JP2010070739A - Method for producing easily alkali-soluble copolymer polyester, the polyester obtained by the method, and conjugate fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an easily alkali-soluble copolymer polyester simultaneously satisfying excellent alkali elution property and fiber-forming property. <P>SOLUTION: In the method for producing a polyester in which an isophthalic acid component containing a metal sulfonate group is copolymerized in an amount of 3-15 mol% based on the whole acid component, a polycondensation reaction is performed in the presence of (1) a titanium compound, (2) a phosphorus compound, and (3) a lithium compound, and these compounds are mixed and stirred previously and then added. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a readily alkali-soluble copolymer polyester and a composite fiber comprising the polyester. More specifically, it simultaneously achieves alkali elution and spinning performance, has an increased filtration pressure during spinning, and has excellent moldability when made into a composite fiber. The present invention relates to a composite fiber capable of obtaining ultrafine fibers and hollow fibers.

  Polyester is used for various purposes because of its useful functionality, and is used for clothing, materials, and medical use, for example. Among them, polyethylene terephthalate is excellent in terms of versatility and practicality and is preferably used.

  In general, polyethylene terephthalate is produced from terephthalic acid or an ester-forming derivative thereof and ethylene glycol. In a commercial process for producing a high molecular weight polymer, an antimony compound is widely used as a polycondensation catalyst. However, polymers containing antimony compounds have some undesirable properties as described below.

  For example, when a polyester obtained by using an antimony catalyst is melt-spun into a fiber, it is known that a residue of the antimony catalyst is deposited around the mouthpiece hole. As this deposition progresses, it becomes a cause of defects in the filament, so that it needs to be removed in a timely manner. It is believed that the accumulation of antimony catalyst residue occurs because the antimony compound in the polymer is transformed near the die, partially vaporizes and dissipates, and then an antimony-based component remains in the die. .

  Also, the antimony catalyst residue in the polymer tends to become relatively large particles, and it becomes a foreign substance, causing an increase in the filter pressure during molding, causing yarn breakage during spinning or film breakage during film formation, etc. Have unfavorable properties. In particular, when a composite fiber is spun using an alkali-eluting copolyester as one component, it is easily affected by foreign particles, and problems such as thread breakage occur remarkably.

  In view of the above background, there is a demand for polyesters that contain very little or no antimony.

  As polycondensation catalysts other than antimony compounds, it has been proposed to use titanium compounds as polycondensation catalysts (Patent Document 1). However, when such a titanium compound is used as a catalyst, the heat resistance of the obtained polymer is insufficient when the catalyst compound is used alone, and the degree of polymerization is lowered during the molding process of the polymer. There was a problem that it was inferior. In order to solve this problem, studies have been made to improve the heat resistance of a polymer by using a titanium compound in combination with a phosphorus compound having a specific structure (Patent Documents 2 and 3). A certain improvement in the heat resistance of the polymer was obtained by these methods.

  However, in the alkali-soluble copolymer polyester used as a composition for obtaining ultrafine fibers and irregular cross-section fibers by compounding with different components, for example, metal sulfonate group-containing isophthalic acid or polyalkylene glycol is included as a copolymer component ( Patent Document 4) has problems that cannot be solved by conventional techniques because heat resistance and oxidative degradation are poor and molding processability is inferior, and fibers are fused by heat during stretching. It was. In response to this problem, there has been reported a method for providing a readily alkali-soluble copolymer polyester having improved heat resistance by using a specific titanium complex as a polymerization catalyst (Patent Document 5). The spinning property was not satisfactory.

A number of polyesters containing a metal sulfonate group-containing isophthalic acid as a copolymerization component as representative examples of alkali-elutable copolymer polyesters have been reported so far (for example, Patent Document 6). However, in this polyester copolymerized with a certain amount or more of the metal sulfonate group-containing isophthalic acid, the polymer exhibits a thickening action due to the metal sulfonate group-containing isophthalic acid component, so that the melt viscosity of the polymerization reaction product is remarkably increased. It has been difficult to sufficiently increase the degree of polymerization, and has a problem that the yarn-making property is deteriorated. In response to this problem, a method of using a sulfonic acid quaternary phosphonium salt as a copolymerization component as an alternative to a metal sulfonate group-containing isophthalic acid has been reported (Patent Document 7), but when a titanium compound is used as a polymerization catalyst. Since the phosphorus compound deactivates the catalytic activity of the titanium compound, the degree of polymerization of the reaction product could not be sufficiently increased.
JP-A-60-108422 (Claims) JP 2007-224106 A (Claims) JP 2008-115243 A (Claims) JP 2000-95850 A (Claims) JP-A-2004-137319 (Claims) JP 63-159525 A (Claims) JP 2006-176628 A (Claims)

  An object of the present invention is to provide a method for producing a readily alkali-soluble copolymer polyester that solves the above-described problems and achieves excellent alkali elution and yarn forming properties at the same time.

  The object of the present invention is to produce a polyester in which 3 to 15 mol% of an isophthalic acid component containing a metal sulfonate group is copolymerized with respect to the total acid component, in which (1) a titanium compound, (2) phosphorus The compound and (3) a polycondensation reaction in the presence of a lithium compound, and each of these compounds are added after mixing and stirring in advance, and this is achieved by a method for producing a readily alkali-soluble copolyester.

  According to the present invention, the above object is achieved. The polyester obtained by the production method of the present invention can be suitably used for a composite fiber that can easily obtain ultrafine fibers and hollow fibers by removing alkali in order to achieve excellent alkali elution and yarn forming at the same time. it can.

  The alkali-soluble copolymerized polyester of the present invention is a polyester comprising a dicarboxylic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof, and an isophthalic acid component containing a metal sulfonate group with respect to the total acid component is 3 to 3. 15 mol% copolymerized polyester.

  Specific examples of the polyester comprising dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative include, for example, polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2, Examples include 6-naphthalene dicarboxylate, polyethylene-1,2-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate. The present invention is suitable for polyethylene terephthalate or polyester copolymers mainly containing ethylene terephthalate units, which are most commonly used.

  The isophthalic acid component containing a metal sulfonate group refers to an alkali metal salt, alkaline earth metal salt, phosphonium salt of sulfoisophthalic acid, or a derivative thereof, specifically 5-sodium sulfoisophthalic acid. , 5-lithium sulfoisophthalic acid, 5- (tetraalkyl) phosphonium sulfoisophthalic acid, and derivatives thereof. When phosphonium salts and derivatives thereof are used as the isophthalic acid component containing a metal sulfonate group, the polymerization catalyst activity may be deactivated depending on the content. Preferred is 5-sodium sulfoisophthalic acid and its derivatives.

