GB989264A - Microcapsules and method of producing them - Google Patents

Abstract

Microcapsules each composed of a solid or liquid particle enclosed within an aminoplast polymer shell are produced by dispersing the nucleus material in an aqueous medium containing aminoplast polymer precursors and causing the precursors to polymerize whereby aminoplast shells form around the particles. Specified precursors are compounds containing methylol groups which are capable of polymerization with urea in aqueous media, e.g. formaldehyde, paraformaldehyde and hexamethylenetetramine together with a urea, e.g. urea, thiourea, melamine, guanidine and N-alkyl ureas; mono- and di-methylolurea, water soluble, low-molecular weight urea-formaldehyde polymers of mono- and di-methylol urea, urea or formaldehyde. The resins may optionally contain nitrogenous modifiers, e.g. sulphonamides, anilines and amines and polymerization may be induced by an acid catalyst. Numerous materials are stated to be capable of encapsulation by the process of the invention and specific examples relate to the encapsulation of solid and liquid materials including the following agricultural chemicals: 2,4-dichlorophenoxy acetic acid isooctyl and butyl esters, 2,4,5-trichlorophenoxy acetic acid butyl ester, 0,0 - dimethyl - 0 - (1,2 - dibromo - 2,2 - dichloroethyl) phosphate; 1,2,3,4,10,10-hexa-chloro1,4,4a,5,8,8a - hexahydro - 1,4 - endo, exo-5,8 - di - methanonaphthalene; 0,0 - dimethyl dithiophosphate of diethyl mercapto succinate; pentachloronitro benzene; 3 - (3,4 - dichlorophenyl - 1,1 - dimethylurea; 1,2 - dibromo - 3 - chloropropane and N-trichloromethyl thio tetrahydrophthalimide. Materials encapsulated in other examples include toluene, isooctane, tetrachloroethylene, carbon tetrachloride, trichloropropane, trichlorodiphenyl, cyclic C8F16O, n-amyl alcohol, oleic acid, a trimeric C18 unsaturated acid, piccolyte, a polyglycol diacrylate, dioctyl and dibutyl phthalates, mineral oil, pine oil, paraffin wax, shoe polish, rosins, a jasmine odour base, and sulphur. A dye or pigment is incorporated in certain of the phthalates, halogenated solvents, toluene and mineral oil products.ALSO:Microcapsules each composed of a solid or liquid particle enclosed within an aminoplast polymer shell are produced by dispersing the nucleus material in an aqueous medium containing aminoplast polymer precursors and causing the precursors to polymerize whereby aminoplast shells form around the particles. Specified precursors are compounds containing methylol groups which are capable of polymerization with urea in aqueous media, e.g. formaldehyde, paraformaldehyde and hexamethylenetetramine together with a urea, e.g. urea, thiourea, melamine, guanidine and N-alkyl ureas; mono- and di-methylolurea, water-soluble, low-molecular weight urea-formaldehyde polymers of mono- and di-methylol urea, urea or formaldehyde. The resins may optionally contain nitrogenous modifiers, e.g. sulphonamides, anilines and amines and polymerisation may be induced by an acid catalyst. Numerous materials are stated to be capable of encapsulation by the process of the invention and specific examples relate to the encapsulation of solid and liquid materials including the following agricultural chemicals:-2,4-D iso-octyl and butyl esters, 2,4,5-T butyl ester, O,O-dimethyl-O-(1,2-dibromo - 2,2 - dichloroethyl) phosphate; 1,2,3,4,10,10 - hexa - chloro - 1,4,4a,5,8,8a - hexahydro - 1,4 - endo, exo - 5,8 - di - methanonaphthalene; O,O-dimethyl dithiophosphate of diethyl mercapto succinate; pentachloronitro benzene; 3 - (3,4 - dichlorophenyl) - 1,1 - dimethylurea; 1,2 - dibromo - 3 - chloropropane and N-trichloromethyl thio tetrahydrophthalimide.