Graft copolymer

Abstract

To provide a graft copolymer which is suitable for producing acrylic fibers that are excellent in strength.SOLUTION: A graft copolymer contains a stem polymer (A) composed of an acrylic resin, and a branch polymer (B) including a structural unit derived from acrylonitrile (b1), wherein the branch polymer (B) is a graft copolymer which has a first terminal and a second terminal, and is grafted with the stem polymer (A) at the second terminal, the branch polymer (B) includes the first terminal and contains 70 mol% or more of all the structural units derived from the acrylonitrile (b1), in a terminal region including a half of structural units of the number of all the structural units in the branch polymer (B), and the content of the structural units derived from the acrylonitrile (b1) is 3 mol% or more and 30 mol% or less with respect to all the structural units in the branch polymer (B).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a graft copolymer having an acrylic resin as a main polymer.

Background Art

[0002] Acrylic fibers composed of an acrylic 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 acrylic resins have a decomposition start temperature lower than the softening temperature and decompose when melt-processed, they have been fiberized 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, in Patent Document 1, it is disclosed that an acrylic fiber can be produced by the melt spinning method by using a graft copolymer obtained by grafting an acrylic resin obtained by copolymerizing acrylonitrile and other ethylenically unsaturated monomers with a macromonomer composed of an ethylenically unsaturated monomer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since acrylic fibers can be produced by the melt spinning method, there is a need for functional differentiation of the melt spinning method from conventional processing methods such as the wet spinning method, and acrylic resins are also required to be adaptable to various melt processing methods. For example, in order to achieve functional differentiation or expand processing applicability, acrylic fibers with excellent strength are required.

[0006] This invention has been made in view of the above problems, and aims to provide a graft copolymer suitable for producing acrylic fibers with excellent strength. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors of the present invention have discovered that by introducing a predetermined amount of constituent units derived from acrylonitrile into specific regions of macromonomers that serve as constituent materials for branch polymers in graft copolymers, properties not seen in conventional graft copolymers, such as improved strength, can be imparted, thus completing the present invention.

[0008] One aspect of the present invention comprises a stem polymer (A) made of an acrylic resin containing structural units derived from acrylonitrile (a1) and structural units derived from other ethylenically unsaturated monomers (a2), A branched polymer (B) comprising a polymer containing structural units derived from acrylonitrile (b1) and structural units derived from other ethylenically unsaturated monomers (b2), The branch polymer (B) has a first end and a second end, and is grafted onto the stem polymer (A) at the second end, and is a graft copolymer. The branch polymer (B) includes the first end, and the end region containing half the number of constituent units in the branch polymer (B) contains 70 mol% or more of the total constituent units derived from the acrylonitrile (b1). This is a graft copolymer in which the content of constituent units derived from the above-mentioned acrylonitrile (b1) is 3 mol% or more and 30 mol% or less relative to the total constituent units in the above-mentioned branch polymer (B). [Effects of the Invention]

[0009] According to the present invention, a graft copolymer with excellent strength can be provided. Using the graft copolymer according to the present invention, acrylic fibers with excellent strength can be suitably produced. [Modes for carrying out the invention]

[0010] The graft copolymer of the present invention is sometimes referred to as graft copolymer (α). This graft copolymer will be described below.

[0011] <Graft copolymer (α)> The graft copolymer (α) comprises a stem polymer (A) made of an acrylic resin containing structural units derived from acrylonitrile (a1) and structural units derived from other ethylenically unsaturated monomers (a2), The present invention comprises a branched polymer (B) comprising a polymer containing structural units derived from acrylonitrile (b1) and structural units derived from other ethylenically unsaturated monomers (b2).

[0012] (Branch polymer (B)) The branch polymer (B) has a first end and a second end, and the second end is grafted onto the stem polymer (A). The first end is the free end located furthest from the stem polymer (A) within the branch polymer (B). The branched polymer (B) consists of a terminal region including the first end mentioned above and a region other than the terminal region (hereinafter also referred to as the "non-terminal region"). The branched polymer (B) includes the first end, and the end region, which contains half the number of constituent units of the total number of constituent units in the branched polymer (B), contains 70 mol% or more of the total constituent units derived from the acrylonitrile (b1). In this specification, such a structure is referred to as an "α-block type structure".

[0013] From the viewpoint of high strength, branch polymer (B) contains 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more of the total constituent units derived from acrylonitrile (b1) in the terminal region. Branch polymer (B) may contain 100 mol% or less, 99 mol% or less, 98 mol% or less, or 97 mol% or less of the total constituent units derived from acrylonitrile (b1) in the terminal region.

