EP1508639A1 - Procédé de préparation d'une pâte délignifiée avec haute égouttage et grande résistance - Google Patents

Procédé de préparation d'une pâte délignifiée avec haute égouttage et grande résistance Download PDF

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Publication number
EP1508639A1
EP1508639A1 EP03077627A EP03077627A EP1508639A1 EP 1508639 A1 EP1508639 A1 EP 1508639A1 EP 03077627 A EP03077627 A EP 03077627A EP 03077627 A EP03077627 A EP 03077627A EP 1508639 A1 EP1508639 A1 EP 1508639A1
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EP
European Patent Office
Prior art keywords
pulp
iso
low lignin
beating
low
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EP03077627A
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German (de)
English (en)
Inventor
Johannes Cornelis Dekker
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Ato BV
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Ato BV
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Publication date
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Priority to EP03077627A priority Critical patent/EP1508639A1/fr
Publication of EP1508639A1 publication Critical patent/EP1508639A1/fr
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/02—Methods of beating; Beaters of the Hollander type
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/20—Methods of refining
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment

Definitions

  • the present invention relates to a process for the preparation of a high freeness beaten low lignin pulp with a high strength. More particularly, the present invention relates to a process for the preparation of a high freeness beaten low lignin pulp that is produced from a pulp with a low lignin content, wherein said pulp with a low lignin content is subjected to a beating process under relatively high compression forces and relatively low shear forces.
  • fibre slurries made from pulp are formed into a wet web by using e.g. a cylinder machine or a Fourdrinier machine.
  • the wet webs are subsequently formed, pressed and dried to form the final paper sheet.
  • the pulp is subjected to mechanical actions including beating to improve the strength and other mechanical properties of the final paper sheet.
  • the beating process is most often performed in so-called refiners. These have at least one rotor and at least one stator with either disk-shaped or truncated-cone-shaped surfaces.
  • refiners have at least one rotor and at least one stator with either disk-shaped or truncated-cone-shaped surfaces.
  • internal fibrillation, external fibrillation and fines are developed. External fibrillation and fines create more bonding surface.
  • the present invention involves upgrading fibres of a low lignin pulp that is manufactured by for example the Kraft process and modifications thereof such as the Polysulfide process (cf. Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 20, 4 th Ed., page 493 - 582).
  • Mechanical pulps are produced by mechanical deiribrillisation of wood and have a low fibre strength and small particle size. Moreover, essentially all chemical components of the wood subjected to mechanical pulping remain in the pulp.
  • low lignin pulps e.g. chemical pulps are produced in a digester where the wood is cooked under pressure.
  • US 5.879.510 discloses a process for the preparation of bulky chemimechanical pulp having a low shive content and a low fines content and has improved drainability.
  • US 5.879.510 discloses that for the production of pulp whose strength properties are sufficiently good it is necessary that the pulp must contain a very high proportion of fibre fragments and fines, because these materials function as a binder between long and stiff fibres.
  • a high yield pulp is in particular characterised by its chemical constitution, that is that "high yield” refers to those pulps which give a high yield proportion of pulp for the amount of raw material fibre put into the process. Typically, high yield pulps return 85 to 95% pulp, or yield, to the raw material fibre.
  • lignin The major factor influencing yield is lignin.
  • lignin In low yield pulps most of the lignin is chemically removed leaving mainly pure cellulose fibres whereas in high yield pulps, the lignin is largely retained in the pulp product. Law et al. found that increasing shear forces (higher differential speed), resulted in an undesired reduction of freeness. However, this effect diminished when the compression forces were decreased. Fibre shortening was found to be more severe at higher compression forces at lower pulp concentration. Similarly, fines production was reduced at lower compression-shear forces at low pulp concentration whereas shear had little impact on the production of fines. Tensile strength and burst strength increased with increasing shear forces whereas variation of compression forces had little effect. Tearing resistance appeared to be improved at higher shear forces and higher pulp concentrations.
  • a high freeness pulp (or a low beating degree pulp) has generally low strength, high density, good resiliency and a high drainage rate.
  • It is a further object of the present invention is to provide a beaten low lignin pulp having a high freeness or a low beating degree as well as a high air porosity.
  • Another object of the present invention is providing a beaten low lignin pulp having the improved properties disclosed above whereas strength properties such as tensile strength index and tear strength are not deteriorated compared to a similar pulp having a lower freeness or higher beating degree and lower air porosity.
