Silicone coated abrasion resistant polycarbonate article

A non-opaque coated polycarbonate shaped article, and a process for producing the same, having improved abrasion and chemical solvent resistance comprising a polycarbonate substrate having thereon (i) a primer layer comprised of a thermoplastic acrylic polymer containing functional groups; and (ii) a top coat containing a thermoset organopolysiloxane on said primer layer. The process for producing said coated polycarbonate article comprises the steps of: (i) priming the surface of a polycarbonate substrate by forming a primer layer comprised of a thermoplastic acrylic polymer containing functional groups; (ii) applying a top coat composition containing a further curable organopolysiloxane onto the primed substrate; and (iii) curing the further curable organopolysiloxane to form a hard, abrasion and chemical solvent resistant top coat which is tenaciously and durably adhered to the polycarbonate substrate.

This invention relates to non-opaque abrasion and chemical solvent 
resistant organopolysiloxane coated shaped polycarbonate articles wherein 
the organopolysiloxane top coat is uniformly and tenaciously adhered to 
the polycarbonate substrate, and to a process for producing such an 
article. More particularly, the present invention relates to an 
organopolysiloxane coated polycarbonate article having a primer layer 
disposed between the polycarbonate substrate and the organopolysiloxane 
top coat comprising a thermoplastic acrylic polymer containing functional 
groups. The process for producing said article comprises priming the 
polycarbonate substrate with an adhesion promoting theromplastic acrylic 
polymer containing functional groups by forming a film of said acrylic 
polymer on the surface of the polycarbonate article; applying onto the 
primed surface a further-curable organopolysiloxane top coat composition; 
and curing the further-curable organopolysiloxane to form a uniform and 
tenaciously adherent abrasion and chemical resistant top coat. 
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 
substrate, various coatings have been applied to the polycarbonate resins. 
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 
polymethylmethacrylate. 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. An article produced by this 
process, while possessing acceptable initial adherence of the 
organopolysiloxane to the substrate, suffers from the disadvantage that 
upon prolonged exposure to weathering, and particularly to sunlight, the 
organopolysiloxane generally tends to lose its initial adherence to the 
substrate. Furthermore, as the thickness of the thermoset acrylic primer 
layer increases, the abrasion resistance of the coated article generally 
decreases. There thus remains a need for non-opaque polycarbonate articles 
having uniformly, tenaciously and durably adhered abrasion and chemical 
resistant coatings thereon, and it is a primary object of the present 
invention to provide such articles and a relatively simple and economical 
process for producing these articles. 
DESCRIPTION OF THE INVENTION 
This invention relates to non-opaque organopolysiloxane coated 
polycarbonate articles having a thermoplastic functional group containing 
acrylic polymer, adhesion promoting primer layer disposed between the 
polycarbonate surface and the organopolysiloxane, and to a process for 
producing these articles. 
In the practice of the present invention, prior to the application of the 
organopolysiloxane coating to the polycarbonate surface, the surface is 
first primed by the application thereon of a primer layer containing a 
thermoplastic acrylic polymer having functional groups. 
The aromatic carbonate polymer of the instant invention has 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. 
The aromatic carbonate polymer of this invention may be prepared by methods 
well known in the art and as described in U.S. Pat. No. 3,989,672 all of 
which are incorporated by reference. 
Also, included herein are branched polycarbonates wherein a polyfunctional 
aromatic compound is reacted with the dihydric phenol and carbonate 
precursor to provide a thermoplastic randomly branched polycarbonate 
wherein the recurring units of formula I. contain branching groups. 
The preferred polycarbonate resins may be derived from the reaction of 
bisphenol-A and phosgene. These polycarbonates have from 10-400 recurring 
units of the formula: 
##STR3## 
The polycarbonate should have an intrinsic viscosity between 0.3 and 1.0, 
preferably from 0.40 to 0.65 as measured at 25.degree. C. in methylene 
chloride. 
