JP2007039818A - Low-shrinkable meta type wholly aromatic polyamide fiber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-shrinkable wholly aromatic polyamide fiber having excellent heat shrinkage characteristics at high temperatures, suppressing the shrinkage during contact with high-temperature flames or fire balls when formed into a fabric and suitable as a material for protective clothes and to provide a method for producing the fiber. <P>SOLUTION: The low-shrinkable meta type wholly aromatic polyamide fiber is obtained by compounding a layered clay mineral in an amount of 0.1-10 pts.wt. based on the weight of the meta type wholly aromatic polyamide. The maximum heat shrinkage temperature is 300-360°C and the shrinkage percentage thereof is ≤5%. The elongation starts at 320-380°C. The fiber is produced by spinning a solution of the meta type wholly aromatic polyamide containing the amount of the layered clay mineral in an amide polar solvent, coagulating the solution in a coagulation bath of a specific composition, drawing the coagulated strand at a draw ratio of 2.0-10 in a specified wet drawing bath and relaxing the resultant drawn strand at a relaxation ratio of 0.5-1.0 in a specific wet relaxation bath. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a meta-type wholly aromatic polyamide fiber having improved heat shrinkage characteristics and a method for producing the same. More specifically, a novel low-shrinkage meta-type wholly aromatic polyamide fiber blended with a layered clay mineral and the low-shrinkage meta-type wholly aromatic, which can suppress shrinkage when contacted with a high-temperature flame or fireball. The present invention relates to a method for industrially producing polyamide fibers.

  Conventionally, it is well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides are excellent in heat resistance and flame retardancy, and these wholly aromatic polyamides are amide polar solvents. It is also well known that it can be made into a fiber by a method such as dry spinning, wet spinning, semi-dry semi-wet spinning, etc. from a polymer solution in which a wholly aromatic polyamide is dissolved in the solvent. Among such wholly aromatic polyamides, the fibers of meta-type wholly aromatic polyamides typified by polymetaphenylene isophthalamide (sometimes referred to as “meta-aramid”) are particularly useful as heat-resistant and flame-retardant fibers. It is used in fields that exhibit these characteristics, for example, industrial applications such as filters and electronic parts, and disaster prevention and safety clothing applications such as protective clothing where heat resistance, flame resistance, and flame resistance are important. .

  Among them, protective clothing includes protective clothing worn in front of high-temperature furnaces such as blast furnaces, electric furnaces and incinerators, fire-resistant clothing for people engaged in fire fighting work, welding protective clothing for welding work exposed to high-temperature sparks, and ignition. Widely used as flame retardant work clothes for people who handle highly chemicals, meta-type wholly aromatic polyamide fibers are not only excellent heat resistance, flame resistance and self-digestibility, but also general yarn The quality is very similar to clothing fibers, such as natural fibers such as cotton and wool, and synthetic fibers such as nylon, polyester, and acrylic. Therefore, in terms of processability, comfort, washability, and clothing, conventional protective clothing It is recognized as a protective clothing material superior to glass fiber, asbestos fiber, phenol resin fiber, metal foil coating material, etc.

  However, the current protective clothing made of meta-type wholly aromatic polyamide fibers may cause shrinkage of the material when it comes into contact with a high-temperature flame or fireball, and may further cause a perforation phenomenon. There are limits to the scope of fire fighting and lifesaving activities. Therefore, if the fire resistance, flame resistance, heat resistance, etc. of the protective clothing material made of meta-type wholly aromatic polyamide fiber is drastically improved, for example, in fire fighting activities, it will enter the inside of the fire site regardless of the progress of the fire. Thus, it is possible to perform early fire extinguishing / rescue activities, and even when the fire is at its peak, it is possible to extinguish the fire quickly by injecting water close to the fire source. As a result, there are expected merits such as drastically reducing water loss in fire fighting activities, realizing quick and early rescue, and improving the safety of firefighters.

  For this reason, in order to improve the fire protection performance as a protective clothing material made of meta-type wholly aromatic polyamide fiber, it is particularly necessary to suppress the shrinkage of the material when it comes into contact with a high temperature flame or a fireball, and further the perforation phenomenon. It is desired.

  Conventionally, in order to improve flame resistance and low shrinkage of wholly aromatic polyamide fibers, a method of adding an organic phosphorus compound, a phosphorus-containing phenol resin, a halogen compound, etc. to a polymer has been proposed. Has been proposed to improve low shrinkage (see Patent Document 1 below). However, since these are low molecular weight organic compounds, some of them are discharged during the fiber molding process, so they are hardly contained in the fiber of the product. There is a problem that sufficient low contractility is not expressed.

