Polyester monofilament

Abstract

The present invention aims to solve the above problems and provide a monofilament that has low intrinsic viscosity while possessing high hydrolysis resistance, which was not possible with conventional technology. [Solution] A polyester monofilament comprising a resin composition mainly composed of polyester resin, wherein the resin composition contains 0.01 to 4.00 parts by mass of an amine compound and 0.01 to 4.00 parts by mass of an isocyanate compound per 100 parts by mass of polyester resin.

Description

Technical Field

[0001] The present invention relates to a monofilament containing a polyester resin as a main component.

Background Art

[0002] Since polyester has excellent mechanical properties, it has been used in various industrial parts, clothing and industrial fiber materials, and various fabric applications.

[0003] For example, among fibers made of polyester, polyethylene terephthalate monofilaments have been widely and preferably used in papermaking dryer canvases, papermaking wires, various brushes, brush hairs, printing screen yarns, fishing lines, fiber materials for rubber reinforcement, etc., and are particularly widely used in papermaking wires and papermaking dryer canvases of industrial fabrics used in the papermaking process.

[0004] In particular, in the current papermaking industry, for the purpose of improving productivity during the operation of paper machines, in addition to the enlargement of paper machines, a dramatic increase in papermaking speed has been promoted. Among these papermaking products, in the drying process of the papermaking process for producing cardboard, with the increase in papermaking speed, for the purpose of improving drying efficiency, drying is often carried out under very high temperature conditions exceeding 150°C compared to the conventional ones. Along with this, even in industrial fabrics using modified polyester monofilaments with improved hydrolysis resistance, which was not regarded as a problem for product life in the past, the problem of shortened product life has become apparent.

[0005] From such a situation, it is desired to realize a polyester monofilament with higher hydrolysis resistance than conventional modified polyester monofilaments.

[0006] Many technologies for improving the hydrolysis resistance of polyester monofilaments have been proposed so far.

[0007] For example, polyester fibers and filaments in which terminal carboxyl groups are capped by reaction with carbodiimide groups, and these terminal carboxyl groups are capped by reaction with mono and / or biscarbodiimide groups, and these fibers and filaments are present in 30 to 200 ppm based on the mass of polyester, the content of free terminal carboxyl groups in the polyester is less than 3 eq / t, and these fibers and filaments additionally contain at least 0.02 mass% of a reactive substance containing at least one free polycarbodiimide group (see, for example, Patent Document 1). Furthermore, a manufacturing method has been proposed, comprising the step of blending a polyester resin with 0.00005 to 0.03 mol% of a first compound selected from the group consisting of polyalkylene glycol, alkoxy-end capped polyalkylene glycol and mixtures thereof, and 0 to 3 wt% of a second compound selected from the group consisting of glycidyl ether, carbodiimide, ketenimine, aziridine, and isocyanate to produce a blended polyester (see, for example, Patent Document 2).

[0008] While these technologies are all reasonably effective in improving the hydrolysis resistance of polyester and polyester fibers, they have not been sufficient to solve the problem of insufficient hydrolysis resistance and shortened lifespan of industrial textiles when used in the process of drying paper sheets at extremely high temperatures exceeding 150°C in today's large-scale, high-speed paper machines.

[0009] Furthermore, polyester fibers have been proposed (see, for example, Patent Document 3) in which ethylene terephthalate units are the main repeating units, the polycarbodiimide compound has a degree of polymerization of 5 or more and is solid at room temperature, is contained in an amount of 0.3 to 5.0 wt% relative to the polyester, the terminal carboxyl group concentration is 20 eq / t or less, the strength is 6 g / d or more, and the intrinsic viscosity is 0.8 dl / g or more.

[0010] While this technology is reasonably effective in improving the hydrolysis performance of polyester and polyester fibers, it requires an intrinsic viscosity of 0.8 dl / g or higher, which limits the types of raw materials that can be used and thus hinders its versatility. Furthermore, polyester monofilaments have been proposed that contain a polyester resin, a copper-containing compound, and a tertiary amine chelate compound, wherein the ends of the polyester resin contain hydroxyl groups or unsubstituted phenyl groups, and the concentration of unsubstituted phenyl groups at the ends of the polyester resin is 15 eq / ton or more (see, for example, Patent Document 4).

[0011] While this technology is reasonably effective in improving the hydrolysis performance of polyester and polyester fibers, it has been hampered by its limited versatility due to the need to use a specific copper catalyst, which restricts the types of raw materials that can be used. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 4-289221 [Patent Document 2] Patent No. 2968240 [Patent Document 3] Japanese Patent Publication No. 10-168655 [Patent Document 4] Japanese Patent Publication No. 2021-143439 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The present invention aims to solve the above problems and provide a monofilament mainly composed of a polyester resin that has low intrinsic viscosity while possessing high hydrolysis resistance, which was not achievable with conventional technology. [Means for solving the problem]

[0014] As a result of diligent research to achieve the above objective, the inventors have found that by including 0.01 to 4.00 parts by mass of an amine compound and 0.01 to 4.00 parts by mass of an isocyanate compound per 100 parts by mass of polyester resin in the monofilament, a monofilament containing a polyester resin as the main component can be obtained that has low intrinsic viscosity while exhibiting high hydrolysis resistance.

