US2103463A - High temperature insulating composition - Google Patents

Description

Dec. 28, 1937. o. JONES 2,103,463

HIGH TEMPERATURE INSULATING COMPOSITION Original Filed 001;. 18, 1933 Patented Dec. 28, 1937 OtisL. Jones, Jollet,Ill., assignor, by direct and mesne assignments, of one-half to The Illiunois Clay :Products Company, Joliet, 111., a corporation of, Illinois, and one-half to F. E.

Schundler & Compa'ny,lnc., Joliet, 111., a corporation of Illinois Continuation of application Serial No. 694,061,

October 18, 1933.

This application April 9, 1934, Serial No. 719,728

6 Claims. (Cl. 1 06--10).

This invention relates to formed articles made from plastic and other materials, and among other objects aims inexpensively to provide articles of this character with superficial cohesive strength to withstand damage in handling and in use.

. The invention may be readily understood by reference to one illustrative object embodying the invention and made in accordance with the method herein disclosed.

10 The drawing illustrates an insulation brick embodying the invention and shown partly imsection to reveal the superficial and reinforcing shell.

An insulation brick, slab or other formed article is generally characterized by its high porosity (the degree of which is a measure ofits insulating value) and such fragility or weaknesses to require extremely careful handling and surface protection by wrapping or expensive crating or packaging.

. The insulation brick Ill herein disclosed represents a formed article comprising an appropriate aggregate preferably mixed with a small quantity of more finely grained material such asplastic clay and bound together superficially by a hard outer layer or shell II which develops without firing or burning. The aforesaid reinforcing shell [I is formed by mixing with the solid materials a small quantity of liquid binding material whose liquid vehicle evaporates at the surface of the formed articles and causes the binding substance tomigrate, probably by capillary action, toward the surface and there cement the material com prising a superficial layer of the article firmly together into a hard reinforcing shell capable of adequately withstanding such usage as the articlereceives in shipping and in installation withoutthe careful handling or protection usually required for other preformed insulations. The surface of such an article is moreover smooth and dense (as contrasted with the rough absorbent surface of the ordinary molded insulation) which is well adapted to receive surface decoration or coating by paints, water-proofing or plaster. There is of course no sharp plane of division between the reinforcing layer and the interior of the article, but the drying of a brick of ordinary size causes the binding material to be concentrated, so far as the cohesive strength of the superficial layer is concerned, in a layer of about one-six- 50 teenthof an inch in depth. The greatest concentration of binder occurs of course on the surface of the article itself, thereby giving it a vitreous orlyarnish-like skin which istenacious and nonbrittle.

For

convenience, the liquid binding material may be designated as a soluble binder wherein the liquid vehicle is generally water and the binding ingredient is either dissolved therein or carried as a colloidal suspension. A large number of mineral and organic carbohydrate and hydrocarbon binders are available. If only adhesive or binding properties are required, the less expensive binders. are obviously preferable. Pitch liquor is a common and inexpensive binder of this character, as also are what are known as cereal binders. Pitch liquor is a by-product or more properly a waste product, in paper manufacture, comprising the resinous and pectic binding substances removed from wood to liberate the fibre for paper making. It is usually recovered in liquid form but may be reduced to a powder by spray drying for convenience in shipping. To adapt it for use in the present instance it is again mixed with water, the concentration being fairly weak, about 2? Baum. The binding ingredient in soluble or liquid binders not being volatile at ordinary temperatures, is carried toward the surface of the article as the liquid vehicle evaporates but remains at or closely adjacent the surface to bind the material together into a hard and strong layer.

