US2079664A - Method of making lightweight articles - Google Patents

Description

May 11, 1937.

INVENTOR William R. fiezlple.

ATTORNEY Patented May 11, 1937 PATENT OFFICE METHOD OF MAKING ARTICL LIGHTWEIGHT ES William R. Seigle, Mamaroneck, N. Y., assignor to J ohns-Manville Corporation, New York,

N. Y., a corporation of New York Application July 23,

4 Claims.

This invention relates to a light-weight composition and a method of making the same. The invention relates particularly to a compressed and then hardened article including collapsible, void- 5 containing particles and to 'a method of making the article with preservation of the voids.

Exfollated vermiculite, for example, is collapsible. A granule of it may be reduced by compression, in a direction transverse to the plane of the lamination, to perhaps one-tenth of the thickness before compression. I'he result of the compression is a dense, compact product that somewhat resembles unexpanded mica in appearance and that is relatively ineffective in sound absorption and thermal insulation.

It is an object of the present invention to provide a strong, durable, and useful article comprising collapsible, void-containing particles embedded in a compressed binder composition, with preservation of the voids. A further object is to provide such a product in which the voids in the several particles are in communication with the voids in other particles and with an outer surface of the product and/or may be interlocked with barbs in a fibrous material. Other objects and advantages will appear as a description of the invention progresses.

Reference is made to my co-pending application, Serial Number 624,293, filed July 23, 1932, Q for U. S. patent, relating to Light-weight ceramic article and method of making the same.

The invention is illustrated in the drawing in which -Fig. 1 shows a perspective view of a composition including collapsible, void-containing particles embedded in a binder composition.

Fig. 2 shows a side elevation of a modified form of the invention in which the light-weight structure shown in Fig. 1 is integrally united to dense facing layers.

Fig. 3 shows a side elevation of a modification of the invention in which there is intercommunication between the various embedded void-containing particles and also between these particles and an outer surface of the article.

Fig. 4 shows an enlarged perspective view of a granule of material suitable for use with a binder composition in the structures of the present-in- 50 vention.

In the various figures like reference characters denote like parts. 4

The binder composition used should be relatively insoluble in the particular liquid, such as water 55 or a hydrocarbon, that may be present during 1932, Serial No. 624,292

the process of fabrication of an article with the said binder composition. It should be adapted to be shaped and hardened. Among the binder compositions possessing these properties and that may be used are those comprising a hydraulic cementitious material I, such as Portland cement, calcium aluminate or lumnite cement, or magnesium oxychloride cement. Such materials are preferably associated in the binder composition with a reenforcing fibrous material 2, such as relatively short asbestos fibers, jute, steel wool, or the like. The fibers not only reenforce the finished product, but also increase the degree to which the binder composition may be densified by compres sion. Asbestos fibers are particularly desirable in the binder composition. Not only are they convenient to use and fireand heat-proof, but also they are provided with barbs adapted to become engaged between the laminae in an exfoliated mineral, particularly when a wet mixture of the fibers and mineral is compressed.

The binder composition that is preferred at this time is one comprising Portland cement and short asbestos fibers, suitably in the proportions of 20 to 50 parts by weight of Portland cement to 10 to 20 parts of asbestos fibers.

Another binder composition that may be used is one adapted to develop a ceramic bond at high temperatures, such, for example,-as clay. When clay is used, the product is fired.

The collapsible, void-containing granules or particles 3 may consist of expanded slate or micaceous mineral, suitably exfoliated vermiculite or biotite. Expanded vermiculite which is now available commercially under the name .Zonolite is particularly satisfactory.

Such particles contain spaced elements orlaminae 4, defining thin spaces or voids 5 that communicate with outer surfaces of the particles.

In the modification shown in Fig. 3,'there are pores or channels 6 that connect the several particles in such manner as to provide intercommunication between them and an outer surface of the article, and, therefore, permeability to incident sound.

A method of making the products of the present invention is illustrated in the following examples:

Example I In this example and elsewhere in the specification and claims, proportions are expressed as parts by weight.

Forty to 60, suitably 50 parts, of granular exfoliated vermiculite is wetted with water, say

with approximately 250 parts water. The water is allowed to stand in contact with the particles of expanded vermiculite until a large proportion of the water is absorbed, as filling material, into the spaces or voids within the particles. The wetted particles are then mixed with a composition comprising Portland cement, asbestos fibers, and water, say with 20 to 35 parts, suitably 25 parts of Portland cement, 10 to 25 parts, suitably 20 parts of asbestos fibers, and sufiicient water to. make the whole mixture into a deformable paste or slurry. The proportion of water used may be approximately 125 parts to each 45 parts of Portland cement and asbestos fibers, in addition to the water originally added to the exfoliated mineral.

