Composite panel, method for the production thereof and uses thereof

Description

[0001] The present invention relates to a composite panel comprising or consisting of at least one bio-based particulate or rod-shaped natural material (excluding wood), at least one thermosetting resin as a binder, and at least one inorganic flame retardant. The present invention also relates to a method for producing such a composite panel. Furthermore, the present invention specifies possible uses of the composite panel according to the invention.

[0002] Effective insulation materials for buildings are an essential component of modern construction, saving energy when heating or cooling buildings and creating a comfortable indoor climate in all climate zones and at all times of the year. Building insulation is achieved, for example, by attaching panels with low thermal conductivity to walls, roofs, or floors. These insulation materials can be applied to either the exterior or interior surfaces.

[0003] Another method of thermal insulation involves filling cavities with mats or loose fill materials with low thermal conductivity. Materials with low thermal conductivity used for building insulation include mineral, petroleum-based, or renewable resources.

[0004] Metallic materials capable of reflecting heat represent a special case. However, due to their high price, they only have a small market share.

[0005] Mineral insulation materials include, for example, glass wool or rock wool, the production of which is energy-intensive. Insulation materials made from fossil raw materials are predominantly foamed plastics such as polystyrene (PS) in the form of expanded polystyrene (EPS) or extruded polystyrene (XPS) boards, which are of great importance in the insulation market. Other foams used for this purpose are based on polyurethane, phenol-formaldehyde resin, or polyethylene. Expanded polystyrene (EPS) holds a large market share among insulation materials due to its numerous advantages. Polystyrene foam boards consist of over 95% air and yet offer good stability at a low density, ideal insulating properties, and a low price. Further advantages of expanded polystyrene foam boards include their ease of handling, good integration into buildings, and suitability for use in external thermal insulation composite systems (ETICS).

[0006] A crucial criterion when evaluating a material intended for use as insulation is its fire behavior. DIN EN 13501-1:2010 provides a classification for this. For approval in a wide range of applications, low flammability is necessary. Polystyrene foam is inherently a highly flammable material, to which a brominated polymer is added as a flame retardant to achieve a classification as low flammability. This ensures the widespread use of polystyrene foam as insulation material.

[0007] However, EPS insulation boards, being entirely petroleum-based, are not conducive to a sustainable, resource-conserving, and environmentally conscious approach to raw materials. The disadvantages of petroleum-based products, such as raw material scarcity, CO2 emissions, and disposal problems, are well known. For this reason, the use of materials made from renewable resources as replacements for traditional insulation materials is of great interest and is increasingly in demand.

[0008] Bio-based insulation materials are described in scientific and patent literature and are also used in practice. Most bio-based insulation materials are available as loose-fill or blown-in insulation, but there are some concerns regarding settling if installation is not carried out by a specialist company. Insulation boards made from renewable raw materials are also used, but they have various disadvantages, such as insufficient compressive strength. Furthermore, insulation materials made from renewable raw materials are classified as normally flammable (building material class E according to DIN EN 13501-1:2010). It would therefore be advantageous to have insulation materials made from renewable raw materials that are easy to handle, i.e., available as boards, have acceptable mechanical properties, and are also flame-retardant.

[0009] Numerous bio-based base materials suitable for use as insulation are described in the specialist literature, most of which are by-products of forestry and agriculture. Examples include fibers from flax, hemp, jute, sisal, kenaf, miscanthur, grass, banana, or coconut, as well as straw from cereals, rice, flax, hemp, corn, or rapeseed, or even wood shavings, coconut pulp, corn husks, peanut shells, pineapple leaves, sunflower stalks, reeds, cattails, bagasse, cotton stalks, bark, pecan shells, durian fruit peels, corn cobs, rice hulls, cork, olive pits, or seagrass. Overviews of materials from renewable resources suitable for insulation are provided, for example, by C. Aciu and N. Corbirzan in ProEnvironment 6 (2013) 472–478, and by H. Wang and P.-C. Chiang, Y. Cai, C. Li, X. Wang, T.-L. Chen, S. Wei and Q. Huang in Sustainability 10 (2018), 3331, S. Liuzzi, S. Sanarica and P. Stefanizzi in Energy Procedia 126 (2017) 242-249, L. Liu, H. Li, A.Lazzaretto, G. Manente, C. Tong, Q. Liu, N. Li in Renewable and Sustainable Energy Reviews 69 (2017) 912-932, P.S. Dhivar, A.R. Patil in IOSR Journal of Mechanical and Civil Engineering special issue "6th National Conference on Recent Developments In Mechanical Engineering- 2017"Vol. 6, 53-61, C. Jivrajani in International Journal of Advance Engineering and Research Development 4, (2017) oder F. Asdrubali, F. D'Alessandro, S. Schiavoni in Sustainable Materials and Technologies 4 (2015) 1-17.

