CA1287940C - Aqueous polymer compositions containing surface- active evaporation suppressants - Google Patents

Abstract

AQUEOUS POLYMER COMPOSITIONS CONTAINING
SURFACE-ACTIVE EVAPORATION SUPPRESSANTS

ABSTRACT

Low levels of surface-active, aliphatic C16 or greater hydrocarbon-type compounds are used to reduce the rate of evaporation of water from waterborne polymer products such as latex coatings. This increases the wet-edge or open time of the freshly applied coating, improves integrity and adhesion of the dried coating, and reduces skin formation in containers and on application equipment.

Description

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BACKGROUND OF THE INVENTION
Water-containing polymeric product~ ~uch as waterborne paint~, ~talns, adhe~lves, prlntlng lnks and coatlngs ~lnd lncreaslng utlllty because Or thelr ~qarety, economy and ease of applicatlon. However, the drying characterlqtlcq of ~uch products are varlable and cannot be easlly controlled, because they are baslcally llmlted to the evaporation characterlstlc3 o~
water. Thu , the drying behavior of aqusous polymer products ls hi~hly ~ependent on the conditions of temperature, humidlty and alr velocity. For example, coatlng ~ilms o~ such products can dry practlcally lnstantaneously under hot, dry, wlndy condltions leadln~ to poor lappln~ characterlstic~. F~urther, such ~0 drylng condl~lons tend to ~palr thé quallty of fllm ~ormatlon, penetratlon o~ and adhe~ion to the sub~trate.
Polymeric composltlon borne ln organio solvents are dlfferent from the waterborne product~, in that solvent~ or solvent blends wlth a wlde range Or boiling polnt~ and volatlllty can be used to control the drying characterl~tlcs accordlng to appllcation requlrementq. For example, consumer paint~ employing alkyd re in3 are made wlth hydrocarbon ~olvents o~

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volatility selected such that the drying rate is sufflcient to allow setting of the film to minlmize sagging, running, and dust pickup, yet which permits good "melting in" of paint at overlapping brush or roller strokes. The disadvantages of such organic solvent based compositions are the difficulties of clean-up, the toxic nature of organic solvents, environmental pollution, and the relatively high cost of organic solvents which are ultimately wasted.
The conventional practice ln solving the drying rate problems of water-based compositions is to add substantial levels of water soluble solvents to such systems to increase the wet-edge or open time. These techniques are dlscussed by M. D~ Andrews, "Influence of Ethylene and Propylene Glycols on Drylng Characteristics of Latex Palnt~," Journal of Paint Technology, vol. 46, page 40 (1974); D. A. Sullivan, "Water and Solvent Evaporation from Latex and Latex Paint Films," Journal of Paint Technology, vol. 479 ~0 page 60 (1975); and C. R. Martens, Waterborne Coatings, Van Nostrand Reinhold, page 153 (1981). These references disclose the use of short chain water-soluble alcohols and glycols as cosolvents for water-based coatlngs to improve freeze-thaw stability, ald ~5 coalescence of the latex partlcles, improve leveling, etc., in addition to prolonging wet-edge or open tlme. To obtain significant lmprovement in wet-edge or open time, hl~h levels of these low molecular weight cosolvents are required, often 10 to 20 percent or more 3~ based on total volatile content, since they are belleved to function slmply by belng completely soluble ln water; thus reduclng the vapor pressure of water.
These cosolvents exhlblt low surface actlvity, and the use of high levels tend to negate the intrinslc advantages of the water-based composltions.
The use of evaporation retarders on the surface of 2 2~379 reservoirs to control water evaporatlon i~ known in the art. The evaporation retarders are typlcally aliphatlc alcohols and ether alcohols containlng 16 to 30 carbon~, ~uch as described ln U.S. Patent No. 3,146,059 and Indlan Patent No. 70,670 The use Or the~e long chaln alcohols as surface monolayers on water 18 further dlscu~sed by E. R. Noe and R. G. Dressler, "Per~ormance of Odd and Even-Chain Pure Alcohol Monolayer~ in W~ter E~aporation Retardatlon," I & EC
Product Research and Development, vol. 6, page 132 (1967) and in other literature. Although these long chain alcohols and ether alcohol~ have been erfective on relatlvely pure water due to their surface actlvity, thelr utility ln multi-component, water-based polymerlc composltions had not prevlously been recognlzed or dlscovered.
U.S. Patent No. 2,965,678 dlsclo3es the use of branched-chaln alcohols a~ wetting agents and detergent~. However there ls no teachlng or suggestlon that unbranched-chaln compounds are effectlve for water evaporatlon retardation ln aqueous polymer composltlons.
U.S. Patent No. 3,287,300 teaches the use of allphatic carboxylic aeids ln polyvlnyl ester emulslons to lower the coalescence temperature. The '300 patent teaches nothlng about evaporatlon suppresslon and the lmportance of uslng C16-C24 allphatic straight-chain compounds to reduce water evaporatlon from polymer composltlon~.
U.S. Patent No. 3~3~23 di~close~ cleanlng and pollshln~ ~omp~u~ds w~ic~ are e~ul~on~ of natural and synthetlc waxes and resins, and whlch contaln very large quantitles (l.e. 40-50%) o~ volatlle organlc solvent. Moreover, the emulsiflers disclosed ln the '123 patent would not be effective as evaporatlon suppressants because they are rererred to as belng 75~

