Process for manufacturing a cellulose-based product and product manufactured from cellulose

Abstract

Title: Method for manufacturing a cellulose-based product and product manufactured from cellulose The invention relates to the field of manufacturing molded cellulose-based packaging and more particularly to a method for manufacturing a cellulose-based product and the product manufactured from cellulose. The manufacturing method 10 is essentially such that it comprises the following steps: Providing 12 a preformed cellulose structure,Providing 14 a nanocellulose pulp at a concentration of cellulose nanofibrils substantially between 5 and 50% by weight of dry matter of the nanocellulose pulp,Depositing 16 a layer based on the provided nanocellulose pulp on a surface of the preformed cellulose structure, andDrying 18 the layer based on the nanocellulose pulp by thermocompression.The cellulose-based product is essentially such that it comprises: A preformed cellulose structure, andA layer based on cellulose microfibrils on at least one surface of the preformed cellulose structure. Figure for abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing a cellulose-based product and product manufactured from cellulose Technical field

[0001] The present invention relates to the field of manufacturing packaging based on cellulose and in particular molded cellulose. The present invention relates more particularly to a method of manufacturing a cellulose-based product and the product manufactured from cellulose. STATE OF THE ART

[0002] In the context of the development of cellulose-based packaging, particularly molded cellulose, several studies have been carried out to find solutions for providing barrier properties to this packaging.

[0003] Indeed, cellulose-based structures can replace commonly used plastics, for example for two-dimensional (2D) or three-dimensional (3D) objects such as food trays, but they often lack barrier properties, and in particular barrier properties to grease, liquids and gases. It is therefore necessary to find new solutions to replace plastics by providing barrier properties to 2D or 3D cellulosic objects.

[0004] In this context, it is known that cellulose microfibrils have properties recognized for their very good barrier properties to fats, aromas and oxygen.

[0005] Furthermore, it is known, from the patent document referenced FR1904639, a method for producing cellulose microfibrils, also called cellulose nanofibrils (or CNF according to the English acronym for 'cellulose nanofibers') or even nanocellulose, based on the use of a twin-screw extruder to manufacture a paste of cellulose microfibrils at a concentration substantially equal to 20% by weight of dry matter in cellulose microfibrils, this use generally being carried out at room temperature.

[0006] It is also known that patent US20230115147A1 presents a method of forming a sheet having grease barrier properties, the method using an extruder fed with nanocelluloses previously produced at low concentration in a system other than an extruder (2-3 wt%) and which were then concentrated to 20-30 wt%, and to which CMC (carboxymethyl cellulose) was added for a ratio of between 0.3:1 and 0.03:1. A method of molding the sheet by thermocompression is mentioned, only the drying cannot be carried out entirely by thermocompression because of too great a shrinkage at the drying. The end of drying is therefore carried out in an oven over a long period of time. It is not obvious to the person skilled in the art that the paste mixed in an extruder can be injected into a mold. Only CMC (carboxymethylcellulose) is mentioned.

[0007] Furthermore, the 2023 scientific article “Cellulose Nanofibril (CNF)-Coated PFAS-Free, Grease-Resistant All-Bio-Based Molded Pulp Containers for Food Packaging” presents the addition of the thick CMC+CNF sheet obtained by extrusion onto a molded cellulose. This is a thermoforming process in which the sheet is deformed upon contact with the male mold. A substantial sheet thickness is required in such a process. The molded cellulose + CNF+CMC sheet system is dried under stress in an oven for a very long time of 6 hours at 90°C. It is therefore even less trivial to evaluate the possibility of forming a thin layer of nanocellulose by injection onto a 2D or 3D cellulosic material and dried by thermocompression in a relatively short time.

[0008] Furthermore, nanocellulose coating solutions have been proposed by spray, "slot die", blade or curtain coating. These coating technologies use a suspension of nanocellulose at low concentration, for example equal to 2% by weight of dry matter in microfibrils, or even at very low concentration, for example equal to 0.1% by weight of dry matter in microfibrils. This low concentration requires several passes or several layers to have a sufficient layer that is a barrier. The majority of processes are also limited to 2D cellulosic materials and not suitable, or even impossible for 3D objects.

