JP2003160656A - Method of manufacturing polyester and fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a polyester with improved color clarity which has such excellent performance as excellent color and moldability and very little deposit generation on a spinning spinneret after continuous spinning for a long time through the spinneret. <P>SOLUTION: The polyester has ethylene terephthalate as a principal repeating unit and is obtained by polycondensation using as a source material terephthalic acid obtained by hydrolyzing dimethyl terephthalate obtained by depolymerizing a polyalkylene terephthalate and using as a catalyst a precipitate obtained by heating in a glycol a specific titanium compound and a specific phosphorus compound. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyester and fibers, and more particularly, to a specific titanium compound and phosphorus compound using dimethyl terephthalate obtained by depolymerizing and recovering polyalkylene terephthalate as a raw material. Using a catalyst for polyester production containing and,
A method for producing a polyester with improved sharpness, which has an excellent color tone, has a very small amount of spinneret deposits even when spun continuously for a long time through the spinneret, and has excellent moldability. And fiber.

[0002]

2. Description of the Related Art Polyesters, particularly polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate and polytetramethylene terephthalate are excellent in mechanical, physical and chemical properties, and therefore, fibers, films and other molded products are obtained. Widely used in.

For example, polyethylene terephthalate is usually obtained by directly esterifying terephthalic acid and ethylene glycol, transesterifying a lower alkyl ester of terephthalic acid such as dimethyl terephthalate with ethylene glycol, or terephthalic acid and ethylene. Reacting with oxide to form an ethylene glycol ester of terephthalic acid and / or a low polymer thereof,
Then, this reaction product is heated under reduced pressure in the presence of a polymerization catalyst to carry out a polycondensation reaction until a predetermined degree of polymerization is achieved.

It is well known that the type of catalyst used in these polycondensation reaction steps greatly influences the reaction rate and the quality of the obtained polyester. As a polycondensation catalyst for polyethylene terephthalate, antimony compounds are most widely used because of having excellent polycondensation catalyst performance and obtaining a polyester having a good color tone.

However, when an antimony compound is used as a polycondensation catalyst, when polyester is continuously melt-spun for a long period of time, foreign matter (hereinafter, sometimes simply referred to as die foreign matter) adheres and deposits around the mouth of the die. However, there is a problem of moldability that a bending phenomenon (bending) of the flow of the molten polymer occurs, which causes fuzz and / or yarn breakage in the spinning and drawing steps.

It has been proposed to use a titanium compound such as titanium tetrabutoxide as a polycondensation catalyst other than the antimony compound. However, when such a titanium compound is used, the above-mentioned deposition of foreign matter on the spinneret is prevented. Although the problem of moldability due to the problem can be solved, a new problem arises in that the obtained polyester itself is discolored in yellow and the melt thermal stability is poor.

In order to solve the above coloring problem, it is generally practiced to add a cobalt compound to polyester to suppress yellowing. It is true that the color tone (color b value) of polyester can be improved by adding the cobalt compound, but the addition of the cobalt compound lowers the melt heat stability of the polyester and facilitates decomposition of the polymer. There's a problem.

Further, as another titanium compound, Japanese Patent Publication No.
No. 8-2229 discloses titanium hydroxide and Japanese Patent Publication No.
JP-A 7-26597 discloses the use of α-titanic acid as a catalyst for polyester production. However, in the former method, it is not easy to pulverize titanium hydroxide into powder, while in the latter method, α-titanic acid is likely to be deteriorated, so that its storage and handling are not easy,
Therefore, neither is suitable for industrial use, and it is also difficult to obtain a polymer having a good color tone (color b value).

Further, JP-B-59-46258 discloses a product obtained by reacting a titanium compound with trimellitic acid, and JP-A-58-38722 discloses a titanium compound and a phosphite. It is disclosed that each of the products obtained by reacting with and is used as a catalyst for producing polyester. Indeed, according to this method,
Although the melt heat stability of polyester is improved to some extent, the color tone (color b value) of the obtained polymer is not sufficient, and therefore the polymer color tone (color b value) is
Further improvement of is desired.

As described above, the use of antimony as a catalyst is an effective means for suppressing foreign matter from the spinneret. However, in the method without antimony, the color of the yarn is lowered, and thus it has been conventionally used. I was not able to use it.

