JP2006219767A - Method for removing unsaturated uronic acid in chemical pulp for papermaking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which pulp viscosity is held and an unsaturated uronic acid in the pulp is reduced to improve discoloring properties of the pulp while suppressing bleaching cost for problems in deteriorating the discoloring properties of completed bleached pulp in an ECF (elementary chlorine free) or a TCF (totally chlorine free) bleaching method of chemical pulp for papermaking without using molecular chlorine. <P>SOLUTION: The method for removing the unsaturated uronic acid in the pulp comprises adding glucuronidase in the method for removing the unsaturated uronic acid in the chemical pulp for papermaking. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the treatment of chemical pulp for papermaking, and more particularly relates to the removal of unsaturated uronic acid in chemical pulp.

  Bleaching of chemical pulp for papermaking is carried out by a multi-stage bleaching process. Conventionally, chlorine bleaching chemicals have been used as bleaching agents in this multistage bleaching. Specifically, the combination of chlorine (C), hypochlorite (H), and chlorine dioxide (D), for example, C-E-H-D, C / D-E-H-E-D ( Bleaching by a sequence such as C / D is a combined bleaching stage of chlorine and chlorine dioxide, E is an alkali extraction stage, and-is a washing treatment).

  However, these chlorine bleaching chemicals produce organic chlorine compounds that are harmful to the environment during bleaching, and environmental pollution of bleaching wastewater containing these organic chlorine compounds has become a problem. Organochlorine compounds are generally analyzed and evaluated by AOX methods such as the US Environmental Agency (EPA METHOD-9020).

  It is most effective to reduce or prevent the use of chlorinated chemicals in order to reduce or prevent organochlorine by-products. Especially, it is most effective not to use molecular chlorine in the first stage. Is the method. Pulp produced by this method is called ECF (elementary chlorin free) pulp, and pulp produced without using any chlorinated chemicals is called TCF (totally chlorin free).

  Cooking-Oxygen delignified pulp is bleached without molecular chlorine in the first stage, D-Eo-D or D-Eo-DD sequence using chlorine dioxide in the first stage, or peroxidized in the alkali stage Bleaching by D-Eop-D, D-Eop-PD, and D-Eo-PD sequences using hydrogen is generally known (Non-patent Document 1).

  However, since chlorine dioxide has a lower ability to remove hexeneuronic acid (hereinafter sometimes referred to as “HexA”) than chlorine conventionally used, a large amount of HexA remains in the bleached pulp. This residual HexA is a cause of deterioration of the fading of ECF or TCF bleached pulp (Non-patent Document 2).

  HexA is a substance produced by demethanolation of the end of xylan, which is hemicellulose present in pulp, in the cooking process. Although the influence on the whiteness of the pulp is small, it has a double bond in the molecule, so it reacts with potassium permanganate and is counted as a K value or a kappa value (Non-patent Document 2).

  In order to improve this fading deterioration, there is a method of increasing HexA by increasing the amount of chlorine dioxide or ozone used. However, since HexA consumes these oxidants due to intramolecular double bonds, increasing the amount of these oxidizers that are more expensive than conventional chlorine causes the problem of significantly increasing the bleaching cost. .

  Non-Patent Document 3 discloses a method for removing HexA by high-temperature acid treatment. As the condition, a method of acid-hydrolyzing and removing HexA in an acid treatment at about 90 ° C. to 180 minutes and a pH of about 3 has been proposed. This method is effective because HexA can be removed only by pH adjustment with an inexpensive acid. However, since a large amount of steam is required, an increase in bleaching cost is inevitable. Further, if the processing temperature is about 70 ° C. in order to reduce the steam cost, HexA is hardly removed. In addition, there is a problem that an expensive material such as Hastelloy, which is resistant to corrosion, is required as an apparatus material for acid treatment at a high temperature.