[0010] The natural materials described therein are used in various forms as insulation. Loose fibers or particles are blown into cavities or filled with loose material. Fibers or straw are also manually stuffed into cavities or frames. Insulation boards made from natural fiber-based materials are also commercially available. Jute, flax, hemp, wood fibers, and even meadow grass are generally used to produce insulation boards, mats, or fleeces without the use of a binder. Wood fiber systems are considered particularly pressure-resistant and are suitable for use in external thermal insulation composite systems (ETICS). Materials suitable for ETICS can also be produced from hemp using a special process (http: / / www.caparol.de / imfokus / waermedaemmung / capatect-system-natur.html, accessed on March 27, 2017).

[0011] Pressed reed mats offer another option for a thermal insulation composite system, but are unsuitable for perimeter and core insulation (https: / / www.daemmen-und-sanieren.de / daemmung / daemmstoffe / schilf, accessed on 27.03.2017).

[0012] The production of cork sheets represents a special case. In the so-called "baked cork" process, cork granules are formed into sheets under pressure with the addition of steam at approximately 350°C. At the temperatures prevailing during this process, the natural resin suberin is released from the cells, causing them to expand. The released resin binds the individual particles together. The insulating properties of the natural cork are optimized by this expansion. However, only resin-rich cork is suitable for the production of baked cork, ensuring that the individual particles are sufficiently bonded together. This is generally primary cork, meaning cork from the first harvesting of the cork oak. Cork from later harvesting periods or recycled cork cannot be used for this process.

[0013] Another way to produce panels from renewable raw materials suitable for insulation is to bind particulate natural materials with an adhesive, resin, or latex. For example, A. Paivaa, S. Pereiraa, A. Sáa, D. Cruza, H. Varumc, and J. Pintoa describe a panel made from corn cob meal for building insulation in Energy and Buildings, 45 (2012) 274-279. An unspecified wood glue is mentioned as the binder. Further panels consisting of bio-based residual material particles, in this case durian fruit peels, are described by J. Khedari, S. Charoenvai, and J. Hirunlabh in Building and Environment 38 (2003) 435-441. In this study, the particles are bound with urea-formaldehyde, phenol-formaldehyde, or isocyanate-based adhesives. S. Tangjuank also describes a similar process in Int. J. Phys. Sci. 6 (2011), 4528-4532 the production of sheets from pineapple leaf particles bound with natural rubber latex.

[0014] DE 2457345 A1 discloses a material made of cork surface-coated with sand and cement which, in conjunction with a binder mass such as mortar, gypsum or synthetic resin, can be processed into a component with low density and good thermal and sound insulating properties.

[0015] In addition to natural fiber-based insulation materials, mineral materials such as expanded clay, perlite, and calcium silicates are also known as natural insulation materials. They are generally used in bulk form. Perlite is also used to produce sheet-like thermal insulation systems, and calcium silicates, in particular, are used in mineral insulation boards. Currently, pyrogenic silica is used as an insulation material in vacuum insulation panels (VIPs). VIPs offer very good insulation values ​​with minimal thickness. However, they are difficult to work with; if the vacuum barrier is breached, the insulation performance drops significantly (DE 10 2012 224 201 A1).

[0016] Mineral insulation materials have the major advantage of being non-combustible. However, a clear disadvantage is their complex disposal, as they are not biodegradable. Landfilling is not in line with a future-oriented circular economy.

[0017] In general, insulation materials made from renewable raw materials are considered combustible (fire protection class E according to DIN EN 13501-1:2010). With a few exceptions, such as cellulose fibers or wood wool boards, which sometimes achieve a classification of "flame-retardant", they are generally classified as "normally flammable" (http: / / www.oekologisch-bauen.info / baustoffe / naturdaemmstoffe / , accessed on March 27, 2017).

