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    • 专利摘要:
    method and apparatus for the processing of fibrillar cellulose, and, fibrillar cellulose product. A method for processing fibrillar cellulose which is in the form of aqueous fibrillar cellulose gel comprises - reducing the pH of the aqueous fibrillar cellulose gel to provide aqueous fibrillar cellulose gel of reduced water holding capacity, and - dehydrating the aqueous gel of fibrillar cellulose with reduced water holding capacity to provide dehydrated fibrillar cellulose. dehydration is carried out by filtration under pressure.
    公开号:BR112014018836B1
    申请号:R112014018836-0
    申请日:2013-01-29
    公开日:2021-03-23
    发明作者:Antti Laukkanen；Markus Nuopponen
    申请人:Upm-Kymmene Corporation；
    IPC主号:
    专利说明:

    [0001] [0001] The present invention relates to a method for processing fibrillar cellulose. The invention also relates to an apparatus for processing fibrillar cellulose and a fibrillar cellulose product. Background of the Invention
    [0002] [0002] Fibrillar cellulose refers to isolated cellulose microfibrils or bundles of microfibrils derived from cellulose raw material. Fibrillar cellulose, which is also known as nanofibrillar cellulose (NFC) and by other related names, is based on a natural polymer that is abundant in nature. Fibrillar cellulose has many potential uses, for example, based on its ability to form a viscous gel in water (hydrogel).
    [0003] [0003] Fibrillar cellulose production techniques are based on grinding (or homogenizing) the aqueous dispersion of pulp fibers. The concentration of fibrillar cellulose in dispersions is typically very low, generally about 1 to 5%. After the milling process, the fibrillar cellulose material obtained is a diluted viscoelastic hydrogel. The material itself is usable as such in many applications, but the logistical costs are too high to transport the material from the production site. In some applications, the high water content is not acceptable, that is, the formulations do not tolerate large amounts of water.
    [0004] [0004] Thus, there is an evident need to increase the concentration of the final product so that transport costs would be reduced and NFC could be used at the final destination, in an appropriate concentration desired by the end user, by simple redispersion in cellulose water. fibrillar.
    [0005] [0005] Strong water retention is typical for fibrillar cellulose, since water is linked to fibrils through numerous hydrogen bonds. Conventional separation techniques to reduce the water content, such as filtration or evaporation, are not feasible with fibrillar cellulose hydrogels.
    [0006] [0006] The fundamental problem in the mechanical removal of water is the ability of fibrillar cellulose hydrogel to form a very dense and impermeable nanoscale membrane around itself, for example, during filtration. The formed wrap prevents the diffusion of water from the gel structure, which leads to very slow concentration rates. The same applies to vacuum evaporation, where the formation of a film blocks the evaporation of water.
    [0007] [0007] Another problem in drying fibrillar cellulose is the non-redispersibility of the dry material. During dehydration, the fibril-water bonds are replaced with fibril-fibril interactions and the fibrils are permanently aggregated. This can be avoided with the use of certain additives during the drying phase, such as CMC, or by chemical modification of the microfibril surface, for example, oxidation or carboxymethylation. With these methods, fibrillar cellulose can be reactivated after complete drying.
    [0008] [0008] In the literature, the use of organic solvents in the separation of fibrillar cellulose from water has been described. The proposed processes have been based on the precipitation of the diluted fibrillar cellulose dispersion in a non-solvent, such as isopropanol. Precipitation is typically carried out from diluted solutions with mixing at high speed.
    [0009] [0009] Methods for dehydrating fibrillar cellulose are known, for example, from the international patent publication WO-0166600 and the European patent EP-0859011. Summary of the invention
    [0010] [00010] It is an object of the invention to provide a new method for the processing of fibrillar cellulose.
    [0011] - reduzir o pH do gel aquoso de celulose fibrilar para fornecer gel aquoso de celulose fibrilar de capacidade de retenção de água reduzida, e - desidratar o gel aquoso de celulose fibrilar de capacidade de retenção de água reduzida para fornecer celulose fibrilar desidratada ou concentrada. [00011] The method comprises: - reducing the pH of the aqueous fibrillar cellulose gel to provide aqueous fibrillar cellulose gel of reduced water holding capacity, and - dehydrating the aqueous fibrillar cellulose gel of reduced water retention capacity to provide dehydrated or concentrated fibrillar cellulose.
    [0012] [00012] Reducing the pH of an aqueous medium containing fibrillar cellulose alters fibril-water interactions so that the water-holding capacity of the aqueous fibrillar cellulose gel is reduced, thus allowing water to be removed from it mechanically and / or by evaporation. If the fibrillar cellulose contains anionically charged groups that act as bases (acidic portions in the dissociated form), the pH reduction will convert these groups to the non-dissociated form and the electrostatic repulsion between the fibrils is no longer effective and the fibril-water interaction is changed. This will make the gel even stronger.
    [0013] [00013] When the fibrillar cellulose which has been acidified in the above form is mechanically concentrated to the dry substance of not more than 40%, preferably not more than 30%, for example, from 10 to 30% by weight and, more specifically , from 10 to 25%, is still unexpectedly well redispersible in water, despite the fact that the acid treatment in which the pH is reduced makes the gel stronger. Mechanical concentration means pressing the water out of the fibrillar cellulose, and this can, in practice, be done by filtration under pressure. No additional drying method is needed to remove even more water if the objective is to obtain this type of partially dry redispersible product.
    [0014] [00014] The fibrillar cellulose product that consists of acidified cellulose can thus be left in a dry substance content, where it still contains residual water by drying by mechanical means, to obtain a good redispersibility of the product. Drying can be continued at 100% or almost 100% (for example, at least 90% or 95% DS (dry substance) using other drying methods, where the residual water has been removed by evaporation.
    [0015] [00015] Fibrillar cellulose containing anionically charged groups can be, for example, chemically modified cellulose containing carboxyl groups, as a result of the modification. Cellulose obtained through catalytic oxidation mediated by N-oxyl (for example, through 2,2,6,6-tetramethyl-1-piperidine N-oxide) or carboxymethylated cellulose are examples of anionically charged fibrillar cellulose, where anionic charge is due to a portion of dissociated carboxylic acid. Other types of fibrillar cellulose having dissociable functional groups that can be converted to the acid form to reinforce the fibrillar cellulose gel can also be used. The pH of the gel is brought below the pKa value of the anionically charged fibrils. In the case of fibrils that contain carboxyl groups, typically at a pH below 3-4, the carboxylic acid is not dissociated and the electrostatic repulsion between the fibrils is not effective.
