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Coating: hollow pigments, higher solids: new technology using high solids hollow spheres with a binder can help increase solids levels in coating formulations.

Industry studies indicate that higher solids levels in coating formulations offer many advantages, including faster operating rates and improved gloss and opacity. These advantages result from several factors.

Faster operating rates. With higher solids levels, drying is easier. Paper mills can operate their coaters at higher speeds while maintaining target moisture, since there is less moisture to remove from the formulation. Mills can produce additional tonnage without spending more capital. (Figure 1 shows how much impact an increase in formulation solids can have on sheet moisture and ultimately line speeds.)

[FIGURE 1 OMITTED]

Improved gloss and opacity, with higher solids levels, paper mills receive better coating holdout, which can lead to increased sheet gloss. This improved coating holdout can also give papermakers the flexibility to calender with less pressure, which improves opacity. (Figures 2 and 3 show examples of how a 2% increase in formulation solids can allow papermakers to calendar less to reach a target gloss, and how this can translate into an improvement in opacity.)

[FIGURES 2 & 3 OMITTED]

One way to increase solids levels in coating formulations is to use hollow plastic pigments. For example, Dow Chemical's new HSB 3042NA high solids hollow pigment (applied with a binder product) is produced at 42% solids level, a 6% higher solids level than could be obtained with a simple blend of hollow and latex products. The actual solids increase in coating formulations depends on the level of plastic pigment papermakers use in their formulations. Overall, papermakers can expect to achieve about 2% higher solids levels in formulations.

Dow developed HSB 3042NA using its hollow sphere technology and its S/B Latex technology. The S/B-type binder is included in the product to help obtain higher solids levels. The hollow plastic pigment contributes to a smoother and glossier coated sheet. The pigment is also ammonia-free, which is particularly desirable where low odor levels are necessary.

Note: More information about higher solids coating formulations is available from Dow at the TAPPI Coating Conference, May 11-14, 2003 in Chicago, Illinois, USA.

About the author: David Wolfe is application development leader, Emulsion Polymers business, The Dow Chemical Co., Midland, Michigan, USA. Contact him by email at dlwolfe@dow.com, or by phone at +1 989 636-9124.
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Title Annotation:Practical Solutions
Author:Wolfe, David
Publication:Solutions - for People, Processes and Paper
Date:May 1, 2003
Words:373
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