JP2011226023A - Stretch-broken spun yarn composed of meta-type wholly aromatic polyamide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretch-broken spun yarn composed of a novel meta-type wholly aromatic polyamide fiber having high mechanical strength and capable of suppressing the generation of gas under a high-temperature atmosphere in addition to heat resistance and flame retardancy a meta-type wholly aromatic polyamide fiber originally possesses.SOLUTION: The meta-type wholly aromatic polyamide fiber is obtained by the steps of appropriately controlling the ingredients or condition in a coagulation bath to make a compact coagulated form with no skin-core structure, plastically drawing the coagulated product in the range of a specific ratio, and then performing a hot drawing step under the specific condition.

Description

  The present invention relates to a check spun yarn made of a meta-type wholly aromatic polyamide fiber. More particularly, the present invention relates to a check spun yarn made of a novel meta-type wholly aromatic polyamide fiber that has excellent mechanical properties and can reduce gas generation during high-temperature processing and use in a high-temperature atmosphere.

  Conventionally, it is known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides are excellent in heat resistance and flame retardancy. Among such wholly aromatic polyamides, meta-type wholly aromatic polyamides (sometimes referred to as “meta-aramid”) fibers represented by polymetaphenylene isophthalamide are particularly useful as heat-resistant and flame-retardant fibers. It is.

  Meta-type wholly aromatic polyamide fibers are widely used in fields exposed to high temperatures by taking advantage of their properties.For example, they are widely used as materials for bag filters that collect fine particles in exhaust gas from municipal waste incinerators. in use. Bag filters are generally in the form of woven fabrics or felts, and the characteristics required of filter cloths depend on the gas properties contained in the dust and exhaust gas to be collected. Common strength is required.

  By the way, felt fabric, which is one form of bag filter, is usually obtained by entanglement of short fibers with a needle punch method, so it has excellent breathability but lacks physical properties such as tensile strength and mechanical properties. It has been difficult to apply to the process of removing dust by vibration or reverse airflow. Therefore, for the purpose of improving the physical characteristics of the bag filter, there has been proposed a felt fabric in which a woven fabric made of spun yarn is used as a scrim (base fabric) and in which short fibers are entangled.

  Here, as a method for producing a spun yarn made of a meta-type wholly aromatic polyamide, for example, a check spinning method is used (see Patent Document 1). According to the check spinning method, it is necessary to go through complicated processes such as crimping, cutting, cotton sacking, carding, kneading, roving, and rewinding, which are necessary processes in the conventional spinning yarn manufacturing method. Absent. In addition, according to this method, since there is little influence of crimping and disorder of the orientation of single yarn fiber, unlike conventional spun yarn, it has extremely low elongation, high strength, low crimp, and high creep resistance. A heat-resistant spun yarn can be obtained. However, the meta-type wholly aromatic polyamide fiber obtained by adopting the conventional wet spinning method has a large amount of residual solvent. Therefore, the spun yarn obtained from the fiber and the product processed from the spun yarn are not subjected to a high temperature atmosphere. The problem of generating gas was left.

  Here, Patent Document 2 and Patent Document 3 describe meta-type wholly aromatic polyamide fibers containing layered clay minerals. The meta-type wholly aromatic polyamide fibers described in Patent Documents 2 and 3 become fibers with 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 characteristic of meta-type aromatic polyamides. Furthermore, layered clay minerals may fall off and scatter during cutting and twisting. It was. Therefore, further improvement has been demanded from the viewpoint of improving the insulation and preventing the layered clay mineral from falling off and scattering.

  Furthermore, in Patent Document 4, 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 3.0 cN. A meta-type wholly aromatic polyamide fiber excellent in high-temperature processability, characterized by being / dtex or more is described. However, in Patent Document 4, fibers having a breaking strength of 4.5 cN / dtex or more have not been reported, and further improvement has been demanded for high breaking strength and dimensional stability.

