JP2009007702A - Method for producing exrafine crystalline polymer fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystalline polymer-based extrafine fiber whose diameter is significantly smaller than that of conventional fibers while substantially retaining its own various performances including heat resistance, chemical resistance and flame retardancy, each of which has been preferable in conventional crystalline polymers, and to provide a method for producing the extrafine fiber. <P>SOLUTION: The method for producing the extrafine fiber includes the following steps: the step of obtaining spinning dope mainly consisting of a crystalline polymer or its precursor, at least one fiber-forming polymer and an organic solvent capable of dissolving these components, and the step of spinning by solidifying the spinning dope extruded via fine nozzles to obtain a readily splittable fiber bundle. Then, only the fiber-forming polymer in the fiber bundle is dissolved and removed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrafine fiber having a crystalline polymer compound as a main component and a method for producing the same, and an easily splittable fiber bundle for obtaining the ultrafine fiber and a method for producing the same.

In recent years, organic materials called plastics have been actively developed because they are lightweight, excellent in workability, and do not corrode. Plastics play a major role in the advancement of technology and economic activities in the industrial field, and their uses have spread to every field of our daily lives, including automobiles, computers and home appliances.
Plastic functions are becoming more sophisticated in parallel with the increase in production volume, and engineering plastics (engineering plastics) with improved heat resistance, impact resistance, wear resistance, etc., and now surpass the functions of engineering plastics. There are even so-called super engineering plastics.
There are also significant developments in so-called synthetic fibers that take advantage of the excellent characteristics of plastics. This is because high strength, high heat resistance, and corrosion resistance, which are not found in natural fibers, have been regarded as important in the field of fibers. By making the plastic into a fibrous form, it becomes easy to process into various forms such as cloth, paper, felt, and non-woven fabric.

  Super engineering plastics having high heat resistance and wear resistance have these properties due to their high crystal orientation. One of them, wholly aromatic polyamide-based resin, has particularly high heat resistance and abrasion resistance, and many attempts have been made to utilize its excellent properties as fibers in various applications.

  For example, for polyamide fiber polymerization and spinning, after dissolving an inorganic salt and aromatic diamine in an amide solvent, the polymer obtained by low-temperature polymerization of aromatic diacid chloride is washed with water, and the solvent and inorganic salt are separated and dried. A spinning stock solution is prepared by dissolving about 20% by weight in 98% or more sulfuric acid-based solvent. After passing through a die, spinning, neutralization, washing with water, drying, and mechanical treatment process, aromatic polyamide fiber Alternatively, a method for producing a film (see, for example, Patent Document 1), a low molecular weight aromatic polyamide obtained by interfacial polymerization is dissolved in an amide solvent, and the solution is discharged into a poor solvent to obtain pulp. A method for obtaining a shaped article (see, for example, Patent Document 2) has been introduced.

On the other hand, in the general fiber material field, so-called ultrafine fibers having a small fiber diameter are flexible while being densely packed between the fibers, so that various filters, particularly thin high-performance filters, artificial leather or cleaning fabrics, etc. It is used for various applications.
Of course, in the field of synthetic fibers, there is a demand for ultra-fine fibers that take advantage of the superior characteristics of plastics. Particularly in applications where the size of the surface area is important, there is a high demand for ultrafine fibers.

As a method of obtaining ultrafine fibers made of synthetic resin, a method of spinning a spinning stock solution composed of a plurality of components, each of which is incompatible with each other, and beating or other methods for splitting and thinning (see, for example, Patent Document 3). ), A method in which a so-called conjugate fiber having a core and a sheath made of different polymers is spun, and then the sheath component is removed by some method to obtain an ultrafine fiber of the core component (for example, see Patent Document 4). A spinning solution in which each of these components is incompatible and phase-separated into a sea-island type is spun, and then the sea components are removed to obtain ultrafine fibers (for example, Patent Documents 5 and 6), electrospinning method (See, for example, Patent Document 7). However, all of them only obtain random short fibers, and it is extremely difficult to obtain long fibers.
U.S. Pat. No. 3,869,429 JP-A-51-100151 JP-A-9-302525 JP 2003-253555 A JP-A-8-218223 JP 2007-92205 A JP 2006-144138 A

In the method of Patent Document 1, for example, a polymerization process, a washing process, and production of a spinning stock solution using sulfuric acid, spinning, and a mechanical treatment process are performed. In addition to the fact that the physical properties of the fibers are reduced due to the polymer decomposition reaction, and it is difficult to treat calcium sulfate (CaSO ₄ ) produced as a by-product. In the method of Literature 2, the obtained pulp-like product is further treated with water or alcohol, so that the physical properties are lowered, and it is difficult to produce high-performance polyamide short fibers.

When using physical stress called beating as in Patent Document 3, at least ten minutes or more is required to complete beating, and equipment problems such as using a beater, refiner, mixer or high-pressure water flow are also included. Was.
Furthermore, it was almost impossible to collect a single ultrafine fiber that was completely separated even after beating for a long time. This is a state in which anisotropy is developed in the strength in the fiber by applying a high degree of stretching after spinning and adjusting the molecular arrangement of the resin of the sea component in one direction, that is, in a state where it is easy to tear in the fiber axis direction. This is because it tears.
In addition, the method of making ultrafine fibers by beating can be applied to polymers whose molecular chain arrangement can be easily changed by stretching, but it is unclear whether it can be applied to crystalline polymer compounds. No attempt has been made to this resin.

  As in Patent Document 4, the method using conjugate fiber is not necessarily applicable to all polymers, and even if it can be applied, the sheath component cannot be removed sufficiently and the quality of the ultrafine fiber is impaired. There was a case. At least a conventional method using a conjugate fiber has never been attempted for a crystalline polymer compound. Moreover, the fiber diameter obtained by this was at most about 1 micrometer.

  As in Patent Documents 5 and 6, a method of spinning a spinning stock solution phase-separated into a sea-island type, and then removing sea components to obtain ultrafine fibers is also applicable to limited polymers. In some cases, the quality of the ultrafine fiber was impaired. This method has never been attempted for at least conventional crystalline polymer compounds.

  The electrospinning method disclosed in Patent Document 7 and the like is an excellent method for obtaining extremely fine fibers. However, the obtained ultrafine fibers are limited to the shapes of waste cloths, sheets, and the like, and the obtained ultrafine fibers are obtained. It has been difficult to control the fiber length of the fiber and difficult to knead when processed into a compound.

