CA1174537A - Ultraviolet radiation stabilized coated polycarbonate article - Google Patents

Abstract

ULTRAVIOLET RADIATION STABILIZED
COATED POLYCARBONATE ARTICLE

ABSTRACT OF THE DISCLOSURE

A coated ultraviolet radiation stabilized polycarbonate article having improved abrasion, mar, scratch, and chemical solvent resistance comprising a polycarbonate article with its surface layers impregnated with an ultraviolet radiation absorbing compound having at least one surface thereof coated with (i) an adhesion promoting primer layer comprised of a thermoset acrylic polymer;
and (ii) a top coat disposed on said primer layer comprised of a colloidal silica filled thermoset organopolysiloxane.

Description

, ~ ~

~ 17~$3~ 8CS-3302 This inven~ion relates to a coated and ultraviolet light stabilized polycarbonate article having superior resistance to abrasion, chemical solvents and degradation by ultraviolet light ~ In the article of the present invention the polycarbonate resin S is stabilized against degradation by ultraviolet light by having ` impregnated in its surface layers an ultraviolet light absorbing compound. Protection against abrasion and chemical solvents is provided by a coating comprised of a colloidal silica filled ~ thermoset organopolysiloxane which is tenaciously and durably adhered to the surface of the polycarbonate resin by means of a primer layer containing a thermoset acrylic polymer.

BACKGROUND OF TH~ INVENTIO~

Polycarbonate resins, due to their many advantageous , properties, are widely used in industry and commerce. One of their uses is as transparent glazing ma~erials for windows, wind-! shields, and the like W~tile polycarbonate resins are easilyfabricated into the desired shape and have excellent physical and chemical properties, such as being less dense and having greater breakage resistance than glass, they have a relatively l~w abrasion and chemical solvent resistance, and li.ke many other !
organic polymeric materials are subject to degradation by ultra-,' violet radiation.
In order to overcome this relatively low resistance toabrasion and chemical solvents various protective coatings which possess greater abrasion and chemical solvent resistance than polycclrbonate resins have been applièd onto the surface of poly-carbonate articl~ . However, in order to qualify as a successful ', coating material for polycarbonate resins there are several ,~

. .

1 17~537 ; requirements that the prospective coating material must meet.
The coating material must be harder and more solvent resistant than the polycarbonate resin. The coating material must be , compatible with the polycarbonate and must not degrade the l polycarbonate such as by crazing the polycarbonate or otherwise adversely affecting the properties of the polycarbonate resin.
The coating material must durably adhere to the surface of the polycarbonate U.S. Patents 3,451,838; 3,986,997 and 4,027,073 ` disclose organopolysiloxane coating compositions and techniques for the application of these organopolysiloxan~ coatings onto polycarbonate surfaces. While these organopolysiloxane coatings have many desirable properties, e.g., they are hard, , abrasion and solvent resistant, and are compatible with the underlying polycarbonate, these organopolysiloxanes do not in all instances possess the requisite degree of adhesion to and durability on the polycarbonate. In order to improve the adhesion, of these organopolysiloxane coatings to the polycarbonate sub-strate it has been suggested to use adhesion promoting primer ~ layers between the organopolysiloxane and the polycarbonate.
However, the use of a primer layer adds an additional degree of uncertainty and complexity to this already dificult and ; largely imperical area oE coating technology. n order to function i' e~Eectively the primer layer must not only increase the adhesion oE ~he organopolyslloxane coating to the polycarbona~e but must ' also be compatible with both the polycarbonate and the organo-polysiloxane. U.S. Patent 3,707,397 describes a process Eor providing a hard coating on, inter alla,~ polycarbonate resin by priming the polycarbonate surface with an adhesion promoting thermosettable acrylic polymer and applying onto this primer 30 ; a thermosettable organopolysiloxane An article produced by this~ !

- 2 -7~3~ 8cs-33n2 process, while possessing acceptable initial adhesion of the organopolysiloxane to the polycarbonate, suffers from the dis-advantage that upon prolonged exposure to weathering, particularly to sunlight, the organopolysiloxane coating generally tends to ~lose its initial good adhesion to the polycarbonate resin sub-strate. Furthermore, the abrasion resistance of the coated article is generally dependent upon the thickness of the thermoset acrylic !
polymer primer layer. The abrasion resistance of the coated arti-;
cle generally decreases as the thickness of the primer layer increases. The deterioration of the adhesion of the organo-polysiloxane coating to the polycarbonate substrate upon exposure to weathering is rectified to a certain degree in articles produced according to the methods disclosed in U.S. Patents 1 4,197,335 and 4,207,357. In the processes disclosed in these two patents the polycarbonate substrate is primed with a primer composition comprising an emulsion of a thermosettable acrylic polymer, water and a hydroxy ether, and the organopolysiloxane containing top coating is then applied onto the primed poly-carbonate substrate. However, the abrasion resistance of the coated articles thus produced is still generally dependent on the thi.ckness of the primer layer.
Whlle these prior art methods generally provicle a protectlve ~coatin~ fc)r the polycarbonate article e:EEective to protect it i~rom abra~lon and chemical solvents, they do not provide pro-25 ! tection against ~egraclation by ultraviolet racliation. It wouldappear at irs-t glance in view of the prior art that there are three methods of protecting the coated polycarbonate article Erom (legraclation by ultraviolet radiation~ incorporating an ultraviolet radiation absorber into the silicone tcpcoat;

. . , _ . _ _ ~ 17~53~ 8CS-3302 ;
;; (2) Incorporaking an ultraviolet radiakion absorber into the thermoset acrlic pol~ner containing primer layer; and (3) in-. corporating an ultra violet radiation absorber into the poly-carbonate resin itself. However, UpOIl closer scrukiny and ,! i in light of the mostly empirical knowledge gained in this area each of these three methods turns out to contain certain inherent ~.
problems. Incorporating an ultraviole~ radiation absorbing compound into the silicone top coat generally results in a decrease in the abrasion resistance provided by the silicone. The greater the amount of ultraviolet radiation absorbing compound present in the silicone top coa~ the greater the loss of abrasion resistance provided by the top coat. Thus, if the silicone top coat contains sufficient amounts of ultraviole~ radiation absorber to effectively protect the underlying polycarbonate resin, from degradation by ultraviolet radiation its abrasion resistance !
is generally unacceptably lowered. If the ultraviolet radiation absorbing compound is incorporated into the thermoset acrylic polym~r containing primer layer the aforediscussed relationship . between primer thickness and abrasion resistance of the silicone top coat comes inko effect. In order to efiectively protect .the polycarbonate resin from ultraviolet radiatlon the primer layer must contain relatively large amounts of ultraviolet radiation abosrbing compounds. But in order to contain these . relatively large amounts of ultraviolet radiation absorbing `compounds the thlckness of the primer layer must be increased.
:;However, this increase in thickness of the primer Layer which is required to accomodate the necessary amounts of ultra-`viol'et racliation absorbers results in a corresponding decrease inthe abrasion resiskance of the silicone top coat. Thus in bokh , r .. .. . ~

S 3 ~t ; 8CS-3302 ~of these methods protection against ultraviolet radiation is provided only at the expense of protection against abrasion.
The third method of providing protection against ultra- i ;violet radiation involves incorporating the ultraviolet radiation S labsorbing compound directly into the polycarbonate resin. This ; method involves either (i) blending the absorber with the buLk polymer, or (ii) impregnating the surface layers of the resin with the absorber. Blending the absorber w:ith the bulk polymer results in the absorber being distributed throughout the entire : polymer system. This procedure is both uneconomical, as these ultraviolet radiation absorbing compounds are usually quite expensive, and not completely successful. Since most o~ the absorber resides in the polymer's interior instead of at the ' surface where it is mos-t needed, much of the harmful ultraviolet radiation penetrates and deteriorates the surface layers of the polymer structure before reaching the majority of the interiorly distributed absorber. Furthermore, since the concentration of !
the absorber in the resin is limited by the degree of compatibility of the absorber with the reisn, using sufficiently high con-, centrations of absorber effective to provide adequate surfaceprotection generally tends to adversely affect the physical properties of the polymer. In the surface impregnation technique i t ~he ultraviolet radiation absorber resides in the surface ~! reg:lons of the polymer where it is most needed. Examples of typical surEace impregnation techniques generally include applying the ultraviolet radiation absorber from a stabilizing solution containing a compound which is aggres~sive towards the polycar~onate an(l tends to swell or soften the re~in thus en-abling the absorber to ~iEEuse into the swelled and softened 1 17~53~ 8CS-3302 ' surface of the polycarbonate layer, as disclosed in U S. Patent Nos. 3,892,889 and 4,146,658; melting the ultraviolet radiation absorber on the surface o~ the polycarbonate resin and allowing the molten absorber to diffuse into the surface layers of the resin, as disclosed in U.~.Patent 3,043,709; and immersin~ , the polycarbonate resin in a stabilizing solution containing an ultraviolet radiation absorbing compound wherein the compound is more soluble in the polycarbonate resin than in the stabilizing solution~ as disclosed in U.S. Patent Nos.

