CN103334331B

CN103334331B - TCE bleaching technology for sulfate pulp of growing poplar by biological chemical method

Info

Publication number: CN103334331B
Application number: CN201310303232.XA
Authority: CN
Inventors: 吉兴香; 陈嘉川; 杨桂花; 田中建; 刘玉; 王鲁燕
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2013-07-17
Filing date: 2013-07-17
Publication date: 2014-07-30
Anticipated expiration: 2033-07-17
Also published as: CN103334331A

Abstract

The invention discloses a TCE (Total Chlorine-Free) bleaching technology for sulfate pulp of growing poplar by biological chemical method. The technology comprises the following steps: (1), cooking: getting fast-growing polar pieces; putting the fast-growing polar pieces into a distilling pan for cooking, so as to obtain primary pulp, and then washing and screening the primary pulp to obtain paper pulp; (2), pre-treating the paper pulp with xylanase; (3), TCE bleaching: bleaching the paper pulp pre-treated with the xylanase, wherein the bleaching process is one of OP-Q-P, O1-O2P-Q-P or O1P-O2P-Q-P. According to the TCE (Total Chlorine-Free) bleaching technology for sulfate pulp of growing poplar by biological chemical method, the xylanase is adopted to pre-treat the paper pulp, then one of the bleaching processes OP-Q-P, O1-O2P-Q-P or O1P-O2P-Q-P is adopted for bleaching, so that the paper pulp with higher whiteness and viscosity is obtained; compared with the paper pulp obtained through directly bleaching without xylanase pre-treatment, the paper pulp provided by the invention has the advantages that the loss value of whiteness is lesser, the folding strength is higher 45 times averagely, the bursting index is higher 0.45 N*m*g <-1> averagely, the breaking length is higher 0.35 KM, and the tearing index is quite. The beating revolution number is lesser when the paper pulp reaches the same or similar beating degree, and the 20% of beating energy consumption can be saved approximately.

Description

The sulfate pulp biochemical process TCF bleaching process of a kind of fast-growing poplar

Technical field

The sulfate pulp biochemical process TCF bleaching process that the present invention relates to a kind of fast-growing poplar, belongs to pulp technology for making paper.

Background technology

Fast-growing poplar is the chief species that the northern area of China woods paper My Perspective On The Co-building adopts, belong to fast-growing leaf wood, they have fast growth, strong adaptability, nature whiteness is high, material loose, the absorbability of liquid is good, and lignin content is lower, and the content of cellulose and hemicellulose is higher, can be used for producing chemical pulp, semi-chemical pulp and mechanical pulp etc., is one of main high-quality paper making raw material of northern China.Fast-growing poplar in Northern Europe, the northern area of North America and China is widely cultivated, it has comprised a plurality of kinds, representational have black poplar, Triploid of Populus Tomentosa, a middle forest poplar etc., the growth characteristic of these fast-growing poplars, constituent are all very approaching.

In recent years, high yield pulp development is swift and violent, but high yield pulp exists shortcomings such as refining energy consumption is large, pulping intensity is lower and retention of whiteness is poor, easy brightness reversion cause high yield pulp to be difficult to the paper that some paper strengths are high, be difficult for brightness reversion, Heat stability is good of manufacturing paper with pulp.Therefore within the quite a long time from now on, the manufacture paper with pulp superiority of high-grade paper of chemical pulp can not become.Fast-growing poplar is as a kind of good paper making raw material, its yield of producing chemical pulp is higher, generally in 51% left and right, and the own whiteness of fast-growing poplar is high, and the former pulp brightness after chemical pulping is generally in 30%ISO left and right, compared with the former pulp brightness of other leaf woods, exceed 3-5%ISO left and right, and fast-growing poplar is as a kind of broad-leaved wood paper making raw material of high-quality, the black liquor producing in its digestion process, there is ripe treatment technology, can be to environment.

Fast-growing poplar chemical pulp is to adopt chemical agent, under specific conditions of cooking, by the most of lignin stripping in plant fiber material, retain cellulose the paper pulp of reservation hemicellulose in various degree as much as possible.The yield of chemical pulp is relatively low, and generally between 40-55%, but content of cellulose in chemical pulp is high, paper strength greatly, easily bleach, be difficult for brightness reversion, good endurance.Therefore adopt biological enzyme formulation bio-bleaching to bleach with chemical method the Bleaching Technology that combines, the low oligosaprobic chemical pulp production technology of the easy beating energy consumption of high-whiteness high-strength of preparation fast-growing poplar, is one of important channel of China's pulping and paper-making development.

Summary of the invention

For above-mentioned prior art, the object of the invention is to change the technique of traditional pure chemistry method association with pulp bleaching, the method that adopts bio-bleaching to combine with complete free from chloride chemical bleaching technique, when reaching identical pulp brightness, while consuming identical chemical bleaching liquor, more Gao Gengyi making beating of the whiteness that makes paper pulp, when reducing the beating energy consumption of paper pulp to environment substantially without any pollution, thereby realize the high efficiency total chlorine free bleaching of low consumption of fast-growing poplar sulfate pulp.

The present invention is achieved by the following technical solutions: the concentration of following related slurry if no special instructions, is mass percent; Related reagent, the consumption of medicine, if no special instructions, be all for oven dry stock.

A sulfate pulp biochemical process TCF bleaching process for fast-growing poplar, step is as follows:

(1) boiling: get quick growth poplar wood sheet, put into digester boiling, obtain magma, then wash fully, screen, obtain paper pulp, the Kappa number of paper pulp is 16～21;

(2) xylanase pretr eatment;

(3) TCF bleaching: the above-mentioned paper pulp of processing through enzyme is bleached, and bleaching process is O _p-Q-P, O ₁-O _2P-Q-P or O _1P-O _2Ptri-kinds of-Q-P float one of order, and the step of bleaching process is: first, the paper pulp of processing through enzyme is carried out to deoxidation lignin or strengthening deoxidation lignin; After oxygen delignification finishes, paper pulp is washed, then carry out Q section chelation treatment; After Q section chelation treatment finishes, paper pulp is washed, then carry out P section H ₂o ₂bleaching, completes.

Further, the concrete mode of described boiling is: the quick growth poplar wood sheet of getting length 15～25mm, width 10～20mm, thickness 3～5mm, after natural air drying, in 15L electric heating rotating autoclave, carry out boiling, make fast-growing poplar sulfate magma, the condition of boiling is: alkali charge 20%(is to over dry raw material, Na ₂o meter), sulphidity 24%, liquor ratio 1:4,165 ℃ of boiling maximum temperatures are carried out little venting 15min, heating-up time 120min, temperature retention time 90min in the time of 105 ℃; After boiling, fully wash, screen, obtain paper pulp, the Kappa number of paper pulp is 16～21.

Further, the concrete mode of described xylanase pretr eatment is: adjusting pulp density is 10%, then uses zytase X ₁, X ₂or X ₃process, in processing procedure, at interval of 10～15min, rub once, to guarantee that enzyme mixes with the even of paper pulp; After processing, take out, put into boiling water bath 10min, make zytase inactivation cessation reaction, with entering next step bleaching process after running water cleaning paper pulp.

Described zytase X ₁by Novozymes Company, provide (the letter zytase Pulpzyme HC of trade name Novi, article number CKN00117 and CDN00429), liquid state, cellulose-less enzyme is lived; Zytase X ₂, X ₃by Shenzhen, the biological Co., Ltd of green micro-health provides (trade name zytase, article number LV-1 and LV-2), is white powder solid, and all cellulase is not lived.

Described zytase X ₁, X ₂or X ₃the concrete technology condition of processing is as follows: X ₁the process conditions of processing: enzyme dosage 8IU/L(is for the cumulative volume of paper pulp), 50～55 ℃ of temperature, pH8, time 120min; X ₂the process conditions of processing: enzyme dosage 6IU/g(is for the quality of exhausted paper pulp), 55～60 ℃ of temperature, pH8～9, time 120min; X ₃the process conditions of processing: enzyme dosage 8IU/g(is for the quality of exhausted paper pulp), temperature 50 C, pH8～9, time 120min.

Further, described O _pthe concrete mode of-Q-P bleaching process is: Oxygen Delignification of Fast-Growing is: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, MgSO ₄consumption 0.5%, Na ₂siO ₃consumption 0.7%, H ₂o ₂consumption 3%, time 80min; Q section: starch dense 8%, DTPA(Chinese diethylene triamine pentacetic acid (DTPA)) consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min.

Further, described O ₁-O _2Pthe concrete mode of-Q-P bleaching process is: the process conditions of first paragraph oxygen delignification and second segment strengthening oxygen delignification: first paragraph O ₁: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 20min, MgSO ₄consumption 0.5%; Second segment O _2P: supplement 0.5% NaOH, add 3% H ₂o ₂, Na ₂siO ₃consumption 0.7%, oxygen is pressed 0.5MPa, time 60min; Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min.

