JP2018084000A - Meta-type wholly aromatic polyamide fiber and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel meta-type wholly aromatic polyamide fiber that has high breaking strength, and can resist coloration or discoloration at high temperature, while maintaining the original characteristics of the meta-type wholly aromatic polyamide fiber, such as heat resistance and flame retardancy.SOLUTION: Such a specific coagulation bath that has no skin core and takes a compact coagulation form, is used to conduct wet-spinning for a specific time, and plastic stretching is conducted in a specific ratio.SELECTED DRAWING: None

Description

  The present invention relates to a meta-type wholly aromatic polyamide fiber having an extremely small amount of residual solvent. More specifically, the present invention relates to a novel meta-type wholly aromatic polyamide fiber having excellent mechanical properties and capable of obtaining a high-quality product.

It is well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dichlorides are excellent in heat resistance and flame retardancy. It is also well known that these wholly aromatic polyamides are soluble in amide solvents and 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 wholly 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. . As methods for producing such meta-aramid fibers, the following two methods (a) and (b) are mainly employed.

  (A) A polymetaphenylene isophthalamide solution is prepared by subjecting metaphenylenediamine and isophthalic acid chloride to low temperature solution polymerization in N, N-dimethylacetamide. A method for producing a meta-aramid fiber by neutralizing with calcium oxide to obtain a polymer solution containing calcium chloride and dry spinning the obtained polymer solution (Patent Document 1).

  (B) contacting a non-good organic solvent system (eg, tetrahydrofuran) of the resulting polyamide containing metaphenylenediamine salt and isophthalic acid chloride with an aqueous system containing an inorganic acid acceptor and a soluble neutral salt; A method of isolating a polymetaphenylene isophthalamide polymer powder (Patent Document 2), re-dissolving the polymer powder in an amide solvent, and then wet spinning in an inorganic salt-containing aqueous coagulation bath (Patent Document 3).

  However, since the method (a) is dry spinning, in the fibrous polymer solution spun from the spinneret, the solvent is volatilized and dried from the vicinity of the surface of the formed fibrous material. A dense and strong skin layer is formed on the surface. For this reason, it was difficult to sufficiently remove the remaining solvent even if the fibrous material was subsequently washed with water or the like. Thus, the fiber obtained by the method (a) was yellowed during use in a high temperature atmosphere due to the solvent remaining in the fiber. For this reason, it is necessary to avoid heat treatment at a high temperature, and as a result, there is a problem that it is difficult to increase the strength.

  On the other hand, since the method (b) is wet spinning, the solvent does not volatilize at the spinning stage. However, when the fibrous polymer is introduced into an aqueous coagulation bath or an aqueous coagulation bath containing a high concentration of inorganic salt, the solvent is desorbed from the vicinity of the surface of the fibrous polymer into the aqueous coagulation bath and coagulated at the same time. The water contained in the coagulation bath liquid entered the inside of the fibrous material from the vicinity of the surface of the fibrous material, and a strong skin layer was generated. For this reason, it is difficult to sufficiently remove the solvent remaining in the fiber as in the case of the fiber by the dry spinning method, and coloring or discoloration (particularly yellowing) in a high temperature atmosphere caused by the remaining solvent can be avoided. There wasn't. Therefore, the fiber obtained by the method (b) also needs to avoid heat treatment at a high temperature, and there remains a problem that it is difficult to increase the strength of the fiber.

Patent Document 4 describes a meta-type wholly aromatic polyamide fiber containing a layered clay mineral.
The meta-type wholly aromatic polyamide fiber described in Patent Document 4 becomes a fiber having a low residual solvent amount by blending the layered clay mineral. However, meta-type wholly aromatic polyamide fibers containing these layered clay minerals have low insulation, which is a feature of meta-type wholly aromatic polyamides. Furthermore, layered clay minerals may fall off and scatter during cutting and twisting. there were. Therefore, further improvement has been demanded from the viewpoint of improving the insulation and preventing the layered clay mineral from falling off and scattering.

