Modacrylic fiber production method

Abstract

To provide a modacrylic fiber production method that enables recycling of modacrylic fiber products while dissolving the modacrylic fiber products in a spinning dope at a high concentration and performing wet spinning with the resulting spinning dope.SOLUTION: A modacrylic fiber is produced by a method comprising: contacting a modacrylic fiber product containing an oil-based agent with an organic solvent as a cleaning liquid to provide a deoiled fiber having the content of the oil-based agent reduced to a specified level or less; dissolving the deoiled fiber in a specific solvent to provide a spinning dope; and performing wet spinning with the spinning dope.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing modacrylic fibers.

Background Art

[0002] Modacrylic fibers, known as acrylic fibers, are used in various applications such as clothing, construction, and industrial materials because of their unique texture, excellent color development, and dyeing fastness. Regarding modacrylic fibers, which are petroleum products, there is a strong demand for their recycling in terms of the sustainability of human activities. As a method for recycling acrylic fibers, a method has been proposed in which crushed acrylic fibers are dissolved in a solvent, and then wet spinning is performed using the resulting solution of acrylic resin (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when dissolving a modacrylic fiber product containing an oil agent in a solvent, since the modacrylic fiber product is difficult to dissolve in the solvent, it is often impossible to prepare a dope (spinning stock solution) containing a modacrylic resin at a sufficiently high concentration.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing modacrylic fibers that recycles modacrylic fiber products by dissolving a modacrylic fiber product in a solvent at a high concentration to prepare a spinning stock solution and performing wet spinning using the resulting spinning stock solution.

Means for Solving the Problems

[0006] The inventors of the present invention have found that the above problems can be solved by a method for producing modacrylic fibers, which includes bringing a modacrylic fiber product containing an oil agent into contact with an organic solvent as a cleaning liquid to obtain degreased fibers with the oil agent content reduced to a specific amount or less, dissolving the degreased fibers in a specific solvent to obtain a spinning dope, and performing wet spinning using the spinning dope, and thus completed the present invention.

[0007] More specifically, the present invention provides the following (1) to (7). (1) Obtaining degreased fibers in which at least a part of the oil agent is removed by bringing a modacrylic fiber product containing an oil agent into contact with a cleaning liquid; Dissolving the degreased fibers in at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone to obtain a spinning dope; Performing wet spinning using the spinning dope, and the cleaning liquid contains an organic solvent, in the degreased fibers, the following formula (a): Oil agent adhesion amount (%omf) in degreased fibers = mass of oil agent adhering to degreased fibers / mass of degreased fibers × 100 Formula (a) A method for producing modacrylic fibers, wherein the oil agent adhesion amount calculated by the formula is 0.15%omf or less. (2) The method for producing modacrylic fibers according to (1), wherein the organic solvent is at least one selected from the group consisting of hydrocarbons, alcohols, ketones, and ethers. (3) The method for producing modacrylic fibers according to (1) or (2), wherein the organic solvent is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, 1-butanol, and 2-butanol. (4) The method for producing modacrylic fibers according to any one of (1) to (3), wherein the temperature of the cleaning liquid is 45°C or higher and 98°C or lower. (5) The method for producing modacrylic fibers according to any one of (1) to (4), which includes filtering the spinning dope before performing wet spinning. The method for producing a modacrylic fiber according to any one of (1) to (5), wherein the concentration of the defatted fiber in the spinning dope is 5% by mass or more and 35% by mass or less. The method for producing a modacrylic fiber according to any one of (1) to (6), wherein the electric conductivity of the spinning dope is 350 μS / cm or less.

Advantages of the Invention

[0008] According to the present invention, there is provided a method for producing a modacrylic fiber that recycles a modacrylic fiber product by dissolving the modacrylic fiber product at a high concentration in a solvent to prepare a spinning dope and performing wet spinning using the obtained spinning dope.

Embodiments for Carrying Out the Invention

[0009] ≪Method for Producing Modacrylic Fiber≫ The method for producing a modacrylic fiber comprises: obtaining a defatted fiber in which at least a part of an oil agent is removed by bringing a modacrylic fiber product containing the oil agent into contact with a cleaning liquid; dissolving the defatted fiber in at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone to obtain a spinning dope; performing wet spinning using the spinning dope. The cleaning liquid contains an organic solvent. In the defatted fiber, the following formula (a): Oil agent adhesion amount (%omf) in defatted fiber = mass of oil agent adhering to defatted fiber / mass of defatted fiber × 100 Formula (a) The oil agent adhesion amount calculated by the formula is 0.15%omf or less. According to the above method for producing a modacrylic fiber, the solubility of a modacrylic fiber product containing an oil agent in an organic solvent is increased, and insoluble components derived from the modacrylic fiber product are removed, so that wet spinning can be performed favorably.

