Method for manufacturing modacrylic fibers

Abstract

This invention provides a method for producing modacrylic fibers that allows for the recycling of modacrylic fiber products by dissolving modacrylic fiber products in an organic solvent to prepare a low-viscosity spinning stock solution, and then stably performing wet spinning using the obtained spinning stock solution. [Solution] A method for producing modacrylic fiber, comprising the steps of: dissolving a modacrylic fiber product in a solvent containing an organic solvent to obtain a spinning stock; and wet spinning the spinning stock, wherein the solvent further contains a surfactant, the surfactant is at least one selected from the group consisting of cationic surfactants and amphoteric surfactants, and the content of the surfactant is 0.1 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the modacrylic fiber product.

Description

Technical Field

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

Background Art

[0002] Modacrylic fibers, known as acrylic fibers, have characteristics such as their unique texture, excellent color development, and dye fastness, and are therefore used in various applications such as clothing, construction, and industrial materials. 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 modacrylic fiber products in an organic solvent, depending on the type of fiber, the viscosity of the resulting spinning dope may not be sufficiently reduced. Therefore, when discharging the spinning dope from a nozzle for wet spinning, yarn breakage due to nozzle clogging often occurs, and it is often impossible to stably prevent wetting.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing modacrylic fibers that recycles modacrylic fiber products by dissolving modacrylic fiber products in an organic solvent to prepare a low-viscosity spinning dope and stably performing wet spinning using the resulting spinning dope.

Means for Solving the Problems

[0006] The inventors of the present invention have found that the above problems can be solved by dissolving the modacryl fiber product in a solution containing an organic solvent and a specific surfactant in the process of obtaining the spinning solution, and have completed the present invention.

[0007] Aspects of this disclosure relate to the following methods for producing modacrylic fibers.

[0008] [1] A process of dissolving modacryl fiber products in a solvent containing an organic solvent to obtain a spinning stock, The process includes a step of wet spinning the aforementioned spinning stock, The aforementioned dissolving solution further contains a surfactant, The surfactant is at least one selected from the group consisting of cationic surfactants and amphoteric surfactants. A method for producing modacrylic fibers, wherein the amount of the surfactant is 0.1 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the modacrylic fiber product. [2] A method for producing modacrylic fibers according to [1], comprising a pretreatment step of breaking up the modacrylic fiber product into smaller pieces before the dissolution step. [3] The method for producing modacrylic fibers according to [1] or [2], wherein the viscosity of the spinning solution is 0.1 Pa·s or more and 5.5 Pa·s or less. [4] A method for producing modacrylic fibers according to any one of [1] to [3], wherein the dissolution temperature in the step of obtaining the spinning solution is 45°C or higher and 70°C or lower. [5] A method for producing modacryl fibers according to any one of [1] to [4], wherein the cationic surfactant is at least one selected from the group consisting of quaternary ammonium salts and fatty acid amidoamine salts. [6] A method for producing modacryl fibers according to any one of [1] to [5], wherein the amphoteric surfactant is at least one selected from the group consisting of amino acid betaine amine oxide and lecithin. [Effects of the Invention]

[0009] According to the present invention, a method for producing modacrylic fibers that allows for the recycling of modacrylic fiber products can be provided by dissolving modacrylic fiber products in an organic solvent to prepare a low-viscosity spinning stock solution, and then stably performing wet spinning using the obtained spinning stock solution. [Modes for carrying out the invention]

[0010] ≪Method for manufacturing modacrylic fibers≫ The method for producing modacrylic fibers in this embodiment is: A process of dissolving modacryl fiber products in a solvent containing an organic solvent to obtain a spinning solution, The process includes a step of wet spinning the above-mentioned spinning stock solution. The above dissolving solution further contains a surfactant, The above-mentioned surfactant is at least one selected from the group consisting of cationic surfactants and amphoteric surfactants. The amount of the surfactant is 0.1 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the modacryl fiber product. According to the above method for producing modacrylic fibers, a modacrylic fiber product is dissolved in an organic solvent to prepare a low-viscosity spinning stock, and stable wet spinning can be performed using the obtained spinning stock.

[0011] In this specification, the process of dissolving modacrylic fiber products in a solvent to obtain a spinning solution is also referred to as the "spinning solution acquisition process." The process of wet spinning the above-mentioned spinning stock is also called the "spinning process."

