Microcapsules and microencapsulation process

Microcapsules containing a substantially water-insoluble liquid material, such as an anilide herbicide, and optionally also a herbicide antidote, within a porous shell to effect a slow rate of release of said herbicide (and optionally said antidote) through said shell, are produced by a process which comprises (a) providing an organic solution comprising said material and an etherified amino resin prepolymer dissolved therein which from about 50% to about 98% of the methylol groups of said prepolymer have been etherified with a C.sub.4 -C.sub.10 alcohol; (b) creating an emulsion of said organic solution in a continuous phase aqueous solution comprising water and a surface-active agent, wherein said emulsion comprises discrete droplets of said organic solution, there being formed thereby an interface between the discrete droplets of organic solution and the surrounding continuous phase aqueous solution; and (c) causing in situ self-condensation and curing of said amino resin prepolymer in the organic phase of said discrete droplets adjacent to said interface by simultaneously heating said emulsion to a temperature between about 20.degree. C. to about 100.degree. C., and adding to said emulsion an acidifying agent and maintaining said emulsion at a pH of between about 0 to about 4 for a sufficient period of time to allow substantial completion of in situ condensation of said resin prepolymers to convert the liquid droplets of said organic solution to capsules consisting of solid permeable polymer shells enclosing said liquid material. Also disclosed are the microcapsules formed by the above-described process.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
This invention relates to microcapsules and to a process for their 
production. In particular, this invention relates to encapsulated droplets 
of a liquid material which is substantially insoluble in water, where the 
encapsulating agent is a film formed from a modified amino resin polymer. 
B. Description of the Prior Art 
The use of membranes, coatings, and capsules for the controlled release of 
liquid materials is well known in the art of both agricultural and 
non-agricultural chemicals. In agriculture, controlled-release techniques 
have improved the efficiency of herbicides, insecticides, fungicides, 
bactericides, and fertilizers. Non-agricultural uses include encapsulated 
dyes, inks, pharmaceuticals, flavoring agents, and fragrances. 
The most common forms of controlled-release materials are coated droplets 
or microcapsules, coated solids including both porous and non-porous 
particles, and coated aggregates of solid particles. In some instances, a 
watersoluble encapsulating film is desired, which releases the 
encapsulated material when the capsule is placed in contact with water. 
Other coatings are designed to release the entrapped material when the 
capsule is ruptured by external force. 
Still further coatings are porous in nature and release the entrapped 
material to the surrounding medium at a slow rate by diffusion through the 
pores. In addition to providing controlled release, such coatings also 
serve to facilitate the dispersion of water-immiscible liquids into water 
and water-containing media such as wet soil. Droplets encapsulated in this 
manner are particularly useful in agriculture, where water from 
irrigation, rain, and water sprays is frequently present. A variety of 
processes for producing such capsules is known. 
In one process, the capsules are formed by phase separation from an aqueous 
solution through the coacervation of a hydrophilic colloid sol. This is 
described in U.S. Pat. Nos. 2,800,457 (Green et al., Jul. 23, 1957) and 
U.S. Pat. No. 2,800,458 (Green, Jul. 23, 1957). 
An interfacial polymerization process is disclosed in U.S. Pat. Nos. 
4,046,741 (Scher, Sept. 6, 1977) and U.S. Pat. No.4,140,516 (Scher, Feb. 
20, 1979), whereby the film-forming reactants are dissolved in the 
hydrophobic liquid which is dispersed in water, the reaction occurring at 
the interface when the phases are placed in contact as an emulsion. 
A further interfacial polymerization process is described in U.S. Pat. No. 
3,726,804 (Matsukawa et al., Apr. 10, 1973) whereby all the film-forming 
ingredients initially reside in hydrophobic droplets which also contain a 
low boiling or polar solvent in addition to the material to be 
encapsulated. Upon heating, the solvent is released into the aqueous phase 
(the continuous phase of the emulsion), and the film-forming materials 
accumulate at the interface and polymerize. 
Olefin polymerization using a peroxide catalyst is described in Japanese 
Patent Publication No. 9168/1961, whereby an oil-insoluble polymer is 
formed at the surfaces of oil drops. 
British Patent Nos. 952,807 and 965,074 describe a process whereby a solid 
such as a wax or a thermoplastic resin is melted, dispersed and cooled to 
form an encapsulating film around liquid droplets. 
U.S. Pat. No. 3,111,407 (Lindquist et al., Nov. 19, 1963) describes a spray 
drying method which forms encapsulated droplets at the instant of 
atomization. 
These processes vary in terms of equipment expense, energy requirements, 
ease of controlling the microcapsule size, the need for extra reagents 
such as catalysts and anti-settling agents, and percent microcapsule 
phase. It is therefore an object of the present invention to provide a 
simple, inexpensive method for producing microcapsules of uniform and 
readily controlled size, which are suitable for use without further 
treatment. Other objects of the invention will be apparent from the 
following description. 
SUMMARY OF THE INVENTION 
It has now been discovered that a liquid material which is substantially 
insoluble in water can be microencapsulated within a porous shell by a 
process which comprises: 
(a) providing an organic solution comprising said material and an 
etherified amino resin prepolymer dissolved therein in which from about 
50% to about 98% of the methylol groups of said prepolymer have been 
etherified with a C.sub.4 -C.sub.10 alcohol; 
(b) creating an emulsion of said organic solution in a continuous phase 
aqueous solution comprising water and a surface-active agent, wherein said 
emulsion comprises discrete droplets of said organic solution dispersed in 
said continuous phase aqueous solution, there being formed thereby an 
interface between the discrete droplets of organic solution and the 
surrounding continuous phase aqueous solution; and 
(c) causing in situ self-condensation and curing of said amino resin 
prepolymers in the organic phase of said discrete droplets adjacent to 
said interface by simultaneously heating said emulsion to a temperature 
between about 20.degree. C. to about 100.degree. C., and adding to said 
emulsion an acidifying agent and maintaining said emulsion at a pH of 
between about 0 to about 4 for a sufficient period of time to allow 
substantial completion of in situ condensation of said resin prepolymers 
to convert the liquid droplets of said organic solution to capsules 
consisting of solid permeable polymer shells enclosing said liquid 
material. 
Microcapsules formed by this process are capable of effecting a slow rate 
of release of the encapsulated liquid by diffusion through the shell to 
the surrounding medium. The present invention resides in both the process 
described above and the microcapsules thus formed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention can be readily adapted to accommodate variations in 
the materials used, the kind of product desired, and economic factors in 
general. As the following indicates, both essential and optional features 
of the process and the product thereof can be varied over a wide range. 
A. Core Liquid 
It is essential that the organic solution which forms the interior of the 
capsules (i.e., the core liquid) be substantially insoluble in water. 
Preferably, its solubility under ambient conditions is approximately 5000 
parts per million (ppm) by weight or less. The organic solution may 
consist of a single liquid material or one or more active liquid or solid 
materials dissolved in an inert solvent which has at most a slight 
solubility in water. In the latter case, the liquid or solid solute must 
reside preferentially in the organic phase when the two phases are in 
equilibrium. 
