EP4097292B1 - Method for obtaining a cellulosic pulp based on hemp, cellulosic pulp obtained from the method and products obtained from said cellulosic pulp - Google Patents

Method for obtaining a cellulosic pulp based on hemp, cellulosic pulp obtained from the method and products obtained from said cellulosic pulp Download PDF

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Publication number
EP4097292B1
EP4097292B1 EP21702231.8A EP21702231A EP4097292B1 EP 4097292 B1 EP4097292 B1 EP 4097292B1 EP 21702231 A EP21702231 A EP 21702231A EP 4097292 B1 EP4097292 B1 EP 4097292B1
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Prior art keywords
stage
cellulose pulp
hemp
obtaining
cooking
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EP21702231.8A
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German (de)
French (fr)
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EP4097292A1 (en
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Charles REBOUX
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Rbx Creations
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Rbx Creations
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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/12—Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/02—Pretreatment of the finely-divided materials before digesting with water or steam
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
    • D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/001—Modification of pulp properties
    • D21C9/007—Modification of pulp properties by mechanical or physical means

Definitions

  • the present application relates to a process for obtaining a cellulosic pulp based on hemp, to a cellulosic pulp obtained from said process as well as to a product obtained from said cellulosic pulp.
  • stem means the part of a plant consisting of the heart, called hemp in the case of hemp, and the fibrous bark surrounding the heart.
  • the mown plant material is subjected to a first retting step, consisting of macerating it in a humid environment or letting it ret in the field after mowing, to facilitate the separation of the fibers from the heart of the stem (also called hemp) then to a second scutching stage consisting of separating the fibers from the heart of the stems by crushing and beating.
  • a first retting step consisting of macerating it in a humid environment or letting it ret in the field after mowing
  • a second scutching stage consisting of separating the fibers from the heart of the stems by crushing and beating.
  • the hemp fibers obtained in the same way as according to the first procedure are then shortened and mixed, at most to the extent of 70% hemp fibers, with short fibers (such as cotton for example). ) so that the fibers obtained can be spun on cotton spinning tools, widely used in the textile industry.
  • the textile material obtained comprises, at most, 70% hemp and its applications are limited.
  • Hemp textile is generally obtained from fibers from plants cut before the seeds mature, so the hemp is not used optimally, which deprives farmers of the income linked to the harvest of the seeds.
  • the retting stage degrades the hemp, generally limiting its use to low added value mulch.
  • hemp is cultivated until the seeds mature.
  • the whole plant can be valued.
  • the heart of the stem or hemp which represents approximately 45% to 55% of the weight of the plant, can be used in the form of hemp concrete in construction, mulch or animal bedding.
  • the fibrous bark of the stem which represents 25% to 35% of the weight, can be used to make paper, insulating materials or bio-sourced plastic.
  • hemp seeds can be used in bird making, human food and cosmetics, for example.
  • the flowers can also be used in herbal teas or food supplements for example (well-being hemp), or even in the pharmaceutical industry (therapeutic hemp).
  • hemp fibers from the mixed agricultural protocol are generally not exploited to obtain textile fibers for clothing given the difficulty in exploiting them with tools from the textile industry or with the specific tools of hemp from the agricultural protocol. textile.
  • the document CN106368030 describes processes for obtaining a cellulosic pulp for the manufacture of paper for packaging food and not textile products, using hemp hemp and bleaching techniques without chlorinated agent such as TCF.
  • the present invention aims to remedy all or part of the drawbacks of the prior art.
  • the subject of the invention is a process for obtaining a cellulosic pulp from a hemp-based plant material, characterized in that at the start of the process, the plant material comprises, by weight, at least 50% hemp stalks harvested at a stage of maturity greater than or equal to flowering, said hemp stalks having a rate of at least 30% hemp and a length less than 80 cm and in that the process comprises at least one cooking step and at least one treatment step before and/or after the cooking step, these steps being configured to remove at least part of the lignins and at least 20% by weight of the hemicelluloses in order to obtain a cellulose rate greater than 80% by weight.
  • This process produces cellulosic pulp from hemp grown using a mixed agricultural protocol, from which textile products can be produced using tools widely used in the textile industry.
  • the invention also relates to a cellulosic pulp obtained from the process, characterized in that it comes from a plant material comprising, by weight, at least 50% of hemp stalks harvested at a higher stage of maturity or equal to flowering, said hemp stems having a rate of at least 30% hemp and a length of less than 80 cm, and in that the cellulose pulp obtained comprises a rate of cellulose, more particularly alpha-cellulose, greater than 80%.
  • This cellulose pulp has a degree of polymerization of less than 1400.
  • the subject of the invention is a product obtained from this cellulosic pulp, in particular a textile product obtained from a process for transforming the cellulosic pulp comprising a dilution and/or dissolution step as well as possibly a step regeneration of cellulose pulp.
  • hemp stalks used for the process of obtaining cellulosic pulp come from a mixed agricultural protocol. Hemp is harvested after the flowers have ripened, preferably after the seeds have ripened. Thus, hemp is not cultivated exclusively for textile use.
  • hemp is planted with a seeding density of around 35 to 50 kg per hectare.
  • the ripe seeds are harvested then the stems are mowed and harvested in bales or crushed material.
  • the seeds and the stems are harvested simultaneously, the stems can be placed in a windrow.
  • Harvesting tools or machines for oilseed plants, such as rapeseed for example, can be used for harvesting hemp.
  • the harvested hemp stalks are subjected to at least one grinding step in order to obtain crushed hemp stalks having a length of less than 80 cm.
  • the hemp stems have a length of less than 10 cm.
  • the crushing step can be carried out at the same time as the harvesting step at the place of cultivation using a forage harvester or subsequently using a mechanical crushing tool.
  • the grinding step can be coupled with a sieving step.
  • the plant material has a content of approximately 60 to 75% by weight of hemp, the remainder being essentially fibers.
  • the invention is not limited to this rate.
  • the hemp stalks can be partially defibered and the fibers resulting from this defibration stage can be used for the manufacture of paper, insulating materials or bio-sourced plastic, as for the prior art.
  • the hemp rate can be higher and reach almost 100%.
  • part of the hemp can be used to obtain hemp concrete for example and the hemp content can be less than 60%.
  • Crushed hemp stalks can be mixed with other plants, such as flax stalks for example.
  • the plant material used for the process of obtaining cellulosic pulp comprises, by weight, at least 50% of hemp stems having, at the time of harvest, a stage of maturity greater than or equal to flowering, a rate of at least 30% hemp and a length of less than 80 cm, preferably less than 10 cm, after a crushing step.
  • a hemp content of at least 30% by weight is essential because, despite its lower cellulose content, hemp has cellulose molecule chains on average shorter than those of the bark corresponding to the fibrous part of the stem. To give an order of magnitude, a short cellulose molecule chain has a length less than or equal to 0.9 mm.
  • the flax stems which can be mixed with the hemp stems are preferably composed of a shives content of at least 30% by weight because, like hemp shives, flax shives are characterized by chains of cellulose molecules on average shorter than those of the fibrous part of the stem.
  • the plant material may include 100% crushed hemp stalks.
  • this process comprises a step of cooking the plant material.
  • plant material is placed in a humid environment, with a humidity level greater than 50%.
  • plant material can be moistened with or immersed in a solvent such as water.
  • the plant material is placed in an alkaline medium, with a pH greater than 7.5, thanks to the addition of an alkaline agent such as soda for example.
  • an alkaline agent such as soda for example.
  • the concentration of alkaline agent is between 10 and 25% of the total mass (sum of the masses of the plant material and the alkaline agent).
  • the invention is not limited to this operating mode for cooking which can be carried out in any type of medium, at any type of pH.
  • the cooking can be kraft, alkaline or other type.
  • the plant material is subjected to a temperature of between 70 and 200°C, preferably less than 180°C, greater than 80°C, and/or a pressure of between 5 and 20 bars, of preferably between 8 and 15 bars.
  • the duration of the cooking stage is between a few tens of minutes, approximately 50 minutes, and several hours, of the order of 12 hours. This duration varies in particular depending on the temperature, pressure, solvent, solvent concentration and pH.
  • the cooking step is carried out in a digester or in an autoclave. This cooking step makes it possible to obtain a delignification of the plant material and/or an extraction of certain components and, incidentally, a reduction in the length of the cellulose molecule chains.
  • the cooked mixture of plant material and solvent subsequently called raw pulp
