JP4591281B2 - Umijima fiber, method for producing the same, and method for producing ultrafine acrylic fiber - Google Patents

Description

  The present invention relates to a sea-island fiber composed of an acrylonitrile-based polymer and an ester-based polymer, a method for producing the sea-island fiber, and a method for producing an ultrafine acrylic fiber obtained therefrom.

  As a conventional method for producing an ultrafine acrylic fiber, a method using an ultrafine die, a composite die, or a polymer blend is known. The method for producing ultrafine acrylic fibers by using an ultrafine die is a method of using a die having a smaller pore diameter than usual and obtaining fibers with a fineness only by the yarn making process. The method for producing ultrafine acrylic fibers using a composite die is a method of obtaining ultrafine acrylic fibers by using a composite die, performing composite spinning with a different polymer, and then removing or splitting the different polymer. Among these, when using an ultra-thin die, the single yarn fineness is small, so process troubles such as yarn breakage and wrapping frequently occur in the yarn making process. In order to lead out to the die surface, it is necessary to increase the distance between the holes as compared with the conventional spinneret of acrylic fiber, and there is a problem that it is difficult to increase the number of holes in the die and productivity is poor.

  On the other hand, the method for producing ultrafine acrylic fibers by polymer blending comprises a yarn production process for blend fibers and a removal process for removing different polymers from the blend fibers. In the spinning process, by mixing different polymers with an acrylic polymer and spinning, blend fibers with a sea-island structure by polymer phase separation without using special caps such as ultrafine caps and composite caps, A sea-island fiber is obtained in which the polymer is a sea part and the acrylic polymer is stretched in the fiber axis direction to form an island part. Subsequently, in the removing step, ultrafine acrylic fibers are obtained by removing the different polymer from the obtained sea-island fibers. In this method, it is possible to use the conventional acrylic fiber die and the yarn making step in the yarn making process, and it is possible to realize multi-holes of the die that were impossible with the composite die. Moreover, since the single yarn fineness of the obtained sea-island fiber is equivalent to that of the conventional acrylic fiber, troubles in the yarn production process such as yarn breakage and winding, which are problematic when using an ultrafine die, have been improved (Patent Document 1, 2). However, in the method for producing ultrafine acrylic fibers by polymer blending, it is very difficult to select different polymers, and in the known technology, problems in the spinning process or removal process remain as problems as shown below. For example, polyvinyl acetate, polystyrene, polymethyl methacrylate, and the like have been used as heterogeneous polymers that can be solidified with the coagulation liquid used in the acrylic fiber spinning process for the purpose of utilizing the conventional acrylic fiber spinning process. . However, these polymer species are resistant to alkalis and acids, so it is harmful to human bodies such as methanol, trichloroethylene, methanol, and acetone to remove foreign polymers after obtaining sea-island fibers, and it explodes. In order to protect the environment and ensure safety, a large capital investment such as solvent recovery, exhaust, and explosion-proof equipment was required in the removal process of the different polymers. Furthermore, since these different types of polymers are difficult to decompose, it is difficult to reduce the molecular weight of the polymer during removal, and it is necessary to remove the polymer by elution with a solvent in the state of slowly diffusing polymer molecules. For this reason, the elution efficiency is very poor, the removal process takes enormous time, the productivity of the ultrafine acrylic fiber is poor, and the equipment cost is high because a long equipment is required.

  To solve the problem of these removal processes, after spinning sea-island fibers using vinyl alcohol polymer as a different polymer, it is split by beating in water or splitting with a high-pressure water stream, or kneading with resin, and an ultrafine acrylic The manufacturing method which obtains a fiber is indicated (refer to patent documents 3). In this production method, water is used or not removed in the removal process of the different polymer, so that the equipment cost of the removal process and the environmental load can be reduced. However, the yarn production process for obtaining the sea-island fibers has the following problems. As a coagulation solvent in the spinning process when using a vinyl alcohol polymer as a different polymer, organic solvents such as alcohols and ketones having a solidifying ability with respect to a vinyl alcohol polymer and an acrylonitrile polymer were used. Alcohols and ketones have low boiling points, low flammability, and explosive properties. For this reason, in order to ensure safety in the yarn production process, in addition to conventional acrylic fiber production facilities, explosion-proof and exhaust facilities are necessary, and a large capital investment is required. Furthermore, there is a problem with the handling property of the obtained sea-island fiber itself, and since polyvinyl alcohol, which is a sea component, has an affinity for water, single yarn adhesion is likely to occur when the humidity is high, and it is transported in the state of sea-island fiber. It was necessary to control the humidity of the atmosphere during processing. In addition, in ultrafine processing by splitting or kneading, the obtained ultrafine fiber is a mixture of different fibers, and the use is limited because acrylic fiber cannot be obtained alone.

