JPS6130987B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention mainly relates to packaging containers for foods that are heated and cooked using a microwave oven. In recent years, cooking methods using microwave ovens have diversified, and in addition to microwave heating, there are many devices such as ovens, steam heating devices, and microwave ovens that can be seen on the market. When cooking, heat-resistant glass or ceramic containers were used instead of metal containers. For this reason, frozen foods, etc., must be thawed in the same packaging container used for freezing, then transferred to a newly prepared glass or ceramic container before being heated and cooked, which saves the cook's time. It has been desired to complete the defrosting-cooking and heating process for microwave ovens using only one container. The above is said to be one of the reasons why retort containers for microwave ovens have not become widespread and sales of microwave ovens themselves have not increased rapidly. In an effort to overcome these drawbacks, the market is now selling retort containers made of heat-resistant plastics, heat-resistant paper, and plastics that have improved the heat resistance of various types and are able to withstand microwave cooking, ovens, and steam heating. Retort containers made of two-layer composite sheets are becoming commercially available. Typical commercially available products include: styrene plastic containers with improved heat resistance; two-layer composite containers made of heat-resistant polyolefin and paper; two-layer composite containers made of polyester (PET) and paper; and two-layer composite containers made of polyamide and paper. be. However, styrene plastic containers can only withstand heating up to 90°C. Another olefin-based composite container is 120℃~130℃
Although it can withstand heating at temperatures above 150°C, oil contained in or added to the food may seep out, impairing the flavor of the food, and it is not suitable for foods that reach temperatures above 150°C, such as oil dishes. . The heat resistance of polyester composite containers and polyamide composite containers can be used for cooking up to 180℃, and they are completely usable for microwave heating, and they also show good oil resistance. There is. However, when a container is made from a two-layer composite sheet of polyester, it is difficult to release it from a mold, and there is a problem in the moldability of the container. In addition, with two-layer polyamide composite containers, there are problems with the suitability of the container, such as the textured container shrinking due to moisture or causing blisters, and as mentioned above, there are problems with the diversification of microwave cooking methods. The container is not strong enough to withstand the steam heating and oven heating that are used in conjunction with this, especially when the oil reaches a maximum temperature of 200°C.
It could not be used at temperatures up to 250°C. The present invention strives to develop a retort container that can cope with the diversification of microwave cooking methods, and by using the three-layer composite sheet of paper and plastic described below, the above-mentioned ~
To compensate for the shortcomings of various commercially available containers, to eliminate the labor of cooks, to perform thawing and cooking of frozen foods in one step, and to have made possible a container that does not lose the flavor of the food during thawing and cooking. In other words, for a composite structure of paper and plastics, a thin heat-resistant and oil-resistant paper (hereinafter referred to as heat-resistant paper) is used for the surface layer (the surface that comes into contact with food), and a heat-resistant and oil-resistant thermoplastic plastic is used as the middle layer. The lower layer is paperboard or western paperboard, and the three layers are laminated together to create a three-layer composite sheet of heat-resistant paper/plastics/paperboard, which improves heat resistance to a maximum of 250°C and greatly improves the wrinkle processability. We have developed an improved material. The optimal heat-resistant paper to be used for the surface layer is Pulv base paper, J Pack base paper, etc. with a weight of 50g to 150g per square meter, and is intended to prevent thermal deterioration of the thermoplastic resin used as the intermediate layer. be. It is even better to use heat-resistant paper coated with a surface coating such as fluororesin or silicone resin to further improve heat resistance. As a heat-resistant and oil-resistant resin as an intermediate layer,
There is a need for a material that has good hot-melt properties when laminated with paper of a different quality and is completely resistant to food oils that seep through the heat-resistant paper used for the surface layer. The thickness of the resin used for this intermediate layer needs to be 40 microns or more in order to prevent pinholes that occur during hot melting or heat forming during grain processing. The thermoplastic resin used for this intermediate layer is preferably one with higher heat resistance, but the following are optimal from the viewpoint of moldability and non-toxicity. That is, polyester, polyamide (nylon 6, nylon 66, nylon 11, nylon 12, nylon 6)
-12 or copolymers thereof, etc.), single films such as polysulfone, or polyolefin resins,
It is a multilayer film such as ionomer. The paperboard or western paper that forms the bottom of the container is thicker and weighs less per square meter than the heat-resistant paper used for the surface layer.
100g to 300g is required, and paperboard or Western paper such as silk, carton, cardboard base paper, J-Pack base paper, etc. is suitable as a material that can easily maintain its shape during the shibori process of the retort container and does not lose its shape even when cooked in a microwave oven. . The most suitable method for laminating the above-mentioned three-layer composite film is three-layer lamination by ordinary extrusion lamination. According to this method, there is almost no distortion in the thermoplastic resin present as an intermediate layer when the retort container is wrinkled, and a container that can be smoothly wrinkled and has less wrinkle return can be produced. This feature is especially noticeable when polyester is used for the intermediate layer. In some cases, an already produced film may be heated and pressed using a hot roller or press. In this case, a film with unprecedented length and molecular orientation is required. In the case of this hot pressing method, special care must be taken when using nylon resin for the intermediate layer, as the moisture and thermal decomposition components contained in the film may form pinholes and pristars during hot pressing. Water must be sufficiently removed during pretreatment. The following is a more detailed explanation using examples using a three-layer composite sheet produced as described above. Example 1 Heat Resistance Test Containers with a length of 10 cm, a width of 8 cm, and a depth of 5 cm were made from various multilayer films laminated using an extruder by shibori processing. This container was filled with butter, and a high temperature heat resistance test was conducted using a microwave oven cooking method. The results are shown in Table-1.

【table】

【table】

[Table] Samples No. E, F, and G are containers that can completely withstand microwave cooking methods, and they all have a three-layer structure with a thermoplastic resin as an intermediate layer, a heat-resistant paper surface layer, and a base paper as a bottom layer. It was a composite film with heat resistance and oil resistance. Example 2 Molding processability test A, B, C, D, E, F, G used in Example 1
Using various composite films, tests were conducted to determine the quality of staining of containers with a length of 10 cm, a width of 8 cm, and a depth of 5 cm. The results are shown in Table-2.

[Table] Example 3 Applicability test of containers using various cooking methods Tests of containers with a length of 10 cm, width of 8 cm, and depth of 5 cm in various cooking methods using the various composite films A to G used in Example 1. I took an aptitude test. The results are shown in Table-3.

【table】

[Table] From the comprehensive judgment of (1) heat resistance test, (2) shibori processability test, and (3) suitability test for various cooking in the above examples, heat-resistant paper/thermoplastic resin/Western paper or It has become clear that a container made of a three-layer composite film constructed of paperboard is optimal as a container for a microwave oven.

Claims (1)

[Claims] 1. A heat-resistant electronic product manufactured using a three-layer composite sheet made by laminating heat-resistant, oil-resistant paper and Western paper or paperboard with a thermoplastic resin that is heat-resistant, oil-resistant, and has good stain processing properties for containers. Retort container for microwave.