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A known procedure is to render fumed silica hydrophobic

A known procedure is to render fumed silica hydrophobic, grind it in a pinned-disc mill, and then classify it (U.S. 2004/0110077 A1). This known silica is used as an external additive in toner mixtures. Reducing the agglomerate size by dispersing outside a liquid system, in other words, in practice, in the air, or by grinding in the conventional sense, is possible only to a limited extent since in the case of material with a given propensity to agglomerate the comminution is followed immediately by the re-establishment of the old agglomeration state. This effect comes about no later than after compaction of the material, which, as a result of the mechanical intervention, has undergone a high degree of loosening and which, in this form, is not amenable to dispatch and storage. The storage time as well would have the effect of renewed agglomerate enlargement. A value taken as a dimensional number and evaluation variable for the distribution stage of dispersible silica and the maximum agglomerate size of the dispersion (granularity) is the so-called goniometer value to DIN 53203. Hydrophilic fumed silica with a BET surface area possesses a goniometer value as determined in UP resin (unsaturated polyester resin Ludepal P6 from BASF, 2% dispersion) by the DIN specification of 50 to 60. Suppose this fumed silica is highly compact (100 to 120 g/l). In that case, the goniometer value is also significantly higher, specifically more than 100, necessitating additional, not inconsiderable energy as a thickener and thixotropic agent. If you are looking for high quality, high purity, and cost-effective Fumed silica, or if you require the latest price of Fumed silica, please feel free to email contact mis-asia.

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