GYPSUM-BASED ACOUSTIC PANEL

Abstract

A gypsum-based acoustic panel wherein in the panel includes a core layer of foamed gypsum, face side and back side layers of non-woven encasing the core layer, and the panel has an alpha.sub.w-value of between 0.4 and 0.7 and specific flow resistances of <15000 Pa s/m, methods for their preparation and their uses.

Claims

1. A gypsum-based acoustic panel wherein in the panel comprises: a core layer of foamed gypsum; a first and a second cover sheet encasing the core layer; and the panel has an alpha.sub.w-value of between 0.4 and 0.7 and a specific flow resistance of <15000 Pa s/m.

2. The gypsum based acoustic panel according to claim 1, characterized in that the first and second cover sheet are non-wovens.

3. The gypsum based acoustic panel according to claim 1, characterized in that before setting the gypsum comprises a hemihydrate mixture consisting of: 32 to 62% of titanogypsum; 13 to 43% of citrogypsum and 10 to 40% of FGD gypsum; the percentages being by weight and based on the entire hemihydrate mixture and adding up to 100%.

4. The gypsum based acoustic panel according to claim 1, characterized in that the acoustic panel contains an organic calcium salt, in the range of 0.20 to 0.30% by weight, based on the entire amount of gypsum in each case, and/or polyvinyl alcohol in the range of 1.5 to 2.5% by weight, based on the entire amount of gypsum in each case.

5. The gypsum based acoustic panel according to claim 1, characterized in that the gypsum contains fibres in an amount of up to 1.0 to 2.0% by weight in relation to amount of gypsum.

6. The gypsum based acoustic panel according to claim 5, characterized in that the fibres are selected from the group consisting of glass fibres, carbon fibres, mineral fibres, basalt fibres, cellulose fibres, fibres or synthetic organic polymer and mixtures thereof.

7. The gypsum based acoustic panel according to claim 1, characterized in that it has a density of <450 kg/m.sup.3.

8. The gypsum based acoustic panel according to claim 1, characterized in that it has the following set of properties and features: alpha.sub.w-values of up to 0.6; specific flow resistance of <15000 Pa s/m; density of <450 kg/m.sup.3; the gypsum is encased with a non-woven; a thickness of 20 mm?0.7 mm; a square meter weight of <7.5 kg/m.sup.2; the employed gypsums/hemihydrates have a purity of at least 90% by weight; an amount of 1.5 to 2.5% by weight of polyvinyl alcohol, based on the entire amount of employed gypsum; glass fibres having chopped strands lengths of between 5 mm and 15 mm and filament diameters of between 13 ?m and 17 ?m; the surface is optionally neither holed nor perforated; pore sizes of the core layer in the range of 20 ?m to 300 ?m; and the amount of pores is within the range of 40 to 60% by volume.

9. The gypsum based acoustic panel according to claim 1, characterized in that the acoustic panel is structured, and covered with a further layer of non-woven.

10. A process for preparing a gypsum based acoustic panel having an alpha.sub.w-value of between 0.4 and 0.7 and a specific flow resistance of <15000 Pa s/m comprising of the following steps: I) providing beta-hemihydrate from a synthetic gypsum source; II) mixing the compound of I) with water to provide a slurry; III) mixing an active pore-forming compound with the compound of I) or the slurry of II) and/or mixing a surfactant-based foam with the slurry of II) to provide a foamed slurry; IV) applying the resulting foamed slurry to a first cover sheet, made of non-woven; V) applying a second cover sheet, made of non-woven, to the foamed slurry opposite to the side of the first cover sheet; VI) drying the product of VI) to obtain an acoustic panel; wherein the foamed slurry has a slump test value of between 155 and 190 mm and slurry-litre weight of between 520 and 580 g/l; wherein during and after the application of the foamed slurry no distributor roller is used; and the foamed slurry is distributed by vibration.

