Controlled release fertilizer with biopolymer coating and process for making same

Abstract

A controlled release fertilizer including a fertilizer granule, having an outer surface, a coating of biopolymer composition on the outer surface of the fertilizer granule, wherein the biopolymer composition includes at least one biopolymer, and a process of making the controlled release fertilizer including the steps of screening fertilizer granules to a preselected granule size, heating a biopolymer to become substantially fluid, and applying the biopolymer onto the surface of the fertilizer granule to produce a coating on the granule of a predetermined amount.

1 . A controlled release fertilizer comprising:
 a fertilizer granule, having an outer surface;   a coating of biopolymer composition on the outer surface of the fertilizer granule, wherein said biopolymer composition includes at least one biopolymer.   
     
     
         2 . The controlled release fertilizer of  claim 1 , wherein the biopolymer is selected from the group consisting of polylactic acid, polylactide, lactide, and oligomers thereof. 
     
     
         3 . The controlled release fertilizer of  claim 2 , wherein the biopolymer is polylactic acid oligomers. 
     
     
         4 . The controlled release fertilizer of  claim 1 , wherein the amount of biopolymer coating is 1.0 to 10 wt. %. 
     
     
         5 . The controlled release fertilizer of  claim 1 , wherein the biopolymer composition further includes at least one flow-sealant modifier. 
     
     
         6 . The controlled release fertilizer of  claim 5 , wherein the flow-sealant modifier is selected from the group consisting of corn syrup, high fructose syrups, cane syrup, rice syrup and glucose syrup. 
     
     
         7 . The controlled release fertilizer of  claim 1 , further comprising a second outer coating of a water proof or resistant sealant coating over the first coating of biopolymer composition resulting in a twice coated fertilizer granule. 
     
     
         8 . The controlled release fertilizer of  claim 7 , wherein the sealant coating is selected from the group consisting of polyvinyl acetate, waxes, polymer blends, paraffins and micro crystalline waxes. 
     
     
         9 . The controlled release fertilizer of  claim 7 , wherein the amount of sealant coating is 0.05 to 5 wt. %. 
     
     
         10 . The controlled release fertilizer of  claim 1 , wherein the fertilizer granule includes a plant nutrient selected from the group consisting of nitrogen, phosphorus and potassium compounds. 
     
     
         11 . The controlled release fertilizer of  claim 10 , wherein the nitrogen compound is selected from the group consisting of urea, ammonia, ammonium nitrate, ammonium sulfate, calcium nitrate, diammonium phosphate, monoammonium phosphate, potassium nitrate and sodium nitrate. 
     
     
         12 . The controlled release fertilizer of  claim 10 , wherein the phosphorous compound is selected from the group consisting of diammonium phosphate, monoammonium phosphate, monopotassium phosphate, dipotassium phosphate, tetrapotassium pyrophosphate, and potassium metaphosphate. 
     
     
         13 . The controlled release fertilizer of  claim 10 , wherein the potassium compound is selected from the group consisting of potassium chloride, potassium nitrate, potassium sulfate, monopotassium phosphate, dipotassium phosphate, tetrapotassium pyrophosphate, and potassium metaphosphate. 
     
     
         14 . The controlled release fertilizer of  claim 10 , wherein the fertilizer contains nitrogen, phosphorous and potassium compounds in a N:P:K ratio selected from the group consisting of 29-3-4, 16-4-8, 10-10-10, 15-5-10, 15-0-15, 22-3-14, 20-28-5 and 12-6-6. 
     
     
         15 . The controlled release fertilizer of  claim 1 , wherein the fertilizer granule includes a macronutrient selected from the group consisting of sulfur, calcium and magnesium and/or micronutrients including boron, copper, iron, manganese, molybdenum and zinc. 
     
     
         16 . A process of making a controlled release fertilizer comprising the following steps:
 screening fertilizer granules to a preselected granule size;   heating a biopolymer to become substantially fluid; and   applying the biopolymer onto the surface of the fertilizer granule to produce a coating on the granule of a predetermined amount.   
     
     
         17 . The process of  claim 16 , wherein the biopolymer coating, is applied to the surface of the fertilizer granule surface by pouring, hydraulic spraying or pneumatic atomized spraying. 
     
     
         18 . The process of  claim 16 , wherein the amount of coating of biopolymer is determined on a percent weight basis to result in a range of 1.0 to 10 wt. %. 
     
     
         19 . The process of  claim 16 , further comprising after the biopolymer application step, the step of passing a cooling gas over the coated granules to quickly set the biopolymer. 
     
     
         20 . The process of  claim 16 , further comprising after the biopolymer application step, a step of applying a parting agent to the surface of the biopolymer coated fertilizer granules.