CA2439484C

CA2439484C - Coatings for building products

Info

Publication number: CA2439484C
Application number: CA 2439484
Authority: CA
Inventors: Basil Naji; Milton O'chee
Original assignee: James Hardie Technology Ltd
Current assignee: James Hardie Technology Ltd
Priority date: 2001-03-02
Filing date: 2002-03-04
Publication date: 2011-10-25
Anticipated expiration: 2022-03-04
Also published as: EP1370369B1; JP2004523351A; EP1373157A2; AR032923A1; WO2002070421A2; EP1370369A4; US20050208287A1; CN1500038A; HUP0303320A2; WO2002070247A1; ATE459466T1; CN1612847A; EP1372952A4; US20030000424A1; HUP0303327A2; BR0207804A; US20030165624A1; KR20030077661A; TW574164B; US20020170467A1

Abstract

A method for coating a building product in which a coating formulation is provided which includes an hydraulic binder and a quantity of dewatering agent. A slurry is produced from said formulation and applied to the product to be coated. The resultant coating is then dewatered through said product. Dewatering can be accomplished with or without vacuum assistance. The method is suitable for producing a composite product which comprises a base structural layer with the coating thereon.

Description

4`O OW070249 ;PG'T . Y: 242 ~TTME: COAnNGS FOP, BUILDING PROD
IV, S
Technical. VWd `p'ees present invention relates to coatings and in particular.eoatiugs.for b, uilding produc w 4 l iiEnated ti ildI g. products, Backgreux*d...Art is Any discussion of he prior art tbro?ugbout the speei&astioit should, in. no wray be coitsideatid as an admission that such Prior at is widelyknowa *a fe nns part of consrnon general knowledge in the field.
Th area huge vari dyofinea-saniszns for .applying coatings to bui lug' Products such as building bot rds.
20 The coatings can be divided into two main:groups ramelyth istuag coatings, which are intended p arsly for aesthetic purposes;, and fuzcctional caaiings wbid provide some additional structural or other property}attribute to the resultant pn d; ct..
The application technique depends to -a large extent an the properties c+ftlbe coating eornposition.amd ba se_:iayer of product: to be coated. Maim.
application and..
spry bg etc are most pepular but they restrict t e types of:' oat tig to be appl ed and indeed the bu'clutg product-te be coated. For exampleõ when usir g a spray technique *ne;c-nnst ansueihe coatw' gcor tposition is of's 3icient.flowabilty to pass.
throng thespray nozzle but at the same times, the base mat xrial to be coated mast be suf cie-utly rigid to withst d the-impact of'tt a spay mating:
<34 For cc rtain huldingpreducts, such as iztc real wall systems, a:splooth surrace finish is vital. Gypsum or plaste=r board s used almost xclus ly as am, ni ternirtl wall bo=ard: due to itcexcellentsurface Bush.

