JPH11106490A - Polyester resin and sheetlike material and blow molding product comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester resin excellent in transparency, heat resistance, mechanical characteristics and smell retaining properties, useful as a container for foods and beverages and a packaging material. SOLUTION: This polyester resin has <=10 ppm liberated ethylene glycol content, <=30 ppm increased amount of liberated monohydroxyethyl terephthalate content, <=60 ppm increased amount of liberated bishydroxyethyl terephthalate content, <=70 ppm of total increased amounts of the liberated monohydroxyethyl terephthalate content and the liberated bishydroxyethyl terephthalate content and <=150 ppm increased amount of a liberated bishydroxyethyl terephthalate dimer content and comprises an ethylene terephthalate unit as a main component. A sheetlike material and a blow molding product comprise the polyester resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin which is excellent in transparency, gas barrier properties, heat resistance, mechanical properties and fragrance retention, and is useful as a container or package for food or beverages and the like. It relates to a molded article.

[0002]

2. Description of the Related Art Polyethylene terephthalate resin is used as a material for containers of carbonated beverages, juices, mineral water, etc. due to its excellent transparency, mechanical strength, heat resistance, gas barrier properties and the like. Have been. However, a polyester resin containing ethylene terephthalate as a main repeating unit contains a by-product acetaldehyde.
When the content of acetaldehyde in the polyester resin is large, the content of acetaldehyde in the material of a container or other packaging formed therefrom also increases, which affects the flavor and odor of the beverage or the like filled in the container or the like. Therefore,
Conventionally, various measures have been taken to reduce the acetaldehyde content in the polyester resin. In recent years, containers made of polyester resin, mainly polyethylene terephthalate, have come to be used as containers for low-flavor beverages such as mineral water and Wurong tea. In the case of such beverages, these beverages are generally heat-filled or sterilized by heating after filling, but the reduction of the acetaldehyde content of the beverage container alone may not improve the flavor and odor of these contents. I understand. In addition, metal cans for beverages have ethylene terephthalate on the inner surface for the purpose of process simplification, hygiene, and pollution prevention.
A method of making a can using a metal plate coated with a polyester film having a main repeating unit as a main unit has been adopted. Also in this case, the contents are heat-sterilized at a high temperature after filling, and it has been found that the flavor and odor of the contents are not improved even if a film having a low acetaldehyde content is used.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and is excellent in transparency, gas barrier properties, heat resistance, mechanical properties and fragrance retention, and Another object of the present invention is to provide a polyester resin useful as a container for beverages and the like and a packaging material, and a molded article comprising the same.

[0004]

Means for Solving the Problems The present inventors have assiduously studied in view of the above problems, and have reached the present invention. That is,
A polyester resin whose main repeating unit is ethylene terephthalate, wherein when the polyester resin is injection molded at 290 ° C., the free ethylene glycol content increases by 10 ppm or less; 30 ppm increase in ethyl terephthalate content
In the following, the increase in free bishydroxyethyl terephthalate content is 60 ppm or less, the total increase in free monohydroxyethyl terephthalate content and free bishydroxyethyl terephthalate content is 70 ppm or less, and free Is a polyester resin having an increased amount of bishydroxyethyl terephthalate dimer of 150 ppm or less.

The polyester resin of the present invention is a polyester resin whose main repeating unit is composed of ethylene terephthalate unit, and has an intrinsic viscosity of 0.65.
dl / kg or more, the density is 1.37 g / cm ³ or more, and when the polyester resin is injection-molded at 290 ° C., the increase in free ethylene glycol content is 10 pp.
m or less, the increase in free monohydroxyethyl terephthalate content is 20 ppm or less, the increase in free bishydroxyethyl terephthalate content is 50 ppm or less, the free monohydroxyethyl terephthalate content and free A polyester resin having a total increase of bishydroxyethyl terephthalate content of 60 ppm or less and a free bishydroxyethyl terephthalate dimer content of 120 ppm or less.

Further, the polyester resin of the present invention preferably has an acetaldehyde content of 10 ppm or less and a formaldehyde content of 7 ppm or less. The polyester resin of the present invention preferably has a cyclic trimer content of 0.5% by weight or less. The polyester resin of the present invention preferably has a copolymerized diethylene glycol content of 1.0 to 5.0 mol% of the glycol component.