  It is essential that the copolymerization amount of the isophthalic acid component containing a metal sulfonate group is 3 to 15 mol% copolymerized with respect to all the acid components constituting the copolymerized polyester. Alkali elution improves as the copolymerization amount of the isophthalic acid component containing a metal sulfonate group increases, but at the same time, thickening of the polyester is caused and molding processability and yarn-making property are lowered. It is difficult to add. On the other hand, if it is less than 3 mol%, sufficient elution cannot be obtained. It is preferable that the alkali solubility and molding processability are both preferably 7 to 13 mol%, and particularly preferably 8 to 10 mol%.

  The alkali-soluble copolymer polyester of the present invention is a polyalkylene glycol, adipic acid, isophthalic acid, sebacic acid, phthalic acid, naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, as long as the object of the present invention is not impaired. Acids, dicarboxylic acids such as cyclohexanedicarboxylic acid and ester-forming derivatives thereof, dioxy compounds such as diethylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexanedimethanol, oxycarboxylic acids such as p- (β-oxyethoxy) benzoic acid, and The ester-forming derivative or the like may be copolymerized.

  Among them, it is preferable that 0.1 to 15.0% by weight of a polyalkylene glycol having a weight average molecular weight of 400 to 10000 is copolymerized because the alkali elution property and the dyeability are improved. The weight average molecular weight of the polyalkylene glycol is preferably 1000 to 6000, and the copolymerization amount is more preferably 1.5 to 10.0% by weight.

  The alkali-soluble copolymer polyester of the present invention is a polyester obtained by polycondensation reaction in the presence of (1) a titanium compound, (2) a phosphorus compound, and (3) a lithium compound, It is essential to add each compound after mixing and stirring in advance. By adding the (1) titanium compound, (2) phosphorus compound, and (3) lithium compound after mixing and stirring in advance, the polymerization activity is improved, and the elution and yarn-making properties of the polyester of the present invention are improved. Is good. The reason for this is not yet clearly understood, but (1) the titanium compound and (2) the phosphorus compound are mixed and stirred in advance, so that the catalytic activity of the titanium compound is adjusted by the phosphorus compound, which is a side reaction. By suppressing the thermal decomposition reaction, heat resistance and yarn-making property are improved. By mixing and stirring (2) phosphorus compound and (3) lithium compound, fine particles composed of phosphorus compound and lithium compound are generated and eluted. This is considered to improve the properties and the spinning performance. This effect is manifested only when (1) a titanium compound, (2) a phosphorus compound, and (3) a lithium compound are mixed and stirred in advance. The (1) titanium compound, (2) phosphorus compound, and (3) lithium compound may be mixed with a solvent containing a diol component forming a polyester such as ethylene glycol or propylene glycol, and mixed and stirred as a solution or slurry. preferable. The conditions for mixing and stirring are not particularly limited, but it is preferable to mix and stir at a temperature of 0 to 200 ° C for 1 minute or more, preferably at a temperature of 15 to 100 ° C for 10 to 120 minutes. The reaction pressure at this time is not particularly limited, and may be normal pressure.

  (1) The addition timing of the titanium compound, (2) phosphorus compound, and (3) lithium compound mixed and stirred is used as an esterification reaction catalyst by adding a catalyst immediately after the addition of the raw material, or accompanying the raw material. There is a method of adding a catalyst. In addition, when added as a polycondensation reaction catalyst, it may be substantially before the start of the polycondensation reaction, and may be added before the esterification reaction or after the completion of the reaction and before the start of the polycondensation reaction. Good.

  (1) The titanium compound used in the present invention is a titanium complex having a polyvalent carboxylic acid and / or hydroxycarboxylic acid and / or nitrogen-containing carboxylic acid as a chelating agent, from the viewpoint of thermal stability and color tone of the polymer. preferable. Examples of chelating agents for titanium compounds include polyvalent carboxylic acids such as phthalic acid, trimellitic acid, trimesic acid, hemititic acid, pyromellitic acid, and hydroxycarboxylic acids such as lactic acid, malic acid, tartaric acid, and citric acid. As the nitrogen-containing carboxylic acid, ethylenediaminetetraacetic acid, nitrilotripropionic acid, carboxyiminodiacetic acid, carboxymethyliminodipropionic acid, diethylenetriaminopentaacetic acid, triethylenetetraminohexaacetic acid, iminodiacetic acid, iminodipropionic acid Hydroxyethyliminodiacetic acid, hydroxyethyliminodipropionic acid, methoxyethyliminodiacetic acid and the like. These titanium compounds may be used alone or in combination. As the addition amount of the titanium compound, it is preferable to add the titanium compound excluding the titanium oxide particles added for the purpose of the matting agent so as to be 0.1 to 20 ppm in terms of titanium atom with respect to the obtained polymer. The content of 0.5 to 10 ppm is preferable because the thermal stability and color tone of the polymer become better.

