JPH11100783A - Pulp formation from lignocellulose material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly obtain pulp in high yield by stabilizing the reducible terminal groups of hemicellulose to efficiently solubilize lignin in the production of pulp through the polysulfide process. SOLUTION: A tightly closed vessel in which chips are contained is evacuated and a PS digestion liquid containing a proper amount of a digestion aid is charged into the evacuated vessel thereby penetrating the PS digestion liquid into chips without resistance of air. Then, the vessel is held under the conditions of 80-140 deg.C for at least 10 minutes to stabilize hemicellulose in the first step. In the second step, a pressure of >=1,200 kpa is applied to improve the yield of hemicellulose and cellulose, lower the molecular weight of lignin and elute low-molecular-weight lignin by the action of 9, 10-anthraquinone that is a pulp- digesting aide and a catalyst for improving the pulp yield, even after the pulp digestion temp. reaches 140 deg.C and the PS digestion liquid becomes undetectable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for pulping lignocellulosic materials, and more particularly to a method for producing high-yield pulp by a polysulfide method.

[0002]

2. Description of the Related Art In pulping lignocellulose materials, chemical methods aimed at obtaining high-yield pulp include polysulfide (hereinafter referred to as PS) digestion, kraft digestion with sodium borohydride, and the like. Anthraquinone (AQ) -added kraft digestion methods and the like exist. These use oxidation, reduction, and catalytic reactions, respectively. PS
Polysulfide (Na ₂ S _x ) is one of the characteristics of cooking.
It is known that it decomposes substantially at 0 to 140 ° C. and has poor penetration into wood chips. It is known that wood chips are preferably small chips, and that air-dried and bone-dried chips have little improvement in pulp yield. Therefore, in PS digestion, a yield improvement range may not be obtained depending on the conditions, and a method of constantly improving the pulp yield is desired.

[0003]

The first condition for reliably performing the pulping treatment by the PS digestion method is that the temperature is 1
It is necessary that Na ₂ S _x has sufficiently penetrated into the wood chip before the temperature reaches 40 ° C. and Na ₂ S _x is decomposed and the ability to stabilize the reducing terminal groups of cellulose and hemicellulose by the oxidation reaction is lost. And secondly, the Na ₂ S _x of the PS cooking liquor.
In the oxidation reaction temperature range of 80 to 140 ° C., 1
It is necessary to satisfy a reaction time of 0 to 60 minutes. However, high yields could not be constantly obtained due to poor permeation of the PS cooking liquor, poor oxidation of hemicellulose reducing terminal groups to carboxyl groups at 80 to 140 ° C, and poor stability. An object of the present invention is to constantly obtain a high yield in the production of pulp by the polysulfide method.

[0004]

In order to achieve the above object, a first aspect of the present invention is to provide a polysulfide cooking liquor, 9 / 10-anthraquinone (digestion) in a lignocellulosic material while changing the pressure in a closed vessel. Auxiliaries) and polysulfide cooking liquor to the lignocellulosic material,
By forcibly penetrating the cooking aid composition, the air-containing chips floating in the polysulfide cooking liquor are degassed by a decompression operation, and the polysulfide cooking liquor is injected into the chips, so that hemicellulose and cellulose are polysulfide cooked. It is characterized by obtaining high-yield pulp by sedimentation in a liquid. In the second step, the air in the chips was degassed as the first stage by reducing the pressure of the closed vessel containing the chips and introducing a PS cooking liquid containing an appropriate amount of a cooking aid. In this state, the PS digestion liquid permeates the chips without air resistance.
In the second stage, after applying a pressure of 1200 (kpa) or more and maintaining the temperature at 80 to 140 ° C. for at least 10 minutes to decompose the polysulfide at 140 ° C. or more, hemicellulose is catalyzed by anthraquinone. It is characterized in that a high yield pulp is obtained by improving the yield of cellulose, reducing the molecular weight of lignin and accompanying elution.