The wet slurry is shaped, compressed with preservation of the voids within the particles of exfoliated vermiculite, and then hardened. Thus, the slurry may be placed in a mold with a filtering bottom and compressed and shaped at a moderate pressure, such as 30 pounds per square inch. During this compression, the binder composition of cement and asbestos fibers is compressed and densified and much water is removed from the mass, by filtration through the mass and through the filtering bottom of the mold.

The presence of water originally filled into voids in the particles of exfoliated vermiculite has desirable effects. The water filling minimizes the collapsing of the otherwise collapsible particles and also minimizes the forcing of the water-insoluble binder composition under pressure into the voids. These effects are retained to a certain extent at higher pressure. Pressure up to 500 pounds per square inch or more may be used without complete collapsing of the exfoliated vermiculite particles prefilled with a suitable liquid filling material.

The compressed article is removed from the mold and allowed to harden. It is also dried, as at ordinary temperatures or at a moderately elevated temperature adapted to permit the setting and hardening of the Portland cement. Usually the drying may be accomplished during the hardening of the cement, as by allowing the shaped mass to stand exposed to air on all sides.

The hardened and dried product may be trimmed to size desired. It is rigid, light-weight, and suitable for use as thermal insulating material in building structures or the like.

In this example water is a non-solvent for the particles into whose voids it is filled. The binder composition, being also insoluble in the water, is not drawn into the voids, by the water, to a large extent.

Example II The procedure of Example I is followed, with the exception that there is provided initially, in the voids in the particles of exfoliated vermiculite, a viscous filling material that is difiiculty removable by pressure applied to the particles. The filling material may consist of a viscous, aqueous composition, such as one comprising starch or gelatin dispersed in water.

For example, granules of expanded vermiculite are soaked with 4 times their weight of a hot dispersion of starch in water, say in the proportion of 2 to 10 parts of starch to 100 parts of water. The vermiculite absorbs the hot, mobile composition. After the absorption has progressed adequately, say for 10 minutes, the excess or unabsorbed starch mixture is drained from the particles of vermiculite. The treated vermiculite is allowed to cool approximately to at- .mospheric temperature, so that the starch composition within the voids becomes very viscous or gelatinous, say, a stiff paste.

The thus filled granules are mixed with binder composition and treated as described under Example I. On compression, the starch composition within the spaces is not squeezed from the voids in the particles as readily as is pure water. The resulting compressed and hardened article is of very low density, and useful as thermal insulation.

Another viscous filling material that may be used is an aqueous mixture containing a precipitated gelatinous, inorganic material. For example, expanded vermiculite may be soaked in a water solution of a salt, such as magnesium or aluminum sulfate, and then placed in a solution of an alkali, such as ammonium hydroxide, whereby precipitation of gelatinous material within the vermiculite; and an increase in viscosity of the composition are obtained.

When the article so made dries, for instance, as described under Example I, water evaporates from the viscous filling. The small proportion of non-volatile content of the filler that remains is far from adequate in amount to fill the voids in the vermiculite. The voids, therefore, reappear during the drying.

Example III The procedure of Example I is followed, with the exception that the void-containing particles are prefilled with amaterial that is insoluble in the liquid in the binder composition and adapted to be removed by volatilization during the hardening of the complete mixture, suitably at a temperature below the boiling point of water, to

provide channels or pores connecting the various particles with each other and with an outer surface of the product. Thus, the particles of expanded vermiculite may be soaked in 3 times their weight of low boiling gasoline or benzol. The particles with the voids thus filled are made into a mixture with an aqueous binder composition, and the mixture is shaped, compressed and hardened, as described in Example I.

During hardening, the volatile water-insoluble filling within the voids of the particles embedded in the binder composition is caused to escape and to provide intercommunicating channels between the various particles and an outer surface of the product.

The hardening and removal of the water-insoluble filling material may be effected simultaneously, at an elevated temperature, say in saturated steam at 100 pounds pressure, in order to remove the volatile filler material rapidly and cause the production of larger channels or pores than would be produced if the filler were removed slowly. Finally, the product is dried.

Escample IV There is made a mixture of Portland cement. asbestos fibers, and water, in the form of a freely flowing slurry. The proportion of cement to asbestos may be one that is used in making cement-asbestos slabs at present in wide commercial use, say, equal proportions by weight. The slurry is placed in a mold provided with removable side walls, a bottom, and a filtering die plate attached to the ram of a hydraulic press. The die plate may be perforated and covered with a fabric, to permit filtration of water under pressure.

The slurry is formed into a layer, as with a rake, and then compressed by means of the filtering die plate, first, moderately, and, finally, strongly, as, for example, at approximately 2,000 pounds per square inch. This operation compresses and densifies the layer into a sheet adapted to be very strong after the cement therein is hardened. During this compression, water is removed by filtration from the material and through the die plate.