Therefore, there has been a demand for a polyester fiber which does not use antimony as a catalyst and has an excellent hue.

On the other hand, recently, polyesters such as polyethylene terephthalate have been reused in textile products such as clothes by collecting PET bottles, washing, crushing and remelting. However, polyesters such as PET bottles that are collected from the market often contain various impurities, and their quality is often different, so they are mixed especially when recycled into long fibers. There has been a problem that it is difficult to efficiently produce recycled fibers because the spinning process becomes unstable due to the influence of impurities and the difference in polymer quality.

[0013]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of the prior art described above, to provide an excellent color tone, and to generate spinneret deposits even after continuous spinning for a long time through the spinneret. It is an object of the present invention to provide a polyester fiber having an improved hue, which has an excellent performance that the amount is very small and the moldability is excellent. Still another object of the present invention is to provide a more environmentally friendly textile product by using recycled raw materials.

[0014]

The present inventors have completed the present invention as a result of intensive investigations in view of the above-mentioned prior art.

That is, an object of the present invention is to subject an aromatic dicarboxylic acid and an alkylene glycol to an esterification reaction,
A method for producing a polyester polymer having ethylene terephthalate as a main repeating unit, which is obtained by polycondensation reaction, wherein recycled terephthalic acid obtained by depolymerizing polyalkylene terephthalate as methanol as the aromatic dicarboxylic acid. The terephthalic acid obtained by hydrolyzing dimethyl is used in an amount of 70% by weight or more based on the total acid components constituting the polyester, and
As the catalyst, the titanium compound represented by the following formula (I) and the phosphorus compound represented by the following formula (II) are used, wherein the number of moles of phosphorus element relative to the number of moles of titanium element (P / Ti) is 1 to 4
And a polycondensation reaction using a precipitate obtained by heating in glycol.

[0016]

[Chemical 4]

[0017]

[Chemical 5]

Further, another object of the present invention is to provide a method according to claims 1 to 9.
It is achieved by polyester fibers obtained by melt spinning a polyester produced by the method according to any one of 1.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The polyester in the present invention is a polyester having ethylene terephthalate as a main repeating unit, which is obtained by subjecting an aromatic dicarboxylic acid and an alkylene glycol to an esterification reaction and then a polycondensation reaction. This polyester may be copolymerized polyethylene terephthalate obtained by copolymerizing a third component other than the component constituting the ethylene terephthalate unit. The third component (copolymerization component) may be either a dicarboxylic acid component or a glycol component. Examples of the dicarboxylic acid component preferably used as the third component include aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, isophthalic acid and phthalic acid, adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid. Aliphatic dicarboxylic acids, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, etc., and glycol components include trimethylene glycol, tetramethylene glycol, 1,4-cyclohexanedimethanol, etc. More than one species can be used.

In the method for producing a polyester of the present invention, terephthalic acid obtained by hydrolyzing dimethyl terephthalate obtained by depolymerizing polyalkylene terephthalate as an aromatic dicarboxylic acid is used as a total acid component constituting the polyester. It is necessary to use 70% by weight or more based on Here, polyethylene terephthalate is preferable as the polyalkylene terephthalate, and in particular, recovered PET bottles, recovered polyester fiber products, recovered polyester film products, and scrap polymers generated in the manufacturing process of these products are recovered. Polyesters are preferably used. When terephthalic acid obtained by hydrolyzing dimethyl terephthalate obtained by depolymerizing polyalkylene terephthalate is less than 70% by weight, the polyester finally obtained or a component contained in the polyester fiber Among them, the ratio of the components derived from the recovered terephthalic acid is less than 50%, which is not preferable because the impression that the product is environmentally friendly is weakened. The terephthalic acid obtained by hydrolyzing dimethyl terephthalate obtained by depolymerizing polyalkylene terephthalate is preferably 80% by weight or more, more preferably 9% by weight or more.
It is 0% by weight or more.

The method for producing terephthalic acid obtained by hydrolyzing dimethyl terephthalate obtained by depolymerizing polyalkylene terephthalate used in the present invention is not particularly limited. After depolymerization with glycol,
Examples thereof include a method in which transesterification is performed with methanol, and the obtained dimethyl terephthalate is purified by recrystallization or distillation and dimethyl terephthalate is hydrolyzed with water under high temperature and high pressure.

