JPH04239624A - Food-packing vessel excellent in cutting off ultraviolet ray - Google Patents

Abstract

PURPOSE:To provide the vessel for packing the food apt to be deteriorated by ultraviolet rays by giving ultraviolet-ray properties to the packaging vessel composed of polyethyleneterephthalate excellent in transparency or strength. CONSTITUTION:Ethyleneterephthalate unit is added, as the form of copolymer or polymer, to polyethylene terephthalate containing ethyleneterephthalate unit mainly, whereby the packaging vessel which is excellent is food-hygiene and ultraviolet-ray cutting off properties and is suitable for packing food-oil, alcohol drink or meat, is obtained.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a food packaging container with excellent ultraviolet blocking ability, and more specifically to a food packaging container that is excellent for packaging alcoholic beverages, cooking oil, and meat that are easily deteriorated by ultraviolet rays. It is.

0002

[Prior Art] Packaging containers made of polyethylene terephthalate have excellent transparency and strength, and are widely used in the form of bottles, trays, cups, etc. for beverages, edible oil, meat, processed foods, etc. .

However, since polyethylene terephthalate transmits light including ultraviolet rays with a wavelength of about 320 μm or more, it is not suitable for packaging foods that are easily deteriorated by ultraviolet rays, such as alcoholic beverages, especially brewed liquor, cooking oil, and meat. Hard to say.

[0004] To solve these problems, organic and inorganic ultraviolet absorbers have been developed to date, and attempts have also been made to apply them to polyethylene terephthalate (PET) resin. However, when used as food packaging containers, there is a risk of problems such as toxicity, changes in taste and odor due to migration to the contents, and coloring of the containers may cause problems such as changes in taste and odor. There are disadvantages such as the inability to accurately determine the color, the difficulty in distinguishing the deterioration of the contents due to a change in color, and the inability to effectively create a display that takes advantage of the color tone of the contents themselves.

For these reasons, it has been desired to develop a packaging container made of thermoplastic polyester, particularly PET, which has improved ultraviolet blocking properties and excellent transparency.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a food packaging container with excellent ultraviolet blocking properties. Another object of the present invention is to provide a food packaging container made of colorless and transparent polyester with excellent ultraviolet blocking properties and suitable for packaging foods that are easily deteriorated by ultraviolet rays.

[0007]

[Means for Solving the Problems] The present inventor focused on the problem that PET is transparent to ultraviolet rays, and conducted intensive research into improving the ultraviolet blocking properties of polyester packaging containers that are colorless and transparent and have excellent hygiene. As a result, a packaging container made of a polyester of a copolymer or a mixture containing 99.8% to 90% by weight of ethylene terephthalate units and 0.2% to 10% by weight of ethylene naphthalene dicarboxylate units as a molding material was obtained. We discovered that it is possible to prevent the contents from deteriorating by blocking ultraviolet rays from the inside, leading to the present invention.

That is, in the present invention, the material constituting the container wall is mainly composed of ethylene terephthalate units and ethylene naphthalene dicarboxylate units, and based on the total weight of these two units, 99 ethylene terephthalate units are used.
．． The food packaging container is characterized by being made of a copolyester or a blend polyester containing 8 to 90% by weight of ethylene naphthalene dicarboxylate units and 0.2 to 10% by weight of ethylene naphthalene dicarboxylate units.

In the present invention, the weight ratio of ethylene naphthalene dicarboxylate units contained in the polyester of the copolymer or mixture is from 0.2% by weight based on the total weight of ethylene terephthalate units and ethylene naphthalene dicarboxylate units. 10% by weight, preferably 0
．． It is 2% to 5% by weight.

[0010] If the content of ethylene naphthalene dicarboxylate units is less than 0.2% by weight, the ultraviolet blocking property will be insufficient. Moreover, if it exceeds 10% by weight, the properties such as the strength of the packaging container will deteriorate.

[0011] The copolymer polyester (A
) contains ethylene terephthalate units and ethylene naphthalene dicarboxylate units, but when producing this copolymer polyester (A), ethylene terephthalate units and ethylene naphthalene dicarboxylate units are copolymerized using a predetermined amount by a conventional method. obtained by the method of Alternatively, by a method of melt blending a thermoplastic polyester homopolymer or modified polymer (B) containing ethylene terephthalate as a main repeating unit and a thermoplastic polyester homopolymer or modified polymer (C) containing ethylene naphthalene dicarboxylate as a main repeating unit. The obtained polyester mixture (D) can also be used.

