SE506440C2 - Control of softwood fiber length distribution by enzymatic and mechanical treatment - Google Patents

Abstract

Process for utilizing softwood pulp for the production of paper and board, where essential product properties, e.g. a good print quality are obtained by controlling the fibre length distribution of the pulp through enzymatic treatment, followed by a mechanical or other equivalent treatment of the fibres.

Description

15 20 25 30 506 440 2 ra, which method makes it possible to reduce the specific energy consumption in the production of mechanical pulp and to improve the technical properties of the fis.

The inventors describe a special enzyme preparation which at the same time exhibits both cellobiohydrolase activity and mannase activity. This avoids hydrolysis of insoluble cellulose and does not impair the strength properties of the fibers. Here too, shortening would be a negative effect. Furthermore, according to the examples presented in WO 94/20667, this process requires a colder and more dilute pulp than is the case in the industrial production of pulp and paper. Furthermore, the long treatment times given in the examples indicate that very large stock volumes are required.

WO 92/18688 relates to a cellulase preparation with a high content of endoglucanase and little or no cellobiohydrolase for use in the treatment of pulp, inter alia to improve the dewatering properties of the pulp. It is obvious that such an enzyme treatment mainly solubilizes ñnes, and thus improves the drainage. It is noted, also in this description, that the damage to the cellulose fibers in the pulp is less, due to the low cellobiohydrolase activity.

It is obvious that the known methods for the enzymatic treatment of pulp do not relate to controlled shortening. Known methods do not address the problem which the present invention seeks to solve. In contrast to all conventional methods, the present inventors have worked to devise an enzyme preparation and to develop a treatment process which, in fact, is to cause local damage to the cellulosics. The purpose was to find a way to control the length of softwood pulp and make it useful for the production of foam paper with better forming and better printability.

The present invention mainly relates to a method for treating chemical softwood pulp, leather bleached chemical softwood pulp. The process according to the present invention can of course also be applied to unbleached chemical pulp, but then the enzyme dosage and / or process conditions such as treatment time, temperature and pH must be adjusted accordingly. For the sake of simplicity, the present description deals only with the treatment of bleached softwood pulp.

It has now surprisingly been found that the simultaneous use of endo- and exocellular lasers in a treatment step before the opening leads to controlled shortening of the softwood pulp.

The fibers present in chemical pulp are always mechanically damaged to a certain extent, ie the fibers have more or less sharp knees and turning points (kinks and 10 15 20 25 30 506 z 3 Å bends) in their three-dimensional structure. It has now been shown that a combination of endo- and exocellulase activity, eg endo- and exoglucanase activity, attacks these damages: I cause changes in the crystal structure of the cellulose. Thus, weakening of the fibers is achieved. In other words, before the enzymatic treatment - damage, hereinafter referred to as "gross entry" on the fibers. Later, when mechanical treatment in the form of folding is subjected to the use of conventional equipment for this purpose, the edges are broken in a controlled manner at these. This surprising effect leads to a shorter average omsnitt length and a fi length distribution in the pulp, which better corresponds to a length distribution advantage. This in turn is favorable for the production of thick cardboard. Normally, conventional storage of softwood pulp, without prior action, results in an excess length distribution with a large amount of very short so-called fmes and a significant amount of unnecessarily long fibers. This uneven distribution leads to irregularities in the paper and reduces the print quality. Controlled fiber shortening according to the present invention makes it possible for the first time to use only softwood pulp for the production of high quality printing paper. The invention is further illustrated in the following applicable embodiments, figures: p Figure 1 is a graphical representation showing the zero-span tensile strength index: (ie at the input voltage zero) as a function of enzymatic treatment at single doses and temperatures, I in Figure 2 is a A graphical representation showing the length distribution in unprocessed pulp compared to the length distribution in pulp as enzymatic treatment according to the present invention. 1 The degree of fiber shortening can be controlled in your ways. First, in the practice of the invention, the ratio of endocellulase activity and activity can be varied. Endoglucanase can be used together with small amounts and vice versa, preferably in a range of 100: 100 to 10011. More preferably, no exocellulase activity is substantially greater than the amount of endocellulase activity. Most läriigšig is ratio: exeeeiiuies: in enaeeeiiuias in the range from ee 4: 1 1111 s = 1, viiiieifge; a synergistic effect. An optimum ratio depends on the actual enzymes and their sources, and this optimum ratio can be easily determined by those skilled in the art. According to the present invention, the endocellulase is suitably endoglucan fi and the exocellulase is suitably exoglucanase. The endoglucanase and exoglucanase can be used in pure, isolated form or as a mixture of enzymes from different sources. Commercially available enzyme mixtures that exhibit the previously specified activities can also be used. An example of such a commercially available product is Celluclast® 1.5L from Novo Nordisk A / S. It is obvious that other commercial or independently developed enzyme products may be available to those skilled in the art.

