Stable inorganic coating composition for adherent, inorganic coatings

Disclosed are coating compositions containing a vehicle comprising a dispersion of colloidal silica, a hydrolyzable alkoxysilane, an alcohol, water, and an acidifying agent selected from a soluble metal acid phosphate, phosphoric acid, and a mixture thereof.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
This invention relates to coating compositions containing colloidal silica, 
alkoxysilanes, and acidifying agents, to methods of preparation and use, 
and to coated articles therefrom. 
2. Description of the Prior Art 
Attempts have been made to provide stable coating compositions based on 
aqueous colloidal silica, alkoxysilanes and various acids which cure to 
adherent crack and temperature resistant, glossy coatings. However, 
achievement of these goals has been elusive, especially the attainment of 
stable compositions which are pigmented and yet provide cured coatings 
which are highly adherent, for example to a metal substrate, are highly 
temperature resistant, and exhibit a high degree of gloss. 
U.S. Pat. No. 3,976,497 to Clark relates to a paint composition containing 
a pigment carried in a vehicle consisting essentially of a dispersion of 
colloidal silica in a lower aliphatic alcohol-water solution of the 
partial condensate of a silanol of the formula RSi(OH).sub.3 in which R is 
selected from specified groups at least 70 weight percent of the silanol 
being CH.sub.3 Si(OH).sub.3. The vehicle contains 10 to 50 weight percent 
solids consisting essentially of 10 to 70 weight percent colloidal silica 
and 30 to 90 weight percent of the partial condensate. The vehicle further 
contains sufficient acid to provide a pH in the range of 3.0 to 6.0. The 
acids disclosed as useful include such inorganic and organic acids as 
hydrochloric, acetic, formic, propionic, toluenesulfonic and oxalic among 
others. These reference compositions while providing coatings having 
improved abrasion resistance suffer from some disadvantages. For example, 
the stability of these reference compositions is inadequate. Additionally, 
coatings prepared from these reference compositions tend to lose adhesion 
from a steel substrate after curing if applied so as to produce dry film 
thicknesses greater than about 0.5 mils (1.27.times.10.sup.-5 meters). 
U.S. Pat. No. 4,159,206 to Armbruster et al is directed to compositions 
having improved craze resistance and weatherability over compositions of 
the type disclosed in U.S. Pat. No. 3,976,497. The compositions of U.S. 
Pat. No. 4,159,206 do not contain pigment. These unpigmented compositions 
contain colloidal silica and a mixture of dialkyldialkoxysilane and 
alkyltrialkoxysilane such as dimethyldimethoxysilane and 
methyltrimethoxysilane prepared by adding a mixture of dialkoxysilane and 
trialkoxysilane to colloidal silica hydrosols and adjusting the pH with 
sufficient acid to provide a pH in the range of 3.0 to 6.0. The acids 
disclosed as useful for adjusting the pH in U.S. Pat. No. 4,159,206 are 
the same as those disclosed as useful for adjusting the pH in U.S. Pat. 
No. 3,976,497. 
U.S. Pat. No. 3,986,997 to Clark relates to a pigment-free coating 
composition containing essentially the same components as in U.S. Pat. No. 
3,976,497 except without pigment. 
U.S. Pat. No. 4,197,230 to Baney et al relates to a modification in the 
pigment-free compositions shown in U.S. Pat. No. 3,986,997 to Clark by 
incorporation into the Clark composition of at least 1 weight percent of 
.phi. Si(OH).sub.3 based on the weight of total RSi(OH).sub.3 present in 
the composition. 
The present invention is directed to compositions based on a dispersion of 
colloidal silica, water and alkoxysilanes which have improved stability 
and can provide coatings which are temperature resistant, water resistant, 
crack resistant, highly adherent, and/or glossy. 
SUMMARY OF THE PRESENT INVENTION 
Compositions of the present invention comprise: a dispersion of colloidal 
silica, a hydrolyzable alkoxysilane, alcohol, water, an acidifying agent, 
and optionally a pigment. The acidifying agent in compositions of the 
invention comprises a soluble metal acid phosphate and/or phosphoric acid. 
Compositions of the invention containing soluble metal acid phosphate as 
acidifying agent have enhanced stability over known compositions having 
vehicles based on colloidal silica, alkoxysilane, water and alcohol. The 
compositions having phosphoric acid as the acidifying agent while 
providing a number of advantages over known compositions having vehicles 
based on colloidal silica, alkoxysilane, water and alcohol, do not provide 
the enhanced stability provided by the compositions containing soluble 
metal acid phosphate. 
DETAILED DESCRIPTION OF THE INVENTION 
A composition of the invention comprises: 
I. a vehicle comprising, 
A. a dispersion of colloidal silica, 
B. a hydrolyzable alkoxysilane, 
C. an alcohol, 
D. water, and 
E. sufficient soluble acidifying agent to provide a pH of the vehicle 
ranging from about 2.8 to about 6 wherein the soluble acidifying agent is 
selected from a soluble metal acid phosphate, phosphoric acid and a 
mixture thereof, and 
II. optionally a pigment. 
The silica is present in the vehicle in the form of a colloidal dispersion. 
It is to be understood that the colloidal silica may be provided from any 
suitable source including, for example, colloidal silica dispersed in 
essentially an organic solvent such as ethylene glycol monoethyl ether and 
colloidal silica dispersed in water. However, it is preferred to utilize 
an aqueous dispersion of colloidal silica as the source of colloidal 
silica for the vehicle in a composition of the invention. 
Aqueous dispersions of colloidal silica suitable in the present invention 
generally have an average particle size ranging from about 5 to 150 
milligrams (about 50.times.10.sup.-10 to 1500.times.10.sup.-10 meters). 
These silica dispersions are generally known, examples of which include 
those sold under the trademarks of "Ludox" (E. I. duPont de Nemours), 
"Nalcoag" (NALCO Chemical Company) and "Nyacol" (PQ Corporation). Such 
colloidal silicas are available as both acidic and basic hydrosols and 
both types are suitable for the purposes of the present invention. 
Basic, aqueous dispersions of colloidal silica such as "Nalcoag 1060" are 
suitable and in certain circumstances are even preferable. The pH of these 
basic colloidal silicas is adjusted using an acidifying agent during 
preparation of the compositions of the invention. Colloidal silicas are to 
be distinguished from either water dispersible forms of SiO.sub.2, such as 
polysilicic acid, or aqueous alkali metal silicates. 
Alkoxysilanes useful in compositions of the invention are hydrolyzable and 
comprise hydrolyzable trialkoxysilanes, hydrolyzable dialkoxysilanes, or 
mixtures thereof. 