[0010] In the specification of this application, the process of obtaining degreased fibers in which at least a part of the oil agent is removed by bringing a modacrylic fiber product containing an oil agent into contact with a cleaning liquid is also referred to as the "degreasing process". The process of dissolving the degreased fibers in at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone to obtain a spinning dope is also referred to as the "spinning dope preparation process". The process of performing wet spinning using the spinning dope is also referred to as the "spinning process".

[0011] Hereinafter, each process included in the above method for producing modacrylic fibers will be described.

[0012] <Degreasing process> In the degreasing process, degreased fibers in which at least a part of the oil agent is removed are obtained by bringing a modacrylic fiber product containing an oil agent into contact with a cleaning liquid containing an organic solvent. The method of bringing the modacrylic fiber product containing an oil agent into contact with the cleaning liquid is not particularly limited as long as degreased fibers with an oil agent adhesion amount of 0.15% omf or less in the degreased fibers can be obtained. Examples of the method of bringing the modacrylic fiber product containing an oil agent into contact with the cleaning liquid include, for example, a method of immersing the modacrylic fiber product containing an oil agent in the cleaning liquid, and a method of pouring the cleaning liquid over the modacrylic fiber product containing an oil agent. Examples of the method of pouring the cleaning liquid over the modacrylic fiber product containing an oil agent include a method of spraying the cleaning liquid onto the modacrylic fiber product containing an oil agent with a spray, and a method of spraying it with a shower. As the method of bringing the modacrylic fiber product containing an oil agent into contact with the cleaning liquid, a method of immersing the modacrylic fiber product containing an oil agent in the cleaning liquid is preferable.

[0013] When the modacrylic fiber product containing an oil agent is brought into contact with the cleaning liquid by immersion, the modacrylic fiber product containing an oil agent may be stirred or shaken in the cleaning liquid.

[0014] When a modacrylic fiber product containing an oil agent and a cleaning liquid are brought into contact by immersion, the immersion time is not particularly limited as long as a degreased fiber having an oil agent adhesion amount of 0.15% omf or less can be obtained. As the immersion time, for example, 30 minutes or more is preferable, 2 hours or more is more preferable, 4 hours or more is further preferable, and 6 hours or more is most preferable. The upper limit of the immersion time is not particularly limited, but it may be, for example, 2 days or less, 1 day or less, or 12 hours or less.

[0015] By bringing a modacrylic fiber product containing an oil agent and a cleaning liquid into contact, at least a part of the oil agent contained in the modacrylic fiber product is removed from the modacrylic fiber product. When at least a part of the oil agent is removed from the modacrylic fiber product so that the content of the oil agent in the degreased fiber is the above-specified amount, a degreased fiber that dissolves in an organic solvent at a high concentration can be obtained.

[0016] Hereinafter, a method for obtaining a degreased fiber will be described.

[0017] (Oil agent) The oil agent is not particularly limited as long as it is an oil agent that has been conventionally added to modacrylic fiber products. Also, the oil agent may be a compound that is usually used for the purpose of antistatic, preventing adhesion of modacrylic fibers, or improving the texture during the production of modacrylic fibers that constitute the modacrylic fiber product. Typically, the oil agent adheres to the fiber surface in the modacrylic fiber product. It is considered that the oil agent adhering to the fiber surface particularly inhibits the dissolution of the modacrylic fiber product in an organic solvent. Therefore, by reducing the content of the oil agent in the degreased fiber to the above-specified amount, the degreased fiber can be dissolved in the solvent at a high concentration.

[0018] Examples of the oil agent include anionic surfactants such as phosphate esters and sulfate esters; 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 fats and oils; mineral oils; fatty acid esters; silicone surfactants such as amino-modified silicone, and the like.

[0019] (Modacrylic fiber products) Modacrylic fiber products are not particularly limited. Modacrylic fiber products include not only modacrylic fibers manufactured for sales purposes, but also modacrylic fibers manufactured for test and research purposes, and modacrylic fibers manufactured for the purpose of being used by companies and individuals that produce modacrylic fibers.

