JP2021154653A - Multilayer film and package - Google Patents

Abstract

To provide a multilayer film which has oxygen barrier property and can suppress deterioration in transparency in retort treatment, and a package using the same.SOLUTION: A multilayer film, in which an outer layer 2, an oxygen barrier layer 3, an anchor coat layer 4, a pinhole-resistant layer 5 containing a polyamide resin, and a sealant layer 7 containing a polyolefin resin are layered in this order, has a haze after 24 hours after having been subjected to retort treatment at a pressure of 2.5 kgf/cm2 and 120°C and for 30 minutes of 30% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to multilayer films and packages.

Retort foods that can be stored at room temperature for a long period of time are required from the viewpoint of improving the quality of life in an aging society and securing a lifeline in the event of a disaster. Retort-packed foods are foods that have been sterilized by retort (pressurization and heating), and since the products that have been sterilized by retort-packing can be put into a commercially sterile state, they can be distributed at room temperature.

The film for retort food packaging includes, for example, a multilayer polyamide layer including two or more polyamide layers via an adhesive layer, a gas barrier layer, an adhesive layer, and a sealant layer, and these are in this order. Various films such as laminated composite films (for example, Patent Documents 1 and 2) have been proposed.

Packaging materials used for packaging retort foods and the like are required to have an oxygen barrier property that prevents oxygen from permeating from the viewpoint of maintaining quality such as the taste and freshness of foods.

Japanese Unexamined Patent Publication No. 3-136851 Japanese Unexamined Patent Publication No. 3-138149

However, in the conventional film in which the gas barrier layer has an oxygen barrier property, there is a problem that the transparency of the entire film is lowered during the retort treatment.

The present disclosure has been made in view of the above circumstances, and it is an object of the present invention to provide a multilayer film having an oxygen barrier property and capable of suppressing a decrease in transparency during retort treatment, and a packaging material using the same. And.

In order to solve the above problems, the present invention adopts the following configuration.
[1]. An oxygen barrier layer, a pinhole-resistant layer containing a polyamide resin, and a sealant layer containing a polyolefin resin are laminated in this order, and are retorted at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes, and then 24. A multilayer film with an hourly haze of 30% or less.
[2]. The multilayer film according to [1], wherein the multilayer film is for packaging retort foods.
[3]. When the multilayer film is retorted at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes, the difference between the oxygen permeability of the multilayer film after the retort treatment and the oxygen permeability of the multilayer film before the retort treatment. ^but the multilayer film according to or less 5ml / m 2 · 24hr · atm , [1] or [2].
[4]. The pinhole-resistant layer includes a first pinhole-resistant layer and a second pinhole-resistant layer, and in the pinhole-resistant layer, from the oxygen barrier layer side, the first pinhole-resistant layer and the second pinhole-resistant layer. A multilayer film in which the pinhole-resistant layer and the pinhole-resistant layer are laminated in this order, and when the first pinhole-resistant layer is retorted at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes, the first pinhole-resistant layer is said. The multilayer film according to any one of [1] to [3], wherein the rate of change in tensile strength before and after the retort treatment of the pinhole layer is 25% or less.
[5]. Any one of [1] to [4], wherein the multilayer film further includes an outer layer on the surface of the oxygen barrier layer opposite to the pinhole-resistant layer side, and the outer layer contains a polyolefin resin. The multilayer film described in 1.
[6]. The multilayer film according to [5], wherein the outer layer is not stretched.
[7]. The multilayer film according to any one of [1] to [6], wherein the multilayer film further includes an anchor coat layer between the oxygen barrier layer and the pinhole resistant layer.
[8]. A packaging body comprising the multilayer film according to any one of [1] to [7].

In the multilayer film of the present invention, an oxygen barrier layer, a pinhole-resistant layer containing a polyamide resin, and a sealant layer containing a polyolefin resin are laminated in this order, and the pressure is 2.5 kgf / cm ² , and the pressure is 30 at 120 ° C. The haze 24 hours after the minute retort treatment is 10 to 30%.
When the multilayer film 1 has such a structure, it has an oxygen barrier property and can suppress a decrease in transparency during the retort treatment.

Further, since the package of the present invention includes the above-mentioned multilayer film, it has an oxygen barrier property and can suppress a decrease in transparency during retort treatment.

It is sectional drawing of the multilayer film of this embodiment.

Hereinafter, the multilayer film and the package to which the present invention is applied will be described in detail. In addition, in the drawings used in the following description, in order to make the features easy to understand, the featured parts may be enlarged for convenience, and the dimensional ratio of each component may not be the same as the actual one. No.

<Multilayer film>
The configuration of the multilayer film of the present embodiment will be described. FIG. 1 is a schematic cross-sectional view of the multilayer film 1 of the present embodiment. As shown in FIG. 1, the multilayer film 1 of the present embodiment has an outer layer 2, an oxygen barrier layer 3, an anchor coat layer 4, and a pinhole resistant layer 5 (first pinhole resistant layer 51 and second pinhole resistant layer 51). A hole layer 52), an adhesive layer 6, and a sealant layer 7 are provided, and these are laminated in this order to form a schematic structure.

The multilayer film 1 can be used as a packaging application for performing a pressure heat sterilization treatment such as a retort treatment. The multilayer film 1 can be used for packaging foods such as meat, raw noodles, processed foods, and pickles, and can be particularly used for packaging retort foods.

