may be used.

In the present invention, the above-mentioned solution of the meta-type aromatic polyamide polymer is subjected to the steps described below.

As the polymer solution, a solution containing a meta-type aromatic polyamide obtained by the above-described interfacial polymerization or the like may be used, or a solution containing a meta-type aromatic polyamide obtained by the above-mentioned solution polymerization or the like may be used. Isolating meta-type aromatic polyamide,
A solution obtained by dissolving this in an amide-based solvent may be used.

Examples of such amide solvents include N, N-dimethylformamide, N, N-dimethylacetamide,
N-methyl-2-pyrrolidone, dimethylimidazolidinone, and the like can be used.In particular, from the viewpoint of the stability of the polymer solution from solution polymerization to the wet spinning step,
It is more preferable to use N-methyl-2-pyrrolidone (abbreviated as “NMP” in the present invention).

The polymer solution used in the present invention may contain water. Such water may be added as needed, but may be formed inevitably in the solution preparation process. The concentration may be any concentration as long as the solution is in a stable range. For example, it is usually preferable to add and contain the solution in a range of 0 to 60% based on the weight of the polymer, particularly 15%. The following is preferred. If the concentration exceeds this, the stability of the polymer solution may be impaired, and the spinnability may be significantly impaired due to precipitation and gelation of the polymer.

According to the present invention, a coagulation bath having a very simple composition of an aqueous solution of an amide-based solvent is used, thereby coagulating the polymer solution as a homogeneous porous linear body. That is, in the present invention, the above-described polymer solution is preferably adjusted to a temperature corresponding to the coagulation bath temperature within the range of 20 to 90 ° C., and then the composition and the temperature in the coagulation bath described below are adjusted from the spinneret. After spinning (yarning) to form the yarn as a porous material, the yarn is pulled out of the coagulation bath, and then continuously put into the air while leaving the coagulating liquid in the porous linear body. Two
It is stretched at a draw ratio of 1 to 10 times and heat-treated at 100 to 200 ° C to promote densification.Furthermore, after washing with water and drying, it is heat-treated at a temperature of 250 to 400 ° C to form a fiber. I do. In the present invention, a coagulation method for forming a homogeneous porous material by wet spinning under the coagulation conditions in the specific temperature range as described above was invented, whereby a high spinning speed and a uniform porous structure were obtained in wet spinning. It has established a method to balance the formation.

[Step (1)] In the present invention, the structure of the porous body formed in the solidification stage should be as homogeneous as possible in order to make the material sufficiently dense in the subsequent step. Very important. The porous structure and the conditions of the bath are closely related, and the selection of the composition of the coagulation bath and the temperature conditions are extremely important.

The coagulation bath according to the present invention is substantially free of salts, and is composed of an aqueous solution consisting essentially of two components, an amide solvent and water (H 2 O). As the solvent, a meta-aramid can be suitably used as long as it dissolves in water and is well-mixed with water.N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylimidazolidinone and the like are particularly preferable. Can be used.

Although the optimum mixing ratio of the amide solvent and water slightly varies depending on the conditions of the polymer solution, the weight ratio of the amide solvent is preferably in the range of 40% to 70%. Under the conditions below this range, very large voids are likely to be generated in the yarn, which is likely to cause subsequent yarn breakage. Under the conditions above this range, coagulation does not proceed and the yarn is fused.

Although the temperature of the coagulation bath is closely related to the composition of the coagulation solution, it is generally preferable that the temperature is high because pores on coarse bubbles called fingers are not formed. However, when the concentration of the coagulating liquid is high, the fusion becomes severe at a high temperature, so the preferable range is 20 to 90 ° C, more preferably 30 to 80 ° C.

It is preferable that the coagulation liquid is substantially composed of only the amide solvent and water, and may contain a small amount of salts. In particular, very small amounts of salts such as calcium chloride and calcium hydroxide may be extracted from the polymer solution, but this does not inhibit porous coagulation at all and is included at low concentrations. There is no problem even if it is done. Thus, but not by way of limitation, this preferred concentration is in the range of 0 to 10% by weight of the coagulation liquid.

The dipping time of the yarn in the coagulation bath is 0.1 to
30 seconds is preferred. If the immersion time is too short, the formation of the thread is insufficient and the yarn breaks.

As described above, the porous linear body obtained as a yarn is preferably as high in density as possible for smooth subsequent densification, but is preferably 0.3 or more, and more preferably 0.3 or more. Is a density of 0.5 or more. If the density is less than 0.3, the porosity is so high that it is difficult to densify the linear body in the subsequent stretching step. This density is ASTM D2130
Is a value calculated based on the yarn thickness and fineness measured according to the above. The density is preferably 0.3 or more and 1.25 or less. At a porosity lower than this, the solvent extraction speed and the subsequent stretchability become insufficient, making it difficult to spin.At a porosity higher than this, the linear body can be densified in the subsequent stretching step. It becomes difficult. This porosity is
This is a value calculated based on the yarn thickness and fineness measured according to TM D2130.

