JPS59179633A - Polystyrene sheet foam for forming deep-drawn container - Google Patents

Abstract

PURPOSE:The titled sheet foam excellent in moldability and capable of forming deep-drawn containers such as cup-shaped moldings in good yields, prepared by laminating an unfoamed resin film on a specified sheet foam containing polystyrene resin as a base resin. CONSTITUTION:A base resin comprising polystyrene resin [a polymer containing a styrenic vinyl monomer such as (methyl)styrene as a principal structural unit] is mixed with 1-30wt% rubber component (e.g., butadiene rubber or ethylene/ propylene rubber) and 1-20wt% filler (e.g., talc, calcium carbonate or metal powder). The produced mixture is formed by extrusion foaming into a sheet foam in which the amount of the remaining gas produced from the blowing agent used is 0.3mol/kg or below. Next, a 5-600mu-thick unfoamed resin film 3 comprising a thermoplastic resin (e.g., polystyrene) is laminated on the sheet foam 2 to obtain a 1-3mm.-thick polystyrene sheet foam for forming deep-drawn cobtainers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polystyrene foam sheet for forming deep-drawn containers. More specifically, polystyrene for forming deep-drawn containers, which is a raw material for sheet forming of deep-drawn containers such as pot-shaped molded bodies, has excellent moldability, and is especially advantageous as a raw material for mass production. The present invention relates to a foam sheet.

Conventionally, a method using an extruder has been known as one of the methods for manufacturing polystyrene foam molded products. This method involves extrusion foaming of a polystyrene resin composition together with a foaming agent to form a sheet (original fabric), which is heated above the softening point of the sheet and then fed into a mold. This method is performed after subsequent molding.
Various molded products are manufactured by this method.

However, such a forming method has various problems associated with the secondary formability of the sheet. In other words, due to secondary foaming of the sheet due to heating during secondary molding, the dimensional accuracy and dimensional stability of the molded product relative to the molding die (hereinafter referred to as "mold ejection n") is insufficient, making it difficult to mold a fitted lid, etc. However, there was a problem in that there was a limit to the elongation of the sheet during heating, and the degree of freedom in forming deep-drawn containers such as cots was extremely limited. In particular, when conventional polystyrene foam sheets are used to continuously manufacture pot-shaped containers with a drawing ratio of 1 or more, due to the limit of sheet elongation, at least sufficient space must be provided between each mold as shown in Figure 8. It was necessary to set the following parameters, which had the disadvantage that the production efficiency of molded products from the original fabric was poor. In particular, cup-shaped containers have recently been used in large quantities as food containers for cup noodles and the like, so it is important to efficiently obtain molded products from raw fabric, or in other words, to obtain more desired molded products from the same area of raw fabric. was desperately needed.

This invention has been made in view of the above-mentioned conventional problems, and one of its objects is to provide a raw fabric for forming that allows a desired deep-drawn container to be obtained more efficiently than in the past. be.

The wood inventors first determined that the amount of residual gas in the blowing agent was 0.3 mol/kg.
We have discovered that a specific polystyrene foam sheet controlled as follows is extremely suitable as a raw material for molded products such as trays. This invention was discovered as a result of studies conducted from a different perspective on polystyrene foam sheets having a residual gas amount of 0.8 mol/kg or less.

Thus, according to the present invention, a base sheet having a thickness of 1 to Bmyx is formed by layering a non-foamed resin film 81 on at least one surface of a sheet-like foam whose base resin is polystyrene resin, and the sheet-like foam has a base material of 1~ for material resin
The non-foamed resin film is made of a sheet-like foam containing a rubber component equivalent to 30% by weight and a filler equivalent to 1 to 20% by weight, and in which the residual gas amount of the blowing agent is controlled to 0.1 mol/kg or less. A polystyrene foam sheet for forming deep-drawn containers is provided, which is characterized by being made of a thermoplastic resin film having a thickness of 5 to 600 μm.

Hereinafter, the foamed sheet of the present invention will be explained in detail with reference to specific examples shown in the accompanying drawings.

FIG. 1 is a sectional view showing a polystyrene foam sheet (1) for deep-drawn container molding of the present invention. In the figure, a foamed sheet (1) is a non-foamed resin film (
It consists of a composite sheet with a thickness of 1 to 3, which is obtained by laminating 3) by fusion bonding. And the sheet-like foam (2) has a ratio of 1 to the base resin.
It contains a rubber component equivalent to ~30% by weight and a filler equivalent to 1~20% by weight, and the residual gas amount of the volatile blowing agent is controlled to 0.3 mol/kg or less. On the other hand, the non-foamed resin film (3) is made of a thermoplastic resin film having a thickness of 5 to 600 μm.

The foamed sheet of this invention exhibits extremely good formability for deep drawing, and is especially suitable for deep drawing with a draw ratio (b/a) of 1.0 or more, as shown in FIG. A shaped article (4) can be easily obtained without losing the desired strength. Furthermore, a large number of molded products can be produced more efficiently from the same size of original fabric than in the past. For example, 600 sheets made of conventional polystyrene sheet
When making a pot-shaped molded product (4) as shown in Fig. 2 with a diameter of 92mm and a depth of 1051mm from the original fabric of avX600 (including non-foamed resin film laminate products), use a conventional molding sheet). (l'), as shown in FIG.
It is possible to make 5 pieces, and it is also possible to make more dense molds.