  In view of the above facts, the present invention has been completed by the present inventors through extensive research. That is, the problem is that the fiber diameter is remarkably smaller than that of the conventional one without almost reducing the performance such as heat resistance, chemical resistance, and flame retardancy, which were good in the conventional crystalline polymer compound. An object of the present invention is to provide an ultrafine fiber mainly composed of a crystalline polymer compound that is ultrafine and whose fiber length can be arbitrarily controlled, and a method for producing the same. Another object of the present invention is to provide an easily split fiber bundle for obtaining this ultrafine fiber and a method for producing the same.

The present invention includes the following aspects.
[1] A step of obtaining a spinning dope mainly comprising a crystalline polymer compound or a precursor thereof, at least one fiber-forming polymer compound, and an organic solvent for dissolving them, and discharging through pores A method of producing an easily splittable fiber bundle, characterized by comprising a step of solidifying and spinning the obtained spinning solution.
[2] The production of the easily splittable fiber bundle according to [1], wherein the spinning step is a step of spinning the spinning dope discharged through the pores in a coagulating solution for solidifying the fiber-forming polymer compound. Method.
[3] The method for producing an easily splittable fiber bundle according to [1] or [2], wherein the spinning solution is directly discharged from the pores into the coagulation solution.
[4] The method for producing an easily splittable fiber bundle according to [1] or [2], wherein the spinning dope is discharged from the pores with an air gap provided in the coagulation liquid.
[5] The mass ratio between the crystalline polymer compound or a precursor thereof and the fiber-forming polymer compound is in the range of 8: 2 to 2: 8, according to any one of [1] to [4] A method for producing an easily splittable fiber bundle.
[6] Crystalline polymer compounds or precursors thereof are aromatic polyamide, polyphenylene sulfide, polyphenylene ether, polyether ether ketone, polypropylene, polyethylene, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, and copolymers thereof. The method for producing an easily splittable fiber bundle according to any one of [1] to [5], which is one or more.
[7] The fiber-forming polymer compound is cellulose diacetate, cellulose triacetate, polyacrylonitrile, polyvinyl butyral, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyamide, polyvinylidene fluoride, and a copolymer thereof The method for producing an easily splittable fiber bundle according to any one of [1] to [6], excluding the combination that is the same as the crystalline polymer compound according to [6] or a precursor thereof .
[8] After obtaining an easily splittable fiber bundle by the method for producing an easily splittable fiber bundle according to any one of [1] to [7], only the fiber-forming polymer compound in the easily splittable fiber bundle A method for producing an ultrafine fiber, which comprises dissolving and removing the fiber.
[9] A crystalline polymer compound or a precursor thereof and at least one fiber-forming polymer compound in a range of 8: 2 to 2: 8, wherein the crystalline polymer compound or a precursor thereof is An easily splittable fiber bundle characterized by extending a large number in the axial direction.
[10] An ultrafine fiber having a diameter of 0.01 μm or more and less than 2 μm, a fiber length of 0.01 mm or more, and produced by the method for producing an ultrafine fiber according to [8].

According to the method for producing an easily splittable fiber bundle of the present invention, the main component is a crystalline polymer compound in which the fiber diameter is extremely small and various performances such as heat resistance, chemical resistance and flame retardancy are maintained. An easily split fiber bundle capable of obtaining ultrafine fibers can be produced.
In addition, according to the easily splittable fiber bundle of the present invention, by splitting the fiber bundle, the diameter of the fiber is remarkably small, and various performances such as heat resistance, chemical resistance, and flame retardancy are maintained. Ultrafine fibers containing a compound as a main component can be easily obtained.
Furthermore, the ultrafine fiber of the present invention can easily obtain an ultrafine fiber bundle that can be arbitrarily controlled with a fiber length of 0.01 mm or more.

<Method for producing easily splittable fiber bundle>
A crystalline polymer compound or a precursor thereof (hereinafter, the “crystalline polymer compound or precursor thereof” may be collectively referred to as “crystalline polymer compound”) and at least one fiber-forming property A step of obtaining a spinning stock solution mainly composed of a polymer compound and an organic solvent that dissolves the polymer compound, and the spinning stock solution discharged through the pores are solidified in a coagulation solution for solidifying the fiber-forming polymer compound and spinning. The process of carrying out.

(Crystalline polymer compound)
In the present invention, the ultrafine fiber substrate includes aromatic polyamide, polyphenylene sulfide, polyphenylene ether, polyether ether ketone, polypropylene, polyethylene, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, and a copolymer thereof. The above is used. Of these, the present invention will be described using aromatic polyamide as a representative example of the most typical crystalline polymer compound.
First, the aromatic polyamide resin has a skeleton in which aromatic benzene rings are bonded in a straight chain via an amide group as the name suggests. Depending on the position of the benzene ring to which the amide group is bonded, it is classified as a meta-aromatic polyamide or a para-aromatic polyamide, but the aromatic polyamide resin used in the present invention is not special and is not particularly limited.

There are no particular restrictions on the method for producing the aromatic polyamide resin. Although it is obtained by a generally performed method, it will be exemplified and explained below.
The aromatic polyamide resin comprises (a) a method in which an aromatic diamine and an aromatic dicarboxylic acid are polycondensed in the presence of a condensing agent in an organic solvent at a reaction temperature of 10 to 150 ° C., and (b) an aromatic diamine and A method in which an aromatic dicarboxylic acid dihalide is polycondensed in an organic solvent at a reaction temperature of 60 ° C. or less in the presence of a dehydrohalogenating agent; (c) an aromatic diamine and an aromatic dicarboxylic acid dialkylate and / or an aromatic In this method, dicarboxylic acid diarylate is polycondensed in an organic solvent at a reaction temperature of 100 to 300 ° C. The aromatic diamine used in these methods is bis [4- (4-aminophenoxy) phenyl] ketone and / or bis [4- (3-aminophenoxy) phenyl] ketone, 2-chloroparaphenylenediamine, 4 4,4'-diaminodiphenyl ether or the like is used. In addition, as the aromatic dicarboxylic acid to be used, aromatic dicarboxylic acid is used in the method (a). For example, phthalic acid, methylphthalic acid, ethylphthalic acid, methoxyphthalic acid, ethoxyphthalic acid, chlorophthalic acid, bromophthalic acid, isophthalic acid, methylisophthalic acid, ethylisophthalic acid, methoxyisophthalic acid, ethoxyisophthalic acid, chloroisophthalic acid, bromoisophthalic acid Acids, terephthalic acid, methyl terephthalic acid, ethyl terephthalic acid, methoxy terephthalic acid, ethoxy terephthalic acid, chloroterephthalic acid, bromoterephthalic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4 '-Diphenyl ether dicarboxylic acid, 4,4'-diphenyl sulfide dicarboxylic acid, 4,4'-benzophenone dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 4,4'-di Phenylmethanedicarboxylic acid, 2,2-bis (4-carboxyphenyl) propane, 2,2-bis (4-carboxyphenyl) -1,1,1,3,3,3-hexafluoropropane, 1,4- Naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and the like can be mentioned. These aromatic dicarboxylic acids are used alone or in combination of two or more. In the method (b), aromatic dicarboxylic acid dihalide is used. Examples thereof include dihalides of the above-mentioned aromatic dicarboxylic acids, that is, aromatic dicarboxylic acid dichlorides, aromatic dicarboxylic acid dibromides and the like. These aromatic dicarboxylic acid dihalides are used alone or in combination of two or more.

