JPH10175626A - Paper case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve oil-resistance and waterproofness to the heating of a microwave oven by forming a protective layer on the side face of a storage section in a manner of generating the thermal shrinkage larger than that of a protective layer on the side of not facing the storage section in a paper case composed of a sheet material with protective layers formed on both faces of a paper as a base. SOLUTION: A storage section is formed on the inner side of a peripheral wall 4 by opening the upper edge of the peripheral wall 4 on which a sheet material 2 with a rib is disposed in upright on the peripheral edge of a bottom wall 3 of a paper case 1. Protective layers 6 formed of single layers are formed on both faces of a glassine paper as a base 5 of the sheet material 2, and the protective layers 6 are formed of polyethylene or the like, and a protective layer 6A on the face on the side facing a storage section is formed thicker than a protective layer 6B on the side not facing the storage section S at the time of forming the paper case 1. When the paper case 1 is heated and then cooled, the paper case 1 is shrunk more toward the side facing the storage section than toward the side not facing the storage section by the arrangement, and the paper is protected from absorbing the water content and the oil content of a stored material by protective layers 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper case, and more particularly, to a paper case for food packaging having durability against heating by a microwave oven or the like.

[0002]

2. Description of the Related Art Heretofore, for food packaging, a case has been used in which a peripheral wall having a plurality of ribs is erected from the peripheral edge of a bottom wall, and the upper end of the peripheral wall is opened. ing.

[0003] Sheet materials constituting the case include:
Maintains oil resistance and water resistance by using a sheet of paper such as glassine or parchment as the base material coated with silicon on both sides, a metal foil of aluminum or the like or a sheet of metal thin film deposited on the base material. At the same time, it is trying to maintain the shape of the case itself.

[0004] For example, a sheet in which silicon is coated on both sides of the base material is formed by immersing paper as a base material in a silicon solution to entangle silicon with paper fibers.
It is manufactured by a plurality of steps of performing thermoforming.

[0005]

However, when the contents such as prepared foods stored in the case formed by using the sheet in which the paper fiber is entangled with silicon as described above are heated by the microwave oven, The paper fibers as a base material are loosened by the heating, so that the oil resistance and water resistance are weakened, and the fibers of the paper that have loosened the moisture and oil oozing from the contents of the case are absorbed and the upper end of the peripheral wall of the case Has a disadvantage that the diameter of the case is widened and the ribs formed on the peripheral wall are elongated, and the shape of the case itself cannot be maintained.

Further, when a case using a metal foil such as aluminum is subjected to heating by a microwave oven, oil resistance and water resistance can be maintained, but there is a risk of sparking if certain conditions are not satisfied. However, there is a disadvantage that the cost is high in order to satisfy the above-mentioned certain condition.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and has a process of reducing the number of paper cases that retains oil resistance, water resistance, the shape of the case itself, and has no risk of sparking when heating a microwave oven. It is intended to be manufactured in a number and to be provided at a low cost.

[0008]

In order to achieve the above object, a paper case according to claim 1 of the present invention has a protective layer made of a heat-resistant and water-resistant synthetic resin formed on both sides of a paper as a base material. In a paper case formed from a single sheet material so as to have a bottom wall and a peripheral wall erected on the peripheral edge of the bottom wall, and a storage portion formed inside the peripheral wall, a protective layer on a side facing the storage portion is provided. Is characterized in that it is formed so as to thermally shrink more than the protective layer on the side not facing the housing portion.

According to the first aspect of the present invention, when the paper case is cooled after being heated, the paper case shrinks more to the side facing the storage section than the side not facing the storage section, and the protective layer By protecting the paper as a base material, it is possible to prevent the paper from absorbing moisture and oil content of prepared foods and the like as a container, and since the sheet material does not use metal, it can be used in a microwave oven. There is no danger of sparking when served.

According to a second aspect of the present invention, in the paper case of the first aspect, the protective layer on the side facing the housing and the protective layer on the side not facing the housing have the same coefficient of thermal expansion. Wherein the protective layer on the side facing the housing section is formed thicker than the protective layer on the side not facing the housing section.