A wide variety of liquids can be encapsulated by the present process. The 
most useful liquids are those which do not react with either the 
prepolymer, the acid used in the self-condensation wall-forming step, or 
any of the other components in the system. Thus, any nonreactive liquid 
which will diffuse through the shell membrane is suitable. The liquid can 
be a single chemical compound or a mixture of two or more compounds. It 
can diffuse into water, soil, air, or any other surrounding medium. 
Liquids suitable for encapsulation include chemical-biological agents such 
as herbicides, insecticides, fungicides, nematocides, bactericides, 
rodenticides, molluscides, acaricides, larvicides, animal, insect, and 
bird repellents, plant growth regulators, fertilizers, pheromones, sex 
lures and attractants, and flavor and odor compositions. The microcapsules 
of the present invention are particularly well adapted to pesticides, 
including thiocarbamates, dithiocarbamates, acetamides, anilides, 
sulfonamides, triazines, organophosphorus compounds, and pyrethroids. The 
following are examples of such compounds, followed in parentheses by their 
common names where available: 
HERBICIDES 
S-ethyl-N-cyclohexyl-N-ethylthiocarbamate (cycloate) 
S-ethyl hexahydro-1H-azepine-1-carbothioate (molinate) 
S-2,3-dichloroallyl di-isopropylthiocarbamate (diallate) 
S-2,3,3-trichloroallyl di-isopropylthiocarbamate (triallate) 
S-ethyl dipropylthiocarbamate (EPTC) 
S-4-chlorobenzyl diethylthiocarbamate (benthiocarb) 
S-ethyl diisobutylthiocarbamate (butylate) 
S-benzyl di-sec-butylthiocarbamate 
S-propyl dipropylthiocarbamate (vernolate) 
S-propyl butylethylthiocarbamate (pebulate) 
N,N-diallylchloroacetamide (allidochlor) 
.alpha.-chloro-6'-ethyl-N-(2-methoxy-1-methylethyl)-acetanilide 
(metolachlor) 
N-butoxymethyl-.alpha.-chloro-2',6'-diethylacetanilide (butachlor) 
S-(0,0-diisopropyl phosphorodithioate) ester of 
N-(2-mercaptoethyl)benzenesulfonamide (bensulide) 
N-benzyl-N-isopropyltrimethylacetamide (butam) 
2-chloroallyl diethyldithiocarbamate (CDEC) 
2-sec-butyl-4,6-dinitrophenol (dinoseb) 
2,6-dinitro-N,N-dipropylcumidine (isopropalin) 
N-(cyclopropylmethyl)-.alpha.,.alpha.,.alpha.,-trifluoro-2,6-dinitro-N-prop 
yl-p-toluicine (profluralin) 
2-(1,2-dimethylpropylamino)-4-ethylamino-6-methylthio-1,3,5-triazine 
(dimethametryn) 
b 2-ethyl-5-methyl-5-(2-methylbenzyloxy)-1,3-dioxane 
INSECTICIDES 
S-tert-butylthiomethyl 0,0-diethyl phosphorodithioate (terbufos) 
0,0-diethyl-0-4-methylsulfinylphenyl phosphorothioate (fensulfotnion) 
0,0-diethyl 0-2-isopropyl-6-methylpyrimidin-4-yl phosphorotnioate 
(diazinon) 
0,0-diethyl S-2-ethylthioethyl phosphorodithioate (disulfoton) 
S-chloromethyl 0,0-diethyl phosphorodithioate (chlormephos) 
0-ethyl S,S-dipropyl phosphorodithioate (ethoprophos) 
0,0-diethyl S-ethylthiomethyl phosphorodithioate (phorate) 
0-(4-bromo-2-chlorophenyl) 0-ethyl S-propyl phosphorodithioate 
(prophenofos) 
S-1,2-di(ethoxycarbonyl)ethyl 0,0-dimethyl phosphorodithioate (malathion) 
0,0,0',0'-tetraetnyl S,S'-methylene di(phosphorodithioate) (ethion) 
0-(4-bromo-2,5-dichlorophenyl) 0,0-diethyl phosphorothioate 
(bromophosethyl) 
S-4-chlorophenylthiomethyl 0,0-diethyl phosphorodithioate (carbophenothion) 
2-chloro-1-(2,4-dichlorophenyl)vinyl diethyl phosphate (chlorphenvinphos) 
0-2,5-dichloro-4-(methylthio)phenyl 0,0-diethyl phosphorodithioate 
(chlorthiophos) 
0-4-cyanophenyl 0,0-dimethyl phosphorothioate (cyanophos) 
0,0-dimethyl 0-2-methylthioethyl phosphorothioate (demephion) 
0,0-diethyl 0-2-ethylthioethyl phosphorothioate (demeton) 
0-2,4-dichlorophenyl 0,0-diethyl phosphorothioate (dichlorofenthion) 
0-2,4-dichlorophenyl 0-ethyl phenylphosphonothioate (EPBP) 
0,0-diethyl 0-5-phenylisoxazol-3-yl phosphorothioate (isoxathion) 
3-di(methoxycarbonyl)-1-propen-2-yl dimethyl phosphate 
S,S'-(1,4-dioxane-2,3-diyl) 0,0,0,0,-tetraethyl di(phosphorodithioate) 
(dioxathion) 
0,0-dimethyl-0-4-nitro-m-tolyl phosphorothioate (fenitrothion) 
0,0-dimethyl 0-4-methylthio-m-tolyl phosphorothioate (fenthion) 
0-(5-chloro-1-isopropyl-1,2,4-triazol-3-yl) 0,0-diethyl phosphorothioate 
(isazophos) 
S-2-isopropylthioethyl 0,0-dimethyl phosphorodithioate (isothioate) 
4-(methylthio)phenyl dipropyl phosphate (propaphos) 
1,2-dibromo-2,2-dichloroethyl dimethyl phosphate (naled) 
0,0-diethyl .alpha.-cyanobenzylideneamino-oxyphosphonothioate (phoxim) 
0,0-diethyl 0-4-nitrophenyl phosphorothioate (parathion) 
0-2-diethylamino-6-methylpyrimidin-4-yl 0,0-diethyl phosphorothioate 
(pirimiphos-ethyl) 
0-2-diethylamino-6-methylpyrimidin-4-yl 0,0-dimethyl phosphorothioate 
(pirimiphos-methyl 
(E)-0-2-isopropoxycarbonyl-1-methylvinyl 0-methyl ethylphosphoramidothioate 
(propetamphos) 
0,0,0',0'-tetraethyldithiopyrophosphate (sulfotep) 
0,0,0',0'-tetramethyl 0,0,-thiodi-p-phenylene diphosphorothioate (temephos) 
S-2-ethylthioethyl 0,0-dimethyl phosphorodithioate (thiometon) 
0,0-diethyl 0-1-phenyl-I,2,4-triazol-3-yl phosphorothioate (triazophos) 
0-ethyl 0-2,4,5-trichlorophenyl ethylphosphonothioate (trichloronate) 
(.+-.)-3-allyl-2-methyl-4-oxocyclopent-2-enyl 
(.+-.)-cis,transchrysanthemate (allethrin) 
(.+-.)-3-allyl-2-methyl-4-oxocyclopent-2-enyl (.+-.)-transchrysanthemate 
(bioallethrin) 
3-phenoxybenzyl (.+-.)-cis,trans-chrysanthemate (phenothrin) pyrethrins 
2-(2-butoxyethoxy)ethyl thiocyanate 
isobornyl thiocyanoacetate (terpinyl thiocyanoacetate) 
carbon disulfide 
2-(4-tert-butylphenoxy)cyclohexyl prop-2-ynyl sulphite (propargite) 
4,6-dinitro-6-octylphenyl crotonates (dinocap) 
ethyl 4,4'-dichlorobenzilate (chlorobenzilate) 
DEFOLIANTS 
S,S,S-tributyl phosphorotrithioate 
tributyl phosphorotrithioite (merphos) 
FUNGICIDES 
copper naphthenates 
5-ethoxy-3-trichloromethyl-l,2,4-thiadiazole (etridiazole) 
