CA1091106A - Coated polycarbonates - Google Patents

Abstract

TITLE
COATED POLYCARBONATES
ABSTRACT OF THE DISCLOSURE
Polycarbonates having a coating thereon containing (1) from about 5 to 62 percent by weight of a polyester diol formed from the polycondensation of a glycol and dicarboxylic acids, at least one of the dicarboxylic acids being aromatic, (2) from about 8 to 35 percent by weight of a thermosetting acrylic resin having a sufficient amount of an .alpha.-.beta. unsaturated carboxylic acid polymerized therein to provide an acid value to the acrylic resin of 40 to 120 and (3) from about 17 to 87 percent by weight of a crosslinking agent.

Description

109ilO6 Mo-1610-P

:, COATED POLYCARBONATES
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BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to polycarbonates and more -particularly to coated polycarbonates.

Description of the Prior Art Thermoplastic polycarbonates are commercially ~- important materials which find utility in many diverse ,' applications as a result of their excellent chemical and physical properties. Indeed polycarbonates are useful in a whole range of applications from paints, lacquers and threads to foils, films and shaped objects which can withstand high impact without shattering. Because of the ~' high impact properties of polycarbonate, many uses have been proposed particularly for molded articles. Among these uses are those in which transparency is required - such as in glazing and similar applications where the ;
article will be exposed to a broad range of weather conditions. Further, many polycarbonate articles both transparent and opa~ue are exposed to moisture along with a wide variation in temperature. Unfortunately, however, because polycarbonate surfaces have little or no scratch resistance and are susceptible to attack by many commercial solvents, their full commercial exploitation has been impeded.

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;` Some attempts have been made to overcome the surface maring problem of polycarbonates by providing ~ a surface layer of a composition diverse from the poly--: carbonate with mar resistant characteristics. Some .,.
previous efforts have either required complicated lamination or the application of a surface layer which ~,~ invariably adversely affected the polycarbonate by stress cracking and crazing, by causing crack propagation into . ..
~ the polycarbonate as a result of brittleness of the coating . :., ~; 10 itself and/or by reducing the mechanical and physical `` properties. Some degree of success has been achieved , ~"~ by the use of a coating composition such as described in U.S. Patent 3,843,390 which utilizes a three component "; system of diol, acrylic resin and a crosslinking agent.
However the coated polycarbonate, coated with the specific composition taught in U.S. Patent 3,843,390 are reduced ~; in properties on weathering and/or exposure to hydrolyzing conditions.
In accordance with the present invention coated polycarbonates are provided which have mar resistance along - with resistance to weathering and to hydrolyzing conditions.

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Polycarbonates have a coating thereon comprised of (1) from about 5 to 6~ percent by weight of a polyester diol formed from the polycondensation of a glycol and dicarboxylic acids, at least one of the dicarboxylic acids being aromatic, (2) from about 8 to 35 percent by weight ~ ,. .
of a thermosetting acrylic comprising a sufficie~t amount of an -~ unsaturated carboxylic acid polymerized therein - to provide an acid value to the acrylic resin of 40 to 120 and (3) from about 17 to 87 percent by weight of a crosslinking agent.
The linear polyester diols useful in the practice of the invention are those obtained by the condensation of glycols and dicarboxylic acids or the anhydrides of dicarboxylic acids. Although the use of linear diols have been generally taught in coating compositions such as disclosed in U.S. Patent 3,843,390 the most advantageous diols are taught to be the aliphatic diols and more .:. .
particularly polycaprolactone diols. Surprisingly the ~; coatings of the invention herein are superior to those ' 20 specifically taught in U.S. Patent 3,843,390 by the use of a polyester diol containing at least 40 mole percent of aromatic dicarboxylic acid condensed therein based on ' the total moles of dicarboxylic acid. The polyester portion of the composition of the invention provides .
, enhanced weathering characteristics over those coatings "., , using aliphatic polyesters which are specifically taught of the prior art.

