JP2020045451A - Polyester resin and blow molding formed of the same - Google Patents

Abstract

To provide a polyester resin which is excellent in thermal stability without causing problems in draw down in blow molding and whitening due to crystallization, and can obtain a blow molding excellent in transparency with good productivity, and provide a polyester resin which can satisfactorily mold an end material formed by blow molding even when being used in blow molding again, and is also excellent in recycle property.SOLUTION: In a polyester resin, 70 mol% or more of an acid component constituting polyester is a terephthalic acid, 60-98 mol% of a glycol component is ethylene glycol, and 2-20 mol% thereof is 2-butyl-2-ethyl-1,3-propanediol, intrinsic viscosity is 0.5-1.4, a ratio (weight average molecular weight/number average molecular weight) of a weight average molecular weight to a number average molecular weight is 1.8 to 2.5, and a carboxyl terminal group concentration is 50 et./t or less.SELECTED DRAWING: None

Description

  The present invention relates to a polyester resin capable of obtaining a blow-molded article having excellent transparency with high productivity.

  Polyethylene terephthalate (PET) is excellent in mechanical properties, chemical stability, transparency, etc., is inexpensive, and is widely used as various sheets, films, containers, and the like. The use of hollow containers (bottles) for fruit juice drinks, liquid seasonings, edible oils, alcohol, wine, etc., has been growing remarkably. In addition, since there is little concern about residual monomers and harmful additives as in the case of a hollow molded article made of a vinyl chloride resin, and hygiene and safety are high, replacement with a conventional bottle made of a vinyl chloride resin or the like is also progressing.

  Generally, when manufacturing plastic bottles, the melt-plasticized resin is die-orificed from the viewpoints of ease of molding, high productivity, and relatively low equipment costs for molding machines and molds. A so-called direct blow molding method in which a cylindrical parison is extruded to form a cylindrical parison, and this is sandwiched between molds and air is blown into the parison. In the case of direct blow molding, it is necessary to prevent the parison extruded in a molten state from drawing down during blow molding in order to smoothly perform molding, and therefore, a high melt viscosity is required for the resin used. Is done. Therefore, vinyl chloride resins, polyolefin resins, and the like are widely used in direct blow molding as resins having a high melt viscosity.

  Although replacement of vinyl chloride resin with polyester resin is also being studied for direct blow molded products, 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, so that blow molding cannot be performed.Also, since crystallization tends to occur at the time of blowing, whitening occurs even if molding is possible, and transparency is increased. There was a problem that it became insufficient.

  In order to improve transparency, a polyester resin obtained by copolymerizing polyethylene terephthalate with another monomer component has been proposed. Although crystallization can be suppressed by this, the melt viscosity alone cannot be increased. Therefore, a method of solving the drawdown problem by increasing the viscosity by means of crosslinking with a trifunctional or higher polycarboxylic acid / polyhydric alcohol has been proposed (for example, see Patent Document 1). However, when the viscosity is increased by such a crosslinking means, the moldability is improved, but when the amount of the polyhydric carboxylic acid or polyhydric alcohol is large, the gelation easily occurs, the thermal stability is poor, and the resulting molding is not performed. There was a problem that the product was inferior in color tone and transparency.

  In the direct blow molding, a cylindrical parison extruded through a die from an extruder was clamped and sandwiched by a vertically divided split mold, and arranged at the bottom of the cavity of the split mold. The lower portion of the molten resin is cut at the pinch-off portion, which is a blade portion, and heat-sealed, and the upper portion of the cylindrical molten resin is cut at the upper portion with a parison cutter to form a bottomed parison as a bottomed body. Since blow air is blown into the parison by an air nozzle inserted from the top of the mold and blow molding is performed, cut resin scraps are generated. The dried material is dried and crystallized, then dry-blended into a raw resin chip as a recycled material, and recycled for use in direct blow molding again to reduce costs. However, since the limit viscosity is reduced due to the heat history at the time of molding, there is a problem that if a large amount of the end material is dry-blended and recycled, drawdown occurs at the time of molding and molding cannot be performed.