11. A process for preparing a gypsum based acoustic panel having an alpha.sub.w-value of between 0.4 and 0.7 and a specific flow resistance of <15000 Pa s/m comprising of the following steps: I) providing beta-hemihydrate from a synthetic gypsum source; II) mixing the compound of I) with water to provide a slurry; III) mixing an active pore-forming compound with the compound of I) or the slurry of II) and/or mixing a surfactant-based foam with the slurry of II) to provide a foamed slurry; IV) applying the resulting foamed slurry to a first cover sheet, made of non-woven; V) applying a second cover sheet, made of non-woven, to the foamed slurry opposite to the side of the first cover sheet; and VI) drying the product of VI) to obtain an acoustic panel; wherein the foam generation is started: i) before entering the mixer, with aid of surfactant; ii) upon entering of dry components, via a component screw, into the mixer; or i) before entering the mixer and upon entering of dry components into the mixer.

12. The process according to claim 10, wherein the foam generation is started: i) before entering the mixer, with aid of surfactant; ii) upon entering of dry components, preferably via a component screw, into the mixer; or iii) before entering the mixer and upon entering of dry components into the mixer.

13. The process according to claim 10, characterized in that an accelerator is added to the mixture in step II), and the accelerator is based on a calcium sulphate dihydrate.

14. (canceled)

15. A use of the acoustic panel according to claim 1 for suspended ceilings, coffered ceilings, insert ceilings, as separate acoustic element, ceiling elements or wall panel for rooms, as part of a system-solution to optimize acoustical properties, and to reduce the reverberation time in rooms.

16. A use of the acoustic panel prepared according to the process of claim 10 for suspended ceilings, coffered ceilings, insert ceilings, as separate acoustic element, ceiling elements or wall panel for rooms as part of a system-solution to optimize acoustical properties, and to reduce the reverberation time in rooms.

Description

[0160] In the following the invention is additionally described with reference to the figures. The figures are not necessarily true to scale and simplified. As such, features readily know to the person skilled in the art are not necessarily shown (like screws, valves, mixers, cutters, connections of the respective devices, exact configuration of known devices and such) in order to enhance the intelligibility and clarity of the figures. The invention, however, is not to be reduced to the figures, which are understood to be illustrative.

[0161] FIG. 1 is an illustration of how the acoustic sound damping with the acoustic panels of the present invention works. Here, a ceiling panel of a room is depicted with ambient air above the panel. The panel is illustrated by two thick horizontal lines representing the face side and the back side (cover sheets). The closed circles illustrate gypsum particles and the spaces in between the closed circles illustrate the channels and cavities of the foamed structure.

[0162] It should be understood that this is an idealised depiction and the actual gypsum particles, channels and cavities in reality are not that orderly and far more irregular. Typically, sharp edges predominate over smooth and round structures.

[0163] An impinging sound wave from the lower left (the length of the arrow depicts the direction of travel of the sound wave, whereas the intensity of the sound wave is depicted by the concentric circle segments) is partly reflected at the face side surface, which is illustrated by the dashed arrows at the bottom. The part of the soundwave entering into the porous core layer can no longer travel straight, but has to follow the various channels and cavities. This leads to a spread of the sound in virtually all directions. During this process, a significant amount of the sound is converted to heat energy, which reduces the sound energy in the gypsum core layer. Thus, the portion of the initial soundwave that reaches the inner back side cover sheet (on which, again a part is reflected) is greatly reduced. Therefore, only a highly reduced soundwave is transmitted through the panel and escapes through the back side, which is illustrated by the much shorter arrow.

[0164] FIG. 2 is another, more simplified version of the working principle of the present invention. A soundwave is shown coming from the lower right towards the acoustic panel. Upon entering through the face side cover sheet, formed from a non-woven, into the porous core layer of the panel, the sound is spread in several directions and thus both the intensity of the sound being reflected and also the sound being able to reach the ambient air through the back side of the panel are greatly reduced.

[0165] FIG. 3 is a side-view photograph of a cut through an acoustic panel according to the present invention. The monolithic foamed structure of gypsum can be seen between the face and backside cover sheets that were made from the glass fibre/polyester fibre composite non-woven.

[0166] FIGS. 4 and 5 show micrographs of a core layer according to the invention. FIG. 4 shows a 50-fold magnification, while FIG. 5 depicts a 100-fold magnification. For comparative purposes, both micrographs include a bar representing 1000 ?m. An extensive network of pores and channels runs through the gypsum matrix. Compared to other lightweight gypsum panels, the pores of the inventive panels are smaller and shaped irregularly.