,, '1091106 The aromatic dicarboxylic acids useful in synthe-sizing the polyesters useful in the practice of the invention , are o-phthalic acid or anhydride, m-phthalic (isophthalic), `i:
acid p-phthalic (terephthalic) acid and the like. The other aliphatic dicarboxylic acids which may be used are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, methyl ....
- adipic acid, pimelic acid, suberic acid, azeleic acid, bras-sylic acid, sebacic acid, thapsic acid, maleic acid, fumaric acid, maleic acid, ~-hydromuconic acid, tetrahydrophthalic acid and the like. It is to be understood that the anhydrides o~ such acids can be utilized where they exist. In any event -~ at least 40 mole percent of the dicarboxylic acids are aromatic and preferably between 40 and 70 mole percent.
In selecting the aromatic dicarboxylic acid to be incorporated into the polyester, a balance of ortho, meta and para dicarboxylic acids must be selected to provide for a workable viscosity. Thus, when terephthalic acid is used, sufficient o-phthalic and/or isophthalic acid must be incorporated into the polyester to provide a workable viscosity.
In addition a mixture of polyesters may be used provided the mixture contains greater than 40 le percent of the aromatic dicarboxylic acid based on the total dicarboxylic acid polymerized in the mixed polyesters.
ln the case of the polyester which contains the aromatic groups, a weight average molecular weight between 250 and 2000 is necessary to provide adequate properties to the coating. While the average molecular weight of the i ` ~ lO9ilO6 ~ .
polyester composition must be between 100 and 2000 in the case of blends of polyesters. In all cases the polyesters must have an average equivalent weight of 50 to 1000 and more preferably 500 to 1000.
The dicarboxylic acids can be condensed with any suitable diol such as ethylene glycol, 1,3-propylene glycol, 1,2-butane diol, 1,3-butylene glycol, 1,4-butane diol 1,5-pentane diol, neopentyl glycol 1,6-heptane diol-1,7-heptane diol, 1,20-eicosanyl diol and the like and mixtures thereof. Where the polyester diol is a blend of polyesters one being based on the aromatic dicarboxylic acid and the other being aliphatic, any of the above ~ -glycols may be used in place of the non-aromatic polyester .-.~, Also the aliphatic polyester may be a polycaprolactone in the case of blends or in the case of a single polyester . ~ .
-'j a lower molecular weight polycaprolactone may be chain ,~, ~ extended by the aromatic dicarboxylic acids to provide j~ the necessary level of aromaticity.
......
Any of the known methods for synthesizing polyesters `~ 20 may be used to prepare the polyesters useful in the practice of the invention. Typical methods of synthesis are shown in U.S. Patents 3,201,372; 3,523,101, 3,245,956 and the like. In the case of the polycaprolactone poly-;- esters typical synthetic methods are shown in U.S. Patents 2,914,556, 2,933,477, 3,169,945, 3,186,971, 3,190,358, ~;, 3,224,982; 3,240,730, 3,523,101 and the like.

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` The thermosetting acrylic resin component of the ~oating composition of the invention can be prepared from any suitable alkyl ester of an -~ ethylenically unsaturated carboxylic acid such as an alkyl acrylate or methacrylate. The alkyl acrylates and methacrylates generally employed include methyl, propyl, butyl, pentyl, hexyl, octyl, lauryl, and the like acrylates and meth-~- acrylates along with isomers thereof where they exist as ~ well as other free radically polymerizable ~-~ ethylenically -~ 10 unsaturated monomers up to about 23 carbon atoms.
The thermosetting acrylic resin has an acid value of between 40 and 120 which is imparted by an ~-~
unsaturated acid polymerized into the acrylic resin.
; Preferably, such acids are acrylic and methacrylic although other acids may be employed such as crotonic acid, cinnamic acid, atropic acid, ~-chloracrylic acid, alpha-fluoroacrylic acid, maleic acid, fumaric acid, the mono esters of maleic and fumaric acid, itaconic acid and the anhydrides of such acids where they exist.
In addition, hydroxyalkyl esters of the ~-~
unsaturated carboxylic acids may be used in preparing the ` thermosetting acrylic resins and preferably the alkylene glycol monoesters in which the alkylene moiety contains up to 12 c=rbon atoms.