  Further, Non-Patent Document 3 discloses a method of removing HexA by strengthening chlorine dioxide treatment conditions. That is, it is a method of removing HexA by a bleaching temperature of 90 ° C., a pH of 3, and a treatment time of 120 minutes to 180 minutes. This method is a combination of high-temperature acid treatment and chlorine dioxide treatment, which requires a large amount of steam as in the case of acid treatment. There are problems such as poor improvement. Moreover, since it processes at high temperature, there exists a problem that an expensive material is needed as an apparatus material.

  Non-Patent Document 4 searches for microorganisms that produce α- (1 → 2) -glucuronidase that releases 4-O-methyl-D-glucuronic acid from hardwood xylan. The purpose of this study is to remove 4-O-methyl-D-glucuronic acid (saturated uronic acid) with α-glucuronidase to saccharify hardwood xylan. The present inventors aim to remove hexeneuronic acid (unsaturated uronic acid) bonded to xylan in hardwood pulp bleached with oxygen after cooking, and Non-Patent Document 4 does not disclose any suggestions regarding the present invention. Not.

  Patent Document 1 describes a method of treating pulp with a bleaching enzyme and recovering and reusing the enzyme. The use of hemicellulase as one of the bleaching enzymes and glucuronidase as an example of the hemicellulase are described, but the removal of unsaturated uronic acid by α-glucuronidase, which is the inventive method, is not disclosed at all.

  Non-patent document 4 and Patent document 1 describe studies on glucuronidase, which is an enzyme generally used for removing saturated uronic acid. Thus, it is surprising that α-glucuronidase can remove unsaturated uronic acid as found in the present invention.

JP-A-5-247865 Chlorine Dioxide in Delignification, Pulp & Paper, University of Toronto Tappi Journal May 2003, vol.2, No.5 Papehi ja Puu-Paper and Timber Vol.86 No.1 2004 Forestry Research Institute Research Report No. 359 141-157

  The object of the present invention is to produce chemical pulp for papermaking. In ECF bleaching or TCF bleaching without molecular chlorine in the first stage, the increase in bleaching cost is minimized and the viscosity of the pulp is maintained. It is to provide a method for removing residual HexA.

  As a result of diligent study on enzyme treatment of pulp subjected to digestion-oxygen delignification treatment, the present inventors have found that glucuronidase obtained by culturing basidiomycetes and filamentous fungi as microorganisms remains in the pulp while maintaining pulp viscosity. The present invention has been completed by finding that HexA can be removed. That is, the present invention relates to a method for removing unsaturated uronic acid in pulp, which comprises adding glucuronidase in a method for removing unsaturated uronic acid in chemical pulp for papermaking. Here, α-glucuronidase is suitable as the glucuronidase.

  According to the present invention, there is no need to increase the amount of expensive chlorine dioxide or ozone, or to newly heat, for the problem that the bleaching quality of the finished bleached pulp deteriorates in chlorine-free bleaching mainly composed of chlorine dioxide. HexA in the pulp can be removed at the temperature of the conventional bleaching process. As a result, it is possible to improve the thermal fading properties of pulp produced by an ECF or TCF bleaching method that does not use molecular chlorine while maintaining excellent pulp physical properties and keeping the bleaching cost low.

  The pulp to be treated in the present invention is preferably a pulp containing polysulfide, or a pulp derived from a chemical pulping method such as an ordinary kraft pulping method (KP), a sulfide pulping method (SP), or an alkali pulping method (AP). More preferably, it is a pulp obtained by a kraft pulping method. Moreover, it does not specifically limit about the woody plant and herbaceous plant used for pulping. In addition, the pulp to be treated has been subjected to a known oxygen delignification treatment so as to have a kappa number of 20 or less as a pretreatment, and preferably has a kappa number of 12 or less.

