METHOD FOR MANUFACTURING A BIO-BASED PACKAGING DEVICE MADE FROM HEMP FIBER

Abstract

PROCESS FOR MANUFACTURING A BIO-BASED PACKAGING DEVICE MADE FROM HEMP FIBER The process comprises a first phase (P1) of preparing a fibrous suspension from raw hemp fibers and a second phase (P3) of manufacturing the packaging device (PL) from the suspension by thermo-pressing, injection molding or extrusion, the first phase comprising the steps of: a) cleaning and separation treatment of the raw fibers and lignin reduction; b) processing in a deburring stack of the fibers obtained in step a) so as to shorten them to a length between 0.5 and 1 mm; c) preparation in a non-shear helix disintegrator of the suspension by mixing a predetermined quantity of additives with a predetermined quantity of deburred fibers obtained in step b) with a predetermined quantity of water, the additives comprising alkylketene dimers (AKD) and a vegetable wax;and d) wringing and drying the suspension until a predetermined moisture level is obtained. Fig.1;

Description

Title of the invention: METHOD FOR MANUFACTURING A BIOSOURCED PACKAGING DEVICE MADE OF FIBERS HEMP

[0001] The invention generally relates to the field of packaging and wrapping of products. More particularly, the invention relates to a method for manufacturing a bio-sourced packaging device made from hemp fibers.

[0002] Current environmental and climate concerns are leading to the implementation of increasingly stringent regulations aimed at promoting the circular economy and combating resource waste. Reducing the environmental impact of plastic has become a priority objective in recent years. For example, European Directive (EU) 2019 / 904 has banned the marketing of certain single-use plastic products since June 3, 2021. In France, the so-called "EGALIM" and "AGEC" laws aim to reduce waste and gradually phase out single-use plastic, particularly plastic packaging, by 2040.

[0003] For packaging manufacturers, ensuring their activities comply with environmental regulations is a major challenge, given the significant share of plastic in their products. Indeed, currently the majority of primary packaging is made of plastic, and many secondary packaging products are also made of plastic. Significant efforts are being made in research and development to design new environmentally friendly packaging solutions.

[0004] The use of biomass materials to replace plastic is a promising avenue. Indeed, these so-called "bio-sourced" materials are renewable and biodegradable and offer, compared to plastic, much better compatibility with the objectives of environmental protection, biodiversity and sustainable development.

[0005] Paperboard is made primarily from cellulose fibers derived from wood and therefore falls into the category of renewable bio-based materials. Paperboard is recycled on a large scale in developed countries, which allows for a reduction in the quantity of virgin fibers required for its manufacture. Wood from sawmill waste and forest thinning is now mainly used for the manufacture of virgin paper pulp. The paper industry is not, however, without its challenges, given its significant energy and water requirements, and the polluting load of the effluents discharged.

[0006] The recovery in a biosourced material of an organic matter from a sub- agricultural or industrial product, formerly discarded or incinerated, has also been proposed. Thus, by international patent application WO2018013397A1, a method is known for manufacturing a secondary packaging device made of bio-sourced material in the form of a six-ring can holder, called a "six-pack ring", used for multiple packaging, called a "multi-pack", of beverage cans.

[0007] The method according to application WO2018013397A1 uses a liquid paste comprising plant fibers, at least one ground by-product of the brewing industry to be recovered, an oleophobic chemical substance, a hydrophobic chemical substance and water. A mixture of two types of plant fibers is recommended, among those coming from wheat straw, bamboo, sugar cane and miscanthus. The ground by-product is derived from at least one of the following cereals: barley, wheat, corn, rice, rye and oats.Application WO2018013397A1 discloses perfluoroalkylethyl phosphate and alkylketene dimers (AKD) as useful oleophobic and hydrophobic substances.

