Microencapsulation of Liquid Active Agents

Functional Coatinp. Edited by Swapan Kumar Ghosh 

Copyright 2006 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim 

Several reviews on microencapsulation processes are available [1-5]. In this section, those methods that are novel and related to the microencapsulation of liquid active agents are discussed. 

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Microencapsulation can be used to provide a temporary barrier between a chemical species and its surrounding environment see also Section 14.3). This permits controlled (slow) release of the active agents following application. Depending on the product and the situation, an active ingredient such as a pesticide may need to be released slowly at low concentration, or slowly at high concentrations. Such controlled release can both reduce the number of crop applications that are required and also help prevent over use and subsequent run-off. The barrier can be provided by a polymer film, in the case of suspensions [867], or a liquid membrane, in the case of single or multiple emulsions [865], Microemulsions have also been used [234,865],... 

Microencapsulation by a polycondensation process, which may be either normal dispersion polycondensation or interfacial polycondensation, is especially attractive for liquid active agents. The important advantage of this method is that in most cases very high active agent loadings can be obtained. These methods are well reviewed by Arshady [6], and are discussed in detail elsewhere in this book. 

It is sometimes possible to add properties in liquid formulations that provide additional functions. Examples in development or in commercial use as of 1993 include microencapsulation (qv) of enzymes for protection against bleach when dispersed in a liquid detergent addition of certain polymers to protect the enzyme after it has been added to liquid deteigents (32), or to boost activity in the final application addition of surfactants or wetting agents,... 

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