JPH03266641A - Film having metallizable surface - Google Patents

Abstract

PURPOSE: To obtain a metallizable oriented plastic film which has excellent transparency and bond strength in laminate, low vapor and oxygen permeability, and excellent metal attachment and metal uniformity by comprising a co- extruded copolyester attached to one surface of a core layer of isotactic polyprophylene and a co-extruded heat-sealable layer attached to the opposite surface. CONSTITUTION: A metallizable oriented plastic film comprises a core layer of isotactic polyprophylene, a co-extruded copolyester layer attached to one end of the core layer, and a co-extruded heat sealable layer attached to the opposite surface of the core layer. The metallizable film also has a metal coating on the co-extruded copolyester layer. A polypropylene homopolymer core layer and a copolyester layer are not compatible in the normal state. Thus it is necessary for an attachment accelerator in the homopropylene homopolymer to bond the core layer with the copolyester layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to metallizable oriented plastic films, and more particularly, the present invention relates to such films having excellent lamination bond strength and heat sealability, and to metallized such films.

The attachment of metals such as aluminum, silver and chromium to plastic film has made it possible to replace the film with metal foil in many applications of plastic film.

Film flexibility requires the formation of a strong metal-plastic bond, and many methods have been developed for imparting that bond.

The present invention is a heat-sealable plastic film with excellent transparency and lamination bonding strength, low water vapor and oxygen permeability, and a metallizable oriented plastic film with excellent metal adhesion and metal uniformity. This is what we are trying to provide.

According to a first aspect of the invention, (i) a core layer comprising isotactic polypropylene; (ii) a coextruded copolyester layer adhered to one side of the core layer; A metallizable oriented plastic film is provided that comprises adhered coextruded heat sealable layers.

The present invention also provides a metallized oriented plastic film comprising a metallizable film as herein referred to with (jv) metallization on the coextruded copolyester layer (i1). , and metallization (iv
Also provided is the use of the copolyester layer (ii) in attaching a polypropylene core layer (ii) to a polypropylene core layer (ii).

A multilayer metallizable oriented plastic film is provided that includes a core layer (i) of highly stereoregular polypropylene homopolymer. This interactive polymer is well known in the packaging industry and has a luminous intensity of 0.90 to 0.91, a crystalline melting point of 160'' to 165°C, and 2.
It has a melt index of 0 to 6 grams/10 minutes, preferably 3 to 4 grams/10 minutes. The polymer is 80 to 100 χ isotactic, preferably 95 to 96% isotactic. It is desirable to include an adhesion promoter in this layer; suitable adhesion promoters include:
It is an emulsifiable polyolefin wax containing a small amount of maleic acid, which acts as a coupling agent to attach dissimilar materials to each other. The wax is commercially available from Eastman Chemical Products Company under the trade name EPOLENE E-43.

A metallizable surface is provided by the polyester layer (i1). Since the polypropylene homopolymer core layer and the copolyester layer are not compatible under normal conditions and may delaminate, an adhesion promoter is required in the homopropylene homopolymer to bind the core layer to the copolyester layer. .

Copolyesters are made from one or more dibasic acids and/or glycols. Copolyesters are often used as extruded sheets for blister packaging and sometimes bottles. 1-ethylene, 4-cyclohexylene-
Amorphous (non-crystalline) thermoplastic copolyester materials, such as dimethyl terephthalate, have been found to impart suitable properties to the films disclosed herein, such as gloss, transparency, and stiffness. ing. This substance is KODAII PE Ding G C0POLYESTER6
It is commercially available under the trade name 763. The acid copolyester itself can be attached with Saran (PvDC) paint.

Adhesive strengths approaching 100 grams/inch can be obtained.

Suitably, a heat-sealable layer of ethylene-propylene random copolymer or ethylene-butylene-propylene turbopolymer is coextruded with the core layer onto the surface of the copolyester layer and the reflective core layer. EP cocopolymers usually contain 1 to 7% by weight ethylene, the balance being propylene. This copolymer is 5.5 to 6.5% by weight.
Preferably, it contains ethylene. The melting point of the copolymer is lower and broader than that of polypropylene homopolymer.