  • the process for obtaining cellulosic pulp comprises at least one step of removing at least part of the residual cooking liquid, by filtration or by precipitation for example.
  • the raw pulp is filtered.
  • the raw pulp is washed with water then drained.
  • the quantity of residual cooking liquid must be as low as possible in order in particular to reduce the quantity of chemicals used during a subsequent purification step.
  • This removal step increases the cellulose level by reducing the levels of lignins, hemicellulose and other components in the pulp.
  • the residual cooking liquid removed contains approximately 10 to 20% by weight of recoverable dry matter, for example by concentrating it to be able to burn it in order to produce energy or extract aromatic molecules.
  • the process for obtaining cellulosic pulp comprises at least one refining step, before or after cooking, aimed at reducing the length of the fibers and/or pieces contained in the pulp.
  • the fibers and pieces contained in the pulp have a length less than or equal to 10 mm.
  • This refining step can be carried out using at least one shearing and/or splitting tool, such as a single-screw or twin-screw extruder.
  • This refining step can be carried out at a temperature between 30 and 220°C in the presence of water in liquid or gaseous form.
  • This refining step makes it possible in particular to reduce the degree of polymerization and to facilitate the separation of the cellulose from the other components or the extraction of the cellulose from the other components.
  • the process for obtaining cellulosic pulp may include several alternating withdrawal and refining stages.
  • the process for obtaining cellulosic pulp comprises a purification step.
  • This step is carried out with at least one bleaching agent, such as hydrogen peroxide for example, placed in contact with the pulp.
  • at least one bleaching agent such as hydrogen peroxide for example
  • the quantity by volume of peroxide in 50% solution represents approximately 2 to 5% of that of the pulp.
  • Other bleaching agents can be used, such as chlorine dioxide for ECF type bleaching, or any other non-chlorine agent for TCF type bleaching.
  • the purification can be a combination of an oxygen stage (at 100°C for 90 minutes, paste consistency of 10%, with 4 bars of 02 in an alkaline medium) followed by an ozone stage (at room temperature , paste consistency of 35%, introduction of 0.5% O3) and two stages with hydrogen peroxide (at 70°C for 90 then 120 minutes, paste consistency of 10%, with 0.5% H2O2 then 1.5% H202 in an alkaline medium).
  • the purification step can be coupled to the refining step.
  • the bleaching agent can be introduced into contact with the pulp, into the shearing and/or splitting tool.
  • the purification step can be extended in order to increase the duration of contact of the pulp with the bleaching agent(s).
  • the pulp is placed in a stirring bath containing the bleaching agent(s), at atmospheric pressure, at a temperature of around 50 to 90°C, for one to four hours .
  • the pulp is rinsed and pressed in order to recover the effluents from the purification stage.
  • the process for obtaining cellulosic pulp comprises a step of removing heavy metal ions.
  • it can be concomitant with the step of removing at least part of the residual cooking liquid, in using deionized water to wash the raw pulp.
  • the step of removing heavy metal ions is concomitant with the purification step, by incorporating sequestering or chelating agents into the pulp.
  • the dose of sequestering or chelating agents is of the order of 0 to 5 kg per ton of pulp.
  • the incorporation of sequestering or chelating agents into the pulp can be carried out after washing with demineralized water.
  • the use of sequestering or chelating agents also helps prevent the degradation of hydrogen peroxide during purification.
  • the cellulosic pulp can be dried so as to be packaged into plates, bricks, powders or kept in a wet state in order to be directly transformed into textile products, such as filaments, yarns, membranes or others.
  • the process for obtaining cellulose pulp comprises at least one pretreatment, before the cooking step, aimed at facilitating the extraction of cellulose and/or promoting delignification and/or contributing to the removal of hemicelluloses. .
  • the pretreatment step can be coupled with a refining step.
  • the pretreatment includes an operation of destructuring the plant material using thermo-mechano-chemical or thermo-mechanical fractionation. This destructuring operation is carried out in an alkaline, acidic or neutral medium, at a temperature of around 30 to 220°C, by passing it through an extruder type tool for example, for 1 to 20 minutes.
  • the pretreatment includes a filtration operation making it possible to separate the solid part used during the process of obtaining cellulosic pulp and the liquid part which contains certain undesirable water-soluble elements of the plant material as well as a part of the hemicelluloses. This pretreatment is not limited to this first operating mode.
  • the pretreatment is of the enzymatic type.
  • the pretreatment includes an operation of maceration of the plant material with at least one type of enzyme.
  • the pretreatment by prehydrolysis comprises an operation of cooking the plant material, at a pressure of between 5 and 15 bars and at a temperature of between 120 to 220°C, for a period not exceeding 120 minutes. , followed by a rapid return to atmospheric pressure.
  • the pretreatment is of the photochemical or ultrasonic type.
  • the pretreatment includes only one of these operating modes, includes several of these operating modes carried out successively or combines several of these operating modes carried out simultaneously.
  • the process for obtaining a cellulosic pulp from a hemp-based plant material comprises a prehydrolysis step as pretreatment, a Kraft, alkaline or other type cooking step then a step of purification based on the use of bleaching agents.
  • the process may not include any pretreatment or purification steps.
  • the process comprises a pretreatment, a cooking step then a refining step (this refining step is not necessarily carried out with bleaching agents).
  • the process comprises at least one cooking step and at least one treatment step before and/or after the cooking step, these steps being configured to remove at least part of the lignins and at least one less 20% by weight of hemicelluloses in order to obtain a cellulose content greater than 80% by weight.
  • the cooking step can be followed by a filtration or precipitation step.
  • hemp-based cellulosic pulp from which textile products can be produced using tools widely used in the textile industry. Hemp makes it possible to obtain short cellulose molecule chains more suitable for dissolution and regeneration into textile fibers.
  • the combination of the cooking and treatment steps before and/or after the cooking step is configured to remove, by weight, at least 90% of the lignins and/or at least 50%, preferably 75%, of the lignins. hemicelluloses.
  • the process comprises, before cooking, a pretreatment in an aqueous medium, at a temperature above 80°C, aimed at promoting the separation of the hemicelluloses from the other components of the plant material.
  • the cellulose pulp obtained comprises, by weight, a rate of cellulose, more particularly alpha-cellulose, greater than 80% and a degree of polymerization less than 1400, between 300 and 1400 .
  • the rate of alpha cellulose is greater than 85% and a degree of polymerization less than 1400.
  • the degree of polymerization can be adjusted and possibly reduced by increasing the number of refining steps, by carrying out a pretreatment before the cooking step, by carrying out the purification step.
  • the degree of polymerization must be both high enough to guarantee the mechanical properties of the derivatives (filaments, etc.) and low enough to ensure that the cellulose pulp can be dissolved and then extruded.
  • the cellulosic pulp obtained can be transformed by dilution and/or dissolution as well as regeneration processes into filaments, membranes or other cellulosic materials.
  • cellulose For its transformation into filaments, threads or membranes, if the cellulose is in a dried state, it is returned to an aqueous medium, at a temperature between 20 and 180°C.
  • the cellulose diluted and/or dissolved in an aqueous medium is spread/coated then dried to form plates or rolls, with a weight of between 12 and 30 g/m 2 .
  • the drying temperature is between 40 and 250°C.
  • the produced plates or rolls are then split longitudinally into strips 1 to 25 mm wide. The dried cellulose strips are slightly moistened and then twisted to form a thread.
  • the cellulose is diluted and/or dissolved in a non-sulfur medium comprising at least one solvent.
  • concentrations of solvents other than water are between 2 and 80%.
  • a solvent the following elements can be used: water, sodium, sodium hydroxide, N-methylmorpholine N-oxide, propyl gallate, distilled water, enzymes, ionic liquids, etc.
  • diluted cellulose and/or dissolved is regenerated in a dry or aqueous environment via spinnerets in order to form filaments. During this regeneration phase, the cellulose concentration is 5 to 90% of the total mass and the temperature is between 40 and 150°C.
  • the cellulose filaments produced are regularly cut into short fibers of 30 to 40 mm to pass through cotton spinning mills or 60 to 100 mm to pass to wool spinning mills, while the continuous filaments are milled on spinning tools. silk or synthetic filaments.
  • the cellulose is diluted and/or dissolved and regenerated in a sulfur medium through grooves allowing the formation and shaping of a bioplastic type membrane.
  • the cellulosic pulp can be used to obtain a textile product, such as a filament, short fibers, yarn or fabric.
  • a process for transforming the cellulosic pulp comprises a dilution and/or dissolution step and possibly a regeneration step in order to obtain a textile product, such as a filament then a textile yarn.
  • the cellulosic pulp transformation process includes a dissolution step and a regeneration step in order to obtain a textile product.
  • dry cellulose from hemp or hemp and flax can be mixed with at least one other dry cellulose from other plant sources.

