JP2018099818A - Multilayer film and package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film that can maintain excellent oxygen barrier properties even after being heated at a high temperature, and can prevent fusing of a sealant layer to a lid material, and provide a package.SOLUTION: A multilayer film has a sealant layer having at least one polyolefin resin with a melting point of 125°C or more, a core layer having polyolefin resin with a density of less than 0.95 g/cm, and an oxygen barrier layer in this order.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multilayer film and a package.

  From the viewpoint of improving the quality of life in an aging society and securing a lifeline in the event of a disaster, retort foods that can be stored for a long time at room temperature are required. Retort food means food that has been sterilized by retort (pressurization and heating). Since the retort-sterilized product can be aseptic, it can be distributed at room temperature.

  For example, in Patent Documents 1 and 2, as a film for retort food packaging, a multilayer polyamide layer including two or more polyamide layers via an adhesive layer, an oxygen barrier layer, an adhesive layer, and a sealant layer A composite film in which these are laminated in this order has been proposed.

  Patent Document 3 discloses that high density polyethylene of 30% by mass to 50% by mass, linear low density polyethylene of 40% by mass to 50% by mass, and high pressure method low of 10% by mass to 20% by mass. A film for retort food packaging having a sealant layer made of a resin mainly composed of a polyethylene resin composition made of high density polyethylene has been proposed.

  A packaging material used for packaging retort foods or the like is required to have an oxygen barrier property that prevents permeation of oxygen from the viewpoint of quality assurance such as taste and freshness of the food. From the viewpoint of user friendliness, it is also important that the packaging material is easily opened when the retort food is opened.

Japanese Patent Publication No. 05-077556 Japanese Patent Publication No. 05-075587 Japanese Patent Laid-Open No. 2015-229301

  However, in the composite films disclosed in Patent Documents 1 and 2, when the temperature is returned to room temperature after the heat treatment at high temperature, the oxygen barrier layer may be whitened and eluted, and the characteristics such as oxygen barrier may be reduced. When the food is opened, the sealant layer may be fused with the lid. Moreover, in the composite film provided with the sealant layer disclosed in Patent Document 3, the sealant layer may be fused to the lid material when the retort food is opened.

  The present invention has been made in view of the above circumstances, and can maintain excellent oxygen barrier properties even after heat treatment at a high temperature, and prevents fusion of the sealant layer with the lid material. It is an object of the present invention to provide a multilayer film and a package that can be used.

As a result of intensive studies on the above problems, the present inventors unexpectedly heated retort food at a high temperature by using a multilayer film and a package including a specific sealant layer, a core layer, and an oxygen barrier layer. It has been found that it has an excellent oxygen barrier property even after being treated, and can prevent fusion between the sealant layer and the lid material, and has completed the present invention.
That is, the present invention is as follows.

[1] A sealant layer including at least one polyolefin resin having a melting point of 125 ° C. or higher, a core layer including a polyolefin resin having a density of less than 0.95 g / cm ^3, and an oxygen barrier layer in this order. Characteristic multilayer film.
[2] The multilayer film according to [1], wherein the oxygen barrier layer includes a heat-resistant ethylene-vinyl alcohol copolymer (EVOH) having heat resistance or an aromatic polyamide resin.
[3] The multilayer film according to [1] or [2], wherein the oxygen barrier layer contains normal EVOH having no heat resistance in an amount of 1% by mass to 50% by mass with respect to the total mass of the oxygen barrier layer. .
[4] The multilayer film according to any one of [1] to [3], wherein the polyolefin resin having a melting point of 125 ° C. or higher is high-density polyethylene or polypropylene.
[5] The multilayer resin according to any one of [1] to [4], wherein the polyolefin resin having a density of less than 0.95 g / cm ³ is medium density polyethylene, linear low density polyethylene, or low density polyethylene. the film.
[6] The multilayer film according to any one of [1] to [5], wherein the sealant layer has an easy peel function.
[7] The multilayer film according to any one of [1] to [6], wherein the ratio of the thickness of the sealant layer to the total thickness is 1% to 15%.
[8] A package comprising the multilayer film according to any one of [1] to [7].