[0018] To reduce flammability, flame retardants are added to bio-based materials that can be used as insulation. EP 2 721 121 B1, for example, describes waste paper treated with various mixtures of different flame retardants from the group consisting of aluminum hydroxide, ammonium sulfate, sodium sulfate, monoammonium phosphate, diammonium phosphate, triammonium phosphate, ammonium polyphosphate, aluminum sulfate, trisodium phosphate, calcium hydroxide, and magnesium hydroxide.

[0019] Similarly, in US 4182681, waste paper is impregnated with a mixture of various flame retardants to reduce its fire behavior. However, in both cases, no insulation boards are produced; instead, the flame-retardant cellulose is used as a loose filler for thermal insulation in cavities.

[0020] A flame-retardant wood fiberboard, on the other hand, is disclosed in DE 10 2016 121 590 A1. Here, wood fibers are treated with a flame retardant and processed into boards using either a wet or dry process. Optionally, a binder is added to increase strength. Neither the description nor the claims provide precise quantities of the compositions. The only components that all the insulation boards claimed therein contain are fibers from renewable raw materials and a flame retardant, while the other components are optional. This process is limited to the use of fibers from renewable raw materials, preferably wood, as the sole base material with insulating properties. However, with regard to a globally functioning bioeconomy, the widespread use of a wide variety of bio-based raw materials is desirable.

[0021] The other systems available on the market are more suitable for between-rafter or cavity insulation, less so for ETICS.

[0022] DE 196 21 573 A1 discloses thermosetting mixtures consisting of hydroxyalkylated polyamines and polycarboxylic acids, wherein the compositions do not contain formaldehyde and can be used in particular as binders for the production of molded parts.

[0023] The object of the present invention was therefore to offer a composite panel that does not have the disadvantages mentioned above, i.e., that meets the requirements for modern efficient insulating materials with regard to density, thermal conductivity and fire behavior, is self-supporting and is not limited to a class of bio-based raw materials with insulating properties, but can generally be realized with a wide variety of renewable raw materials and has the potential for recyclability.

[0024] This problem is solved with respect to a composite panel with the features of claim 1, with respect to a method for its manufacture with the features of claim 10, and with respect to possible uses with the features of claim 15.

[0025] The present invention thus relates in a first aspect to a composite panel containing or consisting of at least one bio-based particulate or rod-shaped natural material, excluding wood as a natural material, at least one thermosetting cured synthetic resin as a binder, and at least one inorganic flame retardant, wherein the composite panel contains wood chips, wherein a maximum of 20 wt.% of the total amount of the at least one bio-based particulate or rod-shaped natural material or the combination of particulate and rod-shaped natural materials is replaced by wood chips, and the composite panel has a thermal conductivity, measured according to EN 12667:2001, of a maximum of 50 mW / mK.

[0026] For the purposes of this invention, a natural material is understood to be a material obtained from a plant, an animal, an alga, or a fungus, or a part thereof. However, wood is excluded from the definition of natural materials, so that, in particular, wood-based composite panels, such as particleboard, OSB, etc., are not part of the subject matter of the invention. The at least one natural material is replaced to a minor extent by wood chips, such as those used in the production of particleboard (e.g., flat-pressed boards, oriented strand board, etc.). However, the inclusion of wood chips does not qualify the composite panel according to the present invention as a wood-based panel according to the relevant standards, such as DIN EN 312, DIN EN 14755, and DIN EN 13986.

[0027] The composite panel according to the invention therefore always contains at least one natural material other than wood and will additionally contain wood-based materials - but in subordinate quantities.

[0028] Particulate natural products are defined as particles of the natural product that are spherical or of a similar shape and have an aspect ratio between 1 and 5, preferably with a minimum length of at least 2 mm in all directions. The maximum length in all directions should preferably not exceed 40 mm. The natural product particles can either occur naturally in this shape or be brought into this shape by a processing step such as milling, cutting, threshing, expansion by heating, etc.

[0029] For the purposes of this invention, "natural rods" are understood to be those that have grown in rod form and whose length may be shortened by a processing step such as chopping, cutting, threshing, etc. The length of the rods must be at least 5 mm, and the width preferably at least 2 mm. However, the length of a rod is always greater than its width.