  (2) Phosphorus compounds used in the present invention are phosphoric acid, phosphorous acid, phosphonic acid, phosphinic acid, phosphine oxide, phosphonous acid, phosphinic acid, phosphine compounds or ester compounds thereof. Any one or two selected are preferable. Specifically, for example, phosphoric acid, phosphoric acid trimethyl ester, phosphoric acid triethyl ester, phosphoric acid triphenyl ester and the like, phosphorous acid, phosphorous acid, trimethyl phosphite, triethyl phosphite, triphenyl phosphite Bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol-di-phosphite, tris (mono Nonylphenyl) phosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octylphosphite, etc. Phosphorous acid system, methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid, butylphosphone Acid, phenylphosphonic acid, benzylphosphonic acid, tolylphosphonic acid, Silylphosphonic acid, biphenylphosphonic acid, naphthylphosphonic acid, anthrylphosphonic acid, 2-carboxyphenylphosphonic acid, 3-carboxyphenylphosphonic acid, 4-carboxyphenylphosphonic acid, 2,3-dicarboxyphenylphosphonic acid, 2, 4-dicarboxyphenylphosphonic acid, 2,5-dicarboxyphenylphosphonic acid, 2,6-dicarboxyphenylphosphonic acid, 3,4-dicarboxyphenylphosphonic acid, 3,5-dicarboxyphenylphosphonic acid, 2, 3,4-tricarboxyphenylphosphonic acid, 2,3,5-tricarboxyphenylphosphonic acid, 2,3,6-tricarboxyphenylphosphonic acid, 2,4,5-tricarboxyphenylphosphonic acid, 2,4, 6-tricarboxyphenylphosphonic acid, methylphos Acid dimethyl ester, methylphosphonic acid diethyl ester, ethylphosphonic acid dimethyl ester, ethylphosphonic acid diethyl ester, phenylphosphonic acid dimethyl ester, phenylphosphonic acid diethyl ester, phenylphosphonic acid diphenyl ester, benzylphosphonic acid dimethyl ester, benzylphosphonic acid diethyl Ester, benzylphosphonic acid diphenyl ester, lithium (ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate), sodium (ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate), Magnesium bis (ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate), calcium bis (3,5-di-tert-butyl-4-hydroxybenzyl) Phosphonic acid compounds such as ethyl phosphonate), diethylphosphonoacetic acid, methyl diethylphosphonoacetate and ethyl diethylphosphonoacetate, hypophosphorous acid, sodium hypophosphite, methylphosphinic acid, ethylphosphinic acid, propylphosphinic acid , Isopropylphosphinic acid, butylphosphinic acid, phenylphosphinic acid, tolylphosphinic acid, xylylphosphinic acid, biphenylylphosphinic acid, diphenylphosphinic acid, dimethylphosphinic acid, diethylphosphinic acid, dipropylphosphinic acid, diisopropylphosphinic acid, dibutylphosphine Acid, ditolylphosphinic acid, dixylylphosphinic acid, dibiphenylylphosphinic acid, naphthylphosphinic acid, anthrylphosphinic acid, 2-carboxyphenylphosphinic acid, 3-carboxyl Phenylphosphinic acid, 4-carboxyphenylphosphinic acid, 2,3-dicarboxyphenylphosphinic acid, 2,4-dicarboxyphenylphosphinic acid, 2,5-dicarboxyphenylphosphinic acid, 2,6-dicarboxyphenylphosphinic acid 3,4-dicarboxyphenylphosphinic acid, 3,5-dicarboxyphenylphosphinic acid, 2,3,4-tricarboxyphenylphosphinic acid, 2,3,5-tricarboxyphenylphosphinic acid, 2,3,6 -Tricarboxyphenylphosphinic acid, 2,4,5-tricarboxyphenylphosphinic acid, 2,4,6-tricarboxyphenylphosphinic acid, bis (2-carboxyphenyl) phosphinic acid, bis (3-carboxyphenyl) phosphinic acid Bis (4-carboxyphenyl) Sphine acid, bis (2,3-dicarboxyphenyl) phosphinic acid, bis (2,4-dicarboxyphenyl) phosphinic acid, bis (2,5-dicarboxyphenyl) phosphinic acid, bis (2,6-di Carboxyphenyl) phosphinic acid, bis (3,4-dicarboxyphenyl) phosphinic acid, bis (3,5-dicarboxyphenyl) phosphinic acid, bis (2,3,4-tricarboxyphenyl) phosphinic acid, bis (2 , 3,5-tricarboxyphenyl) phosphinic acid, bis (2,3,6-tricarboxyphenyl) phosphinic acid, bis (2,4,5-tricarboxyphenyl) phosphinic acid, and bis (2,4,6) -Tricarboxyphenyl) phosphinic acid, methylphosphinic acid methyl ester, dimethylphosphinic acid methyl ester Methyl phosphinic acid ethyl ester, dimethyl phosphinic acid ethyl ester, ethyl phosphinic acid methyl ester, diethyl phosphinic acid methyl ester, ethyl phosphinic acid ethyl ester, diethyl phosphinic acid ethyl ester, phenyl phosphinic acid methyl ester, phenyl phosphinic acid ethyl ester, phenyl Phosphinic acid phenyl ester, diphenylphosphinic acid methyl ester, diphenylphosphinic acid ethyl ester, diphenylphosphinic acid phenyl ester, benzylphosphinic acid methyl ester, benzylphosphinic acid ethyl ester, benzylphosphinic acid phenyl ester, bisbenzylphosphinic acid methyl ester, bisbenzyl Phosphinic acid ethyl ester, bisbenzylphosphinic acid phenyl ester Phosphinic acids such as trimethylphosphine oxide, triethylphosphine oxide, tripropylphosphine oxide, triisopropylphosphine oxide, tributylphosphine oxide, triphenylphosphine oxide, methylphosphonous acid, ethylphosphonous acid, propyl Phosphonic acid, isopropylphosphonous acid, butylphosphonous acid, phenylphosphonous acid, phenylphosphonous acid diethyl ester, phenylphosphonous acid diisopropyl ester, tetrakis (2,4-di-t-butyl-5-methylphenyl) [ 1,1-biphenyl] -4,4′-diylbisphosphonite, tetrakis (2,4-di-tert-butylphenyl) {1,1-biphenyl} -4,4′-diyl Phosphonites such as sphosphonite, methylphosphinic acid, ethylphosphinic acid, propylphosphinic acid, isopropylphosphinic acid, butylphosphinic acid, phenylphosphinic acid, dimethylphosphinic acid, diethylphosphinic acid, dipropylphosphite Phosphinic acid series such as phosphinic acid, diisopropylphosphinic acid, dibutylphosphinic acid, diphenylphosphinic acid, methylphosphine, dimethylphosphine, trimethylphosphine, melephosphine, diethylphosphine, triethylphosphine, phenylphosphine, diphenylphosphine, triphenyl Examples include phosphine compounds such as phosphine. In view of cost and ease of handling, phosphoric acid is preferably used. The amount of the phosphorus compound added is preferably 1 to 500 ppm in terms of phosphorus atoms with respect to the polymer obtained. When the content is 5 to 200 ppm, the thermal stability and color tone of the polymer are improved, which is preferable.

