JPH08118551A - Gas barrier packing material - Google Patents

Abstract

PURPOSE: To suppress oxygen transmission quantity under the action of heat and moisture to a low level by providing a protective layer composed of a resin compsn. compounded with an oxygen scavenger or the oxygen scavenger and a moisture absorbent on the single surface of a specific gas barrier resin and forming layered constitution not melting and bonding the gas barrier resin and the protective layer. CONSTITUTION: A protective layer II12 compounded with an oxygen scavenger 15 or the oxygen scavenger 15 and a moisture absorbent 16 is provided on at least the single surface of a gas barrier resin 13 of which the oxygen transmission quantity at 20 deg.C and 65%RH is 20cc/m<2> .24hr.atm or less at the time of a thickness of 20μm. Oxygen transmitted through the protective layer II12 is absorbed by the oxygen scavenger 15 to reduce the amt. of oxygen transmitted through the gas barrier resin 13 and, further, steam is caught by the moisture absorbent 16 to suppress the lowering of the transmission coefficient of oxygen generated by moisture absorption of the gas barrier resin 13. An extremely slight space is allowed to be present between the gas barrier resin 13 and the protective layer II12 without melting and bonding them and oxygen and steam transmitted through the protective layer II12 again come into contact with the oxygen scavenger 15 and moisture absorbent 16 of the protective layer II12 to be caught.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas barrier packaging material for a food container to be heat sterilized, which has a plastic material containing oxygen even under heat sterilization conditions in which the gas barrier property is lowered by the action of heat and moisture. An object of the present invention is to provide a composite packaging material capable of suppressing the permeation amount to a significantly low level.

[0002]

2. Description of the Related Art Conventionally, metal cans, glass bottles, and various types of plastic containers have been used as containers for foods that are sterilized by heating and stored for a long period of time.
The amount of oxygen permeation from a plastic material is a level that cannot be ignored, which is a problem in terms of the preservability of the food product.

In particular, when heat sterilizing with hot water or steam, such as retort pouch foods, etc.
Since a high temperature of 20 ° C. or higher and moisture act on the glass container, maintaining the gas barrier property of the plastic container has been a serious problem. Therefore, for gas barrier packaging materials for long-term storage of food, a method of providing a protective layer using an adhesive or an adhesive resin on both sides of the barrier packaging material, kneading a desiccant on both sides of the gas barrier resin Layer, a method of further providing a protective layer thereon, a method of adding a deoxidizer and a hygroscopic agent to the adhesive resin provided on both sides of the gas barrier resin, and further providing a protective layer thereon. Retains barrier properties.

[0004]

However, in the above case, the oxygen permeability coefficient of the barrier resin increases during the hot water sterilization treatment, and after the sterilization, oxygen permeates from the packaging material to cause oxidative deterioration of the food product. There is a drawback that In, it is possible to suppress the oxygen permeation during the hot water treatment to a low level, but since an adhesive resin or the like is used, there is a problem that the manufacturing cost of the packaging material becomes high. In addition, the deoxidizer or hygroscopic agent exhibits its effect only in the presence of oxygen or water, and the layer structure of the packaging material is one in which the deoxidant or hygroscopic agent has a lot of opportunities to come into contact with oxygen or water. However, it was not possible to maintain sufficient gas barrier properties.

Therefore, in a plastic packaging material, under the condition that heat and water act simultaneously, that is, under the condition of heat sterilization by hot water or steam, the oxygen permeability coefficient of the packaging material becomes very large compared to room temperature. Under these conditions, suppressing the oxygen permeation amount of the packaging material to a low level has been a major issue. The present invention solves these drawbacks, suppresses the oxygen permeation amount of the packaging material to a low level even under the condition that heat and moisture act simultaneously, and further, even in the storage state after heat sterilization, the oxygen permeation of the packaging body is reduced. It is an object to provide a packaging material that maintains a low amount.

[0006]

Means for Solving the Problems When the oxygen permeation amount at 20 ° C. and 65% RH is 20 μm, 20 cc /
At least one side of the gas barrier resin having m ² · 24 h · atm or less has a protective layer made of a resin composition containing an oxygen scavenger or an oxygen scavenger and a moisture absorbent, and the gas barrier layer and the protective layer are A gas barrier packaging material having a layer structure that does not melt and adhere.

