Pesticidal microcapsules with a shell made of tetramethylxylylene diisocyanate, cycloaliphatic diisocyanate, and aliphatic diamine

Abstract

The present invention relates to a composition comprising microcapsules, which comprise a polyurea shell and a core, wherein the core comprises a water-insoluble pesticide and the shell comprises a polymerization product of a tetramethylxylylene diisocyanate, an cycloaliphatic diisocyanate, and an aliphatic diamine; to a method for preparing the composition comprising the steps of contacting water, the pesticide, the tetramethylxylylene diisocyanate, the cycloaliphatic diisocyanate, and the aliphatic diamine; and to a method of controlling phytopathogenic fungi and/or undesired plant growth and/or undesired insect or mite attack and/or for regulating the growth of plants, wherein the composition is allowed to act on the respective pests, or the crop plants to be protected from the respective pest, 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 a pesticide and the shell comprises a polymerization product of a) a tetramethylxylylene diisocyanate, b) an cycloaliphatic diisocyanate, and c) an aliphatic diamine, wherein: the composition is the product of a method comprising reacting the tetramethylxylylene diisocyanate and the cycloaliphatic diisocyanate with the aliphatic diamine in the presence of water and the pesticide, and wherein the pesticide has a solubility in water of up to 10 g/1 at 20 C.; the composition is an aqueous composition comprising an aqueous phase, and the aqueous phase comprises a lignosulfonate; and the core is free from acetamide herbicides.

2. The composition according to claim 1 where the cycloaliphatic diisocyanate is the compound of formula (I) ##STR00003##

3. The composition according to claim 1 where the tetramethylxylylene diisocyanate is the compound of formula (II) ##STR00004##

4. The composition according to claim 1 where the aliphatic di amine is of the formula H.sub.2N(CH.sub.2).sub.nNH.sub.2, wherein n is an integer from 2 to 8.

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

6. The composition according to claim 1 where the weight ratio of the tetramethylxylylene diisocyanate to the cycloaliphatic diisocyanate is in the range from 25:1 to 2:1.

7. The composition according to claim 1 where the polyurea shell comprises at least 45 wt % of the tetramethylxylylene diisocyanate.

8. The composition according to claim 1 where the polyurea shell comprises up to 20 wt % of the cycloaliphatic diisocyanate.

9. The composition according to claim 1 where the polyurea shell comprises up to 10 wt % of further polyisocyanates, which have at least two isocyanate groups and which are different from the tetramethylxylylene diisocyanate and from the cycloaliphatic diisocyanate.

10. The composition according to claim 1 where the polyurea shell comprises up to 10 wt % of further polyamines, which have at least two amine groups and which are different from the aliphatic diamine.

11. The composition according to claim 1 where the composition comprises 0.3 to 3.0 wt % of the lignosulfonate.

12. The composition according to claim 1 where the core comprises a water immiscible organic solvent.

13. A method of controlling phytopathogenic fungi and/or undesired plant growth and/or undesired insect or mite attack and/or for regulating the growth of plants, the method comprising applying the composition of claim 1 to one or more of pests, a crop plant to be protected from the pests, soil, undesired plants, and an environment of the crop plants.

14. The composition according to claim 1, where the weight ratio of the core to the polyurea shell is in the range from 40:1 to 10:1.

15. The composition according to claim 1, where the weight ratio of the core to the polyurea shell is in the range from 30:1 to 15:1.

16. The composition according to claim 1, wherein: the polyurea shell comprises at least 45 wt % of the tetramethylxylylene diisocyanate; the polyurea shell comprises up to 20 wt % of the cycloaliphatic diisocyanate; the weight ratio of the tetramethylxylylene diisocyanate to the cycloaliphatic diisocyanate is in the range from 12:1 to 7:1; the weight ratio of the core to the polyurea shell is in the range from 30:1 to 15:1; and the composition comprises 0.3 to 3.0 wt % of the lignosulfonate.

17. The composition according to claim 16, wherein: the cycloaliphatic diisocyanate is the compound of formula (I) ##STR00005## and the tetramethylxylylene diisocyanate is the compound of formula (II) ##STR00006##

Description

EXAMPLES

(1) TMXDI: Tetramethyl-m-xylylene diisocyanate, CAS 2778-42-9.

(2) Cyclic Diisocyanate: bis(4-isocyanotocyclohexyl) methane (compound of formula (I)).

(3) Additive A: Sodium salt of naphthalene sulfonate condensate.

(4) Additive B: hydrophobically modified polyacrylate, anionic polymeric dispersant, powder, molecular weight 1-20 kDa, pH 7-8.5 (1 wt % in water).