Japanese Patent Laid-Open No. 02-234932 JP 2007-254915 A JP 2007-262589 A International Publication No. 2007/089008 Pamphlet

  The present invention has been made in view of the above prior art, and the object of the present invention is a novel meta-type total fragrance having high mechanical strength and capable of suppressing gas generation in a high-temperature atmosphere. It is to provide a check spun yarn made of a group polyamide fiber.

  The present inventors have intensively studied to solve the above problems. As a result, the components or conditions of the coagulation bath are adjusted as appropriate so as to obtain a dense solidification form without a skin core, and plastic stretching is performed within a specific magnification range, and the subsequent hot stretching process is performed under specific conditions. The present inventors have found that the above-mentioned problems can be solved by using a meta-type wholly aromatic polyamide fiber obtained in this way, and have completed the present invention.

  That is, the present invention is a check spun yarn composed of a meta-type wholly aromatic polyamide fiber, wherein the meta-type wholly aromatic polyamide fiber does not substantially contain a layered clay mineral and the amount of solvent remaining in the fiber Is a meta-type wholly aromatic polyamide check spun yarn having a fiber breaking strength of 4.5 to 6.0 cN / dtex.

  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, A check spun yarn comprising a polymetaphenylene isophthalamide fiber) is provided. That is, the check spun yarn of the present invention has strength in addition to the inherent properties of meta-type wholly aromatic polyamide fibers such as heat resistance or flame retardancy, but also has the strength of gas in processing and use at high temperatures. Occurrence can be suppressed. Therefore, the check spun yarn of the present invention can be used in a field that cannot be used with a check spun yarn using a conventional meta-type wholly aromatic polyamide fiber, and its industrial value is extremely large.

<Meta type wholly aromatic polyamide fiber>
The meta-type wholly aromatic polyamide fiber used as the material for the check spun yarn of the present invention has the following specific physical properties. The physical properties, configuration, production method and the like of the meta-type wholly aromatic polyamide fiber used in the present invention will be described below.

[Physical properties of meta-type wholly aromatic polyamide fibers]
The meta-type wholly aromatic polyamide fiber used in the present invention has a breaking strength within a certain range, and the amount of the solvent remaining in the fiber is very small. Specifically, the layered clay mineral is not substantially contained, the amount of the solvent remaining in the fiber is 1.0% by mass or less, and the breaking strength of the fiber is 4.5 to 6.0 cN / dtex. is there. For this reason, the meta-type wholly aromatic polyamide fiber used in the present invention reduces the generation of gas as compared with conventional meta-type wholly aromatic polyamide fiber even in processing and use at high temperatures. Can do.

[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 used in the present invention, the amount of the solvent remaining in the fiber is 1.0% by mass or less with respect to the fiber mass. It is essential that it is 1.0 mass% or less, and it is more preferable that it is 0.5 mass% or less. Most preferably, it is 0.01-0.1 mass%.

When the solvent remains in the fiber in excess of 1.0% by mass with respect to the fiber mass, gas is generated during processing and use in a high temperature atmosphere exceeding 200 ° C., This is not preferable because the strength is significantly reduced.
In order to reduce the amount of residual solvent in the meta-type wholly aromatic polyamide fiber to 1.0% by mass or less, plastic stretching is performed within a range of a specific magnification, and further thermal stretching is performed under specific conditions.
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)
The fibers are sampled on the exit side of the washing step, and the fibers are subjected to a centrifuge (rotation speed: 5,000 rpm) for 10 minutes, and the fiber mass (M1) at this time is measured. The fiber is boiled for 4 hours in methanol having a mass of 2 g, and the amide solvent and water in the fiber are extracted. The fiber after extraction is dried at 105 ° C. for 2 hours, and the fiber mass (P) after drying is measured. Further, the mass concentration (C) of the amide solvent contained in the extract is determined by gas chromatography.
The amount of solvent (amide solvent mass) N (%) remaining in the fiber is calculated by the following equation using M1, M2, P, and C described above.
N = [C / 100] × [(M1 + M2-P) / P] × 100

