Microcapsules with readily adjustable release rates

• US 5,925,595 A
• Filed: 09/05/1997
• Issued: 07/20/1999
• Est. Priority Date: 09/05/1997
• Status: Expired due to Term

• Current Assignee: Monsanto Technology LLC (Bayer AG)
• Original Assignee: Monsanto Company (Bayer AG)
• Inventors: Seitz, Michael E., Travers, Jeff N., Brinker, Ronald J.
• Primary Examiner(s): CLARDY, S
• Application Number:
  US08/924,671
• Time in Patent Office: 683 Days
• Field of Search: 504/116, 504/342, 424/405, 514/963
• US Class Current: 504/359
• 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 37/26 containing the group; Thio analogues thereof
• CPC Class Codes: C08G 18/0866 the dispersing or dispersed phase being an aqueous medium
• CPC Class Codes: C08G 18/3228 acyclic
• CPC Class Codes: C08G 18/765 alpha, alpha, alpha', alpha', -tetraalkylxylylene diisocyanate or homologues substituted on the aromatic ring
• CPC Class Codes: C08G 18/7831 containing biuret groups

Abstract

A process for the preparation of a microencapsulated composition comprises: (a) combining (i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula O═C═N--(CH₂)_n --N═C═O, where n is from about 4-18, (ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, most preferably from about 8-18 carbon atoms, and (iii) a water-immiscible composition comprising a core chemical; (b) adding an aqueous liquid and forming an oil-in-water emulsion; (c) adding a polyamine to the emulsion; and (d) reacting the triisocyanate, the diisocyanate, and the polyamine, thereby producing a plurality of microcapsules having a capsule wall, with at least a major portion of the core chemical encapsulated within the capsule wall of the microcapsules. Suitable core chemicals include agricultural chemicals such as herbicides and safeners. By adjusting the composition of the capsule walls and the contents of the capsule core, the rate of release of the core materials from the microcapsules can be adjusted. When the core contains two or more materials to be released, the microcapsules can provide a more rapid rate of release for one core material than for another.

Claims

1. A process for the preparation of a microencapsulated composition, comprising:

(a) combining (i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from about 4-18, (ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and (iii) a water-immiscible composition comprising a core chemical;

(b) adding an aqueous liquid and forming an oil-in-water emulsion;

(c) adding a polyamine to the emulsion; and

(d) reacting the triisocyanate, the diisocyanate, and the polyamine, thereby producing a plurality of microcapsules having a capsule wall, with at least a major portion of the core chemical encapsulated within the capsule wall of the microcapsules.

2. The process of claim 1, where the core chemical comprises a herbicide.

3. The process of claim 2, where the herbicide is an acetanilide.

4. The process of claim 2, where the herbicide is selected from the group consisting of alachlor, acetochlor, and butachlor.

5. The process of claim 1, where the core chemical comprises a first agricultural chemical, and where the water-immiscible composition further comprises and a second agricultural chemical.

6. The process of claim 5, where the first agricultural chemical is a herbicide and the second agricultural chemical is a safener.

7. The process of claim 1, where the triisocyanate has the formula ##STR5## where R₁, R₂, and R₃ are independently alkyl groups having from 1-18 carbon atoms;

and

where X is a coupling agent selected from the group consisting of tertiary carbon, polycarbodiimide, polyurethane derived from an aliphatic alcohol or polyol, or combinations thereof.

8. The process of claim 1, where the triisocyanate is selected from the group consisting of ##STR6## where R is --(CH₂)_n --, and where n is from about 4-18.

9. The process of claim 1, where the diisocyanate has from about 8-18 carbon atoms.

10. The process of claim 1, where the diisocyanate has the formula

11. The process of claim 1, where the diisocyanate is selected from the group consisting of meta-tetramethylxylylene diisocyanate, 4,4'"'"'-diisocyanato-dicyclohexyl methane, and isophorone diisocyanate.