To secure effective migration of the adhesive toward the surface, the liquid binder must be adequately dilute, particularlyas contrasted with I the concentration necessary'where the adhesive must not migrate to the surface but must remain adequately distributed through the entire mass to bind together all portions of the mass. It should therefore not initially be so concentrated that slight additional concentration will convert it into an adhesive and ,render it incapable of migrating toward the surface. In other words, thedilution of the binder should be such that regardless of the physical character of the aggregates comprising the formed article, there is sufficient liquid vehicle to carry a large proportion of the adhesive to the surface during the drying of the, article. However, the amount of adhesive necessary to form an outer reinforcing shell is so small that in practice the amount of liquid necessary for the foregoing purposes does not exceed what would ordinarily be necessary to make a sufficiently plastic or coherent mass to permit convenient handling for forming or. molding. The interior of the article need not be bonded together since the shape of the article is preserved by the strong outer shell. Indeed, for in-' sulation purposes, the lack of a closely bonded interior is advantageous since the interstices between the solid materials and remain as pores.

are therefore unfilled the surface of the brick.

The invention is particularly advantageous in connection with insulating and other brick subjected to high temperatures. Such brick need only be dried and need not be burned. The reinforcing shell provided by the soluble binder protects the brick against damage until it is installed. Thereafter the heat to which the brick is subjected serves to convert the plastic clay or other ordinary bonding material in the brick into the usual ceramic bond which would have resulted had the brick been burned according to regular practice. In such cases it is immaterial that the soluble binder may be burned away, it having served its purpose.

As here shown, the illustrative brick comprises particles l2 of exfoliated vermiculite mixed with a small quantity of plastic clay and a soluble binder. Exfoliated vermiculite is an alteration productof particles of certain micaceous minerals, such as biotite, which exfoliate or expand to many times their original size upon the application of heat, and produce a granular insulating material both highly refractory and extremely light inweight (about six pounds per cubic foot). The plastic clay in this case also serves as a matrix to protect the compressible particles of exfoliated vermiculite from injury, and may advantageously comprise about 25% of the dry weight of the mass,the balance (with the exception of an equivalent of about 4% of binder powder) consisting of exfoliated vermiculite. The amount of binder and clay may be considerably varied. Brick containing as little as 10% of clay has still higher insulating qualities but the ultimate ceramic bond between the particles is weaker. Greater strength can be secured by increase in the amount of clay even to the point where it fills all the interstices, but in the latter case the brick would have a lower insulating efficiency. The clay of course does not form a fired or ceramic bond unless and until the brick when in use has been subjected to sumciently high temperatures to develop such a bond. Initially substantially the entire practical strength is provided by the hard shell formed by concentration of the soluble binder adjacent Although the interior of the article is highly porous and fragile, the outer shell is dense and tough. In this particular instance the molding or forming operation flattens the outer layer of vermiculite particles into a smooth unbroken surface. Nails may be driven into the articles and are firmly held thereby. The article may be readily cut without crumbling to fit it into odd or irregular places; the remaining shell preserves the integrity of the article.

The present invention, moreover, makes practical the formation of bricks, slabs and the like of such porous, weak, or highly fragile interiors (of high insulating efficiency) as not otherwise to be capable of practical manufacture, handling, or use. In such instances the tough outer shell provided by the outwardly migrating binder endows materials of this character with high practicality. Even where no adequate ceramic bond subsequently develops, the integrity of the article is maintained even though the superficial binder be burned away at one end of the article. The

. insulating efliciency of the article is generally cabrick or other articles. The usual plastic mass to which the soluble binder has been added, is formed, and ordinary molding or forming practices may be followed. In handling relatively delicate, porous or compressible aggregates, a method of formation should preferably be employed which compresses the mass as little as possible. After formation the articles are then dried; the rate of drying should be as rapid as possible without reaching temperatures which would damage or destroy the binder. Drying temperatures which ultimately reach 400 F. are satisfactory for many binders. Rapid drying seems to produce a greater concentration of binder at the surface than slow drying.

The articles may advantageously be waterproofed where the conditions of service make this desirable, by employing a water-proof binder such as a dilute asphalt preparation. Although quite viscous in concentrated condition, the asphalt will migrate to the surface if the binder be initially suiliciently dilute.

