JP5500862B2 - Laminated material for food containers and method for producing the same - Google Patents

Description

  The present invention relates to a laminated material for food containers, which has a gas barrier property that blocks oxygen gas, odorous substances, and the like, is excellent in heat resistance, and is further excellent in heat insulation, and a method for producing the same.

  In recent years, in one-way food containers, a laminated material mainly composed of paper and polyolefin resin has been widely used. For example, a paper container for milk or juice usually has a configuration of low-density polyethylene / paper / low-density polyethylene (hereinafter, low-density polyethylene is abbreviated as LDPE), and particularly has a gas barrier property for long life. Are added to the structure described above (for example, refer to Patent Document 1), such as an aluminum foil, a polyester resin layer, and an ethylene-vinyl alcohol copolymer resin layer. Moreover, the same structure is employ | adopted also with the packaging container of frozen food with much moisture. Furthermore, recently, a multi-layer packaging material using paper is also used for mineral water, sake, whiskey, tea, and the like, and the configuration has been diversified. The target characteristics of these packaging substrates vary depending on the type of contents and expiration date, etc., but they all prevent oxidative degradation of the contents by blocking oxygen gas, and prevent odor substances and off-flavor substances from transferring to the contents. It can be said that this is a necessary characteristic.

  On the other hand, for applications that require heat insulation, such as instant food cups, containers made of expanded polystyrene resin have been widely used. However, in recent years, a paper substrate is coated with a thermoplastic resin and heated. A method of evaporating moisture contained in a paper base material to foam a thermoplastic resin (see Patent Document 2), a container in which the adhesive strength between the paper base material and the thermoplastic resin is limited (see Patent Document 3), heat Foamed paper in which the foamed layer of the plastic resin is an ethylene-α-olefin copolymer using a single-site catalyst (see Patent Document 4), and a paper container with a limited melt mass flow rate (MFR) of the thermoplastic resin A body member raw material sheet (see Patent Document 5) is also provided.

  However, a paper material and a container having both gas barrier properties, heat resistance, and heat insulation properties have not yet been provided. That is, if heat insulation is to be imparted to a paper container having gas barrier properties as described in Patent Document 1 by the method described in Patent Documents 2 to 5, an aluminum foil or polyester is used during heat treatment. Gas barrier layers such as a resin-based resin layer and an ethylene-vinyl alcohol copolymer resin layer peel off, and even if an adhesive layer is provided between these gas barrier layers and other layers, they are deformed by heat, The problem that wrinkles and unevenness occur occurs.

JP-A-7-76336 JP-A-57-110439 Japanese Patent No. 3596681 Japanese Patent Laid-Open No. 10-128928 JP 2008-247458 A

  In view of such circumstances, the present invention solves the above-mentioned problems of the prior art, has excellent gas barrier properties and heat resistance, and also has heat insulation properties and strong adhesion between the gas barrier layer and other layers. Then, it aims at providing the laminated material for food containers which can produce the paper container which does not produce a wrinkle and an unevenness | corrugation by the heating process at the time of use or the heat processing at the time of manufacture, and its manufacturing method.

The present invention has been made to achieve the above object, and claim 1 of the present invention includes a first polyolefin-based resin layer A, a second gas-barrier resin layer B, and a third layer. It consists of a paper base layer C and a fourth polyolefin resin layer D,
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. The content is a laminated material for food containers, characterized by comprising a laminate in which adhesive polyolefin resin layers h1 and h2 made of high-density or medium-density polyethylene resin are interposed.

Claim 2 of the present invention is the first polyolefin resin layer A, the second gas barrier resin layer B, the third paper base layer C, and the fourth polyolefin resin layer. D and
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. Adhesive polyolefin resin layers h1 and h2 made of high density or medium density polyethylene resin are interposed, and a fourth polyolefin resin layer D is formed by heat evaporation of water in the third paper substrate C. The content is a laminated material for food containers, which is made of a laminate that is the foam layer E.

  A third aspect of the present invention includes the laminated material for food containers according to the first or second aspect, wherein the second gas barrier resin layer B is made of a polyester resin.

