BASE-TRIGGERED RELEASE MICROCAPSULES

• US 20020004059A1
• Filed: 07/28/1999
• Published: 01/10/2002
• Est. Priority Date: 07/29/1998
• Status: Active Grant

• Current Assignee: Zeneca Incorporated (Astrazeneca PLC)
• Original Assignee: Syngenta Limited (China National Chemical Corporation)
• Inventors: SHIRLEY, IAN MALCOLM, WADE, PHILIP, FOLLOWS, RICHARD, LEE, KUO-SHIN, VAN KOPPENHAGEN, JUANITA ELENA, SCHER, HERBERT BENSEN
• Granted Patent: US 6,544,540 B2
• Time in Patent Office: Days
• 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 containing an ester moiety having the formula:

core(A₁—

XCH₂N<

)_t(A₂—

XCH₂N<

)_u . . . (A_n—

XCH₂N<

)_y+B R₁OH 

 

(IV)

where R₁=H, or C₁-C₄ alkyl;

“

core”

is derived from a multifunctional C₁-C₂₀ aliphatic or cycloaliphatic alcohol containing at least two functional groups capable of esterification;

A₁—

XH, A₂—

XH, . . . A_n—

XH each constitute one or more randomly oligomerized esters of 2-hydroxy C₂-C₆ substituted alkanoic acids and/or 2-thiol C₂-C₆ substituted alkanoic acids, where XH represents the terminal alcohol or sulfhydryl capable of reacting with an etherified amino formaldehyde prepolymer;

n is the number of functional groups on the core capable of reacting with derivatives of the 2-hydroxy and/or 2-thiol C₂-C₆ substituted alkanoic acids;

2 ≦

B≦

t+u+ . . . y; and

t+u+ . . . y≦

n.

2. A microcapsule according to claim 1 in which the alcohol has at least three functional groups capable of esterification.

3. A microcapsule according to claim 1 in which the ester moiety has the formula

C[CH₂OH]_a[CH₂O(COCHR— X)_m—

CH₂N<

]_b[CH₂O(COCHR—

X)_n—

CH₂N<

]_c[CH₂O(COCHR—

X)_p—

CH₂N<

]_d[CH₂O(COCHR—

X)_q—

CH₂N<

]_e 

 

(V)

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;

2 ≦

B≦

b+c+d+e; and

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

or

[>

NCH₂—

(X—

CHR—

CO)_p, OCH₂]_d[>

NCH₂—

(X—

CHR—

CO)_n, OCH₂]_c, [>

NCH₂—

(X—

CHR—

CO)_m, OCH₂]_b, [HOCH₂]_a, C—

CH₂OCH₂C[CH₂OH]_a[CH₂O (COCHR—

X)_m—

CH₂N<

]_b[CH₂O(COCHR—

X)_n—

CH₂N<

]_c [CH₂O(COCHR—

X)_p—

CH₂N<

]_d 

 

(VI)

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;

2 <

B<

b+b′

+c +c′

+d+d′

; 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 ester moiety has the formula

C[CH₂OH]_a[CH₂O(COCHR—

X)_m—

CH₂N<

]_b[CH₂O(COCHR—

X)_n—

CH₂N<

]_c[CH₂O(COCHR—

X)_p—

CH₂N<

]_d[CH₂O(COCHR—

X)_q—

CH₂N<

]_e 

 

(V)

 

and a is zero.

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

6. A microcapsule according to claim 1 in which the hydrolyzable ester moiety is derived from a cross-linking agent produced by the reaction of pentaerythritol, dipentaerythritol, trimethylolpropane, glycerol, mercaptoethanol, 1, 2, 4-butanetriol, 1, 3, 5-cyclohexanetriol, 1, 2, 3-heptanetriol, sorbitol, or 2,3-dimercapto-1-propanol with a 2-(hydroxy or thiol)-substituted C₂-C₆ alkanoic acid.

7. A microcapsule according to claim 11 in which the ester moiety is derived from a cross-linking agent produced by the reaction of pentaerythritol or dipentaerythritol with the alkanoic acid.

8. A microcapsule according to claim 3 in which the alkanoic acid is selected from glycolic aid, mercaptoacetic acid, lactic acid, 2-mercaptopropionic acid, thiolactic acid, and the cyclic dimer of lactic acid.

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

6.

13. A microcapsule according to claim 6 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 microcapsule according to claim 19 in which the encapsulated material comprises one or more organophosphorus insecticides.

24. A microcapsule according to claim 23 in which the encapsulated ingredient comprises chlorpyrifos.

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 nucrocapsule 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 combination package comprising a first compartment containing microcapsules according to claim 1 and a second compartment comprising a basic substance.

37. A combination package according to claim 36 in which the first compartment contains an aqueous suspension of microcapsules.

38. A combination package according to claim 36 in which the basic substance is selected from alkali and alkaline earth metal hydroxides, ammonium hydroxide, quaternary ammonium hydroxides, and amines.

