FR2575137A1 - Heat-shrinkable composite sheath and process for manufacturing it - Google Patents

Abstract

The invention relates to a thermoplastic sheath (and sections or sleeves cut to a given length in this sheath) intended to be used for the partial or total packing and/or the decoration of containers by placing it around the latter, followed by shrinking caused by external heating so that it matches perfectly the forms of these containers. According to the invention, the structural material of the sheath consists of the assembly, by means of a cold adhesive without solvent, of a thermoplastic film having a preponderant monoorientation and of a nonoriented thermoplastic film, free of elastic memory, acting as a barrier impervious to gases and light rays.

Description

The present invention relates to the field of protec
tion and / or decoration of objects, more particularly packaging
and containers, by sheath sections or sleeves made of plas
retractable tick, generally printed and which, subject to milking
external heat, perfectly match the shape of the object.

It relates, more particularly to a composite sheath, the
structure consists of two glued films, of nature and character
different aspects, and which makes it possible to broaden the applications of
thermoplastic sleeves shrunk around containers.

It is well known to provide containers such as
bottles, aerosol cans, flasks, canisters and other items
packaging jets, a protective sleeve or sheath or a
tamper-evident ring made of heat-shrinkable plastic. This man
chon is placed around the container and, after external heating, it
must conform without deformation to the outline of the container.

To make such retractable sleeves,
during the production of sheaths, plastic films (generally
polyvinyl chloride) which are lettered essentially in the direction
the perimeter of the objects to be coated, so that they acquire a
memory (shrinkage percentage) of the order of 40 to 50%, the same
moire in the longitudinal direction, i.e. the one corresponding to
the height of the sheath section being only of the order of 9 to 15%.

Such films, which generally are printed and / or decorated to serve
of labels on the receptacle to be coated, are said to be "monoriented
or "predominantly oriented".

In a number of application cases, such as for example packaging containing light-sensitive products
and / or oxidation, the use of the aforementioned films, which are permeable to
gas, poses problems regarding the long-term preservation of products
conditioned and it is normally necessary to plan around
these latter8 .. the presence of a protective film called "barrier" presents
both the gas impermeability and insensitivity characteristics
to light rays, in particular an absence of transmission of rays
ultra-violet.

However, these films cannot be applied to
receptacles only by gluing, or equivalent means, because they do not
do not have an elastic memory (they are called "non-oriented") and therefore cannot justify the use of the modern technique of shrinking, recalled above.

 It has now been found that this difficulty could be overcome and by thermal shrinkage of the sleeves printed on containers protected by a protective barrier film.

 To achieve this aim, the invention proposes the use, as a constituent film of the thermoplastic sheath intended to be cut into sections, of a composite material comprising the assembly, using a cold glue without solvent, of a monooPiente thermoplastic film, by stretching essentially in the transverse direction, and of an undirected thermoplastic film, devoid of elastic memory, playing the role of barrier for gases and light rays.

 Such a barrier film, of a type known per se, can be constituted, for example, by polyvinylidene chloride> polyvinyl alcohol, copolymers of acylene and vinyl acetate, ionomer resins such as, for example, ethylene copolymers. Methacrylic acid salified by metals, tersphthalic polyesters, etc. It is also advantageous to use metallized films, including thin aluminum films.

 The adhesive used for the production of the composite material must be of the thermoplastic type allowing cold and dry bonding, we can cite in this regard, without limitation, a polyurethane adhesive or of acrylic type or any other heat-activatable adhesive .

 The monoriented film can be constituted by crystal polyvinyl chloride as used for making decorative shrink sleeves. However, it is known that the optimum temperature range for shrinking without overheating and without wrinkling for such films is between fairly narrow ranges, generally between 600 and 1100C depending on the products on the market. Therefore, it should be expected that the non-oriented film, in the composite material according to the invention, constitutes a constraint on shrinking when the external device for supplying calories is not adjusted for the aforementioned range of temperature.

 It has now been found, according to another characteristic of the invention, that said range could be widened notably (or in other words, flatten the temperature-viscosity curve for the monetired film) and obtain a uniform shrinkage for the composite material, using a polyvinyl chloride modified film, for example a chloride-vinyl acetate copolymer in which a small proportion of polymer with long paraffin chains has been incorporated, for the manufacture of the monoriented film. With this particular adaptation, the retraction can be carried out later of the composite material - by passage in tunnel oven, exposure to IR lamps or any other device without having to monitor very strictly a limit temperature range.

 The invention also relates to a process for preparing the above-mentioned sheath made of composite material. According to an advantageous embodiment, when the barrier film is applied to the same layer of dry glue, solvent-free, with which the elastic memory film is coated beforehand, the edges of the latter a free space, for example from one to three millimeters, coated with glue but not covered with barrier film, so that the sheath of composite material can then be formed by folding this free space over the other end of the composite film then longitudinal bonding to obtain the sheath.

 According to a variant, it is also possible, during the application of the barrier film, to keep a free border on each side of the composite and then to make a median and longitudinal cut of the latter in order to obtain two composite films which will then be folded in sheath by gluing. longitudinal as said above.

 Of course, other embodiments can be conceived without departing from the general scope and scope of the present invention.

Claims (6)

- R E V E N D I C A T I O N S  1. Thermoplastic sheath (and sections or sleeves cut to length given in this sheath) intended to be used for the total or partial covering and / or the decoration of receptacles by laying around them then shrinking by external heating to perfectly match the forms of these receptacles, characterized in that its structural material is constituted by the assembly, using a cold glue without solvent, of a thermoplastic film in preponderant monoorientation, by stretching -essentially in the transverse direction, and a non-oriented thermoplastic film, devoid of elastic memory, playing the role of impermeable barrier to gases and light rays  2 sheath according to claim 1, characterized in that the monorient film is based on polyvinyl chloride.  3. Sheath according to claim 1, characterized in that the monoriented film is based on a copolymer of vinyl chloride and  of vinyl acetate modified by incorporation of polymer with long paraffinic chains.  4. Sheath according to any one of claims 1 to 3, characterized in that the cold glue is chosen from the group of dry adhesive thermoplastics and that the barrier-effect film, not oriented, is chosen from the group copolymers and terpolymers of alkyl vinyl acetate, polyvinyl alcohol, terephthalic polyesters, ionomer resins.  5. Sheath according to claim 4, characterized in that the non-oriented film is of metallized type and can be constituted by aluminum.  6. Method of manufacturing a thermoplastic sheath according to any one of claims 1 to 4, characterized in that a thin layer of the solvent-free glue is deposited on the monooriented thermoplastic film and then the film is applied to the latter barrier effect while providing at one end and. all along the oriented film a free border, and in that the composite material thus obtained is sheathed, by folding said free border on the other end of the composite then by ensuring, by gluing and / or welding, the longitudinal fixing.