The use of fibre reinforced cement building board for instance as an internal wall board has significant advantages including cost and structural integrity as compared with gypsum board. However, some techniques for production of fibre reinforced cement sheets do not provide a gypsum like surface finish. In response to public demand, builders require an internal wall board with a near perfect surface finish. Even minute irregularities which arise from production of fibre reinforced cement sheets can be sufficient to reject the product. Sanding the surface of the FRC
sheet has been used to improve its surface finish but in some instances such sanding can 'feather' or leave exposed the reinforcing fibres thereby exacerbating the problem.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
Disclosure of the Invention In a first aspect, the present invention provides a method for coating a building product comprising providing a coating formulation including an hydraulic binder and a quantity of dewatering agent, producing a slurry of said formulation, applying said slurry to the product to be coated and dewatering said slurry through said product.
In a second aspect, the present invention provides a formulation for use in coating a building product comprising an hydraulic binder and a quantity of dewatering agent sufficient to permit dewatering of a slurry produced from said formulation through the building product.
In a third aspect, the present invention provides a dewaterable slurry for coating a building product, said slurry comprising water, an hydraulic binder and a quantity of dewatering agent sufficient to permit dewatering of said slurry through said building product.
In a fourth aspect, the present invention provides a composite product comprising a base structural layer with a coating thereon, the coating including an hydraulic binder and a quantity of dewatering agent sufficient such that the coating may be dewatered through the base layer.
In a fifth aspect, the present invention provides a method of improving an hydraulic binder based coating formulation for coating a building product comprising adding to said binder a quantity of dewatering agent such that after application of a slurry of said formulation to said building product, said slurry can be dewatered through the building product.
In a sixth aspect, the present invention provides a dewatering aid for dewatering a cementitious slurry coating on a product, said dewatering aid comprising a quantity of particulate material sufficient to permit dewatering of the slurry through the product to be coated.
Unless the context clearly requires otherwise, throughout the description and the claims, the words `comprise', `comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".
The dewatering agent serves to maintain sufficient porosity in the slurry and product to be coated to permit dewatering of the slurry through the product to be coated. Preferably, the dewatering agent is a particulate material such as fly ash, alumina trihydrate, silica flour, cenospheres (ceramic hollow spheres) or similar.
Fly ash is particularly preferred as it permits dewatering of the slurry within a few minutes. Other particulate dewatering agents such as alumina trihydrate or silica flour may also be used, however, they increase the time required for dewatering of the slurry through the product to be coated.
In a preferred embodiment, the slurry applied to the product to be coated has a high water content. Preferably, the water content can be up to 50%. This is in contrast to previous cementitious formulations which generally have a higher solids content.
By combining the various components of the coating formulation described above, a dewaterable slurry is obtained which can be applied to the building product, dewatered through the building product and thereby provide a uniform coating over the building product.
Normally, after application of the coating, the resultant product would be normally cured, steam cured or hydrothermally cured, ie autoclaved, and if required, sanded to a smooth flat finish.
The building product to which the coating can be applied is virtually limitless provided the slurry can be dewatered through the building product.
Cementitious and gypsum building boards are typical examples of suitable building products on which the coating can be applied.
The resultant coating, which may optionally contain fibres, results in a decorative finishing layer which is sandable, smooth, flat, low permeable, crack free and/or flexible, ready to be finished, for example by painting.
The thickness of such a coating layer prior to sanding would range from around 0.1 to 10 mm, preferably 0.5 to 5 mm and most preferably 1 to 3 mm.
After sanding, the finish layer may have a depth of around 0.05 to 5 mm, preferably 0.1 to 2 mm and most preferably 0.5 to 1 mm. The thus produced coated product is comparable in its workability to monolithic (single layer) composites. It can be flexed, cut, drilled and fixed by nails etc to a frame without surface cracking or chipping.
The applicant's have found an extremely good interlaminer bond and compatibility between the dewatered slurry layer and base layer resulting in excellent composite action, compatibility and resistance to delamination.
The term 'hydraulic binder' as used throughout the specification refers to a pulverised material in the solid, dry state which, when mixed with water, yields plastic mixtures that are able to set and harden, for example a cement. Included within the definition are white, grey or pigmented cements and hydraulic limes.
The term 'cement' includes hydraulic and alite cements such as portland cement, blended cements such as portland cement blended with fly ash, blast-furnace slag, pozzalans and the like and mixtures thereof, masonry cement, oil well cement, natural cement, alumina cement, expansive cements and the like, or mixtures thereof.
The quantity of binder in the formulation is preferably between 10 to 50 wt%
based on the total dry ingredients, more preferably 15 to 40 wt% and most preferably 20 to 30 wt%.
The fly ash used in the present invention provides a number of advantages including, particularly, as an aid to dewatering of the slurry as defined above.
The term 'fly ash' as used herein refers to a solid powder having a chemical composition similar to or the same as the composition of material that is produced during combustion of powdered coal, ie 25 to 60 wt% silica, 10 to 30 wt%
A1203, 5 to 25 wt% Fe203, 0 to 20 wt% CaO and 0 to 5 wt% MgO.

