JPH0741700B2 - Shrink film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shrink film having excellent metallic luster, and more particularly to a shrink film which can be mechanically automatically loaded as a bottle cap seal or a body label.

[0002]

2. Description of the Related Art Shrink film with excellent metallic luster used for bottle cap seals and body labels is 10%.
It is necessary that the above heat shrinkage is possible, and that even if the heat shrinkage is 10% or more, a desired appearance is required. Therefore, the present inventor has conducted diligent research and found that the heat shrinkable film is
It was found that a desired effect can be obtained by laminating a metal thin film via an adhesive having a dry film elongation of 00% or more, and a patent application has been filed for this (Japanese Patent Laid-Open No. 63-37931). And JP-A-2-43041). Here, it is also disclosed that a protective film is formed on the metal thin film.

However, in the shrink film disclosed in JP-A-63-37931, a large amount of foil dust is generated due to heat shrinkage, and only a product having a low commercial value can be obtained, and JP-A-2-43041. As described in Japanese Patent Publication, a shrink film having heat-shrinkable films on both front and back surfaces of a metal thin film can prevent the occurrence of foil dust, but it has poor shrinkability, and heat shrinkage reduces the metallic luster and is costly. There was a flaw. Further, these conventional shrink films cannot be mechanically automatically loaded as a bottle cap seal or the like, but have been used by hand.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves all of the drawbacks of the conventional shrink film, has high stability of metallic luster when heat-shrinked, and does not cause foil dust at all. It is an object of the present invention to provide a shrink film which has good heat shrinkability and is practical as a cap seal for bottles and a body label, and which can be easily mechanically automatically loaded and is easy to handle.

[0005]

In the present invention, the dry film elongation (JIS K-7113) is provided on one surface of the heat-shrinkable film.
The dry film elongation according to (hereinafter, simply referred to as elongation) is 20
0% or more adhesive layer, metal thin film, dry film elongation 20%
The following low elongation resin layers, dry film elongation is 100-800%
The above problems were solved by sequentially laminating the high-elongation resin layers of 1 and adding a lubricant to the high-elongation resin layers.

First, the shrink film of the present invention has a unique structure in which a high elongation resin layer having a high elongation is provided on the surface of a metal thin film via a low elongation resin layer having a low elongation. By taking, the desired effect was obtained.

The thickness of the high elongation resin layer is larger than that of the low elongation resin layer, and the thickness of the low elongation resin layer is 0.5 to 0.5.
It is preferable that the thickness of the high elongation resin layer is 3 μm and the thickness of the high elongation resin layer is 1 to 5 μm.

The shrink film of the present invention is made of, for example, polyvinyl chloride, polyethylene, polypropylene, polyester, etc., a metal thin film, a low elongation resin layer, and a low elongation resin layer on one side of a heat shrinkable film having a heat shrinkability of 10% or more. It can be manufactured by transferring a transfer foil composed of a high elongation resin layer with an adhesive such as an adhesive.

The heat-shrinkable film and the metal thin film are adhered to each other using an adhesive having a dry film elongation (according to JIS K-7113) of 200% or more, so that the heat-shrinkable film and the metal thin film can be shrunk in good quality, It is possible to obtain a product having a uniform metallic luster. As such an adhesive, generally 20
An acrylic resin-based adhesive having a dry film elongation of about 0 to 1000%, urethane or other rubber-based adhesive, vinyl chloride / vinyl acetate copolymer-based adhesive, or so-called adhesive can be used. The use of adhesives is especially preferred.

Next, the metal thin film may be made of any of aluminum, chromium, nickel, silver, tin, and other metals or alloys, and the formation method thereof is not particularly limited. For example, it can be formed by vacuum vapor deposition, sputtering, ion plating or the like.

Further, the low elongation resin layer located on the metal thin film protects the metal thin film, and at the same time, the metal thin film having no elasticity does not distort due to the displacement of the adhesive layer at the time of heat shrinkage, and a uniform metal is formed. It is useful for maintaining gloss. Therefore, it is preferable that this resin layer is formed of a resin that is relatively hard and has an elongation of 20% or less, particularly 10% or less, which does not change during heat shrinkage. For example, acrylic resin, melamine resin, phenol resin, which has excellent metal vapor deposition characteristics,
It is preferably formed of urethane resin, vinyl chloride resin, epoxy resin, unsaturated polyester resin, or the like.