  • a process for the preparation of a high freeness beaten low lignin pulp with high strength, wherein a low lignin pulp is subjected to a beating process in a beating mill, said beating mill comprising at least two moving and/or rotating means between which said low lignin pulp is beaten, under such conditions that the amount of shear controlled by the speed difference between the at least two moving and/or rotating means is higher than about 0 m/s but not higher than about 6 m/s.
  • the present invention provides a process for the preparation of a high freeness beaten low lignin pulp with high strength, wherein a low lignin pulp is subjected to a beating process under such conditions that prevail in a laboratory PFI mill (see below), wherein the speed difference between internal roll and bedplate is higher than about 0 m/s but not higher than about 6 m/s.
  • FIGs 1- 9 show the results for bleached softwood Kraft pulp, bleached Birch pulp and bleached Eucalyptus pulp.
  • Figure 1 shows the beating degree development as function of the number of PFI revolutions which is a measure of the amount of beating for a bleached softwood Kraft pulp at speed differences of 2 m/s and 6 m/s..
  • Figure 2 shows the tensile strength index development as function of the number of PFI revolutions for a bleached softwood Kraft pulp at speed differences of 2 m/s and 6 m/s.
  • Figure 3 shows the tensile strength index development as function of beating degree for a bleached softwood Kraft pulp at speed differences of 2 m/s and 6 m/s.
  • Figure 4 shows the tear strength development as function of the tensile strength index for a bleached softwood Kraft pulp at speed differences of 2 m/s and 6 m/s.
  • Figure 5 shows porosity (Bendtsen) as function of PFI revolutions for a bleached softwood Kraft pulp at speed differences of 2 m/s and 6 m/s.
  • Figure 6 shows the fibre flexibility (Cyberflex) as function of number of PFI revolutions for a bleached softwood Kraft pulp at speed differences of 2 m/s and 6 m/s.
  • Figure 7 shows the tensile strength index as a function of beating degree for a beaten softwood Kraft pulp and for a beaten pulp from which the fines are removed.
  • Figure 8 shows the fibre and fines surface area at 3000 revolutions as function of speed difference for a bleached softwood Kraft pulp at speed differences of 2 m/s, 6 m/s and 12 m/s.
  • Figure 9 shows the net specific power consumption as function of tensile strength index for a bleached softwood Kraft pulp at speed differences of 2 m/s and 6 m/s.
  • Figure 10 shows the tensile strength index as a function of beating degree for a beaten Eucalyptus pulp at speed differences of 2 m/s and 6 m/s.
  • Figure 11 shows the tensile strength index as a function of beating degree for a beaten Birch pulp at speed differences of 2 m/s and 12 m/s.
  • Figure 12 shows the tensile strength index as a function of beating degree for the three pulps ( Figures 3, 10, 11) at 2 m/s (invention) and 6 m/s (prior art).
  • the PFI mill beats pulp under laboratory conditions that simulate commercial beating processes.
  • the PFI Mill produces standardised reference pulp in accordance with ISO 5264/2 and TAPPI T-248.
  • the PFI Mill is suitable for use in evaluating all types of pulps in common use.
  • the PFI Mill consists of an internal roll with beating bars revolving inside a heavy bowl (bedplate). Both the roll and bedplate rotate, but at different speeds and in the same direction. The difference between the rotation speeds, expressed in m/s, is a measure for the shear force. As the roll is pressed against the bedplate it transfers energy to the fibres. Pulp consistency is constant throughout the operation as roll and bedplate revolve at constant speed.
  • the rate of pulp development is governed by the pressure between the roll and bedplate and can be adjusted to suit the pulp type under evaluation.
  • the degree of beating is proportional to the beating time and expressed by the amount of revolutions of the inner roll. Separate pulp samples are required for each point on the beating development curve. Beating in the PFI Mill is carried out automatically once the pulp charge has been placed in the bedplate.
  • the beating elements consist of a stainless steel roll with 33 chiselled bars and a smooth sided circular bedplate. The bedplate is charged with pulp, forming an endless band around the circumference. As the roll rotates with a higher peripheral speed than the bedplate, the roll bars cut out sections of the pulp band, transporting them into the beating zone.
  • the beating pressure (compression force, expressed in kN/m) is obtained from a load applied by means of a weight lever action via a cantilever mounted on the base of the supporting pillar that is rigidly attached to the frame or by a adjustable air pressure cylinder.
  • the PFI Mill also allows pulp to be beaten with a fixed gap set by means of a micrometer placed against the pillar adjusting the amount of swing made by the cantilevered arm. This practice is used also for grinding-in and calibration purposes.
  • the PFI Mill is a precision instrument that is preferred by many laboratories because of its good calibration characteristics and ease of operation, both of which enhance the reproducibility of pulp evaluation.
  • the automation of the PFI Mill both reduces the risk of operator error and allows more free time for other tasks in the laboratory.
  • Beating equipment used in the industry may have different geometries. For example continuos operating equipment like, single disc refiners, double disc refiners and conical refiners, or batch wise operating equipment like Hollanders and Kollergangs.
  • the inventors have modified the standard PFI-mill by means of adding a speed control to the motor for the beating roll and by adding a electrical power measurement unit.
  • the inventors have surprisingly found that lower shear forces at comparable compression forces lead to lower beating degree (higher freeness) and higher porosity with a similar strength development.
