WO2020152411A1

WO2020152411A1 - Rigid packaging and method for producing said packaging

Info

Publication number: WO2020152411A1
Application number: PCT/FR2020/050067
Authority: WO
Inventors: Julien Hebert
Original assignee: Hebert P.
Priority date: 2019-01-22
Filing date: 2020-01-17
Publication date: 2020-07-30
Also published as: FR3091856B1; FR3091856A1; EP3914530B1; EP3914530A1

Abstract

Disclosed is a rigid packaging comprising: - a skeleton (30) made of thermoplastic material, this skeleton comprising strands (42) which form meshes of a grid which defines the framework of a side wall (16) of the packaging, - a sheet (32) comprising: • an inner layer made of thermoplastic material, heat welded on the strands (42) of the skeleton, • a cardboard layer, the mass of which represents more than 50% of the total mass of the sheet, - the heat-welded sheet comprising a gripping appendage (62) for the hand of a human being, this appendage being rigidly attached to the cardboard layer and enabling, by manually pulling on this appendage, the manual peeling of the cardboard layer in order to mechanically detach it from the inner layer.

Description

DESCRIPTION

RIGID PACKAGING AND METHOD OF MANUFACTURING SUCH PACKAGING

[001] The invention relates to a rigid packaging and to a method of manufacturing this packaging.

By rigid packaging is meant all packaging which is not flexible such as bags or films. In other words, a package is considered rigid if it does not collapse under the effect of its own weight. It therefore has a three-dimensional shape which is preserved during conventional operations of storage, filling and distribution of a product contained in this packaging.

[003] Today it is desirable to reduce the environmental impact of packaging while retaining their mechanical properties and keeping manufacturing costs as low as possible. To limit manufacturing costs, this packaging must typically be manufactured by injection molding.

[004] The state of the art is known from CA2445553A1 and EP2803598. Document CA2445553A1 describes a package comprising a skeleton and a sheet of thermoplastic material.

[005] The invention aims to provide such packaging. It therefore relates to a rigid packaging according to claim 1.

[006] The subject of the invention is also a method of manufacturing this packaging.

[007] The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and made with reference to the drawings in which:

- Figure 1 is a schematic illustration, in partial section and in perspective, of a rigid packaging,

- Figure 2 is an enlarged schematic illustration of part of the partial section of the packaging of Figure 1, and

- Figure 3 is a flowchart of a manufacturing process of the packaging of Figure 1.

[008] In these figures, the same references are used to designate the same elements. In the remainder of this description, the characteristics and functions well known to those skilled in the art are not described in detail.

[009] Figure 1 shows a rigid package 2 defining a hollow volume 4 intended to receive a product.

The product packaged inside the package 2 is here a food product. The food product can be liquid, pasty or solid. For example, the food product can be a dairy product such as sour cream. The product food can also be ice cream, candy, vegetables or any other food product which needs to be distributed in a package.

In this embodiment, the volume 4 is a solid of revolution having as axis of revolution a vertical axis 6.

In the figures, the horizontal is marked by the X and Y directions of an orthogonal reference C, U, Z. The Z direction is parallel to the vertical direction. Terms such as "top", "bottom", "upper", "lower" and the like are defined with respect to this Z direction.

The hollow volume 4 extends between a lower horizontal plane P _inf and an upper horizontal plane P _sup . Here, the hollow volume 4 is tapered. The volume 4 is typically greater than 50 cm ³ or 100 cm ³ or 500 cm ³ and, generally, less than 1 m ³ or 0.5 m ³ .

The packaging 2 is a rigid packaging. For this purpose, the package 2 has sufficient horizontal rigidity and vertical rigidity. By "horizontal stiffness" is meant the resistance of the packaging to a compressive force along a horizontal direction, that is to say a force whose direction belongs to a plane parallel to the X and Y directions. The term “vertical rigidity” denotes the resistance of the packaging 2 to a vertical compressive force, that is to say to a force the direction of which is parallel to the Z direction.