In Patent Document 5, the amount of solvent remaining in the fiber is 1.0% by weight or less, the dry heat shrinkage at 300 ° C. is 3% or less, and the breaking strength of the fiber is 4.5-6. A meta-type wholly aromatic polyamide fiber excellent in high-temperature processability, characterized by being 0.0 cN / dtex, is described.
However, Patent Document 5 does not report a fiber having a judgment strength of 6.1 cN / dtex or more, and has high breaking strength and dimensional stability as required for high-temperature filter base fabric use or rubber reinforcement use. There was a need for further improvements.

Japanese Patent Publication No. 35-14399 Japanese Patent Publication No.47-10863 Japanese Patent Publication No. 48-17551 JP 2007-254915 A Japanese Patent No. 5710593

  The present invention has been made in view of the above-described background art, and the object of the present invention is to maintain the properties inherent to the meta-type wholly aromatic polyamide fiber such as heat resistance and flame retardancy, while having a breaking strength. It is an object of the present invention to provide a novel meta-type wholly aromatic polyamide fiber that is high and can suppress coloring or discoloration of a product even under high temperature processing and use conditions.

  The inventors of the present invention have made extensive studies in view of the above problems. As a result, it has been found that the above-mentioned problems can be solved by performing wet spinning using a specific coagulation bath that does not have a skin core and takes a dense solidification form, and performing plastic drawing within a specific magnification range. The invention has been completed.

  That is, the present invention is a meta-type wholly aromatic polyamide fiber substantially free of layered clay mineral, and the amount of solvent remaining in the fiber is 0.01 to 0.1% by mass or less based on the whole fiber. It is a meta-type wholly aromatic polyamide fiber having a breaking strength of 6.1 to 7.0 cN / dtex.

  Another aspect of the present invention is a method for producing the above fiber, wherein the coagulated yarn is obtained by setting the mass composition ratio of the amide solvent and water in the coagulation bath to 50/50 to 60/40 and the coagulation time to 15 to 70 seconds. A method for producing a meta-type wholly aromatic polyamide fiber obtained by plastic stretching the obtained coagulated yarn at a draw ratio of 4.0 to 10.0 times and 1.1 to 1.8 times using a hot plate or the like It is.

  According to the present invention, meta-type wholly aromatic polyamide fibers (especially, having good mechanical properties, heat resistance, etc., having a very small amount of solvent remaining in the fibers, and substantially free of layered clay minerals, Polymetaphenylene isophthalamide fiber). The fiber of the present invention has a very high strength in addition to the performance inherent in meta-type wholly aromatic polyamide fibers such as heat resistance or flame retardancy, and is a fiber or fiber product in processing and use at high temperatures. Coloring or discoloration (particularly yellowing) can be suppressed. Therefore, the fiber of the present invention can be used in fields that cannot be used with conventional meta-type wholly aromatic polyamide fibers, and its industrial value is extremely high.

Hereinafter, embodiments of the present invention will be described in detail.
<Meta type wholly aromatic polyamide fiber>
The meta-type wholly aromatic polyamide fiber of the present invention has the following specific physical properties. The physical properties, configuration, and production method of the meta-type wholly aromatic polyamide fiber of the present invention will be described below.

[Physical properties of meta-type wholly aromatic polyamide fibers]
The meta-type wholly aromatic polyamide fiber of the present invention has a remaining solvent amount of 0.01 to 0.1% by mass or less and a fiber breaking strength of 6.1 to 7.0 cN / dtex. For this reason, the meta-type wholly aromatic polyamide fiber of the present invention can suppress the coloring or discoloration of the fiber or the product even in processing and use at a high temperature.

