Base-triggered release microcapsules

• US 6,544,540 B2
• Filed: 07/28/1999
• Issued: 04/08/2003
• Est. Priority Date: 07/29/1998
• Status: Expired due to Term

• Current Assignee: Syngenta Limited (China National Chemical Corporation)
• Original Assignee: Syngenta Limited (China National Chemical Corporation)
• Inventors: Lee, Kuo-Shin, Follows, Richard, Shirley, Ian Malcolm, Scher, Herbert Benson, Wade, Philip, Van Koppenhagen, Juanita Elena
• Primary Examiner(s): Levy, Neil S.
• Application Number:
  US09/363,324
• Publication Number:
  US 20020004059A1
• Time in Patent Office: 1,350 Days
• Field of Search: 424/405, 424/406, 424/408, 424/419, 424/497, 424/418, 424/489, 424/493, 424/DIG.8, 424/DIG.11, 525/923, 264/4.3, 264/4.7, 427/213.33, 428/402.21, 514/521, 514/531, 514/532
• US Class Current: 424/408
• CPC Class Codes: A01N 2300/00 Combinations or mixtures of active ingredients covered by classes A01N27/00 - A01N65/48 with other active or formulation relevant ingredients, e.g. specific carrier materials or surfactants, covered by classes A01N25/00 - A01N65/48
• CPC Class Codes: A01N 25/28 Microcapsules or nanocapsules
• CPC Class Codes: A01N 47/12 containing a —O—CO—N< group, or a thio analogue thereof, neither directly attached to a ring nor the nitrogen atom being a member of a heterocyclic ring
• CPC Class Codes: A01N 53/00 Biocides, pest repellants or attractants, or plant growth regulators containing cyclopropane carboxylic acids or derivatives thereof
• CPC Class Codes: A01N 57/16 containing heterocyclic radicals
• CPC Class Codes: Y10S 424/08 Systemic pesticides
• CPC Class Codes: Y10T 428/2985 Solid-walled microcapsule from synthetic polymer

Abstract

Microcapsules formed from an aminoplast shell wall and an encapsulated ingredient or ingredients enclosed within the wall in which the wall contains a base-cleavable ester moiety.

These capsules have been found to be sensitive to the presence of base such that in the presence of base, the capsule walls are relatively quickly disintegrated or degraded so as to produce a relatively quick release of the encapsulated materials.

Microcapsules of this invention are particularly suitable for use in controlling insects having an alkaline gut such as certain lepidoptera in that the capsule shell wall may be designed so as to quickly disintegrate under the alkaline conditions present in the gut of the insect thus providing a microcapsule which is safe to handle but which is selectively effective against certain undesirable insects while not harmful to beneficial insects or insects which do not feed on the capsule materials.

Claims

1. A microcapsule formed of an aminoplast shell wall and an encapsulated ingredient or ingredients enclosed within the wall, the wall having been produced by a microencapsulation process comprising reacting an etherified amino resin prepolymer with a cross-linking agent wherein said cross-linking agent is the ester or thioester reaction product of (a) a multifunctional alcohol selected from the group consisting of pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, glycerol, 3-mercaptopropane-diol, 1,2,4-butanetriol, 1,3,5-cyclohexanetriol, 1,2,3-heptanetriol and sorbitol, and (b) one or more 2-(hydroxy) and/or 2-(thiol) C₂-C₆ alkanoic acids, wherein the resulting ester and/or thioester groups are capable of being cleaved under basic conditions.

2. A method of controlling a pest comprising applying to the pest, to the locus of the pest, or to a location in which the pest may be present, a composition comprising a microcapsule according to claim 1 in which the encapsulated ingredient comprises a pesticide, said composition being applied in a pesticidally effective amount.

3. A microcapsule according to claim 1 in which the multifunctional alcohol is pentaerytbritol and the cross-linking agent has the formula

where R is —

H or C₁-C₄ alkyl groups which may alternate randomly;

X is oxygen or sulfur which may alternate randomly;

a≦

2; and

b, c, d, e are zero or a number from 1 to 4, where a+b+c+d+e=4; and

m, n, p, and q are independent values from 1 to 20 or

where R is —

H or C₁-C₄ alkyl groups which may alternate randomly;

X is oxygen or sulfur which may alternate randomly;

a, a′

≦

2 and b, b′

, c, c′

, d, and d′

are zero or a number from 1 to 3 where a+b+c+d+a′

+b′

+c′

+d′

=6; and

m, m′

, n, n′

, p, and p′

are independent values from 1 to 20.

