Manufacturing method of modacrylic fiber and modacrylic fiber

Abstract

To provide a manufacturing method of a modacrylic fiber capable of suppressing an occurrence of thread breakage during melt spinning and obtaining the fiber with high strength, and the modacrylic fiber having the high strength obtained by the method.SOLUTION: The manufacturing method of the modacrylic fiber uses a melt spinning device comprising: a spinneret for spinning a yarn; and a heating part having a heating space for heating the yarn. The manufacturing method includes the steps of: spinning a melted and kneaded product of a resin composition containing a modacrylic resin and a plasticizer from the spinneret to spin the yarn; and passing the spun yarn through the heating space of the heating part. A preset temperature of the heating part is 125°C or higher and 210°C or lower.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Modacrylic fibers composed of a modacrylic resin obtained by copolymerizing acrylonitrile and vinyl halide or the like have been used in various products such as artificial hair, flame-retardant materials, and pile fabrics. Conventionally, since the modacrylic resin has a decomposition start temperature lower than the softening temperature and decomposes when melt-processed, it has been made into fibers by the wet spinning method. However, in the case of the wet spinning method, the drainage load is high and the solvent recovery cost is high.

[0003] Therefore, Patent Document 1 discloses that a modacrylic fiber can be produced by the melt spinning method by using a thermoplastic modacrylic resin composition containing a modacrylic resin obtained by copolymerizing acrylonitrile and vinyl halide or the like and a plasticizer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 discloses a method for melt spinning modacrylic fibers by installing a heating cylinder for heating the modacrylic fibers discharged from a die. However, in the method described in Patent Document 1, yarn breakage may occur and productivity may decrease. In addition, improvement is also required in the strength of the fibers obtained by stretching.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a modacrylic fiber in which the occurrence of thread breakage is suppressed during melt spinning and high-strength fibers can be obtained, and a modacrylic fiber having high strength obtained by the method.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the inventors have found that the above problems can be solved by significantly reducing the set temperature of the heating unit in a method for producing a modacrylic fiber using a melt spinning apparatus including a die for spinning a yarn and a heating unit having a heating space for heating the yarn, and have completed the present invention.

[0008] Aspects of the present invention relate to the following method for producing a modacrylic fiber and a modacrylic fiber.

[0009] [1] A method for producing a modacrylic fiber using a melt spinning apparatus including a die for spinning a yarn and a heating unit having a heating space for heating the yarn, comprising: a step of spinning a melt kneaded product of a resin composition containing a modacrylic resin and a plasticizer from the die to spin a yarn; a step of passing the spun yarn through the heating space of the heating unit, wherein the set temperature of the heating unit is 125°C or higher and 210°C or lower. The method for producing a modacrylic fiber according to [1]. [2] The modacrylic resin according to [1], contains 35 to 84.5% by mass of a structural unit derived from acrylonitrile, contains 15 to 64.5% by mass of a structural unit derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, contains a structural unit derived from an ethylenically unsaturated monomer as a main chain and 0.5 to 40% by mass of a structural unit derived from a macromonomer having a double bond functional group at one end. [3] The method for producing modacrylic fibers according to [2], wherein the double bond functional group is represented by the following general formula (1). CH 2 =C(R)-C(O)O- (1) (In the general formula (1), R represents hydrogen or an organic group having 1 to 20 carbon atoms.) [4] The method for producing modacrylic fibers according to [2] or [3], wherein the ethylenically unsaturated monomer contains one or more monomers selected from the group consisting of (meth)acrylate monomers, styrene monomers, nitrile group-containing vinyl monomers, amide group-containing vinyl monomers, fluorine-containing vinyl monomers, silicon-containing vinyl monomers, maleimide monomers, vinyl esters, maleic acids, alkenes, and conjugated dienes. [5] The method for producing modacrylic fibers according to any one of [1] to [4], wherein the content of the plasticizer is 2.0 to 12.0 parts by mass with respect to 100 parts by mass of the thermoplastic modacrylic resin. [6] The method for producing modacrylic fibers according to any one of [1] to [5], wherein the distance between the heating part and the die is 15 mm or more. [7] An undrawn yarn of modacrylic fibers obtained by spinning a melt-kneaded product of a resin composition containing a modacrylic resin and 2.0 to 12.0 parts by mass of a plasticizer with respect to 100 parts by mass of the modacrylic resin, The undrawn yarn of modacrylic fibers having a maximum draw ratio of 360% or more. [8] The modacrylic resin is Contains 35 to 84.5% by mass of structural units derived from acrylonitrile, Contains 15 to 64.5% by mass of structural units derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, The undrawn yarn of modacrylic fibers according to [7], which contains structural units derived from an ethylenically unsaturated monomer as the main chain and 0.5 to 40% by mass of structural units derived from a macromonomer having a double bond functional group at one end. [9] A drawn yarn of modacrylic fibers obtained by drawing the undrawn yarn of modacrylic fibers according to [7] or [8], A drawn yarn of modacrylic fiber having a strength of 1.0 cN / dtex or more.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a method for producing a modacrylic fiber in which the occurrence of yarn breakage is suppressed during melt spinning and a high-strength fiber can be obtained, and a modacrylic fiber having high strength obtained by the method.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] ≪Method for Producing Modacrylic Fiber≫ The method for producing a modacrylic fiber is a spinneret for spinning a yarn, a method for producing a modacrylic fiber using a melt spinning apparatus including a heating section having a heating space for heating the yarn, a step of spinning a melt kneaded product of a resin composition containing a modacrylic resin and a plasticizer from the spinneret to spin a yarn, a step of passing the spun yarn through the heating space of the heating section, and the set temperature of the heating section is 125°C or more and 210°C or less. By the above production method, the occurrence of yarn breakage is suppressed during melt spinning, and high-strength fibers can be obtained.

