CA2108492A1

CA2108492A1 - Quick-set exterior coatings

Info

Publication number: CA2108492A1
Application number: CA002108492A
Authority: CA
Inventors: Xiaohong Ci
Original assignee: Individual
Current assignee: Rohm and Haas Co
Priority date: 1992-10-23
Filing date: 1993-10-15
Publication date: 1994-04-24
Also published as: MX9306397A; JP3611586B2; TW289764B; JPH06145590A; CN1086237A; KR940009302A; BR9304316A

Abstract

ABSTRACT OF THE DISCLOSURE:

This invention solves the problems encountered with conventional exterior coating compositions by providing an aqueous, exterior, quick-set coating composition having early washout resistance and dirt pick-up resistance. The invention is particularly useful as a binder used in a traffic paint and as a base coat and/or top coat in exterior insulation finishing systems. This invention also provides a method for improving the early washout resistance and dirt pick-up resistance of an aqueous, exterior, quick-set coating.

The aqueous, exterior, quick-set coating composition of this invention requires four components:
(1) a film forming latex polymer having anionic character;
(2) an amine-containing polymer formed from at least 20% by weight monomer containing amine functional groups;
(3) a volatile base; and (4) a water-soluble or water-dispersible multivalent metal.

The method of improving the early washout resistance and dirt pick-up resistance of an aqueous, exterior, quick-set coating involves:
(1) forming an coating composition containing:
(a) an anionically stabilized latex polymer;
(b) an amine-containing polymer;
(c) a volatile base; and (d) a water-soluble or water-dispersible multivalent metal;
and (2) applying the coating to a substrate.

Description

210~92 IMPROVED QUICK-SET EXTERIOR COATINGS

FIELD OF THE INVENTION

This invention relates to aqueous, exterior quick-set coatings which are storage stable, provide early washout and dirt pick-up resistance and long term durability and to a method for improving the early washout and dirt pick-up resistance of aqueous, exterior quick-set coatings.

BACKGROUND OF THE INVENTION

Exterior insulation and finishing systems ("EIFS") are multilayered composite systems installed on the outsides of buildings and other outdoor structures to insulate, protect and beautify. The exterior surface of the building or other outdoor structure may be constructed of concrete, cinder block, stone, brick, wood, gypsum board and the like. A layer of material, typically in the form of a solid or foamed sheet of material such as for example foamed and extruded polystyrene, is applied to the exterior surface of the building or other outdoor structure and is covered with a mesh-reinforced basecoat and then a topcoat. The basecoat provides weather resistance, flexibility, toughness, mechanical strength and impact strength to the system.
The topcoat provides aesthetic features to the surface of the system, such as for example color and texture.

, . I
Contractors typically install EIFS in layers at the job site and as ~;
such their installation efficiency is limited by the time each layer or coating hkes to set or dry. In addition, a quick drying exterior coating is ,..,.. :: -~108~92 , needed so that it develops resistant to dirt pickup and washout b~ rain,snow, wind and the like so after its application. These problems associated with slow drying are exacerbated under certain environmental conditions, particularly cool and wet or humid conditions.

To reduce the cure time of the coatings, formulators have attempted to decrease the level of water in the coating formulation.
However, this leads to coating formulations which are too viscous to -apply.

Quick curing coatings are also needed for traffic paints so that they are not washed out by rain or marked by tire tread soon after application. Solvent-based paints dry quickly but pose serious safety, health and environmental problems. Conventional aqueous-based paints do not dry quickly enough, especially under cold and wet or humid conditions. Attempts to remedy this drying problem have lead to multiple step applications and storage stability problems.

For example, European Patent Application 200,249 discloses applying an aqueous dispersion of polymer to the road and then contacting the composition with a second treatment containing a water soluble salt to cause the coating to dry rapidly and resist washout by a rain shower five m~nutes after application.

European Patent Application 0,066,108 discloses an aqueous road marking composition in which the binder is a mixture of a pure acrylic resin, a carboxylated styrene/dibutyl fumarate copolymer and a polymeric, polyfunctional amine, such as polypropylenimine. The : "~

2~08492 compositions are not storage stable beyond 48 hours after which more polyfunctional amine must be added to restore activity.

It is an object of the present invention to solve the problems normally associated with conventional coatings by providing an aqueous, exterior, quick-set coating which is storage stable and easily applied and provides early washout resistance and dirt pick-up resistance.

It is further object of the present invention to provide a method for improving the early washout resistance and dirt pick-up resistance of an aqueous, exterior, quick-set coating.

.

..:. ~ . ' .. ' 3 ~
~,:.'. :

': '' 2108~2 , .
SUMMARY OF THE INVENTION

This invention solves the problems encountered with conventional exterior coating compositions by providing an aqueous, exterior, quick-set coating composition having early washout resistance, dirt pick-up resistance and storage stability. This invention also provides a method for improving the early washout resistance and dirt pick-up resistance of an aqueous, exterior, quick-set coating.

The aqueous, exterior, quick-set coating composition of this invention requires four components:
(1) a film-forming latex polymer having anionic character;
(2) an amine-containing polymer formed from at least 20%
by weight monomer containing amine functional groups;
(3) a volatile base; and (4) a multivalent metal ion.