--` 109110~ .

Some suitable hydroxyalkyl esters include the acrylic and methacrylic acid monoesters of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,10-dodecylene glycol and the like but poly-hydroxyalkyl esters such as hylodihydroxypropyl acrylate, 6,10-dihydroxydecyl methacrylate and the li,ke can be utilized also. One may also employ similar hydroxy esters of other unsaturated acids such as, for example, those having up :., ~-~ to about 6 carbon atoms and including unsaturated dicar-; 10 boxylic acids such as those listed herein including ~; maleic acid, fumaric acid, itaconic acid and their anhydrides, The crosslinking component of the coating composition of this invention is an amine-aldehyde resin, i.e., an ., ~, ., aldehyde condensation product of melamine, urea, aceto-guanamine or a similar compound. Generally, the aldehyde employed is formaldehyde, although the products can be made from other aldehydes, such as acetaldehyde, croton-i;, aldehyde, acrolein, benzaldehyde, furfural and others.
i~i While resins produced from melamine or urea are most common and are preferred, condensation products of other aminesand amides can also be employed, for example, those of triazines, diazines, triazoles, guanidines, guanamines and alkyl and aryl substituted derivatives of such compounds including alkyl and aryl substituted ureas and alkyl and aryl substituted melamine provided at least one amino group is present. Some examples of such compounds are N,N'-dimethylurea, benzylurea, dicyandiamide, formoguanamine, .,~ .
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benzoguanamine, ammeline, 2-chloro-4,6-diamino-1,3,5-triazine, 6-methyl-2,4-diamino-1,3,5-triazine, 2~phenyl-4-amino-6-hydroxy-1,3,5-triazine, 3,5-diaminotriazole, triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine, 2,4,6-trihydrazine-1,2,5-triazine, 2,4,6-triethyltriamino-1,3,5-triazine, 2,4,6-triphenyltriamino-1,3,5-triazine and the like.
These aldehyde condensation products contain methylol or similar alkylol gr,oups, the structure of the alkylol group depending upon the paxticular aidehyde employed.

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At least a portion,-i.e., all,or part, of these alkyloli groups should be etherified by reaction with an alcohol.
Any mGnohydric alcohol can be employed for this purpose, including such alcohols as methanol, ethanol, propanoi, butanol, pentanol, hexanol, heptanol and other alkanols, usually having up to about 12 carbon atoms, as well as benzyl alcohol and other aromatic alcohols; cyclic alcohols such as cyclohexanol; monoethers of glycols and halogen-substituted or other substituted alcohols such as 3-., , chloropropanol.
-, The amine-aldehyde resin is produced in a manner well known in the art using acidic or basic catalyst and varying conditions of ~ime and temperature in accordance . :
~ with conventional practice. The formaldehyde is often ~ .
employed as a solution in water or alcohol and the conden-sation etherification and polymerization reactions may be -~ carried out either sequentially or simultaneously.

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`` lO9i~06 In order to provide protection to the coated polycarbonate from light a suitable ultraviolet stabilizer is to be incorporated into the coating composition.
Any suitable ultraviolet stabilizer may be used in the preferred embodiment of this invention at any . concentration effective to protect the polycarbonate from : the degradative effects of light but preferably a -sufficient quantity should be employed to provide the polycarbonate surface with at least 0.4 gram, most preferably, : 10 from about 3 to about 30 grams of the ultraviolet stabilizer , ~. .
`; per square meter of surface of the polycarbonate. Any .-~ suitable ultraviolet absorber may be used, such as, for ,. .
.. ; example benzophenone derivatives including:
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2,2'-dihydroxybenzophenone;

~ 15 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;

.l 2,2'-dihydroxy-4-methoxy-4'-propoxybenzophenone;
.,., ~ .
~'~ 2,2'-dihydroxy-4-methoxy-4'-butoxybenzophenone;

