Abrasion resistant silicone coated polycarbonate article having an acrylic primer layer containing a U.V. absorbing compound

A shaped, non-opaque coated polycarbonate article having improved abrasion and chemical solvent resistance comprising a polycarbonate substrate having disposed on the surface thereof a non-opaque primer layer comprised of from about 25 to about 85 weight percent of a thermoset acrylic polymer and from about 15 to about 75 weight percent of at least one ultraviolet light screening compound, and disposed on said primer layer a non-opaque top coat comprised of a colloidal silica filled thermoset organopolysiloxane.

This invention relates to non-opaque abrasion and chemical solvent 
resistant colloidal silica filled thermoset organopolysiloxane coated 
shaped polycarbonate articles wherein the colloidal silica filled 
organopolysiloxane top coat is uniformly and tenaciously adhered to the 
polycarbonate substrate. More particularly, the present invention relates 
to a colloidal silica-filled organopolysiloxane coated polycarbonate 
article having a primer layer disposed between the polycarbonate substrate 
and the colloidal silica-filled organopolysiloxane top coat, said primer 
layer comprising from about 25 to about 85 weight percent of a thermoset 
acrylic polymer and from about 15 to about 75 weight percent of at least 
one ultraviolet light screening compound. 
BACKGROUND OF THE INVENTION 
The use of transparent glazing materials utilizing polycarbonate resin as a 
structural component for windows, windshields, and the like are well 
known. While these polycarbonate resins are easily fabricated into the 
desired shape and have excellent physical and chemical properties, such as 
being less dense than glass and having more breakage resistance than 
glass, their abrasion and chemical solvent resistance is relatively low. 
In order to overcome this relatively low abrasion resistance and to 
otherwise improve the surface characteristics of the polycarbonate, 
various coatings have been applied onto the polycarbonate substrate. U.S. 
Pat. No. 3,582,398 describes a fabricated polycarbonate part having 
improved optical properties consisting of a polycarbonate substrate having 
a transparent coating thereon consisting of a thermoplastic polymethyl 
methacrylate. U.S. Pat. No. 4,061,652 describes a coating for 
polycarbonate resins comprised of (i) an acrylic resin which is a mixture 
of olefinically unsaturated organic monomers in combination with an 
acrylic polymer, and (ii) certain urethanes of hydroxybenzotriazoles and 
hydroxybenzophenones in combination with certain catalysts. U.S. Pat. Nos. 
3,451,838, 3,986,997 and 4,027,073 disclose organopolysiloxane coating 
compositions and techniques for the application of these 
organopolysiloxane coatings onto polycarbonate surfaces. While these 
coatings have many desirable properties, e.g., they are hard, abrasion 
resistant, and chemical solvent resistant, these organopolysiloxane 
coatings do not in all instances possess the requisite degree of uniform 
adherence to and durability on these polycarbonate surfaces. U.S. Pat. No. 
3,707,397 describes a process for providing a hard coating on, inter alia, 
polycarbonate articles, said process including priming the polycarbonate 
surface with an adhesion promoting thermosettable acrylic and applying an 
organopolysiloxane onto the primed surface. This reference further teaches 
that the thickness of the thermosettable acrylic polymer primer layer 
varies between 0.01 mil up to as much as 0.5 mil or even more. 
However, organopolysiloxane coated polycarbonate articles which contain a 
thermoset acrylic primer have suffered from the problem of loss of 
adhesion of the organopolysiloxane top coat to the polycarbonate substrate 
upon exposure to weathering. 
It has now been discovered that if the primer layer is loaded with high 
amounts of ultraviolet light screeners, i.e., contains from about 15 to 
about 75 weight percent of at least one ultraviolet light screening or 
absorbing compound, then the adhesion of the organopolysiloxane top coat 
is not deleteriously affected upon exposure to weathering. 
