JPH0929901A - Laminate for packing liquid food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight laminate preventing the deterioration of content by oxygen to safely preserve the content over a long period of time by using a resin layer formed from a hydrophobic thermoplastic resin in which a porous inorg. substance having ascorbic acid supported thereon is dispersed as the innermost layer. SOLUTION: The innermost layer directly coming into contact with liquid food of a laminate for packing liquid food is composed of a resin layer formed from a hydrophobia thermoplastic resin in which a porous inorg. substance having ascorbic acid supported thereon (supported porous inorg. substance) is dispersed. As a method for supporting ascorbic acid on the porous inorg. substance, a method bringing both of them into contact with each other in the presence of a proper solvent is used. The supported porous inorg. substance is dispersed in the hydrophobia thermoplastic resin by kneading both of them in a proper kneader, especially, an extruder at temp. equal to or higher than the melting temp. of the hydrophobic thermoplastic resin. The resin layer composed of this kneaded matter is set to the innermost layer of the laminate. A container for liquid food molded from the laminate develops oxygen absorbing capacity because moisture from packed and sealed liquid food acts on the resin layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated body for packaging aqueous liquid foods such as fruit juice, milk and liquor.

[0002]

2. Description of the Related Art A resin container or a paper container for packaging liquid foods has a wide range of applications because it has sufficient strength and is lightweight.

However, resin containers and paper containers have a large oxygen permeation amount as compared with metal cans and the like, and the flavor of the contents is deteriorated during sealed storage, and the shelf life of the contents is short. Had.

In order to extend the shelf life, an oxygen barrier resin such as an ethylene-vinyl alcohol copolymer is interposed in the case of a resin container, or an aluminum foil or ethylene-containing resin in the case of a paper container. Vinyl alcohol copolymer, oxygen barrier resin such as polyvinylidene chloride resin, or a resin film deposited with an inorganic oxide such as silica deposited on a paper base has been developed and used for storage of liquid foods. .

In addition, in the resin layer and the adhesive layer constituting the laminate,
Oxidation catalysts such as cobalt stearate and oxygen absorbing containers containing iron powder and a reducing organic compound have been proposed.

However, even the container in which the above oxygen barrier resin is laminated does not have a perfect barrier property, and in the container in which the aluminum foil or the resin film on which the inorganic oxide is vapor deposited is laminated, at the time of lamination or molding of the container. There is a risk of microcracks (pinholes) sometimes occurring, and the oxygen gas barrier tends to deteriorate.

In addition, when iron powder is contained, the weight increases remarkably in order to obtain a sufficient effect, and the characteristics as a lightweight container are lost. In addition, there is a problem with hygiene. When an oxidation catalyst is used, there are problems in its hygiene and control of function expression.

Furthermore, when a reducing organic compound is used, it is difficult to use a safe one and pay attention to the heat resistance of the organic compound and the elution from the resin layer.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a laminate for packaging a liquid food having a resin layer containing a reducing organic compound, which is lightweight, prevents deterioration due to oxygen, and can store contents safely and for a long time. Intended to provide the body.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have determined that a resin layer such as a polyolefin resin containing a porous inorganic substance carrying ascorbic acid is the innermost layer or a layer adjacent to the innermost layer. The present invention has been reached by finding that a laminate can achieve the object of the present invention.

That is, according to the present invention, a laminated body for liquid food packaging having a resin layer in which a porous inorganic substance carrying ascorbic acids is dispersed in a hydrophobic thermoplastic resin as an innermost layer, and at 40 ° C. and 90% RH. water vapor permeability of 5g / m ² · ²
A liquid food packaging laminate comprising a resin layer for 4 hours or more as an innermost layer and a resin layer in which a porous inorganic substance carrying ascorbic acid is dispersed in a hydrophobic thermoplastic resin as a layer adjacent to the innermost layer And

In the laminate of the present invention, the innermost layer means the layer closest to the liquid food when the liquid food is packaged using the laminate, that is, the layer which the liquid food directly contacts.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the ascorbic acid used in the present invention include ascorbic acid, araboascorbic acid and salts thereof (sodium salt, potassium salt, etc.), acyl derivatives (stearoyl and palmitoyl derivatives) and the like.

Examples of the porous inorganic substance used in the present invention include zeolite, silica gel, sepiolite, porous silica, porous silica-alumina and the like. Of these, zeolite is particularly desirable.

