Method for manufacturing polyester resin fibers

Abstract

To provide a method for producing polyester resin fibers using a resin composition obtained with a modifier. [Solution] A method for producing polyester resin fibers, comprising: step 1, melt-kneading a polyester resin and a modifier to obtain a polyester resin composition; and step 2, winding the polyester resin composition obtained in step 1 at a winding speed of 400 m / min or more.

Description

Technical Field

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

Background Art

[0002] Each time a polyester resin is processed (for example, melt-mixed, etc.), it may deteriorate due to, for example, heat, etc., such that the molecular chains of the resin become shorter, etc., and the physical properties may decrease. The resin with decreased physical properties has limitations in processing applications or cannot be processed as compared with the resin before processing.

[0003] As a technique for improving the melt viscosity of a polyester resin decreased by processing, a technique of melt-kneading a polyester resin with a chain extender (which may also be referred to as a "viscosity improver" or "Melt viscosity improver: MVI") is known (for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the production of polyester resin fibers using a polyester resin composition obtained by using a conventional chain extender (modifier), there were cases where the resin composition could not be wound at high speed (for example, at a speed of 400 m / min or more). That is, the conventional technology was not sufficient from the viewpoint of productivity and there was room for further improvement.

[0006] One embodiment of the present invention has been made in view of the above-mentioned problems, and its purpose is to provide a novel method for producing polyester resin fibers that enables the production of polyester resin fibers with high productivity even when a modifier is used. [Means for solving the problem]

[0007] The inventors of this invention have diligently studied and conducted research to solve the aforementioned problems, and as a result, have completed this invention.

[0008] In other words, one embodiment of the present invention includes the following configuration. [1] A method for producing polyester resin fibers, comprising: step 1, melt-kneading a polyester resin and a modifier to obtain a polyester resin composition; and step 2, winding the polyester resin composition obtained in step 1 at a winding speed of 400 m / min or more. [2] The method for producing polyester resin fibers according to [1], further comprising a stretching step of stretching the polyester resin fibers obtained in step 2. [3] A method for producing polyester resin fibers according to [1] or [2], wherein the polyester resin is polyethylene terephthalate (PET). [4] A method for producing polyester resin fibers according to any one of [1] to [3], wherein the modifier comprises a polymer (A) containing a reactive functional group-containing unit and a reactive functional group-free unit. [5] The method for producing polyester resin fibers according to [4], wherein the modifier further comprises polymer (B). [6] The method for producing polyester resin fibers according to [5], wherein the epoxy equivalent of the polymer (B) is 6,000 g / eq to 50,000 g / eq. [7] The method for producing polyester resin fibers according to [5] or [6], wherein the polymer (B) contains more than 2.5% by weight and 10.0% by weight or less of reactive functional group-containing units in 100% by weight of the polymer (B). [8] The method for producing polyester resin fibers according to [7], wherein the polymer (B) contains a glycidyl methacrylate unit as the reactive functional group-containing unit. [9] A method for producing polyester resin fibers according to any one of [5] to [8], wherein the modifier contains 15% to 70% by weight of polymer (A) and 30% to 85% by weight of polymer (B) in 100% by weight of the modifier.

[10] A method for producing polyester resin fibers according to any one of [5] to [9], wherein the modifier contains 50% to 90% by weight of polymer (A) and 10% to 50% by weight of polymer (B) in 100% by weight of the modifier.

[11] The polymer (A) has an average of 2 to 10 reactive functional groups per molecule, a method for producing polyester resin fibers according to any one of [4] to

[10] .

[12] A method for producing polyester resin fibers according to any one of [1] to

[11] , wherein the weight-average molecular weight of the modifier is 20,000 Da or more and less than 200,000 Da.

[13] A method for producing polyester resin fibers according to any one of [4] to

[12] , wherein the number average molecular weight of the polymer (A) is less than 10,000 Da.

[14] A method for producing polyester resin fibers according to any one of [4] to

[13] , wherein the polydispersity index of the polymer (A) is 2.0 to 10.0.

[15] The polymer (A) is (i) The reactive functional group containing unit includes an epoxy group containing (meth)acrylate unit, (ii) A method for producing polyester resin fibers according to any one of [4] to

[14] , wherein the reactive functional group-free unit comprises one or more constituent units selected from the group consisting of reactive functional group-free styrene units and reactive functional group-free (meth)acrylic units.

[16] The method for producing polyester resin fibers according to any one of [5] to [9], wherein the polymer (B) comprises one or more constituent units selected from the group consisting of styrene units and (meth)acrylic units.

[17] A method for producing polyester resin fibers according to any one of [5] to [9], wherein the weight-average molecular weight of the polymer (B) is 80,000 Da to 500,000 Da.

[18] A method for producing polyester resin fibers according to any one of [1] to

[17] , wherein the modifier has a reactive functional group-containing monomer residue of less than 50 ppm and a total monomer residue of less than 100 ppm, based on the weight of the modifier. [Effects of the Invention]

[0009] According to one embodiment of the present invention, it is possible to provide a method for producing polyester resin fibers that enables the production of polyester resin fibers with high productivity, even when a modifier is used. [Modes for carrying out the invention]

[0010] One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic and patent documents mentioned herein are incorporated herein by reference. Furthermore, unless otherwise specified herein, "A to B" representing a numerical range means "A or greater (including A and greater than A) and B or less (including B and less than B)."

[0011] Unless otherwise specified in this specification, constituent units contained in polymers, copolymers, or resins are referred to as "constituent units derived from X monomers," "constituent units derived from X compounds," or "constituent units derived from X acids," as "X units."

[0012] [1. Method for manufacturing polyester resin fibers] The method for producing a polyester resin fiber according to an embodiment of the present invention includes Step 1 of melt-kneading a polyester resin and a modifier to obtain a polyester resin composition, and Step 2 of winding up the polyester resin composition obtained in Step 1 at a winding-up speed of 400 m / min or more.

[0013] In this specification, the "polyester resin composition" may be referred to as the "resin composition", the "method for producing a polyester resin fiber" may be referred to as the "production method", and the "method for producing a polyester resin fiber according to an embodiment of the present invention" may be referred to as the "present production method".

[0014] Since the present production method has the above-described configuration, even when a modifier is used, it has the advantage that polyester resin fibers can be produced with high productivity. Further, in a preferred embodiment of the present invention, the present production method has the advantage that it can provide polyester resin fibers having physical properties (such as heat shrinkage rate, maximum elongation, breaking elongation, and Young's modulus, etc.) equivalent to those of polyester resin fibers obtained using virgin polyester resins.

[0015] Hereinafter, first, raw materials (such as polyester resins and modifiers) will be described, and then specific steps will be described.

[0016] [Polyester resin] The polyester resin used in the present production method is not particularly limited, and may be, for example, a polyester resin commonly used as a raw material for polyester resin fibers.

[0017] The polyester resin may be an aromatic polyester having a structure in which an aromatic dicarboxylic acid or its ester derivative component and a diol component such as an aliphatic diol or an alicyclic diol are linked by an ester reaction. The polyester resin may be obtained by polycondensing an aromatic dicarboxylic acid or its ester derivative component and a diol component such as an aliphatic diol or an alicyclic diol by a known method.

[0018] Aromatic dicarboxylic acids are not particularly limited, but examples include phthalic acid, terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-diphenylethercarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 4,4'-diphenylisopropylidenedicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, bis(4,4-carboxyphenyl)methane, anthracenedicarboxylic acid (e.g., 2,5-anthracenedicarboxylic acid, 2,6-anthracenedicarboxylic acid, etc.), 4,4'-p-ta-phenylenedicarboxylic acid, and 2,5-pyridinedicarboxylic acid. As the aromatic dicarboxylic acid, only one type may be used, or two or more types may be used in combination.

[0019] Aliphatic diols are not particularly limited, but examples include ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, 2-methyl-1,3-propanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, bisphenol A ethylene oxide adduct diol, polyethylene oxide glycol, and polypropylene oxide glycol. Alicyclic diols are not particularly limited, but examples include 1,4-cyclohexanedimethanol, 4,4-dicyclohexylhydroxymethane, and 4,4'-dicyclohexylhydroxypropane. Only one type of diol component may be used, or two or more types may be used in combination.

[0020] The polyester resin may be a polymer formed by copolymerizing an aromatic dicarboxylic acid or its ester derivative component as the main component, an aliphatic diol, and another dicarboxylic acid or its ester derivative component or another diol. The other dicarboxylic acid is not particularly limited, but examples include alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 4,4'-dicyclohexyldicarboxylic acid.

[0021] The polyester resin may have structural components derived from trifunctional or more monomers such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, and pyromellitic acid.

[0022] While there are no particular limitations on specific examples of polyester resins, examples include polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polybutylene naphthalate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-1,2-bis(phenoxy)ethane-4,4'-dicarboxylate, polyethylene isophthalate / terephthalate, polybutylene terephthalate / isophthalate, polybutylene terephthalate / decanedicarboxylate, polycyclohexanedimethylene terephthalate / isophthalate, polyester / polyether, and glycol-modified polyethylene terephthalate. Glycol-modified polyethylene terephthalate refers to a copolymer of terephthalic acid, ethylene glycol, and a glycol component other than ethylene glycol.

[0023] From the viewpoint of moldability and mechanical properties, the polyester resin preferably contains (i) one or more selected from the group consisting of polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polybutylene naphthalate, poly-1,4-cyclohexylenemethylene terephthalate, and polyester / polyether, and may consist only of one or more selected from this group; and (ii) it is more preferably to contain one or more selected from the group consisting of polyethylene terephthalate and polybutylene terephthalate, and may consist only of one or more selected from this group.

[0024] As the polyester resin, a polymer alloy obtained from a mixture of multiple polymers including the polyester resin may be used. Examples of polymer alloys include polycarbonate / polyethylene terephthalate, polyethylene terephthalate / glycol-modified polyethylene terephthalate, and polyethylene terephthalate / copolymerized polyethylene terephthalate. In other words, the polyester resin may contain one or more selected from the group consisting of polycarbonate / polyethylene terephthalate, polyethylene terephthalate / glycol-modified polyethylene terephthalate, and polyethylene terephthalate / copolymerized polyethylene terephthalate, or may consist only of one or more selected from the group. Note that copolymerized polyethylene terephthalate refers to a resin in which a component other than the two components constituting polyethylene terephthalate (a third component) is copolymerized.

[0025] The polyester resin may contain recycled polyester resin, or it may consist solely of recycled polyester resin. If the polyester resin contains recycled polyester resin, this manufacturing method can also be called a "method for manufacturing recycled polyester resin fibers," and the polyester resin fibers obtained by this manufacturing method can also be called "recycled polyester resin fibers."

[0026] In this specification, "recycled polyester resin" refers to polyester resins and / or polyester resin compositions obtained by recycling the following (Ai) and / or (Aii): (Ai) Polyester resin, polyester resin composition, and / or polyester resin molded articles that have been used and / or discarded after being commercialized as polyester resin, polyester resin composition, and / or polyester resin molded articles; (Aii) Polyester resins, polyester resin compositions, and / or polyester resin molded articles that are discharged and discarded during the manufacturing process of polyester resins, polyester resin compositions, and / or polyester resin molded articles.

[0027] The aforementioned recycling method can be any known recycling method, and is not particularly limited; for example, material recycling can be used.

[0028] Here, the required melt viscosity (IV value) of polyester resins used as raw materials for molded products such as fibers may vary depending on the type of molded product. This is because (i) the molding method differs depending on the type of molded product, and the melt viscosity required for such molding differs, or / or (ii) the strength required for the specifications of the molded product (product) differs depending on the type of molded product. For example, polyester resins used as raw materials for PET bottles require a relatively high melt viscosity. Also, polyester resins used as raw materials for sheets and films require a relatively high melt viscosity, although lower than that of polyester resins used for PET bottles. On the other hand, polyester resins used as raw materials for fibers do not require a relatively high melt viscosity, but a certain melt viscosity (e.g., 0.50 to 0.75) is required.

[0029] Typically, during the recycling process, water is added to the resin (resin composition) and / or the resin (resin composition) is heated (melt-kneaded). As a result of the addition of water and / or heating, recycled polyester resins tend to have a lower molecular weight than the polyester resins constituting the polyester resins, polyester resin compositions, and / or molded articles shown in (Ai) and / or (Aii) above, and the melt viscosity also tends to decrease along with the decrease in molecular weight. Furthermore, the polyester resins constituting the polyester resin compositions and / or molded articles also tend to have a lower molecular weight due to the passage of time and heating during use, and the melt viscosity also tends to decrease along with the decrease in molecular weight. Therefore, conventionally, recycled polyester resins were often used in applications requiring a lower melt viscosity than the original polyester resins. For example, recycled polyester resins obtained from PET bottles were often used in sheet, film, or fiber applications, and recycled polyester resins obtained from sheets and / or films were often used in fiber applications. In other words, conventionally, large quantities of recycled polyester resins were distributed for fiber applications where relatively low melt viscosity was acceptable.