According to a fourth aspect of the present invention, the polyolefin resin layer A as the first layer, the gas barrier resin layer B as the second layer, the paper base material layer C as the third layer, and the polyolefin resin layer as the fourth layer D and
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. , high-density or consists of medium density polyethylene resin adhesive polyolefin-based resin layer h1, h2 is a laminate that is interposed, according to claim 1 or 3 Symbol characterized by curing 48 to 96 hours at 40 to 60 ° C. The manufacturing method of the laminated material for food containers described above is included.

Claim 5 of the present invention is the first polyolefin resin layer A, the second gas barrier resin layer B, the third paper substrate layer C, and the fourth polyolefin resin layer. D and
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. The laminated body in which the adhesive polyolefin resin layers h1 and h2 made of high-density or medium-density polyethylene resin are interposed is cured at 40 to 60 ° C. for 48 to 96 hours,
Then, according to claim 2 or 3 SL, characterized in that the polyolefin resin layer D of heat treatment to the fourth layer is foamed by vaporization of the water of the third layer of the paper substrate in C to form a foamed layer E The manufacturing method of the laminated material for food containers described above is included.

Claim 6 of the present invention is the food according to claim 4 or 5 , wherein the surface of the second gas barrier resin layer B that contacts the adhesive polyolefin resin layers h1 and h2 is subjected to corona discharge treatment. The production method of the laminated material for containers is the content.

A seventh aspect of the present invention is the method according to any one of the fourth to sixth aspects, wherein a surface of the third paper base layer C that is in contact with the fourth polyolefin resin layer D is subjected to corona discharge treatment. The manufacturing method of the laminated material for food containers is included.

Claim 8 of the present invention, according to claim 4 to 7, characterized in that sand laminating a gas barrier resin layer B of the second layer a paper substrate layer C of the third layer with an adhesive polyolefin resin layer h2 The manufacturing method of the laminated material for food containers described in any of the above.

A ninth aspect of the present invention is characterized in that the first polyolefin resin layer A and the adhesive polyolefin resin layer h1 are laminated by coextrusion and lamination on the second gas barrier resin layer B. The manufacturing method of the laminated material for food containers in any one of Claim 4 thru | or 8 .

Claim 10 of the present invention, according to one of claims 4 to 9, characterized in that the stacking by the polyolefin resin layer D of the fourth layer extrusion laminated to a paper base layer C of the third layer The manufacturing method of the laminated material for food containers is included.

Food container laminate material of the present invention, a gas barrier resin layer and the paper substrate layer, by using an adhesive polyolefin-based resins composed of high density or medium density polyethylene resin as an adhesive layer, gas It has both barrier properties and heat resistance, as well as heat insulation, and the adhesion between the gas barrier resin layer and other layers is strong, and it can be heated with a microwave oven or hot water during use or heat treatment to form a foam layer. A paper container free from wrinkles and unevenness can be produced.

Moreover, according to the manufacturing method of the laminated material for food containers of this invention, the adhesive polyolefin-type resin layer of a gas barrier resin layer and another layer is obtained by curing a laminated body at 40-60 degreeC for 48 to 96 hours. As a result, the gas barrier resin layer and other layers will not be peeled off by heating during use and heat treatment during production, and generation of wrinkles and irregularities will occur. Is suppressed.
Further, it is preferable that the surface of the gas barrier resin layer that contacts the adhesive polyolefin resin layer is subjected to corona discharge treatment.

  Further, if the surface of the second paper base layer contacting the polyolefin resin layer is subjected to corona discharge treatment, the fourth polyolefin resin layer is heated by heat treatment and the evaporation of moisture in the third paper base material. When foaming, the paper base layer and the polyolefin resin layer are not peeled off and a uniform foamed state is obtained.

  As a specific lamination method, the second gas barrier resin layer and the third paper base material layer are sand-laminated with an adhesive polyolefin resin layer, and then bonded to the first polyolefin resin layer. A method of coextruding and laminating the conductive polyolefin resin layer to the second gas barrier resin layer and further extruding and laminating the fourth polyolefin resin layer to the third paper base material layer is preferable. .

