CA1057884A - Mar-resisting polyurethane coatings - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Compositions of matter consisting of (A) urethane prepolymers having terminal hydroxy groups produced from (1) a polyol of 200 - 3,000 molecular weight, (2) an organic polyisocyanate and (3) a polyhydric alcohol which are admixed with (B) a polyalkylether of a polymethylol melamino and (C) an acid catalyst are rendered more adherent to polymeric substrates by incorporating therein various ultraviolet light absorbers such as 2-[(2-hydroxy-5-t-octyl-phenyl)]benzotriazole, 2,2'-dihydroxy-4-methoxy-benzophenone and the like and improved articles of manufacture comprising polymeric substrates comprising polymeric substrates coated with said compositions result.

Description

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I`his invention relates to compositions o mat~er consisting of CA) urethane prepolymers having terminal hydroxy groups produced from Cl~ a polyol o~ 20Q-3,Q0Q molecular weight, ~2) an organic polyisocyanate and (3) a polyhydric ; alcohol which are admixed with (B) a polyalkylether of a poly-methylol melamine and (C) an acid catalyst in which is incor-porated an ultraviolet light absorber and to an article of manufacture comprising polymerîc substrates coated with such i ~ ;
compositions. ~ ~-; 10 The use of polycarbonate resins for both home and '!'.
industrial applications has increased tremendously in recent years. One of the most widely accepted applications of poly~
: , . :.
carbonates has been in the field of optical lenses, such as those used in the manufacture of eyeglasses, including safety . ,~ .
glasses, and apparatus requiring lenses such as binoculars, ~ microscopes and the like.
$ While the polycarbonates are excellent or these I applications due to their excellent optical clarity and im-pact resistance among other features~ they are disappointing :1 :
in regard to their mar-resistance, as are many other polymeric substrates. The surfaces of lenses produced from these poly-' carbonates are, therefore, relatively easily scratched or otherwise marred, thereby rendering their lifetimes somewhat shorter than desired. ~-~; The tendency of these lenses to suffer surface dam-age has been most recently overcome by coating the lenses with mar-resistant coatings. There has recently been disclosed a novel coating composition useful in the improvement of the mar-resistance of polymeric substrates. These coatings pro-- ; ;
- 30 vide excellent mar-resistance to polymeric subst~ s but , usually tend to lose their adhesive quality after exposure ;j to ultraviolet light.

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The present invention, provi~es an improved composition of the recently disclosed coating composition in which there is incorporated various ultravioletlight absorbers. Surprisinglyl such provision results in mater-ially improved adhesivenPss of the polyurethane coating compositian. The resultant polymeric substrates which are coated wi1:h these novel coating ; compositions retain their excellent mar-resistance~ clarity and impact resis~
tance over an extended period of time.
According to the present invention, thereforel thereis provid~d a ~oating composition consisting essentially of a mixture of (l), (2), (5) and (4), in which ~l) is a saturated urethane prepolymer having terminal hydroxy groups which is the reaction product of ~aterials consisting essentially of a mixture of (a) and tb), at a molar ratio of 1:2J respectively, in which (a) .
is an isocyanate-terminated urethane which is the reaction product of a mix-ture of ~I) and (II), at a molar ratio of 1:2, respectively, in which (I) is a saturated diol having a molecular weight of from about 200 to about 3000 and (II) is a saturated organic diisocyanate and Ib) is a monomeric, steri-cally bulky, polyhydric alcohol containing 2-6 hydroxyl groups and being free of oxyalkylene units (2) is a polyalkyl ether of a polymethylol melamine, (3) is an aeid catalyst and ~4) is an ultraviolet light absorber comprising 2-[(2-hydroxy-5-t-octylphenol)] benzotriazole or 2,2'-dihydroxy-4-methoxybenzo-j phenone, the ratio Qf tl) to ~2) being in the range of from about 5:1 to about l:l, about 1% to about 10% b~ weight of ~l) and (2) of acid catalyst (3) being present in the co~position, with about 1.0% to about 5.0~ by weight based on the total weight of solids in the composition of ultraviolet light ' absorber being present in the composition.
-~ Coatings derived from the reaction of alkylated melamine/formalde-hyde materials and hydroxy-terminated urethane prepolymers are not new per se, but the products of the instant invention have exceptional light stabil-; {
~ ity and adhesiveness when used to coat polymeric supports, a result which is ''J~ 30 totally unexpected.

