FR2947205A1 - BIODEGRADABLE MULTILAYER MATERIAL AND PROCESS FOR OBTAINING SUCH MATERIAL - Google Patents

Abstract

A multilayer material according to the present invention comprises: a first biodegradable agromaterial layer made of at least 90% agro-resources, and a layer of paper on one side of said first layer, the paper being covered on a facing a resin so that the resin is outside the multilayer material. A method for producing such a material consists, for example, in placing in a mold a sheet of paper covered with resin so that said sheet covers at least partially a wall of the mold, then injecting a biodegradable agromaterial made from at least 90% of agro-resources according to a molding labeling method.

Description

The present invention relates to a biodegradable multilayer material and a method for obtaining such a material. Biodegradable materials are increasingly present in our environment. They are most often made from plant materials while competing materials are most often made from polymers or other compounds derived from petrochemicals. The use of biodegradable materials therefore saves energy resources of the planet. In addition, the biodegradable materials are easy to treat after use. They are therefore recoverable without being incinerated or subjected to other transformations. The present invention relates more particularly to the field of application of the package. In this field, trays are used, for example, for packaging food. It is known here to use for example a material called PLA (abbreviations for polylactic acid). This material is used either pure or mixed with other biodegradable materials. When used for PLA is waterproof but has the disadvantage of being brittle. It is therefore most often mixed with another biodegradable material. Another disadvantage of biodegradable materials, including PLA, is that they do not form a gas barrier, for example oxygen. In the field of food packaging, if a tray of biodegradable material is used and that it is desired to achieve a barrier to gases (and possibly water) a film, usually non-biodegradable, is used. The present invention therefore aims to provide a biodegradable material waterproof and / or gas barrier and a method for obtaining such a material. For this purpose, the present invention provides a multilayer material comprising a first agromaterial layer made from at least 90% agro-resources. According to the present invention, said first layer is associated with a paper layer on one side, the paper is coated on one side of resin and the paper is disposed in the multilayer material so that the resin is on the outside . Surprisingly, it has been observed that the paper adheres very well to biodegradable agromaterials and could therefore be combined with such materials to increase the performance of the biodegradable material. The multilayer material is made essentially from agroresources which are the plants providing the basic compounds necessary for energy, chemistry and materials, in particular: lipids and proteins obtained from rapeseed, sunflower, soybean, linseed, ..., carbohydrates obtained from cereal and sugar beet crops, lignocellulosic fibers from crop residues, such as straw, annual crops such as hemp and sorghum, and silviculture, as well as specific products derived from co-products of various plants, these agro-resources being or not transformed, the transformation being able to lead to materials such as PLA (polylactic acid), PHB (polyhydroxy butyrate), PHA (polyhydroxyalkanoate), polyesters biodegradable, .... To increase the performance of the multilayer material in terms of water tightness and also form a barrier to gases, the paper is coated on one side with a resin, and the paper is disposed in the multilayer material so that the resin is on the outside. Here it is necessary to maintain a direct connection between the paper and the agromaterial. Advantageously, the paper used is kraft paper. Such a paper is on the one hand known for its mechanical properties and on the other hand is biodegradable. A preferred embodiment of a multilayer material according to the present invention provides that the agromaterial layer has the following composition, the percentages being expressed by weight of the dry matter: between 20% and 60% of starch, between 3% and 20% of proteins, - between 15% and 60% of cellulose, hemicellulose and lignin, - between 1% and 15% of lipids, and - between 0.01% and 10% of sugars. The present invention also relates to a method of producing a multilayer material. According to the invention, this method consists in disposing in a mold a sheet of paper covered on one side with a resin such that said sheet at least partially covers a wall of the mold and that the face covered with resin is disposed against the mold wall, then to inject a biodegradable material made of at least 90% agro-resources according to a molding labeling method so that the resin is outside the multilayer material after injection . A molding labeling method is commonly referred to by the acronym IML, "In-Mold Labeling".