The latter polyester mixture (D) can be used, for example, when a container is made by injection blowing, just before the resin is put into an injection mold when molding a preform, or by injection blowing. When the resin is produced by a method, the thermoplastic polyester (B) and the thermoplastic polyester (C) may be blended just before the resin is extruded from a die.

[0013] For example, when a container is made from a sheet by thermoforming, the resin is melted in an extruder when the sheet is made prior to thermoforming, and just before the sheet is extruded from a die. Thermoplastic polyester (B
) and the thermoplastic polyester (C) may be blended.

[0014] Therefore, the thermoplastic polyester (B) and the thermoplastic polyester (C) may be supplied to an injection molding machine, an extrusion molding machine, or an extruder in the form of pellets, etc., and kneaded, or they may be melted beforehand. A pelletized state of a mixed polyester prepared by kneading may also be used. It is preferable to use one that has been melt-kneaded and pelletized in advance.

[0015] In melt-blending and preparing the polyester mixture (D) of the present invention, equipment used for melt-blending ordinary rubbers or plastics, such as hot rolls, Banbury mixers, extruders, etc., is used. can do. Usually, single-screw or twin-screw extruders are advantageously used. The blending operation is continued until a homogeneous clear molten blend is obtained. The blending temperature is set to be above the temperature at which the blended system can melt and below the temperature at which the blended system begins to thermally decompose. The blending temperature is preferably between the softening point +20°C and the softening point +40°C.

[0016] The thermoplastic polyester (B
), the main target is a homopolymer of polyethylene terephthalate, but some of the terephthalic acid components can be used, such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, etc. Other aromatic dicarboxylic acids such as; alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, etc.; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, etc.; p-β-hydroxyethoxybenzoic acid acid, one or more other difunctional carboxylic acids such as oxyacids such as epsilon-oxycaproic acid, and/or a portion of the ethylene glycol component, such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene Glycol, neopentyl glycol, diethylene glycol, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4'-β-hydroxyethoxyphenyl) ) 1 of other polyfunctional compounds such as sulfonic acid
It may also be a copolymer that is copolymerized with at least 5% by weight of substitution.

The thermoplastic polyester (C) in the present invention is mainly a homopolymer of polyethylene-2,6-naphthalenedicarboxylate (hereinafter sometimes abbreviated as PEN), but 2,6-naphthalene For example, a part of the dicarboxylic acid component is 2,7-, 1,5-, 1,
6-, 1,7- and other isomers of naphthalene dicarboxylic acids or terephthalic acid or one or more of the aforementioned polyfunctional carboxylic acids, and/or a portion of the ethylene glycol component is replaced by one of the aforementioned polyfunctional glycols. 2 each for species and above
A copolymer copolymerized in a range of 0% by weight or less may also be used.

[0018] Such polyester resin (B) or (C)
Blend polyester obtained by melt blending (D
) and the intrinsic viscosity (IV) of the copolymerized polyester (A)
is the range in which an amorphous preform or sheet can be formed,
The range is preferably 0.000000000000000000000000000000000000000000000000000000000000000000000000000000.
It is in the range of 5 to 1.2, more preferably 0.6 to 0.9.

As a method for molding the container of the present invention, when the container is a hollow molded body such as a bottle, general molding methods such as injection blowing, oriented blowing, extrusion blowing, etc. can be applied. . To give a suitable example of the injection blow method, first, a polymer is melted, the polymer is injected into a cavity formed by an injection core and an injection mold to form a preform, and the injection core and preform are blown. It is guided into a mold and blown into a hollow molded body. The temperature of the molten polymer at this time is preferably above the softening point of the polymer and below 380°C, particularly preferably between 250°C and 380°C.
The temperature is 60°C. The temperature of the injection core is preferably -30℃~
The temperature is 170°C, more preferably 0°C to 150°C. The time for contacting the polymer with the injection mold and cooling the preform is preferably 1 to 30 seconds, particularly preferably 2 to 15 seconds. The time for contacting the blow mold with the polymer and cooling the container is preferably 1 to 30 seconds, especially 2 seconds.
~15 seconds is advantageous. Although either gas or liquid may be used for blowing, gas has the advantage of being easier to use.