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As mentioned briefly ab~e, the crux of the instant invention resides in increasing the adhesion of a urethane prepolymer-based coating composition for polymeric substrates and, in particular, polycarbonates~
which enables the resultant coated article to be used in such applications as glazing, safety lenses, display panels, furniture and the like, over ; greater lengths of time.
The use o~ a sterically bulky polyhydric alcohol as the urethane prepolymer end groups and the stepwise sequential preparation of the pre~
polymer result in a product having uniqu~ chemical properties whenit is compounded with an alkylated melaminelormaldehyde material and an acid catalyst, applied as a coating to non-mar-resistant, polymeric art:Lcles of manufacture and cured. However, the coating seriously deteriorates upon weathering to the extent that it actually separates from tha substrate.
In accordance with the present inven~ion, one molar ~. .

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l portion of a saturated diol having a molecular weight of from about 200 to about 3,000 is reacted with two molar portions of a saturated organic polyisocyanate to produce an isocyanate--terminated saturated urethane prepol~mer which, in turn, is reacted a~ a molar ratio ~f about l:2, respectively, with a monomeric, sterically bulky, polyhydric alcohol which contains

2-6 hydroxyl groups and whi~h is free of oxyalkylene groups to produce a prepolymer having terminal hydroxy groups. The prepolymer, in turn, is then admixed with a polyalkylether of a polymethylol melamine and an acid catalyst. ~o this composite mixture is then added an ultraviolet light absorber to produce the novel composition of the instant invention.
The resultant composition possesses a greater adhesive capac-ity when used as a cured coating on polymeric 9ub9trates than lS does the coating without the ultraviolet absorber.
~ he prepolymer haviny terminal hydroxy groups con-forms to the general formula:
(I) O H H O O ~I H O
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HO~nY-O-C-N-X-N-C-O-R-O-C-N-X-N-C-O-Y-~OH~n ~ ~ 20 whèrein R is the reaction residue of a saturated diol having ': ~
a molecular weight of 200 to 3,000, X is the reaction residue of an organic diisocyan-ate, Y is the reaction residue o~ a monom`eric, sterical-~ .. . . .
ly bulky, ~olyhydric alcohol of 4-18 carbon~atoms containin~
no oxyalkylene groups, and n is l to 5.

The saturated urethane prepolymer having terminal hydroxy groups described above is produced from diols such ~as the polyoxyalkylene adducts o dIOlS and alkylene oxides ~; ~ 30 such as ethylene oxide, propylene oxide, butylene oxide and - mixtures thereof and the like. The diols useful in preparing , ' .
J ; these adducts include ethylene glycol, l,2-propylene glycol, l,3-propylene glycol, l,2-butanediolj l,4-butan~ediol, l t 6-

- 3 -1 -hexanediol, hydroquinone, bisphenol A, and the l'ike.
Typical polyoxyalkylene diols include polyethylene-ether qlycol, polypropyleneether glycol, polybutyleneether glycol, polytetramethyleneether glycol" block copolymers, 5 e.g. combinations and propylPneether and polyethyleneether ~ :
.
' glycols; poly-1,2-oxybutylene and polyethyleneether glycols;
and poly-1,4-oxybutylene and polyethyleneether glycols; and random copolyether glycols prepared from blends, or sequen-tial addition, o~ two or more alkylene oxides.
Thus, the polyoxyalkylene diols which can be em-ployed in this process are polyoxyalkylene polymers which have an oxygen/carbon atom ratio from about 1:2 and 1:4 and preferably, an oxygen/carbon atom.ratio from about }:2.8 to 1:4 and no more than 2 terminal hydroxyl group~. The poly- :
', ,~ 15 oxyalkylene diols generally have an,average equivalent weight '~' , from about 200 to 3,000 and pre~erably have an average:equiva-.: . , ~
' : , lent weight from about 500 to 2,000. Also diol blends such .. .
~ as a mixture of high molecular weight polyoxyalkylene diols :' ~ can be used in preparing urethane prepolymers having good " 20 properties. ~ ' , Polyoxyalkylene arylene diols which also have mol-... .
', eculax weights ranging from about 200 to a~out 3,000 but which differ from the above-described polyoxyalkylene diols ' in having arylene radicals, such as phenylene, naphthylene and anthrylene radicals, either unsubstituted or substituted, . e.g. with alkyl or aryl groups, and the likej in place of , ~ , some of the alkylene radicals o said polyoxyalkylene diols .:~ , . , may also be employed. Polyoxyalkylenearylene glycols of the : . .. .
, type ordinarily used for this purpose will usually contain at least one alkylene ether radical having a molecular weight . , ' of about 200 or each arylene radical present.

