NZ203120A - In flight encapsulated particles - Google Patents

Description

a— miiLiiiiiiHH— 'III If HI— »J—■.npw — uwiMna/aw Priority Date(s): CompSeta Specification Fllsd:^ PSJujvSCcE'lVOfl O3u!0! a • eSi^^-1 a........

P.O. Js-jms!, Me: ... J$$P......... ppfllSIf, KJH ' ' v/r I $*' iu w n**? 2 031 2 0 Und«r the provisions of R«gir-talion 23 (I) the Specification has been ante-datetf to <&3 \r8L- Initials Patents Form No. 5 Number PATENTS ACT 1953 Dated COMPLETE SPECIFICATION IN-FLIGHT ENCAPSULATED PARTICLES i/We ENVIRONMENTAL CHEMICALS INC., a corporation of the State of Illinois, United States of America, of P.O. Box 346, 1111 North Old Rand Road, Wauconda, Illinois 60084, United States of America do hereby declare the invention for which fc(we pray that a Patent may be granted to n^us, and the method by which it is to be performed, to be particularly described in and by the following statement: 1 2 0312 0 The present invention relates to in-flight encapsulated particles encapsulated from a composition of a self-encapsulating polymeric-containing solution and according to a process for the in-flight encapsulation of particles such as insecticides, fungicides, herbicides, etc., contained therein as described in our specification No. 196991. More specifically, the present invention relates to particles encapsulated during passage between the egress of a spray apparatus and a target.

Heretofore, the encapsulation of a chemical substance within an enveloping polymer membrane has been well recognized by the art. For example, U. S. Patent Nos. 3,242,051, 3,2^5,629, 3,575,882, and 3, 607,776 all relate to processes dependent upon phase separation and polycondensation reactions. Specifically, the 3,242,051 patent relates to preparing a solution of a liquid phase-forming micromolecular polymer in a first non-aqueous liquid, dispersing in said solution a plurality of individual discreet parti- p n cles, adding a second liquid soluble in the first liquid, but not soluble with regard to said micro-molecular polymer, whereby phase separation is induced and precoats the dispersed particles, settling the polymer-rich precoat, separating the precoated parti- cles, suspending the precoated particles in an aqueous solution of a gel, and using phase separation so as to cause the formation of a colloidal-enriched phase and the encapsulation of each of these suspended precoated particles, and cooling.

U. S. Patent No. 3,265,629 is similar but relates to the application of two coatings to the particles, namely a solid lipid and a polymer. 2031 U.S. Patent No. 2,648,609 relates to an air suspension technique wherein a sugar solution is sprayed onto a suspended item such as candy, gum, etc. Another technique heretofore utilized is the 5 utilization of charging a first solution with ions so that the solution exhibits a specific charge, applying an opposite charge to a second solution, and then coating the first solution with the second « solution via air flow.

U.S. Patent No. 3, 202,533 relates toi-.the encapsulation of liquids by the use of a fluidized bed wherein the fluidized liquid is frozen and spray coated.

Common to all such above-described inventions 15 and prior art processes is the utilization of multiple compounds or compositions of matter as well as the necessity of processing the encapsulated or microencapsulated article prior to usage or application. Moreover, costly and complex processing equipment as 20 well as difficult technology is required to produce articles of a defined size and to meet mandatory environmental controls or regulations.

In contrast, encapsulated particles of the present invention are encapsulated utilising a single self-encap-25 sulating polymer containing solution, from a particle phase via a polymer by in-flight encapsulation; that is, during the passage from the spraying or ejection equipment to the target substance or area, including an agricultural or forested area.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide in-flight encapsulated particles. 203120 Particles according to the invention are encapsulated from a composition comprising generally a film-forming polymer in a solvent system for solubilizing said polymer, said particles being either soluble or dispersed in the solvent medium.

Particles according to the invention are encapsulated from said composition upon ejection from a spray apparatus and during flight through the intervening earth's atmosphere, the solution rapidly losing the solvent component through evaporation with coacervation occurring resulting in the formation of a polymer membrane about the particles.

During the in-flight encapsulation of particles, as above, said particles are encapsulated by said polymer upon the evaporation of some or most, if not all, of the solvent in the process of passage of particles between an ejector or a spray apparatus and a target.

Preferably the particles are very small so that a microencapsulated product is produced.

Preferably particles encapsulated as described above are such that said encapsulated product is of fairly uniformed particle size.

Preferably particles encapsulated as described above comprise an outer polymer membrane about an inner partial core.

Preferably particles encapsulated as described above are of uniform product size, so that target specificity can be incorporated into the in-flight system. 2031 20 Encapsulated particles according to the present invention can comprise insecticides, acaricides, fungicides, herbicides, nutrients, trace minerals, nematicides, molluscicides, pheromenes, odorants, fragrances, attractants, repellants, or any other desired particle.

Encapsulated particles according to the present invention provide for the leaching of said particles on a target to occur in from a day to a period of months, rather than in a matter of minutes or hours, and crosslinking agents may be added to said solution to control the leaching time period.

Various adhesive and film-modifying agents may similarly be added to said solution so that improved adhesion of said encapsulated product to said target occurs.

These and other objects of the present invention will become apparent from the following preferred embodiment of the invention.