In this embodiment, by way of example, it is considered that the rigidity is sufficient when a predetermined support force applied to an outer wall of the packaging causes this outer wall to sink in, in the direction support, less than 15% or 10% or 5% of the largest of the dimensions of the package 2. Here, the predetermined support force is a force of 0.5 N applied to an area of 1 cm ² of the outer wall of the packaging and in a direction perpendicular to this outer wall. The largest of the dimensions of the package 2 is the largest of the dimensions chosen from the group consisting of:

- the width of the packaging 2,

- the length of the packaging 2, and

- the height of the packaging 2.

The width, the length and the height of the package 2 are equal, respectively, to the width, the length and the height of the parallelepiped of smaller volume which entirely contains the package 2.

Preferably, the maximum depression in the bearing direction is less than 1 cm or 5 mm.

[0018] The package 2 is also a light package. For this, typically, the weight of the package 2, expressed in grams, is less than 10% or 5% of the hollow volume 4 expressed in cm ³ . For example, the weight of the package 2 is here less than 500 g or 250 g or 100 g and, generally, greater than 5 g. In this embodiment, the package 2 comprises a lower wall 14 and a side wall 16 as well as an upper rim 18. The wall 14 is a disc centered on the axis 6 and of radius R _I4 . The radius R _i4 is typically greater than 2 cm or 4 cm. Generally, the radius R _i4 is less than 50 cm or 25 cm. The lower wall 14 extends here mainly in the plane P _inf .

The side wall 16 is a truncated cone which extends, widening, from the periphery of the wall 14 to the rim 18.

The rim 18 extends mainly in the plane P _su . The rim 18 surrounds a circular opening 20 through which the food product can be introduced and then withdrawn from the package 2.

Here, the rim 18 and the opening 20 are circular and centered on the axis 6.

The rim 18 is arranged to receive a cover and / or a cover making it possible to completely close the opening 20. Here, it is arranged to receive a cover 22, for example, heat-sealed to the rim 18.

By "heat-sealed" is meant the fact that the weld which mechanically connects two thermoplastic elements together, without any degree of freedom, is obtained by heating these two elements until the melting point of these thermoplastic elements of so that the thermoplastic materials of these elements interpenetrate. By cooling, a rigid weld is thus obtained between these two elements. This welding is carried out without the addition of external material such as an adhesive. With this definition, two thermoplastic elements welded using a process known as "ultrasonic welding" are considered to be heat sealed. In fact, ultrasonic welding heats thermoplastic elements beyond their melting point.

Here, the rim 18 and the cap 22 are made of a thermoplastic material capable of being heat-sealed to one another. To this end, the rim 18 has a horizontal annular face 24 facing upwards onto which the periphery of the cover 22 is welded.

Preferably, the strength of the weld between the cover 22 and the flange 18 is adjusted so that this cover 22 can be manually torn off by a user of the package 2 when it is opened.

The flange 18 is here a solid of revolution generated by the rotation, over 360 ° and around the axis 6, of a vertical section 26. The vertical section 26 is shaped to give sufficient horizontal rigidity to this flange 18. For example, for this purpose, the vertical section 26 has, in places, in a horizontal direction, a thickness greater than 0.5 mm or 1 mm. The section 26 is also shaped so that a cover can additionally fit on the rim 18. Here, the section 26 has for this purpose a projection 28 towards the outside of the package 2 on which a cover can come s. 'fit together by elastic mechanical deformation. So that the packaging 2 is both rigid and light, it comprises a skeleton 30 of thermoplastic material and a sheet 32 heat-sealed to this skeleton 30. It is the skeleton 30 which determines the shape of the packaging 2 and which provides most of the horizontal rigidity of this packaging. The sheet 32 provides, in this embodiment, most of the vertical rigidity of the packaging 2, which makes it possible to reduce the quantity of thermoplastic material used to make the skeleton 30.

[0029] The skeleton 30 comprises:

- rim 18,

- a bottom 40 which forms the framework of the lower wall 14, and

- Strands 42 mechanically connected to the bottom 40 and to the rim 18 to produce a mesh which forms the framework of the side wall 16.

In this embodiment, the bottom 40 is also formed by strands to produce a mesh which forms the framework of the lower wall 14. For this purpose, the bottom 40 comprises a strand 44 which defines the edge between the walls 14 and 16. Here, this strand 44 is circular and centered on the axis 6. To increase the horizontal rigidity of the packaging 2, the strand 44 has the shape of an angle, one of the wings of which is s' extends vertically and the other wing extends horizontally towards axis 6.