[0015] In other words [1] A polyester monofilament comprising a resin composition mainly composed of polyester resin, wherein the resin composition contains 0.01 to 4.00 parts by mass of an amine compound and 0.01 to 4.00 parts by mass of an isocyanate compound per 100 parts by mass of polyester resin. [2] The polyester monofilament according to [1], wherein the amine compound is a primary amine compound. [3] The polyester monofilament according to [1] or [2], wherein the resin composition further contains 0.01 to 4.00 parts by mass of a carbodiimide compound per 100 parts by mass of the polyester resin. [4] The polyester monofilament according to [3], wherein the carbodiimide compound is contained in an amount of 0.15 to 3.00 parts by mass per 100 parts by mass of the polyester resin. [5] The polyester monofilament according to any one of [1] to [4], wherein the amine compound is contained in an amount of 0.15 to 3.00 parts by mass per 100 parts by mass of the polyester resin. [6] The polyester monofilament according to any one of [1] to [5], wherein the isocyanate compound is contained in an amount of 0.15 to 3.00 parts by mass per 100 parts by mass of the polyester resin. [7] The polyester monofilament according to any one of [1] to [6], wherein the resin composition has an intrinsic viscosity of 0.40 to 1.00 dl / g. [8] The polyester monofilament is vaporized at a vapor pressure of 1.2 kg / cm². 2The polyester monofilament according to any one of [1] to [7], having a tensile strength retention rate of 15% or more after continuous heat and humidity treatment for 240 hours in a heat and humidity environment of (0.12 MPa) and a temperature of 121°C.

Advantages of the Invention

[0016] According to the present invention, there is provided a monofilament that has high strength and can be used for a long time in a heat and humidity environment.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail.

[0018] The monofilament of the present invention is a monofilament composed of a resin composition mainly containing a polyester resin, and the resin composition contains 0.01 to 4.00 parts by mass of an amine compound and 0.01 to 4.00 parts by mass of an isocyanate compound with respect to 100 parts by mass of the polyester resin.

[0019] The resin composition of the present invention contains a polyester resin as a main component. Here, containing a polyester resin as a main component means containing more than 50% by mass of the polyester resin, more preferably 70% by mass or more, and even more preferably 90% by mass.

[0020] The polyester resin contained in the resin composition constituting the monofilament of the present invention is a resin having a structure obtained by polycondensing dicarboxylic acid or its ester-forming derivative and diol as main raw materials. Here, expressing the structure in terms of raw materials is because there are cases where a plurality of raw materials in each category are used in combination, and it is difficult to specify the structure of the resin itself by chemical name. Therefore, the raw material name is used to specify the structural unit, and it is not limited to those synthesized from the raw materials. In the following description, when referring to the structural parts derived from dicarboxylic acid or its ester-forming derivative and diol that constitute the polyester resin, it shall be conveniently referred to as "dicarboxylic acid or its ester-forming derivative that constitutes the polyester resin" or "diol that constitutes the polyester resin". Here, the main raw materials indicate that the structural units having structures derived from dicarboxylic acid, its ester-forming derivative, and diol in the polyester resin are 80 mol% or more in total. The total of these structural units is more preferably 90 mol% or more, further preferably 95 mol% or more, and most preferably 100 mol%.

[0021] The dicarboxylic acid or its ester-forming derivative that constitutes the polyester resin used in the present invention is not particularly limited, and examples include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyl thioether-4,4'-dicarboxylic acid, 5-tetrabutylphosphonium isophthalic acid, 5-sodium sulfoisophthalic acid, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, undecanedioic acid, dodecanedioic acid, or their ester-forming derivatives, etc.

[0022] Here, ester-forming derivatives refer to lower alkyl esters, acid anhydrides, acid halides, etc., of the dicarboxylic acid mentioned earlier. As lower alkyl esters of dicarboxylic acids, methyl esters, ethyl esters, hydroxyethyl esters, hydroxybutyl esters, etc., are preferably used. As acid anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids and acetic acid, etc., are preferably used. As halogens of dicarboxylic acids, acid chlorides, acid bromides, acid iodides, etc., are preferably used.

[0023] In the present invention, aromatic dicarboxylic acids or their ester-forming derivatives are preferred as the dicarboxylic acids or their ester-forming derivatives, given that the resulting polyester resin exhibits excellent heat resistance. Preferred aromatic dicarboxylic acids or their ester-forming derivatives are terephthalic acid, 2,6-naphthalenedicarboxylic acid, or their dimethyl esters.

[0024] Examples of diols constituting the polyester resin used in the present invention include ethylene glycol, 1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclohexanedimethanol, xylylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A-ethylene oxide adduct, and the like. Among these, ethylene glycol, 1,3-propanediol, and 1,4-butanediol are preferred in that the resulting polyester resin exhibits excellent heat resistance.

[0025] Furthermore, dicarboxylic acids, ester-forming derivatives of dicarboxylic acids, and diols may be used individually or in combination of two or more types.

[0026] Examples of polyester resins applicable to the present invention include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyethylene isophthalate, polypropylene isophthalate, polybutylene isophthalate, polycyclohexanedimethylene isophthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, polycyclohexanedimethylene terephthalate / polyethylene terephthalate, polyethylene isophthalate / terephthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polyethylene terephthalate / 5-sodium sulfoisophthalate, polypropylene terephthalate / 5-sodium sulfoisophthalate, and polybutylene terephthalate / 5-sodium sulfoisophthalate. Here, " / " indicates a copolymer containing the components on either side. Among these, polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, and polyethylene naphthalate are preferred, with polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate being more preferred due to their excellent heat resistance.