In general, a process for producing in-flight encapsulated particles according to the present invention comprises the steps of: preparing a self-encapsulating polymeric-containing solution; said solution comprising by weight from about 0.3 percent to about 25 percent of polymer, from about 35 percent to about 99 percent of a solvent, said solvent being a compound which will solubilize said polymer, and from about 1 percent to about 40 percent of the particles, said particles being either soluble or ° 0 3 1, 2 0 insoluble (in which case particles will be present in the form of a dispersion) in said solvent; said polymer selected from the class consisting of (a) polyvinyl acetate, (b) a polyvinyl ether wherein the repeating unit has from 2 to 10 carbon atoms, (c) an acrylic polymer or a copolymer made from monomers having the formula ['■ h0c= c c — or, I5 1 where R^ is hydrogen or an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 30 carbon atoms and R^ is hydrogen or an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 12 carbon atoms, (d) the salt of (1) an interpolymer having the structure h- R I C c— o I oh n R- -ch.

C= o I nh ch2oh Jx ch2—ch T c = o I OR^ ch. ch C I C=° I or-. wherein R and R^ are members of the group consisting of hydrogen and methl; R2 is a member of the group consisting of methyl, ethyl, propyl and butyl; R3 is a member of the group consisting of methyl and ethyl; n represents from 3 to 12 weight percent based on the combined weight of n, x, y, and z; x represents from 8 to 25 weight percent based on the combined weight of n, x, y and z; ^ 4. OCT V383 2031 2 y represents from 4 5 to 89 weight percent based on the combined weight of n, x, y and z; z represents from 0 to 44 weight percent based on the combined weight of n, x, y and z; the sum of the numerical value of n .+ x + y 5 + z is always exactly 100 and the groups n, x, y and z are present in a heterogeneous relative position, and (2) a member of the group consisting of ammonia, hydrazine, a low boiling point primary aliphatic amine and a low boiling point second aliphatic amine, said salt being soluble in 10 water in the pH range of from about 5 to 8, and (e) combinations thereof; spraying said solution from a spray apparatus such that in-flight encapsulation of said solution by evaporation of said solvent so that said polymer encapsulates said particles occurs.

Generally, a self in-flight encapsulating polymeric- containing solution for production of encapsulated particles of the invention according to the aforesaid process comprises, by weight, based upon the total weight of said solution from about 0.3 percent to about 25 percent of a polymer, 20 from about 35 percent to about 99 percent of a solvent, and from 1 percent to about 4 0 percent of a particle, said particle being either soluble or insoluble (in which case the particle will be present in the form of a dispersion) in said solvent; said polymer being selected from the class 25 consisting of (a) polyvinyl acetate, (b) a polyvinyl ether wherein the repeating unit has from 3 to 10 carbon atoms, (c) an acrylic polymer or copolymer made from monomers having the formula r5 O H2C—-k 1 OR4 where R^ is hydrogen or an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 30 carbon atoms and R,- is hydrogen or an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 12 carbon atoms, (d) the salt of (1) an interpolymer having the structure i 203120 R I :h-=tC 2 i i OH -0 CH; Rn C= t NH .0 n L_ CH90H Jx _ -CH2—CH t=0 I OR2 y u CH.

CH. i=0 I 0R3 where R and R^ are members of the group consisting of hydrogen and methyl; R2 is a member of the group consisting of methyl, ethyl, propyl, and butyl; R^ is a member of the group consisting of methyl and ethyl; n represents from 10 3 to 12 weight percent based on the combined weight of n, x, y and z; x represents from 8 to 25 weight percent based on I the combined weight of n, x, y and z; y represents from 45 to 8 9 weight percent based on the combined weight of n, x, y and z; z represents from 0 to 44 weight 15 percent based on the combined weight of n, x, y and z; the sum of the numerical value of n+x+y+z is always exactly 100 and the groups n, x, y and z are present in a heterogeneous relative position and (2) a member of the group consisting of ammonia, hydra-20 zine, a low boiling primary point aliphatic amine and a low boiling point second aliphatic amine, said salt being soluble in water in the pH range of from about 5 to about 8, and (e) combinations thereof; said particle 25 being soluble or dispersible in said solvent; and said solvent being a compound in which said polymer is soluble.