Fly ash particles are typically spherical and range in diameter from 1 to 100 microns. In a preferred embodiment, the fly ash comprises two components. A
first 'larger' size particles of fly ash with preferably a 100 micron maximum size.
This size range of fly ash is used in the slurry to aid in improving the dewatering characteristics of the slurry but also as a moderately reactive pozzalan.
The second 'smaller' fly ash size zone which preferably has a 10 micron maximum size also adds an improving dewatering characteristic but is a more highly reactive pozzalan. This 'smaller' fly ash particle zone also improves the sanded surface quality of the finish layer.
In a preferred embodiment, the first fly ash comprises 10 to 60 wt% of the formulation based on total dry ingredients, more preferably 20 to 50 wt% and most preferably 30 to 40 wt%.
The second fly ash component preferably provides 5 to 30 wt% of the formulation based on total dry ingredients, more preferably 10 to 25 wt% and most preferably 15 to 20%.
In another preferred embodiment, the dewatering agent may include a coarse fraction fly ash which is greater than 100 microns. This coarse fraction fly ash includes bottom ash or similar products from coal combustion. There is an advantage to using these products over the aforementioned particle size fly ash since it is cheaper. Of course, as will be clear to persons skilled in the art, some reformulation of the slurry maybe required to provide a suitable coating and appropriate dewatering characteristics when the dewatering agent is such a coarse fraction fly ash.
The coating may optionally contain other additives such as fillers. Such fillers may also be used to improve the dewatering characteristics of the slurry. For example, cenospheres (hollow ceramic microspheres) diatomite, wollastonite, ground rice hulls, ground perlite or the like, are particularly suitable for this purpose.
These and other fillers may also be used to provide additional benefits, for example calcium carbonates or alumina hydrates improve sandability and flexibility of the coated layer respectively. Silica flour improves hardness of the sanded surface of the coating layer and the acoustic/thermal insulation properties of the layer can be improved by including rubber particles, vermiculite, perlite, expanded polystyrene or gypsum.