  Since the multilayer film of the present invention includes one or more polyolefin resins having a melting point of 125 ° C. or more as a sealant layer while having oxygen barrier properties, the sealant layer and the lid material are fused even after retorting. The retort food can be easily taken out without doing so.

  Moreover, since the package of this invention is equipped with the said multilayer film, it can maintain the oxygen barrier property outstanding even after the retort process, and can improve openability.

It is a cross-sectional schematic diagram of the multilayer film which is one Embodiment to which this invention is applied.

  Hereinafter, the multilayer film and package which are one Embodiment to which this invention is applied are demonstrated in detail. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

<Multilayer film>
First, the structure of the multilayer film which is one embodiment to which the present invention is applied will be described. FIG. 1 is a schematic cross-sectional view of a multilayer film 1 which is an embodiment to which the present invention is applied. As shown in FIG. 1, the multilayer film 1 of this embodiment includes an outer layer 2, an adhesive resin layer 3, a pinhole layer 4, an oxygen barrier layer 5, a pinhole layer 6, and an adhesive layer 7. And a core layer 8 and a sealant layer 9, and these are laminated in this order for a schematic configuration.
The multilayer film 1 of the present embodiment can be used as a film for food packaging, particularly for retort food packaging.

The outer layer 2 is the outermost layer on one side of the multilayer film 1.
Although there is no restriction | limiting in particular as resin contained in the outer layer 2, For example, a polyamide resin etc. are mentioned. The outer layer 2 may include one type of polyamide resin, or may include two or more types together with other resins. When the outer layer 2 contains a polyamide resin, the pinhole resistance of the multilayer film 1 can be improved. Moreover, by producing a package using this multilayer film 1, it is possible to suppress a decrease in strength that occurs when retorting is performed. Moreover, you may use resin other than a polyamide resin as resin contained in the outer layer 2. FIG. For example, polypropylene or polyethylene may be used from the viewpoint of suppressing curling after retorting.

  In addition, in this embodiment, "retort process" means the process heated at the temperature of 100-121 degreeC for 1 to 60 minutes in order to preserve | save a foodstuff for a long term.

  Specifically, the polyamide resin contained in the outer layer 2 is, for example, a polyamide resin obtained by polymerizing or copolymerizing a 3-membered or higher lactam, amino acid, or nylon salt composed of a diamine and a dicarboxylic acid. Is mentioned.

  Specific examples of the lactam having three or more members include ε-caprolactam, ω-enantolactam, ω-laurolactam, α-pyrrolidone, α-piperidone, and the like.

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

  Specific examples of the diamine constituting the nylon salt include aliphatic amines, alicyclic diamines, and aromatic diamines. Aliphatic amines include tetramethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4-trimethylhexamethylene diamine, And 2,4,4-trimethylhexamethylenediamine and the like. Examples of the alicyclic diamine include 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, isophorone diamine, piperazine, bis (4-aminocyclohexyl) methane, and 2,2-bis- (4-aminocyclohexyl) propane and the like. Examples of the aromatic diamine include metaxylylenediamine and paraxylylenediamine.

  Specific examples of the dicarboxylic acid constituting the nylon salt include aliphatic dicarboxylic acids, alicyclic carboxylic acids, and aromatic dicarboxylic acids. Examples of the aliphatic dicarboxylic acid include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, cepatic acid, undecanedioic acid, and dodecanedioic acid. Examples of the alicyclic carboxylic acid include hexahydroterephthalic acid and hexahydroisophthalic acid. Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid (1,2-isomer, 1,3-isomer, 1,4-isomer, 1,5-isomer, 1,6-isomer, 1,7 -Form, 1,8-form, 2,3-form, 2,6-form, or 2,7-form).

  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 Copolymer of nylon and 12-nylon (nylon 6/66/12), copolymer of 6-nylon and 66-nylon and 612-nylon, copolymer of 66-nylon and 6T-nylon, copolymer of 66-nylon and 6I-nylon, Examples thereof include copolymers of 6T-nylon and 6I-nylon, and copolymers of 66-nylon, 6T-nylon and 6I-nylon. Among these, 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. .

