Polyester resin and its manufacturing method

Abstract

To provide a polyester resin which enables production of fibers that are excellent in easy solubility in alkali and yarn quality characteristics (strength and elongation) with good operability.SOLUTION: A polyester resin contains an aromatic dicarboxylic acid having a metal sulfonate group as a dicarboxylic acid component, and 5-25 mass% of a polyether compound having a number average molecular weight of 500-15,000. A glycol component of the polyester resin contains ethylene glycol as a main component, and a content of triethylene glycol is 0.5-5.5 mol%. Diethylene glycol is contained as the glycol component, and a content of the diethylene glycol is preferably 2.5 mol% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester resin and a method for producing the same. [Background technology]

[0002] Polyester resins, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), have excellent mechanical and chemical properties and are used in a wide range of fields (for example, fibers for clothing and industrial materials, films and sheets for packaging and magnetic tape, hollow molded bottles, casings for electrical and electronic components, and other engineering plastic molded products).

[0003] Among various applications, polyester resins for fiber applications that are readily alkali-soluble are known that contain aromatic dicarboxylic acids having sulfonate groups and polyether compounds (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-156453 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, a metal-based polycondensation catalyst is used, which causes problems such as deterioration of operability and yarn quality due to metal precipitation during polymerization, or poor color tone. Furthermore, when a metal-based polycondensation catalyst is used, heavy metals derived from the catalyst are eluted during alkali dissolution, raising concerns about environmental impacts. Therefore, polyester resins using organic catalysts are also being considered. In recent years, there has been a demand for polyester resins with improved thread properties such as alkali solubility, strength and elongation.

[0006] An object of the present invention is to provide a polyester resin which is excellent in alkali solubility, workability when made into fibers, and yarn quality characteristics when made into fibers, and which can suppress the elution of heavy metals when dissolved in alkali. [Means for solving the problem]

[0007] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that a polyester resin of the present invention, which contains a predetermined amount of a polyether compound, an aromatic dicarboxylic acid having a metal sulfonate group as a dicarboxylic acid component, and has a triethylene glycol content within a specific range in the glycol component, has excellent alkali solubility and, when made into fibers, also has excellent yarn quality properties such as strength and elongation, and has arrived at the present invention.

[0008] That is, the gist of the present invention is as follows: (1) 5 ) as follows. (1) Aromatic dicarboxylic acids having metal sulfonate groups are used as dicarboxylic acid components. 0.5 to 4.3 mol% and a polyester resin containing 5 to 25 mass % of a polyether compound having a number average molecular weight of 500 to 15,000, wherein the glycol component of the polyester resin contains ethylene glycol as a main component and the content of triethylene glycol is 0.5 to 5.5 mol %. (2) The polyester resin according to (1), characterized in that it contains diethylene glycol as a glycol component and the content of diethylene glycol is 2.5 mol % or more. ( 3 ) The content of sulfur components other than aromatic dicarboxylic acids having metal sulfonate groups is 5 to 100 ppm. (1) or ( 2 ) The polyester resin described in ( 4 )(1)~( 3 ) A fiber made of any one of the polyester resins. ( 5 ) (1)~(3)The method for producing the polyester resin according to any one of claims 1 to 10, comprising the steps of adding an organic sulfonic acid compound to a polyester raw material, and heating the mixture at a temperature of 240°C or higher for 5 to 120 minutes under normal pressure or pressure to carry out an etherification reaction of the glycol component. [Effects of the Invention]

[0009] According to the polyester resin of the present invention, fibers having excellent alkali solubility and excellent yarn properties such as strength and elongation can be obtained with good operability. DETAILED DESCRIPTION OF THE INVENTION

[0010] The polyester resin of the present invention will be described in detail below. The polyester resin of the present invention contains an aromatic dicarboxylic acid having a metal sulfonate group as a dicarboxylic acid component. By copolymerizing the aromatic dicarboxylic acid having a metal sulfonate group, it is possible to impart alkali solubility to the polyester resin.

[0011] When the total amount of all acid components constituting the polyester is taken as 100 mol %, the content of the aromatic dicarboxylic acid having a metal sulfonate group is 0.5 to 100 mol %. 4.3 % by mole necessary . If the content of aromatic dicarboxylic acid having a metal sulfonate group is less than 0.5 mol%, sufficient alkali solubility may not be obtained when the polyester resin is used to form fibers. On the other hand, if the content exceeds 5.5 mol%, the melt viscosity of the polyester tends to be too high in the polycondensation process, making it difficult to sufficiently increase the degree of polymerization. As a result, the operability, yarn quality characteristics, and material strength (e.g., yarn strength when formed into fibers) may be reduced. Furthermore, since the aromatic dicarboxylic acid having a metal sulfonate group acts as a catalyst in the etherification step described below, by setting the content within the above range, it becomes easier to set the contents of ethylene glycol and triethylene glycol in the glycol component within the specific range.

