US 2010O288415A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2010/0288415 A1 Biguenet et al. (43) Pub. Date: Nov. 18, 2010
(54) GYPSUM BASED COMPOSITIONS (30) Foreign Application Priority Data (75) Inventors: Cedric Biguenet, Leicestershire May 1, 2007 (GB) ...... 07.08382.7 (GB); Sam O'Keefe, Leicestershire (GB); Agnes Smith, Limoges cedex Publication Classification E. Thierry Chotard, Limoges (51) Int. Cl. cedex (FR) C04B II/024 (2006.01) Correspondence Address: B32B 37/2 (2006.01) Gray Robinson (52) U.S. Cl...... 156/39; 1067775 ATTN; STEFAN. V. STEIN/ IP DEPT. 201 N. Franklin Street, Suite 2200, Post Office Box (57) ABSTRACT 3324 A gypsum stucco composition comprising the following TAMPA, FL 33601-3324 (US) components finely divided; calcium Sulphate hemihydrate in calcined solid beta crystalline form; and in intimate mixture (73) Assignee: BPB Limited, Coventry (GB) with said finely divided calcium sulphate hemihydrate and (21) Appl. No.: 12/S98.184 mixed therewith no later than calcination to form the hemi y x- - - 9 hydrate, a Sulphate salt comprising at least one of ammonium (22) PCT Filed: Apr. 11, 2008 Sulphate and aluminium Sulphate, in an amount Such that 9 when the stucco composition is mixed with water and allowed (86). PCT No.: PCT/GB08/SO255 to set, the resulting set plaster has increased compressive strength, flexural strength and/or E-modulus compared to a S371 (c)(1), set plasterproduced from said finely divided calcium sulphate (2), (4) Date: Aug. 2, 2010 hemihydrate containing no said Sulphate salt.
Ground gypsum with A2(SO4)3.8H2O andfor (NH4)2SO4 bierided at together and sieved at 212 in
Ground aluminium sulphate and for ammonium sulphate
3 Caciation
occo co C C C C O s Stucco with auririum supiate andfor l annotium sulphate in its structure
Ground gypsum
40°C tap water - |->
Set gypsum Patent Application Publication Nov. 18, 2010 Sheet 1 of 4 US 2010/0288415 A1
Ground gypsum with Al(SO4)3.8H2O and/or (NH4)2SO4 biended all together and sieved at 212 in
Ground aluminium sulphate 2 and/or anni Orium Suiphate
3 Caicination
C.C. C. C. C.C.C OC O. C C C C O W f Od Stucco with aluminium sulphate and/or aminorium sulphate in its structure
Ground gypsum
40°C tap water - ar
Set gypsum
F. Patent Application Publication Nov. 18, 2010 Sheet 2 of 4 US 2010/0288415 A1
Dried gypsum in a 40°C over and ground sieved at 212 i? gy Sun
4 Caciatior
Stucco with aluminium sulphate andfor ammoniu sulphate in its structure
Auritium sulphate and for armonium sulphate dissolved 40°C tap water
40°C tap water
Set gypsuit
F. 2 Patent Application Publication Nov. 18, 2010 Sheet 3 of 4 US 2010/0288415 A1
Spray of Aluminium sulphate and for annonium
Ground gypsum -> si? Hemihydrate with aluminium Caiciatio: sulphate and/or ammonium Sulpate if its structure
40C tap water
Set gypsu.
