JPS6245062B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminate including an aluminum layer,
More specifically, it is a laminate containing metallic aluminum and an aluminum layer mainly made of plastic or paper material, which retains its metallic luster even after undergoing steam treatment such as retort heat sterilization treatment or hot water treatment such as hot water sterilization treatment. Regarding.

Conventional packaging materials, especially those used for containers (pouches, bottles, cans, etc.) that can withstand long-term storage of foods at room temperature, and whose main layer is plastic or paper, have gas barrier properties ( In order to ensure a good gas barrier (especially against oxygen gas), organic films with excellent gas barrier properties (ethylene-vinyl alcohol copolymer, polyvinylidene chloride, cellophane, etc.) or aluminum foil (manufactured by rolling, the thickness is usually 8 μm) are used. However, the gas barrier properties of the former organic film are not sufficient, and it is usually necessary to store the food in a refrigerator or by increasing the thickness of the organic film. Efforts are being made to prevent deterioration due to oxidation.

On the other hand, when using the latter aluminum foil, during the retort heat sterilization treatment or hot water sterilization treatment after filling and sealing the food contents, high-temperature water vapor permeates through the plastic thin film on the aluminum foil and reacts with the aluminum surface. The problem is that the surface changes unevenly, loses its metallic luster, and tends to take on a mottled, grayish, dull appearance. Furthermore, aluminum foil is relatively expensive and cannot be used in containers such as bottles.

The present invention was made in view of the problems of the prior art described above, and the present invention maintains metallic luster even when high-temperature water vapor permeates through treatments such as retort heat sterilization treatment and hot water sterilization treatment. An object of the present invention is to provide a packaging laminate whose main layers are aluminum metal and plastic or paper, which has a high-quality image, has an excellent gas barrier, and has low material cost.

In order to achieve the above object, the present invention provides a base layer with a thickness of approximately 300 mm on a base layer mainly made of plastic or paper material.
A laminate comprising a vapor-deposited metal aluminum layer of ~3000 Å and a protective film layer formed on the metal aluminum layer, wherein at least a portion of the base layer and/or the protective film layer is in contact with the aluminum layer. , free carboxyl groups per 100 grams of resin
The object of the present invention is to provide a laminate including an aluminum layer characterized by being made of the resin containing 0.1 to 1700 milliequivalents.

The present invention will be described below with reference to the drawings which are examples.

The laminate 1 shown in FIG. 1 consists of a base layer 2, a vapor-deposited metal aluminum layer 3 (hereinafter referred to as the aluminum layer), and a protective film layer 4. Aluminum layer 3
has a thickness of about 300 to 3000 Å and is formed by depositing metallic aluminum on the base layer 2 by a so-called vapor phase plating method such as vacuum evaporation, ion plating, or sputtering.

The base layer 2 needs to have mechanical strength (especially in the case of a film) and heat resistance to withstand this formation. After forming the container, filling it with contents and sealing it,
When undergoing treatments such as retort heat sterilization treatment and hot water sterilization treatment, it is necessary to have properties such as hot water resistance, thermal dimensional stability, and water swelling resistance to withstand these treatments. Satisfying these physical conditions,
Plastics that can be used for the base layer 2 include linear polyester resins such as oriented polyethylene terephthalate, low density polyethylene, high density polyethylene, polypropylene, polyolefin resins such as ethylene-propylene copolymers, acrylic resins, polystyrene resins, and AS. Resin, ABS resin, polyamide resin, polyimide resin, polyimine resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, vinylidene copolymer, urea resin, phenolic resin, epoxy resin, Melamine resin, urethane resin, xylene-formaldehyde resin, acetal resin,
Examples include coumaron indene resin, diallyl phthalate resin, and fluorine resin.

Furthermore, in order to prevent the aluminum layer 3 from losing its metallic luster due to the permeation of high-temperature water vapor, the resin in at least the portion of the base layer 2 in contact with the aluminum layer 3 (for example, in the case of a laminate, the resin in the layer in contact with the aluminum layer 3 must be resin) has free carboxyl groups per 100 grams of the resin (i.e. plastic).
It is desirable to contain 0.1 to 1700 milliequivalents, preferably 0.2 to 500 milliequivalents. However, at least the portion of the protective film layer 4 in contact with the aluminum layer 3 contains free carboxyl groups of 0.1 to 0.1 to 100 grams per 100 grams of resin.
In the case of the resin containing 1700 milliequivalents, this is not necessarily necessary.

If the amount of free carboxyl groups is less than the above 0.1 milliequivalent, the preservation of metallic luster will be poor, while if it is contained in excess of 1700 milliequivalents,
The physical properties of such resins pose application difficulties.

The base layer 2 is made of a single resin that satisfies the above-mentioned physical and chemical conditions, or a blend or laminate of these resins. When the base layer 2 includes a paper material, parchment paper, kraft paper, cellophane, etc., coated on both sides with a resin containing a carboxyl group within the above range, is used. The base layer 2 may be in the form of a film or a sheet, or may be a molded object (for example, a bottle, a cup, or a can).