An encapsulated particle according to the present invention typically comprises: a particle, said particle coated with a film-forming polymer; said polymer being 30 selected from the class consisting of (a) a polyninyl acetate, (b) a polyvinyl either wherein the repeating unit has from 3 to 10 carbon atoms, (c) an acrylic polymer or^copolymer made from monomers having the formula jh4 203120 H2C«= R f -C- 0 -OR, where is hydrogen or an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 30 carbon atoms and R^ is hydrogen or an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 12 carbon atoms, (d) the salt of (1) an interpolymer having the structure R I CH„ — C I i c—o I OH -CH, -c I C—0 I NH —■ n — CH2OH— x ■CH2—CH- I OR- rO 2 y - CH CH0—C 1 I C=0 I OR., wherein R and R^ are members of the group consisting of hydrogen and methyl; R2 is a member of the group consisting of methyl, ethyl, propyl and butyl; R^ is a member of the group consisting of methyl and ethyl; n represents from 3 to 12 weight percent based on the combined weight of n, x, y and z; x represents from 8 to 25 weight percent based on the combined weight of n, x, y and z; y represents from 45 to 89 weight percent based on the combined weight of n, x and z; z represents from 0 to 44 weight percent based on the combined weight of n, x, y and z; the sum of the numerical value of n + x + y + z is always exactly 100 and the groups n, x, y and z are present in a heterogeneous relative position, and (2) a member of the group consisting of ammonia, hydrazine, a low boiling point primary aliphatic amine and a low boiling point second aliphatic amine, said salt being soluble in water in the pH range of from about 5 to about 8, and (e) combina^^apSff^^lereof. t 2 0312 0 IN THE DRAWINGS Fig. 1 is a photograph of an encapsulated particle, according to the present invention, wherein 5 a polymeric film is shown about the particle and the film is adhered to a glass strand; Fig. 2 is a photograph similar to Fig. 1 wherein the encapsulated particle is adhered to the junction of two glass strands; Fig. 3 is another photograph showing a particle polymerically encapsulated about a glass strand; and Fig. 4 is another photograph showing an encapsulated particle attached to the intersection 15 of two glass strands. preferred embodiment of the invention The concept of the present invention relates to self in-flight encapsulated particles. 20 Numerous applications exist through conventional ejection equipment such as conventional spraying apparatus to apply encapsulated particles for various utilities, for example, public health protection, agricultural 2 5 applications, and any other area or field in which the encapsulation of particles, especially micro-encapsulation, is desired. By the term "in-flight encapsulation" it is meant that the particle is covered, surrounded, coated, or encapsulated by a film-forming 30 polymer by a coacervation process during or between the passage from an ejector or a spraying apparatus to a desired target, material, area, or the like. Moreover, the encapsulated material of the present invention results in a controlled release of the 35 particle through a leaching mechanism so that in il.0312 0 effect a slow release of the particle is achi from a matter of a day or two to several weeks or months.

The self-encapsulating polymer-containing solution 5 comprises a film-forming polymer in a solvent in which the polymer is soluble, and the particle itself. Therefore, the polymeric-containing solution exists as a particle either dissolved or dispersed in the solvent-polymer phase..

On a weight basis, the total amount of polymer utilized ranges from about 0.3 percent to about 25 percent, with from about 2 to about 18 percent being desirable, and from 4 to 13 percent being preferred. Often times, instead 15 of a single film-forming polymer, two or even three types of polymers can be utilized. The amount of solvent ranges from about 35 percent to about 99 percent « with from about 5 0 to about 9 0 being preferred. The amount of particle ranges from about 1 percent to about 20 40 percent with from about 5 to about 3 0 percent being preferred. Naturally, as will be better understood by referring to the examples in the specification, the various components or compounds can be varied to achieve specific changes in properties of the final product; that 30 is, the encapsulated particle. Additionally, various adhesive agents, crosslinking agents, emulsifying agents, and other additives may be added to further modify either the process or the end product properties.

Suitable polymers 35 comprise^ film-forming polymers which are capable of . encapsulating the particle by coacervation and which form a polymeric film about the particle. Such a specific polymer is polyvinyl acetate having a molecular weight range of from about 10,000 to about 100,000. Another 4 0 suitable and desired polymer 2031 20 is the polyvinyl ethers wherein the repeating hydrocarbon group is an alkyl having from 2 to 10 carbon atoms, preferably 2 carbon atoms, and with the polymer having a molecular weight of. from about 10,000 to about 100,000.

Preferred polymers comprise carboxylated acrylic polymers and copolymers such as those made from monomers having the formula ?c O I5 II H 2 C=— C C 0R4 where R^is a hydrogen radical or a hydrocarbon group having from 1 to 30 carbon atoms and R,. is a hydrogen radical or a hydrocarbon group having from 1 to 12 carbon atoms, both hydrocarbon groups being selected from i the class consisting of alkyl, cycloalkyl, aryl, and aralkyl. Desirably, R^ is an alkyl having from 1 to 4 carbon atoms and preferably is hydrogen. , desirably, has from 1 to 3 carbon atoms and, preferably, either has 1 carbon atom or is hydrogen. By carboxylated, it is meant that a substantial number of the pendant groups of the polyacrylate contains carboxyl groups. Moreover, by copolymers, it is meant that the polymer may be made from 2 or more monomers having the above formulation. A preferred polymer is made from methacrylate monomers with a preferred polymer being made from acrylic acid monomers. The molecular weight of the carboxylated acrylic polymers generally ranges from 10,000 to 600,000 with a preferred range being from about 30,000 to about 300,000.

A highly preferred polymeric compound comprises the salts of interpolymers of alphabeta olefinically unsaturated carbonyl monomers which contain N-methylol acrylic amides as set forth in 203120 U.S. Patent No. 3,007,887, which is hereby fully incorporated by reference with regard to the preparation, content and description of the inner polymers. Generally, the interpolymer has the following structure : R -ch~—c 1 I Y" oh 0 —in R- ch„ — c z l c=0 I nh ch2oh _k ch2—ch- I OR- 0 2 v ch.