[0020] Modacrylic fiber products may be either colored fibers or uncolored fibers. When modacrylic fiber products are colored, typically, modacrylic fiber products contain pigments. The pigments may be either organic pigments or inorganic pigments. Modacrylic fiber products may contain two or more pigments, or may contain dyes together with pigments. Carbon black is preferably used because it is easily available. According to the above method, even if modacrylic fiber products contain pigments such as carbon black, wet spinning can be favorably performed while recycling the modacrylic fiber products to produce modacrylic fibers.

[0021] In addition to the above-described oil agents and pigments, modacrylic fiber products may contain various additives. Examples of the various additives contained in modacrylic fiber products include brightening agents such as titanium dioxide, silicon dioxide, and esters and ethers of cellulose derivatives; stabilizers for improving light resistance and heat resistance; dyes; anti-odor stabilizers such as polyglycidyl methacrylate, and the like.

[0022] Modacrylic fiber products mainly consist of modacrylic resins. Hereinafter, the modacrylic resins will be described.

[0023] (Modacrylic resin) For example, a modacrylic copolymer in which the ratio of the mass of the structural unit derived from acrylonitrile to the mass of the modacrylic resin is 35% by mass or more and less than 85% by mass, and the ratio of the structural unit derived from other monomers other than acrylonitrile is more than 15% by mass and 65% by mass or less can be preferably used as the modacrylic resin. As such a modacrylic copolymer, a modacrylic copolymer in which the ratio of the mass of the structural unit 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 the structural unit derived from other monomers other than acrylonitrile is 20% by mass or more and 65% by mass or less is more preferable.

[0024] More specifically, a modacrylic copolymer in which the ratio of the mass of the structural unit derived from acrylonitrile to the mass of the modacrylic resin is 35% by mass or more and 79.5% by mass or less, the ratio of the mass of the structural unit derived from vinyl chloride and / or vinylidene chloride is 20% by mass or more and 64.5% by mass or less, and the ratio of the mass of the structural unit derived from a sulfonic acid group-containing vinyl 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 the structural unit 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 the structural unit 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 the sulfonic acid group-containing vinyl monomer in the modacrylic copolymer, the hydrophilicity of the resulting modacrylic fiber is good.

[0025] Regarding the modacrylic resin, the ratio of the mass of the structural unit derived from acrylonitrile to the mass of the modacrylic copolymer is 35% by mass or more and 74.5% by mass or less, and the ratio of the mass of the structural unit derived from vinyl chloride and / or vinylidene chloride is 25% by mass or more and 64.5% by mass or less. It is more preferable that the ratio of the structural unit derived from the sulfonic acid group-containing vinyl monomer is 0.5% by mass or more and 5% by mass or less. In terms of obtaining modacrylic fibers with excellent touch, it is preferable that the modacrylic copolymer contains a structural unit derived from vinyl chloride.

[0026] Examples of the sulfonic acid group-containing vinyl monomer include allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, isoprene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and metal salts and amine salts such as sodium salts thereof. The sulfonic acid group-containing vinyl monomer may be used alone or in combination of two or more.

[0027] (Cleaning liquid) The cleaning liquid contains an organic solvent. The cleaning liquid is not particularly limited as long as degreased fibers with an oil agent adhesion amount of 0.15% omf or less can be obtained. Examples of preferable organic solvents include at least one selected from the group consisting of hydrocarbons, alcohols, ketones, and ethers.

[0028] Examples of the hydrocarbon include chain aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. Specific examples of the hydrocarbon 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.

[0029] Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, 1-butanol, 2-butanol, and 1-pentanol.

[0030] Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, 2-pentanone, and the like.

[0031] Examples of the ether include diethyl ether, diisopropyl ether, and the like.

[0032] From the viewpoint of efficiently removing the oil agent from the modacrylic fiber product containing the oil agent, 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.

[0033] The content of the organic solvent contained in the cleaning liquid is appropriately selected according to the type of the organic solvent contained in the cleaning liquid. When it is difficult to remove the oil agent due to the low content of the organic solvent contained in the cleaning liquid, the oil agent can be removed to a desired degree by extending the contact time between the modacrylic fiber product and the cleaning liquid.

