JP2016008256A - Polyester resin composition and blow molded article composed of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin composition capable of obtaining a blow molded article having excellent heat stability and transparency with good productivity without causing a problem of whitening by draw down or crystallization during blow molding, and to provide a polyester resin composition having excellent recyclability so that an edge material of the polyester resin once generated during blow molding can be molded favorably when used for blow molding again.SOLUTION: There is provided a polyester resin composition which is a resin composition mainly comprising ethylene terephthalate as a main repeating unit and containing 2 to 20 mol% of p-hydroxyethoxy benzoic acid as a copolymerization component, in which the intrinsic viscosity is 0.7 to 1.4, the ratio between the weight average molecular weight and the number average molecular weight (weight average molecular weight/number average molecular weight) is 1.9 to 2.5 and the carboxyl terminal group concentration is 20 equivalent/t or less.

Description

  The present invention relates to a polyester resin composition capable of obtaining a blow molded product excellent in 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. 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 inferior, and the resulting molding is obtained. The product had a problem that it was inferior in color tone and transparency.

  In direct blow molding, a cylindrical parison extruded through a die from an extruder is clamped and clamped by a vertically split split mold and placed at the bottom of this split mold cavity. The lower part of the molten resin is cut at the pinch-off part, which is the blade part, and heat-sealed and sealed, and the upper part of the cylindrical molten resin is cut with a parison cutter at the upper part to form a bottomed cylindrical parison, Since blow air is blown into the parison by an air nozzle inserted from the top of the mold and blow molding is performed, a cut resin end material is generated. The mill ends are dried and crystallized, and then recycled to the raw material resin chips as recycled materials and recycled for direct blow molding to reduce costs. However, since the intrinsic viscosity of the mill ends is lowered due to the heat history during molding, there is a problem that if the mill ends are dry blended and recycled, drawdown occurs during molding and molding cannot be performed.

Japanese Patent No. 3173755

  The present invention solves the above-mentioned problems, does not cause problems of whitening due to drawdown or crystallization at the time of blow molding, has excellent thermal stability, and has excellent productivity for blow molded products with excellent transparency. It is intended to provide a polyester resin composition that can be obtained, and it is possible to mold well even once it has been used as an end material in blow molding. An object of the present invention is to provide an excellent polyester resin composition. Furthermore, the present invention intends to provide a blow molded article formed by using the polyester resin composition of the present invention.

The inventors of the present invention have arrived at the present invention as a result of intensive studies in order to solve the above problems.
That is, the gist of the present invention is the following (1) to (3).
(1) A resin composition mainly comprising a polyester resin containing ethylene terephthalate as a main repeating unit and 2 to 20 mol% of p-hydroxyethoxybenzoic acid as a copolymerization component,
The intrinsic viscosity is 0.7 to 1.4, the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) is 1.9 to 2.5, and the carboxyl end group concentration is 20 equivalents. / T or less, The polyester resin composition characterized by the above-mentioned.
(2) The polyester resin composition according to (1), wherein the content of the cyclic trimer is 0.6% by mass or less.
(3) A blow molded article formed by using 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, the intrinsic viscosity suitable for blow molding, the ratio of weight average molecular weight to number average molecular weight (weight average molecular weight / number average molecular weight), carboxyl end group Since it satisfies the concentration, it has excellent thermal stability, and can produce a blow-molded product with excellent transparency without causing problems of whitening due to drawdown or crystallization during blow molding. . In addition, the polyester resin composition of the present invention can obtain a blow molded product excellent in transparency with high productivity even if it is once used in blow molding and used again for blow molding. Is also excellent.
And since the blow molded product of this invention is formed using the polyester resin composition of this invention, it is excellent in transparency and can be used for various uses.

Hereinafter, the present invention will be described in detail.
The polyester resin composition of the present invention is suitable for blow molding. Among them, a melt-plasticized resin is extruded through a die orifice to form a cylindrical parison, which is sandwiched between molds and air is put inside. It is suitable for a direct blow molding method for blowing or a stretch blow molding method in which a parison is formed by injection molding and stretch blow molded.

The polyester resin composition in the present invention is mainly composed of a polyester resin containing ethylene terephthalate as a main repeating unit and 2 to 20 mol% of p-hydroxyethoxybenzoic acid as a copolymerization component.
The polyester resin in the present invention has a copolymerization amount of p-hydroxyethoxybenzoic acid of 2 to 20 mol%, preferably 3 to 18 mol%, more preferably 4 to 15 mol%. . By copolymerizing p-hydroxyethoxybenzoic acid, the crystallization speed of the polyester resin can be adjusted to be suitable for blow molding, and whitening due to crystallization during blow molding can be prevented.

