WO2000016975A1

WO2000016975A1 - A process for the production of a laminated film

Info

Publication number: WO2000016975A1
Application number: PCT/NZ1999/000158
Authority: WO
Inventors: Geoffrey John Harnett
Original assignee: FLEX PACK INTERNATIONAL (HOLDINGS) Ltd
Current assignee: FLEX PACK INTERNATIONAL (HOLDINGS) Ltd
Priority date: 1998-09-22
Filing date: 1999-09-22
Publication date: 2000-03-30
Anticipated expiration: 2001-03-22
Also published as: AU5886899A

Abstract

A process for manufacturing a laminated film structure which includes the steps of reverse printing and coating on one substrate, metallising said one substrate on the printing and/or coating, and laminating with an adhesive a second substrate to the metallised layer on said one substrate to thereby form a laminated film substrate. The said one substrate is preferably a biaxially orientated polypropylene or the like film and said second substrate is preferably a polyethylene film. The coating can be a nitrocellulose, polyamide, acrylic or other coating which protects the ink before it has applied thereto a metallised layer.

Description

A PROCESS FOR THE PRODUCTION OF A LAMINATED FILM

Field Of The Invention

The invention relates to laminated film structures and their processes of manufacture and particularly to packaging films such as those used for packaging snack and other foods as well as other products.

Background To The Invention

Films used for packaging snack foods are normally laminated structures. The laminated structures are formed from plastics films and the plies are usually selected to give the foodstuff shelf life, by providing a barrier against oxygen, moisture and light as well as providing good product presentation.

Currently used structures (Prior Art Figure 1 attached) are generally a biaxially orientated film such as a biaxially orientated polypropylene or the like (BOPP) layer which is reverse printed with advertising and presentation material. This is laminated by adhesive to a second layer of BOPP film which has been metallised. A large number of patent specifications disclose such multi-layer laminated structures.

In such film structures the metallised layer is incorporated to make the laminated structure less permeable to oxygen, moisture and light.

With current structures such as a BOPP layer laminated to a metallised BOPP layer products can be wrapped and sealed and the sealing is achieved by virtue of the fact that the exposed surface of the BOPP layer is coated with a thin layer of sealing material. This seal however, has limited strength and integrity due to the very thin layer of sealant web coated onto the BOPP layer.

Historically in situations where higher integrity seals and seal strength are required this has required moving to a pack constructed from a triple ply laminate. The three plies of this structure are as follows:

Ply A - the outside surface of the pack is typically reverse printed polyester PET or BOPP film;

Ply B - the second ply of the structure is typically metallised polyester or metallised BOPP film which is adhesive laminated to Ply A;

Ply C - the third layer of this laminate structure is typically polyethylene which is adhesive laminated to Ply B.

This construction provides barrier properties through the metallised Ply B film and high seal integrity through the Ply C layer.

It has not been practical in the past to apply a metallised film to ink because the particles tend to migrate into the ink and discolour the printing and the barrier properties of the metallised surface are reduced due to the rough surface created by the ink.

The provision of three layers or plies in the laminated structure also means that the final cost of the structure includes the costs of the three substrate layers and the additional processing costs. Each additional layer can add markedly to the final cost and this is particularly the case if a special extra cost biaxially orientated film is incorporated. These films are significantly more costly to produce than, for example, a polyethylene film. For example, in New Zealand, a kilogram of BOPP film currently costs about $4.00 whereas a kilogram of polyethylene film costs $2.00.

An object of the present invention is to provide an alternative laminated film structure which is available at a reduced cost by substituting for a relatively high cost biaxially orientated polypropylene film a less expensive plastics film such as a polyethylene or the like film and producing a laminated film structure with the same characteristics but as a two ply laminate structure.

A further object of the invention is to provide a method of manufacture of a 2 ply structure that achieves all the benefits of 3 ply structures detailed above.

Summary Of The Invention

According to a first aspect of the invention there is provided the metallising of a web or ply after it has been printed due to a special coating applied behind the print and prior to metallising.

The invention provides in another aspect a process for manufacturing a laminated film structure, the process including the steps of: reverse printing and coating on one substrate, metallising said one substrate on the printing and/or coating, laminating with an adhesive a second substrate to the metallised layer on said one substrate to thereby form a laminated film substrate. The said one substrate is preferably a biaxially orientated polypropylene or the like film and said second substrate is preferably a polyethylene film.

According to another aspect of the invention there is therefore provided a laminated film structure which incorporates a biaxially orientated polypropylene or the like film one face of which is reversed printed, the reverse printed face of the film can or can not have applied thereto a coating which protects the ink before it has applied thereto a metallised layer, the metallised layer is laminated to a polyethylene or other substrate with an adhesive to create the film structure.

