CA1072232A - Water-based coatings with improved solvent or water popping and sagging characteristics - Google Patents

Abstract

Abstract of the Disclosure This invention relates to water-based coating compositions in which solvent or water popping and sagging are eliminated or at least substantially reduced. The composition comprises a thermosetting, film-forming organic binder dispersed in an aqueous medium containing from 60 to 100 parts by weight of water and 0 to 40 parts by weight of a volatile organic solvent. The organic binder is formulated from ( ) an acid-containing interpolymer adapted to be dissolved or dispersed in water with the aid of a base and (b) a water-soluble or water-dispersible polyether polyol or polyester polyol having a molecular weight of at least 300. The interpolymer consists essentially of the interpolymerization product of an N-alkoxyalkyl-substituted amide, an alpha, beta-ethylenically unsaturated carboxylic acid, and at least one other monomer containing a group.
The properties of coatings formed from the compositions can be further enhanced if desired by incorporating (c) a water-soluble or water-dispersible aldehyde condensation resin into the organic binder.

Description

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Bac~Lround o~ the Invention D recent times, the:increa ed emphasis on environmental pollu-: tion probIems has a~fected all areas o~ society~ In the coatings lndustry,:
~ ~ thls mphasis has taken the form of a major ef~ort to el~inate or substan-.
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tially reduce~organic sol~ent ~m~s~io~3 ~rom coa~ing composltions. This ~
has led to an increasing intexest ,on ~he part o~ the coat~ngs industry ~ :in water~baJed coatin~g ~n wh~h. oxganic 801vent6 are eliminated or at . :
~leas~ greatly reduced~ In even more ~ecent tl:mes, this interest in water- -; based COJtingS has received added impetus as a result of the energy:shortage, .:
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particularly the decline in U~S~ oil production and the high cost of imported oil~
~ ater-based coating compositions derived from interpolymers of substituted, unsaturated carbox~lic acid a~ides, alpha, beta-ethylenically unsaturated carboxylic acids, and other ethylenically unsaturated monomers are known in the art, e~g~, see U.S~ ~atent ~o. 3,247,139 issued April 19, 1966, and Example X~ of U~S~ ~atent ~o~ 3,079,434, issued February 26, 1963.
However, the water-based coating compositions of the aforementioned patents differ materially in composition from the compositions of this invention in that the compositions therein do not contain either a polyol component or an aldehyde condensation resln~ ~oreoVert while the compositions of .
these patents are useful in certain applications, they have been found to exhibit a number of serious disadvantages which materially limit their -.
usefulness~ Thus, the compositions of the aforementioned patents and, for that matter, water~based coatings in general? have been found to be very susceptible to solvent or water popping and sagging, or "curtaining`', particularl~ when relatively thick films are deposited therefrom. Solvent or water popping manifests ltself.in the Porm of bubbles or pinholes in the cured film surface.
~ The exact cause oP solve~t or water popping is not known with -certitude, but it has been theori~d that the film sets up structurally, or actually begins to crosslink before the last portion of the solvent or water is eliminated~ This residual solvent or water cannot evaporate through the tough surface film, and collects in tiny bubbles which may or may not rupture, depending upon t~e curing conditions~ _ nother theo~ i3 th~ ~S. the ~es~n cures? the water ~nd~or alkanol given of~ during t~e c~osslink~ng cure process ~s actually entrained under the film surface i~ t~e Porm. o~ tiny bub.bles~

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Sagging or "curtaining~' occurs ~hen relatively thick films of the coating composition are applied to other than horizontal sur~aces and is due to gravitational flo~ of the film, and/or to film resoftening during the curlng period~ In the coatings art, ~he term "sagging" denotes the tendency of a film to drain o~ ~low ~rom a non~horizontal surface in an uneven manner, while the term '~curtaining~`denotes ~he tendency of the fllm to drain or flow from said su~face in a smooth, continuous manner.
Water-based coating compositions such as those described in the aforementioned patents also exhibit additional disadvantages. Thus, such compositions have been found to have ~nadequate moisture and detergent resistance ~or certain coating applications, such as~ for example, coatings ~or ~ashers, dryers and the like.
Very recently, water-based coat;ing compositions comprising methylolated amide interpolymers of hlgh acid content and low molecular weight polyhydric alcohols ha~e been disclosed in U~S. Patent No. 3,860,549 to Sek~akas, issued ~anuary~14~ 1975~ However, the compositions of the patent are speci~ic to interpolymers derived from unetherified methylolated amldes and also do not contain aldehyde condensation resins, and this differ materially ~rom the compositlons o~ this invention~ The compositions of the aforementioned patent also exhibit ssrious disadvantages~ Thus, compositlons based upon -methylolated amide interpolymers tend to exhibit short potlife and be prone to gelation~ Additionally, compositions o~ the type described ln Sekmakas also exhibit inadequate moisture and detergent resistance in certain coating applications, such as, for example, coat~ngs for washers9 dryers and the like.
In accordance with thls ln~ention, a ~ater-baséd coating composition ~s prov~ded ~hich overcome6 s~bs~antiall~ all of the dlsadvantages ~e~erred to above~ Thus; the w~ter~b~sed coat~ng composition of the invention is one in which solvent popping or water popping and sagging is eliminated or at least s~bstantially reduced~ ~oreover~ t~e composi~ions of the invention are based ~ 3 ~

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~L~7Z;Z32 upon etherified amide interpolymers ~discussed below) and hence have excellent stability. Finally, the compositions o~ the invention form ~ s having improved water, salt spray~ detergent and stain resistance.