As described above, conventionally, after obtaining sea-island fibers by blending an acrylonitrile-based polymer and a different polymer, the production of the ultra-fine acrylic fiber by removing or splitting the different polymer components, the yarn-forming process for forming the sea-island fibers. In order to safely handle the organic solvent used in the process or the removal process for removing the foreign polymer from the sea-island fibers, a huge capital investment is required, and the elution efficiency in the removal process is a problem. There was also a problem with the handling properties of the obtained sea-island fibers themselves. In order to solve these problems in both the spinning process and the removal process, and to form sea-island fibers that are easy to handle, it is essential to select a different polymer blended with the acrylonitrile-based polymer. It has been desired to establish a sea-island fiber comprising a possible polymer species and an acrylonitrile-based polymer, a method for producing the sea-island fiber, and a method for producing an ultrafine acrylic fiber.
JP 58-174622 A (pages 1 to 3) JP-A-3-130411 (Pages 1-5) JP-A-9-170115 (pages 1 to 9)

  An object of the present invention is to provide a sea-island fiber that can solve the above-described problems of the prior art, a method for producing the sea-island fiber, and a method for producing an ultrafine acrylic fiber obtained therefrom.

  In order to achieve the above object, the present invention is summarized as follows.

  The first invention of the present invention is a sea-island fiber comprising an acrylonitrile-based polymer (A) and an ester-based polymer (B), wherein the polymer (A) is an island component and the polymer (B) is a sea component. A characteristic sea-island fiber.

  According to a second aspect of the present invention, a polymer stock solution mixed so that the ratio of the weight of the polymer (A) to the total weight of the polymer (A) and the polymer (B) is less than 30% by weight is obtained by wet spinning or dry / wet. The sea-island fiber manufacturing method according to the first aspect of the invention for spinning.

  According to a third aspect of the present invention, there is provided a method for producing ultrafine acrylic fibers, characterized in that the polymer (B) is decomposed and eluted from the sea-island fibers described in the first aspect with an alkaline solution.

  The sea-island fiber of the present invention is superior in transportation and workability because single yarn adhesion due to moisture absorption hardly occurs compared to sea-island fiber in the conventional method for producing ultrafine acrylic fiber by polymer blend. In addition, it becomes possible to significantly reduce the capital investment required for the solvent safety measures in the removal process.

  According to the method for producing sea-island fibers of the present invention, such fibers can be produced by a method having excellent productivity and low environmental load.

  By the method for producing ultrafine acrylic fibers of the present invention, it is possible to efficiently remove the sea component polymer from the sea-island fibers in a short time compared to the conventional method, and the productivity of the ultrafine acrylic fibers is improved. Furthermore, since no organic solvent is used in the removal process, no special explosion-proof equipment is required, so that the equipment cost can be reduced as compared with the conventional method. Furthermore, in the production method of the present invention, the low molecular weight substance of the ester polymer eluted with a solvent can be separated and recovered and reused, which can contribute to high yield and resource saving.

  Hereinafter, the sea-island fiber of the present invention will be described in detail.