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Description

La présente demande se rapporte à un procédé d'obtention d'une pulpe cellulosique à base de chanvre, à une pulpe cellulosique obtenue à partir dudit procédé ainsi qu'à un produit obtenu à partir de ladite pulpe cellulosique.The present application relates to a process for obtaining a cellulosic pulp based on hemp, to a cellulosic pulp obtained from said process as well as to a product obtained from said cellulosic pulp.

Pour la présente demande, on entend par tige la partie d'une plante constituée du coeur, appelé chènevotte dans le cas du chanvre, et de l'écorce fibreuse entourant le coeur.For the present application, stem means the part of a plant consisting of the heart, called hemp in the case of hemp, and the fibrous bark surrounding the heart.

Selon un mode de fabrication, le textile de chanvre est fabriqué à partir de fibres issues de l'écorce du chanvre. Pour favoriser la production des fibres et leur qualité, le chanvre est cultivé selon un protocole agricole dit textile consistant à récolter le chanvre avant la maturation des graines afin d'éviter que les fibres ne s'épaississent et se rigidifient. Ce protocole agricole textile se caractérise par une densité de semis élevée, de l'ordre de 80 kg/ha.According to one manufacturing method, hemp textile is made from fibers from the bark of hemp. To promote the production of fibers and their quality, hemp is cultivated according to a so-called textile agricultural protocol consisting of harvesting the hemp before the seeds mature in order to prevent the fibers from thickening and stiffening. This textile agricultural protocol is characterized by a high sowing density, of the order of 80 kg/ha.

Selon un premier mode opératoire, la matière végétale fauchée est soumise à une première étape de rouissage, consistant à la faire macérer dans un milieu humide ou la laisser rouir sur le champ après fauchage, pour faciliter la séparation des fibres du coeur de la tige (également appelé chènevotte) puis à une deuxième étape de teillage consistant à séparer les fibres du coeur des tiges par broyage et battage. La filasse ainsi obtenue est relativement longue, de l'ordre de 50 à 80 cm, et doit être filée sur des outils spécifiques pour obtenir du fil pour la confection de tissu. Ces équipements de défibrage et de filature sont peu communs dans l'industrie textile aujourd'hui.According to a first operating mode, the mown plant material is subjected to a first retting step, consisting of macerating it in a humid environment or letting it ret in the field after mowing, to facilitate the separation of the fibers from the heart of the stem ( also called hemp) then to a second scutching stage consisting of separating the fibers from the heart of the stems by crushing and beating. The tow thus obtained is relatively long, of the order of 50 to 80 cm, and must be spun on specific tools to obtain thread for making fabric. These defibering and spinning equipment are uncommon in the textile industry today.

Selon un deuxième mode opératoire, les fibres de chanvre obtenues de la même façon que selon le premier mode opératoire sont ensuite raccourcies et mélangées, tout au plus à hauteur de 70% de fibres de chanvre, avec des fibres courtes (comme le coton par exemple) pour que les fibres obtenues puissent être filées sur des outils pour filer le coton, largement utilisés dans l'industrie textile. Toutefois, selon ce deuxième mode opératoire, le matériau textile obtenu comprend, au plus, 70% de chanvre et ses applications sont limitées.According to a second procedure, the hemp fibers obtained in the same way as according to the first procedure are then shortened and mixed, at most to the extent of 70% hemp fibers, with short fibers (such as cotton for example). ) so that the fibers obtained can be spun on cotton spinning tools, widely used in the textile industry. However, according to this second operating mode, the textile material obtained comprises, at most, 70% hemp and its applications are limited.

Le textile de chanvre est généralement obtenu à partir de fibres issues de plantes coupées avant la maturation des graines si bien que le chanvre n'est pas utilisé de manière optimale, ce qui prive les agriculteurs des revenus liés à la récolte des graines. De plus, l'étape de rouissage dégrade la chènevotte, limitant en général son utilisation au paillage à faible valeur ajoutée.Hemp textile is generally obtained from fibers from plants cut before the seeds mature, so the hemp is not used optimally, which deprives farmers of the income linked to the harvest of the seeds. In addition, the retting stage degrades the hemp, generally limiting its use to low added value mulch.

Selon un deuxième protocole agricole dit mixte, le chanvre est cultivé jusqu'à la maturation des graines. Dans ce cas, toute la plante peut être valorisée. Le coeur de la tige ou chènevotte qui représente environ 45% à 55% du poids de la plante, peut être exploité sous la forme de béton de chanvre dans le bâtiment, de paillage ou de litières animales. L'écorce fibreuse de la tige, qui représente 25% à 35% du poids, peut être utilisée pour la fabrication de papier, de matériaux isolants ou de plastique biosourcé. Enfin, les graines de chanvre peuvent être utilisées en oisellerie, en alimentation humaine et en cosmétique par exemple. Les fleurs peuvent aussi être valorisées en tisanes ou compléments alimentaires par exemple (chanvre bien-être), voire dans l'industrie pharmaceutique (chanvre thérapeutique).According to a second so-called mixed agricultural protocol, hemp is cultivated until the seeds mature. In this case, the whole plant can be valued. The heart of the stem or hemp, which represents approximately 45% to 55% of the weight of the plant, can be used in the form of hemp concrete in construction, mulch or animal bedding. The fibrous bark of the stem, which represents 25% to 35% of the weight, can be used to make paper, insulating materials or bio-sourced plastic. Finally, hemp seeds can be used in bird making, human food and cosmetics, for example. The flowers can also be used in herbal teas or food supplements for example (well-being hemp), or even in the pharmaceutical industry (therapeutic hemp).

Ces fibres de chanvre issues du protocole agricole mixte ne sont généralement pas exploitées pour obtenir des fibres textiles pour l'habillement compte tenu de la difficulté à les exploiter avec des outils de l'industrie textile ou avec les outils spécifiques du chanvre issu du protocole agricole textile.These hemp fibers from the mixed agricultural protocol are generally not exploited to obtain textile fibers for clothing given the difficulty in exploiting them with tools from the textile industry or with the specific tools of hemp from the agricultural protocol. textile.

Le document CN106368030 décrit des procédés d'obtention d'une pulpe cellulosique pour la fabrication de papier pour l'emballage des aliments et non de produits textiles, utilisant la chènevotte du chanvre et des techniques de blanchiment sans agent chloré de type TCF.The document CN106368030 describes processes for obtaining a cellulosic pulp for the manufacture of paper for packaging food and not textile products, using hemp hemp and bleaching techniques without chlorinated agent such as TCF.

La présente invention vise à remédier à tout ou partie des inconvénients de l'art antérieur.The present invention aims to remedy all or part of the drawbacks of the prior art.

A cet effet, l'invention a pour objet un procédé d'obtention d'une pulpe cellulosique à partir d'une matière végétale à base de chanvre, caractérisé en ce qu'en début de procédé, la matière végétale comprend, en poids, au moins 50% de tiges de chanvre récoltées à un stade de maturité supérieur ou égal à la floraison, lesdites tiges de chanvre présentant un taux d'au moins 30% de chènevotte et une longueur inférieure à 80 cm et en ce que le procédé comprend au moins une étape de cuisson et au moins une étape de traitement antérieure et/ou postérieure à l'étape de cuisson, ces étapes étant configurées pour retirer au moins une partie des lignines et au moins 20% en poids des hémicelluloses afin d'obtenir un taux de cellulose supérieur à 80% en poids.For this purpose, the subject of the invention is a process for obtaining a cellulosic pulp from a hemp-based plant material, characterized in that at the start of the process, the plant material comprises, by weight, at least 50% hemp stalks harvested at a stage of maturity greater than or equal to flowering, said hemp stalks having a rate of at least 30% hemp and a length less than 80 cm and in that the process comprises at least one cooking step and at least one treatment step before and/or after the cooking step, these steps being configured to remove at least part of the lignins and at least 20% by weight of the hemicelluloses in order to obtain a cellulose rate greater than 80% by weight.