3,309,220 and 3,594,264.
However, the very feature which makes the surface im pregnation method appear attractive, i.e., that the ultraviolet radiation absorber is distributed in the surface layers of the polycarbonate resin where it is most needed, also makes this method appear to be untenable to one skilled in the art when this method is used in conjunction with the application of a protective coating onto the polycarbonate surface. The complexity and problems associated with providing a protective coating which adheres tenaciously and durably to a polycarbonate surface have been discussed above. The modification of a polycarbonate sur~ace by incorporating therein an ultraviolet radiation i absorber, as is done by the surface impregnation technique, adds yet Eurther complications to this already complex area o~
adhering protective coatings to polycarbonate. It is well 2S known to those skilled in the coating art that modifying the surEace oE polycarbonate by incorporating an additive therein has generally unpredictable and often adverse e~fects upon the physicaL properties oE the polycarbonate surface. These eEfects upon the polycarbonate surface depend upon the particular P17~3 additive employed. It is generally quite well known that the incorporation of certain additives into the surface areas of polycarbonate resin often results in the deterioration of both lnitial adhesion and durability of adhesion between the poly- j carbonate surface and a protective coating applied onto this ' surface. In view of this one skilled in the art would generally be led to conclude that the i.ncorporation in the surface layers of a polycarbonate resin of an amount of ultraviolet radiation absorbing compound effective to protect the polycarbonate from degradation by ultraviolet radiation would deleteriously affect 'I , the adhesion of a protective coating to this modified poly-carbonate surface.
There thus-exists a need for a means of simply and e~fectively protectlng a polycarbonate resin form degradation by ultraviolet radiation, ~rom surface abrasion, and from attack by chemical solvents. The present inventlon provides such a method as well as the article produced by this method.

DESCRIPTION OF THE INVENTION
In accordance with the present invention there is provided ~0 a polycarbonate article which is resistant to degradation by ultraviolet radiation, abrasion, and chemical solvents, ~he articl,~
of the present invention comprises a polycarbonate article having impregnated in its surface layers at least one ultraviolet radlation absorbing compound and ~aving adhered to at least one s~lrface thereof (i) a thermoset acrylic polymer con~aining primer layer, and (ii) on said primer layer a top coat comprised of a colloidal silica ~illed thermoset organopolysi ~ xane.
In accordance with the present invention an article comprised of polycarbonate is formed in a conventional manner, - ~ ~7~53~ , for example by injection molding! extrusion, cold forming, vacu~lm forming, blow molding~ compression molding, transfer molding, and the like~ The article may be in any shape and need not be a ; finished article of commerce, ~hat is, it may be sheet material or l~ iilm which would be cut or sized or mechanically shaped into a finished article. Therefore, as used herein, the terrn "article"
refers to any shape or form of polycarbonate resin whether finished or stock material. I
The aromatic carbonate polymers used in the practice of the , instant invention have recurring structural units of the formula ~ O - A - O - 8 3 .

where A is a divalent aromatic radical of the dihydric phenol employed in the polymer producing reaction. These polycarbonate resins are high molecular weight aromatic carbonate polymers which may be prepared by reacting a dihydric phenol with a carbonate precursor such as phosgene, a haloformate or a carbonate ester.
The aromatic carbonate polymers of this invention may be prepared by methods well known in the art and described in U~S. Patents 3,161,615; 3,220,973; 3,312,659; 3,312,660;
3,313,777; 3,666,614; and 3,989,672 .
!
;i I
' ~lso included herein are branched polycarbonates wherein a polyfunct:ional aromatic compound is reacted with the dihydri~
phenol and the carbonate precursor to provide a thermoplastic randomly branched polycarbonate wherein the r~ecurring units o~
~ormu].a I contain branching groups.
The preferred polycarbonate resin is one which may be derived from the reac,tion of bisphenol-A with phosgene : T~hese ~, .

- ~ 1 7 ~ 5 3 ~ 8CS-3302 . . .
- preferred polycarbonates have from about 10 to about 400 rec-urring , structural units of the general formula - 0 - ~ - C ~ - 0 - C - Il The polycarbonate should preferably have an intrinsic S viscosity between about 0.3 and about 0.1, more preferably from between about 0.4 to about 0.65 as measured at 25C. in methylene chloride.
At least one surface of the polycarbonate article, usually the surface which is to be exposed to the source of ultraviolet radiation, is impregnated with at least one ultraviolet radiation absorbing compound. The ultraviolet radiation absorber is `disposed throughout the surface layers of the polycarbonate article.
By sur~ace layers is meant the layers immediately adjacent to and ! below the surface of the polycarbonate article, and including the surface itself. ~ !
The ultraviole~ radiation absorbers employed in the practice of this invention can be any of the known ultraviolet radiation absorbing compounds which flmction by reason oE their ability to Iscreen out the damaging ultraviolet por~ion of light due to 20 ~ their very high absorptivity in this region of the spectrum.
The~e compounds include benzophenone and the benzophenone derivatives, benzotriazole and benzotriazole deriva~ives, ben- t zoate esters, phenyl salicylates, deriva~ives of crotonic acid, ; ~lonic acid esters, and cyanoacrylates.
Inclucled among the ultraviolet radiation absorbers which fall into the categories of benzophenone and benzotriazole der- I
ivatives are those compounds disclosed in United States i _ g ~174537 8CS-3302 Patents Number 3,309,220; 3,049,443; 3,043,709; and , I
2,976,259. some non-limiting examples of these compounds include:

` 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'-dihydroxy-4-ethoxy-4'- propxybenzophenone;
,; 2,2'-dihydroxy-4-ethoxy-4'-butoxybenzophenone;
; 2,3'-dihydroxy-4,4'-dime-thoxybenzophenone;
2,3'-dihydroxy-4-methoxy-4'-butoxybenzophenone;
: 2-hydroxy-4,4',5'-trimethoxybenzophenone;
. 2-hydroxy-4,4',6'-tributoxybenzophenone;
2-hydroxy-4-butoxy-4',5'-dimethoxybenzophenone;
2-hydroxy-4-ethoxy-2',4'-dibutylbenzophenone;
2-hydroxy-4-propoxy-4'6'-dichlorobenzophenotle;
,, 2-hydroxy-l~-propoxy-4',6'-dibromobenzophenone;
!1 2,4-dlhydroxybenzophenone;
' 2-hydroxy-4-methoxybenzophenone;
1 2-hydroxy-4-ethoxybenzophenonei 2-hydroxy-4-propoxybenzophenone, 2-h~droxy-4-butoxybenzophenone;
2-hydroxy-4-rnethoxy-4'-methylbenzophenone;

-- 10 -- i ~ 17~37 2-hydroxy-4-methoxy-4'-ethylbenzophenone;
2-hydroxy-4-methoxy-4'-propylbenzophenone;
2-hydroxy-4-methoxy-4'-butylbenzophenone;
2-hydroxy-4-methoxy-4'-tertiarybutylbenzophenone;
2-hydroxy-4-methoxy-4'-chlorobenzophenone;
. 2-hydroxy-4-methoxy-2'-chlorobenzophenone;
2-hydroxy-4-methoxy-4'-bromobenzophenone;
2-hydroxy-4,4'-dimethoxybenzophenone;
~ 2-hydroxy-4,4'-dimethoxy-3-methylbenzophenone;
i2-hydroxy-4,4'-dimethoxy-2'-ethylbenzophenone;
2-hydroxy-4,4',5'-trimethoxybenzophenone;
2-hydroxy-4-ethoxy-4'-methylbenzophenone;
2-hydroxy-4-ethoxy-4'-ethylbenzophenone;
2-hydroxy-4-ethoxy-4'-propylbenzophenone;
. 2-hydroxy-4-ethoxy-4'-butylbenzophenone;
2-hydroxy-4-ethoxy 4'-methoxybenzophenone;
2-hydroxy-4,4'-diethoxybenzophenone;
2-hydroxy-4-ethoxy-4'-propoxybenzophenone;
2-hydroxy-4-ethoxy-4'-butoxybenzophenone;
2-hydroxy-4-ethoxy-4'-chlorobenzophenone;
2-hydroxy-4-ethoxy-4'-bromobenzophenone;
2-(2'-hydroxy-5'-methylphenyl)-benzotriazole 2-(2'-hydroxy-5'-ter~-butylphenyl)-benzotriazole;
' !
2-(2'-hydroxy-3'-methyl-S'-tert-butylphenyl)-benzotriazole;
., 2-(2'-hydroxy-5~-cyclohexylphenyl)-benzotriaæole;
2-(2'-hydroxy 3',5'-dimethylphenyl~-benzotriazole;
2-(2'-hydroxy-5'-tert-butylphenyl)-5-chlorobenzotriazole; and 2-(2'-hydroxy-3'-di-tert-butylphenyl)-benzotriazole.
Two non-limiting examples of the derivatives of crotonic 1.

- I 1 - i 53~

' acid which function as ultraviolet radiation absorbers are alpha-cyano-beta-methyl-beta-(p-methoxyphenyl)-crotonic acid methyl ester and alpha-cyano-beta-N-(2-methyl-indolinyl)-crotoni.c I acid methyl ester. The benzoate ester ultraviolet radiation absorbing compounds include the C8-C20 alkyl and aryl benzoates, alkyl and aryl hydroxybenzoates, alkaryl and aralkyl benzoates, and alkaryl and aralkyl hydroxybenzoates. 1, The malonic acid esters which are ultraviolet radiation absorbing compounds include the dimethyl, diethyl, dipropyl and the like esters of malonic acidt i.e., the dialkyl esters of malonic acid. Particularly useful esters of malonic acid are the benzylidene malonates. The benzylidene malonates are compounds represented by the general formula R10 \ CH / OR
; ~ C - C - C ~ III.
, 0 0 wherein X is selected from hydrogen, hydroxyl, halogen, alkyl, pre~erably Cl-C10 alkyl, and alkoxy, preferably Cl-C10 alkoxy, ; raclical~; and R and Rl are independently selectecl from alkyl raclicals, preferably alkyl radicals containing from 1 to about 10 carbon atoms, substi~uted alkyl radicals, preEerably those containing from 1 to about 10 carbon atoms and hydroxyl or hal.ogen substltuents, aryl radicals, preferably the phenyl radical, alkaryl radicals, preferably those alkaryl radicals containing from about 7 to about 12 carbon atoms, aralkyl radicals', preferably aralkyl radicals containing from about 7 to about 12 . -~ 1 7 ~ 5 3 7 8CS-3302 carbon atoms, and substitued aryl radicals, preferably phenyL
radicals containing hydroxyl or halogen substituents~ Preferred benzylidene malonates represented by fxomula III are those wherein X represents an alkoxy group and R and Rl are lndependent-t ly selected from alkyl radicals. Examples of these benzylidene malonates include diethyl paramethoxybenzylidene malonate and dimethyl paramethoxybenzylidene malonate.
Among the cyanoacrylates which are useful ultraviolet radiation absorbers are those cyanoacrylates represented by ~ the general formula CN o C _ C - C - OR IV~

wherein R2 is alkyl or hydroxyalkyl. These compounds are .disclosed in U.S. Patent 4,129,667 to Lorenz ~ated December 12, 1978.
The preferred ultraviolet radiation absorbing compounds, Eor the purposes of the present invention, are the benzophenone ;and benzophenone derivatives, benzotriazole and benzotriazole ; derivatives, the benzylidene malonates, and the cyanoacrylates.
~ The amount oE ultraviolet radiation absorbing compound ' present in the surface layers o the polycarbonate resin is an amount efective to protect the polycarbonate resin against de~radatiorl by ultraviolet radiation, Only one ultraviolet radi.atlon absorbing compound may be present in the surface layers o~ the polycarbonate resin or two or more ultraviolet radiation absorbing compounds may be impregnated in the surface layers.

