US2294247A - Surface covering - Google Patents

Description

Aug; 25, 1942. w, $M|TH 2,294,247

SURFACE COVERING Filed May 5, 1941 H' mx Patented Aug. 25, 1942 UNITED STATES PATENT OFFlCE 4 Claims.

This invention relates to surface covering and has particular application as wearing surfaces for floors, walls, ceilings, for either indoor or outdoor use.

With the exception of monolithic concrete construction, it is customary and necessary to provide a covering layer or surface for taking up wear and weathering and for decoration in many instances. Where the wearable surface is supported throughout its entire extent in face to face relationship with a base surface, as composition fiooring over wood or concrete surfaces, serious problems arise. The most troublesome problem involves the difference in thermal expansion between the covering layer and the base subsurface such as' wood, concrete, steel, etc. If any difference in thermal response exists-and this is practically impossible to avoid--a cleavage between the two materials gradually takes place.

Thus, surface coverings are generally divided into two groups. One general group comprises prefabricated material cemented in place. Thus, so-called parquette flooring consists of solid blocks of wood, stone, etc. cemented in place. For walls and ceilings, tile is an example of solid sheet material cemented in place. The other group consists of cementitious material formed in situ, such as plaster walls on a backing of lath, or terrazzo flooring.

Th'e first group of coverings requires intimate surface contact between the dissimilar areas. Thus, if wooden blocks are cemented over a concrete or wooden sub-floor, it is necessary to have a strong cement joint. For good gripping, rough surfacesare necessary. On the other hand, extreme roughness creates a weak section since the bonding material is relied upon to fill up irregularities. In any event, repeated relative expansion and contraction creates grinding forces at the cemented junction which destroy the bond. The net result is that such surface coverings work loose from their foundations. Cracks and fissures result and finally, the surface layer is destroyed by the grinding of the loose parts.

The second group, of which terrazzo is an example, ultimately ends its useful life in much the same manner. Because the covering is formed in situ, the conformation between the two surfaces may be quite precise. However, there is no real bonding between the two final solid materials; 1. e., the supporting surface and the terrazzo layer. Thus there is no real monolithic construction. Hence, the terrazzo covering is merely a cast layer which is separable and separate from the supporting layer. For this reason, a terrazzo floor must be quite thick since its weight retains it in place and its thickness provides strength against cracking.

For walls, plaster is formed in situ and as is well-known may crack away readily. When it does crack, large pieces come off. The same is true of terrazzo. This action indicates that the cohesive strength of the surface layer particles for each other is greater than the adhesive strength of the surface layer to the support material.

This invention provides a cementitious surface layer formed in situ of any suitable material and thickness which layer is tightly but flexibly bonded to the underlying supporting or base material. The intimate bonding involves the formation of air tight joints so that suction probably has a substantial effect. By forming the material in situ, no preparation of the base surface is necessary. By bonding the formed material to the base layer throughout its entire extent, no cleavage or lamination is possible. Even if cracks are present, the loss of suction is localized to the crack. In fact, I have observed that the bonding force is so great, compared to the strength of the surface-covering material that it is practically impossible for large surface layers to be pulled off. The bonding junction is elastic so that differences in expansion of the materials will not destroy the bond.

In general, this invention contemplates the use of a rubber film as a bonding material between a suitable base material and a covering material formed in situ thereover. The thickness of the covering material may vary from a thin layer to a flooring surface having a thickness of as much as an inch or more. There is no upper limit to the thickness. Obviously, the thinner the entire covering material, the less the cost; assuming, of course, satisfactory life and characteristics. Thus, for flooring, a thickness of about inch is suflicient to withstand heavy duty,

The rubber may either be dissolved in a' suitable solvent as ether or may be in the form of a latex emulsion. The latter is preferred. The latex may be obtained in the open market under various trade names and having varying compositions. Fundamentally, the latex used by me consists of an emulsion of the rubber sap in a suitable vehicle, usually water. Anti-coagulants, usually alkaline such as ammonia, are usually provided to stabilize the suspension.

The covering material may be any magnesite base cementitious compounds formed in situ well known in the art and preferably comprises the mixture hereinafter set forth in detail. The magnesite base is preferred because of its acid reaction and works particularly well with latex. When used with dissolved rubber, care must be exercised to have the solvent evaporated substantially before the covering layer is applied.

Referring now to the drawing, the single figure shows a covering surface embodying the invention, with part of the covering surface broken awa A base surface Ill may be of any suitable material, such as wood, steel, concrete, stonework or brickwork. The base surface is preferably cleaned as with soap and water. Over the base surface, a layer. ll of latex is applied as a bonding interliner. The latex may be sprayed, brushed, flowed or smeared to cover the entire base surface. The coating may be any desired thickness within limits. Excessive latex will form a rubber film of too great thickness. The ordinary application of latex to cover the entire base surface, however, will automatically provide a satisfactory film. As applied, the latex is milky and forms a milky layer. Within about an hour,.under ordinary conditions of room temperature, the latex dries to form a transparent tough fihn of rubber. covering the base surface.

