A LABORATORY MEASUREMENT METHOD FOR PRESSURE SENSITIVE ADHESIVES IN AGGLOMERATION DEINKING OF MIXED OFFICE WASTE PAPER: THE HIGH-LOW SCANNING CONTRAST METHOD

Abstract

A simple measurement method for pressure sensitive adhesives (PSA) in an agglomeration deinking system of mixed office waste paper was studied. This method was based on the different scanning performance of ink and PSA specks in hot-pressed and oven-dried handsheets with the change of contrast values that had been selected and set in the image analysis software. The numbers of ink specks per square meter (NPM) were well recognized at both low and high contrast values and exhibited a very good linear relationship within a range of contrast values. The PSA specks, on the other hand, could not be recognized at the low contrast values and could only be recognized at high contrast values. The NPM value of the ink specks was found to have the highest values at the high contrast values and could be accurately predicted by its NPM value at the low contrast values. Thus, the NPM value of the PSA specks could be easily calculated by the total NPM of the handsheet at the high contrast value minus the projected NPM of the ink specks from its low contrast conditions. Compared to the dye method, which was also used on the measurement of microstickies, this method is suggested as a simple and quick laboratory tool to measure the relative quantity of PSA in the mixed office waste paper with minimum interference from the residual toner ink.