DESCRIPTION OF THE INVENTION 
This invention relates to non-opaque colloidal silica-filled 
organopolysiloxane coated polycarbonate articles having an adhesion 
promoting primer layer containing from about 25 to about 85 weight percent 
of a thermoset acrylic polymer and from about 15 to about 85 weight 
percent of at least one ultraviolet light screening compound disposed 
between the polycarbonate surface and the colloidal silica-filled 
thermoset organopolysiloxane top coat. 
in the practice of the present invention, prior to the application of the 
colloidal silica-filled organopolysiloxane coating to the polycarbonate 
surface, the surface is first primed by the application thereon of a 
primer layer of controlled thickness containing a thermoset acrylic 
polymer. 
The aromatic carbonate polymers of the instant invention are known 
compounds and have recurring units of the formula: 
##STR1## 
wherein each --R-- is selected from the group consisting of phenylene, 
halo-substituted phenylene and alkyl substituted phenylene; and A and B 
are each selected from the group consisting of hydrogen, hydrocarbon 
radicals, free from aliphatic unsaturation and of radicals which together 
with the adjoining 
##STR2## 
atom form a cycloalkane radical, the total number of carbon atoms in A and 
B being up to 12. 
These aromatic carbonate polymers may be prepared by methods well known in 
the art and described in U.S. Pat. Nos. 3,989,672, 3,275,601 and 
3,028,365, all of which are incorporated herein by reference. 
In the practice of this invention, any of the aromatic polycarbonates can 
be employed herein. However, particularly useful are the aromatic 
polycarbonates prepared by reacting a dihydric phenol, such as bisphenol-A 
(2,2-bis(4-hydroxyphenyl)propane) with a carbonate precursor. Typical of 
some of the dihydric phenols that may be employed in the practice of this 
invention are bis(4-hydroxyphenyl)methane, 
2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 
4,4-bis(4-hydroxyphenyl)heptane, 
2,2-(3,5,3',5'-tetrabromo-4,4'-dihydroxydiphenyl)propane, 
2,2-(3,5,3',5'-tetrabromo-4,4'-dihydroxydiphenyl)propane, 
(3,3'-dichloro-4,4'-dihydroxydiphenyl)methane. Other dihydric phenols of 
the bisphenol type are also available and are disclosed in U.S. Pat. Nos. 
2,999,835, 3,028,365 and 3,334,154. 
In addition, the reaction is carried out with the carbonate precursor in 
the presence of a molecular weight regulator, an acid acceptor and a 
catalyst. The preferred carbonate precursor generally employed in 
preparing carbonate polymers is carbonyl chloride. However, other 
carbonate precursors may be employed and this includes other carbonyl 
halides, carbonate esters or haloformates. 
The acid acceptors, molecular weight regulators and catalysts employed in 
the process of preparing polycarbonates are well known in the art and may 
be any of those commonly used to prepare polycarbonates. 
The thermosettable acrylic polymers which are contained in the primer 
compositions are well known in the art. Exemplary thermosettable acrylics 
which may be utilized in the practice of this invention are set forth in 
Encyclopedia of Polymer Science and Technology, Vol. 1, Interscience 
Publishers, John Wiley & Sons, Inc., at p. 273 et seq., and in the 
Chemistry of Organic Film Formers, by D. H. Solomon, John Wiley & Sons, 
Inc., 1967, at p. 251 et seq., and the references cited therein, all of 
which are hereby incorporated herein by reference. 
Generally, the term "thermosettable acrylics" as used herein includes an 
acrylic polymer or copolymer having reactive functional groups which are 
capable of reacting between themselves to effect a cross-linkage thereof. 
These functional groups may be the same, provided they are of the type 
which will react between themselves, or the polymer or copolymer may 
contain two or more different types of reactive functional groups, such 
as, for example, an epoxide group and a carboxyl group. The term 
"thermosettable acrylics" also includes acrylic polymers or copolymers 
having a reactive functional group to which there is added an appropriate 
cross-linking agent which reacts with the functional group to effect 
cross-linking. The term "thermosettable acrylics" still further includes a 
mixture of two or more polymers containing cross-linkable functional 
reactive groups. These polymers may be acrylic polymers or copolymers 
having reactable, cross-linkable, functional groups thereon, or at least 
one of the polymers may be an acrylic polymer or copolymer having a 
reactive functional group and the other polymer or copolymer may be one or 
more other types of known polymers having functional groups which are 
reactive with the acrylic functional group to provide the thermoset 
product as a result of cross-linking. 