[0027] The number-average molecular weight of the polyester resin used in this invention is preferably 5,000 to 100,000. More preferably, it is 7,000 to 80,000, and even more preferably 9,000 to 50,000. A number-average molecular weight greater than 5,000 tends to result in higher mechanical strength. On the other hand, a number-average molecular weight of 100,000 or less tends to result in easier melt processing. The number-average molecular weight can be determined by gel permeation chromatography.

[0028] The resin composition constituting the monofilament of the present invention contains an amine compound. This is because the inclusion of an amine compound allows for the capture of hydrogen ions from carboxyl groups generated by hydrolysis, thereby suppressing the progression of the hydrolysis reaction.

[0029] The amine compounds contained in the resin composition constituting the monofilament are not particularly limited, but examples include methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, cetylamine, methylenediamine, ethylenediamine, tetraethylenepentamine, and dimethylamine. Diethylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine, N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, N,N-dimethyltetraethylenepentamine, trimethylamine, triethylamine, tri-n-propylamine N, triisopropylamine, tri-n-butylamine, triisobutylamine, tri-sec-butylamine, tripentylamine, tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tridodecylamine, tricetylamine, N,N,N',N'-tetramethylmethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyltetraethylenepentamine, dimethylethylamine, methyl Tylpropylamine, benzylamine, phenethylamine, benzyldimethylamine, aniline, N-methylaniline, N-ethylaniline, N-propylaniline, N,N-dimethylaniline, N,N-bis(hydroxyethyl)aniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, ethylaniline, propylaniline, dimethylaniline, 2,6-diisopropylaniline, trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-Dinitroaniline, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, N,N-dimethyltoluidine, diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene, pyrrole, 2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, N-methylpyrrole, oxazole, isoxazole, thiazole, isothiazole, imidazole, 2-ethylimidazole, 2 -Ethyl-4-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecylimidazole, 4,5-diphenylimidazole, 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-isopropylimidazole, 2-butylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole, 2-ethylimidazole, 2- Phenyl-4-methylimidazoline, benzimidazole, 1-cyanoethylimidazole, 1-vinylimidazole, pyrroline, 2-methyl-1-pyrroline, pyrrolidine, N-methylpyrrolidine, pyrrolidinone, N-methylpyrrolidone, pyridine, methylpyridine, ethylpyridine, propylpyridine, butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine, triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine, 4-tert-butylpyridine, DIFF Examples include phenylpyridine, benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridone, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, dimethylaminopyridine, 2,6-di-t-butyl-4-methylpyridine, 4-(3-phenylpropyl)pyridine, pyrazine, piperidine, piperazine, morpholine, indole, quinoline, 3-quinoline carbonitride, isoquinoline, carbazole, etc.

[0030] In the present invention, the amine compound used is preferably a primary amine compound with the highest basicity, from the viewpoint of capturing hydrogen ions.

[0031] The resin composition constituting the monofilament of the present invention contains 0.01 to 4.00 parts by mass of an amine compound per 100 parts by mass of polyester resin, preferably 0.15 to 3.00 parts by mass, and more preferably 0.25 to 2.50 parts by mass.

[0032] If the amine compound content is greater than 4.00 parts by mass, the strength characteristics of the monofilament are significantly impaired. Furthermore, in the process of manufacturing the monofilament, it is necessary to add a large amount of amine compound to the polyester. In the spinning machine used to manufacture the monofilament, the amine compound may dissolve into a liquid state due to the heat generated to melt the polyester resin. This can lead to unstable kneadability with the molten polyester resin composition, or the liquid amine compound may accumulate in the spinning machine, potentially degrading the extrusion performance of the polyester mixed resin composition from the spinning machine.

[0033] Furthermore, when the amine compound content is less than 0.01 parts by mass, hydrolysis resistance is insufficient.

[0034] The resin composition constituting the monofilament used in the present invention contains an isocyanate compound. This is because the inclusion of an isocyanate compound allows for the encapsulation of carboxyl groups that are present in trace amounts at the ends of the polyester resin or that have been generated by hydrolysis.

[0035] The isocyanate compound contained in the resin composition constituting the monofilament is not particularly limited, but examples include monoisocyanate compounds such as phenyl isocyanate, 2,6-dimethylphenyl isocyanate, 3,5-dimethylphenyl isocyanate, 2,6-diisopropylphenyl isocyanate, 4-fluorophenyl isocyanate, 2,4-difluorophenyl isocyanate, 2,4,6-trifluorophenyl isocyanate, 3-(trifluoromethyl)phenyl isocyanate, and 4-(trifluoromethyl)phenyl isocyanate.

[0036] The resin composition constituting the monofilament of the present invention contains an isocyanate compound in an amount of 0.01 to 4.00 parts by mass, preferably 0.15 to 3.00 parts by mass, and more preferably 0.25 to 2.50 parts by mass, per 100 parts by mass of polyester resin.