According to the second aspect of the present invention, the protective layer of the paper case is made of the same synthetic resin, and the thickness of the protective layer is greater on the side facing the housing than on the outer protective layer. By forming the paper case, upon cooling after heating the paper case, the paper case shrinks more to the side facing the storage section than the side not facing the storage section, and the protective layer forms the paper as the base material. By protecting the paper, it is possible to prevent the paper from absorbing moisture and oil content of prepared foods and the like as contents, and since metal is not used for the sheet material, there is a danger of sparking when used in a microwave oven. Not even.

According to a third aspect of the present invention, in the paper case according to the first aspect, the protective layer on the side facing the housing and the protective layer on the side not facing the housing are formed to have the same thickness. The protective layer on the side facing the housing section is made of a material having a larger coefficient of thermal expansion than the protective layer on the side not facing the housing section.

According to the third aspect of the present invention, the protective layer on the side facing the storage portion of the paper case is made of a material having a larger coefficient of thermal expansion than the outer protective layer and has the same thickness as the outer protective layer. By being formed to a thickness, upon cooling after heating the paper case, the paper case shrinks more in the side direction facing the storage portion than in the side not facing the storage portion, and the protective layer is formed of a base material. By protecting the paper, it is possible to prevent the paper from absorbing moisture and oil content of prepared foods and the like as contents, and since the metal is not used for the sheet material, the paper is used in a microwave oven. There is no danger of spark.

Further, in the paper case according to the fourth aspect, in the paper case according to the first aspect, the protective layer on the side facing the housing and the protective layer on the side not facing the housing are formed of different materials. According to a combination of the thermal expansion coefficient and the thickness of the material of each protective layer, the protective layer on the side facing the housing portion is formed so as to thermally contract more than the protective layer on the side not facing the housing portion. It is characterized by being.

According to the fourth aspect of the present invention, the protective layer on the side facing the storage section of the paper case faces the storage section by a combination of the coefficient of thermal expansion and the thickness of the material forming each protection layer. By forming so that the heat shrinks more than the protection layer on the non-contained side, upon cooling after heating the paper case, the paper case is larger toward the side facing the storage part than the side not facing the storage part. While shrinking, the protective layer protects the paper as a base material, thereby preventing the paper from absorbing moisture or oil content of prepared foods and the like as a container, and using metal for the sheet material. Since there is no spark, there is no danger of sparking when used in a microwave oven.

The paper case according to claim 5 is the paper case according to any one of claims 1 to 4, wherein each of the protective layers is formed as a single layer or a multilayer. Features.

According to the fifth aspect of the present invention, the protection layer on the side facing the storage section of the paper case faces the storage section by a combination of the coefficient of thermal expansion and the thickness of the material forming each protection layer. By forming so that the heat shrinks more than the protection layer on the non-contained side, upon cooling after heating the paper case, the paper case is larger toward the side facing the storage part than the side not facing the storage part. While shrinking, the protective layer protects the paper as a base material, thereby preventing the paper from absorbing moisture or oil content of prepared foods and the like as a container, and using metal for the sheet material. Since there is no spark, there is no danger of sparking when used in a microwave oven.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a first embodiment of a paper case 1 according to the present invention, in which one sheet material 2 blank-cut in a circular shape by a mold has a rib on the peripheral edge of a bottom wall 3. The paper case 1 is press-formed so that the peripheral wall 4 is erected and the upper end of the peripheral wall 4 is opened so as to have the accommodation portion S inside the peripheral wall 4. In practice, blanking and press forming are performed in a state where about 10 to 20 sheets 2 are stacked.

The sheet material 2 corresponds to the sheet material 2 shown in FIG.
As shown in the cross-sectional view, a protective layer 6 composed of a single layer is formed on both sides of glassine as a base material 5. The base material 5
The paper 7 used as the paper is not limited to the glassine, but may be another paper 7 such as a parchment. The paper having a thickness of 20 to 110 g / m ² is most suitable for forming the sheet material 2 of the paper case 1. .