Ce procédé permet d'obtenir de la pulpe cellulosique à base de chanvre cultivé selon un protocole agricole mixte, à partir de laquelle des produits textiles peuvent être produits à l'aide d'outils largement utilisés dans l'industrie textile.This process produces cellulosic pulp from hemp grown using a mixed agricultural protocol, from which textile products can be produced using tools widely used in the textile industry.

Selon d'autres caractéristiques prises isolément ou en combinaison :

  • les étapes de cuisson et de traitement antérieure et/ou postérieure à l'étape de cuisson sont configurées pour retirer au moins 90% des lignines et/ou au moins 50% des hémicelluloses ;
  • lors de l'étape de cuisson, la matière végétale est soumise à une température comprise entre 70 et 200 °C et/ou une pression comprise entre 5 et 20 bars, pendant une durée d'au moins quelques dizaines de minutes, dans un milieu humide ;
  • le procédé d'obtention comprend une étape de raffinage, les fibres et/ou les morceaux contenus dans la pulpe cellulosique présentant une longueur inférieure ou égale à 10 mm à l'issue de cette étape de raffinage ;
  • l'étape de raffinage est réalisée à une température comprise entre 30 et 220°C ;
  • le procédé d'obtention comprend un prétraitement, avant l'étape de cuisson, visant à faciliter une extraction de la cellulose et/ou favoriser une délignification et/ou un retrait des hémicelluloses ;
  • le prétraitement comprend une opération de déstructuration de la matière végétale grâce à un fractionnement thermo-mécano-chimique ou thermo-mécanique ;
  • le prétraitement est une préhydrolyse ou un prétraitement enzymatique, photochimique ou ultrasonique ;
  • la procédé d'obtention comprend une étape de retrait des ions de métaux lourds ;
  • la matière végétale comprend des tiges de lin composées d'un taux d'anas d'au moins 30% en poids ;
  • l'étape de cuisson et l'étape de traitement antérieure et/ou postérieure à l'étape de cuisson sont configurées pour obtenir une pulpe cellulosique avec un degré de polymérisation inférieur à 1400 .
According to other characteristics taken individually or in combination:
  • the cooking and treatment steps before and/or after the cooking step are configured to remove at least 90% of the lignins and/or at least 50% of the hemicelluloses;
  • during the cooking step, the plant material is subjected to a temperature of between 70 and 200°C and/or a pressure of between 5 and 20 bars, for a period of at least a few tens of minutes, in a medium humid ;
  • the process for obtaining it comprises a refining step, the fibers and/or pieces contained in the cellulosic pulp having a length less than or equal to 10 mm at the end of this refining step;
  • the refining step is carried out at a temperature between 30 and 220°C;
  • the process for obtaining it comprises a pretreatment, before the cooking step, aimed at facilitating extraction of the cellulose and/or promoting delignification and/or removal of the hemicelluloses;
  • the pretreatment includes an operation of destructuring the plant material using thermo-mechano-chemical or thermo-mechanical fractionation;
  • the pretreatment is prehydrolysis or enzymatic, photochemical or ultrasonic pretreatment;
  • the process for obtaining it includes a step of removing heavy metal ions;
  • the plant material comprises flax stems composed of a shives content of at least 30% by weight;
  • the cooking step and the treatment step before and/or after the cooking step are configured to obtain a cellulosic pulp with a degree of polymerization less than 1400.

L'invention a également pour objet une pulpe cellulosique obtenue à partir du procédé, caractérisée en ce qu'elle est issue d'une matière végétale comportant, en poids, au moins 50% de tiges de chanvre récoltées à un stade de maturité supérieur ou égal à la floraison, lesdites tiges de chanvre présentant un taux d'au moins 30% de chènevotte et une longueur inférieure à 80 cm, et en ce que la pulpe cellulosique obtenue comprend un taux de cellulose, plus particulièrement d'alpha-cellulose, supérieur à 80%. Cette pulpe cellulosique présente un degré de polymérisation inférieur à 1400.The invention also relates to a cellulosic pulp obtained from the process, characterized in that it comes from a plant material comprising, by weight, at least 50% of hemp stalks harvested at a higher stage of maturity or equal to flowering, said hemp stems having a rate of at least 30% hemp and a length of less than 80 cm, and in that the cellulose pulp obtained comprises a rate of cellulose, more particularly alpha-cellulose, greater than 80%. This cellulose pulp has a degree of polymerization of less than 1400.

Enfin, l'invention a pour objet un produit obtenu à partir de cette pulpe cellulosique, notamment un produit textile obtenu à partir d'un procédé de transformation de la pulpe cellulosique comprenant une étape de dilution et/ou dissolution ainsi qu'éventuellement une étape de régénération de la pulpe cellulosique.Finally, the subject of the invention is a product obtained from this cellulosic pulp, in particular a textile product obtained from a process for transforming the cellulosic pulp comprising a dilution and/or dissolution step as well as possibly a step regeneration of cellulose pulp.

L'invention est maintenant décrite en détail.The invention is now described in detail.

Les tiges de chanvre utilisées pour le procédé d'obtention de pulpe cellulosique sont issues d'un protocole agricole mixte. Le chanvre est récolté après la maturation des fleurs, de préférence après la maturation des graines. Ainsi, le chanvre n'est pas cultivé exclusivement pour un usage textile.The hemp stalks used for the process of obtaining cellulosic pulp come from a mixed agricultural protocol. Hemp is harvested after the flowers have ripened, preferably after the seeds have ripened. Thus, hemp is not cultivated exclusively for textile use.

Selon un protocole agricole privilégié, le chanvre est planté avec une densité de semis de l'ordre de 35 à 50 kg par hectare.According to a preferred agricultural protocol, hemp is planted with a seeding density of around 35 to 50 kg per hectare.

Selon une première technique de récolte, les graines mûres sont moissonnées puis les tiges sont fauchées et récoltées en ballots ou en broyat.According to a first harvesting technique, the ripe seeds are harvested then the stems are mowed and harvested in bales or crushed material.

Selon une deuxième technique de récolte, les graines et les tiges sont récoltées simultanément, les tiges pouvant être mises en andain. Les outils ou machines de récolte pour les plantes oléagineuses, comme le colza par exemple, peuvent être utilisés pour la récolte du chanvre.According to a second harvesting technique, the seeds and the stems are harvested simultaneously, the stems can be placed in a windrow. Harvesting tools or machines for oilseed plants, such as rapeseed for example, can be used for harvesting hemp.

Les tiges de chanvre récoltées sont soumises à au moins une étape de broyage afin d'obtenir des tiges de chanvre broyées présentant une longueur inférieure à 80 cm. De préférence, les tiges de chanvre présentent une longueur inférieure à 10 cm.The harvested hemp stalks are subjected to at least one grinding step in order to obtain crushed hemp stalks having a length of less than 80 cm. Preferably, the hemp stems have a length of less than 10 cm.

L'étape de broyage peut être réalisée en même temps que l'étape de récolte sur le lieu de culture grâce à une moissonneuse ensileuse ou ultérieurement grâce à un outil de broyage mécanique.The crushing step can be carried out at the same time as the harvesting step at the place of cultivation using a forage harvester or subsequently using a mechanical crushing tool.

L'étape de broyage peut être couplée avec une étape de tamisage.The grinding step can be coupled with a sieving step.

A l'issue de ces étapes de broyage et éventuellement de tamisage, qui permettent aussi de retirer les poussières des tiges, la matière végétale présente un taux d'environ 60 à 75% en poids de chènevotte, le reste étant essentiellement des fibres. Bien entendu, l'invention n'est pas limitée à ce taux. Ainsi, après la récolte, les tiges de chanvre peuvent être partiellement défibrées et les fibres issues de cette étape de défibrage peuvent être utilisées pour la fabrication de papier, de matériaux isolants ou de plastique biosourcé, comme pour l'art antérieur. Dans ce cas, le taux de chènevotte peut être plus important et atteindre quasiment 100%. A contrario, une partie de la chènevotte peut être utilisée pour obtenir du béton de chanvre par exemple et le taux de chènevotte peut être inférieur à 60%.At the end of these grinding and possibly sieving stages, which also make it possible to remove dust from the stems, the plant material has a content of approximately 60 to 75% by weight of hemp, the remainder being essentially fibers. Of course, the invention is not limited to this rate. Thus, after harvest, the hemp stalks can be partially defibered and the fibers resulting from this defibration stage can be used for the manufacture of paper, insulating materials or bio-sourced plastic, as for the prior art. In this case, the hemp rate can be higher and reach almost 100%. Conversely, part of the hemp can be used to obtain hemp concrete for example and the hemp content can be less than 60%.