  If the copolymerization amount of p-hydroxyethoxybenzoic acid is less than 2 mol%, the resin will have a high crystallization speed, so that the molded product will crystallize and whiten when blow molded, resulting in poor transparency. It will be a thing. On the other hand, if the copolymerization amount of p-hydroxyethoxybenzoic acid exceeds 20 mol%, the resin becomes amorphous, so that drying at a high temperature and solid phase polymerization are likely to be difficult, Blocking is likely to occur in the solid phase polymerization process.

  In addition, it is preferable that 60 mol% or more of an acid component is a terephthalic acid, and it is preferable that the ratio of a terephthalic acid is 70 mol% or more, Furthermore, it is preferable that it is 80 mol% or more. When the proportion of terephthalic acid is less than 60 mol%, the crystallinity of the resin is lowered and the resin tends to be amorphous.

  Examples of dicarboxylic acid components other than terephthalic acid and p-hydroxyethoxybenzoic acid include phthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, dimer acid, and the like. Often, ester-forming derivatives of these acids may be used.

  On the other hand, the glycol component in the polyester resin is preferably 80 mol% or more of ethylene glycol, and more preferably 85 mol% or more of 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 resin crystallinity is lowered and the resin tends to be amorphous, which is not preferable.

  The polyester resin composition of the present invention has the above-described polyester resin as a main component and satisfies the characteristic values described in detail below. In order to achieve these characteristic values, it is preferable to contain an additive such as an antioxidant as described later. The content of the polyester resin in the polyester resin composition is preferably 90% by mass or more, and more preferably 95% by mass or more.

  The polyester resin composition of the present invention needs to have an intrinsic viscosity (IV) of 0.7 to 1.4, especially 0.9 to 1.4 when used for direct blow molding. Preferably there is. 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 0.7, since the viscosity of the resin is low, the drawdown of the parison becomes large at the time of blow molding, and the molding itself becomes difficult. In particular, during direct blow molding, the parison drawdown becomes significant, making molding difficult. On the other hand, when the intrinsic viscosity exceeds 1.4, it is necessary to raise the molding temperature, and the color tone and transparency of the obtained molded product are deteriorated. Moreover, since the thermal decomposition of the resin is promoted by increasing the molding temperature, the drawdown of the parison becomes large and molding becomes difficult, and the obtained molded product has uneven thickness. Furthermore, if the milled material is used again as a recycled material for blow molding, the resin is likely to be thermally decomposed during blow molding, making stable production difficult, and the resulting molded product has uneven thickness.

  The polyester resin composition of the present invention has a ratio of weight average molecular weight to number average molecular weight (weight average molecular weight / number average molecular weight) of 1.9 to 2.5, and a carboxyl end group concentration of 20 equivalents / It is particularly important to satisfy both of being t or less. When the ratio of the weight average molecular weight to the number average molecular weight is within the above range, the composition has a viscosity suitable for blow molding. However, even if the ratio of the weight average molecular weight to the number average molecular weight is within the above range before molding, if the resin is thermally decomposed by heat treatment during blow molding, drawdown occurs during molding, making molding difficult Even if a molded product is obtained, thickness unevenness occurs. Therefore, in order to prevent the thermal decomposition of the resin due to the heat treatment at the time of molding, the carboxyl end group concentration needs to be 20 equivalent / t or less.

First, the polyester resin composition of the present invention is required to have a ratio of weight average molecular weight to number average molecular weight (weight average molecular weight / number average molecular weight) of 1.9 to 2.5, among which 2.0 to 2.4 is preferable.
When the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) is less than 1.9, the molecular chain is entangled in the resin and the crosslink density is insufficient. It cannot be assumed. For this reason, the drawdown of a parison becomes large at the time of blow molding, and molding becomes difficult, or the obtained molded product has uneven thickness.

  On the other hand, when the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) exceeds 2.5, the viscosity is high, and it is necessary to increase the molding temperature. Color tone and transparency deteriorate. Moreover, since the thermal decomposition of the resin is promoted by increasing the molding temperature, the drawdown of the parison becomes large and molding becomes difficult, and the obtained molded product has uneven thickness. Furthermore, if the milled material is used again as a recycled material for blow molding, the resin is likely to be thermally decomposed during blow molding, making stable production difficult, and the resulting molded product has uneven thickness.

