Method and system for enzymatic treatment of fibrous cellulosic material and rigid cellulosic products

Abstract

An enzyme treatment method and system for fibrous cellulosic material and rigid cellulosic products, the method comprising: introducing a raw fibrous cellulosic material (1) into an agitator (20); enzymatically treating the raw fibrous cellulosic material (1) for a certain period of time to obtain a treated cellulosic material, the enzymatic treatment comprising adding enzymes (11, 12, 13, 14) to the raw fibrous cellulosic material and agitating to uniformly distribute the enzymes in the raw fibrous cellulosic material; drying the treated cellulosic material, at least a portion of which is derived from an industrial waste product.

Description

[Technical field]

[0001] The present invention relates to a method for the enzymatic treatment of fibrous cellulosic material, a rigid cellulosic product, and a method for forming a rigid cellulosic product. In particular, the proposed method allows for the enzymatic treatment to be carried out on raw fibrous cellulosic material, at least part of which originates from industrial waste, without the need for the addition of large amounts of water, with the economic and environmental benefits of reducing the overall water consumption and therefore the amount of sewage produced.

[0002] Additionally, the present invention allows for the production of rigid cellulosic products that include at least a portion of raw fibrous cellulosic material derived from industrial waste, which is typically defined as non-recyclable waste and therefore cannot be reused or recycled, or would otherwise be deposited in landfills with associated negative environmental impacts.

[0003] The present invention focuses on the upcycling of the aforementioned industrial waste cellulose fibers to obtain rigid cellulose products with suitable mechanical properties. Cellulosic fibers are considered non-reusable if at least one of the following applies: the average length of the fibres is less than 5 mm; - the average thickness of the fibers is less than 0.1 mm; - The proportion of fines in the cellulosic waste exceeds 10% by mass, where fines are defined as the smallest component of the cellulosic fiber fraction that can pass through a 76 micrometer diameter hole [SCAN. Mechanical and chemical pulps-Fines content. Standard CM 66:052005], or Cellulosic fibers are mixed with other compounds that cause recycling complications. These other compounds include inorganic charges, synthetic compounds, material impurities, etc.

[0004] <Technical level> Waste paper and waste cardboard can be effectively recycled if they contain low amounts of adhesives, inks, water-resistant resins, and other additives. Examples of these water-resistant resins and additives are alkyl ketene dimers, alkenyl succinic anhydrides, epichlorohydrin, melamine, urea formaldehyde, polymines, styrene, dextrin, or other polymers that improve certain material properties (i.e., polyurethane, vinyl, and acrylic adhesives improve mechanical properties). However, recycling costs and the quality of the resulting cellulosic products can be significantly affected if the waste paper and waste cardboard contain large amounts of these additives, requiring additional processing steps and / or increasing the consumption of additives or energy during processing of the cellulosic material.

[0005] Furthermore, typical recycling methods for waste paper and discarded cardboard require the use of large amounts of water that is then disposed of, and generate wastewater that must be treated, thereby reducing the environmental benefits of recycling.

[0006] The paper and cellulose manufacturing industries also generate significant amounts of industrial waste, including liquid or primary sludge (or sludge) containing cellulosic material that is considered non-recyclable as defined by the above characteristics, which is considered an effluent that has significant environmental liability for the producers, but which can be mitigated by appropriate enzymatic treatment to produce raw fibrous cellulosic material.

[0007] Another source of industrial waste is for example the cellulose fibre residue streams from the textile industry, where the presence of different types of cellulose fibres and plastic mixtures causes difficulties in reusing or recycling these residues.

[0008] A further source of industrial waste is construction waste cellulose fibres, e.g. cardboard recovered when recycling gypsum board. Gypsum-based recovery processes by mechanical crushing and subsequent dry double pressing separate the gypsum from the paper, resulting in a finished product with the same properties as natural gypsum. The recovered gypsum powder is 97.6% pure and substantially free of paper. While the gypsum by-product can be reused, the cellulose fibres are typically burned without being used to form useful products. Typically, the cellulose fibres have a length of around 1 mm.

[0009] Applicant has discovered that with appropriate processing, including enzyme treatment, previously non-recyclable cellulosic fibers derived from industrial waste can ultimately be used to produce useful cellulosic products that not only have the environmental benefits associated with reusing materials that would otherwise end up in landfills, along with reduced water consumption and resulting waste, but importantly provide cellulosic products that can perform at least as well as products derived from other cellulosic fibers and using alternative processes that have greater negative environmental impacts.

[0010] Document EP 2569480 B1 describes an enzymatic treatment method for cellulosic materials, mainly waste paper and waste cardboard (such waste paper and waste cardboard are not considered industrial waste), in which said cellulosic materials are diluted with water in a pulper to obtain a liquid mixture having 5% to 10% pulp and thus containing 90% or 95% water. Enzymes are then added to the liquid mixture to subject the cellulosic materials to an enzymatic treatment, obtaining a treated cellulosic material suitable for the production of new cellulosic products. The liquid mixture is introduced into a former, where it is filtered and the solid fraction obtained therefrom is compressed or molded and dried to produce a rigid cellulosic material product.

[0011] The filtration and drying process consumes time and energy and produces large volumes of wastewater containing enzymes and other beneficial components that require expensive treatment to reduce its environmental impact and enable its reuse in the process.

[0012] The rigid cellulose products obtained from the process may be used for construction and packaging, or as decorative materials.

[0013] The method described in EP2569480B1 presents several problems, the most prominent of which are listed below: One problem is that the cellulosic material contained in the liquid mixture is composed of different elements having different densities, and when the liquid mixture is introduced into a former, it results in a greater accumulation of the higher density elements, producing an uncontrolled, non-uniform, rigid cellulosic product, which directly affects other parameters such as density, thickness, and mechanical resistance.

[0014] The second problem is that the formation of the rigid cellulose product and the filtration of the liquid mixture occur simultaneously, so that the process is limited to the production of a single layer of rigid cellulose product made entirely from cellulosic material filtered from one single liquid mixture. A liquid mixture containing only 5%-10% of cellulosic material is mixed with any other different liquid mixtures fed simultaneously onto the same former before having time to be filtered and settled, producing an initial layer of the laminated product; if the second liquid mixture is fed after the first liquid mixture has already been filtered, the 95% of water contained on the second liquid mixture will dissolve said initial layer and prevent the formation of the laminated product.

[0015] Since this process only allows obtaining a single layer of rigid cellulose product, the properties of the surface layer are indistinguishable from the rest of the product, which precludes the creation of a surface layer with reduced porosity, for example to reduce absorption of paints or sealants.