The thickness of the aluminum layer 3 needs to be about 300 to 3000 Å. If it is thinner than about 300 Å, it will be difficult to form a continuous film, resulting in poor gas barrier properties and insufficient metallic luster.On the other hand, if it is thicker than about 3000 Å, there will be little improvement in gas barrier properties. This is because, on the contrary, this results in higher material and manufacturing costs.

The protective film layer 4 has a function of preventing the aluminum layer 3 formed on the base layer 2 from coming off due to friction or the like. Therefore, it is desirable that the aluminum layer 3 is made of a strong organic coating, and furthermore, it needs to be made of a coating that maintains the metallic luster of the aluminum layer 3 even when high-temperature water vapor passes through it. In addition, it is desirable that the material has hot water resistance and high temperature steam resistance to the extent that it does not change in quality even when subjected to retort heat sterilization treatment or the like.

Materials that can form such an organic film include low-density polyethylene, high-density polyethylene,
Polyolefin resins such as polypropylene, ethylene-propylene copolymers, ionomers, linear polyester resins, polyamide resins, polyvinyl chloride resins, vinyl chloride-vinyl acetate copolymers, polyvinyl acetate resins, ethylene-vinyl acetate copolymers, ABS resin, ethylene-vinyl alcohol copolymer, phenolic resin, furan resin, xylene-formaldehyde resin, urea resin, melamine resin, coumaron indene resin, alkyd resin, thermosetting acrylic resin, epoxy resin, urethane resin, thermosetting Examples include resins such as type polyester resins, unsaturated polyester resins, diallyl phthalate resins, acrolein resins, bismaleimide resins, cyclopentanediene resins, triallyl cyanurate resins, and combinations thereof.

If at least the portion of the base layer 2 that is in contact with the aluminum layer 3 is not made of the resin containing 0.1 to 1,700 milliequivalents of free carboxyl groups per 100 grams of the resin, as described above, the protective film layer 4
At least the part in contact with the aluminum layer has a free carboxyl group of 0.1 to 100 grams per 100 grams of resin.
It is necessary that the resin contains 1700 milliequivalents, preferably 0.2 to 500 milliequivalents. The reason for this is the same as mentioned above regarding base layer 2.

The protective film layer 4 is formed by coating or laminating, and its thickness is approximately 0.5 to 1000 μm, more preferably, depending on the type of resin.
Preferably, it is about 2 to 500 μm. Approximately 0.5μm
If it is thinner, it will not provide enough protection and will be around 1000
This is because it is not practical if it is thicker than μm.

In order for the aluminum layer 3 to retain its metallic luster without being corroded by high-temperature water vapor passing through the base layer 2 and/or the protective film layer 4, a resin containing free carboxyl groups in the above-mentioned range is required. , must be in contact with the aluminum layer 3 as described above.

Examples of resins containing free carboxyl groups in the polymer chain include polyester resins having terminal carboxyl groups, or monomer units containing acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc., which have carboxyl groups in side chains. Examples include polymers.

In addition, aliphatic linear monocarboxylic acids having 4 to 18 carbon atoms such as lauric acid and caproic acid, aliphatic monocarboxylic acids such as malonic acid, succinic acid, and maleic acid, so as to contain free carboxyl groups in an amount within the above range. Compounds containing carboxyl groups such as dicarboxylic acids, aromatic carboxylic acids such as benzoic acid, phthalic acid, terephthalic acid, salicylic acid, gallic acid, and pyromellitic acid, and carboxylic acids from natural lipids such as dimer fatty acids, polymerized fatty acids, and rosin acid ( A) or the above compound
It may be a resin blended with a polymer containing (A) or a polymer (for example, an acrylic acid polymer) in which a compound containing a carboxyl group is used as a monomer unit.

In addition, acid anhydrides that generate free carboxyl groups by reacting with other coexisting substances, moisture in the air, or moisture that permeates during retort sterilization, such as maleic anhydride, octylsuccinic anhydride, anhydride It may be a resin blended with phthalic acid, tetrahydrophthalic anhydride, pyromellitic anhydride, derivatives thereof, glutaric anhydride and derivatives thereof, or polymers containing these.

Since the laminate of the present invention contains an appropriate amount of free carboxyl groups in the resin of the base layer and/or the protective film layer that are in contact with both sides of the aluminum layer, the laminate is subjected to retort heat sterilization treatment (for example, 120°C x 30 minutes, or 145
Even if high-temperature water vapor permeates through the base layer and protective film layer by treatment such as sterilization with hot water (℃ x 3 minutes),
It is possible to maintain the metallic luster.

Furthermore, since the aluminum layer is made of a very thin vapor-deposited metal aluminum layer with a thickness within a predetermined range, it has the advantage of excellent gas barrier properties, low material and manufacturing costs, and the ability to be applied to molded objects such as bottles.

Examples will be described below.

