JPH08281882A - Polystyrene film - Google Patents

Abstract

PURPOSE: To provide an inexpensive polystyrene film composed of a sandwich like laminate of polystyrene layer/acrylonitrile/butadiene/ethylene copolymer layer/polystyrene layer, excellent in transparency and impact resistance and improved in the balance of tear strengths in longitudinal and lateral directions. CONSTITUTION: A polystyrene film is composed of of a sandwich like laminate of general polystyrene (GPPS) layer/transparent acrylonitrile/butadiene/ethylene copolymer (transparent ABS) layer/GPPS layer. The transparent ABS layer is set to an intermediate layer and the GPPS layers are arranged on both surfaces thereof to obtain the polystyrene film excellent in transparency, glossiness and impact strength. As a molding method, a T-die method and an inflation method can be used and the polystyrene film good in the balance of tear strengths in longitudinal and lateral directions is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polystyrene film (hereinafter referred to as PS film) which is inexpensive, has excellent transparency and impact resistance and has a good balance of tear strength in the machine direction or the transverse direction.

Such a polystyrene film is, for example, a film for packaging fresh leafy vegetables such as lettuce; a laminating film for forming fruit containers, lunch boxes, trays, donburi, cups, lids, molded articles with paints, envelopes, etc. Films for window pasting, display panels, flower packaging, cake packaging, labels; table cloths, toys, ornaments, etc.

Incidentally, "film" is used throughout this specification.
The term is not defined in a strict sense based on the thickness, but includes a relatively thick one that usually belongs to a sheet.

[0004]

2. Description of the Related Art To obtain a transparent PS film, if a general-purpose polystyrene (hereinafter referred to as GPPS) is formed into a thin film by extrusion molding, only a brittle and easily tearable film can be obtained. Therefore, in order to improve the impact strength of this film, conventionally, GPPS is once formed into a sheet shape, and the sheet is reheated to be biaxially stretched in the longitudinal direction and the transverse direction, whereby a transparent and tear-resistant stretch is obtained. A polystyrene film (referred to as an OPS film) was obtained.

Further, a blend of GPPS with a styrene thermoplastic elastomer such as a styrene-butylene-styrene copolymer (SBS) or a styrene-ethylene-butadiene-styrene copolymer (SEBS), or a combination of GPPS and transparent resistance. Blend with impact polystyrene (hereinafter referred to as transparent HIPS), and further GPPS and transparent acrylonitrile-butadiene-styrene copolymer (transparent ABS)
A PS film was obtained by using a blend of and as a material.

[0006]

However, in the film manufacturing method by the biaxial stretching as described above, the equipment cost of the manufacturing apparatus is increased and a large installation area of the apparatus is required, and in addition, the number of steps is large. There is a drawback.

Further, in the method using the blend of GPPS and the styrene thermoplastic elastomer, the obtained film becomes opaque, and in the method using the blend of GPPS and the transparent HIPS, the transparent HIPS is expensive and the material cost is high. The bulk and method using a blend of GPPS and clear ABS also resulted in an opaque film.

In view of the above points, an object of the present invention is that the obtained film becomes opaque even when an expensive biaxial stretching equipment is not required and the impact resistance is improved without stretching. Another object of the present invention is to provide a PS film that solves the problem that the material cost is very expensive, is inexpensive, has excellent transparency and impact resistance, and has a good balance of tear strength in the machine direction or the transverse direction.

[0009]

The present invention has been devised to solve the above problems by laminating a specific combination of resins in a sandwich form by three-layer coextrusion, not by stretching or blending.

That is, the polystyrene film according to the present invention comprises a sandwich-like laminate of GPPS layer / transparent ABS layer / GPPS layer.

The layer thickness ratio of GPPS layer / transparent ABS layer / GPPS layer is preferably in the range of 2: 1: 2-1: 8: 1.

The total thickness of the PS film obtained is preferably 15 to 500 μm.