This porous structure is formed of very uniform fine pores, and is characterized in that there are no large pores called voids or fingers having a size of several μm or more.
The pore size has a submicron order size of about 0.1 μm to 1 μm as measured by a scanning microscope.
It is known that such a homogeneous porous structure is formed, for example, by spinodal decomposition accompanying solidification.
By having such a very fine microporous structure, it is possible to prevent breakage of yarn at the time of stretching, and to achieve densification at the time of final heat setting and development of yarn physical properties.

When the polymer solution is discharged into a coagulation bath, a multi-hole spinneret can be used. The number of holes is 50,000 or less, preferably 300 to 30
000.

[Step (2)] The porous linear body obtained by coagulation is continuously drawn out into the air while containing the coagulation liquid and stretched. The stretching ratio at this time is preferably in the range of 2 times or more. Below this range, the orientation is substantially insufficient, and it is difficult to obtain a yarn having sufficient strength.

Generally, in wet spinning, a method of performing plastic stretching using a plastic bath is known. However, since stretching in a bath is performed under conditions where very thin resistance is applied, yarn breakage during stretching may occur. It is easy to occur and it is difficult to achieve both good quality and productivity. In the present invention, since the porous yarn is used, the coagulation liquid can be taken out into the air in a state where the coagulating liquid is sufficiently contained as a plasticizer. It is possible to do. Besides,
Since the stretching can be performed in air having low resistance, it is possible to perform the stretching at a higher stretching ratio than the stretching in the liquid.

In the present invention, it is possible to achieve plastic stretching in air by including a plastic liquid in the porous body. As the plastic liquid, it is possible to use the coagulation liquid as it is, but in addition to controlling the plastic state, changing the drawing orientation and expressing the desired yarn physical properties, Then, the composition of the plastic liquid to be included may be changed. In this case, the porous coagulated yarn may be passed through a bath of a plastic liquid having a desired composition before drawing.

As the solvent used for the plasticizer, any solvent may be used as long as it can plasticize the polymer. Preferred examples thereof include an aqueous solution of an amide solvent and an aqueous alcohol solution. In particular, the same solvent as the coagulating liquid and the polymer solvent or an aqueous solution thereof is preferable because the recovery step is simplified. As such a solvent, it is convenient to use one or a mixture of two or more of N-methyl-2-pyrrolidone, dimethylacetamide, and dimethylformamide.

Although any method can be used for heating in stretching, for example, a method of heating by contact heating using a hot plate, a heating roller, or the like, a method of using a heated gas such as steam, or the like is preferably used. Can be.
The heating temperature varies depending on the solvent used, etc., and is not particularly specified. In a region lower than this range, plasticization does not proceed sufficiently, and it is difficult to take a sufficient stretching ratio,
Above this range, good spinning becomes difficult because the surface of the yarn is melted and fused.

In the present invention, usually 1.5 times or more
The film is stretched at a draw ratio of at most 2 times, preferably at least 2 times and at most 10 times, more preferably at least 2.1 times and at most 6 times. By stretching at a high magnification, the strength and elastic modulus of the yarn are improved and good physical properties are exhibited, and at the same time, the holes are crushed and the densification by heat setting proceeds well. In addition, when the film is drawn at an extremely high magnification, the condition of the process is deteriorated, and it becomes difficult to produce a good yarn. The drawn yarn is wound up in cold water and applied to the next step in order to quench the orientation state.

[Step (3)] In the present invention, a coagulated yarn is produced in a porous state, and then densified after stretching to obtain a dense meta-aramid fiber. This step plays an important role for that. By performing a heat treatment at a temperature of 100 ° C. to 200 ° C. without washing the yarn quenched in the previous step, the porous yarn can be converted into a very transparent and dense yarn. Since the quenched yarn contains sufficient plasticizing solvent, it can be sufficiently dissolved and densified in the steam temperature range.

[Step 4] Next, after washing with cold water of, for example, 30 ° C. or less, further washing with warm water of 50 to 90 ° C., and drying at a temperature of usually 100 ° C. or more with a heating roller, hot air or the like. Thereafter, as described below, it is preferably subjected to a heat treatment such as a dry heat drawing at a temperature of 250 to 400 ° C. using a hot plate, a heat roller or the like.

This dry heat drawing step is an important step for densifying the porous linear body to develop strength and elongation. In particular, the temperature of dry heat drawing is closely related to the density,
It is preferable to perform the treatment in a temperature range of 250 ° C. or more and 400 ° C. or less. The temperature is more preferably 270 ° C or more and 370 ° C or less. At a high temperature exceeding 400 ° C., the yarn is severely deteriorated, colored, and further broken. On the other hand, if the temperature is lower than 250 ° C., it is not possible to sufficiently densify, and it is difficult to develop yarn physical properties.

The stretching ratio at this time is closely related to the development of the elastic modulus and the strength, and can be set to an arbitrary ratio as required, but is usually in the range of 0.7 to 3 times. By setting at, good spinnability, and the development of strength and elastic modulus can be obtained. Accordingly, the total draw ratio including plastic drawing and hot plate drawing is 3.0 to 12, and more preferably 2.5 to 8 times for the expression of densification and the development of yarn physical properties and stable spinning properties. It is more preferable to set as follows.