.. ,_ _ . . . ~ _ .

~CS 3302 ~ 17~537 ; Generally, a sufficient amount of ultraviolet radiation absorbing compound is presen~ in the surface layers of the polycarbonate resin article so that the absorbance of the polycarbonate at ~ maximum is at least 1, which corresponds to absorption at ~ maximum of at least 90% of the incident ultraviolet radiation by the polycarbonate surface layers. The absorbance is cal-culated using the relationship A=log(IO/I) wherein A is the absorbance, Io is the intensity of incident light, and I is ; the intensity of transmitted light.
The ultraviolet radiation absorbing compound can be impregnated into the surface layers of the polycarbonate resin article by any of several known methods. One of these methods involves applying the ultraviolet radiation absorber from a solution containing the ultraviolet radiation absorber and a compound which is aggressive towards the polycarbonate resin and tends to swell and/or soften the resin thus allowing the ultraviolet radiation a~sorber to diffuse into the softened and/or swelled surface of the polycarbonate. In this method the solution containing the ultraviolet radiation absorber and the aggressive compound is brought into contact with ~he surface of the polycarbonate resin article and is kept in contact I therewith Eor a period o~ time effective for the ag~ressive ; compound ~o swell the surface layers of the polycarbonate and for the ultraviole~ radiation absorbing compound to diEuse into these swelled surface layers, Some speclfic e~amples of thls type o technique are described in U.S. Patents 3,617,330;
3,892,8~39; and 4,146,658.
' Another method of impregnating the surface layers of poly-carbonate resin with ultraviolet radiation absorbing compounds - _. .

1~7~53~ 8CS-3302 involves applying the ultraviolet light absorber to the surface of the resin article, as for example from a solution, from a dispersion such as a dispersion in water, a~s a solid in the , form of a powder or dust, or as a liquid in the form of a melt, 5 ,i and therea~ter heating the coated resin to a temperature above the melting point of the absorber and below the melting point : : oE the resin~ i Yet another method of surface impregnating a polycarbonate resin with an ultraviolet radiation absorbing compound involves immersing a polycarbonate resin article in a bath containing an ultraviolet radiation absorbing compound which is more : soluble in the polycarbonate resin than in the solvent component : of the bath. Generally, the solvent component of the bath is ; water or oil. This method of impregnating the surface layers of a polycarbonate resin with an ultraviolet radiation absorb-ing compound is disclosed in U.S. Patents 3,309,220 and 3,594,264.
Still another method, and one which is generally prefer-red, of impregnating the surface layersdof a polycarbonate resin article with an ultraviolet radiation absorbing compound involves the utilization of a stabilizing composition containing an ultra-violet radiation absorbing compound and a nonaggressive liquid carrier ~or said compound. By nonaggressive is meant that the liquid carrier is nonaggressive towards t~e polycarbonate resin, I
~ i.e., it does not attack and/or deleteriously affect the poLy- j carbonate resin, Since a nonaggressive stabilizing composition is used there is no degradation or adverse ef~ect on ~he poly-carbona~e resin . Furthermore, since the stabilizing composition is nonaggressive towards the polycarbonate the processing step does not need to be as rigidly controlled, with respect to the residence time of the stabilizing composition on the i.

1 17~53~ 8CS-3302 surface of the polycarbonate resin, as in the case of an aggressive stabilizing composition~
There are basically two ways of practicing this method. In ~
, the first way a stabilizing composition containing the ultraviolet!
i' ~
- radiation absorber and the nonaggressive liquid carrler there-fore is applied onto the surface o a preheated polycarbonate article by anyof several known methods such as spraying, flow coating, brushing, and the like. The stabilizing composition ~ is kept in contact with the preheated polycarbonate resin article for a period of time sufficient for the ultraviolet radiation absorber to e~fectively impregnate the surface layers of the polycarbonate article, that is for the ultraviolet radiation absorber to diffuse throughout the surface layers of the poly-~ carbonate article in concentrations sufficient to provide15 protection against the deleterious e~fects of ultraviolet radiation. Since the stabilizing composition is nonaggressive towards the polycarbonate there is no upper time limit that the composition can remain in contact with the polycarbonate.
Rather, the residence time of the stabilizing composition on the surface of the polycarbonate resin article is goverened by .uch secondary considerations as speed of processlng o~ the polycarbonate article, rate o~ cooling of the polycarbonate -l~ the polycarbQnate resin cools below the critical temperature ~ no Eurther difusion o~ the absorber into the surE~ce layers o ~ the re~in will take place - rate of evaporation of the liquid carrier, and the like, The minimum period o~ time that the ; stabilizing composition is kept in contact with the polycarbonate , article is the period of time which is,sufficient for the ultra- l violet radiation absorber to impregnate the surface layers of f the resin article in concentrations effective to protect the polycarbonate resin against degradation by ultraviolet radiation.
''' .

1, ~ 1~4537 8CS-3302 This minimum period generally depends to a certain degree upon the particular ultraviolet radiation absorber present in the stabilizing composition, the particular liquid carrier present in the stabilizing composition) and the temperature to which , the polycarbonate article has been preheated. Generally, the ; stabilizing composition is kept in contact with the polycarbonate article from about 5 seconds to about 2 hours, preferably from about 30 seconds to about 15 minutes.
It is critical to the practice of this process that the polycarbonate resin article be at a temperature sufficiently high when the stabilizing composition is contacted therewith for the ultraviolet radiation absorber to impregnate ~he surface layers~thereof in concentrations effective to provide protection against degradation of the polycarbonate by ultraviolet radiation.
If the polycarbonate is not at a temperature effective for the impregnation of the absorber into the polycarbonate surface layers when the stabilizing composition is applied onto the ' surface o~ the polycarbonate resin article the ultraviolet radiation absorber will not diffuse into or impregnate the surface layers of the polycarbonate and, consequently, the polycarbonate will not be protected against degradation by ultraviolet radiation. Generally, the minlmum temperature at which impregna~ion of the sur~ace layers o~ the polycarbonate ,l I re9in article by the ultraviolet radiation absorber takes place is!
about 65C. Preferably the polycarbonate resin article should be at about at least 75C. as at this temperature and above the ultraviolet radiation absorber generally diffuses readily and in l.arge amounts into the surface layers of the polycarbonate resin. The maximum temperature to which the polycarbonate resin - 17 - ~

1.

~7~537 8CS-3302 . ~
is preheated, and the maximum temperature of the polycarbonate ~' resin at the time that the stabilizing composition is applied onto the surface o~ the polycarbonate resin article, is governed by the fact that the temperature of the polycarbonate be not ' sufficiently high so as to deleteriously affect the physical properties o~ the polycarbonate resin. Thus the upper temp-erature limit is below about 150C which is the glass transition !
temperature of the polycarbonate. Preferably it should be ; below about 135C., the temperature at which bubbles and other imperfections begin to appear in the polycarbonate resin Thus in the practice of this method the polycarbonate resin article should be at a temperature between about 65C. and about 150C~ during contact with the stabilizing composition. i~
For optimum results and optimum operating conditions Lhe poly-carbonate article should preferably be at a temperature betweenabout 75C. and about 135C.. The polycarbonate article is preheated to this temperature before the stabilizing composition is brought into contact with the surface thereof. There is no active heating of the polycarbonate article during the period that the s~abilizing composition is in contact with the surface of~the resin article. The stabilizing compositi.on is not ' heated but is generally at about room -temperature at the time ;' of its application onto the surface of the preheated polycarbonate~
~, xesin article.
; ,The second technique involving the utilization of a ; stabilizing composition containing an ultraviolet radiation absorber and a nonaggressive liquid carrier therefore comprises applying onto the surEace of a polycarbonate resin article the stabilizing composition and thereater heating the poly- i carbonate article having a layer of the stabilizing composition .

1.

