JPH10331084A - Solution for pulping use and production of pulp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high-whiteness pulp by treating a phytomaterial with a pulping solution containing both oxalic acid (salt) and hydrogen peroxide. SOLUTION: First, a pulping solution is prepared by incorporating an aqueous alkaline solution of at least one kind selected from alkali metal hydroxides and (bi)carbonates containing 0.01-4 wt.%, in terms of oxalic acid, of oxalic acid or a soluble salt thereof and 0.02-7 wt.% hydrogen peroxide with at least one kind of bleaching auxiliary selected from the group consisting of (alkyl) anthraquinone-based compounds, anthracene-based compounds each bearing hydroxyl groups on the 9 and 10 sites such as 9,10-dihydroxyethylanthracene, chelating agents and magnesium compounds such as magnesium oxide. Subsequently, a phytomaterial is treated with the above pulping solution at normal temperatures to 190 deg.C under an oxygen partial pressure of at least 1 kg/cm<2> to obtain the objective pulp. The phytomaterial should be stored or transported in such a condition as to be in contact with the above pulping solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution for pulping, a method for producing pulp using the solution, and a method for storing and transporting plant raw materials.

[0002]

2. Description of the Related Art Trees are becoming woody while a large amount of lignin is being synthesized during growth. The amount of lignin is usually 2
It ranges from 0 to 30%. Many types of wood are colored to varying degrees, but some are less colored, such as birch. In the production of mechanical pulp, raw wood having high whiteness is generally selected, and unbleached mechanical pulp having high whiteness is obtained. However, when producing semi-chemical pulp or chemical pulp, the color of the resulting pulp is deeper than the color of the raw wood used, and the color of the pulp is higher than the color of the raw wood, the pulp manufacturing method, that is, the pulping process used. It depends greatly on the chemical. The plant material contains lignin, hemicellulose, cellulose and other small amounts of pigments, resins and ash, etc., which react with the chemical solution at high temperature during pulping, and the majority of lignin, hemicellulose and cellulose The other components are decomposed and eluted, and furthermore, they complicate each other in the cooking liquor, and the pulping liquor (pulp waste liquor) is markedly colored due to the formation of a new dark pigment. Along with that, the cooked product (pulp) is also dyed and the whiteness is significantly reduced. Particularly in KP, coloring proceeds in a way that cannot be imagined from the raw material, and unbleached pulp exhibits a dark brown color. Heretofore, bleached pulp has been obtained by using a reducing agent or an oxidizing agent as a bleaching agent in unbleached pulp in order to obtain pulp having high whiteness. As a bleaching agent, it is generally more effective to use an oxidizing agent than to use a reducing agent.
In the case of bleached pulp that usually has high whiteness, such as chemical pulp, treating with chlorine compounds such as hypochlorite and chlorine dioxide in addition to elemental chlorine is effective for bleaching. It has been widely used. Among them, unbleached KP is considered to be not bleached sufficiently while the pigment contained therein coexists with residual lignin, and hypochlorite is obtained after chlorination with elemental chlorine and extraction of lignin with alkali. Repeat treatment with acid salt or chlorine dioxide 4
It has been commonly practiced that a multi-stage bleaching process with ~ 7 stages of processing is required. However, as global environmental problems became more serious, the following three movements emerged. In other words, (1) a movement to endure a little black color without using chlorine, and (2) a bleaching process using oxygen to reduce the amount of chlorine to be used. (3) The most advanced movement to obtain bleached pulp with high whiteness without using elemental chlorine or chlorine bleach. Representative examples of (3) include ozone bleaching and hydrogen peroxide bleaching. When bleaching unbleached pulp with ozone, pulp is liable to be painful because cellulose, hemicellulose and lignin are simultaneously oxidatively decomposed. Various attempts have been made toward practical use, for example, by developing and researching auxiliary agents for protecting cellulose from decomposition, and the like, in order to eliminate the disadvantages. Although bleaching of pulp with an alkaline aqueous solution containing hydrogen peroxide is a method for bleaching pulp with less damage to pulp fibers, pulp with high whiteness cannot be obtained only by the conventional hydrogen peroxide bleaching method.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new pulping solution capable of obtaining pulp of high brightness, a method for producing pulp using the same, and a method for storing and transporting plant-based raw materials. The subject.

