Waterborne latex coatings of color: I. Component influences on viscosity decreases.

For almost two decades, it has been known that the addition of colorants to a waterborne latex coating thickened with an associative thickener will result in a viscosity loss. The influence of surfactants on viscosity variations in waterborne latex coatings, as discussed in our most recent JCT COATINGSTECH article, (1) is the source of the viscosity decreases. To evaluate this problem, aqueous solutions containing large quantities of five different surfactants, and the smallest particle size of the colorants, carbon black (CB), were prepared. Large quantities of surfactant were used to allow for adsorption on, and stabilization of, CB. When traditional associative polymers (HMHEC, HASE, and a telechelic HEUR) were used to thicken carbon black dispersions, viscosity decreases were not observed, for most of the surfactant is adsorbed on the CB's surface. There is enough surfactant, however, to promote viscosity decreases in comb-HEUR thickened CB dispersions. Moving beyond the colorant dispersions, the CB, yellow, or red colorants were then added to a commercial latex paint that contains many surfactants, glycol ether, and coalescing aids, and significant viscosity decreases were observed. The decreases were very dramatic as the colorant concentration was increased to obtain deeper color tones, due to the additional excess surfactant added to the coating. Reduction in total surfactant levels in the colorant was an obvious solution, but this led to rub-up incompatibility. The conflict between viscosity retention and rub-up incompatibility was resolved when the surfactant concentration was reduced by adding to the colorant formulation compositionally different hydrophobically-modified poly(oxyethylenes) and hydrophobe-modified maleic acid co-oligomers.

Keywords: Colorant, color retention, surfactant, latex, carbon black, thickener

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Colorant formulations contain pigments, surfactants, dispersant, polyethylene glycol, defoamer, and biocide. There are generally two types of pigments: the colorant and the extender, (2) such as talc and calcium carbonate, etc. Such formulations also contain large amounts of different surfactants and dispersants that stabilize the pigment by steric, electrostatic, or electrosteric stabilization, and aid in improving the compatibility of the colorant with the paints.

Surfactants are also important when associative polymers are used as thickeners in waterborne coatings. Our group has addressed many aspects of waterborne latex coatings, but like Henry Ford's black Motel T autos, our latex studies have all been of one color--white, arising from the hiding pigment, Ti[O.sub.2]. In this final series of studies we go out with a splash of color, by examining the influence of components added with carbon black, red, and yellow colorants. This contribution will discuss the viscosity response when colorants with their components are added to waterborne coatings. In the two contributions to follow this study, structural differences among surfactants and dispersants, and the influence of talc and laponite on color retention in waterborne coatings will be addressed.

MATERIALS AND METHODS

Colorant Formulation

Three different colorants, a black, a red, and a yellow, were examined in this study. The carbon black colorant was black pearls (Cabot); the yellow colorant: monoazo Yellow 3 (Clariant); and the red colorant: Naphthol AS Pigment Red 188 (Clariant). The colorant premix contained water, poly(ethylene glycol) (Huntsman Chemical), AMP95 (ANGUS Chemical), defoamer (Drew, Ashland Chemical), isopropyl amine pentadecyl sulfonate (Rhodia), octadecanol polyethylene oxide phosphate potassium salt (Dexter), Tergitol 15-S-9, a random PO/EO copolymer (Dow), octadecyl polyethylene oxide (Brij), and 0.80 wt% dispersant (various dispersants were used). All of the colorants contained talc (Barrett's Minerals).

[FIGURE 1 OMITTED]

HMHEC, HASE, and three HEUR thickeners were used in this study. HMHEC (Hercules) has a molecular weight of 300,000 and an ethylene oxide molar substitution of 3.3, with approximately 1 wt% of grafted [C.sub.12]-[C.sub.18] alkyl side chains. HASE 9835 (Dow) is a crosslinked terpolymer of acrylic acid, ethyl acrylate, and hydrophobic termonomer with an acid content (wt%) of 60 and [M.sub.w] of 1,020,000. The chemical structure of the active component in the telechelic step growth (SG) HEUR is [C.sub.12][H.sub.25]-[[H.sub.12]MDI-(EtO)[.sub.182]][.sub.3]-[H.sub.12]MDI-[C.sub.12][H.sub.25] with a [M.sub.w] of 37,000. The [C.sub.14][H.sub.29] comb-HEUR is a PO[E.sub.198](IPDI-[C.sub.14][H.sub.29]-IPDI-PO[E.sub.198])[.sub.10]-IDPI-PO[E.sub.198] comb thickener that contains 2.5 hydrophobes per polymer with a [M.sub.w] of 97,000. The nonyl phenol (NP) comb-HEUR is a PO[E.sub.198](IPDI-NP-IPDI-PO[E.sub.198])[.sub.6]-IDPI-PO[E.sub.198] comb thickener with a [M.sub.w] of 71,000. All three of the HEUR thickeners are step-growth products.

