JPH081878A - Heat-shrinkable composite film - Google Patents

Abstract

PURPOSE:To provide a heat-shrinkable composite film excellent in center sealability and pinhole resistance and capable of being suitably used for lateral pillow shrink packing capable of applying tight packing to a package and capable of imparting surface gloss, the so-called stretch like appearance. CONSTITUTION:A heat-shrinkable composite film is obtained by laminating a polyamide resin layer composed of nylon 6 or nylon 12, a polyolefinic adhesive resin layer, a saponified ethylene/vinyl acetate copolymer layer, a polyamide resin layer, a polyolefinic adhesive resin layer and a sealable resin layer in this order and the heat shrinkage factor thereof at 130 deg.C (heating time;3sec) is 15% or more in both of the longitudinal and lateral directions of the film and the shrinkage stress thereof at this time is 70gf/15mm width or less. By this constitution, the heat-shrinkable composite film excellent in center sealability and pinhole resistance is obtained and can be suitably used in lateral pillow shrink packing capable of imparting stretch like appearance to a package and packing content in a stated arranged in a tray.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable composite film, which is particularly excellent in center sealability and pinhole resistance, can be tightly packed with a package, and has a glossy surface. The present invention relates to a heat-shrinkable composite film that can be suitably used for horizontal pillow shrink-wrapping that can impart a unique appearance.

[0002]

2. Description of the Related Art A horizontal pillow shrink wrapping method in which contents are stored in a tray that moves in a horizontal direction (horizontal direction) and at the same time a heat-shrinkable film is covered while center-sealing, and then the film is heat-shrinked It is used to package things.

Examples of the heat-shrinkable composite film used in such a horizontal pillow shrink-wrapping method include polyolefin resin / adhesive resin / ethylene-vinyl acetate copolymer saponified product / adhesive resin / polyolefin resin, From polyolefin resin / adhesive resin / polyvinylidene chloride resin / adhesive resin / polyolefin resin, polyolefin resin / adhesive resin / polyamide resin / saponified ethylene / vinyl acetate copolymer / adhesive resin / polyolefin resin The heat shrinkable composite film is known.

However, in any of the composite films having the above-mentioned constitution, since the polyolefin resin layer is the outermost layer, there is a problem that the film is apt to adhere to the surface of the heat sealer at the time of center sealing and the center sealing property is poor.
Further, there is a problem that the shrinkage stress at the time of heat shrinkage is too large and the tray is deformed. Furthermore, the composite film of the above and the above has a problem that the pinhole resistance is inferior.

[0005]

The present invention has found a heat-shrinkable composite film capable of solving the above problems.
The main points are nylon 6 or nylon 12
A heat-shrinkable composite film in which a polyamide resin layer, a polyolefin-based adhesive resin layer, a saponified ethylene-vinyl acetate copolymer layer, a polyamide resin layer, a polyolefin-based adhesive resin layer, and a sealing resin layer are laminated in this order. The heat shrinkage rate at 130 ° C (heating time, 3 seconds) is 15% or more in both the longitudinal and transverse directions of the film, and the shrinking stress at that time is 70 gf / 15 mm width or less. It is in a shrinkable composite film.

The composite film of the present invention has the outermost layer (first layer): polyamide resin layer / second layer as the layer structure of the film.
Layer: Polyolefin adhesive resin layer / Third layer: Ethylene-
A six-layer composite film comprising a saponified vinyl acetate copolymer layer / fourth layer: polyamide resin layer / fifth layer: polyolefin-based adhesive resin layer / innermost layer (sixth layer): sealing resin layer, The outermost layer is nylon 6 (hereinafter "6Ny")
A polyamide resin layer made of nylon 12 (hereinafter referred to as “12Ny”) is provided. By providing such a specific polyamide resin layer as the outermost layer,
The heat resistance can be improved, the film can be prevented from adhering to the surface of the heat sealer at the time of center sealing, and gloss can be imparted to the surface of the film to make it stretch-like.