Hydrolyzable trialkoxysilanes useful in compositions of the invention 
generally correspond to the formula 
EQU RSi(OR').sub.3 
wherein, 
R is selected from the group consisting of alkyl radicals having 1 to 5 
carbon atoms, the phenyl radical, the vinyl radical, the 
3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, and the 
gamma-methacryloxypropyl radical; and 
R' is selected from the group consisting of methyl, ethyl, n-propyl, 
isopropyl, and n-butyl. 
Examples of hydrolyzable trialkoxysilanes include: methyltrimethoxysilane, 
methyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, 
phenyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 
gamma-methacryloxypropyltrimethoxysilane, 
gamma-glycidoxypropyltrimethoxysilane, and 
gamma-glycidoxypropyltriethoxysilane. Of the above hydrolyzable 
trialkoxysilanes, methyltrimethoxysilane is preferred. Mixtures of 
trialkoxysilanes also may be used in compositions of the invention. 
Hydrolyzable dialkoxysilanes useful in compositions of the invention 
generally correspond to the formula 
EQU R R"Si(OR').sub.2 
wherein, 
R and R" independently are selected from the group consisting of alkyl 
radicals having 1 to 5 carbon atoms, the phenyl radical, the vinyl 
radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl 
radical, and the gamma-methacryloxypropyl radical; and 
R' is selected from the group consisting of methyl, ethyl, n-propyl, 
isopropyl, and n-butyl. 
Examples of hydrolyzable dialkoxysilanes include dimethyldimethoxysilane, 
dimethyldiethoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane, 
methylphenyldimethoxysilane, methyl (gamma-glycidoxypropyl) 
dimethoxysilane and methyl (gamma-methacryloxypropyl) dimethoxysilane. Of 
the above dialkoxysilanes, dimethyldimethoxysilane is preferred. Mixtures 
of dialkoxysilanes also may be used in compositions of the invention. 
Mixtures of hydrolyzable trialkoxysilanes and hydrolyzable dialkoxysilanes 
can be utilized in compositions of the present invention. It should be 
pointed out that compositions containing pigment and a vehicle comprising 
a dispersion of colloidal silica, a mixture of hydrolyzable 
trialkoxysilane and hydrolyzable dialkoxysilane, alcohol, water, and 
acidifying agent are the subject of U.S. patent application to Paul P. 
Greigger et al filed the same day as the present application. Mixtures of 
the hydrolyzable trialkoxysilanes and hydrolyzable dialkoxysilanes are 
preferred as the alkoxysilane component in compositions of the present 
invention. 
Alkoxysilanes suitable for compositions of the present invention are 
hydrolyzable materials. In aqueous media they can at least partially 
hydrolyze to the corresponding silanols which can, in turn, at least 
partially condense to form mixtures of compounds containing siloxane 
linkages. For example, hydrolysis of alkoxysilanes containing methoxy, 
ethoxy, propoxy and n-butoxy substituents produces the corresponding 
alcohols and silanols. The silanols partially condense in aqueous media to 
form 
##STR1## 
linkages. The condensation, for example, in acidic aqueous media, takes 
place over a period of time and may not be complete such that the siloxane 
material may retain an appreciable quantity of silicon-bonded hydroxyl 
groups. The presence of these residual hydroxyl groups in partially 
condensed alkoxysilanes is believed to not only contribute to the 
solubility of the condensed material in water but also to provide sites 
for at least partial reaction with hydroxyl groups believed to be present 
at the surface of colloidal silica particles in the aqueous dispersion of 
colloidal silica. Although alkoxysilanes which have been hydrolyzed and 
partially condensed without the presence of colloidal silica are useful in 
compositions of the invention, it is preferred that the compositions 
contain alkoxysilanes hydrolyzed and partially condensed in the presence 
of colloidal silica. Cured coatings prepared from mixtures of hydrolyzable 
trialkoxysilanes and hydrolyzable dialkoxysilanes partially condensed in 
the presence of colloidal silica typically are more adherent to the 
substrate and crack resistant than those prepared from mixtures of the 
alkoxysilanes hydrolyzed and partially condensed separate from the 
colloidal silica component. 
Alcohols useful in compositions of the invention typically include lower 
aliphatic alcohols which are miscible with water such as methanol, 
ethanol, isopropanol, and tertiary-butanol. Mixtures of such alcohols can 
be utilized. Of the above alcohols, isopropanol is preferred and when 
mixtures of alcohols are used, it is preferred that at least 50 weight 
percent of isopropanol be present in such mixture. 
The vehicle of the composition contains sufficient acidifying agent to 
provide a pH ranging from about 2.8 to about 6.0, preferably from about 
3.5 to about 4.5. A composition of the invention incorporates an 
acidifying agent which is selected from a soluble metal acid phosphate 
and/or phosphoric acid. The soluble metal acid phosphate is the preferred 
acidifying agent because not only do cured coatings prepared from 
compositions of the invention containing soluble metal acid phosphate have 
advantageous properties such as temperature resistance, water resistance, 
crack resistance, adhesion and gloss, but also the uncured compositions 
have highly desirable, improved composition stability. The compositions of 
the invention having phosphoric acid as the acidifying agent while 
providing a number of advantages over known compositions having vehicles 
based on colloidal silica, alkoxysilane and alcohol, do not provide the 
enhanced stability provided by the composition containing soluble metal 
acid phosphate. Composition stability, as will be appreciated by those 
skilled in the art, is very important particularly in one package coating 
compositions. Examples of such acidifying agents include aluminum 
dihydrogen phosphate, calcium dihydrogen phosphate, chromium (III) 
dihydrogen phosphate, iron (III) dihydrogen phosphate, manganese (II) 
dihydrogen phosphate and the like. Further examples of such acidifying 
agents include the soluble forms of polymeric metal phosphates such as the 
soluble forms of generally known condensed metal phosphates produced, for 
example, by heating and at least partially dehydrating a nonpolymeric 
metal phosphate such as aluminum dihydrogen phosphate. Additionally, 
mixtures of the acidifying agents also may be utilized. Of the above metal 
acid phosphate acidifying agents, aluminum dihydrogen phosphate is 
preferred. Compositions in which such a soluble metal acid phosphate 
acidifying agent is present tend to be more stable than compositions 
containing acids such as those disclosed in U.S. Pat. No. 3,976,497 at 
column 2, lines 63-67. Additionally, compositions of the invention 
containing the required acidifying agent provide cured coatings which tend 
to be more adherent to the substrate than the compositions without the 
required acidifying agent present. 
In addition to the required acidifying agents discussed above, compositions 
of the invention may include one or more acids such as hydrochloric, 
acetic, chloroacetic, citric, benzoic, dimethylmalonic, formic, glutaric, 
glycolic, maleic, malonic, toluene sulfonic, oxalic and the like. However, 
it is preferred that compositions of the invention not contain these 
optional acids since it is believed that such optional acids may tend to 
destabilize the compositions. 