Essentially linear polyesters containillg two iso-::
~ cyanate-reactive hydroxyl groups,constitute another class ,. . ..

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1 of reactive organic diols which may be lemployed ~n preparing urethane prepolymers used in the present invention. While the preparation of polyest2rs suitable for ~hi~ purpo9e has been described in great detail in the prior art and forms no part of the present invention per se, it may be mentioned here by way of illustration that polyesters o~ this type may ; be prepared by the condensation of a dihydric alcohol, gen-erally a saturated aliphatic diol such as ethylene glycol, propanediol-1,2 ! propanediol-1,3, butanediol-1,3, butanediol--1,4, pen~anediol-1,2, pentanediol-1,5, hexanediol-1,3, hex-anediol-1,6, diethylene glycol, dipropylene glycol, triethyl-ene glycol, tetraethylene glycol, and the like, as well as mixtures of such diols with each othert and the like, with a dicarboxylic acid, e-caprolactone, or anhydride which is either saturated or which contains only benzenoid unsatura-tion, such as oxalic, malonic, succinicv glutaric t adipic, pimelic, suberic, azelaic, terephthalic, sebacic, malic, phthalic, cyclohexanedicarboxylic and endomethylenetetrahy-dxophthalic acids, and the like, and their isomers, homologs, and other substituted derivatives9 e.g. chloro derivatives.
The linear polyesters u~d in preparing the ure~hane prepoly-mers also have molecular weights ranging from about 200 to about 3,000. In addition, they generally have relatively low acid numbers, e.g. acid numbers not appreciabIy in excess o~ about 60 and preferably as lo~ as can be practicably ob-tained, e.g. 2 or less. Correspondingly, they have relative-ly high hydroxyl numbers, e.g~ from about 30 to about 700.
When preparing these polyesters, an excess of diol over di-carboxylic acid is generally used.
Ni~rogen-containing diols may also be used as diol : .
reactants. Among such materials there are included the poly-.
esteramides conventionally employed in the preparation of urethane prepol~mers, i.e~ those having molecular weights .

