Method for producing a cellulose-based product

Abstract

The invention relates to the field of producing moulded cellulose-based packages and more particularly to a method for producing a cellulose-based product and to the cellulose-based product produced in this way. The production method 10 is essentially such that it comprises the following steps: • providing 12 a preformed cellulosic structure; • providing 14 a nanocellulosic pulp with a cellulose nanofibril concentration of substantially 5 to 50% by weight of solids of the nanocellulosic pulp; • depositing 16 a layer based on the provided nanocellulosic pulp on a surface of the preformed cellulosic structure; and • drying 18 the layer based on the nanocellulosic pulp by means of thermocompression. The cellulose-based product produced is essentially such that it comprises: • a preformed cellulosic structure; and • a layer based on cellulose microfibrils on at least one surface of the preformed cellulosic structure.

Description

[0001] “Process for manufacturing a cellulose-based product”

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the field of manufacturing cellulose-based packaging, particularly molded cellulose. The present invention relates more particularly to a method for manufacturing a cellulose-based product.

[0004] STATE OF THE ART

[0005] In the context of the development of cellulose-based packaging, particularly molded cellulose, several studies have been carried out to find solutions to provide barrier properties to this packaging.

[0006] 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, particularly 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.

[0007] In this context, we know that cellulose microfibrils have properties recognized for their very good barrier properties to fats, aromas and oxygen.

[0008] 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 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.

[0009] It is also known that patent US20230115147A1 presents a method for forming a sheet having grease barrier properties, the process 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 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 much shrinkage during drying. The end of the drying is therefore carried out in an oven over a long time. It is not obvious to the person skilled in the art to think that the paste mixed in the extruder can be injected into a mold. Only CMC (carboxymethyl cellulose) is mentioned.

[0010] 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 on a molded cellulose. This is a thermoforming process also called overmolding in which the sheet is deformed in contact with the male mold. A significant 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 on a 2D or 3D cellulosic material and dried by thermocompression in a relatively short time.

[0011] Furthermore, nanocellulose coating solutions have been proposed by spray, slot die, blade or curtain coating. These coating technologies use a nanocellulose suspension 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 obtain a sufficient barrier layer. The majority of processes are also limited to 2D cellulosic materials and are not suitable, or even impossible, for 3D objects.

[0012] In this context, it is necessary to propose a process 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, must be avoided.

[0013] SUMMARY OF THE INVENTION

[0014] 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:

[0015] - Provide a preformed cellulosic structure (2D or 3D), composed for example of traditional papermaking cellulosic fibers (from softwood, hardwood or annual plant, bleached or not, with a grammage between 100 and 3000 g / m 2 and / or a density between 0.5 and 2 g / cm 3 ,

[0016] - Providing a nanocellulose pulp with a concentration of cellulose nanofibrils 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,

[0017] - Deposit a layer based on the supplied nanocellulose paste on a surface of the preformed cellulose structure by injection, and

[0018] - Dry the layer based on nanocellulose paste by thermocompression.

[0019] Note that the layer based on the nanocellulose paste is thin relative to the thickness of the preformed cellulose structure.

[0020] Note that the deposition of a thin layer by injecting one material onto another at room temperature does not exist in current processes but can be adapted to injection or transfer molding machines. "Injection deposition" is defined as the ability to deposit a thin layer onto a preformed structure using a system similar to an injection head, i.e. with a piston or extrusion system, a small diameter capillary and a mold (in which the preformed shape is already present).

[0021] According to another aspect of the invention, there is provided a cellulose-based product comprising:

[0022] - A preformed cellulosic structure (2D or 3D), and

[0023] - A layer based on cellulose microfibrils on at least a portion of a surface of the preformed cellulose structure.

[0024] 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:

[0025] - The implementation of a deposition step and a thermocompression step already present in industries,

[0026] - The possibility of manufacturing on a large scale the nanocellulose paste to be deposited, and

[0027] - Limiting manufacturing costs by depositing a thin functional layer, while providing barrier properties to cellulose-based products, particularly those with complex three-dimensional shapes.