WO 021070248 PiC:'I','ALIM00242 T be fillers preferably Ãrirnprise SAO 30 wt% of t ie foxtxnulatt on based an total d r y i n g r e d i e n t s . m o r e p r = e f e r a b l y 10 t o 25 W 6 l a , a n d most preferably. 25 to 20 %
The coating may also contain other organic additives. Cement plasticising:
agents, . br example, may be used to alter the rheology of the slurry.
Suitable cement plasticising agents include melamine sulphonato form lehyde condensates, naphtbaleue salplaouate fozmaldehyde condensates, naphthalene sulp?' natoa. -calcium lignosulponates, sodtutn li sulpuonates,saccharose, sodium glucortate;
wlphottsc acids, caibo11yc ratos, amino carboxylic acids, polyhydroxycarboxilic ac ,.
sulphonated n.elomine and the ldce.
T The amount of ce ricnt plasticiser of course wil depend upon the faidis ng ability of the partict3ilar plasticisers- Generally tbe:quantity of plasticiser will be in the range of 0,3 to about 3 % and more preferably 0.5 to 2 wt n based ?rt: the LQta1 s3 f.
dry ingredients in the fonualation.
Particularly preferred cement plasticisers are..Meln sit r-? 0, a melamine IS fomaldehyde sodium bisulphate polymer dispersant;ia aAeted by.SKW .Trustbui the form of a Sue white;powde r, Another suitable plasticiser Is Neosyn. , acende secf sodium salt of stnlphonatednaphthalene fortrtaidebyde available from Hodgson.
Che icais.
t uothc preffcrrcd component in the coating :s a 1azc+p0lyrner wbicl arts to 20 enhance the flowabiity, sagregation..resistance and self l -yelling qualities of the r.~xnenP t ouc sh cry, Par~iculazly sriitable biopl 'mere axe x.anathan, :andlor w elan gum, eg KELCO-G ETETM; KIC 376 manufactured by Mons.nto.
Latex may also be included in the coating composition to improve adbiereec,:
elasticity, stabil_ifiy and:unpenneobWty ofthe caatieg_. The latex also mVrOVes 25 flexibility of the formed coating The latex maybe selected; from the group 0omsisting of acrylic 'atex, styrene latex,,hatadiene latex or mmi di=es thereof and is providedpreferablyin an amount beftreen G 5 to 20%, more preferably I to 15% annd most pre 'erably --bout 10%
by weight: of cement (on pol,'mcr solids basis) so ?s., 3n Vinyl polymers may also be incorporated into the coating Ait" . it in addition ora.M
a substitute to the latex emulsions. Such vinyl poly hers or equivalent polymeric WO OVO 70248 P(MA JO'iJttO242 materials enhance adhesion, resilience and flexural strength and abrasion resistance of the coating.
Preferred vinyl polymers include po`yv: yl acetate or a copolymer vinyl acetate:
with another monomer such as elltyleue. A particularlypreferred vinyl aeelate resit is .S VIN NAPAS L L5O 4 thenno piasbc resin powdet which contains a % tyI acetate-ethylene copolymer available from Wacker. Such powdered vinyl polymer is preferably provided iii quantities similar to the latex emulsion eferred.to above.
In addition to the above, conventional other additives snub as thneral oxides, hydroxide; and clays, metal oxides and hydroxides, fire retardants s u h as xaag esite, thickeners, silzca fie or amorphous silica, water sealing agwtts, vt:awt ' educing agents,. setting modifiers, bardeners, dispersants, foaming agents or florcidati ig agents; water-proofing agents and density mochl ers are suitable for use wib the present invention.
In this regard, one particular advantage arising from the present inventioxi i. the ability to treat the product to be coated by -providing :widshves `n the eoa +g. To explain, since the coating is dewateredbroui the product to be coated, it is possible to provide additives to the base layer by incorpora ion in the slurry. For irstarcceõ a water- uafgg ~igent.sleh:as silane maybe included ini;:the coatingin excess ofthe~
coating ay rs. requirements. Duringdewatering;, the s Zane will be drawn into ind.
2f; through the base layer being coated hereby treating tl w base-layer, Thb simultaaeous tecab ent of the base layer as well as coating the base layer is a valuable addib benefit w isingfrom the aibredescribed met bd.
Best: Mode tor ear Ing Out the-Invention The present invention: will now be described byway of exatnpie: only with 'reference. to the following a nbodimezts.
in eaeb of the following Wiles, the proel t was produces as fellows.
Step epara irA
A slurry of She. formulation is prepared bything the hydraulic binder:, :ly ash and other op tional corn onents with. water. Tie solids codtent in the sbitryis 30 preferably between 50 and 9tf%, more prefrxably 5:, to R
.aztcl.ntostpreferably 0 to Wt) 021070249 PCTIAUO7JO0242 Sty 2 t _I ap k*io ciOivateri, n ,e siDny is applied to the bast 1a by any cQrtveMent means such as brushes rollers, :fives or sprays. etc. In a particular embodiment the slurry is applied-:by, .Weans Of a: Knawn Zpparatus, and Method de$cribed in WO 2002/ 70145 and WO 20Q2iO7Q218, The slurry is preferably designed to self level and ford a uaai fc vi coat -ag on the prodmt. The h ding product to bo coated e ibits scextain degree of porosity causing the spry to c ewater and fom. a iinifartr deposited cemenhilioiis layer, Time for dewatering can vary quite drarnat cally'cut z3artrially door s, between 10 and 140 ?0scoxs #sdepeading.can the porosity- of the -a&atcxial to be coated, its water content anal, ttiic c ess and viscosity of the slurry formulatio ,. A vacuux rosy bee used to reduce the slurry dewatering dine if required. 'I his is particularly Yisefui when:
tailorin the ccatin recess to the speed of a building ct forn ing prrc~cessu g i? ~ ~ ~7du , ep betweeti 40 to 45 Winds an a Hatschek production line.
tt%3 tri AJ forinzing,_ the greet larsitiate article compris-rig the building product Iriu coating is preferably precured for a short time., eg up to 48 hours, then awed by a&moist curing at mom temperature, steam curing t hem 40 and OQOV or autoclaving in: a steairi press-me, vessel between 120 at 200 C.
For either of these three curing techniques, a ctni:ng t t nc:rauge between 0 and 72 :hours, preferably up to 48 bouis,:s suitable: Of co zrse, as will be clear to penxma skilled in the art, the length of time chos= for i uriragis dependent on the..foxrnulation, the manufacturing process and form of the article.
The following examples relate to speeibc forx* ulation connpos%tiofs.
Example.1, S*ndable O watered Slurry Composition.
?lmct ?a: sandal le, diuable Bois ing layer for facade applications.
The low vzscosit ,r slurry (drainage time in 5t), bi of itrxe ftinuel = 3.4 smoncdi ) was applied on the :base laver ((aidi`fortri "` 1.2 thick cell ode fibre reinforced:
cement based: gÃeern sheet uia +,ifactured bby Taies.Iiardie:lndustrics). The slurry dewatered in: ptl seconds (w.-aided t?y vacump) forming a.1..25 imn thick.
costing. The coated sheet was autoclave-cured for 8 h s at 180 ''C temperature and: 0.80 W
a pressure. It was then sanded flat to 0.60 mm thick using industrial sanders equipped with 100 grit sand paper belts.

WO 02i07 248 PCTIAC;0Z/I0.241 14) -.