. 2,2'-dihydroxy-4-ethoxy-4'-propoxybenzophenone;

` 2,2'-dihydroxy-4-ethoxy-4'-butoxybenzo;-enone;

,` 25 2,3'-dihydroxy-4,4'-dimethoxybenzophenone;

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2,3'-dihydroxy-4-methoxy-4'-butoxybenzophenone;
: 2-hydroxy-4,4',5'-trimethoxybenzophenone;
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2-hydroxy-4,4',6'-tributoxybenzophenone;
2-hydroxy-4-butoxy-4',5'-dimethoxybenzophenone;
: 5 2-hydroxy-4-ethoxy-2',4'-dibutylbenzophenone;
. 2-hydroxy-4-propoxy-4',6'-dichlorobenzophenone;
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2-hydroxy-4-propoxy-4',6'-dibromobenzophenone;
~, : 2,4-dihydroxybenzophenone;
. 2-hydroxy-4-methoxybenzonphenone;
~ 10 2-hydroxy-4-ethoxybenzophenone;
b 2-hydroxy-4-propoxybenzophenone;
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; 2-hydroxy-4-butoxybenzophenone;
v 2-hydroxy-4-methoxy-4'-methylbenzophenone;
~-:; 2-hydroxy-4-methoxy-4'-ethylbenzophenone;
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-; 15 2-hydroxy-4-methoxy-4'-propylbenzophenone;
2-hydroxy-4-methoxy-4'-butylbenzylphenone;
.- 2-hydroxy-4-methoxy-4'-tertiary butylbenzophenone;
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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;
2-hydroxy-4,4'-dimethoxy-2'-ethylbenzophenone;
2-hydroxy-4,4'-5'-trimethoxybenzophenone; ~-~
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PC-006 10.

~ ' , , . ` . 11091106 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;
., and the like. Any suitable benzotriazole derivatives may , . .:
- also be employed including:

2-(2'-hydroxy-5'-methylphenyl)-benzotriazole, , ,~ 2-(2'-hydroxy-5'-tert.-butylphenyl)benzotriazole, ,.,:,. ~
,i 15 2-(2'-hydroxy-3'-methyl-5'-tert.-butylphenyl)-benzotriazole, ," .;
''?~ , 2-(2'-hydroxy-5'-cyclohexylphenyl)-benzotriazole, 2-(2'-hydroxy-3,5'-dimethylphenyl)-benzotriazole, .,:,, ; 2-(2'-hydroxy-5'-tert.-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-di-tert.-butylphenyl)-benzotriazole and derivatives of crotonic acid such as ~-cyano-~-methyl-,,~, .. . .
-(p-methoxyphenyl)-crotonic acid methyl ester, ~-cyano-~-N-(2-methyl-indolinyl-crotonic acid methyl ester, substituted acrylates such as 2 ethyl-hexyl-2-cyano-3,3 ~ diphenyl acrylate as well as malonic acid esters such as, i~ 25 for example the dimethyl, diethyl, dipropyl and the like esters of malonic acid and the like mixtures thereof. It ,, ~ is to be understood that any ultraviolet absorber may be ~: .
~ used in the practice of this invention and that any one or i~ combination of absorbers can be used.
., PC-006 11.

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The coating compositions of this invention preferably contain a flow agent and/or a slip agent to improve the ' flow and slip, most preferably a silicone or polysiloxane slip and/or flow agent. Any suitable slip and flow agents may be employed including silicone oils as described in U.S. Patents 2,834,748 and 3,201,372 or any other such agents including sulfonated castor oil, polydimethyl siloxanes and the like. The preferred amount of such agents range from about 0.1 to 1 percent by weight based on the weight of the solids in the coating composition.
The coating compositions of this invention may also . .:
contain other additives such as pigments, antioxidants and fillers as desired. The pigments may be of any conventional type and may include metallic pigments which produce a j~ 15 polychromatic finish.
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~- In a preferred method for preparing the coated poly-carbonate of this invention, the mixture of components . . .
(1), (2) and (3) is applied to the polycarbonate in a solvent system that will not stress crack or craze a ; 20 polycarbonate sheet or a polycarbonate molded article when tested under the conditions of the American Standards :.
~ Association 26.1 test paragraph 5.20.1 to 5.20.3. While : ::
, the preferred solvent system is a mixture of butanol, Cello-SlVe and toluol at a 5:2:3 ratio, it is to be understood that other ratios and any solvents or mixtures of solvents which will not stress crack or craze a polycarbonate under the conditions specified herein may be . ' PC-006 12.

