Modified biochar and polymer-based shaped objects and methods for producing same

Abstract

The subject of the present invention is a method for producing shaped objects for construction applications, comprising the steps of (a) providing biochar in particulate form that has been subjected to an oxidation reaction, (b) coupling the biochar with a silane coupling agent, (c) mixing the biochar with a polymer, and (d) molding the mixture. The present invention also relates to the shaped objects and construction materials obtained by the method, as well as to the biochar material.

Description

[Technical Field]

[0001] The present invention relates to a method for producing shaped objects for construction applications based on biochar and polymers. The present invention also relates to shaped objects, construction materials and biochar materials in particulate form. [Background technology]

[0002] Currently, various approaches to controlling the carbon dioxide content in the atmosphere are being proposed and investigated. One of the most relevant approaches is to reduce the carbon dioxide content in the atmosphere by carbon (carbon dioxide) sequestration and storage. For such an approach, it is important to provide functional materials that are valuable and highly acceptable to users, and that are suitable for the efficient storage of large amounts of carbon. Construction materials, such as building materials, are particularly relevant in this regard, since the construction sector is responsible for a large portion of global carbon dioxide emissions. Construction materials are also used in large quantities and have the potential to store large amounts of carbon over long periods of time.

[0003] Biochar (biochar) is produced by pyrolysis, the partial thermal degradation of biomass in an oxygen-controlled atmosphere. Biochar is widely used in agriculture to reduce stormwater runoff and increase soil fertility and crop yields. Because biochar is based on carbon from the atmosphere, it may be an interesting material for carbon sequestration and storage. Compared to other carbon-storing organic matter, such as carbohydrates, biochar exhibits high recalcitrance, which prevents the stored carbon from re-entering the atmosphere after decomposition. As demonstrated by a growing body of data, biochar can potentially remain stable for hundreds of years under normal environmental conditions.

[0004] To date, the use of biochar for permanent carbon storage in functional materials has been limited due to various drawbacks of biochar-based materials. The inclusion of biochar as a filler in composite materials has been proposed in the art. However, biochar-based composites are often unsuitable for construction applications due to undesirable properties such as low mechanical, thermal, or chemical resilience and high water absorption.

[0005] To improve the stability of polymer composites, the art has proposed modifying the surface of carbon-based fillers with, for example, coupling agents. Pongdong et al., "Influence of Filler from a Renewable Resource and Silane Coupling Agent on the Properties of Epoxidized Natural Rubber Vulcanizates," 2015, J. Chem., Article ID No. 796459, discloses a composite based on epoxidized natural rubber and rice husk ash filler. The composite is produced by adding a mixture of ash and coupling agent to a rubber compounding formulation and curing the formulation. The coupling agent is bis(triethoxysilylpropyl) tetrasulfide, which contains sulfur and can therefore support the vulcanization reaction. The disadvantages of this system are that it is relatively complex and requires a specific curing reaction. The epoxidized rubber and sulfur-containing coupling agent are relatively complex and expensive, so the composite is not suitable for large-scale application. Furthermore, the vulcanized rubber is elastic and has poor thermal stability. There is no suggestion of using this composite for construction applications or permanent carbon storage.

[0006] US Patent Application Publication No. 2014 / 0329976 A1 relates to composites based on polymers and carbon-based fillers containing hydrolyzable silanes with cleavable aziridine groups. In the examples, multi-walled carbon nanotubes are coated with cleavable silane compounds in an ethanol-based solution. However, aziridine compounds can already decompose under mild conditions, making their preparation and handling relatively complicated. Therefore, such fillers and coatings are not suitable for large-scale applications. Use for construction purposes or permanent carbon storage is not disclosed.

[0007] CN112143211A relates to a composite material based on polyurethane elastomer, charcoal fiber, and inorganic filler. The composite material is prepared by mixing all components with a silane coupling agent, compounding, and extruding. No use for construction applications is disclosed, and the properties of such materials could still be improved.

[0008] There is a continuing need for improved and efficient products and methods that overcome the problems of the prior art outlined above. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent Application Publication No. 2014 / 0329976A1 [Patent Document 2] Chinese Patent Application Publication No. 112143211A [Non-patent literature]

[0010] [Non-Patent Document 1] Pongdong et al., "Influence of Filler from a Renewable Resource and Silane Coupling Agent on the Properties of Epoxidized Natural Rubber Vulcanizates," 2015, J. Chem., Article Identification Number 796459 Summary of the Invention [Problem to be solved by the invention]

[0011] The problem underlying the present invention is to provide materials and methods that overcome the problems of the prior art outlined above.

[0012] The problem underlying the present invention is to provide an improved material for storing carbon sequestered from the atmosphere, which should be suitable for construction applications, especially building applications, so as to be able to store carbon in large quantities over long periods of time.