〔Breaking strength〕
The meta-type wholly aromatic polyamide fiber used in the present invention has a breaking strength in the range of 4.5 to 6.0 cN / dtex. It is essential to be in the range of 4.5 to 6.0 cN / dtex, and preferably in the range of 5.5 to 6.0 cN / dtex. Further, it is particularly preferably in the range of 5.7 to 6.0 cN / dtex, 5.8 to 6.0 cN / dtex. When the breaking strength is less than 4.5 cN / dtex, it is not preferable because the strength of the product obtained is low and the product cannot be used for use. On the other hand, when it exceeds 6.0 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, in order to make the “breaking strength” within the above range, the components or conditions of the coagulation bath are adjusted as appropriate so that the solid coagulation form does not have a skin core, and the specific magnification range. The plastic stretching is performed, and the subsequent thermal stretching is performed under specific conditions.

In addition, the "breaking strength" before the check-out process in the present invention refers to a value obtained by measurement under the following conditions using JIS L 1013 and using model number 5565 manufactured by Instron as a measuring instrument.
(Measurement condition)
Grasp interval: 20mm
Initial load: 0.044 cN (1/20 g) / dtex
Tensile speed: 20 mm / min

[Elongation at break]
The meta-type wholly aromatic polyamide fiber used in 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.

The “breaking elongation” of the meta-type wholly aromatic polyamide fiber can be controlled by providing a dense solidified form without a skin core in the solidification step in the production method described later. In order to achieve 15% or more, the coagulation liquid may be an aqueous solution having an NMP (N-methyl-2-pyrrolidone) concentration of 45 to 60% by mass, and the bath liquid temperature may be 10 to 50 ° C.
Here, the “breaking elongation” refers to a value obtained by measurement under the above-mentioned “breaking strength” measurement conditions based on JIS L 1013.

[300 ° C dry heat shrinkage]
Further, the meta-type wholly aromatic polyamide fiber used in the present invention preferably has a 300 ° C. dry heat shrinkage of 5.0% or less, and more preferably in the range of 1.0 to 4.0%. . In the case where the 300 ° C. dry heat shrinkage ratio is large, the fiber structure shrinks when the formed fiber structure is exposed to a high temperature, making it difficult to design the fiber structure. Especially preferably, it is 0.1 to 3.0% of range.

In the meta-type wholly aromatic polyamide fiber, in order to reduce the 300 ° C. dry heat shrinkage to 5.0% or less, in the production method described later, the heat treatment temperature in the heat stretching step is in the range of 310 to 335 ° C. Good. If it is less than 310 ° C., the dry heat shrinkage rate becomes large.
In the present invention, “300 ° C. dry heat shrinkage” refers to a value obtained by the following method.

(Measurement method of 300 ° C dry heat shrinkage)
A load of 98 cN (100 g) is hung on a tow of about 3,300 dtex and marked at 30 cm away from each other. After removing the load, the tow is placed in an atmosphere of 300 ° C. for 15 minutes, and then the length L between the marks is measured. Based on the measurement result L, the value obtained by the following equation is defined as 300 ° C. dry heat shrinkage (%).
300 ° C. dry heat shrinkage (%) = [(30−L) / 30] × 100

[Initial elastic modulus]
Meta-type wholly aromatic polyamide fibers used in the present invention preferably has an initial modulus of 800~1,500cN / mm ^2, more preferably in the range of 900~1,500cN / mm ^2. If the initial elastic modulus is in the range of 800 to 1,500 cN / mm ² , the durability of the product obtained can be satisfied.

