Method for producing a gypsum plasterboard

Abstract

A method for producing a gypsum plasterboard comprising the steps of providing bundler dust obtained from gypsum plasterboard leftovers of a plasterboard trimming process by a trimming device, in particular by a bundler saw; and adding at least a part of the bundler dust to a gypsum slurry for producing the gypsum plasterboard.

Claims

1. A method for producing a gypsum plasterboard consisting of the steps of: preparing a gypsum slurry and drying it (on a support and/or transporting device) in order to provide a dry gypsum layer; providing the dry gypsum layer; trimming the gypsum layer in order to finalize single gypsum plasterboards; providing bundler dust obtained from gypsum plasterboard leftovers of a plasterboard trimming process using a trimming device; and adding at least a part of the bundler dust to the gypsum slurry for producing the gypsum plasterboard, wherein the bundler dust is obtained from the production process of impregnated plasterboards using a hydrophobic agent, wherein the hydrophobic agent is silicone oil.

2. The method of claim 1, wherein the amount of bundler dust is controlled and/or regulated.

3. The method of claim 1, wherein the step of providing the bundler dust comprises a milling of the leftovers preferably in a pin mill.

4. The method of claim 1, wherein the bundler dust is obtained from the production process of impregnated plasterboards, wherein the hydrophobic agent is polymethylhydrogen siloxane.

5. The method of claim 1, wherein a foaming agent is added to the gypsum slurry.

6. The method of claim 1, wherein several gypsum plasterboards are continuously produced wherein (only a part of) the leftovers of a preceding plasterboard is returned to the production process.

7. The method of claim 1, wherein the amount of bundler dust added to the gypsum slurry is X, wherein 0.1 g/m.sup.2x30 g/m.sup.2.

8. The method of claim 1, wherein a (naftalen) sulfonate-based liquefier is added to the gypsum slurry in an amount of 2 to 15 g/m.sup.2.

9. A method for producing a gypsum plasterboard consisting of the steps of: preparing a gypsum slurry and drying it (on a support and/or transporting device) in order to provide a dry gypsum layer; providing the dry gypsum layer; trimming the gypsum layer in order to finalize single gypsum plasterboards; providing bundler dust obtained from gypsum plasterboard leftovers of a plasterboard trimming process using a trimming device; and adding at least a part of the bundler dust to the gypsum slurry for producing the gypsum plasterboard, wherein the bundler dust is obtained from the production process of impregnated plasterboards using a hydrophobic agent, wherein the hydrophobic agent is silicone oil; and providing bundler dust obtained from a method of preparing bundler dust for producing gypsum plasterboards in accordance with claim 1, comprising the steps: mixing a mixture of stucco, water and silicone oil, forming a cake of the mixture, drying and grinding the cake in order to prepare the bundler dust; and adding at least a part of that bundler dust to the gypsum slurry for producing the gypsum plasterboard.

10. The method of claim 7, wherein the amount of bundler dust added to the gypsum slurry is X, wherein 0.2 g/m.sup.2X10 g/m.sup.2.

11. The method of claim 10, wherein the amount of bundler dust added to the gypsum slurry is X, wherein 0.5 g/m.sup.2x4 g/m.sup.2.

12. The method of claim 11, wherein the amount of bundler dust added to the gypsum slurry is X, wherein 0.6 g/m.sup.2X 2 g/m.sup.2.

13. The method of claim 11, wherein the amount of bundler dust added to the gypsum slurry is X, wherein 2.4 g/m.sup.2X3 g/m.sup.2.

14. The method of claim 8, wherein a (naftalen) sulfonate- based liquefier is added to the gypsum slurry in an amount of 4 to 8 g/m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described in detail by way of example with reference to the enclosed drawings.

(2) FIG. 1 shows a schematic illustration of the method steps for producing a gypsum plasterboard according to the invention; and

(3) FIG. 2 shows a schematic illustration of an apparatus for producing a gypsum plasterboard according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) The last step in producing gypsum plasterboards is the trimming of the gypsum plasterboard. Said trimming shall be also regarded as starting point of the procedure. At a certain point of time, gypsum plasterboards (in this embodiment, impregnated plasterboards where the hydrophobic agent is silicone oil, polymethylhydrogen-siloxane) are trimmed. The trimmed plasterboards may be prepared for transportation to the customer. The leftovers of the trimming process, however, are collected by a de-dusting system and milled to a fine powder in a pin mill. A part of the leftovers may be collected and stored so that only a part of the leftovers are milled in the pin mill. This means, neither is the material fully returned into the production process nor completely thrown away.