    [0016] [00016] The method comprises placing the aqueous fibrillar cellulose gel and acidic medium, preferably an aqueous acidic medium, to contact each other, and maintaining contact for a time sufficient to effect the changes in the gel structure necessary for the reduced water holding capacity. According to one embodiment, the fibrillar cellulose gel and the acid are simply mixed with a homogeneous gel, which has a reduced water-holding capacity. This stage could already be integrated in the manufacture of fibrillar cellulose, performing the mixing stage with the same device that is used in the last stage of fibrillation. According to another embodiment, the fibrillar cellulose gel is carefully introduced into the acidic medium, so that it remains as physical entities. This can be done by extruding or spraying the gel into the acidic medium, for example, to make objects like "worm" or "sphere" of the gel, or supply the gel in large "blocks" to the medium and break them into particles smaller ones in the middle. These blocks can be mechanically disintegrated into smaller entities in the volume of acid medium, for example, by stirring. The shape of the entities depends on how the fibrillar cellulose is supplied in an acid medium.
    [0017] [00017] In the second stage of the process, according to the first embodiment, the water is removed from the homogeneous acidic volume of gel by mechanical means, such as filtration under pressure. According to the second embodiment, the entities are physically separated from the acidic medium, and the residual water is removed from them by dehydration. Dehydration of the entities can occur mechanically, by pressure, for example, using pressure filtration.
    [0018] [00018] According to both embodiments, dehydration can be continued by evaporation, depending on the desired degree of dehydration (final dry matter content) of the product. Evaporation can be carried out in a vacuum and / or at an elevated temperature.
    [0019] [00019] In the second embodiment, the fibrillar cellulose hydrogel is introduced into the acid medium with care so that it remains coherent and does not become dispersed, that is, a gel phase limit against the volume of acid medium exists all the time after contact of the hydrogel with the medium, although the phase limit may change due to the disintegration of larger entities, such as gel or blocks, into smaller ones in the acidic medium.
    [0020] [00020] When the fibrillar cellulose hydrogel is in contact with the acidic medium, in the form of physical entities, they maintain their original dimensions and the shapes where the gel was initially supplied to the acidic medium, or the dimensions and shapes of change the final dimensions and shapes of the entities, due to the disintegration of the original gel entities.
    [0021] [00021] The acidic medium that is used for the dehydration of the hydrogel is any aqueous medium that has a sufficiently low pH. In principle, any organic or inorganic acid, capable of reducing the pH of the water can be used. The acidic medium can be in the form of an acid bath in a tank or vessel in which the aqueous fibrillar cellulose gel is introduced in any of the above forms, or to make a homogeneous mixture, or keeping the original fibrillar cellulose gel as separate entities . The acidic medium can also be added to the aqueous fibrillar cellulose gel, which is previously placed in a tank or vessel, or as a side flow for an emission of fibrillar cellulose product from the last fibrillation stage.
    [0022] [00022] The fibrillar cellulose that has been in contact with the acid medium, can be neutralized with a base at a later drying stage, for example, after pressure dehydration, such as after the pressure filtration step. This can be followed by washing to remove the salt. If organic acid of sufficient volatility, such as acetic acid or formic acid, is used in the acidic medium, the residual acid can be removed by evaporation.
    [0023] [00023] The dehydration that occurs during the process leads to an execution of the hydrogen bonds between the fibrillar cell fibrils and to a mechanical stabilization of the formed physical entities.
    [0024] [00024] When water is used for the liquid carrier of the acid medium, the process can be carried out without organic solvents.
    [0025] [00025] During the introduction of the fibrillar cellulose hydrogel to the acidic environment, the mixing or stirring can be of great intensity, and the result is a homogeneous gel. According to another embodiment, in which the limits of the original gel phase and the acidic medium are to be preserved, the mixture or agitation if used, must be taken care to avoid the dispersion of the fibrillar cellulose hydrogel in acidic medium so that the hydrogel is maintained as discrete physical entities.
    [0026] [00026] A possibility according to the second embodiment is to supply the hydrogel through a port comprising several holes or nozzles, and the shape of the entities in the solvent volume is thus determined by the shape of the holes or nozzles and the rate of delivery of the hydrogel in the solvent. The port is preferably immersed in the acidic medium, so that the hydrogel is immediately in contact with the acidic medium, after the emission of the holes or nozzles. The rate of supply can be uniform and continuous, in which case continuous physical entities are formed in an acidic medium, or intermittent, which creates discontinuous entities, for example, granules.
    [0027] [00027] According to the second embodiment, another possibility is to disintegrate the hydrogel while in the acidic medium. In this case, the hydrogel is supplied in larger blocks for the volume of solvent, after which it disintegrates to the physical entities so mechanically that the phase limits remain between the acidic medium and the fibrillar cellulose. This can be done, for example, by the blades of the agitator. The NFC hydrogel can, for example, be disintegrated into a smaller volume of acid medium, after which this volume together with the physical entities formed is combined with a larger, final volume of the acid medium.
    [0028] [00028] According to the second embodiment, after completing dehydration, the physical entities obtained are crushed to a smaller size, for example, particulate matter or powder, which is an easily transportable form of dry fibrillar cellulose, that has retained its rheological properties. This crushed form of fibrillar cellulose can be used as a redispersible dry product, which the end user can make with a gel of the desired concentration by simply adding water, preferably at the place of use of the gel.
    [0029] [00029] According to the first embodiment, the homogeneous acid gel can be mechanically dehydrated to a DS content (dry substance) of 10 to 30%, after which it can eventually be neutralized. This product, in acid or neutralized form, can be used as a redispersible product. The filter cake obtained after pressing the acid gel can be crushed to an appropriate size to make a product easily transportable and redispersible.