FIG. 1 is a schematic cross-sectional view showing an example of a laminated material for food containers according to the present invention. FIG. 2 is a schematic cross-sectional view showing another example of the laminated material for food containers of the present invention.

As shown in FIG. 1, the laminated material M1 for food containers in the present invention comprises a first polyolefin resin layer A, a second gas barrier resin layer B, and a third paper base layer C. And a polyolefin resin layer D as a fourth layer, and between the first layer A and the second layer B and between the second layer B and the third layer C, a high density or medium density polyethylene resin. It consists of the laminated body in which the adhesive polyolefin-type resin layers h1 and h2 which consist of consist of.
In addition, as shown in FIG. 2, the laminated material M2 for food containers according to the present invention is a water content in the paper base material C of the third layer in the fourth layer of the polyolefin resin layer D in the laminated material M1 for food containers. It is characterized by comprising a foamed layer E formed by heating and evaporation.
In the laminated materials M1 and M2 for food containers of the present invention, the first polyolefin resin layer A constitutes the inside of the food container, and the fourth polyolefin resin layer D constitutes the outside of the food container.

In the food container laminate materials M1 and M2, the polyolefin resin used for the first polyolefin resin layer A is polyethylene, a copolymer of ethylene and propylene, ethylene and other α-olefins. And copolymers of polypropylene, propylene and other α-olefins, and mixtures thereof. Other α-olefins include butene-1, hexene-1 and the like, and these are preferably 30% by weight or less.
In particular, polyethylene which is easy to be extrusion laminated is suitable. The thickness of the first polyolefin-based resin layer A is preferably about 10 to 20 μm.

  Examples of the resin used for the gas barrier resin layer B of the second layer in the present invention include polyester resin, polyamide resin, ethylene-vinyl alcohol copolymer resin, polyvinylidene chloride resin and the like. From the viewpoint of adhesiveness, a polyester resin is preferable, and polyethylene terephthalate is particularly preferable. The thickness of the second gas barrier resin layer B is preferably about 15 to 30 μm.

The paper substrate C of the third layer in the present invention, preferably 100 to 400 g / m ² approximately, more preferably 200-30Og / m ² about paperboard, particularly for food, does not contain fluorescent dyes The paper is preferably composed of virgin pulp, and for example, cup base paper is suitable.
When the moisture in the third layer paper substrate C is evaporated and the fourth polyolefin resin layer is used as a foam layer, the water content in the paper substrate is usually 2 to 15% by weight, preferably 4 to 10% by weight.

As the polyolefin resin used for the fourth polyolefin resin layer D in the present invention, as in the first polyolefin resin layer A, polyethylene and its copolymer, polypropylene and its copolymer, and these And the like. In particular, low density polyethylene that is easy to extrusion laminate is suitable.
When the foamed layer (heat insulating layer) is formed by foaming using the moisture contained in the paper substrate C by heat-treating the laminated sheet after laminating the fourth polyolefin-based resin layer D Preferably has a high melt flow rate (MFR), specifically about 13.0 to 23.0 g / 10 min.
The thickness of the fourth polyolefin resin layer D is preferably about 50 to 90 μm.

In the present invention, the adhesion between the polyolefin resin layer A of the first layer and the gas barrier resin composition B of the second layer, and between the paper substrate C of the second layer B and the third layer. Conductive polyolefin resin layers h1 and h2 are interposed. Resins with high gas barrier properties generally have low adhesion to other resins, so resins with good adhesion to these high gas barrier properties are used as adhesives and are heated in the range during use. In many cases, an adhesive having excellent heat resistance is used. As such an adhesive polyolefin resin, specifically, a high-density or medium-density polyethylene resin with little odor is used. Examples of commercially available products include “Petrocene (registered trademark) DLZ15E (melting point 133 ° C., density 944 kg / m ³ )” manufactured by Tosoh Corporation. Further, the heat resistance required can be ensured by mixing a high-density polyethylene resin having high heat resistance with an adhesive polyolefin resin having low heat resistance. For example, “G1801 (melting point 134 ° C., density 962 kg / m ³ )” manufactured by Keiyo Polyethylene Co., Ltd. is mixed with “Novatec (registered trademark) LC605Y (melting point 107 ° C., density 918 kg / m ³ )” manufactured by Nippon Polyethylene Corporation. Etc.