The vehicle portion of a composition of the invention typically is prepared 
by adding the alkoxysilane component to an aqueous dispersion of colloidal 
silica and adjusting the pH to the desired level by addition of the 
acidifying agent. As used herein the vehicle is understood to include the 
components of the composition except for any pigment which may be present. 
The acidifying agent can be combined with the alkoxysilane component or 
with the aqueous dispersion of colloidal silica before mixing the 
alkoxysilane with the colloidal silica. Typically, the acidifying agent is 
combined with the aqueous dispersion of colloidal silica before combining 
the alkoxysilane component with the silica. The amount of acidifying agent 
necessary to obtain the desired pH will vary depending on the alkali 
content of the aqueous dispersion of colloidal silica but is usually less 
than about 1 percent by weight of the composition. 
Alcohol is generated by hydrolysis of silicon-bonded alkoxy substituents on 
the alkoxysilane component. For example, hydrolysis of one mole of 
methyltrimethoxysilane, assuming complete hydrolysis of the methoxy 
substituents, can generate 3 moles of methanol. Alcohol generated by 
hydrolysis of the alkoxysilane component is to be considered at least part 
of the alcohol component of a composition of the invention. Depending on 
the weight percent solids desired in the final vehicle component, 
additional alcohol water, or a water-miscible solvent such as acetone, 
butyl cellosolve and the like, can be added. 
Following combination of the typically aqueous colloidal silica, 
alkoxysilane component, and acidifying agent, the vehicle is stirred at 
room temperature typically for several hours. During this period, the 
vehicle becomes an essentially single phase material while hydrolysis and 
partial condensation occurs. The vehicle thus obtained typically is a 
milky white, low viscosity dispersion which typically is stable against 
gelation at room temperature for a period as long as 6 months or longer. 
Compositions of the invention containing pigment typically are stable at 
120.degree. F. (48.9.degree. C.) for periods at least as long as 4 weeks 
or longer. 
Optionally, latent condensation catalysts and catalysts for the vehicle as 
described in U.S. Pat. No. 3,976,497 at column 3, lines 38-62 can be 
incorporated in the compositions of the present invention, and lines 
38-62, column 3, of U.S. Pat. No. 3,976,497 are hereby incorporated by 
refernce. However, it has been found that compositions of the present 
invention particularly those incorporating the soluble metal acid 
phosphate acidifying agent can be prepared without the catalysts described 
in U.S. Pat. No. 3,976,497 and yet cure to films having excellent 
properties. Compositions of the present invention which do not contain 
such catalysts are in fact preferred. 
A wide variety of pigments can be incorporated in compositions of the 
invention. Examples of suitable pigments include: white and colored 
pigments based on titanium dioxide, iron oxide red, iron oxide black, 
manganese black, carbon in its various forms, barium yellow, strontium 
chromate, calcium chromate, zinc yellow, zinc green, cadmium yellow, 
cadmium red, cadmium vermilion, cadmopone, vermilion, ultramarine, lead 
chromate, chromium yellow, molybdate red, molybdate orange, chromoxide 
green, chromoxidehydrate green, manganese violet, manganese blue, cobalt 
blue, cobalt green, cobalt violet, naples yellow, alkaline earth 
carbonates such as chalk, magnesium carbonate, dolomite, precipitated 
calcium carbonate and barium carbonate, talc, alumina hydrates, zinc 
oxide, magnesium oxide, fluorite, basic lead carbonate, organic pigments 
of the azo series, and mixtures thereof. Ceramic and vitreous frits can 
also be used in the pigment portion of compositions of the invention. 
Powdered metals such as zinc dust, aluminum flakes, bronze powder and the 
like, form another class of pigments suitable for use in the present 
invention. Glass beads can be incorporated in the pigments to provide a 
reflective coating such as used on highway signs and pavement markings. 
The pigments listed above are merely illustrative of the large number of 
generally known pigments. A detailed listing of both organic and inorganic 
pigments can be found in The Encyclopedia of Chemistry, Clark and Hawley, 
Reinhold Publishing Corp., New York (1966) beginning at page 833. 
Typically, a pigment is incorporated in a composition of the invention 
following combination of the colloidal silica, the alkoxysilane component, 
water, and acidifying agent. 
Coating compositions of the invention may include additives generally known 
in the art such as dyes, defoamers, release agents, antimar agents, flow 
control agents, surfactants, thickeners, fungicides and mildewcides. 
As stated previously, the vehicle is understood to include the components 
of the composition of the invention except for pigment. Thus, the vehicle 
of a composition of the invention is understood to include, for example, 
the colloidal silica, the hydrolyzable alkoxysilane, the alcohol, the 
water, the acidifying agent, and any organic solvents and additives which 
may be present. The water is understood to include water from any source, 
for example, the water in an aqueous dispersion of colloidal silica which 
typically is used to provide the colloidal silica in a composition of the 
invention, and water which can be added separately during formulation of a 
composition of the invention as, for example, where a dispersion of 
colloidal silica in organic solvent rather than water is used as the 
source of colloidal silica. 
The vehicle component of a composition of the invention generally contains 
from about 10 to about 60 percent by weight total solids based on the sum 
by weight of silica solids and alkoxysilane component (i.e., excluding 
pigment) in the total weight of the vehicle. Whenever used herein, the 
alkoxysilane solids from the alkoxysilane component are calculated on the 
basis of the corresponding hydrolyzed species (i.e., the corresponding 
silanols) assuming for purposes of calculation a theoretical extent of 
hydrolysis of 100 percent. Thus, for example, the amount of 
dimethyldimethoxysilane as a percent of total solids of a composition 
would be calculated on the basis of the corresponding silanol, 
(CH.sub.3).sub.2 Si(OH).sub.2. 
In preferred compositions of the invention wherein a mixture of 
trialkoxysilane and dialkoxysilane is utilized as the alkoxysilane 
component, the ratio by weight of trialkoxysilane to dialkoxysilane solids 
(calculated on the basis of the corresponding hydrolyzed species as 
discussed above) in the vehicle may vary widely. However, in preferred 
compositions, this ratio typically ranges from about 93:7 to about 50:50. 
Compositions of the invention containing pigment wherein the combination 
of hydrolyzable trialkoxysilane and hydrolyzable dialkoxysilane is used as 
the alkoxysilane component are not nearly as subject to the problems of 
loss of adhesion to the substrate and cracking as are, for example, the 
coatings prepared from the pigmented compositions disclosed in U.S. Pat. 
No. 3,976,497, particularly at dry film thicknesses greater than about 0.5 
mils (1.27.times.10.sup.-5 meters). The ability of compositions of the 
invention containing pigment and a mixture of hydrolyzable trialkoxysilane 
and hydrolyzable dialkoxysilane to resist loss of adhesion and cracking at 
such higher dry film thicknesses is especially important considering the 
difficulty in controlling application parameters for coating compositions 
to consistently provide dry film thicknesses, for example, of less than 
about 0.5 mils (1.27.times.10.sup.-5 meters). The resistance to loss of 
adhesion and cracking of cured films prepared from compositions of the 
invention even without incorporating reinforcing materials such as mica is 
especially noteworthy. 