According to a third aspect of the present invention, a closed vessel containing the chips is filled with carbon dioxide gas to replace the air in the chips and in the atmosphere of the chips, and a PS cooking liquid containing an appropriate amount of a cooking aid is introduced. This allows the PS digestion liquid to penetrate into the chips while absorbing carbon dioxide gas at the same time as the pressure in the closed vessel is reduced. Thereafter, the digestion temperature is raised to 80 ° C. or higher, and the oxidation reaction between Na ₂ S _x and the wood chips proceeds. More specifically, the atmosphere of the wood chips and the air in the wood chips were exchanged with carbon dioxide gas by blowing carbon dioxide gas into a closed type chip bottle filled with wood chips, and then the first stage permeation tank (top; 60 ° C.), while mixing the wood chips, the polysulfide cooking liquor and the quinone-based cooking aid composition while maintaining the reduced pressure, and allowing the Na ₂ S _x of the polysulfide cooking liquor to penetrate into the wood chips,
From the time when the wood chips having absorbed the a ₂ S _x and the cooking aid composition reached 80 ° C. while descending the digester, the reducing terminal groups of hemicellulose and cellulose were converted into carboxyl groups and the degree of polymer polymerization was increased. Along with stabilizing, the lignin is reduced in molecular weight by a synergistic effect with the digestion aid composition, and then reaches 140 ° C. or higher, and Na ₂ S _x is almost disappeared, and then the digestion aid composition containing A high-yield pulp is obtained by performing a KP digestion treatment. By the method described in the above claims, the pulp yield is improved by constantly forcing the PS cooking liquor into the chips.

[0006]

[Action] During the digestion, PS and anthraquinone are efficiently penetrated into the chips through a pressure change method such as a decompression method or the use of CO ₂ gas. By converting the reducing end groups of cellulose and hemicells into carboxyl groups, while stabilizing without reducing the degree of polymerization of hemicells,
Efficient solubilization of lignin to improve pulp yield.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In PS digestion, the variation in yield is larger than in KP digestion, because of poor penetration of PS digestion liquor, oxidation of hemicellulose reducing terminal groups to carboxyl groups at 80 to 140 ° C, and stability. Insufficiency is considered the biggest cause. Therefore, the first stage, that is, a treatment stage for the purpose of infiltrating the PS cooking liquor and oxidizing and stabilizing the hemicellulose reducing terminal group, is carried out in a closed vessel under reduced pressure (or blowing carbon dioxide gas), and then 80-1
It is kept at 40 ° C. for 10 to 60 minutes to perform the PS digestion liquid permeation treatment. This first stage is characterized by Na _{2 Sx} and is 80 ° C. to 140 ° C.
By converting the reducing end groups of cellulose and hemicells into carboxyl groups by effectively utilizing them at limited temperature and time, it is possible to stabilize without reducing the degree of polymerization of hemicells, etc. Solubilize. Then the second
As a stage, a KP digestion stage with the addition of 9.10-anthraquinone is performed to improve the yield.

In the present invention, PS digestion liquid permeation treatment is performed while changing the pressure in a closed vessel. However, when there is no pressure change, the mixing of the pulp and the chemical does not proceed so much, and Becomes insufficient. On the other hand, by increasing the reduced pressure, the air in the chip and the chemical solution are replaced. Therefore, by reducing the pressure as much as possible, the PS digestion liquid can be stably and reproducibly penetrated with the chemical solution into the chip, and as a result, the yield can be improved. The pressure change is set to a reduced pressure of -400 to -700 mmHg. The temperature of the polysulfide cooking liquor (cooking liquor) when depressurizing is
It fluctuates between about 40-80 ° C. during the initial stages of the actual cooking process. Note that the pressure change during the first stage permeation is not limited to reduced pressure, and CO ₂ gas may be blown. The concentration of the CO ₂ gas is preferably 100%, but there is no problem even if the concentration is close to 100%. Since the carbon dioxide gas is absorbed by the alkali, when the air in the chips is replaced, the cooking liquor containing PS quickly penetrates the chips as the pressure is reduced, and the ideal chemical reactants are mixed. , Serves as a pressure reducing agent.

(Chemical composition) The mixing ratio of anthraquinone to the raw material chips is 0.02 to 0.1% by weight, preferably 0.02 to 0.05% by weight. Note that 0.0
If it is less than 2% by weight, it is difficult to obtain the desired effect of the present invention, while if it is more than 0.1% by weight, it tends to cause operational problems (the supply pump or the like may not operate satisfactorily). ). The addition amount of polysulfide is in the range of 1 to 2% by weight (in terms of sulfur) with respect to chips (based on solid content). By the way, if it is less than 1% by weight, a satisfactory effect cannot be obtained. Substantially 2% by weight or more is impossible. In normal KP cooking (basic cooking), the more the cooking is advanced, the more pulp fibers and lignin are destroyed, and the lower the pulp yield. This pulping situation is usually
The kappa number k-No. Is 15 to 21, but if the kappa number is reduced, the yield difference increases, and it is difficult to set uniform conditions depending on the concentration of the white liquor, the temperature of the chemical solution, and the like. So, the Kappa price is held at 15th place.