In this embodiment, the sheet material 2 is
As the protective layer 6 on both sides of the paper 7 by co-extrusion coating of a T-die, PE (polyethylene,
Hereinafter, referred to as PE), and the protective layer 6
The protective layer 6A on the side of the sheet material 2 that faces the storage section when the paper case 1 is formed, that is, the side of the paper case 1 that faces the storage section S for prepared foods and the like, is also on the outside, that is, the storage section S. It is formed thicker than the protective layer 6B on the surface that does not face. If each of the protective layers 6 is formed to have a thickness of 10 to 40 μm, in the present embodiment, the function as the protective layer 6 is exhibited well.

Here, the co-extrusion coating of the T-die will be briefly described. In the T-die co-extrusion coating, usually, two or more kinds of resins are simultaneously extruded from separate extruders to form a resin inside or outside the T-die. This is a processing technique in which extruded molten webs are laminated to produce two or more layers of films, sheets and the like in one step without using an adhesive. In the present embodiment, the heat resistance to be added to the paper 7 serving as the base material 5,
By co-extrusion coating a material having performances such as cold resistance, water resistance and oil resistance as the protective layer 6, the various properties of these materials are satisfied according to the required degree.

As described above, the paper 7 as the base material 5 is
One or a plurality of sheet materials 2 formed in a layer are stacked, a peripheral wall 4 having a rib is provided upright on the peripheral edge of the bottom wall 3, the upper end of the peripheral wall 4 is opened, and a housing portion S is formed inside the peripheral wall. Molding to have

The paper case 1 thus formed is
Needless to say, it functions as a shape retention, water resistance and oil resistance as a mere food container.

[0025] Even when the lunch box using the paper case 1 as a side dish case is heated in a microwave oven, only the base material 5 having the property of absorbing moisture and oil oozing out of the heated side dish. Since the paper 7 is protected by being coated on both sides by PE as the protective layer 6, the peripheral wall 4 of the paper case 1 does not absorb the moisture or oil.

The protective layer 6A formed inside the paper case 1 has the same P as the protective layer 6B formed outside.
Due to E, since the protective layer 6B is formed thicker than the outer protective layer 6B, the PE constituting the protective layer 6A thermally expands more than the PE constituting the protective layer 6B when heated by a microwave oven. However, since both of the protective layers 6A and 6B are softened by heating, the PE constituting both of the protective layers 6A and 6B does not function to greatly expand the peripheral wall 3 of the paper case 1, and the paper case is not heated during heating. 1, and when the PE shrinks by cooling after heating by the microwave oven, the inner protective layer 6A formed thicker than the outer protective layer 6B is more preferable. As a result, the shape of the storage portion S of the paper case 1 is stably maintained.

Accordingly, it is possible to prevent the peripheral wall 4 of the paper case 1 from opening outward due to the heating of the microwave oven, thereby preventing the stored prepared food and the moisture and oil content of the prepared food from leaking out of the paper case 1.

Further, since the paper case 1 of the present embodiment does not use metals such as aluminum foil as in the conventional case, there is no possibility of sparking even when it is subjected to heating by a microwave oven.

The protective layer 6 is made of PE because it can withstand high-temperature heating for bonding to the paper 7 as the base material 5 and that the food safety is ensured.
However, the synthetic resin forming the protective layer 6 is not limited to the PE, but may be a polyolefin such as PP (polypropylene, hereinafter, referred to as PP) or PET (polyester, hereinafter, referred to as PET). It is also possible to use a system resin.

In place of the co-extrusion coating,
Even if extrusion coating is used, the substrate 5 can be used without using an adhesive.
PP can be adhered to the surface of the paper 7 as a sheet.

Further, it is of course possible to produce a protective sheet by ordinary dry lamination or wet lamination, and to adhere these protective sheets to the paper 7 as the base material 5 using an adhesive to function as a protective layer. The same effect can be obtained in terms of shrinkage of the paper case 1, oil resistance, and water resistance, but in this case, the number of working steps cannot be denied. In this case, by providing the function of protecting the base material 5 with the adhesive, the protective layer 6 is configured as a multilayer.