  In addition, although the means which makes the ratio of a weight average molecular weight and a number average molecular weight the thing of the said range is not limited, The method of adding the hindered phenolic antioxidant mentioned later at the time of the polymerization reaction of a polyester resin, and below-mentioned And adding a hindered phenol-based antioxidant to the polyester resin by melt kneading.

  Further, the polyester resin composition of the present invention needs to have a carboxyl end group concentration of 20 equivalent / t or less, preferably 18 equivalent / t or less. By setting the carboxyl end group concentration of the polyester resin composition to 20 equivalent / t or less, thermal decomposition of the resin does not occur during blow molding, and stable molding becomes possible. In addition, the recyclability is excellent.

  When the carboxyl end group concentration exceeds 20 equivalents / t, even if the intrinsic viscosity of the resin composition or the ratio of the weight average molecular weight to the number average molecular weight is in the above range, Thermal decomposition of the resin occurs due to the heat treatment, which increases the drawdown of the parison, making it difficult to mold, and resulting molded products having uneven thickness.

  Further, since the obtained molded product has an increased carboxyl end group concentration, the end material generated during molding also has a high carboxyl end group concentration. For this reason, when the end material is subjected to blow molding again as a recycled material, thermal decomposition of the resin occurs at the time of blow molding, and stable production becomes difficult, and the resulting molded product has uneven thickness.

Furthermore, the polyester resin composition of the present invention preferably has a cyclic trimer content of 0.6% by mass or less, and more preferably 0.5% by mass or less. By using a polyester resin composition having a cyclic trimer content of 0.6% by mass or less for molding, improvement of contamination of molds and the like is observed. If the content of the cyclic trimer exceeds 0.6% by mass, it adheres to and contaminates devices such as molds and nozzles during molding. Since these contaminations cause surface roughness and whitening of the molded product, it is necessary to frequently clean the mold and nozzle.
In addition, in order to make the carboxyl terminal group concentration of the polyester resin composition 20 equivalent / t or less, or to make the content of the cyclic trimer 0.6 mass% or less, after the melt polymerization reaction for obtaining the polyester resin, This is possible by performing a solid phase polymerization reaction under specific conditions.

  And it is preferable that antioxidant is added in the polyester resin composition of this invention. Among them, it is preferable that the hindered phenol-based antioxidant is added so as to be 0.01 to 0.5% by mass in the polyester resin composition. By adding an appropriate amount of a hindered phenol antioxidant, it has an effect of suppressing thermal decomposition of the phthalic acid component. Further, the hindered phenol antioxidant preferably contains two or more hindered phenol groups in the molecule. When these antioxidants are added during the polymerization reaction step, a part of the compound is copolymerized in the polyester resin and incorporated in the molecular chain of the polyester, so that the entanglement of the molecular chain and the cross-linked structure are reduced. And the viscosity of the polyester resin composition becomes high. As a result, the ratio between the weight average molecular weight and the number average molecular weight can be within the above range.

  If the hindered phenolic antioxidant in the polyester resin composition is less than 0.01% by mass, it is difficult to achieve the above effects. On the other hand, if it exceeds 0.5 mass%, the viscosity becomes high, and the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) often exceeds 2.5, and the color tone of the obtained molded product And transparency tends to deteriorate. Moreover, recyclability is also reduced.

  Examples of hindered phenol antioxidants include 2,6-di-t-butyl-4-methylphenol and n-octadecyl-3- (3 ′, 5′-di-t-butyl-4 ′. -Hydroxyphenyl) propionate, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanate Nurate, 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol), triethylene glycol-bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate], 3, 9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1'-dimethylethyl}- , 4,8,10-tetraoxaspiro [5,5] undecane, etc. are used, but tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) is effective and cost-effective. ) Propionate] methane is preferred.

  Further, in the polyester resin composition of the present invention, in addition to the above-described antioxidants, examples of coloring inhibitors include phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite. Phosphorus compounds such as trimethyl phosphate, tridecyl phosphate and triphenyl phosphate can be used, and these phosphorus compounds may be used alone or in combination of two or more. In addition, additives such as cobalt compounds such as cobalt acetate, manganese compounds such as manganese acetate, anthraquinone dye compounds, and copper phthalocyanine compounds may be contained in order to suppress coloring due to thermal decomposition of the polyester resin.

