JPH0381142A - Metal deposited plastic film - Google Patents

Abstract

PURPOSE:To enhance the bonding strength of deposited film and improve the printability and laminating properties of deposited surface by a method wherein plastic film obtained out of composition, which is prepared by mixing specified ethylene-acrylic alkyl copolymer with polypropylene-based resin, is adoped as base film. CONSTITUTION:Metal is deposited on plastic film obtained out of composition, which mainly consists of 100 pts. wt. of polypropylene-based resin and 1 - 20 pts.wt. of ethylene-acrylic methyl copolymer or/and ehtylene-acrylc ehtyl copolyme. At this time, polypropylene-base resin and ethylene-acrylic alkyl copolymer, the ratio of the melt flow rate of the latter (MI-OR) to the melt flow rate of the former (MFROPP) of which satisfed 0.2<MI-OR/MFR-PP<4.0, are used. Further, said metal-deposited plastic film may well be constituted by laminating a plurality of single layer films to one another under the condition that the deposited surface is faced outside.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a metal-deposited plastic film, and more specifically, it is a metal-deposited film based on a plastic film mainly made of polypropylene resin. The present invention relates to a metal-vapor-deposited plastic film that has high adhesive strength with vapor-deposited films, excellent brightness and gloss on the metal-vapor-deposited surface, and also has excellent printability on the vapor-deposited surface and adhesion to other films.

[Conventional technology]

In recent years, metal-deposited plastic film, which is made by depositing metal on plastic film under vacuum, has been utilized for its excellent decorative properties, gas barrier properties, light blocking properties, etc., and has been used to replace existing materials such as gold and silver thread and building materials. Applications are expanding to a wide range of areas, including packaging materials for food products. In particular, aluminum vapor-deposited plastic film is widely used mainly for packaging purposes, but in most cases, the vapor-deposited surface (aluminum surface) is printed or laminated with other films. be.

By the way, polypropylene-based films (here, polypropylene-based include not only propylene homopolymers but also copolymers of propylene as a main component with ethylene or other α-olefins) means)
is the main type of plastic film, and metal-deposited polypropylene films having a polypropylene film as a base film have traditionally been used in large quantities for the above-mentioned purposes. However, this metal-deposited polypropylene film has low adhesion strength between the base film and the deposited film, that is, the deposition strength, and when the deposited metal is aluminum, the printability of the deposited surface and the adhesion with other films (hereinafter referred to as lamination property) are low. ) is extremely low, making it unusable for applications that require printing, laminating, etc., and has been a major obstacle in the development of applications.

On the other hand, low-density polyethylene plastic films with strong vapor deposition strength have a rough film surface and low gloss on the metal vapor-deposited surface, making it impossible to obtain a metal vapor-deposited plastic film exhibiting beautiful metallic luster.

The reason for the low vapor deposition strength of metal-deposited films using polypropylene as a base film is due to the inherent inertness of the polypropylene resin, and the reason for the low printability and lamination properties of the vapor-deposited surface is due to the low vapor deposition strength in the polypropylene resin. The neutralizing agent, slip agent 7, antioxidant, etc. added to the evaporation layer migrates to the surface, and on the evaporation surface side, it further passes through the evaporation layer and oozes out.On the opposite side, when the layer is rolled up, the evaporation surface (Tokuko Sho 58-
49574 and JP-A-59-25829). To further explain the latter cause, among additives, fatty acid derivatives used as neutralizing agents, particularly higher fatty acid salts such as calcium stearate and sodium stearate, oleic acid amide, and stearic acid amide.

Higher fatty acid amides such as erucic acid amide reduce the wetting index of the vapor-deposited surface (aluminum surface) to 33 dyn/am or less even when the content is as small as 0.01% by weight, making it difficult to print on the vapor-deposited surface. Laminate adhesion becomes impossible6 Various proposals have been made in the past to solve these problems. For example, methods for increasing the deposition strength include methods of physically or chemically roughening the film surface, methods of oxidizing the film surface by corona discharge, gas flame, radiation irradiation, etc. to impart polar groups, or A method of coating a film surface with an adhesive material is known.

