Fireproof potassium silicate coating composition, insoluble in water after applicatio

Schutt, J. B.

Stuart, J. W.

English

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It is a further object to provide such a compts i i r c~  
3,493,401 which will retain conventional pigments, exhabit sl-snJ.i,nrlba 
FIRE RESISTANT COATIhiG COMPOSITION flaking and be abrasion resistant. 
Jolipl PI. Schuff and John W. Stuart, Silver Spring, Md., It is still a further object of this invenat13n to provide 5 
assignors to the United States of America as represented 
bJ Administrator of the National Aeronautics and fireproof inorganic coating whicTl is cmwosca of a 
Space Administration minimal number of components which nteracyo c-o- 
ho Drawing. Filed Nov. 28, 1967, Ser. No. 686,296, duce the desired effects. 
Int. CI. C09d 5/18, 5/00 These and other objects will become apparent i ~ c ~ -  
U.S. C1. 106-15 9 Claims the following detailed description, examples and d z r ~ r s  
It has been discovered that a co~~?posh'tiopp. c o n f a ~ n ~ ~ r g  a 
combination of potassium oxide and silicon dioxide ;-? 
ABSTRACT O F  T H E  DISCLOSURE mol ratios of (Si02/K20)  of 4.8-5 3 togethea kith Gbrr uc 
Fire resistant coating compositions which, when dried, calcium silicate (wollastonmite) as a crack and craze sup- 
are flake, crack, craze and abrasion resistant and of pressant and silica insolubilizer and cerrc o-rlde, altp: 
reatly reduced leachability. comprising a 15 trialkoxy silane, the alkyl and alkoxy grc~ups tax  la: QEJ 
of potassium silicate solution a silicon dioxide to to  8 carbon atoms and mixtures thereof as -:hy i n =  3~ 
potasslum oxide mol ratlo of about to 3, ceric oxide suppressants provide the desired affects. Prcf~iably t.2 
and,or an trialhoxy silane as rehydration composition includes talc andlor  kaolinite fa es,wn,e 
sants, and wollastonlte as a film builder, said composition crack and craze suppression. T o  this basec c.smpucr1ro-n 
be,ng with selected conventional pigments 20 may be added conventional pig~ients,  f~llsrs p-oper~ 
and fillers. enhancers and of course the carrner rnab2i:ai geser-1'1 
water. 
The combination of potassium oxide ulth s-lrza, L e 
The invention herein described was made by employees potassium silicate, has been used extensnvely up. jaerganrc 
of the United States Government and may be mnnufac- 26 coatings. However, such compositions have beeq Znm~tc~ 
tured and wed by or for the Government for  govern- to standard commercial ratios of sallca to potasslur13 oxA.iit. 
mental purposes without the payment of any royalties the maximum of such ratio on a mol basrs being 3 9. 6, 
thereon or  therefor. so doing, an  excess of fully hydrated w'lca #as nelre- 
SUMMARY O F  DISCLOSURE present to any substantial degree. Dy euirnfnateng u.l-*hjaa- 30 ized bare by raising the SiOz t o  K20 ratio sclcsst-r?tra'S:: 
p hi^ invention relates to coating compositions, and above 3 9, it has been found that. not only ~c L I L  c s i ~ c r  
more particularly to combinations of inorganic materials dispersion effect obtained, which made the 393~a;s, 
for such compositions which are both fireproof and in- silicate necessary in !he first place but a coa"ng of d r  
soluble after application, Specifically, this in- minished !eachability is prov~ded cEue to the ~n te rac t~an  defines a unique combinatlon of potassium slli- 35 of the excess SiIicic acid anIons wEih the otbe , e - ~o~t.1- 
cate ulth other matenals to produce a superior coatlng tlon as described 
for space vehicles and the like. The rehydration suppressant noted atlove iczcts ,. 
follows after the coating has been applicd I f ,  ic , 
DISCLOSURE ceric oxide is the additwe, it reacts with the eTcess ~ 1 1 c a  
40 and/or potasslum (produced from silica bcndta g) c pi? 
