Paint & Coatings Industry - November 2008 - (Page 47)

Enabled Coatings sions are increasingly undesirable in an era of global warming concerns. Nanoparticle-Enabled Formulation The paradigm shift was extended to the use of pigment and other particle additions that are incorporated as acrylates or other carrier dispersions. This avoids pigment agglomeration often associated with the use of neat pigment additions, and also results in long-term durability of the dispersion, i.e., long package shelf life. These nano-enabled product formulations have resulted in five U.S. patents with several other applications pending. Additions of pigment and other particles are made in a relatively wide particle size range from several microns down to nanoparticles (less than 20 nm) that can include silicon dioxide, aluminum oxide and titanium dioxide among others. This combination of particle sizes results in enhanced coverage of substrates such as bare aluminum, chrome and brass metals. FIGURE 1 | Conventional coating product design. Medium – High MW resins with functional groups for performance and/or crosslinking sites New Formulation Paradigm1 Given the preceding context, formulation activity was directed to modification of UV-cure systems to meet the previously noted objectives. This approach was dictated by the perceived ability of UV-cured systems to avoid solvent use insofar as they are in-situ reactive systems, can often be cured at high rates (seconds), and can incorporate high-durability resins. In fact, the starting premise of the present design paradigm was to use no solvents (water or organic) in products that utilized acrylics, epoxies and aliphatic urethanes. With that as a given, adhesion to bare metal was set out as the initial task to gain wide-spread use. The paradigm shift in this instance was to avoid the use of medium-to-large molecular weight polymers (resins and certain oligomers) and, in fact, begin the formulation with smallmolecule polymers (monomers and some oligomers) targeted to achieve initial critical functions such as adhesion to bare metal in this case, and then build up the required combination of film properties with additional monomer additions as needed. Cure is achieved using unsaturated crosslinkable functionalities such as acrylate groups. Since lowmolecular-weight oligomers and monomers of about 100 to a few thousand Daltons are used they are generally low-viscosity (20-500 cps) solutions compared to oligomers and resins of more than 1000 to 10,000 or higher Daltons. Thus, the compositions of this new design paradigm are readily applied by common processes including HPLV, HPLV turbine, roll and curtain coaters. More important, the approach illustrated in Figure 2 eliminates the need for organic solvents with all but a very small amount of the photoinitiator becoming part of the final film upon curing with a UV-light source. Resin A Resin B Vehicle (volatile carrier of polymers and additives) Multiple additives (for color, gloss, rheology, and features not in the resins) Dry coating thickness ~ 1/2 to 1/4 of the wet film FIGURE 2 | New paradigm design. Selected monomers and oligomers Oligomer A Monomers act as components Few additives for color, gloss, etc. Dry coating thickness ~ wet film Nanoparticles impart new properties (scratch resistance, vapor barrier, etc.) PA I N T & C O A T I N G S I N D U S T R Y 45

Table of Contents Feed for the Digital Edition of Paint & Coatings Industry - November 2008

Paint and Coatings Industry - November 2008 Contents Viewpoint Industry News Calendar of Events Company News Mergers and Acquisitions Names in the News HiTone Resins for Enhanced Pigment Affinity of Powder Coatings New Water-Based Interior Coatings Combine Innovation and Quality With Respect for the Environment Novel, UV-Curable Nanotechnology-Enabled Coatings Highly Weather-Resistant Radiation-Curable Monomers and Oligomers for Exterior Applications Konica Minolta — Sensing Success for Viracon Self-Crosslinkable Thermosetting Acrylics for Use in Water-Dilutable Coatings Paint and Criminal Forensic Science Supplier and Application/Curing Showcases Materials Watch Classifieds Advertiser Index

Paint & Coatings Industry - November 2008

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