JP2014139275A - Polyester resin composition and direct blow-molded article comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin composition capable of providing a direct blow-molded article excellent in heat stability, color tone and transparency in a good productivity without causing problems such as draw-down or crystallization during a direct blow molding.SOLUTION: There is provided a polyester resin composition containing tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane of 0.1 to 1.0 mass% in a polyester resin of which 50 to 98 mol% of an acid component is terephthalic acid, 2 to 20 mol% of the acid component is p-hydroxyethoxy benzoic acid, and 80 mol% or more of a glycol component is ethylene glycol, and a germanium compound of 5×10mol to 3.0×10to 1 mol of the acid component of the polyester resin, and having an intrinsic viscosity (IV) of 0.8 to 1.5 and a swell ratio (SW) of 1.2 to 1.4.

Description

  TECHNICAL FIELD The present invention relates to a polyester resin composition containing a specific compound in a polyester resin, which can obtain a direct blow molded article excellent in color tone and transparency with high productivity.

  Polyethylene terephthalate (PET) is excellent in mechanical properties, chemical stability, transparency and the like, is inexpensive, and is widely used as various sheets, films, containers and the like. The growth in the use of hollow containers (bottles) for fruit juice drinks, liquid seasonings, edible oils, liquors, wines, etc. is remarkable. Moreover, since there is little concern about residual monomers and harmful additives in hollow molded articles made of vinyl chloride resin, and hygiene and safety are high, replacement from conventional bottles made of vinyl chloride resin and the like is also progressing.

  In general, when plastic bottles are manufactured, melt-plasticized resin is used as die orifices in terms of ease of molding, high productivity, and relatively low equipment costs such as molding machines and molds. A so-called direct blow molding method is employed in which a cylindrical parison is formed through extrusion, and air is blown into the mold by sandwiching the parison between the molds. In the case of this direct blow molding, it is necessary to avoid that the parison extruded in the molten state is drawn down during the blow molding in order to perform the molding smoothly. Therefore, a high melt viscosity is required for the resin used. Is done. Accordingly, vinyl chloride resins, polyolefin resins, and the like are widely used in direct blow molding as resins having a high melt viscosity.

  In direct blow molded products, replacement of vinyl chloride resin with polyester resin has been studied, but polyester resins generally do not have a high melt viscosity suitable for direct blow molding. For this reason, there is a problem that the extruded parison draws down during blow molding, and blow molding cannot be performed, and crystallization is likely to occur during blow, so whitening occurs even if molding is possible, and transparency is increased. There was a problem of becoming insufficient.

  In order to improve transparency, a polyester resin obtained by copolymerizing polyethylene terephthalate with other monomer components has been proposed. This can suppress crystallization, but it cannot increase the melt viscosity by itself. Therefore, a method has been proposed in which the viscosity is increased by means of crosslinking with a trifunctional or higher polyvalent carboxylic acid / polyhydric alcohol to solve the drawdown problem (see, for example, Patent Document 1). However, when the viscosity is increased by such a cross-linking means, the moldability is improved, but when the amount of polyvalent carboxylic acid or polyhydric alcohol is large, the gel is easily gelled, the heat stability is poor, and the obtained molding The product had a problem that it was inferior in color tone and transparency.

Japanese Patent No. 3173755

  The present invention solves the above-mentioned problems, does not cause problems of whitening due to drawdown or crystallization during direct blow molding, has excellent thermal stability, and has excellent color tone and transparency. It is intended to provide a polyester resin composition that can be obtained with good productivity, and to provide a direct blow molded article comprising the resin composition of the present invention.