  Further, as another method, a fiber excellent in dry heat shrinkage at a high temperature, and a method for producing the same, comprising a blend of wholly aromatic polyamide and a soluble resin such as polycarbonate, polyethersulfone, polysulfone, polyarylate, polysulfidesulfone, etc. Has been proposed (see Patent Document 2 below). However, the patent document 2 mentions the dry heat shrinkage rate at 200 ° C. in the examples. As described above, the shrinkage of the material when it comes into contact with a high-temperature flame or fireball, that is, the shrinkage property under high temperature. Is not mentioned at all, and it can be easily imagined that, in reality, the composition / manufacturing method of the fiber does not provide excellent shrinkage characteristics at high temperatures.

JP-A-53-122817 JP-A-5-321026

  The present invention has been made to solve the problems of the prior art as described above, and one object of the present invention is to provide a low-shrinkage meta-type wholly aromatic polyamide fiber excellent in heat shrinkage properties at high temperatures. In particular, another object is to provide a method for industrially producing a low-shrinkage meta-type wholly aromatic polyamide fiber having excellent heat-shrinkage properties at high temperatures.

  According to the present invention, as a meta-type wholly aromatic polyamide fiber that solves the above-mentioned problems, a meta-type wholly aroma containing 0.1 to 10% by weight of a layered clay mineral based on the weight of the meta-type wholly aromatic polyamide. Low shrinkage meta, characterized in that it has a maximum heat shrinkage temperature of 300 ° C. to 360 ° C., a shrinkage rate of 5% or less, and starts stretching at 320 ° C. to 380 ° C. A type wholly aromatic polyamide fiber is provided.

  In this fiber, the average layer thickness of the layered clay mineral is 10 to 500 nm, and the dispersibility (Y) of the layered clay mineral is 0.1 to 40 in the heat shrink property at high temperature. This is particularly preferable because it is an excellent low shrinkage meta-type wholly aromatic polyamide fiber.

  Further, according to the present invention, as a method for producing the low shrinkage meta-type wholly aromatic polyamide fiber, (1) 0.1 to 10 parts by weight of layered clay mineral based on the weight of the meta-type wholly aromatic polyamide is used. Prepare an amide polar solvent solution of the meta-type wholly aromatic polyamide contained, and (2) introduce the solution into a coagulation bath composed of an amide polar solvent and water or an amide polar solvent, an inorganic salt and water. (3) The coagulated yarn is stretched 2.0 to 10 times in a wet stretching bath composed of water, an amide polar solvent and water, or an amide polar solvent and an inorganic salt and water. Later (4) The drawn yarn is relaxed 0.5 to 1.0 times in a wet relaxation bath composed of water, an amide polar solvent and water, or an amide polar solvent, an inorganic salt and water. A method for producing a low shrinkage meta-type wholly aromatic polyamide fiber is provided. .

  In this method, a low-shrinkage meta-type wholly aromatic polyamide fiber that is particularly good to be subjected to relaxation heat treatment at 100 to 380 ° C. by 0.5 to 1.0 times after the wet relaxation is preferable. is there.

  The meta-type low-shrinkage wholly aromatic polyamide fiber of the present invention contains a specific amount of layered clay mineral having an average layer thickness of 10 to 500 nm and a dispersibility (Y) of 0.1 to 40. Various fiber products having extremely low heat shrinkability and excellent heat resistance can be provided. For this reason, it is extremely useful as a material particularly for use in protective clothing, and for example, it is suitably used as a material for fire fighting clothes, furnace work clothes, welding protective clothing, and the like.

  Further, according to the production method of the present invention, it is possible to industrially stably produce a low shrinkage meta-type wholly aromatic polyamide fiber having the advantages as described above.

  The meta-type wholly aromatic polyamide in the present invention is a polyamide produced by, for example, solution polymerization or interfacial polymerization using a meta-type aromatic diamine and a meta-type aromatic dicarboxylic acid halide as raw materials. For example, other copolymer components such as the para type may be copolymerized within a range that does not inhibit the above.

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

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

Examples of copolymer components that can be used other than the above diamine and dicarboxylic acid halide include aromatic diamines such as paraphenylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene, and aminoanisidine. 1,5-naphthylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ketone, 4,4′-diaminodiphenylamine, 4,4′-diaminodiphenylmethane, etc., while aromatic Examples of the dicarboxylic acid halide include terephthalic acid chloride, 1,4-naphthalenedicarboxylic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, 4,4′-biphenyldicarboxylic acid chloride, 4,4′-diphenyl ether dicarboxylic acid chloride, and the like. . The copolymerization ratio of these copolymer components is preferably 20 mol% or less based on the total acid component of the polyamide, since the properties of the meta-type wholly aromatic polyamide are liable to deteriorate if it is too large. In particular, a suitable meta-type wholly aromatic polyamide is a polyamide in which 80 mol% or more of all repeating units are composed of metaphenylene isophthalamide units, and among them, polymetaphenylene isophthalamide is preferable.
The degree of polymerization of the meta-type wholly aromatic polyamide is suitably in the range of 1.3 to 3.0 as the intrinsic viscosity (IV) measured using concentrated sulfuric acid at 30 ° C. as a solvent.

