JP2013136723A - Polyester resin composition and direct blow molded product thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin composition capable of efficiently producing a direct blow molded product excellent in color tone and transparency and further excellent in thermal stability without causing troubles such as draw down or crystallization during direct blow molding.SOLUTION: The polyester resin composition includes a polyester resin comprising an acidic component ≥70 mol% of which is terephthalic acid, a glycol component 60-95 mol% of which is ethylene glycol, an ethylene oxide adduct 3-18 mol% of which is bisphenol A; 0.1-1.0 mass% of tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane; and 5×10mol to 3.0×10mol of a germanium compound for one mol of the acidic component in the polyester resin, wherein the intrinsic viscosity (IV) is 0.8-1.5 and the swell ratio (SW) is 1.2-1.4.

Description

  The present invention relates to a polyester resin composition capable of obtaining a direct blow molded product 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 at the time of blow molding, and blow molding cannot be performed. Further, since crystallization is likely to occur at the time of blow, transparency is insufficient even if molding is possible. There was a problem.

  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 inferior, and the resulting molding is obtained. 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) Polyester in which 70 mol% or more of the acid component constituting the polyester is terephthalic acid, 60 to 95 mol% of the glycol component is ethylene glycol, and 3 to 18 mol% is an ethylene oxide adduct of bisphenol A The resin contains 0.1 to 1.0% by mass of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, and the germanium compound is an acid of the polyester resin. 5 × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol per mol of component, 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 claim 1, wherein the compound is contained in an amount of 1.0 × 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 resin having a specific composition, contains a specific compound, and has an intrinsic viscosity and swell ratio suitable for direct blow molding. There is no problem of drawdown or crystallization at the time of molding, and it is excellent in thermal stability, and a direct blow molded product excellent in color tone and transparency can be obtained with good productivity (good moldability).
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.
In the polyester resin of the present invention, 70 mol% or more of the acid component is terephthalic acid, and among them, 85 mol% or more is preferably terephthalic acid. When the proportion of terephthalic acid is less than 70 mol%, the resulting polyester resin has poor crystallinity and heat resistance.
Examples of acid components other than terephthalic acid contained in the polyester resin include phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, dimer acid, and the like. May be used in combination of two or more, and ester-forming derivatives of these acids may be used.

On the other hand, in the glycol component, 60 to 95 mol% of the glycol component is ethylene glycol, and 3 to 18 mol% is an ethylene oxide adduct of bisphenol A. That is, the main component is ethylene glycol and the ethylene oxide adduct of bisphenol A is a copolymer component.
The content (copolymerization amount) of the ethylene oxide adduct of bisphenol A is 3 to 18 mol%, preferably 4 to 12 mol% of the total glycol component. By copolymerizing an appropriate amount of the bisphenol A ethylene oxide adduct, the crystallization speed of the polyester resin can be adjusted to be suitable for direct blow molding, and whitening due to crystallization during direct blow molding can be prevented. .

  When the content of the ethylene oxide adduct of bisphenol A is less than 3 mol%, the resin composition has a high crystallization rate, and the resulting direct blow molded product is crystallized and whitened. On the other hand, when it exceeds 18 mol%, it becomes amorphous, and drying at high temperature and solid phase polymerization become difficult. Alternatively, blocking is likely to occur during high temperature drying or in a solid phase polymerization process, which is not preferable.

Ethylene glycol is 60 to 95 mol% of the total glycol component, and preferably 70 to 90 mol%. When the content of ethylene glycol is less than 60 mol%, the resulting polyester resin has poor crystallinity and heat resistance. On the other hand, if it exceeds 95 mol%, the proportion of the ethylene oxide adduct of bisphenol A decreases, and it becomes difficult to adjust the crystallization speed, and the effect of preventing whitening due to crystallization during blow molding becomes poor.
The total amount of the ethylene oxide adduct of ethylene glycol and bisphenol A is preferably 70 mol% or more, more preferably 80 mol% or more of the total glycol component.

  Examples of the diol component other than the ethylene oxide adduct of ethylene glycol and bisphenol A include, for example, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexamethylenediol, 1,4 -Cyclohexanedimethanol, diethylene glycol, dimer diol, ethylene oxide adduct of bisphenol S, and the like can be used.

In the polyester resin composition of the present invention, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane is added in 0.1 to 0.1 in the above polyester resin. 1.0 mass% is contained, and it is preferable to contain 0.2-0.8 mass% especially.
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 preferably used as a polymerization catalyst when obtaining a polyester resin. By using a germanium compound, a polyester resin having a target degree of polymerization can be obtained, and at the same time, a polyester resin having excellent color tone and transparency can be obtained.
When 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 the polymerization time becomes longer in the polymerization reaction. Transparency deteriorates. 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 8.0. It is preferable that ^x10-4 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. As a result, 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 an ester-forming derivative thereof as an acid component and ethylene glycol as a glycol component are charged into an esterification reactor at a predetermined ratio, and an esterification reaction is performed at a temperature of 160 to 280 ° C. under pressure. Thereafter, the reaction product is transferred to a polymerization reactor, and an ethylene oxide adduct of bisphenol A, a germanium compound as a polymerization catalyst, a cobalt compound and an alkali metal compound, tetrakis [methylene-3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate] methane is added, and a melt polymerization reaction is usually carried out at a temperature of 240 to 290 ° C., preferably 250 to 280 ° C. under a reduced pressure of 1 hPa or less. The intrinsic viscosity of the copolymerized polyester resin (prepolymer) obtained here is preferably in the range of 0.5 to 0.8.

