JPS63160826A - Multilayer film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a multilayer film, and more specifically, the present invention relates to a multilayer film that provides good protection for articles, has an excellent appearance, and is effective for packaging home appliances, office equipment, furniture, etc. The present invention relates to a multilayer film that can be used for.

[Prior art and problems to be solved by the invention] A three-layer film in which the middle layer is a foamed polyolefin layer and both outer layers are unfoamed polyolefin layers, or its inflation molding method is known (Japanese Patent Application Laid-open No. 57-2
0345. 61-16853゜61-130025.
6l-139435).

This film is described as being used for things such as cloaks, tablecloths, and square-bottom bags for shopping, taking advantage of its properties such as heat insulation, cushioning, and opacity. However, when this film is used to package home appliances, etc., the physical characteristics and appearance of the foam layer alone cannot provide sufficient product protection.

For this reason, the applicant has proposed a multilayer film in which the intermediate layer is made of a foamed resin and the two outer layers have different coefficients of friction (Japanese Patent Application No. 61-57070). However, simply making the friction coefficients of the two outer layers different is not necessarily sufficient, and scratches and the like occur during storage and transportation, especially for home appliances that have transparent resin parts. There was a problem that it could not be put into practical use.

In addition, a commercially available low-density polyethylene foam sheet (thickness 5
A laminate film of 00μ) and high-density polyethylene (13μ thick) requires many steps and is thick, resulting in problems not only in terms of cost and storage and transportation of packaging materials, but also in terms of handling.

It is an object of the present invention to solve the above-mentioned conventional problems and provide an inexpensive multilayer film that provides good protection for articles and has an excellent appearance.

[Means for solving problems]

That is, the present invention provides a multilayer film in which the intermediate layer is a polyolefin resin foam layer, the outer layer (A) is an ethylene-vinyl acetate copolymer layer, and the outer layer (B) is a high-density polyethylene resin layer.

The intermediate layer in the present invention is a polyolefin resin foam layer. Here, the polyolefin resins include high density polyethylene (HDPE), low density polyethylene (LDPE),
In addition to polyethylene resins such as linear low-density polyethylene (LLDPE) and ethylene-unsaturated carboxylic acid copolymers, polypropylene, polybutene, and copolymers of these with other α-olefins and mixtures thereof. can be mentioned. Among these, polyethylene resins are preferred as polyolefin resins, and low density polyethylene and linear low density polyethylene are particularly preferred. Here, the linear low density polyethylene is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, such as propylene, butene-1,4-methylpentene-1, octene-1, and the like. These low density polyethylenes and linear low density polyethylenes have a density of 0.900 to 0.
．． 940g/cd, melt index (Ml) 0.1
~50g/10min, preferably density 0.910-0.9
30 g/c+d, MlO, 2 to 20 g/10 minutes are used.

The foaming agents that can be used to form the polyolefin resin foam layer can be broadly classified into chemical foaming agents and physical foaming agents based on their foaming mechanism.

Among these, chemical blowing agents include azodicarbonamide,
Examples include dinitropentamethylenetetramine and azodiisobutyronitrile, and physical blowing agents include butane, heptane, and hexane.

Examples include dichlorodifluoromethane, nitrogen, carbon dioxide gas, etc.

In this polyolefin resin foam layer, the blending ratio of the raw material resin polyolefin resin and the blowing agent is not particularly limited and varies depending on the type of blowing agent, etc., but the foaming ratio is 1.2 to 1.2.
It may be set to 5 times, usually 1.5 to 3 times. This polyolefin resin foam layer preferably has small cell diameters. In addition, this polyolefin resin foam layer may contain a nucleating agent such as non-n fine powder, a coloring agent, and rubbers as necessary.

Carboxylic acid metal salts and the like can also be added as appropriate.

This polyolefin resin foam layer has the role of making the multilayer film opaque and giving it a pearl-like appearance, as well as providing cushioning properties to the multilayer film.

Next, regarding the outer layers of the present invention, one outer layer (8) is made of an ethylene-vinyl acetate copolymer layer, and the other outer layer (B) is made of a high-density polyethylene resin layer.

The ethylene-vinyl acetate copolymer (EVA) forming one of the outer layers (8) has a vinyl acetate content of 5 to 35% by weight, preferably 7 to 30% by weight, and a density of 0.920.
~0.950 g/ca, MI 0.5~20g/
A 10 minute test is used. This ethylene-vinyl acetate copolymer layer may be made of low-density polyethylene if necessary.
It may be blended in a proportion of 0% by weight or less. This ethylene-vinyl acetate copolymer layer is usually used as a surface layer of a multilayer film, and serves to impart anti-slip properties and flexibility to the multilayer film. That is,
The static friction coefficient of this ethylene-vinyl acetate copolymer layer is usually 0.8 or more, and can impart anti-slip properties to the multilayer film.

In this case, the static friction coefficient is the same as the static friction coefficient between two layers of the same type.

Next, the high density polyethylene resin layer forming the other outer layer (B) has a density of 0.945 to 0.975 g/cJ,
M I 0.01-5 g710 min, preferably 0.0
2 to 2 g/10 minutes is used. This high-density polyethylene resin layer may contain linear low-density polyethylene in an amount of 50% by weight or less, if necessary. This high-density polyethylene resin layer is used as an inner layer of the multilayer film, and serves to impart slipperiness and strength to the multilayer film. In addition, instead of this high-density polyethylene resin layer, it is possible to use low-density polyethylene with a slip agent added, but in reality, the slip agent would migrate to the intermediate foam layer and the surface would become slippery. can't get it. Here, the static friction coefficient of the high-density polyethylene resin layer is usually 0.3 or less.

