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] "Manufacturing process for a cellulose-based product"

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the field of manufacturing cellulose-based packaging, and in particular molded cellulose packaging. More specifically, the present invention relates to a process for manufacturing a cellulose-based product.

[0004] STATE OF THE ART

[0005] In the context of the development of cellulose-based packaging, and in particular molded cellulose, several studies have been conducted to find solutions to provide barrier properties to this packaging.

[0006] Indeed, cellulose-based structures can replace commonly used plastics, for example in two-dimensional (2D) or three-dimensional (3D) objects such as food trays, but they often lack barrier properties, particularly against fats, 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, it is known that cellulose microfibrils have recognized properties for their very good barrier properties against fats, aromas and oxygen.

[0008] Furthermore, a method for producing cellulose microfibrils, also called cellulose nanofibrils (or CNF according to the English acronym for 'cellulose nanofibers') or nanocellulose, is known from the patent document referenced FR1904639, based on the implementation of a twin-screw extruder to manufacture a cellulose microfibril paste at a concentration approximately equal to 20% by weight of dry matter in cellulose microfibrils, this implementation being generally carried out at room temperature.

[0009] It is also known that US patent 20230115147A1 describes a method for forming sheets with grease-barrier properties. The process uses an extruder fed with nanocellulose previously produced at a low concentration (2-3 wt%) in a separate system (not an extruder), which is then concentrated to 20-30 wt%. CMC (carboxymethyl cellulose) is then added to this nanocellulose at a ratio of 0.3:1 to 0.03:1. A method for molding the sheet by thermocompression is mentioned, but drying cannot be carried out entirely by thermocompression due to excessive shrinkage. Therefore, the final drying stage is completed in an oven over a long period. It is not immediately obvious to those skilled in the art that the paste mixed in the extruder could be injected into a mold. Only the 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 a thick CMC+CNF sheet obtained by extrusion onto molded cellulose. This is a thermoforming process, also called overmolding, in which the sheet is deformed upon contact with the male mold. A significant sheet thickness is required in such a process. The molded cellulose + CNF+CMC sheet system is then dried under stress in an oven for a very long time, 6 hours at 90°C. It is therefore even more complex to assess the feasibility of forming a thin nanocellulose layer by injection onto a 2D or 3D cellulosic material that has been dried by thermocompression in a relatively short time.

[0011] Furthermore, nanocellulose coating solutions have been proposed using spray, slot die, sheet coating, or curtain coating. These coating technologies use a low-concentration nanocellulose suspension, for example, 2% by weight of dry matter in microfibrils, or even a very low concentration, for example, 0.1% by weight of dry matter in microfibrils. This low concentration necessitates several passes or layers to achieve a sufficient barrier layer. Most of these processes are also limited to 2D cellulosic materials and are unsuitable, or even impossible, for 3D objects.

[0012] In this context, it is necessary to propose a manufacturing process for a product, especially 3D, based on cellulose which allows, preferably via a single deposition of microfibrils, the cellulose-based product thus manufactured to have barrier or surface smoothing properties making it suitable for packaging applications, for example for food products such as trays or for completely different products, such as anti-covid test devices or compact discs (or CDs), whose abrasion, especially by packaging, must be avoided.

[0013] SUMMARY OF THE INVENTION

[0014] To achieve this objective, according to a first aspect of the invention, a manufacturing process for a cellulose-based product is provided, comprising the following steps:

[0015] - To provide a pre-formed cellulose structure (2D or 3D), composed for example of traditional papermaking cellulose fibers (from softwood, hardwood or annual plant, bleached or unbleached, with a basis weight between 100 and 3000 g / m²) 2 and / or with a density between 0.5 and 2 g / cm³ 3 ,

[0016] - To supply a nanocellulosic paste with a cellulose nanofibril concentration of approximately between 5 and 50%, preferably approximately between 20 and 30%, and even more preferably approximately 25%, by weight of dry matter of the nanocellulosic paste,

[0017] - Deposit a layer of the supplied nanocellulosic paste onto a surface of the injection-molded preformed cellulosic structure, and

[0018] - Dry the layer based on the nanocellulosic paste by thermocompression. Note that the layer based on the nanocellulosic paste is thin relative to the thickness of the preformed cellulosic structure.

[0019] Note that the deposition of a thin layer by injecting one material onto another at room temperature is not possible with current processes but can be adapted to injection molding 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 tube, and a mold (containing the preformed shape).

[0020] According to another aspect of the invention, a cellulose-based product is provided comprising:

[0021] - A preformed cellulosic structure (2D or 3D), and

[0022] - A layer based on cellulose microfibrils on at least part of a surface of the preformed cellulosic structure.