?H3 -c — I c=o I ORn _lz where R and R^ are members of the group consisting of hydrogen and methyl; R2 is a member of the group consisting of methyl, ethyl, propyl and butyl; R^ is a member of the group consisting of methyl and ethyl; n represents from 3 to 12 weight percent based on the combined weight of n, x, y and z; x represents from 8 to 25 weight percent based on the combined weight of n, x, y and z; y represents from 45 to 89 weight percent based on the combined weight of n, x, y and z; z represents from 0 to 44 weight percent based on the combined weight of n, x, y and z; the sum of the numerical value ofn+x+y+zis always exactly 100 and the groups n, x, y and z are present in a heterogeneous relative position. The interpolymer is converted from an alcohol solution to water solutions by the addition of water having neutralizing agents such as ammonia, a hydrazine, or a low-boiling amine to the alcoholic solution of the interpolymer followed by an azeotropic distillation which removes the last traces of the alcohol and the excess neutralizating agent. The final aqueous solution of the polymer salt is preferably in the range of pH 5-8 and more preferably in the range of pH 6-7 with a total solids content of from about 2 to 40 percent by weight fv Vh" I from about 5 to about 30 2 031 2 0 percent by weight of polymer in water.

Preferred polymers are those compositions comprising from 45 to 89 parts by weight of a lower acrylic acid ester, from 0 to 44 parts by weight of a lower methacrylic acid ester, from 3 to 12 parts by weight of an alpha-beta olefinically unsaturated carboxylic acid having a terminal group and having from 3 to 4 carbon atoms I Z03f zd> and from 8 to 25 parts by weight of an N-methylol alpha-beta olefinically unsaturated carboxylic acid amide having a terminal c<\ 9rouP an^ having from 4 to 5 carbon atoms.

The lower acrylic acid esters useful in this invention include those in which in the above formula is an aliphatic hydrocarbon group having from 1 to 4 carbon atoms such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-10 butyl acrylate, isobutyl acrylate and secondary butyl acrylate. The most preferred lower acrylic acid esters are methyl acrylate and ethyl acrylate. The lower acrylate acid esters are useful in the range of from about 4 5 to about 89 weight percent based on the weight i of the other monomers.

The lower methacrylic acid esters useful in this invention include those in which in the above formula is an aliphatic hydrocarbon group having from 1 to 2 carbon atoms such as methyl methacrylate and 20 ethyl methacrylate. The preferred methacrylic acid ester is methyl methacrylate. The lower methacrylic acid esters are useful in the range of from about 0 to about 44 weight percent based on the weight of the other monomers.

The alpha-beta olefinically unsaturated carboxylic acids embodied in this invention include acrylic acid and methacrylic acid. The alpha-beta olefinically unsaturated carboxylic acids are useful in the range of from about 3 to about 12 weight per-30 cent based on the weight of the other monomers.

The N-methylol acrylic amides embodied in this invention include N-methylol acrylamide and N-methylol methacrylamide. The most preferred N-methylol acrylic amide is N-methylol acrylamide. The N- ' I methylol acrylic amides are useful in the range of 2 031 from about 8 to 25 weight percent based on the weight of the other monomers.

The molecular weight of the polymer represented by the above interpolymer structure generally ranges from about 20,000 to about 1,000,000 with a weight of from about 30,000 to about 250,000 being preferred.

Specific examples of the above interpolymers include Carboset XLll (molecular weight of about 45,000), Carboset 514 (molecular weight of about 30,000), Carboset 515 (molecular weight of about 70,000), Carboset 525 (molecular weight of about 260,000), Carboset 526 (molecular weight of 300,000), all manufactured by the B.F. Goodrich Company. Generally, the higher the identification number, the higher the molecular weight of the particular interpolymer .

I The solvent may be any solvent which will solubilize the above polymers. Generally, water and alkanols having from 1 to 5 carbon atoms, and combinations thereof, may be utilized. Examples of specific alcohols include methanol, propanol, isopropanol, butanol, isobutanol, pentanol, etc., with ethanal being preferred. Other suitable solvents include acetone, diisobutyl ketone methyl ethyl ketone, dioxane, and methylene chloride. Moreover, other solvents may be used in which the particle is generally soluble or dispersible therein.

The particle is usually a solid.However, in some instances, the particle can be a liquid. Regardless of whether the particle is a solid or a liquid, it can be any compound which, as part of the self-encapsulating solution can be ejected or sprayed by either known or conventional ejecting or spraying apparatus. Although the particles may be of any size so long as they can 2 03120 be sprayed or ejected by an apparatus, they are desirably small to facilitate in the ease of ejecting or spraying the solution or, generally, due to their nature of application. For example, at least 90 percent of the particles having a size ranging from less than 1 micron to 200 may be utilized, although, generally, they are from a much smaller range as from about 1 to about 100 microns. For insecticides, odorants, etc., the application of particles smaller than 100 microns, as from 1 to 50 microns are preferred.

Naturally, it is desirable that the particle, the solvent, and the polymer be compatible with each other in that they lack chemical interaction.

The particle compounds include nutrients i such as fertilizers or vital trace minerals, insecticides, acaricides , nematicides, molluscicides, herbicides, fungicides, pheromenes, odorants, fragrances, attractants, repellants, and innocuous materials for scientific effort, keyed to elucidating spray equipment design, spray effects depending upon environmental influences, and the like, or other materials where rapid and controlled delivery to a given target is desired. Specific examples of these classes of particles are set forth below.

