Associative acrylic thickeners

The introduction of these new rheology modifiers provides paints manufacturers with a very attractive alternative to cellulosic thickeners. These rheology modifiers are the first acrylic associative thickeners that offer a similar rheology, in-can feeling, appearance, and application properties as cellulosic thickeners. They also show some key advantages compared to cellulosic thickeners. Supplied as liquids, they are easier to handle and because of their polymeric chemistry, they are less sensitive to microbial attack In application trials, professional painters found that new rheology modifier based paint performs similarly to cellulose thickened paint but with a better spattering resistance. 

The LSV dependence on surface acid concentration observed with most associative thickeners in this pigmented 20-latex study is illustrated in Figure 17. A latex-associative thickener network model for viscosities at low shear rates is proposed in Figure 18. This model is not the poly(acrylic acid)-poly(oxyethylene) complex observed over 2 decades ago (36). The coatings discussed are alkaline (pH 9). Examination of the data presented in... 

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. 

In practical latex formulations, the latex particle size can play a major role in determining the rheology obtained with a given associative thickener. A thickener which provides nearly Newtonian flow with a large particle size, relatively hydrophilic latex (such as an interior paint grade vinyl-aciylic latex) may produce veiy high low-shear viscosity, and shear thinning when a smaller particle size, more hydrophobic acrylic latex is used in the same formulation. 

Chem. Descrip. Acrylic alkali-swellable associative thickener Uses Thickener in interior flat paints, textiles Featiaes Provides low cost/high performance alternative to traditional cellulosic thickeners provides outstanding resist, to roller spattering, better film build and leveling alkali-sol. 

Uses Associative thickener, stabilizer in aq. systems, latex paints, esp. suitable in paints with binders like PVA, PVA/acrylic, and VA/VeoVa which have weak association with associative thickeners Features Increases low shear vise. 

Uses Acrylic tor interior semigloss and exterior house paints Features Provides improved response to associative thickeners to provide higher gloss high scrub resist. 

Uses Associative thickener, rheology modifier for industrial latex paints, adhesives, waterborne architectural coatings, printing inks, suitable for acrylics, PVC/PVdC, PU Features Maximizes high sheer vise. 

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. 

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. 

Uses Rheology control agent, associative thickener, leveling agent for acrylic and vinyl acrylic latex paints, flat/matte and semigloss paints, gloss enamels, interior architectural topcoats, adhesives, cementitious prods., inks, mastics, slurries Features Good roller spatter resist. 

Progress in Organic Coatings 42, Nos.1-2, June 2001, p.110-5 THICKENING OF BUTYL ACRYLATE/ STYRENE/2-HYDROXYETHYL METHACRYLATE/ACRYLIC ACID LATICES WITH AN HEUR ASSOCIATIVE THICKENER Quadrat O Horsky J Mrkvickova L Mikesova J Snuparek J... 

Table 3 Various Hydrophobically Modified, Acrylate-Based Associative Thickeners...

Table 3 lists several of the hydrophobic acrylate-based polymers currently being investigated. This list can be broken down into two categories, separated by the horizontal line through the table. Hydrophobic acrylates in the upper portion (page 244) have their hydrophobic entity in close proximity to the acrylate backbone. Those in the lower (page 245) portion of the table have their hydrophobic entity separated from the acrylate backbone by a polyether (typically polyethylene oxide) chain. While the presence of the polyether chain is not required for an associative mechanism to operate, it has been demonstrated that its presence can influence viscosity (84). In particular, nonionic surfactants that themselves contain polyether chains seem to have a particular attraction to the polyether chains of the associative thickener. 

Usually pH has to be adjusted with a suitable base, since the acrylate is a polyacid, to get an optimal extended polymer conformation [16] which leads to thickening of emulsions. Final emulsion viscosity depends on acrylate concentration and is independent of temperature control during preparation in contrast to common emulsions. In emulsions acrylate adsorbs at the oil/water interface at low concentrations of acrylate stabilization results from electro-steric effects and in the upper concentration range an associative thickening mechanism is postulated [17]. 

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). 

Synthetic products comprise polyvinyl alcohol (PVOH), polyvinyl pyrrolidone (PVP) in combination with PVOH, acrylic copolymers, and associative thickeners. 

The main products used as thickeners are CMC, PVOH (both already described in Section 3.6.9.3.4.1), acryhc copolymers and associative thickeners. The acrylic copolymers are nonionic monomers and acrylic acid or methacrylic acid. The nonionic monomers are mainly esters of acrylic acid (principally methyl acrylate and ethyl acrylate) and methacryhc add (principally methyl methacrylate), and acrylamide. The monomers that are selected need to be fairly hydrophihc and polar in... 

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