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Descrlption of t~e lnvention The water-based coati~ng compositions of the invention comprise a thermosetting, film-forming organic blnder dis~exsed in an aqueous medium containing from 60 to 100 parts by weight of water and 0 to 40 parts by ~eight o~ a volatile organic solvent~ The water-.reducible organic binder o~ the composition is for~ulated from GA) an acid~ccntaining interpolymer adapted to be dissolved or dispersed in water with the aid of a base and CB~ a water-soluble or water-dispersible polyether polyol or polyester polyol having a molecular weight o~ at least about 300.
The properties o~ coatings fo~med fro~ the compositlons can be further enhanced (i.e., improved) if desired by incorporating (C) a water-soluble or water-dispersible ald.ehyde condensation resin into the organic binder.-(~ T'ne ~cid-Containing Interpolymer Component The interpolymer component of the compositions of the invention N' .
consists essentially o~ the interpolymerization product of an-a-alkoxyalkyl-substituted amide, an alpha, beta-ethylenically unsaturated carboxylic acid and at least one other monomer con~aining a CH2 = C ~ group.
The N-alkoxyalkyl-substi~uted amides e~ployed in for~ing the interpolymer hereln may be~epresented by the structure:

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R~ - C ~ ~H ~ CH~ ~ O ~ R

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wherein R' is an aliphatic hydrocarbon radical containing from 2 to 6 carbon atoms and having a single polymerizable alpha, beta-ethylenically unsaturated group and R is a lower alkyl radical containing from 1 to 8 carbon atoms.
These substituted amides can be prepared by reacting an unsaturated amide (e.g., acrylamide) with formaldehyde and an alkanol (e.g., butanol) under acidic conditions and in the presence of a polymerization inhibitor. For a detailed description of this method, see U.S. Patent No. 3,079,434. The resultant N-alkoxyalkyl-substituted amide Ce.g., N- (butoxymethyl)acrylamide~
is then interpolymerized with the other monomers (described below) to form the interpolymer containing the substituted amide units.
The preferred N-alkoxyalkyl-substituted amide employed in formin~ the interpolymer is N-(butoxymethyl)acrylamide, although other N-alkoxyalkyl substituted unsaturated carboxylic acid amides such as N-(methoxymethyl)-acrylamide, N- (propoxyme-thyllacrylamide, N-~ isopropoxymethyl)acrylamide, N-(iso-butoxymethyl)acrylamide and N- (butoxymethyl)methacrylamide, or the like may be employed.
The interpolymer may contain in polymerized form from about 10 to about 40 percent by weight of these N-alkoxyalkyl-substituted amides with a preferred range being from about 20 to about 30 percent.
Alpha/ beta-ethylenically unsaturated carboxylic acid monomers which are preferably utilized in forming the acid units of the interpolymer include acrylic or methacrylic acid but itaconic acid, crotonic acid, maleic acid and half esters of maleic and fumaric acids may also be used. In the half esters, one of the carboxyl groups is esterified with an alcohol, the identity of which is not significant so long as i.t does not prevent polymerization or preclude the desired utilization of the pxoduct. Butyl hydrogen maleate and ethyl hydrogen maleate are examples.
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3L~72~32 The interpolymer ~ay contain in polymerized form from about 5 to about 20 percent by weigh~ o~ suc~ ~cld units. Howeve~ ~or greater efficiency in solubilization and overall properties, it is preferred that from 7 to 15 percent of such acid units be present in the interpolymer.
As indicated, the interpolymer? in addition to the substituted amide and acid units, contains units of at least one other monomer contain-ing a CH2 = C ~ group. The other monomer containing the CH2 = C < group can by any ethylenically unsaturated compound which is copolymerizable with the substituted amide and acid with the polymerization taking place through the ethylenically unsaturated linkages~ These include monoolefinic and diolefinic hydrocarbons, unsaturated esters of organic and inorganic acids, esters of unsaturated acids and unsaturated organonitriles such as acrylonitrile and the like~ It is preferred, in order to provide desirable properties in the interpolymer~ to utilize a combination of hardening and flexibilizlng monomers. The preferred hardening monomer is styrene, but others such as vinyl toluene or alk~l methacrylates having from 1 to 4 carbon atoms can also be utilized~
The interpolymer may contain in polymerized form from about 5 percent to about 75 percent by weight of hardening monome~s with a preferred range being from about 50 to about 60 percent of such monomers.
The flexibilizing monomers u~ilized may be one or more alkyl or substituted alkyl esterg of acrylic or methacrylic acid, the alkyl groups having 1 to 13 carbon atoms in the case of acrylic esters and 5 to 16 carbon atoms in the case of methacrylic esters~ Illustrati~e of such flexibilizing monomers are ethyl acx~late~ ~UtY~l ~cr~late, 2~ethylhexyl acrylate~ 2-ethyl-hexyl methacrylate, decyl ~ethacr~late, l~uryl methac~ylate, and the like.

