US2038034A - Refractory material and method of making the same - Google Patents

Description

106. COMPOSITIONS, 0 cross g f Examinar COATING 0R PLASTIC.

April 21, 1936. A, A F W L 2,038,034

REFRACTORY HATERIAL AND METHOD OF MAKING THE SAME 0 7 Filed March 27, 19s:

Patented Apr. 21, 1936 UNITED STATES PATENT OFFICE 1'7 Claims.

In this specification and the accompanying drawing, we shall describe and show a preferred form of our invention and specifically mention certain of its more important objects. We do not limit ourselves to the forms disclosed, since various changes and adaptations may be made therein without departing from the essence of our invention as hereinafter claimed; and objects and advantages other than those specifically mentioned are included within its scope.

I An object of our invention is to produce a very light refractory material which shall be a good heat insulator.

Another object of our invention is to provide a method of making a heat insulator, which material shall be cheap, fireproof, strong, and indestructible by insects and vermin.

Another object is to make a material in the interstices of which there shall exist a partial vacuum.

Another object is to produce a light material which shall be stout enough to be employed in load bearing portions of building structures.

A further object is to provide a heat insulator that is water-proof.

Still another object of our invention is to make a material that is a good absorber of sound.

The exact nature of the invention will be better understood from a description thereof in connection with the accompanying drawing.

Fig. 1 is a sectional drawing of the form used to mold one type of our material, showing in crosssection the contents of the form as arranged in one stage of a process for manufacturing this material.

Fig. 2 is a cross-sectional view of the finished insulation material.

Fig. 3 is a drawing in perspective of one type of insulating material applied to a surface being insulated, one end of the insulation being shown in section.

Fig. 4 is a drawing in perspective of another type of insulation material applied to a surface REFRACTORY MATERIAL AND IHETHOD OF MAKING THE SAME Albert A. Fowler, North 'Hollywood, and Russell M. Otis, Pasadena, Calif.

Application March 27, 1933, Serial No. 663,034

gerat ure again.

silicate or water glass of 42 deg. B. specific' gra'P of spumiform character, that is, they have the appearance and the structure of foam; but they are nevertheless solidified. Whether the mateis in the form of powder or of thick slabs,

close examination will reveal this foam-like strucii ture, and the word spumiform is intended to describe this internal structure regardless of the external size or shape of the body possessing it.

Another characteristic is that they are substantially completely desiccated, by which we mean 1 that they are substantially devoid of all moisture. It is the process of desiccation performed after the manner of our invention that results in the spumiform state of the silicate and in its solidi- 15 fication while in that state.

One type of our material we make by boilin a for ix ity i's used. If it is desired to form the material to any particular shape, the liquid silicate is placed in a form which is provided .with some means of escape for the steam generated during the process. A loosely fitting but confined cover will permit the escape of steam without allowing the silicate to escape. In order to avoid sticking of the molded article to Wlii'h case the paper is burned during the being insulated, one end of the insulation being 'opera 0 firing operation. One quart of the liquid silicate is used for every 250 cubic inches of space re- .quired to be filled by the molded article.

In making this type of material it is necessary to desiccate the silicate very slowly or large holes will be found in the finished article. When the 40 material is to be ground up for useas powder, this defect is not important but in a slab of heat insulating material it cannot be tolerated.

A method of making our spumiform material which has marked advantages over that above- 45 mentioned consists of two steps and is as fole purpose of this cooking operaconsists in a preliminary cooking I tion is to produce a partially desiccated solid sfli- '50 cate which may be more advantageously handled than the liquid silicate, and which will not tend to stick to a molding form, but which when further desiccated, as specified, will result in the spumiform material desired. -Sodlum silicate so- 55 egfshaman-l...