Japanese Patent No. 3177353

  The present invention solves the above problems, and does not cause a problem of whitening due to drawdown or crystallization during blow molding, has excellent heat stability, and provides a blow molded product excellent in transparency with good productivity. It is intended to provide a polyester resin that can be obtained, and it is also excellent in recyclability, which can be molded well even if it is used as a remnant in blow molding once again for blow molding. It is intended to provide a polyester resin. Another object of the present invention is to provide a blow molded article comprising the polyester resin of the present invention.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention.
That is, the present invention has the following (1) to (3).
(1) 70% by mole or more of the acid component of the polyester is terephthalic acid, 60 to 98% by mole of the glycol component is ethylene glycol, and 2 to 20% by mole is 2-butyl-2-ethyl-1,2. A polyester resin that is 3-propanediol, having an intrinsic viscosity of 0.7 to 1.4, and a ratio of weight average molecular weight to number average molecular weight (weight average molecular weight / number average molecular weight) of 1.8 to 2. 5. A polyester resin having a carboxyl terminal group concentration of 50 equivalents / t or less.
(2) The polyester resin according to (1), wherein the content of the cyclic trimer is 0.6% by mass or less.
(3) A blow molded article comprising the polyester resin according to (1) or (2).

The polyester resin of the present invention uses a polyester having a specific composition and satisfies a specific intrinsic viscosity, a ratio of a weight average molecular weight to a number average molecular weight (weight average molecular weight / number average molecular weight), and a carboxyl end group concentration. Therefore, it is excellent in thermal stability, and a blow molded product excellent in transparency can be obtained with high productivity without causing drawdown or whitening due to crystallization during blow molding. In addition, the polyester resin of the present invention can produce a blow-molded article having excellent transparency with good productivity even if it is once used as an end material in blow molding, and is also excellent in recyclability. ing.
And since the blow molded article of the present invention is obtained from the polyester resin of the present invention, it has excellent transparency and can be used for various applications.

Hereinafter, the present invention will be described in detail.
The polyester resin 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 to blow air into the interior. The method is suitable for a stretch blow molding method in which a parison is formed by blow molding or injection molding, and this is stretch blow molded.

In the polyester resin of the present invention, 70% by mole or more of the acid component is terephthalic acid, and preferably 85% by mole or more is terephthalic acid. If the proportion of terephthalic acid is less than 70 mol%, the resulting polyester resin will have poor crystallinity and heat resistance.
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 98 mol% of the glycol component is ethylene glycol, and 2 to 20 mol% is 2-butyl-2-ethyl-1,3-propanediol. That is, ethylene glycol is a main component, and 2-butyl-2-ethyl-1,3-propanediol is a copolymer component.
The copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol is 2 to 20% by mole of the total glycol component, preferably 3 to 15% by mole, and more preferably 3 to 12% by mole. %. By copolymerizing an appropriate amount of 2-butyl-2-ethyl-1,3-propanediol, the crystallization speed of the polyester resin can be adjusted to a value suitable for blow molding, and crystallization during blow molding is prevented. be able to.

  When the copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol is less than 2 mol%, the crystallization rate of the resin composition becomes high, and the obtained blow-molded product is crystallized. Whiten. On the other hand, if it exceeds 20 mol%, it becomes amorphous, and drying at a high temperature and solid phase polymerization become difficult. Alternatively, it is not preferable because blocking is likely to occur during drying at a high temperature or in a solid phase polymerization step.

Ethylene glycol accounts for 60 to 98 mol% of the total glycol component, preferably 70 to 90 mol%. If the content of ethylene glycol is less than 60 mol%, the resulting polyester resin will have poor crystallinity and heat resistance. On the other hand, if it exceeds 98 mol%, the proportion of 2-butyl-2-ethyl-1,3-propanediol decreases, making it difficult to adjust the crystallization rate, and preventing whitening due to crystallization during blow molding. The effect is poor.
The total amount of ethylene glycol and 2-butyl-2-ethyl-1,3-propanediol is preferably at least 70 mol% of all glycol components, and more preferably at least 80 mol%.

