Лако-красочные материалы — производство

Coalescents used in wood finishes include butoxy propanol, butoxy propoxy propanol, Texanol and propylene glycol. Butoxy ethanol (butyl glycol) was a very popular coalescent, but due to its toxicity, it is much less popular now. (i) Matting Agents Conventional silica matting agents can be used. Some suppliers manufacture specific grades for use in water based […]

The various components, some or all of which go to make up a finished lacquer, are as follows; • Acrylic resins — emulsion or water soluble • Coalescent or co-solvent • Defoamers • Wetting agents • Matting agents • Slip and mar additives • Surface tension additives • Dispersing agents • Preservatives • pH adjusters […]

by Graham Raynor BSc Water based systems have in the past been of only minor significance and end users have usually only used them reluctantly when they have been forced to. This is due to the inherent problems associated with water based systems, namely; • Slow drying due to slow evaporation of water • Drying […]

The preceding formulation guidelines will on occasion appear to contradict themselves. pH value recommendations, for example, fluctuate wildly depending upon the need to prevent flash rusting, accommodate an aluminium pigment or prevent flocculation in a black. As with many formulating requirements in the coatings industry, the final result is a compromise, reached empirically rather than […]

Aqueous dispersions of epoxy resins can be reacted with the carboxyl groups of an acrylic latice, as shown in Figure 7-20. Curing needs to be carried out at above 100°C for several minutes. он о I II A/W CH —CH2—О—C- Figure 7-20: Reaction of Epoxy Group with Carboxyl Group

Melamine formaldehyde can be crosslinked at elevated temperatures with both hydroxyl and carboxyl functional groups. (See thermosetting acrylics chapter for reaction mechanisms.) The temperature required is at least 120°C, at which point the hydroxyl group will react, but the carboxyl group needs a slightly higher heat input, approximately 150°C. Systems are unlikely to require an […]

Polymer latices containing carboxyl functional groups can be crosslinked via the formation of an ionic bridge, with divalent and bivalent inorganic ions, e. g. Mg2+, Al3+, Zn2+ and Ca2+, as shown in Figure 7-19. Figure 7-19: Reaction of Inorganic Salts with Carboxyl Groups Zinc crosslinked acrylic polymer latices have been widely used in the manufacture […]

Solventless, multifunctional isocyanates are available based on aromatic diphenyl methene-4-4’-di-isocyanate (MDI) or aliphatic hexamethylene di-isocyanate (HMDI), although due to toxicity reasons, HMDI itself would not be used, but lower volatility adducts may be an alternative. In dried coatings, the water dispersible isocyanates undergo the usual reaction with active hydrogen groups. See Figure 7-18. (Also see […]

Multifunctional carbodiimides are designed for low temperature crosslinking with carboxyl functional polymers as shown in Figure 7-17. N-acyl urea Figure 7-17: Reaction of Carbodiimides with Carboxyl Group Pot life is limited due to the hydrolysis of the carbodiimide group to urea, and these systems are best supplied as two component systems. Hydrolysis is slowest at […]

(i) Polyaziridene*12^ Two component coating systems based on the reaction between acrylics and multifunctional aziridenes, as shown in figure 7-16, have been used for many years. In general, crosslinking with polyaziridenes improves the blocking resistance, adhesion and chemical resistance of the coating. The formulations have long pot lives, up to 48hrs, and the coatings crosslink […]