0-ethyl S,S-diphenyl phosphorodithioate (edifenphos) 
INSECT REPELLENTS 
6-butoxycarbonyl-2,3-dihydro-2,2-dimethylpyran-4-one (butopyronoxyl) 
N,N-diethyl-m-toluamide (deet) 
dibutyl phthalate 
dibutyl succinate 
1,5a, 6,9,9a,9b-hexahydro-4a(4H)-dibenzofurancarboxaldehyde 
dipropyl pyridine-2,5-dicarboxylate 
Of the many different types of core liquids useful in the present 
composition, pesticides are preferred, and certain classes of pesticides 
are particularly preferred. One such class is that of substituted 
thiocarbamates, particularly those of the formula 
##STR1## 
in which R.sup.1 is selected from the group consisting of C.sub.1 -C.sub.6 
alkyl, C.sub.2 -C.sub.6 alkenyl, and C.sub.7 -C.sub.9 phenylalkyl, and is 
optionally substituted with up to three groups selected from halogen and 
nitro; and R.sup.2 and R.sup.3 are either independently C.sub.1 -C.sub.6 
alkyl or C.sub.5 -C.sub.7 cycloalkyl, or conjointly form C.sub.4 -C.sub.7 
alkylene. The terms "alkyl", "alkenyl", and "alkylene" are intended to 
include both straight-chain and branched-chain groups, and all carbon atom 
ranges are intended to be inclusive of the upper and lower limits stated. 
More preferred thiocarbamates are those in which R.sup.1 is C.sub.2 
-C.sub.4 alkyl and R.sup.2 and R.sup.3 either independently form C.sub.2 
-C.sub.4 alkyl or conjointly form hexamethylene. The most preferred are 
those in which R.sup.1, R.sup.2, and R.sup.3 are all independently C.sub.2 
-C.sub.4 alkyl. Thiocarbamates are particularly useful as pre-emergence 
and post-emergence herbicides. 
Another class of pesticide which is particularly preferred is that of the 
anilide herbicides, preferably the subclass of these known in the art as 
.alpha.-haloacetanilide, or more specifically .alpha.-chloroacetanilide 
herbicides. This latter group can be represented by the formula 
##STR2## 
in which X is halogen R.sup.4 is one or more of C.sub.1 -C.sub.6 alkyl, 
C.sub.1 -C.sub.6 alkoxy or halogen, n is 0 or an integer from 1 to 5; and 
R.sup.5 is C.sub.1 -C.sub.6 alkyl, C.sub.2 -C.sub.8 alkoxyalkyl or 
pyrazol-1-methyl. 
Preferably, X is chloro or bromo (most preferably chloro; n is 0, 1, or 2, 
R.sub.4 is C.sub.1 -C.sub.4 alkyl (most preferably methyl, ethyl or 
tertiary butyl); and R.sub.5 is C.sub.2 -C.sub.6 alkoxyalkyl. Some 
specific compounds of this class include: 
.alpha.-chloro-2'-methyl,6'-ethyl-N-(2-methoxy-1-methylethyl) acetanilide 
(metolachlor) 
N-butoxymethyl-.alpha.-chloro-2',6'-diethylacetanilide (butachlor) 
.alpha.-chloro-2',6'-diethyl-N-(methoxymethyl) acetanilide (alachlor) 
.alpha.-chloro-2'-methyl,6'-ethyl-N-(ethoxymethyl) acetanilide (acetochlor) 
.alpha.-chloro-2',6'-dimethyl-N-(lH-pyrazol-1-yl-methyl) acetanilide 
(metazochlor) 
.alpha.-chloro-2',6'-diethyl-N-(2-propoxyethyl) acetanilide (pretilachlor) 
.alpha.-chloro-2',6'-dimethyl-N-(methoxyethyl) acetanilide (dimethachlor) 
.alpha.-chloro-N-isopropyl acetanilide (propachlor) 
One can broaden the variety of crops on which certain pesticides, 
particularly herbicides, can be effectively used by including an antidote 
or safener in the composition. The antidote helps to protect the crop from 
injury by the herbicide, without appreciable effect on the potency of the 
herbicide against the undesired weed species. The antidote thus renders 
the herbicide more selective in its action. Useful antidotes include 
dichloroacetamides such as N,N-diallyl-2,2-dichloroacetamide, 
2,2-dimethyl-3-dichloroacetyl oxazolidine, 
2,2-dimethyl-5-phenyl-3-dichloroacetyl oxazolidine, 
2,2,5-trimethyl-3-dichloroacetyl oxazolidine and 
2,2-spirocyclohexyl-3-dichloroacetyl oxazolidine, dioxolanes such as 
2-(dichloromethyl)-2-methyl-1,3-dioxolane and 
2-(dichloro-methyl)-2-methyl-4-ethyl-1,3-dioxolane, S-thiazolecarboxylic 
acid, 2-chloro-4-(trifluoromethyl)(phenylmethyl) ester ("flurazole"), 
ethanone-2,2-dichloro-1-(1,2,3,4-tetrahydro-1 -methyl2-isoquinolyl) and 
other compounds disclosed in U.S. Pat. No. 4,936,901, various substituted 
aryl cyclopropane carbonitriles as disclosed in U.S. Pat. No. 4,859,232, 
and 1,8-naphthalic anhydride. For maximum effect, the antidote is present 
in the composition in a non-phytotoxic, antidotally effective amount. By 
"non-phytotoxic" is meant an amount which causes at most minor injury to 
the crop. By "antidotally effective" is meant an amount which 
substantially decreases the extent of injury caused by the herbicide to 
the crop. The preferred weight ratio of herbicide to antidote is about 
0.1:1 to about 30:1. The most preferred range for this ratio is about 3:1 
to about 20:1. 
The use of this invention for the production of microencapsulated products 
which contain an anilide, or more particularly an .alpha.-haloacetanilide 
herbicide, especially those mentioned above as being preferred, can 
provide exemplary results with those anilides or .alpha.-haloacetanilides 
which normally require an antidote for application to certain crops. 
Acetochlor and metolachlor are two examples of such herbicides. By 
appropriate choice of the amino resin and the process conditions, 
microencapsulated compositions of anilides, especially 
.alpha.-haloacetanilides may be prepared which, as compared to other 
compositions of the same herbicide, may contain a smaller amount of the 
same antidote, may contain a weaker antidote, or may even dispense with 
the need for an antidote. While not intending to be bound by any theory, 
it is believed that the microcapsules of this invention have walls which 
are sufficiently permeable to permit passage, in a controlled manner, of 
anilide, or particularly, .alpha.-haloacetanilide herbicide in an amount, 
or at a rate, sufficient to control weeds, but insufficient to cause 
material damage to certain crops, particularly corn. 
