JP2000079668A - Laminated film for packaging - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A boil treatment that does not have environmental problems like a film containing a chlorine-containing polymer layer, has a simple layer structure, has an air-proof layer with high heat resistance, and has a boil treatment It is an object of the present invention to provide a laminated film for packaging that can be retorted and can be heated or cooked by a microwave oven. SOLUTION: The essential layers include a base film (1) and a gas-proof layer (2) and a sealant layer (3) and / or a moisture-proof layer (4), and the gas-proof layer (2) It is a laminated film located between at least two layers having moisture resistance. As the Boki layer (2), a carboxyl group-containing vinyl alcohol-based polymer (a ₁₎ and composition synthetic polymer formed from (a) with the carboxyl group-containing natural polymer (a ₂₎ - a natural polymer composition The material layer (A) is used in which the synthetic polymer-natural polymer composition layer (A) is crosslinked by a polyvalent metal ion (i).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film for packaging having an air-proof layer having high heat resistance, and more particularly to a laminated film for packaging which can be boiled or retorted.

[0002]

2. Description of the Related Art A film in which a thin layer of polyvinylidene chloride is provided on a base film is generally called a K-coated film and has excellent oxygen barrier properties, transparency, physical properties, and packaging machinability. It is also cheap. The K-coated film provided with a sealant layer (heat-sealable layer) on the surface of the polyvinylidene chloride layer is widely used as a film suitable for maintaining the quality of foods and pharmaceuticals. It is useful as a packaging film that can be used. A typical example of the base film is a biaxially oriented polyester film (PET) or a biaxially oriented polypropylene film (OPP), and a typical example of the sealant layer is a polyolefin layer.

However, there is a doubt that polyvinylidene chloride may cause harmful chlorine compounds when incinerated. In recent severe environmental requirements, chlorine-containing compounds such as polyvinylidene chloride have been considered. It is desirable to avoid using a polymer as a constituent layer of a packaging film as much as possible.

Therefore, it is necessary to replace the polyvinylidene chloride layer with another transparent oxygen barrier layer, for example, a polymer layer such as polyvinyl alcohol, an ethylene-vinyl alcohol copolymer, or an acrylonitrile copolymer having a high acrylonitrile content. Conceivable.

[0005] In place of these polymer-based oxygen barrier layers, metal-deposited layers such as aluminum-deposited layers and inorganic oxide layers such as silica and alumina have also been used.

More recently, a film has been proposed in which a coating liquid in which fine plate-like ore such as laponite or vermiculite is suspended in water together with an organic binder is coated on a polyester film. In the coating layer, plate-shaped ores are multiplexed in the thickness direction in a state of being aligned in the layer direction, so that the distance from the oxygen to the layer passing from one side to the other side becomes extremely long, resulting in an oxygen barrier. The principle is that the property can be obtained.

[0007]

However, among the polymer-based oxygen barrier layers, polyvinyl alcohol and ethylene-vinyl alcohol copolymer have a problem that the oxygen barrier property decreases at high humidity, and acrylonitrile copolymer The union has a problem that the oxygen barrier property is inferior to other oxygen barrier polymers.

[0008] Of the inorganic oxygen barrier layers, metal deposited layers such as aluminum deposited layers are opaque, which greatly limits the usable field. In this regard, forming an inorganic oxide layer such as silica and alumina by a vacuum evaporation method can form a transparent layer,
In addition, since coloring remains, this layer is brittle and it is not easy to obtain adhesion to the base material.Therefore, there is a possibility that cracks may be formed during the formation of the sealant layer and the oxygen barrier property may be reduced, so that it is practically used. Still have doubts.

A film obtained by coating a polyester film with a coating liquid in which a plate-like ore is suspended in water together with an organic binder has an oxygen permeability of about 1 cc / m ² · 24 hours, but has a water vapor barrier property of K. -Inferior to coated PET (polyvinylidene chloride coated polyester film), and it is necessary to provide a top coat layer on the coating layer in order to increase abrasion resistance.
A practical laminate construction of a packaging material using this film is abrasion-resistant top coat / plate-like inorganic coating layer / polyester film / print layer / extruded polyethylene or adhesive layer / polyethylene sealant layer.