[0008] The method according to application WO2018013397A1 has the disadvantage of a process for producing the liquid paste which comprises a large number of steps, with a mixture of several different organic components in the form of plant fibers and ground by-products to be recovered. This complexity of the paste production process impacts the investment requirements and the manufacturing costs of the packaging device. Furthermore, perfluoroalkylethyl phosphate, recommended in application WO2018013397A1 as an oleophobic substance, is included in the class of PFAS substances (for "Per- and Poly-FluoroAlkyl Substances") which are considered harmful to human health and the environment by the European Chemicals Agency ECHA (for "European Chemicals Agency").

[0009] Hemp is an annual plant with a short cycle that offers many advantages in agriculture and industrial development. The plant has a high capacity to adapt to different climates, does not require fertilizer, does not consume much water and has a good yield per hectare. For the paper industry in particular, the productivity of hemp is much higher than that of wood thanks to the rapid growth of the plant, its increased cellulose content compared to wood and its low lignin content. Hemp seeds and straw are recoverable. The plant is currently used in several areas such as human and animal food, cosmetics, construction and insulation, biofuels, papermaking and others. Hemp fibers are used in the composition of composite materials, in association with plastic.In construction, a hemp brick is known, made from hemp shiv in combination with a mineral binder, as well as hemp concrete used as a filling material.

[0010] The efficiency of the process of extracting fibers from straw is around 93%. Hemp fiber can be longer than 20 mm. This fiber is longer, stronger, more abundant and more insulating than cotton fiber and wood fiber. Hemp fibers are obtained by a mechanical defibering process which treats hemp straw to separate the shiv, located inside the stem, and the fibers. Hemp fibers have different dimensions. They are sorted according to their size. Currently, short fibers, called "KF", are not recovered other than by incineration.

[0011] It is desirable to propose a new process for the manufacture of bio-sourced packaging devices made from hemp fibers, thus providing an alternative to plastic packaging, while complementing the recovery of hemp, in particular the recovery of short fibers.

[0012] According to a first aspect, the invention relates to a method for manufacturing a bio-sourced packaging device made from hemp fibers comprising a first phase of producing a fiber suspension from raw hemp fibers and a second phase of manufacturing by thermo-pressing, injection molding or extrusion of the packaging device from the fiber suspension, the first phase comprising the steps of a) cleaning and separation treatment of the raw hemp fibers and reduction of the lignin; b) treatment in a decoiler stack of the treated hemp fibers obtained in step a) so as to shorten them to a length of between 0.5 and 1 mm;c) preparing the fibrous suspension in a non-shearing propeller disintegrator by mixing a predetermined quantity of additives with a predetermined quantity of unwound hemp fibres obtained in step b) with a predetermined quantity of water, the additives comprising alkyl ketene dimers (AKD) and a vegetable wax; and d) dewatering and drying the fibrous suspension until a predetermined humidity level is obtained.

[0013] According to a particular characteristic of the process, in step b), the hemp fibers are shortened to a length of between 0.6 and 0.7 mm, when they have an average width of between 20 and 25 μm.

[0014] According to another particular characteristic of the process, in step c), the quantity of additives in dry mass is between 3% and 8%, optimally 5%, of the total dry mass of the hemp fibers and the additives.

[0015] According to yet another particular characteristic of the process, in step c), the quantity of alkylketene dimers (AKD) in dry mass is between 2.5 and 5 percent (%), optimally 4 percent (%), of the total dry mass of the hemp fibers and the additives, and the quantity of vegetable wax in dry mass is between 0.5 and 3 percent (%), optimally 1 percent (%), of the total dry mass of the hemp fibers and the additives.

[0016] According to yet another particular characteristic of the process, in step c), the mixing with the non-shearing propeller is carried out with a rotation speed of the propeller of between 2500 and 3500 rpm, optimally 3000 rpm, for a duration of between 5 and 15 minutes, optimally 10 minutes.

[0017] According to yet another particular characteristic, the method also comprises an intermediate phase (P2) of storage of the fibrous suspension obtained in step d), with a humidity level of between 15 and 25 percent (%), optimally 20%.

