Water-in-oil capsule manufacture process and microcapsules produced by such process
View Patent ↗A novel method of forming water in oil microcapsules is disclosed. According to the invention microcapsules are obtained by steps comprising dispersing an oil soluble amine modified polyfunctional polyvinyl monomer and an oil soluble bi- or polyfunctional vinyl monomer along with a thermal or UV free radical initiator (optionally included in one or both of the oil or water phases) and an organic acid into an internal phase oil; heating or UV exposing for a time (and temperature) sufficient to oligomerize the amine modified polyfunctional polyvinyl monomer and oil soluble bi- or polyfunctional vinyl monomer forming a pre-polymer. Thereafter the process involves adding to the oil phase oil a water phase comprising a dispersion in water of an anionic emulsifier (and optionally initiator), and adding an emulsifying agent. Emulsifying the water phase into the oil phase (W/O) is controlled through the quantity of water employed. The emulsion is then UV exposed or heated for a time (and temperature) sufficient to decompose the free radical initiators in the oil and/or water phases; thereby forming microcapsule wall material at the interface of the water and oil phases.
1. A process for preparing microcapsules encapsulating a water phase, the process comprising:
dispersing an oil soluble amine modified polyfunctional polyvinyl monomer or oligomer and an oil soluble bi- or polyfunctional vinyl monomer or oligomer along with a free radical initiator and an organic acid into an excess of an oil phase which is a nonsolvent for the water phase; the organic acid selected from the group consisting of monoalkyl maleate, alkyl benzene sulfonic acid, and alkyldiphenyloxide sulfonic acid;
a first heating step comprising, heating for a time and temperature sufficient to oligomerize or further oligomerize the amine modified polyfunctional polyvinyl monomer or oligomer and oil soluble bi- or polyfunctional vinyl monomer oligomer forming a pre-polymer;
adding to the oil phase a water phase comprising a dispersion in water of an anionic emulsifier and a free radical initiator and a core material, and emulsifying the water phase into the oil phase forming droplets of the water phase dispersed in the oil phase;
a second heating step comprising, heating for a time and temperature sufficient to decompose the free radical initiators in the oil and water phases;
thereby forming microcapsule wall material at the interface of the water and oil phases, the microcapsules encapsulating the water phase droplets;
and a third heating step comprising heating to a temperature equal to or greater than the second heating step temperature for a time sufficient to polymerize the wall material.
2. The process for preparing microcapsules according to claim 1 wherein a free radical initiator is selected from an azo or peroxy initiator.
3. The process according to claim 1 wherein the oligomerization is accomplished by heating, in the first heating step, to at least 55° C. for at least one hour to form the prepolymer.
4. The process according to claim 1 wherein the amine modified polyvinyl monomer is selected from amine modified ethoxylated trimethylol propane triacrylate, diacrylate amine, dimethacrylate amine, amine modified polyetheracrylate, and amine modified polyethermethacrylate.
5. The process according to claim 1 wherein the bi- or polyfunctional vinyl monomer or oligomer is selected from a polyacrylate, a polymethacrylate, a dimethacrylate, a diacrylate, a triacrylate, diethylene glycol dimethacrylate, pentaerythritoltriacrylate, trimethylol propane triacrylate, urethane diacrylate, urethane dimethacrylate, ethoxylated aliphatic difunctional urethane acrylate, and ethoxylated aliphatic difunctional urethane methacrylate.
6. The process according to claim 1 wherein the emulsifier is selected from polyacrylic acid, polymethacrylic acid, acrylic acid alkyl acrylate copolymer, alkyl succinamate, an alkylaryl sulfonic acid salt or an alkyl sulfate salt.
7. The process according to claim 1 wherein the organic acid is selected from carboxy acid, organic sulfonic acid, or monoalkyl maleate.
8. The process according to claim 1 wherein the third heating step comprises heating to at least 90° C. for at least three hours.
9. The process according to claim 1 wherein the initiator in the oil phase decomposes at a first temperature and the initiator in the water phase decomposes at a second temperature.