The amount of silica solids (calculated as SiO.sub.2) in the vehicle as a 
percent of total solids defined above generally ranges from about 10 to 
about 80 percent by weight, preferably from about 40 to about 60 percent 
by weight. The amount of alkoxysilane solids as a percent of total solids 
defined above generally range from about 20 to about 90 percent by weight 
of the total solids, the alkoxysilane solids calculated on the basis of 
the hydrolyzed species assuming for purposes of calculation theoretically 
complete hydrolysis of the alkoxysilane to the respective silanol. 
The amount of water in a composition of the invention may vary widely. The 
amount by weight of water based on the total weight of the vehicle 
component of a composition of the invention generally may range from about 
1 percent to about 90 percent by weight and typically ranges from about 10 
percent to about 70 percent by weight. 
The amount of pigment in a composition of the invention generally ranges 
from 0 to about 80 percent by volume solids, typically from about 10 to 
about 80 percent by volume solids, based on the total volume of solids 
present in the composition. Where highly glossy, pigmented, cured coatings 
are desired, typically an amount of pigment up to about 40 percent by 
volume solids is employed. 
The ratio of the weight of pigment to the weight of binder (i.e., P/B 
ratio) in a composition of the invention will vary, for example, depending 
on the density of the pigment utilized in the composition. However, 
generally the P/B ratio in a composition of the invention ranges from 0/1 
to about 10/1, and typically, where glossy cured coatings are desired, 
ranges from about 0.1/1 to about 2/1. As used in the present context, the 
binder is understood to include the silica solids calculated as SiO.sub.2 
and the alkoxysilane component calculated on the basis of the 
corresponding hydrolyzed species assuming for purposes of calculation a 
theoretical extent of hydrolysis of 100 percent. 
Compositions of the invention are particularly useful as stable coating 
compositions to provide cured films which are glossy, highly adherent and 
crack resistant even at high temperatures. They may be applied to a wide 
variety of substrates including, for example, metal, glass, ceramic 
materials, wood, wallboard, cement, and the like. They are especially 
useful for providing highly adherent coatings over metal substrates. 
Coating compositions of the invention also may be particularly useful as 
relatively low temperature curing substitutes for porcelain. The coating 
compositions may be applied by any known method including, for example, 
brushing, dipping, flow coating, doctor roll coating, spraying and the 
like. Generally known spray techniques and equipment may be utilized. 
Properties of the cured compositions of the invention vary depending on the 
temperature at which the compositions are cured. 
The following examples illustrate the invention. Amounts and percentages 
are by weight unless specified otherwise. When used herein, "pbw" means 
"parts by weight." Tests referred to in the following examples are 
conducted as follows. 
TESTS 
(1) Adhesion--Adhesion is measured by scoring the coating down to the 
substrate with a razor blade in a crosshatch pattern thereby defining a 
plurality of approximately square areas each having a dimension of about 2 
millimeters by 2 millmeters. Masking tape 2 inches wide (SCOTCH Masking 
Tape from 3M Corporation) is applied securely to the scored surface of the 
coating and then is ripped quickly from the scored area. The numerical 
value given for the test represents the scored area which is not removed 
by the tape. 
(2) Hardness--An EAGLE Turquoise Drawing Pencil (from BEROL Corporation) is 
sharpened and the point is sanded to provide a flattened surface. The 
flattened tip is scraped at about a 45.degree. angle to the coating while 
strong downward pressure is applied to the pencil. The value for hardness 
represents the designation of the "lead" in the hardest EAGLE Turquoise 
Drawing Pencil which does not scratch the coating in this test. 
(3) Gloss 60.degree. --The value for gloss 60.degree. represents the 
percent specular reflectance of light from the surface of the coating at 
an angle of 60 degrees from the direction normal to the surface of the 
coating. 
(4) Adhesion/Boiling Water--A substrate having a cured coating thereon is 
soaked in boiling water for 24 hours and thereafter rinsed with tap water 
and allowed to dry at room temperature. Next, the adhesion test described 
above is performed on the cured coating. 
(5) Gloss 60.degree./Heat--A substrate having a cured coating thereon is 
heated at 700.degree. F. (371.degree. C.) for 6 hours. Next, the Gloss 
60.degree. test described above is performed on the cured coating. 
(6) Adhesion/Heat--A substrate having a cured coating thereon is heated at 
700.degree. F. (371.degree. C.) for 6 hours. Next, the first adhesion test 
described above is performed on the cured coating. 
(7) Double Rubs/Water Soak--The number of double rubs is understood to mean 
the number of back and forth finger rubs with a cloth dipped in water 
across a coating that has been soaked in water at room temperature for 1 
hour. The number of double rubs indicated is the number that the cured 
coating can withstand before the substrate becomes visible through the 
coating. 
(8) Hardness/Heat--A substrate having a cured coating thereon is heated to 
700.degree. F. (371.degree. C.) for 6 hours. Next, the hardness test 
described above is performed on the cured coating.

EXAMPLE 1 
(a) 60 pbw of aqueous colloidal silica having a silica solids content of 50 
percent by weight and an average silica particle size of 60 millimicrons 
(60.times.10.sup.-9 meters) available as Nalcoag 1060 from NALCO Chemical 
Company is acidified at room temperature to a pH of 4.0.+-.0.1 with an 
aqueous solution of aluminum dihydrogen phosphate (from Alfa Products, 
Thiokol/Ventron Division, having the following analysis assay: 30 percent 
by weight as P.sub.2 O.sub.5 and 7 percent by weight as Al.sub.2 O.sub.3). 
(b) Next, 37.0 pbw of methyltrimethoxysilane and 3.7 pbw of 
dimethyldimethoxysilane are mixed together and then added to the above 
acidified colloidal silica. The resulting composition is stirred at room 
temperature for about 18 to 24 hours. Following stirring, the composition 
is a one-phase system. 
(c) Next, 70 pbw of isopropanol is added to the composition produced in 
part (b) immediately above. 
(d) Next, 43 pbw of a black inorganic pigment (available as Shepherd Black 
#101 from the Shepherd Chemical Company) is ground for about 5 minutes 
into the composition produced in part (c) immediately above using ZIRCOA 
beads spun by a TEFLON blade. The beads are then removed. The resulting 
material is a composition of the invention. 
EXAMPLES 2-3 
(a) The parts by weight indicated of the materials represented in the 
following TABLE 1 are combined in the following manner to produce the 
vehicles herein designated 2V and 3V. 