In the present embodiment, "retort treatment" means, for example ^{, pressurizing and heating food at a pressure of 1.3 to 3.0 kgf / cm 2} and a temperature of 100 to 130 ° C. for 3 to 60 minutes in order to store the food for a long period of time. To say.

Multilayer film 1, the oxygen permeability before retorting, is preferably ^{0.5~20ml / m 2 · 24hr · atm} , more preferably from 0.5~10ml ^/ m 2 · 24hr · atm , further preferably ^{0.5~5ml / m 2 · 24hr · atm} .
Multilayer film 1, for example, as described above, when retorted for 30 minutes at a pressure 2.5kgf ^/ cm 2, 120 ℃, oxygen permeability after retorting, 0.5~25ml ^/ m 2 · 24hr · is preferably atm, more preferably from ^{0.5~15ml / m 2 · 24hr · atm} , more preferably from ^{0.5~10ml / m 2 · 24hr · atm} .

When the multilayer film 1 is retorted at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes as described above, the multilayer film 1 has the oxygen permeability of the multilayer film 1 after the retort treatment and the multilayer film 1 before the retort treatment. difference ^is preferably not more than 5ml / m 2 · 24hr · atm , more preferably not more than 3ml / m 2 · 24hr · atm , 1ml / m 2 · 24hr · atm in the following with oxygen permeability It is more preferable to have.
Not only in the case of the multilayer film 1 before and after the retort treatment, the oxygen permeability of the film can be measured by the JIS K7126B method (isopressure method).

When the deeply drawn package is molded using the multilayer film 1, the multilayer film 1 is preferably molded at a drawing depth of 10 mm, and more preferably at a drawing depth of 50 mm.
The multilayer film 1 exhibiting such moldability is excellent in moldability.

The multilayer film 1 has a haze of 30% or less 24 hours after being retorted at a pressure of 2.5 kgf / cm ^{2 and 120 ° C. for 30 minutes.} Further, it is preferably 10 to 30%, more preferably 10 to 20%, and even more preferably 10 to 15%.
If the haze of the multilayer film 1 24 hours after the retort treatment at 120 ° C. for 30 minutes is within the above range, the multilayer film 1 is excellent in transparency.

As a method for obtaining the haze multilayer film 1 as described above, for example, selection of a resin having less whitening due to moisture absorption or crystallization during the retort treatment can be mentioned.

The thickness of the multilayer film 1 is preferably 50 to 300 μm, more preferably 80 to 250 μm, and even more preferably 100 to 200 μm.
When the thickness of the multilayer film 1 is at least the above lower limit value, the strength of the multilayer film 1 can be improved. On the other hand, when the thickness of the multilayer film 1 is not more than the upper limit value, it is possible to prevent the multilayer film 1 from becoming excessively thick.

[Outer layer]
The multilayer film 1 preferably further has an outer layer on the surface of the oxygen barrier layer 3 opposite to the pinhole-resistant layer 5 side. The outer layer 2 is the outermost layer on one side of the multilayer film 1. The outer layer 2 preferably contains a polyolefin resin.
The outer layer 2 contains a polyolefin resin, and the coefficient of thermal expansion of the polyolefin resin matches or approximates the coefficient of thermal expansion of the polyolefin resin contained in the sealant layer 6 which is the outermost layer on the other side of the multilayer film 1. It is possible to suppress the curling of the subsequent multilayer film 1.
The outer layer 2 may contain one type of polyolefin resin, or may contain two or more types.

Specific examples of the polyolefin resin contained in the outer layer 2 include polypropylene (PP), polyethylene (PE), ethylene / vinyl acetate copolymer (EVA), ethylene / acrylic acid copolymer (EAA), and ethylene. / Ethylene / methyl methacrylate copolymer (EMAA), ethylene / methyl acrylate copolymer (EMA), ethylene / methyl methacrylate copolymer (EMMA), ethylene / ethyl acrylate copolymer (EEA), ionomer resin, etc. Can be mentioned. Examples of polyethylene (PE) include low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE).

Among the polyolefin resins, polypropylene is preferable. Since polypropylene is a general-purpose resin among polyolefin resins, cost reduction is possible.

The content of the polyolefin resin in the outer layer 2 is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and 95 to 100% by mass with respect to the total mass of the outer layer 2. Is even more preferable.
When the content of the polyolefin resin in the outer layer 2 is within the above range, the effect of suppressing curl after the retort treatment can be further improved.

The outer layer 2 is preferably not stretched. Since the outer layer 2 is not stretched, the moldability of the multilayer film 1 can be improved.

The thickness of the outer layer 2 is preferably 5 to 90 μm, more preferably 8 to 60 μm, and even more preferably 10 to 40 μm.

The thickness of the outer layer 2 is preferably 5% or more and 30% or less, more preferably 8% or more and 25% or less, and further preferably 10% or more and 20% or less of the total thickness of the multilayer film 1. preferable.

When the thickness of the outer layer 2 or its ratio is within the above range, it is possible to suppress the occurrence of poor appearance in the film forming process.

[Oxygen barrier layer]
The oxygen barrier layer 3 is laminated between the outer layer 2 and the anchor coat layer 4 so as to be adjacent to each other.

The oxygen barrier layer 3 imparts excellent oxygen barrier properties to the multilayer film 1. Therefore, when the package is formed by using the multilayer film 1, oxygen can be suppressed from entering the inside of the package from the outer layer 2 side.

