JP7227689B2 - Packaging materials for high-pressure processing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a packaging material for high-pressure processing, which maintains low adsorptivity to the components of the contents even when the packaging container hermetically filled with food and drink as contents is subjected to high-pressure processing. .

In recent years, attention has been focused on the application of high-pressure processing technology to food and drink. By using high-pressure treatment technology for sterilization or processing of foods and drinks, it is possible to retain components such as flavor, nutrients, and pigments that were conventionally lost by heat treatment.
However, when sterilization or processing by high-pressure treatment is applied to the contents sealed and filled in a packaging container, high pressure of several thousand atmospheres (hundreds of MPa) is applied, so that the contents components such as aroma and nutrients is likely to be adsorbed to the packaging container, which causes a problem that the components of the contents are spoiled.
In order to solve this problem, Patent Document 1 discloses a method for reducing adsorption of content components to packaging containers promoted by high-pressure treatment by using a polyester-based resin as a packaging container material subjected to high-pressure treatment. is proposed. However, the polyester-based resin used for the packaging container material described in Cited Document 1 is crystalline and has weak sealing strength, so it can only be used for small contents.

JP-A-4-23974

The present invention solves the above-mentioned problems, even if a packaging container sealed and filled with food and drink as contents is subjected to high pressure treatment, the packaging container maintains low adsorption to the components of the contents. The purpose is to provide excellent packaging materials.

The present inventors have proposed a packaging material for high-pressure processing having at least a base material layer and a low-adsorptive sealant layer serving as the innermost layer, wherein the low-adsorptive sealant layer is made of cyclic polyolefin, amorphous polyester or ethylene The inventors have found that the packaging material for high-pressure processing, which contains at least one selected from vinyl alcohol copolymers, achieves the above objects, and have completed the present invention.

That is, the present invention is characterized by the following points.
1. A packaging material for high-pressure processing having at least a substrate layer and a low-adsorptive sealant layer serving as the innermost layer, wherein the low-adsorptive sealant layer is made of cyclic polyolefin, amorphous polyester, or ethylene-vinyl alcohol copolymer The packaging material for high-pressure processing, comprising at least one selected.
2. 1. The low-adsorption sealant layer comprises a cyclic polyolefin; The packaging material for high-pressure processing described in .
3. 1. The low-adsorption sealant layer comprises amorphous polyester; The packaging material for high-pressure processing described in .
4. 1. The low-adsorption sealant layer comprises an ethylene-vinyl alcohol copolymer; The packaging material for high-pressure processing described in .
5. 1. having a barrier layer between the substrate layer and the low-adsorption sealant layer; ~ 4. The packaging material for high-pressure processing according to any one of .
6. 5. The barrier layer is selected from the group consisting of aluminum foil, aluminum deposited film, silicon oxide deposited film, and alumina deposited film; The packaging material for high-pressure processing described in .
7.1. ~6. A packaging container using the packaging material for high-pressure processing according to any one of the above.

According to the present invention, even if a packaging container in which foods and drinks are hermetically filled as contents is subjected to high-pressure treatment, the packaging container maintains low adsorption to components of the contents, such as aromas, nutrients, and pigments. However, since the loss of the components of the contents can be suppressed, it is possible to prevent deterioration of the flavor, quality, etc. of food and drink due to high-pressure treatment.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows an example about the layer structure of the packaging material for high pressure processing of this invention.

The invention is described in more detail below.
<1> Layer configuration of packaging material for high-pressure processing The packaging material for high-pressure processing of the present invention, as shown in FIG. The adhesive sealant layer B forms the innermost layer, ie the layer in contact with the contents. Also, if desired, a barrier layer 1 may be provided between the substrate layer A and the low-adsorptive sealant layer B, and these layers are laminated via adhesive layers 2, 2', respectively. It is possible to laminate by

<2> Substrate layer In the present invention, as the substrate layer, a resin film having a single-layer or multi-layer laminate structure is used. can be used.