  he de%elopment of inorgamc coating materials for  duce hydrates which, although soIu7le in fhc sob 
fire protect~on and the llhe has recently become a malor tion, form upon drying the insoEubHe cnmpourc ,e-e I- 
effoit of man1 researches. partlc~llarly those provldlng potassium srlicate due to the loss of wate- on ~ y d - a f ~ o -  paints and other surface finlshes for space vehicles. These However. this drying rekclion i s  revelcrdic, c7c 
efioits have been accelerated since the Apollo Proglam 45 the drying has occurred, the coatif g is s u b $  .eh;a I j r  rfi- 
traged), the seberlty of which resulted to some degree soluble. The i~llnimal leaching of d 3 i i l E  avajhbte q#21ubi:: 
from the u5e of non-fireproof coating materials wl th~n potassium slllca:e is of  no substantial col?scqrBenctl, frr 
the s p d ~ e  caprule. 7 h e  research nlth Inorganic, hasically the cerium zilicate maintains the coating f i e  a~1dkt~o.r 0" 
fireproof mdter~als has produced a munber of quite use- alkyl alhoxy silane ~ u c h  as methy1trinzet~~nxyci~3ne a?cs 
ful comPosltlon% many of which have already found aP- 60 tends to diminish leaching of the coiiting acter catic.n 
pllcdtlon in spaLC ds well as other fields where fireproof- and drying. Here the silane provides sl~e.: lol. ~itacpmcs-: 
lng 1s so essential. These ComPo~ltlOns have combined of silrcic acid groups, the s1Iane being n o ~ - ~ \ i a t z r  scir~blc 
lnorganlc materials in various ProPortlons to Pro- due to the methyl groups, serving to bind any water solu- 
duce the deslred effects, but t o  the present no completely ble groups thereto. the combination thereor , Ico bcinr 
satlsfactorp coating material has been forthcoming. This 55 water insoluble. nus, leaching of the coatanS 
1s pr~nc~pal ly  due to the mult~pl~city of properties neces- plication and drying IS suppressed. 
sary for such a coating and the d~fficulty of finding fire- Although this concept appears to solve the p cbIem DL' 
  roof lnorganlc rnatenals nhich, when combined, will making the coating resistant to water, abrasion$ and of 
produce such properties. Such ProPertles include, inter course fire, it does not alleviate the cracknng Err craz1i-g 
aha. qulch air drying, crack and craze reststance, sub- 00 so prevalent in inorganic coatings. To this end r t  rias beerA 
stantial water ~nsolub~lity when drled, abil~ty to retaln discovered that the mineral wollastonite (fibrous s a i c i l , ~  
plgment. mlnimal flaking. abrasion reslstance. and of silicate) may he added and a procfuct outa,ii,o; i. ilaci 
course fire reslstance. Many inorganic materlals possess aftei drying. IS not only crack and craze resxsrant bur alsc 
one or more of these properties and attempts have been water insoluble. Wollastonite appears In the f o m  of 
made t o  comblne them kith other materlals to produce fi.5 rod-like structures which Ferve as a blnder txtmieei? the 
the desrred effects. but even with such multl-component silicate compounds drscusted above. Allhaugh no corn 
cornple~ cornPosillon\, '111 of the above defined dc\itlera- plete evalr~ation has heen conduci:d to deeermlpe t h e  
trim h.~vc not heen mct exact mechanimz which provide the high ci-gtee: of crack 
*I hcrcforc. i t  1s ,in object of thc prcwnt invcnlron to and c r ~ e  rcs~stance obtained thrcmi:h the iiic or vvolla*s- 
p ~ o \ l r l c  ,in Inotg'tnlc fireproof composltlon whlch will be 70 tonrte, ~t may he hypothewed th ,~ t .  the tony raS-Elkc 
( 4 1 1 i ~ k  cltying in , , i t ,  cr'tck .tnd c~ . t f c  ~c\ i \ lant  and sub- strliclrires containing branching silic,~te g r o u p  form ready 
sc,int~:~lly wake1 ~nsoluhlc when d~tccl. vtcs for attachment of the avarlable an1014 i;i. 5olutnoa- 
3,493,401 
3 4 
n I o o n  z r v e  to f o ~ m  a chcmical ionic bond EXAJII'LE IV 
i x i w e e n  all of the composition components. This bond- 
ing within t h e  intertwined and overlapping fiber structures lllgra,li,,,lt 
I'arts h y  Ferctint b y  
weight wv~ght 
of wolias!onitc serve to hold cach of the multiplicity of 
.............. conjponents in place afler drying hits occurred. I'ota~siuni Silict~t~t (23 K 5.1). lilr) 66.0 5 Wollastonito (CuSioJ. ..................... 16 10. ii 
To this iiasic cornpo\ition. it is preferred to add a supple- #;~olinitn .................................. Y 6. r) 
i i icnii l i  bi:3ilcr-fjjlcr from kaolinite, talc, and St~:'inI~ss S t t : ~ !  Hakrs ...................... 20 L: 3 
M~.thyl Tri1nt:thosy Siluilc idiiuttai.. ....... 4 -. 5 
hinations ihei-cof. These are most desirable where fast ,I':I!~ ........................................ 2. j 1. i 
Furnace drying is utilized o r  the composition is to be 151. 5 1 ~ ) .  0 
applied lo structures subjected to high temperatures, 
the  talc and  kaolinite strving to further suppress any 
cracking or crazing of the coating. 