    [0030] [00030] According to the second embodiment, the acid gel, which is formed as separate physical entities, can be mechanically dehydrated for DS from 10 to 30% after which it can be neutralized eventually. This product in acidic or neutralized form, possibly after crushing, can be used as a redispersible product. Brief description of the drawings
    [0031] [00031] Figs. 1 and 2 show the principles of the two alternative embodiments, where fibrillar cellulose gel is placed in contact with an acidic medium, (Fig. 1: the second embodiment and Fig. 2 the first embodiment); and
    [0032] [00032] Figs. 3 to 5 show the results of the experiments carried out with the obtained products.
    [0033] [00033] Fig. 3 shows the increase in the solids content of the filter cake as a function of time during filtration under pressure (from above) and the increase in pressure during filtration under pressure, as a function of time (below) ,
    [0034] [00034] Fig. 4 shows the 0.5% viscosity of fibrillar cellulose dispersions, after the concentration cycle as a function of the applied shear stress, compared to a 0.5% non-concentrated sample, from the left to right (in the vertical portion of the 10 Pa.s graph): A2, concentrated to 11.1%, pH 3.4; A2, 11.1%, pH 7.0; A1, 14.3%, pH 3.5; non-concentrated starting material, pH 7.1; A1, 14.3%, pH 7.6.,
    [0035] [00035] Fig. 5 shows the 0.5% viscosity of fibrillar cellulose dispersions, after the concentration cycle, as a function of the applied shear stress, in comparison with a 0.5% non-concentrated sample, with the left side: sample B1, and on the right side: sample B2. Detailed description of the invention
    [0036] [00036] In this context, the term “fibrillar cellulose”, sometimes also called “nanofibrillated cellulose” or nanofibrillar cellulose (NFC for short), or simply “nanocellulose” is used, it being understood that also “microfibrillary cellulose” or “cellulose microfibrillated ”(MFC) are terms commonly used for the substance to be described in more detail below.
    [0037] [00037] Fibrillar cellulose consists of cellulose fibrils, whose diameter is in the sub micronic range. It forms a self-assembling hydrogel network, even at low concentrations. These fibrillar cellulose gels are highly shear thinners and thixotropic in nature.
    [0038] [00038] Fibrillar cellulose is usually prepared from cellulose raw material of plant origin. The raw material can be based on any plant material that contains cellulose. The raw material can also be derived from certain bacterial fermentation processes. The plant material can be wood. The wood may be from softwood tree, such as pine, spruce, larch, douglas fir or hemlock, or from hardwood tree such as birch, poplar, poplar, alder, eucalyptus or acacia, or from of a mixture of softwoods and hardwoods. Non-wood materials can be from agricultural residues, grasses or other plant substances, such as straw, leaves, husks, seeds, pods, flowers, vegetables or fruits from cotton, corn, wheat, oats, rye, barley, rice, flax, hemp, Manila hemp, sisal, jute, ramie, kenaf, cane bagasse, bamboo or reed. The cellulose raw material can also be derived from cellulose-producing microorganisms. The microorganisms can be of the genus Acetobacter, Agrobacterium, Rhizobium, Pseudomonas or Alcaligenes, preferably of the genus Acetobacter and more preferably of the species Acetobacter xyliem um or Acetobacter pasteurianus.
    [0039] [00039] The term "fibrillar cellulose" refers to a collection of isolated fibrillar microcellulose or bundles of microfibrils derived from cellulose raw material. Microfibrils typically have a high aspect ratio: the length can be greater than one micrometer in diameter, while the average number is typically below 200 nm. The diameter of the microfibril bundles can also be larger, but in general, less than 1 μm. The smallest microfibrils are similar to the so-called primary fibrils, which are typically 2 to 12 nm in diameter. The dimensions of the fibers or bundles of fibrils are dependent on the raw material and the disintegration method. Fibrillar cellulose can also contain some hemi-celluloses; the amount depends on the origin of the plant. Mechanical disintegration of fibrillar cellulose from cellulose raw material, cellulose pulp, or refined pulp is carried out with suitable equipment, such as a refiner, mill, homogenizer, colloid forming device, friction mill, sonicator ultrasound, fluidizing such as fluidizing, microfluidizing or macrofluidifying type homogenizer. In this case, fibrillar cellulose is obtained through the disintegration of plant cellulose material and can be called "fibrillated cellulose".
    [0040] [00040] "Fibrillar cellulose" can also be isolated directly from certain fermentation processes. The cellulose-producing microorganism of the present invention can be of the genus Acetobacter, Agrobacterium, Rhizobium, Pseudomonas or Alcaligenes, preferably of the genus Acetobacter and more preferably of the species Acetobacter xyliem um or Acetobacter pasteurianus.
    [0041] [00041] "Fibrillar cellulose" can also be any chemically or physically modified derivative of fibrillar nanocellulose or bundles of nanofibril. The chemical modification can be based, for example, on the reaction of carboxymethylation, oxidation, esterification, or etherification of cellulose molecules. Modification can also be carried out by physical adsorption of anionic, cationic surfactants, or non-ionic substances or any combination of them on the cellulose surface. The described modification can be carried out before, after or during the production of microfibrillary cellulose, or any combination of these processes.
    [0042] [00042] Fibrillar cellulose can be made of cellulose, which is chemically pre-modified to make it more labile. The starting material for this type of fibrillar cellulose is labile cellulose pulp or cellulose raw material, which results from certain modifications to the cellulose raw material or cellulose pulp. For example, N-oxyl-mediated oxidation (eg 2,2,6,6-tetramethyl-1-piperidine N-oxide) leads to very labile cellulose material, which is easy to disintegrate into fibrillar cellulose. For example, patent applications WO 09/084566 and JP 20070340371 disclose such modifications.
    [0043] [00043] Fibrillar cellulose is preferably made of plant material. An alternative is to obtain the nanofibrils from a non-parenchymal plant material where the fibrils are obtained from secondary cell walls. A plentiful source of cellulose fibers are wood fibers. Fibrillar cellulose is manufactured by homogenizing fibrous raw material derived from wood, which can be chemical pulp. When NFC, where cellulose is modified cellulose, is made from wood fibers, cellulose can be stabilized by oxidation prior to the disintegration of fibrils. The disintegration in some of the equipment mentioned above produces fibers, which have a diameter of just a few nanometers, which is a maximum of 50 nm, and gives a clear dispersion in water. The fibrils can be reduced to the size that the diameter of most fibrils is in the order of only 2 to 20 nm only. Fibrils originating from secondary cell walls are essentially crystalline with a degree of crystallinity of at least 55%.