[0004]

Means for Solving the Problems The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, according to the present invention, there is provided a pulping solution comprising an alkaline aqueous solution containing oxalic acid or a soluble salt thereof and hydrogen peroxide. Further, according to the present invention, there is provided a method for producing pulp, comprising pulping a plant-based material using the pulping solution. Further, according to the present invention, there is provided a method for storing and transporting a plant-based material, wherein the plant-based material is stored or transported while being in contact with the pulping solution.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pulping raw material used in the present invention is as follows.
It is a plant material and includes woody plant materials and non-woody plant materials. Examples of the woody plant raw materials include wood from various kinds of trees such as conifers such as red pine, larch, and fir, broadleaf trees such as birch, mizuna, and buna, and tropical trees such as giant ipiruipir and lauan. Non-woody plant raw materials include bees, bamboo, rice straw, straw, bagasse (squeezed cake of sugarcane), corn stalks and skins, abaca, ramie, in addition to bast obtained from plants such as honey, mulberry, mulberry, etc.
Cancer skin and the like. These plant-based materials are cut into appropriate dimensions to obtain pulp materials.

[0006] The pulping solution of the present invention (hereinafter also simply referred to as a solution) comprises an alkaline aqueous solution containing oxalic acid or a soluble salt thereof and hydrogen peroxide. In this solution, the concentration of the oxalic acid or its soluble salts, oxalic acid (C ₂ H ₂ O ₄₎ in terms of amount, 0.01～4Wt%,
Preferably, it is 0.05 to 2 wt%, and its hydrogen peroxide concentration is 0.02 to 7 wt%, preferably 0.05 to 5 wt%, in terms of H ₂ O ₂ . The pH of the cooking liquor is 7.
5 or more, usually 8 to 12. The pulping solution of the present invention can be obtained by dissolving oxalic acid or a soluble salt thereof and hydrogen peroxide or a hydrogen peroxide generator in water. Examples of soluble salts of oxalic acid include sodium salts, potassium salts, ammonium salts, zinc salts, aluminum salts and the like. As the hydrogen peroxide generator, any agent can be used as long as it generates hydrogen peroxide in water. Such compounds include water-soluble metal peroxides such as sodium peroxide and potassium peroxide; water-soluble adducts of compounds such as sodium carbonate and boric acid with hydrogen peroxide; and percarbonates and perboric acids. Water-soluble inorganic peracids or water-soluble salts thereof; water-soluble organic peracids such as formic acid and peracetic acid, and water-soluble salts thereof.

[0007] The pH of the solution can be adjusted by adding an alkaline substance. As alkaline substances,
Hydroxides, carbonates and bicarbonates of alkali metals such as sodium and potassium. The concentration of the alkaline substance in the solution is 0.1 to 5 in terms of Na ₂ O or K ₂ O.
%, Preferably 0.3 to 3% by weight. When the pulping solution of the present invention is applied to the production of high-yield pulp having a high lignin content such as mechanical pulp and / or semi-chemical pulp, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate are used. It is preferable to carry out lignin-preserving pulping under weak alkaline conditions (pH 8 to 9.5) using an alkali metal salt such as On the other hand, when applied to the production of pulp with a low lignin content such as chemical pulp, use an alkali compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate,
It is preferable to carry out delignification pulping under strong alkaline conditions (pH 10 to 12).