Sufficient aqueous aluminum dihydrogen phosphate (described in Example 1) 
is added dropwise, at room temperature, with stirring to the aqueous 
colloidal silica to raise the pH of the aqueous colloidal silica to about 
4. Next, a mixture of the methyltrimethoxysilane and the 
dimethyldimethoxysilane is added at room temperature with stirring to the 
aqueous colloidal silica whereupon a slight exotherm is observed. The 
resulting composition is stirred and allowed to hydrolyze for about 16 
hours at room temperature. Next, the isopropanol is added at room 
temperature with stirring to produce the vehicle. 
With 170.7 pbw of vehicle 2V and 137.4 pbw of vehicle 3V, each prepared as 
described above, is ground for 5 minutes utilizing ZIRCOA beads the amount 
by weight of pigment set forth in Table 1 to produce compositions of the 
invention herein designated 2C and 3C having a percent by volume of 
pigment of 22 percent and 10 percent, respectively. 
TABLE 1 
______________________________________ 
Vehicle 2V 3V 
Aqueous colloidal silica* 
60.0 60.0 
Aqueous aluminum dihydrogen 
To pH of about 4 
To pH of 
phosphate** about 4 
Methyltrimethoxysilane 
37.0 37.0 
Dimethyldimethoxysilane 
3.7 3.7 
Isopropanol 70.0 36.7 
Final Composition 2C 3C 
Vehicle 170.7 137.4 
Pigment*** 43.0 17.0 
______________________________________ 
*Nalcoag 1060 described in EXAMPLE 1. 
**From Alfa Products and described in EXAMPLE 1. 
***A pigment composition containing oxides of copper, manganese and 
chromium available as Shepherd Black No. 101 from Shepherd Chemical 
Company. 
(b) The ZIRCOA beads are filtered from compositions 2C and 3C. Next, each 
of compositions 2C and 3C is sprayed onto two aluminum panels (available 
as ALODINE 407-47 pretreated panels from Amchem Products, Inc.). The 
compositions are cured to a dry film thickness of about 0.5 mil at either 
350.degree. F. (177.degree. C.) for 5 minutes or 600.degree. F. 
(316.degree. C.) for 30 minutes as set forth in the following Table 2. 
Next, tests (1) and (3) through (6) described above are performed on the 
cured coatings prepared from compositions 2C and 3C. The results of the 
tests are set forth in Table 2. 
TABLE 2 
______________________________________ 
Ad- 
Ad- Adhesion 
Gloss he- 
Coat- Gloss he- Boiling 
60.degree./ 
sion/ 
ing Cure 60.degree. 
sion Water Heat Heat 
______________________________________ 
2C 350.degree. F./5 min 
22-28 95 0 17-19 95 
2C 600.degree. F./30 min 
18-24 100 90 16-18 100 
3C 350.degree. F./5 min 
59-68 100 10 53-56 95 
3C 600.degree. F./30 min 
66-70 95 90 63-65 95 
______________________________________ 
The following Example 4 illustrates the excellent storage stability of a 
composition of the invention. 
EXAMPLE 4 
(a) To 120.0 pbw of aqueous colloidal silica (Nalcoag 1060) is added 
dropwise with stirring sufficient aqueous aluminum dihydrogen phosphate 
(described in Example 1) to raise the pH of the aqueous colloidal silica 
to about 4. 
Next, a mixture containing 46.0 pbw of methyltrimethoxysilane, 20.8 pbw of 
phenyltrimethoxysilane and 6.95 pbw of phenylmethyldimethoxysilane is 
added at room temperature with stirring to the aqueous colloidal silica. 
The resulting composition is stirred at room temperature for about 16 
hours. Next, 110.0 pbw of isopropanol is added at room temperature with 
stirring to the composition to produce a vehicle herein designated 4V. 
40.0 pbw of mica coated with titanium dioxide (available as Gold 
Afflair.RTM. from EM Laboratories, Inc.) is ground with the vehicle 4V for 
2 minutes utilizing ceramic beads to produce a pigmented coating 
composition herein designated 4C. 
(b) A first glass panel, P.sub.1, is spray coated with pigmented 
composition 4C shortly after the composition is prepared. The coating is 
cured at 250.degree. F. (121.degree. C.) for 30 minutes and tests (1)-(3) 
are conducted on the cured coatings. The test results are summarized in 
the following Table 3. 
A second glass panel, P.sub.2, is spray coated with pigmented composition 
4C which has been stored for 2 weeks at 120.degree. F. (48.9.degree. C.). 
The coating is cured at 250.degree. F. (121.degree. C.) for 30 minutes and 
tests (1)-(3) are conducted on the cured coatings. The tests results are 
summarized in Table 3. 
A third glass panel, P.sub.3, is spray coated with pigmented composition 4C 
which has been stored for 4 weeks at 120.degree. F. (48.9.degree. C.) and 
the coating cured and the tests conducted in the same manner as for the 
coatings on panels P.sub.1 and P.sub.2. The tests results are summarized 
in Table 3. 
A fourth glass panel, P.sub.4, is spray coated with pigmented composition 
4C which has been stored for 4 weeks at 120.degree. F. (48.9.degree. C.) 
and has been allowed to remain at room temperature for an additional 85 
days. The coating is cured and the tests conducted in the same manner as 
for the coatings on panels P.sub.1, P.sub.2, and P.sub.3. The tests 
results are summarized in Table 3. 
TABLE 3 
______________________________________ 
Adhesion 
Gloss 60.degree. 
Hardness 
______________________________________ 
P.sub.1 /Composition 4C applied 
95 15 3H 
shortly after preparation 
P.sub.2 /Composition 4C applied 
95 13 H 
after 2 weeks at 120.degree. F. 
P.sub.3 /Composition 4C applied 
90 12 3H 
after 4 weeks at 120.degree. F. 
P.sub.4 /Composition 4C applied 
95 11-12 3H 
after 4 weeks at 120.degree. F. 
followed by 85 days at room 
temperature 
______________________________________ 
Thus composition 4C is not only storage stable for at least 4 weeks at 
120.degree. F., but the cured coatings prepared from the stored 
composition 4C exhibit excellent properties. 
The following Examples 5-11 illustrate coating compositions showing various 
ratios by weight of trialkoxysilane to dialkyoxysilane and some properties 
of the cured coatings prepared therefrom. The ratios by weight of 
trialkoxysilane to dialkoxysilane solids calculated on the basis of the 
corresponding silanols in compositions 10C and 11C fall outside the range 
of about 93:7 to about 50:50 for preferred compositions as discussed 
previously. 
EXAMPLES 5-11 
(a) The ingredients set forth in the following Table 4 are combined in the 
following manner to produce pigmented coating compositions herein 
designated 5C through 11C. 
First a mixture of the aqueous colloidal silica and water is acidified to a 
pH in the range of 4-5. Next, the isopropanol or a mixture of isopropanol 
and ethylene glycol monoethyl ether is added with stirring to the 
acidified aqueous colloidal silica. Next, a mixture of the 
methyltrimethoxysilane and dimethyldimethoxysilane is added with stirring 
to the mixture containing the aqueous colloidal silica and isopropanol. 
