JP2002292803A - Paper packaging material having high barrier properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper packaging material having high barrier properties for liquid food or the like developing excellent capacity preventing the dispersion of aroma of internally filled matter or the oxidation of the internally filled matter and using no metal foil in place of a conventional paper packaging material having an aluminum foil heavy because of the presence of a metal foil and having a problem from an aspect of disposal environment. SOLUTION: An adhesive layer containing an oxygen absorbent is provided inside a paper layer and polymer layers having barrier properties are provided on both sides of the adhesive layer containing the oxygen absorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper packaging material having a high barrier property, and more particularly to a paper packaging material having a high barrier property suitable for protecting an internal filling such as a liquid food.

[0002]

2. Description of the Related Art Conventionally, paper is mainly used as a packaging material for liquid foods and the like, and paper and a material such as a plastic film such as polyethylene, polypropylene, polyester, polyvinyl chloride, etc. are used to protect the paper and internal filling material. Laminated ones are used. In particular, the dissipation of the scent of the internal filling,
Although the use of a barrier polymer to prevent oxidation of the internal filling material has also been performed, one disadvantage of all plastic films having such a barrier property is that oxygen permeates through the plastic film. The degree of oxygen permeation can be set to some extent by the type of barrier polymer, the selection of temperature and humidity, and the like.

[0003] However, even if polyvinyl alcohol is said to be the best barrier polymer, even if the humidity is zero, which is the most preferable condition, a polymer that permeates a small amount of oxygen and does not transmit oxygen at all. Does not exist. The oxygen permeability can be made close to zero by using a metal foil, such as an aluminum foil, having no pinholes, and making the metal foil thicker. But,
Given the current environmental situation, packaging materials using such metal foils are becoming more and more difficult to separate from the other, and high-barrier packaging materials without metal foils are required. ing.

[0004]

DISCLOSURE OF THE INVENTION The present invention is directed to a method for preventing the scent of the internal filling from escaping and eliminating the disadvantages of the conventional paper packaging material having a metal foil which is heavy and has the above-mentioned environmental problems. It is another object of the present invention to provide a high-barrier paper packaging material for liquid foods and the like that does not use metal foil and exhibits excellent performance for preventing oxidation of the internal filler.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to improve the above-mentioned problems, and as a result, provided an oxygen-absorbing agent-containing layer inside a paper layer, and provided on both sides of the oxygen-absorbing agent-containing layer. The inventors have found that the object of the present invention can be achieved by providing a barrier polymer layer, and have reached the present invention. In the present invention, the inner layer refers to a layer on the side in contact with the inner filler when packaging the inner filler using a packaging material, and the outer layer refers to a layer on the opposite side. Similarly, when packing the internal filling, the inside refers to the side near the internal filling, and the outside refers to the opposite side.

That is, the present invention provides a paper packaging having a high barrier property, comprising an adhesive layer containing an oxygen absorbent inside a paper layer, and the adhesive layer having a barrier polymer layer on both sides thereof. The material is the gist. Further, the paper packaging material of the present invention,
An adhesive layer is provided inside the barrier polymer layer inside the adhesive layer. Further, the paper packaging material of the present invention is characterized by having a seal layer inside the adhesive layer. Further, the paper packaging material of the present invention is characterized in that the seal layer is made of linear low-density polyethylene produced by using a metallocene catalyst. Further, the paper packaging material of the present invention has a polyolefin layer outside the paper layer. Further, the paper packaging material of the present invention is characterized in that the polyolefin layer is a polyethylene layer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As the paper forming the paper layer of the paper packaging material of the present invention, a normal paper having a basis weight of 50 to 350 g / m ² can be used.

The adhesive layer containing the oxygen absorbent provided inside the paper layer of the paper packaging material of the present invention keeps the oxygen concentration and the humidity relatively high in order to make the moisture triggering property of the layer function optimally. Must be something. The adhesive layer is composed of an oxygen absorbent and an adhesive serving as a matrix material containing the oxygen absorbent. Examples of the oxygen absorbent include a sulfite, a reducing organic compound, and a reduced metal. As sulfites,
Examples include sodium sulfite and potassium sulfite, and examples of the reducing organic compound include ascorbic acids, polyhydric phenols, and catechins. Examples of ascorbic acids include ascorbic acid, alaboscorbic acid, and salts thereof (sodium salt, potassium salt, etc.), and mixtures thereof can also be used. Examples of polyhydric phenols include pyrogallol, catechol, gallic acid, resorcinol, hydroquinone, and the like, and mixtures thereof can also be used. Examples of the catechins include epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, and the like, and a mixture thereof may also be used. Among these reducing organic compounds, ascorbic acids and catechins, particularly ascorbic acid and alaboascorbic acid, are desirable. The reduced metal includes reduced iron. Among these oxygen absorbers,
Sodium sulfite, ascorbic acid, reduced iron, especially sodium sulfite are preferred.