Trace Nutrients Zinc chloride Zinc sulfate Ferric chloride Ferric sulfate Copper sulfate Copper oxychloride Boric acid Sodium borate Sodium selenate Cobalt sulfate Sodium molybdate Manganese chloride 2031 20 Insecticides and Acaricides 0,0-diethyl-0-p-nitrophenyl phosphorothioate (Para-thion) 0,O-dirnethyl-O-p-nitrophenyl phosphorothioate (Methyl parathion) 0,O-dimethyl-O-(3-methy1-4-nitrophenyl)phosphorothioate (Sumithion) 0,0-diethy1-0-(2-isopropyl-5-methyl-5-pyrimidiny1) phosphorothioate (Diazinon) 0,O-dimethyl-O-[3-methyl-4-(methylthio)phenyl]phosphorothioate (Fenthion) Pyrethrin-piperonyl butoxide 1-naphthyl methylcarbamate (Carbaryl) 2-(1-methylethoxy)phenol methylcarbamate (Baygon, manufactured by Chemagro) 2-methyl-2-(methylthio)propionaldehyde-0-(methyl carbamoyl) oxime (Aldicarb, manufactured by Union Carbide) S-methyl N-[methylcarbamoyl(oxy)3 thioacetamide (lannate) Chlorinated camphene, 6 7 percent Octachlorocamphene (Toxaphene, manufactured by Hercules) 2Q Tricalcium aresenate Sodium aluminum fluoride Dichlorodiphenyltrichloroethane Tricyclohexyltin hydroxide (Plictran, manufactured by Dow Chemical) 2 5 Nematicides 0,0-diethyl-o-2,4-dichlorophenyl phosphorothioate (dichlofenthion) O-Ethyl S,S-dipropyl phosphorodithioate (Ethoprop) Molluscicides Copper sulfate Tributyltin fluoride n-tritylmorpholine (trifenmorph) Sodium pentachloro- phenate 2031 20 Herbicides 2 , 4-dichlorophenoxyacetic acid (2,4-D) Alkylamine salts of 2,4-D 5 Butoxyethanol ester of 2,4-D 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) 2-(2,4,5-trichlorophenoxy)propionic acid (Silvex) 3-amino-2,5-dichlorobenzoic acid (chloramben) 3,6-dichloro-0-anisic acid (Dicamba) 2 , 3,6-trichlorophenylacetic acid (Fenac) 2,6-dichlorobenzonitrile (Dichlobenil) N,N-diallyl-2-chloroacetamide (Handox) S-Ethyl diisobutylthiocarbamate (Sutan) Isopropyl N-(3-chlorophenyl) carbamate (chloropropham) 3-amino-l,2,4-triazole ('Amitrole) 2-chloro-4,6-Bis(ethylamino)-S-triazine (Simazine) 2-chloro-4~ethylamino-6-isopropylamino-S-triazine (Atrazine) Fungicides Triphenyltin acetate Methyl-1-(butacarbamoyl)-2-benzimidazole carbamate (Benomyl) The self-encapsulating polymeric-containing 25 solution is applied by ejecting or spraying a liquid solution or emulsion from known or conventional spray equipment. Such spray equipment can be affixed to any suitable vehicle such as an aircraft, truck, a spray system in a 30 field, and the like, utilizing techniques and artifices common to the particular art, for example, as in the agricultural and public health areas. Subsequently and immediately after ejection, the spray during flight through the intervening atmosphere rapidly loses 35 solvent via evaporation, coacervation occurs, and small solid spheres are formed having generally a very 2031 2 0 uniformed shape and size. Thus, in-flight encapsulated particles are produced during the short passage between the egress of a spray or ejection apparatus and a target area with the delivered encapsulated product being a 5 solid. Each sphere or microcapsule is comprised of an outer enveloping polymeric membrane and an inner core of the particle or an agglomeration of particles. The encapsulated product can be delivered to and within the target area using narrow spectrum sprays 10 (for example, that produced by the Beeco Mist Nozzle, designed to provide a sufficient transport of the active ingredient to its target area). Generally, the various spray systems can be adjusted such that a few ounces of the composition or solution is utilized 15 for each acre or up to about 2 to 5 gallons of solution per acre. In the latter case, water is generally utilized as a solvent.

Moreover, applicants' composition, solution and process, aided by the film-forming polymer coat-20 j_ng of a particle or particles, can result in fairly uniform-sized encapsulated products, that is, encapsulated products in which at least 9 0 percent of the products fall within a narrow range, and as set forth hereinabove. Of course, the size of the 25 encapsulated products can be varied by changing the proportion of the various ingredients, the amount of crosslinking agent, and the like, as set forth hereinbelow as well as utilizing different spray equipment, particularly the nozzles thereon which 30 largely determine the initial egress droplet size spectrum. Thus, encapsulated products having a particle size of from 1 micron to 500 microns or larger can be produced. Generally, however, encapsulated products of from about 1 to about 100 microns are 35 desired for many applications. ft. specific example 2031 20 of a suitable spraying apparatus which delivers droplets over a narrow range is manufactured by the Beeco Products Corporation. As a rough rule of thumb, the encapsulated particle size will be 80 percent of the 5 initial droplet size leaving a spray or ejecting apparatus, when the amount of solvent is equal to the amount of particles on a weight basis. Since great uniformity and droplet size as well as the encapsulated product can be controlled as described herein, 10 the microcapsules of the present invention are ideal as a research tool for the study and evaluation of spray equipment and effects of atmospheric parameters upon the spraying art.

