JPH0531861A - Hermetically sealed container - Google Patents

Abstract

PURPOSE:To provide a container not damaging the flavor possessed by food of every kind being content and excellent in preservability and hermetic sealability. CONSTITUTION:A hermetically sealed container is characterized by that a container wherein polycarbonate (A), polypropylene (B) and an ethylene/vinyl alcohol copolymer (C) are laminated from the innermost layer of the container in the order of A-B-C-B and the thickness of the polycarbonate layer (A) being the innermost layer is 10% or less of the total thickness and the melt flow rate of polypropylene being the constitutional resin is 2.0 or less and the polypropylene layer is 50% or more of the whole is hermetically sealed by a lid body having gas barrier properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetically sealed container having excellent storage stability and physical properties against contents.

[0002]

2. Description of the Related Art Conventionally, storage containers made of plastic have a construction in which ethylene vinyl alcohol copolymer or vinylidene chloride copolymer is used as a gas barrier layer, and both sides thereof are laminated with a polyolefin such as polypropylene or polyethylene. Has been used. These have been heavily used as those having both gas barrier properties and sealing properties with lids. However, as researches such as alteration of contents proceed, in containers containing polyolefin in the innermost layer, the flavor of the contents is adsorbed by the innermost layer, or the odorous component of the resin layer of the innermost layer is transferred to the contents. It was found that the innermost layer other than polyolefin was required.

As containers having these flavor characteristics, containers having polyethylene terephthalate or an ethylene vinyl alcohol copolymer as an inner layer have been proposed, but these are the contents of hot filling and pasteurization (100 ° C. or less).
However, it cannot be used for high temperature sterilization (retort foods) and the like because it has a drawback that the innermost layer is softened by heat. On the other hand, polycarbonate was considered as a resin that compensates for these drawbacks, but when combined with other resins, polycarbonate is a heat-resistant resin, and therefore, when vacuum forming or the like is performed with a multilayer sheet layer, the molding cannot be satisfied. It had the drawback.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made by various investigations to solve these problems of the conventional hermetically sealed containers, and the object of the present invention is to prepare various foods whose contents are different depending on the container. Without spoiling the flavor of
An object is to provide a container having excellent storability and sealing property.

[0005]

According to the present invention, polycarbonate (A), polypropylene (B) and ethylene vinyl alcohol copolymer (C) are used in the order of AB from the innermost layer of the container.
-CB is laminated in this order, the innermost polycarbonate layer (A) is 10% or less of the total thickness, the melt flow rate of polypropylene as the constituent resin is 2.0 or less, and the polypropylene layer is Is a hermetically sealed container obtained by hermetically sealing a container having 50% or more of the total with a lid having a gas barrier property.

Any polycarbonate can be used as the polycarbonate used in the present invention. Also, a mixture of a small amount of polyethylene terephthalate or the like can be used as long as the flavor characteristics are not affected.

The polypropylene used in the present invention is homo, if its melt flow rate is 2.0 or less.
Various polypropylenes such as copoly and random can be used. Further, other resins such as polyethylene may be mixed within a range that does not change the melt flow rate.

Any ethylene vinyl alcohol copolymer can be used in the present invention as long as the ethylene copolymerization ratio is 20 to 45%.

As a method for laminating these resins, known laminating techniques such as a coextrusion method, a coextrusion laminating method, an extrusion laminating method and a dry laminating method are used. Further, in order to bond the resins to each other for stacking them, an adhesive suitable for the individual resins or an adhesive resin is used.

As a method of molding these multilayer sheets into a container, generally, a vacuum forming method, a pressure forming method,
A vacuum pressure molding method is used.

As the lid material used in the present invention, any material can be used as long as it can seal the innermost layer and has gas barrier properties. For example, a three-layer film in which the sealant layer is polycarbonate, the barrier layer is vinylidene chloride copolymer, and the outermost layer is nylon, and the sealant layer is heat-sealable polyethylene terephthalate,
The barrier layer is aluminum foil, and the outermost layer is polyethylene terephthalate. Further, the lid is not limited to the film shape, and a molded article form may be used. For example, a multilayer sheet having a heat sealable polyethylene terephthalate as a sealant, an ethylene vinyl alcohol copolymer as a barrier layer, and a polypropylene as an outer layer can be formed into a drop lid shape by vacuum forming and used.