[0013] <Melt Spinning Apparatus> FIG. 1 is a schematic diagram of a melt spinning apparatus used in a method for producing a modacrylic fiber according to an embodiment of the present invention. The melt spinning apparatus 1 has at least a spinneret 2 for spinning a yarn Y and a heating section 10 having a heating space for heating the yarn Y.

[0014] The heating unit 10 is disposed at the lower end of the base 2, and a gap is provided between the lower end of the base 2 and the upper end of the heating unit 10.

[0015] (Heating unit) The heating unit 10 is preferably a cylindrical member having a heating space through which the yarn Y can pass on the inner peripheral side. The heating unit 10 preferably heats the air in the space on the inner peripheral side by an electric heater provided on the inner peripheral surface side, and heats the yarn Y passing through the space on the inner peripheral side. The temperature of the space on the inner peripheral side of the heating unit 10 is preferably not less than the glass transition temperature Tg + 0°C and not more than 120°C of the resin composition that is the raw material of the modacrylic fiber. Further, the temperature of the space on the inner peripheral side of the heating unit 10 is preferably uniform from one end to the other end in the direction in which the yarn Y is fed in the heating unit 10. The heating unit 10 is preferably formed to have a length in the central axis direction of, for example, 30 cm. The length of the heating unit 10 in the central axis direction is preferably not less than 10 cm and not more than 50 cm. When the length of the heating unit 10 in the central axis direction is less than 10 cm, the time for performing drafting becomes short, and yarn breakage is likely to occur. Further, when the length of the heating unit 10 in the central axis direction exceeds 50 cm, the cooling of the yarn Y becomes insufficient, and there is a possibility that fineness spots are likely to occur in the yarn Y.

[0016] The heating unit 10 is not particularly limited, and a commercially available electric heater can be used.

[0017] The glass transition temperature Tg means the temperature at which, by heating the target resin composition to a certain temperature or higher, the molecules are in a soft rubbery state in which they can move easily, and then by cooling, the movement of the molecules is restricted and it becomes a hard glassy state. The glass transition temperature Tg can be measured by a general method, and for example, a differential scanning calorimeter (DSC) can be used.

[0018] The lower limit of the above-mentioned gap between the base 2 and the heating unit 10 is not particularly limited, but from the viewpoint of suppressing the occurrence of yarn breakage during melt spinning, it is preferably 15 mm or more, and more preferably 25 mm or more. The upper limit of the gap between the nozzle 2 and the heating unit 10 is not particularly limited, but is preferably 80 mm or less, more preferably 70 mm or less, and even more preferably 60 mm or less.

[0019] <Resin composition> The resin composition contains a modacrylic resin and a plasticizer. Hereinafter, the essential or optional components contained in the resin composition will be described.