[0034] From the viewpoint of ease of removing the oil agent, the content of the organic solvent contained 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, still more preferably 90% by mass or more and 100% by mass or less, and most preferably 100% by mass. Also, from the viewpoint of the low flash point of the cleaning liquid, the cleaning liquid may contain water together with the organic solvent.

[0035] It is preferable that the cleaning liquid is ethanol in terms of efficiently and easily removing the oil agent from the modacrylic fiber product and easily removing the cleaning liquid adhering to the degreased fiber after removing the oil agent.

[0036] The temperature of the cleaning liquid is not particularly limited. The temperature of the cleaning liquid is appropriately determined in consideration of the freezing point, boiling point, flash point, etc. of the organic solvent used as the cleaning liquid. As the temperature of the cleaning liquid, for example, 0°C or higher and 98°C or lower is preferable. From the viewpoint of enhancing the degreasing effect of removing the oil agent from the modacrylic fiber product containing the oil agent, 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 it is difficult to remove the oil agent by using a low-temperature cleaning liquid, the oil agent can be removed to a desired degree by extending the contact time between the modacrylic fiber product and the cleaning liquid.

[0037] (Degreased fiber) The degreased fiber is a fiber obtained by removing at least a part of the oil agent from a modacrylic fiber product containing the oil agent. The amount of the oil agent adhered to the degreased fiber is 0.15% omf or less. The amount of the oil agent adhered to the degreased fiber is calculated by the following formula (a): Amount of the oil agent adhered to the degreased fiber (% omf) = mass of the oil agent adhered to the degreased fiber / mass of the degreased fiber × 100 Formula (a) It can be calculated by. Specific measurement methods for the amount of the oil agent adhered to the degreased fiber will be described in detail in the examples.

[0038] Hereinafter, a method for obtaining a degreased fiber from which at least a part of the oil agent has been removed will be described. By bringing a modacrylic fiber product containing an oil agent into contact with a cleaning liquid, a degreased fiber from which at least a part of the oil agent has been removed can be obtained. Specifically, after bringing a modacrylic fiber product containing an oil agent into contact with a cleaning liquid, the degreased fiber can be obtained by separating the cleaning liquid and the degreased fiber. The method for separating the cleaning liquid and the degreased fiber is not particularly limited. Examples of the method for separating the cleaning liquid and the degreased fiber include filtration and the like.

[0039] The degreased fiber thus obtained usually has the cleaning liquid adhered thereto. The degreased fiber is supplied to the spinning dope preparation process in a state where the cleaning liquid is adhered or in a state where the cleaning liquid has been removed. Typically, the cleaning liquid adhering to the degreased fibers can be removed from the degreased fibers by drying them by various known methods.

[0040] By using the degreased fibers obtained by the above method, at least a part of the oil agent of which has been removed, the degreased fibers can be dissolved in an organic solvent at a high concentration, and in the spinning process described later, spinning can be performed well. The degreased fibers are then subjected to a spinning dope preparation process.

[0041] <Spinning Dope Preparation Process> In the spinning dope preparation process, the degreased fibers are dissolved in at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone to obtain a spinning dope. By using the above solvent, the degreased fibers can be dissolved well, and in the spinning process described later, spinning can be performed well. From the viewpoint of safety, it is preferable to dissolve the degreased fibers in dimethyl sulfoxide to obtain a spinning dope.

[0042] 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 preferably, for example, 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 a value of the electrical conductivity corrected to the electrical conductivity measured at 25°C by the temperature correction function of the portable conductivity meter is obtained. This corrected value of the electrical conductivity is taken as the value of the electrical conductivity of the spinning dope.

[0043] The concentration of defatted fibers in the spinning dope is not particularly limited as long as the desired effect is not impaired. From the viewpoint of performing spinning well in the spinning process described later, the concentration of defatted fibers 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, based on the mass of the spinning dope.

[0044] 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 the modacrylic resin in the spinning dope can be adjusted by dissolving a virgin material of the modacrylic resin in the spinning dope containing defatted fibers in a dissolved state. When the spinning dope contains a modacrylic resin derived from defatted fibers and a modacrylic resin not derived from defatted fibers, the preferred concentration of the modacrylic resin in the spinning dope is the same as the preferred concentration of the defatted fibers in the spinning dope described above. When the spinning dope contains a modacrylic resin derived from defatted fibers and a modacrylic resin not derived from defatted fibers, the ratio of the mass of the modacrylic resin derived from defatted fibers to the total mass of the modacrylic resin may be 1% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 50% by mass or more, 80% by mass or more, or 90% by mass or more.