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~i72,232 The irlterpolymer ma~ contain~ in polymerized form, from about 5 percent to about 75 percent b~ wei~t of such ~lexibili~ing mono~ers with a preferred range being ~rom about 20 pe~cent to about 50 percent~
~ The above-described acid-containing interpolymer is prepared by conventional vinyl polymerization technlques utilizing ~inyl polymerization catal~æts which are well known in the art~ These include the azo compounds such as alpha, alpha~azobis(isobutyronitrile), which are the preferred ~atalysts herein, and the well known peroxygen catalysts such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide and the like. Other useful catalysts include tertiary-bu~yl perbenzoate, tertiary-butyl pivalate, ~-isopropyl percarbonate and similar compounds. In addition~ the interpolymer may be prepared, if desired, by conventional emulsion polymerization techniques. In that e~ent, it is often desirable and preferred to employ water-soluble initiators such as hydrogen perox`ide, ammonium persulfate, potassium persulfate and other similar persuIfates.
As indicated, ~he above-described acid-containing interpolymer is adapted to be dissolved or dispersed in an aqueous medium with the aid of a base. This is accomplished by neutralizing alI or a portion of the carboxylic acid groups of the interpolymer with an appropriate base. Virtually any ;~
basic compound can be utilized ~or that purpose, including inorganic bases such as alkali metal hydroxides and organic bases such as amines. However, the preferred basic compounds utilized herein are the monomeric amines. These may be any of the a~ines used ~or solubilizing pUxposes known hereto~ore, including ammonia, ethylamine~ butylamine, dimethylamine, cyclohexylamine, morpholine, monoethanolamineS d~ethanolamine~ dimethylethanolamine, diethyl- -ethanolamine and the l~he~ 0~ these amines, di~e~hylethanola~ine is pre~erred~ -The amount o~ a~ne employed i~ neutralizing the acid groups of the interpolymer may ~ary considerabl~ Howe~er; i~ is preferred in this invention 7 ~

~7~Z,232 tllat the amount of amine employ~d be su~icient to neutralize at least about 40 percent o~ the theoretical quantity of acid groups p~esent in the interpolymer~
~ Several procedurefi may be emploved in dispersing the inter-polymer in the aqueous medlu~ One known method is to first ~orm the interpolymer in solution by polymeri~ng the monomers in a water-miscible volatile organic sol~ent or mi~ture of suc~ solvents, following which the acid groups of the resultant interpolymer are neutralized with the basic compound, if deslred~ in the pre~ence of water~ to form the salt or partial salt of the interpolymer, thus enabl~ng the interpolymer to be dissolved or dispersed in the aqueous medium. In this method~ any excess organic solvent utili~ed i~ the polymeri~ation process can be removed from the aqueous medium by dlstillation if desired. Alternatively, in the practice o~ this invention, the monomers can firs~ be polymeri~ed in a mixture of ~ water-mlscible ~olat~le organic solvent and the water- -soluble or ~ater-dispersible polyether or poIyester polyols (described hereinafter~ or in the water-soluble or water-dispersible polyether or polyester polyol alone, following whlch the acid groups o~ the resultant interpolymer are neutrallzed to form the salt or partial salt of the interpolymer, thereby rendering the interpolymer dissolvable or dispersible in the aqueous mediu~ ~hese alternative procedures have t~e advantage of eliminating the necessity for a separate distillation step to remove .
any excess organic solvent~
Yarious water-miscible or wate~soluble organic solvents can suitably be employed in producing the water~soluble or water-dispersible interpolymer~ ~us~ th.e ether t~pe ~lc0~018 such as ethylene glycol monobutyl ether (i~e~, but~l Cellosolre~,.eth~lene glycol monoethyl ether ~'~ ~k -~8 ~

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~ZZ32 (i.e , ethyl Cellosolve~, dlethylene glycol monomethyl etherg diethylene glycol n-butyl ether (i.e. 3 butyl Carbitol~ and the like may be advantageously employed~ In addition, lower alkanol~ ha~ing 2 to 4 carbon atoms such as ethanol, propanol9 ~sopropanol~ Butanol and the like can be used.
Mixtures of the ether type alcohols and lo~er alkanols are often advan- - -tageously employed. ~inor proportions of ~drocarbon solvents such as Y~ylene, toluene and the like may also be included.
The liquid portlon o~ ~he coating compositions herein may contain from about 60 to about 100 percent by weight o~ water and correspondingly from 0 to about 40 percent by weight of organic solvents, such as those mentioned above, with a preferred ratio being from 80 to 90 percent by weight of water and 10 to 20 percent by weight of organic solvent.
In any case, at least about 6Q percent by~weight of the liquid medium will be water.

C~2 The ~ater~Soluble o~ ~ater-Dispersible Polyol-Component As indicated above, in addition to the previously-described interpolymers, the organic binder of the water-based coating compositions of the invention contains a non-volatile, water-soluble or water-dispersible polyether polyol or polyester polyol~
Polyether polyols or polyester polyols which can suitably be employed in the binder of the compositions of this invention are those havlng a molecular weight of at least 300 and which are soluble or disper-sible in water. These polyols must have molecular weights of at least 300 and may have molecular weights of up to 5000 or even higher~ provided they are water-soluble or water~di`spexsible~ ~he preferred water~soluble or water-dispersible polyet~e~ polyo~s ox polyester polyols employed in the compositions o~ t~e inventio~ are those h~v~ng molecular weights of from C~ trk _ 9 _ ~

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Subject to the above li~itations, essentially any polyether polyol or polyester polyol can be e~ployed in the compositions of the lnvention, with the preferred polyols being polyether polyols which are the reaction products of an alkylene oxide, preferable ethylene oxide or 1,2-propylene oxide, with a polyol such as glycerine, trime-thylol-! -propane, hexanetriol, pentaerythritol, sorbitol~ sucrose or the like.
The particularly preferred polyether polyols used in the invention are the reaction products of 1,2-propylene oxide with a mono- or disaccharide such as sucrose? dextrose~ lactose and alpha-methyl d-glucoside~
Polyethers of mono- and disaccharides are known in the art~ -One prsferred method o~ preparlng these sugar-containing polyether polyols (e~g., sucrose polyether polyol~ is to ~irst dissolve the saccharids In water, following wh~ch an oxyalkylation catalyst is added, and the alkylene o~ide addition is carried out to that point at which the saccharide-alkylene oxide reaction product is a liquid at roo~ te~perature. At this point, substantially all of the ~ter present is re~oved by distillation or other means~ and the balance o~ the alkylene oxide is added until the desired polyether polyol is obtained~ For a detailed description of these saccharide-containing polyether polyols and their method o~ preparation~ see U~S. Patent No. 3,085,085, issued April 9~ 1963~ -Polyester polyols ~hl~h are sultable ~or use. in the instant Invention a~e ~ormed from the pol~este~ication of organic polyols and organlc polycarboxylic acids or acld anhydrlde~ The polyols and poly-a ~