As the zeolite, natural zeolite can be used, but synthetic zeolite is preferable from the viewpoint of uniformity and containing no impurities, and especially A type, X type and Y type.
Type zeolites are preferred. These synthetic zeolites
It may be hydrogen type or cation type (sodium type, potassium type, calcium type, etc.).

It is desirable to use these porous inorganic substances after drying.

As the hydrophobic thermoplastic resin, polyolefin resin, polystyrene resin, polyvinyl chloride resin, methacrylic resin, ethylene-α-unsaturated carboxylic acid copolymer, ionomer, unsaturated carboxylic acid modified polyolefin, cyclic olefin copolymer Coalescence and the like can be used.

As the polyolefin resin, polyethylene resin (low density polyethylene, medium density polyethylene,
High density polyethylene, linear low density polyethylene, etc., polypropylene resin (homo polypropylene, ethylene-
Propylene random copolymer, ethylene-propylene block copolymer, etc.), polybutene-1, polyhexene-
1, polymethylpentene-1 and the like.

Examples of the ethylene-α-unsaturated carboxylic acid copolymers include copolymers of ethylene and α-unsaturated carboxylic acids such as acrylic acid and methacrylic acid.

The unsaturated carboxylic acid-modified polyolefin used in the present invention is obtained by grafting an unsaturated carboxylic acid or its derivative onto the above polyolefin resin.

Examples of unsaturated carboxylic acids include α-unsaturated carboxylic acids, α, β-unsaturated dicarboxylic acids, and alicyclic unsaturated dicarboxylic acids having a cis-type double bond in the ring. Examples of the α-unsaturated carboxylic acid include acrylic acid, methacrylic acid and crotonic acid, and examples of the α, β-unsaturated dicarboxylic acid or its derivative include maleic acid and maleic anhydride. Examples of the alicyclic unsaturated dicarboxylic acid having a bond or its derivative include hymic acid, hymic acid anhydride, tetrahydrophthalic acid, tetrahydrophthalic acid anhydride, and chloridene acid.

The cyclic olefin copolymer is a copolymer of cyclic olefin and ethylene or α-olefin.

The cyclic olefin includes cyclopentene, cyclohexene, cycloheptene, cyclooctene, 2-norbornene and the like, and the α-olefin includes
Propylene, 1-butene, 1-hexene, 4-methyl-
And 1-pentene.

Among the above thermoplastic resins, polyolefin resins, particularly polyethylene resins and polypropylene resins are preferred.

As a method of supporting the ascorbic acid on the porous inorganic substance, a method of contacting both in the presence of an appropriate medium can be mentioned. As the medium, alcohols, ethers, ketones, hydrocarbons, halogenated hydrocarbons and the like can be used.

A desirable supporting method is to immerse the porous inorganic substance in a lower alcohol solution of ascorbic acid such as ethanol, or pass the solution through a column filled with the porous inorganic substance to make the solution porous. It is a method of adsorbing and acting on a porous inorganic substance. These methods may be performed under heating.

The ascorbic acid and the porous inorganic substance are used in a ratio such that the porous inorganic substance is 1 to 50 times by weight, particularly 1.2 to 10 times by weight that of the ascorbic acid.

As a method for dispersing the porous inorganic substance carrying the ascorbic acid (hereinafter, referred to as a supported porous inorganic substance) in the hydrophobic thermoplastic resin as described above,
A method of kneading both of them at a temperature equal to or higher than the melting temperature of the thermoplastic resin in a suitable kneader, particularly preferably in an extruder is preferable.

The supported porous inorganic substance and the thermoplastic resin are
Although it cannot be specified in a general manner depending on the type of aqueous food to be stored, the storage period, the atmosphere inside and outside the storage, etc., the supported porous inorganic substance is 2 to 50% by weight, preferably 5 to 5 in the kneaded product of both.
Knead at a ratio of 30% by weight.

These kneading ratios are the ratios in the resin layer when it becomes the innermost layer of the laminate of the present invention or the layer adjacent to the innermost layer, so that the content of the supported porous inorganic substance exceeds the above range. It is also possible to prepare the masterbatch in advance and dilute it with the thermoplastic resin to obtain the above kneading ratio when forming a laminate.

The laminate of the present invention has a resin layer made of the above kneaded material as the innermost layer. Further, the laminate of the present invention has a water vapor permeability of 5 g at 40 ° C. and 90% RH.
/ M ² · 24 hours or more is the innermost layer, and the resin layer is the adjacent layer. The thickness of these laminates is not specified, but is 10 to 600 μm, which is the usual thickness of a package for packaging liquid foods. Of course, it may be thinner or thicker than this.