(5) The resulting bundler dust may also be collected or stored and (a part of) the bundler dust (coming directly from the pin mill and/or the collected/stored bundler dust) is added to a gypsum slurry. The amount of bundler dust in this example may vary between 0.1 g/m.sup.2 to 30 g/m.sup.2, preferably 0.2 g/m.sup.2 to 10 g/m.sup.2, further 0.6 to 2 g/m.sup.2 (for A13) and 2.4 to 3.0 g/m.sup.2 for (H2 13). In any case, the (green) bundler dust is added in a small, controlled quantity.

(6) It will be understood that a suitable controlling device should be used for controlling the amount of (green) bundler dust which is added to the production process (the gypsum slurry, respectively).

(7) Moreover, a foaming agent is added to the gypsum slurry. Therefore, the (green) bundler dust is used as catalyst for the creation of large air pores. Without the (green) bundler dust, the same amount of foaming agent would result in a higher number of finer pores. Preferably, a controlled correlation between the amount of (green) bundler dust and the amount of foaming agent is (approximately) linear. Therefore, if the addition of (green) bundler dust is increased, the consumption of the foaming agent is higher. The exact amount of (green) bundler dust and a corresponding amount of foaming agent depends on the requirements for weight and stability of the plasterboards.

(8) The (green) bundler dust allows a pore agglomeration similar to the pore agglomeration observed for well known unstable foams.

(9) In essence, the amount of (green) bundler dust added to the production process influences the plasterboard core porosity. The correlation is (approximately) linear; a bigger amount of (green) bundler dust results in a higher gypsum (core) porosity. Precisely, the correlation between the amount of (green) bundler dust and core porosity depends on the production conditions. For the same product, however, this correlation is (more or less) linear.

(10) The above described solution with an addition of (green) bundler dust as foaming catalyst has been tested. The result was a substantial board weight reduction without lower paper bonding (on the contrary, the paper bonding was even improved). The present invention therefore allows the production of low-weight plasterboards.

(11) In the present embodiment, the bundler dust is prepared from leftovers of the trimming process. Alternatively, it is possible to obtain (green) bundler dust material (or bundler dust light material) in a separate line. For example, stucco, water and silicone oil can be mixed together to create a cake. This cake can be dried and ground in a grinder. Then, the ground material can be added to a stucco stream in a plasterboard production process. Tests have shown that similar effects for porosation can be expected. Since the (green) bundler dust from the trimming process is available in sufficient amounts, however, it is preferred to use this (green) bundler dust.

(12) FIG. 2 shows an apparatus 10 for producing a gypsum plaster board 11 containing bundler dust particles 12 in a highly schematic illustration. The apparatus 10 comprises a trimming device (bundler saw) 13 which finalizes the paster board 11. Furthermore, a device 15 for providing the bundler dust particles 12 collects the bundler dust particles 12 being leftovers of the trimming process of the trimming device 13 and transports the bundler dust particles 12 to a slurry container 16. In the slurry container 16, the bundler dust particles 12 are mixed with gypsum slurry. The device 15 for providing the bundler dust contains a mill (pin mill) 18 for milling the leftovers of the trimming process. The gypsum slurry together with the bundler dust particles 12 in the container 16 is delivered to a further container 19 where it is mixed with a foaming agent and/or a liquefier coming from a corresponding container 20. The container 20 provides the gypsum slurry containing the bundler dust particles to a manufacturing line 21 so that the manufactured gypsum plaster board 11 contains the bundler dust particles 12. The amount of bundler dust within the gypsum slurry can be controlled by a regulation means 22.

(13) Optionally, the bundler dust 12 can be stored in a storage container 23. From this storage container 23, the bundler dust 12 can be delivered to the container 16. In other words, the storage container 23 may function as intermediate container for intermediate storing of the bundler dust (before delivering to the slurry).