Slurry % by tszfal Weight ingz CompwciYiQu -y gAt e~f E snftr~B , S}
Dewatered Cemetuttous Cpm , vsitiv n PorLami Cement 30 12000 Silica Flour (400 10 4000 de i Fly ash (larger size 40 ? 6000 fiat :on Fly asn (smaller size 20 8000 fracizvn T fal 100 14000.0 Water (W) 14001 Water!Solids (W:/S Ø3S
xatio Solids Coateut 0.74 /?#
organic Additives Welan Gum = 0.0075 3<0 (KE:icocrete naphthalene , 0 1fIG.t1' fotxnadebyde Pisstic isi Agent e yr Aexyhc Emulsion I,U 460.0 H.hopie~[tMM ts34 Exarnp)t 2: Rubberised Dewat+ere d Slurry camgusitio 1 nt tion: Finishing layeria skid-resistant flooring, bard wear ng static dissipative flooring and acoustic insulating ceiling panels.
The l o w v i s c o s i t y s l u i r y ( d r a i n a g e tine in: 5D vol. nie funnel `~ 4.2 : t2 rids) vv-,% applied on the base layer .-14 12 xnzsz thick volluloses fibre re nfbreed r-euc =based gem sheet raancf ctkre. by James Hardie J dustries): The3,sluir de watered in 60 sccctnds. (i;n-aided by vacuum) forcing a 1.25 m.W .thick coating. Ilia:
r iat:,d sheet ww; autociave-aired for 8 -his at 1813 "{õ 1 nperature and 0..80':+ a ssur ,. It wa,S then sanded flat to 0.60 r.= dick n. ing Indus a1 sanders egwpped with 100 gri sand paper belts.

'e:Y AY{axrr vaa WO 02,1070248 Cluny %~ by total Weight in gm.
Composition weight of solids Dewatered Cementiteus Composition Portland Cemout 30 12000 RecyeledRubbercrumbs 4000 ---(minus 30 mesh) Ply ash (larger size 40 16000 fi-Action) 11y ash (smaller size 1 20 8004 fraction i Total 100 40000 Wate 13000 Water/ Solids (WIS 0125 ratio) Solids Content 0.755 Organic Additives Welan Gum (V elcoc ete 0.0075. 3.0 104.E
naphthalene US
fnxnaldethyde }
Plasticising Agent (Neosyn') Acrylic Emulsion 1.0 400.0 Rhopfext MC!934 I

Example 3; :t`le rible &Saudable Dewatered Slurry Composition Function Flexible t sandable fit sizing layer on thin fibre cement reinforced .eiue :t-based lining.
The tour y-iscosit> sl,=y (drainege *.ime in50 volume :finÃ1= 2.8 seconds) Was applied on the vase layer (Nardi f'.e c'~" 4,5 nnn thick cellulose fibre, reinforced. a ent-based. green sheet manufactured by James Har i-c ledustries). `1hhe slurry de t red in 120 seconds (im-aided. by vacuum) (oaring a. I - ? 5 r=an thick coating. The coated sheet -was precured for 48 ho m. then was amoclave-cured for 8 his at 180 C: temve attire and 00.80 Mfa;pressu- e:. It was then sanded flat to 0.60 mm thick using industrial sanders egaipped with 100 pit sand per belts.

pO Elz1E- o', Tl I'MAU62 42442 -12.-Slurry % by total Weight in gm Compisition.
weight of eoli is , Dewatered. Cemeut ts Coosidoxt Portland Ccment 20 .8000 Calsiuu Carlaana 10 4000 Grade 10 (df)tm avg.
size i Alunxina Trl hydrate : 2000 8() um av, size .
.F1 ash (larger site 45 18CC51}
fraction} _. _ Fly 4b (mailer size = 20 8000 fraciion~ , Total 101) 40000 Water 1..2t7Eitl Water/ Solids (W/S 0.30 ratio) Solids Content 0.77 IW+S) Or&anic Additive Wela rk Gum (KelcocreteZ~) 01007.5 3.0 ba.b*,k~xlene ; C.2 1.00.0 fomWdehlyde Plasticising Agent (Neosyn , _ Styrene Acrylic tat= } 2.000 F.attnlszon b% solids}

I?;xarnple 4. Fler bl* & Sandaab)e Dewatered s itrry Composition (Low Content}
F-Ur ct. cln: . lexible & zanda}ble fit sting lay r o n thin ibm cement rwrAorped cerneut-base / lining.
The low viscosity slurry (drainage time in 50 i3 it voituue ninxiel $ 5 s nds) aped on the baw 1aye:
,vas (Harcifiex'" 4:5 nm Ncic r;eljt)yss fib= }rei.szfcireed cemczlt based greet shoe zxtaz~t 'ac: rl b 3arnes. and a 1ndnst ). 7`lxe= s ui Ey dawatered. in 90 seconds (un-aided by vacintrx:,) ft rming'a 1.25 mra thick coali)ig. T.
coated sheet was antpclave-cured for 8 ins at Igo C tenspexature and 0.80 i 4Pa ......... .... . .... .

