JPS6337701B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum foil laminated packaging material suitable for packaging for retort or boil sterilization, and a method for producing the same.

Conventionally, laminates made by laminating aluminum foil and polyolefin have high light-shielding properties, high gas-blocking properties,
It is used as a food packaging material because of its properties such as good heat-sealability and good heat-sealability.
A three-layer laminate made of a polyolefin having a high softening point such as high-density polyethylene or polypropylene and a heat-resistant resin is widely used, especially as a packaging material for retort sterilized foods. However, in this laminate of aluminum foil and synthetic resin, a polymer having a hydroxyl group at the end, such as polyester polyol, polyether polyol, or polyurethane polyol, and a low molecular weight isocyanate compound, such as ethyl acetate, methyl ethyl ketone, toluene, isopropyl alcohol, etc. It is manufactured by applying a solution dissolved in an organic solvent to the surface of an aluminum foil or synthetic resin film, then evaporating the contained organic solvent to dryness, and then bonding the aluminum foil and synthetic resin film together. The solvent used in the adhesive or the low molecular weight compound in the adhesive remains between the layers of the resulting laminate, and this residual substance permeates through the synthetic resin layer of the laminate and transfers to the contents, so When used as food packaging materials, the transfer of odor from residual substances to the contents causes a significant reduction in product value.

By the way, it is already known to use modified polyolefin as an adhesive layer between the metal and polyolefin layers, and to laminate the metal and polyolefin (see Japanese Patent Publication No. 10757/1983). Applying this technology,
Polyolefin can be laminated onto aluminum surfaces without using adhesives containing solvents. That is, a layered structure of aluminum foil/modified polyolefin/polyolefin can be obtained without using conventional adhesives that may leave solvents or low molecular weight substances behind. However, in order to use it as a packaging material for retort or boil sterilization, it is necessary to laminate one or more layers of heat-resistant film on the aluminum foil side to provide strength. Usually, the polyolefin layer is the layer that comes into contact with the contents, and the heat-resistant film layer is the outside layer. The heat-resistant film is laminated with the aluminum foil by a normal dry lamination method since the adhesive layer is located outside the aluminum foil. However, aluminum foil has the disadvantage of being susceptible to pinholes, which may occur during processes such as lamination, bag making, and filling. Therefore, even if a dry laminating adhesive is not used to laminate aluminum foil and polyolefin, residual solvent between the heat-resistant film and aluminum foil or low-molecular weight compounds of the adhesive component may be absorbed through pinholes in the aluminum foil. There is a risk that it will shift to the material side.

Therefore, the present inventor conducted research to obtain a packaging material for retort or boil sterilization without using conventional adhesives for dry lamination. A composite film of a biaxially oriented polyester film and an aluminum foil is formed by laminating them through the film, and then an ethylenically unsaturated monomer having a carbonyl group is melt-extruded onto the aluminum foil side of the composite film and copolymerized. It was discovered that an aluminum foil laminated packaging material could be obtained without using a dry laminating adhesive by laminating polyolefin films via a modified polyolefin layer and heating the modified polyolefin to a temperature higher than the softening temperature of the modified polyolefin. The present invention has been completed based on this.

The gist of the first invention is that a linear copolymerized polyester layer, an aluminum foil, a modified polyolefin layer formed by copolymerizing an ethylenically unsaturated monomer having a carbonyl group, and a polyolefin film are provided on one side of a biaxially oriented polyester film. This is an aluminum foil laminated packaging material in which a biaxially stretched polyester film and an aluminum foil are laminated via a linear copolyester layer obtained by melt extruding a biaxially stretched polyester film and an aluminum foil. A composite film of foil is formed, and then a polyolefin film is laminated on the aluminum foil side of the composite film via a modified polyolefin layer formed by copolymerizing an ethylenically unsaturated monomer having a melt-extruded carbonyl group, This is a method for producing an aluminum foil laminated packaging material, which is characterized by heating the modified polyolefin to a temperature higher than the softening temperature.