T h e  a,.liiition of suppleniental complemental com- ESA31PLE: V 
ronents to the hasic composition may be effected by Pnrts h y  ~ c r c e t ~ t  h y  
simple addition thereof during solution blending. Such l"gredie"t wright woight 
adititlves include standard pigments and fillers as well P o t ~ s i u r n S i l i c a t o ( 2 ~ 3 K 5  .3) ............... 100 74.8 
.is compounds having unique enchancement effects to the ~~~$$~~~~(.c~s.lI~~I'I:::::::::::::::::::: 16 '3 12.0 6 5
......... above noted critical components. Typical fillers include hletliyl Trimc-thoxy Silano (dilute) 4 3.0 
ciay-iike materials, jnetals including zinc dust, Talc........................................ 5 3.8 
stainless steel flakes, etc. Pigments such as  the oxides of 20 134 100.1 
titanium, iron, cop.;e:r, chromium and manganese as  well 
;;:j cadn?ii:m siiifid~ or carbon black may be used. while 
organic d:,.es are also contemplated, but not preferred due 
!:i their low decomposition temperature. 
Having dcsci-ibed the components of the invention. fol- 25 The blending of each of these examples was identical, 
iowi rp  is a generic table as well as specific examples of  each of the components being mixed into the silicate 
ihe practice thereof: solution with continuous stirring. Where no water was 
added. the potassium silicate initial solution was SUE- 
Relative parts ficientfy fluid to allow complete mixing. Before surface 
Ingredieni-- percent by weight 30 application, the compositions were shaken for two min- 
Pot;r:3sisim silicate sol. 10-24 1 K 4.8-5.3 2 -- 36-80 utes to provide complete homogeneity. 
i'eric oxide -__-_-__--_--_------------- 30 10 'The surfaces to which the composi~ions are applied may 
Metby] lrjmcthoxy silane -__--_------_--- 3 (1-2.6 be metal such as steel o r  aluminum o r  plastic. The surfaces 
Woll:i\toni~c - _ _ _ _ _ _ _ _ _ _ _ - - _ _ - _ - - - _ - - - _ -  5-15 may be pretreated as proposed in the commonly assigned 
'8';nlc 0-10 35 co-pending application of John B. Schutt and Charles M.  
Kaoii.iile ___-__-__- - - - - -_ - -_-_- - - - -__-  0-7.5 Shai, Ser. No. 452,945, filed May 3, 1965, entitled Alltali 
99jgrnt.nes and filEers - -_ -_____- - -_ - -_ - - - -  0 60 Metal Silicate Protective Coatings, now issued as  Parent 
Wate: -___-___--_-_------------------- 0-10 NO. 3,454,410 on July 8, 1969. 
The compositions of the examples were applied to pre- 
1 !>(~Y~.P:I, . O I ~ ~ ! C  i n  \s:ttt?s SOIV. 40 cleaned aluminum substrates by conventional spray appli- 
! r , ~ r i t >  <itb2'1<~O. 
'I ,., <  1 ,,b:\.i .,i:i. I)I .PsPllt  in n lnn , ln ts  ,,f Ionst 1 p,rt I,>. cation. After quick air drying, the c0mpositiop.s were 
s t  t i ~ t . i i  iii:lriiiiulii parts by ~ \ . e i g l ~ t  c o ~ ~ ~ b i l ~ n t j ~ n  : 10. tested by water washing and air aging. Both before and 
after washing and aging, the surfaces were smooth, non- 
Specific examples kvithin this range are: flaking and substantially crack and ct-aze free. They were 
43 completely fire resistant and substantially abrasion re- 
ES.~\IPI,E : s~stant.  
