[1]United States Patent - Office 3@ I9@89656 3,198,656 COLOR, COATED CELLULAR INO-@RGAr,4iC AGGF,EGATE F-ichard D. Narlan, San Clemente, Calif., qssignor to CO@o.-!4te Co-.npany, a p@-rfnersh-p o-I CaEfornia No Drawin-.. FBed Nov. 19, 1962, Ser. No. 238,796 I Claim. (Cf. 117-100) This invention pertains to color coated, bloated aggregate. The term "b'loated" aggre.-al,e is now commonly employed to designate a type of light weight cellular product produced from various clays and related compostions having "bloating" characteristics. In the maiufaclure of thi:s type of product the ranv material used is forined into rela' ively small p--Ilets or balls, and these pellets or balls are heated u-iider controlled conditions so as to cause a vitrication of their outer surfaces I and the liberation of vo'latile materials after surface vibration takes place wlile the intemal structure of the pellets is flexible. These cOnditions result in internal expansion or "bloatin.-" of 'Lhe pellets. The bloated product restiltin.- from this heatin@ can be used as a.-gre-,ate in concrete when cooled. T.Iiis type of process is described in the Bureau of Mines Report of Investigations R.I. 4401 dated November, 1948, as well as in a great deal of other L@terature. Although there are a great many theories as to what causes the bloating process in various clays and shales, the mechanism of this process is at this time essentially unknown. Very little is also known about the physical and chemical structure of the internal and surface cell walls within bloated aggregate. It is believed that these cell walls have, substantially the same chemical composition as the raw material from which they are created, but that th.-y differ from such raw materials as to the manner in which the various oxides Nvithin them are oriented with respect to one another. It is also bel-eved that sil-ch cell walls differ fror@i conventional ceramic a-ticies produced from the same raw materials in the same manner and that the surfaces of such bloated particles are of a semi or partially vitrified character. Because of these factors, a bioated a.-.-re@-ate cantiot be considered in the saire category as a convent:ional claytype ceramic. Hence, the various techniques and the like which are normally expected to apply to the treatment or processing of clay-type ceramics cannot be expected to be operelive with bloated aggre-,ate. This is particularly the case when such aggregate as produced has a relatively smooth, glazed type of surface coatin,@ whien makes it impenetrable bysignifi-@ant amounts of water. It is, however, true with a po.-ous type of bloated aggregate capable of absorbing sufficient moisture so as to.have a density greater than that of water. The present invent;on can be summarized as being based upon the discovery that conventional bloated aggregate can be processed so as to have a color coating virtually any color or shade or hue, enabeng th-.s ag.@re.oate to be employed for other purposes than those pti-poses or which it has been previously used. The preser@t invention is also based upon the discovery that certain essenlially conventional techniques in the field of ceramic glazing can be modiiied se.-htly so as to be used as hereinafter explained in order to produce a slbstantially uniformly coated type of aggre.-ate particle. Depending upon variations in these techniques so as to use inorganic oxides of dif.Ferent colors, color coated aggregates of a bloated type can be produced in accordance with this invention. These aggregates are intended to be used in various fields where colored rock or aggregate is desired for asthetic or similar reasons. At the present time, certa;n Pa@Ler.ted Aug. 3, 1965 2 types of roo@'s are covered with colored rocks. These rocks are relatively heavy. Because of this, they are relatiiely ex,,)e--isi-ve to ship. They are also undesirable since they increase the weight load upon a roof to an Lindesired exlent, necessitating "hea-,,ier" or better des-igned roofs than are des;red for economic reasons. S-'@iaiilarly colored rocl-,s are us--d for decorative effects in aquariums, mosaics and the like. In all of these cases the weiglit of these roc,,,s is econon-iically detrimental to their use. 10 A coated, bloated aggregate of the present invention is produced startin-. Nvith conventio-.ial bloated aggregate particles as the raw material. Suea particles are considered to cons-st prim-arily of complex aluminum silicates containin,- minor amounts of other oxides such as iron 15 or titan:Um in cliemical combination with th@-se alliminiam sihcates. These particles normally have a vitrification temperature of betwe--n 1800' F and 2000' F. Although the color of these bloat.