[0018] According to yet another particular characteristic of the process, step a) comprises cooking the raw hemp fibers with soda at a temperature of between 140°C and 200°C, optimally 170°C, for a holding time of between 70 minutes and 110 minutes, optimally 90 minutes, and temperature rise and fall times of between 20 minutes and 40 minutes, optimally 30 minutes, with a quantity of soda in dry mass of between 8 and 12 percent (%), optimally 10 percent (%), of the dry mass of the raw hemp fibers and with a quantity of water equal in mass to 4 to 6 times, optimally 5 times, the dry mass of the raw hemp fibers.

[0019] According to yet another particular characteristic of the process, step a) is carried out using a twin-screw type extruder.

[0020] According to yet another particular characteristic of the process, the hemp fibers are short fibers of the so-called “KF” type.

[0021] The invention also relates to a bio-sourced packaging device made from hemp fibers obtained by implementing the method as briefly described above.

[0022] Other advantages and characteristics of the present invention will appear more clearly on reading the detailed description below of several particular embodiments of the invention, with reference to the appended drawings, in which:

[0023] [Fig. 1] [Fig. 1] is a general flowchart of the device manufacturing process packaging made from hemp fibers according to the invention.

[0024] [Fig.2] [Fig.2] is a first flowchart of a soda cooking step of the hemp fibers for the preparation of a fibrous suspension used in the process according to the invention.

[0025] [Fig.3] [Fig.3] is a curve of a soda cooking cycle of the fibers of hemp.

[0026] [Fig.4] [Fig.4] is a flowchart of a hemp fiber unwinding step for the preparation of the fibrous suspension used in the process according to the invention.

[0027] [Fig.5] [Fig.5] is a flowchart of a suspension preparation step fibrous, with the addition of additives, for use in the process according to the invention.

[0028] With reference to Figs. 1 to 5, a particular embodiment PF of the manufacturing method according to the invention is now described. As an example, the following is considered here: manufacture of a packaging device in the form of a PL tray made of hemp fibers intended to receive foodstuffs.

[0029] As can be seen in [Fig. 1], the method of the invention essentially comprises three main phases PI to P3. Phase PI is a phase of producing a fibrous suspension, also called fibrous paste thereafter. Phase P2 is a phase of storing the fibrous suspension. Phase P3 is a phase of manufacturing the packaging device PL from the fibrous suspension.

[0030] Phase PI of preparation of the fibrous suspension comprises three main steps P10 to P12, which are described in detail below. Briefly, steps P10 to P12 are respectively a step of cooking the hemp fibers with soda, a step of unspooling the hemp fibers and a step of preparing the fibrous suspension from the unspooled hemp fibers.

[0031] The storage phase P2 is necessary or not in the manufacturing process, depending on the organization of the work, the geographical location of the premises, logistics and others. The fibrous suspension can be stored in a refrigerated enclosure, typically at a temperature between 0°C and 4°C, for a maximum period of 2 months.

[0032] Phase P3 of manufacturing the PL packaging device comprises two main steps P30 and P31. Steps P30 and P31 are respectively a molding step and a demolding step.

[0033] Typically, the PL packaging device is manufactured by heat pressing or injection molding, from the fibrous suspension. An extrusion process may also be used for the manufacture of the PL packaging device.

[0034] In the case of manufacturing by thermo-pressing, typically, a form can be produced beforehand from the fibrous suspension, by draining and cutting, and then placed in a thermo-pressing mold in step P30. In the case of manufacturing by injection, the fibrous suspension is injected by pressure into an injection mold. In the two aforementioned manufacturing techniques, thermo-pressing and injection molding, once the fibrous suspension is in the mold, provision is made in step P30 for the application by the press of a pressure P and a temperature T for a duration D, so as to obtain the forming of the packaging device PL with the desired densification and drying.The initial humidity of the fibrous suspension, the pressure P, the temperature T and the duration D, as well as other parameters, will be optimized by the person skilled in the art through tests, for the chosen manufacturing technique and according to the PL packaging device. The demolding, at step P31, may include a cooling time for the PL packaging device prior to its ejection from the mold.