[0009] In this context, it is necessary to propose a method for manufacturing a product, in particular a 3D product, based on cellulose which makes it possible to confer, preferably via a single deposit of microfibrils, on the cellulose-based product thus manufactured, barrier properties or surface smoothness making them suitable for packaging applications, for example for food products such as trays or for completely different products, such as anticovid test devices or compact discs (or CDs), the abrasion of which, in particular by the packaging, is to be avoided. SUMMARY

[0010] To achieve this objective, according to a first aspect of the invention, a method of manufacturing a cellulose-based product is provided comprising the following steps: - Provide a preformed cellulosic structure (2D or 3D), - Provide a nanocellulose paste at a nanofibril concentration of cellulose substantially between 5 and 50%, preferably substantially between 20 and 30%, even more preferably substantially equal to 25%, by weight of dry matter of the nanocellulose pulp, - Apply a layer of the supplied nanocellulose paste to a surface of the preformed cellulose structure, and Dry the layer based on nanocellulose paste by thermocompression.

[0011] Note that the layer based on the nanocellulose paste is thin relative to the thickness of the preformed cellulose structure.

[0012] According to another aspect of the invention, there is provided a cellulose-based product comprising: A preformed cellulosic structure (2D or 3D), and A layer of cellulose microfibrils on at least a portion of a surface of the preformed cellulose structure.

[0013] Thanks to the different aspects of the invention, an economic gain and / or an improvement in environmental impact are obtained on multiple scales, and in particular by: The implementation of a deposition step and a thermocompression step already present in industries, The possibility of large-scale manufacturing of nanocellulose paste to be deposited, and Limiting manufacturing costs by depositing a thin functional layer, while providing barrier properties to cellulose-based products, particularly those with complex three-dimensional shapes. BRIEF DESCRIPTION OF THE FIGURES

[0014] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0015] [Fig.l] [Fig.l] represents a flowchart of an embodiment of the manufacturing method according to the first aspect of the invention.

[0016] [Fig.2] [Fig.2] schematically represents a section in a mode of realization Production of a cellulose-based product according to the second aspect of the invention, the product taking the form of a container, and more particularly of a plate.

[0017] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to the scale of practical applications. In particular, the relative thicknesses of the different layers illustrated in [Fig.2] are not necessarily representative of reality. DETAILED DESCRIPTION

[0018] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in combination or alternatively are set out below:

[0019] According to an example of the first aspect of the invention, the step of depositing a layer based on the nanocellulose paste comprises injecting the nanocellulose paste.

[0020] According to an example of the first aspect of the invention, alternative to the previous example, the step of depositing a layer based on the nanocellulose paste comprises transfer molding of the nanocellulose paste.

[0021] According to an example of the first aspect of the invention, the step of depositing a layer based on the nanocellulose paste is carried out at room temperature, without the need for heating.

[0022] According to an example of the first aspect of the invention, the step of drying the layer based on the nanocellulose paste is carried out in a heat press at a temperature substantially between 110 and 250°C, preferably substantially between 150 and 200°C and at a pressure substantially between 0.5 and 40 MPa, preferably substantially between 0.5 and 10 MPa.

[0023] According to an example of the first aspect of the invention, the manufacturing method further comprises, concomitantly with the drying by thermocompression, a suction of the water vapor. The drying time is thus advantageously reduced.

[0024] According to an example of the first aspect of the invention, the preformed cellulosic structure is chosen from a preformed cellulosic container such as a tray, a preformed cellulosic utensil or a preformed cellulosic cap.

[0025] According to an example of the first aspect of the invention, said surface of the preformed cellulosic structure comprises at least a portion of an internal surface of the preformed cellulosic structure.

[0026] According to an example of the first aspect of the invention, said surface of the preformed cellulosic structure comprises at least a portion of an external surface of the preformed cellulosic structure.

[0027] According to an example of the first aspect of the invention, the step of providing the nanocellulose pulp uses a twin-screw extruder. According to this example, a water-soluble polymer may be added to pre-treated cellulose fibers at the input of the twin-screw extruder.

[0028] According to an example of the first aspect of the invention, the layer based on the deposited nanocellulose paste has a thickness substantially between 0.5 and 100 μm, preferably substantially between 10 and 70 μm, for example substantially equal to 50 μm.

[0029] According to an example of the first aspect of the invention, the step of depositing the layer based on the nanocellulose paste is carried out on the wet preformed cellulose structure. The manufacturing method according to the invention is a continuation of the manufacturing method of the preformed cellulose structure, before its drying, and can thus be carried out in the continuity of a preformed cellulosic structure production line.

