Free-flowing coated rubber particles, methods for their production and use

1. A free-flowing particle comprising:

(a) a rubber particle, and

(b) a coating deposited over at least a portion of the rubber particle, wherein the coating comprises:

(1) a polyurethane-urea resin that is a reaction product of a reaction mixture comprising:

(i) a polyol having a number average molecular weight of 1800 to 12.000;

(ii) an aromatic diamine;

(iii) a polyisocyanate; and

(iv) a catalyst for the reaction between hydroxyl groups and isocyanate groups; and

(2) a solid particle anti-clumping agent.

2. The free-flowing particle of claim 1 , wherein the free-flowing particles have an angle of repose that is less than 60° degrees when the particles are passed through a 10 mesh sieve and wherein at least 85% by weight of the particles are pourable after 1 week at 140° F./95% relative humidity.

3. The free-flowing particle of claim 1 , wherein the polyol having a number average molecular weight of 1800 to 12,000 comprises a polyether polyol having 2 or 3 hydroxyl groups per molecule and is present in an amount of at least 50% by weight, based on the total weight of the isocyanate-reactive composition.

4. The free-flowing particle of claim 1 , wherein the aromatic diamine comprises at least one alkyl substituent in the ortho-position to a first amino group and two alkyl substituents in the ortho-position to a second amino group and is present in an amount of 10 to 30% by weight, based on the total weight of the isocyanate-reactive composition.

5. The free-flowing particle of claim 4 , wherein the aromatic amine is 1-methyl-3,5-diethyl-2,4-diaminobenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene, 1,3,5-triethyl-2,6-diaminobenzene, and/or 3,5,3′,5′-tetraethyl-4,4′-diaminodiphenylmethane.

6. The free-flowing particle of claim 1 , wherein the isocyanate-reactive composition further comprises an aminosilane having the formula:

in which: (A) each X, which may be the same or different, is an organic group that is inert to isocyanate groups below 100° C., provided that at least one of these groups are alkoxy or acyloxy groups, such as where each X is an alkyl or alkoxy group having 1 to 4 carbon atoms; (B) Y is a linear or branched alkylene group containing 1 to 8 carbon atoms; and (C) R 1 is hydrogen or an organic group which is inert to isocyanate groups at a temperature of 100° C. or less, or R 1 represents a group corresponding to the formula:

—Y—Si—(X) 3

in which X and Y have the same meanings described above.

7. The free-flowing particle of claim 1 , wherein the polyisocyanate comprises polymeric MDI having a viscosity, at 25° C., of no more than 300 mPa·s, when measured using a Brookfield DVE viscometer, spindle #6.

8. The free-flowing particle of claim 1 , wherein the reaction mixture has a flow time of less than 15 seconds.

9. The free-flowing particle of claim 1 , wherein the reaction mixture is present in an amount of at least 0.5% by weight up to 10% by weight, based on the total weight of rubber particles.

10. The free-flowing particles of claim 1 , wherein the solid particle anti-clumping agent comprises silica that is present in an amount of at least 0.05% by weight and up to 2% by weight, based on the total weight of the sum of the reaction mixture and the rubber particles.

11. The free-flowing particle of claim 1 , wherein the coating has an inner surface adhered to the rubber particle and an outer surface, in which the solid particle anti-clumping agent is disposed at the outer surface of the coating, such that a majority of the surface area of the solid particle anti-clumping agent is not disposed beneath the outer surface of the coating.

12. A method comprising:

infilling a synthetic turf athletic field with free-flowing particles of claim 1 .

13. A synthetic turf structure comprising:

(a) a primary backing sheet;

(b) a plurality of fibers tufted into the primary backing sheet and extending substantially vertically away therefrom; and

(c) an infill disposed between the fibers, wherein the infill comprises a free-flowing particle of claim 1 .

14. A method of making the free-flowing particles of claim 1 comprising:

(a) mixing rubber particles with an isocyanate-reactive composition comprising:

(i) a polyol having a number average molecular weight of 1800 to 12,000;

(ii) an aromatic diamine; and

(iii) a catalyst for the reaction between hydroxyl groups and isocyanate groups to produce treated rubber particles;

(b) mixing treated rubber particles produced in step (a) with a polyisocyanate to form rubber particles at least partially coated with a cured polyurethane-urea resin; and

(c) mixing the coated rubber particles produced in step (b) with a solid particle anti-clumping agent.

15. The method of claim 14 , wherein the aromatic diamine comprises at least one alkyl substituent in the ortho-position to a first amino group and two alkyl substituents in the ortho-position to a second amino group.

16. The method of claim 14 , comprising:

prior to mixing with the isocyanate-reactive composition, mixing the rubber particles with an aminosilane having the formula:

in which: (A) each X, which may be the same or different, is an organic group that is inert to isocyanate groups below 100° C., provided that at least one of these groups are alkoxy or acyloxy groups; (B) Y is a linear or branched alkylene group containing 1 to 8 carbon atoms; and (C) R 1 is hydrogen or an organic group which is inert to isocyanate groups at a temperature of 100° C. or less or R 1 represents a group corresponding to the formula:

—Y—Si—(X) 3

in which X and Y have the same meanings described above.

17. The method of claim 14 , wherein the polyisocyanate comprises polymeric MDI having a viscosity, at 25° C., of no more than 300 mPa·s, when measured using a Brookfield DVE viscometer, spindle #6.

18. The method of claim 14 , wherein the solid particle anti-clumping agent comprises silica.

19. The method of claim 18 , wherein:

(1) the polyol having a number average molecular weight of 1800 to 12,000 is present in an amount of at least 50% by weight, based on the total weight of the isocyanate-reactive composition;

(2) the aromatic amine is present in an amount of 10 to 30% by weight, based on the total weight of the isocyanate-reactive composition;

(3) the solid particle anti-clumping agent is present in an amount of at least 0.05% by weight and up to 2% by weight, based on the total weight of the stun of the reaction mixture and the rubber particles, and

(4) the reaction mixture is present in an amount of at least 0.5% by weight up to 10% by weight, based on the total weight of rubber particles.

20. The method of claim 18 , wherein the coating has an inner surface adhered to the rubber particle and an outer surface, in which the solid particle anti-clumping agent is disposed at the outer surface of the coating, such as where a majority of the surface area of the solid particle anti-clumping agent is not disposed beneath the outer surface of the coating.

21. A method comprising infilling a synthetic turf athletic field with free-flowing particles made by the method of claim 18 .