Sulfur coating of urea containing gelling clays

Abstract

The present invention teaches a technique and provides for apparatus eminently useful for reducing the amount of sulfur currently needed by industry to sulfur coat water-soluble fertilizer materials such as, for example, granular or prilled urea. A further advantage of and benefit derived from the practice of the instant invention relates to the production of sulfur-coated urea products which have substantially higher nitrogen values than do urea products produced by prior art processes.

What we claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. An improved product of substantially enhanced relatively low aqueous media dissolution rate and/or relatively high impact resistance resulting from the coating of a substrate with from about 5 percent to about 30 percent by weight based on the weight of coated product of sulfur, said substrate consisting essentially of a substantially homogeneous admixture of urea and a channelized 2:1 clay mineral, the quantity of said mineral ranging from about 0.03 percent to about 4 percent by weight of said admixture. 
     
     
       2. The improved product of claim 1 wherein said mineral ranges from about 0.05 percent to about 1.0 percent by weight of said admixture. 
     
     
       3. The improved product of claim 2 wherein said mineral ranges from about 0.08 percent to about 0.3 percent by weight of said admixture. 
     
     
       4. The improved product of claim 2 wherein said sulfur coating ranges from about 5 percent to about 20 percent by weight based upon the weight of coated product. 
     
     
       5. The improved product of claim 3 wherein said sulfur coating ranges from about 10 percent to about 16 percent by weight based upon the weight of coated product. 
     
     
       6. The improved product of claim 1 wherein said channelized 2:1 clay mineral is selected from the group consisting of attapulgite, sepiolite, and mixtures thereof. 
     
     
       7. The improved product of claim 4 wherein said channelized 2:1 clay mineral is selected from the group consisting of attapulgite, sepiolite and mixtures thereof. 
     
     
       8. The improved product of claim 5 wherein said channelized 2:1 clay mineral is selected from the group consisting of attapulgite, sepiolite, and mixtures thereof. 
     
     
       9. The improved product of claim 6 wherein said substantially enhanced relatively low aqueous media dissolution rate ranges from about 5 percent to about 25 percent in 7 days. 
     
     
       10. The improved product of claim 7 wherein said substantially enhanced relatively low aqueous media dissolution rate ranges from about 10 percent to 20 percent in 7 days. 
     
     
       11. The improved product in claim 8 wherein said substantially enhanced relatively low aqueous media dissolution rate is about 10 percent in 7 days. 
     
     
       12. An improved method for imparting to sulfur-coated particulate urea fertilizer the properties of substantially enhanced relatively low aqueous media dissolution rate and/or relatively high-impact resistance, which improved method comprises the steps of: (1) mixing channelized 2:1 clay mineral into an essentially anhydrous molten melt of urea or a highly concentrated urea synthesis solution subsequently utilized to produce said melt until a homogeneous mixture thereof results;   (2) converting said melt resulting in step (1) into particulate form;   (3) subsequently coating the surfaces of the particulate urea resulting in step (2) supra with from about 5 to about 30 percent, by weight based on the weight of said resulting urea, or molten sulfur; and   (4) converting said resulting molten sulfur-coated particulate urea, resulting in step (3) supra, into particulate form; said improved method characterized by the fact that the resulting individual particles in step (2) supra contain from about 0.03 to about 4 percent by weight based on the weight of said urea of said clay and said improved method being further characterized by the fact that said weight percent sulfur coating and said substantially enhanced relatively low aqueous media dissolution rate are in direct and inversely proportional relationship to one another through the range of sulfur coating of from about 5 percent to about 30 percent and through the range of 7-day dissolution rate of from about 5 percent to about 25 percent.     
     
     
       13. The improved method of claim 12 wherein the said mount of channelized 2:1 clay mineral admixed with said anhydrous molten melt or said synthesis solution utilized for the production thereof is utilized in amounts ranging from about 0.05 percent to about 1.0 percent by weight of said clay mineral in the particulate urea resulting in step (2) thereof, wherein said sulfur coating resulting in the product therefrom ranges from about 5 percent to about 20 percent, and wherein said substantially enhanced relatively low aqueous media 7-day dissolution rate ranges from about 10 percent to about 20 percent. 
     
     
       14. The improved method of claim 13, wherein the amount of channelized 2:1 clay mineral admixed with said anhydrous molten melt, and said synthesis solution utilized for the production thereof is utilized in amount ranging from about 0.08 percent to about 0.3 percent by weight of said mineral in the particulate urea resulting in step (2) thereof, wherein said sulfur coating resulting in the product therefrom ranges from about 10 percent to about 16 percent, and wherein said substantially enhanced relatively low aqueous media 7-day dissolution rate is about 10 percent. 
     
     
       15. The improved method of claim 12 wherein said channelized 2:1 clay mineral is selected from the group consisting of attapulgite, sepiolite, and mixtures thereof. 
     
     
       16. The improved method of claim 13 wherein said channelized 2:1 clay mineral is selected from the group consisting of attapulgite, sepiolite, and mixtures thereof. 
     
     
       17. The improved method of claim 14 wherein said said channelized 2:1 clay mineral is selected from the group consisting of attapulgite, sepiolite, and mixtures thereof. 
     
     
       18. The improved product of claim 1 resulting from the coating of said substrate sulfur coating with a sealant comprising polyethylene, brightstock oil, and mixtures thereof and further resulting from coating the resulting sealed sulfur coating with conditioner dust. 
     
     
       19. The improved method of claim 12 wherein a sealant comprising polyethylene and brightstock oil, and mixtures thereof is applied to said sulfur coating and the resulting sealed sulfur coating is subsequently coated with conditioner dust.