12. The process of claim 1, where the polyamine is selected from the group consisting of diethylene triamine, triethylene tetraamine, iminobispropylamine, bis(hexamethylene)triamine, polyoxypropylenetriamines, amine epoxy adducts, and alkyl diamines in which the alkyl group has from about 2-6 carbon atoms.

13. The process of claim 1, where the ratio of triisocyanate to diisocyanate is selected to provide a desired release rate from the microcapsules.

14. The process of claim 1, where the reaction of step (d) is performed by heating the mixture until the isocyanate infrared absorption peak at 2270 cm^-1 substantially disappears.

15. The process of claim 1, where the reaction of step (d) is performed by heating the mixture at between about 40-60°

C. for between about 0.5-3 hours.

16. The process of claim 1, where the ratio of the triisocyanate to the diisocyanate, on an isocyanate equivalent basis, is between about 90:

10 and about 30;

70.

17. The process of claim 1, further comprising adding to the core chemical in step (a) a hydrophobic diluent.

18. The process of claim 16, where the hydrophobic diluent is selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.

19. A process for the preparation of a microencapsulated herbicidal composition, comprising:

(a) combining (i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from 4-18, (ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and (iii) a water-immiscible composition comprising a herbicide;

(b) dispersing the mixture from step (a) in an aqueous liquid that contains a colloid, forming an oil-in-water emulsion;

(c) adding a polyamine to the emulsion; and

(d) heating the mixture from step (c) at a temperature above about 40°

C., thereby producing a plurality of microcapsules having a capsule wall, with at least a major portion of the agricultural chemical encapsulated within the capsule wall of the microcapsules.

20. The process of claim 19, where the herbicide is an acetanilide.

21. The process of claim 19, where the herbicide is selected from the group consisting of alachlor, acetochlor, and butachlor.

22. The process of claim 19, where the water-immiscible composition further comprises a safener.

23. The process of claim 19, where the triisocyanate has the formula ##STR7## where R₁, R₂, and R₃ are independently alkyl groups having from i-18 carbon atoms;

and

where X is a coupling agent selected from the group consisting of tertiary carbon, polycarbodiimide, polyurethane derived from an aliphatic alcohol or polyol, or combinations thereof.

24. The process of claim 19, where the triisocyanate is selected from the group consisting of ##STR8## where R is --(CH₂)_n --, and where n is from about 4-18.

25. The process of claim 19, where the diisocyanate has from about 8-18 carbon atoms.

26. The process of claim 19, where the diisocyanate has the formula

27. The process of claim 19, where the diisocyanate is selected from the group consisting of meta-tetramethylxylylene diisocyanate, 4,4'"'"'-diisocyanato-dicyclohexyl methane, and isophorone diisocyanate.

28. The process of claim 19, where the polyamine is selected from the group consisting of diethylene triamine, triethylene tetraamine, iminobispropylamine, bis(hexamethylene)triamine, polyoxypropylenetriamines, amine epoxy adducts, and alkyl diamines in which the alkyl group has from about 2-6 carbon atoms.

29. The process of claim 19, where the ratio of triisocyanate to diisocyanate is selected to provide a desired release rate from the microcapsules.

30. The process of claim 19, where the mixture is heated in step (d) until the isocyanate infrared absorption peak at 2270 cm^-1 substantially disappears.

31. The process of claim 19, where the mixture is heated in step (d) at between about 40-60°

C. for between about 0.5-3 hours.

32. The process of claim 19, where the colloid is selected from the group consisting of gelatin, casein, polyvinyl alcohol, alkylated polyvinyl pyrrolidone polymers, maleic anhydride-methyl vinyl ether copolymers, styrene-maleic anhydride copolymers, maleic acid-butadiene copolymers, maleic anhydride-diisobutylene copolymers, sodium and calcium lignosulfates, sulfonated naphthalene-formaldehyde condensates, modified starches, and modified cellulose.