[0012] Examples of aromatic dicarboxylic acids having a metal sulfonate group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, sodium sulfophenyldicarboxylic acid, and 5-sodium sulfoterephthalic acid, and in the present invention, 5-sodium sulfoisophthalic acid is preferably used in terms of its alkali solubility, operability during melt spinning, and cost. These acids may be used as they are, or ester-forming derivatives may be used, and among these, esters with ethylene glycol are preferably used in terms of operability.

[0013] The proportion of terephthalic acid in the acid component is preferably 94.5 to 99.5 mol%, and more preferably 95 to 99 mol%. If the proportion of terephthalic acid is less than 94.5 mol%, the crystallinity of the resin composition may decrease, and the melting point may be lowered, which may result in a decrease in operability during melt spinning and drawing. On the other hand, if the proportion of terephthalic acid exceeds 99.5 mol%, the amount of aromatic dicarboxylic acid having a metal sulfonate group copolymerized may decrease, which may reduce the effect of alkali solubility.

[0014] In the polyester resin of the present invention, examples of acid components other than terephthalic acid and aromatic dicarboxylic acid having a metal sulfonate group include isophthalic acid, phthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, dodecanedioic acid, and other dimer acids, as well as trimellitic anhydride, trimellitic acid, pyromellitic acid, 1,4-cyclohexanedicarboxylic acid, sebacic acid, and dimer acids. Two or more of these may be used in combination, and ester-forming derivatives of these acids may also be used.

[0015] The polyester resin of the present invention contains triethylene glycol, and the content of triethylene glycol in all glycol components is 0.5 to 5.5 mol %. Note that the content (mol %) of glycol components referred to here is calculated without including the polyether compound described below. The triethylene glycol content of the total glycol components is preferably 0.6 to 5.0 mol%, more preferably 0.7 to 4.0 mol%. If it is less than 0.5 mol%, the melting point will be too high, resulting in poor alkali solubility and poor operability, and excellent yarn properties (strength and elongation) will not be fully exhibited. On the other hand, if it exceeds 5.5 mol%, the resulting resin will be amorphous, have a low melting point, and poor heat resistance, resulting in poor operability and yarn properties when made into fibers.

[0016] The total content of triethylene glycol and tetraethylene glycol in the total glycol components is preferably 7.0 mol% or less, more preferably 0.6 to 4 mol%, and even more preferably 0.8 to 3 mol%. If it exceeds 7.0 mol%, the heat resistance may decrease, and the operability when forming fibers and the yarn quality characteristics of the fibers may be poor. On the other hand, if it is less than 0.6 mol%, the operability when forming fibers and the alkali solubility of the fibers may be poor.

[0017] The content of tetraethylene glycol in the total glycol components is preferably 0.0 to 2.0 mol%, more preferably 0 to 1.0 mol%, and even more preferably 0.0 to 0.5 mol%. If it exceeds 2.0 mol%, the heat resistance and yarn quality characteristics may deteriorate.

[0018] The polyester resin of the present invention preferably contains diethylene glycol as a glycol component. The diethylene glycol content is preferably 2.5 mol% or more, more preferably 3.5 mol% or more, and even more preferably 4.5 mol% or more of the total glycol components. By setting the diethylene glycol content within this range, the alkali solubility of the resulting fiber can be further improved. The upper limit of the diethylene glycol content is preferably 12 mol% in terms of operability when forming the fiber and the yarn quality characteristics of the fiber.

[0019] In order to adjust the content of each of diethylene glycol, triethylene glycol, and tetraethylene glycol, for example, the content of aromatic dicarboxylic acid having a metal sulfonate group can be set within a preferred range, an organic sulfonic acid compound can be used as a polymerization catalyst in the production method of a polyester resin described below, the amount of organic sulfonic acid compound added can be set within a preferred range, the molar ratio (G / A) of glycol component (G) to acid component (A) before being subjected to the etherification reaction can be set within a preferred range, or the temperature or time of the etherification reaction can be adjusted.

[0020] The polyester resin of the present invention may contain a glycol component other than those mentioned above, such as 1,2-propylene glycol, neopentyl glycol, 1,6-hexanediol, 1,4-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, dimer diol, an ethylene oxide adduct of bisphenol S, or an ethylene oxide adduct of bisphenol A.

[0021] The polyester resin of the present invention must contain 5 to 25 mass % of a polyether compound, preferably 6 to 20 mass %, and more preferably 7 to 15 mass %.

[0022] If the content of the polyether compound is less than 5% by mass, the alkali solubility of the polyester resin of the present invention will decrease, while if the content of the polyether compound is more than 25% by mass, the thermal stability of the polyester resin will be impaired, resulting in poor operability and poor yarn quality, such as the occurrence of yarn breakage when the resulting polyester resin is made into fibers.

[0023] Examples of polyether compounds include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymers of ethylene oxide and propylene oxide, with polyethylene glycol and polytetramethylene glycol being preferred.