[0028] BRIEF DESCRIPTION OF THE FIGURES

[0029] 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:

[0030] Figure 1 represents a flowchart of an embodiment of the manufacturing method according to the first aspect of the invention.

[0031] Figure 2 schematically represents a section in an embodiment 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.

[0032] Figure 3 represents the injection force required to deposit a nanocellulose paste (TSE-MFC) and an additive nanocellulose paste on a dry preformed cellulose structure.

[0033] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the 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 Figure 2 are not necessarily representative of reality.

[0034] DETAILED DESCRIPTION OF THE INVENTION

[0035] Before commencing a detailed review of embodiments of the invention, optional features which may optionally be used in combination or alternatively are set out below:

[0036] 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.

[0037] 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. More particularly, the step of depositing a layer based on the nanocellulose paste comprises injection coating of the nanocellulose paste

[0038] 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.

[0039] According to an example of the first aspect of the invention, the step of depositing a layer based on the non-additive nanocellulose paste is carried out on a dry preformed cellulose structure. The injection force required to deposit this layer is high and unstable. The deposited layer is non-homogeneous. Migration of the water contained in the nanocellulose paste towards the preformed cellulose structure is observed. The deposited layer has a dry matter concentration gradient from the injection point to the periphery of the layer. The method and the product are thus non-reproducible and non-repeatable.

[0040] According to an example of the first aspect of the invention, the step of depositing a layer based on the non-additive nanocellulose paste is carried out on a wet preformed cellulose structure. The injection force required to deposit this layer is low and stable. The deposited layer is homogeneous. The method and the product are reproducible and repeatable.

[0041] According to an example of the first aspect of the invention, the step of depositing a layer based on the additive nanocellulose paste is carried out on a dry or wet preformed cellulose structure. The injection force required to deposit this layer is low and stable [Fig. 3], The deposited layer is homogeneous. The method and the product are reproducible and repeatable.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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 inner surface of the preformed cellulosic structure.

[0046] 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.

[0047] 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.

[0048] 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 pm, preferably substantially between 10 and 70 pm, for example substantially equal to 50 pm.

[0049] 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 as a continuation of a preformed cellulose structure production line.

[0050] 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.

[0051] According to an example of the first aspect of the invention, the nanocellulose paste provided comprises at least one additive, a 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:

[0052] - cellulose ethers (HPMC, HEC, HPC, CMC),

[0053] - a synthetic polymer (e.g. Poly ethylene glycol, polyvinyl alcohol),

[0054] - guar gum, carob gum, xanthan gum,

[0055] - an alginate, agar-agar, carrageenan,

[0056] - pectins or hemicelluloses,

[0057] - modified or unmodified starches, - functionalized or unfunctionalized cellulose nanocrystals or nanofibrils,

[0058] - mineral fillers, such as water-retaining fillers,

[0059] - hydrophobizing additives such as wax, drying oils or polymer emulsion, for example,

[0060] - additives for functionalizing cellulose microfibrils such as AKD (Alkyl Ketene Dimer) or ASA (Alkenyl Succinic Anhydride) for example, and

[0061] - their mixtures.

[0062] 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.

[0063] 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.

[0064] A film or layer or paste based on a material A means a film or layer or paste comprising this material A and possibly other materials.

[0065] A parameter that is "substantially equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value, within plus or minus 20% or even 10% of this value. A parameter that is "substantially between" two given values ​​means that this parameter is at least equal to the smallest given value, within plus or minus 20% or even 10% of this value, and at most equal to the largest given value, within plus or minus 20% or even 10% of this value.

[0066] 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. 1.

[0067] This process is essentially as it includes the following steps:

[0068] - Provide 12 a preformed cellulosic structure 2,

[0069] - Providing 14 a nanocellulose pulp at a concentration of cellulose nanofibrils 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,

[0070] - Deposit 16 a layer based on the provided nanocellulose paste 14 on a surface of the preformed cellulose structure 2, and

[0071] - Dry 18 the layer based on nanocellulose paste by thermocompression.

