GYPSUM BUILDING MATERIAL WITH IMPROVED HIGH-TEMPERATURE RESISTANCE

Abstract

A gypsum building material, characterised in that the gypsum building material comprises at least gypsum, H-siloxane and/or amorphous silicon dioxide and optionally further additives, wherein the H-siloxane is uniformly distributed in the gypsum building material and/or is applied to at least one surface of the gypsum building material, characterised in that the gypsum building material under the effect of temperatures of at least 80° C. has a longer expansion phase than a gypsum building material without H-siloxane and/or amorphous silicon dioxide, wherein the gypsum building material is otherwise of identical composition.

Claims

1. A gypsum building material comprising at least gypsum, an H-siloxane and/or an amorphous silicon dioxide, wherein the H-siloxane is uniformly distributed in the gypsum building material and/or is applied to at least one surface of the gypsum building material, wherein the gypsum building material under an effect of temperatures of at least 80° C. has a longer expansion phase than another gypsum building material without the H-siloxane and/or the amorphous silicon dioxide, wherein the other gypsum building material is otherwise of an identical composition.

2. The gypsum building material according to claim 1, wherein the expansion phase of the gypsum building material is at least 1.2 times a time of the expansion phase of the other gypsum building material of the identical composition but without the H-siloxane or the amorphous silicon dioxide.

3. The gypsum building material according to claim 1, wherein the gypsum building material under the effect of temperature in accordance with a temperature/time curve according to DIN EN 1363-1: 2012-10 for a first 60 min. and under constantly 950° C. during a next 60 min. has a smaller degree of shrinkage than the other gypsum building material of the identical composition, but without the H-siloxane and/or the amorphous silicon dioxide.

4. The gypsum building material according to claim 3, wherein a degree of shrinkage of the gypsum building material is at least 10% lower than the degree of shrinkage of the other gypsum building material of the identical composition, but without the H-siloxane and/or the amorphous silicon dioxide.

5-6. (canceled)

7. The gypsum building material according to claim 6, wherein the gypsum building material comprises 1 to 2.5 wt.-% of the H-siloxane and 1 to 5 wt.-% of the amorphous silicon dioxide.

8. The gypsum building material according claim 1, wherein the amorphous silicon dioxide comprises microsilica and/or pyrolytically produced silicon dioxide.

9. The gypsum building material according to claim 1, wherein the gypsum building material is a gypsum building board.

10. The gypsum building material according to claim 1, wherein at least one surface of the gypsum building board is treated with the H-siloxane.

11. The gypsum building material according to claim 10, wherein at least two surfaces, preferably an upper side and an underside, of the gypsum building board are treated with the H-siloxane.

12. The gypsum building material according to claim 9, wherein the gypsum building board has at least one first edge layer and a core layer, wherein at least the first edge layer contains the H-siloxane and/or the amorphous silicon dioxide.

13. A method for producing a gypsum building board, wherein at least one slurry is produced in that at least stucco and water are mixed with one another, the slurry is formed into an endless strand of gypsum building board, which is then separated into the gypsum building boards and the gypsum building boards are dried, the method comprising producing the slurry, wherein H-siloxane and/or amorphous silicon dioxide are/is additionally used, and/or applying H-siloxane is applied to at least one surface of the endless strand of the gypsum building board or of the separated gypsum building boards, such that the gypsum building board under an effect of temperature of at least 80° C. has a longer expansion phase than another gypsum building board without the H-siloxane and/or the amorphous silicon dioxide, wherein the other gypsum building board is otherwise of an identical composition.

14. The method according to claim 13, wherein at least one first and one second slurry are produced, and the first slurry contains the H-siloxane and/or the amorphous silicon dioxide, and wherein the first slurry is used to form at least one edge layer of the gypsum building board.