A gas barrier packaging material is prepared by adding 1 to 200 parts by weight of an oxygen absorber and / or 1 to 200 parts by weight of a hygroscopic agent to the protective layer resin. Further, the gas barrier resin is a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol% and a saponification degree of 96 mol% or more, a polyamide resin, a vinylidene chloride copolymer, or an acrylic resin. A gas barrier packaging material comprising a nitrile resin, wherein the protective layer is a gas barrier packaging material comprising an olefin resin, a styrene resin, a polyester resin or a polycarbonate resin and a blend thereof.

The above gas barrier resin is a gas barrier resin as the oxygen permeability coefficient and the water vapor permeability coefficient of the protective layer that protects the gas barrier resin increases under heat sterilization conditions such as hot water or steam. Since the oxygen permeability coefficient of (1) is much larger than that at room temperature, a deoxidizer or a deoxidizer and a hygroscopic agent was added to the protective layer to suppress the deterioration of the gas barrier property of the laminated material.

That is, by providing a protective layer containing a deoxidizer or a deoxidizer and a hygroscopic agent on the outside of the gas barrier resin, oxygen permeating from the protective layer is absorbed by the deoxidizer and the gas barrier resin is absorbed. The amount of oxygen that permeates through the protective layer is reduced, and the water vapor that enters from the outside of the protective layer is captured by the hygroscopic agent to suppress the decrease in the oxygen permeation coefficient caused by the moisture absorption by the gas barrier resin.

Further, the protective layer to which the oxygen scavenger and the hygroscopic agent are added and the gas barrier resin layer are not melt-bonded to each other, and a very small gap is present between the layers so that oxygen permeated through the protective layer and The water vapor is again brought into contact with the deoxidizer and the moisture absorbent on the back surface of the protective layer to be trapped, and the trapping rate of oxygen and water vapor in the protective layer is increased to enhance the effect of the protective layer.

In particular, when the gas barrier resin is a saponified ethylene-vinyl acetate copolymer, the gas barrier film has an increased amount of oxygen permeation as the water content increases.
When the water content is 80% or more, the amount of oxygen permeation also increases sharply, and the gas barrier film no longer functions. Therefore, a hygroscopic agent is added to the protective layer to suppress the amount of water permeation to the gas barrier film, to keep the water content of the gas barrier film at a low concentration, and to suppress the increase in the amount of oxygen permeation of the film. It is intended to exhibit the original performance as a film.

Therefore, even under heat sterilization conditions such as hot water or steam, a hygroscopic agent is added to the protective layer in order to keep the oxygen permeation amount of the gas barrier film made of saponified ethylene-vinyl acetate copolymer at a low level. Then, the object is achieved by laminating it with a gas barrier film. Also, by providing a resin layer containing an oxygen scavenger inside the barrier film, the slight amount of oxygen that has permeated the barrier film is further captured by the oxygen scavenger, so the amount of oxygen permeation into the container is very small. Therefore, a low level of oxygen concentration will be maintained in the container.

[0013]

According to the present invention, since the barrier resin layer is protected by the oxygen scavenger or the protective layer to which the oxygen scavenger and the hygroscopic agent are added, the barrier resin layer is protected even under heat sterilization conditions in which heat and water act simultaneously. The resin layer has little deterioration in its barrier function, and the oxygen permeation amount can be maintained at a low level almost equal to that under room temperature conditions. Therefore, the oxygen concentration in the container can be maintained at a low level in the field of retort food that is heat-sterilized by hot water or steam. Further, even when the packaging material is distributed under conditions of high temperature and high humidity, the oxygen permeation amount of the packaging material hardly changes, and the oxygen concentration in the container can be maintained at a low level. Therefore, the drawbacks of the conventional plastic gas barrier packaging material can be greatly improved, and it can be used as a food packaging material that requires long-term storage such as retort food.

[0014]

The present invention will be described in detail below with reference to the drawings based on the embodiments. FIG. 1 is a cross-sectional view showing an example of the layer structure of the gas barrier packaging material of the present invention. Figure 2
FIG. 3 is a cross-sectional view showing another layer structure of the gas barrier packaging material of the present invention. FIG. 3 is a cross-sectional view of a gas barrier packaging material in which a protective layer containing an oxygen absorber and a hygroscopic agent is provided on both sides of the gas barrier resin layer, and FIG. 4 is a packaging material of FIG. It is sectional drawing of the provided thick gas barrier packaging material. FIG. 5 is a cross-sectional view of a molding container using the gas barrier packaging material of the present invention. In order to measure the gas barrier property of the molding container, FIG. 5 (a) shows a cloth piece containing water. This is the case, and FIG. 5B shows the case where the agar solution containing methylene blue was added. FIG. 6 is a perspective view of a packaging bag using the gas barrier packaging material of the present invention. In order to measure the gas barrier property of the packaging bag, FIG. 6 (a) shows a cloth piece containing water. This is the case, and FIG. 6B shows the case where the agar solution containing methylene blue was added.