  In the present invention, apart from the phosphorus compound added after premixing with the titanium compound and lithium compound, the polycondensation is carried out by reducing the pressure in the reactor after adding the polycondensation catalyst for the purpose of further improving the heat resistance. A phosphorus compound may be added and added after the reaction is started until the polymerization reaches the target degree of polymerization. In the case of adding a phosphorus compound by the above method, if a large amount of a diol component such as ethylene glycol is brought in and added, depolymerization of the polyester (polyester main chain cleavage reaction) proceeds. A method of adding alone or adding a master pellet containing phosphorus at a high concentration is preferable. At this time, the phosphorus compound may be added in several portions, or may be continuously added with a feeder or the like. In addition, the above-described method for adding a phosphorus compound is preferably added in a container that can be dissolved or melted in a polymerization system and is made of a polymer having substantially the same component as the polymer obtained in the present invention. . When the phosphorus compound is added to the container as described above and added, the addition of the polymerization reactor under the reduced pressure condition may cause the phosphorus compound to scatter and prevent the phosphorus compound from flowing out to the reduced pressure line. In addition, a desired amount of phosphorus compound can be added to the polymer. The container referred to in the present invention is not limited as long as it contains phosphorus compounds, and includes, for example, an injection-molded container having a lid or a stopper, or a sheet or film formed into a bag shape by sealing or sewing. More preferably, the container described above creates an air vent. When a phosphorus compound is added to a container that has been vented, even if it is added to the polymerization reactor under vacuum conditions, the container bursts due to air expansion and the phosphorus compound flows out to the decompression line, or the upper part of the polymerization reactor. The phosphorus compound can be added to the polymer in a desired amount without adhering to the wall surface. If the container is too thick, it takes longer to dissolve and melt, so it is better to make the container thinner. However, the container should be thick enough not to rupture when the phosphorus compound is sealed or added. For this purpose, a material having a thickness of 10 to 500 μm and uniform thickness is preferable.

  Examples of the lithium compound (3) used in the present invention include lithium acetate, lithium carbonate, and lithium formate. Lithium acetate is preferably used from the viewpoint of polymer yarn-making property and color tone. The addition amount of the lithium compound is preferably 10 to 1000 ppm in terms of lithium atoms with respect to the polymer obtained. When it is 50 to 500 ppm, the thermal stability and color tone of the polymer become better, which is preferable.

  It is preferable from the viewpoint of polymerization activity and color tone that the molar ratio Ti / P of the titanium atom in the titanium compound of the present invention and the phosphorus atom in the phosphorus compound is 0.001-1. Preferably it is the range of 0.01-0.5, Most preferably, it is the range of 0.02-0.2.

  The molar ratio Ti / Li between the titanium atom in the titanium compound of the present invention and the lithium atom in the lithium compound is preferably from 0.0001 to 0.1 from the viewpoints of yarn production and easy elution. Preferably it is the range of 0.0005-0.05, Most preferably, it is the range of 0.001-0.01.

  Further, at least one selected from the group consisting of an aluminum compound, a magnesium compound and a calcium compound may be added within a range not impairing the effects of the present invention. Examples of the aluminum compound include inorganic aluminum compounds, aluminum alcoholates, aluminum chelates, and aluminum carboxylates. Specific examples of the inorganic aluminum compounds include aluminum hydroxide, aluminum chloride, aluminum hydroxide chloride, and aluminum alcoholates. Aluminum acetate, aluminum isopropylate, aluminum tri-n-butylate, aluminum tri-sec-butylate, aluminum tri-tert-butylate, mono-sec-butoxyaluminum diisopropylate, etc. Diisopropylate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum dii Propylate, aluminum monoacetyl acetate bis (ethyl acetoacetate), aluminum tris (acetyl acetate), aluminum monoisopropoxy monooroxyethyl acetoacetate, aluminum acetylacetonate, etc., as aluminum carboxylate, aluminum acetate, aluminum benzoate, Examples thereof include aluminum lactate, aluminum laurate, and aluminum stearate. Specific examples of the magnesium compound include magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. Specific examples of the calcium compound include calcium oxide, calcium hydroxide, calcium alkoxide, calcium acetate, and calcium carbonate. These compounds may be used alone or in combination.

  The polyester obtained by the production method of the present invention is preferably in the range of 0.3 to 15 in the solution haze measurement (polymer turbidity measurement) described later. In solution haze measurement, the amount of particles generated in the polymer can be measured. Conventionally, it was thought that the lower the numerical value, the lower the amount of particles generated and the better the yarn-making property. However, the polyester obtained by the production method of the present invention does not simply reduce the solution haze, but falls within the above range. As a result, it has been found that the spinning performance is specifically improved. This is because, in the system using a titanium compound as a polymerization catalyst, the crystallinity is poor and the spinning property is deteriorated. On the contrary, the fine particles are actively created to improve the crystallinity, and the solution haze is increased as described above. It is considered that the yarn forming property is improved by being within the range. Preferably it is the range of 0.4-12, Most preferably, it is the range of 0.5-7.

  The polyester obtained by the production method of the present invention preferably contains 0 to 10 ppm by weight of a metal element having a true specific gravity of 5.0 or more. In the present invention, the true specific gravity refers to the specific gravity not including voids, and the specific gravity refers to the ratio of the mass of a substance in the same volume to the standard substance (water at 4 ° C.). Specific examples of the metal having a true specific gravity of 5.0 or more include antimony, germanium, manganese, cobalt, tin, zinc, and the like, and these are usually polyesters as catalysts, metallic color adjusters, additives, and the like. It is contained in. Other examples include iron, nickel, niobium, molybdenum, tantalum, and tungsten. On the other hand, titanium, calcium, potassium, aluminum, magnesium, sodium, lithium, and the like do not correspond to metals having a true specific gravity of 5.0 or more.

  The polyester of the present invention has different characteristics and properties depending on the type of metal contained. For example, when the content of antimony metal is more than 10 ppm by weight, it becomes a foreign substance and accumulates around the die during spinning or film formation. Causes pressure rise, thread breakage, film breakage, etc., and adversely affects long-term continuous formability. Since germanium is expensive, the higher the content, the higher the price of polyester, which is not preferable. In addition, since the polyester of the present invention is an alkali-elutable polyester, for example, when an alkali elution process is performed, the metal component contained in the polyester flows out into the wastewater component, so that a metal element having a true specific gravity of 5.0 or more is as much as possible. It is preferable to reduce it. The content of the metal element having a true specific gravity of 5.0 or more is preferably 0 to 5 ppm by weight, and more preferably 0 to 3 ppm by weight.

  Moreover, in the manufacturing method of polyester of this invention, you may add a blue-type regulator and / or a red-type regulator as a color tone regulator. The color tone adjusting agent of the present invention is a dye used for a resin or the like. Specifically, in the COLOR INDEX GENERIC NAME, blue color tone adjusting agents such as SOLVENT BLUE 104, SOLVENT BLUE 122, SOLVENT BLUE 45, SOLVENT RED 111, SOLVENT RED 179, SOLVENT RED 195, SOLVENT RED 135, PIGMENT RED 263, VAT RED 41, etc. Examples thereof include system color adjusting agents. Among them, SOLVENT BLUE 104, SOLVENT BLUE 45, SOLVENT RED 179, SOLVENT RED 195, SOLVENT RED 135, which do not contain halogen that tends to cause corrosion of equipment, have relatively good heat resistance at high temperatures and excellent color developability, SOLVENT VIOLET 49 is preferably used. Further, one or more of these color tone adjusting agents can be used depending on the purpose. In particular, it is preferable to use one or more blue-type adjusting agents and red-type adjusting agents, since the color tone can be finely controlled. Furthermore, in this case, the color tone of the resulting polyester is particularly preferable when the ratio of the blue-based regulator is 50% by weight or more with respect to the total amount of the color-tone regulator to be added. Finally, the content of the color tone adjusting agent with respect to the polyester is preferably 30 ppm or less in total. If it exceeds 30 ppm, the transparency of the polyester may be lowered or the color may become dull.