-d aggregates may vary sorlewhat depending upon the amounl and type of minor 20 quantities of impurities within them in general they may all be referred to as having an "earthy" or "clayish", type o.f appearance. IL is preferred to util@ize with the present invention particles ol' bloated aggregate which as produced have a rela25 tively smooth glazed type of sirface coating or appearance so as to avoid any tendency for internal coloring within the aggregate particles. The process of creating colored, coated aggregate herein expla-ined can, however, be used with what is comw@only referred to as porous 30 bloated ag.aregate. This latter type of a.-gregate tends to have an irregular aigular surface appearance. The size of the particles of bloated aggregate which are used willh the present invertion may be varied over substaiitially very ivide limils. In general, tl-@e siz-. of these 35 pe,,rticies is determined by the ul'Li-nate use to which they will be placed. Thus, for example, colored aggregate of this i-nvention -,vhich will be used for roofing purposes should be sufficiently large .o as to eff-ectivej'.y preclude - wind blowing it from its ultimate locati6n, while coated 40 a.ugr.-gite particles of this invention designed fordecorative effects ii-i patios and the like may b-- sufficiently small to provide a surface covering of a relatively smooth category. In all cases, however, such a@.-gregate particles should be stifficiently large so that thp-y can be easily dis45 cerned by the eye. In accordance with tlus invention, the bloated aggregate particles used as a raw material are coated with a ceramic type of overglaze comdosition containin@, various fluxes, binders and coloring age@it or agents dispersed within a-Ti 50 appropriate liquid vehicle of which water is the most cotiveniently used. This glazing compositioii is preferably proportioned in accordance with known practice so as to have a softenin.- point or point at which it, after removal of the vehicle, will become tacky and tend to flow below 55 th-- temperature at which the bloated aggregate will terid to be affected by heat. In general, the lower the temperature at which at the glaze composition Nvill t-,nd to become soft and tacky the betler, since there is less danger of the bloc'ted aggregate used with it bein,@ si.,,bjected to thermal 60 shock during processing. Such shock will tend to break up the particles of this aggregate. Presently prefered results have been achieved using glaze compositions which :adhere @to cerariie bbdies at a temp--ratdr,-- correspoliding to the softenin.- point of Se,@er Cone 017. Such a cone 65 will deform at about 1328' F. if heated at the rate of 68' F. per hour at about 1418' F. if heated at the rate ol- 302' F. per hour. A glaze, composition to be useable wilh this invention should, of course,-be finely ground so that the vanous ox70 ides within it are Liniformly dispersed. Preferably all particles of such a composition should at least pass a stand-
[2]3 ard Tyler 200 riesh scr,-,-n, and preferably should pass a 325 n-@esh screen ol' this type. In -encral, such a composition should have a viscosity rou.-hly correspondin.a to the viscosity of conventional paint so that it can be easily handled and applied to tlie surface of coated a@gregate 5 particles. Such application may be accomplished in a number of differeiit ways. The glaze composition may be poured over the a.-gregate particles as these particles are b-.ing stirred, and the stirring can be continued until such time 10 as all of the particles are coated to a substantially uniform extent. It is also possible to accomplish such coatih-0 by placin.- a quantity, of the glaze composition with a qtiantity of ag.-regate particl,-s in a shaker or sim;lar vibrating device which will caiise the particles o'l ag,regate ;5 to roll and otherwise rnove in contact with one another in the glaze until these particles are uniformly coated with the glaze coriiposition. Such coatin.@ can also be accorr@ plished by tumbhng the a-gregate particles in an appropiiate tumblin.- drum together with a quantity of the glaz.. go All of these m.