The protective layer (I) serves as a surface protective layer of the gas barrier laminate packaging material, and is made of a material having heat resistance and low moisture permeability. Further, the protective layer (II) is a resin layer to which an oxygen scavenger or a hygroscopic agent is added, and has a protective function to capture oxygen and water vapor and maintain the oxygen permeation amount of the barrier resin layer at a low level. is there. Then, FIGS.
Of the layer structure shown in FIG.
(II) 12 is not melt-bonded and oxygen molecules and water molecules can move freely. However, since the oxygen scavenger or hygroscopic agent kneaded with the protective layer resin is present on the surface of the protective layer, the barrier resin layer 13 and the protective layer (II) are in close contact with each other due to the wedge effect. There is almost no delamination, and it cannot be used as a packaging material.

However, an adhesive is used as the protective layer (II), and a deoxidizer and a hygroscopic agent are added to the adhesive to form a protective layer.
By laminating (I) and the barrier resin layer, it is also possible to form a laminated material which does not separate the layers even under special conditions such as high temperature and high humidity. Also, depending on the usage conditions of the packaging material, a protective layer
A laminated material may be formed by bonding the protective layer (II) and the barrier resin layer between (I) and the protective layer (II) with an adhesive. As described above, when the adhesive is used, the layers are attached by the dry lamination method or the wet lamination method. As the adhesive, polyethyleneimine-based, polybutadiene-based, organic titanium-based compounds, isocyanate-based, urethane-based, polyester-based, etc. can be used.

Further, a protective layer (II) is provided with a barrier resin layer interposed therebetween.
When the protective layers (II) are provided on both sides, one of the protective layers (II) may not be heat-sealed, and the other may be a heat-sealed laminated material. For example, protective layer (I) / protective layer (II) / barrier resin layer / protective layer
(II) / protective layer (II) /
The barrier resin layers are not heat-sealed, but the inner barrier resin layer / protective layer (II) is heat-sealed with an adhesive resin.
Alternatively, the above adhesive may be used for adhesion. Protective layer (I) /
Completely adhere between the protective layer (II) and the protective layer (II) / sealing layer with an adhesive or an adhesive resin. Incidentally, if the same resin is used for the protective layer (II) and the seal layer between the protective layer (II) and the seal layer, lamination by an extrusion method can also be used.

As the adhesive resin, a resin modified with a carboxylic acid is used. For example, ethylene-acrylic acid copolymer, ion-crosslinked olefin copolymer, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, acrylic acid grafted polyolefin, ethylene-vinyl acetate copolymer, copolymer polyester, copolymer polyamide Etc. These resins are used alone or in combination of two or more.

The various layer structures of the gas barrier packaging material of the present invention will be described below. As shown in Fig. 1, from the surface, protective layer (I) / protective layer
By making (II) / barrier resin layer / sealing layer (inner surface), oxygen and water vapor which have permeated the protective layer (I) are protected.
Since it is captured by the oxygen scavenger and the hygroscopic agent of (II) and has a low concentration, the oxygen that permeates the barrier resin layer and reaches the contents has an extremely low level. In particular, since water vapor is captured by the hygroscopic agent of the protective layer (II), the water content of the barrier resin layer does not increase to a high level,
The oxygen permeability coefficient of the barrier resin layer hardly changes, and it functions as an oxygen barrier layer. Therefore, the protective layer
Oxygen captured by the oxygen scavenger of (II) and having a low concentration is further prevented from permeating by the barrier resin layer, and the amount of permeation into the contents becomes very small.

Usually, most foods to be heat-sterilized have a large amount of water, so that water vapor permeates from the inside of the packaging material during heat-sterilization. That is, there is a possibility that water vapor may permeate through the seal layer of the gas barrier packaging material, increasing the water content of the barrier resin layer. But usually
In a packaging material that is heat-sterilized, such as a retort packaging material, the inner sealing layer is made of unstretched polypropylene (hereinafter referred to as CPP) that has heat resistance and excellent moisture resistance, and its thickness is 60 μm or more. Since it is used, it has specifications that prevent the permeation of water vapor from the inner surface. When water vapor permeation from the inner surface becomes a problem, the thickness of CPP should be increased, or the barrier resin layer and seal layer (CP
By providing a resin layer containing a hygroscopic agent between P), water vapor permeation from the inner surface can be prevented.