The oxygen permeability of the oxygen barrier layer 3 ^is preferably not more than 20ml / m 2 · 24hr · atm , more preferably not more than 10ml / m 2 · 24hr · atm , 5ml / m 2 · 24hr · atm or less Is more preferable.

The oxygen barrier layer 3 preferably contains polyvinylidene chloride.
Since the oxygen barrier layer 3 contains polyvinylidene chloride, it is possible to impart excellent oxygen barrier properties to the multilayer film 1.

The content of polyvinylidene chloride in the oxygen barrier layer 3 is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and 95 to 100% by mass, based on the total mass of the oxygen barrier layer 3. It is more preferably 100% by mass.
When the content of polyvinylidene chloride in the oxygen barrier layer 3 is within the above range, it is possible to impart more excellent oxygen barrier properties to the multilayer film 1.

The oxygen barrier layer 3 may contain a known resin having an oxygen barrier property, for example, an ethylene-vinyl alcohol copolymer resin (EVOH) or the like.

The thickness of the oxygen barrier layer 3 is preferably 5 to 100 μm, more preferably 10 to 50 μm, and even more preferably 15 to 30 μm.

The thickness of the oxygen barrier layer 3 is preferably 1% or more and 40% or less, more preferably 5% or more and 30% or less, and 10% or more and 20% or less of the total thickness of the multilayer film 1. Is even more preferable.

When the thickness of the oxygen barrier layer 3 or the ratio thereof is at least the above lower limit value, the oxygen barrier property of the multilayer film 1 is improved. On the other hand, when the thickness of the oxygen barrier layer 3 or its ratio is not more than the above upper limit value, productivity (particularly cost reduction) can be improved.

[Anchor coat layer]
The multilayer film 1 preferably further includes an anchor coat layer 4 between the oxygen barrier layer 3 and the pinhole resistant layer 5.
Since the multilayer film 1 includes the anchor coat layer 4, the adhesion between the oxygen barrier layer 3 and the pinhole resistant layer 5 is enhanced, and peeling between the layers can be prevented.

The anchor coat layer 4 preferably contains a polyester urethane resin.
Since the anchor coat layer 4 contains the polyester urethane resin, the adhesion between the oxygen barrier layer 3 and the pinhole resistant layer 5 can be further improved.
The anchor coat layer 4 may contain one type of polyester urethane resin or may contain two or more types.

The content of the polyester urethane resin in the anchor coat layer 4 is preferably 10 to 100% by mass, more preferably 30 to 90% by mass, and 60 to 60 to 100% by mass with respect to the total mass of the anchor coat layer 4. It is more preferably 80% by mass.
When the content of polyester urethane in the anchor coat layer 4 is within the above range, the adhesion between the oxygen barrier layer 3 and the pinhole resistant layer 5 can be further improved.

The anchor coat layer 4 may also contain polyvinylidene chloride or the like.

The thickness of the anchor coat layer 4 is preferably 0.1 to 5 μm, more preferably 0.2 to 3 μm, and even more preferably 0.3 to 1 μm.

When the thickness of the anchor coat layer 4 or the ratio thereof is at least the above lower limit value, the adhesion between the oxygen barrier layer 3 and the pinhole resistant layer 5 is further improved. On the other hand, when the thickness of the anchor coat layer 4 or its ratio is not more than the above upper limit value, productivity (particularly cost reduction) can be improved.

[Pinhole resistant layer]
The pinhole-resistant layer 5 is laminated so as to be adjacent to the anchor coat layer 4 and the adhesive layer 6. The pinhole resistance layer 5 can improve the pinhole resistance (impact resistance) of the multilayer film 1. Further, by producing a package using this multilayer film 1, it is possible to suppress a decrease in strength that occurs during retort treatment.

The pinhole resistant layer 5 contains a polyamide resin.
Since the pinhole-resistant layer 5 contains the polyamide resin, the pinhole-resistant property of the multilayer film 1 can be improved. Further, by producing a package using this multilayer film 1, it is possible to suppress a decrease in strength that occurs during retort treatment.
The pinhole-resistant layer 5 may contain one type of polyamide resin, or may contain two or more types in combination with other resins.

Further, the pinhole resistant layer 5 may contain other resins in addition to the polyamide resin. As the other resin, for example, polypropylene, polyethylene or the like may be used from the viewpoint of suppressing curling after the retort treatment.

The polyamide resin contained in the pinhole-resistant layer 5 is specifically obtained by polymerizing or copolymerizing, for example, a nylon salt composed of a three-membered ring or more of lactam, an amino acid, or a diamine and a dicarboxylic acid. Polyamide resin and the like can be mentioned.

Specific examples of the three-membered ring or more lactam include ε-caprolactam, ω-enantractam, ω-laurolactam, α-pyrrolidone, and α-piperidone.

Specific examples of the amino acid include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and the like.

Specific examples of the diamine constituting the nylon salt include aliphatic amines, alicyclic diamines, and aromatic diamines. Examples of the aliphatic amine include tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and the like. And 2,4,4-trimethylhexamethylenediamine and the like. Alicyclic diamines include 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, isophorone diamine, piperazine, bis (4-aminocyclohexyl) methane, and 2,2-bis-. Examples thereof include (4-aminocyclohexyl) propane. Examples of the aromatic diamine include metaxylylenediamine and paraxylylenediamine.

