Protective film for cans or drink and food containers in general

Protective film for cans or drink and food containers in general, consisting of a thin layer from biodegradable plastic material, which wraps up the upper base of the can (2). The envelope (1) is easily removed by hand, thanks to simple tabs (3) provided along the circumference of the can (2) or on the upper face of the latter, or on the vertical symmetry plane of said can. The protective film solves the problem of dirt which builds up on cans when they are put up for sale and which enters the mouth when the can (2) is opened.

BACKGROUND OF THE INVENTION 
This invention relates to a protective film for cans or drink and food 
containers in general. 
The protective film subject matter of this invention is suitable to be 
utilized in the alimentary field and, in particular, in the field of 
canned drinks, beer, cooking oils, meats and vegetables in general. 
BACKGROUND OF THE PRIOR ART 
As it is known, in these last decades, the sale of canned foodstuff has 
increased greatly. Especially in the case of sparkling soft drinks and 
beers, for volumes of less than half liter, this type of packing has 
replaced almost completely the traditional method of bottles from glass or 
plastic material. 
Cans offer many advantages: easy production, storing and transport, almost 
impossible breaking, recycling of the utilized material. 
There exists however a health problem. Cans are generally supplied in 
packages containing each 2 to 6 cans. Once cans have been taken out from 
the package, they are placed on the shelves of the shops or sale and/or 
refreshment outlets without any protection. 
In this way, dust, more or less harmful micro-organisms and any kind of 
dirt settle on the exposed surfaces of the can. The same happens, although 
to a lesser extent, when cans are kept in houses, before consumption. Dust 
and impurities in general build up especially on the upper base of the 
can, and in particular along the contact line between the can base and its 
edge. The fluid which comes out from the container during the emptying 
absorbs and drags along between sips such dust and impurity particles, 
which enter therefore easily the mouth and pass from the mouth to the 
digestive system, with the consequence that they are sometimes harmful to 
the health. 
Also the unaesthetic aspect of this packing system is obvious and causes a 
sense of disgust to the user who must put his or her lips in touch with a 
dirty container. 
This problem is even worsened by the recent opening system utilized for 
soft drinks. This opening system comprises a snap-tab which is no longer 
snapped off but squashed in the inside of the metal container. In this 
way, all the aforementioned impurities flow directly into the drink 
contained in the can. Different types of caps are known in the art, whose 
main aim is to close the slot which forms in the can once the tab has been 
snapped off, so as to protect and preserve the organoleptic 
characteristics of the drink in time. These types of caps satisfy such 
aim, but they have the drawback of being rather expensive. Even though 
mass-produced from low-cost materials, they are nevertheless expensive for 
can (or foodstuff) producers. Besides, one should not forget the pollution 
which a high number of such protections would cause to the environment, 
taking into account the fact that they are made from resistant materials, 
having to be long-lasting, and that they have to be remarkably thick to 
resist the pressure exercised by carbon dioxide incorporated in the fluid. 
Another type of known envelope is the film from plastic material which 
wraps up multiple sale packs (two or more cans). However, also this type 
of protection from dirt and micro-organisms has the drawback of a poor 
ecologicity. In fact, the film from plastic material utilized as an 
envelope has to be resistant and lasting, to allow can transport and 
preservation also for a rather long time. 
SUMMARY OF THE INVENTION 
The object of this invention is to solve the aforementioned problem. More 
particularly, the object of this invention is to realize a protection for 
cans having a very low cost and a relatively rapid degradation time. 
A further object of this invention is to provide a protective envelope for 
cans with a method so simple as to allow firms producing drinks and food 
in general to apply directly said envelope during the packing stage, 
without burdening economically the final consumer, and with a sure image 
yield. 
A further object of this invention is to provide the final purchaser of 
canned foodstuff with a protection capable of protecting it from the 
contact with impurities, dust, dirt and various micro-organisms. 