[0023] Thanks to the various aspects of the invention, economic gains and / or improvements in environmental impact are achieved at multiple levels, including through:

[0024] - The implementation of a deposition stage and a thermocompression stage already present in industries,

[0025] - The possibility of manufacturing the nanocellulosic paste for deposition on a large scale, and

[0026] - Limiting manufacturing costs by depositing a thin functional layer, while providing barrier properties to cellulose-based products, particularly those with complex three-dimensional shapes.

[0027] BRIEF DESCRIPTION OF THE FIGURES

[0028] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0029] Figure 1 represents a flowchart of an implementation method of the manufacturing process according to the first aspect of the invention.

[0030] Figure 2 schematically represents a cross-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.

[0031] Figure 3 represents the injection force required to deposit a nanocellulosic paste (TSE-MFC) and an additively treated nanocellulosic paste onto a dry preformed cellulosic structure.

[0032] The drawings are provided by way of example and are not intended to limit the invention. They are schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the relative thicknesses of the different layers illustrated in Figure 2 are not necessarily representative of reality.

[0033] DETAILED DESCRIPTION OF THE INVENTION

[0034] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:

[0035] According to an example of the first aspect of the invention, the step of depositing a layer based on the nanocellulosic paste includes the injection of the nanocellulosic paste.

[0036] According to an example of the first aspect of the invention, alternative to the preceding example, the step of depositing a layer based on the nanocellulosic paste includes transfer molding of the nanocellulosic paste. More particularly, the step of depositing a layer based on the nanocellulosic paste includes injection coating of the nanocellulosic paste.

[0037] According to an example of the first aspect of the invention, the step of depositing a layer based on the nanocellulosic paste is carried out at room temperature, without the need for heating.

[0038] According to an example of the first aspect of the invention, the step of depositing a layer based on the unadditized nanocellulosic paste is carried out on a dry, preformed cellulosic structure. The injection force required to deposit this layer is high and unstable. The deposited layer is non-homogeneous. Migration of water contained in the nanocellulosic paste into the preformed cellulosic structure is observed. The deposited layer exhibits a dry matter concentration gradient from the injection point to the periphery of the layer. The process and the product are therefore neither reproducible nor repeatable.

[0039] According to an example of the first aspect of the invention, the step of depositing a layer based on the unadditized nanocellulosic paste is carried out on a preformed, moist cellulosic structure. The injection force required to deposit this layer is low and stable. The deposited layer is homogeneous. The process and the product are reproducible and repeatable.

[0040] According to an example of the first aspect of the invention, the step of depositing a layer based on the additively treated nanocellulosic paste is carried out on a preformed dry or wet cellulosic structure. The injection force required to deposit this layer is low and stable [Fig. 3]. The deposited layer is homogeneous. The process and the product are reproducible and repeatable.

[0041] According to an example of the first aspect of the invention, the step of drying the layer based on the nanocellulosic paste is carried out in a thermopress 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.

[0042] According to an example of the first aspect of the invention, the manufacturing process further comprises, concurrently with drying by thermocompression, the extraction of water vapor. This advantageously reduces the drying time.

[0043] 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 stopper.

[0044] According to an example of the first aspect of the invention, said surface of the preformed cellulosic structure comprises at least a part of an internal surface of the preformed cellulosic structure.

[0045] According to an example of the first aspect of the invention, said surface of the preformed cellulosic structure comprises at least a part of an external surface of the preformed cellulosic structure.

[0046] According to an example of the first aspect of the invention, the process of supplying the nanocellulosic paste employs a twin-screw extruder. In this example, a water-soluble polymer can be added to pre-treated cellulose fibers at the inlet of the twin-screw extruder.

[0047] According to an example of the first aspect of the invention, the layer based on the deposited nanocellulosic 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.

[0048] According to an example of the first aspect of the invention, the step of depositing the layer based on the nanocellulosic paste is carried out on the preformed, moist cellulosic structure. The manufacturing process according to the invention is a continuation of the manufacturing process of the preformed cellulosic structure, prior to its drying, and can thus be carried out as part of a preformed cellulosic structure production line.

[0049] According to an example of the first aspect of the invention, the step of depositing the layer based on the nanocellulosic paste is carried out on the dry, preformed cellulosic structure. The manufacturing process according to the invention then consists of a post-treatment of the preformed cellulosic structure once it has dried.

[0050] According to an example of the first aspect of the invention, the nanocellulosic 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 may be selected from:

[0051] - cellulose ethers (HPMC, HEC, HPC, CMC),

[0052] - a synthetic polymer (e.g., polyethylene glycol, polyvinyl alcohol),

[0053] - guar gum, carob gum, xanthan gum,

[0054] - alginate, agar-agar, carrageenan,

[0055] - pectins or hemicelluloses,

[0056] - modified or unmodified starches, - functionalized or unfunctionalized cellulose nanocrystals or nanofibrils,

[0057] - mineral fillers, such as water-retaining fillers,

[0058] - hydrophobic additives such as wax, drying oils or polymer emulsion, for example,

[0059] - cellulose microfibril functionalization additives such as AKD (Alkyl Ketene Dimere) or ASA (Alkenyl Succinic Anhydride) for example, and - their mixtures.

