Non-weathering, flame-proof composite material

Abstract

The invention relates to a method for producing a composite material, using an alkaline binder containing alkali silicate glass; an organic gelling agent and SiO2 particles; and a biological carrier material. The composite material is particularly stable, flame-proof and also suitable for the exterior.

Description

[0001] Weather-resistant, flame-resistant composite material Description Field of the invention The invention relates to a method for producing a composite material and to a produced composite material and its use. State of the art Wood chip materials are composite materials which are produced from wood chips and a binder under pressure and heat. There are many variations, particularly with regard to chip properties and chip orientation, as well as numerous production processes using different binder systems, whereby wood chip materials can be produced as compact materials for a wide range of applications and a wide range of products. Essentially, organic binders based on phenolic and aminoplast resins are used, and more recently, those based on polyurethane resins.The disadvantage here is that the resins mentioned can release harmful formaldehyde during use of the chipboard, and that both the wood chips and the binding agents are flammable due to their organic nature. To enable the use of such composite materials, for example in the construction sector, inorganic additives are added that produce a flame-retardant effect. These include, in particular, borates and phosphates, but also tannins, which react in the event of a fire to form more highly condensed products, which in turn shield the surface of the component from further oxygen ingress. An additional oxygen barrier effect is achieved, for example, by incorporating layered silicate fillers, such as vermiculite. For particularly demanding fire protection requirements, however, the flame-retardant effect achievable with such composite materials is not sufficient to meet the corresponding standards.Even the use of expandable matrices with thermally insulating foam structures in the event of a fire (intumescent materials) using hydroxymethyl cellulose, combinations of dicyandiamide and boric acid, and layers containing ammonium phosphate does not bring about a satisfactory improvement in the situation. In addition, the release of formaldehyde from the matrix material remains an unsolved problem, despite all efforts to improve fire protection with these material approaches. Inorganic, non-combustible binders are also used in technology. However, binders based on MgCl2 / MgO / polyethyleneimine or gypsum lead to boards with low mechanical strength. Other inorganic binder phases in chipboard or fiberboard are cements, which, however, are also heavy and cannot be easily machined.In addition, cements used as binders have a very poor carbon footprint, as CO2 is released during the manufacturing process both during the temperature generation in the kiln (1400 °C) and through the thermal separation of CO2 from the CaCO3 precursor. Water-repellent substances, fungicides, or insecticides are also frequently used to make the panels resistant to weathering and other natural influences. For example, stilbenes, quinones, or pyran derivatives are used to improve termite resistance, or thallium chloride, fluorosilicic acid, and potassium arsenite are used as contact insecticides against house longhorn beetle larvae. Sodium silicate-based binders would be an alternative in terms of achievable flame retardancy combined with weight savings and a better carbon footprint, but have so far not achieved any significance for wood particle materials due to their lack of hydrolysis resistance and high brittleness.According to DIN EN 312, particle boards are divided into different categories (P1: particle boards for general purposes; P2: particle boards for interior fittings, including furniture, for use in dry areas; P3: particle boards for non-load-bearing purposes for use in humid areas; P4: particle boards for load-bearing purposes in dry areas; P5: particle boards for load-bearing purposes in humid areas; P6: heavy-duty particle boards for load-bearing purposes in dry areas; P7: heavy-duty particle boards for load-bearing purposes in humid areas). In order to generally improve the flexibility and handling of water glasses, they have been mixed with hydrogel-forming organic polymers (e.g., galactomannans) in the past. Halliburton [US3390723] discloses a binder made of sodium water glass and galactomannan, which is used as an aid for the in-situ establishment of diversions for fluid flows in rock formations.Its use in wood chipboard materials is not described. The German Fire Protection Industry Association [DE3439929A1] describes a translucent fire protection compound for the manufacture of fire protection components and for the coating of components and structural parts made of sodium water glass, an organic binder (e.g., galactomannan) with a solid consistency. For this purpose, the water glass is mixed with a gel-forming acid (e.g., citric acid, B(OH)3, H3PO4) and water to form a