-thods provide substantia'lly uniformly coated aggre,@ate particles. The amount of glaze composition used in producing this intermediate product should be just sufficient to substantiauy cover all of the surfaces of the aggregate particles being coated. If a de'-)5 ficiency in 'Lhe amount of -laze composition is present, th-- final coated, bloated aggregate particles produced in aecordance with tl-tis invention will not hqve a desired uniform color. An excess of -laze co@nposition of a quantity sufficient to create processing difficulties -,vill not ad3( her-- to the particles of ag-regate under normal conditions. One of the surprising aspects of the present invention lies in the fact that bloated ag,@regate particles coated as described in the preceding can be satisfactorily handled to a nominal extent after they are coated without the coating rubbin-. off, and that tley can be heated so as to cause the glaze coriposition used to form a firm adherent I coating without the individual particles stiel@,ing to one ano other to any significant extent. Thus, in practicin.- the 4@ present invention, so-called "blotches" or "pull-outs" encountered in conventional ceramic practice where an object is in contact with a surface being glazed are not of importance since to all practical extents they are not encountered. 45 In accordance with this invention, the bloated aggregate particles coated with a glaze composition or binder are heated to a temperaure sufficie.,it to volatitize the vehicle used in the glaze ccmposition and to cause the oxides within this coriposit;on to soften to a point where fusion 50 tends to occur. In effect, such fusion bonds the individual particles of the glaze to one another and to what is considered to be the very peculiar complex inorganic structure of the surface of the aggregate. This heat;ng preferably is carried out at a tei-nperatur-- below 1800' F.; the lowest point at which any ch-,in,-e or alteration o'l the surface of 55 a bloated ag-,regate particle can be expected to take place. This results in the final product which may be air cooled. The reactions during this heatiii.- are o'l a time-temperature character. L-1 general, temperatures between th temperature at which the glaze inixture tends to soften ani@ 60 temperatures at which any change in the aggregate per se are encountered can be used. As indicated in the preceding, presently prefered results are achieved within the range of temperature ran,@e of 1328' F. to 1418' F. 65 at Nvhich the Se.-er Pyrometric Cone 017 tends to softeii. If lower temperatures of from 1238' F. to 1328' F. within the softening range of Seger Co-iie 018 are used the glaze composition tends to powder on the particles employed. Temperatures in excess of 1418' F. tend to cause 70 the glaze composition on the particle to stick, holdin.- the particles together to a slight extent, and, hence, should be avoided in creating coated, bloated a.@.@regate particles in accordance with tMs invention. The heating step emp'loyed in order to cr--ate the final 75 product of this invention c,,in be carried out with theintermediate coated a.-gre-,ate particles restin.@ upon a suitable support, or in rotanj kilns or with various other similar nieces of equipment. Although it is not consi4lered absol@utely necessary it ;s cor@s@dered preferable that such equipment be constructed so as to provide for relatively slow cooling o'L the final coated a@-gre@-ate particles in order to minimize any possible or potential problem of thermal shock cracking the aggregate, Coat@d, blooted aggregate formed as indicated in the preceding discuss;on ir@ay be shipped without any dan@-er ol'L piysical damage so long as normal handlin@- procedures are observed. This aggregate can also be used in a variety o@P differ--nt @vays for decorative or other purposes. It will be realized from the foregoing that it may be manufactured at a comparatively nominal cost. As an aid to understanding the following specific exampl@-s are given of the procedure in formin.- colored, bloated a-@-gre--.ate of th.- present inven'lion., It is to be understood that these examples are given for explanatory purposes only, and are not to be considered as linliting this invention in any resr)ect. Exa7?7ple 1 Bloated a-gregite particles ran.,in.@ froni about one inch. to about'two inches in diameter and havin- a vitrified surfac-- appearance and the follonvin@ chemical composition expressed as percent by wei,-bt: SiO2 54%; A1203 16%; -U-e2O3 6.5%; CaO 4%; MgO 3%; Na2O and K20 3%; and TiO2 1% were coat,-d in a tumbling drum with an over.-laze composition havin- the following inoredients: 60 @rams frit No. 33 (havin,@ the followin.