CA1181636A - Article comprising silicone resin coated, methacrylate-primed substrate - Google Patents

Abstract

ARTICLE COMPRISING SILICONE RESIN
COATED, METHACRYLATE-PRIMED
ABSTRACT OF THE DISCLOSURE

Improved air-drying primer compositions for solid substrates adapted for top coating with curable colloidal silica filled thermoset silicone resins comprise an acrylic ester dissolved in a mixture of 2-ethoxyethanol and 4-hydroxy-4-methyl-2-pentanone.
In comparision with prior art primer compositions, there is no need for heat and/or ultraviolet curing of the present compositions.

Description

3~

; . -1- 60SI- 305 BA~KGROUND OF THE INVE~lTIO~

This invention relates to substrates covered wit~ a protecti~e coati~ ~re particularly, lt relates 5- to impr~ve~ primers ~r substr~tes- ~dapt~- tn recei~re a siliccne resi~ top coat composition. Curi~g the top caa~
with he~t formg aSI adherent protectiv2, abrasic~n-resistant ye~ therecn~

Recently~ the substitution of glass ~azing with transparent materialQ which do not shatter or are more resistant to sha~tering than glass, has become widespre~dO For example~ tr2nsparent glazing made from s~nthetic organic polymers is now utilized in public tr~ns-15 portation vehicles, such as trains, buses, tax~s and air-planes. Lenses~ such as for eye glasses and other optical instruments, as well as glazing for large buildlngs, also employ sha~ter-resistant transparent plastics. The ligh~er weigh~ of these plastics in comparison to glass is a fur-ther advantage, especially in the transportation industry - where the weight of the v nicle is a major factor in its fuel economy.

While transparent plastics provide the major advantage of being more resistant to shatterin~ and ligh~er than glass~ a serious drawback lies in the ease with wh;ch these plastics mar and scratch, due to ever~day contact with abrasives7 such as dust, cleaning equipment and marri~
results in impaired visibility and poor aesthetics, and 3Ei 60SI-3~5 oftentimes requires replacement of the glazing or lens or the like.
One of the most promising and widely used trans-parent plastics for glazing is polycarbonate, such as that known as LEXAN@~, sold by General Electric Company.
It is a tough material, having high impact strength, high heat deflection temperature, good dimensional stability, as well as being self-extinguishing, and is easily fabri-cated. Acrylics, such as polymethylmethacrylate, are also widely used transparent plastics for glazing.
Attemps have been made to improve the abrasion resistance of transparent plastics. For example, scratch-resistant coatings formed from mixtures of silica, such as colloidal or silica gel, and hydroly2able silanes in a hydrolysis medium; such as alcohol and water, are known.
Misch, U.SO 3,708,225 dated Jan.2,1973, Clark, U.S. 3,986,997 dated October 19, 1976, 3,976,497 to Clark dated August 24, 1976, and U.S. 4,027,073 to Clark dated May 31, 1977;
Armbruster et al., U.S. 4,159,206 dated June 2~,1979;
20 and Ubersax U.S. 4,177,315 dated Dec.,4,1979 for example, describe such compositions. Improved such compositions are also described in commonly-assigned Canadian application Serial No. 339,538 ~iled on November 9, 1979, and in Canadian application Serial No. 339,539, filed Nov 9, 1979.
The application of silicone hard coat materials to LEXAN ~ and other thermoplastic materials, e.g., poly-(methylmethacrylate) is pre-treatment dependent, i.e., it is good practice, if not essential, to prime the substrate.
See, for example, ~Iumphrey,U.S. 4,188,451 dated Feb.,5,1980, which uses as a primer, a UV~cured reaction production of a poly~unctional acrylic ester monomer and a silane containing a siliconbonded unsaturated hydrocarbon radical, and the above-mentioned Canadian S.# 339,539, which discloses the use of a thermoset ing acrylic resin. It is apparent that the i3~

current state of the art in primers requires a stoving (i.e., heating) step or a ultraviolet (uv) radiation step for proper performance.

It has now been discovered that thermoplastic acrylates can be laid down as primers by flowingt dipping and the like from a unique solvent system and, after simply air drying for 20-45 minutes, top coating with a thermally curable silica filled silicone will produce ultimately articles having a top layer with excellent adhesion, abrasion resistance and moisture resistance.