[0045] When dissolving the defatted fibers in at least one 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 thermal degradation of the defatted fibers and the solvent does not occur.

[0046] 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 degreased fiber 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.

[0047] The spinning dope may contain a pigment. As the pigment, various well-known pigments can be used as necessary. The pigment may be an organic pigment or an inorganic pigment. Further, the spinning dope may contain two or more pigments, and may also contain a dye together with the pigment.

[0048] As the pigment added to the spinning dope, a solid powdery pigment may be used, or a pigment dispersion liquid containing a pigment dispersed in a dispersion medium may be used. From the viewpoint of the dispersibility of the pigment in the spinning dope and the modacrylic fiber, it is preferable to prepare the spinning dope using the pigment dispersion liquid.

[0049] As the pigment, carbon black is preferable because it can color the modacrylic fiber into black of a desired hue and is easily available.

[0050] From the viewpoint of suppressing the occurrence of yarn breakage in the spinning process while coloring the modacrylic fiber to a desired degree, the content of the pigment in the spinning dope is preferably 0.01 part by mass or more and 2.00 parts by mass or less, more preferably 0.02 part by mass or more and 0.60 part by mass or less, based on 100 parts by mass of the spinning dope.

[0051] The spinning dope may contain other additives for improving fiber properties as necessary, as long as the desired effect is not inhibited. Examples of such additives include gloss modifiers such as titanium dioxide, silicon dioxide, and esters and ethers of cellulose derivatives such as cellulose acetate; stabilizers for improving light resistance and heat resistance, and the like.

[0052] The spinning dope is then subjected to a spinning process.

[0053] <Spinning process> In the spinning process, wet spinning is carried out using a spinning dope. As the wet spinning method, extruding the spinning dope from a nozzle into a coagulation bath to solidify it, and stretching the fibers produced by solidifying the spinning dope in a stretching bath are preferably included.

[0054] Hereinafter, extruding the spinning dope from a nozzle into a coagulation bath to solidify it is also referred to as the "coagulation step". Stretching the fibers produced by solidifying the spinning dope in a stretching bath is also referred to as the "stretching step".

[0055] (Coagulation step) In the coagulation step, the spinning dope is extruded in a fibrous form from a nozzle into a coagulation bath, and the spinning dope extruded in a fibrous form is solidified. 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.

[0056] In the coagulation step, first, the spinning dope is extruded through a spinning nozzle into the coagulation bath. The coagulated liquid extruded in a fibrous form solidifies in the coagulation bath and is fibrillated. From the viewpoint of easily controlling the solidification state, it is preferable to use a mixed liquid of water and an organic solvent as the coagulation bath. For example, as the liquid introduced into the coagulation bath, an aqueous solution of an organic solvent is preferable. The concentration of the organic solvent in the aqueous solution of the organic solvent 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.

[0057] The organic solvent contained in the liquid extruded into the coagulation bath is not particularly limited as long as it is a good solvent for the modacrylic resin. From the perspective of the productivity of modacrylic fibers, one or more 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 perspective of safety, dimethyl sulfoxide is more preferred. From the perspective of the quality of modacrylic fibers and the simplicity of process control, it is preferable that the organic solvent in the spinning dope and the organic solvent in the liquid extruded into the coagulation bath are the same organic solvent.

[0058] The temperature of the spinning dope extruded into the coagulation bath is preferably 35°C or lower. The temperature of the liquid extruded into the coagulation bath is preferably 10°C or higher and 30°C or lower, more preferably 10°C or higher and 25°C or lower.

[0059] (Drawing process) The fibers produced by coagulating the spinning dope in the coagulation bath are then drawn in the drawing bath. The method of transferring the fibers to be drawn from the coagulation bath to the drawing bath is not particularly limited. Typically, the fibers to be drawn are passed over a roll in the coagulation bath and one or more fiber transfer rolls outside the coagulation bath, and by rotating the rolls, the fibers to be drawn are transferred into the drawing bath.