  Examples of the diol component other than ethylene glycol and 2-butyl-2-ethyl-1,3-propanediol include neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-pentane glycol. Hexamethylenediol, 1,4-cyclohexanedimethanol, diethylene glycol, dimer diol, and ethylene oxide adducts of bisphenol A and bisphenol S can be used.

  The polyester resin of the present invention needs to have an intrinsic viscosity (IV) of 0.5 to 1.4, and especially 0.9 to 1.4 when used for direct blow molding. Is preferred. The intrinsic viscosity (IV) is measured at a temperature of 20 ° C. using an equal mass mixture 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. Above all, during direct blow molding, the drawdown of the parison becomes remarkable, 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 deteriorate. In addition, 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 molded product obtained has uneven thickness. Further, when the scrap material is subjected to blow molding again as a recycled material, thermal decomposition of the resin is apt to occur during blow molding, and stable production becomes difficult, and the resulting molded product has uneven thickness.

  In the polyester resin of the present invention, the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) is 1.8 to 2.5, and the carboxyl end group concentration is 50 equivalents / t or less. It is particularly important to satisfy both. When the ratio between the weight average molecular weight and the number average molecular weight is within the above range, the composition has a viscosity suitable for blow molding. However, even if the ratio between the weight average molecular weight and the number average molecular weight is within the above range before molding, if thermal decomposition of the resin occurs due to heat treatment during blow molding, drawdown occurs during molding and molding is difficult. Or 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, it is necessary to set the concentration of the carboxyl terminal group to 50 equivalents / t or less.

First, the polyester resin of the present invention needs to have a ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) of 1.8 to 2.5, and particularly 2.0 to 2. It is preferably 4.
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 1.8, the entanglement of the molecular chains in the resin and the insufficient crosslink density have a viscosity suitable for blow molding. I can't do it. For this reason, the drawdown of the parison becomes large at the time of blow molding, and molding becomes difficult, and the molded product obtained 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 raise the molding temperature, and the resulting molded article Color tone and transparency deteriorate. In addition, 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 molded product obtained has uneven thickness. Further, when the scrap material is subjected to blow molding again as a recycled material, thermal decomposition of the resin is apt to occur during blow molding, and stable production becomes difficult, and the resulting molded product has uneven thickness.

  Means for setting the ratio of the weight average molecular weight to the number average molecular weight in the above range is not limited, and a method of adding a hindered phenol-based antioxidant described below during the polymerization reaction of the polyester resin, and a method described below. Hindered phenolic antioxidants are added to the polyester resin by melt-kneading.

  Further, the polyester resin of the present invention needs to have a carboxyl terminal group concentration of 50 equivalents / t or less, preferably 40 equivalents / t or less, more preferably 30 equivalents / t or less. . By setting the concentration of the carboxyl terminal group of the polyester resin to 50 equivalents / t or less, the resin is not thermally decomposed at the time of blow molding, and stable molding can be performed. Also, the recyclability is excellent.

  When the carboxyl end group concentration exceeds 50 equivalents / t, even if the intrinsic viscosity of the resin or the ratio of the weight average molecular weight to the number average molecular weight is in the above range, the heat treatment at the time of blow molding causes Thermal decomposition of the resin occurs, which increases the drawdown of the parison, making molding difficult, and the resulting molded article has uneven thickness.

  In addition, since the obtained molded article also has an increased carboxyl end group concentration, the end materials generated during molding also have a high carboxyl end group concentration. For this reason, when the scrap 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.

Further, in the polyester resin of the present invention, the content of the cyclic trimer is preferably 0.6% by mass or less, and particularly preferably 0.5% by mass or less. By subjecting the polyester resin having a cyclic trimer content of 0.6% by mass or less to molding, improvement in contamination of a mold and the like is recognized. If the content of the cyclic trimer exceeds 0.6% by mass, it adheres to devices such as a mold and a nozzle during molding and becomes contaminated. Since these contaminations cause the surface roughness and whitening of the molded product, it is necessary to frequently clean the molds and nozzles.
In order to set the carboxyl end group concentration of the polyester resin to 50 equivalents / t or less or the content of the cyclic trimer to 0.6% by mass or less, a specific polymerization reaction is required after the melt polymerization reaction for obtaining the polyester resin. It becomes possible by performing a solid-phase polymerization reaction under the conditions.