increasing from at 106. COMPOSITIONS,

COATING R PLASTIC. Cross Raerente fixammcr lution is poured into shallow open pans and is scribed previously, is pulverized to desired size cooked over an open flame, not in an oven, for and step 2 is carried out by cooking this parit from 1 to 1% hours at from 300 deg. F. to 200, tially desiccated pulverized silicate in a revolvdeg. F. ing hot drum until complete desiccation has been 5 It is desirable not to cook it in an oven achieved. Usually, 15 minutes per batch at 650 5 because when this is done the top skin of silicate deg. F. to 850 deg. F. is sufficient. The result is in the pan becomes hard, tends to prevent the an exceedingly light white powder composed of escape of steam from below and the resultant individual particles each of which appears upon pressure causes the whole mass to pufi and rise. detailed examination as a small round spumi- If, however, the silicate is cooked in an open pan rm m ss, itself composed of a multitude of 10 over a fire, the bottom will be hotter than the minute air cells enclosed by thin silicate walls. top and Consequently water will be evaporated The size of the individual particles is determined from the bottom first mama, by the size of the partially desiccated particles When the cooking is done as specified and the from which y are P d and e y Small pan with its silicate content is allowed to cool, a p rm p i l m y b m y impl p 15 solid cake of material results. The top layer is verizing the part y desiccated ma to BX- generally of glassy appearance whil th part treme fineness. The finished powder of spuminext. to the pan is white and m re spumiform in form material should not be confused with DOW- character than the glass-like upper layer due to der made y pulverizing the p e y si its more nearly complete desiccation. A et l cated silicate, for the particles of the former ma- 20 pan i d, d is coated t graphite or plated terial are stronger, more symmetrical and uniwith tin to prevent the silicate cake from sticking. form, and contain more eells- The Powder In this preliminary cooking operation th process resulting from the process here specified is used of desiccation is stopped when the silicate beas heat insulation by Pouring it into a pace 5111- comes sufiiciently gummy that, on cooling to orrounding the body to be insulated, it s packed 25 dlnary atmospheric temperature t, becomes a in boxes of asphalted paper for refrigerator use. solid as distinct from a liquid. In this state it It is also p d n Sealed cellophane packages may be described as a hydrous solid silicate, one which are Placed in the Walls Of refrigeratorscontaining water, as distinct f om the completely This packing of the powder into boxes is more desiccated or anhydrous sihcate desirable than pouring it into a space surround- 30 I nd te completing the process under ing the to be insulated because in packing, consideration, 'consistsin cooking the material rethe individual 1min-Wallet! particles of p suitin from step one described above, until form silicate are compressed. Being under complete desiccation is achieved As desiccation pression, any tendency of the particles to settle proceeds, the silicate fis into a spumjform and occupy a smaller volume is thwarted, since 35 t -m1 presumably because of the passage f the particles merely expand sufliciently to mainevaporated water through the remaining viscous tain the total volume the same. In practice, it substahce AS the process continues the spumh is found that in a box into which the powder has form material gets larger and more viscous until been Packed the Particles remain in compres- 40 h n the water has been evaporated, pumng sion throughout the life of the insulation, and 40 has ceased and the viscous material has solidified hence the box is always Asphahed Paper into an anhydmH gpumiform material of fivg and cellophane are used as box materials betimes the 70mm? that is composed of millions of cause they are moisture-proof and prevent the air g' by exceedingly thin Sim accumulation of moisture in the interior of the cate walls-a material that is amazingly light and msulatlon'- 5 strong and an excellent insulator of heat. The The powder may 8156 wlhjmi l fi quid solution of sodium silicate or with the pulcooking is preferably conducted at de F. to n 850 deg. a closed oven 50 fi venzed partially desiccated silicate and the whole Feifififie exists at all surfaces of the material be- W