  The sea-island fiber of the present invention is a blend fiber composed of an acrylonitrile-based polymer (A) and an ester-based polymer (B), and is a continuous phase composed of an ester-based polymer (B), that is, an acrylonitrile-based polymer (A) in the sea part. It is characterized by having a morphology in which an independent phase composed of is extended in a streak shape in the fiber axis direction and finely dispersed to form islands. It is preferable that the independent phase comprising the acrylonitrile-based polymer (A) in the cross section of the sea-island fiber, that is, the maximum diameter of the island portion is 5 μm or less and the average diameter is 1 μm or less. By making the maximum diameter of the island part 5 μm or less and the average diameter 1 μm or less, the texture of the ultrafine acrylic fiber obtained after removing the sea-based ester polymer (B) from the sea-island fiber becomes very soft. . Depending on the cross section, sea components may be present in the island. The observation of the morphology of the sea-island fibers and the measurement of the maximum diameter and the average diameter of the independent phase mainly composed of the acrylonitrile-based polymer (A) are performed by electron microscope observation of the fiber cross section by the method described in Examples.

  As the acrylonitrile-based polymer (A) used in the present invention, an acrylonitrile homopolymer and / or an acrylonitrile-based copolymer of an acrylonitrile monomer and another monomer can be used depending on the application. Examples of other types of monomers include styrene, vinyl toluene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, vinyl fluoride, vinylidene fluoride, etc., for the purpose of changing the texture and dyeability of acrylic fibers. Unsaturated monomers, p-sulfophenyl methallyl ether, methallyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and alkali metal salts thereof may be mentioned. In addition, when used as a carbon fiber precursor, a monomer or acrylamide monomer having a carboxylic acid group or its esterified product is copolymerized for the purpose of accelerating the cyclization of the acrylonitrile polymer (A) in the flameproofing step. May be. The ratio of the acrylonitrile monomer to the other monomer can be appropriately selected according to the use of the fiber, but the acrylonitrile monomer in the acrylonitrile copolymer is preferably 40% by weight or more, more preferably 80% by weight or more. By increasing the ratio of the acrylonitrile monomer, the unique properties of the acrylic fiber of the ultrafine acrylic fiber obtained after removing the sea component from the sea-island fiber of the present invention are maintained.

  The acrylonitrile-based polymer (A) used in the present invention preferably has a viscosity of 100 to 1000 poise in a 20% by weight dimethyl sulfoxide solution at 45 ° C. from the viewpoint of spinnability.

  The ester polymer (B) used in the present invention refers to a polymer having an ester bond in the main chain. By using the ester-based polymer (B), the coagulating liquid has explosive properties such as alcohols and ketones in the spinning process of sea-island fibers, and it can be coagulated with water without using an organic solvent with a large environmental load. This is possible and does not require special equipment, and a conventional method for producing acrylic fibers can be used. In addition, since the ester-based polymer (B) is easily decomposed by an alkaline solution, an organic solvent is not used in the step of removing the ester-based polymer (B) when producing ultrafine acrylic fibers from sea-island fibers. Efficient removal is possible by simultaneously reducing the molecular weight and extracting the ester-based polymer (B) by using a polymer, and the treatment in the removal process compared to the sea-island fiber in the production method of ultrafine acrylic fiber by the conventional polymer blend The speed is dramatically improved, and the capital investment required for the safety measures for the solvent used in the yarn forming process and the removing process can be greatly reduced. Furthermore, sea-island fibers are excellent in transportation and processability because single yarn adhesion due to moisture absorption hardly occurs.

  The ester-based polymer (B) of the present invention is not particularly limited in terms of monomer type, structure, and degree of polymerization as long as it contains an ester bond in the main chain, but from the viewpoint of solubility in a solvent when preparing a stock solution and stretchability. The viscosity of a 15% by weight dimethyl sulfoxide solution at 45 ° C. is preferably 1000 poise or less.

  The ester polymer (B) of the present invention increases the decomposition rate of the ester polymer (B) when the ester polymer (B) is removed from the sea-island fiber using an alkaline solution to form an ultrafine acrylic fiber. A block polyether ester copolymerized with a polyalkylene glycol is more preferable for the purpose of elution in a short time. Furthermore, for the purpose of improving the compatibility with the acrylonitrile-based polymer (A) and improving the stability of the spinning dope, graft copolymerization of a monomer having good compatibility with the acrylonitrile-based polymer (A) is performed on this block polyether ester. Is most preferred.