The talc and colorant were added to the premix, and the pigments were dispersed for one hour with the Cowles blade. The Hegman fineness of grind values were below 7 for all formulations.

Surface Tension

Surface tension measurements were performed on a SensaDyne 6000 Tensionmeter. Surface tensions were measured based on the maximum bubble pressure method using heptane and triply distilled water for calibration. The bubble rate was varied from 1 sec per bubble to 13 sec per bubble to obtain dynamic surface tension measurements.

[FIGURE 2 OMITTED]

Compatibility Tests

One major criterion of a colorant is that the colorant dispersion be compatible in the paint base. The lack of compatibility of the colorant will result in poor color properties, such as low tint strength (the power of a pigment to tint paints) and color changes when the paint is either shaken again or reapplied by touchup. For this reason, compatibility tests were conducted. Colorants were added to the paint bases, and two identical samples were shaken on a Red Devil shaker for three minutes and 15 min. The paints were cast, and the color of the paints was compared visually. A visual change in color between the two different shake times indicated that the colorant was not compatible in the paint.

Rheology Measurements

Shear rate profiles (0-1000 [s.sup.-1] shear rate; 0-597 Pa shear stress) were measured on a Carri-Med CSL100 controlled stress rheometer (Cleveland, OH) with a cone and plate (cone angle = 2[degrees], with 4 cm diameter) or double-concentric cylinder ([R.sub.3] = 21.96 mm, [R.sub.2] = 20.38 mm, [R.sub.1] = 20.00 mm; cylinder immersed height = 20.50 mm; and gap = 1000 [micro]m) geometry. All measurements were performed at 25[degrees]C.

Phase Behavior Study

The phase behavior of the associative thickeners was examined in the presence of the five surface active surfactants. These data are not presented in this study for brevity. Those interested in such data should contact the corresponding author.

RESULTS AND DISCUSSION

In our previous publication (1) the role of surfactants in associative thickener (AT) solutions and AT thickened latex paints was discussed. The concentration of AT hydrophobes in a coating is low and would not promote a significant viscosity increase without interactions with other components in the coating. Surfactants provide association sites for AT hydrophobes; however, this does not lead to detectable viscosity increases until at least two hydrophobes from different polymers participate in a surfactant aggregate, and there are enough associations to build a larger network. This occurs as the surfactant concentration is increased. At a certain concentration, a viscosity maximum is reached. With an anionic surfactant, this generally occurs between 60 to 80% of the surfactant's CMC.

[FIGURE 3 OMITTED]

As the surfactant's concentration is increased beyond that, surfactant micelles begin to completely surround each individual polymer hydrophobe and the network starts to disconnect (illustrated schematically in Figure 1). To the author's knowledge, this concept was first proposed by Landol and Sau (3) and has been embraced by many. There was no verification of this mechanism, until the fluorescence studies (1) in our recent JCT article. As the concentration of surfactant increased, the number of surfactant molecules in the micelle increased and the number of HEUR hydrophobes in the aggregate decreased, resulting in a decreasing viscosity.

Surfactants and other surface active components are in a colorant formulation to stabilize the pigments. For over a decade, it has been known by those practicing the art that the addition of a colorant formulation to a latex coating thickened with an associative polymer may exhibit a dramatic decrease in viscosity. This study starts with the premise that the phenomenon in commercial paints is related to an excess of surfactant in the total coating and evaluates additive approaches to minimize viscosity loss without incurring compatibility problems. We start by formulating a colorant with an excess of surfactants, two anionic and two nonionic, and a dispersant that is surface active.

