Field of invention:
The present invention is related to a chemical composition used in crystallization of stones
containing calcium carbonate.
Prior art:
Marble and similar calcium carbonate based stones installed in buildings require regular
polishing and surfacing to maintain gloss on the surface. Various methods and technologies have
been developed in the past to achieve and maintain the polished surface. These technologies and
processes include buffing the marble surface with abrasives, acids, coating with suitable resins
and crystallization.
Various abrasives and polishes that produce acceptable degree of gloss are composed of tin
oxide, alumina, silica, zirconium oxide, cerium oxide, red oxide, chromium oxide etc in various
proportions. Also these oxides are used along with some acids, salts and other chemicals to
improve gloss and speed up the polishing rate. These include oxalic acid, citric, stearic acid,
sodium bi sulphate, ammonium bi fluoride, ammonium fluoride, zinc sulfate, zinc chloride,
potassium oxalate, barium salts etc.
Commercial products based on such formulations fail to achieve high degree of gloss compared
to crystallization and are also time consuming. Since the rate of polishing is very slow these old
techniques are getting obsolete.
Another way of polishing stone is by coating with suitable resins such as acrylic and epoxy. The
marble surfaced is honed and coated with suitable resin. After the resin has dried, the surface is
polished by abrasives such as diamond tools and powders of oxides mentioned above. This
process is time consuming and not cost efficient and the disadvantage of using resins is that
regular surface maintenance is not possible when the surface looses shine after usage for some
period. And the surface needs to be honed again with suitable grits and tools.
The latest and most efficient way for polishing and maintaining glossy marble is crystallization.
Crystallization is a process in which crystallizing composition is buffed with or without the steel
wool on the surface of the calcareous stones and the calcium carbonate of the stone is converted
to calcium silicofluoride. The surface of the stone which is converted to calcium silicofluoride is
hard and glossy. These crystallizing compositions are based on magnesium and zinc
silicofluorides and other metallic silicofluorides. Crystallization is cheaper, one step procedure
and high degree of gloss can be achieved and is easy to maintain.
Various crystallization compositions have been developed in the past that produce high gloss on
the surface of the stones especially marble stone surface. Some of these compositions are
.effective but there are some disadvantages associated with their use. The proposed composition
overcomes these disadvantages.
Disadvantages of the prior art:
Various compositions have been developed in the past to crystallize the calcareous stone. All the
formulations based on metallic silicofluorides such as magnesium silicofluoride also called
magnesium hexafluorosilicate and zinc silicofluoride also called zinc hexafluorosilicate and
other metallic silicofluorides.
JHON H. THROWER in U.S patent no 4756766 dated July 12, 1988 gives a composition to
crystallize the stone surface especially marble. This composition includes a mixture of zinc and
magnesium hexafluorosilicate dissolved in water and acidified with acid. The composition is
buffed on the surface of the stone with steel wool to achieve gloss.
U.S patent no 5830536 proposes a cream to crystallize the stone surface. This composition
includes magnesium silicofluoride, fatty acid mixture, and alumina as abrasive, tartaric acid,
oleic acid, magnesium hydroxide, calcium chloride, phosphoric acid, surfactant and other minor
ingredients. The cream is buffed on the surface to achieve gloss.
U.S patent no 5490883 gives a composition containing magnesium silicofluoride, oxalic acid,
phosphoric acid and water to be used on stone surface with steel wool pad.
U.S patent no 4738876 proposes a two step polishing of stone surface. In first step stone surface
is primed with solution containing oxalic acid, stannic chloride, methylated spirits, surfactant and
water. Then in the second step the surface is crystallized with synthetic pad with solution
containing zinc silicofluoride, magnesium citrate, oxalic acid and water.
All such formulations are available in the market under various trade names. All these
formulations are based on magnesium and zinc silicofluoride in various proportions.
Crystallization is done by the acidified metallic silicofluorides such as magnesium and zinc
silicofluoride. The acids normally include oxalic acid, fatty acids, phosphoric acid, acid mixtures
and other organic and inorganic acids in various proportions and ratios.
Various other chemicals are added to facilitate the buffing action. These include wax, gum,
surfactants and other facilitating agents etc.
The compositions are sprayed on the stone surface, and buffed to dryness to achieve final gloss.
During crystallization process the calcium carbonate in the stone gets converted to calcium
silicofluoride which is hard and glossy by nature. And to achieve this glossy surface, the surface
of calcareous stone is buffed with acidified metallic silicofluorides as mentioned above.