highly branched, havlng a relatlvely low number of carbon atom (i.e. 12-1~), or havlng a high number o~
oxyethylene unlts.
U.S. Patent No. 3,847,855 di~closes a latex polymerlzation proce~ which uses a volatlle surfactant for the polymerlzatlon. The '855 patent teaches nothing about evaporatlon suppres~ion, and there iR no teaching or suggestlon that any of the dlverse surfacta~ mentioned would be effective ln retarding evaporation o~ water~ ~at~er, the ~ugltive surfactants descrlbed ln the '855 patent are u~éd a~ an lngredlent durlng the polymerlzation proce~s.
U.S. Patent No. 3,988,275 dlsclose~ a polymerizatlon proces~ for maklng concentrated latex of synthetic rubbers uslng emul~i~ying agent~ ~uch as fatty acids. Methods to achleve ~uppresslon of evaporatlon rate of water from the latex rormulatlons are not taught or lmplied. The emulsi~lers dlsclosed ln the '275 patent are generally not suitable for evaporation suppres~lon because they are generally too asymmetrical~and of relatlvely Ahort chaln length.
U.S. Patent NoO 4,131,585 dlsclo~e~ pla~tlcizer-type levellng agents for floor poll~h emulslon~. The levellng agents are requlred to contaln elther non-llnear alkyl or alkyl~en$ene hydrocarbon group~, and would therefore not be ~uitable evapor~tlon ~uppressant~ be~au~e they do not form compact ~urPace film~ to ~etard wa~e~ evaporation. Moreo~er, they are required to contaln 15 ~ les~ carbon atom~ ln the alkyl chaln. The '585 patent speclflcally teaches agalnst the ~Re of llnear alcohol derlvatlve~.
UOS. Patent No. 4,330,338 dl~clo~es emulslon~ ln water of reslns dlssolved in organlc Rolvent for u~e a~
pharmaceutlcal coating composltlon~. The '338 patent teaches ~r suggests nothlng regarding the selection of surfactants except ~hat they are to assi~t ln produclng .