  In the method (c), an aromatic dicarboxylic acid dialkyl ester and / or an aromatic dicarboxylic acid diallyl ester is used. For example, each of the above-mentioned aromatic dicarboxylic acids is a dialkyl ester having 1 to 10 carbon atoms, diphenyl ester, di (fluorophenyl) ester, di (chlorophenyl) ester, di (bromophenyl) ester, di (methylphenyl) ester, Di (ethylphenyl) ester, di (propylphenyl) ester, di (isopropylphenyl) ester, di (butylphenyl) ester, di (isobutylphenyl) ester, di (t-butylphenyl) ester, di (methoxyphenyl) ester , Di (ethoxyphenyl) ester, di (nitrophenyl) ester, di (phenylphenyl) ester, dinaphthyl ester and the like. These aromatic dicarboxylic acid diesters are used alone or in combination of two or more.

  The diamine component and aromatic dicarboxylic acid or derivative thereof are polymerized in a solvent. Examples of the solvent used include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, 1,3- Dimethyl-2-imidazolidinone, N-methylcaprolactam, dimethylsulfoxide, dimethylsulfone, sulfolane, tetramethylurea, hexamethylphosphoramide, pyridine, α-picoline, β-picoline, γ-picoline, 2,4-lutidine 2,6-lutidine, quinoline, isoquinoline, triethylamine, tripropylamine, tributylamine, tripentylamine, N, N-dimethylaniline, N, N-diethylaniline, dichloromethane, chloroform, carbon tetrachloride, 1,1, 1-trichloroethane, 1, , 2-trichloroethane, trichloroethylene, 1,1,2,2-tetrachloroethane, tetrachloroethylene, n-hexane, cyclohexane, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, acetonitrile, propionitrile, acetone, methyl ethyl ketone, methyl butyl Ketone, methyl isobutyl ketone, cyclohexanone, acetophenone, isopropyl ether, tetrahydrofuran, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, anisole, phenetole, benzyl ether, phenyl ether, 1,2-dimethoxyethane, bis (2 -Methoxyethyl) ether, 1,2-bis (2-methoxyethoxy) ethane, benzene, toluene, o-xylene, m-xylene, p-xylene, dipheny , Terphenyl, benzyl chloride, nitrobenzene, 2-nitrotoluene, 3-nitrotoluene, 4-nitrotoluene, chlorobenzene, 2-chlorotoluene, 3-chlorotoluene, 4-chlorotoluene, o-dichlorobenzene, p-dichlorobenzene, bromobenzene , Phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol O-chlorophenol, p-chlorophenol, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, t-butanol, cyclohexanol, benzyl alcohol, water and the like. These solvents may be used alone or in combination of two or more depending on the kind of the reaction raw material monomer and the polymerization method. When an aromatic dicarboxylic acid dihalide is used as the monomer for the reaction raw material, a dehydrohalogenating agent is usually used in combination. Examples of dehydrohalogenating agents used include trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, N, N-dimethylbenzylamine, N, N-diethylbenzylamine, N, N-dimethylcyclohexylamine, N, N-diethylcyclohexylamine, N, N-dimethylaniline, N, N-diethylaniline, N-methylpyrrolidine, N-ethylpyrrolidine, N-methylpiperidine, N-ethylpiperidine, N-methylmorpholine, N-ethyl Morpholine, pyridine, α-picoline, β-picoline, γ-picoline, 2,4-lutidine, 2,6-lutidine, quinoline, isoquinoline, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, sodium carbonate , Potassium carbonate, charcoal Lithium, calcium carbonate, sodium bicarbonate, potassium bicarbonate, calcium oxide, lithium oxide, sodium acetate, potassium acetate, ethylene oxide, propylene oxide, and the like.

  Moreover, when using aromatic dicarboxylic acid as a reaction raw material monomer, a condensing agent is usually used. Examples of the condensing agent used include sulfuric anhydride, thionyl chloride, sulfite ester, picryl chloride, phosphorus pentoxide, phosphorus oxychloride, phosphite-pyridine condensing agent, triphenylphosphine-hexachloroethane condensing agent, propyl phosphorus An acid anhydride-N-methyl-2-pyrrolidone-based condensing agent is exemplified.

  The reaction temperature varies depending on the polymerization technique and the type of solvent, but is usually 300 ° C. or lower. The reaction pressure is not particularly limited, and can be sufficiently carried out at normal pressure.

  The reaction time varies depending on the type of reaction raw material monomer, the polymerization method, the type of solvent, the type of dehydrohalogenating agent, the type of condensing agent, and the reaction temperature, but the reaction time is sufficient to complete the formation of the aromatic polyamide. Let Usually, 10 minutes to 24 hours is sufficient.

  In addition to the above aromatic polyamides, crystalline polymer compounds such as polyphenylene sulfide, polyphenylene ether, polyether ether ketone, polypropylene, polyethylene, polyvinyl alcohol, polyvinylidene fluoride, and polytetrafluoroethylene can also be used. There are no particular limitations on the raw materials and the production method.

(Fiber-forming polymer compound)
Examples of the fiber-forming polymer compound used in the present invention include cellulose diacetate, cellulose triacetate, polyacrylonitrile, polyvinyl butyral, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyamide, polyvinylidene fluoride, and copolymers thereof. It is preferable to select and use.
In particular, it is preferable to use cellulose diacetate and / or cellulose triacetate. Cellulose diacetate and / or cellulose triacetate is readily soluble in organic polar solvents. Therefore, it can be removed by dissolution with a common organic solvent such as acetone and / or methylene chloride. Moreover, since the strength when it is used as a fiber is high, there is an advantage that spinning can be easily performed.
The fiber-forming polymer compound may be used in combination of two or more.
However, it is limited to those excluding the combination that is the same compound as the crystalline polymer compound described above.