<Example 1> 800 g of domestic hardwood chips
(Moisture; 50%) was packed in a 5 liter standing autoclave, and carbon dioxide gas was blown from the lower part of the autoclave. Next, 9,
10-Anthraquinone (Nippon Shokubai, trade name DAQ-N)
Is charged from the lower part of the autoclave.
The carbon dioxide gas in the upper part of the autoclave is absorbed and the pressure is reduced. After the temperature was raised to 80 ° C., the temperature was raised to 140 ° C. in 30 minutes, followed by digestion at 170 ° C. for 90 minutes. The cooking aid is added to the cooking liquor at 0.05% by weight of the absolute dryness of the raw material chips. For comparison, Table 1 also shows the results of digestion between the prior art and the present invention.

[0011]

[Table 1]

The pressure of the pot is 2-3 kg / cm ² at the top,
Since the water pressure is applied, the lower part of the pot is determined by the length of the pot and the level of the cooking temperature. In addition, PS-AQ (this invention), KP, KP-
As an example of comparison of pulp yield (%) of AQ and PS digestion, 49.5%, 45.0%, 46.5%, 46.5%
Met.

<Example 2> At the time of cooking, P
S and 9.10-anthraquinone (Nippon Shokubai, trade name DA
QN) By infiltrating the liquid efficiently, the reaction between the chemical and the chip in the KP digestion does not reduce the degree of polymerization of cellulose or hemicellulose, and on the other hand, the lignin is efficiently made soluble to obtain To improve the yield of pulp. First stage: PS can be evenly distributed in the chip at a temperature lower than 80 ° C without decomposition loss of PS (decompression: -400 to -700
mmHg). Chemical reaction is carried out at the best reaction temperature of 80 ° C to 140 ° C for the optimum time to stabilize hemicellulose and cellulose by oxidation. Stage 2 KP digestion containing 9,10-anthraquinone (= 14
(0 ° C. or more, pressurized 1200 kpa or more) The above anthraquinone is used in an amount of 0.1 to the absolute dry amount of the raw material chips.
Add 05% by weight to the cooking liquor. The cooking results are almost the same as those shown in Table 1.

[0014]

As described above, according to the present invention, in the pulp digestion, the polysulfide and the anthraquinone liquid are efficiently penetrated into the chips through a certain pressure change, whereby the chemicals and the chips in the KP digestion are mixed. During the reaction, the reducing end group of cellulose or hemicellulose is converted into a carboxyl group to stabilize the polymerization degree of hemicellulose or the like without lowering it, while the lignin is efficiently solubilized to stably collect pulp. The rate can be improved.

Claims (3)

[Claims] 1. A polysulfide cooking liquor and a 9.10-anthraquinone as a cooking aid are mixed with a lignocellulose material while changing the pressure in a closed vessel, and the polysulfide cooking liquor and the cooking aid are forced into the lignocellulosic material. The air-containing chips floating in the polysulfide cooking liquor are degassed by depressurizing operation, and the polysulfide cooking liquor is injected into the chips, thereby allowing hemicellulose and cellulose to settle in the polysulfide cooking liquor. A pulping method for a lignocellulosic material, which comprises obtaining a pulp with a high yield. 2. The pressure change in the closed vessel is as follows. First, a lignocellulose material, a polysulfide cooking liquor, and a cooking aid are mixed in a closed vessel as a first stage, and the mixture is placed under reduced pressure. Pressure of 1200 (kpa) or more, and at least 1
2. The pulping method of a lignocellulosic material according to claim 1, wherein KP-anthraquinone is digested after holding for 0 minutes. 3. A polysulfide digestion method, wherein carbon dioxide gas is blown into an airtight chip bin filled with wood chips to exchange the atmosphere of the wood chips and air and carbon dioxide in the wood chips, and then carry out the first stage permeation. kettle; promote mixing of the while keeping the (top vapor temperature 60 ° C.) to feed vacuum wood chips and polysulfide cooking liquor and 9-10- anthraquinone (cooking aid), wood Na ₂ S _x of the polysulfide cooking liquor From the time when the wood chips, which had penetrated into the chips and had sufficiently absorbed Na ₂ S _x and the cooking aid, reached 80 ° C. while descending the digester, the reducing terminal groups of hemicellulose and cellulose were converted into carboxyl groups. To stabilize the degree of polymerization, and to reduce the molecular weight of lignin by a synergistic effect with the cooking aid. Reached with Na ₂ S _x is to obtain a high yield pulp performing KP digestion process anthraquinone added After almost disappeared, pulping process for lignocellulosic material, characterized in that.