F. 3 Patent Application Publication Nov. 18, 2010 Sheet 4 of 4 US 2010/0288415 A1
se Ground aluminium sulphate and/or Ground gypsum annonium sulphate added during the Caciatio when a 12OC
Kette, Caciation
S. lenihydrate with aituminium Suiphate and for anoniu sulphate in its structure
40C tap water
Set gypsurr
F.G. 4 US 2010/0288415 A1 Nov. 18, 2010
GYPSUM BASED COMPOSITIONS minium Sulphate no later than calcination thereof (that is, prior to or during calcination of the gypsum to calcium Sul phate hemihydrate). 0001. The present invention concerns gypsum-based com 0010. The finely divided calcium sulphate hemihydrate positions which can be used to form plaster products. used in the composition according to the invention has gen 0002 Gypsum is a naturally occurring form of calcium erally been obtained by gypsum calcination. If the original sulphate, in the form of a stable dihydrate (CaSO2H2O). The Source of the gypsum is natural, it may be crushed and ground term 'gypsum”, as used herein, means calcium Sulphate in before converting to the hemihydrate; if it is derived from an that stable dihydrate state; and includes the naturally occur industrial Source, drying may be all that is required before ring mineral, the synthetically derived equivalents, and the conversion to the hemihydrate. It is even possible in some dihydrate material formed by the hydration of stucco (cal cases to omit the drying step when using a process known as cium Sulphate hemihydrate) or anhydrite. wet calcination. 0003. The properties of gypsum make it highly suitable for 0011. The finely divided calcium sulphate hemihydrate use in industrial and building plasters and other building used in the composition according to the invention preferably products such as gypsum wallboard. It is a plentiful and is such that it has a do value of no more than 3 microns and/or generally inexpensive raw material which, through Succes a do of no less than 100 microns. (Ado Value of no more than sive steps of dehydration and rehydration, can be cast, moul 3 microns means that no more than 10% by weight of the ded or otherwise formed to useful shapes. For example, gyp Solids has a particle size of less than 3 microns; similarly a doo Sum wallboard; also known as plasterboard or drywall, is value of no less than 100 microns means that no more than formed as a set gypsum core Sandwiched between paper cover 10% by weight of the solids has a particle size of greater than sheets. 100 microns.) 0004 Gypsum is generally prepared for use as plaster by 0012. It is, of course, known to use aluminium sulphate as grinding and calcining at relatively low temperature (such as an accelerator in the production of gypsum plaster; the from about 120 to 170° C.), generally at atmospheric pres amount used for acceleration purposes would have signifi Sure. This results in partially dehydrated gypsum, typically in cantly less effect on compressive strength than is achieved the form of the beta crystalline form of the hemihydrate, according to the invention. Furthermore, in the manufacture which generally has an irregular crystal structure. The beta of plasterboard, accelerators are added just prior to the step of hemihydrate may be used as a building or construction mate mixing with water, in order to provide control over the addi rial by mixing it with water to form an aqueous stucco slurry, tion rates and therefore the set time, whereas the Sulphate paste or dispersion, and then allowing the slurry to set by used according to the present invention is in an intimately recrystallisation from the aqueous medium. Such setting is mixture with the stucco. In some embodiments, this can be typically rapid in the production of plasterboard (typically with the composition in Substantially dry form, prior to being within 2.5 to 10 minutes). mixed with water to produce an aqueous slurry or the like. 0005 Gypsum is inherently a brittle, crystalline material 0013 When aluminium sulphate is employed in the com which has relatively low tensile, compression and flexural position according to the invention, it is preferably present in strength. There have been many attempts to improve one or an amount of 1 to 6 grams per 100 grams of hydratable more of these properties. calcium sulphate (about 0.5 to 3 molar percent, based on the 0006 We have now found that the addition of