  On the other hand, the layered clay mineral used in the present invention has a cation exchange ability, and further exhibits a property of being swollen by taking water between the layers, and preferably includes smectite clay and swellable mica. Specifically, for example, as a smectite type clay, hectorite, saponite, stevensite, beidellite, montmorillonite (which may be natural or chemically synthesized), and substituted or derivative thereof Or a mixture. In addition, examples of the swellable mica include synthetic swellable mica having Li and Na ions between chemically synthesized layers, or a substituted product, derivative, or mixture thereof.

  In the present invention, it is preferable to use the layered clay mineral surface-treated with organic onium ions. By treating the clay clay mineral with organic onium ions, the dispersibility in the wholly aromatic polyamide is improved, and the spinning property and the low shrinkage of the resulting fiber are improved.

上記式（１）において、Ｒ_１、Ｒ_２、Ｒ_３及びＲ_４は、それぞれ独立に、炭素数１〜３０のアルキル基又は(ＣＨ_２ＣＨ_２Ｏ)_ｎＨであらわされるヒドロキシポリオキシエチレン基である。ここで、炭素数１〜３０のアルキル基としては、炭素数１〜１８のアルキル基が好ましい。 The organic onium ion used for the surface treatment is preferably a quaternary ammonium ion having a structure of the following formula (1).

In the above formula (1), R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydroxypolyoxyethylene group represented by an alkyl group having 1 to 30 carbon atoms or (CH ₂ CH ₂ O) _n H. It is. Here, as a C1-C30 alkyl group, a C1-C18 alkyl group is preferable.

  Examples of the compound having a quaternary ammonium ion include dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, oleyltrimethylammonium chloride, didodecyldimethylammonium chloride, ditetradecyl. Dimethylammonium chloride, dihexadecyldimethylammonium chloride, dioctadecyldimethylammonium chloride, dioleyldimethylammonium chloride, dodecyldiethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride, hexadecyldimethylbenzylammonium chloride, octade Didimethylbenzylammonium chloride, oleyldimethylbenzyl chloride, trioctylmethylammonium chloride, hydroxypolyoxypropylenemethyldiethylammonium chloride, hydroxypolyoxyethylenedodecyldimethylammonium chloride, hydroxypolyoxyethylenetetradecyldimethylammonium chloride, hydroxypolyoxyethylenehexa Decyldimethylammonium chloride, hydroxypolyoxyethylene octadecyldimethylammonium chloride, hydroxypolyoxyethyleneoleyldimethylammonium chloride, dihydroxypolyoxyethylenedodecylmethylammonium chloride, bis (hydroxypolyoxyethylene) tetradecylmethyla Examples include, but are not limited to, monium chloride, bis (hydroxypolyoxyethylene) hexadecylmethylammonium chloride, bis (hydroxypolyoxyethylene) octadecylmethylammonium chloride, and bis (hydroxypolyoxyethylene) oleylmethylammonium chloride. It is not something.

The average layer thickness of the layered clay mineral contained in the low shrinkage meta-type wholly aromatic polyamide fiber of the present invention is preferably 500 nm or less, particularly preferably 200 nm or less. The average layer thickness of the layered clay mineral referred to here is the layer thickness obtained from all the layered clay minerals observed in a cross-sectional area of 25 μm ² in an electron microscope measurement (magnification of 100,000 times) of the longitudinal section of the fiber. Average value. If the average layer thickness of the layered clay mineral is larger than 500 nm, it may be difficult to ensure molding stability during yarn production. On the other hand, when trying to disperse the layered clay mineral to the molecular level, it is necessary to reduce the solution concentration in order to ensure the thickening effect and dispersibility of the layered clay mineral, which not only reduces the productivity of spinning, Since the effect of improving the toughness of the obtained fibers tends to be small, the average layer thickness is preferably 10 nm or more, particularly preferably 12 nm or more.

Furthermore, the dispersibility (Y) required from all layered clay minerals observed in a cross-sectional area of 25 μm ² in an electron microscope measurement (magnification of 100,000 times) of the longitudinal section of the fiber is 0.1 to 40, particularly It is preferable that it is 0.5-30.