Further, the polyester resin of the present invention is a polyester resin characterized in that when the polyester resin is injection-molded at 290 ° C., the increase in formaldehyde content is 10 ppm or less. A polyester resin having the above properties provides a container or packaging material having excellent transparency, heat resistance, mechanical properties, and fragrance retention.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester resin having a main repeating unit composed of ethylene terephthalate according to the present invention is a linear polyester resin containing 85 mol% or more of ethylene terephthalate unit. It is a linear polyester resin containing 95 mol% or more. As the dicarboxylic acid used for copolymerization of the polyester resin,
Aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, and functional derivatives thereof, p-oxybenzoic acid, oxycaproic acid, etc. Oxyacids and functional derivatives thereof, adipic acid, sebacic acid, succinic acid, aliphatic dicarboxylic acids such as glutaric acid and its functional derivatives, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and its functional derivatives and the like. Can be

Glycols used for copolymerization of the polyester resin include aliphatic glycols such as diethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, and cyclohexanediol. Examples thereof include alicyclic glycols such as methanol, aromatic glycols such as bisphenol A and alkylene oxide adducts of bisphenol A.

Further, other copolymerizable components comprising a polyfunctional compound in the polyester resin include trimellitic acid and pyromellitic acid as acid components, and glycerin and pentaerythritol as glycol components. Can be mentioned. The amount of the above-mentioned copolymer component to be used must be such that the polyester resin maintains a substantially linear shape.

When the polyester resin of the present invention is injection-molded at 290 ° C., the free ethylene glycol content in the molded product is increased by 10 pp.
m, the free monohydroxyethyl terephthalate content increase is 30 ppm or less, the free bishydroxyethyl terephthalate content increase is 60 ppm or less, the free monohydroxyethyl terephthalate content and the free A polyester resin having a total increase in bishydroxyethyl terephthalate content of 70 ppm or less and a free bishydroxyethyl terephthalate dimer content of 150 ppm or less. The increase in free ethylene glycol content is preferably 9 ppm or less, more preferably 8 ppm or less, and the increase in free monohydroxyethyl terephthalate content is preferably 25 pp.
m or less, more preferably 20 ppm or less, and the increase of the free bishydroxyethyl terephthalate content is preferably 55 ppm or less, more preferably 50 ppm or less. The free monohydroxyethyl terephthalate content and the free bishydroxyethyl The total increase in terephthalate content is preferably 65 ppm or less, more preferably 6 ppm or less.
0 ppm or less, and the increase of the free bishydroxyethyl terephthalate dimer content is preferably 130 pp
m or less, more preferably 110 ppm or less.

When the above polyester resin is injection-molded at 290 ° C., the increase in free ethylene glycol content is 10 ppm or more, the increase in free monohydroxyethyl terephthalate content is 30 ppm or more, The increase in bishydroxyethyl terephthalate content is 60p
pm or more, the total increase in free monohydroxyethyl terephthalate content and free bishydroxyethyl terephthalate content is 70 ppm or more, and the increase in free bishydroxyethyl terephthalate dimer content is 70 ppm or more. Fifteen
When the content is 0 ppm or more, the flavor and aroma of the contents in a container or the like obtained from the polyester resin become extremely poor. It is considered that these low-molecular-weight compounds such as free monomers are eluted in the content from the material of the polyester resin container or the like, though in a very small amount, and as a result, affect the flavor and the like of the content.

In the present invention, the content of a free low-molecular compound in an injection-molded article is measured. This injection-molded article is molded under the following conditions. That is, the polyester resin to be subjected to the test is dried in a vacuum dryer so that the water content becomes 50 ppm or less. The dried polyester resin is injection-molded at a set temperature of 290 ° C. at a mold temperature of 15 ° C. using an M-100 injection molding machine manufactured by Meiki Seisakusho Co., Ltd.
(Former thickness = about 3.7 mm, length = about 165 mm, diameter = about 29.5 mm).
This injection molding was performed for 9 seconds, 17 seconds for injection, and about 2 seconds for cooling.
Perform in 0 seconds. 1 for the measurement of low molecular compound content
In the preform of the 0th to 20th shots, the center part of the trunk is used. The amount of increase in the content of each free low-molecular compound is determined as the free low-molecular compound content of the preform minus the free low-molecular compound content of the resin pellet before molding.