The method of improving the early washout resistance and dirt pick-up resistance of an aqueous, exterior, quick-set coating involves:
(1) forming an coating composition containing:
(a) a film-forming latex polymer having anionic character;
(b) an amine-containing polymer;
(c) a volatilebase; and :
(d) a multivalent metal ion; and (2) applying the coating to a substrate.
: , In one embodiment the invention provides an aqueous road or pavement marking paint. The paint can be used to mark lines or symbols on roads, parking lots, walkways and the like formed from 4 : ;:

~' ' '' ';': ' ' : , ~ -., . , ~ .
, ~ . .

2108~92 various substances such as asphalt, bitumen, concrete and the like, with or without aggregate filler or top dressing. The paint dries quickly to develop early washout resistance and tire tread printing.

In another embodiment the invention provides an aqueous, exterior, quick-set coating useful as a base coat or top coat in multilayered exterior insulation and finishing systems ("EIFS").

.....

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2108~92 .
DETAILED DESCRIPIlON OF THE INVENTION

The aqueous coating composition of the present invention requires:
(1) a film-forming latex polymer having anionic character;
(2) an amine-containing polymer;
(3) a volatile base; and (4) a multivalent metal ion.

The aqueous coating composition of the present invention provides early washout resistance, dirt pick-up resistance and storage stability. As used herein, the term "early" refers to the period when the coating is still wet. "Washout resistance," as used herein refers to the ability of a coating to resist becoming soft and blemished and washed away by rain, wind, snow and other harsh weather conditions and remaining an integral, unblemished coating. "Dirt pick-up resistance,"
as used herein refers to the ability of a coating to resist soiling, particularly when the coating is still wet.

"Glass transition temperature," or "Tg," as used herein means the glass transition temperature of a polymer as calculated by the Fox equation ~Bulletin of American Phvsics Society 1, 3, page 123 (1956)]:

Wl_ + W~
Tg Tg(l) Tg(2) For a copolymer, wl and w2 refer to the weight fraction of the two comonomers and Tg(l) and Tg(2) refer to the glass transition temperatures of the two corresponding homopolymers.

.. , ., - .... ,,, .. ~
..

- ~10~92 FILM FORMING LATEX POLYMER

The aqueous quick-set coating composition of the present invention requires a film-forming latex polymer having anionic character. "Latex" as used herein refers to a water-insoluble polymer which may be prepared by conventional polymerization techniques such as, for example, by emulsion polymerization. The latex polymer is formed from any monomer or mixture of monomers which yields a water-insoluble latex polymer which will form a film under the application conditions.

The Tg of the latex polymer is limited only by the particular application for which the coating composition is to be used. For example, if the coating is to be applied outdoors in hot summer weather, then the composition of latex polymer may be selected to yield a Tg greater than if the coating is to be applied outdoors in cold winter weather. Generally, the latex polymer has a Tg from about -50C to about 50C. A coating containing a latex polymer having a Tg below -50C is generally not useful since it is too soft and sticky for coating applications. A coating containing a latex polymer having a Tg above 50C is generally not useful since it is too hard to form a film even at higher than ambient temperatures. Polymers having a Tg from about -15C to about 10C are preferred. Polymers having a Tg from about -10C to about 5C are most preferred.
,;.., The invention may also be practiced using polymers of more complex morphology, such as core-shell particles. These complex polymer morphologies usually display multiple Tg's and may display a Tg value outside the range of from about -50C to about 50C as one of :
7 ~.

, . , . ~'" :, - : . , , - ,' , ~--` 210~92 its multiple Tg's, however the average or effective T~ of the polymer must be from about -50C to about 50C.

The anionic character of the film-forming latex polymer is obtained in any of several ways, the most common being the use of anionic surfactants or dispersants as the stabilizer during the emulsion polymerization or added to the emulsion after polymerization.
Nonionic surfactants may also be present in the latex during or after polymerization of these anionically stabilized latexes. Among the useful surfactants and dispersants are the salts of fatty rosin and naphthenic acids, condensation products of napthalene sulfonic acid and formaldehyde of low molecular weight, carboxylic polymers and copolymers of the appropriate hydrophile-lipophile balance, higher alkyl sulfates, such as sodium lauryl sulfate, alkyl aryl sulfonates, such as dodecylbenzene sulfonate, sodium or potassium isopropylbenzene sulfonates or isopropylnaphthalene sulfonates; sulfosuccinates, such as sodium dioctylsulfosuccinate alkali metal higher alkyl sulfosuccinates, e; g . sodium octyl sulfosuccinate, sodium N-methyl-N-palmitoyltaurate, sodium oleyl isethionate, alkali metal salts of alkylarylpolyethoxyethanol sulfates or sulfonates, e.g.. sodium t-octylphenoxy-polyethoxyethyl sulfate having 1 to 5 oxyethylene units, and the various other anionic surfactants and dispersants well-known in the art.

Another type of latex polymer having anionic character is that which is obtained as a result of including in the polymer small amounts of acidic groups, which may be in the salt form, such as an alkali metal or ammonium salt. Examples of such acidic groups are those derived from incorporated initiator fragments, maleic acid, vinyl . . .

