Electrostatic deposition distribution

Koppers "Book Keeping" Process. In view of the limitation of the Wei T o process, chemists at the Koppers Company developed a "Book Keeper" process by dispersing submicron particles of basic metal oxides, hydroxides or salts of calcium, magnesium, or zinc, in a suitable gas such as Freon or liquid medium, so that the active chemicals can be transferred and deposited electrostatically on the surface of paper. It also does not require pre-drying of books as is required for both the DEZ and Wei T o processes. The testing results appear satisfactory as shown in Table I. The major concern with this process is the distribution of the alkaline reserve on the paper. It appears the process deposits alkaline chemicals on the surface of paper and achieves surface deacidification. However, acid formed in the core of the paper is not neutralized. Koppers intends to prove the degrees of chemical penetration and neutralization of acid in the center layers by examination of the cross-section of paper by SEM. 

The combined effect of attraction and repulsion forces has been treated by many investigators in terms borrowed from theories of colloidal stability (Weiss, 1972). These theories treat the adhesion of colloidal particles by taking into account three types of forces (a) electrostatic repulsion force (Hogg, Healy Fuerstenau, 1966) (b) London-Van der Waals molecular attraction force (Hamaker, 1937) (c) gravity force. The electrostatic repulsion force is due to the negative charges that exist on the cell membrane and on the deposition surface because of the development of electrostatic double layers when they are in contact with a solution. The London attraction force is due to the time distribution of the movement of electrons in each molecule and, therefore, it exists between each pair of molecules and consequently between each pair of particles. For example, this force is responsible, among other phenomena, for the condensation of vapors to liquids. 

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