Further, described O _1P-O _2Pthe concrete mode of-Q-P bleaching process is: the process conditions of two sections of strengthening oxygen delignifications: first paragraph O _1P: starch dense 10%, NaOH consumption 2.5%, H ₂o ₂consumption 1%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 20min, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%; Second segment O _2P: supplement 0.5% NaOH, add 2.5% H ₂o ₂, oxygen is pressed 0.5MPa, time 60min; Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min.

The present invention adopts zytase to carry out preliminary treatment to paper pulp, then passes through XO _pqPXO ₁o _2PqP, XO _1Po _2Ptri-kinds of QP float one of order and bleach, and have obtained the paper pulp that whiteness and viscosity are higher, (X refers to xylanase pretr eatment) specific as follows:

XO _pqP floats order at H ₂o ₂in the situation of total consumption 5%, the whiteness of bleached pulp is up to 83.3%ISO, minimum 83.1%ISO; O _pthe whiteness of QP bleached pulp is 81.2%ISO, through enzyme process than with enzyme, do not process float after the whiteness of slurry exceed 1.9-2.1%ISO, and kept higher pulp viscosity and lower Kappa number;

XO ₁o _2PqP floats order at H ₂o ₂in the situation of total consumption 5%, the whiteness of bleached pulp is up to 82.7%ISO, minimum 82.4%ISO; O ₁o _2Pthe whiteness of QP bleached pulp is 80.6%ISO, through enzyme process than with enzyme, do not process float after the whiteness of slurry exceed 1.8-2.1%ISO, and kept higher pulp viscosity and lower Kappa number;

XO _1Po _2PqP floats order at H ₂o ₂in the situation of total consumption 5.5%, the whiteness of bleached pulp is up to 83.5%ISO, minimum 83.1%ISO; O _1Po _2Pthe whiteness of QP bleached pulp is 81.6%ISO, through enzyme process than with enzyme, do not process float after the whiteness of slurry exceed 1.8-2.1%ISO, and kept higher pulp viscosity and lower Kappa number;

With respect to not using xylanase pretr eatment, directly bleaching for the paper pulp obtaining, making beating loss of whiteness value of the present invention compared with the latter still less; The former folding strength on average exceeds 45 times compared with the latter, and burst index on average exceeds 0.45Nmg ^-1, fracture length on average exceeds 0.35KM, and tear index is suitable.When reaching identical or close beating degree, the former required making beating revolution still less, can be saved beating energy consumption 20% left and right.

Paper pulp after enzyme is processed carries out O _pqP, O ₁o _2PqP, O _1Po _2Pthe TCF bleaching of QP, in the situation that consume identical chemicals, can improve the final whiteness 1.5-2.1%ISO of paper pulp, kept higher pulp viscosity, and become the physical indexs such as folding strength, bursting strength, fracture length of paper to be all better than the paper pulp of not processing with enzyme, this shows that these three kinds of enzymes have kept better bleaching selectivity, has improved more significantly the physical property of floating rear slurry, wherein helps to float effect and it would be desirable X ₂, be secondly X ₁, be finally X ₃.

Accompanying drawing explanation

Fig. 1: KP magma fiber properties schematic diagram.

Fig. 2: through zytase X ₁the paper pulp fiber characteristic schematic diagram of processing.

Fig. 3: through zytase X ₂the paper pulp fiber characteristic schematic diagram of processing.

Fig. 4: through zytase X ₃the paper pulp fiber characteristic schematic diagram of processing.

Fig. 5: KP magma is through O _pthe paper pulp fiber characteristic schematic diagram of QP bleaching.

Fig. 6: KP magma is through X ₁o _pthe paper pulp fiber characteristic schematic diagram of QP bleaching.

Fig. 7: KP magma is through X ₂o _pthe paper pulp fiber characteristic schematic diagram of QP bleaching.

Fig. 8: KP magma is through X ₃o _pthe paper pulp fiber characteristic schematic diagram of QP bleaching.

The specific embodiment

Below in conjunction with embodiment, the present invention is further illustrated.In embodiment not the method for detailed description be under the conventional method in field, raw materials used, reagent etc. is existing product in prior art.

The process optimization of embodiment 1 xylanase treatment fast-growing poplar sulfate pulp

Zytase is a kind of protein with single-minded catalytic, and it is stricter to the requirement of environment, that is to say that each enzyme has its specific optimal environmental condition.Zytase is all being obtained obvious effect aspect chemical pulping and bleaching preliminary treatment.According to pertinent literature, the factor that affects xylanase pretr eatment mainly contains enzyme dosage, temperature, pH value and time etc., and these factors have impact in various degree to oxygen delignification effect and follow-up bleaching.In these influence factors, temperature is relevant with the characteristic of zytase itself with pH value, and relatively less on the character impact of slurry.This experiment, by conversion experiment condition, is inquired into the most suitable preliminary treatment fast-growing of different xylanase preparations poplar sulfate pulp process conditions.

When different xylanase preparations is discussed in consumption, temperature, pH value, the optimum value of time, adopt identical Oxygen Delignification of Fast-Growing condition below, this is with reference to oxygen delignification condition preferably in the past: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 80min, MgSO ₄the all drug dosages of consumption 0.5%(are all for oven dry stock, as follows).

This tests raw material sources used:

Experiment is to mix quick growth poplar wood sheet with quick growth poplar wood sheet, takes from Shandong sun Paper Co., Ltd.Chip dimensions length 15-25mm, width 10-20mm, thickness 3-5mm, the qualification rate of wood chip is more than 90%, and wood chip is from fetch in stock ground, standby after natural air drying equilibrium water conten.

Zytase X ₁by Novozymes Company, provided, liquid state, cellulose-less enzyme is lived; Zytase X ₂, X ₃all have Shenzhen biological Co., Ltd of green micro-health to provide, be white powder solid, all cellulase is not lived.

During experiment, fast-growing poplar is carried out to boiling, obtain after paper pulp, then carry out xylanase pretr eatment.Digestion process is: in 15L electric heating rotating autoclave, carry out boiling, make fast-growing poplar sulfate magma.The condition of boiling is: alkali charge 20%(is to over dry raw material, Na ₂o meter), sulphidity 24%, liquor ratio 1:4,165 ℃ of boiling maximum temperatures are carried out little venting 15min, heating-up time 120min, temperature retention time 90min in the time of 105 ℃.Boiling disposed slurry is through fully washing, screening.Paper pulp yield 49.3%, the Kappa number 18.5 of paper pulp, viscosity 842.7mL/g, whiteness 36.5%ISO.

After xylanase pretr eatment, carry out oxygen delignification, oxygen delignification experiment is carried out in JF-DSTE polymerization reaction kettle (have and stir and automatic constant-temperature function).Its Oxygen Delignification of Fast-Growing is: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 80min, MgSO ₄consumption 0.5%.

The impact of the consumption of 1.1 zytases on fast-growing poplar sulfate pulp oxygen delignification

In order to obtain best enzyme treatment effect, the consumption of zytase must carry out optimization selection.This is because the content of different paper pulp kind xylans is different, the xylan content of hardwood pulp is higher than the content of softwood pulp, such as the xylan content of Eucalyptus Kraft Pulp is higher than masson s pine pulp, and xylan more easily can and, so the consumption of enzyme is less, in the suitable situation of pH value and temperature, the consumption of zytase with greater activity is just few than common zytase consumption.Starch dense too low required enzyme dosage and also want corresponding increase.Therefore, zytase consumption number affect the effect that enzyme is processed fast-growing poplar sulfate pulp oxygen delignification, affect whiteness and the Kappa number of oxygen delignification paper pulp, also affect following bleaching effect and the production cost of paper pulp after oxygen delignification, the consumption of therefore inquiring into three kinds of different zytases has important practical significance.Three kinds of Novel xylanase X ₁, X ₂, X ₃consumption experimental studies results in Table 1,2,3.

Table 1 zytase X ₁the impact of consumption on the oxygen delignification performance of pretreating paper pulp

Note: zytase X ₁other conditions of processing: 55 ℃ of temperature, time 120min, starch dense 10%, pH value 8-9.

As can be seen from Table 1, along with zytase X ₁the increase of consumption, the whiteness of the paper pulp after oxygen delignification tends towards stability after progressively increasing, and the Kappa number of paper pulp reduces amplitude and no longer changes from large to small, and the viscosity of paper pulp declines after first rising to some extent slightly, as zytase X ₁when consumption is 8IU/L, the better effects if of oxygen delignification is a little.From the experimental data of table 1, can find out, through the paper pulp of xylanase treatment, than untreated paper pulp, compare, the whiteness of paper pulp raises and viscosity also slightly raises, and the pulp property after oxygen delignification increases.

Table 2 zytase X ₂the impact of consumption on the oxygen delignification performance of pretreating paper pulp

Note: zytase X ₂other conditions of processing: temperature 50 C, time 120min, starch dense 10%, pH value 8-9.

