JPH02180168A - Heat-resistant package - Google Patents

Abstract

PURPOSE:To provide sufficient sealing strength and enable heat-sealing easy to open by a method wherein in a package made of polybutylene terephthalate, etc., a line of continuous belt-like protrusion is provided along an opening of a package on an upper face of a flange while an upper corner is provided with curve having a specific radius of curvature. CONSTITUTION:In a package 1 mainly made of polybutylene terephthalate resin or polyethylene terephthalate resin and having a flange around its openings, at least one line of continuous belt-like protrusion 4 is provided on the upper face of the flange while a corner of at least of an inner periphery of the belt-like protrusion upper face has curve with radius of curvature of 0.3 to 5mm. In order to obtain excellent heat-sealing characteristics and easy-to- open characteristics at the same time, width of a lower part of the belt-like protrusion is preferably 1 to 10mm with height 0.1 to 3mm. As a lid material, one which is fit to polybutylene terephthalate resin or polyethylene terephthalate resin constituting the package is preferable.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a heat-resistant container made of resin that has excellent heat-sealing properties and easy-opening properties of the heat-sealed lid, and also has excellent heat resistance, preservation properties, etc. This invention relates to a sealed container formed by heat-sealing a lid using the same.

In particular, the present invention relates to a resin container that is suitable for applications in which heat treatment is performed in a sealed state, such as after filling with food, heat-sealing the lid, and cooking in a microwave oven.

[Conventional technology and its issues]

In recent years, there has been a rapid increase in the number of products in which plastic containers are filled with foods and the like and sealed. Conventionally, in such applications, containers made of polyethylene, polypropylene, polystyrene, or composite materials of these materials have been used, and the contents are placed in the containers and sealed by heat-sealing a film or the like made of the same material as the container. It is being said. As this heat sealing method, a method is generally used in which a film to be coated is applied to the welding surface of a flat flange portion 2 of a container as shown in FIG. There is.

However, in this method, when the film is heat-sealed to the flange portion, the film is likely to be cut at the corners of both ends of the flange (3 in FIG. 1) by the shear force of the pressure bonding, resulting in insufficient sealing or unsealing properties. Furthermore, if the heat seal is weakened to avoid this, there is a problem that the heat seal portion will peel off even with a slight internal pressure. In particular, foods that can be cooked directly in a microwave oven have been in the spotlight in recent years, but in applications where heat treatment is applied in a sealed state, conventional polyethylene, polypropylene, polystyrene, etc., have poor heat resistance as containers. In addition, the odor from the container transfers to the food and affects the taste and taste of the food.
There is a problem of loss of flavor, and there is a need to develop a replacement container that has better heat resistance and retention properties, and also has sufficient sealing strength even after heat treatment in a microwave oven, etc., and is easy to open. There has been a particular desire for an improved heat-sealing method that is capable of high-temperature heat-sealing and is free from problems such as cutting of the film during the heat-sealing process as described above.

[Means to solve the problem]

In order to solve this problem and obtain a resin container with excellent heat resistance and heat sealability, the inventors of the present invention have made intensive studies from the viewpoint of materials and the shape of the heat sealing part, and have developed polybutylene terephthalate resin or polyethylene terephthalate resin. The resin has the required properties, and it is possible to heat-seal containers made of such resin with excellent sealing performance and ease of opening by forming the heat-sealing part into a specific shape. Heading, we arrived at the present invention.

That is, the present invention provides a method for wiping a container mainly made of polybutylene terephthalate resin or polyethylene terephthalate resin and having a flange around an opening, and forming at least one continuous band-shaped protrusion on the upper surface of the flange along the opening. A heat-resistant container characterized by having a rounded surface with a radius of curvature of 0.3 to 5 mm on at least the inner corner of the upper surface of the convex portion, and a sealed container obtained by heat-sealing a lid using the same. It is related to.

First, the shape of the resin container of the present invention will be explained with reference to the drawings.