[0030] According to an example of the first aspect of the invention, the step of depositing the layer based on the nanocellulose paste is carried out on the dry preformed cellulose structure. The manufacturing method according to the invention then consists of a post-treatment of the preformed cellulose structure once the latter has been dried.

[0031] According to an example of the first aspect of the invention, the nanocellulosic paste provided comprises at least one water-soluble polymer, preferably natural and cold-soluble, and even more preferably of long molecular chain, and / or a functional additive which can be chosen from: cellulose ethers (HPMC, HEC, HPC, CMC), - a synthetic polymer (e.g. Poly ethylene glycol, polyvinyl alcohol), - guar gum, carob gum, xanthan gum, - alginate, agar-agar, carrageenan, - pectins or hemicelluloses, - modified or unmodified starches, - functionalized or non-functionalized cellulose nanocrystals or nanofibrils, - mineral fillers, such as water-retaining fillers, - hydrophobizing additives such as wax, drying oils or polymer emulsion, for example, - additives for functionalizing cellulose microfibrils such as AKD (Alkyl Ketene Dimere) or PAS A (Alkenyl Succinic Anhydride) for example, and - their mixtures.

[0032] According to an example of the second aspect of the invention, the layer based on cellulose microfibrils has a thickness substantially between 0.5 and 100 μm, preferably substantially between 10 and 70 μm.

[0033] According to an example of the second aspect of the invention, the cellulose microfibril-based layer comprises substantially between 50 and 100%, preferably substantially between 70 and 100%, by dry weight of cellulose microfibrils.

[0034] A film or layer or paste based on a material A is understood to mean a film or layer or paste comprising this material A and possibly other materials.

[0035] A parameter “substantially equal / greater / less than” a given value means that this parameter is equal / greater / less than the given value, plus or minus 20%, or even 10%, close to this value. A parameter “substantially between” two given values ​​means that this parameter is at least equal to the smallest given value, plus or minus 20%, or even 10%, close to this value, and at most equal to the largest given value, plus or minus 20%, or even 10%, near this value.

[0036] The first aspect of the invention relating to a method of manufacturing 10 a cellulose-based product 1 is described below with reference to [Fig.l].

[0037] This method is essentially such that it comprises the following steps: - Providing 12 a preformed cellulosic structure 2, - Provide 14 a nanocellulose paste at a nanofibril concentration of cellulose substantially between 5 and 50%, preferably substantially between 20 and 30%, even more preferably substantially equal to 25%, by weight of dry matter of the nanocellulose pulp, - Deposit 16 a layer based on the provided nanocellulose paste 14 on a surface of the preformed cellulose structure 2, and - Dry 18 the layer based on nanocellulose paste by thermocompression.

[0038] The preformed cellulosic structure 2 provided 12 can take any shape, simple or complex, open or closed, hollowed out or solid. In a non-limiting manner, it can for example constitute a preformed cellulosic container, such as a plate (Cf. [Fig.2]) or a yogurt pot, a preformed cellulosic utensil, such as cutlery, and a preformed cellulosic cap, including one having a thread.

[0039] The preformed cellulose structure 2 provided 12 may come directly from a molding process and have retained a wet surface appearance, for example at the end of the molded cellulose production line, before the nanocellulose paste is directly deposited 16. Alternatively, the preformed cellulose structure 2 provided 12 may have been dried following its molding; the deposition 16 of the nanocellulose paste may then appear as a post-treatment of the preformed cellulose structure 2.

[0040] The preformed cellulosic structure 2 has at least one deposition surface 16, which may be internal and / or external depending on the intended use of the manufactured cellulose-based product 10, and on which it is desired, depending on the intended use of the manufactured cellulose-based product 10, to provide barrier properties, for example to grease, liquids or gases.

[0041] To this end, it is planned to deposit 16, on this surface, the provided nanocellulose paste 14. The latter can be obtained, from pretreated cellulose fibers, passed through a high shear rate twin-screw extruder, for example in the manner described in the patent document referenced FR1904639, to allow significant fibrillation and produce a homogeneous nanocellulose paste containing cellulose nanofibers at high concentration.