V
.During this action the metallic ions of metallic silicofluorides remains on the crystallized surface
such as zinc and magnesium from their respective silicofluorides. And due to heat generated by"
buffing action these metallic ions get oxidized and get converted to their respective oxides,
hydroxides and carbonates such as magnesium and zinc hydroxides and oxides and their
carbonates respectively. These metallic oxides, hydroxides and carbonates on the crystallized
surface get attached in the crystallized layer and produces dullness on the surface. The surface
becomes dull in appearance and gloss achieved is not maximum. Also usage of such
compositions creates a need to again buff the surface of the stone with some suitable soft pads to
remove the buildup of these metallic compounds with water and surfactants which makes the
process time consuming and laborious.
The disadvantages of using prior art compositions can be summed up as:
1) Less gloss than what is expected.
2) Re buffing of floor is laborious and time consuming.
Object of the invention:
The object of the invention is to provide a composition which overcomes the disadvantages of
using prior art compositions by the usage of ammonium silicofluoride as a crystallizer which is a
non metallic silicofluoride and ammonium acetate as a gloss enhancer in the same composition.
The proposed composition is used in same manner as earlier compositions were used. Means by
spraying the composition on the floor, buffing the surface with steel wool pad up to dryness to
achieve high gloss
The proposed composition provides excellent gloss on the surface in one step and no second step
of rebuffing is required to remove magnesium and zinc and other metallic compounds formed on
the surface during crystallization and hence is very effective, time and manpower saving.
The proposed chemical composition is chemically stable and does not damage the surface of
stone.
The main object of the invention is to replace metallic silicofluorides with ammonium
silicofluoride which is non metallic so that no metallic compounds are left on the surface after
the completion of the crystallization. The ammonium ion of silicofluoride breaks and nitrogen
gets released to atmosphere which is non dangerous.
Further, the invention also proposes ammonium acetate as the gloss enhancer used in the same
composition which is found to be very effective.
Detailed description of the invention:
To overcome the disadvantages stated above intense research and testing was done on various
marbles available and it was found that ammonium silicofluoride can crystallize the marble
surface leaving no residue behind and the gloss can further be enhanced by using ammonium
acetate in the same composition.
The stone crystallizing composition according to present invention is mainly composed of four
ingredients:
1) Non metallic silicofluoride i.e. ammonium silicofluoride also called ammonium
hexafluorosilicate
2) An acid to initiate the reaction
3) Gloss enhancer
4) Water
These four ingredients are the essential ingredients of the proposed composition.
Ammonium silicofluoride can be present in the composition from 0.1 to 25%. The higher the
percentage faster is the crystallization and higher is the gloss achieved. However, only up to 20%
is soluble in the water. Solvents that can increase the solubility of ammonium silicofluoride can
be added according to the need. The preferable amount of ammonium silicofluoride is 10-20%.
The second ingredient is an acid. Among the organic acids oxalic acid, stearic acid, palmitic
acid, citric acid, tartaric acid, oleic acid, fatty acid mixture, acetic acid, formic acid, propanoic
acid etc are preferable. Among the inorganic acids nitric acid, hydrochloric acid, phosphoric
acid, sulfuric acid, hydrofluoric acid can also be used. Various mixtures and combinations of
inorganic and organic acids can be used. The main purpose of the acid is just to initiate the
reaction. The percentage of the acid depends upon the hydrogen ions it liberates and the rate at
which it liberates. This percentage depends on the type of acid being used and it should be
adjusted accordingly. For example in many patents which use metallic silicofluorides 0.1% to
10% acids are preferred. Such patents are US patent no 5830536, US patent no 5490883 and
many others. Similar percentages are applicable here also. The preferable percentage of acid
according to current invention is 0.5-6%
The acid reacts with the steel wool or mild steel wool and produces hydrogen ions which then
initiate the reaction and calcium reacts with the silicofluoride ions.
Third ingredient of the present invention is ammonium acetate which acts as a gloss enhancer.
This ingredient may or may not be included in the composition but from the coming examples it
will be clear that ammonium acetate improves the gloss of the surface compared to the
composition which does not include ammonium acetate and based only on ammonium
silicofluoride.
Various tests were conducted to further improve the gloss of the marble stone surface with
different materials and it was found that ammonium acetate present in the composition increases
the gloss of the surface. However the reason of this effect is unknown. The amount of
Ammonium acetate in the composition is dependent on the amount of ammonium silicofluoride
in the composition. In order to achieve best results the molar ratio of ammonium silicofluoride to
ammonium acetate should not be less than 0.2 and should not be greater than 10. The preferable
ratio is 3 to 6.
