Microcapsules with readily adjustable release rates

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
• O.dbd.C.dbd.N--(CH.sub.2).sub.n --N.dbd.C.dbd.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.degree. 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.

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
• O.dbd.C.dbd.N--(CH.sub.2).sub.n --N.dbd.C.dbd.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.

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
• O.dbd.C.dbd.N--(CH.sub.2).sub.n --N.dbd.C.dbd.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.

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
• O.dbd.C.dbd.N--(CH.sub.2).sub.n --N.dbd.C.dbd.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.

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
• O.dbd.C.dbd.N--(CH.sub.2).sub.n --N.dbd.C.dbd.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.

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
• O.dbd.C.dbd.N--(CH.sub.2).sub.n --N.dbd.C.dbd.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.

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
• O.dbd.C.dbd.N--(CH.sub.2).sub.n --N.dbd.C.dbd.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.