[0030] However, in recent years, the demand for horizontal recycling, such as recycling PET bottles into PET bottles or sheets and / or films into sheets and / or films, has increased, leading to a decrease in the volume of recycled polyester resins used for textile applications. Consequently, in the field of resin fibers, there has been a growing demand for horizontal recycling from polyester resin fibers to polyester resin fibers. As mentioned above, recycled polyester resins obtained by recycling polyester resin fibers tend to have a lower melt viscosity (e.g., 0.45 to 0.70) than the polyester resin that was the raw material for the polyester resin fibers (e.g., 0.50 to 0.75). Therefore, it has sometimes been difficult to manufacture polyester resin fibers using recycled polyester resin obtained by recycling polyester resin fibers as a raw material.

[0031] When using recycled polyester resins, techniques for improving the melt viscosity of a resin composition containing recycled polyester resin to a certain extent by adding a viscosity modifier to the recycled polyester resin were known (for example, Patent Documents 1-3). However, when the present inventors attempted to manufacture polyester resin fibers using conventional resin compositions containing viscosity modifiers, they independently discovered a problem in which the molten mixture of the resin composition could not be wound at high speed (for example, at a speed of 400 m / min or more). In other words, conventional resin compositions obtained by melt-mixing viscosity modifiers and recycled polyester resins tended not to produce polyester resin fibers with high productivity.

[0032] However, the modifier used in this manufacturing method (in other words, the modifier according to one embodiment of the present invention) has the advantage of improving the melt viscosity of the recycled polyester resin by melt kneading with the recycled polyester resin, thereby providing a resin composition with high melt viscosity, and also enabling high-speed winding (for example, at a speed of 400 m / min or more) of the resulting resin composition. Furthermore, the resin composition obtained by mixing the modifier according to one embodiment of the present invention with the recycled polyester resin has the surprising advantage of being reusable, especially as long fibers (filament fibers). Therefore, even when using recycled polyester resin, especially recycled polyester resin obtained by recycling polyester resin fibers, as the polyester resin, this manufacturing method can provide polyester resin fibers (especially long fibers) with good productivity. In other words, this manufacturing method has the advantage of enabling horizontal recycling. Therefore, the polyester resin that is the raw material for this manufacturing method may be derived from discarded polyester resin fibers. That is, the polyester resin compositions in (Ai) and (Aii) above may be polyester resin compositions for polyester resin fibers, and the polyester resin molded articles may be polyester resin fibers.

[0033] When the polyester resin includes recycled polyester resin, one embodiment of the present invention can significantly reduce the amount of plastic waste generated and the amount of plastic used in its manufacture. As a result, one embodiment of the present invention can contribute to achieving Sustainable Development Goals (SDGs), such as Goal 12, "Ensure sustainable consumption and production patterns."

[0034] In this specification, polyester resins that have never been commercialized may be referred to as "virgin polyester resins." In this specification, "recycled polyester resins" also include mixtures obtained by mixing "virgin polyester resins" with recycled polyester resins.

[0035] As described above, in step 1 of this manufacturing method, a resin composition having a higher melt viscosity than the polyester resin used as the raw material can be obtained. Therefore, this manufacturing method can, as a result, provide polyester resin fibers having physical properties (e.g., heat shrinkage rate, maximum elongation, elongation at break, and Young's modulus) equivalent to those of polyester resin fibers obtained using virgin polyester resin. In other words, one embodiment of the present invention can be suitably used for horizontal recycling from polyester resin fibers to polyester resin fibers. In this manufacturing method, it is preferable to use a polyester resin as a raw material that has a melt viscosity lower than the melt viscosity required for the polyester resin used as the raw material for polyester resin fibers, such as a polyester resin obtained by recycling discarded polyester resin fibers (recycled polyester resin). The melt viscosity (IV value) of the polyester resin used in this manufacturing method varies depending on the fiber production conditions and application, but is generally preferably 0.45 to 0.75, more preferably 0.50 to 0.75, even more preferably 0.55 to 0.75, even more preferably 0.60 to 0.75, and particularly preferably 0.60 to 0.70.

[0036] The melt viscosity of a resin or resin composition may have a negative correlation with the melt flow rate (MFR) of the resin or resin composition. The MFR of the polyester resin used in this manufacturing method, measured at a temperature of 270°C and a load of 2.16 kgf, is preferably 10 g / 10 min to 120 g / 10 min, more preferably 20 g / 10 min to 100 g / 10 min, even more preferably 35 g / 10 min to 90 g / 10 min, even more preferably 40 g / 10 min to 80 g / 10 min, and particularly preferably 45 g / 10 min to 70 g / 10 min. In this specification, the MFR of the resin or resin composition shall be the value obtained by the method described in the later examples.

[0037] [Modifier] The modifier used in this manufacturing method is not particularly limited, as long as it is an agent that can change the physical properties of the raw material polyester resin (for example, improve the melt viscosity). In other words, the modifier used in this manufacturing method is not particularly limited, as long as it is an agent that can be used in step 1 to obtain a polyester resin composition having different physical properties from the raw material polyester resin (for example, a higher melt viscosity than the raw material polyester resin). In this specification, "melt viscosity of polyester resin" and "melt viscosity of polyester resin composition" refer to the values ​​obtained by the method described in the following examples.

[0038] (Polymer (A)) The modifier preferably comprises a polymer (A) containing reactive functional group-containing units and reactive functional group-free units.

[0039] (Units containing reactive functional groups) In this specification, "reactive functional group" means a functional group that can react with terminal functional groups of polyester resins. In this specification, "reactive functional group-containing unit" means a constituent unit having a reactive functional group, and is a constituent unit derived from a monomer having a reactive functional group (hereinafter sometimes referred to as "reactive functional group-containing monomer").

[0040] In step 1 of this manufacturing method, the polyester resin and the modifier are melt-kneaded. During this melt-kneading process, it is presumed that the reactive functional groups (e.g., epoxy groups) of the reactive functional group-containing units in polymer (A) contained in the modifier react with the terminal functional groups (e.g., hydroxyl groups or carboxyl groups) of the polyester resin, and that this reaction elongates the molecular chains of the polyester resin. In other words, polymer (A) contained in the modifier may have the function of elongating the molecular chains of the polyester resin, or to put it another way, polymer (A) contained in the modifier may function as a chain extender (or viscosity modifier) ​​for the polyester resin. Furthermore, it is presumed that by including the polymer (A) described above in the modifier, in step 1, more specifically during the melt-kneading of the modifier and the polyester resin, the modifier and the polyester resin are mixed more uniformly, i.e., the dispersibility of the modifier is improved. As a result of improving the dispersibility of the modifiers and extending the molecular chains of the polyester resin, it is presumed that the melt viscosity (IV value) of the raw material polyester resin can be improved, and a resin composition with a higher melt viscosity than the raw material polyester resin can be obtained. Furthermore, it is presumed that as a result, polyester resin fibers can be manufactured using the resin composition obtained by this manufacturing method. However, the present invention is not limited in any way to these presumptions.

[0041] As described above, in step 1 of this manufacturing method, the reactive functional groups (e.g., epoxy groups) of the reactive functional group-containing units in polymer (A) contained in the modifier may react with the terminal functional groups (e.g., hydroxyl groups or carboxyl groups) of the polyester resin. Therefore, in the modifier, which is the raw material before melt kneading, the reactive functional group-containing units exist in a state where they are reacting with the terminal functional groups of the polyester resin. On the other hand, in the modifier constituting the resulting resin composition, that is, in the constituent units derived from the modifier in the resin composition, at least a portion of the reactive functional group-containing units may exist in a state where they are covalently bonded to the terminals of the constituent units derived from the polyester resin in the resin composition.

[0042] The reactive functional group is not particularly limited as long as it is a functional group that can react with the terminal functional groups of the polyester resin, and may be, for example, at least one functional group selected from the group consisting of epoxy groups, oxetane groups, hydroxyl groups, amino groups, imide groups, carboxylic acid groups, and carboxylic acid anhydride groups.

[0043] The reactive functional group-containing units may be constituent units derived from cyclic ester-containing monomers and constituent units derived from cyclic amide-containing monomers.

[0044] In this specification, a "reactive functional group-containing monomer having an X group as a reactive functional group" may be referred to as an "X group-containing monomer," and a "constituent unit derived from a reactive functional group-containing monomer having an X group as a reactive functional group," that is, a "constituent unit having an X group as a reactive functional group," may be referred to as an "X group-containing unit."

[0045] Specific examples of epoxy group-containing monomers include glycidyl group-containing vinyl monomers such as glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, 3,4-epoxycyclohexyl (meth)acrylate, allyl glycidyl ether, β-methylglycidyl (meth)acrylate, and 4-vinylbenzyl glycidyl ether. Among these, glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether are preferred as epoxy group-containing monomers from the viewpoint of reactivity, glycidyl methacrylate and 4-hydroxybutyl acrylate glycidyl ether are more preferred, and glycidyl methacrylate is even more preferred. In this specification, "(meth)acrylate" means "acrylate and / or methacrylate".

[0046] Specific examples of oxetane group-containing monomers include, for example, (vinyloxyalkyl)alkyloxetane, (meth)acryloyloxyalkyloxetane, and [(meth)acryloyloxyalkyl]alkyloxetane. In this specification, "(meth)acryloyl" means "acryloyl and / or methacryloyl."

[0047] Specific examples of hydroxyl group-containing monomers include, for example, (a) hydroxylinear alkyl(meth)acrylates such as 2-hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate (particularly preferred are hydroxylinear C1-6 alkyl(meth)acrylates); (b) caprolactone-modified hydroxy(meth)acrylates; (c) hydroxybranched alkyl(meth)acrylates such as methyl α-(hydroxymethyl)(meth)acrylate and ethyl α-(hydroxymethyl)(meth)acrylate; (d) hydroxyl group-containing (meth)acrylates such as mono(meth)acrylates of polyester diols obtained from divalent carboxylic acids (such as phthalic acid) and divalent alcohols (such as propylene glycol) (particularly preferred are saturated polyester diols); and (e) hydroxyl group-containing maleates. Note that "linear C1-6 alkyl" refers to linear alkyls having 1 to 6 carbon atoms. In this specification, "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid."

[0048] Specific examples of amino group-containing monomers include, for example, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-diethylaminopropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, 2-vinylpyridine, 4-vinylpyridine, and these H + X -Examples include compounds having a structure obtained by neutralization with an acid represented by [the specified formula].

[0049] Specific examples of imide group-containing monomers include maleimide, phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, Nt-butylmaleimide, N-cyclohexylmaleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide, N-bromophenylmaleimide, N-naphthylmaleimide, N-laurylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide, and N-benzylmaleimide.

[0050] Specific examples of monomers containing carboxylic acid groups include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, as well as dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. From the viewpoint of reactivity, monocarboxylic acids are preferred as monomers containing carboxylic acid groups.

[0051] Specific examples of monomers containing carboxylic acid anhydride groups include, for example, maleic anhydride.

[0052] The reactive functional group-containing units in polymer (A) may consist of (i) only one reactive functional group-containing unit derived from any one of the reactive functional group-containing monomers described above, or (ii) any combination of two or more reactive functional group-containing units derived from any two or more reactive functional group-containing monomers described above.

[0053] From the viewpoint of the reactivity between terminal functional groups generated by the decomposition and degradation of polyester resins and modifiers, the reactive functional group-containing units in polymer (A) preferably include one or more selected from the group consisting of epoxy group-containing units, hydroxyl group-containing units, carboxylic acid group-containing units and carboxylic acid anhydride group-containing units, and may consist only of one or more selected from this group; (ii) more preferably include one or more selected from the group consisting of epoxy group-containing (meth)acrylate units, hydroxyl group-containing maleate units, monocarboxylic acid units, dicarboxylic acid units and carboxylic acid anhydride group-containing units, and may consist only of one or more selected from this group; (iii) more preferably include one or more selected from the group consisting of epoxy group-containing (meth)acrylate units, hydroxyl group-containing maleate units, acrylic acid units, methacrylic acid units, maleic acid units and maleic acid anhydride units, and may consist only of one or more selected from this group; and (iv) particularly preferably include epoxy group-containing (meth)acrylate units, and may consist only of epoxy group-containing (meth)acrylate units.

