JPS6346169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing synthetic fibers. More particularly, the present invention relates to a method for producing synthetic fibers made of polyester that have special pores and exhibit improved color depth and clarity when colored. Polyester is widely used as a synthetic fiber because it has many excellent properties. However, compared to natural fibers such as wool and silk, cellulose fibers such as rayon and acetate, and acrylic fibers, polyester fibers have the disadvantage that when colored, they lack depth of color and are inferior in color development and clarity. be. Conventionally, attempts have been made to improve dyes, chemically modify polyester, etc. in an attempt to overcome this drawback, but none of them have been sufficiently effective. In addition, methods have been proposed in which a transparent thin film is formed on the surface of polyester fibers, and a method in which plasma irradiation of 80 to 5000 mA·sec/cm ² is applied to the surface of a woven or knitted fabric to form fine irregularities on the fiber surface. however,
Even with these methods, the effect of improving the depth of color is insufficient, and in addition, the transparent thin film formed on the fiber surface easily falls off when washed, etc., and its durability is insufficient. In the method of applying plasma irradiation, unevenness does not occur on the surface of the fiber in the part of the fiber that will be in the shadow of the irradiated surface, so the smooth fiber surface does not appear on the surface due to the rolling of threads within the fiber structure that occurs during wear. It has the disadvantage of causing color spots. On the other hand, as a method for imparting irregularities to the surface of polyester fibers, fibers made of polyoxyethylene glycol or polyester blended with polyoxyethylene glycol and a sulfonic acid compound are treated with an alkaline aqueous solution to form wrinkles arranged in the fiber axis direction. A method for producing hygroscopic fibers in which micropores are formed on the surface of the fibers, or polyester fibers prepared by adding fine particles of an inert inorganic substance such as zinc oxide, calcium phosphate, etc. to a polyester reaction system are treated with an alkaline aqueous solution. A method for producing hygroscopic fibers has been proposed in which fine pores are formed by eluting inorganic fine particles. however,
In the fibers obtained by these methods, no effect of improving the depth of color is observed, and on the contrary, a decrease in visual density is observed. That is, in these methods, if the treatment with the alkaline aqueous solution is not sufficient, no effect of improving the color depth is observed at all, and when the treatment with the alkaline aqueous solution is sufficient, the color depth is not improved, The visual density decreases, probably due to the diffuse reflection of light by the micropores.
Even if the fiber is dyed in a dark color, it will look whitish, and furthermore, the strength of the obtained fiber will be significantly reduced and it will easily become fibrillated, making it unsuitable for practical use. In addition, fibers made of polyester containing inorganic fine particles such as silica with a particle size of 80 μm or less are subjected to an alkali weight reduction treatment to give irregular irregularities of 0.2 to 0.7 μm on the fiber surface, and 50 to 50 μm in diameter within these irregularities.
A method has been proposed to improve the depth of color by creating fine irregularities of 200 mμ. However, even with this method, the effect of improving the depth of color is insufficient, and in addition, perhaps due to the extremely complicated shape of the unevenness, the unevenness is destroyed by external physical action such as friction, and the unevenness is destroyed. There are disadvantages in that the portions are significantly discolored or have a difference in gloss compared to other undestructed portions, and furthermore, they easily become fibrillated. The inventor of the present invention has conducted intensive studies to provide a polyester fiber that does not have the above-mentioned drawbacks and has excellent color depth and clarity by adding micropores to polyester fiber, and has found that a specific amount of 5 Without reacting a calcium compound in a specific amount ratio with a valent phosphorus compound and this pentavalent phosphorus compound in advance,
By treating the polyester fiber obtained by melt-spinning the polyester synthesized by adding it to the polyester reaction system with alkali, it is possible to form a large number of special microvoids. It was discovered and proposed earlier that polyester fibers with excellent depth and clarity, sufficiently small discoloration due to friction, and excellent fibril resistance can be obtained. However, the polyester fibers obtained in this manner can only be dyed with disperse dyes, which cannot be said to have very good color vividness. Therefore, in order to obtain even more excellent color depth and clarity, it is desirable to modify polyester fibers into a type that can be dyed with cationic dyes so that cationic dyes with excellent clarity can be used. In an attempt to obtain a polyester fiber having a large number of microvoids on and near the fiber surface and dyeable with cationic dyes, as obtained in the polyester fiber described above, the present inventor developed an isophthalic acid component having an alkali metal sulfonate group. Various methods were investigated for adding the above-mentioned pentavalent phosphorus compound and calcium compound without reacting them in advance during the synthesis of the modified polyester. As a result, when a phosphorus compound and a calcium compound are added during the synthesis of a polyester modified with an isophthalic acid component having an alkali metal sulfonate group, it is difficult to synthesize a normal polyester that is not modified with an isophthalic acid component having an alkali metal sulfonate group. The dispersion state of the internally precipitated particles in the resulting polyester tends to be poor compared to when the polyester is added at the same time, making it difficult to obtain a polymer with good transparency. It has been found that there is a problem in that macrovoids are formed on the surface of polyester fibers, making it difficult to see the effect of improving the depth and clarity of color when dyed, and that the visual density may even decrease. The inventors of the present invention have made extensive studies to solve this problem, and have surprisingly found that by using a lithium compound instead of a calcium compound, the internally precipitated particles can have good dispersibility and become transparent. A cationic dye-dyeable polyester with excellent properties can be reliably obtained with good reproducibility, and a large number of microvoids can be formed on the fiber surface and its vicinity by alkali treatment of polyester fibers melt-spun from this polyester.