  The glucuronidase or glucuronidase containing xylosidase or xylanase used in the present invention is produced from basidiomycetes or filamentous fungi. Basidiomycetes include Agrocybe cylindracea, Anellaria semiovata, Asterophora lycoperdoides, Auricularia auricular-judae, Auriscalpium vulgare, Bonderzewia montana, Chlorosplenium aercynos , Cortinarius cinnamomeus, Crinipellis stipitaria, Cryptoporus volvatus, Cyathus stercoreus, Cyclomyces fuscus, Cymatoderma elegans, Daedaleopsis tricolor, Daldinia concentrica, Favolus arcularius, Filoboletus manipularis, lutlamus lacteus, Lactarius chrisorheus, Laetiporus sulphureus, Lampteromyces japonicus, Lentinus edodes, Lentinus lepideus, Lenzites betulina, Lepista nuda, Lyophyllum shmeji, Macrolepiota procera, Merurius tremellosus, Naematol, Naematol entalis, Oudemansiella mucida, Oudemansiella radicata, Panellus serotinus, Panus rudis, Phanerochaete chrysosporium, Pholiota adipose, Pholiota aurivella, Pholiota nameko, Pleurotus ostreatus, Podostroma cornu-damae, Polyporellus Preferred are coccineus, Schizophyllum commune, Stereum annosum, Stereum frustulosum, Stereum hirsutum, Stereum roseum, Stropharia aeruginosa, Trametes albida, Trametes gibbosa, Tremella foliacea, Tremella fuciformis, Urnula craterium, and Wynnea agrumino.

  The fungi include Aspergillus niger, Aspergillus japonicus, Aspergillus pulverulentus, Aspergillus terreus, Aspergillus genus such as Aspergillus versicolor, Trichoderma aureoviride, Trichoderma hamatum, Trichoderma harzianum, Trichoderma dercho, Trichoderma dercho Aspergillus niger is preferable.

  Glucuronidase can also be a crude product that is produced from basidiomycetes or filamentous fungi and is not purified. Further, xylanase or other xylan-degrading enzyme added with and mixed with glucuronidase can also be used. A glucuronidase produced by Snail (snail) can also be used.

 For example, when Aspergillus niger is used as a production bacterium, it is cultured at 35 ° C. for 24 hours in a liquid medium containing 2% xylan as a carbon source. This culture solution is filtered, and the obtained bacterial cells are crushed, and a glucuronidase-containing crude enzyme extracted with 0.1 M acetate buffer (pH 5) is obtained. The enzyme is then purified by ion exchange chromatography and gel chromatography to obtain glucuronidase. Moreover, you may use the crude enzyme which does not refine | purify.

  In the enzyme treatment performed in the present invention, the amount of glucuronidase added is 40 to 40,000 units per g of pulp, the treatment pH is 2.0 to 7.0, and the treatment time is 1 to 12 hours. The treatment temperature is 30 to 90 ° C., and the pulp concentration is 3 to 30%. As addition sites, unbleached pulp after oxygen bleaching, intermediate portions of various ECF bleaching stages, and after completion of bleaching, any location may be used as long as it meets the processing conditions of glucuronidase.

  After the enzyme treatment, it is sent to the next ECF or TCF bleaching sequence without washing or after washing. As bleaching sequences not using molecular chlorine, D-Ep-D, D-Eop-D, D-Ep-P-D, D-Eop-P-D, D-Ep-D-D, D-Eop There are chlorine dioxide based ECF sequences such as -DD, D-Ep-DP, and D-Eop-DP. Moreover, Z-Ep-D, Z-Eop-D, Z-Ep-PD, Z-Eop-PD, Z-Ep-DD, Z-Eop-DD, Z-Ep- OCF-based ECF sequences such as DP and ZD-Eop-DP, Z / D-Ep-D, Z / D-Eop-D, Z / D-Ep-PD, Z / D Ozone such as Eop-PD, Z / D-Ep-DD, Z / D-Eop-DD, Z / D-Ep-DP, Z / D-Eop-DP And ECF sequences that use chlorine dioxide together. Further, TCF such as Z-Ep-P, Z-Eop-P, Z-Ep-P-P, Z-Eop-P-P, Z-Ep-Q-P, Z-Eop-Q-P There is a sequence. These bleaching sequences do not limit the invention in any way. Here, the addition site of glucuronidase may be added to the intermediate stage of the bleaching sequence and to the finished pulp after completion of bleaching.

  In the present invention, the first feature of the method for improving the discoloration of ECF bleached or TCF bleached pulp by treating the pulp with an enzyme is that the enzyme reaction is very selective and only HexA, which is a problem with discoloration, is used. Therefore, an excellent pulp can be produced without affecting the physical properties of the pulp at all.

