Acoustic panel and method of manufacture

Abstract

The present invention lies in the technical field of acoustic room design and provides an acoustic panel (1) comprising a composite material made of cereal husks (2) and glutin (4). A method for producing an acoustic panel (1) according to the invention and the use of such a panel for sound absorption and / or sound interruption are also provided.

Description

[0001] The present invention lies in the technical field of acoustic room design and provides an acoustic panel comprising a composite material made of cereal husks and gluten. A method for producing an acoustic panel according to the invention and the use of such a panel for sound absorption and / or sound interruption are also provided.

[0002] The acoustics in large spaces, such as open-plan offices, meeting rooms, and trade fair and exhibition spaces, have a significant impact on the indoor climate. Sound absorbers or acoustic panels are typically made of foam, various polymers, felt, or mineral wool.

[0003] In recent years, particular attention has been paid to sustainable materials, preferably made from sustainable raw materials. For example, panels made from mushroom mycelium or hemp are used for this purpose.

[0004] One possible material for this purpose is fiber-reinforced plastics with biological fillers, some of which are not based on petrochemical materials such as plastics, but are combined with biological materials such as rice husks, rice husks, sisal, etc., as described in EP 1 338 405 B1. The described materials can be used in a variety of ways, for example, as windows and doors due to their good weather resistance.

[0005] The use of waste products from side streams of the agricultural industry is described in German patent application DE 10 2018 111 210 A1, which discloses a material consisting of cereal husks and an organic polymer, which is processed into a polymer-husk composite material. This material can be used as doors, windows, paneling, or insulation. The material can be coated with a fire retardant, thus reducing flammability.

[0006] A material based on cereal husks, a byproduct of the agricultural industry, is described in European application EP 3 865 422 A1. This application discloses a molded packaging component based on cereal husks for packaging, for example, fragile items for shipping. The material is a composite material made of cereal husks and a plant-based binder.

[0007] In addition to state-of-the-art applications, it is preferable that materials used as sound absorbers also be made from sustainable materials. Side streams from the food and agricultural industries are suitable as starting materials.

[0008] The primary object of the present invention was therefore to provide a material based on renewable raw materials that can be used as a sound-absorbing material. Short description of the characters

[0009] Figure 1 shows schematically the structure of an acoustic panel 1 according to the invention. The acoustic panel 1 comprises a composite material made of cereal husks 2 and glutin 4 and can be coated with a fire retardant 6.

[0010] The primary object of the present invention has been achieved by providing an acoustic panel 1 comprising or consisting of a composite material of cereal husks 2 and glutin 4.

[0011] Figure 1 shows schematically the structure of an acoustic panel 1 according to the invention. The acoustic panel 1 comprises a composite material made of cereal husks 2 and glutin 4 and can be coated with a fire retardant 6.

[0012] An acoustic panel 1 within the meaning of the present invention is a material that absorbs sound energy and converts it into heat. Acoustic panels can be used as ceiling and wall absorbers, table top panels, partition walls, and room dividers or partition walls. Acoustic panels lead to an acoustic improvement in the indoor climate.

[0013] Grain husks 2 are the bracts in the spikelet, which is a partial inflorescence of the grass family (Poaceae). Husks fulfill the natural function of protecting the flowers of a grass, such as wheat. These are removed from the grain during threshing and are a waste product, along with the awns, seed coats, and stem parts, known as chaff in the agricultural industry.

[0014] Glutin 4 is a mixture of denatured protein based on collagen and can be obtained by boiling collagen-containing ingredients such as bones, cartilage, skins, or fish bones. Glutin is used as a glue in the wood industry, in restorations, and in traditional handicrafts, among other applications.

[0015] In the context of the present invention, glutin 4 leads to a very good and stable bonding of the grain husks 2 among each other and thus to the stability of the acoustic panel.

[0016] An acoustic panel 1 made of glutin 4 and grain husks 2 has the advantage that the raw materials are generated as side streams of the food industry and are therefore sustainable. It is therefore particularly preferred that the acoustic panel 1 contains no ingredients of petrochemical origin.

[0017] Furthermore, the glutin 4 interacts with the grain husks 2 to produce a porous absorber material. The grain husks 2 are preferably evenly distributed throughout the material and are held together by the glutin 4. The grain husks 2 form a cavity that is essentially unfilled by the glutin 4, so that the acoustic panel 1 has a porous structure.

[0018] Due to their growth, the grain husks 2 exhibit essentially closed cavities. This means, in particular, that there is a completely closed and / or essentially closed cavity into which glutin 4 cannot penetrate, or can penetrate only with difficulty or to a limited extent.

[0019] The provided acoustic panel 1 is completely biodegradable as it does not contain any petrochemical components.

[0020] The grain husks 4 are preferably selected from the group consisting of wheat husks, rye husks, rice husks, millet husks, and spelt husks, with spelt husks being particularly preferred. Furthermore, mixtures of different grain husks 2 are preferably used. The porosity and thus the properties of the acoustic panel can be specifically influenced by the grain husks 2 used.

