JP2018062141A - Multilayer film and package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film that resists being whitened due to retort treatment, and can maintain excellent oxygen barrier properties, and a package.SOLUTION: A multilayer film 1 has a first laminate layer 2 containing an outer layer 5, a second laminate layer 3 containing a sealant layer 11, and an oxygen barrier layer 4. The first laminate layer 2 has a water vapor permeability of 1.0 g/mday or more and 15 g/mday or less in an atmosphere of 40°C, 90%RH.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. In addition, as a resin contained in the oxygen barrier layer, an ethylene-vinyl alcohol copolymer (EVOH) resin is disclosed.

  Packaging materials used for packaging retort foods, etc. are required to have oxygen barrier properties to prevent oxygen permeation from the viewpoint of quality assurance such as food taste and freshness. From the viewpoint of securing, high transparency is required.

Japanese Patent Publication No. 05-077556 Japanese Patent Publication No. 05-075587

  However, in the composite films disclosed in Patent Documents 1 and 2, when retorting is performed, the film may be whitened due to water absorption of the EVOH resin used as the oxygen barrier layer, and the oxygen barrier property is reduced due to elution of the EVOH resin. There was a fear. In particular, the actual situation is that there is a particularly high demand for suppression of whitening of the film by retort treatment.

  This invention is made | formed in view of the said situation, Comprising: While preventing the whitening by a retort process, it aims at providing the multilayer film and package which can maintain the outstanding oxygen barrier property. .

  In order to solve the above-mentioned problems, the present inventor has intensively studied and found that whitening of the film due to retort treatment can be suppressed by adjusting the water vapor barrier value of the entire resin layer laminated on the surface of the oxygen barrier layer. It was.

That is, the present invention has the following configuration.
[1] A first laminate layer including an outer layer provided to be one outermost layer, a second laminate layer including a sealant layer provided to be the other outermost layer, and the first laminate An oxygen barrier layer provided between the body layer and the second laminate layer, and the water vapor transmission rate of the first laminate layer in an atmosphere of 40 ° C. and 90% RH is 1.0 g / The multilayer film which is m ² · day or more and 15 g / m ² · day or less.
[2] The multilayer film according to [1], wherein the first laminated body layer includes a pinhole-resistant layer and an adhesive resin layer.
[3] The multilayer film according to [2], wherein the adhesive resin layer includes a high-density polyethylene resin.
[4] The multilayer film according to [2] or [3], wherein the thickness ratio of the adhesive resin layer is 5% or more and 40% or less of the total thickness of the multilayer film.
[5] The multilayer film according to any one of [1] to [4], wherein the multilayer film has a haze value of 80% or less after being boiled at 110 ° C. for 40 minutes.
[6] A package comprising the multilayer film according to claim 1.

  In the multilayer film of the present invention, the water vapor permeation amount of the first laminated body layer including the outer layer provided on one surface side of the oxygen barrier layer is within a required range, so that the oxygen barrier layer is subjected to the retort treatment. Intrusion of moisture can be prevented and moisture can be quickly discharged from the oxygen barrier layer after retorting. Therefore, whitening due to retort treatment can be prevented and excellent oxygen barrier properties can be maintained.

  Moreover, since the package of this invention is equipped with the said multilayer film, while being able to prevent the whitening by a retort process, it can maintain the outstanding oxygen barrier property.

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 is provided between the first laminate layer 2 and the second laminate layer 3 in which two or more resin layers are laminated, and these laminate layers. The oxygen barrier layer 4 is generally configured. The multilayer film 1 of the present embodiment can be used as a film for food packaging, particularly for retort food packaging.

  The 1st laminated body layer 2 is provided with the outer layer 5, the adhesive resin layer 6, and the pinhole resistant layer 7, and these resin layers are laminated | stacked in this order. The first laminated body layer 2 is laminated with the oxygen barrier layer 4 so that the outer layer 5 becomes one outermost layer of the multilayer film 1. In other words, the pinhole resistant layer 7 and the oxygen barrier layer 4 are laminated so as to face each other.

  The 2nd laminated body layer 3 is equipped with the pinhole-resistant layer 8, the contact bonding layer 9, the core layer 10, and the sealant layer 11, and these resin layers are laminated | stacked in this order. The second laminate layer 3 is laminated with the oxygen barrier layer 4 so that the sealant layer 11 becomes the other outermost layer of the multilayer film 1. In other words, the pinhole resistant layer 8 and the oxygen barrier layer 4 are laminated so as to face each other.