[0024] The number-average molecular weight of the polyether compound is 500 to 15,000, preferably 1,000 to 15,000, more preferably 2,000 to 7,000, and even more preferably 3,000 to 6,000. If the number-average molecular weight of the polyether compound is less than 500, the alkali solubility of the polyester resin of the present invention decreases. Furthermore, if the number-average molecular weight of the polyether compound in the polyester resin exceeds 15,000, the thermal stability of the polyester resin is impaired, and for example, thread breakage occurs when the resulting polyester resin is spun.

[0025] The polyester resin of the present invention preferably has an intrinsic viscosity of 0.45 dL / g or more, more preferably 0.5 dL / g or more, and even more preferably 0.6 to 0.8 dL / g. If the intrinsic viscosity is less than 0.45 dL / g, sufficient yarn quality may not be obtained when the polyester resin is made into fibers.

[0026] The intrinsic viscosity in the present invention is a value measured at a temperature of 20°C using an equal weight mixture of phenol and tetrachloroethane as a solvent.

[0027] The polyester resin of the present invention may contain any polymer, antistatic agent, antifoaming agent, dye, pigment, matting agent, fluorescent brightener, stabilizer, antioxidant, colorant, flame retardant, or other additives, as long as the effects of the present invention are not impaired. Examples of antioxidants include aromatic amine-based and phenol-based antioxidants. Examples of stabilizers include phosphorus-based, sulfur-based, and amine-based stabilizers such as phosphoric acid or phosphate ester-based stabilizers.

[0028] The polyester resin of the present invention may contain organic, inorganic, or organometallic toners, fluorescent brighteners, etc., to the extent that the effects of the present invention are not impaired. This can further suppress coloration, such as yellowing, of the polyester resin. Alternatively, other resins such as polyethylene, or inorganic nucleating agents such as talc may be added to improve crystallinity.

[0029] The polyester resin of the present invention may be mixed with waste resin generated in the manufacturing process or recycled polyester resin recovered from the market (for example, PET bottles).

[0030] (Method of producing polyester resin) The method for producing a polyester resin of the present invention includes a step of adding an organic sulfonic acid compound to a polyester raw material and heating the mixture at a temperature of 240°C or higher for 5 to 120 minutes under normal pressure or pressure to carry out an etherification reaction of the glycol component.

[0031] In the present invention, by including a step of carrying out an etherification reaction under specific conditions before carrying out the polycondensation reaction, the contents of diethylene glycol, triethylene glycol, and tetraethylene glycol can be set within specific ranges, thereby making it possible to obtain a polyester resin that is excellent in operability when made into fibers and that is also excellent in alkali solubility when made into fibers.

[0032] Examples of raw materials for polyester resins include glycol components containing ethylene glycol as a main component, dicarboxylic acid components, and esters as low-order condensates of glycol components and dicarboxylic acid components.

[0033] For example, when producing polyethylene terephthalate as a polyester resin, the esterified product can be obtained by directly reacting terephthalic acid, ethylene glycol, and, if necessary, other copolymerization components, distilling off water, and esterifying the mixture to obtain an esterified product as a raw material for the polyester resin. Alternatively, dimethyl terephthalate, ethylene glycol, and, if necessary, other copolymerization components can be reacted, distilling off methyl alcohol, and then transesterifying the mixture to obtain an esterified product.

[0034] The method for preparing the esterified product will be described below. A slurry containing preferably 1.02 to 2.5 mol, more preferably 1.03 to 1.8 mol, of ethylene glycol per mol of dicarboxylic acid or its ester derivative is prepared, and this is continuously fed to an esterification reactor to obtain an esterified product.

[0035] The esterification reaction is carried out under reflux conditions of ethylene glycol while removing water or alcohol produced by the reaction from the system using a rectification column. The esterification reaction can be carried out using a multistage apparatus in which multiple esterification reactors are connected in series.

[0036] When the esterification reaction is carried out in multiple stages, the temperature of the first stage esterification reaction is preferably 240 to 270°C, more preferably 245 to 265°C. The pressure is 0.2 to 3 kg / cm. 2 G is preferably 0.5 to 2 kg / cm 2 G is more preferred.

[0037] The temperature of the final stage esterification reaction is preferably 250 to 290°C, more preferably 255 to 275°C. The pressure is 0 to 1.5 kg / cm. 2G is preferably 0 to 1.3 kg / cm 2 G is more preferred.

[0038] When the esterification reaction is carried out in three or more stages, the reaction conditions for the intermediate stages are preferably intermediate between the reaction conditions for the first stage and the reaction conditions for the final stage. The reaction rate of the multi-stage esterification reaction is preferably increased smoothly in each stage. The final esterification reaction rate preferably reaches 90% or more, more preferably 93% or more. These esterification reactions can produce an esterified product, the molecular weight of which is preferably about 500 to 5,000.

[0039] When terephthalic acid is used in the esterification reaction, the reaction proceeds due to the catalytic action of terephthalic acid as an acid.