hydrogel, along with a preservative (Cu-II salt), and then solidified with the organic binder to form the translucent solid fire protection compound. The gel-forming acid accelerates the reaction, which, although it contributes to the transparency of the claimed reaction product, would be unsuitable for the manufacture of wood chipboard materials.Seamans [US4212920A] describes a flame-retardant composition made of sodium water glass, gum arabic, and epoxy resin or latex, which, in combination with cellulose fibers, can be used to produce a sheet-like product using the compression molding process. The proportional addition of up to 20% epoxy resin or latex serves to improve the moisture resistance of the binder composition. The application [WO2015010690A2] describes a flexible fire-protection compound containing inorganic gelling agents and hydrogel-forming biomacromolecules (= galactomannans). The use of the galactomannans serves to achieve dimensional stability and transportability through the formation of an organic framework structure that stabilizes the inorganic gelling agents. The fire-protection compound is processed by casting, rolling, or calendering and is used as an interlayer between two glass panes.A special moisture resistance of the composition is not required here, as the glass panes are sealed at the edges. Due to the lack of moisture resistance, the described composition cannot be used effectively as a binder for the production of wood particle materials for use in the construction sector, as the resulting workpieces would not be weather-resistant. There is also a need for weather-resistant, fire-resistant, formaldehyde-free composite materials, especially wood particle materials, which can be obtained at least partially from local resources and have a low carbon footprint. In addition, the composite materials should also be resistant to insects such as termites. Furthermore, production should also be possible using simple means.Object The object of the invention is to provide a method for producing a weather-resistant, preferably fire-resistant, composite material, as well as the composite material and its use. Solution This object is achieved by the inventions having the features of the independent claims. Advantageous developments of the inventions are characterized in the subclaims. The wording of all claims is hereby incorporated by reference into the content of this description. The inventions also encompass all reasonable and, in particular, all mentioned combinations of independent and / or dependent claims.The object is achieved by a method for producing a composite material, comprising the following steps: a) Providing an alkaline composition comprising at least one alkali silicate water glass and at least one organic gelling agent; b) Adding at least one type of SiO2 particle; c) Combining the composition with at least one biological carrier material, such as fibers, chips, or nonwovens from biological sources; d) Compacting the resulting composite under pressure and at elevated temperature in a mold; e) After demolding, drying the composite to obtain the composite material. Individual process steps are described in more detail below. The steps do not necessarily have to be carried out in the specified order, and the process to be described may also comprise further, unspecified steps.An alkaline composition comprising at least one alkali silicate waterglass and at least one organic gelling agent is provided. The alkali silicate waterglass is preferably a sodium, potassium, and / or lithium silicate waterglass, particularly preferably a sodium and / or potassium silicate waterglass, particularly preferably a potassium silicate waterglass. The waterglass is preferably a waterglass with a high concentration, high viscosity, and high solids content. Preference is given to a waterglass with a solids content of more than 40% by weight, preferably 40% to 70% by weight, in particular 40% to 60% by weight. A further characteristic of waterglass is the molar ratio of SiO2 and alkali oxide (M2O) in the waterglass. This molar ratio SiO2:M2O is referred to as the modulus. The waterglass preferably has a molar SiO2 / M2O ratio (modulus) of 0.8 to 4. The water glass is dissolved in the composition.The water glass used is preferably liquid water glass. If necessary, only water is preferably added to the composition as a solvent. The composition is an alkaline composition. Its pH is preferably above 12, in particular above 13. The composition preferably comprises at least one alkali hydroxide, preferably LiOH, KOH and / or NaOH, preferably KOH and / or NaOH, particularly preferably KOH. The alkali hydroxide and the alkali silicate water glass preferably contain the same alkali metal, e.g., a potassium silicate water glass and KOH. The alkali hydroxide activates the SiO2 particles, in particular the ground sand. The composition also comprises at least one organic gelling agent. The organic gelling agent is preferably a polysaccharide, which may also be chemically modified. Suitable polysaccharides are preferably base-stable.The organic gelling agent is preferably selected