The resulting composition is stirred at room temperature for about 16 
hours after which the pigment is added to and dispersed in the composition 
to produce a pigmented coating composition containing 40 percent by volume 
pigment based on the total volume of solids in the coating composition. 
The ratio by weight of methyltrimethoxysilane to dimethyldimethoxysilane 
for each of coating compositions 5C through 11C is also set forth in Table 
4. This ratio of alkoxysilane is calculated on the basis of the 
corresponding silanols, that is CH.sub.3 Si(OH).sub.3 and (CH.sub.3).sub.2 
Si(OH).sub.2. 
TABLE 4 
______________________________________ 
Composition 
5C 6C 7C 8C 9C 1OC 11C 
______________________________________ 
Colloidal silica.sup.1 
59.9 59.9 59.9 59.9 59.9 59.9 59.9 
Water 25.9 25.9 102.0 25.9 25.9 25.9 25.9 
Aluminum To raise pH of colloidal silica 
dihydrogen and water to 4-5 
phosphate.sup.2 
Isopropanol 
31.2 62.4 -- 31.4 31.9 32.3 32.6 
Ethylene glycol 
35.3 -- -- 35.5 36.0 36.5 36.8 
monoethyl ether 
Methyltrimeth- 
36.5 36.5 36.5 30.5 20.3 10.1 4.1 
oxysilane 
Dimethyldimeth- 
3.2 3.2 3.2 8.1 16.2 24.3 29.2 
oxysilane 
Titanium dioxide.sup.3 
77.9 77.9 77.9 80.4 83.7 87.2 89.5 
% by volume 
40 40 40 40 40 40 40 
pigment 
CH.sub.3 Si(OH).sub.3 / 
103/ 103/ 103/ 33.9/ 
11.3/ 
3.75/ 
1.27/ 
(CH.sub.3).sub.2 5:(OH).sub.2 
10 10 10 10 10 10 10 
P/B.sup.4 1.35/ 1.35/ 1.35/ 1.40/ 
1.48/ 
1.57/ 
1.62/ 
1 1 1 1 1 1 1 
______________________________________ 
.sup.1 Nalcoag 1060 described in Example 1. 
.sup.2 Aqueous aluminum dihydrogen phosphate from Alfa Products described 
in Example 1. 
.sup. 3 Pigment available as R900 from E. I. duPont de Nemours and 
Company. 
.sup.4 Ratio by weight of pigment to binder. 
(b) Each of the coating compositions 5C through 11C is spray coated to 
approximately the same film thickness onto a metal phosphate pretreated 
steel panel (BONDERITE-40 from Parker Division of Oxymetal Corp.) and a 
metal chromate/metal phosphate pretreated aluminum panel (ALODINE 407-47 
from Amchem Products, Inc.). The coatings are cured at 250.degree. F. 
(121.degree. C.) for 30 minutes and tests (1) through (3) and (5) through 
(8) as described previously are performed on each of the cured coatings. 
The test results are summarized in the following Table 5. 
TABLE 5 
__________________________________________________________________________ 
Composition 
5C 6C 7C 8C 9C 1OC 11C 
__________________________________________________________________________ 
Adhesion 
Aluminum 
100 100 100 100 100 100 100 
Steel 100 100 100 100 100 100 100 
Hardness 
Aluminum 
2H 3H 2H 2H H B &lt;4B 
Steel 8H 8H 8H 8H 2H B 4B 
Double Rubs/ 
Water Soak 
Aluminum 
&gt;200 
&gt;200 
&gt;200 &gt;200 
&gt;200 
&gt;200 
25 
Steel &gt;200 
&gt;200 
&gt;200 &gt;200 
&gt;200 
100 
7 
Gloss 60.degree. 
Aluminum 
82-86 
72-82 
Not measured/ 
89-93 
88-90 
81-85 
70-79 
Steel 72-79 
66-77 
Many craters 
75-80 
81-86 
74-80 
61-66 
in film 
Adhesion/Heat 
Aluminum 
100 100 -- 100 100 100 95 
Steel 70 80 -- 70 95 90 5 
Gloss 60.degree. Heat 
Aluminum 
82-84 
73-78 
-- 86-88 
88-92 
81-83 
67-73 
Steel 72-73 
55-61 
-- 75-80 
81-85 
71-76 
55-60 
Hardness/Heat 
Aluminum 
3H 3H -- 3H 3H H 4B 
Steel &gt;9H &gt;9H -- &gt;9H 8H H &lt;4B 
__________________________________________________________________________ 
The following Example 12 illustrates properties of cured films prepared 
from compositions utilizing acetic, citric, phosphoric, and sulfuric acids 
and aluminum dihydrogen phosphate. 
EXAMPLE 12 
(a) Five mixtures, each containing 59.9 pbw of Nalcoag 1060, and 25.9 pbw 
of water, are acidified to a pH of about 4 utilizing the five acidifying 
agents set forth in the following Table 6 to prepare five compositions. 
Next, a mixture of 36.4 pbw of methyltrimethoxysilane and 3.6 pbw of 
dimethyldimethoxysilane is added with stirring to each of the above five 
compositions after which each of the compositions is stirred at room 
temperature for 11/2 hours. Next, 60.4 pbw of isopropanol is added at room 
temperature with stirring to each of the compositions followed by 
continued stirring at room temperature for about 16 hours. Next, 78.5 pbw 
of titanium dioxide pigment (R-900 from E. I. duPont de Nemours and 
Company) is ground for 5 minutes using ceramic beads into each of the five 
compositions to produce pigmented coating compositions each containing 
about 40 percent by volume pigment based on the total volume of solids in 
the composition or a ratio by weight of pigment to binder (P/B) of about 
1.36/1. 
(b) The ceramic beads are removed from the five coating compositions of 
part (a) immediately above, and the compositions are spray applied to zinc 
phosphate pretreated steel panels (BONDERITE-40) and cured for 30 minutes 
at 250.degree. F. (121.degree. C.) to produce coatings having the dry film 
thicknesses as set forth in Table 6. Next, tests (1) through (3) as 
described previously are performed on each of the cured coatings. The test 
results are summarized in Table 6. 
TABLE 6 
______________________________________ 
Phos- 
Acidifying Acetic.sup.2 
Citric.sup.3 
phoric.sup.4 
Sulfuric.sup.5 
Agent Al(H.sub.2 PO.sub.4).sub.3.sup.1 
Acid Acid Acid Acid 
______________________________________ 
DFT (mil) 
0.8-1.0 0.7-0.8 0.5 1.1 0.8 
Adhesion 
85 20 95 80 90 
Gloss 60 
83-88 69-75 15-17 77-82 62-67 
Hardness 
5H 4H HB 4H 4H 
______________________________________ 
.sup.1 From Alfa products and described in Example 1. 