However, this plate-like inorganic coating film has limitations in terms of transparency and haze, the oxygen barrier layer is outside the substrate film, and the adhesion between the oxygen barrier layer and the substrate film is insufficient. There are some concerns, such as the possibility of the occurrence of boil and retort treatment.

Under such a background, the present invention provides a gas-proof layer having a simple layer structure and high heat resistance without environmental problems such as a film containing a chlorine-containing polymer layer. It is an object of the present invention to provide a laminated film for packaging, which can be boiled or retorted, and can be heated or cooked by a microwave oven.

[0012]

The laminated film for packaging of the present invention comprises, as essential layers, a base film (1) and a gas-proof layer (2) and a sealant layer (3) and / or a moisture-proof layer ( 4), and wherein the air-proof layer (2) is a laminated film positioned between at least two layers having moisture-proof properties, wherein the air-proof layer (2) is a carboxyl group-containing vinyl alcohol-based polymer ( a ₁₎ a carboxyl group-containing natural polymer (a ₂₎ and synthetic polymer formed from the composition (a) of - a natural polymer composition layer (a), the synthetic polymer - natural polymers The composition layer (A) is characterized in that it is crosslinked by a polyvalent metal ion (i).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

<Synthetic polymer-natural polymer composition layer (A)>
The synthetic polymer-natural polymer composition layer (A) is formed from a composition (a) of a carboxyl group-containing vinyl alcohol polymer (a ₁ ) and a carboxyl group-containing natural polymer (a ₂ ).
In this case, the composition (a) may further contain a crosslinking agent (a ₃ ) for the component (a ₁ ) and / or the component (a ₂ ) other than the polyvalent metal ion (i). preferable.

Examples of the carboxyl group-containing vinyl alcohol polymer (a ₁ ) include (a) saponified ethylenically unsaturated carboxylic acid-vinyl acetate copolymers (random copolymers and block copolymers); Suitable examples include a graft copolymer obtained by polymerizing an ethylenically unsaturated carboxylic acid in the presence of a vinyl alcohol-based polymer. The carboxyl group of this polymer may be of the COOH type, COONa or COOK type.

The above ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic anhydride, maleic acid, maleic anhydride, fumaric acid, butenetricarboxylic acid, polyfunctional (meth) acrylic acid. Acids and the like, and in the case of a dibasic acid, a half ester may be used. The carboxyl group-containing vinyl alcohol polymer (a ₁ ) may contain other comonomer components in addition to the ethylenically unsaturated carboxylic acid as long as the spirit of the present invention is not impaired.

The proportion of the ethylenically unsaturated carboxylic acid component in the carboxyl group-containing vinyl alcohol polymer (a ₁ ) is suitably from 1 to 30% by weight, especially from 2 to 20% by weight. When the ratio is too small, the heat resistance of the synthetic polymer-natural polymer composition layer (A) is insufficient, while when the ratio is too large, the air-proof property is insufficient.
Tends to be brittle.

Examples of the carboxyl group-containing natural polymer (a ₂ ) include alginic acid, pectin, xanthan gum, guar gum, tragacanth gum, tamarind gum, locust bean gum, gum arabic, curdlan, pullulan, dextran, carrageenan, karaya gum, succinoglucan , Casein, albumin, gluten, carboxymethylcellulose, and viscous polysaccharides derived from animals and plants (including microorganisms). These are often in the form of water-soluble salts. Alginic acid and pectin are preferred representatives.

The crosslinking agent (a ₃ ) optionally used includes:
An initial condensate or a partially or completely etherified product of a melamine-urea-phenol compound and formaldehyde; an epoxy compound; a polyisocyanate compound;
Ingredients including dialdehyde; carbodiimide resin;
Compounds and resins which can crosslink by reacting with (a ₁ ) and / or a carboxyl group or a hydroxyl group of component (a ₂ ) can be mentioned.

The ratio of the component (a ₁ ) to the component (a ₂ ) in the composition layer (a) is 15:85 to 85:15 by weight, especially 20:85.
The ratio is preferably from 80 to 80:20, more preferably from 25:75 to 75:25. Insufficiency of either component (a ₁ ) or component (a ₂ ) results in insufficient air-proofing under use conditions.
The ratio of the crosslinking agent (a ₃ ) to 100 parts by weight of the total of the components (a ₁ ) and (a ₂ ) is 0 to 30 parts by weight, further 1 to 15 parts by weight, particularly 2 to 10 parts by weight. Department. Crosslinking agent (a
_{Although 3} ) is not necessarily used, it is preferable to use it in terms of water resistance. Excess of the cross-linking agent (a ₃ )
The solution for the formation of (a) is liable to gel, and also has insufficient moisture resistance, heat resistance, and air resistance.