It has been found that a polyester fiber can be obtained which exhibits improved color depth and clarity when dyed with a cationic dye, has excellent color fastness, has sufficiently low discoloration due to friction, and has excellent fibrillation resistance. The present invention was completed as a result of further studies based on this knowledge. That is, the present invention involves producing synthetic fibers made of polyester synthesized by the reaction of dicarboxylic acids, mainly terephthalic acid, or their ester-forming derivatives, and at least one glycol or their ester-forming derivatives. At any stage until the synthesis of the polyester is completed, (a) isophthalic acid or its ester-forming derivative having an alkali metal sulfonate group in an amount of 0.5 to 10 mol% based on the total acid component; 0.3 to 3 mol% of the following general formula [In the formula, R ¹ and R ² are a hydrogen atom or a monovalent organic group, X is a hydrogen atom, a monovalent organic group, or a metal, m
indicates 0 or 1. ] A phosphorus compound (c) represented by a lithium compound is prepared without reacting (a), (b) and (c) in advance, and the total number of equivalents of metals (b) and (c) is ( Add it in an amount of 2.0 to 3.2 times the number of moles of the phosphorus compound in b), then complete the synthesis of polyester, melt-spun the obtained polyester, and add 2% by weight or more of the aqueous solution of an alkali compound. This is a method for producing synthetic fibers characterized by eluting. The polyester in the present invention is a polyester having terephthalic acid as the main acid component and at least one type of glycol, preferably at least one alkylene glycol selected from ethylene glycol, trimethylene glycol, and tetramethylene glycol as the main glycol component. The main target is It may also be a polyester in which a part of the terephthalic acid component is replaced with another difunctional carboxylic acid component, and/or a part of the glycol component is replaced with the above-mentioned glycol other than the main component or other diol component. It may also be made of polyester. Examples of difunctional carboxylic acids other than terephthalic acid used here include isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid,
Aromatic, aliphatic, and alicyclic difunctional carboxylic acids such as diphenoxyethanedicarboxylic acid, β-hydroxyethoxybenzoic acid, p-oxybenzoic acid, adibic acid, sebacic acid, and 1,4-cyclohexanedicarboxylic acid. can be given. Examples of diol compounds other than the above-mentioned glycols include aliphatic, alicyclic, and aromatic diol compounds such as cyclohexane-1,4-dimethanol, neopentyl glycol, bisphenol A, and bisphenol S, and polyoxyalkylene glycols. etc. can be given. Such polyesters may be synthesized by any method. For example, in the case of polyethylene terephthalate, usually terephthalic acid and ethylene glycol are directly esterified, a lower alkyl ester of terephthalic acid such as dimethyl terephthalate is transesterified with ethylene glycol, or terephthalic acid and ethylene glycol are transesterified. The first stage reaction is to react with terephthalic acid to produce a glycol ester and/or its low polymer, and the first stage reaction product is heated under reduced pressure until the desired degree of polymerization is achieved. It is produced through a two-step polycondensation reaction. Isophthalic acid having an alkali metal sulfonate group or an ester-forming derivative thereof is added to the polyester of the present invention at any stage until its synthesis is completed, and by copolymerizing the polyester, it is added to the main chain of the polyester. Alkylene-5-alkali metal sulfoisophthalate units are introduced. Preferred specific examples of isophthalic acid or its ester-forming derivative having an alkali metal sulfonate group include sodium 3,5-di(carboxy)benzenesulfonate, lithium 3,5-di(carboxy)benzenesulfonate, 3, Potassium 5-di(carboxy)benzenesulfonate, 3,
Sodium 5-di(carbomethoxy)benzenesulfonate, lithium 3,5-di(carbomethoxy)benzenesulfonate, potassium 3,5-di(carbomethoxy)benzenesulfonate, 3,5-di(β-hydroxyethoxycarbonyl) ) Sodium benzenesulfonate, lithium 3,5-di(β-hydroxyethoxycarbonyl)benzenesulfonate, potassium 3,5-di(β-hydroxyethoxycarbonyl)benzenesulfonate, 3,5
-Sodium di(γ-hydroxypropoxycarbonyl)benzenesulfonate, 3,5-di(δ-
Examples include sodium hydroxybutoxycarbonyl)benzenesulfonate and lithium 3,5-di(δ-hydroxybutoxycarbonyl)benzenesulfonate. The amount of the isophthalic acid having an alkali metal sulfonate group or its ester-forming derivative is determined based on the total acid components constituting the polyester.