[0021] Spelt husks have two husks, a small and a large husk, and therefore provide particularly good stability for the acoustic panel, which is achieved through the interlocking of the husks. The hollow spaces created by the spelt husks ensure particularly high porosity, which leads to high sound absorption and therefore provides a particularly preferred acoustic panel.

[0022] Further preferably, the glutin 4 originates from an animal glue, preferably selected from the group consisting of bone glue, fish glue, rabbit glue, hide glue or mixtures thereof.

[0023] An animal glue within the meaning of the present invention is a glutin glue which is obtained by boiling bones, cartilage, skins or fish bones.

[0024] Glutin is not synonymous with gelatin. Glutin is an unpurified form and contains impurities resulting from the manufacturing process. The biggest difference, however, is the chemical structure. Glutin is obtained through a gentle manufacturing process, resulting in undenatured collagen fibers in the resulting glutin glue. This results in glutin glue possessing strong adhesive properties, whereas gelatin consists of denatured collagen and its gelling properties are more prominent. Gelatin is particularly pure, odorless, and colorless. Glutin has a yellowish to brownish color, a strong odor, and is impure. Processing glutin is extremely challenging because it is less pure than gelatin. Gelatin is suitable for food use, whereas glutin is not due to the impurities that are advantageous in the context of the present invention.

[0025] With regard to the desired sustainability of building and insulation materials, the use of glutin is preferred because it requires less energy to produce, releases less CO2, and is a by-product of slaughterhouse waste.

[0026] Preferably, the composite material of the acoustic panel 1 is coated with a fire retardant 6, which is preferably selected from the group consisting of amorphous sodium, potassium, and lithium silicate, or mixtures thereof. Fire retardants are also referred to as flame retardants.

[0027] Furthermore, the acoustic panel 1 preferably has a water content of between 0.5 and 25 wt.%, preferably between 1 and 20 wt.%, and particularly preferably between 5 and 20 wt.%. The water content is determined using a method familiar to the person skilled in the art, such as constant dryness or Karl Fischer titration.

[0028] The acoustic panel 1 according to the present invention has the property that it can absorb and release water and thus contributes to the regulation of humidity and the room climate.

[0029] The acoustic panel 1 preferably has a bulk density of between 100 and 450 kg / m 3< , preferably between 150 and 350 kg / m 3< and particularly preferably between 200 and 250 kg / m 3< .

[0030] The acoustic panels according to the present invention can have different thicknesses and thus be suitable for different applications.

[0031] A further aspect of the present invention is the provision of a method for producing an acoustic panel 1 according to the invention, comprising or consisting of the steps: a) Providing water and glutin 4; b) Mixing water and glutin 4 and heating the resulting mixture to a temperature in a range of between 50°C and 100°C, preferably in the range of between 55°C and 75°C; c) Providing cereal husks 2, preferably spelt husks, and mixing the cereal husks 2 with the heated mixture obtained in step b); d) Filling the mixture obtained in step c) into molds and drying the mixture; e) Obtaining an acoustic panel 1.

[0032] In steps a) and b), a mixture of glutin (4) and water is first prepared. This mixture has the advantage that the viscosity of the resulting mixture after heating is particularly advantageous for further processing. In particular, this creates a particularly advantageous mixture together with the grain husks (2), which are added in step c). The water-glutin mixture from step b) ensures uniform wetting of the grain husks (2), thus resulting in a uniform bond between glutin (4) and grain husks (2), as well as ensuring the adhesion of the grain husks (2) to one another. This means that the resulting acoustic panel (1) is highly stable and suitable for many applications.

[0033] Particularly preferably, the heating in step b) is carried out at 60°C (±2 °C).

[0034] Heating the water-gluten mixture produces a flowable mixture that can be poured into any desired mold (step d). The molds can preferably have straight or curved sections.

[0035] As the acoustic panels dry, the water from the water-gluten mixture evaporates, resulting in an acoustic panel 1 made of grain husks 2 and gluten 4 as a binding agent, which contains only a low residual moisture content. This reduces the weight of the resulting acoustic panel 1 and makes it well-suited for a wide range of applications. Weight optimization is also achieved by the fact that the water used causes the grain husks 2 to swell, thus increasing their volume while maintaining the same mass of grain husks 2. This makes the resulting acoustic panels 1 lighter than those known from the prior art.

[0036] Preferably, the acoustic panel 1 is dried in step d) in a drying chamber at a temperature of between 30°C and 80°C, preferably between 35°C and 70°C and preferably at a temperature of between 40°C and 60°C.

[0037] Preferably, in step a) water is provided in an amount of 20 to 60 wt.%, preferably in an amount of 30 to 50 wt.% and Glutin 4 in an amount of 5 to 30 wt.%, preferably in an amount of 10 to 20 wt.%.

[0038] Furthermore, in step c) cereal husks 2 are preferably provided in an amount of 20 to 60 wt.%, preferably in an amount of 30 to 50 wt.%.

