JPH0911326A - Molding of foamed resin sheet container - Google Patents

Abstract

PURPOSE: To make a mouth form sharp and seal width enough without broadening the width by a method in which a foamed resin sheet, after being molded in advance at a molding clearance larger than that to obtain a prescribed container form which is formed in a male-female engagement mold, is compressed to the molding clearance to obtain a prescribed container form. CONSTITUTION: A vacuum suction hole A which holds a foamed resin sheet in the bottom part of a male mold to secure the moldability and a vacuum suction hole B for promoting the forming of a mouth shape are made in the male mold 1, and a vacuum suction hole C for forming the outer corner shape of the bottom part is made in a female mold 2, respectively. A vacuum of -620mmHg is applied during molding. A sheet in which a high impact polystyrene film is laminated on one side of a foamed polystyrene sheet is preheated in an oven for secondary foaming. In the molding, although a molding clearance to obtain a container form is 2.0mm, the sheet is molded in advance at the molding clearance of 2.0-6.0mm and then compressed to the prescribed molding clearance of 2.0mm with vacuum suction actuated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a foamed resin sheet container, and more particularly, it is easy to form a foamed resin container having an appearance similar to that of foamed resin bead molding by molding a foamed resin sheet. It is about how to get to.

[0002]

2. Description of the Related Art Foamed resin sheet containers have excellent heat insulation,
Due to its characteristics such as light weight and low price, it is widely used in various containers such as ramen containers. However, since the foamed resin sheet container forms a thick sheet, in addition to the problem that it is difficult to form a deep container (so-called deep drawing container),
Since the shape of the bent portion such as the mouth portion (opening portion) is difficult to appear, there is a problem in that a sharp appearance does not appear. Also, when using a seal lid etc. on the mouth (opening), the shape of the mouth becomes round and it is not possible to secure a horizontal seal width accordingly, so it is necessary to widen the width of the seal at the mouth. However, this includes problems such as a poor appearance and a poor mouth feel. On the other hand, a foamed styrene bead molding container is used as a container that does not have such a problem, but since it is foamed resin bead molding, it is unavoidable that a gap occurs between the fused foamed resin beads, and therefore The container has high moisture permeability, and there are new problems such as leakage of juice.

In forming a foamed resin sheet container, in order to sharply form the shape of the mouth portion, the stack portion, the bottom portion, etc., a vacuum suction hole is provided in the portion of the mold corresponding to these portions and vacuum suction is performed. Although we are trying to shape it, the effect is not sufficient, especially in the molding of deep-drawing containers, because the stretch rate of the sheet at the time of molding is high,
The appearance of sharp shapes is more difficult.

[0004]

SUMMARY OF THE INVENTION In view of the above situation, the present invention makes the shape of the mouth portion appear sharp, improves the feeling of mouth feel and appearance, and secures a sufficient seal width without particularly widening the seal width. In addition, when the shape of the corner of the bottom part also appears sharply, a good shape comparable to foamed resin bead molding is secured by forming a foamed resin sheet, and further when a shape such as a stack part is given by vacuum suction, these It is intended to provide a method for molding a foamed resin sheet container that clearly reveals the shape and surely exhibits the functions of the stack portion and the like.

[0005]

That is, according to the present invention, when a foamed resin sheet is introduced into a molding gap defined between male and female fitting dies and molded into a container shape, a predetermined container shape is obtained. After pre-molding with a molding gap larger than the molding gap,
The present invention is directed to a method for molding a foamed resin sheet container, which comprises compressing to a molding gap for obtaining a predetermined container shape.

Examples of the foamed resin sheet of the present invention include polystyrene resins, polystyrene resins such as copolymer resins of styrene and maleic anhydride, methacrylic acid, etc., and those polystyrene resins or polystyrene resins and polyphenylene oxide resins. A foamed resin sheet composed of one or more thermoplastic resins composed of a mixed resin, a polyolefin resin such as polyethylene and polypropylene, and a polyester resin such as polyethylene terephthalate, and polystyrene resin, high resin Impact polystyrene resin such as styrene resin, polyolefin resin such as polyethylene and polypropylene,
Examples thereof include a foamed resin sheet in which resin films such as polyvinylidene chloride resin, ethylene-vinyl alcohol copolymer resin, polyester resin, and polyamide resin are used alone or in combination of two or more, and are laminated on one side or both sides. Among these foamed resin sheets, a foamed resin sheet having excellent moldability and capable of forming a deep-drawing container is a polystyrene or polystyrene-based foamed resin sheet and a foamed resin sheet obtained by laminating various films on one side or both sides of these foamed resin sheets. It is suitable.

