FR2774078A1 - Solids, especially sweets, wrapped in twist or fold retaining polymer film - Google Patents

Abstract

Solid is wrapped in a film having at least one twist or fold. The film comprises at least one polyester layer. Independent claims are also included for the following: (1) a film comprising at least three layers, including a middle polyolefin layer and at least two polyester layers, where the total polyester content of the film is \- 20 wt.%; and (2) tubular coextrusion of the thermoplastic compositions.

Description

FILM FOR THE WRAPPING OF OBJECTS

  The invention relates to an assembly comprising a solid and its packaging, said packaging comprising at least one film comprising at least one foil and / or a fold, said film comprising at least one layer comprising at least one polyester. The invention relates directly to the field of packaging food materials such as sweets such as chocolates, candies, boiled or caramel sugars, "chewing gum", lollipops, but also that of any other solid object such as soaps, cheeses in portions, culinary additives in doses such as bouillons in cubes. Figures 1 and 2 show, by way of example, candies after wrapping in the context of the present invention. The packaging in question in the present application can therefore be a film directly marrying most, if not almost all, of the surface of the packaged solid, the latter generally being made up of a single element (as opposed for example to a powder made up of several elements in the form of particles), as is the case for example for a candy. Of course, in the context of the present invention, the assembly may include - the solid object, itself first wrapped by a first film or paper, if necessary metallized, - itself wrapped by the film comprising at least one foil and / or a fold and comprising at least one

  layer comprising at least one polyester.

  According to the prior art, the candies can be wrapped using polyvinyl chloride (PVC) or cellophane films. PVC is, in general, in the process of substitution, and is moreover of high density so that it significantly increases the batches of packaged candies. Cellophane is made by a complex process making it expensive and

  its producers are fewer and fewer. There is therefore a need for substitutes for these two materials, in particular in the field of films for wrapping solid objects such as candies.

  A film suitable for wrapping a solid must meet several technical criteria.

  In particular, the film must be suitable for wrapping, that is to say it must keep the shape which was given to it during the wrapping.

  with the weakest possible tendency to return to its original form, i.e. flat film. This property makes it possible to avoid having to use an adhesive or a glue, for example at the level of the tightest zone of a foil, that is to say between the wrapped solid and the foil itself.

  even, to keep the packaging in the form it was given. This tendency of the film not to keep the shape that we tried to give it is more particularly difficult to overcome when

  one wishes to impart one or more twists to the packaged solid, as for the candies represented in FIG. 1.

  One can easily test the ability of a film to wrap a solid to make a package comprising at least one foil and / or a fold, by observing whether a foil tends to go back after it has been formed. This test can be carried out by forming a twist of a half turn, that is to say by making the part of the film which does not grip the solid perform 1/2 turn with respect to the wrapped solid. A film for wrapping solid objects must also be easily manipulated by the machines responsible for wrapping said objects, from which the highest possible rates are expected, for example 50

  1,500 objects wrapped per minute per machine.

  The film must therefore also be easy to cut. Indeed, before wrapping an object, it is necessary to cut the surface of film useful for wrapping said object, generally from a reel of said film. The film, before wrapping the object, before and after mechanical cutting, must remain flat and must not show any tendency to roll up on itself. Indeed, such a trend could disrupt the production chain and lead to its blocking. In addition, depending on the case, the film may have to present a good

  suitable gloss and / or transparency, and / or good suitability for food contact and / or satisfactory organoleptic properties.

  If necessary, the film must be able to present a good aptitude

  printing and / or metallization. The film must also be easy to manufacture from its basic materials.

  'A single-material film made of bi-oriented high-density polyethylene or bi-oriented polypropylene does not satisfactorily meet the specifications of the intended application in particular because its capacity for wrapping is low. In addition, these materials extruded by the extrusion-blowing method, commonly called the "bubble" method, have poor optical properties due to the presence on the surface of nodules causing light diffraction. The film used in the context of the present invention comprises at least one layer comprising at least one polyester. It can therefore be an essentially monolayer film or a multilayer film. This film generally has a thickness ranging from 5 to 100 μm and more generally from 10 to 60 μm. The film is said to be essentially monolayer if its manufacture only required the extrusion of a single thermoplastic material even if, if necessary, it received, after said extrusion, the usual finishing layers such as a metallization layer and / or printing and / or coating with an antistatic agent. The film is said to be multilayer in the context of the present application

  s15 if it comprises at least two layers of different thermoplastics.