[0012] The following describes each step involved in the above-mentioned method for manufacturing modacrylic fibers.

[0013] <Process for obtaining spinning solution> In the spinning solution acquisition process, modacrylic fiber products are dissolved in a solvent containing an organic solvent to obtain the spinning solution.

[0014] [Modacrylic fiber products] The modacrylic fiber products are not particularly limited. The 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 enterprises or individuals that produce modacrylic fibers.

[0015] The modacrylic fiber products may be either colored fibers or uncolored fibers. When the modacrylic fiber products are colored, typically, the modacrylic fiber products contain pigments. The pigments may be either organic pigments or inorganic pigments. The modacrylic fiber products may contain two or more kinds of pigments, and may also contain dyes together with the pigments. Carbon black is preferably used because it is easily available. According to the above method, even if the modacrylic fiber products contain pigments such as carbon black, it is possible to recycle the modacrylic fiber products and perform wet spinning well to produce modacrylic fibers.

[0016] In addition to the aforementioned pigments, the modacrylic fiber products may contain various additives. Examples of the various additives contained in the modacrylic fiber products include, for example, gloss modifiers 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.

[0017] Also, the modacrylic fiber products often contain an 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. The oil agent may be a compound that is usually used for the purpose of antistatic, preventing the adhesion of modacrylic fibers, and improving the texture during the production of the modacrylic fibers that make up the modacrylic fiber products. Typically, the oil agent adheres to the fiber surface in the modacrylic fiber products.

[0018] Examples of the oil agent 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, partial esters of polyhydric alcohols, etc.; animal and vegetable fats and oils; mineral oils; fatty acid esters; silicone surfactants such as amino-modified silicone, etc.

[0019] The modacrylic fiber product mainly consists of a modacrylic resin. Hereinafter, the modacrylic resin will be described.

[0020] (Modacrylic resin) For example, a modacrylic copolymer in which the mass ratio 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. In addition, the structural unit derived from other monomers other than acrylonitrile essentially includes a structural unit derived from a hydrophilic functional group-containing monomer.

[0021] As such a modacrylic copolymer, a modacrylic copolymer in which the mass ratio 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.

[0022] More specifically, a modacrylic copolymer in which the mass ratio 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 mass ratio 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 mass ratio of the structural unit 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 modacryl copolymer, if the content of structural units derived from acrylonitrile is 35% by mass or more and 79.5% by mass or less, the resulting modacryl fibers have good heat resistance. In the modacryl copolymer, if 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 resulting modacryl fibers have good flame retardancy. In the modacryl copolymer, if the content of hydrophilic functional group-containing monomers is 0.5% by mass or more and 5% by mass or less, the resulting modacryl fibers have good hydrophilicity.

[0023] With respect to the modacryl resin, it is more preferable that the ratio of the mass of constituent units derived from acrylonitrile to the mass of the modacryl copolymer is 35% by mass or more and 74.5% by mass or less, the ratio of the mass of constituent units derived from vinyl chloride and / or vinylidene chloride is 25% by mass or more and 64.5% by mass or less, and the ratio of constituent units derived from hydrophilic functional group-containing monomers is 0.5% by mass or more and 5% by mass or less. It is preferable that the modacryl copolymer contains constituent units derived from vinyl chloride in order to obtain modacryl fibers with excellent tactile properties.

[0024] The ratio of constituent units derived from hydrophilic functional group-containing monomers to the mass of modacryl resin is preferably 0.5% by mass or more and 3% by mass or less, and more preferably 0.5% by mass or more and 2.5% by mass or less.

[0025] The monomer containing hydrophilic functional groups is a monomer copolymerizable with acrylonitrile and is not particularly limited as long as it has hydrophilic functional groups. The hydrophilic functional group is not particularly limited as long as it is a functional group capable of forming hydrogen bonds. Specifically, examples include hydroxyl groups, carboxyl groups, sulfonic acid groups, phosphate groups, sulfonylamide groups, and sulfonylimide groups. These groups may also form salts. As described above, among the hydrophilic functional group-containing monomers, sulfonic acid group-containing monomers are preferred in terms of preventing void formation.

[0026] Examples of sulfonic acid group-containing monomers that can be used include allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, isoprene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and their sodium salts and other metal salts and amine salts. The sulfonic acid group-containing monomer may be used individually or in combination of two or more types.