The term "theromplastic acrylic polymer having functional groups" as used 
herein is meant to embrace within its scope those thermoplastic polymers 
resulting from the polymerization of at least one substituted acrylic or 
methacrylic ester monomer represented by the general formula 
EQU CH.sub.2 .dbd.CY-COOR.sup.1 X III. 
wherein Y is hydrogen or a methyl radical; R.sup.1 is an alkyl group, 
preferably an alkyl group containing from 1 to about 20 carbon atoms; and 
X is a hydroxyl, carboxyl, amine, epoxide, amide, SH, SO.sub.3 H, 
COOR.sup.2 and Si(OR.sup.3).sub.3 group, wherein R.sup.2 and R.sup.3 are 
alkyl groups, preferably alkyl groups containing from 1 to about 20 carbon 
atoms. Copolymers resulting from the polymerization of two or more of 
substituted acrylic ester and substituted methacrylic ester monomers are 
also included within the term thermoplastic acrylic polymer having 
functional groups as it appears herein. Also included within the term 
thermoplastic acrylic polymers containing functional groups as used herein 
are copolymers resulting from the copolymerization of acrylic acid esters, 
i.e., acrylate, monomers and/or methacrylic acid esters, i.e., 
methacrylate, monomers with the aforedescribed substituted acrylic ester 
or substituted methacrylic ester monomers. Exemplary acrylate and 
methacrylate monomers which can be copolymerized with the substituted 
acrylic ester and/or substituted methacrylic ester monomers to form the 
thermoplastic acrylic polymers containing functional groups include methyl 
acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexylacrylate, methyl 
methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 
etc. Examples of copolymers of this type include copolymers containing 
ethyl methacrylate and hydroxyethyl methacrylate, ethyl methacrylate and 
.gamma.-methacryloxy-propyltrimethoxysilane, methyl acrylate and 
hydroxyethyl acrylate, and the like. The polymerization of the above 
monomeric substituted acrylates and methacrylates to provide the 
thermoplastic acrylic polymer having functional groups useful in the 
practice of the present invention may be accomplished by any of the well 
known polymerization techniques. 
Typical substituted acrylic and methacrylic acid ester monomers represented 
by formula III are set forth in Table I. 
TABLE I 
______________________________________ 
CH.sub.2C(CH.sub.3)COOCH.sub.2 CH.sub.2 OH 
CH.sub.2CHCOOCH.sub.2 CH.sub.2 OH 
CH.sub.2CHCOOCH.sub.2 CHOHCH.sub.3 
CH.sub.2CHCOOCH.sub.2 CHNH.sub.2 CH.sub.3 
CH.sub.2CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 NH.sub.2 
CH.sub.2CHCOOCH.sub.2 CH.sub.2 NH.sub.2 
CH.sub.2CHCOOCH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 
CH.sub.2 CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 
CH.sub.2CHCOOCH.sub.2 CH.sub.2 COOH 
CH.sub.2CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 COOH 
CH.sub.2CCH.sub.3 COO(CH.sub.2).sub.6 SH 
##STR4## 
CH.sub.2CH COO CH.sub.2 CH.sub.2 CH.sub.2 CONH.sub.2 
##STR5## 
CH.sub.2CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 COOCH.sub.2 CH.sub.3 
##STR6## 
##STR7## 
______________________________________ 
The term thermoplastic acrylic polymers containing functional groups as 
used herein thus includes homopolymers obtained from the polymerization of 
substituted acrylic ester monomers and substituted methacrylic ester 
monomers, copolymers obtained from the polymerization of two or more 
substituted acrylic ester monomers, copolymers obtained from the 
polymerization of two or more substituted methacrylic ester monomers, 
copolymers obtained from the polymerization of at least one substituted 
acrylic ester monomer with at least one substituted methacrylic ester 
monomer, and copolymers obtained from the polymerization of at least one 
substituted methacrylic ester and/or substituted acrylic ester monomer 
with at least one acrylic ester and/or methacrylic ester monomer. 
Mixtures of two or more of the aforedescribed homopolymers or copolymers 
can also be used in the practice of the present invention. 
For acceptable results, the thermoplastic acrylic polymers containing 
functional groups should have a molecular weight of at least 20,000 and 
preferably at least 50,000. 