The use of a liquid binder to produce such a shell is not confined to insulations or to those articles which would otherwise require burning to give them strength for handling and service, but may be employed as a substitute for superficial or other reinforcement in those articles in which no ceramic or equivalent bond would be formed. It is far simpler to provide the superficial reinforcing shell automatically by adding a small quantity of liquid binder to the mass of material prior to formation, than subsequently to apply separate reinforcingmaterial in the form of a covering fabric or the like, as is the case with the insulating brick known as 85% magnesia.

This material is not otherwise adequately bonded- (indeed it is converted to a powder when sub- Jected to a temperature of about 600 F.) and when not previously protected by a fabric cover it must be very carefully handled when installed after which, in most cases, protection must be applied.

This application is a continuation of my application, Serial No. 694,061.

Obviously the invention is not limited to the details of the illustrative embodiment of the invention herein disclosed since these may be variously modified. Moreover it is not indispensable that all features of the invention be used con- Jointly since various features may be used to advantage in different combinations and subcombinations.

Having described my invention, I claim:

1. A high temperature insulating material of the character described comprising in combination a substantially thick body of eiiicient insulating material comprising granules of exfoliated vermiculite bonded together by a heat destructible liquid binder, said binder migrating to the surface of the body on drying to form a relatively thin reinforcing shell for the body, and a ceramic bonding material mixed with the granules of vermiculite and adapted to develop a ceramic bond when said body is subjected to high temperatures and the other bonding material is destroyed.

2. A high temperature insulating material of the character described comprising in combination a substantially thick body of efficient insulating material consisting substantially entirely of granules of exfoliated vermiculite, said body containing not exceeding 25% of ceramic material adapted to develop a ceramic bond at high temperatures, said granules of vermiculite being 76 initially bonded together by aheat destructible liquid binder which on drying of the material migrates to and is concentrated in the surface of. the material forming a strong reinforcing shell for the body adapting it to be handled and applied without pre-burning, themigrating of the binder from between the particles in the .body of the materialleaving the latter porous taining a small percentage of dry ceramic bond forming material, drying said material and etfectinga migration of theliquid binder to the surface of the material to form atough reinforcing shell for the material and to leave the body of the material in its initially highly porous and friable condition, then exposinga face of the material in use to temperatures suiiicient to destroy said liquid binder and to develop a ceramic bond at said exposed face with the aforesaid ceramic bonding material, and retarding substantial penetration of heat into the body of the material by means of the exfoliated vermiculite, whereby a portion of the initial binding material is protected against destruction and serves to support the material duringthe development of the ceramic bond at said exposed face of the material.

' 4. As an articleof manufacture, an insulation brick or the like comprising'a body of particles andflrm outer shell which is relatively thin and formed by the superficial layer of the material cementedtogether by aheat destructible binder,

the interior of the body being relatively loose and incapable itself of being handled, said clay being adapted to form a ceramic bond when, in

use, the article is subjected to a burning tem- I perature.

5. The method of forming a refractory heat insulating material without initial burning which is characterized by forming a plastic mixture of granules of exfoliated vermiculite containing a ceramic bond forming material and a heat destructible binding material, moldingsaid mixture into a body of substantial thickness and allowing the, same to dry to develop a bond with said heat destructible binding material, then exposing a face 'of said body to high temperatures which destroy said heat destructible binder and develop a ceramic bond with said ceramic bond forming material, and retarding substantial penetration of high temperatures into the body of the material by means of said exfoliated vermiculite to protect the heat destructible binding material within the body during the formation of'a ceramic bond at said exposed surface,

6. A high temperature insulating material of the character described comprising in combination a substantially thick body of highly eflicient refractory insulating material comprising substantially entirely granules of exfoliated vermiculite containing a ceramic bond forming material adapted to develop a ceramic bond at high temperatures, said vermiculite being initially bonded together by a heat destructible binder which develops without firing, thereby binding the material together in handling and in installation until a ceramic bond is developed by exposure of the material to high temperatures.

OTIS L. JONES.

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