JPH04356525A - Production of polyester - Google Patents

Abstract

PURPOSE:To produce a polyester having a high crystallization rate and excellent heat resistance and mechanical strengths as well as moldability. CONSTITUTION:A process for producing an aromatic polyester by reacting a lower alkyl ester of an aromatic dicarboxylic acid with an aliphatic diol, wherein the transesterification reaction is performed in the presence of 0.02-1.80mol%, based on the lower alkyl ester of the aromatic dicarboxylic acid, aromatic sulfonic acid compound of the general formula: HO-R-O-Ar-SO3M (wherein -Ar- is p-substituted benzene or 2,6-disubstituted naphthalene, R is a bivalent group selected from among -CH2CH2-, -CH(CH3)CH2-, -CH2CH(CH3) and-CH2CH2OCH2CH2- M is an alkali metal selected from among lithium, sodium and potassium) by using a titanate compound as a catalyst, and the polycondensation reaction is then performed.

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 a polyester resin which has excellent moldability and mechanical properties, and particularly has an improved crystallization rate.

0002

BACKGROUND OF THE INVENTION Aromatic polyesters represented by polybutylene terephthalate (PBT) are widely used as engineering plastics due to their excellent heat resistance, chemical resistance, and mechanical strength. Among these, although PBT itself has a crystallization rate sufficient for injection molding, it is desired that the molding cycle be further increased. In addition, in copolyesters produced by using copolymerization components such as PBT and polybutylene naphthalate (PBN), the copolymerization components generally act as an inhibitor of crystallization and significantly reduce the crystallization rate, resulting in poor moldability and mechanical properties. In addition to mechanical strength, there are also problems in the process such as sticking of pellets during production. On the other hand, homopolyesters such as polyethylene terephthalate (PET), polypropylene terephthalate (PPT), and polyethylene naphthalate (PEN) have a low crystallization rate, resulting in problems in not only moldability but also heat resistance and mechanical strength. ing. In order to improve the crystallization rate of these aromatic polyesters, many proposals have been made, including the addition of crystallization promoters. For example, Tokuko Sho 45-1876
In No. 8, the glass fiber composition was
JP-B-45-26225 discloses the formulation of an ionic polyolefin copolymer. However, these crystallization accelerators have low solubility with polyester, and even after sufficient kneading, they still exhibit a non-uniform dispersion state in the resin, and their crystallization accelerating effect is still insufficient, especially when using multi-component polyesters. The effect on copolyesters using comonomers is small. Furthermore, if the amount added is increased in order to increase the effect of promoting crystallization, the mechanical strength will be significantly impaired, which is not practical. In addition, special public service
Although the compound consisting of the alkali metal salt of aromatic sulfonic acid disclosed in No. 180 has better dispersibility than inert powder, etc., it is difficult to make it compatible with the resin, and it does not exhibit sufficient crystallization promoting effect. has not yet been reached. On the other hand, although the blend of high melting point polyester resins disclosed in JP-A-58-149942 has excellent compatibility, it still does not have a sufficient effect of promoting crystallization. As described above, the improvement in the crystallization rate of polyester cannot be said to be fully satisfactory. An object of the present invention is to provide a polyester having excellent performance in solving these problems and a method for producing the same.