    [0044] [00044] Particularly preferred cellulose material for use in the present invention is derived from cellulose, wherein the cellulose molecules in the fibrils contain some additional functional groups, in comparison with the chemical structure of the native cellulose to make the cellulose and anionically charged. Such groups can be, by way of example only, carboxymethyl cellulose and / or carboxyl. This type of fibrillar cellulose samples is obtained, for example, by fibrillation of carboxymethylated or oxidized cellulose pulp (mediated by N-oxyl), respectively. The modification can also be carried out during, or after fibrillation, or any combination of these. When a gel consisting of any of these types of modified fibrillar cellulose is brought into contact with an acid, the gel will remain more easily coherent than with a gel based on native cellulose. All types of fibrillar cellulose, where cellulose contains functional groups that make cellulose behave like a weak acid whose dissociation is dependent on pH can be used.
    [0045] [00045] Fig. 1 shows the basic principle of a process that can be applied on an industrial scale. Aqueous fibrillar cellulose gel is introduced into a volume of aqueous acid medium. Thus, the volume of acid medium can be called an "acid bath" for the fibrillar cellulose gel. The pH of the acidic medium is less than 4, preferably less than 3.
    [0046] [00046] On an industrial scale, the fibrillar cellulose gel is introduced into the acid bath through an appropriate port that allows the formation of discrete physical entities whose shape is determined by the port and the rate of introduction of the gel. The port may comprise several holes through which the hydrogel is extruded. The hydrogel can be introduced, for example, through an extruder with a suitable carrier plate that generates numerous elongated entities, tapes or hydrogel "worms", objects that can generally be called "strings", in the acid bath. Alternatively, spray nozzles can be used if the objective is to obtain small spheres or granules, in which case the hydrogel is introduced in short intervals, “drop by drop”, instead of as a continuous wick. A port for introducing the hydrogel in this way can comprise several spray nozzles, in parallel from which the hydrogel emits as drops. The holes or nozzles are preferably immersed in the acid bath.
    [0047] [00047] Another method for industrial application is to supply the aqueous fibrillar cellulose gel in larger blocks for the extraction bath and mechanically disintegrate the physical entities within the bath. In this case, the entities formed are more random in shape.
    [0048] [00048] The concentration of fibrillar cellulose in the gel is preferably 0.5 to 5%, more preferably 1.5 to 3.5%, based on the total weight of the gel. Fibrillar cellulose usually exists at these concentrations after manufacture. However, higher concentrations are possible, if the objective is to dehydrate the gel more efficiently, or to increase its strength to avoid its dispersion during the initial phases of the extraction process in the extraction bath.
    [0049] [00049] For the physical entities of the hydrogel made of fibrillar cellulose to remain in a processable form in the solvent, its dimensions must be sufficiently large. Without limiting the scope of the invention, it can be estimated that the smallest dimension of the entity (for example, diameter in the case of an entity similar to an elongated filament) in the extraction bath must be at least 100 μm, preferably at least 0, 5 mm.
    [0050] [00050] After contact with the acid medium, the physical entities are dehydrated, separating them from the acid medium and applying pressure to them. This is possible on a large scale, by pressure filtration. Dehydration can be continued by evaporating water from the physical entities already mechanically dehydrated, so that a desired dry matter content can be achieved. Before evaporative dehydration, physical entities can be made smaller in size by mechanical disintegration. Evaporative dehydration is preferably carried out by drying by forced gas at an elevated temperature and / or vacuum (reduced pressure).
    [0051] [00051] It is also possible that the form that the physical entities were acquired in the acidic medium is maintained, when, for example, elongated filamentous tape-like or sheet-like objects are to be made, which are later used as structural parts or as self-supporting elements . In this case, the aqueous fibrillar cellulose gel can emit in the acid medium through a door, which gives the desired shape for the product, and the entities are only cut to shorter lengths and / or trimmed (non-redispersible product). For use as structural parts or self-sustaining elements, it is possible to introduce additional substances into the fibrillar cellulose gel before being introduced into the acid medium. These substances can be completely miscible with the gel at neutral pH, but coagulable by the effect of the pH of such that they clot at low pH when the fibrillar cellulose comes in contact with the acid. The acid bath may also contain other substances that may enter the gel during contact with the acid bath.
    [0052] [00052] The acid filtrate from the pressure filtration can be recirculated and constituting acid can be added to keep the pH in the acid bath at a low enough level.
    [0053] [00053] After drying is complete, the physical entities can be crushed by a mechanical process suitable for a final size. The dry fibrillar cellulose will be transported in this size to the end user, for redispersion. However, physical entities can be left in their original state after dehydration and transported in this state to the end user. Entities can also be left in a “semi-dry” state, as explained above, for example, omitting one or more final stages of dehydration, as can be done by removing the water mechanically so that a certain dry substance content is reached, for example, not more than 40% of SD, preferably not more than 30%, for example, in the range of 10 to 30%. It is also possible that the fibrillar cellulose remains acidic (not neutralized), if the end use of the redispersed fibrillar cellulose allows the presence of acid residues within the fibrillar cellulose, or if it can still be useful for the final use.
    [0054] [00054] Fig. 2 shows the same procedural steps as Fig. 1, except that the acidified fibrillar cellulose is not kept as separate entities, but mixed homogeneously with the acidic medium, according to the first embodiment above explained. According to this process as well, the product can be left in a semi-dry state, omitting one or more final stages of dehydration.