The covering material may be applied at any time after the latex is applied. Preferably under normal room conditions between 30 minutes to anhour is permitted to elapse before the covering material is applied. However, I have successfully cut down this period to practically nothing and have also extended the period to beyond an hour. Best results are obtained, however, by applying the covering material right after the latex has lost its milky appearance and becomes transparent.

Over latex film II a covering material i2 is formed in s'itu. As previously pointed out, this material is preferably a magnesite base composition and may be of any desired thickness. In the practice of my invention, I have successfully used the following mixture. To magnesite, preferably in finely divided form, there is mixed 2% by weight of tri-basic calcium .phosphate (tri-calcium orthcphosphate) also in finely divided form. These materials may be of 200 mesh, for example, although this is not essential. To this mix is added magnesium chloride. The amount of magnesium chloride is such that when the entire mix, including filler, aggregate, etc., is made up with water to form a paste, the solution of magnesium chloride in that quantity of water has a specific gravity of about 20 Baum.

It is believed that an oxy-chloride complex compound is formed. As a rule, the quantity of magnesium chloride in the above example, represents near the top range used generally by the industry. Due to heat of solution of the magnesium chloride, an excessive quantity had resulted in spoiling the entire construction. However I have successfully increased the amount of magnesium chloride to the point where a 40 Baum reading resulted. It is therefore to be understood that the proportion of magnesium chloride may be varied over the limits indicated by the two specific gravity ranges. Increasing the magnesium chloride results in a harder layer.

' As is well-known, the filler and aggregate may vary up to about 70% by volume of the entire covering material and the nature and amount of aggregate is an important factor in determin- 7 6 ing the water content. The entire mix must be pasty to be flowed over the latex and may be smoothed down by a trowel or other instrument. The consistency of the mix is well-known to workmen andmay be varied to suit individual tastes. The filler and aggregate may be crushed rock, mineral compounds, sand, powdered or crushed glass, all well-known in the art. Titanium oxide may be added for carrying any desired colors or pigments. This, of course, is wellknown in the art.

The above covering material will generally set in about four to six hours under ordinary room conditions and may then be sanded or ground if desired.

'A surface formed as above has been found to adhere tenaciously to any base surface such as steel or iron, wood, concrete, asphalt or the like. Unless the latex is peeled away from the base surface by a knife or sharp instrument, the bond between the base surface and covering material is strong enough to withstand all normal conditions of use to which any floor may be exposed. This includes factory or heavy duty use where heavy loads are wheeled, dropping of heavy hard objects such as hammers or the like and includes all temperature changes from winter cold to summer heat. The thickness of the covering layer if used as a floor will vary with load. However, for store use, as little as t; inch thickness may be used. If a solid, continuous smooth base layer is provided, as concrete, a thin layer even for heavy factory use may be suflicient.

A covering material of the above mixture has been found particularly effective under highly variable moisture conditions. Thus, in many instances, the tendency of magnesite coverings to bloom or eflloresce has militated against it. The material described herein will merely bloom initially in the setting and thereafter will be unaffected. The above material may be used for wall or ceiling coverings, both inside and outside, and when used in this manner need not be thick. Various colors and decorative eifects may be obtained.

Where dissolved rubber is used instead of latex, the same procedure may be used except that the rubber solvent should be evaporated prior to the application of-cement. With this form of rubber, a cement having an acid reaction, such as magnesite base, is preferred.

It is understood that in all cases, the base surface may be concrete or Portland cement. Since this base surface has set to form generally insoluble compounds, there will be no trouble in applying rubber in emulsion form. It is also possible to apply cementitious materials having a basic reaction over a rubber interliner formed from evaporation of a rubber solvent. However, as previously pointed out, the solvent must be substantially completely evaporated prior to application of outer material.

It is understood also that prior art magnesite mixtures may be used in which case the calcium phosphate is generally omitted. While the 2% proportion in the example yields excellent results, the proportion may be varied.

What is claimed is:

1. The combination of a substantially continuous base supporting surface, an outer magnesium oxychloride cementitious wearing layer having an acid reaction and a bonding layer of latex between the two, said entire construction being characterised by great strength and being free of deleterious effects due to differences in thermal expansion. I

2. The method of providing a. strong durable wearing layer in a building construction or the like, said method comprising applying a latex emulsion to a substantially continuous base surface and then disposing a plastic mass of magnesium oxychloride cementitious material over said latex, said mass hardening to form a strong wearing layer.

3. The method of providing a strong durable wearing layer which comprises forming a latex layer over a base surface, and disposing over the latex a plastic mass of magnesium oxychloride cementitious material, said mass hardening to form a strong wearing surface.

4. The method of claim 3 wherein said plastic mass includes magnesite, tri-calcium phosphate and magnesium chloride.

WALTER J. SMITH.

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