The outer layer 2 may contain an antioxidant.
Specific examples of the antioxidant contained in the outer layer 2 include hydroxyphenylpropionic acid esters, phenolic antioxidants, phosphorus antioxidants, and sulfurous antioxidants.

  Examples of the hydroxyphenyl propionate include hydroxyphenyl propionate 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 hydroxyphenylpropionic acid ester, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4, 8,10-tetraoxaspiro [5.5] undecane, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-ethylphenyl) propionyloxy] -1,1-dimethylethyl ] -2,4,8,10-tetraoxaspiro [5.5] undecane and 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-isopropylphenyl) propionyl Oxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane and the like.

  Hydroxyphenylpropionic acid ester represented by the formula (I) is a reactive derivative such as 3- (3-alkyl-5-tert-butyl-4-hydroxyphenyl) propionic acid or its acid chloride or acid anhydride. , 3,9-bis (1,1-dimethyl-2-hydroxyethyl) 2,4,8,10-tetraoxaspiro [5 · 5] undecane can be produced by a known method. it can.

  Known phenolic antioxidants, phosphorus antioxidants, and sulfur antioxidants can be used. Examples of phosphorus antioxidants include tris (2,4-di-t-butylphenyl) phosphite and tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylene phosphite. It is done.

  The contents of the polyamide resin and the antioxidant in the outer layer 2 are not particularly limited, but the polyamide resin 100 can be used because it can reduce the strength reduction of the multilayer film after retorting and is excellent in pinhole resistance. It is preferable to contain 0.01-1.0 mass part of antioxidant with respect to a mass part, It is more preferable to contain 0.01-0.5 mass part, 0.05-0.25 mass part is included. Is particularly preferred.

  Specifically, the thickness ratio of the outer layer 2 is preferably in the range of 5 to 20% of the total thickness of the multilayer film 1, and more preferably in the range of 7 to 15%. . When the ratio of the thickness of the outer layer 2 is within the above range, appearance defects can be suppressed during the film forming process, and the flexibility of the film can be ensured.

  The adhesive resin layer 3 is laminated so as to be adjacent between the outer layer 2 and the pinhole resistant layer 4. The adhesive resin layer 3 increases the adhesive force between the outer layer 2 and the pinhole-resistant layer 4 and can prevent peeling between the layers.

  The adhesive resin layer 3 is a resin layer containing an adhesive resin. The adhesive resin contained in the adhesive resin layer 3 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 a polyethylene resin, a polypropylene resin, and a cyclic olefin resin. The adhesive resin layer may include one type of adhesive resin, or may include two or more types.

  Specifically, the thickness ratio of the adhesive resin layer 3 is preferably, for example, 5 to 40% of the total thickness of the multilayer film 1, and more preferably 10 to 20%. When the ratio is 5% or more, the water vapor barrier property is improved, and the water absorption of the oxygen barrier layer 5 during the heat treatment can be suppressed. On the other hand, when the ratio is 40% or less, the water absorbed by the oxygen barrier layer 5 is easily released when the temperature is returned to room temperature after the heat treatment, and thus the oxygen barrier layer 5 is easily recovered from whitening.

  The pinhole resistant layer 4 is laminated so as to be adjacent between the adhesive resin layer 3 and the oxygen barrier layer 5. The pinhole resistant layer 4 can improve the pinhole resistance of the multilayer film 1. Moreover, by producing a package using this multilayer film 1, it is possible to suppress a decrease in strength that occurs when retorting is performed.

  The anti-pinhole layer 4 includes a polyamide resin. Specifically, as the polyamide resin contained in the anti-pinhole layer 4, for example, the same polyamide resin contained in the outer layer 2 can be used.

  Specifically, the thickness ratio of the anti-pinhole layer 4 is preferably in the range of 3 to 20% of the total thickness of the multilayer film 1, and more preferably in the range of 5 to 15%. preferable. Here, when the thickness ratio of the anti-pinhole layer 4 is within the above range, it is possible to improve the strength of the film and suppress the decrease in flexibility.