from xanthan gum, gum arabic, guar gum, galactomannans, or mixtures thereof, whereby the gelling agent may be chemically modified. Galactomannans are preferred. The ratio between galactose and mannose can be 1:1 to 1:5, preferably 1:2. Examples of chemical modifications are hydroxyethyl, hydroxypropyl, carboxyl, carboxylalkyl ether groups (e.g., carboxymethyl ether), and combinations of various chemical modifications in a polysaccharide. In a preferred embodiment of the invention, the alkali water glass and alkali hydroxide are first combined before the organic gelling agent is added. Water is preferably used as a solvent in the composition. This can be added to adjust the solids content and / or viscosity of the composition, or is predetermined by the water glass solution, so that no additional solvent is added.The composition is preferably stirred for at least 3 hours, preferably at least 10 hours, particularly preferably at least 20 hours. Preference is given to 3 to 96 hours, particularly preferably 10 to 96 hours, in particular 20 to 48 hours. In a preferred embodiment, stirring is carried out at a temperature between 10 and 40°C, in particular 15 to 25°C. This is preferably ambient temperature. Stirring is preferably carried out in a closed vessel. The resulting composition (precursor composition) is storable and can be stored until further processing. During storage, the gelling agent may swell. However, the composition remains activatable and suitable for processing. The composition is preferably storable for at least 6 months, in particular at least 1 year. At least one type of SiO2 particle is added to the composition.Preferably, these are SiO2 particles which comprise particles in the micrometer range as their main constituent. Preference is given to SiO2 particles having an average particle size of 0.05 µm to 70 µm, preferably 0.2 µm to 30 µm. Preference is given to particles with a particle distribution of d90 of less than 30 µm. Preference is given to particles with a particle distribution of d. 90 of less than 30 µm and d 10 below 6 µm. Particles with a particle distribution of d are particularly preferred. 90 between 2 µm and 30 µm and d 10 of between 0.1 and 6 µm, in particular particles with a particle distribution of d90 of between 10 µm and 30 µm and d10 of between 0.2 and 2 µm. Particularly preferred are particles with a d 90 of between 2 µm and 30 µm, d 50 of between 1 and 8 µm and d 10 of between 0.1 and 6 µm, preferably with a particle distribution of d 90 of between 10 µm and 30 µm, d50 of between 2 and 5 µm and d10 of between 0.2 and 2 µm. The distributions are determined as powder and as an aqueous dispersion by laser diffraction; determination in an aqueous dispersion is preferred. In a preferred embodiment of the invention, the particles comprise ground sand; they are preferably ground sand, which has preferably been ground to the above particle distribution. The specific surface area of ​​the particles is preferably 1 to 5 m 2 / g, especially 1.5 to 3.5 m 2 / g (determined by BET). The SiO2 content is preferably above 90 wt.%, in particular above 95 wt.%, very particularly above 99 wt.% (determined by ICP-OES (after microwave digestion, Horiba Jobin Yvon Ultima2, digestion in 1 ml of 65% HNO3, 3 ml of 35% HCl, 1 ml of 50% HF and 2 ml of ultrapure water. The hydrolysate is analyzed for mineral content by ICP-OES. Quantitative determination is carried out using standard calibration curves)). The resulting composition is preferably homogenized with stirring. In one embodiment of the invention, pyrogenic silica is added alternatively or in addition to the particles described above. This can have a smaller particle distribution. For example, the pyrogenic silica can comprise particles with a size of less than 1 µm. Examples of pyrogenic silica include Aerosil with a particle diameter of 200-300 nm.The fumed silica can shorten the drying time until complete water resistance is achieved. However, the pot life of the activated composition is usually also reduced. It is also possible, but not preferred, to add further inorganic substances, for example up to 10 wt.%. Inorganic substances with an SiO2 content of over 50 wt.% are preferred. Examples of this would be quartz, phyllosilicates such as mica, and wollastonite. Further examples are shown in Table 1. The resulting activated composition is preferably processed into a paste. The viscosity can be adjusted for the addition of solvent according to the desired processing. The composition preferably has a pot life of up to 48 hours. The pot life can be adjusted, in particular, by the size distribution of the SiO2 particles. At temperatures below 10°C or when stored in a closed container, the pot life can be extended to up to 8 days.In a preferred embodiment, the weight ratio between alkali water glass and SiO2 particles is 30:70 to 70:30, preferably 40:60 to 60:40. In a preferred embodiment of the invention, the activated composition comprises 35 to 60 wt.% alkali water glass, 1.5 to 5 wt.% at least one alkali hydroxide, 0.3 to 2.5 wt.% at least one gelling agent, and 30 to 60 wt.