The chemical compositions of the surfactants used in this study, and their aqueous solution surface tensions at ca. 0.1 wt%, are listed in Table 1. The amount of water-soluble polymer (4) or surfactant that will adsorb at a liquid-liquid interface or on a latex's surface (5,6) in an aqueous dispersion is proportional to the surface activity of the latex and/or surfactant. The data reflect the ability of the surfactant to adsorb on and stabilize the pigment, and to influence interactions with associative thickeners. (7) The surfactants represent a broad mixture of compositions that incorporate different hydrophobe groups with anionic head groups (sulfate and phosphate) or with pendant nonionic oxyethylene hydrophilic units. The last component in Table 1 is a random oxyethylene/oxypropylene copolymer, not normally considered a surfactant, but it does lower the surface tension of water to < 32 mN/m (surfactant behavior). The random copolymer does not, however, adsorb competitively on disperse phases (discussed in a forthcoming manuscript) containing real surfactants nor promote hydrophobic associations among associative thickeners. It is an effective compatibilizer and is used in the initial stages of this study.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

To begin the study, aqueous dispersions of carbon black (3 wt% dispersion, containing 7.9 wt% or 0.06VF CB) were prepared and added to five different associative thickeners. (8) This provided thickened solution with 0.24 wt%, 0.01 VF CB dispersions. The concentration of associative thickener used to prepare each aqueous solution was the amount needed to achieve a 110 KU Stormer viscosity, a common coating formulator practice. Carbon black (CB) was chosen as our first colorant because there are numerous surfactant ad- and absorption studies on CB. (9-15) The thickened dispersion contained the components listed in Table 1. This colorant formulation has a high surfactant total concentration (referred to as S-5 hereafter) and could influence the associative polymer's viscosity maximum; therefore, the two most surface active surfactants in Table 1 (i.e., C[H.sub.3](C[H.sub.2])[.sub.15]S[O.sub.3.sup.-](C[H.sub.3])[.sub.2]CHN[H.sub.3.sup.+] and C[H.sub.3](C[H.sub.2])[.sub.12](EO)[.sub.6]P[O.sub.4.sup.-][K.sup.+]) were removed from the formulation (referred to hereafter as the S-3 surfactant formulation). The influence of these two surfactant level colorant formulations (S-5 and S-3) on the viscosity of common associative thickener aqueous solutions is illustrated in Figures 2 through 4. The viscosity of HASE-thickened solutions was dramatically increased by the addition of either S-5 or S-3 surfactant packages to the CB formulation (Figure 2). The increases in viscosity in HMHEC solutions were not as dramatic (Figure 3). All of the HEUR thickeners examined in this study were synthesized by a step-growth synthesis. (16) When the colorant CB-surfactant mixtures were added to a step-growth telechelic HEUR ([C.sub.12][H.sub.25]-[[H.sub.12]MDI-(EtO)[.sub.182]][.sub.3]-[H.sub.12]MDI-[C.sub.12][H.sub.25]), a viscosity increase (Figure 4) also was observed with both the S-5 and S-3 surfactant formulations, but the increases were smaller than noted in the HASE and HMHEC CB-dispersions. Considering the amount of total surfactant added, the viscosity increases would be surprising if most of it was not adsorbed on the CB.

When colorant formulations were added to the comb-HEUR (Figures 5A and B) solutions, a viscosity decrease was observed with the addition of the higher concentration S-5 formulation. The comb-HEURs appeared to be more surfactant-sensitive than the other associative thickeners; however, the phenomenon is more complex. Some surfactants may also form strong complexes with water-soluble polymers; if the interactions are strong enough, gels are observed. We have investigated the influence of surfactant types and concentrations for their ability to gel the different associative thickeners used in this study. Those interested in such data should contact the corresponding author, as it will be omitted in this article for brevity.

Formulating at the Viscosity Maximum Surfactant Concentration

The S-5 surfactant mixture represents a balance of anionic and nonionic surfactants; removing the two more surface-active components makes the S-3 surfactant combination a nonionic package only. From a solubility viewpoint, anionic surfactants might appear best. In some of the data to follow, the S-3 formulation concentration in a commercial coating will facilitate greater viscosity retention, but this may be due only to a lower amount of surfactant and its relationship to the associative thickener's viscosity maximum (Figure 1). To this end, it was decided to keep all five surfactants but reduce their total concentration to that needed to achieve the viscosity maximum for a given thickener. The data are illustrated in Figures 6A and B for the comb-HEURs that exhibited decreases in aqueous solution viscosity with the S-5 CB formulation addition (Figures 5A and B). The S-5 formulation concentration facilitates a response beyond the viscosity maximum, whereas the viscosity promoted by the S-3 formulation concentration is at or near the broad viscosity maximum downside. The magnitude of the viscosity influenced by the surfactant concentration in Figure 6A accounts for the data in Figure 5A.