A number of endo- and exoglucanases are known and these can be used in accordance with the present invention. Enzyme of microbial origin is preferred due to economic reasons. The enzyme must be active and stable under the conditions, in particular pH and temperature, prevailing in the pulp production processes. Examples of suitable enzymes are those derived from the microorganisms in Table 1 and Table 2.

Table 1: Examples reach cellulase-producing fungi Agaricus bisporus Ascoboulus furfiiraceus Aspergillus aculeatus, A. fumigatus, A. niger, A. phoenicis, A. terreus and A. wentii Botryodiploida theobromae * Chaetomium cellulolyticum, C. globosum Chosporladium and C. therosporio Coriolus versicolor Dichomitus squalens Eupenicillium javanicum Fomes famentarium Fusarium moniliforme, F. solani och Fusarium spp.

Humicola grisea and H. insolens Hypocapra merdaria Irpex lacteus Lenzites trabea Mycellophtora therrnophila Myriococcum albomyces Myrothecium verrucarla Neocallirnastix frontalis Neurospora crassa Paecilomyces fusisporus, P. variotly Papulaspio citria Penicophia P. P. , P. variabile and P. verruculosum Pestalotiopsis versicolor Phanerochaete chrysosporium Phialophora malorum Phoma hibernica 10 15 20 25 30 35 (1 The bacteria within quotation marks are not completely classified.

Physarum polycephalum Pleurotus ostreatus and P. sajor-caju Podospora deciplens Polyporus schweinitzil and P. versicolor, Poria placenta poronia punctata Pyricularia orzyzae saccobolus trunctatus Schizophyllum commune Sclerotinia libertiana Sclerotium rolfsii Scytalidium lignicola Sordaria ñmicola Sporotrichum pulverulentum and S. thermophile Stereum sanguinolentum Talaromyces emersonii Thermoascus aurantiacus Thrausiotheca clavata Torula thermophile Trichoderma koningii, T. pseudokoningii and T. reesei Trichurus spiralis Verticillium albo-atrum Volvariella volvacea T 1 2- x 1 1 ri rÜ Cellulomonas fl avigena, C. biazotea, C. cellasea, C. fi mi, C. gelida, C.

C. uda and C. turbata t; Bacillus brevis, B. fi rmus, B. lichenformis, B. pumilus, B. subtilis, B.f och B. cereus “Serrata marcescens 5oe 44o Cllftaß, 'Pseudomonas fl uorescens var. cellulose 'V ...

'Cellvibrio viridus, C. fl avescens, C. ochraceus, C. fulvus, C. vulgaris C. gilvus' Cytophaga hutchinsonii, C. aurantiaca, C. rubra, C. tenulssima, C. och C. lcrzemienlewskoe Herpetosiphon geysericolus Sporocytccous or 'Thermoactinomyces sp. 'Thermomonospora curvata The fungi and bacteria listed above are listed only. example. The scope of the present invention is not limited to any of the named microorganisms. It is very possible that other enzyme-producing microorganisms suitable for the present invention already exist or will be developed using mutation and selection or genetic engineering methods. It is also possible that the enzyme-producing properties of an existing microorganism can be enhanced by genetic engineering methods.