[0037] Here, if the isocyanate compound content is greater than 4.00 parts by mass, the strength characteristics of the monofilament are significantly impaired. Furthermore, in the process of manufacturing the monofilament, it is necessary to add a large amount of amine compound to the polyester, and in the spinning machine used to melt the polyester resin, the isocyanate compound may dissolve into a liquid state due to the heat generated, which can lead to unstable kneadability with the polyester resin composition or the accumulation of liquid isocyanate compound in the spinning machine, potentially degrading the extrusion performance of the polyester mixed resin composition from the spinning machine.

[0038] Furthermore, when the isocyanate compound content is less than 0.01 parts by mass, the hydrolysis resistance is insufficient.

[0039] The resin composition constituting the polyester monofilament of the present invention preferably contains a carbodiimide compound. This is because the inclusion of a carbodiimide compound allows for the encapsulation of carboxyl groups present in trace amounts at the ends of the polyester resin or generated by hydrolysis. Carbodiimide compounds can be classified into monocarbodiimide compounds having one carbodiimide group per molecule and polycarbodiimide compounds having two or more carbodiimide groups per molecule. In the present invention, any carbodiimide compound selected from the group consisting of monocarbodiimide compounds and polycarbodiimide compounds can be used.

[0040] Examples of monocarbodiimide compounds include N,N'-di-o-tolylcarbodiimide, N,N'-diphenylcarbodiimide, N,N'-dioctyldecylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, N-tolyl-N'-cyclohexylcarbodiimide, N,N'-di-2,6-diisopropylphenylcarbodiimide, N,N'-di-2,6-di-tert-butylphenylcarbodiimide, N-tolyl-N'-phenylcarbodiimide, and N,N'-di-p-nitro Phenylcarbodiimide, N,N'-di-p-aminophenylcarbodiimide, N,N'-di-p-hydroxyphenylcarbodiimide, N,N'-di-cyclohexylcarbodiimide, N,N'-di-p-tolylcarbodiimide, p-phenylene-bis-di-o-tolylcarbodiimide, p-phenylene-bis-di-o-dicyclohexylcarbodiimide, hexamethylene-bis-dicyclohexycarbodiimide, ethylene-bis-diphenylcarbodiimide, etc. can be appropriately selected and applied.

[0041] The polycarbodiimide compound is preferably a polycarbodiimide compound in which alkyl-substituted phenylcarbodiimide is used as the repeating unit. In particular, a polycarbodiimide compound in which the ortho position of the phenyl group relative to the carbodiimide group is substituted with an alkyl group such as a methyl group, ethyl group, isopropyl group, or t-butyl group, and especially preferably with an isopropyl group, i.e., the 2,6- and / or 2,4,6- and / or 2,3- and / or 2,5- positions are substituted with isopropyl groups, and the main repeating unit is a phenylcarbodiimide compound in which the repeating unit is primarily phenylcarbodiimide.

[0042] In the present invention, one or more of these carbodiimide compounds can be arbitrarily selected and included in the polyester. However, from the viewpoint of the stability of the polyester resin composition after addition, carbodiimide compounds having an aromatic skeleton are more preferred. Among these, N,N'-di-2,6-diisopropylphenylcarbodiimide, N,N'-di-2,6-di-tert.-butylphenylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, and N,N'-di-o-tolylcarbodiimide are particularly suitable, and N,N'-di-2,6-diisopropylphenylcarbodiimide (hereinafter sometimes abbreviated as TIC) is the most suitable due to its excellent reactivity.

[0043] The resin composition constituting the monofilament of the present invention preferably contains 0.01 to 4.00 parts by mass of a carbodiimide compound per 100 parts by mass of polyester resin, more preferably 0.15 to 3.00 parts by mass, and even more preferably 0.25 to 2.50 parts by mass.

[0044] In this case, if the content of the carbodiimide compound is greater than 4.00 parts by mass, the strength characteristics of the monofilament may be significantly impaired. Furthermore, in the process of manufacturing the monofilament, it is necessary to add a large amount of carbodiimide compound to the polyester. In the spinning machine used to manufacture the monofilament, the heat generated to melt the polyester resin may cause the carbodiimide compound to dissolve into a liquid state, potentially leading to unstable kneadability with the polyester resin composition or the accumulation of liquid carbodiimide compound in the spinning machine, which may worsen the extrusion performance of the polyester mixed resin composition from the spinning machine.

[0045] Furthermore, when the content of the carbodiimide compound is less than 0.01 parts by mass, the hydrolysis resistance tends to be weaker.

[0046] The intrinsic viscosity of the polyester resin used in this invention is preferably 0.40 to 1.00 dl / g, and more preferably 0.50 to 0.80 dl / g. When the intrinsic viscosity of the polyester resin is within this range, it leads to desirable effects such as sufficient strength, high strength, and high hydrolysis resistance.

[0047] If the intrinsic viscosity falls below 0.40 dl / g, the yarn will not have sufficient strength and will also have poor hydrolysis resistance. Furthermore, if the intrinsic viscosity exceeds 1.00 dl / g, there is a tendency for many very short sections of abnormal diameter increase fluctuations in the fiber axis direction to occur during spinning, which can worsen the spinning operability of the monofilament and significantly impair the strength characteristics of the monofilament.

[0048] Furthermore, the polyester resin contained in the resin composition constituting the monofilament of the present invention preferably satisfies the condition of having a carboxyl terminal group concentration of 10 equivalents / ton or less from the viewpoint of hydrolysis resistance, more preferably 8 equivalents / ton or less, and even more preferably 5 equivalents / ton or less. Here, if the carboxyl terminal group concentration is 10 equivalents / ton or more, hydrolysis degradation will progress significantly under a humid and hot environment, causing a significant decrease in the strength of the monofilament. As a result, this will not only lead to a decrease in the strength of industrial textiles, but also to extremely undesirable consequences such as the inability to achieve a long product life for the textiles.