[0013] A further object of the present invention is to provide such materials that have high mechanical, thermal, and chemical stability. On the other hand, the materials should be capable of containing a relatively large amount of carbon. They should be readily available at reasonable cost from conventional raw materials and therefore suitable for mass production so that the effects associated with carbon sequestration can be achieved. [Means for solving the problem]

[0014] Surprisingly, it has been found that the problems underlying the present invention are overcome by the shaped objects, construction materials, biochar materials and methods set forth in the claims. Further embodiments of the present invention are outlined throughout the specification.

[0015] The subject of the present invention is a method for producing a shaped object for construction purposes, comprising the steps of: (a) forming a molded object; (b) forming a molded object; and (c) forming a molded object. The method comprises the steps of: (a) providing biochar in particulate form that is subjected to an oxidation reaction; (b) coupling the biochar with a silane coupling agent; (c) mixing the biochar with a polymer; (d) shaping the mixture; The method includes:

[0016] According to the method of the present invention, a shaped object is produced. The shaped object is a three-dimensional object (solid, part) with a predetermined shape. This shape is intentionally imparted to the object. Therefore, this shape is not the result of a random process. For example, the object may be a brick or a panel, but not a powder or irregular granules. The shape is imparted to the object in the forming step (d). This allows for the production of multiple shaped objects of the same shape.

[0017] The structure is intended for use in construction applications, particularly in construction engineering and architecture, including building applications but also infrastructure such as bridges or tunnels.

[0018] In step (a), biochar is provided. Biochar is a lightweight carbonaceous material produced by pyrolysis of organic material, such as wood or other plant materials. Pyrolysis is the partial thermal degradation of biomass in an oxygen-controlled atmosphere. Biochar can be crushed or ground into a fine powder. Preferably, biochar is derived from wood. Biochar is also characterized by its high C isotope level, which distinguishes it from fossil-derived coal and its reaction products and derivatives. Biochar sequestration alone can contribute to carbon sequestration from the atmosphere. The use of biochar in the method of the present invention is advantageous for environmental reasons, since a large amount of carbon can be permanently stored in the composite material. 1 kg of biochar contains approximately 680 to 820 grams of carbon, which is equivalent to approximately 2.5 to 3 kg of carbon dioxide. When biochar is permanently stored in the composite material, an equivalent amount of carbon dioxide can be permanently removed from the atmosphere. This can have relevant environmental impacts when biochar-based materials are used in large quantities in construction applications. Therefore, the inventive combination of polymeric materials and biochar imparts a beneficial environmental footprint to construction materials by enabling the sequestration and permanent storage of large amounts of carbon from the atmosphere.

[0019] The shaped articles of the present invention are derived from composite materials. The polymer forms a matrix in which biochar particles are distributed. Thus, the biochar functions as a filler. Biochar can be added to the composite material in any desired amount. For example, the composite material can contain at least 1% by weight, at least 5% by weight, or at least 10% by weight of biochar. For example, the composite material can contain 1-99% by weight of biochar, or 5-95% by weight of biochar, or 10-90% by weight of biochar, with the remainder preferably being polymer.

[0020] In preferred embodiments, the amount of biochar is relatively high. Preferably, the composite comprises 25-90 wt.% biochar and 10-75 wt.% polymer. More preferably, the composite comprises 30-85 wt.% biochar and 15-70 wt.% polymer, and even more preferably 40-80 wt.% biochar and 20-60 wt.% polymer. It is particularly preferred that the proportion of biochar in the composite be at least 30 wt.%, at least 50 wt.%, or at least 70 wt.%. In these embodiments, the polymer can impart stability to the composite. The environmental footprint can be particularly advantageous when the biochar is present in relatively high amounts.

[0021] In a preferred embodiment, the average particle size (particle size) of the biochar particles is in the range of 10 μm to 10 mm, preferably 50 μm to 5 mm, more preferably 100 μm to 1 mm. In a preferred embodiment, the particle size of the biochar particles is in the range of 10 μm to 10 mm, preferably 50 μm to 5 mm, more preferably 100 μm to 1 mm. Preferably, the particle size is determined by the method according to DIN ISO 2591-1:1988. It has been found that such biochar fillers can provide composite molded parts with high uniformity and strength.

[0022] The biochar provided in step (a) is subjected to an oxidation reaction. Typically, this oxidation reaction is carried out after the biochar is produced from organic material. Thus, the oxidation reaction is different from the pyrolysis by which the biochar was produced. In a preferred embodiment, the method includes a preceding step (a0) of subjecting the biochar to an oxidation reaction prior to step (a).