The utility of many pesticides can also be broadened by the inclusion in 
the microcapsule core, of synergists in the pesticide composition. 
Synergists are compounds which have little or no pesticidal activity of 
their own, but when combined with a pesticide produce a combination with a 
potency significantly greater than the additive sum of the potencies of 
the compounds applied individually. Useful synergists include 
5-1-[2-(2-ethoxyethoxy)-ethoxy]-ethoxy-1,3-benzodioxole (sesamex), 
1,4-di-(1,3-benzodioxol-5-yl)-tetrahydrofuro [3,4-c] furan (sesamin), 
1-methyl-2-(3,4-methylenedioxyphenyl)ethyl octyl sulphoxide (sulfoxide), 
and 5-[2-(2butoxyethoxy)ethoxymethyl]-6-propyl-1,3-benzodioxole (piperonyl 
butoxide). When included, synergists are present in effective amounts, 
i.e., at any pesticide-to-synergist ratio at which a synergistic effect is 
observed. This ratio varies widely from one combination to the next. 
B. Prepolymer 
Prepolymers suitable to the present invention are partially etherified 
amino resin prepolymers with a high solubility in the organic phase and a 
low solubility in water. In its non-etherified form, the prepolymer 
contains a large number of methylol groups, --CH.sub.2 OH, in its 
molecular structure. Etherification is the replacement of the hydroxyl 
hydrogens with alkyl groups, and is achieved by condensation of the 
prepolymer with an alcohol. When the alkyl groups comprise four carbon 
atoms or more and they have replaced more than about 50% of the hydroxyl 
hydrogen atoms on the prepolymer molecule, the prepolymer becomes soluble 
in the organic phase. Complete etherification is to be avoided, however, 
since hydroxyl groups are needed for the in situ self-condensation 
polymerization which occurs in the wall-forming step. Therefore, the 
prepolymers useful in the present invention are those in which from about 
50% to about 98% of the hydroxyl hydrogen atoms have been replaced by 
alkyl groups of 4 to 10 carbon atoms each. In preferred practice, about 
70% to about 90% of the groups have been etherified with a C.sub.4 
-C.sub.6 alcohol. Both straight-chain and branched-chain alcohols are 
useful in the present invention, and all carbon atom ranges quoted herein 
are to be inclusive of their upper and lower limits. 
Amino resins are a known class of polymer and are described, for instance, 
in "50 Years of Amino Coating Resins", Albert J. Kirsch, ed., Winchell Co. 
(Philadelphia), 1986. These are prepared from an amine-containing compound 
and formaldehyde. Amino resins generally fall into four subclasses: 
urea-formaldehyde, melamine-formaldehyde, benzoguanamine-formaldehyde and 
glycoluril-formaldehyde. The first two mentioned are preferred in this 
invention, with urea-formaldehyde prepolymers being most preferred. 
Etherified amino resin prepolymers are commercially available as solutions 
in alcohol or in a mixture of alcohol and xylene. The alcohol used as the 
solvent is normally identical to that used as the etherifying agent. Those 
in most common use are n-butanol and iso-butanol. The degree of 
etherification (butylation) in these commercial products ranges between 
70% and 90%, and the solution contains from 50% to 85% by weight of 
prepolymer. Minor amounts of free formaldehyde are also frequently 
present. These solutions are typically sold as cross-linking agents for 
alkyd resins and used primarily for the formulation of coating and 
finishing products such as paints and lacquers. 
Amino resin prepolymers which have not been etherified are also available 
commercially, either in aqueous solutions or as water-dissolvable solids, 
for use as adhesives. These can be etherified by condensation with the 
desired alcohol in a weakly acidic alcohol solution. The water of 
condensation is distilled off as an azeotrope with the alcohol until the 
desired degree of condensation (etherification) has been reached. 
Some commercially available prepolymers, in addition to those mentioned in 
the Examples, are those sold by American Cyanamid Co. under the trademark 
CYMEL.RTM. (melamineformaldehyde, benzoguanamine-formaldehyde and 
glycolurilformaldehyde). 
The amino resin prepolymers themselves can be prepared by known techniques, 
by the reaction between the amine (preferably urea or melamine) and 
formaldehyde. Urea-formaldehyde prepolymers, for instance, can be prepared 
by the base-catalyzed reaction between urea and formaldehyde in water at a 
weight ratio of 0.6 to 1.3 parts formaldehyde to one part urea by weight 
(1.2:1 to 2.6:1 on a molar basis), at a pH of 7.5 to 11.0 and a 
temperature of 50.degree. C. to 90.degree. C. Etherification is then 
accomplished as described in the preceding paragraph. 
The degree of etherification can be monitored by the quantity of water 
driven off during the distillation. Although the degree of etherification 
can be varied over a wide range to accommodate the needs of the reaction 
system, the rate of polymerization in the subsequent wall-forming step 
decreases as the degree of etherification increases. Too high a degree of 
etherification, therefore, tends to inhibit the progress of the wall 
formation. However, the water solubility of the prepolymer also decreases 
with increasing degree of etherification. Since low water solubility is a 
desirable feature of the prepolymer, it is best to avoid too low a degree 
of etherification. Thus, the suitable and preferred ranges are those 
stated above. 
The organic solution comprising the core liquid and the etherified 
prepolymer is most conveniently formed when the latter is predissolved in 
a solvent, as it is when commercially sold for the coatings and finishings 
industry. In the absence of such a solvent. There is a high degree of 
hydrogen bonding between the hydroxyl groups, and the prepolymer is a waxy 
solid which is difficult to dissolve in the capsule core liquid. Polar 
organic solvents are particularly useful for preventing the hydrogen 
bonding and dissolving the prepolymer; examples include alcohols, ketones, 
esters, and aromatics. When etherifying agents of high chain length are 
used, aliphatics and other non-polar solvents can also be used. The most 
useful solvents are the same alcohols used as the etherifying agents, the 
solution being taken directly from the reaction mixture of the 
etherification process. 
The concentration of the prepolymer in the organic phase is not critical to 
the practice of the invention, but can vary over a wide range depending on 
the desired capsule wall strength and the desired quantity of core liquid 
in the finished capsule. It will be most convenient, however, to use an 
organic phase with a prepolymer concentration of from about 1% to about 
70% on a weight basis, preferably from about 5% to about 50%. 
C. Optional Additives 
Optional additives include solvents, polymerization catalysts, and 
wall-modifying agents. 
Solvents provide a means for controlling the wallforming reaction. As 
explained in Section E below, the reaction occurs when protons come in 
contact with the urea-formaldehyde prepolymer. The organic phase must be 
sufficiently hydrophilic to attract protons to the interface from the bulk 
of the aqueous phase, yet sufficiently hydrophobic to prevent large 
amounts of protons from crossing the interface and causing polymerization 
to occur throughout the bulk of the droplet. An appropriately selected 
solvent added to the organic phase can correct the character of the 
organic phase to achieve these results. Clearly, the need for a solvent 
and the type of solvent needed--hydrophobic or hydrophilic--depends on the 
nature of the liquid core material. Aliphatic and alicyclic solvents are 
examples of hydrophobic solvents, and alcohols and ketones are examples of 
hydrophilic solvents. The amount of solvent can be varied as needed to 
achieve the desired results. 