The limiting viscosity of the polyester resin of the present invention is 0.55 to 1.30 dl / g, preferably 0.60 to 1.30 dl / g.
1.20 dl / g, more preferably 0.65 to 0.9
The range is 0 dl / g. At 0.55 dl / g or less,
The mechanical properties of the obtained molded article are poor. Also, 1.30
If the dl / g exceeds dl / g, the resin temperature rises during melting by a molding machine or the like, and thermal decomposition becomes severe, and the amount of free low molecular weight compounds that affect fragrance retention increases significantly, or Problems such as yellowing of the body occur.

The polyester resin of the present invention has an intrinsic viscosity of 0.65 dl / g or more, preferably 0.68 dl / g.
/ G or more, more preferably 0.70 dl / g or more, and a density of 1.37 g / cm ³ or more, preferably 1.38 g / cm3.
cm ³ or more, still more preferably 1.39 g / cm ³ or more, when injection-molding the polyester resin at 290 ° C., free Echirenguko - increase in Le content 10pp
m, preferably 9 ppm or less, more preferably 8 p
pm or less, and the increase in free monohydroxyethyl terephthalate content is 20 ppm or less, preferably 19 ppm or less.
Or less, more preferably 18 ppm or less, and the increase in the free bishydroxyethyl terephthalate content is 50 ppm
Or less, preferably 45 ppm or less, more preferably 40 ppm or less.
ppm or less, free monohydroxyethyl terephthalate
The total increase in the content of free bishydroxyethyl terephthalate and the content of free bishydroxyethyl terephthalate is 60 ppm or less, preferably 55 pp.
m or less, more preferably 50 ppm or less, and the increase of the free bishydroxyethyl terephthalate dimer content is 120 ppm or less, preferably 110 ppm or less,
The polyester resin is more preferably 100 ppm or less. When this polyester resin is used for a packaging material, the flavor and the like of the contents are further improved.

The polyester resin used in the present invention comprises:
For example, melt polycondensation is carried out at a temperature as low as possible in a short time, and after the completion of the melt polycondensation, it is kept in a molten state at a temperature as low as possible and for a short time until it is extruded from the pores to form chips. It can be obtained by:

The temperature of the polycondensation reaction is preferably from 260 to 285 ° C., and the degree of vacuum is from 600 to 0.1 Torr. In the case of polycondensation in a batch-type apparatus, the polycondensation reaction in the final
It should be completed within 1.5 hours at ２８285 ° C. under a reduced pressure of 5 to 0.1 Torr. When polycondensation is performed in a continuous apparatus, the final polycondensation reaction is performed at 260 to 285 ° C and at 5 to 0.
It is important to complete within 1 hour under the condition of 1 Torr. The holding condition in the molten state after the completion of the melt polycondensation should be within 260 minutes at 260 to 285 ° C., preferably within 15 minutes, more preferably within 10 minutes. 28
When polycondensation is performed at a high temperature of 5 ° C. or more, or when polycondensation is performed for a long time of 2 hours or more, the content of the low-molecular compound such as the above-mentioned free monomer becomes the above-mentioned limit amount, The flavor and odor of the contents of the packaging material from the obtained polyester resin become very poor.

In the case of the direct esterification method, compounds of Ge, Sb, and Ti are used as a polycondensation catalyst, and a Ge compound is particularly advantageous. Examples of the Ge compound include amorphous germanium dioxide, crystalline germanium dioxide powder or a slurry of ethylene glycol, a solution of crystalline germanium dioxide dissolved in water by heating, or a solution prepared by adding ethylene glycol to this solution and heating. In order to obtain the polyester resin used in the present invention, it is particularly preferable to use a solution obtained by heating and dissolving germanium dioxide in water or a solution obtained by adding ethylene glycol to the solution and heating the solution. These polycondensation catalysts can be added during the esterification step. In particular, it is preferable to add the polycondensation catalyst at an early stage of the esterification step to obtain the polyester resin used in the present invention. When a Ge compound is used, the amount used is 20 to 1 as the amount of Ge remaining in the polyester resin.
It is 50 ppm, preferably 80 ppm or less, more preferably 60 ppm or less.

As the stabilizer, it is preferable to use phosphoric acid, polyphosphoric acid, phosphate esters such as trimethyl phosphate, and the like. These stabilizers can be added from a slurry blending tank of terephthalic acid and ethylene glycol during the esterification reaction step. In particular, in order to obtain the polyester resin used in the present invention, the slurry blending tank and the esterification reaction are required. It is preferable to add by the middle stage.

