EP0030778B1 - Verfahren zur Herstellung raffinierter Pulpe - Google Patents

Verfahren zur Herstellung raffinierter Pulpe Download PDF

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Publication number
EP0030778B1
EP0030778B1 EP19800302722 EP80302722A EP0030778B1 EP 0030778 B1 EP0030778 B1 EP 0030778B1 EP 19800302722 EP19800302722 EP 19800302722 EP 80302722 A EP80302722 A EP 80302722A EP 0030778 B1 EP0030778 B1 EP 0030778B1
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Prior art keywords
pulp
effected
temperature
mechanical
weight
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Expired
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EP19800302722
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English (en)
French (fr)
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EP0030778A1 (de
Inventor
Adrian John Barnet
Alan Caughey Shaw
Charles Donald Logan
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Qns Paper Co Ltd
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Qns Paper Co Ltd
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
    • D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites

Definitions

  • the present invention is directed to the formation of improved mechanical wood pulps useful for substitution for chemical pulps.
  • mechanical pulp as used herein has its normal meaning in the art and refers to the product of disruption of a woody substance by mechanical action to yield a product consisting mainly of liberated and separated single woody fibres and their fragments and which is suitable for use in the manufacture of paper.
  • fibre as used herein also has its normal meaning in the art and refers to individual plant cells which make up the woody material and which, in softwoods, are known botanically as parenchyma cells and tracheids. These fibres inherently have diameters generally below 0.05 mm and in the case of wood species commonly used in pulp formation and paper making, such as, spruce, balsam, pine, aspen and poplar, considerably below 0.05 mm.
  • Refiner pulps are a class of mechanical pulps formed by passing particulated cellulosic fibrous material, usually wood chips through a small gap between two ribbed parallel plates rotating with respect to each other (known as a disc refiner). The procedure may be effected at atmospheric pressure, the product being known as “refiner mechanical pulp” (RMP), or under pressure, typically 1 to 2 atmospheres greater than atmospheric pressure, and at elevated temperature, such as, 120°C, the product being known as “thermomechanical pulp” (TMP).
  • RMP refiner mechanical pulp
  • TMP thermomechanical pulp
  • the refining process usually is effected in two stages. In the first stage, the fibres are separated and liberated and in the second stage, additional refining energy is supplied to increase the fibre flexibility and conformability, fibrillation and bonding. Usually half the overall refining energy of 7 to 8.5 megajoules per kilogram is applied to the fibre-liberation stage.
  • Runability refers to that combination of properties which allows the wet web to be transported at high speed through the forming, pressing and drying sections of the paper making machine and allows the dry sheet to be reeled and printed with not more than an acceptable number of breaks. In effect, runability is a measure of the efficiency with which the paper passes through the paper machine and printing press.
  • the chemical pulp component is usually manufactured by thr kraft or sulphite process in yields ranging from 45 to 65%. Chemical pulps are expensive, make heavy demands on the mills wood resources, and entail daunting pollution problems. As already noted, mechanical wood pulps are obtained in yields in excess of 95% with minimal pollution problems.
  • the process of this invention results in an increase in the elongation to rupture (hereinafter known as 'wet stretch”) and an improvement in the stress-strain properties of the wet web formed from the pulp, while simultaneously maintaining rapid drainage.
  • 'wet stretch elongation to rupture
  • the fibre-to-fibre bonding within a dry paper sheet formed from the pulp.produced by the process of the invention is improved, thereby resulting in the desirable properties of increased tensile and burst strengths and increased sheet density.
  • One important feature of this invention is that there is formed a refiner pulp which can be used as a substitute, in whole or in part, for chemical pulp in many of its applications and which results from a procedure which does not produce more than insignificant quantities of polluting effluents, in complete contrast to chemical pulping procedures, where large quantities of polluting effluents must be handled.
  • the overall energy requirements of the refining operation to provide a predetermined level of pulp quality also are decreased, as compared with the conventional refiner pulp-formation operation.