  The molecular weight of the polyalkylene glycol is preferably 1000 to 20000 from the viewpoint of polymerizability with the polyester, and is preferably 3000 to 6000 in order to make the block polyether ester uniform with a soluble point in the solvent. More preferred. The mixing ratio of the polyalkylene glycol is preferably 1 to 60% by weight based on the total weight of the ester polymer (B). By setting the content to 1% by weight or more, the decomposition rate during alkali treatment is promoted, and the water resistance of the sea-island fibers obtained by setting the content to 60% by weight or less improves. Specific examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. Among these, it is particularly preferable to use polyethylene glycol from the viewpoints of polymerizability and alkali decomposability.

  About the composition of the polyester part of the block polyether ester described above, the purpose is to suppress the crystallinity of the ester polymer (B), improve the solubility in a solvent when preparing a stock solution, and improve the decomposability during alkali treatment A combination of an aliphatic dicarboxylic acid or a mixture of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid with respect to an aliphatic diol is preferred. Examples of aliphatic diols include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, neopentyl glycol and the like, and aliphatic dicarboxylic acids include succinic acid, glutaric acid, adipic acid, suberic acid, Examples of azelaic acid, sebacic acid, dodecanedioic acid and aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylene dicarboxylic acid and the like. Moreover, it is more preferable that a C6 or less aliphatic dicarboxylic acid component is included for the purpose of improving the polymerizability with polyalkylene glycol.

  The monomer for graft copolymerization may be any monomer that is compatible with one or more acrylonitrile-based polymers (A), and examples thereof include acrylonitrile and methyl methacrylate.

  As for the fineness of the sea-island fiber of the present invention, the single yarn fineness is preferably 0.1 dtex or more and 500 dtex or less. By setting the single yarn fineness to 0.1 dtex or more, yarn breakage in the yarn production process is reduced and process passability is improved, and by setting it to 500 dtex or less, the removal efficiency in the removal process is increased. More preferably, it is 1 dtex or more and 100 dtex or less.

  Below, the manufacturing method of the sea-island fiber of this invention is demonstrated in detail.

  As a method of mixing the acrylonitrile polymer (A) and the ester polymer (B) to make a polymer stock solution, it is sufficient that the acrylonitrile polymer (A), the ester polymer (B) and the solvent can be mixed uniformly. After mixing the polymers, they may be dissolved in a good solvent common to both polymers, the other polymer may be mixed with the polymer solution in which one polymer is dissolved, or the solutions of both polymers may be mixed together. As the mixing method, for example, kneading with an extruder, mixing and stirring of a polymer solution, or mixing with a static kneader immediately before the spinneret can be used alone or in combination.

  The solvent used in the polymer solution is preferably a common solvent for the acrylonitrile polymer (A) and the ester polymer (B), and examples thereof include dimethylformamide, dimethylacetamide, and dimethylsulfoxide.

  The temperature and concentration of the polymer stock solution are preferably 20 to 90 ° C. from the viewpoint of yarn production and operability, and the concentration of the polymer stock solution may be adjusted so that the viscosity at 20 to 90 ° C. is 20 to 1000 poise. preferable.

  As a mixing ratio of the acrylonitrile polymer (A) and the ester polymer (B) in the polymer stock solution, the acrylonitrile polymer (A) with respect to the total weight of the acrylonitrile polymer (A) and the ester polymer (B) in the stock solution Is less than 30% by weight. By making it less than 30% by weight, continuous phase formation by fusion of independent phases mainly composed of acrylonitrile polymer (A) in the obtained blended fiber is suppressed, the maximum diameter is 5 μm or less, and the average diameter is 1 μm. Therefore, the texture of the ultrafine acrylic fiber obtained after removing the ester polymer (B) from the blend fiber becomes very soft. Moreover, it is more preferable that the mixing ratio is 10% by weight or more and less than 30% by weight for the purpose of reducing the production cost of the ultrafine acrylic fiber.

  The spinning method is a wet spinning in which the mixed polymer stock solution is discharged into a coagulation bath filled with a solvent capable of solidifying both the acrylonitrile polymer (A) and the ester polymer (B). Dry-wet spinning that can be run and then led to a coagulation bath can be applied.

