PLASTERBOARD

Abstract

A plasterboard includes a first layer of plaster and a second layer of plaster, wherein the first layer includes activated carbon; the second layer includes a scavenging agent, wherein a content of scavenging agent in the first layer, expressed as percentage by weight of dry matter, is less than a content of scavenging agent in the second layer, and wherein the second layer is free of activated carbon.

Claims

1-15. (canceled)

16. A plasterboard comprising: a first layer of plaster and a second layer of plaster that is in contact with the first layer of plaster, wherein the first layer of plaster comprises activated carbon, and the second layer of plaster comprises a scavenging agent, wherein the second layer of plaster is free of activated carbon, wherein the first layer of plaster is a roller coating layer that has a density greater by at least 5% than a density of the second layer of plaster, wherein a thickness of the second layer of plaster is greater than a thickness of the first layer of plaster, the thickness of the second layer of plaster being at least equal to half a total thickness of the plasterboard.

17. The plasterboard of claim 16, wherein the density of the first layer of plaster is greater by at most 40% than the density of the second layer of plaster.

18. The plasterboard of claim 16, wherein the density of the first layer of plaster is from 0.8 to 1.5.

19. The plasterboard of claim 16, wherein the density of the second layer of plaster is from 0.4 to 1.5.

20. The plasterboard of claim 16, wherein the thickness of the first layer of plaster is from 0.1 mm to less than 4 mm.

21. The plasterboard of claim 20, wherein the thickness of the first layer of plaster is from 0.1 mm to less than 2 mm.

22. The plasterboard of claim 16, wherein the total thickness of the plasterboard is from 6 mm to 25 mm.

23. The plasterboard of claim 22, wherein the total thickness of the plasterboard is from 10 mm to 1.5 mm.

24. The plasterboard of claim 16, wherein a content of the scavenging agent in the first layer of plaster, expressed as percentage by weight of dry matter, is less than a content of scavenging agent in the second layer of plaster.

25. The plasterboard of claim 16, wherein the activated carbon is a powdered activated carbon.

26. The plasterboard of claim 16, wherein the activated carbon has a mean particle size of 1 to 100 m.

27. The plasterboard of claim 16, wherein said plasterboard comprises from 0.01 to 2% by weight of activated carbon, with respect to the dry weight of plaster.

28. The plasterboard of claim 16, wherein the scavenging agent is chosen from compounds comprising a hydrazide group, compounds comprising an active methylene and their mixtures.

29. The plasterboard of claim 16, wherein said plasterboard comprises from 0.01 to 2% by weight of scavenging agent, with respect to the dry weight of plaster.

30. The plasterboard of 16, further comprising a first external sheet and a second external sheet opposite the first external sheet, the first layer of plaster and the second layer of plaster being provided between the first and the second external sheets, the first layer of plaster being in contact with the first external sheet.

31. A process for the manufacture of a plasterboard, said process comprising a forming stage, a setting stage and a drying stage, wherein the forming stage comprises: providing a first facing sheet; pouring a first mixed batch over the first facing sheet to form a roller coating layer, the roller coating layer fowling a first layer of plaster; pouring a second mixed batch over the first mixed batch to form a second layer of plaster in contact with the first layer of plaster; providing a second facing sheet over the second mixed batch; and forming the plasterboard using an extruder; wherein the first mixed batch comprises activated carbon and the second mixed batch comprises a scavenging agent and is free of activated carbon, wherein the first layer of plaster has a density greater by at least 5% than a density of the second layer of plaster, wherein a thickness of the second layer of plaster is greater than a thickness of the first layer of plaster, the thickness of the second layer of plaster being at least equal to half a total thickness of the plasterboard.

32. The process of claim 31, wherein the density of the first layer of plaster is greater by at most 40% than the density of the second layer of plaster.

33. The process of claim 31, wherein the density of the first layer of plaster is from

0. 8 to 1.5.

34. The process of claim 31, wherein the density of the second layer of plaster is from 0.4 to 1.5.

35. The plasterboard of claim 31, wherein the thickness of the first layer of plaster is from 0.1 mm to less than 4 mm.

Description

EXAMPLE

[0060] Reference boards R1 to R3 and according to the invention I1 were manufactured from different main mixed batches, intended for the formation of the body of the boards, and secondary mixed batches, intended for the formation of the roller coating layers. Each main mixed batch has, as base composition, 100 parts by weight of plaster (CaSO.sub.4.H.sub.2O), 75 parts of water, 3 parts of foam (obtained from water containing 1% by weight of sodium lauryl sulfate), 5 parts of starch, 3 parts of plasticizer and 0.5 part of setting accelerator. Each secondary mixed batch has, as base composition, 100 parts by weight of plaster (CaSO.sub.4.H.sub.2O), 77 parts of water, 5 parts of starch, 3.2 parts of plasticizer and 0.5 part of setting accelerator.