33. The process of claim 19, where the ratio of the triisocyanate to the diisocyanate, on a cyanate equivalent basis, is between about 90:

10 and about 30;

70.

34. The process of claim 19, further comprising adding to the agricultural chemical in step (a) a hydrophobic diluent.

35. The process of claim 34, where the hydrophobic diluent is selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.

36. A selective-release microencapsulated composition, comprising a plurality of microcapsules, the microcapsules comprising:

(a) a capsule wall that comprises the polymerization product of;

(i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from 4-18,

(ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and

(iii) a polyamine; and

(b) an internal phase encapsulated within the capsule wall that comprises a first core chemical and a second core chemical, where the first core chemical has a different rate of release from the microcapsules than the second core chemical.

37. The composition of claim 36, where the internal phase further comprises a hydrophobic diluent.

38. The composition of claim 37, where the hydrophobic diluent is selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.

39. The composition of claim 36, where the first core chemical is a herbicide and the second core chemical is a safener.

40. The composition of claim 36, where the first core chemical is an acetanilide herbicide and the second core chemical is a safener.

41. The composition of claim 40, where the safener is furilazole.

42. The composition of claim 36, where the triisocyanate has the formula ##STR9## where R₁, R₂, and R₃ are independently alkyl groups having from 1-18 carbon atoms;

and

where X is a coupling agent selected from the group consisting of tertiary carbon, polycarbodiimide, polyurethane derived from an aliphatic alcohol or polyol, or combinations thereof.

43. The composition of claim 36, where the triisocyanate is selected from the group consisting of ##STR10## where R is --(CH₂)_n --, and where n is from about 4-18.

44. The composition of claim 36 where the diisocyanate has the formula

45. The composition of claim 36, where the diisocyanate is selected from the group consisting of meta-tetramethylxylylene diisocyanate, 4,4'"'"'-diisocyanato-dicyclohexyl methane, and isophorone diisocyanate.

46. The composition of claim 36, where the polyamine is selected from the group consisting of diethylene triamine, triethylene tetraamine, iminobispropylamine, bis(hexamethylene)triamine, polyoxypropylenetriamines, amine epoxy adducts, and alkyl diamines in which the alkyl group has from about 2-6 carbon atoms.

47. The composition of claim 36, where the triisocyanate and the diisocyanate are used in a ratio that is selected to provide a desired release rate from the microcapsules.

48. The composition of claim 36, where the ratio of the triisocyanate to the diisocyanate, on a cyanate equivalent basis, is between about 90:

10 and about 30;

70.

49. A microencapsulated herbicide composition, comprising an aqueous dispersion of microcapsules, the microcapsules comprising:

(a) a capsule wall that comprises the polymerization product of;

(i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from 4-18,

(ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and

(iii) a polyamine; and

(b) an internal phase that comprises a herbicide and is encapsulated within the capsule wall.

50. The composition of claim 49, where the herbicide is an acetanilide.

51. The composition of claim 49, where the herbicide is selected from the group consisting of alachlor, acetochlor, and butachlor.

52. The composition of claim 49, where the internal phase further comprises a safener.

53. The composition of claim 49, where the safener is more soluble in the capsule wall than the herbicide.

54. The composition of claim 49, where the safener has a smaller molecular size than the herbicide.

55. The composition of claim 49, where the triisocyanate has the formula ##STR11## where R₁, R₂, and R₃ are independently alkyl groups having from 1-18 carbon atoms;

and

where X is a coupling agent selected from the group consisting of tertiary carbon, polycarbodiimide, polyurethane derived from an aliphatic alcohol or polyol, or combinations thereof.

56. The composition of claim 49, where the triisocyanate is selected from the group consisting of ##STR12## where R is --(CH₂)_n --, and where n is from about 4-18.

