CA1162448A - Abrasion resistant silicone coated polycarbonate article - Google Patents

Abstract

ABRASION RESISTANT SILICONE COATED
POLYCARBONATE ARTICLE
ABSTRACT OF THE DISCLOSURE

A shaped p 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 thermoset organopolysiloxane.

Description

1 1 62~

This invention relates to non-opaque abrasion and chemical solvent resistant thermoset organopolysiloxane coated shaped polycarbonate articles wherein the organopolysiloxane top coat is uniformly and tenaciously adhered to the polycarbonate substrate. More particularly, the present invention relates to an organopolysiloxane coated polycarbonate article having a primer layer comprised of from about 25 to about 85 weight percent thermoset acrylic polymer and from about 15 to about 75 weight percent of at least one ultraviolet light screening compound disposed between the polycarbonate substrate and the organopolysiloxane 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, various coatings have been applied onto the polycarbonate substrates. U.S. Patent 3,582,398 H.R. Ringler - issued June 1, 1971 describes a fabricated polycarbonate part having improved optical properties consisting of a polycarbonate substrate ~ 3 62~ 8Cs~3417 having a transparent coating thereon consisting of a thermoplastic polymethylmethacrylate. U.S. Patent 4,061,652 - S.F. Schroeter, issued December 6, 1977, 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. Patents 3,451,838 - A~Jo Burzynski, issued June 24, 1969j 3,983,997 - H.A. Clark, issued October 19, 1976 and 4,027,073- H.A. Clark, issued May 31, 1977 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 xesistant, 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. 3,707,397 D.F. Gagnon, issued December 26, 1972 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.

11 fi2~ 8CS-3417 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 primed polycarbonate substrate upon exposure to weathering.
It has now been discovered that, if the primer layer is loaded with high amounts of ultraviolet light absorbers, i.e., contains from about 15 to about 75 weight percent of at least one ultraviolet lîght 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 organopolysiloxane coated polycarbonate articles having an adhesion promoting 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 absorbing compound disposed between the polycarbonate surface and the thermoset organopolysiloxane top coat.
In the practice of the present invention, prior to the application of the organopolysiloxane top coat 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.

~ 1 ~2~$ 8CS-3~17 The aromatic carbonate polymers of the instant invention are known compounds and have recurring units of the formula:

A

- R - C - R - O - C - O (I)-B O
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 -C- 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. Patents 3,989,672 - J.H. Vestergarrd, issued November 2, 1976; 3,275,601 - H. Schnell, issued September 27, 1966; and, 3,028,365 - H. Schnell et al, issued April 3, 1962.
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 oE
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, ~ 1 6 2 4 ~ 3 8CS-3417

2,2-(3,5,3',5'-tetrabromo-4,~'-dihydroxydiphenyl)propane, (3,3'-dichloro-4,4'-dihydroxydiphenyl)me-thane. Other dihydric phenols of the bisphenol type are also available and are disclosed in U.S. Patent Nos.
2,99 ,835 - E.P. Goldberg, issued September 12, 1961;

3,028,365 - H. Schnell et al, issued April 3, 19~2;
and, 3,334,154 - J.K.S. Kim, issued August l, 1967.
In addition, the reaction is earried 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 earbonate polymers is earbonyl ehloride. 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 eommonly used to prepare polyearbonates.
The thermosettable aerylie polymers whieh 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 page 251 et seq., and the references cited therein.

1 3 62~4g Generally, the term, thermosettahle acrylics, as used herein includes an acrylic polymer or copolymer having reactive functional groups which are capable of reacting between themselves to erfect 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 groupO 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 wi~h 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. ~hese polymers may be acrylic polymers or copolymers having reactable, cross-linkable, functional groups thèreon, or at least one of the polymèrs 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 2; 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; sarboxyl functional groups and N-methylol or N-methylol-ether functional groups; interreaction between carboxyl _ 6 ~

1 ~ 6 ~

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 ~ypically, 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 anhydxide, itaconic anhydride, allyl alcohol, monoallyl ethers of polyols, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxy-propyl 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 (Cl-C3) alkyl acrylic ester or mixtures thereof, e.g , methyl acrylate, ethyl ~5 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.