15. A method to reduce the degree of shrinkage of a gypsum building material under an effect of temperature, the method comprising the step of adding an H-siloxane and/or an amorphous silicon dioxide to said gypsum building material, wherein the gypsum building material in accordance with a temperature/time curve according to DIN EN 1363-1: 2012-10 is heated from 0 to 60 min to 950° C. and is treated from 60 to 120 min with a constant temperature application of 950° C., and wherein the gypsum building material has a longer expansion phase and/or a smaller degree of shrinkage as compared to another gypsum building material without the H-siloxane and/or the amorphous silicon dioxide but of otherwise identical composition.

16. The gypsum building material according to claim 1, wherein the gypsum building material comprises further additives.

17. The gypsum building material according to claim 2, wherein the expansion phase of the gypsum building material is at least 2 times the time of the expansion phase of the gypsum building material of the identical composition but without the H-siloxane or the amorphous silicon dioxide.

18. The gypsum building material according to claim 17, wherein the expansion phase of the gypsum building material is at least 2.5 times the time of the expansion phase of the gypsum building material of the identical composition but without the H-siloxane or the amorphous silicon dioxide.

19. The gypsum building material according to claim 4, wherein the degree of the shrinkage of the gypsum building material is at least 50% lower than the degree of the shrinkage of the other gypsum building material of the identical composition, but without the H-siloxane and/or the amorphous silicon dioxide.

20. The gypsum building material according to claim 19, wherein the degree of the shrinkage of the gypsum building material is at least 75% lower than the degree of the shrinkage of the other gypsum building material of the identical composition, but without the H-siloxane and/or the amorphous silicon dioxide.

21. The gypsum building material according to claim 1, wherein the gypsum building material is produced from at least one slurry which is produced in that at least stucco and water are mixed with one another, wherein the gypsum building material comprises between 0.01 and 10 wt.-% of the H-siloxane, in relation to a mass of the used stucco.

22. The gypsum building material according to claim 1, wherein the gypsum building material is produced from at least one slurry which is produced in that at least stucco and water are mixed with one another, wherein the gypsum building material comprises at least 0.5 wt.-% in relation to an amount of the used stucco, and at most 20 wt.-% in relation to the amount of the used stucco of the amorphous silicon dioxide.

Description

[0037] The examined prisms (test specimen) were produced as follows: stucco and an accelerator were pre-mixed to form a dry mix. The samples for which the change in length is shown in FIGS. 1 to 5 were produced using a stucco obtained from 70 wt.-% FGD (flue gaz desulfurization) gypsum and 30 wt.-% natural gypsum. The prisms for which the change in length is shown in FIG. 6 were produced from a stucco which was obtained substantially from natural gypsum with 7 wt.-% FGD gypsum. The dry mix was scattered into water, the amount of which corresponded to a water-gypsum value of 0.6, and was mixed after a short soaking time using a whisk. The slurry thus produced was used to cast prisms measuring 16×4×2 cm.sup.3, which were demoulded 25 min after the mixing. The prisms thus produced were dried in a drying cabinet at 40° C. to a constant weight. The prisms were then sawn to size (10×4×2 cm.sup.3).

[0038] If the prisms contained H-siloxane (BlueSil WR 68 from Bluestar Silicones, now Elkem) or microsilica (Elkem 940U), these substances were either added to the slurry or, in the case of a siloxane coating, were applied to the prisms using a brush.

[0039] The change in length under temperature application was brought about in a quickly heating chamber furnace. The chamber furnace was heated heavily for the first 60 min. in accordance with the temperature/time curve according to DIN EN 1363-1: 2012-10. Thereafter, the furnace temperature was held constant for a further 60 min. at 950° C. The prisms were placed on roller holders which did not put up any resistance to the change in length of the prism. One narrow side of the prism was arranged on an abutment face, and a spring arm with distance recorder exerted a force against the opposite narrow side, which force fixes the prism against the abutment. The distance recorder continuously recorded the length of the prism. The change in length of the prism was obtained by subtracting the length of the prism at certain moments in time (substantially continuously measured) during the temperature application from the length of the prism prior to the temperature application.