  Preferably, an antioxidant is added to the polyester resin of the present invention. In particular, it is preferable that the hindered phenol-based antioxidant is added so as to be 0.01 to 0.5% by mass of the polyester resin. By adding an appropriate amount of a hindered phenolic antioxidant, it has an effect of suppressing the thermal decomposition of the phthalic acid component. Further, the hindered phenol-based antioxidant preferably contains two or more hindered phenol groups in the molecule. By adding these antioxidants during the polymerization reaction step, a part of the compound is copolymerized in the polyester resin and incorporated into the molecular chain of the polyester. As a result, the viscosity of the polyester resin becomes high. As a result, the ratio between the weight average molecular weight and the number average molecular weight can be set in the above range.

  If the amount of the hindered phenolic antioxidant is less than 0.01% by mass, it is difficult to achieve the above effects. On the other hand, if it exceeds 0.5% by 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 is high. And the transparency tends to deteriorate. In addition, recyclability also decreases.

  Examples of hindered phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol, 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-t-butylphenol), triethylene glycol-bis [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate], 3, 9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1'-dimethylethyl}- , 4,8,10-Tetraoxaspiro [5,5] undecane and the like 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 of the present invention, in addition to the above-described antioxidant, as a coloring inhibitor, for example, phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphite Phosphorus compounds such as 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 a cobalt compound such as cobalt acetate, a manganese compound such as manganese acetate, an anthraquinone dye compound, and a copper phthalocyanine compound may be contained in order to suppress coloring due to thermal decomposition of the polyester resin.

  The polyester resin of the present invention can be used by mixing (blending) with another thermoplastic resin or a polyester resin containing another copolymerization component. And the molded article obtained using the resin (or resin composition) mixed in this way can improve the impact resistance in some cases.

  Next, a method for producing the polyester resin of the present invention will be described. 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. It is difficult to obtain a polyester resin having a target intrinsic viscosity only by an esterification reaction and a melt polymerization reaction. Even if it is obtained, the reaction time of the melt polymerization reaction is prolonged, and the resulting polyester resin has a poor color tone. Then, the polyester resin of the present invention can be obtained by making the steps and conditions in the solid-state polymerization reaction specific.

Specifically, for example, it can be manufactured 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 the esterification reaction is performed under pressure at a temperature of 160 to 280 ° C. Thereafter, the reaction product is transferred to a polymerization reactor, and 2-butyl-2-ethyl-1,3-propanediol, a polycondensation catalyst, and if necessary, additives such as an antioxidant and a coloring inhibitor are added. The melt polymerization reaction is carried out at a temperature of 240 to 290 ° C., preferably 250 to 280 ° C., usually 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, known compounds generally used for PET, for example, one or more compounds such as germanium, antimony, titanium, and cobalt compounds can be used, but a compound of germanium or antimony is preferably used. Further, when importance is placed on the transparency of the obtained polyester resin, it is preferable to use a germanium compound. Examples of the compound of germanium or antimony include oxides, inorganic acid salts, organic acid salts, halides, and sulfides thereof. These polycondensation catalysts are used in an amount of 5 × 10 ⁻⁵ mol to 5.0 × 10 ⁻⁴ mol, especially 6 × 10 ⁻⁵ mol to 3.0 × 10 mol, per 1 mol of the acid component of the produced polyester resin. It is preferably used in such an amount as to fall 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, a cobalt compound such as cobalt acetate, a manganese compound such as manganese acetate, an anthraquinone dye compound, and a copper phthalocyanine compound may be used.

  Subsequently, the prepolymer obtained by the above-described melt polymerization reaction is formed into chips having an arbitrary shape such as a dice shape and a column shape, and the polyester chips are continuously supplied to a crystallizer and crystallized at a temperature of 150 to 180 ° C. After being supplied to a drier, dried at a temperature of 180 ° C. or less for 4 to 10 hours, and then sent to a pre-heater and heated to the following solid phase polymerization temperature for 2 to 5 hours. A polyester resin having a target intrinsic viscosity is obtained by continuously supplying the polyester resin 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 performed at a temperature in the range of 170 to 230 ° C, more preferably at a temperature in the range of 180 to 220 ° C. Further, the polymerization time is in the range of 20 hours to 60 hours, and the reaction is carried out in a solid phase polymerization machine.

