Paint & Coatings Industry - March 2009 - (Page 42) New Sulfonic Acid Catalysts for Coil Coatings FIGURE 4 | Cure comparisons at 300 °C oven temperature. 120 100 80 60 40 20 0 Arom. SA/Polymer Arom. SA/Amine Nacure XC-181 fonic acid Nacure XC-181 was compared with its amineblocked and polymer-blocked counterparts at equivalent acid levels of 1.3% at an oven temperature of 300 °C for 25, 30 and 35 seconds respectively. The corresponding peak metal temperatures were 228 °C, 241 °C and 250 °C. In a second study, popping tendencies of the new acid catalyst were evaluated in comparison to an amineblocked acid catalyst, using an oven temperature of 435 °C at 15 seconds, which corresponded to a peak metal temperature of 240 °C. A small amount of phthalo blue tint paste was added for this part of the study to improve the visual impact of the blistering. MEK RUBS 25 sec. 30 sec. 35 sec. Results and Discussion The cure data (Figure 4) indicates that the new acid catalyst, Nacure XC-181, was able to provide rapid cure at a peak metal temperature of 250 °C, (oven 300 °C/35 sec), without any significant cure at lower peak metal temperatures, compared to an amine-blocked and polymer-blocked sulfonic acid catalyst. The snap cure response allows release of volatiles in the formulation, thereby preventing popping seen in coil clear coats with conventional catalysts. The popping phenomena was evaluated at a peak metal temperature of 240 °C, and the snap cure profile, seen with the new catalyst, resulted in no visible popping compared to the coating cured with the corresponding amine-blocked catalyst (Figure 5). TABLE 5 | White coil coating master batch formulation. Ingredients Aroplaz 6126-z-65 Aromatic 150 EEP Tiona 472 Disparlon L-1984 Resimene 747 Total White Master Batch Formula 42.47 10.34 9.71 32.13 0.53 4.82 100.00 Component Type High MW PE resin Solvent Solvent Titanium dioxide Flow-and-leveling agent Melamine crosslinker XC-194, better initial cure and superior cure after sevSummary and Conclusions In summary, the new sulfonic acid catalysts are pareral weeks of 50 °C oven aging were achieved. Also the ticularly suitable for coil primer formulations containtrue non-interacting behavior of the new catalysts was ing basic anti-corrosive pigments, where they resist seen by the superior viscosity stability of these formulahigh pH pigment absorption, prevent popping, protions. Also exceptional humidity resistance and corromote good intercoat adhesion, and provide exceptional sion resistance were seen as compared to the current storage stability and corrosion resistance. In addition, state-of-the-art formulations. products from this class of cataThe results are tabulated in Tables lysts also are effective in topcoats 3-5, and Figures 1-3. FIGURE 5 | Popping phenomena compariwhere their snap cure response Evaluations in a White Coil Coating son of amine-blocked catalyst with the new acid catalyst. A master batch of the white coil coating system was prepared, as shown in Table 5, without any catalyst for use in our evaluations. All formulations used in this study were made from this white master batch with the addition of the appropriate catalyst package. allows release of volatiles before cure, thereby preventing popping, while providing exceptional storage stability. Acknowledgements We thank Marvin Blair, Max Gandhi, John Florio and Rui Gloria for experimental support and for evaluations of the new catalysts in various coating systems. We thank King Industries for permission to publish this work. Preparation and Evaluation of White PE Coatings All formulations were applied by the drawdown method to B-1000 steel panels, with an average dry film thickness of approximately 1.0 mil. Films were cured in a coil oven at the desired cure temperature/time to provide appropriate peak metal temperatures. Cure properties were measured using double MEK rubs. In the first study, new blocked sul42 MARCH 2009 | W W W . P C I M A G . C O M References Skeist VII, 2004 Coatings Report. Shieldex® C 303 - technical information-Grace Division updates 02/05. 1 2 Nacure XC-181 Amine-blocked Catalyst For further information, visit www.kingindustries.com. http://www.kingindustries.com http://www.kingindustries.com http://WWW.PCIMAG.COM
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