[0014] From the viewpoint of high strength, the proportion of constituent units derived from acrylonitrile (b1) in the terminal region is preferably 10% to 100%, and more preferably 15% to 100%, of the total number of constituent units in the terminal region. If the proportion of constituent units derived from acrylonitrile (b1) in the terminal region is less than 100%, the terminal region contains constituent units derived from the other ethylenically unsaturated monomers (b2). The ratio (b1 / b2) of constituent units derived from acrylonitrile (b1) and constituent units derived from other ethylenically unsaturated monomers (b2) in the terminal region is preferably 10 / 90 or more and 100 / 0 or less, and more preferably 15 / 85 or more and 100 / 0 or less.

[0015] In the above-mentioned non-terminal region, an embodiment in which no constituent units derived from acrylonitrile (b1) are included is preferably an embodiment consisting only of constituent units derived from the above-mentioned other ethylenically unsaturated monomers (b2) and not containing any constituent units derived from acrylonitrile (b1), but an embodiment in which a small amount of constituent units derived from acrylonitrile (b1) are included is also included. That is, the absence of constituent units derived from acrylonitrile (b1) in the above-mentioned non-terminal region means that the above-mentioned non-terminal region does not substantially contain constituent units derived from acrylonitrile (b1). Specifically, constituent units derived from acrylonitrile (b1) may be included, but if constituent units derived from acrylonitrile (b1) are included, the proportion of constituent units derived from acrylonitrile (b1) in the non-terminal region is preferably 5% or less, and more preferably 3% or less, of the total number of constituent units in the non-terminal region. When the non-terminal region contains constituent units derived from acrylonitrile (b1), the proportion of constituent units derived from other ethylenically unsaturated monomers (b2) in the non-terminal region is preferably 95% or more, and more preferably 97% or more, of the total number of constituent units in the non-terminal region.

[0016] As the other ethylenically unsaturated monomer (b2) which is a constituent raw material of the dendritic polymer (B) having an α-block type structure, one or more selected from the group consisting of (meth)acrylate-based monomers, styrene-based monomers, nitrile group-containing vinyl monomers, and amide group-containing vinyl monomers are preferable. In the present specification, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0017] Examples of the (meth)acrylate-based monomer include (meth)acrylic acid aliphatic hydrocarbon esters having an aliphatic hydrocarbon group with 1 to 18 carbon atoms, (meth)acrylic acid alicyclic hydrocarbon esters, (meth)acrylic acid aromatic hydrocarbon esters, and (meth)acrylic acid aralkyl esters.

[0018] Examples of the (meth)acrylic acid aliphatic hydrocarbon ester having an aliphatic hydrocarbon group with 1 to 18 carbon atoms include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Examples of the (meth)acrylic acid alicyclic hydrocarbon ester include cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. Examples of the (meth)acrylic acid aromatic hydrocarbon ester include phenyl (meth)acrylate and toluyl (meth)acrylate. Examples of the (meth)acrylic acid aralkyl ester include benzyl (meth)acrylate.

[0019] In addition, as the above-mentioned (meth)acrylic acid ester monomer, for example, a (meth)acrylic acid ester 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)acrylic acid ester monomer having a heteroatom in the ester moiety include 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, γ-(methacryloyloxypropyl)trimethoxysilane, an ethylene oxide adduct of (meth)acrylic acid, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethyl ethyl (meth)acrylate, 2-perfluoroethyl ethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutyl ethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, dipentafluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethyl methyl (meth)acrylate, 2-perfluorohexyl ethyl (meth)acrylate, 2-perfluorodecyl ethyl (meth)acrylate, and 2-perfluorohexadecyl ethyl (meth)acrylate.

[0020] Examples of the styrene monomer include styrene, vinyltoluene, α-methylstyrene, chlorostyrene, styrenesulfonic acid, and salts thereof.

[0021] Examples of the nitrile group-containing vinyl monomer include monomers other than acrylonitrile, such as methacrylonitrile.

[0022] Examples of the amide group-containing vinyl monomer include acrylamide and methacrylamide.

[0023] From the viewpoint of high strength, the number of constituent units of the branch polymer (B) is preferably 10 to 400, and more preferably 15 to 150.

[0024] The content of structural units derived from acrylonitrile (b1) in the branch polymer (B) is, from the viewpoint of high strength, 3 mol% to 30 mol%, preferably 4 mol% to 20 mol%, and more preferably 4.5 mol% to 15 mol%, relative to the total structural units in the branch polymer (B). The ratio of molar content of constituent units derived from acrylonitrile (b1) and constituent units derived from other ethylenically unsaturated monomers (b2) in the branched polymer (B) (b1 / b2) is preferably 0.1 / 99.9 or more and 20 / 80 or less, and more preferably 1 / 99 or more and 15 / 85 or less.