[0027] [Dissolution solution] The dissolving solution contains an organic solvent and a specific surfactant. The presence of this specific surfactant along with the organic solvent in the dissolving solution prevents yarn breakage during wet spinning, enabling stable wet spinning.

[0028] (organic solvent) As the organic solvent, any organic solvent conventionally used to dissolve modacryl resin can be used without particular limitation. Preferred organic solvents include at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone. Among these organic solvents, dimethyl sulfoxide is more preferred from the viewpoint of safety.

[0029] The amount of organic solvent used is preferably 100 parts by mass or more and 400 parts by mass or less, and more preferably 150 parts by mass or more and 300 parts by mass or less, per 100 parts by mass of modacryl fiber product.

[0030] (Surfactants) The surfactant is at least one selected from the group consisting of cationic surfactants and amphoteric surfactants.

[0031] (Cationic surfactants) Examples of cationic surfactants include quaternary ammonium salts, fatty acid amidoamine salts, heterocyclic quaternary ammonium salts, and aromatic quaternary ammonium salts. Among these, it is preferable that at least one selected from the group consisting of quaternary ammonium salts and fatty acid amidoamine salts is used, from the viewpoint of preventing yarn breakage during wet spinning and enabling stable wet spinning.

[0032] Examples of quaternary ammonium salts include tetraalkylammonium halides and alkyltrimethylammonium halides. Examples of tetraalkylammonium halides include tetramethylammonium halide, tetrapropylammonium halide, and tetrabutylammonium halide. Examples of alkyltrimethylammonium halides include dodecyltrimethylammonium chloride, octyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, cetyltrimethylammonium chloride, behenyltrimethylammonium chloride, benzyltrimethylammonium chloride, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, lauryltrimethylammonium bromide, cetyltrimethylammonium bromide, stearyltrimethylammonium bromide, octyldimethylbenzylammonium chloride, dioctyldimethylammonium chloride, decetyldimethylbenzylammonium chloride, stearyldimethylbenzylammonium chloride, distearyldimethylammonium chloride, didodecyldimethylammonium chloride, dioctadecyldimethylammonium chloride, and cetylpyridinium chloride. These quaternary ammonium salts may be used individually or in combination of two or more. Among these, dodecyltrimethylammonium chloride and dioctyldimethylammonium chloride are preferred.

[0033] Examples of fatty acid amidoamine salts include diethylaminoethyl stearate and dimethylaminopropyl stearate. These fatty acid amidoamine salts may be used individually or in combination of two or more.

[0034] (Amphoteric surfactant) Examples of amphoteric surfactants include amino acid betaine amine oxide and lecithin. Among these, it is preferable to use at least one selected from the group consisting of amino acid betaine amine oxide and lecithin, from the viewpoint of preventing yarn breakage during wet spinning and enabling stable wet spinning.

[0035] Examples of amino acid betaine amine oxides include cocamidopropyl betaine, lauramidopropyl betaine, myristamidopropyl betaine, palm kernel fatty acid amidopropyl betaine, and lauryl betaine. These fatty acid amidoamine salts may be used individually or in combination of two or more.

[0036] The amount of surfactant used is preferably 0.1 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of modacrylic fiber product, more preferably 0.9 parts by mass or more and 1.5 parts by mass or less, and even more preferably 1.0 part by mass or more and 1.5 parts by mass or less, from the viewpoint of preventing yarn breakage during wet spinning and having excellent spinning speed stability.

[0037] (Other ingredients) The dissolving solution may contain components other than the organic solvent and surfactant described above (hereinafter also referred to as "other components"), as long as they do not impair the effects of the present invention. Examples of other components include water, oil, etc.

[0038] The amount of water used is preferably 0.5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of modacrylic fiber product, more preferably 1 part by mass or more and 60 parts by mass or less, and even more preferably 2 parts by mass or more and 40 parts by mass or less.

[0039] (Dissolution conditions) In the process of obtaining the spinning solution, the dissolution temperature is not particularly limited, but is preferably 45°C to 70°C, and more preferably 50°C to 70°C.

[0040] In the process of obtaining the spinning solution, the dissolution time is not particularly limited, but is preferably 60 minutes or more and 300 minutes or less, and more preferably 120 minutes or more and 240 minutes or less.

