JPH11198321A - Multilayered sheet and container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered sheet capable of being formed into a container good in transparency even in molding using a continuous deep drawing machine of a type heating the single surface on the side of a seal layer and sterilizable at high temp. or heatable by an electronic oven. SOLUTION: A multilayered sheet consists of five layers of a seal layer (A), an adhesive resin layer (B), an oxygen gas barrier layer (C), an adhesive resin layer (D) and an outer layer (E) successively formed from the inside. In this case, the seal layer (A) comprises polypropylene with an m.p. of 150 deg. or higher or a mixture wherein 1-49 wt.% polypropylene with an m.p. of below 150 deg.C is compounded with 51-99 wt.% polypropylene with an m.p. of 150 deg.C or higher and the outer layer (E) comprises polypropylene with an m.p. of below 150 deg.C or a mixture wherein 1-49 wt.% polypropylene with an m.p. of 150 deg.C or higher is compounded with 51-99 wt.% polypropylene with an m.p. of below 150 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer sheet and a container which are excellent in moldability, transparency after molding, oxygen gas barrier property and sealing property, and which can be sterilized at high temperature and heated in a microwave oven. More specifically, the present invention relates to a container having good transparency even when molded by a single-sided heating type continuous deep drawing molding machine on the seal layer side of the sheet.

[0002]

2. Description of the Related Art There is a container in which food is sealed in a plastic container, sterilized at a high temperature, and stored and distributed. In addition, the number of cases where a consumer uses a microwave oven to heat the contents is increasing, and when the contents include oil, the contents may become high in temperature. The packaging forms for preserving fresh foods are roughly classified into gas packaging and vacuum packaging. As a gas pack package, a multi-layer sheet having a layer configuration composed of each resin is deep-drawn, and after filling the deep-drawn bottom material with a side dish or meat, an inert gas such as nitrogen gas is sealed, and the lid material is sealed. It has been done. As a packaging system, there are a batch type and a continuous filling type.However, from the viewpoint of productivity, cost, etc., a continuous deep drawing packaging machine is used to perform a series of operations from bottom material molding to content filling, gas replacement, sealing with lid material. System is used. As a sheet having good transparency used for the bottom material for continuous deep drawing packaging, a sheet mainly using polyester or vinyl chloride is used. However, since the heat resistance is low, high-temperature sterilization such as retort sterilization or a microwave oven is used. Heating is not possible. Further, there is a sheet mainly composed of polypropylene (hereinafter referred to as PP) having good heat resistance and transparency used in an off-line pressure molding machine capable of high-temperature sterilization and microwave heating. However, unlike a pressurized air molding machine that is heated indirectly by a heater from above and below the seal layer side and outer layer side of a sheet, a general continuous deep drawing molding machine integrates the heating and molding zones, and only one side of the seal layer side Is heated directly, it is necessary to raise the molding temperature to near the melting point of PP in order to give heat that can be molded up to the outer layer. When a continuous deep drawing molding machine in which the sheet heating method is direct heating, the molding temperature is raised to near the melting point of PP to form a PP sheet for air pressure molding, the external haze increases because the seal layer is transferred to the hot plate and transferred. There is a problem that transparency is remarkably reduced.

[0003]

SUMMARY OF THE INVENTION According to the present invention, a container having good transparency can be obtained without lowering the transparency even in molding with a single-sided heating type continuous deep drawing molding machine on the seal layer side, and high-temperature sterilization can be performed. And a multi-layer sheet and a container which can be heated in a microwave oven.

[0004]

According to the present invention, at least a sealing layer (A), an adhesive resin layer (B), an oxygen gas barrier layer (C), an adhesive resin layer (D) and an outer layer (E) are provided from the inside. A multilayer sheet composed of five layers, wherein the sealing layer (A) has a melting point of 150 ° C. or higher polypropylene or a melting point of 150 ° C.
The outer layer (E) is a polypropylene having a melting point of less than 150 ° C. or a polypropylene having a melting point of less than 150 ° C. A multilayer sheet comprising a mixture of 51 to 99% by weight of polypropylene having a melting point of 150 ° C. or higher and 1 to 49% by weight of a polypropylene, and using the multilayer sheet to heat one side of the seal layer (A) side And a container formed by air pressure molding.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The melt index (JIS K6758) of polypropylene having a melting point of 150 ° C. or more and polypropylene having a melting point of less than 150 ° C. used in the seal layer (A) and the outer layer (E) of the present invention is 0.1 to 10; Is more preferably 0.5 to 7. It is also possible to blend 3 to 20 parts by weight of polyethylene in consideration of moldability. In addition to polyethylene, a blend of a thermoplastic resin such as an unsaturated carboxylic acid-modified polyolefin or ethylene vinyl acetate is also possible as long as it is not taken on a hot platen during molding. The sealing layer (A) is made of polypropylene having a melting point of 150 ° C. or more, or polypropylene 5 having a melting point of 150 ° C. or more.
It consists of a mixture of 1 to 99% by weight and 1 to 49% by weight of polypropylene having a melting point of less than 150 ° C. If the melting point of the polypropylene having a melting point of less than 150 ° C. exceeds 49% by weight, the sealing layer is easily taken on a hot plate at the time of molding, and the transparency is reduced. The outer layer (E) is a polypropylene having a melting point of less than 150 ° C. or a polypropylene 5 having a melting point of less than 150 ° C.
It is composed of a mixture of 1 to 99% by weight and 1 to 49% by weight of polypropylene having a melting point of 150 ° C. or higher. If the melting point of the polypropylene having a melting point of 150 ° C. or more exceeds 49% by weight, it is necessary to increase the molding temperature at the time of molding, and the sealing layer is easily taken on a hot plate and the transparency is lowered.