.. . ~ ., ~ , ---" 2108~2 sulfonic acid, crotonic acid, acrylic acid, methacrylic acid, itaconic acid, and the like.

A third useful type of latex polymer having anionic character is a latex polymer which includes a basic monomer which has been neutralized, such as for example acrylamide, methacrylamide and the like.

The latex polymer may have more than one type of anionic character.
.
The latex polymer having anionic character can be prepared by known procedures, which are published in texts on the subject such as Emulsion Polvmerization: Theorv and Practice by D. C. Blackley published by Wiley in 1975 and Emulsion Polvmerization by F. A
Bovey et al. published by Interscience Publishers in 1965. In general, the latex polymer is a polymer or copolymer prepared from monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acryate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, styrene, butadiene, ethylene, vinyl acetate, vinyl ester of "Versatic" acid (a tertiary monocarboxylic acid having Cg, Clo and C
chain length, the vinyl ester is also known as "vinyl versatate"), vinyl chloride, vinyl pyridine, vinylidene chloride, acrylonitrile, chloroprene, acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. Polymers and copolymers of a"B-ethylenically unsaturated monomers and their esters, especially the acrylic and methacrylic esters, are preferred and are preferably prepared by processes given in "Emulsion Polymerization of Acrylic Monomers:
May, 1966" published by the Rohm and Haas Company, Philadelphia, Pennsylvania, incorporated herein by reference.
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~ 2108~92 AMINE-CONTAINING POLYMER

The aqueous quick-set coating composition of the present invention requires an amine-containing polymer which has been formed from at least 20% by weight of a monomer which contains amine functional groups. A polymer having at least 50% by weight of monomer containing amine functional groups is preferred. It is also preferable that the average molecular weight of the water-soluble or water-dispersible amine-containing polymer is from about 5,000 to about 100,000.

The examples of monomer containing amine functional groups include the following:

1. Aminoalkyl vinyl ethers or sulfides wherein the alkyl groups may be straight-chain or branched-chain type and have from two to three carbon atoms and wherein the nitrogen atom may be a primary, secondary, or tertiary nitrogen atom (U.S. Patent 2,879,178). In the latter instance, one of the remaining hydrogen atoms may be substituted by alkyl, hydroxyalkyl, or alkoxyalkyl groups, the alkyl components of which may have one to four carbon atoms, preferably one carbon atom only.

Specific examples include: ~-aminoethyl vinyl ether;
,B-aminoethyl vinyl sulfide; N-monomethyl-~-aminoethyl vinyl ether or sulfide; N-monoethyl-,B-aminoethyl vinyl ether or sulfide;
N-monobutyl-,B-aminoethyl vinyl ether or sulfide; and N-mono-methyl-3-aminopropyl vinyl ether or sulfide.

2. Acrylamide or acrylic esters, such as those of the formula II:

H2C= C~R~C--~X~n A--NR RO (II) wherein :
RisHorCH3;
n is O or 1;
X is O or N(H);
When n is zero, A is O(CH2) x wherein x is 2 to 3, or ~ .
(O-alkylene) y wherein (aalkylene)y is a poly(oxyalkylene) group, having a molecular weight in the range from 88 to 348, in which the individual alkylene radicals are the same or different and are either ethylene or propylene;
and when n is 1, A is an alkylene group having two to 4 :;:
carbon atoms; . ~
R* is H, methyl, or ethyl; and ~ :
Rl IS H, methyl, or ethyl; and R is H, phenyl, benzyl, methylbenzyl, cyclohexyl, or (Cl-C6) alkyl.

Examples of compounds of formula II include:
dimethylaminoethylacrylate or methacrylate; ~-aminoethyl acrylate or methacrylate; N-,B-aminoethyl acrylamide or methacrylamide; . ~ ~
N-(monomethylaminoethyl)-acrylamide or methacrylamide; :
N-(mono-n-butyl)-4-aminobutyl acrylate or methacrylate;
methacryloxyethoxy ethylamine; and acryloxypropoxypropylamine. . ~ :

3. N-acryloxyalkyl-oxazolidines and N-acryloxyalkyl tetrahydro-1,3-oxazines and the corresponding components in which the "alkyl" linkage is replaced by alkoxyalkyl and poly(alkoxy-alkyl), all of which are embraced by Formula III:

H~2C=C~R)II--A'--N/ ~

R' R (III) wherein R is H or CH3;
m is an integer having a value of 2 to 3;
R', when not directly joined to R2, is selected from the group consisting of hydrogen, phenyl, benzyl, and (Cl-Cl2) aLkyl groups;
R2, when not directly joined to R', is selected from the group consisting of hydrogen and (Cl-C4) aLIcyl groups;
R'and R2, when directly joined together, form a 5- to 6-carbon ring with the attached carbon atom of the ring in the formula, i.e., R'and R2, when joined together, are selected from the group consisting of pentamethylene and tetramethylene; and A' is O(CmH2m)- or (O-alkylene)n in which (O-alkylene)nis a poly(oxyalkylene) group, having a molecular weight in the range from 88 to 348, in which the individual alkylene radicals are the same or different and are either ethylene or propylene.