As can be seen from Table 2, along with zytase X ₂the increasing of consumption, after oxygen delignification, the whiteness of paper pulp progressively increases, and while waiting zytase to be increased to 10IU/g, pulp brightness no longer changes; The viscosity of paper pulp first increases and tends towards stability afterwards and slightly reduce; The Kappa number of paper pulp reduces amplitude with the increase of zytase consumption and first strengthens and be tending towards afterwards constant.As can also be seen from Table 2, as zytase X ₂when consumption is 6IU/g, after oxygen delignification, the performance of paper pulp is best.

Table 3 zytase X ₃the impact of consumption on the oxygen delignification performance of pretreating paper pulp

Note: zytase X ₃other conditions of processing: temperature 50 C, time 120min, starch dense 10%, pH value 8-9.

As can be seen from Table 3, along with zytase X ₃the increase of consumption, after oxygen delignification, the whiteness of paper pulp first raises and is tending towards afterwards constant; The Kappa number of paper pulp first declines to tending towards stability afterwards and no longer changes; After the viscosity of paper pulp first increases to some extent, increasing degree slows down and tends towards stability.As can also be seen from Table 3, work as X ₃when consumption is 8IU/g, the performance improvement effect of the paper pulp after oxygen delignification is best.

From table 1,2,3, can find out, three kinds of zytases that cellulase is not lived are when improving pulp oxygen delignification performance, show some common features: along with the increase of enzyme dosage, the whiteness of paper pulp progressively improves, and finally can improve pulp brightness 1.3-1.5%ISO; The Kappa number of paper pulp reduces amplitude at 1-1.2; The viscosity rise amplitude of paper pulp is in 30mL/g left and right.After xylanase treatment, the improvement of oxygen delignification pulp property provides good precondition to the improvement of follow-up bleached pulp performance.Meanwhile, due to the production unit of three kinds of zytases and the difference of technique, while having caused three kinds of enzyme pulp treatment, the effect of generation is also incomplete same, is mainly manifested in: when reaching same treatment effect, the consumption of enzyme is different.

The impact of 1.2 reaction temperatures on fast-growing poplar sulfate pulp oxygen delignification

Zytase is a kind of biocatalyst, and within the scope of certain active temperature, the reaction speed of enzyme and paper pulp is accelerated along with the rising of temperature, if temperature reduces, its reaction speed declines.But when temperature surpasses a certain boundary, the activity decreased of enzyme is inactivation even.Generally, the effect of zytase and paper pulp mainly contains two aspects: the one, and when temperature raises, the speed of reaction is accelerated, and the 2nd, along with the rising enzyme of temperature loses activity gradually, the reaction speed of enzyme and the functioning efficiency of enzyme are reduced.Therefore select suitable reaction temperature, the usefulness of giving full play to zytase is significant.Temperature is to three kinds of Novel xylanase X ₁, X ₂, X ₃fast-growing poplar NaOH anthraquinone slurry oxygen delignification effect affected to result of study in Table 4,5,6.

Table 4 temperature is to zytase X ₁the impact of the oxygen delignification performance of pretreating paper pulp

Note: enzyme dosage is 8IU/L, time 120min, starch dense 10%, pH value 8-9.

As can be seen from Table 4, along with the rising of temperature, zytase X ₁the usefulness of performance first increases afterwards and weakens, and when temperature is during at 55 ℃, the whiteness of paper pulp reaches 60.1%ISO, reaches maximum, and the Kappa number of paper pulp is down to minimum, and viscosity remains on best level; When temperature surpasses 60 ℃, pulp brightness starts to reduce, and the viscosity of paper pulp declines obviously.This shows zytase X ₁enzyme activity in the time of 55 ℃, be more satisfactory.But from actual production, consider zytase X ₁select treatment temperature be 50-55 ℃ relatively good, be conducive to the practical operation of producing and the adjusting difficulty that reduces temperature, be conducive to reduce production costs and increase economic efficiency.

As can be seen from Table 5, along with temperature raises, zytase X ₂the effect of performance first increases afterwards and weakens.As can be seen from Table 5, along with the rising of pretreatment temperature, the pulp brightness after oxygen delignification starts to improve, but when temperature surpasses 55 ℃, after oxygen delignification, the whiteness of paper pulp starts to reduce; When temperature is during lower than 55 ℃, the Kappa number of paper pulp reduces along with the rising of temperature, but when temperature surpasses 55 ℃, and the rising that Kappa number starts no longer to reduce on the contrary with temperature raises; When temperature is during at 55 ℃-60 ℃, the viscosity of paper pulp becomes along with the rising of temperature greatly, but when temperature surpasses 60 ℃, viscosity decrease speed is obvious.These experimental results show zytase X ₂when temperature is 55-60 ℃, the usefulness of preliminary treatment fast-growing poplar sulfate pulp performance is maximum.

Table 5 temperature is to zytase X ₂the impact of the oxygen delignification performance of pretreating paper pulp

Note: enzyme dosage is 6IU/g, time 120min, starch dense 10%, pH value 8-9.

As can be seen from Table 6, as zytase X ₃while being 50 ℃ with the temperature of paper pulp effect, the pulp brightness after oxygen delignification is the highest, reaches 60%ISO, and it is minimum 7.2 that the Kappa number of paper pulp reaches, and the viscosity of paper pulp reaches maximum 731mL/g.As can also be seen from Table 6, along with the further rising of temperature, after oxygen delignification, the whiteness of paper pulp starts to reduce, and Kappa number starts to raise, and the viscosity of paper pulp declines.This shows, zytase X ₃when temperature is 50 ℃, performance helps that to float effect best.

Table 6 temperature is to zytase X ₃the impact of the oxygen delignification performance of pretreating paper pulp

Note: enzyme dosage is 8IU/g, time 120min, starch dense 10%, pH value 8-9.

From table 4,5,6, can find out, after the oxygen delignification of the temperature of three kinds of zytases preliminary treatment fast-growing poplar sulfate pulp when 50-60 ℃ of scope, the character of paper pulp is better.Zytase X ₁when temperature is 50-55 ℃, the usefulness of enzyme is better, zytase X ₂when temperature is 55-60 ℃, the efficiency of enzyme is comparatively desirable, zytase X ₃when temperature is 50 ℃, enzyme is most effective.When respectively three kinds of zytases being carried out to zymologic property research, using pure xylan as substrate, the optimum temperature of three kinds of zytases is 55-60 ℃, but in actual experiment, zytase X ₁and X ₃during pretreating paper pulp, when reaching optimum efficiency, than ideal temperature, decrease, this may with paper pulp in xylan and the structure of pure xylan or character there are differences and cause.But zytase X ₂the optimal temperature of pretreating paper pulp is consistent with the temperature of zymologic property research, and this may be relevant with the characteristic of enzyme self.

The impact of 1.3pH value on fast-growing poplar sulfate pulp oxygen delignification

The scope of application difference of different zytase pH is also very large, and their applicable pH values can be divided into acidity, neutrality and alkaline.The activity of most of zytase need to competence exertion effect within the scope of applicable pH value, and the too high too low conformation that all can affect zymoprotein of pH value, even makes zytase lose activity, thereby directly has influence on the effect of xylanase treatment paper pulp.The zytase of the paper pulp after the most applicable processing boiling is alkaline enzyme, the present invention first three kinds of enzymes that Novel xylanase is all meta-alkalescence of use.Different pH values to the experimental data of these three kinds of xylanase treatment fast-growing poplar sulfate pulp oxygen delignification effects in Table 7,8,9.

Table 7pH value is to zytase X ₁the impact of pretreating paper pulp on oxygen delignification effect

Note: enzyme dosage is 8IU/L, temperature 50 C, time 120min, starches dense 10%.

As can be seen from Table 7, zytase X ₁after preliminary treatment fast-growing poplar sulfate pulp oxygen delignification, the whiteness of paper pulp is along with the increase of pH value first increases rear reduction, and when pH value 8, the whiteness of paper pulp is up to 60.1%ISO; The Kappa number of paper pulp is along with the increase of pH value first reduces rear increase, when pH value 8, and Kappa number minimum 7.1; The viscosity of paper pulp is along with the increase of pH value first increases rear reduction, and when pH value 8, the viscosity of paper pulp reaches maximum 740mL/g.As can be seen from Table 7, pH value when 9-10, zytase X ₁usefulness also good, kept higher whiteness, lower Kappa number and higher viscosity.From the angle of actual production, consider, using zytase X ₁time pH value the best be modulated to 8, if but be modulated at the scope of 8-10, also can bring into play better and more stable effect and usefulness.

As can be seen from Table 8, zytase X ₂after preliminary treatment fast-growing poplar sulfate pulp oxygen delignification, the whiteness of paper pulp is along with the increase of pH value first increases rear reduction, and when pH value 8, the whiteness of paper pulp is up to 60.2%ISO; The Kappa number of paper pulp is along with the increase of pH value first reduces rear increase, when pH value 9, and Kappa number minimum 7.2; The viscosity of paper pulp is along with the increase of pH value first increases rear reduction, and when pH value 9, the viscosity of paper pulp reaches maximum 740mL/g.This shows zytase X ₂effect when pH value is 8-9 is best, has kept the whiteness that paper pulp is the highest, minimum Kappa number and maximum viscosity.PH value be 7 and the pretreating effect of 10 o'clock while being 8-9 compared with pH value effect slightly poor, but from the angle of actual production, zytase X ₂applicable pH value be that alkalescent or neutrality are fine, but preferably pH value in the scope of 8-9.