(Organic solvent)
The organic solvent used in the step of obtaining the spinning dope is a solvent that can dissolve both the crystalline polymer compound and the fiber-forming polymer compound.
For example, when cellulose diacetate and / or cellulose triacetate is used as the fiber-forming polymer compound, N-methyl-2-pyrrolidone can be suitably used as the organic solvent. When polyacrylonitrile is used as the fiber-forming polymer compound, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and the like can be suitably used. The solvent may be appropriately selected for other fiber-type performance polymer compounds. It is also possible to use two or more kinds of mixed solvents.

(Other ingredients)
Other components can be appropriately added to the spinning dope depending on the purpose. Examples of components that can be added include dispersants, surfactants, pigments, dyes, and antistatic agents.

(Process for obtaining spinning dope)
The mass ratio of the crystalline polymer compound and the fiber-forming polymer compound in the spinning dope can be arbitrarily selected from fiber-forming polymer compound: crystalline polymer compound, etc. = 8: 2 to 2: 8 depending on the purpose of use. Selected. For example, when emphasis is placed on the ease of spinning, it is desirable that the fiber-forming polymer compound: the crystalline polymer compound and the like = about 8: 2 to 5: 5.
From another point of view, when only the fiber-forming polymer compound in the easily splittable fiber bundle is dissolved and the ultrafine fibers are recovered individually for each fiber, the fiber-forming polymer compound: high crystallinity Molecular compound, etc. = 8: 2 to 6: 4 is good. Conversely, when a fiber in which ultrafine fibers are partially bound is obtained, fiber-forming polymer compound: crystalline polymer compound, etc. = 4: 6 ~ 2: 8 is good.
That is, the ratio of the crystalline polymer compound or the like and the fiber-forming polymer compound may be changed according to which form ultrafine fibers are used.
When the mass ratio of the crystalline polymer compound or the like and the fiber-forming polymer compound is out of the above range, the ultrafine fiber corresponding to the present invention cannot be obtained.
Fiber-forming polymer compound: crystalline polymer compound, etc. = 8: 2, when the content ratio of the fiber-forming polymer compound is large, the proportion of the crystalline polymer compound in the spinning dope is small. Fine fibers are not formed, and a crystalline polymer compound in the form of grains or rods is obtained. Also, since fiber-forming polymer compound: crystalline polymer compound, etc. = 2: 8, when the content ratio of crystalline polymer compound is large, the ratio of fiber-forming polymer compound is conversely reduced. The crystalline polymer compound used as the fiber significantly increases the binding with the adjacent ultrafine fiber, and the crystalline polymer compound that contains the fiber-forming polymer compound inside has a fiber that is not easily splittable. End up.
The ratio of the organic solvent in the spinning dope is preferably 50 to 85% by mass with respect to the whole spinning dope. This facilitates ultra-thinning of the crystalline polymer compound and the like, and prevents the crystalline polymer compound from being shredded.

There is no particular limitation on the method of mixing and dissolving the crystalline polymer compound and the fiber-forming polymer compound in an organic solvent.
For example, a predetermined amount of a fiber-forming polymer compound may be prepared by synthesizing a crystalline polymer compound in a predetermined organic solvent and adding a predetermined amount of the fiber-forming polymer compound to a varnish. , A crystalline polymer compound and the like and an organic solvent are placed in a mixing container, and 100 to 10000 R. P. Stirring may be continued at M for 30 minutes or more, and mixed and dissolved. At this time, if the viscosity is high and it is difficult to stir, it may be heated to about 40 to 60 ° C. However, if stirring is continued for 30 minutes or more at a temperature exceeding 80 ° C., there is a problem of volatilization depending on the organic solvent used. In particular, care should be taken in the open state because the concentration proceeds as the organic solvent volatilizes.
Further, a crystalline polymer compound or the like and a fiber-forming polymer compound dissolved in an organic solvent may be mixed.
In order to prevent yarn breakage during spinning after stirring and uniform mixing and dissolution, it is desirable to depressurize or statically degas the ultrafine bubbles in the mixed solution.
Further, in the spinning process described later, in order to maintain a uniform mixed state in the stock solution storage tank of the spinning device, 5 to 20 R.S. P. It is desirable to keep stirring gently at M.

(Spinning process)
In the present invention, the spinning dope discharged through the pores (nozzles) is solidified and spun. The solidification is preferably performed in a coagulation liquid that solidifies the fiber-forming polymer compound.
In this case, a dry-wet spinning method in which the spinning stock solution is once discharged from the spinning nozzle into air or an inert gas may be used, but a wet spinning method in which the spinning stock solution is directly discharged from the spinning nozzle into the coagulating solution is preferable. Thereby, the sticking of the fibers immediately after nozzle discharge can be prevented.

As the coagulation liquid, one having a solidifying ability for the fiber-forming polymer compound in the spinning dope is used. The composition of the coagulation liquid varies depending on the type of the fiber-forming polymer compound.
For example, when cellulose diacetate and / or cellulose triacetate is used as the fiber-forming polymer compound, water or a mixture of water and alcohol can be used. Even when polyacrylonitrile is used, water or a mixture of water and alcohol is effective.

When water or a mixture of water and alcohol is used as the coagulation liquid, an operation such as addition of inorganic salts such as ammonium sulfate or sodium sulfate is effective in order to increase the coagulation rate due to salting out and dehydration effects. Conversely, when the coagulation speed is too high and the yarn is broken or difficult to draw, the general wet spinning method such as mixing the solvent used for dissolving the spinning dope into the coagulation solution is adopted. can do.
What is necessary is just to select the temperature which becomes the solidification ability desired in the range of -5 degreeC to 60 degreeC as the temperature of coagulation liquid. Generally, the higher the temperature of the coagulation liquid, the higher the solidification ability. However, if the coagulation liquid is too high, there is a problem that the viscosity of the spinning dope decreases and the ultrafine fibers are shredded. desirable.

In the wet spinning method, the yarn stock can be obtained by discharging the spinning dope from the spinning nozzle to the coagulating liquid through a device such as a gear pump that controls the discharge amount to be constant.
Thereafter, the speed at which the yarn is pulled out from the coagulation liquid is 1.1 times to less than 500 times, preferably 4 times to less than 100 times, more preferably 5 times to less than 10 times the discharge linear velocity of the spinning nozzle. is there. Depending on the mixing ratio of the fiber-forming polymer compound to be solidified, if it is stretched too much, it becomes difficult to maintain the fiber form at the time of solidification. If it is less than 1.1 times, the fibers tend to stick together.