  The coagulation solvent may be a solution containing a poor solvent for both components of the acrylonitrile polymer (A) and the ester polymer (B). From the viewpoint of solvent recovery, it is used for adjusting the poor solvent and the polymer stock solution for both components. A mixed solvent with a solvent is particularly preferred. Examples thereof include alcohols such as methanol, ethanol and propanol, and mixed solutions of a poor solvent such as water and a solvent used for preparing the stock solution. It is most preferable to use a mixed solution of water and a solvent used for preparing a stock solution from the viewpoint of reduction of environmental burden and equipment cost for safely handling the coagulation solvent. As the concentration of the mixed solution, it is preferable that the concentration of the solvent in preparing the stock solution in the coagulation liquid is 10 to 90% by weight. By adjusting the concentration of the solvent in the coagulation liquid to 10% by weight or more, the cost for collecting, purifying and reusing the coagulation liquid can be reduced, and by setting it to 90% by weight or less, the spinning solution is coagulated. Is more preferably 20 to 80% by weight. The temperature of the coagulation bath is preferably 0 to 90 ° C., more preferably 5 to 70 ° C. from the viewpoint of operability.

  The take-up speed of the coagulated yarn is preferably 1 to 100 m / min from the viewpoint of operability. The blended fiber thus obtained is a sea-island fiber in which the acrylonitrile-based polymer (A) is a sea component and the ester-based polymer (B) is an island component. Furthermore, in order to reduce the diameter of the island part which the acrylonitrile-type polymer (A) in the obtained sea-island fiber comprises, and extending the orientation of an acrylonitrile-type polymer (A), it is preferable to extend | stretch. Stretching is preferably performed in multiple stages by liquid bath stretching following coagulation, and the total stretching ratio can be appropriately adjusted according to the purpose, but is preferably about 2 to 20 times. Moreover, you may perform drying, oil supply, and washing | cleaning suitably in the middle of the process or at the end.

  Next, a method for producing ultrafine acrylic fibers from sea-island fibers will be described in detail.

  In the present invention, an ester-based polymer (B) is prepared from an sea-island fiber using (A) consisting of an acrylonitrile-based polymer (A) and an ester-based polymer (B) as an island component and (B) as a sea component using an alkaline solution. It is characterized by elution and elution. Decomposition and elution means lowering the molecular weight of the ester-based polymer (B) by an alkali decomposition reaction and subsequent removal of the ester-based polymer (B) from the sea-island fibers by diffusion of the low-molecular weight compound into the solution. By performing dissolution and elution, it is possible to remove sea components in a short time compared to the conventional removal process that does not involve lowering the molecular weight of the polymer, and the productivity of ultrafine acrylic fibers is dramatically improved. In addition, the removal process can be performed without using low-boiling explosive organic solvents such as alcohols and ketones, and no special explosion-proof equipment is required, reducing equipment costs compared to conventional methods. Is possible. Further, in the production method of the present invention, ester monomers eluted with a solvent can be separated, recovered and reused, which can contribute to high yield and resource saving.

  Examples of the alkali used in the present invention include sodium hydroxide and potassium hydroxide. The alkali solvent is not particularly limited as long as it is hardly soluble in the acrylonitrile-based polymer (A), but a solvent that has low environmental burden, high safety, and easy separation and recovery is preferable, and water is used. Most preferred.

  The concentration of the alkaline solution is preferably 0.1 to 10% by weight. When the concentration is 0.1% by weight or more, the decomposition elution rate of the ester polymer (B) is increased, and when the concentration is 10% by weight or less, the decomposition reaction of the acrylonitrile polymer (A) can be suppressed. The temperature of the alkaline solution is preferably 10 to 100 ° C. for the purpose of suppressing the evaporation of water from the alkaline solution and keeping the solution concentration constant while maintaining the decomposition and elution rate of the ester polymer (B).

  The decomposition and elution step of the present invention may be performed after the sea-island fiber is wound up and wound up, or may be performed continuously with the yarn forming step. Moreover, as a state to process, you may process by the shape of a long fiber or a short fiber, and you may process by a skein shape, a package, and a fabric form.