In the present invention, a high elongation resin layer is further formed on such a low elongation resin layer, and this high elongation resin layer is useful for preventing foil dust during heat shrinkage. It also has the effect of improving the stability of metallic luster and improving heat shrinkability. In order to exert all these effects synergistically, the thickness of the high elongation resin layer and the low elongation resin layer is limited to the above range, and moreover, the thickness of the high elongation resin layer is It is necessary to make it thicker than the thickness of the low elongation resin layer.

As the resin forming the high elongation resin layer, for example, synthetic rubber such as urethane rubber, fluororubber, polyisobutylene rubber, silicone rubber, nitrile rubber, styrene-butadiene rubber or natural rubber can be used.

The total thickness of the high elongation resin layer and the low elongation resin layer is 1/5 or less, particularly 1/10 or less, of the thickness of the heat shrinkable film which is the main component of the shrink film of the present invention. It is preferably set.

Further, a lubricant such as white carbon or polyethylene wax is added to the high elongation resin layer to enhance the surface smoothness of the shrink film and improve the mechanical automatic loading property in the cap seal and the like. The amount of the lubricant added is preferably about 2 to 10% by weight, particularly about 6 to 7% by weight, based on the solid content of the high elongation resin.

[0016]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples. In addition, all the thicknesses shown in the examples are the thickness of the dry film. The cap seal test in the examples was carried out under the following conditions using a Coca-Cola regular size bottle having a maximum diameter of 28.5 mm.

1. Thermal shrinkage condition Model used Kokusai Denki Hiace tunnel Temperature and time 200 ℃ × 10 seconds Margin ratio Margin ratio to maximum aperture 20%

2. Foil dust resistance After heat shrinking under the condition of 1, the inner surface of the cap seal is touched with a finger 10
The foil was rubbed repeatedly and the peeled state of the foil was examined. When the foil was not peeled, it was evaluated as ◯, when it was slightly peeled, as Δ, and when it was significantly peeled, as x.

3. Metallic gloss Compared with the metallic gloss before heat shrinkage, the metallic gloss after heat-shrinking under the conditions of 1 is ○ when the metallic gloss is unchanged, Δ when the metallic gloss is slightly changed, and the metallic gloss is considerably The deterioration was evaluated as x.

4. Thermal shrinkage suitability Under the conditions of 1, the one that fits the cap and surely undergoes the heat shrinkage is evaluated as ◯, and the one that does not heat shrink well with good adhesion to the cap is evaluated as Δ.

Example 1-Drying Film Elongation of High Elongation Resin Layer-Olestar NL type (urethane elastomer, dry film elongation 80%, 100%, 300% of Mitsui Toatsu) on the untreated surface of the polypropylene film. , 400%, 500%, 8
00%, 1000% of 5%) was coated to a thickness of 2 μm by a gravure coating method, and acrylic / urethane resin (dry film elongation 10%) was coated thereon to a thickness of 1.50 m by the gravure coating method. After that, aluminum was vapor-deposited with a vacuum vapor deposition machine to a thickness of 500 Å. A 20% liquid adhesive (COPONYL 8020 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) on this aluminum vapor-deposited surface, 2 μm thick, and a heat shrinkage ratio of 60% or more, Hishirex 503 (heat shrinkable vinyl chloride film manufactured by Mitsubishi Plastics Co., Ltd., 60 μm (Thickness) and then the polypropylene film was peeled off to obtain the intended shrink film. This shrink film was formed into a tube and the cap seal test was performed. The results are shown in Table 1.

[0022]

[Table 1]

As shown in Table 1, a product using a resin having a dry film elongation of 100 to 800%, particularly 300 to 500% as a high elongation resin does not cause foil dust at all.
A cap seal with a very good metallic luster and a stone wall-like appearance and good adhesion was obtained. However, the product using a resin having a dry film elongation of 80% as the high-elongation resin was distorted in metallic luster after heat shrinkage, and foil dust could not be completely prevented. On the contrary, when the dry film elongation of the high elongation resin exceeds 800% and becomes 1000%, the resin becomes too soft and the metallic luster is deteriorated. In this case, it is difficult to obtain a product compatible with an automatic machine even if an additive is added.

Example 2-Thickness of High Elongation Resin Layer- As a high elongation resin, Mitsui Toatsu's Orestar NL type (urethane elastomer, dry film elongation 300%) was used, and the coating film The thickness is 0.8μm, 1μm, 3μm,
Except having changed into 5 micrometers and 6 micrometers, the method similar to Example 1 was implemented and 5 types of shrink films were obtained.
The results of testing each shrink film in the same manner as in Example 1 are shown in Table 2.

[0025]

[Table 2] However, products H and L are comparative examples.