  Alternatively, an ethylene oxide adduct of terephthalic acid, ethylene glycol and bisphenol A is charged into an esterification reactor at a predetermined ratio, pressurized, and subjected to esterification reaction at a predetermined temperature, and then the reaction product is polymerized into a reactor. And a germanium compound as a polymerization catalyst, a cobalt compound and an alkali metal compound, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, if necessary, The melt polymerization reaction is performed at a predetermined degree of vacuum and reaction temperature.

  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 for 50 hours in the reactor.

  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 5 g of the obtained resin composition is put in a metal crucible, and 2 ml of concentrated sulfuric acid is added and ashed in an electric furnace. The ash content in the crucible was dissolved in a dilute hydrochloric acid aqueous solution and quantified with an ICP analyzer ARIS-AP manufactured by Nippon Jarrell Ash.
(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.
(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.
60.3 parts by mass of a reaction product of TPA and EG were charged into a polymerization reactor, followed by 7.6 parts by mass of an ethylene oxide adduct of bisphenol A, 0.008 parts by mass of germanium dioxide as a polymerization catalyst, tetrakis [methylene- 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (Irganox-1010 manufactured by Ciba Specialties) 0.12 parts by mass was added respectively, and the reactor was decompressed for 60 minutes. Thereafter, a melt polymerization reaction was performed at a final pressure of 0.9 hPa and a temperature of 280 ° C. for 4 hours to obtain a prepolymer of a copolyester resin.
The intrinsic viscosity of this prepolymer was 0.74. 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 at an extrusion temperature of 260 ° C., a parison diameter of 3 cm and a length of 25 cm, and a 500 cc hollow container (direct blow molded product) )

Examples 2-6, Comparative Examples 1-5
Table 1 shows the copolymerization amount of the ethylene oxide adduct of bisphenol A, the content of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, and the content of the germanium compound. The polyester resin composition was obtained in the same manner as in Example 1 except that the composition was changed so as to be a value, the solid phase polymerization reaction time was changed, and the intrinsic viscosity was the value shown in Table 1. It was.
And the hollow container (direct blow molded product) was 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-state polymerization reaction time was changed and the intrinsic viscosity was the value shown in Table 1.
And the hollow container (direct blow molded product) was 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 was obtained. Then, 55.5 parts by mass of the reaction product of TPA and EG was charged into the polymerization reactor, followed by 7.6 parts by mass of bisphenol A ethylene oxide adduct, 0.008 parts by mass of germanium dioxide as a polymerization catalyst, and cobalt acetate. (Cobalt compound) 0.004 parts by mass, lithium acetate (alkali metal compound) 0.015 parts by mass, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (Ciba 0.12 parts by mass of Irganox-1010 manufactured by Specialties Co., Ltd. were added, respectively, and the reactor was decompressed, and after 60 minutes, a melt polymerization reaction was performed for 4 hours at a final pressure of 0.9 hPa and a temperature of 280 ° C. A resin prepolymer 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 hollow container (direct blow molded article) was obtained in the same manner as in Example 1.

Examples 8-19
Copolymerization amount of ethylene oxide adduct of bisphenol A, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane content, germanium compound content, cobalt compound content A polyester resin composition was obtained in the same manner as in Example 7 except that the composition was changed so that the content, the type and content of the alkali metal compound were the values shown in Table 1.
And the hollow container (direct blow molded product) was obtained like Example 1 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 instead of germanium dioxide as a polymerization catalyst and 0.018 parts by mass of antimony trioxide was added.
And the hollow container (direct blow molded product) was 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 specific amount of 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 small copolymerization amount of the ethylene oxide adduct of bisphenol A, the molded product crystallized and whitened when direct blow molding was performed, and the transparency was poor. It became a thing. In Comparative Example 2, since the copolymerization amount of the bisphenol A ethylene oxide adduct was large, fusion occurred during solid phase polymerization, and a polyester resin could not be obtained. The polyester resin composition obtained in Comparative Example 3 was poor in thermal stability because it contained less tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane. The obtained 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. Since the polyester resin composition obtained in Comparative Example 7 did not use a germanium compound as a polymerization catalyst but used an antimony compound, the resulting molded product was inferior in both color tone and transparency.

Claims (3)

In a polyester resin in which 70 mol% or more of the acid component constituting the polyester is terephthalic acid, 60 to 95 mol% of the glycol component is ethylene glycol, and 3 to 18 mol% is an ethylene oxide adduct of bisphenol A. 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. 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 1.0 × 10 ⁻⁴ mol to 1.0 × 10 ⁻³ mol per mol of the acid component of the resin. A direct blow molded article comprising the polyester resin composition according to claim 1 or 2.