    [0055] [00055] In both embodiments, the removal of water from acidified fibrillar cellulose is done using pressure filtration. The pressure filtration proceeds to the end point, where the fibrillar cellulose forms a pie with a desired final DS (dry matter). The final DS of the filter cake can be 10 to 30% (concentration of fibrillar cellulose, the rest being liquids and other possible ingredients). Filtration can be carried out so that the filtrate is clear without any particles penetrating through the filter cloth. The filtration temperature is preferably greater than 30 ° C. The pressure during filtration can be from 5 to 100 bar (1 bar = 100 kPa). Pressure filtration device can be a fixed volume chamber filter press or membrane filter press. In a fixed volume chamber filter press, the pressure is caused by the increase in pumping pressure, as solids accumulate in the chamber during the filtration of the liquid through the filter cloth. In a membrane filter press, pressure builds up, initially, as above, and in the final stage of filtration, the pie formed in the chamber is compressed or squeezed by a membrane or diaphragm on one side or on both sides to remove additional liquid of the pie. The filtration chamber is limited by a filter cloth on one side or both sides, which determine the flat sides of the cake to be formed from the solids (fibrillar cellulose). The cake is formed during filtration, either by the pumping pressure of the fibrillar cellulose or by the combined pumping pressure and subsequent compression / squeezing by a membrane / diaphragm or a pair of membranes / diaphragms. The pie formed is a flat piece in which the flat opposite sides are formed according to the opposite sides of the chamber and in which the removal of liquid occurs through one or both sides of the pie due to the filter cloth in one or in both sides of the chamber, respectively. The pie size perpendicular to the flat sides (thickness) is considerably smaller than for any dimension along the flat faces, which are wide surfaces.
    [0056] [00056] The removal of liquid from two sides is recommended for the efficiency of the pressure filtration process, because more filtration area (filter cloth area) is available per unit volume of the fibrillar cellulose.
    [0057] [00057] Fibrillar cellulose, both dry and semi-dry, can also be redispersed to a solvent other than water. It is also possible that the fibrillar cellulose that was left in acid, after transportation or dry or semi-dry storage, is neutralized after redispersion in water or another solvent. Examples of production with fibrillar cellulose Starting materials
    [0058] (1) 10 ml de grau fluidificante de 0,9 % de celulose fibrilar carboximetilada é colocado em um bequer (diâmetro de 4 cm). 5 ml de ácido acético (10 % de concentração) são vertidos no topo do gel. (2) Após 12 horas, o ácido acético é vertido para fora do bequer. O gel é reforçado devido à queda de pH e que é possível levantar a fatia de gel a partir do bequer. (3) O gel solidificado é enxaguado com água e colocado entre duas folhas de papel. A água é retirada pressionando o gel manualmente por meio de uma superfície plana durante 30 segundos. Imediatamente depois da prensagem, a água flui livremente a partir do gel e é sugada para as folhas de papel. Após a prensagem, o volume de gel é entre 1/10 e 1/20 do volume original, ou seja, a concentração é aumentada para 10 a 20 %. [00058] The fibrillar cellulose raw material was functionalized cellulose in which the cellulose had been oxidized by oxidation mediated by N-oxyl prior to the disintegration of the fibrillar cellulose fibers, or functionalized by carboxymethylation before the disintegration of the fibers. General Example (1) 10 ml of fluidizing grade of 0.9% of carboxymethylated fibrillar cellulose is placed in a beaker (diameter of 4 cm). 5 ml of acetic acid (10% concentration) are poured on top of the gel. (2) After 12 hours, acetic acid is poured out of the beaker. The gel is reinforced due to the drop in pH and it is possible to lift the gel slice from the bequer. (3) The solidified gel is rinsed with water and placed between two sheets of paper. The water is removed by pressing the gel manually on a flat surface for 30 seconds. Immediately after pressing, water flows freely from the gel and is sucked into the sheets of paper. After pressing, the gel volume is between 1/10 and 1/20 of the original volume, that is, the concentration is increased to 10 to 20%.
    [0059] [00059] The raw material for fibrillar cellulose was functionalized cellulose in which the cellulose had been oxidized by oxidation mediated by N-oxyl prior to the disintegration of the fibrillar cellulose fibers. Two types of acid were used, either glacial acetic acid (99.9%) or hydrochloric acid (2.0 M). Example 1. Acid treatments - Process 1
    [0060] (1) 6 litros de água destilada foi colocado em um bequer e o pH foi reduzido com ácido clorídrico até pH 2. (2) 2,0 litros de gel de 2,3 % de celulose fibrilar (Exemplo 1 tipo), a pH 7, foi deixado cair no banho de ácido, sob a forma de 20 ml de entidades de gel em um período de tempo de 15 minutos. (3) Imediatamente após as entidades de gel terem sido imersas no banho de ácido, os géis foram solidificados e preservados separados. (4) Depois de 12 horas, o excesso de ácido clorídrico foi vertido a partir do bequer. As partículas de gel foram fortalecidas devido à diminuição do pH e que era possível separar o gel com um filtro de arame grosso. A concentração do gel permaneceu aproximadamente a mesma, ou seja, perto de concentração inicial. (5) A amostra obtida por este tratamento é nomeada como Amostra B1. [00060] This example describes the acid treatment part of process 1, described in figure 1 (second embodiment). Weak acid treatment: (4) 6 liters of distilled water was placed in a beaker and the pH was reduced with acetic acid to pH 3. (5) 2.0 liters of 2.3% fibrillar cellulose gel, at pH 7, was dropped into the acid bath, in the form of 20 ml of gel entities over a period of 15 minutes. (6) Immediately after the gel entities were immersed in the acid bath, the gels were solidified and preserved separately. (7) After 12 hours, the excess acetic acid was poured out from the beaker. The gel particles were strengthened due to the decrease in pH and it was possible to separate the gel with a thick wire filter. The concentration of the gel remained approximately the same, that is, close to the initial concentration. (8) The sample obtained by this treatment is named Sample A1. Strong acid treatment: (1) 6 liters of distilled water was placed in a beaker and the pH was reduced with hydrochloric acid to pH 2. (2) 2.0 liters of 2.3% fibrillar cellulose gel (Example 1 type), at pH 7, was dropped into the acid bath, in the form of 20 ml of gel entities over a period of time 15 minutes. (3) Immediately after the gel entities were immersed in the acid bath, the gels were solidified and preserved separately. (4) After 12 hours, the excess hydrochloric acid was spilled from the beaker. The gel particles were strengthened due to the decrease in pH and it was possible to separate the gel with a thick wire filter. The concentration of the gel remained approximately the same, that is, close to the initial concentration. (5) The sample obtained by this treatment is named Sample B1.
