Patent ID: 6364925
Filing Date: 2002-04-02
Classification: C08G,C09D

Abstract:
A process for producing polyurethane encapsulated, slow release fertilizer particles comprising1) applying a) an isocyanate-reactive component comprising a polyesterether polyol to fertilizer particles to form coated fertilizer particles, wherein said polyesterether polyol comprises: (i) 20 to 90% by weight, based on 100% by weight of a)(i) and a)(ii), of castor oil having an OH number of about 160 to about 170, a viscosity of about 500 to about 900 mPa.s, and a water content of less than 0.5% by weight, based on the total weight of castor oil, and (ii) 10 to 80% by weight, based on 100% by weight of a)(i) and a)(ii), of a polyether polyol having an OH number of from 28 to 700, a functionality of from 3 to 8, a molecular weight of from about 240 to about 6,000 and a viscosity of from 50 to 35,000 mPa.s at 25Â° C., said polyether polyol being prepared by reacting at least one suitable initiator compound with one or more alkylene oxides wherein the alkylene oxide comprise at least 70% by weight of propylene oxide, based on the 100% by weight of the alkylene oxides; and 2) applying b) a polyisocyanate component onto the coated fertilizer particles from step 1) to form polyurethane encapsulated fertilizer particles, wherein these two steps are optionally repeated successively as many times as necessary, with the polyurethane encapsulated fertilizer particles from step 2) being substituted for the fertilizer particles in step 1), so as to form polyurethane encapsulated fertilizer particles containing from about 2 to about 20% by weight of polyurethane, based on the total weight of the encapsulated fertilizer composition, wherein the polyurethane forming the encapsulated fertilizer particles is characterized by a water absorption of less than 1% by weight, based on the total weight of the polyurethane encapsulant.