Here, the dispersibility (Y) is a value determined by the following equation from the area (S1) of the region where the change is recognized by the influence of the layered clay mineral in the longitudinal section and the area (S2) of the entire region observed. is there.

  In the fiber of the present invention, the layered clay mineral is contained in an amount of 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the meta-type wholly aromatic polyamide. is required. When the content of the layered clay mineral is less than 0.05 parts by weight with respect to 100 parts by weight of the wholly aromatic polyamide, the target low shrinkage cannot be obtained, while when it exceeds 10 parts by weight. Is not preferable because the moldability becomes poor.

  In the present invention, fillers other than the layered clay mineral can be used in combination as long as the physical properties of the fiber are not impaired. Examples of the filler used here include non-fibrous fillers such as fibrous or plate-like, scaly, granular, indeterminate, and crushed products, but non-fibrous fillers are particularly preferred. Specifically, for example, potassium titanate whisker, barium titanate whisker, aluminum borate whisker, silicon nitride whisker, mica, talc, kaolin, silica, calcium carbonate, glass beads, glass flake, glass microballoon, clay, disulfide Examples include molybdenum, wollastonite, titanium oxide, zinc oxide, calcium polyphosphate, graphite, metal powder, metal flake, metal ribbon, metal oxide, carbon powder, graphite, carbon flake, and scaly carbon. Furthermore, when the single yarn fineness of the wholly aromatic polyamide fiber is large, glass fiber, PAN-based or pitch-based carbon fiber, stainless steel fiber, metal fiber such as aluminum fiber or brass fiber, wholly aromatic polyamide fiber, etc. Organic fibers, gypsum fibers, ceramic fibers, asbestos fibers, zirconia fibers, alumina fibers, silica fibers, titanium oxide fibers, silicon carbide fibers, rock wool, metal ribbons, and the like can also be used. Two or more of these fillers may be used in combination. The filler can also be used by treating the surface with a known coupling agent (for example, silane coupling agent, titanate coupling agent, etc.) or other surface treatment agents.

  In addition to the above requirements, the low shrinkage meta-type wholly aromatic polyamide fiber of the present invention needs to have a maximum heat shrinkage of 5% or less, preferably 0 to 2%. When the maximum heat shrinkage rate exceeds 5%, the heat resistance of the finally obtained fiber product becomes insufficient, and problems such as perforation are likely to occur when it comes into contact with a high-temperature flame or fireball. Cannot achieve the goal.

  The maximum heat shrinkage and the extension start temperature here are measured by the following methods. That is, the total fineness is about 200 dtex, the temperature is increased from 25 ° C. to 450 ° C. at a measurement sample length of 10 mm, a load of 0.5 cN, and a temperature increase rate of 100 ° C./min. Measure the shrinkage relative to the initial sample length. A point at which the shrinkage rate becomes maximum is obtained from the obtained graph of temperature / shrinkage rate, this is set as the maximum heat shrinkage rate, and the temperature at which the fiber begins to stretch beyond the initial fiber length is taken as the stretching start temperature.

The low shrinkage meta-type wholly aromatic polyamide fiber of the present invention having various characteristics as described above can be industrially produced, for example, by the following method.
That is, (1) Spinning for preparing an amide polar solvent solution (spinning for spinning) of a meta type wholly aromatic polyamide containing 0.1 to 10 parts by weight of the layered clay mineral based on the weight of the meta type wholly aromatic polyamide (2) The solution (spinning dope) is prepared from a spinneret in a coagulation bath comprising water, an amide polar solvent and water, or an amide polar solvent, an inorganic salt and water. (3) in a wet drawing bath composed of water, an amide polar solvent and water, or an amide polar solvent and an inorganic salt and water. A stretching step of stretching 0 to 10 times, and (4) the stretched yarn is 0.5 in a wet relaxation bath composed of water, an amide polar solvent and water, or an amide polar solvent and an inorganic salt and water. Wet relaxation process that relaxes up to 1.0 times, and (5 If necessary, the target low-shrinkable fiber is industrially produced by performing a series of relaxation heat treatment steps in which the relaxation yarn is subjected to relaxation heat treatment at a temperature of 100 to 380 ° C. by 0.5 to 1.0 times. Can be manufactured stably.

Hereinafter, the production method of the present invention will be described in detail for each step.
(1) Step of adjusting dope for spinning (spinning stock solution) The meta-type wholly aromatic polyamide solution used as the dope for spinning (spinning stock solution) in the method of the present invention includes the above-mentioned meta-type wholly aromatic polyamide and layered clay mineral, In addition, it is prepared by dissolving a filler and other additives added as necessary in an amide polar solvent. As described above, the layered clay mineral preferably has an average layer thickness of 500 nm or less, particularly 200 nm or less.