The impurities of terephthalic acid obtained by hydrolyzing dimethyl terephthalate obtained by depolymerizing polyalkylene terephthalate used in the present invention include 4-carboxybenzaldehyde, paratoluic acid, benzoic acid and hydroxy. The content of dimethyl terephthalate is preferably 1 ppm or less.

In the method for producing a polyester of the present invention, the titanium compound represented by the following general formula (I) and the phosphorus compound represented by the following general formula (II) are used in the number of moles of phosphorus element relative to the number of moles of titanium element. It is necessary to polymerize using a titanium / phosphorus reaction product which is reacted in a composition in which (P / Ti) is 1 to 4.

[0025]

[Chemical 6]

[0026]

[Chemical 7]

When the number of moles of phosphorus element relative to the number of moles of titanium element (P / Ti) is less than 1, the polyester obtained may have poor color tone and its heat resistance may deteriorate, which is not preferable. If greater than 4,
The catalytic activity for the polyester-forming reaction becomes insufficient, which is not preferable. The number of moles of phosphorus element relative to the number of moles of titanium element (P / Ti) is preferably in the range of 1.2 to 3.5, and more preferably in the range of 1.5 to 3.0.

Further, the catalyst preparation of the titanium compound component (I) and the phosphorus compound component (II) needs to be heated and reacted in ethylene glycol. The reaction method is, for example, the phosphorus compound (II). Component and ethylene glycol are mixed, a part or all of the phosphorus compound component is dissolved in a solvent, and the titanium compound component (I) is added to this mixed solution.
Is added dropwise, and the reaction system is heated to a temperature of 0 to 200 ° C. for 30 minutes or more, preferably 60 to 150 ° C. for 40 to 90 minutes. In this reaction, there is no particular restriction on the reaction pressure, and it is usually carried out under normal pressure.

Examples of the titanium compound represented by the above formula (I) include titanium tetraalkoxides such as titanium tetrabutoxide, titanium tetraisopropoxide, titanium tetrapropoxide and titanium tetraethoxide, and octaalkyl trititanate. , Hexaalkyl dititanate, alkyl titanate, titanium acetate and the like.

Further, in the phosphorus compound represented by the above formula (II), when p is 0 in the formula, for example, phenylphosphonic acid, methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid, butylphosphonic acid. Acid, tolylphosphonic acid, xylylphosphonic acid, biphenylphosphonic acid, naphthylphosphonic acid, anthrylphosphonic acid, 2-carboxyphenylphosphonic acid, 3-carboxyphenylphosphonic acid, 4-carboxyphenylphosphonic acid, 2,3-di Carboxyphenylphosphonic 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-
Examples thereof include tricarboxyphenylphosphonic acid and 2,4,6-tricarboxyphenylphosphonic acid, and among them, monoarylphosphonic acid is preferable.

When p is 1, for example, monomethyl phosphate, monoethyl phosphate, monotrimethyl phosphate, mono-n-butyl phosphate, monohexyl phosphate, monoheptyl phosphate, monononyl phosphate, monodecyl phosphate, monododecyl phosphate. , Monophenyl phosphate, monobenzyl phosphate, mono (4-dodecyl) phenyl phosphate, mono (4-methylphenyl) phosphate, mono (4-ethylphenyl) phosphate, mono (4-propylphenyl) phosphate, mono (4-dodecyl) (Phenyl) phosphate, monotolyl phosphate, monoxylyl phosphate, monobiphenyl phosphate, mononaphthyl phosphate, monoanthryl phosphate, etc. It is.

A method in which the titanium compound represented by the above formula (I) is used by previously reacting it with a polyvalent carboxylic acid of the following formula (III) and / or its anhydride is also preferably used.
In that case, the reaction molar ratio of the titanium compound to the polycarboxylic acid and / or its anhydride is preferably in the range of (2: 1) to (2: 5). A particularly preferred range is (1: 1) to (1:
2).

