Water-borne polyurethanes

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. Aliphatic PC-based polyurethane water-borne disp. with... 

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. 

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). 

Scheme 4.23 Two-component water-borne polyurethane by the prepolymer method.

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

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

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,... 

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... 

Polymerizing acrylic monomers in the presence of oil-modified polyurethane leads also to a grafting onto the polyacrylics, resulting in dispersions suitable for stable water-borne latexes with good adhesion properties and fair hardness properties [103]. 

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). 

The Clean Air Act demands the elimination of organic solvents use, hence a number of plasticisers and solvents (such as methylene dichloride (MEK), toluene, xylene) are classified as hazardous, which led to development of new, environment compliant systems to develop, such as water borne systems, or use of rapidly curable/dryable oligomers (i.e., printing inks use oligomeric bis acrylates, polyester acrylates and polyurethane acrylates, which can be crosslinked quickly by UV light with the aid of certain sensitisers). 

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. 

Water-based paints are dispersions based on synthetic polymers. Dispersions of polyacrylates are the most common. Examples of these paints include acrylic latex paint, heavy-bodied latex wall paint, latex enamel, latex primer, latex wall paint and sealing water-borne paint. Water-based paints can also contain water-soluble alkyd resin and a mixture of polyacrylate and polyurethane. Although water is the main solvent in these types of paints, comprising about 30-85% weight-to-weight ratio (w/w) of the raw materials, about 10% organic solvents are added to improve the film forming properties of the paint. (Hansen et al. 1987 van Faassen and Borm 1991 Wieslander et al. 1997). The differences between SBP and WBP can be seen in Table 2. 

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]. 

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. 

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