Proppants with improved dust control
Provided are proppants for use in hydraulic fracturing operations. The proppants comprise particles having coatings disposed on them as described herein. The proppants exhibit reduced dust generation, for instance during transloading, conveying and/or offloading of the proppant at a wellsite and/or at intermediate shipping transload points.
1. A proppant for use in hydraulic fracturing, comprising:
a particle; and
a coating disposed on the particle that is formed from an aqueous coating composition, the aqueous coating composition comprising, based on the total weight of the aqueous coating composition, from 2 to 65 weight percent of a surfactant, from 1 to 35 weight percent of a polymer binder that is a water insoluble emulsion polymer, and balance water, the polymer binder comprising an aqueous dispersion of particles made from a copolymer, based on the weight of the copolymer, comprising:
i) from 90 to 99.9 weight percent of at least one ethylenically unsaturated monomer not including component ii; and
ii) from 0.1 to 10 weight percent of (meth)acrylamide.
2. The proppant of claim 1 wherein the surfactant is an alkoxylate.
3. The proppant of claim 1 wherein the coating further comprises an optical brightener.
4. The proppant of claim 3 wherein the optical brightener is coumarin or a coumarin derivative, a bis-stilbene compound, a bis(benzoxazolyl) thiophene compound, a 4,4′-bis(2-benzoxazolyl)stilbene compound, or a mixture of two or more thereof.
5. The proppant of claim 1 wherein the coating further comprises an anti-freeze solvent.
6. A process for making the proppant of claim 1 comprising blending in a mixer with mechanical agitation the particle and the aqueous coating composition; or by spraying the aqueous coating composition onto a moving bed or a falling stream of the particles.
7. A method for reducing dust generation associated with hydraulic fracturing operations, the method comprising using the proppant of claim 1 .
8. The method of claim 7 wherein the hydraulic fracturing operation is transloading, conveying or offloading of the proppant at a wellsite and/or at intermediate shipping transload points.
9. The proppant of claim 1 wherein the coating covers less than 50 percent of the particle.
10. The proppant of claim 1 wherein the aqueous coating composition comprises from 5 to 50 weight percent of the surfactant and from 5 to 20 weight percent of the polymer binder, based on the total weight of the aqueous coating composition.
11. The proppant of claim 1 wherein the surfactant is a nonionic alkoxylate surfactant and the polymer binder is derived from butyl acrylate, styrene, (meth)acrylamide, and optionally hydroxyethyl methacrylate.
12. The proppant of claim 1 wherein an amount of coating on the particle, on a dry basis, is between 300 ppm and 700 ppm of particle weight.