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, employed. Thus, a single solvent alone may be employed or a mixture of solvents may be used even though one or more of the solvents in the mixture may, when tested alone, fail the specified test. Accordingly, it can be appreciated that the term solvent as used herein encompasses both solvents and non-solvents for the polycarbonate, either per se or in mixtures, which functions as solvents ~or the mixture of components (1), (2) and (3). Any desired solvent or mixture thereof as specified herein can be employed including, for example, aliphatic hydrocarbons, aromatic hydrocarbons, silicones, mineral splrits, chlorinated aliphatic and aromatic hydro-carbons, ethers, esters, ketones, alcohols, water and the like. Examples of some such suitable materials include iso-butylene, pentane, hexane, heptane, octane, methylcyclohexane, turpentine, cyclohexane, dipentene, ethylbenzene, xylene, toluene, benzene, tetraline, 2-nitropropane, 3,3-dichloro-propane, carbon tetr!achloride, 1,2-dichloropropane, chloro-form, trichloroethylene, tetrachloroethylene, chlorobenzene, methylene chloride, ethylene dichloride, o-dichlorobenzene, diethyl ether, dimethyl ether, dichloroethyl ether, dioxane, isobutyl-n-butyrate, isopropyl isobutyrate, methyl amyl acetate, butyl butyrate, sec. butyl acetate, sec. amyl acetate, isobutyl acetate, isopropyl acetate, amyl acetate, .
~ butyl acetate. Ethylene glycol monoethyl ether acetate, ,',! propyl acetate, ethylene glycol monobutyl ether, ethyl acetate, propyl formate, dibutyl phthalate, methyl acetate, ethyl lacate, butyronitrile, acetonitrile, propylene carbonate, ethylene carbonate, diisobutyl ketone, diisopropyl ketone, ' .

~09jl106 methyl isobutyl ketone, methyl amyl ketone, methyl propyl ketone, diethyl ketone, isophorone, diacetone alcohol, methyl cyclohexanone, methyl ethyl ketone, cyclohexanone, acetone, cyclopentanone, cyclobutandione, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, diethylene glycol, 2-ethylene glycol, methyl isobutyl carbinol, n-octanol, 2-ethyl butanol, n-hexanol, sec.-butanol, n-pentanol n-butanol, cyclohexanol, isopropanol, n-propanol, ethanol, ethylene glycol, methanol, glycerol, and the like and mixtures thereof.~ Other suitable solvents within the scope of the definition set forth herein which may also be employed alone or in admixture as required are exemplified in Solubility Parameters for Film Formers, Official Digest, October 1955, pp. 726-758. Generally, the ketones, acetates and aromatic hydrocarbons are used only in admixtur~ with compounds that act as weaker solvents for the polycarbonate.and are employed to improve the bite -into the surface where required.
: The coating composition of the invention can be applied to the polycarbonate surface by any conventional techniques as discussed hereirbefore and then baked to provide a hard, glossy coating. Typical baking schedules are a function of catalyst type and amount and range from 1 to 60 minutes at temperatures not in excess of 275F. ~ ~.
In some cases, itiis desirable to cure the compositions at somewhat lower temperatures such as 150F. This can be ~:~
done by the addition of an acid catalyst and heating at 109:1106 150 F. to 275F. for 1 to 60 minutes. Essentially any acid which is soluble in hydrocarbons can be employed for this purpose, the amount added being generally between about 0.3 percent and about 10 percent by weight based on the vehicle resin solids. Smaller amounts of acid catalyst are sometimes added even when curing at higher temperatures is contemplated.
The preferred catalysts are alkyl acid phophates, such as monomethyl acid phosphate, monoethyl acid phosphate, l 10 monopropyl acid phosphate and monobutyl acid phosphate, i~ as well as the corresponding dialkylcompounds such as dibutyl acid phosphate. A mixture of mono- and dialkyl phosphates is often utilized. In addition to the alkyl acid phosphates, examples of other acid catalysts which can be used include phosphoric acid, maleic acid and anhydride, fumaric acid, chloromaleic acid and anhydride, alkyl acid phthalates -such as methyl, ethyl, propyl and butyl acid phthalates, monoalkyl succinates and maleates such as methyl, ethyl, propyl and butyl succinates and maleates and others having sufficient solubility to permit them to be dissolved ; in the coating composition at the desired proportion.
Catalysts which have been found to be particularly suitable are compounds such as the sulfonic acids and derivatives thereof including, for example p-toluene sulfonic acid, methyl-p-sulfonic acid and the like.