As shown in FIG. 2, the following layer structure has a protective layer (I) / protective layer (II) / barrier resin layer / thickness adjusting layer /
This is a case where a sealing layer (inner surface) is provided and a thickness adjusting layer is provided on the laminated material to provide a packaging material applicable to a molding container or the like.
That is, when used as a packaging material for vacuum forming, pressure forming, or vacuum / pressure forming, it is necessary to have a certain degree of thickness, and it is necessary to make the specifications excellent in formability. Use a material with good properties.

As another layer structure, as shown in FIG. 3, protective layer (I) / protective layer (II) / barrier resin layer / protective layer
(II) / Seal layer (inner surface) and protective layers (II) on both sides of the barrier resin layer to make the barrier resin layer function more efficiently and to reduce the amount of oxygen permeation into the contents. To do. That is, water vapor permeation from the inner surface is almost completely blocked, and the oxygen permeation preventing function of the barrier resin layer is sufficiently exerted, and from the surface, the protective layer (I)
, A small amount of oxygen that has permeated the protective layer (II) and the barrier resin layer is captured by the oxygen scavenger of the protective layer (II) to completely prevent the permeation of oxygen into the contents.

The structure shown in FIG. 4 corresponds to a molding container by providing a thickness adjusting layer on the laminated material shown in FIG. That is, as a protective layer (I) / thickness adjusting layer / protective layer (II) / barrier resin layer / protective layer (II) / thickness adjusting layer / sealing layer (inner surface), a laminated packaging material that can be applied to various container shapes And For example, in the case of a deep-drawing container, it is necessary to select a resin having good moldability for the thickness adjusting layer and to make the thickness considerably thick. The thickness adjusting layer does not necessarily have to be provided in two layers, and even one layer can achieve the purpose. Also,
As the thickness adjusting layer, 1 layer or 2 layers of each of the seal layer, the protective layer (I) and the protective layer (II) without providing an independent layer,
By making the three layers thicker, it is possible to obtain a formable laminated material.

The barrier resin layer used in the present invention is 2
Oxygen permeation amount at 0 ° C, 65% RH, thickness of 20 μm
At that time, it is necessary to reduce the pressure to 20 cc / m ² · 24 h · atm or less. For example, in the case of protective layer (I) / protective layer (II) / barrier resin layer / thickness adjusting layer / seal layer (inner surface), the oxygen permeation amount of the barrier resin layer is 20 cc / m ^{2 under the} above conditions.
・ If it exceeds 24 h · atm, a sufficient oxygen barrier property of the laminated material cannot be obtained. However, the oxygen barrier effect can be enhanced by increasing the amount of the oxygen scavenger added to the protective layer (II), but since the amount of the oxygen scavenger affects the film forming characteristics of the protective layer resin, If the amount of oxygen agent added increases, film formation becomes difficult. The oxygen scavenger for the protective layer (II) has an auxiliary effect on the oxygen barrier of the barrier resin layer, and it is desirable to reduce it from the viewpoint of physical properties of the film. Therefore, it is necessary to minimize the amount of the oxygen scavenger added.

The barrier resin is obtained from a saponified ethylene-vinyl acetate copolymer (having an ethylene content of 20 to 60 mol% and a saponification degree of 96% or more), metaxylene diamine (MXDA) and adipic acid. Polyamide (MXD-6 nylon), acrylonitrile copolymer, vinylidene chloride copolymer and the like are used. In the saponified product of ethylene-vinyl acetate copolymer, when the ethylene content is less than 20 mol%, the oxygen permeation amount is reduced and the gas barrier property is improved, but the melting point is increased, so that the heat processability is deteriorated. Further, when the ethylene content exceeds 60 mol%, the gas barrier property is deteriorated under high temperature and high humidity, so that the amount of the hygroscopic agent or the oxygen absorber is increased,
It leads to cost increase. The saponification degree is 96 mol%.
If the amount is less than the above, not only the gas barrier property is deteriorated, but also the heat resistance and water resistance of the resin are deteriorated, and heat sterilization may become impossible.

As the oxygen absorber added to the protective layer (II),
There are the following. Reducing metal powder: reducing iron, reducing zinc, reducing tin, etc. Metal oxides: ferrous oxide, ferric oxide, etc. Reducing metal compounds: iron carbide, silicon iron, iron carbonyl, iron hydroxide, etc. A substance containing one or a combination of two or more of the above substances as a main component and further added with another substance is used. These are alkali metal and alkaline earth metal hydroxides, carbonates, sulfites, thiosulfates, tertiary phosphates, secondary phosphates, organic acid salts, halides, and activated carbon as required. It can also be used in combination with auxiliary agents such as activated alumina, activated clay and phenols. Polymer compound having polyhydric phenol in the skeleton: polyhydric phenol-containing phenol / aldehyde resin, etc. Ascosbic acid or its compound. The above-mentioned deoxidizer preferably has an average particle size of 100 μm or less, particularly 50 μm or less.