  The oxygen barrier layer 5 is laminated so as to be adjacent between the anti-pinhole layer 4 and the anti-pinhole layer 6. The oxygen barrier layer 5 imparts excellent oxygen barrier properties to the multilayer film 1. Therefore, when a package is formed using the multilayer film 1, it is possible to suppress oxygen from entering the package from the outer layer 2 side. The resin contained in the oxygen barrier layer 5 is not particularly limited as long as it has an oxygen barrier property. For example, an ethylene-vinyl alcohol copolymer resin (hereinafter sometimes simply referred to as “EVOH”). Is mentioned.

  EVOH can be produced by copolymerizing ethylene and vinyl acetate and then hydrolyzing the vinyl acetate component to produce vinyl alcohol groups. The oxygen barrier layer 5 of this embodiment is described as EVOH (hereinafter referred to as “heat-resistant EVOH”) to which heat resistance, water resistance, and the like have been imparted by adding nylon or a crosslinking accelerator during the copolymerization. Can be included). When the oxygen barrier layer 5 contains the heat resistant EVOH, the heat resistance and water resistance of the oxygen barrier layer 5 are improved.

  Moreover, as EVOH contained in the oxygen barrier layer 5, in addition to the above heat-resistant EVOH, EVOH produced without adding nylon or a crosslinking accelerator during copolymerization (hereinafter referred to as “normal EVOH”) May be included). By including normal EVOH in addition to the heat resistant EVOH, the film formability of the oxygen barrier layer 5 can be improved.

  Here, when the oxygen barrier layer 5 includes normal EVOH and heat-resistant EVOH, the normal EVOH is preferably included in an amount of 1 to 50% by mass of the total mass of the oxygen barrier layer 5, and is 20 to 40% by mass. More preferably it is included. By including 1% by mass or more of normal EVOH, the film forming property of the oxygen barrier layer 5 can be improved. On the other hand, a sufficient oxygen barrier property can be obtained by containing 50% by mass or less of normal EVOH. On the other hand, when the normal EVOH is contained in the oxygen barrier layer 5 in an amount of more than 50% by mass of the total mass, the retort resistance performance is deteriorated (whitening after retorting, elution of EVOH and generation of delamination, etc.). Absent.

  The amorphous polyamide contained in the oxygen barrier layer 5 may be a polyamide lacking crystallinity as shown by the lack of endothermic crystal melting peak at 10 ° C./min in a differential scanning calorimeter test (ASTM D-3417). There is no particular limitation.

  Specific examples of the amorphous polyamide contained in the oxygen barrier layer 5 include hexamethylenediamine, 2-methylpentamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and bis (4-aminocyclohexyl). Amine, 2,2- (4-aminocyclohexyl) isopropylidine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, meta-xylenediamine, 1,5-diaminopentane, 1,4-diaminobutane, 1, 3-diaminopropane, 2-ethyldiaminobutane, 1,4-diaminomethylcyclohexane, p-xylenediamine, m-phenylenediamine, p-phenylenediamine, alkyl-substituted m-phenylenediamine, and alkyl-substituted p- Diamine such as phenylenediamine Amorphous polymer produced and the like.

  Amorphous polyamides also include amorphous polymers made from dicarboxylic acids such as isophthalic acid, terephthalic acid, alkyl-substituted iso-terephthalic acid, adipic acid, sebacic acid, and butanedicarboxylic acid. Also good. The amorphous polyamide may include semi-crystalline aliphatic polyamides such as 6-nylon and 66-nylon.

  The amorphous polyamide contained in the oxygen barrier layer 5 is preferably contained in an amount of 5 to 30% by mass of the total mass of the oxygen barrier layer 5, and more preferably 15 to 25% by mass. When the content of the amorphous polyamide is included in the above range, sufficient oxygen barrier properties can be obtained, and at the same time, appearance deterioration due to whitening after retorting can be suppressed.

  The ethylene content in EVOH is preferably 20 to 60 mol% from the viewpoint that sufficient oxygen barrier properties can be obtained in the oxygen barrier layer 5 and deterioration in appearance such as whitening after retort treatment can be suppressed. It is more preferable that it is 25-50 mol%. Further, the saponification degree in EVOH is preferably 90% or more from the viewpoint that a sufficient oxygen barrier property can be obtained in the gas barrier layer and deterioration in appearance such as whitening after retort treatment can be suppressed. More preferably.

