O USOO5332584A United States Patent (19) 11) Patent Number: 5,332,584 Scher et al. 45 Date of Patent: k Jul. 26, 1994 54) MICROCAPSULES 4,221,710 9/1980 Hoshi et al. ..................... 264/4.7 X (75) Inventors: Herbert B. Scher, Moraga; Marius 4,223,023. 2,3-1980 Ea.Rai - - - - - a a a -a - 428/402.214. i. Rodson, El Cerrito, both of Calif. 4,576,891 3/1986 Adair et al. .. ... 428/402.21 X 73 Assignee: Zeneca Inc., Wilmington, Del. 4,956,1295,160,529 11/19929/1990 Scher et al. ..................................................... 264/4.771/118 * Notice: The portion of the term of this patent subsequent to Sep. 11, 2007 has been OTHER PUBLICATIONS disclaimed. Nylen et al.: Modern Surface Coatings, Interscience (21) Appl. No.: 803,870 Publishers, New York, (1965), pp. 190-193. 22 Filed: Dec. 9, 1991 Primary Examiner-Richard D. Lovering Attorney, Agent, or Firm-Joel G. Ackerman Related U.S. Application Data 57 ABSTRACT 63 Continuation of Ser. No.a 540,560,- Jun. 20, 1990, aban- A process is disclosed forf the microencapsulation of a g 3. "Yes i. NR substantially water-insoluble liquid material within a tion-in-pfS.N.366. No porous shell to effect a slow rate of release of said mate doned, which is a continuation-in-part of Ser. No. rial through said shell which comprises (a) providing an 499,973, Jun. 1, 1983, abandoned, which is a continua- organic Solution comprising said material and an etheri tion-in-part of Ser. No. 201,686, Oct. 30, 1980, aban- fied urea-formaldehyde prepolymer dissolved therein in doned. which from about 50% to about 98% of the methylol 51) Int. Cl.5Vak ea e o a no ooooooo so A01N 25/28:9 AON 37/18: groups of said prepolymer have been etherified with a B01J 13/18 C4-C10 alcohol; (b) creating an emulsion of said organic 52) U.S. Cl 424/408; 71/DEG. : solution in an continuous phase aqueous solution com Ohio Yaake ou o aw o a o on a a o 0 0 e o 0 & 8 s> & 4 so a us a so 9 • as prising water and a surfaceactive agent, wherein said 26/2: 2.78.7. emulsion comprises discrete droplets of said organic 58) Field of Search 264/4.3, 4.33, 4.7: solution dispersed in said continuous phase aqueous o solution, there being formed thereby an interface be 428/402.21; 424/40s:ARE's tween the discrete droplets of organic solution and the surrounding continuous phase aqueous solution; and (c) 56 References Cited causing in situ self-condensation and curing of said urea U.S. PATENT DOCUMENTS formaldehyde prepolymers in the organic phase of said discrete droplets adjacent to said interface by simulta 3,016,308 1/1963 Macaulay - - - - - - - - - - - - - - - - - - 264/4.6 X neously heating said emulsion tO a temperature between 3,074,845 1/1963 Geary .................................... 424/19 about 20 C. to about 100 C., and adding to said emul 3:63 Slyay .... 427 s: sion an acidifying agent and maintaining said emulsion 35ió941 6/1970 Mason. ... 264747 X at a pH of between about 0 to about 4 for a sufficient 3,686,015 8/1972 Powell et al.. ... 264/4.3 X period of time to allow substantial completion of in situ 4,001,140 1/1977 Foris et al............. 264/4.7 x condensation of said resin prepolymers to convert the 4,073,968 2/1978 Miyamoto et al. ................... 427/54 liquid droplets of said organic solution to capsules con 4,087,376 5/1978 Foris et al......... ... 264/4.7 X sisting of solid permeable polymer shells enclosing said 4,089,802 5/1978 Foris et al. .... ... 264/4.7 X liquid material. 2: $3. Siaka 223: Also disclosed are the microcapsules formed by the 4,157,983 6/1979 Golden ...... .264/467 x above-described process. 4,219,604 8/1980 Kakimi et al. ...................... 428/307 4,219,631 8/1980 Hunsucker et al. ................. 525/398 15 Claims, No Drawings 5,332,584 1. 2 is released into the aqueous phase (the continuous phase MCROCAPSULES of the emulsion), and the film-forming materials accu mulate at the interface and polymerize. This is a continuation of Ser. No. 07/540,560, filed Olefin polymerization using a peroxide catalyst is Jun. 20, 1990 now abandonment which in turn is a con described in Japanese patent publication No. 9168/1961, tinuation of application Ser. No. 07/151,048, filed Feb. whereby an oil-insoluble polymer is formed at the sur 1, 1988 “now U.S. Pat. No. 4,956,129'; which in turn is faces of oil drops. a continuation-in-part application of Ser. No. 595,136, British Patent Nos. 952,807 and 965,074 describe a filed Mar. 30, 1984, now abandoned; which in turn is a process whereby a solid such as wax or a thermoplastic continuation-in-part application of Ser. No. 499,973, 10 resin is melted, dispersed and cooled to form an encap filed Jun. 1, 1983, now abandoned; which in turn is a sulating film around liquid droplets. continuation-in-part application of Ser. No. 201,686, U.S. Pat. No. 3,111,407 (Lindquist et al., Nov. 19, filed Oct. 30, 1980, now abandoned. 