The adhesive used as the matrix material preferably has compatibility with the below-mentioned polymer which is preferably used as a barrier polymer layer provided on both sides of the adhesive layer containing the oxygen absorbent. Examples include an adhesive, a modified polyolefin-based adhesive, an ethylene-vinyl acetate copolymer, a polyamide-based adhesive, and an epoxy resin-based adhesive.

Examples of the acrylic resin-based adhesive include polymers and copolymers of acrylic acid or methacrylic acid or an alkyl ester thereof. As a modified polyolefin adhesive, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, nadic acid, and nadic acid or an anhydride thereof may be used as an organic compound on polyethylene, polypropylene, or the like. Grafted in the presence of peroxide. Particularly, a modified polyolefin adhesive is preferable. The content of the oxygen absorbent in the adhesive layer containing the oxygen absorbent is 5 to 30% by mass, preferably 10 to 15% by mass. The thickness of the adhesive layer containing the oxygen absorbent is preferably 3 to 15 μm.

Examples of the polymer of the barrier polymer layer provided on both sides of the adhesive layer include an ethylene-vinyl alcohol copolymer and a polyamide resin, and a polyamide resin is preferable. Examples of polyamide resins include polyamide MXD6, aromatic polyamide resins such as polyhexamethylenediamine terephthalate (polyamide 6T), polyhexamethylenediamine isophthalamide, and xylene group-containing polyamide, polyamide 4-6, polyamide 6, polyamide 6-6, polyamide And aliphatic polyamides such as 6-10, polyamide 6-12, polyamide 11, and polyamide 12.

The barrier polymer layer provided on the outer side of the adhesive layer is impermeable to moisture, and the barrier polymer layer provided on the inner side is water-permeable and acts as an oxygen absorber to act as a moisture trigger. Preferably, among the polyamide resins, the polyamide resin used outside the adhesive layer is particularly preferably an aromatic polyamide resin, and the polyamide resin used inside the adhesive layer is particularly an aliphatic polyamide. preferable. The thickness of the barrier polymer layer used inside and outside the adhesive layer is preferably 5 to 15 μm.

The adhesive layer provided inside the barrier polymer layer provided inside the adhesive layer includes an acrylic resin-based adhesive, a modified polyolefin-based adhesive which is an adhesive serving as a matrix material of the adhesive layer, An ethylene-vinyl acetate copolymer, a polyamide-based adhesive, an epoxy resin-based adhesive, and the like can be used, and among them, a modified polyolefin-based adhesive is particularly preferable. The thickness of the adhesive layer is 2
１５15 μm is preferred.

[0014] The paper packaging material of the present invention is characterized by having a seal layer inside the adhesive layer. As the sealing layer, polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, and polybutene-1, particularly polyethylene are preferable. As polyethylene,
High-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear low-density polyethylene (hereinafter referred to as mLLDPE) produced by using a metallocene catalyst, and the like,
Particularly, mLLDPE is preferable.

MLLDPE has a narrow molecular weight distribution (weight average molecular weight / number average molecular weight) of 2 to 4 and a density of 0.900.
Preferably those ~0.925g / cm ^3, but those density of 0.900~0.915g / cm ³ is particularly preferred. Also, the melt flow index (MFI: 190
(° C, load 2.16 kg) is preferably 10 to 20 g / 10 min.

[0016] Such mLLDPE is prepared by using ethylene and a comonomer having 4 to 8 carbon atoms in the presence of a metallocene catalyst.
Α-olefins, preferably 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, etc., produced by copolymerizing α-olefins having 6 or more carbon atoms are desirable. .

The above-mentioned metallocene catalyst is a compound having a structure in which a transition metal such as titanium, zirconium or hafnium is sandwiched by an unsaturated cyclic compound containing a π-electron cyclopentadienyl group or a substituted cyclopentadienyl group. It is a combination of a metallocene and a cocatalyst such as an aluminum compound such as alkylaluminoxane, alkylaluminum, aluminum halide, and alkylaluminum halide. The thickness of the seal layer is 5 to 15
μm is preferred.

The paper packaging material of the present invention may further have a polyolefin layer outside the paper layer. Examples of the polyolefin of the polyolefin layer include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, and the like, with polyethylene being particularly preferred. As polyethylene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and mLLDPE can be used. The thickness of the polyolefin layer is preferably from 5 to 15 μm.

The paper packaging material of the present invention having the above-mentioned structure can further be provided with a printed layer. For example, between the paper layer and the polyolefin layer, it can be provided outside the polyolefin layer, the formation of the printing layer, using a normal ink,
What is necessary is just to print on those places.

The laminate for packaging material of the present invention is obtained by laminating each of the above-mentioned layers. The method of joining these layers is as follows when the layers are an adhesive layer or an adhesive layer.
It may be joined with other layers, otherwise, a method of hot-melting a layer that can be melted and bonding it with a layer that contacts it, a method of simultaneously extruding layers that can be simultaneously extruded and a method of laminating them, Any of the methods conventionally used when manufacturing a laminated body, such as a method of combining the same, can be adopted.