[0049] Here, the hydrolysis resistance of the polyester resin contained in the resin composition constituting the monofilament in the present invention can be indicated by the strength retention rate obtained by the method described in the following examples, and it is preferable that this strength retention rate is 15% or higher. When the strength retention rate, which is an indicator of the hydrolysis resistance of the monofilament, is 15% or higher, it becomes possible to use it for a longer period of time as a raw yarn for industrial textile applications used in humid and hot environments.

[0050] Furthermore, the resin composition constituting the monofilament used in the present invention may contain, within a range that does not impair the effects of the present invention, specifically within 1% by mass or less, various inorganic particles such as titanium dioxide, silicon dioxide, calcium carbonate, silicon nitride, clay, talc, kaolin, zirconium acid, and crosslinked polymer particles, as well as conventionally known antioxidants, waxes, silicone oils, various surfactants, fluororesins, polyamides, and polystyrene.

[0051] Furthermore, the polyester resin contained in the resin composition constituting the monofilament of the present invention may contain various additives, such as pigments, dyes, lightfasteners, ultraviolet absorbers, antioxidants, crystallization inhibitors, and plasticizers, to the extent that they do not impair the desired performance. These additives can be added to the resin composition constituting the monofilament during the polymerization process of the polyester resin, after polymerization, or immediately before spinning the monofilament.

[0052] The monofilaments of the present invention, having the above characteristics, exhibit excellent hydrolysis resistance. Specifically, these monofilaments are subjected to a vapor pressure of 1.2 kg / cm². 2 The tensile strength retention rate is high after 240 hours of continuous moist heat treatment in a humid heat environment at 0.12 MPa and a temperature of 121°C. In this case, the tensile strength retention rate is preferably 15% or more, more preferably 20% or more, more preferably 25% or more, and most preferably 50% or more.

[0053] The monofilament of the present invention, having the above-described characteristics, possesses extremely excellent hydrolysis resistance, which is required for monofilaments that make up fabrics used in papermaking processes under extremely high temperature and high humidity conditions, as well as sufficient tensile strength characteristics, making it suitable for use in various industrial fiber materials and fabrics. Industrial fabrics using this monofilament are particularly preferable when used as papermaking dryer canvases, papermaking wires, net conveyors for thermal bonding nonwoven fabric heat bonding processes, conveying belts in dryers and heat treatment machines, and filters, due to the excellent hydrolysis resistance of the monofilament of the present invention.

[0054] In this invention, "industrial textile" refers to a textile in which the monofilament of the present invention is used in at least a portion of the warp and / or weft threads of the textile.

[0055] The monofilament of the present invention may have a cross-sectional shape perpendicular to the fiber axis that is circular, elliptical, flattened, regular polygonal, and polygonal, including irregular shapes, in order to satisfy its intended use and properties, and may be a composite fiber if necessary. Here, "flattened" means elliptical or rectangular, but includes not only mathematically defined exact ellipses and rectangles but also shapes that are generally elliptical, rectangular, or similar, and "regular polygonal" includes shapes that are generally similar to mathematically defined regular polygons.

[0056] Furthermore, the diameter of the monofilament of the present invention can be appropriately selected according to its application, but typically a diameter in the range of 0.05 to 5 mm is preferred.

[0057] Next, an example of a method for producing a monofilament according to the present invention is given, but various modifications are possible without departing from the spirit of the present invention.

[0058] The monofilament of the present invention can be obtained by melting, kneading, and reacting polyester, carbodiimide compound, amine compound, and isocyanate compound in a desired mixing ratio using a spinning machine such as an extruder, then extruding it from a die nozzle installed at the tip of the spinning machine, and cooling and stretching it using known methods.

[0059] Furthermore, it is possible to obtain the compound by stirring a polyester resin containing a carbodiimide compound under high temperature and pressure to thermally decompose it into amine compounds and isocyanate compounds, then pelletizing it, extruding it from a die nozzle using a spinning machine such as an extruder, and then cooling and stretching it using known methods.

[0060] The monofilament of the present invention thus possesses excellent hydrolysis resistance and sufficient strength characteristics for industrial textiles, which are not found in conventional monofilaments, and can be suitably used as a constituent material for industrial textiles. In particular, due to its extremely excellent hydrolysis resistance, it exhibits particularly favorable effects in papermaking dryer canvases, papermaking wires, net conveyors for thermal bonding nonwoven fabric bonding processes, conveying belts in dryers and heat treatment machines, and filters. [Examples]

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Each item in the examples was measured by the following method. Unless otherwise specified, n=1 was used for each measurement.

[0062] (1) Amine content / Amine grade The amine content of the monofilaments was analyzed by gas chromatography (GC). The GC measurement conditions are shown below. Equipment: LECO Pegasus BT 4D GCxGC-TOFMS Column: Shimadzu SH-I-5Sil MS (30 m, 0.25 mm ID, 0.25 μm df) Carrier gas: Helium Detector: Mass spectrometer (MS) Measurement: 1 mg of monofilament was placed in a GC, the sample was gasified at 300°C, and the measurement was performed. Similarity analysis was performed on the obtained mass spectrum to identify the spectrum of the amine compound. Content: The content of amine compounds whose structures were determined by similarity analysis was quantified using the absolute calibration curve method, and the amount per 100 parts by mass of polyester resin was calculated. Amine Classification: The classification of an amine compound whose structure has been determined by similarity analysis is used to determine its classification.

