CA1071518A - Method of film coating articles - Google Patents

Abstract

ABSTRACT

The surface of an object is covered with a plastics film by a process in which a preformed solid and tacky plastics film is brought into contact with the surface, the film is stretched over the surface and substantially all the film made to adhere substantially permanently to the object surface through its own tackiness and without the use of an adhesive. Thus, the tacky plastics film may be held in a frame and the object pushed through the film. Alterna-tively the object may be conveyed on a moving belt to a position adjacent to a heated tacky plastics film and the film brought into contact with the object. The plastics film may for example be an ethylene-vinyl acetate copolymer.

Description

This invention relates to the covering of surfaces of objects such as bot-tles or cans with a thin preformed film.
Although glass bottles are often printed with the name of the supplier etc.
printing on glass objects is not easy or particularly cheap. Arlother great disadvantage is that glass objects are liable to break when dropped, projecting sharp dangerous pieces.
We have now found a method whereby surfaces of objects such as glass bottles, jars, etc. can be covered easily with a plastics film. The film can be more readily printed than glass with the required information and various other advantages accrue as will be seen from the following description. The surfaces of flat objects such as glass window panes and metal sheets, can also easily be covered.
According to this invention surfaces of objects are covered by a plastics film by process in which a preformed solid and tacky plastics film is brought into contact Wit~
said surface and the film is stretched said surface whereby substantially all the film adheres substantially permanently to the surface through its own tackiness and without the use of an adhesive. In this manner surfaces are covered with an adhering plastics film which is usually continuous. Usually the surface of the object is substantially completely covered by plastics film. The adhesion between film and surface is substantially permanent as opposed to objects which are wrapped with a temporary packaging film.
The objects whose surfaces are to be covered by this process are manifold, but particularly suitable are glass objects such as glass bottles, glass phials, glass jars and glass window panes. Other objects include plastics and metal containers.
The plastics film can for example be a polyalkylene e.g. polyethylene or polypropylene, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, styrene acry]onitrile copolymers, acrylonitrile~ butadiene styrene copolymers, ethylene propylene copolymers and terpolymers and polybutadienes.
Other films include those made from random and graft copolymers where one of the monomers is ethylene or a polar monomer including acrylic acid, methacrylic acid, acrylate esters, maleic and other anhydrides and ionomeric materials formed by adding metal salts to such copolymers.

- 2 -Particularly suitable examples of plastics film include the plastics film disclosed and claimed in our U.K. patent specification 57680/72 (Serial No: 1401880). This is a transparent self-sealing film made from a composi-tion comprising (i) 90 to 99.95 wt. % of a copolymer of ethylene and a vinyl (or hydrocarbyl substituted) vinyl ester of a Cl to C30 monocarboxylic acid containing at least 89 wt. % of ethylene (e.g. ethylene-vinyl copolymer) and (ii) either 0.05 to 10 wt. % of a hydrocarbon resin (i.e. an amorphous hydrocarbon polymer having an average number MW of not more than 3000), or 0.05 to 5 wt. % of liquid polyisobutene or liquid polybutene or a combination of 0.05 ~o 10 wt % of the hydrocarbon resin and 0.05 to 5 wt. % of the poly-- isobu~ene or polybutene, provided the combined weight of the resin and polyisobutene or polybutene is not more than 10 wt. %. Thus, a particular example is a film made from a composition comprising 99 wt. % of an ethylene-; vinyl acetate copolymer containing 10 wt. % vinyl acetate and 1 wt. % of a liquid polyisobutene rubber (viscosity average MW of 30,000 - 50,000).
Another example of a suitable plastics film is that described and claimed in our copending Canadian application 210392. This is a self-sealing film made from a composition comprising (i) 90-99.95 wt. % of a copolymer of ethylene and a vinyl (or hydrocarbyl substituted vinyl) ester of Cl - C30 monocarboxylic acid, (ii) either 0.05 to 10 wt. % of a hydrocarbon resin, or 0.05 to 5 wt. % of polybutene or polyisobutene or a combination of 0.05 to 10 wt. % of the hydrocarbon resin and 0.05 to 5 wt. % of polybutene or polyisobutene provided the combined weight of the resin and polybutene or polyisobutene is not more than 10 wt. % and (iii) 0.01 to 3.0 wt. % based on the combined weight of (i) and (ii) of a partial carboxylic acid ester of~a polyol (e.g. sorbitan monolaurate).
Thus a particular example is a film made from a composition comprising 96.2 wt. % of an ethylene-vinyl acetate copolymer containing 95 wt. % of . ' ' .

