JPH04239640A - Food packing container excellent in ultraviolet screening properties - Google Patents

Abstract

PURPOSE:To provide a container packing food easily deteriorated by ultraviolet rays by imparting ultraviolet screening properties to a packing container composed of polyethylene terephthalate excellent in transparency. CONSTITUTION:A container having a multilayer wall together using a layer of a material obtained by adding an ethylene naphthalene dicarboxylate unit to polyethylene terephthalate containing ethylene terephthalate as a main repeating unit in a copolymer or polymer form is excellent from the aspect of food sanitation and ultraviolet screening properties and suitable for packing edible oil, alcohol beverage or edible meat.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention relates to a food packaging container with excellent ultraviolet blocking properties, and more specifically, it is used for packaging alcoholic beverages, cooking oil, and meat that are easily deteriorated by ultraviolet rays. This article relates to food packaging containers that are excellent for use in food packaging. [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, 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. 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. [Means for Solving the Problems] The present inventor focused on the problem that PET is transparent to ultraviolet rays, and has developed a method for improving the ultraviolet blocking properties of polyester packaging containers that are colorless and transparent and have excellent hygiene. As a result of extensive research, we have found that a multilayer packaging container containing at least one layer made of a polyester made of a copolymer of ethylene terephthalate units and ethylene naphthalene dicarboxylate units, or a mixture of each unit, is highly resistant to external ultraviolet rays. The present invention was achieved by discovering that it is possible to prevent deterioration of the contents by blocking . That is, in the present invention, the container wall has a multilayer structure,
The material constituting each layer of the multilayer structure mainly consists of at least one of ethylene terephthalate units and ethylene naphthalene dicarboxylate units, at least one layer of the multilayer structure contains ethylene naphthalene dicarboxylate units, and The material constituting the multilayer structure contains ethylene naphthalene dicarboxylate units in a proportion of 0.2 to 10% by weight based on the total weight of ethylene terephthalate units and ethylene naphthalene dicarboxylate units. It is a food packaging container with excellent properties. [0009] In the present invention, the weight ratio of ethylene naphthalene dicarboxylate units contained in the polyester of the copolymer or mixture is the sum of ethylene naphthalene dicarboxylate units and ethylene terephthalate units with respect to the materials of all layers of the multilayer structure. Based on weight, 0.
2% to 10% by weight, preferably 0.2% 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, it may become difficult to form into packaging containers. [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 layer containing ethylene naphthalene dicarboxylate units for a container is produced by an injection blowing method. If prepared by blending the thermoplastic polyester (B) and the thermoplastic polyester (C) immediately before the injection of the resin, or just before the resin is extruded from the die in the case of injection blowing, good. [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. [0019] As a method for molding the container of the present invention, for example, when the container is a hollow molded body such as a bottle, a preformed body is prepared using, for example, a co-injection molding machine, and then blowing is carried out in a blow mold. A method can be adopted in which a hollow molded body is created by performing the following steps. Hollow molded bodies such as cups and trays can be obtained, for example, as follows. That is, a multilayer unstretched sheet or film is produced by molding by co-injection molding, or by first melting the resin using a coextruder, passing it through a multilayer die into a sheet or film, and casting it on a cooling drum. Then, the unstretched sheet or film is preheated or the unstretched sheet or film is prestretched, the sheet or film is preheated, and the thermoforming method, i.e., the vacuum forming method, the pressure forming method, the vacuum pressure forming method, etc. Created by [0020] There are various combinations of multilayer structures. For example, two layers, a layer (I) mainly consisting of polyester (B) and a layer (II) mainly consisting of polyester (C),
Alternatively, a combination of three or more layers such as layer (I) - layer (II) - layer (I), furthermore, a layer (III) mainly composed of polyester (A) or a layer (IV) mainly composed of polyester (D). There are multilayer structures in combination with layer (I) and layer (II). In the present invention, the material constituting two adjacent layers of the multilayer structure of the container wall is ethylene naphthalene dicarboxylate based on the total weight of the ethylene terephthalate units and ethylene naphthalene dicarboxylate units of the material constituting the multilayer. It is preferable that the difference in weight % (content ratio) of rate units does not exceed 10 (weight %). If the difference in content ratio of ethylene naphthalene dicarboxylate units between adjacent layers is too large, peeling between the layers may occur when stretch blow molding, thermoforming, etc. are performed, for example. [0022] In the multi-layer walled container of the present invention described in detail above, regardless of the combination of the multi-layer structures, each layer of the multi-layer structure contains ethylene terephthalate units and ethylene naphthalate units of the materials constituting each layer. It is preferable that the material is made of a material having a content of ethylene naphthalene dicarboxylate units in the range of 0.2 to 10% by weight based on the total weight of carboxylate units. Layers (I) to (IV) made of polyester
Among any of the above combinations, aromatic polyamides (for example, polyamides consisting of metaxylylene diamine groups and adipic acid groups) and copolymer polymers consisting of ethylene groups and polyvinyl alcohol groups are included for the purpose of improving gas barrier properties. Additional layers can also be added. [Examples] The present invention will be explained in more detail with reference to Examples below. The main experimental conditions and measurement conditions for physical property values are as follows. 002
5] Ultraviolet irradiation test: The UV irradiation test on food packaged in containers was carried out using a germicidal lamp GL-15 manufactured by Toshiba Corporation.
An acceleration test was performed by placing the food at a distance of 5 cm from the food, and irradiating the food at room temperature unless otherwise specified. Physical property measurement method Ultraviolet irradiation test: (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: Measured using a SEP-DI model Poick integrating sphere light transmittance meter manufactured by Mitsubishi Kasei Corporation. (4) Viscosity of cooking oil: Measured at 25° C. using a B-type viscometer B8M manufactured by Tokyo Keiki Co., Ltd. (5) Tensile test: A test piece with a width of 1 cm and a length of 10 cm was cut 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: Measured by a transmission method using a color difference meter CZ-Σ90 manufactured by Nippon Denshoku Co., Ltd. (7) Layer thickness: Before the end of the coextrusion or co-injection test, a coloring agent was added to some of the resins, and the cross section of the molded product was observed through a microscope. The thickness of the layer was determined. In the case of bottles and cups, measurements were taken at each position divided into four equal parts in the circumferential direction at the center of the height, and the measurements were averaged. Examples 1 and 2 and Comparative Examples 1 and 2IV
1.1, Tg 70°C PET and IV 0.67, Tg1
After each PEN chip at 13°C was dried with hot air at 160°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 chip was cut into m. The IV of the obtained chip was 0.71 to 0.76. After drying this chip with hot air at 160° C. for 3.5 hours, a one-stage stretch-blown bottle was obtained using a co-injection bottle molding machine manufactured by Nissei ASB Machinery Co., Ltd. The total height of the bottle is 230mm, and the outer diameter of the body is 70m.
m, body wall thickness 320-430μm, internal volume approximately 680ml
Met. The wall structure of the bottle consists of three layers, the first layer (outer layer) and the third layer (inner layer) are made of the same composition, and the middle second layer (intermediate layer) is made of the first layer (outer layer) and the third layer (inner layer). The layer (inner layer) is made of a material with a different composition. [0036] Sesame oil was placed in the bottle thus obtained and an ultraviolet irradiation test was conducted. The results obtained are summarized in Table 1. [Table 1] Examples 3 to 5 and Comparative Examples 3 to 6 Example 1,
After drying at 150°C for 5 hours using the melt-blended chips of PET and PEN obtained in Comparative Examples 1 and 2 and Comparative Examples 1 and 2, a coextrusion die was added using a coextruder consisting of two extruders. A film of about 200μ was obtained by casting on a cooling drum. The obtained films consisted of two layers (Comparative Examples 3 and 4 and Examples 3 and 4).
), a film consisting of three layers, that is, the first layer and the third layer are made of a material with the same composition, and the second layer (intermediate layer) is made of a material with a different composition from the first and third layers (Comparative Example 5) , 6 and Example 5). Next, the film was preheated with an infrared heater, and then a cup was molded using a plug assist pressure forming method. The cup had a depth of 6.5 cm and an opening diameter of 6 cm. The cup thus obtained was filled with white wine and subjected to an ultraviolet irradiation test. [0040] Also, a part of the cup was cut out and the light transmittance was measured. The results obtained are shown in Table 2 and FIG. 1. [Table 2] Example 7 After packaging beef with the film prepared in Example 4,
Ultraviolet rays were irradiated at a temperature of about 10°C. [0043] After 10 hours of irradiation, the beef was taken out and the surface color was compared with that of unirradiated beef. The color of the meat irradiated with ultraviolet rays was almost the same as that of unirradiated beef. Comparative Example 7 After packaging beef with the film prepared in Example 3,
Ultraviolet rays were irradiated under the same conditions as in Example 7. The color of the beef irradiated with ultraviolet rays was slightly brownish compared to the beef that had not been irradiated. [0046] The packaging container obtained by the present invention can effectively block ultraviolet rays, and can protect foods that are easily deteriorated by ultraviolet rays from UV rays,
Useful for packaging wine, etc.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the light transmittance of a cup wall made of the polyester blend of the present invention.

