JP2003170526A - Packaging film which shuts off light and can be heated by microwave and packaging material including this film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging material which shows sufficient light-barrier properties and a long-term shelf stability life and enables its packaged content such as liquid food to be heated by a microwave. <P>SOLUTION: The packaging material is formed of a laminate constituted of a packaging film made of a thermoplastic resin with an electrical insulating tin vapor-deposited layer formed on the surface, a paper layer and a thermoplastic resin layer formed on both sides of the paper layer. In addition, the oxygen-barrier properties can be enhanced with the use of an oxygen-barrier resin such as an ethylene/vinyl alcohol copolymer or a polyamide as the thermoplastic resin for the packaging film, or an oxygen-barrier resin layer as the laminate, and consequently, the shelf stability life can be prolonged. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a light blocking property,
The present invention relates to a packaging film that can be heated by microwaves, and a packaging material for foods that includes a laminate including the packaging film.

[0002]

2. Description of the Related Art Conventionally, milk, juice, coffee, tea,
As a packaging material for making containers for filling liquid foods such as alcoholic beverages, paper is mainly used, and paper and polyethylene, polypropylene, polyester, polyvinyl chloride, etc. plastic films, etc. are used to protect the paper and internal fillings. A stack of materials is used.

Manufactured using this liquid food paper packaging material,
The container filled with the internal filler is usually stored at a low temperature (about 5 ° C.) or room temperature by placing it on a shelf in the distribution process. In this storage, the quality of the liquid food, which is the content, is deteriorated by light and oxygen. Aluminum foil is used as one of the best packaging materials which can prevent the deterioration of the quality of liquid food due to light and oxygen and has a long shelf life. However, the use of aluminum foil is not preferable from the viewpoint of environmental problems. Further, in the case of using the aluminum foil, it is impossible to heat the liquid food, which is the content, by the microwave using a household microwave oven or the like.

As a packaging material which is intended to replace aluminum foil and has a long shelf life, it is proposed to use a silicon oxide vapor deposition film. The silicon oxide layer has an oxygen barrier property, and since the package does not have a metal layer in its structure, it can be heated by microwaves. However, the package does not have a light barrier property. Therefore, in order to extend the shelf life at room temperature, an additional light barrier layer is required.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a packaging film having a sufficient light barrier property and having a long shelf life on the shelf that enables heating of liquid foods by microwaves, and a packaging film using the same. The purpose is to provide wood.

[0006]

Means for Solving the Problems As a result of intensive investigations aimed at improving the above-mentioned problems, the present inventors have found that the use of a packaging film made of a thermoplastic resin having an electrically insulating tin vapor-deposited layer can provide the present invention. Find that you can achieve the purpose of
The present invention has been reached. In the present invention, the inner layer refers to a layer on the side in contact with the inner filling when the packaging material is used to package the inner filling, and the outer layer refers to the layer on the opposite side. Similarly, when the inner filling is packaged, the inner side means the side closer to the inner filling, and the outer side means the opposite side.

[0007] That is, the gist of the present invention is a packaging film which is made of a thermoplastic resin having an electrically insulating tin vapor deposition layer on its surface and which can be shielded from light and heated by microwaves.
Further, the packaging film of the present invention is characterized in that the thermoplastic resin is polyolefin. Further, the packaging film of the present invention is characterized in that the thermoplastic resin is polyester. Further, the packaging film of the present invention is characterized in that the thermoplastic resin is an oxygen barrier resin. Further, the packaging film of the present invention is characterized in that the oxygen barrier resin is an ethylene-vinyl alcohol copolymer or a polyamide.

The present invention further provides a paper packaging material formed from the above-mentioned packaging film, a paper layer, and a laminate having a thermoplastic resin layer on both sides of the paper layer. The paper packaging material of the present invention is characterized by having an oxygen barrier layer inside the paper layer.

Further, the gist of the present invention is a food filling and packaging system comprising forming a container from the above-mentioned paper packaging material and filling the container with food.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the thermoplastic resin forming the film of the present invention include polyolefin, polyester, polyvinyl chloride, polyamide, polycarbonate, ethylene-vinyl alcohol copolymer, polystyrene, methacrylic resin, ethylene-α-nonpolymer. Saturated carboxylic acid copolymer,
Ionomer, unsaturated carboxylic acid modified polyolefin,
Examples thereof include cyclic olefin copolymers, polyvinyl alcohol having a saponification degree of 95% or more, and acetyl cellulose.
Of these, polyolefin is particularly preferable, but in order to make the film have an oxygen barrier property, a polyamide or an ethylene-vinyl alcohol copolymer having an oxygen barrier property is preferable.