Examples of the resin constituting the resin film include olefin-based resins (polyethylene-based resins, polypropylene-based resins, etc.), halogen-containing resins (vinyl chloride-based resins, etc.), vinyl alcohol-based resins, (meth)acrylic-based resins, and styrene-based resins. , polyester resins (polyalkylene arylate resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, etc.), polyamide resins (polyamide 6, polyamide 66, etc.), polycarbonate resins, polysulfone resins (polyethersulfone, polysulfone etc.), polyphenylene ether-based resins, and cellulose esters, preferably polyester-based resins and polyamide-based resins. These resins may be used alone or in combination of two or more.

The resin film may be unstretched, or may be a uniaxially or biaxially stretched film.
In the present invention, the substrate layer may be a composite film in which two or more layers are laminated.
Further, the lamination surface of these base layers may be surface-treated (for example, corona discharge treatment, anchor coating treatment, primer treatment, etc.) in order to enhance adhesion with the barrier layer.

The thickness of the substrate layer can be determined as appropriate, but is preferably 5-30 μm, more preferably 10-30 μm. If the base layer is too thin, sufficient strength cannot be obtained, and if it is too thick, it is not preferable from the viewpoint of cost.

Substrates that satisfy the above requirements are commercially available, and examples of substrates suitable for use in the present invention include biaxially oriented PET films E5100 (thickness 12 μm) and E5102 (thickness 12 μm) manufactured by Toyobo Co., Ltd. 12 μm in thickness) and Biaxially Stretched Ny Film ON (15 μm in thickness) manufactured by Unitika Ltd. can be mentioned.

<3> Low-adsorptive sealant layer The low-adsorptive sealant layer in the present invention contains at least one selected from cyclic polyolefins, amorphous polyesters, and ethylene-vinyl alcohol copolymers.

The low-adsorptive sealant layer in the present invention contains the at least one component in total of 65% by mass or more, preferably 90% by mass or more, based on the total mass of the resin components forming the low-adsorptive sealant layer. .

The layer thickness of the low-adsorptive sealant layer can be determined as appropriate, but is preferably 10 to 250 μm, more preferably 30 to 150 μm. If it is too high, the rigidity will be too high, and it is not preferable from the viewpoint of cost.

<4> Cyclic polyolefin In the present invention, the cyclic polyolefin is a ring-opening metathesis polymer (COP) obtained by polymerizing a cyclic olefin by a metathesis ring-opening polymerization reaction, and a copolymerization of a cyclic olefin and an α-olefin (chain olefin). It includes coalescence, ie cyclic olefin copolymers (COC).

Any cyclic hydrocarbon having an ethylenically unsaturated bond and a bicyclo ring can be used as the cyclic olefin, and in particular those having a bicyclo[2.2.1]hept-2-ene (norbornene) skeleton can be used. preferable.

Specifically, bicyclo[2.2.1]hept-2-ene and its derivatives, tricyclo[4.3.0.1 ^2.5 ]-3-decene and its derivatives, tricyclo[4.4.0.1 ^2.5 ]-3-undecene and its derivatives, tetracyclo[4.4.0.1 ^2.5 .1 ^7.10 ]-3-dodecene and its derivatives, pentacyclo[6.5.1.1 ^3.6 .0 ^2.7 .0 ^9.13 ]- 4-pentadecene and its derivatives, pentacyclo[7.4.0.1 ^2.5 .1 ^9.12 .0 ^8.13 ]-3-pentadecene and its derivatives, pentacyclo[6.5.1.1 ^3.6 .0 ^2.7 .0 ^9.13 ]- 4,10-pentadecadiene and its derivatives, pentacyclo[8.4.0.1 ^2.5 .1 ^9.12 .0 ^8.13 ]-3-hexadecene and its derivatives. More than seeds may be used. The cyclic olefin may have a polar group such as an ester group, a carboxyl group, and a carboxylic anhydride group as a substituent.

As α-olefins to be copolymerized with cyclic olefins, ethylene and α-olefins having 3 to 20 carbon atoms can be used. Specifically, ethylene, propylene, 1-butene, 1-pentene, 3-methyl -1-butene, 1-hexene, 4-methyl-1-pentene and the like, preferably ethylene, and these may be used alone or in combination of two or more.

