Manufacturing method for modacrylic fiber

Abstract

To provide: a manufacturing method for a modacrylic fiber, in which spinning is carried out using a spinning solution obtained by dissolving a modacrylic fiber product into a solvent, and a modacrylic fiber can be manufactured by using a spinning solution that exhibits a Newtonian fluid property; and a modacrylic fiber.SOLUTION: Wet spinning is carried out by using a spinning solution obtained by mixing a modacrylic fiber product made of a modacrylic resin having a structural unit derived from a hydrophilic functional group-containing monomer and hydrophobic resin fine particles containing a small amount or without containing a structural unit derived from a hydrophilic functional group-containing monomer into a specific type of organic solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing modacrylic fibers. [Background technology]

[0002] Modacrylic fibers, known as acrylic fibers, are used in a variety of applications, including clothing, construction, and industrial materials, due to their unique texture, excellent color development, and color fastness. Since modacrylic fibers are petroleum products, there is a strong demand for their recycling in terms of the sustainability of human activities. One proposed method for recycling acrylic fibers involves dissolving crushed acrylic fibers in a solvent and then wet-spinning the resulting acrylic resin solution (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-112114 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when modacrylic fiber products are dissolved in a solvent, the spinning solution may exhibit non-Newtonian fluid properties. Non-Newtonian fluids behave as low-viscosity liquids under high shear stress, but become excessively viscous under low shear stress. When a spinning solution exhibits non-Newtonian fluid properties, it is prone to blockage of pipes and fiber breakage during spinning. For this reason, when modacrylic fiber products are recycled to produce modacrylic fiber, it is required to be able to prepare a spinning dope that exhibits Newtonian fluid properties rather than non-Newtonian fluid properties.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a method for producing a modacrylic fiber product, which involves spinning a spinning dope obtained by dissolving a modacrylic fiber product in a solvent, and which can produce modacrylic fiber using a spinning dope that exhibits Newtonian fluid properties, and a modacrylic fiber. [Means for solving the problem]

[0006] The present inventors have discovered that the above-mentioned problems can be solved by wet spinning using a spinning dope obtained by mixing a modacrylic fiber product made of a modacrylic resin having structural units derived from a hydrophilic functional group-containing monomer and hydrophobic resin microparticles containing a small amount or no structural units derived from a hydrophilic functional group-containing monomer with a specific type of organic solvent, and have thus completed the present invention.

[0007] More specifically, the present invention provides the following (1) to (7). (1) A method for preparing a spinning solution by mixing a modacrylic fiber product made of a modacrylic resin having a structural unit derived from a hydrophilic functional group-containing monomer and hydrophobic resin fine particles with at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone; and performing wet spinning using the spinning dope, Modacrylic fiber products are dissolved in spinning dope, Hydrophobic resin particles are dispersed in the spinning solution, A method for producing modacrylic fibers, wherein the ratio of the number of moles of structural units derived from a monomer containing a hydrophilic functional group to the number of moles of all structural units of a hydrophobic resin constituting the hydrophobic resin particles is 0.5 mol % or less. (2) The method for producing modacrylic fiber according to (1), wherein the ratio of the mass of the hydrophobic resin particles to the mass of the modacrylic fiber product is 5% by mass or more and 20% by mass or less. (3) The method for producing modacrylic fibers according to (1) or (2), wherein the hydrophobic resin microparticles are microparticles made of one or more resins selected from the group consisting of polyacrylonitrile, fluorocarbon polymer, maleic anhydride polymer, and polyvinyl chloride. (4) A method for producing a modacrylic fiber according to any one of (1) to (3), wherein, when the modacrylic fiber product contains an oil, a deoiling treatment is carried out to remove at least a part of the oil from the modacrylic fiber product containing the oil before dissolving the modacrylic fiber in a spinning dope. (5) The method for producing modacrylic fibers according to any one of (1) to (4), wherein the hydrophilic functional group possessed by the hydrophilic functional group-containing monomer is at least one selected from the group consisting of a hydroxy group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a sulfonyl amide group, and a sulfonylimide group. (6) The method for producing modacrylic fibers according to any one of (1) to (5), wherein the ratio V2 / V1 of the viscosity V2 to the viscosity V1 is 0.5 or more and 1 or less. Viscosity V1: After preparing the spinning dope, the spinning dope is left to stand at 25°C for 12 hours or more, and then the temperature of the spinning dope is raised from 25°C to 50°C, and the viscosity of the spinning dope is measured at 50°C. Viscosity V2: Following the measurement of viscosity V1, the spinning dope was heated from 50°C to 80°C, and then cooled from 80°C to 50°C, after which the viscosity of the spinning dope was measured at 50°C. (7) The method for producing modacrylic fibers according to (6), wherein the viscosity V1 is 0.5 Pa·s or more and 10 Pa·s or less. (8) Modacrylic resin and hydrophobic resin particles, A modacrylic fiber in which the ratio of the number of moles of structural units derived from a monomer containing a hydrophilic functional group to the number of moles of all structural units of a hydrophobic resin constituting the hydrophobic resin particles is 0.5 mol % or less. (9) The modacrylic fiber according to (8), wherein the ratio of the mass of the hydrophobic resin particles to the mass of the modacrylic resin is 5% by mass or more and 20% by mass or less. (10) Modacrylic fiber according to (8) or (9), wherein the hydrophobic resin particles are particles made of one or more resins selected from the group consisting of polyacrylonitrile, fluorocarbon polymers, maleic anhydride polymers, and polyvinyl chloride. [Effects of the Invention]

[0008] According to the present invention, there can be provided a method for producing modacrylic fiber products, which involves spinning using a spinning dope obtained by dissolving a modacrylic fiber product in a solvent, and which can produce modacrylic fiber using a spinning dope that exhibits Newtonian fluid properties. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Modacrylic fiber manufacturing method> The manufacturing method of modacrylic fiber is as follows: A method for producing a spinning dope by mixing a modacrylic fiber product made of a modacrylic resin having a structural unit derived from a hydrophilic functional group-containing monomer and hydrophobic resin fine particles with at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone; and performing wet spinning using the spinning dope. In the spinning dope, the modacrylic fiber product is dissolved in the spinning dope, and hydrophobic resin particles are dispersed in the spinning dope. The ratio of the number of moles of structural units derived from a monomer containing a hydrophilic functional group to the number of moles of all structural units of the hydrophobic resin that constitutes the hydrophobic resin particles is 0.5 mol % or less. According to the above-described method for producing modacrylic fibers, excessive thickening of the spinning dope at low temperatures can be suppressed, and when the spinning dope that has thickened at low temperatures is heated, the viscosity of the spinning dope is sufficiently reduced.