Additionally, ihicro-encapsulated products 15 of the present invention result in a controlled leaching rate of the particular particle at the site of application or target area so that the particle availability is greatly prolonged and leads to greater efficacy, reduced contamination, and economic 20 benefit. Also, non-persistent agents can be encapsulated and essentially rendered persistent at the microcapsule application site, so that once released in the environment, it becomes subject to natural . degradation factors so that persistency is low at the 25 site of application; again a positive contribution to enhance environmental quality.

In addition to varying the components of the system, additional com pounds or agents may be added to the solution to 30 control various parameters or functions such as capsule size, the enveloping polymeric membrane thickness, the leaching rate, the rate of evaporation, the emitted droplet size, adhesion, and the like. Naturally, such additives should,not have any chemical 35 interaction with any of the components of the system. 2031 2 Generally, the enveloping polymeric membrane of the polymers and, parti cularly, the preferred interpolymer have relatively little environmental resistance and, thus, the 5 effects of the rain and sun are detrimental to the longevity of the particle. However, longevity can be enhanced in several ways as by increasing the amount or thickness of the enveloping polymer membrane. This can be achieved by utilizing a greater ratio of 10 polymer. Moreover, longevity can be increased by utilizing specific types of polymers such as various specific interpolymers which show improved leaching rates over similar polymers. Crosslinking agents may also be added to the(SOlution -so that, upon encap-15 sulation, the polymeric membrane is crosslinked.

Crosslinking decreases the pore size and, hence, increases duration or longevity so that the final particle may be utilized over a period of several months. Suitable crosslinking agents include the 20 alkaline earth metal salts wherein the alkaline earth is beryllium, magnesium, barium, or preferably, calcium. Suitable anions include carbonate, bicarbonate, nitrate, oxide, hydroxide, and the various halogens, for example, F , Cb , I , and Br . Of 25 these, the calcium salts, especially calcium hydroxide, are desirable and calcium chloride is preferred. Moreover, the interpolymers may be crosslinked with zinc oxide as taught in U. S. Patent No. 3,749,772 Generally, the extent of the crosslinking agent may 30 range from about 0.01 to about 0.5 percent by weight based upon the total weight of the solution with the range of from about 0.05 to about 0.25 being preferred. Naturally, the crosslinking agents should be non-toxic, generally, non-reactive with the components, * I and soluble in the solvents of the present invention. 2031 The self-encapsulating polymeric-containing solution generally, must be maintained in relatively a non-acidic state, usually at a pH of 6.5 to 8.0, to prevent corsslinking 5 prior to solvent evaporation. Typical alkaline agents may be utilized to achieve such a pH range, such as ammonia, sodium hydroxide, and the like. Normally, only very small amounts are required as on the range of 0.01 to about 1.0 percent by weight 10 of the total solution.

In many applications, especially those involving the delivery of insecticides to protect crops and the like, long term adhesion of the microcapsule to foliage or other plant structures is 15 desired. Improved adhesion can be obtained by generally utilizing the lower molecular weight interpolymers and/or adhesive agents such as small amounts of alkyl esters as from 0.01 to 3 percent by weight based upon the total solution. The alkyl esters are 20 of the formula 0 I! Rl- C—° —R2 where and R^ contain from 2 to 5 carbon atoms with 25 Ethyl acetate being preferred.

The effect of the various ingredients upon the membrane thickness, adhesion, longevity of release and the like will be better understood by reference to Table I which sets forth formulations 30 in Examples 1 through 12. In Example 1, the interpolymer utilized was 16 percent of a high molecular type such as Carboset 52 5, 50 percent by weight of alcohol, and 34 percent by weight of the particle. In Example 1, the particle was actually in solution 35 as a 50-50 mixture of benzoic acid and ortho-toluic 2031 2 acid. This example, as well as the other examples were sprayed through a Beeco Mist spray gun utilizing a 60-micron pore size nozzle. The polymeric film totally encapsulated the crystallized acids used as a 5 particle and the encapsulated product were spheres. Example 2 illustrates a crosslinked version of Example 1 wherein calcium chloride was used as a crosslinking agent along with a small amount of ammonia to prevent premature crosslinking prior to solvent 10 evaporation. The thickness of the polymer membrane was greater than that for Example 1. Decreasing the average molecular weight of the polymer component as in Example 3 decreases the membrane or wall thickness and, thus, lowers the field life of the capsule. For r long life, that is from about 3 to 6 months, the polymer of Example 4 may be crosslinked as shown in Example 5.

As previously noted, the use of low molecular weight polymers provide some degree of tackiness so 20 that the encapsulated product will adhere to leaves, stems, and the like. However, since lower molecular weight polymers are often diliterious to film-forming properties, increased adhesion time of several weeks and even several months can be obtained by 2 5 adding small amounts of ethyl acetate or butyl cello-solve, as set forth in the formulation of Example 6. The process of adhesion promotion is as follows. Utilizing the formulation of Example 7, the microcapsule forms and crosslinking occurs, as soon as the 30 alcohol and ammonia evaporate, the process being essentially complete in a few seconds after the egress from a spraying apparatus and also depending upon the droplet surface area. However, the ethyl acetate or butyl cellosolve is occluded by the forming envelope 35 and, thus, for the most part, is''present at the time 2031 2 of foliage contact. At the instant of such contact and for several seconds thereafter, the ethyl acetate moves from the microcapsule, penetrating the outermost dermis of the plant. This process, mainly a 5 desorption phenomenon, results in a slight flow of the polymer envelope into the foliage structure, thus enhancing adhesion. The process is rapid and relies on a very minute quality of an adhesive aid, such as ethyl acetate. Moreover, no damage to agricultural 10 important plants arises from momentary contact with the ethyl acetate.