[0025] From the viewpoint of high strength, the number-average molecular weight (Mn) of the branched polymer (B) is preferably 1,000 to 50,000, and more preferably 2,000 to 20,000. From the viewpoint of a narrow molecular weight distribution, the ratio of the mass-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the branched polymer (B) is preferably 1.1 to 1.5.

[0026] (Stem polymer (A)) As described above, the core polymer (A) consists of an acrylic resin containing constituent units derived from acrylonitrile (a1) and other ethylenically unsaturated monomers (a2).

[0027] Vinyl acetate is preferred as the other ethylenically unsaturated monomer (a2) that is a constituent material of the core polymer (A).

[0028] From the viewpoint of high strength, the content of the constituent units derived from the above acrylonitrile (a1) is preferably 15% to 85% by mass, and more preferably 30% to 70% by mass, relative to the total graft copolymer (α). From the viewpoint of high strength, the content of the constituent units derived from the above other ethylenically unsaturated monomer (a2) is preferably 15% to 85% by mass, and more preferably 30% to 70% by mass, relative to the total graft copolymer (α). From the viewpoint of high strength, the content of the above branch polymer (B) is preferably 0.5% to 40% by mass, and more preferably 1% to 30% by mass, relative to the total graft copolymer (α).

[0029] The mass-average molecular weight (Mw) of the graft copolymer (α) is preferably 10,000 to 300,000, and more preferably 20,000 to 150,000, from the viewpoint of high strength.

[0030] <Method for producing graft copolymer> The graft copolymer (α) can be produced, for example, by copolymerizing the above-mentioned acrylonitrile (a1) and other ethylenically unsaturated monomers (a2) for preparing the acrylic resin constituting the stem polymer (A), and the macromonomers constituting the branch polymer (B).

[0031] A macromonomer refers to an oligomer molecule having a reactive functional group at the end of a polymer. The macromonomer constituting the branched polymer (B) preferably has at least one polymerizable carbon-carbon double bond group per molecule at the end of a copolymer containing constituent units derived from acrylonitrile (b1) and constituent units derived from other ethylenically unsaturated monomers (b2), as a reactive functional group, selected from the group consisting of, for example, an allyl group, a vinylsilyl group, a vinyl ether group, a dicyclopentadienyl group, and a polymerizable carbon-carbon double bond group represented by the following general formula (1). The macromonomer can usually be produced by radical polymerization. In particular, because of its good reactivity with acrylonitrile (a1) and other ethylenically unsaturated monomers (a2), it is preferable that the reactive functional group in the macromonomer has a polymerizable carbon-carbon double bond represented by the following general formula (1).

[0032] CH2=C(R)-C(O)O- (1) In general formula (1), R represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. Specific examples of R include, for example, preferably -H, -CH3, -CH2CH3, and -(CH2). n The group is selected from the group consisting of CH3 (where n is an integer between 2 and 19), -C6H5, -CH2OH, and -CN, and more preferably from the group consisting of -H and -CH3.

[0033] Copolymers containing the main chain of the above macromonomer, which includes the structural units derived from acrylonitrile (b1) and the structural units derived from other ethylenically unsaturated monomers (b2), are produced by radical polymerization. Radical polymerization can be classified into "general radical polymerization," which simply copolymerizes monomers having specific functional groups with vinyl monomers using azo compounds, peroxides, etc., as polymerization initiators, and "controlled radical polymerization," which makes it possible to introduce specific functional groups at controlled positions such as terminals.

[0034] In "conventional radical polymerization," monomers with specific functional groups are introduced into the polymer only probabilistically. Therefore, to obtain polymers with a high degree of functionalization, a considerable amount of these monomers must be used. Furthermore, because it is free radical polymerization, it has a broad molecular weight distribution, making it difficult to obtain polymers with low viscosity.

[0035] "Controlled radical polymerization" can be further classified into "chain transfer agent methods," which use chain transfer agents with specific functional groups to perform polymerization and obtain vinyl polymers with functional groups at their terminals, and "living radical polymerization methods," which allow polymerization to proceed without termination reactions at the polymerization growth ends, thereby obtaining polymers with molecular weights that are almost as designed.

[0036] The "chain transfer agent method" can yield polymers with a high functionalization rate, but it requires a chain transfer agent with a specific functional group relative to the initiator. Also, similar to the "general radical polymerization method" mentioned above, it is a free radical polymerization method, resulting in a broad molecular weight distribution and making it difficult to obtain polymers with low viscosity.

[0037] Unlike these polymerization methods, the "living radical polymerization method," as described in the international publication WO99 / 65963 relating to the applicant's own invention, is a radical polymerization method that is difficult to control due to its high polymerization rate and susceptibility to termination reactions such as coupling between radicals. However, it is less prone to termination reactions, yields polymers with a narrow molecular weight distribution, for example, a ratio of mass-average molecular weight Mw to number-average molecular weight Mn (Mw / Mn) of about 1.1 to 1.5, and allows for free control of the molecular weight by adjusting the charging ratio of monomer and initiator.