Les tiges de chanvre broyées peuvent être mélangées avec d'autres végétaux, comme des tiges de lin par exemple.Crushed hemp stalks can be mixed with other plants, such as flax stalks for example.

Quel que soit le mode de réalisation, la matière végétale utilisée pour le procédé d'obtention de pulpe cellulosique comprend, en poids, au moins 50% de tiges de chanvre présentant, au moment de la récolte, un stade de maturité supérieur ou égal à la floraison, un taux d'au moins 30% de chènevotte et une longueur inférieure à 80 cm, de préférence inférieure à 10 cm, après une étape de broyage.Whatever the embodiment, the plant material used for the process of obtaining cellulosic pulp comprises, by weight, at least 50% of hemp stems having, at the time of harvest, a stage of maturity greater than or equal to flowering, a rate of at least 30% hemp and a length of less than 80 cm, preferably less than 10 cm, after a crushing step.

Un taux de chènevotte d'au moins 30% en poids est essentiel car, malgré son plus faible taux de cellulose, la chènevotte présente des chaînes de molécule de cellulose en moyenne plus courtes que celles de l'écorce correspondant à la partie fibreuse de la tige. Pour donner un ordre de grandeur, une chaîne de molécule de cellulose courte a une longueur inférieure ou égale à 0,9 mm.A hemp content of at least 30% by weight is essential because, despite its lower cellulose content, hemp has cellulose molecule chains on average shorter than those of the bark corresponding to the fibrous part of the stem. To give an order of magnitude, a short cellulose molecule chain has a length less than or equal to 0.9 mm.

De façon similaire, les tiges de lin qui peuvent être mélangées aux tiges de chanvre sont de préférence composées d'un taux d'anas d'au moins 30% en poids car, comme la chènevotte du chanvre, les anas de lin se caractérisent par des chaînes de molécules de cellulose en moyenne plus courtes que celles de la partie fibreuse de la tige.Similarly, the flax stems which can be mixed with the hemp stems are preferably composed of a shives content of at least 30% by weight because, like hemp shives, flax shives are characterized by chains of cellulose molecules on average shorter than those of the fibrous part of the stem.

Au début du procédé d'obtention de la pulpe cellulosique, la matière végétale peut comprendre 100% de tiges de chanvre broyées.At the start of the process of obtaining cellulosic pulp, the plant material may include 100% crushed hemp stalks.

Selon l'invention, ce procédé comprend une étape de cuisson de la matière végétale.According to the invention, this process comprises a step of cooking the plant material.

Durant cette étape de cuisson, la matière végétale est placée dans un milieu humide, avec un taux d'humidité supérieur à 50%. Ainsi, la matière végétale peut être humidifiée avec ou immergée dans un solvant comme de l'eau.During this cooking stage, the plant material is placed in a humid environment, with a humidity level greater than 50%. Thus, plant material can be moistened with or immersed in a solvent such as water.

Selon un mode opératoire, lors de l'étape de cuisson, la matière végétale est disposée dans un milieu alcalin, avec un pH supérieur à 7,5, grâce à un apport d'agent alcalin comme la soude par exemple. A titre indicatif, la concentration en agent alcalin est comprise entre 10 et 25% de la masse totale (somme des masses de la matière végétale et de l'agent alcalin). Bien entendu, l'invention n'est pas limitée à ce mode opératoire pour la cuisson qui peut être réalisée dans tout type de milieu, à tout type de pH. A titre d'exemple, la cuisson peut être de type kraft, alcaline ou autre.According to one procedure, during the cooking step, the plant material is placed in an alkaline medium, with a pH greater than 7.5, thanks to the addition of an alkaline agent such as soda for example. As an indication, the concentration of alkaline agent is between 10 and 25% of the total mass (sum of the masses of the plant material and the alkaline agent). Of course, the invention is not limited to this operating mode for cooking which can be carried out in any type of medium, at any type of pH. For example, the cooking can be kraft, alkaline or other type.

Lors de cette étape de cuisson, la matière végétale est soumise à une température comprise entre 70 et 200°C, de préférence inférieure à 180°C, supérieure à 80°C, et/ou une pression comprise entre 5 et 20 bars, de préférence entre 8 et 15 bars.During this cooking step, the plant material is subjected to a temperature of between 70 and 200°C, preferably less than 180°C, greater than 80°C, and/or a pressure of between 5 and 20 bars, of preferably between 8 and 15 bars.

La durée de l'étape de cuisson est comprise entre quelques dizaines de minutes, environ 50 minutes, et plusieurs heures, de l'ordre de 12 heures. Cette durée varie notamment en fonction de la température, de la pression, du solvant, de la concentration en solvant, du pH. Selon un mode opératoire, l'étape de cuisson est réalisée dans un lessiveur ou en autoclave. Cette étape de cuisson permet d'obtenir une délignification de la matière végétale et/ou une extraction de certains composants et, accessoirement, une réduction de longueur des chaînes de molécule de cellulose.The duration of the cooking stage is between a few tens of minutes, approximately 50 minutes, and several hours, of the order of 12 hours. This duration varies in particular depending on the temperature, pressure, solvent, solvent concentration and pH. According to one operating mode, the cooking step is carried out in a digester or in an autoclave. This cooking step makes it possible to obtain a delignification of the plant material and/or an extraction of certain components and, incidentally, a reduction in the length of the cellulose molecule chains.

En fin de cuisson, le mélange cuit de la matière végétale et du solvant, appelé par la suite pulpe brute, contient un liquide résiduaire de cuisson renfermant, entre autres, des lignines. Le procédé d'obtention de pulpe cellulosique comprend au moins une étape de retrait d'au moins une partie du liquide résiduaire de cuisson, par filtration ou par précipitation par exemple.At the end of cooking, the cooked mixture of plant material and solvent, subsequently called raw pulp, contains a residual cooking liquid containing, among other things, lignins. The process for obtaining cellulosic pulp comprises at least one step of removing at least part of the residual cooking liquid, by filtration or by precipitation for example.

Selon un mode opératoire, lors de cette étape de retrait d'au moins une partie du liquide résiduaire de cuisson, la pulpe brute est filtrée. Lors d'au moins une étape de retrait, la pulpe brute est lavée à l'eau puis essorée.According to one procedure, during this step of removing at least part of the residual cooking liquid, the raw pulp is filtered. During at least one removal step, the raw pulp is washed with water then drained.

A l'issue de cette (ou ces) étape(s) de retrait, la quantité de liquide résiduaire de cuisson doit être la plus faible possible afin notamment de réduire la quantité de produits chimiques utilisés lors d'une étape ultérieure de purification.At the end of this (or these) removal step(s), the quantity of residual cooking liquid must be as low as possible in order in particular to reduce the quantity of chemicals used during a subsequent purification step.

Cette étape de retrait permet d'augmenter le taux de cellulose en réduisant les taux de lignines, d'hémicellulose et d'autres composants dans la pulpe.This removal step increases the cellulose level by reducing the levels of lignins, hemicellulose and other components in the pulp.

Le liquide résiduaire de cuisson retiré contient environ 10 à 20% en poids de matière sèche valorisable, par exemple en la concentrant pour pouvoir la brûler afin de produire de l'énergie ou extraire des molécules aromatiques.The residual cooking liquid removed contains approximately 10 to 20% by weight of recoverable dry matter, for example by concentrating it to be able to burn it in order to produce energy or extract aromatic molecules.

