COMPOSITE PIGMENTARY MATERIAL

摘要

A process for the production of a structured composite pigmentary material in the form of a dispersion comprises mixing an aqueous dispersion of inorganic pigmentary particles and an aqueous dispersion of polyvinyl chloride (PVC) particles. The inorganic pigment particles carry a positive surface charge and the PVC particles carry a negative surface charge and the particles in the composite are held in association as a result of these charges. The inorganic pigment particles and PVC particles are mixed in the presence of a surfactant system which provides both anionic and steric stabilisation. In one embodiment the surfactant system comprises a nonionic surfactant having an HLB value greater than 12 and at least 2% by weight of an anionic surfactant with respect to the weight of PVC particles. In a second embodiment the surfactant system comprises at least 2% by weight (with respect to PVC) of one of more surfactants providing anionic and steric stabilisation and being ethylene oxide condensation products having a polyoxyethylene chain with an average length of at least 8 oxyethylene units. The product is useful in paints and provides improved opacity compared to conventional pigments and improved gloss compared to known structured composite pigments.