In the resin container of the present invention, in a container having a flange portion 2 around the opening as shown in FIG. 1, at least one continuous strip is formed on the upper surface of the flange portion along the opening of the container as shown in FIG. A band-shaped convex portion 4 is provided, at least on the opening side (
It is characterized in that the upper corners of the band-shaped protrusions on the inner peripheral side), preferably on both sides, are rounded with a radius of curvature of 0.3 to 5 mm.

Here, if the radius of curvature of the roundness is smaller than 0.3 mm, it is preferable because when the film is heat-sealed to the band-shaped convex part, the film is likely to be cut at the curvature part due to the shear force of compression, resulting in poor sealing performance. do not have. On the other hand, if an attempt is made to have a radius of curvature larger than 5 degrees, the shape of the band-like convex portion will be extremely unnatural, and the effects of the present invention cannot be fully exhibited. A more preferable radius of curvature is 0.5 to 3 mm. Although there are no particular restrictions on the width and height of the band-shaped protrusion, in order to effectively demonstrate its effect and obtain excellent heat-sealing properties as well as ease of opening, the width of the lower part of the band-shaped protrusion should be set to 1. It is preferable that the height is 0.1 to 3 mm. Particularly preferably a width of 2 to 5 mm and a height of 0.3 to 2 mm.
It is mm. The band-shaped protrusions provided on the flange portion can also be made into a plurality of two or more strips as shown in FIG. In this case, it is sufficient that any one of the strips meets the above regulations, but it is preferable that the band-shaped convex portion provided on the opening side (inside) of the container meet the regulations. Of course, it is preferable that all the band-like protrusions meet the regulations. Further, in the case where a single band-shaped convex portion is provided, the width of the convex portion may be substantially the same width as the flange.

It is not necessary to intentionally create a curvature on the outer corner of the band-shaped convex part, but in that case, there is a risk that the film will be cut at this part during heat sealing, resulting in good sealing performance but insufficient ease of opening. be. In order to avoid this, it is preferable to provide the outer corners of the convex portion with a curvature as defined above. In this case, the curvature does not need to be provided over the entire circumference of the band-shaped convex portion, and may be provided only on a portion of the film to the extent that a portion of the film remains uncut and opening can be started.

Next, the materials constituting the container of the present invention will be explained.

The container of the present invention is mainly made of polybutylene terephthalate resin or polyethylene terephthalate resin. More specific examples include containers made entirely of polybutylene terephthalate resin or polyethylene terephthalate resin, as well as containers made entirely of polybutylene terephthalate resin or polyethylene terephthalate resin and paper, expanded polystyrene, polystyrene resin, polyethylene resin, polypropylene. Also included are containers etc. in which a laminate of two or more layers composed of resin or the like is molded such that a layer of polybutylene terephthalate resin or polyethylene terephthalate resin forms a band-shaped convex portion on the inside of the container and on the upper surface of the flange portion.

Among these, containers mainly made of polybutylene terephthalate resin are preferred because they are superior in terms of heat-sealability, odor transfer from the container to the contents, and the like. Among these, containers made entirely of polybutylene terephthalate resin are not only economically advantageous because they can be obtained extremely easily by injection molding, but also have the advantage that the shape of the container can be designed freely. Yes, it is desirable. In particular, as polybutylene terephthalate resin, 235°C, load 2 according to ASTM D-1238
Melt index measured at 160 g is 30
It is preferable to use a material having a diameter of 150 to 150 because it is possible to obtain a thin container that has sufficient heat resistance, strength, shape retention, etc.

The polybutylene terephthalate resin or polyethylene terephthalate resin in the present invention includes not only polyesters obtained by condensing 1,4-butanediol or ethylene glycol with terephthalic acid or its lower alcohol ester, but also polyesters mainly composed of these. It may be a polymer, for example, one into which a soft segment, a halogen-substituted segment, etc. are introduced, or one modified by grafting or the like. Further, it is also possible to blend other thermoplastic resins into these base resins within a range that does not impair the purpose of the present invention.