  The polyester obtained by the method for producing a polyester of the present invention preferably has an intrinsic viscosity ([IV]) of 0.3 to 1.1 dl / g when measured at 25 ° C. using orthochlorophenol as a solvent. As described above, when the metal sulfonate group-containing isophthalic acid component is contained as a copolymerization component, the melt viscosity of the polymerization reaction product is remarkably increased due to the thickening action of the polymer. The spinning performance is deteriorated. Even if the degree of polymerization is too low, yarn breakage is likely to occur at the time of winding and spinning, and the yarn-making property is deteriorated. More preferably, it is 0.4-0.8 dl / g, and it is especially preferable that it is 0.45-0.6 dl / g.

  Further, the polyester obtained by the production method of the present invention preferably has a melt viscosity at 290 ° C. of 20 to 250 Pa · s because the moldability of the composite fiber is improved. More preferably, it is 60-200 Pa.s. The melt viscosity can be measured, for example, using a melt indexer manufactured by Takara Industries under the conditions described later.

  In the polyester obtained by the production method of the present invention, it is preferable that the terminal carboxyl group concentration of the polyester is in the range of 1 to 30 equivalents / ton because thermal stability is improved. As the terminal carboxyl group concentration is lower, the thermal stability is improved, and the dirt adhering to the mold during molding and the dirt adhering to the die during yarn production are significantly reduced. When the terminal carboxyl group concentration exceeds 30 equivalents / ton, the effect of reducing dirt adhering to the mold or die may be reduced. The terminal carboxyl group concentration is preferably 25 equivalent / ton or less, particularly preferably 20 equivalent / ton or less.

  The polyester obtained by the method for producing a polyester of the present invention may have a chip-like color tone with a Hunter value, an L value of 50 to 90, an a value of -6 to 2, and a b value of 4 to 14. From the viewpoint of the color tone of molded products such as fibers and films. More preferably, the L value ranges from 60 to 80, the a value ranges from -5 to 1, and the b value ranges from 5 to 12.

  If the polyester obtained by the production method of the present invention has an alkali weight loss rate of 1 to 15% by weight / min in a sodium hydroxide aqueous solution having a concentration of 10 g / l and a temperature of 90 ° C., the alkali elution property of the composite fiber becomes good. preferable. More preferably, it is 4 to 12% by weight / min.

  The polyester obtained by the production method of the present invention is added with particles for the purpose of reducing friction with various guides, rollers, and other contact materials in the molding process, improving process passability, and adjusting the color tone of the product. It doesn't matter. The type of the particle is not particularly limited, and any conventionally known particle can be used. Specifically, for example, inorganic particles such as silicon dioxide, titanium dioxide, calcium carbonate, barium sulfate, aluminum oxide, and zirconium oxide, and organic polymer particles such as crosslinked polystyrene can be used. Among these particles, titanium dioxide particles are preferable because of their good dispersibility in the polymer and relatively low cost. These particles are produced by various wet and dry methods and, if necessary, are subjected to pretreatment such as pulverization and classification before being added to the polyester reaction system. The particles may be added to the polyester reaction system at any stage where the intrinsic viscosity of the reaction system is 0.3 or less, but if the addition is performed after the esterification reaction or transesterification reaction is substantially completed, the particles in the polymer Is preferable because the dispersibility of the resin becomes good. The amount of particles added to the polymer and the particle diameter in the present invention vary depending on the application to be applied, and are not particularly limited. When the particle size is in the range of 1000 particles / 0.4 mg or less, coarse particles having a particle size of 4 μm or more are preferable because processability and color tone are particularly good.

  Further, pigments such as carbon black, surfactants such as alkylbenzene sulfonates, conventionally known antioxidants, anti-coloring agents, light-proofing agents, antistatic agents, etc. may be added within the range not impairing the object of the present invention. Of course it is good.

  The alkali-soluble copolyester of the present invention is synthesized by any method. For example, for polyethylene terephthalate, terephthalic acid and ethylene glycol are usually esterified directly, terephthalic acid lower alkyl ester such as dimethyl terephthalate is transesterified with ethylene glycol, or terephthalic acid and ethylene oxide. And the desired polymerization by heating the reaction product of the first stage under reduced pressure in the presence of a polymerization catalyst. It is produced by a second stage reaction in which a polycondensation reaction is performed until The timing for adding the copolymerization component is not particularly limited. For example, before the transesterification reaction, from the time when the transesterification reaction is substantially completed until the polycondensation reaction is started, etc. Is added at any stage. Here, the reaction proceeds even without a catalyst. However, in the transesterification reaction, a compound such as manganese, calcium, magnesium, zinc, or lithium is usually used as a catalyst, and the transesterification reaction is substantially carried out. After completion, a phosphorus compound is added for the purpose of inactivating the catalyst used in the reaction.

  By using the alkali-soluble copolymerized polyester of the present invention as a component of a composite fiber, to obtain a composite fiber that satisfies both unprecedented yarn forming stability during molding and alkali solubility, and does not impair fiber properties. Can do. In the case of forming a composite fiber, it is preferable that the copolymer polyester composition of the present invention has a structure exposed on the fiber surface in order to improve the spinning stability and the alkali solubility.

  In the present invention, examples of the fiber-forming polymer include polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate and polybutylene terephthalate, but are not limited thereto. Polyamides such as polyesters mainly composed of polyethylene terephthalate, nylon 6, nylon 66, etc., which are the most versatile as synthetic fibers for clothing, are preferable. Further, when a polyester such as polyethylene terephthalate is used, it is preferable to use the same titanium compound as that of the present invention as the polymerization catalyst because of the effect of improving the yarn-forming stability during the molding process.

