Biobased packagingmaterial with high wet strength

Important results from the project

The goal was to produce a wet-strength fiber-based material with as little additive of chemicals as possible. The material produced should be competitive with materials available on the market today but manufactured with higher resource efficiency. In the project we have managed to press sheets under simulated mill conditions with temperatures well above lignin softening temperature under high pressure, which means that both dry strength and wet strength increase markedly without adding strength enhancing chemicals. The lignin in the pulp is used as dry and wet strength additive.

Expected long term effects

The major conclusion is that we are successively learning how to come closer to the hot-pressing properties reached at the laboratory or higher. -No delamination problems, which has been a problem in previous processes such as Impulse drying. -The amount of dry matter can increase from 60% to 90% within 150 msec. This would mean significantly shortening of the drying section on a paper machine. -At pressure with 220 ° C at a speed equivalent to about 500 m/min, a tensile index of 60 kNm/ g has been achieved which is more than double of that using traditional technique.

Approach and implementation

Trials have been made at a Valmet plant in Finland. They have developed an experimental equipment where paper sheets can be subjected to rapid pressure pulses in the relevant pressurized pressure area after heating. The effect of temperature and pressure pulses at varying dry matter (40-65%) have been tested. The experiments have led to increased understanding of the importance of dry matter on the sheets in order to avoid delamination, that preheating must be sufficient to heat the sheets before the press pulse and that different types of pulses produce different effects.