The above-mentioned synthetic polymer-natural polymer composition layer
(A) needs to be cross-linked by the polyvalent metal ion (i), otherwise the water resistance is insufficient. The polyvalent metal ion (i) can be added at the time of preparing the composition layer (a), but since the prepared solution may gel,
As described below, after the formation of the composition layer (A), the layer is brought into contact with an aqueous solution of a water-soluble polyvalent metal salt, then dried, and the layer is crosslinked by permeation of the polyvalent metal ion (i). Is preferred.

Examples of the polyvalent metal ion include calcium ion, barium ion, zinc ion, copper ion, magnesium ion and aluminum ion. The operation for infiltrating the polyvalent metal ion (i) is achieved by bringing the synthetic polymer-natural polymer composition layer (A) into contact with an aqueous solution of a water-soluble polyvalent metal salt and then drying. . Upon contact, the synthetic polymer-natural polymer composition layer (A) may be formed on a support (for example, a base film (1)). The aqueous solution of the water-soluble polyvalent metal salt may contain a water-miscible solvent. Examples of water-soluble polyvalent metal salts include calcium chloride, calcium lactate, and calcium acetate for calcium salts, and barium chloride, barium lactate, barium acetate, and barium gluconate for barium salts.
In the case of a zinc salt, zinc acetate, zinc lactate, zinc chloride, zinc sulfate and the like are used. In the case of a copper salt, copper sulfate and the like are used. The temperature during the infiltration treatment is often from about 5 ° C. to about 70 ° C., but may be outside this range. The immersion time is often about several seconds to about several tens of minutes.

<Laminated Film for Packaging> The laminated film for packaging of the present invention contains, as essential layers, a base film (1) and a gas-proof layer (2) and a sealant layer (3) and / or a moisture-proof layer ( 4) is included. In addition, an optional layer may include an anchor coat layer (ac), an adhesive layer (ad) or a print layer (pt). The air-proof layer (2) is located between at least two layers having moisture-proof properties. Here, the gas-proof layer (2) is composed of the synthetic polymer-natural polymer composition layer (A) crosslinked by the polyvalent metal ion (i) described above.

The base film (1) may be a biaxially oriented polyester film (biaxially oriented polyethylene terephthalate film, biaxially oriented polybutylene terephthalate film, biaxially oriented polynaphthalene terephthalate film), a biaxially oriented polypropylene film, Examples include a biaxially stretched nylon film, a non-stretched polypropylene film, a non-stretched nylon film, and a polyethylene film having a relatively high melting point. The thickness of the base film layer (1) is not particularly limited, but is often about 8 to 500 μm. The base film (1) may be subjected to an adhesion improving treatment such as a corona discharge treatment, a low-temperature plasma treatment, a short-wavelength ultraviolet irradiation treatment, and a solvent treatment.

As the gas-proof layer (2), the synthetic polymer-natural polymer composition layer (A) cross-linked by the above-mentioned polyvalent metal ion (i) is used.

Examples of the sealant layer (3) include layers of polypropylene, polyolefin having a bicyclo ring, polystyrene, polyester, polyamide, rubber resin, polyethylene, and copolymers thereof. The thickness of the sealant layer (3) is often about 5 to 200 μm.

As the moisture-proof layer (4), SiO ₂ , SiO x, MgO, Al ₂ O ₃ , InO
₂ , SnO ₂ , ZnO, and a mixture of two, three or more of these. Not only oxides but also nitrides, carbides, borides and the like can be used. The inorganic moisture-proof layer (4) is formed by a sputtering method, a vacuum deposition method, an ion plating method, a normal pressure plasma method, a sol-gel type coating method, or the like.
The thickness of the inorganic moisture-proof layer (4) is not particularly limited as long as transparency can be ensured.
Angstroms (preferably about 50 to 500 Angstroms) is appropriate. However, when heatless glass is obtained by the coating method, 10
Acceptable to about μm. The inorganic moisture-proof layer (4) serves not only as a moisture-proof layer but also as an air-proof layer and a heat-resistant layer.

