JP3046084B2 - Hollow molded articles and food packaging containers with excellent ultraviolet blocking properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded article and a food packaging container having excellent ultraviolet blocking properties. For more information,
UV-blocking and transparent cosmetics, detergents comprising a thermoplastic polyester containing ethylene terephthalate units and butylene naphthalenedicarboxylate units,
The present invention relates to a polyester hollow molded article which can be advantageously used as a container for food or beverages, and a food packaging container for packaging a food which is easily deteriorated by ultraviolet rays using the hollow molded article.

[0002]

2. Description of the Related Art Conventionally, a hollow molded article obtained by biaxially stretch-blowing a thermoplastic polyester, particularly polyethylene terephthalate (hereinafter abbreviated as PET), has excellent properties such as mechanical strength, transparency and chemical resistance. Because of this, it is widely used as a container for cosmetics, detergents, foods, beverages, and the like.

[0003] However, depending on the application, the ultraviolet ray blocking property is not sufficient, so that the irradiation of ultraviolet rays from the outside deteriorates the content of the food due to the deterioration of the taste, and the fading of the cosmetics lowers the commercial value. There is.

In order to solve such problems, organic and inorganic ultraviolet absorbers have been developed so far.
Attempts have also been made to apply it to PET resins. However, when used as a food packaging container, there is a risk that problems such as changes in taste and odor due to toxicity and migration to the contents (elution: migration) may occur, and coloring of the containers may cause problems with the contents. There are drawbacks such as the inability to accurately determine the color, the difficulty in determining the alteration of the content due to a change in color, and the inability to effectively perform a display utilizing the color tone of the content itself.

[0005] For these reasons, thermoplastic polyesters having improved transparency to ultraviolet rays and excellent transparency, particularly PET hollow containers, and foods which are easily deteriorated by ultraviolet light using the containers, such as alcoholic beverages, edible oils and meat packaging. The development of a container was desired.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a colorless and transparent polyester hollow molded article having improved ultraviolet blocking properties.

[0007] Another object of the present invention is to provide a food packaging container suitable for packaging foods that are easily degraded by ultraviolet rays.

[0008]

Means for Solving the Problems The present inventor has paid attention to the problem that PET is transparent to ultraviolet light, and has made intensive studies on the improvement of the ultraviolet light shielding property of a polyester hollow molded article which is colorless, transparent and excellent in hygiene. As a result, a hollow molded article using a polyester of a copolymer or a mixture containing ethylene terephthalate unit of 99.8% by weight to 90% by weight and butylene naphthalenedicarboxylate unit of 0.2% to 10% by weight as a molding material is obtained. The present invention has been found that the above problems can be solved, and that a packaging container using such a hollow molded article can block external ultraviolet rays and prevent the contents from being deteriorated.

That is, according to the present invention, the material constituting the molded body wall is mainly composed of ethylene terephthalate units and butylene naphthalenedicarboxylate units, and based on the total weight of both units, 0.2 to 0.2 of butylene naphthalenedicarboxylate units. A hollow molded article having excellent ultraviolet shielding properties, characterized by being a copolymerized polyester or a mixed polyester having 10% by weight and 99.8 to 90% by weight of ethylene terephthalate units.

In the present invention, the weight ratio of butylene naphthalenedicarboxylate units contained in the polyester of the copolymer or the mixture is from 0.2% by weight based on the total weight of ethylene terephthalate units and butylene naphthalenedicarboxylate units. It is 10% by weight, preferably 0.2 to 5% by weight.

When the content of butylene naphthalenedicarboxylate unit is less than 0.2% by weight, the ultraviolet ray blocking property is insufficient. On the other hand, if the content exceeds 10% by weight, the properties such as the strength of the hollow molded article, for example, the packaging container, deteriorate.

The copolymer polyester (A) used in the present invention contains an ethylene terephthalate unit and a butylene naphthalenedicarboxylate unit. When producing the copolymer polyester (A), the ethylene terephthalate unit and the butylene are used in a conventional manner. It is obtained by a method of copolymerizing using a predetermined amount of a naphthalenedicarboxylate unit. Further, by a method of melt-blending a thermoplastic polyester homopolymer or modified polymer (B) having ethylene terephthalate as a main repeating unit and a thermoplastic polyester homopolymer or modified polymer (C) having butylene naphthalenedicarboxylate as a main repeating unit. The obtained mixed polyester (D) can also be used.

[0013] The latter mixed polyester (D) is used, for example, when a hollow molded article is produced by an injection blow method, immediately before a resin is put into an injection mold at the time of molding a preformed article, or In the case of using the injection blow method, the thermoplastic polyester (B) and the thermoplastic polyester (C) may be blended and prepared just before the resin is extruded from the die. Therefore, the thermoplastic polyester (B) and the thermoplastic polyester (C) may be supplied and kneaded in the form of respective pellets or the like to an injection molding machine, an extrusion molding machine or an extruder, or may be melt-kneaded in advance. A pelletized state of the prepared mixed polyester may be used. It is preferable to use those which have been previously melt-kneaded and pelletized.