Selon un mode opératoire non limitatif, Le procédé d'obtention de pulpe cellulosique comprend au moins une étape de raffinage, avant ou après cuisson, visant à réduire la longueur des fibres et/ou des morceaux contenus dans la pulpe. A l'issue de cette (ou ces) étape(s) de raffinage, les fibres et morceaux contenus dans la pulpe ont une longueur inférieure ou égale à 10 mm. Cette étape de raffinage peut être réalisée à l'aide d'au moins un outil de cisaillement et/ou de fractionnement, comme un extrudeur mono-vis ou bi-vis par exemple. Cette étape de raffinage peut être réalisée à une température comprise entre 30 et 220°C en présence d'eau sous forme liquide ou gazeuse.According to a non-limiting operating mode, the process for obtaining cellulosic pulp comprises at least one refining step, before or after cooking, aimed at reducing the length of the fibers and/or pieces contained in the pulp. At the end of this (or these) refining step(s), the fibers and pieces contained in the pulp have a length less than or equal to 10 mm. This refining step can be carried out using at least one shearing and/or splitting tool, such as a single-screw or twin-screw extruder. For example. This refining step can be carried out at a temperature between 30 and 220°C in the presence of water in liquid or gaseous form.

Cette étape de raffinage permet notamment de réduire le degré de polymérisation et de faciliter la séparation de la cellulose avec les autres composants ou l'extraction de la cellulose des autres composants.This refining step makes it possible in particular to reduce the degree of polymerization and to facilitate the separation of the cellulose from the other components or the extraction of the cellulose from the other components.

Le procédé d'obtention de pulpe cellulosique peut comprendre plusieurs étapes de retrait et de raffinage alternées.The process for obtaining cellulosic pulp may include several alternating withdrawal and refining stages.

A l'issue de l'étape de retrait et/ou raffinage, la pulpe cellulosique est plus ou moins purifiée. Selon un mode opératoire non limitatif, le procédé d'obtention de pulpe cellulosique comprend une étape de purification. Cette étape est réalisée avec au moins un agent de blanchiment, comme du peroxyde d'hydrogène par exemple, mis en contact avec la pulpe. A titre indicatif et de manière non limitative, la quantité en volume de peroxyde en solution à 50% représente environ 2 à 5% de celle de la pulpe. D'autres agents de blanchiment peuvent être utilisés, comme le dioxyde de chlore pour les blanchiments de type ECF, ou tout autre agent sans chlore pour les blanchiments de type TCF.At the end of the withdrawal and/or refining stage, the cellulosic pulp is more or less purified. According to a non-limiting operating mode, the process for obtaining cellulosic pulp comprises a purification step. This step is carried out with at least one bleaching agent, such as hydrogen peroxide for example, placed in contact with the pulp. As an indication and not limitation, the quantity by volume of peroxide in 50% solution represents approximately 2 to 5% of that of the pulp. Other bleaching agents can be used, such as chlorine dioxide for ECF type bleaching, or any other non-chlorine agent for TCF type bleaching.

Selon un mode opératoire, la purification peut être une combinaison d'un stade oxygène (à 100°C pendant 90 minutes, consistance en pâte de 10%, avec 4 bars de 02 en milieu alcalin) suivi par un stade ozone (à température ambiante, consistance en pâte de 35%, introduction de 0,5% de O3) et deux stades au peroxyde d'hydrogène (à 70°C pendant 90 puis 120 minutes, consistance en pâte de 10%, avec 0,5% de H202 puis 1,5% de H202 en milieu alcalin).According to one procedure, the purification can be a combination of an oxygen stage (at 100°C for 90 minutes, paste consistency of 10%, with 4 bars of 02 in an alkaline medium) followed by an ozone stage (at room temperature , paste consistency of 35%, introduction of 0.5% O3) and two stages with hydrogen peroxide (at 70°C for 90 then 120 minutes, paste consistency of 10%, with 0.5% H2O2 then 1.5% H202 in an alkaline medium).

Selon un mode opératoire, l'étape de purification peut être couplée à l'étape de raffinage. Ainsi, l'agent de blanchiment peut être introduit au contact de la pulpe, dans l'outil de cisaillement et/ou de fractionnement.According to one operating mode, the purification step can be coupled to the refining step. Thus, the bleaching agent can be introduced into contact with the pulp, into the shearing and/or splitting tool.

L'étape de purification peut être prolongée afin d'augmenter la durée de contact de la pulpe avec le (ou les) agent(s) de blanchiment. Selon un mode opératoire, la pulpe est placée dans un bain remuant contenant le (ou les) agent(s) de blanchiment, à la pression atmosphérique, à une température de l'ordre de 50 à 90°C, pendant une à quatre heures. En sortie du bain, la pulpe est rincée et pressée afin de récupérer les effluents issus de l'étape de purification. Selon un mode opératoire, le procédé d'obtention de pulpe cellulosique comprend une étape de retrait des ions de métaux lourds. Selon une première variante, elle peut être concomitante à l'étape de retrait d'au moins une partie du liquide résiduaire de cuisson, en utilisant de l'eau déminéralisée pour laver la pulpe brute. Selon une autre variante, l'étape de retrait des ions de métaux lourds est concomitante à l'étape de purification, en incorporant des agents séquestrants ou de chélation dans la pulpe. A titre indicatif et de manière non limitative, la dose d'agents séquestrants ou de chélation est de l'ordre de 0 à 5 kg par tonne de pulpe. L'incorporation d'agents séquestrants ou de chélation dans la pulpe peut être réalisée après un lavage à l'eau déminéralisée. L'utilisation d'agents séquestrants ou de chélation permet également d'empêcher la dégradation du peroxyde d'hydrogène pendant la purification.The purification step can be extended in order to increase the duration of contact of the pulp with the bleaching agent(s). According to one procedure, the pulp is placed in a stirring bath containing the bleaching agent(s), at atmospheric pressure, at a temperature of around 50 to 90°C, for one to four hours . At the end of the bath, the pulp is rinsed and pressed in order to recover the effluents from the purification stage. According to one operating mode, the process for obtaining cellulosic pulp comprises a step of removing heavy metal ions. According to a first variant, it can be concomitant with the step of removing at least part of the residual cooking liquid, in using deionized water to wash the raw pulp. According to another variant, the step of removing heavy metal ions is concomitant with the purification step, by incorporating sequestering or chelating agents into the pulp. As an indication and not limitation, the dose of sequestering or chelating agents is of the order of 0 to 5 kg per ton of pulp. The incorporation of sequestering or chelating agents into the pulp can be carried out after washing with demineralized water. The use of sequestering or chelating agents also helps prevent the degradation of hydrogen peroxide during purification.

La pulpe cellulosique peut être séchée de manière à être conditionnée en plaques, en briques, en poudres ou être conservée à l'état humide afin d'être directement transformée en produits textiles, comme des filaments, des fils, des membranes ou autres.The cellulosic pulp can be dried so as to be packaged into plates, bricks, powders or kept in a wet state in order to be directly transformed into textile products, such as filaments, yarns, membranes or others.

Selon un mode de réalisation, le procédé d'obtention de pulpe cellulosique comprend au moins un prétraitement, avant l'étape de cuisson, visant à faciliter l'extraction de la cellulose et/ou favoriser la délignification et/ou contribuer au retrait des hémicelluloses.According to one embodiment, the process for obtaining cellulose pulp comprises at least one pretreatment, before the cooking step, aimed at facilitating the extraction of cellulose and/or promoting delignification and/or contributing to the removal of hemicelluloses. .

L'étape de prétraitement peut être couplée à une étape de raffinage. Selon un premier mode opératoire, le prétraitement comprend une opération de déstructuration de la matière végétale grâce à un fractionnement thermo-mécano-chimique ou thermo-mécanique. Cette opération de déstructuration est réalisée en milieu alcalin, acide ou neutre, à une température de l'ordre de 30 à 220°C, en la passant à travers un outil de type extrudeur par exemple, pendant 1 à 20 minutes. Après ce fractionnement, le prétraitement comprend une opération de filtration permettant de séparer la partie solide utilisée lors du procédé d'obtention de pulpe cellulosique et la partie liquide qui contient certains éléments hydrosolubles indésirables de la matière végétale ainsi qu'une partie des hémicelluloses. Ce prétraitement n'est pas limité à ce premier mode opératoire.The pretreatment step can be coupled with a refining step. According to a first operating mode, the pretreatment includes an operation of destructuring the plant material using thermo-mechano-chemical or thermo-mechanical fractionation. This destructuring operation is carried out in an alkaline, acidic or neutral medium, at a temperature of around 30 to 220°C, by passing it through an extruder type tool for example, for 1 to 20 minutes. After this fractionation, the pretreatment includes a filtration operation making it possible to separate the solid part used during the process of obtaining cellulosic pulp and the liquid part which contains certain undesirable water-soluble elements of the plant material as well as a part of the hemicelluloses. This pretreatment is not limited to this first operating mode.