57. The composition of claim 49, where the diisocyanate has from about 8-18 carbon atoms.

58. The composition of claim 49, where the diisocyanate has the formula

59. The composition of claim 49, where the diisocyanate is selected from the group consisting of meta-tetramethylxylylene diisocyanate, 4,4'"'"'-diisocyanato-dicyclohexyl methane, and isophorone diisocyanate.

60. The composition of claim 49, where the polyamine is selected from the group consisting of diethylene triamine, triethylene tetraamine, iminobispropylamine, and bis(hexamethylene)triamine, polyoxypropylenetriamines, amine epoxy adducts, and alkyl diamines in which the alkyl group has from about 2-6 carbon atoms.

61. The composition of claim 49, where the ratio of triisocyanate to diisocyanate is selected to provide a desired release rate from the microcapsules.

62. The composition of claim 49, where the composition is a liquid concentrate that is suitable for spraying onto plants, soil, or a growth medium after dilution with water.

63. The composition of claim 49, where the composition is a spray solution that is suitable for spraying onto plants, soil, or growth medium without further dilution with water.

64. The composition of claim 49, where the ratio of the triisocyanate to the diisocyanate, on a cyanate equivalent basis, is between about 90:

10 and about 30;

70.

65. The composition of claim 49, where the internal phase further comprises a hydrophobic diluent.

66. The composition of claim 49, where the hydrophobic diluent is selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.

67. A microencapsulated herbicide composition, comprising a plurality of microcapsules, the microcapsules comprising:

(a) a capsule wall that comprises the polymerization product of;

(i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from 4-18,

(ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and

(iii) a polyamine; and

(b) an internal phase that comprises

(i) a herbicide selected from the group consisting of alachlor, acetochlor, and butachlor;

(ii) furilazole in an amount effective to protect desirable crops from herbicidal effects of the herbicide; and

(iii) a hydrophobic diluent selected from selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.

68. A herbicidal method, comprising applying to a plant, soil, or a growth medium a herbicidally effective amount of a composition that comprises an aqueous dispersion of microcapsules, the microcapsules comprising:

(a) a capsule wall that comprises the polymerization product of;

(i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from 4-18,

(ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and

(iii) a polyamine

(b) an internal phase that comprises a herbicide and is encapsulated within the capsule wall.

69. The method of claim 68, where the herbicide is an acetanilide.

70. The method of claim 68, where the herbicide is selected from the group consisting of alachlor, acetochlor, and butachlor.

71. The method of claim 68, where the internal phase further comprises a safener.

72. The method of claim 68, where the safener is more soluble in the capsule wall than the herbicide.

73. The method of claim 68, where the safener has a smaller molecular size than the herbicide.

74. The method of claim 68, where the triisocyanate has the formula ##STR13## where R₁, R₂, and R₃ are independently alkyl groups having from 1-18 carbon atoms;

and

where X is a coupling agent selected from the group consisting of tertiary carbon, polycarbodiimide, polyurethane derived from an aliphatic alcohol or polyol, or combinations thereof.

75. The method of claim 68, where the triisocyanate is selected from the group consisting of ##STR14## where R is --(CH₂)_n --, and where n is from about 4-18.

76. The method of claim 68, where the diisocyanate has from about 8-18 carbon atoms.

77. The method of claim 68, where the diisocyanate has the formula

78. The method of claim 68, where the diisocyanate is selected from the group consisting of meta-tetramethylxylylene diisocyanate, 4,4'"'"'-diisocyanato-dicyclohexyl methane, and isophorone diisocyanate.

79. The method of claim 68, where the polyamine is selected from the group II consisting of diethylene triamine, triethylene tetraamine, iminobispropylamine, and bis(hexamethylene)triamine, polyoxypropylenetriamines, amine epoxy adducts, and alkyl diamines in which the alkyl group has from about 2-6 carbon atoms.

80. The method of claim 68, where the ratio of triisocyanate to diisocyanate is selected to provide a desired release rate from the microcapsules.