1 1 ~2~ 8CS-3417 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 screening compound 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 and the ultraviolet light screening compound.
The primer compositions contain sufficient thermosettable acrylic polymer and ultraviolet light screening compound to provide a primer layer containing from about 2S to about 85 weight percent thermoset acrylic polymer and from about lS 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 solid 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 screening compound or it can contain a mixture of two or more ultraviolet light screening compounds.

~ ~ 624~ 8CS-3417 The ultraviolet light screening 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 benzylidene malonates. Examples of these include: 2-hydroxy-4-n-o toxybenzophenone, 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-3-cyanoacylate, and octyl 3,3-diphenyl-2-cyanoacrylate. Further examples of ultraviolet light screening compounds which may be used in the practice of this invention may be found in U.S. Patent No. 3,043,709 - L.E. Amborski, issued July lO, 1962.
The primer compositions of the instant invention may also optionally contain various flatting I ~ 62~ 8CS-3417 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 agents and stabilizing 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 ~ork, 1969, pp. 507-593, and Encyclopedia of Polymer Science and Technology, Vol. 13, Interscience Publishers, New York, 1960, pp. 477-486.
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 ~ 8CS-3417 from about 25 to about 85 weight percent of the thermoset acrylic polymer and from about 15 to about 75 weight p rcent of the ultraviolet light absorbing system, i.e., at least one ultraviolet light screening compound;
preferably from about 25 to about 80 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.
&enerally, if less than about 15 weight percent of the ultraviolet light absorber i5 present in the primer layer, there is no appreciable improvement upon the durability of adhesion of the silicone top coat. If the primer layer contains more than about 75 weight percent of an ultraviolet light absorber, the adhesion promoting properties of the primer begin to be deleteriously 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 thermosettable organopolysiloxane top coating. In the practice of this invention, an organopolysiloxane coating composition containing a further curable organopolysiloxane is applied onto the cured 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 hydrolysis and partial condensation product of a~ least one compound represented by the general formula n (4-n) II.
wherein R2 represents a monovalent hydrocarbon radical and a hologenated monovalent hydrocarbon radical, Z represents a hydrolyzable group and n may vary from 0 to 2. More specifically, Z is independently a member such as halogen t alkoxy, acyloxy and aryloxy.
Preferably, R 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 II are silanes of the formula R aSi(OR )4 aIII.
and silanes of the formula R bSi(OCOR )4 bIV.

1 31 ~2~

wherein R3 and R5 represent a monovalent hydrocarbon radical and a halogenated monovalent hydrocarbon radical, preferably an alkyl radical containing from 1 to about a carbon atoms, an alkenyl radical containing from 2 to about 8 carbon atoms, and the phenyl radical; R4 and R6 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 O or l; and b varies from O to 2.
Upon hydrolysis, the compounds of formula II, and more specifically those of formulae III and IV, 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 ~0 condensable, siloxanol polymer.
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 pre-curing and solidifying the concentrated product.

~ ~ ~24~

Examples of good silicone top coats are the foregoing alkoxy and aryloxy functional silanes represented by formula III and acyloxy functional silanes represented by formula IV. 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. Prefexably, the silanes of Formula IV, that is the acyloxy functional silanes, are applied at 100~ solids or from 2Q 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 IV.
The alkoxy and aryloxy functional silanes of Formula III 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 silan~s, 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.

~ J ~ 2 ~ 8CS-3A17 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 ins-tance, in U.S. Patents 2,888,815 - S.J. Bessmer, issued June 10, 1975 and 3,701,753 - H.P. Shaw, issued October 31, 1972.