- a ~ 537 ~CS-3302 ', .on.^its surface to ~ temperature effective.for the ultraviol2t radiation absorber tQ. diffuse into the'surface layers of the polycarbonate article,' Heating at the effective temperature is ~, continued and the stabilizing composi~ion is kept in contact J
5 ¦ with the'surface'of the article'at the 'ef~ective temperature .¦ for a period of time sufficient for the ultraviolet radiation :. I absorber to effectively imp~egnate'the sur~aca layers of t'ne polycarbonate'article,' i,e., for the ultraviolet radiation absorber to diifuse ~hroughout the sur~ace layers of the poly- ¦
c~rbonate'resin article in concentrations sufficient to provide protection agains~ the deleterious effects of ultraviolet light, Since the.stabilizin~ composition is nonaggressive towards polycarbonate there'is no upper time limit that the composition can remain in contact with the polycarbonate resin article during heating at the effective temperature,' The minimum period of time that the stabilizing composition is kept in contaet with the surface.of the article at the effective temperature is that : period of ti~e which is sufficient ~or the absorber to impregnate , the surface layers of the polycarbonate resin article in co~- 5 centrations effective to provide protection to the polycarbonate . ~esin against degradation by ultraviole~ radiation. This ' minimum period of time generally depends to a certain de~ree upon the .particular:ultraviolet radiation absorber employed, the particular nonaggressive li~uid carrier utilized, and the 25' ¦ ~emperature'at which the coa~ed polycarbonate article is heated.
¦ Generally, the'article with the stabilizing composition on its surface'is actively heated for a period o~ time ranging from about Il' 5 seconds to about 2 hours, preferably from about 30 seconds 'I to about 30 min'utes~
, Il .

- 1 17~537 8CS-3302 As in the technique wherein the stabilizing co-mposition is applied onto a preheated polycarbonate surface,so also in this technique it is critical that the polycarbonate article j; with the stabilizing composition on its surface be heated to ,, a temperature suuficiently high for the ultraviole~ radiation l absorber to impregnate the surface layers of the article in : concentrations effective to provide protection against ultraviolet radiation but insu~ficiently high for degradation of the poly-,' carbonate resin to occur. Generally, the minimum temperature at which effective impregnation of the surface layers of the poly-carbonate resin article takes place is at about 65C. Preferabl~
the polycarbonate resin article with a layer of the stabilizing ~ composition disposed on its surface is heated ~o at least about I`i 75C., as at this temperature and above the ultraviole~ radiation absorber generally diffuses readily and in large amounts into ,' the surface layers of the polycarbonate resin. The maximum temp- i erature to which the polycarbonate article coated with the stabiliæing composition can be heated is goverene~ by the fact that this temperature be not sufficieneLy high so as to deleter-iously affect the physical properties of the polycarbonate resin,i e., that heat degradation of the polycarbonate resin not occur.
Thus ~he upper temperature limit is below about 150C. which is the glass transition temperature of polycarbonate resin.
'i Preerably the temperature should be below about 135G., the 2S ~ pOillt at wh~.ch bubbles and other imper~ec~ions begin ~o appear in the resin.
In both of these techniques utilizing a nonaggressive stab'ilizing composition the nonaggressive liquid carrier for the ultraviolet radaition absorber is selected from the group consisting of hydroxy ethers, alcohols, preferably the alkanols, '.

. .

~ ~7~53~ 8CS-3301 ~,alcohol-water mixtures, preferably alkanol-water mixtures, liquid aliphatic hydrocarbons, preferably liquid saturated aliphatic hydrocarbons, liquid cycloaliphatic hydrocarbons, preferably i,liquid saturated cycloaliphatic hydrocarbons, and chlorofluoro- !
carbons such as those marketed by the E. I. duPont Company under ;~the tradename Freon, e.g., dichlorodifluoromethane, trichloro-monofluoromethane, and the like.
The stabilizing compositions contain from about 0,01 ' to about 15 weight percent of an ultraviolet radiation absorbing -compound, preferably from about 0.1 to about 10 weight percent ofan ultraviolet radiation absorber, and more preferably from about 1 to about 8 weight percent of an ultraviolet radiation absorber.
The stabilizing compositions may contain only one ultraviolet radiation absorber or a combination of two or more ultràviolet ~radiation absorbers. If two or more ultraviolet radiation ab-sorbing compounds are present in the stabilizing compositions their combined weight percentages generally range from from about 0.01 to about 15 weight percent of the stabilizing composition.
These amounts are generally amounts effective to provide protect-ion from degradation by ultraviolet radiation to the polycarbonateresin article.
On the sur~ace oE the polycarbonate resin article with its surface layers impregnated with at least one ultraviolet ~,radiation absorbing compound is adherently disposed a primer llayer comprised of a thermoset acrylic polymer, The thermoset acrylic polymer oE the primer layer is obtained from the thermo-; setting of a thermosettable acrylic polymer which is appliedonto the surface of the ultraviolet radiation stabilized poly- !
carbonate resin article from a primer composition containing 1 ~7~3~
this thermosettable acrylic polymer. The thermosettable acrylic polymers are compounds well known in the art.
Exemplary, non-limiting, thermosettable acrylics which may be employed in the practice of this invention are disclosed, for example, in Encyclopedia of Polymer Science and Technology, Vol 1, Interscience Publishers, John Wiley and Sons, Inc., 1964, at page 273 e~ seq.,and in Chem try of Organic FiIm Formers, by D. ~. Solomon, John Wiley & Sons, Inc., 1967, at page 251 et seq.
These thermosettable acrylic polymers generally include: (I) acrylic copolymers having reactive functional groups which are capable of reacting between themselves to e~fect a cross-linkage thereo~; (II) acrylic copolymers having reactive functional groups to which ; there is added an appropriate cross-linking agent which will react with the functional groups to effect cross-linking; and (III) a mixture of two polymers having cross-linkable functional reactive groups.
Typically, the reactions involved in cross-linking the thermosettable acrylic polymers are reactions between, for example epoxide functional groups and amine functional groups; epoxide func-tional groups and acid anhydride functional groups; epoxide functional groups and acrboxyl functional groups; including phenolic hydroxyl groups;
epoxide ~unctional groups and N-methylol or N-~ethylol-ether groups; aarboxyl Eunctional groups and N-methylol or N-methylol-ether functional groups; interreaction between carboxyl and isocyanate groups; reactions between hydrox~1, 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 ~ 3 ! 8CS-3302 ~be present in a ma~or proportion, i.e., greater than 50 weight percent and, more typically, will be present in an amount in excess o~ 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 neededreactive 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 l and 20 weight percent of the monomer mass which is polymerized. Some non-limiting examples of these functional group supplying monomers include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, dimethylaminoethyl methacrylatel, vinyl pyridine, tert-butylaminoethyl-methacrylate, maleïc I
anhydride,. itaconic anhydride, allyl alcohol, monoallyl ethers of polyols, hydroxyethyl methacrylate, hydroxypropyl methacrylate, !
hydroxypropyl acrylate, acrylamide, methacrylamide, maleamide, N-methylolmethacrylamide, vinyl isocyanate, allyl isocyanate.
Usually, the other monomer which will be polymerized along with the monomer supplying the functional group is a lower (Cl-C3) alkyl acrylic ester or mixtures thereo~, e.g., methyl ,acrylate1 ethyl acrylate, methyl me~hacrylate, ethyl me~hacrylate, ¦
styrene, or mixtures thereof, in an amount ranging between about ','75 parts by weight to about 99 parts by weight and, more ~ypically"
betweerl about 80 parts by weight to about 97 parts by weight.
The primer compositions useEul in applying the thermosettable~
acrylic polymer onto the surface of the ultraviolet radiation t stabiliæed polycarbona~e may be of several general types. The first type of primer composition contains the thermosettable 30 acrylic polymer and a solvent ~or said polymer. This solvent ls I 17~53~ ~

, generally an organic solvent which dissolves the thermosettable acrylic polymer, which is inert towards the ultraviolet radiation i stabilized polycarbonate resin, and which is readily vol2tilized. !
Some nonlimiting examples of such solvents include the hydroxy-ethers, alcohols, liquid aliphatic hydrocarbons, and liquld cycloaliphatic hydrocarbons~
A second type of primer composition is one generally comprised of an emulsion of a thermosettable acrylic polymer and water. These emulsions are commercially available and are sold, for example1 by the Rohm & Haas Company, of Yhiladelphia, Pa., under the tradename Rhoplex~ Generally, these emulsions are in the form of emulsion concentrates which contain from about 40 to about 55 percent by weight solids. However, in formulating !
the primer emulsion compositions it is desirable that the primer emulsion composition contain from about 1 to about lO
weight percent solidsA Thus it is generally necessary to dilute these commercially available emulsion concentrates by ' the addition of additional water thereto. These primer emulsion compositions may additionally contain a curing ca~alyst for the thermoset~able acrylic polymer. If such a catalyst is presen~
it may be present in from about 0.05 to about 2 weight percent based on ~he weight of tha ~hermose~table acryLic polymer solids present. Examples o~ such catal.ysts include toluene sulfonic ,~ acld, cltric acid, phosphoric acid, and the like.
A third and preferred type, from the standpoint of providing a coated article with superlor appearance and adhesion j oE the top coat, primer composition is an emulsion comprlsed of (i) from about 1 to about 10 weight percent oE a thermosettable acrylic polymer solids; ~ii) from about 20 to about 45 weight percent of a hydroxy ether, an alkanol, or a mixture of a 1.