Table 8pH value is to zytase X ₂the impact of pretreating paper pulp on oxygen delignification effect

Note: enzyme dosage is 6IU/g, 55 ℃ of temperature, time 120min, starches dense 10%.

As can be seen from Table 9, zytase X ₃after preliminary treatment fast-growing poplar sulfate pulp oxygen delignification, the whiteness of paper pulp is along with the increase of pH value first increases rear reduction, and when pH value 8, the whiteness of paper pulp is up to 60.2%ISO; The Kappa number of paper pulp is along with the increase of pH value first reduces rear increase, when pH value 8, and Kappa number minimum 7.1; The viscosity of paper pulp is along with the increase of pH value first increases rear reduction, and when pH value 8, the viscosity of paper pulp reaches maximum 734mL/g.When pH value 9, the whiteness 60%ISO of paper pulp, Kappa number 7.2, the viscosity 731 of paper pulp, effect gap a little during with pH value 8, but gap is very little, can draw thus, zytase X ₁pretreating paper pulp preferably pH value is 8-9.

Table 9pH value is to zytase X ₃the impact of pretreating paper pulp on oxygen delignification effect

Note: enzyme dosage is 8IU/g, temperature 50 C, time 120min, starches dense 10%.

From table 7,8,9, can find out, the pH value of three kinds of zytases is all more satisfactory to the treatment effect of paper pulp within the scope of 8-10.Zytase X ₁best pH value is 8, zytase X ₂optimal pH be 8-9, zytase X ₃optimal pH be 8.When respectively three kinds of zytases being carried out to zymologic property research, using pure xylan as substrate, the optimum pH value of three kinds of zytases is all 8, zytase X when for the treatment of paper pulp ₁and X ₃most suitable pH value is all 8, and the zymologic property of this and they matches.And zytase X ₂the optimum value of pulp treatment is 8 and 9, not quite identical with its zymologic property, and when pulp treatment, alkali resistance increases, and can reduce like this number of times of pulp washing after boiling, and saving water resource and reduce energy consumption is conducive to the application of actual production.

The impact of 1.4 times on fast-growing poplar sulfate pulp oxygen delignification effect

There is certain influence time to xylanase treatment fast-growing poplar sulfate pulp, if the time is too short, the performance of enzyme cannot be performed to ultimate attainment, if overlong time is unfavorable for enhancing productivity.Based on this, in immobilized enzyme consumption, temperature, pH value with starch and studied the impact of time on pretreatment effect under dense condition.Experimental result is in Table 10,11,12.

Table 10 time is to zytase X ₁the impact of pretreating paper pulp on oxygen delignification effect

Note: enzyme dosage is 8IU/L, temperature 50 C, pH value 8-9, starches dense 10%.

As can be seen from Table 10, along with the prolongation of time, zytase X ₁fast-growing poplar sulfate pulp after processing is after oxygen delignification, and the whiteness of paper pulp starts after progressively improving to reduce, and when the time is 120min, the whiteness of paper pulp reaches peak 60.1%ISO; The Kappa number of paper pulp starts to raise after first progressively reducing, when the time is during at 120min, and Kappa number near minimum 7.1; The viscosity of paper pulp starts after progressively raising to reduce, and when the time is 120min, the viscosity of paper pulp reaches maximum 740mL/g.From the experimental data of table 10, also can find out, along with the prolongation of time, the action effect of enzyme starts to decline, and this may be because zytase and paper pulp be long action time, and enzymolysis product has produced certain inhibitory action to enzyme with reacting of paper pulp.So zytase X ₁the time 120min of pulp treatment is advisable.

As can be seen from Table 11, along with the prolongation of time, zytase X ₂fast-growing poplar sulfate pulp after processing is after oxygen delignification, and the whiteness of paper pulp is also first to raise and reduce afterwards, and when the time is 120min, the whiteness of paper pulp is up to 60.2%ISO; The Kappa number of paper pulp first declines and starts afterwards to uprise, and when the time reaches 120min, the Kappa number of paper pulp is minimum to 7.2; The viscosity of paper pulp starts to reduce after first becoming greatly, and when the time is 120min, the viscosity of paper pulp is up to 745mL/g.The experimental data of consolidated statement 11 can draw, zytase X ₂the time of pulp treatment is not that the longer the better, when the time, surpasses after 120min, and the action effect of enzyme starts to weaken, so zytase X ₃the time 120min of pulp treatment is advisable.

Table 11 time is to zytase X ₂the impact of pretreating paper pulp on oxygen delignification effect

Note: enzyme dosage is 6IU/g, 55 ℃ of temperature, pH value 8-9, starches dense 10%.

As can be seen from Table 12, along with the prolongation of time, zytase X ₃fast-growing poplar sulfate pulp after processing is after oxygen delignification, and the viscosity of paper pulp first raises and reduces afterwards, and when the processing time is 120min, the viscosity of paper pulp reaches maximum 731mL/g; The whiteness of paper pulp is also first to raise and reduce afterwards, and when the processing time is 120min, the whiteness of paper pulp is also first to improve rear reduction, and when the processing time is 120min, the whiteness of paper pulp reaches maximum 60%ISO; It is large that the Kappa number of paper pulp first reduces rear change, and when the processing time is 120min, the Kappa number of paper pulp is down to minimum 7.2.From table 12, also can find out, when reaching the highest whiteness, minimum Kappa number and the highest viscosity, zytase X ₃the pulp treatment time is 120min, surpasses this time treatment effect and just starts to weaken, and this may be because zytase and paper pulp be long action time, and enzymolysis product has produced certain inhibitory action to enzyme with reacting of paper pulp.

Table 12 time is to zytase X ₃the impact of pretreating paper pulp on oxygen delignification effect

Note: enzyme dosage is 8IU/g, temperature 50 C, pH value 8-9, starches dense 10%.

From table 10,11,12, can find out that these three kinds of zytases are basically identical to the treatment effect of paper pulp: the one, along with the prolongation of time, the whiteness of paper pulp first raises and reduces afterwards, and the Kappa number of paper pulp first reduces rear rising, and the viscosity of paper pulp first increases afterwards and diminishes; The 2nd, the time of continuing these three kinds of xylanase treatment paper pulp of prolongation, the whiteness of paper pulp starts to reduce, Kappa number starts to raise, pulp viscosity starts to decline.When therefore the optimization process time is all controlled at 120min, be advisable.Table 10,11,12 experimental result also show, be not that the longer the better action time for zytase and paper pulp, but there is time preferably, if overlong time, may affect the activity of enzyme, also may make the part lignin of stripping start again to deposit on fiber, reduce the usefulness of zytase, overlong time is also unfavorable for enhancing productivity simultaneously.Therefore it is very important selecting the time of suitable xylanase treatment paper pulp.

Comprehensive above-mentioned experimental technique analysis result, can show that three kinds of zytases preferably process the process conditions of fast-growing poplar sulfate pulp: zytase X ₁preferred process condition be: enzyme dosage 8IU/L, temperature 50 C, pH8, time 120min; Zytase X ₂preferred process condition be: enzyme dosage 6IU/g, 55 ℃ of temperature, pH8-9, time 120min; Zytase X ₃preferred process condition be: enzyme dosage 8IU/g, temperature 50 C, pH8-9, time 120min.

The optimization of embodiment 2 bleaching conditions

2.1.1 raw material

Zytase X ₁by Novozymes Company, provided, liquid, cellulose-less enzyme is lived; Zytase X ₂, X ₃all have Shenzhen biological Co., Ltd of green micro-health to provide, be white powder solid, all cellulase is not lived.

2.1.2 boiling experiment

In 15L electric heating rotating autoclave, carry out boiling, make fast-growing poplar sulfate magma.The condition of boiling is: alkali charge 20%(is to over dry raw material, Na ₂o meter), sulphidity 24%, liquor ratio 1:4,165 ℃ of boiling maximum temperatures are carried out little venting 15min, heating-up time 120min, temperature retention time 90min in the time of 105 ℃.Boiling disposed slurry is through fully washing, screening.Paper pulp yield 49.6%, the Kappa number 18.9 of paper pulp, viscosity 950ml/g, whiteness 36.5%ISO.

2.1.3 xylanase pretr eatment

Three kinds of xylanase pretr eatment experiments all complete in polyethylene plastic bag.The poplar sulfate pulp of having washed after boiling is mixed in plastic bag with enzyme, enzyme treatment process condition and the experimental procedure according to embodiment 1, optimized, after regulating pH value and starch zytase liquid that dense rear handle modulates and putting into bag and evenly mix, put into the water-bath that sets temperature and carry out constant temperature processing.In processing procedure, at interval of 10-15min, with hand, rub once, to guarantee that enzyme mixes with the even of paper pulp.Slurry takes out after processing the stipulated time, then puts into boiling water bath 10min, makes zytase inactivation cessation reaction, with entering following bleaching operation after running water cleaning paper pulp.

