Repulpability of Dispersion-Coated Substrates, 2000 Coating Conference Proceedings

M. Vaha-Nissi, S. -M. Taskinen, A. Savolainen--Off-machine converting lines and printing presses are traditionally used for dispersion barrier coatings. However, the trend is towards on-machine coating. In both cases the coated material must be repulpable regardless of whether it is originated from packaging waste or on-line coated broke. Ideally, repulped dispersion-coated material can be used as such in the paper-making process without impairing the paper / board quality or runnability. The aim of this study was to evaluate the repulpability of barrier dispersion-coated substrates. The coating was as a rule well separated from the fibers during disintegration. Filler-containing dispersions broke down into smaller pieces, compared to pure latex coatings. Temperature affected the large particle fraction and lowered the tensile index in handsheets produced from repulped coating-containing pulp. However, coat weight and substrate properties will affect the result. Repulping in alkaline conditions gave the highest tensile index. Blocking of the handsheets occurred with non-filled latex coatings, particularly with PVAc-latex. The repulpability is dependent on processing conditions, coat weight, and polymer properties. In general, the results indicated good repulpability of barrier coated board, particularly for filled dispersion-coatings.