In the meta type wholly aromatic polyamide fiber, in order to set the initial elastic modulus to 800 to 1,500 cN / mm ² , plastic stretching is performed in the range of 3.0 to 10.0 times in the plastic stretching step of the manufacturing method described later. Should be implemented. When the draw ratio is less than 3.0 times, the initial elastic modulus is not achieved. On the other hand, when the draw ratio is higher than 10.0 times, thread breakage frequently occurs and the process condition deteriorates.
Here, the “initial elastic modulus” refers to a value obtained by measurement under the above-mentioned “breaking strength” measurement conditions based on JIS L 1013.

[Cross-sectional shape and fineness of single fiber]
The cross-sectional shape of the meta-type wholly aromatic polyamide fiber used in the present invention may be circular, elliptical, or any other shape. The fineness (single yarn fineness) of the single fiber is not particularly limited, but is preferably 2.2 dtex or less. If it exceeds 2.2 dtex, the strength tends to decrease due to a decrease in the number of components of the spun yarn, which is not preferable.

<Check spun yarn made of meta-type wholly aromatic polyamide fiber>
The check spun yarn comprising the meta-type wholly aromatic polyamide fiber of the present invention can be obtained by subjecting the meta-type wholly aromatic polyamide fiber to a check process without imparting crimp due to indentation crimp or the like.

[Physical properties of spun yarn]
[Average fiber length (single yarn length)]
In the checked spun yarn of the present invention, the average fiber length (single yarn length) constituting the checked yarn is preferably in the range of 130 mm to 600 mm. An average fiber length (single yarn length) of less than 130 mm is not preferable because fuzzing increases and the strength of the spun yarn is significantly reduced. On the other hand, if it exceeds 600 mm, it approximates that of a normal filament yarn, and the characteristics as a spun yarn are impaired.

[Uses of spun yarn]
The check spun yarn comprising the meta-type wholly aromatic polyamide fiber of the present invention exhibits excellent heat resistance and durability even in a severer high temperature acidic atmosphere. For this reason, a wide range of scrims such as bag filters that collect particulates in exhaust gas from municipal waste incinerators and factory exhaust gas, as well as high-speed rotating sewing threads, canvas for yarn making, and canvas for belts. Can be used.

<Meta-type wholly aromatic polyamide>
[Configuration of meta-type wholly aromatic polyamide]
The meta-type wholly aromatic polyamide used as the material of the meta-type wholly aromatic polyamide fiber used in the present invention is composed of a meta-type aromatic diamine component and a meta-type aromatic dicarboxylic acid component. Other copolymer components such as the para type may be copolymerized within a range not impairing the purpose.

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.

  The meta-type wholly aromatic polyamide fiber used in the present invention does not substantially contain a layered clay mineral. “Substantially free” means that when the meta-type wholly aromatic polyamide and the meta-type wholly aromatic polyamide fiber are produced, no layered clay mineral is intentionally added. The concentration is not particularly defined, but is, for example, 0.01% by mass or less, preferably 0.001% by mass or less, and more preferably 0.0001% by mass or less.

[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 used in the present invention uses the aromatic polyamide obtained by the above production method, for example, a spinning solution preparation process, a spinning / coagulation process, and a plastic stretching bath stretching process 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. Among these solvents, NMP or DMAc is preferably used from the viewpoint of solubility and handling safety.
As the solution concentration, an appropriate concentration may be appropriately selected from the viewpoint of the coagulation rate and the polymer solubility in the spinning / coagulation step which is the next 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 10 to 30% 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 coagulating solution and coagulated.
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, and the hole shape are not particularly limited as long as they can be stably wet-spun. For example, the number of holes is 1,000 to 30,000, the diameter of the spinning hole May use a multi-hole spinneret or the like having a thickness of 0.05 to 0.2 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.