[0038] Therefore, the "living radical polymerization method" is a more preferred polymerization method because it can produce polymers with a narrow molecular weight distribution and low viscosity, and because monomers having specific functional groups can be introduced at almost any position in the polymer.

[0039] Among the "living radical polymerization methods," "atom transfer radical polymerization" (ATRP), which polymerizes vinyl monomers using organic halides or sulfonyl halogenated compounds as initiators and transition metal complexes as catalysts, is even more preferable as a method for producing macromonomers having specific functional groups, in addition to the characteristics of the above-mentioned "living radical polymerization methods," because it has halogens at the terminals that are relatively favorable for functional group transformation reactions, and offers a great degree of freedom in the design of initiators and catalysts. Examples of this atom transfer radical polymerization method include Matyjaszewski et al., Journal of the American Chemical Society (J.Am.Chem.Soc.), 1995, Vol. 117, p. 5614.

[0040] While there are no particular restrictions on which of the above macromonomers can be produced, controlled radical polymerization is usually used, and living radical polymerization is preferred due to its ease of control, with atom transfer radical polymerization being the most preferred method.

[0041] When producing macromonomers for graft copolymers (α) by atom transfer radical polymerization, for example, a homopolymer of acrylonitrile (b1) or a random copolymer using acrylonitrile (b1) and other ethylenically unsaturated monomers (b2) can be prepared, then the other ethylenically unsaturated monomer (b2) is reacted with the ends of the homopolymer or copolymer, and finally, a reactive functional group is introduced to the ends of the resulting polymer.

[0042] As a method for producing the graft copolymer (α), solution polymerization is preferred from the viewpoint of ease of polymerization and mitigation of polymerization exothermic reactions.

[0043] <Acrylic resin composition> In one or more embodiments of the present invention, an acrylic resin composition can be obtained by blending an acrylic resin made of a graft copolymer (α) with a plasticizer compatible with the acrylic resin.

[0044] The plasticizer can be any organic compound that is compatible with acrylic resins and has a boiling point of 200°C or higher, and is not particularly limited. For example, sulfone compounds such as dimethyl sulfone, diethyl sulfone, dipropyl sulfone, dibutyl sulfone, diphenyl sulfone, vinyl sulfone, ethylmethyl sulfone, methylphenyl sulfone, methylvinyl sulfone, and 3-methylsulfolane; sulfoxide compounds such as dipropyl sulfoxide, tetramethylene sulfoxide, diisopropyl sulfoxide, methylphenyl sulfoxide, dibutyl sulfoxide, diisobutyl sulfoxide, di-p-tolyl sulfoxide, diphenyl sulfoxide, and benzyl sulfoxide; lactides such as lactide lactide; lactams such as pyrrolidone, N-vinylpyrrolidone, ε-caprolactam, and N-methylcaprolactam; and lactones such as γ-butyrolactone, γ-hexalactone, γ-heptalactone, γ-octaractone, ε-caprolactone, and ε-octaractone can be used. Furthermore, the plasticizer may be used alone or in combination of two or more types.

[0045] When plasticizers are held at a temperature higher than the melting point of the fibers, they can become liquid and seep out onto the fiber surface, which can reduce the appearance and feel of the fibers. Furthermore, when the fibers return to room temperature (25±5℃), they can solidify, leading to problems such as fiber adhesion. In particular, during overseas transport, the temperature inside the shipping container can rise to 60℃, and during fiber processing, it can reach 90℃ for a short period of time. Therefore, it is preferable, and more preferably, that the melting point of the plasticizer for acrylic resins be 60℃ or higher. For example, it is preferable to use one or more selected from the group consisting of dimethyl sulfone, lactide lactate, and ε-caprolactam, and more preferably to use one or more selected from the group consisting of dimethyl sulfone and lactide lactate.

[0046] From the viewpoint of melt processability, the acrylic resin composition preferably contains 0.1 parts by mass to 50 parts by mass of the plasticizer per 100 parts by mass of the acrylic resin. When the amount of plasticizer is 50 parts by mass or less, the melt processability is good, and the viscosity of the resin during melt kneading is improved, which tends to improve the kneading efficiency.

[0047] The acrylic resin composition may further contain a stabilizer for thermal stability. The stabilizer is not particularly limited as long as it provides thermal stability. From the viewpoint of improving melt processability, suppressing discoloration, and ensuring transparency, the stabilizer is preferably at least one stabilizer selected from the group consisting of epoxy-based thermal stabilizers, hydrotalcite-based thermal stabilizers, tin-based thermal stabilizers, Ca-Zn-based thermal stabilizers, and β-diketone-based thermal stabilizers. The stabilizer may be used alone or in combination of two or more types.