    [0061] (1) 2,0 litros de gel de 2,3 % de celulose fibrilar (Exemplo 1 tipo), a pH 7, foi colocado em um bequer. O pH foi reduzido com ácido clorídrico até pH 2. (2) Após a mistura inicial, a mistura foi efetivamente homogeneizada com um misturador de alta velocidade (homogeneizador Buch). Após a homogeneização, a concentração permaneceu aproximadamente a mesma, ou seja, perto de concentração inicial. (3) A amostra obtida por este tratamento é nomeada como Amostra B2. [00061] This example describes the acid treatment part of process 2, as described in figure 2 (first embodiment). Weak acid treatment: (1) 2.0 liters of 2.3% fibrillar cellulose gel (Example 1 type), at pH 7, was placed in a beaker. The pH was reduced with acetic acid to pH 3. (2) After the initial mixing, the mixture was effectively homogenized with a high speed mixer (Buch homogenizer). After homogenization, the concentration remained approximately the same, that is, close to the initial concentration. (3) The sample obtained by this treatment is named Sample A2. Strong acid treatment: (1) 2.0 liters of 2.3% fibrillar cellulose gel (Example 1 type), at pH 7, was placed in a beaker. The pH was reduced with hydrochloric acid to pH 2. (2) After the initial mixing, the mixture was effectively homogenized with a high speed mixer (Buch homogenizer). After homogenization, the concentration remained approximately the same, that is, close to the initial concentration. (3) The sample obtained by this treatment is named Sample B2.
    [0062] [00062] On an industrial scale, the mixing step can be carried out with the same device that is used in the last fibrillation stage or it can be carried out with a separate mixing device in the subsequent step. The acid can be a weak acid such as formic acid or acetic acid, etc., or a strong acid such as hydrochloric acid, sulfuric acid, etc. The pH is adjusted below the pKa value of anionic groups on the fibrillar cellulose, which normally means a pH between 2 to 3. Example 3. Filtration under pressure
    [0063] [00063] The samples of A1, A2, B1, and B2 were concentrated with a pressure filtration apparatus, as follows.
    [0064] (1) Após o tratamento com ácido ser realizado, os géis foram colocados em forma ácida em um aparelho de filtração sob pressão. (2) A água foi removida por meio de um arame grosso aplicando um excesso de pressão sobre o gel. (3) Depois de determinado período de tempo, o gel concentrado, isto é, a torta de filtro pressionada foi removida. [00064] Filter cloth (Tamfelt): S2181-V2L1 K3 (0.4 m3 / (m2min) (200 Pa) (1) After the acid treatment was carried out, the gels were placed in an acid form in a pressure filtration apparatus. (2) The water was removed by means of a thick wire applying excess pressure on the gel. (3) After a certain period of time, the concentrated gel, that is, the pressed filter cake was removed.
    [0065] [00065] The dehydration rate increased significantly from the gels to a low pH, as can be seen from Figure 3. At neutral pH, most of the water remained in the gel structure, but under acidic conditions, the dry matter content was easily increased to 10 or 20%. Respectively, the filtration capacity was high, that is, typically from 3 to 5 kg / m2 / hour.
    [0066] [00066] If the result is compared to the situation of the original fibrillar cellulose hydrogel, the difference is notable: water from a neutral aqueous hydrogel cannot be removed with pressure filtration in any reasonable way.
    [0067] [00067] After filtration under pressure, the dry matter content of the samples increased as indicated in Table 1. Table 1: Concentration of samples before and after filtration under pressure
    [0068] [00068] The filtered pressure samples can be further concentrated or completely dried by subsequent air drying. This was demonstrated with example B2 by evaporating the waste water at an elevated temperature in the oven, at 50 ° C for 10 hours. This completely dry sample is marked as a B2-dry sample. Example 4. Vacuum filtration
    [0069] (1) Dispersão aquosa de celulose fibrilar foi diluída primeiro com 0,1 % de dispersão, a pH 7 (2) O pH foi reduzido com ácido clorídrico até pH 2. Devido à queda de pH, a dispersão de celulose fibrilar começou a flocular (3) A mistura foi colocada na membrana de filtração sob vácuo e o valor de retenção de água foi medido como sendo de cerca de 30 segundos. A quantidade de celulose fibrilar adicionado corresponde a 20 g/m2. [00069] Reducing the pH below the pKa value improves the removal of water also in vacuum filtration. This was demonstrated with a sample of fibrillar cellulose grade 1 as follows: (1) Aqueous dispersion of fibrillar cellulose was first diluted with 0.1% dispersion, at pH 7 (2) The pH was reduced with hydrochloric acid to pH 2. Due to the drop in pH, the dispersion of fibrillar cellulose began to flocculate (3) The mixture was placed on the filtration membrane under vacuum and the water retention value was measured to be about 30 seconds. The amount of fibrillar cellulose added corresponds to 20 g / m2.
    [0070] [00070] Without reducing the pH, that is, conducting the same experiment, at pH 7, the water retention value varies between 90 to 120 minutes, which is about 200 times higher compared to the same experiment, at pH 2. Example 5. Redispersibility
    [0071] (1) Tortas pressionadas foram trituradas primeiro com liquidificador Waring para granulados de 1 a 3 mm. (2) Material triturado redispersado com liquidificador Waring para teor de matéria seca de 0,5 %. Normalmente as dispersões foram misturadas pelo misturador por 3 ou 4 intervalos de 10 s subsequentes. (3) Viscosidade foi medida como tal (pH ácido) e após a neutralização com NaOH a 18 %. Em alguns casos, o pH foi aumentado a região básica, isto é, próximo de pH 10. [00071] Redispersibility of the concentrated samples A1, A2, B1, and B2 was demonstrated in the following ways. (1) Pressed pies were first crushed with a Waring blender for 1 to 3 mm granules. (2) Crushed material redispersed with Waring blender for 0.5% dry matter content. Usually the dispersions were mixed by the mixer for 3 or 4 intervals of 10 s subsequently. (3) Viscosity was measured as such (acidic pH) and after neutralization with 18% NaOH. In some cases, the pH was increased to the basic region, that is, close to pH 10.
    [0072] [00072] Viscosity fibrillar cellulose dispersions were measured over a wide range of shear stress (rate) on a rotational rheometer (AR-G2, TA Instruments, UK) using paddle geometry. The flow curves obtained for the concentrated samples were compared with a sample that was not concentrated, see figures 4 and 5. It was evident that samples B1 and B2 were well redispersed after the concentration process. The flow profile of sample B1 (9.8% concentrate) was identical to the reference sample. Likewise, sample B2 recovered most of its rheological properties after the 19.7% concentration cycle.