[0010] Modacrylic resins containing structural units derived from hydrophilic functional group-containing monomers that constitute modacrylic fiber products are often produced using a spinning dope containing water, and are often immersed in water or washed with water during spinning. Therefore, modacrylic fiber products often contain small amounts of water. When modacrylic fiber products made from modacrylic resins containing structural units derived from hydrophilic functional group-containing monomers contain water, the water hydrates the hydrophilic functional groups and is incorporated into the modacrylic resin as structural water. In this case, a mesh-like network is formed in the modacrylic resin via the water. This network of molecular chains due to the water as structural water is thought to be one of the reasons why the spinning solution exhibits non-Newtonian fluid properties.

[0011] However, when hydrophobic resin microparticles are added to a spinning solution containing a modacrylic resin having structural water, the hydrophobic portions of the modacrylic resin interact with the molecules of the hydrophobic resin, causing the hydrophobic resin microparticles to enter the mesh-like network consisting of the modacrylic resin and structural water, and the ratio of the content of the hydrophilic functional group-containing monomer to the total amount of resin decreases, thereby relaxing the mesh-like network. For the above reasons, it is believed that by adding a modacrylic fiber product made of a modacrylic resin having structural units derived from a hydrophilic functional group-containing monomer and hydrophobic resin microparticles to the spinning dope, the spinning dope is less likely to exhibit non-Newtonian fluid properties. Whether or not the spinning dope exhibits non-Newtonian fluid properties can be confirmed by checking whether or not hysteresis occurs, which is a large difference between the viscosity of the spinning dope when the temperature of the spinning dope is increased and the viscosity of the spinning dope when the temperature of the spinning dope is increased.

[0012] In the specification of the present application, the step of obtaining a spinning dope by mixing the modacrylic fiber product and the hydrophobic resin microparticles with at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone is also referred to as the "spinning dope obtaining step." Wet spinning using the spinning dope is also referred to as the "spinning process."

[0013] Each step included in the above-mentioned method for producing modacrylic fibers will be described below.

[0014] <Spinning dope obtaining process> In the spinning dope obtaining process, a modacrylic fiber product made of a modacrylic resin having structural units derived from a hydrophilic functional group-containing monomer and hydrophobic resin microparticles are mixed with at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone to obtain a spinning dope.

[0015] [Modacrylic fiber products] Modacrylic fiber products are not particularly limited as long as the modacrylic resin constituting the modacrylic fiber has structural units derived from a hydrophilic functional group-containing monomer. Modacrylic fiber products include not only modacrylic fibers produced for sale, but also modacrylic fibers produced for research and testing purposes, and modacrylic fibers produced for personal use by the company or individual that produced the modacrylic fiber.

[0016] Modacrylic textiles may be colored or uncolored. When modacrylic textiles are colored, they typically contain a pigment. The pigment may be an organic pigment or an inorganic pigment. Modacrylic textiles may contain two or more pigments, or may contain a dye in addition to a pigment. Carbon black is preferably used because of its availability. According to the above method, even if the modacrylic fiber product contains a pigment such as carbon black, the modacrylic fiber can be produced by wet spinning satisfactorily while recycling the modacrylic fiber product.

[0017] Modacrylic textile products may contain various additives in addition to the aforementioned oils and pigments, such as gloss regulators (e.g., titanium dioxide, silicon dioxide, and esters and ethers of cellulose derivatives), stabilizers for improving light resistance and heat resistance, dyes, and deodorizing stabilizers (e.g., polyglycidyl methacrylate).

[0018] Modacrylic fiber products are mainly made of modacrylic resin, which will be explained below.

[0019] [Modacrylic resin] For example, a modacrylic copolymer in which the mass ratio of structural units derived from acrylonitrile to the mass of the modacrylic resin is 35% by mass or more but less than 85% by mass and the mass ratio of structural units derived from monomers other than acrylonitrile is more than 15% by mass but not more than 65% by mass can be preferably used as the modacrylic resin. Note that the structural units derived from monomers other than acrylonitrile essentially include structural units derived from monomers containing a hydrophilic functional group.

[0020] As such a modacrylic copolymer, a modacrylic copolymer in which the ratio of the mass of structural units derived from acrylonitrile to the mass of the modacrylic resin is 35% by mass or more and 80% by mass or less, and the ratio of structural units derived from monomers other than acrylonitrile is 20% by mass or more and 65% by mass or less, is more preferred.

[0021] More specifically, a modacrylic copolymer in which the mass ratio of structural units derived from acrylonitrile relative to the mass of the modacrylic resin is 35% by mass or more and 79.5% by mass or less, the mass ratio of structural units derived from vinyl chloride and / or vinylidene chloride is 20% by mass or more and 64.5% by mass or less, and the mass ratio of structural units derived from a hydrophilic functional group-containing monomer is 0.5% by mass or more and 5% by mass or less can be particularly preferably used. In the above modacrylic copolymer, when the content of structural units derived from acrylonitrile is 35% by mass or more and 79.5% by mass or less, the heat resistance of the resulting modacrylic fiber is good. In the modacrylic copolymer, when the content of structural units derived from vinyl chloride and / or vinylidene chloride is 20% by mass or more and 64.5% by mass or less, the flame retardancy of the resulting modacrylic fiber is good. By including 0.5% by mass or more and 5% by mass or less of a hydrophilic functional group-containing monomer in the modacrylic copolymer, the hydrophilicity of the resulting modacrylic fiber is good.