[0041] In the process of obtaining the spinning solution, the rotation speed during dissolution is not particularly limited, but is preferably 100 rpm to 300 rpm, and preferably 150 rpm to 250 rpm.

[0042] (Spinning solution) The spinning solution obtained in the manner described above will be explained below.

[0043] The concentration of modacryl fiber product in the spinning solution is not particularly limited, as long as the desired effect is not impaired. From the viewpoint of good spinning in the spinning process described later, the concentration of modacryl fiber product (solid content concentration) relative to the mass of the spinning solution 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.

[0044] The spinning solution may contain modacrylic resin not derived from modacrylic fiber products. Modacrylic resin not derived from modacrylic fiber products is usually virgin material. For example, the concentration of modacrylic resin in the spinning solution can be adjusted by dissolving a virgin modacrylic resin material in a spinning solution containing a modacrylic fiber product in a dissolved state. If the spinning solution contains modacrylic resin derived from modacrylic fiber products and modacrylic resin not derived from modacrylic fiber products, the ratio of the mass of modacrylic resin derived from modacrylic fiber products to the total mass of 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] The spinning solution may contain water. The water content of the spinning solution is not particularly limited, as long as the desired effect is not impaired. From the viewpoint of the solubility of modacryl fiber products in the spinning solution, the water content of the spinning solution 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.

[0046] The spinning solution may contain a pigment. Various well-known pigments can be used as the pigment, as needed. The pigment may be an organic pigment or an inorganic pigment. Furthermore, the spinning solution may contain two or more pigments, and may also contain dyes along with the pigments.

[0047] The pigment added to the spinning solution may be a solid powder pigment, or a pigment dispersion containing pigment dispersed in a dispersion medium may be used. In terms of the dispersibility of the pigment in the spinning solution and modacrylic fibers, it is preferable to prepare the spinning solution using a pigment dispersion.

[0048] As a pigment, carbon black is preferred because it can color modacrylic fibers to a desired shade of black and is readily available.

[0049] To color the modacrylic fibers to the desired degree while suppressing yarn breakage during the spinning process, the pigment content in the spinning solution 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, per 100 parts by mass of the spinning solution.

[0050] The spinning solution may, if necessary, contain other additives to improve fiber properties, provided that 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, including cellulose acetate; and stabilizers to improve light resistance and heat resistance.

[0051] The viscosity of the spinning solution is measured using a viscoelasticity measuring instrument. The viscosity of the spinning solution is the dynamic viscosity measured at a rotor angular velocity of 1.0 Hz for a sample dissolved at a dissolution temperature of 60°C and a dissolution time of 180 minutes. From the viewpoint of enabling stable wet spinning without yarn breakage during wet spinning, the dynamic viscosity of the spinning solution is preferably between 0.1 Pa·s and 5.5 Pa·s, more preferably between 0.1 Pa·s and 5.2 Pa·s, and even more preferably between 0.1 Pa·s and 5.0 Pa·s.

[0052] <Spinning Process> In the spinning process, wet spinning is performed using a spinning solution. As for wet spinning methods, The process involves extruding the spinning solution from a nozzle into a coagulation bath and allowing it to coagulate, A preferred method includes stretching the fibers produced by coagulating the spinning solution in a stretching bath.

[0053] Hereafter, the process of extruding the spinning stock solution from a nozzle into a coagulation bath and allowing it to coagulate will also be referred to as the "coagulation process." The process of stretching the fibers produced by coagulating the spinning stock solution in a stretching bath will also be referred to as the "stretching process."

[0054] (solidification process) In the coagulation process, the spinning solution is extruded in fibrous form from a nozzle into the coagulation bath, and the extruded fibrous spinning solution is then coagulated. The spinning solution is discharged into the coagulation bath from a nozzle of a size and shape corresponding to the fiber diameter and cross-sectional shape of the modacrylic fiber.

[0055] In the coagulation process, the spinning solution is first extruded through the spinning nozzle into the coagulation bath. The coagulated solution, extruded in fibrous form, coagulates and becomes fibers in the coagulation bath. As the coagulation bath, it is preferable to use a mixture of water and an organic solvent, from the viewpoint of being able to easily control the coagulation state. For example, an aqueous solution of an organic solvent is preferred as the liquid to be poured into the coagulation bath. 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.