Typically, the reactions involved in cross-linking the thermosettable 
acrylic polymers are reactions between, for example, epoxide functional 
groups and amine functional groups; epoxide functional groups and acid 
anhydride functional groups; epoxide functional groups and carboxyl 
functional groups, including phenolic hydroxyl groups; epoxide functional 
groups and N-methylol or N-methylol-ether; carboxyl functional groups and 
N-methylol or N-methylol-ether functional groups; interreaction between 
carboxyl and isocyanate groups; reactions between hydroxyl, for example 
polyols, and isocyanate groups, and reactions between amine groups and 
N-methylol or N-methylol-ether groups. In the usual case of resin 
mixtures, the acrylic will be present in a major proportion, i.e., greater 
than 50 weight percent and, more typically, will be present in an amount 
in excess of about 70 percent. The needed functional group in the acrylic 
copolymer, which is the foundation of the thermosettable acrylic polymer, 
is provided by employing in the copolymerization a monomer which supplies 
the needed reactive functional group into the polymer chain. Usually, this 
copolymerizable functional group-supplying monomer will be present in 
small amounts, that is, on the order of 25 weight percent or less, and 
typically, between about 1 and 20 percent of the monomer mass which is 
polymerized. Exemplary of these functional group-supplying monomers are 
glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, 
dimethylaminoethyl methacrylate, vinyl pyridine, 
tert-butyl-aminoethyl-methacrylate, maleic anhydride, itaconic anhydride, 
allyl alcohol, monoallyl ethers of polyols, hydroxyethyl methacrylate, 
hydroxypropyl methacrylate, hydroxypropyl acrylate, acrylamide, 
methacrylamide, maleamide, N-methylolmethacrylamide, vinyl isocyanate, 
allyl isocyanate. Usually, the other monomer which will be polymerized 
along with the monomer supplying the functional group is a lower (C.sub.1 
-C.sub.3) alkyl acrylic ester or mixtures thereof, e.g., methyl acrylate, 
ethyl acrylate, methyl methacrylate, ethyl methacrylate, or mixtures 
thereof, in an amount ranging between about 75 parts to about 99 parts 
and, more typically, between about 80 parts to about 97 parts. 
The thermosettable acrylics are in general applied from primer compositions 
containing (i) the thermosettable acrylics and the ultraviolet light 
absorber dissolved in an organic or inorganic solvent, or (ii) an emulsion 
containing the thermosettable acrylics, the ultraviolet light absorber, an 
alcohol and water. In the case wherein the primer composition contains a 
thermosettable acrylic dissolved in an organic solvent, the solvent should 
generally be relatively volatile and inert, i.e., one that will not 
readily react with or too deleteriously affect the polycarbonate 
substrate, but which is capable of dissolving the thermosettable acrylic. 
The primer compositions contain sufficient thermosettable acrylic polymer 
and ultraviolet light absorber to provide a primer layer containing from 
about 25 to about 85 weight percent thermoset acrylic polymer and from 
about 15 to about 75 weight percent of the ultraviolet light absorbing 
compound. Generally, this requires that the primer compositions contain 
from about 1 to about 20 weight percent of thermosettable acrylic solids 
and a sufficient amount of an ultraviolet light absorbing system to 
provide a thermosettable acrylic solids to ultraviolet light absorber 
weight ratio of from about 1:0.2 to about 1:3. The ultraviolet light 
absorbing system can be one which contains only one ultraviolet light 
absorbing compound or it can contain a mixture of two or more ultraviolet 
light absorbing compounds. 
The ultraviolet light absorbing compounds are well known in the art and are 
compounds which act to absorb or screen out the ultraviolet radiation. 