[0022] For the modacrylic resin, it is more preferable that the mass ratio of structural units derived from acrylonitrile is 35% by mass to 74.5% by mass, the mass ratio of structural units derived from vinyl chloride and / or vinylidene chloride is 25% by mass to 64.5% by mass, and the mass ratio of structural units derived from hydrophilic functional group-containing monomers is 0.5% by mass to 5% by mass, relative to the mass of the modacrylic copolymer. In order to obtain modacrylic fibers with excellent touch, it is preferable that the modacrylic copolymer contains structural units derived from vinyl chloride.

[0023] In terms of easily achieving the desired effect, the ratio of constitutional units derived from hydrophilic functional group-containing monomers is preferably from 0.5 to 3% by mass, more preferably from 0.5 to 2.5% by mass.

[0024] The hydrophilic functional group-containing monomer is not particularly limited as long as it is a monomer that can be copolymerized with acrylonitrile and has a hydrophilic functional group. The hydrophilic functional group is not particularly limited as long as it is a functional group capable of forming a hydrogen bond. Specific examples include a hydroxy group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a sulfonyl amide group, and a sulfonylimide group. These groups may form salts. Of the above-described hydrophilic functional group-containing monomers, sulfonic acid group-containing monomers are preferred in terms of preventing voids.

[0025] Examples of the sulfonic acid group-containing monomer that can be used include allylsulfonic acid, methallyl sulfonic acid, styrenesulfonic acid, isoprene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and metal salts thereof such as sodium salts and amine salts thereof. The sulfonic acid group-containing monomer may be used alone or in combination of two or more.

[0026] [Oil removal treatment] Modacrylic textile products often contain an oil, and in this case, it is preferable to subject the modacrylic textile product to a deoiling treatment to remove at least a portion of the oil before dissolving the modacrylic textile product in at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone. Deoiled modacrylic fibers are easily dissolved in the spinning solution at a high concentration.

[0027] Typically, a modacrylic textile product containing an oil agent is brought into contact with a cleaning solution to obtain a modacrylic textile product from which at least a portion of the oil agent has been removed.

[0028] The method for contacting the modacrylic fiber product containing an oil with the cleaning solution is not particularly limited as long as the oil can be removed to the desired extent. Specifically, it is preferable to carry out the deoiling treatment so that the amount of oil adhering to the deoiled modacrylic fiber product is 0.15% omf or less.

[0029] Examples of methods for contacting a modacrylic textile product containing an oil agent with a cleaning solution include immersing the modacrylic textile product containing an oil agent in the cleaning solution and pouring the cleaning solution over the modacrylic textile product containing an oil agent. Methods for pouring the cleaning solution over the modacrylic textile product containing an oil agent include spraying the cleaning solution onto the modacrylic textile product containing an oil agent with a sprayer or showering it with the cleaning solution. A preferred method for contacting a modacrylic textile product containing an oil agent with a cleaning solution is immersing the modacrylic textile product containing an oil agent in the cleaning solution.

[0030] When the modacrylic textile product containing an oil agent is brought into contact with the cleaning solution by immersion, the modacrylic textile product containing an oil agent may be stirred or shaken in the cleaning solution.

[0031] When a modacrylic textile product containing an oil agent is brought into contact with a cleaning solution by immersion, the immersion time is not particularly limited as long as the oil agent can be removed to the desired extent. The immersion time is, for example, preferably 30 minutes or more, more preferably 2 hours or more, even more preferably 4 hours or more, and most preferably 6 hours or more. The upper limit of the immersion time is not particularly limited, but may be, for example, 2 days or less, 1 day or less, or 12 hours or less.

[0032] By contacting a modacrylic fiber product containing an oil agent with a cleaning solution, a deoiled modacrylic fiber product from which at least a portion of the oil agent has been removed can be obtained. Specifically, the deoiled modacrylic fiber product can be obtained by contacting the modacrylic fiber product containing an oil agent with a cleaning solution and then separating the cleaning solution from the modacrylic fiber product. The method for separating the cleaning solution from the modacrylic fiber product is not particularly limited, and examples of the method for separating the cleaning solution from the deoiled modacrylic fiber product include filtration.

[0033] The deoiled modacrylic fiber product thus obtained usually has the cleaning liquid attached thereto, and is subjected to the spinning dope obtaining step with the cleaning liquid attached thereto or with the cleaning liquid removed. The deoiled modacrylic product with the cleaning solution attached thereto may be rinsed with water and / or dried, if desired.

[0034] (oil) The oil agent is not particularly limited as long as it is an oil agent that has conventionally been added to modacrylic fiber products. Furthermore, the oil agent may be a compound that is typically used during the production of modacrylic fibers that constitute modacrylic fiber products for the purposes of preventing static electricity, preventing sticking of modacrylic fibers, and improving texture. Typically, the oil agent adheres to the fiber surface of a modacrylic fiber product. It is believed that the oil agent adhered to the fiber surface particularly inhibits the dissolution of modacrylic fiber products in organic solvents. Therefore, by reducing the content of the oil agent in a deoiled modacrylic fiber product to the above-mentioned specific amount, it is possible to dissolve a highly concentrated deoiled modacrylic fiber product in a solvent.

[0035] Examples of oil agents include anionic surfactants such as phosphate ester salts and sulfate ester salts; cationic surfactants such as quaternary ammonium salts and imidazolium salts; nonionic surfactants such as ethylene oxide and / or propylene oxide adducts of fats and oils and partial esters of polyhydric alcohols; animal and vegetable oils and fats; mineral oils; fatty acid esters; and silicone surfactants such as amino-modified silicones.

