US2448186A - Heat insulation - Google Patents

Description

| B. MILLER ETA| HEAT INSULATION Filed June 29, 1942 a v3 IIardK Patented Aug. 31, 1948 um'rso STATES PATENT, orrics m'r INSULATION Lewis B. Miller, Ambler, and-Willard R. Seipt,

alsimrl North Wales, Pm,

Mattison Company, Ambler, Pa

of Pennsylvania to Kealbey & a corporation Application June 29, 19, Serial No. 448,928

Claims. 1

This invention relates to heat insulation, and particularly to insulation adapted for use over a wide range of heat conditions and up to relatively high temperatures.

The object of the invention is to provide an insulation which will have low density for the relatively high temperature which it is adapted to withstand.

A further object is to provide an inexpensive, adaptable process for the production 01' such insulation composed of a combination of fibrous and powdery materials.

In the accompanying drawing Figs. 1, 2 and 3 are diagrammatic views illustraging one method of producing the insulation, an

Fig. 4 is a perspective view of the insulation in rectangular block form.

The raw materials are composed of fibers, a powdered filling material and a powdered binder. Preferably the fibrous material is asbestos in the form of amosite, this being in proportion of 25- 40%. The powdered filler is diatomaceous earth in proportion of 35-45% and the powdered binder is bentonite in proportion of 25-30%, all of the proportions being by relative dry weights.

In the formation of the insulation the raw materials are first proportioned and dry mixed so that the powdery materials are well blended and distributed among the asbestos fibers giving a very open, fiufiy structure. This ilufiy material is then spread in a thin layer I on a base or on a movable support, such as an endless belt or rotary table in case of a continuous process. In Fig. 1 of the drawings the base 5 has a layer 1 of the material within a surrounding rim or retainer 6.

means of an atomized spray, the mixture of materials in dampened form thus being built upto desired depth on the base plate, belt or table.

The accumulated dampened mass of asbestos,-

instance, as indicated in Fig. 3 with the block insulation, plunger 2! may be used within the rim or retainer 8 to press the layers into more compact dorm, designated 8, this compacting being variable in amount depending upon the desired density of the final insulation. The result is a rectangular insulating block 8 as illustrated in Fig. 4 with the upper and lower surfaces in and the edge surfaces 9. In this block the tendency is for the fibers, particularly the long ones, to run ilatwise withthe layers; however, in each layer the fibers may run in all directions and may even run from one layer to another, and entangle with the powdery materials, all of the surfaces of the mixture being evenly dampened.

The shaped piece is then dried driving off the moisture and developing the adhesive bond of the bentonite between the particles of diatomaoeous earth and between the asbestos fibers and the other materials, the particles of the whole mass being thoroughly cemented together to im- D rt great strength to the block as a whole.

During this drying the bentonite is subjected to a heated moisture-laden atmosphere as the wetting water is vaporized and the bentonite is The thin layer I of raw materials is then uni- Preferably an air spray nozzle 20 is used to eflect the moistening, the water being atomized by an air jet so as to form a cloud or mist penetrating and permeating the layer 1 from surface to surface.

Successive layers 1 are then accumulated on top of each other one by one as indicated in Fig. 2, each layer of the fibrous powdery mixture being dampened down as above described by supplied with moisture from the mixture of fibers and diatomaceous earth, the great surface areas of which adsorb the atomized moisture. If desired. this moisture treatment may be accentuated by steaming the shaped pieces for a few minutes before drying further to develop the binding effect. After drying the shaped and dried pieces are ready for packaging.

By this method insulation which will withstand 1000 to 1200 F. may be made with a density of six to eight pounds per cubic foot and insul a. tion withstanding a temperature of 900?;to 1000 F. may be made with a density as low as 3.9

pounds per cubic foot and with sufilcient strength for usual service conditions. A light weight high temperature thermal insulation will result when the mixture is compressed under a pressure of about fifty pounds per square inch or less to give a final product weighing eleven pounds per cubic foot and capable of withstanding a temperature of at least 1900 F. and in the neighborhood of at 1900 F. is 1.05%

l a 2200 F. to 2300" F. for the higher pressures and densities.

The density of the final product will depend upon the degree to which the dampened mixture is compressed and this centre very accurately predetermined depending upon the insulating surface to which the product is to be put". A

is 30.0, the Pusey and Jones hardness 1.10 and under the Navy abrasion test the percent loss in ten minutes is 43 and in twenty minutes 6'7. At 850 F. the modulus of rupture is 17.6 and'the linear shrinkage 0.35%; at 1100 F. the modulus of rupture is 14.3 and the linear shrinkage is 0.59%: at 1500 F. the modulus of rupture is 13.? and the linear shrinkage 1.10%; and at assures 4 a I. v V v terial may be applied without failure is considerably dependent on the composition of the product. The light weight product composed of bentonite and fiber in. th ratio of about -70 has a density variable ordinarily from about four pounds per cubic foot to eight pounds per cubic foot and will tdndto disintegrate beyond usefulness above a temperature of about 900 With less fiber ftype of "composition using still less fiber and more diatomaceous earth (30 parts fiber, parts diatomace'ous earth and 30 parts bentonite) will shrink somewhat above 1900 F. and will be used 1900 F. the modulus of rupture is 19.8 and the linear shrinkage is 1.77%, these latter figures being on the basis of a six hour soaking heat} subjecting the whole piece to the temperature indicated. Under normal conditions of usage insulations are subjected to high temperatures only upon one side and any thermal deterioration encountered is therefore in general less in practice than under the conditions of the test.