The polyester resin composition of the present invention may contain a foaming agent as shown below, and the blow molded product of the present invention may be made into a foam blow molded product by foam blow molding.
Examples of the foaming agent include pyrolysis-type organic compounds containing decomposable groups such as azo, N-nitroso, heterocyclic nitrogen and sulfonyl hydrazide groups, and inorganic compounds such as ammonium carbonate and sodium hydrogen carbonate. Can be mentioned. Specific examples thereof include azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, diazoaminobenzene, dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitrosotephthalamide, benzenesulfonyl Hydrazide, 4,4′-oxy-bis (benzenesulfonyl) hydrazide, diphenylsulfone-3,3′-disulfonylhydrazide, 4-toluenesulfonyl hydrazide, 4,4′-oxy-bis (benzenesulfonyl) semicarbazide, 4- Examples include toluenesulfonyl semicarbazide, barium azodicarboxylate, 5-phenyltetrazole, trihydrazinotriazine, 4-toluenesulfonyl azide, 4,4′-diphenyldisulfonyl azide, and the like.

  In addition, as the foaming agent, gaseous materials such as gaseous fluorocarbon, nitrogen, carbon dioxide, air, helium and argon, and liquid materials at ordinary temperatures such as liquid fluorocarbon and pentane can be used.

  The polyester resin composition of the present invention can also be used by mixing (blending) with other thermoplastic resins and polyester resins containing other copolymerization components. And the molded object obtained using the resin composition mixed in this way may be able to improve impact resistance.

  Next, the manufacturing method of the polyester resin composition of this invention is demonstrated. The polyester resin in the present invention is preferably obtained through an esterification reaction, a melt polymerization reaction and a solid phase polymerization reaction step. Only by the esterification reaction and the melt polymerization reaction, it becomes difficult to obtain a polyester resin having a target intrinsic viscosity. Even if it is obtained, the reaction time of the melt polymerization reaction becomes longer, and the resulting polyester resin has a poor color tone. And the polyester resin composition of this invention can be obtained by making the process and conditions in a solid-phase polymerization reaction into a specific thing.

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. After this, the reaction product 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 polycondensation catalyst, and if necessary, antioxidant Additives such as a colorant and an anti-coloring agent are 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 (prepolymer) obtained here is preferably in the range of 0.5 to 0.8.

As the polycondensation catalyst, one or more known compounds generally used for PET, for example, germanium, antimony, titanium, and cobalt compounds can be used, but germanium or antimony compounds are preferably used. Further, when the transparency of the resulting polyester resin is very important, it is preferable to use a germanium compound. Examples of germanium or antimony compounds include oxides, inorganic acid salts, organic acid salts, halides, and sulfides thereof. These polycondensation catalysts are used in the range of 5 × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol, particularly 6 × 10 ⁻⁵ mol to 2.0 × 10, with respect to 1 mol of the acid component of the polyester resin to be produced. It is preferably used in such an amount that it is within the range of ^-4 mol.

  Examples of the coloring inhibitor include phosphorus compounds such as phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, tridecyl phosphate, and triphenyl phosphate. Further, cobalt compounds such as cobalt acetate, manganese compounds such as manganese acetate, anthraquinone dye compounds, and copper phthalocyanine compounds may be used.

  Subsequently, the prepolymer obtained by the above-described melt polymerization reaction is used as a chip having an arbitrary shape such as a die or a column, and the polyester chip is continuously supplied to a crystallization apparatus and crystallized at a temperature of 150 to 180 ° C. After being made into a solid, it is supplied to a dryer, dried at a temperature of 180 ° C. or less for 4 to 10 hours, sent to a preheater and heated to the following solid phase polymerization temperature for 2 to 5 hours, and then solidified. A polyester resin composition having a target intrinsic viscosity is obtained by continuously supplying to a phase polymerization machine and performing a solid phase polymerization reaction. The solid phase polymerization is preferably performed under an inert gas such as nitrogen gas. The solid phase polymerization is usually preferably carried out at a temperature in the range of 170 to 230 ° C, more preferably in the range of 180 to 220 ° C. The polymerization time is in the range of 20 to 60 hours, and the reaction is carried out in a solid phase polymerization machine.

  The polyester resin composition of the present invention is suitable for blow molding as described above. However, even if an injection molding or stretching method is adopted, a molded product (injection molded body) having excellent color tone and transparency. Sheet, film, etc.).

  Next, the blow molded product of the present invention is formed using the polyester resin composition of the present invention. The blow molded product of the present invention can be manufactured using a general-purpose direct blow molding machine or stretch blow molding machine, and the temperature of each part of the cylinder and the nozzle of the molding machine is in the range of 230 to 280 ° C. Is preferred.