  Here, as the amide polar solvent used for the preparation of the dope for spinning (spinning stock solution), the meta-type wholly aromatic polyamide and the layered clay mineral (and fillers added if necessary) are dissolved and / or dispersed. Any one can be used as long as it can be used. Examples of such amide polar solvents include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethylimidazolidinone and the like. Among them, NMP or DMAc is It is preferable from the viewpoint of the stability of the solution.

  Further, the concentration of the meta-type wholly aromatic polyamide in the dope for spinning (hereinafter sometimes referred to as polymer concentration) is suitably 15 to 25% by weight, particularly 15 to 22% by weight. When the polymer concentration exceeds 25% by weight, the solubility of the polyamide is insufficient and it becomes difficult to perform normal spinning. On the other hand, when the polymer concentration is less than 15% by weight, the coagulation property at the time of wet spinning is lowered and it becomes difficult to perform stable spinning.

  The spinning dope may contain an inorganic salt such as water or calcium chloride as long as the object of the present invention is not impaired. Such water and inorganic salts may be added as necessary, but they may be inevitably produced by a solution preparation process (for example, a polymer production process). Here, the water content in the dope for spinning is at most 70% by weight, preferably 50% by weight or less, particularly preferably 15% by weight or less, based on the weight of the meta-type wholly aromatic polyamide. The content of the inorganic salt is about 45% by weight (the amount of calcium chloride usually produced as a by-product in solution polymerization) based on the weight of the meta-type wholly aromatic polyamide.

The procedure for adjusting the dope for spinning consisting of the meta-type wholly aromatic polyamide, the layered clay mineral and the solvent is arbitrary, and examples thereof include the following methods.
(A) Method of adding layered clay mineral to solution of meta-type wholly aromatic polyamide (B) Method of mixing solution of meta-type wholly aromatic polyamide and layered clay mineral (C) Method of adding layered clay mineral to solution of layered clay mineral To add and dissolve a fully aromatic polyamide

  As the meta-type wholly aromatic polyamide solution, an amide polar solvent solution containing the meta-type wholly aromatic polyamide obtained by solution polymerization or the like may be used as it is, or obtained by solution polymerization, interfacial polymerization or the like. The meta type wholly aromatic polyamide may be isolated from the solution containing the obtained meta type wholly aromatic polyamide and dissolved in an amide polar solvent.

(2) Spinning Step When the spinning dope prepared as described above is discharged into the coagulation bath by wet spinning, a multi-hole spinneret can be used. The number of holes is about 50000 or less, preferably 500 to 30000.

Coagulating liquid constituting the coagulation bath in the present invention, water (H 2 _O), 2 component of the amide-based polar solvent and water (H 2 _O), or an amide based polar solvent and water (H 2 _O) Inorganic It consists essentially of three components with salt. In this coagulation liquid, any amide-based polar solvent may be used as long as it dissolves the meta-type wholly aromatic polyamide and is miscible with water. Particularly, N-methyl-2- Pyrrolidone (NMP), dimethylacetamide (DMF), dimethylformamide (DMAc) can be preferably used. Among these, in consideration of solvent recovery, the same amide-based polar solvent in the spinning dope is preferable.

  The appropriate mixing ratio of these coagulating liquid components depends on the spinning dope conditions and the type of coagulating liquid, but in a coagulating liquid substantially composed of an amide polar solvent and water, the amide in the coagulating liquid The proportion of the system polar solvent is suitably in the range of 30 to 70% by weight. On the other hand, in a coagulating liquid substantially composed of an amide polar solvent, an inorganic salt, and water, the ratio of the amide polar solvent + inorganic salt is suitably in the range of 30 to 70% by weight.

  The appropriate temperature range of the coagulation bath is closely related to the composition of the coagulation solution, but a range of 20 to 135 ° C. is appropriate. Preferably, when the proportion of the amide polar solvent in the coagulation liquid is 15% by weight or less, it is in the range of 30 to 90 ° C., and when the proportion of the amide polar solvent is 15 to 25% by weight, 40 to 125 ° C. When the ratio of the amide polar solvent is 30 to 70% by weight, the range of 20 to 70 ° C. is appropriate.

  The speed at which the coagulated yarn is drawn out from the coagulation bath is suitably in the range of 5 to 25 m / min, but is preferably in the range of 10 to 25 m / min from the viewpoint of improving productivity. The immersion time of the coagulated yarn in the coagulation bath is suitably in the range of 0.1 to 30 seconds. If the immersion time is too short, the formation of the yarn may be insufficient and the yarn may break.

