System for coatings for granular materials

Abstract

A coating is applied in one or more layers on a granular material, such as a granular fertilizer material or the like. The coating may include a diisocyanate in either pure form or partially polymerized form, a polyol or polyol mix, and optionally a wax. The polyol or polyol mix may be, for example, a polyester polyol, a polyether polyol, or combinations thereof. In some examples, the polyol or polyol mix may be an aliphatic glycerine initiated polyether polyol, an aliphatic amine initiated trifunctional polyol, castor oil or castor oil derivative, or ethylene diamine that has been propoxylated or ethoxylated, and combinations thereof. The coating is reacted on the granular material.

1 . A coating for a granular substrate, the coating comprising:
 a polyisocyanate;   at least one of a polyether polyol, wherein the polyether polyol comprises at least one of an aliphatic glycerine initiated polyether polyol or an aliphatic amine initiated trifunctional polyol, or combinations thereof and at least 25% ethylene diamine that has been ethoxylated and/or propoxylated; and   optionally a wax.   
     
     
         2 . The coating of  claim 1 , wherein the coating is a water-insoluble polyurethane polymer. 
     
     
         3 . The coating of  claim 1 , wherein the polyisocyanate is aliphatic or aromatic and comprises at least two isocyanate groups per molecule. 
     
     
         4 . The coating of  claim 3 , wherein the polyisocyanate is a partially polymerized methylene diphenyl diisocyanate (pMDI). 
     
     
         5 . The coating of  claim 1 , wherein the polyether polyol comprises an aliphatic glycerine initiated polyether polyol with a molecular weight in a range of about 500 Daltons to about 1200 Daltons. 
     
     
         6 . The coating of  claim 5 , wherein, the aliphatic glycerine initiated polyether polyol is a reaction product of glycerine and propylene oxide. 
     
     
         7 . The coating of  claim 5 , wherein the polyether polyol, comprises the aliphatic glycerine initiated polyether polyol and the aliphatic amine initiated trifunctional polyol. 
     
     
         8 . The coating of  claim 1 , wherein at least one of the polyisocyanate, the polyether polyol, or the wax when applied to the granular substrate has a viscosity of between about 120 centipoise (cP) to about 50,000 cP at 25° Celsius. 
     
     
         9 . The coating of  claim 1 , wherein the granular substrate comprises a mineral fertilizer or a mineral salt fertilizer. 
     
     
         10 . The coating of  claim 15 , wherein the granular substrate comprises at least one of urea, calcium nitrate, ammonium nitrate, potassium chloride, monoammonium phosphate, or diammonium phosphate. 
     
     
         11 . The coating of  claim 6 , wherein the ethylene diamine is propoxylated or ethoxylated to an average molecular weight from between about 227 Daltons to about 282 Daltons. 
     
     
         12 . The coating of  claim 1 , wherein the polyether polyol has a hydroxyl number of between about 130 to 850 and has a functionality of between about 2.5 and 4. 
     
     
         13 . The coating of  claim 1 , wherein the coating includes the wax, and the wax is petroleum or petrolatum wax, a microcrystalline wax, a paraffin wax or olefin wax, or a combination thereof. 
     
     
         14 . The coating of  claim 1 , wherein the wax is a high alpha (HA) olefin wax with from 16 to 40 carbons in average chain length and has more than about 90% by weight chains of 30 or more carbons. 
     
     
         15 . A method for coating a granular material, the method comprising:
 applying a polyurethane coating on the granular material, wherein applying the polyurethane coating comprises:
 pre-heating the granular material; 
   combining a polyisocyanate and a polyether polyol and optionally a wax, to form a reaction mix, wherein the polyether polyol comprises at least one of an aliphatic glycerine initiated polyether polyol or an aliphatic amine initiated trifunctional polyol, or combinations thereof, and at least 25% ethylene diamine that has been ethoxylated and/or propoxylated;   reacting the reaction mix on the granular material; and   forming the polyurethane coating on the granular material.   
     
     
         16 . The method of  claim 15 , wherein reacting the reaction mix on the granular material comprises forming a water-insoluble polyurethane coated granular material. 
     
     
         17 . The method of  claim 15 , further comprising separately applying a plurality of layers of the reaction mix on the granular material. 
     
     
         18 . The method of  claim 15 , further comprising applying at least one layer of the reaction mix on the granular material at a temperature between about 48.8° Celsius and about 82.2° Celsius. 
     
     
         19 . The method of  claim 17 , wherein applying the at least one layer of the plurality of layers of the reaction mix on the granular material comprises dispersing the polyether polyol onto a substrate of the granular material and mixing the reaction mix and the granular material for between about 30 seconds and 5 minutes. 
     
     
         20 . The method of  claim 19 , wherein the polyether further comprises a liquid wax, and wherein the first layer comprises no more than 60% of a total amount of the liquid wax in the plurality of layers and a third layer comprises no more than 40% of the total amount of the liquid wax in the plurality of layers.