[0030] Surprisingly, it was found that the aforementioned combination of materials results in a composite panel that is essentially based on raw materials that are mostly considered waste materials. Compared to composite panels based on raw materials specifically manufactured for this purpose, the composite panel according to the invention is therefore extremely advantageous from an ecological perspective. The composite panel according to the invention is characterized by its low weight and, at the same time, low thermal conductivity. Furthermore, the composite panel can be classified as flame-retardant, making it particularly suitable as insulation material in the construction sector or as a building material.

[0031] Surprisingly, it was also found that the use of particulate natural materials, especially those containing cavities, is particularly suitable. The resulting panels have lower densities than those made from fibers or chip-like natural materials, or those with a particle size significantly less than one millimeter, i.e., in powder form. Similar thermal conductivities can be achieved as with panels made from fibers or chip-like natural materials.

[0032] In particular, compared to the patent DE 10 2016 121 590 A1 described above, the present invention offers two significant advantages. Firstly, by using particulate or rod-shaped natural materials or mixtures of particulate and rod-shaped natural materials, lower component densities can be achieved than with fibrous materials. Secondly, stable plates can be obtained with smaller amounts of binder when using particulate and / or rod-shaped natural materials.

[0033] The panels can also be manufactured extremely economically.

[0034] The composite panel according to the present invention can be based on bio-based particulate natural substances alone, or on rod-shaped natural substances alone. Mixtures or combinations of particulate or rod-shaped natural substances are also possible.

[0035] A preferred embodiment provides that the particle size of the at least one bio-based particulate natural substance is at least 2 mm, preferably 2 to 40 mm, and particularly preferably 2 to 25 mm.

[0036] In the event that rod-shaped natural materials are used in the composite plate, the rod length of the at least one bio-based rod-shaped natural material is preferably greater than 2 mm, more preferably 5 to 100 mm, and particularly preferably 10 to 75 mm.

[0037] The size fractions of particulate or rod-shaped natural substances that are preferably used for the purposes of the present invention can be obtained by classification methods known from the prior art, in particular by sieve classification.

[0038] Preferred is at least one bio-based particulate natural substance selected from the group consisting of cork meal, corn cob meal, nutshells (e.g. peanut shells), nutshell meal, bark granules, fruit kernels, cereal husks, corn husks, crushed pineapple leaves, pecan shells and meal, crushed durian fruit peels, rice hulls, olive kernels and mixtures thereof.

[0039] The at least one bio-based, rod-shaped natural material is preferably selected from the group consisting of sunflower stalks, reeds, cattails, cotton stalks, and straw from cereals, rice, flax, hemp, maize, or rapeseed, as well as mixtures thereof. The aforementioned exemplary rod-shaped natural materials can be used as is, provided they are of a suitable length; if necessary, the respective rod-shaped natural materials may need to be shortened to a desired or suitable length by a suitable process, such as chopping, cutting, threshing, etc.

[0040] It is also advantageous if at least one bio-based particulate or rod-shaped natural material is porous. Examples of porous natural materials include cork granules, peanut shells, sunflower stalks, pineapple leaves, bark granules, and flax and hemp straw.

[0041] Another preferred embodiment provides that the at least one binder is selected from the group consisting of aqueous phenol-formaldehyde resins, urea-formaldehyde resins, acrylate resins, alkyd resins, melamine-formaldehyde resins, lignin-formaldehyde resins, tannin-urotropin resins, or 100% systems such as epoxy resins, unsaturated polyester resins, polyurethanes, furan resins, powder resins; as well as mixtures thereof.

[0042] Particularly preferred is at least one flame retardant selected from the group consisting of inorganic substances such as aluminium hydroxide (ATH), magnesium hydroxide (MDH), aluminium oxide hydroxide (AOH), ammonium phosphates such as ammonium polyphosphate (APP) or ammonium diphosphate, but also layered silicates such as montmorillionite, kaolinite, talc, mixed-valent hydroxides (LDH; English: layered double hydroxides) and organic salts such as melamine derivatives, e.g. melamine polyphosphate or melamine cyanurate, and expandable graphite as well as mixtures thereof.

[0043] Another preferred embodiment of the composite plate according to the invention provides that, based on 100 parts by weight of the at least one bio-based particulate or rod-shaped natural substance, 5 to 200 parts by weight, preferably 10 to 100 parts by weight, particularly preferably 12 to 70 parts by weight of the at least one binder, and 2 to 100 parts by weight, preferably 5 to 60 parts by weight, particularly preferably 10 to 50 parts by weight of the at least one inorganic flame retardant, which contains or consists of.

