PLASTER COMPOSITION FOR FIRE RESISTANT PLASTERBOARD

Abstract

The present invention concerns a plaster composition for manufacturing of a fire resistant plasterboard, said composition comprising hydratable calcium sulphate, water with a water/hydratable calcium sulphate ratio between 0.50 and 1.00 and the following components: 0.5-10 wt. % of SiO2 particles having a particle size distribution d50>10 m; 2.5-10 wt. % of CaCO3; 0.2-2.5 wt. % of polysiloxane wherein the wt. % are expressed relative to the weight of the hydratable calcium sulphate.

Claims

1. A plaster composition for fire resistant plasterboard, comprising hydratable calcium sulphate, water with a water/hydratable calcium sulphate ratio between 0.50 and 1.00, and the following components, 0.5-10 wt. % of SiO2 particles having a particle size distribution d50>10 m, 2.5-10 wt. % of CaCO3, and 0.2-2.5 wt. % of polysiloxane, wherein the wt. % is relative to the weight of the hydratable calcium sulphate.

2. Plaster composition according to the claim 1, wherein the SiO2, CaCO3 and polysiloxane have the following concentration, 2-7 wt. % of SiO2 particles having a particle size distribution d50>10 m, 2-7 wt. % of CaCO3, and 0.2-2.5 wt. % of polysiloxane.

3. Plaster composition according to claim 1, wherein CaCO3 is in the form of limestone.

4. Plaster composition according to claim 1, wherein SiO2 is in the form of quartz.

5. Plaster composition according to claim 1, wherein SiO2 is in the form of ground glass.

6. Plaster composition according to claim 1, wherein more than 90 wt. % of hem i-hydrate calcium sulphate (HH), preferably more than 94 wt. % wt. % based on the total weight of hydratable calcium sulphate, SiO2, CaCO3 and polysiloxane, is present in the plaster composition.

7. Plaster composition according to claim 1, free of vermiculite.

8. Plaster composition according to claim 1, wherein the polysiloxane is liquid.

9. Plaster composition according to claim 1, wherein the polysiloxane is solid in the form of particles having a granulometry below 3 mm, more preferably having a D90<2000 m measured by laser diffraction, and the concentration is between 1 and 2.5 wt. %.

10. Plaster composition according to claim 9, wherein the SIO2 content of the polysiloxane determined by X-Ray fluorescence is 35 wt. %, preferably 45 wt. % based on the total weight of the polysiloxane.

11. Plaster composition according to claim 1, wherein mica is present in the composition between 0.7-7.5 wt. %, and preferably between 0.7-5 wt. %.

12. A plasterboard comprising a gypsum core obtainable by setting of a plaster composition according to claim 1, and wherein the density is >0.55.

13. A method for the manufacture of a plasterboard having a density >0.55, comprising the following steps: (a) providing a plaster composition according to claim 1; (b) forming said plaster composition into a plasterboard; and (c) allowing said plasterboard to set.

14. Partition wall comprising two superimposed layers of plasterboards, one external and one internal layer, wherein at least the external layer of plasterboard is obtained by the method of claim 13.

15. The method of claim 13, comprising the additional step of reducing the shrinkage during heat exposure at a temperature of up to 1050 C. of a plasterboard, the shrinkage being measured by TMA on samples of 8818 mm.sup.3, at a rate of 10 degree/min with a preload of while maintaining a structural core cohesion for at least 1.5 hour.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0038] FIG. 1 shows a structural core cohesion fall down test.

DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be described with respect to particular embodiments.

[0040] When reference is made to weight percentage (wt. %), this is to be understood, unless differently specified, as the weight of the component expressed as percentage over the hydratable calcium sulphate of the composition in which the component is present.

[0041] The term gypsum as used herein refers to calcium sulfate dihydrate (DH), i.e. CaSO4.Math.2H.sub.2O. Gypsum which is present in plasterboards typically is obtained via the hydration of plaster.

