Old corrugated containers given new life
Jan Erik Kaarø
A "porridge" of re-slushed paper treated with ozone may solve one of the major problems of recycling paper and board.
Ass. Professor Per Johan Houen (left), with director Peder J. Kleppe of M. Peterson & Søn and Håvar Fjerdingen.
Research carried out at NTH's Dept. of Chemical Engineering has shown that this special treatment restores much of their original strength to fibres from old recycled paper and board.
Associate Professor Per Johan Houen and Håvar Fjerdingen, a doctoral student, have given themselves the task of putting new life into old paper and board. In the first instance they have concentrated on corrugated board. The scientists are looking at several different methods of making better use of recycled fibre. The project is being carried out in close collaboration with M. Peterson & Søn, Norway biggest manufacturer of packaging materials. The company has installed a recycled fibre plant in the city of Moss and currently uses about 25% recycled corrugated board in its production process. The company aims to increase this to 33% in Moss.
If the NTH scientists manage to develop a process that functions on an industrial scale, it could be of great environmental and economic importance.
An important cause of the problem is that old paper fibre loses its bonding capacity. As a result, when it is reused, the paper is weaker than paper containing virgin fibre.
Changes in material properties
The reduction in bonding strength is greatest when the fibres pass through the paper mill for the first time, but continues to take place every time the material is recycled. Per Kirkebak, R & D manager at M. Peterson & Søn, estimates that a corrugated container can be recycled for a maximum of four or five times before its fibre content is worn out.During the paper manufacturing process, the fibres become harder and less flexible, a process known as hornification. Through the electron microscope the scientists can see that this is largely due to the pores in the virgin fibres closing, thus losing much of their ability to absorb water. When recycled fibres are wetted, hemicellulose, their built-in glue, which is supposed to hold the paper together, cannot swell up.
The research project started in autumn 1992 and will continue until the end of 1995. The NOK 3.3 million budget is being shared by the Research Council of Norway and M. Peterson & Søn. "at Peterson Moss A/S we are very pleased with the results of the collaboration with NTH so far, and we have great expectations for the future", says Kirkebak.