% at least one type of SiO2 particle. In a particularly preferred embodiment of the invention, the activated composition comprises 40 to 55 wt.% alkali water glass, 1.5 to 5 wt.% at least one alkali hydroxide, 0.3 to 1.1 wt.% at least one gelling agent, and 30 to 55 wt.% at least one type of SiO2 particle. An example of a composition would be 49.3 wt.% alkali water glass, 4 wt.% at least one alkali hydroxide, 0.8 wt.% gelling agent, and 45.9 wt.% ground sand. The wt.% preferably refers to the initial weight of the alkali hydroxide.Preferably, it is alkali hydroxide with at least 75 wt.% alkali hydroxide, in particular at least 80 wt.%, very particularly at least 85 wt.%, based on the initial weight. For example, potassium hydroxide is usually available as a solid with a KOH content of 85 wt.% and 15 wt.% water. When calculating the M2O or K2O content, only the MOH or KOH is taken into account. Surprisingly, it was found that the alkaline environment of the binder in combination with the SiO2 particles and the water glass forms a particularly stable binder. It is assumed that μ-scale SiO2 particles such as ground sand in particular act as reactive fillers, since in the alkaline environment the surface of the particles is dissolved and partially converted into alkali silicates on the surface.Their filler character is retained, particularly with a multimodal and / or broad size distribution, resulting in extremely dense packing of the dissolved particles after compaction and curing. Curing is particularly supported by increasing the SiO2 / M2O modulus of the binder, in particular to values ​​above 8, especially above 9, and the additional SiO2 input by the particles. Due to the good bond, composite materials, in particular wood-based materials, with very good mechanical and water-resistant or weather-resistant properties can be obtained. The precursor composition and the activated composition preferably contain no other crosslinking agents such as boric acid or refractory components such as aluminum salts. Preferably, no other solvents other than water are added.Furthermore, apart from the gelling agent, the precursor composition and the composition do not comprise any polyols such as glycol, glycerol, or polyethylene glycol diglycidyl ether. Therefore, such organic crosslinkers are preferably not used for polysaccharide gel. The activated composition preferably has an SiO2 / M2O modulus of more than 8, in particular more than 9. Preference is given to an SiO2 / K2O modulus of 8 to 16, preferably 9 to 14, very particularly 9 to 10. The composition preferably does not comprise any further hydroxides, in particular alkaline earth hydroxides such as Ca(OH)2. The composition preferably does not comprise organosilanes or modified colloidal nanoparticles. The activated composition can optionally contain up to 2% by weight, in particular up to 1% by weight, of additives which particularly facilitate processing, for example thixotropic additives upon dilution if the composition is to be sprayed on.An example of such an additive is microfibrillated cellulose (MFC). The activated composition is combined or contacted with biological carrier material, such as fibers, chips, or nonwovens from biological sources. This can be done by impregnation, soaking, coating, spray coating, or other application methods. Multiple layers of wood fibers and / or wood chips, as well as activated compositions, can also be applied. The biological carrier material is preferably obtained from a renewable raw material. The biological carrier materials, such as fibers, chips, or nonwovens from biological sources, can be obtained from any plant or wood suitable for composite materials. The biological filler is preferably obtained from rice husks, rice husks, reed, sisal, hemp, cotton, kenaf, bamboo, flax, palm trees such as nipal or coconut, wood, and / or sugarcane.Examples of woods are conifers such as pine, spruce, fir; linden, birch, pine, walnut, oak, acacia, or similar. Local sources are particularly preferred, which are also preferable with regard to the CO2 footprint. The carrier material, in particular wood, does not need to be dried. The carrier material is preferably in the form of chips or fleece. The biological carrier material preferably has a SiO2 content of > 1 wt.%, in particular > 2 wt.%, which supports the bonding of the activated composition to the carrier material. This is the case, for example, with acacia or rice straw, which have a content of over 5 wt.