Mariam" 50 ing cooked. The required time of cooking depreferably 45 'q q i 50 pends upon the shape and mass of material a en the binder consists of dilute liquid ing treated. The important consideration deterfg l g ig g gg ggg gf gg g f g gf i ESiifiitifihftti 332% 823232555332 hard e joining the Particles of powdergthg t lilartially desiccated or hydrous silicate and fg f gfi g gggg ig igt fg sfig gg g 55 ye e remaining spumiform material must not he melted down. If the water is not substantialggfi gg ifigg i fg g g ggh 53 i ig zig y all removed, further heating at any later time a particles of the completely desiccated powder cause f pumng of t matenal and employed in this operation are made large 60 partlauy mammal is not as good enough the resulting tile is an excellent absorber an insulator as a completely desiccated one. If of somid This is because the individual an heating at a high temperature is prolonged bep ticles touch and are bonded together at only a yond the point of complete desiccation, the silicate y melt destroy the fine Sp 0 st 0: few points, leaving rather large mtersticial mterco uni ture because while water was still present the mamm catmg volds through which the unpmg b0 in sound can ass t .terial was hmited in temperature by the evaporaabgsorhmg f l f 3 2 232 the large Internal tion process, but after complete desiccation the A When it is desired to form a slab of spumiincreased te p y be exeeSSlVeform material having the advantage of struc- 7 This Second St p lt be earned out in a tural strength, the partially desiccated material "0 nety of ways conveniently secure the spumiresulting from step 1, as described previously, is form material In Ve forms a p cooked to complete desiccation in a molding .For certain applications it is desirable to have form. In Fig. 1, the lower half 2 of form I has it in the form of a .powder. To produce this at one end several circularly shaped portions 3 form, the material resulting from step 1, dewhich are adapted to carry a rod 4. The upper 75 portion 5 of the form I also has circularly shaped portions 9 which surround rod 4 and which cooperate to form a hinge about rod 4. Both the top 5 and the bottom 2 have horizontally extending edges 6 which are adapted to be clamped together at intervals around the periphery of the form by bolts 1 and nuts 8. The form I is generally coated with graphite both inside and out to prven 0x1 a 1011 an lessen the tendency of the silicate to stick to the walls. In preparation for the cooking operation, a cake 20 of the partially desiccated silicate which is shaped approximately to cover the bottom of the form but may be only one-fourth the height of the form, is placed in the form so that the side of the cake 20 which has been more nearly completely desiccated is toward the bottom of the form. The cake 20 can have been made in the required shape by cutting it from a larger piece or by partially desiccating it in a pan having the same area as the bottom of the form Atop the cake 20 is placed another cake 2| identical to it, but with its more nearly completely desiccated side toward the top 5. The cakes 20 and 2| as prepared to completely fill the form I in this operation should have resulted from the partial desiccation of one quart of 42 deg. B. sodium silicate for each 250 cubic inches of the form to be filled. After the cakes 20 and 2| are in place, the top 5 is shut and bolted down by means of bolts 1 and nuts 8. It is not desirable to bolt the form so tightly closed that a dangerous pressure builds up in the form before the steam incident to desiccation can escape. The form is closed tightly enough to prevent the silicate from being forced out, however. For a form two inches high, cooking is carried out at 650 deg. F. to 850 deg. F., preferably for about 50 minutes at 750 deg. FL The cooking is determined in time and intensity by the condition that desiccation shall be complete, yet the material shall not be melted down. As desiccation proceeds, the inner portions of cakes 20 and 2| puff more than the outer more nearly completely desiccated portions and the cake 2| is pushed tightly against the top 5 of the form. As the process continues, the pressure in the form compresses the hot and still pliable layer next to the form into what develops, when cold, into a hard strong outer shell 22 on the finished slab 23. The interior 24 of the finished slab 23 is solidified and is of a light spumiform character.