0003

[Means for Solving the Problems] In order to solve the above problems, the present inventors have made extensive studies, and have found that when producing aromatic polyester, a titanium-based compound is used as a catalyst, and a specific monofunctional compound component is used as a catalyst. The transesterification reaction is carried out in the presence of
Furthermore, it was discovered that the crystallization rate was significantly accelerated by polycondensation, and a polyester having excellent moldability and mechanical strength could be provided, and the present invention was completed based on this finding. That is, in the present invention, when producing an aromatic polyester by reacting a lower alkyl ester of an aromatic dicarboxylic acid with an aliphatic diol, the lower alkyl ester component of an aromatic dicarboxylic acid is reacted with an alkyl ester of 0.02 to 1.80.
A method for producing polyester, which comprises performing a transesterification reaction using a titanium-based compound as a catalyst in the presence of a mol% of an aromatic sulfonic acid compound represented by the following general formula (I), followed by a polycondensation reaction. It is related to. HO-R-O-Ar-SO3M (I)
(However, -Ar- is a group selected from p-substituted benzene and 2,6-substituted naphthalene. R is -CH2C
H2-, -CH(CH3)CH2-, -CH2CH(C
H3)-, -CH2CH2OCH2CH2-. M is an alkali metal selected from lithium, sodium, and potassium. ) The aromatic polyester of the present invention is prepared by subjecting a lower alkyl ester of an aromatic dicarboxylic acid to a transesterification reaction with an aliphatic diol in the presence of a specific amount of the compound of formula (I) and a titanium compound catalyst, and then polycondensing the polyester. It includes not only homopolyesters but also copolyesters into which multiple components have been introduced. The lower alkyl ester of aromatic dicarboxylic acid is mainly selected from dimethyl terephthalate, dimethyl 2,6-naphthalene dicarboxylate, and dimethyl 2,7-naphthalene dicarboxylate, and the amount of these components is preferably 60 mol based on the total acid components. % or more, particularly preferably 70 mol% or more. Further, the aliphatic diol is mainly selected from ethylene glycol, 1,3-propanediol, and 1,4-butanediol, and the amount of these components is preferably 60 mol% or more based on the total diol components, and is particularly preferably is 70 mol% or more. The main structural repeating units include ethylene terephthalate, ethylene-2,6-naphthalate, ethylene-2,7-naphthalate, propylene terephthalate, propylene-2,6-naphthalate, propylene-
2,7-naphthalate, butylene terephthalate, butylene-2,6-naphthalate, butylene-2,7-
Examples include naphthalate. Among them, ethylene terephthalate, propylene terephthalate, butylene terephthalate, ethylene-2,6-naphthalate, propylene-2,6-naphthalate, butylene-2,6
- Those having naphthalate as the main constituent repeating unit are preferred.

[0004] When forming a copolymerized polyester,
In addition to the above-mentioned two or more different acid constituents, dimethyl diphenate, 4,4'-
It is possible to use one or more types of conventionally known lower alkyl esters of difunctional carboxylic acids such as dimethyl diphenyldicarboxylate, dimethyl adipate, dimethyl sebacate, and dimethyl 1,4-cyclohexanedicarboxylate. In addition to the above-mentioned diol constituents, diol constituents include diethylene glycol, triethylene glycol, 1,5-propanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, 1 ,4-
Cyclohexane dimethanol, 1,4-cyclohexanediol, p-xylidene glycol, ethylene oxide adduct of hydroquinone, 2,2-bis(4-
ethylene oxide adduct of bis(4-hydroxyphenyl)propane, ethylene oxide adduct of bis(4-hydroxyphenyl)sulfone, ethylene oxide adduct of 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,6-dihydro It is possible to use one or more conventionally known bifunctional diols such as ethylene oxide adducts of shikinaphthalene. In addition, trimethyl or higher functional compounds such as trimethyl trimesate, trimethyl trimellitate, trimethylolpropane, and pentaerythritol, stearyl alcohol, o-
Monofunctional compounds such as methyl benzoylbenzoate, p-
It is also possible to use hydroxycarboxylic acid derivatives such as methyl hydroxyethoxyphenylcarboxylate, polyalkylene glycols such as polybutylene glycol, and the like.

The present invention is characterized in that a specific amount of an aromatic sulfonic acid compound represented by the following general formula (I) is further present as a raw material compound for forming the polyester during the transesterification reaction. HO-R-O-Ar-SO3M (I)
(However, -Ar- is a group selected from p-substituted benzene and 2,6-substituted naphthalene. R is -CH2C
H2-, -CH(CH3)CH2-, -CH2CH(C
H3)-, -CH2CH2OCH2CH2-. M is an alkali metal selected from lithium, sodium, and potassium. )concrete(
Compounds of formula I) include 1 mole ethylene oxide adduct of sodium p-phenolsulfonate, 1 mole propylene oxide adduct of sodium p-phenolsulfonate, 2 mole ethylene oxide adduct of sodium p-phenolsulfonate, p-phenol 1 mole ethylene oxide adduct of lithium sulfonate, p-
1 mole ethylene oxide adduct of potassium phenolsulfonate, 1 mole ethylene oxide adduct of sodium 2-naphthol-6-sulfonate, 2-naphthol-6
Examples include a 1 mol propylene oxide adduct of sodium sulfonate, a 2 mol ethylene oxide adduct of sodium 2-naphthol-6-sulfonate, and a 1 mol ethylene oxide adduct of lithium 2-naphthol-6-sulfonate.

