JPH08420B2 - Thermoforming method and molding container - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molded container, and more particularly to a method for thermoforming a biaxially oriented polypropylene film and a molded container.

[0002]

2. Description of the Related Art Conventionally, as a simple side dish container,
Containers molded of aluminum foil were often used.
However, with the increasing use of microwave ovens in recent years, it is not possible to use aluminum foil, which is a metallic material, as a side dish container for cooked foods and bento boxes, which is premised on its use. In addition, even a container that does not use a microwave oven may be inspected by a metal detector in a food manufacturing process in order to prevent foreign matter from being mixed into food in a lunchbox manufacturer. Even in such a case, the aluminum foil cannot be used for the molding container.

From such a background, recently, a film case in which a plastic film is heat-molded instead of the aluminum foil is becoming the mainstream as the container.

[0004]

The conventional film case as described above is formed by laminating plastic films in the same manner as a container using aluminum foil, punching it out into various desired shapes, and then punching and laminating. The one in the state is heated and molded in a mold. Heating in this case (12
(0 to 180 ° C.), the films formed in a laminated state come into close contact with each other, and if the film case does not easily come off, the productivity will be reduced.

The present invention has been made to solve the above problems, and an object thereof is to provide a highly productive thermoforming method capable of easily peeling a laminated and thermoformed film case. It is also an object of the present invention to provide a molded container that is easy to handle when stacked.

[0006]

According to a first aspect of the present invention, there is provided a thermoforming method, which comprises a step of laminating a plurality of biaxially oriented polypropylene films each having both surfaces corona-treated, and a laminated biaxially oriented film. And a step of heat-molding the polypropylene film as one body.

A molding container according to a third aspect of the present invention is a molding container made of biaxially stretched polypropylene formed into a predetermined shape by heat molding, wherein both surfaces of the biaxially stretched polypropylene have a wettability of 37 dyne / cm. The above is a feature.

[0008]

In the invention of claim 1, since both surfaces of each are corona treated, the wettability of the surface of the heat-molded biaxially oriented polypropylene film is improved.

In the third aspect of the invention, the wettability of both surfaces of the molded container is high.

[0010]

EXAMPLE FIG. 1 is a diagram showing a state in which a plurality of biaxially oriented polypropylene films (hereinafter referred to as OPP films) according to an example of the present invention are laminated.

Referring to the figure, both sides of each of a plurality of laminated OPP films 1 (which are shown in a simplified manner in the figure but usually about 25 to 30 sheets) are corona treated. Therefore, the respective corona treated surfaces of the OPP films face each other.

Generally, the corona-treated surface of the OPP film is active against organic substances, so that the adhesive strength of the adhesive or the like is improved. However, when the corona treated surfaces come into contact with each other, the adhesive effect is rather reduced and the releasability is improved.

FIG. 4 is a table showing the results of experiments for showing this releasability. With reference to the drawing, the characteristics of releasability are shown when three heat-sealing conditions are set and the wetting property of the treated surface of the OPP film is changed for each condition.
In the figure, “treated surfaces” indicates the case where corona treatment is applied, and the wetting property thereof is 46 dyne / cm. Further, "untreated surfaces" in the figure indicate the case where no corona treatment is applied, and the wettability thereof is 35 dyne / cm. From this experimental result, it is found that the heat-sealing property between the surfaces having high wetting property is worse than the surface having low wetting property, that is, it is preferable from the viewpoint of releasability.

Further, as is clear from the figure, when the heat-sealing temperature is raised, the releasability is lowered, but the degree of the reduction is gentler between the treated surfaces. Since the molding time can be shortened by raising the heating temperature, the above result means that the productivity of the heat-molding treatment is improved, while the allowable range of the heating temperature is expanded.

FIG. 2 is a perspective view of a film case formed by heat-molding the laminated OPP films of FIG. 1 into a predetermined shape, and FIG. 3 is a III-I of FIG.
It is sectional drawing of a II line.

Referring to both figures, a plurality of film cases 3 are molded at a time in a laminated state. Therefore, the OPP film 5 forming each film case 3 is in a close contact state. However, since both sides of the OPP film 5 are corona-treated, it is easy to peel off and use each film case 3 one by one, as is clear from the result of FIG.

The following may be considered as the OPP film whose both surfaces are corona treated.

Both sides of a milky white OPP film with a thickness of 50 μm subjected to corona treatment 40 μm thickness of a transparent OPP film subjected to corona treatment with both sides of the OPP film with a thickness of 15 to 20 μm corona treatment Those which have been subjected to the printing treatment and dry lamination in the middle thereof and adhered to each other. In addition, according to the above-mentioned examples, since both surfaces of the molded film case have high wettability, they are stacked as a product. Even in the case of the above, the mutual adhesion will not be excessively high, and the mounting and handling will be easy.

Further, although the OPP film is the object in the above embodiment, the present invention can be similarly applied to other plastic films having similar surface characteristics.

Further, in the above-mentioned embodiment, the corona treatment is applied to improve the wetting property, but other treatment may be applied as long as the wetting property is improved.

[0021]

According to the first aspect of the present invention, as described above,
Since the heat-molded OPP film has a high surface wetting property, the productivity of the heat-molding treatment can be improved and the allowable range of molding conditions can be expanded.

As has been described above, the invention of claim 3 has high wettability on both surfaces of the container, so that it is easy to mount and handle when stacked.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a plurality of OPP films according to an embodiment of the present invention are laminated.

2 is a perspective view of a film case obtained by heat molding from the laminated OPP films of FIG.

3 is a cross-sectional view taken along the line III-III in FIG.

FIG. 4 is a table showing experimental results for showing the characteristics of releasability by heat molding in one example of the present invention.

[Explanation of symbols]

 1 OPP film 3 film case 5 OPP film

Claims (3)

[Claims] 1. A heat treatment comprising: a step of laminating a plurality of biaxially oriented polypropylene films, both surfaces of which are corona-treated, and a step of integrally heat-molding the laminated biaxially oriented polypropylene films. Molding method. 2. The wettability of both surfaces of the biaxially stretched polypropylene film obtained by the corona treatment is 37 dynes / c.
The thermoforming method according to claim 1, which is at least m. 3. A molding container made of biaxially stretched polypropylene formed into a predetermined shape by heat molding, characterized in that the wettability of both surfaces of the biaxially stretched polypropylene is 37 dynes / cm or more. , Molded container.