SUM~RY OF THE INVENTION
Accordingly, it is one object of the present invention to provide a novel primer for use with a protective coating resin for solid substrates.
Another object of this invention is to provide articles primed with the new composition which, after appliG~tion of a silicone resin top coat provide improved abrasion-resistant surfaces thereon.
Still another object of the present invention is to provide an improved primer composition coated on a substrate and air dried, especially well suited for top coating with silica sol filled silicone resin compositions.
These and other objects are accomplished herein by providing articles comprising a solid substrate having at least one surface on which is deposited:

~i) a layer of a primer cor.lposition, and, a Layer of a cured top coat con~ainin~
~ a colloidal silica ~illed tllermoset organopoly5iloxane 9 ¦; said primer composition comprising (a) fro~n about 2 to about 10 parts 'by we~gh~
of a hig~l molecular wei~,ht thermoplastic ~ethacrylic o~ster polymer or copsLym~r selected from (1) polymers and copolymers comprising - Cl-C~ alkyl methacrylate;
(2~ copolymer~ comprising Cl-C6 alkyl meth~
acrylates and a reaction produc~ of glycidyl methacry-La~ and a hydroxy-benznphenone ultraviolet Light screen-ing agent~r . (3)- cQpoLymers comprising Cl-C6 ~lkyI metacry lates and (A) a re~ction pro(luct comprising, unit~ o methacrylic acid and y-chtor~prop~ltrimethoxys~ane (~
acrylic or-Me~hacrylic^ac~d~ or (C), a mixture of (A) an~
(B); or ~4) a ~ixture of any of the fore~oing;
(b~ fro~ about 60 to abo~t 90 parts by wei~,ht of 2-ethoxyethanol;
(c) from abou~ 10 to about 30 parts by weight of 4-hydroxy-4-me~hyl-2-pen~anone; and ~d) from about O to about 20 parts by wei~ht of glacial acetic arid, per 100 parts by weigh~ of (a~, (b), (c) and (d~ combined.

' DETAILED DESCRIPTIO~ OF TEE IN~ENTION
i - The primer compositions can be applied to a variety of sol~d substrates by conventional methods~
such as flowing, spraying or dipping to form a continu-ous surface film. Substrates which are especi~ally con-templated herein are transparent, as well as n~n-trans-parent, as ~Jell as non-transparent plastics and metals.

! More particul2rly, the plastics are synthetic organlc ¦ polymeric su~st~ate5 such as acr~lic polymer like poly-i (methylme~hacrylate~, polyesters, such as poly(ethylene ~erephthalate), poly~butylene terephthalate3, etc., poly-æmides, polyimides,acrylonitrile-Styrene copolymers,s~yrenec acrylonitrile-butadiene copolymers, poly(~inyl chloride) 3 butyrates, polyethylene and t~e like. The coated sub-strates especially contempla~ed are polycarbonates, su~h , 10 as the poly(bisphenol-A carbonates) known as LEXA~ ~ ;
g sold by Genera~ E~ectric Com~any, and also iniection molded9 extruded or cast acrylics, such as poly(m thyI
~e~h~c~ t~3~ Me~al sub~trate~ f~r use in the presen~
i~.e~io~ in~lude bright a~d dul~ metalliz2d surfaces 15~ Iik~ sputtere~ chromium alLoys. Other illustrative substrates contemplated herein include wood, p~inted sl7~faces, lea~her, glass~ ceramics and ~ex~iles~

~ith respect to the high ~olecular weight thermoplastic polymers or copolymers to be used in the pr~mer composition, these can be made in known ways and so~e are commercially a~ailabLe.
.
The polymers and copolymers of CL-C6 alkyl methacrylate include, for example, poly(methyl methacry-late), poly(n-butyl methacrylate) poly(methyl-co-butyl methacrylate) and the likeO These are made by thernal -- or peroxide or azo-bis-isobutyronitrile catalyzed poly-merization of the corresponding monomer~ or mixture of monomers in well known bulk, suspension, en~lsion, a71d the like ~echniques. In general, the molecular weight should be high, that is, at least 50,000, preferably at least 100,000~. The ~pper limit is not particularly critical. A satisfactory range Cor most pur~oses is 3~ 100,000 to 250,000. A suitable com~ercial product is poly(methyl methacrylate) ~ype designation Elvacite 2O4~D

