Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Reexamination Certificate
1999-07-28
2003-04-08
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
C424S406000, C424S417000, C424S418000, C424S419000, C424S497000, C424SDIG008, C514S521000, C514S531000, C264S004300, C264S004700, C427S213330, C428S402210
Reexamination Certificate
active
06544540
ABSTRACT:
This invention pertains to certain microencapsulated compositions which contain an active ingredient encapsulated within a polymeric shell wall, particularly an aminoplast shell wall, in which the shell wall contains an ester containing a cross-linking unit, as well as processes for the production of such microcapsules, and methods for their use. The base-sensitive cross-linking unit triggers release of the encapsulated contents on exposure of the capsules to basic conditions.
The microcapsules of this invention have been found particularly suitable for use in producing encapsulated formulations of pesticides, for both agricultural and non-agricultural use. They are also suitable for encapsulated formulation of non-pesticidal agricultural chemicals such as plant growth regulators, insect growth regulators, fertilizers, and other agriculturally useful materials. In addition, they are useful for encapsulation of materials outside the agricultural field such as detergent powders.
In many instances, particularly in agriculture, the object of producing microencapsulated compositions has been to provide controlled release of the encapsulated active ingredient, and particularly to provide a release for longer term efficacy so that the active ingredient is released over a period of time and is available throughout the effective period. This is particularly significant for pesticides or other ingredients which are degraded or decomposed over a relatively short period of time under certain environmental conditions. Use of microencapsulated compositions in these situations provides effective activity of the encapsulated ingredient over a longer period of time since it will be released continuously into the environment in the amount needed rather than in one large initial dose.
Currently, microencapsulated pesticides are used primarily as preemergence pesticides, that is, they are applied to soil prior to the emergence of vegetation or the appearance of insects, so that they are available to kill or control newly emerged weed species or insects in their larval stages. Again, in those applications, relatively slow release rates are desired so that the pesticide is released into the environment over a period of time, usually over at least several weeks.
Microencapsulated formulations for quick release are known in a number of other applications, such as the printing and xerography industries, in which materials such as inks, pigments, toner particles, etc., are microencapsulated and released quickly upon application of physical force or heat. Microcapsules with comparatively quick release could have utility in agriculture in situations in which controlled release is not desired, but microencapsulation of the active ingredient is desired for any of a number of reasons. For example, microencapsulation can be desired to protect against dermal effects of pesticides during their handling (for instance, production, storage or loading into spray equipment). However, a comparatively quick release of the pesticide may be desired in order to make the pesticide readily available to control a pest, as is usually the case with nonencapsulated or non-controlled release formulations such as solutions, emulsions, dusts, powders, granules, etc. Another instance in which it is desirable to have encapsulation but comparatively quick release of a pesticide is in the production of pesticidal products containing two active ingredients which may be reactive with each other or otherwise incompatible in a single system.
Microencapsulation of pesticides may often provide an increase in the safety of pesticide handling, to the extent that the polymer wall of a microcapsule minimizes contact of the handler with the active pesticide, particularly if the pesticide is in the form of a suspension of microcapsules. The provision of a comparatively quick release microencapsulated formulation of a pesticide could minimize contact of a handler with the active pesticide, yet provide the necessary release of the active ingredient when applied to protect plants from an insect pest which is already present or about to invade. Additionally, such encapsulated products containing pyrethroids could be useful in industrial, commercial or residential pest control.
SUMMARY OF THE INVENTION
This invention provides microcapsules which satisfy the above-mentioned objectives.
In one aspect, this invention comprises a microcapsule formed of an aminoplast shell wall and an encapsulated ingredient or ingredients enclosed within the wall, the wall produced by a microencapsulation process comprising reacting an amino resin prepolymer with a compound having one or more ester or thioester groups which are cleaved under basic conditions and two or more other functional groups capable of reacting with the resin.
Preferably this compound is a cross-linking agent produced by reaction of a multifunctional C
1
-C
20
aliphatic or cycloaliphatic alcohol containing at least two, preferably at least 3, functional groups which are capable of esterification, such as pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, glycerol, mercaptoethanol, 3-mercaptopropane-diol, 1,2,4-butanetriol, 1,3,5-cyclohexanetriol, 1,2,3-heptanetriol, sorbitol, or 2,3-dimercapto-1-propanol with one or more 2-(hydroxy or thiol) substituted C
2
-C
6
alkanoic acids.
In another aspect, this invention comprises a process for the production of such microcapsules comprising reacting an amino resin prepolymer with a compound having one or more ester or thioester groups which are cleaved under basic conditions and two or more other functional groups capable of reacting with the resin.
Preferably this compound is a cross-linking agent produced by reaction of a multifunctional C
1
-C
20
aliphatic or cycloaliphatic alcohol containing at least two, preferably at least 3, functional groups which are capable of esterification, such as pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, glycerol, mercaptoethanol, 3-mercaptopropane-diol, 1,2,4-butanetriol, 1,3,5-cyclohexanetriol, 1,2,3-heptanetriol, sorbitol, or 2,3-dimercapto-1-propanol with a 2-(hydroxy or thiol) substituted C
2
-C
6
alkanoic acid.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to microcapsules containing an encapsulated substance which are cleaved in the presence of base; and can be designed so as to break down or disintegrate relatively quickly under basic conditions so as to release the encapsulated substance into the surrounding environment.
The microcapsules are characterized by having an aminoplast shell wall produced by a microencapsulation process comprising reacting an amino resin prepolymer with a compound having one or more ester or thioester groups which are cleaved under basic conditions and two or more other functional groups capable of reacting with the resin. Preferably the amino resin is an etherified resin.
Preferably this compound is a cross-linking agent produced by reaction of a multifunctional C
1
-C
20
aliphatic or cycloaliphatic alcohol containing at least two, preferably at least 3, functional groups which are capable of esterification, such as pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolpropane, glycerol, mercaptoethanol, 3-mercaptopropane-diol, 1,2,4-butanetriol, 1,3,5-cyclohexanetriol, 1,2,3-hepanetriol, sorbitol, or 2,3-dimercapto-l-propanol with one or more 2-hydroxy C
2
-C
6
alkanoic acids and/or 2-thiol C
2
-C
6
alkanoic acids. If the capsules are not in a basic environment, they function as typical diffusion controlled release microcapsules, permitting release of the encapsulated substance into the surrounding area in a controlled manner which is determined primarily by wall characteristics of the shells such as thickness, capsule size, permeability, etc. If, on the other hand, the capsules are placed in a basic environment, preferably in a situation in which the resulting pH is from about 8 to about 13, preferably from about 9 to about 11, the cross-linking moieties in the capsule wall are cleaved so as t
Follows Richard
Lee Kuo-Shin
Scher Herbert Benson
Shirley Ian Malcolm
Van Koppenhagen Juanita Elena
Levy Neil S.
Syngenta Limited
Townsend and Townsend / and Crew LLP
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