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1 ranging from about 200 to about 3,000, acid num~er~ ranging from about 60 a~ a maximum to as low as can be practicably obtained, elg. 2 or less, and hydroxyl numbers ranging from about 30 to about 700.
As can be rea~ily appreciatecl, mix~ures of the various reactive organic diols described hereinahove may also be employed in preparing the urethane prepolymers o the present invention.
The organic diisocyanates which can be employed to produce the urethane prepolymer used in the present in-vention include, for example, the aliphatic~ cycloaliphatic ; and aromatic diisocyanates including m-xylene diisoc:yanate, methylen-diisocyanate, ~etramethylene diisocyanate, hexa-.
methylene diisocyanate, 4,4'-methylenebis(cyclohexyl i~ocy-:. 15 anate), 4-chloro-m-phenylene diisocyanate, isophorone diiso-.~ cyanate, o, p or m-phenylenediisocyanateO trimethylhexamethyl-~ : ene diisocyanate 4-t-butyl-m-phenylenediisocyanate, 4,4'~
- ~ methylene bis(phenyl isocyanate), tolylene diisocyanate, 1,5-naphthalene diisocyanate, 4-methoxy-m-phenylene diisocyanate, 20 biphenylene diisocyanate, cumene-2,4-diisocyanate, 3,3'-di-~; methyl-4,4'-biphenylene diisocyanate, p,p'-diphenylene diiso-" .
cyanate, 3,3l-dimethoxy-4,4'-biphenylene diisocyanate, mix-. ~ . .
tures thereof and the like.
:~ The diol is completely reacted with the diisocyan-ate utilizing a molar ratio of about 1:2, respectively, in ;
.~ ~ the pre~ence of a suitable catalyst such as an organotin com-:. ~ pound, e.g. dibutyltin dilaurate, dibutyltin octoate and the like; a tertiary amine, e.y. trie~hylene diamine; an organo ~.
. .:
: lead compound, e.g. lead octoate and the like, at concentra- :
. : 30 tions of from about 0.001% to about 0.1%, by weight, based . . on the total weight of the diol and diisocyanate. The reac-.~ tion i5 allowed to proceed at a temperature of from about .~; 60C. to about 180C~ until the isocyanate terminat:ed urethane ~i78~
1 prepolymer forms, l.e. Erom about 4 to about 24 hoursO
The isocyanate-terminated urethane prepolymer i5 then reacted at a temperature ranging from about 60C. to about 120C. ~or from about 1/2 - 9 hours, with a monomeric/
sterically bulky, polyhydric alcohol containing 2~6 hydroxyl groups but free oE oxyalkylene units, in a molar ratio of 1:2 respectively. ~y "monomeric" is me.ant that the~e alco-hols contain no repeating unit of themselves or other poly-meric building blocks such as those exhibited by reaction adducts of glycols with ethylene or propylene oxide. By "sterically bulky" is meant that the steric dimension of the alcohol molecule is greater than simple ethylene glycol or propylene glycol, i.e. it contains at lea~t 4 but no more than 18 carbon atoms. Examples o alcohols which fit this description include 1,4-cyclohexane dimethanol, 1,4-butane~
diol, mannitol, trimethylol propane, trimethylol ethane, ~ cyclohexane dimethanol, hydrogenated bisphenol A, cyclo-;I ~ hexane diol, neopentyl glycol, trimethylpentanediol, pentaery-. . . ~
thritol, trimethylhexanediol and the like. The results oE
the second sequential step is the production o~ a urethane . . ~ . - , .
prepolymer having 2-10 terminal h~droxy groups, i.e. l-S
.
~ groups at each end of the prepolymer.
. ~
he ultraviolet light absorbers which may be ù~ed to produce the novel composi~ions of the present invention ~- 25 may be added thereto in admixture with the urethane prepoly--. .:.~ ~ . . .
mer, the alkylated melamine/formaldehyde material or indi-vidually after the prepolymer and melamine/formaldehyde ma-. .
~ terial have been blended. Ultraviolet li~ht compounds which .
~ ~ may~be employed include 2-[(2-hydroxy-5-t-octylphenyl)]benzo-. :
i ~ 30~ triazole, 2,2'-dihydroxy-4-methoxy-benzophenone and the like.
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;/ ~ The quantity of ultraviolet light absorber employed may range Erom about 1.0 to about 5.0% by weight, preferably from about 2.5-3.5%, by weight, based on the total weight of the solids . .
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in the final composition.
As set forth above, ~he urethane prepolymer having terminal hydroxy groups is then admixed with a polyalkyl ether of a polymethylolmelamine to form the coating composition. Examples o these melamine materials encompass the dimethyl, diethyl, dipropyl, dibutyl, etr~ ethers the trimethyl, triethyl, tripropyl, tributyl, etc. ethers, the tetramethyl, tetraethyll tetrapropyl, tetrabutyl, etc. ethers, the pentamethyl, pentaet}lyl, pentapropyl, pentabutyl, !
etc. ethers, and the hexamethyl, hexaethyl, hexapropyl, hexabutyl, etc. ethers -; of the dimethylol, trimethylol, tetramethylol, pentameithylol or hexamethylol melamines. Of course, mixed polyalkyl ethers such as the dimethyl, tetra- -ethyl ethers, etc. of the poIymeithylol melamines may also be used. The pre-ferred melamine is hexakismethoxymethylmelamine~
The proportlon of polyhydroyy urethane prepolymer to melamlne com-pound should range from about S:l to about 1:1, respectively. The mixture ; . .
of polyhydroxy urethane prepolymer and melamine compo~md is prepared at room temperature and ultimately cured, after having been coated on a suitable polymsric substrate, at a te~perature of from about 50-150C. for 3-90 minutes. ~;~
From about 1.0% to about 10.0%, by weight, based on the weight of ~, the polyhydroxyprepolymer and the melamine compound, of an acid catalyst is ;~ 20 added to the polyhydr~xy urethane prepolymer-melamine compound mixture before ', curing. Para-toluene sulfonic acid is preerred; however, xylene sulfonic ~-acid, o- and m-toluenesulfonic acids, ethyl acid phosphatel n-butyl phosphor- ;;
ic acid, phosphoric acid, hydrochloric ` 1 !. ,' ,~. :~.