Specific examples of the dicarboxylic acid constituting the nylon salt include aliphatic dicarboxylic acid, alicyclic carboxylic acid, and aromatic dicarboxylic acid. Examples of the aliphatic dicarboxylic acid include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sepatic acid, undecandionic acid, dodecandic acid and the like. Examples of the alicyclic carboxylic acid include hexahydroterephthalic acid and hexahydroisophthalic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid (1,2-body, 1,3-body, 1,4-body, 1,5-body, 1,6-body, 1,7). -Body, 1,8-body, 2,3-body, 2,6-body, or 2,7-body) and the like.

Specific examples of the polyamide resin include 4-nylon, 6-nylon, 7-nylon, 11-nylon, 12-nylon, 46-nylon, 66-nylon, 69-nylon, 610-nylon, 611-. Nylon, 612-nylon, 6T-nylon, 6I nylon, 6-nylon and 66-nylon copolymer (nylon 6/66), 6-nylon and 610-nylon copolymer, 6-nylon and 611-nylon copolymer, 6 -Nylon and 12-nylon copolymer (nylon 6/12), 6-nylon and 612 nylon copolymer, 6-nylon and 6T-nylon copolymer, 6-nylon and 6I-nylon copolymer, 6-nylon and 66- Nylon and 610-nylon copolymer, 6-nylon and 66-nylon and 12-nylon copolymer (nylon 6/66/12), 6-nylon and 66-nylon and 612-nylon copolymer, 66-nylon and 6T- Examples include nylon copolymers, 66-nylon and 6I-nylon copolymers, 6T-nylon and 6I-nylon copolymers, 66-nylon and 6T-nylon and 6I-nylon copolymers, and the like. Among them, 6-nylon, 12-nylon, 66-nylon, nylon 6/66, nylon 6/12, nylon 6/66/12 and the like are preferable from the viewpoint of heat resistance, mechanical strength and availability. ..

Further, the pinhole resistant layer 5 may contain an antioxidant.
Specific examples of the antioxidant contained in the pinhole-resistant layer 5 include hydroxyphenylpropionic acid ester, phenolic antioxidant, phosphorus-based antioxidant, and sulfur-based antioxidant.

Examples of the hydroxyphenyl propionic acid ester include hydroxyphenyl propionic acid esters represented by the following formula (I).

In the formula (I), R ¹ represents an alkyl group having 1 to 3 carbon atoms, and a methyl group is preferable from the viewpoint of thermal stability. As the hydroxyphenylpropionic acid ester, 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4 8,10-Tetraoxaspiro [5.5] undecane, 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-ethylphenyl) propionyloxy] -1,1-dimethylethyl ] -2,4,8,10-Tetraoxaspiro [5.5] undecane, and 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-isopropylphenyl) propionyl) Oxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane and the like can be mentioned.

The hydroxyphenylpropionic acid ester represented by the formula (I) is a 3- (3-alkyl-5-t-butyl-4-hydroxyphenyl) propionic acid, or a reactive derivative such as an acid chloride or an acid anhydride thereof. , 3,9-Bis (1,1-dimethyl-2-hydroxyethyl) 2,4,8,10-tetraoxaspiro [5.5] Undecans can be produced by reacting them by a known method. can.

As the phenol-based antioxidant, the phosphorus-based antioxidant, and the sulfur-based antioxidant, known ones can be used. Examples of the phosphorus-based antioxidant include tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphite and the like. Be done.

The content of the polyamide resin in the pinhole-resistant layer 5 is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and 95, based on the total mass of the pinhole-resistant layer 5. It is more preferably ~ 100% by mass.
When the content of the polyamide resin in the pinhole-resistant layer 5 is within the above range, the pinhole resistance (impact resistance) of the multilayer film 1 can be further improved.

The content of the antioxidant in the pinhole-resistant layer 5 is not particularly limited, but the polyamide resin is excellent in that it can further reduce the decrease in strength of the multilayer film after the retort treatment and is excellent in pinhole resistance. The antioxidant is preferably contained in an amount of 0.01 to 1.0 parts by mass, more preferably 0.01 to 0.5 parts by mass, and 0.05 to 0.25 parts by mass with respect to 100 parts by mass. Is particularly preferred.

The thickness of the pinhole-resistant layer 5 is preferably 20 to 100 μm, more preferably 30 to 80 μm, and even more preferably 40 to 60 μm.

The ratio of the thickness of the pinhole-resistant layer 5 is preferably 10 to 60%, more preferably 15 to 50%, and even more preferably 20 to 40% of the total thickness of the multilayer film 1. ..

When the thickness of the pinhole-resistant layer 5 or its ratio is within the above range, both the strength improvement and the flexibility of the film can be achieved.

The multilayer film 1 preferably has a pinhole resistant layer 5 including a first pinhole resistant layer 51 and a second pinhole resistant layer 52.

In the multilayer film 1, in the pinhole resistant layer 5, the second pinhole resistant layer 52 and the first pinhole resistant layer 51 may be laminated in this order from the oxygen barrier layer 3 side. As shown here, it is preferable that the first pinhole resistant layer 51 and the second pinhole resistant layer 52 are laminated in this order from the oxygen barrier layer 3 side.
In the pinhole resistant layer 5, when the first pinhole resistant layer 51 and the second pinhole resistant layer 52 are laminated in this order from the oxygen barrier layer 3 side, the first pinhole resistant layer 52 is on the outer layer 2 side. Since the layer 51 is located, the pinhole resistance (impact resistance) of the multilayer film 1 can be further improved.