  This film comprises a plane of symmetry which is parallel to it, said symmetry applying both to the geometry and to the composition of the film.

  This implies that if the film is multilayer and comprises at least two layers of different composition, the film necessarily comprises at least three layers. The sum of the mass of the layers comprising a polyester can represent at least 20% by weight of the mass of the film. The film may consist of at least three main layers, one of which, with a composition different from the other two, is in the middle of the film, so that it includes the plane of symmetry of the film. By "three main layers" is meant that the sum of the mass of these three

  layers constitutes at least 80% of the total mass of the film and that each of these three layers obtained from a thermoplastic material constitutes at least 10% by weight of the total mass of the film.

  In the case of a film comprising at least three main layers in the sense given above, the middle layer may comprise at least one polyolefin and the other two substantially identical layers may comprise at least one polyester. The film comprising at least three main layers in the sense given above have an excellent ability to tear (substantially linear tear) in all directions, in particular both in the direction of the coextrusion and in the direction perpendicular to the 4 coextrusion. This film is therefore also particularly suitable for applications requiring good tearability in the direction perpendicular to the direction of coextrusion. Throughout the present application, when mention is made of a layer "based" on a certain material, this means that the layer comprises at least 60% by weight of said material. By polyolefin is meant a polymer of at least one olefin, the term polymer having to be taken in the broad sense, so that it covers the notions of homopolymer, copolymer, terpolymer, lo of interpolymer, or a mixture of polymers. As olefin, there may be mentioned ethylene, propylene, butene, hexene, 1-octene. As the polyolefin, a polymer of propylene or ethylene is preferred, the latter being more preferred. The polymer of at least one olefin can therefore result from the polymerization of at least one olefin with at least one other monomer, which can be an olefin or another monomer such as, for example, vinyl acetate, maleic anhydride or an acrylic ester. In the case of a film comprising at least three main layers in the sense given above, the middle layer is advantageously based on a polymer of ethylene. This ethylene polymer can be such that at least 80% of the monomer units constituting it is ethylene. By polyester is meant a polymer comprising at least one ester function as a repeating unit, the term polymer covering here

  also the notions of homopolymer, copolymer, terpolymer, interpolymer and mixture of polymers.

  The polyester can be derived from the condensation of terephthalic acid and at least one diol.

  Preferably, the polyester is amorphous.

  A preferred polyester is a copolymer which can be obtained from the condensation of terephthalic acid with ethylene glycol and a diol

  comprising at least three carbon atoms. A particularly suitable polyester is a copolymer resulting from the copolymerization of terephthalic acid with ethylene glycol and cyclohexane dimethanol, in particular when it is amorphous.

  In the case of a film comprising at least three main layers in the sense given above, the middle layer may represent

  at 80% by weight of the mass of the film.

  For the case of a film comprising at least three main layers in the sense given above, one can for example cite the combination in which the middle layer is based on an ethylene polymer and represents from 40 to 80 % by weight of the mass of the film, each of the other two layers being based on a polyester which is a copolymer resulting from the condensation of terephthalic acid with

  ethylene glycol and a diol comprising at least three carbon atoms, each of these two other layers representing from 10 to 30% of the mass of the film, said polyester preferably being amorphous, and said diol10 comprising at least three carbon atoms possibly cyclohexanedimethanol.

  Where appropriate, for the case where the film is multilayer, the film may comprise one or more binders, adhesion promoters

  interfaces, between the different layers. Such binders are generally present between the layers of the film in an amount of 1 to 5, m.

  It is also possible to mix one or more binder (s) with at least one of the materials constituting at least one of the layers of the film,

  so as to increase the compatibility and therefore the adhesion of said layer to at least one of the layers which is juxtaposed thereto.z20 Generally, such a binder may be present in the selected layer, at a rate of 10 to 40% by weight .