[0016] A third problem is that, according to this method, although any additives included are soluble in water to obtain a uniform distribution, most of said additives are disposed of with the sewage, creating pollution and economic waste.

[0017] A fourth problem relates to the need to improve filtration waste energy for heating the liquid mixture to reduce its surface tension and heat the water that becomes wastewater after filtration.

[0018] A fifth problem is that the filtration process during formation requires a vacuum system which is very expensive in terms of energy and maintenance.

[0019] Finally, high energy is consumed during the drying process, which increases gradually with the density and thickness of the resulting rigid cellulose product.

[0020] WO 03 / 047826 A1 discloses a method for producing a fiberboard or similar wood-based product, which includes the steps of providing a lignocellulosic material, contacting the lignocellulosic material with an activator to produce a modified lignocellulosic material containing free radicals, forming the modified lignocellulosic material into a layered structure, and pressing the layered structure into a compressed product.

[0021] WO 2008 / 026932 A1 discloses a method for the thermoenzymatic hydrolysis of lignocellulose.

[0022] WO 2014 / 160262 A1 provides a method for converting cellulosic waste, such as municipal waste, into bioproducts, such as monosaccharides and fermentation products.

[0023] US 2016 / 0060667 A1 provides a continuous process for the enzymatic hydrolysis of pretreated biomass.

[0024] WO 2015 / 150620 A1 provides a method for producing fibrillated cellulose, the method comprising the steps of providing a pulp, treating the pulp with cellulase at a consistency of at least 10%, and fibrillating the pre-treated pulp to obtain fibrillated cellulose. DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0025] The proposed method solves or at least mitigates the problems associated with the prior art. [Means for solving the problem]

[0026] According to a first aspect, the present invention relates to a method for the enzymatic treatment of fibrous cellulosic material, i.e. a method for subjecting fibrous cellulosic material to an enzymatic treatment.

[0027] Fibrous cellulosic material is understood to be a material composed primarily of fibers of any length made from cellulose and other plant compounds that are capable of forming bonds with other cellulosic fibers.

[0028] The method allows the use of a portion of fibrous cellulosic material derived from industrial paper, cardboard, textiles, construction waste, or other waste sources, the residual cellulosic material being, as mentioned above, a low quality fibrous cellulosic material that is otherwise not recyclable and typically comprises mainly recycled fibres shorter than 5mm, and / or brittle fibres, and / or fibres that are typically partially combined with impurities and therefore have reduced bonding capacity with other cellulosic fibres. By recycled fibres we mean fibres that are not virgin fibres, that come from industrial process waste streams and / or that have been part of a product used in the market for at least one life cycle. The enzymatic method (or process) allows post-industrial fibres to bond with other non-industrial fibres and / or with each other, provided that the fibres are natural fibres and capable of generating hydrogen bonds.

[0029] The raw fibrous cellulosic material introduced into the mixer may contain some impurities other than cellulose fibers that have the ability to bond with other cellulose fibers.

[0030] Preferably, the raw fibrous cellulosic material from an industrial waste or another source will not contain large particles or clusters over 5 mm, since such particles or clusters have reduced or no ability to form bonds with other cellulosic fibers. A particle size reducer, such as a grinder, shredder or pulper, may be used prior to the agitator to reduce particle size or remove particles or clusters.

[0031] Alternatively, the raw fibrous cellulosic material may contain larger particles or clusters greater than 5 mm, provided that such particles or clusters are soluble or breakable by an agitator into smaller particles or clusters less than 5 mm, or fibers of any length. Examples of large soluble or breakable particles or clusters may be, for example, cardboard, or sludge lumps.

[0032] Applicants have discovered that the enzyme treatment process can be used with raw fibrous cellulosic material, including at least a portion of an industrial waste material, having a low moisture content and specific flow properties.

[0033] Preferably, at least 20% of the raw fibrous cellulosic material in the formed product is industrial waste generated from the paper or cellulose manufacturing industry, especially primary sludge from physico-chemical treatment plants.

[0034] In the present invention, the terms primary sludge and sewage sludge (or sewage sludge) may be used in an unclear manner. In a preferred embodiment, at least 40% of the raw fibrous cellulosic material is primary sludge from the paper industry, more preferably at least 50% of the raw fibrous cellulosic material is primary sludge from the paper industry, even more preferably at least 60% of the raw fibrous cellulosic material is primary sludge from the paper industry, and even more preferably at least 70% of the raw fibrous cellulosic material is primary sludge from the paper industry.

[0035] The primary sludge is composed of about 40-90% by weight of cellulose fibers and about 10-60% by weight of inorganic fillers. These inorganic fillers are added during the paper manufacturing process to improve the properties of the paper. The raw cellulose material derived from the primary sludge described in the present invention is characterized by containing a large amount of fines, more than 15% of cellulose fibers. Fines are small particles composed of cellulose, but do not have the shape of fibers due to their size. This means that the raw cellulose material used in the method of the present invention cannot be used to manufacture paper or other products that require good mechanical properties, since the ends do not provide mechanical bonding. Since the above-mentioned peculiarities of this raw cellulose material make it very difficult to obtain products that require low humidity, low pressure and low temperature processes, it is very important to improve the properties of the raw cellulose material in order to reduce the amount of adhesive used in the obtained product, if there is not a large amount of adhesive present. It should be noted that it is the short overall length of the cellulose fibers that make up said material that is considered waste from the paper industry.

[0036] Furthermore, the raw cellulosic material according to the present invention is preferably substantially free of lignin or accounts to a trace amount of lignin present.

[0037] To complement the amount of raw fibrous cellulose material to 100%, other sources of cellulose fibers are not derived from industrial waste, but from, for example, waste paper from high quality printing paper, or any kind of cellulose fiber from plants, preferably from post-consumer waste, which is a material that is already in use.

[0038] The raw cellulose material can be pre-characterized by, but not limited to, microscopy, Heizberg evaluation, leakage test, enzymatic reaction test, or inorganic content determination, among other complementary techniques, to determine the mixture of the raw cellulose material in order to obtain a product that meets the product standard specifications (reduction tolerance quality control parameters).

[0039] Standardization of the product by adjustment of the % w / w (dry) of different types of raw cellulosic materials to match the feedstock can be automated by computational algorithms based on statistics, preferably generated from a database linking the raw cellulosic materials, to provide quality control.