The polyester resin of the present invention has an acetaldehyde content of 10 ppm or less, preferably 8 ppm.
Or less, more preferably 5 ppm or less, and the formaldehyde content is 7 ppm or less, preferably 6 ppm or less, more preferably 4 ppm or less. Acetaldehyde content is 10 ppm or more, and formaldehyde content is 7 pp
In the case of m or more, the contents such as containers molded from the polyester resin have poor flavor and odor. In particular, 28
When a polyester resin having an increased amount of a low molecular compound such as a free monomer when the injection molding is carried out at 0 ° C. is less than the regulated amount according to claim 2, the acetaldehyde content is 10%.
When the content is not more than 7 ppm and the formaldehyde content is not more than 7 ppm, the flavor and odor of the contents are further improved.

The method of reducing the acetaldehyde content of the polyester resin of the present invention to 10 ppm or less and the formaldehyde content to 7 ppm or less is not particularly limited. For example, a low molecular weight polyester resin is reduced under reduced pressure or in an inert gas atmosphere. Below 195 ° C to 2
A method of performing solid-phase polymerization at a temperature of 30 ° C. or lower can be mentioned.

The cyclic 3 of the polyester resin of the present invention
Content of the monomer is 0.50% by weight or less, preferably 0.4% by weight or less.
It is at most 5% by weight, more preferably at most 0.40% by weight. When a heat-resistant hollow molded article or the like is molded from the polyester resin of the present invention, heat treatment is performed in a heating mold. However, when the content of the cyclic trimer is 0.50% by weight or more, the heating mold is used. Oligomer attachment to the mold surface increases sharply,
The transparency of the obtained hollow molded article or the like is extremely deteriorated.

The amount of diethylene glycol in the polyester resin of the present invention is from 1.0 to 5.0 mol%, preferably from 1.3 to 4.5 mol%, more preferably from 1.5 to 5.0 mol% of the glycol component. 4.0 mol%. When the amount of diethylene glycol is 5.0 mol% or more, the thermal stability becomes poor,
It is not preferable because the molecular weight is greatly reduced during molding and the acetaldehyde content and the formaldehyde content are increased.

When the polyester resin of the present invention is injection-molded at 290 ° C., the amount of increase in formaldehyde content is 10 ppm or less, preferably 8 ppm or less.
The polyester resin is more preferably 6 ppm or less. When a polyester resin having a formaldehyde content increase of 10 ppm or less is used, the flavor and the like of the contents of containers and the like obtained from the polyester resin are further improved.

For the measurement of the increase in the formaldehyde content, a parison for measuring the increase in the content of the free low-molecular compound is used, and the central part of the body is used. The increase in the formaldehyde content is determined as the formaldehyde content of the parison minus the formaldehyde content of the resin pellets before molding.

As a method for obtaining the polyester resin of the present invention, the above-mentioned Ge compound and the above-mentioned phosphorus compound are used as a polycondensation catalyst and a stabilizer, and the content of diethylene glycol copolymerized as a diol component is 3.0. ~ 1.0 mol%
Polyethylene terephthalate (PET) is melt-polycondensed at a temperature as low as possible in a short time, and after completion of the melt polycondensation, it is as short as possible at a temperature as low as possible until it is extruded from chips to form chips. The method of holding in a molten state below is mentioned. More specifically, the amount of the Ge compound added as a polycondensation catalyst is 20 to 20 as a residual amount of Ge metal in the resin.
70 ppm, the added amount of the phosphorus compound as a stabilizer was 5 to 60 ppm as the residual amount of phosphorus (P), and the residual Ge metal /
The molar ratio of residual P is 0.2 to 2.0, preferably 0.3 to 2.0.
1.0, more preferably 0.4 to 0.8, and the content of diethylene glycol copolymerized as a diol component is preferably 2.7 to 1.0 mol%, more preferably 2.5 to 1.0 mol%. ~ 1.0 mol%. As another method, a melt polycondensation polymer (prepolymer) before solid-phase polymerization is used.
A method in which oxygen is absorbed as little as possible, and this is crystallized under an inert gas flow, followed by solid phase polymerization. As another method, there is a method in which a molten polycondensation polymer (prepolymer) before solid-state polymerization is made to absorb as little oxygen as possible, which is crystallized under reduced pressure, and then solid-phase polymerization is performed. Can be In the case where the prepolymer having absorbed oxygen is subjected to solid-phase polymerization, even if solid-phase polymerization is performed using an inert gas containing almost no oxygen, the formaldehyde content increase amount used in the present invention is 10 ppm or less. No polyester resin is obtained. There are various methods for preventing oxygen from being absorbed by the prepolymer before the solid-phase polymerization. For example, after the melt polycondensation, the mixture is cooled and cut into pellets.
For example, there is a method of transporting the gas to a storage tank or a silo with an inert gas of pm or less and storing the gas in an inert gas atmosphere. Further, the polyester resin of the present invention can be obtained by combining these methods.

