Ppg Industries, Inc.

Ppg Industries Ohio, Inc.

Donald B Jones

Ken W Niederst

Leland H Carlblom

Mary Ellen Rosenberger

Paul S Chirgott

The detrimental effects of fluctuating humidity are neutralized by adjusting the viscosity of a waterborne coating as it is being conducted to the spraying device. A predetermined amount of water or other viscosity modifying additive is mixed continuously with the coating in the coating supply line immediately upstream from the spray device. The amount of water or other additive to be added may be determined by monitoring the humidity in the spray zone. Preferably, an automated feedback control system is employed to adjust the amount of water or other viscosity altering additive being mixed into the coating stream.

Method and apparatus for spraying waterborne coatings under varying

The present invention provides an apparatus for controlling the spray of positively-charged coating particles towards a grounded or negatively-charged dielectric material having a dielectric constant less than 4.0 and in the form of a hollow container. This apparatus includes: (a) a device for inducing a positive charge onto a coating composition, (b) a device for creating a field of positively-charged coating particles, (c) a device for supporting a series of hollow containers in spaced relation to one another which includes a series of vertically-oriented spindles, (d) a device for transporting the spindles in series through the field of positively-charged coating particles, (e) a gripping chuck made from, or coated with, a dielectric material, or both, mounted to the upper end of a spindle, the chuck having a recess defined therein for receiving the opening of a hollow container, and (f) a grounding device positioned such that, when the dielectric container is in the path of the sprayed, positively-charged coating particles the grounding device is also in the path but shielded therefrom by the dielectric material. The grounding device is insulated from direct electrical contact with the supported container. The grounding device can be replaced by an internal charging device for inducing a negative charge onto a hollow container being supported by the gripping chuck. Moreover, the grounding device or the internal charging device can be used in conjunction with an external charging device for inducing a negative charge onto a hollow container being supported by the gripping chuck.

Electrostatic deposition of charged coating particles onto a dielectric

This invention provides a process for electrostatically applying a coating composition onto dielectric materials which have a dielectric constant less than 4.0. In this process, a positive charge is induced onto a coating composition. The dielectric material is electrically isolated, negatively charge, or both. The positively-charged coating composition is sprayed onto the dielectric material. If the dielectric material is charged negatively, the process of the present invention further includes the step of maintaining at least a portion of the negative charge on the dielectric material while positively-charged coating particles are being sprayed thereon.

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Wildwood, PA, United States of America

Donald B Jones