  Further, the surface of the second gas barrier resin layer B in contact with the adhesive polyolefin resin layers h1 and h2 is subjected to corona discharge treatment, whereby the gas barrier resin layer B and the adhesive polyolefin resin layers h1 and h2 are treated. It is preferable to increase the adhesiveness.

The lamination method is not particularly limited, and any lamination method may be used as long as the resin and the paper base material are laminated in the order shown in FIG. As a preferred laminating method, first, the second layer B and the adhesive layer h2 are obtained by sand laminating the sheet or film-like gas barrier resin layer B and the paper base material C with the resin for the adhesive polyolefin resin layer h2. Then, a laminate composed of the third layer C is formed.
Next, for the first polyolefin resin layer A and the adhesive polyolefin resin layer h1, the first polyolefin resin layer B is added to the second gas barrier resin layer B formed as described above. A is formed by coextruding and laminating the resin for the adhesive polyolefin-based resin layer h1.
Further, in order to form the fourth polyolefin resin layer D, the fourth polyolefin resin layer D is extruded and laminated on the third paper base layer C formed as described above. Form.

  In this invention, it is preferable to age | cure the laminated body laminated | stacked as mentioned above at 40-60 degreeC for 48 to 96 hours. Here, the term “curing” refers to adhesion between each layer, in particular, the first polyolefin-based resin layer A and the second gas-barrier resin layer B via the adhesive polyolefin-based resin layer h1, and the adhesive polyolefin. For strengthening the adhesion between the gas barrier resin composition B of the second layer and the paper substrate C of the third layer through the resin layer h2, and the paper substrate layer of the third layer In order to transfer the moisture contained in C to the polyolefin-based resin layer D of the fourth layer, it means keeping for a certain time at a predetermined temperature.

  The laminate obtained as described above is prevented from being peeled or wrinkled or uneven when heated by a microwave oven or hot water. It is suitable as a laminated material for food containers of retort pouches such as pasta sauce, stewed dishes and soups.

  In order to obtain the food container laminate material M2 in which the heat insulation layer is provided on the food container laminate material M1, as shown in FIG. 2, the above laminate material (food container laminate material M1) is 50 to 400 at 110 to 150 ° C. By heating for 2 seconds, the moisture transferred from the third paper base layer C to the fourth polyolefin resin layer D is evaporated, and the fourth polyolefin resin layer D is foamed by the vapor pressure. A foam layer, that is, a heat insulating layer is formed. The food container laminated material M2 having the heat insulating layer thus obtained is useful as a heat insulating container for cups such as coffee and soup and instant ramen.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited only to these Examples.

Example 1
(Formation of second layer B, adhesive layer h2, and third layer C)
Cup base paper (basis weight 250 g / m ² , manufactured by Nippon Paper Industries Co., Ltd.) as the paper base layer C, and biaxially stretched polyethylene terephthalate film (product name: S25, thickness 25 μm, Unitika Co., Ltd.) as the gas barrier resin layer B Manufactured, hereinafter abbreviated as PET film) as a high-density polyethylene resin (trade name: Petrocene (registered trademark) DLZ15E, MFR: 9.0 g / 10 min, density: 944 kg / m ³ ) as an adhesive polyolefin-based resin layer h2. Melting point: 133 ° C., manufactured by Tosoh Corporation) was used.
A corona discharge treatment is applied to both sides of the PET film in advance, and then an adhesive polyolefin resin is extruded at a resin temperature of 330 ° C. at a thickness of 20 μm, and the cup base paper and the PET film are sand-laminated to form a second layer comprising a PET film layer A first laminate L1 comprising a gas barrier resin layer B, an adhesive polyolefin resin layer h2, and a third paper base layer C made of cup base paper was obtained.