The compounds of Formula III can hydrolyze under various conditions to secondary amines. The hydrolysis produces products having the Formula IV:

12 : .

210~4~2 ol :
H 2C = C~R}C--A--N~H~--~CmH~m ~--OH (IV) The compounds of Formula III are disclosed in U.S. Patents 3,037,006 and 3,502,627 in the hands of a common assignee, and their corresponding foreign applications and patents and any of the monomeric compounds disclosed therein may be used in making the copolymers to be used in the composition of the present invention.

Examples of compounds of Formula III include:
oxazolidinylethyl methacrylate; ~: .
oxazolidinylethyl acrylate;
3~ methacryl-oxypropyl)-tetrahydro-1,3-oxazine;
3-(~-methacryloxyethyl)-2,2-pentamethylene-oxazolidine;
3-,B-methacryloxyethyl-2-methyl-2-propyloxazolidine;
N-2-(2-acryloxyethoxy)ethyl-oxazolidine;
N-2-(2-methacryloxyethoxy)ethyl-oxazolidine;
N-2-(2-methacryloxyethoxy)ethyl-5-methyl-oxazolidine;
N-2-(2-acryloxyethoxy)ethyl-5-methyl-oxazolidine; :~
3-[2-(2-methacryloxyethoxy)ethyl)]-2,2-penta-methylene-oxazolidine;
3-[2-(2-methacryloxyethoxy)ethyl)]-2,2-dimethyl-oxazolidine;
3-[2-(methacryloxyethoxy)ethyl]-2-phenyl-oxazolidine. .
- ~ .

4.; Polymers of monomers which readily generate amines by ~ :
hydrolysis are useful as the amine-containing component or to generate the amine-containing component polymer of this binder --` 2~084~2 composition. Examples of such monomers are acryloxy-ketimines and -aldimines, such as those of Formulas V and VI following:

H2C=(CR)-COOA"N=Q (V) H2C = C(R)-CO-(D)n l - (B)n.l ~ (A)n I ~ N = Q ~VI) wherein R is H or CH3;
Q is selected from the group consisting of /R
=~ \ 5 =C:--~CHR6~

R6 is H or it may be methyl in one CHR6 unit;
R5 is selected from the group consisting of (Cl-Cl2)-alkyl and cyclohexyl groups;
R4 is selected from the group consisting of (C~-CI2)-alkyl and cyclohexyl;
R3 is selected from the group consisting of phenyl, halophenyl, (Cl-Cl2)-alkyl, cydohexyl, and (Cl-C4) alkoxyphenyl groups;
A" is a (Cl-Cl2) alkylene group;
A, B and D are the same or different oxyalkylene groups having the formula -OCH(R7 )-CH(R7 )-wherein R7 is H, CH3, or C2Hs;
x is an integer having a value of 4 to 5; ::
no is an integer having a value of 1 to 200;
n' is an integer having a value of 1 to 200; and n" is an integer having a value of 1 to 200, the sum of n-1, n'-1 and n"-1 having a value of 2 to 200.

:

~10~492 Illustrative compounds of formulas V and VI are:
2-[4-(2,6-dimethylheptylidene)-amino]-ethylmethacrylate;
3-[2-(4-methylpentylidine)-aminol-propyl methacrylate;
,~-(benzylideneamino)-ethyl methacrylate;
3-[2-(4-methylpentylidene)-amino]-ethylmethacrylate;
2-[4-(2,6-dimethylheptylidene)-amino]-ethyl acrylate;
12-(cyclopentylidene-amino)-dodecylmethacrylate;
N-(1,3-dimethylbutylidene)-2-(2-methacryloxyethoxy)-ethylamine;
N-(benzylidene)-methacryloxyethoxyethylamine;
N-(1,3-dimethylbutylidene)-2-(2-acryloxyethoxy)-ethylamine;
N-(benzylidene)-2-(2-acryloxyethoxy)ethylamine.

The compounds of Formulas V and VI hydrolyze in acid, neutral, or alkaline aqueous media to produce the corresponding primary amines or salts thereof in which the group -N = Q of the formulas becomes -NH2 and O = Q. The compounds of Formulas V and VI are disclosed in U.S. Patents 3,037,969 and 3,497,485, and any of the monomeric compounds therein disclosed may be used in the making of the copolymers to be used in the water-soluble polymer portion of the compositions of the present invention.

The preferred class of amine-containing polymers of this invention are water-soluble. By water-solubility is meant that the polymer is completely soluble either in free-base, neutral, or salt form.
The solubility preferably exists at all pH's, especially in the range of about 4 to 10. A less preferred class of water-soluble amine-containing polymers are generally insoluble at high pH and soluble or partly soluble at acidic pH values, particularly in the pH range from about 4 to about 7. By partly soluble is meant both the situation in which some of the polymer is soluble in water as well as that in which the entire 2108~92 polymer dissolves in the form of micelles or aggregates individual molecules, generally, highly water swollen aggregates. The latter are often called colloidal solutions. It is preferred that most of the polymer be soluble at the acidic pH values. The water-soluble amine-containing polymers of this invention include both the completely soluble and the partly soluble polymers as described immediately above.

