Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
  • C08H8/00—Macromolecular compounds derived from lignocellulosic materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L97/00—Compositions of lignin-containing materials
• • 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
  • D21H15/00—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution
• • 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
  • D21H15/00—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution
  • D21H15/02—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution characterised by configuration

Definitions

• the present application relates to a process for obtaining at least two cellulosic pulps having different characteristics.
• a hemp-based textile can be made from fibres from the bark of the hemp plant.
• hemp is grown using a so-called textile agricultural protocol which consists of harvesting the hemp before the seeds mature in order to prevent the fibres from thickening and stiffening.
• This textile agricultural protocol is characterised by a high seeding density, generally around 80 kg/ha.
• the mown plant material is subjected to a first retting stage, consisting of macerating it in a humid environment or leaving it to ret in the field after mowing, to facilitate the separation of the fibres from the heart of the stem (also called hemp shiv) then to a second scutching stage consisting of separating the fibres from the heart of the stems by crushing and beating.
• a first retting stage consisting of macerating it in a humid environment or leaving it to ret in the field after mowing
• a second scutching stage consisting of separating the fibres from the heart of the stems by crushing and beating.
• the hemp fibers from the defibering are shortened and mixed 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 while being limited in fineness, which reduces the scope of applications.
• hemp textile is generally obtained from fibres from plants cut before the seeds have matured, so that the hemp is not used optimally, which deprives farmers of income from the seed harvest.
• the retting stage degrading the hemp shiv, which can limit its use to low-value mulching.
• hemp is grown until the seeds mature. In this case, the entire plant can be used.
• hemp fibers from the mixed agricultural protocol are generally not used to obtain textile fibers for clothing given the low yields of sufficiently fine bast fibers and the difficulty of using them with textile industry tools or with the specific tools of hemp from the textile agricultural protocol.
• Documents FR31O66OO and W02021151904 propose a method for obtaining a hemp-based cellulosic pulp which, after dilution and/or dissolution and then regeneration steps, makes it possible to obtain a textile product such as a textile filament.
• This method uses a plant material comprising by weight at least 50% of hemp stalks harvested after flowering, said hemp stalks having a rate of at least 30% of hemp shiv and a length of less than 80 cm.
• This method comprises a step of cooking the plant material as well as at least one refining step aimed at reducing the length of the fibers and/or pieces contained in the cooked plant material.
• a cellulosic pulp can be used for the production of a paper pulp.
• this cellulosic pulp is prepared from bast fibers originating from a plant material resulting from a specific agricultural protocol. This plant material is subjected to pretreatment steps of the defibration type aimed at selecting a fraction of the plant material, namely the bast fibers, by removing in particular the core of the stem (or woody core) of the plant material. These bast fibers are then transformed into cellulosic pulp by a transformation process comprising at least one cooking step.
• bast fiber plants such as flax, hemp, kenaf and nettle
• producing plant material according to specific specifications restrictive for farmers
• the pre-treatment steps (defibration, scutching, etc.) of the plant material prior to the production of pulp, aimed at fractionating the plant material to extract the bast fibers in particular are generally energy-intensive, demanding in terms of cleanliness of the products to be achieved, these pre-treatment steps being specific to agricultural protocols and/or to the plant.
• the steps of transformation into cellulosic pulp of the selected fraction of the selected plant material are specific to this fraction and result in a single type of cellulosic pulp.
• the same production of cellulosic pulp made from a specific fraction of a plant material produced according to specific specifications makes it possible to obtain a single cellulosic pulp with specific characteristics.
• Document WO2017/035535 proposes a method for producing a nanocellulosic material comprising a step of selecting a biomass and a set of steps for transforming the selected biomass according to the nanocellulosic material to be obtained.
• the production of two cellulosic pulps consists in using two separate production processes, one for each cellulosic pulp to be obtained, and comprises two steps of selecting separate plant materials, one for each process, as well as two sets of separate transformation steps, one for each process.
• the present invention aims to remedy all or part of the drawbacks of the prior art.