Catalysts capable of enhancing the wall-forming reaction can be placed in 
either the aqueous or organic phase. Catalysts are generally used when the 
core material is too hydrophobic, since they serve to attract protons 
toward the organic phase. Any water-soluble catalyst which has a high 
affinity for the organic phase and is capable of carrying a proton can be 
used. Carboxylic and sulfonic acids are particularly useful. Examples 
include orthochlorobenzoic acid, 2-phenyl-2,2-dichloroacetic acid, benzoic 
acid, salicylic acid, p-toluenesulfonic acid and dodecylbenzene sulfonic 
acid. The same catalytic effect can be accomplished by dissolving salts of 
these acids in the aqueous or organic phase and then acidifying the 
aqueous phase. The acid form is produced by ion exchange. 
Wall-modifying agents serve to modify the character of the wall by varying 
its permeability to the core material. Suitable wall-modifying agents 
contain a substantial number of hydroxyl or mercapto groups capable of 
reacting with the methylol groups on the prepolymer. The wall modifier can 
be used in the organic solution to add multiple linkages to the methylol 
groups to increase the degree of cross-linking, or to exhaust active sites 
on the prepolymer to decrease the degree of cross-linking. Thus, depending 
on the kind of modifier used and the ratio of modifier to prepolymer, the 
permeability of the wall (and consequently the release rate of the core 
liquid) can be either increased or decreased. Castor oil is one example of 
a cross-linking agent. The preferred cross-linking wall-modifying agent is 
pentaerythritol tetrakis (mercaptopropionate) sold under the tradename 
Mercaptate Q-43 Ester, by Cincinnati Milacron Chemicals. Other 
poly-functional mercaptan esters of a similar nature can be used. 
D. Emulsion Formation 
Once the organic solution is formed, an emulsion is formed by dispersing 
the organic solution in an aqueous solution comprising water and a 
surface-active agent. The relative quantities of organic and aqueous 
phases are not critical to the practice of the invention, and can vary 
over a wide range, limited mostly by convenience and ease of handling. In 
practical usage, the organic phase will comprise a maximum of about 55% by 
volume of the total emulsion and will comprise discrete droplets of 
organic solution dispersed in the aqueous solution. 
The surface-active agent can be any of the .wide variety of compounds known 
to be useful for lowering the surface tension of a fluid interface. 
Nonionic and anionic types are both useful. Examples of nonionic agents 
are long chain alkyl and mercaptan polyethoxy alcohols, alkylaryl 
polyethoxy alcohols, alkylaryl polyether alcohols, alkyl polyether 
alcohols, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene 
ethers, and polyethylene glycol esters with fatty or rosin acids. Examples 
of anionic agents are the calcium, amine, alkanolamine, and alkali salts 
of alkyl and alkylaryl sulfonates; vegetable sulfonates; and ethoxylated 
and propoxylated mono- and diethers of phosphoric acid. Blends of 
surface-active agents are also useful. Preferred surface-active agents are 
polyethylene glycol ethers of linear alcohols and alkali salts of alkyl 
and alkylaryl sulfonates. 
The quantity of surface-active agent is not critical to the invention, and 
can vary over a wide range. For convenience, the agent generally comprises 
from about 0.1% to about 5.0% by weight of the aqueous phase. The agent 
can be added before or after the emulsion is formed. 
In some systems, emulsion stability can be enhanced by adding a protective 
colloid to the aqueous phase. A protective colloid stabilizes a dispersed 
system against aggregation, flocculation, and coalescense. Many materials 
are known to function as protective colloids and are available 
commercially, including polyvinyl alcohols, alginates, alpha-and 
gamma-protein, casein, methyl cellulose, carboxymethyl cellulose, gelatin, 
glues, natural gums, polyacids, and starch. The colloid can be added to 
the aqueous phase prior to the formation of the emulsion, or to the 
emulsion itself after it has been formed. Although the colloid is an 
optional additive, its inclusion in the present system is preferred. 
Polyvinyl alcohol protective colloids are particularly preferred. 
Additional compounds which serve as protective colloids are the salts of 
lignin sulfonate, such as the sodium, potassium, magnesium, calcium or 
ammonium salts. Among commercial lignin sulfonates are Treax.RTM., LTS, 
LTK and LTM, respectively, the potassium, magnesium and sodium salts of 
lignosulfonate (50% aqueous solutions), Scott Paper Co., Forest Chemical 
Products; Marasperse CR.RTM. and Marasperse CBOS-3.RTM., sodium 
lignosulfonate, American Can Co.; Polyfon 0.RTM., Polyfon T.RTM., Reax 
88B.RTM., Reax 85B.RTM., Reax 100M.RTM., sodium salts of lignin sulfonate 
and Reax C-21.RTM., calcium salt of lignin sulfonate, Westvaco 
Polychemicals; Orzan S and Orzan A, the sodium and ammonium salts of 
lignosulfonate, ITT Rayonier, Inc. 
The actual quantity of colloid is not critical and any amount which is 
effective in enhancing the stability of the emulsion can be used. It is 
most convenient to use between about 0.1% and about 5.0% colloid by weight 
in terms of the aqueous phase. 
The droplet size in the emulsion is not critical to the invention. For 
greatest utility of the final product, the droplet size will fall in the 
range of about 0.5 microns to about 4000 microns in diameter. The 
preferred range for most pesticidal applications is from about I micron to 
about 100 microns in diameter. The emulsion is prepared by the use of any 
conventional high shear stirring device. Once the desired droplet size is 
attained, mild agitation is generally sufficient to prevent droplet growth 
throughout the balance of the process. 
E. Wall Formation 
Once the dispersion and desired droplet size are attained, the system is 
acidified to a pH of between about 0 and about 4.0, preferably between 
about 1.0 and about 3.0. This causes the prepolymer to polymerize by 
self-condensing in situ and form a shell completely enclosing each 
droplet. Acidification can be accomplished by any suitable means, 
including adding any acid which is water-soluble, including formic acid, 
citric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and the 
like. Acidification can also be achieved by the use of acidic dispersants 
or surface-active agents, provided that such components are added to the 
system after the emulsion has been formed. 
As the polymer wall becomes more rigid, contact between the active groups 
on the prepolymer becomes increasingly more difficult. Thus, the in situ 
self-condensation polymerization reaction is self-terminating and is 
generally allowed to run to completion. The reaction can be arrested 
before completion, however, by raising the pH. In this manner, the wall 
tightness, rigidity, and permeability can be controlled. This can also be 
accomplished in most cases by a wall modifier as described above. 
The rate of the in situ self-condensation polymerization reaction increases 
with both acidity and temperature depending upon the pH. The reaction can 
therefore be conducted anywhere within the range of about 20.degree. C. to 
about 100.degree. C., preferably between about 40.degree. C. and about 
70.degree. C. The reaction will generally be complete within a few hours, 
although with high acidity and high temperature, the reaction can be 
completed within minutes. 