In the present invention, the production of the ring-opening metathesis polymer may be, for example, a ring-opening metathesis polymerization reaction, and can be produced by subjecting the cyclic olefin to ring-opening polymerization using a polymerization catalyst.

Also, the production of cyclic olefin copolymers can be achieved by using 25-45 mol % α-olefin and 5
5 to 75 mol % of a cyclic olefin is randomly polymerized using a single-site catalyst such as a metallocene catalyst or a multi-site catalyst.

Several ring-opening metathesis polymers and cyclic olefin copolymers suitable for use in the present invention are commercially available. ) and the like.

<5> Amorphous polyester In the present invention, the amorphous polyester is an amorphous copolyester having a glass transition point of 70 to 90°C, preferably 70 to 80°C.

The amorphous polyester in the present invention is a copolymerized polyester containing terephthalic acid and ethylene glycol as main components, and further containing a polyvalent carboxylic acid other than terephthalic acid and/or a polyvalent polycarboxylic acid other than ethylene glycol as a copolymer component. Modified PET obtained by adding alcohol so as to be amorphous and having a glass transition point of 70 to 90° C. and copolymerizing it is used.

In the present invention, amorphous means having no melting peak when the temperature is raised from −100° C. to 300° C. at a rate of 20° C./min using a differential scanning calorimeter (DSC). do.
Moreover, in the present invention, the glass transition point is measured according to JIS K7121.

Examples of polyvalent carboxylic acids added as copolymer components include isophthalic acid, orthophthalic acid, adipic acid, azelaic acid, sebacic acid, and dimer acid (mainly composed of unsaturated fatty acid dimers or hydrogenated products thereof). , diphenylcarboxylic acid, trimellitic acid, pyromellitic acid, sodium 5-sulfoisophthalate and the like.

Polyhydric alcohols added as copolymer components include diethylene glycol, propylene glycol, 1,4-cyclohexanedimethanol, trimethylolpropane, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, pentaerythritol, bisphenol A ethylene oxide adduct and the like.

Specific examples of the modified PET include a cocondensation polymer of a combination of terephthalic acid, isophthalic acid and ethylene glycol, terephthalic acid, ethylene glycol and 1,4-cyclohexanedimethanol, terephthalic acid, isophthalic acid and propylene glycol. Modified PET can be mentioned.

The mixing ratio of the main component and the copolymer component is preferably one that exhibits amorphousness and has a desired glass transition point. 50 mol % or more of polyhydric alcohol as a raw material is ethylene glycol. If the amounts of terephthalic acid and ethylene glycol as starting materials are less than this, the impact resistance and non-adsorptive properties may be impaired.

Further, the total amount of terephthalic acid and ethylene glycol, which are the main components, is 50 to 95 mol% with respect to 100 mol% of the total amount of polyhydric carboxylic acid and polyhydric alcohol as raw materials, and the total amount of copolymerization components Preferably the amount is between 5 and 50 mol %. If the total amount of the copolymer components is less than 5 mol %, the amorphous property is lost and the seal strength is impaired.

Furthermore, in the present invention, the amorphous polyester having a glass transition point of 70 to 9
A copolyester adjusted to 0° C. is used. This preparation can be appropriately carried out by those skilled in the art by changing the mixing ratio, the degree of polymerization, etc. of the polyhydric carboxylic acid and the polyhydric alcohol used as raw materials in accordance with the chemical structures and the like.

Amorphous copolyester having a glass transition point of 70 to 90° C., which satisfies the above requirements, is commercially available. Byron (registered trademark), Eastar (registered trademark) PETG manufactured by EASTMAN CHEMICAL Co., Ltd., and the like.