[0033]

[Chemical 8]

In the method for producing polyester of the present invention, the amount of titanium element is 2 to 40 based on the total dicarboxylic acid component.
It is preferable to add it in the range of millimole%. When the amount of titanium element is less than 2 mmol%, the polymerization reaction becomes slow, and when it exceeds 40 mmol%, the color tone of the obtained polyester may be poor and the heat resistance thereof may be deteriorated, which is not preferable. The amount of titanium element is 5 to 3
The range of 5 mmol% is preferable, and 10 to 30 mmol%
Is more preferable.

The titanium compound is a part of the total addition amount and / or
Alternatively, a method of adding the whole amount thereof into the reaction system after the completion of the esterification reaction is preferably adopted.

In the esterification reaction, 0.0
A method of carrying out under pressure of 5 to 0.20 MPa is preferable, but for the oligomer once produced under pressure reaction,
In the case of a production method in which additional addition of terephthalic acid and ethylene glycol is repeated, the esterification reaction may be carried out under normal pressure. Since terephthalic acid serves as an autocatalyst for the esterification reaction in the esterification reaction, it is not necessary to add a catalyst separately, but the titanium compound may be present during the esterification reaction.

The intrinsic viscosity of the polyester in the present invention is preferably in the range of 0.40 to 0.80,
Furthermore, the range of 0.45 to 0.75, especially 0.50 to 0.70 is preferable. When the intrinsic viscosity is less than 0.40, the strength of the fiber becomes insufficient, which is not preferable. On the other hand, when the intrinsic viscosity exceeds 0.80, it is uneconomical to increase the intrinsic viscosity of the raw material polymer excessively.

In the method for producing the polyester of the present invention, if necessary, a small amount of additives such as lubricants, pigments, dyes, antioxidants, solid-state polymerization accelerators, optical brighteners, antistatic agents, antibacterial agents are used. UV absorbers, light stabilizers, heat stabilizers, light-shielding agents, matting agents, etc. may be added, and titanium oxide etc. are particularly preferably added as matting agents.

The method for producing the polyester fiber of the present invention is not particularly limited, and a conventionally known method of melt spinning a polyester can be used. For example, polyester is melted in the range of 270 ° C to 300 ° C. It is preferably produced by spinning, and the melt spinning speed is 400.
It is preferable to spin at ~ 5000 m / min. When the spinning speed is in this range, the strength of the obtained fiber is sufficient and the fiber can be wound stably.
In addition, the stretched yarn can be obtained by winding the polyester fiber or by continuously stretching the fiber without once winding it. Further, the polyester fiber of the present invention is also preferably subjected to alkali weight reduction treatment in order to enhance the texture.

In the production of the polyester fiber of the present invention, there is no limitation on the shape of the spinneret used during spinning, and any shape such as circular, irregular, solid or hollow can be adopted.

[0041]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. The amount of dimethyl 2-hydroxyterephthalate, the intrinsic viscosity, the hue, the amount of diethylene glycol, the titanium content, and the layer of deposits generated on the spinneret were measured by the methods described below.

(1) Amount of 4-carboxybenzaldehyde, paratoluic acid, benzoic acid and dimethyl 2-hydroxyterephthalate in dimethyl terephthalate: After dissolving the obtained terephthalic acid in 2N-ammonia water, Shimadzu Corporation Liquid Chromatograph System (LC-6
A) and STRφDS-H column were separately measured.

(2) Intrinsic viscosity: The intrinsic viscosity of the polyester polymer is 35 ° C. in an orthochlorophenol solution.
It was determined from the viscosity value measured at 35 ° C. according to a conventional method.

(3) Color tone (color L value and color b
Value): The polymer sample was melted at 290 ° C. under vacuum for 10 minutes, and the thickness was 3.0 ± 1.0 mm on an aluminum plate.
Immediately after being molded into a plate of No. 1, the plate is rapidly cooled in ice water, dried and crystallized at 160 ° C. for 1 hour, and then placed on a white standard plate for adjusting a color difference meter.
Value and b value are measured by Minolta Co., Ltd. Hunter type color difference meter C
It measured using R-200. The L value indicates the lightness, the larger the value, the higher the lightness, and the larger the value, the higher the yellowness.

