Polyurethane dispersion

DMF as solvent [FORMIC ACID AND DERIVATIVES - DITffiTHYLFORMAMIDE] (Vol 11) Polyurethane dispersions... 

Polyurethane dispersions (PUD s) are usually high-performance adhesives based on crystalline, hydrophobic polyester polyols, such as hexamethylene adipate, and aliphatic diisocyanates, such as methylene bis(cyclohexyl isocyanate) (H12MDI) or isophorone diisocyanate (IPDI). These PUD s are at the more expensive end of the waterborne adhesive market but provide excellent performance. 

The chain extension step may then take place in the water phase. Hydrazine and ethylene diamine are commonly used chain extenders for waterborne urethane dispersions. The isocyanates react with the diamine chain extenders much faster than with the water, thus forming polyurea linkages and building a high molecular weight polymer. More detailed information regarding the synthesis and process of making waterborne polyurethane dispersions is found in Dieterich s review article [58]. 

Fig. 5. Viscosity versus time — bonding process for a waterborne polyurethane dispersion.

Two-component waterborne urethane dispersions are similar to the one-component PUD s in that a polyurethane dispersion comprises one of the two components. The second component is usually a crosslinker from the following classes of materials (a) polyisocyanates, (b) aziridines, (c) polycarbodiimides, and (d) epoxies. Many of the crosslinkers are not inherently water-soluble or water-dispersible. Therefore, they must be modified with surface active agents themselves, so as to become emulsifiable in water. 

Fig. 8. Crosslinking reactions of carboxylated waterborne polyurethane dispersions.

Example 8. Water-Borne Polyurethane Dispersion (PUD). This example illustrates the synthesis of a water-dispersible, OH-terminated polyurethane... 

One-component (1-K) polyurethane dispersions (PUDs), 206. See also 1 -K products... 

Nasrullah MJ, Bahr JA, G lagher-Lein C, Webster DC, Roesler RR, Schmitt P (2009) Automated parallel polyurethane dispersion synthesis and characterization J Coatings Tech Res 6 1-10... 

Another resin application based on the same hyperbranched polyester structure described herein is low-VOC alkyds, which have very low viscosity and high reactivity compared to conventional high-solid alkyds. Other resin structures are unsaturated polyesters, polyurethane dispersions, and epoxides. ... 

The coating is applied by traditional trade practices, namely, using rubber squeegees and paint rollers. The applied coating is cured by a mobile curing unit, which consists of a cart housing power supply for the UV lamp (see Figure 111)T If the concrete is porous, a seal coat should be applied (aqueous UV curable polyurethane dispersion (PUD) is recommended). 

Waterborne UV curable polyurethane dispersions have been developed that yield excellent performance when tested for exterior weathering. They... 

Specialty Chemicals Polymer Products Additives Polymer Processing Equipment Agrochemicals Polyurethane Dispersions Rubber Urethane Products Pool Spa Chemicals Household Cleaners... 

Polyurethane dispersion for textile coatings, imparting extremely good softness dry cleaning and washing resistant. 

Polyurethane dispersion for finishing and coating, can be coagulated with acids or cationics. 

The growing commercial use of polymer colloids whose preparation involves step polymerisations, hybrid systems and/or new routes to dispersion of polymers has not yet spawned an equivalent level of activity in academic studies. The success of the Avecia ex Zeneca Resins) technology for preparation of polyurethane dispersions is a good example of the importance of such developments. There also is the attraction of using conventional solvent-borne coating vehicles e.g., alkyd resins) in aqueous media and hybrid systems... 

The above groups function as internal emulsifiers, and introduction of these hydrophilic groups makes it possible to produce stable aqueous emulsions. Most of the polyurethane dispersions used are anionic. 

Figure 224 Scheme for an aqueous, anionically stabilised polyurethane dispersion. Source Klein H.P. and Schwab, M., Aqueous polyurethane dispersions - an environment friendly alternative for high quality paint systems, Resin News, number 29 (July) published by Hoechst AG, Frankfurt, 1993... 

Tramontane and Blank (1995) reported the preparation of a low molecular weight, hydroxyl/carboxyl functional water-borne polyurethane dispersion via monoisocyanate chemistry which is readily cross-linkable with melamine-formaldehyde resin. Such cross-linking can improve the water resistance because of the reaction of some of the hydrophilic groups (Tramontano and Blank, 1995). 

Polyurethane dispersions (PUDs) can be hybridised with acrylics. The compatibility of both resins displays several important benefits (Howarth and Manok, 1996) ... 

Howarth, G.A. and Manok, H.L. (19%) Zero VOC and high solids waterborne polyurethane dispersions. Coatings World, 10(1), 18-22. 

Because of its low boiling point and low toxicity, acetone is particularly suitable for preparing polyurethane dispersions. This procedure is therefore called the "acetone process." Although this process is rather uneconomical, it has certain advantages such as a wide scope for variation in structure and particle size, high quality of end products, and good reproducibility. 

The above-described method can be simplified by masking the diamine with a ketone to form a diketimine. Ketimines can be mixed with NCO-prepolymers without a reaction occurring. This mixture can be mixed with water to form a dispersion subsequently the ketimine hydrolyzes to form a diamine that reacts with the NCO-prepolymer to form a chain-extended, high molecular weight polyurethane dispersion. Similarly, NCO-prepolymers can be mixed with a... 

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