Selon un deuxième mode opératoire, le prétraitement est de type enzymatique. Dans ce cas, le prétraitement comprend une opération de macération de la matière végétale avec au moins un type d'enzyme.According to a second operating mode, the pretreatment is of the enzymatic type. In this case, the pretreatment includes an operation of maceration of the plant material with at least one type of enzyme.

Selon un troisième mode opératoire, le prétraitement par préhydrolyse comprend une opération de cuisson de la matière végétale, à une pression comprise entre 5 et 15 bars et à une température comprise entre 120 à 220°C, pendant une durée n'excédant pas 120 minutes, suivie d'un retour rapide à la pression atmosphérique.According to a third operating mode, the pretreatment by prehydrolysis comprises an operation of cooking the plant material, at a pressure of between 5 and 15 bars and at a temperature of between 120 to 220°C, for a period not exceeding 120 minutes. , followed by a rapid return to atmospheric pressure.

Selon d'autres modes opératoires, le prétraitement est de type photochimique ou ultrasonique.According to other operating modes, the pretreatment is of the photochemical or ultrasonic type.

Selon les cas, le prétraitement ne comprend qu'un seul de ces modes opératoires, comprend plusieurs de ces modes opératoires réalisés successivement ou combine plusieurs de ces modes opératoires réalisés simultanément.Depending on the case, the pretreatment includes only one of these operating modes, includes several of these operating modes carried out successively or combines several of these operating modes carried out simultaneously.

Selon un mode de réalisation, le procédé d'obtention d'une pulpe cellulosique à partir d'une matière végétale à base de chanvre comprend une étape de préhydrolyse comme prétraitement, une étape de cuisson de type Kraft, alcaline ou autre puis une étape de purification reposant sur l'utilisation d'agents de blanchiment. Le procédé peut ne comprendre aucun prétraitement ou aucune étape de purification.According to one embodiment, the process for obtaining a cellulosic pulp from a hemp-based plant material comprises a prehydrolysis step as pretreatment, a Kraft, alkaline or other type cooking step then a step of purification based on the use of bleaching agents. The process may not include any pretreatment or purification steps.

Selon un autre mode de réalisation, le procédé comprend un prétraitement, une étape de cuisson puis une étape de raffinage (cette étape de raffinage ne se faisant pas nécessairement avec des agents de blanchiment).According to another embodiment, the process comprises a pretreatment, a cooking step then a refining step (this refining step is not necessarily carried out with bleaching agents).

Quel que soit le mode de réalisation, le procédé comprend au moins une étape de cuisson et au moins une étape de traitement antérieure et/ou postérieure à l'étape de cuisson, ces étapes étant configurées pour retirer au moins une partie des lignines et au moins 20% en poids des hémicelluloses afin d'obtenir un taux de cellulose supérieur à 80% en poids. L'étape de cuisson peut être suivie d'une étape de filtration ou de précipitation.Whatever the embodiment, the process comprises at least one cooking step and at least one treatment step before and/or after the cooking step, these steps being configured to remove at least part of the lignins and at least one less 20% by weight of hemicelluloses in order to obtain a cellulose content greater than 80% by weight. The cooking step can be followed by a filtration or precipitation step.

Ce procédé permet d'obtenir de la pulpe cellulosique à base de chanvre à partir de laquelle des produits textiles peuvent être produits à l'aide d'outils largement utilisés dans l'industrie textile. La chènevotte permet d'obtenir des chaînes de molécule de cellulose courte plus adaptée pour la dissolution et la régénération en fibres textiles.This process produces hemp-based cellulosic pulp from which textile products can be produced using tools widely used in the textile industry. Hemp makes it possible to obtain short cellulose molecule chains more suitable for dissolution and regeneration into textile fibers.

Cette pulpe cellulosique pourrait convenir pour la fabrication de produits papetiers. Avantageusement, la combinaison des étapes de cuisson et de traitement antérieure et/ou postérieure à l'étape de cuisson est configurée pour retirer, en poids, au moins 90% des lignines et/ou au moins 50%, de préférence 75%, des hémicelluloses.This cellulose pulp could be suitable for the manufacture of paper products. Advantageously, the combination of the cooking and treatment steps before and/or after the cooking step is configured to remove, by weight, at least 90% of the lignins and/or at least 50%, preferably 75%, of the lignins. hemicelluloses.

Selon un mode de réalisation privilégié mais non limitatif, le procédé comprend, avant cuisson, un prétraitement en milieu aqueux, à une température supérieure à 80°C, visant à favoriser la séparation des hémicelluloses des autres composants de la matière végétale.According to a preferred but non-limiting embodiment, the process comprises, before cooking, a pretreatment in an aqueous medium, at a temperature above 80°C, aimed at promoting the separation of the hemicelluloses from the other components of the plant material.

A la fin du procédé d'obtention, la pulpe de cellulose obtenue comprend, en poids, un taux de cellulose, plus particulièrement d'alpha-cellulose, supérieur à 80% et un degré de polymérisation inférieur à 1400, compris entre 300 et 1400.At the end of the production process, the cellulose pulp obtained comprises, by weight, a rate of cellulose, more particularly alpha-cellulose, greater than 80% and a degree of polymerization less than 1400, between 300 and 1400 .

A titre d'exemple, lorsqu'avant cuisson la matière végétale de chanvre comprend, en poids, de 50 à 95% de chènevotte et 50 à 5% de fibres et que les morceaux de tiges ont une longueur inférieure à 10 cm, le taux d'alpha cellulose est supérieur à 85% et un degré de polymérisation inférieur à 1400.For example, when before cooking the hemp plant material comprises, by weight, from 50 to 95% hemp and 50 to 5% fiber and the pieces of stems have a length of less than 10 cm, the rate of alpha cellulose is greater than 85% and a degree of polymerization less than 1400.

Enfin, le degré de polymérisation peut être ajusté et éventuellement réduit en augmentant le nombre d'étapes de raffinage, en réalisant un prétraitement avant l'étape de cuisson, en effectuant l'étape de purification. Le degré de polymérisation doit être à la fois suffisamment élevé pour garantir les propriétés mécaniques des dérivés (filaments...) et suffisamment faible pour s'assurer de pouvoir dissoudre la pulpe cellulosique puis extruder la solution.Finally, the degree of polymerization can be adjusted and possibly reduced by increasing the number of refining steps, by carrying out a pretreatment before the cooking step, by carrying out the purification step. The degree of polymerization must be both high enough to guarantee the mechanical properties of the derivatives (filaments, etc.) and low enough to ensure that the cellulose pulp can be dissolved and then extruded.

La pulpe cellulosique obtenue peut être transformée par des procédés de dilution et/ou de dissolution ainsi que de régénération en filaments, membranes ou autres matériaux cellulosiques.The cellulosic pulp obtained can be transformed by dilution and/or dissolution as well as regeneration processes into filaments, membranes or other cellulosic materials.

Différents procédés peuvent être utilisés pour transformer la pulpe de cellulose, comme le procédé viscose ou le procédé lyocell par exemple.Different processes can be used to transform cellulose pulp, such as the viscose process or the lyocell process for example.

Pour sa transformation en filaments, en fils ou en membranes, si la cellulose est à l'état séché, elle est remise en milieu aqueux, à une température comprise entre 20 et 180°C.For its transformation into filaments, threads or membranes, if the cellulose is in a dried state, it is returned to an aqueous medium, at a temperature between 20 and 180°C.

Selon un premier mode de réalisation, la cellulose diluée et/ou dissoute en milieu aqueux est étalée/couchée puis séchée pour former des plaques ou des rouleaux, avec un grammage compris entre 12 et 30 g/m2. A titre indicatif, la température de séchage est comprise entre 40 et 250°C. Les plaques ou les rouleaux produits sont ensuite fendus dans le sens longitudinal en bandelettes de 1 à 25 mm de large. Les bandelettes de cellulose séchées sont légèrement humidifiées puis torsadées afin de former un fil.According to a first embodiment, the cellulose diluted and/or dissolved in an aqueous medium is spread/coated then dried to form plates or rolls, with a weight of between 12 and 30 g/m 2 . As an indication, the drying temperature is between 40 and 250°C. The produced plates or rolls are then split longitudinally into strips 1 to 25 mm wide. The dried cellulose strips are slightly moistened and then twisted to form a thread.