One particular class of further-curable organopolysiloxanes wh.ich 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 ~0 organopolysiloxanes are generally prepared by a process wherein the alkyltrial~oxysilane, aryltrialkoxysilane, or a m~ixture 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 ~ 8CS-3417 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 to 300C to produce the solvent-soluble, further-curable organopolysiloxane. This pre-cured solvent-soluble, urther-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 to 135C for times between about l hour to about 72 hours, depending on the temperature at which the cure is effected. The silicone top coat generally shouId 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 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 l to 10 hours at a temperature t ~ ~ 6~8 8CS-3417 generally between 409C and reflux kemperature, 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 to about 300C 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 organopolysiloxane is prepared by hydrolyzing a mixture of methyltriethoxysilane and phenyltriethoxysilane with water in the presence of a hydrolysis catalyst such as HC1 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, ~ 8CS-3417 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 trifunctional units may be selected from hydrocarbon radicals of 1 to about 8 carbon atoms and are preferab:Ly methyl, phenyl and vinyl; and wherein the organo substitutent 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 radical to silicon atom ratio of 1:1 to 1.9:1; may have a silanol con-tent that varies I ~ 62d~ 8CS-3417 anywhere from 4 to 10 weight percent and optionally may have an alkoxy content that varies from 2 to 4%O
The preparations of such silicone resins which may be utilized as top coats in the invention of the instant case are, for instance, to be found in U.S.
Patents, 3,375,223 - D.F. Merrill, issued March 26, 1968; 3,435,001 - D.F. Merrill, issued March 25, 1969;
3,450,672 - D.F. Merrill et al, issued June 17, lg69;
3,790,527 - D.F. Merrill, issued February 5, 1974;
3,832,319 - D.F. Merrill, issued August 27, lg74;
3,865,766 - D.F. Merrill, issued February 11, 1975;
3,887,514 - D.F. Merrill, issued June 3, 1975 and 3,925,276 - W.J. Lampe, issued December 9, 1975.
Particularly prefered, filled further-curable organopolysiloxane top coat compositions are disclosed in U.S. Patents 3,986,997 and U.S. Patent 4,027,073.
These compositions comprise a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of a silanol having the formula R Si(OH)3 wherein R 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-glycioxypropyl radical and the gamma methacryloxypropyl radical, with at least 70 percent by weight of said silanol being CH3Si(OH)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 ~ 3 6~
8CS-3~19 condensate of a silanol. The partial condensate of a silanol, i.e., a siloxanol, is obtained, preferably, entirely from the condensation of CH3Si(OH)3, however, the partial condensate may also optionally be comprised of a major portion which is obtained from the condensation of CH3Si(OH)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 6Ø 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, ~0 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 1 1 ~ 8 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 SiO3/2.
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 diameterO
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 lO to 30 millimicrons in diameter ; 20 in order to obtain dispersions having a greater stability and to provide top coatings having superior optical properties.
The silica-filled organopolysiloxane top coa~ 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.
Depeinding 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, su-Eficient 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.
The top coat compositions containing the afore-described 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 -~ 8CS-2317 further curable organopolysiloxane is cured to form a thermoset organopolysiloxane top coat. Preferably, the further-curable organopolysiloxane is cured at ele ated 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.
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. In the Examples set forth below, all parts and percentages, unless otherwise indicated, are on a weight basis.

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 o 0.57. The product is then fed to an extruder, which extruder is operated at about 265C and the extrudate is comminuted into pellets.
The pellets are then injection molded at about 315C into test panels of about 4in. by 4 in.
by about 1/8 in. thick.

A further curable organopolysiloxane top coat composition is prepared as follows: To 100 parts by weight of a commercially available solution containing a further-curable organopolysiloxane 8CS~3~17 dissolved in a suitable solvent is added 2 parts by weight of a commercially available curing catalyst solution to form a top coat composition. This further-curable organopolysiloxane is available from Resart-Ihm A.G., Mainæ, Federal Republic of Germany, as their Resarix SF/PC/TM and is a solution containing about 32 weight percent of a partial hydrolysis and condensation product of methyl triethoxysilane dissolved in an ethanol-tetrahydrofuran-n-butanol-ethoxyethanol solvent system. The catalyst consists of a solution containing 2 weight percent of tetraethylammonium hydroxide dissolved in methanol.

This Example illustrates a primed, top coated polycarbonate ar~icle falling outside the scope of the instant invention in that no ultraviolet light absorbing compound is present in the primer layer~
A solution of 120 parts by weight of freshly distilled methyl methacrylate, 2 parts by weight of methacrylic acid, 0.03 parts by weight of dodecanethiol, and 0.15 parts by weight of 2,2'-azobisisobutyronitrite in 360 parts by weight of butoxyethanol is stirred under nitrogen at 100C for 24 hours.
A thermosettable acrylic primer formulation hereinafter referred to as "primer formulation A", is made by combining 10 parts by weight of the afore--prepared solution, 0.12 parts by weight of a cycloaliphatic diepoxide, 0.01 parts by weight of toluenesulfonic acid, and 1 dxop of a flow agent in 32 parts by weight of butoxyethanol and 14 parts by weight of ethylene glycol diacetate.