  As a coagulation bath used for obtaining the fiber used in the present invention, an amide solvent, preferably an aqueous solution having an NMP concentration of 45 to 60% by mass, substantially free from inorganic salts, is used. Use in the range of 50 ° C. When the concentration of the amide solvent (preferably NMP) is less than 45% by mass, the skin has a thick structure, the cleaning efficiency in the cleaning step is lowered, and it is difficult to reduce the residual solvent amount of the fiber. On the other hand, when the concentration of the amide solvent (preferably NMP) exceeds 60% by mass, uniform coagulation cannot be performed up to the inside of the fiber, and therefore, the residual solvent amount of the fiber can be reduced. It becomes difficult. In addition, the range of 0.1-30 seconds is suitable for the immersion time of the fiber in a coagulation bath.

  Here, it is preferable that the coagulating liquid substantially containing no salt is substantially composed only of an amide solvent and water. However, since inorganic salts such as calcium chloride and calcium hydroxide are extracted from the polymer solution, the coagulating liquid actually contains a small amount of these salts. A suitable concentration of the salt in industrial implementation is in the range of 0.3% by mass to 10% by mass with respect to the entire coagulating liquid. In order to make the inorganic salt concentration less than 0.3% by mass, the recovery cost for purification in the recovery process of the coagulating liquid becomes remarkably high, which is not appropriate. On the other hand, when the inorganic salt concentration exceeds 10% by mass, the coagulation rate becomes slow, so that the fiber immediately after being discharged from the spinneret is likely to be fused, and the coagulation time is long. Therefore, the coagulation equipment must be enlarged, which is not preferable.

By setting the components or conditions of the coagulation bath as described above, the skin formed on the fiber surface can be made thin, and a uniform structure can be formed even inside the fiber, and the breaking elongation of the resulting fiber can be improved. Can be made.
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 used in the present invention, the draw ratio in the plastic drawing bath needs to be in the range of 3.5 to 10.0 times, more preferably in the range of 4.0 to 6.5 times. And In the present invention, the strength of the finally obtained fiber 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 3.5 times, it becomes difficult to obtain a fiber having a breaking strength of 5.0 cN / dtex or more. On the other hand, when the draw ratio exceeds 10.0 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. More preferably, it is 20-60 degreeC.

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

  The temperature condition and the 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 at a stretch, generating huge voids in the fiber, leading to 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. Occurs. For this reason, the amount of solvent contained in the fiber used in the present invention must be 1.0% by mass or less, and more preferably 0.5% by mass or less.

[Dry heat treatment process]
In order to obtain the fiber used in the present invention, a dry heat treatment step is preferably performed on the fiber that has undergone the above washing step. In the dry heat treatment step, the fiber that has been washed in the washing step is preferably subjected to a dry heat treatment in the range of 100 to 250 ° C., more preferably 100 to 200 ° C.

  If the drying heat treatment is subsequently applied after the washing step, the fluidity of the polymer can be improved moderately, and 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 order to obtain the fiber used in the present invention, a hot stretching process is performed on the fiber that has undergone the dry heat treatment process. In the hot stretching process, the film is stretched 1.1 to 1.8 times while applying heat treatment at 310 to 335 ° C. When the heat treatment temperature in the hot drawing process is higher than 335 ° C., the yarn is colored, and the yarn is remarkably deteriorated to reduce the breaking strength, and the yarn may be broken in some cases. On the other hand, if the temperature is lower than 330 ° 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. Moreover, the fiber whose 300 degreeC dry heat shrinkage rate is 5.0% or less can be obtained by making the heat processing temperature in a heat | fever extending process into the range of 310-335 degreeC. 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 used in the present invention, it is usually necessary to set a range of 1.1 to 1.8 times, preferably 1.1 to 1.5 times. Necessary strength and elastic modulus can be expressed while maintaining excellent heat stretchability.