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a qtable emulsion. Nothlng ls taught or ~ugge~ted concernlng thelr sur~ace actlvlty or effect on water evaporation. The fatty alcohol ethoxylates disclo~ed as emulslfiers have only lauryl (12 carbon atoms) hydrophobes, and generally have too ex¢es~lve a degree of ethoxylatinn for use as efrective evaporatlon ~uppressants.
U.S. Patent No. 4,454,26~ discloses suspen~ions of water-soluble polymer~ ln organic solvent and the use o~ surfactant~q therefor. Such materlalQ are then later dissolved ln water to make a polymer solutlon for oil recovery fro~ well~. The '260 patent ls tot~lly unrelated to the u~e Or long stralght-chain allphatic compound~ for reductlon ln evaporation rate of water from waterborne polymer composltlons. Rather the '260 patent teache~ the use of alkali or alkallne-earth metal salt~ of fatty acids as thlckeners for the suspenslons of water-soluble polymers ln organlc ~olvent.
2~ Appllcants have ~urprl~lngly dlscovered that low levels o~ surface actlve, long chaln, aliphatlc hydrocarbon-type compounds can be used to control and improve the drylng characterlstlcs of aqueous-ba~ed polymer composltlons. These long chaln aliphatlc 2~ compounds sre effectlve a~ evaporatlon suppre~slng agents at leYe~s as low as 1% by weigh~ or less. Their ef~ectlveness ls belleved to be attributed to their abillty t~ become hlgh~ aon~entrated and compactly ordered at the alr/~a~er in~errace~ ~Yen when lnltlally uniformly mlxed lnto the aqueous-based polymer compositlons.
It 1~ the obJect o~ thls lnventlon to provlde a method ~or reducing the evaporatlon rate o~ water rrom aqueous polymer compo~itlons u~ing low levels of ~ur~ace active, long chaln, unbranched allphatlc compound~. It i~ also an obJect of this lnventlon to extend the wet-edge or open time of aqueous-based coatings and the like when applied to a substrate. It is a further ob~ect of the lnvention to reduce skinning of waterborne polymer compositions in contalners, and to retard drying out on application equipment such as rollers and brushes. It is an even further ob~ect of the present invention to improve the quality of film formation/adhesion of aqueous polymerlc coatings by incorporating therein low levels of surface active evaporation suppressants.
SUMMARY OF THE INVENTION
This invention relates to a method for reducing the rate of evaporation of water from waterborne polymer products, by incorporating therein low levels of surface-active allphatic C16 or greater hydrocarbon-type compounds. The invention also relates to aqueous polymer compositions containlng these Cl6 or greater surface-active evaporation suppressants. Useful surface-active, aliphatic evaporatlon-suppressing agents for the invention include hydrocarbon-type compounds consi~ting of a saturated, unbranched carbon-carbon chain length of about 16 atoms or greater and contalnlng one or more hydrophilic groups. The evaporation ~uppressing agents can be unlformly ~S incorporated into aqueou~ polymer compositions preferably at levels of about 1% or less by weight.
The evaporation ~uppressant~ preferably include the long, straight-chain alcohol~, ether alcohols, and salt~ of carboxylic acids.
~he evaporatlon suppressant are effective in extending the wet-edge or open time of waterborne polymer coatings to allow good meldlng or melting-in of the coating at overlapplng brush or roller strokes.
The evaporation suppressant are also ef~ective in retarding skinnlng of waterborne polymer~ in containers, reducing drying out on application ."' ,,, ' ....
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DETAILED DESCRIPTION
This invention involves a novel method for reducing the evaporation rate of water from waterborne polymer products, and involves novel aqueous polymer compositions containing low levels of surface-active, aliphatic C16 or greater evaporation-suppress~ng agents. The use of low concentrations of these long-chain aliphatlc evaporation suppressants in waterborne polymerlc products, such as latex coatlng, increases the wet-edge or open time of the coating, improves film ~ormation/adhesion, and reduces skinning.
The evaporation suppressing agents useful in practicing this inventlon include sur~ace-active aliphatic compounds havlng a saturated, unbranched carbon-carbon chain length of about 16 atoms or greater, and containing one or more hydrophillc groups. Particularly useful evaporation suppressants include, for example, stralght chain alcohols, ether alcohols, carboxylic acids and salts thereof. The evaporation suppressants have the structural formulae:
CH3(aH2)m(OcH2lH)n[o~cH2)y]zoH or ~5 CH3(CH2)m_lCOOR or CH3(cH2)mocH2cH(oH)cH2oH

whereln m is an lnteger from about 15 to about 25; n is an integer from 0 to about 3; y is an integer from 1 to about 4; z ls an integer ~rom 0 to about 3; X i8 -H or -CH3; R is -H, -NH4, amine or alkali metal salt; and the sum of n and z does not exceed 3. Preferably m ls 18 to 24, n ls 0 to 2, y is 2 to 4, z is 0 to 2, R is amlne or alkali metal salt, and the sum of n and z does ... .