Selon un deuxième mode de réalisation, la cellulose est diluée et/ou dissoute dans un milieu non soufré comportant au moins un solvant. A titre indicatif, les concentrations en solvants autres que l'eau sont comprises entre 2 et 80%. Comme solvant, les éléments suivants peuvent être utilisés : eau, sodium, hydroxyde de sodium, N-oxyde de N-méthylmorpholine, propyl gallate, eau distillée, enzymes, liquides ioniques, .... En suivant, la cellulose diluée et/ou dissoute est régénérée en milieu sec ou aqueux via des filières afin de former des filaments. Lors de cette phase de régénération, la concentration en cellulose est de 5 à 90% de la masse totale et la température comprise entre 40 et 150°C.According to a second embodiment, the cellulose is diluted and/or dissolved in a non-sulfur medium comprising at least one solvent. As an indication, the concentrations of solvents other than water are between 2 and 80%. As a solvent, the following elements can be used: water, sodium, sodium hydroxide, N-methylmorpholine N-oxide, propyl gallate, distilled water, enzymes, ionic liquids, etc. Next, diluted cellulose and/or dissolved is regenerated in a dry or aqueous environment via spinnerets in order to form filaments. During this regeneration phase, the cellulose concentration is 5 to 90% of the total mass and the temperature is between 40 and 150°C.

Les filaments de cellulose produits sont régulièrement coupés en fibres courtes de 30 à 40 mm pour passer sur des filatures à coton ou de 60 à 100 mm pour passer sur des filatures à laine, tandis que les filaments continus sont moulinés sur les outils de filature à soie ou de filaments synthétiques.The cellulose filaments produced are regularly cut into short fibers of 30 to 40 mm to pass through cotton spinning mills or 60 to 100 mm to pass to wool spinning mills, while the continuous filaments are milled on spinning tools. silk or synthetic filaments.

Selon un autre mode de réalisation, la cellulose est diluée et/ou dissoute et régénérée en milieu soufré à travers des sillons permettant la formation et le façonnage d'une membrane de type bioplastique.According to another embodiment, the cellulose is diluted and/or dissolved and regenerated in a sulfur medium through grooves allowing the formation and shaping of a bioplastic type membrane.

Bien entendu, l'invention n'est pas limitée à ces modes de réalisation concernant la mise en forme ou le façonnage de la cellulose de chanvre.Of course, the invention is not limited to these embodiments concerning the shaping or shaping of hemp cellulose.

Selon une application, la pulpe cellulosique peut être utilisée pour obtenir un produit textile, comme un filament, des fibres courtes, un fil ou un tissu. Dans ce cas, un procédé de transformation de la pulpe cellulosique comprend une étape de dilution et/ou dissolution et éventuellement une étape de régénération afin d'obtenir un produit textile, comme un filament puis un fil textile.Depending on one application, the cellulosic pulp can be used to obtain a textile product, such as a filament, short fibers, yarn or fabric. In this case, a process for transforming the cellulosic pulp comprises a dilution and/or dissolution step and possibly a regeneration step in order to obtain a textile product, such as a filament then a textile yarn.

Généralement, le procédé de transformation de la pulpe cellulosique comprend une étape de dissolution et une étape de régénération afin d'obtenir un produit textile.Generally, the cellulosic pulp transformation process includes a dissolution step and a regeneration step in order to obtain a textile product.

De plus, la cellulose sèche de chanvre ou de chanvre et de lin peut être mélangée à au moins une autre cellulose sèche issue d'autres sources végétales.In addition, dry cellulose from hemp or hemp and flax can be mixed with at least one other dry cellulose from other plant sources.

Claims (15)

  1. Process for obtaining a cellulose pulp from a hemp-based plant material, characterized in that, at the start of the process, the plant material comprises, by weight, at least 50% of hemp stems harvested at a stage of maturity of greater than or equal to flowering, said hemp stems exhibiting a content of at least 30% of hemp chaff and a length of less than 80 cm, and in that the process comprises at least one stage of cooking and at least one stage of treatment prior and/or subsequent to the cooking stage, these stages being configured in order to remove at least a portion of the lignins and at least 20% by weight of the hemicelluloses, in order to obtain a cellulose content of greater than 80% by weight.
  2. Process for obtaining cellulose pulp according to Claim 1, characterized in that the stages of cooking and of treatment prior and/or subsequent to the cooking stage are configured in order to remove at least 90% of the lignins and/or at least 50% of the hemicelluloses.
  3. Process for obtaining cellulose pulp according to either of the preceding claims, characterized in that, during the cooking stage, the plant material is subjected to a temperature of between 70 and 200°C and/or a pressure of between 5 and 20 bars, for a period of time of at least a few tens of minutes, in a humid environment.
  4. Process for obtaining cellulose pulp according to one of the preceding claims, characterized in that it comprises a refining stage, the fibres and/or the pieces contained in the cellulose pulp exhibiting a length of less than or equal to 10 mm on conclusion of this refining stage.
  5. Process for obtaining cellulose pulp according to the preceding claim, characterized in that the refining stage is carried out at a temperature of between 30 and 220°C.
  6. Process for obtaining cellulose pulp according to one of the preceding claims, characterized in that it comprises a pretreatment, before the cooking stage, targeted at facilitating extraction of the cellulose and/or promoting delignification and/or withdrawal of the hemicelluloses.
  7. Process for obtaining cellulose pulp according to the preceding claim, characterized in that the pretreatment comprises an operation of destructuring of the plant material by virtue of a thermal/mechanical/chemical or thermal/mechanical fractionation.
  8. Process for obtaining cellulose pulp according to Claim 6 or 7, characterized in that the pretreatment is a prehydrolysis or an enzymatic, photochemical or ultrasonic pretreatment.
  9. Process for obtaining cellulose pulp according to one of the preceding claims, characterized in that the process comprises a stage of withdrawal of the heavy metal ions.
  10. Process for obtaining cellulose pulp according to one of the preceding claims, characterized in that the plant material comprises flax stems composed of a content of shives of at least 30% by weight.
  11. Process for obtaining cellulose pulp according to the preceding claim, characterized in that the cooking stage and the treatment stage prior and/or subsequent to the cooking stage are configured in order to obtain a cellulose pulp with a degree of polymerization of less than 1400.
  12. Cellulose pulp obtained from the process according to one of the preceding claims, characterized in that the cellulose pulp results from a plant material comprising, by weight, at least 50% of hemp stems harvested at a stage of maturity of greater than or equal to flowering, said hemp stems exhibiting a content of at least 30% of hemp chaff and a length of less than 80 cm, and in that the cellulose pulp obtained comprises a cellulose content of greater than 80% and/or a degree of polymerization of less than 1400.
  13. Product obtained from the cellulose pulp according to Claim 12 obtained from the process according to one of Claims 1 to 11.
  14. Textile product obtained by a process of transformation of the cellulose pulp according to Claim 12 comprising a stage of dilution and/or dissolution and optionally a stage of regeneration of the cellulose pulp.
  15. Textile product according to Claim 14, characterized in that it comprises a stage of dissolution and a stage of regeneration of the cellulose pulp.
EP21702231.8A 2020-01-28 2021-01-26 Method for obtaining a cellulosic pulp based on hemp, cellulosic pulp obtained from the method and products obtained from said cellulosic pulp Active EP4097292B1 (en)

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FR2000801A FR3106600B1 (en) 2020-01-28 2020-01-28 Process for obtaining a hemp-based cellulosic pulp, cellulosic pulp obtained from said process and product obtained from said cellulosic pulp
PCT/EP2021/051776 WO2021151904A1 (en) 2020-01-28 2021-01-26 Method for obtaining a hemp-based cellulosic pulp, cellulosic pulp obtained using the method and product obtained using the cellulosic pulp

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FR2965570B1 (en) * 2010-09-30 2012-11-02 Arjo Wiggins Fine Papers Ltd METHOD FOR THE ENZYMATIC REFINING OF A PAPER PULP COMPRISING CELLULOSIC FIBERS TO REDUCE THEIR LENGTH
CN106087503A (en) * 2016-06-16 2016-11-09 浙江理工大学 Preparation method for the Fructus Cannabis root bast filter paper of haze mask
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