The aluminum laminated packaging material of the present invention is suitable as a food packaging material for boil sterilization or retort sterilization, and has the advantage that no odor is transferred to the contents due to solvents or low molecular weight compounds.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the aluminum foil laminated packaging material of the present invention. A biaxially stretched polyester film 1 and an aluminum foil 3 are laminated with a linear copolymerized polyester layer 2 interposed therebetween, and a polyolefin film 5 is further laminated on the aluminum foil 3 with a modified polyolefin layer 4 interposed therebetween.

FIG. 2 shows an example of a method for producing an aluminum foil laminated packaging material.

A biaxially oriented polyester film 1 and an aluminum foil 3 are laminated via a linear copolymerized polyester layer 2 melt-extruded from a first T die 6, and a polyolefin film 5 is further applied to the third surface of the aluminum foil by a second T die. After being superimposed via the modified polyolefin layer 4 melt-extruded from the die 7, the aluminum foil laminated packaging material 9 is obtained by heating with a heating roll 8 to a temperature equal to or higher than the softening temperature of the modified polyolefin.

Therefore, as a biaxially oriented polyester film, an esterification reaction is performed from a dibasic acid component consisting of at least 85 mol% of terephthalic acid and a glycol component consisting of an aliphatic glycol such as ethylene glycol, propylene glycol, trimethylene glycol, etc. A biaxially stretched resin film having dibasic acid residues and glycol residues thus obtained can be used. The thickness of this biaxially stretched polyester film is suitably 5 to 50 microns, preferably 7 to 25 microns.

Next, in the present invention, as the linear copolymer polyester, a linear copolymer resin having an aromatic dibasic acid residue, an aliphatic dicarboxylic acid residue, and a glycol residue can be applied. Here, aromatic dibasic acid residues include terephthalic acid, isophthalic acid, phthalic acid, diphenyl dicarboxylic acid, etc., and aliphatic dicarboxylic acid residues include adipic acid, sebacic acid, dodecanedicarboxylic acid, etc. Glycol residues include diethylene glycol residues, trimethylene glycol residues, alkylene glycol residues having 2 to 10 carbon atoms (propylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol) , octamethylene glycol, nonamethylene glycol, decamethylene glycol, etc.).

The thickness of the linear copolyester layer is suitably 2 to 50 microns, preferably 5 to 20 microns.

Next, in the present invention, the thickness of the aluminum foil is 5
~100μ is appropriate.

Next, the modified polyolefins used in the present invention include ethylene, propylene, butene, pentene, hexene, octene, nonene, decene, 4-
One or more olefins such as methylpentene-1, acrylic acid, maleic acid, fumaric acid,
It is a copolymer of one or more ethylenically unsaturated monomers having a carbonyl group, such as itaconic acid, maleic anhydride, ethyl acrylate, methyl methacrylate, acrylamide, and maleimide.

The copolymerization referred to herein means block copolymerization, random copolymerization, or graft copolymerization to polyolefin.

Further, a metal compound such as aluminum hydroxide or aluminum carbonate may be mixed with the modified polyolefin.

The thickness of the modified polyolefin layer is 1 to 50 microns, preferably 2 to 20 microns.

Next, the polyolefin film used in the present invention includes ethylene, propylene, butene, pentene, hexene, octene, nonene, decene,
-Methylpentene- It is made by molding a resin obtained by polymerizing one or more olefins such as 1, and its thickness is suitably 20 to 200μ, preferably
It is 30-100μ.

In the present invention, heating the laminate to a temperature higher than the softening temperature of the modified polyolefin may be performed either inside or outside the extrusion laminator line, and the heating may be performed using any method such as a hot roll oven, high-frequency induction heating device, infrared heater, etc. It doesn't matter if it depends on you.