.~87 not exceed 2. More preferably i) m is 20 to 24, n 1S
O, y is 2 or 3, and æ i9 0 or 1, or ii) n i8 1 or 2 and z is 0. Most preferably n i8 O, y iS 2, and z is O
or 1. The evaporation suppressants preferably contain hydrophilic groups selected from -OH, salts of -COOH, -OCH2~H(OH)CH20H, and -(OCH2CH)n[O(CH2)y]zOH

wherein X, n, y and z are as defined above. Other diver3e hydrophilic groups are believed to be suitable l for this invention, such as, for example, sulfates, sulfonates, amines, amine oxides, amides, phosphates, and phosphonates.
Some examples of suitable evaporation suppressants for practlcing this invention are hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol and related ether alcohols and carboxylic acids. The most preferred evaporation suppressant for use ln this invention is l-eicosanol CCH3(CH2)18CH2OH].
The evaporation suppressants are preferably 2~ uniformly incorporated into the waterborne polymer compositions. They can be added to the compositlon by a variety Or methods, such as, as a dilute solution in organic solvent, as a fine powder, as a molten liquid, and as an emulsion in water. The evaporation suppressants may be mixed or blended into the polymer compositions using any techniques known in the art. To be useful for this invention, the evaporation suppressants themselves must be solid at standard conditions, although they may be added as a solution or molten liquld as mentioned above.
The lnventlon is practiced using relatively low levels of the evaporation suppressants ln the polymeric compositions. Thls allows control of drylng characteristics, as with solvent-based systems, but retains all the advantages of aqueous based compositlons. The specific concentration of :.
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evaporatlon suppresAant3 wlll depend on the specl~lc compound u~ed, the Apeciflc polymerlc ~ormulatlon, and appllcatlon needs. Effectlve concentratlons o~
evaporatlon suppressant are generally les~ than 5% by welght based on the total wel~ht of the polymer composltions, and preferably the concentration is about 1% by weight or less. Either one or a mlxture of evaporatlon suppre~sants may be used in carrying out the lnventlon.
A pre~eP~ed embodlment is to add the evaporatlon suppressant~ to the aqueous polymerlc compositions as a pre-emulsion in water. More preferably the pre-emulslon of ~uppres~ants ln water contaln~ an auxiliary surfactant to ald ln stabllizlng the emulsion. It is lmportant to select an emul~lfler which does not lnterfere with the sur~ace barrier properties or surface actlvlty of the ~uppressants;
wlth ~alts o~ aliphatic long chaln carboxyllc aclds belng pre~erred. The evaporatlon suppressant~ may also be added as a ~olutlon in a suitable organlc solvent.
The effectlveness of the evaporatlon suppres~ants in aqueous polymer composltlonA ls believed to be attributed to thelr abillty to form hlghly compact and dense monolayers at ~he alr/water lnterface. It ls ~5 speculated that th~ hydrocarbon portlon o~ the molecule 1~ orlented toward the air, w~ile ~he ~ydrophilic groups are ~n khe surf~ce reglon Or the water.
Surprisingly, the e~p~ratlon suppres~ants can exhlblt good Rurface activlty even ln the presence of the multiple components and other competing surface actlve lngredlents ln the polymer composltlons, and even when unlformly mlxed thereln. The evaporation suppressant~
that are useful ln forming the arorementloned compact and dense monolayers appear to be those that are solld~
by them~elves at ~tandard conditions.
The evaporatlon suppressants are useful ln .~ ' .. . , . . -.. , , ~ -' ' i~
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controlllng the drylng characterlstlcs of a varlety of aqueous polymer compo~ltions, ~uch as palntsJ ~talns, varnlshes, coatings, adheslves, an~ ink~. These aqueous polymer compo~itlons lnclude, for example, S polymeric latexe~, solutlon polymer~, and colloldal dlspersion~, ~uch as descrlbed by C0 R. Martens, Waterborne C~atin~ , Van Nostrand Reinhold, page~ 41-51 (1981). The ~uppressants are p~rtlcularly sultable for use in acrylic latex type compo~ltions such as de3cribed in U.S. Patent Nos. 4,129,448; 4,102,843; and 3,736,286. In a preferred embodLment o~ the lnventlon, the polymerlc composltlon i8 an aqueous dlspersion of a vlnyl or acryllc emulslon, such a~ thoqe used in maklng water-based paints, stalns, adhesive~ and varnishes.
Suitable aqueous polymer compo~ltlons ~or paint~
are aqueous addltlon polymer dlsperslon~, generally obtained ~ost convenlently by dlrect emul~ion polymerlzstlon. Also sultable aqueous polymer compo~itions lnclude aqueous ~olution polymer~, emulsions of resln ln water, and colloidal disperslons. The most lmportant of these di~per~ion~
used in ~aking w~te~-ba~ed paints are polymers including homopolymers and copolymers o~: (l) vlnyl ~5 e~ters of an allphatlc acld havlng l to 18 carbon ato~s, e~pecl~lLy ~Inyl acetate; (2) acrylic acld esters and methacryllc acid ~ter~ of an alcohol having l to 18 carbon atoms, e~peclally methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate; and (3) mono- and dl-ethylenlcally unsaturated hydrocarbons, quch a~ ethylene, lsobutylene, styrene, and allphatlc dlenes, such a~
butadl ene9 i 30pr ene, and chloroprene.
Poly(vinyl acetate) and copolymers oP vlnyl ,. ...
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~ 9~0 acetate ~ith one or more of the following monomers;
vlnyl chloride, vinylldene chloride, styrene, vinyltoluene, acrylonitrile, methacrylonitrile, one or two o~ the acrylic and methacrylic acid esters mentioned above are well known a~ the film-forming component of aqueous-based paints. Similarly copolymers of one or more of the acrylic or methacrylic acid esters mentioned above with one or more of the following monomers: vinyl acetate, vinyl chloride, vinylidene chloride, ~tyrene, vlnyltoluene, acrylonitrile, and methacrylonitrile are also more or less conventlonally employed in aqueous base paints.
Homopolymers of ethylene, i~obutylene, and styrene, and copolymer~ of one or more of these hydrocarbons with one or more esters, nitriles or amide~ of acrylic acld or of methacrylic acid or with vinyl esters, such as vinyl acetate and vinyl chloride, or with vinylidene chloride are also used. The dlene polymers are generally used in aqueous base paints in the form of 2~ copolymer~ with one or more monomers following:
styrene, vinyltolueneg acrylonitrlle, methacrylonitrile3 and the abovementioned esters of acryllc acid or methacrylic acid. It is al~o quite common to include a small amount, such a~ l/2 to 2.5%
~5 or more, of an acid monomer in the monomer mlxture u~ed for making the copolymers for all three general type~
mentioned above by emul~lon polymerization. Aclds used include acrylic, methacrylic, itaconlc, aconitic, citraconic, crotonic, maleic~ fumaric3 the dimer o~
acrylic acid, and so on.
These aqueous dispersions as the emul~ion polymer in the paint may be made using one or more emulslfier~
of anionic, cationic, or non-ionic type. Mixtures of two or more emulslfier~ regardles~ of type may be used, except that it is generally undesirable to mix a cationic with an anionlc type in any appreciable "