[FIGURE 7 OMITTED]

With the PO[E.sub.198](IPDI-[C.sub.14][H.sub.29]-IPDI-PO[E.sub.198])[.sub.10]-IDPI-PO[E.sub.198] comb-HEUR, a greater surfactant sensitivity was observed (Figure 6B). The S-5 concentration was well beyond the viscosity maximum and facilitated a viscosity lower than that observed in the thickener solution without the colorant addition. The S-3 was on the declining side of the viscosity maximum, but above the paint base viscosity. The data fit the observation in Figure 5B. From the data in Figure 6, we define an (S-5)[.sub.max] concentration.

Approaching Reality: The CB Colorant In a Waterborne Coating

Based on our own latex syntheses (17) and analysis of selected commercial small particle size latices, a significant amount of surfactant (ca. 0.45 wt%) resides in the aqueous phase of a ca. 100 nm latex dispersion. When surfactant is added in preparation of the titanium dioxide grind, an additional 0.3 wt% enters the dispersion. In our formulations over the past three decades, the fourth surfactant in Table 1, ([C.sub.6][H.sub.13])[.sub.2]CH(OC[H.sub.2]C[H.sub.2])[.sub.9]OH, has been the one added to the Ti[O.sub.2] grind. When the excess package of surfactants in a colorant formulation (e.g., Table 1) is added to a paint base at 3 wt%, or at 12 wt% for deeper color tones, there is a large excess of surfactant in the aqueous solution or in the paint. Calculated amounts are given in Table 2.

Colorant Additions to a Waterborne Coating

The discussion from this point will be limited to HEUR thickeners, where we have a knowledge base of structural effects. Without knowledge of a commercial coating's composition (except that it was a 35 PVC coating, 25 NVV of a 350 nm vinyl acrylic latex, and 10 VF Ti[O.sub.2], but without knowledge of the other components) the S-5, S-3, and (S-5)[.sub.max] surfactant compositions, containing CB, were added to a commercial pastel coating. The amount of surfactant required to promote a viscosity maximum is proportional to the associative thickener's concentration. (1,18) The associative thickener concentrations used in the data presented in Figures 2 through 5 are high (to obtain a 110 KU viscosity). In the presence of disperse phases (i.e., latex, pigment, fillers, etc.) the amount of thickener needed to bring a coating formulation to 110 KU is much less, probably 0.5 wt% versus the 4 wt% used in CB dispersions. Thus, the total amount of surfactant from the latex and pigment, with that coming in with the colorant, would be far above that promoting a viscosity maximum at a low thickener concentration (Figure 1). Nevertheless, we will move forward to address the viscosity loss problem observed when colorants are added to waterborne coatings, whose compositions are unknown.

[FIGURE 8 OMITTED]

With all five surfactants (the S-5 formulation, Table 1), addition of the CB colorant to the pastel paint dramatically decreased the viscosity of the paint (Figure 7). When the two most surface active surfactants, C[H.sub.3](C[H.sub.2])[.sub.15]S[O.sub.3.sup.-](C[H.sub.3])[.sub.2]CHN[H.sub.3.sup.+] and C[H.sub.3](C[H.sub.2])[.sub.12](EO)[.sub.6]P[O.sub.4.sup.-][K.sup.+], were removed from the colorant formulation (the S-3 formulation), a viscosity decrease did not occur. The viscosity actually increased above shear rates of 300 [s.sup.-1] when only the three less surface active surfactants in the CB colorant were added to the pastel paint. This viscosity increase was also observed with all five surfactants when their concentration was lowered [i.e., (S-5)[.sub.max]]. There was a slight incompatibility problem (to be discussed in a later section) observed when the surfactant concentrations were reduced. The lack of compatibility of the colorant resulted in poor color properties, such as low tint strength and color changes when the paint was either shaken again or reapplied by touchup.

[FIGURE 9 OMITTED]

This trend was also observed when the colorant was added at 12 wt% (Figure 8) to obtain deeper color tones, except that the viscosity decrease was more dramatic, and it was not recoverable with the S-3 and (S-5)[.sub.max] surfactant adjustments, due in part to dilution effects. The volume fractions of the latex, pigment, etc. were lowered as well as the thickener concentration.