    [0073] [00073] Importantly, both samples B1 and B2 showed the characteristic rheological behavior also at low pH, without neutralization, that is, at a pH of 3 to 4.
    [0074] [00074] One or more additional substances can be incorporated into the redispersible product by adding the same / them in the fibrillar cellulose hydrogel, or in the volume of acid medium (acid bath), in which the fibrillar cellulose hydrogel is then introduced or with which it is mixed homogeneously, or in both fibrillar cellulose hydrogel and volume of acid medium.
    [0075] [00075] More specifically, for example, latex or anionically stabilized polymer particles in dispersion form can be coagulated in the same process step, reducing the pH of the mixture. This allows a fast and economically viable process to homogeneously mix fibrillar cellulose for different matrix polymers and, simultaneously, remove water from the formed standard mixture. When the goal is a standard blend of fibrillar cellulose - polymers, redispersibility is not necessary, but water removal is important. Potentially interesting polymer particles are, for example, various latex particles, such as styrene-butadiene latex, natural rubber latex, etc.
    [0076] [00076] The invention is not, however, limited to the use of dehydrated fibrillar cellulose as a redispersible product, but the fibrillar cellulose made according to the above embodiments can be used as structural parts in various structures, such as in composite materials , or as such, in sheets or membranes that may already be formed when the aqueous fibrillar cellulose gel is brought into contact with the acidic medium. It is also possible to mold the fibrillar cellulose gel, while it is in the acid form (as a result of its contact with acid), preferably in connection with its dehydration by pressing, so that it will at the same time obtain a desired shape . Additional substances can be incorporated in any of the aforementioned ways in which the fibrillar cellulose is to be molded.
    [0077] [00077] The final product can remain in a certain dry substance content, when the dehydration is not complete, for example, between 10 to 30%, the rest being mainly water. This product can be in the acid form, which originates from the acidification of the fibrillar cellulose gel, before dehydration, or it can be in the neutral form, which is the result of neutralization after dehydration. The products in this DS range are easy to handle and easily redispersible in a liquid medium. However, it is possible to make the product that was mechanically dehydrated first at 10-30% DS, completely dried by air drying, for example, at an elevated temperature.
    [0078] [00078] The redispersible product preferably has the following properties, when redispersed in water: zero shear viscosity from 1,000 to 50,000 Pa.s and yield stress from 1 to 30 Pa, preferably from 3 to 15 Pa, measured at a concentration of 0.5% in water by rotational rheometer (AR-G2, TA Instruments, United Kingdom), using paddle geometry.
    [0079] [00079] When pressure filtration is used for the initial concentration of fibrillar cellulose, both for final DS and as a preliminary drying step, it can be carried out at elevated temperature, preferably between 30 and 70 ° C.
    [0080] - meios para armazenar um meio ácido - meios para armazenar um gel aquoso de celulose fibrilar - meios para colocar a celulose fibrilar aquosa em contato com o meio ácido, e meios para a desidratação do gel aquoso de celulose fibrilar depois de colocar o gel aquoso de celulose fibrilar em contato com o meio ácido.[00080] The apparatus for processing fibrillar cellulose comprises: - means for storing an acidic medium - means for storing an aqueous fibrillar cellulose gel - means for bringing aqueous fibrillar cellulose into contact with the acidic medium, and means for dehydrating the aqueous fibrillar cellulose gel after placing the aqueous fibrillar cellulose gel in contact with the acidic medium.
    [0081] [00081] The means for dewatering the aqueous fibrillar cellulose gel is preferably a pressure filtration apparatus, as described above.
    [0082] [00082] The apparatus also contains means for transporting the aqueous fibrillar cellulose gel from the means of contact of the fibrillar cellulose with the acid (such as from a mixing tank) to the pressure filtration apparatus. The means of transport is a pump suitable for pumping highly viscous products, such as a screw-type pump.
    [0083] - Fluidos de fraturamento hidráulico, - Fluidos carreadores para recheio de cascalho, - Fluido espaçador, - Fluidos de deslocamento, “fluidos de inundação” em recuperação avançada de petróleo, - Fluidos de perfuração e - Fluido de completação de poço e de trabalho (tal como descrito na patente US 3.882.029, por exemplo). [00083] In a particular application, the place of use to which the product is transported semi-dry or dry is an oil field. When redispersed in the oil field, the high viscosity at low shear rates, good pumping capacity at high shear rates, oil immiscibility and good solids suspension capacity make redispersed fibrillar cellulose ideal for preparing different working fluids for oil recovery or assistance operations. These fluids include: - hydraulic fracturing fluids, - Carrier fluids for gravel filling, - Spacer fluid, - Displacement fluids, “flood fluids” in advanced oil recovery, - Drilling fluids and - Well completion and working fluid (as described in US patent 3,882,029, for example).
    [0084] [00084] The pore blocking capacity of fibrillar cellulose is also a useful property when a fluid containing NFC as a viscosity agent is used in underground formations.
    权利要求:
    Claims (27)
    [0001]
    Method for processing anionically charged fibrillar cellulose, which is derived from nanofibrillar cellulose containing additional functional groups producing anionically charged cellulose, made from wood fiber and in which the fibrils have a maximum diameter of 50 nm, and the derivative is in the form of aqueous viscoelastic fibrillar cellulose hydrogel, the method characterized by the fact that it comprises: - reducing the pH of the aqueous fibrillar cellulose hydrogel below the pKa value of the anionically charged fibrillar cellulose to pH between 2 and 3 to provide aqueous fibrillary cellulose hydrogel with reduced water holding capacity, and - dehydrating the aqueous fibrillar cellulose hydrogel with reduced water retention capacity in a pressure filtration step where positive pressure is applied to the aqueous fibrillar cellulose hydrogel to provide dehydrated fibrillar cellulose.
    [0002]
    Method according to claim 2, characterized in that the anionically charged fibrillar cellulose is chemically modified cellulose containing portions of dissociated acid.
    [0003]
    Method according to claim 2, characterized in that the portions of dissociated acid are carboxyl groups.
