| 摘要 |
The present invention provides for controlled release chemical compositions having improved controlled release properties wherein core substrate particles comprising a water soluble chemical compound, such as a fertilizer or oil well chemical, which are surrounded and encapsulated by a controlled release coating which is slowly permeable to water, such as a thin layer of polymeric material, are further overcoated with one or more coating layers comprising a finely divided filler preferably talc, dispersed in a metal or ammonium lignosulfonate binder. The outer coating serves to protect the underlying, thin film, controlled release coating from abrasion and impact damage occasioned by packaging, blending and dispensing equipment, thereby preserving the water permeating properties designed into such coating. The outer protective coating is itself permeable to water, allowing the layer beneath it to control the rate of water contact with the substrate core and subsequent release of the core substance into its environment.
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