pC-006 15.

10911~6 The surface of any polycarbonate or polycarbonate blend may be treated with the coating composition of this invention. The polycarbonate or polycarbonate blend can be prepared by any suitable process including those , outlined in U.S. Patents 3 ! 0,28,365; 2,999,846, 3,248,414,

3,153,008, 3,215,668, 3,187,065- 2,964,974, 2,970,13/, 2,991,273, 2,999,835; 3,014,891, 3,030,331, 3,431,224, 3,290,412 and the like.
The unexpected advantages of this invention will be further illustrated by reference to the following examples -~
in which all parts and percentages are by weight unless . ,i .
otherwise specified.
Example I
An illustrative thermosetting acrylic was prepared using a solvent system of 50 parts of 1,4-dioxane, 25 parts of isopropanol andi25 parts of ethylene glycol mono-ethyl ether. In this example, ~herever solvent is mentioned the above-described mixture is intended. A monomer solution of 83.3 grams of eth`yl acrylate, 50 grams of . 20 methyl methacry~ate, 16.7 grams of acrylic acid, 16.7 grams of 2-hydroxypropyl methacrylate and 1.3 grams of 1-dodecanethiol in 90 grams of solvent was charged into a 300 ml. addition funnel. A solution of 8.3 grams of . . .
~ benzoyl peroxide in 55 grams of 1,4-dioxane was charged ii, - .
into a 125 ml. addition funnel. The reactor consists of a two liter reaction kettle equipped with a water cooled reflux condensor, mechanical stirrer, thermometer, a nitrogen inlet and the two addition funnels containing -the monomer solution and the benzoyl peroxide solution, respectively.

,B 16 -lO9ilO6 About 125 ml. of the monomer solution were charged into the reaction flask and heated under a nitrogen blanket to 80C. with stirring. About 15 ml. of the benzoyl peroxlde solution were added and the temperature began to rise. The reaction mixture was maintained at from about 75 to about 85 C. by heating and cooling as required. After about 10 minutes, additional 10 ml. of the benzoyl peroxide solution were added. After another 20 minutes, an additional 20 ml. of monomer solution were added as well as about 10 ml. of benzoyl peroxide solution. After a further 10 minutes, another 20 ml. of monomer solution were added and another 10 ml. of benzoyl peroxide solution. Following 15 more minutes, about 30 ml. of monomer solution were added followed by the slow addition of the remainder of the benzoyl peroxide solution. The temperature rose to about 92C. and was maintained at about 97C. while the remainder of the monomer solution was added dropwise. The reaction mixture was maintained at about 98C. for about five hours with stirring under a nitrogen blanket, following which the reaction mixture was poured into wide mouth bottles and placed in a water bath to cool.
The thermosetting acrylic thus prepared has a Brook-field viscosity at 25C. of 2,152 cps., a saponification number of 209, an acid number of 75, an hydroxyl number of 36 and a percent solids content of 56.
In the following experiments which were carried out using a thermosetting acrylic as described above, (hereinafter referred to as acrylic resin A), the following tests were employed:

PC-006 17.