The polyolefin-based adhesive resin layers (hereinafter referred to as "PO contact") used for the second and fifth layers are acid-modified by grafting at least one monomer selected from unsaturated carboxylic acids or their derivatives. Polyolefin resin can be preferably used, and the first layer and the third layer, and the fourth layer and the sixth layer can be firmly adhered to each other.

The third saponified ethylene-vinyl acetate copolymer layer (hereinafter referred to as "EVOH") is a barrier resin layer having an ethylene content of 30 to 60 mol% and a saponification degree of 95% or more. From the viewpoint of moldability and barrier properties, the above are preferable.

For the innermost sealing resin layer, an ionomer resin, polyethylene, or a copolymer of ethylene and other components, such as ethylene-vinyl acetate copolymer, can be used, especially in the sealing portion with the lid material. It is preferable to use an ionomer resin that can improve the transparency of the. The thickness of the sealing resin layer is preferably in the range of 30 to 150 μm. Further, although a polyamide resin layer is arranged in the fourth layer, the polyamide resin used may be the same as or different from the resin in the first layer, and the film strength such as pinhole resistance can be improved. From the viewpoint of shrinkage characteristics, it is preferable to use a copolymer of nylon 6 and nylon 66 (hereinafter referred to as "6-66 Ny").

In the composite film of the present invention, it is necessary that the composite film has a specific heat shrinkage property together with the above-mentioned layer constitution,
The heat shrinkage rate (heating time, 3 seconds) is 15% or more in the longitudinal and transverse directions of the film, and the shrinkage stress at that time is 7
The width is 0 gf / 15 mm or less. Thermal shrinkage of 130 ° C ×
In 3 seconds, 15% or more in both the vertical and horizontal directions,
This is to improve the filling property of the tray and to make it more tightly packed to give a stretch-like appearance. The heat shrinkage is 15 mm wide and the samples cut into strips are spaced at 100 intervals.
It was mounted on a chuck set to mm and immersed in silicone oil at 130 ° C. for 3 seconds for measurement. Further, the reason why the shrinkage stress during heat shrinkage is 70 gf / 15 mm width or less is to prevent the deformation of the tray.

The shrinkage stress is measured by attaching a sample cut into a rectangular shape with a width of 15 mm so that the main shrinkage direction is the longitudinal direction, mounting it on a chuck with a gap of 150 mm and immersing it in silicone oil at 130 ° C. The maximum shrinkage stress was measured. As a method of imparting the above-mentioned heat shrinkage property to the composite film, the conditions such as the stretching ratio and the relaxation rate of the film may be appropriately determined. Usually, the stretching ratio of the film is about 3.0 times in the longitudinal direction and the transverse direction, and after stretching. The relaxation rate of the film may be about 13 to 15%.

The present invention will be described below with reference to examples.

[0013]

【Example】

Example 1 Layer structure: Outermost layer (first layer): 6Ny layer, second layer: carboxylic acid-modified ethylene-vinyl acetate copolymer (PO contact), third layer: EVOH, fourth layer: 6-66Ny, Fifth layer: carboxylic acid modified ethylene-vinyl acetate copolymer (PO contact), sixth layer: ethylene-vinyl acetate copolymer (EVA). Thickness: 6Ny / PO contact / EVOH / 6-66Ny / PO contact / EVA (2 μm / 2 μm / 3 μm / 7 μm / 2 μm / 9 μm) The composite film having the above-mentioned constitution is stretched by a co-extrusion molding method so that the stretching ratio is vertical and horizontal. Both films were 3.0 times, and the relaxation rate was 15% in the longitudinal direction and 13% in the lateral direction. The heat shrinkage rate of the obtained composite film at 130 ° C. (heating time, 3 seconds) was 30% in the longitudinal direction of the film and 18% in the transverse direction, and the shrinkage stress at that time was 60 gf / 15 mm width in the longitudinal direction and transverse direction. The width was 50 gf / 15 mm. Then, the composite film was laterally pillow-wrapped with a lateral pillow wrapping machine manufactured by Omori Machinery Co., Ltd. with the first layer facing outside.