[0020] (Modacrylic resin) The modacrylic resin is a copolymer composed of acrylonitrile and a monomer copolymerizable therewith, and is a resin in which the acrylonitrile component is 35% by mass or more and less than 85% by mass. As the monomer copolymerizable with acrylonitrile, usually, halogen compounds such as vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, 2,3-dibromoacrylate, and / or allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, isoprenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and metal salts and amine salts such as sodium salts thereof are used.

[0021] Further, a preferred embodiment of the modacrylic resin includes a structural unit (a1) derived from acrylonitrile, a structural unit (a2) derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, and a structural unit derived from a macromonomer having a double-bonded functional group at one end and containing a structural unit derived from an ethylenically unsaturated monomer as a main chain (a3).

[0022] The content of the above structural unit (a1) is preferably 35 to 84.5% by mass, more preferably 35 to 69.5% by mass, and even more preferably 38 to 64% by mass with respect to the total amount of the modacrylic resin.

[0023] The content of the above structural unit (a2) is preferably 15 to 64.5% by mass, more preferably 25 to 64.5% by mass, and even more preferably 35 to 64.5% by mass with respect to the total amount of the modacrylic resin.

[0024] The content of the above structural unit (a3) is more preferably 0.5 to 40% by mass, more preferably 1.0 to 30% by mass, and even more preferably 1.5 to 20% by mass with respect to the total amount of the modacrylic resin.

[0025] (Structural unit (a3) derived from the macromonomer) As described above, the macromonomer that provides the structural unit (a3) contains a structural unit derived from an ethylenically unsaturated monomer as the main chain and has a double-bonded functional group at one end. Examples of the above ethylenically unsaturated monomers include (meth)acrylate monomers, styrene monomers, vinyl monomers containing a nitrile group, vinyl monomers containing an amide group, fluorine-containing vinyl monomers, silicon-containing vinyl monomers, maleimide monomers, vinyl esters, maleic acids, alkenes, conjugated dienes, and the like. Among them, from the viewpoint of excellent spinnability, one or more selected from the group consisting of (meth)acrylate monomers, styrene monomers, and vinyl monomers containing a nitrile group are preferable. In the present specification, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0026] As the (meth)acrylate monomer, for example, a (meth)acrylate monomer having a heteroatom in the ester moiety may be used. The heteroatom is not particularly limited, and examples thereof include oxygen (O), fluorine (F), nitrogen (N), and the like. Examples of the (meth)acrylate monomer having a heteroatom in the ester moiety include methyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, and 2,2,2-trifluoroethyl (meth)acrylate.

[0027] Examples of the styrene monomer include styrene, vinyltoluene, α-methylstyrene, chlorostyrene, styrenesulfonic acid and its salts.

[0028] Examples of the nitrile group-containing vinyl monomer include monomers other than acrylonitrile, such as methacrylonitrile.

[0029] Examples of the amide group-containing vinyl monomer include (meth)acrylamide, vinylpyrrolidone and the like.

[0030] Examples of the fluorine-containing vinyl monomer include perfluoroethylene, perfluoropyrene, vinylidene fluoride and the like.

[0031] Examples of the silicon-containing vinyl monomer include vinyltrimethoxysilane, vinyltriethoxysilane and the like.

[0032] Examples of the maleimide monomer include maleimide, methylmaleimide, phenylmaleimide, cyclohexylmaleimide and the like.

[0033] Examples of the vinyl esters include vinyl acetate, vinyl propionate, vinyl benzoate, vinyl cinnamate and the like.

[0034] Examples of the maleic acids include maleic acid, maleic anhydride and the like.

[0035] Examples of the alkenes include ethylene, propylene and the like.

[0036] Examples of the conjugated dienes include butadiene, isoprene and the like.

[0037] The above double bond functional group preferably has a polymerizable carbon-carbon double bond represented by the following general formula (1). CH 2=C(R)-C(O)O- (1) In general formula (1), R represents hydrogen or an organic group having 1 to 20 carbon atoms. Specific examples of R include, for example, preferably -H, -CH 3 , -CH 2 CH 3 , -(CH 2 ) n CH 3 (n represents an integer of 2 or more and 19 or less), -C 6 H 5 , -CH 2 OH, and a group selected from the group consisting of -CN, more preferably a group selected from the group consisting of -H and -CH 3 .

[0038] From the viewpoint of high strength, the number average molecular weight (Mn) of the above macromonomer is preferably 1000 or more and 50000 or less, more preferably 2000 or more and 20000 or less.