(1st pinhole resistant layer)
The first pinhole-resistant layer 51 preferably contains a polyamide resin and an antioxidant in order to suppress hydrolysis by hot water. As the polyamide resin / antioxidant, for example, the above-mentioned ones can be arbitrarily used.
When the first pinhole layer 51 has the above-described configuration, the pinhole resistance (impact resistance) of the multilayer film 1 can be further improved.

When the first pinhole resistant layer 51 was retorted at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes, the rate of change in tensile strength of the first pinhole resistant layer 51 before and after the retort treatment was 25% or less. It is preferably 20% or less, more preferably 15% or less.
When the first pinhole layer 51 has such physical properties, the pinhole resistance (impact resistance) of the multilayer film 1 can be further improved.

The tensile strength of the first pinhole resistant layer 51 can be measured by JIS Z1702.

The thickness of the first pinhole resistant layer 51 is preferably 5 to 25 μm, more preferably 8 to 20 μm, and even more preferably 10 to 15 μm.

The thickness ratio of the first pinhole resistant layer 51 is preferably 3 to 15%, more preferably 4 to 13%, and 5 to 10% of the total thickness of the multilayer film 1. More preferred.

The ratio of the thickness of the first pinhole resistant layer 51 is preferably 10 to 40%, more preferably 15 to 35%, and 20 to 30% of the thickness of the pinhole resistant layer 5. Is even more preferable.

When the thickness or the ratio thereof of the first pinhole resistant layer 51 is within the above range, the pinhole resistance (impact resistance) of the multilayer film 1 can be further improved.

(Second pinhole resistant layer)
As the polyamide resin contained in the second pinhole resistant layer 52, specifically, for example, a normal polyamide resin contained in the pinhole resistant layer 5 can be used, and nylon may be used.
Since the second pinhole-resistant layer contains a normal polyamide resin, productivity (particularly cost reduction) can be improved.

Specifically, for example, the above-mentioned polyamide resin can be used as the ordinary polyamide resin, and the layer may not contain an antioxidant.

The thickness of the second pinhole resistant layer 52 is preferably 15 to 75 μm, more preferably 22 to 60 μm, and even more preferably 30 to 45 μm.

The thickness ratio of the second pinhole resistant layer 52 is preferably 7 to 45%, more preferably 11 to 37%, and preferably 15 to 30% of the total thickness of the multilayer film 1. More preferred.

The ratio of the thickness of the second pinhole resistant layer 52 is preferably 60 to 90%, more preferably 65 to 85%, and 70 to 80% of the thickness of the pinhole resistant layer 5. Is even more preferable.

When the thickness of the second pinhole resistant layer 52 or its ratio is within the above range, productivity (particularly cost reduction) can be improved.

The ratio of the thickness of the first pinhole resistant layer 51 to the thickness of the second pinhole resistant layer 52 is preferably 1: 1.5 to 1: 9, and is 1: 2 to 1: 6. Is more preferable, and 1: 2 to 1: 3 is even more preferable.

It is preferable that the total value of the thickness of the first pinhole resistant layer 51 and the thickness of the second pinhole resistant layer 52 satisfies the condition of the thickness of the pinhole resistant layer 5 described above.

[Adhesive layer]
The adhesive layer 6 is laminated between the pinhole resistant layer 5 and the sealant layer 7 so as to be adjacent to each other.
The adhesive layer 6 enhances the adhesive force between the pinhole-resistant layer 5 and the sealant layer 7, and can prevent peeling between the layers.

The adhesive layer 6 is a resin layer containing an adhesive resin. The adhesive resin contained in the adhesive layer 6 is not particularly limited, and examples thereof include acid-modified polyolefin resins, isocyanate compounds, polyester compounds, and polyurethane compounds. Specific examples of the polyolefin resin include polyethylene, polypropylene, and cyclic olefins. Of these, polypropylene is preferred.
The adhesive layer 6 may contain one type of adhesive resin or may contain two or more types of adhesive resin.

The thickness of the adhesive layer 6 is preferably 1 to 60 μm, more preferably 2 to 40 μm, and even more preferably 3 to 20 μm.

The ratio of the thickness of the adhesive layer 6 is preferably 1% or more and 20% or less, more preferably 2% or more and 15% or less, and 3% or more and 10% or less of the total thickness of the multilayer film 1. Is even more preferable.

When the thickness of the adhesive layer 6 or its ratio is within the above range, the adhesive strength between the layers is improved, and the effect of suppressing delamination during molding is improved.

[Sealant layer]
The sealant layer 7 is the outermost layer on the opposite side of the outer layer 2 of the multilayer film 1. The sealant layer 7 can be adhered to each other or to other members. The bonding method is not particularly limited, and specific examples thereof include heat sealing, ultrasonic sealing, high frequency sealing, and impulse sealing. In this way, the package can be formed by adhering the multilayer films 1 having the sealant layer 7 to each other or to other members.

The sealant layer 7 contains a polyolefin resin.
Since the sealant layer 7 contains the polyolefin resin, the sealant layers 7 can be easily adhered to each other or to other members.
The sealant layer 7 may contain one type of polyolefin resin, or may contain two or more types.