Adding Hydrophobe-Modified Components To the CB Colorant

Associative thickeners impart two benefits to paints. They increase the viscosity of the paint and they aid in stabilizing the dispersed phases, such as latex and titanium dioxide. For this reason, the three HEUR associative thickeners examined in Figures 4 and 5 were added to the original black colorant formulation in replacement of the random C[H.sub.3](C[H.sub.2])[.sub.3](EO/PO)[.sub.r](EO)[.sub.y]H copolymer. Compositionally, HEUR thickeners are very close to the C[H.sub.3](C[H.sub.2])[.sub.3](EO/PO)[.sub.r](EO)[.sub.y]H copolymer, HEURs do not lower the surface tension to 32 mN/m, but they are capable of competitively adsorbing at latex surfaces in the presence of surfactants. (19) More importantly, they are capable of building viscosity in the presence of surfactants. This additional viscosity build should help in minimizing the viscosity decrease when the colorant is added to the commercial paint base.

[FIGURE 10 OMITTED]

The colorants containing CB, 1.65 wt% thickener and all of the S-5 surfactants in Table 1 were added at 3 wt% to the commercial pastel paint. The colorants with associative thickeners led to slight increases in viscosity when compared to the paint base without colorant (Figure 9) even though the surfactant levels were high. The viscosity data are a little different than the original data because the samples were tested for a longer period of time after shaking as compared to the previous samples, and the viscosity of the colorant/coatings blends are history dependent.

The colorants were then added at 12 wt% to the commercial paint base, and notable decreases in coating viscosities (Figure 10) were observed due to the dilution effect. However, they were not as large as the decreases noted when the original S-5 colorant was added without HEUR thickeners (Figure 8). When added to the commercial latex coating, the CB colorant with the comb-PO[E.sub.198](IPDI-NP-IPDI-PO[E.sub.198])[.sub.6]-IPDI-PO[E.sub.198] has the smallest decrease in viscosity, followed by the telechelic-[C.sub.12][H.sub.25]-[[H.sub.12]MDI-(EtO)[.sub.182]][.sub.3]-[H.sub.12]MDI-[C.sub.12][H.sub.25] and the surfactant sensitive comb-PO[E.sub.198](IPDI-[C.sub.14][H.sub.29]-IPDI-PO[E.sub.198])[.sub.10]-IPDI-PO[E.sub.198] comb. In the studies previously mentioned, the colorant formulation at the surfactant viscosity maximum and formulating with associative thickeners eliminated the viscosity decrease at 3 wt% but not at 12 wt%.

The remainder of this study focuses on minimizing the viscosity loss when 12 wt% CB formulations were added to the commercial pastel coating. With the increased surfactant coming into the pastel coating with a 12 wt% CB formulation, the total surfactant concentration was lowered to the viscosity maximum level [(S-5)[.sub.max], Figure 6] in the presence of the HEUR thickener in the colorant formulation. Colorants formulated with either [C.sub.12][H.sub.25]-[[H.sub.12]MDI-(EtO)[.sub.182]][.sub.3]-[H.sub.12]MDI-[C.sub.12][H.sub.25] or PO[E.sub.198](IPDI-NP-IPDI-PO[E.sub.198])[.sub.6]-IPDI-PO[E.sub.198] thickener and surfactant levels at the viscosity maximum concentration did not lead to a viscosity decrease even with 12 wt% colorant in the paint base (Figure 11). With the most surfactant sensitive comb-HEUR, PO[E.sub.198](IPDI-[C.sub.14][H.sub.29]-IPDI-PO[E.sub.198])[.sub.10]-IDPI-PO[E.sub.198], only a minor decrease in viscosity was observed. In the previous colorant formulated with (S-5)[.sub.max] surfactants, without HEURs, incompatibilities were observed. With the inclusion of HEURs, the compatibility of the CB colorant coating improved.

[FIGURE 11 OMITTED]

[FIGURE 12 OMITTED]

Effects of Alpha Olefin/Maleic Acid Dispersant Addition To the Colorant Formulation

Hydrophobically modified dispersants are very effective in stabilizing Ti[O.sub.2] and enhancing film gloss. (20-22) Oxidized carbon black contains many different types of oxygen functional groups on its surface (23) that could allow the surface to interact with alpha olefin dispersants, much like Ti[O.sub.2]. Alpha olefin dispersants are also lower cost items than HEURs. For this reason, two hydrophobically modified (one with 1-octadecene ([C.sub.18][H.sub.36]) and the other with a diisobutylene) co-oligomers with maleic acid (Figure 12), at 0.8 wt%, were compared with a styrene acrylic acid in the CB S-5 colorant.