• the invention relates to a process for obtaining at least two cellulosic pulps each having at least one characteristic different from each other, characterized in that the process comprises:
• At least one step of mixing plant materials comprising at least 60% of a first material, called lignocellulosic, having a lignin content greater than or equal to a given value, of the order of 10%, as well as at least 2% of a second material, called fibrous, having a lignin content less than or equal to the given value, at least one step of cooking the mixture of plant materials with a cooking liquid, at a temperature greater than or equal to 80°C, with, at least during part of the cooking time, at least one delignifying agent, at least one step of removing the liquid phase from the cooked mixture of plant materials in order to isolate a cellulosic pulp, at least one step of separating the cellulosic pulp into at least two cellulosic pulps each having at least one characteristic different from each other.
• a first material called lignocellulosic
• a less selective mixture of plant materials is used to obtain a cellulosic pulp which is then separated to isolate cellulosic pulps each having at least one given characteristic different from one pulp to another.
• the specifications of agricultural protocols are less restrictive, which helps to increase the resource and promote biodiversity.
• the invention allows for greater versatility in the supply of agricultural materials.
• some steps of separation of the plant material in order to isolate a part of the raw plant material can be simplified or eliminated, thus helping to reduce energy consumption and facilitating the adoption of these plants as raw material for the production of cellulosic pulps.
• the process of the invention makes it possible to obtain, from the same production, at least two distinct cellulosic pulps.
• a process for obtaining cellulosic pulps comprises at least one step of mixing plant materials comprising at least 60% of a first material, called lignocellulosic, having a lignin content greater than or equal to a given value as well as at least 2% of a second material, called fibrous, having a lignin content less than or equal to the given value.
• the value given for the lignin content is of the order of 10%. According to one example, the lignin content is greater than or equal to 12%, preferably 18% for the first material and less than or equal to 9%, preferably 7% for the second material.
• lignin rate can be measured by chemical analysis using for example the Van Soest method or defined by standards called TAPPI formulated by the TAPPI association for “Technical Association of the Pulp and Paper Industry” in English.
• the percentages correspond to percentages by weight of dry matter.
• the mixture of plant materials comprises at most 98% lignocellulosic material.
• the mixture of plant materials comprises between 70 and 90% lignocellulosic material.
• the mixture of plant materials comprises at least 80% lignocellulosic material. This percentage facilitates the step of separating the cellulosic pulps.
• Lignocellulosic material means a lignocellulosic material or a mixture of lignocellulosic materials.
• the lignocellulosic material is selected from annual plants or parts of annual plants such as flax shives, hemp shiv, kenaf woody core, nettle woody core, miscanthus, reed, bamboo, bagasse, certain cereal straws, pericarps or flower stems. This list is not exhaustive.
• Lignocellulosic material comes in the form of chips that are less than 8 cm long, preferably less than 4 cm.
• the mixture of plant materials comprises at most 40% fibrous material.
• the mixture of plant materials comprises between 10 and 30% fibrous material, and optimally between 5 and 20% fibrous material.
• Fibrous material means a fibrous material or a mixture of fibrous materials.
• the fibrous material is selected from bast fibers such as hemp fibers, flax fibers, jute fibers, kenaf fibers, nettle fibers or ramie fibers for example; pseudostem fibers such as banana fibers for example; leaf fibers such as abaca fibers or sisal fibers for example. This list is not exhaustive.
• the fibrous material is more flexible as opposed to a lignocellulosic material, which is more rigid and/or brittle.
• the fibers of the fibrous material have a length of less than 80 cm, preferably less than or equal to 8 cm. According to another characteristic, 90% of the fibers of the fibrous material have a length of greater than 5 mm.
• the mixture of plant materials includes several different plant species and/or different fractions of the same plant species containing bast fibers.
• the process for obtaining cellulosic pulps comprises at least one step of cooking the mixture of plant materials with a cooking liquid, at a temperature greater than or equal to 80°C, preferably greater than 140°C. According to one operating method, the cooking temperature is less than or equal to 190°C.
• the cooking liquid is water in liquid and/or gaseous form.
• the liquid/solid ratio is greater than or equal to 2, preferably greater than 3.5.
• a cooking step is carried out for a duration, at maximum temperature, less than or equal to 480 min, preferably less than 300 min.
