Water-Based Polyurethane Dispersions

Q: Water-Based Polyurethane Dispersions: What Drives Their Innovation and Adoption?
 
A: Water-based polyurethane dispersions (PUDs) are a type of coating and adhesive technology that utilizes urethane polymer particles dispersed in water. One commonly used technique for achieving this dispersion is through the use of "self-dispersing ionomeric PU prepolymers." In this process, Dimethylolpropionic acid (DMPA) is frequently employed as a component to react with a PU prepolymer, resulting in the synthesis of an ionomeric prepolymer for water-based polyurethane dispersions.
 
The chemistry behind the formation of water-based polyurethane dispersions involves the reaction of stoichiometric excess of isocyanate with hydroxy groups and a specific moiety. The structures of the polyol and isocyanate in PUD prepolymers can vary significantly depending on the desired application and requirements of the water-based polyurethane. For instance, isocyanate-terminated prepolymers are typical for water-based polyurethane dispersions, but hydroxyl-terminated prepolymers are used in the formulation of two-component water-based polyurethane systems.
 
Prior to the water-dispersing process, the carboxylic acid groups in the prepolymer must be neutralized with a strong base to convert them into carboxylate groups. This neutralization step enables the urethane particles to disperse and stabilize in water. Following base neutralization, the aqueous dispersion process must be initiated promptly. During this process, a chain extender, such as primary or secondary polyamines, is added to the water-based polyurethane dispersions to convert the remaining isocyanate groups into the final polymer within the particles. Primary or secondary polyamines are chosen as chain extenders due to their higher reactivity towards isocyanates compared to water. Once all the reactions are complete, the final products of the reaction consist of ionomeric prepolymer and residual monomeric isocyanate.
 
The formulation and application of water-based polyurethane dispersions (PUDs) have experienced significant growth in recent years. This growth is primarily driven by the need to comply with environmental and occupational safety regulations, which aim to reduce exposure to organic solvents. Water-based polyurethane coatings and adhesives are now widely used in various industries, including footwear, leather goods, fiberglass, textile fibers, automobiles, and floor polishes. Particularly in well-developed countries like those in North America and the European Union, solvent-based coatings and adhesives are being phased out in favor of water-based polyurethane systems. These water-based alternatives are solvent-free, safe for human health, environmentally friendly, and possess properties comparable to solvent-based polyurethane systems.
 
Related products:
https://www.taiwanpu.com/en/about/Water-Based-PU-Resin-Directory