[0040] FIG. 1 shows the change in length of gypsum prisms with different contents of H-siloxane mixed into the slurry. The solid curve shows a reference sample, containing no H-siloxane. The reference sample prism expands moderately during the first approximately 20 min. It is assumed that in this phase of expansion the crystallisation water is driven out from the gypsum crystals, but can escape only slowly from the prims. The result is an increase in the volume of the prism. This period of time was recorded within the scope of this invention as expansion phase. Between 20 and 45 min. there is a moderate shrinkage of the prism. In the period of time between 45 and 59 min. there is then an abrupt reduction in volume. Without wanting to be bound to this theory, it is assumed that in this period the material sinters. The sintering process continues in slightly weakened form up to approximately 70 min. Afterwards, the prism length decreases continuously, but only to a very small degree.

[0041] Considering the change in length to the prisms that contain different H-siloxane concentrations, it can be determined that the phase of the expansion in all samples with H-siloxane is significantly extended. Depending on the concentration of the H-siloxane, the expansion phase lasts from 50 (0.2 wt.-% H-siloxane) up to 75 min. (5 wt.-% H-siloxane) and extends with increasing H-siloxane content. The prisms contained between 0.2 and 1 wt.-% H-siloxane then transition seamlessly into the sintering process, which leads to a drastic decrease in the length of the prisms. Interestingly, the prisms that contain H-siloxane in higher concentrations do not appear to experience any sintering process, or only appear to experience a sintering process to a small degree. Anyhow, these prisms show no significant shrinkage within the space of just a few minutes as the other prisms do. A shrinkage lasting a long period of time was observed and appeared to approach a threshold value. The effect of the different H-siloxane concentrations on the degree of shrinkage at the end of the temperature application is also interesting. Low H-siloxane concentrations of up to approximately 1% by weight in relation to the used stucco appear to have only a very small influence on the overall shrinkage. Compared to the reference sample, the degree of shrinkage of which is more than 15%, the prisms with up to 1 wt.-% H-siloxane are only slightly better. Their degree of shrinkage lies between 13 and 14%.

[0042] The influence on the degree of shrinkage appears to rise suddenly when a H-siloxane content of between 1 wt.-% and 2.5 wt.-% was used. In any case the prisms with 2.5 and 5 wt.-% H-siloxane present a degree of shrinkage of only 1 to 2%. It is supposed that there is a threshold value or a limit range from which H-siloxane effectively influences the degree of shrinkage. In the samples shown here this limit lies between 1 and 2.5 wt.-% H-siloxane. It must be assumed, however, that the actual threshold value for each gypsum type is slightly different on account of different impurities.

[0043] It seems that the degree of shrinkage hardly improves if the concentration of H-siloxane increases further still (to 5 wt. % or more).

[0044] The phase of the significant reduction in volume of the prisms, characterised in these tests by the significant change in length, is supposedly triggered by a sintering process of the sample material. The significant reduction in volume is very dangerous for example in the case of drywalls exposed to a fire, because parts of the boards can detach from their supports and fall into rooms. The dropping board parts can directly injure people or can indirectly block escape routes. In addition, the parts absent from the drywalls mean that the fire can spread to adjacent rooms. Fire protection in the case of a drywall on the one hand thus aims to suppress the volume reduction of the gypsum material to the greatest possible extent. On the other hand, should a volume reduction nevertheless occur, this should be as late as possible and as small as possible.

[0045] The test prisms shown in FIG. 1 show that even small amounts of H-siloxane in the sample material cause the expansion phase of the prisms to be extended significantly. Even 0.2 wt.-% H-siloxane extend this period by 2.5 times. If it turns out that these test results translate well into actual drywall constructions, the following could be deduced: In the event of a fire this would mean that drywalls retained their integrity for at least twice as long because they would not shrink in the same way as drywalls not containing any H-siloxane. Thus, twice the amount of time would be available for rescue measures and for escape, which could save human lives. If boards with higher H-siloxane contents are used, the shrinkage could be almost completely prevented.