Its crystal melting point is usually 125 to 130°C. 23
The melt index at 0°C is usually between 2 and 15, preferably between 3 and 8. The molecular weight is 25,000 to 100,000 and the density is 0.89 to 0.92. Random copolymers have better transparency and rigidity than homopolymers, and have lower melting points, so random copolymers can be used as heat-sealing layers.

It is desirable that an anti-blocking agent be added to the EP random copolymer layer before extrusion. For this purpose, silica,
Materials such as clay, talc and glass can be used. Spherical or low aspect ratio particles are often preferred. A suitable antiblocking agent is 3400 to 46
Clay (0POLITE to K) added in an amount of 00pp-
5F-0). A significant number of particles will have portions extending beyond the exposed surface of the EP random copolymer layer.

The following examples illustrate the invention.

EXAMPLE A multilayer film comprising the core layer, copolyester layer, and EP random copolymer layer as described above is coextruded and quenched on a casting drum at between 110 and 135°C, then reheated and oriented. Copolyester layer is approximately 170″
Reheat to F or EP random copolymer layer to 230
? Reheat. The film is stretched in the machine direction by transport rolls rotating at different speeds. Stretching in the machine direction is carried out at a stretch ratio of about 4 to 8. After orientation in the machine direction, the film is stretched in the transverse direction in a suitably heated oven and tenter. The stretching ratio is between 7:1 and 9:1. (The preferred range is 5:1 to 10:1).

The resulting film structure has a total thickness of about 0.80 mil. The core layer is approximately 0.66 mil and the copolyester layer is approximately 0.
．． 10 mil, and the EP copolymer sealant layer is approximately 0
．． It is 04 mil. The copolyester layer is subjected to a corona discharge treatment in a known manner and then a metallized coating is applied. (Techniques such as electroplating, sputtering and vacuum deposition can be used). Corona discharge treatment increases the wet tension to greater than about 56 dynes/cm compared to 35-36 dynes/cm without treatment. The treatment is carried out only on the surface of the copolyester after two-wheel stretching.

In the sample prepared as described above, both surface layers had a
It was found to have a seal strength of about 300 grams under 7 inches. The uniformity of the metal is less than 0.20 unit variation in optical density across a 15 inch piece of film. Good metal adhesion on corona-treated surfaces is also obtained.

Prior to metallization, the moisture vapor transmission rate (-VTR) is approximately 0.51 g/100 in at temperatures below 100 and 90% relative humidity.
/day.

This moisture permeability decreases to approximately 0.05 after metallization. A similar reduction in oxygen permeability was obtained, with the metallized substrate achieving a 0.5 cc/100 in”/day compared to 71 cc/100 in”/day for the untreated film.
It shows an oxygen permeability of 39cc/100in''/day.

(4 other people)

Claims (13)

[Claims] 1. (i) a core layer consisting of isotactic polypropylene; (ii) a coextruded copolyester layer attached to one side of the core layer; and (iii) a coextruded heat sealable layer attached to the opposite side of the core layer. A metallizable oriented plastic film consisting of a layer; 2. A film according to claim 1, wherein the core layer (i) comprises an adhesion promoter. 3. 3. The film according to claim 1 or 2, wherein the copolyester constituting layer (ii) is amorphous. 4. A film according to any one of the preceding claims, wherein the copolyester layer (ii) comprises 1-ethylene, 4-cyclohexylene-dimethylene terephthalate. 5. A film according to any one of the preceding claims, wherein the copolyester layer (ii) is subjected to a corona discharge treatment. 6. A film according to any one of the preceding claims, comprising a vinylidene chloride copolymer coating on the copolyester layer (ii). 7. The film of claim 1, wherein the coextrusion sealable layer (iii) comprises an ethylene-propylene random copolymer. 8. 8. A film according to claims 1 to 7, wherein the coextruded heat sealable layer (iii) comprises an antiblocking agent. 9. 2. The film of claim 1, which is biaxially oriented. 10. The film according to claim 1, which is stretched 4 to 8 times in the machine direction. 11. A film according to any one of the preceding claims, which is stretched 7 to 9 times in the transverse direction. 12. (iv) on the coextruded copolyester layer (ii)
A metallized oriented plastic film comprising a film according to any one of the preceding claims having a metallization. 13. Polypropylene core layer (i) with metal coating (iv)
Use of copolyester layer (ii) when deposited on.