[0039] The polymer containing a structural unit derived from an ethylenically unsaturated monomer, which is the main chain of the above macromonomer, is not particularly limited, and a conventionally known production method, for example, a radical polymerization method can be used. For example, known methods such as a general radical polymerization method and a controlled radical polymerization method as described in JP-A-2006-299240 can be mentioned, and any production method can be used. Usually, a controlled radical polymerization method is used, and further, a living radical polymerization method is preferably used from the viewpoint of ease of control, etc., and an atom transfer radical polymerization method is particularly preferred. For example, in the atom transfer radical polymerization method, an organic halide or a sulfonyl halide compound, etc. may be used as a polymerization initiator, and a transition metal complex may be used as a polymerization catalyst. Specifically, a method described in JP-A-2005-232209 may be used. A macromonomer can be obtained by introducing a reactive functional group into a polymer having a halogen group at the terminal obtained by the atom transfer radical polymerization method, for example, by the method described in JP-A-2005-232209. The molecular weight of the macromonomer can be adjusted by the charging ratio of the ethylenically unsaturated monomer and the polymerization initiator. For example, by reducing the ratio of the monomer to the polymerization initiator (monomer / polymerization initiator), the molecular weight of the macromonomer can be lowered.

[0040] When producing a macromonomer by the atom transfer radical polymerization method, for example, a polymer containing a structural unit derived from an ethylenically unsaturated monomer can be prepared, and then a reactive functional group can be introduced into the terminal of the obtained polymer for production.

[0041] From the viewpoint of high strength, the mass average molecular weight of the above modacrylic resin is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 80,000 or less.

[0042] As a method for producing the above modacrylic resin, solution polymerization is preferred from the viewpoints of simplicity of polymerization and moderation of polymerization heat generation.

[0043] (Plasticizer) The plasticizer is not particularly limited, and examples thereof include organic sulfur compounds, epoxy compounds, polyester compounds, trimellitic compounds, chlorine compounds, phthalic acid, adipic acid and citric acid compounds, and reactive compounds such as (meth)acrylic acid esters. Among these, organic sulfur compounds are preferred. Hereinafter, these plasticizers are also referred to as "organic plasticizers". The organic plasticizer may be used alone or in combination of two or more.

[0044] The content of the organic plasticizer is not particularly limited, and is preferably 2.0 to 12.0 parts by mass, more preferably 4.0 to 10.0 parts by mass, and even more preferably 5.0 to 8.0 parts by mass with respect to 100 parts by mass of the modacrylic resin.

[0045] (Other components) The resin composition may contain components other than the modacrylic resin and the plasticizer (hereinafter also referred to as "other components") as long as the effects of the present invention are not impaired. As the other components, any known additives can be used, and examples thereof include stabilizers, lubricants, antistatic agents, pigments and the like.

[0046] As stabilizers, for example, epoxy stabilizers, hydrotalcite stabilizers, Ca-Zn stabilizers, β-diketone stabilizers, etc. can be used. From the viewpoint of improving melt processability, suppressing coloring, and ensuring transparency, epoxy stabilizers can use polyglycidyl methacrylate, tetra-bromobisphenol A diglycidyl ether, hydrotalcite, lead 12-hydroxystearate, calcium 12-hydroxystearate, stearoyl benzoyl methane (SBM), dibenzoyl methane (DBM), etc. Hydrotalcite stabilizers may be natural products or synthetic products as long as they are hydrotalcite compounds. For example, Alcamaizer (registered trademark) manufactured by Kyowa Chemical Industry Co., Ltd. can be used. As Ca-Zn stabilizers, for example, calcium stearate, zinc 12-hydroxystearate, calcium 12-hydroxystearate, etc. can be used. As β-diketone stabilizers, for example, stearyl benzoyl methane, dibenzoyl methane, etc. can be used. These stabilizers may be used alone or in combination of two or more.

[0047] <Melt spinning> The modacrylic fiber is obtained by including a step of spinning a melt-kneaded product of the above resin composition from the above die to form a yarn, and a step of passing the spun yarn through the heating space of the above heating section.