[0042] The term plaster or stucco as used herein and in the generally accepted terminology of the art, refers to a partially dehydrated gypsum of the formula CaSOxH.sub.2O, where x can range from 0 to 0.6. The term plaster is also referred to herein as hydratable calcium sulfate. The term dry weight when referred to plaster in a plaster composition, refers to the weight of the calcium sulfate including hydration water (i.e. the xH.sub.2O of the above formula), but excluding any gauging water in the composition. Plaster can be obtained via the calcination of gypsum, i.e. the thermal treatment of gypsum in order to remove (a part of) the combined water. For the preparation of plaster, natural or synthetic gypsum may be used. Natural gypsum may be obtained from gypsum rock or gypsum sand. Synthetic gypsum typically originates from flue gas desulfurization (FGD) or phosphoric acid production or can also be titanogypsum. More generally, synthetic gypsum can originate from any process comprising calcium sulfate production as a by-product.

[0043] The plaster contained in the plaster composition is a hydratable calcium sulfate, such as calcium sulfate hemihydrate (HH). Preferably, the plaster contains at least 70 wt. % calcium sulfate hemihydrate, or even at least 85 wt. % calcium sulfate hemihydrate. The calcium sulfate hemihydrate may be in its or form, and preferably in the form. The plaster is typically provided in powder form, as is known in the art.

[0044] Plaster wherein x is 0.5 is known as calcium sulfate hemihydrate (HH) or calcium sulfate semihydrate (SH), i.e. CaSO4.0.5H.sub.2O. Calcium sulfate HH can occur in different crystalline forms; known as a and . Calcium sulfate HH is also known as gypsum plaster or plaster of Paris.

[0045] Plaster wherein x is 0 is known as calcium sulfate anhydrite or anhydrous calcium sulfate. Calcium sulfate anhydrite III (AIM) refers to a dehydrated HH with the potential of reversibly absorbing water or vapor. Calcium sulfate anhydrite II (All) refers to the completely dehydrated calcium sulfate (CaSO.sub.4). All is formed at higher temperatures and is preferably not used for the preparation of plasterboard.

[0046] The terms plasterboard and gypsum board as used herein interchangeably and refer to a panel or board comprising a gypsum core, obtainable from a plaster slurry as described herein. Accordingly, the term plasterboard refers to a board or panel which is obtainable via the setting (hydration) of plaster. The term board or panel as used herein refers to any type of wall, ceiling or floor component of any required size.

[0047] The term Polysiloxane designates all polymeric organosilicon compounds containing SiOSi bonds and SiC bonds. Especially polysiloxane formula is

[R.sub.nSiO.sub.((4-n)/2].sub.m

where n is 0-3 and m is larger than 2, preferably larger than 20, preferably larger than 40 and preferably larger than 200 before or after mixture with plaster and gauging water. R can be Hydrogen or organic group, indifferently methyl or phenyl groups or a mixture of both.

[0048] For the reason exposed above, the concentration of polysiloxane was limited to a maximum of 2.5 wt. %. The composition comprises between 0.2 up to 2.5 wt. %, preferably up to 2 wt % of polysiloxane based on the hydratable calcium sulphate.

[0049] The most commonly polysiloxane used are methylhydrogen polysiloxane (PHMS) or dimethyl polysiloxane (PDMS). Suitable PHMS are Xiameter MHX 1107 sold by Dow Chemical Company SILRES BS94 sold by Wacker-Chemie GmbH. A suitable PDMS is Dowsil 3-0133 sold by Dow Chemical Company.

[0050] Besides common polysiloxane, recycled polysiloxane can also be used: the polysiloxane are either liquid or solid having a granulometry below 3 millimetres. The granulometry is measured by microscope and image analysis. Preferably the solid polysiloxane has a D90 below or equal 2000 m. D90 being the particle size distribution D90 which represents the particle diameter corresponding to 90% cumulative (from 0 to 100%) undersize particle size distribution. It is measured by a laser diffraction method.

