New nanocoating improves the printing surface of paper
The polymer technology group at the School of Chemical Technology has developed a new nanocoating that makes the characteristics of inexpensive and low-quality paper resemble higher quality, coated fine papers.
Since it is only needed in small amounts, the new coating is an affordable and environmentally friendly alternative. Compared to the fine paper qualities currently on the market that require from 5 to 10 grams per square metre of various polymers and mineral fillers, the new coating’s favourable characteristics emerge regularly with coating volumes of less than one gram per square metre.
Paper recycling is easier because the developed coating is water-soluble and does not include disturbing polymer components. Moreover, the new coating enables a better print quality; when test printing on nanocoated paper, the print quality was found to be sharper. This is due to the interaction between the paper surface and print ink.
Including components that both repel and favour water, the structure of the polymer used in the nanocoating is amphiphilic. A completely untreated base paper absorbs ink uncontrollably, resulting in a messy print quality. When the polymer includes a hydrophobic part it can be used to control the penetration of the ink in the paper fibre.
Thanks to the interaction, the nanocoated paper partly repels the printing ink preventing it from penetrating too deep. In such a way, the quality of double-sided printing is also improved, since the print is not visible on the other side of the paper.
The polymer technology group has studied the interaction of several polymers with printing ink. Understanding the mechanism by which the polymers self-organize on the surface of the paper has been of primary importance. With the help of a manufacturing method developed at the laboratory, the surface of the paper can easily be adapted so that it forms a good printing surface for a range of printing methods.
The new coating agent can be mixed with water, and its use in normal paper manufacturing does not require major changes to printing machines. In addition, the raw materials needed for the coating are readily available.
The study began in 2004 funded by the Finnish Funding Agency for Technology and Innovation, Tekes. In the future, the goal is to increase the scale of the developed method and develop it for financially profitable industrial production of paper.
Jukka Seppälä, Professor
School of Chemical Technology
Department of Biotechnology and Chemical Tecnology
jukka.seppala [at] aalto [dot] fi
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