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1 acid and the like can also be used.
While the u~e o~ a solvent is not essential in the sequential step production of the polyhydroxy urethane pre-polymer or the addition of the melamine compound thereto, the use of a sol~ent iq preferr~d both in the production of the prepolymer composition and in its use as coatings. U9e-ful solvents should be suficiently low boiling that they will vaporize from ~he composition when it is coated on the polymeric substrate ~u~ high enough boiling that they will not vaporize out of the reaction kettle when the composition is being prepared. Examples of suitable solvents include ethyl acetate, ethanol, methanol, cellosolv ~ butanol-cello-solve blends, xylene, toluene, butane, 2-ethoxyethyl acetate, methoxyethyl acetate, butoxybutyl acetate, amyl acetate, and other similar esters, ketones, chlorinated compounds, diox-ane and ~he like. A practical range of ~olids in the sol-vent for coating purposes is between about 5% and 90% solid~
The resultant ooatin~ composition may be applied ~ to the polymeric support by conventional means such as by~
- ~ ~ 20 brushing, sprayin~, dipping or coating with a doctor blade.
~ The polymeric materials which~may be coated with~
`~ the coating compositions discussed above include the poly-carbonates, polyacrylates such as polymethyl methacrylate, - ~ polysulfones, phenoxy polymers, pol~vinyl chloride, polyole-~ 25 fins such as polyethylene, polypropylene and the like. In ;~` general, any polymeric material whose surface requires mar-~ ~ resistance improvement can be coated with the coating com-: , .
; position formed from the hydroxy-ter~inated ur~thane prepoly-mer, the melamine compound and the acid ca~alyst.
~ ThP coatings should be applied to these polymeric matPrials at a thickness ranging from about 0.01 mil to l~Q