2.1.4 oxygen delignification and the experiment of strengthening oxygen delignification

The experiment of fast-growing poplar sulfate pulp oxygen delignification is carried out in JF-DSTE polymerization reaction kettle (have and stir and automatic constant-temperature function).Its Oxygen Delignification of Fast-Growing is: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 80min, MgSO ₄the all drug dosages of consumption 0.5%(are all for oven dry stock, as follows).

The process conditions of two sections of oxygen delignifications: first paragraph O ₁: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 20min, MgSO ₄consumption 0.5%; Second segment O ₂: supplement 0.5% NaOH, oxygen is pressed 0.5MPa, time 60min.

Fast-growing poplar sulfate pulp strengthening oxygen delignification O _pprocess conditions be: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, MgSO ₄consumption 0.5%, Na ₂siO ₃consumption 0.7%, H ₂o ₂consumption 3%, time 80min.

The process conditions of first paragraph oxygen delignification and second segment strengthening oxygen delignification: first paragraph O ₁: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 20min, MgSO ₄consumption 0.5%; Second segment O _2P: supplement 0.5% NaOH, add 3% H ₂o ₂, Na ₂siO ₃consumption 0.7%, oxygen is pressed 0.5MPa, time 60min.

The process conditions of two sections of strengthening oxygen delignifications: first paragraph O _1P: starch dense 10%, NaOH consumption 2.5%, H ₂o ₂consumption 1%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 20min, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%; Second segment O _2P: supplement 0.5% NaOH, add 2.5% H ₂o ₂, oxygen is pressed 0.5MPa, time 60min.

2.1.5 the bleaching experiment of paper pulp

The bleachings such as D, E, Q, P or processing section carry out respectively in polyethylene plastic bag.Get 30g oven dry stock at every turn, according to the experimental procedure of drafting, after required liquid is evenly mixed, pour in plastic bag, after slurry and liquid are mixed, put into thermostat water bath and bleach or process.In the process of bleaching or processing, at interval of 15min, take out and rub even mixing once with hand, guarantee paper pulp and the even mixing of floating agent.

2.1.6 analytical method

The mensuration of viscosity: the method according to standard GB/T 1548-1989 regulations is carried out.

The mensuration of Kappa number: according to GB1546-1989 standard test.

The mensuration of whiteness: paper pulp is discongested after device discongests through fiber, copies into the scraps of paper on Buchner funnel, air-dry rear with YQ-Z-48B

Whiteness instrument is measured.

Folding number: in using, domestic MIT folding strength tester is measured.

Burst index: measure with the bursting strength tester that swedish company L & W produces.

Fracture length: measure with the anti-tensile tester that swedish company L & W produces.

Tear index: measure with the tearability tester that the TMI of u s company produces.

2.1.7 making beating and the mensuration of beating energy consumption

Slurry after defibrination adopts KRK company to produce PFI mill and pulls an oar, and beating consistency is 10%, and beater roll(er) and beater chamber gap are 0.2mm, and beating pressure is 3.4Nmm ^-1.The beating degree of making beating disposed slurry is measured and is adopted Xiao Baier-Rui Gele YQ-Z-13 beating degree analyzer to measure.

The revolution of making beating specific energy consumption: PFI mill is linear with beating energy consumption within the specific limits, and this experiment required making beating revolution when reaching identical beating degree calculates energy loss-rate.Bleached pulp making beating revolution * 100% of the beating energy consumption reduction rate in this experiment=(enzyme is processed the bleached pulp making beating revolution of after bleaching slurry making beating revolution-do not process with enzyme)/do not process with enzyme.

2.1.8 ESEM

The paper pulp of processing through different enzymes is carried out respectively to oxygen-delignified pulp from magma, carries out the different orders of floating subsequently and bleach gained paper pulp etc. under the identical experiment condition of embodiment 1 " oxygen delignification experiment ", after running water washing, utilizing the quick handshcet former of triumphant match to copy formulation amount is 60g/m ²l Water Paper page, then by l Water Paper page in vacuum drier dry 48 hours, after metal spraying is processed, is observe and take pictures on the ESEM of QUANTA200 in model, and accelerating potential is 10kV.

2.1.9 atomic force microscope observation

Getting slurry sample 0.1g to be measured is distributed in the distilled water of 200mL, with dispersing device, break up, fiber is evenly distributed in water, then with pipette, getting a droplet is put on mica sheet, single fiber is distributed on mica sheet, air-dry 24h under room temperature, then uses MultiModeSPM model AFM (AFM) produced in USA to carry out scanning and photograph, and the model of probe is NP-20.

2.1.10 xylanase activity is measured

Adopt DNS method to measure (being conventional determining method of the prior art).

2.1.11 enzyme preparation characteristic is determined

Zytase X ₁, X ₂, X ₃enzyme activity determination according to DNS method, measure, it the results are shown in Table 13 and table 14.

The characteristic of table 13 liquid xylanase preparation

The characteristic of table 14 solid xylanase preparation

2.2 results and the effect of discussion xylanase treatment to fast-growing poplar sulfate pulp TCF bleaching

Want thoroughly to eliminate the pollution of organic chloride, must adopt and bleach completely without chlorine (TCF).TCF bleaching is mainly with O ₂, O ₃and H ₂o ₂for mainly floating agent, the conventional order of floating has OQP, O ₁o ₂qP, O _pqP etc.In the present embodiment, adopted (X) O _pqP, (X) O ₁o _2PqP and (X) O _1Po _2Pthree kinds of QP etc. float ordered pair fast-growing poplar sulfate pulp and carry out TCF bleaching experiment, inquire into the effect of novel commercial xylanase in fast-growing poplar sulfate pulp TCF bleaching.

All bleaching process of the oxygen delignification section bleaching containing in this experiment all carry out during xylanase treatment paper pulp before oxygen delignification, and its process conditions are the xylanase treatment process conditions of optimizing in chapter 2.

2.2.1 three kinds of xylanase pretr eatments are to fast-growing poplar sulfate pulp O _pthe impact of QP bleaching results

Adopt zytase X ₁, X ₂and X ₃at fast-growing poplar sulfate pulp O _pqP carries out preliminary treatment before floating order bleaching, inquires into the impact of xylanase treatment on fast-growing poplar kraft bleaching performance.

The process conditions of three kinds of xylanase treatment fast-growing poplar sulfate pulp oxygen delignification best results optimizing according to embodiment 1, in conjunction with strengthening oxygen delignification and H ₂o ₂bleaching conditions carry out this experiment.Concrete process conditions are as follows: X ₁the process conditions of processing: enzyme dosage 8IU/L, temperature 50-55 ℃, pH8, time 120min; X ₂the process conditions of processing: enzyme dosage 6IU/g, temperature 55-60 ℃, pH8-9, time 120min; X ₃the process conditions of processing: enzyme dosage 8IU/g, temperature 50 C, pH8-9, time 120min.

O _pqP floats the bleaching conditions of order: strengthening oxygen delignification O _pthe process conditions of section are shown in 2.1.4.Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min.

Poplar sulfate pulp through xylanase treatment and untreated paper pulp are carried out to O under above-mentioned identical bleaching process _pqP bleaches, and guarantees the comparativity of bleaching results.Xylanase pretr eatment is to fast-growing poplar sulfate pulp O _pqP bleaching results is in Table 15.Paper pulp after bleaching is pulled an oar with PFI mill, and the making beating revolution of controlling various slurries makes its beating degree be controlled at 46 ° of SR left and right, then copies and makes quantitative 60g/m ²the paper of left and right, then detects physical properties such as its folding strength, bursting strength, tear index, fracture lengths, and its result is as table 16.

Table 15 xylanase pretr eatment is to fast-growing poplar sulfate pulp O _pthe impact of QP bleaching results

As can be seen from Table 15, fast-growing poplar sulfate pulp is through XO _pqP floats the bleaching results that order completes and is better than O _pqP floats order.X wherein ₂o _pthe final bleaching whiteness that QP floats order is the highest, reaches 83.3%ISO, compared with O _pthe final whiteness that QP floats order exceeds 2.1%ISO, and is these four kinds of maximum 735mL/g that float pulp viscosity in order; Next is X ₁o _pqP and X ₃o _pthe final whiteness that QP floats order all reaches 83.1%ISO, compared with O _pthe final whiteness that QP floats order exceeds 1.9%ISO, and has kept respectively higher pulp viscosity 730mL/g and 728mL/g.

As can be seen from Table 15, through paper pulp xylanase treatment and that do not pass through xylanase treatment, at process O _pqP floats after order bleaching, and the final Kappa number of paper pulp is also different, X ₂o _pit is minimum 1.8 that QP floats the Kappa number of order, compared with O _pqP floats the Kappa number Di0.5Ge unit of order, is secondly X ₁o _pthe Kappa number that QP floats order is 1.9, compared with O _pqP floats the Kappa number Di0.4Ge unit of order, is finally X ₃o _pthe Kappa number that QP floats order is 2.0, compared with O _pqP floats the Kappa number Di0.3Ge unit of order.These experimental datas show, through the paper pulp of enzyme processing, at O _pqP floats in order bleaching process, is more conducive to removing of lignin, further reduces the Kappa number of paper pulp, improves the whiteness of paper pulp, has kept than the conventional higher pulp viscosity of order bleaching that floats.