[0014] For example, in order to form a hollow molded body from a film or a sheet, first, a resin is melted by an extruder.
Thermoplastic polyester (B) and thermoplastic polyester (C) just before the film or sheet is extruded from the die
And then formed by a usual thermoforming method, for example, a vacuum forming method, a pressure forming method or a vacuum / pressure forming method, or by stretching the film or the film in a uniaxial or biaxial direction. Then, if necessary, the heat-fixed film is formed into a bag shape by a method such as heat fusion.

The mixed polyester (D) in the present invention
For melt-blending and preparing, a device used for melt-blending ordinary rubber or plastics, for example, a hot roll, a Banbury mixer, an extruder, or the like can be used. Usually, single or twin screw extruders are advantageously used. The blending operation is continued until a homogeneous transparent melt blend is obtained. The blending temperature is set at a temperature higher than the melting temperature of the blending system and lower than the temperature at which the blending system starts to thermally decompose. The blending temperature is preferably a temperature between the softening point + 20 ° C. and the softening point + 40 ° C.

As the thermoplastic polyester (B) in the present invention, a homopolymer of polyethylene terephthalate is mainly used, and a part of the terephthalic acid component is, for example, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid. Acid, diphenyl ether dicarboxylic acid, other aromatic dicarboxylic acids such as diphenylsulfone dicarboxylic acid; alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid; adipic acid, sebacic acid;
An aliphatic dicarboxylic acid such as azelaic acid; one or more other difunctional carboxylic acids such as oxyacids such as p-β-hydroxyethoxybenzoic acid and ε-oxycaproic acid; The part is, for example, trimethylene glycol, tetramethylene glycol,
Hexamethylene glycol, decamethylene glycol,
Neopentyl glycol, diethylene glycol, 1,
Other polyfunctional compounds such as 1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl) propane, bis (4'-β-hydroxyethoxyphenyl) sulfonic acid May be substituted and copolymerized in a range of 5% by weight or less.

The thermoplastic polyester (C) in the present invention is mainly a homopolymer of polybutylene-2,6-naphthalenedicarboxylate (hereinafter sometimes abbreviated as PBN). Part of the acid component is, for example, 2,7-, 1,5-, 1,6
1,1,7-other isomers of naphthalenedicarboxylic acid or terephthalic acid or one or more of the above-mentioned polyfunctional carboxylic acids, and / or a part of the butylene glycol component is one of the above-mentioned polyfunctional glycols 20% by weight for each
It may be a copolymer copolymerized in the following range.

The polyester resin (B) or (C)
Of the blended polyester (D) and copolymerized polyester (A) obtained by melt-blending
V) is more preferable than the range in which an amorphous preform or sheet or film can be formed, the range in which the stretchability during blow molding or thermoforming is good, and the mechanical properties of the obtained molded body. Is in the range of 0.5 to 1.2, more preferably 0.6 to 0.9.

As a method of molding the hollow molded article of the present invention, for example, a container, for example, when the hollow molded article is a hollow molded article such as a bottle, a general molding method such as an injection blow method, an orientation blow method, and an extrusion method. A blow method or the like can be applied. As a preferred example of the injection blow method, first, a polymer is melted, a polymer is injected into a cavity formed by an injection core and an injection mold to form a preform, and the injection core and the preform are blown. It is guided into a mold and blown to form a hollow molded body. The temperature of the molten polymer at this time is preferably not lower than the softening point of the polymer and not higher than 380 ° C, particularly preferably from 250 ° C to 360 ° C. The temperature of the injection core is preferably from -30C to 170C, more preferably from 0C to 150C. The time for cooling the preform by contacting the polymer with the injection mold is preferably 1
-30 seconds, especially 2-15 seconds. The time for contacting the blow mold with the polymer and cooling the container is preferably from 1 to 30 seconds, in particular from 2 to 15 seconds. Either gas or liquid may be used for blowing, but gas has the advantage that it can be used more easily.

As a suitable example of the orientation blow method, a polymer is formed into an amorphous molded article having a hollow cylindrical bottom having a suitable shape (for example, a length of 10 cm, an inner diameter of 1 cm, and an outer diameter of 1.8 cm). Above the glass transition point (Tg) of 190 ° C
Pre-heated to an average magnification of about 1.5 to
Extend to about 16 times. The heat treatment of the container can be appropriately performed.

A suitable example of the extrusion blow method is to first melt a polymer to form a preform having an appropriate thickness,
Seal the bottom of this with the required shape, eg -30 ° C
This is a method in which a gas or a liquid is blown into the inside so as to be in contact with a mold at about 170 ° C.