A useful but still less preferred class of amine-containing polymers are those which are water-insoluble and, as will be noted below, have a molecular weight corresponding to the lower end of the range for the water-soluble counterparts. These water-insoluble amine-containing polymers perform the same function as the water-soluble polymers. When these water-insoluble polymers are substituted for the water-soluble polymers, the early cohesive strength of the anionically stabilized latex polymer is improved; however, the improvement is usually not as great as that produced by the water-soluble polymers.

In general, the amine-containing polymers of at least 20 % by weight of a monomer of categories 1, 2, 3, and 4, supra, may be obtained by solution polymerization in aqueous media, either neutral, alkaline, or acidic, depending upon the particular polymer sought. Generally, the polymerization is carried out in an aqueous medium containing a small amount of an acid, either organic or inorganic, such as acetic acid or hydrochloric acid. The amine-containing polymers include copolymers with up to 80% by weight one or more such as methyl acrylate, acrylamide, methacrylamide, and quaternary ammonium salts derived from the amine monomers, such as 2-methacryloxyethyl trimethyl ammonium chloride. Small amounts of relatively insoluble comonomers may also be used to obtain the water-soluble polymers.

- 2108~2 The insoluble polymers may contain larger amounts of these comonomers. Such monomers include, as examples, acrylic acid esters with (C1 to C1g) alcohols and methacrylic acid esters with alcohols having one to 18 carbon atoms, especially (Cl~4) alkanols; styrene, vinyltoluene, vinyl acetate, vinyl chloride, vinylidene chloride, substituted styrenes, butadiene, substituted butadienes, ethylene; and the nitriles and amides of acrylic or of methacrylic acid. The particular comonomer or comonomers used in making a given amine-containing polymer depends upon the proportion of amine-containing monomer used in making the copolymer.
Preferably, a comonomer with relatively high solubility in water is exclusively used to make the water-soluble polymers. The polymers are thus polymers or copolymers of cationic and, optionally, nonionic vinyl monomers. Examples of the cationic monomers are the amines, imines and quaternary ammonium salts; the other recited monomers are nonionic. Thus, these water-soluble copolymers contain no acid groups other than trace amounts which may be present due to impurities in the monomers used or to small extent of hydrolysis during synthesis, storage or use.

The insoluble amine-containing polymers have a viscosity average molecular weight from about 5,000 to about 100,000, with the range of from about 15,000 to about 90,000 preferred. The molecular weight of the water-soluble polymers may fall within a wide range;
typically, the ViSCQsity average molecular weight is from about 5,000 to about 300,000, with the range of from about 40,000 to about 100,000 preferred. The amount of the amine-containing polymer may range from about 0.1% to about 20% by weight of the total weight of anionic latex polymer and amine-containing polymer, the range from 1% to 8%
being preferred.
. ~, .

210~92 Water-soluble amine-containing polymers include both the completely soluble and the partly soluble polymers. The term water-soluble amine-containing polymer describes polymer that is completely soluble either in free-base, neutral, or salt form. Some polymers are soluble at all pH's, while others are soluble over a range of pH for example from about 5 to 10. Other amine-containing polymers are generally insoluble at high pH and soluble or partly soluble at acidic pH values, particularly in the pH range from about 5 to about 7. By partly soluble is meant both the situation in which some of the polymer is soluble in water as well as that in which the entire polymer dissolves in the form of micelles or aggregates of individual molecules, generally, highly water swollen aggregates. The latter are often called colloidal solutions. It is preferred that most of the polymer be soluble at the acidic pH values.

In general, the amine-containing polymers may be obtained by solution polymerization in aqueous media, either neutral, alkaline, or acidic, depending upon the particular polymer sought, as generally known in the art, for example as taught in U.S. Patent 4,119,600.
Generally, the polymerization is carried out in an aqueous medium containing a small amount of an acid, either organic or inorganic, such as acetic acid or hydrochloric acid. The amine-containing polymers include copolymers with up to 80% by weight one or more monoethylenically unsaturated monomers, such as methyl acrylate, acrylamide and met.hacrylamide. Small amounts of relatively insoluble comonomers may also be used to obtain the water-soluble polymers. The insoluble polymers may contain larger amounts of these comonomers. Such monomers include, as examples, acrylic acid esters with (C1 to C1g) alcohols and methacrylic acid esters with alcohols 2108~2 having one to 18 carbon atoms, especially (C1~4) alkanols; styrene, vinyltoluene, vinyl acetate, vinyl chloride, vinylidene chloride, substituted styrenes, butadiene, substituted butadienes, ethylene; and the nitriles and amides of acrylic or of methacrylic acid. The particular comonomer or comonomers used in making a given amine-containing polymer depends upon the proportion of amine-containing monomer used in making the copolymer. The polymers are thus polymers or copolymers of cationic and, optionally, nonionic vinyl monomers. Examples of the cationic monomers are the amines and imines; the other recited monomers are nonionic.
Thus, these water-soluble copolymers contain no acid groups other than trace amounts which may be present due to impurities in the monomers used or to small extent of hydrolysis during synthesis, storage or use.