[0035] The above-mentioned steps P10 to P12 of phase PI are now described in detail with reference to Figs.2 to 5.

[0036] With particular reference to Figs. 2 and 3, the step of cooking the hemp fibers with soda P10 is a step of chemical treatment of the hemp fibers. In this embodiment of the process, the hemp fibers are not bleached. Step P10 is carried out here to separate and clean the fibers, removing binding materials, remains of hemp shiv and other unwanted materials. Step P10 also allows a reduction of the lignin present in the fibers, which improves the flexibility of the fibers.

[0037] As visible in [Fig.2], the chemical treatment step P10 essentially comprises six sub-steps P100 to P105 and is carried out using a cooker.

[0038] Sub-step P100 concerns the preparation of the soda cooking bath in the cooking tank of the cooker. Tests carried out by the inventive entity with a ball-type cooker and a quantity of dry matter to be treated of 150 g of raw hemp fibers made it possible to determine the proportions required for satisfactory results. Thus, in this sub-step P100, a quantity of water equal in mass to 4 to 6 times, typically 5 times, the dry mass of raw hemp fibers to be treated is poured into the cooking tank. Soda is also added to the cooking tank with a quantity by mass of between 8 and 12 percent (%), typically 10 percent (%), of the mass of raw hemp fibers (dry matter) to be treated. In sub-step P101, the raw hemp fibers are poured into the liquid and the contents of the cooking tank are mixed.In accordance with this particular embodiment of the process of the invention, the raw hemp fibers used are the aforementioned short fibers, called “KF” fibers, which in the state of the art are not recovered other than by incineration.

[0039] Sub-steps P102 to P104 concern the actual cooking of the fibers in the soda bath. An example of a cooking cycle is shown in [Fig.3]. Sub-step P102 corresponds to a rise in temperature MT of the cooking tank and its contents. Sub-step P103 corresponds to a temperature plateau PT for cooking the hemp fibers. Sub-step P104 corresponds to a fall in temperature RT of the cooking tank and its contents. In sub-step P102, the cooking tank, which is initially at room temperature TA, is heated for a duration DI of between 20 min and 40 min, typically 30 min, to bring the contents of the cooking tank to a plateau temperature TP of between 140°C and 200°C, typically 170°C.In sub-step P103, the temperature in the cooking tank is regulated at the stage temperature TP between 140°C and 200°C, typically 170°C, for a duration D2 between 70 min and 110 min, typically 90 min, for cooking the hemp fibers. In sub-step P104, the heating of the cooking tank is interrupted and the temperature of the contents of the tank is allowed to drop. for a duration D3 of between 20 min and 40 min, typically 30 min, until reaching a temperature close to ambient temperature TA.

[0040] Sub-step P105 follows the cooling sub-step P104 and concerns the extraction of the hemp fibers from the tank at the end of the cooking cycle. Typically, the hemp fibers are drained during their extraction and rinsed with water afterwards.

[0041] The chemical treatment step P10 described above made it possible to achieve a mass yield after cooking of substantially 65 percent (%), with the aforementioned typical values. In other words, the dry mass of the hemp fibers after cooking in step P10 is reduced by substantially 35 percent (%) compared to the initial dry mass of raw hemp fibers. Still with the aforementioned typical values, the chemical treatment step P10 made it possible to achieve a lignin content of substantially 2.5 percent (%), compared to a lignin content of approximately 5 percent (%) for raw hemp fibers.

[0042] It will be noted that the cooking efficiency of step P10 may be increased by modifying certain cooking parameters, such as for example by reducing the quantity of soda in the cooking bath. Alternatively, a twin-screw extruder may also be used in step P10, instead of cooking with soda, to improve the cooking efficiency, which will then reach approximately 85 percent (%).