  The second feature is that not only the removal of HexA, but also the oxidants such as ozone and chlorine dioxide not only remove lignin and saccharides in the pulp excessively, but the physical properties such as the viscosity of the pulp are not only lowered. Although there is an environmentally unfavorable aspect that wastewater COD increases, if the enzyme of the method of the present invention is used, there is almost no such thing and pulp can be produced.

  The third feature is that chlorine dioxide and ozone require a large amount of energy to produce them, but the enzyme of the present invention can be produced with very little energy because microorganisms produce it.

  That is, the feature of the present invention is that by introducing an enzyme treatment into a normal ECF bleaching and TCF bleaching sequence, while maintaining a pulp viscosity in a low temperature treatment of 40 ° C. to 70 ° C., which has been conventionally difficult to remove HexA, HexA can be removed. Furthermore, since there is little damage to substances other than HexA, it can be implemented without increasing the wastewater COD value. In addition, the use of the enzyme of the present invention makes it possible to produce a bleached pulp that minimizes the use of chemicals, so that the pulp is extremely excellent in terms of environment.

  Next, the present invention will be described specifically by way of examples. In addition, the Example shown below is shown in order to demonstrate this invention concretely, This invention is not restrict | limited at all.

1. Preparation of Substrate 30 g of hardwood oxygen bleached kraft pulp (LOKP) having a copper number of 10 was treated with cellulase “Onozuka” 3S. The pulp concentration was 5%. The obtained soluble part (saccharified solution) was treated with activated carbon in a batch manner, and the activated carbon was adsorbed with enzymes, colored substances, and products having a large molecular weight, and the activated carbon was filtered off to remove them. The filtrate flowed into a column containing activated carbon. Water was passed through the column to elute inorganic salts and monosaccharides. Next, a 40% ethyl alcohol / 60% water mixture was poured to elute oligosaccharides. From 600 g of the saccharified solution, 5.3 g of oligosaccharide was obtained. Oligosaccharides contained acidic and neutral sugars.

  Anion exchange resin (Dowex IX2) was equilibrated with 0.1 M aqueous acetic acid solution, converted into acetic acid form, and packed in a column. On the other hand, the aqueous solution of oligosaccharide was adjusted to pH 8-9 with NaOH and allowed to stand for 1 hour to open the lactone ring. This flowed into the column. Neutral sugars were eluted by flowing 0.1 M acetic acid aqueous solution through the column. Next, 2M acetic acid aqueous solution was flowed to elute the acidic sugar. The acidic sugar solution was neutralized with NaOH, electrodialyzed, and lyophilized. The main component of the freeze-dried sample was a pentamer acidic sugar oligomer (Δ-X4) in which one hexeneuronic acid (Δ) was bound to xylose tetramer (X4).

2. Preparation of enzyme solution Six types of microorganisms were used for enzyme preparation. Irpex lacteus, Chlorosplenium aeruginosum, Merulius tremellosus, Coriolus pubescens, Coriolus versicolor were liquid cultured in a liquid medium containing 1% broad-leaved xylan at 25 ° C. for 7 days, and Aspergillus niger was cultured in a medium containing 2% xylan at 35 ° C. Cultured for 24 hours. Each culture solution was filtered, the filtrate was used as an extracellular enzyme, and the obtained cells were disrupted and extracted with 0.1 M acetate buffer (pH 5.0). This enzyme was used as a crude enzyme. This enzyme contained α-glucuronidase, β-xylosidase, and β-xylanase. From this crude enzyme, purified α-glucuronidase was obtained by ion exchange chromatography and gel chromatography.
3. Analysis Method Enzyme reaction products were analyzed by carbohydrate fluorescent labeling electrophoresis (FACE).