[0063] (2) Isocyanate content The isocyanate content of the monofilaments was analyzed by gas chromatography (GC). The GC measurement conditions are shown below. Equipment: LECO Pegasus BT 4D GCxGC-TOFMS Column: Shimadzu Corporation SH-I-5Sil MS (30m, 0.25mm ID, 0.25μm df) Carrier gas: Helium Detector: Mass spectrometer (MS) Measurement: 1 mg of monofilament was placed in a GC, the sample was gasified at 300°C, and the measurement was performed. Similarity analysis was performed on the obtained mass spectrum to identify the spectrum of the isocyanate compound. Content: The content was quantified using the absolute calibration curve method for isocyanate compounds whose structures were determined by similarity analysis, and the amount per 100 parts by mass of polyester resin was calculated.

[0064] (3) Carbodiimide content The carbodiimide content of the monofilaments was analyzed by gas chromatography (GC). The GC measurement conditions are shown below. Equipment: LECO Pegasus BT 4D GCxGC-TOFMS Column: Shimadzu Corporation SH-I-5Sil MS (30m, 0.25mm ID, 0.25μm df) Carrier gas: Helium Detector: Mass spectrometer (MS) Measurement: 1 mg of monofilament was placed in a GC, the sample was gasified at 300°C, and the measurement was performed. Similarity analysis was performed on the obtained mass spectrum to identify the spectrum of the carbodiimide compound. Content: The content was quantified using the absolute calibration curve method for carbodiimide compounds whose structure was determined by similarity analysis, and the amount per 100 parts by mass of polyester resin was calculated.

[0065] (4) Intrinsic viscosity In a dissolution test tube (hereinafter referred to as the test tube), 25 ml of orthochlorophenol (hereinafter referred to as OCP) and 2 g ± 0.001 g of PET monofilament sample cut to approximately 3 mm were placed. The test tube containing the sample was placed in a dry block bath and heated at 100°C for 30 minutes to dissolve the PET monofilament sample in OCP (hereinafter referred to as the OCP solution). After cooling this OCP solution with running water for 15 minutes, 20 ml of the OCP solution was measured with a volumetric pipette and collected in an Ostwald viscosity tube. Subsequently, the Ostwald viscosity tube containing the OCP solution was placed in a constant temperature water bath adjusted to 25°C and left for 30 minutes. The intrinsic viscosity value was calculated by measuring the flow time of the OCP solution flowing through the Ostwald viscosity tube according to the standard method.

[0066] (5) Hydrolysis resistance test Monofilaments were placed in a 100-liter autoclave and subjected to forced hydrolysis degradation (hereinafter referred to as hydrolysis treatment) for 240 hours continuously under a saturated steam atmosphere at 121°C. The tensile strength of the monofilaments after treatment and those that had not undergone hydrolysis treatment was measured, and the tensile strength retention rate of the monofilaments before and after treatment was calculated and used as a measure of hydrolysis resistance. The formula for calculation was tensile strength retention rate (%) = (tensile strength of monofilament after hydrolysis treatment ÷ tensile strength of monofilament before hydrolysis treatment) × 100. Furthermore, in accordance with JIS L1013:2010 8.5.1, the tensile strength was measured by leaving the monofilament in a temperature and humidity controlled chamber at 20°C and 65%RH for 24 hours, and then measuring five samples using an Orientec Co., Ltd. "Tensilon (registered trademark)" UTM-4-100 tensile testing machine under the conditions of thread length: 250 mm and tensile speed: 300 mm / min. The average tensile strength (cN / dtex) was calculated by dividing the tensile strength at which the sample broke by the fineness.

[0067] (6) Carboxylate-termined equivalent The carboxyl terminal equivalent was calculated using the following procedure. (I) Weigh 0.500 ± 0.002 g of monofilament sample into a 10 mL test tube. (II) 10 mL of cresol is poured into the test tube, and the sample is heated and stirred at 100°C for 30 minutes to dissolve it. (III) Transfer the contents of the test tube to a 30 mL beaker (wash the remaining liquid in the test tube with 3 mL of dichloromethane and add it to the beaker). (IV) Allow the liquid in the beaker to cool until the temperature reaches 25°C. (V) Titrate with a 0.02N NaOH methanol solution. (VI) Perform the same procedure as in (1) to (5) above without a sample, and determine the carboxyl terminal group equivalent per 106 g of monofilament from the titration volume of 0.02 N NaOH methanol solution required for sample titration.

[0068] (7) Spinning properties Continuous spinning was performed for 12 hours, and the results were evaluated according to the following criteria. ○ (Good): There were no instances of yarn failure due to poor raw material feeding or yarn breakage during yarn production. Furthermore, the occurrence of abnormal diameter fluctuations in the fiber axis direction, which were very short in length and exceeded +10% relative to the average monofilament diameter, was less than 10 times per ton. The number of abnormal diameter fluctuations was calculated as: total polymer mass (kg) / 1000 kg × number of abnormal diameter fluctuations. × (Poor): This was evaluated in two stages: the machine became unable to spin due to poor raw material feeding, or the yarn broke during spinning, or the number of times the diameter increased or fluctuated abnormally was 10 times or more per ton.