[0044] If the composite panel according to the invention consists of the aforementioned material components, the composite panel contains no further components. However, it is also possible that the composite panel according to the invention contains further components, such as fillers, pigments, dyes, biocides, etc.

[0045] It is also possible that the composite panel according to the invention can be surface-coated. The surface coating can, for example, be a paper or veneer coating.

[0046] Preferred thicknesses of the composite plate according to the invention range from 5 to 250 mm, preferably from 10 to 150 mm, and particularly preferably from 50 to 120 mm.

[0047] The composite panel according to the invention is characterized in particular by a low bulk density. The density of the composite panel is preferably below 250 kg / m³.

[0048] Furthermore, the composite panel according to the invention exhibits high insulating properties. The thermal conductivity, measured according to EN 12667:2001, is, according to the invention, a maximum of 50 mW / mK, preferably from 30 to 45 mW / mK.

[0049] Due to the material combination according to the invention, which forms the basis of the composite panel according to the present invention, it also exhibits excellent fire protection properties. The composite panel according to the invention can therefore preferably be classified as flame-retardant in accordance with DIN EN 13501-1:2010.

[0050] As mentioned at the outset, the composite panel will contain wood chips in minor quantities. According to the invention, a maximum of 20 wt.%, preferably a maximum of 15 wt.%, more preferably a maximum of 10 wt.%, and particularly preferably a maximum of 5 wt.%, of the total quantity of the at least one bio-based particulate or rod-shaped natural material or the combination of particulate and rod-shaped natural materials is replaced by wood chips, such as cutting chips, shavings, planing chips, sawdust, or wood strands.

[0051] According to a further aspect, the present invention relates to a method for producing a composite panel described above, in which at least one bio-based particulate or rod-shaped natural material, wherein wood is excluded as a natural material, at least one thermosetting resin as a binder and at least one inorganic flame retardant are mixed and the mixture is subsequently subjected to a shaping process, whereby the composite board is formed, wherein a maximum of 20 wt.% of the total amount of the at least one bio-based particulate or rod-shaped natural material or the combination of particulate and rod-shaped natural materials is replaced by wood chips, and the composite board has a thermal conductivity, measured according to EN 12667:2001, of a maximum of 50 mW / mK.

[0052] The terminology used for the purposes of describing the method according to the invention is identical to that of the composite plate introduced above in connection with the present invention.

[0053] Preferably, based on 100 parts by weight of the at least one bio-based particulate or rod-shaped natural substance, 5 to 200 parts by weight, preferably 10 to 100 parts by weight, particularly preferably 12 to 70 parts by weight of the at least one binder, and 2 to 100 parts by weight, preferably 5 to 60 parts by weight, particularly preferably 10 to 50 parts by weight of the at least one inorganic flame retardant are used.

[0054] According to a preferred embodiment, the shaping process comprises heating the mixture to temperatures of 80 to 200 °C, preferably 100 to 180 °C, particularly preferably 120 to 150 °C, preferably for a period of 10 s to 90 min, more preferably 3 min to 60 min, particularly preferably 5 min to 40 min.

[0055] Furthermore, it is advantageous that the heating is carried out by applying saturated steam, hot air, microwaves and / or infrared radiation to the mixture.

[0056] In particular, the shaping process may include pressing the mixture, whereby the pressing may be carried out in particular on a continuously operating press.

[0057] In the process according to the invention, a maximum of 20 wt.%, preferably a maximum of 15 wt.%, more preferably a maximum of 10 wt.%, particularly preferably a maximum of 5 wt.%, of the total amount of the at least one bio-based particulate or rod-shaped natural substance or the combination of particulate and rod-shaped natural substances is replaced by wood chips, such as cutting chips, hammer chips, planing chips, sawdust or wood strands.

[0058] It is also possible to add at least one additive to the mixture, in particular an additive selected from the group consisting of fillers, pigments and biocides.

[0059] Furthermore, the present invention relates to the use of the composite panel according to the invention as a thermal insulation material in general and in particular in external thermal insulation composite systems for facade insulation, as a building material, as impact sound insulation, as sound insulation.