The surfactant packages will still be referred to as S-5 and (S-5)[.sub.max], although we have replaced the EO/PO random copolymer with HEURs and refer to the latter outside the box, since the HEURs vary in composition. When added to the pastel commercial coating, with the high S-5 surfactant composition at a 12 wt% coating load, the dispersants alone or in combination with any of the three HEURs were not effective in maintaining paint viscosities (Figure 13A).

When the surfactant loading was reduced to the viscosity maximum concentration (Figure 7; this is a device, for in the coating formulation there are many components that would distort such an estimate), the dispersants, alone, were not effective in maintaining the viscosity (Figure 13B). However, the two hydrophobe-containing MA dispersants with any of the HEURs were effective in maintaining the pastel coatings viscosity, at a 12 wt% loading, even with the most surfactant sensitive [C.sub.14][H.sub.29]-comb-HEUR. The remaining question is: how do these variations affect the rub-up compatibility of the paints?

With the large [C.sub.18][H.sub.36]/MA dispersant, compatibility was observed with or without an HEUR in the colorant (Tables 3 and 4), even in the lower (S-5)[.sub.max] level. With the smaller hydrophobe dispersant, DIBMA, compatibility was not observed, particularly in the lower surfactant levels. One of the two less surfactant sensitive HEURs was required at the lower (S-5)[.sub.max] surfactant concentration with the DIBMA to achieve compatibility. As noted in the 12 wt% loading at the lower surfactant concentration (Figure 13B), an HEUR is needed to compliment the hydrophobe/MA dispersant to maintain the original paint viscosity level without colorant.

[FIGURE 13 OMITTED]

Changing the Colorants

To determine the effects of using different colorant pigments, organic red and organic yellow were formulated with the S-3 surfactant formulation and compared to the CB S-3 formulation. The pastel paint containing the three different colorants had similar viscosity profiles at 3 wt% and 12 wt%, suggesting that the colorant had little or no effect on the viscosity of the pastel paint. That is not surprising, for the volume fraction of the colorant in the final coating was ca. 1.0.

The commercial coating used in this study encompassed one latex and probably a thickener combination. The influence of known variations in these entities and their synergies with the components in the colorant will be studied in the next article and will focus on the structural aspects of surfactants on color development.

CONCLUSIONS

Colorants with high levels of surface-active components result in a decrease in the viscosity of paints. This viscosity decrease is related to surfactant/associative thickener interactions. The surfactants can also greatly influence the phase behavior and network formation of associative thickeners in aqueous solutions. The decreases in viscosity can be inhibited by altering the amount of surfactant in the colorants. Two separate modifications were made: one with the surfactant levels at or near the viscosity maximum of the two comb-HEURs, and one with the two most surface-active surfactants removed. In both cases, the viscosity decrease in the paint was inhibited at 3 wt% colorant. However, when larger colorant concentrations (12 wt%) were added to a commercial coating, there were still decreases in viscosity even with surfactant reduction because of dilution effects, and additional surfactant addition. Incorporating HEUR thickeners and hydrophobically modified maleic acid dispersants into colorants retained the paint's viscosity, even at 12 wt% colorant, and improved its compatibility. This improved compatibility occurred despite reduction in the surfactant by 67 wt%. Similar surfactant packages were added to an organic red and organic yellow colorant, and the viscosity profiles did not change when varying the colorant.

References

(1) Mahli, D.M., Steffenhagen, M.J., Xing, L.L., and Glass, J.E., "Surfactant Behavior and Its Influence on the Viscosity of Associative Thickeners Solutions, Thickened Latex Dispersions, and Waterborne Latex Coatings," JOURNAL OF COATINGS TECHNOLOGY, 75, No. 938, 39 (2003).

(2) Berns, R.S., Billmeyer and Saltzman's Principles of Color Technology, 2nd Ed., Wiley-Interscience, New York, 2000.

(3) Sau, A. and Landoll, L.M., Advances in Chemistry 223: Polymers in Aqueous Media, Performance through Association, Glass, J.E. (Ed.), American Chemical Society: Washington, D.C., Chapt. 18, 1989.

(4) Glass, J.E., "Adsorption Characteristics of Water-Soluble Polymers at Aqueous-Organic Liquid Interfaces," J. Polym. Sci., 34C, 141-157 (1971).

(5) Vijayendran, B.R., in Polymer Colloids II, Fitch, R.M. (Ed.), Perseus Publishing, p. 209, 1980.