  The oxygen barrier layer 5 may be made of a known resin having gas barrier properties and low moisture absorption, such as an aromatic polyamide resin having an aromatic ring in the main chain. Examples of the aromatic polyamide resin include those represented by the following general formulas (II) and (III).

(In formula (1), n represents an integer of 2 or more.)

(In formula (2), n represents an integer of 2 or more, and X and Y represent an organic group.)

  Specifically, the thickness ratio of the oxygen barrier layer 5 is preferably in the range of 1 to 20% of the total thickness of the multilayer film 1, for example, in the range of 5 to 15%. More preferred. When the ratio of the thickness of the oxygen barrier layer 5 is within the above range, the performance of oxygen permeability required for the multilayer film 1 can be obtained, and the productivity (particularly cost) can be improved.

  The pinhole resistant layer 6 is laminated so as to be adjacent between the oxygen barrier layer 5 and the adhesive layer 7. The pinhole resistance layer 6 can improve the pinhole resistance of the multilayer film 1. Moreover, by producing a package using this multilayer film 1, it is possible to suppress a decrease in strength that occurs when retorting is performed.

  The pinhole resistant layer 6 includes a polyamide resin. Specifically, as the polyamide resin contained in the anti-pinhole layer 6, for example, the same polyamide resin contained in the outer layer 2 can be used.

  Specifically, the thickness ratio of the anti-pinhole layer 6 is preferably in the range of 3 to 20% of the total thickness of the multilayer film 1, and more preferably in the range of 5 to 15%. preferable. When the ratio of the thickness of the pinhole-resistant layer 6 is within the above range, both improvement in film strength and flexibility can be achieved.

  The adhesive layer 7 is laminated so as to be adjacent between the pinhole resistant layer 6 and the core layer 8. The adhesive layer 7 increases the adhesive force between the pinhole-resistant layer 6 and the core layer 8, and can prevent peeling between the layers.

  The adhesive layer 7 contains an adhesive resin. Specifically, as the adhesive resin contained in the adhesive layer 7, for example, the same resin as the adhesive resin layer 3 can be used.

  Specifically, the thickness ratio of the adhesive layer 7 is preferably in the range of 3 to 20% of the total thickness of the multilayer film 1, and more preferably in the range of 5 to 15%. preferable. If the ratio of the thickness of the adhesive layer 7 is within the above range, sufficient adhesive force can be obtained.

  The core layer 8 is laminated so as to be adjacent between the adhesive layer 7 and the sealant layer 9. The core layer 8 provides the multilayer film 1 with excellent flexibility, impact resistance, and water vapor barrier properties.

The core layer 8 includes a polyolefin resin having a density of less than 0.95 g / cm ³ . Specific examples of polyolefin resins having a density of less than 0.95 g / cm ³ include, for example, polyethylene resins and polypropylene resins, more specifically, medium density polyethylene, linear low density polyethylene, and low resin. A density polyethylene is mentioned.

  Specifically, the ratio of the thickness of the core layer 8 is preferably in the range of 20 to 60% of the total thickness of the multilayer film 1, for example. Here, if the ratio of the core layer 8 is within the above range, the productivity is improved and the ratio of other functional layers can be maintained.

  The sealant layer 9 is the outermost layer on the opposite side of the outer layer 2 of the multilayer film 1. By the sealant layer 9, the sealant layers 9 can be bonded to each other or to other members. Although it does not specifically limit as an adhesion method, Specifically, a heat seal, an ultrasonic seal, a high frequency seal, an impulse seal etc. are mentioned, for example. Thus, a package can be formed by adhering the multilayer films 1 having the sealant layer 9 together.

  The sealant layer 9 includes one or more polyolefin resins having a melting point of 125 ° C. or higher. Specific examples of the polyolefin resin having a melting point of 125 ° C. or higher included in the sealant layer 9 include, for example, polypropylene, polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer. Examples thereof include a copolymer, an ethylene / methyl acrylate copolymer, an ethylene / methyl methacrylate copolymer, and an ethylene / ethyl acrylate copolymer. More specifically, high density polyethylene and polypropylene are mentioned, for example. The sealant layer 9 may be made of the above resin, may include one type of the resin, or may include two or more types.