-1 1 62~

Polycarbonate test panels prepared in accordance with the procedure of ~xample 1 are flow coated with this primer formulation A, are drained for 10 minutes, and then are baked at 125C for 15 minutes. After cooling, the primed test panels are flow coated with the organopolysiloxane top coat composition prepared substantially in accordance with t'ne 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 125C to effect the cure of the further curable organopolysiloxane. The primed and top coated test panels are subjected to an adhesion test,-both beore and after weathering, and he results are set forth in TABLE I. The adhesion test 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 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 QU~ TM
accelerated weathering tester, sold by Q-Panel Company, which is set to cycles of 4 hours of fluorescent ultraviolet light at about 60C and 4 hours of dark/condensation at about 45C.
`EX_MPLE 3 A thermosettalbe acrylic primer formulation containing a hiyh amount of a benzotriazole ultraviolet ~ 25 I ~ ~2A~

light absorber is prepared by combining 56 parts by weight of the thermosettable acrylic primer formulation A of Example 2 with 3 parts by weight of Cyosorb TM 5411 (a benzotriazole ultraviolet light absorber sold by American Cyanamid). Test panels prepared in accordance with the procedure of Example l are primed with this primer formulation and top coated in accordance with the procedure of 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.

A thermosettable acrylic primer formulation containing a high amount of dihydroxybenzophenone ultraviolet light absorber is prepared by combining 56 parts by weight of the thermosettable acrylic primer formulation A of Example 2 with 3.5 parts by weight of 2,~-dihydroxybenzophenone. 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 of Example 2. These primed and top coated test panels are subjected to the adhesion test, before and after weatheringr and the results are set forth in TABLE I.

-A thermosettable acrylic primer formulation containing a high amount of a benzophenone ultraviolet li ht absorber is prepared by co~;bining 56 parts by weight of the thermosettable acryli~ primer formulation A of Example 2 with 3.5 parts by weight of Cyasorb 531 (a benzophenone ultraviolet light absorber sold by American Cyanamid). Test panels prepared in accordance I 1 ~2~

with the procedure of Example 1 are primed with this primer formulation and top coated in accordance with the procedure of 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 1.
EXA~E 6 A thermosettable acrylic primer formulation containing a high amount of a cyanoacrylate ultraviolet light absorber is prepared by combining 56 parts by weight of the thermosettable acrylic primer formulation A
of Example 2 with 3.5 parts by weight of Uvinul TM 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 of 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.

A thermosettable acrylic primer formulation containing a high amount of a benzylidene malonate ultraviolet light absorber is prepared by combining 56 parts by weight of the thermosettable acrylic primer formulation A of Example 2 with 3.5 parts by weight of Cyasorb W-1988 (a benzylidene malonate 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 of 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.

~ 27 7 3 ~2~ 8CS-3417 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 100C 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 butoxy ethanol.
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 125C for 30 minutes. After cooling the primed test panels are flow coated with the 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 125C to cure the further-curable organopolysiloxane. The primed and top coated test panels are subjected to an adhesion test, before weathering, after weathering for 144 hours, and after weathering for 503 hours, and the results are set forth in TABLE II.

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 formulation 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 8 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 8. 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 II.

A thermosettable acrylic primer formulation containing a high amount of dihydroxybenzophenone ultraviolet light absorber is prepared by comhining 19.8 parts by weight of the thermosettable acrylic primer formulation B of Example 8 with 2.2 parts by weight of 2,4-dihydroxybenzophenone. 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 8.

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 II.