[0051] Solid polysiloxane can be Silicone elastomers and silicone rubbers, composed of high molecular weight silicone polymers such as dimethylsiloxanes, methylpheylsiloxanes, methylvinylsiloxanes, fluorovinylmethylsiloxanes or fluoroalkylsiloxanes. Polysiloxane comprises Polysiloxane-organic copolymer.

[0052] When polysiloxane are originated from silicone rubbers, fillers can be present.

[0053] Any form of polysiloxane or recycled polysiloxane can be suitable provided that the SIO2- content of the polysiloxane determined by X-Ray fluorescence is comprised: [0054] between 35 wt. % and 94 wt. % based on the total weight of the polysiloxane [0055] preferably 45 wt. % and 94 wt. % [0056] most preferably 75 wt. % and 94 wt. %

[0057] Table 1 gives typical characteristics of solid recycled polysiloxanes.

TABLE-US-00001 TABLE 1 Polysilox 1 Polysilox 2 SiO2 content 46% 59% D10 40 d50 94 D90 2000 Granulometry <800 m <3000 m

[0058] The composition also comprises CaCO3 preferably under the form of limestone. A suitable Calcium carbonate is Mikhart 10 sold by La Provenale having a purity of at least 98% % and a granulometry below 50 m and a d50 of 10 m.

[0059] The range of the concentration is between 2.5 and 10 wt. %, preferably up to 7 wt. % based on the hydratable calcium sulphate. A maximum should be below 10 wt. % in order to not impact drastically the mechanical resistance at room temperature and avoiding then the use of an increase of polysiloxane.

[0060] SiO2 particles have a particle size distribution d50>10 m. It was observed that Fume silica was not suitable. Quartz or amorphous ground recycled glass/ground recycled fibre glass are used. Particle Size Distribution d50 is also known as the median diameter or the medium value of the particle size distribution, it is the value of the particle diameter at 50% in the cumulative distribution. It is measured by a laser diffraction method.

[0061] A suitable quartz is C400 sold by Sibelco.

[0062] The range of concentration of SiO2 is between 0.5-10 wt. % based on hydratable calcium sulphate weight.

[0063] Mica can be optionally used if further mechanical resistance at high temperature is required. Between 7.5 wt. % of mica and preferably between 0.7-5 wt. % of mica related to the weight of the hydratable calcium sulphate are used. More preferably mica under the form of Muscovite particle having a d50 between 40 and 70 m is used.

[0064] The plaster composition has a water/hydratable calcium sulphate ratio between 0.50 and 1.00. The water/hydratable calcium sulphate ratio refers to the weight of water in the plaster composition divided by the dry weight of hydratable calcium sulphate in the plaster composition. In preferred embodiments, the plaster composition described herein has a water/hydratable calcium sulphate ratio below 0.80. In further embodiments, the plaster composition has a water/hydratable calcium sulphate ratio below below 0.70, below 0.65, or even below 0.60. When a low water/hydratable calcium sulphate ratio is desired, the plaster composition will typically comprise a fluidizer, as is known in the art.

[0065] The plasterboards have a density varying between 0.55 to 0.92 corresponding to a 12.5 mm plasterboard which weights between 7-11.5 kg/m.sup.2.

[0066] Preferably, the plaster composition contains no vermiculite.

[0067] Preferably, the method for the manufacture of a plasterboard having a density >0.55, comprises the following steps: [0068] (a) providing a plaster composition as defined supra [0069] (b) forming said plaster composition into a plasterboard; and [0070] (c) allowing said plasterboard to set;

[0071] Wherein the forming step (b) comprises the following steps: [0072] providing a first facing sheet; [0073] pouring the plaster composition over the first facing sheet; [0074] providing a second facing sheet over.

[0075] The plasterboards are used inside a building.

EXPERIMENTAL

[0076] Different formulations of plaster composition were prepared as shown in Tables 2-4.

