Durable coatings and uses thereof

Abstract

Coatings and compositions are provided for coating particulates that can be used as, for example, as proppants. The proppants can be used, for example, to extract oil and gas from subterranean formations.

1 . A coated particulate, wherein the coating comprises:
 an inner coating adjacent to the particulate comprising a polyurethane and an outer coating comprising a polyurethane dispersion;   a coating comprising a polyurethane admixed with a polyurethane dispersion; or   a polyurethane dispersion layer and is free of an inner polyurethane layer.   
     
     
         2 . The coated particulate of  claim 1 , wherein the polyurethane is formed from a reaction of a polyol and an isocyanate. 
     
     
         3 . The coated particulate of  claim 2 , wherein the isocyanate is at least a diisocyanate. 
     
     
         4 . The coated particulate of  claim 2 , wherein the isocyanate is a mixture of a diisocyanate and a triisocyanate. 
     
     
         5 . The coated particulate of  claim 2 , wherein the isocyanate comprises 4,4′-methylenediphenyl diisocyanate. 
     
     
         6 . The coated particulate of  claim 5 , wherein the 4,4′-methylenediphenyl diisocyanate is present in a concentration amount of about 18 to about 25%. 
     
     
         7 . The coated particulate of  claim 2 , wherein the isocyanate comprises a diphenylmethane diisocyanate. 
     
     
         8 . The coated particulate of  claim 2 , wherein the polyol is a mixture of a polyol and a polyether polyol. 
     
     
         9 . The coated particulate of  claim 8 , wherein the polyol is a mixture of about 20 to about 30% polyol by weight and the polyether polyol is about 70 to about 80% by weight, wherein the total of the polyol and the polyether polyol is 100%. 
     
     
         10 . The coated particulate of  claim 1 , wherein the polyurethane dispersion is an aqueous polyurethane dispersion, siloxane-polyurethane dispersion, polycarbonate-polyurethane dispersion, polyether-polyurethane dispersion, polyester/acrylic polyurethane dispersion or an aliphatic polycarbonate polyurethane dispersion. 
     
     
         11 - 12 . (canceled) 
     
     
         13 . The coated particulate of  claim 10 , wherein the polycarbonate-polyurethane dispersion is free of organic solvents and emulsifiers. 
     
     
         14 - 16 . (canceled) 
     
     
         17 . The coated particulate of  claim 1 , wherein the polyurethane dispersion is an aqueous, anionic, solvent-free, low viscous dispersion of an aliphatic polyester-polyurethane substantially free of free isocyanate groups. 
     
     
         18 . The coated particulate of  claim 1 , wherein the polyurethane dispersion is:
 an aqueous, anionic, solvent-free, low viscous dispersion of an aliphatic polyester-polyurethane without free isocyanate groups;   an aqueous, colloidal, anionic, low viscous dispersion of an aliphatic polyester-polyurethane without free isocyanate groups;   an aqueous, anionic, solvent-free dispersion of an aliphatic polyester polyurethane;   a self-crosslinking polycarbonate/polyester polyurethane dispersion;   a polyisocyanate cross-linked polycarbonate/polyester polyurethane dispersion;   a polyester, self-crosslinking polyurethane dispersion; or   a solvent-free self-crosslinking acrylated polyurethane dispersion.   
     
     
         19 - 24 . (canceled) 
     
     
         25 . The coated particulate of  claim 1 , wherein the polyurethane dispersion is a waterborne, aliphatic polyurethane dispersion, free of solvents and emulsifiers. 
     
     
         26 . The coated particulate of  claim 1 , wherein the polyurethane dispersion is a polyester polyurethane dispersion. 
     
     
         27 . The coated particulate of  claim 1 , wherein the polyurethane dispersion has a König hardness of about 50 to about 170. 
     
     
         28 - 36 . (canceled) 
     
     
         37 . The coated particulate of  claim 1 , wherein the polyurethane dispersion is crosslinked with an aziridine crosslinker. 
     
     
         38 . (canceled) 
     
     
         39 . The coated particulate of  claim 1 , wherein the inner layer is about 0.65% to about 1.5% of the weight of the particulate. 
     
     
         40 - 45 . (canceled) 
     
     
         46 . The coated particulate of  claim 1 , wherein the particulate is sand. 
     
     
         47 . A method of preparing a multi-layer coated particulate, the method comprising:
 a) coating the particulate with a first layer, wherein the first layer is a polyurethane to produce a polyurethane coated particulate; and   b) coating the polyurethane coated particulate with a second layer to produce the multi-layer coated particulate, wherein the second layer comprises a polyurethane dispersion   
     
     
         48 - 86 . (canceled)