Particulate encapsulation of liquid beads

Details Particulate encapsulation of liquid beads Particulate encapsulation of liquid beads

2000-05-10

2002-07-02

Acquah, Samuel A. (Department: 1711)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Particulate form

C428S402200, C428S402210, C428S403000, C428S407000, C424S490000, C424S491000, C424S493000, C424S497000, C424S498000

Reexamination Certificate

active

06413548

ABSTRACT:

BACKGROUND OF THE ART
1. Field of the Invention
The present invention relates to the carrying of liquid materials within a readily rupturable form that can be easily released. In particular, the liquid materials may be provided in the form of a relatively stable encapsulation or microencapsulation that can be applied to a surface leaving little observable residue of the encapsulation mechanism.
2. Background of the Invention
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 water-soluble 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 coating 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 well-known process, 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 2,800,458 (Green, Jul. 23, 1957). An interfacial polymerization process is disclosed in U.S. Pat. Nos. 4,046,741 (Scher, Sep. 6, 1977) and 4,140,516 (Scher, Feb. 20, 1979), where film-forming reactants are dissolved in a hydrophobic liquid that is dispersed in water, the shell-forming reaction occurring at the interface when the phases are placed in contact as an emulsion. Another interfacial polymerization process is described in U.S. Pat. No. 3,726,804 (Matsukawa et al., Apr. 10, 1973) where all the film-forming ingredients initially reside in hydrophobic droplets 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, where an oil-insoluble polymer is formed at the surfaces of oil drops.
British Pat. Nos. 952,807 and 965,074 describe a process where a solid such as wax or a thermoplastic resin is melted, dispersed and cooled to form an encapsulating film around liquid droplets.
Microencapsulation of fragrances and hydrophobic liquid fill via the polyoxymethyleneurea (or urea-formaldehyde) method is taught by (Matson, 1970) U.S. Pat. No. 3,516,846.
U.S. Pat. No. 3,111,407 (Lindquist et al., Nov. 19, 1963) describes a spray drying method that forms encapsulated droplets at the instant of atomization.
U.S. Pat. No. 5,342,597 describes a method of providing “dry water” by mixing water and fumed silica under strong mixing conditions, providing a water droplet covered by silica particles in a highly distributional form, with low concentrations, if any, of true spheres of water surrounded by spherically disposed silica particles.
U.S. Pat. No. 4,008,170 discloses another format for providing silica and water, but not in an encapsulated silica shell water core format.
U.S. Pat. No. 6,045,650 describes surfaces that have coatings thereon which alter, control and/or adjust the hydrophobic/hydrophilic properties of the surface of the underlying material. As surfaces of specific compositions or materials have their own specific characteristic properties including surface charge and those properties with respect to their affinity for different types of materials (e.g., hydrophobicity, hydrophilicity, oleophobicity and oleophilicity, as well as polar and non-polar attractiveness), it is often desirable to be able to provide treatments and coatings which can affect and/or alter those innate properties. These treatments can allow for broader use or improved use of the materials in differing environments. The basic process of that invention comprises applying a liquid coating onto a surface (e.g., a flat, shaped, irregular or particulate surface) having a relative property (e.g., of hydrophobicity), the liquid coating comprising, consisting essentially of, or consisting of a first compound having an inorganic oxidizable group or moiety, and then oxidizing said first compound to form a second compound which is bound to the surface, the second compound changing said relative property. In most cases this relative property will change to greater hydrophilicity, depending upon the essential nature of the first compound used. Preferred compounds comprise inorganic or more preferably metallic, metalloid or semimetallic ester containing compounds such as oxides MxOy (as described above) and most preferably as silicon compounds such as silanes (e.g., Rm Si[OR1]n), that is compounds wherein R is an organic group (preferably bonded to the Si atom through a carbon atom), halogen or hydrogen, R1 is H, or an organic group, such as alkyl, aryl or heterocycle, preferably alkyl of 1 to 4 carbon atoms, wherein m is 0, 1, 2 or 3 and n is 1, 2, 3 or 4; titanate counterparts of the silanes, such as Rm Ti[O R1]n in which R, R1, m and n are as defined above; and any other oxidizable metallo or semimetallo compounds of the general formula Rm M[R1]n wherein M is a metal or semimetal such as those selected from the group consisting of Si, Ti, Zn, Al, Sn, Fe, Cu, Zr, B, Mg, Mn, W, Sb, Au, Ag, Cr, and the like, R and R1 are as defined above, m plus n equals the valence state of M, and n must be at least 1. In addition to the preferred silanes, mainly preferred because of their ease of use and ready commercial availability, silicon compounds such as silazanes, siloxane cyclics, siloxane dimers, siloxane trimers, silane fluids, and tris-(alkoxysiloxy)-3-methacryloxyalkylsilanes (less preferred) may be used in the practice of the present invention. In addition to these specific classes of compounds and metals/metalloids, and in addition to monometallic, monometalloid compounds as the starting materials, dimetallic (having two different metal/metalloid atoms, bimetallic (having two of the same metal/metalloid atoms in the compound), heterometallic (having one metal and one metalloid atom in the same compound), dimetalloid and bi-metalloid compounds, and mixtures of any of these groups of compounds are useful in the practice of the present invention. Mixtures and blends of the compounds provide unique capabilities for uniformly distributing different properties over a surface, or balancing (averaging) properties over the surface. An extremely wide range of these classes of oxidizable metal or metalloid compounds are commercially available, as exemplified by the lists of compounds in the 1996 Gelest, Inc. chemical catalog (e.g., pages 287 for a generic description of heterometallic and heterometalloid alkoxides, including alkali metal combinations; and especially pages 21-217; 220-221; 231-233; and 258-265) and the 1994 PCR, Incorporated General Catalog of “Chemicals for Research Scientists, especially pages 192-193 and 198-199). Germanium compounds have a functional similarity to silicon compounds in the practice of that invention

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