1 3 5~a~
8CS~3417 EXAMPLE II
A thermosettable acrylic primer formulation containins a high amount of benzotriazole ultraviolet light absorber is prepared by combining 19.95 parts by weight of the thermosettable acrylic primer formulation B
of Example 8 with 1.05 parts by weight of Cyasorb UV-1988 (a benzotriazole ultraviolet light screener sold by American Cyanamid). Test panels prepared in accordance with the procedure of Example 1 are primed with this prior primer formulation and top coated in accordance with the procedure set forth in Example 8. 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 II.
TABLE I

Color of Test Adhesion Test Adhesion Test Panel After Before After 144 Hrs. 144 Hours Example Weatherlng Weathering Weathering 2 Pass Fail Yellow 3 Pass ~Pass Colorless

4 Pass Pass Colorless Pass Pass Colorless 6 Pass Pass Colorless 7 Pass Pass Colorless TABLE II

Color of Adhesion Ad~esion Adhesion Test Panel Test ~est After' Test After After 144 Before 144 Hrs. of 503 Hrs. of Hours of Example Weathering Weathering Weathering W
8 Pass Fail Fail Yellow 9 Pass Marginal Fail Yellow Pass Pass Pass Colorless 11 Pass Pass Pass Colorless gCS-3417 As can be seen by comparison of Examples 2 and 8 with Examples 3-7 and 10-ll in TABLES I and II above, the adhesion of the thermoset organopolysiloxane containing top coat composition to polycarbonate panels primed with a primer containing a thermoset acrylic polymer but no ultraviolet light screener rapidly deteriorates upon exposure to weathering, while the adhesion of the top coat to a primer containing relatively high amounts of ultraviolet light screener is not deleteriously affected by weathering. Example 9, in which the primer layer contains 9 weight percent of an ultraviolet light screener, shows that the presence of relatively small amounts of ultraviolet light screener in the primer layer is ineffective in remedying the problem of adhesive failure of the top coat upon exposure to weathering.

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 265C and the ~xtrudate is comminuted into pellets.
The pellets are then injection molded at about 315C 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 a~ueous ~ ~ ~24 ~ ~ 8cs-34l7 dispersion of colloidal silica having an initial p~ of 3.1 containing 34% SiO2 of approximately 15 millimicron particle size and having a Na2O content of less than 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 composi~ion 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 CH2Si(OH)3 in the silica methanol-water dispersion.
The composition contains 40% solids, half of which is SiO2 and the other half silicone calculated on the basis CH3SiO3/2 weight available in the cured composition.
The aged composition is diluted to 25 weight percent solids by addition of isopropanol.

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 aci and 0.1 parts by weight of 2,2'-azobisisobutyronitrile in 160 parts by weight of butoxyethanol i~ stirred, under nitrogen at 100C 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 ~ ~ ~24~ 8CS-3417 toluenesulfonic acid, and 160 parts by weight of butoxyethanol.
Polycarbonate test panels prepared in accordance with the procedure of Example 12 are flow coated with this primer formulation B, are drained for 10 minutes, and then are baked at 125C for 30 minutes. After cooling the primed test panels are flow coated with the colloldal 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 125C 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 III.
The adhesion test consists of using a multiple blade tool to cut parallel grooves about lmm apart through the top coat and primer layer into the substrate, rotating the sample 90 and repeating the cutting process thereby forming a grid pattern of lmm 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 Q W accelerating weathering tester, sold by Q-Panel Company, which is set to cycles of 8 hours of fluorescent ultraviolet light at about 70C and 4 hours of dark/condensation at about 60 C.

-~ ~ $24 4 ~ 8CS 3417 -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 3 weight percent of an ultraviolet light absorber.
A thermosettable acrylic primer formulation 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 12 are primed with this primer formulation and top coated in accordance with the procedure set forth in Example 13. 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 III.

-~0 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 12 are primed with this primer formulation and top coated in accordance with the procedure set forth in Example 13. These primed and top coated test panels are subjected to the adhesion test, before and after weathering, and the results are set forth in TABIE III.

~ ~2~

A thermosettable acrylic primer formulation containing a high amount of a 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 12 are primed with this primer formulation and top coated in accordance with the procedure set forth in Example 13. These primed and top coated test panels are subjected to the adhesion test, before and after weatheringl and the results are set forth in TABLE III.

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 ta benzophenone ultraviolet light absorber sold by American Cyanamid). Test panels prepared in accordance with the procedure of Example 12 are primed with this primer formulation and top coated in accordance with the procedure set forth in Example 13. 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 III.