[0048] The acrylic resin composition preferably contains 0.1 to 30 parts by mass of stabilizer per 100 parts by mass of acrylic resin, more preferably 0.2 to 20 parts by mass, and even more preferably 0.5 to 10 parts by mass. A concentration of 0.1 parts by mass or more provides good color suppression. A concentration of 30 parts by mass or less provides good color suppression, ensures transparency, and minimizes the deterioration of the mechanical properties of the acrylic resin molded article.

[0049] The acrylic resin composition may contain a lubricant, to the extent that it does not impair the objectives of the present invention, from the viewpoint of reducing friction between the acrylic resin and the processing machine, reducing heat generation due to shear, and improving fluidity and mold release properties. Examples of lubricants that can be used include fatty acid ester lubricants such as monoglyceride stearate and stearyl stearate, hydrocarbon lubricants such as liquid paraffin, paraffin wax, and synthetic polyethylene wax, fatty acid lubricants such as stearic acid, higher alcohol lubricants such as stearyl alcohol, aliphatic amide lubricants such as stearamide, oleamide, and erucamide, alkylene fatty acid amide lubricants such as methylenebisstearate and ethylenebisstearate, and metal soap lubricants such as lead stearate, zinc stearate, calcium stearate, and magnesium stearate. These may be used individually or in combination of two or more. The amount of lubricant added should be 10 parts by mass or less per 100 parts by mass of acrylic resin.

[0050] The acrylic resin composition may contain processing aids such as modacrylic processing aids, to the extent that it does not impair the objectives of the present invention. When the acrylic resin composition is used to construct fibers, it is preferable to include a (meth)acrylate polymer and / or styrene-acrylonitrile copolymer as processing aids from the viewpoint of improving spinnability. As the (meth)acrylate polymer, copolymers of (meth)acrylate and copolymer components such as butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, styrene, vinyl acetate, and acrylonitrile can be used. As the (meth)acrylate polymer, commercially available products such as Kaneka's "KaneAce PA20" and "KaneAce PA101" can be used. The amount of processing aid added can be 10 parts by mass or less per 100 parts by mass of acrylic resin.

[0051] The acrylic resin composition can be used in a molten state, i.e., as a molten product. A molten product can be obtained by melt-kneading the above-mentioned acrylic resin composition. The method of melt-kneading is not particularly limited, and a general method for melt-kneading resin compositions can be used.

[0052] A molded article can be obtained by processing the acrylic resin composition obtained above into a predetermined shape. The molding method is not particularly limited and includes extrusion molding, injection molding, insert molding, sandwich molding, foam molding, press molding, blow molding, calendering, rotational molding, slush molding, dip molding, and cast molding. Examples of molded articles include films, plates, fibers, extruded articles, and injection-molded articles. The molded article may be a foam or a porous material. In the present invention, "film" refers to a thin film with a thickness of 200 μm or less that is flexible, and "plate" refers to a thin film or plate with a thickness exceeding 200 μm that is not flexible.

[0053] Acrylic fibers can be constructed from acrylic resin compositions. Specifically, acrylic fibers can be obtained by melt spinning the above-mentioned acrylic resin composition (for example, a pelletized acrylic resin composition after melt kneading). First, the acrylic resin composition is melt-spun to form fibrous, undrawn yarn. Specifically, the melt-kneaded acrylic resin composition (pelletized acrylic resin composition) obtained by melt-kneading in an extruder, such as a single-screw extruder, an asymmetrical twin-screw extruder, or a conical twin-screw extruder, is discharged from a spinning nozzle in the extruder, passed through a heating cylinder to raise the temperature above a temperature at which the fibrous acrylic resin composition can be taken up by a taker, and then taken up while cooling to a temperature below the glass transition point by means of air cooling, etc., to form fibrous yarn. The extruder is preferably operated in a temperature range of 120°C to 200°C. The take-up speed / discharge speed ratio is not particularly limited, but it is preferable to take up at a speed ratio in the range of 1 to 100 times, and more preferably in the range of 5 to 50 times from the viewpoint of spinning stability. The diameter of the spinning nozzle is not particularly limited, but it is preferable to be 0.05 mm to 2 mm, and more preferably 0.1 mm to 1 mm. It is preferable to extrude the material discharged from the spinning nozzle at a nozzle temperature above which melt fracture does not occur. The spinning nozzle temperature is preferably 160°C or higher, and more preferably 170°C or higher. The heating cylinder temperature is preferably 200°C or higher, and more preferably 230°C or higher. The cooling temperature is preferably -196°C to 40°C for air cooling, more preferably 0°C to 30°C, and preferably 5°C to 60°C for water cooling, and more preferably 10°C to 40°C.