W() 02i0702.4$'CIX~1Ox'f)f)Z

pressz;re. It was then sanded f tat to 0.60 mm thick using industrial sanders equipped with. 1 00 it .and paper belts.

luny % by Weight in gin Composition tote Weight of solids S.
1?ewatered ~C emexitatous Composition .
Poi land C'err ent 10 4000 Calcium Carb mate 20 8000 CTade 10 (40um. avg.
size!
Alumina Trl- ydrate 5 2000 80 uox av < sits Fly ash (larger size 40 18000 fractioi Fly ash (smaller size 25 10000 fraorz Total 100 - 40000 Water 116000 W=ater! Solids (W/S 0.40 'ratio}
Solids Content 0.715 EMS) {hc Additives Welan Gum (fie}cocrefe " 0.00.7.5 3,0 naphthalee .0-25 100.0 formaldehyde Plasticising Agent (Nrr Vinyl acetatee-ethylene ' 11.625 650 povt'4ered copolyncr S 'The. aforemerttiored examples provide a coated product comparable in workability to rnonoixtl o or single layer composite-s. They can be flexed, put, drilled.
or f -axed b y ails or the like to a frame without = -face c<rack_ing or cbippirtg.
The surface is `fish.-ready and: remains smooth, flat, crack-free and with to peimeabil ty even when used in a curved cou fi ation.
Each examples provided. excellent .t er bon4.betwee the baaa sheet and coating exhibitin good composite action, compatibility and resistance to dal iia!iorl:

It can be seen that the present process provides a significant improvement not only in the attributes of the product but also in the ability to tailor the surface finish of a building product to match particular requirements. Examples of particular formulations to provide the desired finish characteristic include a) Terrazzo (hardwearing decorative finish) - the finishing layer of the dewatered slurry can contain marble chips and pigmented cements and fillers.
It may then be sanded and polished to form a hardwearing decorative finish. Such a coating on, for example, a fibre cement backing board, could be used as flooring tiles, decorative wall lining or external prefinished fibre cement cladding.
b) Stucco (orange peel) Finish -this may be achieved by manipulating speed and volume of the applied slurry to achieve a stucco look on the finishing layer.
Once again, such a product may be used as an external pre-finished cement cladding.
c) Sandable finish - this is probably the simplest and most straightforward application of the coating technique to provide a coating layer which may be sanded and sealed, thereby providing a paint ready smooth, crack-free and low permeable surface. Such a product may be used for a variety of internal and external uses.
d) Flexible finish - the coating layer may include various fillers and other additives to improve its flexibility, eg ethylene vinyl acetate, styrene butadiene rubber, styrene acrylic. It is designed to be a sandable, workable ie by score and snap, nailable, crack-free, non-chipping, flexible and bendable, paint ready surface. Such a coating could normally be applied to reasonably thin building product to permit flexibility. It has a wide variety of uses but is particularly suitable as an internal lining in wet area applications or as an external cladding element, eg as a paint ready fibre cement siding.
e) Skim-coated finish - such a coating of the dewatered slurry maybe applied to gypsum based building products thereby providing a smooth, flat, pre-skim coated and paint ready surface.
f) Rubberised finish - by the addition of rubber crumbs into the slurry formulation, a coating layer may be provided on say a fibre cement backing for use as a skid resistant flooring, hardwearing static dissipative flooring or acoustic insulating ceiling panels.

It will be understood by persons skilled in the art that the present invention may be embodied in other forms without departing form the spirit or scope of the inventive idea as described herein. In particular, it will be appreciated that the formulations, coatings, additives, methods and composite products of the present invention are suitable or may be adapted for use in conjunction with the methods and apparatus as described in the various priority documents.

Claims

CLAIMS:

1. A method for coating a building product comprising providing a coating formulation including a hydraulic binder and a quantity of dewatering agent, producing a slurry of said formulation:, applying said slurry to the product to be coated and dewatering said slurry through said product, wherein the dewatering agent is fly ash.

2. A method according to claim 1, wherein the dewatering agent is provided in a sufficient quantity to maintain porosity in the slurry and the product to be coated during dewatering.

