Method for recycling mineral wool, a method for production of acoustical panel elements and such an acoustical panel element

Abstract

An acoustical geopolymer panel element includes a layer including a fibre component and a geopolymer binder made from a mixture including ground mineral wool, and an additional layer including mineral wool. The layer including a fibre component and a geopolymer binder has a density in the range of 20-400 kg/m.sup.3, a porosity in the range of 0.75-0.99 and a thickness in the range of 5-75 mm. The ground mineral wool may be ground glass or stone wool and the fibre component may be a wood fibre component, a polymer fibre component and/or a mineral wool component. Further, a geopolymer mixture is provided upon recycling mineral wool which is ground to powder and mixed with an alkali activator component. Additionally, a method for producing acoustical geopolymer panel elements includes grinding elements including mineral wool for provision of a powder component.

Claims

1. An acoustical geopolymer panel element comprising: a layer comprising a fibre component and a geopolymer binder comprising ground mineral wool, and an additional layer comprising mineral wool, wherein the layer comprising a fibre component and a geopolymer binder has a density in the range of 20-400 kg/m.sup.3, a porosity in the range of 0.75-0.99 and a thickness in the range of 5-75 mm.

2. The acoustical geopolymer panel element according to claim 1, wherein the ground mineral wool is ground glass or stone wool.

3. The acoustical geopolymer panel element according to claim 1, wherein the fibre component is a wood fibre component, a polymer fibre component and/or a mineral wool component.

4. A method for recycling mineral wool, comprising: grinding elements comprising mineral wool for provision of a powder component, and mixing the powder component and an alkali activator component for provision of a geopolymer mixture.

5. The method according to claim 4, further comprising removing any surface layer attached to the elements comprising mineral wool prior to the grinding the elements.

6. The method according to claim 4, further comprising neutralization of any binder present in the mineral wool.

7. A method for production of acoustical geopolymer panel elements, comprising: grinding elements comprising mineral wool for provision of a powder component, mixing the powder component with an alkali activator component for provision of a geopolymer mixture, mixing the geopolymer mixture with a fibre component, forming the mixture into acoustical geopolymer panel elements, and activating the mixture.

8. The method according to claim 7, wherein the activating the geopolymer mixture is made by water.

9. The method according to claim 7, wherein the forming the geopolymer mixture into acoustical geopolymer elements is performed as an intermittent moulding process or as a continuous feeding process.

10. The method according to claim 7, wherein the powder component comprises mineral wool fibre fragments having an average fibre length in the range of 20-150 μm.

11. The method according to claim 7, wherein the powder component comprises mineral wool fibre fragments having an average fibre width in the range of 5-25 μm.

12. The method according to claim 7, wherein the ground elements comprise mineral wool in the form of stone or glass wool.

13. The method according to claim 7, wherein the alkali activator is selected from the group consisting of NaOH, K-Silicate, K.sub.2CO.sub.3, Na-Aluminate, KOH, LiOH, Na-Silicate or CA(OH).sub.2.

14. The method according to claim 7, wherein the fibre component is a wood fibre component, a polymer fibre component and/or a mineral wool component.

15. The method according to claim 7, wherein the activating the geopolymer mixture is performed prior to the forming the geopolymer mixture into acoustical elements.

16. The method according to claim 10, wherein the average fibre length is in the range of 30-60 μm.

17. The method according to claim 11, wherein the average fibre width is in the range of 5-10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:

(2) FIG. 1 is a schematic perspective view of an acoustical geopolymer panel element in accordance with an embodiment.

(3) FIG. 2 is block scheme illustrating a method for producing acoustical geopolymer panel elements in accordance with an embodiment.

DESCRIPTION OF EMBODIMENTS

(4) The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

(5) The invention is based on the realization that elements comprising mineral wool may be recycled and used as a component in production of acoustical geopolymer panel elements.

(6) The term geopolymer, or alkali activated material, refers to an inorganic material that form long-range, covalently bonded, non-crystaline networks.

(7) In FIG. 1, an acoustical geopolymer panel element 1 is illustrated.

(8) In the shown embodiment, the panel element 1 comprises two opposing major surfaces 2 and four side surfaces 3 extending between the two opposing major surfaces 2.

(9) The acoustical geopolymer panel element 1 may be used as a horizontally arranged ceiling tile, a vertically arranged baffle element, a wall mounted element or a free standing screen.

(10) In the shown embodiment, the panel element 1 comprises a single layer.

(11) The layer of the panel element 1 may have a density in the range of 20-400 kg/m.sup.3.

(12) The porosity of the layer of the panel element 1 may be in the range of 0.75-0.99. The porosity Ø, or the void fraction, of a material is a measurement of the empty space in a material and is calculated as the relationship between the volume of the void V.sub.V, i.e. the empty space in the material, and the total volume of the material V.sub.T:
Ø=V.sub.V/V.sub.T

(13) The porosity is thus a fraction between 0 and 1 and may also be represented in percent by multiplying the fraction by 100.

(14) The layer of the panel element 1 may have a thickness in the range of 5-75 mm.

(15) The layer of the panel element 1 comprises a fibre component and a geopolymer binder comprising ground or milled mineral wool.

(16) The mineral wool may be obtained from recycled elements comprising mineral wool in the form of glass or stone wool.