[0042] The provided nanocellulose paste 14 may comprise at least one soluble polymer

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] in water, preferably natural and cold soluble, and even more preferably long molecular chain, and / or a functional additive which can be chosen from: Cellulose ethers (HPMC, HEC, HPC, CMC), - a synthetic polymer (e.g. Polyethylene glycol, polyvinyl alcohol), - guar gum, carob gum, xanthan gum, - an alginate, agar-agar, carrageenans, - pectins or hemicelluloses, - modified or unmodified starches, - functionalized or non-functionalized cellulose nanocrystals or nanofibrils, - mineral fillers, such as water-retaining fillers, - hydrophobizing additives such as wax, drying oils or polymer emulsion, for example, - additives for functionalizing cellulose microfibrils such as AKD (Alkyl Ketene Dimere) or PAS A (Alkenyl Succinic Anhydride) for example, and - their mixtures. This advantageously confers specific spreading properties on the provided nanocellulose paste 14 and possible additional or improved barrier properties. Preferably, the provided nanocellulose pulp 14 always has, despite the addition of additives, a minimum of 80% fibrillated cellulose by weight of dry matter. When additives are added, they may represent between 0.1 and 20%, preferably between 0.5 and 5%, by weight of dry matter of the provided nanocellulose pulp 14. It should be noted that the nanocellulose paste thus provided 14 comprises between 50 and 85% by weight of water. The deposition 16 of the nanocellulose paste on said surface of the preformed cellulose structure 2 can be carried out by injection, for example directly from the outlet of the twin-screw extruder, or by transfer molding. The deposition 16 can advantageously be carried out at room temperature without heating, but also by heating if necessary. When the provided nanocellulose paste 14 does not include a natural water retention additive, it is recommended to moisten the deposition surface before depositing 16 the nanocellulose paste thereon. The deposition 16 of the nanocellulose paste is preferably configured so that the layer based on the deposited nanocellulose paste has a thickness substantially between 0.5 and 100 pm, preferably substantially between 10 and 70 pm, for example approximately equal to 50 pm.

[0049] The drying 18 of the layer based on the deposited nanocellulose paste 16 is preferably carried out in a heat press, for example at a temperature substantially between 110 and 250°C, preferably substantially between 150 and 200°C, and / or at a pressure substantially between 0.5 and 40 MPa, preferably substantially between 0.5 and 10 MPa. The drying 18 of the layer based on the deposited nanocellulose paste 16 can under these conditions be achieved in just a few tens of seconds, or in just a few minutes. When the thermocompression is carried out concomitantly with suction of the released water vapor, the drying time can advantageously be further reduced.

[0050] The cellulose-based product 1 thus manufactured 10 is a two-dimensional or three-dimensional product having, on at least one of its surfaces, a thin layer of fibrillated cellulose giving it barrier properties. This product is advantageously recyclable. And its manufacturing process is of low cost, in particular because, the nanocellulose pulp being highly concentrated in cellulose nanofibers, its transport represents a lower cost relative to that of nanocellulose pulps having a lower concentration of cellulose nanofibers and its drying is easier.

[0051] An economic gain is therefore achieved as well as an improvement in terms of environmental impact, and this on multiple scales: - the proposed solution implements a system of injection or transfer molding without heating and thermocompression which are already present in industries, - the proposed solution makes it possible to manufacture cellulose-based products 1 on a large scale with the required barrier properties depending on the intended use of the product, in particular since the supply 14 of the nanocellulose pulp can be carried out on an industrial scale, - the proposed solution makes it possible to deposit thin nanocellulosic layers on preformed cellulose structures 2 of different shapes and dimensions, more or less complex, two-dimensional or three-dimensional, already existing, thus limiting the cost while providing the required barrier properties, - the proposed solution makes it possible to insert the manufacturing process 1 according to the first aspect of the invention downstream of a molded cellulose production line or in post-treatment on a finished, i.e. dried, molded cellulose structure 2.

[0052] More particularly, the present invention relates, according to a second aspect, to a cellulose-based product 1 comprising: - A preformed cellulose structure 2, and - A layer based on cellulose microfibrils 3 on at least a portion of a surface of the preformed cellulose structure 2.

[0053] The cellulose microfibril-based layer 3 preferably has a thickness substantially between 0.5 and 100 μm, preferably substantially between 10 and 70 μm, for example substantially equal to 50 μm. This gives it in particular an oxygen barrier property, and more particularly an oxygen transmission rate (or OTR) advantageously between 1 and 150 cm3 / m2 / day (instead of more than 3000 cm3 / m2 / day for the starting preformed cellulose), in particular for a deposit 16 of 50 microns in thickness.

[0054] The surface condition of the cellulose microfiber-based layer 3 is advantageously very smooth and not very rough, making this coating slightly abrasive, and consequently, making the cellulose-based product 1 suitable for constituting packaging for products susceptible to abrasion, such as CDs, DVDs, etc., or requiring a smooth surface.