A thermosettable acrylic primer formulation containing a high amount of benzotriazole ultraviolet light screener is made by combining 19.95 parts by ~CS-3417 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 12 are primed with this primer formulation and top coated in accordance with the procedure set forth in Example 13. 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 III.
TABLE III

Colo~ 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 Pass Pass Colorless 6 Pass Pass Colorless 7 Pass Pass Colorless As can be seen by comparison of Example 13 where the primer layer contains no ultraviolet light screener) and 14 (where the primer layer contains a relatively small amount, i.e., 9 weight percent, of an ultraviolet light screener) with Examples 15-18 (wherein the primer layer contains high amounts of an ultraviolet light screener), the presence of relatively high amounts o~ an ultraviolet light screener in the primer layer greatly improves the adnesion of the colloidal silica filled thermoset organopolysiloxane containing top coat 8CS-3~19 to the polycarbonate upon exposure to weathering.
Thus, while in test panels of Examples 13 and 14 the top coat failed the adhesion test after 503 hours e~posure to weathering, the adhesion of the top coat of test panels of Examples 15-18 was not delet~riously affected by exposure to weathering for this same period of time.
The foregoing disclosure of this in~ention 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.

Claims (32)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A coated polycarbonate article having improved abrasion and chemical solvent resistance and improved adhesion of the coating to the polycarbonate comprising a polycarbonate substrate having adhered thereto on at least one surface thereof (i) 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 75 weight percent of at least one ultraviolet light screening compound; and (ii) a top coat on said primer layer comprised of a thermoset organopolysiloxane.

2. The article of claim l wherein said primer layer contains from about 25 to about 80 weight percent of a thermoset acrylic polymer and from about 20 to about 75 weight percent of at least one ultraviolet light screening compound.

3. The article of claim 2 wherein said primer layer contains from about 25 to about 75 weight percent of a thermoset acrylic polymer and from about 25 to about 75 weight percent of at least one ultraviolet light screening compound.

4. The article of claim 3 wherein said primer layer contains from about 25 to about 70 weight percent of a thermoset acrylic polymer and from about 30 to about 75 weight percent of at least one ultraviolet light screening compound.

5. The article of claim 4 wherein said thermoset organopolysiloxane is the hydrolysis and condensation product of an alkyl trialkoxysilane.

6. The article of claim 5 wherein said alkyl trialk-oxysilane is an alkyl triethoxysilane.

7. The article of claim 5 wherein said alkyl trialkoxysilane is a methyl trialkoxysilane.

8. The article of claim 7 wherein said methyl trialkoxysilane is methyl triethoxysilane.

9. A coated polycarbonate article having improved abrasion and chemical solvent resistance and improved adhesion of the coating to the polycarbonate comprising a polycarbonate substrate having adhered thereto on at least one surface thereof (i) 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 75 weight percent of at least one ultraviolet light absorbing compound; and (ii) a top coat on said primer layer comprised of a colloidal silica filled thermoset organopolysiloxane.

10. The article of claim 9 wherein said primer layer contains from about 25 to about 80 weight percent of a thermoset acrylic polymer and from about 20 to about 75 weight percent of at least one ultraviolet light absorbing compound.

11. The article of claim 10 wherein said primer layer contains from about 25 to about 75 weigh-t percent of a thermoset acrylic polymer and from about 25 to about 75 weight percent of at least one ultraviolet light absorbing compound.

12. The article of claim 11 wherein said primer layer contains from about 25 to about 70 weight percent of a thermoset acrylic polymer and from about 30 to about 75 weight percent of at least one ultraviolet light absorbing compound.

13. The article of claim 12 wherein said colloidal silica-filled thermoset organopolysiloxane is a condensation product of a silanol having the formula RSi(OH)3, wherein R is selected from an alkyl radical of from 1 to 3 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, at least 70 weight percent of the silanol being CH3Si(OH)3.

14. The article of claim 13 wherein said colloidal silica-filled thermoset organopolysiloxane is the condensation product of CH3Si(OH)3.

15. The article of claim 13 wherein said colloidal silica-filled thermoset organopolysiloxane contains from about 10 to about 70 weight percent of colloidal silica.

16. The article of claim 14 wherein said thermoset silica-filled organopolysiloxane contains from about 10 to about 70 weight percent of colloidal silica.