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ethylene9 3 wt. % of hydrogenated polycyclopentadiene resin and 0.8 wt. % of sorbitan monolaurate~
The specification of our Canadian application 230845 describes a further example of suitable plastics films. Such films are self-sealing films c~mprieing .~' .

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~, (i) 95.0 to 99.9 wt. % of either a copolymer of ethylene and a vinyl (or hydrocarbyl substituted vinyl) ester of a Cl - C30 monocarboxylic acid f said copolymer containing 0.10 to 1.95 wt. % of the vinyl (or hydrocarbyl substi-tuted vinyl) ester (e.g. ethylene-vinyl acetate copolymer) or 95.0 to 99.9 wt. % of a mixture of a thermoplastic polyolefin and a copolymer of ethylene and a vinyl (or hydrocarbyl substituted vinyl) ester of a Cl - C30 monocar-boxylic acid, the proportion of polymerised vinyl (or hydrocarbyl substituted vinyl) ester in the mixture being from 0.10 to 1.95 wt. % and (ii) 0.1 to 5.0 wt. % of a partial ester of a carboxylic acid and a polyol. Thus, a particular example of such films is a film made from a mixture comprising 62.5 wt. % of a homopolymer of ethylene, 36.0 wt. % of an ethylene vinyl acetate copolymer containing 5 wt. % of vinyl acetate and 1.5 wt. % of sorbi-tan monolaurater Also the specification of our Canadian application 231039 describes a further example of suitable plastics films. Such films are self-sealing films made from compositions comprising (i) 85 to 99.8 wt. % of a thermoplastic polyolefin (ii) 0.1 to 10.0 wt. % of a partial ester of a carboxylic acid and a polyol and (iii) either 0.1 to 10 wt. % of a hydrogenated hydrocarbon resin or 0.1 to 10 wt. % of polybutene or polyisobutene. Thus a particular example is a film made from a composition comprising 98.5 wt. % of an ethylene homopolymer, 1.0 wt. % of sorbitan monolaurate and 0.5 wt. % polyisobutene.
Another example of such a film is made from suspension PVC powder. A
formulation suitable for blown film comprises 100 parts by weight of PVC, 10-20, e.g. 15 parts by weight of plasticizer such as dioctyl adipate (DOA), 5-15 e.g. 10 parts by weight of epoxidized soya bean oil and O to 5 parts by weight of a lubricant such as stearic acid or a glyceride.
Fllms made from polar copolymers and ionomers are particularly advan~
tageous when heat is used in the covering process as the polar character en-~ - 4 _ , .

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hances the adhesion to many substrates.

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These films are normally made by blowing a tube but can also be made by casting onto a chill ro]l or into water. More details are given in Chapter 9 "The Processing of Crystalline Olefin Polymers", Part II, 1964 RaffO and DOAK by Interscience Publishers~
These plastics films can be of different thicknesses but suitable films are for example those of 5-20 microns, e.g. 10-15 microns thickness. If the main purpose of the covering is to make a bottle shatterproof, thicker films would be used.
The degree of stretching of the film varies with the particular film and objects and method used.
One suitable method of covering a surface of an object is to hold a tacky plastics film in a frame and push the object throu~h the film. Afterwards the film may be trimmed to the desired shape. Thus for example, a bottle such as a lemonade bottle can be covered by holding a tacky plastics film in a circular frame, pushing the bottle bottom first through the film and thereafter cutting the film so that it terminates at the top edge of the neck of the bottle. When the film is cut near the neck of the bot-tle it retracts due to the tension acquired by the film when pushing the bottle through - the film. As an ~lternative the film may be cut near the neck and heat shrunk to a tight fit. Heat shrinking also increases the adhesion between the film and the bottle.
In this method the film is usually stretched linearly to between 200 and 400~0 As another alternative the plastics film may be cut to a suitable shape and the end of the cut film twisted over the top of an already filled bottle, jar, etc.
Using coloured or decorated films, this is a very economical way of improving the appearance of a package.
; ~ Another suitable method of coating the surface of an object relies on obtaining the desired surface and mechanical properties in the plastics film by heating the film.
., ; The coefficient of friction, the str~ss-strain characteristics, and the adhesion to the object are all altered by heating the film before contacting the object whose surface is to be covered. Plastics films which are heated are more tacky, more extensible and adhere better to the object and even more so if the object is also heated. To operate this method ~y`