[0023] In the art, biochar is obtained by pyrolysis at temperatures between about 200°C and 900°C. In principle, such biochar can be used in the present invention. In a particular embodiment, biochar produced by pyrolysis at temperatures below 750°C, or preferably below 700°C, is used in step (a).

[0024] In accordance with the present invention, it has been discovered that producing biochar by pyrolysis at lower temperatures results in more stable shaped articles. In a preferred embodiment, the biochar provided in step (a) is produced by pyrolysis at a temperature below 650°C, preferably below 600°C, more preferably below 550°C, or even more preferably about 450°C. Such low pyrolysis temperatures produce specific biochar structures characterized by relatively low porosity and specific surface structures. Typically, the surface contains relatively high levels of aliphatic groups and relatively low levels of aromatic groups. It has been discovered that such biochars can react favorably with silane coupling agents to form stable shaped articles of the present invention. In contrast, if the pyrolysis temperature is too high, the porosity may be higher, and the biochar surface will be characterized by increased crystallinity, increased carbon content, and decreased functional groups.

[0025] Preferably, the biochar provided in step (a) has a relatively low porosity. Generally, porosity can be correlated with specific surface area. In a preferred embodiment, the biochar has a specific surface area of ​​75 to 500 m, as determined according to the BET method of ISO 9277:2010, prior to being subjected to the oxidation reaction. 2 / g, more preferably 200 to 450m 2 / g, most preferably 300-400m 2 / g. By adjusting the specific surface area accordingly and subsequently subjecting the biochar to an oxidation reaction, a stable and advantageous composite material can be obtained. In another embodiment, the oxidized biochar provided in step (a), and thus after the oxidation reaction, has a specific surface area in the range specified above.

[0026] The pyrolyzed biochar provided in step (a) is subjected to an oxidation reaction after pyrolysis to produce biochar. In the oxidation reaction, biochar is contacted with an oxidizing agent under conditions that allow a redox reaction to proceed. The oxidation reaction results in a modified biochar containing a high level of reactive functional groups on its surface. Typically, these functional groups contain oxygen, such as hydroxyl, carboxyl, or keto groups. As outlined above, this effect may be even more pronounced if the biochar is pyrolyzed at low temperatures. Therefore, biochar characterized by a relatively high O / C ratio can be provided in step (a). In a preferred embodiment, the O / C ratio of the biochar provided in step (a) is 0.6 or less, preferably 0.05 to 0.5, and most preferably 0.1 to 0.4, as determined according to DIN 51733. This O / C ratio range may be advantageous because biochar can be tightly and easily bound to silane coupling agents, forming highly stable composites.

[0027] In a preferred embodiment, the biochar provided in step (a) is oxidized in a liquid phase in the presence of an oxidizing agent. Preferably, the oxidizing agent is selected from hydrogen peroxide, nitric acid, potassium permanganate, ammonium persulfate, ozone, phosphoric acid, or sulfuric acid. It is particularly preferred that the oxidizing agent is hydrogen peroxide or nitric acid. These oxidizing agents can impart a particularly advantageous surface structure to the biochar, enabling it to form strong bonds with silane coupling agents. This allows for the production of stable shaped articles suitable for construction applications.

[0028] Preferably, the liquid is water or at least comprises a solvent with a high level of water, preferably greater than 80% by weight (based on the total amount of solvent). The use of water is preferred for cost and environmental reasons. For example, aqueous solutions of hydrogen peroxide or nitric acid can be used at concentrations of around 25-40%, preferably 30-35%. Preferably, the liquid-phase oxidation reaction is carried out at elevated temperatures, e.g., 60-100°C, preferably with stirring. The biochar can be exposed to the oxidizing agent for a suitable time range, e.g., 1-10 hours, especially 2-6 hours.

[0029] In another preferred embodiment, oxidation is carried out in the presence of a gaseous oxidizing agent, preferably air or oxygen. Oxidizing the biochar surface with air or oxygen in the gas phase can result in advantageous surface structures. Typically, gas-phase oxidation is carried out at elevated temperatures, e.g., 350°C to 400°C. Typically, the biochar starting material is subjected to an airflow of about 10-20 ml / min for about 10-60 minutes. The temperature can be increased during oxidation, e.g., from room temperature to a maximum temperature.

[0030] In step (b), the biochar provided in step (a) is reacted with a silane coupling agent. Generally, silane coupling agents are known in the art. Silane coupling agents are bifunctional, non-polymeric, low-molecular-weight compounds. They are used in the art to impart desired properties to the surface of solid substrates. Silane coupling agents contain a silane functional group for covalently bonding to the substrate surface, a second functional group for functionalizing the substrate surface after coupling, and a linker moiety.