FIG. 3 is a sectional view showing the sheet material 2 of the paper case 1 of the second embodiment.

Hereinafter, only the differences between the sheet member 2 constituting the paper case 1 of the present embodiment and the first embodiment will be described.

The sheet material 2 of the present embodiment is formed by applying a protective layer 6 on the inner side of the paper case 1 to the base material 5 made of glassine by co-extrusion coating of a T-die.
A and the protective layer 6B on the outer side are formed of different materials to have the same thickness.

The protective layer 6A on the inner side when the paper case 1 is formed is made of a material having a larger coefficient of thermal expansion than the protective layer 6B on the outer side. In the present embodiment, the inner protective layer 6A is 14 to 15 (× 10
^-5 / ° C.), and the outer protective layer 6B is formed of PP having a thermal expansion coefficient of 11 (× 10 ⁻⁵ / ° C.).

Also, according to the paper case 1 of the present embodiment, the paper 7 as the base material 5 is protected by being coated on both sides with PE and PP as the protective layer 6. It does not absorb the moisture and oil content of prepared foods stored in the kitchen.

The protective layer 6A formed inside the paper case 1 is made of a synthetic resin having a larger coefficient of thermal expansion than the protective layer 6B formed outside, so that the microwave oven or the like is used. When cooling after heating by
The sheet material 2 constituting the paper case 1 contracts inward where the protective layer 6A formed of a material having a large thermal expansion coefficient is provided. Therefore, it is possible to prevent the peripheral wall 4 of the paper case 1 from opening outward due to the heating of the microwave oven, thereby preventing the stored prepared foods and the moisture and oil content of the prepared foods from leaking out of the paper case 1.

Further, since the paper case 1 of the present embodiment does not use metals such as aluminum foil, there is no risk of sparking even when it is subjected to heating by a microwave oven. The protective layer may be formed by forming a protective sheet by ordinary dry lamination or wet lamination and bonding the protective sheet to paper 7 as a base material 5 using an adhesive. It is the same as the above-described first embodiment, such as good points.

FIG. 4 is a sectional view showing the sheet material 2 of the paper case 1 of the third embodiment.

Hereinafter, only the differences between the sheet material 2 constituting the paper case 1 of the present embodiment and the first and second embodiments will be described.

The sheet material 2 of the present embodiment is formed on the base material 5 made of glassine by co-extrusion coating of a T-die, and the protective layer 6A on the inner side when the paper case 1 is formed.
And the protective layer 6B on the outer surface are formed in different thicknesses with different materials, and the protective layer 6A on the inner surface at the time of molding the paper case 1 takes into account its thermal expansion coefficient and thickness. In this state, it is formed so as to thermally shrink more than the protective layer 6B on the outer surface.

In this embodiment, the inner protective layer 6A is formed of a medium density PE having a coefficient of thermal expansion of 14 to 15 (× 10 ^-5 / ° C.), and the outer protective layer 6B is formed of 11 ( (× 10 ⁻⁵ / ° C.).

Even if the inner protective layer 6A and the outer protective layer 6B have the same thickness, the inner protective layer 6A has a large thermal shrinkage, so that the paper case 1 is cooled when heated.
Of the peripheral wall 4 is largely inwardly contracted. Therefore,
In the paper case 1 of the present embodiment, the inner protective layer 6A is formed to be as thin as possible as a result of thermal contraction inside the paper case 1 during cooling after heating due to the relationship between the coefficient of thermal expansion and the thickness. It was done. This makes it possible to supply a low-cost product.

In the paper case 1 of the present embodiment, since the paper 7 as the base material 5 is protected by being coated on both sides with PE and PP as the protective layer 6, It does not absorb the moisture and oil content of stored side dishes.

The protective layer 6A formed on the inside of the paper case 1 is larger than the protective layer 6B formed on the outside.
As a result, the sheet material 2 forming the paper case 1 becomes large by cooling after heating by the microwave oven or the like because the material 2 is formed so as to be largely thermally contracted due to the relationship between the thermal expansion coefficient and the thickness of the material. It will shrink inward, formed so as to shrink thermally. Therefore, it is possible to prevent the peripheral wall 4 of the paper case 1 from opening outward due to the heating of the microwave oven, thereby preventing the stored prepared foods and the moisture and oil content of the prepared foods from leaking out of the paper case 1.