[0054] The undrawn yarn obtained above can be subjected to a drawing treatment by known methods, and, if necessary, a heat relaxation treatment. For example, when used as artificial hair, it is preferable to have fibers with a single fiber fineness of 2 dtex or more and 100 dtex or less. The drawing treatment conditions are preferably a dry heat atmosphere with a drawing treatment temperature of 70°C to 150°C, and a drawing ratio of approximately 1.1 to 6 times, and more preferably 1.5 to 4.5 times. By applying a heat relaxation treatment to the drawn fibers, preferably with a relaxation rate of 1% to 50%, more preferably 5% to 40%, the thermal shrinkage rate can be reduced. Heat relaxation treatment is also preferable to smooth the surface irregularities of the fibers and give them a smooth texture similar to human hair. Furthermore, it is possible to control the fineness by washing the undrawn or drawn yarn with water. [Examples]

[0055] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0056] First, we will explain the various measurement and evaluation methods. (1) Mass-average molecular weight and number-average molecular weight The measurements and calculations were performed using gel permeation chromatography (HLC-8320GPC, manufactured by Tosoh Corporation). (2) Storage modulus G' Using a dynamic viscoelasticity analyzer (TA Instruments' "ARES-G2"), the storage modulus G' at an angular frequency of 1 rad / s was measured for the graft copolymers obtained in each example and comparative example at 60°C and 120°C. The measurement conditions were as follows. • Mode: Twist Mode • Plate diameter: 8mmφ • Distortion: 0.01% (25℃) (3) Glass transition temperature Using a differential scanning calorimeter (SEIKO INSTRUMENTS' "DSC-6100"), the graft copolymers obtained in each example and comparative example were measured by raising the temperature from -80°C to 160°C at 20°C / min, then lowering the temperature back down to -80°C at 20°C / min to eliminate the thermal history, and finally raising the temperature again from -80°C to 160°C at 10°C / min.

[0057] [Production of macromonomers] (Manufacturing Example 1) In a reaction vessel, 2.1 parts by mass of acrylonitrile, 17.9 parts by mass of 2-methoxyethyl acrylate, 12 parts by mass of methanol (MeOH), 3.43 parts by mass of ethyl 2-bromobutyrate, and 0.18 parts by mass of triethylamine were charged, and the charged raw materials were stirred under a nitrogen atmosphere at 40°C. Next, 0.0197 parts by mass of copper(II) bromide (CuBr2) was dissolved in 8 parts by mass of methanol, and this was added to 0.0203 parts by mass of hexamethyltris(2-aminoethyl)amine (Me6TREN). This mixture was then added to the reaction system, and the raw materials in the reaction system were mixed. Furthermore, 0.031 parts by mass of ascorbic acid and 0.036 parts by mass of triethylamine were dissolved in 3.0 parts by mass of methanol, and the resulting ascorbic acid solution was added dropwise to the reaction system to start polymerization. During polymerization, the reaction solution was heated and stirred while adjusting the dropping rate of the ascorbic acid solution to maintain the temperature of the reaction solution at 40-60°C. 240 minutes after the start of the dropwise addition of ascorbic acid solution, when the monomer consumption rate in the reaction vessel reached 70% (total monomer consumption rate 14%), 80 parts by mass of 2-methoxyethyl acrylate were added dropwise to the reaction system over 75 minutes. Thereafter, heating and stirring of the reaction solution were continued while adjusting the dropwise addition rate of the ascorbic acid solution to maintain the temperature of the reaction vessel at 40°C to 60°C. 435 minutes after the start of the dropwise addition of ascorbic acid solution, when the monomer consumption rate in the reaction vessel reached 92%, the dropwise addition of ascorbic acid was stopped to terminate the reaction. The resulting reaction product was diluted with toluene, passed through an activated alumina column, and then the volatile components were removed by vacuum distillation to obtain one-terminated Br group polymer 1.

[0058] 100 parts by mass of one-terminated Br group polymer 1 was charged into a flask, diluted with 100 parts by mass of dimethylacetamide, and 3.9 parts by mass of potassium acrylate was added. The mixture was heated and stirred at 70°C for 3 hours. After that, dimethylacetamide was removed from the reaction mixture by distillation, the reaction mixture was dissolved in toluene, passed through an activated alumina column, and then the toluene was removed by distillation to obtain one-terminated acryloyl group macromonomer 1, in which the constituent units derived from acrylonitrile were predominantly contained on the side opposite to the acryloyl group end. The number-average molecular weight of the obtained one-terminated acryloyl group macromonomer 1 was 6000, and the molecular weight distribution (mass-average molecular weight / number-average molecular weight) was 1.2. The one-terminated acryloyl group macromonomer 1 includes the end opposite to the acryloyl group end, and the terminal region containing half the total number of constituent units in the one-terminated acryloyl group macromonomer 1 contains 90 mol% of the total constituent units derived from acrylonitrile.