(4) Copolymerization amount of diethylene glycol (DEG): The polymer is decomposed using hydrazine hydrate,
Gas Chromatography (Hitachi, Ltd. "263
-70 ").

(5) Titanium metal content of the catalyst: The titanium metal concentration in the catalyst compound was measured using a fluorescent X-ray measuring device 3270 manufactured by Rigaku Corporation.

(6) Layer of deposits generated on the spinneret: polyester is made into chips, which are melted at 290 ° C.,
It was discharged from a spinneret having a hole diameter of 0.15 mmφ and 12 holes, and was spun at 600 m / min for 2 days, and the height of a layer of deposits generated on the outer edge of the discharge port of the spinneret was measured. The larger the height of the deposit layer, the easier the bending of the discharged filament of the polyester melt is, and the lower the moldability of the polyester. That is, the height of the deposit layer generated on the spinneret is an index of the moldability of the polyester.

[Reference Example 1] Production of recovered terephthalic acid: 200 parts of ethylene glycol was charged into a 500 ml separable flask, and then 1.5 parts of sodium carbonate and 50 parts of polyethylene terephthalate scraps such as crushed PET bottles were charged. Then, the temperature was raised to 185 ° C. with stirring. When this state was maintained for 4 hours, the polyethylene terephthalate scrap was dissolved and the depolymerization reaction was completed. The obtained depolymerized product was concentrated by vacuum distillation, and 150 parts of ethylene glycol was recovered as a fraction.

0.5 parts of sodium carbonate as a transesterification reaction catalyst and 100 parts of methanol were added to this concentrated liquid, and the liquid temperature was stirred at normal pressure at 75 ° C. for 1 hour to carry out the transesterification reaction.

The resulting mixture was cooled to 40 ° C and filtered through a glass filter. The crude dimethyl terephthalate collected on the filter was put into 100 parts of MeOH, heated to 40 ° C., washed with stirring and again filtered through a glass filter. This washing was repeated twice.

Crude dimethyl terephthalate captured on the filter was charged into a distillation apparatus and vacuum distillation was carried out under the condition of a pressure of 6.65 kPa and a reflux ratio of 0.5 to obtain dimethyl terephthalate as a fraction.

Next, 1% of the obtained dimethyl terephthalate was added.
00 parts and 200 parts of water were mixed, dimethyl terephthalate and water were stirred and held at 180 ° C., and supplied to the hydrolysis reaction device. The liquid temperature of the hydrolysis reaction apparatus was set to 250 ° C., the reaction was carried out with stirring, and methanol produced by the hydrolysis reaction was distilled out together with water. The terephthalic acid / water weight ratio in the obtained terephthalic acid / water slurry was about 1/1. The amount of 4-carboxybenzaldehyde, paratoluic acid, benzoic acid and dimethyl 2-hydroxyterephthalate in the obtained slurry was 1 ppm by weight or less based on terephthalic acid.

Next, 166 parts of the obtained terephthalic acid / water slurry and 4150 parts of ethylene glycol were put into a centrifugal separator and mixed. The weight ratio of terephthalic acid / water / ethylene glycol was 1: 1: 50, and the ethylene glycol slurry of terephthalic acid was treated with a centrifuge to obtain a terephthalic acid cake. The terephthalic acid / water / ethylene glycol weight ratio of the terephthalic acid cake was about 83: 0.4: 14.3. Ethylene glycol was further added to the slurry and mixed to finally give a terephthalic acid / ethylene glycol slurry having a weight ratio of 66:34.

Reference Example 2 In 131 parts by weight of ethylene glycol, 3.6 parts by weight of phenylphosphonic acid was heated at 120 ° C. for 10 minutes to be dissolved. 134.5 parts by weight of this ethylene glycol solution was further added with 40 parts of ethylene glycol.
After adding parts by weight, titanium tetrabutoxide 3.
8 parts by weight were dissolved. The resulting reaction system was heated at 120 ° C for 6
After stirring for 0 minutes, the titanium compound was reacted with phenylphosphonic acid to obtain a white slurry of the catalyst containing the reaction product. The titanium content of this catalyst slurry was 0.3% by weight, and the molar ratio of titanium element to phosphorus element (P / Ti) was 2.
It was 0.