[0060] The fibers transferred into the drawing bath are passed over a first drawing roll provided on the upstream side in the moving direction of the fibers to be drawn and a second drawing roll provided on the downstream side in the moving direction of the fibers to be drawn in the liquid extruded into the drawing bath, and are drawn by rotation. Here, the draw ratio is adjusted by adjusting the tension applied to the fibers drawn by the first drawing roll and the second drawing roll and the rotational speeds of the first drawing roll and the second drawing roll. The draw ratio is preferably more than 100% and 800% or less, more preferably 120% or more and 300% or less. The drawn modacrylic fibers are passed over a roll such as a clover roll provided outside the drawing bath and are appropriately recovered from the drawing bath.

[0061] The bath solution immersed in the stretching bath is not particularly limited as long as good stretching can be performed. For example, water or an aqueous solution containing an organic solvent can be used. As the bath solution in the stretching bath, an aqueous solution of an organic solvent containing 10% by mass or more and 90% by mass or less of water based on the mass of the bath solution is preferred. The temperature in the stretching bath is preferably in the range of 30°C or higher and 110°C or lower, and more preferably in the range of 40°C or higher and 95°C or lower.

[0062] The stretching in the stretching bath is preferably carried out in multiple steps. Further, it is preferable that the average values of the stretching speeds are different in at least two of the multiple stretches. When the stretching in the stretching bath is carried out in multiple steps, it is easy to control the stretching conditions for each period such as the initial, middle, and later stages in the stretching process. Here, the stretching being carried out in multiple steps means that stretching and the release of the tension for stretching are repeated any number of times of two or more. The multiple stretches may be carried out in the same stretching bath or may be carried out using a plurality of different stretching baths. It is preferable to use a plurality of different stretching baths in that the temperature of the stretching bath and the composition of the liquid immersed in the stretching bath can be changed for each stretching bath.

[0063] (Water washing step) The drawn modacrylic fibers are usually washed in a water-washing process. In the water-washing process, the drawn modacrylic fibers in the drawing bath are washed with water to remove the organic solvent from the modacrylic fibers. In the water-washing process, it is preferable to use an aqueous solution of an organic solvent having a lower concentration of the organic solvent than warm water or a coagulation bath at 25°C or higher as the washing liquid. The water-washing can be carried out by immersing the drawn modacrylic fibers in a bath filled with these washing liquids or spraying water onto the moving modacrylic fibers. The means for spraying water in the water-washing process is not particularly limited, but from the viewpoint of easy spraying, it is preferable to spray water with a nozzle. The direction of spraying water is not particularly limited, and it may be sprayed from the side or from below. From the viewpoint of uniformly spraying water, it is preferable to use a shower nozzle having a plurality of 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 effect of removing the organic solvent, the temperature of the water is preferably 40°C or higher, and more preferably 50°C or higher.

[0064] Although not particularly limited, in the water-washing process, from the viewpoint of enhancing the effect of removing the organic solvent, 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.

[0065] (Dehydration process) When the drawn modacrylic fibers are washed with water, the washed modacrylic fibers are dehydrated in the dehydration process. In the dehydration process, the washed modacrylic fibers are dehydrated by passing them between nip rolls while sandwiching them between the nip rolls.

[0066] The "nip roll" is generally not particularly limited as long as it is used when manufacturing fibers by the wet spinning method. As the nip roll, for example, a rubber nip roll, a metal nip roll, etc. can be used. As the upper nip roll, a rubber nip roll (also referred to as a rubber roll) is preferably used, and as the lower nip roll, a metal nip roll (also referred to as a metal roll) is preferably used.

[0067] The above-described water washing step and dehydration step may be alternately repeated a plurality of times one by one. After performing the above-described water washing two or more times, pressing by nip rolls may be performed one or more times.

[0068] (Drying step) The modacrylic fibers stretched in the stretching bath and the modacrylic fibers dehydrated as described above are then dried in the drying step. In the drying step, it is preferable that the moisture contained in the modacrylic fibers is almost completely removed. The drying method is not particularly limited as long as it can remove the moisture of the modacrylic fibers. Examples of the drying method include hot air drying and drying by contacting a heating roll. The drying temperature is not particularly limited, but for example, 110°C or higher and 190°C or lower is preferable, and 110°C or higher and 170°C or lower is more preferable.

[0069] The fineness of the modacrylic fibers obtained as described above is appropriately determined according to the use of the modacrylic fibers.

[0070] Before drying the modacrylic fibers, an oil agent may be attached to the modacrylic fibers. The oil agent is as described above.

[0071] The dried modacrylic fibers obtained by the above method may be further stretched as necessary. The stretching method is not particularly limited and includes dry and wet methods.