The die plate is then withdrawn, and a composition of the kind described under Example I and containing pressure-collapsible particles of exfoliated vermiculite or the like is placed over the compressed and densified sheet initially formed in the mold. The newly added composition is then leveled roughly into a layer, as by raking followed by smoothing with a plate, such as the die plate, at a few pounds pressure. Over this leveled composition there is then spread a layer of material of composition like that in the initial layer, namely, a composition consisting of Portland cement, asbestos fibers, and water. The

. whole is then compressed by means of the filtering die plate for a short time, at moderate pressure only, say; at 30 to 100 pounds per square inch. This unites integrally the several layers, removes some of the excess water from the two layers last added, and shapes the mixture into the form of a composited slab.

The die plate is then withdrawn, as are also the sides of the mold. The composited slab is then allowed to set and harden, suitably after removal from the bottom of the mold. If desired, the cement may be hardened at an elevated temperature, say, in saturated steam at super-atmospheric pressure. Finally, the product is dried.

The resulting laminated article comprises a light-weight core material I (Fig. 2), a dense facing unit 8 of great strength, and an oppositely disposed facing unit 9 of lesser density and strength.

A use for such a product is in a load bearing structure, such as in a floor of abuilding or in a roof that may be loaded occasionally.

When the product in the form of a slab, that may be 3 x 11 feet or of other large dimension, is used as a floor panel, for example, the slab may be so installed that the facing layer of greater density and strength is on the under side, that is, on the side of the slab that is tensed or subjected to tension when the slab is loaded and, consequently, somewhat flexed. In such a case, the weaker, less highly densified facing on the opposite face of the unit is slightly compressed under load. In this manner there is obtained a structural unit of great strength where needed, without the necessity of subjecting the core material containing collapsible particles to injuriously high pressures, during fabrication, that might adversely affect the lightness or insulating power of the unit. It will be understood that compressed and densifled and hardened cement and asbestos boards are several times as strong under compression as under tension. In some cases, the compression strength may be 'as much as 7 to 10 times the tensile strength. A great advantage is obtained, therefore, in having the stronger facing layer on the face opposite that to which the load is applied.

Various thicknesses of the composite may be made. Thus, there may be used to advantage a core 1 to 4 inches, say 1.5 to 2 inches, thick and facing units each to' inch thick. For some purposes, only one facing unit, either a highly densified one or a less dense one, may be used.

The whole may be sealed against penetration by water, by means of a sealing coat of waterimpermeable material such as an oil varnish or asphalt.

In the above examples, other binder compositions of the type described may be substituted for the Portland cement and asbestos compositions.

Particles of expanded vermiculite or the like of various sizes may be used, as, for example, particles that pass through a 2-mesh screen and are retained on a 30-mesh screen. Particles that are principally between 4-mesh and 10-mesh in size are preferred for many purposes.

It will be understood that the details that have been given are for the purpose of illustration and not restriction, and many variations therefrom may be made without departing from the spirit and scope of the invention.

What I claim is:

1. In making an article of manufacture including a binder and collapsible particles containing voids, the method which comprises providing the voids in the said particles with a filling of a warm, mobile mixture of starch and water, allowing the particles with the filled voids to cool to convertthe mobile liquid to a stiff paste, forming a mixture of a binder composition with the thus filled particles, shaping and compressing the mixture, and then hardening and drying the shaped product.

2. In making an article of manufacture including a binder and collapsible particles containing voids, the method which comprises providing the voids in the said particles with a filling of a mobile liquid composition, subjecting the composition to treatment to cause precipitation therein, forming a mixture of a binder composition with the thus treated particles, shaping and compressing the mixture, and then hardening and drying the shaped product.

3. In making an article of manufacture including a binder and collapsible particles containing voids, the method which comprises providing the voids in the said particles with a volatile,

water-insoluble liquid adapted to be volatilized at a temperature below the boiling point of water, forming a mixture of an aqueous binder composition with the particles with the filled voids, shaping the mixture, and subjecting the shaped mixture to treatment to harden it and to cause the removal of the said volatile liquid.

4. In making a light-weight article including a binder composition and collapsible particles of an exfoliated micaceous mineral provided with voids adapted originally to be penetrated to a substantial extent by the binder, the method which comprises pre-filling the said voids with a composition comprising a large proportion of a volatile liquid, forming a mixture of the thus filled particles with a binder composition including Portland cement, asbestos fibres intimately mixed therewith, and water, shaping and strongly compressing the resulting product and removing excess of water therefrom by filtration, and hardening the shaped article.

- WILLIAM R. SEIGLE.

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