Hydrophobically modified alkali swellable

Hydrophobically Modified Alkali-Swellable Emulsions. The hydrophobe modification of acryHc acid represents an important class of... 

The two associative thickeners examined in the remainder of this text whose synthesis has not been discussed are hydrophobe-modified alkali-swellable emulsions (HASE) discussed in Chapters 25, 27, and 28, and hydrophobe-modified (hydroxyethyl)cellulose (HMHEC, discussed in Chapters 17, 18, and 27). HASE thickeners, by far the lowest cost hydrophobe-modified thickeners produced, should have achieved the largest market share on the basis of cost of production, but this situation does not appear to be the case (discussed in Chapter 28) in large part because of the poor properties observed with the lowest cost latex, vinyl acetate, used to form the continuous film. The applied-film properties 46) of vinyl acetate can be substantially improved through the use of HEUR polymers. HMHEC, synthesized by a matured (30-year-old) commercial slurry process (47) has achieved commercial acceptance, in large part because of linear high shear rate viscosities achieved in blends with HEUR thickeners (Chapter 27). 

The AST process receiving the greatest industrial and academic attention by far has been that of emulsion polymerization, and because of the relative importance of the emulsion thickeners, these polymers will be the object of considerable discussion in this review. When conventional ASTs are specifically prepared by this process, alkali-swellable or alkali-soluble emulsions (ASE) are obtained. For conventional ASTs produced by processes other than emulsion polymerization (nonemulsion), the acronym ASNE has been adopted herein. The associative ASTs have analogous designations. HASE is the common acronym for hydrophobically modified, alkali-swellable or alkali-soluble emulsion, and HASNE is the adopted acronym for the associative nonemulsion thickeners. The family of AST polymers reflecting this classification scheme is shown in Figure 2. 

HASE Hydrophobically modified alkali-swellable or alkali-soluble emulsion... 

X HE RELATIVE COST OF MANUFACTURING hydrophobically modified, water-soluble polymers is the primary determinant in their market acceptance. The lowest-cost associative thickeners used in coating formulations are hydrophobically modified, alkali-swellable emulsions (HASE). The extensive history leading to the development of this technology is reviewed in the preceding chapter their utilization and limitations are discussed in Chapters 27 and 28. 

HASE (hydrophobically modified alkali-swellable emulsion, discussed in Chapters 25 and 28) and HEUR thickeners are readily displaced from acrylic latex surfaces (32) by sodium dodecyl sulfate (SDS). A surface-active cellulose ether was also reported (33) to desorb from monodispersed poly(styrene) latices with SDS addition. In these studies, the relative critical micelle concentrations of the anionic surfactant and thickener appear to be more important than buffering of surface charges. 

HEUR/Hydrophobically Modified Alkali-Swellable Latex. 

Hydrophobically modified alkali-swellable latex thickeners (Chapter 25) can also be used as cothickeners for HEURs, and, like hydrophobically modified HEC, do not suppress the ICI viscosity of HEURs. Therefore, blend ratios of HEUR/hydrophobically modified alkali-swellable latex systems will have less HEUR thickener and be less expensive than HEUR/cellulosic systems. Some hydrophobically modified alkali-swellable latexes are even more cost-efficient than cellulosic thickeners, so a further savings may be realized. Another advantage to this approach is that the HEUR/hydrophobically modified alkali-swellable latex thickener systems are not biodegradable however. 

The reduction of scrub resistance is the main disadvantage of HEUR/ hydrophobically modified alkali-swellable latex thickener systems 18, 19). Hydrophobically modified alkali-swellable latex-thickened paints often show increased water and alkali sensitivity, reduced wet and dry adhesion, and lower scrub resistance than similar cellulosic-thickened paints. 

Two base paints should be blended, one with a high ICI viscosity and one with a low ICI viscosity, to obtain the desired ICI viscosity. During this process, the Stormer viscosity should remain constant. Typical thickener combinations used are HEUR/cellulosic, HEUR/hydrophobically modified HEC, and HEUR/hydrophobically modified alkali-swellable latex. 

Hydrophobically modified alkali-swellable latex thickener. 

Rheology results are shown in Figure 5 for combination of dispersants with a commercially available HASE (hydrophobically modified alkali swellable acrylic emulsion) thickener. 

Chem. Descrip. Hydrophobically modified alkali-swellable emulsion Uses Rheology control agent for paper and paperboard coatings, esp. lightweight coatings... 

Pulsed gradient spin echo NMR was used to measure the diffusion coefficients of hydrophobically modified alkali-swellable (HASH) associating polymers (AP) in aqueous solution. The HASH APs consisted of a methacrylic acid-ethyl acrylate copolymer to which hydrophobic sticker ... 

The rheological properties of hydrophobe-modified alkali-swellable emulsion (HASE) thickener solution are studied, with emphasis on surfactant and electrolyte (NaCl) effect. Similar studies in model HASE thickeners have been reported. Two commercial HASE thickeners (HASE-615 and HASE-935) are examined for comparison. In the absence of SDS, the NaCl addition changes solution viscosity depending on the relative concentration of the NaCl and thickener. The viscosities of HASE type thickeners are enhanced by an anionic surfactant, sodium dodecyl sulphate (SDS) and viscosity maxima are observed due to mixed micelle formation among thickener hydrophobes and surfactants. The addition of NaCl suppresses the viscosity of HASE-615/ SDS solutions, with HASE-935 at higher concentrations actually increasing in viscosity with NaCl addition. 2 refs. USA... 

Siu H, Duhamel J (2006) Associatimis between a pyrene-labeled hydrophobically modified alkali swellable emulsion copolymCT and sodium dodecyl sulfate probed by fluorescence, surface tension, and rheology. Mataomolecules 39 1144—1155... 

Associative acrylic thickeners are also known as hydrophobically modified alkali-swellable emulsions (EASE). Chemically, they are copolymers composed of three blocks ... 

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