[Residual solvent amount]
Since the meta-type wholly aromatic polyamide fiber is usually produced from a spinning stock solution in which a polymer is dissolved in an amide solvent, the solvent necessarily remains in the fiber. However, in the meta-type wholly aromatic polyamide fiber of the present invention, the amount of the solvent remaining in the fiber is 0.01 to 0.1 mass with respect to the mass of the fiber. It is essential that the content is 0.01 to 0.1% by mass, and more preferably 0.01 to 0.08% by mass. Most preferably, it is 0.01-0.06 mass%.
When the solvent remains in the fiber in excess of 0.1% by mass with respect to the mass of the fiber, yellowing easily occurs during processing and use in a high-temperature atmosphere exceeding 200 ° C. Further, the strength is remarkably lowered, which is not preferable.
In the present invention, in order to make the residual solvent amount in the meta-type wholly aromatic polyamide fiber 0.01 to 0.1% by mass, in the fiber manufacturing process, a dense solidified form without a skin core is taken. Wet spinning using a specific coagulation bath.
In the present invention, the “amount of solvent remaining in the fiber” refers to a value obtained by the following method.

(Measurement method of residual solvent amount)
About 8.0 g of fibrils are collected, dried at 105 ° C. for 120 minutes, allowed to cool in a desiccator, and the fiber mass (M1) is weighed. Subsequently, this fiber is subjected to reflux extraction using a Soxhlet extractor in methanol for 1.5 hours to extract an amide solvent contained in the fiber. The fiber after extraction is taken out, vacuum-dried at 150 ° C. for 60 minutes, allowed to cool in a desiccator, and the fiber mass (M2) is weighed. The amount of solvent (amide solvent mass) N (%) remaining in the fiber is calculated by the following formula using M1 and M2 obtained.
N (%) = [(M1-M2) / M1] × 100

[Breaking strength]
The meta-type wholly aromatic polyamide fiber of the present invention has a breaking strength in the range of 6.1 to 7.0 cN / dtex. It is essential to be in the range of 6.1 to 7.0 cN / dtex. The range is preferably 6.9 cN / dtex. Furthermore, the range of 6.2 to 6.9 cN / dtex is more preferable, and the range of 6.3 to 6.9 cN / dtex is most preferable.
If the breaking strength is less than 6.1 cN / dtex, the resulting product has low mechanical strength, which makes it difficult to withstand use for products. On the other hand, when it exceeds 7.0 cN / dtex, problems such as a significant decrease in elongation and difficulty in handling the product occur.
In the meta-type wholly aromatic polyamide fiber of the present invention, in order to bring the “breaking strength” within the above range, a specific coagulation bath that does not have a skin core and takes a dense solidification form is used in the fiber production process. It is used to wet-spin over a specific time, and plastic stretching is performed within a specific magnification range.

[Elongation at break]
The meta-type wholly aromatic polyamide fiber of the present invention preferably has a breaking elongation of 15% or more, more preferably 18% or more, and particularly preferably 20% or more. When the elongation at break is less than 15%, the process passability in the post-processing step is lowered, which is not preferable.
In the present invention, the “breaking elongation” of the meta-type wholly aromatic polyamide fiber is specified by using a specific coagulation bath that does not have a skin core and takes a dense solidification form in the coagulation step in the production method described later. It can be controlled by wet spinning over time.

[Cross-sectional shape and fineness of single fiber]
The cross-sectional shape of the meta-type wholly aromatic polyamide fiber of the present invention may be circular, elliptical, or any other shape, and the fineness (single yarn fineness) of the single fiber is generally 0.5 to 10.0 dtex. It is preferable that it is the range of these.
Further, the meta-type wholly aromatic polyamide fiber of the present invention is obtained by wet spinning using a spinneret having a large number of spinning holes, for example, 1,000 to 70,000 dtex with 500 to 30,000 holes per die, preferably Is obtained as a tow of 3,300-45,000 dtex with 1,500-20,000 holes.