Illustrative of these compounds are those of the hydroxy benzophenone and 
benzotriazole series, the cyanoacrylates and the benzylidene malonates. 
Examples of these include: 2-hydroxy-4-n-octoxybenzophenone, substituted 
hydroxyphenylbenzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 
2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxybenzophenone, 
2,2',4,4'-tetrahydroxybenzophenone, 
2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 
2,2'-dihydroxy-4,4'-diethoxybenzophenone, 
2,2'-dihydroxy-4,4'-dipropoxybenzophenone, 
2,2'-dihydroxy-4,4'-dibutoxybenzophenone, 
2,2'-dihydroxy-4-methoxy-4'-ethoxybenzophenone, 
2,2'-dihydroxy-4-methoxy-4'-propoxybenzophenone, 
2,2'-dihydroxy-4-methoxy-4'-butoxybenzophenone, 
2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 
2-(2'-hydroxy-3'-methyl-5'-tert-butylphenyl)benzotriazole, 
2-(2'-hydroxy-5'-cyclohexylphenyl)-benzotriazole, 
2-(2'-hydroxy-3',5'-dimethylphenyl)benzotriazole, ethyl 
3,3-diphenyl-2-cyanoacrylate, and octyl 3,3-diphenyl-2-cyanoacrylate. 
Further examples of ultraviolet light absorbers which may be used in the 
practice of this invention may be found in U.S. Pat. No. 3,043,079 which 
is incorporated herein by reference. 
The primer compositions of the instant invention may also optionally 
contain various flatting agents, stabilizers such as antioxidants, 
surface-active agents and thixotropic agents. All of these additives and 
the use thereof are well known in the art and do not require extensive 
discussions. Therefore, only a limited number will be referred to, it 
being understood that any compounds possessing the ability to function in 
such a manner, i.e., as a flatting agent, surface active agent and 
stabilizing agent, can be used. 
The various surface-active agents, including anionic, cationic and nonionic 
surface-active agents are described in Kirk-Othmer Encyclopedia of 
Chemical Technology, Vol. 19, Interscience Publishers, New York, 1969, pp. 
507-593, and Encyclopedia of Polymer Science and Technology, Vol. 13, 
Interscience Publishers, New York, 1960, pp. 477-486, both of which are 
references and incorporated herein. 
A uniform film of the primer composition containing the further curable 
thermosettable acrylic and the ultraviolet light absorbing system is 
applied onto the polycarbonate surface by any of the known means such as 
dipping, spraying, roll-coating and the like. After the formed 
polycarbonate part is coated with the primer composition, the inert 
volatile solvent is removed by drying the coated article until a 
substantial portion of the volatile solvent evaporates leaving a solid 
residue, and thereafter heat is applied to thermoset the thermosettable 
acrylic, thereby forming a primer layer or coating containing the 
thermoset acrylic and the ultraviolet light absorbing system on the 
polycarbonate surface to which the primer composition was applied. This 
primer layer contains from about 25 to about 85 weight percent of the 
thermoset acrylic polymer and from about 15 to about 75 weight percent of 
the ultraviolet light absorbing system, i.e., at least one ultraviolet 
light absorbent compound; preferably from about 25 to about 80 weight 
percent of the thermoset acrylic polymer and from about 20 to about 75 
weight percent of the ultraviolet light absorbing system; more preferably, 
from about 25 to about 75 weight percent of the thermoset acrylic polymer 
and from about 25 to about 75 weight percent of the ultraviolet light 
absorbing system; and most preferably from about 25 to about 70 weight 
percent of the thermoset acrylic polymer and from about 30 to about 75 
weight percent of the ultraviolet light absorbing system. 
If the primer layer contains less than about 15 weight percent of the 
ultraviolet light absorber, there is no appreciable improvement in the 
durability of adhesion of the colloidal silica filled silicone top coat. 
If the primer layer contains more than about 75 weight percent of the 
ultraviolet light absorber, the adhesion promoting character of the primer 
begins to be adversely affected. 