[0060] According to an example of the second aspect of the invention, the cellulose microfibril-based layer has a thickness of substantially between 0.5 and 100 pm, preferably substantially between 10 and 70 pm.

[0061] 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.

[0062] A film, layer, or paste based on a material A is understood to mean a film, layer, or paste comprising that material A and possibly other materials.

[0063] A parameter that is "approximately equal to / greater than / less than" a given value means that the parameter is equal to / greater than / less than the given value, within 20% or 10% of that value. A parameter that is "approximately between" two given values ​​means that the parameter is at least equal to the smaller of the two given values, within 20% or 10% of that value, and at most equal to the larger of the two given values, within 20% or 10% of that value.

[0064] The first aspect of the invention relating to a manufacturing process 10 of a cellulose-based product 1 is described below with reference to Figure 1.

[0065] This process essentially consists of the following steps:

[0066] - Provide 12 a preformed cellulosic structure 2,

[0067] - To supply 14 a nanocellulosic paste with a cellulose nanofibril concentration of substantially between 5 and 50%, preferably substantially between 20 and 30%, and even more preferably substantially equal to 25%, by weight of dry matter of the nanocellulosic paste,

[0068] - Deposit 16 a layer based on the supplied nanocellulosic paste 14 onto a surface of the preformed cellulosic structure 2, and

[0069] - Dry the nanocellulosic paste-based layer by thermocompression. The preformed cellulosic structure provided can take any shape, simple or complex, open or closed, hollow or solid. For example, it can 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 with a thread.

[0070] The preformed cellulosic structure 2 supplied 12 may be directly from a molding process and may have retained a wet surface appearance, for example at the end of the molded cellulose production line, before the nanocellulosic paste is directly deposited 16. Alternatively, the preformed cellulosic structure 2 supplied 12 may have been dried following its molding; the deposition 16 of the nanocellulosic paste may then appear as a post-treatment of the preformed cellulosic structure 2.

[0071] The preformed cellulosic structure 2 has at least one deposition surface 16, which can 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 against grease, liquids or gases.

[0072] To this end, it is planned to deposit 16, on this surface, the nanocellulosic paste provided 14. The latter can be obtained, from pretreated cellulose fibers, passed through a twin-screw extruder with high shear rate, for example in the manner described in the patent document referenced FR1904639, to allow significant fibrillation and produce a homogeneous nanocellulosic paste containing cellulose nanofibers at high concentration.

[0073] The nanocellulosic paste supplied 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 selected from:

[0074] - Cellulose ethers (HPMC, HEC, HPC, CMC),

[0075] - a synthetic polymer (e.g., polyethylene glycol, polyvinyl alcohol),

[0076] - guar gum, carob gum, xanthan gum,

[0077] - alginate, agar-agar, carrageenan,

[0078] - pectins or hemicelluloses,

[0079] - modified or unmodified starches,

[0080] - functionalized or non-functionalized cellulose nanocrystals or nanofibrils,

[0081] - mineral fillers, such as water-retaining fillers,

[0082] - hydrophobic additives such as wax, drying oils or polymer emulsion, for example,

[0083] - cellulose microfibril functionalization additives such as AKD (Alkyl Ketene Dimere) or ASA (Alkenyl Succinic Anhydride) for example, and - their mixtures. This advantageously confers specific spreading properties to the supplied nanocellulosic paste 14 and possible additional or improved barrier properties.

[0084] Preferably, the supplied nanocellulosic paste 14 always contains, despite the addition of additives, a minimum of 80% fibrillated cellulose by dry weight. When additives are added, they may represent between 0.1 and 20%, preferably between 0.5 and 5%, by dry weight of the supplied nanocellulosic paste 14.

[0085] It should be noted that the nanocellulosic paste thus supplied 14 comprises between 50 and 85% water by weight.

[0086] The deposition 16 of the nanocellulosic paste onto the surface of the preformed cellulosic 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 with heating if necessary.

[0087] When the supplied nanocellulosic paste 14 does not include a natural water retention additive, it is recommended to moisten the deposition surface before depositing 16 the nanocellulosic paste on it.

[0088] The deposition 16 of the nanocellulosic paste is preferably parameterized so that the layer based on the deposited nanocellulosic 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.