3. A method according to any one of claims 1 to 2, wherein the slurry has a water content of up to 50 wt%.

4. A method according to any one of claims 1 to 3, wherein, after dewatering, the coated product is cured by air curing steam curing or hydrothermally cured in an autoclave.

5. A method according to any one of claims 1 to 4, wherein the product to be coated is cemeutitious building board or product or gypsum building board.

6. A method according to any one of claims 1 to 5, wherein the coating includes fibres.

7. A method according to any one of claims 1 to 6, wherein the thickness of the coating layer on the product is between 0.1 and 10 mm.

8. A method according to any one of claims 1 to 7, further comprising sanding said coating wherein the thickness of the coating layer after a sanding is between 0,05 and 5 mm.

9. A method according to any one of claims 1 to 8, wherein the hydraulic binder used in the coating is selected from the group consisting of white, grey or pigmented cements, hydraulic limes and mixtures thereof.

10. A method according to any one of claims 1 to 9, wherein the hydraulic binder includes cement selected from the group consisting of Portland cement, blended cements, blast furnace slag, pozzalans, masonry cement; oil well cement, natural cement, alumina cement, expansive cements and mixtures thereof.

11. A method according to any one of claims 1 to 10, wherein the binder in the formulation is between 10 and 50 wt% based on total dry ingredients.

12. A method according to any one of claims 1 to 11, wherein the dewatering agent comprises:

i) 10 to 60 wt% of the formulation based on total dry ingredients of a first fly ash component having a particle diameter between 1 and 100 microns; and ii) 5 to 30 wt% of the formulation based on total dry ingredients of a second fly ash component having a maximum particle size diameter of 10 microns.

13. A method according to any one of claims 1 to 12, wherein the dewatering agent includes a coarse fraction fly ash having a particle size diameter greater than 100 microns.

14. A method according to any one of claims 1 to 13, wherein the coating formulation includes additives to improve resultant properties of the coating.

15. A method according to any one of claims 1 to 14, wherein the formulation includes additives to improve workability and applicability of the slurry to the product to be coated.

16. A method according to any one of claims 1 to 15, wherein the formulation includes, additives to improve the properties of the building product to be coated such that upon dewatering of the coating through the product, the building product is thus treated with said additive.

17. A method according to any one of claims 1 to 16, wherein dewatering occurs with or without vacuum assistance.

18. A formulation for use in coating a building product comprising a hydraulic binder and a quantity of dewatering agent sufficient to permit dewatering of a slurry produced from said formulation through the building product, wherein the dewatering agent is fly ash,

19. A formulation according to claim 18, wherein the dewatering agent is provided in a sufficient quantity to maintain porosity in the slurry and the product to be coated during dewatering.

20. A formulation according to claims 18 or 19, wherein the coating includes fibres.

21. A formulation according to any one of claims 18 to 20, wherein the hydraulic binder used in the coating is selected from the group consisting of white, grey or pigmented cements, hydraulic, limes and mixtures thereof,

22. A formulation according to any one of claims 18 to 21, wherein the hydraulic binder includes cement selected from the group consisting of Portland cement, blended cements, blast furnace slag, pozzalans, masonry cement, oil well cement; natural cement, alumina cement, expansive cements and mixtures thereof.

23. A formulation according to any one of claims l8 to 22, wherein the binder in the formulation is between 10 and 50 wt% based on total dry ingredients.

24. A formulation according to any one of claims 18 to 23, wherein the dewatering agent comprises:
i)10 to 60 wt% of the formulation based on total dry ingredients, of a first fly ash component having a particle diameter between 1 and 100 microns; and ii) 5 to 30wt% of the formulation based on total dry ingredients of a second:
fly ash component having a maximum particle size diameter of 10 microns.

25. A formulation according to any one of Claims 18 to 24, wherein. the dewatering agent includes a coarse fraction fly ash having a particle size diameter greater than 100 microns.

26. A formulation according to any one of claims 18 to 25, wherein the formulation includes additives to improve resultant properties of the coating.

27. A formulation according to any one of claims 18 to 26, wherein the formulation includes additives to improve workability and applicability of the slurry to the product to be coated.

28. A formulation according to any one of claims 18 to 27, wherein the formulation includes additives to improve the properties of the building product to be coated such that upon dewatering of the coating through the product, the building product is thus treated with said additive.

29. A dewaterable slurry for coating a building product, said slurry comprising water, a hydraulic binder and a quantity of dewatering agent sufficient to permit dewatering of said slurry through said building product, wherein the dewatering agent is fly ash.