The thermoplastic acrylic polymers containing functional groups of the 
instant invention differ from thermosettable acrylic polymers in that 
these thermoplastic polymers are formed and applied as primers under 
conditions such that these functional groups do not react between 
themselves to effect a cross-linkage between the polymer chains. Thus, the 
primer layer contains thermoplastic acrylic polymers containing functional 
groups. 
The thermoplastic acrylic polymers containing functional groups are in 
general applied as primers from a primer composition containing said 
thermoplastic acrylic polymers and a volatile solvent, either organic or 
inorganic in nature, which is generally substantially inert, i.e., will 
not greatly affect the polycarbonate part to be treated, but which is 
capable of dissolving the thermoplastic acrylic polymers. Generally, the 
concentrations of the thermoplastic acrylic polymer in the priming 
composition ranges from about 0.5 to about 25 percent by weight, 
preferably from about 1 to about 15 percent. Examples of suitable solvents 
include ethylene glycol diacetate, butoxyethanol, methylene-dichloride, 
1,2-dichloroethylene, chloroform, benzene, toluene and the like. 
The primer compositions of the instant invention may also optionally 
contain various flatting agents, ultraviolet light absorbent agents, 
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 
ultraviolet light absorbent agents 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. 
Exemplary ultraviolet light absorbent compounds or stabilizers include 
those of the hydroxy benzophenone or benzotriazole series. Examples of 
these are: 2-hydroxy-4-n-octoxybenzophenone, substituted 
hydroxyphenylbenzotriazole, 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole, 
and 2-hydroxy-4-methoxybenzophenone. Further examples of ultraviolet light 
absorbers which may be used in the practice of this invention may be found 
in U.S. Pat. No. 3,043,709. In general, the amount of the ultraviolet 
light absorber may vary from about 0.5 to about 15 percent by weight based 
upon the weight of the priming composition. 
A uniform film of the primer composition 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 may be removed by drying 
the coated article until the volatile solvent evaporates, leaving a primer 
layer or coating containing the thermoplastic acrylic polymer containing 
functional groups on the polycarbonate surface to which the primer 
composition was applied. The drying operation may be hastened by the use 
of drying apparatus such as, for example, a drying oven. Generally, the 
primer layer is a uniform film having a thickness varying between about 
0.002 mil to about 1 mil, preferably between about 0.01 mil to about 0.5 
mil. 
After the polycarbonate article which is to be coated has been primed by 
the application thereon of the primer composition and the evaporation of 
the solvent component of the primer composition, the primed surface of the 
polycarbonate article is then coated with the organopolysiloxane coating. 
In the practice of this invention, an organopolysiloxane coating 
composition containing a further curable organopolysiloxane is applied 
onto the solid primer and is then cured to form a thermoset 
organopolysiloxane coating. 
The further-curable organopolysiloxane used in the practice of the instant 
invention is the partial hydrolysis and condensation product of at least 
one compound represented by the general formula 
EQU R.sup.2.sub.n SiZ(.sub.4-n) IV. 
wherein R.sup.2 represents a monovalent hydrocarbon radical and a 
halogenated monovalent hydrocarbon radical, Z represents a hydrolyzable 
group and n may vary between 0 and 2. More specifically, Z is 
independently a member such a halogen, alkoxy, acyloxy and aryloxy. 
Preferably, R.sup.2 represents an alkyl radical containing from 1 to about 
8 carbon atoms such as methyl, ethyl, and propyl through octyl (both 
normal and isomeric), an alkenyl radical containing from 2 to about 8 
carbon atoms, such as vinyl and the normal and isomeric forms of propenyl 
through octenyl, and the phenyl radical; Z preferably represents an alkoxy 
radical containing from 1 to about 8 carbon atoms such as methoxy, ethoxy, 
propoxy, heptoxy, octoxy and the like, an acyloxy radical containing from 
2 to about 9 carbon atoms such as acetoxy, propionoxy, butyroxy, 
pentanoxy, hexanoxy, and the like, and a phenoxy radical; and n varies 
from 0 to 2. 