On the other hand, -Ar- in general formula (I)
is a benzene ring having a sulfonic acid group (-SO3M) and an esterification functional group (HO-R-O-) other than the p-position,
In the case of a naphthalene ring having these substituents at positions other than the 2 and 6 positions, for example, 1 mole of ethylene oxide adduct of sodium m-phenolsulfonate, 1-naphthol-
Aromatic sulfonic acid compounds such as 1 mole ethylene oxide adduct of sodium 2-sulfonate, 1 mole ethylene oxide adduct of sodium 1-naphthol-4-sulfonate, and 1 mole ethylene oxide adduct of sodium 1-naphthol-7-sulfonate. As shown in the comparative example described later, a sufficient effect of promoting crystallization cannot be obtained and is therefore undesirable. The reason for this is not clear, but it is thought that the position of the ionic group (-SO3M) bonded to the end of the main chain influences the mobility of the main chain. Furthermore, those having two or more reactive functional groups, such as the ethylene oxide adduct of sodium 1,4-diphenyl-2-sulfonate, are contrary to the spirit of the present invention, and do not efficiently introduce ionic groups to the ends of the main chain. It is difficult to do so, and as shown in the comparative example, a sufficient crystallization promoting effect cannot be obtained, which is not preferable. The amount of the compound represented by the general formula (I) to be used is 0.02 to 1.0% (the same applies hereinafter) based on the lower alkyl ester component of the aromatic dicarboxylic acid.
It is preferable to use 80 mol%. Particularly preferably 0.
05 to 1.50 mol%. The above mole fraction is 0.02
If it is less than 1.80 mol%, the effect of improving the crystallization rate of the resulting polyester will be small, and if it is more than 1.80 mol%, the degree of polymerization of the polyester produced will be low,
Either case is unfavorable because the mechanical strength is significantly reduced. It was confirmed that the compound of formula (I) was hardly distilled out of the reaction system during the transesterification reaction and polycondensation, and the entire amount used was introduced into the produced polymer.

These aromatic sulfonic acid compounds represented by the general formula (I) can be added to the reaction system together with other polyester raw materials and the titanium-based compound catalyst described below, before or at the beginning of the transesterification reaction, and in a specific manner. In this case, it is preferable to add the compound before the amount of lower alcohol produced by the transesterification reaction that is distilled out of the reaction system reaches 90% by weight of the theoretical distilled amount. In particular, it is preferable to add it to the reaction system before starting the transesterification reaction, that is, when the distilled amount is almost zero. Here, the theoretical distillation amount is the amount of lower alcohol calculated from the above-mentioned lower alkyl ester of carboxylic acid. When the aromatic sulfonic acid compound represented by general formula (I) is added at the end of the transesterification reaction, that is, when the distillation amount of lower alcohol reaches 90% by weight or more, or during polycondensation, crystallization of the produced polyester occurs. In addition, the accelerating effect of the aromatic sulfonic acid compound becomes insufficient, and the undissolved aromatic sulfonic acid compound is dispersed non-uniformly, causing variations in the crystallization rate. is undesirable as it precipitates and impairs the appearance.

The present invention is further characterized in that it is produced using a titanium compound catalyst. Here, as the titanium-based compound catalyst, titanium tetrabutoxide, titanium tetrapropoxide, titanium tetraethoxide,
Titanium isopropoxyoctylene glycol, titanium butoxyoctylene glycol, titanium isopropoxybutylene glycol, titanium dihydroxybislactate, titanium diisopropoxybisacetylacetonate, titanium dibutoxybistriethanolaminate, titanium isopropoxytriisostearate, etc. Among them, titanium tetrabutoxide, titanium tetrapropoxide,
Particularly preferred are titanium tetraalkoxides such as titanium tetraethoxide.

The polyester resin of the present invention is produced by further performing a conventionally known polycondensation reaction following the above transesterification reaction. Further, by using a solid phase polymerization method in which the obtained resin is subjected to reduced pressure or in the presence of an inert gas, it is also possible to obtain a product with an even higher degree of polymerization.

In the polyester resin of the present invention obtained as described above, a predetermined amount of the aromatic sulfonic acid compound residue is efficiently bonded to the terminal position of the main chain, and crystallization is achieved without reducing the degree of polymerization of the polyester. It is possible to obtain a polyester having a good effect of promoting chemical conversion.