[Reference Example 3] 0.8 parts by weight of trimellitic anhydride was dissolved in 2.5 parts by weight of ethylene glycol, and 0.7 part by weight of titanium tetrabutoxide (based on the molar amount of trimellitic acid anhydride) was added to this solution. 0.5 mol%) was added dropwise, and the reaction system was kept in the air at 80 ° C. for 60 minutes under atmospheric pressure to react titanium tetrabutoxide with trimellitic anhydride to age the reaction product. After that, the reaction system was cooled to room temperature, 15 parts by weight of acetone was added thereto, and the precipitate was separated into No. 5. Filter with 5 filter paper and collect it.
It was dried at the temperature of 2 hours. The titanium content of the obtained reaction product was 11.2% by weight.

Next, 3.6 parts by weight of phenylphosphonic acid was dissolved in 131 parts by weight of ethylene glycol by heating at 120 ° C. for 10 minutes. This ethylene glycol solution 13
After further adding 40 parts by weight of ethylene glycol to 4.5 parts by weight, 5.0 parts by weight of the above titanium compound was dissolved therein. The resulting reaction system is stirred at 120 ° C. for 60 minutes to react the titanium compound with phenylphosphonic acid,
A white slurry of catalyst containing the reaction product was obtained. The titanium content of this catalyst slurry was 0.3% by weight, and the molar ratio of titanium element to phosphorus element (P / Ti) was 2.0.

Reference Example 4 3.5 parts by weight of mono-n-butyl phosphate was dissolved in 131 parts by weight of ethylene glycol by heating at 120 ° C. for 10 minutes. After adding 40 parts by weight of ethylene glycol to 134.5 parts by weight of this ethylene glycol solution, 3.8 parts by weight of titanium tetrabutoxide was dissolved therein. The reaction system obtained was 1
The mixture was stirred at 20 ° C. for 60 minutes to react the titanium compound with mono-n-butyl phosphate to obtain a white slurry of the catalyst containing the reaction product. The titanium content of this catalyst slurry was 0.3% by weight, and the molar ratio of titanium element to phosphorus element (P / Ti) was 2.0.

[Reference Example 5] 0.8 parts by weight of trimellitic anhydride was dissolved in 2.5 parts by weight of ethylene glycol, and 0.7 parts by weight of titanium tetrabutoxide was added to this solution (the anhydrous trimellitic acid used in the production of polyester described later). 0.5 mol% based on the molar amount of mellitic acid) was added dropwise, and the reaction system was kept at 80 ° C. for 60 minutes in air under normal pressure to react titanium tetrabutoxide with trimellitic anhydride, thereby producing a reaction. Aged. Then cool the reaction system to room temperature,
Acetone (15 parts by weight) was added to this, and the precipitate was collected. It was filtered with 5 filter paper, collected, and dried at a temperature of 100 ° C. for 2 hours. The titanium content of the obtained reaction product was 11.2.
% By weight.

Next, 3.5 parts by weight of mono-n-butyl phosphate was added to 120 parts of 131 parts by weight of ethylene glycol.
It melt | dissolved by heating at 10 degreeC for 10 minutes. After adding 40 parts by weight of ethylene glycol to 134.5 parts by weight of this ethylene glycol solution, 5.0 parts of the above titanium compound was added thereto.
Part by weight was dissolved. The obtained reaction system is 60 at 120 ° C.
After stirring for a minute, the titanium compound was reacted with mono-n-butyl phosphate to obtain a white slurry of the catalyst containing the reaction product. The titanium content of this catalyst slurry was 0.3% by weight, and the molar ratio of titanium element to phosphorus element (P / Ti)
Was 2.0.

Example 1 200 parts of the terephthalic acid / ethylene glycol slurry produced in Reference Example 1 was stirred with a stirrer.
The reactor was equipped with a rectification column and a methanol distillation condenser, and the esterification reaction was carried out at 270 ° C. and a pressure of 0.3 MPa for 240 minutes. After removing half of the obtained reaction product, the remaining half was kept at 250 ° C., and terephthalic acid / ethylene glycol slurry 100 prepared in Reference Example 1 was prepared.
Parts were fed into the reaction system under atmospheric pressure for 150 minutes, and then esterified for 90 minutes under atmospheric pressure.