1963) describes a spray drying method which forms BACKGROUND OF THE INVENTION encapsulated droplets at the instant of atomization. 15 These processes vary in terms of equipment expense, A. Field of the Invention energy requirements, ease of controlling the microcap This invention relates to microcapsules and to a pro sule size, the need for extra reagents such as catalysts cess for their production. In particular, this invention and settling agents, and percent microcapsule phase. It relates to encapsulated droplets of a liquid material is therefore an object of the present invention to pro which is substantially insoluble in water, where the 20 vide a simple, inexpensive method for producing micro encapsulating agent is a film formed from a modified capsules of uniform and readily controlled size, which urea-formaldehyde aldehyde polymer. are suitable for use without further treatment. Other B. Description of the Prior Art objects of the invention will be apparent from the foll The use of membranes, coatings, and capsules for the lowing description. controlled release of liquid materials is well known in 25 the art of both agricultural and non-agricultural chemi SUMMARY OF THE INVENTION cals. In agriculture, controlled-release techniques have It has now been discovered that a liquid material improved the efficiency of herbicides, insecticides, fun which is substantially insoluble in water can be micro gicides, bactericides, and fertilizers. Non-agricultural encapsulated within a porous shell by a process which uses include encapsulated dyes, inks, pharmaceuticals, 30 comprises: flavoring agents, and fragrances. (a) providing an organic solution comprising said The most common forms of controlled-release mate material and an etherified urea-formaldehyde prepoly rials are coated droplets or microcapsules, coated solids mer dissolved therein in which from about 50% to including both porous and non-porous particles, and about 98% of the methylol groups of said prepolymer coated aggregates of solid particles. In some instances, a 35 have been etherified with a C4-C10 alcohol; water-soluble encapsulating film is desired, which re (b) creating an emulsion of said organic solution in an leases the encapsulated material when the capsule is continuous phase aqueous solution comprising water placed in contact with water. Other coatings are de and a surface-active agent, wherein said emulsion com signed to release the entrapped material when the coat prises discrete droplets of said organic solution dis ing is ruptured by external force. persed in said continuous phase aqueous solution, there Still further coatings are porous in nature and release being formed thereby an interface between the discrete the entrapped material to the surrounding medium at a droplets of organic solution and the surrounding contin slow rate by diffusion through the pores. In addition to uous phase aqueous solution; and providing controlled release, such coatings also serve to (c) causing in situ self-condensation and curing of said facilitate the dispersion of water-immiscible liquids into 45 unreaformaldehyde prepolymers in the organic phase of water and water-containing media such as wet soil. said discrete droplets adjacent to said interface by si Droplets encapsulated in this manner are particularly multaneously heating said emulsion to a temperature useful in agriculture, where water from irrigation, rain, between about 20° C. to about 100 C., and adding to and water sprays is frequently present. A variety of said emulsion an acidifying agent and maintaining said processes for producing such capsules is known. 50 emulsion at a pH of between about 0 to about 4 for a In one process, the capsules are formed by phase sufficient period of time to allow substantial completion separation from an aqueous solution through the coac of in situ condensation of said resin prepolymers to ervation of a hydrophilic colloid sol. This is described . convert the liquid droplets of said organic solution to in U.S. Pat. Nos. 2,800,457 (Green et al., Jul. 23, 1957) capsules consisting of solid permeable polymer shells and 2,800,458 (Green, Jul. 23, 1957). 55 enclosing said liquid material. An interfacial polymerization process is disclosed in Microcapsules formed by this process are capable of U.S. Pat. Nos. 4,046,741 (Scher, Sep. 6, 1977) and effecting a slow rate of release of the encapsulated liq 4,140,516 (Scher, Feb. 20, 1979), whereby the film uid by diffusion through the shell to the surrounding forming reactants are dissolved in the hydrophobic medium.