According to this invention, these and still other objects are achieved by 
utilizing a thin protective film for cans of drink and food containers in 
general, consisting of a biodegradable plastic material, preferably 
transparent, applied on the base provided with an opening of the can or 
container. 
The plastic material utilized for the protective film subject matter of 
this invention has an average duration of about three months in the 
presence of external bacterial and atmospheric agents (in particular, 
light and heat); while its duration is much longer if it is well protected 
from said bacterial and atmospheric agents. Between the protective film 
and the upper base of the can, an inert gas or chemical sanitizing 
substances not harmful for human health may be interposed. 
The above film is applied on each can by means of any of the methods known 
today: by means of heat, by immersion or spraying, by means of a 
biodegradable melt composition, by means of vacuum methods, pressure 
methods, or non toxic glues, etc., during the can filling and/or closing 
cycle. 
The film can be easily removed by hand, thanks to simple tabs or other 
easily utilizable means, obtained along the circumference of the can or on 
the upper face of same, or along its vertical symmetry plane or in any 
other position. The envelope may even have two or more opening systems. 
The film may be applied on either the upper base of the can or on the part 
which comes in touch with the consumer's lips during the use or on both 
bases of the can, and it may also wrap up the can completely. 
The protective film from biodegradable plastic material is insoluble and 
water-tight, and also impermeable to all bacteria which may be harmful for 
human health. 
Any biodegradable and recyclable plastic material can be utilized for the 
production of the envelope or protective film subject mater of this 
invention. In particular, a material is preferred which is biodegradable, 
thermoplastic, self-supporting, adhesive and thermoretractable, to make 
its appplication easier. Besides, the protective film should preferably 
have a high modulus of elasticity; high ultimate tensile stress 
(stretching resistance of at least 50%); high abrasion resistance; high 
bending capacity and high tightness to water and micro-organisms. 
Biodegradable and recyclable thermoplastic materials are will known on the 
market and are produced and sold by several companies. Such materials are 
generally based on starch or polyvinyl alcohol or degradable plastic 
materials. 
Among the biodegradable thermoplastic materials and the relating kwown 
films, we mention, only by way of example: 
the thermoplastic material constituted of biodegradable polyesters and 
maize starch, produced and sold by Novamont under the trade name 
MATER-BI.sup.R ; 
the thermoplastic material constituted of 3-hydroxybutyrate and 
3-hydroxyvalerate, produced and sold by Imperial Chemical Industries under 
the trade name BIOPOL.sup.R ; this material is described in patent WO 
92/01733; 
the biodegradable polyester based on polyethylene terephthalate (PET), 
copolymerized with cycloaliphatic diacids, described in patent WO 
93/07197; 
the biodegradable films described in U.S. Pat. No. 3,472,804, obtained by 
fusion of polymeric compositions comprising: polyvinl alcohol (with high, 
middle and low molecular weight), starch, preferably dextrin, formaldehyde 
polymers, preferably urea formaldehyde polymers, and a plasticizer; 
the biodegradable films described in U.S. Pat. No. 3,949,145, obtained from 
aqueous solutions of poyvinyl alcohol, starch and glycerine, covered with 
a water-resistant polymer; 
the biodegradable films described in WO 94/25493, composed by mixes of 
pectin and gelatinized starch; 
the biodegradable films produced from raw material containing PIHT (sorgum, 
kemaf or cereals); 
the biodegradable films described in patent WO 94/04600, based on vegetable 
raw materials (carbohydrates), such as potato starch, maize, bitter 
cassava, wheat, barley, sorgum, etc., and polysaccharides; 
the biodegradable films applied by spraying and composed by a biodegradable 
thermoplastic polymer, such as polyethylene, polyamide, polyurethane, 
polyphospharenes, chitin, etc., and by an organic solvent such as acetone, 