[0072] The dried modacrylic fiber obtained by the above method is preferably further relaxed in a heat relaxation treatment step. The relaxation rate is not particularly limited, but for example, 5% or more is preferable, and 10% or more is more preferable. The heat relaxation treatment can be carried out in a dry heat atmosphere at a high temperature, for example, 130°C or higher and 200°C or lower, preferably 140°C or higher and 190°C or lower, or in a superheated steam atmosphere. Alternatively, it can be carried out in a pressurized steam or heated pressurized steam atmosphere at 120°C or higher and 180°C or lower, 0.05 MPa or higher and 0.4 MPa or lower, preferably 0.1 MPa or higher and 0.4 MPa or lower.

Examples

[0073] The present invention will be described more specifically by the following examples. Note that the present invention is not limited to the following examples.

[0074] 〔Example 1〕 (Degreasing step) 200 parts by mass of a modacrylic fiber product (AFRELLE (manufactured by Kaneka)) was immersed in 1400 parts by mass of ethanol at 70°C for 240 minutes. Then, the degreased fiber was filtered off from the ethanol in which the degreased fiber was immersed to obtain a degreased fiber. The obtained degreased fiber was allowed to stand at room temperature and dried. When the obtained degreased fiber was dissolved in dimethyl sulfoxide at 60°C, the degreased fiber dissolved in dimethyl sulfoxide whether the concentration of the degreased fiber was 25.0% by mass or 27.5% by mass.

[0075] (Spinning dope preparation step) 200 parts by mass of the dried degreased fiber, 588 parts by mass of dimethyl sulfoxide, and 12 parts by mass of pure water were placed in a dissolution tank. The internal temperature of the dissolution tank was maintained at 60°C for 30 minutes to dissolve the degreased fiber in dimethyl sulfoxide containing a small amount of water. Then, the solution in the dissolution tank was stirred at 170 rpm for 30 minutes. Next, the solution in the dissolution tank was stirred at 330 rpm for 30 minutes. After stirring, the solution in the dissolution tank was filtered through a mesh filter with an aperture of 2 mm to obtain a spinning dope. The concentration of the degreased fiber in the obtained spinning dope was 25% by mass. In addition, as a result of measuring the electric conductivity of the obtained spinning dope by the method described below, the electric conductivity of the spinning dope was 184 μS / cm.

[0076] (Spinning process) The spinning dope at 35°C was supplied to a nozzle having 10 discharge holes with an opening area of 0.085 mm 2 and discharged into a coagulation bath filled with a 47 mass% aqueous dimethyl sulfoxide solution at a temperature of 25°C with a nozzle discharge speed of 10 m / min, and spinning was performed at a draft ratio of 1.25. After washing with water in an 80°C water bath, the fibers were immersed in an oil agent (a mixed solution of 65 mass% castor oil ether and 35 mass% sorbitan stearate). Then, they were dried, and then the fibers were drawn at 125°C with a draw ratio of 230%, and relaxation treatment was performed at 155°C to obtain modacrylic fibers.

[0077] [Comparative Example 1] (Spinning dope preparation process) Without performing the deoiling process, 200 parts by mass of a modacrylic fiber product, 588 parts by mass of dimethyl sulfoxide, and 12 parts by mass of pure water were put into a dissolution tank. The internal temperature of the dissolution tank was maintained at 60°C for 30 minutes to dissolve the modacrylic fiber product in dimethyl sulfoxide containing a small amount of water. Then, the solution in the dissolution tank was stirred at 170 rpm for 30 minutes. Next, the solution in the dissolution tank was stirred at 330 rpm for 30 minutes. After stirring, needle-like undissolved residues were observed in the solution in the dissolution tank. Therefore, a spinning dope could not be prepared.

[0078] [Comparative Example 2] In the deoiling process, except that ethanol was changed to pure water, the deoiled fibers were recovered from pure water in the same manner as in Example 1. The obtained deoiled fibers were dried at 140°C for 4 hours. Attempts were made to prepare a spinning dope in the same manner as in Example 1 using the obtained deoiled fibers, but needle-like undissolved residues were observed and a spinning dope could not be prepared.