Once the capsules are formed, they can be stored and used as an aqueous 
dispersion, or filtered and recovered as dried capsules. In either form, 
the capsules are useful and effective in the slow release of the core 
liquid. Dispersions are preferably stabilized by dispersants dissolved in 
the continuous phase. Since most dispersants are more effective in neutral 
or basic solutions, it is preferable to raise the pH of the dispersion 
once the wall has been formed. This is accomplished by any water-soluble 
base. Any conventional dispersant can be used. Typical dispersants include 
lignin sulfonates, polymeric alkylnaphthalene sulfonates, sodium 
naphthalene sulfonate, polymethylene bis-naphthalene sulfonate, and 
sodium-N-methyl-N-(long chain acid) taurates. 
A unique feature of the process of the invention is that the solid 
permeable polymer shells enclosing the organic phase droplets are formed 
by means of condensation of the prepolymer in the organic phase adjacent 
to the interface formed between the organic phase droplets and the aqueous 
phase solution. This is a consequence of the prepolymers being dissolved 
in the organic phase. 
The advantages of forming the polymer shells on the organic side of the 
interface are several. The first is that the process itself is more easily 
controlled than the prior art processes, which involve wall-forming 
condensation in the aqueous phase. When the condensation takes place in 
the aqueous phase, the wall-forming polymer can deposit upon the walls of 
the container in which the emulsion is present, on the agitator or any 
other structure which may be present, in addition to depositing on the 
droplets. In contrast, the wall-forming polymer that condenses on the 
organic side of the interface does not deposit on any of the container 
walls or other structures. 
Additionally, when the condensation takes place in the aqueous phase, as in 
the prior art, a reduced amount of dispersed organic phase must be used 
inasmuch as if a higher dispersed organic phase content is utilized, the 
dispersion gets too thick and gels, thus effectively preventing formation 
of the microcapsules. Condensation on the organic side of the interface 
thus allows higher dispersed organic phase loading to be obtained because 
a gel is not formed in the aqueous phase. 
In the examples set forth herein, in which the organic phase contains a 
pesticide, a higher loading of organic phase results in a more 
concentrated pesticide formulation. This enables substantial cost savings 
to be achieved in manufacturing, packaging and transportation. 
The following examples are offered as illustrative of both the process and 
product of the present invention, and are intended neither to define nor 
limit the invention in any manner. 
EXAMPLE 1 
An aqueous solution was prepared, comprising 2.0% (weight) Gelvatol.RTM. 
40-20 and 0.3% Tergitol.RTM. 15-S-7, with a total solution weight of 300 
g. Gelvatol.RTM. 40-20 is a polyvinyl alcohol protective colloid (degree 
of hydrolysis 73-77%), with an average molecular weight of about 3000, 
obtained from Monsanto Company, Indian Orchard, Massachusetts. 
Tergitol.RTM. 15-S-7 is a nonionic surfactant consisting of a polyethylene 
glycol ether of a linear alcohol, obtained from Union Carbide Chemicals 
and Plastics Company, New York, N.Y. 
In a separate vessel, 100 g of S-ethyl diisobutylthiocarbamate (a herbicide 
known by the common name "butylate") and 50 g of Beckamine.RTM. 21-625 
were blended into a homogeneous solution. Beckamine.RTM. 21-625 is a 
70-75% n-butanol in which the degree of butylation is approximately 
80-90%, obtained from Reichhold Chemicals, Inc., White Plains, N.Y. 
The thiocarbamate/prepolymer (organic) solution was added to the aqueous 
solution and an emulsion was formed by means of a high shear stirrer, the 
organic solution forming the dispersed phase with droplets ranging in size 
from 5 to 40 microns in diameter. While mild agitation was maintained, the 
pH of the emulsion was adjusted to 2.0 with concentrated hydrochloric acid 
and the temperature was raised to 50.degree. C. for three hours. The 
resulting suspension was then allowed to cool to room temperature and 
concentrated aqueous sodium hydroxide was added to raise the pH to 7.0. 
Observation of the suspension under both a laboratory microscope and an 
electron microscope revealed discrete, roughly spherical, fully enclosed 
capsules with smooth-surfaced outer walls. The capsules were about 5 to 40 
microns in diameter and although some were touching each other, none were 
fused together. 
EXAMPLE 2 
An organic solution was prepared, comprising 162.2 g of 
2-methoxy-9-(p-isopropylphenyl)-2,6-dimethylnonane (a known insect 
maturation inhibitor--see U.S. Pat. No. 4,002,769, issued Jan. 11, 1977, 
to Schwarz et al.) and 48.0 g of Resimene.RTM. X-918 The latter is a 70% 
n-butanol solution of a partially butylated ureaformaldehyde prepolymer 
with a degree of butylation of approximately 80-90%, a product of Monsanto 
Plastics and Resins Company, Newport Beach, Calif. 
This solution was added to an aqueous solution comprising 168.1 g of water 
and 1.87 g of Gelvatol.RTM. 40-20 and an emulsion was formed as in Example 
1, with droplets ranging in diameter from 1 to 40 microns. To this 
emulsion Was added 20 g of water containing 1.87 g each of the dispersants 
Lomar NCO.RTM. and Darvan.RTM. #2. The former is a product of Diamond 
Shamrock Chemical Company, Nopco Division, Morristown, N.J., and is a 
sodium salt of a condensed mononaphthalene sulfonic acid. The latter is a 
product of R. T. Vanderbilt Company, Inc., Norwalk, Conn., and is 
comprised of sodium salts of polymerized substituted benzoic alkyl 
sulfonic acids. A 5% hydrochloric acid solution was added to lower the pH 
of the emulsion to 2.0 and the temperature was raised to 50.degree. C. 
with continued stirring for three hours. The resulting dispersion was then 
cooled to room temperature and concentrated caustic solution was added to 
raise the pH to 9.0. 
Microscopic observation of the dispersion revealed fully formed, discrete 
capsules as in Example 1. 
EXAMPLE 3 
The organic solution for this example consisted of 139.9 g of 0-ethyl 
S-phenyl ethylphosphonodithioate (a commercial insecticide also known by 
the common name "fonofos") and 39.9 g of Resimene.RTM. X-918. This 
solution was emulsified in an aqueous solution consisting of 200 g of 
water and 2.35 g of Gelvatol.RTM. 40-20 to a droplet size of 1 to 40 
microns, and 35 g of water containing 2.35 g each of the dispersants Lomar 
NCO and Darvan #2, as well as 2.4 g of p-toluene sulfonic acid, was added. 
The temperature was raised to 60.degree. C. and stirring was continued for 
three hours. The dispersion was then allowed to cool to room temperature 
and the pH was raised to 9.0 with caustic solution. 
Microscopic observation of the dispersion revealed fully formed, discrete 
capsules as in Example 1. 