As the hygroscopic agent to be added to the protective layer (II), a deliquescent inorganic salt, a deliquescent organic compound, a highly water-absorbent resin or the like is used, and there are the following ones. Deliquescent inorganic salt: sodium chloride, calcium chloride,
Zinc chloride, ammonium chloride, ammonium sulfate, sodium sulfate, magnesium sulfate, sodium hydrogen phosphate,
Sodium diphosphate, sodium pyrophosphate, potassium pyrophosphate, potassium carbonate, sodium nitrate, etc. Deliquescent organic compounds: glucose, fructose, sucrose, gelatin, modified casein, modified starch, tragacanth gum, polyvinyl alcohol, carboxymethylcellulose, sodium alginate, etc. Superabsorbent resin: starch-sodium acrylate graft polymer, starch-acrylonitrile graft polymer hydrolyzate, starch graft polymer of these salts, partially cross-linked polyacrylic acid salt, polyisobutylene-maleic anhydride Copolymers, crosslinked synthetic resins such as hydrolysates of methyl metamurilate-vinyl acetate copolymers, polyethylene oxide modified products and the like. In addition to these, there are silica gel, alumina gel, silica-alumina gel, various zeolites and the like.

The highly water-absorbent resin is a substance that is insoluble in water and retains 10 to 1000 times its own weight of water. Product name: Sumitomo Chemical Co., Ltd .: Sumikagel, Meisei Chemical Co., Ltd .: Aquaprene, Steel Manufacturing Co., Ltd.
Made: Aqua Keep, Kuraray Isoprene Chemical Co .: K
I gel, Sanyo Kasei Kogyo Co., Ltd .: Sunwet, Showa Denko KK: Pre-apple, Henkel Co .: SGP absorber polymer, etc. are mentioned.

The amount of the oxygen scavenger or hygroscopic agent added is determined in consideration of the film-forming property of the protective layer and the physical properties of the film formed, or the protective effect of the barrier resin layer. It is used in the range of 1 to 200 parts by weight, but 5 to
The addition amount of 50 parts by weight is preferable from the viewpoint of film forming property and the like. If the amount added to the protective layer resin is less than 1 part by weight, the effect of the addition is not exerted, and if it exceeds 200 parts by weight, the film forming property of the protective layer resin is deteriorated and film formation becomes difficult. Further, even if the added amount exceeds 200 parts by weight, the effect does not increase so much in the ratio of the added amount, resulting in high cost.

As the protective layer resin, a thermoplastic resin having moisture resistance is used, and the representative examples thereof are as follows. Polyolefin resin: low density polyethylene, medium density polyethylene, high density polyethylene, isotactic polypropylene, syndiotic polypropylene, ethylene-polypropylene copolymer, polybutene-1-ethylene-butene-1 copolymer, ethylene-pyrene-butene Copolymers, ion-crosslinked olefin copolymers (ionomers) or blends thereof.

Styrenic resin: polystyrene, acrylonitrile-butadiene-styrene copolymer, styrene-butadiene copolymer, hydrogenated product of styrene-butadiene copolymer, or a blend thereof.

Polyester resin: polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate or a blend thereof.

Polyamide resin: nylon 6, nylon 6,6, nylon 6-nylon 6,6 copolymer, metaxylene adipamide, nylon 6,10, nylon 11,
Nylon 12, nylon 13, etc. Furthermore, a polycarbonate resin, a polyacrylic resin, a polymethylpentene resin, or the like can be used.

As other resins, polyarylate, polymethyl methacrylate, thermoplastic elastomer, copolymer of ethylene and acrylic acid derivative or acrylic acid derivative, amorphous polyolefin and the like can be used. Furthermore, a laminated material obtained by laminating an aluminum foil, a paper, a nonwoven fabric, a thermoplastic resin film having an inorganic thin film layer such as SiO ₂ or Al ₂ O ₃ can also be used.