However, when used alone, the film surface is roughened or oxidized, the strength of the vapor deposition is still insufficient, and the method of coating the film surface with an adhesive material requires that the film surface be physically or chemically coated prior to coating. This method has disadvantages in that it requires pretreatment, which complicates the process and increases the cost of the deposited film.

In addition, as a method to improve the vapor deposition strength as well as the printability and lamination properties of the vapor-deposited surface, we have developed a film based on a mixed polymer in which graph 1-ized polypropylene, which is obtained by graft polymerizing maleic anhydride, etc. to polypropylene, is blended with polypropylene. It is also known to be made into a film (Japanese Patent Publication No. 50-61469, Japanese Patent Publication No. 58-49574).
(see issue). However, in this case as well, the cost of the film increases as described above, and the odor from unreacted maleic acid remaining in the film and decomposition products generated by thermal decomposition is strong, and when used for food packaging, foreign odors transfer to the contents. There were drawbacks such as:

Furthermore, we do not use compounds that migrate to the film surface, such as fatty acid derivatives and higher fatty acid amides, and use a large amount of inorganic fillers to improve the film's slipperiness and anti-blocking properties, and to reduce wrinkles during one winding. Methods have been proposed to prevent this from occurring, and to prevent the occurrence of local enlargement of a wound film roll, so-called bulges. However, in the above method, although the vapor deposition strength is improved due to the wedge effect, the glossiness of the metal vapor deposited surface is reduced and a beautiful metal vapor deposited film cannot be obtained.

[Problem to be solved by the invention]

The present invention eliminates the drawbacks of the prior art described above, and although it is a metal vapor deposited film based on a plastic film mainly made of polypropylene resin, it has high adhesion strength of the vapor deposited film, printability of the vapor deposited surface, and lamination. The challenge is to make it excellent in terms of performance as well.

[Means to solve the problem]

As a result of various studies, the present inventors solved the problem in item 2'a by using a plastic film obtained from a composition obtained by mixing a specific ethylene-alkyl acrylate copolymer with a polypropylene resin as a base film. The present invention was completed by investigating the following.

The present invention will be explained in detail below.

The present invention comprises 100 parts by weight of a polypropylene resin and an ethylene-methyl acrylate copolymer or/and an ethylene-methyl acrylate copolymer.
This metal-deposited plastic film is obtained by vapor-depositing a metal onto a plastic film obtained from a composition mainly consisting of 1 to 20 parts by weight of ethyl acrylate copolymer. The vapor deposited film is usually formed on only one side, but depending on the application, it may be formed on both sides. Furthermore, the present invention also includes a metal vapor deposited plastic film having a structure in which a plurality of single layer films are laminated with the above metal vapor deposited plastic film as the outermost layer with the metal vapor deposition surface facing outward.

The polypropylene resin used in the present invention is a crystalline propylene autopolymer, a crystalline copolymer of propylene and ethylene or other α-olefin having propylene as a main component, or a mixture thereof. The above-mentioned homopolymers and copolymers can be obtained, for example, by polymerizing the respective heptamers in the presence of a Ziegler-Natsuta type catalyst. Among these, crystalline ethylene-propylene copolymer, crystalline propylene-butene-1 copolymer, crystalline propylene-butene-1 copolymer containing 80 to 98% by weight of propylene component and having a crystal melting point (Tm) in the range of 115 to 150°C Ethylene-propylene-butene-e terpolymer (in this case, the content ratio of ethylene:butene-1 is preferably 10:1 to 15:1), or a mixture thereof, is an ethylene-alkyl acrylate copolymer described later. The film obtained from the composition mixed with the copolymer has excellent adhesion to the deposited film, as well as excellent impact resistance and heat sealability.
Particularly desirable.