In the dry-wet spinning method, as in the wet spinning method, the spinning solution is discharged through a spinning nozzle through a device that controls the discharge rate of a gear pump or the like, but the spinning solution discharged from the nozzle is once in a gas phase such as air. The yarn thread can be obtained by discharging it into the coagulating liquid. The distance (air gap) for passing through the gas phase at this time may be experimentally determined so as to be appropriate from the composition of the spinning dope used, the solid content concentration, and the like.
The gas used for the gas phase is generally air, but an inert gas such as nitrogen or argon may be used. The gas phase temperature is generally room temperature, but may be heated in order to promote desolvation.
In the case of using the dry and wet spinning method, the speed of drawing the yarn from the coagulation bath is usually equal to the discharge linear speed of the spinning nozzle, but it may be increased several times as in the wet spinning method. However, when making it faster than a discharge linear velocity, it is necessary to control so that a fiber is not stuck during a gaseous-phase passage.
In addition to the dry and wet spinning methods and the wet spinning method, dry spinning in which solidification is performed in a gas phase is also possible. In this case, the gas used for desolvation is generally air heated to the boiling point of the solvent or higher. When using a solvent with a low flash point or low ignition point, or when oxidation becomes a problem, it is desirable to use an inert gas such as nitrogen or argon.
However, the dry spinning method is easy to stick and difficult to control, so it is preferable to use a wet or dry wet spinning method.

(Stretching process)
Stretching may be applied with dry heat or wet heat for the purpose of making the yarns obtained in the spinning process finer or leveling the molecular arrangement.
In the case of stretching with wet heat, for example, the film is preferably stretched to about 2.0 to 8.0 times in the range of 10 ° C. to 80 ° C. while being immersed in a liquid having the same composition as the coagulation liquid. However, wet stretching, in which a large amount of organic solvent remains in the fiber, has a low molecular alignment leveling effect, and therefore dry stretching is more desirable.
In the case of dry-heat stretching, a method of stretching from about 2.0 times to about 8.0 times in an atmosphere of 200 ° C. to 400 ° C., preferably 300 ° C. to 380 ° C. is exemplified. In this case, the reaction is generally performed in an inert gas such as nitrogen, helium or carbon dioxide.
However, the stretching is intended to promote ultrathinning of the crystalline polymer fiber in the easily split fiber bundle, and is not an absolute condition. Therefore, it is not necessary to add a high degree of drawing after spinning.

(Drying process)
After the spinning process or after the drawing process, the yarn is heated and dried as necessary. The heating is 100 ° C. to 400 ° C., but this should be determined in consideration of the type of organic solvent used. However, since the fiber-forming polymer compound undergoes thermal decomposition or melting at an excessively high temperature, it is preferably performed at 300 ° C. or less in as short a time as possible. In this case, a treatment such as heating in an inert gas such as nitrogen, helium, or argon gas can be performed for the purpose of preventing oxidation of the fiber-forming polymer compound.
In the drying process, it is effective to attach a hydrophobic oil agent such as mineral oil, silicon-based or fluorine-based before drying so that the yarns do not stick together.

<Easily splittable fiber bundle>
By the above operation, an easily split fiber bundle can be obtained. The easily splittable fiber bundle of the present invention contains a crystalline polymer compound or a precursor thereof and at least one fiber-forming polymer compound in a range of 8: 2 to 2: 8.
As for the form, for example, staple, toe and the like can be selected according to the purpose of use. In addition, when processing such as spinning or woven fabric is performed before obtaining ultrafine fibers, a treatment such as a crimping treatment may be performed.

In the easily splittable fiber bundle of the present invention, a large number of crystalline polymer compounds and the like extend in the axial direction. In the present invention, the extended crystalline polymer compound or the like can be brought into a connected state almost without interruption. The fiber length of the ultrafine fibers in the easily splittable fiber bundle can be adjusted by appropriately adjusting the crystallinity of the crystalline polymer compound used, the speed of desolvation in the coagulation liquid, and the speed at which the string is pulled out of the coagulation liquid. It is possible to control. The speed of solvent removal can be adjusted by the temperature of the coagulation liquid, the salt concentration, and the organic solvent concentration.
According to the present invention, it is possible to easily obtain an easily split fiber bundle including ultrafine fibers having a length of 0.01 mm or more and possibly several cm or more connected without interruption.

  In the present invention, a method of physically tearing the easily splittable fiber bundle in a state in which it is easy to tear is not adopted, and the easily splittable fiber bundle has a structure in which ultrafine fibers separated from the time of formation are assembled in a single unit. It is a body. Therefore, the easily splittable fiber bundle of the present invention is particularly excellent in that splitting is extremely easy.

The inventors presumed the formation mechanism of this unique easily splittable fiber bundle in the present invention as follows.
The spinning dope of the present invention is formed under conditions where both the crystalline polymer compound and the fiber-forming polymer compound are dissolved, and the sea-island (emulsion) spinning dope as in the conventional method for producing ultrafine fibers. is not.
When such a spinning dope is spun, it is common that two types of polymers become non-uniformly mixed fibers. In the present invention, one of the two types of polymers is a polymer having high crystallinity. Therefore, the spinning dope discharged from the spinning nozzle is subjected to a strong shearing force in the fiber axis direction, and the crystalline polymer compound is oriented to form ultrafine fibers.
Furthermore, it is considered that the fiber is fixed by desolvating the spinning solution solvent in the coagulation liquid, and an ultrafine fiber bundle can be formed. The cross-section of the solidified fiber has a sea-island structure such that the island component is a crystalline polymer compound and the sea component is a fiber-forming polymer compound.

  A shish kebab structure is known in which precipitates with high crystallinity are obtained around the stirring shaft when the polymer compound solution is stirred at a high speed, but the shear force generated around the stirring shaft in the ultrafine fiber manufacturing method of the present invention is known. Is considered to correspond to the shearing force when discharged from the spinning dope.

  Also, the reason for forming an ultrafine fiber bundle without adhering adjacent ultrafine fibers is that crystal aggregation occurs during crystal orientation by shearing force, and the crystalline polymer compound crystallizes along the fiber axis. To go. Here, the spinning dope is extruded into the coagulation liquid, and solidification rapidly proceeds by desolvation, the polymer crystals are fixed in the form of ultrafine fibers, and the fiber-forming polymer compound is interposed between the ultrafine fibers. It is considered that an ultrafine fiber bundle is formed without the adjacent ultrafine fibers adhering to each other.