109iiO6 ., Cross-hatch adhesion test. A cured coated sur-face is cross-hatched with a scalpel (1/16" side on square) and adhesive tape is applied to the cross-hatched surface.
The number of cross-hatched squares which remain on the surface after the adhesive tape is pulled off indicates the percentage of adhesion of the coating to the surface.
Rubber abrasion test. - A common pencil eraser is rubbed several times across a cured coated surface. Where severe abrasions occur, the coating fails, where little abrasion occurs, the coating passes. This is a rapid screening test. The results of which correlate extremely well with the results obtained via other tests.
Slip. A coin is placed on a flat cured coated surface which is then raised at an angle until the angle is reached at which the coin begins to slide and that angle is recorded. The minimum angle of slip is 45. This is an excellent test for determining resistance to dirt pick-up and dragging during cleaning operations.
Impact resistance-Gardner impact test. A coat-ing is rapidly distended by dropping a known weight througha known distance onto a cured coated sample, causing a deep hemispherical indentation. Impact values are reported as inch-pounds of impact that the coated sample will with-stand without cracking or separation from the substrate.
Taber Abrasion. American Standards Association test 26.1, paragraph 5.17 was used. The maximum allowable change in haze is 15%. A cured coated sample is subject to 100 revolutions on a Tabler Abraser using SC-lOF whéels under a constant load of 500 grams.

~W9:~106 Example II
A coating was prepared by homogeneously mixing 15.77 parts of hexamethoxymethyl melamine, 28.67 parts ~ .
of n-butyl alcohol, 9.57 parts ethylene glycol monoethyl ether solvent, 0.88 parts of p-toluene sulfonic acid, 18.09 parts of acrylic resin A and 11.70 parts of a poly-ester diol solution based on a mixture of 60 mole percent mixed isophthalic and terephthalic acids 38 mole percent of adipic acid and 2 mole percent of butenedioic acid .
(based on the total moles of moles of dicarboxylic acid) reacted with 1,2-propylene glycol. Sufficient propylene ~ -glycol was reacted with the dicarboxylic acids to com~ .
pletely esterify all of the carboxylic acid functionality The polyester solution was 63 to 67 percent solids by weight in 85/15 Solvesso 150 (a trade mark of Humble Oil and Refining Co., now Exxon, U.S.A., for aromatic solvents)/
diacetone alcohol, and had an acid number of less than 10 on a solids basis and a Gardner-Holdt viscosity of Zl to Z3. The particular polyester solution was Cyplex 1544 a trade mark of American Cyanamid Co. The hydroxy number of the polyester solid resin was between 75 and 85 correspond-~ . .
ing to an equivalent weight of 660 to 748.

i ~ - 19 -lO91iO~

Along with the polyester resin solution, melamine, acrylic resin and p-toluene sulfonic acid, 28.45 parts of n-butyl alcohol, 9.57 parts of ethylene glycol monoethyl ether, 1.09 parts of p-methoxybenzylidene malonic acid diethylester ultraviolet absorber, 2.26 of isopropanol and 11.59 parts of 2-nitropropane were homogeneously mixed to form the coating composition.
The coating composition was applied using a draw down bar to the surface of a 1/8" sheet of polycarbonate 10 prepared as described in Example I of U.S. Patent 3,640,951.
The coating was cured for about 30 minutes at 250F.- The coating on the polycarbonate was tested for various pro--; perties and the test results are reported in Table I.
Example III
A coated polycarbonate was prepared.in accordance : with the procedure of Example II having the following formulation: :
Inqredient ~Parts ~y Weiqht Hexamethoxymethyl melamine 23.82 ,n-butyl alcohol 32.10 Cello-Solve 9,86 p-toluene sulfonic acid 1.00 Acrylic Resin A 11.36 p-methoxybenzylidene malonic acid diethyl ester 1.24 ~' .