In the range 0.5-10 mol%, preferably 1-6 mol%
is within the range of If the amount added is less than 0.5 mol%, the final polyester fiber cannot be dyed in a sufficiently deep color with the cationic dye, and if it exceeds 10 mol%, not only will the affinity for the cationic dye become saturated, This is not preferable because the excellent physical properties unique to polyester fibers are impaired and the manufacturing cost increases significantly. The timing of addition of isophthalic acid having an alkali metal sulfonate group or its ester-forming derivative is not particularly limited as long as it is before the second stage reaction of polyester synthesis is completed, but a particularly preferable addition timing is 3,5-di (β-
In the case of bisglycol esters such as alkali metal salts of hydroxyethoxycarbonyl)benzenesulfonic acid, the stage from the end of the first step transesterification reaction, esterification reaction, or ethylene oxide addition reaction to before the start of the second step depressurization reaction. In the case of a lower alkyl ester such as an alkali metal salt of 3,5-di(carbomethoxy)benzenesulfonic acid, the alkali metal salt of 3,5-di(carboxy)benzenesulfonic acid is In the case of a salt, this is the stage before the start of the esterification reaction. Furthermore, when copolymerizing an isophthalic acid component having a metal sulfonate group, a large amount of ether bonds may be produced as a by-product. can be avoided. The phosphorus compound used in the present invention has the following general formula: It is a phosphorus compound represented by the formula, where R ¹ and
R ² is a hydrogen atom or a monovalent organic group. This monovalent organic group is specifically an alkyl group, an aryl group, an aralkyl group, or [-(CH ₂ ) _l O] _k R ³ (however,
R ³ is preferably a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group, l is an integer of 2 or more, k is an integer of 1 or more, and R ¹ and R ² may be the same or different. X is a hydrogen atom, a monovalent organic group, or a metal, and examples of the monovalent organic group include the above R ¹ and R ²
This is the same as the definition of organic group in R ¹ , R ²
The metal may be the same as or different from the above, and the metal is particularly preferably an alkali metal or an alkaline earth metal, with Li being particularly preferred. m is an integer of 0 or 1. Such phosphorus compounds include, for example, orthophosphoric acid,
Phosphoric acid triesters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, phosphoric acid mono- and diesters such as methyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, phosphorous acid,
Phosphite triesters such as trimethyl phosphite, triethyl phosphite, triphenyl phosphite, phosphorous acid mono- and diesters such as methyl acid phosphite, ethyl acid phosphite, butyl acid phosphite, the above-mentioned phosphorus compounds A phosphorus compound obtained by reacting with glycol and/or water, a phosphorus compound obtained by further reacting the above-mentioned phosphorus compound with a lithium compound in an equimolar amount to the phosphorus compound, etc.
More than one type of phosphorus compound can be used. The lithium compound to be used in combination with the above phosphorus compound is not particularly limited as long as it reacts with the above phosphorus compound to form a salt insoluble in polyester, including lithium acetate, oxalate, benzoate, phthalate. acid salts, organic carboxylates such as stearates, borates, sulfates, silicates, carbonates,
Inorganic acid salts such as bicarbonates, halides such as chlorides, chelates such as ethylenediaminetetraacetic acid complexes, hydroxides, oxides, methylates,
Alcoholates such as ethylate and glycolate,
Examples include phenolate. Particularly preferred are organic carboxylates, halides, chelate compounds, and alcoholates that are soluble in ethylene glycol, and among them, organic carboxylates are particularly preferred. The above lithium compounds may be used alone or in combination of two or more. When adding the above-mentioned phosphorus compound and lithium compound, in order to give the final polyester fiber excellent color depth and friction durability, it is necessary to It is necessary to specify the ratio of the amount of lithium compounds used. That is, if the amount of the phosphorus compound used in the present invention is too small, the color depth of the final polyester fiber obtained will be insufficient, and as the amount is increased, the color depth will increase.