I ti3$
-sold by DuPont Co.
i I A second embodiment (a)(2) 9 includes a co-i poly~erized ultraviolet screen in the acryla~e primer.
Copolymerization of 2,4-dihydroxybenzophenone or other hydroxy-functional be~zophenone, e.g., 2,2',4,4l-tetra-hydroxybenzophenone wi~h met~yl methacrylate is achieved by functionalizing the benzophenone f~ rst ~by refluxing ! with gl~cidoxy ~ethacrylate and a catalytic amount of atrialkyl amine. When all of the glycidoxy methacrylate has been consumPd~ the mixture is reduced in ~olume to remoYe the catalyst and methyl methacrylate 15 adde~. .
- ~ preferred ~inal ratio o~ the methacrylate~ w screen to - acrylate ester is 1:10, by weight~ A suita~l~ catalyst (azQbisisobutyronitrile~ is add~d and the solutio~ i~
he~ted at ~0-120C. for two hours. Two more portions of the catalyst are added at t~o hour intervals. Re va~
of the solvent gives an ac~ylate copolymer uhich is use-ful herein, alone, or in further admixture with poly(methyl methacrylate) homopolymer, etc.
A third embodiment, (a)(3), includes a copoly-merized methacryloxypropyltrimethoxysilane and/or acrylic or methacrylic acid copol-~mer with a Cl-C6 alkyl methacry-late. To make these,a solution of methacryloxypropyl-trimethoxysilane 1-10 parts and/or acrylic acld or me~h-acrylic acid 1-10 parts, methyl methacrylate 90-99 parts, a catalyst 1-5 parts, and an appropriate solvent, if desired~
e.g., benzene,can be hea~ed at ~0C. for 4 hours. A second portion of catalyst can be added and the solution can be heated for another four hours. The solution can be dilu~ed to 2-10 parts of solids per 100 parts of composition~ eOg., with 2-ethoxyethanol and 4-hydroxy-4-methyl-2-pentanone, and, optionally, acetic acid. If desired, also, pol~(met~l methacrylate) homopolymer can be a~ded. Heatin~, to compleLe ;

~ i 34~
.. .

o ~ solution7 can be used. Filtra~ion prior ~o use is often ¦ desirable~
!
' In embodiments (a~(l) and (a)(3), if the .
i 5 substrate material is photQlytically uns~able9 the addi-tio~ of ultr~viole,~ screening agents to the primer will . prolong ~he lifQ of the su~strate and, thus, the ~inal ; product. Seleeted uY screens c~n be added a~ .5 $o 50%
of the total solids. Illustrati~e such screening agen~s 10 are benzophenones, triazoles, hindered amines, salicylate esters ~ me~cal complexes, other known screening and/or ~ree radical quenching agents, and the like.

A ~wo to 10 perce~t solids solution o~ the primer co~position in the sol~ents combination (all of which are items of commerce) is applied, e.g., by dipping9 flowing or sprayLng, and the primed substrate is ~ir dricd~ eOg., for 2~-30 minutes, e.g., at 15 to 31~C:, The air dried primed substrate is then flow, dip or spray oated wi~h the ilica ~illed curable organo-polysiloxane top coat composition.

The curable top coatings used in this invention comprise generally a dispersion of colloidal silîca in an aliphatic alcohol-water solution of the partial condensa~e o a silanol of the formula RSi~OH)3, wherein R is selected fro~ the group consistlng of alkyl having from l to 3 carbon atoms and aryl, at least 70 weight percent o~ the silanol 30 being CH3Si(OH)3, said co~position containing 10 to 50 weighl-p~rcent solids, said sol.ids consisting essentially of 10 to 70 ueight percent colloidal silica and 30 to 90 weigh~ per-cent of the partial condensate. Preferably tll~ composition has a pH of from 7.1 to about 7.8. They are prepared by 35 hydrolyzing a trialkoxysilane or a mixture o:E trialkoxysilarle~