[0054] From the viewpoint of polymerization productivity of reactive functional group-containing monomers from which reactive functional group-containing units are derived, the reactive functional group-containing units in polymer (A) preferably contain one or more selected from the group consisting of (i) glycidyl (meth)acrylate units, 4-hydroxybutyl (meth)acrylate glycidyl ether units, 3,4-epoxycyclohexyl (meth)acrylate units and β-methylglycidyl (meth)acrylate units, and may consist only of one or more selected from the group, and (ii) glycidyl (meth)acrylate units, 4-hydroxybutyl acrylate glycidyl (iii) It is more preferable to include one or more selected from the group consisting of ether units and 3,4-epoxycyclohexyl (meth)acrylate units, and may consist only of one or more selected from said group; (iv) It is most preferable to include glycidyl (meth)acrylate units and 4-hydroxybutyl acrylate glycidyl ether units, and may consist only of one or more selected from said group; (iv) It is most preferable to include glycidyl methacrylate units, and may consist only of glycidyl methacrylate units.

[0055] The content of reactive functional group-containing units in polymer (A) is not particularly limited, but is preferably 10% to 60% by weight per 100% by weight of polymer (A). The upper limit of the content may be 55%, 50%, 45%, or 40% by weight, and the lower limit may be 15%, 20%, 25%, or 30% by weight. If the content of reactive functional group-containing units in polymer (A) is within the above range, the effect of improving the melt viscosity of the resin composition by the modifier can be good. As a result, (i) the windability of the polyester resin composition in step 2 is further improved, and polyester resin fibers can be produced with high productivity, and (ii) the polyester resin fibers have the advantage of being more moldable and strong. In this specification, "polyester resin fibers have excellent moldability" means that the thickness distribution of the polyester resin fibers is more uniform.

[0056] The content of epoxy group-containing units in polymer (A) is not particularly limited, but is preferably 10% to 60% by weight per 100% by weight of polymer (A). The upper limit of the content may be 55%, 50%, 45%, or 40% by weight, and the lower limit may be 15%, 20%, 25%, or 30% by weight. If the content of epoxy group-containing units in polymer (A) is within the above range, the effect of the modifier on improving the melt viscosity of the resin composition may be better. As a result, (i) the windability of the polyester resin composition in step 2 is further improved, and polyester resin fibers can be produced with high productivity, and (ii) the polyester resin fibers have even better moldability and strength.

[0057] (Units without reactive functional groups) In this specification, "reactive functional group-free units" are constituent units derived from monomers that do not have reactive functional groups capable of reacting with the terminal functional groups of polyester resins (hereinafter sometimes referred to as "reactive functional group-free monomers"). In other words, reactive functional group-free units contained in polymer (A) of the modifier cannot react with the terminal functional groups of polyester resins. Furthermore, reactive functional group-free units in polymer (A) are also constituent units derived from monomers copolymerizable with monomers containing reactive functional groups in polymer (A).

[0058] The reactive functional group-free monomer from which the reactive functional group-free units in polymer (A) originate is not particularly limited. Examples of such reactive functional group-free monomers include reactive functional group-free (meth)acrylic monomers, reactive functional group-free vinyl cyanide compounds, and reactive functional group-free aromatic vinyl compounds.

[0059] Specific examples of reactive functional group-free (meth)acrylic monomers include, for example, (meth)acrylic acid and reactive functional group-free (meth)acrylates. "Reactive functional group-free (meth)acrylate" refers to "(meth)acrylate ((meth)acrylic acid ester) that does not have a reactive functional group and is substituted or unsubstituted with a functional group other than a reactive functional group." Specific examples of reactive functional group-free (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ocryl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate, which are alkyl (meth)acrylates without reactive functional groups and having alkyl groups with 1 to 22 carbon atoms.

[0060] The number of carbon atoms in the alkyl group in the reactive functional group-free alkyl (meth)acrylate unit is not particularly limited. From the viewpoint of the polymerizability of the monomer from which the constituent unit is derived, it is preferable that the number of carbon atoms in the alkyl group in the reactive functional group-free alkyl (meth)acrylate unit is 22 or less. Furthermore, from the viewpoint of compatibility with polyester resins, it is more preferable that the number of carbon atoms in the alkyl group in the reactive functional group-free alkyl (meth)acrylate unit is 12 or less, even more preferable that it is 8 or less, and particularly preferable that it is 1 to 4.

[0061] From the viewpoint of the dispersibility of the modifier in step 1, polymer (A) may more preferably contain (i) reactive functional group-free (meth)acrylic units, or may consist only of reactive functional group-free (meth)acrylic units, (ii) reactive functional group-free alkyl (meth)acrylate units, or may consist only of reactive functional group-free alkyl (meth)acrylate units, (iii) epoxy group-free alkyl (meth)acrylate units, or may consist only of epoxy group-free alkyl (meth)acrylate units, (i (v) It is more preferable to include one or more selected from the group consisting of methyl (meth)acrylate units, ethyl (meth)acrylate units, propyl (meth)acrylate units, and butyl (meth)acrylate units, and it may consist of only one or more selected from this group; (v) It is even more preferable to include one or more selected from the group consisting of methyl methacrylate units and butyl acrylate units, and it may consist of only one or more selected from this group; (vi) It is most preferable to include methyl methacrylate units, and it may consist of only methyl methacrylate units.

[0062] The content of reactive functional group-free (meth)acrylic units in polymer (A) is not particularly limited, but is preferably 40% to 90% by weight of polymer (A) per 100% by weight. The upper limit of the content may be 85%, 80%, 75%, or 70% by weight, and the lower limit may be 45%, 50%, 55%, or 60% by weight. If the content of reactive functional group-free (meth)acrylic units in polymer (A) is within the above range, the dispersibility of the modifier in step 1 is improved. Furthermore, if the content of reactive functional group-free (meth)acrylic units in polymer (A) is within the above range, the elongation of the resin (resin composition) in step 2, described later, can be made more uniform by restricting the branching structure during crosslinking to fewer directions. As a result, the effect of improving the melt viscosity of the resin composition by the modifier can be improved without impairing processability. As a result, (i) the windability of the polyester resin composition in step 2 is improved, and polyester resin fibers can be manufactured with high productivity, and (ii) the polyester resin fibers have superior moldability and strength.

[0063] Specific examples of vinyl cyanide compounds that do not contain reactive functional groups include, for example, acrylonitrile and methacrylonitrile.

[0064] Specific examples of reactive functional group-free aromatic vinyl compounds include, for example, reactive functional group-free styrene monomers and 1-vinylnaphthalene. In this specification, "reactive functional group-free styrene monomer" means "styrene that does not have a reactive functional group and is substituted or unsubstituted with a functional group other than a reactive functional group." Specific examples of reactive functional group-free styrene monomers include, for example, styrene, vinyltoluene, α-methylstyrene, 4-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 4-ethylstyrene, 4-ethoxystyrene, 3,4-dimethylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chloro-3-methylstyrene, 3-(tert-butyl)styrene, 2,4-dichlorostyrene, and 2,6-dichlorostyrene.

[0065] The reactive functional group-free units in polymer (A) may consist of (i) only one reactive functional group-free unit derived from any one of the reactive functional group-free monomers described above, or (ii) any combination of any two or more reactive functional group-free units derived from any two or more reactive functional group-free monomers described above.

[0066] From the viewpoint of polymerization productivity of monomers from which the constituent units are derived, polymer (A) preferably contains reactive functional group-free units, and may consist only of reactive functional group-free aromatic vinyl compound units, (ii) preferably contains reactive functional group-free styrene units, and may consist only of reactive functional group-free styrene units, (iii) preferably contains one or more selected from the group consisting of 4-methylstyrene units, 3-methylstyrene units, α-methylstyrene units and styrene units, and may consist only of one or more selected from the said group, (iv) more preferably contains one or more selected from the group consisting of 4-methylstyrene units, α-methylstyrene units and styrene units, and may consist only of one or more selected from the said group, (v) even more preferably contains one or more selected from the group consisting of α-methylstyrene units and styrene units, and may consist only of one or more selected from the said group, and (vi) most preferably contains styrene units, and may consist only of styrene units.

[0067] The content of reactive functional group-free aromatic vinyl compound units in polymer (A) is not particularly limited, but is preferably 40% to 90% by weight per 100% by weight of polymer (A). The upper limit of the content may be 85%, 80%, 75%, or 70% by weight, and the lower limit may be 45%, 50%, 55%, or 60% by weight. If the content of reactive functional group-free aromatic vinyl compound units in polymer (A) is within the above range, there is the advantage that the dispersibility of the modifier in step 1 is improved.

[0068] The total content of reactive functional group-free styrene units and reactive functional group-free (meth)acrylic units in polymer (A) is not particularly limited. Preferably, the total content of reactive functional group-free styrene units and reactive functional group-free (meth)acrylic units in polymer (A) is 40% to 90% by weight of polymer (A) per 100% by weight. The upper limit of the content may be 85% by weight, 80% by weight, 75% by weight, or 70% by weight, and the lower limit may be 45% by weight, 50% by weight, 55% by weight, or 60% by weight. If the total content of reactive functional group-free styrene units and reactive functional group-free (meth)acrylic units in polymer (A) is within the above range, there is an advantage that the transparency derived from the polyester resin is not impaired even after melt kneading with the polyester resin in step 1 by optimizing the refractive index. In other words, there is an advantage that a resin composition with higher transparency can be obtained in step 1.

[0069] The total content of reactive functional group-free units other than reactive functional group-free alkyl (meth)acrylate units in polymer (A) is not particularly limited. Preferably, the content of reactive functional group-free units other than reactive functional group-free alkyl (meth)acrylate units in polymer (A) is 0 to 10% by weight of polymer (A) per 100% by weight. The upper limit of the content may be 8% by weight or 5% by weight, and the lower limit may be 2% by weight or 4% by weight. If the total content of reactive functional group-free units other than reactive functional group-free alkyl (meth)acrylate units in polymer (A) is within the above range, there is an advantage in that productivity is improved.

[0070] The total content of reactive functional group-free units in polymer (A) is not particularly limited, but is preferably 40% to 90% by weight of polymer (A) per 100% by weight. The upper limit of the content may be 85%, 80%, 75%, or 70% by weight, and the lower limit may be 45%, 50%, 55%, or 60% by weight. If the total content of reactive functional group-free units in polymer (A) is within the above range, the dispersibility of the modifier in step 1 may be improved, thereby improving the effect of the modifier on improving the melt viscosity of the resin composition. As a result, (i) the windability of the polyester resin composition in step 2 is further improved, and polyester resin fibers can be produced with high productivity, and (ii) the polyester resin fibers have the advantage of being more moldable and stronger.

[0071] In addition, from the viewpoint of (i) compatibility between the modifier and the polyester resin and the dispersibility of the modifier in step 1, and (ii) productivity of the modifier itself, it is preferable that polymer (A) contains the constituent units shown in (i) and (ii) below: (i) The reactive functional group-containing unit is an epoxy group-containing (meth)acrylate unit; (ii) One or more constituent units selected from the group consisting of reactive functional group-free styrene units and reactive functional group-free (meth)acrylic units as the reactive functional group-free units.

[0072] When the number average content of reactive functional groups in polymer (A) is high, the reactivity between polymer (A) and the terminal functional groups of the polyester resin is improved in step 1. As a result, the effect of increasing the molecular weight of the polyester resin and the effect of increasing the melt viscosity of the polyester resin become greater. From this viewpoint, polymer (A) may have an average of preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more reactive functional groups per molecule. Polymer (A) may have an average of 5 or more, 6 or more, or 7 or more reactive functional groups per molecule. In this specification, the "number average content of reactive functional groups" per molecule of polymer is the value obtained by measurement using a conventionally known method. For example, in this specification, the "epoxy group content" is the value obtained by calculation based on the epoxy equivalent obtained by measurement using the titration method described in JIS K 7236. In this specification, "hydroxyl group content" shall be the value calculated based on the hydroxyl value obtained by titration according to the titration methods described in JIS K 0070 and JIS K 1557-1. In this specification, "amino group content" shall be the value calculated based on the total amine value obtained by titration according to the titration method described in JIS K 7237. In this specification, "carboxylic acid group content" shall be the value calculated based on the acid value obtained by titration according to the titration methods described in JIS K 0070 and JIS K 1557-5. The content of reactive functional groups may also be calculated based on the saponification value and iodine value obtained by titration according to the titration method described in JIS K 0070.

[0073] On the other hand, if the amount of reactive functional groups (number average) in polymer (A) is below a certain amount, the degree of branching of the constituent units derived from the polyester resin in the resin composition obtained in step 1 will not become too high, and the entanglement of the constituent units derived from the polyester resin will be suppressed, thus preventing the rigidity of the resin composition from becoming excessively high. As a result, in step 2 described later, there is no risk of the resin composition breaking and the thread snapping due to the stress applied when winding the resin composition. In other words, by setting the amount of reactive functional groups (number average) in polymer (A) to below a certain amount, the stability in the production of polyester resin fibers is improved, and there is an advantage in being able to produce polyester resin fibers more stably. From this viewpoint, polymer (A) may have, on average, 10 or fewer, more preferably 9 or fewer, more preferably 8 or fewer, even more preferably 7 or fewer, and particularly preferably 6 or fewer reactive functional groups per molecule. Furthermore, if the upper and lower limits of the reactive functional group content (number average) per molecule of polymer (A) are within the aforementioned preferred range, the melt viscosity of the resin composition can be suitably improved without causing gelation and without impairing the mechanical properties, heat resistance, rheological properties, etc., of the polyester resin fibers.