  In the case of filament yarn, in addition to the above-described wet spinning, a spinneret is provided on the liquid surface of the coagulation bath, and the spinning dope is discharged from the spinneret into the air and then introduced into the coagulation bath. Dry semi-wet spinning may be employed.

(3) Stretching process The solidified yarn drawn from the coagulation bath is stretched in a wet stretching process after passing through a washing process and a plasticizing process as necessary, and further through a washing process, a heat treatment process and the like as necessary. It is sent to the next relaxation heat treatment process.
In the plasticizing step performed as necessary, the fiber is introduced into a plasticizing bath composed of an amide polar solvent and water, or an amide polar solvent, an inorganic salt, and water.

  Moreover, although the washing | cleaning process implemented as needed may be only after a wet extending process, the case where it wash | cleans before wet extending | stretching is demonstrated as an example here. The washing step is preferably performed in multiple stages at a temperature of 20 to 95 ° C. The amount of water replenished in the washing bath, the solvent concentration in the washing water, and the immersion time of the fibers in the washing bath are such that the amount of residual solvent in the fibers leaving the washing step is in the range of 5 to 40% by weight relative to the polymer. It is preferable to control. If the amount of residual solvent is less than 5% by weight, single yarn breakage is likely to occur during stretching, whereas if it exceeds 40% by weight, the amount of residual solvent in the fiber exiting the water washing step may be lowered. It becomes difficult.

  The fiber in which the residual solvent amount and the amount of the inorganic salt are adjusted in the washing step is 2.0 to 10 times in the drawing bath at 10 to 100 ° C. (particularly preferably 40 to 100 ° C.) in the drawing wet drawing step. In particular, the remaining solvent and salt are washed away while stretching to 2.0 to 6.0 times. In the case of not performing plastic stretching in a plasticizing bath composed of an amide polar solvent and water or an amide polar solvent, an inorganic salt and water as wet stretching, that is, when stretching in a normal hot water bath The film is preferably stretched in the range of 2.0 to 5.0 times.

(4) Wet relaxation process The fiber after drawing is relaxed to 0.5 to 1.0 times, particularly 0.6 times or more and less than 1.0 times in the subsequent wet relaxation process. In the case of not performing plastic stretching in a plasticizing bath composed of an amide polar solvent and water or an amide polar solvent, an inorganic salt and water as wet relaxation, that is, when relaxing in a normal warm water bath, Usually, it is preferable to relax in the range of 0.6 times or more and less than 1.0 times.

  In the present invention, relaxation is performed in both steps of the wet relaxation and the relaxation heat treatment described later. Basically, the total relaxation magnification in both steps may be set to a magnification of 0.25 to 0.99 times, Therefore, for example, when the relaxation is considerably large by wet relaxation, the magnification may be 1.0 times (in this case, constant length treatment) in the subsequent relaxation heat treatment at a high temperature. Conversely, even when the wet relaxation magnification is 1.0 times (constant length treatment), the purpose of the present invention can be achieved by increasing the relaxation magnification in the subsequent relaxation heat treatment. The suitable temperature of the wet relaxation bath varies depending on the amount of residual solvent (apparent Tg) in the treated fiber. For example, in the case of spinning using an inorganic salt as a coagulating liquid, a suitable temperature range is 50 ° C. to 100 ° C., but when spinning in a coagulating bath containing no inorganic salt, the apparent Tg is considerably low. A slightly low temperature range, for example, 10 to 80 ° C. is preferable.

  The relaxed fiber is further washed and removed of the remaining solvent and salt in the washing step as necessary. The washing step at this time is preferably performed at a temperature of 20 to 95 ° C. Since the fiber after wet relaxation contains a considerable amount of moisture, it is preferable that after wet relaxation, the fiber is once dried at a temperature of 100 ° C. or higher and then supplied to the next step.

(5) Relaxation heat treatment process The dried fiber is subjected to relaxation heat treatment at a temperature of 100 to 380 ° C in a relaxation heat treatment process at a temperature of 0.5 to 1.0 times as necessary. The relaxation heat treatment at this time may be performed under any conditions of a hot plate, a dry heat atmosphere, or a steam atmosphere. At this time, the vapor may contain an amide polar solvent in addition to water. When the heat treatment temperature exceeds 380 ° C., the resulting fiber is severely deteriorated and colored, and in some cases, the yarn may be broken. On the other hand, when the temperature is less than 100 ° C., the fiber is not sufficiently relaxed. Therefore, it is not possible to achieve low fiber shrinkage, which is the object of the present invention. In the case of performing a relaxation treatment with a hot plate, a temperature in the range of 200 to 380 ° C., particularly 250 to 350 ° C. is preferable. Moreover, 250-380 degreeC is preferable in a dry-heat atmosphere, and 100-300 degreeC is preferable in a steam atmosphere.