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the object can be conveyed on a moving belt to a position adjacent to, and preferably beneath, a plastics film. The plastics film is heated to give the required properties. Optionally the surEace of the object itself can also be heated.
The film is then brought into contact with the surface. Excess film can then be removed.
This sequence can be repeated by removing waste plastics film and covered object and replacing these with the new plastics film and object. In this method the film is usually stretched linearly to between 20 and 50%0 The temperature to which the films or surface is heated varies widely with the particular film and the time involved in the processO Normally the film remains below its melting point (e.g. 20-50G below) until it has covered the surface properly. Thus for polyethylene having a melting point of abou~ 100 C the film is beated to about 80C.
Either of the two above-mentioned methods can be modified by applying a vacuum (reduced pressure) below the film or a pressure above the film so as to force the film into contact with the surface to be covered. This modification is advantageous for processes where several surfaces are to be covered in each operation.
Any of these methods can be modified further by the use of coextruded films for the covering operation. In this manner the surface characteristics needed for the covering operation can be controlled independently from the properties of the exposed outside surrace. Thus, the outside layer can be made with a low coefficient of friction by incorporating a slip additive, or it can be made from a coloured material.
Although the invention has been described with details for 3 dimensional objects, it is also suitable for flat objects such as plate glass or metal sheeting.
Here again the ability to give a decorated, attractive, protective covering is often a great advantage.
By the process of the invention the following advantages are obtained:
(i) the film can be more easily and more attractively printed than for example a glass bottle "- ~

(ii) glass objects such as bottles are protected during transport, preventing scratches which cause breakage due to the notch sensitivity of glass (iii) should the object, eOg. a glass bottle or glass pane, break the plastic film is not usually ruptured and this reduces the possibility of flying or dangerous glass fragments (iv) a plastics coated bottle makes much less noise during transit than the normal glass bottle The invention is now illustrated with reference to the accompanying drawings in which Figo 1 shows the sequence of operations where a frame is used to hold the film and Figo 2 shows the sequence of operations where a heated film is used.
Referring to Fig. 1 in sequence 1 the preformed plastics film 1 is held in a rigid clamping device 2. In sequence 2 a bottle 3 is moved down into the film 2. This movement is continued in sequence 3 until the bottle is covered up to the neck with plastics film~ Sequence 4 shows three alternative ways of finishing the film coverings. In (a) the film 4 is cut at the clamping ring and twisted. In (b) the film is cut at the neck (5) with a rotating knifeO In (c) the film is cut at the neck with a hot wire and heat shrunk to give a neat finish~
Referring to Fig~ 2 in sequence 1 a plastics film ll is heated to make it so~t and tacky. In sequence 2 an object 13 supported on a porous plate 12 is brought into contact with the tacky plastics film 11. In sequence 3 vacuum is applied on the porous plate 12 and this causes the tacky film 11 to adhere firmly to the object 130 Finally in sequence 4 the covered object 13 is cut away from the film 11.

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Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for covering a surface of an object with a plastics film in which a preformed solid and tacky plastics film is brought into contact with said surface and the film is stretched over said surface whereby substantially all the film adheres substantially permanently to the surface through its own tackiness and without the use of an adhesive.