From table 15, also can find out, paper pulp is through O _pqP and XO _pafter QP bleaching, through making beating, copying make quantitative is 60g/m ²paper, its whiteness has decline in various degree.Wherein, do not pass through the O of xylanase treatment _pthe whiteness reduction that QP floats order is at most 1.9%ISO, the X processing through enzyme ₂o _pqP floats the minimum 1.6%ISO of being of whiteness reduction value of order, through X ₁o _pthe whiteness reduction value that QP floats order is 1.7%ISO, through X ₃o _pthe whiteness reduction value that QP floats order is 1.8%ISO, these experimental datas show through the loss of whiteness of the bleached pulp of xylanase treatment paper pulp after making beating still less, this may be because after floating after enzyme is processed, the Kappa number of slurry is lower, lignin content still less, paper pulp is more difficult for brightness reversion.

As can be seen from Table 16, XO _ppaper pulp after QP bleaching compares O _ppaper pulp after QP bleaching is more easily pulled an oar.When reaching close 46 ° of SR of beating degree, required making beating revolution few 3000 turns, save beating energy consumption in 20% left and right, this may be because the processing of paper pulp process zytase, sub-fraction hemicellulose degraded in paper pulp, bleaching liquid is more easily impregnated in the gap of cellulose and hemicellulose, when impelling more lignin strippings, make fiber further softening, pull an oar more easily more energy-conservation.

Table 16O _pqP/XO _pthe comparison of QP bleached pulp physical properties of paper

As can be seen from Table 16, XO _ppaper pulp after QP bleaching compares O _pthe physical indexs such as the folding strength of the paper pulp after QP bleaching, bursting strength, fracture length are more better.XO _pqP and O _pthe bleached pulp that QP floats order is all copied and is made quantitative 60g/m ²the paper of left and right, through X ₂o _pphysical property of pulp after QP bleaching is best, and folding strength is than exceeding 57 times of not processing with enzyme, and fracture length has improved 0.4Km, and burst index exceeds 0.4Nmg ^-1, several slurry tear indexes are very approaching, but X ₂o _pit is also that this severally floats rear slurry and copy the maximum 5.21mNm that makes paper that QP floats rear slurry ²g ^-1.Through X ₁o _pqP and X ₃o _pqP floats the rear slurry of floating of order, has shown equally good physical property: these two kinds of bleached pulps are compared with O _pqP bleached pulp is copied the paper folding strength of making and is improved respectively 42 and 33 times, and fracture length improves respectively 0.32 and 0.34Km.But through X ₁o _pthe tear index that QP floats rear slurry declines slightly, and X ₃o _pqP floats rear slurry compared with O _pthe tear index that floats rear slurry of QP is substantially suitable.This may be because the effect of zytase, makes to bleach liquid and soaks into more fully, and the damage to fiber when removing more lignins is very little.

In sum, through XO _pqP floats after the TCF bleaching of order, and the whiteness maximum of paper pulp reaches 83.3%ISO, and keeps relatively high viscosity, compared with O _pthe paper pulp of QP bleaching in the situation that consume identical chemicals, can improve the final whiteness 1.9-2.1%ISO of paper pulp, XO _pqP floats rear slurry compared with O _pqP floats rear slurry and has kept higher pulp viscosity, has also kept better bleaching selectivity, has improved more significantly the physical property of floating rear slurry.

2.2.2 three kinds of xylanase pretr eatments are to fast-growing poplar sulfate pulp O ₁o _2Pthe impact of QP bleaching results

Adopt zytase X ₁, X ₂and X ₃at fast-growing poplar sulfate pulp O ₁o _2PqP carries out preliminary treatment before floating order bleaching, inquires into the impact of xylanase treatment on fast-growing poplar kraft bleaching performance.

O ₁o _2PqP floats the bleaching conditions of order: oxygen delignification O ₁with strengthening oxygen delignification O _2Pthe process conditions of section are shown in 2.1.4.Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min.

Poplar sulfate pulp through xylanase treatment and untreated paper pulp are carried out to O under above-mentioned identical bleaching process ₁o _2PqP bleaches, and guarantees the comparativity of bleaching results.Xylanase pretr eatment is to fast-growing poplar sulfate pulp O ₁o _2PqP bleaching results is in Table 17.Paper pulp after bleaching is pulled an oar with PFI mill, and the making beating revolution of controlling various slurries makes its beating degree be controlled at 44.7 ° of SR left and right, then copies and makes quantitative 60g/m ²the paper of left and right, then detects physical properties such as its folding strength, bursting strength, tear index, fracture lengths, and its result is as table 18.

Table 17 xylanase pretr eatment is to fast-growing poplar sulfate pulp O ₁o _2Pthe impact of QP bleaching results

As can be seen from Table 17, fast-growing poplar sulfate pulp is through XO ₁o _2PqP floats the bleaching results that order completes and is obviously better than O ₁o _2PqP floats order.X wherein ₂o ₁o _2Pthe final bleaching whiteness of QP is the highest, reaches 82.7%ISO, compares O ₁o _2Pthe final whiteness that QP floats order exceeds 2.1%ISO, and is these four kinds of maximum 751mL/g that float pulp viscosity in order; Next is X ₁o ₁o _2Pthe final whiteness of QP reaches 82.5%ISO, compared with O ₁o _2Pthe final whiteness that QP floats order exceeds 1.9%ISO, and its viscosity of floating rear slurry is 747mL/g, with the rear slurry that floats that enzyme is processed, does not exceed 16mL/g; X ₃o ₁o _2Pthe final whiteness that QP floats order is 82.4%ISO, compared with O ₁o _2Pthe final whiteness that QP floats order exceeds 1.8%ISO, and the viscosity of floating rear slurry is 745mL/g, compared with O ₁o _2Pthe pulp viscosity of QP exceeds 14mL/g.Comparison sheet 15 and 17 can be found out, O _pqP and O ₁o _2PqP floats order, XO _pqP and XO ₁o _2PqP floats order, at identical H ₂o ₂in the situation of consumption, O _pqP and XO _pqP floats the whiteness of rear slurry will be higher than O ₁o _2PqP and XO ₁o _2PqP floats order, differs 0.6%ISO left and right, but the low 17mL/g of the viscosity of paper pulp.During actual production, can select the suitable order of floating according to actual conditions.

As can be seen from Table 17, through paper pulp xylanase treatment and that do not pass through xylanase treatment, at process O ₁o _2PqP floats after order bleaching, and the final Kappa number of paper pulp is also different, X ₂o ₁o _2Pit is minimum 1.9 that QP floats the Kappa number of order, compared with O ₁o _2PqP floats the Kappa number Di0.5Ge unit of order, is secondly X ₁o ₁o _2Pthe Kappa number that QP floats order is 2.0, compared with O ₁o _2PqP floats the Kappa number Di0.4Ge unit of order, is finally X ₃o ₁o _2Pthe Kappa number that QP floats order is 2.1, compared with O ₁o _2PqP floats the Kappa number Di0.3Ge unit of order.These experimental datas show, XO ₁o _2PqP compares O ₁o _2PqP floats order bleaching and is more conducive to removing of lignin, further reduces the Kappa number of paper pulp, improves the whiteness of paper pulp, and has kept higher pulp viscosity.Comparison sheet 15 and 17 can be found out, floats order O _pqP compares O ₁o _2PqP, XO _pqP compares XO ₁o _2Pthe Kappa number that QP reduces is more, but the reduced viscosity of paper pulp is also some more.

From table 17, also can find out, paper pulp is through O ₁o _2PqP and XO ₁o _2Pafter QP bleaching, through making beating, copying make quantitative is 60g/m ²paper, the whiteness of paper all declines to some extent.Wherein, do not pass through the O of xylanase treatment ₁o _2Pthe whiteness decline that QP floats order is at most 2.0%ISO, the X processing through enzyme ₂o ₁o _2PqP floats the minimum 1.6%ISO of being of whiteness decline of order, through X ₁o ₁o _2Pthe whiteness reduction value that QP floats order is 1.8%ISO, through X ₃o ₁o _2Pthe whiteness reduction value that QP floats order is 1.9%ISO, these experimental datas show through the loss of whiteness of the bleached pulp of xylanase treatment paper pulp after making beating still less, this may be because the paper pulp after enzyme is processed in bleaching process, can remove more lignin, thereby in pulping, lignin content still less, the Kappa number of paper pulp is lower, and paper pulp is more difficult for brightness reversion.