The inventor of the present invention has arrived at the present invention as a result of intensive studies to solve the above problems. That is, the gist of the present invention is the following (1) to (3).
(1) In a polyester resin in which 50 to 98 mol% of the acid component constituting the polyester is terephthalic acid, 2 to 20 mol% is p-hydroxyethoxybenzoic acid, and 80 mol% or more of the glycol component is ethylene glycol. Tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane in an amount of 0.1 to 1.0% by mass and a germanium compound in an amount of 1 mol of the acid component of the polyester resin 5 × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol, intrinsic viscosity (IV) is 0.8 to 1.5, and swell ratio (SW) is 1.2 to 1.4. A polyester resin composition characterized by the above.
(2) Further, it contains a cobalt compound and an alkali metal compound, and the cobalt compound is contained in an amount of 1 × 10 ⁻⁵ mol to 2.0 × 10 ⁻⁴ mol per mol of the acid component of the polyester resin. The polyester resin composition according to (1), wherein the compound is contained in an amount of 1 × 10 ⁻⁴ mol to 1.0 × 10 ⁻³ mol per mol of the acid component of the polyester resin.
(3) A direct blow molded article comprising the polyester resin composition according to (1) or (2).

The polyester resin composition of the present invention uses a polyester having a specific composition, contains a specific compound, and has an intrinsic viscosity and a swell ratio suitable for direct blow molding. There are sometimes no problems of whitening due to drawdown or crystallization, and the thermal stability is excellent, and a direct blow molded product excellent in color tone and transparency can be obtained with high productivity.
And since the direct blow molded article of this invention is obtained from the polyester resin composition of this invention, it is excellent in color tone and transparency, and can be used for various uses.

Hereinafter, the present invention will be described in detail.
The polyester resin in the polyester resin composition of the present invention requires that 50 to 98 mol% of the acid component is terephthalic acid and 2 to 20 mol% is p-hydroxyethoxybenzoic acid. That is, terephthalic acid is the main component and p-hydroxyethoxybenzoic acid is the copolymerization component. In particular, the copolymerization amount of p-hydroxyethoxybenzoic acid is preferably 3 to 18 mol%, and more preferably 4 to 15 mol%. By copolymerizing p-hydroxyethoxybenzoic acid, the crystallization speed of the polyester resin can be adjusted to those suitable for direct blow molding, and whitening due to crystallization during direct blow molding can be prevented.

  When the copolymerization amount of p-hydroxyethoxybenzoic acid is less than 2 mol%, the resin composition has a high crystallization speed. Therefore, when direct blow molding is performed, the molded product crystallizes and whitens and becomes transparent. It becomes inferior. On the other hand, if the copolymerization amount of p-hydroxyethoxybenzoic acid exceeds 20 mol%, the resin composition becomes amorphous, so that drying at a high temperature and solid-phase polymerization are likely to be difficult, or high temperature drying is performed. Blocking tends to occur at times and in the solid phase polymerization process.

  Examples of dicarboxylic acid components other than terephthalic acid and p-hydroxyethoxybenzoic acid include phthalic acid, isophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, sebacic acid, and dimer acid. Two or more of these may be used in combination, and ester-forming derivatives of these acids may be used.

  The proportion of terephthalic acid in the acid component is 50 to 98 mol%, and among them, the proportion of terephthalic acid is preferably 60 to 90 mol%, and more preferably 85 to 96 mol%. When the proportion of terephthalic acid is less than 50 mol%, the crystallinity of the resin composition is lowered and it tends to be amorphous. On the other hand, when the proportion of terephthalic acid exceeds 98 mol%, the copolymerization amount of p-hydroxyethoxybenzoic acid decreases, so that it is difficult to adjust the crystallization speed, and whitening due to crystallization during blow molding is prevented. The effect is poor.

  On the other hand, 80 mol% or more of the glycol component in the polyester resin is ethylene glycol, and among them, 85 mol% or more of the glycol component is preferably ethylene glycol. Examples of glycol components other than ethylene glycol include neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexamethylenediol, diethylene glycol, 1,4-cyclohexanedimethanol, dimer diol, An ethylene oxide adduct of bisphenol A or bisphenol S can be used.

  If the proportion of ethylene glycol in the glycol component is less than 80 mol%, the crystallinity of the resin composition is lowered and it tends to be amorphous, which is not preferable.