[Configuration of meta-type wholly aromatic polyamide]
The meta-type wholly aromatic polyamide constituting the meta-type wholly aromatic polyamide fiber of the present invention is composed of a meta-type aromatic diamine component and a meta-type aromatic dicarboxylic acid component, and the object of the present invention is impaired. Other copolymer components such as the para type may be copolymerized within the range not included.
Particularly preferred for use in the present invention is a meta-type wholly aromatic polyamide mainly composed of a metaphenylene isophthalamide unit from the viewpoints of mechanical properties, heat resistance and flame retardancy.
As the meta-type wholly aromatic polyamide composed of metaphenylene isophthalamide units, the metaphenylene isophthalamide units are preferably 90 mol% or more of the total repeating units, more preferably 95 mol% or more, particularly preferably. 100 moles.

[Raw material for meta-type wholly aromatic polyamide]
(Meta-type aromatic diamine component)
Examples of the meta-type aromatic diamine component used as a raw material for the meta-type wholly aromatic polyamide include metaphenylene diamine, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfone, and the like, halogens in these aromatic rings, Examples of derivatives having a substituent such as an alkyl group having 1 to 3 carbon atoms, such as 2,4-toluylenediamine, 2,6-toluylenediamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene, etc. can do. Of these, metaphenylenediamine alone or a mixed diamine containing metaphenylenediamine in an amount of 85 mol% or more, preferably 90 mol% or more, particularly preferably 95 mol% or more is preferable.

(Meta-type aromatic dicarboxylic acid component)
Examples of the raw material of the meta type aromatic dicarboxylic acid component constituting the meta type wholly aromatic polyamide include a meta type aromatic dicarboxylic acid halide. Examples of the meta-type aromatic dicarboxylic acid halide include isophthalic acid halides such as isophthalic acid chloride and isophthalic acid bromide, and derivatives having substituents such as halogen and alkoxy groups having 1 to 3 carbon atoms on the aromatic ring, such as 3 -Chloroisophthalic acid chloride etc. can be illustrated. Of these, isophthalic acid chloride itself or a mixed carboxylic acid halide containing isophthalic acid chloride in an amount of 85 mol% or more, preferably 90 mol% or more, particularly preferably 95 mol% or more is preferable.

[Method for producing meta-type wholly aromatic polyamide]
The production method of the meta-type wholly aromatic polyamide is not particularly limited. For example, it is produced by solution polymerization or interfacial polymerization using a meta-type aromatic diamine component and a meta-type aromatic dicarboxylic acid chloride component as raw materials. be able to.
In addition, the molecular weight of the meta-type wholly aromatic polyamide used in the present invention is not particularly limited as long as it can form fibers. In general, in order to obtain a fiber having sufficient physical properties, a polymer having an intrinsic viscosity (IV) measured in a concentrated sulfuric acid at 30 ° C. with a polymer concentration of 100 mg / 100 mL sulfuric acid is in a range of 1.0 to 3.0. Appropriate polymers in the range of 1.2 to 2.0 are particularly preferred.

<Method for producing meta-type wholly aromatic polyamide fiber>
The meta-type wholly aromatic polyamide fiber of the present invention uses, for example, the aromatic polyamide obtained by the above production method, for example, a spinning solution preparation step, a spinning / coagulation step, a plastic drawing bath drawing step described below, It is manufactured through a washing process, a dry heat treatment process, and a heat stretching process.

[Spinning liquid preparation process]
In the spinning solution preparation step, the meta type wholly aromatic polyamide is dissolved in an amide solvent to prepare a spinning solution (meta type wholly aromatic polyamide polymer solution). In preparing the spinning solution, an amide solvent is usually used, and examples of the amide solvent used include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc). be able to. Of these, NMP or DMAc is preferably used from the viewpoints of solubility and handling safety.
The solution concentration 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 a meta type such as polymetaphenylene isophthalamide. When it is a wholly aromatic polyamide and the solvent is an amide solvent such as NMP, it is usually preferably in the range of 15 to 40% by mass.