%. The wood fibers and / or wood chips are preferably produced by machining or hammer-milling solid wood or wood waste from the sawmill industry. For the production of particleboard, the material is usually sieved, with a sieve fraction being characterized according to the mesh size.Those skilled in the art of chipboard production know that the properties and appearance of the composite material can be influenced by choosing the size distribution. Different layers with fibers and / or chips of different sizes can also be applied, for example to obtain finer cover layers. These are preferably fibers and / or chips, in particular wood fibers and / or wood chips, of at least one sieve fraction with a range selected from a range between 0.5 mm and 10 mm. Preferably a sieve fraction with a range of > 1.4 mm to 4 mm. For finer layers, such as cover layers, for example, the sieve fraction 1 mm to 2 mm, or 1 mm to 1.4 mm can be used. The bringing together preferably takes place in a corresponding mold that corresponds to the shape of the composite material to be obtained.The ratio between composition (binder) and the biological support material can be selected according to the composite material to be obtained. Different biological support materials, e.g. different sieve fractions, can also be used within a composite in order to obtain, for example, a different surface structure. The ratio between solid in the composition and the biological support material can be freely selected. It can be selected depending on the material to be produced. It can also depend on the surface area and / or density of the support material and / or the SiO2 particles. With a high density, less binder is required. Also, with a large surface area of ​​the biological support material, more binder is needed for wetting. Preferably, at least as much binder is used as is needed to wetting the surface of the biological support material.The ratio can therefore be chosen from a wide range. A ratio of mass of solid in the binder to carrier material by weight of 1:10 to 10:1 is preferred, preferably 1:5 to 5:1, particularly preferably 20:80 to 80:16 is preferred. By reference to the mass, the ratios correspond in principle to the ratios of binder and carrier material in the composite material. A weight ratio of 0.5:1 to 5:1 is preferred. For example, a ratio of 1:1 to 4:1, in particular 2.89:1 to 3.29:1, based on the mass of solid in the binder to the biological carrier material for compact panels is preferred. For example, a ratio of 0.3:1 to 1:1, in particular 0.4:1 to 1:1, based on the mass of solid in the binder to the biological carrier material for lightweight panels is preferred.Depending on the biological carrier material, it may be advantageous to allow the resulting composite to mature for up to 200 hours, preferably up to 180 hours, and especially up to 150 hours, before compaction. This can be done while at rest or while stirring. This allows the materials to bond better. The resulting composite is compacted in a mold under pressure and at elevated temperature. This can be the mold in which the composite was assembled in the previous step. A temperature between 60 and 100°C is preferred, particularly preferably 80 to 90°C. The composite is compacted until sufficient strength is achieved. This is the case, for example, after at least 4 hours, and especially after 5 to 30 hours. The necessary duration and temperature can be selected for the respective application. A higher temperature also generally shortens the compaction time. The pressure used can be adjusted accordingly.The pressure is normally between 15 and 50 bar. It can be advantageous to use activated mixtures that have been stored for at least 48 hours. The increased viscosity reduces the amount of pressed-out binder. The resulting composite is demolded and dried to obtain the composite material, preferably under the influence of a CO2 source. These are preferably conditions under which carbonation of the composite material occurs. The absorption of CO2 leads to further hardening of the composite material. Carbonation within less than 240 hours is preferred, in particular less than 120 hours, and most particularly less than 48 hours. These are usually conditions with a CO2 content that is higher than the atmosphere. This can be achieved, for example, by storing the samples in glycerol carbonate or propylene carbonate solutions.In an alkaline environment, these compounds release CO2, which binds the excess hydroxide, for example, KOH, in the composite material. This can also occur at elevated temperatures. The samples can then be washed and dried. Alternatively, the composite materials can also be stored in a climate chamber together with dry ice, for example, at 20°C and 65% relative humidity. Carbonation is also possible by storage in a natural atmosphere. Storage for at least 30 days is preferred, more preferably at least 50 days. Storage at ambient temperature, in particular room temperature of 20 to 30°C, is preferred. Drying can occur at elevated temperatures, for example, 60°C to 100°C, in particular 70°C to 90°C. It is also possible to provide the composite material with additional layers, such as decorative layers, lacquer layers, or veneers.The resulting composite material according to the invention exhibits many advantageous properties. The water glass-based binder cures without cracking. The precursor composition can be stored well until use. This simplifies handling and transport. The pot life of the activated composition can be controlled. The CO2 footprint is up to four times lower than that of cement. Despite the use of water glass, high weathering and hydrolysis stability is achieved. The use of water glass makes the composite material intrinsically flame-resistant. The composite material is suitable for the