As a suitable example of the oriented blowing method, the polymer is made into a hollow cylindrical amorphous molded article with an appropriate shape (for example, length 10 cm, inner diameter 1 cm, outer diameter 1.8 cm), and the polymer is Above the glass transition point (Tg) of 190℃
Preheat the container to an average magnification of about 1.5~
Extend it to about 16 times. Note that the container can be heat-treated as appropriate.

A suitable example of an extrusion blow method involves first melting the polymer to form a parison of appropriate thickness;
Seal the bottom of this and the required shape, for example -30℃
This is a method of blow molding in which gas or liquid is injected into the mold so that it comes into contact with a mold at about 170°C.

[0022] Containers such as cups and trays can be manufactured by the usual injection molding method, or by first making a sheet and then using a female mold, or by using a male mold (in some cases, a plug) in combination with the female mold. It can be manufactured by a thermoforming method carried out by, for example, a vacuum forming method, a pressure forming method, a vacuum pressure forming method, or the like.

[0023] Thus, the hollow molded article of the present invention produced by a conventional method has improved ultraviolet blocking properties as compared to the conventional hollow molded article made of thermoplastic polyester (B) or the like.

[0024]

[Examples] The present invention will be explained in detail with reference to Examples below. The measurement conditions and experimental methods for the main physical property values 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 was melted and then rapidly cooled to 0°C and measured using a differential calorimeter (model DSC-20 manufactured by Seiko Electronics Co., Ltd. was used) at a heating rate of 20°C/min.

(3) Haze: manufactured by Mitsubishi Kasei Corporation, SEP
- Measured using a DI type Poick integrating sphere light transmittance meter.

(4) Viscosity of cooking oil: B manufactured by Tokyo Keiki Co., Ltd.
Measurement was performed at 25°C using a model viscometer B8M.

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

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

[0031] Ultraviolet irradiation test: The UV irradiation test on food packaged in a container was carried out using Germicidal Lamp G manufactured by Toshiba Corporation.
L-15 was installed at a distance of 5 cm from the food, and unless otherwise specified, acceleration tests were conducted by irradiating at room temperature.

Examples 1 and 2 and Comparative Examples 1 and 2IV
1.0, Tg 70°C PET and IV 0.66, Tg1
After each PEN chip at 13°C was dried with hot air at 170°C for 3 hours, the cylinder temperature was set at 320°C and the screw rotation speed was 1 using a TEX44S twin-screw extruder manufactured by Japan Steel Works, Ltd.
Melt blended at 20 rpm. The molten blend is discharged from the outlet of the above-mentioned twin-screw extruder, is quenched with cooling water, and cut into approximately 3 m in diameter and length using a cutter.
The chips were cut into m-sized chips. The IV of the obtained chip was 0.70 to 0.74.

After drying this chip with hot air at 160° C. for 3 hours, using an M-100DM injection molding machine manufactured by Meiki Seisakusho,
A preform was obtained by injection molding into a mold that had been cooled with cooling water at 10° C. at a cylinder temperature set at 300° C. This preform has a cylindrical body with an outer diameter of 22 to 24 mm.
, has a wall thickness of 3.5 mm, a total length of 175 mm, and has a bottomed end, and a density of 1.330 to 1.335 g/
It was a substantially amorphous, colorless and transparent molded product with a size of cm3.

[0034] This bottomed preform was stretched in the axial direction in a bottle-shaped mold at 95 to 110°C, and
/cm2 of nitrogen gas to laterally expand the body to have an outer diameter of 82 mm, a total height of 280 mm, and a body wall thickness of 280 to 350 mm.
A bottle with an internal volume of 1040 to 1050 ml was molded.

[0035] Sesame oil was placed in the bottle and an ultraviolet irradiation test was conducted. The results are shown in Table 1.

On the other hand, the chips obtained by melt blending were dried with hot air at 160° C. for 3 hours, then melted in an extruder, passed through a die to form a film (about 200 μm in thickness), and cast on a cooling drum. .