.sup.2 Glacial acetic acid. 
.sup.3 A 50 percent by weight solution of citric acid in H.sub.2 O. 
.sup.4 An 85 percent by weight solution of H.sub.3 PO.sub.4 in H.sub.2 O. 
.sup.5 Reagent grade. 
The following Example 13 illustrates the improved stability of a 
composition of the invention containing aluminum dihydrogen phosphate 
compared to compositions containing phosphoric acid or acetic acid. 
EXAMPLE 13 
(a) Three coating compositions herein designated 13A, 13B and 13C are 
prepared from the materials in the amounts by weight set forth in the 
following Table 7. The compositions are prepared according to the 
procedure described in Example 12 except that a mixture of isopropanol and 
ethylene glycol monoethyl ether is utilized in Example 13 instead of only 
isopropanol as in Example 12. 
TABLE 7 
______________________________________ 
Composition 13A 13B 13C 
______________________________________ 
NALCOAG 1060 60 60 120 
Water 26 26 52 
Aluminum dihydrogen phosphate.sup.1 
to pH 0 0 
4-5 
Phosphoric Acid.sup.2 
0 to pH 0 
4-5 
Acetic Acid.sup.3 0 0 to pH of 4 
Methyltrimethoxysilane 
37 37 74 
Dimethyldimethoxysilane 
3.7 3.7 7.4 
Isopropanol 25.0 25.0 50 
Ethylene glycol monoethyl ether 
29 29 58 
Pigment.sup.4 43 43 86 
______________________________________ 
.sup.1 From Alfa Products and described in Example 1. 
.sup.2 An 85 percent by weight solution of H.sub.3 PO.sub.4 in H.sub.2 O. 
.sup.3 Glacial Acetic Acid. 
.sup.4 Shepherd Black No. 101 from Shepherd Chemical Company. 
Compositions 13A, 13B and 13C are stored at 120.degree. F. (48.9.degree. 
C.). Composition 13B gels within 14 days and 13C gels within 19 days 
whereas composition 13A remains fluid even after 21 days. 
Moreover, compositions of the invention similar to 13A such as composition 
4C of Example 4 remained fluid after 4 weeks at 120.degree. F. 
(48.9.degree. C.) and an additional 85 days at room temperature. 
The following Examples 14-15 illustrate the excellent storage stability of 
two compositions of the invention. Example 15 also illustrates a 
composition of the invention prepared from a mixture of soluble, acidic 
aluminum and chromium phosphates. 
EXAMPLES 14-15 
(a) Two samples herein designated 14S and 15S, each containing 240 pbw of 
Nalcoag 1060, are acidified to a pH of 4.0 as follows. 
Sample 14S is acidified by adding at room temperature with stirring 
aluminum dihydrogen phosphate (from Alfa Products and described in Example 
1) until a pH of 4.0 is obtained. 
Sample 15S is acidified by adding at room temperature with stirring EMBIX 
(a green, aqueous solution from Hi-Purity Materials, Inc. containing about 
50 percent by weight of acid aluminum chromium phosphate and having the 
following assay: about 30 percent by weight as P.sub.2 O.sub.5, about 7.5 
percent by weight as Al.sub.2 O.sub.3, and about 4.5 percent by weight as 
Cr.sub.2 O.sub.3). 
(b) Next, 148 pbw of methyltrimethoxysilane and 14.8 pbw of 
dimethyldimethoxysilane is added at room temperature with stirring to each 
of samples 14S and 15S and allowed to hydrolyze overnight. 
(c) Next, 201 pbw of each of samples 14S and 15S from part (b) immediately 
above is mixed at room temperature with 116 pbw of isopropanol and 
thereafter pigmented according to the procedure set forth in Example 12 
with 80 pbw of titanium dioxide (available as R-900 from E. I. DuPont 
deNemours and Company) to produce compositions 14C and 15C respectively. 
(d) Six aluminum panels (available as ALODINE 407-47 pretreated panels from 
Amchem Products, Inc.) are spray coated to about the same wet film 
thickness and the coatings cured as follows. 
Two of the aluminum panels, herein designated P14(0) and P15(0), are spray 
coated with compositions 14C and 15C, respectively, shortly after the 
compositions are prepared. The coatings are both cured at 600.degree. F. 
(316.degree. C.) for 30 minutes and tests (1)-(3) are conducted on the 
cured coatings. The test results are summarized in the following Table 8. 
Two of the aluminum panels, herein designated P14(1) and P15(1) are spray 
coated with compositions 14C and 15C, respectively, which have been stored 
for 1 week at 120.degree. F. (48.9.degree. C.). The coatings are cured and 
the tests are conducted in the same manner as for the coatings on panels 
P14(0) and P15(0). The test results are summarized in Table 8. 
Two of the aluminum panels, herein designated P14(2) and P15(2) are spray 
coated with compositions 14C and 15C, respectively, which have been stored 
for 2 weeks at 120.degree. F. (48.9.degree. C.). The coatings are cured 
and the tests are conducted in the same manner as for the coatings on 
panels P14(0), P15(0), P14(1), and P15(1). The test results are summarized 
in Table 8. 
TABLE 8 
______________________________________ 
Adhesion 
Hardness Gloss 60.degree. 
______________________________________ 
P14(0)/Composition 14C applied 
100 2H 56 
shortly after preparation 
P15(0)/Composition 15C applied 
100 4H 52 
shortly after preparation 
P14(1)/Composition 14C applied 
90 7H 13 
after 1 week at 120.degree. F. 
P15(1)/Composition 15C applied 
100 7H 20 
after 1 week at 120.degree. F. 
P14(2)/Composition 14C applied 
100 3H 15 
after 2 weeks at 120.degree. F. 
P15(2)/Composition 15C applied 
95 7H 15 
after 2 weeks at 120.degree. F. 
______________________________________ 
The following Examples 16-17 illustrate the excellent properties of cured 
coatings prepared from two compositions of the invention each stored for 
various periods at both room temperature and 120.degree. F. (48.9.degree. 
C.). Example 17 also illustrates the use of the soluble portion of a 
polymeric metal phosphate as the acidifying agent. 
EXAMPLES 16-17 
(a) Two samples, herein designated 16S and 17S, each containing 120.0 pbw 
of Nalcoag 1060, are acidified to a pH or 4.0 as follows. 
Sample 16S is acidified by adding at room temperature with stirring 
aluminum dihydrogen phosphate (from Alfa Products and described in Example 
1) until a pH of 4.0 is obtained. 
Sample 17S is acidified by adding at room temperature with stirring a 
condensed aluminum phosphate (available as HB Hardener from Pennwalt 
Corporation) until a pH of 4.0 is obtained and thereafter removing the 
insoluble portion of the condensed aluminum phosphate by filtration. 