  The blow molded article of the present invention may be a single-layer blow molded article formed using only the resin composition of the present invention, or at least a part of the resin composition of the present invention is used. It may be a blow molded article having a multilayer structure.

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) Composition of polyester resin The obtained polyester resin composition was dissolved in a mixed solvent having a volume ratio of deuterated hexafluoroisopropanol and deuterated chloroform of 1/20, and LA-400 type manufactured by JEOL Ltd. 1H-NMR was measured with an NMR apparatus, and the type and content of the copolymerization component were determined from the integrated intensity of the proton peak of each component of the obtained chart.
(C) Ratio of weight average molecular weight and number average molecular weight The obtained polyester resin composition was measured for polystyrene-reduced number average molecular weight and weight average molecular weight under the following conditions using gel permeation chromatography (GPC). The weight average molecular weight / number average molecular weight was calculated.
Liquid feeding device: Isocratic HPLC Pump 1515 manufactured by Waters
Detector: Waters RefractiveIndexDetector 2414
Column: Mixed-D
Solvent: hexafluoroisopropanol / chloroform = 5/95 (mass ratio)
Flow rate: 1 ml / min Measurement temperature: 40 ° C
(D) Carboxyl end group concentration 0.1 g of the obtained polyester resin composition was dissolved in 10 ml of benzyl alcohol, 10 ml of chloroform was added to this solution, and then titrated with 1/10 N potassium hydroxide benzyl alcohol solution. Asked.
(E) Cyclic trimer content 100 mg of the obtained polyester resin composition was dissolved in a mixed solvent having a volume ratio of hexafluoroisopropanol and chloroform of 1/20, and acetonitrile was added for extraction, followed by liquid chromatography. It was measured under the following conditions, and the amount of cyclic trimer was calculated.
Column: Waters Micro Bonder Sphere
Filler: Si-C18 5μ 100A
Detector: Waters Model 2996 PDA detector (light source wavelength 254nm)
Measurement flow rate: 1 ml / min Mobile phase solvent: acetonitrile / water = 7/3 and acetonitrile

(F) Direct blow moldability The thickness of the body part of the obtained molded product (100 samples) was measured, and the thickness difference between the thickest part and the thinnest part was 0.30 mm. , Showed the number of samples passed. A sample having 90 or more acceptable samples was evaluated as “◯”, and a sample having less than 90 samples as “×”.
(g) Direct blow molding recyclability After blending 50 parts by mass of a pulverized product obtained by pulverizing the obtained molded product with a pulverizer and 50 parts by mass of the polyester resin obtained in each example, the mixture was put into a dehumidifying dryer and dried. Direct blow molding was performed in the same manner as in Example 1 to obtain a molded product. About the obtained molded product (100 samples), the moldability was evaluated in the same manner as (f).
(H) Direct blow molding haze In each of the molded product obtained and the molded product obtained in (g), a test piece (100 pieces) of size: 2 mm thick × 5 cm long × 5 cm wide was cut out. Was measured with a turbidimeter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: haze 0%), and the average value of n number 100 was obtained. 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.
(I) Stretch blow moldability The thickness of the body of the obtained molded product (100 samples) is measured, and the thickness difference between the thickest part and the thinnest part is up to 30 μm. The number of samples was shown. A sample having 90 or more acceptable samples was evaluated as “◯”, and a sample having less than 90 samples as “×”.
(J) Stretch blow molding recyclability After blending 50 parts by mass of a pulverized product obtained by pulverizing the obtained molded product with a pulverizer and 50 parts by mass of the polyester resin obtained in each example, the mixture was put into a dehumidifying dryer and dried. Direct blow molding was performed in the same manner as in Example 1 to obtain a molded product. About the obtained molded article (100 samples), the moldability was evaluated in the same manner as (i).
(K) Stretch blow molding haze In each of the obtained molded product and the molded product obtained in (j), a test piece (100 pieces) of size: thickness 300 μm × length 5 cm × width 5 cm was cut out. Was measured with a turbidimeter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: haze 0%), and the average value of n number 100 was obtained. The smaller this value, the better the transparency, and if it was 3% or less, it was judged that the transparency was 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 another esterification can, a slurry composed of p-hydroxyethoxybenzoic acid (EPOB) and EG (EPOB / EG molar ratio = 1 / 3.1) was charged, and the esterification reaction was performed at 200 ° C. for 3 hours. A reaction solution of p-hydroxyethoxybenzoic acid and ethylene glycol was obtained. 55.5 parts by mass of a reaction product of TPA and EG were charged into a polymerization reactor, followed by 6.1 parts by mass of a reaction solution of EPOB and EG, 0.008 parts by mass of germanium dioxide as a polymerization catalyst, and 0.004 of cobalt acetate. 0.12 parts by mass of a hindered phenol antioxidant (manufactured by ADEKA: ADK STAB AO-60) was added respectively, and the reactor was evacuated for 60 minutes, and the final pressure was 0.9 hPa and the temperature was 280 ° C. A melt polymerization reaction was performed for a time to obtain a prepolymer of a copolyester. The intrinsic viscosity of this prepolymer was 0.66.
Subsequently, the prepolymer was continuously supplied to a crystallization apparatus and crystallized at 150 ° C., then supplied to a dryer, dried at 160 ° C. for 8 hours, then sent to a preheater and heated to 190 ° C. The solid phase polymerization machine was supplied to a solid phase polymerization machine, and a solid phase polymerization reaction was performed at 190 ° C. for 50 hours under nitrogen gas.
After the obtained polyester resin composition is chipped and dried, a direct blow molding machine (Tahara Co., Ltd.) is used to extrude the resin at an extrusion temperature of 260 ° C. to form a cylindrical parison, and the parison is in a softened state. Inside, it was sandwiched between molds, the bottom was formed, and this was blown to form a bottle. At this time, when the parison diameter was 3 cm and the length was 25 cm, the bottom was formed and blow molded to obtain a 500 cc hollow container (direct blow molded product).
Moreover, after drying using this polyester resin composition, each part of the cylinder and the nozzle temperature were set to 260 ° C., screw rotation speed 100 rpm, injection time 10 seconds, cooling time 10 seconds, mold temperature 15 ° C. A preform was molded using (Nissei ASB Co., ASB-50TH type). Next, this preform was stretch blow molded at a blow pressure of 2 MPa in an atmosphere of 100 ° C., and a cylindrical bottle (a hollow container having an internal volume of 150 cc; stretched; an average thickness of 300 μm, an inner diameter of 3.5 cm, and a height of 15 cm) A blow molded product) was obtained.