In such a process, the paper used is preferably a kraft paper. The present invention also relates to a tray for packaging food products, characterized in that it is made of a multilayer material as described above. In such a tray, the paper is preferably disposed within the tray. In order to obtain a water-tight and gas-barrier tray, the paper used is preferably kraft paper combined with a biodegradable resin in the form of a film. The present invention will be better understood with the aid of the detailed description which follows, describing some examples of embodiment of the invention as well as a method according to the invention.

The present invention relates to the production of a multilayer material which is preferably entirely biodegradable and which can be used in particular for the production of packaging. For the packaging of certain food products, a packaging that forms a gas barrier and / or is watertight should be used.

The biodegradable agromaterials described for example in document FR-2 783 740 do not make it possible to achieve such a seal. The idea behind the present invention is to associate with such materials a film to form a gas barrier which is preferably also waterproof. Many tests have been done but to no avail. Indeed, it is difficult to obtain good cohesion between a sealed film and agromaterial. Surprisingly, it has been found that an injectable biodegradable agromaterial, of the type described in FR-2 783 740, binds very well with paper using, for example, a molding labeling method. Such a method is better known under the initials IML (English In-Mold Labeling). According to a preferred embodiment, a multilayer material according to the invention consists of a biodegradable agromaterial layer, a layer of paper and a layer of resin, the layer of paper being sandwiched between the agromaterial and the resin.

The biodegradable agromaterial may consist of fibers, starch and an adjuvant such as for example PLA (English abbreviations of Poly Lactic Acid or in French, polylactic acid) or biodegradable polyesters. The agromaterial used here preferably consists of more than 90% (on the dry matter) of compounds derived from agro-resources, that is to say from components such as starch, flours, fibers biodegradable polyesters, etc. The proportion of these compounds from agroresources can even be preferably 100% but it can also contain components such as dyes, for example not from agro-resources.

Preferably, the biodegradable agromaterial is a plant material based on at least one whole cereal plant. FR-2 783 740 discloses a method for obtaining such materials and gives examples of such materials. For example, a biodegradable agromaterial obtained from aggregates will be used here, said granulates having a composition such that (the percentages being expressed by weight relative to the dry matter): between 20% and 60% of starch between 3% and 20%. % of proteins between 15% and 60% of cellulose, hemicellulose and lignin, between 1% and 15% of lipids, and between 0.01% and 10% of sugars. Such granules, having possibly undergone extrusion, exhibit a behavior comparable to that of a thermoplastic material and can then be injected into a mold. The use of such aggregates is quite comparable to that of synthetic plastics such as polyethylene, polypropylene and polystyrene. Nonlimiting examples of materials used can be used here, such as those obtained during the implementation of the processes described in Examples 1 to 4 of document FR-2 783 740. In the multilayers according to the invention, the thickness of the agromaterial layer will depend on the desired use of the multi-layer material. Depending on the desired strength, the agromaterial will have a greater or lesser thickness. In the field of packaging, for example, a thickness of the order of a millimeter or a few millimeters will be provided. The paper used for making a multilayer according to the present invention is preferably paper known as kraft paper. Such paper is biodegradable. The multilayer obtained by combining the biodegradable material described above and the kraft paper will therefore also be biodegradable. This type of paper also has the advantage of being very resistant. It is obtained with pasta based on wood treated with soda. The wood used generally is softwood, type pine or fir. The paper used here can have different weights depending on the use of the multilayer material. By way of non-limiting example, the kraft paper used has a grammage of between 40 and 180 g / m2. Finally, the resin used is also preferably biodegradable. Such a resin is for example known under the trademark NatureFlex. By way of nonlimiting example, mention may be made of the use of a biodegradable film as described in document WO-2009/024812, for producing the resin layer. The term "resin" is used here in its broad sense and here designates a solid, semi-solid or pseudo-solid organic material which has a tendency to flow when it is stressed. The multilayer material described here, comprising a layer of biodegradable agromaterial, a layer of kraft paper and a layer of resin in the form of a film marketed under the trademark NatureFlex is a biodegradable material according to standard NF EN 13432. To make a material multilayer according to the present invention, it is proposed to use a method of the labeling type molding but adapting it. A multilayer product according to the invention comprises firstly an agromaterial layer and secondly a layer of paper associated with a resin. When the paper is associated with a resin, it covers only one side of the paper layer and the other side of the paper layer, not covered with resin, comes into direct contact with the biodegradable agromaterial.