[0031] In a preferred embodiment, the silane coupling agent contains an alkoxysilane group. Such a group can be hydrolyzed in the presence of water to form a silanol intermediate, which can then be covalently bonded to the biochar surface. In the methods of the present invention, coupling agents with alkoxysilane groups can effectively bond to biochar. Typically, the alkoxy group is methoxy or ethoxy. Ethoxysilane groups are particularly preferred because they have a slow hydrolysis rate in water, thereby allowing for precise control of the coupling reaction.

[0032] In a preferred embodiment, the silane coupling agent contains an amine group. Preferably, the amine group is a secondary amine group or a tertiary amine group, more preferably a tertiary amine group. In the method of the present invention, it has been found that silane coupling agents having an amine group can provide strong bonding to polymers, particularly polyamides. Furthermore, likely due to their structure and properties in aqueous solution, silane coupling agents having an amine group, particularly a tertiary amine group, can modify not only the surface of biochar particles but also the interior of biochar micropores in the method of the present invention. This allows for a high degree of surface modification and strong bonding to polymers.

[0033] In a preferred embodiment, the silane coupling agent is an (aminoalkyl)trialkoxysilane, where the alkyl group contains 1 to 4 carbon atoms and the alkoxy is methoxy or ethoxy. In a preferred embodiment, the silane coupling agent is (3-aminopropyl)triethoxysilane (APTES). Such coupling agents are preferred because they combine the advantageous properties of trialkoxysilane groups, especially triethoxysilane groups, with the benefits of amine groups. Because the molecule is relatively small, steric hindrance effects do not occur when it is attached to biochar, and therefore, even the micropores of biochar can be coated. Furthermore, favorable rates of hydrolysis and bonding can be achieved compared to undesirable condensation of the silane coupling agent. When using such reactive silane coupling agents, it is desirable for the predominant reaction to be covalent bonding to the biochar surface. However, due to the high reactivity of silane coupling agents, undesirable side reactions can also occur. These include self-condensation and the formation of oligomers or polymers in the reaction solution. If this occurs, these by-products may be less likely to react with biochar, significantly reducing coupling efficiency.

[0034] Such amine-containing silane coupling agents can advantageously provide a dense coating on the surface of biochar particles and within the micropores. Without being bound by theory, this is believed to be a result of their low condensation rate and small molecular size, combined with the oxidized biochar used in the present invention. Another advantage of amino-group silane coupling agents is that they are very stable in the presence of water. This particular coupling reaction can be effectively controlled by adding a catalyst such as an acid or base. Therefore, the overall coupling system and reaction can be easily controlled, and the degree and distribution of coupling can be adjusted.

[0035] In another embodiment, a silane coupling agent that does not contain an amine group is used. Alternatively, such a coupling agent may contain a vinyl functional group, for example, when the silane coupling agent is triethoxyvinylsilane (TEVS). However, such coupling agents are less preferred because self-condensation can occur, which can reduce the efficiency of the coupling reaction on the biochar surface.

[0036] Preferably, the silane coupling agent does not contain a cleavable group such as a vinyl group or an aziridine group, or sulfur or a sulfur-containing group for vulcanization. Preferably, the silane coupling agent does not contain any additional reactive groups other than the amine group and the silane group. Therefore, the coupling agent can have a relatively simple structure and can be handled and reacted in a relatively simple and convenient manner.

[0037] The coupling reaction with the silane coupling agent in step (b) is carried out in a liquid phase, thus in a composition containing a solvent. Preferably, the solvent is water or at least contains water. In preferred embodiments, the solvent contains at least 80% by volume, more preferably at least 90% by volume, of water. Preferably, the composition contains a catalyst, preferably an acid or a base. In these embodiments, it is advantageous to require no or only a small amount of organic solvent, which is desirable for cost and environmental reasons. Furthermore, the reaction in water can be easily controlled, inter alia, using a catalyst and / or adjusting the pH.

[0038] Typically, the coupling reaction in step (b) is carried out at an elevated temperature, e.g., 50°C to 100°C, with stirring for a suitable time, e.g., 1 to 48 hours. The pH of the solution is adjusted to control the desired reaction rate. For example, the reaction can be efficient at a moderate pH, e.g., in the range of about 3 to 5, preferably 3.5 to 4. After the reaction is complete, the biochar can be filtered, washed with water and / or ethanol, and dried, e.g., in an oven at elevated temperatures. It may be desirable to provide the biochar in a dry form for subsequent polymer blending.