[0011] Depending on the purpose, one or more types of other thermoplastic resins, additives, organic fillers, inorganic fillers, etc. may be added to the polyester of the present invention. It is valid.

0012

Effect of the invention: The polyester resin obtained by the present invention has improved crystallization speed, excellent molding processability in injection molding (especially improved molding cycle), mechanical strength of molded products, and heat resistance, making it extremely useful as a molding material. It is useful for

[0013]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

Example 1 Dimethyl terephthalate 306.5 parts by weight, 1,4 -
283.1 parts by weight of butanediol, 1 mol of ethylene oxide adduct of sodium p-phenolsulfonate (
I-a) 3.8 parts by weight (1.0 mol%) was charged into a reactor equipped with a stirrer and a distillation tube together with a predetermined amount of titanium tetrabutoxide, and after the atmosphere was sufficiently purged with nitrogen, stirring was started and the mixture was kept constant. The temperature was raised to 160°C under pressure. Furthermore,
The temperature was gradually raised to distill off methanol as a by-product. When the distilled methanol exceeded 90% by weight of the theoretical amount, the temperature reached 240 °C, at which point the pressure in the reactor was gradually reduced and stirring was continued for 2.5 hours at a pressure of 0.1 torr to obtain a polyester resin. Ta. The obtained polyester had an intrinsic viscosity of 0.7 at 25°C in orthochlorophenol.
It had 7. In addition, 1 using trifluoroacetic acid-d as a solvent
In measurements based on H-NMR method and fluorescent X-ray method, p-
Sodium phenolsulfonate ethylene oxide 1
The ratio of molar adduct introduced into the polymer was 1.0 mol%. The resulting resin pellets were sufficiently dried and their crystallization properties were evaluated. The results are shown in Table 1. In addition, Tm in the table is a temperature increase rate of 10 specified by JIS K 7121.
The melting peak temperature determined in °C/min, Tc is JI
It represents the crystallization peak temperature determined at a cooling rate of 10°C/min as defined in SK 7121, and Tm - Tc calculated from this is an index of the crystallization rate. Tm −
A small Tc value indicates a high rate of crystallization promotion. Moreover, Xc is a value calculated by 2ΔH/Y from the crystallization peak height (Y) based on JIS K 7121 and the heat of transition of crystallization (ΔH) based on JIS K 7122,
The smaller the Xc value, the greater the rate of crystallization promotion.

Comparative Example 1 A PBT homopolyester was obtained in the same manner as in Example 1 without adding the compound of formula (I). Table 1 shows the evaluation of crystallization properties.

Examples 2 to 4, Comparative Examples 2 to 5 Instead of the 1 mol ethylene oxide adduct of sodium p-phenolsulfonate (I-a), 1 mol propylene oxide adduct of sodium p-phenolsulfonate (I-a) was used. b
), 2-mol ethylene oxide adduct of sodium p-phenolsulfonate (I-c), 2-naphthol-6
- 1 mole ethylene oxide adduct of sodium sulfonate (I-d), and for comparison, methyl-sodium m-sulfobenzoate (I'-1), 1,4-diphenyl-
2 moles of ethylene oxide adduct of sodium 2-sulfonate (I'-2), 1 mole of ethylene oxide adduct of sodium m-phenolsulfonate (I'-3), ethylene oxide of sodium 1-naphthol-2-sulfonate 1 A predetermined amount (1.0
% by mole) to obtain a polyester resin in the same manner as in Example 1. The introduction rates of these were all 1.0 mol%. Table 1 shows the evaluation of crystallization properties.

Comparative Example 6 100 parts by weight of the PBT homopolyester obtained in Comparative Example 1 and 0.01 parts by weight of boron nitride fine powder (BN manufactured by Denki Kagaku Kogyo Co., Ltd.) as a crystallization nucleating agent were added to a screw feeder and a vent equipped with a screw feeder and a vent. The mixture was melt-kneaded using a twin-screw extruder with an inner diameter of 30 mm at a cylinder temperature of 260° C. to obtain a pelletized resin composition. Table 1 shows the evaluation results of crystallization properties. From the results shown in Table 1, it was found that the polyester resin obtained using the aromatic sulfonic acid compound of formula (I), represented by the ethylene oxide 1 mol adduct of sodium p-phenolsulfonate (I-a), exhibited excellent crystallization. While having a promoting effect,
It can be seen that a sufficient crystallization promoting effect cannot be obtained when aromatic sulfonic acid compounds and polyfunctional aromatic sulfonic acid compounds having different substitution positions are used.