[0040] To the esterified product obtained as described above, a polyether compound and an aromatic dicarboxylic acid having a metal sulfonate group are added, and an organic sulfonic acid compound is added as a polymerization catalyst to carry out an etherification reaction. Thereafter, a polycondensation reaction is carried out to obtain the polyester resin of the present invention. Before the etherification reaction, an alkali metal compound may be added to carry out a depolymerization reaction, if necessary.

[0041] The amount of aromatic dicarboxylic acid having a metal sulfonate group added relative to the esterified product is, for example, a mass ratio of (esterified product) / (aromatic dicarboxylic acid having a metal sulfonate group)=4.0 to 70.0, which makes it easier to keep the content of aromatic dicarboxylic acid having a metal sulfonate group within the range of the present invention and to keep the contents of diethylene glycol, triethylene glycol, and tetraethylene glycol in the resulting polyester resin within specific ranges.

[0042] The amount of polyether compound added relative to the esterified product is, for example, a mass ratio of (esterified product) / (polyether compound)=4.0 to 60.0, which makes it easier to adjust the content of the polyether compound in the obtained polyester resin to a specific range.

[0043] In the present invention, by using an organic sulfonic acid compound as a polymerization catalyst, the content of diethylene glycol, triethylene glycol, and tetraethylene glycol in the obtained polyester resin can be set to a specific range. Examples of the organic sulfonic acid compound include benzenesulfonic acid, m- or p-benzenedisulfonic acid, 1,3,5-benzenetrisulfonic acid, o-, m-, or p-sulfobenzoic acid, benzaldehyde-o-sulfonic acid, acetophenone-p-sulfonic acid, acetophenone-3,5-disulfonic acid, o-, m-, or p-aminobenzenesulfonic acid, sulfanilic acid, 2-aminotoluene-3-sulfonic acid, phenylhydroxylamine-3-sulfonic acid, and phenylhydrazine-3-sulfonic acid. acid, 1-nitronaphthalene-3-sulfonic acid, thiophenol-4-sulfonic acid, anisole-o-sulfonic acid, 1,5-naphthalenedisulfonic acid, o-, m- or p-chlorobenzenesulfonic acid, o-, m- or p-bromobenzenesulfonic acid, o-, m- or p-nitrobenzenesulfonic acid, nitrobenzene-2,4-disulfonic acid, nitrobenzene-3,5-disulfonic acid, nitrobenzene-2,5-disulfonic acid, 2-nitrotoluene-5-sulfonic acid, 2-nitrotoluene-4 -sulfonic acid, 2-nitrotoluene-6-sulfonic acid, 3-nitrotoluene-5-sulfonic acid, 4-nitrotoluene-2-sulfonic acid, 3-nitro-o-xylene-4-sulfonic acid, 5-nitro-o-xylene-4-sulfonic acid, 2-nitro-m-xylene-4-sulfonic acid, 5-nitro-m-xylene-4-sulfonic acid, 3-nitro-p-xylene-2-sulfonic acid, 5-nitro-p-xylene-2-sulfonic acid, 6-nitro-p-xylene-2-sulfonic acid, 2,4-dinitrobenzene sulfonic acid acid, 3,5-dinitrobenzenesulfonic acid, o-, m- or p-fluorobenzenesulfonic acid, 4-chloro-3-methylbenzenesulfonic acid, 2-chloro-4-sulfobenzoic acid, 5-sulfosalicylic acid, 4-sulfophthalic acid, 2-sulfobenzoic anhydride, 3,4-dimethyl-2-sulfobenzoic anhydride, 4-methyl-2-sulfobenzoic anhydride, 5-methoxy-2-sulfobenzoic anhydride, 1-sulfonaphthoic anhydride, 8-sulfonaphthoic anhydride, 3,6-disulfophthalic anhydride, 4,Examples of the sulfonyl anhydride include 6-disulfoisophthalic anhydride, 2,5-disulfoterephthalic anhydride, methanesulfonic acid, ethanesulfonic acid, methionic acid, cyclopentanesulfonic acid, 1,1-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,2-ethanedisulfonic anhydride, 3-propanedisulfonic acid, β-sulfopropionic acid, isethionic acid, dithionic acid, dithionic anhydride, 3-oxy-1-propanesulfonic acid, 2-chloroethanesulfonic acid, phenylmethanesulfonic acid, β-phenylethanesulfonic acid, α-phenylethanesulfonic acid, ammonium chlorosulfonate, methyl benzenesulfonate, ethyl p-toluenesulfonate, ethyl methanesulfonate, dimethyl 5-sulfosalicylate, trimethyl 4-sulfophthalate, and salts thereof. Among these, from the viewpoint of versatility, 2-sulfobenzoic anhydride, o-sulfobenzoic acid, m-sulfobenzoic acid, p-sulfobenzoic acid, 5-sulfosalicylic acid, benzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzenesulfonic acid, p-toluenesulfonic acid, methyl p-toluenesulfonate, 5-sulfoisophthalic acid, and salts thereof are listed.

