JPH0269213A - Container - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sealed container for food packaging that is excellent in hygiene, sole properties, transparent gas barrier properties, easy opening, dimensional stability, and container strength.

[Prior art]

BACKGROUND ART Conventionally, air pressure molding, vacuum molding, and injection molding are known as methods for manufacturing molded products, particularly containers, from thermoplastic resins. The method of manufacturing molded products using compressed air and vacuum forming methods has low equipment costs, can produce molded products of various sizes and sizes relatively efficiently, and has a seal layer, barrier layer, physical Although it has the advantage of being able to use a laminated sheet that also has a strength-retaining layer, it is difficult for the molded product obtained by this method to have uniform wall thickness in each part, so there is no stiffness throughout, and when the sheet used is thin, etc. It is extremely delicate, and the thickness of the flange part is not uniform, resulting in heat-sealed gaps, variations in seal strength, and sealing defects.Also, dimensional accuracy is poor. Therefore, not only are the applications limited, but if the sheet used is thin, the molded product after vacuum forming becomes extremely delicate and has little commercial value, which is an unavoidable drawback.

On the other hand, in the method of manufacturing molded products by injection molding,
Compared to the vacuum forming method, the molded product has excellent Torah thickness, can produce molded products with uniform wall thickness, has firmness, and has stable seal strength, but the molding machine Not only do molds and the like become expensive, but multi-layering is also extremely difficult, and even if it were possible, it would be expensive and practically impossible. In particular, it has been difficult to manufacture thin-walled molded products by injection molding.

As a method to solve this drawback, Japanese Patent Application Laid-Open No. 48-819
50, a method in which a sheet is sent to an injection mold, subjected to vacuum and pressure forming, and then injection molded;
Unexamined Japanese Patent Publication No. 5, 1987 as a method for imparting various physical properties such as barrier properties
A method of injecting to the outside or inside of a laminated molded product has been proposed as in Japanese Patent No. 7-163544.

However, in these methods, the resin constituting the seal layer of the flange part is limited to one type due to its manufacturing method, and in order to maintain the sealability of the container and the ease of opening with the lid, the resin constituting the nol layer must be
It was necessary to use a resin with good heat sealing properties such as polyolefin resin or styrene resin. However, in recent years, the hygienic and odorless properties of sealed containers have been advocated, and as a sealing layer, hygienic and odorless
There is a demand for the use of thermoplastic copolyester that has excellent odor-free properties, but this resin has poor sealing properties, and even if it is sealed, it remains a complete seal and cannot be opened easily. Ta.

The present invention eliminates this drawback and as a result of intensive research to obtain an excellent molded product, the flange part of the molded product is made of two resins.
The present invention was completed based on the discovery that it is possible to obtain a sheet that has good sealing properties, is hygienic, and does not transfer odor.

[Problem to be solved by the invention]

The present invention was developed as a result of research aimed at creating a sealed container that satisfies hygiene, sole properties, transparency, gas barrier properties, ease of opening, and dimensional stability, which had not been possible before. We discovered that the solution could be solved by injection molding the outside of the multilayer pressure- and vacuum-formed product, so that the filling part is made of two types of thermoplastic resin with excellent hygiene. Based on this knowledge, we conducted various research. By proceeding with this process, we have completed the present invention.

[Failure to solve the problem]

The present invention is a multilayer sheet in which styrene resin, saponified ethylene vinyl acetate copolymer or vinylidene chloride resin, and thermoplastic copolyester are laminated in this order through an adhesive resin, with the thermoplastic copolyester layer on the inside. In a molded product that is molded by compressed air or vacuum forming method so that the molded product is formed by an air pressure or vacuum forming method, and a styrene resin is injection molded on the outside of the molded product, the sealing layer side of the flange portion of the molded product is coated with styrene resin, Thermoplastic copolyester 2
The container is made of a seed resin, and the inner layer of the filling part is a thermoplastic copolyester layer.

In the present invention, the multilayer sheet used is composed of the following constituent resins. The thermoplastic copolyester used in this multilayer sheet is one in which a part of the glycol component is replaced with 1,4-cyclohexane dimetatool, such as rPET-GJ manufactured by Eastman-Kodak Company.
corresponds to this.

The saponified ethylene vinyl acetate copolymer used as a gas barrier layer has an ethylene content of 20 to 60 mol%, especially 2
5 to 50 mol% of ethylene-vinyl acetate copolymer and 96
% or more is preferable, such as "EVAL" manufactured by Kuraray Co., Ltd.

Furthermore, a vinylidene chloride resin can also be used as the barrier layer, and this resin is made by copolymerizing vinyl chloride, methacrylnitrile, acrylonitrile, vinyl acetate, acrylic acid, etc., with vinylidene chloride as the main component.

Any styrene resin can be used as the styrene resin. This styrenic resin may be a styrene homopolymer or a copolymer of styrene and other monomers such as conjugated diene or acrylic monomer. From this point of view, styrene-conjugated diene copolymers are used.

As the adhesive resin, a blend of an ethylene vinyl acetate copolymer having a vinyl acetate content of 15% or more and a partially saponified ethylene vinyl acetate copolymer is used.

In this blend system, the ethylene-vinyl acetate copolymer desirably has a vinyl acetate content of 25 to 35 mol%, considering its fluid adhesive properties.

The partially saponified ethylene-vinyl acetate copolymer is a partially saponified ethylene-vinyl acetate copolymer, and preferably has a saponification rate of 40% or more.