[0048] (Step of spinning a yarn) In the step of spinning a melt-kneaded product of the above resin composition from the above die to form a yarn, the melt-kneaded product is obtained using an extruder. The extruder is not particularly limited, and examples include single-screw extruders, co-rotating twin-screw extruders, conical twin-screw extruders, etc. The extruder is preferably operated in a temperature range of, for example, 120°C or higher and 200°C or lower. The ratio of the take-up speed to the discharge speed is not particularly limited, but it is preferably taken up at a speed ratio in the range of, for example, 1 time or more and 100 times or less, and more preferably in the range of 5 times or more and 50 times or less from the viewpoint of spinning stability. The diameter of the spinneret 2 is not particularly limited, but for example, it is preferably 0.05 mm or more and 2 mm or less, and more preferably 0.1 mm or more and 1 mm or less. It is preferable to extrude at a temperature equal to or higher than the temperature of the spinneret 2 at which the discharge from the spinneret 2 does not exhibit melt fracture. The temperature of the spinneret 2 is preferably 160°C or higher, and more preferably 170°C or higher.

[0049] (Step of passing the spun yarn through the heating space of the heating section) In the step of passing the spun yarn through the heating space of the heating section, the set temperature of the heating section is 125°C or higher and 210°C or lower, preferably 130°C or higher and 190°C or lower, and more preferably 135°C or higher and 185°C or lower, from the viewpoint of suppressing the occurrence of yarn breakage during melt spinning and obtaining fibers with high strength.

[0050] (Winding step) The yarn Y that has passed through the heating section is preferably cooled to a temperature below the glass transition point by means such as air cooling as shown in FIG. 1, and is taken up by a pair of take-up rollers 4 and 5 and a winder 6 for winding the yarn Y through an oil agent attaching member 3 for attaching an oil agent, thereby obtaining a yarn (undrawn yarn). The cooling temperature is preferably -196°C or higher and 40°C or lower by air cooling, more preferably 0°C or higher and 30°C or lower, and preferably 5°C or higher and 60°C or lower by water cooling, more preferably 10°C or higher and 40°C or lower. The oil agent is not particularly limited, and examples thereof include polyether-based oil agents. The amount of the oil agent attached is not particularly limited, and for example, it is preferably 0.05% omf or more and 0.5% omf or less based on the total mass of the dry fiber.

[0051] ≪Undrawn yarn of modacrylic fiber≫ The undrawn yarn of modacrylic fiber is an undrawn yarn obtained by spinning a melt kneaded product of a resin composition containing a modacrylic resin and 2.0 to 12.0 parts by mass of a plasticizer with respect to 100 parts by mass of the modacrylic resin, and has a maximum draw ratio of 360% or more. The maximum draw ratio is determined as the ratio of the fiber length at break to the initial fiber length when an undrawn yarn of modacrylic fiber is allowed to stand in a thermostat preheated to 105°C for 2 minutes and then drawn and broken in the thermostat. The maximum draw ratio of the undrawn yarn is preferably 400% or more, more preferably 420% or more, from the viewpoint of obtaining a high-strength drawn yarn.

[0052] The undrawn yarn of modacrylic fiber is obtained by melt-spinning a melt-kneaded product of the resin composition according to the above-described embodiment under the above-described conditions using a melt-spinning apparatus according to the embodiment described in <<Method for Producing Modacrylic Fiber>>.

[0053] A preferred embodiment of the resin composition is also as described above, and preferably contains a modacrylic resin and a plasticizer.

[0054] A preferred embodiment of the modacrylic resin is also as described above, and includes 35 to 84.5% by mass of a structural unit derived from acrylonitrile, 15 to 64.5% by mass of a structural unit derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, a structural unit derived from an ethylenically unsaturated monomer as the main chain, and 0.5 to 40% by mass of a structural unit derived from a macromonomer having a double-bond functional group at one end. Examples thereof include a graft copolymer.

[0055] <<Drawn Yarn of Modacrylic Fiber>> The drawn yarn of modacrylic fiber is a drawn yarn obtained by drawing an undrawn yarn of modacrylic fiber, and has a strength of 1.0 cN / dtex or more. The strength of the drawn yarn is measured in accordance with JIS L 1013 using, as a sample, a drawn yarn obtained by drawing an undrawn yarn of modacrylic fiber at a draw ratio of 3 times in a heating atmosphere at 105°C. The strength of the drawn yarn is preferably 1.2 cN / dtex or more, more preferably 1.4 cN / dtex or more.

[0056] As the stretching treatment conditions, it is preferable that the stretching treatment is performed in a heating atmosphere at a stretching treatment temperature of 70°C or higher and 150°C or lower, and the stretching ratio is preferably about 1.1 times or more and 6 times or less, and more preferably about 1.5 times or more and 4.5 times or less.