~ mil.
.j ~ The following examples are set forth for purposes Tr~\er~
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1 of illustration only and are not to be construed as limita-~ions on the present inven~ion except a3 se~ forth in the app~nded claims. All part~ and percentage9 are by weight unl~ss otherwise speciEied.
_xample 1 ~Comparative) To a suitable reaction vessel are added 1500.0 parts of polytetramethyleneether glycol having a molecular weight of about 2,000, 15500 parts of polytetramethyleneether glycol having a molecular weight of about 620 and 760.0 parts of toluene. The vessel is blanketed with nitrogen and the mixture stirred until homogeneous. 520.0 Parts o~ 1,4-meth-ylenebis(cyclohexylisocyanate) and 20.0 parts of a 1~ by weight solution of dibutyltin dilaurate in ethyl acetate are added. The reaction mixture is heated at 70C. for 5 hours and 300.0 parts of 1,3-cyclohexanedimethanol (dried at 95'C.
for 4 hours before use) are added khereto with stirring.
Heating at 70C. i8 continued or 1-1/4 hours and 1565.0 parts of n-butanol are added and stirred until homogeneous. The resultant solution of hydroxy-terminated polyurethane pre-polymer has a solids content of 51.4%, by weight.
To 480.0 parts o the prepolymer solution are added 240.0 parks of hexakismethoxymethylmelamine, 133.0 parts of the mono methyl ether of ethylene glycol, 450.0 parts of n- '!
-butanol, 14.4 parts of xylene, lOo 36 parts of methanesulfonic acid and 1.0 part of a commercially availahle leveling agent. ~`
The resultant coating formulation is coated onto polycarbonate eyeglass l~nses by dipping khe lenses into the formulation and curing them for 5 minutes at about 125C.
A hard, well adhered, mar-resistant coating results.
The adhesion of the coatin~ to the lenses is deter-mined by cross-hatchi}lg of the surface o aach len~ with a sharp knife to form a pattern of 1/16" squares. The pattern i9 covered with a piece o~ cellophane tape which i3 then rap-idly pulled off. The coated adhesion is rated by ~he follow~
ing scale:
Excellent: No coating is pulled of or loosened from the lens.
Very good: No coating i5 pulled of:E the lens but pat tern corners may be loosened.
Good: Some small squares are removed.
Fair-Poor: Most o~ the coatiny pU115 off.
The following results are obtained after exposing the above-coated len~es to carbon arc light in a Facleometer.
Hours Exposed Adhesion 0 Excellent 100 Poor This comparative example illustrates that the coat-ing composition of Example 1 t which contains no ultraviole~
light ab~orber, has poox adhesion to cast polycarbonate sur-faces after exposure for 100 hours in a Fadeometer.
Example 2 The procedure of ~xample 1 is ollowed except that 2.43 parts of 2-[2-hydroxy-5-t-octylphenyl)] ben~otriazole`
; are added to 133.0 parts of the final mixture produGed there-in. Lenses are coated and cured a~ described in ~xample 1.
-~ The following results are obtained after exposing the coated .~ 25 lenses to carbon arc light in a FadeometerO
Hour 9 Ex~o ed Adhesion 0 Excellent 100 Excellent 200 ~xcellent 30 300 Very Good 400 Very Good .~ 500 Eair - Good 60 n P~or ~S'7~
l This ex~mple shows ~hat the adhesion o~ the co~t-ing of Example 1 is greatly improved by addin~ ther~to the above-specified benzotriazole .
Example 3 The procedure of Example 1 is conducted except that 0.48 part of 2,2'-dihydroxy-4-methoxybenzophenone i~ added ~o 133.0 parts of the Example 1 mixture. The following re~
sults are obtained:
Adhesion lO0 Excellent 10 0 Very Good 200 Fair 400 Poor As can be seen, the use of the spec1fied benzophen-one also improves the adhesion of the Example l coating to the polycarbonate.
Example 4 Under a nitrogen blanket, 93.0 parts of a polytetra- ~
. . . ,~ .
methyleneether glycol having a molecular weight of about 620, and lO0.0 par~s of a polytetramethyleneether glycol having . ~ .
a molecu}ar wei~ht of about 2,000 are dissolved in 152.0 parts of toluene and to the solution are added 104.0 part~ o l,4--methylenebis(cyclohexylisocyanate) and 4.0 parts oE a 1~
solution of dibutyltin dilaurate in ethyl acetate. ~he re sultant mixture is hea~ed with stirring at 70C. for 5 hours ~-; and 60.0 parts of a 1,4-cyclohexanedlmethanol, previously dried by heating at 95C. for 4 hours, are added with stirr-~ ~ ing. Heating is continued for l-l/4 hours and 152.0 par~s i of n-butanol are then added and stirred until the mixture ~ 30 is homogeneou~.

