Pigment & Resin Technology

Purpose – The purpose of this paper is to provide a novel method for encapsulation of phthalocyanine blue pigment for inkjet printing inks.

Design/methodology/approach – Phthalocyanine blue pigment was encapsulated by emulsion polymerisation of styrene and a polymerisable dispersant, allyloxy nonyl-phenoxy propanol polyoxyethylene ether ammonium sulphonate (ANPS). The encapsulated phthalocyanine blue pigment was further formulated into dispersion. The encapsulated phthalocyanine blue pigment was characterised with transmission electron microscopy (TEM), thermogravimetric analyses (TGA), X-ray diffraction (XRD), Zeta potential and contact angle measurements. The encapsulated phthalocyanine blue pigment dispersion was evaluated in terms of rheological behaviour, particle size distribution and stability.

Findings – TEM and TGA proved that polymer encapsulation layer was formed onto phthalocyanine blue pigment surface. XRD indicated that the crystal structure of phthalocyanine blue pigment was not changed during the encapsulation process. The wettability of phthalocyanine blue pigment was improved after polymer encapsulation. The dispersion formulated with encapsulated phthalocyanine blue pigment had a narrow particle size distribution, excellent stability to temperature and centrifugal forces. Its rheological behaviour was close to Newtonian fluid.

Practical implications – The methods provided a novel and practical solution for preparing the encapsulated phthalocyanine blue pigment dispersion for formulation of inkjet printing ink.

Originality/value – The paper demonstrates how emulsion polymerisation technique is employed to encapsulate phthalocyanine blue pigment using a polymerisable dispersant, ANPS, which imparts to dispersion a small particle size, narrow particle size distribution and high stability.