[0167] The invention is now described in more detail with reference to the following non-limiting examples. The following exemplary, non-limiting examples are provided to further describe the embodiments presented herein. Those having ordinary skill in the art will appreciate that variation of these examples are possible within the scope of the invention.

EXAMPLES

[0168] Five different acoustic panels with a gypsum core layer and a non-woven cover sheets on the face and back sides were prepared in accordance with a process according to the present invention.

[0169] Key data and production parameters: [0170] panel size: 2000*1250*20 mm [0171] encasing material: glass fibre/polyester composite non-woven

[0172] The basic composition of for the gypsum was in any case the same and comprised 47% of titanogypsum, 28% of citrogypsum and 25% of FGD gypsum.

[0173] Polyvinyl alcohol, calcium carbonate and tartaric acid were employed as pre-mixed additive compounds in each case.

TABLE-US-00001 TABLE 1 parameter unit No. 01 No. 02 No. 03 No. 04 No. 05 nominal thickness mm 20 20 20 20 20 non-woven (face) blend of glass fibres and polyester fibres non-woven (back) blend of glass fibres and polyester fibres foam concentrate anionic surfactant glass fibres.sup.1 g/m.sup.2 110 110 110 110 110 Polyvinyl alcohol % 2.0 2.0 2.0 2.0 2.0 calcium carbonate (<63 ?m) % 0.25 calcium carbonate (<100 ?m) % 0.25 0.25 0.25 0.25 L(+)-tartaric acid % 0.25 0.25 0.25 0.25 0.25 square meter weight kg/m.sup.2 7.11 7.04 6.82 7.13 6.58 density kg/m.sup.3 358 355 342 352 331 measured thickness mm 19.88 19.80 19.94 20.27 19.87 Rs Pa s/m 10502 10608 10192 12304 7760 alpha.sub.w-value 0.55 0.55 n.d. 0.50 0.60 specific flexural strength.sup.2 N/mm.sup.2 1.98 2.03 2.25 2.79 2.06 1.79 1.93 2.04 2.54 1.97 2.21 2.16 2.39 3.06 2.19 specific flexural strength.sup.3 N/mm.sup.2 1.73 1.83 1.85 2.49 1.71 1.44 1.71 1.64 1.99 1.45 2.02 1.93 2.04 2.89 1.97 Young's modulus.sup.4 N/mm.sup.2 521 523 553 637 534 452 494 505 596 523 587 550 589 675 544 Young's modulus.sup.5 N/mm.sup.2 401 411 409 553 398 335 393 373 492 377 462 418 454 611 427 adhesive tensile strength.sup.6 N/mm.sup.2 0.14 0.14 0.16 0.19 0.16 0.12 0.13 0.13 0.17 0.14 0.16 0.16 0.18 0.30 0.18 adhesive tensile strength.sup.7 N/mm.sup.2 0.16 0.14 0.18 0.25 0.15 0.14 0.12 0.16 0.17 0.13 0.19 0.16 0.20 0.30 0.17 The foam concentrate is a blend of anionic surfactant (35%) in water (65%) .sup.1= glass fibres from Johns Manville J.M. M300-13 Rs = specific flow resistivity (with non-woven) according to EN ISO 9053-1/EN 29053 alpha.sub.w-value determined according to DIN EN ISO 11654 n.d. = not determined .sup.2face side, lengthwise, sigma.sub.Fmax, according to EN 15283-1:2009/DIN 18180, values are (from top) average, minimum and maximum .sup.3= back side, crosswise, dto .sup.4= face side, lengthwise, according to EN 15283-1:2009/DIN 18180, dried at 40? C., values are (from top) average, minimum and maximum .sup.5= back side, crosswise, dto .sup.6= face side, according to EN 13963:2014, values are (from top) average, minimum and maximum .sup.7= back side, dto

[0174] Additionally, in the sound testing, all the samples achieved the additional designation H for particularly high absorption of high frequencies.

[0175] As is apparent from the above table, the acoustic panels prepared show a very good balance of good acoustic properties and at the same time mechanical properties.

[0176] As can be seen examples 1 to 4 can be assigned to absorber class D, i.e. absorbing and example 5 to absorber class C, i.e. highly absorbing. At the same time, example 5 has the lowest specific flow resistivity.