[0059] (Manufacturing example 2) In a reaction vessel, 4.3 parts by mass of acrylonitrile, 15.7 parts by mass of 2-methoxyethyl acrylate, 12 parts by mass of methanol (MeOH), 3.54 parts by mass of ethyl 2-bromobutyrate, and 0.18 parts by mass of triethylamine were charged, and the charged raw materials were stirred under a nitrogen atmosphere at 40°C. Subsequently, 0.0203 parts by mass of copper(II) bromide (CuBr2) was dissolved in 8 parts by mass of methanol, and this was added to 0.0209 parts by mass of hexamethyltris(2-aminoethyl)amine (Me6TREN). This mixture was then added to the reaction system, and the raw materials in the reaction system were mixed. Furthermore, 0.799 parts by mass of ascorbic acid and 0.918 parts by mass of triethylamine were dissolved in 14.3 parts by mass of methanol, and the resulting ascorbic acid solution was added dropwise to the reaction system to initiate polymerization. During polymerization, the reaction solution was heated and stirred while adjusting the rate of dropping of the ascorbic acid solution to maintain a reaction solution temperature of 40-60°C. 240 minutes after the start of dropping of the ascorbic acid solution, when the monomer consumption rate in the reaction vessel reached 89% (total monomer consumption rate 18%), 80 parts by mass of 2-methoxyethyl acrylate were added dropwise to the reaction system over 75 minutes. Thereafter, the reaction solution was heated and stirred while adjusting the rate of dropping of the ascorbic acid solution to maintain a reaction vessel temperature of 40-60°C. 410 minutes after the start of dropping of the ascorbic acid solution, when the monomer consumption rate in the reaction vessel reached 96%, the dropping of ascorbic acid was stopped and the reaction was terminated. The obtained reaction product was diluted with toluene, passed through an activated alumina column, and then the volatile components were removed by vacuum distillation to obtain one-terminated Br group polymer 2.

[0060] The obtained single-ended Br group polymer 2 was converted to a single-ended acryloyl group in the same manner as in Production Example 1, to obtain single-ended acryloyl group macromonomer 2, in which the constituent units derived from acrylonitrile are predominantly contained on the side opposite to the acryloyl group end. The number-average molecular weight of the obtained single-ended acryloyl group macromonomer 2 was 6000, and the molecular weight distribution (mass-average molecular weight / number-average molecular weight) was 1.2. In addition, single-ended acryloyl group macromonomer 2 contains the end opposite to the acryloyl group end, and the terminal region containing half the total number of constituent units in single-ended acryloyl group macromonomer 2 contains 90 mol% of the total constituent units derived from acrylonitrile.

[0061] (Manufacturing Example 3) In a reaction vessel, 40 parts by mass of 2-methoxyethyl acrylate, 12 parts by mass of methanol (MeOH), 3.33 parts by mass of ethyl 2-bromobutyrate, and 0.18 parts by mass of triethylamine were charged, and the charged raw materials were stirred under a nitrogen atmosphere at 40°C. Subsequently, 0.0191 parts by mass of copper(II) bromide (CuBr2) was dissolved in 8 parts by mass of methanol, and this was added to 0.0197 parts by mass of hexamethyltris(2-aminoethyl)amine (Me6TREN). This mixture was then added to the reaction system, and the raw materials in the reaction system were mixed. Furthermore, 0.015 parts by mass of ascorbic acid and 0.017 parts by mass of triethylamine were prepared with 3.0 parts by mass of methanol, and the resulting ascorbic acid solution was added dropwise to the reaction system to start polymerization. During polymerization, the reaction solution was heated and stirred while adjusting the dropping rate of the ascorbic acid solution to maintain the temperature of the reaction solution at 40-60°C. Sixty minutes after the start of the dropwise addition of ascorbic acid solution, when the monomer consumption rate in the reaction vessel reached 37% (total monomer consumption rate 15%), 60 parts by mass of 2-methoxyethyl acrylate were added dropwise to the reaction system over 60 minutes. Thereafter, the reaction solution was heated and stirred while adjusting the dropwise addition rate of the ascorbic acid solution to maintain the temperature of the reaction vessel at 40°C to 60°C. Three hundred minutes after the start of the dropwise addition of ascorbic acid solution, the monomer consumption rate in the reaction vessel reached 95%, and the dropwise addition of ascorbic acid was stopped to terminate the reaction. The resulting reaction product was diluted with toluene, passed through an activated alumina column, and then the volatile components were removed by vacuum distillation to obtain one-terminated Br group polymer 3.