VOLATILE BASE

The aqueous quick-set coating composition of this invention requires a volatile base. The type and amount of volatile base used must be sufficient to raise the pH of the composition to about the point where the amine functional groups of the amine-containing polymer are non-ionized (deprotonated), typically to at least pH 5, preferably from pH 7 to pH 9, to avoid interaction with the anionically stabilized latex polymer and other anionic components in the adhesive composition.

A starting point estimate of the amount of volatile base required to reach this point can be calculated from the number of equivalents of base needed to neutralize all of the acid groups in the latex (i.e. acid groups from: copolymerized carboxylic-bearing monomer; surfactant;

19 ~ ~ :

.... . ..

2108~2 or initiator) and the conjugate acid of the amine base. If the amine is not sufficiently deprotonated, the emulsion will exhibit observeable signs of instability over time, such as viscosity increase and microscopically observeable "particle rafting," an early stage of aggregation/gellation. One equivalent of volatile base (based on latex acids and polyamine titers) is usually enough to yield a stable system although higher levels of volatile base (~3 to 4 equivalents) may be necessary for long term stability. Higher amounts of volatile base can be used without departing from the spirit of the invention although the "quick dry" properties of the coating may be reduced. If the equipment used in the process of manufacture presents opportunities ---for loss of the volatile base by evaporation at any stage from when the volatile base is added until after the product is packaged in a sealed container, the amount of volatile amine loaded to the production equipment should be increased to offset the loss.

After application, the volatile base evaporates lowering the pH
of the composition. When the pH of the composition falls to a point where the protonation of the amine functional group begins to occur, the amine functional group becomes cationic. The quick dry is -believed to be initiated by this conversion of the amine functional ~ ~
group to a cationic state in the presence of the anionically stabilized ~ ~:
emulsion polymer, although the exact mechanism that produces the quick-dry property has not been established and we do not wish to bound by the theory of the exact mechanism.

Suitable volatile bases include but are not limited to ammonia, morpholine, alkyl amines, 2-dimethylaminoethanol, N-methylmorpholine, ethylenediamine, and mixtures thereof.
Ammonia is preferred. -.

.: . .

MULTIVALENT METAL

The aqueous quick-set coating compositions also contain a water-soluble or water-dispersible multivalent metal in the form of a metal ion, salt, complex or oxide. Multivalent metal ions such as calcium, aluminum, magnesium, zinc, barium, strontium, and the like may be used. Complexes of multivalent metal ions, such as zinc hexammonia, zinc ammonium bicarbonate and the like, and salts of multivalent metal ions with counterions, such as chloride, acetate, bicarbonate and the like, may be used. Zinc is the preferred multivalent metal.

The multivalent metal ion, salt, complex or oxide is useful at a level of from about 0.5% by weight to about 10% by weight, based on the weight of the latex polymer solids. A level of from about ~% by weight to about ~% by weight, based on the weight of the latex polymer solids, is preferred. -In addition, conventional coating components such as, for example, pigments, binders, vehicles, extenders, dispersants, surfactants, coalescents, wetting agents, rheology modifiers, thickeners, drying retarders, antifoaming agents, colorants, waxes, preservatives, heat stabilizers, solvents, anti-skinning agents, driers and the like may be used in this invention. ~ -Care must be exercised when selecting the type and amount of additives to avoid altering the pH of the composition to an extent that interferes with storage stability or buffering the pH to an extent that after application the pH does not fall sufficiently to initiate protonation of the polyamine. For example an adhesive prepared using a polyamine with a relatively low pKa and too large an amount of ~-: , ' ':

calcium carbonate as filler, may display an unacceptably extended cure time.

The aqueous, quick-set coating compositions typically have a solids content in the range of from about 10% by weight to about 75%
by weight and a viscosity of from about 50,000 centipoises to about 300,000 centipoises.

The aqueous, quick-set coating compositions of the present invention may contain fillers such as sand, calcium carbonate and the like. The coating may be applied by trowel, spraying and the like, typically in thickness of from about 1/32 inch to about 1/8 inch.

The method of the present invention is useful for improving the early wash-out resistance and dirt pick-up resistance of an aqueous, quick-set coating. The method involves:
(1) forming an aqueous, quick-set coating containing:
(a) a film-forming latex polymer having anionic character;
(b) an amine-containing polymer formed from at least 20% by weight monomer containing arnine functional groups;
(c) a volatile base; and (d) a water-soluble or water-dispersible multivalent metal; and (2) applying the an aqueous, quick-set coating to a substrate.

The substrate may be formed from concrete, cement, brick, cinder block, wood, gypsum board, particle board, asphalt, bitumen and the like.

:: - . .

- 2108~32 . .
The following examples illustrate some aspects of the invention and should not be construed as limiting the scope of the invention which is described in the specification and claims.

EXAMPLE 1. PREPARATION OF COATING FORMULATIONS

.
The coatings were prepared according to the following formulation by grinding together the ingredients listed as grind ingredients in Table 1.1 and then adding the remaining letdown ingredients for each coating formulation.