highest mechanical requirements for wood-based materials, particularly particleboard, in the construction sector (indoors and outdoors). It also exhibits particular resistance to termites. Since local resources can be used as the wood source or the source of the biological carrier material, the composite material can be produced locally in a variety of ways.The SiO2 particles can also be obtained from local sand sources. This allows for easy local production of the wood-based materials. The composite material is free of formaldehyde. Preferably, no cement additives such as Ca(OH)2 are used. During drying, CO2 is even absorbed. The invention therefore also relates to a composite material produced according to the process described above. The composite material can have many different shapes. It is suitable, for example, for chipboards, furniture, doors, chairs, tables, interior furnishings, worktops, cabinets, sideboards, floor panels, terrace planks, wall elements, ceiling elements, or roof elements. The composite material preferably comprises wood fibers and / or wood chips from acacia. The invention also relates to a precursor composition obtained according to step a) of the above process.The invention also relates to the use of the precursor composition for producing a composite material. Further details and features emerge from the following description of preferred embodiments in conjunction with the subclaims. The respective features can be implemented individually or in combination with one another. The possibilities for achieving the object are not limited to the embodiments. The embodiments are shown schematically in the figures. Identical reference numerals in the individual figures designate identical or functionally equivalent elements or elements which correspond to one another in terms of their functions. In detail: Fig. 1 Dependence of the mechanical properties on the binder / fiber weight ratio; Fig. 2 Dependence of the E-modulus and the 3-point flexural strength on the age of the binder / fiber mixture.Preparation of the binder: Example 1a: Precursor composition (precursor NMC4210913) 13.15 g of potassium hydroxide (85 wt%) are dissolved with stirring in 161.73 g of van Baerle potassium water glass (SiO2 / K2O modulus: 2.93:1; density 1.42 g / ml, viscosity 40-50 mPas, approx. 41.3 wt% solids). After the solution has cooled to room temperature, 2.63 g of guar (galactomannan with a galactose / mannose ratio of 1:2) are added in small portions with vigorous stirring. After all the guar has been added, the solution exhibits a slightly increased viscosity. To further swell the guar, the mixture is stirred at low speed at room temperature for at least another 24 h. In this form, the binder precursor can be stored indefinitely. Example 1b: Activation (NMC4210913) In 177.51 g of highly viscous binder precursor, 142.93 g of ground sand (size distribution: e.g. d(10)= 0.547 µm; d(50)= 3.793 µm; d(90)= 19.642 µm and a specific surface area of ​​approx. 4.01 m) are first added.2 / g) is homogeneously distributed using a dissolver disk. Then, 7.6 g of pyrogenic silica (fumed silica: primary particle distribution approx. 200 – 300 nm) are stirred in small portions until homogeneous. This results in 328.04 g of a milky-white binder paste (solids content: approx. 58.35%). The pot life of the activated binder is approx. 12 hours. The size distribution is determined by laser diffraction. A Mastersizer 2000 from Malvern Panalytics was used for this purpose. The particle size was determined by laser diffraction for both wet and dry dispersion. A Scirocco 2000 unit was used for automated dry dispersion. The automated Hydro 2000 S wet dispersion unit was used for wet dispersion. While the dry dispersion detected fine particles up to approximately 200 nm, the wet method yielded fine particles from 350 nm onwards, but with better reproducibility across 3 measurements / sample.The size distributions for the dry process yielded values ​​of 0.547 µm (d10), 3.793 µm (d50), and 19.642 µm (d90). Values ​​determined using the wet process were 0.951 µm (d10), 3.722 (d50), and 19.982 (d90). Aqueous dispersion yielded more homogeneous data, although the dispersion of sub-µ-sized particles was apparently under-resolved due to agglomeration in the aqueous solution. The preferred values ​​refer to the wet process. Various binder compositions are listed in Table 2. Betol is another water glass. Wöllner: Betol K57M: Modulus approx. 1:1; Density 1.65 g / ml; Solids: approx. 52%; Viscosity approx. 60 mPas. MFC is used as a thixotropic additive when diluted. For KOH, the initial weight refers to KOH with an 85 wt.% KOH content.Example 1c: Production of a wood chip-based composite board. 