JP2870850B2 - Highly transparent heat-resistant synthetic resin container - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a container for storing various foods and storing them for a long time at room temperature through a sterilization process using a retort and a boiler. The present invention provides a synthetic resin container having high transparency, high durability, high impact resistance, good gas barrier properties, and high transparency.

(Conventional technology) As a container which is transparent and has high gas barrier properties and is suitable for long-term storage, a glass container has conventionally been generally used. However, glass containers have the drawback of being heavy and easily broken, and are recently being replaced by various types of synthetic resin containers.

However, considering synthetic resin as a material for food containers,
For example, when polypropylene is used, the heat resistance is sufficient but there is a ground glass-like haze, and it cannot be said that it is completely transparent. When a transparent polystyrene is used, it becomes weak to heat, and when heat sterilization such as retort or boiling is applied, shrinkage or deformation occurs, or the impact resistance is reduced and the material is easily cracked. In the case of using polyethylene terephthalate, when sterilized by heating, whitening due to crystallization proceeds, the transparency decreases, and at the same time, shrinkage and deformation occur. Among them, when using polycarbonate (PC), transparency, heat resistance,
Both impact resistance is high and it is the best material in terms of physical properties,
When used as a storage container, both oxygen and water vapor easily permeate and cannot be used as a single layer.

In order to solve this problem, there is known a multilayer sheet in which various thermoplastic resins are coextruded and integrated. Multilayer sheets have the properties of individual thermoplastic resins laminated and therefore have properties that cannot be obtained with a single-layer sheet, and are therefore widely used as materials for various molded containers. However, even if it is attempted to make a multilayer sheet, the saponified ethylene-vinyl acetate copolymer (EVOH) in the resin, which is usually used for the central layer that supplements the gas barrier, has a low water vapor barrier property of PC, so that it can be used for boiling and retorting. When heat sterilization is applied, water vapor reaches the central layer.
EVOH absorbs moisture and cannot exhibit its original gas barrier properties. In addition, polyvinylidene chloride (PVDC) has low heat resistance, so when extruded with PC, it causes thermal decomposition and cross-linking and can be extruded normally. A multilayer container with high gas barrier properties using PC could not be made due to the lack of a PC.

Also, when PC is used for the inner surface, the method of sealing the container, the usual heat-sealed lid has low adhesive strength, and cannot be used when heat sterilization is applied.

(Problems to be Solved by the Invention) The present invention is intended to meet the above demands. That is, an object of the present invention is to provide a synthetic resin container that is transparent, has heat resistance of about 130 ° C., has barrier properties, is easy to mold, and has impact resistance.

(Means for Solving the Problems) In the present invention, a combination of polycarbonate (hereinafter, referred to as PC) and amorphous nylon (MXD-Ny) having a barrier property was selected from many thermoplastic resins.

PC has the properties of being transparent, heat-resistant, and having high impact resistance, but has the disadvantage that it has high water absorption and therefore low barrier properties.

Considering a container that uses amorphous nylon for the gas barrier layer that is the center layer of the multilayer sheet, the processing temperature of amorphous nylon is 250 to 300 ° C. High barrier properties.

A co-extruded sheet is made using these two resins,
By manufacturing the container by thermoforming, a synthetic resin container that is transparent, has high heat resistance and high impact resistance, and has good gas barrier properties can be obtained.

 Hereinafter, the present invention will be described more specifically.

As the amorphous nylon used in the present invention, a crystalline polyamide having an aromatic ring in a main chain obtained from a polycondensation reaction of meta-xylene diamine (MXDA) and adipic acid, which is excellent in high gas barrier properties and heat resistance, That is, Is suitable and is available from Mitsubishi Gas Chemical as nylon MXD-6.

The polycarbonate resin used in the present invention is a polycarbonate resin formed from bisphenol A and phosgene or diphenyl carbonate.
That is, The resin has the structure of Panlite of Teijin Ltd., Teflon of Idemitsu Petrochemical Co., Ltd., Lexan of Engineering Plastics Co., Ltd., Mitsubishi Gas Chemical Co., Ltd.
Any ordinary grade such as Iupilon, Novaflex of Mitsubishi Kasei Co., Ltd. having a heat resistance of about 130 ° C., which is the retort sterilization temperature, can be used.

The thickness of the amorphous nylon layer and the polycarbonate layer can be arbitrarily adjusted, for example, amorphous nylon 100 μm, polycarbonate each 300 ~ 700μ
It is.

The laminated material of the present invention is obtained by merging the above MXD-Ny and a polycarbonate resin and co-extruding them,
In the present invention, another resin layer such as an adhesive layer can be further provided if necessary. As the resin used for such an adhesive layer, an unsaturated carboxylic acid-modified polyolefin can be used. Examples of the polyolefin include polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and ethylene-α-olefin copolymer. Here, the unsaturated carboxylic acid modification means copolymerizing or graft-polymerizing with a carboxylic acid group, an acid anhydride and a derivative thereof, and specifically as a carboxylic acid group, an acid anhydride group and a derivative thereof. Examples include methacrylic acid, maleic acid, fumaric acid, methacrylic anhydride, maleic anhydride, ethyl methacrylate, glycidyl acrylate, and dicricidyl methacrylate.

The thickness of the adhesive layer is optional, but is preferably 20 to 50 μm
It is.