[0057] In addition, the drawn yarn of the modacrylic fiber can be subjected to a heat relaxation treatment as necessary. For example, by subjecting the drawn modacrylic fiber to a relaxation treatment at a relaxation rate of preferably 1% or more and 50% or less, and more preferably 5% or more and 40% or less, the heat shrinkage rate can be reduced.

[0058] The drawn yarn of the modacrylic fiber also has a strength of 1.0 cN / dtex or more. Therefore, the drawn yarn of the modacrylic fiber is suitably used, for example, as a flame-retardant material and an awning.

Examples

[0059] Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples.

[0060] <Production Example of Macromonomer> 554 g of CuBr was charged into a 2 L separable flask equipped with a reflux tube and a stirrer, and the inside of the reaction vessel was purged with nitrogen. Next, 73.8 mL of acetonitrile was added, the separable flask was placed in an oil bath at 70°C, and the contents were stirred for 30 minutes. Then, 132 g of 2-methoxyethyl acrylate, 14.4 mL of methyl 2-bromopropionate, and 4.69 mL of pentamethyldiethylenetriamine were added to the separable flask to start the reaction. While heating and stirring at 70°C, 2-methoxyethyl acrylate (528 g) was continuously added dropwise over 90 minutes, and further heated and stirred at 70°C for 80 minutes. The reaction mixture was diluted with toluene, passed through an activated alumina column, and then the volatile components were distilled off under reduced pressure to obtain a mono-terminal Br group poly(2-methoxyethyl acrylate).

[0061] Into a 500 mL flask equipped with a reflux tube, 150 g of the single-terminal Br-group poly(2-methoxyethyl acrylate) obtained above, 7.45 g of potassium acrylate (CH 2 =CHCO 2 K), and 150 mL of dimethylacetamide were charged, and the mixture was heated and stirred at 70 °C for 3 hours. Then, dimethylacetamide was distilled off from the reaction mixture, the reaction mixture was dissolved in toluene, passed through an activated alumina column, and then toluene was distilled off to obtain a single-terminal acryloyl-group poly(2-methoxyethyl acrylate) macromonomer. The number-average molecular weight of the obtained single-terminal acryloyl-group poly(2-methoxyethyl acrylate) macromonomer was 6000, and the molecular weight distribution (weight-average molecular weight / number-average molecular weight) was 2.68. The weight-average molecular weight and number-average molecular weight were measured and calculated by the GPC method using gel permeation chromatography (HLC-8320GPC manufactured by Tosoh Corporation). GPC-MALS was measured using "HLC-8220GPC" manufactured by Tosoh, equipped with two TSKgel GMHxL columns, one TSKgel G3000xL column, and one TSKgel G2000xL column, and using DMF containing 50 mM of lithium bromide hydrate as the eluent. The weight-average molecular weight of the following modacrylic resin was also measured by the same method.

[0062] <Production Example 1 of Modacrylic Resin> Into a polymerization reactor, 56 parts by mass of vinyl chloride, 41 parts by mass of acrylonitrile, 3 parts by mass of a macromonomer with an acryloyl group at one end obtained in the <Production Example of Macromonomer> described above, 210 parts by mass of ion-exchanged water, 0.25 parts by mass of partially saponified polyvinyl acetate (saponification degree of about 70 mol%, average degree of polymerization of 1700), and 1.5 parts by mass of 1,1,3,3-tetramethylbutyl peroxyneodecanoate were charged. After that, with the temperature inside the polymerization reactor cooled to 15°C or lower, stirring and dispersion were carried out for 15 minutes. Then, the temperature inside the polymerization reactor was raised to 45°C to initiate polymerization. Polymerization was carried out at a polymerization temperature of 47.5°C for 4 hours, then the polymerization temperature was raised to 52.5°C and further polymerized for 2 hours, and then raised to 55°C and further suspension polymerization was carried out for 2 hours. During polymerization, 41 parts by mass of acrylonitrile and 0.225 parts by mass of 2-mercaptoethanol were continuously added at a constant rate from immediately after the start of polymerization until the 7.25th hour. After recovering the unreacted monomers in the polymerization reactor, the slurry was discharged. The obtained slurry was dehydrated and dried in a hot air dryer at 60°C for 24 hours to obtain a graft copolymer of modacrylic resin / poly(2-methoxyethyl acrylate) (thermoplastic modacrylic resin). The obtained graft copolymer consisted of 40.9% by mass of acrylonitrile, 56.1% by mass of vinyl chloride, and 3.0% by mass of poly(2-methoxyethyl acrylate), and the conversion rate of the macromonomer with an acryloyl group at one end of poly(2-methoxyethyl acrylate) was 94%. The mass average molecular weight of the obtained graft copolymer was about 47,000.