In addition, such base resins include known substances added to general thermoplastic resins and thermosetting resins, such as plasticizers, stabilizers such as antioxidants and ultraviolet absorbers, antistatic agents, surfactants, flame retardants, Coloring agents such as dyes and pigments for fuels, lubricants for improving fluidity, crystallization accelerators (nucleating agents), inorganic fillers, etc. are also used depending on the required performance and the effect of the present invention and the purpose of use as a container. It can be added and used as appropriate within a range that does not inhibit.

A container configured as described above is filled with food or the like, and the lid is heat-sealed for use.

The lid material is not particularly limited, but it is preferably one that is compatible with the polybutylene terephthalate resin or polyethylene terephthalate resin constituting the container, and from this point of view, it is preferably one that is mainly composed of polybutylene terephthalate resin or polyethylene terephthalate resin. Examples include a film made of polybutylene terephthalate resin or polyethylene terephthalate resin, a composite film in which a film of polybutylene terephthalate resin or polyethylene terephthalate resin is laminated with paper, a film of other resin, aluminum, etc., and the polybutylene terephthalate resin or It is preferable that the polyethylene terephthalate resin layer is coated so as to be in contact with the band-shaped convex portion of the resin container flange portion and heat-sealed. That is, it is preferable to heat seal so that the same resin layer of the lid material and the resin constituting the band-shaped protrusions on the inside of the container and the upper part of the flange are in contact with each other at the protrusions provided on the container flange. Any known heat sealing method can be used. For example, as shown in FIG. 4, the flange portion may be placed on a heat-sealing fixing base 8, the lid film 5.6 may be covered so as to be in contact with the band-shaped convex portion, and the heat-sealing heating element 7 may be pressed against the flange portion.

The hermetically sealed container thus obtained has good heat-sealing properties because the container is mainly made of polybutylene terephthalate resin or polyethylene terephthalate resin, and the flange portion thereof is provided with a band-shaped convex portion of a specific shape. The film does not break during sealing and the sealing performance is not impaired, the sealed portion does not easily peel off even when heated in a microwave oven, etc., and it is easy to open. In addition, since the container is mainly made of polybutylene terephthalate resin or polyethylene terephthalate resin, it has excellent strength, heat resistance, shape retention, and retention properties, and even during heat treatment such as cooking in a microwave oven, the odor from the container can be reduced. There is no inconvenience that the particles transfer to food and impair the taste and flavor of the food. These effects are particularly remarkable when polybutylene terephthalate resin is primarily used.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 3 and Comparative Examples, 1 to 3 Containers made of polybutylene terephthalate resin with a melt index of 65 as measured by the above measurement method, with a container body having a shape as shown in FIG. 1 and a flange portion having a shape as shown in FIG. 2. was molded by injection molding. The shape of the band-shaped convex portion provided on the flange portion was varied as shown in Table 1. The main body of the container is cylindrical with a diameter of 100 mm and a depth of 50 mm, with a thickness of 0.
It was within the range of 5 to 0.7 stops.

Next, as shown in FIG. 4, a polybutylene terephthalate resin film 5 and a polyethylene terephthalate resin film 6 are prepared.
The polybutylene terephthalate resin side of the laminated film made of the laminated film was coated and heat-sealed so that it was in contact with the convex part of the container flange, and the heat-sealability was observed.
Beer strength and pinhole tests were conducted in the following manner.

In addition, for comparison, there is also one in which the flange does not have a band-shaped protrusion (Comparative Example 1), a flange in which the band-shaped protrusion is provided but the corners are not rounded (Comparative Example 2), and a shape other than the one specified in the present invention. The same test was also carried out on the one provided with the band-shaped convex portion (Comparative Example 3). The results are also shown in Table 1.

The test method is as follows.

・Number of samples: n=5 ・Beer strength: Grasp one end of the film with a chuck and measure the strength using an autograph when peeling it off from the sealed part ・Pinhole test color check method Using color check penetrating liquid, ,
Measurements were made in accordance with JIS T-9111, which examines leakage from heat-sealed parts.