In a container such as a cup or a tray, the resin is melted by an ordinary injection molding method or an extruder, formed into a sheet or film through a die, and then cast on a cooling drum to temporarily form the sheet or film. Then, it can be manufactured by a thermoforming method in which a female mold is used or a male mold (in some cases, a plug) is used in combination with the female mold, such as a vacuum forming method, a pressure forming method, or a vacuum pressure forming method. .

Further, in the bag-like container, the sheet or film obtained as described above is stretched as it is, or vertically or horizontally, and if necessary, further heat-fixed sheet or film is heat-sealed. It is obtained by bonding the ends using an adhesive or the like and forming the bag into a bag shape.

Thus, the hollow molded article of the present invention produced by an ordinary method has improved ultraviolet shielding properties as compared with a conventional hollow molded article made of thermoplastic polyester (B) or the like. A food packaging container using a molded article is suitable for packaging food that is easily degraded by ultraviolet rays.

[0025]

The present invention will be described below in detail with reference to examples. The main experimental methods and measurement conditions of physical properties are as follows.

(1) Intrinsic viscosity (IV): Measured at 35 ° C. using o-chlorophenol as a solvent.

(2) Glass transition temperature (Tg): 290 ° C.
The sample which was melted in the above and rapidly cooled to 0 ° C. was measured at a heating rate of 20 ° C./min by a differential calorimeter (using a DSC-20 type manufactured by Seiko Instruments Inc.).

(3) Cloudiness: SEP, manufactured by Mitsubishi Kasei Corporation
-Measured with a DI-type poic integrating sphere light transmittance meter.

(4) UV absorption curve: Measured with a multi-purpose self-recording spectrophotometer MPS-5000 manufactured by Shimadzu Corporation.

(5) Tensile test: A test piece having a width of 1 cm and a length of 10 cm was cut out from a sheet or a film and pulled at a rate of 200% / min using a tensile tester UTM-4-100 manufactured by Toyo Baldwin. .

(6) Viscosity of cooking oil: B manufactured by Tokyo Keiki Co., Ltd.
It measured at 25 degreeC using the mold viscometer B8M.

(7) Hue: Color difference meter C manufactured by Nippon Denshoku Co., Ltd.
It was measured by a transmission method using Z-Σ90.

(8) UV irradiation test: The UV irradiation test on food packed in a container is performed by setting a sterilizing lamp GL-15 manufactured by Toshiba Corporation at a distance of 5 cm to the food, unless otherwise specified. Was irradiated at room temperature to perform an acceleration test.

Examples 1 and 2 and Comparative Examples 1 and 2 IV 1.1, Tg 70 ° C. PET and IV 0.62, Tg
The PBN chips at 78 ° C. were each dried with hot air at 150 ° C. for 5 hours, and then a cylinder set temperature of 310 ° C. and a screw rotation speed of 1 were set using a TEX44S twin screw extruder manufactured by Japan Steel Works, Ltd.
Melt blended at 20 rpm. The melt blend is quenched by cooling water from the outlet of the twin screw extruder, and the diameter and length are about 3 m by a cutter.
The chip was cut into m. The IV of the obtained chip was 0.70 to 0.75.

After the chips were dried with hot air at 150 ° C. for 5 hours, an M-100DM injection molding machine manufactured by Meiki Seisakusho was used.
The cylinder was set at a temperature of 300 ° C., and injection molding was performed in a mold cooled with cooling water at 10 ° C. to obtain a preform (preformed body). This preform has a cylindrical body having an outer diameter of 22 to 24 mm, a wall thickness of 3.5 mm, and a total length of 175 mm, with one end having a bottom and a density of 1.330 to
It was a substantially amorphous, colorless and transparent molded article of 1.335 g / cm ³ .

This preform with bottoms is stretched axially in a bottle mold at 95 to 110 ° C., and 10 to 20 kg
/ Cm ^{2 with} a nitrogen gas at a lateral direction of 82 mm, a total height of 280 mm, and a wall thickness of 280 to 330
A bottle with a volume of 1040 to 1050 ml was formed.

Table 1 shows the appearance of the obtained bottles and the haze measured using the body. FIG. 1 shows the results of the UV absorption curve. Next, sesame oil was put into the bottle, and an ultraviolet irradiation test was performed. The results are as shown in Table 1.

[0038]

[Table 1]

Examples 3 and 4 and Comparative Examples 3 and 4 Chips obtained by melt-blending PET and PBN obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were dried with hot air at 160 ° C. for 3 hours. The mixture was melted in an extruder, formed into a film (thickness: about 200 μ) through a die, and cast on a cooling drum.