(b) Next, two compositions herein designated 16C and 17C are prepared from 
the acidified samples 16S and 17S, respectively, from part (a) immediately 
above by combining each of the acidified samples 16S and 17S according to 
the procedure described in parts (b) and (c) of Examples 14-15 immediately 
above with the following ingredients: a mixture of 74.0 pbw of 
methyltrimethoxysilane with 7.4 pbw of dimethyldimethoxysilane, 116.0 pbw 
of isopropanol, and 80.0 pbw of titanium dioxide pigment (R-900 from E. I. 
duPont deNemours and Company). 
(c) Six aluminum panels of the type described in part (d) of Examples 14-15 
are spray coated to about the same wet film thickness and the coatings 
cured as follows. 
Two of the aluminum panels, herein designated P16(0) and P17(0), are spray 
coated with compositions 16C and 17C, respectively, shortly after the 
compositions are prepared. The coatings are both cured at 600.degree. F. 
(316.degree. C.) for 30 minutes and test (1)-(3) are conducted on the 
cured coatings. The test results are summarized in the following Table 9. 
Two of the aluminum panels, herein designated P16(1) and P17(1) are spray 
coated with compositions 16C and 17C, respectively, which have been stored 
for 27 days at room temperature followed by 8 days at 120.degree. F. 
(48.9.degree. C.). The coatings are cured and the tests are conducted in 
the same manner as for the coatings on panels P16(0) and P17(0). The test 
results are summarized in Table 9. 
Two of the aluminum panels, herein designated P16(2) and P17(2) are spray 
coated with compositions 16C and 17C, respectively, which have been stored 
for 27 days at room temperature followed by 8 days at 120.degree. F. 
(48.9.degree. C.) followed by an additional 18 days at room temperature 
followed by an additional 39 days at 120.degree. F. (48.9.degree. C.). The 
coatings are cured and the tests are conducted in the same manner as for 
panels P16(0), P17(0), P16(1) and P17(1). The test results are summarized 
in Table 9. "RT" in Table 9 represents "room temperature." 
TABLE 9 
______________________________________ 
Adhesion 
Hardness Gloss 60.degree. 
______________________________________ 
P16(0)/Composition 16C applied 
100 5H 57 
shortly after preparation 
P17(0)/Composition 17C applied 
100 7H 61 
shortly after preparation 
P16(1)/Composition 16C applied 
100 4H 12 
after 27 days at RT and 8 days 
at 120.degree. F. 
P17(1)/Composition 17C applied 
90 7H 19 
after 27 days at RT and 8 days 
at 120.degree. F. 
P16(2)/Composition 16C applied 
95 5H 16 
after 27 days at RT, 8 days at 
120.degree. F., 18 days at RT and 
39 days at 120.degree. F. 
P17(2)/Composition 17C applied 
100 5H 22 
after 27 days at RT, 8 days at 
120.degree. F., 18 days at RT and 
39 days at 120.degree. F. 
______________________________________ 
The following Examples 18-19 illustrate the excellent properties of cured 
coatings prepared from two compositions of the invention each stored for 
various periods at 120.degree. F. (48.9.degree. C.). Example 19 also 
illustrates a composition of the invention prepared from an aqueous 
solution containing calcium acid phosphate. 
EXAMPLES 18-19 
(a) An aqueous solution containing calcium acid phosphate is prepared as 
follows. An aqueous solution containing 85 percent by weight phosphoric 
acid is diluted with 54 pbw of distilled water. With the diluted 
phosphoric acid solution is reacted 14.8 pbw of calcium hydroxide. The 
reaction is exothermic. The reaction mixture is stirred for 1 hour and 
thereafter filtered to remove precipitate formed during the reaction. The 
filtrate is an aqueous solution containing calcium acid phosphate. 
(b) Two samples herein designated 18S and 19S, each containing 300.0 pbw of 
Nalcoag 1060, are acidified to a pH of 4.0 as follows. 
Sample 18S is acidified by adding at room temperature with stirring 
aluminum dihydrogen phosphate (from Alfa Products and described in Example 
1) until a pH of 4.0 is obtained. 
Sample 19S is acidified by adding at room temperature with stirring the 
calcium acid phosphate solution of part (a) immediately above until a pH 
of 4.0 is obtained. 
(c) Next, a mixture of 185.0 pbw of methyltrimethoxysilane and 18.5 pbw of 
dimethyldimethosyxilane is added at room temperature with stirring to each 
of samples 18S and 19S and allowed to hydrolyze overnight. 
(d) Next, 428.0 pbw of isopropanol is mixed at room temperature with each 
of samples 18S and 19S from part (c) immediately above. Thereafter, 372.6 
pbw of each of the samples is pigmented according to the procedure set 
forth in Example 12 with 80 pbw of titanium dioxide (R-900 from E. I. 
duPont) to produce compositions 18C and 19C respectively. 
(e) Eight aluminum panels of the type described in part (d) of Examples 
14-15 are spray coated to about the same wet film thickness and the 
coatings cured as follows. 
Two of the alminum panels, herein designated P18(0) and P19(0), are spray 
coated with compositions 18C and 19C, respectively, shortly after the 
compositions are prepared. The coatings are both cured at 600.degree. F. 
(316.degree. C.) for 30 minutes and tests (1)-(3) are conducted on the 
cured coatings. The test results are summarized in the following Table 10. 
Two of the aluminum panels, herein designated P18(1) and P19(1) are spray 
coated with compositions 18C and 19C, respectively, which have been stored 
for 1 week at 120.degree. F. (48.9.degree. C.). The coatings are cured and 
the tests are conducted in the same manner as for the coatings on panels 
P18(0) and P19(0). The test results are summarized in Table 10. 
Two of the aluminum panels, herein designated P18(2) and P19(2), are spray 
coated with compositions 18C and 19C, respectively, which have been stored 
for 2 weeks at 120.degree. F. (48.9.degree. C.). The coatings are cured 
and the tests are conducted in the same manner as for the coatings on 
panels P18(0), P19(0), P18(1) and P19(1). The test results are summarized 
in Table 10. 
Two of the aluminum panels, herein designated P18(3) and P19(3), are spray 
coated with compositions 18C and 19C, respectively, which have been stored 
for 3 weeks at 120.degree. F. (48.9.degree. C.). The coatings are cured 
and the tests are conducted in the same manner as for the coatings on 
panels P18(0), P19(0), P18(1), P19(1), P18(2) and P19(2). The test results 
are summarized in Table 10. 
TABLE 10 
______________________________________ 
Adhesion Hardness Gloss 60.degree. 
______________________________________ 
P18(0) 100 2H 65 
P19(0) 100 2H 37 
P18(1) 100 4H 24 
P19(1) 100 4H 46 
P18(2) 100 4H 14 
P19(2) 100 3H 23 
P18(3) 100 4H 9 
P19(3) 100 4H 11 
______________________________________