The outer layer 5 is a resin layer that 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 5, For example, a polyamide resin etc. are mentioned. The outer layer 5 may include one type of polyamide resin, or may include two or more types together with other resins. When the outer layer 5 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.

  A resin other than the polyamide resin may be used as the resin contained in the outer layer 5. For example, polypropylene or polyethylene may be used from the viewpoint of suppressing curling after retorting.

  In addition, in this embodiment, "retort process" refers to the process heated for 1 to 60 minutes at the temperature of 100-130 degreeC in order to preserve food for a long period of time.

  Specifically, the polyamide resin contained in the outer layer 5 is, for example, a polyamide resin obtained by polymerizing or copolymerizing a three-membered or more 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 5 may contain an antioxidant.
Specific examples of the antioxidant contained in the outer layer 5 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 5 are not particularly limited, but the polyamide resin 100 can be used because it can reduce a decrease in strength of the multilayer film after the retort treatment and has excellent 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 5 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 5 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 6 is laminated so as to be adjacent between the outer layer 5 and the pinhole resistant layer 7. The adhesive resin layer 6 increases the adhesive force between the outer layer 5 and the pinhole resistant layer 7 and can prevent peeling between the layers.

  The adhesive resin layer 6 is a resin layer containing an adhesive resin. The adhesive resin contained in the adhesive resin 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 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.

  Among these, the adhesive resin layer 6 preferably includes a high-density polyethylene resin (HDPE). Here, a high density polyethylene resin means a thing with a density of 0.942 or more. Further, the content of the high-density polyethylene resin in the adhesive resin layer 6 is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass. When the content is at least the lower limit of the above range, it can greatly contribute to the improvement of the water vapor barrier property of the first laminate layer 2 described later.

  Specifically, the thickness ratio of the adhesive resin layer 6 is preferably 5 to 40%, more preferably 8 to 20%, of the total thickness of the multilayer film 1, for example. When the ratio is 5% or more, the water vapor barrier property is improved, and the water absorption of the oxygen barrier layer 4 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 4 is easily released when the temperature is returned to room temperature after the heat treatment, and thus the oxygen barrier layer 4 is easily recovered from whitening.

  The pinhole resistant layer 7 is laminated so as to be adjacent between the adhesive resin layer 6 and the oxygen barrier layer 4. The pinhole resistant layer 7 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 7 is not particularly limited, but preferably contains a polyamide resin from the viewpoint of improving the pinhole resistance. Specifically, as the polyamide resin contained in the anti-pinhole layer 7, for example, the same polyamide resin contained in the outer layer 5 can be used.

  Specifically, the thickness ratio of the pinhole-resistant 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. Here, when the ratio of the thickness of the anti-pinhole layer 7 is within the above range, it is possible to improve the strength of the film and suppress a decrease in flexibility.

  The oxygen barrier layer 4 is laminated so as to be adjacent between the anti-pinhole layer 7 and the anti-pinhole layer 8. The oxygen barrier layer 4 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 5 side. The resin contained in the oxygen barrier layer 4 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.

  By the way, EVOH can be manufactured by copolymerizing ethylene and vinyl acetate, and then hydrolyzing the vinyl acetate component to produce a vinyl alcohol group. The oxygen barrier layer 4 of this embodiment is described as EVOH (hereinafter referred to as “heat-resistant EVOH”) to which heat resistance, water resistance, etc. are imparted by adding nylon or a crosslinking accelerator during the copolymerization. Are preferred). When the oxygen barrier layer 4 contains the heat resistant EVOH, the heat resistance and water resistance of the oxygen barrier layer 4 are improved.

  Moreover, as EVOH contained in the oxygen barrier layer 4, in addition to the above heat-resistant EVOH, EVOH produced without adding nylon or a crosslinking accelerator at the time of 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 4 can be improved.

  Here, when the oxygen barrier layer 4 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 4, 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 4 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 4 in an amount of more than 50% by mass of the total mass, the retort resistance is deteriorated (whitening after retorting, elution of EVOH and generation of delamination, etc.). Absent.

