Patent EA-003359-B1 (EA)
Title: Acid-triggered release microcapsules
Inventor: VAN KOPPENHAGEN JUANITA
IPC: A01N25/28
Filed: 1999-07-28
Abstract: 1. A microcapsule formed of a polyurea shell wall and an encapsulated ingredient or ingredients enclosed within the shell wall, the wall comprising at least one oligomeric acetal moiety. 2. A microcapsule according to claim 1 in which the oligomeric acetal moiety is hydrolyzed under exposure to acidic conditions. 3. A microcapsule according to claim 1 in which the oligomeric acetal moiety has the formula in which R is (a) a moiety containing a chain of from 5 to about 40 optionally substituted carbon atoms, (b) a moiety containing a chain of from 4 to about 40 carbon atoms and one or more internally linked oxygen or sulfur atoms or -NH-groups, or (c) an optionally substituted ethylene or propylene moiety; Z is (a) an optionally substituted phenyl group; (b) an optionally substituted C1-C20 alkyl, C2-C20 alkenyl, C3-C8 cycloalkyl or C5-C8 cycloalkenyl group; or benzoyl; and n is 1 if R is (a) or (b), or is 2-20 if R is (c). 4. A microcapsule according to claim 2 or 3, which is stable under basic conditions. 5. A microcapsule according to claim 3 in which R is a C5-C40 alkyl or a group having the formula -CH2-R2-CH2 in which R2 is an optionally substituted phenyl or C5-C15 cycloalkyl or cycloalkenyl ring and the methylene groups are situated no closer than the 1, 3 positions on the ring. 6. A microcapsule according to claim 3 in which the oligomeric acetal moiety has the formula in which R1 is an aliphatic or aromatic moiety received from diisocyanate with formula OCN-1-NCO , R, Z and n have values, indicated in claim 3. 7. A microcapsule according to claim 3 or 6 in which R is an optionally substituted alkyl group having from 5 to about 40 carbon atoms and n is 1. 8. A microcapsule according to claim 3 or 6 in which R is ethylene or propylene and n is a value of from 2 to about 20. 9. A microcapsule according to claim 3 or 6 in which Z is an optionally substituted phenyl group. 10. A microcapsule according to claim 3 or 6 in which R is a group having the formula -CH2-R2-CH2-, wherein R2 is optionally substituted phenyl or C5-C15 cycloalkyl or cycloalkenyl in which the methylene groups are substituted at least three carbons apart on the ring. 11. A microcapsule according to claim 10 in which R2 is an optionally substituted phenyl or C5-C15 cycloalkyl or cycloalkenyl ring. 12. A microcapsule according to claim 3 or 6 in which Z is unsubstituted phenyl. 13. A microcapsule according to claim 1 in which the encapsulated ingredient is an agricultural chemical. 14. A microcapsule according to claim 13 in which the agricultural chemical is a pesticide. 15. A microcapsule according to claim 1 in which the shell wall further comprises a moiety which generates acid when exposed to light. 16. An aqueous suspension of microcapsules wherein the microcapsules are as defined in claims 3 or 6. 17. An aqueous suspension of microcapsules according to claim 16 in which the encapsulated ingredient comprises a first pesticide and the aqueous phase contains a second pesticide. 18. An aqueous suspension according to claim 17 in which the encapsulated pesticide is substantially incompatible with the second pesticide. 19. An aqueous suspension of microcapsules according to claim 16 in which a pesticide is contained in the microcapsules and/or the aqueous phase. 20. An aqueous suspension of microcapsules according to claim 19 further containing an agriculturally effective amount of a humectant. 21. A composition comprising a microcapsule according to claim 3 or 6 and an acidic substance. 22. A composition according to claim 21 in which the acidic substance is selected from organic and inorganic acids. 23. A combination package comprising a first compartment containing microcapsules according to claims 3 or 6 and a second compartment comprising an acidic substance. 24. A combination package according to claim 23 in which the first compartment contains an aqueous suspension of microcapsules. 25. A combination package according to claim 23 in which the acidic substance is selected from organic and inorganic acids. 26. A combination package according to claim 24 in which the microcapsules contain a first active substance and the aqueous phase contains a second active substance. 27. A combination package according to claim 26 in which the first and second active substances are substantially chemically incompatible. 