[0008] If necessary, a hydrogen peroxide stabilizer can be added to the solution used in the present invention. Such stabilizers include chelating agents and alkali metal silicates. As a chelating agent, citric acid or a salt thereof, ED
TA (ethylenediaminetetraacetic acid) or a salt thereof, DTP
A (diethylenetriaminepentaacetic acid salt) or a salt thereof, phosphonic acid or a salt thereof, particularly aminotriethylenephosphonic acid or a salt thereof, or 1-hydroxyalkylene-1,1-diphosphonic acid represented by the following general formula (1) or And salts thereof.

Embedded image (Wherein, R represents an alkyl group having 1 to 11 carbon atoms) Examples of the alkali metal silicate include sodium silicate and potassium silicate, and these can be added to the solution as water glass. . The concentration of the chelating agent in the solution is 0.05 to 1% by weight, preferably 0.1 to 0.5%.
wt%. The concentration of the alkali metal silicate in the solution is 0.05 to 2 wt%, preferably 0.1 to 1 wt%.
%.

The pulping solution of the present invention may contain an anthraquinone compound and / or an anthracene compound having a hydroxyl group at the 9,10-position as an auxiliary. The addition of these auxiliaries improves the pulp yield. Atraquinone-based compounds include alkylanthraquinones in addition to anthraquinones. As the alkylanthraquinone, one having one alkyl group having 1 to 12, preferably 2 to 5 carbon atoms is preferable. The anthracene-based compound having a hydroxyl group at the 9,10-position includes unsubstituted anthracene as well as substituted anthracene, for example, alkylanthracene.
In 9,10-dihydroxyalkylanthracene, the carbon number of the alkyl group is usually 12 or less,
Preferably it is 2-8, more preferably 2-6. 9,
Specific examples of the 10-dihydroxyl anthracene compound include 9,10-dihydroxylethyl anthracene, 9,10-dihydroxybutyl anthracene,
10-dihydroxylpropylanthracene, 9,10
-Dihydroxylamylanthracene, 9,10-dihydroxylhexylanthracene, 9,10-dihydroxyloctylundracene, 9,10-dihydroxyldecylanthracene, 9,10-dihydroxyldodecylanthracene and the like. The concentration of the anthraquinone-based compound and / or 9,10-dihydroxyanthracene-based compound in the solution is 0.0003 to 1 wt%, preferably 0.01 to 0.3 wt%.

The pulping solution of the present invention may optionally contain a magnesium compound as a pulping aid. The magnesium compound includes water-soluble and poorly water-soluble magnesium compounds. Examples of such a magnesium compound include magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium chloride, magnesium sulfate, magnesium lactate, and magnesium acetate. The poorly water-soluble magnesium compound having low solubility in water, such as magnesium oxide, magnesium hydroxide, and magnesium carbonate, is the phosphonic acid or a water-soluble salt thereof, particularly, 1-hydroxyalkylidene- represented by the general formula (1). 1,1
-It is preferred to use together with diphosphonic acid or a water-soluble salt thereof, whereby the solubility of the poorly water-soluble magnesium compound in water can be improved. The concentration of magnesium compound in the solution is 0.001-0.2wt
%, Preferably 0.003 to 0.03 wt%. The poorly water-soluble magnesium compound is prepared by converting 1-
When a chelating agent composed of hydroxyalkylidene-1,1-diphosphonic acid or a salt thereof is used in combination, the proportion of the chelating agent is determined by using the poorly water-soluble magnesium compound 1
0.3 to 5 mol, preferably 0.5 to 2.0 mol per mol
It is a mole ratio. In this case, the chelating agent acts as a solubilizer for the poorly water-soluble magnesium compound, and enables the poorly water-soluble magnesium compound to be dissolved in water. When a poorly water-soluble magnesium compound is added to a solution, the poorly water-soluble magnesium compound is added to the chelating agent in an amount of 0.1 to 1.0.
0.05-1.5 g per liter of wt% aqueous solution,
Preferably, it is added at a ratio of 0.1 to 1.0 g to prepare an aqueous solution containing magnesium in a dissolved state, and the aqueous solution is preferably added to the solution. The magnesium compound protects the cellulose in the solution, increases the pulp yield, and enables the production of pulp having improved mechanical strength, especially tear strength and folding strength.