[0039] In step (c), the biochar from step (b) modified with a silane coupling agent is mixed with a polymer. This mixture is molded in step (d). The biochar functions as a filler in the product. In principle, the surface-modified biochar can be combined with various polymers, such as elastomers, thermoplastics, or duromers. For example, the polymer may be polyamide, polyolefin, such as polyethylene or polypropylene, polyester, polyurethane, silicone, acrylic polymer, or rubber, or a copolymer or mixture thereof. Preferably, the polymer is a recycled polymer and / or a bio-based polymer, which is advantageous for the overall environmental balance. Preferably, the polymer is a synthetic polymer, which may be advantageous for efficient molding.

[0040] In a preferred embodiment, the polymer in step (c) is a thermoplastic polymer. It has been found that when a thermoplastic polymer is combined with modified biochar, a shaped object can be efficiently produced. When such a mixture is molded and solidified, a stable shaped object can be obtained. For example, the thermoplastic polymer may be polyamide, polyolefin, acrylonitrile butadiene styrene (ABS), or polylactide, or a mixture thereof. Preferably, the thermoplastic polymer is polyamide or polyolefin. It has been found that when these thermoplastic polymers are used, a shaped object with high mechanical stability can be obtained.

[0041] In a preferred embodiment, the polymer is a polyamide, typically a synthetic polyamide. Polyamides are characterized by repeating amide bonds in the polymer chain. The polyamide can be an aliphatic polyamide, a polyphthalamide, or an aromatic polyamide. Preferably, the polyamide is aliphatic, such as PA6 or PA66. It has been found that advantageous shaped objects can be obtained when polyamides are combined with modified biochar. Despite high levels of charcoal filler, polyamide-based shaped objects can have particularly high stability. They are highly suitable for construction applications that allow permanent and efficient carbon sequestration. In this regard, it is particularly advantageous to combine polyamides with biochar modified with a silane coupling agent containing amine groups. Strong bonding can also result from the use of oxidized biochar, as outlined above. Overall, highly stable objects for construction applications can be obtained from the above formulations and by the above means.

[0042] In another preferred embodiment, the polymer is a polyolefin, such as polyethylene or polypropylene. The polyethylene may be HDPE (high density polyethylene). It has been found that stable shaped objects can also be obtained from polyethylene. This is advantageous because polyethylene is available in large quantities at low cost and can be easily recycled. Thus, each material is suitable for large-scale construction applications and permanent carbon storage.

[0043] The mixing in step (c) can be carried out using conventional means such as a static mixer or an extruder. The mixture from step (c) is subjected to a molding process in step (d). Polymer molding equipment and molding methods are known in the art. Typically, the mixture is heated to a liquid or paste of desired viscosity, which is filled into a mold (mold) and subjected to heat and pressure. After cooling, a molded part is obtained, which hardens and is removed from the mold. If a thermoplastic mixture is used, the molded part becomes the shaped object after solidification and cooling. If a hardenable mixture is used, the molded part is typically hardened by heating to become the shaped object. Preferably, the shape of the shaped object corresponds to the mold.

[0044] The present invention also relates to a shaped article obtainable by the method outlined above, comprising a polymer and biochar in particulate form, the biochar having been subjected to an oxidation reaction after pyrolysis, the oxidized biochar having been modified with a silane coupling agent.

[0045] The use of the composite material to prepare such shaped objects is highly advantageous, since such objects can be easily, reliably, and in large quantities obtained by molding. The shaped objects (shaped parts, shaped bodies) have a defined three-dimensional shape, which can be purposefully imparted to the object during the molding process. For example, the shaped objects can have lengths of 5 cm to 2 m and weights of 50 g to 10 kg, if desired. After molding, the shape can be modified, for example, by cutting or polishing. The composition and properties of the shaped objects can be adjusted as outlined above for the method.

[0046] In a preferred embodiment, the shaped object comprises biochar pyrolyzed at a temperature below 700° C., more preferably below 600° C. Preferably, the specific surface area of ​​the biochar is between 75 and 500 m, as determined according to the BET method of ISO 9277:2010. 2 / g. Preferably, the O / C elemental ratio of the biochar is 0.6 or less, as determined according to DIN 51733. In preferred embodiments, the polymer is a polyamide. In these embodiments, the biochar and polymer may be selected, obtained, and processed as outlined above.

[0047] The present invention also provides a construction material comprising the above-outlined shaped object, which in a preferred embodiment is a panel, an insulating board, a building component or a building block.

[0048] Typically, the shaped article is not porous. Preferably, the shaped article does not contain open or closed pores in the polymer matrix. Non-porous materials may be advantageous for storing large amounts of carbon. Furthermore, non-porous materials may have higher stability and barrier properties. However, biochar particles typically contain micropores that are not filled by polymer. Therefore, a relatively light product can be obtained when the biochar content is high.