As the resin for the resin layer having the above-mentioned water vapor permeability as the innermost layer, polyolefin resin, polyamide resin, polyester resin, ethylene-vinyl acetate copolymer, ethylene-α-unsaturated carboxylic acid copolymer, Examples thereof include ionomers and mixtures thereof. The polyolefin resin and the ethylene-α-unsaturated carboxylic acid copolymer are arbitrarily selected from the above. Among the above, a polyolefin resin is preferable, and a polyethylene resin and a polypropylene resin are particularly preferable. The thickness of the resin layer satisfying the water vapor permeability depends on the type of resin, the processing method, etc., but is usually 80 μm or less. In the case of polyethylene resin and polypropylene resin, the thickness is usually 30 μm or less.
μm or less.

The base material layer of the laminate may be any synthetic resin film or sheet, paper, metal foil or the like, or any base material layer commonly used for liquid food packaging such as laminates. Both can be used.

The method for laminating the base material layer and the resin layer is not particularly limited, and a usual laminating method can be adopted.

For example, an extrusion lamination method in which the resin layer is extrusion-coated on the base material layer, a dry lamination method in which the base material layer and the resin layer in a film or sheet form are laminated with an adhesive or the like, the base material Direct lamination method in which at least the surface of the material layer or the film or sheet-shaped resin layer is melted and laminated on each other, and the base material layer and the film or sheet-shaped resin layer are formed as an adhesive layer between the two. Extruding and laminating materials such as, so-called sandwich lamination method, the synthetic resin to be the base material layer and the resin kneaded product to be the resin layer,
Examples thereof include a coextrusion lamination method of extruding from a flat die or a circular die attached to an extruder or the like, and laminating the both.

The method for laminating the innermost layer composed of the resin layer having the water vapor permeability and the resin layer adjacent to the innermost layer is as follows.
The method for laminating the base material layer and the resin layer may be applied.

The laminate of the present invention comprises a base material layer and the above resin layer, and further a resin layer having the above water vapor permeability as a basic layer as described above. The same member or other members (for example, a gas barrier resin layer,
It is optional to provide a layer composed of an inorganic oxide vapor deposition synthetic resin film or the like) to form a multilayer body.

The liquid food container molded from the laminate of the present invention having the above-mentioned structure has an oxygen absorbing ability by the water content of the liquid food having the filled and sealed contents acting on the resin layer. Is expressed.

That is, since the ascorbic acid in the resin layer is stable in the dry state at room temperature even in the presence of oxygen, the above-mentioned capacity is maintained during the storage of the packaging material. However, when the contents are filled, moisture gradually reaches the supported porous inorganic substance through the thermoplastic resin, and the ascorbic acid exhibits oxygen absorbing ability.

When the innermost layer is a resin layer having a water vapor transmission rate of 5 g / m ² · 24 hours or more at 40 ° C. and 90% RH, the content of the resin is maintained while maintaining the oxygen absorbing ability of the adjacent resin layer. Of the ascorbic acid in the resin layer and the risk of elution of ascorbic acid in the resin layer is reduced.

[0041]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 A solution prepared by dissolving 300 g of ascorbic acid in 7.2 l of warm ethanol was slowly passed through a glass column filled with 500 g of A-type zeolite to support ascorbic acid on the zeolite. The supported zeolite was washed with cold ethanol and dried under reduced pressure to prepare an ascorbic acid-supported zeolite.

The obtained ascorbic acid-supported zeolite 3
0 parts by weight, low-density polyethylene (density 0.919 g / c
m ³⁾ (LDPE) 70 parts by weight were kneaded by supplying to a twin-screw extruder to obtain ascorbic acid loaded zeolite content of 30% by weight of the masterbatch.

The masterbatch and the LDPE used above were further mixed with an ethylene-acrylic acid copolymer (density 0.94 g / cm ³ ) (EAA) so that the content of the ascorbic acid-supported zeolite was 10% by weight. Are each supplied to an extruder and coextruded from a circular die attached to the extruder to obtain the supported zeolite-containing LDP.
An inflation film composed of two layers, an E layer of 30 μm and an EAA layer of 10 μm, was molded.

Next, the two-layer blown film and LDPE (15 μm) -paperboard (basis weight 200 g / m ² ).
-LDPE (15 μm) -a base material made of aluminum foil (7 μm), using EAA (20 μm) as an adhesive layer,
Sandwich lamination was performed at 280 ° C. to prepare a laminate of the present invention having the following constitution.