[0074] The number-average molecular weight of polymer (A) is not particularly limited, but is preferably less than 10,000 Da, more preferably 8,000 Da or less, even more preferably 7,000 Da or less, and particularly preferably 6,000 Da or less. The lower limit of the number-average molecular weight of polymer (A) is not particularly limited, but is preferably 1,000 Da or more, more preferably 3,000 Da or more, even more preferably 4,000 Da or more, even more preferably 5,000 Da or more, and particularly preferably 6,000 Da or more. When the number-average molecular weight of polymer (A) is within the above preferred range, the effect of improving the melt viscosity of the resin composition by the modifier can be good. As a result, (i) the windability of the polyester resin composition in step 2 is further improved, and polyester resin fibers can be produced with high productivity, and (ii) the polyester resin fibers have the advantage of being more moldable and stronger. Furthermore, when the number-average molecular weight of polymer (A) is within the aforementioned preferred range, there is also the advantage of a good balance between the thermal stability and productivity of the modifier. In this specification, the "number-average molecular weight" of the polymer refers to the value obtained by the method described in the later examples.

[0075] The weight-average molecular weight of polymer (A) is not particularly limited, but is preferably 80,000 Da or less, more preferably 70,000 Da or less, even more preferably 60,000 Da or less, and particularly preferably 50,000 Da or less. Furthermore, the lower limit of the weight-average molecular weight of polymer (A) is not particularly limited, but is preferably 3,000 Da or more, more preferably 5,000 Da or more, even more preferably 6,000 Da or more, even more preferably 7,000 Da or more, and particularly preferably 8,000 Da or more. When the weight-average molecular weight of polymer (A) is within the above preferred range, the softening point of the resin composition is raised, preventing sticking, and it has the advantage of good handling when added to polyester resin, as well as the advantage of being less likely to adversely affect the strength and / or properties of the fibers. In this specification, the "weight-average molecular weight" of the polymer refers to the value obtained by the method described in the later examples.

[0076] The polydispersity index of polymer (A) is preferably 2.0 to 10.0, more preferably 2.0 to 8.0, even more preferably 2.0 to 6.0, and particularly preferably 2.0 to 4.0. This configuration has the advantage of being less prone to unintended side effects in terms of quality and having high quality stability. In this specification, the "polydispersity index" of the polymer is the value obtained by the method described in the later examples.

[0077] The modifier may contain monomers. For example, if there are monomers that were not consumed in polymerization among the monomers used in the production of polymer (A) and / or polymer (B) described later, the resulting modifier may contain monomers derived from those monomers. In this specification, monomers contained in the modifier may be referred to as "monomer residue." The modifier may contain, as monomer residue, residue of reactive functional group-containing monomers (i.e., "reactive functional group-containing monomer residue"). In this specification, all monomer residues that the modifier may contain may be collectively referred to as "total monomer residue."

[0078] The lower the content of total monomer residue in the modifier, the better. The content of total monomer residue in the modifier is preferably less than 2000 ppm, more preferably 500 ppm or less, even more preferably 100 ppm or less, and particularly preferably less than 100 ppm, based on the weight of the modifier. It is particularly preferable that the content of total monomer residue in the modifier is below the detection limit of the instrument used to measure the monomer residue in the modifier, that is, it is particularly preferable that the total monomer residue is not detected. This configuration has the advantage of reducing the risk of monomer migration into food, especially in food contact applications. Furthermore, the lower the content of reactive functional group-containing monomer residue in the modifier, the better. The content of reactive functional group-containing monomer residue in the modifier is preferably less than 1000 ppm, more preferably 500 ppm or less, even more preferably 100 ppm or less, even more preferably less than 100 ppm, and particularly preferably less than 50 ppm, based on the weight of the modifier. It is particularly preferable that the content of reactive functional group-containing monomer residue in the modifier is below the detection limit of the instrument used to measure the reactive functional group-containing monomer residue in the modifier, i.e., it is particularly preferable that the reactive functional group-containing monomer residue is not detected. This configuration has the advantage of reducing the risk of migration of reactive functional group-containing monomers to food, especially in food contact applications. The lower limit for both the total monomer residue content and the reactive functional group-containing monomer residue content in the modifier is 0 ppm. In this specification, the "total monomer residue content" and "reactive functional group-containing monomer residue content" in the modifier are values ​​obtained by the method described in the later examples.

[0079] The epoxy equivalent of polymer (A) is preferably 100 g / eq to 3000 g / eq, more preferably 350 g / eq to 2500 g / eq, even more preferably 500 g / eq to 2500 g / eq, and particularly preferably 1000 g / eq to 2000 g / eq. This configuration has the advantage of good processability in the fiber stretching process.

[0080] In this specification, the epoxy equivalent of a polymer refers to the molecular weight per epoxy group contained in the polymer, and specifically, is a value calculated based on the following formula: The epoxy equivalent weight (g / eq) of a polymer = number-average molecular weight (Mn) of the polymer / number of epoxy groups per polymer molecule (average number). Furthermore, epoxy equivalent can also be measured in accordance with JIS K7236.

[0081] In this specification, the epoxy equivalent of polymer (A) is defined as the value obtained by the method described in detail in the following examples.

[0082] Polymer (A) is preferably a non-rubber polymer. A non-rubber polymer is a polymer that does not have crosslinking structures between its molecular chains. The advantage of polymer (A) being a non-rubber polymer is that the reaction between the reactive functional groups (e.g., epoxy groups) of polymer (A) and the terminal functional groups of the polyester resin proceeds more efficiently, making it easier to improve the melt viscosity of the resin composition.

[0083] (Method for producing polymer (A)) The polymerization method for polymer (A) can be any known method and is not particularly limited. For example, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc., can be used as the polymerization method for polymer (A), but emulsion polymerization is preferred.

[0084] When producing polymer (A), it is preferable to carry out polymerization in the presence of a chain transfer agent in order to control the molecular weight. It is preferable to use a chain transfer agent in the production of polymer (A). Polymers obtained using a chain transfer agent may contain structural units derived from the chain transfer agent. In other words, polymer (A) preferably contains structural units derived from the chain transfer agent.

[0085] Examples of chain transfer agents, though not particularly limited, include primary mercaptan chain transfer agents such as n-butyl mercaptan, n-octyl mercaptan, n-hexadecyl mercaptan, n-dodecyl mercaptan, and n-tetradecyl mercaptan; secondary mercaptan chain transfer agents such as sec-butyl mercaptan and sec-dodecyl mercaptan; tertiary mercaptan chain transfer agents such as t-dodecyl mercaptan; mercaptan compounds; thioglycolic acid esters such as 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris(thioglycolate), and pentaerythritol tetrakis(thioglycolate); thiophenols; tetraethyl thiuram disulfide; pentanephenylethane; acrolein; methacrolein; allyl alcohol; carbon tetrachloride; ethylene bromide; styrene oligomers such as α-methylstyrene dimer; terpinolenes; and others. The chain transfer agent may be used alone or in combination of two or more types. The amount of chain transfer agent used should be appropriately set according to the desired number average molecular weight of polymer (A).

[0086] The emulsifiers (dispersants) that can be used in emulsion polymerization are not particularly limited, but include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives may also be used. The emulsifiers (dispersants) may be used individually or in combination of two or more.

[0087] When employing emulsion polymerization, a pyrolysis-type initiator can be used as a radical polymerization initiator. Examples of known pyrolysis-type initiators include 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate.

[0088] Redox-type initiators can also be used as radical polymerization initiators. The redox-type initiator is an initiator that combines (a) peroxides such as organic peroxides and inorganic peroxides, and (b) optionally a reducing agent such as sodium formaldehyde sulfoxylate or glucose, optionally a transition metal salt such as iron(II) sulfate, optionally a chelating agent such as disodium ethylenediaminetetraacetate, and optionally a phosphorus-containing compound such as sodium pyrophosphate. Examples of organic peroxides include t-butyl peroxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and t-hexyl peroxide. Examples of inorganic peroxides include hydrogen peroxide, potassium persulfate, and ammonium persulfate.

[0089] When a redox-type initiator is used, polymerization can be carried out even at low temperatures in which the peroxide does not substantially decompose thermally, allowing the polymerization temperature to be set over a wide range. For this reason, it is preferable to use a redox-type initiator. Among redox-type initiators, those using organic peroxides such as cumene hydroperoxide, dicumyl peroxide, paramenthane hydroperoxide, and t-butyl hydroperoxide as peroxides are preferred. The amount of the initiator used, and the amounts of the reducing agent, transition metal salt, and chelating agent used when a redox-type initiator is used, can be used within known ranges.

[0090] Known surfactants can also be used in the polymerization of polymer (A).

[0091] When polymer (A) is produced by emulsion polymerization, a latex containing polymer (A) (e.g., aqueous latex) can be obtained. Polymer (A) can be obtained by separating polymer (A) from the latex containing polymer (A). The obtained polymer (A) can be used as a modifier. There are no particular limitations on the method for separating polymer (A) from the latex containing polymer (A), but examples include salting out of polymer (A) using an acid and a metal salt, and precipitation of polymer (A) using an organic solvent. Polymer (A) separated from the latex containing polymer (A) may be washed and further dried. By separating polymer (A) from the latex containing polymer (A), washing, and further drying, a powder of polymer (A) (also referred to as "powder") can be obtained. Alternatively, a powder of polymer (A) can be obtained by spray drying the latex containing polymer (A). The polymer (A) powder obtained in this way can be used as a modifier.

[0092] (Polymer (B)) The modifier may or may not contain polymer (B) in addition to polymer (A). The polymer component in the modifier may consist only of polymer (A), or only of polymer (A) and polymer (B), or may consist of polymer (A), polymer (B), and other polymers.

[0093] The case in which the modifier includes polymer (A) and polymer (B) (hereinafter also referred to as "Case A") will be described below. In Case A, it is preferable to polymerize polymer (A) and then polymerize polymer (B) in the presence of polymer (A). In Case A, if polymer (A) is obtained by emulsion polymerization, for example, it is particularly preferable to produce polymer (B) in latex containing polymer (A) after producing polymer (A). When polymer (B) is produced in latex containing polymer (A), a composite consisting of polymer (A) and polymer (B) (or containing polymer (A) and polymer (B)) can be obtained. In the composite, polymer (B) may cover a part of polymer (A). Therefore, in the composite, polymer (A) can be referred to as the core part and polymer (B) as the shell part. The composite may have a core-shell structure in which polymer (A) is the core part and polymer (B) is the shell part. In other words, when polymer (B) is produced (polymerized) in latex containing polymer (A), a composite consisting of polymer (A) and polymer (B) can be obtained, in which polymer (A) forms the core and polymer (B) forms the shell, i.e., a composite having a core-shell structure. In the composite, polymer (B) may cover the entire polymer (A), or at least a portion of polymer (B) may be impregnated into the interior of particulate polymer (A).

[0094] When the modifier comprises polymer (A) and polymer (B), and the composite composed of polymer (A) and polymer (B) has a core-shell structure in which polymer (A) forms the core and polymer (B) forms the shell, it has the advantage of improving productivity.

[0095] Polymer (B) is not particularly limited. The composition of the constituent units of polymer (B) may be the same as or different from the composition of the constituent units of polymer (A). In other words, the composition of monomer mixture (B) may be the same as or different from the composition of monomer mixture (A).

[0096] In case A, it is particularly preferable that polymer (B) has a configuration that allows polymer (A), which can function as a chain extender during melt kneading of the modifier and the polyester resin, to react more uniformly with the polyester resin, thereby allowing polymer (A) to be dispersed more uniformly within the polyester resin; in other words, it has a configuration that allows polymer (B) to function as a carrier.

[0097] It is particularly preferable that polymer (B) has a configuration that can improve granulation properties during the manufacture of the modifier. When polymer (A) is polymerized alone and powdered, it may become a fine powder that is difficult to handle. In such cases, polymer (B), which has a configuration that facilitates granulation (powdering), is polymerized together with polymer (A), and polymers (A) and (B) are isolated together to obtain a modifier that is easy to handle.