@ composition by weight 6.46% NapO; 59.17% PbO; 14.53% B203 and 19-84% SiO2), 30 grams Kentucky No. 4 clay (containing 51.65% SiO2 by weight), and 21/2 -rams of COC03 and suffic-ient watet so that the glaze composition had substantially the viscosity of a conventional paint. The particles ii the glaze were sufficiently small so as to all pass a standard 325 m,-sh Tyler screen. After the ag@regate particles were completely coated, they were then ' placed against one another upon an inert support and heated in a tunnel kiln at the rate of about 302' F. per hour until a temperature of about 1418' F. was achieved. The particles were then removed from the kiln and allowed to cool in air. The particles obtained in this manner were coated a uniform light blue color. They did not stick to one another as a result of contact with one another d@,iring the heatin.- step, and in each case the color on the surface appeared to b.- fus,-d in place and was unif orri. Exa7nple 2 The procedure set forth in the preceding example was tis,-d in creatin.- dark bltie particles by varyin.- the precedin.- examd!e so as to use 6 @rams by wei@ t Of COC03 @h i-istead of 21/2 @rams COC03- In this case the aggregate particles produc@ed were coated a dark blue. Exarr7ple 3 Green coated aggregate particles were produced using the procedure set forth in Example I by varyin- the glaze composition so as to us,. 5 @rams of Cr2O3 inst@ead of the CO'-03 sp,-cified. Eraniple 4 Bloated ag-,re,@ate particles ran,-ing from about on-mesh standard Tyler scre@.-n size up to about 50 mesh standard Tyler screen size in dimension havid.@ a vitrified surface appearance and having the same chemical composition as the aggregate particles specified in Example 1 were coated by being placed on a vibratin.- tray with an overglaze composition havin- the following ingredients: 60 grams frit No. 33 (as s'pecified in Example 1); 15 grams Kentucky No. 4 clay (containin.- 51.6% SiO2 by wei,-ht) 10 grims of a chrome tin red ceramic color as specified in the test "Parnielle,. Ceramic Glazes," Industrial Publications, Incorporated, Chicago 3, Illinois (1948),
[3]5 and sufficient water so that the glaze coatin.- had substantially the viscosity of a conventional wall paint. After the a,-Qre-ate pa.-ticles were completely coated they were placed a,-ainst one another in a pile upo@-1 an inert support and heated in a tunnel kiln at the rate of 68' F. per hour until the temperature of the particles was approxima'cely 1328' F. The partiel-,s N@iere then remov.-d from the ki'n and cooled in air. Tl-,e particles obtained in this manner were coated a uniform red color. They did not stick to one another as a result of contact with one another during the heatin.- step and in each case the color on the surface of the particles was uniform and appeared to be fused in place. Example 5 Black coated aggre.-ate particles were produced usin.a the procedure set forth in Example 4 by varyiii.- the glaze composition so as tD omit the chrome tin red color and so as to substitute for it the same Nvei.-ht of a black inorganic mixture havin,- the following composit;on: cobalt oxid,- 19.0% by weight; chrome oxide 18.0%;.ferric oxide 36.5%; man.-anese dioxide 20.5%; nickelous oxide 12.8%, this color having been created by calrining this miy,ture at a temperature 800 to 900' C. and then grin-ding it. Exar,iple 6 Bloated a.agre.aate particles ran.-ing in size from about 1/4 inch in diameter to about 3/4 inch in diameter havin.- a glaze surface appearance and a composition as specified in Example I were coated in a tunnel drum withan over-lazecomposition having the followina ingredients: 60 grarns frit No. 33 (as specified in Example 1), 50 grams Kentucky No. 4 clay (containing 51.65% SiO2 by weight) and 20 grams by weight of a yellow inorganic color prepared by mixin- 132.4 parts by wei.-ht lead nitrate, 123.6 parts by w--i.-ht calcittm stannite, 10.2 parts by weight aluminum, 57.6 parts by weight antimony ox-ide, 162.1 parts by wei.-ht sodium chloride and calcining this mixture under oxidizin.- conditions at about 800 to 900' C., grind3,198,656 and sufficient water so that '(he -laze composition hadsubstantially the viscosity of paint. After the aggr,-gate particles were completely coated they were then placed upon an inert support against one another and heated in a tunnel kiln at the rate of about 302' F. per hour unlil a temperature of about 1418' F. was achieved. The particles were then removed from the kiln and allowed to cool to roo@n temperature in air. The particles resulting from this series Df operations were coated a uniform yel10 low color. They did not stick to one another as a result of contact with one another during the heating step, and in each case the color on the stirfaces of the particles appeared to be fused in place. 1