  The sealant layer 9 can have an easy peel function, that is, a function excellent in peelability. “Having an easy peel function” means that, for example, when the heat seal strength of the heat-sealed portion is measured according to JIS Z 0238, it is 3 N / 15 mm or more and less than 10 N / 15 mm.

  Specifically, the thickness ratio of the sealant layer 9 is, for example, preferably 1% to 15% of the total thickness of the multilayer film 1, and more preferably 3% to 15%. preferable. If the ratio of the thickness of the sealant layer 9 is within the above range, the sealing performance can be sufficiently exhibited, and even if it has an easy peel function, no peeling failure occurs.

<Method for producing multilayer film>
Next, an example of the manufacturing method of the multilayer film 1 mentioned above is demonstrated.
The production method of the multilayer film 1 described above is not particularly limited, but a coextrusion T-die method such as a feed block method or a multi-manifold method in which a raw material resin is melt-extruded by several extruders, An air-cooled or water-cooled co-extrusion inflation method and a laminating method can be mentioned. Among these, a method of forming a film by the co-extrusion T-die method is particularly preferable in terms of excellent thickness control of each layer.

  Subsequent steps include dry laminating, extruding laminating, hot melt laminating, wet laminating, thermal (thermal) laminating, etc., in which a single layer sheet or film forming each layer is bonded using an appropriate adhesive. And a combination of these methods. Moreover, you may laminate | stack by the method by coating.

<Packaging body>
Next, an example of the structure of the package which is one Embodiment to which this invention is applied is demonstrated. The packaging body of this embodiment is a packaging body formed by softening the multilayer film 1 described above and vacuum forming or pressure forming the same. Specific examples of the package of this embodiment include a skin pack package and a deep-drawn package.

  Deep-draw packaging is one of a pair of films used for packaging containers, which is formed into a bottom material by indenting one film into a shape suitable for the product at the container forming part of the deep-drawing packaging machine. And the other film serving as a lid is deaerated and the contact portions of the pair of films are heat sealed.

Next, an example of the manufacturing method of the packaging body mentioned above is demonstrated.
Although the manufacturing method of the package mentioned above is not specifically limited, Specifically, first, a to-be-packaged object is mounted in a mount. Next, the multilayer film 1 described above is softened, and this is used to cover the package object so that the sealant layer 9 faces the mount. Next, the multilayer film 1 is extended along the outer shape of the package by suction, and then the mount and the multilayer film 1 are bonded. The package of this embodiment can be manufactured by the above manufacturing method. In addition, the structure of the package mentioned above is an example, and is not limited to this. Specifically, for example, a packaging body in which the storage portion is formed by deep drawing may be used.

<How to use the package>
Next, the usage method of the packaging body mentioned above is demonstrated.
Although it does not specifically limit as a usage method of the package mentioned above, Specifically, first, food is enclosed in a package. Next, it heat-processes on the conditions of 100-121 degreeC and 1 to 60 minutes (retort process). Then, by returning to room temperature, a retort food that can be stored for a long time is completed.

  By the way, in the structure of the conventional package, the resin used as the sealant layer is fused to the lid material or the like during the retort process pressurized at a high temperature, and the product is opened when the package is opened. There was a risk that it would be difficult to remove. In addition, there is a problem that the oxygen barrier property is lowered when the temperature is returned to room temperature after the retort treatment.

  On the other hand, since the package of this embodiment is provided with the sealant layer containing one or more polyolefin resin with melting | fusing point 125 degreeC or more, it can provide the outstanding openability. Moreover, since it has a laminated structure of the outer layer, the adhesive resin layer, and the pinhole-resistant layer on the surface layer side of the oxygen barrier layer, excellent oxygen barrier properties can be maintained even after retorting.

  As described above, according to the multilayer film 1 of the present embodiment, since the sealant layer including one or more polyolefin resins having a melting point of 125 ° C. or more is provided, the sealant layer and the lid material and the like are not fused. And the retort food etc. inside a package can be taken out easily. Moreover, since it has a laminated structure of an outer layer, an adhesive resin layer, and a pinhole-resistant layer on the surface layer side of the oxygen barrier layer, it can have oxygen barrier properties even after retorting.