Preferred compounds of formula IV. are silanes of the formula 
EQU R.sub.a.sup.3 Si(OR.sup.4).sub.4-a V. 
and silanes of the formula 
EQU R.sub.b.sup.5 Si(OCOR.sup.6).sub.4-b VI. 
wherein R.sup.3 and R.sup.5 represent a monovalent hydrocarbon radical and 
a halogenated monovalent hydrocarbon radical, preferably an alkyl radical 
containing from 1 to about 8 carbon atoms, an alkenyl radical containing 
from 2 to about 8 carbon atoms, and the phenyl radical; R.sup.4 and 
R.sup.6 represent monovalent hydrocarbon radicals and halogenated 
monovalent radicals such as alkyl radicals and phenyl radicals, but are 
preferably alkyl radicals of 1 to 8 carbon atoms; a is 0 or 1; and b 
varies from 0 to 2. 
Upon hydrolysis, the compounds of formula IV, and more specifically those 
of formulas V and VI, are converted to the corresponding silanols. Upon 
generation of the silanol, there is condensation of the hydroxyl 
substituents to form --Si--O--Si-- bonding. The condensation is not 
complete, but rather the organopolysiloxane retains a quantity of 
silicon-bonded hydroxyl group. This partial condensate can be 
characterized as a further-curable, i.e., further condensable, siloxanol 
polymer. During curing of the further-curable organopolysiloxane which has 
been deposited on the primed polycarbonate substrate, these residual 
hydroxyls condensate to give a silsequioxane, R.sup.7 SiO.sub.3/2, wherein 
R.sup.7 represents R.sup.2, R.sup.3 or R.sup.5 above. 
The further-curable organopolysiloxane may be formulated into the top-coat 
composition as a solution of the further-condensable siloxanol polymer in 
water and alcohol by-product as a concentrated solution of 
further-condensable siloxanol in water and alcohol by-product formed by 
evaporating off a substantial quantity of the alcohol by-product and 
water, or it may be formulated onto the top-coat composition as a solid 
partially pre-cured product by evaporating off a substantial amount of 
alcohol by-product and water and then partially precuring and solidifying 
the concentrated product. 
Examples of good silicone top coats are the foregoing alkoxy and aryloxy 
functional silanes represented by formula V. and acyloxy functional 
silanes represented by formula VI. Such alkoxy functional, aryloxy 
functional, and acyloxy functional silanes are well known materials to 
silicone manufacturers and are easily obtainable. 
With respect to the acyloxy functional silanes, these materials are 
generally applied without any solvent since it has been found that the use 
of solvents in the application of such top coats at times seriously 
degrades the applied silicone top coat. Preferably, the silanes of Formula 
VI, that is the acyloxy functional silanes, are applied at 100% solids or 
from 20 to 100% solids, in the case of the acyloxy silanes where the 
solids are less than 100% the silane is simply the water hydrolysis and 
partial condensation product of the foregoing acyloxy functional silanes 
of Formula VI. The alkoxy and acyloxy functional silanes of Formula V are 
generally applied from a top-coat composition containing solvents in a 
solids concentration of from about 20 to 95% by weight. Examples of 
solvents which may be used in the formulation of the top-coat composition 
include methanol, ethanol, butanol, ethyl acetate, benzene, toluene, 
xylene, ethylene glycol and the like. However, the alkoxy and aryloxy 
functional silanes may also, similarly to the acyloxy functional silanes, 
be applied from a top-coat composition which contains no solvents other 
than the alcohol by-product and water used to form the partial hydrolysis 
and condensation products of these silanes. 
With respect to the foregoing aryloxy functional, alkoxy functional and 
acyloxy functional silanes mentioned above, such materials are well known 
in the art as, for instance, in U.S. Pat. Nos. 3,888,815 and 3,701,753, 
both of which are incorporated herein by reference. 