~7~3~ 8CS 3302 .,' i hydroxy ether and an alkanoL; and (iii) from about ~5 to about 79 weight percent of water In this preferred type of primer composition the thermo-. settable acrylic polymer, as is the case with the commercially ~l available emulsions described above, is generally in the form ' of discrete spherical particles (approximately 0.1 micron in ' diameter) dispersed in water. Since the polymer particlesare separate from the continuous aqueous phase, the viscosity l of the dispersion or emulsion is relatively independent of the polymer's molecular weight. Consequently the emulsion can contain polymers of high molecular weight and yet have a relative-ly low viscosity. The concentration of the acrylic polymer solids in this preferred primer emulsion composition is generally quite important. Organopolysiloxane top coats applied bnto thermoset acrylic primer layers derived from primer emulsion compositions containing less than about 1 or more-than about 10 weight percent of a thermosettable acrylic polymer generally tend to exhibit a marked decrease in durability of adhesion, especially after exposure to weathering, and abrasion resistance relative to organopolysiloxane top coats applied onto thermoset acrylic primer layers derived from primer emulsion compositions il containing ~rom about 1 to about 10 weight percent of a thermo- ¦
jl se~table acrylic polymer. Primer emulsion composltions con-I taining rom about 2 to about 6 weight percent o a thermosettable acrylic polymer are preerred.
The hyclroxy ethers which are present in these preferred primer emulsion compositions are compounds represented by the ~,eneral formula R3 - 0 - R4 - 0ll V.
wherein R4 is a saturated divalent aliphatic radical, preferably one containing from 1 to about 6 carbon atoms, and R3 is an . - 25 -~ 17~537 ~,C5-3302 ,~ alkyl radical or an alkoxy alkyl radical containing from 1 to about 6 carbon atoms.
The alkanols that may be present in this preferred 1 primer emulsion composition are those containing from 1 to ,' about 4 carbon atoms.
; ' The presence of these afore-described hydroxy ethers, alkanols, or hydroxy ether-alkanol mixtures in amounts of ; from about 20 to about 45 weight percent of the primer emulsion composition is very important to the satisfactory performance of the primer emulsion composition in forming an effective primer layer. If no hydroxy ether or alkanol is present, or if an amount of hydroxy ether or alkanol less than about 20 weight percent is present, the primer emulsion composltion does no~
, generally flow evenly over the polycarbonate substrate; i e., there is uneven distribution of the primer emulsion composition over the substrate with excessive concentrations of the comp-osition in certain areas and a dearth of the composition in other areas, This results in an unevenly distributed and ~ non-uniorm primer layer being formed which in turn results in inferior adhesion of the silicone top coat, and in a streaked appearance o the Einal coated product. If too much hydroxy ether or alkanol is present, i.e,,amounts greater than about ,, 45 wei~ht percent, coa~,ulation and precipitation of the thermo- j '¦ settable acryllc polymer 90~ ids genexally occurs, This preferred primer emulsion composition may also contain, when needed, a curing catalyst for the thermosettable acrylic polymer, IE such a catalyst is present it is usually present in from about 0.05 to about 2 weight percent based on the weight of the thermosettable acrylic polymer solids.

l, 7~3~ 8CS-3302 ., . I
Examples of such catalysts include toluene sulfonic acid, citric acid, phosphoric acid, and the like.
All three of the aforedescribed primer compositions are ; generally applied onto the surface of the ultraviolet radiation 5 ~l stabilized polycarbonate resin article in substantially the I same way, and a~ter application are subjected to generally the same procedure to produce the solid thermoset acrylic poiymer containing primer layer. A thin layer o~ the primer composition I is applied onto the sur~ace of the polycarbonate substrate J
10 ` by any of the well known methods such as spraying, dipping, flow-coating, roll-coating and the like. Generally the primer composition is applied in an amount sufficient to provide a cured primer layer of from about 0.01 to about 0.1 mil thick, and j preferably from about 0.02 to about 0.08 mil thick. After the ~ primer composition has been applied onto the ~olycarbonate , surface a substantial portion of the volatile liquids present in the primer composition, e.g., the organic solvents in the first type of primer composition, the water in the second type ~of primer emulsion composition, and the water and hydroxy ether j or alkanol in the preferred type o~ primer emulsion composition~
are evaporated of~. This evapora~ion is accomplished by air I dryin~ or mild heating. The evaporation oE a substantial ;,portion, if not all, of the liquid component o~ the primer composition leaves deposited on the substrate sur~ace an even and generally solid layer comprised o~ a thermosettable acrylic polymer, ~his thermosettable acrylic polymer is then cured or thermoset (cross-linked~ by heating at a temperature effective to c~re the tllermosettable acrylic polymer to a thermoset acrylic polymer. Generally this temperature ranges from about 90C.

8CS~3302 ~ ~ 7~ ~3~
to abou-t 130C. The end result of this proceduxe is a solid primer layer comprised of a thermoset acrylic polymer durably and tenaciously adhered to the surface of the ultraviolet radiation stabilized polycarbonate resin article surface.
This thermoset acrylic polymer containing primer layer acts to promote the adhesion of the colloidal silica filled thermoset organopolysiloxane containing top coat, which is disposed on the outer surface of said primer layer, to the underlying surface of the polycarbonate substrate. In the practice of this invention a top coat composition comprising a colloidal silica filled further curable organopolysiloxane is applied onto the surface of the cured primer layer and the organopolysiloxane is then cured to form a top coat containing a colloidal silica filled thermoset organopolysiloxane.
One type of colloidal silica filled further curable organo-polysiloxane composition useful as the top coat composition in the practice of the present inuention is that described in U.S.
Patents 3,986r997 and 4,027,073 and comprises a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of a silanol having the formula R Si(OH)3 VI.

wherein R5 is selected from the group consisting of alkyl radicals containing Erom 1 to about 3 carbon atoms, the vinyl radical, the 3l3,3-tri~:Luoropropyl radical, the gamma-glycidoxypropyl ~5 radical and the gamma-methacryloxypropyl radical, with at least 70 percent by weight of said silanol being CH3Si(oH)3. This composition generally contains ~rom about 10 to about 50 percent by weight of solids, said solids consisting essentially of a mixture o:E from about 10 to about 70 percent by weight of colloidal silica and ~rom about 30 to about 90 percent by ~17~S37 ,l 8CS-3302 weight of the partial condensate of a silanol. The partial condensate of a silanol, i.e., a siloxanol, is preferably obtained , entirely from the condensation of CH3Si(OH)3, however, the :l~artial 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-methacryloxypropyltrisilanol, mono gamma-glycidoxy-propyltrLsilanol, 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 composition and to obtain the optimum properties in the cured coating obtained , rom this composition. Suitable acids include both organic and ino~rganic acids such as hydrochIoric, chloroacetic, acetic, ;, citric, benzoic, formic, propionic, maleic, oxalic, glycolic , and the like. The acid can be added to either the silane, which hydrolyzes to form the silanol component of the composition, or the!
hydrosol prior to mixing the two components.
The trisilanol component oE this composition is generated in si~u by the addition o the corresponding trialkoxysilanes ~o aqueous dispersi.ons o~ colloidal silica. Suitable tri- ¦
alkoxysilanes are those containing methoxy, ethoxy, propoxy, l isopropoxy and sec-butoxy substituents~ Upon generation o the silanol in the acidic aqueous medium there ls condensation I o~ the hydroxyl substituents to orm -Si-O-Si- bonding. The condensation is not complete, but rather the siloxane retains an appreciable quantity of silicon-bonded hydroxyl groups, thus 1 17453~ ' 8~5-3302 rendering the organopolysiloxane polymer soluble ln 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 l curing of the top coat composition,which has been applied as i a thin layer onto the surface of the primer layer,further conden-sation o~ the uncondensed silanol groups occurs resulting in the formation o~ a substantially fully condensed thermoset (cross-linked) colloidal silica filled organopolysiloxane.
The silica component of the top coat co~position is present in the form of colloidal silica. Aqueous colloidal silica ; dispersions generally have a particle size in the range of from ~ abou~ 5 to about 150 millimicrons in diameter. These silica i, dispersions are prepared by methods well known in the art and are commercially available. It is preferred to use colloidal silica having a particle si~e in the range of from about 10 to ` about 30 millimicrons in diameter in order to obtain dispersions having a greater stability and to provide top coatings having superior optioal properties.
The silica Eilled Eurther curable organopolysiloxane top coat compositions are prepared by adding triallcoxysilanes to , coll.oidal silica hydrosol and adjusting the pH to a range ~ !
between 3.0 and 6.0 by ~he addltion o~ acid. As mentioned !Ipreviously, the acid can be added ~o either the silane or the ~silica hydrosol be~ore the two components are mixed. Alcohol is generated during the hydrolysis of the trialkoxy silanes to the trisilanols, Depending upon the percent solids desired in the final coating composition, additional alcohol, water, or a water-miscible solvent can be added~ Suitable alcohols are the lower aliphatic alcohols such as methanol, ethanol, ' i 1 ~7~537 8CS-3302 ll !

isopropanol, tert-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 acet-¦
one, butyl Cellosolve, and the like can be added to the water alcohol solvent system. Generally, sufficient alcohol or water-alcohol solvent is added to give a composition containing from about 10 to about 5Q percent by weight of solids, said solids generally comprising from about 10 to about 70 percent by weight - of co'lloidal 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 ~he partial condensate of the silanol. This condensation occurs upon the generation of the silanol in the acidic aqueous medium through the hydroxyl groups to form -Si-O-Si- bonding.
i The condensation is not complete, resulting in a siloxane having an appreciable amount of silicon-bonded hydroxyl groups. This aged, colloidal silica filled further curable organopolysiloxane ; top coat composition is then appLied onto the primed polycarbonate surface by any of the commonly known methods such as dipping, I spraying, flow-coating and the like~ After the top coat compo-si~ion has been applied onto the primed polycarbonate surface ;l a substantial amoun~ of the volatlle solvents presen~ in the ' ~op coat composition are evaporatedafE by either air drying or mild heating., After evaporation of a substantial portion of the solvents from the top coat composition there is let on the surface of the primer layer a g'enerally soLid layer comprised of a colloidal silica filled Eurther curable organo-polysiloxane. Heat is then app'lied to this further curableorganopolysiloxane to effectuate further condensation of the _31-: i.

1 17~53~ 1 ,silanols and cross-linking o~ the polymer. The result is ;a colloidal silica filled thermoset organoploysiloxane top coat which is highly resistant to scratching, abrasion, marring, j! and organic solvents, and which is tenaciously and durably 5 ' adhered, by means of the adhesion promoting primer layer, to , the ultraviolet radiation stabilized polycarbonate sur~ace.
Generally, this top coat contains from abou~ 10 to about 70 weight percent o~ colloidal silica and from about 30 to about 70 .; weight percent of organopolysiloxane.
10 ~ The thickness of the cured top coat is generally dependent upon the method of application and upon the weight percent solids present in the top coat composition. In general, the higher the weight percent solids present in the top coat composition, and ~ the longer the application or residence time of the top coat I composition on the primed polycarbonate surface, the greater the thickness o~ the cured top coat. Preferably the cured ; top coat has a thickness of from about 0.1 to about 0.7 mils, more preferably from about 0.15 to about 0.5 mils, and most preferably from about 0.2 to about 0.3 mils.