Examples 2, 8 and Comparative Examples 1, 5-6
In the same manner as in Example 1 except that the composition was changed so that the copolymerization amount of p-hydroxyethoxybenzoic acid and the content of the hindered phenol antioxidant became the values shown in Table 1, the copolymer polyester A prepolymer was obtained. And using the obtained prepolymer, the solid-state polymerization reaction was performed like Example 1, and the polyester resin composition was obtained.
Furthermore, using the obtained polyester resin composition, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1. In Comparative Example 6, the extrusion temperature in the direct blow molding machine and the stretch blow molding machine was 290 ° C.

Example 3
Except that the copolymerization amount of p-hydroxyethoxybenzoic acid was changed to the value shown in Table 1, esterification reaction and melt polymerization reaction were carried out in the same manner as in Example 1 to obtain a copolymerized polyester prepolymer. . Then, using the obtained prepolymer, a solid-state polymerization reaction was performed in the same manner as in Example 1 except that the drying conditions of the dryer were 130 ° C., 10 hours, and the heating temperature of the preheater was 180 ° C. A composition was obtained.
Further, using the obtained polyester resin composition, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 4
Except that the copolymerization amount of p-hydroxyethoxybenzoic acid was changed to the value shown in Table 1, esterification reaction and melt polymerization reaction were carried out in the same manner as in Example 1 to obtain a copolymerized polyester prepolymer. . Then, using the obtained prepolymer, a solid state polymerization reaction was performed in the same manner as in Example 1 except that the drying conditions of the dryer were 120 ° C. for 18 hours, and the heating temperature by the preheater was 175 ° C. A composition was obtained.
Further, using the obtained polyester resin composition, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 5
Except that the copolymerization amount of p-hydroxyethoxybenzoic acid was changed to the value shown in Table 1, esterification reaction and melt polymerization reaction were carried out in the same manner as in Example 1 to obtain a copolymerized polyester prepolymer. . Then, using the obtained prepolymer, a solid state polymerization reaction was performed in the same manner as in Example 1 except that the drying conditions of the dryer were 110 ° C. for 24 hours, and the heating temperature by the preheater was 170 ° C. A composition was obtained.
Further, using the obtained polyester resin composition, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 6
An esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1 to obtain a copolymerized polyester prepolymer. Then, using the obtained prepolymer, a solid phase polymerization reaction was performed in the same manner as in Example 1 except that the solid phase polymerization reaction time was 40 hours to obtain a polyester resin composition.
Further, using the obtained polyester resin composition, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 7
Except that the composition was changed so that the content of the hindered phenol antioxidant was the value shown in Table 1, the esterification reaction and the melt polymerization reaction were carried out in the same manner as in Example 1, and the prepolymer of the copolyester was obtained. Obtained. Then, using the obtained prepolymer, a solid phase polymerization reaction was performed in the same manner as in Example 1 except that the solid phase polymerization reaction time was changed to 60 hours to obtain a polyester resin composition.
Further, using the obtained polyester resin composition, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 9
An esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1 to obtain a copolymerized polyester prepolymer. Then, using the obtained prepolymer, a solid phase polymerization reaction was performed in the same manner as in Example 1 except that the solid phase polymerization reaction time was set to 15 hours to obtain a polyester resin composition.
Furthermore, the obtained polyester resin composition was subjected to direct blow molding and stretch blow molding in the same manner as in Example 1.