[0049] In a preferred embodiment, the shaped object comprises at least one additional filler or reinforcing agent, such as fibers not derived from biochar. The additional filler or reinforcing agent is preferably also based on organic materials and has a favorable environmental footprint. Additional fillers can be added to modify properties, for example, by including color pigments or conductive particles. Fibers, such as glass or carbon fibers, can be added to enhance mechanical stability. Preferably, the amount of filler and / or reinforcing agent is less than 20% by weight, preferably less than 10% by weight, for example, in the range of 1-20% by weight or 2-10% by weight.

[0050] The composite materials and shaped parts may contain at least one additive that is not a structural polymer, filler, or reinforcing agent. For example, the additive may be selected from processing aids, plasticizers, colorants, flame retardants, heat stabilizers, and compatibilizers. The processing aid may improve workability during compounding or molding. For example, the processing aid may be a fatty acid salt, such as calcium stearate, available from Peter Greven, Germany, under the trademark Ligastar. Such additives may also impart desired properties, such as color or stability, to the composite materials and molded parts. Preferably, the amount of additive is up to 5% by weight or up to 2% by weight, for example, in the range of 0.01-5% by weight or 0.1-2% by weight.

[0051] Preferably, the shaped object is stiff and rigid and therefore not elastic. Preferably, the tensile modulus is at least 2000 N / mm when determined according to ISO 527-1:2019. 2 , more preferably 2000 to 6000 N / mm 2 Rigid materials may be advantageous for construction applications due to their high dimensional stability. Preferably, the tensile strength according to ISO 527-1:2019 is high, for example, greater than 10 MPa, preferably greater than 20 MPa, or even greater than 30 MPa. Such high tensile strength is advantageous for construction applications, as the material can withstand mechanical stress. Preferably, the polymer is not a curable or cured polymer, such as rubber. Preferably, the polymer does not contain reactive groups for curing, such as vinyl or epoxy groups.

[0052] In a preferred embodiment, the shaped object is a construction material, i.e., a material used in construction. In a preferred embodiment, the construction material is a wall panel, an insulating board, a building component, or a block or structural component for assembling a building component such as a wall. A panel is a flat object for covering a building component such as a wall, floor, or furniture surface. The use as a panel is advantageous due to the high stability of the composite material. Because the composite material can be mechanically, thermally, and chemically stable, the panel can shield the substrate to which it is attached.

[0053] The shaped articles are intended for construction applications and are not filters, adsorbents, or catalysts, for example in soil or water cleaning, which makes them different from char-based materials in the art, which are typically provided in powder form.

[0054] The construction material may comprise the shaped object and at least one additional material. For example, it may be a laminate of two, three, or more layers. In a preferred embodiment, the shaped object comprises a coating. For example, a functional coating may impart a desired property, such as color, to the shaped object, or may protect the object against moisture, UV radiation, mechanical damage, or weathering, or may impart a texture to the surface. Since biochar can impart a dark color to the composite material, a colored coating may be applied. The coating may be applied by conventional means, such as liquid coating with a resin, impregnation, electron scattering (Trespa process), physical or chemical vapor deposition, lamination, etc. The coating may cover the shaped object completely or partially, for example, on only one side.

[0055] A biochar material in particulate form, the biochar having been subjected to an oxidation reaction after pyrolysis, the oxidized biochar being modified with a silane coupling agent containing a tertiary amine group, the biochar having been pyrolyzed at a temperature of less than 700°C, more preferably less than 600°C, and the specific surface area of ​​the biochar prior to the oxidation reaction is between 75 and 500 m, as determined according to the BET method of ISO 9277:2010. 2 The present invention also relates to biochar material in particulate form, in which the O / C elemental ratio of the biochar is less than or equal to 0.6, as determined according to DIN 51733. As outlined above, such modified biochar is a useful filler for polymer formulations, especially polyamide formulations, for producing shaped bodies with high stability suitable for construction applications.

[0056] The shaped articles, methods, and construction materials of the present invention solve the underlying problem. Stable construction materials are provided, which can be used as carbon sinks for the long-term storage of carbon from the atmosphere. Overall, the shaped articles of the present invention can have high mechanical and dimensional stability, even when they contain relatively high amounts of charcoal filler.

[0057] Illustrative embodiments of the invention and aspects of the invention are illustrated in the drawings. [Brief explanation of the drawings]

[0058] [Figure 1] Figure 1 shows a comparison of FT-IR results for unmodified biochar substrate (dotted line, top), biochar after oxidation with nitric acid (dotted line, middle), and oxidized biochar after silane agent coupling (solid line, bottom), as described in the Examples. [Figure 2] Figure 2 shows the results of thermal stability analysis by TGA of biochar before and after modification according to the example. Results are shown for unmodified biochar substrate, biochar after oxidation with nitric acid, and oxidized biochar after silane coupling. [Example]

[0059] Example 1: Biocarbonation Biochar (BC) produced from woody lignocellulosic biomass at low pyrolysis temperatures (approximately 450°C) was used. The biochar was sieved to standardize the particle size distribution so that the particles were in the 100–500 μm range, and then dried in an oven at 90°C for 24 hours.