  Of course, at least one of the ingredients (binder and / or thermoplastic resin) useful in the manufacture of the film may contain at least one adjuvant or additive, such as a dye or pigment, antioxidant, anti-UV agent, slip agent, anti-blocking agent, incorporated in a usual manner and known to a person skilled in the art, taking into account the ingredient

  selected. In the case of a multilayer film and in the case where this film is intended to wrap a food material, it may, depending on the case, prefer to incorporate the adjuvant or additive in the middle layer of the film, if it is desired to reduce the risk of pollution of the food material finally wrapped, by said adjuvant or additive.

  At least one slip agent can be incorporated into at least one ingredient of the film, prior to its preparation by extrusion or coextrusion. If the film is multilayer, the slip agent is preferably incorporated in the outermost coextruded layers. Such a slip agent can for example be chosen from amides of fatty acids such as erucamide and can be introduced at a rate of 200 to 5,000 ppm 6 into the thermoplastic material from which the film layer or layers will be derived.

  containing this slip agent. In general, such a slip agent is incorporated into the film if it is not intended to metallize or print it.

  At least one antiblocking agent can be incorporated into at least one ingredient of the film, prior to its preparation by extrusion or coextrusion. In the case where the film comprises several layers, the anti-blocking agent is preferably introduced so as to be present towards the o10 external layers of the film, for example the two outermost layers having been coextruded, but lying just below the non-coextruded layer or layers, that is to say printing and / or metallization and / or coating with an antistatic agent, if the latter are provided. This anti-blocking agent has the function of reducing the tendency of the film to adhere to itself when it is wound in a reel, so as to facilitate its unwinding. Such an antiblocking agent comprises

  generally particles of mineral filler such as silica and can be incorporated within at least one of the layers in the form of a master batch of mineral filler / thermoplastic resin.

  For the case where the anti-blocking agent comprises a mineral filler, the anti-blocking agent can be incorporated in at least one layer so that the mineral filler is present in said layer at the rate of 100 to 10,000 ppm. Prior to its use for wrapping objects, it is possible to give the film antistatic properties. These antistatic properties allow the film to stay flat and slide well on the manufacturing machines, without having a tendency to roll up on itself, which would risk disturbing or even blocking the entire manufacturing process.30 These antistatic properties can be applied to the film on the basis of principles known to those skilled in the art, that is to say, either by adding at least one antistatic agent in at least one of the ingredients (resin and / or binder ) entering into the composition of the film, prior to the manufacture of the latter, either by coating the film on its external layers using a solution of an antistatic agent, or by any other suitable means. Antistatic agents from the family of

  alkylamines are known to those skilled in the art.

  In general, the coating with an antistatic agent corresponds to a final surface treatment of the film, so that it results in the production of the external layers of the film. This coating with an antistatic agent is therefore carried out in particular after the possible printing step.

  In general, it is not necessary to use a coating with an antistatic agent if the film has been metallized.

  For the case where it is desired to apply printing and / or metallization to the film, it is preferable to carry out a corona treatment 11 on the film prior to said printing and / or metallization. Such a corona treatment can be applied to the film according to the invention, to the

  basis of the principles known to those skilled in the art. However, if the film is essentially monolayer or produced so that its outermost coextruded layers contain at least one polyester, a satisfactory metallization result is obtained even in the absence of corona treatment.

  The film used in the context of the invention can for example be obtained by extrusion or coextrusion in a flat die (often called "cast" extrusion) or by extrusion or coextrusion blow molding (also called "tubular"). The term extrusion applies to the production of a monolayer film, while the term coextrusion applies to the production of a film comprising at least two layers. In the extrusion or coextrusion process in a flat die, a flat film is extruded or coextruded and continuously deposited on a cylinder

  cooler also called "chill-roll".

  After extrusion or coextrusion in a flat die, the film preferably undergoes monoaxial or biaxial stretching (respectively producing a mono or biorirection) on the basis of the principles known to those skilled in the art. Monoaxial stretching is performed in the direction of extrusion or coextrusion ("machine direction"), while biaxial stretching is performed both in the direction of extrusion or coextrusion and in the direction perpendicular to the extrusion or coextrusion. The use of the "cast" process allows to benefit from a surfacing effect of the cooling cylinder, leading to a particularly smooth film and having this

makes a good surface finish.

