Study On The Use Of Plastic Pigments In The Printing Coated Paper

Plastic pigments are the new organic pigments; they are somewhat thermoplastic in nature and more readily deform on calendering than do any other mineral pigments; the density of the plastic pigments is far below those of mineral pigments; their system is more steady.In order to investigate the effect of plastic pigments to the coated paper and their functionary mechanism, we choose two kinds of plastic pigments, solid bead and hollow sphere, as primary investigative objects. Firstly, under the condition of different finishing requirement, comparing the plastic pigments with clay and calcium carbonate comprehensive; and then using scanning electron microscope to investigate the effect of plastic pigments to coating structure.According to the comparison of hollow sphere and mineral pigments, clay and calcium carbonate, hollow sphere is better than mineral pigments in terms of gloss, brightness, opacity, smoothness, bulk. In aspect of whole physical property improvement, using hollow sphere to substitute the part of clay will be better than to substitute the part of calcium carbonate; and clay is more expensive than calcium carbonate, So that it will be more advantage and benefit to use hollow sphere to substitute the part of clay.In response to the comparison of solid bead and mineral pigments, clay and calcium carbonate, solid bead is better than mineral pigments in terms of gloss, brightness, but not so good in aspect of opacity, smoothness, bulk. The reason of this result is due to the particle size and structure of solid bead. In addition, clay is more expensive than calcium carbonate, so it will be fine to be used as gloss additive in place of clay in the glazed coated paper and paperboard.From the coating structure SEM pictures, we can obviously see the changes of the coating structures before and after adding plastic pigments. During the finishing process, due to thermoplastic performances of plastic pigments, the shapes of them will be changed. However, the shapes of mineral pigments will not be changed. Increasing calender conditions only crush the mineral pigments particles.Because plastic pigments are finishing aids, milder calender conditions often can be used to achieve a target gloss value. These milder conditions lead to less compaction of the coated paper, thus decreasing the losing of brightness and opacity, increasing bulk and stiffness. Increased bulk leads to improved...