[0077] The composition of the plaster respects a water/hydratable calcium sulphate ratio of 0.70 and was poured in molds to produce cubic samples of 555 cm.sup.3 which were then dried at 50 C. until the sample reaches a constant weigh and stored at room temperature (20 C.+/1 C., HR: 65%). Other additives may have been added to these formulations, without being essential to the findings of the present invention. The % are wt % relative weight of hydratable calcium sulphate

[0078] The shrinkage is firstly assessed by a Thermo Mechanical Analysis (TMA) measurement. TMA was conducted with the TMA model 1100/132 distributed by METTLER TOLEDO on samples of 8818 mm.sup.3. A rate of 10 degree/min with a preload of 0.05N was used.

[0079] EX1: Liquid polysiloxane

TABLE-US-00002 TABLE 2 1 2 3 4 5 6 Composition 2.44% PDMS 2.44% PDMS 0.6% PDMS 10% C400 5% E400 5% E400 Temperature REF 2.44% 5% C400 10% 5% 5% (C.) Stucco 1 PDMS 5% Mikhart10 Mikhart10 Mikhart10 Mikhart10 800 6.19% 2.20% 4.55% 1.68% 1.74% 1.96% 1050 12.01% 11.53% 10.91% 9.8% 9.84% 9.46% PDMS: dimethylpolysiloxane Dowsil 3-0133 C400: quartz Mikhart10: CaCO3

[0080] The use of a polysiloxane impacts the shrinkage at 800 C. when comparing with the reference stucco without polysiloxane. Adding SiO2 and CaCO3 in the reference stucco improves slightly the shrinkage at 800 as well as at 1050 C. The combination of PDMS/SIO2/CaCO3 improves drastically the shrinkage at 800 C. but also at 1050 C. What was more surprising is that the same shrinkage is obtained by lowering drastically (by a factor of 4) the amount of polysiloxane used!

[0081] This improvement was also obtained with 0.25 wt. % of PHMS with another stucco: plaster 2

TABLE-US-00003 TABLE 3 9 7 8 0.25% PHMS Temperature ref 0.75% 3.3% CaCO3 C. Plaster 2 PHMS 3.3% SiO2 800 4.28% 2.36% 3.0% 1050 13.99% 13.6% 8.6%

[0082] EX2. Solid polysiloxane and substitution of Quartz by Ground Glass Fibre

[0083] Lab test were carried out using a third stucco to produce small plasterboards (0.1 m.sup.2) having a weight of 11.0 kg/m.sup.2 (d=0.88). The composition of the plaster respects a water/hydratable calcium sulphate ratio of 0.80. Samples were prepared from the plaster composition according to the recipes set out in Table 4. The amounts of the additives are given as a wt. % relative to the hydratable calcium sulphate weight. Other additives may have been added to these formulations, without being essential to the findings of the present invention. The plaster composition was cast between two layers of paper.

TABLE-US-00004 TABLE 4 Ground Sol Sol E400/ Glass Mik40 PHMS PolySilox1 PolySilox2 SI02 Fibre CACO3 PRM011 0.5% REF PRM012 0.5% 5.0% 5.0% PRM013 0.5% 5.0% 5.0% PRM014b 1.5% 5.0% 5.0% PRM015 1.5% 5.0% 5.0% PRM017 2.0% REF PRM018 2.0% 5.0% 5.0% PRM019 2.0% 5.0% 5.0%

[0084] The shrinkage was assessed by a Thermo Mechanical Analysis (TMA) measurement on samples of 8818 mm.sup.3. A rate of 10 degree/min with a preload of 0.05N was used.

TABLE-US-00005 TABLE 5 TMA shrinkage TMA shrinkage at TMA at 800 C. 1050 C. PRM011 REF 2.33% 17.02% PRM012 2.34% 10.53% PRM013 2.66% 9.16% PRM014b 2.28% 11.09% PRM015 2.46% 8.85% PRM017 REF 2.24% 13.42% PRM018 1.93% 9.87% PRM019 2.49% 9.06%

[0085] The target of a shrinkage below or equal to 3% at 800 C. and below 13% at 1050 C. was obtained by using polysiloxane (liquid or solid) in combination with quartz or ground glass fiber and limestone.