As can be seen from Table 18, XO ₁o _2Ppaper pulp after QP bleaching compares O ₁o _2Ppaper pulp after QP bleaching is more easily pulled an oar.When reaching close 44.7 ° of SR of beating degree, required making beating revolution few 3000 turns, save beating energy consumption about 20%, this may be due to paper pulp process xylanase treatment before oxygen delignification, sub-fraction hemicellulose degraded in paper pulp, is more easily impregnated in the gap of cellulose and hemicellulose following bleaching liquid, when impelling the more strippings of lignin, fiber soak into liquid fully act on down more softening, thereby when reaching close beating degree, required making beating revolution still less.

From table 18, it can also be seen that XO ₁o _2Ppaper pulp after QP bleaching compares O ₁o _2Ppaper pulp after QP bleaching becomes the physical indexs such as the folding strength, bursting strength, fracture length of paper more better.XO ₁o _2PqP and O ₁o _2Pthe bleached pulp that QP floats order is all copied and is made quantitative 60g/m ²the paper of left and right, through X ₂o ₁o _2Pphysical property of pulp after QP bleaching is best, and folding strength is than exceeding 56 times of not processing with enzyme, and fracture length has improved 0.38Km, and burst index exceeds 0.6Nmg ^-1, several slurry tear indexes are very approaching, but X ₂o ₁o _2Pit is also that this severally floats rear slurry and copy the maximum 5.26mNm that makes paper that QP floats rear slurry ²g ^-1.Through X ₁o ₁o _2PqP and X ₃o ₁o _2PqP floats the rear slurry of floating of order, has shown equally good physical property: these two kinds of bleached pulps are compared with O ₁o _2PqP bleached pulp is copied the paper folding strength of making and is improved respectively 42 and 35 times, fracture length improves respectively 0.29 and 0.3Km, but these two kinds of tear indexes that float rear slurry decline slightly, this may be because beating degree is different, zytase effect situation is different, or exists the reasons such as error to cause.

Table 18O ₁o _2PqP/XO ₁o _2Pthe comparison of QP bleached pulp physical properties of paper

In sum, through XO ₁o _2PqP floats after the TCF bleaching of order, and the whiteness maximum of paper pulp reaches 82.7%ISO, and keeps relatively high viscosity, compared with O ₁o _2Pthe paper pulp of QP bleaching in the situation that consume identical chemicals, can improve the final whiteness 1.8-2.1%ISO of paper pulp, XO ₁o _2PqP floats rear slurry compared with O ₁o _2PqP floats rear slurry and has kept higher pulp viscosity, has also kept better bleaching selectivity, has improved preferably the physical property of floating rear slurry.

2.2.3 three kinds of xylanase pretr eatments are to fast-growing poplar sulfate pulp O _1Po _2Pthe impact of QP bleaching results

Adopt zytase X ₁, X ₂and X ₃at fast-growing poplar sulfate pulp O _1Po _2PqP carries out preliminary treatment before floating order bleaching, inquires into the impact of xylanase treatment on fast-growing poplar kraft bleaching performance.

O _1Po _2PqP floats the bleaching conditions of order: strengthening oxygen delignification O _1Po _2Pthe process conditions of section are shown in 2.1.4.Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min.

Poplar sulfate pulp through xylanase treatment and untreated paper pulp are carried out to O under above-mentioned identical bleaching process _1Po _2PqP bleaches, and guarantees the comparativity of bleaching results.Xylanase pretr eatment is to fast-growing poplar sulfate pulp O _1Po _2PqP bleaching results is in Table 19.Paper pulp after bleaching is pulled an oar with PFI mill, and the making beating revolution of controlling various slurries makes its beating degree be controlled at 45.5 ° of SR left and right, then copies and makes quantitative 60g/m ²the paper of left and right, then detects physical properties such as its folding strength, bursting strength, tear index, fracture lengths, and its result is as table 20.

Table 19 xylanase pretr eatment is to fast-growing poplar sulfate pulp O _1Po _2Pthe impact of QP bleaching results

As can be seen from Table 19, fast-growing poplar sulfate pulp is through XO _1Po _2PqP floats the bleaching results that order completes and is better than O _1Po _2PqP floats order.X wherein ₂o _1Po _2Pthe final bleaching whiteness that QP floats order is the highest, reaches 83.5%ISO, compared with O _1Po _2Pthe final whiteness that QP floats order exceeds 1.9%ISO, and is these four kinds of maximum 738mL/g that float pulp viscosity in order; Next is X ₁o _1Po _2Pthe final whiteness of paper pulp that QP floats order is 83.3%ISO, and viscosity is 733mL/g, compared with O _1Po _2Pthe whiteness that QP floats order exceeds 1.7%ISO, and viscosity exceeds 11mL/g; X ₃o _1Po _2Pthe final whiteness that QP floats order reaches 83.1%ISO, and viscosity is 734mL/g; Compared with O _1Po _2Pthe final whiteness that QP floats order exceeds 1.5%ISO, and viscosity exceeds 12mL/g.

Comparison sheet 15 and 19 can be found out, O _1Po _2PqP floats order and compares O _pqP floats order at the H of strengthening oxygen delignification second segment multiplex 0.5% ₂o ₂under consumption, X ₂o _1Po _2Pthe pulp brightness that QP floats order is up to 83.5%ISO, although the whiteness value improving is compared with X ₂o _pqP floats order and only has 0.2%ISO, but as TCF bleaching, can float to 83.5%ISO has been to be quite not easy; And O _1Po _2PqP floats the whiteness of order compared with O _pqP floats order and has improved 0.5%ISO, but the viscosity of paper pulp is also than O _pqP floats the slightly high of order, and this shows two sections of strengthening oxygen delignification O _1Po _2Pcompared with one section of strengthening oxygen delignification O _pbetter effects if a little.

As can be seen from Table 19, through paper pulp xylanase treatment and that do not pass through xylanase treatment, at process O _1Po _2PqP floats after order bleaching, and the final Kappa number of paper pulp is also different, X ₂o _1Po _2Pit is 1.7 that QP floats the Kappa number of order minimum, compared with O _1Po _2PqP floats the Kappa number Di0.4Ge unit of order, is secondly X ₁o _1Po _2PqP and X ₃o _1Po _2Pthe Kappa number that QP floats order is 1.9, compared with O _1Po _2PqP floats the Kappa number Dou Di0.2Ge unit of order.These experimental results show, through the paper pulp of enzyme processing, at O _1Po _2PqP floats in order bleaching process, is more conducive to removing of lignin, further reduces the Kappa number of paper pulp, improves the whiteness of paper pulp, has kept than the conventional higher pulp viscosity of order bleaching that floats.Compare O _1Po _2PqP floats order and O _pqP floats the bleaching results of order and can find, XO _1Po _2PqP floats order at the H that increases by 0.5% ₂o ₂in the situation of consumption, Kappa number and XO _pqP floats order and approaches or slightly reduce, but the whiteness of paper pulp and viscosity are higher.This further shows two sections of strengthening oxygen delignification O _1Po _2Pcompared with one section of strengthening oxygen delignification O _pbetter effects if a little.

From table 19, also can find out, paper pulp is through O _1Po _2PqP and XO _1Po _2Pafter QP bleaching, through making beating, copying make quantitative is 60g/m ²paper, the whiteness of paper has decline in various degree.Wherein, do not pass through the O of xylanase treatment _1Po _2Pthe whiteness reduction that QP floats order is at most 1.8%ISO, the X processing through enzyme ₂o _1Po _2PqP floats the minimum 1.6%ISO of being of whiteness reduction value of order, through X ₁o _1Po _2PqP and X ₃o _1Po _2Pthe whiteness reduction value that QP floats order is all 1.7%ISO, these experimental datas show through the loss of whiteness of the bleached pulp of xylanase treatment paper pulp after making beating still less, this may be with floating after enzyme is processed after in slurry lignin content still less, lower, the more difficult brightness reversion of Kappa number.

As can be seen from Table 20, XO _1Po _2Ppaper pulp after QP bleaching compares O _1Po _2Ppaper pulp after QP bleaching is more easily pulled an oar.When reaching close 45.5 ° of SR of beating degree, required making beating revolution few 3000 turns, save beating energy consumption in 20% left and right, this may be because the processing of paper pulp process zytase, sub-fraction hemicellulose degraded in paper pulp, bleaching liquid is more easily impregnated in the gap of cellulose and hemicellulose, when impelling more lignin strippings, make fiber further softening, more easily making beating.