[Spinning and coagulation process]
In the spinning / coagulation step, the spinning solution (meta-type wholly aromatic polyamide polymer solution) obtained above is spun into a coagulation solution and coagulated to obtain a coagulated yarn.
The spinning device is not particularly limited, and a conventionally known wet spinning device can be used. In addition, the number of spinning holes of the spinneret, the arrangement state, the hole shape and the like are not particularly limited as long as they can be stably wet-spun. For example, the number of holes is 1,00 to 30,000, the diameter of the spinning hole May be a multi-hole spinneret for sufu having a diameter of 0.04 to 0.07 mm.
The temperature of the spinning solution (meta-type wholly aromatic polyamide polymer solution) when spinning from the spinneret is suitably in the range of 20 to 90 ° C.

In order to obtain the fiber of the present invention, it is important to use a specific coagulation bath. In the present invention, it is essential that the mass composition ratio of the amide solvent and water in the coagulation bath is 55/45 to 65/35, and preferably 56/44 to 64/36. Furthermore, it is especially preferable to set it as 57 / 43-63 / 37.
When the ratio of the amide solvent (preferably NMP) to the mass composition ratio of water is less than 55 wt%, the water in the coagulation liquid penetrates into the coagulated yarn, and a void is formed in the yarn, thereby forming a plastic drawing bath. The stretching ratio cannot be increased in the process, and as a result, high strength cannot be achieved. In addition, the skin formed on the surface of the obtained coagulated yarn has a thick structure, the cleaning efficiency in the subsequent cleaning process is lowered, and it is difficult to reduce the residual solvent amount of the fiber. On the other hand, when the ratio of the amide solvent (preferably NMP) to the mass composition ratio of water exceeds 65 wt%, the amount of residual solvent inside the fiber is large, so that the orientation does not progress in the plastic stretching bath process, and the Unable to achieve strength. In addition, uniform solidification cannot be performed up to the inside of the fiber, which makes it difficult to reduce the residual solvent amount of the fiber.

In order to obtain the fiber of the present invention, it is important to set a specific coagulation time. In the present invention, the immersion time of the fibrous material (thread body) in the coagulation bath is indispensable for 15 to 70 seconds, and preferably 20 to 65 seconds. Further, it is particularly preferably 30 to 60 seconds. If it is less than 15 seconds, the shape of the fibrous material is insufficient, so that yarn breakage occurs before the orientation is improved in the stretching step. When the immersion time exceeds 70 seconds, productivity is lowered, which is not preferable.
In the present invention, by setting the conditions of the coagulation bath as described above, the skin layer formed on the fiber surface can be thinned to have a uniform structure up to the inside of the fiber. Strength can be improved.
By this spinning / coagulation step, a fiber (tow) made of a coagulated yarn of a porous meta-type wholly aromatic polyamide is formed in the coagulation bath, and then drawn from the coagulation bath into the air.

[Plastic stretching bath stretching process]
In the plastic drawing bath drawing step, the fiber is drawn in the plastic drawing bath while the fiber obtained by coagulation in the coagulation bath is in a plastic state.
It does not specifically limit as a plastic drawing bath liquid, A conventionally well-known thing can be employ | adopted. For example, an aqueous solution composed of an aqueous solution of an amide solvent and substantially free of salts can be used, and industrially, it is particularly preferable to use the same type of solvent as that used in the coagulation bath. That is, the amide solvent used for the polymer solution, the coagulation bath, and the plastic drawing bath is preferably the same, and a single solvent of N-methyl-2-pyrrolidone (NMP) or a mixture of two or more containing NMP. It is particularly preferable to use a solvent. By using the same kind of amide solvent, the recovery process can be integrated and simplified, which is economically beneficial.
The temperature and composition of the plastic stretching bath are closely related to each other, but can be suitably used as long as the mass concentration of the amide solvent is 20 to 70% by mass and the temperature is in the range of 20 to 70 ° C. . In a region lower than this range, plasticization of the porous fibrous material does not proceed sufficiently, and it becomes difficult to obtain a sufficient stretching ratio in plastic stretching. On the other hand, in a region higher than this range, the surface of the porous fiber is melted and fused, making it difficult to produce a good yarn.