;Ingredient Parts by ~,~eiqht 2-nitropropane 11.24 polyester (Same as Example II) 8.28 ; The test results of the coated polycarbonate are reported in Table I, Example IV
A coated polycarbonate was prepared in accordance with Example II having the following formulation:

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` Inqredient Parts by Weiqht Hexamethoxymethyl melamine 17.89 n-butylalcohol 28.35 . Ethylene glycol monoethyl e~her ~,76 ,~ p-toluene sulfonic acid (4~/0 in Isopropanol) 1.0 Acrylic Resin A 20.52 ; p-methoxybenzylidene malonic acid , diethyl ester 1.24 Toluene 13.82 : Polycaprolactone-(Hydroxyl number ~, of 212) polyol- -8.82 Example IV is prepared in accord-ance with the , .. .
. teachings of U.S. Patent 3,843,390 and uses a polycapro-lactone polyester polyol in place of the aromatic poly-; ester diol of Examples II and III.
Test results of the coated polycarbonate are reported in Table I.

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Example V --Example V is the uncoated polycarbonate subjected to the solvent resistance and abrasion resistance testing procedures for Examples II-IV.
5The test results of Example V are repor~ed on Table I.

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PC-006 23.

~ 91106 As is demonstrated by Table I, Examples II and III
; which are prepared in accordance with the invention, demonstrate improved adhesion after being subjected to high temperature and humidity when compared to Example IV which is prepared with an aliphatic diol.

Example VI
` Example II was repeated except the polycaprolactone polyester diol of Example IV was substituted for the aromatic ; polyester diol.
The coated polycarbonates of Examples II, III, VI and ~; the following Example (VII), and uncoated polycarbonate (Example V) were subjected to exterior weathering conditions and tested for various properties at certain time intervals.
- The exposure time is computed in Langleys which is a measure of the radiant energy to which the sample has been exposed.
The test results are reported in Table II.
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Example VII
Example III was repeated except the polycaprolactone polyol of Example IV was used instead of the aromatic polyester diol.

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PC-006 24.
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Table II demonstrates that the coated polycarbonates - of the invention exhibit improved adhesion after being subjected to exterior aging conditions over the prior art coating compositions and substantially improved weathering characteristics over uncoated poly-carbonates.

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Pc-oo6 26.

Claims (7)

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

1. A coated polycarbonate having as a surface layer a coating comprising:
(a) from about 5 to 62 percent by weight of a poly-ester diol having an average equivalent weight of 50 to 1000 formed from the polycondensation of at least one glycol and at least one dicar-boxylic acid or acid anhydride, said at least one dicarboxylic acid or acid anhydride com-prising at least 40 mole percent of at least one aromatic dicarboxylic acid or anhydride, based on the total moles of dicarboxylic acid or anhydride in said polyester;
(b) from about 8 to 35 percent by weight of a thermosetting acrylic resin having a sufficient amount of .alpha.-.beta. unsaturated carboxylic acid poly-merized therein to provide said acrylic resin with an acid value of 40 to 120; and (c) from about 17 to 87 percent by weight of a cross-linking agent.

2. The coated polycarbonate of claim 1, wherein said polyester diol has a molecular weight of about 100 to 2000.

3. The coated polycarbonate of claim 2, wherein said polyester diol has a molecular weight of about 1000 to 2000.

4. The coated polycarbonate of claim 1 or 2, wherein said polyester diol comprises greater than 40 mole percent of at least one aromatic dicarboxylic acid based on the total moles of dicarboxylic acid in said polyester.

5. The coated polycarbonate of claim 1, wherein said polyester diol has an average equivalent weight of 500 to 1000.

6. The coated polycarbonate of claim 1, 2 or 5, wherein said crosslinking agent is hexamethoxymethyl melamine.

7. The coated polycarbonate of claim 1, 2 or 5, wherein the coating contains an ultraviolet stabilizer for the polycarbonate.