The environmental conditions during the enzymatic treatment are not critical to the extent of the invention, but can of course be used to control the enzymatic reaction. The conditions of the enzymatic treatment are governed to some extent by the normal process parameters of pulp and paper production processes. At the same time, the requirements of the enzyme or mixture of enzymes must be taken into account. A pH in the range 2 - 13 is possible while a range from 4 - 10 is suitable, depending on the enzymes used. The temperature of the reaction mixture is of considerable importance because it affects the reaction rate of the enzymes. The reaction rate directly affects the time required for the desired reaction and thus the necessary storage volumes. Depending on the enzymes used, their heat tolerance and temperature optimum, the temperature can be in a range from about 5 - 95 ° C, theoretically also higher, eg around 100 ° C but preferably about 30 - 60 ° C and most preferably about 45 - 50 ° C. One can expect a future development with high heat tolerance, which would make it possible to carry out the enzymatic treatment at considerably higher temperatures. It is possible that it gives rise to unexpected synergistic effects.

A person skilled in the art can, with knowledge of the requirements of the enzymes used, determine more precisely the optimal conditions for application of the enzyme or enzyme mixture.

The presence of heavy metals can also affect the enzyme activities and should therefore be avoided.

One skilled in the art of both paper making and enzyme use can modify the processes to enable the enzymatic treatment of the present invention.

According to one embodiment of the present invention, the enzymatic treatment is interrupted before the pulp is subjected to folding. The enzymatic treatment is suitably interrupted by adjusting the pH of the reaction mixture to a range outside, preferably higher than the functional range of the enzyme mixture. This functional range depends on the pH stability of the enzyme, the temperature and other environmental factors. When the commercially available enzyme product Celluclast® is used, the pH is adjusted to about pH 8 10 15 20 25 30 5 0 6 4.4.0 to terminate the reaction. According to another embodiment of the invention, the look-up is modified in relation to the enzymatic treatment. In general, enzymatically treated pulp requires a lower energy consumption at the storage stage. It is, of course, desirable to minimize both energy consumption and the formation of fi nes during storage. According to one embodiment of the invention only a part of the chemical mass is subjected to the enzymatic treatment and then returned to the main huvud ödetiš I According to another embodiment of the invention, the enzyme or enzyme mixture used is bound / bound to a carrier to facilitate its removal and possible reuse. Suitable carriers and methods of incorporation can be found in the literature. The invention is further described in the following examples which are not intended to limit in any way the scope of the invention as set forth in the appended claims.

Example 1 Laboratory scale experiments were performed to determine the effect of enzymatic treatment on the zero-span tensile strength index (ie at the input voltage length zero). Two series of experiments with increasing enzyme concentrations were performed, one at a temple temperature of 40 ° C and the other at a temperature of 50 ° C. The treatment time at both temperatures was 2 hours. The enzyme mixture used was Celluclast® from Novo Nordisk A / S, Denmark, with an enzyme activity of 1500 NCU / g enzyme. 1 NCU [Novo víCellulas Unit]) is the amount of enzyme which, under standard conditions, breaks down CMC to reduce: carbohydrates with a reduction force corresponding to one molar glucose per minute.) The results are presented in Table 3 and shown graphically in fi g. 1. i 10 15 20 25 506 440 8 Table 3: Zero-spam tensile strength index (Nm / g) Dosage (NCU / 10 g mass) 2 h / 40 ° C 2 hl 50 ° C 0 118 118 25 87 45 50 75 26 * 70 51 23 * 100 46 19 * * The reading accuracy was low for these values.

It is clear that the effect depends on both dosage and treatment temperature.

With a temperature increase, the same effect can be achieved with a significantly lower enzyme dose.

An increase from 40 ° C to 50 ° C allows a reduction of the required enzyme dose from 100 to 25 NCU / 10 g pulp while maintaining the same results.