If the amount is too large, the depth of the color will no longer be significantly improved, the abrasion resistance will deteriorate, and furthermore, it will be difficult to obtain a polyester with a sufficient degree of polymerization and softening point, and furthermore, yarn breakage will occur frequently during spinning. This will cause trouble. Therefore, the amount of phosphorus compound added should be in the range of 0.3 to 3 mol% based on the total acid components constituting the polyester.
Particularly preferred is a range of 0.5 to 2 mol%. In addition, the total number of metal equivalents contained in the above phosphorus compound and lithium compound is 2.0 with respect to the number of moles of the phosphorus compound.
If the amount is less than twice the amount, the color depth of the resulting polyester fiber will be insufficient, the polycondensation rate will decrease, making it difficult to obtain a polyester with a high degree of polymerization, and the softening point of the resulting polyester will be significantly lowered. begins to decline. On the other hand, if this amount exceeds 3.2 times, coarse particles will be generated, and instead of improving the depth of color, the visual density will decrease. Therefore, the total number of metal equivalents of the phosphorus compound and the lithium compound should be in the range of 2.0 to 3.2 times the number of moles of the phosphorus compound, and in particular, the range of 2.0 to 3.0 times is the number of moles of the phosphorus compound. preferable. The above-mentioned isophthalic acid compound having an alkali metal sulfonate group, phosphorus compound, and lithium compound need to be added to the polyester reaction system without being reacted in advance. By doing so, the insoluble particles can be produced in the polyester in the form of uniform ultrafine particles.
If the above-mentioned isophthalic acid compound and/or phosphorus compound having an alkali metal sulfonate group is reacted with a lithium compound in advance to form insoluble particles externally and then added to the polyester reaction system, the dispersibility of the insoluble particles in the polyester may be affected. It gets worse,
In addition, since coarse agglomerated particles are included,
The effect of improving the color depth of the finally obtained polyester fiber is no longer recognized. The above-mentioned addition of the phosphorus compound and the lithium compound can be carried out in any order at any stage until the synthesis of the polyester is completed. However, if only the phosphorus compound is added before the first stage reaction is completed, the completion of the first stage reaction may be inhibited, and if only the lithium compound is added before the first stage reaction is completed. If added, coarse particles may be generated during the esterification reaction, or the reaction may proceed abnormally quickly and cause bumping phenomena during the transesterification reaction. In this case, it is preferable to reduce the amount to about 20% by weight or less. It is preferable that at least 80% by weight of the lithium compound and the total amount of the phosphorus compound be added after the first stage reaction of polyester synthesis is substantially completed. In addition, if the phosphorus compound and lithium compound are added at a stage where the second stage reaction has progressed too much, the particles tend to aggregate and become enlarged, resulting in insufficient color depth of the final polyester fiber. Therefore, it is preferable that the intrinsic viscosity of the reaction mixture in the second stage reaction is before reaching 0.3. The above-mentioned isophthalic acid compound, phosphorus compound, and lithium compound having an alkali metal sulfonate group may be added all at once, added in two or more divided portions, or added continuously. Some of the lithium compounds used in the present invention have the effect of suppressing the above-described by-product of ether bonds, and when such lithium compounds are used, there is no need to use a separate ether formation inhibitor. A lithium compound can also be added as an ether production inhibitor by adding it before or during the first stage reaction, but as mentioned above, when the reaction is an esterification reaction, coarse particles may be generated or transesterification may occur. During the reaction, since bumping may occur, the amount used is preferably limited to about 20% by weight or less of the total amount of the lithium compound added. As explained above, a specific amount of the above-mentioned isophthalic acid compound having an alkali metal sulfonate group and a phosphorus compound and a lithium compound in a specific amount ratio to the phosphorus compound are added to a polyester reaction system without reacting in advance, After that, by completing the synthesis of polyester, a fiber with a high degree of polymerization, high softening point, and good ability to pass through the spinning process, and finally has excellent color depth and friction durability. polyester can be obtained. There is no need to employ any special method to melt-spun the polyester obtained in this manner to form fibers, and any ordinary melt-spinning method for polyester fibers may be employed. The fibers spun here may be solid fibers having no hollow portions or hollow fibers having hollow portions. Further, the outer shape and the shape of the hollow portion in the cross section of the fiber to be spun may be circular or irregular. Further, when spinning, using the cationic dye-dyeable polyester to which the above-mentioned phosphorus compound and lithium compound are added, unmodified polyester without the addition, and/or cationic dye-dyeable polyester without the addition,