• the cooking step comprises at least first and second successive phases, the first phase consisting of cooking the mixture of plant materials with water, without delignifying agent, at a temperature greater than or equal to 80°C, optionally followed by removal of at least part of the liquid phase of the mixture of plant materials cooked at the end of the first phase of the cooking step, the second phase of the cooking step consisting of cooking the remainder of the mixture in the presence of at least one delignifying agent, at a temperature greater than or equal to 80°C.
• the mixture gradually becomes acidic.
• the first phase is stopped.
• the first phase is stopped when the liquid phase contains at least 10% of the hemicelluloses present in the starting material.
• These hemicelluloses generally have a xylan content of at least 50%, the quantity of xylans being greater than that of mannans.
• the liquid phase containing in particular hemicelluloses, polysaccharides or any other recoverable by-product such as furfural and acetic acid, can be separated from the solid phase of the mixture.
• the second phase of the cooking step is carried out at a temperature greater than or equal to 80°C, the solid phase of the mixture resulting from the first phase of the cooking step being remixed with water and at least one delignifying agent.
• cooking only comprises one phase, the cooking step being carried out from the start with at least one delignifying agent.
• carrying out the cooking step in two phases promotes delignification and makes it possible to obtain a purer cellulosic pulp.
• Delignifying agent means a delignifying agent or a mixture of delignifying agents.
• the delignifying agent is selected from the following non-exhaustive list: sulfites, deep eutectic solvents, Kraft liquors, ionic liquids, oxygen, ozone, hydrogen peroxide, acetic acid, peracetic acid, ethanol, methanol, acetone, dimethyl sulfoxide (DMSO), aldehydes, chlorine, sodium chlorite, chlorine dioxide, sodium hydroxide, sulfuric acid, acetic anhydride.
• the production process comprises at least one step of removing (or drawing off) the liquid phase of the cooked mixture of plant materials, also called liquor and which contains in particular lignins, in order to isolate a cellulosic pulp.
• This by-product containing lignins can be used, for example, to generate energy.
• These lignins can also be extracted from the liquor to obtain products in the fields of cosmetics, glues, resins or carbon fibers.
• these lignins have a low mineral content, less than 10%, generally less than 5%; an EC50 value (antioxidant power) generally between 0.15 and 0.7 mg/mL as well as a carboxylic group content generally between 0.7 and 1.6 mmol/g.
• the process for obtaining cellulosic pulps comprises at least one step of separating the cellulosic pulp into at least two cellulosic pulps each having at least one characteristic different from each other.
• the separation step makes it possible to separate the cellulosic pulp resulting from cooking into at least two cellulosic pulps each having at least two characteristics different from each other, including in particular the length of the fibers, the degree of polymerization, the kappa index, the cellulose purity, the whiteness and the ash content, the cellulosic pulps being used for differentiated applications.
• the at least two different characteristics of the cellulosic pulps may relate to the characteristics of the fibers or particles of these cellulosic pulps.
• the invention uses a less selective mixture of plant materials to obtain a cellulosic pulp which is then separated to isolate cellulosic pulps each having at least one given characteristic different from one pulp to another. Consequently, the specifications of the agricultural protocols are less restrictive, which contributes to increasing the resource and promoting biodiversity.
• the cellulosic pulp is separated by sieving by passing through a sieve having slots between 0.2 mm and 0.5 mm.
• the rate of passage of the fibers or particles according to their length is closely linked to the dimensions of the sieve openings.
• the yield by type of cellulosic pulp is in particular a function of the dimensions of the sieve openings as well as the initial rate of fibrous material.
• the invention is not limited to this operating mode for the separation step.
• the cellulosic pulp resulting from the cooking step can be separated using, for example, a centrifugation and/or decantation process. These processes can replace or complement the screening process.
• the first pulp consists of fibres or particles that are passed through the sieve, which ensures a homogeneous quality of cellulosic pulp in terms of fibre length (and width) and a lower degree of polymerisation. This first cellulosic pulp can be used as is or undergo additional treatments.
• the second pulp consists of fibers or particles that do not pass through the sieve openings during the separation operation.
• This second cellulosic pulp comprises fibers with a higher average fiber length than the first cellulosic pulp, more heterogeneous in terms of fiber length.
