Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Reexamination Certificate
1997-04-07
2001-06-19
Webman, Edward J. (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
C424S408000, C264S004700
Reexamination Certificate
active
06248364
ABSTRACT:
BACKGROUND OF THE INVENTION
Use of interfacial condensation to encapsulate substances such as pharmaceuticals, pesticides and herbicides is discussed in U.S. Pat. No. 3,577,515, issued on May 4, 1971. The encapsulation process involves two immiscible liquid phases, one being dispersed in the other by agitation, and the subsequent polymerization of monomers from each phase at the interface between the bulk (continuous) phase, and the dispersed droplets. The immiscible liquids are typically water and an organic solvent. Polyurethanes and polyureas are included in the types of materials suitable for producing the microcapsules. The use of emulsifying agents (also known as suspending or dispersing agents) is also discussed. The United States patent discloses formation of microcapsules comprising a polymeric sphere and a liquid centre, ranging from 30 micron to 2 mm in diameter, depending on monomers and solvents used.
United Kingdom Patent No. 1,371,179 discloses the preparation of polyurea capsules for containing dyes, inks, chemical reagents, pharmaceuticals, flavouring materials, fungicides, bactericides and pesticides such as herbicides and insecticides. The capsules are prepared from various di- and polyisocyanates in a dispersed organic phase. Some of the isocyanate present reacts to yield an amine which reacts further with remaining isocyanate at the interface with water and subsequently polymerizes to form a polyurea shell. The aqueous phase also contains a surfactant, for example an ethoxylated nonylphenol or a polyethylene glycol ether of a linear alcohol. In addition, the aqueous phase contains protective colloids, typically polyacrylates, methylcellulose and PVA. Particle sizes as low as 1 micron are exemplified. Encapsulation of insect hormones and mimics are among the systems mentioned.
U.S. Pat. No. 4,046,741 and U.S. Pat. No. 4,140,516 appear to relate to developments of the process disclosed in United Kingdom Patent No. 1,371,179. According to U.S. Pat. No. 4,046,741, a problem with microcapsules is instability caused by evolution of carbon dioxide from residual isocyanate entrapped in the microcapsules. U.S. Pat. No. 4,046,741 discloses a post-treatment of polyurea microcapsules with ammonia or an amine such as diethylamine. This removes the residual isocyanate, allowing subsequent storage of the microcapsules at lower pH's without generation of carbon dioxide. U.S. Pat. No. 4,140,516 discloses the use of quaternary salts as phase transfer catalysts to speed up the formation of polyurea microcapsules.
U.S. Pat. No. 4,417,916 discloses encapsulation of water-immiscible materials such as herbicides in a polyurea shell. A polyisocyanate and a polyamine are used to form the polyurea, and the invention appears to reside in the use of a lignin sulfonate compound as emulsifier in the polyurea-forming reaction. The concentration range of water-immiscible material encapsulated in the examples listed is 320 to 520 g/L of composition.
U.S. Pat. No. 4,563,212 is similar in teaching to U.S. Pat. No. 4,417,916, but uses emulsifiers other than lignin sulfonates, particularly sulfonated naphthalene formaldehyde condensates and sulfonated polystyrenes.
European Patent No. 611 253 describes reaction of polyisocyanates and polyamines to encapsulate materials such as pesticides in polyurea, using non-ionic surfactants that are block copolymers containing hydrophillic blocks together with hydrophobic blocks.
Canadian Patent No. 1,044,134 is concerned with microencapsulation of insecticides, particularly pyrethroids. The insecticide is dissolved, together with a polyisocyanate, in a water-immiscible organic solvent. The solution in organic solvent is then dispersed in water by agitation, and a polyfunctional amine is added while agitation is continued. The polyisocyanate and the polyfunctional amine react to form a polyurea shell wall that surrounds the dispersed droplets containing the insecticide.
Canadian Patent No. 1,179,682 discusses encapsulation of pheromones. Microcapsules containing pheromones are produced from toluene diisocyanate and ethylene diamine and/or diethylene triamine. In one described embodiment, a polyamine in the form of a salt is added to a dispersion of isocyanate, to allow polymerization to be initiated by addition of a base. It is said that this may improve the stabilization of behaviour modifying compounds that are aldehydes, but this is not exemplified. Canadian Patent No. 1,179,682 states that pheromones are photolabile and lose efficacy after exposure to sunlight. A tertiary phenylene diamine is used as a light stabilizer, and is added with the water-immiscible phase so that it is ultimately encapsulated with the pheromone.
SUMMARY OF THE INVENTION
In one aspect the present invention provides a process for encapsulating a partially water-miscible organic material within a polyurea or polyurethane shell, which process comprises:
(a) providing an aqueous phase containing a surfactant;
(b) dispersing in said aqueous phase a water-immiscible organic solvent in which the partially water-miscible material to be encapsulated and a polyisocyanate are dissolved or dispersed, to form a dispersion of droplets of organic solvent in the continuous aqueous phase;
(c) adding to the dispersion a water-soluble tertiary amine;
(d) thereafter adding to the dispersion a polyfunctional compound containing functional groups selected from the group consisting of primary amine, secondary amine and hydroxy groups, whereby there is formed discrete capsules composed of the material encapsulated in a polyurea or polyurethane shell.
In another aspect the invention provides microcapsules composed of a material encapsulated within a polyurea or polyurethane shell, which microcapsules contain a water-soluble tertiary amine. In one preferred embodiment the encapsulated material is a partially water-miscible material and the amount of the partially water miscible material encapsulated is at least 5%, preferably at least 90%, based on the total weight of microcapsules.
In another aspect the invention provides microcapsules composed of a partially water-miscible organic material of molecular weight greater than about 100 and less than about 400 and containing at least one heteroatom, encapsulated within a polyurea or polyurethane shell, the amount of the said material encapsulated being at least 5%, preferably at least 9%, based on the total weight of the microcapsules.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention is concerned particularly, but not exclusively, with encapsulation of partially water-miscible organic molecules of compounds that have a molecular weight in the range of about 100 to about 400, especially about 150 to 300. The compounds contain a heteroatom that confers some degree of water-miscibility. For many compounds of interest the sole heteroatom is oxygen, and there may be up to three heteroatoms per molecule in, for instance, hydroxy-substituted or keto-substituted carboxylic acids. Unsubstituted carboxylic acids of course contain two oxygen atoms and simple aldehydes, ketones and ethers contain only one oxygen atom. Compounds that contain nitrogen and/or sulphur atoms are also of interest, however.
The compounds are released gradually over time from the microcapsules. This contrasts with microcapsules that release the active ingredient at one time when the shell of the microcapsule is ruptured. The encapsulated compounds may be aldehydes, alcohols, epoxy compounds, ethers, ketones, especially reactive ketones in which the double bond of the carbonyl group is conjugated with one or more double bonds, for example acetophenone where the carbonyl group is conjugated with double bonds of the aromatic ring. Of particular interest are biologically active compounds. For purposes of the present invention, the term “biologically active” means materials that affect the life processes of organisms. Materials that are biologically active include herbicides, pesticides, pharmaceuticals, and semiochemicals, including naturally and artificially produced pheromones. Mat
Barinshteyn Galina
Li Kai
Nielsen Kent E.
Sengupta Ashok
3M Innovative Properties Company
Bjorkman Dale A.
Webman Edward J.
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