The molding labeling method, also known under the initials IML for In-Mold Labeling, consists in depositing a plastic label in an injection tool during the manufacture of a packaging, also made of synthetic material. It is not at all usual to use such a process with paper. In addition, when it comes to labeling, the label is of course glued to the outside of the package to be visible to the consumer. The present invention proposes in an original way to use a process resulting from the IML process. It is proposed here to place in the mold a sheet of paper, associated or not with resin, especially in the form of a film, in the injection tool, an uncoated paper face lying inside the mold. tooling. In addition, unlike an IML process usually used, the paper layer is deposited on the wall of the tool corresponding to the inner face of the package (and not its outer face).

Once the injection tool is lined with the paper sheet, biodegradable agromaterial is injected into the tooling by a conventional injection method, known to those skilled in the art and not described in detail here. A multilayer material according to the invention is thus obtained with an excellent bond between the paper and the biodegradable agromaterial which has been injected.

The multilayer thus obtained makes it possible to provide a gas barrier and to obtain a good watertightness. This multilayer material is well suited for the production of packaging, particularly in the field of food but other uses may be considered.

In any case, the present invention is not limited to the preferred embodiments described above by way of non-limiting examples. It also relates to all the variants within the scope of those skilled in the art within the scope of the claims below. For example, other methods could be implemented to obtain a multilayer material according to the present invention. In such a material, many variants of agromaterial can be used. The paper is preferably kraft paper for its high mechanical strength and its biodegradable character but other papers, preferably biodegradable, can be envisaged. The examples of resins used are also given for illustrative purposes and are not limiting. Depending on the characteristics that one wishes to obtain, for example barrier to certain gases, the choice of resins can be adapted. The resin may, instead of being in the form of a film, be sprayed for example on the surface of the paper or associated with the paper in any other way.

Claims (9)

REVENDICATIONS1. Multilayer material comprising a first biodegradable agromaterial layer made from at least 90% agro-resources, characterized in that said first layer is associated with a layer of paper on one side, in that the paper is covered on one side of a resin, and in that the paper is disposed in the multilayer material so that the resin is on the outside. 2. Multilayer material according to claim 1, characterized in that the paper used is kraft paper. 3. Multilayer material according to one of claims 1 to 2, characterized in that the biodegradable agromaterial layer has the following composition, the percentages being expressed by weight of the dry matter: between 20% and 60% of starch, - between 3% and 20% of protein, - between 15% and 60% of cellulose, hemicellulose and lignin, - between 1% and 15% of lipids, and - between 0,01% and 10% of sugars. 20 4. A method of producing a multilayer material, characterized in that it consists in placing in a mold a sheet of paper coated on one side with a resin such that said sheet at least partially covers a wall of the mold and that the resin coated side is disposed against the wall of the mold, and then injecting a biodegradable material made of at least 90% agro-resources according to a molding labeling method so that after injection the resin is outside. 5. Production method according to claim 4, characterized in that the paper used is a kraft paper. 6. Production method according to one of claims 4 or 5, characterized in that the resin is in the form of a film attached to one side of the paper sheet. 7. Tray for packaging food products, characterized in that it is made of a multilayer material according to one of claims 1 to 3. 8. Tray according to claim 7, characterized in that the paper is disposed inside the tray. 9. Tray according to one of claims 7 or 8, characterized in that the paper used is kraft paper associated with a biodegradable resin in the form of film.