  Low-shrinkage meta-type wholly aromatic polyamide fiber containing layered clay mineral produced through each of the above steps can be collected as a tow as needed, wound up, or sent directly to the subsequent process Is provided after crimping and cut into short fibers.

  The fiber obtained from the meta-type wholly aromatic polyamide solution not containing the layered clay mineral cannot obtain the desired shrinkage property even if the same process as in the present invention is performed, whereas the fiber containing the layered clay mineral does not contain the layered clay mineral. Fibers obtained from type fully aromatic polyamide solutions achieve the desired heat shrinkage characteristics. This is considered to be because the relaxation of the oriented molecular chain is promoted particularly in the wet relaxation process by the inclusion of the layered clay mineral. The reason why this effect is manifested by the inclusion of layered clay minerals is not yet clear, but the highly oriented layered clay mineral structure is easily relaxed in a wet atmosphere by promoting relaxation of polymer molecular chains. It seems that there is.

  Thus, according to the production method of the present invention, the maximum heat shrinkage temperature is 300 ° C. to 360 ° C., the shrinkage rate is 5% or less, and the product starts to stretch at 320 ° C. to 380 ° C. To produce industrially stable low-shrinkage meta-type wholly aromatic polyamide fibers, which have the advantage that they have sufficient heat resistance and do not generate holes even when they come into contact with high-temperature flames or fireballs. Can do.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. Each physical property value in the examples was measured by the following method.
<Intrinsic viscosity (IV)>
The polymer was dissolved in 97% concentrated sulfuric acid and measured at 30 ° C. using an Ostwald viscometer.
<Fineness>
It measured according to JIS-L-1015.
<Strength and elongation>
According to JIS-L-1015, the sample length was 20 mm, the initial load was 0.44 mN / dtex, and the extension rate was 20 mm / min.
<Maximum heat shrinkage>
For the measurement, a thermomechanical analyzer “TMA-50” manufactured by Shimadzu Corporation was used. The fiber sample was split into 200 dtex, which was sandwiched between chucks to obtain a measurement sample. The measurement sample length at this time was 10 mm. The measurement conditions were a temperature increase rate of 25 ° C. to 450 ° C., an isothermal increase rate of 2 ° C./min, and a shrinkage ratio with respect to the initial length of the sample fiber at each temperature with a load of 0.5 cN applied to the fiber fiber sample. Was measured. The shrinkage rate at the temperature at which the shrinkage rate becomes maximum was obtained from the obtained shrinkage rate results at each temperature, and this was taken as the maximum heat shrinkage rate, and the temperature at which the fiber began to stretch beyond the initial fiber length was taken as the stretching start temperature.

[Example 1]
N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) was prepared by using 0.16 parts by weight of polymetaphenylene isophthalamide with IV = 1.9 produced by an interfacial polymerization method according to the method described in Japanese Patent Publication No. 47-10863. It melt | dissolved in 1.46 weight part and stirred until it became a uniform transparent dope. To this, 0.18 part by weight of “Lucentite SPN” (registered trademark) manufactured by Cope Chemical treated with polyoxypropylene methyldiethylammonium chloride as a layered clay mineral was added and stirred to obtain a polymer solution A. Similarly, 17.44 parts by weight of polymetaphenylene isophthalamide having IV = 1.9 was dissolved in 63.68 parts by weight of NMP to obtain a transparent polymer solution B.

  After the polymer solution A and polymer solution B thus obtained were mixed and stirred, 17.08 parts by weight of NMP was further added, 17.60 parts by weight of polymetaphenylene isophthalamide, “Lucentite SPN” (registered trademark) A polymer solution C consisting of 0.18 parts by weight and NMP 82.22 parts by weight was obtained.

  The polymer solution C was heated to 85 ° C. to obtain a dope for spinning (spinning raw solution), and spun from a spinneret having a hole diameter of 0.07 mm and a hole number of 3000 into a coagulation bath at 85 ° C. The composition of the coagulation bath was 40% by weight of calcium chloride, 5% by weight of NMP, and the remaining 55% by weight was water. The spun yarn was passed through this coagulation bath at an immersion length (effective coagulation bath length) of 100 cm at a yarn speed of 7.0 m / min, and then pulled out into the air.