The moisture-proof layer (4) may be a layer of polyester, polypropylene, polyolefin having a bicyclo ring, polystyrene, polyethylene, or a copolymer thereof. At this time, the thickness of the organic moisture-proof layer (4) is 2
It is often about 100 μm. In addition, the organic moisture-proof layer (4) is the base film (1) and the sealant layer (3) described above.
In many cases, a resin or a resin film common to the above is used, and in some cases, it also plays a role of reinforcement together with moisture prevention.

Examples of the anchor coat layer (ac) include resin layers of isocyanate type (urethane type), epoxy type, acrylic type, polyester type, imine type and butadiene type. The thickness of the anchor coat layer (ac) is 0.1 to 2
It is often about μm.

As the adhesive layer (ad), the same resin layer as the above-mentioned anchor coat layer (ac) is used, and a polyolefin-based extrusion coat layer can also be used. The thickness of the adhesive layer (ad) is often about 1 to 100 μm.

The printing layer (pt) may be a layer formed by any ordinary printing method. The printing layer (pt) is free to be printed on the entire surface, printed on a portion, or both.

Examples of the layer structure when focusing on the essential layers of the packaging laminated film of the present invention include the base film (1),
The air-proof layer (2), the sealant layer (3), and the moisture-proof layer (4) are, for example, (1) / (2) / (3), (1) / (2) / (4) / (3), (1) / (4) / (2) /
(3), (1) / (4) / (2) / (4) / (3), (1) / (2) / (4) / (2) / (3),
This is a combination of (3) / (1) / (2) / (4) and (1) / (2) / (4).

The formation of the gas-proof layer (2) is usually carried out by a coating method. However, in some cases, a film-shaped gas-proof layer (2) formed in advance can be used.
The formation of the sealant layer (3) may be performed by dry lamination of a heat sealable film, or may be performed by a melt extrusion method (extrusion coating method).

In the present invention, a synthetic polymer-natural polymer composition layer crosslinked by a polyvalent metal ion (i)
Since the printability of the air-proof layer (2) made of (A) is particularly excellent, it is preferable to provide a print layer (pt) on the air-proof layer (2). This air-proof layer (2) has the advantage that not only solvent-based inks but also water-based inks have excellent printability, and when water-based inks are used, it also leads to improvement of the working environment.
Further, as conventionally, the printing layer (pt) can be provided on the inner surface side, the outer surface side, or both the inner surface side and the outer surface side of the base film (1).

[0035] In bag making, typically, the sealant layer (3) side of the laminated film may be opposed to be heat-sealed at a necessary portion. The laminated film can be used as a lid material or a main body of a tray-shaped container.

<Application> The laminated film for packaging of the present invention comprises:
It is suitable as a packaging film that requires heat resistance, particularly a packaging film that can be boiled or retorted. It is also useful as a packaging film that can be heated or cooked in a microwave oven.

<Operation> The packaging laminated film of the present invention
The synthetic polymer-the natural polymer that constitutes the gas barrier layer (2)
Composition layer (A) is a carboxyl group-containing vinyl alcohol
Based polymer (a ₁) And a carboxyl group-containing natural polymer (a_Two)
(Furthermore, the crosslinking agent (a_Three)) And a composition (a) with
And cross-linked by polyvalent metal ions (i),
Polyvinyl alcohol and ethylene used since then
-Vinyl alcohol copolymer, high acrylonitrile content
Film such as acrylonitrile copolymer
Higher heat resistance than layer and oxygen barrier even in high humidity conditions
Less deterioration in boil, retort, or
In microwave cooking of foods containing water
Also have sufficient resistance.

[0038]

The present invention will be further described with reference to the following examples.

Examples 1 to 3 and Comparative Examples 1 to 5 FIG. 1 is a sectional view schematically showing one example of the laminated film for packaging of the present invention.

As an example of the carboxyl group-containing vinyl alcohol polymer (a ₁ ), the polymerization degree is 1700 and the saponification degree is 9
Acrylic acid and butenetricarboxylic acid are polymerized in the presence of 8 mol% of polyvinyl alcohol to obtain a graft copolymer (a _1- ) having an acrylic acid component content of 2% by weight and a butenetricarboxylic acid component content of 5% by weight. 1) was obtained.