[0036] (cleaning solution) The cleaning liquid is not particularly limited as long as it can remove the oil to a desired extent, and organic solvents and alkaline aqueous solutions are preferred as cleaning liquids.

[0037] Preferred examples of the organic solvent include at least one selected from the group consisting of hydrocarbons, alcohols, ketones, and ethers.

[0038] Examples of hydrocarbons include chain aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. Specific examples of hydrocarbons include chain aliphatic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane, and dodecane; alicyclic hydrocarbons such as cyclohexane and cyclopentane; and aromatic hydrocarbons such as benzene, toluene, and xylene.

[0039] Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, 1-butanol, 2-butanol, and 1-pentanol.

[0040] Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, and 2-pentanone.

[0041] Examples of ethers include diethyl ether and diisopropyl ether.

[0042] From the viewpoint of efficiently removing the oil from modacrylic fiber products containing the oil, it is preferable that the organic solvent contained in the cleaning liquid is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, 1-butanol, and 2-butanol.

[0043] The content of the organic solvent contained in the cleaning liquid is appropriately selected depending on the type of organic solvent contained in the cleaning liquid. If the oil is difficult to remove due to a low content of organic solvent in the cleaning solution, the oil can be removed to the desired extent by extending the contact time between the modacrylic textile product and the cleaning solution.

[0044] From the viewpoint of ease of removing the oil agent, the content of the organic solvent in the cleaning liquid is preferably 60% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and most preferably 100% by mass. In order to lower the flash point of the cleaning liquid, the cleaning liquid may contain water in addition to the organic solvent.

[0045] The cleaning liquid is preferably ethanol, since this makes it easy to efficiently remove the oil from the modacrylic fiber product and makes it easy to remove the cleaning liquid that adheres to the deoiled modacrylic fiber product after the oil has been removed.

[0046] The temperature of the cleaning liquid containing an organic solvent is not particularly limited. The temperature of the cleaning liquid containing an organic solvent is appropriately determined taking into consideration the freezing point, boiling point, flash point, etc. of the organic solvent used as the cleaning liquid. The temperature of the cleaning liquid is preferably, for example, 0°C or higher and 98°C or lower. From the viewpoint of enhancing the deoiling effect of removing oil from modacrylic fiber products containing oil, the temperature of the cleaning liquid is more preferably 45°C or higher and 98°C or lower, and even more preferably 55°C or higher and 98°C or lower. When the oil is difficult to remove by using a low-temperature washing solution, the oil can be removed to the desired extent by extending the contact time between the modacrylic textile product and the washing solution.

[0047] The type of alkaline aqueous solution used as a cleaning solution is not particularly limited as long as the aqueous solution exhibits alkalinity. Examples of alkaline compounds that provide alkaline aqueous solutions include alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkaline earth metal bicarbonates, ammonium salts, and amine compounds. Specific examples of alkaline compounds include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; and alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate. From the viewpoint of ease of obtaining the alkaline compound or the alkaline aqueous solution and ease of preparing the alkaline aqueous solution, the alkaline aqueous solution is preferably an aqueous solution containing at least one selected from the group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide, sodium hydrogen carbonate, and calcium hydroxide.

[0048] The pH of the alkaline aqueous solution is preferably 9.0 or higher, more preferably 10.0 or higher. When the pH of the alkaline aqueous solution is 9.0 or higher, the degreasing effect of removing oil from modacrylic fiber products containing oil is high. Note that in the specification and claims of this application, the pH of the alkaline aqueous solution is the value at 25°C. The pH of the alkaline aqueous solution is preferably 14.0 or less, more preferably 13.0 or less. From the viewpoint of efficiently removing the oil from the modacrylic fiber product containing the oil, the pH of the alkaline aqueous solution is preferably 9.0 or more and 14.0 or less, more preferably 10.0 or more and 14.0 or less, and even more preferably 10.0 or more and 13.0 or less. When the oil is difficult to remove by using an alkaline aqueous solution having a low pH value, the oil can be removed to the desired extent by extending the contact time between the modacrylic textile product and the alkaline aqueous solution.

[0049] The temperature of the alkaline aqueous solution used as the cleaning solution is not particularly limited. The temperature of the alkaline aqueous solution is preferably, for example, from 0° C. to 98° C. From the viewpoint of enhancing the deoiling effect of removing oil from modacrylic fiber products containing oil, the temperature of the alkaline aqueous solution is more preferably from 45° C. to 98° C., and even more preferably from 55° C. to 98° C. When the oil is difficult to remove by using a low-temperature alkaline aqueous solution, the oil can be removed to the desired extent by extending the contact time between the modacrylic fiber product and the alkaline aqueous solution.

[0050] (Deoiled modacrylic textile products) The amount of oil attached to the deoiled modacrylic fiber product is preferably 0.15% omf or less. The amount of oil attached to the deoiled modacrylic fiber product is calculated by the following formula (a): Amount of oil attached (% omf) = Mass of oil attached to deoiled modacrylic textile product / Mass of deoiled modacrylic textile product × 100 Formula (a) It can be calculated as follows.

[0051] Specifically, the amount of oil applied can be measured according to the following method. First, a deoiled modacrylic textile product was thoroughly mixed with a 1:1 mixed solvent of cyclohexane and ethanol in a test tube. The mixed solvent in the test tube, containing the oil extracted from the deoiled modacrylic textile product, was then dropped onto a tray. After evaporating the mixed solvent on the tray, the mass of the residue on the tray was measured. The mass of the deoiled modacrylic textile product added to the test tube was taken as the "mass of the deoiled modacrylic textile product" in formula (a), and the mass of the residue was taken as the "mass of oil adhering to the deoiled modacrylic textile product" in formula (a), and the amount of oil adhering was calculated according to formula (a).