• This second pulp is different in terms of morphology compared to the first pulp. It generally has a higher degree of polymerization and the fibers present are more delignified.
• This second cellulosic pulp is particularly suitable for packaging applications or molding of objects that have good strength, in particular due to the cohesion of its fibers.
• This second cellulosic pulp can be used as is or undergo additional treatments.
• the invention is not limited to the length of the fibers as a characteristic for the step of separating the cellulosic pulp.
• Other characteristics are conceivable, such as the distribution of the fibers, the degree of polymerization, the whiteness, the kappa index, the cellulose purity or the ash content. This list is not exhaustive.
• the process for obtaining cellulosic pulps can include several successive separation stages.
• Each cellulosic pulp obtained from the process of the invention can be mixed with at least one other cellulosic pulp.
• At least one of the cellulosic pulps obtained from the process of the invention can be used to obtain products, such as a dissolving pulp, a textile product (such as filaments obtained by dissolving and then spinning for example), a membrane, a molded object, packaging or any other product obtained from the cellulosic pulp obtained alone according to the process of the invention or mixed with at least one other cellulosic pulp.
• products such as a dissolving pulp, a textile product (such as filaments obtained by dissolving and then spinning for example), a membrane, a molded object, packaging or any other product obtained from the cellulosic pulp obtained alone according to the process of the invention or mixed with at least one other cellulosic pulp.
• the mixture of plant materials includes 50% fibrous hemp shiv (in which there remains
• the hemp straw is dusted and shortened to a length of less than 10 cm and preferably less than 5 cm.
• the hemp does not undergo any defibration or scutching stage.
• miscanthus has the following chemical composition: approximately 40 to 45% cellulose, 16 to 24% lignin and 25 to 28% hemicellulose.
• this mixture of plant materials and water is subjected to a two-phase cooking step.
• the mixture is brought to a temperature of around 120°C to 200°C for a maximum duration of 150 min.
• the pH becomes acidic, the filtrate is extracted.
• the latter contains in particular a part of the hemicelluloses (more than 10% by weight).
• a delignifying agent and water are added to the hydrolyzed material present in a reactor.
• the delignifying agent is a Kraft liquor or a deep eutectic solvent.
• the liquid/solid ratio is of the order of 3.5 to 7.5.
• the mixture is brought to a temperature of the order of 100°C to 170°C for a maximum duration of 60 to 300 min.
• the cooking liquor is drawn off.
• the latter notably includes a portion of the lignins (more than 60% by weight).
• the cellulosic pulp is rinsed, resuspended and then passed through a sieve to perform the separation step.
• the sieve has slots measuring from 0.2 to 0.5 mm.
• the cellulosic pulp passing through the sieve corresponds to the first cellulosic pulp and that remaining above the sieve or blocked by it corresponds to the second cellulosic pulp.
• the second cellulosic pulp represents 4 to 25%, generally 10 to 25%, of the total cellulosic pulp before the separation step.
• the first cellulosic pulp is in the majority at the end of the separation step. Consequently, this first cellulosic pulp is called the majority pulp, the second cellulosic pulp being called the minority pulp.
• the first cellulosic pulp is homogeneous and has a kappa index of the order of 10 to 30, generally 12 to 25, as well as a degree of polymerization of between 800 and 1300.
• This first cellulosic pulp can be subjected to at least one additional step such as bleaching to adjust its degree of polymerization and/or increase its purity.
• this first cellulosic pulp can be used as a dissolving pulp after a purification step.
• the second cellulose pulp is more heterogeneous in terms of fiber length and has a kappa number at least 2 points lower than that of the first pulp.
• This second cellulose pulp can be used as molding pulp and/or specialty papers. It can also be used for the production of textile fibers, for example after a micro-fibrillation step.

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• Chemical & Material Sciences (AREA)
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• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
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• Polymers & Plastics (AREA)
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• 2023
  • 2023-03-08 FR FR2302151A patent/FR3146481B1/fr active Active
• 2024
  • 2024-03-07 WO PCT/EP2024/056051 patent/WO2024184474A1/fr not_active Ceased
  • 2024-03-07 EP EP24709075.6A patent/EP4677149A1/de active Pending

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