Further, since the paper case 1 of the present embodiment does not use metals such as aluminum foil, there is no risk of sparking even when it is subjected to heating by a microwave oven. The above-described two methods may be used, such as using a coating, manufacturing a protective sheet by ordinary dry lamination or wet lamination, and bonding the protective sheet to paper 7 as a base material 5 using an adhesive. This is the same as the embodiment.

The present invention is not limited to the above embodiment, but can be variously modified as needed.

For example, in each of the three embodiments described above, the case where the protective layer 6 is formed as a single layer has been described, but the protective layer 6 is formed on any surface of the substrate 5. Even if it is, it can be formed in multiple layers. In that case, the synthetic resin to be laminated is laminated so that the protective layer 6 formed on the inner surface of the paper case 1 of the base material 5 expands more thermally than the protective layer 6 formed on the outer surface. It goes without saying that the thickness is selected and the thickness is adjusted.

[0049]

As described above, according to the paper case according to the present invention, a wide opening can be ensured, so that it is easy to store the contents, and the paper material constituting the paper case can be used. Does not use metals such as aluminum foil, so there is no danger of sparking even when subjected to heating by a microwave oven, and the sheet material constituting the paper case is made of paper as a base material. Is protected by being coated on both sides by a protective layer, so that it does not absorb moisture and oil content of prepared foods and the like stored in the storage portion, and further, the sheet material is not cooled after heating. Because the paper case is configured to shrink inward, the heating of the microwave oven opens the peripheral wall of the paper case to the outside, and the prepared foods and the moisture and oil content of the prepared foods may leak out of the paper case. In addition, if the paper case is manufactured using coextrusion coating or extrusion coating, the protective layer of the paper case can be bonded to the substrate without using an adhesive. In addition, the number of manufacturing steps can be reduced, and the paper case can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a paper case according to the present invention.

FIG. 2 is an enlarged view of a cut surface of a sheet material of the paper case 1 of FIG.

FIG. 3 is a perspective view showing a cut surface of a sheet material of a paper case according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a cut surface of a sheet material of a third embodiment of the paper case according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper case 2 Sheet material 3 Bottom wall 4 Peripheral wall 5 Base material 6 Protective layer 6A Protective layer 6A (on the side facing the containing section) 6B Protective layer (on the side not facing the containing section) 7 Paper S containing section

Claims (5)

[Claims] 1. A bottom wall made of one sheet material having a protective layer made of a heat-resistant and water-resistant synthetic resin formed on both sides of a paper as a base material and a peripheral wall standing upright on the peripheral edge of the bottom wall. In the paper case formed in such a manner that the housing portion is formed inside the peripheral wall, the protective layer on the side facing the housing portion is formed so as to be more thermally shrunk than the protective layer on the side not facing the housing portion. A paper case characterized by the fact that: 2. The protective layer on the side facing the housing section and the protective layer on the side not facing the housing section are made of a material having the same coefficient of thermal expansion, and the protective layer on the side facing the housing section. The paper case according to claim 1, wherein the paper case is formed to be thicker than a protective layer on a side not facing the storage portion. 3. The protection layer on the side facing the storage section and the protection layer on the side not facing the storage section are formed to have the same thickness, and the protection layer on the side facing the storage section is provided on the storage section. The paper case according to claim 1, wherein the paper case is formed of a material having a larger coefficient of thermal expansion than the protective layer on the non-opposite side. 4. The protection layer on the side facing the storage section and the protection layer on the side not facing the storage section are formed of different materials, and are formed by combining the thermal expansion coefficient and the thickness of the material of each protection layer. 2. The paper case according to claim 1, wherein the protective layer on the side facing the storage portion is formed so as to thermally contract more than the protective layer on the side not facing the storage portion. 3. 5. The paper case according to claim 1, wherein each of the protective layers is formed in a single layer or a plurality of layers.