The multilayer film of the present invention has the above-mentioned structure, and usually consists of a three-layer film including an intermediate layer and both layers (outer layer (A) and outer layer (B)). The thickness of the multilayer film of the present invention is usually 30-300μ, particularly 40-200μ. In addition, the layer ratio of each layer is outer layer (A): intermediate layer: outer layer (
B)=5-60:10-90:5-70. Especially 10-4
It is preferable to set it as 0:20-80:10-50. In addition, since it is difficult to measure the thickness of the foamed film, the layer ratio in this case is shown as the usage ratio of the raw material resin when the intermediate layer is not foamed.

Such a multilayer film of the present invention can be produced, for example, by coextrusion blow forming or T-die coextrusion. In the case of coextrusion inflation molding, the raw material resins are thoroughly melted and kneaded using each extruder, and then coextruded with an ethylene-vinyl acetate copolymer layer as an outer layer in a die to form a coextruded cylindrical shape. It can be made into a film, and it can also be opened to make a flat film. In this case, the die temperature is usually 130-180
゛The C1 die lip gap is 0.5 to 2.0, and the blow ratio is 1.5 to 5.0. According to this coextrusion inflation molding, the foaming agent-containing resin layer is completely wrapped in the two resin layers, so foaming is good, and there are no problems such as eye stains etc. adhering to the die, and it is stable for a long time. Since a multilayer film can be obtained, this method is particularly preferred as the method for producing the multilayer film of the present invention.

In the case of T-die coextrusion, it is preferable to use a so-called enveloping type die in which the outer layer (A) and the outer layer (B) enclose the polyolefin resin foam layer as the intermediate layer.

〔Example〕

Next, the present invention will be described in detail, but the present invention is not limited thereto unless it exceeds the scope of the present invention.

Examples 1 to 4 The resins shown in Table 1 were melt-kneaded using three extrusion molding machines, introduced into a circular die with internal adhesive for coextrusion, and inflation molded at a blow ratio of 3 to form a predetermined layer. A three-layer cylindrical film having a foamed intermediate layer was obtained. In addition, 4 parts by weight of azodicarbonamide foaming agent master bunch was added to the intermediate layer, and the film thickness calculated from the raw materials when the intermediate layer was not foamed was 60 μm. but,
The intermediate foam layer had a foaming ratio of 1.8 to 2.2 and a total thickness of about 80 μm. Table 1 shows the results of measuring the physical properties of the obtained film.

Next, this multilayer film is cut open and the electrical appliance (amplifier with a transparent polycarbonate resin plate) is packaged with the outer layer inside, then packed in a cardboard box and placed in a vibration tester.
Vibration condition 30Hz, 7G using Shin Nippon Sokki F-800)
The polycarbonate resin plate was vibrated for 15 minutes, and the occurrence of scratches on the surface of the polycarbonate resin plate was observed and evaluated according to the following criteria.

The results of this vibration test are shown in Table 1.

◎: No scratches ○: Almost no scratches △: Many dotted scratches occurred ×: Many large dotted scratches occurred Comparative Example 1 According to Example 1 except that low density polyethylene resin was used as the outer layer resin. I did it. The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was followed except that a low density polyethylene resin containing a slip agent was used. The results are shown in Table 1.

Comparative Example 3 The procedure of Example 1 was followed except that no blowing agent was added to the intermediate layer. The results are shown in Table 1.

Table 1 shows the physical property measurement results for a laminate film of polyethylene foam film and high-density polyethylene with a thickness of 13 μm.

*Resin used: HDPE: manufactured by Idemitsu Petrochemical ■, Idemitsu Polyethylene 640 UF, density 0.950 g/cJ MI 0.03 g/10 minutes LDPE
-A: Manufactured by Toyo Soda Kogyo ■, Petrocene 205° density 0.
9248/c1)! , M13g/10min LDPE-B: manufactured by Toyo Soda Kogyo ■, Petrocene 175
゜Density 0.921 g/cnl, Ml 0.6 g/1
0 minute LLDPE: Manufactured by Idemitsu Petrochemical ■, Moretic 0138
N, density 0.920 g/crl.

MI Ig/10 minutes LDPE-C: LDPE-A with a slip agent (erucic acid amide 2% by weight) EVA: Toyo Soda Kogyo Ogiku, Ultrasen 540,
Density 0.927 g/cfll.

Ml 3g/10 min, vinyl acetate containing NIO weight % [Effects of the invention] Since the multilayer film of the present invention adopts the above-mentioned structure, it has good protection properties for articles and can protect products that are prone to scratches. can be effectively protected.

The multilayer film of the present invention also has a pearl-like luster in appearance.

It exudes a sense of luxury with its Japanese paper windows.

Furthermore, the multilayer film of the present invention can be coextruded, has high productivity, and is inexpensive.

Therefore, the multilayer film of the present invention can be effectively used for packaging various products including home appliances.

Claims (3)

[Claims] (1) Middle layer is polyolefin resin foam layer, outer layer (A)
A multilayer film consisting of an ethylene-vinyl acetate copolymer layer and an outer layer (B) of a high-density polyethylene resin layer. (2) The multilayer film according to claim 1, which is a coextruded cylindrical film having an ethylene-vinyl acetate copolymer layer as an outer layer. (3) The multilayer film according to claim 1, which is used for packaging and has an ethylene-vinyl acetate copolymer layer as a wrapping surface.