Still to increase the horizontal rigidity of the package 2, the bottom 40 also comprises one or more other horizontal strands 46 which define several stitches in the bottom 40. For example, these strands are straight strands. Here, these strands 46 extend from a portion of the strand 44 to a portion facing the strand 44 by cutting the axis 6. To simplify Figure 1, a single strand 46 has been shown.

The strands 42 define the shape of the side wall 16. These strands 42 form a mesh which extends from the strand 44 to the rim 18. For example, these strands 42 are straight strands. Here, these strands 42 each extend in a respective vertical plane from a portion of the strand 44 to a corresponding portion of the flange 18. To simplify Figure 1, only one of these strands 42 has been shown.

The skeleton 30 is made in a single block of thermoplastic material which can be injection molded. Here, by way of illustration, the backbone 30 is made of polypropylene.

The sheet 32 is heat sealed on each strand and on the lower part of the flange 18 so as to completely close off all the meshes which define the walls 14 and 16 of the package 2. The sheet 32 is a light and flexible sheet. In particular, the sheet 32 is also designed to limit as much as possible the environmental impact of the packaging 2. To this end, the sheet 32 is essentially made from an aggregate of paper fiber. The term “essentially achieved” denotes here the fact that the mass of the paper fiber aggregate is greater than 50% of the total mass of the sheet 32.

More specifically, the sheet 32 is composed of several layers directly stacked one on top of the other. The structure of the sheet 32 is shown further in detail in Figure 2. The sheet 32 comprises successively, going from the inside of the package 2 to the outside of the package 2:

- an internal layer 50,

- a tie layer 52,

- a cardboard layer 54, and

- an outer layer 56.

The internal layer 50 is suitable for being heat sealed to the skeleton 30. For this purpose, the internal layer 50 is made of thermoplastic material. In addition, this internal layer insulates the cardboard layer 54 from humidity. Finally, in the case where the packaging 2 contains a food product, the internal layer 50 is also made of a material compatible with this application. Preferably, the internal layer 50 is made of the same thermoplastic material as that used to make the skeleton 30. Here, the internal layer is therefore made of polypropylene.

The thickness of the internal layer 50 is chosen as small as possible while remaining capable of performing its various functions. Typically, its thickness is less than 200 µm or 100 µm or 50 µm. Generally, its thickness is greater than 20 µm.

At the level of the welds between the sheet 32 and the skeleton 30, the thermoplastic material of the skeleton 30 has fused with the inner layer 50 so that the inner layer 50 no longer forms a single block of material with the skeleton 30 .

The cardboard layer 54 is only composed of the aggregate of paper fibers. Typically, the mass of the layer 54 represents more than 50% and, preferably, more than 60% or more than 70% of the mass of the sheet 32. Here, it is mainly this cardboard layer 54 which ensures the vertical rigidity. of the packaging 2. For this purpose, its thickness is generally greater is, most often two or three times greater than the thickness of the other layers of the sheet 32. For example here, the thickness of the cardboard layer 54 is greater than 100 µm or 200 µm. Its weight per unit area is conventionally between 50 g / m ² and 400 g / m ² and advantageously between 100 g / m ² and 300 g / m ² . Here, the cardboard layer 54 is thick enough so that its mass represents more than 50% of the total mass of the package 2 without the cover 22 and without the cover. The cardboard layer 54 is recyclable like paper or cardboard. The face of the layer 54 in contact with the layer 56 is generally printed before being associated with the layer 56. This printing makes it possible to indicate various information on the product contained in the package 2 such as, for example, the name of the product. product, the manufacturer's brand, ... etc.

The outer layer 56 is made of a transparent material so that the printed face of the layer 54 is visible from the outside by a user. Additionally, the outer layer 56 insulates the cardboard layer 54 from exterior moisture. Typically, the layer 56 is a varnish or a transparent film deposited on the printed face of the layer 54. Here this varnish or this transparent film is made of a plastic material.

The thickness of the outer layer 56 is also chosen as small as possible to fulfill its functions. Generally, its thickness is less than 50 µm or 30 µm or 20 µm. Its thickness is usually also greater than 5 µm.

