Brushstrokes - October 2011 - Surface Coatings Association of New ...

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similar to current market standards, paints made on EM8683 have been evaluated and compared to six commercially available paints; three high gloss solvent borne alkyd trim enamels, two high gloss waterborne trim enamels and a water based trim enamel based on an alkyd emulsion. The open time was tested using a standardised method very similar to ASTM D7488-10, and evaluated a number of properties including how long the open time is in the wet (open time a’) and dry (open time b) films. It was found that the open time of EM8683 was nearly as long as the waterborne alkyd and 250% longer than a commercial waterborne acrylic market standards. Significantly, and unlike paints based on self crosslinking acrylics, the open time in the wet film was identical to that in the dry film. As previously mentioned, EM8683 utilises oxidative crosslinking technology. There have been a number of advantages in doing this, such as reducing the coalescent demand and improving the resistances to water and hydrophilic stains. To ensure that the coating did not suffer from loss of dry, it was placed in the oven at 60°C for seven and 42 days (1000 hours.) In this test it was found that EM8683 had dry times longer than acrylics but still shorter than solvent borne enamels. It was also found that the dry time of the heat aged samples was similar to the un-aged sample, unlike three commercial solvent borne standards. To observe the mechanical properties of the coatings; block resistance and pendulum (Koenig) hardness tests were undertaken. Block resistance was carried out using a method based upon ASTM D4946-89 (2003.) In this test EM8683 had a block resistance within the solvent borne and waterborne market standards, even though the MFFT of EM8683 is much lower than the self cross-linking acrylics, and a pendulum hardness akin to the solvent borne alkyds. Finally the 20° gloss of the coating based in EM8683 was 67%. This is a step improvement from the current technology as it places it roughly half way between the solvent borne Coatings that Michelman has successfully tested for repulpability and their applications include: VaporCoat® 330C – a wax replacement solution typically used on roll wrap, produce boxes, poultry boxes and anywhere packaged goods require protection from water and/or moisture vapor. Michem® Coat 40EAF - another wax replacement coating that is water resistant and also demonstrates some grease resistance. Typically used on fruit, vegetable and protein/meat boxes. Nomar 70AF - a water based, abrasion resistant coating, generally used to provide abrasion protection for gas flushed food packaging or small appliances. Coating X300AF - another waterborne coating that provides a high level of water resistance and good moisture resistance on kraft paper. It is used to protect food products from excessive moisture, freezer burn and sticking. MaxWhite 17 - a decorative white coating that provides excellent brightness before and after wax applications. 10 SURFACE COATINGS ASSOCIATION OF NEW ZEALAND alkyds and the water borne self cross-linking acrylics. Conclusion With commercial pressures from the marketplace and our share holders, environmental pressures from legislators, specifiers and consumers and performance pressures from all of the above, we are all continually trying to formulate for the future. One of the last bastions of solvent borne technology in architectural coatings is gloss trim paints. To overcome the limitations of acrylic water borne enamels in both open time and telegraphing, Nuplex has developed a new binder resin. Whilst the ultimate parameters of this resin are currently being finalised, the results, thus far, look very promising. It is anticipated that this binder will be utilised in one of two ways, either in coatings with the same volume solids but much better open time; or in coatings with higher volume solids to minimise telegraphing. This second route may be a way of reducing TiO2 demand as coverage will be better with the higher film build. Either way, the coalescent demand will be lower which may lead to lower formulation costs, reduced VOC’s and due to the low MFFT and hydrophobic nature of this resin, it is believed that it will be a good candidate for DTS applications as it is expected have good tannin bleed resistance. While this polymer is being commercialised we will still be formulating for the future – working on the next generation of polymers which will give even longer open times and emit even less VOC’s and having physical and chemical properties in advance of those already achieved. Acknowledgements: Nuplex Technical team in Australia and New Zealand Nuplex Technical Team in Holland and Adam Berry References: 1. Akkerman, J. Bosma, M. Berry, A. Fallani, F. Adolphs, R. Mestach, D. “New developments op open time resins for waterborne decorative coatings” European Coatings Congress, 2009 2. Turner (ed) “The Condensed Chemical Dictionary” Forth Edition, Reinhold Publishing Corporation, 1950
Bridging the gap in performance deficiency of eco-friendly waterborne coatings by making use of a nanoparticle containing additive Eco-friendly waterborne paints and coatings already gained considerable interest and market shares compared to traditional solvent borne systems driven by stricter legislation as well as the general environmental awareness. Nevertheless waterbornes have well known limitation in overall performance compared to classical solvent borne systems. A innovative concept based on metal oxide nanoparticle technology potentially improving waterborne coatings will be introduced. With a chemo-mechanical milling process particles with tailored surface properties were generated. A overall good compatibility of the particles with a broad variety of binders was observed. Especially acrylic binders and copolymers with acrylic compartments are very well suited for the use with Oxylink. This also includes acrylic modified alkyds and PUDs. MEK double rubs [#] 120 80 40 0 ? = 85 0.00 1.00 2.00 wt.-% Oxylink 3101 (solids on solids) Figure 1: Concentration of Oxylink 3101 in transparent wood stain formulation based on Primal AC 337ER versus the MEK rub resistance The particles in the additive improve the overall coating performance due to direct particle-to-resin interaction. This effect closely depends on the high degree of dispersion as well as on the high surface area of the nanoparticles. We recommend a usage level of 1.0 % additive for first formulation experiments (see. Fig. 1). In particular the MEK rub stability, drying time, blocking resistance and stability against humidity will be improved. Detailed test results for a wood stain and a direct-to-metal By Marc Herold and Frank Tabellion Figure 2: Performance charts of a transparent Coating for wood based on Primal AC-337 ER (top) and a white DTM formulation based on Neocryl XK 86 (bottom). coating are depicted in Figure 2. The main performance benefit for the wood coating by the additive is a reduced drying time and a higher blocking resistance. The humidity resistance and the MEK-double rub resistance are the main effects for the direct-to-metal coating. The above shown results demonstrate that a nanoparticle based additive like Oxylink can significantly improve the overall properties of waterborne coatings. With steadily improving the properties of waterborne coatings, the gap between waterbornes and solvent borne coatings becomes narrower and the hurdles for using waterbornes become lower. As a consequence, nanotechnology can play an important role in bringing greener coatings forward. Bühler PARTEC GmbH Science Park 2 66123 Saarbrücken Phone: +49 681 394 6550 oxylink@buhlergroup.com SURFACE COATINGS ASSOCIATION OF NEW ZEALAND 11
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