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~L~7Z~32 carboxylic acids or anhydrides are often aliphatic or aromatic diolsand diacids but i~ is advantageous ~ o~e cases to employ polyols or polycarboxylic acids having hydrox~l or carboxyl functionalities of 3 or more.
The pre~erred polyols e~ployed i~ formi~g the polyesters are diols and triols~
Diols which may be employed in making the polyester polyol include alkylene glycols such as eth~lene glycol, propylene glycol, butylene glycol, h OEylene glycol, and neopentyl glycol and other glycols such as hydrogenated Bisphenol ~p cyclohexane dimethanol, caprolactone dlol (for example the reaction product of caprolactone and ethylene glycol), hydroxyalkylated bisphenols, and polyether glycols such as poly(oxytetramethy-lene) glycol and the like~ In addition~ many other diols of various types can be utilized.
Triols which are pre~erabl~ employed in maki~g the polyester polyols lnclude compounds such as t~imethylolpropane, trimethylolethane, 1,2,2-propane-triol, 1,2,4-butanetriol, polycaprolactone triols and triols based on adducts of propylene oxide and glycerine.
Polycarboxylic acids which may~be e~ployed in making the polyester polyol consist primarily of monomeric carbo~ylic acids or anhydrides having 2 to 14 carbon atoms per molecule. A~ong the acids ~hich are useful are phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, adip~c acid, sebacic acid, maleic acid, glutarlc acid, chlorendic acid, tetrachlorophthalic acid, and other dicarboxylic acids of varying types~ , ~
The pol~ester may I~c~ude ~inor amounts of monobasic acids, such ; ~s benæoic acid, and thexe ~a~ ~lso be employed herein polycarboxylic acids such as trimellitic acid and tricarballyl~c acid (where acids are referred to above, it is understood that t~e anhydrides of those acids which form anhy-, : ,, . ' ' '. . ' ' ,. ' ~ ................................. :
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~7~232 drides can be used in place o~ the acid2~ It is preferred that the polyester include an aliphatic dicarboxylic acid as at least part of the acid component. It should be noted that if both tricarboxylic acids and triols are used in the same pol~ester, care must be exercised else gelation will occur and the pol~ester will be so highly crosslinked that it will not be water soluble or water dispersible. In general, high contents o~ triols rather than the tricarbox~lic acids are favored~
The polyester polyols useful herein also include polyester amide polyols, and polyhydric compounds h~ving polyester structures but not formed from the reaction o~ a polyol and a polycarboxylic acid, Examples o~ this latter type includes the so-called lactone polyesters, such as the poly-caprolactone polyols described in U.S~ Patent 3,169,945 to Hostettler et al.
~ he polyether or polyester polyols used in the water~based coating compositions of this invention provide a number of advantages thereto. First, these polyols participate ~ the curlng oE the compositions by being cross~ -linked through their hydroxyl functionality~ Therefore, these polyols are incorporated into the film ormed by curing the composition. ~ore impor~antly, the use of these polyols in the compositions of the invention produces water-based coatings in which sol~ent and water~popping and sagging are eliminated or substantially red~lced~ This is of great importance since solvent and water-popping and sagging have been serious problems with water-based coatings prior to the instant invention~
The amounts of these polyet~er or polyester polyols ~hich are ordlnarily included in the binder of the comyositions of the lnvention vary considerably depending upon the thickness o~ the coating desired, humidity conditlons and the llke~ ~n general~ from about 5 percent to about 50 percent by ~eigh~ o$ t~e pol701 based upon total binder solids may be included wIth a pFe~erred amount being from lO percent to 25 percent~

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(C? The Water-Soluble or ~ater-Dis~e~_ ble Aldehyde Condensation Resin Component As indicated hexeto~o~e, the properties of coatings ~ormed ~rom the compositions can be ~urther enhanced i~ desired by incorporating a water-soluble or water-dispersible aldehyde condensation ~esin into the organic binder.
~ ater-soluble or dlspersible aldehyde condensation resins which may be employed include the water-soluble or dispersible condensation products of an aldehyde, pa~ticularly ~ormaldehyde, with an alnino- or amido- group containing compounds such as urea, melamine, benzoguana~ine and the like, including the transethers thereof ~ith methanol, butanol or other lower alcohol (i.e.~ aminoplast resins) are water-soluble or dispersible condensation products of an aldehyde ~ith a phenolic resin.
Illustrative of water~soluble ox dispersible aminoplast resins which may be employed are al~y~là~ed melamine ~ormaldehydes such as methylated melamine formaldehyde, butyla~.ed melamine formaldehyde and the like; alkylated urea formaldehydes such as methylated urea formaldehyde, butylated urea ~ormaldehyde and the llke; urea formaldehyde; benzoguanamine formaldehyde; hexa(methoxymethyl)melamine; hexakis(methoxymethyl)melamine and similar compounds. 0~ these compounds, hexa(methoxymethyl)melamine is the preferred compound~
Uhile the aldehyde employed in ~orming the water-soluble or dispersible aminoplast resin is most ofeen fonnaldehyde, other similar condensatlon products can be ~ade from other aldehydes or mixtures ~hereof, such as acetaldehyde, cro~onaldeh~de, acrolein~ benzaldehyde, furfural, g~yaxal and the li~e.
~ s indicated~ th~ w~te~ solub~e or dispersible aldehyde con~
densatlon resin may~also be a water soluble or dispersiU e phenolic resin (i.e., phenol-aldehyde res~n~ As ~n the case of the aminoplast resins, the .' ' .