In order to produce pulp using the pulping solution of the present invention, the plant-based raw material and the solution are placed in a hydrogen peroxide-resistant container, for example, a stainless steel container, and are kept at room temperature to 190 ° C.
C., preferably at 50-150.degree. The pulping in this case can be performed under oxygen pressure. Oxygen partial pressure in the pulping vessel is at least 0.1 kg
/ cm ² , preferably 0.2 to 15 kg / cm ² , more preferably 0.5 to 5 kg / cm ² . As an oxygen source,
In addition to pure oxygen, air, oxygen-enriched air and the like are used. The usage ratio (liquid ratio) of the solution to the plant-based material is 1 to 15 L.
/ Kg, preferably about 2 to 12 L / kg. When producing pulp at room temperature, the pulping can be achieved in 5 to 20 hours. When pulping is achieved in a short time, 50 to 150 ° C., preferably 50 to 10 ° C.
It is preferable to employ a heating of 0 ° C. When pulping under oxygen pressure, the pulping temperature is preferably 15
0 ° C, more preferably 90 to 130 ° C. In this pulping under oxygen pressurization, pulp with stable whiteness and high whiteness is relatively produced from plant raw materials having a large lignin content or tannin content, which were difficult to pulp with conventional pulping technology. It can be obtained in high yield.

The pulping solution of the present invention is applied to the production of various pulps. Such pulp includes non-woody plant pulp (straw pulp, bagasse pulp, bast pulp, etc.) and woody plant pulp (softwood pulp, hardwood pulp, etc.). Further, the pulp may be a chemical pulp, a semi-chemical pulp, a mechanical pulp, or the like, and is not particularly limited. Specific examples of the pulp obtained by the pulping solution of the present invention include mechanical pulp such as groundwood pulp, refiner pulp, and thermomechanical pulp, NSSCP (neutral sulfite semi-chemical pulp), and CTMP (chemi-thermomechanical pulp). , SC
Semi-chemical pulp such as P (semi-chemical pulp) and CGP (chemical glazed pulp); AP (soda pulp), S
Chemical pulp such as P (sulfite pulp) and KP (kraft pulp) can be mentioned.

In the present invention, the plant-based material is heated to 150 ° C.
After pulping in one stage at the following temperature, the resulting treated product is mechanically defibrated to obtain pulp in high yield.

The method for producing pulp using the pulping solution of the present invention can be carried out by a liquid phase pulping method and a gas phase pulping method. In the liquid phase pulping method, the ratio of the plant material to the solution (liquid ratio) is generally 4 to 1%.
5 L / kg, preferably 4.5 for wood-based raw materials.
6.0 to 6.0 L / kg, and 6 to 9 L / kg for non-wood raw materials.
kg. On the other hand, in the gas phase pulping method, 1 to 4 L / k
g, preferably 1.5 to 2.5 L / kg. The method for producing pulp of the present invention is preferably carried out by a gas phase pulping method. In the case of the gas phase pulping method, the chemical concentration in the solution can be increased, so the pulping temperature is lowered,
The pulping time can be shortened, and the pulp waste liquid can be recovered at a high concentration and in a small volume. As a result, it is possible to reduce the construction cost of a waste liquid concentrating device and the like in a pulp mill, and it is also possible to save energy for pulping and concentrating and burning pulp waste liquid. When the method of the present invention is carried out by a gas phase pulping method, it is preferable that the pulping solution of the present invention is brought into contact with a plant-based material in advance before the pulping, and the plant-based material is preliminarily pulped. . In this case, the preliminary pulping can be performed by mixing or impregnating the plant-based raw material with the solution of the present invention at a temperature of room temperature to 40 ° C.

The pulp waste liquor obtained during the production of the pulp of the present invention has almost no coloring and is very easy to treat. Further, the pulp obtained in the present invention,
It has high whiteness without dyeing by waste liquid and usually does not require bleaching treatment.