[0069] [Example 1] A polyethylene terephthalate resin composition recovered from fibers containing a primary amine compound, an isocyanate compound, and a carbodiimide compound was fed into an extruder at 300°C and pelletized. Analysis of the pellets revealed that per 100 parts by mass of polyester resin, the composition contained 1.76 parts by mass of primary amine compound, 1.76 parts by mass of isocyanate compound, and 0.10 parts by mass of carbodiimide compound. 1.00 part by mass of carbodiimide compound was added to 100 parts by mass of the polyester resin composition pellets and kneaded and melted at a spinning machine temperature of 290°C. The molten polyester resin composition was then extruded from the die nozzle and immediately cooled and solidified in hot water at 70°C to obtain undrawn yarn.

[0070] Subsequently, the above undrawn yarn was drawn to a total magnification of 5.5 times according to a conventional method and heat-set to obtain a monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.64 dL / g, and 1 eq / ton of carboxyl terminal groups. The isocyanate content and carbodiimide content of the monofilament were 1.14 parts by mass and 0.52 parts by mass, respectively, because the respective groups reacted with the terminals of the polyethylene terephthalate resin and some of the carboxyl groups generated by hydrolysis. Hereafter, "carboxyl groups generated at the terminals of the polyethylene terephthalate resin and by hydrolysis" will be abbreviated as "carboxyl groups derived from polyethylene terephthalate resin".

[0071] Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0072] [Example 2] Polyethylene terephthalate resin (intrinsic viscosity 0.90 dl / g) was supplied to an extruder spinning machine at 290°C. Further, 0.40 parts by mass of a primary amine compound, 1.00 part by mass of an isocyanate compound, and 1.00 part by mass of a carbodiimide compound were added to the spinning machine per 100 parts by mass of polyester resin. The mixture was kneaded and melted at a spinning machine temperature of 290°C, and the molten polyester resin composition was extruded from the die nozzle. Immediately afterward, it was cooled and solidified in hot water at 70°C to obtain undrawn yarn.

[0073] Subsequently, the undrawn yarn was drawn to a total magnification of 5.5 times according to a conventional method and heat-set to obtain a monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.71 dL / g, and 1 eq / ton of carboxyl terminal groups. The isocyanate and carbodiimide content of the resin composition constituting the monofilament was 0.30 parts by mass and 0.30 parts by mass, respectively, because the respective groups reacted with some of the carboxyl groups derived from the polyethylene terephthalate resin.

[0074] Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0075] [Example 3] Except for adding 2.30 parts by mass of a primary amine compound and 3.00 parts by mass of an isocyanate compound to a spinning machine per 100 parts by mass of polyester resin, the conditions were the same as in Example 2 to obtain a monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.69 dL / g, and 2 eq / ton of carboxyl-terminated groups. The isocyanate content of the monofilament was 2.41 parts by mass, due to some reaction of the isocyanate groups with the carboxyl groups derived from the polyethylene terephthalate resin.

[0076] Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0077] [Example 4] Except for adding 0.40 parts by mass of a primary amine compound and 1.00 part by mass of an isocyanate compound to a spinning machine per 100 parts by mass of polyester resin, the conditions were the same as in Example 2 to obtain a monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.73 dL / g, and 4 eq / ton of carboxyl-terminated groups. The isocyanate content of the monofilament was 0.40 parts by mass, due to the reaction of the isocyanate groups with some of the carboxyl groups derived from the polyethylene terephthalate resin.

[0078] Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0079] [Example 5] A monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.65 dL / g, and 6 eq / ton of carboxyl-terminated groups was obtained using the same conditions as in Example 2, except that 0.40 parts by mass of a tertiary amine compound, 1.00 part by mass of an isocyanate compound, and 1.00 part by mass of a carbodiimide compound were added to the spinning machine per 100 parts by mass of polyester resin. The isocyanate and carbodiimide content of the resin composition constituting the monofilament was 0.40 parts by mass and 0.40 parts by mass, respectively, because the respective groups reacted with some of the carboxyl groups derived from the polyethylene terephthalate resin. Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0080] [Comparative Example 1] Except for adding 1.00 part by mass of a carbodiimide compound to 100 parts by mass of polyester resin in the spinning machine, the conditions were the same as in Example 2 to obtain a monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.77 dL / g, and 8 eq / ton of carboxyl-terminated groups. The carbodiimide content of the resin composition constituting the monofilament was 0.40 parts by mass, as the carbodiimide groups reacted with some of the carboxyl groups derived from the polyethylene terephthalate resin. Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0081] [Comparative Example 2] Except for adding 1.00 part by mass of isocyanate compound and 1.00 part by mass of carbodiimide compound to 100 parts by mass of polyester resin in the spinning machine, the conditions were the same as in Example 2 to obtain a monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.75 dL / g, and 7 eq / ton of carboxyl-terminated groups. The isocyanate content and carbodiimide content of the resin composition constituting the monofilament were 0.40 parts by mass and 0.40 parts by mass, respectively, because the respective groups reacted with some of the carboxyl groups derived from the polyethylene terephthalate resin.