3~ ~

~, .
by hydrolyzing a trial~oxysil~ne or a mixture o~ trialkoxyG
silanes of the for~ula R~S~(OR)3, wherein R' is alkyl o from 1 to 3 carbons or aryl, 5uch as phenyl, and R is alkyl, in an aqueous dispersion of colloidal silica.
. In the practice of the present i~ve~tion9 sui~! able a~ueous colloidal silic~ dispersions generally have a particle size of from 5 ~o 150 millimicrons in diameterO
These silica dispersions are well known in the axt and co~mercially a~ailable ones incl~de, for example, ~hose sold under the trademarks of Ludox (DuPo~t) and Nalcoag (N~LCO Chemical Co.). Such colloidal silicas are ava~l-able as bot~ acidic and basic hydrosol~. For ~h~ purpo~e of this in~entio~, w~erei~ the pH of the coatin~ compo~i-15 tions is orl the basic sideg basic colloi~al silicæ sol~are preferred. However, acidic colloidal silicas ~
wherein ~he pH i5 adjusted to a basic level, are also contempLated. In addition,i~ has bPen found th t col~oi-dal silicas having a low alkali con~ent (e.g., Na20~ yield a ~ore stable coating composition. Thus, colloidal sili~
cas having an alkali con~ent of less than 0.35~ (calculated as Na2O) ha~e been Iound to be preferable. Moreo~er, colloi-dai silicas havin~ average particle size of from 10 to 30 millimicrons are also preferred. A particularly preferred aqueous colloidal silica dispersion for the purposes herein is known as Ludox LS, sold by DuPon~ Company.

~ To make the ,op coat, the aqueous colloidal silica ~ispersion is added to a solution of a small amount of alkyl~
- 30 triacetoxylsiLane in alk~ltrialkoxysilane or aryltrialkoxy~
silane. For the purposes herein, fro~ about 0.07 parts by weight, to about 0.1 parts by weight, based on 100 parts by ~eight of the total composition of the alkyltriacetoxy-silane is used. The temperature of the reaction mixture is maintain_d at about 2~C. to about 40C., preferably 20C~

118163fi ~ .
to about 30C., ~nd mos~ preferably belo~ 25C. It has , bee~ found that in about six ~o eight hours sufficien~
¦~ ~rialkoxysilane has hydrol~zed so as to reduce the ini ial ~, two phase liquid mix~ure to one liquid phase in which the : 5 now treated silica (i.e., treated by its admixture wi~h ! the alkyltrialkoxysilane or aryltrialkoxysilane) is d~s-j persed. I~ general, the hydrolysis reàctio~ is allowed i to continue for a to~al of abou. 12 to 48 hours, depending UpQn the des~red viscosi~y of the final product. The more time the hydrolysîs reaction is permitted ~o continue, the higher will be the viscosity of the produc~:. After the hydrolysi s has been completed to the desired extent t the solids con~e~t is adiusted by the addItlonal of ~lcohol"
prefera~ly isopropan~L or isobuta~ol to the reactio~ mi~-ture. Qther alcoholc which are suitable ~lutio~ solvents - incIud~:Lower aliphatic aIcoholsr suc~ ~ ~ethanol, ~thano~
: propanoL, ~-butyl alcohol ~nd ~-butyl alcohol. M~xtures of such alcohols can be used, too. The so~vent system should contain from about 2û to 75 weight p~rcent alcohol

2~ to ensure solubility of the partial condensate(siloxanol).
Optionally, additional water-miscible polar solvents, such - as acetone, butyl cellosolve and the like ~n minor amount~ 9 like no more tb.an ~0 weight percent of the co-solvent sys-tem can also be used. The solids contPnt of the top coat-ing composition is generally preferred to ~e in the range ,~ - of from about 10 to 2570, most preferably, about 13 ~o about 20% by weight of the total composition. The pH of the re-._ . sultant coating compositions.. of the invention is in the range o from about 3. 5 to about 8.0, pre~erably from about 3û 7.1 to about 7.8, especially preferably higher than 7.2, such as rom 7.3 to about 7.5. If necessary, dilute base, such as ammoni~m hydroxide~ or weak acid, such as acetic acid, can be added to the top coating composition to adjus~
the inal pH to this desired range. At these basic p~' s 35 the compositions are translucent liquids which arP stable i. ~ .

i3~

o at room tempera~ura for at least several weeks. Whe~
s~ored at temperatures below about 5C. (40F.) the ; period of stability is incressed even further.