[0044] When a metal catalyst is not used as the polymerization catalyst, the content of metal components derived from the metal catalyst in the resulting polyester resin of the present invention can be reduced. A high content of metal components may result in the generation of foreign matter during melt processing or the elution of metal components during alkali dissolution. The content of metal components is preferably 1 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0 ppm. Examples of metal catalysts include compounds of antimony, germanium, tin, titanium, zinc, aluminum, iron, magnesium, manganese, nickel, cobalt, and the like.

[0045] The organic sulfonic acid compound can be added, for example, in the form of a solid, a slurry, or a solution dissolved in water, glycol, or the like.

[0046] The amount of organic sulfonic acid compound added depends on the type, but is generally 0.5 x 10 per mole of the acid component that constitutes the polyester resin. -4 ~9.0×10 -4 The amount is preferably 1.0 to 8.0 × 10 -4 It is more preferable that the amount is less than the above range and is therefore too small to obtain a polyester resin with a high degree of polymerization, and thus it may be impossible to obtain a fiber with excellent strength and alkali solubility. Alternatively, the content of diethylene glycol, triethylene glycol, and tetraethylene glycol may not fall within the specific range. On the other hand, if the amount is in excess of the above range, the content of diethylene glycol, triethylene glycol, and tetraethylene glycol may become too high, or this may cause discoloration of the polyester resin.

[0047] By adjusting the amount of the organic sulfonic acid compound to fall within the above range, the content of sulfur components other than the aromatic dicarboxylic acid having a metal sulfonate group (i.e., sulfur components derived from the catalyst) in the resulting polyester resin can be adjusted to preferably 5 to 100 ppm, more preferably 6 to 60 ppm. If the sulfur component content is less than 5 ppm, the resulting fiber may have poor yarn quality. On the other hand, if it exceeds 100 ppm, it may cause discoloration of the polyester.

[0048] The temperature of the etherification reaction is preferably 240°C or higher, more preferably 240 to 300°C, and even more preferably 250 to 280°C. If the temperature is lower than 240°C, the reaction may not proceed sufficiently, and the contents of diethylene glycol, triethylene glycol, and tetraethylene glycol may not be within the specified range. If the temperature exceeds 300°C, decomposition of the esterified product may proceed during the reaction, which may result in a decrease in operability when producing fibers and in the yarn quality characteristics of the fibers.

[0049] The etherification reaction time is preferably 5 to 120 minutes, more preferably 10 to 60 minutes. If the reaction time is less than 5 minutes, the reaction may not proceed sufficiently, and the contents of diethylene glycol, triethylene glycol, and tetraethylene glycol may not fall within the specified range. If the reaction time exceeds 120 minutes, the etherification reaction may proceed too far, and the contents of diethylene glycol, triethylene glycol, and tetraethylene glycol may not fall within the specified range, or decomposition of the esterified product may proceed during the reaction, which may result in a decrease in operability when producing fibers and in the yarn quality characteristics of the fibers.

[0050] The etherification reaction is preferably carried out under normal pressure or pressure, and the pressure is 0 to 3.0 kg / cm. 2 Preferably it is G.

[0051] By adjusting the ratio (G / A) of glycol components to acid components in the raw materials used in the etherification reaction, the contents of diethylene glycol, triethylene glycol, and tetraethylene glycol can be adjusted to a specific range. G / A is preferably 1.05 to 3.00, and more preferably 1.10 to 2.00. To adjust G / A, additional glycol components such as ethylene glycol may be added to the polyester raw material as needed. If the G / A is less than 1.05, the amounts of diethylene glycol, triethylene glycol, and tetraethylene glycol produced tend to decrease, while if it exceeds 3.00, the amounts of diethylene glycol, triethylene glycol, and tetraethylene glycol produced tend to increase.

[0052] After the etherification reaction, a polycondensation reaction can be carried out to obtain the polyester resin of the present invention. Examples of the polycondensation reaction include a melt polycondensation reaction. The polycondensation reaction may be carried out in one stage or in multiple stages.

[0053] The polycondensation reaction conditions are not particularly limited, but the temperature of the first stage polycondensation reaction is preferably 250 to 290° C., more preferably 260 to 280° C. The pressure is preferably 500 to 20 hPa, more preferably 200 to 30 hPa.

[0054] In the case of a multi-stage process, the temperature of the polycondensation reaction in the final stage is preferably 265 to 300°C, and more preferably 275 to 295°C. The pressure is preferably 10 to 0.1 hPa, and more preferably 5 to 0.5 hPa. When the process is carried out in three or more stages, the reaction conditions in the intermediate stages are preferably between those in the first stage and the final stage. It is preferable to smoothly increase the degree of polymerization in each of these stages.