These foamed resin sheets are formed by using a general-purpose foamed resin sheet molding machine, by heating and softening the foamed resin sheet in a heating furnace attached to the molding machine and by secondary foaming, by a male and female fitting mold. It is introduced into the molding gap and molded. The heating in the heating furnace is appropriately adjusted according to the foamed resin sheet used and the shape of the intended container, but it is controlled based on the degree of secondary foaming. For example, in the case of polystyrene resin or polystyrene-based resin, Foaming ratio is 1.9 ~
It is common to heat up to about 2.7 times.

The male and female fitting mold used for molding is designed so that a container having a predetermined shape can be obtained by setting a predetermined molding gap. A temperature adjusting function is added to the mold, if necessary. When molding a deep-drawing container, it is preferable to control the heating temperature of the male mold. In addition, it is preferable that a vacuum suction hole is provided in a portion such as a mouth corner portion, a bottom corner portion, and a stack portion where shaping is required in the die, and vacuum suction assists shaping. The degree of vacuum suction is preferably -300 mmHg or more, more preferably -5.
It is more than 00 mmHg.

Although the appearance of the shape is improved by vacuum suction,
The outer corners of the mouth of the deep drawn container are
Since the foamed resin sheet is stretched, it is difficult to form the shape only by vacuum suction.In addition, the shape of the vacuum suction hole is good only at the place where it is installed. Difference is likely to occur. Moreover, like commercial manufacturing molds,
When performing multi-cavity molding, there is variation in vacuum suction,
Variations in the appearance of the obtained containers can occur.

It is one of the features of the present invention that the above problems can be solved. That is, after preforming with a molding gap that is larger than the molding gap that obtains the predetermined shape, and by compressing until the molding gap that obtains the predetermined shape, the lack of appearance of the shape due to only vacuum suction as described above is compensated. It is possible to reduce the variation in the appearance. Therefore, although the present invention has the effect of improving the appearance of the shape without using vacuum suction in combination, it is more preferable to use it in combination with vacuum suction. Also, when compressing to a predetermined molding gap, activating vacuum suction gives better results.

It is preferable that the molding gap at the time of preforming by making it larger than the molding gap for obtaining a predetermined shape is 1 to 3 mm larger than the molding gap for obtaining a predetermined shape. If it is smaller than 1 mm, the effect of shaping is less, and if it is larger than 3 mm, the foamed resin sheet is completely introduced into the molding space.
It cannot be pinched, and as a result, vacuum leakage occurs and the shape does not appear, or when it is compressed to a predetermined shape, wrinkles etc. occur on the inner surface of the container, which is not preferable.

[0012]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but these do not limit the present invention in any way.

Examples 1 to 4 and Comparative Examples 1 to 2 A container having the shape shown in FIG. 1 was molded by the male and female fitting mold shown in FIG. The male die 1 is provided with a vacuum suction hole A for holding the foamed resin sheet on the bottom of the male die to ensure moldability, and a vacuum suction hole B for facilitating the shaping of the mouth portion. The mold 2 was provided with vacuum suction holes C for forming the outer corner shape of the bottom, and a vacuum of -620 mmHg was applied during molding. The mold temperature was adjusted to 90 ° C for the male mold and 50 ° C for the female mold. The foamed resin sheet used for molding is a polystyrene foam sheet having a thickness of 2.4 mm and a basis weight of 350 g / m ² laminated with a high-impact polystyrene film having a thickness of 180 μm on one side (which constitutes the inner surface when used as a container). Heated in a heating furnace to a thickness of 6.2
Secondary foaming up to mm was performed and used for molding. As shown in FIG. 1, the molding has a molding gap of 2.0 mm to obtain the container shape. As shown in Table 1, the molding gap is 2.0 to 6.0 mm in advance, and then vacuum suction is performed. In the activated state, it was compressed to a predetermined molding gap of 2.0 mm. The curvature R of the corner shape a at the mouth and the corner shape b at the bottom of the obtained container was measured. Table 1 shows the results.