The concentration of 12 of the graft copolymer of the above (a ₁ -1)
Wt% aqueous solution containing carboxyl group-containing natural polymer (a ₂ )
Concentration of sodium alginate (a ₂ -1) as an example of 6% by weight
An aqueous solution, optionally a crosslinking agent (a ₃₎ methylol melamine-based crosslinking agent as an example of (Sumitomo Chemical Co., Ltd. of "Sumitekku M-3") and an aqueous solution of concentration 80% by weight of (a ₃ -1) Is added and mixed, and the composition (a) of the treatment method in Table 1 described below is added.
Was prepared. For comparison, the graft copolymer (a
_An aqueous solution was also prepared in the case where either one of ₁ -1) and sodium alginate (a ₂ -1) was lacking.

The thickness 16 as an example of the base film (1)
An anchor coating layer (ac) having a thickness of about 0.3 μm was formed on one surface of a μm polyester film (biaxially oriented polyethylene terephthalate film).

Next, an aqueous solution of the composition (a) was cast on the anchor coating layer (ac) of the base film (1) and dried at 85 ° C. for 15 minutes to form a film layer having a thickness of 10 μm. did. Then, the base film (1) having the film layer was prepared by adding a 5% by weight aqueous solution of calcium chloride to 50% by weight.
C. for 2 minutes to convert sodium alginate in the film layer into a calcium salt form, and then heat-treated at 130 ° C. for 20 minutes to form a gas barrier layer (2) (synthetic polymer-natural polymer composition layer (A )). Then, printing was performed on the surface of the air-proof layer (2) with an aqueous ink to form a print layer (pt). Experiments were also conducted when the contact with the aqueous solution of calcium chloride was omitted.

As a result, a laminated film consisting of the base film (1) / anchor coating layer (ac) / airproof layer (2) / print layer (pt) was obtained. Printing layer
(pt), a polyester film having a thickness of 12 μm as an example of the organic moisture-proof layer (4) was applied to the urethane-based adhesive (a
d), and a polypropylene film is adhered on the moisture-proof layer (4) using a urethane adhesive (ad) to form a sealant layer (3) having a thickness of 60 μm. Material film (1) / anchor coating layer (ac)
/ Airproof layer (2) / Print layer (pt) / Adhesive layer (ad) / Moistureproof layer (4)
A laminated film for packaging having a layer structure of / adhesive layer (ad) / sealant layer (3) was produced. The adhesion between the layers was good.

A large number of bags are manufactured from this laminated film by heat sealing, and after filling with food, the opening is heat-sealed and sealed, and then retorted in a pressurized steam oven at 120 ° C. for 30 minutes. Sterilization was performed. No abnormalities were observed during the retort sterilization, and a test was conducted in which the obtained package was subjected to a distribution process.
An operation of heating in a microwave oven was performed, but no trouble occurred. When boil sterilization was performed at 95 ° C. for 40 minutes, no trouble occurred.

Separately from the above, the same synthetic polymer-natural polymer composition layer as described above is formed on a polyester film.
(A) (Those subjected to a crosslinking treatment with polyvalent metal ions (i)) is formed (however, the thickness is set to 15 μm). In the case of the following (B), this layer (A) is peeled off. The following items were measured. (A) Oxygen permeability: film thickness 15 μm, 30 ° C. × 50% R
H, the unit is cc / m ² · 24 hr (b) Heat resistance: Temperature having a film thickness of 15 μm and having a viscosity of 1 × 10 ¹⁰ dyne / cm ² or more using a viscoelasticity tester (indicative of hardness at high temperature) (C) Surface hardness: pencil hardness, film thickness 15 μm, load 100
g

The results are shown in Table 1 together with the conditions. In the column of the measured values in Table 1, the evaluation of ○ and × was also added.

