Low volatility formulations of microencapsulated clomazone

DETAILED DESCRIPTION We claim: 1.
A process for the preparation of herbicidally effective formulations of clomazone having a volatility less than fifty percent of the volatility of an emusifiable concentrate of clomazone containing four pounds of clomazone per gallon of formulation which comprises microencapsulating the clomazone by interfacial polymerization by the steps of: a) providing an aqueous phase containing 0.
3 to 3.
0 wt.
% of one or more emulsifiers; optionally 0.
02 to 0.
20 wt.
% of a xanthan gum viscosity modifier/stabilizer, and 0.
1 to 1.
0 wt.
% of an antifoam agent; b) providing a water immiscible phase consisting of clomazone, polymethylene polyphenyl isocyanate (PMPPI), and a hydrocarbon solvent; the weight ratio of clomazone to PMPPI being in the range of 1:1 to 6:1; c) emulsifying the water immiscible phase in the aqueous phase, forming a dispersion of water immiscible droplets throughout the aqueous phase; d) agitating the dispersion while adding thereto an aqueous solution of 15 to 100 weight percent of at least one polyfunctional amine selected from ethylenediamine (EDA), diethyltriamine (DETA), triethylenetetramine (TETA), and 1,6-hexanediamine (HDA), with the proviso that (EDA) is used only in a mixture, the weight ratio of polyfunctional amine to PMPPI being in the range of 0.
1:1 to 1:1, thus forming microcapsules having a polyurea shell wall around the water immiscible droplets; e) curing the microcapsules by continuing the agitation while heating the dispersion at a temperature in the range of 35.
degree.
to 60.
degree.
C.
for a period of 3 to 10 hours to produce a formulation in which the average size of the microcapsules is in the range of 5 to 50 microns; f) optionally adjusting the pH to between 6.
5 and 9.
0.
2.
A process according to claim 1 in which the emulsifier is a polyvinyl alcohol; the antifoam agent is a polydimethyl siloxane; the ratio of clomazone to PMPPI is 4.
5:1 to 4.
7:1; the polyamine is a mixture of TETA and HDA in which the ratio of TETA to HDA is 3:1 to 1:3; the microcapsules are cured at 45