Novel bio-based cross-linkers for improving performance of packaging paper

Purpose and goal:

The aim of the project was to replace harmful paper chemicals with new bio-based cross-linkers that can be used to reduce creep, i.e. gradual deformation over time, of paper and paper packaging when exposed to high or varying humidity. The goal was to verify a concept where carboxymethylated hemicellulose is used to crosslink the cellulose. In the project, good crosslinking and increased resistance to creep of the paper were achieved while maintaining other paper properties

Expected results and effects:

The project has verified that carboxymethylated hemicellulose can be used to crosslink cellulose and reduce creep. This gives the paper industry a way to improve the properties of packaging paper, and an opportunity to utilise the hemicellulose from wood, which is otherwise a waste product in the pulp production. Carboxymethylated hemicellulose is also a sustainable alternative to current fossil-based paper chemicals.

Approach and implementation:

In the project, carboxymethylation of a commercially available hemicellulose from beech was carried out. The carboxymethylated hemicellulose was used to impregnate paper, which was then dried and heat treated to initiate the crosslinking process. The crosslinking in the treated paper was characterised and creep at both constant and cyclic humidity was measured. The results showed that crosslinking took place already at relatively low temperatures, and the papers exhibited good creep resistance.