Correlation between chemical, fibre and paper properties of peracid- and chlorine dioxide-bleached pine and birch kraft pulps by multivariate analysis

摘要

Pine and birch kraft pulps were bleached with sequences containing peracetic acid, perfor-mic acid, Caro's acid or chlorine dioxide. The chemical, fibre and paper properties of the pulps were determined after each bleaching stage in order to find out in which stage differences between the pulps appear. Correlations between the pulps and pulp properties were studied using multivariate analysis (Principal Component Analysis, PCA). According to the results the bonding and strength properties of unbeaten ECF bleached pulps were higher than those of TCF bleached pulps. The TCF pine pulps were very similar to each other, whereas the TCF birch pulp differed from the others in having lower strength. The TCF_(Pfa) pulps also had lower surface lignin contents than the other pulps. In both pine and birch pulps higher paper strength properties could be obtained with high carboxyl group content, but the carboxyl group content alone could not explain the differences between the pulps. On the other hand, the ECF pulps had both longer fibres and less fibre deformations, which could partly explain their higher strength. Viscosity was a good indication of the strength properties in the case of birch pulps. After beating for 2000 revs in a PFI mill the strength properties of the TCF pulps were inferior to those of the ECF pulp. In the case of pine this was probably due to the higher zero-span strength and the better bonding properties of the ECF fibres, while the difference between the birch pulps was mainly in the bonding properties. Bleaching to 85% brightness instead of by using less peracid in bleaching brought the strength properties closer to those of the ECF pulp, but the same level could not be reached.%Mänty- ja koivusulfaattimassat valkaistiin sekvensseillä, jotka sisälsivät peretikkahappo, per-muurahaishappo-, Caronhap-po- tai klooridioksidivaiheen. Massojen kemialliset sekä kuitu- ja paperiominaisuudet määritettiin jokaisen valkaisuvai-heen jälkeen. Siten pystyttiin tarkkailemaan missä valkaisu-vaiheessa eroja massojen välille syntyisi. Korrelaatiota massojen sekä massaominaisuuk-sien välillä tarkasteltiin multi-variaattianalyysin avulla (Principal Component Analysis, PCA). Tulokset osoittivat, että jauhamattomien ECF-massojen sitoutumis- ja lujuusominaisuudet olivat paremmat kuin vastaavien TCF-massojen. Män-ty-TCF-massat olivat keskenään hyvin samankaltaisia, mutta koivumassoista TCF -massa poikkesi muista heikomman lujuutensa vuoksi. TCF_(Pfa)-mas-sojen pintaligniinipitoisuus oli myös alhaisempi kuin muilla massoilla. Sekä mänty- että koivumassoilla saavutettiin korkeat lujuusominaisuudet, kun karboksyyliryhmien määrä oli korkea, mutta eroja massojen välillä ei pystytty selittämään ainoastaan karboksyyliryhmien määrän perusteella. ECF-massojen korkeampia lujuus-arvoja pystyttiin toisaalta selittämään TCF-massoja korkeamman kuidun pituuden sekä alhaisemman kuituvaurioiden määrän avulla.