[0040] Preferably, the moisture content of the raw fibrous cellulosic material is comprised between 20% and 80%, preferably between 20% and 60%, more preferably between 20% and 50%, and most preferably between 20% and 40%, and is adjusted to produce a raw fibrous cellulosic material having a particular fluidity, being a flowable viscous sludge-like granular texture and not a liquid-like fluidity.

[0041] The particular fluidity is adjusted to allow uniform and efficient agitation of the raw fibrous cellulose material to produce a uniform distribution of the enzyme, and to be the minimum moisture content required to allow transport of the raw fibrous cellulose material and the treated cellulose material through a production plant.

[0042] The transport may be produced, for example, by conveyor belts, conveyor screws, and other paste or granular material conveyors, since the particular fluidities mentioned above are usually too dense to efficiently use liquid conveyors such as pumps (although this is possible and not the preferred method).

[0043] According to the proposed method, no filtration step is required for the initial separation of the solid and liquid fractions, since the water content is low enough that conventional filtration without additional measures such as pressure does not significantly reduce this water content.

[0044] The low moisture content of the present invention can be easily achieved using less energy, for example by heating, to obtain a dry treated cellulose material, which requires much less energy than the prior art wet method (where the moisture content is still high after the first filtration and requires much more drying energy than the proposed method), saving energy, saving time, and reducing its cost and environmental impact.

[0045] Preferably, once the enzyme is added to the raw fibrous cellulosic material, no further water or diluent is added and the moisture content remains unchanged during said enzyme treatment.

[0046] It is also proposed that the operating parameters of the agitator can be configured to generate a dynamic current that affects the entire volume of raw fibrous cellulose material contained within the agitator over the raw fibrous cellulose material having a particular fluidity, ensuring uniform distribution of the enzyme and maximum contact of the enzyme with all the raw fibrous cellulose material processed within the agitator.

[0047] The dynamic agitation can also optionally generate high turbulence over the raw fibrous cellulosic material during enzyme treatment.

[0048] Since the mixture has a lower moisture content compared to the wet enzymatic process, a uniform distribution of the enzyme affecting all the fibers of the raw fibrous cellulosic material is not easily achieved because, due to the viscosity of the proposed raw fibrous cellulosic material with low moisture content, the required agitation cannot be obtained by simple agitation, as in the case of liquid textures, but requires precise dynamic agitation designed and provided to ensure that the enzyme affects all the raw fibrous cellulosic material to be treated contained in the agitator.

[0049] For example, the operating parameters may include the temperature of the raw fibrous cellulosic material and / or the speed of movement of a number of active stirring elements included in an agitator for agitating the raw fibrous cellulosic material.

[0050] Increasing the temperature of the raw fibrous cellulosic material results in increased fluidity, but requires additional water and an associated higher additional energy consumption during heating to remove this additional water.

[0051] The movement of each active stirring element creates a stirred volume of the raw fibrous cellulose material around it, the size of which depends on the moving speed and the specific flow properties of the raw fibrous cellulose material. The moving speed of all active stirring elements of the stirrer is configured such that the combined stirred volume is sized to cover the entire volume of the raw fibrous cellulose material contained in the stirrer. To achieve this effect, it is also preferred to include said active stirring elements equidistant from each other in the stirrer.

[0052] For example, the agitator may include multiple stirring elements, such as parallel blades and / or rotating and non-rotating blades with the same or different rotational speeds or directions, to generate a dynamic flow and increase the turbulence generated. The stirring elements may also include blades attached to the walls of the agitator, which may be static or rotating.

[0053] More specifically, the movement of each active stirring element creates a pushing force in front of the active stirring element and a suction force behind the active stirring element on the material being stirred, creating a bulk current loop in the surrounding stirred material, affecting the particular stirred volume. Depending on the speed of movement of the active stirring element and the fluidity of the stirred material, the size of the bulk current loop changes, modifying the stirred volume. For example, an increase in the fluidity of the raw fibrous cellulosic material due to an increase in moisture content results in an increase in the stirred volume, and in addition, an increase in the speed of movement of the active stirring element also results in an increase in the stirred volume.

[0054] Preferably, the speed of movement of the active stirring element remains below the cavitation limit of the raw fibrous cellulosic material having a particular flowability to prevent undesirable effects and inefficiencies.

[0055] Preferably a plurality of active stirring elements are distributed inside the stirrer, preferably evenly distributed at known distances from each other.

[0056] The flow properties of the material being stirred and the speed of movement of the active stirring elements can be configured to ensure that the aggregation of all the volumes being stirred covers the entire volume of material contained in the mixer.

[0057] The processing method can be adapted to process batches of raw fibrous cellulosic material, or it can be adapted to process a continuous flow of raw fibrous cellulosic material, in which case the agitator is an agitator tunnel or column having inlet and outlet ends opposite each other, during which it produces a continuous flow of raw fibrous cellulosic material that takes a certain time from inlet to outlet.

[0058] The moisture content of the raw fibrous cellulosic material can be adjusted within the range of 20% to 80% to obtain a predetermined specific flowability, for example within the range of acceptable flowability within which the agitator can operate properly to obtain said dynamic flow affecting all of the raw fibrous cellulosic material contained in the agitator.

[0059] Said adjustment of moisture content may be achieved by spraying additional water during the addition of the enzyme or by increasing or decreasing the dilution of the enzyme prior to its addition to the raw fibrous cellulosic material. The flowability of the raw fibrous cellulosic material may be measured based on a viscosity measurement test to determine any additional adjustment of moisture content or may be estimated from the moisture content measured for the raw fibrous cellulosic material. Said measurements may be obtained prior to the introduction of the material into the mixer.

[0060] Alternatively, the fluidity of the stirred raw fibrous cellulosic material can be estimated from the energy required to generate the required agitation. For example, active stirring elements can be powered by electric motors, and the electrical consumption is indicative of the fluidity of the raw fibrous cellulosic material. Depending on the results of these measurements, additional water can be added to the stirred material to increase its fluidity.

[0061] Alternatively, it is proposed that the flowability of the raw fibrous cellulose material is measured and then the operating parameters of the agitator are adjusted according to the specific measured flowability in order to obtain a dynamic flow that affects all the raw fibrous cellulose material contained in the agitator.

[0062] In this case, depending on the measured flowability of the raw fibrous cellulosic material, the moving speed of the active stirring element can be increased or decreased to ensure that the stirring affects the entire volume of the raw fibrous cellulosic material, or its temperature can be adjusted to obtain a dynamic flow without requiring unnecessary energy expenditure. The stirrer includes a heater for heating its contents to a target temperature considered optimal.