  • the process of the invention comprises three steps, namely (a) subjecting particulated cellulosic fibrous material to mechanical action in a disc refiner to form a pulp consisting mainly of single fibres and fragments thereof, (b) chemical reaction of the pulp with a soluble salt of sulfurous acid under certain precise elevated temperature and pressure conditions as detailed below, and (c) subjecting the chemically-treated pulp to mechanical action to refine the same and improve the pulp quality.
  • the cellulosic fibrous material species and refining conditions required to manufacture a usable mechanical pulp are well known to the art. For example, it is well known that most hardwoods cannot be refined to yield mechanical pulps with adequate strengths. Application of the invention is restricted to refiner pulps which are generated from softwoods, or other cellulosic fibrous material species which are recognized in the industry as being suitable for the preparation of refiner pulps. The invention is described further with particular reference to wood species.
  • a wood fibre consists essentially of a cell wall, whose outer surface is made up of cellulose-rich fibrillar layers known as the S 1 and S 2 layers. In wood, the space between the fibres, known as the middle lamellae, is filled with a lignin-rich material.
  • the process of the invention requires that, in the initial liberation of the fibre from the wood in a disc refiner, the feature occurs mainly in the S 1 and S 2 layers, thus exposing the cellulose-rich fibrillar material which is the source of the fibrillation characteristic of a good mechanical pulp. Since this fibre morphology is established at the moment of fibre liberation, it is necessary that the process of fibre liberation proceed largely to completion. Therefore, the product of the initial mechanical fibre separation step of the process of the invention must consist mainly of single wood fibres, which inherently have average diameters less than 0.05 mm. More than the minimum energy to accomplish this separation may be applied, but is unnecessary.
  • the initial fibre separation step in this invention is effected at a temperature below the thermal softening point of lignin.
  • the latter temperature is variable with the wood species, duration of heating and refining conditions, but is generally below 150°C.
  • a product of step (a), suitable for further treatment in accordance with this invention is obtainable simply by following the first stage refining procedures well known to the art, for the production of a good mechanical pulp. This is usually accomplished by presteaming wood chips, usually at a temperature of 120° to 135°C and 1 to 2 atmospheres pressure for 2 to 10 minutes, then passing the presteamed wood chips, which have not been softened by chemical action, through a disc refiner at a temperature below the thermal softening temperature of the lignin, and applying sufficient refining energy to yield a mechanical wood pulp consisting mostly of single fibres and their fragments, such fibres and fragments being predominantly below 0.05 mm in average diameter. This operation is generally effected at a consistency of 10 to 40% by weight, usually 25 to 30% by weight.
  • step (a) the chemical nature of the fibre is modified by reaction with an aqueous solution of a soluble salt of sulphurous acid, usually sodium sulphite.
  • the reaction is effected at temperatures above 110°C under a superatmospheric pressure for a time sufficient to yield a chemically-treated mechanical wood pulp capable of forming a paper web having improved wet stretch and stress-strain properties and exhibiting rapid drainage, but for a time insufficient to cause substantial dissolution of lignin with consequent loss of yield and generation of polluting effluents.
  • the exact nature of the chemical reactions involved in the chemical treatment effected in this invention are not fully understood, but are thought to involve sulphonation.
  • the alkali requirement may be met entirely with sodium sulphite. However, since only half of the sodium of sodium sulphite is available for neutralization, it is usually more economical to meet part of the alkali requirements by additions of sodium hydroxide or sodium carbonate.
  • the pH of the mixture is preferably kept below 12 because hemicelluloses are dissolved from wood fibre by higher pH's, with consequent loss in yield.
  • the amount of sodium sulphite used in the chemical treatment is in the range of 4% to 15% by weight based on the mechanical wood pulp resulting from step (a), although lower concentrations down to 1 % by weight may be used with reduced beneficial effect, with the provision that the residual sulphite content of the mixture, as measured iodimetrically, does not fall substantially to zero before termination of the reaction.
  • concentrations down to 1 % by weight may be used with reduced beneficial effect, with the provision that the residual sulphite content of the mixture, as measured iodimetrically, does not fall substantially to zero before termination of the reaction.
  • Below 1 % by weight of sodium sulphite improvements are too small to justify the expense of treatment.