Here, the crystal melting point (Tm) is the endothermic curve associated with the melting of the crystal obtained by heating a 10 cm sample at a rate of 10°C/min in a nitrogen atmosphere using a scanning differential calorimeter. Say peak temperature. In the case of a crystalline copolymer containing propylene as a main component, Tll1 decreases as the content of ethylene or α-olefin as a comonomer component increases. For example, in the case of a crystalline ethylene-propylene random copolymer, the ethylene content will vary slightly depending on the randomness of the copolymer, but if the ethylene content exceeds approximately 2.5% by weight, the
The temperature will be below 0℃. Incidentally, polymers having a plurality of Tm can be obtained by copolymerizing in two or more stages by changing the polymerization conditions, but in this case, it is desirable that the main peak is 150° C. or lower.

The ethylene-methyl acrylate copolymer or ethylene-ethyl acrylate copolymer used in the present invention is produced by autoclaving ethylene monomer and methyl acrylate or ethyl acrylate (sometimes collectively referred to as alkyl acrylate) monomer. It is obtained by copolymerization using a catalyst and a reaction initiator. Copolymers of ethylene and other monomers such as vinyl acetate, acrylic acid, methacrylic acid, methyl methacrylate, etc. can also be obtained in the same manner as above, but
Even if these are used in the present invention, the effect is small.

The alkyl acrylate component content in the ethylene-alkyl acrylate copolymer is usually 0.5 to 40% by weight, preferably 3 to 30% by weight, and more preferably 10 to 25% by weight.
It is. Alkyl acrylate component content is 0.5% by weight
If the amount is less than 100%, the effect of improving the vapor deposition strength, the printability of the vapor deposition surface, and the lamination property cannot be obtained.

As the content of the alkyl acrylate component increases to 0.5% by weight or more, the melting point of the ethylene-alkyl acrylate copolymer decreases, and by blending it with polypropylene, the above-mentioned improvement effect can be obtained, as well as resistance at low temperatures. Impact resistance is improved and heat sealing is possible at low temperatures. However, when the content of the alkyl acrylate component exceeds 40% by weight, the ethylene-alkyl acrylate copolymer no longer exhibits crystallinity, resulting in poor compatibility with polypropylene resins and the resulting film's transparency and surface. The smoothness will be impaired, and a beautiful metal-deposited film will no longer be obtained.

The respective melt flow rates of the polypropylene resin and the ethylene-alkyl acrylate copolymer are not particularly limited as long as the compatibility between the two is not impaired.From many experiments conducted by the present inventors, the melt flow rate of the polypropylene resin The ratio of the melt flow rate (symbolized as MI-OR) of the ethylene-alkyl acrylate copolymer to the melt flow rate (symbolized as MFR-PP) (hereinafter sometimes referred to as the melt flow rate ratio of the composition) is 0.
It has been found that the range of 2<MI-OR/MFR-PP<4.0 is particularly preferable in terms of improving the compatibility between the two. If this melt flow rate ratio is less than 0.2, the compatibility between the two will decrease, resulting in streaks or fish eyes on the film, and the vapor deposited film with metal vapor deposited on this film will have gaps in the vapor deposited film. The film loses its function as a metal vapor deposited film (loss of the metal vapor deposit film causes a decrease in gas barrier and moisture proof properties).

Furthermore, if the melt flow rate ratio of the composition is 4.0 or more, there will be a difference in fluidity between the two, making it impossible to perform uniform melt extrusion, and uneven thickness (surging phenomenon) will occur in the resin film along the flow direction. Even if the obtained film is vapor-deposited, thickening and wrinkles are likely to occur.

In the composition of the present invention, the ethylene-alkyl acrylate copolymer is limited to 1 to 20 parts by weight per 100 parts by weight of the polypropylene resin. If the amount exceeds 20 parts by weight, the surface of the film will become rough, making it impossible to obtain a film with a beautiful metallic luster, and a unique odor will be generated in the film, causing damage to the packaged contents. This is because it is undesirable because it may mix with the odor of the product and reduce the product value.