The tie layer 52 allows manual detachment of the cardboard layer 54 of the inner layer 50 by peeling. More precisely, thanks to the layer 52, the energy of adhesion of the cardboard layer 54 on the inner layer 50 is less, and preferably two or three times less, than the energy of adhesion of the inner layer 50 on the backbone 30. The term “adhesion energy” denotes the energy necessary to effect the separation of these layers. The adhesion energy is also referred to as "cleavage energy".

For example, the tie layer 52 is made so that the energy of adhesion of this layer 52 on the inner layer 50 is greater and, preferably two or three times greater than the energy d adhesion of the layer 52 on the cardboard layer 54. Under these conditions, when pulling on the cardboard layer 54, the latter separates from the inner layer 50 at the interface between the tie layer 52 and the internal layer 50. Thus, the internal layer 50 remains fixed and integral with the backbone 30. The backbone 30 and the internal layer 50 then form an object entirely of plastic material that it is easy to sort and recycle. After separation, there is also obtained a complex 60 formed of the tie layer 52, the cardboard layer 54 and the outer layer 56. The proportion, by mass, of the paper fiber aggregate in this complex 60 is very high. larger than in the case of the sheet 32, which simplifies its sorting and recycling.

[0044] So that the user can detach the complex 60 from the inner layer 50, the sheet 32 has a gripping appendage 62 (Figure 1). The appendix 62 allows the user to pull the complex 60 in a direction perpendicular to the outer face of the sheet 32. For example, the appendix 62 is a tab which protrudes from the wall 14 or 16 of the package. 2. In Figure 1, the appendix 62 protrudes from the side wall 16. The appendix 62 is fixed without any degree of freedom directly on this complex 60. Here, the adhesion energy of the outer layer 56 on the cardboard layer 54 is also greater than the adhesion energy of the cardboard layer 54 on the inner layer 50. Under these conditions, the appendage 62 is for example a protuberance of the complex 60 which extends in a direction given beyond the inner layer 50 over a predetermined distance. This predetermined distance is chosen so that the user can directly grasp the appendage 62 with his fingers and pull on it. For example, the appendix 62 extends beyond the inner layer 50 for a distance greater than 5 mm or 1 cm. This predetermined distance is also generally less than 5 cm or 3 cm. Here, the tie layer 52 is made so that the force, perpendicular to the plane of the sheet 32, to be exerted to detach the complex 60 from the inner layer 50, is between 0.3 N and 10 N and, preferably, between 0.5 N and 5 N or between 1 N and 3 N. For this, numerous embodiments of the tie layer 52 are possible. For example, the tie layer is made for this purpose in a copolymer of ethylene and vinyl acetate.

FIG. 3 represents a method of manufacturing the packaging 2.

Initially, during a step 70, the sheet 32 is manufactured. During the manufacture of sheet 32, the outer face of layer 54 is printed. Printing can be done by offset printing with oxidative drying inks or UV (ultraviolet) inks or by gravure or others.

Once the sheet 32 has been manufactured, during a step 74, it is placed inside a female shell of a mold and the outer layer 56 is directly pressed against the walls of this female shell. Typically, the female shell is a movable shell. The walls of the female shell have the same shape as the walls 14 and 16. For example, the sheet 32 is pressed against the walls of the female shell using a mandrel which pushes it in and then presses it against the walls. walls of the female shell. The sheet 32 is then kept pressed against these walls, for example, by suction or by electrostatic forces. In parallel, the mandrel is withdrawn.

In a step 76, a male shell of the mold is positioned inside the female shell. This male shell bears directly on the sheet 32 at the level of the meshes of the skeleton 30. The male and female shells define, by cooperation of shape, a hollow imprint of the skeleton 30. This hollow imprint is directly in contact with the sheet. 32 at the level of the parts of the skeleton 30 which are to be welded to the sheet 32.

[0050] The male shell is typically a fixed shell which also comprises channels making it possible to inject the thermoplastic material of the skeleton 30 inside the hollow impression.

During a step 78, the molten thermoplastic material is injected inside the hollow impression. The temperature of the injected thermoplastic material is higher than its melting temperature and the melting temperature of the inner layer 50. Under these conditions, the inner layer 50 is heated beyond its melting temperature, which at the same time causes as the backbone 30 is molded, soldering the inner layer 50 to the backbone 30.