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most commonly used aldehyde is formaldehyde9 although other aldehydes, such as acetaldehyde, can also be employed~ ~ethylene-releasing and aldehyde releasing agents, such as paraformaldehyde and hexamethylene tetramine, can arso be utili~ed as the aldehyde if desix~d~ Vaxious phenols can be used;
for instance, the phenol emplo~ed can be phenol per se, a cresol, or a substituted phenol in which a hydrocarbon radical having either a straight chain, a branched chain or a cyclic structure is substituted for a hydrogen in the aromatic ring. M~xtures of phenols are also often employed Some specific examples o~ phenols utilized to produce these resins include p-phenylphenol, p-tert~butylphenol, p-tert-amylphenol~ -cyclopentylphenol and unsaturated hydrocarbon-substituted phenols such as the ~onobutenyl phenols containing a butenyl group in the ortho, meta or para position, and where the~double bond occurs in various positions in the hydrocarbon chain~ Illustrative o~ such compounds are the well know~ non-gelled alkaline conden$a~es o~ ~phenol with ~xcess formaldehyde kno~n as t~` stage resole~
While water-soluble or dispersible phenol aldehyde resins of the type mentioned above inay be employed àn the invention, the preferred phenolic res~ns for use in the binder of the compositions of the invention are ~he methylolphenol ethers of the structure: ~

~ I H20H)n when n is an integer o~ ~om 1 to 3 a~nd R ~s an unsaturated aliphat~c group or a halogen~substi~ted aliphatic group~ The groups represented by R should contain at least 3 caDP~n a~o~s and can be ally~l groups (~hich are pre~erred~ or others suc~ as ~ethaliy~l, c~ot~ll buteny~l and the like~

~he halogen~substituted unsaturated groups represented b~ ~ can he various mono- and poly~halogenated de~i~ati~es o~ the above unsaturated aliphatic groups, for example, 2-chloro-allyl, 3-chloro~allyl, 3~chloro-2 methallyl, :. :

~(~7ZZ3~2 l-chloro-2-butenyl and corresponding groups containing halogens such as bromine or ~luorine~
The methylol phenol et~exs which ~ay be employed herein are described in U.S~ Patent ~o~ 2~597p330 and~, as described therein, can be produced from sodium or barium salts o~ 2,4,6-tris(hydroxymethyl)phenols which are ob~ained by reacting formaldehyde with phenol in the presence of sodium or barium hydroxide. Several methylol phenol ether compositions o~ th~s type are commercially available and these generally comprise mixtures of allyl e~hers of mono~, di~ and trimethylol phenols (substituted in the ortho, para and meta positionsS~ The trimeth~lolated derivative is generally the predominant component o~ the composition. Such commercially available methylol e~her compositions are especially preferred for use in the invention~
Whlle any of the above~described aldehyde condensation resins can be utilized singly in the compositions o~ the invention, it is often advan-tageous in obtaining desired ph~sical and chemical properties to employ -mixtures of such resins~ Thus, for example, th~ utilization in the coating compositi.on of a mixture.of water-soluble or dispersible aldehyde condensation resins comprising an aminoplast.resin and a methylol phenol ether of the type described above signieicantl~ improves the detergent resistance of a film formed from the coating compositlon~ ~
Water~soluble or d~spe~sible aldehyde condensation resins may when desired.b~ included in the organic binder of the composition of the invention in amounts ranging from 5 percent to about 40.percent, pre~erably 5 to 20 percent by weight based on total binder solids~
In addition to th~ thermosetting film~forming organic binder and the aqueous medium~ the water~based coatlng composi~ions of this lnvention may conta:in v~rious additi~e~ commonly utilized in the coa~ings 7;~3;~

industry. Thus, these compositions may contain conventional pigments such as tltanium dioxide~ aluminum, silica, lead silica chromate~ carbon black, talc, barium sulfate and the like~ Colored pigments such as cadmium red, cadmium yellow? phthalocyanîne blue, phthalocyanine green, chrome green~ toluidine red~ h~drated iron oxide, and the like may be included if desired~ ~lso, other adJuvants may be incorporated, such as dispersing agents, surface-acti~e agents, adhesion promoting agents, melting agents, flow agentsl antioxidants~ and the like.
The water-based coating compositions o~ the invention can be applied by me~hods conventionally employed in the coatings industry, such as brushing, dlpping~ flow coating, roll coating, spraying and the like.
After application, the compositions are ordinarily dried and cuxed by baking at ele~ated temperatures to produce a hard, thermoset film.
~he precise baking schedule ~ill depend upon the particular composition utilized~ the nature o~ ~he substrate~ thickness of the coating and the like. However? it should be observed t~t the baking temperature employed must not be so high to ~ol~tilize the polyol component be~ore it can be crosslinked into the ~ilm~ Thus, the baking temperature usually should not exceed about 500F~ unless ~or very short periods~ ~he normal curing time may convenien~ly range from 5 to 45 minutes for usual industrial situations. In coil coating applications, baking schedules of short times and high temperatures can be used~
The water-based coat~ng compositions o~ the invention may have solids contents ranging from 25 to 70 percent b~ weight~ Solids include the interpolymer; polyol, aldehyde condensation resin when employed and any desired pigmentation~

~ 16 _ ~6~72Z32 The following examples set forth specific embodiments o~ the instant invention~ Howe~e~, ~he inventlon is not to be co~strued as being limited to these embod~nents ~or there are, of course, numerous possible variations and modificatlons~ All parts and percentages in the Exa~ples as well as throughout the speci~ication are by weight unless otherwise indicated.