[0052] [Hydrophobic resin particles] The spinning dope contains hydrophobic resin microparticles dispersed in addition to the modacrylic fibers dissolved in the spinning dope. The hydrophobic resin constituting the hydrophobic resin microparticles is a resin in which the ratio of the number of moles of structural units derived from a monomer containing a hydrophilic functional group to the number of moles of all structural units is 0.5 mol % or less. The ratio of the number of moles of structural units derived from a monomer containing a hydrophilic functional group to the number of moles of all structural units in the hydrophobic resin is preferably 0.3 mol % or less, more preferably 0.1 mol % or less. Suitable examples of hydrophobic resin particles include particles made of one or more resins selected from the group consisting of polyacrylonitrile, fluorocarbon polymers, and polyvinyl chloride. Among these, polyvinyl chloride is preferred because it is readily available and inexpensive.

[0053] The average particle size of the hydrophobic resin particles is not particularly limited as long as the desired effect is not impaired. The average particle size of the hydrophobic resin particles is, for example, preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. The lower limit of the average particle size of the hydrophobic resin particles may be, for example, 5 μm or more, 10 μm or more, or 20 μm or more. The average particle size of the hydrophobic resin fine particles can be measured as a volume average particle size using a laser diffraction / scattering particle size distribution measuring device. A specific example of the laser diffraction / scattering particle size distribution measuring device is Partica LA-960V2 manufactured by Horiba Ltd.

[0054] Examples of fluorocarbon polymers include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene / hexafluoropropylene copolymer, vinylidene fluoride / tetrafluoroethylene copolymer, and vinylidene fluoride / hexafluoropropylene copolymer.

[0055] The amount of hydrophobic resin particles used is not particularly limited as long as the desired effect is not impaired. The amount of hydrophobic resin particles used is preferably 5% by mass or more and 20% by mass or less, more preferably 7% by mass or more and 19% by mass or less, and even more preferably 10% by mass or more and 18% by mass or less, based on 100 parts by mass of the modacrylic fiber product. [Preparation of spinning dope] In the spinning dope obtaining step, a modacrylic fiber product and hydrophobic resin particles are mixed with at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone to obtain a spinning dope. The modacrylic fiber product is dissolved in the spinning dope. The hydrophobic resin particles are dispersed in the spinning dope. Note that a portion of the hydrophobic resin particles may be dissolved in the spinning dope to the extent that the desired effect is not impaired. The use of the above solvents allows the modacrylic fiber product to be dissolved well, and also allows for good spinning in the spinning step described below. Among the above solvents, dimethyl sulfoxide is preferred from the viewpoint of safety.

[0056] The electrical conductivity of the spinning dope is not particularly limited as long as the desired effect is not impaired. From the viewpoint of performing wet spinning well, the electrical conductivity of the spinning dope is, for example, preferably 350 μS / cm or less, more preferably 300 μS / cm or less. The lower limit of the electrical conductivity is not particularly limited. The lower limit of the electrical conductivity may be, for example, 50 μS / cm or more, or 100 μS / cm or more. The electrical conductivity of the spinning dope is measured using a portable conductivity meter (Hanchen DDB-303A). Specifically, the terminals of the portable conductivity meter are inserted into the spinning dope, and the electrical conductivity value corrected to the electrical conductivity measured at 25°C is obtained using the temperature correction function of the portable conductivity meter. This corrected electrical conductivity value is used as the electrical conductivity value of the spinning dope.

[0057] The sum of the concentration of the modacrylic resin and the concentration of the hydrophobic resin microparticles in the spinning dope is not particularly limited as long as the desired effect is not impaired. Hereinafter, the sum of the concentration of the modacrylic resin and the concentration of the hydrophobic resin microparticles will also be referred to as the "resin concentration." From the viewpoint of performing good spinning in the spinning step described below, the resin concentration in the spinning dope is preferably 5% by mass or more and 35% by mass or less, more preferably 10% by mass or more and 35% by mass or less, and even more preferably 20% by mass or more and 35% by mass or less, relative to the mass of the spinning dope.

[0058] The spinning dope may contain a modacrylic resin not derived from a modacrylic fiber product. The modacrylic resin not derived from a modacrylic fiber product is usually a virgin material. For example, the concentration of modacrylic resin in the spinning dope can be adjusted by dissolving virgin modacrylic resin in the spinning dope containing the modacrylic fiber product in a dissolved state. When the spinning dope contains a modacrylic resin derived from a modacrylic fiber product and a modacrylic resin not derived from a modacrylic fiber product, the ratio of the mass of the modacrylic resin derived from a modacrylic fiber product to the total mass of the modacrylic resins may be 1 mass% or more, 5 mass% or more, 10 mass% or more, 20 mass% or more, 50 mass% or more, 80 mass% or more, or 90 mass% or more.

[0059] When mixing the modacrylic fiber product and the hydrophobic resin particles with at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone, heating may be performed as necessary. The heating temperature is not particularly limited as long as it does not cause thermal degradation of the modacrylic resin, the hydrophobic resin particles, and the solvent.

[0060] The spinning dope may contain water. The water content of the spinning dope is not particularly limited as long as the desired effect is not impaired. From the viewpoint of the solubility of the modacrylic fiber product in the spinning dope, the water content of the spinning dope is preferably 0.5% by mass or more and 12.0% by mass or less, more preferably 1.0% by mass or more and 9.0% by mass or less, and even more preferably 1.5% by mass or more and 7.0% by mass or less.

[0061] The spinning dope may contain a pigment. Various well-known pigments can be used as the pigment, if necessary. The pigment may be an organic pigment or an inorganic pigment. The spinning dope may contain two or more pigments, or may contain a dye in addition to a pigment.

[0062] The pigment to be added to the spinning dope may be a solid powder pigment or a pigment dispersion containing a pigment dispersed in a dispersion medium. In terms of the dispersibility of the pigment in the spinning dope and the modacrylic fiber, it is preferable to prepare the spinning dope using a pigment dispersion.

[0063] As the pigment, carbon black is preferred because it can color modacrylic fibers to a desired black hue and is easily available.