81. The method of claim 68, where the ratio of the triisocyanate to the diisocyanate, on a cyanate equivalent basis, is between about 90:

10 and about 30;

70.

82. The method of claim 68, where the internal phase further comprises a hydrophobic diluent.

83. The method of claim 82, where the hydrophobic diluent is selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.

84. A herbicidal method, comprising applying to a plant, soil, or a growth medium a herbicidally effective amount of a composition that comprises an aqueous dispersion of microcapsules, the microcapsules comprising:

(a) a capsule wall that comprises the polymerization product of;

(i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from 4-18,

(ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and

(iii) a polyamine; and

(b) an internal phase that comprises

(i) a herbicide selected from the group consisting of alachlor, acetochlor, and butachlor;

(ii) furilazole in an amount effective to protect desirable crops from herbicidal effects of the herbicide; and

(iii) a hydrophobic diluent selected from selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.

85. A method of controlling weeds in a field containing both weeds and crops, comprising applying to a field an amount effective to provide herbicidal control of the weeds in that field of a plurality of microcapsules, the microcapsules comprising:

(a) a capsule wall that comprises the polymerization product of;

(i) a triisocyanate that is an adduct of linear aliphatic isocyanates having the formula

space="preserve" listing-type="equation">O═

C═

N--(CH.sub.2).sub.n --N═

C═

O

where n is from 4-18,

(ii) an aliphatic diisocyanate that contains a cycloaliphatic or aromatic ring moiety, the aliphatic diisocyanate having from about 6-32 carbon atoms, and

(iii) a polyamine

(b) an internal phase that is encapsulated within the capsule wall and that comprises;

(i) a herbicide, and

(ii) a chemical antidote for the herbicide, in an amount effect to protect the crops from the herbicidal effects of the herbicide, where the chemical antidote is released initially from the microcapsules at a greater rate than the herbicide.

86. The method of claim 85, where the herbicide is an acetanilide.

87. The method of claim 85, where the herbicide is selected from the group consisting of alachlor, acetochlor, and butachlor.

88. The method of claim 85, where the chemical antidote is more soluble in the capsule wall than the herbicide.

89. The method of claim 85, where the chemical antidote has a smaller molecular size than the herbicide.

90. The method of claim 85, where the triisocyanate has the formula ##STR15## where R₁, R₂, and R₃ are independently alkyl groups having from 1-18 carbon atoms;

and

where X is a coupling agent selected from the group consisting of tertiary carbon, polycarbodiimide, polyurethane derived from an aliphatic alcohol or polyol, or combinations thereof.

91. The method of claim 85, where the triisocyanate is selected from the group consisting of ##STR16## where R is --(CH₂)_n --, and where n is from about 4-18.

92. The method of claim 85, where the diisocyanate has from about 8-18 carbon atoms.

93. The method of claim 85, where the diisocyanate has the formula

94. The method of claim 85, where the diisocyanate is selected from the group consisting of meta-tetramethylxylylene diisocyanate, 4,4'"'"'-diisocyanato-dicyclohexyl methane, and isophorone diisocyanate.

95. The method of claim 85, where the polyamine is selected from the group consisting of diethylene triamine, triethylene tetraamine, iminobispropylamine, and bis(hexamethylene)triamine, polyoxypropylenetriamines, amine epoxy adducts, and alkyl diamines in which the alkyl group has from about 2-6 carbon atoms.

96. The method of claim 85, where the ratio of triisocyanate to diisocyanate is selected to provide a desired release rate from the microcapsules.

97. The method of claim 85, where the ratio of the triisocyanate to the diisocyanate, on a cyanate equivalent basis, is between about 90:

10 and about 30;

70.

98. The method of claim 85, where the internal phase further comprises a hydrophobic diluent.

99. The method of claim 98, where the hydrophobic diluent is selected from the group consisting of paraffinic oils having from about 12-28 carbon atoms, alkylated biphenyls, and naphthalenes.