39. 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.

40. A method according to claim 39 in which the pest is selected from undesirable vegetation, insects, acarids, mites and rodents.

41. A method according to claim 39 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.

42. A method according to claim 39 in which the composition also comprises a basic substance sufficient to cause cleavage of the ester moiety.

43. A method according to claim 39 comprising applying to a locus at which insects feed, a microcapsule according to claim 1 containing an insecticide which is a stomach poison, the ester moiety 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.

44. A method according to claim 43 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.

45. A process for the production of microcapsules formed of an aminoplast shell wall and containing an encapsulated ingredient or ingredients comprising incorporating into the shell wall an ester moiety having the formula

core(A₁—

XH)_t(A₂—

XH)_u . . . (A_n—

XH)_y 

 

(I)

where “

core”

represents a structure derived from a multifunctional C₁-C₂₀ aliphatic or cycloaliphatic alcohol containing at least two functional groups capable of esterification;

A₁—

XH, A₂—

XH, . . . A_n—

XH each constitute one or more randomly oligomerized esters of 2-(hydroxy or thiol) substituted C₂-C₆ alkanoic acids and/or 2-thiol C₂-C₆ substituted alkanoic acids, where XH represents the terminal alcohol or sulfhydryl capable of reacting with an amino-formaldehyde prepolymer;

n is the number of functional groups on the core capable of reacting with derivatives of the 2-hydroxy and/or 2-thiol C₂-C₆ substituted alkanoic acids; and

t+u+ . . . y≦

n.

46. A process for the production of microcapsules according to claim 45 in which the hydrolyzable ester moiety has the formula

C[CH₂OH]_a[CH₂O(COCHR— X)_m—

H]_b[CH₂O(COCHR—

X)_n—

H]_c[CH₂O(COCHR—

X)_p—

H]_d[CH₂O(COCHR—

X)_q—

H]_e 

 

(II)

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 1to 4, where a+b+c+d+e=4; and

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

or

When dipentaerythritol is the reactant the cross-linking agents have the formula

[H—

(X—

CHR—

CO)_p,OCH₂]_d,[H—

(X—

CHR—

CO)_n,OCH₂]_c,[H—

(X—

CHR—

CO)_m,OCH₂]_b,[HOCH₂]_aC—

CH₂OCH₂C[CH₂OH]_a[CH₂O (COCHR—

X)_m—

H]_b[CH₂O(COCHR—

X)_n—

H]_c[CH₂O(COCHR—

X)_p—

H]_d 

 

(III)

where R is —

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

X is oxygen or sulfur which may alternate;

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.

47. A process according to claim 45 in which the aminoplast shell wall is formed from an etherified amino resin prepolymer.

48. A process according to claim 46 in which the amino resin prepolymer is a urea-formaldehyde or melamine-formaldehyde prepolymer.

49. A process according to claim 46 in which the amino resin prepolymer is a urea-formaldehyde prepolymer.

51. A process according to claim 45 wherein the material to be encapsulated comprises one or more agricultural or non-agricultural pesticides.

50. A process for producing a microcapsule having an aminoplast shell wall comprising (i) reacting an etherified amino resin prepolymer with a cross-linking agent having the formula

core(A₁—

XH)_t(A₂—

XH)_u . . . (A_n—

XH)_y 

 

(I)

where “

core”

represents a structure derived from a multifunctional C₁-C₂₀ aliphatic or cycloaliphatic alcohol containing at least two functional groups capable of esterification;

A₁—

XH, A₂—

XH, . . . A_n—

XH each constitute one or more randomly oligomerized esters of 2-(hydroxy or thiol) substituted C₂-C₆ alkanoic acids and/or 2-thiol C₂-C₆ substituted alkanoic acids, where XH represents the terminal alcohol or sulfhydryl capable of reacting with an amino-formaldehyde prepolymer;

n is the number of functional groups on the core capable of reacting with derivatives of the 2-hydroxy and/or 2-thiol C₂-C₆ substituted alkanoic acids; and

t+u+ . . . y≦

n. (ii) providing an organic phase comprising the product of step (i) and a material or materials to be encapsulated;

(iii) creating an emulsion of the organic phase in a continuous phase aqueous solution comprising water and a surface agent, wherein the emulsion comprises discrete droplets of the organic phase dispersed in the continuous phase aqueous solution, there being formed thereby an interface between the discrete droplets of organic solution and the surrounding continuous phase aqueous solution; and

(iv) causing in situ condensation and curing of the amino resin prepolymer and the organic phase of the discreet droplets adjacent to the interface by simultaneously heating the emulsion to a temperature between about 20°

C. to about 100°

C. and adding to the emulsion an acidifying agent and maintaining the emulsion at a pH of between about 0 to about 4 for a sufficient period of time to allow substantial completion of in situ condensation of the amino resin prepolymer to convert the liquid droplets of the organic phase to capsules consisting of solid permeable polymer shells enclosing the material to be encapsulated.