Moreover, since the multilayer film 1 and package of this embodiment are equipped with the core layer containing the polyolefin-type resin of density less than 0.95 g / cm < ³ >, it is excellent in a softness | flexibility and impact resistance.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention. For example, in the multilayer film 1 described above, the outer layer 2, the adhesive resin layer 3, the pinhole layer 4, the oxygen barrier layer 5, the pinhole layer 6, the adhesive layer 7, the core layer 8, Although the example comprised with the sealant layer 9 was demonstrated, you may newly provide the layer which has another function between each layer and an outermost layer.

  Hereinafter, although the effect of the present invention is explained in detail using an example and a comparative example, the present invention is not limited to the following example.

<Production of multilayer film>
The multilayer film of Examples 1-2 and Comparative Examples 1-2 was produced as shown below.

Example 1
As the multilayer film of Example 1, the multilayer film having the configuration shown in FIG.
A polyamide resin (manufactured by Ube Industries, product number: Ube nylon 1022B) was prepared as a resin contained in the outer layer, the first pinhole-resistant layer, and the second pinhole-resistant layer.
Further, as an adhesive resin layer and a resin contained in the adhesive layer, a polyolefin resin (manufactured by Mitsui Chemicals, product number: Admer NF536) was prepared.
Further, as the resin contained in the oxygen barrier layer, heat-resistant EVOH (manufactured by Kuraray, product number: FR101B) and normal EVOH (manufactured by Kuraray, product number: J171B) were prepared.
In addition, a polyolefin resin (manufactured by Prime Polymer Co., Ltd., product number: Neozex 2540R, density: 0.923 g / cm ³ ) was prepared as the resin contained in the core layer.
Further, as a resin contained in the sealant layer, a high-density polyethylene resin (HDPE; manufactured by Prime Polymer Co., Ltd., product number: Hi-Zex 2100J, melting point: 131 ° C.) was prepared.

  Next, the outer layer, the adhesive resin layer, the first pinhole-resistant layer, the oxygen barrier layer, the second pinhole-resistant layer, the adhesive layer, the core layer, and the sealant layer are shared in this order. A multilayer film was produced by extrusion molding. In that case, it adjusted so that 70 mass% of heat resistant EVOH was contained with respect to the gross mass of an oxygen barrier layer, and 30 mass% of normal EVOH was contained.

  The total thickness of the multilayer film was 120 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is as follows: outer layer 13%, adhesive resin layer 15%, first pinhole layer 8%, oxygen barrier layer 7%, second pinhole layer The layer was 8%, the adhesive layer was 8%, the core layer was 31%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

(Example 2)
In Example 2, as a resin contained in the sealant layer, a low density polyethylene resin (LDPE; manufactured by Sumitomo Chemical Co., Ltd., product number: Sumikasen L211, melting point: 112 ° C.) and a polypropylene resin (PP; manufactured by Sumitomo Chemical Co., Ltd., product number: FS2011DG2), A multilayer film was produced in the same manner as in Example 1 except that the resin mixture was blended at a mass ratio of 80:20.
The total thickness of the multilayer film was 120 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is as follows: outer layer 13%, adhesive resin layer 15%, first pinhole layer 8%, oxygen barrier layer 7%, second pinhole layer The layer was 8%, the adhesive layer was 8%, the core layer was 31%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

(Comparative Example 1)
In Comparative Example 1, a multilayer film was prepared in the same manner as in Example 1 except that a linear low density polyethylene resin (LLDPE; manufactured by Dow Chemical Co., product number: ELITE 5220G) was used as the resin contained in the sealant layer. Produced.
The total thickness of the multilayer film was 120 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is as follows: outer layer 13%, adhesive resin layer 15%, first pinhole layer 8%, oxygen barrier layer 7%, second pinhole layer The layer was 8%, the adhesive layer was 8%, the core layer was 31%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