4. A microcapsule according to claim 3 in which the cross-linking agent has the formula

and a is zero.

5. A microcapsule according to claim 4 in which R is hydrogen.

6. A method according to claim 2 in which the pest is selected from undesirable vegetation, insects, acarids, mites and rodents.

7. A method according to claim 2 in which the microcapsules are placed in a basic environment such that cause cleavage of the ester moiety occurs, resulting in breakdown of the capsule walls.

8. A microcapsule according to claim 3 in which the alkanoic acid is selected from glycolicacid, mercaptoacetic acid, lactic acid, thiolactic acid, and the cyclic dimer of lactic acid.

9. A microcapsule according to claim 3 in which the cross-linking agent has the formula (IIa) and is prepared by reaction of pentaerythritol with glycolic and mercaptoacetic acids in a molar ratio of 1:

2;

2 respectively.

10. A microcapsule according to claim 3 in which the cross-linking agent has the formula (IIa) and is prepared by reaction of pentaerythritol with mercaptoacetic acid in a molar ratio of 1:

4.

11. A microcapsule according to claim 3 in which the cross-linking agent has the formula (IIa) and is prepared by reaction of pentaerythritol with glycolic and mercaptoacetic acids in a molar ratio of 1:

1;

3 respectively.

12. A microcapsule according to claim 3 in which the cross-linking agent has the formula (IIb) and is prepared by reaction of dipentaerythritol with thiolactic acid in a molar ratio of 1:

6.

13. A microcapsule according to claim 1 in which the wall is produced by a microencapsulation process comprising in situ condensation of an amino resin prepolymer and in which the prepolymer is reacted with the cross-linking agent.

14. A microcapsule according to claim 13 in which the amino resin prepolymer is a urea-formaldehyde or a melamine-formaldehyde prepolymer.

15. A microcapsule according to claim 14 in which the prepolymer is an etherified urea-formaldehyde or melamine-formaldehyde prepolymer.

16. A microcapsule according to claim 1 which is stable under neutral or mildly acidic conditions.

17. A microcapsule according to claim 1 in which the encapsulated material comprises one or more agricultural chemicals.

18. A microcapsule according to claim 1 in which the encapsulated material comprises one or more agricultural or non-agricultural pesticides.

19. A microcapsule according to claim 18 in which the encapsulated material comprises one or more insecticides.

20. A microcapsule according to claim 19 in which the encapsulated material comprises one or more pyrethroid insecticides.

21. A microcapsule according to claim 19 in which the encapsulated material comprises lambda-cyhalothrin.

22. A microcapsule according to claim 19 in which the encapsulated material comprises one or more insecticides effective as stomach poisons.

23. A method according to claim 2 in which the composition also comprises a basic substance sufficient to cause cleavage of the ester moiety.

24. A method according to claim 2 comprising applying to a locus at which insects feed, a microcapsule according to claim 1 containing an insecticide which is a stomach poison, the cross-linking agent being selected so as to produce relatively rapid disintegration or degradation of the microcapsule wall when in contact with an alkaline environment in an insect'"'"'s gut.

25. A microcapsule according to claim 1 in which the ester moiety comprises from about 5 to about 80 percent by weight of the shell wall.

26. A microcapsule according to claim 1 in which the shell wall comprises from about 1 to about 70 percent by weight of the microcapsule.

27. A microcapsule according to claim 1 in which the shell wall comprises from about 5 to about 50 percent by weight of the microcapsule.

28. A microcapsule according to claim 1 having an average diameter of from about 1 to about 100 microns.

29. An aqueous suspension of microcapsules wherein the microcapsules are as defined in claim 1.

30. An aqueous suspension of microcapsules according to claim 29 wherein the aqueous phase further comprises a phase transfer catalyst.

31. An aqueous suspension of microcapsules according to claim 29 in which a pesticide is contained in the microcapsules and/or in the aqueous phase.

32. An aqueous suspension of microcapsules according to claim 29 wherein the encapsulated ingredient comprises a pesticide and the aqueous phase contains a second pesticide.

33. An aqueous suspension of microcapsules according to claim 32 in which the encapsulated pesticide is substantially incompatible with the second pesticide.

34. A composition comprising a microcapsule according to claim 1 and a basic substance.

35. A composition according to claim 34 in which the basic substance is selected from alkali and alkaline earth metal hydroxides, ammonium hydroxide, quaternary ammonium hydroxides, and amines.

36. A method according to claim 24 in which the hydrolyzable ester moiety is selected so as to produce disintegration or degradation of the microcapsule wall within approximately four hours or less.