Comparative Example 7 Dimethyl terephthalate 306.5 parts by weight, 1,4 -
283.1 parts by weight of butanediol was charged together with a predetermined amount of titanium tetrabutoxide into a reactor equipped with a stirrer and a distillation tube, and after the atmosphere was sufficiently purged with nitrogen, stirring was started and the temperature was raised to 160° C. under normal pressure. Furthermore, the temperature was gradually raised to distill off methanol as a by-product. When the distilled methanol exceeded 92% by weight of the theoretical amount, 3.8 parts by weight (1.0 mol%) of an ethylene oxide 1 mol adduct of sodium p-phenolsulfonate (I-a) was added, and then The temperature was raised to 240° C., the pressure in the reactor was gradually reduced, and stirring was continued for 2.5 hours at a pressure of 0.1 torr to obtain a polyester resin. Table 2 shows the evaluation results of crystallization properties.

Comparative Example 8 Dimethyl terephthalate 306.5 parts by weight, 1,4 -
283.1 parts by weight of butanediol and a predetermined amount of titanium tetrabutoxide were charged into a reactor equipped with a stirrer and a distillation tube, and after the atmosphere was sufficiently purged with nitrogen, stirring was started and the temperature was raised to 160° C. under normal pressure. Furthermore, the temperature was gradually raised to distill off methanol as a by-product. When the distilled methanol exceeds 90% by weight of the theoretical amount, the temperature is 24%.
At this point, the pressure in the reactor was gradually reduced to 0.
Stirring was performed at a pressure of 1 torr for 2.0 hours. Subsequently, 3.8 parts by weight (1.
0 mol %) was added thereto, and the mixture was further stirred for 0.5 hours to obtain a polyester resin. Evaluation of crystallization properties is shown in Table 2.

Comparative Example 9 700 parts by weight of the PBT homopolyester obtained in Comparative Example 1, 7.6 parts by weight of 1 mol of ethylene oxide adduct (I-a) of sodium p-phenolsulfonate (based on the constituent ester units of the polyester) 1.0 mol%)
were melt-kneaded using the same twin-screw extruder as in Comparative Example 6 at a cylinder temperature of 260°C to obtain a pelletized resin composition. Table 2 shows the evaluation results of crystallization properties.

Comparative Example 10 700 parts by weight of the PBT homopolyester obtained in Comparative Example 1 and 7.6 parts by weight of sodium benzenesulfonate were melt-kneaded in a twin-screw extruder at a cylinder temperature of 260°C to obtain a pelletized resin composition. I got it. Table 2 shows the evaluation results of crystallization properties. From the results shown in Table 2, 1 mol of ethylene oxide adduct of sodium p-phenolsulfonate (I
-A polyester resin obtained by adding the aromatic sulfonic acid compound represented by a) to the reaction system at the beginning of the transesterification reaction, that is, before the amount reaches 90% by weight of the theoretical distillation amount. It can be seen that this exhibits a particularly excellent crystallization promoting effect. In addition, as in Comparative Examples 9 and 10,
Because the melt-kneaded product of 1 mole of ethylene oxide adduct (I-a) of sodium p-phenolsulfonate has the same degree of crystallization promoting effect as sodium benzenesulfonate, which does not have an esterification-reactive functional group. , it can be seen that in this case, almost no binding to the molecular terminal occurs and the crystallization promoting effect is insufficient. Also, Comparative Example 9,
Minute precipitates of undissolved aromatic sulfonic acid compounds were observed on the outside of the pelletized resin obtained in step 10.

Examples 5 to 7 Polyester resins were obtained by carrying out polymerization in the same manner as in Example 1, except that the amount of the 1-mole ethylene oxide adduct of sodium p-phenolsulfonate (I-a) was changed. Crystallization properties were evaluated, and tensile test pieces were prepared by conventional injection molding, and mechanical strength was evaluated (tensile test) according to ASTM D 638. The evaluation results are shown in Table 3.