[0082] Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0083] [Comparative Example 3] Except for adding 0.40 parts by mass of a primary amine compound and 1.00 part by mass of a carbodiimide compound to a spinning machine per 100 parts by mass of polyester resin, the conditions were the same as in Example 2 to obtain a monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.72 dL / g, and 8 eq / ton of carboxyl-terminated groups. The carbodiimide content of the resin composition constituting the monofilament was 0.40 parts by mass, due to the reaction of the carbodiimide groups with some of the carboxyl groups derived from the polyethylene terephthalate resin.

[0084] Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0085] [Comparative Example 4] Spinning was carried out under the same conditions as in Example 2, except that 4.50 parts by mass of a primary amine compound was added to the spinning machine per 100 parts by mass of polyester resin. However, the amine compound dissolved into a liquid state in the spinning machine, making it difficult to mix with the molten polyester resin composition, and thus a monofilament could not be obtained.

[0086] [Comparative Example 5] Spinning was carried out under the same conditions as in Example 2, except that 4.50 parts by mass of isocyanate compound were added to 100 parts by mass of polyester resin in the spinning machine. However, the isocyanate compound dissolved into a liquid state in the spinning machine, making it difficult to mix with the molten polyester resin composition, and thus a monofilament could not be obtained.

[0087] [Comparative Example 6] Spinning was carried out under the same conditions as in Example 2, except that 4.50 parts by mass of carbodiimide compound were added to the spinning machine for every 100 parts by mass of polyester resin. However, the carbodiimide compound dissolved into a liquid state in the spinning machine, making it difficult to mix with the molten polyester resin composition, and thus a monofilament could not be obtained.

[0088] [Comparative Example 7] A monofilament with a diameter of 0.40 mm, an intrinsic viscosity of 0.68 dL / g, and 9 eq / ton of carboxyl terminal groups was obtained under the same conditions as in Example 2, except that 1.00 part by mass of polyethylene glycol (PEG) and 1.00 part by mass of polycarbodiimide compound were added to the spinning machine per 100 parts by mass of polyester resin. Table 1 shows the results of evaluating the tensile strength retention rate and other parameters of the obtained monofilaments after hydrolysis resistance testing.

[0089] [Table 1]

[0090] The monofilaments of Examples 1 to 5 all exhibited high hydrolysis resistance and were suitable for use as industrial textiles. In addition, in the monofilament of Example 5, a tertiary amine compound with relatively low basicity was used as the amine compound, resulting in poor capture of hydrogen ions generated during hydrolysis, and thus a monofilament with slightly inferior hydrolysis resistance compared to Examples 1-4.

[0091] On the other hand, the resin composition constituting the monofilament of Comparative Example 1 did not contain primary amine compounds or isocyanate compounds, resulting in a monofilament with poor hydrolysis resistance.

[0092] Furthermore, the resin composition constituting the monofilament of Comparative Example 2 did not contain a primary amine compound, resulting in a monofilament with poor hydrolysis resistance. Furthermore, the resin composition constituting the monofilament of Comparative Example 3 did not contain an isocyanate compound, resulting in a monofilament with poor hydrolysis resistance. Furthermore, in Comparative Examples 4-6, the amounts of primary amine compounds, isocyanate compounds, and carbodiimide compounds added were too high, making it impossible to knead them into the polyester resin, and thus monofilaments could not be obtained. Furthermore, in Comparative Example 7, PEG and a polycarbodiimide compound were used instead of the primary amine compound and isocyanate compound, but the resulting monofilament had poor hydrolysis resistance. [Industrial applicability]

[0093] According to the present invention, as described above, it is possible to obtain a monofilament that has high strength and can be used for a long period of time in a humid and hot environment. Such a monofilament can be suitably used in papermaking dryer canvases, papermaking wires, net conveyors for the thermal bonding process of nonwoven fabrics, conveying belts in dryers and heat treatment machines, and filters, among other things.

Claims

1. A polyester monofilament comprising a resin composition mainly composed of polyester resin, wherein the resin composition contains 0.01 to 4.00 parts by mass of an amine compound and 0.01 to 4.00 parts by mass of an isocyanate compound per 100 parts by mass of polyester resin.

2. The polyester monofilament according to claim 1, wherein the amine compound is a primary amine compound.

3. The polyester monofilament according to claim 1 or 2, wherein the resin composition further contains 0.01 to 4.00 parts by mass of a carbodiimide compound per 100 parts by mass of the polyester resin.

4. The polyester monofilament according to claim 3, wherein the carbodiimide compound is contained in an amount of 0.15 to 3.00 parts by mass per 100 parts by mass of the polyester resin.

5. The polyester monofilament according to claim 1 or 2, wherein the amine compound is contained in an amount of 0.15 to 3.00 parts by mass per 100 parts by mass of the polyester resin.

6. The polyester monofilament according to claim 1 or 2, wherein the isocyanate compound is contained in an amount of 0.15 to 3.00 parts by mass per 100 parts by mass of polyester resin.

7. The polyester monofilament according to claim 1 or 2, wherein the intrinsic viscosity of the resin composition is 0.40 to 1.00 dl / g.

8. The aforementioned polyester monofilament is vaporized at a vapor pressure of 1.2 kg / cm². ２ The polyester monofilament according to claim 1 or 2, wherein the retention rate of tensile strength after 240 hours of continuous moist heat treatment in a moist heat environment at 0.12 MPa and a temperature of 121°C is 15% or more.

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