  The amorphous polyamide contained in the oxygen barrier layer 4 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 4 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, m-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 4 is preferably contained in an amount of 5 to 30% by mass of the total mass of the oxygen barrier layer 4, 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 4 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.

  Specifically, the thickness ratio of the oxygen barrier layer 4 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 4 is within the above range, the oxygen permeability performance required for the multilayer film 1 can be obtained, and productivity (particularly, cost) can be improved.

  The pinhole-resistant layer 8 is laminated so as to be adjacent between the oxygen barrier layer 4 and the adhesive layer 9. The pinhole resistant layer 8 can improve the pinhole resistant property 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 8 preferably contains a polyamide resin from the viewpoint of improving the pinhole resistance. Specifically, as the polyamide resin included in the anti-pinhole layer 8, for example, the same polyamide resin as included in the outer layer 5 can be used.

  Specifically, the thickness ratio of the pinhole-resistant layer 8 is preferably in the range of 3 to 20% of the total thickness of the multilayer film 1, for example, in the range of 5 to 15%. Is more preferable. When the ratio of the thickness of the pinhole-resistant layer 8 is within the above range, both improvement in film strength and flexibility can be achieved.

  The adhesive layer 9 is laminated so as to be adjacent between the pinhole resistant layer 8 and the core layer 10. The adhesive layer 9 increases the adhesive force between the pinhole-resistant layer 8 and the core layer 10 and can prevent peeling between the layers.

  The adhesive layer 9 includes an adhesive resin. Specific examples of the adhesive resin contained in the adhesive layer 9 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 layer 9 may include one type of the adhesive resin or may include two or more types.

  Specifically, the thickness ratio of the adhesive layer 9 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 thickness ratio of the adhesive layer 9 is within the above range, a sufficient adhesive force can be obtained.

  The core layer 10 is laminated so as to be adjacent between the adhesive layer 9 and the sealant layer 11. The core layer 10 provides the multilayer film 1 with excellent flexibility, impact resistance, and water vapor barrier properties.

  The core layer 10 preferably contains a polyolefin resin from the viewpoint of improving flexibility, impact resistance, and water vapor barrier properties. Specific examples of the polyolefin resin include a polyethylene resin and a polypropylene resin.

  Specifically, the thickness ratio of the core layer 10 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 10 is within the above range, the productivity is improved and the ratio of other functional layers can be maintained.

  The sealant layer 11 is the outermost layer on the opposite side of the outer layer 5 of the multilayer film 1. The sealant layer 11 can be bonded to the sealant layers 11 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 packaging body can be formed by bonding the multilayer films 1 having the sealant layer 11 together.

  The sealant layer 11 preferably contains a polyolefin-based resin from the viewpoint of improving adhesiveness. Specific examples of the polyolefin resin contained in the sealant layer 11 include, for example, polypropylene, polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, and ethylene / acrylic. Examples include an acid methyl copolymer, an ethylene / methyl methacrylate copolymer, an ethylene / ethyl acrylate copolymer, and an ionomer resin. Specific examples of polyethylene include low-density polyethylene and linear low-density polyethylene. The sealant layer 11 may include one kind of the above resin, or may include two or more kinds.

  Moreover, the sealant layer 11 may further have an easy peel function. Thereby, when the multilayer film 1 is used for a package or the like, it can be easily opened. In order to give an easy peel function, as a resin raw material which forms the sealant layer 11, what contained ethylene copolymers, such as EMAA resin or EMMA resin, and PP resin is mentioned, for example. The content of the ethylene copolymer in the sealant layer is not particularly limited, but is preferably 10% by mass or more and 90% by mass or less. By setting the content of the ethylene copolymer to 10% by mass or more (that is, the content of the PP resin is 90% by mass or less), the sealant layer 11 has a good easy peel property. By setting the content of the ethylene copolymer to 90% by mass or less (that is, the content of the PP resin is 10% by mass or more), variation in peel strength of the sealant layer 11 is reduced.

  Specifically, the thickness ratio of the sealant layer 11 is preferably in the range of 1 to 20% of the total thickness of the multilayer film 1, and more preferably in the range of 3 to 15%. If the ratio of the thickness of the sealant layer 11 is within the above range, the sealing performance can be sufficiently exhibited, and no peeling failure occurs even in the case of the easy peel specification.