<Method for producing checked spun yarn made of meta-type wholly aromatic polyamide fiber>
In the method for producing a check spun yarn made of the meta-type wholly aromatic polyamide fiber of the present invention, the continuous yarn (tow) having no crimp is checked without applying crimp by indentation crimp or the like. When the tow has a crimp, a part of the crimp tends to remain even if the tow is checked, which is an obstacle to lowering the elongation of the obtained checked spun yarn.
When checking the tow, it can be checked in one step between the pair of supply rollers and the check roller, or can be checked in multiple steps in multiple steps.

  Furthermore, in order to obtain the check spun yarn of the present invention, conjugation property is imparted to the check yarn. In conjugation, it is necessary to continue conjugation after checking, and as means for imparting conjugation, for example, methods such as interlace treatment, fluff brazing treatment by swirling flow, twisting yarn, etc. Or it can be used in combination. As an overfeed rate at the time of imparting conjugation property, it is preferable to maintain a tension state as 4% or less, and more preferably 3% or less. When conjugation is imparted exceeding 4%, the elongation of the spun yarn obtained becomes too high, and creep deformation becomes large, which is not preferable.

  Further, in the production of the check spun yarn of the present invention, it may be heat-treated after winding, or a method of making the heating roller make a plurality of turns after imparting conjugation, traveling on a heat plate, etc. The heat treatment may be performed continuously by the above method.

  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>
Each physical property value in Examples and Comparative Examples was measured by the following 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.

[Fineness]
In accordance with JIS L 1013, the measurement based on the A method of the positive fineness was carried out and expressed in apparent fineness.

[Fracture strength, elongation at break, initial elastic modulus of fiber before toe cutting (tow)]
Based on JIS L 1013, the strength of the single yarn was measured under the following conditions 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

[Break strength of check spun yarn]
The strength was measured under the following conditions based on JIS L 1095 using a tensile tester (Instron, model: 5565). In addition, the number of twists at this time was 200 t / m.
(Measurement condition)
Grasp interval: 250 mm
Initial load: 7.4 cN / dtex
Tensile speed: 250 mm / min

[Amount of solvent remaining in fiber (residual solvent amount)]
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.
The amount of solvent (amide solvent mass) N (%) remaining in the fiber was calculated by the following formula using M1, M2, P, and C described above.
N = [C / 100] × [(M1 + M2-P) / P] × 100

[300 ° C dry heat shrinkage]
A load of 98 cN (100 g) is hung on a tow of about 3,300 dtex and marked at 30 cm away from each other. After removing the load, the tow was placed in an atmosphere of 300 ° C. for 15 minutes, and then the length L between the marks was measured. Based on the measurement result L, the value obtained by the following formula was defined as 300 ° C. dry heat shrinkage (%).
300 ° C. dry heat shrinkage (%) = [(30−L) / 30] × 100

<Example 1>
[Spinning stock solution (spinning dope) preparation process]
20.0 parts of polymetaphenylene isophthalamide powder having an intrinsic viscosity (IV) of 1.9 produced by an interfacial polymerization method according to the method described in Japanese Patent Publication No. 47-10863 is cooled to −10 ° C. It was suspended in 80.0 parts of methyl-2-pyrrolidone (NMP) to form a slurry. Subsequently, the suspension was heated to 60 ° C. and dissolved to obtain a transparent polymer solution.

[Spinning process]
The obtained polymer solution was spun as a spinning solution from a spinneret having a pore diameter of 0.07 mm and a pore number of 1,500 into a coagulation bath having a bath temperature of 40 ° C. The composition of the coagulation liquid was water / NMP (quantity ratio) = 45/55, and was spun by discharging into a coagulation bath at a yarn speed of 7 m / min.

[Plastic stretching process]
Subsequently, the film was stretched at a draw ratio of 5.0 times in a plastic stretching bath having a composition of water / NMP (quantity ratio) = 40/60 at a temperature of 40 ° C.

[Washing process]
After stretching, 20 ° C. water / NMP (quantity ratio) = 70/30 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 (immersion length: 3.6 m) at 80 ° C. to perform sufficient washing.