As a molding method, a method using a T-die is suitable in terms of thickness accuracy, and is superior in transparency, gloss and impact resistance to the method using expensive transparent HIPS, and in the longitudinal direction or the lateral direction. A PS film having a good tear strength balance can be obtained.

As another molding method, an inflation molding method can be adopted. By the inflation molding method, a PS film having a particularly well-balanced tear strength in the machine direction or the transverse direction can be obtained.

In order to prevent the formation of wrinkles in the inflation molding method, it is preferable to provide a heat retaining tube between the tip of the mold and the folding guide plate to gradually cool the tubular molded article. Cut the resulting tube-shaped molded product into pieces 2
Use a flat film.

[0016]

[Function] SBS, SEBS, transparent ABS, etc. are all rubber components (butadiene) to improve impact resistance.
When these are blended with GPPS, the compatibility is not so good, so that only an opaque film is obtained.

In the present invention, the transparent ABS layer is used as an intermediate layer,
By arranging the GPPS layer, which is a transparent styrene layer, on both sides of this, P excellent in transparency, glossiness and impact resistance strength can be obtained.
An S film is obtained.

By adopting the inflation molding method, a PS film having a well-balanced tear strength in the machine direction or the transverse direction can be obtained.

Further, the PS film according to the present invention has O
Since the molecules are not oriented like the PS film, it is suitable for vacuum forming applications such as trays and cups.

[0020]

EXAMPLES Next, the present invention will be specifically described with reference to Examples.

Example 1 "DIAREX HF-" manufactured by Mitsubishi Chemical Corporation as GPPS
77 307 crystal "and" JSR ABS57NP "manufactured by Japan Synthetic Rubber Co., Ltd. as an ABS, and a GPPS layer / transparent ABS layer / GPPS layer sandwiched by three-layer coextrusion by a T-die method at a molding temperature of 180 to 220 ° C. A PS film composed of a laminate was obtained.

The layer thickness ratio of GPPS layer / transparent ABS layer / GPPS layer was 1: 1: 1, and the total thickness of the PS film obtained was 25 μm.

Example 2 The layer thickness ratio of GPPS layer / transparent ABS layer / GPPS layer is 1:
PS was obtained by the same operation as in Example 1 except that the ratio was changed to 2: 1.
I got a film.

Example 3 The layer thickness ratio of GPPS layer / transparent ABS layer / GPPS layer is 1:
PS was obtained by the same operation as in Example 1 except that the ratio was changed to 4: 1.
I got a film.

Example 4 A PS film was obtained by the same operation as in Example 1 except that the inflation method (BUR = 2.0) was used instead of the T-die method.

Example 5 A PS film was obtained by the same operation as in Example 3 except that the inflation method (BUR = 2.0) was used instead of the T-die method.

Comparative Example 1 "OPS film" manufactured by Asahi Kasei Corporation was prepared for the performance test described later.

Comparative Example 2 An unstretched PS film was obtained using a 1: 1 blend of GPPS and transparent SBS as a material.

Performance Test For each PS film obtained in Examples and Comparative Examples, haze, glossiness, tear strength and impact strength were measured.

The test method for each item is as described in the following JIS standard.

Haze: JIS K 7105 Gloss: JIS K 7105 Tear strength: JIS P 8116 Impact strength: JIS K 8134

Table 1 shows the obtained measurement results.

[0033]

[Table 1] As is clear from Table 1, it is recognized that the PS films of Examples show good values in all items.

[0034]

The PS film according to the present invention is transparent AB.
Since the S layer is used as an intermediate layer and the GPPS layer which is a transparent styrene layer is arranged on both surfaces thereof, the transparency, the glossiness,
It has excellent impact resistance and strength.

By adopting the inflation molding method, a PS film having a well-balanced tear strength in the machine direction or the transverse direction can be obtained.

In addition, the PS film according to the present invention is
It is suitable for vacuum forming applications such as trays and cups because the molecules do not orient like in PS films.

Claims (1)

[Claims] 1. A polystyrene film comprising a sandwich layer laminate of polystyrene layer / acrylonitrile-butadiene-styrene copolymer layer / polystyrene layer.