[0055] Furthermore, during the polycondensation reaction, a hindered phenol-based antioxidant and a phosphorus compound capable of suppressing thermal decomposition of the resin may be added in addition to the above-mentioned polymerization catalyst, if necessary.

[0056] Examples of hindered phenol antioxidants include 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 4,4'-butylidenebis-(3-methyl-6-t-butylphenol), ... Examples of suitable compounds include ethylene glycol-bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate] and 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1'-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, but tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane is preferred from the standpoint of effectiveness and cost. These compounds can be used alone or in combination of two or more.

[0057] Examples of phosphorus compounds that can be used include phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, tridecyl phosphate, triphenyl phosphate, etc. These compounds can be used alone or in combination of two or more.

[0058] (Uses of polyester resin) The polyester resin of the present invention can be used in a variety of applications, including, for example, fibers, molded articles, and films.

[0059] The polyester resin of the present invention can be used to form the fiber of the present invention. The fibers of the present invention can be obtained, for example, by melting and spinning a raw material containing the polyester resin of the present invention. The spinning method can be carried out under known conditions. For example, the polyester resin is dried by a conventional method, fed to a conventional melt spinning machine, and melt-spun at a temperature at least 20°C higher than the melting point of the polyester. The resulting undrawn or semi-undrawn yarn can be wound at a speed of 1000 to 4000 m / min, or the yarn can be stretched 1.5 to 3.5 times without being wound, and then heat-treated at 80 to 180°C to obtain the desired fiber.

[0060] The fibers of the present invention may be ultrafine fibers having a single fiber fineness of 0.8 dtex or less (preferably 0.6 to 0.3 dtex).

[0061] The fibers of the present invention may be, for example, monofilaments, multifilaments, or the like, and may be either long fibers or short fibers.

[0062] The shape of the single fibers constituting the fiber of the present invention is not particularly limited, and they may have not only a round cross section but also a non-circular cross section such as a polygonal cross section. The fibers of the present invention may be subjected to post-processing such as crimping and false twisting, if necessary.

[0063] The fiber of the present invention may be not only a fiber in which all of the single fibers are formed from the polyester resin of the present invention, but also a conjugated fiber in which the polyester resin of the present invention is conjugated with other polyester resins (such as virgin polyester resins or polyester resins containing other copolymer components). Examples of the form of the conjugated fiber include a core-sheath type, a side-by-side type, and an islands-in-sea type.

[0064] When the fiber of the present invention is a multifilament, its characteristic values ​​may include, for example, a single yarn fineness of 0.3 to 30 decitex, a single yarn count of 2 to 300, a total fineness of 5 to 350, a strength of 1 to 5 cN / decitex, and an elongation of 10 to 400%.

[0065] The fiber of the present invention has excellent alkali solubility and also has excellent yarn quality properties such as elongation and strength. [Example]

[0066] The present invention will be specifically described below based on examples, but the present invention is not limited to these. Measurements and evaluations were carried out by the following methods.

[0067] (1) Intrinsic viscosity [IV] The measurement was carried out at 20°C using an equal weight mixture of phenol and tetrachloroethane as a solvent.

[0068] (2) Composition of polyester resin 10 mg of sample was dissolved in 1 mL of a mixed solvent of deuterated chloroform / deuterated trifluoroacetic acid = 9 / 1 (mass ratio), and the sample was analyzed using a JEOL LA-400 NMR spectrometer. 1 H-NMR was measured, and the total amount of the dicarboxylic acid component, triethylene glycol component, and tetraethylene glycol component, as well as the molar ratio of each other glycol component, were calculated from the integrated proton peak intensity of each component in the obtained chart. Furthermore, the content (mass%) of the polyether compound in the polyester resin was calculated.

[0069] Next, the amounts of triethylene glycol and tetraethylene glycol were determined as follows. The polyester resin was hydrolyzed in a 0.75N potassium hydroxide / methanol solution, and then neutralized by adding terephthalic acid. The filtrate was then measured by gas chromatography, and the molar ratio of triethylene glycol to tetraethylene glycol was calculated using a calibration curve prepared in advance. 1 The contents of triethylene glycol and tetraethylene glycol in the total glycol components were calculated from the results of H-NMR measurement (molar ratio of the total component of triethylene glycol and tetraethylene glycol to each of the other glycol components). The contents (mol %) of the glycol components ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol were calculated without including the polyether compound.

[0070] (4) Melting point (Tm), glass transition temperature (Tg) The measurements were carried out using a PerkinElmer DSC-7 differential scanning calorimeter in a nitrogen stream at a temperature range of 25 to 280°C and a heating rate of 20°C / min.