[0098] Polymer (B) may contain reactive functional group-containing units or may not contain reactive functional group-containing units. Polymer (B) may consist only of reactive functional group-containing units or only of units without reactive functional groups. Preferably, polymer (B) contains both reactive functional group-containing units and units without reactive functional groups. When polymer (B) contains both reactive functional group-containing units and units without reactive functional groups, the softening point of the modifier (composite) is raised, making it less likely for problems such as sticking to the surface to occur. As a result, there is the advantage of improved productivity. Furthermore, when polymer (B) contains both reactive functional group-containing units and units without reactive functional groups, there is also the advantage that the dispersibility of polymer (A) is improved because the dispersibility of the modifier (composite) is improved.

[0099] Specific examples of reactive functional group-containing units in polymer (B) are the same as those described in the section on (reactive functional group-containing units) in the section on (polymer (A)) above, so we will refer to that description and omit the explanation here. Preferred embodiments of reactive functional group-containing units in polymer (A) are also preferred embodiments of reactive functional group-containing units in polymer (B). Specific examples of reactive functional group-free units in polymer (B) are the same as those described in the section on (reactive functional group-free units) in the section on (polymer (A)) above, so we will refer to that description and omit the explanation here. Preferred embodiments of reactive functional group-free units in polymer (A) are also preferred embodiments of reactive functional group-free units in polymer (B).

[0100] The case in which polymer (B) contains reactive functional group-containing units will be described. In this case, the reactive functional group-containing units preferably contain epoxy group-containing (meth)acrylate units, and more preferably contain glycidyl methacrylate units. In other words, polymer (B) preferably contains epoxy group-containing (meth)acrylate units, and more preferably contains glycidyl methacrylate units, as reactive functional group-containing units. This configuration has the advantage that in step 1, the compatibility between the modifier and the polyester resin and the dispersibility of the modifier are improved.

[0101] The case in which polymer (B) contains reactive functional group-containing units will be described. In this case, polymer (B) preferably contains more than 2.5% by weight and 10.0% by weight or less of reactive functional group-containing units per 100% by weight of polymer (B), more preferably 2.5% to 9.0% by weight, even more preferably 3.0% to 8.0% by weight, and particularly preferably 4.0% to 6.0% by weight.

[0102] The polymer (B) preferably contains one or more constituent units selected from the group consisting of styrene units and (meth)acrylic units. The "styrene units" include both constituent units derived from reactive functional group-containing styrene monomers (e.g., 4-vinylbenzylglycidyl ether) and constituent units derived from reactive functional group-free styrene monomers. The "(meth)acrylic units" include both constituent units derived from reactive functional group-containing (meth)acrylic monomers and constituent units derived from reactive functional group-free (meth)acrylic monomers. For specific examples of reactive functional group-containing (meth)acrylic monomers, the description in the (Reactive Functional Group-Containing Units) section of the (Polymer (A)) section can be appropriately referenced. For specific examples of reactive functional group-free styrene monomers and reactive functional group-free (meth)acrylic monomers, the same as those described in the (Reactive Functional Group-Free Units) section of the (Polymer (A)) section can be referenced, and the explanation is omitted here.

[0103] Polymer (B) more preferably contains one or more constituent units selected from the group consisting of (i) styrene units without reactive functional groups and alkyl (meth)acrylic units, and may consist only of one or more units selected from the group, and (ii) more preferably contains one or more constituent units selected from the group consisting of styrene units, (meth)acrylate units containing reactive functional groups, methyl (meth)acrylate units without reactive functional groups, ethyl (meth)acrylate units without reactive functional groups, propyl (meth)acrylate units without reactive functional groups, and butyl (meth)acrylate units without reactive functional groups, and selected from the group It may consist of only one or more of the following, (iii) it is more preferable to include one or more constituent units selected from the group consisting of styrene units, glycidyl (meth)acrylate units, methyl (meth)acrylate units, ethyl (meth)acrylate units and butyl (meth)acrylate units, and it may consist of only one or more selected from the group, (iv) it is more preferable to include one or more constituent units selected from the group consisting of styrene units, glycidyl methacrylate units, methyl methacrylate units and butyl acrylate units, and it may consist of only one or more selected from the group.

[0104] The total content of styrene units and (meth)acrylic units in polymer (B) is not particularly limited, but is preferably 40% to 99% by weight per 100% by weight of polymer (B). The upper limit of the content may be 99% by weight, 90% by weight, 80% by weight, or 70% by weight, and the lower limit may be 40% by weight, 50% by weight, 60% by weight, or 70% by weight. If the total content of styrene units and (meth)acrylic units in polymer (B) is within the above range, it is possible to improve the dispersibility of the modifier (composite) by preventing or reducing gelation of the modifier (composite), and it has the advantage of good productivity of polymer (B).

[0105] It is preferable that the number-average molecular weight of polymer (B) is different from that of polymer (A). More preferably, the number-average molecular weight of polymer (B) is greater than that of polymer (A). This configuration raises the softening point of the modifier (composite), making it less likely for problems such as sticking to the surface to occur. As a result, it has the advantage of improving productivity.

[0106] The number-average molecular weight of polymer (B) is preferably 8,000 Da to 300,000 Da, more preferably 10,000 Da to 200,000 Da, even more preferably 12,000 Da to 150,000 Da, and particularly preferably 15,000 Da to 100,000 Da. This configuration raises the softening point of the modifier (composite), making it less likely for problems such as sticking to the surface to occur. As a result, it has the advantage of improving productivity. Furthermore, when the number-average molecular weight of polymer (B) is within the aforementioned range, the high softening point of polymer (B) allows for a slower initiation rate of the crosslinking reaction when added to polyester resins. This prevents a rapid reaction from occurring during addition, making it possible to suppress gel formation. As a result, suppressing gel formation has the advantage of reducing the number of break points in processes such as fiber stretching, thereby improving fiber productivity.

[0107] It is preferable that the weight-average molecular weight of polymer (B) is different from that of polymer (A). More preferably, the weight-average molecular weight of polymer (B) is greater than that of polymer (A). This configuration raises the softening point of the modifier (composite), making it less likely for problems such as sticking to the surface to occur. As a result, it has the advantage of improving productivity.

[0108] The weight-average molecular weight of polymer (B) is preferably 80,000 Da to 500,000 Da, more preferably 100,000 Da to 300,000 Da, even more preferably 120,000 Da to 250,000 Da, and particularly preferably 140,000 Da to 200,000 Da. This configuration raises the softening point of the modifier (composite), making it less likely for problems such as sticking to the surface to occur. As a result, it has the advantage of improving productivity. Furthermore, when the weight-average molecular weight of polymer (B) is within the above range, the dispersibility of the modifier (composite) is improved, which also has the advantage of improving the dispersibility of polymer (A). Moreover, when the weight-average molecular weight of polymer (B) is within the above range, the high softening point of polymer (B) allows for a slower initiation rate of the crosslinking reaction when added to polyester resins. This prevents a rapid reaction from proceeding upon addition, making it possible to suppress gel formation. As a result, suppressing gel formation has the advantage of reducing the number of break points in processes such as fiber stretching, thereby improving fiber productivity.

[0109] It is preferable that the number-average content of reactive functional groups in polymer (B) differs from the number-average content of reactive functional groups in polymer (A). It is preferable that the number-average content of reactive functional groups in polymer (B) is greater than the number-average content of reactive functional groups in polymer (A). This configuration has the advantage of improving the dispersibility of the modifier (complex) by preventing or reducing gelation of the modifier (complex).

[0110] If polymer (B) contains reactive functional groups, polymer (B) preferably has an average of 2 to 35 such reactive functional groups per molecule, and more preferably 15 to 35. The lower limit of the number average content of reactive functional groups in polymer (B) may be 5 or more, 10 or more, 20 or more, or 25 or more, and the upper limit may be 33 or less. When the number average content of reactive functional groups in polymer (B) is within the above range, the melt viscosity of the resin composition can be suitably improved without causing gelation and without impairing the mechanical properties, heat resistance, rheological properties, etc. of the polyester resin fiber.

[0111] Preferably, the epoxy equivalent of polymer (B) is different from that of polymer (A). Preferably, the epoxy equivalent of polymer (B) is greater than that of polymer (A). This configuration has the advantage of improving the dispersibility of the modifier (composite) by preventing or reducing gelation of the modifier (composite).

[0112] The epoxy equivalent of polymer (B) is preferably 6,000 g / eq to 50,000 g / eq, more preferably 6,500 g / eq to 45,000 g / eq, even more preferably 7,000 g / eq to 40,000 g / eq, and particularly preferably 8,000 g / eq to 35,000 g / eq. This configuration has the advantage that polymer (B) does not inhibit the compatibility between the modifier (polymer (A)) and the polyester, nor does it adversely affect the physical properties. In this specification, the epoxy equivalent of polymer (B) is the value obtained by calculating it using the method described in detail in the following examples.

[0113] It is preferable that polymer (B) is a non-rubber polymer. This configuration has the advantage that the reaction between the reactive functional groups of polymer (B) and the terminal functional groups of the polyester resin proceeds more efficiently, and the melt viscosity of the resin composition tends to improve. In case A, it is preferable that (i) polymer (A) is a non-rubber polymer or polymer (B) is a non-rubber polymer, and it is more preferable that both polymer (A) and polymer (B) are non-rubber polymers (for example, the entire modifier (composite) is a non-rubber polymer).

[0114] Polymer (A) and polymer (B) may differ in one or more of the following: composition of constituent units, number-average molecular weight, weight-average molecular weight, content of reactive functional groups per molecule (number-average), and epoxy equivalent.

[0115] In case A, the content ratio of polymer (A) and polymer (B) in the modifier is not particularly limited. In case A, for example, from the viewpoint of raising the softening point of the modifier (composite) and consequently improving the productivity of the modifier (composite), it is preferable that the modifier contains 15% to 70% by weight of polymer (A) and 30% to 85% by weight of polymer (B) per 100% by weight of the modifier, more preferably 20% to 70% by weight of polymer (A) and 30% to 80% by weight of polymer (B), even more preferably 30% to 60% by weight of polymer (A) and 40% to 70% by weight of polymer (B), and particularly preferably 40% to 50% by weight of polymer (A) and 50% to 60% by weight of polymer (B). Furthermore, in case A, for example, from the viewpoint of the production cost of the modifier, it is preferable that the modifier contains 50% to 90% by weight of polymer (A) and 10% to 50% by weight of polymer (B) in 100% by weight of the modifier, more preferably 70% to 90% by weight of polymer (A) and 10% to 30% by weight of polymer (B), and particularly preferably 80% to 90% by weight of polymer (A) and 10% to 20% by weight of polymer (B).

[0116] (Method for producing polymer (B)) The polymerization method for polymer (B) can be any known method and is not particularly limited. For example, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc., can be used as the polymerization method for polymer (B), but emulsion polymerization is preferred.

[0117] When producing polymer (B), it is preferable to carry out polymerization in the presence of a chain transfer agent in order to control the molecular weight. In other words, it is preferable that polymer (B) contains constituent units derived from the chain transfer agent.

[0118] Regarding polymer (B), the information in section [polymer (A)] may be applied as appropriate, except for the matters mentioned above.

[0119] (Physical properties of the modifier) The weight-average molecular weight of the modifier is preferably 20,000 Da or more and less than 200,000 Da, more preferably 25,000 Da to 150,000 Da, even more preferably 30,000 Da to 120,000 Da, and particularly preferably 40,000 Da to 100,000 Da. With this configuration, the effect of the modifier on improving the melt viscosity of the resin composition can be further improved. As a result, (i) the windability of the polyester resin composition in step 2 is further improved, and polyester resin fibers can be manufactured with high productivity, and (ii) the polyester resin fibers have even better moldability and strength.

[0120] [Other resins] In this manufacturing method, resins other than polyester resins may or may not be used. For example, in step 1, the polyester resin, the resin other than polyester resin, and the modifier may be melt-kneaded together.

[0121] Resins other than polyester resins are not particularly limited, but examples include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, polytetrafluoroethylene, ABS resin, AS resin, acrylic resin, polyacetal, polycarbonate, modified polyphenylene ether, polyamide, and cyclic polyolefin.

[0122] The amount of resin other than polyester resin used in this manufacturing method is not particularly limited, but for example, it may be 0 to 60 parts by weight per 100 parts by weight of polyester resin. The upper limit may be any of the following: 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 20 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less.

[0123] [Other additives] In this manufacturing method, other additives may be used. For example, in step 1, a polyester resin, a modifier, optionally a resin other than a polyester resin, and other additives may be melt-kneaded together.

[0124] Other additives are not limited to, but include, for example, flame retardants, flame retardant enhancers, anti-dripping agents, strengtheners, fillers, antioxidants, pigments, dyes, conductivity imparters, hydrolysis inhibitors, thickeners, plasticizers, lubricants, UV absorbers, antistatic agents, flow improvers, release agents, compatibilizers, and heat stabilizers.