As the polyolefin, polyethylene,
Examples thereof include polypropylene, ethylene-propylene copolymer, polybutene-1, and the like, with polyethylene being particularly preferable. As polyethylene, high-density polyethylene,
Medium density polyethylene, low density polyethylene, linear low density polyethylene, linear low density polyethylene produced by using a metallocene catalyst (hereinafter, mLLDP
It is called E. ) Etc., but low density polyethylene and mLLDPE are particularly preferable. mLLDPE is an α-olefin having 4 to 8 carbon atoms in ethylene and a comonomer in the presence of a metallocene catalyst, preferably 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like. Is preferably produced by copolymerizing 6 or more α-olefins.

Examples of polyesters include polyethylene terephthalate and polybutylene terephthalate. Examples of polyamides include aliphatic polyamide resins such as polyamide 4-6, polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 6-12, polyamide 11 and polyamide 12, polyamide MXD6, polyhexamethylene diamine terephthalate (polyamide). 6
T), polyhexamethylenediamine isophthalamide,
An aromatic polyamide resin such as a xylene group-containing polyamide can be used. A colorant such as a pigment may be dispersed in these thermoplastic resins. The thickness of the thermoplastic resin film is preferably 5 to 30 μm.

The film of the present invention has an electrically insulating tin vapor deposition layer on the surface of the thermoplastic resin film. At this time, the degree of electrical insulation is preferably 10 ⁶ Ω / □ or more. As the vapor deposition method, a vacuum vapor deposition method is particularly preferable. For example, high-purity electrically insulating tin metal is used.
It is heated at a normal temperature (1,300 to 1,450 ° C.) and evaporated by high-frequency induction heating, direct current heating, electron beam heating, etc., and the vacuum degree is about 10 to 100 mPa. The thickness of the electrically insulating tin metal film formed by vapor deposition is 50 to 600 angstrom (5 to 60 nm),
It is particularly preferably 20 to 40 nm.

Before providing the electrically insulating tin vapor deposition layer on the surface of the film, an undercoat layer may be provided on the surface of the film. The undercoat layer is preferably made of a cured product of acrylate or methacrylate. Specific examples of acrylate and methacrylate include dipentaerythritol hexaacrylate, dipentaerythritol pentahexaacrylate, trimethylolpropane trimethacrylate, and pentaerythritol trimethacrylate. Examples thereof include acrylate, trimethylolpropane ethoxytriacrylate, dimethylolpropane tetraacrylate, tricyclodecane dimethanol diacrylate and the like. The method of providing the undercoat layer is preferably a method of applying the above acrylate or methacrylate solution and then irradiating it with hot air or ultraviolet rays or an electron beam to dry and cure. The thickness of the undercoat layer is preferably 5 μm or less. Furthermore, it is preferable to perform plasma treatment, corona discharge treatment or flame treatment on the surface of the film before providing the anchor coat layer.

The film of the present invention having an electrically insulating tin vapor-deposited layer on its surface does not cause an ignition phenomenon in a metal such as aluminum, which ignites when irradiated with microwaves, a metal foil, or a metal vapor deposition film. Therefore, the food packaged using this film can be shielded from light and heated by microwaves.

The present invention also provides a food paper packaging material formed from the above-mentioned packaging film, a paper layer, and a laminate having a thermoplastic resin layer on both sides of the paper layer. The above-mentioned packaging film may be provided on either side of the paper layer, but when the packaging film is formed of a thermoplastic resin having an oxygen barrier property, it is preferably provided inside the paper layer.

The paper forming the paper layer of the paper packaging material of the present invention is
A normal one having a basis weight of 50 to 350 g / m ² can be used.

The thermoplastic resin of the thermoplastic resin layer provided on both sides of the paper layer can be selected from the thermoplastic resins forming the above-mentioned packaging film, but polyolefin is preferable, and polyethylene is particularly preferable. The thermoplastic resin layers are provided on both sides of the paper layer, but may be in contact with or apart from the paper layer, and they may be one layer or multiple layers. The resins in those layers may be the same or different. The thickness of the thermoplastic resin layer is preferably 5 to 30 μm.

The paper packaging material of the present invention may further have an oxygen barrier layer inside the paper layer. Examples of the oxygen barrier layer include a layer formed of an ethylene-vinyl alcohol copolymer or polyamide and a layer containing an oxygen scavenger in polyolefin. Examples of the oxygen scavenger include sulfite, reducing organic compound, reduced metal and the like. Examples of the sulfite include sodium sulfite, potassium sulfite, and the like, and examples of the reducing organic compound include ascorbic acid, polyhydric phenols, catechins, and the like. Examples of the ascorbic acid include ascorbic acid, araboascorbic acid and salts thereof (sodium salt, potassium salt, etc.), and a mixture thereof can also be used. Examples of polyhydric phenols include pyrogallol, catechol, gallic acid, resorcin, hydroquinone and the like, and mixtures thereof can also be used.
Examples of catechins include epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, and the like, and a mixture thereof can also be used. Among these reducing organic compounds, ascorbic acids and catechins, particularly ascorbic acid and araboascorbic acid are preferable. Further, examples of the reducing metal include reduced iron. Among these oxygen scavengers, sulfite, particularly sodium sulfite is preferable. The above-mentioned polyolefin is suitable as the polyolefin. Of course, ethylene-vinyl alcohol copolymer or polyamide containing these oxygen scavengers can also be used. The content of the oxygen scavenger in the polyolefin is 1 to 20% by mass, particularly 3 to 1
0 mass% is preferable. The oxygen barrier layer may be provided anywhere inside the paper layer, but should be avoided in the innermost layer of the packaging material. The thickness of the oxygen barrier layer is 5 to 2
0 μm is preferable.