The alkyltriacetox~silane is used to buffer the basicity o the initial two liquid phase reaction mixtures and thereby also temper the hydrolysis rate.
While the use o alkyltriacetoxysilane is preferred herein, glacial ace~ic acid may be used in i~s place, as well as other acids such as organic acids like propio~icp butyric, citric, benzoic r formic, oxalic ~nd the like~
Alkyltriacetoxysil2nes-wherein the alkyl g~oup co~tains from I to 6 carbo~ atoms ca~ be used, alkyL groupC h~ving from l to 3 carbon atoms being preferred. ~ethy~riaceto~-silane is most preferre~ for th~ purpases ~erein.

-The silane~riol~-, R5i(0~)3; hereInbefore me~-tioned, are formed in situ as a result of the adDixture of ~he corresponding trialkoxysilanes with the a~ueou~
mediu~, i.e., the aqueous dispersion o c~lloidal silica.
Exemplary trial~oxysilanes are those contalning methoxy, e~hoxy, isopropoxy and n-butoxy substituents ~hich, upo~
hydrolysis~ generate the silanetriol and ~urther liberate the corresponding alcohol. In this way, a~ least, a por-tion of ~he alcohol content present in the ~inal coatingcomposition is provided~ Of course, if a ~ xture of ~ri al~;oxysilanes is employed, as provided for hereinabove~ a -. mi~ture of different silanetriols, as well as different alcohols, is generated. Upon the generat1on of the sila~e-3Q triol or ~ixtures of silanetriols in the basic aqueoug mediu~, condensation of the hydroxyl substituents to form I I ' -- Si -- Q -- Si - ~ .

bonding occurs. This condensation takes place over a 63~i period of time and is not an exhaustive condensation but rather the siloxane retains an appreciable quantity of silicon-bonded hydxoxyl groups which render the polymer solubl~ in the alcohol-water cosolvent. This soluble partial condensate can be characterized as a siloxanol polymer having at least one silicon-bonded hydroxyl group per every three -SiO - units.
I

The non-volatile solids portion of the top coating composition herein is a mixture of colloidal silica and the partial condensate (or siloxanol) of a silanol.
The major portion or all of the partial condensate or siloxanol is obtained from the condensation of CH3Si(OH)3 and, depending upon the input of ingredients to the hydro-lysis reaction, minor portions of partial condensate canbe obtained, for example, from the condensation of CH3Si(OH)3 with C2H5si(~)3 or C3H7Si(OH)3; CH3Si(OH)3 with C6H5si(OH)3 or even mixtures of the foregoing. For optimum results in the cured coating it is preferred to use all methyltrimethoxy-silane (thus generating all monomethylsilanetriol) inpreparing the coating compositions herein. In the preferred top coating compositions herein the partial condensate is present in an amount of from about 55 to 75 weight percent of the total solids in a solvent of alcohol and water, the alcohol comprising from about 50% to 95% by weight of the cosolvent.
At low solids content, such as about 13%, it has been found that the polysiloxane polyether copolymers disclosed in Canadian application Serial No.339,538, filed Nov.,9,1979, may be employed in the top coating compositions of this invention as flow control additives which assist in the precention of flowmarks, dirtmarks and the like on the surface of the substrate which is coated. Generally, - - :
-~ 36 these polysiloxane polyether ropolymers m~y be employed i~ amounts of fro~ abou~ 2.5 ~o about 15% by wei~t of the total solids of ~he compositionO
!

The coating composition~ of thi5 inve~tion ! will cure on a substrate at ~emperatures o, for exæmple~
L20 C. wi~houc the aid of an added curing catalyst.
Ho~ever, in general, catalyst in the amoun~s of from about O.G5 to a~ou~ 0.5 weight percent, preferably about 0.1 weigh~ percen~, of the composi~ion ca~ be used.
Compositions containing catalysts in these amounts can be cured QIL a solid subs~rate in a relatively short time at temperatures i~ the range of fr~m about 75~C-150C.. to provid~ ~ transparen. abrasion resista~t s~rface coatingO
1~
By choice o the proper formulation,. appliea-tion conditions and pretreatment of the su~strate, the top coatings can be adhered to su~stantially ~1 primed solid substrates. A hard coating having all of:~he aforementioned characteristics and advantages is obtaine~ ~y the removal of the solvent and volatile materials. The top coating composition will air-dry to a tack-free c~dition, but heating in the range of 75~C. to 200C. is necessary to obtain condensation of residual silanols i~ the partial condensateO This final cure results in the formation of silsesquioxane (P~iO3j2~. I~ the finishe~ cured top cGating the ratio of RSiO3l2 units to SiO2 will range - from about 0.43 to about 9~0, preferably I to 3.. A cured top coa~ing ha~ing a ratio of RSiO3/~ to S~02~ where R is methyl, of 2 is ~ost preferred. Coating thicknesses may vary but for the ~ proved abrasion resista~ce desi-red herein, coating thickness~es of 3~10 microns, preferably 5 microns, are-utilizedO

!