After the polycarbonate article which is to be coated with the top coat 
composition has been primed by the application of the primer composition 
and the evaporation of the solvent component of the primer composition and 
the thermosetting of the thermosettable acrylic, the primed surface of the 
polycarbonate article is then coated with the colloidal silica-filled 
organopolysiloxane coating. In the practice of this invention, a colloidal 
silica-filled organopolysiloxane coating composition containing a 
further-curable organopolysiloxane and colloidal silica is applied onto 
the cured primer and is then cured to form a thermoset colloidal 
silica-filled organopolysiloxane coating. 
The colloidal silica-filled further-curable organopolysiloxane top coat 
composition is disclosed in U.S. Pat. Nos. 3,986,997 and 4,027,073 and 
comprises a dispersion of colloidal silica in a lower aliphatic 
alcohol-water solution of the partial condensate of a silanol having the 
formula 
EQU R.sup.4 Si(OH).sub.3 (II). 
wherein R.sup.4 is selected from the group consisting of alkyl radicals 
containing from 1 to 3 carbon atoms, the vinyl radical, the 
3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the 
gamma-methacryloxypropyl radical, with at least 70 percent by weight of 
said silanol being CH.sub.3 Si(OH).sub.3. This composition generally 
contains from about 10 to about 50 percent by weight of solids, said 
solids consisting essentially of a mixture of from about 10 to about 70 
percent by weight of colloidal silica and from about 30 to about 90 
percent by weight of the partial condensate of a silanol. The partial 
condensate of a silanol, i.e., a siloxanol, is obtained, preferably, 
entirely from the condensation of CH.sub.3 Si(OH).sub.3, however, the 
partial condensate may also optionally be comprised of a major portion 
which is obtained from the condensation of CH.sub.3 Si(OH).sub.3 and a 
minor portion which is obtained from the condensation of 
monoethyltrisilanol, monopropyltrisilanol, monovinyltrisilanol, mono 
gamma-methacryloxy-propyltrisilanol, mono gamma-glycidoxypropyltrisilanol, 
or mixtures thereof. The composition further contains sufficient acid to 
provide a pH in the range of 3.0 to 6.0. The pH is maintained in this 
range in order to prevent premature gellation and increase the shelf life 
of the silica-filled organopolysiloxane top coat composition and to obtain 
optimum properties in the cured coating. Suitable acids include both 
organic and inorganic acids such as hydrochloric, chloroacetic, acetic, 
citric, benzoic, formic, propionic, maleic, oxalic, glycolic and the like. 
The acid can be added to either the silane, which hydrolyzes to form the 
silanol component of the composition, or the hydrosol prior to mixing the 
two components. 
The trisilanol component of the top coat composition of the present 
invention is generated in situ by the addition of the corresponding 
trialkoxysilanes to aqueous dispersions of colloidal silica. Suitable 
trialkoxysilanes are those containing methoxy, ethoxy, isopropoxy and 
t-butoxy substituents. Upon generation of the silanol in the acidic 
aqueous medium, there is condensation of the hydroxyl substituents to form 
--Si--O--Si bonding. The condensation is not complete, but rather the 
siloxane retains an appreciable quantity of silicon-bonded hydroxyl 
groups, thus rendering the organopolysiloxane polymer soluble in the 
water-alcohol solvent. This soluble partial condensate can be 
characterized as a siloxanol polymer having at least one silicon-bonded 
hydroxyl group per every three --SiO-- units. During curing of the top 
coating composition on the primer, these residual hydroxyl groups condense 
to give a silsesquioxane, R.sup.4 SiO.sub.3/2. 
The silica component of the top coat composition is present in the form of 
colloidal silica. Aqueous colloidal silica dispersions generally have a 
particle size in the range of 5 to 150 millimicrons in diameter. These 
silica dispersions are prepared by methods well known in the art and are 
commercially available. It is preferred to use colloidal silica having a 
particle size in the range of 10 to 30 millimicrons in diameter in order 
to obtain dispersions having a greater stability and to provide top 
coatings having superior optical properties. 