[0079] [Comparative Example 3] In the defatting process, except for changing ethanol to an aqueous solution of an anionic surfactant containing 1 part by mass of sodium alkyl ether sulfate, the defatted fibers were recovered from the aqueous solution of the anionic surfactant in the same manner as in Example 1. The obtained defatted fibers were washed by pouring 2000 parts by mass or more of pure water over them for 3 minutes. The washed defatted fibers were dried at 140 °C for 4 hours. Using the obtained defatted fibers, an attempt was made to prepare a spinning dope in the same manner as in Example 1, but needle-like residues were observed and the spinning dope could not be prepared.

[0080] [Comparative Example 4] (Defatting process) 200 parts by mass of a modacrylic fiber product (AFRELLE (manufactured by Kaneka)) was immersed in 1480 parts by mass of dilute hydrochloric acid at 50 °C. The dilute hydrochloric acid was prepared by mixing pure water and a 37.0% hydrochloric acid aqueous solution at a mass ratio (pure water: hydrochloric acid aqueous solution) of 10:2. During the immersion, the dilute hydrochloric acid was colored. This is because the pigment contained in the modacrylic fiber product was dispersed in the dilute hydrochloric acid. From this, it is considered that the modacrylic resin has been chemically damaged and decomposed by immersing the modacrylic fiber product in hydrochloric acid. Therefore, in Comparative Example 4, defatted fibers were not obtained, and a spinning dope was not prepared.

[0081] <Oil agent adhesion amount in defatted fibers> The oil agent adhesion amount in the defatted fibers is calculated by the following formula (a): Oil agent adhesion amount in defatted fibers (%omf) = mass of oil agent adhering to defatted fibers / mass of defatted fibers × 100 Formula (a) It was calculated according to. Specifically, the oil agent adhesion amount was measured according to the following method. First, a mixed solvent of cyclohexane and ethanol with a mass ratio of 1 to 1 and degreased fibers were thoroughly mixed in a test tube. Then, the mixed solvent in the test tube containing the oil agent extracted from the degreased fibers was 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 degreased fibers added to the test tube was taken as the "mass of degreased fibers" in formula (a), and the mass of the residue was taken as the "mass of the oil agent adhering to the degreased fibers" in formula (a). According to formula (a), the amount of oil agent adhesion on the degreased fibers was calculated. The results are shown in Table 1. Note that the amount of oil agent adhesion in the modacrylic fiber product of Comparative Example 1 was measured according to the above method except that the degreased fibers were changed to modacrylic fiber products. In Table 1, the amount of oil agent adhesion in the modacrylic fiber product of Comparative Example 1 was described for convenience as the amount of oil agent adhesion in the degreased fibers.

[0082] <Electrical conductivity of spinning dope> The electrical conductivity of the spinning dope of Example 1 was measured using a portable conductivity meter (Hanchen DDB-303A). The terminals of the portable conductivity meter were inserted into 50 mL of the spinning dope, and a value corrected to the electrical conductivity measured at 25°C by the temperature correction function of the portable conductivity meter was obtained.

[0083]

Table 1

Claims

1. By bringing a modacrylic fiber product containing an oil agent into contact with a cleaning liquid, obtaining degreased fibers from which at least a part of the oil agent has been removed; Dissolving the degreased fibers in at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone to obtain a spinning dope; Performing wet spinning using the spinning dope, wherein the cleaning liquid contains an organic solvent, in the degreased fibers, the following formula (a): Oil agent adhesion amount (%)omf in degreased fibers = mass of oil agent adhering to degreased fibers / mass of degreased fibers × 100 Formula (a) A method for producing modacrylic fibers, wherein the oil agent adhesion amount calculated by the formula is 0.15%omf or less.

2. The method for producing modacrylic fibers according to claim 1, wherein the organic solvent is at least one selected from the group consisting of hydrocarbons, alcohols, ketones, and ethers.

3. The method for producing modacrylic fibers according to claim 1, wherein the organic solvent is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, 1-butanol, and 2-butanol.

4. The method for producing modacrylic fibers according to claim 1, wherein the temperature of the cleaning liquid is 45°C or higher and 98°C or lower.

5. The method for producing modacrylic fibers according to claim 1, including filtering the spinning dope before performing the wet spinning.

6. The method for producing modacrylic fibers according to claim 1, wherein the concentration of the degreased fibers in the spinning dope is 5% by mass or higher and 35% by mass or lower.

7. The method for producing modacrylic fibers according to claim 1, wherein the electrical conductivity of the spinning dope is 350 μS / cm or lower.

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