The composition used in the present invention optionally contains an antioxidant,
Inorganic fillers, lubricants, anti-blocking agents, etc. can be included as appropriate within the range that does not impair the purpose of the present invention, but in order not to reduce the adjacency of the deposited film, the printability and lamination properties of the deposited surface. It is preferable not to use higher fatty acid salts or higher fatty acid amides.

As the antioxidant, phosphorus type and phenol type antioxidants having a molecular weight of 500 or more are particularly desirable. Specifically, tetrakis-[methylene-3-(3',5'-di-t-
Butyl-4'-hydroxyphenyl)propionate comethane.

1.3.5-trimethyl-2,4,6,-tris(3,
5-di-t-butyl-4-hydroxybenzyl)benzene.

1.3.5-Tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)in cyanurate.

6-(4-hydroxy-3,5-di-t-butylamino)-2,4-bisn-octylthio-, 3°5-triazine.

1.1.3-tris(2-methyl-4-hydroxy-5
-t-butylphenyl)butane.

Tris(3,5-di-t-butyl-4-hydroxyphenyl)isocyanurate.

Tetrakis (2,4-di-t-butylphenyl) 4.4
'-biphenylene diphosphonite and the like can be mentioned, and these can be used alone or in combination of two or more.

The content is 0.0% per 100 parts by weight of polypropylene resin.
0.3 to 0.3 parts by weight is suitable.

The inclusion of the above-mentioned antioxidant is extremely effective in improving the stability of the composition during film formation and film use.

Further, as the inorganic filler, calcium carbonate, silica, clay, talc, hydrotalcite, zeolites, etc. can be used.

The above-mentioned additives may be added to polypropylene resin, etc. by any method as long as they can be uniformly dispersed, but they may be mixed using a ribbon blender, Henschel mixer (trade name), etc., and the mixture may be mixed using an extruder, etc. A method of melting and kneading is desirable.

The polypropylene film used in the present invention can be obtained from the above composition by the usual T-die method or inflation method. Not only these -axially or biroaxially stretched films, but also unstretched films can be used as the base film. Further, in the present invention, in addition to the single-layer plastic film as described above, a composite film in which a plurality of films are laminated with this plastic film as a surface layer on one or both sides can also be used as the base film.

In this case, it is a matter of course that the metal vapor deposition film is formed on the plastic film, that is, the plastic film obtained from the composition forming the surface layer. The metallized plastic film obtained in this way is
When expressed based on the single-layer metal-deposited plastic film, it has a structure in which a plurality of single-layer films are laminated as the outermost layer with the metal-deposited surface facing outward.

Hereinafter, metal vapor deposition on the base film will be explained in the case of a single layer film, but the same applies to the case of a composite film.

Although the plastic film obtained from the composition can be directly subjected to metal vapor deposition, corona discharge treatment in air or under a special gas atmosphere such as nitrogen or oxygen,
It is a commonly known method in which metal vapor deposition is applied to a long plastic film (usually in roll form), which may be used after surface treatment such as flame treatment to improve the wettability of the film surface and further improve adhesion. The vacuum deposition method is as follows.

The degree of vacuum in the vacuum evaporation equipment equipped with the roll-wound film feeding section, evaporation section, and winding section is set to 10-'Torr.
In this apparatus, a desired metal such as aluminum is heated in a container or in the form of a filament to melt and evaporate the metal, and vapor deposition molecules are continuously deposited on the surface of the unrolled film and wound up.

The method of using such vacuum evaporation equipment is a batch type, and it is necessary to improve productivity. As a result, the requirements for high-speed deposition, roll shape, etc. of the raw film for deposition have become more severe.

There are various deposition methods other than the vacuum deposition method described above. Examples include sputtering deposition and ion blating, which utilize the phenomenon in which metal constituting the cathode scatters when discharged in a vacuum.