[0062] The obtained single-ended Br group polymer 3 was converted to a single-ended acryloyl group in the same manner as in Production Example 1 to obtain a single-ended acryloyl group macromonomer 3 that does not contain any constituent units derived from acrylonitrile. The number-average molecular weight of the obtained single-ended acryloyl group macromonomer 3 was 6000, and the molecular weight distribution (mass-average molecular weight / number-average molecular weight) was 1.2.

[0063] [Fabrication of graft copolymers] (Example 1) In a polymerization reactor, 66.5 parts by mass of vinyl acetate, 6.7 parts by mass of acrylonitrile, 5 parts by mass of the terminally acryloyl group macromonomer 1 obtained in Production Example 1, 40 parts by mass of dimethylacetamide, and 1.35 parts by mass of 2,2'-azobis(2-methylbutyllonitrile) were charged and stirred under a nitrogen atmosphere for 15 minutes. Then, the polymerization reactor was raised to 70°C and polymerization was started. 30 minutes after the start of heating, 26.8 parts of acrylonitrile were added continuously at a constant rate for 7 hours. Solution polymerization was carried out until 30 minutes after the end of acrylonitrile addition (8 hours after the start of heating). The obtained polymer was dried in a hot air dryer at 50°C for 3 hours, and then dried in a vacuum dryer at 120°C for 12 hours to obtain graft copolymer 1. The obtained graft copolymer 1 consisted of 57.0% by mass of constituent units derived from vinyl acetate, 37.4% by mass of constituent units derived from acrylonitrile, and 5.7% by mass of constituent units derived from one-terminated macromonomers, with a mass-average molecular weight of approximately 31,000.

[0064] (Example 2) Graft copolymer 2 was obtained in the same manner as in Example 1, except that the monocarpone macromonomer 2 obtained in Production Example 2 was used instead of the monocarpone macromonomer 1 obtained in Production Example 1. The obtained graft copolymer 2 consisted of 58.2% by mass of vinyl acetate-derived constituent units, 36.1% by mass of acrylonitrile-derived constituent units, and 5.7% by mass of monocarpone-derived constituent units, with a mass-average molecular weight of approximately 31,000.

[0065] (Comparative Example 1) Graft copolymer 3 was obtained in the same manner as in Example 1, except that the monocarpone macromonomer 3 obtained in Production Example 3 was used instead of the monocarpone macromonomer 1 obtained in Production Example 1. The obtained graft copolymer 3 consisted of 59.3% by mass of constituent units derived from vinyl acetate, 35.2% by mass of constituent units derived from acrylonitrile, and 5.6% by mass of constituent units derived from the monocarpone macromonomer, with a mass-average molecular weight of approximately 30,000.

[0066] The storage modulus of the graft copolymers obtained in Examples 1 and 2 and Comparative Example 1 was evaluated as described above, and the results are shown in Table 1 below. In Table 1, "AN" refers to acrylonitrile.

[0067] [Table 1]

[0068] The results in Table 1 show that, compared to the graft copolymer of Comparative Example 1, in which acrylonitrile was introduced into the branch polymer, the graft copolymers of Examples 1 and 2, in which acrylonitrile was introduced into regions far from the stem polymer, showed improved storage modulus at 60°C and higher strength. These experimental results demonstrate that by introducing acrylonitrile into branch polymers in a block-like manner, it is possible to impart different properties, such as increased strength, depending on the location.

Claims

1. A stem polymer (A) made of an acrylic resin containing structural units derived from acrylonitrile (a1) and structural units derived from other ethylenically unsaturated monomers (a2), A branched polymer (B) comprising a polymer containing structural units derived from acrylonitrile (b1) and structural units derived from other ethylenically unsaturated monomers (b2), The branch polymer (B) has a first end and a second end, and is grafted onto the stem polymer (A) at the second end, and is a graft copolymer. The branch polymer (B) includes the first end, and the end region containing half the total number of constituent units in the branch polymer (B) contains 70 mol% or more of the total constituent units derived from the acrylonitrile (b1). A graft copolymer in which the content of constituent units derived from acrylonitrile (b1) is 3 mol% or more and 30 mol% or less relative to the total constituent units in the branch polymer (B).

2. The graft copolymer according to claim 1, wherein the other ethylenically unsaturated monomer (a2) is vinyl acetate.

3. The aforementioned other ethylenically unsaturated monomer (b2) is one or more selected from the group consisting of (meth)acrylic acid ester monomers, styrene monomers, nitrile group-containing vinyl monomers, and amide group-containing vinyl monomers. The graft copolymer according to claim 1 or 2, wherein the nitrile group-containing vinyl monomer is a monomer other than acrylonitrile.

4. The graft copolymer according to any one of claims 1 to 3, wherein the number average molecular weight of the branch polymer (B) is 1,000 or more and 50,000 or less.

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