The resultant construction can be as follows:

Ply A - this is typically BOPP or polyester film which is typically reverse printed with advertising material. A special coating is sometimes required and applied to the printed surface to firstly protect the print from the metallisation process and secondly provide an exceptional surface for metallisation that enables extremely high barrier properties to oxygen and moisture to be achieved; and

Ply B - this ply is typically polyethylene as this substrate is significantly cheaper than alternatives but also has exceptional sealing properties; and

Ply B is then laminated to Ply A with an adhesive.

The biaxially orientated polypropylene film if used in Ply A can have a thickness of between 1 8 and 30 microns. The alternative film used in Ply A can be a polyester film or another non-extensible web film. The alternative film used in Ply A can have a thickness of 10 to 1 5 microns.

The adhesive can be a two pot polyurethane adhesive or solventless adhesive.

The coating can be a nitrocellulose coating applied to form a flat planar surface which bonds to ink giving a good surface for metallising and hence improved barrier properties. Alternatively, the coating can be a polyamide, acrylic or other coating which protects the ink from at least discoloration before the surface is metallised.

The replacement of the second metallised biaxially orientated polypropylene film with polyethylene enables higher seal integrity on the finished product while giving better product presentation due to retained inflation. High barrier properties of the finished film structure are obtained due to both the improved seal integrity and the improved metallisation to the coated surface.

Description Of The Drawings

Figure 1 shows diagrammatically in section the logos of a typical prior art structure. Figure 2 of the attached drawing shows a cross-section through a section of film structure according to the present invention.

Preferred Examples Of The Invention

In Figure 2 of the drawings is shown an example of the new construction. In this construction the BOPP layer is indicated by arrow 1 and the print is on surface 2. The coating is indicated by arrow 3 and the metallised layer by arrow 4. An adhesive 5 holds a polyethylene layer 6 to thereby form the complete structure. Where in the aforegoing description particular compounds are mentioned it is to be appreciated that their equivalents can be substituted as if they were individually set forth herein.

Thus by this invention there is provided a laminated film structure and a process for its manufacture, the structure being particularly useful for packaging snack foods and other products.

A particular example has been described and it is envisaged that improvements and modifications can take place without departing from the scope of the attached claims.

Claims

1 . A process for the production of a laminated film structure which includes applying a coating to a web or ply after it has been printed and prior to metallising over the coating.

2. A process as claimed in claim 1 for manufacturing a laminated film structure, the process including the steps of: reverse printing on one substrate,

optionally applying a coating over the reverse printing, metallising said one substrate on the printing and/or coating, laminating with an adhesive a second substrate to the metallised layer on said substrate to thereby form a laminated film substrate.

3. A process as claimed in claim 2 wherein said one substrate is a biaxially orientated polypropylene or the like film.

4. A process as claimed in claim 2 wherein said one substrate is a polyester film or another non-extensible web film.

5. A process as claimed in claim 2 to 4 wherein said second substrate is a polyethylene film. δ

6. A process for the production of a laminated film structure substantially as

hereinbefore described with reference to Figure 2 of the drawings.

7. A structure which incorporates a biaxially orientated polypropylene or the like film one face of which is reversed printed, the reverse printed face of the film

can or can not have applied thereto a coating which protects the ink before it

has applied thereto a metallised layer, the metallised layer is laminated to a polyethylene or other substrate with an adhesive to create the film structure .

8. A laminated film structure as claimed in claim 7 wherein:

Ply A, the first substrate, is a BOPP or polyester film, which optionally requires a special coating applied to the printed surface to protect the print from a metallisation process and secondly provide an exceptional surface for metallisation that enables extremely high barrier properties to oxygen and moisture; and

Ply B is polyethylene or the like non-extensible web film which is inexpensive and has exceptional sealing properties.

9. A laminated film structure as claimed in claim 7 or claim 8 wherein the first substrate is a biaxially orientated polypropylene film with a thickness of between 1 8 and 30 microns.

10. A laminated film structure as claimed in claim 8 wherein the first substrate is a

polyester film or another non-extensible web film with a thickness of 10 to 1 5

microns.

1 1 . A laminated film structure as claimed in any one of claims 7 to 10 wherein the

adhesive is a two pot polyurethane adhesive or solventless adhesive.

1 2. A laminated film structure as claimed in any one of claims 7 to 1 1 wherein the coating is a nitrocellulose coating applied to form a flat planar surface which bonds to ink giving a good surface for metallising while providing improved

barrier properties.

1 3. A laminated film structure as claimed in any one of claims 7 to 1 1 wherein the coating is a polyamide, acrylic or other coating which protects the printing ink thereon.

14. A laminated film structure substantially as hereinbefore described with reference to the examples and as shown in Figure 2 of the drawings.