[0125] [Process 1] In step 1, a raw material containing at least a polyester resin and a modifier, and optionally other resins and / or additives, is melt-kneaded. The melt-kneading of the polyester resin and the modifier in step 1 allows the reactive functional groups (e.g., epoxy groups) of the reactive functional group-containing units in the polymer (A) contained in the modifier to react with the terminal functional groups (e.g., hydroxyl groups or carboxyl groups) of the polyester resin, thereby extending the molecular chains of the polyester resin. As a result, step 1 yields a polyester resin composition containing constituent units derived from the polyester resin and constituent units derived from the modifier. Therefore, step 1 can also be described as a step of reacting the polyester resin with the modifier.

[0126] For melt-mixing raw materials containing polyester resins and modifiers, mixing machines such as single-screw or twin-screw extruders, Banbury mixers, pressure kneaders, and mixing rolls can be used.

[0127] In step 1, before melt-kneading the raw materials containing the polyester resin and modifier, all of the raw materials containing the polyester resin and modifier may be mixed to obtain a mixture, and the resulting mixture may be melt-kneaded. Alternatively, some of the raw materials may be mixed to obtain a mixture, and the resulting mixture and the remaining raw materials may be melt-kneaded. For mixing all or some of the raw materials, for example, a Henschel mixer or a tumbler mixer can be used.

[0128] In step 1, the amount of modifier used relative to the amount of polyester resin used (hereinafter also simply referred to as "amount of modifier used") is not particularly limited. The amount of modifier used may be determined according to the desired melt viscosity (IV value) of the resulting resin composition. For example, the amount of modifier used may be such that the melt viscosity (IV value) of the resulting resin composition is about the same as the melt viscosity (IV value) of the virgin polyester resin. The amount of modifier used may be determined according to the melt viscosity (IV value) of the polyester resin and the type of modifier (for example, the content (number average) of reactive functional groups in the polymer (A) contained in the modifier).

[0129] In one embodiment of the present invention, the amount of modifier used in step 1 relative to the amount of polyester resin used (amount of modifier used) may be 0.3 to 3.0 parts by weight, 0.1 to 5.0 parts by weight, 0.05 to 7.0 parts by weight, or 0.01 to 10.0 parts by weight per 100 parts by weight of polyester resin used.

[0130] (Physical properties of polyester resin compositions) As described above, in step 1, the modifier reacts with the polyester resin, extending the molecular chains of the polyester resin, thereby improving the melt viscosity (IV value) of the polyester resin. In other words, the resin composition obtained in step 1 has the advantage of having a higher melt viscosity than the raw material polyester resin.

[0131] The melt viscosity (IV value) of the resin composition is preferably 0.50 to 0.75, more preferably 0.53 to 0.75, even more preferably 0.56 to 0.75, even more preferably 0.60 to 0.70, and particularly preferably 0.63 to 0.70. When the melt viscosity (IV value) of the resin composition is within the above range, the resin composition has the advantage of excellent processability when made into polyester resin fibers. In this specification, the melt viscosity (IV value) of the resin or resin composition is the value obtained by the method described in the later examples.

[0132] The MFR value of the resin composition obtained by step 1 may be lower than the MFR value of the polyester resin used as the raw material. The MFR of the resin composition when measured at 270°C and under a 2.16 kgf load is not particularly limited, but is preferably 5 g / 10 min to 150 g / 10 min, more preferably 15 g / 10 min to 120 g / 10 min, even more preferably 30 g / 10 min to 80 g / 10 min, and particularly preferably 40 g / 10 min to 70 g / 10 min. When the MFR of the resin composition is 5 g / 10 min or higher, the resin composition has the advantage of good fluidity when made into polyester resin fibers and superior processability. When the MFR of the resin composition is 150 g / 10 min or lower, it has the advantage of excellent drawdown and processability.

[0133] [Process 2] This manufacturing method includes step 2, in which the polyester resin composition obtained in step 1 is wound at a winding speed of 400 m / min or more. Step 2 can be used to obtain a fibrous polyester resin composition (or polyester resin), i.e., polyester resin fibers.

[0134] In step 2, the method for winding the polyester resin composition is not particularly limited, and a known winding method commonly used in the production of polyester resin fibers can be employed, regardless of whether it is POY (Partially Oriented Yarn) or FDY (Fully Drawn Yarn).

[0135] In step 2, the winding speed of the polyester resin composition is high, at 400 m / min or more. When the winding speed is high, the amount of polyester resin composition wound per unit time increases, that is, the amount of polyester resin fiber produced increases. Therefore, by using a high winding speed of 400 m / min or more, polyester resin fiber can be produced with high productivity.

[0136] [Cooling process, cutting process, and drying process] This manufacturing method may further include a cooling step after step 1, in which the molten kneaded resin composition obtained in step 1 is cooled. In step 1, for example, the molten kneaded resin composition is extruded in strand form from a die provided in a kneader. In the cooling step, for example, the molten kneaded resin composition extruded in strand form from the die provided in the kneader is cooled (water-cooled) in a water tank by passing it through the water tank.

[0137] The process may further include a cutting step after step 1 or after the cooling step, in which the resin composition is cut. In the cutting step, for example, the strand-like resin composition is cut into any shape (e.g., particulate or pellet-like).

[0138] This manufacturing method may further include a drying step of drying the resin composition (for example, the pelletized resin composition after the cutting step).

[0139] If the manufacturing method further includes a cooling step and / or a drying step after step 1, the resin composition may be melted before step 2, and the molten resin composition may be wound up in step 2.

[0140] In this manufacturing method, for melting the resin composition, equipment such as a single-screw extruder and a twin-screw extruder can be used. In this manufacturing method, for melting the resin composition, the resin composition is heated to, for example, 240°C to 270°C, 270°C to 300°C, or 300°C to 320°C to melt it.

[0141] (Discharge process) This manufacturing method may further include a dispensing step before step 2 in which a molten resin composition is dispensed from a nozzle having holes. In the dispensing step, the molten resin composition dispensed from the nozzle may be (i) a molten kneaded product of the resin composition obtained in step 1, or (ii) a resin composition obtained by melting the resin composition obtained after step 1, which has undergone a cooling step and / or a drying step.

[0142] The nozzle only needs to have one or more holes. The number of holes provided in the nozzle is not particularly limited. The arrangement of the holes provided in the nozzle is also not particularly limited.

[0143] The cross-sectional area per hole in the nozzle is not particularly limited. From the viewpoint of easily obtaining fine-denier undrawn yarn, for example, undrawn yarn with a single fiber density of 60 dtex or less, preferably 30 dtex or less, the cross-sectional area per hole in the nozzle is 0.200 mm². 2 Preferably, it is 0.130 mm 2 Preferably, it is 0.060 mm 2 The following is even more preferable: The lower limit of the cross-sectional area per hole in the nozzle is not particularly limited, but for example, from the viewpoint of preventing clogging of the holes, 0.008 mm 2 That's fine too.

[0144] In this specification, "fineness" of a fiber (yarn or resin composition) refers to the thickness of the fiber (yarn or resin composition) and is defined as the mass per unit length. The unit (dtex) is expressed as the mass (g) per 10,000 m.

[0145] The shape of the nozzle hole is not particularly limited and can be selected according to the properties required for the drawing multifilament (e.g., appearance, fineness, strength, cross-sectional shape, etc.). Examples of nozzle hole shapes include circular shapes (concepts including perfect circles, approximate circles, ellipses, and approximate ellipses).

[0146] [Stretching process] The present manufacturing method may further include a stretching step after step 2, in which the wound polyester resin fibers are stretched. If the present manufacturing method further includes a stretching step, the fiber strength of the polyester resin fibers can be improved. In other words, if the present manufacturing method further includes a stretching step, polyester resin fibers with higher fiber strength can be obtained.

[0147] In the stretching process, the method for stretching the polyester resin fibers obtained in step 2 is not particularly limited, and known methods for stretching fibers, such as heat stretching, can be employed. When heat stretching is employed in the stretching process, known means such as heating rollers, heat plates, steam jet devices, and hot water baths can be used as heating means in the heat stretching, and these means can also be used in appropriate combinations.

[0148] The fineness of the polyester resin fiber after stretching can be adjusted by the fineness of the polyester resin fiber after winding obtained in step 2 and the stretching conditions such as the stretching ratio in the stretching step. Here, the suitable fineness of the polyester resin fiber varies depending on the application of the polyester resin fiber. Therefore, the suitable stretching conditions in the stretching step can be appropriately adjusted according to the application of the polyester resin fiber and the fineness of the polyester resin fiber itself obtained in step 2. The fineness of the polyester resin fiber itself obtained in step 2 can be adjusted by the manufacturing conditions in step 2, such as the winding speed. Furthermore, if a discharge step is included, the fineness of the polyester resin fiber may also change depending on the conditions of the discharge step.

[0149] In the stretching process, the stretching ratio of the polyester resin composition is not particularly limited, but from the viewpoint of fiber strength, for example, it is preferably 1.1 to 5.0 times, more preferably 1.5 to 4.5 times, and particularly preferably 2.0 to 4.0 times.

[0150] The polyester resin fibers obtained in step 2 and the stretching step may be long fibers. "Long fibers" may also be referred to as "filaments" or "filament fibers." In other words, step 2 and the stretching step can be described as steps that process the polyester resin composition into long fibers. Furthermore, short fibers of polyester resin can be produced by cutting the long fibers of the polyester resin fibers obtained in step 2 and the stretching step. "Short fibers" may also be referred to as "staples" or "staple fibers."

[0151] [Physical properties of polyester resin fibers] The polyester resin fibers produced by this manufacturing method have the advantage of possessing physical properties (e.g., thermal shrinkage rate, maximum elongation, elongation at break, and Young's modulus) equivalent to those of polyester resin fibers obtained using virgin polyester resin. The method for measuring the thermal shrinkage rate, maximum elongation, elongation at break, and Young's modulus of the polyester resin fibers is not particularly limited, and the method described in the examples can be used. The polyester resin fibers produced by the method for producing polyester resin fibers according to one embodiment of the present invention are also one embodiment of the present invention.

[0152] [3.Applications] One embodiment of the present invention has the advantage of providing a method for producing polyester resin fibers that enables high productivity even when a modifier is used. Therefore, one embodiment of the present invention can be suitably used in the field of polyester resin fibers, particularly recycled polyester resin fibers using recycled polyester resin. Furthermore, polyester resin fibers obtained using one embodiment of the present invention can be suitably used in various fields such as clothing and interior applications. [Examples]

[0153] The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to these, and examples obtained by appropriately combining the technical means disclosed in each example are also included within the scope of the present invention.

[0154] [Measurement methods and evaluation methods] 1. Particle size of the composite The particle size of the polymer or composite was measured using Microtrac UPA (manufactured by Nikkiso Co., Ltd.) and obtained by calculating the volume-average particle size.

[0155] 2. Polymerization conversion rate The polymerization conversion rate was defined as the ratio (%) of the actual solid content to the solid content at the ideal conversion rate.

[0156] 3. Number-average molecular weight and weight-average molecular weight The number-average molecular weight and weight-average molecular weight of polymer (A), the number-average molecular weight and weight-average molecular weight of polymer (B), and the weight-average molecular weight of the modifier were calculated by GPC measurement. A GPC instrument manufactured by Tosoh Corporation was used. The analysis conditions were as follows: Column 1 (low molecular weight column) Column 1: TSKgel SuperH5000 Second column: TSKgel SuperH4000 Third column: TSKgel SuperH3000 Column 4: TSKgel SuperH2000 Column 2 (polymer column) Column 1: TSKgel SuperHZM-H Second column: TSKgel SuperHZM-H Injection method: Syringe measurement Loop volume: 100 μL Preliminary aspiration volume: 150 μL Air volume: 3.5 μL Automatic washing capacity: 1.0 mL Syringe speed Sampling rate: 10 μL / s Washing speed: 100 μL / s Measuring speed: 5μL / s Sample flow rate: 0.350 mL / min Reference flow ratio: 1x Flow rate increase / decrease control: Disabled Flow rate increase: 0.35 mL / min Flow rate reduction rate: 0.35mL / min Pressure limit Column 1 Sample pressure limit: 12.0 MPa Sample pressure lower limit: 0.2 MPa Reference pressure limit: 25.0 MPa Reference pressure lower limit: 0.2 MPa Column 2 Sample pressure limit: 25.0 MPa Sample pressure lower limit: 0.2 MPa Reference pressure limit: 12.0 MPa Reference pressure lower limit: 0.2 MPa flow rate Column 1 Sample flow rate: 0.600 mL / min Reference flow rate ratio: 1 / 2 Column 2 Sample flow rate: 0.350 mL / min Reference flow ratio: 1x Flow rate increase / decrease control: Disabled Flow rate increase rate: 0.35 mL / min / min Flow rate reduction rate: 0.35mL / min / min Pressure limit Column 1 Sample pressure limit: 12.0 MPa Sample pressure lower limit: 0.2 MPa Reference pressure limit: 25.0 MPa Reference pressure lower limit: 0.2 MPa Peak detection conditions RI Detection sensitivity (front): 3,000 mV / min Detection sensitivity (rear side): 3,000 mV / min Base detection value: 1.000mV / min Exclusion area: 10.000mVs Exclusion height: 0.000mV Excluding half-width: 0.000s UV / EXT Detection sensitivity (front): 3,000 mV / min Detection sensitivity (rear side): 3,000 mV / min Base detection value: 1.000mV / min Exclusion area: 10.000mVs Exclusion height: 0.000mV Excluding half-width: 0.000s Polystyrene was used as the reference material. Specifically, GPC was performed using polystyrene with known number-average molecular weight and weight-average molecular weight under the conditions described above to obtain a calibration curve. Subsequently, GPC was performed on the samples (polymer (A), polymer (B), and modifier) ​​under the conditions described above, and the number-average molecular weight and weight-average molecular weight of each sample were calculated from the calibration curve. The number-average molecular weight and weight-average molecular weight of the modifier were calculated by volume calculation based on the GPC measurement described above.