The resin composition of the present invention contains 0.1 to 1 tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane in the polyester resin as described above. 0.0% by mass, and 0.2 to 0.8% by mass is particularly preferable.
Tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane is preferably added during the polymerization reaction step of the polyester resin. By adding it during the polymerization reaction step, a part of the compound is copolymerized in the polyester resin. As a result, entanglement of molecular chains occurs in the polyester resin, and it is assumed that a state similar to cross-linking occurs, and the melt viscosity of the polyester resin increases and the swell ratio (SW) satisfies the range defined in the present invention. To be.

  Further, by containing tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane in the resin composition of the present invention, the thermal stability of the resin composition is improved. The resulting molded product is improved in color tone and transparency.

  When the content of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane is less than 0.1% by mass, the resin composition in which the molecular chain is entangled as described above. Therefore, the swell ratio of the resin composition is low, and the parison draw-down during direct blow molding cannot be prevented. It also becomes difficult to increase the melt viscosity of the resin composition. Furthermore, the thermal stability of the resin composition is not improved, and the resulting molded product is inferior in heat resistance, color tone and transparency.

  On the other hand, if the content exceeds 1.0% by mass, the swell ratio of the resin composition increases, the expansion of the resin composition at the exit of the extrusion die during molding becomes too large, and the surface of the resulting molded product becomes rough. The glossiness is impaired. Further, the melt viscosity of the resin composition becomes too high, and it is necessary to increase the molding temperature during molding, resulting in poor color tone of the molded product. Furthermore, the effect of improving the thermal stability is saturated and disadvantageous in terms of cost.

Next, in the polyester resin composition of the present invention, the germanium compound is contained in an amount of 5 × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol with respect to 1 mol of the acid component of the polyester resin. It is preferable that 10 < ^-5 > mol-2.0 * 10 < ^-4 > mol is contained.
The germanium compound is used as a polymerization catalyst when obtaining a polyester resin, and if the content of the germanium compound is less than 5 × 10 ⁻⁵ mol, a polyester resin having a target degree of polymerization cannot be obtained, or In the polymerization reaction, the polymerization time becomes longer, and as a result, the color tone of the resulting polyester resin is deteriorated. On the other hand, even if it exceeds 3.0 × 10 ⁻⁴ mol, the effect as a polymerization catalyst is saturated and disadvantageous in cost.

  Examples of the germanium compound include germanium dioxide, germanium tetrachloride, germanium tetraethoxide, and the like, and germanium dioxide is preferred from the viewpoint of polymerization catalyst activity, physical properties of the resulting polyester resin, and cost.

Furthermore, it is preferable that the polyester resin composition of the present invention contains a cobalt compound and an alkali metal compound. By containing both compounds, it can be set as the resin composition which was excellent in color tone, and it becomes possible to obtain the direct blow molding goods which were excellent in color tone. Cobalt compound is preferably is 1 × ^{10 -5} mol to 2.0 × ^{10 -4} mol content based on the acid component to 1 mole of the polyester resin, among others 3 × ^{10 -5} mol to 1.0 × 10 ^- It is preferable that ⁴ mol is contained.
When the content of the cobalt compound is less than 1 × 10 ⁻⁵ mol, the effect of improving the color tone of the polyester resin composition is small. On the other hand, when the content exceeds 2.0 × 10 ⁻⁴ mol, the transparency of the polyester deteriorates, This is not preferable because the stability over time also deteriorates.
The cobalt compound is preferably used as a polymerization catalyst, and specific examples include cobalt acetate, cobalt formate, cobalt oxide, and cobalt chloride. Of these, cobalt acetate is preferred from the viewpoints of polymerization catalyst activity and physical properties and cost of the resulting polyester resin composition.