[0043] With particular reference to [Fig. 4], the step of unwinding the hemp fibers P11 has the function of reducing their length. This reduction in the length of the fibers facilitates the preparation of the fiber suspension in the following step P12, by reducing the compactness and rigidity of the fiber assembly. Furthermore, this makes it possible to improve the dispersion of the fibers during the formation of the fiber mat and thus to obtain a final material with a more homogeneous finish. Tests carried out by the inventive entity for fibers having an average width of between 20 μm and 25 μm have shown that a fiber length of between 0.5 mm and 1 mm gives good results. The best results were obtained for a fiber length of between 0.6 mm and 0.7 mm.

[0044] As seen in [Fig.4], the step of unwinding the Pli hemp fibers essentially comprises five sub-steps PI 10 to PI 14.

[0045] Sub-step PI 10 is the filling of the tank of the unwinding pile, typically with water. Then, in sub-step PI 11, the treated hemp fibers, resulting from step P10, are immersed and dispersed in the water bath of the unwinding pile. In sub-step PI 12, the cylinder of the pile is rotated for a period of between 20 min and 40 min, typically 30 min, so as to carry out the unwinding treatment itself. Sub-steps P113 and P114 respectively concern the extraction of the unwinded fibers from the tank of the pile and an operation optional spinning / drying of these. A spinning / drying machine can be used at step PI 14.

[0046] With particular reference to [Fig. 5], in step P12, the fibrous suspension is prepared by mixing the unwound hemp fibers obtained in step P1 1 with additives and water. The additives are distributed throughout the mass so as to obtain a final material having homogeneous characteristics.

[0047] According to the invention, the additives used for their oleophobic and hydrophobic properties comprise alkylketene dimers (AKD) and a vegetable wax as a substitute for perfluorinated substances.

[0048] Alkyl ketene dimers (AKD) are well known and have been used as additives in the paper industry for over sixty years. These substances are not harmful in small quantities, which is the case in the present invention. In addition to their hydrophobic properties, alkyl ketene dimers (AKD) improve the mechanical strength of the final material.

[0049] The vegetable wax "TopScreen® BW100 Water Based Barrier Coating" from the company SOLENIS® can be used with good results. This wax from the company SOLENIS® is a water-based anionic dispersant with barrier properties against grease and water.

[0050] Tests carried out by the inventive entity made it possible to determine the proportions required for these additives in order to obtain satisfactory results. Thus, in mass of dry matter, the proportions of AKD and vegetable wax are optimally 4 percent (%) and 1 percent (%). Thus, on a total of 100 percent (%) of dry matter, the mixture of hemp fibers and additives optimally consists of 95 percent (%) of fibers and 5 percent (%) of additives. More generally, depending on the applications, in mass of dry matter, the proportions of AKD and vegetable wax may be between 2.5 and 5 percent (%) and between 0.5 and 3 percent (%), respectively. Thus, on a total of 100 percent (%) of dry matter, the proportion of additives may be between 3 percent (%) and 8 percent (%).

[0051] As visible in [Fig.5], step P12 of preparing the fibrous suspension from the unwound hemp fibers essentially comprises three sub-steps P120 to P122 and is carried out using a disintegrator, of the paper pulp disintegrator type, equipped with a non-shearing propeller.

[0052] Sub-step P120 corresponds to the pouring into the tank of a disintegrator of a quantity of unwound hemp fibers, a quantity of additives (AKD and vegetable wax) and a quantity of water, in the aforementioned required proportions. Thus, for example, for 95 g of unwound hemp fibers, 4 g of AKD and 1 g of vegetable wax will be added, as well as water to obtain a total mass of 2 kg.

[0053] Sub-step P121 corresponds to the operation of mixing by stirring the solution present in the disintegrator tank in order to obtain the fibrous suspension. Thus, typically, the agitation will last 10 minutes, with a propeller rotating at 3000 revolutions per minute. More generally, the agitation duration will be between 5 and 15 minutes and the rotation speed of the propeller will be between 2500 and 3500 revolutions per minute.

[0054] In sub-step P122, the fibrous suspension obtained in sub-step P121 is treated in a spinning / drying machine so as to obtain a fibrous paste with a desired moisture content, optimally 20 percent (%). More generally, this moisture content may be between 15 percent (%) and 25 percent (%) and will depend on the application and, in particular, on the manufacturing technique, heat-pressing, injection molding or extrusion, implemented during phase P3 to produce the packaging device PL.

