Powder coating is an innovative coating process for paper. It could
enable cost savings, quality improvements, and new coated paper
grades. However, innovations are needed as far as high coating speeds,
thin coatings and composition are concerned. The goal of the study was
to test the feasibility of highly filled powders for paper coatings by evaluating
laboratory deposition tests and performing coating trials with
the dry surface treatment (DST) unit. It was demonstrated that highly
filled powders with 100 parts per weight CaCO3 and 10 or 20 parts of
polymer binder can indeed be charged and deposited onto wood free
paper by electrostatic means when the paper is backed up with a
grounded backing.Although pressing coated paper in a hot roll nip clearly improved adhesive
and cohesive strengths of the coating, low adhesion between the
coating and the base paper turned out to be a challenge in line with the
results from other studies. This will likely be an issue at high coating
speeds. Low adhesion was due to poor mechanical interlocking and uneven
pressure profile during pressing both in and out of plane. The coating
had uneven thickness probably due to a higher initial attachment of