The silica-filled organopolysiloxane top coat compositions are prepared by 
adding trialkoxysilanes to colloidal silica hydrosol and adjusting the pH 
to a range of 3.0 to 6.0 by the addition of acid. As mentioned previously, 
the acid can be added to either the silane or the silica hydrosol before 
the two components are mixed. Alcohol is generated during the hydrolysis 
of the trialkoxy silanes to the trisilanols. Depending upon the percent 
solids desired in the final coating composition, additional alcohol, 
water, or a water-miscible solvent can be added. Suitable alcohols are the 
lower aliphatic alcohols such as methanol, ethanol, isopropanol, 
t-butanol, and mixtures thereof. Generally, the solvent system should 
contain from about 20 to about 75 weight percent alcohol to ensure 
solubility of the siloxanol formed by the condensation of the silanol. If 
desired, a minor amount of an additional water-miscible polar solvent such 
as acetone, butyl cellosolve, and the like can be added to the 
water-alcohol solvent system. Generally, sufficient alcohol or 
water-alcohol solvent is added to give a composition containing from about 
10 to about 50 percent by weight of solids, said solids generally 
comprising from about 10 to about 70 percent by weight of colloidal silica 
and from about 30 to about 90 percent by weight of the partial condensate 
of the silanol. The composition is allowed to age for a short period of 
time to ensure formation of the partial condensate of the silanol, i.e., 
the siloxanol. This condensation occurs upon generation of the silanol in 
the acidic aqueous medium through the hydroxyl substituents to form 
Si-O-Si bonding. The condensation is not complete, resulting in a siloxane 
having an appreciable quantity of silicon-bonded hydroxyl group. This 
aged, silica-filled further-curable organopolysiloxane top coat 
composition is then applied onto the primed polycarbonate by any of the 
commonly known methods such as dipping, spraying, flow-coating and the 
like. After the top coat composition is applied to the primed 
polycarbonate, the polycarbonate is air dried to evaporate the volatile 
solvents from the top coat composition. Thereafter, heat is applied to 
cure the top coat. During curing, the residual hydroxyls of the siloxane 
codense to give a silsesquioxane, R.sup.4 SiO.sub.3/2. The result is a 
silica-filled cross-linked organopolysiloxane top coat which is 
tenaciously adhered to the substrate and is highly resistant to 
scratching, abrasion, chemical solvents and marring. Generally, the top 
coat contains from about 10 to about 70 weight percent silica and from 
about 30 to about 90 weight percent of the organopolysiloxane present as 
the silsesquioxane, R.sup.4 SiO.sub.3/2. 
The thickness of the top coat generally is dependent upon the method of 
application and upon the weight percent solids present in the colloidal 
silica-filled further curable organopolysiloxane top coat composition. In 
general, the higher the percent solids, and the longer the application 
time, the greater the thickness of the top coat. It is preferred that the 
cured top coat have a thickness of from about 0.1 to about 0.5 mil, more 
preferably from 0.15 to about 0.4 mil, and most preferably from about 0.2 
to about 0.25 mil.

PREFERRED EMBODIMENT OF THE INVENTION 
In order that those skilled in the art may better understand how the 
present invention may be practiced, the following examples are given by 
way of illustration and not by way of limitation. Unless otherwise 
specified, all percentages and parts are by weight. 
EXAMPLE 1 
An aromatic polycarbonate is prepared by reacting 
2,2-bis(4-hydroxyphenol)propane and phosgene in the presence of an acid 
acceptor and a molecular weight regulator and having an intrinsic 
viscosity of 0.57. The product is then fed to an extruder, which extruder 
is operated at about 265.degree. C. and the extrudate is comminuted into 
pellets. 
The pellets are then injection molded at about 315.degree. C. into test 
panels of about 4 in. by 4 in. by about 1/8 in. thick. 