amounts ~ln¢e they tend to neutrallze ea¢h other. The average particle slze or diameter of the3e dispersed polymers may be rrom about 0.03 to 3 micron~ or even larger. ~he partlcle size, whenever referred to hereln, iq the "welght average dlameter." Thlq number, expressed ln mlcrons, ¢an be determined by electron mi¢roscopy. In general~ the molecular welghts Or these emulAlon polymers are hlgh, e.g., from about 100,000 to 10 milllon vi~cosity average, most commonly above 500,000.
In ~eneral, a gallon o~ emulslon palnt ~s Gomprl~d o~ about 0.5 to 3 lbs. of film-~ormlng resin and about 0.2 to about 5 lbs. o~ rlnely-dlvided pigment. ~yplcal plgment~ are titanium dloxide and other titanium pigment~, whlte lead, zlnc oxlde, zlnc sul~ide, barium sul~ate, calclum carbonateJ llthopone, slllca, talc, mica, clays, lron oxide, carbon black3 cadmlum sulrlde, toluidine red, chrome orange, chrome yellow, chrome green, and otherq known in the art.
Typlcal latlces o~ ~llm~formlng reslns are those Or the alkyl acrylates and methacrylates, vlnyl acetate, styrene-butadlene~ and others known in the art. Mlnor amount~ of oth~r coatlngs addl~lves may be lnoluded ln the palnt formulatlons, ~or example, antl-foa~s~
mlldew¢ldes, thlckener~, wetting agents, ba¢terlostats, etc. ~he present inventlon i~ also useful ln clear unpigmented latex coatlngs, stains and varnishes.
The ~ollowin~ ~xamples are presented to rurther illustrate thls lnvention, but are not intended in a limltative sense.
EXAMP~ES I - VIII
Varlous long chaln aliphatlc hydro¢arbon-type compounds were evaluated as evaporation ~uppre~sant~ ln both a latex and a ~ormulated latex coating. The latex was an aqueous emulslon o~ qynthetic acrylic polymer havlng a 45% by welght ~ollds content which ls sold by .