The most common metal to be vapor-deposited is aluminum, but other metals such as gold, silver, copper, nickel, chromium, germanium,
Examples include selenium, titanium, tin, and zinc. The thickness of the metal deposited layer is usually in the range of 50-800 angstroms, and can be deposited not only on one side of the entire surface but also partially. Additionally, a top coat can be applied to the vapor-deposited surface for coloring and protection.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The measurement methods and evaluation criteria for physical properties shown in Examples and Comparative Examples are as follows.

(1) Melt flow rate: Based on JIS 7210-1976, the melt flow rate (MFR-PP) of polypropylene resin is the Melt flow rate (MI-OR) was determined under test condition 4 (190'C, 2, 1
6kgf).

(Unit: g/10 minutes).

In addition, when using a mixture of two or more types of ethylene-alkyl acrylate copolymers, the M I -OR is as follows: a, b
The melt flow ratio was calculated using the representative MI-OR value calculated by the calculation formula illustrated for the three cases of , c.

((M l-0R)aX (a)/(T))+((M
l-0R)bX (b)/(T))+((MI-O
R)0X(c)/(T)) where: (a), (b), (c); Amount (T) of each ethylene-alkyl acrylate copolymer; Total ethylene-alkyl acrylate copolymer Total amount of combination. That is, (T)=(a)+(b)+(c)(M I −
0R)a, (M I -0R)b, (M I -O
R) 0; 1 for each ethylene-alkyl acrylate copolymer
-OR ゐ(2) Haze: According to ASTM D 1003, the undeposited film is
The value (unit: %) measured by stacking the sheets is shown as the haze of the four sheets. The smaller this value is, the better the transparency is.

(3) Vapor deposition strength of aluminum vapor-deposited film: Surlyn film (ionomer manufactured by Tamapoli Co., Ltd.) is layered on the vapor-deposited film side of the vapor-deposited film, and conditions are as follows: sealing temperature: 120°C, sealing pressure: 2.0 kg/a#, sealing time: 1.0 seconds Seal for 10 seconds + x 15 mm.

The 90 degree peel strength was measured using a tensile tester.

(Unit: g/15n+m).

(4) Metallic gloss: According to ASTM D 523 specular gloss method, sensitivity 1/
It is expressed as a gloss level measured at 10. The indicated angle is measured at 20 degrees, and an angle of 70 or more is considered good.

(5) Wetting index: The wettability index was measured according to the method of JIS K 6758.

(Unit: dyn/(2)).

(6) Printability of vapor-deposited surface: The vapor-deposited surface (metal surface) of a film with metal (aluminum) vapor-deposited on one side and the non-vapor-deposited surface (base film surface) were overlapped and a load of 4.2 kg/100a+f was applied. After being left in an atmosphere at a temperature of 40° C. and a relative humidity of 95% for 72 hours, the wettability index of the vapor-deposited surface is measured. In order to be evaluated as having good printability, this wettability index must be 35 or more, preferably 37.
The above is necessary, and the printability of the vapor-deposited surface was ranked as follows based on this wettability index.

(7) Lamination property: The vapor deposition surface of the film with gold a (aluminum) vapor deposited on one side and the biaxially stretched polypropylene film (thickness 2
07a) using a dry laminating adhesive, knee-song at 60°C for 3 days, and after the adhesive had completely dried, a test piece with a width of 15 nn was prepared.
The 0 degree peel strength was measured using a tensile tester and was 200 g/
A width of 15 mm or more was set as 0.

(8) Odor: 10 g of film was sealed in an odor-like form (500 mQ), and 80
The odor generated after heating at ℃ for 2 hours was evaluated according to the following 3.
It was classified into stages.