In conductivity th present'insulation is very low being only about of the standard high temperature insulations up to 700 F., and is dis tinctly superior in the lower ranges of temperature, i. e., below 1000 F. The higher densities and larger proportions of diatomaceous earth render the insulation more eifective at higher temperatures and the composition oi a corresponding block or other shape may be varied to be denser at the portions adjacent the heated surface. Larger proportions of the diatomaceous earth may also be used at these portions of the insulation by correspondingly varying the composition of the successive layers i and variations in density may be effected by subjecting the earlier deposited layers to separate higher compacting pressure so that a plurality of pressures successively lower in intensity are used to produce the block or other shape.

The material in dampened form is relatively plastic and may be pressed to any desired shape and will retain. this shape during drying. No pressures are required in the drying operation and the material is self-setting in that the drying operation does not require the shape to be retained in the shaping mold.

The drying shrinkage of the blocks is negligible and'they may be cast substantially to the exact size of the finished piece.

This insulation is relatively simple in manufacture and low in cost and widely adaptable'to different conditions of use.

The heat insulation of this invention combines mineral fibers, such as asbestos or rock wool with powdery particles, to give a highly porous unit structure withstanding a very high temperature in proportion to the density of the insulating material. It maintains its form under continuous six hours heating at least to the temperatures as above described. The withstood temperature or the maximum temperature to which the mo,-

at densities of eleven pounds per cubic foot to sixteen pounds per cubic foot. Thus the maximum temperature is relatively high in relation to the density of the insulation.

In place of the bentonite or in conjunction with it, other binders may be used, such as kaolins or other clays in temperatures up to 1900 F. silicates may be used in place of the bentonite, but only up to temperatures of about 700 F. while gums and other emulsified or water soluble organic binders may be employed up to about 200-300" F. To give temporary strength at normal air temperatures and facilitate handling before and during application of the insulation, a small. percentage of a water soluble gum may be added as an additional binder. Other fiber may also be used in place or together with the amoslte such as chrysotile and. 'amphibole asbestos up to 2:900 R, rock wool or glass wool up to 1000 F. or organic fibers up to 200 F.

' In the formation of these insulations the characteristics are controllable by the proportions of the ingredients and by the compacting pressures employed making the insulation widely adaptable while at the same time maintaining a relatively low density in proportion to the temperatures involved. This represents not only a saving in weight and-material over prior insulations but is accompanied by a. lower conductivity as above explained. 4 v

' The process for producing the product of this invention is described and claimed in our cobendingapplication Serial No. 534,650, filed May 8,- 1944.

We claim:

1. A heat insulating structure formed by a series of layers of similar composition, each layer comprising whole mineral fibers in proportion of the order of 25 to 40% by dry weight and tending to run fiatwise of the structure and entangled with evenly distributed separate particles of powdery mineral material and evenly distributed separate powdery particles of a binder material of the group bentonite, clays and silicates of the order of 25 to 30% of the dry weight of the insulation and set in place adhering to the fibers and to the powdery'material and to each other by surface contact between the individual fibers and individual particles leaving intervening voids to provide an open highly porous structure having a low density of the order of 8 to 15 lbs. per cu. ft. and capable of withstanding for at least six hours a temperature in degrees F. which is over times the weight of a cu.-ft. of the insulation.

2. A heat insulating structure as set forth in claim 1 in which successive layers of the structure vary in density and correspondingly vary in heat resistance. j

"' A heat insulatingstructure' as set forth in 5 claim 1 in which successive-layers vary in the proportion of powdery material and correspondingly vary in heat resistance.

4. A heat insulating structure comprising whole mineral fibers in proportion of the order of 70% by dry weight and tending to run ilatwise of the perature in degrees 1". which is over 200 times the 5 weight 01' a cu. ft. of the insulation.

5. A heat insulating structure composed of 25-30% of a bonding material of the group bentonite, clays and silicates and the remainder noncementitious mineral particles including whole mineral fibers forming at least 25% 01' the entire composition, the bonding material being in the form of powdery particles intermixed and. entangled and evenly distributed among the noncementitious particles and bonded thereto by sur-.

face contact between the individual particles of the bonding material and the individual non-- cementitious particles to provide an open highly porous structure having a low density of the order of 4-15 pounds per cubic foot and capable oi withstanding for at least six hours a temperature in degrees F. which is over 100 times the weight of a cubic foot of the insulation.

6. A heat insulating structure as set forth in claim 5 in which the noncementitious mineral 5 material is composed of asbestos and diatomaceous earth.- 7 1 4 LEWIS a. mum. I wmaan a. sm 'r.

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

UNITED STATES PATENTS Number Name Date 248,324 Johns -1 Oct. 18, 1881 1,045,933 Belknap Dec. 3, 1912 1,387,348 Burgstresse'r Aug. 9, 1921 1,513,723 Bohlander Oct. 28; 1924 1,544,196 Teitsworth June 30, 1925 1,568,415 .Pilllod Jan. 5, 1926 1,613,137 Seigle Jan. 4, 1927 1,715,977 Bates et a1. June 4, 1929 1,830,253 Bechtner Nov. 3, 1931 1,851,038 Clark Mar. 29, 1932 1,887,726 Weber Nov. 15,1932 2,008,718 Jenkins -..s- July 23, 1935 2,033,106 Cummins Mar, 3, 1936 2,184,316 Plummet -Dec. 26, 1939 2,276,869 Pond Mar. 17, 1942 I 2,309,206 Newman Jan. 26. 1943 MacArthur et al. May 16, 1944

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