[0060] The present invention is explained in more detail in the following examples, without limiting the invention to the specific embodiment. Example 1 according to the invention:

[0061] InOne hundred parts by weight of expanded cork granules are added to a beaker. Expanded cork granules are obtained from baking cork residues through regranulation. (http: / / www.materialarchiv.ch / detail / 1866 / Daemmkorkexpandiert# / detail / 1866 / daemmkork-expandiert, accessed March 28, 2019). The particle size of the expanded cork is 2–10 mm. Previously, 21.5 parts by weight of a melamine-formaldehyde resin (MF) with a solids content of 67% are finely dispersed with 21.5 parts by weight of aluminum trihydrate (ATH). The mixture is added to the cork granules and thoroughly mixed. Then, 2600 ml of the mixture are placed in a 240 x 240 x 40 mm frame mold and compacted to a height of 34 mm at a temperature of 130 °C for 40 minutes. After demolding, a stable test specimen with a density of 143 kg / m³ is obtained. The thermal conductivity λ-10, measured according to EN 12667:2001, is 43.41 mW / (m·K). Comparative example 1:

[0062] InOne hundred parts by weight of wood shavings measuring 2-4 mm are placed in a beaker. Prior to this, 50 parts by weight of a melamine-formaldehyde resin (MF) are finely dispersed with 20 parts by weight of aluminum trihydrate (ATH). This mixture is added to the cork granules and thoroughly mixed. Subsequently, 2600 ml of the mixture are poured into a 240 x 240 x 40 mm frame mold and compacted to a height of 34 mm at a temperature of 130 °C for 40 minutes. After demolding, a stable test specimen with a density of < 200 kg / m³ is obtained. The thermal conductivity λ-10, measured according to EN 12667:2001, is 43.67 mW / (m K). Comparison of example 1 according to the invention - Comparison example 1

[0063] Example 1 according to the invention shows the optimized variant using a pure natural material. Lower amounts of binder and thus a lower density are possible compared to Comparative Example 1. In Comparative Example 1, an insulating board was produced from a material that is used in a similar form in DE 10 2016 121 590 A1. The amount of resin used was selected to produce a dimensionally stable board with a density within the range described in DE 10 2016 121 590 A1. Surprisingly, the thermal conductivity remains virtually unaffected. Example 2 according to the invention:

[0064] For direct comparison to comparative example 1, an insulation board according to the invention was produced with a mixture of cork granules and straw instead of wood shavings.

[0065] InOne hundred parts by weight of a natural material mixture are added to a beaker. The mixture consists of 75 parts expanded cork granules with a particle size of 2–10 mm and 25 parts rapeseed straw with a rod length of 2–50 mm. Prior to this, 50 parts by weight of a melamine-formaldehyde resin (MF) are finely dispersed with 20 parts by weight of aluminum trihydrate (ATH). This mixture is added to the natural material mixture and thoroughly blended. Subsequently, 2600 ml of the mixture are poured into a 240 x 240 x 40 mm frame mold and compacted to a height of 34 mm at a temperature of 130 °C for 40 minutes. After demolding, a stable test specimen with a density of < 135 kg / m³ is obtained.

[0066] Despite having the same weight proportions of natural material, resin and flame retardant in comparative example 1 and example 1 according to the invention, the plate according to the invention has a significantly lower density. Comparative example 2:

[0067] In One hundred parts by weight of wood shavings measuring 2-4 mm are placed in a beaker. Prior to this, 21.5 parts by weight of a melamine-formaldehyde resin (MF) are finely dispersed with 21.5 parts by weight of aluminum trihydrate (ATH). The mixture is added to the cork granules and thoroughly mixed. Subsequently, 2600 ml of the mixture are poured into a 240 x 240 x 40 mm frame mold and compacted to a height of 34 mm at a temperature of 130 °C for 40 minutes. After demolding, a stable test specimen is not obtained. Therefore, if an attempt is made to transfer the resin quantity of the inventive board to the board with wood shavings, a stable board cannot be obtained. Example 3 according to the invention:

[0068] InOne hundred parts by weight of expanded cork granules are added to a beaker. The particle size of the expanded cork is 2–10 mm. Prior to this, 21.5 parts by weight of a melamine-formaldehyde resin (MF) are finely dispersed with 10 parts by weight of ammonium polyphosphate (APP). This mixture is added to the cork granules and thoroughly mixed. Subsequently, 2600 ml of the mixture are poured into a 240 x 240 x 40 mm frame mold and compacted to a height of 34 mm at a temperature of 130 °C for 40 minutes. After demolding, a stable test specimen with a density of < 130 kg / m³ is obtained. The thermal conductivity λ⁻¹⁰ is 39.67 mW / (m·K). Example 3 according to the invention shows the possibility of changing the flame retardant and slightly reducing the density and thermal conductivity compared to Example 1 according to the invention by using a lower proportion of ammonium polyphosphate. Example 4 according to the invention:

[0069] InOne hundred parts by weight of a natural material mixture are added to a beaker. The mixture consists of 72 parts expanded cork granules with a particle size of 2–10 mm and 28 parts rapeseed straw with a rod length of 2–50 mm. Prior to this, 21.5 parts by weight of a melamine-formaldehyde resin (MF) with 10 parts by weight of ammonium polyphosphate (APP) are finely dispersed. This mixture is added to the natural material mixture and thoroughly blended. Subsequently, 2600 ml of the mixture are poured into a 240 x 240 x 40 mm frame mold and compacted to a height of 34 mm at a temperature of 130 °C for 40 minutes. After demolding, a stable test specimen with a density of 141 kg / m³ is obtained. The thermal conductivity λ⁻¹⁰ is 42.11 mW / (m·K). Example 4 according to the invention shows the possibility of replacing part of the cork granules with straw.Density and thermal conductivity remain within the same range as in examples 1 and 2 according to the invention, significantly below the values ​​for comparative example 1.

[0070] Surprisingly, it was found that particulate natural material granules and rod-shaped natural materials, as well as mixtures of particulate and rod-shaped natural materials, can be bonded to form composite boards in which the flame-retardant resin matrix protects the natural materials from fire. In the event of a fire, the composite boards remain dimensionally stable and do not drip burning components from them. The dispersion of the flame retardant within the resin binder and its subsequent fine distribution on the granules ensures ideal distribution of the flame retardant throughout the composite boards. This allows flammable natural materials to be safely used in insulation. The high proportion of renewable raw materials enables low energy consumption and carbon dioxide emissions during production.

Claims

1. A composite panel, comprising or consisting of at least one bio-based, particulate or rod-shaped, natural material and combinations of particulate and rod-shaped natural materials, excluding wood as natural material, at least one thermosetting cured resin as a binder, and at least one inorganic flame retardant, characterized in that the composite panel contains wood chips, wherein a maximum of 20% by weight of the total amount of the at least one bio-based, particulate or rod-shaped, natural material, or the combination of particulate and rod-shaped natural materials, respectively, is replaced by wood chips, and the composite panel has a thermal conductivity of maximally 50 mW / mK, measured in accordance with EN 12667:2001.

2. The composite panel according to claim 1, characterized in that the particle size of the at least one bio-based, particulate natural material is at least 2 mm, preferably 2 to 40 mm, particularly preferably 2 to 25 mm and / or the rod length of the at least one bio-based, rod-shaped natural material is greater than 2 mm, preferably 5 to 100 mm, particularly preferably 10 to 75 mm.

3. The composite panel according to one of the preceding claims, characterized in that the at least one bio-based, particulate natural material is selected from the group consisting of cork meal, corn husk meal, nut shells (e.g. peanut shells), nut shell meal, bark granules, fruit husks, cereal husks, corn husks, crushed pineapple leaves, pecan nut shells and meal, crushed durian fruit husks, rice hulls, olive pits and mixtures thereof, and the at least one bio-based, rod-shaped natural material is selected from the group consisting of sunflower stalks, reeds, cattails, cotton stalks and straw of cereals, rice, flax, hemp, maize or rapeseed and mixtures thereof.

4. The composite panel according to any one of the preceding claims, characterized in that the at least one bio-based, particulate or rod-shaped, natural material is porous.