The above polyester resin can be produced by a conventionally known production method. That is, it is produced by a direct esterification method in which terephthalic acid is directly reacted with ethylene glycol and / or a third component to remove water and esterify, followed by polycondensation under reduced pressure. Further, solid-state polymerization may be performed to increase the intrinsic viscosity and decrease the acetaldehyde content and the like.

The above-mentioned melt polycondensation reaction may be carried out in a batch reactor or a continuous reactor. In any of these systems, the melt polycondensation reaction may be performed in one stage, or may be performed in multiple stages. It can be done with the device. The melt polycondensation and the solid phase polymerization may be performed continuously or may be performed separately.

In order to control the DEG content, a basic compound such as triethylamine, tri-
A tertiary amine such as n-butylamine and a quaternary ammonium salt such as tetraethylammonium hydroxide can be added. In addition, a coloring agent, an ultraviolet absorber, an antioxidant, an antistatic agent, a lubricant, a nucleating agent, a release agent, and the like may be added to the polyester resin of the present invention as necessary, as long as the object of the present invention is not impaired. Can be. The polyester resin of the present invention can be preferably used as a packaging material such as a hollow molded container, a sheet, a tray, a biaxially stretched film, a film for covering a metal can, and the like.

The sheet-like material of the present invention may be a single-screw extruder or a twin-screw extruder generally used for a polyester resin such as polyethylene terephthalate or a polyolefin resin.
It is obtained by an extrusion molding method using a screw extruder, and includes a stretched film. The stretched film of the present invention is obtained by uniaxially or biaxially stretching the above-mentioned sheet-like material. The hollow molded article of the present invention may be a two-stage method (cold parison method) in which a preformed article (parison) formed by a known injection molding machine or the like is stretch blow-molded by a stretch blow molding machine, or preformed. One-step method (hot parison method) in which the molding of the body and the stretching blow are performed by the same machine (hot parison method), the direct blow molding method,
It can be manufactured by an extrusion blow molding method.

[0031]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. The method of measuring the characteristic values is as follows. 1) Intrinsic viscosity of polyester resin (hereinafter referred to as “PET resin”) (hereinafter referred to as “IV”) 30 ° C. in a 1,1,2,2-tetrachloroethane / phenol (2: 3 weight ratio) mixed solvent From the solution viscosity at 2) Diethylene glycol content (hereinafter referred to as "DEG content") Decomposed with methanol, the amount of DEG was quantified by gas chromatography, and expressed as a ratio (mol%) to the total glycol components.

3) Free ethylene glycol content (hereinafter referred to as "EG content") A resin pellet or a molded plate sample is dissolved in a mixed solution of hexafluoroisopropanol / chloroform, and then homogenized by adding water. EG was quantified by gas chromatography of the solution obtained by filtering the aqueous phase 4) Content of low molecular compounds such as free monomer Resin pellets or molded plate samples were dissolved in a mixed solution of hexafluoroisopropanol / chloroform, and further chloroform was added. Then, methanol was added to precipitate a polymer, followed by filtration, and the filtrate was evaporated to dryness, made up to a constant volume with dimethylformamide, and quantified by liquid chromatography.