[0055] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

Claims

Claims

1. A method of manufacturing (10) a cellulose-based product (1) comprising the following steps: • Providing (12) a preformed cellulose structure (2), • Providing (14) a nanocellulose pulp at a concentration of cellulose nanofibrils substantially comprised between 5 and 50%, preferably substantially comprised between 20 and 30%, by weight of dry matter of the nanocellulose pulp, • Depositing (16) a layer based on the provided nanocellulose pulp (14) on a surface of the preformed cellulose structure (2), and • Drying (18) the layer based on the nanocellulose pulp by thermocompression.

2. Manufacturing method (10) according to the preceding claim, wherein the step of depositing (16) a layer based on the nanocellulose paste comprises injecting the nanocellulose paste.

3. The manufacturing method (10) of claim 1, wherein the step of depositing (16) a layer based on the nanocellulose paste comprises transfer molding the nanocellulose paste.

4. A manufacturing method (10) according to any preceding claim, wherein the step of depositing (16) a layer based on the nanocellulose paste is carried out at room temperature.

5. Manufacturing method (10) according to any one of the preceding claims, wherein the step of drying (18) the layer based on the nanocellulose pulp is carried out in a heat press at a temperature substantially between 110 and 250°C, preferably substantially between 150 and 200°C and at a pressure substantially between 0.5 and 40 MPa, preferably substantially between 0.5 and 10 MPa.

6. Manufacturing method (10) according to any one of the preceding claims, further comprising, concomitantly with the drying (18) by thermocompression, a suction of water vapor.

7. A manufacturing method (10) according to any preceding claim, wherein the preformed cellulosic structure (2) is selected from a preformed cellulosic container, a cellulosic utensil preformed lulosic and a preformed cellulose plug.

8. A manufacturing method (10) according to any preceding claim, wherein said surface of the preformed cellulosic structure (2) comprises at least a portion of an inner surface of the preformed cellulosic structure (2).

9. A manufacturing method (10) according to any preceding claim, wherein said surface of the preformed cellulosic structure (2) comprises at least a portion of an external surface of the preformed cellulosic structure (2).

10. A manufacturing method (10) according to any preceding claim, wherein the step of providing (14) the nanocellulose paste uses a twin-screw extruder.

11. Manufacturing method (10) according to any one of the preceding claims, in which the layer based on the deposited nanocellulose paste has a thickness substantially between 0.5 and 100 pm, preferably substantially between 10 and 70 pm, for example substantially equal to 50 pm.

12. Manufacturing method (10) according to any one of the preceding claims, wherein the step of depositing (16) the layer based on the nanocellulose paste is carried out on the wet preformed cellulose structure (2).

13. Manufacturing method (10) according to any one of claims 1 to 12, wherein the step of depositing (16) the layer based on the nanocellulose paste is carried out on the dry preformed cellulose structure (2).

14. Manufacturing method (10) according to any one of the preceding claims, in which the provided nanocellulose paste (14) comprises at least one water-soluble polymer, preferably natural and cold-soluble, and even more preferably of long molecular chain, and / or a functional additive which can be chosen from: • Cellulose ethers (HPMC, HEC, HPC, CMC), • a synthetic polymer (e.g. Polyethylene glycol, polyvinyl alcohol), • guar gum, carob gum, xanthan gum, • an alginate, agar-agar, carrageenans, • pectins or hemicelluloses, • modified or unmodified starches, • functionalized or non-functionalized cellulose nanocrystals or nanofibrils • mineral fillers, such as water-retaining fillers • hydrophobization additives such as wax, drying oils or polymer emulsion for example • cellulose microfibril functionalization additives such as AKD (Alkyl Ketene Dimere) or ASA (Alkenyl Succinic Anhydride) for example, and • mixtures thereof.

15. Cellulose-based product (1) comprising: • A preformed cellulose structure (2), and • A cellulose microfibril-based layer (3) on at least a portion of a surface of the preformed cellulose structure (2).

16. Cellulose-based product (1) according to the preceding claim, in which the cellulose microfibril-based layer (3) has a thickness substantially between 0.5 and 100 pm, preferably substantially between 10 and 70 pm, for example substantially equal to 50 pm.

17. Cellulose-based product (1) according to any one of claims 15 and 16, wherein the cellulose microfibril-based layer (3) comprises between 50 and 100%, preferably substantially between 70 and 100%, by dry weight of cellulose microfibrils.

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