The polystyrene resin that is the base resin of the sheet-like foam of this invention refers to a polymer whose main constituent unit is a styrene vinyl monomer such as styrene, methylstyrene, or dimethylstyrene, and other vinyl monomers, For example, acrylic acid, methacrylic acid or esters thereof,
It may also be a copolymer with acrylonitrile, acrylamide, methacrylnitrile, maleic anhydride, or the like.

The sheet-like foam of the present invention is obtained by subjecting the resin composition containing this polystyrene resin, rubber component, and filler to extrusion foam molding.

The rubber component is contained in an amount of 1 to 30% by weight based on the polystyrene resin as a blend component or copolymer component. Various rubber components can be used, but when used as a blend component, it is appropriate to add nihaftadiene rubber, ethylene-propylene rubber, styrene-butadiene rubber, polyethylene, etc. to the polystyrene resin. When used as a polymerization component, it is appropriate to use a polystyrene resin made by copolymerizing monomers or oligomers such as butadiene, isoprene, chlorobrene, etc. in a predetermined molar ratio (in this case, copolymerization as a polystyrene resin) is appropriate. It will be understood that when a polymer is used, it will be in a terpolymer state including the rubber component).

If the rubber component is less than 1% by weight, the opening of the resulting deep-drawn product, especially the lip in the case of a tap, will have insufficient strength and break easily, making it unsuitable for practical use, and furthermore, it will not elongate during molding. Even if it is sufficient, production efficiency decreases and it is inappropriate. In addition, if the weight exceeds 30, air bubbles become interconnected, making the molded product soft and lacking in stiffness.Additionally, if hot water or the like is poured into the molded product, bubbles will occur, making it unsuitable, and the smell of rubber will become stronger. , it is unsuitable as a raw material for forming deep-drawn containers, which are commonly used as food containers. Usually, the preferred content is 1 to 20% by weight.

On the other hand, fillers are effective in improving the appearance, dimensional accuracy, and dimensional stability of molded products. If the content of the filler is less than 1% by weight, the amount of gas and bubbles cannot be adjusted sufficiently, and the thickness of the product during molding cannot be controlled sufficiently, which is inappropriate. If it exceeds 20 inches, the gas amount and bubbles can be adjusted, but the elongation of the original fabric during molding becomes poor, which is inappropriate. Usually, the preferred content is 4 to 5% by weight. Examples of such fillers include general inorganic fillers such as Merck, calcium carbonate, shirasu, gypsum, carbon black, white carbon, magnesium carbonate, clay, natural guinic acid, and metal powder.

The thickness of the sheet-like foam is adjusted so that the resulting composite sheet has a thickness of 1 to Btmtt. When the thickness of the composite sheet is less than 1M1, it is difficult to perform deep drawing even when other conditions are adjusted (particularly when the drawing ratio is 1 or more), and when it exceeds 3mg, the formability, especially the quality of the molded product, is difficult. It is difficult to balance the side wall and bottom thickness, making it inappropriate.
In particular, it is preferable to adjust the thickness to 2 to 3M as a point-bonded sheet that can be obtained with higher efficiency than conventional container-shaped molded products such as the pot shown in Figure 2, which has a high drawing ratio. .

Such a sheet-like foam can be obtained by a so-called extrusion foaming method using various foaming agents.

As the blowing agent, various volatile blowing agents and decomposable blowing agents can be used in a conventional manner. Volatile blowing agents include hydrocarbons with boiling points of about -40°C to 45°C, such as haflobane, butane, and pentane, and boiling points of about -47°C to 45°C, such as trichloromonofluoromethane, dichlorodifluoromethane, and 1,2-dichlorotetrafluoroethane. ℃ halogenated hydrocarbons and mixtures thereof are suitable. Examples of decomposable blowing agents include organic blowing agents such as azodicarbonamide, dinitrosopentamethylenetetramine, and 4,4-oxybis(benzenesulfonylhydrazide), and organic blowing agents such as sodium bicarbonate or citric acid or their salts. A combination with a carbonate (however, each of these may be coated with a coating agent such as liquid paraffin) is suitable. Depending on the case, carbon dioxide, nitrogen gas, water, etc. can also be applied.
These are fed into the extruder in a conventional manner.

However, the amount of residual gas of the blowing agent in the sheet-like foam is 0.3 mol/kg or less. If the amount of residual gas is large, secondary foaming due to heating during secondary molding will be large, and the resulting molded product will not come out easily, which is inappropriate. A preferable amount of residual gas is 0.03 to 0.8 mol/glume. In particular, if the extrusion conditions such as the amount of blowing agent are adjusted so that the amount of residual gas is 0.03 to 0.3 mol/kg immediately after sheet creation, secondary molding can be performed continuously on the same line without aging. Simultaneous molding (
In-line molding) becomes possible, making it more economical. In addition, if the amount of residual residue exceeds 0.3 mol/kg immediately after sheet production, the sheet may be heated at 40 to 50°C, for example.
It is necessary to heat the product to a certain temperature to degas it, or to set the degassing time.