  • the inventors have also surprisingly found that a high fines content is not necessary to provide a paper having sufficient tensile strength, tear strength and burst strength.
  • the inventors have also surprisingly found that beating with less shear consumes less energy then beating under standard conditions
  • the speed difference between the at least two moving and/or rotating means or between roll and bedplate as present in the PFI mill is higher than about 0 m/s but not higher than about 6 m/s, preferably not higher than about 3 m/s and most preferably not higher than about 2 m/s. Additionally, it is also preferred that at the same time the compression force expressed as the line force is at least about 2 kN/m but less than about 8 kN/m and in particular at least 3.3 kN/m.
  • the compression force can also be expressed as a pressure range.
  • a line force of 2 - 8 kN/m corresponds to a pressure force of 400-1600 kN/m 2 .
  • the process is conducted at a pulp concentration in the range of about 2 to about 30 wt.%, preferably at a pulp concentration of about 5 to about 25 wt.% and most preferably at least about 10 wt.%, based on the total weight of the pulp.
  • the high freeness beaten low lignin pulp has preferably a beating degree of less than about 25 °SR, preferably less than about 23 °SR and in particular less than about 21 °SR, at about 6000 PFI revolutions (see Figure 1).
  • 80 g/m 2 handsheets made on a Rapid Koethen according to ISO 5269-2:1980 from the high freeness beaten low lignin pulp have a tensile index level of at least 70 Nm/g according to ISO 1924/2:1994, preferably at least 75 Nm/g and in particular at least 80 Nm/g.
  • the high freeness beaten low lignin pulp according to the invention has preferably a porosity of at least 600 ml/min according to ISO 5636-3:1992 part 3, Bendtsen method.
  • the low lignin pulp used as starting material is preferably a low yield pulp.
  • a very suitable low yield pulp has a lignin content of not more than 5 wt.%, preferably not more than 4 wt.%, based on the total dry weight of the pulp.
  • the low lignin pulp is a low yield chemical pulp, even more preferably a low yield bleached chemical pulp. Even more preferred is that the low yield bleached chemical pulp is obtained by the Kraft process and is in particular a softwood or hardwood pulp.
  • the softwood pulp is preferably Northern Bleached Softwood Kraft comprising about 70 wt.% spruce and about 30 wt.% pine, based on the total dry weight of the pulp.
  • the hardwood pulp is preferably Birch or Eucalyptus, wherein the Birch comprises about 78 wt.% Birch and about 22 wt.% Aspen.
  • the present invention also relates to a high freeness beaten low lignin pulp with high strength that is characterised by the following features:
  • the high freeness chemical pulp according to the invention is very suitable for making paper.
  • Tests were performed in a standard PFI mill with commercial available bleached softwood Kraft pulp, bleached Birch pulp and bleached Eucalyptus pulp. All pulps were present in pulp sheet form. The tested pulps have a lignin content less than 5 wt.%. Beating curves were determined at 0, 3000 and 6000 revolutions which is a measure of the amount of beating. Tests were performed at different speed differences, i.e. 2, 6 and 12 m/s for the bleached softwood Kraft, 2 and 12 m/s for the bleached Birch, i.e. 2 and 6 m/s for the Eucalyptus pulp. The compression force was kept constant at 3.3 kN/m.
  • the tested pulps were produced into 80 g/m 2 paper samples according to ISO 5269-2:1980 part 2, Rapid Koethen method from which the following properties were determined: tensile strength index (ISO 1924-2:1994), tear strength (ISO 1974:1990), burst strength (ISO 2758:1983), thickness (ISO 534:1988) and porosity (ISO 5636-3:1992)
  • the data are shown in the Figures as well as in Tables 1 - 3.
  • Figure 1 shows the beating degree as function of the number of PFI revolutions., the beating degree increased with increasing speed difference, i.e. higher shear forces resulted in a higher beating degree (a lower freeness).
  • Figure 3 clearly shows that for bleached softwood Kraft pulp at lower beating degree and lower shear forces a higher tensile strength index is attained.
  • Figure 4 shows that the speed difference in PFI beating does not effect the relation between tensile strength index and tear strength.
  • Figure 6 shows that flexibility development of the fibres is hardly effected by speed difference.
  • the inventors have shown that the development of fibre flexibility has the same trend as the development of tensile strength as a function of PFI revolutions.
  • Figure 7 shows that removal of fines from beaten chemical pulp lowers the beating degree significantly and has a minor effect on tensile strength index.
  • Figure 8 shows that beating with less shear force generates less fines.
  • beating with less shear force creates less fines and therefore creates a pulp with a low beating degree at a comparable strength level as standard beating.
  • Figure 9 shows that speed difference have significant effect on the relation between tensile strength index and net specific energy consumption, i.e. less shear forces resulted in less energy consumption compared at the same tensile strength index.
  • the present inventors have surprisingly shown that reducing the amount of shear force in the beating process of a low lignin pulp the beating degree of a pulp can be better controlled thereby leading to improved drainage properties without affecting other desired properties of the paper produced. Sometimes one or more of these properties are improved.
  • the present inventors have also surprisingly shown that reducing the amount of shear force reduces the amount of beating energy. Obviously this has clear advantages regarding production rate (higher capacity of the paper machine) and energy consumption (decreased energy consumption).