Comparative Examples 11 to 12 Polyester resins were obtained by carrying out polymerization in the same manner as in Example 1, except that the amount of the 1-mol ethylene oxide adduct (I-a) of sodium p-phenolsulfonate was changed. The resulting resin pellets were thoroughly dried, the crystallization properties were evaluated, and tensile test pieces were prepared by conventional injection molding, and the mechanical strength was evaluated (tensile test) in accordance with ASTM D 638. I did it. The evaluation results are shown in Table 3. From the results shown in Table 3, when the usage rate of the 1 mol ethylene oxide adduct (I-a) of sodium p-phenolsulfonate was reduced below 0.02 mol%, almost no crystallization promotion effect was obtained; It can be seen that when the content exceeds 1.80 mol %, the mechanical strength decreases significantly.

Examples 8-9 246.0 parts by weight of dimethyl terephthalate, 61.5 parts by weight of dimethyl isophthalate, 2 parts by weight of 1,4-butanediol
84.5 parts by weight, 1 mol of ethylene oxide adduct of sodium p-phenolsulfonate (I-a) 1.9
Part by weight (0.5 mol%) or 3.8 parts by weight (1.
0 mol %) was charged into a reactor equipped with a stirrer and a distillation tube together with a predetermined amount of titanium tetrabutoxide, and after the atmosphere was sufficiently purged with nitrogen, stirring was started and the temperature was raised to 160° C. under normal pressure. Furthermore, the temperature was gradually raised to distill off methanol as a by-product. The theoretical amount of distilled methanol is 90
When the weight percentage was exceeded, the temperature reached 235° C. At this point, the pressure in the reactor was gradually reduced and stirring was continued for 3.0 hours at a pressure of 0.1 torr to obtain a polyester resin. The resulting polyester had an intrinsic viscosity of 0.75 at 25° C. in orthochlorophenol. The introduction rates of the 1 mol ethylene oxide adduct of sodium p-phenolsulfonate were 0.5 mol % and 1.0 mol %, respectively. The resulting resin pellets were sufficiently dried and their crystallization properties were evaluated. The results are shown in Table 4. The amount of dimethyl isophthalate residue introduced was measured based on 1H-NMR method using trifluoroacetic acid-d as a solvent.

Comparative Example 13 Polymerization was carried out in the same manner as in Example 8 except that the 1 mol ethylene oxide adduct of sodium p-phenolsulfonate was not used to obtain a copolymerized polyester resin. Table 4 shows the evaluation of crystallization properties.

Comparative Examples 14 to 15 The polyester resin obtained in Comparative Example 13 and a predetermined amount of boron nitride fine powder (BN) were melt-kneaded in a twin-screw extruder at a cylinder temperature of 235° C. to obtain a pellet-like resin composition. I got it. Table 4 shows the evaluation of crystallization properties. Table 4 and the results of Comparative Examples 1 and 6 show that the crystallization promoting effect of boron nitride fine powder (BN) is significantly reduced in copolymerized polyester, whereas when the aromatic sulfonic acid compound of formula (I) is It can be seen that the effects of the introduced products are sufficiently maintained.

Example 10, Comparative Example 16 Dimethyl terephthalate 329.6 parts by weight, 1,3 -
258.3 parts by weight of propanediol and 1.9 parts by weight (0.5 mol%) of 1 mol of ethylene oxide adduct (I-a) of sodium p-phenolsulfonate were mixed with a predetermined amount of titanium tetrabutoxide using a stirrer and distilled. After the mixture was charged into a reactor equipped with a tube and the atmosphere was sufficiently purged with nitrogen, stirring was started and the temperature was raised to 175° C. under normal pressure. Furthermore, the temperature was gradually raised to distill off methanol as a by-product. When the distilled methanol exceeded 90% by weight of the theoretical amount, the temperature reached 250 °C, at which point the pressure in the reactor was gradually reduced and stirring was continued for 3.0 hours at a pressure of 0.1 torr to obtain a polyester resin. Ta. The resulting polyester had an intrinsic viscosity of 0.66 at 25° C. in orthochlorophenol. Further, the introduction rate of the 1 mol ethylene oxide adduct of sodium p-phenolsulfonate was 0.5 mol %. The resulting resin pellets were sufficiently dried and their crystallization properties were evaluated. Also, for comparison, p-
Sodium phenolsulfonate ethylene oxide 1
PPT homopolyester was polymerized in a similar manner without using the molar adduct. The results are shown in Table 5.

