Hydrophobically modified ethoxylated thickeners

Hydrophobically Modified, Ethoxylated Urethane. HEUR associative thickeners are in effect poly(oxyethylene) polymers that contain terminal hydrophobe units (66). They can be synthesized via esterification with monoacids, tosylation reactions, or direct reaction with monoisocyanates. There are problems associated with all of the methods of synthesis. The general commercial procedure for their synthesis is by a step-growth addition of... 

During these developments, hydrophobically modified ethoxylated urethane (HE UR) thickeners were synthesized and patented (6, 7). Their application in coatings was discussed, but the emphasis was on improved barrier properties (8), not on rheological influences. The HEUR polymers of the... 

Hydrophobically modified, ethoxylated urethanes (HEURs) are the thickeners of choice in exterior coatings and in corrosion-resistant, high-gloss industrial latex finishes. This chapter presents an overview of our research efforts and discusses approaches to the synthesis of HEUR polymers with different molecular architectures, geometrical influences on solution properties, and viable mechanisms by which this class of associative thickener effects desirable coatings rheology and applied film properties. 

Chem. Descrip. Hydrophobe modified ethoxylate Uses Rheology control agent, associative thickener for latex systems, high gloss and semi-gloss coatings, waterborne architectural and industrial paints, printing inks, suitable for acrylics, styrene-acrylics Properties Clear liq. dens. 8.75 Ib/gal vise. 1800 cps VOC 20% (EPA Method 24) 40% act., 40% water Use Level 1.0-3.0% on total wt. 

Finally, by way of illustration, we mention a polymer type currently receiving much attention. The polymer is referred to as hydrophobically modified ethoxylated urethane (HEUR), the reaction product of a PEG and a diisocyanate, end-capped with a long chain alcohol or amine. HEURs are already recognized as having much potential as associative thickeners in coating formulations. Their structure suggests they will show pronounced interaction with surfactants in solution and this is indeed the case. Here we refer to two recent studies. The first by Hulden (95) included surface tension studies of the polymer... 

Glass JE (1999) Adsorption of hydrophobically modified, ethoxylated urethane thickeners on latex and titanium dioxide disperse phases. Adv Colloid Interface Sci 79 123-148... 

Associative thickeners increase the viscosity of the paint by interacting with other paint ingredients through bridging of particles (surface to surface) or interaction of adsorbed layers. The interactions are assumed to be through hydrophobic forces. The operative mechanism is illustrated in Figure 5.9. Important groups in this class are associative acrylic thickeners, associative cellulose ethers and hydrophobically modified ethoxylated urethanes (HEUR). 

Hydrophobically modified ethoxylated urethane thickeners, also known as polyurethane thickeners, are a more recent type of asso-... 

In addition, hydrophobically modified ethoxylated urethanes (HEUR) are prepared by hydrophobe capping of urethane prepolymers. Comb, block and star HEUR s have been synthesized. (Schemes 1.2-1.4) [27]. Such polymers are very effective associative thickeners for urethane paints and coatings. 

In the second study Wang and Winnik [6] reported pyrene probe fluorescence experiments on PEO polymers end-capped with n-hexadecyl groups through urethane linkages. These polymers are examples of hydrophobically-modified ethoxylated urethane (HEUR) associative thickeners (Fig. 2.7). Two... 

Chem. Descrip. Hydrophobe modified urethane ethoxylate Uses Rheology control agent, associative thickener, flow control agent for water-based architectural and industrial coatings, adhesives, acrylic and epoxy coatings, printing inks, latex food pkg. adhesives Features Improves applic. props. 

From a theoretical point of view, any WSP potentially can be suitably modified to construct an associative thickener. Associative ASTs, however, are usually terpolymers consisting of a carboxylic monomer, a hydrophobic monomer, and a third monomer that is associative. These thickeners are prepared by using many of the same polymerization procedures used for conventional ASTs, and many of the same carboxylic acid monomers and hydrophobic monomers are employed. The presence of carboxylic or anhydride monomer is, of course, mandatory, but the hydrophobic monomer can be omitted if the associative monomer is able to impart the proper hydrophilic-hydrophobic balance for the necessary pH-dependent solubility. In Figure 1, the schematic structure of an associative AST is contrasted with that of a conventional AST. Also depicted are other associative moieties, including a nonionic surfactant, an ethoxylated anionic surfactant, and a typical nonionic associative thickener structure. The structural features common to the anionic species and those common to the associative species become obvious. 

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