Dry coating process

Modification of the coating process will also influence drug release, because the porosity of the film coating may be influenced by the spray rate or the inlet air temperature. This dry coating process provides short processing times and is thus more economical. 

In dry coating processes the frit is ground dry with or without additives to the required fineness. For powder coating no further additives are necessary. Powders for electrostatic coating have to be hydrophobized to adjust the specific resistivity of the powder surface to lO to 10 Clem. This is achieved by adding charging agents to the mill. Special silicones are especially suitable therefor. 

Among the novel technologies, electrostatic coating merits to be considered [121]. The interesting advantage of this dry coating process is the elimination of blending powders. 

Environmental friendliness is needed not only for products, but also for processes. Hazardous materials used or produced in the production process should be transformed into harmless substances or retained in a closed system (Fig. 1). The latter is a topic and problem-solving issue for wastewater treatment. The latter is composed of many different processes. Several of them are physical vapor deposi-ti(Mi (PVD) and chemical vapor deposition (CVD). Both are called dry coating processes. In this chapter, the dry processes such as PVD and CVD will be introduced and explained as enviromnentally friendly coating processes. 

There has inevitably been a great deal of industrial interest in examining the effect of fatty acids other than stearic acid. However little of this work has been published. Pure fatty acids are all considerably more expensive than the blends generally described as stearic acid and dramatic effects would be needed to make their use worthwhile. This probably explains why there are very few commercial examples of other acids being used. Iso-stearic acid is sometimes used, probably because it is a liquid and easier to use in dry coating processes. The branched structure may also improve the dispersion effects obtainable, but would be expected to reduce the mono-layer amount and prevent a tightly... 

J. P. Nunes, J. R Silva, L. Silva, A. T. Marques, P. J. Novo (2000) The development of a dry coating process to produce glass reinforced thermoplastic matrix towpregs, Proc. 9 European Conf. Composite Materials ECCM-9, Brighton. 

The use of nylon-11 for powder coatings or dry coatings (qv) has been developed in response to a growing concern for the environment (44) (see Coating PROCESSES, powder technology). Electrostatic deposition allows thin films to be appHed to metal substrates. Once the powder is appHed, it must be melted and coalesced into a continuous plastic film. Eorced draft or irradiant ovens are used for fusion, and because no polymerization or cross-linkage are required for curing, coated objects can be processed quickly and air-cooled (45). 

Typical of the temporary or manufacturing aid coating systems is the RISTON dry film photoresist for printed circuit (PC) board fabrication. This was the first of these systems developed. The RISTON product stmcture and the basic steps in its use are shown in Figure 2. It consists of a photopolymer sheet laminated between a Mylar cover sheet and a polyolefin separation sheet. It is manufactured as a continuous web (see Coating PROCESSES, survey), and is suppHed in roUs of varying width and photopolymer composition. 

The dry powder process has several additional advantages over the wet process. For example, much less waste of enamel occurs because the dry over-spray is airborne and recycled in a closed system. No-pidde ground coats have broadened the apphcation of both wet-process and dry-process systems. These enamels are appHed over cleaned-only metal. Thus the problems of disposing of pickling acid wastes containing iron sulfates and nickel wastes are eliminated (see Metal surface treatments) (7). 

First, two ELAT catalyst disks were coated with liquid Nation 117. The coating only went on the active side that was to be bonded to the PEM. We used a cosmetic brush to put on a single coat (thick enough to give a wet appearance) then let it air dry at room temperature in a clean place for one hour. The liquid Nation 117 has a strong alcohol odor, so do this coating process in a well-ventilated area. 

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