21~492 Table 1.1 Comparadve ComparadveComparative Comparative 1 2 Grlnd In~
Anlonicaily stabilized 330.7 330.7 263 6 263.6 330.7 263.6 Latex Polymer (PhoplextD AC-264 latex ) ~60% solids) Ammonium hydroxide (28%) 5 5 to pH 10 to pH 10 5 to pH 10 Polyoxazolidinylethyl 0 2.4 0 1.9 2.4 3.2 methacrylate (25% solids) Zinc oxide o o o o 7inc ammonium bicarbonate 0 0 0 0 0 3.2 (8.4%) Caidnm ca bonab 100 100 0 0 0 0 Anionic dispersant 2.5 25 0 0 2.5 0 (Tarnol 11\ 850 dispersant) (30% total sollds) , Potassium tripolyphosphate 1.5 15 0 0 1.5 0 Ethylene giycol 2 2 1 1 2 Texanol~ coalescent 2 2 6.5 65 2 6.5 (2 2 4-trimethyl~hydroxypentyl acetate) Antifoamlng a8ent 5 5 2 2 5 2 (Nopco(lD i~XZ antifoamer) Clay filler 15 15 0 0 15 0 .
Marble dust 400 400 0 0 400 0 Sand ~70 400 400 0 400 Sand ~1125 0 0 905.3 905.3 0 905.3 Sll~cafiour~120 0 0 250.0 250.0 0 250.0 Mica (Alzlbronz'lD 88) 0 0 30.0 30.0 0 30.0 Polyester fiber (l/4 1nch) 0 0 2.0 2.0 0 2.0 : .
' 1(~ ,, , , ~, Water 20 20 209.S 209.5 20 2095 ~ ::
Hydroxyethylcellulose 0.3 0.3 0.35 0.35 0.3 035 . .
(NatrAsoll- HR thlckener) : ~, ": ", .
'.''''~' ~"','~"
.' . '.'; ~ ' ' , ~ ,.' '. -'' .,,~ :~:' ~.~, ;'.'- '~' 21~8~92 EXAMPLE 2. SET TIME

The coating formulations were tested to determine how long they took to completely set. The test specimens were prepared by casting each coating formulation on Teflon~9-coated glass at a thickness of from about 1/32 inch to about 1/16 inch.

Testing was done at a temperature of 72F and relative humidity of 32.8%. A Gardner Set Time Recorder was then placed on each freshly made test specimen. The probe on the recorder moves at one revolution per hour through or on top of the coating. Set time is reported in minutes and was established when the probe completely moved on the surface of the adhesive without making any trace mark on the surface. Short set times are desirable because they indicate that the adhesive builds early cohesive and adhesive strength. The results are reported in Table 2.1.
Table 2.1 --- :
TedSp~ell TedMe~hod SetTlme (mi~r~
-Comparatlve I par~al 60 Comparatlve 1 complete 85 Comparatlve 2 partial 43 Comparatlve 2 complete 60 partial 18 complete 35 The set time test demonstrated that the coating of the invention(Coating 1) gave a shorter partial and complete set time as compared to the coating containing no amine-containing polymer and no multivalent metal (Comparative 1) and as compared to the coating containing amine-containing polymer but no multivalent metal (Comparative 2).

- ,. ~ .

210~92 EXAMPLE 3. EARLY WASHOUT RESISTANCE

The coating formulations were tested for early washout resistance. The test specimens were prepared by casting each coating formulation at a thickness of 1/16 inch on an expanded polystyrene board.

The test specimens were then cured at the following conditions:
.. _ . _ , . ..
Condition Temperature Relative Duration (C) Humidity (hour~) . -A 10 80% 5 :
B 24 70% 2 ; ~ .
C 24 50% 2 :
D 24 50% 3 E 24 50% 4 F 4 50-60% 3 G 4 5~60% 4 ' H 4 50bO% 5 4 50-60% 6 ;-.: , , The test specimens were then held at a 45 under a stream of cold running water at a flow rate of 180 gallons/hour. Failure was noted at the time when erosion of the coating was first seen. The higher the time to washout, the better the washout resistance. The ~ .
results are shown in Table 3.1. ~ ~
.: , .
'.:.
" ' "~'' . . .

Table 3.1 Test Specimen Condition Wash-out Resistance Comparative 3 A complete washout in <2 hours Comparative 3 B surface washout at 5 hours Comparative 3 C complete washout immediately Comparative 3 D complete washout immediately Comparative 3 E complete washout in 2 minutes Comparative 3 F complete washout immediately Comparative 3 G complete washout in I minute Comparative 3 H complete washout in 3 minutes Comparative 3 I comp1ete washout in 5 minutes Comparative 4 C complete washout immediately Comparative 4 D complete washout in 2 minutes Comparative 4 E complete washout in 4 minutes Comparative 4 F complete washout in immediately Comparative 4 C complete washout in 2 minutes Comparative 4 H complete washout in 10 minutes -Comparative 4 I complete washout in 14 minutes A only one soft spot in >5 hours B no washout or soft spots in 7 hours C complete washout in 5 minutes D complete washout in 16 minutes E complete washout in 30 minutes F complete washout in I minute G complete washout in 6 minutes H complete washout in 18 minutes complete washout in 30 minutes . _ 2 C complete washout in 5 minutes 2 D complete washout in 17 minutes 2 E complete washout in 30 minutes 2 F complete washout in 2 minute 2 G complete washout in 4 minutes 2 H complete washout in 15 minutes 2 I complete washout in 30 minutes The early washout resistance test demonstrated that the coatings of the invention (Coatings 1 and 2) gave better washout resistance as compared to the coating containing no amine-containing polymer and no multivalent metal (Comparative 3) and as compared to the coating containing amine-containing polymer but no multivalent metal (Comparative 4) under all curing conditions.