Protective layer (II) to which an oxygen absorber or a hygroscopic agent is added
As the film forming method of (3), it is possible to manufacture by a known method.
For example, a T-die method, an inflation method, a co-extrusion method, etc. can be used. A molded product such as a container can be manufactured by an injection molding method or a blow molding method. Further, a cup-shaped or tray-shaped container can be produced by vacuum forming, pressure forming, vacuum / pressure forming of a film or sheet. The thickness of the protective layer (II) to which an oxygen scavenger or a hygroscopic agent is added is selected depending on the film forming method and can be used in the range of 5 to 2000 μm, but from the viewpoint of film forming stability, it is preferably about 20 to 1000 μm.

Next, the present invention will be described in more detail with reference to specific examples. (Example 1) Protective layer to which oxygen absorber and hygroscopic agent are added (II)
Polypropylene resin (hereinafter referred to as PP) is used as the resin of 10 to 20% by weight of an iron-based oxygen scavenger having an average particle diameter of 40 μm and calcium chloride (CaCl ₂ ) as a hygroscopic agent to PP pellets, respectively. And mixed in a batch-type mixer, after melt-kneading in a twin-screw kneader,
Pelletized with a pelletizer. Hereinafter,% means% by weight. Next, PP containing the iron-based oxygen scavenger and calcium chloride (hereinafter referred to as PPmix), PP, saponified ethylene-vinyl acetate copolymer (ethylene content 3
Using 2 mol% and a saponification degree of 99 mol% (hereinafter referred to as EVOH), a multilayer sheet of 3 types and 5 layers as described below was produced by a multilayer extruder.・ PP 100 / PPmix 60 / EVOH 20 / PPmix 60 / PP 40 (inner surface) The number of each layer indicates the thickness, and the unit is μm. The same applies hereinafter.

Example 2 A polyvinyl alcohol resin (hereinafter referred to as PVA) was used as a hygroscopic agent in place of calcium chloride, and the oxygen absorber 10 was prepared in the same manner as in Example 1.
%, PVA 20% were added to prepare PP pellets, and the PP pellets were used to prepare the following multilayer sheet in the same manner as in Example 1.・ PP 100 / PPmix-a 60 / EVOH 20 / PPmix-a 60 / PP 40 PPmix-a is PP added with 10% iron-based oxygen scavenger and 20% PVA.

Example 3 An acrylic resin (hereinafter referred to as PAA) was used as a hygroscopic agent in place of calcium chloride, and a deoxidizer of 10% and PAA were used in the same manner as in Example 1.
20% added PP pellets were produced, and using the PP pellets, the following multilayer sheet was produced in the same manner as in Example 1.・ PP 100 / PPmix-b 60 / EVOH 20 / PPmix-b 60 / PP 40 PPmix-b is PP added with 10% iron-based oxygen scavenger and 20% PAA.

(Example 4) As in Example 1, a PP layer containing an iron-based oxygen scavenger and calcium chloride and EVOH as a barrier resin layer were used to protect the inside of the barrier resin layer as follows. A multilayer sheet provided with the layer (II) was prepared.・ PP 100 / EVOH 20 / PPmix 60 / PP 40

(Example 5) In the case of using ascorbic acid instead of the iron-based oxygen scavenger as the oxygen scavenger, Example 1
In the same manner as above, a PP pellet having 10% ascorbic acid added was prepared, and the PP pellet was used to prepare a multilayer sheet in the same manner as in Example 1. The layer structure is as follows.・ PP100 / EVOH 20 / Ascorbic acid added PP 60 / PP 4
0

Examples 6 to 9 PP containing only 10% of iron-based oxygen scavenger as the protective layer (II) (hereinafter referred to as PP-Fe)
Using, the barrier resin was variously changed, and the following multilayer sheet was prepared in the same manner as in Example 1.・ PP100 / barrier resin 20 / PP-Fe60 / PP100 (Example 6) Barrier resin: EVOH 20 μm, OTR: 1.
5cc (Example 7) Barrier resin: meta-xylene-6-nylon
20 μm, OTR: 3.5cc (Example 8) Barrier resin: acrylonitrile copolymer
20 μm: OTR: 15cc (Example 9) Barrier resin: polyvinylidene chloride 20 μ
m, OTR: 7cc OTR shows the oxygen permeation amount of the barrier resin, and the unit is cc / m ² · 24h · atm.