  By such a mechanism, the higher the crystallinity of the crystalline polymer compound, the higher the orientation, and the ultrafine and long fiber length is formed. On the other hand, in the aromatic polyamide resin, in the polymer compound in which the crystallinity is lowered by introducing a structure with low crystallinity such as an alkyl chain in the molecular chain, the fiber diameter becomes thicker due to the lowering of the orientation, resulting in a high fiber diameter. It is considered that the fiber length is shortened because the molecular chain has a strong cohesive force.

  The present inventors have found through experiments combining many factors that the fiber length and fiber length of ultrafine fibers differ depending on the difference in crystallinity (introduction amount of alkyl chain) of the crystalline polymer compound and the like. . Furthermore, the following knowledge was acquired regarding the compounding ratio of a crystalline polymer compound etc. and a fiber formation polymer compound.

  Under the condition that the crystalline polymer compound has a volume fraction of 75% or more of the fiber-forming polymer compound, there is no sufficient amount of fiber-forming polymer compound between the crystalline polymer ultrafine fibers oriented by shearing force. Adjacent ultra-fine fibers are bonded, and easy splitting is reduced.

  Under the condition that the crystalline polymer compound has a volume fraction of 75% or less, a sufficient amount of fiber-forming polymer compound exists between the ultrafine fibers, so that the adhesion of adjacent ultrafine fibers can be eliminated, A fiber bundle having easy splitting can be manufactured.

  However, in the case where the easy-dividing property is lowered, by removing the fiber-forming polymer compound, it is possible to obtain a fiber in which the adjacent ultrafine fibers are bonded to each other.

<Method for producing ultrafine fiber>
In order to obtain ultrafine fibers from an easily splittable fiber bundle, the fiberformable polymer compound is dissolved and removed by immersing the easily splittable fiber bundle in a solvent that selectively dissolves only the fiberformable polymer compound. To do.

The solvent that selectively dissolves only the fiber-shaped polymer compound is appropriately selected depending on the fiber-shaped polymer compound used.
For example, acetone is suitable when the fibrous polymer compound used is cellulose diacetate, and methylene chloride is preferred when cellulose triacetate is used. In the case of polyacrylonitrile, dioxane, sodium thiocyanate aqueous solution and the like are preferable.
The operation of obtaining the ultrafine fibers by dissolving and removing the fiber-shaped polymer compound may be performed immediately after obtaining the easily splittable fiber bundle, and once in the form of easily splittable fiber bundle, paper, nonwoven fabric, thread, fabric, etc. It may be performed after processing.
When collecting ultrafine fibers individually, it is desirable to recover the ultrafine fibers by dissolving and removing the fiber-shaped polymer compound immediately from the easily splittable fiber bundle.
On the other hand, when obtaining a fiber in which ultrafine fibers are partially bound, after processing a paper, nonwoven fabric, thread, woven fabric, etc., with an easily split fiber bundle, an unnecessary fibrous polymer compound is added. A method of dissolving and removing is effective. In this case, if the desired degree of fibrillation cannot be obtained by simply immersing the work piece in a solvent, it is possible to apply physical beating force or rub the surface to raise the material. It is desirable to perform a typical process.

<Ultra fine fiber>
By the above operation, ultrafine fibers mainly composed of a crystalline polymer compound can be obtained. The ultrafine fiber of the present invention preferably has a fiber length of 0.01 mm or more.
As described above, according to the present invention, an ultrafine fiber aggregate having a length of several centimeters or more can be easily obtained. Therefore, it is possible to obtain ultrafine fibers having a desired fiber length by cutting the ultrafine fiber bundle into a desired length in advance.
According to the experiments by the present inventors, an ultrafine fiber having a fiber length exceeding 10 mm is entangled during handling, and can no longer be easily solved, and is practically difficult to use. A fiber length in the range of 0.01 mm or more and less than 10 mm, particularly 0.05 mm or more and less than 2 mm is appropriate for all applications.

The ultrafine fiber of the present invention preferably has a diameter of 0.01 μm or more and less than 2 μm.
If the diameter is in this range, it can be processed into high density and thin paper, which has been impossible in the past, and can be used for applications such as woven fabric and nonwoven fabric.
The diameter of the ultrafine fiber can be adjusted by the crystallinity of the crystalline polymer compound, the size of the draw ratio, and the like.

  The ultrafine fiber of the present invention is ultrafinened with almost no deterioration in various performances that were good in the crystalline polymer compound. Therefore, paper, non-woven fabric, string, fabric, etc., various filters, electrolytic capacitors, separators for electric double layer capacitors, covering materials for electronic parts, reinforcing materials for the same adhesive, reinforcing materials such as rubber, cement, etc. It can be used in applications that require high heat resistance, chemical resistance, electrical characteristics, sliding characteristics, dimensional stability and radiation stability.

For example, when used as a separator for an electrolytic capacitor, (1) the gap cross-sectional area is large so that most of the area of the separator serves as a current path, (2) the separator is as thin as possible, and (3) the separator The constituent fibers are required to be as cylindrical as possible, and (4) the constituent fiber diameter of the separator is required to be as small as possible. The ultrafine fiber of the present invention can easily satisfy these conditions.
According to the present invention, since the fiber length of the ultrafine fibers can be 0.01 mm or more, sufficient entanglement between the fibers can be obtained without using a special binder. Therefore, high strength and good handleability can be obtained. In addition, it can be molded with a very thin and uniform thickness and can prevent the occurrence of voids and breakage, so it can efficiently prevent internal short circuit due to contact between electrodes.
Moreover, it leads to an increase in the electrode plate area and an increase in capacitance by reducing the occupied volume of the separator. Furthermore, the excellent reduction in tan δ makes it possible to cope with high frequencies, and provides extremely effective effects such as prevention of heat generation.

  In another example, the ultrafine fiber of the present invention can be used in place of the glass woven fabric base epoxy resin prepreg which has been widely used in the multilayer printed wiring board by the built-up method. In this case, it is possible to reduce the thickness of the prepreg caused by strength, low dielectric constant, and low specific gravity, and the effects of improving the rigidity of the printed wiring board and preventing breakage of the board during manufacturing or component mounting can be obtained. In addition, a high density fine line can be realized along with improvement of the surface smoothness of the prepreg. Also when used for a prepreg, the ultrafine fiber preferably has a diameter of 0.01 μm or more and less than 2 μm and a fiber length of 0.01 mm or more and less than 10 mm.

