Note: Descriptions are shown in the official language in which they were submitted.
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.
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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-
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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.
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; 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
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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
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(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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