  • improvements are observed with chemical charges up to 25% by weight of the pulp, but the additional cost is not justified by the small additional improvement.
  • a chemical charge of between 1% and 25% by weight, preferably between 4% and 15% by weight, of the mechanical pulp is used.
  • the chemical charge preferably has a pH between 7 and 12, and contains sodium sulphite and sufficient alkali to maintain a pH greater than 3 throughout the reaction.
  • the reactions of sulphite with wood are known to consist of a large number of different reactions, whose rates are dependent on reaction conditions, particularly pH and temperature.
  • the present state of our knowlede of this complex subject has been summarized by G. Gellerstedt in Svensk Papper- stidning nr. 16, 1976, p. 537 to 543. It has been established that the reactions necessary for the application of the process of the invention and the results attained thereby are those that proceed at pH's greater than 3 and preferably over 7, and at temperatures over 110°C, and preferably over 130°C.
  • Other reactions of woody substances with sulphite which proceed at lower pH's and at temperatures below 100°C are known, such as those described by J. J.
  • step (c) the maximum improvement, namely, maximum increase in wet stretch, maximum improvement'in stress-strain, maximum increase in strength characteristics, and maximum decrease in refiner power requirements for the second stage (step (c) discussed below), is obtained from the process of the invention when the mechanical pulp from step (a) with added chemical is heated at 160°C for 30 minutes.
  • the temperature can be lowered if the reaction time is increased. Below 120°C, reaction time becomes impractically long, and below 110°C, the required reactions effectively cease.
  • the reaction temperature can be increased if the reaction time is shortened.
  • the practical upper limit of temperature appears to be 200°C with reaction times of 1 to 2 minutes. We prefer not to operate under these extreme conditions because the precise control of conditions and reaction times needed to achie ⁇ t ; an optimum product are difficult to secure.
  • reaction time is shorter than optimum, the improvements in wet starch, stress-strain and strength properties and energy requirements are less than may be otherwise obtained by operating under optimum conditions. If the reaction time is too long, substantial dissolution of the lignin from the pulp, in the treating chemical occurs, with consequent loss of yield and formation of polluting effluent. While the process is still operable to produce property improvements under these conditions some of the advantages of wood economy and low pollution are lost and generally are avoided.
  • the chemical treatment is operable over a time-temperature range from 110°C for 12 hours to 200°C for 1 minute. It is understood that an increase in temperature must be accompanied by a concomittant decrease in reaction time. For example, the process is not operable at a temperature of 200°C for 12 hours. To derive maximum benefits from the chemical treatment step, it is preferred to operate in the more limited range of 130°C for 2 hours to 180°C for 15 minutes.
  • step (b) on the mechanical wood pulp resulting from step (a) is quite distinct from the methods used in the pulping of woody substances with sulphite or bisulphite to form chemical pulp.
  • sulphite pulping heat and chemical are supplied to the woody material in chip form (i.e., fibre bundles) by circulating hot cooling liquor through a bed of the woody material.
  • the resistance to flow of liquor is so great that circulation of liquor therethrough is impractical.
  • all of the chemical required to effect the reaction of step (b) must be incorporated in the pulp when it enters the reactor.
  • the chemical treatment step in the process of the invention is also distinguished from chemical pulping processes in that the process of the invention cannot be conducted practically in a batch process, such as is used in chemical pulping. This is because the thermal insulating properties of the mechanical pulp are so high that a large pulp mass cannot be heated to reaction temperature by conduction in a reasonable length of time.
  • the chemical treatment may be carried out batchwise using dielectric or microwave heating techniques but such methods are expensive. It is preferred to carry out the chemical reaction step in an apparatus wherein pulp is continuously raised to reaction temperature and introduced into one end of a reaction vessel of such size as to provide the desired reaction duration, while treated pulp is removed simultaneously from the other end.
  • step (c) the product of step (c) is subjected to further refining action in a disc refiner, following the usual practice of the industry for second stage refining of a mechanical wood pulp.