[0063] The temperature also affects the enzyme treatment. The gas pressure and / or gas composition into the agitator can optionally be adjustable to regulate the enzyme treatment.

[0064] One of the major current problems in enzyme processing under high consistency conditions (i.e., raw cellulosic material has a moisture content of 40% or less) is the difficulty of the enzymes to fit the cellulosic fibrous substrate, which is due to poor dispersion of the enzymes in the low humidity environment.

[0065] The presence of dense gas improves enzyme-substrate contact, increases the yield of the enzymatic process, allows for an efficient process with low moisture content (or high consistency conditions), and significantly improves the process yield relative to turbulent mixing with countercurrent gas flow, because the enzyme-substrate contact time is much shorter in the countercurrent flow than with dense gas turbulent mixing. Dense gas in a closed reactor increases the relative pressure during enzymatic processing, which can improve the dynamics of the mixing process.

[0066] Dense gas is defined herein as a gas that has a density twice that of air at normal atmospheric conditions (25°C, 1 atm). The density of air is 1.2 kg / m under normal conditions. 3 It is.

[0067] Thus, according to a further embodiment, the enzymatic treatment of the raw fibrous cellulosic material is carried out in the presence of a dense gas. Such gas preferably comprises sulfur hexafluoride and / or sulfur dioxide. The dense gas may have a concentration of up to 5% by weight relative to the total volume of the reactor in which the enzymatic treatment is carried out. Under normal conditions, the density of sulfur hexafluoride is 6.2 kg / m 3 and the density of sulfur dioxide is 2.9 kg / m 3 It is.

[0068] Preferably, the raw fibrous cellulosic material during the enzyme treatment is maintained at a pH between 5 and 9 and / or a temperature between 40° C. and 70° C. to improve the enzyme treatment.

[0069] It has also been proposed to carry out the enzymatic treatment in a stirrer, preferably stirring the raw fibrous cellulosic material for the entire or nearly the entire period of a particular period, which is suggested to be between 15 and 60 minutes.

[0070] Once the enzyme treatment is complete, the treated cellulosic material is transferred from the agitator to a dryer and optionally stored in an intermediate vessel.

[0071] The enzyme is preferably liquid or dissolved in a liquid and is added to the raw fibrous cellulosic material by spraying. This method ensures maximum distribution of the enzyme and requires minimal addition of water to the raw fibrous cellulosic material. The spray can, for example, be produced on the top surface of the raw fibrous cellulosic material contained in the agitator while the agitator is running, ensuring constant renewal of the material exposed to the top surface to receive the enzyme.

[0072] The concentration of the enzyme on the sprayed liquid is optimized to ensure that after all the required enzyme has been added to the raw fibrous cellulosic material, the moisture content of the final mixture remains within defined parameters.

[0073] The added enzymes are preferably selected to lubricate the fibers, remove radicals from the exterior of the fibers and increase the specific surface area of ​​the fibers. These effects can be obtained, for example, by different combinations of the following enzymes: xylanases, laccases, cellulases and / or combinations thereof.

[0074] Depending on the specific composition of the raw cellulosic material and the characteristics of the cellulose fibers therein, variability in the enzymes added can be expected, with the enzyme composition being adapted accordingly.

[0075] Optimization of the enzyme mixture (or cocktail) may be automated, for example, by computational algorithms based on statistics derived from a database linking the raw cellulosic material, the enzymes used and the quality control results obtained.

[0076] If variations of raw cellulosic materials according to the invention require different enzyme cocktails, each of those types of raw cellulosic materials can be treated specifically, i.e. the best combination of enzymes can be matched to the particular raw cellulosic material to be treated by the method according to the invention.

[0077] It is believed that cellulases defibrillate cellulose fibers and increase their specific surface area, hemicellulases attack various components of hemicellulose, loosening cellulose fiber bundles and increasing cellulase access to the fibers, xylanases cleanse the fiber surface from impurities and degrade xylan groups, and laccases bleach and soften the fibers. Although specific enzymes are mentioned, the skilled artisan may identify other enzymes that perform the same functions on cellulose fibers.

[0078] According to a further embodiment, the composition of the raw fibrous cellulosic material introduced into the mixer is analyzed and the proportions of different enzymes added are adjusted depending on the results of said analysis. Depending on their origin, raw fibrous cellulosic materials have different compositions and require different amounts of different enzymes to achieve the desired result.

[0079] Preferably, after the drying process, the dried cellulosic material has a moisture content of less than 20%. This low moisture content allows for storage of the dried cellulosic material without the need for special measures beyond keeping the dried cellulosic material clean and dry until its use is required.

[0080] The treated cellulosic material can be screened and separated into different fractions according to fiber size. This can be done during the drying step, which can be done in a trommel screen, or after the drying step, where the drying and screening are done on different successive devices, the dryer and the screener.

[0081] The screening process allows the separation of the inorganic fraction from the rest of the material and further allows the use of said inorganic fraction in the preparation of a product (or article), for example in the outer layer (or surface) of a panel. The increase in the inorganic content at the surface of the panel face improves the dimensional stability and resistance to deformation, i.e. the product obtained may exhibit characteristics that solve the bending problems associated with panels, especially fiber-based panels, in conditions of humidity and temperature changes.

[0082] The dried cellulosic material may be compressed and heated in a product forming machine, such as in a mold, press, or between drums, to produce a rigid cellulosic product.

[0083] It has also been proposed to deposit different cellulosic material fractions having different fiber lengths in overlapping layers in a mold, press, or conveyor passing between drums to produce a rigid layered cellulosic product.

[0084] The method of the present invention also proposes mixing additives which may comprise adhesives, or alternatively additives which do not comprise adhesives, with at least one of the cellulose material sections constituting the rigid layered cellulose product prior to overlapping of said different cellulose material fractions.

[0085] The additive or adhesive-free additive is different from additives or adhesive-free additives that are not present in and / or mixed with other cellulosic material fractions that make up the same rigid layered cellulose product.

[0086] The presence of an adhesive on the additive is not required as it produces a sufficient binding effect by itself when the treated cellulosic material is dried and compressed, although the use of an adhesive may improve the resistance or other properties of the resulting cellulosic product.

[0087] Said additive or additives without adhesives may be in solid or powder form and can be mixed with the cellulosic material fraction in its dry form to avoid its dissolution and therefore be more effective.

[0088] Said additive or additives without adhesives may be in liquid form, for example dissolved in water or an organic solvent, and subsequently added to the cellulosic material fraction, for example by spraying.

