Water-borne polyurethane coatings

Water-borne polyurethane coatings are formulated by incorporating ionic groups into the polymer backbone. These ionomers are dispersed in water through neutrali2ation. The experimental 1,12-dodecane diisocyanate (C12DI Du Pont) is especially well suited for the formation of water-borne polyurethanes because of its hydrophobicity (39). Cationomers are formed from IPDI, /V-methyIdiethan olamine, and poly(tetramethylene adipate diol)... 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

Waterborne coatings, 7 127-128, 10 443 Waterborne coating technologies, 10 349 Waterborne contact adhesives, phenolic resins in, 18 784 Waterborne polyamides, 10 400 Water-borne polyurethane coatings,... 

Like SAA resins, the water-soluble or water-dispersible terpolymer of allyl propoxylate, styrene and methacrylic acid can be used in water borne polyurethan, melamine, polyester, and many other water borne coatings and thermoset polymers to improve performance. 

Abrasion and impact resistance of acrylic coatings can be improved with the addition of up to 30% of a water borne polyurethane. The addition of a polyurethane dispersion as a physical blend improves the inherent film strength and film formation of the aciylic latices. Polyurethanes generally have better film forming properties because of their lower MFFT at identical surface hardness. 

Such polyurethanes have excellent hydrolytic stability compared to water-reducible polyesters and superior abrasion resistance. In view of the importance of developing low solvent emission coatings, considerable effort is being devoted to new types of water-borne urethane resins (62,63). 

Polyurethane block copolymers, 24 707 Polyurethane coatings, 17 845 uses for, 25 481-482 water-borne, 25 474... 

Therefore, die polarity and solubility of polymer can be modified deliberately by varying the nature of the components. High aqueous solubilities of polyamides and polyurethane threaded with crown ethers or CD are intriguing, because this observation implies potential applications of the polyrotaxane concept in coatings, adhesives, and water-borne processing. The observation of the emulsification of... 

Some of the paint types belonging to classes such as alkyds, coaltar epoxies, epoxy, heat-resistant, inorganic zinc types, polyurethanes, water-borne coatings as described by Sigma coatings are given in Table 1.29. 

Chem. Descrip. Linear poly (1,6-hexanediol neopentyl glycol adipate) Uses PU intermediate for durable polyurethane coatings and adhesives Features Can be formulated into either water- or solv.-borne systems appropriate for outdoor applies, when reacted with an aliphatic isocyanate... 

Chem. Descrip. y-Glycidoxypropyltrimethoxysilane CAS 2530-83-8 EINECS/ELINCS 219-784-2 Uses Adhesion promoter in water-borne acrylic sealants, urethane and epoxy coatings coupling agent in polysulfide and polyurethane caulks and sealants, min.-filled or glass-reinforced thermosets and thermoplastics, and in glass roving size-binders Properties Colorless transparent liq. m.w. 236.4 dens. 1.065-1.075 vise. 

The superprimer formulation is usually based on an ionic or non-ionic aqueous resin dispersion. The solid content of the water-borne resin is often around 55wt% and it may contain small amounts of organic solvents. Typical resins used in the primers are epoxies, acrylates and polyurethanes. The minor binder is incorporated in order to improve a particular coating property such as cold formability. Table 1 gives an overview of the family of superprimers based on different resin-cross-linker-silane-pigment combinations invented and investigated in our laboratory [7-11]. 

Polyurethane coatings are used as a single-pack system or a two-pack system. There are three basic types of single-pack systems and two of the two-pack system. More recently water-borne urethanes have been developed to reduce solvent emmission. 

An approach to this problem is by the appropriate modification of acrylic primary dispersions to suit automotive coating requirements or solvent-free secondary dispersions of conventional resin types Hke epoxies, polyesters, polyurethanes. Today, the latest water-borne coatings are much more robust in terms of usage or appHca-tion friendhness and require significantly less heating or air-conditioning than two decades ago. They still require some additional dehydration or special kinds of flashes before going into ovens to help remove the water. 

Anionic coatings systems for water-borne topcoats are emulsion polymers, miniemulsion polymers, polyurethane dispersions, different types of dispersions of acrylic resins in water and amino resins, water-borne polyesters, polyurethanes. Many of the polymers are hydroxyl containing and cured with various melamines and blocked isocyanates. The polymers are mainly stabilized in the water phase by neutralization of anionic groups with volatile amines (2-amino-2-methyl-l-propanol). Cross-linkers like aminoplast resins, alkoxy silanes, blocked epoxy resins, carbodi-imides can be used. 

The blending of resins is a simple and useful technique for improving paint properties. While water-borne acrylic resins and polyurethanes have been widely used as polymers for automotive coatings, both water-borne resins are inferior to corresponding solvent based counterparts because of hydrophilic functional groups or surfactants which are introduced to impart dispersion stability to these resins. Table 7-6 shows some of the advantages and disadvantages of polyurethane and acryhc resins. 

The coatings technologies used in these applications vary significantly from solvent-borne 2K polyurethanes, solvent-borne and water borne acrylic and other technologies. However, actinic radiation cured coatings (including UV) currently accounts for over 1/5 of the market. ... 

Polyesterpolyols based on dimer acids or dimer diol have been largely used in sol-vent-borne and water-based coating applications including alkyd resins and aqueous polyurethane dispersions. ... 

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