From the paper wrapping material of the present invention, a rectangular parallelepiped such as a brick type, a rectangular parallelepiped with a roof represented by a 1 l milk container, a cube, a cylindrical shape, a parallel octagonal prism, and a central octagonal prism at the body are parallel octagonal prisms. A conventionally known arbitrary shape packaging container such as a so-called prism type or a pouch having a square top and bottom can be formed.

[0022]

The present invention will be described below in detail with reference to examples. (Example 1) Sodium sulfite (Na
₂ SO ₃ ), a polyamide MXD6 film (15 μm) as a barrier polymer layer on the outside of an adhesive layer film (15 μm) composed of a modified polyolefin-based adhesive (trade name: Vinel, manufactured by DuPont) containing 15 mass% Was bonded to a polyamide 6-6 film (5 μm) as a barrier polymer layer. Above inner barrier polymer layer and density: 0.915 g / cm ³ , MI: 14 g / 1
A 0 minute mLLDPE film (20 μm) was bonded using the modified polyolefin-based adhesive film (4 μm), and further, the outer barrier polymer layer, kraft paper (basis weight: 220 g / m ² ) and the outside A low-density polyethylene film (20 μm) is laminated using an adhesive,
The paper packaging material of the present invention was manufactured. Using the paper packaging material produced above, a brick-type liquid food container containing 200 ml was prepared and filled with a vitamin C solution. As a result of observing a change in the concentration of vitamin C immediately after filling and in a container in which it was stored at 23 ° C. for 4 weeks, the concentration of vitamin C was 93% of the initial concentration.

Example 2 Adhesive layer film (15 μm) containing 15% by mass of ascorbic acid as an oxygen absorbent
A paper packaging material of the present invention was produced in the same manner as in Example 1 except that を was used. A container was prepared and a vitamin C solution was filled in the same manner as in Example 1, and the change in the concentration of vitamin C in the container was observed. As a result, the concentration of vitamin C was 91% of the initial concentration.

(Example 3) 1% of reduced iron was used as an oxygen absorbent.
A paper packaging material of the present invention was produced in the same manner as in Example 1 except that an adhesive layer film (15 μm) containing 5% by mass was used. Preparation of container and vitamin C in the same manner as in Example 1.
After filling the solution and observing the change in the concentration of vitamin C in the container, the concentration of vitamin C was 91% of the initial concentration.
Met.

Comparative Example 1 Low density polyethylene film (20 μm), kraft paper (basis weight: 220 g /
m ² ), adhesive layer (25 μm), aluminum foil (6.
5 μm), a low-density polyethylene film (15 μm), and a typical paper packaging material laminated with a low-density polyethylene film (20 μm). In the same manner as in Example 1,
As a result of preparing a container and filling the container with a vitamin C solution and observing a change in vitamin C concentration in the container, the concentration of vitamin C was 78% of the initial concentration.

As is clear from the above results, the container molded using the paper packaging material of the present invention is superior to the container molded using the conventional paper packaging material using general aluminum foil. It can be seen that it has antioxidant performance.

[0027]

The container formed by using the paper packaging material of the present invention is lighter in weight than the container formed by the conventional paper packaging material using heavy metal foil such as aluminum foil, and the metal foil is not used. It is easy to dispose of because it is not possible, and is very effective from an environmental point of view. Further, the plastic layer constituting the paper packaging material has a higher strength than the metal foil, so that the container can be handled roughly, which is advantageous in transportation.

Continued on the front page F-term (reference) 3E067 AA03 AB01 BA06A BA12A BB15A BC03A BC06A CA06 GB13 GD02 3E086 AD01 AD02 BA04 BA14 BA15 BA40 BB02 BB05 CA11 4F100 AA07B AA07H AK01C AK01D AK03B04 AK03E04 AK03 AK03 AK03B BA10A BA10C BA10D BA10E CA09B CB00 DG10A GB15 GB16 JD02C JD02D JL00 JL11B JL12E

Claims (6)

[Claims] 1. A paper packaging material having high barrier properties, comprising an adhesive layer containing an oxygen absorbent inside a paper layer, wherein the adhesive layer has a barrier polymer layer on both sides thereof. 2. The paper packaging material having a high barrier property according to claim 1, further comprising an adhesive layer inside the barrier polymer layer inside the adhesive layer. 3. The paper packaging material having a high barrier property according to claim 1, further comprising a sealing layer inside the adhesive layer. 4. The paper packaging material having a high barrier property according to claim 3, wherein said seal layer is made of linear low-density polyethylene produced by using a metallocene catalyst. 5. The paper packaging material having a high barrier property according to claim 1, further comprising a polyolefin layer outside the paper layer. 6. The paper packaging material having high barrier properties according to claim 5, wherein said polyolefin layer is a polyethylene layer.