A core-sheath type conjugate fiber or a side-by-side type conjugate fiber with two or more layers may be used, in which a cationic dye-dyeable polyester containing a phosphorus compound and a lithium compound is added as a sheath component or a layer component. To remove a part of the polyester fiber thus obtained, after subjecting it to stretching heat treatment or false twisting as necessary, or after making it into a fabric,
This can be easily carried out by treatment with an aqueous solution of an alkaline compound. Examples of the alkali compound used here include sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, sodium carbonate, potassium carbonate, and the like. Among these, sodium hydroxide and potassium hydroxide are particularly preferred. The concentration of such an aqueous solution of an alkali compound varies depending on the type of alkali compound, processing conditions, etc., but is usually preferably in the range of 0.01 to 40% by weight, particularly
A range of 0.1 to 30% by weight is preferred. The processing temperature is preferably in the range of room temperature to 100°C, and the processing time is 1 minute to 1 minute.
It is usually carried out for a period of 4 hours. Further, the amount of the alkali compound eluted and removed by treatment with the aqueous solution should be in the range of 2% by weight or more based on the weight of the fiber. By treating the fiber with an aqueous solution of an alkali compound in this manner, a large number of microvoids can be formed on the surface of the fiber and in its vicinity, resulting in excellent color depth when dyed. The polyester fiber obtained by the method of the present invention may contain optional additives, such as catalysts, color inhibitors, heat resistant agents, flame retardants, optical brighteners, matting agents, colorants, etc., as necessary. It may be Further explanation will be given below with reference to Examples. Parts and % in Examples indicate parts by weight and % by weight, and the depth of color and frictional discoloration when the resulting polyester fibers were dyed were measured by the following methods. (i) Depth of color Bathochromicity (K/S) is a measure of the depth of color.
was used. This value was determined by measuring the spectral reflectance (R) of the sample fabric using a Shimadzu RC-330 self-recording spectrophotometer.
Munk) formula. The larger this value is, the greater the deep color effect is. (Measurement wavelength 500m
μ) K/S=(1-R) ² /2R Note that K is an absorption coefficient and S is a scattering coefficient. (ii) Resistance to friction discoloration Using a Gakushin type flat abrasion machine for friction fastness testing, the test cloth was abraded a specified number of times under a load of 500 g using a dioset made of 100% polyethylene terephthalate as the friction cloth. hand,
The degree of discoloration was determined using a gray scale for discoloration. The case where the wear resistance was extremely low was rated as 1st grade, and the case where it was extremely high was rated as 5th grade. For practical purposes, level 4 or above is required. Example 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.06 parts of calcium acetate monohydrate were placed in a transesterification tank, and the temperature was raised from 140°C to 230°C over 4 hours in a nitrogen gas atmosphere to produce methanol. The transesterification reaction was carried out while distilling it out of the system. Subsequently, 0.64 parts of lithium acetate anhydrous (relative to dimethyl terephthalate) was added to the resulting reactant.
After 5 minutes, 0.35 parts of orthophosphoric acid (0.69 mol% relative to dimethyl terephthalate) was added.
%), and after a further 5 minutes, 0.04 part of antimony trioxide was added and transferred to a polymerization can. Then 3,5-di(β
4.8 parts of sodium (hydroxyethoxycarbonyl)benzenesulfonate (2.6 mol % based on dimethyl terephthalate) was added to the polymerization kettle. Next, the pressure was reduced from 760 mmHg to 1 mmHg over an hour.
At the same time, the temperature was raised from 230°C to 280°C over 1 hour and 30 minutes. Polymerization was carried out for an additional 2 hours and 30 minutes at a polymerization temperature of 280℃ under reduced pressure of 1 mmHg or less, for a total of 4 hours, and the intrinsic viscosity
A polymer with a softening point of 0.512 and a softening point of 258°C was obtained. After the reaction was completed, the polymer was made into chips according to a conventional method. The chips were dried using a conventional method, and a spinneret with 36 circular spinning holes with a hole diameter of 0.3 mm was used.