(Examples 10 to 16) As the protective layer (II),
PP with 20% calcium chloride (CaCl ₂ ) added (hereinafter PP-C
a)) and 10% iron-based oxygen scavenger PP (PP-Fe)
The barrier resin layer was EVOH 20 μm, and the resin of the protective layer (I) was variously changed to prepare the following multilayer sheet.・ Protective layer (I) 30 / PP-Ca 30 / EVOH 20 / PP-Fe 30 / PP 3
0 (Example 10) is a protective layer (I): polyethylene (PE) 30 (Example 11) is a protective layer (I): polycarbonate (PC)
30 (Example 12) is a protective layer (I): Amorphofus PET (PE
T) 30 (Example 13) is a protective layer (I): polystyrene (PS) 30 (Example 14) is a protective layer (I): 50:50 blend of PC and PET (PC-PET) 30 (Implementation) Example 15) is protective layer (I): maleic anhydride modified PP
30 (Example 16) is a protective layer (I): PP30

(Comparative Example) As a comparative example, a PP2 layer containing no oxygen absorber or hygroscopic agent, and PP containing no oxygen absorber or hygroscopic agent and EVOH as a barrier resin were used.
A multilayer sheet of layers was made. In addition, as in the fourth embodiment,
The protective layer (II) is provided on one side of the barrier resin layer. As the barrier resin layer, nylon 6 having a larger oxygen permeation amount than the barrier resin layer of the present invention (oxygen permeation amount of 20 μm is 6
A multilayer sheet was also produced using 0 cc / m ² · 24 h · atm). The layer structure is as follows. (Comparative Example 1) -PP 100 / PP 100 (Comparative Example 2) -PP 100 / EVOH 20 / PP 100 (Comparative Example 3) -PP 100 / Nylon 6 20 / PPmix 60 / PP
In addition, multilayer sheets having the same layer structure but different in thickness were prepared as Comparative Examples 4, 5, and 6. (Comparative Example 4) -PP 40 / PP 40 (Comparative Example 5) -PP 30 / EVOH 20 / PP 30 (Comparative Example 6) -PP 30 / Nylon 6 20 / PPmix 40 / PP
30

(Barrier Property Test) The following gas barrier property tests were carried out on the multilayer sheets prepared in Examples and Comparative Examples. (Test 1) Using the multilayer sheets of Examples 1 to 9 and Comparative Examples 1 to 3, as shown in FIG. 5, the protective layer (I) was placed outside by a vacuum forming machine with a diameter of 50 mmφ. , Height 30 mm,
A cup-shaped container having an internal volume of 50 cc was molded. Put a piece of cloth containing 2 cc of water in this cup, and in a gas filling machine,
After replacing the air in the cup with nitrogen, aluminum foil 20μ
The lid was sealed with m / PP of 40 μm, and the cup was filled with nitrogen to prepare a test cup as shown in FIG. The nitrogen-filled cup in a retort kettle,
After heat sterilization at 120 ℃ for 30 minutes, 40 ℃, 90%
It was stored under the condition of RH, and after 2 weeks, the oxygen concentration in the container was measured by a gas chromatograph.

Using the multilayer films of Examples 10 to 16 and Comparative Examples 4 to 6, as shown in FIG.
Size (130mm x 150m) so that (I) is on the outside
m, make a pouch with a seal width of 10 mm, and add water 2c to it.
Put a piece of cloth containing c and replace the air in the pouch with nitrogen with a gas filling machine, then fill the pouch with about 80 cc of nitrogen and seal it, then fill with nitrogen as shown in FIG. 6 (a). A pouch was made. Place the pouch filled with nitrogen in a retort kettle for 12
After heat sterilization at 0 ℃ for 30 minutes, 40 ℃, 90% RH
After storing for 2 weeks, the oxygen concentration in the pouch was measured with a gas chromatograph.

(Test 2) The cup and pouch produced in Test 1 were filled with the following composition, and the inside of the container was evacuated by a vacuum packaging machine to hermetically package. ☆ Composition ・ Agar 20g ・ Methylene blue 0.2g ・ Hydrosulfite (Na ₂ S ₂ O ₄ ) 1.2g ・ Water 1000cc After heating the above composition to dissolve the agar, 5 in the cup
The pouch was filled with 0 cc and 100 cc, and vacuum-sealed with a vacuum packaging machine to prepare a test cup and pouch as shown in FIGS. 5 (b) and 6 (b). After sterilizing the vacuum-packaged cup and pouch by heating at 120 ° C for 30 minutes,
It was stored under the conditions of 40 ° C. and 90% RH, and after 2 weeks, the degree of methylene blue discoloration of the composition in the cup and pouch was observed. The evaluation method was as follows.・ ○: Methylene blue changes to a very slight blue color or no discoloration ・ △: Methylene blue changes to a slight blue color ×: Methylene blue changes to a blue color

The test results are shown in Table 1, and all of the multilayer sheets produced in the examples have excellent gas barrier properties even after heat sterilization, demonstrating the effect of the present invention. That is, by providing a resin layer containing a deoxidizer and a moisture absorbent as a protective layer for the barrier resin layer on one side or both sides of the barrier resin layer, the gas barrier property is lowered due to an increase in the water content such as EVOH. It was proved that it is very effective for the resin that does.