  Although the polyester resin of the present invention is suitable for blow molding as described above, even if injection molding or a stretching method is employed, molded products excellent in color tone and transparency (injection molded articles, sheets, etc.) , A film, etc.).

  Next, the blow molded product of the present invention is made of the polyester resin of the present invention. The blow-molded article of the present invention can be manufactured using a general-purpose direct blow molding machine or a 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.

Next, the present invention will be specifically described using examples. The methods for measuring and evaluating various characteristic values in the examples are as follows.
(A) Intrinsic viscosity Measured by the same method as described above.
(B) Composition of Polyester Resin The obtained polyester resin was dissolved in a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform at a volume ratio of 1/20, and an LA-400 NMR apparatus manufactured by JEOL Ltd. The 1H-NMR was measured by using, and the type and content of the copolymer component were determined from the integrated intensity of the proton peak of each component in the obtained chart.
(C) Ratio of weight average molecular weight to number average molecular weight The obtained polyester resin was subjected to gel permeation chromatography (GPC) to measure the number average molecular weight and weight average molecular weight in terms of polystyrene under the following conditions, The molecular weight / number average molecular weight was calculated.
Liquid sending device: Isocratic HPLC Pump1515 manufactured by Waters
Detector: Waters RefractiveIndexDetector2414
Column: Mixed-D
Solvent: hexafluoroisopropanol / chloroform = 5/95 (mass ratio)
Flow rate: 1 ml / min Measurement temperature: 40 ° C
(D) Carboxyl terminal group concentration 0.1 g of the obtained polyester resin was dissolved in 10 ml of benzyl alcohol, 10 ml of chloroform was added to this solution, and the solution was titrated with a 1/10 normal potassium benzyl alcohol solution. .
(E) Cyclic trimer content 100 mg of the obtained polyester resin was dissolved in a mixed solvent of hexafluoroisopropanol and chloroform at a volume ratio of 1/20, acetonitrile was added, and the mixture was extracted. The measurement was performed under the following conditions, and the amount of the cyclic trimer was calculated.
Column: Waters Micro Bonder Sphere
Filler: Si-C18 5μ 100A
Detector: Waters 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 of the obtained molded product (100 samples) was measured, and the one with a difference in thickness between the thickest part and the thinnest part of up to 0.30 mm was accepted. And the number of passing samples. When the number of passing samples was 90 or more, it was evaluated as ○, and when it was less than 90, it was evaluated as ×.
(G) Recyclability of Direct Blow Molding 50 parts by mass of the crushed product obtained by crushing the obtained molded product with a crusher and 50 parts by mass of the polyester resin obtained in each example were blended, and then 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. The moldability of the obtained molded product (100 samples) was evaluated in the same manner as in (f).
(H) Direct blow molding haze For each of the obtained molded article and the molded article obtained in (g), a test piece (100 pieces) having a size of 2 mm thick × 5 cm long × 5 cm wide was cut out and cut out. Was measured with a turbidimeter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: 0% haze), and the average value of n number 100 was obtained. It was determined that the smaller the value, the better the transparency. If it was 5% or less, it was determined that the transparency was excellent.
(I) Stretch-blow moldability The thickness of the trunk of the obtained molded product (100 samples) was measured, and those having a difference in thickness between the thickest part and the thinnest part of up to 30 μm were accepted and passed. The number of samples is shown. When the number of passing samples was 90 or more, it was evaluated as ○, and when it was less than 90, it was evaluated as ×.
(J) Stretch blow molding recyclability 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 are blended, and then 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. The moldability of the obtained molded article (100 samples) was evaluated in the same manner as (i).
(K) Stretch blow molding haze In each of the obtained molded article and the molded article obtained in (j), a test piece (100 pieces) was cut out from a test piece having a size of 300 μm in thickness × 5 cm in length × 5 cm in width. Was measured with a turbidimeter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: 0% haze), and the average value of n number 100 was obtained. It was determined that the smaller the value, the better the transparency. If it was 3% or less, it was determined that the transparency was excellent.