5) Acetaldehyde content (hereinafter referred to as "AA content") A resin pellet sample / distilled water = 1 g / 2 ml was put into a glass ampoule purged with nitrogen, and the upper portion was sealed and heated at 160.degree.
After extraction for a while, acetaldehyde in the extract after cooling was measured by high-sensitivity gas chromatography, and the concentration was determined as pp.
Indicated by m. 6) Formaldehyde content (hereinafter referred to as “FA
1 g of resin pellet or molded plate sample is put into a glass ampoule together with 2 ml of distilled water, and after nitrogen replacement, the upper part is sealed,
Heat treatment was performed at 160 ° C. for 1 hour. After cooling, it is converted into a fluorescent derivative with cyclohexane-1,3-dione, and measured by liquid chromatography to determine FA. For details, see Analytical Chemistry, Vol. 34, p. 314 (1985).

7) Cyclic trimer content of PET resin A resin pellet or a molded plate sample is dissolved in a hexafluoroisopropanol / chloroform mixture, and further diluted with chloroform. After adding methanol to precipitate a polymer, the mixture is filtered. The filtrate was evaporated to dryness, made up to volume with dimethylformamide, and quantified by liquid chromatography. 8) Density 25 with a density gradient tube of carbon tetrachloride / n-heptane mixed solvent
Measured in ° C.

9) Sensory test Using a 50T type stretch blow molding machine of Nissei ASB Machine Co., Ltd., a parison is injection molded at a polymer temperature of 275 ° C., and then stretch blown to form a 1.5 L hollow. A molded container was molded. After ion-exchanged water at 70 ° C. was added and kept for 30 minutes, the mixture was cooled to room temperature and left for one month. Ion exchange water is used as a blank for comparison. The sensory test was carried out by 10 panelists according to the following criteria and compared with the average value. 0: No off-flavor or smell is felt. 1: A slight difference from the blank is felt. 2: Feel the difference from the blank. 3: A considerable difference from the blank is felt. 4: A very large difference from the blank is felt.

Example 1 A PET resin was produced by a continuous polycondensation facility in the following manner. A slurry of 865 parts by weight of high-purity terephthalic acid / hour and 580 parts by weight of ethylene glycol is continuously supplied to the first esterification reactor containing the reactants in advance, and the slurry is stirred for about 250 minutes. ℃,
The reaction was performed at 0.5 kg / cm ² G for an average residence time of 3 hours. In addition, crystalline germanium dioxide is dissolved in water by heating, ethylene glycol is added thereto, and a heat-treated catalyst solution and a phosphoric acid ethylene glycol solution are separately and continuously supplied to the first esterification reactor. did. The reaction was sent to the second esterification reactor and stirred for about 260
The reaction was conducted at a temperature of 0.05 kg / cm ² G at a predetermined degree of reaction. The esterification reaction product is continuously sent to the first polycondensation reactor, and is stirred at about 265 ° C. for 1 hour at 25 torr, and then at about 265 ° C. for 3 hours with stirring in the second polycondensation reactor.
1 hour at torr and about 2 hours with stirring in the third polycondensation reactor
The polycondensation was performed at 75 ° C. and 0.5 to 0.8 torr for 1 hour. The polycondensation reaction product was sent to the pores at a retention time of about 275 ° C. within 5 minutes, extruded into strands, cooled with water, and cut into chips. The obtained PET resin had an IV of 0.72 and DEG.
The content was 2.1 mol%. This PET resin is 290
Injection molding was performed at ℃ to obtain a molded plate. Further, this polyester resin was dried under a nitrogen atmosphere and used for forming a hollow molded container. Table 1 shows the increase in the free low-molecular compound content of the obtained PET resin at 290 ° C. and the results of the sensory test of the hollow molded container. As shown in Table 1, it can be seen that the PET resin of the present invention provides a hollow molded container that does not change the taste of the contents.

(Comparative Example 1) The reaction was carried out under the same conditions as in Example 1 up to the reaction in the second polycondensation reactor. In the third polycondensation reactor, the polycondensation was carried out at about 287 ° C. and 2-3 torr for 1.7 hours. Then, the reaction product was sent to the pores at about 287 ° C. for 30 minutes.
A chip was formed in the same manner as described above. IV of PET resin obtained
Was 0.69 and DEG was 2.2 mol%. Table 1 shows the test results.

