EFFECT OF PH AND TEMPERATURE ON DEINKABILITY OF RECYCLED PAPER PRINTED WITH WATER BASED INK

Abstract

Due to environment concern the usage of oil based ink in printing industry has been diminishing. Oil based ink contains very huge amount of volatile organic compounds Water based ink can be used as an alternative. The purpose of water based is to reduce the volatile organic compound from the ink. Water-based Flexo printing inks are very sensitive to pH. These can be easily dissolved in water. Due to hydrophilic nature it can easily be detached compare to solvent based ink. Pulping when done at higher pH we get the very small ink particles are disperses in water and difficult to remove them in flotation process. Flotation process works efficiently when ink particles size is bigger ranging (>10) μm where as washing best suits for smaller ink particles (< 1 μm). Hydrophilic particles favour the washing process whereas the hydrophobic particles are efficiently removed by flotation. The resins used in water-based Flexo printing inks are soluble at higher pH. They get easily dispersed in the medium and difficult to remove during flotation because of particle size and hydrophilic surface. Difficulty in removing the water based ink is the main motivation for optimising the flotation process for this type of ink particles and tuned the parameters like pH, Temperature, Consistency for the flotation process. So that ink particles get easily agglomerates and removed during the process. The ink elimination is increases on decreasing the pH keeping the minimum chemical needed for their function while temperature shows the direct relation with the ink elimination. But the optimum range for the system temperature is from (40-50) ⁰ C for the soap formation and so for ink removal