., ;36 o In order that those skilled in the art may better understand ho~ to pra tice the pre~ent in~ntionD
tlle following examples are given by way o~ us~ration : and not by way of limi~ation.

A top coating composition is prepared by adding 80.1 lbs. of Ludox LS (aqueous colloidal s~ a d;spersio~
average particle size of 12 millimicrons, pH 8O2 sol by DuPont) over a period of one-half hour, to a solutlon o~
135 g. of met~yltriacetoxysilane in 97.6 Lbs. of methyltri~
methoxysilane. ~he temper~ture of the rea tion mixtuse is maintained between ~O~C. and 30nC, The hydrolysis i5 alIowed . to proceed over a period of sixteen hours. At this time the reaction mixture is diluted with 182 l~s. of isopro-panol. The pH is 7.4; the viscosity is 5.3 centistokes using a cali~rated Cannon-Fenske routine type viscome~er.

A primer composition is prepared.~y charging a cleEn vessel with 76.0 parts by weight ~f 2-et~oxyethanol~
also known as ethylene glycolmonoethyletherO To the agita~ed solution is added 4.0 parts of polytmethyl methacrylate~, EL~ACITE 2041, MW 250,000 . The mig~ure is hea~ed to 100C. and agitation is continued for t~o hours. The so~ution is cooled to about 30~C., and 20.0 parts of 4 hydroxy-4-methyl-2-pen~anonel also known as diacetone alco~
hol, is a~ded. The solids content is 3O8-4~2%; the produe~
is filtered and is ready for use.

Pieces of transparent LEXAN ~poly(bisphenol-A
carbonate are primed with the acrylic composition by flo~
coating or dip coating at four inches per minute and allowed to air dry at 20C. for 20-3~ minutes. The primer coa~in~
thic~ness is frcm 105 tD 5 ~cn, resp~ ely, the primed substrates are next dip coated in-the top cDa~
, ~

3~

composition at ~wo and our inches per minut , allowed to dry for one-hal~ hour and cured one hour at 120C, The cured coatings are hard, adherentp resist~,t to moisture and optically clearD

j Other acrylates may be used in the primer com~
position Quch as poly(n-butyl me~hacryla~e), and selec~ed ultraviolet ~creening ag n~s or mixtures ~hereof can also be dissolved in the primer composition EXA~LE 2 The procedure of Examp~ e L is repeated substitut-ing another primer composition according to this invention.

A solution of 1 mole of 2 3 4-dihydroxybenzophenone (WINUL 400~ and L mole of gl~cidoxy me~hacrylate a~d a catalytic amount of a trialkylamine is refluxed until re-ac~ion is complete~ The solution is reduced in volume to remove the catalys~ and sufficient methylmethacrylate is ~dded to provide L0 parts by weight per 1 part by weight of reaction product. A catalytic amount of azobisisobutyl-nitrile is added and the solution is heated at 80-120C.
for 2 hours; two more portions of catalyst are added at two hour in~ervals. The solvent is removed and the poly mer is dissol~ed in 60-90% of 2-ethoxye~hanol. The final primer solution i~ made by ad~ing 10-50% of poly(methyl methacrylate), 10-30% of 4-hydroxy-4-methyl-2-pen~anone and 5-20% of glacial àcetic acid. A 2 to 6 percent solids solu-tion is used to prime LEXAN by dipping or flowing, and it is air dried at about 18C. for abou~ 20-30 minutes. The air dried pri~ed substrate is then flow or dip coated wi~h a silicone hard coat resin as described in Example lo A
hard, transparèn~, top coated article is obtained. Th~
primer in this instance incoxporates a copolymerized ultra-violet light screen~ Copolymerization of the screening material appears to immobiliz2 it, preventing its leaching ii3~i o or diffusion.

EX~D?LE 3 The proceduse of Example 1 ls repeated su~-stituting another primer composi'cion according t:3 this invention.