[0037] The film was stretched by a length of 3.5 times in each direction at a temperature of 130°C using a long stretching machine.

[0038] Then, the stretched film was heated at 200°C for 30 minutes.
It was heat-set for a fixed length of seconds and then subjected to a tensile test.

The results are shown in Table 1.

[0040]

[Table 1]

As is clear from the results in Table 1, the viscosity of sesame oil packaged in a bottle containing no PEN was significantly increased. Furthermore, when a large amount of PEN is included (Comparative Example 2), the tensile strength at break does not increase even when stretched.

Examples 3 and 4 and Comparative Examples 3 and 4 IV0.9
7. PET with Tg70℃ and IV0.63, Tg112
After drying each PEN chip at 150°C using dehumidified air for 5 hours, the cylinder temperature was set at 310°C and the screw rotation speed was 90 rpm using a single screw extruder.
It was melt-extruded, rapidly cooled in cold water, and further cut into chips with a diameter and length of approximately 2.7 mm. The IV of the obtained chip was 0.67 to 0.71.

The chips were then dried at 150° C. for 3 hours using dehumidified air, melted in an extruder, and cast onto a cooling drum through a die to form a film with a thickness of about 200 μm.

Next, the film was preheated with an infrared heater, and then vacuum formed using plug assist to form an opening with a diameter of 6.5 cm, a depth of 6 cm, and a bottom diameter of 5 cm.
It was molded into a cup shape.

The thus obtained cup was filled with white wine, and ultraviolet rays were irradiated from the side of the cup. The results are in Table 2
Shown below.

[0046]

[Table 2]

It is clear that the white wine packaged in PEN-free bottles changed color due to UV irradiation. In the case where the PEN weight ratio was 35% (Comparative Example 4), a good molded product could not be obtained when molded into a cup, so no UV irradiation test was conducted on wine.

Example 5 The film containing 4.5% PEN prepared in Example 2 was
The film was stretched 3.5 times both vertically and horizontally and heat-set at 200° C. to obtain a biaxially stretched film, and the film was processed into a bag shape by fusing its edges using a heat-sealing method.

[0049] After the beef was wrapped in the film, it was irradiated with ultraviolet rays at a temperature of about 10°C. After 10 hours of irradiation, the beef was taken out and compared with unirradiated beef, but there was almost no difference in surface color.

Comparative Example 5 Beef was packaged in a bag containing 0% PEN prepared in the same manner as in Example 5, and then irradiated with ultraviolet rays at a temperature of about 10°C. After 10 hours of irradiation, the beef was taken out and the surface color was compared with that of unirradiated beef. The color of beef irradiated with ultraviolet rays was slightly browner than that of beef that had not been irradiated.

[0051]

Effects of the Invention The packaging container with excellent ultraviolet blocking ability obtained by the present invention can protect foods that are easily deteriorated by ultraviolet rays from ultraviolet rays, and is useful for packaging cooking oil, wine, etc.

Claims (6)

[Claims] Claim 1: The material constituting the container wall is mainly composed of ethylene terephthalate units and ethylene naphthalene dicarboxylate units, and contains 99.8 to 90 ethylene terephthalate units based on the total weight of both units.
1. A food packaging container having excellent ultraviolet blocking properties, characterized in that it is a copolyester or a blend polyester containing 0.2 to 10% by weight of ethylene naphthalene dicarboxylate units. 2. The method according to claim 1, which is prepared using a resin obtained by melt-mixing a polymer mainly containing ethylene terephthalate units and a polymer mainly containing ethylene naphthalene dicarboxylate units and pelletizing the resultant mixture. food packaging containers. 3. The food packaging container with excellent ultraviolet blocking properties according to claim 1, wherein the ethylene naphthalene dicarboxylate is ethylene 2.6 naphthalene dicarboxylate. 4. The food packaging container with excellent ultraviolet blocking properties according to claim 1, which is used to package foods that are easily deteriorated by ultraviolet rays. 5. The food packaging container with excellent ultraviolet blocking properties according to claim 1, which is used to package alcoholic beverages, cooking oil, or meat. 6. The food packaging container with excellent ultraviolet blocking properties according to claim 1, which is in the form of a bottle, cup, tray, or bag.