(17) The ground or milled mineral wool in the panel element 1 has undergone a chemical reaction together with an alkali activator component thereby forming an geopolymer binder.

(18) The fibre component is embedded in the geopolymer binder as evident from the detached enlargement of FIG. 1 and may be a wood fibre, such as wood-wool, a polymer fibre, such as a PET fibre and/or a mineral wool component. The fibre component may be oriented or non-oriented. By using a fibre component comprising different types of fibres having substantial different fibre diameter or cross section area, such as wood-wool and mineral wool, a double porosity structure may be obtained improving the sound absorbing properties of the layer included in the panel element.

(19) In accordance with the present invention, the acoustical geopolymer panel element may comprise additional layers.

(20) An additional layer may for instance comprise mineral wool. Hereby, the sound absorbing properties of the panel element may be further improved. In such a case, the layer comprising the fibre component and a geopolymer binder comprising ground mineral wool may have at thickness in the range of 5-20 mm and the additional layer may have a density in the range of 15-45 kg/m.sup.3. The additional layer may be obtained from recycled elements comprising mineral wool. The additional layer may be arranged on a side of the panel element corresponding to a not visible side of the panel element, i.e. a rear side of the panel element which is not intended to face a room when installed.

(21) A method for production of acoustical geopolymer panel elements will now be described with reference to FIG. 2.

(22) In step 10 of the method, recycled elements comprising mineral wool are ground or milled for provision of a powder component.

(23) The recycled elements normally constitute waste generated during manufacturing, installation or demounting after end of life of elements comprising mineral wool. The mineral wool may be glass or stone wool.

(24) The recycled elements may comprise surface layers which may be removed prior to the grinding.

(25) The grinding or milling of the recycled panel elements may be performed by a vibratory disc mill or a ball mill.

(26) During the grinding of the mineral wool, the fiber length of the fibres forming the mineral wool is reduced. The powder component may after grinding have an average mineral wool fibre length of 20-150 μm, more preferably 30-60 μm and an average mineral wool fiber width of 5-25 μm, more preferably 5-10 μm. The tapped density of the powder component may be in the range of 900-1 200 kg/m.sup.3.

(27) In step 20 of the method, the powder component is mixed with an alkali activator component for the provision of a geopolymer mixture. In accordance with an embodiment, a fibre component may also be added to the mixture. The fibre component may be added prior, during or after mixing of the powder component with the alkali activator component.

(28) The mixing may be performed in batches or in a continuous process or in a combination thereof. For instance, the powder component and the alkali activator component may be mixed in batches, and subsequently mixed with the fibre component in a continuous process.

(29) The alkali activator component may be NaOH, K-Silicate, K.sub.2CO.sub.3, Na-Aluminate, KOH, LiOH, Na-Silicate or CA(OH).sub.2.

(30) The fibre component may be wood fibre, such as wood wool, polymer fibre, such as a PET fibre, or mineral wool. The fibre component in the form of wood wool may have a fibre length in the range of 80-250 mm, a fibre width in the range of 2-12 mm and a fibre thickness in the range of 0.2-1 mm.

(31) In step 30, the geopolymer mixture is formed into acoustical geopolymer panel elements.

(32) The step of forming the geopolymer mixture may be performed as an intermittent moulding process, for instance by arranging the geopolymer mixture in moulds and kept therein until the geopolymer is sufficiently cured.

(33) Alternatively, the geopolymer mixture may be performed as a continuous feeding process, for instance by feeding the geopolymer mixture onto a conveyor thereby forming an endless web which subsequently after sufficient curing may be converted into acoustical geopolymer panel elements of desired shape and size.

(34) In step 40, the geopolymer mixture is activated. Hereby a curing process is initiated forming the geopolymer binder having long-range, covalently bonded, non-crystaline networks.

(35) The curing time may be several days or even weeks, and thus the step 40 of activating the geopolymer mixture may be performed prior, during or after the step 30 of forming of the geopolymer mixture into acoustical geopolymer panel elements.

(36) The step of activating the geopolymer may for instance be performed during the step 20 of mixing the powder component is with the alkali activator component for the provision of the geopolymer mixture.

(37) The activating of the geopolymer mixture may be made by means of water.

(38) When water is added during step 20, i.e. when mixing the powder component with the alkali activator component and possible the fibre component, the alkali activator component may for instance be diluted in water and the solution may subsequently be mixed with the powder component thereby initiating the geopolymer formation process.

(39) The mass ratio between water and the powder component may be 1:3-4.

(40) The recycled elements comprising mineral wool may also comprise a binder, such as a phenol formaldehyde urea resin. The binder may have a negative impact on the chemical process when the geopolymer mixture is activated. Thus, in accordance with an embodiment of the present invention, the method may comprise an additional step where the binder is neutralized. The neutralization of the binder may be by removal of the binder from the mineral wool, for instance by a washing process or a heating process. Alternatively, the neutralization may be performed by adding an agent inhibiting the negative impact of the binder. Thus, the neutralization step is dependent on the specific type of binder at hand. For instance, for a binder in the form of a phenol formaldehyde urea resin, neutralization of the binder may be best achieved by a heating process in which the binder is burnt.

(41) It will be appreciated that the present invention is not limited to the embodiments shown. Several modifications and variations are thus conceivable within the scope of the invention which thus is exclusively defined by the appended claims.