Rapid mercury-free photochemical microencapsulation/nanoencapsulation at ambient conditions

Inventors

Kurdi, Jamal • Farid, Mohammed

Assignees

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

The invention relates to mercury-free UV or UV/Visible LED photochemical microencapsulation or nanoencapsulation of a phase change active material with a curable material at ambient or cold temperature for five minutes or less. The curable material comprises a mono-functional monomer, and the photochemical encapsulation uses LED radiation with narrow or single wavelength, including a solar monochromator.

The photoreactor includes a transparent tube equipped with a helix stirrer that can be fit inside the tube, and at least one LED lamp with adjustable light intensities. The microencapsulation or nanoencapsulation is carried out with discontinuous droplets phase formed by emulsion preparation including the active material, the curable shell material, and a photo-initiator, together with sufficient mixing exposure of droplets to irradiation.

The transparent photoreactor is configured for photochemical curing under LED wavelength and irradiation conditions that achieve high monomer conversion and high encapsulation efficiency while reducing process time compared to mercury lamps and thermal encapsulation. Documented outcomes include monomer conversion greater than 90% and encapsulation efficiency up to about 100%, with efficiency strongly dependent on radiation intensity and irradiation time.

The disclosed approach is described in the context of reducing energy and waste compared to mercury lamps, and addressing oxygen or wavelength selectivity effects associated with photochemical encapsulation. The use of narrow or single wavelength LED radiation, or a solar monochromator, is presented as enabling selection of irradiation conditions while maintaining encapsulation performance at ambient or cold temperature in minutes or less.

Claims Coverage

Independent claim clm-00001 defines an LED stirrer photoreactor for photochemical microencapsulation or nanoencapsulation at ambient or cold temperature for five minutes or less, with a curable material that comprises a mono-functional monomer. The independent claim is refined by seven inventive features specifying reactor structure, lighting configurations, timing, and curable material composition.

Overall claim coverage centers on an LED stirrer photoreactor that enables photochemical microencapsulation or nanoencapsulation of a phase change active material at ambient or cold temperature for five minutes or less, using a curable material comprising a mono-functional monomer. The inventive features further specify a transparent tube with a helix stirrer, glass tube dimensions, LED wavelength and intensity arrangements, a less-than-five timing constraint, multi-LED configurations, and inclusion of additional mono-functional or di-, tri-, or poly-functional monomers in the curable material.

Stated Advantages

Documented Applications