[0056] The organic solvent contained in the liquid poured into the coagulation bath is not particularly limited, as long as it is a good solvent for modacryl resin. From the viewpoint of modacryl fiber productivity, 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 viewpoint of safety, dimethyl sulfoxide is more preferred. From the viewpoint of modacryl fiber quality and ease of process control, it is preferable that the organic solvent in the spinning solution and the organic solvent in the liquid poured into the coagulation bath are the same organic solvent.

[0057] The temperature of the spinning solution extruded into the coagulation bath is preferably 35°C or lower. The temperature of the liquid placed in the coagulation bath is preferably between 10°C and 30°C, and more preferably between 10°C and 25°C.

[0058] (Stretching process) The fibers produced by coagulating the spinning solution in a coagulation bath are then stretched in a stretching bath. The method of transferring the fibers from the coagulation bath to the stretching bath is not particularly limited. Typically, the fibers to be stretched are placed on a roll in the coagulation bath and on one or more fiber transfer rolls outside the coagulation bath, and the fibers to be stretched are transferred into the stretching bath by rotating the rolls.

[0059] The fibers being transported into the stretching bath are stretched by rotation between a first stretching roll located upstream of the fibers being stretched and a second stretching roll located downstream of the fibers being stretched, while the fibers are submerged in the liquid contained within the stretching bath. Here, the stretching ratio is adjusted by controlling the tension applied to the fibers being stretched by the first and second stretching rolls, and the rotational speed of the first and second stretching rolls. The stretching ratio is preferably between 100% and 800%, and more preferably between 120% and 300%. The stretched modacrylic fibers are then stretched over rolls such as clover rolls located outside the stretching bath and recovered from the stretching bath as needed.

[0060] The bath liquid used in the stretching bath is not particularly limited as long as it allows for good stretching. For example, water or an aqueous solution containing an organic solvent can be used. The bath liquid used in the stretching bath is preferably an aqueous solution of an organic solvent containing 10% to 90% by mass of water relative to the mass of the bath liquid. The temperature of the bath in the stretching bath is preferably in the range of 30°C to 110°C, and more preferably in the range of 40°C to 95°C.

[0061] It is preferable that the stretching in the stretching bath be carried out in multiple stages. Furthermore, it is preferable that the average stretching speed is different in at least two of the multiple stretching stages. Performing the stretching in the stretching bath in multiple stages makes it easier to control the stretching conditions at each stage of the stretching process, such as the initial, middle, and late stages. Here, "stretching is performed in multiple steps" means that the stretching and the release of the tension for stretching are repeated two or more times. Multiple stretching processes may be carried out in the same stretching bath, or they may be carried out using multiple different stretching baths. It is preferable to use multiple different stretching baths because the temperature of the stretching bath and the composition of the liquid placed in the stretching bath can be changed for each stretching bath.

[0062] (Water washing process) Stretched modacryl fibers are typically washed in a water washing process. In the water washing process, the stretched modacryl fibers are washed in a stretching bath to remove organic solvents from the fibers. In the water washing process, it is preferable to use warm water at 25°C or higher, or an aqueous solution of an organic solvent with a lower concentration than that of the coagulation bath, as the washing solution. Water washing can be carried out by immersing the stretched modacryl fibers in a bath filled with these washing solutions, or by spraying water onto the moving modacryl fibers. The means of spraying water in the water washing process are not particularly limited, but from the viewpoint of ease of spraying, it is preferable to spray water using a nozzle. The direction in which the water is sprayed 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 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 to remove organic solvents, the water temperature is preferably 40°C or higher, and more preferably 50°C or higher.

[0063] While not particularly limited, in the water washing process, from the viewpoint of enhancing the effect of removing organic solvents, the ratio of 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.

[0064] (Dehydration process) When the stretched modacrylic fibers are washed with water, the washed modacrylic fibers are dewatered in the dewatering process. In the dewatering process, the washed modacrylic fibers are dewatered by passing them between nip rolls while being sandwiched between them.

[0065] A "nip roll" is generally any type of roll used in the production of fibers by the wet spinning method, and is not particularly limited. Examples of nip rolls 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.

[0066] The aforementioned washing and dewatering processes may be performed alternately multiple times, once each. After performing the aforementioned washing process two or more times, pressing with a nip roll may be performed one or more times.