[0060] To increase the number of surface functional groups, biochar was subjected to oxidation reactions. The susceptibility of biochar to air oxidation decreased with increasing pyrolysis temperature, resulting in the formation of more stable polyaromatic structures. Acid and base oxidation were tested to identify the optimal method for biochar surface oxidation. The optimal method is defined as the one that achieves the maximum amount of functional groups on the char surface, increasing the chances of successful silane coupling in the subsequent coupling reaction.

[0061] Hydrogen peroxide treatment was carried out at 80 °C in a beaker immersed in an oil bath with constant stirring. Nitric acid treatment was carried out under reflux. After treatment, the biochar samples were filtered, rinsed with deionized water until a neutral pH was reached, and dried in an oven at 90 °C overnight. Air-oxidized chars were prepared in an oven with constant airflow, using a temperature ramp of 10–25 °C / min and isothermal conditions at the specified oxidation temperature for 30 min. A summary of the chemicals and oxidation conditions is provided in Table 1.

[0062] [Table 1] * 15 minutes to heat from room temperature to the final oxidation temperature + 30 minutes at the oxidation temperature

[0063] Example 2: Silane Coupling Reaction Six grams of oxidized biochar prepared according to Example 1 was added to a reactor containing 200 grams of deionized water and heated by immersion in a 78°C oil bath with constant stirring for 45 minutes. The pH was adjusted to approximately 3.5-4 to control the kinetics of the silane agent reaction. If necessary, the pH was adjusted by adding acetic acid dropwise. 1.5 grams of (3-aminopropyl)triethoxysilane (APTES) was dissolved at 5% (w / w) in an organic solvent such as ethanol or toluene, and this solution was then added to the biochar suspension. The silane coupling reaction was carried out in the oil bath with constant stirring for 20-24 hours. After treatment, the sample was filtered, washed with water and ethanol to remove excess silane agent, and dried overnight in an oven at 70-100°C. The amounts and conditions are summarized in Table 2.

[0064] [Table 2]

[0065] Example 3: Characterization of modified biochar The sample prepared according to Example 2 was examined by FT-IR, confirming the introduction of functional groups onto the surface of the biochar. Figure 1 shows a comparison of FT-IR results for the unmodified biochar substrate (dotted line, top), after oxidative treatment with nitric acid (dotted line, middle), and the oxidized biochar after silane agent coupling (solid line, bottom).

[0066] The FT-IR spectrum of the oxidized char shows a peak at 1718 cm -1 The results show the appearance of a C=O stretch at , which is characteristic of a carboxyl group and demonstrates the oxidation of the char by nitric acid treatment.

[0067] The spectrum obtained after silane modification of pre-oxidized biochar confirms the presence of a grafted polysiloxane network on the surface of the biochar. The spectrum shows peaks at 2936 and 2871 cm, which correspond to the aliphatic -CH groups in APTES. -1 The CH stretching vibration appears at 1560 cm. The NH scissor vibration appears at 1560 cm. -1 and the peak corresponding to Si-CH2 appears at 1340 cm -1and the Si–O bands appear at 1076 and 663 cm -1 and the Si-OC band appears at 695 cm -1 Finally, 1042cm -1 and 740cm -1 The peak is attributed to the Si-O-Si siloxy group.

[0068] The thermal stability of biochar before and after modification was measured by TGA. Results for unmodified biochar substrate, biochar substrate after oxidation with nitric acid, and oxidized biochar after silane coupling are shown in Figure 2. A basic temperature gradient was selected in the presence of air, heating the samples from 25°C to 800°C at a rate of 10°C / min. After heating to 800°C, the raw biochar experienced a 24% weight loss, attributed to the combustion of free carbon, ash, and volatile organics present in the char. The oxidized char showed a 51% weight loss, demonstrating the increased presence of functional groups. Finally, the silane-treated biochar underwent a slightly smoother weight loss trend than the oxidized biochar, ultimately resulting in a 41% weight loss. These results indicate that the biochar surface is significantly modified in the process outlined above, providing advantageous properties for blending with polyamides or other polymers.

[0069] Example 4: Preparation of shaped object Shaped objects were prepared from the surface-functionalized biochar of Example 2 and a thermoplastic polymer, either polyamide 66 or high-density polyethylene. The char was first compounded with polyamide (PA66 ECO 1000 / 116, Altech) or high-density polyethylene (HDPE SHC7260, Braskem) in a Brabender PL 2100 kneader. The conditions are summarized in Table 3.