The polystyrene foam sheet for forming deep-drawn containers of the present invention can be obtained by laminating a non-foamed resin film on one side of the above sheet-like foam. As the non-foamed resin film, it is appropriate to use a thermoplastic resin film with a thickness of 5 to 600 μm.

In some cases, films may be laminated on both sides.

The resin of the thermoplastic resin film includes polystyrene, polyethylene, high-impact polystyrene which is a mixture or copolymer of polystyrene and rubber, polypropylene,
Examples include resins that can generally be made into sheets, such as polyethylene terephthalate. Among these, polystyrene, high-density polyethylene, and high-impact polystyrene are preferred in terms of moldability, and polystyrene and high-impact polystyrene are more preferred in terms of ease of use. .

If the thickness of the film is less than 5 μm, it will not stretch well as a raw material, and the mechanical strength of the resulting molded product will be low, making it unsuitable. Moreover, if it exceeds 600 μm, the bubbles in the lip part will be crushed and communicated when punching out after molding, which will cause the problem of peeling of the film and the sheet-like foam, which is also disadvantageous in terms of economy, and is therefore not suitable. . The thickness when producing a molded product as shown in Figure 2 is 30 to 500μ.
m is usually preferred.

Note that the thermoplastic resin film may be laminated onto the sheet-like foam by various methods.

For example, when laminating a thermoplastic resin film onto a sheet-like foam in a die, it may be carried out using a merging die (for example, a cross-to-ladder die), or it may be laminated by flowing in before the die slit. good.

In addition, when laminating sheet-like foams after extrusion and foaming, it is also possible to combine a thermoplastic resin film extruder with a take-up machine to extrude the films and laminate them continuously. This may be carried out by appropriately laminating a thermoplastic resin film on a sheet-like foam. In addition,
The above-mentioned lamination may be performed by using an adhesive or by heat fusion. Note that various adhesives can be used, but vinyl acetate-based adhesives such as ETA copolymer and rubber-based adhesives such as BBH are preferred. These adhesives may be used in any form of solvent type, emulsion type, or film type.

The thus obtained polystyrene foam sheet for forming deep-drawn containers of the present invention can be used to form deep-drawn container-like molded products by the bonding effect using a specific sheet-like foam and a specific thermoplastic resin film. can be obtained easily and with good quality,
Furthermore, the production efficiency of molded products is much improved compared to conventional raw fabrics, making it extremely useful as a molding fabric for mass production.

Hereinafter, the foamed sheet of the present invention will be explained in detail with reference to Examples.

Examples Rubber content and amount of filler in the sheet-like foam of the polystyrene foam sheet for deep-drawn container molding of the present invention.

1 foaming ratio to the thickness, and the rubber content of the non-foamed resin film,
The diameter is 106mg with the thickness changed appropriately.

Depth 106ff shoulder, taper 7 degree tip, size 6
The above foam sheet of 00 x 600gffl was molded so that 16 pieces could be made, and the 16 pieces obtained without any damage were evaluated as ○, △ if 1 of them was damaged, and × if 2 or more were damaged. And so. The obtained tip was laid on its side, and the original size of the lip was compressed by 25 inches from the top. If it did not crack, the lip crack was rated as ○, and if it cracked, it was rated as ×.

The overall evaluation was based on moldability and cracking.

Table 1 shows the results along with comparative examples.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view illustrating a polystyrene foam sheet for forming deep-drawn containers of the present invention, FIG. 2 is a perspective view illustrating a pot-shaped molded product that can be efficiently obtained by the sheet of the present invention, and FIG. 8 FIG. 4 is a schematic plan explanatory view showing the molding of a conventional molding sheet, and FIG. 4 is a view corresponding to FIG. 3 showing the molding of the sheet of the present invention. (1)--polystyrene foam sheet for deep drawing p-forming,
(2)...Sheet-like foam, (3)...Non-foamed resin film, (4)...Cop-shaped molded product.

Claims (1)

[Scope of Claims] 1. Consists of a composite sheet with a thickness of 1 to 8H, in which a non-foamed resin film is laminated on at least one side of a sheet-like foam whose base resin is polystyrene resin, and the sheet-like foam has a base material of polystyrene resin. From a sheet-like foam containing a rubber component equivalent to 1 to 30% by weight and a filler equivalent to 1 to 20% by weight based on the resin, and in which the residual gas amount of the blowing agent is controlled to 0.8 mol / kg or less The above non-foamed resin film has a thickness of 5 to 600
A polystyrene foam sheet for forming deep-drawn containers, characterized by being made of a μm thermoplastic resin film. 2. The foamed sheet according to claim 1, wherein the non-foamed resin film has a thickness of 30 to 500 μm. 8. The foamed sheet according to claim 1, wherein the amount of residual gas of the foaming agent is 0.08 to 0.3 mol/kg.