US2442519A - Insulating material and method of making same - Google Patents

Description

WW Ll LHLHUL wimmm 3? .L'U UV Patented June 1, 1948 INSULATINGMATERIALANDMETHOD or Clyde 0. Schuetz, Mount Prospect, 11]., assignor to 'l nited States Gypsum Company, Chicago, 11]., f acorporation of Illinois v spplication August s, 1943, I Serial No. 497,713

-' The'pres'ent invention relates to an improved A mixture of this kind is incorporated in sufiiform of insulating material and the method of making it. J

Primarily. the material consists of a fibrous material such as asbestos, finely pulverized slag, a siliceous material such as, for example, diato- ,maceous earth, lime, and, if desired, a small amount of sodium hydroxide. Its weight ranges from about nine to twenty pounds per cubic foot,

and it possesses high Wane, 10 being particularly useful for er lagging when temperatures up to 1000 F. are encountered.

on of the objects of the present invention is the production of such an insulating material by a process which involves the conversion of the fibrous material into thick, rather viscous, suspension while in admixture with pulverized slag, diatomaceous earth, and lime, and the casting of the resulting mixture into water-tight molds in which it is subjected to curing under steam pressure. followed by drying of the shaped pieces thus obtained. g A further object is the material thus produced. I r A further object concerns itself with the methods of mixing, for the-purpose of producing a :mixture which will not exhibit any marked tendency to settle from an aqueous suspension. 1

While it has already been proposed to bond diatomaceous earth into an insulating material a by means of lime, with or without the incorporaion of asbestos or similar inorganic fibrous material, the products thus obtained, although relatively light in weight, did not have the structural strength of'the products made in accordance with the present invention. By using slag, particularly ground, water-quenched slag, not only is the product stronger, but it also costs less per cubic foot, and moreover has a better resistance against shrinkage and warping when subjected ,toitemperatures near or at the maximum temperature for which it is intended.

v The insulation made in accordance with the l I present invention is the product of a mixture made within the limits of the following formula:

l isbestos fiber j. 5-35 I Finely pulverized .blast-fumace slag -89 Diatomaceous earth 3-425 Limp I. f, 342.5

6 can be accomplished in variousways. such, for

example, as by the use of a turbo-mixe'rpr, preferabl a Bauer mill. The main function, of such mixing is to promote fiber-to-fiber friction by forcing the mixture rapidly through relatively narrow openings. A mixture thus produced .will

not settle out to any reat extent when left quiescent. Satisfactory mixing may be defined as that which results in a mixture which will not show clear water for more than about 7.5%

of the head after being allowed to settle for threehours. The amount of water required, for example, in connection with the preferred mixture above mentioned is about six parts by weight to yield a product having a dry density of substan 0 tially 12 pounds per cubic foot.

After the mixture has attained the required degree of non-settling properties, it may be drawn off into a storage vessel provided witnstirrers which keep the mixture slowly agitated so as to 2 keep it of uniform consistency. From this vessel (or directly from the original mixer) sufiicient quantities of the-mixture are drawn off into .water-tight molds, which may be in the form of pans. These, after filling} are "preferably bumped or vibrated so as to bring to the surface any bubbles of air, primarily to insure;

formity of structure. i q The pans thus filled are then transferred to a suitable autoclave in which they are horizontally 5 supported. The autoclave is then closed and steam is admitted thereto until a pressure of about lbs. per square inch (gauge) is attained. The pressure, and hence the curingof the material in the molds, is continued for about 0 20 hours for slabs in which the maximum dis tance from a heated surface is three inches; i.'e., six-inch slab. As a guide to proper autoclaving procedure, it has been ascertained that for a pressure of 100 lbs. (gauge) saturated steam, the time required for any given thickness of slab can be calculated from the following formula:

se re atin time in hours. an his the 5,0 fanaximum distance in inches, from a heated sur- I'face of the slab. Thus for a ten-inch slab, this am o-la I would be (where D is, oi. course, one-half the thickness) 4X5+8=28 hours. It is believed that a reaction occurs between the slag and the diatomaceous earth on the one hand, and the 4 slag, diatomaceous earth and lime, about 65% to 95%. In the latter, but based in percentage on the total composition, the lime and diatoina'eebus earth are used in about equal proportionsfbut alkaline materials (lime and alkali) on the other. 5 not less than about 3% of each and not more The inorganic fibrous material, such as the asthan about 42.5% of each; the slag, in any case,

:Iestos, serves as a salt of skelieton to maintain accounting for the remainder of the composition, e dimens ons of e mater al, and becomes except for such alkali as may be used as a fixed in position by the formation of a rather catalyst.