ethylenglycol, propylenglycol, N-methyl-2-pyrrolidin, etc.; 
the biodegradable films described in patent WO 93/12986, containing a 
hydrocolloid, such as an alginate, and an elastomer and/or cellulose 
fibers; 
the biodegradable films described in U.S. Pat. No. 4,337,181, obtained by 
blowing a mix of starch and an ethylene-acrylic acid copolymer; 
the biodegradable films described in Japanese patent 62-56481, based on 
polylactic acid, polyglycolic acid or poly-2-oxybutirric acid polymers; 
the biodegradable films described in patent WO 94/13774, based on 
compositions containing starch and water, having an ultimate tensile 
strength of over 50%; 
a mix of starch and an ethylene copolymer with vinyl acetate or methyl 
and/or ethyl acrylate, described in U.S. Pat. No. 5,087,650; 
a polymeric composition consisting of an ethylene copolymer, a condensation 
product of starch and propylene oxide, an ethylene copolymer with vinyl 
acetate and a polyoxydric alcohol as dispersing agent and plasticizers; 
this composition is described In U.S. Pat. No. 5,234,987; 
the biodegradable films described in U.S. Pat. No. 5,254,607, constituted 
of a mix of starch, an ethylene-acrylic acid or ethylene-vinyl alcohol 
copolymer and an aliphatic polyester; 
the biodegradable films described in U.S. Pat. No. 4,133,784, based on 
starch and an ethylene-acrilic acid copolymer; 
the biodegradable films based on polyvinyl alcohol and an ethylene, 
propylene, isobutene or styrene copolymer with acrylic acid, vinyl alcohol 
or vinyl acetate, described in patent WO 93/09171. 
The mechanical properties of the biodegradable thermoplastic films 
containing starch can be improved by monoaxial or biaxial stretching. 
Besides the aforementioned materials, other materials, such as for instance 
paper, may be utilized, provided that they are suitably treated to prevent 
dust, impurities and micro-organisms from passing through. 
The films utilized for the protection of cans for drinks and food in 
general, subject matter of this invention, have a very thin thickness, 
preferably comprised between 1 micrometer and 0,5 mm.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
More particularly, envelope 1 consists of a thin film of biodegradable 
plastic material. The film is hot-applied on the surface to be protected 
of can 2, by immersion or by spraying. In the embodiment shown in the 
figures, the whole upper base of can 2 (i.e. the one provided with opening 
tab 4 in the case of soft drinks), including edges, is covered by the 
protective film 1. 
Envelope 1 is provided with an opening snap-tab 3, obtained along the 
circumference of can 2, in the case shown in FIG. 1, or on the upper base 
of can 2, in the case of FIGS. 2 and 3, which allow an easy hand removal 
of film 1. The opening snap-tab 3 may be a transversal slip, as in FIG. 3, 
or a strip divided into two Y-shaped branches, as in FIG. 2. 
Film 1 is applied on cap 2 directly by the producer or the packager. To 
drink or to eat the food contained in the can, the consumer snaps tab 3, 
removes envelope 1 and opens the slot obtained on the surface of can 2 
through the usual tab 4. 
In this way the surface of can 2 under the protective film 1 remains always 
clean and healthy. 
Film 1, being made from biodegradable material, can be disposed of in any 
way, as after two-three months it destructs itself thanks to the external 
bacterial and atmoshperic agents. Alternatively, such film 1 may remain 
united to can 2 in one or two points, thanks to the presence of special 
glues (non biodegradable, such as silicone) that can be utilized to glue 
the film. 
Between envelope 1 and can 2 any material may be inserted, such as, for 
instance, inert gases, disinfectants, gadgets, promotion leaflets, 
illustrations, receipes, etc. 
FIG. 4 shows the envelope 1 covering the entire can 2 while FIG. 5 shows 
the envelope 1 covering the top and bottom ends of can 2. 
Although this invention has been illustrated with reference to some 
embodiments shown in the attached figures, it is obvious that some 
modifications and alternatives may be introduced in its industrial 
realization, in the light of the above description. Hence, this invention 
covers any alternative and modification falling within the spirit and the 
protection scope of the attached claims.