Example 2 The amount of germanium dioxide added was reduced, and the temperature of the third polycondensation reactor was increased to about 272 ° C.
Polymerization was carried out under substantially the same reaction conditions as in Example 1 except that the prepolymer was changed to a prepolymer having an IV of 0.55. The resin was subsequently crystallized at about 155 ° C. under a nitrogen atmosphere, preheated to about 200 ° C. under a nitrogen atmosphere, and then sent to a continuous solid-state polymerization reactor to undergo solid-state polymerization at about 205 ° C. under a nitrogen atmosphere. The IV of the obtained PET resin was 0.74, DEG
The content was 2.0 mol% and the density was 1.400 g / cm ³ . This resin was dried under the same conditions as in Example 1 to obtain a hollow molded container. Table 2 shows the test results. PE of the present invention
It can be seen that the T resin gives a hollow molded container that does not change the taste of the contents.

Example 3 Polycondensation was carried out under the same conditions as in Example 2 except that the solid-phase polymerization was changed to about 210 ° C.
75, DEG 2.1 mol%, density 1.401 g / c
m ³ , AA content is 3.0 ppm, FA content is 1.5 pp
m, a PET resin having a cyclic trimer content of 0.36% by weight. This resin was molded under the same conditions as in Example 1 to obtain a hollow molded container. Table 2 shows the increase in the free low-molecular compound content of the obtained PET resin and the results of the sensory test of the hollow molded container. As shown in Table 2, it can be seen that the PET resin of the present invention provides a hollow molded container that does not change the taste of the contents.

Comparative Example 2 Example 2 was repeated except that the esterification reaction conditions were changed to change the DEG content, the temperature of the third polycondensation reactor was changed to about 287 ° C., and the degree of vacuum was changed to 3 to 5 torr. Polymerization was carried out under substantially the same reaction conditions, and this reaction product was sent to the pores at a temperature of about 287 ° C. for a residence time of 30 minutes. The IV of the obtained prepolymer was 0.53. This resin was subjected to solid-state polymerization under the same conditions as in Example 2 except that the polymerization temperature was changed to 190 ° C. IV of the obtained PET resin is 0.69,
DEG is 8.5 mol%, density is 1.393 g / cm ³ ,
The AA content was 12.3 ppm and the FA content was 8.4 ppm. This resin was dried under the same conditions as in Example 1 to obtain a container for hollow molding. Table 2 shows the test results.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

The polyester resin of the present invention has transparency,
It has excellent gas barrier properties, heat resistance, mechanical properties and fragrance retention, and is useful as a container or packaging material for food or beverages.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 7:00

Claims (8)

[Claims] 1. A polyester resin whose main repeating unit is composed of an ethylene terephthalate unit,
When the polyester resin is injection molded at 290 ° C.,
The increase in free ethylene glycol content is 10 ppm or less, the increase in free monohydroxyethyl terephthalate content is 30 ppm or less, the increase in free bishydroxyethyl terephthalate content is 60 ppm or less, The total increase in monohydroxyethyl terephthalate content and free bishydroxyethyl terephthalate content is 7
A polyester resin having a content of 0 ppm or less and a free bishydroxyethyl terephthalate dimer content increase of 150 ppm or less. 2. A polyester resin having a main repeating unit composed of an ethylene terephthalate unit,
Intrinsic viscosity is 0.65 dl / kg or more, density is 1.37 g
/ Cm @ 3 or more, and when the polyester resin is injection-molded at 290 DEG C., the increase in free ethylene glycol content is 10 ppm or less, the increase in free monohydroxyethyl terephthalate content is 20 ppm or less, The increase in free bishydroxyethyl terephthalate content is 5
0 ppm or less, the total increase in free monohydroxyethyl terephthalate content and free bishydroxyethyl terephthalate content is 60 ppm or less, and the increase in free bishydroxyethyl terephthalate dimer content is 60 ppm or less. A polyester resin having a content of 120 ppm or less. 3. The polyester resin according to claim 2, wherein the acetaldehyde content is 10 ppm or less and the formaldehyde content is 7 ppm or less. 4. The polyester resin according to claim 2, wherein the cyclic trimer content is 0.5% by weight or less. 5. The amount of diethylene glycol copolymerized is 1.0 to 5.0 mol% of the glycol component.
The polyester resin according to any one of items 1 to 4. 6. The method according to claim 1, wherein the amount of increase in the formaldehyde content when injection molded at 290 ° C. is 10 ppm or less.
The polyester resin according to any one of items 1 to 5. 7. A sheet-like article obtained by extruding the polyester resin according to any one of claims 1 to 5. 8. A hollow molded article comprising the polyester resin according to any one of claims 1 to 5.