  Since the ultrafine acrylic fiber obtained from the sea-island fiber of the present invention is obtained in a long fiber state, it can be knitted and processed. By removing the sea component after weaving and knitting, a fabric made of ultrafine yarn can be obtained. Etc. can be used. In addition, after the sea-island fibers are cut into staples, the sea components are removed and beaten to obtain a dispersion of ultrafine acrylic fibers, which can be used for stencil paper and the like by papermaking. Furthermore, the method for producing ultrafine acrylic fibers of the present invention can remove sea components continuously with the production of sea-island fibers, and ultrafine acrylic fiber aggregate long fibers can be obtained. By making this flame resistant and carbonized, flame resistant fibers and carbon fibers can be obtained.

  The most preferred example of the method for producing sea-island fibers and ultrafine acrylic fibers of the present invention is a dimethylsulfoxide solution of an acrylonitrile-based polymer (A) having a viscosity of 100 to 1000 poise of a 20 wt% dimethylsulfoxide solution at 45 ° C, and 45 ° C. A dimethyl sulfoxide solution of a block polyether ester (B) obtained by graft copolymerization of acrylonitrile whose viscosity of a 15% by weight dimethyl sulfoxide solution is 1000 poise or less is mixed, and the mixing ratio of the acrylonitrile-based polymer (A) is based on the total amount of the polymer It is prepared so that the solution viscosity of the mixed solution at 20 to 90 ° C. is less than 30% by weight and 20 to 1000 poise. This mixed solution is wet or dry-spun into a coagulation bath consisting of a 20 to 80% by weight dimethyl sulfoxide / water mixed solution at 5 to 70 ° C., and the resulting blended fiber is taken up at 1 to 100 m / min, followed by bathing. Stretched 2 to 20 times in multiple stages in the liquid, and the independent phase mainly composed of acrylonitrile polymer (A) is streaked in the fiber axis direction in the continuous phase mainly composed of ester polymer (B). This is a production method for obtaining sea-island fibers that are elongated and finely dispersed, and have an independent phase mainly composed of acrylonitrile-based polymer (A) having a maximum diameter of 5 μm or less and an average diameter of 1 μm. This is a method for producing ultrafine acrylic fibers in which the ester-based polymer (B) is decomposed and eluted by immersing the obtained sea-island fibers in an alkaline aqueous solution of 0.1 to 10% by weight of 10 to 100 ° C.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, although each characteristic value in an Example was calculated | required with the following method, this invention is not limited to these.

A. Viscosity of polymer solution The viscosity was measured using the following measuring apparatus and conditions by the viscosity measurement method, and the viscosity value measured within the following shear rate range was used as the solution viscosity.
Viscosity measuring device: DV-II + Pro VISCOMETER made by BROOKFIELD
Thermostatic device: TC500 made by BROOKFIELD
Shear rate: 10-20 sec ^-1
B. Morphological observation of blended fibers Morphological observation of blended fibers composed of acrylonitrile polymer (A) and ester polymer (B) is performed by impregnating a fiber bundle into an epoxy resin for an electron microscope and then using a microtome. Ultrathin sections were prepared. The obtained slice was placed on a mesh for an electron microscope, and the sea-island phase structure was observed with a transmission electron microscope (Hitachi Ltd., H-7100FA). When it is observed that the acrylonitrile-based polymer (A) is dispersed in an island shape, the resulting image is separated by image processing software (Winroof, Mitani Corporation). The diameter in terms of circle was calculated from the area of the area, and the average diameter and the maximum diameter of the island were determined from the diameter in terms of circle of 100 randomly selected islands.

Example 1
As the acrylonitrile polymer (A), 100 mol% of acrylonitrile was polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent to prepare a dimethyl sulfoxide solution of 20 wt% acrylonitrile homopolymer showing 200 poise at 45 ° C.

  As the ester polymer (B), 12 parts of ethylene glycol was added to 5 parts of adipic acid and 12 parts of azelaic acid, and an esterification reaction was performed to obtain a prepolymer. To this prepolymer, 48 parts of polyethylene glycol (molecular weight 4000) was added and subjected to polycondensation to obtain a block polyether ester (BP) composed of polyadipate, polyazelate, and polyethylene glycol. 100 parts of this block polyether ester was dissolved in 870 parts of dimethyl sulfoxide, and a dimethyl sulfoxide solution of an ester polymer (GP) obtained by graft polymerization of 30 parts of acrylonitrile was obtained. The viscosity of this 15.0 wt% GP solution was 15 poise at 45 ° C.

