Rapid mercury-free photochemical microencapsulation/nanoencapsulation at ambient conditions

Inventors

Kurdi, Jamal • Farid, Mohammed

Assignees

Auckland In New Zealand, University of • Auckland Uniservices Ltd • Doha For Science & Technology, University of

Abstract

A method of mercury-free photochemical micro-/nano-encapsulation of an active material is a process for obtaining Micro-/nano-capsules by means of curing by UV LED radiation at ambient or even cold temperatures. A stirrer photo-reactor made from glass or transparent plastics can be used but mixed flow reactor could be also employed. Appropriate mixing is sufficient to expose all droplets, which contain an active material surrounded by curable-shell materials in the emulsion to the LED radiation. Using the optimum light intensities and reactions' times is critical for encapsulating the active material with a high efficiency and producing a high quality micro-/nano-capsules, Solar monochromator device can also be used as long as it generate the same radiation with a narrow/single wavelengths as the LED device. Light emitted diode (LED) is a mercury-free UV radiation source with a long operating life time and an instant ON-Off, it has a high efficiency, a very low cooling requirements and cost-efficient in photochemical encapsulation. It reduces the time of microencapsulation from 6 hours to a less than 5 minutes. It has a significant decrease in manufacturing cost, waste-water, unconverted monomers, and leftover active phase change material (PCM) compared to other methods. Conversion of more than 90% of monomers can be achieved, and encapsulation efficiency can reach 100% at optimum conditions. This is in addition to the ability of this invented technology for encapsulate volatile and heat sensitive active materials at ambient as well as low temperatures. Normal glass or transparent plastics can be used as a reactor material. Only the matched useful wavelength radiation is emitted by LED without having other wavelengths which might have a bad impact on the encapsulation process.

Core Innovation

A method is provided for photochemical micro- or nano-encapsulation of a phase change active material with a curable material wherein the curable material comprises a mono-functional monomer. The method prepares a discontinuous droplets phase containing at least one phase change active material, at least one curable mono-functional monomer, and at least one photo-initiator, and a continuous liquid phase that is immiscible with the discontinuous droplets phase with water and at least one stabilizer/emulsifying agent without surfactant.

A micro- or nano-emulsion is prepared by emulsifying the discontinuous droplets phase in the continuous phase using a high shear emulsifier. The emulsion is introduced to a photoreactor and irradiated at an ambient or cold temperature for five minutes or less with at least one UV-LED lamp while continuously mixed with a helix stirrer to encapsulate the phase change active material with the curable mono-functional monomer.

The method affords microcapsules or nanocapsules. The disclosed approach focuses on mercury-free photochemical encapsulation and uses UV/visible narrow- or single-wavelength LED curing, including embodiments using a solar monochromator device. The document further emphasizes high conversion of monomers, high encapsulation efficiency, and reduction of effects associated with mercury lamps and thermal processes.

Claims Coverage

The document includes one independent claim. The independent claim covers a complete micro- or nano-encapsulation method based on a discontinuous droplets phase with mono-functional monomer and photo-initiator, an immiscible aqueous continuous phase with stabilizer/emulsifying agent without surfactant, and ambient/cold photochemical curing using at least one UV-LED lamp with continuous helix stirring for five minutes or less, to form microcapsules or nanocapsules.

Overall claim coverage is centered on an emulsion-based photochemical encapsulation method that uses a surfactant-free immiscible aqueous continuous phase, high shear emulsification, and ambient/cold UV-LED photoreactor irradiation with continuous helix stirring to form microcapsules or nanocapsules containing a phase change active material encapsulated with a mono-functional monomer curable material.

Stated Advantages

Documented Applications