28. A combination package according to claim 27in which the microcapsules and the aqueous phase both contain substantially the same active ingredient. 29. A method of controlling a pest comprising applying to the pest, to the locus of the pest, or to a location at which the pest may be present, a composition comprising a microcapsule according to claim 3 or 7 in which the encapsulated ingredient comprises a pesticide, said composition being applied in a pesticidally effective amount. 30. A method according to claim 29 in which the pest is selected from undesirable vegetation. 31. A method according to claim 29 in which the composition also comprises an acidic substance sufficient to cause hydrolysis of the oligomeric acetal. 32. A process for the production of microcapsules formed of a polyurea shell wall and containing an encapsulated ingredient or ingredients comprising incorporating into the shell wall an oligomeric acetal having the moiety in which R is (a) a moiety containing a chain of from 5 to about 40 optionally substituted carbon atoms, (b) a moiety containing a chain of from 4 to about 40 carbon atoms and one or more internally linked oxygen or sulfur atoms or -NH-groups, or (c) an optionally substituted ethylene or propylene moiety; Z is (a) an optionally substituted phenyl group, (b) an optionally substituted C1-C20 alkyl, C2-C20 alkenyl, C3-C8 cycloalkyl or C5-C8 cycloalkenyl group; or (c) benzoyl: and n is 1, if R is (a) or (b), or is 2-20 if R is (c). 33. 4 process according to claim 32 in which the polyurea shell wall is formed from starting materials including one or more diisocyanates having the formula OCNR1-NCO in which R1 is an aromatic or aliphatic moiety formed by reaction of a diisocyanate having the formula OCN-R1-NCO. 34. A process according to claim 32 in which the polyurea shell wall is formed by reaction of a diisocyanate having the formula OCN-R1-NCO in which R1 is an aliphatic or aromatic moiety with a difunctional amine. 35. A process according to claim 39 in which the microcapsule shell wall contains the moiety in which R1 is an aliphatic or aromatic moiety formed by reaction of a diisocyanate having the formula OCN-R1-NCO, R, Z, and n have values indicated in claim 32. 36. A process according to claim 33 or 34 in which an aromatic polyisocyanate having three or more isocyanate groups is also utilized in forming the polyurea shell wall. 37. A process for preparing a microcapsule formed of a polyurea shell wall and an encapsulated ingredient or ingredients enclosed within the wall, the wall comprising an oligomeric acetal having the moiety in which R is (a) a moiety containing a chain of from 5 to about 40 optionally substituted carbon atoms, (b) a moiety containing a chain of from 4 to about 40 carbon atoms and one or more internally linked oxygen or sulfur atoms or -NH-groups, or (c) an optionally substituted ethylene or propylene moiety; Z is (a) an optionally substituted phenyl group, (b) an optionally substituted C1-C20 alkyl, C2-C20 alkenyl, C3-C8 cycloalkyl or cycloalkenyl group; or (c) phenylglyoxal; and n is 1 if R is (a) or (b), or is 2-20 if R is (c) comprising the steps of (a) reacting an oligomeric acetal having the formula with a diisocyanate having the formula OCN-R1-NCO in which R, is an aliphatic or aromatic moiety to produce a pre-polymer having up to 10 acetal-containing units having the general formula (b) preparing an organic liquid which is immiscible with water comprising the pre-polymer of step (a) and an ingredient or ingredients to be encapsulated and an aqueous phase comprising water, a protective colloid and optionally a surfactant capable of maintaining the organic liquid as droplets in the water; (c) mixing the suspension of organic liquid in the aqueous phase under hi-shear to form an oil-in-water emulsion; and (d) adjusting as necessary the temperature and/or pH of the oil in-water emulsion such that a polymerization reaction takes place at the organic liquid/water interface to form the microcapsules. 38. A process according to claim 37 in which the organic liquid additionally contains an aromatic polyisocyanate having three or more isocyanate groups. 39. A process according to claim 37 in which the mole ratio of oligomeric acetal to organic diisocyanate in step (a) is from about 1:2 to about 1:20. 40. A process according to claim 39 in which the mole ratio of oligomeric acetal to organic diisocyanate in step (a) is from about 1:3 to about 1:5.