5. The composite panel according to one of the preceding claims, characterized in that the at least one binder is selected from the group consisting of aqueous phenol-formaldehyde resins, urea-formaldehyde resins, acrylate resins, alkyd resins, melamine-formaldehyde resins, lignin-formaldehyde resins, tannin-urotropine resins, or 100% systems such as epoxy resins, unsaturated polyester resins, polyurethanes, rubbers, furan resins, powder resins; and mixtures thereof and / or the at least one flame retardant is selected from the group consisting of inorganic substances, such as aluminum hydroxide (ATH), magnesium hydroxide (MDH), aluminum oxide hydroxide (AOH), ammonium phosphates, such as ammonium polyphosphate (APP) or ammonium diphosphate, but also layered silicates, such as montmorillionite, kaolinite, talc, mixed-valent hydroxides (LDH; Englisha: layered double hydroxides) and organic salts, such as melamine derivatives, e.g. melamine polyphosphate or melamine cyanurate, and exfoliated graphite as well as mixtures thereof.

6. The composite panel according to any one of the preceding claims, characterized in that, based on 100 parts by weight of the at least one bio-based, particulate or rod-shaped, natural material, it comprises or consists of 5 to 200 parts by weight, preferably 10 to 100 parts by weight, particularly preferably 12 to 70 parts by weight, of the at least one binder and 2 to 100 parts by weight, preferably 5 to 60 parts by weight, particularly preferably 10 to 50 parts by weight, of the at least one inorganic flame retardant.

7. The composite panel according to one of the preceding claims, characterized in that it has a thickness of 5 to 250 mm, preferably 10 to 150 mm, particularly preferably 50 to 120 mm, has a density of less than 250 kg / m3, has a thermal conductivity, measured according to EN 12667:2001, of 30 to 45 mW / mK, and / or is classified as flame-retardant in accordance with DIN EN 13501-1:2010.

8. The composite panel according to one of the preceding claims, characterized in that a maximum of 15 % by weight, further preferably a maximum of 10 % by weight, particularly preferably a maximum of 5 % by weight, of the total amount of the at least one bio-based, particulate or rod-shaped, natural material, or of the combination of particulate and rod-shaped natural materials, respectively, is replaced by wood chips, such as cutting chips, shavings, planing chips, sawdust or wood strands.

9. The composite panel according to one of the preceding claims, characterized in that it comprises at least one additive, in particular an additive selected from the group consisting of fillers, pigments and biocides.

10. A method of manufacturing a composite panel according to any one of the preceding claims, in which at least one bio-based, particulate or rod-shaped, natural material as well as combinations of particulate and rod-shaped natural materials, wherein wood is excluded as natural material, at least one thermosetting resin as a binder, and at least one inorganic flame retardant are mixed and the mixture is then subjected to a shaping process to produce the composite panel, wherein a maximum of 20% by weight of the total amount of the at least one bio-based, particulate or rod-shaped, natural material, or the combination of particulate and rod-shaped natural materials, respectively, is replaced by wood chips, and the composite panel has a thermal conductivity of maximally 50 mW / mK, measured in accordance with EN 12667:2001.

11. The method according to the preceding claim, characterized in that, based on 100 parts by weight of the at least one bio-based, particulate or rod-shaped, natural material, 5 to 200 parts by weight, preferably 10 to 100 parts by weight, particularly preferably 12 to 70 parts by weight, of the at least one binder and 2 to 100 parts by weight, preferably 5 to 60 parts by weight, particularly preferably 10 to 50 parts by weight, of the at least one inorganic flame retardant are used.

12. The method according to the preceding claim, characterized in that the shaping process comprises heating the mixture, in particular by subjecting the mixture to saturated steam, hot air, microwaves and / or infrared radiation, to temperatures of 80 to 200°C, preferably 100 to 180°C, particularly preferably 120 to 150°C, preferably over a period of 10 seconds to 90 minutes, more preferably 3 minutes to 60 minutes, particularly preferably 5 minutes to 40 minutes.

13. The method according to one of claims 10 to 12, characterized in that the shaping method comprises pressing the mixture, the pressing being carried out in particular on a continuously operating press.

14. The method according to one of claims 10 to 13, characterized in that a maximum of 15% by weight, further preferably a maximum of 10% by weight, particularly preferably a maximum of 5% by weight, of the total amount of the at least one bio-based, particulate or rod-shaped, natural material, or of the combination of particulate and rod-shaped natural materials, respectively, is replaced by wood chips, such as cutting chips, shavings, planing chips, sawdust or wood strands.

15. A use of a composite panel according to any one of claims 1 to 9 as thermal insulation material, as building material, as impact sound insulation or as sound insulation.