  Examples of the form of the fiber include a core-sheath type composite fiber, a core-sheath type composite hollow fiber, a sea-island type composite fiber, and the like, and the alkali-soluble copolymerized polyester of the present invention can be used as a constituent in any proportion. For example, in the case of the core-sheath type composite fiber and the core-sheath type composite hollow fiber, the composite ratio (% by weight) of the copolymer polyester in the core part is preferably core / sheath = 5/95 to 90/10. More preferably, it is 7/93-70/30, Most preferably, it is 10/90-50/50. The composite ratio can be designed by arbitrarily selecting the hollow ratio of the resulting composite fiber after alkali weight reduction processing. The lower limit of the composite ratio of the core portion is set for the purpose of imparting a sufficient hollow ratio, and the upper limit of the composite fiber ratio is set from the viewpoint of preventing a decrease in spinnability and fiber properties.

  The composite ratio of the alkali-soluble copolymerized polyester (sea component or one component) used in the sea-island composite fiber is preferably 5 to 90% by weight. More preferably, it is 7 to 60 weight%, Most preferably, it is 10 to 40 weight%. The composite ratio can be arbitrarily selected depending on the fineness of the composite fiber after alkali weight reduction processing. The lower limit of the composite ratio is set for the purpose of imparting alkali weight loss and molding processability, and the upper limit of the composite fiber ratio is set from the viewpoint of preventing a decrease in spinnability and fiber properties.

  In the present invention, as a method for producing a composite fiber using a readily alkali-soluble copolyester and polyester, a conventionally known method can be used. In this case, the polyester (island portion) and the alkali-soluble copolymerized polyester (sea portion) of the present invention are melted separately, led to a spinning pack to form a sea-island composite flow in the mouthpiece device, and spun from the discharge holes. The spun filament yarn is taken up at a predetermined speed, and then wound up on a package, and the obtained undrawn yarn is drawn by a normal drawing machine. Further, the drawing may be performed continuously without winding after taking up the spun yarn, and it may be wound at a high speed of 4000 m / min or more, and the desired fiber performance can be obtained at once without substantially drawing. You may take the method of obtaining. Examples of the direct spinning drawing method include a method in which a spun yarn is taken up at 1000 to 5000 m / min, and subsequently drawn and heat-set at 3000 to 6000 m / min. The filamentous form of the fiber may be either a filament or a staple, and is appropriately selected depending on the application. The fabric form can be appropriately selected according to the purpose, such as woven fabric, knitted fabric, and non-woven fabric.

  Moreover, as a method of reducing the weight of the copolyester component of the polyester composite fiber of the present invention, an alkali weight loss method is used. As the alkali, a compound such as sodium hydroxide, potassium hydroxide, or lithium hydroxide can be used as the aqueous solution. The concentration is preferably in the range of 0.5 to 10%. You may add a weight reduction process accelerator etc. as needed.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the physical-property value in an Example was measured by the method described below.
(1) Intrinsic viscosity of polymer IV
Measurement was performed at 25 ° C. using orthochlorophenol as a solvent.
(2) Content of metal element in polymer The content of metal element in the polymer was determined by melting a chip-shaped sample on an aluminum plate and then forming a compact having a flat surface with a compression press machine. It calculated | required with the analyzer (Rigaku Denki Kogyo make, System3270). That is, the polyester composition is dissolved in orthochlorophenol, the viscosity of the polymer solution is adjusted with chloroform as necessary, and then the particles are precipitated with a centrifuge. Thereafter, only the supernatant liquid is collected by a gradient method, and the polymer is reprecipitated by adding acetone, filtered and washed to obtain a polymer from which particles are removed.
(3) Solution haze About 2 g of the sample to be measured was dissolved in 20 mL of orthochlorophenol, and analysis was performed by an integrating sphere photoelectric photometry method using a haze meter (manufactured by Suga Test Instruments Co., Ltd., HGM-2DP type). In addition, in order to remove the influence of inorganic particles such as titanium oxide particles in the target polyethylene terephthalate, the same pretreatment as described in the above (2) was performed to obtain a polymer.
(4) Melt Viscosity The polymer to be measured was vacuum-dried at 150 ° C. for 15 hours, and then measured with a melt indexer manufactured by Takara Industries at a measurement distance of 2.54 cm, a load of 850 g, and a measurement temperature of 290 ° C.
(5) Alkali weight loss rate A cylindrical knitted fabric using yarn spun and stretched under the conditions described later is 1% hydroxylated at 90 ° C. with a bath ratio of cylindrical knitted fabric: aqueous sodium hydroxide = 1: 50 (weight ratio). It was immersed in an aqueous sodium solution for 5 minutes, and the alkali weight loss rate was measured from the following formula.
Alkali weight loss rate (wt% / min) = (A−B) / A × 100/5
A: Weight before immersion treatment of tubular knitted fabric (g), B: Weight after immersion treatment of tubular knitted fabric (g)
(6) Evaluation of yarn-making property (a) Evaluation of yarn breakage The obtained polyester is dried to an ultimate moisture content of 50 ppm or less, melted at a melting portion of 290 ° C., led to a spin block at a spinning temperature of 300 ° C., and subjected to limit filtration as a filter. After filtering with a metal nonwoven fabric having a diameter of 10 μm, melt spinning was performed from a base of φ0.25 mm, 24 holes with a base surface temperature of 290 ° C., and taken up at a speed of 1000 m / min. Spinning was performed for 72 hours under these conditions, the number of yarn breaks was measured, and the average number of yarn breaks per 6 hours of spinning time was measured. When the average number of yarn breaks was 0 or more and 2 or less, it was accepted as a preferable state, and when it was more than 2 times, it was rejected because yarn breaks were frequent. In particular, it was judged that the number of yarn breaks of 0 or more and 0.5 or less was a particularly preferable state.
(A) Increase in filtration pressure In the evaluation method (A), the determination was made from the pack pressure after 72 hours and the difference at the start of spinning. The increase in the pack pressure was accepted as 0 to 18 MPa as a preferable state, and the increase in the filtration pressure was sharper than 18 MPa. Among these, a range of 0 to 9 MPa was judged as a particularly preferable state.
(C) Observation of deposits in the die In the evaluation method (a), the amount of deposits around the die hole 72 hours after the start of the evaluation was observed using a long focus microscope. The state in which deposits were hardly recognized was judged as ◯, the state in which deposits were seen but operable was judged as Δ, and the state in which deposits were seen and operation became difficult was judged as ×.

Reference Example 1 Preparation method of titanium complex 1 (titanium citrate chelate) Citric acid monohydrate (532 g, 2.52 mol) was dissolved in warm water (371 g) in a 3 L flask equipped with a stirrer, condenser and thermometer. I let you. To this stirred solution was slowly added titanium tetraisopropoxide (288 g, 1.00 mol) from the addition funnel. The mixture was heated to reflux for 1 hour to produce a cloudy solution from which the isopropanol / water mixture was distilled under vacuum. The product was cooled to a temperature below 70 ° C., and a 32 wt / wt% aqueous solution of NaOH (380 g, 3.04 mol) was slowly added via a dropping funnel to the stirred solution. The resulting product was filtered and then mixed with ethylene glycol (504 g, 80 mol) and heated under vacuum to remove isopropanol / water and a slightly cloudy light yellow product (Ti content 3 .85% by weight).