Water systems and water/alcohol systems have also been utilized as where the uses of a diluted alcohol would be advantageous. Examples 8 and 9 15 illustrate such systems', based upon a water soluble interpolymer, particularly, Carboset XLII. In Example 8, a pure water system is utilized and, hence, the particles are limited to water soluble compounds. Although this formulation is of poor environmental re-20 sistance, it is used in delivering trace nutrients such as water soluble zinc, copper, iron, and other salts. The formulations of Examples 8 and 9 result in capsule formation during flight, but due to the amount of 1^0 present at the time of impact, the 25 effects may be a soft capsule that flows to meet the contour of the impingement surface. Rigid spheres are usually not formed. Such systems may also be crosslinked and adhesion promoted. In contrast, the porosity of a microcapsule may be enhanced by the 30 utilization of an alcohol insoluble with a water soluble additive such as calcium benzoate, calcium hydroxide, and calcium carbonate. Considering Example 10, during in-flight encapsulation, most of the calcium chloride is trapped within a polymer mem-35 brane. However, once the crosslinked capsule has 2 031 2 adhered to a given surface and comes into contact with water, the porosigen, calcium benzoate, is rapidly lost through leaching and a pore structure remains allowing water penetration of the core particle.

When calcium hydroxide is used as in Example 11, it not only serves to crosslink the polymer but also imparts alkalinity and, thus, no ammonia is necessary. Since calcium hydroxide is alcohol soluble, a considerable fraction is found in the core area. However, 10 sufficient quantities exist within the polymer envelope to enhance the growth of porosity. «k o INGREDIENT Carboset 525 16% 16% Carboset 526 Carboset XLll Carboset 514 Ethanol 50% 50% Water Ethyl Acetate Calcium Chloride — 0.1% Ammonia — 0.05% Calcium Benzoate Calcium Hydroxide Laurie Acid — -- Agent 34% 33.85% TABLE I RECIPE EXAMPLE 8% 6% 6% 6% 1% 7% 8% 6% 50% 69% 69% 66% 0.2% 0.1% 1% ^ i 33% 18% 17.7% 21% N) O C4 NJ O ' I M <► n TABLE I (continued) RECIPE INGREDIENT EXAMPLE 11 12 Carboset 525 Carboset 526 Carboset XLll Carboset 514 Ethanol Water Ethyl Acetate Calcium Chloride Ammonia Calcium Benzoate Calcium Hydroxide Laurie Acid Agent 6% 6% 66% 1% 0 . 2% 0.1% 4% 89.75% 6.25 87.5% 12% 12% 11% 12% 37.85% 27% 7% 15% 0.1% 0.05% 1% 12% 10% 44% .7% 6.25% 6.25% % 32% 3% 31% 2031 The invention will be better understood by reference to the following additional examples.

EXAMPLE A A solution containing 75 parts by weight of pyrethrin-piperonyl butoxide, 25 parts by weight of Carboset 525, and 100 parts by weight of ethanol was made. The solution was mixed and added to a manual spray ejector such as a hand-operated atomizing pump. 10 The solution was sprayed in the direction of glass fibers located approximately 1 to 2 feet away from the egress of the spray pump. Upon spraying, the Carboset encapsulated the pyrethrin-piperonyl butoxide The graphic analysis, as, shown in photographs 1 15 through 4, clearly depicts the polymeric film formed about the pyrethrin-piperonyl butoxide particle. The glass strands in all photographs are 10 microns in diameter. As apparent from the photographs, Fig. 1 definitely shows a polymer formed about the particle, 20 with the polymer adhered to a glass strand. In Fig. 2 the polymer is formed about the intersection of two strands with another encapsulated particle located about a single strand. Fig. 3 discloses the encapsulated film being located about the liquid particle. 25 in this photograph, the film actually formed com pletely about a portion of the glass strand. Fig. 4 is similar to Fig. 2 in that it reveals a polymeric film formed about the intersection of two glass strands with a liquid particle being located therein.

EXAMPLE B Thirty parts by weight of Carboset XL11 having a molecular weight of approximately 4 5,000 and a 30 percent aqueous dispersion was mixed with 35 100 parts of water. To this was added 120 parts 1 of Dursban containing 7 5 percent of an active ingredient of 0,0-diethy1-0-3,5,6-trichloropyridinyl-thrionophosphate. These ingredients were mixed and the solution had a pH of 6.7. Utilizing a hand spray 5 pump, the solution was sprayed towards a target area. Photographs reveal that the active ingredient was fully encapsulated by the particle.