DES~RIPTION OF THE PREFERRED EMBODI~IENT

In order to more fully and clearly illustrate the present inventlon the ollowing specific examples are presented. It ,i i9 intended that the examples be considered as illustrative rather than limitlng the inven~ion disclosed and clalmed herein.
25 , In the examples, all parts ane percentages are on a weight basis unless o~herwise specified.
,' ' '.

~ .

~ ~7~53~ 8CS-3302 ': I
., EXAMPLE 1 The surface layers of polycarbonate test panels 4" x 4" x ,1/4" are impregnated with an ultraviolet radia-tion absorbing ,compound by flow coating the panels with an ultraviolet radiation ~stabilizing composition comprised of a solution of 1% Cyasorb UV-1988 (a benzylidene malonate ultraviolet radiation absorber ~.
marketed by ~he American Cyanamid Co., and represented by `general Formula III wherein X is the OCH3 radical and R and i;Rl are methyl radicals) dissolved in butoxyethanol. The coated panels are drained for less than one minute and are then heated : :at 125C. for five minutes to surface impregnate the panels.
A primer layer containing a thermoset acrylic polymer is 'applied onto these ultraviolet radiation stabilized polycarbon-.ate panels by flow coating the panels with a primer emulsion 15 ; composition containing 10% of thermosettable acrylic solids containing 0,3% toluene sulfonic acid`(these solids are provided ~M ' by Rhoplex AC-658, a commercially available thermosetting ; '`acrylic polymer containing emulsion containing from about 46 to about 48 percent total solids, which is marketed by the Rohm & Haas Company), 35% butoxyethanol and 65% water. The test panels are drained ~or 15 ~inutes and are then heated for one hour at 125C. to cure the thermosettable acrylic polymer to ;'a thermoset acrylic polymer, ,, A colloidal sillca illed thermoset organopolysiloxane top coat is applied onto the primed test panels by :~low coating the 'I primed panels with a top coat composi~ion containing abou~ 18% 11 solids, about 50% of these solids being colloidal silica and about¦
50% of these solids being the partial. condensation product of CH3SI(OH)3, in a lower aliphatic alcohol-water system, and I

- 33 - ~ I
: ' ~

53'~ I' having a pH of about 3.9. The panels coated with this top coat composition are drained for thirty minutes and are then baked ; at 125C. for one hour to cure the organopolysiloxane to the I thermoset stage.

EX~PLE 2 Ultraviolet radiation stabilized, primed and top coated polycarbonate test panels are prepared substantially in accordance with the procedure of Example 1 except that the ultra-violet radiation stabilizing composition contains 2% of Cyasorb UV-1988 ultraviolet radiation absorbing compound.

; Ultraviolet radiation stabilized, primed and top coated polycarbonate test panels are prepared substantially in ~' accordance with the procedure of Example 1 except that the ultra-violet radiation stabilizing composition contains 3% of CyasorbUV-1988 ultraviolet radiation absorber.

Ultraviolet radiation stabilized, primed and top coated polycarbonate test panels are prepared substantially in 20 ll accordance with the procedure of Example 1 except that the ultraviolet radiation stabilizing composition contains 1% of 2,2',4,4'-tetrahydroxybenzophenone ultraviolet radiation absorber, i ~ Ultraviolet radiation stabilized, primed and top coated polycarbonate test panels are prepared substantially in accordance with the procedure of Example 1 except that the 53~ 8CS-3302 ultraviolet radiation stabilizing composition contains 2V/o of 2,2',4,4'-tetrahydroxybenzophenone ultraviolet radia~ion absorber.
I

S Ultraviolet radiation stabilized, primed and top coated polycarbonate test panels are prepared substantially in accordance with the procedure of Example 1 except that the ultraviolet radiation stabilizing composition contains 3%
of 2,2',4,4t-tetrahydroxybenzophenone ultraviolet radiation absorber.

; EXAMPLE 7 This example is illustrative of a prior art primed and ; top coated, but not ultraviolet radiation stabilized, poly-carbonate resin article falling outside the scope of the present invention. The surface layers of polycarbonate test panels 4" x

4" x 1/4" are primed with a thermoset acrylic polymer primer layer`by flow coating the panels with a prlmer emulsion composition containing 10% of thermosettable acrylic solids containing 0 3% toluene sulonic acids (these solids are provided ¦
~0 by Rhoplex AC-658), 35V/o butoxyethanol and 65% water The test panels are drained for 15 minutes and are then heated ~or one 'iI hour at 125C to cure the thermoset-table acrylic polymer to a thermoset acrylic polymer.
A colloidal silica filled thermoset organopolysiloxane top coat is applied onto the primed test panels by flow coating the primed panels with a top coat composition comprised oE about 18V/o solids, about 50% of these solids being colloidal silica and about 50% o~ these solids bein~ the partial condensat-1,.

117453~ 8CS-3302 ion product of CH3Si(OH)3, in a lower aliphatic alcohol-water system, and having a pH of about 3.9. The panels coated with this top coat composition are drained for 30 minutes and are then I
baked at 125~C. for one hour to cure the further curable organo- ¦
polysiloxane to a thermoset stage.

The test panels prepared in Examples 1-7 are then tested , for initial adhesion of the top coat and for adhesion of the top coat after aging under RS-sunlamps and in a QUV accelerated weathering device. The results of these -tests 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 ~l - 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 the tape off.
A sample fails the a & esion test if any of the squares in the grid are pulled off. In the RS-sunlamp aging test the samples undergo severe exposure to ultraviolet radiation. In this . test the samples are exposed to a RS-sunlamp and during exposure are periodically removed and subjected to the adhesion test.
In the QUV accelerated weathering test the samples are inserted lnto a QUV accelerated weathering device sold by the Q-Panel Company, This device is se~ to alternating consecutive cycles ~' o~ fluorescent ultraviolet light at 60C. for 4 hours and 2S high humidity at 45C, for 4 hours. The test samples are periodically removed from the QUV accelerated weathering device and subjected to the adhesion test.

.' I

17453~ 8CS-3302 " :. I
TABLE I
No. of Hours of No. of Hours o~ t Exposure to RS- Exposure in QUV
Sunlamp at which Weathering Device atl Initial Sample Fails the which Sample Fails " Example No. Adhesion Adhesion Test the Adhesion Test ; 1 Pass Passes after 323 Passes after 329 hours hours 2 Pass Passes after 323 Passes after 329 10 : hours hours 3 Pass Passes after 323 Passes after 329 hours hours : 4 Pass Passes after 323 Passes after 209 : hours hours, Fails at 329 hours Pass Passes after 323 Passes after 209 hours hours, Fails at : . 329 hours : 6 Pass Passes after 323 Passes after 329 : 20 : : hours hours 7 Pass Passes after 323 Passes after 329 hours hours The surface layers of a polycarbonate film 2" x 4" x 1/100"
are impregnated with an ultraviolet radiation absorbing ; compound by flow coating the ~ilm with an ultraviolet radiation ~tabiliæing composition comprised of a solution of 1% Cyasorb UV-1988 dis~olved in butoxyethanol, The coated film is drained for less ~han one minute and then heated at 125C. for five 30 ,! minutes, The treated ilm is placed in the sample beam of a Perkin-Elmer Model Coleman 575 Spectrophotometer and an un-treated ilm is placed in the re~erence. The absorbance o~ the treated Eilm was measured, and the amount of ultraviolet light absorbed by the treated film is calculated using the relation-ship A=log (Io/I) where A is the absorbance, Io is the intensity , I

53~ 8CS-3302 ~, of incident ultraviolet light, and I is the intens-ity of trans- I
mitted ultraviolet light. The results are set forth in Table II. i EX~PLE 9 'I An ultraviolet radiation stabilized film is prepared ,~
' substantially in accordance with the procedure of Example 8 except that the ultraviolet radiation stabilizing composition contains 2% Cyasorb UV-1988. Absorbance of this film is determined , according to the procedure of Example 8 and the results are set ;, forth in Table II. t 10 :. EXAMPLE 10 An ultraviolet radiation stabilized polycarbonate film is prepared substantially in accordance with the procedure of Example 8 except that the ultraviolet radiation stabili2ing composition contains 3% of Cyasorb W -1988. Absorbance of this film is determined according to the procedure of Example 8 and '.i the resuLts are set forth in Table II.
.1 i An ultraviolet radiation stabilized polycarbonate film , is prepared substantially in accordance with the procedure of . Example 8 except that the ultraviolet radiation stabilizing I composition contains 1% o 2,2',4,4'-tetrahydroxybenzophenone.
,' Absorbance of this film is determined according to ~he procedure ! o~ Example 8 and the resuLts are set forth in Table II.
' , EXAMPLE 12 An ultraviolet radiation stabilized polycarbonate film is prepared substantially in accordance with the procedure of Example 8 except that the ul~raviolet radiation stabilizing composition contains 2% of 2,2',4,4'-tetrahydroxybenzophenone.

: - 38 -' .' I
:. I
- ~ ' 1 17453~ 8cs-33o2 Absorbance of this film is determined according to the procedure of Example 8 and the results are set forth in Table II.