The polyolefin resin contained in the sealant layer 7 may be either a homopolymer or a copolymer, and the copolymer may be either a block copolymer or a random copolymer.

Specific examples of the polyolefin resin contained in the sealant layer 7 include polypropylene (PP), polyethylene (PE), ethylene / vinyl acetate copolymer (EVA), ethylene / acrylic acid copolymer (EAA), and the like. Ethylene / methyl methacrylate copolymer (EMAA), ethylene / methyl acrylate copolymer (EMA), ethylene / methyl methacrylate copolymer (EMMA), ethylene / ethyl acrylate copolymer (EEA), and ionomer resin And so on. Examples of polyethylene (PE) include low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE).

Among the polyolefin resins, polypropylene is preferable. Since polypropylene is a general-purpose resin among polyolefin resins, cost reduction is possible.

The content of the polyolefin resin in the sealant layer 7 is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and 95 to 100% by mass with respect to the total mass of the sealant layer 7. Is more preferable.
When the content of the polyolefin resin in the sealant layer 7 is within the above range, the sealant layers 6 can be easily adhered to each other or to other members.

The sealant layer 7 may have an easy peel function, that is, a function excellent in peelability at the time of opening. Having an easy peel function means, for example, that the heat seal strength of the heat-sealed portion is 1N / 15 mm or more and less than 10N / 15 mm when measured according to JIS Z 0238.

The thickness of the sealant layer 7 is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 15 to 50 μm.

The thickness of the sealant layer 7 is preferably 10% or more and 35% or less, more preferably 13% or more and 30% or less, and preferably 15% or more and 25% or less of the total thickness of the multilayer film 1. More preferred.

When the thickness of the sealant layer 7 or its ratio is within the above range, the sealing performance can be sufficiently exhibited, and even if the sealant layer 7 has an easy peel function, peeling failure does not occur.

The sealant layer 7 may have one layer or a multi-layer structure having two or more layers. When the sealant layer 7 has a multilayer structure of two or more layers, the sealant layer 7 is formed by laminating a layer containing a polyolefin resin of a homopolymer or a block copolymer and a layer containing a polyolefin resin of a random copolymer. May be good.
By providing the sealant layer 7 with a layer containing a polyolefin resin of a random copolymer, the sealing property of the multilayer film 1 can be further improved.

In the sealant layer 7, the layer containing the polyolefin resin of the random copolymer and the layer containing the polyolefin resin of the homopolymer or the block copolymer are laminated in this order from the sealant layer 7 side to the outer layer 2 side. Alternatively, the layers may be laminated in this order from the outer layer 2 side to the sealant layer 7 side, but it is preferable that the layers are laminated in this order from the sealant layer 7 side to the outer layer 2 side.

In the sealant layer 7, a layer containing a random copolymer polyolefin resin and a layer containing a homopolymer or block copolymer polyolefin resin are laminated in this order from the sealant layer 7 side to the outer layer 2 side. Since the layer containing the polyolefin resin of the random copolymer is located on the sealant layer 7 side, the sealing property of the multilayer film 1 can be further improved, and at the same time, the homopolymer or block copolymer on the outer layer 2 side can be used. A layer containing a polyolefin resin can impart high impact resistance to the multilayer film 1.

In the sealant layer 7, the layer containing the polyolefin resin of the homopolymer or the block copolymer and the layer containing the polyolefin resin of the random copolymer may be two layers in total, or may be repeated one or more times alternately. It may be a laminated structure.

The thickness of the layer containing the polyolefin resin of the homopolymer or block copolymer is preferably 55% or more and 85% or less, more preferably 60% or more and 80% or less of the total thickness of the sealant layer 7. It is more preferably 65% or more and 75% or less.
The thickness of the layer containing the polyolefin resin of the random copolymer is preferably 15% or more and 45% or less, more preferably 20% or more and 40% or less, and 25% or more of the total thickness of the sealant layer 7. It is more preferably 35% or less.

<Manufacturing method of multilayer film>
Next, an example of the method for producing the multilayer film 1 described above will be described.
The method for producing the multilayer film 1 described above is not particularly limited, but is a coextrusion T-die method such as a feed block method or a multi-manifold method in which a resin or the like as a raw material is melt-extruded by several extruders. Examples thereof include an air-cooled or water-cooled coextrusion inflation method and a laminating method. Among them, the method of forming a film by the coextrusion T-die method is particularly preferable because it is excellent in controlling the thickness of each layer.

Subsequent steps include a dry laminating method, an extrusion laminating method, a hot melt laminating method, a wet laminating method, a thermal (heat) laminating method, etc., in which a single layer sheet or film forming each layer is bonded together using an appropriate adhesive. And those methods are used in combination. Further, it may be laminated by a coating method.

<Packaging body>
Next, an example of the configuration of the package according to the embodiment to which the present invention is applied will be described. The package of the present embodiment includes the multilayer film 1 described above. That is, the package of the present embodiment is a package formed by softening the above-mentioned multilayer film 1 and vacuum forming or vacuum forming the multilayer film 1. Specific examples of the package of the present embodiment include a deep-drawn package and the like.

Deep-drawing packaging means that one of a pair of films used for a packaging container is dented and molded into a shape suitable for the product at the container forming part of the deep-drawing packaging machine to form a bottom material, and the product is contained in the molded bottom material. This is a packaging form in which the other film serving as a lid material is applied to deaerate the film, and the abutting portions of the pair of the films are heat-sealed.