[0055] The invention is not limited to the particular embodiments which have been described here by way of example. Those skilled in the art, depending on the applications of the invention, will be able to make various modifications and variants falling within the scope of protection of the invention.

Claims

Claims

1. A method of manufacturing a bio-sourced packaging device made from hemp fibers (PL) comprising a first phase (PI) of producing, from raw hemp fibers, a fibrous suspension comprising hemp fibers having a length of between 0.5 and 1 mm and having a predetermined moisture content obtained by wringing and drying and a second phase (P3) of manufacturing by thermo-pressing, injection molding or extrusion of the packaging device (PL) from the fibrous suspension, characterized in that the first phase (PI) comprises the steps of a) cleaning and separation treatment of the raw hemp fibers and reduction of the lignin by baking with soda (P 10); b) treatment in a decoiler stack of the treated hemp fibers obtained in step a) so as to shorten their length (Pli);and c) preparing the fibrous suspension in a non-shearing propeller disintegrator by mixing a predetermined quantity of additives with a predetermined quantity of unwound hemp fibres obtained in step b) with a predetermined quantity of water, the additives comprising a vegetable wax in addition to alkylketene dimers (AKD) (P12; P120, P121).;

2. A method according to claim 1, characterized in that, in step b), the hemp fibers are shortened to comprise fibers having a length of between 0.6 and 0.7 mm, when these have an average width of between 20 and 25 pm.

3. Method according to claim 1 or 2, characterized in that, in step c), the quantity of additives in dry mass is between 3% and 8%, optimally 5%, of the total dry mass of the hemp fibers and the additives.

4. Method according to claim 3, characterized in that, in step c), the quantity of alkylketene dimers (AKD) in dry mass is between 2.5 and 5 percent (%), optimally 4 percent (%), of the total dry mass of the hemp fibers and additives, and the quantity of vegetable wax in dry mass is between 0.5 and 3 percent (%), optimally 1 percent (%), of the total dry mass of the hemp fibers and additives.

5. Method according to any one of claims 1 to 4, characterized in that, in step c), the mixing with the non-shearing propeller is carried out with a rotation speed of the propeller of between 2500 and 3500 revolutions / minute, optimally 3000 rpm, for a duration of between 5 and 15 minutes, optimally 10 minutes.

6. Method according to any one of claims 1 to 5, characterized in that it also comprises an intermediate phase (P2) of storage of the fibrous suspension obtained in step d), with a humidity level of between 15 and 25 percent (%), optimally 20%.

7. Method according to any one of claims 1 to 6, characterized in that, in step a), said cooking with soda of the raw hemp fibers is carried out at a temperature of between 140°C and 200°C, optimally 170°C, for a holding time of between 70 minutes and 110 minutes, optimally 90 minutes, and temperature rise and fall times of between 20 minutes and 40 minutes, optimally 30 minutes, with a quantity of soda in dry mass of between 8 to 12 percent (%), optimally 10 percent (%), of the dry mass of the raw hemp fibers and with a quantity of water equal in mass to 4 to 6 times, optimally 5 times, the dry mass of the raw hemp fibers.

8. Method according to any one of claims 1 to 6, characterized in that step a) is carried out using a twin-screw type extruder.

9. Method according to any one of claims 1 to 8, characterized in that the hemp fibers are short fibers of the so-called “KF” type.

10. Bio-sourced packaging device made of hemp fibers obtained by implementing the method according to any one of claims 1 to 9 and comprising alkylketene dimers (AKD) as additives, characterized in that said additives also comprise a vegetable wax, and the quantity of alkylketene dimers (AKD) in dry mass being between 2.5 and 5 percent (%), optimally 4 percent (%), of the total dry mass of the hemp fibers and the additives, and the quantity of vegetable wax in dry mass being between 0.5 and 3 percent (%), optimally 1 percent (%), of the total dry mass of the hemp fibers and the additives.

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