Encapsulation of Pigment Red 122 into UV‐curable resins via a mini‐emulsion technique

The purpose of this paper is to encapsulate aqueous dispersions of nano‐scale CI Pigment Red 122 prepared through ball milling into UV‐curable resins, 1,6 hexanediol diacrylate (HDDA, monomer), and polyester acrylate (oligomer) using the mini‐emulsion technique.

The encapsulation of pigment is achieved by mixing a surfactant‐stabilised pigment dispersions and a monomer/oligomer mini‐emulsions and subjecting both to mini‐emulsification conditions. A film of encapsulated pigment mini‐emulsion is finally UV cured using water‐soluble initiator. Efficient encapsulation is proven by ultra‐centrifugal sedimentation, scanning electron microscopy and thermogravimetric analysis (TGA). The stability of pigment dispersions and also the encapsulation process are investigated.

TGA and ultracentrifuge sedimentation results showed that CI Pigment Red 122 is successfully encapsulated into polyester acrylate/HDDA resins. The oligomer (polyester acrylate) in the presence of organic pigment could stabilise the mini‐emulsion droplets without introducing any other hydrophobes (co‐stabiliser) in the formulation. In addition, the encapsulation percentage and suspension stability of mini‐emulsion are best when the polyester acrylate/HDDA weight ratio is 3:2.

The UV‐curable resins used in the present context are 1,6 HDDA and polyester acrylate. Besides, various oligomer/monomer composition types could be used and its impact on encapsulation efficiency could be also studied.

This method of encapsulation is practically effective for modification of organic pigments for use in UV‐curable ink‐jet printing inks.

The developed method is novel from a literature point of view and can be of a great benefit to achieve the required properties of pigmented UV‐curable system in inkjet printing of textiles. In addition, it could find numerous applications in surface coating.