Paint & Coatings Industry - May 2008 - (Page 59)

Viscosity, cps the liquid ingredients into a blender and mixing for 20 seconds to homogenize. Next, the pigment was added in three equal parts. Each part was mixed in and wetted before the next part was added. After incorporating all the pigment, the mixture (termed the premix) was blended for 10 minutes to begin the process of pigment separation. Once the ingredients had been premixed, the formulation was introduced to an Eiger Mini100 horizontal media mill. The mill contained approximately 75 g of 0.8 mm YTZ Media and was operated at a speed of 5000 rpm to process the samples. Each sample was milled for 10 minutes. An additional 28 g of water is contributed to each formula from the mill media, bringing the total batch size to 400 g; the percentages of pigment and resin shown below each formulation correspond to the 400 g batch size. For phthalo blue, the SMA Ester A dispersion was too thick to mill, so on this sample, no further processing was done. The same was true for the diarylide yellow formulas containing SMA Ester B and SMA Ester A. The amount of work done on the sample can be ascertained from the amperage draw experienced on the mill during processing. Additionally, a rise in sample temperature is an additional confirmation that high shear forces are being generated during dispersion. High shear forces generated often lead to better dispersions with higher color development. TABLE 8 | Lithol rubine dispersions – tint strengths. Sample SAR 102805-1 SAR 102805-2 SAR 102805-3 SAR 102805-4 SAR 102805-5 SAR 102805-6 SAR 102805-7 SAR 102805-8 SAR 102805-9 SAR 102805-10 Resin NTX 7633 NTX 7634 NTX 7635 NTX 7636 NTX 7637 NTX 7638 NTX 7639 NTX 7643 SMA Ester B SMA Ester A Optical Density 0.646 0.656 0.656 0.630 0.646 0.750 0.653 0.660 0.683 0.643 Reflectance Tint Strength 0.2259 0.2208 0.2208 0.2344 0.2259 0.1778 0.2223 0.2188 0.2075 0.2275 100.00 103.69 103.69 94.28 100.00 143.34 102.58 105.20 114.15 98.91 Formula No. SAR 102805-9 SAR 102805-10 SAR 102805-1 SAR 102805-4 SAR 101705-8 SMA Ester SMA Ester B SMA Ester A NTX 7633 NTX 7636 NTX 7643 Viscosity @ 12 rpm 1570 1620 6000 1740 4020 Dispersions containing NTX 7634, NTX 7635, NTX 7637, NTX 7638, and NTX 7639 were too viscous to be measured. FIGURE 3 | Initial viscosities of phthalo blue dispersions versus rpm (shear rate). 30000 25000 20000 15000 10000 5000 0 0 10 20 30 40 50 60 70 NTX 7634 NTX 7635 NTX 7637 NTX 7639 NTX 7643 SMA Ester B Dispersion Preparations The formulations for the phthalo blue and lithol rubine dispersions are shown in the Appendix in Tables 4 and 5, respectively. Based on the results for the phthalo blue and lithol rubine dispersions, only the new SMA esters NTX 7636, 7638, 7639 and 7643 were evaluated in diarylide yellow dispersions, versus SMA Ester A and SMA Ester B. The formulas are shown in the Appendix, Table 6. Brookfield RPM * The formulas containing NTX 7633, NTX 7636, and NTX 7638 were too thick for their dispersions to be measured. The formula containing SMA Ester A was too thick in the premix phase to be milled. Tint Strength Test and Calculations The purpose of evaluating tint strength is to ascertain the amount of color generated during milling. Tint strengths were made of the dispersions in the following manner: each formulation was drawn down vs. the others of the same color on Leneta 3NT-4 paper. The tint formula composition was 50.00 g of Sherwin Williams Extra White Tint Base and 0.50 g of dispersion, which were mixed on a Hauschild centrifugal mixer at 1800 rpm for 1 minute. Tint strength was then assessed by designating one formulation as the standard. The percent deviation in color strength of the other samples was computed versus this standard. Drawdown optical densities were measured using a densitometer (X-Rite 418). The optical density of the samples was measured and converted to reflectance values by: R=10 –O.D. Reflectance values for standard and samples were compared using the Kubelka-Munk equation: (1 − Ru )2 Percent strength vs. standard = (1 − Rs )2 2 Rs 2 Ru × 100 PA I N T & C O A T I N G S I N D U S T R Y 59

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Paint & Coatings Industry - May 2008 Contents Viewpoint Industry News Calendar of Events Company News Mergers and Acquisitions Names in the News Charlotte Dining Guide Exhibits-in-Print Waterborne Alkyds Break Through the Performance Barrier New Matting Agents for Waterborne Coatings and Varnishes Silicon-Based Technology for the Coatings Industry High-Performance Microgrinding The Development of New SMA Esters as Pigment Dispersants for Waterborne Coatings and Inks The Right Choice New Coating Technology Expands Color Choices for Vinyl Building Products BioPreferred Federal Biobased Products-Preferred Procurement Program European Union's REACH Regulation Sustainability - The New Nano Improved Dirt Pickup Resistance Critical to Future Coating Innovation NanoNews Protective Coatings NDT - Energy-Saving Paint Static Electricity - The Hidden Danger in Hazardous Areas Wacker Chemie - A Profile of Success Materials Watch Products and Literature Classifieds Advertiser Index

Paint & Coatings Industry - May 2008

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