CONTROLLED RELEASE DUAL WALLED MICROCAPSULES
A method of forming dual melamine/acrylic walled microcapsules having improved physical properties and release control as well as the microcapsules formed by the process wherein the capsule wall is formed by the use of select (meth)acrylate monomers and/or oligomers and/or select self-condensing melamine resins.
1 . Microcapsules whose shell wall comprises both melamine resin and (meth)acrylate polymer wherein the melamine resin is derived from a first aqueous phase and the (meth)acrylate polymer is derived from a second aqueous phase, said (meth)acrylate polymer comprising the reaction product of (a) at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer alone or in combination with (b) at least one water soluble or dispersible mono- and/or di-functional (meth)acrylate and/or (c) at least one water soluble or dispersible simple base, wherein said shell wall is formed by the sequential polymerization of the wall forming materials of the two aqueous phases, one aqueous phase, either the first aqueous phase or the second aqueous phase, being subjected to wall forming conditions to form a first microcapsule wall before the other aqueous phase is subjected to wall forming conditions to effect deposition and polymerization of the second wall forming material upon the first microcapsule wall.
2 . The microcapsules of claim 1 wherein the (meth)acrylate polymer comprises the reaction product of (a) at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer.
3 . The microcapsules of claim 1 wherein the (meth)acrylate polymer comprises the reaction product of (a) at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer and (b) at least one water soluble or dispersible mono- and/or di-functional (meth)acrylate.
4 . The microcapsules of claim 1 wherein the (meth)acrylate polymer comprises the reaction product of (a) at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer and (c) at least one water soluble or dispersible simple base.
5 . The microcapsules of claim 1 wherein the (meth)acrylate polymer comprises the reaction product of (a) at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer, (b) at least one water soluble or dispersible mono- and/or di-functional (meth)acrylate, and (c) at least one water soluble or dispersible simple base.
6 . The microcapsules of claim 1 wherein the (meth)acrylate polymer is derived from an oligomer/prepolymer formed by the reaction of (a) at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer and (b) at least one water soluble or dispersible mono- and/or di-functional (meth)acrylate.
7 . The microcapsules of claim 1 wherein the (meth)acrylate polymer is derived from an oligomer/prepolymer formed by the reaction of (a) at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer and (c) least one water soluble or dispersible simple base.
8 . The microcapsules of claim 1 wherein the (meth)acrylate polymer is derived from an oligomer/prepolymer formed by the reaction of at least one water soluble or dispersible multifunctional (meth)acrylate monomer or oligomer, (b) at least one water soluble or dispersible mono- and/or di-functional (meth)acrylate and (c) at least one water soluble or dispersible simple base.
9 . The microcapsules of claim 1 wherein the melamine resin is selected from a melamine-based polyurea, a melamine-formaldehyde resin, a melamine-aldehyde resin, dimethylol melamine urea, methylated dimethylol melamine urea, methylated melamine formaldehyde, methylated methylol melamine, and mixtures of melamine formaldehyde with urea formaldehyde.
10 . The microcapsules of claim 1 wherein the melamine resin is derived from a melamine prepolymer that is formaldehyde free and/or a methylated melamine resin.
11 . The microcapsules of claim 1 wherein the melamine resin is a partially methylated or high imino methylated melamine resin.
12 . The microcapsules of claim 1 wherein the shell wall of the microcapsule further comprises a polymeric emulsifier originating from the first aqueous phase which polymeric emulsifier is entrapped or encased in the shell wall material.
13 . The microcapsules of claim 1 wherein the shell wall of the microcapsule further comprises a polymeric emulsifier originating from the second aqueous phase which polymeric emulsifier is entrapped or encased in the shell wall material.
14 . The microcapsules of claim 1 wherein the shell wall of the microcapsule further comprises a polymeric emulsifier originating from both the first aqueous phase and the second aqueous phase, which polymeric emulsifier is entrapped or encased in the shell wall material.
15 . The microcapsules of claim 1 wherein the shell wall comprises two discrete layers, a melamine resin layer and a (meth)acrylate polymer layer, said shell wall having been formed by forming a microcapsule using either the first aqueous phase or the second aqueous phase, isolating the so formed microcapsules, placing them in the other aqueous phase and then subjecting the mixture to conditions to polymerize the wall forming material of that aqueous phase on the preformed microcapsules.
16 . The microcapsules of claim 15 wherein an interface is present between the two discrete layers said interface comprising polymer chains of the melamine resin and the (meth)acrylate polymer which are intertwined and/or embedded in the other.
17 . The microcapsules of claim 1 wherein the shell wall comprises an interior surface, an exterior surface and an intermediary section, wherein the interior surface of the shell is wholly comprised of the wall forming material of the first to be reacted of the two aqueous phases, the exterior surface is wholly comprised of wall forming material of the second to be reacted of the two aqueous phases, and an intermediary section comprising an interpenetrating network and/or copolymer of the wall forming materials of the two aqueous phases.
18 . The microcapsules of claim 17 wherein the shell wall was formed by forming a microcapsule using either the first aqueous phase or the second aqueous phase, which microcapsule is impermeable to the wall forming material of the other aqueous phase, then adding the other aqueous phase and then subjecting the mixture to conditions to polymerize the wall forming material of the added aqueous phase.
19 . The microcapsules of claim 18 wherein the polymerization and wall formation of the first to be reacted aqueous phases completed or substantially completed prior to the addition of the other aqueous phase composition.
20 . The microcapsules of claim 17 wherein the shell wall has been formed by sequentially polymerizing the wall forming materials of one phase before the other, the first polymerization being such that the monomer of the second to be reacted aqueous phase is unable to penetrate the shell wall formed of the first to be reacted aqueous phase.