EXAMPLE 4. DIRT PICK-UP RESISTANCE

The coating formulations were tested for dirt pick-up resistance.
The test specimens were prepared by casting each coating formulation on a 31/4 inch by 17 inch scrub test panel at a thickness of 1/16 inch according to ASTM D-2486. The test specimens were then cured for 24 hours under ambient conditions.

Test Method 1 : .

Brown ferric oxide was mechanically mixed with deionized water until smooth to form a slurry. The ferric oxide slurry was brushed on one half of each panel and then dried for 3 hours at room temperature.
Each panel was then washed thoroughly under running tap water wiping with a cheese cloth to remove all the excess ferric oxide. Each panel was dried for an additional 2 hours.
.
Each panel were then tested using a Menotar C231 Colorimeter reading the reflectance of the stained half and the unstained half. The degree of dirt pick-up is reported as the % reflectance retained~

% reflectance retained = reflectance of stained portion x 100%
reflectance of unstained portion :' ' The higher the % reflectance retained, the better the dirt pick-up resistance. The results are reported in Table 4.1.

.

; ' ':
~ . .

TestMethod2 2108492 Approximately 1-2 grams ASTM standard artificial soil was rolled over a cured panel using a SCUZZOMETER soiling tester. 1-2 grams standard soil was also sprinkled evenly on the roller and its track on the test panel. The soiling tester was then run for the same cycles for each panel (20 cycles -- designated as Test Method 2A or 100 cycles --designated as Test Method 2B). During the cycling, the standard soil was occasionally brushed back into the roller track. At the end of the cycling, the panel was wiped firm with a clean tissue to remove any loose soil.

Each panel were then tested using a Menotar C231 Colorimeter reading the reflectance of the stained half and the unstained half. The degree of dirt pick-up is reported as the % reflectance retained:
reflectance retained = reflectance of stained port_on x 100%
reflectance of unstained portion ) The higher the % reflectance retained, the better the dirt pick-up resistance. The results are reported in Table 4.1.

Table 4.1 Test Specimen TeDt Method % Reflectance Retalned Comparative 1 1 49.1 Comparative l 2A 80.4 Comparative 1 2B 83.1 Comparative 2 1 52.1 Comparative 2 2A 86.8 Comparative 2 2B 84.5 54.1 2A 89.4 2B 89.6 '" ,', The dirt pick-up resistance test demonstrated that the coating of : -the invention (Coating 1) gave better resistance as measured by all of the test methods as compared to the coating containing no amine-containing polymer and no multivalent metal (Comparative 1) and as :
compared to the coating containing multivalent metal but no amine-containing polymer (Comparative 2).

Claims

1. An aqueous exterior coating composition, comprising:
(a) a film-forming latex polymer having anionic character;
(b) a water-soluble or water-dispersible polymer formed from at least about 20% by weight monomer containing amine functional groups;
(c) a volatile base in an amount effective to raise the pH of the composition to a point high enough where essentially all of the amine functional groups are in a nonionic state;
and (d) a water-soluble or water-dispersible multivalent metal.

2. The aqueous exterior coating composition of claim 1 wherein said water-soluble or water-dispersible polymer is formed from at least about 50% by weight monomer containing amine functional groups.

3. The aqueous exterior coating composition of claim 1 wherein said water-soluble or water-dispersible polymer formed from at least about 20% by weight monomer containing amine functional groups is an N-acryloxyalkyl-oxazolidine.

4. The aqueous exterior coating composition of claim 1 wherein said volatile base is ammonia.

5. The aqueous exterior coating composition of claim 1 wherein said water-soluble or water-dispersible multivalent metal is zinc.

6. A method for improving the early washout resistance and dirt pick-up resistance of an exterior coating, comprising:
(a) forming a coating composition containing:
(1) a film-forming latex polymer having anionic character;
(2) a water-soluble or water-dispersible polymer formed from at least 20% by weight containing amine functional groups;
(3) a volatile base in an amount effective to raise the pH of the composition to a point high enough where essentially all of the amine functional groups are in a nonionic state; and (4) a water-soluble or water-dispersible multivalent metal; and (b) applying said coating composition to a substrate.

7. The method of claim 6 wherein said water-soluble or water-dispersible polymer is formed from at least about 50% by weight monomer containing amine functional groups.

8. The method of claim 6 wherein wherein said water-soluble or water-dispersible polymer formed from at least about 20% by weight monomer containing amine functional groups is an N-acryloxyalkyl-oxazolidine.

9. The method of claim 6 wherein wherein said volatile base is ammonia.

10. The method of claim 6 wherein said water-soluble or water-dispersible multivalent metal is zinc.