In order to obtain the fiber of this invention, it is necessary to make the draw ratio in a plastic drawing bath into the range of 5.0-15.0 times, Preferably it is 5.0-12.0 times, More preferably, it is 5. The range is 0 to 10.0 times, and most preferably 5.0 to 8.0 times. In the present invention, the breaking strength of the fiber finally obtained can be ensured by performing stretching in the plastic stretching bath within the range of the magnification and increasing the molecular chain orientation by stretching.
When the draw ratio in the plastic drawing bath is less than 5.0 times, it becomes difficult to obtain a fiber having a breaking strength of 6.1 cN / dtex or more. On the other hand, when the draw ratio exceeds 15.0 times, single yarn breakage occurs, resulting in poor production stability.
The temperature of the plastic stretching bath is preferably in the range of 20 to 90 ° C. When the temperature is in the range of 20 to 90 ° C., the process condition is good, which is preferable. The temperature is more preferably 20 to 60 ° C.

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

The temperature condition and the concentration condition of the amide solvent are not particularly limited as long as the quality of the finally obtained fiber can be satisfied, but if the initial washing bath is at a high temperature of 60 ° C. or higher, water Intrusion into the fiber occurs all at once, and a huge void is generated in the fiber, resulting in quality degradation. For this reason, it is preferable that the first washing bath has a low temperature of 30 ° C. or lower.
If the solvent remains in the fiber, coloring or discoloration (particularly yellowing) of the fiber at high temperatures cannot be suppressed, and physical properties and shrinkage, limiting oxygen index (LOI), etc. Give rise to For this reason, the amount of the solvent contained in the fiber of the present invention needs to be 0.01 to 0.1% by mass, and more preferably 0.01 to 0.08% by mass. Especially preferably, it is the range of 0.01-0.06 mass%.

[Dry heat treatment process]
In order to obtain the fiber of the present invention, a dry heat treatment step is preferably performed on the fiber that has undergone the washing step. In the dry heat treatment step, the fiber that has been washed in the washing step is preferably dry heat treated at a temperature in the range of 100 to 250 ° C, more preferably 100 to 200 ° C. Here, the dry heat treatment is not particularly limited, but is preferably under constant tension.
When the drying heat treatment step is subsequently performed after the washing step, the fluidity of the polymer can be improved moderately, the crystallization can be suppressed while the orientation proceeds, and the densification of the fibers can be promoted. In addition, the temperature of said dry heat processing says the preset temperature of fiber heating means, such as a hot plate and a heating roller.

[Hot drawing process]
In the present invention, a hot drawing step is performed on the fiber that has undergone the dry heat treatment step. In the thermal stretching step, it is preferable to perform stretching within 1.2 to 1.8 times while applying heat treatment at 310 to 335 ° C. When the heat treatment temperature in the hot drawing process is a high temperature exceeding 335 ° C., the yarn is colored and severely deteriorates, not only the breaking strength is lowered, but also it may break. On the other hand, at a temperature lower than 310 ° C., sufficient crystallization of the fiber cannot be achieved, and it becomes difficult to express desired fiber physical properties, that is, mechanical properties such as breaking strength and thermal properties.
There is a close relationship between the treatment temperature in the hot drawing step and the density of the resulting fiber. In order to obtain a product having a particularly good fiber density, it is preferable that the heat treatment temperature in the hot stretching step is in a range of 310 to 335 ° C. The heat treatment is particularly preferably a dry heat treatment, and the heat treatment temperature in the heat drawing step refers to a set temperature of a fiber heating means such as a hot plate or a heating roller.
Further, the draw ratio in the heat drawing step is closely related to the strength and elastic modulus expression of the obtained fiber. In order to obtain the fiber of the present invention, it is usually preferable to set the range of 1.2 to 1.8 times, preferably 1.2 to 1.5 times. Necessary strength and elastic modulus can be expressed while maintaining heat stretchability.