One particular class of further-curable organopolysiloxanes which are 
employed in the top-coat compositions of the present invention are the 
partial hydrolysis and condensation products of alkoxy functional silanes, 
preferably alkyltrialkoxysilanes, preferably those alkyltrialkoxysilanes 
wherein the alkyl group contains from 1 to about 8 carbon atoms, and 
aryltrialkoxysilanes, preferably phenyltrialkoxysilanes, or mixtures 
thereof, wherein the alkoxy group contains from 1 to about 8 carbon atoms, 
such as, for example, methoxy, ethoxy, isopropoxy, butoxy, pentoxy, 
hexoxy, octoxy, and the like. The further-curable organopolysiloxanes are 
generally prepared by a process wherein the alkyltrialkoxysilane, 
aryltrialkoxysilane, or a mixture of alkyltrialkoxysilane and 
aryltrialkoxysilane is heated in the presence of water, wherein the molar 
ratio of water to total silane is at least about 1.5:1 and in the presence 
of an effective amount of a hydrolysis catalyst, such as a mineral acid, 
for example, HCl, for about 1 to about 10 hours at a temperature between 
ambient and reflux to produce a siloxane partial condensation product; the 
partial condensation product is then concentrated by heating to remove 50 
to about 90 mole percent alkanol by-product and some water, and 
thereafter, the concentrated partial condensation product is precured by 
heating at a temperature below the gel point thereof and generally in the 
range of about 70.degree. to 300.degree. C. to produce the 
solvent-soluble, further curable organopolysiloxane. This precured 
solvent-soluble, further-curable organopolysiloxane is then dissolved in a 
suitable solvent to form the top-coat composition and the primed 
polycarbonate substrate is then coated with this top coat composition. The 
solvent is then evaporated and the residual further-curable 
organopolysiloxane is cured to a thermoset state to provide a uniformly 
and tenaciously adhered top coat on the primed polycarbonate substrate. 
The curing is effected at elevated temperatures in the range of about 
50.degree. to 135.degree. C. for times between about 1 hour to about 72 
hours, depending on the temperature at which the cure is effected. The 
silicone top coat generally should be cured preferably at an elevated 
temperature to effect the proper cure, but the temperature should be below 
the glass transition temperature of the polycarbonate. Of course, if the 
glass transition temperature of the polycarbonate is exceeded, then the 
polycarbonate part may become deformed and lose its utility. 
One particular further curable organopolysiloxane that can be employed in 
the top coat composition of the instant invention is the partial 
hydrolysis and condensation product of methyltriethoxysilane. This 
further-curable organopolysiloxane is prepared by hydrolyzing 
methyltriethoxysilane with water in the presence of an effective amount of 
a hydrolysis catalyst, such as HCl, for about 1 to 10 hours at a 
temperature generally between 40.degree. C. and reflux temperature, to 
produce a partial condensation product. This partial condensation product 
is then concentrated by heating to remove some of the alkanol by-product 
and water. This concentrated product is then partially pre-cured at a 
temperature of about 70.degree. to about 300.degree. C. and below the gel 
point thereof and then solidified to provide a solid, solvent-soluble, 
further curable organopolysiloxane. The solid, solvent-soluble, 
further-curable organopolysiloxane is then dissolved to a desired 
concentration in a suitable solvent to form the top coat composition. The 
top coat composition is then applied to the primed polycarbonate 
substrate, after which the solvent is evaporated and the further-curable 
organopolysiloxane finally cured to provide a hard, abrasion and chemical 
solvent resistant, thermoset organopolysiloxane top coat in the 
polycarbonate substrate. 
Another further-curable organopolysiloxane which may be employed in the 
practice of the present invention is the partial hydrolysis and 
condensation product of a mixture of methyltriethoxysilane and 
phenyltriethoxysilane. This organpolysiloxane is prepared by hydrolyzing a 
mixture of methyltriethoxysilane and phenyltriethoxysilane with water in 
the presence of a hydrolysis catalyst such as HCl to produce a partial 
condensation product. This partial condensation product is then 
concentrated by heating to remove a substantial amount of the alkanol 
by-product and some water. This concentrated product is then partially 
pre-cured by heating and then solidified to provide a solid, 
solvent-soluble, further-curable organopolysiloxane. The solid, 
solvent-soluble, further-curable organopolysiloxane is then dissolved to a 
desired concentration in a suitable solvent to form the top-coat 
composition containing a further-curable organopolysiloxane. The top-coat 
composition is then applied to the primed polycarbonate substrate, after 
which the solvent is evaporated and the further-curable organopolysiloxane 
is finally cured to provide a tenaciously and durably adhered, abrasion 
and chemical resistant thermoset organopolysiloxane top coat on the 
polycarbonate substrate. 