Lough solid which is the product of the reac- The amount of water mixed with the ingredion. p ents prior to agitating and molding is at least No evaporation of moisture takes place during three times the weight of the non-aqueous inthe autoclaving. In fact, it is distinctly advangredients. The steam pressure used for autotageous that a small head of water remain above claving may be higher or lower than 100 lbs., the solids in the pans during this operation, as but should not be much below about 50 lbs.

a. better and stronger surface finish is thus 011- ,As an indication of proper autoclaving, it may gamed.mnlltoij;fhse3 $11: cggltfpguiosgging pzeriod the be mentioned tthat the product 21771111811 dmiss e e snipers moved from t e autoc ave shoul ave a ture is slowly allowed to fall. It is imperative green l f" If t is gray, 1t 15 an indication that the pressure not be reduced at such a high 29 that there s" not enough water present during rate that disruptive vamnzation takes place at the autoclaving operation; that is, there has been the center of the cast at any time during .presa partial drymut, probably resulting from steam sure release and cooling cycle. For casts six fl t Th mduct is marketed inches deep, the pressure release time is approxi- Pressure uc ua 8 p bricks blocks or slabs' for inmately three hours; and for casts twelve inches 5 m the forfn of deep th t is approximately five hours. stance, 36 inches by 6 11101153, a Of The Pr in the Pens is then in th fo of a from 1 inch to 4 inches. Other Special shapes coherent, but still thoroughly wet, solid. The can of course be madeshape thereof is substantially that of the molds The importance of the mixing mention is to with but very litle shrinkage, about 0.7% lineal 30 be p in mind, as this wmflbutes to being the maximum for a product having a able extent to the properties of the slurry from density of about 13 lbs. per cubic foot., The which the shapes are cast, and serves to keep ped pieces may then be removed from the the ingredients of the mixture from settling out.

molds, or dried therein. In any ev all It is again emphasized that the mixture is not the water contained in th S p Pieces is filtered, but placed in its entirety into the molds. mved by drying T is mt a As the reaction proceeds during the autoclaving 33d iiiti tfifi ta li g? eifgpi it; 22 mass 3;? pm E3 3; directly heated by gas. Finally, the dried blocks 31: :5 $33 6 g g'fi i g are cooled down and milled or sawed, or otherwise 40 p Th 1 trimmed to the desired dimensions; gather at their points of Contact e mama The density of the products may vary between contains a great deal of empty space which is nine and twenty pounds per cubic foot. The occupied by the water during the process P strength of the insulation thus obtained is quite which when eliminated by the drying high: and on the average, the ratio of the 4 consequently leaves corresponding fined of rupture; Expressed in pounds per with air, for which 169.8011 the material 1188 its square inch, to the density, in pounds per cubic excell nt in l tin Properties It also has foot, is at least 4.5-. high abrasion resistance and low shrinkage loss. The raw materials used for the production of The invention is to be liberally construed so the in ulation Produced as above described are far as mechanical and chemical equivalents are allreadfly availab e. The s a pr e ed s concerned, and accordingly what is novel and quenched blast-furnace slag which has been jnventjvetherem 1' h d pulverized, as for example in a ball mill. The ocess 3 a -j mm is high-calcium, hydrated lime although te ial l iaving gig h t r e gt h all low densityiapaquicklimasuitably hydrated before use, may be ble of use at temperatures up to about 0 0 F" used. The asbestos is preferably the 5K grade having a density of not more than about 20 or better. The diatomaceous earth is the compounds per cubic foot n a modulus of memial mm. of this.mat ena1 knowrfi as ture, in pounds per squareinch, of at least 4% kieselguhr, etc. The alkali, such as the sodium times its density in poundsper cubic foot and or potassium hydroxide be omitted but a lineal shrinkage of not more than about 2% then a longer autoclavingperiod will be required.- when heated to F" which comprises the It is believed that the alkali performs the function steps of mixing asbestos fiber finely pulverized 9 catalyst it is quite mp f Q quenched blast-furnace slag, diatomaceous earth,

zg ag fi g gg iu m r i exploltatmn lime. and an alkali, in the proportions of said hrangeoe The insulation made as hereinabove described 252 3;: 3323 9 m 5 f may safely be used up to temperatures of about 1000' r. without significant deterioration, and Fem! by weigh;

the lineal shrinkage, even under the severest Asbestos conditions, does not exceed about 2%. On a slag (as defined) 10'89 basis of not exceeding a density of about 20 lbs. mammaceous earthper cubic foot, the main ingredients of\ the com- Lime 342:5

position may vary within the following limits: Pf

as s os. or si ila fib r, 5% to 5%; react o with an amount of water, by weight, or from -;P ducts resulting from the autoclavins of the 7 about three times to about six times the weight V l a 1. u e 'r CROSS REFERtNUI:

ponents of the mixture, the material in the molds becomes hard and set, and then reducing the steam pressure slowly enough to prevent disruption of the hardened material, followed by final drying thereof, whereby it is left highly porous by the disappearance of the water from the interstices therein.

2. An insulating material produced in accordance with the process claimed in claim 1.

CLYDE C. SCHUETZ.

6 REFERENCES orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,039,413 Klee Sept. 24, 1912 1,045,933 Belknap Dec. 3, 1912 1,102,358 Siegmann July 7, 1914 1,107,431 Malinovszky Aug. 18, 1914 1,520,893 Teltsworth Dec. 30, 1924 1,552,051 Crume Sept. 1, 1925 1,569,755 Irvin Jan. 12, 1926 1,666,936 Kern Apr. 24, 1928 1,812,306 Russ June 30, 1931 1,867,641 Witty July 19, 1932 1,919,532 Ryder et al. July 25, 1933 1,932,971 Huttemann et al. Oct. 31, 1933 1,977,158 Thurman at al. Oct. 16, 1934 2,062,879 Hammenecker Dec. 1, 1936 2,221,420 Clarvoe et a1 Nov. 12, 1940 MRMINLK