(Formation of first layer A and adhesive layer h1)
Medium density polyethylene resin (Product name: Petrocene (registered trademark) LW04-1, MFR: 6.5 g / 10 min, density: 940 kg / m ³ , melting point: 133 ° C., Tosoh Corporation) as polyolefin resin layer A of the first layer The above-described high-density polyethylene resin (Petrocene (registered trademark) DLZ15E) was used as the adhesive polyolefin resin layer h1.
The two types of polyethylene resins are coextruded at a resin temperature of 330 ° C., and laminated such that the adhesive polyolefin resin layer h1 side is in contact with the second gas barrier resin layer B of the first laminate L1. A second laminate L2 made of a first polyolefin resin layer A made of polyethylene resin and an adhesive polyolefin resin layer h1 made of high-density polyethylene resin was obtained on the first laminate L1. The thickness of the coextruded polyethylene resin was 25 μm for the first layer A and the adhesive layer h1, and the ratio of the thicknesses of the first layer A and the adhesive layer h1 was about 1: 1.

(Formation of fourth layer D)
A low density polyethylene resin (product name: Novatec LC701, MFR: 14.0 g / 10 min, density: 918 kg / m ³ , melting point: 106 ° C., manufactured by Nippon Polyethylene Co., Ltd.) was used as the polyolefin resin.
After the corona discharge treatment is performed on the paper base layer D side of the third layer of the second laminate L2, the low density polyethylene resin is extruded at a resin temperature of 320 ° C. on the paper base layer C of the third layer. Lamination was performed to obtain a third laminate L3 in which a fourth polyolefin resin layer D was further laminated on the second laminate L2. The thickness of the fourth layer D was 70 μm.

(Healing)
The third laminate L3 was placed in an oven at a temperature of 40 ° C. and cured for 3 days to obtain a food container laminate material M1.

(Formation of foam layer of fourth layer D)
The food container laminate material M1 was placed in an oven at a temperature of 120 ° C. and heat-treated for 5 minutes. A food container laminate material M2 was obtained in which a foam layer having a uniform cell diameter and a uniform thickness was formed over the entire surface of the polyolefin resin D of the fourth layer.

(Hot water immersion test)
The food container laminate materials M1 and M2 obtained as described above are immersed in hot water at 95 ° C., left to cool in a room at 20 ° C. and taken out one day later, and then the adhesion site h1 (polyolefin type of the first layer) Observation of adhesive strength between resin layer A and second gas barrier resin layer B) and h2 (between second gas barrier resin layer B and third paper substrate layer C) As a result, they floated (wrinkles and irregularities) at these adhesion sites h1 and h2, and no peeling was confirmed.

(Food material immersion test)
Commercially available Kalerou was dissolved in hot water to obtain a Kaleou with a liquid temperature of 92 ° C. When the laminated materials M1 and M2 for food containers of the present invention are dipped in this curry roux, left to cool in a room at 20 ° C. and taken out one day later, the adhesion strength of the adhesion sites h1 and h2 is observed. It floated on h1 and h2 (wrinkles, unevenness), and no peeling was confirmed.

(Heat resistance test)
Using the food container laminating materials M1 and M2, a cylindrical body is prepared so that the first polyolefin resin layer A is on the inner side and the fourth polyolefin resin layer D is on the outer side. The sample was heated for 6 minutes, and the appearance change (wrinkle and unevenness occurrence state) was observed. No wrinkles or irregularities were observed.

Example 2
The polyethylene resin of the adhesive polyolefin resin layers h1 and h2 is a low-density polyethylene resin “Novatec (registered trademark) LC605Y (density: 918 kg / m ³ , melting point: 107 ° C.)” manufactured by Nippon Polyethylene Co., Ltd. and Keiyo Polyethylene Co., Ltd. Example 1 except that the mixture was changed to a mixture of high density polyethylene resin “G1801 (density: 962 kg / m ³ , melting point: 134 ° C.)” (mixing weight ratio = 60/40, density: 935 kg / m ³ ). By this method, food container laminated materials M1 and M2 were obtained, and a hot water immersion test, a food material immersion test, and a heat resistance test were performed. The results are shown in Table 1.