[Dry heat treatment process]
The washed fibers were subsequently subjected to a drying heat treatment with a hot roller having a surface temperature of 150 ° C.

[Hot drawing process]
Subsequently, while applying heat treatment with a heat roller having a surface temperature of 330 ° C., a heat drawing step of drawing 1.3 times was performed, and finally polymetaphenylene isophthalamide fibers were obtained.

[Measurement / Evaluation]
Various measurement evaluation was implemented with respect to the obtained fiber (tow). The fineness was 2.1 dtex, the breaking strength was 5.5 cN / dtex, and the breaking elongation was 24.0%, both showing good values. The residual solvent amount in the fiber was 0.4%, the dry heat shrinkage at 300 ° C. was 3.9%, and the initial elastic modulus was 1250 cN / mm ² , indicating excellent heat shrink stability. The obtained results are shown in Table 1.

[Production of check spun yarn]
The obtained polymetaphenylene isophthalamide fiber tow (3150 dtex) was checked with a check ratio of 21 times between a pair of rollers at 600 mm intervals to achieve single fiber convergence with an average fiber length of 230 mm. By continuously providing conjugation properties, a 150 dtex check spun yarn was obtained. The breaking strength of the obtained check spun yarn was 4.1 cN / dtex.
(Conjugation conditions)
Take-off nozzle pressure: 4 kg / cm ²
Conjugated nozzle pressure: 5 kg / cm ²
Yarn overfeed rate: 3.0%

<Example 2>
In the process of preparing the spinning dope (spin dope for spinning), the solvent used was changed to N, N-dimethylacetamide (DMAc) to produce a polymer solution, and this was used in the spinning dope as in Example 1. Thus, polymetaphenylene isophthalamide fiber was produced. Table 1 shows various measurement results for the obtained fibers.
Subsequently, a check spun yarn was produced in the same manner as in Example 1 using the obtained polymetaphenylene isophthalamide fiber. Table 1 shows the physical properties of the obtained check spun yarn.

<Comparative Example 1>
In the coagulation step, polymetaphenylene isophthalamide fiber was produced in the same manner as in Example 1 except that the composition of the coagulation liquid was changed to water / NMP (quantity ratio) = 70/30. Table 1 shows various measurement results for the obtained fibers.
Subsequently, a check spun yarn was produced in the same manner as in Example 1 using the obtained polymetaphenylene isophthalamide fiber. Table 1 shows the physical properties of the obtained check spun yarn.

<Comparative example 2>
A polymetaphenylene isophthalamide fiber was obtained in the same manner as in Example 1 except that the draw ratio in the hot drawing step was changed to 1.0. Table 1 shows various measurement results for the obtained fibers.
Subsequently, a check spun yarn was produced in the same manner as in Example 1 using the obtained polymetaphenylene isophthalamide fiber. Table 1 shows the physical properties of the obtained check spun yarn.

<Example 3>
[Spinning stock solution (spinning dope) preparation process]
In a reaction vessel under a dry nitrogen atmosphere, 721.5 parts of NMP having a moisture content of 100 ppm or less was weighed, and 97.2 parts (50.18 mol%) of metaphenylenediamine was dissolved in this NMP and cooled to 0 ° C. . To this cooled NMP solution, 181.3 parts (49.82 mol%) of isophthalic acid chloride (hereinafter abbreviated as IPC) was further added while gradually stirring to carry out a polymerization reaction. In addition, after the viscosity change stopped, stirring was continued for 40 minutes to complete the polymerization reaction.

Next, 66.6 parts 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, Plastic drawing process, Multi-stage washing process, Dry heat treatment process, Thermal drawing process]
The obtained polymer solution was used as the spinning dope, the yarn speed in the spinning step was 5 m / min, and the draw ratio in the plastic drawing bath in the plastic drawing step was 6.5 times. Metaphenylene isophthalamide fiber was obtained. Table 1 shows various measurement results for the obtained fibers.