[0039] Preferably, the acoustic panel 1 obtained in step e) is coated in a further step f) with a fire retardant 6 selected from the group consisting of amorphous sodium, potassium, and lithium silicate, preferably with a layer thickness of 0.2 to 2 kg / m 2 , particularly preferably with a layer thickness of 0.5 to 1 kg / m 2 . A layer thickness of 0.6 kg / m 2 is most preferred.

[0040] The coating is applied with a uniform layer thickness that is consistent across the entire surface of the acoustic panel. The measurements in kg / m2 therefore indicate the layer thickness relative to the panel surface.

[0041] A further aspect of the present invention is the use of an acoustic panel 1 according to the invention or an acoustic panel produced or producible by a method according to the invention as a partition wall, table top, wall absorber, ceiling sail or cabinet top or parts thereof.

[0042] "Absorber" in the context of the present invention means the absorption of sound and thus contributes to an improved indoor climate.

[0043] Furthermore, the acoustic panels according to the invention can also be used as thermal insulation panels, for example to shield houses or rooms against heat loss.

[0044] The invention is further described below by means of illustrative, non-limiting examples: Examples

[0045] 1. Production of an acoustic panel according to the invention a) 4.0 kg of water and 3.0 kg of gluten are mixed and heated to a temperature of approximately 60°C. b) 7.0 kg of spelt husks are added to the warm mixture from step a). c) This mixture is then filled into rectangular molds for the production of sound-absorbing and sound-interrupting partition walls. d) The molds containing the mixture of spelt husks, water, and gluten are transferred to a drying chamber and dried at a temperature of 55°C for 4 hours. e) The resulting panels have a residual moisture content of 10%, determined by drying a sample to constant weight. The acoustic panel according to the invention has a thickness of 32 mm and a weighted sound absorption coefficient of 0.55 according to ISO 354 and ISO 11654 and a thermal conductivity of 0.054 W / m*K according to DIN EN 12667. 2. Coating of the resulting acoustic panels with water glass.

[0046] The resulting acoustic panels are coated with a water glass solution (a mixture of sodium, potassium, and lithium silicate) at a concentration of 0.6 kg / m² as a fire retardant. For this purpose, the panels obtained in step e) are coated on both sides with water glass using a suitable spray device.

[0047] After coating with water glass, the resulting acoustic panel has building material class B1 (flame-retardant) according to DIN 4102-1.

Claims

1. Acoustic panel (1) comprising or consisting of a composite material of cereal husks (2) and glutin (4).

2. Acoustic panel (1) according to claim 1, wherein the cereal husks (2) are selected from the group consisting of wheat husks, rye husks, millet husks, spelt husks, rice husks or mixtures thereof, preferably spelt husks.

3. Acoustic panel (1) according to one of claims 1 or 2, wherein the glutin (4) originates from an animal glue, preferably selected from the group consisting of bone glue, fish glue, rabbit glue, hide glue or mixtures thereof.

4. Acoustic panel (1) according to one of the preceding claims, wherein the composite material is coated with a fire retardant (6), preferably wherein the fire retardant is selected from the group consisting of amorphous sodium, potassium and lithium silicate.

5. Acoustic panel (1) according to one of the preceding claims, wherein the acoustic panel (1) has a water content of between 0.5 and 25 wt.%, preferably between 1 and 20 wt.% and particularly preferably between 5 and 20 wt.%.

6. Acoustic panel (1) according to one of the preceding claims, wherein the acoustic panel (1) has a bulk density of between 100 and 450 kg / m 3 , preferably between 150 and 350 kg / m 3 and particularly preferably between 200 and 250 kg / m 3 owns.

7. A method for producing an acoustic panel (1), preferably an acoustic panel according to one of claims 1 to 6, comprising or consisting of the steps: a) providing water and gluten (4); b) mixing water and gluten (4) and heating the resulting mixture to a temperature in a range of between 50°C and 100°C, preferably in the range of between 55°C and 75°C; c) providing cereal husks (2), preferably spelt husks, and mixing the cereal husks (2) with the heated mixture obtained in step b); d) filling the mixture obtained in step c) into molds and drying the mixture; e) obtaining an acoustic panel (1).

8. The process according to claim 7, wherein in step a) water is provided in an amount of 20 to 60 wt.%, preferably in an amount of 30 to 50 wt.% and glutin (4) is provided in an amount of 5 to 30 wt.%, preferably in an amount of 10 to 20 wt.%.

9. The method according to claim 7 or 8, wherein in step c) cereal husks (2) are provided in an amount of 20 to 60 wt.%, preferably in an amount of 30 to 50 wt.%.

10. The method according to any one of claims 7 to 9, wherein the acoustic panel obtained in step e) is coated with a fire retardant (6) selected from the group consisting of amorphous sodium, potassium and lithium silicate, preferably with a layer thickness of 0.2 to 2 kg / m 2 , particularly preferably with a layer thickness of 0.5 to 1 kg / m 2 .

11. Use of an acoustic panel (1) according to one of claims 1 to 6 or of an acoustic panel manufactured or manufacturable by a method according to one of claims 7 to 10, as a partition wall, table top, wall absorber, ceiling sail, office zone screening or cabinet top or part thereof.

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