Part I ,v  
Whereas the primary use of the instant invention is for  
1; ~:r,.,j'. ! l t  \r .r i~ht w ~ i c l ~ t  the interior of space capsules and the !ike. it may also 
-- 
Potnssi:lm P,!~c.?ti; (13 I; 5.1). .............. 100 , find application as a general purpose fire-proof coating. 
....................... ~ ' , .K !C  o\i~i+. I C V O . . ~  2 1.5 Although the foregoing disclosure relates to  preferred 
l.Yol',uslo~n!~ (t:i.S;O:) ...................... 
" - 
16 
h.:oiinirr.. ................................. 9 embodiments of  the invention. it is obvious that numerous 6. 8 
Wiitvr ....................................... 5 3.9 modifications and alterations may be made without de- 
133 , , parting from the spirit and scope of the invention set forth 
-. in the zppended claims. 
- - ,, What is claimed is: 
ESI3IP1,E IT 1. An non-flaking. crack, craze and fire resistant coating 
composition consisting essentially of from 36-80 parts by 
Ii.t!ri41(.~tt I':rrtst)? Pcrrrnt I)? weight of potassium silicate-water soli~tion containing 10- ~vr.r.18l1t w'i.i!!lit 24 percent soli~ls having a Si02/K20 mol ratio of about 
J'o:,i<iitini ?..lir:t!+ l?? !i 5 , )  1. ............. 1 (X) 
C i . 0 ~  :Ci.rli. O x i ~ i c r  ......................... 2 : j t ; . :  6(, 4.8-5.3; a leach retardant of from 1-10 parts by weight 
W C , ~ ~ L ~ I O I I I ~ ~  1(7:i;1(~jj. ..................... 16 n::l selected from the group consisting of ceric oxide and 
K:iolinili.. ................................. J 
IVater ...................................... 5 
3 . 3  alkq.1 trialkoxy silane, the alkyl and alkoxy groups having 
I. 8 
% i r . .  ....................................... 140 51.5 up to 8 carbon atoms, and mixtures thereof; and 5-15 
272 parts by weight of fibrous calcium silicate wollastonite as 
-- 6j a crack and craze resistor. 
2. The coating composition according to claim 1, 
wherein the leach retardant is ceric oxide. 
E S A I I P L E  111 3. The composition of claim 1, which also includes as  
P a r t s l ) ~  Percrnt h v  high temperature crack and craze resistors of up to  10 I!?prctlit~lit ~ v e i ~ h t  v.eiaht parts by weight of talc, kaolinite and compositions thereof. 
l'ornrsiuni Siiic:ili' (23 Ii 5 .3)  ............... 50 75. R 
Ceric O-;i(i~> (C1.02) 4. The composition of claim 1, which additionally con- ......................... 1 1. li 
~l+'oilnsto:iirc (C:ISJO~)-  ......... ... ...... H 2 ,  tains a pigment selected from the group consisting of 
- - 
............................... haoiiiiirt,. 4. s 7 . 1  titanium oxide, iron oxitie, copper oxide, chromittm oxide, 
-- -- -- 
03. ,5 lmt. I manganese oxide, cadmium sulfide and carbon black of 
75 up to 60 parts by weight. 
3,493,401 
5 6 
5. The composition of claim 1, which additionally in- References Cited 
cludes a filler selected from the group consisting of zinc 
dust and stainless steel flakes of up to 60 parts by weight. 
UNITED STATES PAlrEWTS 
6 .  The composition of  claim 5, wherein the filler is 3,364,065 1/1968 Cutright ---------- 117----I35 1 
steel flakes. 3,389,002 6/1968 Huffcut ------------- I%--84 
7. The composition of  claim 1. wherein the alkyl alkoxy 3,416,939 12/1968 Schutt et  al. --------.  106-8d 
silane is methyl trimethoxy silane. 3,423,229 1/1969 ECompanek et al. --- 106-84 XR 
8. The composition of claim 1, wherein the potassium 
silicate has S i02 /K20  ratio of 5.1 and is present in an JULIUS FROME, Primary Examiner 
amount of  100 parts by weight on the basis of 23% LORENZO B. Assistant Examiner 
solids. the leach retardant is ceric oxide present in an 
amount of 2 parts by weight and the wollasionite content 
is I 6  parts by weight. U.S. en. X.R. 
9. The composition of claim 8 additionally contains up 106-1, 84; 117--135.1, 137; 252-8.1 
to 4 parts by weight methyl trimethoxy silane. 15 


Fire resistant coating composition Patent

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