After the cooking has been completed the form and contents are cooled slowly. If cooling takes place too rapidly the slab 23 may crack. Also, since at the time of solidification the air entrapped in the slab is at a high temperature, and therefore at a low density, when thetemperature has decreased a partial vacuum exists in the slab of spumiform material and if the te rature decreases too rapidly this differential ressure will collapse the slab. The greater heat insulating value of an evacuated substance is taken advantage of by sealing the whole exterior of the slab 23 of spumiform material, immediately after removal from the form, with a sealing substance 25 such as sealing wax or a ceramic glaze. The slab can be removed from the form I soon enough after the cooking is complete to still retain most of the vacuum. After the sealing substance 25 is cold, the slab will consist of a multitude of partially evacuated air cells enclosed by thin silicate walls-an extremely good heat insulator.

As alternative to the air-tight sealing surface,

the slab is made water-proof by dipping in an asphalt paint. It is undesirable for any surface openings to exist which might permit the intrusion of water with its consequent reduction in heat insulation. Another effective water-proof a exterior is often provided by applying a waterproof paper or fabric to the surface of the slab. Asphalted paper has been found well adapted to this use. The paper on .one side of the slab is -made to extend beyond it. The extending paper 10 carries asphalt, and when the slab is put into place in a refrigerator the extending paper is pressed and sealed by the asphalt against the refrigerator frame, making a water-seal for the frame. 10

cooking process to make a more uniform ma- 20 terial; the outside shell is harder and stronger; and the silicate does not tend to stick to the form so much.

Another method of performing step 2 of the double cooking process is as follows: The par- 25 tially desiccated silicate resulting from step 1 is broken into chunks varying in size from about inch to 1 inch in diameter. These chunks are placed in the form and the form is closed. The

amount of the partially desiccated silicate used 0 for every 250 cubic inches of space in the form is that which results from cooking 1 quart of 42 deg. B. sodium silicate. In place of some 01' the partially desiccated silicate, an equivalent amount of the completely desiccategl pulverulent 35 spumiform material previously described may be emplbyedT The form and contents are heated $15650 deg. F. to 850 deg. F., preferably 50 minutes at 750 deg. F. As heating and consequent further desiccation proceeds, the partially desic- 40 cated chunks of silicate pufl. and bond to one another, completely filling the available space, even exerting a pressure on the form that results in an exterior shell of considerable compactness. are slowly cooled. A sealing substance is applied, as described above, to retain the partial vacuum existing within the material, or a waterproof surfacing material such as asphalt is applied to the surface of the formed insulation.

This method has the advantage over that in which cakes 20 and 2| are employed that it is not necessary to shape the partially desiccated silicate to the form being used, and it has the disadvantage that the molded spumiform ma- 5 terial resulting has not quite so strong an outside shell.

When it is desired to make a molded article of spumiform material of superior strfigth, reinforcement is spumif r u l orcement s ery o ia rl tnlightness. The reinforcing able reiagfprrein 1als isyery'greafiiron and alummmre ost heirinaiena sitimtmneahsanq, th

during the filling of the form, in the desired 7 After cooking, the form and contents 45 provided for the article. The

isa tisfactory :nommrcially" prature of cooking are also used: such 'thin"" I06. COMPOSITIONS,

COATING R PLASTIC.

pwition. In the case in which cakes and 2| are employed in filling the form, the reinforcing screen is placed between the two cakes, and the cooking proceeds as previously described. In case the form is filled with chunks of partially desiccated silicate, the screen is placed in the form, after half the chunks have been put in, and the other half of the chunks are placed on top of the screen. The screen is placed in the form with its shortest dimension in a direction substantially perpendicular to the surface it is intended to heat insulate in order that the reinforcing material shall affect to a minimum degree the insulating value of the whole article. Thus in a slab of material such as is made in form I. the reinforcing screen 3| is shown enclosed by spumiform material and parallel to and midway between surfaces 32 and 33. The slab 30 is applied to a surface 34 which it is desired to heat insulate. The surface 32 of slab 30 is higher in temperature than the surface 33 and heat flows from surface 32 to surface 33 through the slab 30. The reinforcing member 3i is positioned with its shortest dimension 36 substantially perpendicular to the surface 34 to be heat insulated.

Instead of a screen, a plate or sheet of reinforcing material is ofh sides of the molded article. This method of reinforcement has the advantage that a. metal or other durable exterior may be provided to a heat insulator without the necessity of any fasteners such as nails, screws, etc. The sheet of reinforcing material is coated with a light coat of liquid sodium silicate on the side which is to be next to the insulator. It is then placed either on the bottom or on the top of the material in the form and cooked in the same manner as specified for making the material without reinforcement. Upon completion of cooking it will be found that the sheet of reinforcing material is bonded to the insulation with as strong a bond as the insulation has to itself. The sheet of reinforcement may also be applied to the completely desiccated material by coating the reinforcing sheet on one side with liquid sodium silicate, sticking it to the insulation and holding it in firm contact while the metal sheet is heated to about 750 deg. F. as by a blow-torch. In Fig. 4, the finished slab 40 is shown applied to a surface 4| which is being heat insulated. Surface 42 of slab 40 rests on surface 4|. Surface 43 of the spumiform slab is covered with and joined to iron sheet 44. This iron sheet is nickel plated or polished to reduce the heat transfer by radiation from its upper surface. Heat conduction is through the spumiform material 45 in a direction perpendicular to surfaces 42 and 43 and it will be noted that this direction is also that of the shortest dimension of the reinforcing sheet 44. Thus, the reinforcing member 44 is positioned with its shortest dimension perpendicular to the surface 4| to be heat insulated.