Examples 1 and 2
To 50 μl of a 2 mM solution of Δ-X4 taken out from LOKP, 20 μl of pH 5 acetate buffer and 30 μl of intracellular enzyme solution were added and reacted at 40 ° C. for 24 hours. Enzyme reaction products were analyzed by carbohydrate fluorescent labeling electrophoresis (FACE).
The crude enzyme produced by Aspergillus niger and Chlorosplenium aeruginosum showed activity against Δ-X4. The results are shown in Table 1.

Comparative Examples 1-4
In place of the microorganisms of Examples 1 and 2, a crude enzyme produced from Irpex lacteus, Coriolus pubescens, Coriolus versicolor, Merulius tremellosus was reacted with Δ-X4 similarly extracted from LOKP. The results are shown in Table 1.

各酵素のΔ−Ｘ４のキシロース４量体とヘキセンウロン酸１つの結合部位を切断する力
＋：切断される −：切断されない

Ability to cleave the binding site of one enzyme Δ-X4 xylose tetramer and hexeneuronic acid
+: Disconnected-: Not disconnected

  That is, intracellular enzymes of Aspergillus niger and Chlorosplenium aeruginosum were able to cut the binding site of Δ-X4 xylose tetramer and hexeneuronic acid and remove hexeneuronic acid. As a result, xylose tetramer (X4) was produced. X4 binding was easily broken by β-xylosidase and β-xylanase to produce xylose. The intracellular enzymes of Irpex lacteus, Coriolus pubescens, Coriolus versicolor, and Merulius tremellosus were unable to cut the binding site of xylose tetramer and hexeneuronic acid.

Examples 3-5
Next, examples of hardwood pulp will be described. The amount of each chemical used is indicated by weight% per dry pulp, and the amount of hydrogen peroxide used is 100% equivalent. The pulp used was L-wood pulp A after kraft cooking-oxygen delignification. Moreover, the analysis evaluation was based on the following method.

Pulp type A: Hunter whiteness 50.1%, K value 6.64, viscosity 28.9 mPa · s, Hex A: 39.8 μmol / g
・ Whiteness: JIS-P8123 (Hunter whiteness method)
-K value: TAPPI K value method-Viscosity: J.P. TAPPI No. Method 44-Amount of HexA: Pulp having an absolute dry amount of 1 g was diluted to a pulp concentration of 1%, adjusted to pH 3.0 with formic acid and then heated at 90 ° C for 240 minutes to convert HexA to 2-furancarboxylic acid and 5- Hydrolyzes to formyl-2-furancarboxylic acid. After cooling, it was separated into pulp and water, and 2-furancarboxylic acid and 5-formyl-2-furancarboxylic acid in water were quantified by liquid chromatography using a UV265 nm detector, and the total was taken as the amount of HexA.
-Fading test: 85 ° C-65% RH, 24 hours-PC value: A measure of the degree of fading
PC = 100 (K / S for fading-K / S before fading)
K / S = (1-whiteness) ² / (2 whiteness)

  10 units, 20 units and 30 units of crude enzyme produced by Aspergillus niger were added to 20 g of L-wood pulp A after kraft cooking-oxygen delignification and treated for 180 minutes under the conditions of pulp concentration 10%, pH 5 and temperature 40 ° C. . After completion of the reaction, it was diluted with cold water to a pulp concentration of 2.5% and dehydrated to a pulp concentration of 20% to obtain an enzyme-treated pulp. The results are shown in Table 2.

Example 6
The same procedure as in Example 3 was performed except that 20 units of separately purified α-glucuronidase was added to the crude enzyme produced by Aspergillus niger. The results are shown in Table 2.

Comparative Example 5
The same treatment was carried out except that the enzyme was added in Example 3. The results are shown in Table 2.

  That is, HexA could be removed by adding the enzyme of the present invention to unbleached pulp. Further, as shown in Example 6, when α-glucuronidase obtained by purifying the enzyme produced by Aspergillus niger was added to and mixed with the crude enzyme of Example 3, it was greatly reduced in the same enzyme unit. HexA could be removed.