Moreover, when the ultrafine fiber of the present invention is used as a filter, a filter having excellent heat resistance, heat resistance, and acid resistance can be obtained. For this reason, for example, it is suitable as a filter medium for collecting dust from high temperature dust discharged from a coal boiler, a garbage incinerator, a metal blast furnace, a diesel automobile, or the like.
Conventionally, there have been filters using various heat-resistant fibers having a fiber diameter of submicron, but there are many examples in which a binder is used to supplement the strength. Since the ultrafine fiber of the present invention does not require a binder and the fiber diameter is ultrafine, excellent filtration accuracy can be obtained as compared with a conventional heat resistant filter.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited at all by these Examples.

Example 1
2-chloroparaphenylenediamine corresponding to 85 mol% and 4,4′-diaminodiphenyl ether corresponding to 15 mol% are dissolved in dehydrated N-methyl-2-pyrrolidone, and this corresponds to 98.5 mol%. 2-chloroterephthalic acid chloride was added, polymerized by stirring for 10 hours, and then neutralized with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 11% by weight. This was heated to 180 ° C. at 60 Torr to volatilize excess N-methyl-2-pyrrolidone to obtain an aromatic polyamide solution having a polymer concentration of 15% by weight.
Separately, after adding 150 g of cellulose diacetate having an acetylation degree of 55% and a polymerization degree of 120 to 850 g of N-methyl-2-pyrrolidone and stirring at room temperature for about 1 hour, the temperature was further raised to 60 ° C. for 30 minutes. The mixture was stirred and confirmed to be completely dissolved, and cooled to obtain a cellulose diacetate solution (solid content: 15%).
This cellulose diacetate solution and the aforementioned aromatic polyamide resin solution were added so that the mass ratio of the solid content was cellulose diacetate: aromatic polyamide resin = 6: 4, and stirred to obtain a spinning dope.
Next, this was extruded into an aqueous solution having an N-methyl-2-pyrrolidone concentration of 10 wt% and 25 ° C. while maintaining a constant discharge rate from a spinneret having a hole diameter of 0.1 mm and a hole number of 80. The rotation speed of the winding roller was adjusted so that the draw ratio was 2 to 3 in the aqueous solution. The immersion time in the aqueous solution was about 60 seconds. The wound spool was air-dried at room temperature for 5 minutes while maintaining a tension state, and then dried at 250 ° C. for 20 minutes in a nitrogen atmosphere to obtain an easily splittable crystalline polymer fiber bundle.

(Example 2)
The easily splittable crystalline polymer fiber bundle obtained in Example 1 was cut to 20 mm, and then a part was immersed in normal temperature acetone in a glass container, and further stirred with a magnetic stirrer. After stirring for 10 minutes, the mixture was allowed to stand for about 10 minutes, and ultrafine fibers settled on the bottom of the container. The supernatant acetone was removed, acetone was newly added, and the mixture was further stirred for 10 minutes and allowed to stand for about 10 minutes. After repeating this operation a total of 5 times, the ultrafine fiber collected from the bottom of the container was observed with a scanning electron microscope, and it was an ultrafine crystalline polymer fiber having a fiber diameter of 50 nm to 500 nm and an average fiber length of 20 mm. It was confirmed. While checking with a scanning electron microscope from ultrafine fibers, fibers having a fiber diameter of 200 to 500 nm were selected and measured for tensile strength, tensile elongation, heat resistance, and flame retardancy (LOI value). Table 1 shows the results obtained by measuring 20 fibers and calculating the average.

(Example 3)
The mass ratio of the solid content of the aromatic polyamide resin solution (solid concentration 15%) and the cellulose diacetate solution (solid content 15%) obtained in Example 1 is cellulose diacetate: aromatic polyamide resin = 3: 7. In addition, the mixture was stirred with a small homogenizer to obtain a uniform slightly yellow transparent mixed solution.
Next, this was extruded into an aqueous solution having an N-methyl-2-pyrrolidone concentration of 10 wt% and 25 ° C. while maintaining a constant discharge rate from a spinneret having a hole diameter of 0.1 mm and a hole number of 80. The rotation speed of the winding roller was adjusted so that the draw ratio was 2 to 3 in the aqueous solution. The immersion time in the aqueous solution was about 60 seconds.
The wound spool was air-dried at room temperature for 5 minutes while maintaining a tension state, and then dried at 250 ° C. for 20 minutes in a nitrogen atmosphere to obtain an easily splittable crystalline polymer fiber bundle.

Example 4
While a part of the easily splittable crystalline polymer fiber bundle obtained in Example 3 was cut into 3 mm, it was immersed in room temperature acetone in a glass container, and further stirred with a magnetic stirrer. After stirring for 10 minutes, the mixture was allowed to stand for about 10 minutes, the supernatant acetone was removed, acetone was newly added, and the mixture was further stirred for 10 minutes and allowed to stand for about 10 minutes. After repeating this operation 5 times in total, the fiber bundle was taken out and washed in running water.
Next, this was beaten with a refiner in water, and the precipitate of the beaten solution was observed with a scanning electron microscope. As a result, it was confirmed that a crystalline polymer ultrafine fiber having a fiber diameter of 50 nm to 500 nm was converged in the fiber axis direction, and a fiber in which adjacent ultrafine fibers were bonded was obtained.

(Example 5)
Using the same spinning stock solution as in Example 1, 1 m in nitrogen heated to 200 ° C. was passed through a spinneret having a hole diameter of 0.1 mm and a hole number of 80 while maintaining a constant discharge rate, and then N-methyl- Extruded into an aqueous solution having a 2-pyrrolidone concentration of 10 wt% and 25 ° C. The rotation speed of the winding roller was adjusted so that the draw ratio was 1 to 1.5 in the aqueous solution. The immersion time in the aqueous solution was about 60 seconds. The wound spool was air-dried at room temperature for 5 minutes while maintaining a tension state, and then dried at 250 ° C. for 20 minutes in a nitrogen atmosphere to obtain an easily splittable crystalline polymer fiber bundle.

(Example 6)
After the easily splittable crystalline polymer fiber bundle obtained in Example 5 was cut to 20 mm, a part thereof was immersed in normal temperature acetone in a glass container, and further stirred with a magnetic stirrer. After stirring for 10 minutes, the mixture was allowed to stand for about 10 minutes, and ultrafine fibers settled on the bottom of the container. The supernatant acetone was removed, acetone was newly added, and the mixture was further stirred for 10 minutes and allowed to stand for about 10 minutes. After repeating this operation a total of 5 times, the ultrafine fiber collected from the bottom of the container was observed with a scanning electron microscope, and it was an ultrafine crystalline polymer fiber having a fiber diameter of 50 nm to 500 nm and an average fiber length of 20 mm. It was confirmed. While checking with a scanning electron microscope from ultrafine fibers, fibers having a fiber diameter of 200 to 500 nm were selected and measured for tensile strength, tensile elongation, heat resistance, and flame retardancy (LOI value). Table 1 shows the results obtained by measuring 20 fibers and calculating the average.

