Coatings, associative thickeners

Resin Solubilizers. In general, water-soluble resins ate amine salts of acidic polymers. Water-soluble coatings formulated with AMP-95 and DMAMP-80 exhibit superior performance (15,16) (see Water-SOLUBLE polymers). AMP-95, used in conjunction with associative thickeners (17) or hydroxy-ethylceUulose, provides for the most efficient utilization of such thickeners. It also is the neutralizer of choice for use with hair spray resins. 

The specific nature of the interactions among hydrophobes would suggest that the associative thickeners will vary in performance with the different latices and components used in coatings formulations. This has been observed(29) in... 

Glass, J.E., ed. "The Influence of Associative Thickeners and Rheology on Coatings Performance," 1983, Fargo, N.D. North Dakota State University Press. 

DSIL [Henkel/G)atii% Chem.] Urethane associative thicken rheology modifier, thickener for paints, adhesives, coatings. 

The historical development of associative thickeners has followed the usual phases of polymer development. The products available in the early 1960s were probably prepared with little thought of the concepts presented in the related chapters of this text. Somewhere, these products sparked the concept of induced micelle participation of polymeric hydrophobes and of a synergistic influence on viscosity. The somewhere was probably two places. Midland, MI, and Rutgers, NJ. These contributions were taken with others from continental Europe and focused on the coatings industry and, with time, on other industries. 

Recently, a new class of surface-active synthetic WSPs called synthetic associative thickeners was introduced to the latex coatings industry. These compounds have generated interest because of their unique rheological characteristics in aqueous systems (i). These synthetic macromolecules are composed of hydrophilic and hydrophobic components. 

HMHEC polymers are improved rheological modifiers for latex paints. They retain the benefits of traditional cellulosic ethers (compatibility with a wide range of coatings ingredients, storage stability, better sag resistance, etc.) but overcome many deficiencies of synthetic associative thickeners (sensitivity to latex systems and pH of paint formulations, poor sag resistance, etc.). The combined advantages offered by HMHEC are best suited for interior and exterior flat paints (5). 

X HE USE OF HYDROPHOBIC INTERACTIONS to produce associative thickeners has increased markedly over the past 10 years in such diverse areas as surface coatings and enhanced oil recovery. The desired thickening properties are produced by relatively low molecular weight polymers that are reversibly cross-linked by pendant hydrophobic moieties to give a three-dimensional network. To maintain solubility, the number of hydrophobes per soluble molecule is low, and the chain length is typical of that used in surfactants (i.e., Cs-Cie). In solution, the hydrophobes appear to associate in an analogous fashion to micellization, in that, in the absence of surfactants. 

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