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' ,.''' , _J - 13 -Rohm and Haa~ Company a~"Emul~lon E 1630" The ~ormulated latex coatlng was prepared uslng ~he same a¢rylic emulslon accordlng to the following reclpe:
Amount In~redient(parts by we lght ) Acryll¢ latex (3-1630) 600 Wettlng agent 2.0 Antlroamer 2.5 Coalescent 40.0 Thickener 24.8 Neutralizing Ba~e 6.4 Water 170.8 25 gram ~amples o~ each Or the unrormulated and formulat~d latex ~oating were placed ln 9 cm diameter dlshe~ and to each was added dropwise 1 ~ram o~ a 0,2%
by weight ~olution of various hydrocarbon compounds in hexane to be tested as evaporatlon retarders. A~ter rlashln~ of r the hexane, weight 108s rrom eaoh ~ample due to water evaporation was measured and ¢ompared with control ~amples contalning no evaporation s~uppre ~ants. The results are expre~ed as the percent reductlon in evaporatlon and are presented in Table I.

TABL~ I
% Reduction ~5 in Evaporatlon Rate (25C) Evaporatlon Fornulated Sup~ressant tex Control None 0 0 E~ample I CH3(CH2)1~H 28 13 Example II CH3(CH2)17H 23 13 E~le III CH3(CH2)19OH 72 60 E~le IV CH3(CH2)21H 17 E~le V CH3(CH2)17(0CH2CH2)20H 19 10 E~le Vl CH3~H~)210CH2CH2H 58 30 Example VII Olelc Aald 0 E~le VIII Stearic Acld 17%

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2~7 EXAMPLES IX - XI
Addltlonal compounds were evaluated for thelr effectlvene3s as evaporation ~uppressants followlng the procedure~ o~ Examples I-VIII above, except that 0.1%
by welght solutlons of the hydrocarbons ln hexane were u~ed. The re~ults of this evaluation are glven ln Table II.
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~ Reductlon ln Evaporatlon Rate (25C) EYaporatlon Formulated SuEp~esaant L~tex L~tex , ControlNbne 0 0 CM3(CH2)210CH2cH2cH20H 54 31 Example X CH3(CH2)1~0CN2~(0H)CH~H 25 25 E~le ~CH3(C~2)210CH2CH~OH)CH20H38 25 EXAMPLE XII
l-elco~anol, CH3(CH2)190H, was evaluated as an evaporatlon suppreqsant when unlformly lncorporated lnto a clear lat~x ~oatlng, ~o 31~5~ of acryllc latex (sold by Roh~ and Haa& ~ompany as"Rhoplex AG-61" havin~
a sollds content o~ 46.5% by welght was added wlth stlrrlng 9.Og water and 3.5g of a 2% by welght aqueous ~olutlon of hydroxyethy~ cell~lo~e thickenlng agent.
To thls m~xture ~as then added wlth stlrrlng 100 mg o~
l-elcosanol that had been dls401ved ln 2 grams of methyl ethyl ketone. A control ~ormulation waR
prepared simllarly but uslng 2 grams o~ methyl ethyl ketone wlthout l-elco~anol.
The rates of water evaporatlon of the test and control formulations at 25C and 55S relative humldity were mea3ured gravlmetrlcally. The open tlme of the samples ~a8 measured by brushlng fre~h coatlng at varlous elapsed times perpendlcular to and including * Trade mark ~'', , , ,... , :
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the edge o~ a ca~t fllm of the coatlng. Open time 19 de~lned a~ the time at whlch a dlstlnct boundary line 1~ left at the edge Or the castlng, lndicatlng that drying at lts edge ha3 occurred to 3uch extent ~hat the brushed ~ilm doe~ not ea~lly mlx ln. The re~ults of thl~ evaluatlon are pre~ented on Table III.