  • the results of this second refining action differ from those obtained with an ordinary mechanical wood pulp because the application of steps (a) and (b) in accordance with this invention places the pulp in the required physical and chemical configuration to utilize further refining energy efficiently and economically. It is well known that the quality of a mechanical wood pulp can be improved by increased refining, but at a cost of slower drainage and increased energy demand.
  • step (b) may be refined to equivalent quantity with significantly less energy, while achieving a faster drainage, as compared to mechanical pulp from step (a) which has not been subjected to step (b).
  • Figure 1 a measure of pulp quality is plotted against refining power for two cases.
  • the measure of pulp quality employed was the tensile strength of the wet web, measured at 5% wet stretch to eliminate the effects of pulp latency. Similar plots are obtained using such other measures of pulp quality as breaking length or burst factor.
  • Point A in Figure 1 defines the state of the pulp at the completion of step (a) of the process of the invention.
  • Point B represents the same pulp after completion of step (b).
  • the line B-C gives the properties of the pulps derived from step (b) by the application of varying amounts of refining energy in accordance with step (c) of the process of the invention.
  • the line A-D represents the properties of pulps obtained by directly refining the product of step (a), without the application of step (b).
  • step (c) The consistencies employed in the application of step (c) may be varied over the range normally employed in the second stage refining of a mechanical wood pulp, but the properties of the product depend to some extent on the refining consistency chosen. Higher consistencies over 20% by weight yield products with higher wet stretch while lower consistencies tend to produce pulps with higher strength. By adjustments in refining consistency, the desired balance between wet stretch and strength for a particular application can be achieved. For most applications, it is preferred to carry out the refining step (c) at consistencies between 1% and 35% by weight.
  • the amount of energy applied in step (c) may be varied according to the desired properties of the product and the intended end use.
  • the degree of refining to which the pulp is subjected is usually controlled by the freeness of the finished pulp. For most applications, this freeness should fall within the range of 50 to 700 C.S.F.
  • boxboard stock is typically of higher freeness than magazine grade paper stock.
  • Spruce chips were pre-steamed for 25 minutes at 33.8 KPa and fed to a 1000 HP Sprout-Waldron 36 ICP refiner under the following conditions:
  • the pulp from the pressurized refiner consisting mainly of single fibers, and substantially free of particles greater than 0.05 mm in diameter, was divided in three portions. One portion was mixed with 1096 by weight of sodium sulphite at pH 9 and heated at 18% consistency at 90°C for 1 hour. Another portion was mixed with 1096 sodium sulphite at pH 7 and heated at 18% consistency and 160°C under a pressure of 614 kPa for 1 hour. A third portion was untreated. Each portion was then refined further in a 30 cm Sprout-Waldron open discharge refiner at 18% consistency and a specific energy input at 4.5 megajoules per kilogram. All three pulps thus received a total of 7.7 megajoules per kilogram of refining energy.
  • the drainage rate is much faster than an untreated TMP of similar quality.
  • the wet caliper and bulk are measures of the fiber's ability to consolidate in the paper sheet.
  • the low values obtained with the pulp treated at 160°C are indicative of a flexible fiber which consolidates well to form a dense, coherent sheet.
  • a TMP prepared in a pressurized refiner as described in Example 1 was mixed with 10% sodium sulphite at pH 9.0 and heated at 18% consistency at 160°C and 614 KPa for 1 hour. Samples of the treated and untreated TMP were then refined to comparable freeness levels, and the pulp properties measured after latency removal at 90°C for 15 minutes. Power consumptions and the corresponding pulp properties are outlined in the following Table II:
  • Southern pine pulp from the pressurized first stage refiner of a commercial newsprint mill was treated at 145°C for 1 hour with 10% by weight of sodium sulphite at pH 9. The resulting pulp was then refined at power inputs of 1.35 and 2.7 megajoules per kilogram in a 30 cm Sprout-Waldron refiner.
  • Spruce chips were refined in a Bauer 420 open discharge refiner at a rate of 59 tonnes per day and a specific energy of 4.3 megajoules per kilogram.
  • One portion of this RMP was mixed with 10% sodium sulphite at pH 9 and heated at 145°C and 440 kPa pressure for one hour. Both treated and untreated pulps were further refined in a 30 cm Sprout-Waldron refiner at 2096 consistency.
  • the resulting RMP's had the properties outlined in the following Table IV, after latency removal at 90°C for 15 minutes.
  • the present invention is directed to the formation of an improved mechanical pulp which .can be used as a substitute for chemical pulp.