<6> Ethylene-vinyl alcohol copolymer In the present invention, the ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer, that is, an ethylene-vinyl acetate random copolymer. It is. Such saponified products include partially saponified products in which several tens of mol % of acetic acid groups remain, to complete saponified products in which only several mol % of acetic acid groups or no acetic acid groups remain. be. From the viewpoint of gas barrier properties, it is desirable to use one having a degree of saponification of preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more. The content of repeating units derived from ethylene in the ethylene-vinyl alcohol copolymer (hereinafter also referred to as "ethylene content") is usually 0 to 50 mol%, preferably 20 to 45 mol%. It is preferred to use

Specific examples of the ethylene-vinyl alcohol copolymer include EVAL (registered trademark) EF-E (ethylene content: 32 mol%) manufactured by Kuraray Co., Ltd., and Soarnol (registered trademark) D2908 manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (ethylene content; 29 mol %) and the like can be used.

<7> Barrier Layer In the present invention, various functional layers such as a gas barrier layer having gas barrier properties can be provided between the substrate layer and the low-adsorptive sealant layer as desired. As a result, it is possible to prevent moisture from evaporating from the inside and odor leakage, and to prevent oxygen and water vapor from entering from the outside, thereby preventing deterioration of the contents.

In the present invention, the barrier layer may be, for example, a metal foil made of aluminum foil or the like, a vapor deposition film of an inorganic substance or inorganic oxide such as aluminum, silicon oxide or alumina, or a resin such as an aluminum vapor deposition film, a silicon oxide vapor deposition film or an alumina vapor deposition film. It may be a vapor-deposited film having a vapor-deposited film on the film, or a layer made of a gas barrier resin such as ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyvinyl alcohol, MXD6, or a combination thereof, preferably a metal foil. Or it is a vapor deposition film.

Generally, the thickness of the barrier layer is preferably 0.01 to 500 μm, more preferably 1 to 300 μm, from the viewpoint of gas barrier properties and transparency. At least one surface of the barrier layer may be subjected to a surface treatment that enhances wettability, such as corona treatment, ozone treatment, or flame treatment.

<8> Lamination In the present invention, the method for laminating the substrate layer (and, if desired, the barrier layer) and the low-adsorptive sealant layer includes a conventional dry lamination method, extrusion coating method, sand lamination method, and the like. can be selected as appropriate.

In the present invention, urethane-based adhesives, vinyl-based adhesives, acrylic-based adhesives, epoxy-based adhesives, and the like can be used as dry-laminating adhesives that are suitably used for lamination. Any heat-sealing resin can be used as the adhesive resin for sandwich lamination.

In the present invention, as a specific example of the laminate, for example, on a biaxially oriented PET film or a biaxially oriented nylon film as a substrate layer, an aluminum foil as a barrier layer, and then a cyclic polyolefin film as a low-adsorptive sealant layer. , an amorphous polyester film or an ethylene-vinyl alcohol copolymer film laminated together via an adhesive layer.

<9> High-pressure treatment In the present invention, high-pressure treatment refers to applying a high pressure of about 1000 atmospheres (about 100 MPa) or more to a packaging container sealed with food and drink as contents using isotropic hydrostatic pressure, sterilizing or processing (eg, enhancing pharmacologically active ingredients in food or drink) the contents thereof. By using high pressure, it is possible to retain the flavor and nutrients of food and drink, which were conventionally damaged by heat treatment.

<10> Packaging Container The packaging material of the present invention can be used to form a bag such that the low-adsorptive sealant layer is the innermost layer, thereby forming a packaging container such as a packaging bag.

In order to manufacture the packaging container, the packaging material is folded in two, or two packaging materials are prepared, the surfaces of the sealant layers are placed on top of each other, and the peripheral edge is formed into, for example, a standing pouch type. , Side seal type, Two side seal type, Three side seal type, Four side seal type, Envelope seal type, Gassho seal type (pillow seal type), Folded seal type, Flat bottom seal type, Square bottom seal type, Gusset type, etc. It is heat-sealed by the heat-sealing form of the above to form packaging containers of various forms.

In the above, as the heat sealing method, for example, bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, ultrasonic sealing, or the like can be used.