During this time, the temperature in the reaction system was kept at 250 ° C. Further, after removing half of the obtained reaction product, 100 parts of the terephthalic acid / ethylene glycol slurry prepared in Reference Example 1 was similarly supplied to carry out an esterification reaction, and this operation was carried out until diethylene glycol in the reaction product became stable. Was repeated.

After the diethylene glycol in the reaction product became stable, half of the reaction product obtained by the esterification reaction was transferred to a polycondensation reactor, and 1.27 parts of the titanium catalyst prepared in Reference Example 2 was added, The temperature was raised to 285 ° C. and 26.
A polycondensation reaction was performed in a high vacuum of 67 Pa or less to obtain a polyester having an intrinsic viscosity of 0.63 and a diethylene glycol amount of 1.0% by weight.

The obtained polyester was made into chips by a conventional method and dried. Next, using this dry-processed tip, a 333 dtex / 36 fil raw yarn is made in accordance with a conventional method,
It was drawn 4.0 times to obtain a multifilament of 83.25 dtex / 36 fil. The results are shown in Table 1.

[Examples 2 to 5 and Comparative Example 1] The procedure of Example 1 was repeated except that the titanium compound was changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 2 The same operation as in Example 1 was carried out except that 0.0313 parts of diantimony trioxide and 0.0028 parts of trimethyl phosphate were added instead of the titanium compound. The results are shown in Table 1.

[0066]

[Table 1]

[0067]

EFFECTS OF THE INVENTION According to the present invention, the deterioration of hue, which was a drawback when using a titanium metal compound as a catalyst, is eliminated, and while maintaining the excellent properties of polyester,
A polyester fiber having an excellent hue can be provided.

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Claims (10)

[Claims] 1. A process for producing a polyester polymer containing ethylene terephthalate as a main repeating unit, which is obtained by subjecting an aromatic dicarboxylic acid and an alkylene glycol to an esterification reaction and then a polycondensation reaction, wherein the aromatic dicarboxylic acid is used. As the terephthalic acid obtained by hydrolyzing the recycled dimethyl terephthalate obtained by depolymerizing the polyalkylene terephthalate with methanol, 70% by weight or more of the terephthalic acid based on the total acid components constituting the polyester is used, and As a catalyst, a titanium compound represented by the following formula (I) and a phosphorus compound represented by the following formula (II) are used, wherein the number of moles of phosphorus element relative to the number of moles of titanium element (P / Ti) is 1 to 4 The polycondensation reaction using the precipitate obtained by heating in glycol. Wherein, process for producing a polyester. [Chemical 1] [Chemical 2] 2. The method for producing a polyester according to claim 1, wherein the recycled terephthalic acid is terephthalic acid obtained by hydrolyzing dimethyl terephthalate recovered by depolymerizing polyethylene terephthalate. 3. The method for producing a polyester according to claim 2, wherein the content of 4-carboxybenzaldehyde, paratoluic acid, benzoic acid and dimethyl hydroxyterephthalate contained as impurities in terephthalic acid is 1 ppm or less. 4. The method for producing a polyester according to claim 1, wherein a phosphorus compound in which the value of p in the formula (II) is 0 is used. 5. The method for producing a polyester according to claim 2, wherein the phosphorus compound is a monoarylphosphonic acid. 6. The method for producing a polyester according to claim 1, wherein a phosphorus compound in which the value of p in the formula (II) is 1 is used. 7. The method for producing a polyester according to claim 4, wherein the phosphorus compound is a monoalkyl phosphate. 8. The production of polyester according to claim 1, wherein the titanium compound of the formula (I) uses a polyester production catalyst selected from titanium tetraalkoxides, octaalkyl trititanates and hexaalkyl dititanates. Method. 9. A titanium compound of the formula (I) is previously reacted with a polyvalent carboxylic acid of the following general formula (III) and / or its acid anhydride in a reaction molar ratio (2: 1) to (2: 5). 2. The method for producing a polyester according to claim 1, wherein the polyester compound is reacted with the phosphorus compound of the formula (II) after the reaction with the composition. [Chemical 3] 10. A polyester fiber obtained by melt spinning a polyester produced by the method according to any one of claims 1 to 9.