Synthesis and application of calcium sulphate pigment for paper coating: Potential and prospects

• Published in: Powder technology 2012-03, Vol.218, p.40-45
• Main Authors: Kumar, Nitin, Bhardwaj, Nishi Kant, Chakrabarti, Swapan Kumar, Kumar, Sunil
• Format: Article
• Language: English
• Subjects: Applied sciences; Aspect ratio; Brookfield viscosity; calcium carbonate; Calcium chloride; Calcium sulfate; Calcium sulphate; Chemical engineering; Coating; coatings; color; Exact sciences and technology; Ink setoff; Miscellaneous; Particle size; Pigments; Rheology; scanning electron microscopes; Scanning electron microscopy; Solid-solid systems; temperature; Water retention value
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2011.11.031

In the present study, calcium sulphate pigment has been synthesized experimentally from commercial grade calcium chloride. The effect of various factors on the particle size of calcium sulphate formed in a wet process and its potential application as pigment in coating recipe has been investigated. The operating factors investigated include concentration of calcium chloride solution, temperature, addition of different rheology modifiers and their optimization. The particle shape and size distribution of synthesized calcium sulphate pigment have been studied through image analyzer, scanning electron microscope (SEM) and particle size analyzer. Significant improvement was observed in various coated paper properties like brightness, whiteness, gloss, stiffness, surface strength and water retention properties of coating color with respect to conventional ground calcium carbonate (GCC) coating pigment. Paper coating grade calcium sulphate pigment has been synthesized at some specific conditions with help of carboxy methyl cellulose as a rheology modifier. The SEM image analysis shows high aspect ratio of synthesized calcium sulphate pigment than traditional ground calcium carbonate based paper coating pigment. The application of high aspect ratio calcium sulphate pigment in paper coating results in benefits as compared to a lower shape factor traditional coating pigment. [Display omitted] ► Calcium sulphate (CS) pigment was synthesized for paper coating application. ► CS improves the water holding capacity of coating color. ► Improvement was also observed in physical and optical properties of coated paper. ► CS pigment in coating also favors in reduction in ink consumption during printing.