In the present invention, the contents to be hermetically packed in the packaging container are non-drying foods and beverages that can be subjected to high-pressure treatment. , liquid seasonings such as sauces, and liquid foods and beverages such as curries, stews, and soups.
EXAMPLES Next, the present invention will be specifically described with reference to Examples.

[Example 1]
Biaxially stretched PET film (manufactured by Toyobo Co., Ltd., Toyobo Ester (registered trademark) film, E5102; thickness 12 μm), aluminum foil (manufactured by Toyo Aluminum Co., Ltd., 1N30; thickness 7 μm), and a cyclic polyolefin resin (polyplastic Co., Ltd., TOPAS (registered trademark) 8007F-600) and a cyclic polyolefin film (thickness 30 μm) formed by a casting method, respectively, a dry lamination adhesive (Rock Paint Co., Ltd., Rockbond J RU-77T /Adlock H-7; mixing ratio 10/1) to obtain a laminate of biaxially stretched PET film/aluminum foil/cyclic polyolefin film.

[Example 2]
In the laminate of Example 1, instead of the cyclic polyolefin film, an amorphous polyester film (thickness A laminate of biaxially stretched PET film/aluminum foil/amorphous polyester film was obtained in the same manner as in Example 1, except that a 30 μm film was used.

[Example 3]
Example 1 except that an ethylene-vinyl alcohol copolymer film (manufactured by Kuraray Co., Ltd., EVAL (registered trademark) EF-E; thickness 30 μm) was used in place of the cyclic polyolefin film in the laminate of Example 1. A laminate of biaxially stretched PET film/aluminum foil/ethylene-vinyl alcohol copolymer film was obtained.

[Comparative Example 1]
Instead of the cyclic polyolefin film of Example 1, a linear low-density polyethylene film (manufactured by Mitsui Chemicals Tocello Co., Ltd., TUX (registered trademark) MC-S; thickness 30 μm) was used. A laminate of biaxially stretched PET film/aluminum foil/linear low-density polyethylene film similar to Example 1 was obtained.

(Absorptive evaluation)
Pouches of 120 mm × 160 mm (seal width 5 mm) were prepared using the laminates obtained in Examples 1 to 3 and Comparative Example 1, filled with orange juice, and high pressure sterilized (600 MPa, 10 ° C., 5 min). and stored in a constant temperature bath at 40° C. for one week. A 100 cm ² film was then cut out and immersed in ethyl acetate for 3 days. Limonene extracted into the ethyl acetate soaked film was determined by gas chromatography. A sample which was not subjected to high-pressure treatment and stored in a constant temperature bath at 40° C. for one week (no treatment) was also measured in the same manner, and the peak areas were compared (see Table 1).
In Examples 1 to 3, the amount of limonene adsorbed to the film was less than in Comparative Example 1 both without treatment and after treatment, and low adsorption was maintained even after high pressure treatment.

A. base layer B. Low adsorptive sealant layer1. Barrier layers 2, 2' . adhesive layer

Claims (3)

Packaging for high-pressure processing at a high pressure of 1000 atmospheres or more, in which a base film layer, an adhesive layer, a barrier layer, an adhesive layer, and a low-adsorptive sealant film layer as the innermost layer are laminated in this order adjacent to each other. material,
The low-adsorptive sealant layer for maintaining low-adsorptiveness to the content components contains 90% by mass or more of an ethylene-vinyl alcohol copolymer with respect to the total mass of the resin components forming the low-adsorptive sealant layer. death,
The base material layer is made of a biaxially stretched resin film,
The adhesive for the adhesive layer is selected from urethane-based adhesives, vinyl-based adhesives, acrylic-based adhesives, and epoxy-based adhesives,
the barrier layer is a metal foil or vapor deposited film,
The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate random copolymer and has a degree of saponification of 90 mol% or more. The unit content is 20 to 45 mol%,
A packaging material for high-pressure processing. 2. The packaging material for high-pressure processing according to claim 1, wherein the barrier layer is selected from the group consisting of aluminum foil, aluminum-deposited film, silicon oxide-deposited film, and alumina-deposited film. A packaging container using the packaging material for high-pressure processing according to claim 1 or 2.

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