[0046] A similar effect appears to be provided by the addition of amorphous silicon dioxide, or what is known as microsilica in the case of the results shown in FIG. 2. The actual expansion phase of the prism with 4 wt.-% microsilica indeed appears to be only insignificantly longer than that of the reference sample. The subsequent shortening of the prism between 20 and 60 min., at less than 1% shortening, is very low however compared to the original length of the prisms. The decrease in length during the sintering is relatively moderate. However, the prism after the temperature application is approximately 10% shorter than the untreated sample. By comparison, the addition of 5 wt.-% H-siloxane leads to a degree of shrinkage of barely 2%.

[0047] FIGS. 3 to 5 show the shrinkage of prisms over time that contain different amounts of a combination of H-siloxane and microsilica. The prisms in FIG. 3 all contain 0.2 wt.-% H-siloxane, apart from the reference sample, which contains neither H-siloxane nor microsilica. The addition of 1 wt.-% microsilica extends the expansion phase of the prism, compared to the prism containing only 0.2 wt.-% H-siloxane, by approximately 5 min. and reduces the degree of shrinkage slightly. If, however, 4 wt.-% microsilica are added, the expansion phase extends by 10 min. and the degree of shrinkage is halved. The combination of the effects of small amounts of H-siloxane with larger amounts of microsilica appears to reduce the degree of shrinkage overporportionally compared to the effect resulting from an addition of the effects of the prisms with 0.2 wt.-% H-siloxane (FIG. 3) on the one hand and 4 wt. % microsilica (FIG. 2) on the other hand.

[0048] Approximately the same reduction of the degree of shrinkage can be achieved with a combination of 1 wt.-% H-siloxane and 2 wt.-% microsilica (see FIG. 4). The higher content of H-siloxane, however, generally leads to an extension of the expansion phase.

[0049] FIG. 5 shows that the shrinkage of the gypsum prisms under temperature application can be almost completely eliminated (<1.5%) if 2.5 wt.-% H-siloxane are combined with 1 wt.-% microsilica. If 4 wt.-% microsilica are added, the degree of shrinkage even lies only at approximately 0.5%.

[0050] It is clear from FIG. 6 that both the expansion phase and the degree of shrinkage likewise can be significantly improved if one or both large surfaces of the prism are coated with H-siloxane. The gypsum used here consists substantially of natural gypsum (see above), which without further additives shrinks by more than 8%. For reference, a prism with 0.2 wt.-% H-siloxane in the slurry was produced. The course of the curve corresponds approximately to the course described in relation to FIG. 1.

[0051] A prism produced from stucco, water and accelerator was coated with H-siloxane after the drying in the drying cabinet. The amount of H-siloxane corresponded to approximately 0.2 wt.-% in relation to the amount of dihydrate in the prism. A further prism was coated on both sides with H-siloxane. The applied amount corresponded to approximately 1.1 wt.-% in relation to the amount of dihydrate in the prism.

[0052] Even one-sided coating with a relatively small amount of H-siloxane leads to a slight extension of the expansion phase. The prism coated on both sides, however, has a sudden improvement both of the duration of the expansion phase and the degree of shrinkage. It has been found that the coating of gypsum building materials with H-siloxane is also an adequate way of improving the fire resistance.

[0053] FIG. 7 shows a photo of its prism which has been coated on both sides with H-siloxane and subjected to the temperature application as described above. The shrinkage of the material in the board core can be clearly seen on the basis of the strong crack formation. The gaps that open up into the cracks, however, become increasingly smaller and disappear completely in the direction of the coated surfaces (at the top and bottom). It can be seen under microscope that the edge regions of the prism have only small and short cracks, and therefore the cohesion of the surface is maintained in spite of the apparently high material loss in the core.