Claims (11)

1. Verfahren zum Herstellen einer Refiner-Pulpe mit verbesserten Eigenschaften, bei welchem (a) nicht durch chemische Einwirkung erweichte Holzschnitzel in einem Scheiben-Refiner bei einer Temperatur unterhalb der thermischen Erweichungstemperatur des Lignins einer mechanischen Einwirkung ausgesetzt werden um das Entstehen eines hauptsächlich aus einzelnen Holzfasern und Bruchstücken hievon bestehenden mechanischen Holzschliffes zu bewirken, (b) der Holzschliff bei einer oberhalb 110°C liegenden erhöhten Temperatur und unter überatmosphärischem Druck mit einer wässerigen Lösung eines löslichen Salzes der schwefeligen Säure behandelt wird, die eine zum Aufrechterhalten eines pH-Wertes von größer als 3 während der Behandlung ausreichende Menge an Alkali enthält, wobei diese Behandlung bei einer Temperatur und während einer Zeit durchgeführt wird, die eine Reaktion mit dem Holzschliff ermöglicht und einen chemisch behandelten Holzschliff ergibt, der in der Lage ist eine Papierbahn erhöhter Dehnung im feuchten Zustand und verbesserter Spannungs-Dehnungs-Eigenschaften unter Beibehaltung rascher Entwässerung zu bilden und wobei diese Behandlung bei einer Temperatur und während einer Zeit durchgeführt wird, die unzureichend ist eine unter 85" Gew.-% liegende Ausbeute an behandeltem Holzschliff zu liefern, und (c) der chemisch behandelte Holzschliff in einem Scheiben-Refiner einer mechanischen Einwirkung unterworfen wird um dessen Pulpenqualität zu verbessern und einen Refiner-Holzschliff zu bilden, der eine Stoffdurchlässigkeit. (Canadian Standard Freeness) von 50 bis 700 besitzt.
2. Verfahren nach Anspruch 1, bei welchem das lösliche Salz der schwefeligen Säure eine wässerige Natriumsulfitlösung ist und die Behandlungsstufe (b) bei einer Stoffdichte von 4 bis 15 Gew.-% und einer auf Holzschliff bezogenen angewendeten chemischen Beschickung von 1 bis 25 Gew.-% an Natriumsulfit durchgeführt wird.
3. Verfahren nach Anspruch 2, bei welchem die Natriumsulfitlösung zu Beginn einen pH-Wert von 9 bis 12 besitzt.
4. Verfahren nach irgendeinem der Ansprüche 1 bis 3, bei welchem die wässerige Lösung eines löslichen Salzes der schwefeligen Säure den Holzschnitzeln vor dem Hindurchführen der letzteren durch den Scheiben-Refiner in Stufe (a) zugesetzt wird, so daß die wässerige Lösung mit den Fasern beim Entstehen derselben vermischt wird.
5. Verfahren nach irgendeinem der Ansprüche 1 bis 4, bei welchem die Behandlungsstufe (b) bei einer Temperatur von 130°C während 2 Stunden bis 180°C während 15 Minuten durchgeführt wird, wobei die Temperatur und Dauer der Behandlung die Aufrechterhaltung einer Ausbeute von über 901 Gew.-% bewirkt.
6. Verfahren nach irgendeinem der Ansprüche 1 bis 5, bei welchem die Holzschnitzel vor Stufe (a) bei einer Temperatur von 120 bis 135°C und unter einem Druck von 1 bis 2 at gedämpft werden.
7. Verfahren nach irgendeinem der Ansprüche 1 bis 6, bei welchem Stufe (a) bei einer Stoffdichte von 10 bis 40 Gew.-% durchgeführt wird.
8. Verfahren nach irgendeinem der Ansprüche 1 bis 7, bei welchem der in Stufe (a) erhalene Holzschliff hauptsächlich aus einzelnen Holzfastern und Bruchstücken hievon mit einem Durchmesser von weniger als 0,05 mm besteht.
9. Verfahren nach irgendeinem der Ansprüche 1 bis 8, bei welchem Stufe (a) unter einem überatmosphärischen Druck durchgeführt wird.
10. Verfahren nach irgendeinem der Ansprüche 1 bis 9, bei welchem Stufe (c) bei einer Stoffdichte von 1 bis 35 Gew.-% durchgeführt wird.
11. Verfahren nach irgendeinem der Ansprüche 1 bis 10, bei welchem Stufe (c) durchgeführt wird um einen Reifiner-Holzschliff mit einer Stoffdurchlässigkeit von 100 bis 400 C.S.F. (Canadian Standard Freeness) zu schaffen.
EP19800302722 1979-12-17 1980-08-08 Verfahren zur Herstellung raffinierter Pulpe Expired EP0030778B1 (de)

