Compositions: coating or plastic – Coating or plastic compositions – Metal-depositing composition or substrate-sensitizing...
Patent
1986-11-12
1990-03-06
Bell, Mark L.
Compositions: coating or plastic
Coating or plastic compositions
Metal-depositing composition or substrate-sensitizing...
106 74, 10628714, C09D 102
Patent
active
049062972
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to silicate-bonded silica materials, and more particularly to structural and masonry units and building components produced from such materials including wall, floor, roof and ceiling tiles, paving materials and special plastering (in situ and masonry unit application) compounds.
BACKGROUND ART
"Artificial" and "reconstituted" stone has long been made by man, many buildings dating from the Imperial Rome epoch being mainly constructed of a kind of concrete which was faced with marble. However, in this latter half of the twentieth century, concrete has proved to be less attractive as a building material because of the high atmospheric pollution obtaining in today's towns and cities, which conditions can destroy concrete, and even such natural materials as marble and sandstone, in the course of time.
DISCLOSURE OF THE INVENTION
It is thus an object of the present invention to overcome the above and other disadvantages of conventional building materials by the provision of "artificial stone" which is extremely resistant to acidic and other atmospheric pollutants, and which has the physical strength and other mechanical characteristics to enable it to be used in building construction.
It is a further object of the present invention to utilise, for the above purpose, one of the Earth's most abundant elements, that is to say, silicon, to produce silicate-bonded silica materials.
According to one aspect of the present invention there is provided a moldable composition comprising a particulate material, including sand, an alkali metal silicate, and optionally an alkyl silicate and/or an ester catalyst or other precipitant. The invention also provides articles of manufacture molded from such compositions and to a process for producing molded articles.
The sand may be any suitable readily available silica sand or mixtures of sand. A preferred silica sand is a pure white silica sand, very large deposits of which have been ascertained to exist, particularly in Australia. One such deposit which has been identified is of very high purity, having a Fe.sub.2 O.sub.3 content of less than 0.008%; the virtually iron-free nature of this raw material being of great natural advantage in avoidance of discolouration, streaking, etc, due to weathering; and producing pristine white units, or combined with additives e.g. pigments, to give subtle shading effects. However, other sands of various colours can also be employed to give different shades of colour or different surface effects to the final moulded product.
In some embodiment of the invention, a predetermined percentage of silica sand is firstly ground to a smaller particle size (e.g. 100-300 mesh), and in some cases finely comminuted silica "flour" is employed in the sand mix. Usually, no more than about 5-20% by weight of the fine sand is used in the sand mix. This flour tends to prevent any voids or occlusions occurring in the finished blocks, and may also reduce the quantity of binder required in the manufacturing process. It has been found that when no fine sand is included in the sand mix the surface of the moulded produce has a rough texture. However, incorporation of even 10% finer silica material is sufficient to substantially eliminate most of this surface roughness. Using an alkyl silicate and an alkali metal silicate also gives quite a smooth surface texture.
The alkali metal silicate is normally selected from sodium silicate or potassium silicate, preferably the latter (preferred SiO.sub.2 :K.sub.2 O ratio in the range of 1.7:1 to 1.4:1). In some cases, it may be of advantage to use mixtures of sodium silicate and potassium silicate.
Sodium silicate has for many years been extensively used in the field of metal-founding as a binder. Spray-on protective coatings have also been proposed, composed of curable silicate compositions containing a phosphate hardener coated with a reaction product of a metal aluminate and/or metal borate.
It is envisaged, however, that a sodium silicate binder may lack the necessary strength ch
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Barron Alexis
Bell Mark L.
Group Karl
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