certain number of moles of hydratable calcium sulphate). When Sulphate salts to gypsum prior to calcination can result in ammonium Sulphate is present, it is preferably in an amount significantly improved compression strength in products of 0.2 to 0.4 grams per 100 grams of hydratable calcium sulphate. (about 0.5 to 1 molar percent, based on the number made from the resulting formulation. of moles of hydratable calcium sulphate). When ammonium 0007. The present invention relates to the use of at least aluminium Sulphate is present, it is preferably in an amount of one of ammonium Sulphate and aluminium Sulphate and 0.6 to 4 grams per 100 grams of hydratable calcium sulphate potassium aluminium Sulphate and ammonium aluminium (about 0.5 to 1 molar percent, based on the number of moles Sulphate for enhancing the compressive strength of gypsum of hydratable calcium sulphate). When potassium aluminium building board. sulphate is present, it is preferably in an amount of 0.6 to 4 0008. The present invention therefore provides a gypsum grams per 100 grams of hydratable calcium Sulphate. (about stucco composition comprising the following components 0.5 to 1 molar percent, based on the number of moles of i) finely divided calcium sulphate hemihydrate, in calcined hydratable calcium Sulphate). solid beta crystalline form; and 0014 When aluminium sulphate and/or ammonium sul ii) in intimate mixture with the finely divided calcium sul phate and/or potassium aluminium Sulphate and/or ammo phate hemihydrate, and mixed therewith no later than calci nium aluminium Sulphate are used, they are typically in nation thereof, a Sulphate salt comprising ammonium and/or amounts such that the total molar percentage of the ammo aluminium Sulphate and/or potassium aluminium Sulphate nium Sulphate plus aluminium Sulphate plus the ammonium and/or ammonium aluminium Sulphate, in an amount Such aluminium Sulphate plus the potassium aluminium Sulphate is that when the stucco composition is mixed with water the at least 0.5 molar percent, typically up to 3 molar percent, resulting mix has reduced water demand and/or viscosity, based on the number of moles of hydratable calcium sulphate. and/or such that when the mix is allowed to set, the resulting 0015 The composition according to the invention is pref set plaster has increased compressive strength compared to a erably substantially free of ingredients (other than the essen set plaster produced from the finely divided calcium sulphate tial calcium Sulphate) which are capable of independently hemihydrate containing no such Sulphate salt. interacting with the water (thus the composition should con 0009. The intimate mixture is achieved according to the tain no more than trace amounts of materials such as clays, invention by mixing gypsum with ammonium and/or alu cements, gels, water-Swellable polymers or the like). US 2010/0288415 A1 Nov. 18, 2010
In use, the stucco composition according to the invention is to sium aluminium Sulphate intimately mixed therewith and be mixed with water to form a slurry, paste or dispersion uniformly dispersed throughout the stucco. which is allowed to set. It has been found surprisingly that the 0025 FIG. 3 shows an embodiment in which ground gyp slurry is less viscous than a comparable slurry containing no Sum was sprayed with an aqueous solution of aluminium aluminium Sulphate and/or ammonium Sulphate and/or Sulphate and/or ammonium Sulphate and/or ammonium alu ammonium aluminium Sulphate and/or potassium aluminium minium Sulphate and/or potassium aluminium Sulphate. The sulphate. The water employed to make the slurry is typically resulting sprayed product was then calcined to produce ground water or tap water, which may have been filtered. stucco having aluminium Sulphate and/or ammonium Sul 0016. At least some of the water may be in the form of a phate and/or ammonium aluminium Sulphate and/or potas pre-generated aqueous foam, Such as is conventionally added sium aluminium Sulphate intimately mixed therewith and to gypsum slurries so as to reduce the weight of the resulting uniformly dispersed throughout the stucco. final board. Various types of foaming agent may be used in 0026 FIG. 4 shows an embodiment in which ground gyp Such a foam; amongst these are ionic Surfactants and non Sum was blended with an aqueous solution of aluminium