The alkali metal compound is preferably contained in an amount of 1 × 10 ⁻⁴ mol to 1.0 × 10 ⁻³ mol with respect to 1 mol of the acid component of the polyester resin, and in particular, 2 × 10 ⁻⁴ mol to 8 × 10. It is preferable that ^-4 mol is contained.
When the content of the alkali metal compound is less than 1 × 10 ⁻⁴ mol, the effect of improving the color tone of the polyester resin composition is small. On the other hand, when it exceeds 1.0 × 10 ⁻³ , there are many fine particles insoluble in the polyester. Therefore, the transparency of the polyester resin composition tends to deteriorate.
The alkali metal compound is preferably used as a polymerization catalyst. Specifically, lithium acetate, sodium acetate, potassium acetate, lithium benzoate, sodium benzoate, potassium benzoate, lithium dihydrogen phosphate, dihydrogen phosphate Sodium, potassium dihydrogen phosphate, lithium pyrophosphate, sodium pyrophosphate, potassium pyrophosphate, lithium tripolyphosphate, sodium tripolyphosphate, potassium tripolyphosphate, lithium hydride, sodium hydride, potassium hydride, lithium methoxide, sodium methoxide Side, potassium methoxide, lithium ethoxide, sodium ethoxide, potassium ethoxide and the like. Among these, lithium acetate, sodium acetate, and potassium acetate are preferable from the viewpoint of physical properties and cost of the obtained polyester resin composition.

  And the polyester resin composition of this invention needs that intrinsic viscosity (IV) is 0.8-1.5, and it is preferable that it is 1.0-1.3 especially. The intrinsic viscosity (IV) is measured at a temperature of 20 ° C. using a mixture of equal mass of phenol and ethane tetrachloride as a solvent.

  When the intrinsic viscosity is less than 0.8, since the viscosity of the resin composition is low, the drawdown of the parison becomes large during direct blow molding, and molding becomes difficult. On the other hand, when the intrinsic viscosity exceeds 1.5, it is necessary to raise the molding temperature, and the color tone and transparency of the obtained molded product are deteriorated. Moreover, it is not preferable because the swell ratio tends to increase.

  The polyester resin composition of the present invention needs to have a swell ratio (SW) of 1.2 to 1.4, and preferably 1.22 to 1.35. The swell ratio (SW) in the present invention means the size of the die swell (indicating the flow state of the molten resin at the extrusion die outlet), and the larger the value, the larger the expansion at the extrusion die outlet. means. If this value is small, it means that the expansion at the exit of the extrusion die is small.

  As mentioned above, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane is used in order to make the swell ratio within the scope of the present invention. It is important to contain 1.0% by mass. That is, it cannot be achieved only that the intrinsic viscosity is within the above range, but entanglement of molecular chains occurs in the resin composition, and a state similar to crosslinking occurs, so that the swell ratio within the above range can be obtained. .

In addition, the measurement of the swell ratio (SW) in the present invention is performed by taking a photograph of the discharge portion of the molten resin when the polyester resin composition is extruded at an extrusion temperature of 260 ° C. using a direct blow molding machine. The maximum diameter of the molten resin strand extruded from the die is measured and calculated by the following formula.
Swell ratio (SW) = maximum diameter of molten resin strand / die inner diameter

  When the swell ratio is less than 1.2, the expansion at the exit of the extrusion die is reduced in direct blow molding, so that the moldability is deteriorated, and the resulting molded product has thickness unevenness, resulting in reduced quality. Become. On the other hand, if the swell ratio exceeds 1.4, the expansion at the exit of the extrusion die increases, so that the resin composition and the metal (mold) are rubbed at the exit of the extruder, and the resulting molded product has a surface. It becomes rough and inferior in gloss and transparency.

  Moreover, the polyester resin composition of this invention may contain the phosphorus compound for the purpose of the further color tone improvement and the thermal stabilization of polyester. From the viewpoint of cost and the color tone of the resulting polyester resin composition, phosphoric acid or phosphoric acid ester is preferable as the phosphorus compound.