(5) Lignosulfonate: Sodium salt of lignosullonate, based on Kraft lignin, molecular weight about 3000 g/mol, water-soluble, CAS 68512-34-5,

Example 1

(6) The oil phase comprising the pesticide, TMXDI and Cyclic Diisocyanate 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 hexamethylene diamine 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 6.5 m.

(7) TABLE-US-00001 TABLE 1 Amount [g/l] Pendimethalin 455 TMXDI 15.05 Cyclic Diisocyanate 1.67 Hexamethylene diamine 6.6 Lignosulfonate 12.5 Additive A 4.7 Magnesium sulfate 114 Xanthan gum 0.45 Silicon defoamer 0.6 Biocide 2 Water Ad 1.0 l

Example 2

(8) 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 7 m.

(9) TABLE-US-00002 TABLE 2 Amount [g/l] Pendimethalin 455 TMXDI 15.05 Cyclic Diisocyanate 1.67 Hexamethylene diamine 6.6 Lignosulfonate 12.5 Additive A 5 1,2-Propylene glycol 70 Xanthan gum 2.5 Silicon defoamer 5 Biocide 2 Water Ad 1.0 l

Example 3

(10) The microcapsules were prepared as in Example 1. The amounts of the components are listed in Table 3. The average size of the microcapsules was 6.9 m.

(11) TABLE-US-00003 TABLE 3 Amount [g/l] Pendimethalin 455 TMXDI 15.05 Cyclic Diisocyanate 1.67 Hexamethylene diamine 6.6 Lignosulfonate 12.5 Additive B 5 Magnesium sulfate 114 Xanthan gum 0.45 Silicon defoamer 0.6 Biocide 2 Water Ad 1.0 l

Example 4

(12) Samples of the microcapsules prepared in Examples 1, 2 and 3 following the procedure as described in Example 1 were tested for dilution stability and for clogging the spray nozzles. The samples were diluted with water to prepare a spray tank mixture suitable for an application rate of 3 L/ha product with 200 L/ha water. The spray tank mixture was circled in a pump circuit over a metal sieve (150 m). After 1 h, 2 h, 2.5 h and 4 h the circuit was refilled with a fresh spray tank mixture. Then the circling was stopped overnight and kept at room temperature. The next day the circuit was refilled and circled for another hour. At the end the circuit was discharged and the residues on the sieves evaluated. Minor amounts of orange residue was observed, which did not clog the sieve.

(13) Thus, it was demonstrated that the compositions of Examples 1, 2 and 3 may be applied after dilution with water without clogging the spray nozzles, and that the composition is stable after dilution with water.

Example 5

Comparative

(14) The comparative microcapsules were prepared following the procedure as described in Example 1, The amounts of the components are listed in Table 4. Basically, this comparative example was identical with the composition of Example 1 but did not comprise the cyclic diisocyanate.

(15) A sample of the microcapsules prepared in this Example 5 were tested for dilution stability and for clogging the spray nozzles as described in Example 4. After the first 2 h the metal sieve in the pump circuit was clogged due to large amounts of an orange residue. The circling could not be continued.

(16) Thus, it was demonstrated that the comparative composition cannot be applied after dilution with water due to clogging the spray nozzles, and that the comparative composition is not stable after dilution with water.

(17) TABLE-US-00004 TABLE 4 Amount [g/l] Pendimethalin 455 TMXDI 15 Cyclic Diisocyanate Hexamethylene diamine 6 Lignosulfonate 11 Additive A 4 Magnesium sulfate 100 Xanthan gum 0.4 Silicon defoamer 0.5 Biocide 2 Water Ad 1.0 l

Example 6

Comparative

(18) The microcapsules were prepared following the procedure as described in Example 1 resulting in a similar average size of the microcapsules. The amounts of the components are listed in Table 5.

(19) For comparison, the recipe in Table 5 was modified by substituting, on a molar basis, the TMXDI by a commercially available isomer mixture of 2,4- and 2,6- toluene diisocyanate (TDI). Attempts to achieve encapsulation in the manner as described in Example 1 failed. After the addition of hexamethylene diamine the viscosity of the resulting aqueous solution increased and a sticky pulp comprising the regular microcapsules as well as large amounts of polymer particles was obtained. The pulp could not be further processed and was discarded.

(20) TABLE-US-00005 TABLE 5 Amount [g/l] Pendimethalin 455 TMXDI 15.05 Cyclic Diisocyanate 1.67 Hexamethylene diamine 6.6 Lignosulfonate 15 Additive A 12 Additive B 15 Magnesium sulfate 120 Xanthan gum 0.45 Silicon defoamer 1 Biocide 2 Water Ad 1.0 l