Example 2 The ability of the enzymatic treatment to achieve the desired limitation of the l length distribution was tested in pilot scale experiments. Enzymatic treatment was performed in batches of 400 kg of pulp overnight. The pH of the pulp was adjusted to 5.0 - 5.5 by adding H2SO4 while beating, after which the enzyme mixture (Celluclast® from Novo Nordisk A / S, Denmark, enzyme activity 1500 NCU / g enzyme) was added to the pulp. Two different enzyme concentrations were used. The enzyme doses were determined on the basis of the previous laboratory experiments and were 7.5 NCU / g pulp and 18.75 NCU / 10 g pulp, respectively. After 13 hours, the reaction was terminated by adjusting the pH to 8.0 - 8.2 by adding NaOH tablets to the mixture. Thereafter, the pulp was processed in an industrial disc mill at a concentration of 3.5%. For an overview of the experimental conditions, see Table 4. 10 15 20 25 506 446 9 Table 4: The experimental conditions Comparative experiments Batch 1 Batch 2 Initial-pn 5.0 - 5.5 5.0 - 5.5 5.5 Enzyme addition - 7 .5 U / 10 g 18.75 Ill / ID g pulp cardboard fi naiassa Processing time 13 h 13 h 155115 _ Temperature ss - 40 ° c ss - 40 ° c ss - ï i Fiber concentration 3.5% 3.5% ii Sludge pH 8 , 0 - 8.2 8.0 - 8.2 saiy-fsšz Changes in ñbear strength after the enzymatic treatment measurement of zero-span tensile strength index on dry and moistened sheets. In addition, the mass viscosity and form factor (also called the "curl index") were determined. Massavi _ can be seen as a measure, which depends on the average chain length of the cellulose.

The form factor on the other hand is the ratio of ñbem's projected length to actual length, thus giving an indication of fibenis curvature or degree. It appears from the results that a stronger enzymatic treatment more strongly degrades the cellulose. This was evident from the viscosity and the tensile strength index. The strongest effect was observed for re-moistened zero-spat? r fl ag-i strength index. The fact that the difference between zero-span results for dry tacll moisturized sheets increased with increasing enzyme dosing, indicates that the degradation as a local weakening of fi bem, in the form of local fracture threads as before The form factor remained unchanged in batch 1. In batch 2 which was subjected a relative- »itïögf I enzyme concentration also increased fi berdeformation. The average ñberlångdeii was not only affected by the enzymatic treatment. The results are summarized in Table 5. - 116 77 47 strength index, moistened (Nm / g) Fiber length (mm) 2.24 2.09 2.22 Form factor (%) 86.7 86.4 85.2 Fiber length distribution after enzymatic treatment and subsequent look-up is displayed graphically in ñg. 2. The curves clearly show the beneficial effect on the excess length distribution of the process of the present invention.

Although the invention has been described with respect to suitable embodiments, which constitute the best embodiments currently known to the inventors, it is to be understood that various changes and modifications apparent to those skilled in the art may be made without departing from the scope of the invention as set forth in the accompanying patent claims.

Claims (10)

10 15 20 25 30 sos 440 1 1 i Patentkrav A process for the use of softwood pulp for the production of printing paper in which essential paper properties which give good print quality are obtained by the longitudinal distribution of the pulp, characterized in that said first is subjected to enzymatic treatment to achieve controlled crime reduction at the said crime areas. IN: 2. A method according to claim 1, characterized in that the enzymatic treatment is terminated before the mechanical processing. : I i _ 3. A method according to claim 1 or 2, characterized in that that treatment is terminated by a pH change, preferably by raising the pH to a level above the functional range of the enzyme. i _, z 4. A method according to claims 1 to 3, characterized in that the enzyme treatment composition comprises that softwood pulp is subjected to an enzyme preparation, which exhibits both i: i in endocellulase and exocellulase activity. in 5. A method according to claim 4, characterized in that the ratio of lasactivity and exoceliuiasakttviæt is the range from 1 = 1oo nu too; 1. 6. A method according to claim 4, characterized in that the exocellulase activitirite is substantially higher than the endocellulase activity. p A method according to claim 4, characterized in that the ratio of phase activity to endocellulase activity is in the range from about 4: 1 to 5: 1. A method according to any one of the preceding claims, characterized in that the exocellulase activity is exoglucanase activity and the endocellulose activity is endogenous »nasal activity. Method according to one of the preceding claims, characterized in that only a part of the total pulp is diverted from the main desolation, subjected to enzymatic treatment and re-fed to the main desolation. i u 10. A method according to any one of the preceding claims, characterized in that the enzyme or enzyme mixture used is bound / bound to a carrier I facilitate its removal and possible reuse.