The center sealability during lateral pillow packaging was good. In addition, 20 packages obtained were placed in a type A double cardboard case and dropped 6 times from a height of 1.5 m to evaluate the occurrence of vacuum leak (pinhole resistance). There was no. As a result of further evaluation of the appearance, there was no deformation of the tray, and a glossy stretch-like appearance was obtained.

Example 2 A composite film was obtained with the same contents as in Example 1 except that the outermost layer was 12 Ny. The shrinkage properties were the same as in Example 1. When the same evaluation as in Example 1 was carried out using the obtained package, the center sealability, pinhole resistance and appearance were all good.

Comparative Example 1 Layer structure: 12 Ny / PO contact / EVOH / 6 Ny / PO contact / EVA (2 μm / 2 μm / 3 μm / 7 μm / 2 μm / 9 μm) The composite film having the above structure was formed under the same conditions as in Example 1. did. The heat shrinkage rate of the obtained composite film at 130 ° C. (heating time, 3 seconds) was 20% in the machine direction and 28% in the machine direction, and the shrinkage stress at that time was 120 gf / 15 mm in both machine direction and machine direction. It was wide. When the same evaluation as in Example 1 was carried out using the obtained package, the center sealability and the pinhole resistance were good, but the shrinkage was too large and the tray was deformed, resulting in a problem in appearance. there were.

Comparative Example 2 A film having the same layer structure as in Example 2 was formed under the conditions that the stretching ratio was 3.0 times in both the longitudinal and transverse directions, and the relaxation rate was 20% in the longitudinal direction and 18% in the transverse direction. The heat shrinkage ratio of the obtained composite film at 130 ° C. (heating time, 3 seconds) was 14 in the longitudinal direction of the film.
%, 10% in the horizontal direction, and the contraction stress at that time is 7 in the vertical direction.
The width was 0 gf / 15 mm and the width was 60 gf / 15 mm in the lateral direction. When the same evaluation as in Example 1 was performed using the obtained package, the center sealability and the pinhole resistance were good, but the shrinkage was too small and the adhesion to the tray was poor, so the stretch It was inferior in likeness and had a problem in appearance.

Comparative Example 3 Example 1 except that the outermost layer was polypropylene (PP).
Stretch ratio is 3.5 in both longitudinal and transverse directions with the same layer structure as
The film was formed under the condition of no doubling and no relaxation. The heat shrinkage rate of the obtained composite film at 130 ° C. (heating time, 3 seconds) was 40% in the machine direction and 41% in the machine direction, and the shrinkage stress at that time was 110 gf / 15 mm in both machine direction and machine direction. It was wide. When the same evaluation as in Example 1 was carried out using the obtained package, the center sealability at the time of heat sealing was inferior, and the shrinkage was so large that the tray was deformed and there was a problem in appearance.

[0019]

As described above, according to the coextrusion composite film for deep drawing of the present invention, it is excellent in gloss, transparency, label adhesiveness, pinhole resistance, etc. It can be suitably used for packaging.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29K 77:00 105: 02 B29L 9:00

Claims (1)

[Claims] 1. A polyamide resin layer made of nylon 6 or nylon 12, a polyolefin-based adhesive resin layer, an ethylene-vinyl acetate copolymer saponified layer, a polyamide resin layer, a polyolefin-based adhesive resin layer, and a sealing resin layer in this order. A heat-shrinkable composite film laminated by
A heat-shrinkable composite characterized in that the heat shrinkage rate at 0 ° C. (heating time, 3 seconds) is 15% or more in both the longitudinal and transverse directions of the film, and the shrinkage stress at that time is 70 gf / 15 mm width or less. Film.