Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
1999-04-22
2001-02-20
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C528S354000, C528S361000, C524S604000
Reexamination Certificate
active
06190773
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a self-water dispersible particle made of a biodegradable polyester and a process for the preparation thereof. More particularly, the present invention relates to a self-water dispersible particle made of an extremely small biodegradable polyester having a size of the order of nanometer which can comprise various hydrophobic core materials encapsulated therein and a process for the preparation thereof.
The self-water dispersible particle made of a biodegradable polyester according to the present invention can find wide application such as various preparations (e.g., pesticide, pharmaceutical preparations, fertilizer), particularly gradually-releasable preparations, coating agents for fishing net, layer farming net, etc., coating for the bottom of ship, gradually-releasable repellent against small animals to be scattered over sandbox in park or the like, coating, ink, toner, adhesive, lamination for paper, foaming resin material, fire extinguishing agent, cosmetic material, construction material, etc.
BACKGROUND OF THE INVENTION
In an attempt to render pharmaceutical preparations or pesticides gradually releasable, extensive studies have been made of particulate or microcapsuled resin comprising a polyester, particularly a biodegradable polyester. For example, JP-A-6-72863 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-8-157389, and JP-A-9-208494 disclose a technique concerning gradually-releasable pharmaceutical preparations comprising a lactic acid-based polymer as an aliphatic polyester.
These microcapsulization processes include a process which comprises adding a solution or dispersion obtained by dissolving a lactic acid-based polymer which doesn't have hydrophilic groups sufficiently in an organic solvent and dissolving or dispersing medicines in the solution dropwise to an aqueous solution containing a surface active agent, stirring the mixture to form an oil-in-water type emulsion or adding the solution or dispersion dropwise to an oil immiscible with the solution or dispersion, stirring the mixture to form an oil-in-oil type emulsion, and then evaporate the solvent away from the emulsion to solidify the microcapsule (submerged drying process) and a process which comprises stirring the foregoing solution or dispersion while a solvent miscible with the solution or dispersion but incapable of dissolving the polymer (so-called poor solvent) is being added thereto so that the polymer undergoes phase separation to prepare a microcapsule (coacervation process).
The microcapsule obtained by these preparation processes comprises a constituent polymer which doesn't have hydrophilic groups sufficiently as defined herein and thus doesn't exhibit so-called self-water dispersibility. Thus, the addition of an auxiliary such as surface active agent during the preparation of microcapsule is indispensable. High speed agitation is required as well. Further, it is difficult to prepare extremely small particles having a size of the order of nanometer.
JP-A-6-313024 discloses a technique concerning an aqueous polyurethane resin prepared by neutralizing with a base a lactone-based polyurethane resin having a carboxylic acid comprising a lactone-based polyester polyol obtained by ring opening polymerization of lactone in the presence of a dihydroxycaboxylic acid as an initiator, a diisocyanate and a chain extender.
The above proposed method can provide a self-water dispersible particle as well. However, this method doesn't allow two or more carboxyl groups to be introduced into molecular chain unless diisocyanates, which are undesirable for living body or environment, are used. Further, in order to reduce the particle size of the particulate material to an extent such that it is rendered self-water dispersible, it is necessary to raise the acid value in the polymer. To this end, the particulate material needs to contain a large amount of urethane bond. Accordingly, the desired physical properties of polyester can be hardly maintained, causing deterioration of biodegradability.
Many methods for the preparation of capsulized pesticides obtained by microcapsulizing pesticide activator components have been known. For example, JP-A-6-362, JP-A-6-238159, JP-A-7-165505, JP-A-8-53306, JP-A-9-249505, and JP-A-9-57091 disclose a method for the preparation of capsulized pesticides by interfacial polymerization method using polyurea or polyurethane as a wall material.
Further, JP-A-5-155714 discloses a method for the preparation of capsulized pesticides involving the copolymerization of an unsaturated polyester resin with a vinyl monomer in the presence of a hardening initiator. JP-A-5-70663 discloses a method for the preparation of capsulized pesticides comprising acryl copolymer. All these methods comprise emulsion-dispersing a resin and a chemical in water, and then allowing the dispersion to undergo polymerization at particle interface or inside the particles to prepare a capsulized pesticide. An emulsifying agent is essential to disperse these components in water.
It has thus been desired to develop a particulate self-water dispersible biodegradable material having an average particle diameter as small as nanometer free of urethane bond and excellent in biodegradability, and a process for the preparation of a particulate self-water dispersible biodegradable material without using any isocyanate which is undesirable for living body or environment or emulsifying agent and any high rotary speed agitator.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a self-water dispersible particle made of a biodegradable polyester having varied average particle diameters of the order of nanometer, free of urethane bond and excellent in biodegradability, an aqueous dispersion thereof, a self-water dispersible particle made of a biodegradable polyester comprising a hydrophobic core material encapsulated therein excellent in gradual releasability such as pesticide, and a process for the simple preparation of these products without using any auxiliary stabilizing material such as emulsifying agent or any high speed agitator.
The inventors made extensive studies. As a result, a process for the simple preparation of a self-water dispersible particle made of a biodegradable polyester, an aqueous dispersion thereof, a self-water dispersible particle comprising a hydrophobic core material encapsulated therein excellent in gradual releasability such as pesticide without using any auxiliary stabilizing material such as emulsifying agent has been found which comprises reacting a biodegradable polyester having hydroxyl groups with a polyvalent carboxylic acid or anhydride or chloride thereof to obtain a biodegradable polyester having acid groups, adding a base to the biodegradable polyester in an organic solvent with stirring to neutralize to form the salt of the biodegradable polyester, and then adding water to the material so that it undergoes phase inversion emulsification. The present invention has thus been worked out.
The present invention has the following constitutions:
(1) A self-water dispersible particle made of a biodegradable polyester.
(2) The self-water dispersible particle made of a biodegradable polyester according to Clause (1), wherein said biodegradable polyester contains carboxyl groups and/or salt thereof.
(3) The self-water dispersible particle made of a biodegradable polyester according to Clause (2), wherein said biodegradable polyester has an acid value of from 4 to 200 KOHmg/g.
(4) The self-water dispersible particle made of a biodegradable polyester according to Clause (3), wherein said biodegradable polyester contains dimethylolpropionic acid residues.
(5) The self-water dispersible particle made of a biodegradable polyester according to any one of Clauses (1) to (4), wherein said biodegradable polyester is a lactic acid-based polymer.
(6) The self-water dispersible particle made of a biodegradable polyester according to any one of Cl
Ariga Nagao
Hirokawa Takashi
Imamura Shoji
Tsukuda Kazuaki
Watanabe Yasuyuki
Acquah Samuel A.
Armstrong, Westerman Hattori, McLeland & Naughton
Dainippon Ink and Chemicals Inc.
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