30. A dewaterable slurry according to claim 29, wherein the dewatering agent is provided in a sufficient quantity to maintain porosity in the slurry and the product to be coated during dewatering.

31. A dewaterable slurry according to claims 29 or 30, wherein the slurry has a water content of up to 50 wt%.

32. A dewaterable slurry according to any one of claims 29 to 31, wherein the coating includes fibres.

33. A dewaterable slurry according to any one of claims 29 to 32, wherein the hydraulic binder used in the coating is selected from the group consisting of white, grey or pigmented cements, hydraulic limes and mixtures thereof.

34. A dewaterable slurry according to any one of claims 29 to 33, wherein the hydraulic binder includes cement selected from the group consisting of Portland cement, blended cements, blast furnace slag, pozzalans, masonry cement, oil well cement, natural cement, alumina cement, expansive cements and mixtures thereof.

35. A dewaterable slurry according to any one of claims 29 to 34, wherein the binder in the formulation is between 10 and 50 wt% based on total dry ingredients.

36. A dewaterable slurry according to any one of claims 29 to 35, wherein the dewatering agent comprises:
i) 10 to 60 wt% of the formulation based on total dry ingredients of a first fly ash component having a particle diameter between 1 and 100 microns; and ii) 5 to 30 wt% of the formulation based on total dry ingredients of a second fly ash component having a maximum particle size diameter of 10 microns.

37. A dewaterable slurry according to any one of claims 29 to 36, wherein the dewatering agent includes a coarse fraction fly ash having a particle size diameter greater than 100 microns.

38. A dewaterable slurry according to any one of claims 29 to 37, wherein the formulation includes additives to improve resultant properties of the coating.

39. A dewaterable slurry according to any one of claims 29 to 38, wherein the formulation includes additives to improve workability and applicability of the slurry to the product to be coated.

40. A dewaterable slurry according to any one of claims 29 to 39, wherein the formulation includes additives to improve the properties of the building product to be coated.
such that upon dewatering of the coating through the product, the building, product is thus treated with said additive.

41. A detwaterable slurry according to any one of claims 29 to 40, wherein the slurry is self levelling.

42. A dewaterable slurry according to any one of claim 29 to 41, wherein the resultant, dewatered slurry is curable by air curing, steam curing or hydrothermal curing in an autoclave.

43. A detwaterable slurry according, to any one of claims 29 to 42, wherein the slurry may be applied to the product to be coated by splattering.

44. A method of improving a hydraulic binder based coating formulation for coating a building product comprising adding to said binder a quantity of dewatering agent such that after application of a slurry of said formulation to said building product, said slurry can be dewatered through the building product, wherein the dewatering agent is fly ash.

45. A method according to claim 44, wherein the dewatering agent is provided in a sufficient quantity to maintain porosity in the slurry and the product to be coated during dewatering.

46. A method according to claims 44 or 45, wherein the slurry has a water content of up to 50 wt%.

47. A method according to any one of claims 44 to 46, wherein the coating includes fibres.

48. A method according to any one of claims 44 to 47, wherein the hydraulic binder used in the coating is selected from the group consisting of white, grey or pigmented cements, hydraulic limes and mixtures thereof.

49. A method according to any one of claims 44 to 48, wherein the hydraulic binder includes cement selected from the group consisting of Portland cement, blended cements;
blast furnace slag, pozzalans, masonry cement, oil well cement, natural cement, alumina cement, expansive cements and mixtures thereof.

50. A method according to any one of claims 44 to 49, wherein the binder in the formulation is between 10 and 50 wt% based on total dry ingredients.

51. A method according to any one of claims 44 to 50, wherein the dewatering agent comprises:
i) 10 to 60 wt% of the formulation based on total dry ingredients of a first fly ash component having a particle diameter between 1 and 100 microns; and ii) 5 to 30 wt% of the formulation based on total dry ingredients of a second fly ash component having a maximum particle size diameter of 10 microns.

52. A method according to any one of claims 44 to 51 wherein the dewatering agent includes a coarse fraction fly ash having a particle size diameter greater than 100 microns.

53. A method according to any one of claims 44 to 52, wherein the formulation includes additives to improve resultant properties of the coating.

54. A method according to any one of claims 44 to 53, wherein the formulation includes additives to improve workability and applicability of the slurry to the product to be coated.

55. A method according to any one of claims 44 to 54, wherein the formulation includes additives to improve the properties of the building product to be coated such that upon dewatering of the coating through the product, the building product is thus treated with said additive.