Sampling, analysis and the determination of the source of contaminants causing hickeys on newsprint

摘要

A major customer of Norske Skog (the Customer) had a severe outbreak of hickeys at one of their pressrooms (Site A) which became a significant issue in April 2013. Initially, newsprint from the Albury Mill (NSW, Australia) was the primary focus of the investigation, as contaminants from the recycled fibre (RCF) process have been known to cause hickeys in the past. Process changes at the Mill around that period were investigated while extensive sampling and analysis was carried out to attempt to understand the issue. Samples of material causing the hickeys as well as reference material from the Mill and pressrooms were analysed by Fourier Transform Infrared (FTIR) spectroscopy. The sampling encompassed other Customer pressrooms as well as Site A to determine the extent of the issue. Intensive sampling led to a clear result, that there were three major types of material causing the hickeys. These were solidified ink particles, pieces of polytetrafluoroethylene (PTFE or Teflon) and a 'plastic-like' material that could not be identified. The 'plastic-like' material did not match to any known spectra in the internal or external FTIR databases that Norske Skog utilises. The same three contaminants were found at other Customer pressrooms to a lesser extent, such as Site B, which consumes paper from the Boyer Mill (TAS, Australia), and Site C, during a trial of paper from the Tasman Mill (New Zealand). The paper from these two mills does not have RCF content. None of the three contaminants had been found in the paper and other customers were not experiencing the same issues. Focus shifted to the ink and an ink filter was installed at Site B on the cyan inlet to the printing press. In September 2014, it was confirmed that all of the three major contaminants were present in the ink line. Further targeted sampling at Site A uncovered large pieces of the same three types of contaminants present in the ink screens at the first point the ink reaches the site. After the removal of the contaminants from the ink screens at Site A, the levels of hickeys reduced significantly, to the point that they were no longer considered a commercial issue. Site A now ensures that ink screens and filters are cleaned during routine maintenance activities.