[0089] One of the most common problems faced by panel-like products made of cellulose fibers obtained in a dry forming process is moisture resistance. It is known in the art that the addition process of the product (or products) described in this application is carried out on a dry material by spraying the additive on the surface. This means that most of the fibers are not impregnated with the additive, which provides, for example, bending strength among other properties. In the present invention, the raw cellulose material is treated by reducing the consistency of the additive (i.e. increasing the concentration of the additive) when sprayed on the raw cellulose material. The additive may be in a solvent such as water or in a non-flammable solvent with a vapor pressure of less than 700 mmHg. The objective is not to increase the proportion of volatile solvents with high vapor pressures that may interfere with the panel forming stage at pressure and temperature, but to improve the dispersion ability of the active ingredients of the additive on the raw cellulose material.

[0090] Furthermore, the use of additives based on resins such as urea formaldehyde (UF) or phenol formaldehyde (PF) is known in the art. Resins are mainly used to provide good mechanical properties to the material. In the present invention, such resins are not used. Preferably, the additive according to the present invention does not contain any kind of resin. At least 20% of the mechanical resistance exhibited by the resulting cellulosic material is provided by the bonds formed between the cellulosic fibers.

[0091] In any case, since the cellulosic material fraction is dry, no filtration step is required and therefore no water containing lost additives is discarded. Thus, all additives mixed with the cellulosic material fraction are incorporated into the layered rigid cellulose product, eliminating additive loss and preventing additive-containing sewage runoff.

[0092] A second aspect of the invention is directed to an enzyme processing system adapted to carry out the above method. The proposed system comprises: an enzyme applicator configured to apply an enzyme to the raw fibrous cellulosic material; an agitator including an active mixing element configured to mix the raw fibrous cellulosic material with the enzyme, and an agitator outlet; a dryer comprising a heater and a dryer outlet, said dryer being fed through said agitator outlet.

[0093] An enzyme applicator is a device that dispenses a controlled amount of enzyme onto a predetermined volume of raw fibrous cellulosic material, such as a batch of raw fibrous cellulosic material.

[0094] According to an optional embodiment, the enzyme applicator is a spray feed from one or several enzyme deposits.

[0095] The agitator is a vessel in which the raw fibrous cellulosic material is agitated to uniformly mix with the enzymes, which is generated by active stirring elements contained in the agitator, e.g., rotating blades movable at a speed controlled by a control unit.

[0096] A dryer is a vessel into which material is introduced and heated by a heater to produce its drying. Preferably, the dryer includes a blower to blow heated air into the vessel, and an agitation means to move the material being dried.

[0097] In a preferred embodiment, the dryer is a hollow drum that rotates about a horizontal axis, creating a tumbling of the material to be dried, and a blower creates circulation of heated air through the vessel.

[0098] The system further comprises the following features: a screener connected to or integrated into the dryer outlet, configured to screen different fiber sizes to produce different fractions of the dried fibrous cellulosic material; - a product forming machine including a conveyor passing between dies, presses or compression drums; a dosing device configured to deposit several overlapping layers of different fractions of the dry processed cellulosic material onto a product former.

[0099] The screener (or sifter) separates the material dried on the dryer into different fractions according to the size of its fibers. The screener can be, for example, a trommel screen.

[0100] The screener can be integrated into the dryer outlet, for example by using different mesh sizes built into the dryer wall, or it can be a separate screener device fed from the dryer outlet.

[0101] Preferably, the dryer and screener are a single trommel screener, although the use of successive dryers and screeners is also contemplated, with the dryer including an agitation device to avoid agglomeration of the treated fibrous cellulosic material during the drying operation.

[0102] The product former is where the layered rigid cellulosic product is formed using compression applied by heat from, for example, a press, die, or compression drum, and a heater.

[0103] Overlapping layers of different fractions of the dry processed cellulosic material are deposited on a product former using a dosing device that provides layers of controlled thicknesses of each fraction of material stacked one on top of the other according to a predetermined design of the product prior to compression and application of heat.

[0104] The application device may, for example, include multiple application heads, one for each fraction to be applied, each application head being fed from a pile containing one fraction of the dried cellulosic material.

[0105] According to another embodiment, multiple stacks, each containing a different fraction of the dried cellulosic material, are connected to the same application head.

[0106] Once molded, the rigid cellulose product can be cooled to ambient temperature in the mold using a cooling device to control the cooling process, thus avoiding possible deformation of the rigid cellulose product produced during the cooling process.

[0107] According to a third aspect, the present invention is directed to a rigid cellulosic product, at least a portion of which, preferably at least 20%, of cellulosic fibres originates from industrial waste.

[0108] Preferably, the rigid cellulosic product comprises a plurality of compressed overlapping layers, each layer being made from cellulosic material having a different fiber length than the fiber length of an adjacent layer, to define the layered rigid cellulosic product.

[0109] The resulting layered rigid cellulose product is made from a cellulose material that can be obtained from regenerated cellulose material and can be easily recycled. It is as hard as some woods, but is moldable. For example, it has a bending strength of more than 30 MP.

[0110] The layered rigid cellulose products have a density of more than 0.5 g / cm3 and less than 1 and exhibit other properties such as thermal insulation, sound insulation, waterproofing, dimensional stability, low density and high mechanical resistance.

[0111] The layered rigid cellulose product offers a fire behaviour corresponding to materials with As1d0 to Cs1d0 according to the EN13501 standard.

[0112] Different fiber lengths of different overlapping layers can also provide other advantages, such as creating a face layer and an optional back layer with different fiber lengths than other intermediate layers, providing different characteristics to said face and back layers, such as less paint absorption, higher resistance, a particular texture provided by the fibers if visible, or by the absence of fibers if not visible due to their size.

[0113] It should be understood that the face and back layers are the exposed layers on the face and back of the layered rigid cellulosic product.

[0114] It is also proposed that at least one of the layers may contain additives that are different from the other layers of the layered rigid cellulosic product or additives that do not contain adhesives. Furthermore, the layers may contain inorganic fillers.

[0115] This allows for functional or aesthetic distinction of different overlapping layers.

[0116] For example, one layer may be colored differently than the other layers. If the colored layer is a top layer and optionally also a back layer, the layered rigid cellulose product may obtain a colored appearance using less additives, since only the top and back layers are colored, and the thickness of these colored layers may then be reduced.

[0117] The front and back layers and / or intermediate layers may contain specific additives to improve, for example, vapor barrier properties, impact or scratch resistance, flame retardancy, and the like.

[0118] The additives may provide improved properties to individual layers of the product, and since only one or a few layers contain the additive, the concentration of the additive may be higher in those layers at reduced cost, while the remainder of the layered rigid cellulose product does not contain such additives.

