David Robinson Bassett

New vinyl ester monomers for emulsion polymers

New vinyl ester monomers are now available for the preparation of emulsion copolymers with improved hydrolytic stability and water resistance. These improved properties are the result of uniform copolymerization of hydrophobic monomers having approximately the same reactivity as vinyl acetate. Latex coatings with excellent gloss, water spot resistance, blocking and other desirable performance properties can now be obtained with vinyl acetate copolymers.

Surfactant co-thickening in model associative polymers

Abstract Associative thickeners act to thicken aqueous systems through the formation of non-specific hydrophobe associations. The formation of these ‘pseudomicellar’ units is driven by the exclusion of the thickener hydrophobes from the aqueous phase, a phenomenon greatly enhanced by the presence of the appropriate level and type of non-ionic surfactant. This enhancement of hydrophobic association is accompanied by a dramatic increase in solution viscosity, commonly referred to as surfactant co-thickening. The selection of an ‘appropriate’ surfactant is dictated by the solubility of the surfactant in the system which is in turn controlled by temperature, the nature of the surfactant hydrophobe, the degree of ethoxylation and the presence of co-solvents.

Synergistic Interactions Among Associative Polymers and Surfactants

The need to improve the performance of formulated aqueous systems containing associative polymers makes elucidating the interactions between associative polymers and surfactants an important contemporary problem in associative polymer technology. For example, adding surfactant to a latex formulation may cause its viscosity to either increase or decrease, depending on the outcome of competitive adsorption of thickener and surfactant at particle interfaces and at network junctions in the aqueous phase [1]. Even though this subject has been widely studied by both academic and industrial laboratories, the capricious nature of these interactions is not understood on a molecular level. Recent studies have examined the interaction of nonionic, anionic, cationic, or zwitterionic surfactants with a variety of associative polymer types, such as those based on backbones of poly(ethylene oxide) [2-13], cellulose [14-16], copolymers of acrylic acid, methacrylic acid, or other carboxylated monomers [6,17-19], and copolymers of acrylamide [20,21]. The charter of the NATO Advanced Study Institute is to “point out unsolved problems and speculate about future research directions” [22]. In the spirit of this charter, this chapter describes the phenomenology that applies to a variety of associative polymer types resulting from interactions between associative polymers and surface active agents to highlight the need for more fundamental research.

Statistical studies of branched ester latex and paint properties

Abstract Vinyl versatate, butyl acrylate and 2-ethylhexyl acrylate were compared as comonomer, for colloid-stabilized vinyl acetate latex polymers to assess their impact on latex coating properties. Vinyl versatate afforded advantages in scrub resistance, gloss, hydrophobicity and higher glass transition temperatures. Butyl acrylate developed better wet adhesion efficiency, gel content and hiding efficiency. 2-Ethylhexyl acrylate offered performance comparable to butyl acrylate in hiding efficiency, lowering copolymer glass transition temperatures, and gloss development. Combinations of these monomers, in many instances, afforded a better balance of performance properties than individual monomers alone. In the subject study, a simplex-centroid design was utilized to statistically map polymer compositions for determining the effect of comonomer composition on latex and paint film properties. In addition to developing contour maps of polymer and paint properties as a function of composition, a technique for studying structure-property relationships is presented.

A study on the chemistry of alkylcarbodiimide ethylmethacrylates as reactive monomers for acrylic and vinyl ester-based latexes

Abstract The preparation of carbodiimide methacrylates from their corresponding urea methacrylate is described. Carbodiimide methacrylates were reacted with waterborne carboxylic acid-containing acrylic polymers to produce waterborne polymers with methacrylate functionality. Nuclear magnetic resonance showed that more than 80% of the theoretical level of methacrylate functionality survived the modification process. Using a similar modification process, the level of methacrylate survival for a variety of epoxy methacrylates and 1-(2-aziridinyl)ethyl methacrylate was compared to carbodiimide methacrylates. Waterborne polymers modified with epoxy methacrylates gave polymers with less methacrylate functionality than carbodiimide methacrylates. The reaction of 1-(2-aziridinyl)ethyl methacrylate with waterborne carboxylic acid containing polymers produced waterborne polymers that contained up to 98% of the theoretical level of methacrylate functionality. The gel fraction of cured films was measured to demonstrate the crosslinking potential of polymers with methacrylate functionality.

Structure and Growth of Latex Particles

The morphology of latex particles is of interest because of the structural implications regarding growth mechanisms involved in emulsion polymerization and because of the practical expectation of certain beneficial effects obtained from structured particles. Since process and properties are so closely linked in the production of emulsion polymers, a variety of processes have been devised as efforts to design and control the microstructure of latex particles have intensified. The central issue is whether, as a general rule, particle growth is better represented in terms of a surface growth model or of a bulk polymerization model. Results obtained by a variety of methods developed to study particle and film morphology will be reviewed, and the special case of water-soluble monomers will be considered along with descriptions of process techniques designed to control particle structure.