From the results shown in Table 2, the high elongation resin layer has a thickness of 1
At ~ 5μm, a very good quality cap seal was possible, but at a thickness of 0.8μm, foil dust is liable to occur after heat shrinkage, and the metallic luster is also lacking. It can be seen that when the thickness is 6 μm, it is too soft to reduce the metallic luster, and at the same time, the heat shrinkability is deteriorated.

Comparative Example 1 A wax release layer having a thickness of 1 μm was provided on one surface of a polyester film by a gravure coater, and an acrylic-urethane protective layer having a thickness of 1.5 μm was formed on the wax release layer having a thickness of 400 to 400 μm.
A transfer foil provided with a 500Å aluminum vapor deposition layer was prepared, and U-Lock N- was placed on the aluminum vapor deposition surface of the transfer foil.
502 (Honey Kasei's adhesive, dry film elongation 700
~ 800%) to a thickness of 2 μm and a thickness of 60 μm
After being attached to the heat-shrinkable vinyl chloride film (Hishirex 503 manufactured by Mitsubishi Plastics Co., Ltd.), the polyester film was peeled off to obtain a shrink film as disclosed in JP-A-63-37931.

Comparative Example 2 A wax release layer having a thickness of 1 μm was provided on one surface of a polyester film by a gravure coater, and an acrylic-urethane protective layer having a thickness of 1.5 μm, a thickness of 400 to 400 μm.
A transfer foil provided with a 500Å aluminum vapor deposition layer was prepared, and U-Lock N-502 was placed on the aluminum vapor deposition surface.
(Honey Chemical Co., Ltd. adhesive, dry film elongation 700-80
(0%) to a thickness of 2 μm and laminated with a heat-shrinkable vinyl chloride film (Hishilex 503 manufactured by Mitsubishi Plastics Co., Ltd.) having a thickness of 30 μm, the polyester film is peeled off, and the transfer foil surface of the obtained film In addition, the same adhesive ULOCK N-502 as described above was coated to a thickness of 2 μm, and a heat-shrinkable vinyl chloride film (Hishirex 503 manufactured by Mitsubishi Plastics Co., Ltd.) having a thickness of 30 μm was laminated thereon. A shrink film as disclosed in JP-A-2-43041 was obtained.

The results of the cap seal test of the products B and C of Example 1 and the products of Comparative Examples 1 and 2 under the above conditions are shown in Table 3.
Shown in.

[0030]

[Table 3]

Example 3-Mechanical automatic loading of cap seal-As a high elongation resin, Mitsui Toatsu's Orestar NL type (urethane elastomer, dry film elongation 300%) was used.
The same method as in Example 1 was carried out except that polyethylene wax (lubricant) added at 6% in terms of solid content was used. The shrink film thus obtained has the same metallic luster as that of the product C of Example 1, with no foil dust.
It enables a reliable cap seal and is extremely suitable for mechanical automatic loading of the cap seal.

Next, this method was carried out by changing the kind and amount of the lubricant added to the high elongation resin layer, and the automatic loading property of the obtained product in the cap seal was examined.
The results are shown in Table 4 (however, the addition amount of the lubricant indicates the solid content ratio in the high elongation resin layer).

[0033]

[Table 4]

When either polyethylene wax or white carbon was used as the lubricant, good results were obtained when the amount added to the high elongation resin was in the range of 2 to 10% by weight. When the amount of the lubricant was too large, the flexibility of the high elongation resin layer was lost, peeling occurred on the surface after shrinkage, and the appearance deteriorated.

[0035]

INDUSTRIAL APPLICABILITY The shrink film of the present invention is extremely excellent in heat shrinkability and can be used efficiently as a cap seal for bottles or a body label without causing foil dust while maintaining a good metallic luster. It is possible, and mechanical automatic loading is also possible. In addition, since it can be manufactured by a simple coating and transfer method, it is economically useful.

Claims (2)

[Claims] 1. A heat-shrinkable film having a dry film elongation of 20.
0% or more adhesive layer, metal thin film, dry film elongation 20%
The following low elongation resin layers, dry film elongation is 100-800%
Of the high elongation resin layer, wherein the low elongation resin layer has a thickness of 0.5 to 3 μm, the high elongation resin layer has a thickness of 1 to 5 μm, and The thickness of the layer is thicker than that of the low elongation resin layer, and the high elongation resin layer solidifies the lubricant.
A shrink film excellent in metallic luster, characterized in that it is contained in a proportion of 2 to 10% by weight . 2. The dry film elongation of the high elongation resin layer is 300 to.
The shrink film according to claim 1, which is 500%.