Paint & Coatings Industry - November 2008 - (Page 40)

HiTone Resins for Enhanced Pigment Affinity of Powder Coatings FIGURE 5 | White light interferometer pictures from coatings with a standard 70/30 hybrid and Uralac P 770. light interferometer pictures were taken of panels with a pigment concentration of 50 wt%. Pictures of the white light interferometer are shown in Figure 5. As can be seen from Figure 5 the Uralac P 770 levels better than the standard resin at a pigment concentration of 50 wt%. According to the flow results, HiTone polyesters showed a better flow at higher pigment levels than standard polyesters. It is clearly demonstrated that the use of the HiTone concept improves the flow ability of highly filled systems. Milling Behaviour FIGURE 6 | Specific grinding power versus pigment concentration. 90 80 70 60 50 40 30 20 10 0 30 Standard 70/30 hybrid, D50 of 30 micron Uralac P 770, D50 of 30 micron Standard 70/30 hybrid, D50 of 50 micron Uralac P 770, D50 of 50 micron Standard 60/40 hybrid, D50 of 30 micron Uralac P 760, D50 of 30 micron Standard 60/40 hybrid, D50 of 50 micron Uralac P 760, D50 of 50 micron 40 50 Pigment Concentration (wt%) TABLE 4 | Grinding test results 70/30 hybrids. Standard Hybrid Hybrid 70/30 D50 of 30 μm 30 wt% TiO2 Specific Power D50 D10 Speed rotor Speed classifier W.h/kg micron micron rpm rpm 51.3 30.51 8.68 6200 2400 40 wt% TiO2 Specific Power D50 D10 Speed rotor Speed classifier W.h/kg micron micron rpm rpm 58.7 33.34 10.34 6200 2400 50 wt% TiO2 Specific Power D50 D10 Speed rotor Speed classifier 38 W.h/kg micron micron rpm rpm 79.3 32.11 9.90 6900 2250 20.5 51.84 15.94 6200 1300 73.5 30.64 8.83 6900 2250 21.4 51.90 15.88 6200 1300 17.8 50.75 15.09 6200 1300 58.8 34.38 10.58 6200 2400 17.1 50.29 14.68 6200 1300 16.3 49.60 14.97 6200 1300 52.7 32.49 9.72 6200 2400 17.0 49.95 15.47 6200 1300 Uralac P 770 D50 of 30 μm D50 of 50 μm D50 of 50 μm To determine the influence of high-filled systems on the specific power consumption during grinding, grinding experiments were performed on an industrial scale. The specific power consumption is expressed by the required electrical power per kg of product to mill the product to a defined particle size. For the grinding experiments Uralac P 770 was tested over the full range of pigment concentrations. Also Uralac P 760 with 50 wt% pigment was tested. Because smaller particle sizes are needed for thinlayer applications, the difference in specific power consumption between a particle size distribution (PSD) of an average size D50 of 30 µm and 50 µm was determined. The experiments were performed on an air classifier mill ACM10 of Hosokawa. Limiting conditions during grinding were the maximum power consumption of the grinding motor and the classifier motor and the maximum pressure drop over the system. The effects of these conditions were especially observed during grinding of the highest pigment loaded systems to the smallest particle size. To overcome this, the speed of the grinding disk and the classifier were adjusted. The most relevant test results obtained are given in Tables 4 and 5. As can be seen in Tables 4 and 5, the speed of the grinding disk and the classifier were adjusted for the grinding experiments with 50 wt% pigmented systems to a D50 of 30 µm. This adjustment was done to prevent clogging. The above-mentioned results are graphically represented in Figure 6. The diagram clearly shows the effect that with increasing pigment content the specific power increases. From Figure 6 the general conclusion may be drawn that with higher pigment loading rates a tougher milling behaviour is observed, especially in combination with a small PSD. Nevertheless, the tougher milling behaviour is independent of the polyester type used and is directly related to the increased pigment content. It can be concluded that the milling behaviour of HiTone resins is not different compared to standard resins. Specific Power (W.hr/kg) NOV EMBER 2008 | W W W . P C I M A G . C O M http://WWW.PCIMAG.COM

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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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