<How to use the package>
Next, the method of using the above-mentioned package will be described. The method of using the above-mentioned package is not particularly limited, but specifically, first, the food is enclosed in the package. Next, for example, pressure heat treatment is performed under the conditions of pressure 1.4 to 2.5 kgf / cm ² , 95 to 121 ° C., and 1 to 60 minutes (retort treatment). After that, by returning to room temperature, a retort food that can be stored for a long period of time is completed.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs and the like within a range that does not deviate from the gist of the present invention. For example, in the multilayer film 1 described above, the outer layer 2, the oxygen barrier layer 3, the anchor coat layer 4, and the pinhole resistant layer 5 (the first pinhole resistant layer 51 and the second pinhole resistant layer 52) are adhered to each other. Although an example in which the layer 6 and the sealant layer 7 are provided has been described, a layer having another function may be newly provided between the layers or the outermost layer.

Hereinafter, the effects of the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Manufacturing of multilayer film>
As shown below, multilayer films of Examples 1 to 3 and Comparative Examples 1 and 2 were produced.

(Example 1)
As the multilayer film of Example 1, a multilayer film having the configuration shown in FIG. 1 described above was produced.

As the resin contained in the outer layer, polypropylene resin (manufactured by Sumitomo Chemical Co., Ltd., product number: FS2011DG3) was prepared.

As a resin contained in the oxygen barrier layer, polyvinylidene chloride (manufactured by Asahi Kasei Corporation, product number: Saran Latex L-509) was prepared.

As the resin contained in the anchor coat layer, a polyester urethane resin (manufactured by Toyobo Co., Ltd., product number: Byron UR-1350) was prepared.

As the resin contained in the first pinhole-resistant layer, 6-nylon (manufactured by Ube Industries, Ltd., product number: 1022FDR3) was prepared.

As the resin contained in the second pinhole resistant layer, 6-nylon (manufactured by Ube Industries, Ltd., product number: 1030B) was prepared.

As a resin contained in the adhesive layer, a polypropylene resin (manufactured by Mitsui Chemicals, Inc., product number: QF551) was prepared.

As a resin contained in the sealant layer, a polypropylene resin (manufactured by Sumitomo Chemical Co., Ltd., product number: FS2011DG3) was prepared.

Next, the first pinhole-resistant layer, the second pinhole-resistant layer, the adhesive layer, and the sealant layer were co-extruded in this order. In coextrusion molding, the temperature of the roll for solidifying the molten resin was set to 40 ° C.

An anchor coat layer was coated on the first pinhole-resistant layer of the film obtained above so that the coating amount was 2 g / m ^{2 · dry.} Further, an oxygen barrier layer was latex-coated on the anchor coat layer so that the coating amount was 16 g / m ^{2 · dry.} Further, the outer layer was dry-laminated on the oxygen barrier layer at a mechanical speed of 30 m / min to prepare a multilayer film.

The total thickness of the multilayer film was 150 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is 20% for the outer layer, 15% for the oxygen barrier layer, 0.3% for the anchor coat layer, 6.7% for the first pinhole resistant layer, and 2nd. The pinhole-resistant layer was 30%, the adhesive layer was 8%, and the sealant layer was 20%. Table 1 below shows the structure of the multilayer film.

(Example 2)
A multilayer film was produced in the same manner as in Example 1 except that the thickness of the oxygen barrier layer was changed. Table 1 below shows the structure of the multilayer film.

(Example 3)
A multilayer film was produced in the same manner as in Example 1 except that the anchor coat layer, the oxygen barrier layer, and the outer layer were not provided on the multilayer film. Table 1 below shows the structure of the multilayer film.

(Comparative Example 1)
A multilayer film was produced in the same manner as in Example 1 except that the multilayer film was not provided with an outer layer. Table 1 below shows the structure of the multilayer film.

(Comparative Example 2)
A multilayer film was produced in the same manner as in Example 1 except that the oxygen barrier layer of the multilayer film was an ethylene vinyl alcohol copolymer (“Evar F171B” manufactured by Kuraray Co., Ltd.). Table 1 below shows the structure of the multilayer film.

<Retort processing>
The retort treatment is a pressure-type hot water cooking sterilization manufactured by Kusunoki Boiler Co., Ltd., in which a bag of 300 mm in width × 300 mm in length made of the multilayer films produced in Examples 1 to 3 and Comparative Examples 1 and 2 is filled with water. It was carried out by an apparatus (TOC-1) at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes. The results are shown in Table 1.

<Evaluation of oxygen barrier property>
The oxygen barrier properties of the multilayer films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated before and after the retort treatment. The evaluation of the oxygen barrier property was carried out by measuring the amount of oxygen permeation per 24 hours under the condition of a pressure of 1 atm and an atmosphere of 25 ° C. and 60% RH.
The oxygen permeation amount was measured by using an oxygen permeation rate measuring device (for example, "OX-TRAN MODEL 2/21" manufactured by MOCON) in accordance with the method described in JIS K 7126B method. The results are shown in Table 1.