Four extruders for each of these resins are used, and each resin from these extruders is led to a multilayer die to obtain a five layer sheet.

A multilayer sheet made of the above-described manufacturing method and constituent resin is molded into a predetermined shape by a vacuum forming method or a pressure forming method. At this time, the thermoplastic copolyester is molded so that it is on the inside of the molded product.

This molded article is inserted into a core portion within a mold of an injection molding machine. At this time, in order to bring the molded product into close contact with the core, it is preferable to vacuum the core portion and bring the molded product into close contact. After this, a desired styrene resin is injected from the cavity side of the injection molding machine to complete the product. Any styrene resin can be used for this injection, but the strength and moldability of the finished product
It is desirable to select the material in consideration of the adhesion to the outer layer of the multilayer sheet molded product.In order to obtain the container according to the present invention, the following points should be kept in mind during injection molding.

After molding, the multilayer sheet is punched out so that any part of the flange remains, but this flange must be smaller than the flange of the product after injection, and it must be punched out so that the flange part remains. If the inside of the flange is too short, the injection resin will flow inside the multilayer molded product after insertion, making it impossible to obtain a good product. Furthermore, if the flange of the product is the same or close to it, the sealing layer of the flange of the product after injection will be a thermoplastic copolyester, and good sealing performance will not be obtained.

Desirably, the outer diameter of this flange portion is 1ffII11 or more than the diameter of the molded product of the multilayer seal, and preferably two barrels shorter than the outer diameter of the flange of the product.

Furthermore, the lid material film used for this container is one that exhibits good sealing and easy-building properties with the container styrene resin, and the seal layer constituent resins include ethylene vinyl acetate copolymer, acid-modified styrene resin, and acid-modified styrene resin. Modified petroleum resins, hot melt resins, etc. are used. This lid body may be a single layer consisting of only a sealing layer, but it may also be a multilayer film containing aluminum foil, polypropylene, etc. with good barrier properties.

(Example) Using the layer thicknesses and constituent resins shown in Table 1, coextrusion 5
A layered sheet is created, and then by vacuum forming, the inner volume is 1.
A vacuum molded product (7) is prepared at 50°C and has a thermoplastic copolyester layer on the sealing surface, and this molded product is subjected to injection molding with outer dimensions that are approximately the same as or slightly smaller than the inner dimensions of the molded product. The molded product was inserted into the core of the molded product, and a styrene resin (6) having sufficient adhesion to the outer resin layer was injected from the cavity side to obtain a molded product as shown in FIG. In Figure 0, which shows an enlarged view of the flange portion in Part 2, 1 to 5 represent the resin Nα in Table 1, and 6 is an injection resin.

8 of the coextruded 5-layer sheet used in Example 1 as Comparative Example 1
A vacuum-formed product was obtained using a 00μ sheet.

As Comparative Example 2, a one-layer styrene container was made using the injection mold and injection styrene resin 6 used in Example 1.

Comparative Example 3 was manufactured using the same manufacturing method as in Example 1 so that the flange portion was entirely a seal layer of a vacuum-formed product, as shown in FIG.

Furthermore, by combining vacuum and pressure molding with injection molding, containers with excellent gas barrier properties, dimensional stability, and container strength can be obtained, which is highly effective in packaging foods, medicines, and the like.

Using the containers of Example 1 and Comparative Examples 1, 2, and 3, using a lid material made of polyester, aluminum foil, and styrene easy-peel sealant laminated in layers of 12μ, 3μ, and 60μ, a commercially available cup sealing machine was used. , fill the contents with miso and seal. Sealing performance, odor migration, easy opening,
We compared the shelf life and strength of the containers. The sole properties were determined by checking the suitability of the sole of the sealing machine and the ease of opening by a monitor.
j Viability was determined by filling the contents with n-water and keeping at 60°C for 1 hour, and then quantifying the extrudate. Odor transfer was measured by a sensory test using a randomly extruded monitor, and the shelf life was always 11 for 3 months! ! The strength of the packaging container after storage was evaluated by investigating the deformation of the container during a transportation test, and Table 2 shows the results.

Table-1 Eastman Kodanok PET-G mixing ratio 50:
50 Eval E, manufactured by Kuraray Co., Ltd. Mixing of butadiene-styrene copolymer and CP styrene Table 2: The sample was generated and could not be evaluated.

〔Effect of the invention〕

According to the method of the present invention, a vacuum and pressure molded product is combined with an injection molded product, and more preferably, two different types of resin can be arranged in the flange. Thermoplastic copolyesters with inferior properties can be used for container contents, contact surfaces, and
When this resin is used, there is less migration of the contents of the resin component, making it suitable for packaging containers for foods, etc.

Patent applicant: Sumitomo Bakelite Co., Ltd. Figure 1 Procedure correction mouth (release)

Claims (1)

[Claims] (1) A multilayer sheet in which styrene resin, saponified ethylene vinyl acetate copolymer or vinylidene chloride resin, and thermoplastic copolyester are laminated in this order through adhesive resin, with the thermoplastic copolyester layer on the inside. In a molded product that is molded by compressed air or vacuum forming method so that the molded product is formed by an air pressure or vacuum forming method, and a styrene resin is injection molded on the outside of the molded product, the sealing layer side of the flange portion of the molded product is coated with styrene resin, A container made of two types of thermoplastic copolyester resins, characterized in that the inner layer of the filling part is the thermoplastic copolyester layer.