Then, during a step 80, the mold is cooled and the male shell is removed. The packaging 2 is then removed from the female shell. At this point, the package 2 comprises the skeleton 30 and the sheet 32 heat-sealed to this skeleton 30.

During a step 82, this packaging 2 is then delivered to a packaging plant which, during a step 82, introduces the product inside the package 2 and welds the cover 22 on the face 24 to close the package 2. During step 82, a cover can also be fitted on the rim 18 to complete the closing of the package 2.

Then, the product thus packaged can be distributed to the end consumers.

Other embodiments of the skeleton 30 are possible. For example, the bottom 40 of the skeleton can be a bottom of solid plastic material, devoid of mesh. In the latter case, preferably, the sheet 32 covers only the side wall 16.

Numerous other arrangements are possible for the strands 42 and 46. In particular, the number of strands can be increased. For example, one or more strands 42 can be added to further stiffen the side wall 16. For example, the side wall 16 can be stiffened by introducing therein additional horizontal and circular strands which surround, from the inside, this side wall. 16. The strands which define the side wall 16 can also cross to increase the number of stitches. Likewise, the width and thickness of the strands of the skeleton 30 are adapted as a function of the rigidity desired for the packaging 2. In particular, in a particular embodiment, the essential of the vertical rigidity of the packaging 2 is provided by the backbone 30 and, in particular, the strands 42.

The skeleton 30 can be made from other thermoplastic materials. For example, the backbone 30 is made from one or more of the materials of a first group of thermoplastic materials. The first group of thermoplastic materials is typically made up of the following thermoplastic materials:

- polypropylene (PE),

- polyethylene (PP),

- polyethylene terephthalate (PET),

- polyhydroxyalkanoate (PHA),

- polylactic acid (PLA).

PHA and PLA have the particular advantage of being biodegradable.

Variants of the heat-sealed sheet:

As a variant, the mass of the cardboard layer 54 is less than 50% or 30% of the total mass of the packaging 2. The remaining mass of the packaging 2 is then essentially constituted by the thermoplastic material.

Other embodiments are possible to bind the cardboard layer 54 to the inner layer 50. For example, in a particular embodiment, the link layer 52 is omitted. In this case, for example, the cardboard layer is directly attached to the inner layer 50. The adhesion energy between the inner layer 50 and the cardboard layer 54 is then adjusted by adjusting, for example, the roughness of the outer face. of the inner layer 50 and / or the roughness of the inner face of the cardboard layer 54.

[0061] Other embodiments of the layer 52 are possible. For example, the layer 52 is designed to destroy itself when the user pulls on the appendix 62. In this case, generally, after having detached the complex 60 from the inner layer 50, remnants of the tie layer 52 remain. both on the inner layer 50 and on the cardboard layer 54. The layer 52 can also be designed so that its adhesion energy on the inner layer 50 is greater than its adhesion energy on the cardboard layer 54. In this case , the separation of the cardboard layer 54 occurs at its interface with the tie layer 52.

Other materials can be used to make the tie layer 52. For example, the tie layer 52 is made of a material chosen from the group consisting of:

- copolymer of ethylene and vinyl acetate,

- an acrylic resin,

- a copolymer of vinyl chloride and vinyl acetate,

- a cellulose resin,

- a polyamide,

- a polypropylene,

- a polyolefin such as a polyethylene.

The tie layer can itself be formed of several sublayers directly stacked on top of each other, each made, for example, in different materials.

The inner layer 50 and / or the outer layer 56 can be a varnish or a film. They can also be made in other materials. For example, they can be made from one of the materials of the first group defined above. The outer layer 56 can also be produced by a varnish or a film of non-plastic material.

The inner layer 50 and / or the outer layer 56 can also be made up of several sublayers. For example, they comprise an inner sub-layer made from one of the materials of the first group and an outer sub-layer made from another material which adheres to the tie layer.

The material of the other sublayer is for example chosen from a second group of thermoplastic material consisting of:

- low density polyethylene,

- an ionomer,

- an ethylene and acrylic acid copolymer (EAA), - an ethylene and methacrylic acid copolymer (EMAA),

- an ethylene and methyl acrylate copolymer (EMAC),

- an ethylene and ethyl acrylate copolymer (EEA),

- of an ethylene and methyl methacrylate copolymer.