[0071] (5) Sulfur content of catalyst The polyester resin was melt-molded at 300°C to form a disk-shaped molded plate with a diameter of 3 cm and a thickness of 1 cm, and quantitative analysis of the sulfur component was performed using a Rigaku ZSX Primus X-ray fluorescence analyzer by the calibration curve method. Next, 10 mg of the sample was dissolved in 1 mL of a mixed solvent of deuterated chloroform / deuterated trifluoroacetic acid = 9 / 1 (mass ratio), and the sample was analyzed using a JEOL LA-400 NMR spectrometer. 1 H-NMR was measured, and the molar ratio of 5-Na sulfoisophthalic acid diglycol ester (SIPG) was calculated from the integrated proton peak intensity of each component in the obtained chart, and the sulfur content derived from SIPG was calculated from that. The amount of sulfur components derived from the catalyst was calculated by subtracting the amount of sulfur derived from SIPG calculated by NMR from the amount of sulfur components quantitatively analyzed by an X-ray fluorescence analyzer.

[0072] The evaluation methods for fibers (operability, strength, elongation, alkali loss rate) are as follows: (6) Operational efficiency of filament manufacturing (cut yarn) A case where the number of times the yarn was broken during 24 hours of continuous melt spinning was 3 times / (day / spindle) or less was marked as "○", and other cases were marked as "×".

[0073] (7) Yarn quality characteristics According to JIS L-1013, strength and elongation were measured using an autograph DSS-500 manufactured by Shimadzu Corporation at a gripping distance of 25 cm and a pulling speed of 30 cm. In the present invention, the strength is preferably 2.0 cN / dtex or more, more preferably 3.0 cN / dtex or more, and the elongation is preferably 28% or more, more preferably 30% or more. A yarn having both strength and elongation within the above ranges was evaluated as "Good", and a yarn having at least one of the strength and elongation not within the above ranges was evaluated as "Poor". A yarn having both strength and elongation within the above ranges is an indicator of an excellent balance of yarn quality characteristics.

[0074] (8) Alkali weight loss rate The polyester resin thus obtained was dried and then spun at 295°C using a spinneret with 48 nozzles. The spinning was cooled and oiled while being wound up at a speed of 1,500 m / min to obtain an undrawn yarn. This was then drawn at a draw ratio of 2.8, with a roll heater temperature of 80°C, a plate heater temperature of 150°C, and a drawing speed of 600 m / min, and then wound up to obtain a drawn yarn of 75 dtex / 48 filaments. Next, this drawn yarn was made into a cylindrical knitted fabric in the usual way, and subjected to a weight reduction treatment for 20 minutes in a 5% by mass aqueous sodium hydroxide solution with a bath ratio of 1:50 and temperature controlled at 70°C, and the weight loss was calculated using the following formula. Weight loss rate (mass% / min)=[(AB) / A]×100 / 20 Here, A indicates the mass (g) of the tubular knitted fabric before weight reduction, and B indicates the mass (g) of the tubular knitted fabric after weight reduction. The rate of alkali weight loss of 5% by mass / min or more was marked "Good", and the rate of alkali weight loss of less than 5% by mass / min was marked "Poor".

[0075] [Preparation of esterified products] A slurry of terephthalic acid and ethylene glycol (molar ratio 1 / 1.6) was continuously supplied to an esterification reactor and reacted at a temperature of 250°C and a pressure of 0.2 MPa for a residence time of 8 hours to obtain an esterified product (terephthalic acid:ethylene glycol = 100:111 (molar ratio)).

[0076] Example 1 [Polyester resin] The heat-melted esterified product, polyethylene glycol (PEG) having a number-average molecular weight of 6,000 as a polyether compound, and 5-Na sulfoisophthalic acid diglycol ester (SIPG) as an aromatic dicarboxylic acid component having a metal sulfonate group were charged into a polycondensation reactor heated to 280°C in the amounts shown in Table 1. Next, 2.0 × 10 5-sulfosalicylic acid dihydrate (SS) was added as a polymerization catalyst. -4 The reaction mixture was added in an amount of 1000 mol / mol of acid component, and the etherification reaction was carried out at 260°C under atmospheric pressure for 10 minutes. Next, while maintaining the reactor temperature at 280°C, the system pressure was gradually reduced to 0.5 hPa or less after 60 minutes. Under these conditions, the polycondensation reaction was carried out with stirring for 3 hours to obtain a polyester resin. The polyester resin contained 25 ppm of catalyst-derived sulfur components and a triethylene glycol content of 1.1 mol%.

[0077] [Production of Long Fibers] The resulting polyester resin was dried and then spun at a spinning temperature of 273°C using a spinneret with 48 nozzles, followed by cooling and oil application while winding at a speed of 1395 m / min to obtain an undrawn yarn, which was then drawn at a draw ratio of 2.5, a roll heater temperature of 80°C, a plate heater temperature of 150°C, and a drawing speed of 600 m / min, followed by winding to obtain an 84 dtex / 48 filament multifilament yarn (drawn yarn).

[0078] Examples 2 to 8, Comparative Examples 1 to 9 [Polyester resin] As shown in Table 1, the polyester resin was obtained by the same procedure as in Example 1, except that the amount of PEG, the amount of 5-Na sulfoisophthalic acid diglycol ester (SIPG), the amount of 5-sulfosalicylic acid dihydrate (SS), and the etherification conditions were changed. Then, a multifilament yarn was obtained in the same manner as in Example 1.