  These polymer solutions were mixed with a mixer at 45 ° C. so that the ratio of acrylonitrile polymer (A) / ester polymer (B) was 25/75 (weight), and a 25 poise spinning stock solution was obtained at 45 ° C. This spinning dope was discharged into a coagulation bath composed of a 45% by weight dimethyl sulfoxide aqueous solution at 45 ° C. using a spinneret having a hole diameter of 0.065 mmφ and a hole number of 400, and taken up at 6.0 m / min to obtain a coagulated yarn. . The coagulated yarn was then stretched 5 times in a two-stage stretching bath consisting of a 30% by weight dimethyl sulfoxide aqueous solution at 75 ° C. and a 15% by weight dimethyl sulfoxide aqueous solution at 95 ° C., and then washed in a 25 ° C. water bath to remain in the yarn. After removing the dimethyl sulfoxide to be obtained, a blend fiber of 800 dtex / 400 f was obtained. The spinning property was good. Morphological observation of the obtained blended fiber confirmed the formation of sea-island fibers in which the acrylonitrile-based polymer (A) was an island, and the average diameter of the island was 237 nm and the maximum diameter was 3.7 μm. When the blended fiber was allowed to stand in an atmosphere of a temperature of 40 ° C. and a humidity of 90% for 24 hours, adhesion between the single yarns was not observed. The blended fiber was wound on a 5 cm diameter skein and immersed in a 3 wt% sodium hydroxide aqueous solution at 60 ° C. for 10 minutes to decompose and elute the ester polymer (B). The fiber weight was 71% before and after the treatment. The weight was reduced, and it was confirmed that 95% of the ester polymer (B) in the blend fiber was removed.

Example 2
Example 1 was the same as Example 1 except that the ratio of acrylonitrile-based polymer (A) / ester-based polymer (B) was 10/90 (weight). The spinning property is good, and by observation of the morphology of the obtained blended fiber, formation of sea-island fibers in which the acrylonitrile-based polymer (A) is an island is confirmed, the average diameter of the island is 214 nm, and the maximum diameter is 3. It was 3 μm. When the blended fiber was allowed to stand in an atmosphere of a temperature of 40 ° C. and a humidity of 90% for 24 hours, no adhesion between the single yarns was observed. The blended fiber was wound on a 5 cm diameter skein and immersed in a 3 wt% sodium hydroxide aqueous solution at 60 ° C. for 10 minutes to decompose and elute the ester polymer (B). The fiber weight was 86% before and after the treatment. The weight was reduced, and it was confirmed that 96% of the ester polymer (B) in the blend fiber was removed.

Example 3
Example 1 was the same as Example 1 except that the ratio of acrylonitrile polymer (A) / ester polymer (B) was 29/71 (weight). The spinning property is good, and by observation of the morphology of the obtained blended fiber, formation of sea-island fibers in which the acrylonitrile-based polymer (A) is an island is confirmed. The average diameter of the island is 335 nm and the maximum diameter is 4. It was 8 μm. When the blended fiber was allowed to stand in an atmosphere of a temperature of 40 ° C. and a humidity of 90% for 24 hours, adhesion between the single yarns was not observed. The blended fiber was wound on a 5 cm diameter skein and immersed in a 3 wt% sodium hydroxide aqueous solution at 60 ° C. for 10 minutes to decompose and elute the ester polymer (B). The fiber weight before and after the treatment was 68%. The weight was reduced, and it was confirmed that 95% of the ester polymer (B) in the blend fiber was removed.

Example 4
In Example 1, it carried out similarly to Example 1 except having used the block polyether ester (BP) which does not graft-copolymerize acrylonitrile as ester type polymer (B). Although the yarn-making property was good, the yarn breakage in the drawing process occurred once per hour. Morphological observation of the obtained blended fiber confirmed the formation of sea-island fibers in which the acrylonitrile-based polymer (A) was an island, and the average diameter of the island was 362 nm and the maximum diameter was 4.9 μm. When the blended fiber was allowed to stand in an atmosphere of a temperature of 40 ° C. and a humidity of 90% for 24 hours, no adhesion between the single yarns was observed. The blended fiber was wound on a 5 cm diameter skein and immersed in a 3 wt% sodium hydroxide aqueous solution at 60 ° C. for 10 minutes to decompose and elute the ester polymer (B). The fiber weight before and after treatment was 73%. The weight was reduced and it was confirmed that 97% of the ester polymer (B) in the blended fiber was removed.