  The coagulated yarn was washed with water through the first to third aqueous washing baths, and the total immersion time of the washing bath at this time was 50 seconds. As the first to third aqueous cleaning baths, 30% NMP aqueous solution having a temperature of 30 ° C. was used. Next, the washed yarn was stretched 3.5 times in a 30% NMP aqueous solution at 50 ° C. and subsequently relaxed 0.65 times in a 30% NMP aqueous solution at 70 ° C. It was immersed in warm water for 48 seconds. Next, the film was wound around a roller having a surface temperature of 130 ° C. and dried, and then subjected to a relaxation heat treatment of 0.95 times with a hot plate having a surface temperature of 320 ° C. to obtain polymetaphenylene isophthalamide fibers.

As a result of TEM measurement of the longitudinal section of the obtained single fiber, the average layer thickness of the layered clay mineral is 90 nm, and the dispersibility (Y) required from all the layered clay minerals observed in the sectional area of 25 μm ² is 4%.

The physical properties of the obtained fiber are a fineness of 2.01 dtex, a strength of 2.81 cN / dtex, an elongation of 75.3%, a maximum heat shrinkage of 3.0% at 315 ° C, and an elongation start temperature of 330 ° C. there were. The results of measuring the shrinkage / extension behavior of this fiber with respect to heat are shown in FIG.
A test fabric was prepared using this fiber and exposed to the flame of a gas burner, but no occurrence of perforation was observed in the portion directly exposed to the flame.

[Examples 2-3]
In Example 1, spinning, stretching, and relaxation heat treatment were performed under the same conditions as in Example 1 except that the content of the layered clay mineral was changed as shown in Table 1. The evaluation results of the obtained fiber are shown in Table 1.

As a result of TEM measurement of the longitudinal section of each single fiber obtained, the average layer thickness of the layered clay mineral is 90 nm, and the dispersibility (Y) required from all the layered clay minerals observed in a sectional area of 25 μm ^2. Were 2% (Example 2) and 12% (Example 3).

[Comparative Example 1]
In Example 1, spinning, stretching, and relaxation heat treatment were performed under the same conditions as in Example 1 except that a spinning stock solution containing no layered clay mineral was used. The evaluation results of the obtained fiber are shown in Table 1. A test fabric was prepared using this fiber and exposed to the flame of a gas burner, but a hole was formed in the portion directly exposed to the flame.

  The low-shrinkage meta-type wholly aromatic polyamide fiber according to the present invention has a very good heat-shrinkage property at a high temperature, and therefore provides a fiber product that hardly causes problems such as perforation even when it comes into contact with a high-temperature flame or fireball. This is particularly useful as a material for protective clothing.

The graph which shows the behavior with respect to the heat | fever of the low-shrinkage wholly aromatic polyamide fiber of this invention shown in Example 1. FIG.

Claims (7)

  Meta-type wholly aromatic polyamide fiber containing 0.1 to 10% by weight of layered clay mineral based on the weight of meta-type wholly aromatic polyamide, having a maximum heat shrinkage temperature of 300 ° C to 360 ° C, A low-shrinkage meta-type wholly aromatic polyamide fiber having a shrinkage rate of 5% or less and starting to stretch at 320 ° C to 380 ° C.   The low-shrinkage meta-type wholly aromatic polyamide fiber according to claim 1, wherein the layer thickness of the layered clay mineral is 10 to 500 nm.   The low-shrinkage meta-type wholly aromatic polyamide fiber according to claim 1 or 2, wherein the dispersibility (Y) of the layered clay mineral is 0.1 to 40. (1) An amide polar solvent solution of a meta type wholly aromatic polyamide containing 0.1 to 10 parts by weight of a layered clay mineral based on the weight of the meta type wholly aromatic polyamide is prepared,
(2) The solution is introduced into a coagulation bath composed of an amide polar solvent and water, or an amide polar solvent, an inorganic salt and water, and coagulated.
(3) The coagulated yarn is stretched 2.0 to 10 times in a wet stretching bath composed of water, an amide polar solvent and water, or an amide polar solvent, an inorganic salt and water, and then (4) the The drawn yarn is relaxed 0.5 to 1.0 times in a wet relaxation bath composed of water, an amide polar solvent and water, or an amide polar solvent and an inorganic salt and water.
A process for producing a low shrinkage meta-type wholly aromatic polyamide fiber, characterized in that   The method for producing a low-shrinkage meta-type wholly aromatic polyamide fiber according to claim 4, further comprising a relaxation heat treatment at 100 to 400 ° C and 0.5 to 1.0 times after the wet relaxation.   6. The low shrinkage property according to claim 4 or 5, wherein at least one solvent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylacetamide and dimethylformamide is used as the amide polar solvent. Method for producing meta-type wholly aromatic polyamide fiber.   The method for producing a low shrinkage meta-type wholly aromatic polyamide fiber according to any one of claims 4 to 6, wherein a layered clay mineral having an average layer thickness of 10 to 500 nm is used.

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