  Next, the manufacturing method of the polyester resin composition of this invention is demonstrated. The polyester resin composition in the present invention is preferably obtained through an esterification reaction, a melt polymerization reaction, and a solid phase polymerization reaction step. It is difficult to obtain a polyester resin composition having a target intrinsic viscosity only by the esterification reaction and the melt polymerization reaction. Even if it is obtained, the reaction time of the melt polymerization reaction becomes long, and the resulting polyester resin composition has a poor color tone.

Specifically, for example, it can be produced by the following method.
Terephthalic acid or its ester-forming derivative as an acid component, ethylene glycol as a glycol component in a predetermined ratio are charged into an esterification reactor, and subjected to an esterification reaction at a temperature of 160 to 280 ° C. under pressure. Is transferred to a polymerization reactor, and a reaction solution of p-hydroxyethoxybenzoic acid and ethylene glycol, or a dispersion of p-hydroxyethoxybenzoic acid and ethylene glycol, a germanium compound as a polymerization catalyst, and a cobalt compound and an alkali metal as required. The compound, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, is added and is usually 240-290 ° C., preferably 250-280 ° C. under reduced pressure of 1 hPa or less. A melt polymerization reaction is performed at temperature. The intrinsic viscosity of the copolymerized polyester (prepolymer) obtained here is preferably in the range of 0.5 to 0.8.

  Subsequently, a polyester resin composition having a target intrinsic viscosity is obtained by performing a solid phase polymerization reaction using the prepolymer obtained by the melt polymerization reaction. In the solid phase polymerization, after prepolymer is dried and crystallized in advance, usually under reduced pressure or under an inert gas such as nitrogen, the temperature is 20 to 30 ° C. lower than the melting point of the polyester resin for 3 hours to The reaction is carried out in the reactor for 70 hours.

  As described above, the polyester resin composition of the present invention is particularly suitable for direct blow molding, but even if an injection molding or stretching method is adopted, it is a molded product excellent in color tone and transparency (injection). Molded bodies, sheets, films, etc.) can be obtained.

  Next, the direct blow molded article of the present invention is composed of the polyester resin composition of the present invention. The direct blow molded article of the present invention can be manufactured using a general-purpose direct blow molding machine, and the temperature of each part of the cylinder and the nozzle of the molding machine is preferably in the range of 240 to 290 ° C.

Next, the present invention will be specifically described using examples. The measurement and evaluation methods for various characteristic values in the examples are as follows.
(A) Intrinsic viscosity It was measured by the same method as described above.
(B) Copolymerization component copolymerization content, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane content The resulting resin composition was deuterated. Hexafluoroisopropanol and deuterated chloroform were dissolved in a mixed solvent having a volume ratio of 1/20, and 1H-NMR was measured with a LA-400 NMR apparatus manufactured by JEOL Ltd. From the integrated intensity of the proton peak, the copolymerization amount and content were determined.
(C) Content of Germanium Compound, Cobalt Compound, Alkali Metal Compound, and Antimony Compound The obtained resin composition was measured using an X-ray fluorescence analyzer 3270 manufactured by Rigaku Corporation.
(D) Swell ratio It measured by the method similar to the above.
(E) Formability The thickness of the body part of the obtained molded product (20 samples) is measured, and the thickness difference between the thickest part and the thinnest part is up to 0.10 mm. In the case where the number of samples is 18 or more, it was evaluated as “◯”, and in the case where the number of accepted samples was 17 or less, it was evaluated as “x”. Even if the difference between the thickness of the thickest part and the thinnest part is 0.10 mm, crystallization occurs in the molded container, and the container is whitened or the container surface is rough. , Rejected (x).
(F) Color tone Sample pieces (20 pieces) were cut out from the obtained molded product, and the color tone of the sample pieces was measured using a color difference meter ND-Σ80 type manufactured by Nippon Denshoku Industries Co., Ltd. The color tone was determined with a Hunter Lab colorimeter, the b value was measured, and the average value of n number 20 was obtained. A b value of 2.0 or less was determined to be good color tone.
(G) Haze Cut out from the obtained molded product to prepare sample pieces (20 pieces), turbidity was measured with a turbidimeter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: haze 0%), n number An average value of 20 was used. The smaller this value is, the better the transparency is, and if it is 5% or less, it is judged that the transparency is excellent.