Comparative Example 1
Example 1 was the same as Example 1 except that a 20% by weight dimethyl sulfoxide solution of polyvinyl alcohol (PVA) having a polymerization degree of 1700 and a saponification degree of 99 mol% was used instead of the ester-based polymer (B). . As a result, yarn production was impossible due to poor coagulation in the coagulation bath.

Comparative Example 2
In Example 1, instead of the ester polymer (B), a 20% by weight dimethyl sulfoxide solution of polyvinyl alcohol (PVA) having a polymerization degree of 1700 and a saponification degree of 99 mol% was used, and the acrylonitrile polymer (A ) / PVA was mixed with a mixer so that the ratio was 25/75 (weight), and a spinning solution of 25 poise was obtained at 45 ° C. This spinning dope was discharged into a coagulation bath of 30% by weight dimethyl sulfoxide at 5 ° C./propanol using a spinneret having a hole diameter of 0.065 mmφ and a hole number of 400, and taken up at 6.0 m / min to obtain a coagulated yarn. It was. The coagulated yarn was stretched 6 times in a two-stage drawing bath consisting of a 30% by weight dimethyl sulfoxide / propanol solution at 20 ° C. and a 10% by weight dimethyl sulfoxide / propanol aqueous solution at 35 ° C. to obtain a blend fiber of 800 dtex / 400 f. It was. Morphological observation of the obtained blended fiber confirmed the formation of sea-island fibers in which the acrylonitrile-based polymer (A) became islands. The average diameter of the islands was 423 nm and the maximum diameter was 2.7 μm. When the blended fiber was allowed to stand for 24 hours in an atmosphere at a temperature of 40 ° C. and a humidity of 90%, the fibers adhered to each other. The blended fibers were wound on a 5 cm diameter skein, immersed in boiling water at 100 ° C. for 10 minutes, and then dried to bond the fibers together. In addition, it was confirmed that the fiber weight was reduced by only 52% before and after the treatment, and only 69% of the pop-PVA in the blended fiber was removed. The adhesion between the fibers indicates that PVA remains in the treated fibers, and the removal treatment for 10 minutes is not enough to elute the PVA. This result shows that the ester polymer (B ) Shows that it takes longer than the decomposition elution with an alkaline solution.

Comparative Example 3
Example 1 was the same as Example 1 except that the ratio of acrylonitrile polymer (A) / ester polymer (B) was 40/60. Sea island fiber structure in which the yarn-making property is good, and it is observed by morphological observation of the obtained blended fiber that the acrylonitrile-based polymer (A) constitutes the sea part, and the acrylonitrile-based polymer (A) becomes the island part. I did not take.

  The sea-island fiber of the present invention has water resistance and is excellent in handling during transportation and processing. Moreover, it can be manufactured by a method that is safe and has a low environmental load by using a conventional manufacturing process of acrylic fiber. In addition, the ultra-fine acrylic fiber obtained from this sea-island fiber is easy to handle because it maintains the form of continuous long fiber, air filter, liquid filter, separator, medical filter, regenerative medical medium, mask, clothing, It can be used for various applications such as interior goods, reinforcing materials, paper, non-woven fabric, carbon fiber precursors.

Claims (3)

  A sea-island fiber comprising an acrylonitrile-based polymer (A) and an ester-based polymer (B), wherein the polymer (A) is an island component and the polymer (B) is a sea component.   The sea-island fiber according to claim 1, wherein the polymer stock solution mixed so that the ratio of the weight of the polymer (A) to the total weight of the polymer (A) and the polymer (B) is less than 30% by weight is wet-spun or dry-wet-spun. Manufacturing method.   A process for producing ultrafine acrylic fibers, wherein the polymer (B) is decomposed and eluted from the sea-island fibers according to claim 1 with an alkaline solution.