(Average value of 210 panelists) Examples 1 to 7. Comparative Examples 1 to 6 Ethylene component: 2.5% by weight, butene-1 content: 4.5%
Weight % crystalline ethylene-propylene-butene-↓ terpolymer with melt flow rate (MFR-PP)
is 6.0. To 100 parts by weight of a polypropylene resin having a Tra of 140°C, 0.0% of tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate tomethane] was added as an antioxidant. 10 parts by weight were added and made into pellets using an extruder. For 100 parts by weight of this pelleted polypropylene resin,
Mix various ethylene-methyl acrylate copolymers or ethylene-ethyl acrylate copolymers with the alkyl acrylate content and melt flow rate (MI-OR) shown in Table 1 in the parts by weight shown in Table 1, and blend them. The resulting m-acid was extruded at a melting temperature of 220°C using an extruder with a diameter of 65mm + φ and a T-die, rapidly cooled in an air chamber and a cooling roll with a surface temperature of 30°C to form a plastic film, and immediately One side of this film was subjected to corona discharge treatment so that the wetting index was 40 dyn/cx, and the film was wound up to a thickness of 25 p1 and a width of 60 p.m.
It was made into a roll-shaped plastic film of QI+. After cutting this plastic film to a width of 50α using a slitter, this was set as a base film in a continuous vacuum evaporation device, and while continuously feeding out the film, the corona-treated surface of the film was subjected to a vacuum of 5 × 1O-sTorr. A single-sided aluminum-deposited plastic film (within ±15 angstroms) with a thickness of approximately 350 angstroms (within ±15 angstroms) is produced by depositing aluminum and rolling it up.
A length of 2,000 m) was obtained in the form of a roll. The properties of the plastic films and metallized films obtained in each Example and Comparative Example are shown in the above table.

Below is a blank space Example 8 In the above examples, a crystalline ethylene-propylene copolymer (M Ding-P
A plastic film and a roll-shaped single-sided aluminum-vapor-deposited plastic film using the slit film as a base film were obtained in the same manner as in Example 1, except that P 7 , Tm 150° C.) was used.

Its properties are shown in Table 2.

Example 9 In Example 1, a crystalline homopolymer of propylene (M F R-P P
A plastic film and a roll-shaped single-sided aluminum-deposited plastic film using the slit film as a base film were obtained in the same manner as in Example 1, except that a film with a Tm of 162°C) was used.

Its properties are shown in Table 2.

Example 10 In Example 3, a plastic film obtained from the composition (however, the thickness was changed to 20 IM) and a film obtained from low density polyethylene (thickness 20 IM).

A roll-shaped single-sided aluminum vapor-deposited film was prepared in the same manner as in Example 3, except that a composite film obtained by laminating 4 sheets (haze value 40%) was used as a base film and vapor-deposited on the side of the film obtained from the composition. A plastic film was obtained.

Its properties are shown in Table 2.

Table 2 Table 12 and Table 2 I: As is clear, the plastic film obtained from the composition defined in the present invention and its metallized film have excellent properties, but
It can be seen that the films of Comparative Examples were significantly inferior in one of the properties.

〔Effect of the invention〕

The metallized plastic film according to the present invention uses a plastic film mainly made of polypropylene resin as its base film, but it also contains specific ethylene-methyl acrylate or/and ethylene-methyl acrylate.
By blending a specific amount of ethyl acrylate, it has high adhesive strength between the base film and the deposited film, a beautiful metallic luster on the deposited surface, and extremely excellent printability and lamination properties on the deposited surface. It can be used more widely and in large quantities for purposes such as packaging and decoration.

Claims (1)

[Scope of Claims] 1. A plastic film obtained from a composition mainly consisting of 100 parts by weight of a polypropylene resin and 1 to 20 parts by weight of an ethylene-methyl acrylate copolymer or/and an ethylene-ethyl acrylate copolymer. A metal-deposited plastic film made by depositing metal on. 2 Melt flow rate of polypropylene resin (MFR-PP)
Polypropylene resin and ethylene-alkyl acrylate copolymer having a melt flow rate (MI-OR) ratio of ethylene-alkyl acrylate copolymer to 0.2<MI-OR/MFR-PP<4.0 The metal-deposited plastic film according to claim 1, wherein the metal-deposited plastic film comprises: 3. A metallized plastic film comprising a plurality of single-layer films laminated with the metallized plastic film according to claim 1 or 2 as the outermost layer with the metallized plastic film facing outward.