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Understanding the fiber development during co-refining of white birch and black spruce mixtures. Part 2. Thermomechanical pulping

Pulp & paper Canada, 2004-12, Vol.105 (12), p.88-92

2005 INIST-CNRS ;Copyright Southam Business Communications, Inc. Dec 2004 ;ISSN: 0316-4004 ;EISSN: 1923-3515 ;CODEN: PPCADD

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  • Title:
    Understanding the fiber development during co-refining of white birch and black spruce mixtures. Part 2. Thermomechanical pulping
  • Author: WU, M. R ; LANOUETTE, R ; VALADE, J. L
  • Subjects: Applied sciences ; Birch ; Exact sciences and technology ; Newsprint ; Paper, paperboard, non wovens ; Polymer industry, paints, wood ; Pulp & paper mills ; Pulp manufacturing ; Pulping ; Spruce ; Technology ; Wood. Paper. Non wovens
  • Is Part Of: Pulp & paper Canada, 2004-12, Vol.105 (12), p.88-92
  • Description: The studies by [Luukko] (8(showed that good relationship between the FISV and fibrillation of fibres existed and correlated well with the tensile index of paper sheet made from fines. As shown in Fig. 6, the R200 and P200 fractions had a much higher HSV than those of the R48 and R100 fractions for all the TMPs except the TMP-B. The microscopic observation proved that the R200 and P200 had a degree of fibrillation higher than that of R48 and R100 for all the samples except the TMP-B. The four fractions of TMP-B had a similar HSV, which indicated that the birch fibres had a low degree of fibrillation. In addition, the R200 of TMP-B was rich in vessel fragments while the P200 was rich in ray cells and their fragments. Both the vessel fragments and the ray cells had low specific surface. Consequently, augmenting the substitution of birch for spruce in the chip mixture had a slight effect on the HSV of the R48 and R100 fractions, but decreased more rapidly the FISV of the R200 and P200 fractions, liven at the substitution of 10% with birch, the HSV of the R200 and P200 fractions decreased about 25% when compared to that of TMP-S. Using up to 40% birch, the HSV of the R200 and P200 fractions decreased about 75%. In view of this point, the use of birch in co-refining has a negative effect on the fibrillation of spruce fibres. The presence of vessel fragments and less fibrillar fibres of birch also decreased the HSV of the R200 and P200 for the TMP-B30. Similar to the R28, the R48 consisted of lots of intact or partly intact but shorter fibres. The earlywood fibres appeared gencmlly to be more flexible and had higher compressibility than the latewood fibres and the birch fibres, as shown in Fig. 7: A. The paper strength and density will benefit from these properties. A few latewood fibres had their S2 completely exposed (Fig. 7: B). The birch fibres showed more cracks across the cell wall in the S2 helix direction (Fig. 7: C). However, the latewood fibres of spruce and the birch fibres still seemed to be rigid. According to Reme et al [14], latewood fibres experienced a larger reduction in wall thickness during refining than earlywood fibres. In our studies, it seems that partially removed cell wall does not improve the fibre flexibility of birch. For the TMP-B30, much more birch fibres were observed in R48 than that in R28. Similar to the R28, the fibres of spruce and birch presented similar characteristics in the TMP-B30 as seen in the TMP-B and the TMP-S. Generally speaking, birch has a poorer fibre development (such as fibrillation and flexibility) in refining than that of spruce due to differences of inherent fibre characteristics of these two species. The birch fibres have a thicker S1 layer than that of black spruce fibres, which causes the lower delamination and fibrillation degree of birch fibres. Being the main portion of the cell wall, the S2 layer (thickness, microfibrillar angle, etc.) has a decisive influence on fibre stiffness and on papermaking properties. Latewood tracheids of spruce have a S2 with thicker wall and higher microfibril angle than that of earlywood tracheids. The S2 layer of birch libriform fibres is also thicker than that of spruce earlywood tracheids but thinner than that of spruce latewood tracheids. Thus, the birch fibres could still have a higher stiffness although the S2 of some birch fibres is exposed partly or completely, as showed by scanning electron microscopy. Koljonen et al [15] obtained similar results on latewood spruce fibres. They studied the delamination of spruce fibres during refining and indicated that the stiffness of the earlywood fibres decreased during refining while that of the latewood fibres did not change.
  • Publisher: Don Mills, ON: Southam
  • Language: English
  • Identifier: ISSN: 0316-4004
    EISSN: 1923-3515
    CODEN: PPCADD
  • Source: ProQuest Central
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