(6) Glass, J.E., "Adsorption and Its Influence on Application Properties," Advances in Chemistry Series 213, Water-Soluble Polymers: Beauty with Performance, Glass, J.E., (Ed.), American Chemical Society, Washington, D.C., Chapt. 5, p. 85-100, 1986.

(7) Glass, J.E., "Adsorption of Hydrophobically-modified, Ethoxylated Urethane Thickeners on Latex and Titanium Dioxide Disperse Phases," Adv. Colloid Interface Sci., 79, 123-148 (1999).

(8) Glass, J.E., "A Perspective on the History of and Current Research in Surfactant-Modified, Water-Soluble Polymers," JOURNAL OF COATINGS TECHNOLOGY, 73, No. 913, 79 (2001).

(9) Douillard, J.M., Pougnet, S., Faucompre, B., and Partyka, S. J. Colloid Interface Sci., 154, 113 (1992).

(10) Ma, C. and Xia, Y., Colloids Surf., 66, 215 (1992).

(11) Bossoletti, L., Ricceri, R., and Garielli, G., J. Dispersion Sci. Technol., 16 (3 & 4), 205-220 (1995).

(12) Schwuger, M.J. and Smolka, H.G., Colloid Polym. Sci., 255, 589-594 (1977).

(13) Miano, F., Bailey, A., Luckham, P.F., and Tadros, T.F., Colloids Surf., 62, 111 (1992).

(14) Musselman, S.W. and Chandler, S., J. Colloid Interface Sci., 256, 1 (2002).

(15) Musselman, S.W. and Chandler, S., Colloids Surf., A, 206, 497 (2002).

(16) Wetzel, W.H., Chen, M., and Glass, J.E., in Hydrophilic Polymers: Performance with Environmental Acceptance, Glass, J.E. (Ed.), Advances in Chemistry 248, American Chemical Society, Washington, D.C., Chapt. 11, 1995.

(17) Karunasena, A. and Glass, J.E., Prog. Org. Coat., 16(3), 301-320 (1989).

(18) Kaczmarski, J.P., Tarng, M.R., Ma, Z., and Glass, J.E., Colloids Surf., A, 146, 39-53 (1999).

(19) Ma, Z., Chen, M., and Glass, J.E., Colloids and Surf., A. 112(2-3), 163-184 (1996).

(20) Lundberg, D.J. and Glass, J.E., "Pigment Stabilization Through Mixed Associative Thickener Interactions," JOURNAL OF COATINGS TECHNOLOGY, 64, No. 807, 53-61 (1992).

(21) Kaczmarski, J.P., Tarng, M.R., Glass, J.E., and Buchacek, R.J., Prog. Org. Coat., 30, 15-23 (1997).

(22) Tarng, M., Chen, M., Glass, J.E., and Dickinson, J.G., "Unifying Model for Associative Thickener Influences on Waterborne Coatings: II. Competitive Adsorption of Nonionic Surfactants and HEUR Thickeners on Titanium Dioxide Pretreated with Inorganic Stabilizers and Organic Oligomers Dispersants," JOURNAL OF COATINGS TECHNOLOGY, 74, No. 935, 45 (2002).

(23) Stoy, W.S. and Garret, M.D., in Pigments: Part 1, Myers, R.R. and Long, J.S. (Eds.), Marcel Dekker, Inc., New York, Chapt. 5, 1975.

David M. Mahli, Jon M. Wegner, and J. Edward Glass** -- North Dakota State University*

Daniel G. Phillips -- Degussa Corp. ([dagger])

Presented in part at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 13-14, 2003 in Philadelphia, PA.

* Dept. of Polymers and Coatings, 1735 NDSU Research Park Dr., Fargo, ND 58105.

([dagger]) 2 Turner Place, Piscataway, NJ 08854.

** Author to whom correspondence should be addressed: University of Lake Wobegon, Coatings Plus Dept., 1751 S. 23rd St., Fargo, ND 58103, email: [e-mail].