Applications Claiming Priority (2)

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US10466879A 1979-12-17 1979-12-17
US104668 1979-12-18

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EP0030778A1 EP0030778A1 (de) 1981-06-24
EP0030778B1 true EP0030778B1 (de) 1983-07-20

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EP (1) EP0030778B1 (de)
JP (1) JPS5691093A (de)
AU (1) AU531907B2 (de)
BR (1) BR8005950A (de)
CA (1) CA1145107A (de)
DE (1) DE3064270D1 (de)
FI (1) FI71779C (de)
MX (1) MX156081A (de)
NZ (1) NZ194407A (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4502918A (en) * 1981-06-10 1985-03-05 Macmillan Bloedel Limited Two-stage chemical treatment of mechanical wood pulp with sodium sulfite
SE456430B (sv) * 1985-11-06 1988-10-03 Sunds Defibrator Sett for framstellning av mekanisk massa
US4718980A (en) * 1985-12-30 1988-01-12 Weyerhaeuser Company Interstage treatment of mechanical pulp
US5607546A (en) * 1990-02-13 1997-03-04 Molnlycke Ab CTMP-process
SE466060C (sv) 1990-02-13 1995-07-11 Moelnlycke Ab Absorberande kemitermomekanisk massa och framställning därav
AU4271596A (en) * 1995-12-19 1997-07-14 Kvaerner Hymac Inc. Process for treating refiner pulp
CA2243228A1 (en) * 1997-07-17 1999-01-17 Donohue Inc. Preparation of mechanical wood pulps with reduced energy

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4145246A (en) * 1976-07-19 1979-03-20 Crown Zellerbach Corporation Process for making high-strength, high-yield sulfite-modified thermomechanical pulp and a linerboard composition produced therefrom

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NZ194407A (en) 1983-02-15
CA1145107A (en) 1983-04-26
FI71779B (fi) 1986-10-31
AU6046080A (en) 1981-06-25
FI802654A (fi) 1981-06-18
BR8005950A (pt) 1981-06-23
EP0030778A1 (de) 1981-06-24
MX156081A (es) 1988-06-30
DE3064270D1 (en) 1983-08-25
FI71779C (fi) 1987-02-09
AU531907B2 (en) 1983-09-08
JPS5691093A (en) 1981-07-23

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