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~his exa~ple illustrates the preparation of an aqueous dis-persion o an amlde type interpolymer employed in the compositions o~
this invention~ ~
~o a reactor e~uipped with re~lux condenser, heating means, stirrer, thermometer and nitrogen inlet were charged 130~0 grams of A ethylene glycol monoeth~l ether Chereina~ter eth~l Cellosolve3 and 325~0 gra~s of a feed mixture cons~sting o~ 58~6 percent styrene, 15.0 percent meth~l methacrylate~ 6~7 percent acr~lic acid, 19 7 percent N~(butoxy-~ethyl)acrylamide and 3~0 percent tertiary dodecyl mercaptan~ The charged matter was then heated under nitrogen to reflux (about 125C.). ~fte~.
reflux had begun, an additional 1063.0 grams of the above ~eed mixture and 12~0 grams of alpha, alpha~-azobisCisobutyronitrile3 were added to the reactor over a period of 3 hours~ Following this addition~ a total ~: oP 5.1 grams of tertiar~ butyl perbenzoate and 22.5 grams of ethyl Cello-sol~e were added to the reactor in 3 e~ual increments (i.e~, 1 7 grams oP.tertlar~ butyl perbenzoate and 7~5 g~a~s o~ ethyl Cellosolve) over : a period o~ about 5 hours with.the ~ir~ two increments being added at 1~5 hour intervals~ At ~h~ end o~ ~his pe~iod, the reactor ~as cooled ~ ;
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. 17 .. .. ..

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~i7;~232 to room temperature~ After approximately one hour~ the reaction mixture was heated to approximately 96PC. and 39.9 grams of dimethylethanolamine was added to the re~ctor~ A~ter ~his addition, heating was continued until a temperature of 108C~ was attRine~ and then 12sO grams of one percent Triton X-100 a non~ionic7 alk~rylethoxyethanol sur~actant, was added to the reactor~ ~ollo~ng the addition of the surfactant? 1845.0 grams of deionized water ~as added to the reaction m-ixture. `
The resultant amide interpoly~er dispersion had a total solids content of 34.7 perce~t, an acid val~e o~ 15~7 and a viscosity of 1850 centipoises~ The aqueous medium consi~ted of 86~3 percent water and 13.7 percent organic solvents EXA~PLE B

This example illustrates an alternat~ve procedure for preparing an aqueous dispersion of amide type interpolymer in which a polyether ~olyol component is utilized as a portion of the polymeri~ation medium.
To a reactor e~uipped with ref-l~x condenser, heating means, stirrer, thermometer and nitrogen lnlet was charged 300~9 gra~s of a 100 percent solids sucrose polyether polyol (formed by reacting l.O mole of sucrose and 20,5 moles of propylene oxide) ha~ing a viscosity of about 6,500 centipoises and an OH value of 325; 137.3 grams of diethylene glycol monomethyl ether Chereinafter DEG~E~; 345 00 grams of a feed mixture (hereinafter referred to fo~ convenlence RS ~eed A~') containing, on a monomer solids basis, 58,6 percent styrene~ 15.0 percent methyl methacry~
late, 6~7 percent acrylic ac~d, 19~7 percent ~(butoxymethyl)acryla~ide?

3~0 percent tert~ary~dodec~l ~ercàptan and 1~0 percent alpha~ alpha~
azobis(lsobutyronitr~le~i and 6~Q gra~s o~ a ~eed mixture ~hereinafter .
~ 7~a~i/~ ~rk ~ 18 _ ~972~:32 referred to for convenience as ~eed B~t~ containing 25 percent 2-acryl-amido~2-methyl propane sulfonic acld, 62.5 percent deionized water, and 12~5 percen~ dimetbylethanola~ine~ The mixture was heated under nitro-gen to about 105C., at which time an exotherm was observed. Heating and nitrogen flow were then suspanded during the period of exotherm After conclusion of the exot~erm, heating under nitrogen was resumed and the mixture was heated to about 130C. ~t this point, an additional 1049~0 grams of feed A and 18~0 grams of feed B were added to the reactor over a period of about 3 hours~ ~hen this addition was completed, a total of 5.1 grams of tertiary butyl perbenzoate and l5~0 grams of DEGMME were added to the reactor in 3 equal increments ~i.e~ 7 grams of tertiary butyl perbenzoate and 5.0 grams of DEGMME) over a period of about 5 hours with the first and second increments being added at 1~5 hour intervals.
Following this addition 46.Q grams o~ dimethylethanolamine were added to the reactor. Then the reaction ~ixture was cooled to 75VC. and 2442 grams of deionized water were added to the reactor. The reaction product was then cooled and filtered.
The resultant amide interpolymer-sucrose polyether polyol dispersion had a total sollds content o~ 34,1 percent, a viscosi~y of 1860 centipoises and an acid value of 13~ The aqueous medium consisted of 87.6 percent water and 12~6 percent organic solyents~

