JPS6220269Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to food containers.

The performance required for food containers is that they are inexpensive, lightweight, have excellent oil resistance, heat resistance, shape retention, and moldability, and have low gas permeability and moisture permeability, and are attractive in terms of sales. .

Although various types of containers have been supplied on the market for a long time in order to maintain such performance, no container that satisfies all of the properties has yet been obtained.

For example, polystyrene foam sheets are a preferred material because they are inexpensive, have good shape retention, have low thermal conductivity, and have good moldability. The disadvantage is that it is easy to wake up.

In order to improve the above-mentioned drawbacks, a material in which a polyolefin film is laminated on the surface of a polystyrene foam layer has been proposed, but the compatibility between the polyolefin film and polystyrene is poor and the adhesion technology is not satisfactory. A practical method is known to use a small amount of ethylene/vinyl acetate copolymer, but this method also has relatively weak adhesive strength and may produce an acetic acid odor during food storage. This is not necessarily satisfactory as a food container. In addition, the polyolefin layer and the foam sheet may peel off due to heating or freezing, which is not necessarily satisfactory as a food container.

Furthermore, it is difficult to print beautifully on the foamed surface of polystyrene, which is not sufficient to add value to products.

As shown in Fig. 1, the present invention is a laminated structure in which a polyolefin film layer 2 is adhered to one side of a styrene resin foam sheet 1 via a thermoplastic rubber 3, and a styrene resin film layer 4 is laminated on the other side. The present invention provides a food container obtained by compression molding a sheet so that the polyolefin film layer forms the inner surface.

The styrenic resin foam sheets used in this invention are styrene homopolymer foam sheets, mixed resin foam sheets of styrene polymer and synthetic or natural rubber, and copolymers of styrene and monomers that can copolymerize with styrene as the main material. It is a foamed sheet made of resin such as styrene/acrylonitrile copolymer resin, styrene/butadiene/acrylonitrile copolymer resin, etc. If desired, a high-impact polystyrene or heat-resistant polystyrene resin foam sheet may be used.

Examples of the polyolefin film used in the present invention include polyethylene, polypropylene, ethylene-propylene copolymer, ionomer, vinyl chloride-propylene copolymer, and ethylene-vinyl alcohol copolymer. Particularly preferred is polyethylene film, which may be either low density polyethylene or high density polyethylene.

The thickness of polyolefin film is approximately 0.01~0.3mm
is appropriate.

As the styrene resin film, biaxially oriented polystyrene, high impact polystyrene, etc. are used. Preferably, the film thickness is about 0.03 to 0.3 mm.

A mixture of polyethylene and a thermoplastic rubber selected from polybutadiene, polyisoprene, styrene-butadiene copolymer, or styrene-isoprene copolymer is used to bond the styrene resin foam sheet and polyolefin film. These adhesives not only adhere well to styrene resin and polyolefin, but also have good moldability when compression molding the resulting sheet, and facilitate secondary processing of the sheet. The amount of adhesive used may be such that the thickness of the adhesive layer is about 0.005 to 0.1 mm.

The styrene resin film is adhered to the opposite side of the polyolefin film. For adhesion, heat fusion, a method using an adhesive, etc. are used, and heat fusion is particularly preferred.

The laminated sheet is arranged so that the polyolefin film layer forms the inner surface of the container, and compression molded into a desired shape.

The resulting food container has an inner surface coated with polyolefin film, making it resistant to oil, making it sufficiently resistant even when used as a container for foods containing a lot of oil, such as instant noodles, and the outer surface is made of styrene. Since it is coated with a resin film, beautiful printing can be performed and the container has extremely high resilience against deformation. Furthermore, since the odor caused by the adhesive is blocked, it is possible to prevent the occurrence of odor, which is the most hated odor in food containers. Additionally, double-sided lamination significantly reduces gas permeability and moisture permeability, extending the effective shelf life of foods. Furthermore, since the polyethylene film and the expanded styrene are strongly bonded, no layer peeling occurs during heating and freezing processes, making it possible to obtain a container that can withstand use under harsh conditions.

Figure 2 shows the moisture permeability of the container obtained by the present invention.

Figure 2 is a graph comparing the changes over time in moisture permeability 5 of a conventional instant food container made of foamed polystyrene laminated with a high-impact polystyrene film and moisture permeation 6 of the container of the present invention. .

The container used for the test was a bowl-shaped container with an inner diameter of 140 mm and a depth of 60 mm. Silica gel was placed in it, the opening was sealed (heat-sealed) with an aluminum-polyethylene laminate film, and the container was kept at a temperature of 40°C and a humidity of 90%.
The weight increase was measured over time to determine the amount of moisture absorbed. The container used had a conventional foamed polystyrene layer with a specific gravity of 0.09 and a thickness of 2.3 mm, and a high-impact polystyrene film layer of 0.15 mm.
The foamed polystyrene layer of the container of this invention has a specific gravity of 0.1, a thickness of 2.1 mm, an adhesive layer (styrene-butadiene copolymer resin) of 0.03 mm, and a high-density polyethylene film layer.
0.07mm, high impact polystyrene film layer
It is 0.08mm. In the figure, the vertical axis shows the amount of moisture permeation g, and the horizontal axis shows the number of days of storage.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a food container, and FIG. 2 is a graph showing the amount of moisture permeable over time between the container of the present invention and a conventional product. In the figure, 1 is a styrene resin foam layer, 2 is a polyolefin film layer, 3 is an adhesive layer, 4 is a styrene resin film layer, 5 is the daily moisture permeability of the conventional food container, and 6 is the food container of the present invention. Indicates the amount of moisture permeable over time. In Figure 2, the vertical axis shows the amount of moisture permeation, and the horizontal axis shows the number of days.

Claims (1)

[Claims for Utility Model Registration] 1. A polyolefin film layer on one side of a styrenic resin foam sheet made of thermoplastic rubber selected from polybutadiene, polyisoprene, styrene-butadiene copolymer, or styrene-isoprene copolymer and polyethylene. A food container obtained by compression molding a laminated sheet, which is adhered via a mixture and has a styrene resin film layer laminated on the other side, so that the polyolefin film layer becomes the inner surface. 2 Styrenic resin foam sheet is polystyrene,
The first material is either high-impact polystyrene, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, or styrene-butadiene-acrylonitrile copolymer.
Containers listed in section. 3. The container according to item 1, wherein the polyolefin film is a polyethylene film. 4. The container according to item 1, wherein the styrenic resin film is polystyrene or high impact polystyrene film.