[0064] In order to color the modacrylic fiber to the desired degree while suppressing the occurrence of yarn breakage during the spinning process, the content of the pigment in the spinning dope is preferably 0.01 parts by mass or more and 2.00 parts by mass or less, and more preferably 0.02 parts by mass or more and 0.60 parts by mass or less, relative to 100 parts by mass of the spinning dope.

[0065] The spinning dope may contain other additives to improve fiber properties, as needed, within the range that does not impair the desired effects. Examples of such additives include gloss adjusters such as titanium dioxide, silicon dioxide, and esters and ethers of cellulose derivatives, including cellulose acetate; stabilizers for improving light resistance and heat resistance; and the like.

[0066] The spinning dope is then subjected to a spinning process.

[0067] <Spinning process> In the spinning step, wet spinning is carried out using a spinning dope. Wet spinning methods include: extruding the spinning dope through a nozzle into a coagulation bath to coagulate it; and coagulating the spinning dope to produce fibers, which are then drawn in a drawing bath.

[0068] Hereinafter, the process of extruding the spinning dope through a nozzle into a coagulation bath to coagulate it is also referred to as a “coagulation step.” The process of drawing the fiber produced by coagulating the spinning dope in a drawing bath is also referred to as a “drawing step.”

[0069] (solidification process) In the coagulation step, the spinning dope is extruded into a coagulation bath from a nozzle in the form of fibers, and the extruded spinning dope is coagulated. The spinning dope is discharged into the coagulation bath from a nozzle having a size and shape corresponding to the fiber diameter and cross-sectional shape of the modacrylic fiber.

[0070] In the coagulation step, the spinning dope is first extruded through a spinning nozzle into a coagulation bath. The extruded fibrous coagulation solution is coagulated in the coagulation bath to form fibers. As the coagulation bath, a mixture of water and an organic solvent is preferably used, from the viewpoint of easy control of the coagulation state. For example, the liquid to be charged into the coagulation bath is preferably an aqueous solution of an organic solvent, the concentration of which is preferably 20% by mass or more and 75% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 70% by mass or less.

[0071] The organic solvent contained in the liquid charged into the coagulation bath is not particularly limited as long as it is a good solvent for the modacrylic resin. From the viewpoint of productivity of modacrylic fiber, one or more organic solvents selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfone, ε-caprolactam, ethylene carbonate, and sulfolane are preferred. From the viewpoint of safety, dimethyl sulfoxide is more preferred. From the viewpoints of quality of modacrylic fiber and ease of process control, it is preferable that the organic solvent in the spinning dope and the organic solvent in the liquid charged into the coagulation bath are the same organic solvent.

[0072] The temperature of the spinning dope extruded into the coagulation bath is preferably 35°C or lower. The temperature of the liquid charged into the coagulation bath is preferably 10°C or higher and 30°C or lower, and more preferably 10°C or higher and 25°C or lower.

[0073] (Stretching process) The fiber produced by coagulating the spinning dope in a coagulation bath is then drawn in a drawing bath. The method for transferring the drawn fiber from the coagulation bath to the drawing bath is not particularly limited. Typically, the drawn fiber is stretched between a roll in the coagulation bath and one or more fiber-transfer rolls outside the coagulation bath, and the drawn fiber is transferred into the drawing bath by rotating the rolls.

[0074] The fibers transported to the drawing bath are stretched between a first stretching roll provided upstream in the direction of fiber movement and a second stretching roll provided downstream in the direction of fiber movement in the liquid contained in the drawing bath, and are stretched by rotation. The stretch ratio is adjusted by adjusting the tension applied to the fiber being stretched by the first stretching roll and the second stretching roll and the rotation speed of the first stretching roll and the second stretching roll. The stretch ratio is preferably more than 100% and not more than 800%, and more preferably 120% to 300%. The stretched modacrylic fibers are stretched between rolls such as clover rolls provided outside the drawing bath and are appropriately recovered from the drawing bath.

[0075] The bath liquid to be filled in the stretching bath is not particularly limited as long as it can perform good stretching. For example, water or an aqueous solution containing an organic solvent can be used. The bath liquid in the stretching bath is preferably an aqueous solution of an organic solvent containing 10% by mass to 90% by mass of water based on the mass of the bath liquid. The temperature in the stretching bath is preferably in the range of 30°C to 110°C, more preferably in the range of 40°C to 95°C.

[0076] Stretching in the stretching bath is preferably carried out in multiple steps. Furthermore, it is preferable that the average stretching speeds are different for at least two of the multiple stretching steps. By carrying out stretching in the stretching bath in multiple steps, it is easy to control the stretching conditions for each stage, such as the initial, middle, and final stages, of the stretching process. Here, "stretching is performed in multiple steps" means that stretching and the release of the tension for stretching are repeated any number of times, two or more times. The multiple stretching steps may be performed in the same stretching bath or in multiple different stretching baths, preferably using multiple different stretching baths, since the temperature of the stretching bath and the composition of the liquid charged in the stretching bath can be changed for each stretching bath.

[0077] (Water washing process) The drawn modacrylic fiber is usually washed in a water-washing step. In the water-washing step, the drawn modacrylic fiber in the drawing bath is washed with water to remove the organic solvent from the modacrylic fiber. In the water-washing step, warm water at 25°C or higher or an aqueous solution of an organic solvent with a lower organic solvent concentration than that of the coagulation bath is preferably used as the washing liquid. The water-washing can be carried out by immersing the drawn modacrylic fiber in a bath containing such a washing liquid or by spraying water onto the moving modacrylic fiber. The means for spraying water in the water-washing step is not particularly limited, but from the viewpoint of ease of spraying, water is preferably sprayed using a nozzle. The direction in which water is sprayed is not particularly limited, and water may be sprayed from the side or below. From the viewpoint of uniform spraying of water, it is preferable to use a shower nozzle with multiple holes. The temperature of the water used for spraying water is not particularly limited. For example, water in the temperature range of 20 to 95°C can be used. From the viewpoint of enhancing the desolvation effect of removing the organic solvent, the water temperature is preferably 40°C or higher, more preferably 50°C or higher.