Comparative Example 2
A copolymer polyester prepolymer was prepared in the same manner as in Example 1 except that the composition was changed so that the copolymerization amount of p-hydroxyethoxybenzoic acid and the content of the hindered phenol antioxidant were the values shown in Table 1. A polymer was obtained. The obtained prepolymer was continuously supplied to the crystallization apparatus in the same manner as in Example 1. However, crystallization could not be performed because of fixing.
Therefore, a prepolymer of a copolyester obtained by carrying out an esterification reaction and a melt polymerization reaction without performing solid phase polymerization was used as a polyester resin composition, and used for direct blow molding and stretch blow molding in the same manner as in Example 1. did.

Comparative Example 3
The copolyester prepolymer obtained in Example 1 was used as a polyester resin composition (no solid phase polymerization reaction was performed).
The obtained polyester resin composition was subjected to direct blow molding and stretch blow molding in the same manner as in Example 1.

Comparative Example 4
An esterification reaction and a melt polymerization reaction were performed in the same manner as in Example 1 to obtain a prepolymer of the obtained copolymer polyester. Then, using the obtained prepolymer, a solid phase polymerization reaction was carried out in the same manner as in Example 1 except that the solid phase polymerization reaction time was 80 hours to obtain a polyester resin composition.
Further, using the obtained polyester resin composition, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1 except that the extrusion temperature in the direct blow molding machine and stretch blow molding was 290 ° C. It was.

Comparative Example 7
Except that the melt polymerization reaction time was 8 hours, an esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1, and the resulting prepolymer of the copolyester was used as a polyester resin composition (solid phase polymerization reaction). Did not do).
And using the obtained polyester resin composition, it carried out similarly to Example 1, and obtained the direct blow molded product and the stretch blow molded product.

Comparative Examples 8 and 9
A polyester resin composition was obtained in the same manner as in Comparative Example 7 except that the content of the hindered phenol-based antioxidant was changed to the values shown in Table 1.
And using the obtained polyester resin composition, it carried out similarly to Example 1, and obtained the direct blow molded product and the stretch blow molded product.
In Comparative Example 9, the extrusion temperature in the direct blow molding machine and the stretch blow molding machine was 290 ° C.

As is clear from Table 1, the polyester resin compositions obtained in Examples 1 to 8 were p-hydroxyethoxybenzoic acid component, intrinsic viscosity, weight average molecular weight / number average molecular weight, carboxyl end group amount, cyclic 3 amount. Since the body weight is within the range specified in the present invention and excellent in thermal stability, direct blow molding and stretch blow molding are performed with good operability without causing problems of whitening due to crystallization and drawdown. I was able to. And the obtained molded product (container) had no thickness unevenness and was excellent in transparency. Furthermore, it is excellent in recyclability, and even if it is used in combination with recycled polyester resin, direct blow molding and stretch blow molding can be performed with good operability, and the obtained molded product (container) has uneven thickness. There was no, and it was excellent in transparency.
Since the polyester resin composition obtained in Example 9 had a low intrinsic viscosity, the drawdown during direct blow molding was increased, and a direct blow molded product could not be obtained. However, stretch blow molding can be performed with good operability as in Examples 1 to 8, and the obtained molded product has no thickness unevenness and is excellent in transparency. It was also excellent in recyclability.

