JPH0245128Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Industrial Application Field) Styrofoam containers are lightweight, have high rigidity, and provide excellent physical protection for the contents. Furthermore, because of their good insulation properties, they are widely used as containers for instant foods. However, it has the disadvantage that the contents tend to deteriorate due to poor gas barrier properties and water vapor barrier properties. The present invention relates to a container that provides barrier properties to a Styrofoam container. (Prior art) Methods for imparting barrier properties to expanded polystyrene containers include polyethylene (PE), polypropylene (PP), polyvinylidene dichloride (PVDC),
The most common method is to use a foamed polystyrene sheet laminated with a single or multilayer film of saponified ethylene vinyl alcohol (EVA saponified product) to form a container by vacuum forming or pressure forming. This method is not suitable for containers with a large drawing ratio because it is difficult to mold them. For containers with a large drawing ratio, it is appropriate to create a Styrofoam container and a container with barrier properties in separate processes, and then combine them to form a double cup.
Hereinafter, a Styrofoam container will be abbreviated as a PSP container, and a container with barrier properties will be abbreviated as a barrier container. The optimal structure for the barrier container is one in which both sides are made of polystyrene (PS) and the middle layer is a barrier layer, in terms of fusion properties with the PSP container and sealing properties with the lid material. Barrier containers use PSP to ensure effective barrier properties.
Must be used as an inner container. PSP containers and barrier containers are made into double cups by heat sealing, but conventional containers with a drawing ratio of 0.7 or more had the drawback of requiring time to seal and resulting in low productivity. (Purpose of the invention) As a result of researching whether it is possible to seal the PSP container and barrier container at high speed even in deep containers with a drawing ratio of 0.7 or more, this invention changes the grade of PS on both sides of the barrier container, and the outer PS layer This objective was achieved by increasing the rubber content to at least 1.5 times the rubber content of the inner PS layer. (Structure of the invention) The present invention has a polystyrene layer (outer layer)/barrier layer/ The inner container of the barrier container consisting of a polystyrene layer (inner layer) and the outer container of the PSP container are heat-sealed, and the barrier property is characterized by having a flange thickness of 0.4 mm or less and a drawing ratio of 0.7 or more. The barrier layer is a single-layer or multi-layer container containing high-density polyethylene, polypropylene, polyvinylidene dichloride, saponified ethylene vinyl alcohol, or acrylic resin. When sealing between a PSP container and a deep barrier container consisting of PS layer/barrier layer/PS layer with a drawing ratio of 0.7 or more, PS and
Poor low-temperature sealing properties of PSP containers, thick seals, and inability to raise sealing temperature high. The sealing temperature between PS and PSP container is
In the case of HIPS, a minimum temperature of 130°C is required, and the thicker the PS, that is, the thicker the seal part of the barrier container, the higher the temperature required. PSP container 2 and barrier container 1
Sealing is performed at part A in FIG. 1, that is, at the flange part. Also, seal parts B and C if necessary.
Containers with a large drawing ratio require a certain level of rigidity for handling the container during vacuum forming (or pressure forming), so the flange must be formed using a thick raw fabric. Therefore, the thickness of the flange portion becomes relatively thick, and high-speed sealing performance deteriorates. Furthermore, if the flange is sealed by crimping it with a hot platen, the sealing temperature cannot exceed 170°C due to problems such as adhesion to the hot platen, shrinkage of the flange part of the barrier container, and decreased smoothness of the flange part of the PSP container. This was a factor that hindered high-speed sealing performance. We researched barrier containers that have good low-temperature sealability, good container shape retention even with thin flange thickness, and can be sealed at high temperatures. The ratio of the rubber component contained in the PS (outer) layer 3 in the barrier container 1 is
The ratio of the rubber components contained in PS (inner) layer 5 is
If it is 1.5 times or more, even if the drawing ratio is 0.7 or more, the flange thickness is 0.4 mm or less, the shape retention is good, and high-speed sealing is possible for PSP containers. Barrier layer 4 has very good water vapor barrier properties because it hardly increases the thickness of the barrier container.
HDPE (high-density polyethylene), PP, PVDC, EVA saponified products with excellent oxygen gas barrier properties, and acrylic resins are desirable. (Effects of the invention) When the barrier container of the invention is sealed with a PSP container, the sealing time, which conventionally required more than 4 seconds, can be shortened to 2 seconds or less, making it possible to put into practical use improved barrier properties of deep PSP containers. (Example 1) As an inner container of a Styrofoam container with a diameter of 80φmm and a depth of 100mm, the oxygen gas permeability is 0.01cc/ ^m2 .
A container consisting of a PS (outer) layer, a barrier layer, and a PS (inner) layer was created using vacuum forming so that the pressure was 24 hours atm or less, and a sealing test was conducted. The results are shown in Table 1.

【table】

[Table] Example 2 The tests shown in Table 2 were conducted using Styrofoam inner containers with a diameter of 100φmm and depths of 50, 100, and 130 mm to ensure good water vapor barrier properties.

【table】 [Brief explanation of the drawing]

Figure 1 shows the state of the double cup before sealing.
FIG. 2 shows a cross-sectional view of a container with barrier properties. 1 is a barrier container, 2 is a styrofoam container, 3
is the PS (outer) layer, 4 is the barrier layer, 5 is the PS (inner) layer,
A is the flange part.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The ratio of the rubber component contained in the polystyrene of the outer layer is 1.5 times or more than the ratio of the rubber component contained in the polystyrene of the inner layer, and the polystyrene layer (outer layer)/barrier An inner container made of layer/polystyrene layer (inner layer) and an outer container made of expanded polystyrene are heat-sealed, the thickness of the flange part is 0.4 mm or less, and the drawing ratio is 0.7.
A barrier container characterized by having the above properties. (2) The barrier container according to claim 1, wherein the barrier layer is a single layer or multilayer containing high-density polyethylene, polypropylene, polyvinylidene dichloride, saponified ethylene vinyl alcohol, or acrylic resin.