Patent EA-003934-B1 (EA)
Title: Base-triggered release microcapsules
Inventor: VAN KOPPENHAGEN JUANITA
IPC: A01N25/28
Filed: 1999-07-28
Abstract: 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-X)tCH2N<][(A2-X)uCH2N<] .... [(An-X)yCH2N<] (IV) where "core" is derived from a multifunctional C1-C20 aliphatic or cycloaliphatic alcohol containing at least two functional groups capable of esterification; (A1-X)t, (A2-X) ... (An-X)y each constitute one or more randomly oligomerized esters of 2-hydroxy C2-C6 alkanoic acids and/or 2-thiol C2-C6 alkanoic acids, where X represents oxygen or sulfur; -CH2N< represents a trivalent nitrogen fragment of the amino formaldehyde prepolymer; and 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 alkanoic acids; t, u.. .y are independent values from 1-20. 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 wall containing an 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<]c (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; 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; 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 wall containing the ester moiety has the formula C[CH2OH)a(CH2O(COCHR-X)mCH2N<]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-l-propanol with a 2-(hydroxy or thiol) C2-C6 alkanoic acid. 7. A microcapsule according to claim 1 in which the ester moiety is derived from a cross-linking agent produced by the reaction of pentaerythritol or dipentaerythritol with the C2-C6 alkanoic acid. 8. A microcapsule according to Claim 7 in which the alkanoic acid is selected from glycolic acid, mercaptoacetic acid, lactic acid, thiolactic acid, and the cyclic dimer of lactic acid. 9. A microcapsule according to Claim 3 in which the wall containing 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 wall containing 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 wall containing 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 wall containing 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 ammo 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, pyrethroid insecticides, lambda-cyhalothrin, one or more insecticides effective as stomach poisons, one or more organophosphorus insecticides. 20. A microcapsule according to claim 19 in which the encapsulated ingredient comprises chlorpyrifos. 21. 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. 22. A microcapsule according to claim 1 in which the shell wall comprises from about 1 to about 70 percent by weight of the microcapsule. 23. A microcapsule according to claim 1 having an average diameter of from about 1 to about 100 microns. 24. An aqueous suspension of microcapsules wherein the microcapsules are as defined in claim 1. 25. An aqueous suspension of microcapsules according to claim 24 wherein the aqueous phase further comprises a phase transfer catalyst. 26. An aqueous suspension of microcapsules according to claim 24 in which a pesticide is contained in the microcapsules and in the aqueous phase. 27. An aqueous suspension of microcapsules according to claim 24 wherein the encapsulated ingredient comprises a pesticide and the aqueous phase contains a second pesticide. 28. An aqueous suspension of microcapsules according to claim 27 in which the encapsulated pesticide is substantially incompatible with the second pesticide. 29. A composition comprising a microcapsule according to claim 1 and a basic substance. 30. A composition according to claim 29 in which the basic substance is selected from alkaline and alkaline earth metal hydroxides, ammonium hydroxide, quaternary ammonium hydroxides, and amines. 31. A combination package comprising a first compartment containing microcapsules according to claim 1 and a second compartment comprising a basic substance. 32. A combination package according to claim 31 in which the first compartment contains an aqueous suspension of microcapsules. 33. A combination package according to claim 31 in which the basic substance is selected from alkali and alkaline earth metal hydroxides, ammonium hydroxide, quaternary ammonium hydroxides, and amines. 34. 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. 35. A method according to claim 34 in which the pest is selected from undesirable vegetation, insects, acarids, mites and rodents. 36. A method according to claim 34 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. 37. A method according to claim 34 in which the composition is a suspension which also comprises a basic substance selected from alkali and alkaline earth metal hydroxides, hydroxides of quaternary ammonium salts and amines. 38. A method according to claim 34 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. 39. A method according to claim 38 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. 40. 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-X)tH][(A2-X)uH] . . .[(An-X)yH] (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-X-, A2-X-,. .. An-X- each constitute one or more randomly oligomerized esters of 2-(hydroxy) C2-C6 alkanoic acids and/or 2 thiol C2-C6 alkanoic acids, where X is oxygen or sulfur which is as a part of XH terminal alcohol or sulfhydryl is capable of reacting with an ammo-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 o