[0067] (drying process) Modacrylic fibers stretched in the stretching bath, and modacrylic fibers dehydrated as described above, are then dried in a drying process. In the drying process, 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 from the modacrylic fibers. Examples of drying methods include hot air drying and drying by contact with heated rolls. The drying temperature is not particularly limited, but for example, 110°C to 190°C is preferred, and 110°C to 170°C is more preferred.

[0068] The fineness of the modacrylic fibers obtained in the manner described above is appropriately determined according to the intended use of the modacrylic fibers.

[0069] Before drying the modacrylic fibers, an oiling agent may be applied to them. The oiling agent is as described above.

[0070] The dried modacrylic fibers obtained by the above method may be further stretched as needed. The stretching method is not particularly limited and can be dry or wet.

[0071] The dried modacrylic fibers obtained by the above method are preferably further relaxed in a heat relaxation treatment step. The relaxation rate is not particularly limited, but is preferably 5% or more, and more preferably 10% or more. The heat relaxation treatment can be carried out in a dry heat atmosphere or superheated steam atmosphere at a high temperature, for example, 130°C to 200°C, preferably 140°C to 190°C. Alternatively, it can be carried out in a pressurized steam or heated pressurized steam atmosphere at 120°C to 180°C, with a pressure of 0.05 MPa to 0.4 MPa, preferably 0.1 MPa to 0.4 MPa.

[0072] <Other processes> The method for producing modacrylic fibers may include steps other than the spinning solution acquisition step and spinning step described above (hereinafter also referred to as "other steps"), as long as they do not impair the effects of the present invention. Examples of other steps include a pretreatment step that breaks down the modacrylic fiber product into smaller pieces before the dissolution step, a water washing step to remove dirt adhering to the modacrylic fiber product, and an oil removal step.

[0073] <Pre-treatment process> In the pretreatment step, the modacrylic fiber product is broken down into smaller pieces before the dissolution step.

[0074] It is preferable to use the modacrylic fiber product that was used as a raw material in the aforementioned process of obtaining the spinning solution.

[0075] The method for breaking down modacrylic fiber products into smaller pieces is not particularly limited, and known pulverizers can be used. [Examples]

[0076] The present invention will be described in more detail by the following examples. However, the present invention is not limited to the following examples.

[0077] [Examples 1-2 and Comparative Examples 1-3] (Materials used) In the examples and comparative examples, AFRELLE (manufactured by Kaneka Corporation) was used as the modacrylic fiber product. The modacrylic resin constituting the modacrylic fiber product (AFRELLE) contains 46% by mass of constituent units derived from acrylonitrile, 52% by mass of constituent units derived from vinyl chloride, and 2% by mass of constituent units derived from sodium styrenesulfonate.

[0078] In the examples and comparative examples, the dissolving solution used in the spinning solution acquisition process contained the following components. Organic solvent: Dimethyl sulfoxide Water: pure water Quaternary ammonium salt: Dodecyltrimethylammonium chloride (Sigma-Aldrich, Japan G.K.)

[0079] [Example 1] (Pre-treatment process) Using a pulverizer, 100g of modacrylic fiber product was crushed to a length of 10mm or less, and then separated through a Φ10mm mesh to break down the modacrylic fiber product into smaller pieces.

[0080] (Process for obtaining spinning solution) 100 g of fragmented modacryl fiber product was placed in a 1 L dissolution container. Next, 234.8 g of dimethyl sulfoxide and 10.0 g of pure water were added to the dissolution container. Then, 1.0 mass% (1.0 g) of quaternary ammonium salt powder relative to the modacryl fiber product was added to the dissolution container. The dissolution in the dissolution container was maintained at 60°C and stirred at 200 rpm for 180 minutes to dissolve the modacryl fiber product. The solid content concentration of the obtained spinning solution was 23 mass%, and the moisture content of the spinning solution was 3.0 mass%. The dynamic viscosity (Pa·s) of the spinning stock solution being dissolved in the dissolving solution was measured at 60°C with a rotor angular velocity of 1.0 Hz using a viscoelasticity analyzer (HAAKE MARS MARS40 rheometer). The results are shown in Table 1.

