pH-sensitive microcapsules

Details pH-sensitive microcapsules pH-sensitive microcapsules

1999-08-13

2002-12-31

Levy, Neil S. (Department: 1616)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

C424S417000, C424S409000, C504S355000, C514S752000, C264S004100, C525S497000, C427S213340

Reexamination Certificate

active

06500447

ABSTRACT:

BACKGROUND OF THE INVENTION
Microencapsulation is a well known method used to formulate water-immiscible materials. Microcapsules are usually designed to prevent their active ingredients from permeating the capsule wall during the storage period before use. For example, the active ingredient present in microcapsules which are formulated as a suspension concentrate may leak from the capsules during storage and cause undesirable changes in the toxicological properties and/or physical properties of the suspension. In particular, active ingredient leakage may effect the flow, viscosity and appearance of the suspension, and lead to crystal growth. Crystal growth is especially problematic because it increases the viscosity of the suspension, causes sediment formation in the suspension and may cause blockages in the equipment used to distribute the suspension.
In the past, thick walled microcapsules have been used to prevent permeation of water-immiscible active ingredients. However, thick walled microcapsules are not entirely satisfactory because they do not readily and/or completely release their active ingredients when used for their intended purpose.
Certain pH-sensitive poly(styrene) microcapsules are described by Kokufuta, et al in Biotechnology and Bioen-gineering, 32, 289-294 (1988). That paper discloses that poly(styrene) microcapsules are coated with a polyelectrolyte to make them pH sensitive. However, water-immiscible materials cannot be encapsulated by the process described by Kokufuta, et al.
Poly(L-lysine-alt-terephthalic acid) microcapsules which exhibit pH dependence are described by Miyauchi, et al, in Journal of Microencapsulation, 9 (3), 329-333 (1992). However, that paper only describes the preparation of water-containing microcapsules and does not disclose a method for the preparation of microcapsules containing a water-immiscible material.
It is, therefore, an object of the present invention to provide microcapsules which contain water-immiscible materials and rapidly release their contents when used for their intended purpose.
It is also an object of the present invention to provide storage stable, aqueous microcapsule compositions which do not readily crystallize. Those and other objects of the present invention will become more apparent from the detailed description thereof set forth below.
SUMMARY OF THE INVENTION
The present invention provides pH-sensitive micro-capsules which comprise a water-immiscible active ingredient within a shell wall wherein said shell wall has free carboxylic acid groups incorporated therein.
The present invention also relates to the pesticidal use of those microcapsules, compositions containing those microcapsules and a method for the preparation of those microcapsules.


REFERENCES:
patent: 3429827 (1969-02-01), Ruus
patent: 3577515 (1971-05-01), Vandegaer
patent: 3959464 (1976-05-01), DeJavigny
patent: 4360376 (1982-11-01), Koestler
patent: 4409201 (1983-10-01), Heinrich et al.
patent: 4563212 (1986-01-01), Becher et al.
patent: 4956129 (1990-09-01), Scher et al.
patent: 5120349 (1992-06-01), Stewart et al.
patent: 5302654 (1994-04-01), Iohii et al.
patent: 5750126 (1998-05-01), Smith et al.
patent: 93668 (1982-05-01), None
patent: 0611253 (1994-08-01), None
patent: 2280164 (1995-01-01), None
patent: WO 93/18853 (1993-09-01), None
patent: WO 94/13139 (1994-06-01), None
Kokufuta, E., et al., 1998, “Preparation of polyelectrolyte-coated pH-sensitive poly(styrene) microcapsules and their application to initiation-cessation control of an enzyme reaction”,Biotechnology and Bioengineering, 32, 289-294.
Miyauchi, E., et al., 1992, “Dependence on pH of permeability towards electrolyte ions of poly(L-lysine-alt-terephthalic acid) microcapsule membranes”,Journal of Microencapsulation, 9, 329-333.
Khare, A. R. and Peppas, N. A., 1991, “The structure and transport properties of environmentally sensitive hydrogels”,Polymer News, 16, (8), 230-236.

Affiliated with

Also associated with

Rating

pH-sensitive microcapsules does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with pH-sensitive microcapsules, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and pH-sensitive microcapsules will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2947886