<Use of meta-type wholly aromatic polyamide fiber>
The meta-type wholly aromatic polyamide fiber of the present invention is subjected to crimping or the like as necessary, cut into a suitable fiber, etc., and provided to spinning and other subsequent processes.
Thus, the meta type omnidirectional polyamide fiber of the present invention can be applied to various uses utilizing its heat resistance, flame resistance and mechanical properties. For example, the fibers of the present invention can be used alone or in combination with other fibers to form a woven or knitted fabric, which can be used as a heat-resistant and flame-resistant garment such as fire-fighting clothes and protective clothing, flame-resistant bedding, and interior materials. Further, it can be effectively used as a nonwoven fabric as various industrial materials such as filters, or as a raw material for synthetic paper and composite materials.

  In particular, the meta-type wholly aromatic polyamide fiber of the present invention can maintain high strength and suppress coloring or discoloration of the product even when processed and used at high temperatures. Therefore, it is used in applications exposed to high temperatures, such as high-temperature felt base fabrics, high-temperature gas filters, or matrix reinforcements such as rubber and resin, taking advantage of high strength. As particularly useful.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and the like, but the present invention is not limited to these examples and the like. “Part” and “%” are based on “mass” unless otherwise specified, and “quantity ratio” indicates “mass ratio” unless otherwise specified. Further, the polymer concentration (PN concentration) in the polymer solution (spinning stock solution) used for spinning is “% by mass of polymer” with respect to “total mass part”, that is, [polymer / (polymer + solvent + others)]. × 100 (%).

<Measurement method>
[Intrinsic viscosity (IV)]
After the aromatic polyamide polymer was isolated from the polymer solution and dried, it was measured in concentrated sulfuric acid at a polymer concentration of 100 mg / 100 mL sulfuric acid at 30 ° C.
[Single yarn fineness]
In accordance with JIS L 1015, the measurement based on the A method of the positive fineness was carried out and expressed in apparent fineness.
[Breaking strength, breaking elongation, initial elastic modulus]
Measurement was performed under the following conditions based on JIS L 1015 using a tensile tester (manufactured by Instron, model: 5565).
(Measurement condition)
Grasp interval: 20mm
Initial load: 0.044 cN (1/20 g) / dtex
Tensile speed: 20 mm / min [amount of solvent remaining in fiber (residual solvent amount) N (%)]
The fibers were sampled on the exit side of the washing step, and the fibers were subjected to a centrifuge (rotation speed: 5,000 rpm) for 10 minutes, and the fiber mass (M1) at this time was measured. This fiber was boiled in methanol having a mass of 2 g for 4 hours to extract the amide solvent and water in the fiber. The fiber after extraction was dried at 105 ° C. for 2 hours, and the fiber mass (P) after drying was measured. Moreover, the mass concentration (C) of the amide solvent contained in the extract was determined by gas chromatography.
N = [C / 100] × [(M1 + M2-P) / P] × 100
[Hue value (L ^* -b ^* )]
Hue values were measured for the obtained fiber and the fiber after heat treatment for 10 minutes in a dryer at 300 ° C. Specifically, using a color measuring device (manufactured by Masbek Co., Ltd., trade name: Macbeth Color Eye Model CE-3100), measurement was performed under the following measurement conditions, and the hue value (L ^* -b ^* ) was changed. Asked. The hue value (L ^* -b ^* ) indicates that yellowing is more remarkable as the numerical value is smaller. Note that L ^* and b ^* can be obtained from tristimulus values defined in JIS Z 8882 (color display method by 10-degree visual field XYZ system).
(Measurement condition)
Field of view: 10 degrees Light source: D65
Wavelength: 360-740 nm