ionic Surfactants. Sulphate and/or ammonium Sulphate and/or ammonium alu 0017. Other non-deleterious materials, adjuvants and minium Sulphate and/or potassium aluminium Sulphate in a ingredients may, when appropriate, be present either in the kettle and the resulting aqueous mix was directly calcined to water or mixed with the stucco composition. Such non-del produce stucco having aluminium Sulphate and/or ammo eterious materials may include optional further ingredients, nium Sulphate and/or ammonium aluminium Sulphate and/or Such as starch, water reducing agents, moisture repellents potassium aluminium Sulphate intimately mixed therewith (such as silicone oils or waxes), reinforcing fibres, set accel and uniformly dispersed throughout the stucco. erators and retarders, deformation inhibitors (such as anti 0027. In all the illustrated embodiments, ammonium sul sagging agents), anti-shrink additives, recalcination inhibi phate, aluminium Sulphate, ammonium aluminium Sulphate tors, foam stabilisers, bactericides, fungicides, pH adjusters, and potassium aluminium Sulphate may be used together, or colouring agents, fire retardants and fillers (such as particu separately. late mineral material or plastics, which may in some embodi 0028. In all the above cases, the stucco was then blended ments be in expanded form). with water (deionised water is shown in each of the drawings) 0018. The pH of the slurry, paste or dispersion formed in the usual way, to form a gypsum slurry which can then be from the stucco composition according to the invention is allowed to set. The set gypsum slurry may be a conventional typically in the range 6.5 to 9.5. form of building material, for example, a plasterboard. 0019 Especially when the composition according to the 0029. Certain features of the present invention will now be invention is used in the production of gypsum board, the illustrated with reference to the following examples. aqueous slurry, paste or dispersion made therefrom may con EXAMPLES tain fibre reinforcement, such as glass fibres (typically cut fibres). 0030 Aluminium sulphate (Al(SO). 18HO) was dis 0020. When gypsum board is produced from the compo Solved in deionised water and stucco (calcium Sulphate hemi sition according to the invention, the board may be with or hydrate) from natural gypsum was added to the aqueous without surface reinforcement or liner sheets; when surface Solution so as to hydrate the stucco and thereby produce reinforcement is used, it may, for example, be of fibre scrim, gypsum intimately mixed with aluminium Sulphate. The fibre mesh or paper. molar of aluminium Sulphate in the aqueous solution to stucco was about 1:100. 0021. The present invention extends to gypsum building 0031. This mix was then dried and subsequently ground board comprising a set aqueous gypsum slurry, paste or dis (with a hammer mill) and the resulting powder was calcined persion derived from a composition according to the inven in a 5 kg batch kettle to produce a modified stucco (now tion, and the use of a formulation according to the invention in incorporating the aluminium Sulphate). This modified stucco the production of Such gypsum building board. was hydrated with agitation in deionised or tap water and the 0022. Certain preferred aspects and features of the present resulting slurry poured into silicon moulds in the shape of invention are illustrated by way of example only with refer cylinders measuring 24 mm of diameter and 48 mm of height. ence to the accompanying drawings, in which. The slurry was then allowed to set. The resultant cylinders 0023 FIG. 1 shows an embodiment in which ground gyp were then dried to constant weight at about 40°C. for about 24 Sum was powder blended with ground aluminium Sulphate hours then conditioned at 23° C./50% RH for at least 24 (namely Al(SO4). 