[0006] The adhesive resin used in the adhesive resin layers (B) and (D) of the present invention is not particularly limited.
Both the ethylene-vinyl acetate copolymer and the polypropylene are preferably maleic anhydride-modified polypropylene having good adhesion.

The resin used for the gas barrier layer (C) of the present invention is preferably a saponified ethylene-vinyl acetate copolymer, and the ratio of commercially available ethylene is 20 to 50.
It can be used properly depending on the purpose from among mol%.
In consideration of moldability in addition to the five layers (A) to (E), a polypropylene having a melting point of less than 150 ° C or a polypropylene having a melting point of 150 ° C or more between the (A) layer and the (B) layer is 1 to 1. 49
It is also possible to laminate a mixture in which the weight% is mixed.

[0008] The layer structure of the present invention, using the above resin,
It can be obtained by coextrusion, lamination, or the like. As the lamination, any method such as extrusion lamination, coextrusion lamination, dry lamination, and thermal lamination can be used.

[0009]

EXAMPLES The present invention will be described below by way of examples, which are merely examples, and the present invention is not limited to these examples. Tables 1 and 2 show the resin mixing ratios of the sealing layer (A) and the outer layer (B) of the multilayer sheets of Examples and Comparative Examples, and their transparency and heat resistance. Example 1
6 and Comparative Examples 1 to 4 are separate extruders each having a seal layer (A) of 110 μ / adhesive resin layer (B) of 10 μ / gas barrier layer (C) of 10 μ / adhesive resin layer (D) of 10 μ / outer layer (E) of 110 μ. And kneaded and extruded to form a multilayer die. Comparative Example 5 is a co-extrusion method in which polyethylene (25μ) / modified carboxylic anhydride polyethylene (5μ) / nylon (10μ) / ethylene vinyl alcohol copolymer (10μ) is kneaded and extruded by separate extruders and led to a multilayer die. Was laminated with A-PET (250 μ) by a dry lamination method.

The resins used in Examples and Comparative Examples are as follows.・ PP1: Polypropylene melting point 158 ° C. Melt index = 2.5 ・ PP2: Polypropylene melting point 163 ° C. Melt index = 0.5 ・ PP3: Polypropylene melting point 132 ° C. Melt index = 5.0 ・ PP4: Polypropylene melting point 137 ° C. Melt index = 1・ Adhesive resin: modified carboxylic anhydride polypropylene ・ Gas barrier layer: ethylene vinyl alcohol copolymer

The evaluation in this example and the comparative example was performed by the following method.・ Transparency Multi-back R530 machine 110mm X150
mm, height 25mm, bottom 100mm x 135mm
And the haze at the center of the bottom was measured with a haze meter. The haze was less than 20%, and the haze was 20% or more. -Heat resistance The container used for the transparency evaluation was filled with 50% vegetable oil, and heated in a microwave oven with an output of 500 W for 2 minutes. After the heating was completed, the appearance of the container was observed, and the case where the container was deformed was evaluated as x, and the case where no deformation was generated was evaluated as ○.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

According to the multilayer sheet of the present invention, a container having good transparency can be obtained without deteriorating the transparency even in molding with a single-sided heating type continuous deep drawing molding machine on the sealing layer side, and high temperature can be obtained. A container that can be sterilized and heated in a microwave oven is obtained.

Claims (2)

[Claims] 1. A multilayer sheet comprising at least five layers of a sealing layer (A), an adhesive resin layer (B), an oxygen gas barrier layer (C), an adhesive resin layer (D), and an outer layer (E) from the inside. The sealing layer (A) is made of polypropylene having a melting point of 150 ° C. or more, or a mixture of 51 to 99% by weight of polypropylene having a melting point of 150 ° C. or more and 1 to 49% by weight of a polypropylene having a melting point of less than 150 ° C. ,
The outer layer (E) is made of polypropylene having a melting point of less than 150 ° C. or polypropylene having a melting point of 150 ° C. or more with respect to 51 to 99% by weight of polypropylene having a melting point of less than 150 ° C.
A multilayer sheet comprising 9% by weight of a mixture. 2. A container which has been subjected to one-side heating on the side of the seal layer (A) using the sheet according to claim 1 and has been subjected to air pressure molding.