[0157] 4. Epoxy equivalent and epoxy group content The epoxy equivalent of the modifier was measured according to the JIS K7236:2001 standard. Specifically, the procedure was as follows: The accurately weighed modifier was dissolved in chloroform. To the resulting solution, acetic acid and tetraethylammonium bromide acetic acid solution were added. The resulting solution was used as a sample and subjected to potentiometric titration using a 0.1 mol / L perchloric acid acetic acid standard solution. In potentiometric titration, following the addition of the perchloric acid-acetic acid standard solution, perchloric acid and tetraethylammonium bromide react to produce hydrogen bromide. The generated hydrogen bromide reacts with the epoxy groups. The endpoint was reached when all epoxy groups had reacted and hydrogen bromide was in excess. The epoxy equivalent (g / eq) of the modifier was calculated by this potentiometric titration. Furthermore, based on the epoxy equivalent (g / eq) of the obtained modifier, the number of epoxy groups per molecule of each polymer (A) and (B) was calculated based on the ratio (concentration) of epoxy group-containing monomers to the total monomers used in the production of each polymer (A) and (B). The epoxy equivalent (g / eq) of each polymer (A) and (B) was then calculated based on the number-average molecular weight (Mn) of each polymer (A) and (B) and the following formula. The epoxy equivalent weight (g / eq) of a polymer = number-average molecular weight (Mn) of the polymer / number of epoxy groups per polymer molecule (average number).

[0158] 5. Content of monomer residue containing reactive functional groups and total monomer residue Gas chromatography (GC) was performed on the modifier under the following conditions to measure the content of reactive functional group-containing monomer residue and total monomer residue in the modifier. Specifically, 0.1 g to 0.15 g of the modifier after accurate weighing and a stirrer tip were placed in a 20 ml screw-cap tube. Furthermore, 3 ml of methylene chloride containing an internal standard was added to the screw-cap tube, and the contents of the screw-cap tube were stirred with a stirrer for 30 minutes or more to dissolve the modifier in methylene chloride and obtain a solution. GC was performed on the obtained solution (sample). From the graph obtained by GC, the area of ​​the peak corresponding to each monomer in the sample and the area corresponding to CB (chlorobenzene) were determined, and the content of each monomer residue was quantified (calculated) from the following formula (1) based on the internal standard method. The total amount of monomer residues corresponding to reactive functional group-containing monomer residue among the above monomer residues was defined as the content of reactive functional group-containing monomer residue. Furthermore, the sum of the contents of each monomer residue was defined as the total monomer residue content. Mo concentration (ppm) = (Area of ​​Mo / Area of ​​CB) × Mo factor × Internal standard amount (μg) / Sample amount (g) ... Equation (1) In formula (1), Mo represents the monomer residue containing reactive functional groups and / or total monomer residue that is the subject of measurement, and the concentration of Mo is the concentration (unit: ppm) when the solid content of the modifier is 100% by weight.

[0159] (GC measurement conditions) Equipment: Gas chromatography GC-2014 (manufactured by Shimadzu Corporation) Column: Capillary column Mobile phase: Gas chromatography Internal standard: Chlorobenzene (CB) Detector: FID Area measurement method: Internal standard method.

[0160] In the manufacturing example below, butyl acrylate (BA), styrene (ST), and glycidyl methacrylate (GMA) were used as monomers. Of these, GMA is a monomer containing a reactive functional group. Table 1 below shows the results for each monomer residue for each modifier. In the results for each monomer residue, "ND" indicates that the monomer (Mo) was below the detection limit (Not Detected), meaning that the peak of the monomer (Mo) was not detected. The detection limits of the equipment used (gas chromatography GC-2014 (manufactured by Shimadzu Corporation)) were 13.5 ppm for BA, 20.8 ppm for ST, and 9.7 ppm for GMA. The ND result for each monomer residue means that BA was less than 13.5 ppm, ST was less than 20.8 ppm, and GMA was less than 9.7 ppm.

[0161] 6. Melt viscosity (IV value) of the resin composition The IV value of the resin composition was measured in accordance with JIS K 7367-5. Specifically, an equiweight mixture of phenol and tetrachloroethane was used as the solvent, and the resin composition was dissolved in this solvent to a concentration of 0.5 g / dL. The solution obtained was used as the sample. The relative viscosity of the solution was measured at 25°C using an Ubbelohde viscosity tube, and the intrinsic viscosity was calculated.

[0162] 7. Melt flow rate (MFR) of resin composition The polyester resin composition pellets obtained in each example and comparative example were placed in a 120°C incubator and dried for 5 hours. The MFR of the dried resin composition pellets was measured using a melt flow index tester (manufactured by Yasuda Seiki Seisakusho) under conditions of 270°C and a load of 2.16 kg.

[0163] 8. Fineness The fineness (in dtex) of polyester resin fibers was measured using DC-21 manufactured by Search Co., Ltd. In this example, the polyester resin fibers may include both unstretched and stretched polyester resin fibers.

[0164] 9. Heat shrinkage rate (heat shrinkage rate at 180°C and 200°C) The dry heat shrinkage rates of the fibers in the examples and comparative examples were measured as follows: The fibers were cut to a length L1 (300 mm), and the L1 length fibers were dried in a dryer at a temperature of 180°C or 200°C for 30 minutes. Next, the length L2 of the fibers dried at each temperature was measured with calipers. The dry heat shrinkage rate was calculated using the following formula: Dry heat shrinkage rate (%)=((L1-L2) / L1)×100(%).

[0165] 10. Maximum elongation, elongation at break, and Young's modulus The tensile strength and elongation of the filament were measured using an INTESCO Model 201 (manufactured by Intesco Corporation). Specifically, the procedure was as follows: A 40mm long filament was taken, and the ends of the filament were sandwiched between pieces of thin paper with adhesive-coated double-sided tape attached. The filament was air-dried overnight to prepare a 20mm long sample. The sample was mounted in the testing machine and tested at a temperature of 24°C, humidity of 80% or less, load of 1 / 30gf × fineness (denier), and tensile speed of 20mm / min. The maximum elongation, elongation at break, and Young's modulus were measured. The test was repeated 10 times under the same conditions, and the average values ​​were taken as the maximum elongation, elongation at break, and Young's modulus of the filament.

[0166] [material] <Polyester resin> Polyester resin 1: Virgin polyester resin (manufactured by Teijin Corporation, product name: TRN-MTJ, melt flow rate (MFR) = 111.2, melt viscosity (IV value) = 0.53) Polyester resin 2: Virgin polyester resin (manufactured by Unitika Corporation, product name: MA-2101M, melt flow rate (MFR) = 66.0, melt viscosity (IV value) = 0.62) <Modifier> Modifier 1: The modifier obtained in Production Example 1 below. Modifier 2: The modifier obtained in Production Example 2 below. Modifiers 1 and 2 are modifiers according to one embodiment of the present invention.

[0167] [Manufacturing example] <Manufacturing Example 1: Preparation of Modifier 1> (Preparation of polymer (A)) First, purified water (180 parts by weight), sodium ethoxyalkylated alkyl phosphate (1.5 parts by weight), ethylenediaminetetraacetic acid (EDTA) (0.0075 parts by weight), iron sulfate heptahydrate (0.3 parts by weight), and t-butyl hydroperoxide (0.1 parts by weight) were added to the reactor.

[0168] Subsequently, a monomer mixture (a1) was prepared by mixing styrene (ST), a monomer without reactive functional groups (68 parts by weight), glycidyl methacrylate (GMA), a monomer containing reactive functional groups (12 parts by weight), and n-octyl mercaptan, a chain transfer agent (1.5 parts by weight), and added to the reactor over 150 minutes to obtain mixture (b1). In the monomer mixture (a1), ST accounted for 85% by weight and GMA for 15% by weight out of a total of 100% by weight of ST and GMA.

[0169] Next, while stirring the mixture (b1) in the reactor, the temperature of the mixture (b1) was raised to 75°C, and nitrogen was bubbled into the mixture (b1) for 30 minutes. After the nitrogen bubbling, ethoxyalkylated alkyl phosphate sodium (0.2 parts by weight) and t-butyl hydroperoxide (0.03 parts by weight), which is a polymerization initiator, were added to the mixture (b1) in the reactor to obtain mixture (c1).

[0170] Next, each monomer in mixture (c1) was reacted until the polymerization conversion rate exceeded 90%, yielding reactant (a1). Then, the temperature of reactant (a1) was lowered to 65°C, and reactant (a1) was left at 65°C for 30 minutes. Through this procedure, polymer (a1), which is polymer (A), was obtained.

[0171] (Preparation of polymer (B) and modifier 1) Next, monomer mixture (d1), which was prepared by mixing butyl acrylate (BA) (5 parts by weight), GMA (1 part by weight), and ST (14 parts by weight), was added to the reactor containing polymer (a1) to obtain mixture (e1). In this monomer mixture (d1), of the total 100% by weight of BA, GMA, and ST, BA accounted for 25% by weight, GMA for 5% by weight, and ST for 70% by weight.

[0172] Next, sodium ethoxyalkylated alkyl phosphate (0.2 parts by weight) and t-butyl hydroperoxide (0.03 parts by weight), which is a polymerization initiator, were added to the mixture (e1) in the reactor to obtain mixture (f1).

[0173] Next, each monomer in mixture (f1) was reacted until the reaction rate exceeded 98% to obtain polymer (b1), which is polymer (B). As a result, latex 1 containing complex 1 composed of polymer (a1) and polymer (b1) was obtained. Complex 1 can be considered a modifier. Polymer (b1) contained 5% by weight of GMA units as reactive functional group-containing units in 100% by weight of polymer (b1).

[0174] Using the method described above, the particle size of composite 1 in latex 1 was measured to be 1100 angstroms. Furthermore, it can be considered that in composite 1, polymer (a1), which is polymer (A), forms the core, and polymer (b1), which is polymer (B), forms the shell. In other words, composite 1 (i.e., the modifier) ​​can be considered to have a core-shell structure. Composite 1 (i.e., the modifier) ​​contained 80% by weight of polymer (a1) and 20% by weight of polymer (b1) in 100% by weight of composite 1. The number-average molecular weight and weight-average molecular weight of composite 1 were measured using the method described above. As a result, composite 1 had two types of number-average molecular weights (Mn), namely, the number-average molecular weight of polymer (a1) was 9,000 Da, and the number-average molecular weight of polymer (b1) was 13,000 Da. Furthermore, complex 1 had two different weight-average molecular weights (Mw): polymer (a1) had a weight-average molecular weight of 50,000 Da, and polymer (b1) had a weight-average molecular weight of 120,000 Da. The weight-average molecular weight of complex 1 (i.e., the modifier) ​​was 55,000 Da. The polydispersity index of polymer (a1) was 3.0, and the polydispersity index of complex 1 was 4.0. The average number of reactive functional groups per molecule of polymer (a1) was 7, the average number of reactive functional groups per molecule of polymer (b1) was 3, and the average number of reactive functional groups per molecule of complex 1 was 6. The epoxy equivalent of polymer (a1) was 1500 g / eq, and the epoxy equivalent of polymer (b1) was 8400 g / eq.

[0175] To recover composite 1 as a powder from latex 1, the obtained latex 1 was quickly added to a 5% calcium chloride aqueous solution while stirring to obtain mixture (g1). The temperature of mixture (g1) was heated to 70°C using steam heating and maintained at 70°C. Next, the temperature of mixture (g1) was raised to 85°C to form aggregates of composite 1, and then the mixture (g1) was dehydrated to obtain aggregates of composite 1 from mixture (g1). The obtained aggregates of composite 1 were dried to obtain composite 1 powder. Subsequently, the composite 1 powder was sieved through an 18-mesh screen to obtain the white powder that passed through the 18-mesh screen. Hereafter, the obtained white powder will be referred to as "modifier 1".

