Preparation and characterization of corn starch–calcium carbonate hybrid pigments

• A new method to integrate corn starch and CaCO3 into a hybrid pigment was developed.
• Raw materials are available and economical and technique is industrially feasible.
• Allows the amount of starch in paper to be increased without process interferences.
• Enables the use of unmodified corn starch instead of expensive modified starch in paper.
• Developed hybrid pigment gives unique paper properties.

This article presents a novel method for integrating native corn starch and calcium carbonate (CaCO3) into a hybrid pigment, which can be applied in papermaking to increase the amount of starch in paper and improve sheet bonding without impairing dewatering. Starch was first thermally treated to partially gelatinize and swell the granules. The aim of the treatment was to change the surface properties of starch and thus to improve the interaction with CaCO3 particles. CaCO3 shell was precipitated around the swollen granules and the encapsulated starch was then cooked to achieve complete gelatinization. When the granules were cooked, the starch became active for bonding, but its solubility was very limited due to the encapsulation. Particle size measurement and scanning electron microscopy were used to analyze the sample properties during the preparation. The hybrid pigment was added to paper sheets and its effect on the paper properties was examined. Starch was shown to be effectively bound to the pigment structure. The hybrid pigment allowed a large amount of native corn starch to be added to paper without interfering with the papermaking process. Furthermore, it gave excellent mechanical paper properties.