JPS5825332A - Metalized polypropylene film - Google Patents

Abstract

PURPOSE:The titled film having a high metalizing strength and excellent laminatability with other substrates and being suitable as a food-packaging material, prepared by subjecting the surface of a polypropylene film having a specified density to a corona discharge treatment and then metalizing the treated film. CONSTITUTION:In forming a film by melting polypropylene or a propylene copolymer and extruding the melt through an extruder die, a polypropylene film, film density 0.895-0.902, or a propylene copolymer film, film density 0.891- 0.899, is prepared by, for example, a process including keeping the surface of the chill roll at 50-80 deg.C or a process including cooling by the use of cooling water of a temperature of 60-90 deg.C. Then the purpose metalized propylene film is prepared by subjecting the above-prepared film to a corona discharge treatment and then metalizing the treated film with a metal such as aluminum or chromium by, for example, vacuum deposition or sputtering.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metallized polypropylene film having high metallization strength and improved lamination adhesion to other substrates.

In recent years, metallized films have been widely used as food packaging materials due to their beautiful metallic luster, gas barrier properties, light blocking properties, and the like. This metal vapor deposition has been attempted on polypropylene film, but since the surface of polypropylene film is smooth and inert, the metal vapor deposition film has poor adhesion and is easily peeled off from the film surface.

In addition, since the adhesive force of metal is weak, the lamination adhesive strength with other base materials is low.

Therefore, in order to solve such problems, various methods are used.
) Proposals have been made such as methods for roughening film images physically or chemically, corona discharge, gas flame,
There are two methods: a method of oxidizing the film surface by irradiation to impart polar groups, and a pretreatment method of coating the film surface with an adhesive material. However, the adhesion of the vapor-deposited metal film is insufficient when using only the method of roughening the surface of the film, and the method of pre-treating the surface of the film by coating it with an adhesive material is difficult. There is a problem in that the process is tedious because it has to be physically or chemically treated.

As a result of various studies to solve these problems, the inventors discovered a polypropylene vapor-deposited film with a metal film that has a large vapor deposition force when a discharge treatment is applied to the film surface of a specific density. The invention was completed nine times.

i.e., made of polypropylene or propylene copolymer), the film density is α891&lnl, a? O2
This is a metal-deposited polytetrapyrene film obtained by vapor-depositing a metal on the film surface after corona discharge treatment.

The polypropylene or propylene copolymer used in the present invention is a propylene homopolymer or propylene containing 90% by weight or more of propylene and other α-olefins, such as ethylene, butene-1,4-methyl-pente/- It is a copolymer with No. 1. In addition, an antioxidant, an antiblocking agent, a lubricant, etc. can be added to these polypropylene blocks or propylene copolymers as necessary.

The density of the film used in the present invention varies depending on the homopolymer, copolymer and stereoregularity of each, but
For homopolymers F1a895snl, l190
2. In the case of coho IJ w -, #ia is preferably 91 to α899, and the film density is homopoly! - with [1895 and #i acupressure mer with α891
If it is less than 16t, the roughening of the film surface that is effective for the vapor deposition strength of the vapor-deposited metal film cannot be obtained. From the adhesion strength of the vapor-deposited metal film, #i is not particularly limited, but if the film density becomes too large, the mechanical properties of the vapor-deposited film, such as a decrease in impact strength and cracking, are undesirable because they reduce the practical properties of the film. .

The above film of polypropylene or propylene copolymer having a film density of 8916 to 1902 can be obtained by the following method. For example, Polypropyref Maku is an unstretched cast made by extruding a propylene copolymer from a T-die at a resin temperature of 200 to 260°C and forming it into a film by setting the surface temperature of a chill roll to 50 to 80°C. It is an unstretched blown film that can be obtained by cooling the film or cooling water at a temperature of 6.0 to 90° C. during extrusion molding from an annular die. In this manner, in the cooling process of the melt-extruded film, by slowing down the cooling rate in the crystallization temperature range, a roughened film can be obtained in which the crystallization of polypropylene molecules is completely promoted and the film density is increased. Generally, when the surface temperature of the chill roll O is set to 30° C. or lower using the method described above, the Fi film density fFi decreases and the film surface becomes smooth without becoming rough. The thickness of the film formed for metal vapor deposition is preferably 35 μm or less.

The metal-deposited surface of the nine films thus obtained is subjected to a corona discharge treatment to further increase the deposition power of the metal-deposited film. This corona discharge treatment has good vapor deposition power when the wetting index is set to 37 (surface tension: 57 dyne/am) or more. However, corona discharge treatment with a wetting index of 50 or more is preferred since increasing the density will impair the roughening of the resulting film and reduce the deposition power of sand metal deposition. stomach.