One of the sub-layers of the inner layer or of the outer layer can also be made from a metal such as aluminum.

In a simplified variant, the outer layer 56 is omitted. This is possible in the event that it is not necessary to protect the cardboard layer 54 against moisture coming from the outside of the package 2.

In another variant, the sheet 32 comprises several appendages, fulfilling the same functions as the appendix 62. These various appendages are for example arranged at different places on the wall of the package 2 to detach the complex 60 from the inner layer 50.

Other variations:

The thermoplastic material used to make the skeleton 30 and some of the layers of the sheet 32 can be a petroleum-based or bio-based thermoplastic material. In the case of petroleum-based plastic materials, at least 71% by mass of the material they are made of comes from petroleum, natural gas or coal. In the case of biobased plastic materials, at least 30%, by mass, and preferably at least 100%, by mass, of the material that composes them comes from renewable resources such as corn, wheat, eucalyptus and potato. Today, the materials from renewable resources that make up a bio-based plastic material are often starch and natural fibers such as wood, flax, hemp and jute fibers. A bio-based plastic is often also called a “bioplastic”.

The packaging 2 can have other shapes than an essentially frustoconical shape such as that described above. For example, the package 2 can also have the shape of any polyhedron. In this case, typically, strands of the skeleton extend along each of the edges of this polyhedron. For example, the polyhedron can be a parallelepiped. The faces of the polyhedron are each a polygon such as for example a rectangle.

The packaging can also be used to contain non-food products such as for example screws.

As a variant, the welding between the cap 22 and the rim 18 is not carried out by heat sealing but by using an adhesive glue interposed between the cap 22 and the rim 18.

The cover 22 can also be welded to another horizontal annular face than the face 24. For example, as visible in Figure 1, the rim 18 has a another horizontal annular face located closer to the axis 6 and which can also be used to glue the cover 22.

The cover 22 can also be omitted. Likewise, it is not always necessary for the package 2 to be closed by a cover.

The presence of a rim and a bottom made of plastic material improves the horizontal rigidity of the packaging. This also makes it possible to close the packaging with a cover attached to the rim and / or with the aid of a cover fitted on this rim. This also improves the ability of this package to be processed efficiently and quickly by automatic packaging lines in step 82. In particular, the package 2 can be processed more efficiently and quickly by automatic packaging lines than identical packaging but entirely made of cardboard. This is explained for example by:

- the fact that the margins of error on the dimensions of packaging 2 are smaller than if this packaging were made entirely of cardboard, and

- the fact that the packaging 2 is more rigid than an identical packaging but entirely made of cardboard.

The strands form a mesh defining the shape of the side walls of the packaging. In addition, this improves the vertical rigidity of this packaging. Due to the fact that these strands simply form a mesh, this additional rigidity is obtained using much less material than if, for the same rigidity, the skeleton had solid walls of plastic material.

The fact that most of the horizontal rigidity of the packaging is the result of the presence of the skeleton made of plastic material, makes it possible to limit the thickness of the sheet 32. In fact, the latter then has mainly for function of closing the meshes of the skeleton and therefore of mechanically isolating the interior volume 4 from the exterior and, optionally, of ensuring most of the vertical rigidity. Because of this, the amount of material used to form the walls of the package 2 is reduced.

Thus, the combination of the skeleton 30 and the sheet 32 makes it possible to obtain a packaging which is as rigid as the existing packaging but using less material. This reduction in the quantity of material is therefore already a first element which in itself contributes to reducing the environmental impact of packaging 2.

The fact that the sheet is essentially composed of an aggregate of paper fibers is a second element which contributes to reducing the environmental impact of this packaging. Indeed, paper fibers come from renewable resources.

Finally, the fact that, after use, the user can easily detach the cardboard layer from the rest of the packaging constitutes a third element which will limit the environmental impact of the packaging 2. Indeed, this facilitates '' on the one hand the recycling of the skeleton 30 and of the internal layer 50 in a sector specializing in the recycling of plastic materials and, on the other hand, the recycling of the cardboard layer in a sector specializing in paper recycling. In addition, the cardboard layer 54 which arrives in a center specializing in the recycling of paper comprises at most the outer layer 56 of plastic material. Therefore, the amount of plastic material associated with the cardboard layer 54 is small, which facilitates its recycling.