The pulping solution of the present invention can be used as a preservation solution for plant-based materials. That is, by bringing the solution of the present invention into contact with a plant-based material at room temperature to 40 ° C. and storing or transporting the solution in this state, the plant-based material can be prevented from spoiling and can be stored for a long time. The liquid ratio in this case is 1 to
It is 5 L / kg, preferably 1.5-3 L / kg. The plant-based material stored or transported using the pulping solution of the present invention has been pre-pulped and can be advantageously used as a conventionally known pulping material.

When pulping the plant-based raw material stored or transported according to the present invention, the pulping depends on the degree of fiber opening of the raw material, but may be a conventionally known mechanical pulping method or a chemical pulping method. More can be done. The chemical pulping method in this case includes a semi-chemical pulping method in addition to various conventionally known chemical pulping methods. In addition, the semi-chemical pulping method is a method of performing a chemical treatment before mechanically fibrillating a plant-based material, and such pulping methods include a semi-chemical pulping method and a chemi-thermomechanical pulping method. And a chemimechanical pulping method.

In the case of pulping the plant raw material stored or transported according to the present invention, a great advantage can be obtained as compared with the case of pulping the plant raw material stored or transported by a conventional method. . That is, in order to pulverize the plant-based raw material stored or transported by the conventional method, it is not pulped because there is no permeability of the alkaline solution and no fibrillation by delignification or the like occurs. It is necessary to increase the ratio of solution / plant-based raw material (liquid ratio), use a reactor with high pressure resistance, and perform cooking at a high pulping temperature over a long period of time. On the other hand, the plant-based material stored or transported according to the present invention is infiltrated with an alkaline solution during the storage or transport period, and a certain degree of fibrillation has already been achieved by delignification from the plant-based material. Therefore, the pulping is very easy, as a result, the liquid ratio is small, the reactor can be downsized, the pulping temperature can be low, and the pulping time is short. Yes. Therefore, pulp productivity is significantly improved. For example, when the pulping temperature and the pulping time of the plant material stored or transported according to the present invention are shown, the cold soda method does not require heating at all, and the cold soda method does not need to be heated. The pulping temperature is from room temperature to 150 ° C., preferably from 60 to 1
It can be as low as 30 ° C.

[0019]

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The percentages described below are percentages by weight. The whiteness shown below is Hunter whiteness (%).

EXAMPLE 1 1,000 kg of abaca (14.3% water) cut into about 10 cm was subjected to a pulping (pulping) experiment. Na
OH190kg, 35% aqueous solution 100kg of H ₂ O _2, oxalic acid 30kg, 1-hydroxy-alkylidene-1,1
-1,320 by adding water to 3 kg of diphosphonic acid, 2.0 kg of anthraquinone and 0.5 kg of aluminum anthraquinone
One liter of pulping solution (pulping liquor) was prepared. Sprinkle the cooking liquor on the abaca and stir well.
Pulping (digestion) was performed at 117 ° C. for 120 minutes in a 0 m ³ earth pot. The obtained pulp waste liquid was pale yellow and almost transparent. 83.5% whiteness, tear length 9.
Unbleached pulp of 2 km, specific burst strength of 5.8, specific tear strength of 192 and bending strength of 1,920 times was obtained in a yield of 63.3%.

Example 2 1,900 kg of bagasse (52.5% moisture) was subjected to a pulping (pulping) experiment. 173 kg of NaOH, 60 kg of 35% aqueous solution of H ₂ O ₂ , 30 kg of oxalic acid, DTPA
Water was added to 3.8 kg and 3.0 kg of 9,10-dihydroxyl anthracene to prepare a 1,300 liter digester. Sprinkle the cooking liquid on bagasse and stir well.
They were transported and stored for 5 weeks, and digested in a 10 m ³ stainless steel earth pot at 114 ° C. for 120 minutes. The obtained pulp waste liquid was pale yellow and almost transparent. After selective washing, whiteness of 78.5%, tear length of 5.1 km, specific burst strength of 3.
8. Unbleached pulp having a specific tear strength of 45 and a bending strength of 3 was obtained at a yield of 51.1%. The bagasse pulp waste liquid was concentrated and burned together with the abaca pulp waste liquid of Example 1, and the obtained ash was extracted with water. Then, the extracted liquid was causticized with quick lime and supplied to the next digestion.