A colloidal silica-filled further-curable organopolysiloxane top coat 
composition is prepared as follows: Glacial acetic acid (0.2 grams) is 
added to 200 grams of a commercially available aqueous dispersion of 
colloidal silica having an initial pH of 3.1 containing 34% SiO.sub.2 of 
approximately 15 millimicron particle size and having a Na.sub.2 O content 
of less then 0.01 weight percent. Methyltrimethoxysilane (138 grams) is 
added to the stirred acidified dispersion generating methanol and 
methyltrisilanol. After standing for about one hour, the pH of the 
composition stabilizes at 4.5. The pH of the composition is adjusted to a 
range of from 3.7 to 5.6. The composition is aged for 4 days to ensure 
formation of the partial condensate of CH.sub.3 Si(OH).sub.3 in the silica 
methanol-water dispersion. The composition contains 40% solids, half of 
which is SiO.sub.2 and the other half silicone calculated on the basis 
CH.sub.3 SiO.sub.3/2 weight available in the cured composition. The aged 
composition is diluted to 25 weight % solids by addition of isopropanol. 
EXAMPLE 2 
This Example illustrates a primed and top coated polycarbonate article 
falling outside the scope of the instant invention in that no ultraviolet 
light absorbing compound is present in the primer layer. 
A solution of 20 parts by weight of methyl methacrylate, 20 parts by weight 
of ethyl methacrylate, 0.6 parts by weight of methacrylic acid and 0.1 
parts by weight of 2,2'-azobisisobutyronitrile in 160 parts by weight of 
butoxyethanol is stirred, under nitrogen at 100.degree. C. for 36 hours. 
A thermosettable acrylic primer formulation, hereinafter referred to as 
primer formulation B, is made by combining 40 parts by weight of the 
afore-described solution with 0.5 parts by weight of 
hexamethoxymethylmelamine, 0.03 parts by weight of toluenesulfonic acid, 
and 160 parts by weight of butoxyethanol. 
Polycarbonate test panels prepared in accordance with the procedure of 
Example 1 are flow coated with this primer formulation B, are drained for 
10 minutes, and then are baked at 125.degree. C. for 30 minutes. After 
cooling the primed test panels are flow coated with the colloidal silica 
filled organopolysiloxane top coat composition prepared substantially in 
accordance with the procedure set forth above. Excess top coat solution is 
drained off and the panels are air dried for 30 minutes. The panels are 
then baked for 1 hour at 125.degree. C. to cure the colloidal silica 
filled further curable organopolysiloxane. The primed and top coated test 
panels are subjected to an adhesion test, before weathering and after 
weathering for 503 hours, and the results are set forth in TABLE I. 
The adhesion test consists of using a multiple blade tool to cut parallel 
goooves about 1 mm apart through the top coat and primer layer into the 
substrate, rotating the sample 90.degree. and repeating the cutting 
process thereby forming a grid pattern of 1 mm squares cut into the 
coating, and applying an adhesive tape over the cross-hatched area and 
quickly pulling said tape off (a sample fails the adhesion test if any of 
the squares in the grid are pulled off). The weathering consists of 
placing the test panels in a QUV accelerating weathering tester, sold by 
Q-Panel Company, which is set to cycles of 8 hours of fluorescent 
ultraviolet light at about 70.degree. C. and 4 hours of dark/condensation 
at about 60.degree. C. 
EXAMPLE 3 
This Example illustrates a primed and top coated polycarbonate article 
falling outside the scope of the instant invention in that the primer 
layer contains about 9 weight percent of an ultraviolet light absorber. 
A thermosettable acrylic primer fomulation containing a low amount of a 
benzotriazole ultraviolet light absorber is prepared by combining 20 parts 
by weight of the thermosettable acrylic primer formulation B of Example 2 
with 0.08 parts by weight of Cyasorb 5411 (a benzotriazole ultraviolet 
light absorber sold by American Cyanamid). Test panels prepared in 
accordance with the procedure of Example 1 are primed with this primer 
formulation and top coated in accordance with the procedure set forth in 
Example 2. These primed and top coated test panels are subjected to the 
adhesion test, before and after weathering, and the results are set forth 
in TABLE I. 