Reference Example 2 Synthesis method of titanium complex 2 (titanium trimellitic acid chelate) Ethylene glycol (2200 g) and trimellitic anhydride (192 g, 1.00 mol) were mixed in a 3 L flask equipped with a stirrer, condenser and thermometer. Titanium tetrabutoxide (170 g, 0.50 mol) was slowly dropped from the dropping funnel into the stirring solution to obtain a transparent ethylene glycol solution of a titanium compound (Ti content: 1.00% by weight).

Reference Example 3. Fiber-forming polymer 100 kg of bis (hydroxyethyl) terephthalate is charged in advance, and 82.5 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) in an esterification reaction tank maintained at a temperature of 250 ° C. and a pressure of 1.2 × 10 ⁵ Pa And 35.4 kg of ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) are sequentially supplied over 4 hours, and after the completion of the supply, the esterification reaction is further carried out over 1 hour, and 101.5 kg of the resulting esterification reaction product is obtained. It was transferred to a polycondensation tank.

  To this esterification reaction product, 10 ppm of phosphoric acid in terms of phosphorus atom, and 20 ppm of magnesium acetate tetrahydrate in terms of magnesium atom, titanium complex 1 obtained in Reference Example 1 was titanium. It added so that it might become 5 ppm in atom conversion. After 5 minutes, an ethylene glycol slurry of titanium oxide particles was added to the polymer in an amount of 0.3% by weight in terms of titanium oxide particles. After another 5 minutes, the reaction system was decompressed to initiate the reaction. The temperature in the reactor was gradually raised from 250 ° C. to 290 ° C., and the pressure was reduced to 40 Pa. The time to reach the final temperature and final pressure was both 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into a strand, cooled, and immediately cut to obtain polymer pellets. The obtained polymer had an intrinsic viscosity of 0.65.

Example 1
100 kg of bis (hydroxyethyl) terephthalate is charged in advance, and 82.5 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) is added to an esterification reaction tank maintained at a temperature of 250 ° C. and a pressure of 1.2 × 10 ⁵ Pa. (Manufactured by Nippon Shokubai Co., Ltd.) 35.4 kg of slurry is sequentially supplied over 4 hours, and after completion of the supply, an esterification reaction is performed over an additional hour, and 101.5 kg of the obtained esterification reaction product is placed in a polycondensation tank. Transferred.

  In this esterification reaction product, the titanium complex 1 obtained in Reference Example 1 is 2 ppm with respect to the copolymer polyester composition obtained in terms of titanium atoms, and the phosphoric acid is obtained in terms of phosphorus atoms. In contrast, 40 ppm of lithium acetate tetrahydrate was added to the copolymerized polyester composition obtained in terms of lithium atoms, and 400 ppm was premixed in a separate mixing tank using ethylene glycol as a solvent before addition under a nitrogen atmosphere. After stirring at 25 ° C. for 60 minutes, it was added. After 5 minutes, a 40% ethylene glycol solution having a transesterification rate of 70% synthesized by transesterification of 5-sodium sulfoisophthalic acid dimethyl ester and ethylene glycol as a copolymerization component was adjusted to 8 mol% with respect to the acid component. Added. Thereafter, while stirring the low polymer at 15 rpm, the reaction system was gradually heated from 250 ° C. to 280 ° C. and the pressure was reduced to 40 Pa. The time to reach the final temperature and final pressure was both 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure, the polycondensation reaction was stopped, discharged into cold water in a strand form, and immediately cut to obtain copolymer polyester pellets.

  As shown in Table 1, the obtained copolymer had an intrinsic viscosity of 0.55, a melt viscosity of 110 Pa · s, and a solution haze of 2.8%. As a result of drying the obtained copolyester and performing the yarn forming test under the above-mentioned conditions, it was excellent in yarn forming property, and the filtration pressure increased during spinning, and almost no deposits around the die were observed, and the moldability was improved. The copolymer was a good copolymer. Next, this stretched yarn was knitted into a cylindrical knitted fabric with a 27 gauge sock knitting machine (manufactured by Eiko Sangyo Co., Ltd.), immersed in a 1% aqueous sodium hydroxide solution at 90 ° C. for 5 minutes, and then dried. From the weight change before and after immersion, the alkali weight loss rate was 7% by weight / min.

Examples 2-9
A copolymer was polymerized in the same manner as in Example 1 except that the copolymerization component and the copolymerization amount were changed, and a yarn-making property test was performed. In Example 4, it was slightly inferior in alkali elution, and in Example 5, it was slightly inferior in spinning, but it was at a level that would not interfere with operation.

Examples 10-13
A copolymer was polymerized in the same manner as in Example 1 except that the conditions for premixing the titanium compound, the phosphorus compound, and the lithium compound were changed, and a yarn production test was performed. In Examples 10 and 13, a slight increase in the filtration pressure was observed, and in Examples 11 and 12, the alkali elution was slightly inferior, but it was at a level that would not interfere with operation.

Examples 14-26
A copolymer was polymerized in the same manner as in Example 1 except that the addition type and addition amount of the titanium compound, phosphorus compound, and lithium compound were changed, and a yarn-making property test was performed. In Example 23, apart from the phosphorus compound to be added after premixing with the titanium compound and the lithium compound, when it reached 85% of the predetermined stirring torque (about 2 hours and 05 minutes from the start of decompression) In a container having a thickness of 0.2 mm and an internal volume of 500 cm ³ prepared by injection molding a polyethylene terephthalate sheet, the polymer was packed with the phosphorus compound 1 and added from the top of the reaction can. In Examples 17, 21, 22, and 26, the yarn forming property was slightly inferior. In Example 26, the filtration pressure was slightly increased and deposits were slightly seen around the base, but this was at a level that would not interfere with operation.

Examples 27-28
Except that the setting of the predetermined stirring torque was changed (in Example 27, the intrinsic viscosity of the obtained polyester was lowered, in Example 28, the intrinsic viscosity of the obtained polyester was increased), the same as in Example 1. Then, the copolymer was polymerized and tested for yarn production. In Example 27, a slight increase in filtration pressure was observed, and a slight amount of deposit was observed around the base, but this was at a level that would not interfere with operation.