As the multilayer film 1 of this embodiment, when the packaging body is manufactured, the water vapor permeation amount in the atmosphere of 40 ° C. and 90% RH of the first laminated body layer 2 that becomes the surface layer side of the oxygen barrier layer 4 is 1 .0g ^/ m 2 · day or more and less 15g ^/ m 2 · day. If the amount of water vapor permeation in the predetermined condition of the first laminated body layer 2 is within the above preferred range, the intrusion of water vapor into the package body from the first laminated body layer 2 side with the outer layer 5 as the outermost layer is suppressed. In addition, since the water absorption of the oxygen barrier layer 4 is suppressed, whitening of the oxygen barrier layer 4 can be prevented. Furthermore, since the water absorbed by the oxygen barrier layer 4 is easily removed from the first laminate layer 2 side when the temperature is returned to normal temperature after the retort treatment, the oxygen barrier layer 4 is likely to recover from whitening.

  Here, the water vapor permeation amount of the first laminated body layer 2 depends on the content of the high density polyethylene resin (HDPE) in the adhesive resin layer 6 constituting the first laminated body layer 2. Although it can adjust so that it may become a required range by selecting suitably the ratio of the thickness of the adhesive resin layer 6, it is not limited to this.

  The amount of water vapor permeation of the first laminate layer 2 is measured according to JIS K7129 B method using a commercially available water vapor transmission rate measuring device (for example, “PERMATRAN-W (registered trademark) 3/33” manufactured by MOCON). It can be measured in compliance.

As the oxygen barrier property of the multilayer film 1 of the present embodiment, the oxygen of the multilayer film 1 measured according to the JIS K 7126 B method (isobaric method) after the multilayer film 1 was boiled at 110 ° C. for 40 minutes. the permeability is preferably at ^{10cc / (m 2 · day ·} atm) or less, and more preferably ^{5cc / (m 2 · day ·} atm) or less.

  As the transparency of the multilayer film 1 of this embodiment, it is preferable that the multilayer film 1 has a haze value of 80% or less after being boiled at 110 ° C. for 40 minutes. The haze value of the multilayer film 1 can be measured according to JIS K7361 using a commercially available haze meter (for example, “NDH 2000” manufactured by Nippon Denshoku Industries Co., Ltd.).

<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 a dry laminating method, an extrusion laminating method, a hot melt laminating method, a wet laminating method, a thermal (thermal) laminating method, 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 the present 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 sealed by heating.

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 the packaged material is coated so that the sealant layer 11 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, heat treatment is performed at 100 to 130 ° C. for 1 to 60 minutes (retort treatment). 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 oxygen barrier layer is provided. However, when the water vapor barrier property of the resin layer from the outermost layer to the oxygen barrier layer is low, the oxygen barrier layer absorbs water during the retort treatment. There is a risk of whitening or elution. On the other hand, when the water vapor barrier property of the resin layer from the outermost layer to the oxygen barrier layer is too high, the water absorbed by the oxygen barrier layer 4 is difficult to escape when the temperature is returned to room temperature after the retort treatment. There was a problem that the barrier layer did not recover from whitening and visibility (transparency) was lowered. Further, although the oxygen barrier performance of the oxygen barrier layer is also lowered, there is a problem that recovery of the lowered oxygen barrier performance is slow.

On the other hand, the package of this embodiment has a water vapor transmission rate of 1.0 g / m in the atmosphere of 40 ° C. and 90% RH of the first laminate layer 2 on the surface side of the oxygen barrier layer 4. ^{Since it is 2} · day or more and 15 g / m ² · day or less, water absorption of the oxygen barrier layer 4 can be suppressed during retort treatment, and whitening and elution can be prevented. Moreover, even if it is whitened, the absorbed water is easily removed and recovery from whitening is quick. Therefore, it is possible to maintain sufficient oxygen barrier properties and visibility before and after the retorting process.

  As described above, according to the multilayer film 1 of the present embodiment, the water vapor transmission amount of the first laminate layer 2 including the outer layer 5 provided on one surface side of the oxygen barrier layer 4 is within a required range. Therefore, water absorption of the oxygen barrier layer 4 can be suppressed during the retort treatment, and moisture can be quickly discharged from the oxygen barrier layer 4 after the retort treatment even when water is absorbed. Therefore, whitening due to retort treatment can be prevented and excellent oxygen barrier properties can be maintained.