[0063] ≪Production Example of Modacrylic Fiber≫ (Melt Spinning Apparatus) In Example 1, modacrylic fibers were produced using the melt spinning apparatus 1 shown in FIG. 1. The embodiment of the melt spinning apparatus 1 is described below. ·Distance from the lower end of the die 2 to the heating section 10: 20 mm ·Length of the heating section 10 in the central axis direction: 300 mm

[0064] (Extruder) The specifications of the extruder, which is a component of the melt spinning apparatus, are described below. Extruder: Single-screw extruder with a diameter of 40 mm. L / D = 26 Screw: Full flight type, compression ratio = 2.5 Die: One-hole cross-sectional area: 0.1124 mm 2

[0065] On the other hand, in Comparative Example 1, in the melt spinning apparatus 1, a melt spinning apparatus not provided with the heating unit 10 was used.

[0066] ≪Production Example of Melting Modacrylic Fiber≫ (Example 1) To 100 parts by mass of the modacrylic resin obtained in Production Example 1, 3.0 parts by mass of an epoxy-based stabilizer, 1.5 parts by mass of a hydrotalcite-based stabilizer, 2.0 parts by mass of a β-diketone-based stabilizer, 0.3 parts by mass of a Ca-Zn-based stabilizer, 2.5 parts by mass of dimethyl sulfone as a plasticizer, 0.75 parts by mass of an oxide of a low molecular weight ethylene / propylene copolymer as a lubricant, and a black pigment as other additives were mixed to obtain a resin composition. The resin composition was supplied to a single-screw extruder, and the resin composition was melt-kneaded at a cylinder temperature of 165°C. The obtained melt-kneaded product was extruded from the die 2 at a shear rate of 31.4 s -1 , a discharge rate of 10.0 kg / h to spin a yarn. Next, the spun yarn was passed through a heating space of the heating unit 10 provided with a 20 mm gap from the die 2 and set at 140°C to heat the yarn. Next, the yarn that had passed through the heating unit 10 was wound up at a winding speed of 93 m / min to obtain a modacrylic fiber (undrawn yarn).

[0067] (Example 2) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1 except that the gap between the die and the heating unit was changed to 40 mm.

[0068] (Example 3) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1 except that the set temperature of the heating unit was changed to 150°C and the gap between the die and the heating unit was changed to 40 mm.

[0069] (Example 4) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the set temperature of the heating unit was changed to 160°C.

[0070] (Example 5) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the set temperature of the heating unit was changed to 160°C and the gap between the die and the heating unit was changed to 30 mm.

[0071] (Example 6) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the set temperature of the heating unit was changed to 160°C and the gap between the die and the heating unit was changed to 40 mm.

[0072] (Example 7) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the set temperature of the heating unit was changed to 160°C and the gap between the die and the heating unit was changed to 50 mm.

[0073] (Example 8) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the set temperature of the heating unit was changed to 180°C.

[0074] (Example 9) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the set temperature of the heating unit was changed to 200°C.

[0075] (Example 10) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the set temperature of the heating unit was changed to 200°C and the gap between the die and the heating unit was changed to 40 mm.

[0076] (Comparative Example 1) In Example 1, a modacrylic fiber was obtained in the same manner as in Example 1, except that the heating unit was not installed.

[0077] (Comparative Example 2) In Example 1, modacrylic fibers were obtained in the same manner as in Example 1, except that the set temperature of the heating section was changed to 120°C and the gap between the die and the heating section was changed to 40 mm.

[0078] (Comparative Example 3) In Example 1, modacrylic fibers were obtained in the same manner as in Example 1, except that the set temperature of the heating section was changed to 100°C and the gap between the die and the heating section was changed to 40 mm.

[0079] <Evaluation> According to the following method, the presence or absence of single - filament breakage during spinning was evaluated, the maximum draw ratio of the obtained undrawn modacrylic fibers was measured, and the strength of the drawn modacrylic fibers was measured. The results are shown in Table 1.