The aluminum foil laminated packaging material obtained by the production method of the present invention is suitable as a food packaging material for boil sterilization or retort sterilization. It is desirable to use high-density polyethylene or polypropylene as the material.

In order to ensure sufficient adhesion between the modified polyolefin layer and the polyolefin layer, it is preferable to use the same polyolefin.

Furthermore, copolymers of ethylene and α-olefins such as butene, octene, and 4-methylpentene-1 produced by a low-pressure method can also be used for boiling or low-temperature retort applications at temperatures below 120°C.

The aluminum foil laminated packaging material obtained by the production method of the present invention does not require the use of conventional solvent-based curable adhesives such as urethane or epoxy when bonding each layer of biaxially oriented polyester, aluminum foil, and polyolefin. In addition, it is suitable as a packaging material for boiled and retort sterilized foods, and there is no odor transfer from solvents or low-volume compounds to the contents.

Next, the manufacturing method of the present invention does not require the process of evaporating an organic solvent to dryness, and in-line lamination of a biaxially oriented polyester film on one side of the aluminum foil and lamination of a polyolefin film on the other side of the aluminum foil. It has the advantage of being able to obtain products extremely efficiently.

Next, the present invention will be specifically explained by giving examples.

Example 1 A biaxially stretched polyethylene terephthalate film with a thickness of 12μ and an aluminum foil with a thickness of 15μ were laminated via a linear copolymer polyester (manufactured by Toagosei Kagaku, trade name: PES-170) melt-extruded to a thickness of 10μ. A composite film of a biaxially oriented polyester film and aluminum foil is formed using a polyester film, and then a modified polypropylene (manufactured by Mitsui Petrochemicals, trade name: Admer QF305) melt-extruded to a thickness of 15 μm is applied to the aluminum foil side of the composite film to form a composite film of 60 μm. An aluminum foil laminated packaging material was obtained by stacking polypropylene films with a thickness of

Example 2 Biaxially oriented polyethylene terphthalate with a thickness of 12μ and aluminum foil with a thickness of 15μ were laminated via a linear copolymer polyester (manufactured by Toyobo Co., Ltd., trade name: Vylon GX150) melt-extruded to a thickness of 15μ. A composite film of an axially oriented polyester film and aluminum foil is formed, and then a 60 μm thick layer of melt-extruded modified polypropylene (manufactured by Toyo Ink, trade name: Liosen M-1063) is applied to the aluminum foil side of the composite film to a thickness of 15 μm. An aluminum foil laminated packaging material was obtained by overlapping thick polypropylene films and then heating them with a hot roll at 210°C.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the aluminum foil laminated packaging material of the present invention, and FIG. 2 is a schematic diagram showing the manufacturing process according to the method of manufacturing the aluminum foil laminated packaging material of the present invention. DESCRIPTION OF SYMBOLS 1... Biaxially stretched polyester film, 2... Linear copolymerized polyester, 3... Aluminum foil, 4...
Modified polyolefin, 5... Polyolefin in film, 6... First T-die, 7... Second T-die, 8...
Heating roll, 9...Aluminum foil laminated packaging material.

Claims (1)

[Claims] 1. A linear copolymerized polyester layer on one side of a biaxially oriented polyester film, an aluminum foil, a modified polyolefin layer formed by copolymerizing an ethylenically unsaturated monomer having a carbonyl group, and a polyolefin film. Sequentially laminated aluminum foil packaging material. 2. A biaxially oriented polyester film and aluminum foil are laminated via a melt-extruded linear copolymerized polyester layer to form a composite film of the biaxially oriented polyester film and aluminum foil, and then on the aluminum foil side of the composite film. Aluminum foil laminated packaging, characterized in that polyolefin films are laminated via a modified polyolefin layer formed by copolymerizing a melt-extruded ethylenically unsaturated monomer having a carbonyl group, and heated to a temperature higher than the softening temperature of the modified polyolefin. Method of manufacturing wood.