ACID-RESISTANT CALCIUM-CARBONATE FOR SIZING IN PAPER MANUFACTURING

The salient features of the process patented for production of acid re sistant calcium carbonate, suitable to be used in acid sizing of paper manufacturing are given. Ground calcium carbonate (GCC) has been chem ical treated and used at pH of 4.5 in alum- ros in sizing of bamboo-ha rd wood bleached pulp. The acid resistance property of the new product (SCC) has been established by titration against alum and the water re pellency of the hand sheet made with the products from measurement of cobb values till circulations to 70 times in the laboratory. The optic al, strength and printability properties of hand sheet loaded with the surface coated calcium carbonate have been determined and compared wi th that of uncoated PCC, GCC and talc. The surface coated product (SCC -I) has higher brightness (by 5 per cent EI) than that of talc with im provement in retention and printability properties.