LDPE-Paperboard-LDPE-Aluminum foil / | EAA / | EAA-supported zeolite-containing LDPE Using the above laminate, a supporting container-containing LDPE layer is placed on the inner surface side of the container in a paper container filling machine, 250 ml of degassed water having a dissolved oxygen concentration of 0.5 mg / l was filled to obtain a brick-type paper container.

The above-mentioned paper container filled with deaerated water was heated to a temperature of 37.
The sample was stored in a thermostatic chamber at 0 ° C for a certain period of time, and the dissolved oxygen concentration of deaerated water was measured. The results are shown in Table 1.

(Example 2) In the same manner as in Example 1, a three-layer blown film having the following constitution was formed.

LDPE (10 μm) -Supported zeolite-containing LDPE (30 μm) -LDPE (10 μm) A laminate was prepared in the same manner as in Example 1 except that this three-layer inflation film was used instead of the two-layer inflation film. However, regarding this laminated body, Example 1
The evaluation was performed in the same manner as described above. The results are shown in Table 1.

Example 3 The thickness of the LDPE layer on one side is 3
A 0 μm 3-layer blown film was molded in the same manner as in Example 2. A laminate was prepared in the same manner as in Example 1 so that the LDPE of 30 μm was on the inner surface side of the container, and this laminate was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 4) A thickness composed of a mixture of 90 parts by weight of polypropylene (density 0.90 g / cm ³ ) and 10 parts by weight of ethylene-1-butene copolymer (density 0.88 g / cm ³ ) on one side. A three-layer blown film, which is a 20 μm resin mixture layer, was molded in the same manner as in Example 2. A laminate was prepared in the same manner as in Example 1 so that the resin mixture layer of 20 μm was on the inner surface side of the container, and this laminate was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 A laminated body was prepared in the same manner as in Example 1 except that A-type zeolite not supporting ascorbic acid was used, and this laminated body was evaluated simultaneously with Example 1.

The evaluation results are shown in Table 1.

Comparative Example 2 A laminate produced in the same manner as in Example 1 without using ascorbic acid-supporting zeolite was evaluated simultaneously with Example 1, but the results were the same as in Comparative Example 1. .

[0055]

[Table 1] Dissolved oxygen concentration (mg / l) Storage period Immediately after filling 7 days 14 days 28 days Example 1 0.5 1.1 1.3 1.8 Example 2 0.5 1.2 1.4 1.9 Example 3 0.5 1.3 1.6 2.3 Example 4 0.5 1.2 1.5 2.2 Comparative Example 1 0.5 1.3 2.0 3.1

[0056]

EFFECTS OF THE INVENTION The laminate of the present invention absorbs and reduces oxygen invading through the base material layer, so that deterioration of liquid food packaged by the laminate due to oxygen can be suppressed, and It is possible to maintain the quality of food and extend the shelf life.

The oxygen absorption capacity can be easily adjusted by changing the concentration of ascorbic acid supported on the porous inorganic substance and the addition amount of the supported porous inorganic substance. Depending on the environment inside and outside the
Can be easily handled.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08K 3/34 KEF C08K 3/34 KEF 9/12 KFU 9/12 KFU C08L 23/04 LBZ C08L 23 / 04 LBZ 23/10 LBZ 23/10 LBZ

Claims (6)

[Claims] 1. A laminate for liquid food packaging, comprising a resin layer in which a porous inorganic substance carrying ascorbic acids is dispersed in a hydrophobic thermoplastic resin as an innermost layer. 2. A porous thermoplastic resin having a water vapor permeability of 5 g / m ² · 24 hours or more at 40 ° C. and 90% RH as an innermost layer, and a porous inorganic substance carrying ascorbic acid as a hydrophobic thermoplastic resin. A laminated body for liquid food packaging, wherein the dispersed resin layer is a layer adjacent to the innermost layer. 3. The water vapor permeability resin layer has a thickness of 30 μm.
The layered product according to claim 2, which is a layer composed of a polyethylene-based resin or a polypropylene-based resin of m or less. 4. The laminate according to claim 1, wherein the porous inorganic substance is synthetic zeolite. 5. The laminate according to claim 1, wherein the hydrophobic thermoplastic resin is a polyolefin resin. 6. The laminate according to claim 5, wherein the polyolefin resin is a polyethylene resin or a polypropylene resin.