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To 480.0 parts of the resultant polyurethane pre-polymer are added 240.0 parts of hexakismethoxymethyl mela-mine~ 133.0 parts o methyl cellosolve~ 450.0 parts of n-r~
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1 -butanol, 145 parts of xylene, 0.5 part of level~r, 10.4 parts of methanesulfonic acid and 14.6 parts of 2-~(2-hydroxy~5 -t-octyl-phenyl)]benzotriazole.
Poly carbonate lenses, coated with the resultant S composition and dried at 100C. for 15 minutes are classified as excellent after 300 hours in a carbon arc Fadeomete Example 5 Usiny the procedure of Example 4, 49.5 parts of a polytetramethyleneether glycol having a molecular weight of about 660 and 50.5 parts of a polytetramethyleneether gly-col having a molecular weight of about 2,000 are dissolved in 152.0 parts of ethyl acetateO 52.0 Parts of the diisocy-anate and 2~0 parts of ~he tin catalyst are added. When the reaction is complete, 30.0 parts of 1,4-cyclohexanedimethanol are reacted to produce th desired urethane prepolymer.
50~0 Parts of the prepolymer, 10.0 parts of hexa-kismethoxymethyl melamine, 20.0 parts of 95~ ethanol, 20.0 parts of methanol, l.D part of methane sulfonic acid and 1.0 part of 2 [(2-hydroxy-5-t-octylphenyl)]benzotriazole are then 20 admixed and coated on~o polycarbonate plano lenses as in Ex~ -ample 1. After 350 houxs in a carbon arc Fadeometer, the adhesion remains excellent.
; Exam~le 6 The procedure of Example 2 i8 followed except that ~he polytetramethyleneether glycol of 2,000 molecular weight is omitted. 73.5 Par~s of the resultant hydroxy terminated urethane prepolymerl 26.5 parts of hexakismethoxymethyl mel-amine and 2.65 parts of p-toluene sulonic acid are used to `produce the coating composition. The composition is coated from a 24% solids mix~ure of ethyl acetate/hydroxyethyl ether/-methanol~ethanol, 1.2/1.0/1.0/1Ø After 400 hours in the carbon arc Fadeometer~ adhesion of the coating ~o the sub-strate i~ rated good.
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1 Example ?
The procedure of Example 2 is followed èxcept that the 650 molecular weight polytetramethyleneether glycol is omitted~ The adhesiveness of the resultant coating composi-tion after 300 hours in the carbGn arc Fadeometer is ratedvery good.
Examples 8-13 The procedure o~ Example 2 is followed except that the diol, dii~ocyanate, catalyst, sterically bulky polyhydric alcohol, curing catalyst and polymeric substrate are varied.
The results are set ~orth in Table I below. In each instance, the ultraviolet light absorber is 2-[(2-hydroxy-5-t~octyl-phenyl)-benzotria~ole except in Examples 10 and 12 wherein 2,2-dihydroxy-4-methoxybenzophenone is used as per Example 3. The adhesiveness results are after 200 hours in a carbon arc Fadeometer.

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Claims (17)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. A coating composition consisting essentially of a mixture of (1), (2), (3) and (4), in which (1) is a saturated urethane prepolymer having terminal hydroxy groups which is the reaction product of materials consisting essentially of a mixture of (a) and (b), at a molar ratio of 1:2, respec-tively, in which (a) is an isocyanate-terminated urethane which is the reaction product of a mixture of (I) and (II), at a molar ratio of 1:2, respectively, in which (I) is a saturated diol having a molecular weight of from about 200 to about 3,000 and (II) is a saturated organic diisocyanate and (b) is a monomeric, sterically bulky, polyhydric alcohol containing 2-6 hydroxyl groups and being free of oxyalkylene units, (2) is a polyalkyl ether of a polymethylol melamine, (3) is an acid catalyst and (4) is an ultraviolet light absorber comprising 2-[(2-hydroxy-5-t-octylphenol)] benzotriazole or 2,2'-dihydroxy-4-methoxybenzophenone, the ratio of (1) to (2) being in the range of from about 5:1 to about 1:1, about 1% to about 10% by weight of (1) and (2) of acid catalyst (3) being present in the composition with about

1.0% to about 5.0% by weight based on the total weight of solids in the composition of ultraviolet light absorber being present in the composition.