The metal vapor deposition method of the present invention is carried out in a conventional manner. This can be done by vacuum evaporation, in which various metals are heated in a vacuum to evaporate and the metal vapor is attached to the film surface, or by other methods such as sputtering evaporation or ion blating. The metals to be vapor-deposited include aluminum, gold, silver, nickel, lithium, gelminilum, selenium, titanium, tin,
Examples include steel and zinc, but aluminum is preferred from the viewpoint of workability, reflectance, economical efficiency, etc.

The thickness of the metallized layer is typically in the 400-600 μm range.

As described above, the film of the present invention has a strong adhesion between the base film of polypropyref 1 or propylene copolymer and the metal vapor-deposited film, and therefore has excellent lamination adhesion with the base film of the hook. Further, the vapor-deposited film of the present invention is such that a film having a specific density is obtained under the conditions during molding, and metal is vapor-deposited on the film without applying an undercoat layer, thereby simplifying the process.

The present invention will be explained below with reference to Examples. In addition, evaluation of metal evaporation strength of the present invention, evaluation of lamination adhesive strength to metal evaporation surface,
Wetting index and film density 0jll19 method is as follows.

(1) Evaluation of metal vapor deposition strength At room temperature of 20°C, apply Chiban Co., Ltd.'s Cellotape (2311 am width x 100 cm length) to the adhesive tape with the metal vapor deposited surface KVff, and when the tape is peeled off by hand, the tape does not peel off. The area percentage of the metal that adhered to the film surface and remained until 9'f is shown in the table below, and the rank of practical vapor deposition strength was set as 5.

(2) During evaluation of laminated adhesive strength to metal vapor deposited surface, 15+m laminated test piece was pulled at a tensile speed of 5oo? O” and 18
The strength when peeled off at an angle of 0@ was measured using an Instron universal tensile tester.

Note that the lamination adhesive strength was set to be 100 g/15 mm or more for practical purposes.

(3) Wetting index A commercially available standard wetting index solution (manufactured by Wako Pure Chemical Industries, Ltd.) was applied to the film surface, and the determination was made according to the method of JXFIK-4768.

(4) Film density Measured according to K-4758 (4.2.4)K from J.

Actual tIIA Examples 1 to 7 Melt Flue Rate (hereinafter referred to as MF)'t)? An ethylene-propylene random copolymer or a propylene homopolymer was melted and extruded at a resin temperature of 230'C, and the surface temperature of a chill roll with a diameter of 200 mm was set at a deposition rate of 4/30B under the conditions shown in Table 1. A film having a moldability of 25 μm was obtained. The density of this film is shown in Table-
This film was subjected to corona discharge treatment using a transistor set corona discharge treatment machine so that the wetting index was 4fl.

Set this film in the vapor deposition machine and
Deposit aluminum under vacuum below Hg (thickness #
'i5・Om). This film was evaluated for its vapor deposition strength. Furthermore, the Al9=Um deposited film surface [2
0μ biaxially oriented polypropylene filler with urethane adhesive (Niatco manufactured by Toyo Morton Co., Ltd.) 503-! 551
e. Hardening agent Atcoat 1! J) to measure the lamination adhesive strength between the two films. Table 1 shows the aluminum vapor deposition strength, layering strength, and lamination adhesive strength.

Examples 8 and 9 VFR9, an ethylene-propylene random copolymer with an ethylene content of 52%, was melted and extruded at a resin temperature of 230°C, and a bottom-blown water cooling inflation method was performed under the cooling water temperature conditions shown in Table IK. A 25μ film was obtained. The density of this film is shown in Table-1. Next, this film was cut open and subjected to corona discharge treatment and aluminum vapor deposition in the same manner as in Example 1, and the vapor deposition strength and lamination adhesive strength were evaluated in the same manner, and the results are also listed in Table 1.

Comparative Examples 1 to 4 Using the same resin as in Examples 1, 4, 6 and 8, a film with a thickness of 2511 mm was formed by the KT die method as in Example 1 under the conditions of the chill roll temperature and cooling water temperature shown in Table 2. And the thickness was 25j by the in7resilon method in the same manner as in Example.
A film of No. 1 was obtained. Example 1 for each film
Aluminum evaporation was performed after film density measurement and corona discharge treatment in the same manner as in . The vapor deposition strength and lamination adhesive strength of this vapor deposited film were evaluated in the same manner as in Example 9% 1 and are shown in Table 2.

Comparison 1'15.4 In Example 3 and Example 7, the films on which aluminum was vapor-deposited without being subjected to corona discharge treatment were evaluated for vapor deposition strength and lamination adhesive strength in the same manner as in Example 1, and the results were Also listed in Table 2.9.

Claims (1)

[Claims] (1) Made of polypropylene or propylene copolymer; in the case of polypropylene, the film density is α8
! 5.il, (1902, in the case of a propylene copolymer, a metal-deposited polypropylene/film obtained by vapor-depositing a metal on a film surface having a film density of a891 to a899 after corona discharge treatment.