As a method for welding these lid and main body container, known heat sealing method, ultrasonic sealing method, and high frequency sealing method are used.

[0013]

The function of the present invention will be described. The innermost polycarbonate layer used in the container of the present invention is used for flavor protection of the contents. Polycarbonate has excellent heat resistance among thermoplastic resins, and can be used for foods that require retort sterilization. However, because of its heat resistance, polycarbonate requires a large amount of heat during container heat molding. Further, the drawdown during heating of the sheet is large, and it is generally said that it is not suitable for the sheet heating molding type vacuum forming method or the pressure forming method. Therefore, in the present invention, therefore, the thickness of the polycarbonate is less than 1 of the total thickness.
This problem is solved by suppressing the content to 0% or less and selecting a polypropylene layer described later. As for the flavor suitability for the contents, the above-mentioned thickness ratio can achieve a sufficient function, and it is desirable to control it to 5% or less.

The polypropylene layer used in the present invention is used as a strength retaining layer, a water vapor barrier layer and a moldability improving layer. In the present invention, the thickness ratio of the polypropylene layer is specified to be 50% or more, and the melt flow rate of the polypropylene used is 2.0 or less because it relates to the moldability of the container. In thermoforming of a sheet mainly composed of polypropylene, the melt flow rate of the resin used for the formed sheet is greatly related to its formability. That is, in the case of polypropylene, if the melt flow rate is large, the drawdown at the time of heating becomes large, and a satisfactory molded product cannot be obtained. Further, the thickness ratio of the polypropylene layer is defined in the present invention, when the thickness ratio of the polypropylene layer is 50% or less, the drawdown at the time of molding becomes large as described above, which is inconvenient for container molding. And to reduce the water absorption of the ethylene vinyl alcohol copolymer, which is the gas barrier layer, during retort sterilization as much as possible. The ethylene vinyl alcohol copolymer, which is the gas barrier layer, has the best oxygen gas barrier property among general-purpose thermoplastic resins, but its water-absorbing property lowers its barrier property. Further, this tendency of water absorption increases as the temperature rises, and when treating the container in heated water, an outer moisture protection layer is required. Therefore, the water vapor barrier layer as the outer layer needs to have a certain thickness.

[0015]

EXAMPLES The effects of the present invention will be described with reference to the following examples. Table 1 shows the configurations of the three types of multilayer sheets used for comparison with Example 3 used in the present invention. These multilayer sheets were prepared by the coextrusion method. These multi-layer sheets use an indirect heating type vacuum forming machine and have a diameter of 80 mm and a height of 50 m.
Create a container with a diameter of 40 mm and a bottom diameter of 40 mm, and fill the contents with two types of orange juice and curry. The former is hot filling at 60 ° C, the latter is 120 ° C for 30 minutes after filling, and then at room temperature. Storage was carried out for one month, and the storage stability and flavor suitability were compared. In addition, comparative evaluation was also performed on the moldability during thermoforming. The results are shown in Table 2.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

EFFECT OF THE INVENTION The sealed container of the present invention can be obtained by a low cost molding method similar to that of the prior art, in which the flavor of the contents is not changed as compared with the conventional plastic barrier multilayer container.

Claims (1)

Claims: 1. Polycarbonate (A), polypropylene (B), ethylene vinyl alcohol copolymer (C)
Is laminated in the order of A-B-C-B from the innermost layer of the container, the polycarbonate layer (A) of the innermost layer is 10% or less of the total thickness, and the melt flow rate of polypropylene which is the constituent resin. Is 2.0 or less and the polypropylene layer is 50% or more of the whole, and the container is hermetically sealed with a lid having a gas barrier property.