Table 1 -- Surface Tension of Surfactants Examined in This Study

                                                 Dynamic Surface Tension
Surfactant Structure                  Conc. wt%  mN/m

C[H.sub.3](C[H.sub.2])[.sub.15]       0.10       27
S[O.sub.3.sup.-](C[H.sub.3])[.sub.2]
CHN[H.sub.3.sup.+]
C[H.sub.3](C[H.sub.2])[.sub.12]       0.10       29
(EO)[.sub.6]P[O.sub.4.sup.-]
[K.sup.+]
C[H.sub.3](C[H.sub.2])[.sub.9]        0.10       30
(EO)[.sub.15]
([C.sub.6][H.sub.13])[.sub.2]         0.10       31
CH(OC[H.sub.2]C[H.sub.2])[.sub.9]OH
C[H.sub.3](C[H.sub.2])[.sub.3]        0.10       31
(EO/PO)[.sub.r](EO)[.sub.y]H

Table 2 -- Surfactant (wt%) in Colorant and in the Final Tinted Paint
Containing a 100 nm Latex and One of Three Colorant Formulations Used in
This Study

                 Surfactant in       Surfactant from Colorant
                 Colorant (wt%)       (wt%) in Tinted Paint
Colorant                         3 wt% Colorant  12 wt% Colorant

S-5                  15.6             0.46             1.86
S-3                   9.1             0.26             1.09
(S-5)[.sub.max]       5               0.15             0.60

                 Total Surfactant (wt%) in Tinted
                 Paint (Colorant+Latex+Ti[O.sub.2])
Colorant          3 wt% Colorant  12 wt% Colorant

S-5                    1.22             2.62
S-3                    1.02             1.84
(S-5)[.sub.max]        0.90             1.35

Table 3 -- Rub-Up Compatibility Tests with S-5 Surfactant CB Colorant
Formulation with Various Thickeners and Dispersants

                            S/AA                   DIBMA

Black S-5                   Slightly incompatible  Slightly incompatible
PO[E.sub.198](IPDI-NP-IPDI  Compatible             Compatible
-PO[E.sub.198])[.sub.6]-
IPDI-PO[E.sub.198] comb-
HEUR
[C.sub.12][H.sub.25]-       Compatible             Compatible
[[H.sub.12]MDI-
(EtO)[.sub.182]][.sub.3]-
[H.sub.12]MDI-[C.sub.12]
[H.sub.25]HEUR
PO[E.sub.198](IPD-          Very slight            Compatible
[C.sub.14][H.sub.29]-IPDI-  incompatibility
PO[E.sub.198])[.sub.10]-
IPDI-PO[E.sub.198]comb-
HEUR

                            [C.sub.18][H.sub.36]MA

Black S-5                   Compatible
PO[E.sub.198](IPDI-NP-IPDI  Compatible
-PO[E.sub.198])[.sub.6]-
IPDI-PO[E.sub.198] comb-
HEUR
[C.sub.12][H.sub.25]-       Compatible
[[H.sub.12]MDI-
(EtO)[.sub.182]][.sub.3]-
[H.sub.12]MDI-[C.sub.12]
[H.sub.25]HEUR
PO[E.sub.198](IPD-          Compatible
[C.sub.14][H.sub.29]-IPDI-
PO[E.sub.198])[.sub.10]-
IPDI-PO[E.sub.198]comb-
HEUR

Table 4 -- Rub-Up Compatibility Tests with (S-5)[.sub.max] Surfactant CB
Colorant Formulation with Various Thickeners and Dispersants

                            S/AA             DIBMA

Black (S-5)[.sub.max]       Incompatible     Incompatible
PO[E.sub.198](IPDI-NP-IPDI  Compatible       Compatible
-PO[E.sub.198])[.sub.6]-
IPDI-PO[E.sub.198]comb-
HEUR
[C.sub.12][H.sub.25]-       Very slight      Compatible
[[H.sub.12]MDI-             incompatibility
(EtO)[.sub.182]][.sub.3]-
[H.sub.12]MDI-[C.sub.12]
[H.sub.25]HEUR
PO[E.sub.198](IPDI-         Very slight      Very slight incompatibility
[C.sub.14][H.sub.29]-IPDI-  incompatibility
PO[E.sub.198])[.sub.10]-
IPDI-PO[E.sub.198]comb-
HEUR

                            [C.sub.18][H.sub.36]MA

Black (S-5)[.sub.max]       Compatible
PO[E.sub.198](IPDI-NP-IPDI  Compatible
-PO[E.sub.198])[.sub.6]-
IPDI-PO[E.sub.198]comb-
HEUR
[C.sub.12][H.sub.25]-       Compatible
[[H.sub.12]MDI-
(EtO)[.sub.182]][.sub.3]-
[H.sub.12]MDI-[C.sub.12]
[H.sub.25]HEUR
PO[E.sub.198](IPDI-         Compatible
[C.sub.14][H.sub.29]-IPDI-
PO[E.sub.198])[.sub.10]-
IPDI-PO[E.sub.198]comb-
HEUR