Process for manufacturing sound absorbing cement tile

1. A continuous process for manufacturing a sound absorbing tile having an NRC above 0.5 and made from a slurry comprising, on a wet basis about 53 to about 68 wt % quick setting cement, about 17% to about 48 wt % water, about 0.05 to about 5 wt % fibers and about 0.01 to about 10 wt % foaming agent, said tile having pores comprising interconnected voids and having a porosity from 75 to 95% by volume of said tile, said process comprising the steps of:

(i) mixing the cement, the water, the foaming agent but without incorporation of a prefabricated foam with the fibers in an amount of from 0.05 to 5% by weight based on the final weight of the tile into a slurry, under first mixing conditions; subsequently

(ii) injecting and distributing air into the slurry of step (i) to form a cellular slurry under second mixing conditions, using a blender comprising a barrel equipped with a rotating shaft, wherein the shear is lower under the second mixing conditions than under the first mixing conditions;

(iii) subsequently depositing said slurry on at least one moving facer comprised of a glass mat to form said tiles or precursor thereof from said cellular slurry; and

(iv) finally allowing said cellular slurry to set into the tile or a precursor thereof; and

(v) optionally finishing the tile or precursor thereof.

2. The process of claim 1 , in which step (i) is performed under high-shear mixing conditions.

3. The process of claim 1 , in which step (ii) is performed under controlled-shear mixing conditions.

4. The process of claim 1 , in which step (ii) is performed under low-shear mixing conditions.

5. The process of claim 1 , in which step (i) is performed under high-shear mixing conditions and step (ii) is performed under controlled-shear mixing conditions.

6. The process of claim 1 , in which step (i) is performed under high-shear mixing conditions and step (ii) is performed under low-shear mixing conditions.

7. The process of claim 1 , in which the water to cement ratio is comprised from 0.25 to 1.1.

8. The process of claim 1 , in which the water to cement ratio is comprised from 0.45 to 0.85.

9. The process of claim 1 , in which the cement is calcium sulfate a-hemi-hydrate, calcium sulfate β-Hemi-hydrate or a blend thereof.

10. The process of claim 1 , in which the precursor of tiles is a flat panel to be cut to size.

11. The process of claim 10 , wherein the process is carried out on a plasterboard line.

12. The process of claim 1 , in which the precursor of tiles is a block to be cut in slices.

13. The process of claim 12 , in which the process is a continuous block casting method.

14. A continuous process for manufacturing a sound absorbing tile having an NRC above 0.5 and made from a slurry comprising, on a wet basis about 53 to about 68 wt % quick setting cement, about 17% to about 48 wt % water, about 0.05 to about 5 wt % fibers and about 0.01 to about 10 wt % foaming agent, said tile having pores comprising interconnected voids and having a porosity from 75 to 95% by volume of said tile, said process comprising the steps of:

(i) mixing, under high-shear first mixing conditions, the cement, the water, the foaming agent but without incorporation of a prefabricated foam with the fibers in an amount of from 0.05 to 5% by weight based on the final weight of the tile into a slurry;

(ii) subsequently injecting and distributing air into the slurry of step (i) to form a cellular slurry, using a blender comprising a barrel equipped with a rotating shaft and operated under controlled-shear or low-shear second mixing conditions, wherein the shear is lower under the second mixing conditions than under the first mixing conditions;

(iii) subsequently depositing said slurry on at least one moving facer comprised of a glass mat to form said tiles or precursor thereof from said cellular slurry; and

(iv) finally allowing said cellular slurry to set into the tile or a precursor thereof; and

(v) optionally finishing the tile or precursor thereof.

15. The process of claim 14 , where the process is carried out on a plasterboard line.

16. A continuous process carried out on a plasterboard line for manufacturing a sound absorbing tile, having a NRC above 0.5, made from a slurry comprising, on a wet basis about 53 to about 68 wt % quick setting cement, about 17% to about 48 wt % water, about 0.05 to about 5 wt % fibers and about 0.01 to about 10 wt % foaming agent, said tile having pores comprising interconnected voids and having a porosity from 75 to 95% by volume of said tile, said process comprising the steps of:

(i) mixing the cement, the water, the foaming agent but without incorporation of a prefabricated foam with the fibers in an amount of from 0.05 to 5% by weight based on the final weight of the tile into a slurry under first mixing conditions;

(ii) subsequently injecting and distributing air into the slurry of step (i) to form a cellular slurry under second mixing conditions, using a blender comprising a barrel equipped with a rotating shaft, wherein the shear is lower under the second mixing conditions than under the first mixing conditions;

(iii) subsequently depositing said slurry on at least one moving facer comprised of a glass mat to form the tile or precursor products of tiles; and

(iv) finally allowing said cellular slurry to set into the tile or a precursor thereof; and

(v) optionally finishing the tile or precursor thereof according to the intended use.

17. The process of claim 1 , in which step (i) is performed under high-shear mixing conditions.

18. The process of claim 1 , in which step (ii) is performed under controlled-shear mixing conditions.

19. The process of claim 1 , in which step (ii) is performed under low-shear mixing conditions.

20. The process of claim 1 , in which step (i) is performed under high-shear mixing conditions and step (ii) is performed under controlled-shear mixing conditions.

21. The process of claim 1 , in which step (i) is performed under high-shear mixing conditions and step (ii) is performed under low-shear mixing conditions.