[0048]

[Table 1]

The symbols in the table are as shown below.・ MB: Methylene blue ・ PP: Polypropylene ・ PPmix: PP with 10% iron-based oxygen scavenger and 20% CaCl ₂・ PPmix-a: PP with 10% iron-based oxygen scavenger and 20% PVA ・ PPmix-b: Iron PP with 10% oxygen scavenger and 20% PAA added ・ EVOH: Saponified ethylene-vinyl acetate copolymer ・ CaCl ₂ : Calcium chloride ・ PVA: Polyvinyl alcohol ・ PAA: Water-absorbing acrylic acid resin ・ PP-As: Ascorbic acid PP added with 10% ・ PP-Fe: PP added with 10% iron-based oxygen scavenger ・ Ny-MXD: Metaxylenediamine-6-nylon ・ PAN: Acrylonitrile copolymer ・ PVDC: Polyvinylidene chloride ・ PE: Polyethylene ・PP-Ca: PP with 20% CaCl ₂ added ・ PC: Polycarbonate ・ PET: Polyethylene terephthalate ・ PS: Polystyrene ・ PC-PET: Resin blending PC and PET at 50:50 ・ Modified PP: Maleic anhydride modified PP ・Ny6: Nylon-6

[0050]

According to the present invention, the barrier resin layer is protected by the oxygen scavenger or the protective layer to which the oxygen scavenger and the hygroscopic agent are added. Therefore, even under heat sterilization conditions in which heat and water act simultaneously. In the gas barrier resin layer, the barrier function is less deteriorated, and the oxygen permeation amount can be maintained at a low level almost equal to that at room temperature. for that reason,
In the field of retort food that is sterilized by heating with hot water or steam,
The oxygen concentration in the container can be maintained at a low level.
Further, even when the oxygen is passed under the conditions of high temperature and high humidity, the amount of oxygen permeation hardly changes, and the oxygen concentration in the container can be maintained at a low level. Therefore, when it is used as a packaging material for foods such as retort foods that require long-term storage, the effect is great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a layer structure showing an example of a composite sheet according to the present invention.

FIG. 2 is a cross-sectional view of a layer structure showing another example of the composite sheet according to the present invention.

FIG. 3 is a cross-sectional view when the protective layer of the composite sheet according to the present invention has two layers.

FIG. 4 is a cross-sectional view of another example in which the composite sheet according to the present invention has two protective layers.

FIG. 5 is a cross-sectional view of a molded container made of the composite sheet according to the present invention.

FIG. 6 is a perspective view of a packaging bag made of the composite film according to the present invention.

[Explanation of symbols]

 1 Composite Sheet (Gas Barrier Laminate) 2 Molding Container 3 Lid 4 Packaging Bag 11 Protective Layer (I) 12 Protective Layer (II) 13 Barrier Resin Layer 14 Sealing Layer 15 Deoxidizer 16 Moisture Absorber 17 Thickness Adjusting Layer 21 Water 22 A cloth solution containing methylene blue

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B32B 27/34 9349-4F B65D 65/40 D 81/26 R

Claims (4)

[Claims] 1. The oxygen permeation amount at 20 ° C. and 65% RH is 20 cc / m ² · 24 h · when the thickness is 20 μm.
At least one side of a gas barrier resin having an atm or less has a protective layer made of a resin composition containing an oxygen scavenger or an oxygen scavenger and a hygroscopic agent, and the gas barrier layer and the protective layer do not melt and adhere to each other. Gas barrier packaging material characterized by 2. A deoxidizer is added to the resin for the protective layer in an amount of 1.
~ 200 parts by weight and / or 1 to 200 parts by weight of a hygroscopic agent are added, The gas barrier packaging material according to claim 1. 3. The gas barrier resin, wherein the ethylene content is 20 to 60 mol%, and the saponification degree is 96 mol% or more, saponified ethylene-vinyl acetate copolymer, polyamide resin, vinylidene chloride copolymer. Or a gas barrier packaging material according to claim 1 or 2, which is made of an acrylonitrile resin. 4. The gas according to claim 1, wherein the protective layer comprises an olefin resin, a styrene resin, a polyester resin or a polycarbonate resin and a blend thereof. Barrier packaging material.