EX~IPLE 13 An ultraviolet radiation stabilized polycarbonate film ' is prepared substantially in accordance with the procedure of : Example 8 except that the ultraviolet radiation stabilizng composition contains 3% of 2,2',4,4'-tetrahydroxybenzophenone.
Absorbance of this film is determined according to the procedure I of Example 8 and the results are set forth in Table II. ', TABLE II
Absorbance at % W -light Absorbed I
Example Number ~ maximum at ~maximum 8 1.17 93%
9 2.64 ~99~/o ~3 799 9%
11 0.87 88%
12 1.77 98%
13 2.61 ~g9%

A first ultraviolet radiation stabilized, primed and top coated polycarbonate test panel is prepared substan~ially in flccorclance with the procedure oE Example 1 except that the ;~ ultravi.olet radiation stabiliæing composition contains 6% of Cyasorb 5411 (a derivative of benzotriazole ultravi.olet light absor~er marketed by American Cyanimid Co.) and the clrained panel i is heated at 125C. for 10 minutes rather than for 5 minutes.
; A second primed and top coated, but not ultraviolet radiation stabilized, polycarbonate test panel is prepared substantially in accordance with the procedure of Example 7. Both of these test panels are exposed to ultraviolet light aging wnder a RS-- 39 _ - ~17~3 'sunlamp system for five days. At the end of five days both test panels are visually inspected. The first test panel is found to be colorless while the second test panel is visibly yellow.
'.; I
'~1 It is clear rom the data in Table I that the initial adhesion and the adhesion after exposure to weathering of the colloidal silica filled silicone top coat to the ultraviolet radiation surace stabilized polycarbonate articles of the present invention, i.e., Examples 1-6, is comparable to that of the prior art polycarbonate articles which do not contain an ultraviolet radiation absorber dlspersed in their surface layers, i.e., Example 7. This is rather surprising as it is .
well known that modification o~ the surface of a polycarbonate resin by ~the inclusion therein of an additive produces unexpected ` and unpredictable effects on the adhesion of a coating thereto.
These efects are otentimes negative in that the adhesion, both initial and after exposure to weathering, but particularly the ; adhesion after exposure to weathering, o the coating to the treated polycarbonate surface is adversely affected. As clearly illustrated by Example 14 the articles o the present invention not only possess good adhesion o~ the colloidal silica illed ,j thermoset organoplyslloxane top coat to the ultraviolet radiation !
! sur.~ace stabilized polycarbonate substrate, but are also resistant to degradation by ultraviolet radiation. The prior j! art articles, as typified by the second polycarbonate test 2S pane]. ln Example 14, while possessing good aclhesion o~ the I colloidal silica illed thermoset organopolysiloxane top coat to ~he polycarbonate substrate are quite susceptible to deg-; radation by ultraviolet radiation.
Table II illustrates the fact that treating polycarbonate .' .

_ 40 - I

1 1 74 5 3 ~ !

resins with the preferred ultraviolet radiation stabilizing composition, i.e., a composition containing an ultraviolet radiation absorbing compound and a nonaggressive liquid carrier therefore, results in a resin whose surface areas absorb the great majority of incident ultraviolet radiation. This protection against ultraviolet radiation is achieved without any visible deleterious effects on the surface of the treated polycarbonate resin.
While one particularly preferred colloidal silica filled further curable organopolysiloxane top coat composition has been described in detail hereinbefore, this is not the only type of colloidal silica filled further curable organopoLysiloxane top coat composition which can be utilized in producing the colloidal silica filled thermoset organopolysiloxane top coa~ of the present invention. Another colloidal silica filled further curable organopolysiloxane containing top coat composition which might be used is that described in U.S. Patent 4,159,206. This composition' comprises about 30-50 parts by weight of a colloidal silica~`and about 50-70 parts by weight of (i) dialkyldialkoxysilane and (ii) alkyltrialkoxysilane wherein the weight ratio of (i) to (ii) is from about 1:19 to about 1:4.
In this composition the siLanes generate ~he corresponding Si1anO1S 1n ~i~u by the ~ddltiQn oE the corresponding di- and ~rialkoxysilanes to the acidic aqueous dispersions of colloidal silica. The resulting composition comprises a dispersion of colloidal silica in the lower aliphatic alcohol-water solution oE the partial condensate of a mixture o~ silanols, one having the ~ormula R6Si(OH)3 and one having the formula R7R6Si(OH)3 in which R6 and R7 are selected independently from the group ~ 17453~

consisting of alkyl radicals o~ 1 to 3 inclusive carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, the gammz-acryloxypropyl radical, and the gamma- methacryloxypropyl radical, said composition containing 10 to 50 weight percent solids, the ratio of colloidal silica to the partial condensate being from 1:1 to about 3:7 by weight, said composition further containing sufficient acid to provide a pH in the range of 3.0 to 6Ø
The nonvolatile solids portion of this coating composition is a mixture of colloidal silica and the partial condensate of a mixture of silanols. The silanols are generated in situ by hydrolysis of the corresponding mixture of (i) dialkyldialkoxy-silane and (ii) alkyltrialkoxysilane. The weight ratio of (i) to (ii) is from about 1:19 to about 1:4. Suitable dialkoxy and trialkoxysilanes'are those containing methoxy, ethoxy, isopropoxy and t-butoxy substituents, which upon hydrolysis liberate the corresponding alcohol, thereby generating at least a portion '.i of the alcohol present in the composition. Upon generation of the silanol in the acidic aqueous medium, there is condensation o the hydroxyl substituents to form -Si-0-Si- bonding. The condensation is not comp'lete, 'but rather the siloxane retains an appreciable quantity oE si'licon-bonded hydroxyl groups, thus rendering the polymer soluble in the water-alcohol solvent. I
This soluble partial condensate can be characterized as a siloxan-l ol polymer having at least one silicon-bondecl hydroxyl group per every three -SiO- units.
Upon curing there is further condensation of the silanols ancl cross linking of the polymer to orm a thermoset organo-polysiloxane.

117~53~ 8CS-3302 From the foregoing it is quite evident that the instant invention provides both articles and a method of producing these articles which are resistant to degradation by ultraviolet light, abrasion and attack by chemical solvents and which retain all of the desirable and excellent physical and chemical properties of unstabiLized and uncoated polycarbonate resin.
The foregoing disclosure of this i.nvention is not to be consldered as limiting, since many varlations may be made by those skilled in the art without departing from the scope or 10 ~ spirit of the foregoing description.
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Claims (61)

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

1. An improved coated polycarbonate article exhibiting improved resistance to degradation by ultraviolet radiation comprising a polycarbonate substrate having durably adhered on at least one surface thereof a coating comprised of (i) an adhesion promoting primer layer containing a thermoset acrylic polymer disposed on said surface, and (ii) adherently disposed on said primer layer a top coat layer containing a colloidal silica filled thermoset organopolysiloxane; the improvement consisting essentially of said polycarbonate surface on which said coating is disposed being impregnated with at least one ultraviolet radiation abosrbing compound.

2. The article of claim 1 wherein said top coat layer contains from about 10 to about 70 weight percent of colloidal silica.

3. The article of claim 2 wherein said top coat layer contains from about 30 to about 70 weight percent of the condensation product of at least one silanol.

4. The article of claim 3 wherein said silanol is selected from the group represented by the formula R5Si(OH)3 wherein R5 is selected from the group consisting of alkyl radicals, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, and the gamma-methacryloxypropyl radical.

5. The article of claim 4 wherein at least 70 weight per-cent of said silanol is CH3Si(OH)3

6. The article of claim 5 wherein said silanol is CH3Si(OH)3.

7. The article of claim 1 wherein said ultraviolet radiat-ion absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

8. The article of claim 5 wherein said ultraviolet rad-iation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzyl-idene malonates, and cyanoacrylates.

9. The article of claim 8 wherein said benzylidene malonates are represented by the formula wherein X is selected from hydrogen, hydroxyl, halogen, alkyl, and alkoxy radicals; and R and R1 are independently selected from alkyl, substituted alkyl, aryl, substituted aryl, alkaryl, and aralkyl radicals.

10. The article of claim 8 wherein said cyanoacrylates are selected from compounds represented by the formula wherein R2 is an alkyl or a hydroxyalkyl radical.

11. The article of claim 8 wherein said polycarbonate resin substrate is non-opaque.

12. An improved coated polycarbonate article exhibiting improved resistance to degradation by ultraviolet radiation comprising a polycarbonate resin substrate having disposed on at least one surface thereof (i) an adhesion promoting primer layer containing a thermoset acrylic polymer disposed adherently on said surface; and (ii) adherently disposed on said primer layer a top coat layer containing the cured product of a top coat composition comprised of a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of at least one silanol, said top coat composition containing from about 10 to about 50 weight percent solids consisting essentially of from about 10 to about 70 weight percent of colloidal silica and from about 30 to about 90 weight percent of said partial condensate;
the improvement consisting essentially of said polycarbonate surface on which said primer layer and said top coat layer are disposed being impregnated with at least one ultraviolet radiation absorbing compound.

13. The article of claim 12 wherein said silanol is selected from the group represented by the formula R5Si(OH)3 wherein R5 is selected from alkyl radicals, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, and the gamma-methacryloxypropyl radical.

14. The article of claim 13 wherein at least 70 percent by weight of said silanol is CH3Si(OH)3.

15. The article of claim 14 wherein said top coat comp-osition contains sufficient acid to provide a pH in the range of 3.0 to 6Ø

16. The article of claim 15 wherein said silanol is CH3Si(OH)3.

17. The article of claim 12 wherein said ultraviolet radiation absorbing compound is selected from the group consist-ing of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

18. The article of claim 15 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylid-ene malonates, and cyanoacrylates.

19. The article of claim 18 wherein said benzylidene malonates are represented by the formula wherein X is selected from hydrogen, hydroxyl, halogen alkyl, and alkoxy radicals; and R and R1 are independently selected from alkyl, substituted alkyl, aryl, substituted aryl, alkaryl, and aralkyl radicals.

20. The article of claim 18 wherein said cyanoacrylates are represented by the formula wherein R2 is an alkyl or a hydroxyalkyl radical.