18HO) and/or ammonium Sulphate and/ hours. The compressive strength of the cylinders, as well as or ammonium aluminium Sulphate and/or potassium alu their densities, were measured. minium Sulphate. The resulting powder blend was then cal 0032. The slurry poured into the moulds was more fluid cined to produce stucco having aluminium Sulphate and/or (less viscous) than a control batch containing no aluminium ammonium Sulphate and/or ammonium aluminium Sulphate sulphate. The control slurry had a Vicat Initial Set (VIS) of 27 and/or potassium aluminium Sulphate mixed therewith and min, and a Vicat Final Set (VFS) of 30 min 30 sec; the uniformly dispersed throughout the stucco. corresponding figures for the slurry containing aluminium 0024 FIG. 2 shows an embodiment in which ground gyp sulphate were VIS=5 min 20 sec, VFS-6 min 30 sec. Sum was blended with an aqueous solution of aluminium 0033. The compressive strength of the resulting cylinders Sulphate and/or ammonium Sulphate and/or ammonium alu were +22.6% greater than that of the control; and even +56% minium Sulphate and/or potassium aluminium Sulphate. The greater than that of the addition of aluminium Sulphate added resulting aqueous mix was then dried and calcined to produce after the calcination as a process water. stucco having aluminium Sulphate and/or ammonium Sul 0034. The experiment (following the procedure illustrated phate and/or ammonium aluminium Sulphate and/or potas in accompanying FIG. 1) was repeated using a range of inor US 2010/0288415 A1 Nov. 18, 2010 ganic compounds other than aluminium Sulphate, namely potassium aluminium Sulphate according to the invention ammonium Sulphate, ferrous Sulphate, magnesium Sulphate, allows higher mechanical performance to be achieved com potassium Sulphate, sodium Sulphate and strontium Sulphate, pared to the absence of such Sulphates or the use of apparently potassium carbonate, ammonium chloride, Zinc Sulphate similar Sulphates. Also the slurries containing aluminium Sul potassium aluminium Sulphate, ammonium aluminium Sul phate and/or ammonium Sulphate and/or ammonium alu phate, molybdic acid, Vanadium oxide Sulphate, tungstosi minium Sulphate and/or potassium aluminium Sulphate are licic acid hydrate. The results are summarised in the follow less viscous potentially leading to commercially significant ing table, which shows that the greatest increases in reductions in the amount of water needed. compressive strength were achieved with the addition of 0038 Although the abovementioned illustrative example ammonium Sulphate, while the greatest decreases in water illustrates use of the compositions according to the invention demand were achieved with the addition of potassium alu in plaster blocks (prisms), comparable advantages can be minium Sulphate (with regard to strength increase). obtained if a slurry made from the composition is sandwiched
Trials with Some additives blended as a Solid before calcination (Water Gauge of 100 and 1 mole 90 added Mass Water VIS VFS Slurry Dry density Compressive added (g) Demand (%) (min:sec) (min:sec) consistency (kg/m) strength (Mpa) Aluminium Sulphate Al2(SO) 18H2O 96.86 81 4:40 6:20 Fluid 855 6.5 Ammonium Sulphate (NH4)2SO4 1921 85 5:05 6:05 Fluid 853 7.6 862 7.4 Iron Sulphate FeSO4·7HO 80.83 100 4:30 5:40 Viscous 859 6.4 864 5.9 Magnesium Sulphate MgSO4·7H2O 71.65 90 8:35 9:50 less viscous 863 6.8 865 6.3 Potassium Sulphate K2SO 25.33 98 4:10 5:25 Viscous 858 6.2 860 4.8 Sodium Sulphate Na2SO4·10H2O 46.83 90 6:35 7:20 less viscous 864 6.2 863 5.8 Strontium Sulphate SrSO S3.11 95 8:05 9:35 Wiscous 853 5.7 869 6.1 Potassium aluminium KAl(SO4)2·12H2O 68.95 70 5:40 7:10 very watery 897 737 Sulphate 872 7.62 863 7.31 Ammonium aluminium NH4Al(SO4)2·12H2O 65.89 76 7:00 8:45 Watery 860 7.27 Sulphate 870 6.88 Zinc Sulphate ZnSO,7HO 83.59 8O 8:00 9:30 Fluid 869 6.36 Molybdic acid MoO. 74.96 69 6:35 8:35 very watery 872 6.98 868 6.67 Potassium carbonate K2CO 2009 90 8:35 9:10 Less viscous 847 5.76 843 5.71 Ammonium chloride NHCI 15.55 61 6:00 7:25 Very watery 868 3.62 866 3.53 Vanadium oxide VOSOHO 47.38 88 5:45 7:35 Less viscous 858 6.68 Sulphate 857 6.11 Tungstosilicic HSiCWO).H2O 69.73 88 10:SO 13:05 Less viscous 866 5.51 acid hydrate 863 4.80