The mixture was melt-spun at 290°C and then drawn at a draw ratio of 3.5 times according to a conventional method to obtain a raw yarn of 75 denier/36 filaments. This raw yarn was strongly twisted with an S twist of 2500 T/m and a Z twist of 2500 T/m, and then the highly twisted yarn was steam-treated at 80° C. for 30 minutes to stop the twist. A pear-skinned jersey fabric was woven by alternately arranging two S and Z twists of the highly twisted yarns at a warp density of 47 threads/cm and a weft density of 32 threads/cm. The obtained gray fabric was relaxed with a rotary washer for 20 minutes at boiling temperature, then grained, preset using a conventional method, and then treated with a 1% aqueous sodium hydroxide solution at boiling temperature to achieve a weight loss rate of 20%. fabric was obtained. The fabric after this alkali treatment is Aizen Cathilon.
Black CD-GLH (Hodogaya Chemical Co., Ltd. product) 8%
After dyeing with OWF at 120° C. for 60 minutes in a dye bath containing 2 g of Glauber's salt, a black cloth was obtained by soaping according to a conventional method. The color depth and wear of this black cloth is 200%
Table 1 shows the friction discoloration resistance after washing. In addition, the cationic dye is Aizen Cthilon Blue CD.
-Dyeing was done with 2% owf instead of RLH to obtain a bright deep blue cloth. The vividness of the color of this blue cloth was visually judged according to the following criteria and is shown in Table 1. ◎ Sharpness is extremely high compared to the standard 〇 Sharpness is high compared to the standard ST Standard △ Sharpness is inferior compared to the standard × Example where the sharpness is significantly inferior compared to the standard 2 Example Example 1 except that the amounts of lithium acetate anhydride and orthophosphoric acid used in Example 1 were changed.
I did the same thing. The results were as shown in Table 1. Example 3 The procedure was the same as in Example 1 except that the phosphorus compounds listed in Table 1 were added in the amounts listed in Table 1 in place of the orthophosphoric acid used in Example 1. The results were as shown in Table 1. Example 4 In place of 4.8 parts of sodium 3,5-di(β-hydroxyethoxycarbonyl)benzenesulfonate that was added before the start of the polycondensation reaction in Example 1, 4 parts of sodium 3,5-di(carbomethoxy)benzenesulfonate was added. of the 0.64 parts of lithium acetate anhydride added after the end of the transesterification reaction (0.177 mol% based on dimethyl terephthalate) was added before the transesterification reaction. The same procedure as in Example 1 was carried out except that 0.58 part was added after the transesterification reaction was completed. The results were as shown in Table 1. Comparative Example 1 The lithium acetate anhydride used in Example 1 was not used, and the amount of orthophosphoric acid added after the transesterification reaction was changed to 0.04 part (0.079 mol% based on dimethyl terephthalate). The procedure was the same as in Example 1 except for this. The results were as shown in Table 1. Comparative Example 2 The same procedure as in Example 1 was conducted except that 0.85 parts of calcium acetate monohydrate (0.94 mol % based on dimethyl terephthalate) was used instead of the lithium acetate anhydride used in Example 1. The results were as shown in Table 1. 【table】

Claims (1)

[Claims] 1. A synthetic fiber made of a polyester synthesized by the reaction of a dicarboxylic acid, mainly terephthalic acid, or its ester-forming derivative, and at least one glycol or its ester-forming derivative. At any stage until the synthesis of the polyester is completed, (a) isophthalic acid or its ester-forming derivative having an alkali metal sulfonate group in an amount of 0.5 to 10 mol% based on the total acid components; 0.3 to 3 mol% of the following general formula based on the acid component [In the formula, R ¹ and R ² are a hydrogen atom or a monovalent organic group, X is a hydrogen atom, a monovalent organic group, or a metal, m
indicates 0 or 1. ] A phosphorus compound (c) represented by a lithium compound is prepared without reacting (a), (b) and (c) in advance, and the total number of equivalents of metals (b) and (c) is ( Add it in an amount of 2.0 to 3.2 times the number of moles of the phosphorus compound in b), then complete the synthesis of polyester, melt-spun the obtained polyester, and add 2% by weight or more of the aqueous solution of an alkali compound. A method for producing synthetic fibers characterized by eluting.