Example 7
Using pulp A that had been subjected to oxygen bleaching after kraft cooking, bleaching was performed by a bleaching sequence of GD-Eop-D in which enzyme treatment was introduced in the first stage. The enzyme used was a crude enzyme produced by Aspergillus niger.
G (enzyme treatment): PC 10%, pH 5, 40 ° C., 180 minutes Enzyme: 100 units First stage D: PC 10%, 60 ° C., 30 minutes, ClO ₂ /0.9%
Eop: PC 10%, 60 ° C., 90 minutes, NaOH / 0.8%, O ₂ /0.15%
H ₂ O ₂ 0.3%
D: PC 10%, 70 ° C., 120 minutes, ClO ₂ /0.4%
Washing conditions: After completion of the reaction at each stage, the pulp was diluted to a pulp concentration of 2.5%, dehydrated to a pulp concentration of 20%, and transferred to the next stage. The results are shown in Table 3.

Example 8
In the bleaching sequence of D-Eop-GD, the same procedure as in Example 7 was performed except that an enzyme treatment was introduced in the middle of the bleaching stage. The results are shown in Table 3.

Example 9
In the bleaching sequence of D-Eop-DG, the same procedure as in Example 7 was performed except that the enzyme treatment was introduced into the final stage of the bleaching stage. The results are shown in Table 3.

Comparative Example 6
It carried out like Example 7 except not performing an enzyme treatment. The results are shown in Table 3.

  In other words, by introducing an enzyme treatment into the bleaching sequence using chlorine dioxide and hydrogen peroxide, the discoloration that was a problem in the finished pulp could be improved.

Example 10
Using pulp A which had been subjected to oxygen bleaching after kraft cooking, bleaching was performed according to a bleaching sequence of GZE-P in which enzyme treatment was introduced in the first stage. The enzyme used was a crude enzyme produced by Aspergillus niger.
G (enzyme treatment): PC 10%, pH 5, 40 ° C., 180 minutes Enzyme: 100 unit first stage Z: PC 10%, 60 ° C., 3 minutes, O ₃ /0.5%
E: PC 10%, 60 ° C., 90 minutes, NaOH / 0.8%
P: PC 10%, 90 ° C., 120 minutes, H ₂ O ₂ /1.5%
Washing conditions: After completion of the reaction in each stage, the pulp was diluted to a pulp concentration of 2.5% and dehydrated to a pulp concentration of 20%.
As a result, a pulp having whiteness of 86.3%, Kappa number of 0.7, HexA amount of 2.9 μmol / g, and PC number of 1.3 was obtained.

Comparative Example 11
The procedure was the same as Example 10 except that no enzyme was added. As a result, a pulp having a whiteness of 84.7%, a Kappa number of 2.3, a HexA amount of 11.4 μmol / g, and a PC number of 3.3 was obtained.
As in Example 10 and Comparative Example 11, even in TCF bleaching, a finished pulp having no problem with fading was obtained by introducing an enzyme.

Claims (13)

  A method for removing unsaturated uronic acid in pulp, wherein glucuronidase is added in the method for removing unsaturated uronic acid in chemical pulp for papermaking.   The method of claim 1, wherein the glucuronidase contains xylosidase or xylanase.   The method according to claim 1 or 2, wherein the glucuronidase is α-glucuronidase.   The method according to claim 1 or 2, wherein the unsaturated uronic acid is hexeneuronic acid.   The method according to claim 1 or 2, wherein the glucuronidase is produced from a basidiomycete or a filamentous fungus.   The method according to claim 2, wherein the xylosidase or xylanase is produced from a basidiomycete or a filamentous fungus.   The method according to claim 5 or 6, wherein the basidiomycete is Chlorosplenium genus.   The method according to claim 5 or 6, wherein the filamentous fungus is Aspergillus.   The method according to claim 7, wherein the genus Chlorosplenium is Chlorosplenium aeruginosum.   The method according to claim 8, wherein the genus Aspergillus is Aspergillus niger.   The method of Claims 5-10 produced in the culture medium containing a xylan.   The method according to claims 5 to 10, wherein the produced glucuronidase is added to the pulp without purification.   The method according to claim 1 or 2, wherein glucuronidase is added to the pulp after the oxygen treatment, between the bleaching steps or after the bleaching treatment.