The Role of Base Paper in Controlling MSP and Spray LWC Paper Quality

摘要

In the last decade, the metered size press (MSP) has become the coater of choice for LWC offset papers. It now accounts for about 40% of the market. Compared to blade coaters, the MSP has the potential to use weaker base papers (e.g. more filler, less kraft fibre or lower weight) or to improve machine efficiency through less coater breaks. The recent introduction of the spray coater allows for these changes to be greater, as there is even less stress applied to the base during spray coating compared to either MSP or blade coating. However, the use of a spray coater means that the base quality needs to be optimised to allow the spray droplets to spread and merge together evenly across the surface without excessive penetration into the base. A pilot coater has been used to apply the same pigment blend using a MSP and spray coater to five commercial base papers. The overall paper quality was found to be similar. However, the properties of the bases that controlled paper quality were not always the same for the two coating systems.