Water-borne laminating adhesives

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. 

High-pressure lamination constitutes a large market for water-borne polychloroprene adhesives. The choice of the polymer has a high impact on end-use properties. 

Uses Solvent for paints, inks, cleaners, epoxy laminates, agric., adhesives, floor polish, oil field, mining, and electronic chems. solvent, coupling agenb welling agent, soil penetrant in cleaners coalescent for architectural water-borne coatings HAPs-free Manuf/Distrib. Aldrich Ashland G.J. Chem. Spectmm Quality Prods. Trade Names Arcosolv DPMA Dowanol DPMA... 

The increasing amount of research in waterborne systems should some day overcome technological difficulties. Howeverr the change-over from some solvent-borne to waterborne systems has presented difficulties (107), for exampler poor coating quality, excessive foam, insufficient water resistance, and even some corrosion and clean-up problems. Despite the problems, some waterborne systems have already been adopted for the manufacture of PSA s, contact adhesives, laminating adhesives, and wood adhesives. However, few applications of the waterborne systems as structural adhesives, especially as aerospace structural adhesives have been found. 

Polychloroprene latices are mainly used for high-pressure lamination, for foam bonding and for vinyl substrates (such as PVC) adhesion. Also, they are used for foil lamination, carpet installation, and PVC floor tile bonding. Bonding and shaping of foams is done with highly crystalhzable water-borne polychloroprene adhesives. The adhesive is sprayed on the foam and immediately the foam pieces are placed in contact. The assembly is wet-bonded because no drying is necessary as the water will dissipate into the foam. 

As with pressure sensitive adhesives, general purpose water-borne adhesives often involve blend combinations to yield the desired balance of properties for a myriad of applications. An evaluation of three emulsions (acrylic, epoxy and a urethane) (using a simplex blending study) was conducted for polyester/LLDPE, polyester/nylon and A1 foil/polyester lamination [142]. In each lamination, a ternary blend gave the optimized performance when a number of properties were considered. 

One-component water-borne polyurethane systems can be derived from polyurethane dispersions or blocked polyisocyanates (refer to Section 3.2.1). Blocked isocyanates are added to the co-reactant resins providing one-component systems with excellent shelf life. This type of adhesives is principally used for non-porous materials and the bonding of unlike metals such as aluminium to steel, and stainless steel to mild steel. They are also usefiil in bonding some of the high pressure laminates such as those based on phenoUcs and melamine [39]. Systems based on water-borne blocked polyisocyanate crosslinkers and suitable waterborne polymers approach the performance levels previously obtained only by solvent-borne systems [16]. 

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