Pendimethanlin microcapsules with a shell made of tetramethylxylylene diisocyanate and a polyamine with at least three amine groups

Abstract

The present invention relates to a composition comprising microcapsules, which comprise a polyurea shell and a core, wherein the core comprises pendimethalin and the shell comprises a polymerization product of a tetramethylxylylene diisocyanate, and a polyamine with at least three amine groups, and where the polymerization product comprises less than 5 wt % of further isocyanate monomers in polymerized form, based on the weight of the tetramethylxylylene diisocyanate; a method for preparing the composition comprising the steps of contacting water, the pendimethalin, the tetramethylxylylene diisocyanate, and the polyamine; and to a method of controlling undesired plant growth, wherein the composition is allowed to act on the soil and/or on undesired plants and/or on the crop plants and/or on their environment.

Claims

1. A composition comprising microcapsules, which comprise a polyurea shell and a core, wherein the core comprises pendimethalin and the shell comprises a polymerization product of a) a tetramethylxylylene diisocyanate, and b) a polyamine with at least three amine groups, and wherein: the polymerization product comprises less than 5 wt % of further isocyanate monomers in polymerized form, based on the weight of the tetramethylxylylene diisocyanate; the polyamine is a compound of formula (I) ##STR00003## where m is an integer from 1 to 8, and R1 is H or methyl; and the pendimethalin is present in the core in an amount of at least 90 wt % relative to the core.

2. The composition of claim 1, wherein the polymerization product is essentially free of further isocyanate monomers in polymerized form.

3. The composition claim 1, wherein m is an integer from 2 to 5, and R1 is H.

4. The composition of claim 1, wherein the tetramethylxylylene diisocyanate is a compound of formula (II) ##STR00004##

5. The composition of claim 1, wherein the weight ratio of the core to the polyurea shell is in the range from 50:1 to 5:1.

6. The composition of claim 1, wherein the molar ratio of the tetramethylxylylene diisocyanate to the polyamine is in the range from 0.8:1 to 1:1.5.

7. The composition of claim 1, wherein the polyurea shell comprises at least 55 wt % of the tetramethylxylylene diisocyanate.

8. The composition of claim 1, wherein the polyurea shell comprises up to 45 wt % of the polyamine.

9. The composition of claim 1, wherein the composition is an aqueous composition and the aqueous phase comprises a lignosulfonate.

10. The composition of claim 1, wherein the lignosulfonate has a molecular weight of up to 10000 g/mol.

11. The composition of claim 1, wherein the composition comprises 0.3 to 3.0 wt % of the lignosulfonate.

12. The composition of claim 1, wherein the core comprises less than 1 wt % of a water immiscible organic solvent.

13. The composition of claim 1, wherein the core comprises less than 0.5 wt % of a water immiscible organic solvent.

14. A method for preparing the composition of claim 1 comprising the steps of contacting water, the pendimethalin, the tetramethylxylylene diisocyanate, and the polyamine.

15. A method of controlling undesired plant growth, wherein the composition of claim 1 is allowed to act on the soil and/or on undesired plants and/or on the crop plants and/or on their environment.

16. The composition of claim 1, wherein the pendimethalin is present in the core in an amount of at least 95 wt % relative to the core.

17. The composition of claim 1, wherein: the weight ratio of the core to the polyurea shell is in the range from 50:1 to 5:1 the polyurea shell comprises at least 55 wt % of the tetramethylxylylene diisocyanate; and the molar ratio of the tetramethylxylylene diisocyanate to the polyamine is in the range from 0.8:1 to 1:1.5.

18. The composition of claim 17, wherein: the pendimethalin is present in the core in an amount of at least 95 wt % relative to the core; and the tetramethylxylylene diisocyanate is a compound of formula (II) ##STR00005##

19. The composition of claim 1, wherein the pendimethalin is present in the core in an amount of at least 99 wt % relative to the core.

20. The composition of claim 1, wherein the core of the microcapsule comprises at least 99 wt. % of the sum of the pendimethalin, any optional water-immiscible organic solvent present, and any optional further solvent present, relative to the core.

21. The composition of claim 1, wherein the core of the microcapsule consists of the pendimethalin, any optional water-immiscible organic solvent present in the core, and any optional further solvent present in the core.

Description

EXAMPLES

(1) TMXDI: Tetramethyl-m-xylylene diisocyanate, CAS 2778-42-9. TEPA: Tetraethylenepentaamine Additive A: Sodium salt of naphthalene sulfonate condensate. Lignosulfonate: Sodium salt of lignosulfonate, based on Kraft lignin, molecular weight about 3000 g/mol, water-soluble, CAS 68512-34-5.

Example 1

(2) The oil phase comprising the pesticide and TMXDI was added at 65° C. to the water phase (comprising Lignosulfonate, magnesium sulfate heptahydrate) and emulsified using high-shear equipment. After emulsification, the emulsification device was replaced by a low shear stirrer and the tetraethylenepentaamine (TEPA) was added. Subsequently, the dispersion was smoothly agitated for 30-60 minutes at 60° C. Under stirring the aqueous finish solution comprising Additive A, xanthan gum, a silicon defoamer, and a biocide was added to the capsule dispersion and the pH adjusted to pH 6-8 by addition of acetic acid. The average size of the microcapsules was 7.4 μm.

(3) TABLE-US-00001 TABLE 1 Amount [g/l] Pendimethalin 455 TMXDI 14.7 TEPA 5.92 Lignosulfonate 11 Additive A 4 Magnesium sulfate 100 Xanthan gum 0.4 Silicon defoamer 0.6 Biocide 2 Water Ad 1.0 l

Example 2

(4) The microcapsules were prepared as in Example 1. The amounts of the components are listed in Table 2. The average size of the microcapsules was 8.0 μm.

(5) TABLE-US-00002 TABLE 2 Amount [g/l] Pendimethalin 455 TMXDI 14.7 TEPA 5.92 Lignosulfonate 11 Additive A 5 1,2 propylene glycol 70 Xanthan gum 2.5 Silicon defoamer 5 Biocide 2 Water Ad 1.0 l

Example 3

(6) The clogging and staining test was used to investigate whether the microcapsule formulation following dilution with water to a sprayable concentration, can be used in standard sprayers without clogging the filters and staining of the spraying machine or the spraying nozzles.

(7) A comparative Example Comp-1 was prepared according to Example 1, but instead of 5.92 g TEPA (tetraethylenepentaamine) 5.8 g hexamethylene diamine was used.

(8) The formulation of Example 1 or the comparative Example Comp-1 was diluted with hard water (CIPAC D) to prepare 1000 ml of a microcapsule suspension containing 1 wt % of the formulation of Example 1 the comparative Example Comp-1. This microcapsule suspension was cycled for 8 h through a cartridge with a metal sieve (150 μm). During the test, the temperature was kept constant at about 10° C. in order to simulate cold well water.

(9) Afterwards the metal sieve was visually inspected for residues. When using the Example 1 only minor residue were found. When using the comparative Example Comp-1 clearly large amounts of an orange sticky residue clogged and stained the filter already after 2 h. The test could not be continued and the equipment had to be cleaned.