<Evaluation of moldability>
The moldability was evaluated by a continuous deep drawing packaging machine (MULTIVAC R535). Specifically, when the deep-drawn package is molded using the multilayer films of Examples 1 to 3 and Comparative Examples 1 and 2, if it can be molded at a drawing depth of 10 mm, it has moldability, and it is molded at a drawing depth of 50 mm. It was evaluated that the moldability was good if possible. The results are shown in Table 1 below.

<Evaluation of Haze>
The multilayer films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated for haze 24 hours after the retort treatment. The haze was evaluated from the outer layer side of the multilayer film based on JIS K7136. Specifically, it was measured with a haze meter (NDH2000) manufactured by Nippon Denshoku Kogyo Co., Ltd. The results are shown in Table 1 below.

<Evaluation of curl prevention>
Test pieces provided with the multilayer films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were prepared. Specifically, the multilayer film was punched into a rectangle having a planar shape of 10 mm × 50 mm to prepare a test piece. The test piece was allowed to stand on a flat surface in a normal temperature environment. The average value (mm) of the heights of the four corners of the test piece from the plane was measured. When the average value of the heights from the plane was small, it was evaluated that the curl prevention property was good. The results are shown in Table 1 below.

<Evaluation of visibility of contents>
A package was prepared from the multilayer films prepared in Examples 1 to 3 and Comparative Examples 1 and 2. Specifically, the multilayer film is packed in a bag having a width of 100 mm and a length of 100 mm in which sardines boiled in soy sauce (100 g) are sealed, retort-packed, and then stored at 23 ° C. for 24 hours. I evaluated the appearance from the outside. The results are shown in Table 1. The external results are shown in Table 1.
The evaluation criteria are as follows.
〇: The food maintains a fresh appearance.
X: Food appears to have deteriorated due to cloudiness.

<Evaluation of color change of contents>
A package was prepared from the multilayer films prepared in Examples 1 to 3 and Comparative Examples 1 and 2. Specifically, a packed product of the multilayer film in which tuna is pickled in oil (100 g, initial color: light pink) is prepared in a bag of 100 mm in width × 100 mm in length, and after retort treatment, the temperature is 23 ° C. It was stored for 240 hours, the contents were taken out, and the appearance was evaluated. The results are shown in Table 1.
The evaluation criteria are as follows.
〇: Keeps a light pink color.
Δ: The color changes to slightly brown.
X: Turns brown.

As shown in Table 1, it was confirmed that the multilayer film of Example 1 had better oxygen barrier properties than the multilayer films of Examples 2 and 3 and Comparative Examples 1 and 2.
Further, the multilayer films of Examples 1 and 2 suppressed the decrease in oxygen barrier property after the retort treatment when compared with Examples 3 and Comparative Examples 1 and 2.
Furthermore, it was confirmed that the multilayer films of Examples 1 and 2 had improved curl prevention properties as compared with the multilayer films of Examples 3 and Comparative Example 1.
Further, it was confirmed that the multilayer films of Examples 1 to 3 were able to ensure the transparency after the retort treatment as compared with Comparative Examples 1 and 2, and the visibility of the contents was good.
Further, it was confirmed that the multilayer film of Example 1 had less change in color tone of the contents than the multilayer films of Examples 2 and 3 and Comparative Examples 1 and 2.

The multilayer film of the present invention can be used as a material for packaging, especially for food packaging that requires heat sterilization. Further, the package of the present invention may be used as a packaging bag, a packaging container, or the like for packaging foods, particularly foods that require heat sterilization treatment.

1 ... Multilayer film 2 ... Outer layer 3 ... Oxygen barrier layer 4 ... Anchor coat layer 5 ... Pinhole resistant layer 51 ... 1st pinhole resistant layer 52 ... 2nd pinhole resistant layer 6 ... Adhesive layer 7 ... Sealant layer

Claims (8)

Oxygen barrier layer and
With a pinhole resistant layer containing polyamide resin,
The sealant layer containing the polyolefin resin and the sealant layer are laminated in this order.
A multilayer film having a haze of 30% or less 24 hours after being retorted at a pressure of 2.5 kgf / cm ^{2 and 120 ° C. for 30 minutes.} The multilayer film according to claim 1, wherein the multilayer film is for packaging retort foods. When the multilayer film is retorted at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes, the difference between the oxygen permeability of the multilayer film after the retort treatment and the oxygen permeability of the multilayer film before the retort treatment. There ^is less 5ml / m 2 · 24hr · atm , the multilayer film according to claim 1 or 2. The pinhole-resistant layer includes a first pinhole-resistant layer and a second pinhole-resistant layer.
In the pinhole resistant layer, a multilayer film in which the first pinhole resistant layer and the second pinhole resistant layer are laminated in this order from the oxygen barrier layer side.
When the first pinhole-resistant layer is retorted at a pressure of 2.5 kgf / cm ² and 120 ° C. for 30 minutes, the rate of change in tensile strength of the first pinhole-resistant layer before and after the retort treatment is 25% or less. , The multilayer film according to any one of claims 1 to 3. The multilayer film further includes an outer layer on the surface of the oxygen barrier layer opposite to the pinhole-resistant layer side.
The multilayer film according to any one of claims 1 to 4, wherein the outer layer contains a polyolefin resin. The multilayer film according to claim 5, wherein the outer layer is not stretched. The multilayer film according to any one of claims 1 to 6, wherein the multilayer film further includes an anchor coat layer between the oxygen barrier layer and the pinhole resistant layer. A packaging body comprising the multilayer film according to any one of claims 1 to 7.

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