Example 3 Akamatsu chips (water 43.5%, lignin-containing material 26.
(2%) 1,300 kg were subjected to a cooking experiment. NaOH2
23 kg, 100 kg of a 35% aqueous solution of H ₂ O ₂ , 20 kg of oxalic acid, 3 kg of 1-hydroxyalkylidene-1,1-diphosphonic acid, 2.5 kg of anthraquinone, 0.3 kg of amylanthraquin, and 1,300 liters of water were added. A cooking liquor was prepared. Sprinkle the digestion solution on the wood chips, stir and transport and store for 42 weeks, place in a 10 m ³ stainless steel earth pot, pressurize oxygen with 1.7 kg / cm ^{2 and} inject 14
The digestion was performed at 5 ° C. for 120 minutes. The obtained pulp waste liquid was pale yellow and almost transparent. Selectively wash and white.
Unbleached pulp having 6%, specific burst strength of 4.8, specific tear strength of 115 and bending strength of 450 was obtained at a yield of 50.8%.

Example 4 A hardwood chip (water content: 18.5) of 1,000 kg was pulped by a cold CGP method. NaOH 105k
g, 100 kg of 35% aqueous solution of H ₂ O ₂ , oxalic acid 20 k
g, 3 kg of DTPA, 3 kg of water glass, and 2.5 kg of anthraquinone, and water was added to prepare a 1,300 liter digestion liquid. Sprinkle cooking liquor on wood chips and stir after 10
The mixture was stored for a day and beaten at a high concentration with a disc refiner to form a pulp. The obtained pulp waste liquid was pale yellow and almost transparent. After careful washing, unexposed cold CGP having a whiteness of 73.6%, a breaking length of 2.9 km, a specific burst strength of 28 and a bending strength of 2 times was obtained in a yield of 80.8%.

[0024]

By using the pulping solution of the present invention, it is possible to obtain pulp having a high whiteness that does not require a subsequent bleaching step. Further, in the present invention, gas-phase cooking for producing chemical pulp is possible. Further, in the present invention, since the bleaching step is not particularly required, equipment, labor,
Significant savings in wastewater treatment are possible.

Claims (8)

[Claims] 1. A pulping solution comprising an alkaline aqueous solution containing oxalic acid or a soluble salt thereof and hydrogen peroxide. 2. The pulping solution according to claim 1, wherein said alkaline aqueous solution contains at least one selected from hydroxides, carbonates and bicarbonates of alkali metals. 3. The pulp according to claim 1, wherein the concentration of oxalic acid or a soluble salt thereof is 0.01 to 4% by weight in terms of oxalic acid, and the concentration of hydrogen peroxide is 0.02 to 7% by weight. Solution. 4. The method according to claim 1, further comprising at least one bleaching aid selected from an anthraquinone compound, an anthracene compound having a hydroxyl group at the 9,10-position, a chelating agent and a magnesium compound. For pulping. 5. A method for producing pulp, comprising subjecting a plant-based raw material to pulping treatment at a temperature from room temperature to 190 ° C. using the pulping solution according to any one of claims 1 to 4. 6. The method according to claim 5, wherein the pulping treatment is performed under an oxygen partial pressure of at least 0.1 kg / cm ² . 7. A method for storing and transporting plant-based raw materials, comprising storing or transporting plant-based raw materials while contacting with the pulping solution according to any one of claims 1 to 4. 8. A method for producing pulp, comprising using a plant-based material stored or transported according to the method of claim 7, and mechanically or chemically defibrating it.