  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 and stretch blow molding were performed, the molded product crystallized and whitened, and the transparency It became inferior to. Moreover, since the crystallization speed of the polyester resin became too fast, the direct blow moldability was also deteriorated, and the number of molded products with uneven thickness increased. In Comparative Example 2, since the copolymerization amount of p-hydroxyethoxybenzoic acid was large, fusion occurred during the solid phase polymerization, and the solid phase polymerization reaction could not be performed. Therefore, the obtained polyester resin composition had a low intrinsic viscosity, and direct blow molding could not be performed. Moreover, the amount of carboxyl end groups and the amount of cyclic trimers were out of the ranges specified in the present invention. Regarding stretch blow molding, the polymer was thermally decomposed due to a large amount of copolymerization, and the moldability, particularly the recyclability, was poor. Since the polyester resin composition obtained in Comparative Example 3 did not undergo a solid phase polymerization reaction, it had a low intrinsic viscosity, and direct blow molding could not be performed. In addition, since the carboxyl end group amount and the cyclic trimer amount were outside the ranges specified in the present invention, the polymer was thermally decomposed, and the moldability, particularly the recyclability, was poor. Since the intrinsic viscosity of the polyester resin composition obtained in Comparative Example 4 was too high, direct blow molding was performed at a higher molding temperature, and thermal decomposition of the polyester resin occurred during molding, resulting in poor haze of the molded product. The moldability also deteriorated and the number of molded products with uneven thickness increased. In addition, when the milled material was used again as a recycled material, the resin was thermally decomposed, resulting in uneven thickness and low recyclability. About stretch blow molding, since the intrinsic viscosity was too high, a stretch blow molded product could not be obtained.

Since the polyester resin composition obtained in Comparative Example 5 has a low content of hindered phenolic antioxidant and the ratio of the weight average molecular weight to the number average molecular weight is less than 1.9, the parison at the time of direct blow molding As a result, the molded product became uneven in thickness. Moreover, since there is little content of a hindered phenolic antioxidant, the thermal stability of the polyester resin composition was bad, and both direct blow molding and stretch blow molding were inferior in recyclability. The polyester resin composition obtained in Comparative Example 6 has a high content of hindered phenolic antioxidant, and the ratio of the weight average molecular weight to the number average molecular weight exceeds 2.5. Since the polyester resin was thermally decomposed during molding, the haze of the obtained molded product was poor, the moldability was deteriorated, and the number of molded products with uneven thickness increased. Also, when the end material was used as a recycled material and again subjected to direct blow molding and stretch blow molding, the resin was thermally decomposed, resulting in uneven thickness and low recyclability. The polyester resin composition obtained in Comparative Example 7 had too many carboxyl end groups, so the thermal stability of the polyester resin was poor, the drawdown of the parison during molding was large, and the molded product was uneven in thickness. It became a thing. Moreover, both direct blow molding and stretch blow molding were inferior in recyclability. The polyester resin composition obtained in Comparative Example 8 has a large amount of carboxyl end groups, a small content of hindered phenol antioxidant, and a ratio of the weight average molecular weight to the number average molecular weight of less than 1.9. As a result, the drawdown of the parison during molding increased, and the molded product had uneven thickness. Moreover, the thermal stability of the polyester resin composition was poor, and both direct blow molding and stretch blow molding were inferior in recyclability. The polyester resin composition obtained in Comparative Example 9 has a large amount of carboxyl end groups, a large amount of hindered phenol antioxidants, and the ratio of the weight average molecular weight to the number average molecular weight exceeds 2.5. Since molding was performed at a higher molding temperature, the polyester resin was thermally decomposed during molding, resulting in poor haze of the molded product, poor moldability, and increased number of molded products with uneven thickness. In addition, when the mill ends were recycled and subjected to direct blow molding again, thermal decomposition of the resin occurred, resulting in uneven thickness, resulting in low recyclability for both direct blow molding and stretch blow molding. It was.

Claims (3)

A resin composition comprising, as a main component, a polyester resin containing ethylene terephthalate as a main repeating unit and 2 to 20 mol% of p-hydroxyethoxybenzoic acid as a copolymerization component, and having an intrinsic viscosity of 0.7 to 1.4 The ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) is 1.9 to 2.5, and the carboxyl end group concentration is 20 equivalents / t or less. Polyester resin composition. The polyester resin composition according to claim 1, wherein the content of the cyclic trimer is 0.6% by mass or less. A blow molded article formed by using the polyester resin composition according to claim 1.