These are not the only silicones that may be utilized in the top-coats of 
the instant invention. Less preferred silicones which can be utilized to 
form the top coats of the present invention are, for instance, silicone 
resins composed of trifunctional and difunctional units, silicone resins 
composed of trifunctional units, difunctional units and tetrafunctional 
units when the organo substituent groups in the trifunctional units may be 
selected from hydrocarbon radicals of 1 to about 8 carbon atoms and are 
preferably methyl, phenyl and vinyl; and wherein the organo substituent 
groups in the difunctional siloxy units may be selected from hydrocarbon 
units of from 1 to about 8 carbon atoms, preferably alkyl radicals, vinyl 
radicals and phenyl radicals. Such silicone resins usually have an organic 
to silicon atom ratio of 1:1 to 1.9:1; may have a silanol content that 
varies anywhere from 4 to 10 weight percent and optionally may have an 
alkoxy content that various from 2 to 4%. The preparations of such 
silicone resins which may be utilized as top-coats in the invention of the 
intant case are, for instance, to be found in U.S. Pat. Nos. 3,375,223, 
3,435,001, 3,450,672, 3,790,527, 3,832,319, 3,865,766, 3,887,514 and 
3,925,276. 
These silicones may also contain various fillers such as, for example, 
glass fibers, talc and silica, preferably colloidal silica. 
The top-coat compositions containing the aforedescribed silicones are 
simply brushed, dipped, sprayed or flowed on top of the primer layer that 
is applied to the polycarbonate substrate. The solvent, or alcohol 
by-product and water, present in the top-coat composition is evaporated 
and the residual further-curable organopolysiloxane is cured to form a 
thermoset organopolysiloxane top coat. Preferably, the further-curable 
organopolysiloxane is cured at elevated temperatures. Although certain 
catalysts may be utilized to accelerate the cure of the further-curable 
organopolysiloxane, such catalysts are not necessary if the 
further-curable organopolysiloxane is cured by itself at the elevated 
temperature for a sufficient length of time. 
Another embodiment of the present invention is a process of producing a 
durably adherent, mar, and chemical resistant silicone coating on a 
polycarbonate article. The process comprises the steps of: (i) applying 
onto the polycarbonate substrate a primer composition containing a 
thermoplastic acrylic polymer dissolved in a suitable solvent; (ii) 
evaporating of the solvent to leave a solid thermoplastic acrylic polymer 
containing primer layer on the polycarbonate substrate; (iii) applying a 
top-coat composition containing a further-curable organopolysiloxane onto 
the primed polycarbonate substrate; (iv) evaporating off the volatile 
solvents present in the top coat composition to form a residue of 
further-curable organopolysiloxane on the primed polycarbonate substrate; 
and (v) curing the further-curable organopolysiloxane to form a top coat 
containing a thermoset organopolysiloxane.

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. 
EXAMPLE 1 
An aromatic polycarbonate is prepared by reacting 2,2-bis(4-hydroxyphenyl) 
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. The test panels are 
subjected to an abrasion test. The abrasion test is one wherein test 
panels having a 1/4 inch diameter hole cut in the center are subjected to 
a Taber Abraser. The Taber Abraser is equipped with CS-10F wheels which 
are resurfaced every 200 cycles by abrading for 25 cycles on a S-11 
refacing disc. The weights used in combination with the CS-10F wheels are 
500 gm. weights. Initial measurements of % Haze are made at four places 
around the future wear track of the sample using a Gardner Hazemeter. The 
sample is abraded for 300 cycles, cleaned with isopropanol, and the % Haze 
is remeasured at the same four places. The four differences in % Haze are 
calculated and averaged to give the .DELTA.% Haze. The results are set 
forth in Table II. 