[0078] Although not particularly limited, from the viewpoint of enhancing the effect of removing the organic solvent in the water washing step, the ratio of the total fineness to the width of the modacrylic fiber bundle is preferably 300,000 dtex / cm or less, more preferably 200,000 dtex / cm or less, and even more preferably 100,000 dtex / cm or less.

[0079] (Dehydration process) When the stretched modacrylic fiber is washed with water, the washed modacrylic fiber is dewatered in a dewatering step in which the washed modacrylic fiber is sandwiched between nip rolls and passed through the nip rolls to be dewatered.

[0080] The "nip roll" is not particularly limited as long as it is one that is normally used when producing fibers by a wet spinning method. Examples of nip rolls that can be used include rubber nip rolls and metal nip rolls. A rubber nip roll (also referred to as a rubber roll) is preferably used as the upper nip roll, and a metal nip roll (also referred to as a metal roll) is preferably used as the lower nip roll.

[0081] The above-mentioned water washing step and dewatering step may be performed alternately once and multiple times. After the above-mentioned water washing step is performed two or more times, pressing with nip rolls may be performed one or more times.

[0082] (drying process) The modacrylic fiber stretched in the stretching bath or the modacrylic fiber dehydrated as described above is then dried in a drying step. In the drying step, it is preferable that the moisture contained in the modacrylic fiber is almost completely removed. The drying method is not particularly limited as long as it can remove moisture from the modacrylic fiber. Examples of the drying method include hot air drying and drying by contact with a heated roll. The drying temperature is not particularly limited, but is preferably 110°C or higher and 190°C or lower, and more preferably 110°C or higher and 170°C or lower.

[0083] The fineness of the modacrylic fiber obtained as described above is determined appropriately depending on the application of the modacrylic fiber.

[0084] Before drying the modacrylic fibers, an oil may be applied to the modacrylic fibers, as described above.

[0085] The modacrylic fiber obtained by the above-mentioned method may be further stretched as required. The stretching method is not particularly limited, and may be a dry method or a wet method.

[0086] The dried modacrylic fiber obtained by the above method is preferably further relaxed in a heat-relaxing step. The relaxation rate is not particularly limited, but is preferably 5% or more, more preferably 10% or more. The heat-relaxing treatment can be carried out at a high temperature, for example, in a dry heat atmosphere or a superheated steam atmosphere at 130°C to 200°C, preferably 140°C to 190°C. Alternatively, the heat-relaxing treatment can be carried out in a pressurized steam or heated pressurized steam atmosphere at 120°C to 180°C and a pressure of 0.05 MPa to 0.4 MPa, preferably 0.1 MPa to 0.4 MPa.

[0087] As described above, according to the above-described manufacturing method, modacrylic fibers can be manufactured using a spinning dope that exhibits Newtonian fluid properties. Whether or not the spinning dope exhibits non-Newtonian fluid properties can be confirmed by checking whether or not hysteresis occurs, which is a large difference between the viscosity of the spinning dope when the temperature of the spinning dope is increased and the viscosity of the spinning dope when the temperature of the spinning dope is increased. Specifically, the ratio V2 / V1 of the viscosity V2 to the viscosity V1 below is preferably 0.5 or more and 1 or less. Viscosity V1: After preparing the spinning dope, the spinning dope is left to stand at 25°C for 12 hours or more, and then the temperature of the spinning dope is increased from 25°C to 50°C, and the viscosity of the spinning dope is measured at 50°C. Viscosity V2: Following the measurement of viscosity V1, the spinning solution was heated from 50°C to 80°C, and then cooled from 80°C to 50°C, after which the viscosity of the spinning solution was measured at 50°C.

[0088] From the viewpoint of operability during spinning, the viscosity V1 is preferably 0.5 Pa·s or more and 10 Pa·s or less.

[0089] <Modacrylic fiber> The modacrylic fiber produced by the above method contains hydrophobic resin particles dispersed in the modacrylic resin. The hydrophobic resin particles are as described above. The content of the hydrophobic resin particles in the modacrylic fiber is not particularly limited as long as the desired effect is not impaired. The content of the hydrophobic resin particles is preferably 5% by mass or more and 20% by mass or less, more preferably 7% by mass or more and 19% by mass or less, and even more preferably 10% by mass or more and 18% by mass or less, based on 100 parts by mass of the modacrylic resin. [Example]

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0091] Example 1 (Spinning dope obtaining process) The modacrylic fiber product used was AFRELLE (manufactured by Kaneka Corporation). The modacrylic resin constituting the modacrylic fiber product (AFRELLE) contains 2% by mass of structural units derived from sodium styrene sulfonate.

[0092] 150 g of modacrylic fiber product, 20.2 g of dimethyl sulfoxide, and 5.4 g of pure water were placed in a 5 L dissolver. Next, 20.55 g of polyvinyl chloride powder (Kanevinyl, M Series 1008 (Kaneka Corporation)) was placed in the dissolver. The average particle size of the polyvinyl chloride powder measured using the above-mentioned method was 70 μm. The internal temperature of the dissolver was maintained at 60°C for 30 minutes, and the modacrylic fiber product and polyvinyl chloride powder were dissolved and dispersed in dimethyl sulfoxide containing a small amount of water. The mixture in the dissolver was then stirred at 170 rpm for 30 minutes. Next, the mixture in the dissolver was stirred at 330 rpm for 30 minutes. After stirring, the mixture in the dissolver was filtered through a mesh filter with 2 mm openings. The filtered mixture was then further filtered through a filter cloth with 120 μm openings to obtain a spinning dope. The solid content of the obtained spinning dope was 25% by mass, and the moisture content of the obtained spinning dope was 3% by mass. The viscosity V1 of the obtained spinning solution during heating and the viscosity V2 of the solution during cooling were measured according to the method described above. A viscoelasticity measuring device (HAAKE MARS rheometer) was used to measure the viscosity. The results were that V1 was 7.2 Pa s, V2 was 4.5 Pa s, and V2 / V1 was 0.63.