Example 11, Comparative Example 17 334.9 parts by weight of dimethyl terephthalate, 247.7 parts by weight of ethylene glycol, 1 mol of ethylene oxide adduct of sodium p-phenolsulfonate (I-
a) 2.1 parts by weight (0.5 mol%) was charged together with a predetermined amount of titanium tetrabutoxide into a reactor equipped with a stirrer and a distillation tube, and after the atmosphere was sufficiently purged with nitrogen, stirring was started and the mixture was heated under normal pressure. The temperature was raised to 185°C. Furthermore, the temperature was gradually raised to distill off methanol as a by-product. Subsequently, the temperature was raised to 270°C, and at this point, the pressure in the reactor was gradually reduced, and stirring was continued for 2.5 hours at a pressure of 0.1 torr to obtain a polyester resin. The obtained polyester had an intrinsic viscosity of 0 at 25°C in orthochlorophenol.
．． 67. The introduction rate was 0.5 mol%. The resulting resin pellets were sufficiently dried and their crystallization properties were evaluated. For comparison, PET homopolyester was polymerized in the same manner without using the 1 mole ethylene oxide adduct of sodium p-phenolsulfonate. The results are shown in Table 5. As shown in Table 5, the crystallization properties of various specific polyesters can be improved by introducing a specific amount of the aromatic sulfonic acid compound, typified by a 1-mole ethylene oxide adduct of sodium p-phenolsulfonate, by a specific method. can be significantly improved.

Comparative Example 18 334.9 parts by weight of dimethyl terephthalate, 247.7 parts by weight of ethylene glycol, 1 mol of ethylene oxide adduct of sodium p-phenolsulfonate (I-
a) 2.1 parts by weight (0.5 mol%) was charged into a reactor equipped with a stirrer and a distillation tube together with a predetermined amount of calcium acetate, and after the atmosphere was sufficiently purged with nitrogen, stirring was started and the mixture was heated under normal pressure. The temperature was raised to 185°C. Furthermore, the temperature was gradually raised to distill off methanol as a by-product. When the distilled methanol exceeds 90% by weight of the theoretical amount, a predetermined amount of antimony trioxide is added, and the temperature is subsequently increased to 270 °C, at which point the reactor is gradually depressurized to 0.1 torr. Stirring was continued at a pressure of 3.5 hours to obtain a polyester resin. The obtained polyester had an intrinsic viscosity of 0.68 at 25°C in orthochlorophenol.
It had The resulting resin pellets were sufficiently dried and their crystallization properties were evaluated. The results are shown in Table 5. It can be seen that when a titanium-based compound is not used as a catalyst, the crystallization promoting effect of the produced polyester is not sufficiently exhibited.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

Claims (5)

[Claims] Claim 1: When producing an aromatic polyester by reacting a lower alkyl ester of an aromatic dicarboxylic acid with an aliphatic diol, 0.02 to 1.80 mol based on the lower alkyl ester component of the aromatic dicarboxylic acid. %
A method for producing polyester, which comprises carrying out a transesterification reaction using a titanium-based compound as a catalyst in the presence of an aromatic sulfonic acid compound represented by the following general formula (I), followed by a polycondensation reaction. HO-R-O-Ar-SO3M (I)
(However, -Ar- is a group selected from p-substituted benzene and 2,6-substituted naphthalene. R is -CH2C
H2-, -CH(CH3)CH2-, -CH2CH(C
H3)-, -CH2CH2OCH2CH2-. M is an alkali metal selected from lithium, sodium, and potassium. ) 2. The method for producing a polyester according to claim 1, wherein the lower alkyl ester of aromatic dicarboxylic acid is mainly selected from dimethyl terephthalate, dimethyl 2,6-naphthalene dicarboxylate, and dimethyl 2,7-naphthalene dicarboxylate. 3. The method for producing a polyester according to claim 1, wherein the aliphatic diol is mainly selected from ethylene glycol, 1,3-propanediol, and 1,4-butanediol. 4. Before the amount of lower alcohol produced by the transesterification reaction that is distilled out of the reaction system reaches 90% by weight of the theoretical amount of distillation calculated from the lower alkyl esters of all the carboxylic acids used, Any one of claims 1 to 3, characterized in that the aromatic sulfonic acid compound is added.
Method for producing polyester as described in Section 1. 5. The method for producing polyester according to claim 1, wherein the titanium compound is titanium tetraalkoxide.