[0079] Comparative Example 10 A polyester resin was obtained in the same manner as in Example 1, except that antimony trioxide (Sb) was used instead of 5-sulfosalicylic acid dihydrate (SS). Then, a multifilament yarn was obtained in the same manner as in Example 1.

[0080] Table 1 shows the raw material composition and production conditions for the polyester resins in the examples and comparative examples. [Table 1]

[0081] Table 2 shows the properties of the polyester resins and fibers obtained in the examples and comparative examples.

[0082] [Table 2]

[0083] As is clear from Tables 1 and 2, the polyester resins obtained in Examples 1 to 8 had a content of aromatic dicarboxylic acid having a metal sulfonate group, a content of polyether compound, and a content of triethylene glycol within the ranges specified in the present invention. Therefore, the operability in obtaining fibers was excellent, and fibers excellent in operability, yarn quality, and alkali solubility were obtained.

[0084] On the other hand, in Comparative Example 1, the content of triethylene glycol in the polyester resin was higher than the range specified in the present invention, resulting in an amorphous resin with poor heat resistance, poor spinning operability, and inability to draw, so that the resin was not evaluated as a fiber.

[0085] In Comparative Example 2, the content of triethylene glycol in the polyester resin was low and outside the range specified in the present invention, resulting in a resin with a high melting point, which was inferior in operability during spinning, yarn quality characteristics when made into fibers, and alkali solubility.

[0086] In Comparative Example 3, the content of the polyether compound was low and outside the range specified in the present invention, and therefore the alkali solubility of the fiber was poor.

[0087] In Comparative Example 4, the content of the polyether compound was higher than the range specified in the present invention, and therefore the thermal stability was low, and the operability in spinning and the yarn quality characteristics when made into fibers were poor.

[0088] In Comparative Example 5, the etherification reaction was not carried out, and therefore the triethylene glycol content in the polyester resin was low and outside the range specified in the present invention, resulting in poor spinning operability, poor yarn quality when made into fibers, and poor alkali solubility.

[0089] In Comparative Example 6, the etherification reaction temperature was low, so the reaction did not proceed sufficiently, and the triethylene glycol content in the polyester resin was low and outside the range specified in the present invention, resulting in poor spinning operability, fiber quality, and alkali solubility.

[0090] In Comparative Example 7, the etherification reaction time was extended, resulting in a high triethylene glycol content in the polyester resin that was outside the range specified in the present invention. As a result, the resin was amorphous and had low heat resistance. The spinning operability was poor and drawing was not possible, so the fiber was not evaluated.

[0091] In Comparative Example 8, the amount of 5-sulfosalicylic acid dihydrate added as a polymerization catalyst was too high, resulting in a high triethylene glycol content in the polyester resin that was outside the range specified in the present invention. As a result, the resin was amorphous and had low heat resistance. Spinning operability was poor and drawing was not possible, so the fiber was not evaluated.

[0092] In Comparative Example 9, the amount of 5-sulfosalicylic acid dihydrate added as a polymerization catalyst was small, so the etherification reaction did not proceed sufficiently and the triethylene glycol content was low and outside the range specified in the present invention. As a result, the spinning operability was poor and the resulting fibers were inferior in terms of yarn quality and alkali solubility.

[0093] In Comparative Example 10, antimony trioxide, a metal catalyst, was added as the polymerization catalyst instead of 5-sulfosalicylic acid dihydrate (SS), resulting in a low triethylene glycol content. As a result, the spinning operability was poor, and the resulting fiber had poor yarn quality and alkali solubility. Furthermore, in the evaluation of alkali solubility, Sb was eluted during alkali dissolution.

Claims

1. A polyester resin containing 0.5 to 4.3 mol % of an aromatic dicarboxylic acid having a metal sulfonate group as a dicarboxylic acid component, and 5 to 25 mass % of a polyether compound having a number average molecular weight of 500 to 15,000, wherein the glycol component of the polyester resin contains ethylene glycol as a main component and has a triethylene glycol content of 0.5 to 5.5 mol %.

2. 2. The polyester resin according to claim 1, which contains diethylene glycol as a glycol component, and the content of diethylene glycol is 2.5 mol% or more.

3. 3. The polyester resin according to claim 1, wherein the content of sulfur components other than the aromatic dicarboxylic acid having a metal sulfonate group is 5 to 100 ppm.

4. A fiber made of the polyester resin according to any one of claims 1 to 3.

5. A method for producing the polyester resin according to any one of claims 1 to 3, comprising the steps of adding an organic sulfonic acid compound to a polyester raw material, and heating the resulting mixture at a temperature of 240°C or higher for 5 to 120 minutes under normal pressure or pressure to carry out an etherification reaction of the glycol component.

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