An adhesive resin layer may be provided inside the paper layer. Examples of the resin of the adhesive resin layer include acrylic resin-based, modified polyolefin-based, ethylene-vinyl acetate copolymer, polyamide-based, and epoxy resin-based resins. Examples of the acrylic resin system include polymers and copolymers of acrylic acid or methacrylic acid or its alkyl ester. As the modified polyolefin type, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, nadic acid, and nadic anhydride are added to polyethylene, polypropylene, etc. Examples include those grafted in the presence of a product. A modified polyolefin type is particularly preferable. The thickness of the adhesive resin layer is 5 to 2
5 μm is preferable.

The following are examples of the constitution of the paper packaging material of the present invention. Polyethylene (PE) (outermost layer) /
Packaging film / paper layer / PE / PE (innermost layer); PE (outermost layer) / packaging film / paper layer / PE / oxygen barrier layer / P
E (innermost layer); PE (outermost layer) / paper layer / PE / packaging film formed of a thermoplastic resin having oxygen barrier properties /
PE (innermost layer).

The paper wrapping material of the present invention having the above structure can be provided with a printing layer or the like which is usually provided. The print layer can be provided, for example, on the outer side of the PE (outermost layer) and between the PE and the packaging film, and the print layer can be formed by printing with ordinary ink using these inks.

The paper packaging material of the present invention is formed by laminating each of the above layers. The method of joining these layers is as it is when the layers are an adhesive layer or an adhesive layer, and the other layers are joined together. It is sufficient to bond them, and if not, a method in which a heat-meltable layer is heat-melted and attached to a layer in contact with it, a method in which layers capable of simultaneous extrusion are simultaneously extrusion-molded and laminated, and a method in which they are combined Any of the methods conventionally used for producing a laminated body can be adopted.

From the above-mentioned paper packaging material of the present invention, a rectangular parallelepiped such as a tetrabrick (registered trademark) type, a rectangular parallelepiped with a roof represented by a container containing 1 l of milk, a cube, a cylinder, a parallel octagonal prism, a central portion of a body It is possible to mold a conventionally known packaging container or the like such as a so-called tetra prism (registered trademark) type having a parallel octagonal prism and a quadrangular top and bottom with a pouch.

Further, the gist of the present invention is a filling and packaging system for a liquid food product, which comprises forming a container having the above-mentioned shape from the paper packaging material and filling the container with a liquid food product. After forming the container from the paper packaging material, the container may be filled with the liquid food, or the container may be formed and the liquid food may be filled at the same time. The filling and packaging system for these liquid foods is carried out according to the method which has been usually carried out conventionally.

[0026]

EXAMPLES The present invention will be described in detail below with reference to examples.

(Example 1) Density: 0.918 g / cm
³ , MI: 3g / 10min low density polyethylene (LD
After the surface of PE) film (30 μm) is subjected to corona discharge treatment, tin metal is vacuum-deposited in the chamber of a vacuum vapor deposition apparatus, and an electrically insulating tin metal layer (30 nm) is formed on the surface.
A packaging film of the present invention having Then, the packaging film (outermost layer), the LDPE film, a paper having a basis weight of 220 g / m ² , the LDPE film and the LDPE film (innermost layer) are laminated in this order by an extrusion molding method to form the paper of the present invention. The packaging material was manufactured. At this time, the tin metal layer of the packaging film is laminated so as to be in contact with the LDPE film.

(Example 2) An adhesive resin layer (a resin obtained by grafting maleic anhydride onto polypropylene), an ethylene-vinyl alcohol copolymer, between the LDPE film and the LDPE film (innermost layer) of Example 1. A paper packaging material of the present invention was produced in the same manner as in Example 1 except that the film (15 μm) and the adhesive resin layer were provided in that order.

(Example 3) Instead of the LDPE film used in Example 1, a polyamide MXD6 film (15) was used.
μm) was used, and the packaging film of the present invention was produced in the same manner as in Example 1. Then, L used in Example 1
DPE film, paper used in Example 1, LDPE film used in Example 1, packaging film produced above,
An adhesive resin layer (a resin obtained by grafting acrylic acid onto polypropylene) and the LDPE film used in Example 1 were laminated in that order by an extrusion molding method to produce a paper packaging material of the present invention. At this time, the tin metal layer of the packaging film is laminated so as to be in contact with the LDPE film.