  Mono or bi-orientation has the particular effect of increasing the density of the film and reducing its resistance to the flow threshold.

  The stretching or the bi-stretching can be carried out continuously or "in recovery", that is to say after rewinding and temporary storage of the film just after the latter has been extruded or coextruded or has already undergone a first stretching .5 In the extrusion or coextrusion blow molding process, the film is extruded or coextruded in the form of a cylindrical bubble obtained by inflation from an annular die. For this process, the draw rate can range from 2 to 50 and preferably from 10 to 30, the inflation rate can range from 1 to 10 and preferably from 1.5 to 3, the air gap can range from 0, 5 to 5lo mm and preferably 0.8 to 1.6 mim. We can play on the printing speed to influence the thickness of the film. Generally, the drawing speed can range from 10 to 150 m / min, and preferably from 30 to 60 m / min. For the case where it is desired to carry out a very sensitive double drawing on the film, the extrusion or the coextrusion can be carried out by application

  of the "double bubble" process, the two "bubbles" of said process being carried out one after the other, generally continuously.

EXAMPLE 1

  An embodiment and use of a three-layer film of the polyester / polyolefin / polyester type will now be described. In this example, the starting materials are designated by abbreviations, the meaning of which is given in this table:

ABBREVIATION NATURE ORIGIN BRAND

  PET Polyethylene terephthalate Eastman Eastar 6763 MDPE Medium polyethylene BASF Lupolen 3220 K density HDPE High density polyethylene DSM Stamylex 9089F Ethylene terpolymer / acrylic ester DuPont Bynel CXA 4033 as / maleic anhydride AB Anti-blocking agent under Eastman C0047 as a masterbatch % by weight of silica and 90% by weight of PET brand Eastar 6763 The three layers of the film are described in this table

  LAYER PERCENTAGE IN COMPOSITION (% BY WEIGHT)

WEIGHT IN THE FILM

  1st external layer 20% 95% PET + 5% AB internal layer 60% 50% MDPE + 30% HDPE + 20% terpolymer 2nd external layer 20% 95% PET + 5% AB The film was produced by tubular coextrusion under the conditions following: - screw temperature of the PET / AB mixture: 220 C - screw temperature of the MDPE / HDPE / terpolymer mixture ....................: 180 C temperature value .......................... 1 9 0 C - head temperature .............. .............. 2000C - drawdown rate.

  ................................. 20 - inflation rate ............ .................... 2 - air gap ..................... DTD: .... ....................: 1.2 mm - pulling speed ..................... DTD: ............ 40 m / min..DTD: The film obtained has a width of 800 mm and a total thickness of 28 pm and a density of approximately 1.1.

  A 60mm x 90mm rectangle is cut from the film and a candy is wrapped manually by making a foil by turning

  the film 1/2 times with one hand compared to the candy held by the other hand. We note that the foil does not show a marked tendency to go back.

  EXAMPLE 2 (comparative) A 60 mm x 90 mm rectangle is cut from a bioriented polypropylene film and a candy is wrapped in the same way as

  for example 1. It can be seen that the foil has a marked tendency to go back.

Claims (33)