EXAMPLE 4 
The organic solution for this example consisted of 156 g of HI-SOL.RTM. 4-3 
(solvent) and 43.5 g of Beckamine.RTM. 21-625. The former is a heavy 
aromatic naphtha, with boiling temperature ranging from 238.degree. C. to 
286.degree. C., a product of Ashland Chemical Company, Industrial 
Chemicals and Solvents Division, Columbus, Ohio. This solution was 
emulsified in an aqueous solution consisting of 194.6 g of Water, 3.9 g of 
Gelvatol.RTM. 40-20, and 7.8 g of Darvan #2, to a droplet size of 1 to 40 
microns. The pH was adjusted to 2.0 with a 5% solution of hydrochloric 
acid and the temperature was raised to 50.degree. C. with continued 
stirring for three hours. The dispersion was then allowed to cool to room 
temperature and the pH was raised to 9.0 with caustic solution. 
Microscopic observation revealed fully formed, discrete capsules as in 
Example 1. 
EXAMPLE 5 
An aqueous solution consisting of 251.6 g of water, 5 g of Gelvatol.RTM. 
40-20, and 2.5 g of Tamol.RTM. SN was heated to 50.degree. C. Tamole SN is 
a dispersant identified as a sodium salt of a condensed naphthalene 
sulfonic acid, obtained from Rohm and Haas Company, Philadelphia, Penna. 
To this heated aqueous solution was added an organic solution consisting 
of 173.4 g of S-ethyl diisobutylthiocarbamate (butylate), 7.5 g of 
N,N-diallyl dichloroacetamide, and 22.5 g of Resimene.RTM. X-918. The 
thiocarbamate/acetamide combination is a known herbicide/antidote 
combination--see U.S. Pat. No. 4,021,224, issued May 3, 1977, to Pallos et 
al. An emuleion was formed by means of a high-speed stirrer as in the 
above examples, to a droplet size of 1 to 40 microns. The high temperature 
was maintained and the pH was lowered to 2.0 with 5% hydrochloric acid. 
After three hours of additional stirring, the dispersion was cooled to 
room temperature and the pH was raised to 9.0 with caustic solution. 
Microscopic observation revealed fully formed, discrete capsules as in 
Example 1. 
EXAMPLE 6 
In this example, an additional feature is demonstrated--the inclusion of an 
organic solvent (kerosene) in the organic phase, the solvent thus becoming 
part of the encapsulated liquid. 
The aqueous solution was prepared with 177.12 g of water, 2 g of 
Gelvatol.RTM. 40-20, and 2 g of Darvan #2. The organic solution Was 
prepared with 132.74 g of S-ethyl hexahydro-1H-azepine-1-carbothioate (a 
commercial herbicide known 35.48 g of Beetle.RTM. 1050-10. The latter is a 
60% n-butanol solution of a partially butylated urea-formaldehyde 
prepolymer in which the degree of butylation is approximately 70-90%, 
obtained from American Cyanamid Company, Resins Department, Wayne, N.J. 
The organic solution was emulsified in the aqueous solution by means of a 
high shear stirrer to an average droplet diameter of 18 microns, and 19.68 
g of water containing 2 g of DAXAD.RTM. LAA was slowly added, lowering the 
pH of the emulsion to 1.7 DAXAD.RTM. LAA is a dispersant in acidic form, 
identified as a polymerized alkyl naphthalene sulfonic acid, a product of 
W. R. Grace and Company, Organic Chemicals Division, Lexington, Mass. 
The emulsion temperature was then raised to 50.degree. C. for three hours 
with continued stirring. The dispersion thus formed was cooled to room 
temperature and the pH was raised to 7.5 with caustic solution. 
Microscopic observation revealed fully formed, discrete capsules as in 
Example 1. 
EXAMPLE 7 
In this example, two additional features are demonstrated--the inclusion of 
kerosene as in Example 6 and the addition of a wall-modifying component 
(castor oil) to the prepolymer. 
The aqueous solution was prepared with 181.6 g of water, 2 g of 
Gelvatol.RTM. 40-20, and 2 g of Darvan #2. The organic solution was 
prepared with 132.7 g of S-ethyl hexahydro-1H-azepine-1-carbothioate, 
44.25 g of kerosene, 22.97 g of Beetle.RTM. 1050-10, and 6.9 g of castor 
oil. An emulsion with an average droplet diameter of 18 microns was 
formed, and 20.2 g of water containing 2 g of DAXAD.RTM. LAA was added, 
lowering the pH to 1.7. The emulsion temperature was then raised to 
50.degree. C. for three hours with continued stirring. The resulting 
dispersion was then cooled to room temperature and the pH was raised to 
7.5 with caustic solution. 
Microscopic observation revealed fully formed, discrete capsules as in 
Example 1. 
EXAMPLE 8 
The organic solution consisted of 154 g of butylate, 6.7 g of N,N-diallyl 
dichloroacetamide, and 47.6 g of Resimene.RTM. X-918 (same ingredients as 
Example 5). This solution was emulsified in 197.8 g of a 4.0% (by weight) 
aqueous solution of Darvan #2 to a droplet size of 1 to 40 microns. The pH 
of the dispersion was then adjusted to 2.0 with a 5% solution of 
hydrochloric acid and the temperature was raised to 50.degree. C. with 
continuous stirring for three hours. The dispersion was then allowed to 
cool to room temperature and the pH was raised to 9.0 with caustic 
solution. 
Microscopic observation of the dispersion revealed fully formed, discrete 
capsules as in Example 1. 
The following examples demonstrate production of microencapsulated products 
containing the anilide herbicide acetochlor 
[.alpha.-chloro-2'-methyl-6'-ethyl-N(ethoxymethyl)acetanilide]. 
EXAMPLE 9 
The organic solution consisted of 189.4 g of acetochlor (95.9% purity), 1.3 
g of Mercaptate Q-43 Ester and 12.7 g of Beetle.RTM. 80 resin. Mercaptate 
Q-43 Ester is pentaerythritol tetrakis (mercaptopropionate), sold by 
Cincinnati Milacron Chemicals. Beetle.RTM. 80 resin is a highly butylated 
(about 95%) liquid urea-formaldehyde resin obtained from American Cyanamid 
Company, Resins Department, Fort Wayne, N.J. 
The organic solution was emulsified with continuous stirring in an aqueous 
solution consisting of 5.7 g of sodium lignosulfonate (DAXAD.RTM. 23, 
obtained from W. R. Grace & Co.), 0.9 g of the sodium 
dialkylnaphthalenesulfonate (Petro BAF.RTM., obtained from Petrochemicals 
Company, Inc., Fort Worth, Tx.) and 185.1 g of water. The pH of the 
resulting emulsion was lowered to 2.0 with 1.5 g of concentrated sulfuric 
acid. The emulsion temperature was then raised to 50.degree. C. for three 
hours with continuous stirring. The resulting dispersion was cooled to 
25.degree. C. and the pH was raised to 7 with 50% caustic solution. 
Microscopic observation revealed fully formed discrete capsules as in 
Example 1. 
EXAMPLE 10 
The organic solution consisted of 25.1 g of Beetle.RTM. 1050-10 resin and 
189.4 g of acetochlor (95.9% purity). It was emulsified in an aqueous 
solution consisting of 5.4 g of DAXAD.RTM. 23, 0.9 g of Petro BAF.RTM.and 
173.2 g of water. 