From table 20, also can find out XO _1Po _2Ppaper pulp after QP bleaching compares O _1Po _2Pthe physical indexs such as the folding strength of the paper pulp after QP bleaching, bursting strength, fracture length are better.XO _1Po _2PqP and O _1Po _2Pthe bleached pulp that QP floats order is all copied and is made quantitative 60g/m ²the paper of left and right, through X ₂o _1Po _2Pphysical property of pulp after QP bleaching is best, and folding strength is than exceeding 57 times of not processing with enzyme, and fracture length has improved 0.39Km, and burst index exceeds 0.7Nm/g, the high 0.07mNm of tear index ²/ g.Through X ₁o _1Po _2PqP and X ₃o _1Po _2PqP floats the rear slurry of floating of order, has shown equally good physical property: these two kinds of bleached pulps are compared with O _1Po _2PqP bleached pulp is copied the paper folding strength of making and is improved respectively 43 and 34 times, and fracture length improves respectively 0.3 and 0.21Km.But through X ₁o _1Po _2Pthe tear index that QP floats rear slurry declines slightly, and X ₃o _1Po _2PqP floats rear slurry compared with O _1Po _2Pthe tear index that floats rear slurry of QP approaches identical.In general, the helping to float of three kinds of enzymes plays a role clearly, and whiteness and the viscosity of floating rear slurry are all higher, but the effect of different zytases there are differences, may be relevant with the performance of these three kinds of enzymes.

Table 20O _1Po _2PqP/XO _1Po _2Pthe comparison of QP bleached pulp physical properties of paper

In sum, the paper pulp after enzyme is processed carries out O _pqP, O ₁o _2PqP, O _1Po _2Pafter the TCF bleaching of QP, the whiteness maximum of paper pulp reaches 83.5%ISO, and keeps relatively high viscosity.With corresponding not comparing with floating order bleached pulp with enzyme processing, in the situation that consume identical chemicals, can improve the final whiteness 1.5-2.1%ISO of paper pulp, kept higher pulp viscosity, and become the physical indexs such as folding strength, bursting strength, fracture length of paper to be all better than the paper pulp of not processing with enzyme, this shows that these three kinds of enzymes have kept better bleaching selectivity, have improved the physical property of floating rear slurry more significantly.

2.2.3 scanning electron microscope analysis

For the variation of further understanding three kinds of xylanase treatments front and back and having bleached rear fiber exterior appearance, with environmental scanning electronic microscope, magma, enzyme processing slurry and corresponding bleached pulp are observed.

2.3.1TCF bleached pulp scanning electron microscopic observation

Choose KP magma, process X ₁the KP slurry of processing, process X ₂the KP slurry of processing, process X ₃the KP slurry, the O that process _pqP bleached pulp, X ₁o _pqP bleached pulp, X ₂o _pqP bleached pulp, X ₃o _pqP bleached pulp, according to the requirement of 2.1.8, obtain as the stereoscan photograph under Fig. 1～8.

From Fig. 1,2,3,4, under the environmental scanning electronic microscope of 1600 times, Aspen KP is starched, X ₁the KP slurry, the X that process ₂the KP slurry and the X that process ₃the electromicroscopic photograph on the KP pulp fibres surface of processing can be found out significantly, does not pass through zytase X ₁, X ₂, X ₃the fiber surface of the KP slurry of processing is smooth, and close structure exists without tiny or microfibre.Fiber surface through the KP slurry of three kinds of xylanase treatments becomes loose, soft, and cavity and gap appear in fiber surface, have fiber fines like free state, and the surface area of fiber increases.

From Fig. 5,6,7,8 under the environmental scanning electronic microscope of 3000 times, O _pqP bleached pulp, X ₁o _pqP bleached pulp, X ₂o _pqP bleached pulp, X ₃o _pthe electromicroscopic photograph of QP bleached pulp fiber surface can be found out, does not pass through the KP slurry of xylanase treatment through O _pthe pulp fiber surface of QP bleaching is smooth, and close structure exists without tiny or microfibre substantially.The X processing through enzyme ₁o _pqP, X ₂o _pqP and X ₃o _pthe specific area of the fiber of QP bleached pulp increases, and it is loose, coarse and mixed and disorderly that fiber becomes, and it is more soft that fiber becomes, and this can explain the O through xylanase treatment to a certain extent _pqP bleached pulp is more easily pulled an oar, more energy efficient.From Fig. 5,6,7,8, also can find out X ₂the fiber surface of OPQP bleached pulp is compared with X ₂o _pqP and X ₃o _pqP bleached pulp is more loose, and this also can further illustrate zytase X ₂action effect is better, matches with experimental result above.

The affect result of 2.3 brief summary xylanase treatments on fast-growing poplar sulfate pulp TCF bleaching:

With with not with the paper pulp of xylanase treatment after TCF bleaching, the former whiteness and viscosity are higher, become the physical property of paper also to make moderate progress, concrete outcome is as follows:

XO above _pqP and O _pqP, XO ₁o _2PqP and O ₁o _2PqP, XO _1Po _2PqP and XO ₁o _2Pthe TCF bleached pulp of QP is copied and is made 60g/m through making beating ²paper, the former making beating loss of whiteness value is compared with the latter still less; The former folding strength on average exceeds 45 times compared with the latter, and burst index on average exceeds 0.45Nmg ^-1, fracture length on average exceeds 0.35KM, and tear index is suitable.When reaching identical or close beating degree, the former required making beating revolution still less, can be saved beating energy consumption 20% left and right.

Claims

1. a sulfate pulp biochemical process TCF bleaching process for fast-growing poplar, is characterized in that: step is as follows:

(1) boiling: get quick growth poplar wood sheet, put into digester boiling, obtain magma, then wash, screen, obtain paper pulp;

(2) xylanase pretr eatment;

(3) TCF bleaching: the above-mentioned paper pulp of processing through enzyme is bleached, and bleaching process is O _p-Q-P, O ₁-O _2P-Q-P or O _1P-O _2Ptri-kinds of-Q-P float one of order, and the step of bleaching process is: first, the paper pulp of processing through enzyme is carried out to oxygen delignification or strengthening oxygen delignification; After oxygen delignification finishes, paper pulp is washed, then carry out Q section chelation treatment; After Q section chelation treatment finishes, paper pulp is washed, then carry out P section H ₂o ₂bleaching, completes;

The concrete mode of described xylanase pretr eatment is: adjusting pulp density is 10%, then uses zytase X ₁, X ₂or X ₃process, in processing procedure, at interval of 10～15min, rub once, after processing, take out, put into boiling water bath 10min, make zytase inactivation cessation reaction, with running water, clean paper pulp;

Described zytase X ₁, X ₂or X ₃the concrete technology condition of processing is as follows: X ₁the process conditions of processing: enzyme dosage 8IU/L, 50～55 ℃ of temperature, pH8, time 120min; X ₂the process conditions of processing: enzyme dosage 6IU/g, 55～60 ℃ of temperature, pH8～9, time 120min; X ₃the process conditions of processing: enzyme dosage 8IU/g, temperature 50 C, pH8～9, time 120min;

Described zytase X ₁purchased from Novozymes Company, the letter zytase Pulpzyme HC of trade name Novi, article number CKN00117 and CDN00429, liquid state, cellulose-less enzyme is lived; Zytase X ₂, X ₃all purchased from the biological Co., Ltd of the green micro-health in Shenzhen, trade name zytase, article number LV-1 and LV-2, be white powder solid, and all cellulase is not lived;

Described O _pthe concrete mode of-Q-P bleaching process is: Oxygen Delignification of Fast-Growing is: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, MgSO ₄consumption 0.5%, Na ₂siO ₃consumption 0.7%, H ₂o ₂consumption 3%, time 80min; Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min;

Described O ₁-O _2Pthe concrete mode of-Q-P bleaching process is: the process conditions of first paragraph oxygen delignification and second segment strengthening oxygen delignification: first paragraph O ₁: starch dense 10%, NaOH consumption 2.5%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 20min, MgSO ₄consumption 0.5%; Second segment O _2P: supplement 0.5% NaOH, add 3% H ₂o ₂, Na ₂siO ₃consumption 0.7%, oxygen is pressed 0.5MPa, time 60min; Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min;

Described O _1P-O _2Pthe concrete mode of-Q-P bleaching process is: the process conditions of two sections of strengthening oxygen delignifications: first paragraph O _1P: starch dense 10%, NaOH consumption 2.5%, H ₂o ₂consumption 1%, oxygen is pressed 0.6MPa, 100 ℃ of temperature, time 20min, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%; Second segment O _2P: supplement 0.5% NaOH, add 2.5% H ₂o ₂, oxygen is pressed 0.5MPa, time 60min; Q section: starch dense 8%, DTPA consumption 0.5%, temperature 70 C, time 60min, pH value 4-5; P section: H ₂o ₂consumption is 2%, Na ₂siO ₃consumption 0.7%, MgSO ₄consumption 0.5%, original ph 12,90 ℃ of temperature, starch dense 10%, time 90min.

2. the sulfate pulp biochemical process TCF bleaching process of fast-growing poplar according to claim 1, it is characterized in that: the concrete mode of described boiling is: the quick growth poplar wood sheet of getting length 15～25mm, width 10～20mm, thickness 3～5mm, after natural air drying, carry out boiling, make fast-growing poplar sulfate magma, the condition of boiling is: alkali charge 20%, and to over dry raw material, Na ₂o meter; Sulphidity 24%, liquor ratio 1:4,165 ℃ of boiling maximum temperatures, the 15min that exits in the time of 105 ℃, heating-up time 120min, temperature retention time 90min; After boiling, wash, screen, obtain paper pulp, the Kappa number of paper pulp is 16～21.