2. A process according to claim 1 in which the surface is covered with a continuous film.

3. A process according to either of claims 1 and 2 wherein the plastics film comprises an ethylene-vinyl acetate copolymer.

4. A process according to either of claims 1 and 2 wherein the film is made from a composition comprising (i) 90 to 99.95 wt.% of a copolymer of ethylene and a vinyl (or hydrocarbyl substituted vinyl) ester of a C1 to C30 monocarboxylic acid containing at least 89 wt.% of ethylene and either (ii) 0.05 to 10 wt.% of an amorphous hydrocarbon polymer having an average number molecular weight of not more than 3000 or 0.05 to 5 wt.% of liquid polyisobutylene or liquid polybutene or a combination of 0.05 to 10 wt.% of the hydrocarbon polymer and 0,05 to 5 wt.% of the polyisobutene or polybutene, provided the combined weight of hydrocarbon polymer and polyisobutene or polybutene is not more than 10 wt.%.

5. A process according to either of claims 1 and 2 wherein the plastics film is made from a composition comprising (i) 90 to 99.95 wt.% of a copolymer of ethylene and a vinyl (or hydrocarbyl substituted vinyl) ester of a C1 to C30 monocarboxylic acid (ii) either 0.05 to 10 wt.% of a hydrocarbon resin, or 0.05 to 5 wt.% of polybutene or polyisobutene or a combination of 0.05 to 10 wt.% of the hydrocarbon resin and 0.05 to 5 wt.% of polybutene or polyisobutene provided the combined weight of the resin and polybutene or polyisobutene is not more than 10 wt.% and (iii) 0.01 to 3.0 wt.% based on the combined weight of (i) and (ii) of a partial carboxylic acid ester of a polyol.

6. A process according to either of claims 1 and 2 wherein the plastics film is made from a composition comprising (i) 95.0 to 99.9 wt.% of either a copolymer of ethylene and a vinyl (or hydrocarbyl substituted vinyl) ester of a C1 to C30 monocarboxylic acid, said copolymer containing 0.10 to 1.95 wt. % of the vinyl (or hydrocarbyl substituted vinyl) ester or 95.0 to 99.9 wt. % of a mixture of a thermoplastic polyolefin and a copolymer of ethylene and a vinyl (or hydrocarbyl substituted vinyl) ester of a C1 to C30 monocarboxylic acid, the proportion of polymerised vinyl (or hydrocarbyl substituted vinyl) ester in the mixture being from 0.10 to 1.95 wt. % and (ii) 0.1 to 5.0 wt. %
of a partial ester of a carboxylic acid and a polyol.

7. A process according to either of claims 1 and 2 wherein the plastics film is made from a composition comprising (i) 85 to 99.8 wt. % of a thermo-plastic polyolefin (ii) 0.1 to 10.0 wt. % of a partial ester of a carboxylic acid and a polyol and (iii) either 0.1 to 10 wt. % of a hydrogenated hydrocar-bon resin or 0.1 to 10 wt. % of polybutene or polyisobutene.

8. A process according to either of claims 1 and 2 wherein the plastics film is made from a composition comprising 100 parts by weight of PVC, 10-20 parts by weight of plasticizer, 5-15 parts by weight of epoxidized soya bean oil and 0 to 5 parts by weight of a lubricant.

9. A process according to either of claim 1 and 2 wherein the plastics film is of 5-20 micron thickness.

10. A process according to claim 1 which comprises holding a tacky plastics film in a frame and pushing the object through the film.

11. A process according to claim 10 wherein the object is a bottle and after the bottle has been pushed through the film, the film is cut near the neck and heat shrunk to a tight fit.

12. A process according to claim 1 wherein the object is conveyed on a moving belt to a position adjacent to a heated plastics film and the film is brought into contact with the object.

13. A process according to claim 12 wherein the moving belt is positioned beneath the plastics film.

14. A process according to either of claims 12 and 13 wherein the surface of the object is heated.

15. A process according to any one of claims 10, 11 and 12 wherein a vacuum is applied below the film or a pressure is applied above the film.