[0176] <Manufacturing Example 2: Preparation of Modifier 2> (Preparation of polymer (A)) Except for the items shown in (i) below, the same procedure as described in the (Preparation of Polymer (A)) section of Production Example 1 was performed to prepare Polymer (a2), which is Polymer (A).

[0177] (i) Instead of monomer mixture (a1), monomer mixture (a2) was used, which consisted of ST (56 parts by weight), GMA (24 parts by weight), and n-octyl mercaptan (1.9 parts by weight). In monomer mixture (a2), ST accounted for 70% by weight and GMA for 30% by weight out of a total of 100% by weight of ST and GMA.

[0178] (Preparation of polymer (B) and modifier 2) Except for using a reactor containing polymer (a2) instead of a reactor containing polymer (a1), the same procedure as described in the section (Preparation of polymer (B) and modifier) ​​of Production Example 1 was carried out to obtain polymer (b2), which is polymer (B). As a result, latex 2 containing polymer (a2) and complex 2 composed of polymer (b2) was obtained. Complex 2 can be considered a modifier. Polymer (b2) contained 5% by weight of GMA units as reactive functional group-containing units in 100% by weight of polymer (b2).

[0179] Using the method described above, the particle size of composite 2 in latex 2 was measured to be 1100 angstroms. Furthermore, it can be considered that in composite 2, polymer (A), polymer (a2), forms the core, and polymer (B), polymer (b2), forms the shell. In other words, composite 2 (i.e., the modifier) ​​can be considered to have a core-shell structure. Composite 2 (i.e., the modifier) ​​contained 80% by weight of polymer (a2) and 20% by weight of polymer (b2) per 100% by weight of composite 2. The number-average molecular weight and weight-average molecular weight of composite 2 were measured using the method described above. As a result, composite 2 had two different number-average molecular weights (Mn): the number-average molecular weight of polymer (a2) was 6,000 Da, and the number-average molecular weight of polymer (b2) was 10,000 Da. Furthermore, complex 2 had two different weight-average molecular weights (Mw): polymer (a2) had a weight-average molecular weight of 20,000 Da, and polymer (b2) had a weight-average molecular weight of 100,000 Da. The weight-average molecular weight of complex 2 (i.e., the modifier) ​​was 80,000 Da. The polydispersity index of polymer (a2) was 3.0, and the polydispersity index of complex 2 was 4.0. The average number of reactive functional groups per molecule of polymer (a2) was 9, the average number of reactive functional groups per molecule of polymer (b2) was 3, and the average number of reactive functional groups per molecule of complex 2 was 8. The epoxy equivalent of polymer (a2) was 700 g / eq, and the epoxy equivalent of polymer (b2) was 8400 g / eq.

[0180] Except for using latex 2 instead of latex 1, the same method used in Production Example 1 to recover composite 1 as powder from latex 1 was used to obtain composite 2 powder from latex 2. Subsequently, the composite 2 powder was sieved through an 18-mesh screen to obtain the white powder that passed through the 18-mesh screen. Hereafter, the obtained white powder will be referred to as "modifier 2".

[0181] Using the method described above, the content of reactive functional group-containing monomer residue and total monomer residue in modifiers 1 and 2 obtained in manufacturing examples 1 and 2 was calculated. Specifically, the content of styrene (ST) residue, glycidyl methacrylate (GMA) residue, and butyl acrylate (BA) residue, which are monomer residues that may be contained in modifiers 1 and 2, was calculated. The results are shown in Table 1 below. Of the monomer residues mentioned above, the residue corresponding to the reactive functional group-containing monomer residue is the GMA residue.

[0182] [Table 1] As shown in Table 1, the content of each monomer residue contained in modifiers 1 and 2, namely ST residue, GMA residue, and BA residue, was all below the detection limit (ND; Not Detected).

[0183] [Example 1] (Step 1: Preparation of polyester resin composition) Polyester resin 1 was left overnight in a 120°C constant temperature oven (Perfect Oven PVH-332, manufactured by ESPEC Corporation) to dry the polyester resin 1.

[0184] A mixture was obtained by dry blending dried polyester resin 1 and modifier 1. The obtained mixture was melt-kneaded using a twin-screw extruder (Technovel Co., Ltd., 25 mm, L / D=40) under the conditions of cylinder temperature 240°C to 270°C, gravimetric feeder discharge rate 20 kg / hour, and screw rotation speed 400 rpm. At this time, the amount of modifier 1 used was 3.0% by weight of the total weight of polyester resin 1 and modifier 1 (100% by weight). Next, the melt-kneaded material extruded from the die was cooled in a water bath and cut with a pelletizer. Through this operation, resin pellets, which are a polyester resin composition containing constituent units derived from the polyester resin and constituent units derived from the modifier, were obtained. The obtained resin pellets are referred to as "Polyester Resin Composition 1".

[0185] The MFR and IV values ​​of the obtained polyester resin composition 1 were measured using the method described above. The results are shown in Table 3.

[0186] (Preparation of polyester resin fibers) (Discharge process) Polyester resin composition 1 was left in the constant temperature oven at 120°C for 24 hours to obtain dried pellets. The obtained dried pellets were subjected to a multifilament manufacturing apparatus using a 40 mm single-screw extruder to produce multifilaments. The nozzle of the multifilament manufacturing apparatus had a hole diameter of φ0.9, a land length of 3.2 L, and 400 holes. In the production of multifilaments, the resin discharge rate during extrusion was set to 15 kg / hour.

[0187] (Process 2) Next, the obtained multifilament was wound onto a paper tube using a winding device at a winding speed of 400 m / min for more than 10 minutes. The wound filament was designated as "polyester resin fiber 1 before stretching." The fineness of polyester resin fiber 1 before stretching was measured using the method described above. The fineness of polyester resin fiber 1 before stretching was 13.8 (dtex).

[0188] (Stretching process: Stretching of polyester resin fibers) The polyester resin fiber 1 before stretching was subjected to a stretching device and stretched at a stretching ratio of 2x, 3x, or 4x according to the conditions described in Table 2 below, and then wound up on a winding machine for 15 minutes or more. The polyester resin fiber wound up after stretching is referred to as "stretched polyester resin fiber 1".

[0189] [Table 2]

[0190] The fineness, dry shrinkage rate, maximum elongation, break elongation, and Young's modulus of the stretched polyester resin fiber 1 were measured using the method described above. The results are shown in Table 4.

[0191] [Example 2] The same procedure as in Step 1 of Example 1 was carried out, except that modifier 2 was used instead of modifier 1, and the amount of modifier 2 used was 1.0% by weight out of the total weight of polyester resin 1 and modifier 2 (100% by weight). Through this procedure, polyester resin composition 2 was obtained, which is a polyester resin composition containing constituent units derived from the polyester resin and constituent units derived from the modifier.

[0192] The MFR and IV values ​​of the obtained polyester resin composition 2 were measured using the method described above. The results are shown in Table 3.

[0193] Next, the same procedure as described in the (Discharge Process) and (Step 2) sections of (Preparation of Polyester Resin Fibers) in Example 1 was carried out, except that polyester resin composition 2 was used instead of polyester resin composition 1, to obtain polyester resin fiber 2 before stretching. The fineness of polyester resin fiber 2 before stretching was measured using the method described above. The fineness of polyester resin fiber 2 before stretching was 13.8 (dtex).

[0194] Next, the polyester resin fiber 2 was stretched using the same method and conditions as described in the section (Stretching process: Stretching of polyester resin fiber) of Example 1, except that the polyester resin fiber 2 was used instead of the polyester resin fiber 1 before stretching. This stretching yielded the stretched polyester resin fiber 2.

[0195] The fineness, dry shrinkage rate, maximum elongation, break elongation, and Young's modulus of the stretched polyester resin fiber 2 were measured using the method described above. The results are shown in Table 4.

[0196] [Reference example 1] In contrast to Examples 1 and 2, Reference Example 1 used polyester resin 2 instead of polyester resin 1, and did not use a modifier.

[0197] For polyester resin 2, the MFR and IV values ​​were measured using the method described above. The results are shown in Table 3.

[0198] Next, the same procedure as described in (Discharge Process) and (Step 2) of (Preparation of Polyester Resin Fibers) in Example 1 was carried out, except that polyester resin 2 was used instead of polyester resin composition 1, to obtain polyester resin fibers 3 before stretching. The fineness of the polyester resin fibers 3 before stretching was measured using the method described above. The fineness of the polyester resin fibers 3 before stretching was 13.9 (dtex).

[0199] Next, the polyester resin fiber 3 was stretched using the same method and conditions as described in the section (Stretching process: Stretching of polyester resin fiber) of Example 1, except that the polyester resin fiber 3 was used instead of the polyester resin fiber 1 before stretching. This stretching yielded the stretched polyester resin fiber 3.

[0200] The fineness, dry shrinkage rate, maximum elongation, break elongation, and Young's modulus of the stretched polyester resin fiber 3 were measured using the method described above. The results are shown in Table 4.

[0201] [Table 3]

[0202] [Table 4] [Industrial applicability]

[0203] According to one embodiment of the present invention, polyester resin fibers can be manufactured with high productivity even when a modifier is used. Therefore, one embodiment of the present invention can be suitably used in the field of polyester resin fibers, particularly recycled polyester resin fibers using recycled polyester resin. Furthermore, polyester resin fibers obtained using one embodiment of the present invention can be suitably used in various fields such as clothing and interior applications.

Claims

1. Step 1 involves melt-kneading a polyester resin and a modifier to obtain a polyester resin composition, A method for producing polyester resin fibers, comprising: step 2 winding the polyester resin composition obtained in step 1 at a winding speed of 400 m / min or more.

2. Furthermore, the method for producing polyester resin fibers according to claim 1, further comprising a stretching step of stretching the polyester resin fibers obtained in step 2.

3. A method for producing polyester resin fibers according to claim 1 or 2, wherein the polyester resin is polyethylene terephthalate (PET).

4. A method for producing polyester resin fibers according to claim 1 or 2, wherein the modifier comprises a polymer (A) containing reactive functional group-containing units and reactive functional group-free units.

5. The method for producing polyester resin fibers according to claim 4, wherein the modifier further comprises polymer (B).

6. The method for producing polyester resin fibers according to claim 5, wherein the epoxy equivalent of the polymer (B) is 6,000 g / eq to 50,000 g / eq.

7. The method for producing polyester resin fibers according to claim 5, wherein the polymer (B) contains more than 2.5% by weight and 10.0% by weight or less of reactive functional group-containing units in 100% by weight of the polymer (B).

8. The method for producing polyester resin fibers according to claim 7, wherein the polymer (B) contains a glycidyl methacrylate unit as the reactive functional group-containing unit.

9. The method for producing polyester resin fibers according to claim 5, wherein the modifier contains 15% to 70% by weight of the polymer (A) and 30% to 85% by weight of the polymer (B) in 100% by weight of the modifier.

10. The method for producing polyester resin fibers according to claim 5, wherein the modifier contains 50% to 90% by weight of polymer (A) and 10% to 50% by weight of polymer (B) in 100% by weight of the modifier.

11. The method for producing polyester resin fibers according to claim 4, wherein the polymer (A) has an average of 2 to 10 reactive functional groups per molecule.

12. The method for producing polyester resin fibers according to claim 1 or 2, wherein the weight-average molecular weight of the modifier is 20,000 Da or more and less than 200,000 Da.

13. The method for producing polyester resin fibers according to claim 4, wherein the number average molecular weight of the polymer (A) is less than 10,000 Da.

14. The method for producing polyester resin fibers according to claim 4, wherein the polydispersity index of the polymer (A) is 2.0 to 10.

0.

15. The polymer (A) is (i) The reactive functional group containing unit includes an epoxy group containing (meth)acrylate unit, (ii) The method for producing polyester resin fibers according to claim 4, comprising one or more constituent units selected from the group consisting of reactive functional group-free styrene units and reactive functional group-free (meth)acrylic units as the reactive functional group-free units.

16. The method for producing polyester resin fibers according to claim 5, wherein the polymer (B) comprises one or more constituent units selected from the group consisting of styrene units and (meth)acrylic units.

17. The method for producing polyester resin fibers according to claim 5, wherein the weight-average molecular weight of the polymer (B) is 80,000 Da to 500,000 Da.

18. The method for producing polyester resin fibers according to claim 1 or 2, wherein the modifier has, based on the weight of the modifier, less than 50 ppm of reactive functional group-containing monomer residue and less than 100 ppm of total monomer residue.

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