Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
1999-07-29
2002-01-08
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C528S230000, C528S245000, C528S259000, C528S059000, C528S061000, C528S065000, C428S402240, C424S078080, C424S078360, C424S078370, C424S462000, C424S489000, C424S497000, C424S405000, C504S116100, C504S148000, C504S189000
Reexamination Certificate
active
06337130
ABSTRACT:
This invention pertains to certain microencapsulated compositions which contain an ingredient or ingredients encapsulated within a polymeric shell wall, particularly a polyurea shell wall, in which the shell wall contains one or more oligomeric unit sensitive to acidic conditions, as well as processes for the production of such microcapsules, and methods for their use. The oligomeric unit(s) enable(s) triggering of the release of the encapsulated contents on exposure of the capsules to acidic conditions.
The microcapsules of this invention have been found especially suitable for use in producing encapsulated formulations of pesticides, for both agricultural and non-agricultural use. They are also suitable for use in encapsulated formulations 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 encapsulation of paint biocides for controlled release into paint films under mildly acidic conditions.
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 biologically active ingredients which are degraded or decomposed over a relatively short period of time or 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. Rapid or quick release microcapsules 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 toxicity effects of pesticides during their handling (for instance, production, storage or loading into spray equipment). However, a quick release of the pesticide may be desired in order to make the pesticide immediately 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 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 triggered release microencapsulated formulation of a pesticide could minimize contact of a handler with the active pesticide, yet provide the necessary quick release of the active ingredient when applied to protect plants from an insect pest which is already present or about to invade. Additionally, triggered release encapsulated products containing pyrethroids could be useful in industrial, commercial or residential pest control.
SUMMARY OF THE INVENTION
This invention provides acid-triggered or -sensitive microcapsules which satisfy the above-mentioned objectives.
In one aspect, this invention comprises a microcapsule formed of a polyurea shell wall and an encapsulated ingredient or ingredients enclosed within the wall, the wall comprising at least one acid-sensitive oligomeric acetal moiety. In a preferred embodiment the acetal moiety as present in the capsule wall has the formula
in which
R is (a) a moiety containing a chain of from 5 to about 40 optionally substituted carbon atoms, (b) a moiety containing a chain of from 4 to about 40 carbon atoms and one or more internally linked oxygen or sulfur atoms or —NH— groups, or (c) an optionally substituted ethylene or propylene moiety;
Z is (a) an optionally substituted phenyl group, (b) an optionally substituted C
1
-C
20
alkyl, C
2
-C
20
alkenyl, C
3
-C
8
cycloalkyl or C
5
-C
8
cycloalkenyl group or (c) benzoyl; and n is 1 if R is (a) or (b), or is 2-20 if R is (c).
In another aspect, this invention comprises a process for the production of such microcapsules comprising the steps of (a) reacting an oligomeric acetal with a diisocyanate having the formula OCN—R
1
—NCO in which R
1
is an aliphatic or aromatic moiety to produce a prepolymer and (b) utilizing the product of (a) as the prepolymer in a polyurea microencapsulation process. In a preferred embodiment the prepolymer contains a moiety having the formula
in which R, R1 and Z are as described above.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to microcapsules which contain encapsulated material and which are sensitive to the presence of acid, and on exposure to an acidic environment break down and/or become porous so as to release the encapsulated substance into the surrounding environment.
The microcapsules are characterized by having shells formed of polyurea and containing an oligomeric acetal moiety. By oligomeric acetal moiety is meant a moiety which contains one or more in-chain acetal linkages and which has functional groups, preferably at the ends of the chain, which may be reacted with other materials such that the oligomeric acetal may be incorporated into a microcapsule wall. Oligomeric acetals may be made by a number of methods known to those skilled in the art, for example, by co-polymerization of diols and aldehydes, by co-polymerization of diols and divinyl ethers, and by homo-polymerization of aldehydes. In general, oligomeric acetals are characterized by having a group of the general formula
HO—[CHX—O]
m
H (III)
in which the identity of X depends on the nature of the reactants and reactions utilized to produce the acetals.
Preferred acetals for use in the microcapsules of this invention are those having the formula
in which
R is (a) a moiety containing a chain of from 5 to about 40 optionally substituted carbon atoms, (b) a moiety containing a chain of from 4 to about 40 carbon atoms and one or more internally linked oxygen or sulfur atoms or —NH— groups, or (c) an optionally substituted ethylene or propylene moiety; Z is (a) an optionally substituted phenyl group, (b) an optionally substituted C
1
-C
20
alkyl, C
2
-C
20
alkenyl, C
3
-C
8
cycloalkyl or C
5
-C
8
cycloalkenyl group, or (c) benzoyl; and
n is 1 if R is (a) or (b), or is 2-20 if R is (c).
Acetals produced by co-polymerization of diols and divinyl/ethers have moieties of the general formula
—[O—CH(CH
3
)—O—Z
1
—O—CH(CH
3
)—O—R
3
]
P
— (V)
in which Z
1
represents a group bridging two vinyl ether moieties, and R
3
represents the skeleton of the diol.
Acetals produced by homopolymerization of aldehydes have moieties of the ge
Follows Richard
Lee Chi Chang
Lee Kuo-Shin
Scher Herbert Benson
Shirley Ian Malcolm
Acquah Samuel A.
Lee Chi Chang
Townsend and Townsend / and Crew LLP
Zeneca Limited
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