Associative Thickeners thickening efficiency

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. 

List 2. Factors Known To Affect the Thickening Efficiency or Rheology of Associative AST Emulsions (HASE Thickeners) ... 

Irrespective of the free surfactant s effect on the maxima in associative thickener viscosity efficiency, the sum of the maxima in the viscosity of the associative thickener and surfactant and of the latex does not equal the viscosity of the combined components in a coating. A synergistic viscosity increase from an interaction between the thickener and the latex is required to account for the total viscosity observed (26). The most popular mechanism for association is the adsorption of the thickener s hydrophobe(s) on the surface of the latex. 

In HEC-thickened formulations, low-shear-rate viscosities increase with decreasing latex particle size. This effect has been a major limitation in formulating small-particle latices. The phenomenon appears to arise from electro viscous, hydration, or flocculation effects, not a depletion layer mechanism. Associative thickeners achieve efficient viscosity in coating formulations via participation in synthesis and formulation surfactant micelles to form pseudo macromolecules and via an ion-dipole interaction between the cations of surface carboxylate groups on the latex and the ether linkages of the associative thickener. Generally, an excess of synthesis surfactant is found in the production of small-particle latices. The achievement of lower viscosities in small-particle ( 100 nm) latex coatings thickened with associative thickener appears to occur by extensive disruption of the polymer hydrophobe s participation in intermicellar networks. 

Polyvinyl acetate or vinyl acrylic based paints tend to show more stability sensitivity with this new type of technology. Because of potential hydrolysis of vinyl acetate, the pH could drop below 7.5 and the rheology modifiers would lose their thickening efficiency. Around pH 7 there is a gelation/levering effect probably due to competition for available base between the associative thickener and the other paint ingredients. 

Because the HEUR thickeners are relatively low in molar mass (30000-100000 g mol ) compared to the alkali soluble or cellulosic associative thickeners, and the poly(ethylene oxide) backbone is so flexible, almost all of the thickening power comes from associations [106,107]. Molar mass must be high enough to provide efficient network formation, but veiy high molar mass simply dilutes the effectiveness of the hydrophobic clusters [108-110]. While the placement of the hydrophobes may have subtle effects on surface-active behaviour, the size and number of hydrophobes appear to be fee major determinants of performance [110,111]. 

Uses Associative thickener for solv.-free furniture/parquet coatings, stains Features Exc. flow and leveling, scrub resist. efficiency in ICI vise, development reduces or eliminates syneresis clear nonsettling, nonseparating sol n. 

Chem. Descrip. Carboxylated styrene-butadiene copolymer latex Uses Associative thickener for adhesives, suitable for coated and uncoated paper. Mylar, cellulose acetate, metalized polyester, aluminum, nonskid coating, and mastic substrates Features Very efficient... 

Associative thickener A thickener which obtains its efficiency presumably by association between thickener molecules or thickener and latex particles rather than through high molecular weight or chain stiffness of the thickener molecules themselves. 

In the first system, the hydrophobic monomer included in the SDS micelle is polymerized in the same polymer chain, but most of the SDS is relarged in the serum in the second system, the hydrophilic part of the surfmer remains associated with the main polymer chain (Fig. 4). In contrast, if the surfmer is mixed with a nonpolymerizable surfactant, the surfmer xmits are randomly distributed in the polyacrylamide polymer (Fig. 5). Surprisingly, the thickening efficiency of that last system is a thousand times higher than the former, it is suggested that the difference is due to the intramolecular nature of the hydrophobic interactions, when the micelles contain the surfmer only. 

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