21. The article of claim 18 wherein said polycarbonate resin substrate is non-opaque.

22. An improved coated polycarbonate article exhibiting improved resistance to degradation by ultra-violet radiation comprising a polycarbonate resin substrate having disposed on at least one surface thereof (i) an adhesion promoting primer layer containing a thermoset acrylic polymer disposed adherently on said surface; and (ii) a top coat composition disposed on said primer layer, said top coat composition comprised of a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of at least one silanol, said composition containing from about 10 to about 50 weight percent solids consisting essentially of from about 10 to about 70 weight percent colloidal silica and from about 30 to about 90 weight percent of said partial condensate; said improvement consisting essentially of said polycarbonate surface on which said primer layer and said top coat composition are disposed being impregnated with at least one ultraviolet radiation absorbing compound.

23. The article of claim 22 wherein said silanol has the formula R5Si(OH)3 wherein R5 is selected from alkyl radicals, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, and the gamma-methacryloxypropyl radical.

24. The article of claim 23 wherein at least about 70 weight percent of said silanol is CH3Si(OH)3.

25. The article of claim 24 wherein said top coat composition contains sufficient acid to provide a pH in the range of from 3.0 to 6Ø

26. The article of claim 25 wherein said silanol is CH3Si(OH)3.

27. The article of claim 22 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

28. The article of cla.im 25 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotrlazole derivatives, benzylidene malonates, and cyanoacrylates.

29. The article of claim 28 wherein said benzylidene malonates are represented by the formula wherein X is selected from hydrogen, hydroxyl, halogen, alkyl, and alkoxy radicals; and R and R1 are independently selected from alkyl, substituted alkyl, aryl, substituted aryl, alkaryl, and aralkyl radicals.

30. The article of claim 25 wherein said cyanoacrylates are represented by the formula wherein R2 is an alkyl or a hydroxyalkyl radical.

31. The article of claim 28 wherein said polycarbonate resin substrate is non-opaque.

32. A method for producing a polycarbonate article having superior resistance to degradation by ultraviolet radiation, abrasion and attack by chemical solvents comprising:
(i) impregnating the surface layers of a polycarbonate resin substrate with at least one ultraviolet radiation absorbing compound by contacting said surface with an

Claim 32 (continued) ultraviolet radiation stabilizing composition containing at least one ultraviolet radiation absorbing compound and a nonaggressive liquid carrier therefor for a period of time and at a temperature effective for said ultraviolet radiation absorbing compound to impregnate the surface layers in a concentration effective to provide protection against degradation by ultraviolet radiation;
(ii) applying onto said impregnated surface a primer emulsion composition containing, in percent by weight, (a) from about 1 to about 10 percent of a thermosettable acrylic polymer, (b) from about 20 to about 45 percent of a hydroxy ether, an alkanol, or a mixture thereof, and (c) from about 45 to about 79 percent of water:
(iii) evaporating off a substantial portion of the liquid components present in said primer emulsion composition to form a thin substantially solid layer comprised of a thermosettable acrylic polymer;
(iv) thermally curing said thermosettable acrylic polymer to form a thermoset acrylic polymer;
(v) applying onto said cured primer layer a top coat 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 from about 10 to about 50 weight percent solids consisting essentially of from about 10 to about 70 weight percent colloidal silica and from about 30 to about 90 weight percent of said partial condensate;

(vi) evaporating off a substantial portion of the volatile liquids present in said top coat composition thereby forming a substantailly solid layer comprised of a colloidal silica filled partial condensate of at least one silanol; and (vii) thermally curing said partial condensate thereby form-ing a colloidal silica filled thermoset organopolysilox-ane containing top coat.

33. The method of claim 32 wherein said silanol has the formula R5Si(OH)3 wherein R5 is selected from alkyl radicals, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, and the gamma-methacryloxypropyl radical.

34. The method of claim 33 wherein at least 70 weight percent of said silanol is CH3Si(OH)3.

35. The method of claim 34 wherein said top coat composition contains sufficient acid to provide a pH in the range from 3.0 to 6Ø

36. The method of claim 35 wherein said silanol is CH3Si(OH)3.

37, The method of claim 35 wherein the nonaggressive liquid carrier present in the ultraviolet radiation stabilizing composition is selected from the group consisting of hydroxy ethers, alcohols, alcohol-water mixtures, liquid aliphatic hydrocarbons, liquid cycloaliphatic hydrocarbons, and chlorofluorocarbons.

38. The method of claim 37 wherein the polycarbonate resin substrate is preheated to a temperature between about 65°C. and about 150°C. and the ultraviolet radiation stabilizing comp-osition is applied onto the preheated polycarbonate resin sub-strate.

39. The method of claim 38 wherein said ultraviolet rad-iation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylid-ene malonates, and cyanoacrylates.

40. The method of claim 37 wherein the ultraviolet radiat-ion stabilizing composition is applied onto the surface of the polycarbonate resin substrate and the coated substrate is then heated to a temperatuer between about 65°C. and about 150°C.

41. The method of claim 40 wherein said ultraviolet radiat-ion absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

42. The method of claim 32 wherein the nonaggressive liquid carrier in the ultraviolet radiation stabilizing composition is selected from the group consisting of hydroxy ethers, alcohols alcohol-water mixtures, liquid aliphatic hydrocarbons, liquid cycloaliphatic hydrocarbons, and chlorofluorocarbons.

43. The method of claim 42 wherein the polycarbonate resin substrate is preheated to a temperature between about 65°C.
and about 150°C. and the ultraviolet radiation stabilizing composition is applied onto the surface of the preheated poly-carbonate resin substrate.

44. The method of claim 43 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

45. The method of claim 42 wherein the ultraviolet radiation stabilizing composition is applied onto the surface of the polycarbonate resin substrate and the coated substrate is then heated to a temperature between about 65°C. and about 150°C.

46. The method of claim 45 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

47. A polycarbonate article exhibiting superior resistance to degradation by ultraviolet radiation, abrasion resistance, and resistance to attack by chemical solvents produced by the process of:
(i) impregnating the surface layers of a polycarbonate resin substrate with at least one ultraviolet radiation absorbing compound by contacting said surface with an ultraviolet radiation stabilizing composition containing at least one ultraviolet radiation absorbing compound and a nonaggressive liquid carrier therefor for a period of time and at a temperature effective for said ultraviolet radiation absorbing compound to impregnate the surface layers in a concentration effective to provide protection against degradation by ultraviolet radiation;
(ii) applying onto said impregnated surface a primer emulsion composition containing, in percent by weight, (a) from about 1 to about 10 percent of a thermosettable acrylic polymer, (b) from about 20 to about 45 percent of a hydroxy ether, an alkanol, or a mixture thereof, and (c) from about 45 to about 79 percent of water;
(iii) evaporating off a substantial portion of the liquid components present in said primer emulsion composition to form a thin substantially solid layer comprised of a thermo-settable acrylic polymer;
(iv) thermally curing said thermosettable acrylic polymer to form a thermoset acrylic polymer;
(v) applying onto said cured primer layer a top coat 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 from about 10 to about 50 weight percent solids consisting essentially of from about 10 to about 70 weight percent colloidal silica and from about 30 to about 90 weight percent of said partial condensate;
(vi) evaporating off a substantial portion of the volatile liquids present in said top coat composition thereby forming a substantially solid layer comprised of a colloidal silica filled partial condensate of at least one silanol;
and (vii) thermally curing said partial condensate thereby forming a colloidal silica filled thermoset organo-polysiloxane containing top coat.

48. The article of claim 47 wherein said silanol has the formula R5Si(OH)3 wherein R5 is selected from alkyl radicals, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, and the gamma-methacryloxy-propyl radical.

49. The article of claim 48 wherein at least 70 weight percent of said silanol is CH3Si(OH)3.

50. The article of claim 49 wherein said top coat composition contains sufficient acid to provide a pH in the range from 3.0 to 6.0

51. The article of claim 50 wherein said silanol is CH3Si(OH)3.

52. The article of claim 47 wherein the nonaggressive liquid carrier present in the ultraviolet radiation stabilizing composition is selected from the group consisting of hydroxy ethers, alcohols, alcohol-water mixtures, liquid aliphatic hydrocarbons, liquid cycloaliphatic hydrocarbons, and chlorofluorocarbons.

53. The article of claim 52 wherein the polycarbonate resin substrate is preheated to a temperature between about 65°C. and about 150°C. and the ultraviolet radiation stabilizing composition is applied onto the preheated polycarbonate resin substrate.

54. The article of claim 53 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

55. The article of claim 52 wherein the ultraviolet radiation stabilizing composition is applied onto the surface of the polycarbonate resin substrate and the coated substrate is then heated to a temperature between about 65°C. and about 150°C.

56. The article of claim 55 wherein said ultraviolet radiation ion absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole deriva-tives, benzylidene malonates, and cyanoacrylates.

57. The article of claim 47 wherein the nonaggressive liquid carrier in the ultraviolet radiation stabilizing composition is selected from the group consisting of hydroxy ethers, alcohols, alcohol-water mixtures, liquid aliphatic hydrocarbons, liquid cycloaliphatic hydrocarbons, and chlorofluorocarbons.

58. The article of claim 57 wherein the polycarbonate resin substrate is preheated to a temperature between about 65°C. and about 150°C. and the ultraviolet radiation stabilizing composition is applied onto the surface of the preheated polycarbonate resin substrate.

59. The article of claim 58 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.

60. The article of claim 51 wherein the ultraviolet radiation stabilizing composition is applied onto the surface of the polycarbonate resin substrate and the coated substrate is then heated to a temperature between about 65°C. and about 150°C.

61. The article of claim 60 wherein said ultraviolet radiation absorbing compound is selected from the group consisting of benzophenone derivatives, benzotriazole derivatives, benzylidene malonates, and cyanoacrylates.