[0119] The cellulosic material contained in the rigid cellulosic product may be a dried cellulosic material obtained from the process described above.

[0120] It will also be understood that any range of values ​​given may not be optimal at the extremes and may require adaptation to the invention where these extremes are applicable, and such adaptation is within the knowledge of one of ordinary skill in the art.

[0121] The terms "residue" and "waste" are used interchangeably in this invention when referring to useless or worthless material.

[0122] The term "consistency" in this invention refers to the percentage of dry raw cellulosic material (usually the residue) in the solvent (usually water).

[0123] Unless otherwise stated, the term "recycled paper" always refers to waste paper originating from high quality printed paper. "Recycled paper" is structurally understood herein as a natural polymer with a cellulose substrate, such as paper cellulose, cotton, straw, etc. In a more preferred embodiment, this waste paper has an ash content (15%-40%) and cellulose fibers (60%-85%), and contains short fiber hardwood (70%-80%) together with long fiber softwood (20%-30%).

[0124] By waste paper derived from "high quality paper" is herein understood waste paper that cannot be repulped or recycled in the paper and board industry, such as offset paper or high quality gravure, magazine paper with high concentrations of waterproof resins, and water-resistant inks.

[0125] Other features of the present invention will become apparent from the following detailed description of the embodiments. [Brief description of the drawings]

[0126] The foregoing and other advantages and features will be more fully understood from the following detailed description of the embodiments, taken in an illustrative and non-limiting manner, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows a schematic diagram of an embodiment of an enzyme treatment system adapted to apply the proposed method to obtain different fractions of a dry treated cellulosic material. [Diagram 2] FIG. 2 shows the same enzyme treatment system as shown in FIG. 1, but also includes a product forming station for producing a layered rigid cellulosic product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0127] The above and other advantages and features will be more fully understood from the following detailed description of embodiments, given in an illustrative and non-limiting manner, with reference to the accompanying drawings, in which:

[0128] The enzyme treatment system shown in FIG. 1 comprises in succession the following work stations: an agitator 20 incorporating an enzyme applicator 10, a dryer 30 incorporating a trommel screener and a screener 40.

[0129] FIG. 2 shows a similar embodiment, but further including a product former 50 fed by dosing devices 61,62,63 after the screener 40.

[0130] A plurality of paste or granular material conveyors, such as conveyor belts or screw conveyors, connect the work stations for transporting the cellulosic material through the proposed enzyme treatment system.

[0131] Raw fibrous cellulose material 1, at least part of which originates from industrial waste, such as sewage or primary sludge from the paper industry and / or waste from cellulose manufacturing industries, is fed to an agitator 20 where enzymes 11, 12, 13, 14 are added and mixed by a number of active stirring elements 21, and the enzymatic treatment takes place within the agitator 20 for a specific period of time.

[0132] In this embodiment, the active mixing elements 21 are parallel rotating blades housed in the mixer 20 .

[0133] According to this embodiment, the enzyme applicator 10 comprises a number of spray nozzles housed within an agitator 20 and faces the upper surface of the raw fibrous cellulosic material 1 contained within the agitator 20. The spray nozzles are supplied with liquid enzymes 11, 12, 13, 14 or with liquid aqueous solutions of the enzymes 11, 12, 13, 14 stored in a separated pile, and additional water may also be supplied.

[0134] The control unit 15 may, for example, adjust the amount of each enzyme 11, 12, 13, 14 added to the raw fibrous cellulosic material 1 in response to a measurement of the particular composition of the raw fibrous cellulosic material 1 being treated.

[0135] The moisture content of the raw fibrous cellulosic material 1 after the enzymes 11, 12, 13 and 14 are added should be comprised between 20% and 80% in order to obtain sufficient fluidity for stirring with a minimum moisture content. The water content of the added enzymes 11, 12, 13 and 14 can be adjusted or additional water can be added to the raw fibrous cellulosic material 1, for example through a spray nozzle.

[0136] The fluidity of the raw fibrous cellulosic material 1 and / or its moisture content are preferably measured or estimated from other measurements, for example from the energy consumption of the motor that operates the active stirring element 21 or by analysis of a sample.

[0137] The control unit 15 may automatically adjust the composition of the enzymes 11, 12, 13, 14 added to the raw fibrous cellulosic material 1, and / or the exact amount of water added to the raw fibrous cellulosic material 1, e.g. the addition of additional water, and / or the operating parameters of the agitator 20. Said operating parameters may for example be the moving speed of the active stirring element 21, and / or the heater 23 for heating the raw fibrous cellulosic material 1 contained in the agitator 20.

[0138] According to this embodiment, the mixer 20 includes an mixer inlet at its top for introducing the raw fibrous cellulose material 1 and an mixer outlet 22 at its bottom for removing the treated cellulose material, which is then transferred to the dryer 30 and screener 40.

[0139] Other alternative embodiments of the agitator 20 are also contemplated. For example, the agitator 20 can be a horizontal rotating hollow drum having an agitator inlet at one end and an agitator outlet 22 at the opposite end, with the active mixing elements being blades mounted inside the wall of the rotating drum and configured not only for mixing but also for pushing the raw fibrous cellulosic material through the agitator 20 from the agitator inlet to the agitator outlet 22 for a specified time period within the agitator 20. This embodiment allows for a continuous flow processing process of the raw fibrous cellulosic material 1 within the agitator 20.

[0140] The trommel screener described above combines a dryer 30 and a screener 40 and comprises a rotating horizontal hollow drum containing a plurality of continuous meshes integrated into the wall of the rotating horizontal hollow drum.

[0141] Treated cellulosic material having a moisture content of 20% to 80% is introduced into the trommel screener through one end and air heated by a heater 31 is blown through a rotating horizontal hollow drum while the drum rotates to reduce the moisture content to produce treated cellulosic material having a moisture content of less than 20%.

[0142] Successive meshes have increasingly larger sized holes for screening different fractions 2, 3, 4 of dried processed cellulosic material of increasingly longer fibers.

[0143] These fractions 2, 3 and 4 have a water content below 20% and therefore can be stored in a simple manner for future use or can be used immediately.

[0144] One proposed use of the dry processed cellulose material is the production of a rigid cellulose product, or more preferably a layered rigid cellulose product 9 consisting of overlapping layers 5, 6, 7 of different fractions 2, 3, 4 in a product former 60.

[0145] According to the embodiment shown in FIG. 2, the product former 60 comprises a conveyor belt that passes between two opposing compression drums.