A sblution of methacryloxytr;methoxysllane, 5 par~s, methyl me~hacrylate, 95 parts, and AIB~
ca~a~yst, 2~5 parts, and 2-ethoxyethanol solve~t, 200 parts, is heated at 80C~ for 4 hours. A second portio~
o:E catalyst is adde~ a~d the solution is heaced for .
arlother 4 hour~v Th2 solution is dilu~ed with 1500-3800 par~s o' 2-ethoxyethanoI and 360-g60 parts o~ 4-hydroxy-4 methyl~2-pentanone to 2 - 5% solids~ The~ 100 parts of poLy~methyl methacrylatè) is added and the co~positio~
i5 heated to complete solution and then flltered prior to use as a primer.
If the procedure is repeated substituting 5 parts of acrylic acid or 5 parts of methacrylic acid for the methacryloxytrimethoxysilane, two other primer compositions for use according to this inve~tion will be obtained.

Obviously, other modifications and variations of the present invention are possible in t~e light of the above teachings. For example, additives and other ~odify~
ing agents, such as pigments, dyes, flow control agents, thickness, and the like, may be added to the compositions of this invention. It is to be understood, however, that changes may be made in the particular embvdiments described above which are within the fu~l intended scop of the in vention as defined in the appended claims.

Claims (22)

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

1. An article comprising a solid substrate having at least one surface on which is deposited:
(i) a layer of a primer composition; and, (ii) a layer of a cured top coat containing a colloidal silica filled thermoset organopolysiloxane, said primer composition comprising (a) from about 2 to about 10 parts by weight of a high molecular weight thermoplastic methacrylic ester polymer or copolymer selected from (1) polymers and copolymers comprising C1-C6 alkyl methacrylate;
(2) copolymers comprising C1-C6 alkyl meth-acrylates and a reaction product of glycidyl methacry-Late and a hydroxy-benzophenone ultraviolet light screen-ing agent;
(3) copolymers comprising C1-C6 alkyl methacry-lates and (A) a reaction product comprising units of methacrylic acid and y-chloropropyltrimethoxysilane (B) acrylic or methacrylic acid, or (C), a mixture of (A) and (B); or (4) a mixture of any of the foregoing;
(b) from about 60 to about 90 parts by weight of 2-ethoxyethanol;
(c) from about 10 to about 30 parts by weight of 4-hydroxy-4-methyl-2-pentanone; and (d) from about 0 to about 20 parts by weight of glacial acetic acid, per 100 parts by weight of (a), (b), (c) and (d) combined.

2. An article as defined in Claim 1 wherein the solid substrate is comprised of a synthetic organic polymer.

3. An article as defined in Claim 2 wherein said polymer is a transparent polymer.

4. An article as defined in Claim 3 wherein said polymer is a polycarbonate.

5. An article as defined in Claim 4 wherein said polycarbonate is transparent.

6. An article as defined in Claim 4 wherein said polycarbonate is a poly(bisphenol-A carbonate).

7. An article as defined in Claim 2 wherein said polymer is a polymethylmethacrylate.

8. An article as defined in Claim 7 wherein said polymethylmethacrylate is transparent.

9. An article as defined in Claim 1 wherein component (a)(1) comprises poly(methyl methacrylate).

10. An article as defined in Claim 9 wherein said poly(methyl methacrylate) has a molecular weight in the range of 100,000 to 250,000.

11. An article as defined in Claim 1 wherein component (a)(4) is a mixture of poly(methyl methacrylate) and a copolymer of methyl methacrylate and the reaction product of the glycidyl ether of methacrylic acid and 2,4-dihydroxybenzophenone.

12. An article as defined in Claim 11 wherein the ratio of methyl methacrylate to reaction product in the copolymer is about 10:1, by weight.

13. An article as defined in claim 1 wherein component (a)(4) is a mixture of poly(methyl methacrylate) and a copolymer of methacryloxypropyltrimethoxysilane and methyl methacrylate.

14. An article as defined in claim 1 wherein the top coat (ii) is an aqueous coating composition comprising a dispersion of colloidal silica in an aliphatic alcohol-water solution of the partial condensate of a silanol of the formula RSi(OH)3, where R is selected from the group consisting of alkyl having 1 to 3 carbon atoms and aryl, at least 70 weight percent of the silanol being CH3Si(OH)3, said composition containing 10 to 50 weight percent solids consisting essentially 10 to 70 weight percent colloidal silica and 30 to 90 weight percent of the partial condensate.