-.
EXA~PLES 1~2 These examples illustrate the e~fect of the pol~ol com~
ponent on the water-popping and solvent popping characteristics of water-based coating compositions. ~n ~hese examples a control coating composition (Example 1~ was ~irst for~lated ~rom the Inte~polymer dispersion o ~xample A.
Then a test composition was prepared by~adding a polyether pol~ol to a sample of the control composltion~

, .. . . .. . . . . . .
!- ... , : . : : , :. - . : . . . . : . ~

'1~7ZZ3~

The cont~ol and test compositions were prepared utilizing standard paint mixing techni~ues. Composition formulations and properties were as follows;

.
: Ra~ts by Weight Example No. 1 Example No. 2 (Control) Ingredients ~nterpolymer dispersion of ~xample.~ 146~5 109~0 Pigment Paste (a) 113.0 113.0 Sucrose polyether polyol (b~ 37.5 Total 259~5 259.5 In~erpolymer/polyol binder ~atio 100/0 50/50 Total solids (percent) ~ . 56~5 56.5 Viscosity (seconds) #4 Ford C~p 18 18 -( ~A pigment paste consisting of 66~7 percent titanium dioxide, 25~9 percent water~ 1.8 percent ethylene glycol, 3.2 percent Triton X~].00 alkarylethoxyethanol surfactant, 0.3 percent NOPCO 3MY, an antifoaming agent available from Nopco Chemical Company and 0.1 ~ ~ercent Tamol 731, a pigment wetting agent available : ~rom Rohm & Haas Company~

(b~A 100 percent soIids sucrose polyether polyol, having a viscosit~ of 6500 centipoises and a : : hydroxyl value of 325, formed by-reacting 1.0 mole of sucrose with 20,5 moles of propylene : : oxide~
' ~ he above compositlons were evaluated for sagging characteristlcs by sprar appl~.ing samples t~e~eof onto.~e~ical steel panels at a film : ~hickness of 1.2 mils~ In evaluatlng the compositions utilizing this test,:the control compoistion, Example 1, sagged badly, virtuallY
running off the panel w~ereas th~.~est composi~ion~ Example 2~.showed nQ ~ag8ing ~

~ ~a~k ~ 20 -.

~637;2Z3Z

~XA~RLES 3~5 These examples illustrate the effect of the polyol and aldehyde condensation resln co~ponents on the water-popping and solvent popping characteristics o~ water-based coating compositions. In these examples a control coating composition (Example 3) was first formulated ~rom the interpolymer dispersion o Example A. Then test compositions were prepared by adding a polyether polyol and an aldehyde condensation resin (in these examples an a~inoplast resin~ to samples o~ the control composition.
The control and test compoai~ions were prepared utilizing standard palnt mixing techni~ues~ Composition formulations and proper-ties were as follows:
Parts by ~ei~h~t - ~ X A M P L~E~ N 0.

(Control) Ingredients Interpolymer dispersion of Example A 146~5 97~4 86.5 Pigment paste (a) 113~0 113.0 113.0 Sucrose polyether polyol (b~ 33.8 30.0 Hexa(methoxymethyl)melamine --- 7.5 15~0 ; Total 259.5 251.7 244.5 Interpolymer/polyol/amino~ -plast binder ratio100[QlO 45/45/10 40/40/20 Total solids (percent) 56~5 58,0 59.5 Viscosity (seconds~
#4 Ford Cup 18 19 20 ; (a)A pigment paste consisting of 66~7 percent titanium dioxide, 25.9 percent wate~ 3~8 pe~cent ethylene glycol, 3~2 percent Triton~X~00 alk~la~lethoxye~hanol surfactant~ 0.3 percent NOPCO 3MY,~an antifoa~ing agent a~ailable from ~opco Chemical Company and 0.1 percent Tamol~731, a pigmen~ wetting agent a~ailable from ~o~m ~ Haas Company.

~ 21 -.. . ~ . . . . . .
., , , ' .

~ 7Z232 ( ~A 100 percent solids sucrose polyether polyol having a viscosity of 6500 centipoises and a hydroxyl value of 325 formed by reacting 1~0 ~ole of sucrose with 20.5 moles of propylene oxide~

The above compositions were eyaluated for sagging character- -istics by spray applying sa~ples thereof onto vertical steel panels at a film thickness of 1~2 mils~ ~n evaluating the compositions utilizing this test, the control composition ci~e.~ Example 3) sagged badly, vir-tually running of the panel whereas the test compositions (i.e., Examples

4~5) showed no sagging~ -The compositions ~ere evaluated for solvent or water popping by spray applying at 8~F~ and 50 percent relati~e humidity samples of the compositions on steel panels~ allowing a 5 minute flash period and then baking the panels in an o~en ~or 10 minutes at 300F~ Popping char~cteristics were measured by determinlng the dry film thickness which could be obtained without popping~ Using this test, the control composition Ci~e., Example 3) could.be sprayed to obtain a dry film thickness of 1.6 mils before popping was observed while the test compo-sitions could be sprayed ~o obtain a dry ~ilm thickness of 2.2 mils without popping.