(Comparative Example 1) Example 1 was repeated except that an aluminum vapor-deposited polyethylene terephthalate film (12 μm) was used in place of the packaging film produced in Example 1.
A packaging film was manufactured in the same manner as in. A paper packaging material was produced in the same manner as in Example 1 except that the packaging film produced above was used instead of the packaging film produced in Example 1. At this time, the aluminum vapor deposition surface of the aluminum vapor deposition polyethylene terephthalate film is L
Laminate so that it contacts the DPE film.

(Comparative Example 2) LDPE film used in Example 1, paper used in Example 1, LDP used in Example 1
The E film and the LDPE film used in Example 1 were laminated in this order by an extrusion molding method to produce a paper packaging material.

The light shielding properties of the paper packaging materials produced in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by Spectro U.
When the transmittance in the wavelength range of 400 to 600 nm was measured and evaluated using a V meter, the paper produced in Examples 1 to 3 and Comparative Example 1 was set to 100% in Comparative Example 2 having no metal deposition layer. The packaging material had a transmittance of less than 50%.

Using the paper packaging materials produced in Examples 1 to 3 and Comparative Examples 1 and 2, a 200 ml-brick type liquid food container was prepared and filled with milk. 600W using a household microwave oven,
When heated for 1 minute, the milk in the container filled with milk produced using the paper packaging materials produced in Examples 1 to 3 and Comparative Example 2 could be heated from 13 ° C to 35 ° C without any problem. On the contrary, the container filled with milk prepared using the paper packaging material produced in Comparative Example 1 was dangerous because sparks were generated during heating, and the heating was stopped.

Further, using the paper packaging materials produced in 1 to 3 and Comparative Examples 1 and 2, a 200 ml-brick type liquid food container was prepared and filled with pasteurized milk. Immediately after filling and under 2,000 lux illumination for 10
A sensory evaluation of the change in the taste of milk after storage for 2 days at ℃ resulted in the results shown in Table 1.

[0035]

[Table 1]

As is clear from the above results, the paper packaging material of the present invention has an excellent light-shielding property, and the liquid food having the contents packaged with the packaging material can be used in a microwave oven (microwave) for any purpose. It is possible to heat without problems.

[0037]

The paper wrapping material of the present invention is the same as the paper wrapping material manufactured by using the existing aluminum foil having excellent light shielding property.
While it is impossible to heat the liquid food in the package contents by microwaves, the liquid food in the package contents can be heated by microwaves without any problem. Moreover, since it is excellent in light-shielding property, it shows an effect that a container prepared using this paper packaging material and filled with liquid food can be stored on the shelf for a long time at low temperature or normal temperature. . By further providing the paper packaging material with an oxygen barrier layer, the period can be further extended.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Peter Frisk             6-12 Kioicho, Chiyoda-ku, Tokyo, Japan             Inside Trapack Co., Ltd. F term (reference) 3E067 AA03 AB01 AB26 BA05A                       BA12A BB01A BB14A BB15A                       BB25A BB30A CA06 CA12                       CA13 CA30 EA06 FA01 FC01                       GD10                 3E086 AB02 AD01 AD02 BA04 BA14                       BA15 BA40 BB05 BB22 BB33                       BB35 CA11 CA12 CA13 CA23                 4F100 AB21A AK01B AK01C AK01E                       AK03B AK06 AK41B AK46B                       AK69B AL01B BA02 BA05                       BA07 DG10D EH66 GB15                       GB23 JB16B JB16C JB16E                       JD03B JG04A JN02                 4K029 AA11 AA25 BA15 BA46 BB02                       BC00 BD00 CA01

Claims (8)

[Claims] 1. A packaging film which is made of a thermoplastic resin having an electrically insulating tin vapor deposition layer on its surface and which can be shielded from light and heated by microwaves. 2. The packaging film according to claim 1, wherein the thermoplastic resin is polyolefin. 3. The packaging film according to claim 1, wherein the thermoplastic resin is polyester. 4. The packaging film according to claim 1, wherein the thermoplastic resin is an oxygen barrier resin. 5. The packaging film according to claim 4, wherein the oxygen barrier resin is an ethylene-vinyl alcohol copolymer or a polyamide. 6. A food paper packaging material formed from the packaging film according to any one of claims 1 to 5, a paper layer, and a laminate having a thermoplastic resin layer on both sides of the paper layer. 7. The food paper packaging material according to claim 6, further comprising an oxygen barrier layer inside the paper layer. 8. A food filling and packaging system comprising forming a container from the paper packaging material according to claim 6 or 7 and filling the container with food.