Example 1
A slurry of terephthalic acid (TPA) and ethylene glycol (EG) (TPA / EG molar ratio = 1 / 1.6) is supplied to the esterification reactor and reacted under the conditions of a temperature of 250 ° C and a pressure of 50 hPa to perform esterification. A reaction product with a conversion of 95% (number average polymerization degree: 5) was obtained.
55.5 parts by mass of a reaction product of TPA and EG were charged into a polymerization reactor, followed by 3.2 parts by mass of 2-butyl-2-ethyl-1,3-propanediol (BEPG), and germanium dioxide as a polymerization catalyst. 0.008 parts by mass, 0.004 parts by mass of cobalt acetate, and 0.12 parts by mass of a hindered phenol-based antioxidant (ADEKA: ADK STAB AO-60) were added, and the reactor was depressurized and 60 minutes later. 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 copolymerized polyester. The intrinsic viscosity of this prepolymer was 0.66.
Subsequently, the prepolymer was continuously supplied to a crystallizer and crystallized at 150 ° C., then supplied to a dryer, dried at 160 ° C. for 8 hours, and then sent to a preheater and heated to 190 ° C. Then, the mixture 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 was chipped and dried, using a direct blow molding machine (manufactured by Tahara), the resin was extruded at an extrusion temperature of 260 ° C. to form a cylindrical parison, while the parison was in a softened state. The bottom was formed by sandwiching it with a mold and blown to form a bottle. At this time, when the parison diameter became 3 cm and the length became 25 cm, the bottom was formed and blow molded to obtain a 500 cc hollow container (direct blow molded product).
After drying using this polyester resin, an injection molding machine (Nissei) was set at a cylinder temperature of 260 ° C., a screw rotation speed of 100 rpm, an injection time of 10 seconds, a cooling time of 10 seconds, and a mold temperature of 15 ° C. after drying the polyester resin. A preform was molded using ASB-50TH type (manufactured by ASB Corp.). Next, this preform is stretch-blow-molded in a 100 ° C. atmosphere at a blow pressure of 2 MPa, and a cylindrical bottle having a body thickness of 300 μm, an inner diameter of 3.5 cm, and a height of 15 cm (a hollow container having an inner volume of 150 cc; stretching). Blow-molded product).

Examples 2, 8 and Comparative Examples 1, 5 to 6
Except that the composition was changed so that the copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol (BEPG) and the content of the hindered phenol-based antioxidant became the values shown in Table 1, A prepolymer of a copolymerized polyester was obtained in the same manner as in Example 1. Then, using the obtained prepolymer, a solid-phase polymerization reaction was carried out in the same manner as in Example 1 to obtain a polyester resin.
Further, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1 using the obtained polyester resin. In Comparative Example 6, the extrusion temperature was 290 ° C. in the direct blow molding machine and the stretch blow molding machine.

Example 3
An esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1 except that the copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol (BEPG) was changed so as to be the value shown in Table 1. Then, a prepolymer of a copolymerized polyester was obtained. 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 set at 130 ° C. for 10 hours and the heating temperature of the pre-heater was set at 180 ° C. I got
Furthermore, using the obtained polyester resin, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 4
An esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1 except that the copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol (BEPG) was changed so as to be the value shown in Table 1. Then, a prepolymer of a copolymerized polyester was obtained. Using the obtained prepolymer, a solid-state polymerization reaction was carried out in the same manner as in Example 1 except that the drying conditions of the dryer were set at 120 ° C. for 18 hours and the heating temperature of the pre-heater was set at 175 ° C. I got
Furthermore, using the obtained polyester resin, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 5
An esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1 except that the copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol (BEPG) was changed so as to be the value shown in Table 1. Then, a prepolymer of a copolymerized polyester was obtained. Using the obtained prepolymer, a solid-state polymerization reaction was carried out 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 of the pre-heater was 170 ° C. I got
Furthermore, using the obtained polyester resin, 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 prepolymer of a copolymerized polyester. Using the obtained prepolymer, a solid-state polymerization reaction was carried out in the same manner as in Example 1 except that the solid-state polymerization reaction time was changed to 40 hours to obtain a polyester resin.
Furthermore, using the obtained polyester resin, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.