[0013]

[Table 1]

As is clear from Table 1, when the molding gap to be molded in advance is set as large as possible and the molding gap is compressed to a predetermined shape, the corner R tends to be smaller and the shape forming tends to be better. In Example 4 in which the molding gap of the predetermined shape was made larger than the molding gap (2.0 mm) by 4.0 mm,
There was a vacuum leak at the mouth and the shape of the mouth was poor.

Examples 5 to 6 and Comparative Example 3 As shown in FIG. 3, a container having a stack portion 4 inside was molded using a male and female fitting mold shown in FIG. In the male mold 1, a foamed resin sheet is held at the bottom of the male mold, and a vacuum suction hole A is provided to promote shaping of the bottom portion, a vacuum suction hole B is provided to promote shaping of the mouth portion, and Vacuum suction holes C for promoting the shaping of the stack portion are provided respectively, and vacuum suction holes D for promoting the shaping of the stack portion are provided on the female die 2. The foamed resin sheet used was one side of a polystyrene foamed sheet with a thickness of 2.6 mm and a basis weight of 470 g / m ² (inside when used as a container)
A high impact polystyrene film having a thickness of 200 μm is laminated on the above, and heated in a heating furnace to have a thickness of 6.
Secondary foaming was performed up to 9 mm and the molding was used. The molding gap to be molded in advance is 2.0 mm, 4.0, and 6.0 mm, which is a predetermined molding gap when the vacuum suction hole is vacuum-operated.
Compressed to mm. Corner c of the mouth of the obtained container,
The curvature R of the bottom corner d and the width e of the stack portion were measured, and the appearance of the inner surface of the container was observed. Table 2 shows the results.

[0016]

[Table 2]

As is clear from Table 2, the corner R tends to be smaller and the shape is better when the molding gap to be molded in advance is made as large as possible and compressed to a molding gap having a predetermined shape. Molding gap (2.0m
In Example 6 in which the thickness was larger than that of m) by 4.0 mm, minute wrinkles were generated on the inner surface of the container, particularly on the stack portion.

[0018]

As described above, according to the present invention, since the shape of the mouth portion is sharply expressed, the appearance is good, the mouth feel at the time of eating and drinking is good, and the width of the seal portion of the mouth portion is wide. The sealing lid is sufficiently sealed without being particularly wide.
In addition, the bottom and stack parts are also revealed sharply. Even when vacuum suction is also used, variations in the shape between the vacuum suction hole and other parts and variations in the degree of vacuum suction are corrected, resulting in a uniform shape and a product value. A high container is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing containers formed in Examples 1 to 4 and Comparative Examples 1 and 2.

FIG. 2 is a schematic cross-sectional view showing male and female molds used in Examples 1 to 4 and Comparative Examples 1 and 2.

FIG. 3 is a cross-sectional view showing containers formed in Examples 5 to 6 and Comparative Example 3.

FIG. 4 is a schematic cross-sectional view showing male and female dies used in Examples 5 to 6 and Comparative Example 3.

[Explanation of symbols]

 1 Male mold 2 Female mold 3 Vacuum line 4 Stack part A, B, C, D Vacuum suction hole

Claims (4)

[Claims] 1. When a foamed resin sheet is introduced into a molding gap defined between male and female fitting dies to be molded into a container shape, it is previously molded with a molding gap larger than a molding gap for obtaining a predetermined container shape. After that, the method for molding a foamed resin sheet container is characterized by compressing to a molding gap for obtaining a predetermined container shape. 2. The molding method according to claim 1, wherein the molding is performed in advance with a molding gap that is 1 to 3 mm larger than the molding gap for obtaining a predetermined container shape. 3. The molding method according to claim 1, wherein a vacuum suction hole provided in the mold is vacuum-operated to perform molding. 4. The molding method according to claim 1, wherein the mold is compressed to a molding gap for obtaining a predetermined container shape while the vacuum suction hole of the mold is vacuum-operated.