EXAMPLE 4 
A thermosettable acrylic primer formulation containing a high amount of a 
cyanoacrylate ultraviolet light absorber is prepared by combining 19.8 
parts by weight of the thermosettable acrylic primer formulation B of 
Example 2 with 2.2 parts by weight of Uvinul N-539 (a cyanoacrylate 
ultraviolet light absorber sold by GAF Corporation). Test panels prepared 
in accordance with the procedure of Example 1 are primed with this primer 
formulation and top coated in accordance with the procedure set forth in 
Example 2. These primed and top coated test panels are subjected to the 
adhesion test, before and after weathering, and the results are set forth 
in TABLE I. 
EXAMPLE 5 
A thermosettable acrylic primer formulation containing a high amount of 
dihydroxybenzophenone ultraviolet light absorber is prepared by combining 
19.8 parts by weight of the thermosettable acrylic primer formulation B of 
Example 2 with 2.2 parts by weight of 2,4-dihydroxybenzophenone. Test 
panels prepared substantially in accordance with the procedure of Example 
1 are primed with this primer formulation and top coated in accordance 
with the procedure set forth in Example 2. These primed and top coated 
test panels are subjected to the adhesion test, before and after 
weathering, and the results are set forth in TABLE I. 
EXAMPLE 6 
A thermosettable acrylic primer formulation containing a high amount of a 
benzophenone ultraviolet light absorber is made by combining 19.8 parts by 
weight of the thermosettable acrylic primer formulation B of Example 2 
with 2.2 parts by weight of Cyasorb 531 (a benzophenone ultraviolet light 
absorber sold by American Cyanamid). Test panels prepared in accordance 
with the procedure of Example 1 are primed with this primer formulation 
and top coated in accordance with the procedure set forth in Example 2. 
These primed and top coated test panels are subjected to the adhesion 
test, before and after weathering, and the results are set forth in TABLE 
I. 
EXAMPLE 7 
A thermosettable acrylic primer formulation containing a high amount of 
benzotriazole ultraviolet light screener is made by combining 19.95 parts 
by weight of the thermosettable acrylic primer formulation B of Example 2 
with 1.05 parts by weight of Cyasorb 5411 (a benzotriazole ultraviolet 
light screener sold by American Cyanamid). Test panels prepared in 
accordance with the procedure of Example 1 are primed with this primer 
formulation and top coated in accordance with the procedure set forth in 
Example 2. These primed and top coated test panels are subjected to the 
adhesion test, before and after weathering, and the results are set forth 
in TABLE I. 
TABLE I 
______________________________________ 
Color of 
Adhesion Test Test Panel 
After 503 After 503 
Adhesion Test Hours of Hours of 
Example 
Before Weathering 
Weathering Weathering 
______________________________________ 
2 Pass Fail Yellow 
3 Pass Fail Yellow 
4 Pass Pass Colorless 
5 Pass Pass Colorless 
6 Pass Pass Colorless 
7 Pass Pass Colorless 
______________________________________ 
As can be seen by comparison of Examples 2 (where the primer layer contains 
no ultraviolet light screener) and 3 (where the primer layer contains a 
relatively small amount, i.e., 9 weight percent, of an ultraviolet light 
screener) with Examples 4-7 (wherein the primer layer contains high 
amounts of an ultraviolet light screener), the pressure of relatively high 
amounts of an ultraviolet light screener in the primer layer greatly 
improves the adhesion of the colloidal silica filled thermoset 
organopolysiloxane containing top coat to the polycarbonate upon exposure 
to weathering. Thus, while the test panels of Examples 2 and 3 the top 
coat failed the adhesion test after 503 hours exposure to weathering, the 
adhesion of the top coat of test panels of Examples 4-7 was not 
deleteriously affected by exposure to weathering for this same period of 
time. 
The foregoing disclosure of this invention is not to be considered as 
limiting, since many variations may be made by those skilled in the art 
without departing from the scope or spirit of the foregoing description.