Feeling when the film is peeled off by hand JIS T-9111 method/Easy peelability Example 4 Containers similar to those used in Examples 1 to 3 were filled with nothing, filled with water, and filled with oil. The filled product was heat-sealed with the lid material used in Examples 1 to 3, and heated in a microwave oven at 2450MH2,500W for 15 minutes.

When the beer strength of the film after heat treatment was subjected to a pinhole test, there was almost no change from the results shown in Table 1.

Example 5 and Comparative Example 4.5 The container used in Example 1 was left empty, or water or oil was added to it and heated in a microwave oven (2450 MHz).

500W) for 15 minutes. At this time, virtually no deformation was observed in the container, and no odor transfer from the container to the contents was observed.

For comparison, similar containers were molded from polypropylene and polystyrene and tested in the same manner.Although there was almost no deformation in the containers filled with water, there was considerable deformation in the empty containers. However, some of the containers containing oil melted. In addition, odor transfer to the contents was observed.

〔Effect of the invention〕

As is clear from the above description and examples, the heat-resistant packaging container of the present invention, which is mainly made of polybutene terephthalate resin or polyethylene terephthalate resin and has a band-shaped convex portion of a specific shape on the flange portion, has good heat sealability. The film does not break during heat sealing and the sealing performance is not impaired, the sealed portion does not easily peel off even when heated in a microwave oven, etc., and it is easy to open.

In addition, it has excellent strength, heat resistance, shape retention, aroma retention, etc., and does not cause the inconvenience that odor from the container transfers to the food and impairs the taste and flavor of the food even during heat treatment such as cooking in a microwave oven. Therefore, the container of the present invention is extremely suitable for use in food preservation, or in applications where food is subjected to heat treatment, such as cooking in a microwave oven.

4,

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the shape of a general resin container. FIGS. 2 and 3 are schematic cross-sectional views showing embodiments of the band-shaped convex portion provided on the flange portion according to the present invention. Further, FIG. 4 is a schematic diagram showing a state in which the lid material (film) is heat-sealed to the band-shaped convex portion provided on the flange portion according to the present invention. 1 Container main body 2 Flange portion 3 Corner of flange portion 4 Belt-shaped convex portion 5.6 Lid film 7 Heating element for heat sealing 8 Fixing stand for heat seal Applicant's agent Kaoru Furuya

Claims (1)

[Scope of Claims] 1. In a container mainly made of polybutylene terephthalate resin or polyethylene terephthalate resin and having a flange around the opening, at least one continuous strip along the opening is provided on the upper surface of the flange. A heat-resistant container comprising a convex portion, and at least an inner corner of the upper surface of the band-like convex portion is rounded with a radius of curvature of 0.3 to 5 mm. 2. The container has a melt index of 30 measured at 235°C and a load of 2160g according to ASTM D-1238.
2. The heat-resistant container according to claim 1, which is obtained by injection molding using a polybutylene terephthalate resin of 150 to 150. 3.Claim 1, wherein the container is a food container for cooking in a microwave oven.
Or the heat-resistant container described in item 2. 4. Using the heat-resistant container according to any one of claims 1 to 3, and using a film or thin plate in which at least one of the surface layers is mainly composed of polybutylene terephthalate resin or polyethylene terephthalate resin as the lid material, the film or thin plate is used. A hermetically sealed heat-resistant container formed by coating and heat-sealing the resin side of the container so that the resin side is in contact with a band-shaped convex portion provided on a container flange. 5. Using the heat-resistant container according to any one of claims 1 to 3, at least one of the surface layers is a film mainly composed of polybutylene terephthalate resin or polyethylene terephthalate resin, on the band-shaped convex portion provided on the upper surface of the flange portion. Alternatively, a method for sealing a heat-resistant container, which comprises using a thin plate as a lid material, covering the resin material side of the film or thin plate so that it is in contact with the resin material side, and heat-sealing.