328.04 g of binder paste (NMC4210913) are thoroughly mixed with 160 g of acacia shavings (fraction > 1.4 mm - < 4 mm). After approximately 30 minutes, the mixture is poured into a mold with a non-stick coating and homogeneously poured. The mold allows the production of a board measuring 20 x 20 x 1 cm. 3To improve the surface, a binder-chip mixture containing a finer sieve fraction of the chopped biomass can also be applied. An example composition is as follows: 72 g of activated binder paste are homogeneously mixed with 24.4 g of a chip fraction of 1–1.4 mm and 12 g of a chip fraction of 500 µm to 1 mm and applied homogeneously to the surface of the coarser-grained chip-binder mixture previously filled into the mold. The binder-chip mixture is compacted in a hot press and cured under vacuum at a temperature of 80°C for 20 hours. The demolded panels are then stored in a drying cabinet at 70 to 90°C until constant weight is reached. The ratio of binder solids to weight of acacia chips is 1.2:1. Carbonation is carried out after the weight of the composite panels has reached constant: a) in the climate chamber at 20°C and 65% rel.Humidity for 3 days under CO2 gassing using dry ice. The dry ice is replaced after 8 hours, 24 hours, 32 hours, 48 ​​hours, and 56 hours. 5 g of dry ice is stored for the 8-hour period and 10 g for the 16-hour period. b) Immersion in propylene carbonate (CO2 source) and storage in a drying cabinet at 80°C for 24 hours. The composite panels are then immersed twice in demineralized water for approximately 10 seconds at room temperature. Drying takes place overnight at 80°C in a drying cabinet. c) As an alternative to propylene carbonate from example b), glycerol carbonate (CO2 source) is used. Figure 1 shows the dependence of the mechanical properties on the binder / fiber weight ratio (binder here is the solid of binder variant NMC4210121, precursor age = 1d (= 1 day old)). The precursor was then activated with ground sand, and the acacia fibers were incorporated.After 2 hours, the molding was carried out in a hot press at 80°C for 20 hours and a pressure of 25 bar. After demolding, the mold was post-cured for 24 hours in a drying cabinet at 80°C. The flexural and transverse tensile strengths were determined after 50-55 days of natural aging. Example 2a: NMC4210121 26.3 g of potassium hydroxide (85 wt%) were dissolved with stirring in 323.46 g of van Baerle potassium water glass (SiO2 / K2O modulus: 2.93:1; density 1.42 g / ml, viscosity 40-50 mPas, approx. 41.3 wt% solids). After the solution had cooled to room temperature, 5.26 g of guar (galactomannan with a galactose / mannose ratio of 1:2) were added in small portions with vigorous stirring. After the guar has been completely added, the solution exhibits a slightly increased viscosity. To further swell the guar, the mixture is stirred at low speed at room temperature for at least another 24 hours. In this form, the binder precursor can be stored indefinitely.301.06 g of ground sand are homogeneously mixed into 355.02 g of highly viscous binder precursor using a dissolver disk. This results in 656.08 g of a cream-colored binder paste (NMC4 210121) (solids content: approx. 58.35%). Example 2b: 140.6 g of acacia fibers are homogeneously mixed with 656.08 g of binder (NMC4 210121). After a 2-hour rest period, the resulting binder / fiber mixture is poured into a mold (cavity: 200 x 200 x 20 mm). 3) and compacted into a 1 cm thick plate using a hot press at 80°C and a pressure of 25 bar. The plate is then pre-cured for 20 hours under these conditions. Final curing takes place at 80°C in a drying cabinet for 24 hours. Example 3: Hemp fleece composite: 98.2 g of potassium water glass (van Baerle) are mixed with 8.6 g of KOH while stirring and cooling in an ice bath. Then, 1.6 g of carboxymethylated guar (Ranie Chemie Produktions- und Vertriebs-GmbH: RAGUM AD type) are added to the mixture in small portions. Once the addition is complete, the ice bath is removed and the mixture is stirred overnight at room temperature. After approximately 20 hours, 89.2 g of silica sol (Levasil 50 / 50) and then 36.6 g of ground sand are added to the precursor for activation while stirring. This results in 234.2 g of activated composition (NMC4 base) with a SiO2 / K2O modulus of 12.31 and a solids content of approximately 46.4%. The binder is then coated into a hemp fleece (basis weight 1000 g / m 2) with a weight of 21.6 g is kneaded in by hand. For a homogeneous distribution of the binder in the sponge-like, absorbent hemp fleece, a corresponding excess of binder is necessary. The previously prepared binder is used in full. The binder-impregnated fleece is then pre-conditioned in an oven preheated to 40°C for 1 h. The fleece is then pre-cured in a hot press at 85°C. This presses out the excess binder. To ensure even evaporation of the residual water, the pre-cured fleece is finally cured between perforated plates for 16 h in the hot press at 80°C under vacuum. The cured hemp composite weighs 92.65 g. This corresponds to a binder-to-hemp fleece ratio of 3.29 parts by weight of cured binder to one part by weight of hemp fleece.Example 4: Lightweight panel spray application of the binder onto the fibers and subsequent composite production: 238 g of fibers are finely distributed in a tub and wetted in a thin layer with the binder NMC4-MFC (Table 2) using a spray gun (SATAjet) with a spray pressure of 1.0 bar. Once the fibers have achieved a uniform, fine wetting, the fiber layer is turned 180° and sprayed again with binder until wetting is clearly visible. The total weight of the wetted fibers is 442.6 g. 220.4 g are sealed in a separate container. The remaining 222.22 g are again finely distributed in the tub and sprayed once more with binder on both sides. The resulting wet weight is 276.8 g. This binder-fiber mixture is also stored in a separate sealed container until further processing.To produce composite panels, the two fiber-binder mixtures are each placed in a press mold lined with baking paper (20x20x approx. 