<Example 1>
[Spinning stock solution (spinning dope for spinning) adjustment process]
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. After the change in viscosity stopped, stirring was continued for 40 minutes to complete the 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 1.25. The polymer concentration in the polymer solution was 20%.
[Spinning process]
The obtained polymer solution was spun as a spinning stock solution from a spinneret having a pore diameter of 0.06 mm and a pore number of 1,500 into a coagulation bath having a bath temperature of 20 ° C. and a length of 5 m. The composition of the coagulation liquid was DMAc / water (amount ratio) = 55/45, and spinning was performed by discharging into a coagulation bath at a yarn speed of 5 m / min (coagulation time 60 seconds).
[Plastic stretching process]
Subsequently, the film was stretched at a draw ratio of 7.0 in a plastic stretching bath having a composition of DMAc / water = 60/40 at a temperature of 40 degrees.
[Washing process]
After plastic stretching, 20 ° C. DMAc / water = 30/70 bath (immersion length 1.8 m), followed by 20 ° C. water bath (immersion length 3.6 m), 60 ° C. hot water bath (immersion length 5.4 m) ) And then passed through a warm water bath (7.2 m) at 80 ° C. for sufficient washing.
[Dry heat treatment process]
The washed fibers were subsequently subjected to a drying heat treatment under constant tension with a hot roller having a surface temperature of 150 ° C.
[Hot drawing process]
Subsequently, a heat treatment step of stretching 1.5 times while applying heat treatment was performed with a heat roller having a surface temperature of 335 ° C., and finally polymetaphenylene isophthalamide fiber was obtained.
[Measurement / Evaluation]
Various measurement evaluation was implemented with respect to the obtained fiber (tow). The results are shown in Table 1.

<Example 2>
A polymetaphenylene isophthalamide fiber was produced in the same manner as in Example 1 except that the spinning speed was 17 m / min (coagulation time 18 seconds) and the composition of the coagulation liquid was DMAc / water = 60/40. Table 1 shows various measurement results for the obtained fibers.

<Comparative Example 1>
A polymetaphenylene isophthalamide fiber was produced in the same manner as in Example 1 except that the composition of the coagulation liquid was DMAc / water = 40/60. The draw ratio in the plastic drawing bath could not be drawn up to 7.0 times, and the draw ratio in the plastic drawing bath was 4.5 times. Others show various measurement results for the obtained fibers in Table 1.

<Comparative example 2>
A polymetaphenylene isophthalamide fiber was produced in the same manner as in Example 1 except that the spinning speed was 23 m / min (coagulation time 13 seconds). The draw ratio in the plastic drawing bath could not be drawn up to 7.0 times, and the draw ratio in the plastic drawing bath was 4.8 times. Table 1 shows various measurement results for the obtained fibers.

<Comparative Example 3>
A polymetaphenylene isophthalamide fiber was produced in the same manner as in Example 1 except that the temperature of the coagulation bath was 30 ° C. and the composition of the coagulation liquid was DMAc / water = 70/30. Table 1 shows various measurement results for the obtained fibers.

<Comparative Example 4>
In order to obtain a fiber of 7.0 cN / dtex or more, polymetaphenylene isophthalamide fiber was produced in the same manner as in Example 1 except that the fiber was drawn at a draw ratio of 16.0 times in a plastic drawing bath. . However, yarn breakage occurred in the drawing bath, and fibers could not be obtained stably.

Claims (2)

  A meta-type wholly aromatic polyamide fiber having a residual solvent amount of 0.01 to 0.1% by mass relative to the mass of the entire fiber and a breaking strength of 6.1 to 7.0 cN / dtex.   A method for producing a meta-type wholly aromatic polyamide fiber according to claim 1, wherein the mass composition ratio (coagulation bath concentration) of the amide solvent and water in the coagulation bath is 55/45 to 65/35, and the coagulation time is A method for producing a meta-type wholly aromatic polyamide fiber in which a coagulated yarn is obtained in 15 to 70 seconds, and the obtained coagulated yarn is plastic-drawn at a draw ratio of 5.0 to 15.0 times.