[0070] [Table 3]

[0071] Tensile test specimens are prepared from press plates according to ISO 527-1:2019 and tested on a Quasar 25 Galdabini UTM.

[0072] Example 5: Evaluation of the properties of the shaped object Both the raw biochar-containing HDPE and the functionalized biochar-containing HDPE samples were subjected to tensile testing. A total of five samples per formulation were tested according to ISO 527 standards to ensure reproducibility of results. The results are summarized in Table 4.

[0073] [Table 4]

[0074] Additionally, samples of both the raw biochar-containing PA and the functionalized biochar-containing PA were subjected to tensile testing. A total of five samples per formulation were tested according to ISO 527 standards to ensure reproducibility of results. The results are summarized in Table 5.

[0075] [Table 5]

[0076] The tensile strength of biochar particle-filled polymer composites depends primarily on the interfacial adhesion between the matrix and the filler, which helps transfer a small portion of the stress to the filler particles during deformation. For both studied matrices, the use of a silane agent as a treatment for the biochar filler clearly affected the tensile properties due to improved affinity and particle-matrix bonding, showing an increase in all tensile values ​​compared to the untreated composites.

[0077] Overall, the results demonstrate that the shaped objects of the present invention have high mechanical and dimensional stability despite containing a relatively high amount of charcoal filler, meeting the requirements for architectural applications and making them suitable for permanent and efficient carbon storage.

Claims

1. A method for manufacturing a shaped object for construction purposes, comprising: (a) providing biochar in particulate form that is subjected to an oxidation reaction; (b) coupling the biochar with a silane coupling agent; (c) mixing the biochar with a polymer; (d) shaping the mixture; A method comprising:

2. 2. The method of claim 1, wherein the biochar in step (a) is pyrolyzed at a temperature below 700°C, preferably below 600°C.

3. The specific surface area of ​​the biochar in step (a) prior to the oxidation reaction is between 75 and 500 m, as determined according to the BET method of ISO 9277:2010. ２ The method according to claim 1 or claim 2, wherein the saturation is 0.05 to 0.15 g.

4. the oxidation reaction is preferably carried out in the liquid phase in the presence of an oxidizing agent selected from hydrogen peroxide, nitric acid, potassium permanganate, ammonium persulfate, ozone, phosphoric acid or sulfuric acid, and / or The oxidation reaction is carried out in the presence of a gaseous oxidant, preferably air or oxygen.

4. The method according to any one of claims 1 to 3.

5. 5. The method of any one of claims 1 to 4, wherein the biochar has an O / C ratio of less than or equal to 0.6, as determined according to DIN 51733.

6. 6. The method of any one of claims 1 to 5, wherein the silane coupling agent comprises an amine group, preferably a tertiary amine group.

7. 7. The method of claim 6, wherein the silane coupling agent is an (aminoalkyl)trialkoxysilane, the alkyl group containing 1 to 4 carbon atoms, the alkoxy group being a methoxy or ethoxy group, and the silane coupling agent is preferably (3-aminopropyl)triethoxysilane.

8. 8. The method of any one of claims 1 to 7, wherein the polymer in step (c) is a thermoplastic polymer.

9. The method of claim 8, wherein the thermoplastic polymer is polyamide or polyethylene.

10. A shaped object obtained by the method according to any one of claims 1 to 9.

11. 1. A shaped object comprising biochar in particulate form and a polymer, wherein the biochar has been subjected to an oxidation reaction after pyrolysis, and the oxidized biochar has been modified with a silane coupling agent.

12. the biochar has been pyrolyzed at a temperature below 700°C, preferably below 600°C; and / or The specific surface area of ​​the biochar prior to the oxidation reaction is between 75 and 500 m, as determined according to the BET method of ISO 9277:2010. ２ / g, and / or The O / C elemental ratio of the biochar is less than or equal to 0.6, as determined according to DIN 51733. The shaped object according to claim 10 or 11.

13. A construction material comprising the shaped object according to any one of claims 10 to 12.

14. 14. A shaped object according to any one of claims 10 to 12 or a construction material according to claim 13, which is a panel, an insulating board, a building component or a building block.

15. A biochar material in particulate form, the biochar having been subjected to an oxidation reaction after pyrolysis, the oxidized biochar being modified with a silane coupling agent containing a tertiary amine group, the biochar having been pyrolyzed at a temperature of less than 700°C, preferably less than 600°C, and the specific surface area of ​​the biochar prior to the oxidation reaction is between 75 and 500 m, as determined according to the BET method of ISO 9277:2010. ２ / g, and the O / C elemental ratio of the biochar is less than or equal to 0.6, as determined in accordance with DIN 51733.

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