[0080] (Single - filament breakage during spinning) Melt spinning was carried out for 5 minutes, and the presence or absence of single - filament breakage during spinning was evaluated according to the following evaluation criteria. ◎: 0 pieces 〇: 1 - 5 pieces △: 5 - 10 pieces

[0081] (Maximum draw ratio) The undrawn modacrylic fibers were left standing in a thermostat PH100 (manufactured by ESPEC) pre - heated to 105°C for 2 minutes. After stretching the fibers in the thermostat, the magnification from the initial length was evaluated.

[0082] (Strength) The undrawn modacrylic fibers were drawn at a draw ratio of 3 times in a heating atmosphere of 105°C. In accordance with JIS L 1013, the strength of the undrawn modacrylic fibers and the obtained drawn modacrylic fibers was measured. Specifically, it was measured using a tensilon universal material testing machine RTF series (manufactured by A&D Company), the strength was measured for 10 samples, and it was represented by the average value of the obtained strength.

[0083]

Table 1

[0084] From the results in Table 1, it can be seen that when the set temperature of the heating section is 125°C or higher and 210°C or lower, the maximum draw ratio of the undrawn yarn of modacrylic fiber becomes 360% or higher, and the strength of the drawn yarn of modacrylic fiber becomes 1.0 cN / dtex or higher.

Explanation of symbols

[0085] 1 Melt spinning apparatus 2 Spinneret 10 Heating section

Claims

1. A method for producing modacrylic fibers using a melt spinning apparatus comprising a spinneret for spinning a yarn and a heating unit having a heating space for heating the yarn, the method comprising: spinning a melt kneaded product of a resin composition containing a modacrylic resin and a plasticizer from the spinneret to form a spun yarn; and passing the spun yarn through the heating space of the heating unit, wherein the set temperature of the heating unit is 125°C or higher and 210°C or lower.

2. The method for producing modacrylic fibers according to claim 1, wherein the modacrylic resin contains: 35 to 84.5% by mass of a structural unit derived from acrylonitrile, 15 to 64.5% by mass of a structural unit derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, a structural unit derived from an ethylenically unsaturated monomer as a main chain, and 0.5 to 40% by mass of a structural unit derived from a macromonomer having a double bond functional group at one end.

3. The method for producing modacrylic fibers according to claim 2, wherein the double bond functional group is represented by the following general formula (1): (In general formula (1), R represents hydrogen or an organic group having 1 to 20 carbon atoms.) CH ２ =C(R)-C(O)O- (1)

4. The method for producing modacrylic fibers according to claim 2 or 3, wherein the ethylenically unsaturated monomer contains one or more monomers selected from the group consisting of (meth)acrylate monomers, styrene monomers, nitrile group-containing vinyl monomers, amide group-containing vinyl monomers, fluorine-containing vinyl monomers, silicon-containing vinyl monomers, maleimide monomers, vinyl esters, maleic acids, alkenes, and conjugated dienes.

5. The method for producing modacrylic fibers according to claim 1 or 2, wherein the content of the plasticizer is 2.0 to 12.0 parts by mass with respect to 100 parts by mass of the modacrylic resin.

6. The method for producing modacrylic fibers according to claim 1 or 2, wherein the distance between the heating unit and the spinneret is 15 mm or more.

7. An undrawn yarn of modacrylic fibers obtained by spinning a melt kneaded product of a resin composition containing a modacrylic resin and 2.0 to 12.0 parts by mass of a plasticizer with respect to 100 parts by mass of the modacrylic resin, wherein the maximum draw ratio is 360% or higher.

8. The method for producing modacrylic fibers according to claim 7, wherein the modacrylic resin contains: 35 to 84.5% by mass of a structural unit derived from acrylonitrile, 15 to 64.5% by mass of a structural unit derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, It contains 15 to 64.5% by mass of a structural unit derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, It contains a structural unit derived from an ethylenically unsaturated monomer as the main chain and 0.5 to 40% by mass of a structural unit derived from a macromonomer having a double-bonded functional group at one end, the undrawn yarn of the modacrylic fiber according to claim 7.

9. The drawn yarn of the modacrylic fiber obtained by drawing the undrawn yarn of the modacrylic fiber according to claim 7 or 8 being a drawn yarn, wherein the strength is 1.0 cN / dtex or more, the drawn yarn of the modacrylic fiber.

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