[0093] (Spinning process) The spinning solution at 35°C is poured into a nozzle with an opening area of ​​0.085 mm 2 The fiber was fed to a nozzle having 10 nozzle holes, and extruded at a nozzle discharge speed of 10 m / min into a coagulation bath filled with a 47% by mass aqueous solution of dimethyl sulfoxide at 25°C, and spun at a draft ratio of 1.25. After washing with water in an 80°C water bath, the fiber was immersed in an oil solution (a mixture of 65% by mass of castor oil ether and 35% by mass of sorbitan stearate). After drying, the fiber was stretched at 125°C at a draw ratio of 230% and then relaxed at 155°C to obtain a modacrylic fiber.

[0094] Comparative Example 1 A spinning dope was obtained in the same manner as in Example 1, except that 170.55 g of a modacrylic fiber product was used instead of using polyvinyl chloride powder. The solid content of the obtained spinning dope was 25% by mass. The moisture content of the obtained spinning dope was 3% by mass. The viscosity V1 of the obtained spinning solution during heating and the viscosity V2 of the solution during cooling were measured according to the method described above. The results were that V1 was 32 Pa s, V2 was 13 Pa s, and V2 / V1 was 0.41. Using the obtained spinning dope, spinning was carried out in the same manner as in Example 1, but thread breakage occurred and could not be prevented.

[0095] Comparative Example 2 A spinning dope was obtained in the same manner as in Example 1, except that the polyvinyl chloride powder was replaced with the same modacrylic resin as that used in the modacrylic fiber product. The solid content of the obtained spinning dope was 25% by mass. The moisture content of the obtained spinning dope was 3% by mass. The viscosity V1 of the obtained spinning solution during heating and the viscosity V2 of the solution during cooling were measured according to the method described above. The results were that V1 was 23 Pa s, V2 was 10 Pa s, and V2 / V1 was 0.43. Using the obtained spinning dope, spinning was carried out in the same manner as in Example 1, but thread breakage occurred and could not be prevented.

[0096] Comparative Example 3 A spinning dope was obtained in the same manner as in Example 1, except that the polyvinyl chloride powder was changed to sodium polystyrene sulfonate. The solid content of the obtained spinning dope was 25% by mass. The moisture content of the obtained spinning dope was 3% by mass. The viscosity V1 of the obtained spinning solution during heating and the viscosity V2 of the solution during cooling were measured according to the method described above. The results were that V1 was 16 Pa s, V2 was 7 Pa s, and V2 / V1 was 0.44. Using the obtained spinning dope, spinning was carried out in the same manner as in Example 1, but thread breakage occurred and could not be prevented.

Claims

1. A method for producing a spinning dope by mixing a modacrylic fiber product made of a modacrylic resin having a structural unit derived from a hydrophilic functional group-containing monomer and hydrophobic resin fine particles with at least one solvent selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone; and performing wet spinning using the spinning dope, The modacrylic fiber product is dissolved in the spinning dope, the hydrophobic resin fine particles are dispersed in the spinning dope, A method for producing modacrylic fibers, wherein the ratio of the number of moles of structural units derived from a hydrophilic functional group-containing monomer to the number of moles of all structural units of the hydrophobic resin constituting the hydrophobic resin particles is 0.5 mol % or less.

2. 2. The method for producing modacrylic fibers according to claim 1, wherein the ratio of the mass of the hydrophobic resin particles to the mass of the modacrylic fiber product is 5% by mass or more and 20% by mass or less.

3. 3. The method for producing modacrylic fibers according to claim 1, wherein the hydrophobic resin fine particles are fine particles made of one or more resins selected from the group consisting of polyacrylonitrile, fluorocarbon polymers, maleic anhydride polymers, and polyvinyl chloride.

4. 3. The method for producing modacrylic fibers according to claim 1, wherein, when the modacrylic fiber product contains an oil, a deoiling treatment is carried out to remove at least a part of the oil from the modacrylic fiber product containing the oil before dissolving the modacrylic fiber in the spinning dope.

5. 3. The method for producing modacrylic fibers according to claim 1, wherein the hydrophilic functional group possessed by the hydrophilic functional group-containing monomer is at least one selected from the group consisting of a hydroxy group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a sulfonyl amide group, and a sulfonylimide group.

6. 3. The method for producing modacrylic fibers according to claim 1, wherein the ratio V2 / V1 of the viscosity V2 to the viscosity V1 is 0.5 or more and 1 or less. Viscosity V1: After preparing the spinning dope, the spinning dope was allowed to stand at 25°C for 12 hours or more, and then the temperature of the spinning dope was increased from 25°C to 50°C, and the viscosity of the spinning dope was measured at 50°C. Viscosity V2: Following the measurement of viscosity V1, the temperature of the spinning dope was increased from 50°C to 80°C, and then the spinning dope was cooled from 80°C to 50°C, and the viscosity of the spinning dope was measured at 50°C.

7. 7. The method for producing modacrylic fibers according to claim 6, wherein the viscosity V1 is 0.5 Pa·s or more and 10 Pa·s or less.

8. It contains a modacrylic resin and hydrophobic resin particles, A modacrylic fiber in which the ratio of the number of moles of structural units derived from a hydrophilic functional group-containing monomer to the number of moles of all structural units of the hydrophobic resin constituting the hydrophobic resin particles is 0.5 mol % or less.

9. 9. The modacrylic fiber according to claim 8, wherein the ratio of the mass of the hydrophobic resin fine particles to the mass of the modacrylic resin is 5% by mass or more and 20% by mass or less.

10. 10. The modacrylic fiber according to claim 8 or claim 9, wherein the hydrophobic resin microparticles are microparticles made of one or more resins selected from the group consisting of polyacrylonitrile, fluorocarbon polymers, maleic anhydride polymers, and polyvinyl chloride.