The film was stretched at a temperature of 130 ° C. using a Long stretching machine at 3.6 times each in the vertical and horizontal directions.

Next, the stretched film is treated at 200 ° C. for 30 minutes.
The sample was heat-fixed for a fixed length of seconds, and a tensile test was performed. The results are shown in Table 2.

[0042]

[Table 2]

Examples 5 and 6 and Comparative Examples 5 and 6 IV 0.97, PET with Tg 70 ° C. and IV 0.62, T
g78 ° C. PBN chips were each dried at 150 ° C. for 3 hours using dehumidified air, and then a single screw extruder was used to set the cylinder temperature to 300 ° C. and rotate the screw 10 times.
It was melt-extruded at 0 rpm, quenched in cold water, and further cut into chips having a diameter and a length of about 2.6 mm. The IV of the obtained chip was 0.67 to 0.71.

Next, the chips were dried with dehumidified air at 150 ° C. for 3 hours, melted by an extruder, and cast on a cooling drum through a die to form a film having a thickness of about 200 μm.

Next, the film was preheated with an infrared heater, and then the opening was 6.5 cm in diameter, the depth was 6 cm, and the bottom was 5 cm in diameter by a vacuum forming method using plug assist.
m cup shape.

The cup thus obtained was filled with white wine, and ultraviolet rays were irradiated from the side of the cup. Table 3 shows the results
Shown in

[0047]

[Table 3]

It is clear that the white wine packaged in a bottle containing no PBN has changed color by irradiation with ultraviolet light. In the case of the PBN weight ratio of 50% (Comparative Example 5), no good molded product was obtained, and thus no ultraviolet irradiation test was performed on the wine.

Example 7 The film containing 3.5% of PBN prepared in Example 2 was
The film was stretched 3.6 times each in the vertical and horizontal directions and heat-set at 200 ° C. to form a biaxially stretched film. Using the film, the ends were fused by a heat fusion method and processed into a bag shape.

After packaging the beef in the film, the film was irradiated with ultraviolet rays at a temperature of about 10 ° C. After irradiation for 8 hours, the beef was taken out and compared with unirradiated beef, but there was almost no difference from the surface color.

Comparative Example 7 Beef was packaged in a bag having a PBN content of 0% prepared in the same manner as in Example 7, and then irradiated with ultraviolet rays at a temperature of about 10 ° C. After irradiation for 8 hours, the beef was taken out, and the color of the surface was compared with that of the unirradiated beef. The color of the beef irradiated with the ultraviolet light was slightly brownish as compared with the unirradiated beef.

[0052]

According to the present invention, it is possible to obtain a colorless and transparent polyester hollow molded article having an improved ultraviolet shielding property, and it is possible to prevent the molded article from being deteriorated by ultraviolet rays. became.

[Brief description of the drawings]

FIG. 1 is a graph showing light transmittance (ultraviolet light and visible light or the like) of a hollow molded article made of a mixed polyester of the present invention.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08J 7/04 B65D 1/00 A // B29K 67:00 B29L 22:00 (56) References JP-A-3-43425 (JP) JP-A-52-69459 (JP, A) JP-A-3-87237 (JP, A) JP-A-64-85732 (JP, A) JP-A-56-113432 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/00 B29C 49/00 B29C 55/02 B65D 1/09 C08G 63/189 C08J 7/04

Claims (6)

(57) [Claims] 1. The material constituting the molded body wall is mainly composed of ethylene terephthalate units and butylene naphthalenedicarboxylate units, and 0.2 to 10% by weight of butylene naphthalenedicarboxylate units based on the total weight of both units. And a copolymerized polyester or a mixed polyester having 99.8 to 90% by weight of ethylene terephthalate unit, and a hollow molded article excellent in ultraviolet shielding property. 2. A mixture polyester comprising a thermoplastic polyester whose main repeating unit is an ethylene terephthalate unit and a thermoplastic polyester whose main repeating unit is a butylene naphthalenedicarboxylate unit, wherein the material constituting the molded body wall is; A polyester hollow molded article having excellent ultraviolet shielding properties, characterized in that the amount of butylene naphthalenedicarboxylate units in the mixed polyester is from 0.2% by weight to 10% by weight. 3. The polyester hollow molded article according to claim 1, wherein the butylene naphthalenedicarboxylate unit is butylene-2.6 naphthalenedicarboxylate. 4. The polyester hollow molded article according to claim 1, which contains a butylene naphthalenedicarboxylate unit in an amount of 5% by weight or less and is colorless and transparent and has improved ultraviolet absorption. 5. A food packaging container using a hollow molded article having excellent transparency and ultraviolet shielding properties according to claim 1 or 2, for packaging a food which is easily deteriorated by ultraviolet rays. 6. The food packaging container according to claim 5, which packages an alcoholic beverage, edible oil or meat.