Paul Ander and Geoffrey Daniel WURC, Dept. of Forest Products / Wood Science, SLU, Uppsala

Transcription

1 Paul Ander and Geoffrey Daniel, Dept. of Forest Products / Wood Science, SLU, Uppsala Pulp fibre testing with the HCl-method and comparison with cellulase activity and phosporic acid swelling COST Action E54 Opening Seminar Riga 5-6 April 7 Our Department: Views from outside and from inside

2 C o n t e n t Dislocations as weak points HCl-method Some results with the HCl-method* Cellulase results Phosphoric acid swelling Conclusions Acknowledgements COST Action E54 Opening Seminar Riga 5-6 April 7 *This method, used in Strength Delivery investigations, can distinguish between kraft pulps cooked in a pulp Mill or in a Laboratory, although the same spruce wood chips have been used. Strength delivery (SD) = The ratio between tear indexes of Mill and Lab pulps at tensile index 9.

3 Dislocations are seen in latewood fibres Large and small dislocations in polarized light in latewood spruce kraft pulp fibres Dislocation cleavage by HCl in latewood spruce kraft pulp fibres

4 Dislocation formation S P S S Dislocations (slip planes) are due to a change in cellulose microfibril direction, caused by wind action in trees, wood/chip cutting and machining, pulping and bleaching. They usually appear as a result of a compressive strain. Other names: Nodes, slip planes, microcompressions, etc. If large, dislocations decrease and fibre and paper strength. Small dislocations give fibre flexibility 4

5 Calculation of dislocations: The HCl/Fibre Length Method Standard method for HCl treatment and Fibre length calculation to obtain Cleavage per fibre: - Swelling of -5 mg fibres in water for -5 minutes with stirring bar - Treatment with N HCl ph at 8ºC for 4h in a water bath (no stirring bar) - Completion of cleavage with 5 mm stirring bar for min during cooling - - Fibre washing with phosphate buffer (ph 7) on 5 cm Munktell filters or or on glass filters G or G - - FibreMaster or Kajaani analyses - Calculation: Length weighted fibre lengths are used to obtain: Cleavage per fibre = (L / L) giving dislocations and weak points in the fibre. L = length weighted fibre length distribution in mm for control in water L = length weighted fibre length distribution in mm for sample. 5

6 Fibre length distribution before and after HCl-clevage & SEM micrograph Length distribution HO Number of fibre particles [%],5,5,5, Length [mm] (.79) Length distribution M HCl Number of fibre particles [%] Length [mm] (.75) 6

7 HCl-induced cleavage in EW fibres Dislocations not visible in EW fibres Mill 9N, HCl h. Earlywood fibre with many large and small cleavage points, the fibre is thus under cleavage. Mill 9N, HCl 6h. Short earlywood fibres cleaved by the acid. Still some small clefts are seen, which can be cleaved. 7

8 Cleavage per fibre 4,5 4,5,5,5,5,7,5,95 Lab Mill 4 Mill 5 Some examples for different kraft & TMP pulp fibres Mill spruce fibres are more sensitive to acid cleavage than Lab fibres. The HCl-method is accurate and can be used in Strength Delivery investigations. Cleavage per fibre,5,5,5,5 Spruce Pine,68,4,,4,8,8 4 6 Time, h Bleached spruce kraft fibres are more sensitive to HCl than pine fibres. A similar result was obtained with spruce and pine TMP. Possible reason: Thicker S cell wall in pine fibres. For TMP pulps delignification increases the acid sensitivity Cleavage per fibre Pulp fibre line samples HCl cleavage of fibres from a pulp fibre line suggesting fibre compression and mechanical effects in the wash press at point. 8

9 Influence of hemicellulose content on HCl cleavage of pulps Pulps Hemicellulose (%) Glucomannan (%) Cellulose (%) LWFL (mm) H O 8ºC (L -values) LWFL (mm) M HCl 8ºC (L-values) Cleavage per fibre PH/CLD ; ;.5 5.9; RDH/DED ; ;.654.7;.57.4 ITC/DED ;.97.74;.7.96;..95 PS/DED ;.97.99;.8.5;.6.4 Cleavage per fibre Influence of hemicellulose on HCl cleavage of spruce pulps R =, Hemicellulose (%) Bleached spruce kraft pulps with different amounts of hemicellulose were tested for HCl-cleavage. Pulp fibres with the lowest hemicellulose content gave the strongest fibre cleavage by HCl. Thus removal of hemicellulose, mainly glucomannan, during pulping may expose the cellulose microfibril surface allowing a stronger effect of HCl. PH: Prehydrolyzed; RDH: Rapid displacement heating; ITC: Isothermal cooking; PS: -step polysulphide pulping. 9

10 Comparison of HCl and Cellulase cleavage of pulp fibres C le avag e p e r fib re 4 Cleavage of short (SF) and long (LF) spruce kraft pulp fibres by HCl and Cellulase (EG + CBH),85 SF Mill HCl,77 LF Mill HCl,47 SF Lab HCl,7 LF Lab HCl,49 SF Mill Cell,9 LF Mill Cell,94 SF Lab Cell,8 LF Lab Cell Cleavage per fibre 4,5 4,5,5,5,5 HCl cleavage of Mill and Lab pulp fibres from two Scandinavian Pulp Mills (Pulp : % spruce; Pulp : 86% spruce),9,95 4,6, Mill Lab Mill Lab HCl cleaves Mill fibres more than Lab fibres, while cellulases cleave Mill & Lab fibres similarily. Short fibres (.4-. mm) are less cleaved than the long mm fibres. HCl cleaves Mill fibres more than Lab fibres. Fibres with more spruce are more cleaved. More results with HCl & Cellulase