It is obvious, of course, that our material can be molded in many different shapes such as in circular cylindrical sections for pipe coverings, etc. Water soluble silicates other than sodium silicate can be used-for example, potassium silicate, and we regard the application of these as coming within the scope of our invention. To

' those skilled in the art, other detail modifications Cross Reference What we claim as new and desire to secure by Letters Patent is:

1. A molded article containing solidified silicate having a spumiform structure, said article being provided with an air-tight outer shell within which exists a partial vacuum.

2. A method of making a pulverulent refractory material which consists in partially desiccating a silicate solution to form a solid silicate containing water, reducing said solid silicate to a powder and cooking said powder until desiccation is substantially complete.

3. A method of making a molded article which consists in partially desiccating a silicate solution to form a solid silicate containing water, reducing said silicate to chunks, confining said chunks of silicate in a molding form sufi'iciently closed to permit escape of water vapor, but not of sillcate, cooking said silicate in said form at a temperature sufiiciently high to create in it a spumiform structure, and continuing the process until desiccation is substantially complete.

4. A method of making a molded article which consists in forming a plurality of cakes of partially desiccated solid silicate in such manner that each cake has one side more nearly completely desiccated than the other side, confining said cakes in a molding form with the more nearly completely desiccated sides toward the walls of the molding form, cooking said silicate in said form at a temperature sufficiently high to create in it a spumiform structure, and continuing the process until desiccation is substantially complete.

5. A molded article comprising spumiform particles and a binder bonding said particles at their points of contact.

6. A molded article comprising particles containing spumiform silicate and a binder bonding said particles at their points of contact.

7. The method of making heat insulation which includes providing an intimate mixture of articles containing spumiform silicate with a nonsolid binder, forming said mixture to desired shape, and solidifying said binder.

8. A heat insulator comprising a confined body of spumiform particles under compression containing substantially anhydrous silicate.

9. The method of producing a non-settling granular heat insulator from a body of spumiform particles containing substantially anhydrous silicate which includes compressing said body of particles and maintaining said body under compression.

10. A molded article comprising spumiform particles containing substantially anhydrous siliform sufiiciently closed to permit the escape of water vapor, but not of silicate, cooking the contents at a temperature suificiently high to create in. them a united spumiform structure, and continuing the process until desiccation is substantially complete.

Examiner 13. A heat insulator comprising a molded body of spumiform material having bonded to the exterior surface thereof a sheet of metal with a heat-reflecting surface. v

14. A heat insulator comprising a molded spumiform body containing anhydrous silicate and having a sheet of metal bonded to the exterior surface thereof by a bond containing anhydrous silicate.

15. A non-settling granular heat insulator comprising a confined body of resilient spumiform particles in a state of compression.

16. The method of making non-settling granular heat insulation which includes heating hydrous particles of sodium silicate at a temperature sufiiciently high to create in them a spumiform structure, continuing said heating until desiccation of said particles is substantially complete, compressing said spumiform particles, and maintaining said spumiform particles under compression.

17. Il'he method of providing a body with a metal exterior through a common bonding layer having a spumiform structure which includes the steps of forming on said metal a coating of hydrous soluble silicate, providing contact between said coating and said body, heating said coating to create therein a spumiform structure and bond said metal to said body, and continuing the heating until desiccation of said bonding layer is substantially complete.

ALBERT A. FOWLER. RUSSELL M. OTIS.

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