    [0004]
    Method according to claim 2 or 3, characterized in that the pH is reduced in such a way that the dissociated acid portions are converted to the acid form.
    [0005]
    Method according to any one of claims 1 to 4, characterized in that the method includes - contacting the aqueous fibrillar cellulose gel with an acidic medium so that the aqueous fibrillar cellulose gel and the acidic medium are mixed homogeneously.
    [0006]
    Method according to any one of claims 1 to 4, characterized in that the method includes - contacting the aqueous fibrillar cellulose gel with a volume of acid medium in a controlled manner so that the aqueous fibrillar cellulose gel is maintained as a separate phase and forms one or more discrete physical entities containing the fibrillar cellulose in the phase - separating one or more physical entities from the volume of acidic medium, and - dehydrating one or more physical entities to supply the dehydrated fibrillar cellulose.
    [0007]
    Method according to claim 6, characterized in that the aqueous fibrillar cellulose gel is mechanically disintegrated into discrete physical entities before or after contact with a volume of acid medium.
    [0008]
    Method according to claim 6, characterized in that the aqueous fibrillar cellulose gel is contacted with the volume of acid medium by introducing the aqueous fibrillar cellulose gel through a port comprising one or more orifices or nozzles through which the gel issues.
    [0009]
    Method according to any one of claims 1 to 8, characterized in that the dehydration is carried out at a temperature of 30 ° C or higher.
    [0010]
    Method according to claim 9, characterized in that the dehydration is carried out at a temperature of 30 to 70 ° C.
    [0011]
    Method according to any one of claims 1 to 10, characterized by the fact that the aqueous fibrillar cellulose gel with reduced water retention capacity is dehydrated in a pressure filtration step to dry the substance content from 10 to 30% by weight of fibrillar cellulose.
    [0012]
    Method according to any one of claims 1 to 11, characterized in that the dehydration of the aqueous fibrillar cellulose gel of reduced water holding capacity comprises the removal of water by evaporation from the aqueous fibrillar cellulose gel after the step filtration under pressure.
    [0013]
    Method according to any one of claims 1 to 12, characterized in that the dehydrated fibrillar cellulose is neutralized with a base.
    [0014]
    Method according to any one of claims 1 to 12, characterized in that the dehydrated fibrillar cellulose is left in the acid form.
    [0015]
    Method according to any one of claims 1 to 14, characterized in that the acidic medium is aqueous acidic medium.
    [0016]
    Method according to any one of claims 1 to 15, characterized in that the concentration of the aqueous fibrillar cellulose gel is 0.5 to 5% by weight.
    [0017]
    Method according to any one of claims 1 to 16, characterized in that the method comprises: - disperse the dehydrated fibrillar cellulose in a liquid medium.
    [0018]
    Method according to claim 17, characterized by the fact that the method comprises: - transport the dehydrated fibrillar cellulose to a place of use and disperse the dehydrated fibrillar cellulose in a liquid medium at the place of use.
    [0019]
    Method according to any one of claims 1 to 18, characterized in that the method comprises: - add coagulable additive with coagulable acid due to the effect of lowering the pH for the aqueous fibrillar cellulose gel before decreasing the pH of the aqueous fibrillar cellulose gel, and - coagulate the additive in the gel by reducing the pH.
    [0020]
    Fibrillar cellulose product, characterized by the fact that the fibrillar cellulose is anionically charged nanofibrillar cellulose, having a dry substance content of 10 to 30% by weight of fibrillar cellulose, where the cellulose is chemically modified cellulose, containing portions of acid in the form acidic, manufactured from wood fiber and in which the fibrils have a maximum diameter of 50 nm.
    [0021]
    Fibrillar cellulose product, characterized by the fact that fibrillar cellulose is anionically charged nanofibrillar cellulose having a dry substance content of 10 to 30% by weight of fibrillar cellulose, in which the cellulose is in the neutralized form in the product, manufactured from wood fiber and where the fibrils have a maximum diameter of 50 nm.
    [0022]
    Fibrillar cellulose product according to either of claims 20 or 21, characterized in that it is redispersible in water as a gel.
    [0023]
    Fibrillar cellulose product according to claim 22, characterized by the fact that it is redispersible in water in such a way that at a concentration of 0.5% it has a maximum viscosity of at least 100 Pa.s in the range of shear stress between 0.01 Pa and the yield stress value, measured at 0.5% water concentration.
    [0024]
    Fibrillary cellulose product according to claim 22 or 23, characterized in that the fibrillar cellulose has a zero shear viscosity of 1,000 to 50,000 Pa.se yield strength from 1 to 30 Pa, preferably from 3 to 15 Pa , as measured at a 0.5% concentration in water.
    [0025]
    Fibrillar cellulose product according to any one of claims 20 to 24, characterized in that the product contains a substance coagulated by coagulated acid due to the effect of lowering the pH within the fibrillar cellulose.
    [0026]
    Fibrillar cellulose product according to claim 25, characterized by the fact that the product is a standard blend of fibrillar cellulose - polymer.
    [0027]
    Fibrillar cellulose product according to any one of claims 20 to 26, characterized in that it is obtained by the method as defined in any one of claims 1 to 19.
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    同族专利:
    公开号 | 公开日
    CA2860956C|2019-03-12|
    EP2815026A1|2014-12-24|
    CN104136681A|2014-11-05|
    FI125941B|2016-04-15|
    JP6537272B2|2019-07-10|
    DK2815026T3|2021-07-26|
    CA2860956A1|2013-08-22|
    CN104136681B|2017-04-19|
    US9409998B2|2016-08-09|
    US20150045549A1|2015-02-12|
    WO2013121086A1|2013-08-22|
    EP2815026B1|2021-06-16|
    JP2015508839A|2015-03-23|
    FI20125158A|2013-08-14|
    EP2815026A4|2015-10-07|
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    法律状态:
    2018-03-27| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2019-09-10| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2021-02-02| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-03-23| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 29/01/2013, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    FI20125158A|FI125941B|2012-02-13|2012-02-13|Method and apparatus for treating fibril pulp and a fibril pulp product|
    FI20125158|2012-02-13|
    PCT/FI2013/050095|WO2013121086A1|2012-02-13|2013-01-29|Method and apparatus for processing fibril cellulose and fibril cellulose product|
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