  Moreover, according to the multilayer film 1 of this embodiment, since the oxygen barrier layer 4 contains heat resistant EVOH, the heat resistance and water resistance of the oxygen barrier layer 4 are high. Therefore, excellent oxygen barrier properties can be maintained even after heat treatment at a high temperature.

  Further, according to the multilayer film 1 of the present embodiment, the oxygen barrier layer 4 contains normal EVOH in an amount of 1% by mass to 50% by mass with respect to the total mass of the oxygen barrier layer 4, High film formability.

  Moreover, since the package of this embodiment is provided with the said multilayer film 1, it can maintain the oxygen barrier property and visibility which were excellent even after the heat processing at high temperature.

  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 5, the adhesive resin layer 6, the pinhole resistant layer 7, the oxygen barrier layer 4, the pinhole resistant layer 8, the adhesive layer 9, and the core layer 10, Although the configuration in which the sealant layer 11 is provided and these are stacked in this order has been described as an example, a layer having another function may be newly provided between the layers or on the outermost layer.

  Moreover, in the multilayer film 1 mentioned above, although the structure which uses the adhesive resin layer 6 as a 1st laminated body layer 2 as a layer which has water vapor | steam barrier property was demonstrated as an example, it is not limited to this. . You may comprise the other layer which has water vapor | steam barrier property, and you may comprise so that the water vapor transmission rate of the 1st laminated body layer 2 may become a required range.

  Furthermore, the multilayer film 1 described above may be used as a lid for the above-described package by providing a further resin layer on the outside of the outer layer 5 by lamination or the like.

  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>
As shown below, the multilayer films of Examples 1 to 6 and Comparative Examples 1 and 2 were produced.

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 a resin contained in the adhesive resin layer, a high-density polyethylene resin (manufactured by Prime Polymer Co., Ltd., product number: 3300F, density 0.950) was prepared.
A polyolefin resin (manufactured by Mitsui Chemicals, product number: Admer NF536) was prepared as the resin contained in the adhesive layer.
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.
Further, a polyolefin resin (manufactured by Prime Polymer Co., Ltd., product number: Neozex 2540R) was prepared as a resin contained in the core layer.
In addition, a polyolefin resin (manufactured by Ube Maruzen, product number: Umerit 1520F) was prepared as the resin contained in the sealant layer.

  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 100 mass% of heat resistant EVOH was contained with respect to the gross mass of an oxygen barrier layer, and 0 mass% of normal EVOH was contained.

  The total thickness of the multilayer film was 140 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is as follows: the outer layer is 13%, the adhesive resin layer (HDPE) is 38%, the first pinhole-resistant layer is 8%, the oxygen barrier layer is 7%, The pinhole-resistant layer was 8%, the adhesive layer was 8%, the core layer was 8%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

(Example 2)
In Example 2, a multilayer film was produced in the same manner as in Example 1 except for the thickness of each layer.
The total thickness of the multilayer film was 140 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is as follows: the outer layer is 13%, the adhesive resin layer (HDPE) is 15%, the first pinhole-resistant layer is 8%, the oxygen barrier layer is 7%, The pinhole-resistant 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 3)
In Example 3, a multilayer film was produced in the same manner as in Example 1 except for the thickness of each layer.
The total thickness of the multilayer film was 140 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 (HDPE) 7%, first pinhole resistant layer 8%, oxygen barrier layer 7% The pinhole-resistant layer was 8%, the adhesive layer was 8%, the core layer was 39%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

Example 4
In Example 4, a multilayer film was prepared in the same manner as in Example 1 except that a polypropylene resin (PP: manufactured by Mitsui Chemicals, product number: QF551, density 0.890) was used as the resin contained in the adhesive resin layer. Produced.
The total thickness of the multilayer film was 140 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 (PP) 15%, first pinhole resistant layer 8%, oxygen barrier layer 7% The pinhole-resistant 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 5)
Example 5 was the same as Example 1 except that a linear low-density polyethylene resin (LLDPE; manufactured by Prime Polymer Co., Ltd., product number: SP1540, density 0.913) was used as the resin contained in the adhesive resin layer. Thus, a multilayer film was produced.
The total thickness of the multilayer film was 140 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 (LLDPE) 15%, first pinhole resistant layer 8%, oxygen barrier layer 7% The pinhole-resistant 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 6)
In Example 6, a multilayer film was produced in the same manner as in Example 1 except for the thickness of each layer.
The total thickness of the multilayer film was 300 μm. The ratio of the thickness of each layer to the total thickness of the multilayer film is as follows: the outer layer is 13%, the adhesive resin layer (HDPE) is 38%, the first pinhole-resistant layer is 8%, the oxygen barrier layer is 7%, The pinhole-resistant layer was 8%, the adhesive layer was 8%, the core layer was 8%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