[0061] The boards R1 and R3 without a roller coating layer were prepared as follows. The different ingredients are weighed and mixed using a mixer and a paddle of deflocculating type at 1600 rev/min for one minute in order to obtain a homogeneous paste. The foam is prepared at the desired density and mixed with the paste obtained in a mixer with a paddle at 250 rev/min in order to obtain a main mixed batch. A first sheet of cardboard is positioned in a mold having dimensions of 2025 cm and with a thickness of 12.5 mm. The main mixed batch is poured onto the first cardboard and leveled at the thickness of the mold. A second sheet of cardboard is positioned on the main mixed batch and the mold is closed in order to maintain a pressure on the board. After hardening of the board, the latter is removed from the mold and dried in a drying oven at 40 C. for 24 hours.

[0062] For the boards R2, R4 and P1 with a layer of roller coating, the ingredients for the secondary mixed batch are weighed and mixed using a mixer and a paddle of deflocculating type at 1600 rev/min for one minute. A first sheet of cardboard is positioned in a mold having dimensions of 2025 cm and with a thickness of 12.5 mm. The secondary mixed batch is poured onto the first cardboard and leveled at a thickness of approximately 1 mm. The main mixed batch is prepared as for the boards R1 and R3 and poured onto the secondary mixed batch when the latter is sufficiently set, and leveled at the thickness of the mold. A second sheet of cardboard is positioned on the main mixed batch and the mold is closed in order to maintain a pressure on the board.

[0063] After hardening of the board, the latter is removed from the mold and dried in a drying oven at 40 C. for 24 hours.

[0064] Tables 1 and 2 show the additives, activated carbon (AC) or acetoacetamide (AA), added, if appropriate, to the mixed batches before manufacture of the boards. The value in brackets indicates the percentage by dry weight of the additive in the layer under consideration. The symbol - indicates that no additive is added to the corresponding mixed batch. The symbol x indicates that the board does not comprise the corresponding layer. The activated carbon used is a powdered activated carbon sold under the reference Pulsorb 208CP and having a specific surface of 1200 m.sup.2/g and a mean particle size of approximately 30 m. For each board, the body has a thickness of 11.5 mm, except for the boards P4, which exhibit a thickness of 12.5 mm, and the roller coating layers each have a thickness of 1 mm.

[0065] The ability of each of the boards to trap VOCs was evaluated from the viewpoint of the absorption and of the desorption according to the standards ISO1600-24:2009 and ISO1600-23:2009 at a temperature of 23 C. 2 C. and a relative humidity of 50% 5% during the test. The load factor of the board is set at 1 and the degree of replacement of the air at 0.5 vol.Math.h.sup.1. Two series of independent measurements were carried out in order to evaluate their ability to trap, on the one hand, toluene and, on the other hand, formaldehyde. For each series of measurements, the boards were subjected to a phase of absorption (14 days for toluene; 7 days for formaldehyde) during which the air is replaced with a stream of air comprising a VOC (at a concentration of 40 g.Math.m.sup.3 for toluene; 100 g.Math.m.sup.3 for formaldehyde), in order to measure the degree of absorption for the VOC under consideration, and then to a phase of desorption (7 days for toluene; 7 days for formaldehyde) during which the air is replaced with a stream of fresh air (without VOC), in order to measure the degree of desorption for the VOC under consideration.

[0066] Table 1 shows the percentage of reduction (absorption) in the content of formaldehyde and toluene and the percentage of desorption of formaldehyde and toluene for each of the boards.

TABLE-US-00001 TABLE 1 R1 R2 R3 R4 P1 Body AA AA (0.12) (0.12) Roller Coating x AC (2) x AC (2) AC (2) AA (1.5) Absorption Formaldehyde 37 50 93 94 89 (%) Toluene 0 98 10 8 85 Desorption Formaldehyde 58 17 <2 n.m. <2 (%) Toluene <1 <1 <1 n.m. <1 n.m.: not measured

[0067]

[0068] The board R3 comprising a scavenging agent exhibits a good absorption of formaldehyde but does not make possible a sufficient reduction in the content of the other VOCs, in particular toluene. The board R2 comprising activated carbon makes possible a correct abatement of a broad spectrum of VOCs, including formaldehyde, but the latter is not permanently fixed, as is shown by the high desorption value for formaldehyde. The board R4 comprising a combination of a scavenging agent and of activated carbon is not very effective with regard to toluene. On the other hand, the board P1 according to the invention makes possible both a significant abatement and a permanent scavenging of the formaldehyde and toluene.