Example 7
An esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1, except that the composition of the hindered phenolic antioxidant was changed so that the content of the hindered phenolic antioxidant became the value shown in Table 1. Obtained. Using the obtained prepolymer, a solid-state polymerization reaction was carried out in the same manner as in Example 1 except that the solid-state polymerization reaction time was changed to 60 hours to obtain a polyester resin.
Furthermore, using the obtained polyester resin, 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 prepolymer of a copolymerized polyester. Using the obtained prepolymer, a solid-state polymerization reaction was carried out in the same manner as in Example 1 except that the solid-state polymerization reaction time was changed to 15 hours to obtain a polyester resin.
Further, the obtained polyester resin was subjected to direct blow molding and stretch blow molding in the same manner as in Example 1.

Comparative Example 2
Example 1 was repeated except that the composition was changed so that the copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol (BEPG) and the content of the hindered phenolic antioxidant became the values shown in Table 1. In the same manner as in 1, a copolymer prepolymer 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 the fixation.
Thus, a prepolymer of a copolymerized polyester obtained by performing an esterification reaction and a melt polymerization reaction without performing solid phase polymerization was used as a polyester resin, and subjected to direct blow molding and stretch blow molding in the same manner as in Example 1.

Comparative Example 3
The prepolymer of the copolymerized polyester obtained in Example 1 was used as a polyester resin (the solid-state polymerization reaction was not performed).
Then, the obtained polyester resin 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 carried out in the same manner as in Example 1 to obtain a prepolymer of the obtained copolymerized polyester. 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 changed to 80 hours, to obtain a polyester resin.
Further, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1, except that the obtained polyester resin was used and the extrusion temperature in the direct blow molding machine and the stretch blow molding was set at 290 ° C.

Comparative Example 7
An esterification reaction and a melt polymerization reaction were carried out in the same manner as in Example 1 except that the melt polymerization reaction time was changed to 8 hours, and a prepolymer of the obtained copolymerized polyester was used as a polyester resin (solid phase polymerization reaction was carried out. Did not.)
Then, using the obtained polyester resin, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1.
I got

Comparative Examples 8 and 9
A polyester resin was obtained in the same manner as in Comparative Example 7, except that the content of the hindered phenolic antioxidant was changed so as to be the value shown in Table 1.
Then, using the obtained polyester resin, a direct blow molded product and a stretch blow molded product were obtained in the same manner as in Example 1. In Comparative Example 9, the extrusion temperature was 290 ° C. in the direct blow molding machine and the stretch blow molding machine.

As is clear from Table 1, the polyester resins obtained in Examples 1 to 8 were 2-butyl-2-ethyl-1,3-propanediol, intrinsic viscosity, weight average molecular weight / number average molecular weight, and carboxyl end group. Amount, the amount of cyclic trimer is within the range specified in the present invention, and because of its excellent thermal stability, there is no problem of whitening due to crystallization, drawdown does not occur, direct blow molding with good operability and Stretch blow molding could be performed. And the obtained molded article (container) had no thickness unevenness and was excellent in transparency. Furthermore, it is excellent in recyclability, and it is possible to perform direct blow molding and stretch blow molding with good operability even when used by mixing with recycled polyester resin, and the obtained molded product (container) has uneven thickness. And was excellent in transparency.
In addition, since the polyester resin obtained in Example 9 had a low intrinsic viscosity, the drawdown at the time of direct blow molding was large, and a direct blow molded product could not be obtained. However, as in Examples 1 to 8, the stretch blow molding could be performed with good operability, and the obtained molded product was free from thickness unevenness and excellent in transparency. Also, it was excellent in recyclability.