Example 1 Toyobo Copolyester resin [acid value 4.5 KOH mg/g] solution [solid content 10 wt] was applied to the vapor deposition surface of a 25 μm biaxially stretched polyethylene terephthalate film on which a metal aluminum layer with a thickness of 500 Å was vapor-deposited on one side.
%, chloroform (commercially available, special grade) solution] using a bar coater, and the solvent was removed in a dry heat oven at 180°C for 5 minutes (the coating film thickness after removing the solvent was 8μ).
m) A laminate with metallic luster was produced. This laminate was treated with superheated steam at 120°C for 30 minutes, but the metallic luster was not lost. The oxygen gas permeability of this laminate was measured using an oxygen gas permeability tester Oxytran manufactured by Mo-con, and the result was 0.4cc/m ²・day・
It was atm (at 27℃).

Example 2 An acrylic-epoxy paint manufactured by Toyo Ink Co., Ltd. [acrylic value:
32.6KOHmg/g, solid content 36wt%] A commercially available product was coated with a bar coater and baked in a dry heat oven at 190°C for 12 minutes (coating film thickness after baking was 7 μm) to produce a laminate with metallic luster. . Heat this laminate to 120℃
Although treated with superheated steam for 30 minutes, the metallic luster was not lost. The oxygen gas permeability of this laminate is
0.4cc/ ^m2 ． It was day.atm.

Example 3 100 parts by weight of epoxy resin Epicoat 1007 manufactured by Ciel Chemical Co., Ltd. was added to Betsucomin P-138 manufactured by Dainippon Ink Co., Ltd. on the vapor deposition surface of the same metal aluminum vapor-deposited polyethylene terephthalate film as in Example 1.
Epoxy-urea resin paint obtained by blending (urea resin) to 14.9 parts by weight [solid content 30wt]
%, toluene-methyl ethyl ketone equivalent mixed solvent solution], 1.15 parts by weight of succinic acid (commercial product special grade)
was added and coated using a bar coater. This film was baked in a dry heat oven at 200° C. for 12 minutes (coating film thickness after baking was 7 μm) to produce a laminate with metallic luster. In addition, a laminate having a metallic luster having a composition not containing succinic acid was also produced by the above method, and the following experiments were conducted.

These two types of laminates (with and without succinic acid) are
As a result of superheated steam treatment at 120°C for 60 minutes, the film coated with succinic acid-free epoxy-urea resin paint became transparent, while the film coated with succinic acid-containing epoxy-urea resin paint lost its metallic luster. I couldn't help it. The oxygen gas permeability of this laminate that did not lose its metallic luster was 0.4cc/
^m2・day・atm (at 27℃).

Example 4 On the vapor deposition surface of the metal aluminum vapor-deposited polyethylene terephthalate film similar to that in Example 1, 100 parts by weight of epoxy resin Epicoat 1007 produced by Ciel Kagaku Co., Ltd. was mixed with Betsucomin P-138 produced by Dainippon Ink Co., Ltd.
Epoxy-urea resin paint obtained by blending (urea resin) to 14.9 parts by weight [solid content 30wt]
%, toluene-methyl ethyl ketone equivalent mixed solvent solution], and further add terephthalic acid (commercial product special grade).
2.2 parts by weight was added and coated using a bar coater. This film was baked in a drying oven at 200° C. for 12 minutes (coating film thickness after baking was 7 μm) to produce a laminate with metallic luster. In addition, a laminate with a metallic luster having a composition not containing terephthalic acid was also produced by the above method, and the following experiments were conducted.

As a result of superheated steam treatment of these two types of laminates (with and without terephthalic acid) at 120°C for 60 minutes, the film coated with epoxy-urea resin paint that does not contain terephthalic acid becomes transparent, while the film that contains terephthalic acid becomes transparent. The film coated with epoxy-urea resin paint did not lose its metallic luster. The oxygen gas permeability of this laminate that did not lose its metallic luster was 0.4cc/m ² . day・atm (at 27℃).

Example 5 Maleic anhydride-modified polyolefin resin powder NS-100 (trade name) manufactured by Mitsui Petrochemical Industries was applied to the aluminum-deposited surface of the same aluminum-deposited polyethylene terephthalate film as in Example 1, and the top was covered with a Teflon sheet. cover the
It was placed between plates of a hot press at 200°C and heated under pressure of 10 kg/cm ² for 2 minutes.

The coating thickness obtained by peeling off the Teflon sheet is approximately 60 μm.
The laminate was treated in superheated steam at 120°C for 60 minutes, but the metallic luster was not lost. The oxygen gas permeability of this laminate is 0.4cc/m ² . day・
It was atm (at 27℃).

[Brief explanation of the drawing]

The figure is a longitudinal cross-sectional view of a laminate that is an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Laminate, 2... Base layer, 3... Metal aluminum layer, 4... Protective film layer.

Claims (1)

[Claims] 1. A laminate comprising a base layer mainly made of plastics or paper, a vapor-deposited metal aluminum layer with a thickness of about 300 to 3000 Å, and a protective film layer formed on the metal aluminum layer. , wherein at least the portion of the base layer and/or the protective film layer that is in contact with the aluminum layer is made of the resin containing 0.1 to 1700 milliequivalents of free carboxyl groups per 100 grams of resin. body.