Claims (7)

[Claims] Claim 1: The container wall has a multilayer structure, the material constituting each layer of the multilayer structure is mainly composed of at least one of ethylene terephthalate units and ethylene naphthalene dicarboxylate units, and at least one layer of the multilayer structure contains ethylene naphthalene dicarboxylate units, and the material constituting the multilayer structure contains 0.2 to 10 ethylene naphthalene dicarboxylate units by weight based on the total weight of ethylene terephthalate units and ethylene naphthalene dicarboxylate units. A food packaging container with excellent ultraviolet blocking properties characterized by containing % of UV rays. 2. The material constituting two adjacent layers of the multilayer structure has a weight percentage of ethylene naphthalene dicarboxylate units based on the total weight of ethylene terephthalate units and ethylene naphthalene dicarboxylate units of the material constituting each layer. 2. A food packaging container with excellent ultraviolet blocking properties according to claim 1, which is made of a material having a content difference of not more than 10 (wt%). 3. Each layer of the multilayer structure has an ethylene naphthalene dicarboxylate unit content of 0.2 to 0.2, based on the total weight of ethylene terephthalate units and ethylene naphthalene dicarboxylate units of the material constituting each layer. The food packaging container with excellent ultraviolet blocking properties according to claim 1, which is composed of a material in the range of 10% by weight. 4. The food packaging container with excellent ultraviolet blocking properties according to claim 1, wherein the ethylene naphthalene dicarboxylate units are ethylene-2.6 naphthalene dicarboxylate units. 5. 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. 6. The food packaging container with excellent ultraviolet blocking properties according to claim 1, which is used to package alcoholic beverages, cooking oil, or meat. 7. 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.