T~E III
Coat ~ with Control Coat~ elco~nol Rate of water evaporatlon 0.072 0.037 (mg/mLn.-cm2 ) Open t ~ (mlnutes) 1.0 2.5 EXAMPLE XI I I
l-eicossnol was evaluated as an evaporatlon ~uppres~ant ln a whlte acryllc latex palnt. An emul310n of l-e~co~anol was prepared by firYt dissolvlng at 80C a mixture of 6.0 gram~ l-elco~anol, 1.4g ~tearlc acld, 1.4g of 30% ammonla, and 10g of allphatlc hydrocarbon solvent (~old by Exxon Co. a~
"Nbrpar 13"*~, followed by ~tlrring ln 60g o~ water preheated to 80C, and qulckly coollng the mlxture ln an ice bath. ~hite palnts were ~hen formulated * Trade mark A
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37 ~3~3 accordlng to the following reclpe:

Ingredient ~ ~nt ~P-rts by we ht) Paint containing Control Paint l-eico anol Mix in "C~wles Dissolver":
Water 35.7 35.7 Dlspersant 6.2 6.2 Wetting Agent 1.4 1.4 Antl~oamer 2~0 2.0 Rutile T102 154.0 154.0 Let Down with:
Acryllc Latex (40.9% solid~) 478.1 478.1 Water 302.0 223.0 Thickener 17.5 15.5 AmmDnlum hydroxide (3~%) 7.2 6.8 l-elcosanol emul~lon 0.0 78.8 (volume % sollds) 25 25 Water evaporatlon rates and open tlme of the palnt samples were mea~ured a~ in Example XII, and the re~ults are presented ln ~able IV.
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TAELE IV
Coating with Control_Coatl~ el008anO
R~te o~ water evaporation 0.067 0.038 (mg~mln _cm2) Open-time (minutes) 2 10 * Trade mark ,~

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~7~ato ! ~ 17 , , EXAMPLE XIV
l-elcosanol wa~ evaluated for it~ effectiveness ln reduclng sklnning of a stored latex. 130g allquots of 46.5% by weights ~ollds content acrylic latex ~Rhoplex s AC-61) were charged to 1/2 pint (7 cm diameter) palnt cans. l-eicosanol was added to the above samples uslng variou~ techniques of addltion. The isamples were monltored 6ravimetrically for water 10~9 and examined for degree of sklnnlng over the surface for a 24-hour and a 48-hour perlod. The results of thls evaluatlon are presented ln Table V.

T~E V
l-elcosanol addition We~t Loss Skinni~
24-hr. 48-hr. 24-hr. _8-hr~
1. None 4.3g 8.4g severe severe 2. ~one (~pread 2g hexane 4.0g 8.3g severe severe on surface) 3. Spread 2g Or 0.2% eicosanol 0.5g l.Og none very ln he ~ e on sur~ace slight 4. Spread O.lg of 0.2~ 1.35g 3.4g sli~ht sllght elcosanol in hexane on surface 5. Stlrred in 2g of 1.55g 3.1g slight slight eico~ol~ emulsion prepar~ in E~le XIII

EXAMPLE XV
l-eicosanol wa~ evaluated for lmprovement of film ~ormation/adh~sion in a whlte acryllc latex palnt, Exterior whlte latex palnts were ~ormulated accordlng to the rollowlng reclpe:

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ount (part.q by weight) Palnt with IngredientControl Paint Eicosanol M1X In Cowles Dissolver:
Thickener ~100%) 3.0 3.0 Water 120.0120.0 Dispersant 1.5 1.5 Wetting Agent 2.5 2.5 Anti~o~mer 225.0225.0 Rutile TiO2 25.0 25.0 Zinc Oxide 25.0 25.0 Aluminum Silicate 147.3147.3 Clay 50-0 50-0 Silica Silicate 5.0 5.0 Let Down With:
Acrylic Latex (Rhoplex AC-61) 398.0398.0 Antlfoam~r 3.0 3.0 Coalescent 3.0 3.0 Water 121.2105.2 Thlckener t2.5% a~ueous solution) 64.o 0.0 l-Elcoisanol emulqlon (prepared in 0.0 80.0 Example XIII) Propertle~
Volume % ~olld~ 36 36 ~5 Stormer n sco ity (KU) 77 69 The palnt qamples were brushed at natural spread rate over predried (250F for 30 minutes in an oven) whlte plne lnslde a laboratory hood, and allowed to dry lnslde the hood. The paint film~ were monitored for the rate of drylng and examlned ~or fllm cracking after complete drying. The re~ults of thls evaluation are pre~ented ln Table VI. It can be seen that the palnt containlng l-eicosanol ha~ a longer drylng time whlch , . .

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8794~) gives the acryllc latex particles a longer time to coalesce and adhere to substrate, thus reduclng film cracking.

TABLE VI
Paint wlth Control Paint Eicosanol Drying time (minuteæ) 5 9 Film Cracking Moderate None The above examples demonstrate the e~fectiveness of unbranched, allphatlc long chaln, surface-actlve compounds as evaporation suppressants in aqueous polymer compositionæ to increa~e open time, reduce sklnning, and improve film formation/adhesion.

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Claims (11)

1. A process for reducing the evaporation rate of water from aqueous-based polymer compositions to retard skin formation and to extend wet-edge time comprising uniformly adding to said aqueous-based polymer compositions a low level of one or more surface active, aliphatic evaporation-suppressing agents consisting of a saturated, unbranched carbon-carbon chain length of about 16 to about 24 carbon atoms and containing one or more hydrophilic groups selected from -OH, -OCH2CH(OH)CH2OH, -(OCH2?H)n[O(CH2)y]zOH, and -COOR, wherein X is -H or -CH3; R is amine or alkali metal salt; n is an integer from 0 to 2; y is an integer from 1 to about 4; z is an integer from 0 to 2;
and the sum of n and z does not exceed 2.

2. A process of claim 1 wherein i) n is 0, y is 2 or 3, and z is 0 or 1, or ii) n is 1 or 2 and z is 0.

3. A process of claim 1 wherein n is 0, y is 2, and z is 0 or 1.

4. A process of claim 1 wherein the level of said evaporation-suppressing agents is about 5% by weight or less based on the total weight of the aqueous polymer composition.

5. A process of claim 1 wherein the level of said evaporation-suppressing agents is about 1% by weight or less based on the total weight of the aqueous polymer composition.

6. A process of claim 1 wherein the aqueous polymer composition is selected from the group consisting of acrylic, styrene acrylic, styrene butadiene, and vinyl acetate polymeric latexes.

7. A process of claim 1 wherein the evaporation suppressing agents are added to the aqueous polymer composition as a pre-emulsion in water or as a solution in an organic solvent.

8. A process of claim 7 wherein the pre-emulsion contains an emulsifier.

9. A process of claim 8 wherein the emulsifier is a salt of aliphatic long chain carboxylic acids.

10. A process of claim 1 wherein the evaporation-suppressing agents are selected from the group consisting ofCH3(CH2)15OH, CH3(CH2)17OH, CH3(CH2)19OH
CH3(CH2)21OH, CH3(CH2)17(OCH2CH2)2OH, CH3(CH2)17OCH2CH(OH)CH2OH, CH3(CH2)21OCH2CH2OH, CH3(CH2)21OCH2CH2CH2OH and CH3(CH2)21OCH2CH(OH)CH2OH.

11. A process of claim 10 wherein the evaporation-suppressing agent is CH3(CH2)19OH.