Finally, the packaging 2 also has the advantage of remaining simple to manufacture by injection molding.

The fact that the bottom of the packaging is also defined by the meshes of a mesh rather than by a solid bottom further limits the amount of plastic material used to make the packaging without degrading its rigidity.

The fact of making the skeleton 30 and the internal layer 50 in the same thermoplastic material facilitates the welding of the sheet to the skeleton. This also facilitates the recycling of the backbone and the inner layer because, in order to recycle them, it is then not necessary to separate them from one another.

Claims

1. Rigid packaging, comprising:

- a skeleton (30) in thermoplastic material, this skeleton comprising:

• a rim (18) surrounding an opening (20) through which a product can be removed from the packaging,

• a background (40),

• strands (42) mechanically connected to the bottom and to the rim and which form meshes of a mesh which defines the framework of a side wall (16) of the packaging, this side wall extending from the bottom to 'at the rim and, in association with the bottom, delimiting a hollow volume of at least 50 cm ³ capable of receiving the product,

- a sheet (32) heat-sealed to the skeleton and closing the meshes which define the side wall,

characterized in that:

- this sheet contains in order:

• an internal layer (50) of thermoplastic material heat-sealed to the strands of the skeleton,

• a cardboard layer (54) of aggregate of paper fibers, the mass of this cardboard layer representing more than 50% of the total mass of the sheet,

- the adhesion energy of the cardboard layer (54) on the internal layer (50) is less than the adhesion energy of the internal layer (50) on the strands (42) of the skeleton, and

- the heat-sealed sheet has an appendix (62) for gripping the hand of a human being, this appendix being integral with the cardboard layer and allowing, by manual traction on this appendix, the manual peeling of the cardboard layer to mechanically detach it of the inner layer.

2. Packaging according to claim 1, wherein:

- the skeleton also comprises strands (44, 46) which form meshes of a mesh which defines the bottom of the packaging, and

- the heat-sealed sheet also closes the meshes which define the bottom of the packaging.

3. Packaging according to any one of the preceding claims, in which the skeleton (30) and the inner layer (50) are made of the same thermoplastic material.

4. Packaging according to any one of the preceding claims, wherein the heat-sealed sheet comprises a bonding layer (52) interposed between the inner layer and the cardboard layer, this bonding layer being suitable for fixing the cardboard layer on the inner layer. with an adhesion energy lower than the adhesion energy of the inner layer on the backbone strands.

5. Packaging according to claim 4, wherein the tie layer is arranged so that the force to be exerted, in a direction perpendicular to the face of the sheet (32), on the appendage (62) to peel the cardboard layer is between 0.5 N and 5 N.

6. Packaging according to any one of the preceding claims, in which the appendage (62) is a tab fixed without any degree of freedom on the cardboard layer.

7. Packaging according to any one of the preceding claims, wherein the packaging comprises a cover (22) heat-sealed to the rim (18) so as to completely close the opening and / or a cover fitted on the rim so as to completely close this opening.

8. Packaging according to any one of the preceding claims, in which the mass of the cardboard layer (54) is greater than 50% of the total mass of the packaging.

9. Packaging according to any one of the preceding claims, wherein the sheet (32) comprises, on the side of the cardboard layer (54) opposite the inner layer (50), an outer layer (56) capable of protecting the layer. cardboard (54) vis-à-vis external humidity.

10. A method of manufacturing a packaging according to any one of the preceding claims, characterized in that this method comprises:

- the placement (74) of the sheet inside a female shell of a mold,

- the positioning (76) of a male shell inside the female shell, this male shell then resting directly on the sheet, the male and female shells thus defining by form cooperation a hollow imprint of the skeleton, this indentation being directly in contact with the sheet at the places where the sheet must be welded to the skeleton, - the injection (78) of the thermoplastic material into the hollow impression, this injection thus causing at the same time the formation of the skeleton and the welding of the sheet on the strands of the skeleton to obtain the packaging, and

- the withdrawal (80) of the packaging obtained from the mold.