  1. Assembly comprising a solid and its packaging, said packaging comprising at least one film comprising at least one foil and / or a fold, said film comprising at least one layer comprising at least one polyester.   2. Assembly according to claim 1, characterized in that the packaging   l0 directly marries most of the surface of the packaged solid.   3. Assembly according to claim 2, characterized in that the packaging   conforms to almost the entire surface of the packaged solid.   4. Assembly according to one of the preceding claims, characterized in   that the solid consists of a single element.   5. Assembly according to one of the preceding claims, characterized in   what the solid is a food material and more particularly a candy.   6. Assembly according to one of the preceding claims, characterized in   that the packaging is not maintained by any adhesive or glue.   7. Assembly according to one of the preceding claims, characterized in   that the film has a thickness of 10 to 60 µm.   8. Assembly according to one of the preceding claims, characterized in   what the film is basically monolayer.   9. Assembly according to one of claims 1 to 7 characterized in that   the film comprises a plane of symmetry which is parallel to it, and comprises at least three layers, one of which is in the middle of the film, the sum of the mass of the layers comprising a polyester   representing at least 20% by weight of the mass of said film.   10. The assembly of claim 9, characterized in that the sum of the mass of the three layers constitutes at least 80% of the total mass of the film and in that each of said three layers constitutes   at least 10% by weight of the total mass of the film.   11. The assembly of claim 9 or 10, characterized in that the middle layer comprises at least one polyolefin and in that each of the two other layers representing at least 10% by   weight of total film mass, include polyester.   12. Assembly according to one of claims 9 to 1 1 characterized in that   that the middle layer comprises at least 60% of an ethylene polymer.   13. Assembly according to one of claims 9 to 12 characterized in that   that the middle layer represents 40 to 80% by weight of the mass of the film.   14. Assembly according to one of the preceding claims, characterized in   that at least one polyester is amorphous.   15. Assembly according to one of the preceding claims, characterized in   that at least one polyester can be derived from the condensation of terephthalic acid with ethylene glycol and a diol comprising at least minus three carbon atoms.   16. The assembly of claim 15 characterized in that the diol is cyclohexane dimethanol.   17. Assembly according to one of the preceding claims, characterized in   that the film includes at least one anti-blocking agent and / or   at least one antistatic agent and / or at least one slip agent.   18. Assembly according to one of the preceding claims, characterized in   that the film has undergone printing and / or metallization.   19 Film comprising a plane of symmetry which is parallel to it and at least three layers, one of which is in the middle, the middle layer comprising a polyolefin, at least two other layers each comprising at least one polyester, the sum of the mass of the layers comprising at least one polyester representing   minus 20% by weight of the mass of the film.   20. Film according to claim 19, characterized in that the sum of the mass of the three layers constitutes at least 80% of the total mass of the film and in that each of said three layers constitutes at   minus 10% by weight of the total mass of the film.   21. Film according to claim 19 or 20, characterized in that the middle layer comprises at least one polyolefin and in that each of the two other layers representing at least 10% by weight of the   total film mass, include polyester.   22. Film according to one of claims 19 to 21 characterized in that the   The middle layer comprises at least 60% of an ethylene polymer.   23. Film according to one of claims 19 to 22 characterized in that the   middle layer represents 40 to 80% by weight of the mass of the movie.   24. Film according to one of claims 19 to 23 characterized in that at the less a polyester is amorphous.   25. Film according to one of claims 19 to 24 characterized in that at   at least one polyester can be derived from the condensation of terephthalic acid with ethylene glycol and a diol comprising at least three carbon atoms.   26. Film according to claim 25 characterized in that the diol is the cyclohexane dimethanol.   27. Film according to one of claims 19 to 26 characterized in that it   includes at least one antiblocking agent and / or at least one agent   antistatic and / or at least one slip agent.   28. Film according to one of claims 19 to 27 characterized in that the   film has undergone printing and / or metallization.   29. Method of manufacturing a film according to one of claims 19 to   28, characterized in that it comprises a step of blowing coextrusion of the different thermoplastic compositions from which the different layers of said film come. 30. The method of claim 29 characterized in that the operating parameters of the blowing coextrusion step are as follows: - draw rate ..........: 2 to 50, - inflation rate. .....: 1 to 10, - air gap ...   ..............: 0.5 to 5 mm - pulling speed .......: 10 to 1 50 m / min 31. Method according to claim 30 characterized in that the operating parameters of the blowing coextrusion step are as follows: draw rate ..........: 10 to 30, - inflation rate .. ... .CLMF: 1.5 to 3, - air gap ................... 0.8 to 1.6 mm - pulling speed ..... .. 30 to 60 m / min..CLMF: 32. Method according to one of claims 29 to 31 characterized in that   the blowing coextrusion step is followed by at least one step stretching or bi-stretching.   33. Method according to one of claims 29 to 32 characterized in that   the film undergoes at least one step of antistatic treatment and / or metallization and / or printing.