COATED UREA-CONTAINING FERTILIZER PARTICLES AND PROCESS FOR THE PRODUCTION THEREOF

Abstract

A process for producing coated urea-containing fertilizer particles, comprising the following steps: A) forming at least one polyurea layer on the uncoated urea-containing fertilizer, and then B) forming at least one polyurethane layer on the at least one polyurea layer on the urea-containing fertilizer.

Claims

1-15. (canceled)

16. A process for producing coated urea-containing fertilizer particles, comprising the following steps: A) forming at least one polyurea layer on the uncoated urea-containing fertilizer, and then B) forming at least one polyurethane layer on the at least one polyurea layer on the urea-containing fertilizer, wherein the weight ratio of the polyurea layer to the polyurethane layer is from 4:1 to 1:4 and, if the coated urea-containing fertilizer particle has multiple polyurethane layers or polyurea layers, the weight ratio is based on the sum total of the respective polyurea layers and polyurethane layers.

17. The process of claim 16, wherein the urea content in the urea-containing fertilizer is at least 30% by weight, based on the urea-containing fertilizer.

18. The process of claim 17, wherein the urea content in the urea-containing fertilizer is at least 50% by weight, based on the urea-containing fertilizer.

19. The process of claim 16, wherein the polyurea layer is formed by the reaction of an organic isocyanate component containing more than one isocyanate group with water on the surface of the urea-containing fertilizer particles.

20. The process of claim 16, comprising, in step A), the following steps: A1) applying water or steam to urea-containing fertilizer particles in order to obtain water-coated fertilizer particles, A2) applying an organic isocyanate component containing at least two isocyanate groups to the water-coated fertilizer particles and reacting it therewith to form a polyurea layer on the urea-containing fertilizer particles.

21. The process of claim 16, comprising, in step B), the following step: B1) applying a polyol component and an isocyanate component to the urea-containing fertilizer particle from step A) and converting them to a polyurethane layer on the polyurea layer.

22. The process of claim 16, wherein the polyurea layer is formed and/or the polyurethane layer is formed in the presence of a basic catalyst.

23. The process of claim 22, wherein the catalyst used is at least one amine compound.

24. The process of claim 22, wherein the catalyst to form the polyurea layer is applied to the urea-containing fertilizer after the isocyanate component and/or the catalyst to form the polyurethane layer after the polyol component and after the isocyanate component.

25. The process of claim 16, wherein the polyurea layer and the polyurethane layer are each formed in an amount of at least 0.5% by weight, based on the untreated urea-containing fertilizer particles.

26. The process of claim 25, wherein the polyurea layer and the polyurethane layer are each formed in an amount of at least 0.75% by weight, based on the untreated urea-containing fertilizer particles.

27. The process of claim 16, wherein the urea-containing fertilizer particles comprise at least one urease inhibitor.

28. The process of claim 16, wherein the polyurethane layer is formed using at least one polyol selected from cardol, cardanol, derivatives or oligomers of cardol or cardanol, condensation products of phenol and at least one aldehyde, or mixtures thereof.

29. The process of claim 16, wherein only one polyurea layer and only one polyurethane layer are present.

30. Coated urea-containing fertilizer particles, comprising, on the uncoated urea-containing fertilizer, at least one polyurea layer and further comprising, on the at least one polyurea layer, at least one polyurethane layer, wherein the weight ratio of the polyurea layer to the polyurethane layer is from 4:1 to 1:4 and, if the coated urea-containing fertilizer particle has multiple polyurethane layers or polyurea layers, the weight ratio is based on the sum total of the respective polyurea layers and polyurethane layers.

31. The coated urea-containing fertilizer of claim 30, wherein the polyurethane layer is the reaction product of at least one isocyanate component with at least one polyol component comprising at least one polyol selected from cardol, cardanol, derivatives or oligomers of cardol or cardanol, condensation products of phenol and at least one aldehyde, or mixtures thereof.

32. The coated urea-containing fertilizer particles of claim 30, further comprising at least one urease inhibitor.

Description

EXAMPLES

Example 1

[0122] 2 kg of urea granules were preheated to 70° C. for 12 hours and then transferred to a coating drum heated to 70° C. In the coating drum, the urea granules were mixed at about 30 revolutions per minute of the coating drum.

[0123] 20 g of demineralized water was added to the granules.

[0124] After the granules had been wetted, 20 g of diphenylmethane diisocyanate (MDI) was added to the moistened granules within one minute. After the urea granule particles had been wetted completely, 2 ml of an amine catalyst containing hydroxyl groups and having a flashpoint of about 88° C. was applied to the wetted material with short spray pulses using compressed air as carrier gas.

[0125] Rotation of the coating drum continued until the material was free-flowing again.

[0126] Then a mixture of 13 g of polyol based on condensation products of phenol and formaldehyde, and also cardol and cardanol, was added to the coated granules together with 13 g of diphenylmethane diisocyanate (MDI) within one minute. Subsequently, 2 ml of the amine catalyst containing hydroxyl groups and having a flashpoint of about 88° C. was applied to the wetted granules with the spray gun in short spray pulses. Rotating of the coating drum was continued until the material was free-flowing again. Subsequently, the coated granules were cooled down and removed.

[0127] The isocyanate used in the first coating was Askocoat™ 500. The polyol used in the second step was Askocoat™ 420. The isocyanate used in the second step was Askocoat™ 500. The catalyst used was catalyst 806. All feedstocks are available from ASK Chemicals GmbH, Hilden.

[0128] Based on the untreated urea granules, 1% by weight of the polyurea layer (primer coating) and 1.3% by weight of the polyurethane layer were applied. According to the invention, the layer thickness is within a range from about 25 to about 50 μm.

Comparative Example 2

[0129] The procedure was as in example 1, except that only 2.3% by weight of the first polyurea layer was applied. There was no polyurethane layer.

Comparative Example 3

[0130] The procedure was as in example 1, except that there was no polyurea layer (primer coating). Instead, 2.3% by weight of the polyurethane layer was applied.

Example 4

[0131] The urea granules produced according to example 1, comparative example 1 and comparative example 2 were subjected to a release test. 5 g of the respective granules were added to 45 g of water at 25° C., agitated gently therein and then left to stand. At time intervals, the amount of urea released from the granules was determined. Then the samples were swirled. Subsequently, 300 μl of solution in each case were removed, and the urea content in the solution was determined by refractometry.

[0132] The release characteristics as a function of time are shown in FIG. 1, which is appended. The proportion of urea released [in percent] is plotted here against time [in hours]. The uppermost curve relates to comparative example 2, the middle curve to comparative example 3, and the lower curve to example 1.

[0133] It becomes clear from the results that the urea granules coated solely with polyurea according to comparative example 2 dissolve very quickly (upper curve). The granules coated solely with polyurethane according to comparative example 3 show much slower dissolution characteristics (middle curve).

[0134] The urea granules coated with polyurea and polyurethane according to example 1 show significantly slowed dissolution characteristics again (lower curve). As a result, desired release of the fertilizer over a prolonged period is enabled. It should be noted here that the total amount of coating applied was identical in all experiments.

[0135] The effect of the invention is achieved even with a small total amount of coating of 2.3% by weight. By comparison, the amounts of coating as described in WO 2012/109432 are 4.3% according to example 1, 5.5% according to example 3, and 4.3%, 5% and 6% according to example 4.