[0048]

[Table 1]  Ratio (solid content weight ratio) Penetration treatment Oxygen transmission Heat resistance Pencil hardness(a ₁ -1) :( a ₂ -1) :( a ₃ -1) CaCl ₂ rate (℃) Degree  Example 1 70 30 0 Yes ○ 0.07 ○ 180 ○ H Example 2 50 50 0 Yes ○ 0.09 ○ 200 ○ 2HExample 3 50 50 10 Yes ○ 0.10 ○ 200 ○ 2H  Comparative Example 1 50 50 0 None × 4.15 ○ 200 ○ 2H Comparative Example 2 50 50 10 None × 3.52 ○ 200 ○ 2H Comparative Example 3 30 70 0 None × 3.75 ○ 210 ○ 3H Comparative Example 4 100 0 10 None × 7.68 × 110 × BComparative Example 5 0 100 0 Yes × 2 or more ○ 230 ○ 4H

Examples 4-7, Comparative Examples 6-7 As the carboxyl group-containing vinyl alcohol-based polymer (a ₁ ), the content of acrylic acid component was 7% by weight and the saponification degree was 9
8 mol% of a polyvinyl alcohol-polyacrylic acid block copolymer (a _1-2 ) was used. As the carboxyl group-containing natural polymer (a ₂ ), the above-mentioned sodium alginate (a ₂ -1) and the crosslinking agent (a ₃ ) as the above-mentioned methylol melamine crosslinking agent (a _3-
The same experiment as in Examples 1 to 3 was performed except that 1) was used, and the above-mentioned calcium chloride was used as a polyvalent metal ion source. Table 2 shows the conditions and results.

[0050]

[Table 2]  Ratio (solid content weight ratio) Penetration treatment Oxygen transmission Heat resistance Pencil hardness(a ₁ -2) :( a ₂ -1) :( a ₃ -1) CaCl ₂ ratio (℃) Degree  Example 4 70 30 0 Yes ○ 0.03 ○ 180 ○ H Example 5 30 70 0 Yes ○ 0.12 ○ 210 ○ 3H Example 6 50 50 0 Yes ○ 0.06 ○ 200 ○ 2HExample 7 50 50 10 Yes ○ 0.06 ○ 210 ○ 3H  Comparative Example 6 50 50 0 None × 4.85 ○ 200 ○ HComparative Example 7 50 50 10 None × 4.27 ○ 200 ○ 2H

Packaging using the synthetic polymer-natural polymer composition layer (A) of Examples 4 to 7 (subjected to crosslinking treatment with polyvalent metal ion (i)) as an airproof layer (2) A multi-layer film is obtained from the multi-layer film, and a number of bags are manufactured from the multi-layer film by heat sealing. After filling the food, the opening is heat-sealed and sealed, and the retort is sterilized at 130 ° C. for 25 minutes. No abnormality was observed during retort sterilization, and a test was conducted in which the obtained package was subjected to a distribution process. Further, heating was performed using a microwave oven, but no trouble occurred. Similarly, when the boil was sterilized at 90 ° C. for 50 minutes, no trouble occurred.

Examples 8 to 9 and Comparative Examples 8 to 9 FIG. 2 is a sectional view schematically showing another example of the laminated film for packaging of the present invention.

A thickness of 20 as an example of the base film (1)
μm biaxially oriented polypropylene film on one side with an isocyanate anchor coating
A μm anchor coating layer (ac) was formed.

[0054] As the carboxyl group-containing vinyl alcohol-based polymer (a _1), using the graft copolymer described above (a ₁ -1), pectin as carboxyl group-containing natural polymer (a ₂₎
(a ₂ -2) using a formulation of the composition of Table 3 below using the above methylol melamine crosslinking agent (a ₃ -1) (a) is prepared as a crosslinking agent (a _3), also A substrate film was prepared in the same manner as in Examples 1 to 3, except that barium chloride (the film was contacted with a 10% by weight aqueous barium chloride solution at 25 ° C. for 5 minutes) was used as a polyvalent metal ion source. 8 μm thick air-proof layer on the anchor coating layer (ac) of (1) (2)
(Synthetic polymer-natural polymer composition layer (A)) was formed.
Then, printing was performed on the surface of the air-proof layer (2) with an aqueous ink to form a print layer (pt).