: This example illustrates the effect of the polyether polyol : and aldehyde condensation ~e~in component on solvent popping and other properties of a coating compositlon ~ormulated from the interpolymer~polyether ; polyol dispersion of Exa~pl~ B~ The composition was prepared by blending the interpoly~er~polyethe~ pol~ol d~spers~on of Example B with an aldehyde condensation resin and other deslxed addit~es utlli~ing conventional paint mixing procedure~ The composi`tion h~d the following formulation and properties:

~L~7~3Z

In~redients Parts by Weight Interpolymex dispersion o~ ~xa~ple B 425.40 Pigment paste (a~ 570.10 Sucrose Polyether polyol of Examples 4~5 56~70 He~a~methoxymethyl)melamine 28.40 Total 1080~60 Interpolymer/polyol/am1noplas~ binder ratio 70/20/lO
Total solids (%) 52~4 Spray viscosity (seconds) ~ #4 ~ord Cup 20 The above composit~on was spray applied to steel panels and cured 20 minutes at 325F. The resultant film was evaluated ~or various properties with results shown in the Table~

T ~ B L E
.
Pencil Hardness 411-5H
Impace (in lb~) ~
Direct 50 Reverse lO
Initlal Gloss R~ T~ Water Immersion (Hours2 500 . . .
Humidity Resistance~(120~ 500 : Salt spray 5% NaCl (Hour6~ . ' 336 Solvent or Water Popping ~ 5 mlnute ~lash (Dr~ ~ilm thickness ~thout pop~ing). . ~3 mils .~ , , ,;

~ 23 :, , , . . . . : .
: , . .

~L~7~23Z

As the above exa~ples illustrate, the incorporation of the polyol and aldehyde condensation resin components in the binder of the compositions of the invention dramatlcally improves resistance to water-popping, solvent-popping, and sagging permïtting the application of thicker films and also provides films having excellent water, humidity, and salt spray resistance.
Similar results to those shown in the examples may be obtained by using other interpolymers of the type described in the specification in place of those utilized in the examples~ Thus? for example, an inter-polymer derived from N~(butoxymeth~l~meth~cr~lamide, methacrylic acid, acrylonltrile, butyl methacrylate, and ethyl acrylate may be utilized.
~dditionally, various other ~ater-soluble or water-dispersible polyether or polyester polyols of the type described may be substituted for the sucrose polyether polyol utilized in the examples. For example, a poly~
caprolactone polyol having a moleculaF weight of about 530 formed by reacting 1~0 moles of diethylene glycol with 3~7 moles of epsilon-capro~
lactone may be employed. Further, various other aldehyde condensation resins and mixtures of such reslns of the type described may be substituted for the hexa(methoxymethyl)melamine utilized ln the examples. For example a mixture of a methylolated melamine formaldehyde resin and a methylol phenol ether may be utllized.
According to the provisions o~ the patent statute~ there are described above the invention and what ~e noW considered to be its best embodime~ts~ Howevex, it is to ~e unders~ood that wi~hin the scope of the appended claims the invent~on may~be p~acticed othe~wise th~n specifically described~

~ 24 .

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A water-based coating composition having reduced solvent popping, water-popping and sagging characteristics com-prising a thermosetting, film-forming organic binder dispersed in an aqueous medium containing at least 60 percent by weight of water, said organic binder consisting essentially of:
A. an interpolymer consisting essentially of the interpolymerization product of:
(1) from about 10 percent to about 40 percent by weight of an N-alkoxyalkyl-substituted amide represented by the structure:

, wherein R' is an aliphatic hydrocarbon radical containing from 2 to 6 carbon atoms and having a single terminal polymerizable alpha, beta-ethylenically unsaturated group and R is a lower alkyl radical containing from 1 to 8 carbon atoms, (2) from about 5 to about 20 percent by weight of an alpha, beta-ethylenically unsaturated carboxylic acid, and (3) at least one other ethylenically unsaturated monomer containing a group, wherein said interpolymer is rendered water-soluble or water-dispersible by neutralizing at least a portion of the carboxylic acid groups thereof with a base; and B. from about 5 percent to about 50 percent by weight of binder solids of a water-soluble or water-dispersible polyether polyol or polyester polyol having a molecular weight of at least 300.

2. The water-based coating composition of Claim 1 wherein the N-alkoxyalkyl-substituted amide is N-(butoxymethyl)acrylamide or N-(butoxymethyl)methacrylamide.

3. The water-based coating composition of Claim 1 wherein said alpha, beta-ethylenically unsaturated carboxylic acid is acrylic acid or methacrylic acid.

4. The water-based coating composition of Claim 1 wherein the other monomer containing a group is a mixture of hardening and flexibilizing monomers.

5. The water-based coating composition of Claim 4 wherein the hardening monomer is of styrene, vinyl toluene or an alkyl methacrylate having from 1 to 4 carbon atoms.

6. The water-based coating composition of Claim 4 wherein the flexibilizing monomer is an alkyl ester of acrylic acid or an alkyl ester of methacrylic acid, and wherein the alkyl groups have from 1 to 13 carbon atoms in the case of acrylic esters and from 5 to 16 carbon atoms in the case of methacrylic esters.

7. The water-based coating composition of Claim 1 wherein said base is a monomeric amine.

8. The water-based coating composition of Claim 1 wherein said base is dimethylethanolamine.

9. The water-based coating composition of Claim 1 wherein said polyether polyol is a sucrose polyether polyol.

10. The water-based coating composition of Claim l wherein said polyester polyol is a polycaprolactone polyol.

11. The water-based coating composition of Claim 1 wherein said organic binder further contains an aldehyde condensation resin.

12. The water-based coating composition of Claim 11 wherein said aldehyde condensation resin is hexa(methoxymethyl)melamine.

13. The water-based coating composition of Claim 11 wherein said aldehyde condensation resin is a methylolphenol ether having the structure:

wherein n is an integer of from 1 to 3 and R is an unsaturated aliphatic group or a halogen-substituted unsaturated aliphatic group,

14. The water-based coating composition of Claim 11 wherein said aldehyde condensation resin comprises a mixture of a methylolated melamine formaldehyde resin and a methylol phenol ether.