EXAMPLE 2 
A top-coat composition is prepared by adding to 100 parts by weight of a 
commercially available further-curable organpolysiloxane 2 parts by weight 
of a commercially available curing catalyst. This further-curable 
organopolysiloxane is available from Resart-Ihm A.G., Mainze, Federal 
Republic of Germany, as their Resarix SFPC.sup.(R) and is a solution 
containing about 32 weight percent of the partial hydrolysis and 
condensation product of methyl triethoxysilane dissolved and a solvent 
system consisting of ethanol-tetrahydrofuran-n-butanol-ethoxyethanol. The 
catalyst consists of a solution containing 2 weight percent of 
tetraethylammonium hydroxide and a methanol solvent. 
EXAMPLE 3 
Primer compositions are formulated by dissolving in a solvent system 
containing 20 parts ethyleneglycol diacetate and 80 parts butoxyethanol a 
desired amount of a thermoplastic acrylic polymer containing functional 
groups formed by the copolymerization of a methacrylate monomer and a 
functionalized methacrylate monomer. This primer composition is flow 
coated on polycarbonate test panels prepared substantially in accordance 
with Example 1. Excess primer composition is permitted to drain off and 
the test panels are dried for 15 minutes at 125.degree. C. to evaporate 
the solvent and produce a solid primer layer. These primed panels are then 
flow coated with the further-curable organopolysiloxane top coat 
composition produced substantially in accordance with Example 1. Excess 
top coat composition is permitted to drain off and the test panels are air 
dried for 30 minutes and are thereafter subjected to 1 hour of heating at 
125.degree. C. to cure the further-curable organopolysiloxane. These 
primed, top coated test panels are then subjected to the above described 
abrasion test and to an adhesion test which consists of using a multiple 
blade tool to cut parallel grooves about 1 mm apart through the coating 
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 results of the adhesion test 
and abrasion test, as well as the concentration of the thermoplastic 
acrylic polymer containing functional groups in the primer composition, 
the thickness of the primer layer and the composition of the monomer 
mixtures used in formulating the thermoplastic acrylic polymer containing 
functional groups are set forth in Table II. 
TABLE II 
______________________________________ 
Primer 
Composition, %, by weight, 
thick- .DELTA.% 
in parts by of solids in 
ness Ad- Haze 
weight, of primer (in he- 300 
monomer mixture 
composition 
mils) sion cycles 
______________________________________ 
Unprimed and 
uncoated test panel 
-- -- -- 34 
of Example 1 
97 parts of methyl- 
methacrylate 
3 parts hydroxy- 5 0.02 Pass 5.3 
ethyl methacrylate 
98 parts ethyl 
methacrylate 2 0.02 Pass 5.2 
2 parts glycidyl 
methacrylate 
49 parts methyl 
methacrylate 
49 parts n-butyl 10 0.05 Pass 4.9 
methacrylate 
2 parts hydroxyethyl 
methacrylate 
97 parts methyl 
methacrylate 15 0.27 Pass 3.1 
3 parts hydroxy- 
ethyl methacrylate 
98 parts ethyl 
methacrylate 20 0.31 Pass 5.2 
2 parts .nu.-methacryloxy- 
propyltrimethoxy- 
silane 
______________________________________ 
EXAMPLE 4 
This example is designed to illustrate the criticality of the particular 
combination of the thermoplastic acrylic polymer primer layer containing 
functional groups and organopolysiloxane top coat in providing a durable 
and tenaciously adhered coating effective to produce an abrasion resistant 
polycarbonate article. Unprimed polycarbonate panels are prepared 
substantially in accordance with Example 1 and are flow-coated with the 
Resarix SF/PC.sup.(R) organopolysiloxane top coat composition prepared 
substantially in accordance with Example 2. Excess top coat composition is 
permitted to drain off and the coated unprimed test panels are air dried 
for 30 minutes to evaporate the solvent, followed by a one-hour bake at 
250.degree. F. to cure the further-curable organopolysiloxane. These 
unprimed coated test panels are subjected to the aforedescribed adhesion 
and abrasion tests and the results are set forth in Table wII. 
TABLE III 
______________________________________ 
Sample Adhesion .DELTA.% Haze, 300 cycles 
______________________________________ 
Example 4 Failed 10.3 
______________________________________ 
As can be seen from Tables II and III, the adhesion of the 
orgonopolysiloxane top coat to the umprimed polycarbonate panels is 
markedly inferior. As a matter of fact, it is unsatisfactory, as compared 
to the adhesion of the organopolysiloxane top coat to the polycarbonate 
panels primed in accordance with the present invention. 