While having described the invention in accordance with the patent statutes, the invention 10 is measured by the following claims. 203120

Claims (8)

WHAT WE CLAIM IS:

1. An inflight insitu encapsulated particle, comprising: a particle, said particle coated with a film-forming polymer, said polymer being selected from the class consisting of (a) a polyvinyl acetate, (b) a polyvinyl ether wherein the repeating unit has from 3 to 10 carbon atoms, (c) an acrylic polymer or a copolymer made from monomers having the formula O (I) h2c or, where R^ is hydrogen or an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 30 carbon atoms and R2 is hydrogen or, an alkyl, cycloalkyl, aryl, or aralkyl having from 1 to 12 carbon atoms, and (d) the salt of .(1) an interpolymer having the structure R t ch_— c 2 I c=0 I oh fi ch0— c 2 | r° nh — n — ch2oh ch — ch ~ 2 I c=0 i 0r„ CH. h. c=0 i °R3 y *— (ii) wherein R and R^ are members of the group consisting of hydrogen and methyl; R2 is a member of the group consisting of methyl, ethyl, propyl ana butyl; R^ is a member of the group consisting of methyl and ethyl; n represents from 3 to 12 weight percent based on the combined weight of n,x,y and z; 14- OCT 1983 | -32- 203120 x represents from 8 to 25 weight percent based on the combined weight of n, x, y and z; y represents from 45 to 89 weight percent based on the combined weight of n, x, y and z; z represents from 0 to 44 weight percent based on the combined weight of n, x, y and z; the sum of the numerical value n + x + y + z is always exactly 100 and the groups n, x, y and z are present in a heterogeneous relative position and (2) a member of the group consisting of ammonia, hydrazine, a low boiling point primary aliphatic amine and a low boiling point secondary aliphatic amine, said salt being soluble in water in the pH range of from 5 to 8, and com binations thereof.

2. An encapsulated particle according to Claim 1 wherein the molecular weight of said polyvinyl acetate ranges from 10,000 to 100,000 wherein the molecular weight of said polyvinyl ether ranges from 10,00 0 to 100,0 00, wherein the molecular weight of said acrylic polymers ranges from 10,000 to 600,000, and wherein the molecular weight of said interpolymer ranges from 20,000 to 1,000,000.

3. An encapsulated particle according to Claim 2, wherein said polymer has been cross-linked, said crosslinking agent being selected from the class consisting of an alkalineearth salt, said alkalire earth salt being selected from the class consisting of calcium, barium, beryllium and magnesium, said anion portion of said salt, being selected from the class consisting of carbonate, bicarbonate, oxide, hydroxide, nitrate, F , Cl , I and Br . -33- 203120

4. An encapsulated particle according to Claim 2, wherein s^id polymer is said interpolymer.

5. An encapsulated particle according to Claim 4, wherein the molecular weight of said interpolymer ranges from ... 30 ,000 to ; 250,000.

6. An encapsulated particle according to Claim 5, wherein said particle is selected from the class consisting of insecticides, fungicides, herbicides, nutrients, trace minerals, nematicides, molluscicides, acaricides, pheromones, odorants, attractants, fragrances and repellants.

7. An encapsulated particle according to Claim 6, wherein said trace mineral is selected from the class consisting of zinc chloride, zinc sulfate, ferric chloride, ferric sulfate, copper sulfate, copper oxychloride, boric acid, sodium borate, sodium selenate, cobalt sulfate, sodium molybdate, and manganese chloride, wherein said insecticides and said acaracides are selected from the class consisting of pyrethrin-piperonyl butoxide, 0,O-dimethy1-0-p-nitrophenyl phosphorothioate, O,O-dimethyl-0-(3-methy1-4-nitrophenyl) phosphorothioate, 0,0-diethyl-O- (2-isopropy1-6-methy1-5-pyrimidiny1) phosphorothioate, 0,C—dimethy1-0-l3~methyl-4-(methylthio) phenylj phosphorothioate, 1-naphthyl methy1-carbamate, 2-(1-methylethoxy) phenol methylcarbamate, 2-methyl-2- -34- ? 1 O 20 (methylthio) propionaldehyde-O-(methyl carbamoyl) oxime, S-methyl-N[(methyl carbamoyl) (oxy)] thioacetamide, chlorinated camphene, 67 percent octachlorocamphene/ tricalcium arsenate, sodium aluminum fluoride, dichlorodi-phenyltrichloroethane, and tricyclohexyltin hydroxide; wherein said nematicides are selected from the class consisting of 0,0-diethyl-0-2,4-dichlorophenyl phosphorothioate and 0-ethyl S,S-dipropyl phosphorodithioate; wherein said moluscicides are selected from the class consisting of copper sulfate, tributyltin fluoride, n-tritylmorpholine and sodium pentachlorophenate; wherein said herbicides are selected from the class consisting of 2,4-dichlorophenoxyacetic acid, alkylamine salts of 2,4-D, butoxyethanol ester of 2,4-D, 2,4,5-trichlorophenoxyacetic acid, 2-(2,4,5-trichlorophenoxy) propionic acid, 3-amino-2, 5-dichlorobenzoic acid, 3,6-dichloro-0-anisic acid, 2,3,6-trichlorophenylacetic acid, 2,6-dichlorobenzonitrile, N,N-diallyl-2-chloroacetamide, isopropyl N-(3-chlorophenyl) carbamate, S-ethyl diisobutylthiocarbamate, 3-amino-l, 2,4-triazole, 2-chloro-4,6-Bis(ethylamino)-S-triazine, and 2-chloro-4-ethylamino-6-isopropylamino-S-triazine; and wherein said fungicides are selected from the class consisting of triphenyltin acetate and methyl-1-(butylcarbamoyl) 2-benzimidazole carbamate.

8. An encapsulated particle substantially as hereinbefore described with reference to the examples. WEST-WALKER, McCAEE ATTORNEYS FOR THE APPLICANT