pH-sensitive microcapsules

• US 6,022,501 A
• Filed: 08/15/1996
• Issued: 02/08/2000
• Est. Priority Date: 08/15/1996
• Status: Expired due to Term

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: American Colloid Company (Minerals Technologies Incorporated)
• Inventors: Dexter, Robin William, Benoff, Brian Eric
• Primary Examiner(s): Mullis, Jeffrey C.
• Application Number:
  US08/702,088
• Time in Patent Office: 1,272 Days
• Field of Search: 264/4.7, 424/405, 424/408, 424/419, 424/497
• US Class Current: 264/4.7
• CPC Class Codes: A01N 2300/00 Combinations or mixtures of active ingredients covered by classes A01N27/00 - A01N65/48 with other active or formulation relevant ingredients, e.g. specific carrier materials or surfactants, covered by classes A01N25/00 - A01N65/48
• CPC Class Codes: A01N 25/28 Microcapsules or nanocapsules
• CPC Class Codes: A01N 33/18 Nitro compounds

Abstract

The present invention provides pH-sensitive microcapsules, compositions containing them, methods for their preparation and methods for their use.

Claims

1. An improved process to make aqueous microcapsules containing a water-immiscible active ingredient having a polyamide, polyester or polyamide/polyester shell wall, the improvement which comprises incorporating free carboxylic acid groups in said shell wall by adding excess polyacid halide during shell wall formation by:

(a) providing an aqueous solution comprising an emulsifier;

(b) dispersing, with agitation, in the aqueous solution, a water-immiscible solution comprising a polyacid halide and a water-immiscible active ingredient to form an emulsion; and

(c) adding, with agitation, to the emulsion of step (b), a polyamine, a polyol or a mixture thereof, provided that the ratio of acid halide groups to amino and/or hydroxy groups is about 2;

1 to less than about 5;

1 and further provided that said shell wall formation occurs essentially in the absence of a diisocyanate, a polyisocyanate, a diisocyanate prepolymer or a polyisocyanate prepolymer.

2. The process according to claim 1 wherein a base is added to step (c) in an amount less than one equivalent relative to the acid halide groups.

3. The process according to claim 1 wherein the ratio is about 2:

1 to 3;

1.

4. The process according to claim 1 wherein the composition has a pH of about pH 2 to pH 4.

5. The process according to claim 1 wherein the aqueous solution comprises about 0.5% to 5% by weight of the emulsifier.

6. The process according to claim 1 wherein the water-immiscible solution further comprises a water-immiscible solvent.

7. The process according to claim 1 wherein the active ingredient is selected from the group consisting of a herbicide, an insecticide, an acaricide, a nematicide, a fungicide and a molluscicide.

8. An improved process to make aqueous microcapsules containing pendimethalin having a polyamide, polyester or polyamide/polyester shell wall, the improvement which comprises incorporating free carboxylic acid groups in said shell wall by adding excess polyacid halide during shell wall formation by:

(a) providing an aqueous solution comprising an emulsifier;

(b) dispersing, with agitation, in the aqueous solution, a water-immiscible solution comprising a polyacid halide and pendimethalin to form an emulsion; and

(c) adding, with agitation, to the emulsion of step (b), a polyamine, a polyol or a mixture thereof, provided that the ratio of acid halide groups to amino and/or hydroxy groups is about 2;

1 to less than about 5;

1.

9. An improved process to make aqueous microcapsules containing water-immiscible active ingredient having a cross-linked amino resin shell wall, the improvement which comprises incorporating free carboxylic acid groups in said shell wall by adding excess polyacid halide during shell wall formation by:

(a) providing an aqueous solution containing an emulsifier;

(b) dispersing, with agitation, in the aqueous solution, a water-immiscible solution comprising a water-immiscible amino resin prepolymer, a polyacid halide and a water-immiscible active ingredient to form an emulsion, provided that the ratio of amino resin prepolymer to polyacid halide is about 20;

1 to 5;

1 on a weight basis; and

(c) heating the emulsion to about 50°

C. to 100°

C.

10. An improved process to make aqueous microcapsules containing a herbicide having a polyamide, polyester or polyamide/polyester shell wall, the improvement which comprises incorporating free carboxylic acid groups in said shell wall by adding excess polyacid halide during shell wall formation by:

(a) providing an aqueous solution comprising an emulsifier;

(b) dispersing, with agitation, in the aqueous solution, a water-immiscible solution comprising a polyacid halide and a herbicide to form an emulsion; and

(c) adding, with agitation, to the emulsion of step (b), a polyamine, a polyol or a mixture thereof, provided that the ratio of acid halide groups to amino and/or hydroxy groups is about 2;

1 to less than about 5;

1.