# US 9,518,214 B2 · Proppant with polyurea-type coating > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,518,214 B2 - Document ID: US9518214B2 - Status: Granted - Kind: B2 - Application number: 13/837,396 - Filed: 2013-03-15 - Published: 2014-09-18 - Granted: 2016-12-13 - Earliest claimed: 2013-03-15 - Assignees: Preferred Technology, LLC - Applicants: Preferred Technology, LLC - Inventors: Avis Lloyd McCrary; Robert Ray McDaniel; Ralph Edward Barthel; Spyridon Monastiriotis - Web page: https://patentgrep.com/patent/US9518214B2 ## CPC - C09K 8/805: {Coated proppants} - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE ## Abstract Proppants for hydraulic fracturing of oil and gas wells are coated with a polyurea-type coating. In a preferred embodiment, the polyurea-type coating is formed by contacting a polymeric isocyanate with an amount of water and a blowing catalyst at a rate and quantity sufficient to generate a reactive amine in situ on the outer surface of the proppant which thereby reacts with unconverted polymeric isocyanate to form a thin polyurea-type surface coating that is substantially solid and lacks foam or substantial porosity. Alternatively, the polyurea-type can be produced by selecting reactive amine compounds and isocyanates to develop the coated proppant. The coated proppants retain the discrete, free-flowing character of the original core solids but with the beneficial effects of the polyurea-type coating of the present invention. ## Claims ### Claim 1 A method for the production of proppant that is coated with a substantially cured, polyurea-type coating, the method comprising: forming a thin, glassy film of said polyurea-type coating on a heated proppant core solid, having a size range of about 16 to about 100 mesh, by contacting said core simultaneously with: (a) an isocyanate comprising at least 2 reactive isocyanate groups; and (b) a mixture of water and a curing agent and/or catalyst in amounts sufficient to promote the formation of said thin, glass film, substantially cured, polyurea-type coating, wherein said water is contacted with said isocyanate at a rate sufficient to form a reactive amine that then reacts with additional isocyanate to form said polyurea-type coating on said proppant and wherein the proppant core solid, water and isocyanate are added a rate sufficient to maintain a proportion of 5-30 wt % water to 95-70% isocyanate, and wherein said coating exhibits an interparticle bond strength of at least 20 psi in unconfined compressive strength testing. ### Claim 2 (depends on 1) A method according to claim 1, wherein said proppant core solid comprises sized sand or ceramic. ### Claim 3 (depends on 1) A method according to claim 1, wherein said isocyanate comprises a polymer or an oligomer of an isocyanate. ### Claim 4 (depends on 1) A method according to claim 1, wherein said catalyst comprises bis-dimethylaminoethylether or bis-morpholinium diethylether. ### Claim 5 (depends on 1) A method according to claim 1, wherein the polyurea-type coating made by said method exhibits an interparticle bond strength of at least 100 psi in unconfined compressive strength testing. ### Claim 6 (depends on 1) A method according to claim 1, wherein said heated proppant core solid has been preheated to a temperature within the range of 50-175° C. ### Claim 7 (depends on 6) A method according to claim 6 wherein said proppant core solid has been heated to a temperature within the range of 75-125° C. ### Claim 8 (depends on 1) A method according to claim 1 wherein said polyurea-type coating is present on said proppant within the range of 1-5 wt % based on total weight of coated proppant. ### Claim 9 (depends on 1) A method according to claim 1, wherein said method further comprises contacting said the heated proppant core solid with a silane adhesion promoter before contact with said isocyanate or said mixture. ### Claim 10 (depends on 1) A method according to claim 1, wherein said coating exhibits an interparticle bond strength of at least 20 psi in unconfined compressive strength testing. ### Claim 11 (depends on 1) The method according to claim 1, wherein the coating is substantially foam-free. ### Claim 12 (depends on 1) The method according to claim 1, wherein the coating is foam-free. ### Claim 13 (depends on 1) A method according to claim 1, wherein said polyurea-type coating is disposed on an outermost skin layer on a polyurethane-coated proppant core solid. ### Claim 14 (depends on 1) A method according to claim 1, wherein said polyurea-type coating is disposed on an outermost skin layer on a phenolic-resin-coated proppant core solid. ### Claim 15 (depends on 1) A method according to claim 1, wherein said polyurea-type coating is cross-linked.