Comparative Example 1
Other than changing the polyethylene resin of the adhesive polyolefin-based resin layers h1 and h2 to a low density polyethylene resin “Novatec (registered trademark) LC605Y (density: 918 kg / m ³ , melting point: 107 ° C.)” manufactured by Nippon Polyethylene Co., Ltd. Laminated materials M1 and M2 for food containers were obtained in the same manner as in Example 1, and a hot water immersion test, a food immersion test, and a heat resistance test were performed. The results are shown in Table 1.

  As described above, the laminated material for food containers according to the present invention has both gas barrier properties and heat resistance, and further heat insulation properties, and when heated with a microwave oven or hot water during use, or heating for forming a foamed layer. Even during processing, peeling between layers, generation of wrinkles and unevenness can be suppressed, and a food container having a high commercial value can be provided.

M1, M2 Laminated materials for food containers A First polyolefin resin layer B Second gas barrier resin layer C Third paper substrate layer D Fourth polyolefin resin layer E Foam layer h1, h2 Adhesive polyolefin resin layer c Corona discharge treatment

Claims (10)

It comprises a first polyolefin resin layer A, a second gas barrier resin layer B, a third paper substrate layer C, and a fourth polyolefin resin layer D.
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. A laminate for food containers, comprising a laminate in which adhesive polyolefin resin layers h1 and h2 made of high-density or medium-density polyethylene resin are interposed. It comprises a first polyolefin resin layer A, a second gas barrier resin layer B, a third paper substrate layer C, and a fourth polyolefin resin layer D.
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. Adhesive polyolefin resin layers h1 and h2 made of high density or medium density polyethylene resin are interposed, and a fourth polyolefin resin layer D is formed by heat evaporation of water in the third paper substrate C. A laminated material for food containers, comprising a laminated body that is a foam layer E.   The laminated material for food containers according to claim 1 or 2, wherein the second gas barrier resin layer B is made of a polyester resin. It comprises a first polyolefin resin layer A, a second gas barrier resin layer B, a third paper substrate layer C, and a fourth polyolefin resin layer D.
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. , high-density or consists of medium density polyethylene resin adhesive polyolefin-based resin layer h1, h2 is a laminate that is interposed, according to claim 1 or 3 Symbol characterized by curing 48 to 96 hours at 40 to 60 ° C. A method for producing a laminated material for food containers as described above. It comprises a first polyolefin resin layer A, a second gas barrier resin layer B, a third paper substrate layer C, and a fourth polyolefin resin layer D.
Between the first polyolefin resin layer A and the second gas barrier resin layer B, and between the second gas barrier resin layer B and the third paper substrate layer C. The laminated body in which the adhesive polyolefin resin layers h1 and h2 made of high-density or medium-density polyethylene resin are interposed is cured at 40 to 60 ° C. for 48 to 96 hours,
Then, according to claim 2 or 3 SL, characterized in that the polyolefin resin layer D of heat treatment to the fourth layer is foamed by vaporization of the water of the third layer of the paper substrate in C to form a foamed layer E A method for producing a laminated material for food containers as described above. 6. The method for producing a laminated material for food containers according to claim 4 or 5 , wherein the surface of the second gas barrier resin layer B in contact with the adhesive polyolefin resin layers h1, h2 is subjected to corona discharge treatment. Manufacture of food containers laminated material according to any one of claims 4 to 5, characterized in that the surface in contact with the polyolefin resin layer D of the fourth layer of the third layer of the paper substrate layer C to corona discharge treatment Method. The food container according to any one of claims 4 to 7 , wherein the second gas barrier resin layer B and the third paper base layer C are sand-laminated with an adhesive polyolefin resin layer h2. For producing laminated materials for use. Any of claims 4 to 8, characterized in that laminating by co-extrusion laminating a polyolefin-based resin layer A of the first layer and the adhesive polyolefin-based resin layer h1 gas barrier resin layer B of the second layer The manufacturing method of the laminated material for food containers of crab. Manufacture of food containers laminated material according to any one of claims 4 to 9, characterized in that the laminate by extrusion laminating a polyolefin resin layer D of the fourth layer to the paper substrate layer C of the third layer Method.

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