As a result, a laminated film composed of the base film (1) / anchor coating layer (ac) / airproof layer (2) / print layer (pt) was obtained. Printing layer
Thickness 3 as an example of the inorganic moisture-proof layer (4) from above (pt)
After forming a heatless glass layer by a sol-gel method with a thickness of μm, a sealant layer (3) of polyethylene having a thickness of 80 μm was formed on the moisture-proof layer (4) by an extrusion coating method, as shown in FIG. Base film (1)
/ Anchor coating layer (ac) / Airproof layer (2) / Printing layer (p
A laminated film for packaging having a layer structure of (t) / moisture-proof layer (4) / sealant layer (3) was produced. The adhesion between the layers was good.

A large number of bags are manufactured from this laminated film by heat sealing, and after filling with food, the opening is heat-sealed and sealed, put into hot water and heated, or heated in a microwave oven. The operation was performed, but no trouble occurred.

Further, separately from the above, the same synthetic polymer-natural polymer composition layer as described above is formed on a polyether film.
After forming (A) (cross-linked by polyvalent metal ion (i)) (thickness was 15 μm),
The layer (A) was peeled off, and the same measurement as in Examples 1 to 3 was performed. Table 3 shows the conditions and results.

[0058]

[Table 3]  Ratio (solid content weight ratio) Penetration treatment Oxygen transmission Heat resistance Pencil hardness(a ₁ -1) :( a ₂ -2) :( a ₃ -1) BaCl ₂ ratio (℃) Degree  Example 8 50 50 0 Yes ○ 0.13 ○ 190 ○ 2HExample 9 50 50 5 Yes ○ 0.17 ○ 190 ○ 3H  Comparative Example 8 50 50 5 None × 5.26 ○ 180 ○ HComparative Example 9 100 0 10 None × 8.65 × 110 × B

[0059]

The laminated film for packaging according to the present invention does not have environmental problems such as a film containing a chlorine-containing polymer layer, and has conventionally used polyvinyl alcohol, ethylene-vinyl alcohol copolymer, Compared with polymer film layers such as acrylonitrile copolymer with high acrylonitrile content, it has higher heat resistance, less decrease in oxygen barrier property even under high humidity conditions, boil treatment and retort treatment, microwave oven It has excellent effects such as being able to be heated by an oven and an oven.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the laminated film for packaging of the present invention.

FIG. 2 is a sectional view schematically showing another example of the laminated film for packaging of the present invention.

[Explanation of symbols]

 (1) ... base film, (2) ... air-proof layer, (3) ... sealant layer, (4) ... moisture-proof layer, (ac) ... anchor coat layer, (ad) ... adhesive layer, (pt) ... Printing layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E086 AD01 BA15 BB01 BB02 BB22 BB41 BB51 BB62 BB87 CA03 4F100 AJ01B AK01A AK01C AK01D AK07 AK21B AK25 AK36H AK42 AK51 AK51 AK51 AK51G AL04 AL05B BA03 BA04 BA05B02 BA03 BA04 BA05 BA07 JD03 JD04D JD05C JJ03 JL00 YY00B YY00H

Claims (4)

[Claims] The essential layers include a base film (1) and a gas-proof layer (2), a sealant layer (3) and / or a moisture-proof layer (4), and the gas-proof layer (2). Is a laminated film located between at least two layers having moisture resistance, wherein the air-proof layer (2) comprises a carboxyl group-containing vinyl alcohol polymer (a ₁ ) and a carboxyl group-containing natural polymer (a ₂ )) And a synthetic polymer-natural polymer composition layer (A) formed from the composition (a).
A laminated film for packaging, characterized in that the natural polymer composition layer (A) is crosslinked by a polyvalent metal ion (i). 2. The synthetic polymer-natural polymer composition layer (A) comprises:
The laminated film for packaging according to claim 1, wherein after the formation of the layer, the film is crosslinked by permeation of a polyvalent metal ion (i). 3. A composition (a) comprising a crosslinking agent (a) for component (a ₁ ) and / or component (a ₂ ) other than polyvalent metal ion (i).
_The laminated film for packaging according to claim 1, comprising ₃ ). 4. The composition layer (a) has a weight ratio of the component (a ₁ ) to the component (a ₂ ) of 15:85 to 85:15, and the component (a)
₁ ) and a crosslinking agent based on 100 parts by weight of the total amount of the component (a ₂ )
(a ₃₎ packaging laminate film according to claim 1 or 3 wherein the amount is 0 to 30 parts by weight of.