[0081] (Spinning process) Spinning solution at 60℃, opening area 0.085mm 2The fibers were supplied to a nozzle having 10 discharge holes, and the nozzle discharge speed was set to 10 m / min. The fibers were discharged into a coagulation bath filled with a 47% by mass aqueous solution of dimethyl sulfoxide at a temperature of 25°C, and spinning was performed at a draft ratio of 1.25. After washing in an 80°C water washing bath, the obtained fibers were immersed in an oil solution (a mixture of 65% by mass castor oil ether and 35% by mass sorbitan stearate). The immersed fibers were then dried, and subsequently stretched at 125°C with a draw ratio of 230%, followed by a relaxation treatment at 155°C to obtain modacrylic fibers. During spinning, there was no yarn breakage, and the spinning speed when the spinning solution was discharged from the nozzle was stable. Furthermore, the resulting modacrylic fibers showed little variation in fineness, and no voids were observed.

[0082] [Example 2] A spinning stock was obtained in the same manner as in Example 1, except that 0.8% by mass of quaternary ammonium salt powder was added as solid content. The solid content concentration of the obtained spinning stock was 23% by mass. The moisture content of the obtained spinning stock was 3% by mass. When spinning was performed using the obtained spinning solution in the same manner as in Example 1, there were no yarn breaks during spinning, but the spinning speed when the spinning solution was discharged from the nozzle was unstable. In addition, the fineness of the obtained modacrylic fibers varied greatly.

[0083] [Comparative Example 1] A spinning stock was obtained in the same manner as in Example 1, except that the quaternary ammonium salt powder was not added. The solid content concentration of the obtained spinning stock was 23% by mass. The moisture content of the obtained spinning stock was 3.0% by mass. The dynamic viscosity (Pa·s) of the spinning stock solution while it was dissolved in the dissolving solution was measured in the same manner as in Example 1. The results are shown in Table 1. When spinning was performed using the obtained spinning solution in the same manner as in Example 1, yarn breakage occurred due to nozzle clogging. This is thought to be due to the higher viscosity compared to Example 1.

[0084] [Comparative Example 2] A spinning stock was obtained in the same manner as in Example 1, except that the quaternary ammonium salt powder was not added and the dissolution temperature was raised to 85°C. The solid content concentration of the obtained spinning stock was 23% by mass. The moisture content of the obtained spinning stock was 3.0% by mass. When spinning was performed using the obtained spinning solution in the same manner as in Example 1, voids derived from dehydrochlorination were generated inside the fiber, making spinning impossible.

[0085] [Comparative Example 3] A spinning stock was obtained in the same manner as in Example 1, except that 1.7% by mass of quaternary ammonium salt powder was added as solid content. The solid content concentration of the obtained spinning stock was 23% by mass. The moisture content of the obtained spinning stock was 3.0% by mass. When spinning was performed using the obtained spinning solution in the same manner as in Example 1, lumps derived from undissolved quaternary ammonium powder remained inside the fiber, and spinning was not possible.

[0086] [Table 1]

[0087] The results in Table 1 show that when the amount of quaternary ammonium salt used is between 0.1 parts by mass and 1.5 parts by mass, no thread breakage occurs.

[0088] [Table 2]

Claims

1. A process of dissolving modacryl fiber products in a solvent containing an organic solvent to obtain a spinning solution, The process includes a step of wet spinning the aforementioned spinning stock, The aforementioned dissolving solution further contains a surfactant, The surfactant is at least one selected from the group consisting of cationic surfactants and amphoteric surfactants. A method for producing modacrylic fibers, wherein the amount of the surfactant is 0.1 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the modacrylic fiber product.

2. A method for producing modacrylic fibers according to claim 1, comprising a pretreatment step of breaking up the modacrylic fiber product into smaller pieces prior to the dissolution step.

3. The method for producing modacrylic fibers according to claim 1 or 2, wherein the viscosity of the spinning solution is 0.1 Pa·s or more and 5.5 Pa·s or less.

4. A method for producing modacrylic fibers according to claim 1 or 2, wherein the dissolution temperature in the step of obtaining the spinning solution is 45°C or higher and 70°C or lower.

5. The method for producing modacryl fibers according to claim 1 or 2, wherein the cationic surfactant is at least one selected from the group consisting of quaternary ammonium salts and fatty acid amidoamine salts.

6. The method for producing modacryl fibers according to claim 1 or 2, wherein the amphoteric surfactant is at least one selected from the group consisting of amino acid betaine amine oxide and lecithin.

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