EXAMPLE 5 
This example is likewise designed to illustrate the criticality of the 
particular combination of the thermoplastic acrylic polymer primer layer 
containing functional groups and organopolysiloxane top coat of the 
instant invention in providing a durable and tenaciously adhered coating 
effective to produce an abrasion resistant polycarbonate article. EV-6174, 
a commercially available thermosettable acrylic (32% solids in butanol) 
available from Bee Chemical Company, is diluted with n-butanol to various 
solids concentrations. Into these solutions are dipped polycarbonate test 
panels prepared substantially in accordance with Example 1. The 
polycarbonate panels are then removed from the priming solutions and are 
allowed to remain in the open air for about 30 minutes, during which time 
the solvent from the priming solutions evaporates and deposits a thin 
priming film on the polycarbonate surface. The primed test panels are then 
flow coated with an organopolysiloxane top coat composition prepared 
substantially in accordance with Example 2. Excess top coat composition is 
permitted to drain off and the test panels are air dried for 30 minutes 
and are thereafter subjected to 1 hour of heating at 125.degree. C. These 
primed and top coated test panels are subjected to the aforedescribed 
adhesion test and to the abrasion test. The results of these tests, as 
well as the concentration of the thermosettable acrylic in the primer 
solution and the thickness of the primer layer are set forth in Table IV. 
TABLE IV 
______________________________________ 
% Solids (thermosettable 
Primer 
acrylic polymer) in 
thickness 
n-butanol solution 
(mils) Adhesion .DELTA.% Haze 
______________________________________ 
2 0.01 Pass 7.1 
20 0.36 Marginal* 7.5 
______________________________________ 
*The results of the adhesion test were uneven. That is to say, some 
samples failed the adhesion test, while other samples passed the adhesion 
test. 
A comparison of Tables II and IV shows that with a thermosettable acrylic 
primer the abrasion resistance of the top coat, as well as the adhesion of 
the top coat, deteriorates as the thickness of the primer layer increases. 
This is not the case with the thermoplastic acrylic primers of the present 
invention, i.e., the adhesion and abrasion resistance of the top coat do 
not deteriorate as the thickness of the primer layer increases. 
Thus, a particular advantage of the instant thermoplastic acrylic primers 
is that the abrasion resistance and adhesion of the silicone top coat is 
generally not a function of primer layer thickness. It is well known to 
those skilled in the art that wedging occurs during the coating of large 
polycarbonate sheets. Thus, it is a great advantage if properties such as 
abrasion resistance and adhesion are generally not dependent upon primer 
coating thickness. 
A further advantage of having a thick primer coating is that ultraviolet 
light and other stabilizers can effectively be incorporated in the 
coating. Polycarbonate generally undergoes photodegradation and turns 
yellow during prolonged weathering. However, if the surface of 
polycarbonate can be protected from ultraviolet light, it can be 
stabilized against photodegradation. Incorporation of ultraviolet 
light-absorbers in a coating on polycarbonate is therefore highly 
desirable since these materials will screen ultraviolet light from 
reaching the surface of the polycarbonate. For practical purposes, 
however, a coating must generally be about 0.2-0.3 mils thick and contain 
about 10% of an ultraviolet light-absorber before more than 90% of the 
incident ultraviolet light can be screened from the surface of the 
polycarbonate. Thinner primer coatings generally require much more 
ultraviolet light-absorbers to effectively screen more than 90% of 
incident ultraviolet light. Due to the fact that the primer layers of the 
instant invention can be relatively thick, ultraviolet light-absorbers can 
therefore be effectively incorporated in the thermoplastic acrylic primers 
of the instant invention. 
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. 
For example, although the above examples are limited to only a few of the 
very many thermoplastic acrylic polymers containing functional groups 
which can be employed in the present invention, it should be understood 
that the present invention includes a much broader class of such polymers 
as shown by formula III and the description preceding these examples.