Example 1
The esterification reactor is fed with a slurry of terephthalic acid (TPA) and ethylene glycol (EG) (TPA / EG molar ratio = 1 / 1.6) and reacted under the conditions of a temperature of 250 ° C. and a pressure of 50 hPa for esterification. A reaction product (number average degree of polymerization: 5) having a reaction rate of 95% was obtained.
In a separate esterification can, a slurry composed of p-hydroxyethoxybenzoic acid (EPOB) and ethylene glycol (EPOB / EG molar ratio = 1 / 3.1) was charged, and the esterification reaction was conducted at a temperature of 200 ° C. for 3 hours. The reaction solution of p-hydroxyethoxybenzoic acid and ethylene glycol was obtained.
55.5 parts by mass of a reaction product of TPA and EG are charged into a polymerization reactor, followed by 7.8 parts by mass of a reaction solution of p-hydroxyethoxybenzoic acid and ethylene glycol, and 0.008 parts by mass of germanium dioxide as a polymerization catalyst. , 0.12 parts by mass of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (Irganox-1010 manufactured by Ciba Specialty Inc.) were added respectively, and the reactor was After 60 minutes under reduced pressure, a melt polymerization reaction was carried out at a final pressure of 0.9 hPa and a temperature of 280 ° C. for 4 hours to obtain a copolymerized polyester prepolymer.
This prepolymer had an intrinsic viscosity of 0.72. This prepolymer was pre-dried at 150 ° C. for 5 hours, and then solid-phase polymerized in a nitrogen stream at 210 ° C. for 15 hours to obtain a polyester resin composition.
After drying using this polyester resin composition, it was molded using a direct blow molding machine when the extrusion temperature was 260 ° C., the parison diameter was 3 cm, and the length was 25 cm to obtain a 500 cc hollow container.

Examples 2-6, Comparative Examples 1-5
Table 1 shows the copolymerization amount of p-hydroxyethoxybenzoic acid, the content of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, and the content of germanium compound. The composition was changed so as to obtain a polyester resin composition in the same manner as in Example 1.
And the direct blow molding goods were obtained like Example 1 using the obtained resin composition.

Comparative Example 6
A polyester resin composition was obtained in the same manner as in Example 1 except that the solid phase polymerization reaction time was changed and the intrinsic viscosity was the value shown in Table 1.
And the direct blow molding goods were obtained like Example 1 using the obtained resin composition.

Example 7
In the same manner as in Example 1, a reaction product of TPA and EG and a reaction solution of EPOB and EG were obtained.
55.5 parts by mass of a reaction product of TPA and EG are charged into a polymerization reactor, followed by 7.8 parts by mass of a reaction solution of p-hydroxyethoxybenzoic acid and ethylene glycol, and 0.008 parts by mass of germanium dioxide as a polymerization catalyst. , 0.004 parts by mass of cobalt acetate (cobalt compound), 0.015 parts by mass of lithium acetate (alkali metal compound), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] 0.12 parts by mass of methane (Irganox-1010 manufactured by Ciba Specialties Co., Ltd.) was added respectively, and the reactor was decompressed, and after 60 minutes, a final polymerization pressure of 0.9 hPa and a temperature of 280 ° C. were performed for 4 hours, and a melt polymerization reaction was performed. A prepolymer of copolyester was obtained. This prepolymer had an intrinsic viscosity of 0.72. Then, this prepolymer was subjected to solid phase polymerization in the same manner as in Example 1 to obtain a polyester resin composition.
Using the obtained polyester resin composition, a direct blow molded article was obtained in the same manner as in Example 1.

Examples 8-18
Copolymerization amount of p-hydroxyethoxybenzoic acid, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane content, germanium compound content, cobalt compound content Example, except that the composition was changed so that the amount, type and content of the alkali metal compound were the values shown in Table 1, the solid phase polymerization reaction time was changed, and the intrinsic viscosity was the value shown in Table 1. In the same manner as in Example 7, a polyester resin composition was obtained.
And the direct blow molding goods were obtained like Example 7 using the obtained resin composition.