17. An improved coated polycarbonate article having improved durability of adhesion of the coating to the polycarbonate comprising a polycarbonate substrate having adhered thereto on at least one surface thereof (i) an adhesion promoting primer layer containing a thermoset acrylic polymer, and (ii) disposed on said primer layer a top coat comprising the thermally cured product of a composition comprising a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of at least one silanol, said composition containing 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 improvement consisting of said primer layer containing from about 15 to about 75 weight percent of at least one ultraviolet radiation absorbing compound and from about 25 to about 85 weight percent of a thermoset acrylic polymer.

18. The article of claim 17 wherein said silanol has the formula RSi(OH)3 wherein R is selected from alkyl radicals containing 1 to 3 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, at least 70 weight percent of said silanol being CH3Si(OH)3.

19. The article of claim 18 wherein said primer layer contains from about 25 to about 80 weight percent of a thermoset acrylic polymer and from about 20 to about 75 weight percent of at least one ultraviolet light absorbing compound.

20. The article of claim 19 wherein said primer layer contains from about 25 to about 75 weight percent of a thermoset acrylic polymer and from about 25 to about 75 weight percent of at least one ultraviolet light absorbing compound.

21. The article of claim 20 wherein said primer layer contains from about 25 to about 70 weight percent of a thermoset acrylic polymer and from about 30 to about 75 weight percent of at least one ultraviolet light absorbing compound.

22. The article of claim 21 wherein said silanol is CH3Si(OH)3.

23. An improved coated polycarbonate article having improved durability of adhesion of the coating to the poly-carbonate comprising a polycarbonate substrate having adhered thereto on at least one surface thereof (i) an adhesion promoting primer layer containing a thermoset acrylic polymer, and (ii) disposed on said primer layer a top coat comprising the thermally cured product 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)3 wherein R is selected from alkyl radicals containing 1 to 3 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxy-propyl radical, at least 70 weight percent of the silanol being CH3Si(OH)3 radical, said composition containing 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, said composition containing sufficient acid to provide a pH in the range of 3.0 to 6.0; the improvement consisting of said primer layer containing from about 15 -to about 75 weight percent of at least one ultraviolet radiation absorbing compound and from about 25 to about 85 weight percent of a thermoplastic acrylic polymer.

24. The article of claim 23 wherein said primer layer contains from about 25 to about 80 weight percent of a thermoset acrylic polymer and from about 20 to about 75 weight percent of at least one ultraviolet light absorbing compound.

25. The article of claim 24 wherein said primer layer contains from about 25 to about 75 weight percent of a thermoset acrylic polymer and from about 25 to about 75 weight percent of at least one ultraviolet light absorbing compound.

26. The article of claim 25 wherein said primer layer contains from about 25 to about 70 weight percent of a thermoset acrylic polymer and from about 30 to about 75 weight percent of at least one ultraviolet light absorbing compound.

27. The article of claim 26 wherein said silanol is CH3Si(OH)3.

28. An improved coated polycarbonate article having improved durability of adhesion of the coating to the polycarbonate comprising a polycarbonate substrate having adhered thereto on at least one surface thereof (i) an adhesion promoting primer layer containing a thermoset acrylic polymer, and (ii) disposed on said primer layer a top coat composition comprising a dispersion of colloidal silica in a lower aliphatic alsohol-water solution of the partial condensate of a silanol of the formula RSi(OH)3 in which R is selected from the group consisting of alkyl radicals of 1 to 3 inclusive carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, at least 70 weight percent of said silanol being CH3Si(OH)3, said composition containing 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, said composition containing sufficient acid to provide a pH
in the range of 3.0 to 6.0, the improvement consisting of said primer layer containing from about 15 to about 75 weight percent of at least one ultraviolet radiation absorbing compound and from about 28 to about 85 weight percent of a thermoset acrylic polymer.

29. The article of claim 28 wherein said primer layer contains from about 25 to about 80 weight percent of a thermoset acrylic polymer and from about 20 to about 75 weight percent of at least one ultraviolet light absorber.

30. The article of claim 29 wherein said primer layer contains from about 25 to about 75 weight percent of a thermoset acrylic polymer and from about 25 to about 75 weight percent of at least one ultraviolet light absorber.

31. The article of claim 30 wherein said primer layer contains from about 25 to about 70 weight percent of a thermoset acrylic polymer and from about 30 to about 75 weight percent of at least one ultraviolet light absorbing compound.

32. The article of claim 31 wherein said silanol is CH3Si(OH)3.