[0146] A number of successive application heads 61, 62, 63 constituting a dosing device 61, 62, 63 face said conveyor belt. A first application head 61 deposits on the conveyor belt a front layer 5 of controlled thickness of the layered rigid cellulose product 9 to be produced, this layer being made of fractions 2 of dried cellulose material 2, 3, 4. Successive application heads 62, 63 deposit additional layers 6, 7 of controlled thickness of the layered rigid cellulose product 9 to be produced on top of the front layer 5.

[0147] As the overlapping layers 5, 6, 7 pass between the compression drums they are compressed and heated by the compression drums to produce a layered rigid cellulosic product 9, in this case a flat panel.

[0148] More complex shapes can be obtained by using a mold or press as the product former 50. In these cases, the mold, press, or application head 61, 62, 63 may be moved in a controlled manner to produce a deposition of overlapping layers covering the entire surface of the mold prior to closing of the mold and application of pressure and heat.

[0149] One or some of fractions 2, 3, 4 may be mixed with additive 8 or additive 8 without adhesive prior to its deposition on the product former 50 to provide some improved characteristics to this particular layer.

[0150] It will be appreciated that the present invention allows for the production of new rigid cellulosic products using fibers that would otherwise be unusable. For fibers derived from primary sludge from the paper industry, there is no possibility to reuse / recycle the fibers since the fibers contained in the sludge have short lengths of less than 5 mm or even less than 2 mm. Furthermore, primary sludge also contains a high percentage of inorganic charges that reduce mechanical properties. Prior to the screen embodiment of the present invention, there was no method to efficiently separate inorganic charges from cellulosic fibers to allow for the subsequent use of these fibers.

[0151] In the case of textile wastes, the reason why there is no possibility of reusing them so far is that they are different from the fibers coming from primary sludge and relate to the difficulties in disintegrating or separating the mixed composition of fibers found in textiles and then reusing these fibers in new textile production.

[0152] Some examples of cellulose products obtained with the proposed method are given below. <Example 1>

[0153] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises 75% (measured by dry weight) of industrial waste in the form of sewage sludge from the paper industry and 25% (measured by dry weight) of waste cardboard.

[0154] Once the enzyme treatment and drying steps are complete, the resulting dried cellulose material is mixed with additives and processed to produce a 13.62 mm thick plate with a density of 1.17 g / cm. 3 It is used to produce rigid cellulose products.

[0155] The additive used is an acrylic binder that is a crosslinkable low formaldehyde binder (less than 100 ppm free formaldehyde in the product) commercially available under the name PRIMAL ECO-15 R acrylic binder.

[0156] The bending strength of the resulting panel was 23.7 MPa. <Example 2>

[0157] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises 75% (measured by dry weight) of industrial waste in the form of sewage sludge from the paper industry and 25% (measured by dry weight) from waste cardboard.

[0158] Once the enzyme treatment and drying steps are complete, the resulting dried cellulose material is mixed with additives and processed to produce a 6.6 mm thick plate with a density of 1.14 g / cm. 3 It is used to produce rigid cellulose products.

[0159] The additive used is an acrylic binder that is a crosslinkable low formaldehyde binder (less than 100 ppm free formaldehyde in the product) commercially available under the name PRIMAL ECO-15 R acrylic binder.

[0160] The bending strength of the resulting panel was 16.5 MPa. <Example 3>

[0161] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises 75% (measured by dry weight) of industrial waste in the form of sewage sludge from the paper industry and 25% (measured by dry weight) of waste cardboard.

[0162] Once the enzyme treatment and drying steps are complete, the resulting dried cellulose material is mixed with additives and spun into a 13.62 mm thick plate with a density of 1.23 g / cm. 3 It is used to produce rigid cellulose products.

[0163] The additive used is an acrylic binder that is a crosslinkable low formaldehyde binder (less than 100 ppm free formaldehyde in the product) commercially available under the name PRIMAL ECO-15 R acrylic binder.

[0164] The bending strength of the resulting panel was 26.7 MPa.

[0165] It will be appreciated that the resulting panel of Example 3 has a higher molding pressure compared to the panel of Example 1, resulting in a panel with higher density and mechanical properties such as bending strength. <Example 4>

[0166] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises 75% (measured by dry weight) of industrial waste in the form of sewage sludge from the paper industry and 25% (measured by dry weight) from waste cardboard.

[0167] Once the enzyme treatment and drying steps are complete, the resulting dried treated cellulose material has a viscosity of 0.89 g / cm without any additives in the form of a 16.3 mm thick board. 3 is used to produce a rigid cellulose product. <Example 5>

[0168] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises 50% (measured by dry weight) sewage sludge from the paper industry and 50% (measured by dry weight) from waste cardboard.

[0169] Once the enzyme treatment and drying steps were completed, the resulting dried cellulose material was used without additives to produce a 8.7 mm thick plate with a density of 1.03 g / cm. 3 The Company manufactures rigid cellulose products.

[0170] The bending strength of the resulting panel was 15.8 MPa. <Example 6>

[0171] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises exclusively industrial waste in the form of sewage sludge from the paper industry.

[0172] Once the enzyme treatment and drying steps are complete, the resulting dried cellulose material is mixed with additives and used to produce a 13.79 mm thick plate with a density of 0.79 g / cm. 3 The Company manufactures rigid cellulose products.

[0173] The additive used is an ecological acrylic binder-based resin.

[0174] The bending strength of the resulting panel was 27.4 MPa. <Example 7>

[0175] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises 30% (measured by dry weight) cellulosic residues from the textile manufacturing industry and 70% (measured by dry weight) from waste cardboard.

[0176] Once the enzyme treatment and drying steps were completed, the resulting dried cellulose material was used without any additives to produce a 11 mm thick plate with a density of 0.79 g / cm 3 The Company manufactures rigid cellulose products.

[0177] The bending strength of the resulting panel was 17.6 MPa. <Example 8>

[0178] The raw fibrous cellulose material 1 introduced into the agitator 20 comprises 90% (measured by dry weight) sewage sludge from the paper industry and 10% (measured by dry weight) from the ground (or crushed or powdered) hard cellulose product of the present invention, i.e. the cellulose product is recycled and used as cellulose material in the enzyme treatment process to produce new cellulose products.

[0179] Once the enzyme treatment and drying steps are complete, the resulting dried cellulose material is mixed with additives and used to produce a 13 mm thick plate with a density of 0.98 g / cm. 3 of rigid cellulose product is produced.