15. An article as defined in claim 14, wherein in top coat composition (ii) the aliphatic alcohol is a mixture of 20-30% methanol 20-50% isobutanol and 0-25% dieth-yleneglycol monoacetate.

16. An article as defined in claim 14, wherein in top coat composition (ii) said partial condensate is of CH3Si(OH)3.

17. An article as defined in claim 14, wherein in top coat composition (ii), the pH is 7.1 to about 7.8.

18. A process for producing a coated article which comprises the steps of:
(i) applying onto at least a surface of a sub-strate a layer of a primer composition of claim 1;
(ii) air drying and evaporating the volatile solvents from said primer composition at a temperature of from about 15° to about 30°C.;
(iii) applying into said air dried primer layer a silica filled curable organopolysiloxane top coat solvent-containing composition;
(iv) evaporating the volatile solvents from said top coat composition; and (v) applying heat to said top coat composition to cure to same.

19. A process as defined in claim 18 wherein the substrate comprises a polycarbonate.

20. A process as defined in claim 19 wherein said polycarbonate is transparent poly(bisphenol-A
carbonate).

21. An article comprising a solid transparent substrate having at least one surface on which is deposited:
(i) a layer of a primer composition; and (ii) a layer of a cured top coat containing a colloidal silica filled thermoset organopolysiloxane, said primer composition comprising (a) from about 2 to about 10 parts by weight of a high molecular weight thermoplastic meth-acrylic ester polymer or copolymer selected from (1) polymers and copolymers comprising C1-C6 alkyl methacrylate having a molecular weight in the range of 100,000 to 250,000;
(2) copolymers comprising C1-C6 alkyl methacrylates having a molecular weight in the range of 100,000 to 250,000 and a reaction product of glycidyl methacrylate and a hydroxy-benzophenone ultraviolet light screening agent;
(3) copolymers comprising C1-C6 alkyl methacrylates having a molecular weight in the range of 100,000 to 250,000 and (A) a reac-tion product comprising units of methacrylic acid and .gamma.-chloropropyltrimethoxysilane (B) acrylic or methacrylic acid, or (C) a mixture of (A) and (B); or (4) a mixture of any of the foregoing;
(b) from about 60 to about 90 parts by weight of 2-ethoxyethanol;
(C) from about 10 to about 30 parts by weight of 4-hydroxy-4-methyl-2-pentanone; and (d) from about 0 to about 20 parts by weight of glacial acetic acid, per 100 parts by weight of (a), (b), (c) and (d) combined.
22. A process for producing a coated article which comprises the steps of:
(i) applying onto at least a surface of a solid transparent substrate a layer of a primer composition, said primer composition comprising (a) from about 2 to about 10 parts by weight of a high molecular weight thermoplastic methacrylic ester polymer or copolymer selected from (1) polymers and copolymers comprising C1-C6 alkyl methacrylate having a molecular weight in the range of 100,000 to 250,000;
(2) copolymers comprising C1-C6 alkyl methacrylates having a molecular weight in the range of 100,000 to 250,000 and a reaction product of glycidyl methacrylate and a hydroxy-benzophenone ultraviolet light screening agent;
(3) copolymers comprising C1-C6 alkyl methacrylates having a molecular weight in the range of 100,000 to 250,000 and (A) a reaction product comprising units of methacrylic acid and .gamma.-chloropropyltrimethoxysilane, (B) acrylic or methacrylic acid, or (C) a mixture of (A) and (B); or (4) a mixture of any of the foregoing;
(b) from about 60 to about 90 parts by weight of 2-ethoxyethanol;
(c) from about 10 to about 30 parts by weight of 4-hydroxy-4-methyl-2-pentanone; and (d) from about 0 to about 20 parts by weight

Claim 22 continued:
of glacial acetic acid, per 100 parts by weight of (a), (b), (c) and (d) combined;
(ii) air drying and evaporating the volatile solvents from said primer composition at a temperature of from about 15° to about 30°C.;
(iii) applying into said air dried primer layer a silica filled curable organopolysiloxane top coat solvent-containing composition;
(iv) evaporating the volatile solvents from said top coat composition; and (v) applying heat to said top coat composition to cure to same