The meta-type aramid fiber obtained by the present invention has good stretchability, and can be smoothly drawn to a high magnification without causing breakage or fluff during hot water bath drawing or dry heat drawing.

In the present invention, wet spinning-drawing-washing-drying
Can be performed in a continuous integrated process, which is one of the advantages of the present invention. However, in some cases, the process may be performed by dividing into several processes and changing the order.

Further, the fiber produced in this way is subjected to crimping as required, cut into an appropriate fiber length, and provided to the next step.

As described above, the meta-type aromatic polyamide (meta-type aramid) fiber according to the present invention can be applied to various uses utilizing its heat resistance, flame resistance, and mechanical properties. It can be suitably used for applications that dislike. For example, it is useful as a heat-resistant and flame-resistant garment such as fire-fighting clothing, protective clothing, flame-resistant bedding, interior material, alone or in combination with other fibers.
In particular, it can be effectively used as a nonwoven fabric as a raw material for various industrial materials such as filters, synthetic paper, and composite materials.

[0058]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. However, these examples and comparative examples are for helping the understanding of the present invention, and the scope of the present invention is not limited by these descriptions. In the examples and comparative examples, the intrinsic viscosity (IV) was determined by isolating an aromatic polyamide polymer from a polymer solution, drying the polymer, and then drying the polymer in concentrated sulfuric acid.
It is a value measured at 30 ° C. at 5 g / 100 ml. Further, “parts” and “%” are all based on weight unless otherwise specified, and quantitative ratios indicate weight ratios unless otherwise specified. Further, the polymer concentration (PN concentration) in the polymer solution used for spinning is the weight part of the polymer with respect to the total weight part [= polymer / (polymer + solvent + others)]. The density of the porous linear body obtained by coagulation is
It was calculated from the fiber diameter and fineness measured according to D2130.

Example 1 (a) Preparation of Polymer Solution 18 parts by weight of polymetaphenylene isophthalamide powder obtained by the interfacial polymerization method was cooled to 0 ° C. in N-methyl-2.
After suspending in 78.5 parts by weight of pyrrolidone to form a slurry, the temperature was raised to 60 ° C. to obtain a transparent polymer solution.

(B) Wet spinning, plastic stretching and dry heat stretching The spinning stock solution prepared in the above (a) was discharged from a die having a pore size of 0.12 mm and 50 holes into a coagulation bath at a bath temperature of 80 ° C. and spun. . This coagulation bath uses a bath having a composition of water / NMP = 45/55, and a yarn speed of 8 m at an immersion length (effective coagulation bath length) of 60 cm.
/ Min, then draw it out into the air, pass it through a plastic bath (10 ° C, water / NMP = 70/30), apply a pin heater at 50 ° C, and stretch it at 3 times the draw ratio. Was done. The drawn yarn was quenched by passing through 20 cm of cold water, and heat-treated using a 140 ° C. heating roller. Further, it is washed with warm water of 80 ° C.
And dried on a hot plate at 300 ° C.
The film was stretched by dry heating twice and wound up. The total draw ratio in this example is 6 times, and the final winding speed of the drawn fiber is 48 m.
/ Min. The density of the porous linear body obtained from the coagulation bath was 0.8 (g / cm ³ ). The mechanical properties of the obtained polymetaphenylene isophthalamide fiber were as follows: a fineness of 1.8.
de (2.0 dtex), density 1.34, tensile strength 4.7 g / de (4.15 cN / dtex), elongation 58
%, Young's modulus 68 g / de (60.0 cN / dtex)
And showed good mechanical properties.

[0061]

According to the present invention, it is possible to provide a method for producing meta-type polyamide fibers having good mechanical properties and heat resistance and containing no salts with high productivity.
More specifically, a meta-type polyamide polymer solution containing a neutralized salt produced by a solution polymerization method, without separating the salt, has excellent mechanical properties, and has excellent heat resistance and flame retardancy. A method for producing meta-aramid fibers with good productivity could be provided.

Claims (2)

[Claims] 1. A method for producing a meta-type aromatic polyamide fiber by wet spinning a meta-type aromatic polyamide polymer solution comprising an amide-based solvent containing a meta-type aromatic polyamide having a meta-phenylenediamine isophthalamide skeleton as a main component. (1) discharging the polymer solution into a coagulation bath which holds a coagulation liquid comprising an amide-based solvent and water, and coagulating the polymer solution as a porous linear body;
Subsequently, the linear body was heated and stretched in the air while the coagulation liquid was contained in the pore or in a plastic bath, and (3) the coagulation liquid was contained in the pore. A method for producing a dense meta-type aromatic polyamide fiber, in which the linear body is heated at a temperature of 100 ° C. or more and 200 ° C. or less, and then (4) the linear body is heat-treated at 250 to 400 ° C. 2. As the amide solvent contained in the polymer solution, the coagulation bath and the plastic bath, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, and dimethylimidazo The method for producing a dense meta-type aromatic polyamide fiber according to claim 1, wherein one or more kinds selected from the group consisting of lydinones are used.