(Comparative Example 1)
In Comparative Example 1, the same as Example 1 except that a linear low density polyethylene resin (LLDPE; manufactured by Prime Polymer Co., Ltd., product number: SP1540, density 0.913) was used as the resin contained in the adhesive resin layer. Thus, a multilayer film was produced.
The total thickness of the multilayer film was 140 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 (LLDPE) 10%, first pinhole resistant layer 8%, oxygen barrier layer 7% The pinhole-resistant layer was 8%, the adhesive layer was 8%, the core layer was 36%, and the sealant layer was 10%. Table 1 below shows the structure of the multilayer film.

(Comparative Example 2)
In Comparative Example 2, a multilayer film was produced in the same manner as in Example 1 except for the thickness of each layer.
The total thickness of the multilayer film was 140 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 (HDPE) 3%, first pinhole resistant layer 8%, oxygen barrier layer 7% The pinhole-resistant layer was 8%, the adhesive layer was 8%, the core layer was 41%, 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 1-6 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 1-6 and Comparative Examples 1-2, the water vapor | steam barrier property of the 1st laminated body layer which comprises the said multilayer film, and after performing before the retort process (before process) (after process) The latter was evaluated for transparency.

(Water vapor barrier property)
The evaluation of the water vapor barrier property was performed by measuring the water vapor transmission amount of the first laminate layer constituting the multilayer film. In addition, the water vapor transmission rate of the first laminate layer is 40 ° C. using a water vapor transmission rate measurement device (manufactured by MOCON, “PERMATRAN-W (registered trademark) 3/33”) based on JIS K7129 B method. , And measured in an atmosphere of 90% RH. The results are shown in Table 1 below.

(transparency)
The evaluation of transparency was performed by measuring the haze of the multilayer film. The haze was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., “NDH 2000”) based on JIS K7361. Moreover, the haze after a retort process was measured after 1 hour passed from the retort process. The results are shown in Table 1 below.

As shown in Table 1, in Comparative Example 1 and Comparative Example 2, since the predetermined water vapor transmission amount of the first laminate layer is 17.6 (g / m ² · day), the multilayer film after the retort treatment is used. Whitening occurred and the transparency was greatly reduced (haze value over 80%).

On the other hand, the multilayer films of Examples 1 to 6 have a predetermined water vapor transmission amount of the first laminate layer of 1.0 g / m ² · day or more and 15 g / m ² · day or less. Later, the transparency did not significantly decrease (haze value of 80% or less).

  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 ... 1st laminated body layer 3 ... 2nd laminated body layer 4 ... Oxygen barrier layer 5 ... Outer layer 6 ... Adhesive resin layer 7 ... Pinhole-resistant layer 8 ... Pinhole-resistant layer 9 ... Adhesive layer 10 ... Core layer 11 ... Sealant layer

Claims (6)

A first laminate layer including an outer layer provided to be one outermost layer;
A second laminate layer including a sealant layer provided to be the other outermost layer;
An oxygen barrier layer provided between the first laminate layer and the second laminate layer,
The multilayer film in which the water vapor permeation amount in the atmosphere of 40 ° C. and 90% RH of the first laminate layer is 1.0 g / m ² · day or more and 15 g / m ² · day or less.   The multilayer film according to claim 1, wherein the first laminate layer includes a pinhole-resistant layer and an adhesive resin layer.   The multilayer film according to claim 2, wherein the adhesive resin layer contains a high-density polyethylene resin.   The multilayer film according to claim 2 or 3, wherein the thickness ratio of the adhesive resin layer is 5% or more and 40% or less of the total thickness of the multilayer film.   The multilayer film according to any one of claims 1 to 4, wherein the multilayer film has a haze value of 80% or less after being boiled at 110 ° C for 40 minutes.   A package comprising the multilayer film according to claim 1.

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