Barrier properties of greaseproof paper

Abstract

The barrier properties of greaseproof paper are achieved by extensive beating of the fibres. This treatment results in high costs for energy, both as beating energy and drying energy. A full-scale trial has been performed to investigate the role of the pulp with respect to energy demand and the barrier properties of the final papers. The paper made of 100% sulphite pulp with a low degree of beating showed the lowest energy consumption at a given level of barrier properties such as air permeance, grease resistance and water vapour transmission rate. The papers produced in the full-scale trial have been used as substrates for coating. Greaseproof paper has a closed surface and should therefore be a good base paper for barrier coatings. Chitosan has been used as a barrier coating because of its good oxygen barrier properties. Moreover, chitosan is a renewable material. Coating trials on a bench-scale showed that greaseproof paper can be upgraded to provide a good oxygen barrier. The oxygen barrier could not be achieved on a pilot-scale using the metered size press technique, because of the low coat weight applied. The influence of the base paper on the barrier properties of chitosan-coated paper has been investigated. It was found that greaseproof paper is better than a paper with a higher porosity. The coating seemed to stay more on the surface of the greaseproof papers and to form a continuous coating layer with better barrier properties