The fourth ingredient is water. The percentage of water depends upon the type of acid used
which affect the solubility. All the ingredients should be fully miscible in water. Amount of
water is variable but normally its 50-97%. The compositions will be clear according to the
examples described.
There are also some other ingredients that may be included in the composition in very minor
quantities which do not adversely affect the gloss of stone surface. These ingredients may
include Surfactants, dispersing agents, wax, and fragrance, thickening agents, solvents, dust
absorbents and suitable color enhancers. These ingredients should not react with the crystallizer
and alter its chemical composition as it can adversely affect the gloss of the surface.
The following example illustrates certain specific embodiments of this invention; however these
examples are for illustrative purposes only and are not to be construed as limitations upon the
invention.
Following ingredients were mixed in the reactor at room temperature and pressure until all the
ingredients dissolved and mixed homogeneously to make crystallization composition.
Example Al
TABLE A1
Ingredients percentages
1) Ammonium silicofluoride 12%
2) Mixture of organic and inorganic acids 3%
3) Ammonium acetate 3%
4) Wax dispersion 0.5%
5) Organic solvent 5%
6) Surfactant 0.1%
7) Fragrance 0.1%
8) Thickening agent 0.3%
9) Water rest
Example B1
TABLE Bl
Ingredients
1) Ammonium silicofluoride
2 Mixture of organic and inorganic
3) Ammonium acetate
4) Organic solvent
5) Surfactant
6) Fragrance
7) Thickening agent
8) Water
acids
percentages
14%
4%
2%
7%
0.1%
0.1%
0.1%
rest
Comparative examples which do not include ammonium acetate as gloss enhancer:
Comparative example A2
TABLE A2
Ingredients
1) Ammonium silicofluoride
2) Mixture of organic and inorganic acids
3) Wax dispersion
4) Organic solvent
5) Surfactant
6) Fragrance
7) Thickening agent
8) Water
Comparative example B2
TABLE B2
Ingredients
1) Ammonium silicofluoride-
2) Mixture of organic and inorganic acids
3) Organic solvent
4) Surfactant
percentages
12%
3%
0.5%
5%
0.1%
0.1%
0.3%
rest
percentages
14%
4%
7%
0.1%
5) Fragrance 0.1%
6) Thickening agent 0.1%
7) Water rest
The above comparative examples A2 and B2 contain all the ingredients in same percentages
except they do not contain ammonium acetate as they were there in example Al and Bl
respectively.
These compositions were tested on the marble surfaces to prove that the compositions that
contain non metallic silicofluoride i.e. ammonium silicofluoride are better than the compositions
that are based upon metallic silicofluorides such as magnesium and zinc silicofluorides. Also the
following tests will prove that the compositions that are based upon ammonium silicofluoride
and contain ammonium acetate as gloss enhancer are better than the compositions that contain
ammonium silicofluoride as a crystallizer but do not contain ammonium acetate as a gloss
enhancer.
2 ft by 2 ft tiles of white natural marble and green marble were taken. All the tiles were honed
with 600 grit silicon carbide tools for equal time intervals. This was done to get same initial gloss
on all the test pieces. Then all the pieces were properly washed to remove any grit ingredients
and marble dust left. Then all the slabs were crystallized with equal amount of crystallizers
which were produced according to examples Al, Bl, A2 and B2. Two commercial crystallizers
were also tested to illustrate the performance of the prior and current art.
Commercial crystallizer 1 contains magnesium silicofluoride as a crystallizer.
Commercial crystallizer 2 contains a mixture of zinc and magnesium silicofluorides.
Triple zero grade steel wool which is the finest wool available in the market was taken, single
disc stone polishing machine was used with 2 horse power motor with 150-250 r.p.m. All the
crystallizers were sprayed equally and uniformly on the test pieces and were buffed to dryness
for two minutes each to reach the final gloss. All the readings were taken by gloss meter at 60
degree angle.