11 Cleavage of pulp fibres by HCl and Cellulase and release of sugars HCl & Pulps: Mill /Lab and Mill /Lab Pulp Relation Spruce / Pine Cleavage / fibre Arabinose (g/l) Galactose (g/l) Glucose* (g/l) Mannose (g/l) Xylose* (g/l) Mill / Lab / Mill 86/ Lab 86/ *OBS: correct to this in the manuscript! Results with HCl. HCl released much xylose ca. g/l, some arabinose, galactose and mannose, and only little glucose (.5 g/l), indicating that degradation of xylan and glucomannan is of some importance for the differencies obtained between Mill and Lab pulp fibres by HCl. HCl swelled the fibres by.7-.7 µm. On the opposite Cellulase released up to.8 g/l of glucose

12 Cleavage of pulp fibres by HCl and Cellulase and release of sugars Cellulase & Pulps: Mill /Lab and Mill /Lab Pulp Relation Spruce/Pine Cellulase *. ml; **.6 ml Cleavage per fibre Glucose (g/l) Xylose (g/l) Mill /67 N Lab /67 N Mill 86/4 N Lab 86/4 N Mill /67 Celluclast* Lab /67 Celluclast* Mill 86/4 Celluclast* Lab 86/4 Celluclast* Mill 86/4 Celluclast** Lab 86/4 Celluclast** Cellulase: Cellulase released up to.8 g/l of glucose, smaller amounts of xylose and very little of the other hemicellulose sugars. N4 and Celluclast decreased fibre width by - µm, indicating removal of S and outer S. Sugar release either by HCl or Cellulase is not of importance for differencies between Mill and Lab pulp fibres.

13 Balloon swelling of unbleached spruce kraft fibres done at our department (Phosphoric acid, LiCl/DMAC, CuEthyleneDiamine) Ander, P. and Daniel, G. 4. Morphology of spruce fibre dislocations as studied by balloon swelling and acid cleavage light and electron microscope observations. COST Action E, SLU, Uppsala, pp. -5. Available at: or From other laboratories: B. Hortling, E. Grönlund and J. Laamanen, KCL, Science and Consulting PB 7, SF- 5 Finland, Swelling of fibres in EWNN for monitoring fibre damages and delignification reactions. COST Action E Wood Fibre Cell Wall Structure. Proc. SLU, Uppsala, 6-8 April,. Different steps in swelling, ballooning, spiral band formation and disintegration of a carboxymethylated cellulose fibre: Stawitz and Kage (958): Das Papier : (In German) Jayme and Harders-Steinhäuser (964): Z. Wiss. Mikrosk (In German).

14 Balloon swelling of unbleached spruce kraft fibres (Phosphoric acid, LiCl/DMAC, CuEthyleneDiamine) Swelling of spruce fibres containing -4 % lignin in 79% phosphoric acid Swelling in LiCl/DMAC Swelling in CuEthyleneDiamine 4

15 Balloon swelling of unbleached spruce kraft fibres (LM and SEM micrographs) Spruce latewood fibre with dislocations seen in polarized light microscopy Spruce fibre swelled in Ph. acid during balloon formation Spruce fibre ballooning in SEM S S Spruce fibre ballooning in SEM. The S wall is rolled off (see also last picture) Balloon swelling showing the S layer, S wall is seen. Typical polarized light patterns of the balloons 5 Stawitz and Kage 958: Jayme and Harders-Steinhäuser 964

16 Fibre swelling and ballooning Fibre swelling & ballooning can be tested in: CuAmmHydroxide CuEthyleneDiamine Fe(III)-tartrate/NaOH LiCl/DMAc Phosphoric acid Use of fibre swelling. The number of balloons and degree of swelling reflects the history of the pulp such as bleaching, mechanical effects, cellulase treatment, early or latewood fibres etc. 6

17 Conclusions - The HCl-method can be used to determine dislocations and weak points in different pulps and may be a complement to wet zero span and other paper tests. Fibre length determination in Fibermaster or Kajaani or other instruments can be done in many paper and fibre research laboratories. - Spruce pulp fibres are more sensitive to HCl than pine pulp fibres. - Pulp samples from fibre lines can be studied with the HCl-method. - Hemicellulose and lignin protect the fibres from the acid. - HCl penetrates deeply into the fibre cell walls, while cellulases act mostly on the fibre surfaces and only penetrate the fibre to a certain extent in dislocations. HCl gives differentiation between Mill and Lab pulp fibres, this is not done by Cellulase. Amount of released sugars by HCl or Cellulase cannot be used to differentiate between Mill and Lab pulp fibres. - Fibre swelling and ballooning in phosphoric acid or copperethylenediamine coupled with image analysis may be used for pulp fibre characterisation. 7

18 Acknowledgement. This research was supported by, Wood Ultrastructure Research Centre, established at SLU and supported by VINNOVA and the following eight Swedish pulp & paper companies: Holmen, Korsnäs, Kappa Kraftliner, M-real, SCA, StoraEnso, Sveaskog and Södra Cell and the chemical company Eka Chemicals. Many thanks to Lars Hildén, Holmen Paper &, for the gift of Novozyme cellulases and for valuable discussions regarding cellulase testing. Thanks to the SD-group (Karin Sjöström et al.) and the TMP group for simplifying cooperation with the pulp and paper industry. 8

19 Thanks for Your attention! Balungen, Dalarna 6 9