The pH of the resulting emulsion was lowered to 2.0 with 1.4 g of 
concentrated sulfuric acid. The emulsion temperature was raised to 
50.degree. C. for three hours with continuous stirring. 
The dispersion was cooled to 25.degree. C. and the pH raised to 7.0 with 
caustic solution. 
Microscopic observation revealed fully formed discrete capsules as in 
Example 1. 
EXAMPLE 11 
The organic solution consisted of 13.4 g of Beetle.RTM. 80 resin, 1.4 g of 
Mercaptate Q-43, 27.9 g of N,N-diallyl dichloroacetamide (95% purity) and 
171.6 g of acetochlor (92.6% purity). It was emulsified in an aqueous 
solution consisting of 1.84 of REAX.RTM. 100 M (sodium lignosulfonate 
obtained from Westvaco Company, Charleston Heights, S.C.), 0.9 g of Petro 
BAF.RTM., and 180 g of water. 
The pH of the resulting emulsion was lowered to 2.0 with 0.5 g of 
concentrated sulfuric acid. The emulsion temperature was raised to 
50.degree. C. for three hours with continuous stirring. The resulting 
dispersion was cooled to 25.degree. C. and the pH was raised to 7.0 with 
caustic solution. 
Microscopic observation revealed fully formed discrete capsules as in 
Example 1. 
EXAMPLE 12 
The organic solution consisted of 250 g Beetle.RTM. 1050-10 resin, 27.9 g 
of N,N-diallyl dichloroacetamide (95% purity) and 171.6 g of acetochlor 
(92.6% purity). It was emulsified in an aqueous solution consisting of 
1.84 g of REAX.RTM. 100 M, 0.9 g of Petro BAF and 180.96 g of water. 
The pH of the emulsion was lowered to 2.0 with 0.5 g of concentrated 
sulfuric acid. The emulsion temperature was raised to 50.degree. C. for 
three hours with continuous stirring. The resulting dispersion was allowed 
to cool to 25.degree. C. and the pH was raised to 7.0 with caustic 
solution. 
Microscopic observation revealed fully formed discrete capsules as in 
Example 1. 
This example demonstrates the production of microcapsules using a 
melamine-formaldehyde prepolymer. 
The organic solution consisted of 12.7 g of butylated melamine-formaldehyde 
resin prepolymer (Cymel.RTM. 1156, from American Cyanamid Co.), 184.4 g of 
acetochlor (95.9% purity) and 1.3 g of pentaerythritol 
tetramercaptopropionate (Evans Chemetics Corp., New York, N.Y.). It was 
emulsified in an aqueous solution consisting of 5.7 g of sodium 
lignosulfonate (DAXAD.RTM. 23), 0.9 g of Petro BAF.RTM., and 185.1 g of 
water. 
The pH of the emulsion was lowered to 2.0 with 1.4 g of concentrated 
sulfuric acid. The emulsion temperature was raised to 50.degree. C. for 
three hours with continuous stirring. The resulting dispersion was allowed 
to cool to 25.degree. C. and the pH was raised to 7.0 with caustic 
solution. Microscopic observation revealed fully formed discrete capsules 
as in Example 1. 
BIOLOGICAL EVALUATION 
Greenhouse Evaluation 
The compositions of Examples 9 and 10 were evaluated in the greenhouse by 
pre-emergence surface treatment for injury to corn, in comparison with 
compositions containing acetochlor alone, and acetochlor with the 
herbicide antidote N,N-diallyl dichloroacetamide. The compositions of 
Examples 9 and 10 do not contain an antidote. The comparison compositions 
were: 
A) an emulsifiable concentrate containing 6.4 pounds acetochlor per gallon 
in Aromatic 100 solvent (Exxon Chemical Co., Houston, Tx.). 
B) Technical grade material containing acetochlor and N,N-diallyl 
dichloroacetamide in a 6:1 weight ratio. 
The corn varieties utilized were Garst 8711 and Pioneer 3475. Corn seeds 
were planted in rows in a flat in 63-18-9% sand-silt-clay soil. Before 
planting, the flats were sprayed with the test compositions, appropriately 
diluted with water (Composition A and Examples 9 and 10) or dissolved in a 
water-acetone mixture (Composition B) to provide application rates of 1 
and 2 kg/ha acetochlor. The flats were rated 8 and 16 days after 
treatment. Rating was performed visually using a scale of 0-100 with 0 
representing no control as compared to an untreated test flat, and 100 to 
complete kill. The results are expressed in Table 1 below. 
TABLE 1 
__________________________________________________________________________ 
Greenhouse Bioassay of Acetochlor Formulations 
% Corn Injury 
8 D.A.T. 16 D.A.T. 
Anti- 
Rate, 
Garst 
Pioneer 
Garst 
Pioneer 
Composition 
Type dote 
kg/ha 
8711 
3475 8711 
3475 
__________________________________________________________________________ 
A emulsifiable 
no 1 40 60 15 30 
concentrate 
B technical 
yes 
1 3 0 3 3 
material 
Example 9 
microcapsules 
no 1 6 11 5 5 
Example 10 
microcapsules 
no 1 10 5 10 13 
A emulsifiable 
no 2 60 85 30 35 
concentrate 
B technical 
yes 
2 1 0 4 1 
material 
Example 9 
microcapsules 
no 2 25 35 20 25 
Example 10 
microcapsules 
no 2 10 8 10 15 
__________________________________________________________________________ 
The performance, i.e., ability to reduce phytotoxicity to corn, of the 
microencapsulated compositions of this invention, without an antidote, at 
times approached that of the nonencapsulated antidoted acetochlor 
(Composition B), particularly in the 8-day ratings. 
Field Evaluation 
The compositions of Example 9 and 10 were tested in comparison to an 
emulsifiable concentrate containing only acetochlor (Composition A), in a 
field near visalia, Calif. The soil composition was 60-26-14% 
sand-silt-clay. Weeds which appeared and were evaluated were wild proso 
millet (Panicum miliaceum) ("WPM") and Rox-orange sorghum (Sorghum vulgare 
v. Rox-organe) ("ROS"). The corn variety utilized was Pioneer 3475. 
application of the compositions was by pre-emergence surface treatment, at 
the indicated rates. Evaluation was done 7 and 15 days after treatment, 
using the same scale. The results are contained in Table 2, below. 
TABLE 2 
__________________________________________________________________________ 
Field Bioassay of Acetochlor Formulations 
% 
weed control 
Rate, % corn injury 
(15 D.A.T.) 
Composition 
kg/ha 
Antidote 
7 D.A.T./15 D.A.T. 
WPM ROS 
__________________________________________________________________________ 
A 1.12 
no 37 43 100 100 
(emulsifiable 
2.24 
no 52 53 100 100 
concentrate) 
4.48 
no 70 77 100 100 
Example 9 
1.12 
no 22 21 100 99 
(microcapsules) 
2.24 
no 37 47 100 100 
4.48 
no 48 65 100 100 
Example 10 
1.12 
no 18 13 98 97 
(microcapsules) 
2.24 
no 29 36 100 100 
4.48 
no 38 41 100 99 
__________________________________________________________________________ 
The results of these tests demonstrate that the compositions of this 
invention exhibited less injury to corn than the acetochlor emulsifiable 
concentrate, while maintaining weed control.