The results of the tests conducted on the white marble and are displayed in the table below:
Table 1
Product/sample
Crystallizer A1
Crystallizer B1
Initial readings at
60 degree angle
5
6
Final Readings at 60
degree angle
95
90
Rebuffing and gloss
after rebuffing
Not required
Not required
_Crystallizer A2
Crystallizer B2
Commercial crystallizer
1
Commercial crystallizer
2
6
4
5
6
88
84
77
72
Not required
Not required
Required and final
gloss was 82
Required and final
gloss was 76
Below are the readings for the green marble slabs:
Table 2
Product/sample
Crystallizer Al
Crystallizer Bl
Crystallizer A2
Crystallizer B2
Commercial crystallizer
1
Commercial crystallizer
2
Initial readings at
60 degree angle
5
6
6
4
5
6
Final Readings at 60
degree angle
96
92
90
89
8
7
Rebuffing and gloss
after rebuffing
Not required
Not required
Not required
Not required
Failed to crystallize
Failed to crystallize
As can be seen in the table 1 that the compositions that were formulated according to current
invention produced better results than the prior art commercial products. Also the composition
that contained ammonium acetate as gloss enhancer produced best results compared to the
compositions that did not contain. Also in table 2 in which green marble were crystallized
solutions containing ammonium acetate along with ammonium silicofluoride produced better
results. Also a surprising effect was seen that compositions according to the present inventions
crystallized the green marble surface which prior art compositions failed to do.
The formulation of the crystallization composition is not only limited to direct addition of
ammonium silicofluorides and ammonium acetate. Similar compositions can also be formulated
by various other chemicals that produce these chemicals after reaction in the solution. For
example:
Mixtures of:
Fluosilic acid and ammonium hydroxide; fluosilic acid and ammonium bi carbonate; ammonium
acetate, ammonium hydroxide or bi carbonate and fluosilic acid etc.
Similarly ammonium hydroxide and acetic acid; ammonium bi carbonate and acetic acid and
many others can form ammonium acetate in the solutions.
Therefore the present invention should not be limited to ammonium silicofluorides and
ammonium acetate only. Various chemicals that produce ammonium silicofluorides and
ammonium acetate in the solution can also be incorporated to produce similar crystallizing
solutions as disclosed above in the description.
It is important to disclose here that ammonium silicofluorides can also be used in combination
with metallic silicofluorides, as it will reduce the metallic compound dust formed i.e. carbonates,
hydroxides, oxides of magnesium and zinc etc formed on the surface of marble. Percentage of
ammonium silicofluorides along with metallic silicofluorides can range from 0.1% to 99.9%.
Ammonium acetate gloss enhancer is not limited to use in combination with ammonium
silicofluorides only. It can also be used along with metallic silicofluorides. The molar ratio of
metallic and/or ammonium silicofluorides to ammonium acetate should not be less than 0.2 and
should not be greater than 10. The preferable ratio is 3 to 6.
Conclusion:
It is clear from the above examples and their results that the crystallizing compositions that are based on non metallic silicofluorides like ammonium silicofluoride are better than the
compositions that are based upon the metallic silicofluorides such as zinc and magnesium
silicofluorides. Also, when ammonium silicofluorides is used as a crystallizer, addition of ammonium acetate as a gloss enhancer in the same composition can considerably increase the gloss of that calcareous stones such as marble.

We claim:
1) A crystallizer composition for stones containing- calcium carbonate such as marble
containing:
Ammonium silicofluoride as the crystallizer in the range of 0.1 to 25%;
An acid or a mixture of acids as an initiator in the range of 0.1 to 10%;
Ammonium acetate as a gloss enhancer in the range in which the molar ratio of
ammonium silicofluoride to ammonium acetate is 0.1 to 10.
2) The composition according to claim 1 wherein the ammonium silicofluoride is present in
about 10-20%o of the composition.
3) The composition according to claim 1 wherein the acid/acid mixture is present in a
concentration about 0.5 to 6% of the composition.
4) The composition according to claim 1 in which ammonium acetate is present in the
composition in which the molar ratio of ammonium silicofluoride to ammonium acetate
is 3 to 6.
5) The composition according to claim 1 is sprayed on the calcium carbonate containing
stone and buffed to dryness with or without steel wool pad to achieve final gloss.
6) The use of ammonium silicofluoride along with other metallic silicofluorides such as
magnesium silicofluoride and zinc silicofluoride.
7) Wherein according to claim 7 the percentage of ammonium silicofluoride to other
metallic silicofluorides ranges from 0.1 to 99.9%.
8) The use of compounds which form ammonium silicofluoride in the composition after
reaction.
9) The use of compounds which form ammonium acetate in the composition after reaction.
10) The use of ammonium acetate with metallic silicofluorides in the molar ratio of metallic
silicofluoride to ammonium acetate from 0.2 to 10.