Comparative Example 7
A polyester resin composition was obtained in the same manner as in Example 1 except that an antimony compound was used as a polymerization catalyst and 0.018 parts by mass of antimony trioxide was added.
And the direct blow molding goods were obtained like Example 1 using the obtained resin composition.

  Table 1 shows the composition of the polyester resin compositions obtained in Examples 1 to 19 and Comparative Examples 1 to 7, the intrinsic viscosity, the swell ratio value, the evaluation of moldability, the color tone of the molded product, and the haze value.

  As is clear from Table 1, the polyester resin compositions obtained in Examples 1 to 19 had values of intrinsic viscosity and swell ratio within the ranges specified in the present invention, and were excellent in thermal stability. The direct blow molding could be performed with good operability without causing the problem of whitening due to crystallization. The obtained direct blow molded article (container) had a high evaluation of moldability, was not colored, had excellent color tone, and had good transparency. Among them, the polyester resin compositions obtained in Examples 7 to 19 further contained a cobalt compound and an alkali metal compound, and thus the b value was low and the color tone was excellent.

On the other hand, since the polyester resin composition obtained in Comparative Example 1 had a low copolymerization amount of p-hydroxyethoxybenzoic acid, when the direct blow molding was performed, the molded product was crystallized and whitened, resulting in poor transparency. It became. In Comparative Example 2, since the copolymerization amount of p-hydroxyethoxybenzoic acid was large, fusion occurred during solid phase polymerization, and polyester could not be obtained. Since the polyester resin composition obtained in Comparative Example 3 had a low content of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, The stability was poor and the molded product was inferior in color tone. Further, since the swell ratio was small and the drawdown of the parison during molding was large, the molded product had a large difference between the thickest part and the thinnest part, and the moldability was poor. Since the polyester resin composition obtained in Comparative Example 4 contained a large amount of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, the swell ratio increased. The expansion of the resin composition at the exit of the extrusion die during molding was too large, and the resulting molded product was rough and the transparency was impaired. The polyester resin composition obtained in Comparative Example 5 had a low intrinsic viscosity because the content of the germanium compound was small, and direct blow molding was not possible. Since the polyester resin composition obtained in Comparative Example 6 had a longer solid phase polymerization reaction time, both the intrinsic viscosity and the swell ratio were too high. For this reason, it is necessary to increase the molding temperature at the time of direct blow molding, and the expansion of the resin composition becomes too large at the time of molding, and the obtained molded product has a poor color tone, the surface is rough, and the transparency is inferior. became. The polyester resin composition obtained in Comparative Example 7 was inferior in both color tone and transparency of the molded product because an antimony compound was used as a polymerization catalyst.

Claims (3)

In a polyester resin in which 50 to 98 mol% of the acid component constituting the polyester is terephthalic acid, 2 to 20 mol% is p-hydroxyethoxybenzoic acid, and 80 mol% or more of the glycol component is ethylene glycol, tetrakis [ Methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] containing 0.1 to 1.0% by mass of methane, and 5% of the germanium compound with respect to 1 mol of the acid component of the polyester resin. It is characterized by containing × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol, intrinsic viscosity (IV) of 0.8 to 1.5, and swell ratio (SW) of 1.2 to 1.4. A polyester resin composition. Furthermore, it contains a cobalt compound and an alkali metal compound, contains 1 × 10 ⁻⁵ mol to 2.0 × 10 ⁻⁴ mol of the cobalt compound with respect to 1 mol of the acid component of the polyester resin, and converts the alkali metal compound into the polyester. The polyester resin composition according to claim 1, comprising 1 × 10 ⁻⁴ mol to 1.0 × 10 ⁻³ mol per 1 mol of the acid component of the resin. A direct blow molded article comprising the polyester resin composition according to claim 1 or 2.