3) and compacted in a hot press to a layer thickness of 1 cm at a pressure of 30 bar and then pre-cured at 85°C. After 1.5 hours, the composite is demolded and post-cured in a drying cabinet - placed in a curing rack for 40 hours at 85°C. This results in panels with a total weight of 169.29 g for panel 1 and 204.59 g for panel 2. Carbonation took place by storage in air and by absorbing CO2 from the air. The weight ratio of fiber to binder (cured) is: Panel 1: approx. 2.33 F to 1 B Panel 2: approx.1.4 F to 1 B The panels were tested using the following methods: Bending tests: (EN 310, classification EN 312), Young's modulus, maximum stress Transverse tensile strength: (EN 319, classification EN 312) Dry and after boiling test EN 1087-1 (90 min 25°C -> 100°C, 120 min @ 100°C) Water storage: (EN 317: thickness swelling, EN 321: moisture resistance by cycle test, EN 1087-1: boiling test) Depending on the specimen, a modulus of elasticity of 2.2 GPa (classification P2 according to EN 312) to 4.4 GPa (P7) could be achieved in the flexural test. The flexural strength was 11 MPa (P1) to 20 MPa (P6). In the transverse tensile test according to EN 319, a strength of 1.2 MPa to 3.6 MPa (P7) was achieved. Even after a boiling test in water (90 min. at 25 °C →). 100 °C; 120 min. 100 °C), a strength of 0.15 MPa to 0.35 MPa was still measured. Samples were also stored in water at 20 °C for 24 hours. Panels made from the inventive composite material with acacia shavings showed only a weight increase of 0 to 4% and an increase in thickness of 0 to 3%. Due to the use of water glass and SiO2 particles, the composite material exhibits good fire resistance. At high temperatures, a glass foam forms, which thermally insulates and prevents the material from burning. A manufactured panel could be directly exposed to a flame at a temperature of over 1000 °C for 1 hour without the panel igniting or being pierced. The resulting composite material shows no signs of termite infestation even after 6 months when stored in a meadow – within the range of termites near a termite mound.Figure 2 shows the dependence of the Young's modulus and the 3-point flexural strength on the age of the binder / fiber mixture. The binder precursor NMC4, which was 23 days old, was used for production. After 5 to 6 days of aging of the binder / fiber mixture, a maximum in flexural strength and Young's modulus is reached (production parameters: 1.5 h in a press at 40 bar and 80 °C; 75.1 wt.% based on the solids in the binder content, NMC4 as the precursor). Table 3 shows the dependence of the composite properties on the age of the storable binder precursor in days (d): 1d, 4d, 7d, 15d, 16d, 21d, 23d. MFC stands for additive with microfibrillated cellulose. The storage time of the produced composites was between 1.5 and 2 months at room temperature. The test specimens were also subjected to accelerated carbonation according to at least one of the above variants.After 2-3 months, the swelling tests were carried out, followed by the cooking tests after drying and conditioning until constant weight.

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Claims

Claims 1. A method for producing a composite material comprising the following steps: a) providing an alkaline composition comprising at least one alkali silicate water glass and at least one organic gelling agent; b) adding at least one type of SiO2 particles; c) combining the composition with at least one biological support material, such as fibers, chips, or nonwovens from biological sources; d) compacting the resulting composite under pressure and elevated temperature in a mold; e) after demolding, drying the composite to obtain the composite material.

2. A method according to the preceding claim, characterized in that the organic gelling agent is a polysaccharide.

3. A method according to any of the preceding claims, characterized in that the alkaline composition comprises at least one alkali hydroxide. 4.Method according to one of the preceding claims, characterized in that the organic gelling agent is selected from xanthan gum, gum arabic, guarana, galactomannans or mixtures thereof, wherein the gelling agent may be chemically modified.

5. A method according to any one of the preceding claims, characterized in that the SiO2 particles comprise ground sand.

6. A composite material obtained according to the method according to any one of claims 1 to 5.

7. A precursor composition obtained from step a) of the method according to any one of claims 1 to 4.

8. Use of the precursor composition according to claim 7 for the production of a composite material.

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