2. A composition according to claim 1 wherein said (I) is a polytetra-methyleneether glycol.

3. A composition according to claim 1 wherein said (II) is methylene bis(cyclohexane isocyanate).

4. A composition according to claim 1 wherein said (b) is 1,4-cyclo-hexane dimethanol.

5. A composition according to claim l wherein said (2) is hexakis-methoxymethyl melamine.

6. A process for the sequential production of the composition of claim 1 which consists of (1) first reacting (a) a one-molar proportion of a saturated diol having a molecular weight of from about 200 to about 3,000 with (b) about a two molar proportion of a saturated organic diisocyanate to produce an isocyanate-terminated urethane prepolymer, (2) then reacting (c) a one-molar proportion of said urethane prepolymer with (d) about a two-molar proportion of a monomeric, sterically bulky, polyhydric alcohol contain-ing 2-6 hydroxyl groups and being free of oxyalkylene groups, to produce a prepolymer having terminal hydroxy groups and (3) admixing said prepolymer with (e) a polyalkyl ether of a polymethylol melamine, (f) an acid catalyst and (g) an ultraviolet light absorber comprising 2-[(2-hydroxy-5-t-octyl-phenyl)] benzotriazole or 2,2'-dihydroxy-4-methoxybenzophenone, the ratio of (1) to (2) being in the range of from about 5:1 to about 1:1, about 1% to about 10% by weight of (1) and (2) of acid catalyst (3) being present in the composition, with about 1.0% to about 5.0% by weight based on the total weight of solids in the composition of ultraviolet light absorber being present in the composition.

7. An article of manufacture comprising a polymeric substrate having a mar-resistant coating thereon, said coating consisting essentially of the acid catalyzed reaction product of a mixture of (1), (2) and (3), in which (1) is a saturated urethane prepolymer having terminal hydroxy groups which is the reaction product of materials consisting essentially of a mixture of (a) and (b), at a molar ratio of 1:2, respectively, in which (a)is an iso-cyanate-terminated urethane which is the reaction product of a mixture of (I) and (II), at a molar ratio of 1:2; respectively, in which (I) is a satur-ated diol having a molecular weight of from about 200 to about 3000 and (II) is a saturated organic diisocyanate and (b) is a monomeric, sterically bulky, polyhydric alcohol containing 2-6 hydroxyl groups and being free of oxy-alkylene units (2) is a polyalkyl ether of a polymethylol melamine (3) is an ultraviolet light absorber comprising 2-[(hydroxy-5-t-octylphenol)] benzo-triazole or 2,2'-dihydroxy-4-methoxybenzophenone.

8. An article of manufacture according to claim 7 wherein said (I) is a polytetramethyleneether glycol.

9. An article of manufacture according to claim 7 wherein said (II) is methylenebis (cyclohexane isocyanate).

10. An article of manufacture according to claim 7 wherein said (b) is 1,4-cyclohexane dimethanol.

11. An article of manufacture according to claim 7 wherein said (2) is hexakismethoxymethyl melamine.

12. An article according to claim 7 wherein said substrate is a lens.

13. A process for the production of the article of manufacture of claim 7 which comprises (A) coating a polymeric substrate with a coating composition consisting essentially of a mixture of (1), (2), (3) and (4), in which (1) is a saturated urethaneprepolymer having terminal hydroxy groups which is the reaction product of materials consisting essentially of a mixture of (a) and (b), at a molar ratio of 1:2, respectively, in which a. is an isocyanate-terminated urethane which is the reaction product of a mixture of (I) and (II), at a molar ratio of 1:2, respectively, in which (I) is a saturated diol having a molecular weight of from about 200 to about 3000 and (II) is a saturated organic diisocyanate and b. is a monomeric, sterically bulky, polyhydric alcohol containing 2-6 hydroxyl groups and being free of oxyalkylene units, (2) is a polyalkyl ether of a polymethylol melamine, (3) is an acid catalyst and (4) is an ultraviolet light absorber comprising 2-[(2-hydroxy-5-t-octylphenol)] benzotriazole or 2,2'-dihydroxy-4-methoxybenzophenone.

14. An article of manufacture according to claim 13 wherein said (I) is a polytetramethyleneether glycol.

15. An article of manufacture according to claim 13 wherein said (II) is methylenebis(cyclohexane isocyanate).

16. An article of manufacture according to claim 13 wherein said (b) is 1,4-cyclohexane dimethanol.

17. An article of manufacture according to claim 13 wherein said (2) is hexakismethoxymethyl melamine.