  On the other hand, the polyester resin obtained in Comparative Example 1 had a low copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol (BEPG). Crystallized and became white, resulting in poor transparency. In addition, since the crystallization speed of the polyester resin was too high, the direct blow moldability was deteriorated, and the number of molded products having uneven thickness increased. In Comparative Example 2, since the copolymerization amount of 2-butyl-2-ethyl-1,3-propanediol (BEPG) was large, fusion occurred during solid-state polymerization, and the solid-state polymerization reaction could not be performed. . Therefore, the obtained polyester resin had a low intrinsic viscosity, and direct blow molding could not be performed. In the case of stretch blow molding, the polymer was thermally decomposed due to a large amount of copolymerization, resulting in poor moldability, particularly poor recyclability. The polyester resin obtained in Comparative Example 3 did not undergo a solid-state polymerization reaction, and thus had a low intrinsic viscosity, so that direct blow molding could not be performed. In addition, the polymer was thermally decomposed, resulting in poor moldability, especially recyclability. Since the intrinsic viscosity of the polyester resin obtained in Comparative Example 4 was too high, the molding temperature was increased and direct blow molding was performed, so that the polyester resin was thermally decomposed at the time of molding. The properties also deteriorated, and the number of molded articles having uneven thickness increased. In addition, when the scrap material was recycled again as a recycled material, the resin was thermally decomposed, so that the obtained molded product had uneven thickness and low recyclability. Regarding stretch blow molding, a stretch blow molded product could not be obtained because the intrinsic viscosity was too high.

The polyester resin obtained in Comparative Example 5 had a low content of the hindered phenolic antioxidant, and the ratio of the weight average molecular weight to the number average molecular weight was less than 1.8. The down was large, and the molded product was uneven in thickness. Further, since the content of the hindered phenolic antioxidant was small, the thermal stability of the polyester resin was poor, and both direct blow molding and stretch blow molding were inferior in recyclability. The polyester resin obtained in Comparative Example 6 had a high content of the hindered phenolic antioxidant, and the ratio of the weight average molecular weight to the number average molecular weight exceeded 2.5. did. For this reason, the polyester resin was thermally decomposed at the time of molding, and the obtained molded product was inferior in transparency, the moldability was also deteriorated, and there were many molded products having uneven thickness. Also, when the remnants were used as recycled materials and subjected to direct blow molding and stretch blow molding again, the resin was thermally decomposed, so that the obtained molded product had uneven thickness and poor recyclability. Was. Since the polyester resin obtained in Comparative Example 7 had too much carboxyl end group, the thermal stability of the polyester resin was poor, the drawdown of the parison at the time of molding was large, and the molded product had uneven thickness. became. In addition, both direct blow molding and stretch blow molding were inferior in recyclability. The polyester resin obtained in Comparative Example 8 had a large amount of carboxyl end groups, a small content of a hindered phenolic antioxidant, and a ratio of the weight average molecular weight to the number average molecular weight was less than 1.8. The drawdown of the parison at the time of molding was increased, and the molded product was uneven in thickness. In addition, the thermal stability of the polyester resin was poor, and both direct blow molding and stretch blow molding were inferior in recyclability. The polyester resin obtained in Comparative Example 9 had a large amount of a hindered phenolic antioxidant, and the ratio of the weight average molecular weight to the number average molecular weight exceeded 2.5. For this reason, the polyester resin was thermally decomposed at the time of molding, and the obtained molded product was inferior in transparency, the moldability was also deteriorated, and the molded product with uneven thickness increased. Also, when the recycled material was subjected to direct blow molding again as a recycled material, thermal decomposition of the resin occurred, resulting in unevenness in the thickness of the obtained molded product, and both direct blow molding and stretch blow molding had low recyclability. Was.

Claims (3)

70% by mole or more of the acid component constituting the polyester is terephthalic acid, 60 to 98% by mole of the glycol component is ethylene glycol, and 2 to 20% by mole is 2-butyl-2-ethyl-1,3-propanediol. Wherein the intrinsic viscosity is 0.5 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 1.8 to 2.5, A polyester resin having a carboxyl end group concentration of 50 equivalents / t or less. The polyester resin according to claim 1, wherein the content of the cyclic trimer is 0.6% by mass or less. A blow molded article comprising the polyester resin according to claim 1.