Novel process to prepare microencapsulated formulations

Abstract

Provided is a method of encapsulating a chemical agent comprising: (a) combining particles of a chemical agent and an encapsulation effective amount of a first encapsulating agent in an aqueous solvent and (b), converting the first encapsulating agent to a polymer to form encapsulated particles of the chemical agent.

What is claimed:  
     
         1 . A method of encapsulating a chemical agent comprising: 
 (a) combining, in an aqueous solvent, particles of a chemical agent suspended in the aqueous solvent and an encapsulation effective amount of a first encapsulating agent; and    (b) converting the first encapsulating agent to an encapsulating polymer, thereby forming encapsulated particles of the chemical agent.    
     
     
         2 . The method of  claim 1 , wherein the converting of step (b) is: 
 (i) where the first encapsulating agent is a polymer, changing the pH of the aqueous solvent to precipitate the polymer; or    (ii) where the first encapsulating agent comprises water-dispersible oligomers, polymers, or mixtures thereof, forming the precipitated polymer from the encapsulating agent.    
     
     
         3 . The method of  claim 2 , wherein the converting is according to (ii) and the converting process further comprises heating the combined particles and first encapsulating agent to at least about 40° C.  
     
     
         4 . The method of  claim 3  wherein the encapsulating polymer is selected from the group consisting of: ureformaldehyde resin, melamine formaldehyde resin, phenol formaldehyde resin, resorcinol formaldehyde resin, butylated urea formaldehyde resin, polyisocyanate, glycoluril formaldehyde resin, and poly(methylolacrylamide).  
     
     
         5 . The method of  claim 4  wherein the polyisocyanate comprises residues derived from an alkylene diisocyanate.  
     
     
         6 . The method of  claim 5  wherein the alkylene diisocyanate is hexamethylene diisocyanate.  
     
     
         7 . The method of  claim 2 , wherein the converting is according to (ii) and wherein the first encapsulating agent forms an encapsulating polymer selected from the group consisting of: polyisocyanates, formaldehyde copolymers, a polyacrylamide, and phenoxy resin.  
     
     
         8 . The method of  claim 2 , wherein the converting is according to (i) and the method further comprises: 
 (c) reacting the encapsulating polymer with a first curing agent.    
     
     
         9 . The method of  claim 8 , wherein reacting comprises heating to a temperature of at least 40° C.  
     
     
         10 . The method of  claim 8  wherein the first curing agent is an inorganic or organic salt having a multivalent cation.  
     
     
         11 . The method of  claim 10  wherein the first curing agent is selected from the group consisting of: calcium chloride, calcium carbonate, magnesium chloride, calcium lignosulfonate, calcium alkylbenzene sulfonate, and calcium stearate.  
     
     
         12 . The method of  claim 11  wherein the first curing agent is calcium lignosulfate.  
     
     
         13 . The method of  claim 9  wherein the first curing agent is selected from the group consisting of: diamines, silanes, aldehydes, polyhydroxides, epoxides, diepoxides, or water soluble amino resins.  
     
     
         14 . The method of  claim 13  wherein the first curing agent is formaldehyde.  
     
     
         15 . The method of  claim 8  further comprising: 
 (d) combining the encapsulated particles of step (c) with a second encapsulating agent.  
 
     
     
         16 . The method of  claim 15 , further comprising heating the combination of step (d) to a temperature of at least about 40° C.  
     
     
         17 . The method of  claim 15  wherein the second encapsulating agent forms a second encapsulating polymer selected from the group consisting of: formaldehyde copolymers, polyisocyanates, a polyacrylamide, and phenoxy resin.  
     
     
         18 . The method of  claim 17  wherein the second encapsulating polymer is selected from the group consisting of: ureformaldehyde resin, melamine formaldehyde resin, polyisocyanates, phenol formaldehyde resin, resorcinol formaldehyde resin, butylated urea formaldehyde resin, glycoluril formaldehyde resin, and methylolacrylamide.  
     
     
         19 . The method of  claim 18  wherein the polyisocyanate comprises residues derived from an alkylene diisocyanate.  
     
     
         20 . The method of  claim 19  wherein the alkylene diisocyanate is hexamethylene diisocyanate.  
     
     
         21 . The method of  claim 1 , wherein the particles have an size ranging from about 1 μm to about 100 μm.  
     
     
         22 . The method of  claim 1 , wherein the viscosity of the suspension does not significantly increase during the converting of step (b).  
     
     
         23 . The method of  claim 1  wherein the converting is effected by lowering the pH of the aqueous solvent.  
     
     
         24 . The method of  claim 23  wherein the first encapsulating agent is a polymer selected from the group consisting of: polyanhydrides, polyanhydride acids, polyanhydride salts, polyanhydride esters, styrene maleic anhydride copolymers and hydrolysis and neutralization products thereof, polysaccharides, acrylic acid polymers, polyacrylamides, acrylic polymers, hydrophobically-modified polyacrylic acids, and salts of alkyl naphthalene sulfonate polymers.  
     
     
         25 . The method of  claim 24  wherein the first encapsulating agent is selected from the group consisting of: maleic anhydride copolymer disodium salt, styrene maleic anhydride copolymer amide ammonium salt, styrene maleic anhydride copolymer ammonium salt, poly(methyl vinyl ether-co-maleic anhydride), N-methylolacrylamide, and poly(vinyl chloride-co-vinyl acetate-co-hydroxyl acrylate).  
     
     
         26 . The method of  claim 23  wherein the pH is lowered by adding an acid selected from the group consisting of: hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, perchloric acid, phosphoric acid, acetic acid, trifluoroacetic acid, citric acid, and 2,2,2-trifluoroethanol.  
     
     
         27 . The method of  claim 26  wherein the acid is acetic acid.  
     
     
         28 . The method of  claim 1  wherein the chemical agent is a bioactive agent.  
     
     
         29 . The method of  claim 28  wherein the bioactive agent is a pesticide.  
     
     
         30 . The method of encapsulating a chemical agent according to  claim 2  wherein the converting is according to (ii) and the change in pH is a decrease in pH, effected by addition of acid, to less than about 6 and further comprising adding a curing agent, which is a calcium salt, and heating the resulting mixture to a temperature above about 40° C.  
     
     
         31 . The method of claim  30  further comprising the steps of combining the product of claim  31  with a water-dispersible polyisocyanate based on hexamethylene diisocyanate and heating the resulting combination to a temperature above about 40° C.