(Example 7)
850 g of N-methyl-2-pyrrolidone was added to 150 g of a commercially available polyvinylidene fluoride resin, stirred for 1 hour while heating to 80 ° C., and after confirming that it was completely dissolved, the mixture was cooled and the solid content concentration was 15% by weight. A polyvinylidene fluoride solution was obtained.
To this was added the same cellulose diacetate solution as in Example 1 so that the mass ratio of the solid content was cellulose diacetate: polyvinylidene fluoride = 6: 4, and the mixture was stirred to obtain a spinning dope.
Next, this was extruded into an aqueous solution having an N-methyl-2-pyrrolidone concentration of 10 wt% and 25 ° C. while maintaining a constant discharge rate from a spinneret having a hole diameter of 0.1 mm and a hole number of 80. The rotation speed of the winding roller was adjusted so that the draw ratio was 2 to 3 in the aqueous solution. The immersion time in the aqueous solution was about 60 seconds. The wound spool was air-dried at room temperature for 5 minutes while maintaining a tension state, and then dried at 250 ° C. for 20 minutes in a nitrogen atmosphere to obtain an easily splittable crystalline polymer fiber bundle.

(Example 8)
The easy-divided crystalline polymer fiber bundle obtained in Example 7 was cut into 20 mm, and a part thereof was immersed in normal temperature acetone in a glass container, and further stirred with a magnetic stirrer. After stirring for 10 minutes, the mixture was allowed to stand for about 10 minutes, and ultrafine fibers settled on the bottom of the container. The supernatant acetone was removed, acetone was newly added, and the mixture was further stirred for 10 minutes and allowed to stand for about 10 minutes. After repeating this operation five times in total, the ultrafine fibers collected from the bottom of the container were confirmed with a scanning electron microscope. As a result, an ultrafine crystalline polymer having a fiber diameter of 200 nm to 1000 nm and a fiber length of 0.01 mm to 20 mm was obtained. The fiber was confirmed. While confirming with a scanning electron microscope from ultrafine fibers, fibers having a fiber diameter of 800 to 1000 nm were selected, and tensile strength, tensile elongation, heat resistance, and flame retardancy (LOI value) were measured. Table 1 shows the results obtained by measuring 20 fibers and calculating the average.

(Comparative Example 1)
Only the crystalline polymer compound solution (solid content 15%) prepared in Example 1 had a N-methyl-2-pyrrolidone concentration of 10 wt% while maintaining a constant discharge rate from a spinneret with a pore diameter of 0.1 mm and a hole number of 80, Extruded into an aqueous solution at 25 ° C. The rotation speed of the winding roller was adjusted so that the draw ratio was 2 to 3 in the aqueous solution. The immersion time in the aqueous solution was about 60 seconds.
The wound spool was air-dried at room temperature for 5 minutes while maintaining a tension state, and then dried at 250 ° C. for 20 minutes in a nitrogen atmosphere to obtain crystalline polymer fibers.
The fiber was measured for tensile strength, tensile elongation, heat resistance, and flame retardancy (LOI value). Table 1 shows the results obtained by measuring 20 fibers and calculating the average.

The evaluation results in Table 1 were obtained by the following method.
Tensile strength / tensile elongation: Evaluated by using a Tensilon RTM25 tensile tester manufactured by Orientec based on JIS R-7601.
Heat resistance: The strength retention was evaluated after 100 hours exposure in air.
Flame retardancy (LOI value): The flame retardancy of fibers was measured according to the method described in JIS K 7201.

  Comparative Example 1 is a general crystalline polymer fiber, which has good strength and elongation properties, heat resistance, and flame retardancy. On the other hand, it was confirmed that Example 1 according to the present invention had almost the same performance as Comparative Example 1.

Claims (10)

  A step of obtaining a spinning dope comprising, as a main component, a crystalline polymer compound or a precursor thereof, at least one fiber-forming polymer compound, and an organic solvent for dissolving them; and a spinning dope discharged through the pores And a step of solidifying and spinning the fiber, and a method for producing an easily splittable fiber bundle.   2. The method for producing an easily splittable fiber bundle according to claim 1, wherein the spinning step is a step of spinning by spinning the spinning solution discharged through the pores in a coagulating solution for solidifying the fiber-forming polymer compound.   The method for producing an easily splittable fiber bundle according to claim 1 or 2, obtained by a wet spinning method in which a spinning dope is directly discharged from pores into a coagulation liquid.   The method for producing an easily splittable fiber bundle according to claim 1 or 2, wherein the spinning dope is obtained by a dry and wet spinning method in which an air gap is provided and discharged from the pores in the coagulation liquid.   The easily splittable property according to any one of claims 1 to 4, wherein the mass ratio of the crystalline polymer compound or a precursor thereof to the fiber-forming polymer compound is in the range of 8: 2 to 2: 8. A method of manufacturing a fiber bundle.   The crystalline polymer compound or its precursor is one or more of aromatic polyamide, polyphenylene sulfide, polyphenylene ether, polyether ether ketone, polypropylene, polyethylene, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, and copolymers thereof. The manufacturing method of the easily splittable fiber bundle in any one of Claims 1-5.   The fiber-forming polymer compound is at least one of cellulose diacetate, cellulose triacetate, polyacrylonitrile, polyvinyl butyral, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyamide, polyvinylidene fluoride, and copolymers thereof. And the manufacturing method of the easily splittable fiber bundle in any one of Claims 1-6 except the combination which is the same compound as the crystalline polymer compound of Claim 6, or its precursor.   After obtaining an easily splittable fiber bundle by the method for producing an easily splittable fiber bundle according to any one of claims 1 to 7, only the fiber-forming polymer compound in the easily splittable fiber bundle is dissolved and removed. A method for producing ultrafine fibers, characterized in that:   A crystalline polymer compound or a precursor thereof and at least one fiber-forming polymer compound in a range of 8: 2 to 2: 8, wherein the crystalline polymer compound or a precursor thereof is axially An easily splittable fiber bundle characterized by extending a large number.   An ultrafine fiber having a diameter of 0.01 µm or more and less than 2 µm, a fiber length of 0.01 mm or more, and produced by the method for producing an ultrafine fiber according to claim 8.