[0072] 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 (see figure 2) or a yogurt pot, a preformed cellulosic utensil, such as cutlery, and a preformed cellulosic cap, including one having a thread.

[0073] 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.

[0074] The preformed cellulose 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.

[0075] 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.

[0076] The provided nanocellulose paste 14 may comprise 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 may be chosen from:

[0077] - Cellulose ethers (HPMC, HEC, HPC, CMC),

[0078] - a synthetic polymer (e.g. Poly ethylene glycol, polyvinyl alcohol),

[0079] - guar gum, carob gum, xanthan gum,

[0080] - an alginate, agar-agar, carrageenan,

[0081] - pectins or hemicelluloses,

[0082] - modified or unmodified starches,

[0083] - functionalized or non-functionalized cellulose nanocrystals or nanofibrils,

[0084] - mineral fillers, such as water-retaining fillers,

[0085] - hydrophobizing additives such as wax, drying oils or polymer emulsion, for example,

[0086] - additives for functionalizing cellulose microfibrils such as AKD (Alkyl Ketene Dimer) or ASA (Alkenyl Succinic Anhydride) for example, and

[0087] - their mixtures. This advantageously confers specific spreading properties on the nanocellulose paste provided 14 and possible additional or improved barrier properties.

[0088] 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.

[0089] It should be noted that the nanocellulose paste thus provided 14 comprises between 50 and 85% by weight of water.

[0090] 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.

[0091] 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.

[0092] 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 substantially equal to 50 pm.

[0093] 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 heat compression is carried out concomitantly with suction of the released water vapor, the drying time can advantageously be further reduced.

[0094] 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 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.

[0095] An economic gain is therefore achieved as well as an improvement in terms of environmental impact, and this on multiple scales:

[0096] - the proposed solution implements a system of injection or transfer molding without heating and thermocompression which are already present in industries,

[0097] - 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,

[0098] - 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,

[0099] - 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.

[0100] More particularly, the present invention relates, according to a second aspect, to a cellulose-based product 1 comprising:

[0101] - A preformed cellulose structure 2, and

[0102] - A layer based on cellulose microfibrils 3 on at least a portion of a surface of the preformed cellulose structure 2.

[0103] 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 cm 3 / m 2 / day (instead of more than 3000 cm 3 / m 2 / day for the starting preformed cellulose), in particular for a 16 deposit of 50 microns thick.

[0104] 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.

[0105] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

Claims

CLAIMS 1. Method of manufacturing (10) a cellulose-based product (1) comprising the following steps: • Provide (12) a preformed cellulosic structure (2), • Provide (14) a nanocellulose pulp at a concentration of cellulose nanofibrils substantially between 5 and 50%, preferably substantially between 20 and 30%, by weight of dry matter of the nanocellulose pulp, • Depositing (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 the nanocellulose paste by thermocompression, • wherein the step of depositing (16) a layer based on the nanocellulose paste comprises injecting the nanocellulose paste.

2. The manufacturing method (10) of claim 1, wherein the step of depositing (16) a layer based on the nanocellulose paste comprises injection coating the nanocellulose paste.

3. Manufacturing method (10) according to any one of the preceding claims, in which the step of depositing (16) a layer based on the nanocellulose paste is carried out at room temperature.

4. Manufacturing method (10) according to any one of the preceding claims, in which the step of drying (18) 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.

5. 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.

6. Manufacturing method (10) according to any one of the preceding claims, wherein the preformed cellulosic structure (2) is chosen from a preformed cellulosic container, a preformed cellulosic utensil and a preformed cellulosic cap.

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

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

9. Manufacturing method (10) according to any one of the preceding claims, in which the step of providing (14) the nanocellulose paste uses a twin-screw extruder.

10. 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.

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

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

13. 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. Poly ethylene glycol, polyvinyl alcohol), • guar gum, carob gum, xanthan gum, • 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 Dimer) or ASA (Alkenyl Succinic Anhydride) for example, and • their mixtures.

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