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EP03077627A 2003-08-22 2003-08-22 Procédé de préparation d'une pâte délignifiée avec haute égouttage et grande résistance Withdrawn EP1508639A1 (fr)

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EP03077627A EP1508639A1 (fr) 2003-08-22 2003-08-22 Procédé de préparation d'une pâte délignifiée avec haute égouttage et grande résistance

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Application Number Priority Date Filing Date Title
EP03077627A EP1508639A1 (fr) 2003-08-22 2003-08-22 Procédé de préparation d'une pâte délignifiée avec haute égouttage et grande résistance

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2066447A1 (fr) * 2006-08-31 2009-06-10 KX Technologies LLC Procédé de fabrication de fibres fibrillées
CN101760984B (zh) * 2008-11-28 2012-06-06 山东福荫造纸环保科技有限公司 一种高强度混合浆料及其制备的文化用纸
CN105088854A (zh) * 2015-08-13 2015-11-25 合肥龙发包装有限公司 一种环保包装纸
CN114960291A (zh) * 2022-05-27 2022-08-30 华南理工大学 一种高透气度伸性纸袋纸及其制备方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JAMES OLSON, BRUCE ALLISON, TIM FRIESEN AND CHRISTINE PETERS: "Fibre Fractionation for high porosity sack kraft paper", TAPPI JOURNAL, vol. 84, no. 6, June 2001 (2001-06-01), pages 1 - 10, XP002267148 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2066447A1 (fr) * 2006-08-31 2009-06-10 KX Technologies LLC Procédé de fabrication de fibres fibrillées
EP2066447A4 (fr) * 2006-08-31 2012-02-08 Kx Technologies Llc Procédé de fabrication de fibres fibrillées
CN101760984B (zh) * 2008-11-28 2012-06-06 山东福荫造纸环保科技有限公司 一种高强度混合浆料及其制备的文化用纸
CN105088854A (zh) * 2015-08-13 2015-11-25 合肥龙发包装有限公司 一种环保包装纸
CN114960291A (zh) * 2022-05-27 2022-08-30 华南理工大学 一种高透气度伸性纸袋纸及其制备方法

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