[Production of check spun yarn]
Subsequently, a check spun yarn was produced in the same manner as in Example 1 using the obtained polymetaphenylene isophthalamide fiber. Table 1 shows the physical properties of the obtained check spun yarn.

<Example 4>
A polymer solution was produced in the same manner as in Example 3 except that the solvent used was changed to N, N-dimethylacetamide (DMAc) in the spinning dope (spinning dope) preparation step, and the resulting polymer solution was used as the spinning dope. As in Example 1, polymetaphenylene isophthalamide fiber was obtained. Table 1 shows various measurement results for the obtained fibers.
Subsequently, a check spun yarn was produced in the same manner as in Example 1 using the obtained polymetaphenylene isophthalamide fiber. Table 1 shows the physical properties of the obtained check spun yarn.

<Comparative Example 3>
In the coagulation step, polymetaphenylene isophthalamide fiber was obtained in the same manner as in Example 3 except that the composition of the coagulation liquid was changed to water / NMP (quantity ratio) = 30/70. Table 1 shows various measurement results for the obtained fibers.
Subsequently, a check spun yarn was produced in the same manner as in Example 1 using the obtained polymetaphenylene isophthalamide fiber. Table 1 shows the physical properties of the obtained check spun yarn.

<Comparative Examples 4-5>
A polymetaphenylene isophthalamide fiber was obtained in the same manner as in Example 3 and Example 4 except that the draw ratio in the hot drawing step was changed to 1.0. Table 1 shows various measurement results for the obtained fibers.
Subsequently, a check spun yarn was produced in the same manner as in Example 1 using the obtained polymetaphenylene isophthalamide fiber. Table 1 shows the physical properties of the obtained check spun yarn.

<Examples 5-7>
A check spinning made of polymetaphenylene isophthalamide fiber in the same manner as in Example 1 except that the distance between check rollers was changed so that the average fiber length (check length) was 350 to 550 mm in the check process. Yarn was produced. Table 2 shows the physical properties of the obtained check spun yarn.

<Examples 8 to 9>
A check spinning made of polymetaphenylene isophthalamide fiber in the same manner as in Example 1 except that the distance between check rollers was changed so that the average fiber length (check length) was 95 and 750 mm in the check process. Yarn was produced.
In Example 8, a spun yarn having a large amount of fluff and a large fineness of the yarn was obtained. Moreover, in Example 9, since there were few fuzz and it was a filament form, the texture as a spun yarn was insufficient.

  According to the present invention, a check spun yarn comprising a meta-type wholly aromatic polyamide fiber having good mechanical strength, heat resistance and the like and having a small amount of solvent remaining in the fiber is provided. The check spun yarn of the present invention has a low gas generation and excellent long-term stability even in a high-temperature atmosphere, and as a scrim for bag filters or the like used in harsh environments, or a rubber reinforcing fiber. It can be preferably used.

Claims (4)

A check spun yarn made of a meta-type wholly aromatic polyamide fiber,
The meta-type wholly aromatic polyamide fiber does not substantially contain a layered clay mineral, the amount of the solvent remaining in the fiber is 1.0% by mass or less with respect to the whole fiber, and the breaking strength of the fiber is 4 A meta-type wholly aromatic polyamide check spun yarn having a viscosity of 0.5 to 6.0 cN / dtex.   The meta-type wholly aromatic polyamide check spun yarn according to claim 1, wherein the meta-type wholly aromatic polyamide fiber has a dry heat shrinkage of 300 ° C of 5.0% or less. 3. The meta type wholly aromatic polyamide check spun yarn according to claim 1, wherein the meta type wholly aromatic polyamide fiber has an initial elastic modulus of 800 to 1,500 cN / mm ² .   The meta type wholly aromatic polyamide check spun yarn according to any one of claims 1 to 3, having an average fiber length of 130 to 600 mm.