The present invention relates to polyurethane encapsulated fertilizer particles which exhibit slow-release properties and to a process for their production. The process comprises applying an isocyanate-reactive component to fertilizer particles, to form fertilizer particles coated with an isocyanate-reactive component, applying a polyisocyanate component onto the coated fertilizer particles to form polyurethane encapsulated fertilizer particles, and, optionally, repeating these steps as many times as necessary to form the polyurethane encapsulated fertilizer particles that contain about 2 to 20% by weight of polyurethane, based on the total weight of the encapsulated fertilizer particles. Suitable isocyanate-reactive components include polyesterether polyols that comprise either a blend of or the reaction product of (i) castor oil having an OH number of about 160 to about 170, a viscosity of about 500 to about 900 mPa·s at 25°C, and a water content of less than 0.5% by weight; and (ii) a polyether polyol having an OH number of from 28 to 700, a functionality of from 3 to 8, and a molecular weight of about 240 to about 6,000, and a viscosity of from about 50 to 35,000 mPa·s at 25°C. The polyether polyol must be prepared from a suitable initiator compound and an alkylene oxide comprising at least 70% by weight of propylene oxide.
本发明涉及具有缓释特性的聚
氨酯封装肥料颗粒及其生产工艺。该工艺包括将
异氰酸酯反应组分涂覆在肥料颗粒上,形成涂覆有
异氰酸酯反应组分的肥料颗粒,将聚
异氰酸酯组分涂覆在涂覆的肥料颗粒上,形成聚
氨酯包封的肥料颗粒,并可选择地根据需要多次重复这些步骤,以形成聚
氨酯包封的肥料颗粒,根据包封的肥料颗粒的总重量,该颗粒含有约 2%至 20%(按重量计)的聚
氨酯。合适的
异氰酸酯反应组分包括聚酯醚多元醇,它包括以下物质的混合物或反应产物:(i) OH 数约为 160 至约 170、25°C 时粘度约为 500 至约 900 mPa-s、
水含量小于 0.(ii)聚醚多元醇,其羟基数为 28 至 700,官能度为 3 至 8,分子量为 240 至 6,000 左右,25°C 时的粘度为 50 至 35,000 mPa-s。聚醚多元醇必须由合适的
引发剂化合物和环氧
丙烷(按重量计至少占 70%)制备。