[0086] EX3. Structural Core Cohesion

[0087] A fourth stucco was used to produce some plasterboards having a weight of 11.3 kg/m.sup.2 (d=0.90). The composition of the plaster respects a water/hydratable calcium sulphate ratio of 0.70. They were prepared from the plaster composition according to the recipes set out in Table 6. The amounts of the additives are given as weight % relative to Calcium Sulphate hemihydrate (HH) weight. Other additives may have been added to these formulations, without being essential to the findings of the present invention. The plaster composition was cast between two layers of paper.

TABLE-US-00006 TABLE 6 PRM 020 ref PRM 025 Polysilox 1 %/HH 1.5% Quartz %/HH 3.0% 5.0% CaCO3 %/HH 2.0% 5.0% Vermiculite %/HH 4.0% Glass Fiber %/HH 0.4% 0.4%

[0088] The reference is a plaster composition typically used to manufacture fire resistant plasterboard, the plaster composition comprises 4 wt. % vermiculite and 0.4 wt. % of glass fiber, the % are wt. % expressed relative to the weight of the Calcium sulphate hemihydrate.

[0089] The shrinkage was assessed by a Thermo Mechanical Analysis (TMA) measurement on samples of 8818 mm.sup.3. A rate of 10 degree/min with a preload of 0.05N was used.

TABLE-US-00007 TABLE 7 PRM 020 PRM 025 Shrinkage TMA 800 C. % 0.94% 1.69% Shrinkage TMA 1050 C. % 11.3% 12.24%

[0090] As expected, the plasterboard of the present invention and the comparative plasterboard comprising vermiculite shows a shrinkage is below 12.5% at 1050 C.

[0091] However, another important parameter to take into account is the integrity of the plasterboard exposed at high temperature.

[0092] The integrity of the plasterboard was assessed by a structural Core cohesion fall down test.

[0093] The structural core cohesion of the plasterboard when exposed to fire is assessed according to 8.3.6 paragraph of DIN 18180-1989 with the following modifications: [0094] Temperature of each burner was adjusted to 1020 C.20 C. [0095] A load of 1000 g was applied at the bottom part of each sample [0096] test was stopped after the fall-down of each sample. Time before the fall-down was recorded [0097] 3 samples were tested each time.

[0098] The test can be described as following:

[0099] Three samples (6) of 300 mm (+/5 mm)50 mm (+/1 mm) are cut according to the Machine Direction. The samples are then conditioned in a ventilated heated cabinet et 40 C.+/4 for at least four hours.

[0100] FIG. 1 shows the structural core cohesion est. The sample (6) is then centred between two Juchheim Meker burners type 1436P (4) and positioned at 25 mm of the sample surface. The burners simulate the fire exposure. The test temperature is 1020 C.20 C. measured by thermocouples (5) positioned at a distance of 15 mm from the burner (4) and 10 mm from the sample surface.

[0101] A tensile force is applied to a vertical sample by applying a load (3) of 1000 g at the bottom of the sample. On heating the stress causes the sample to break.

[0102] The length of time required to break the sample is recorded. The test is repeated on three samples and the shortest recorded time sets in Table 8.

TABLE-US-00008 TABLE 8 PRM 020 PRM 025 Core cohesion fall hours min <10 minutes >1 hr 30 min down

[0103] The comparative example is a plasterboard comprising vermiculite and glass fibres which is a current recipe for fire resistance. Glass fiber is required to maintain a core cohesion according to DIN 18180-1989. Due to high temperature applied, the sample breaks only after 10 minutes. In the present invention even in presence of low amount of glass fiber (0.4 wt %), the sample breaks only after 1 h30!

[0104] The combination of silicone/CaCO3/SiO2 not only restricts the shrinkage at high temperature but improves the structural core cohesion of the board.

TABLE-US-00009 REF DESCRIPTION 1 Distance between the burner and the sample 2 Distance between the burner and the thermocouple 3 Load (1 kg) 4 Burner 5 Thermocouple 6 Sample