0035. The table also shows that ammonium sulphate offers between opposed surface reinforcement or liner sheets to the additional advantage that significant increases in com form a plasterboard. The present invention therefore extends pressive strength are achieved with a lower weight of additive. to plasterboard made from the composition according to the For example, the table compares results achieved with 19.21 invention. The plasterboard is generally made by feeding an grams of ammonium Sulphate compared to 96.86 grams of aqueous slurry (such as a foamed slurry) formed using the aluminium Sulphate. Although ammonium Sulphate is composition according to the invention between spaced Sur slightly more expensive per tonne than aluminium Sulphate face reinforcements so as to form a sandwich structure, and (in 2005 £86 per tonne compared to £71 per tonne) the ability then allowing the slurry to set between the surface reinforce to use a smaller quantity means that ammonium Sulphate can mentS. achieve comparable results to aluminium Sulphate at about a quarter of the cost. 1. A gypsum stucco composition comprising the following 0.036 Further results showed that when ammonium sul components: phate was added before calcination, the average compressive i) finely divided calcium sulfate hemihydrate in calcined strength achieved was 7.5 MPa whereas when it was added solid beta crystalline form; and after calcination, the average compressive strength was only ii) in intimate mixture with said finely divided calcium 5.3 MPa at a given density. Thus the process according to the sulfate hemihydrate and mixed therewith no later than invention resulted in an average 29% increase in compressive calcination to form the hemihydrate, a sulfate salt com strength. prising at least one of ammonium sulfate, aluminium 0037. The use of aluminium sulphate and/or ammonium Sulfate, potassium aluminium Sulfate and ammonium Sulphate and/or ammonium aluminium Sulphate and/or aluminium Sulfate in an amount Such that when the US 2010/0288415 A1 Nov. 18, 2010
stucco composition is mixed with water the resulting 9. A composition according to claim 1, wherein said potas mix has at least one property selected from the group sium aluminium sulfate is present in an amount of 0.5 to 3 consisting of molar percent, based on the number of moles of said calcium reduced water demand; sulfate. reduced viscosity, and 10. A composition according to claim 1, which is Substan increased compressive strength when the composition is tially free of materials other than the calcium sulfate which mixed with water and allowed to set, compared to a set are capable of independently interacting with water. plaster produced from said finely divided calcium sul 11. A method of forming plaster, which comprises mixing fate hemihydrate containing no said Sulfate salt. a composition according to claim 1 with water to form a 2. A composition according to claim 1, wherein said alu slurry, and allowing the slurry to set. minium Sulfate is present in an amount of 1 to 6 grams per 100 12. A method according to claim 11, wherein the slurry is grams of said calcium Sulfate. fed between spaced Surface reinforcements so as to form a 3. A composition according to claim 1, wherein said alu sandwich structure and the slurry is allowed to set between minium sulfate is present in an amount of 0.5 to 3 molar the Surface reinforcements. percent, based on the number of moles of said calcium Sulfate. 4. A composition according to claim 1, wherein said 13. A method according to claim 11, wherein the slurry ammonium sulfate is present in an amount of 0.2 to 1.2 grams contains fibere reinforcement. per 100 grams of said calcium sulfate. 14. A method according to claim 11, wherein the slurry is 5. A composition according to claim 1, wherein said foamed. ammonium sulfate is present in an amount of 0.5 to 3 molar 15. Plaster for gypsum building board when produced by a percent, based on the number of moles of said calcium Sulfate. method according to claim 11. 6. A composition according to claim 1, wherein said 16. A method of reducing the water demand or viscosity of ammonium aluminium sulfate is present in an amount of 0.6 a gypsum stucco composition comprising finely divided cal to 4 grams per 100 grams of said calcium Sulfate. cium sulfate hemihydrate in calcined solid beta crystalline 7. A composition according to claim 1, wherein said form, which comprises intimately mixing said finely divided ammonium aluminium sulfate is present in an amount of 0.5 calcium Sulfate hemihydrate at least one Sulphate selected to 3 molar percent, based on the number of moles of said from the group consisting of ammonium Sulfate, aluminium calcium Sulfate. Sulfate, potassium aluminium sulfate and ammonium alu 8. A composition according to claim 1, wherein said potas minium sulfate and calcining the mixture. sium aluminium sulfate is present in an amount of 0.6 to 4 grams per 100 grams of said calcium sulfate. c c c c c