As the layer constitution of the laminate of the present invention, various constitutions such as polycarbonate / amorphous nylon / polycarbonate, polycarbonate / adhesive layer / amorphous nylon / adhesive layer / polycarbonate, etc. can be adopted. From the viewpoint of protection of the amorphous nylon layer, the structure of polycarbonate // adhesive layer / amorphous nylon / adhesive layer / polycarbonate is preferred.

In addition, as a method for sealing the container, not only a normal heat seal lid, but also a metal EOE tightening lid, that is, a score (a thin groove is provided along the periphery so that it can be easily opened) and a pull tab at an opening portion. By providing the cover and double-tightening it with a lid that is easily opened, complete sealing and easy opening can be ensured.

EXAMPLES Hereinafter, the present invention will be described with reference to examples. FIG. 1 is a partially cutaway front view of a synthetic resin container according to the present invention. FIG. 2 is an enlarged view of a portion 2 in FIG. FIG. 3 is a top view of the container. FIG. 4 is a cross section taken along a line connecting x and y in FIG.

First, the container according to the present invention will be described with reference to FIG. 1 and FIG. The container of FIG. 1 is made of a multilayer sheet, as shown enlarged in FIG. The multilayer container is
An amorphous nylon layer 3 is integrated with an inner and outer PC, that is, a polycarbonate layer 1 via an adhesive layer 2.

In this embodiment, Panlite KT1300 manufactured by Teijin Limited is used for polycarbonate, Admer AT459 (unsaturated carboxylic acid-modified polypropylene) manufactured by Mitsui Petrochemical Co., Ltd. is used for the adhesive layer, and Mitsubishi is used for amorphous nylon. Nylon MXD-6 manufactured by Gas Chemical Co., Ltd. was used.

As a manufacturing procedure, co-extrusion by the feed block method,
The heating and melting temperature conditions at the time of forming a multilayer sheet are as follows: PC: 290 to 310 ° C., adhesive layer: 240 to 260 ° C., MXD-6
The thickness balance of the sheet was 270 to 290 ° C. The total thickness was 1000 μm, the PCs on both sides were 400 μm each, the adhesive layer was 50 μm each, and the central MXDA was 100 μm.

The sheet is formed into a shape having a bottom and side walls by vacuum pressure forming using plug assist. (First
Figure). When the sheet temperature immediately before molding was measured by an infrared thermometer, a container having a substantially uniform thickness distribution in the range of 180 to 190 ° C. was formed.

The above-mentioned container was filled with food, sealed with a metal lid, and then sterilized by heating. (FIGS. 3 and 4).

95 ° C after filling, in case of syrup pickled fruit
Was sterilized in a boil for 30 minutes, but there was no deformation of the container or opening of the sealed portion, and good transparency was maintained. When the haze was measured to confirm the transparency of this container, the container was kept transparent at about 3 before boil and about 5 after boil. When it was tasted after it was present, the taste and texture did not change, and good storage stability was confirmed.

Similarly, when the meat sauce was filled and the mixture was sterilized by retort at 120 ° C. for 30 minutes, there was no deformation of the container or opening of the sealed portion, and the haze after retort was 6 and the transparency was maintained. This container
When the samples were stored for 3 months in an environment of 25 ° C and a humidity of 65%, and tasted, good preservability was confirmed without any change in taste and texture.

The container opening shown in FIG. 1 is sealed by a double wrapping as shown in the sectional view of FIG. 4 by a metal wrapping lid as shown in FIG.

(Effect of the Invention) The multilayer sheet according to the present invention is a one-step co-extruded sheet prepared by melt-extruding PC, MXD-Ny and an adhesive, and is strongly integrated and transparent. Is good. In addition, although PC alone is inferior in barrier properties, MXD-Ny is interposed therebetween, so that the barrier properties are improved as a whole. Furthermore, since both CP and MXD-Ny are thermoplastic and stable, the multilayer sheet is easy to heat and form. Therefore, a container formed by molding this multilayer sheet is suitable as a container that is easy to manufacture and that can be easily deteriorated.
The container also has impact resistance and heat resistance up to 130 ° C. In particular, since both PC and MXD-Ny are harmless resins, they can be brought into direct contact with food. Further, even if the container is heated and disinfected by contact with water vapor, the container is not deformed, so that it is suitable as a food retort and a boil container.

The container according to the present invention, after putting the food therein,
The top is covered with a wrapping lid and double wrapped with a wrapping machine. Further, by using the EOE lid, the container can be easily opened.

The synthetic resin container according to the present invention is a container that can be sterilized in boil and retort and can be placed in a microwave oven, and is a container that can be distributed at room temperature or chilled. The contents include curry, stew, soup, hamburger, and rice. , Miso, side dishes, sake, raw meat, processed fishery products, tsukudani, instant foods, and other general foods, especially taking advantage of its high transparency, canned pudding, jelly, mizuyokan, jam, juice, canned fruits,
There is a high display effect for contents that want to show the contents.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a synthetic resin container according to the present invention. FIG. 2 is an enlarged view of a portion 2 in FIG. FIG. 3 is a top view of the container. FIG. 4 is a cross section taken along a line connecting x and y in FIG. A: Multi-layer container, B: Metal winding closure, 1 ... Polycarbonate, 2 ... Adhesive layer, 3 ... Amorphous nylon, 4 ... Opening score

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] An outer layer and an inner layer are made of polycarbonate, and a central layer has gas barrier properties. Highly transparent heat-resistant synthetic resin container.