[0089] The drying of the layer based on the deposited nanocellulosic paste 16 is preferably carried out in a heat press, for example at a temperature approximately between 110 and 250°C, preferably approximately between 150 and 200°C, and / or at a pressure approximately between 0.5 and 40 MPa, preferably approximately between 0.5 and 10 MPa. Under these conditions, the drying of the layer based on the deposited nanocellulosic paste 16 can be achieved in just a few tens of seconds or a few minutes. When heat compression is carried out simultaneously with the extraction of the released steam, the drying time can advantageously be reduced even further.

[0090] The cellulose-based product thus manufactured 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. Its manufacturing process is also low-cost, particularly because, since the nanocellulosic pulp is highly concentrated in cellulose nanofibers, its transport costs are lower compared to that of nanocellulosic pulps with a lower concentration of cellulose nanofibers, and it is easier to dry.

[0091] An economic gain is therefore achieved, as well as an improvement in terms of environmental impact, and this at multiple scales:

[0092] - The proposed solution implements a heatless injection or transfer molding and thermocompression system, which are already present in industries,

[0093] - the proposed solution makes it possible to manufacture on a large scale cellulose-based products 1 with the required barrier properties depending on the intended use of the product, in particular because the supply 14 of the nanocellulosic pulp can be carried out on an industrial scale,

[0094] - The proposed solution makes it possible to deposit thin nanocellulosic layers onto pre-formed cellulosic structures of various shapes and sizes, more or less complex, two-dimensional or three-dimensional, already existing, thus limiting the cost while providing the required barrier properties,

[0095] - 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 molded cellulose structure 2, i.e. dried.

[0096] More specifically, the present invention relates, according to a second aspect, to a cellulose-based product 1 comprising:

[0097] - A preformed cellulosic structure 2, and

[0098] - A layer based on cellulose microfibrils 3 on at least part of a surface of the preformed cellulosic structure 2.

[0099] The cellulose microfibril layer 3 preferably has a thickness of approximately between 0.5 and 100 pm, preferably approximately between 10 and 70 pm, for example approximately 50 pm. This gives it, in particular, an oxygen barrier property, and more specifically an oxygen transmission rate (OTR) advantageously between 1 and 150 cm⁻¹ 3 / m 2 / day (instead of more than 3000 cm 3 / m 2 / day for the starting preformed cellulose), especially for a 16-layer deposit of 50 microns thickness.

[0100] 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 packaging products that are susceptible to abrasion, such as CDs, DVDs, etc., or that require a smooth surface.

[0101] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

Claims

DEMANDS 1. A process for manufacturing (10) a cellulose-based product (1) comprising the following steps: • Provide (12) a preformed cellulosic structure (2), • To supply (14) a nanocellulosic pulp with a cellulose nanofibril concentration of substantially between 5 and 50%, preferably substantially between 20 and 30%, by weight of dry matter of the nanocellulosic pulp, • Deposit (16) a layer based on the supplied nanocellulosic paste (14) onto a surface of the preformed cellulosic structure (2), and • Dry (18) the layer based on the nanocellulosic paste by thermocompression, • wherein the step of depositing (16) a layer based on the nanocellulosic paste includes the injection of the nanocellulosic paste.

2. Manufacturing method (10) according to claim 1, wherein the step of depositing (16) a layer based on the nanocellulosic paste includes the injection coating of the nanocellulosic paste.

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

4. Manufacturing process (10) according to any one of the preceding claims, wherein the step of drying (18) the layer based on the nanocellulosic paste is carried out in a thermopress 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 process (10) according to any one of the preceding claims, further comprising, concurrently with drying (18) by thermocompression, a steam extraction.

6. A manufacturing method (10) according to any one of the preceding claims, wherein the preformed cellulosic structure (2) is selected from a preformed cellulosic container, a preformed cellulosic utensil and a preformed cellulosic stopper.

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 internal surface of the preformed cellulosic structure (2).

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

9. Manufacturing method (10) according to any one of the preceding claims, wherein the step of supplying (14) the nanocellulosic paste employs a twin-screw extruder.

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

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

13. A manufacturing process (10) according to any one of the preceding claims, wherein the supplied nanocellulosic 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 that may be selected from: • Cellulose ethers (HPMC, HEC, HPC, CMC), • a synthetic polymer (e.g., polyethylene glycol, polyvinyl alcohol), • guar gum, locust bean gum, xanthan gum, • alginate, agar-agar, carrageenans, • pectins or hemicelluloses, • modified or unmodified starches, • Functionalized or unfunctionalized cellulose nanocrystals or nanofibrils • Mineral fillers, such as water-retaining fillers • Hydrophobic additives such as wax, drying oils, or polymer emulsions, for example • cellulose microfibril functionalization additives such as AKD (Alkyl Ketene Dimer) or ASA (Alkenyl Succinic Anhydride), for example, and • their mixtures.

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