[0180] The additive used is an ecological acrylic binder-based resin.

[0181] The bending strength of the resulting panel was 29.7 MPa. <Example 9>

[0182] The raw fibrous cellulose material 1 introduced into the mixer 20 comprises 100% (measured by dry weight) of the ground (or crushed or powdered) hard cellulose product of the present invention, i.e. the new cellulose product is derived entirely from recycled cellulose products.

[0183] Once the enzyme treatment and drying steps were completed, the resulting dried cellulose material was used to produce a 9.5 mm thick plate with a density of 0.96 g / cm 3 The Company manufactures rigid cellulose products.

[0184] The bending strength of the resulting panel was 18.6 MPa. <Example 10>

[0185] The raw fibrous cellulosic material 1 introduced into the mixer 20 comprises 20% (measured by dry weight) of industrial waste in the form of sewage sludge from the paper industry and 80% (measured by dry weight) from waste cardboard.

[0186] Once the enzyme treatment and drying steps were completed, the resulting dried cellulose material was used to produce a 12 mm thick plate with a density of 0.690 g / cm 3 The Company manufactures rigid cellulose products.

[0187] The bending strength of the resulting panel was 15.4 MPa.

[0188] Various parts of one embodiment of the present invention may be freely combined with other parts described in other embodiments, even if this combination is not explicitly described, provided that such combination is within the scope of the claims and that there is no harm in such combination.

[0189]

Claims

1. An enzymatic treatment method for fibrous cellulose materials, comprising: introducing a raw fibrous cellulose material (1) into a stirrer (20); subjecting the raw fibrous cellulose material (1) to an enzymatic treatment for a specific period to obtain a treated cellulose material, said enzymatic treatment including adding enzymes (11, 12, 13, 14) to the raw fibrous cellulose material and achieving a uniform distribution of said enzymes in the raw fibrous cellulose material by stirring; drying the treated cellulose material; and wherein at least a part of the raw fibrous cellulose material (1) is derived from industrial waste.

2. The enzymatic treatment method according to claim 1, wherein the raw fibrous cellulose material derived from industrial waste has fibers having one or more of an average length of less than 5 mm, preferably less than 2 mm, and / or an average width of less than 0.1 mm, and / or a mass percentage of fines exceeding 10%.

3. The enzymatic treatment method according to claim 1, wherein the industrial waste is one or more of primary sludge obtained from the paper-making industry, residues from the fiber manufacturing industry, or cellulose-based construction waste, preferably having fibers with an average length of less than 5 mm, most preferably less than 2 mm.

4. The enzymatic treatment method according to claim 1, wherein after adding the enzymes (11, 12, 13, 14), the raw fibrous cellulose material has a water content between 20% and 80% by weight based on the total amount of the raw fibrous cellulose material, and said water content is maintained within said range during the enzymatic treatment.

5. The enzymes (11, 12, 13, 14) to be added are selected to smooth the fibers, remove radicals from the outside of the fibers, and increase the specific surface area of the fibers, and / or include xylanase, laccase, cellulase, and / or combinations thereof.

6. - During the enzymatic treatment, the raw fibrous cellulose material (1) is maintained at a pH between 5 and 9 and / or a temperature within the range of 40°C to 70°C, and / or - The enzymatic treatment is carried out in the stirrer (20), and the specific period is within the range of 15 to 60 minutes, and / or - The dried cellulose material (2, 3, 4) has a water content of less than 50%, preferably less than 20%.

7. 7. The method of claim 6, wherein the dried cellulose material (2, 3, 4) is screened and separated into different fractions (2, 3, 4) according to fiber size during the drying process or by a trommel screen during the drying process or after the drying process.

8. 10. The enzyme treatment method of claim 1, wherein the dry processed cellulosic material is sieved to produce a mineral fraction that is separate from the remainder of the dry processed cellulosic material.

9. 1. A method for forming a rigid cellulosic product comprising: applying the enzyme treatment method according to any one of claims 1 to 8 to a fibrous cellulosic material; compressing the cellulosic material, preferably by one of molding, preferably injection molding, or pressing in a press or between drums, and heating to form a rigid cellulosic product.

10. 10. The method of forming a rigid cellulosic product of claim 9, wherein the method is a continuous process.

11. 10. The method of forming a rigid layered cellulose product according to claim 9, wherein different cellulosic material fractions (2, 3, 4) having different fiber lengths are deposited in overlapping layers (5, 6, 7) and compressed and heated in a product former (50) comprising a die, press or conveyor passing between compression drums to produce a rigid layered cellulose product (9).

12. 12. A method for forming a rigid layered cellulose product according to claim 11, wherein an additive (8) or adhesive-free additive (8) is mixed with at least one of the cellulosic material fractions (2, 3, 4) constituting the rigid layered cellulose product (9), and the additive (8) or adhesive-free additive (8) is not present in the other cellulosic material fractions (2, 3, 4) constituting the same rigid layered cellulose product (9), or the additive (8) or adhesive-free additive (8) is present in the other cellulosic material fractions (2, 3, 4) constituting the same rigid layered cellulose product (9) and is the same or different from the additive (8) or adhesive-free additive (8) mixed with the other cellulosic material fractions (2, 3, 4) constituting the same rigid layered cellulose product (9).

13. A product forming machine (50) including a conveyor on which different cellulose material fractions are deposited in overlapping layers and passed between a mold, a press, or a compression drum, is compressed and heated to produce a rigid layered cellulose product (9), wherein at least one of the overlapping layers defining the outer surface layer of the rigid cellulose product contains at least a portion of the inorganic fraction. A method of forming the rigid cellulose product according to claim 9.

14. A rigid cellulose product comprising a compressed enzymatically treated fibrous cellulose material derived from industrial waste, preferably at least 20% of the enzymatically treated fibrous cellulose material being derived from industrial waste.

15. A rigid cellulose product according to claim 14, comprising a plurality of compressed overlapping layers (5, 6, 7), each layer (5, 6, 7) being made of a cellulose material having a different fiber length from an adjacent layer (5, 6, 7), preferably at least one of the layers (5, 6, 7) containing an additive (8) or an additive (8) free of an adhesive different from an additive (8) or an adhesive contained in another layer (5, 6, 7), preferably at least one of the layers (5, 6, 7) having a different density from another layer (5, 6, 7).

16. A rigid cellulose product according to claim 14, wherein the enzymatically treated fibrous cellulose material is produced by the method according to claim 1.

17. A rigid cellulose product according to claim 14, wherein the enzymatically treated fibrous cellulose material is substantially lignin-free.

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