(Comparative Example 2)
In Comparative Example 2, multilayer resin was used in the same manner as in Example 1 except that a polyolefin-based resin (manufactured by Prime Polymer Co., Ltd., product number: Hi-Zex 2100J, density: 0.953 g / cm ³ ) was used as the resin contained in the core layer. A film was prepared.
The total thickness of the multilayer film was 120 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is as follows: outer layer 13%, adhesive resin layer 15%, first pinhole layer 8%, oxygen barrier layer 7%, second pinhole layer The layer was 8%, the adhesive layer was 8%, the core layer was 31%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

<Retort processing>
About the produced multilayer film of Examples 1-2 and Comparative Examples 1-2, the retort process was implemented. Specifically, the retort treatment was a heat treatment (boil treatment) at 110 ° C. for 40 minutes.

<Evaluation of film properties>
About the multilayer film of Examples 1-2 and Comparative Examples 1-2, evaluation is performed about the puncture resistance before performing the retort process mentioned above (unprocessed) and the openability after performing the retort process (after process), respectively. went.

(Puncture resistance)
Evaluation of puncture resistance was performed by measuring puncture strength. The puncture strength was measured using a tabletop precision universal testing machine (AGS-1kNX) manufactured by Shimadzu Corporation, φ = 1 mm, R = 0.5 mm. The results are shown in Table 1 below. Here, as the puncture resistance, the puncture strength is preferably 10 N or more, and the puncture strength after retort can be maintained, so that the case of 10 N or more is indicated by ◯ and the case of less than 10 N is indicated by x.

(Fusibility after retort treatment)
Evaluation of adhesion after retorting was performed using a vacuum degassing sealer (CS45) manufactured by Masui Giken Co., Ltd. to prepare a vacuum four-sided bag containing the contents and carrying out retorting for 40 minutes at 110 ° C. This was done depending on whether or not the sealant layers were fused at the time of opening. The results are shown in Table 1 below. The case of not fusing is indicated by ◯, the case of partial fusing is indicated by Δ, and the case of fusing is indicated by ×.

As shown in Table 1, a sealant layer containing one or more polyolefin resins having a melting point of 125 ° C. or higher, a core layer containing a polyolefin resin having a density of less than 0.95 g / cm ^3, and an oxygen barrier layer in this order. It was confirmed that the provided multilayer film was able to prevent fusion with the cover material of the sealant layer after the retort treatment and was excellent in impact resistance.

  The multilayer film of the present invention can be used as a material for a package, particularly a package for retort food. In addition, the package of the present invention can be used for packaging bags, packaging containers, and the like for packaging foods, particularly retort foods.

DESCRIPTION OF SYMBOLS 1 ... Multilayer film 2 ... Outer layer 3 ... Adhesive resin layer 4 ... Anti-pinhole layer 5 ... Oxygen barrier layer 6 ... Anti-pinhole layer 7 ... Adhesive layer 8 ... Core layer 9 ... Sealant layer

Claims (8)

A sealant layer containing at least one polyolefin-based resin having a melting point of 125 ° C. or higher;
A core layer comprising a polyolefin-based resin having a density of less than 0.95 g / cm ³ ;
An oxygen barrier layer;
Are provided in this order.   The multilayer film according to claim 1, wherein the oxygen barrier layer includes a heat-resistant ethylene-vinyl alcohol copolymer (EVOH) or an aromatic polyamide resin having heat resistance.   The said oxygen barrier layer is a multilayer film of Claim 1 or 2 which contains 1 to 50 mass% of normal EVOH which does not have heat resistance of the total mass of the said oxygen barrier layer.   The multilayer film according to any one of claims 1 to 3, wherein the polyolefin resin having a melting point of 125 ° C or higher is high-density polyethylene or polypropylene. The multilayer film according to claim 1, wherein the polyolefin resin having a density of less than 0.95 g / cm ³ is medium density polyethylene, linear low density polyethylene, or low density polyethylene.   The multilayer film according to any one of claims 1 to 5, wherein the sealant layer has an easy peel function.   The multilayer film according to any one of claims 1 to 6, wherein a ratio of the thickness of the sealant layer to the total thickness is 1% or more and 15% or less.   The package provided with the multilayer film as described in any one of Claims 1-7.

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