Compositions: coating or plastic – Coating or plastic compositions – Alkali metal silicate containing
Reexamination Certificate
2000-02-24
2002-10-15
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Alkali metal silicate containing
Reexamination Certificate
active
06464774
ABSTRACT:
BACKGROUND OF THE INVENTION
It has long been known to use sodium silicate (waterglass) as a concrete hardner, where for example, it has been traditional to use a low viscosity solution of sodium silicate which penetrates the concrete surface, and where it reacts with the concrete to produce insoluble calcium silicate. Although such treatments are useful in providing improved protection (for example against oil or acid and/or to improve fire resistance) and also wear resistance of the surface of the concrete, these treatments are basically useful only as clear treatments, since it is impossible to achieve any real opacity using such low viscosity material. This follows because the pigment molecules are larger than the sodium silicate molecules, and they tend not to be absorbed into the concrete and therefore remain on the surface of the concrete, left behind by the absorbing silicate. Thus any pigment that is utilised in such treatments in any attempt to colour the concrete, tends to be easily abraded or to be otherwise removed easily since there is no effective bonding occurring between the concrete and the pigment or with any intermediate bonding material.
Although attempts have been made to produce a surface coating incorporating sodium silicate, (because of its properties noted above and its relative cheapness), these have failed to date largely because sodium silicate itself is highly water sensitive and unless it is converted, say, to calcium silicate in traditional low viscosity treatments as described above, it will basically breakdown as a surface treatment, since it will degrade on exposure to water.
Although there are several known reactants available which will cause sodium silicate to harden, they each have proved to be ineffectual especially with regard to their slow reaction time, or to using a second hardner coat in case of fast reaction time. And consequently have limitations when considering sodium silicate as a surface treatment.
Also, it has long been known to use lithium silicate as a concrete hardner for example, it has been traditional to use a low viscosity solution of lithium silicate too. Attempts to use a high viscosity solution of lithium silicate were failed because of crack with shrinkage of coated film itself.
Furthermore, single coating formulation incorporating much filler and pigment has not been used.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a decorative wear resistant protective surface coating for concrete, timber or steel, based on lithium silicate and sodium silicate formulation which overcomes some or all of the foregoing disadvantages associated with either traditional low viscosity treatments for concrete or ameliorates the effects of previous attempts at producing an opaque surface coating.
It is an another object of the invention to provide a decorative wear resistant protective surface coating for concrete, timber or steel, based on a single formulation which means a lithium silicate and sodium silicate formulation incorporating filler and pigment, avoiding a troublesome use of a second formulation for hardner.
It is an another object of the invention to provide a decorative wear resistant protective surface coating for concrete, timber or steel, based on a single formulation of which dried coat is hardened with flame of gases such as town or propane gas directly for a veryshort time.
At the very least, the invention provides an alternate treatment for protecting a concrete or other surfaces.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, there is provided a decorative wear resistant lithium silicate and sodium silicate formulation incorporating filler and pigment.
This formulation comprises a special ratio of lithium silicate and sodium silicate mixture which is diluted or not diluted with small amount of water to keep a high viscosity, and a non reactive inert filler and a pigment colouring matter.
In this formulation a binder for filler, for example, an emulsion of acryl-stylene co-polymer can be used.
The special ratio of lithium silicate, sodium silicate and water is shown in the followings,
(1) lithium silicate: (silica/lithium oxide molar ratio is 3.5 and specific weight 1.20 at 20° C.)
50 to 90 parts
(2) sodium silicate: (No. 3 sodium silicate regulated in Japanese Industrial Standard code number K-1408)
10 to 30 parts
(3) water:
0 to 20 parts
Whereas typical low viscosity solutions of sodium silicate utilise a ratio of about 1 part sodium silicate to 4 parts water, it is preferred that the solution for the present invention have a ratio of about 4 to 5 parts lithium silicate and sodium silicate to 1 part water, in order to maximise viscosity and thereby, decrease penetration of the coat into the concrete or other substrate.
In the present invention, effects of water is that water beyond 20 parts causes less wear resistant and less water resistant properties.
In the present invention, effect of lithium silicate ratio to sodium silicate is that high ratio of lithium silicate causes good water resistant property but causes shrinkage of hardened coat, and high ratio of sodium silicate causes swelling or bubbling of coat during heat treatment with flame of gases, and causes less water resistance.
The specific ratio of lithium silicate, sodium silicate and water above described is determined under consideration of these effects and defects both.
Examples of a non reactive or inert filler are powdered alumina or powdered quartz, while any suitable pigment of metal oxides such as ferric oxide, chromic oxide, titanium oxide and so on, can be utilised.
The preferable amount of filler is 20 to 65 parts against 100 parts of lithium silicate and sodium silicate solution.
The preferable amount of pigment is 5 to 20 parts against 100 parts of lithium silicate and sodium silicate solution.
The coat may be applied by any suitable means such as roller, brush or spray, once or twice on a cleaned surface of concrete, timber or steel.
The coat will be touch dry in approximately 10 to 30 minutes and the coat is treated with flame of gases directly for 1 second to 3 minutes. Thus, the coat is fully reacted very fast and shows excellent physical and chemical properties.
It is an obvious that the time of the heat treatment depends on the temperature of the flame, the size of the flame and contacting portion of the flame on a coat.
The flame temperature of town gas or propane gas is about 800 to 1100° C.
The crystal change of lithium silicate gels is known to occur at 348° C. and strongly absorbed water in lithium silicate gels is known to lose under 400° C., the temperature of the baked coat may be estimated around at 400 to 450° C.
When a substrate is concrete, long time of this treatment should be avoided, because crystal water of the concrete may be started to lose from at 450° C. and structures of the concrete will be damaged.
Actually, the treatment by propane gas flame is sufficient for several seconds to 10 seconds as is shown in the Examples.
Accordingly, the treatment by propane gas flame on a timber can be done without any damage to it with using the formulation of the present invention.
Thus, an extremely durable, decorative and wear resistant coat can be easily made.
Furthermore, on the next day of the coating works using a formulation of the invention, the coated construction such as concrete parking lots or concrete floor of a warehouse can be used, and an economical merits can be greately enjoyed.
In case of no heat treatment to the coat, there occurs crack and shrinkage of the coat, and also physical properties such as wear resistance and water resistance are much inferior to those of the heat treated coat.
Therefore, a formulation of the invention can be applied to make mortar wall, mortar brick, timber products and etc. decorative and wear resistant, furthermore, to make parking lots, concrete floors of factories, warehouses and etc. decorative and wear resistant. Also, a formulation of the invention can be applied to make concrete floors of foods factories durable a
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