Process for forming dense layers in a gypsum slurry
View Patent ↗A process for manufacturing plasterboard and a plasterboard manufacturing unit are provided, the process including feeding hydratable calcium sulphate and water into a first mixer ( 2 ) and into a second mixer ( 3 ); feeding in a facing ( 5 ); preparing a first gypsum slurry in the first mixer ( 2 ); preparing a second gypsum slurry in the second mixer ( 3 ); applying the first slurry onto the facing and forming a crude surface layer; applying the second slurry onto the crude surface layer and forming a crude core layer with a density lower than that of the crude surface layer; forming a plasterboard; hydrating and drying the board. This process allows the formation of the different layers of gypsum to be controlled independently.
1. A process for manufacturing plasterboard, comprising the following steps:
feeding a first addition into a screw conveyor at a first inlet, wherein the first addition comprises hydratable calcium sulphate and water, wherein the screw conveyor conveys in a downstream direction;
withdrawing a first feed from a first outlet of the screw conveyor;
withdrawing a second feed from a second outlet of the screw conveyor;
feeding a second addition into the screw conveyor at second inlet, wherein the second inlet is downstream from the first inlet, first outlet and second outlet;
withdrawing a third feed from a third outlet of the screw conveyor, wherein the third outlet is downstream from the second inlet, wherein the first and second feed have a different composition from the third feed;
feeding the first feed into a first mixer;
feeding the third feed into a second mixer that is independent of the first mixer;
feeding in a facing;
preparing a first gypsum slurry in the first mixer;
preparing a second gypsum slurry in the second mixer;
applying the first gypsum slurry onto the facing and forming a crude surface layer;
applying the second gypsum slurry onto the crude surface layer and forming a crude core layer that has a different composition to that of the crude surface layer;
feeding in a second facing;
feeding the second feed into a third mixer; preparing a third gypsum slurry in the third mixer;
wherein the third mixer is independent of first mixer and the second mixer;
wherein the first, second and third mixers are arranged in parallel and not in series;
applying the third gypsum slurry onto the second facing and forming a second crude surface layer with a different composition than that of the crude core layer;
applying the second crude surface layer onto the crude core layer;
forming a crude plasterboard; and
hydrating and drying the plasterboard.
2. The process according to claim 1 , wherein the third gypsum slurry is applied over the second facing and in that the process comprises, in addition, after the application stage for the third gypsum slurry, a stage of turning over the second facing.
3. The process according to claim 1 , wherein a layer formation stage comprises an operation of spreading out a gypsum slurry.
4. The process according to claim 1 , wherein the crude surface layer has a density of between 1.2 and 2 kg/L.
5. The process according to claim 1 , wherein the crude core layer has a density of between 1 and 1.2 kg/L.
6. The process according to claim 1 , wherein a surface layer has a density of between 0.8 and 1.2 kg/L after drying.
7. The process according to claim 1 , wherein the core layer has a density of between 0.6 and 1.2 kg/L after drying.
8. The process according to claim 1 , wherein the ratio of surface layer density to core layer density is between 1 and 1.5 kg/L after drying.
9. The process according to claim 1 , wherein a surface layer has a quantity of starch less than 15 g/m2 after drying.
10. The process according to claim 1 , wherein a surface layer has a thickness of between 0.1 and 0.5 mm after the formation of the board.
11. The process according to claim 1 , wherein the facing is a glass fibre mat.
12. The process according to claim 1 , wherein the second facing is a glass fibre mat.
13. The process according to claim 1 , wherein the facing is made out of cardboard.
14. The process according to claim 1 , wherein the second facing is made out of cardboard.
15. The process according to claim 1 , wherein the second addition to the screw conveyor comprises a foaming agent.
16. The process according to claim 15 , wherein the crude surface layer and the second crude surface layer have a higher density than that of the crude core layer.
17. The process according to claim 1 , wherein the second addition to the screw conveyor comprises glass fibres.
18. The process according to claim 1 , further comprising:
feeding the first feed to a second screw conveyor before feeding the first mixer.
19. The process according to claim 1 , further comprising:
feeding the second feed to a third screw conveyor before feeding the third mixer.
20. The process according to claim 1 , further comprising:
feeding the third feed to a fourth screw conveyor before feeding the second mixer.
21. The process according to claim 1 , further comprising:
feeding the first feed to a second screw conveyor before feeding the first mixer;
feeding the second feed to a third screw conveyor before feeding the third mixer; and
feeding the third feed to a fourth screw conveyor before feeding the second mixer.