Examples 29 and 30
A copolymer was polymerized in the same manner as in Example 1 except that the copolymerization component, copolymerization amount, titanium compound, and phosphorus compound were changed as shown in Table 2, and a yarn production test was performed. In Example 29, although the alkali weight loss rate was excellent, the yarn breakage and the increase in the filtration pressure were slightly observed, and the yarn forming property was slightly inferior. Further, in Example 30, the spinning performance was slightly inferior, and deposits were slightly seen around the base, but this was at a level that would not interfere with operation.

Comparative Examples 1-4
A copolymer was polymerized in the same manner as in Example 1 except that the copolymerization component and the copolymerization amount were changed, and a yarn-making property test was performed. In Comparative Examples 1 and 2, alkali elution was inferior, and in Comparative Example 3, pelletizing after ejection was very difficult, and the yarn forming property was very inferior. In Comparative Example 4, the target degree of polymerization was not reached.

Comparative Examples 5-8
A copolymer was polymerized in the same manner as in Example 1 except that the conditions for premixing the titanium compound, the phosphorus compound, and the lithium compound were changed, and a yarn production test was performed. In Comparative Example 5, the titanium compound, the phosphorus compound, and the lithium compound were added in that order at an addition interval of 5 minutes. In Comparative Example 6, the phosphorus compound, the titanium compound, and the lithium compound were added in this order at an addition interval of 5 minutes. In Comparative Examples 5 to 8, the alkali elution property was slightly inferior, and the spinning property was inferior.

Comparative Examples 9-12
A copolymer was polymerized in the same manner as in Example 1 except that the addition amount and addition type of the polymerization catalyst were changed, and a yarn-making property test was performed. In Comparative Example 9, the target degree of polymerization was not reached. Further, in Comparative Examples 9 and 10, the alkali elution was slightly inferior, and the spinning property was inferior. In Comparative Example 12, a metal having a true specific gravity of 5.0 or more was contained, and many deposits around the base were observed.

Example 31
After drying the copolyester obtained in Reference Example 3 and Example 1 described above as the fiber-forming polymer, the copolyester obtained in Example 1 was used as the sea component, and obtained in Reference Example 3. The polyester was melted separately as island components (18 islands), and an undrawn yarn was obtained from the sea-island type composite base with an island / sea ratio of 50% / 50%. After the obtained undrawn yarn was drawn at a first stage liquid bath temperature of 55 ° C. at a draw ratio of 1.5 times, continuously, the second stage liquid bath temperature was set at 80 ° C. and the draw ratio was 2.0 times. Drawing was performed to obtain a sea-island type composite fiber of 83.3 dtex 9 filaments. Yarn breakage at the time of drawing, winding around a roll, and deposits on guides and the like did not occur, and the composite fiber had good moldability. The obtained drawn yarn had no stickiness on the fiber surface, and there was no sticking between the single yarns observed with a microscope. The drawn yarn was formed into a tubular knitting and treated in a 0.9% aqueous sodium hydroxide solution at 90 ° C. for 30 minutes. Thereafter, it was sufficiently washed with hot water and dried. Regarding the weight change by this treatment, the weight before immersion was 1.9 g after the immersion treatment, which was 50% less than that before the treatment. Moreover, the 18 filament thing was divided | segmented into the ultrafine fiber of 188 filament by this immersion process.

Example 32
After drying the copolymerized polyester obtained in Reference Example 3 and Example 1 described above as the fiber-forming polymer, the copolymerized polyester obtained in Example 1 was used as a core component, and obtained in Reference Example 3. The polyester was melted separately as a sheath component (18 islands), and an undrawn yarn was obtained from a concentric core-sheath composite base with a core / sheath ratio = 35% / 65%. After the obtained undrawn yarn was drawn at a first stage liquid bath temperature of 55 ° C. at a draw ratio of 1.5 times, continuously, the second stage liquid bath temperature was set at 80 ° C. and the draw ratio was 2.0 times. Drawing was performed to obtain a core-sheath composite fiber of 80 dtex 24 filaments. Yarn breakage at the time of drawing, winding around a roll, and deposits on guides and the like did not occur, and the composite fiber had good moldability. The obtained drawn yarn had no stickiness on the fiber surface, and there was no sticking between the single yarns observed with a microscope. When this drawn yarn was knitted into a tube and treated in a 1% aqueous sodium hydroxide solution at 90 ° C. for 30 minutes, the core component copolymerized polyester was eluted to obtain a hollow fiber with a hollow ratio of 34%.

Claims (9)

  In a method for producing a polyester in which 3 to 15 mol% of an isophthalic acid component containing a metal sulfonate group is copolymerized with respect to the total acid component, (1) a titanium compound, (2) a phosphorus compound, and (3) a lithium compound A method for producing a readily alkali-soluble copolyester characterized by carrying out a polycondensation reaction in the presence and adding each of these compounds after mixing and stirring in advance. 2. The alkali-soluble co-solvent according to claim 1, wherein the titanium compound is a titanium complex having at least one selected from the group consisting of a polyvalent carboxylic acid, a hydroxycarboxylic acid, and a nitrogen-containing carboxylic acid as a chelating agent. A method for producing a polymerized polyester. The method for producing a readily alkali-soluble copolyester according to claim 1 or 2, wherein the molar ratio Ti / P of the titanium atom in the titanium compound and the phosphorus atom in the phosphorus compound is 0.001-1. The solution haze when dissolved in orthochlorophenol is in the range of 0.3 to 15, and the alkali-soluble copolymer polyester obtained by the production method according to any one of claims 1 to 3. . The alkali-soluble copolyester obtained by the production method according to any one of claims 1 to 3, wherein the content of a metal element having a true specific gravity of 5.0 or more is 0 to 10 ppm by weight. . The alkali-soluble co-polymer obtained by the production method according to any one of claims 1 to 3, wherein the alkali weight loss rate in an aqueous sodium hydroxide solution having a concentration of 10 g / L and a temperature of 90 ° C is 1 to 15 wt% / min. Polymerized polyester.   A composite fiber comprising the alkali-soluble copolymerized polyester according to any one of claims 4 to 6.   8. The composite fiber according to claim 7, wherein the composite fiber is a sea-island type fiber, and an alkali-soluble copolymer polyester is used for either the sea or the island, and a fiber-forming polymer is used for the other island or sea. Sea-island type composite fiber as described.   The core-sheath type composite fiber according to claim 7, wherein the composite fiber is a core-sheath type fiber, wherein a fiber-forming polymer is used for the sheath part, and an alkali-soluble copolymer polyester is used for the core component.