JP2002371487A - Method for producing chemical pulp and chemical - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which an excellent pulp can readily be produced from an unutilized resource such as a long fiber plant such as a flax or a mixed chip, etc., of a tropical timber which has hither been scarcely utilized because of difficult cargo collection and storage in a wet state and slight cookability even if the unutilized resource is abundant. SOLUTION: The method is to readily produce the pulp widely from the unutilized and slightly cooked fiber raw material resource. Thereby, the fiber raw material resource which has hitherto been scarcely utilizable because of the slight cookability even if the fiber raw material resource is abundant can be pulped by carrying out a treatment under atmospheric pressure and normal temperature with a cooking liquor of a neutral hydrogen peroxide-oxalate(NPO) method as a pretreatment prior to the cooking of a hydrogen peroxide- alkali(PA) method or further, as desired, conducting a heating treatment according to the PA process. In addition, the cargo collection and storage are facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing chemical pulp and a chemical solution.

[0002]

2. Description of the Related Art Many methods have been invented for producing chemical pulp from fiber plant raw materials, of which the KP method (craft method), the SP method (sulfurous acid method), the AP method (alkaline method) and the like are still used. Have been done.

In particular, the KP method can easily pulverize various kinds of woods such as softwoods and hardwoods, and the obtained pulp has excellent strength. Further, since a large amount of raw materials can be handled, pulp waste liquid can be concentrated and burned to recover energy and chemicals. The color of unbleached pulp is dark brown, and bleaching is difficult, but is possible by a multi-stage bleaching method. Since sulfur compounds are used in the cooking liquor at the time of production, odors may be generated. However, related technologies such as pollution control technology are in place. Today, wood pulp production accounts for about 90% of total pulp production.
The method is the mainstream of pulping and has an overwhelming share.

However, non-wood is generally bulky and perishable as a raw material for pulp, it is difficult to collect a large amount in one place, product pulp varies greatly in quality depending on the plant material, and except for bagasse pulp and straw pulp. Because a large demand for one type of pulp could not be expected, it is not suitable for production by the KP method, and the AP method, the NSP method (neutral sulfurous acid method), and the like have been used. According to the AP method, many types of non-wood plant raw materials can be pulped. However, it has been a drawback that pulp quality is inferior and pulp yield is reduced due to fiber damage.

[0005] According to the NSP method, the pulp obtained is less in quality and yield because of less fiber pain than the P method.
Superior to law pulp. However, even wood such as conifers and hardwoods and non-woods in which plant materials and lignin having a high lignin content are tightly bound to cellulose are used.
In the pulping of pulp, kenaf and flux, chemical treatment alone is not sufficient, and it has been extremely difficult to pulp without relying on the power of a machine such as a refiner or a beater.
The pulp obtained by such a mechanical treatment has its fibers cut and partially fibrillated, leaving fibers hurting and leaving lignin. If a powerful bleaching treatment is carried out for the delignification effect, the resulting bleached pulp is inferior in strength and drainage, and its use is limited. Further, in the NSP method, since the sulfur derived from the cooking chemical liquid enters the pulp waste liquid, it is very difficult to treat the energy, and the recovery of energy and chemicals.

[0006] If the KP method, the AP method, the NSP method, etc. are introduced for each raw material in the pulping of wood and non-wood fiber raw materials at one factory, the treatment of pulp waste liquid and the recovery of digester liquid are separately performed. The burden of having to process in the system of is introduced. With such troublesome,
In addition, such a system was not usually used because multiple investments were required.

The inventor has studied the use of hydrogen peroxide for digestion, but first, many wood and non-wood fiber plant materials are pulped more easily by the PA method (hydrogen peroxide-alkali method) than by the KP method. It was announced that the pulp obtained was white, easy to bleach, had a high strength and was closer to the KP method than the AP method. In particular, bast fiber raw materials such as kozo, mitsumata, and ganpi, mainly composed of pectocellulose, are NP-free at normal pressure without using any caustic alkali.
The O method (neutral hydrogen peroxide-oxalate method) is extremely easy to digest, and the unbleached pulp can be obtained in high yield with high whiteness and excellent yield without any need for bleaching at all. Announced.

However, jute and flax having a high lignin content even in bast fibers are difficult to digest by the NPO method, and most of them become white, but the epidermis remains without being whitened. The whole was not pulped even if continued. In addition, long fiber raw materials such as abaca and banana can be used in the case of the PA method.
C. For 2 hours of pulping by cooking for 2 hours, a long fiber raw material having a large lignin content such as flax
There is a need for a new pulp method and system because it does not easily pulverize even in PA digestion at 10 ° C. for more than 10 hours.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a method for easily producing unbleached pulp and chemicals having high whiteness from general wood and raw materials of long fiber plant which has been conventionally difficult to digest, and concentrating waste pulp liquor. It is an object of the present invention to improve the way of the industry as a total system, for example, by drastically improving environmental problems caused by drainage and exhaust of a pulp mill by recovering energy and chemicals by burning.

[0010]

The inventor of the present invention has conducted intensive studies for many years to solve the above problems, and as a result, has completed the present invention. That is, according to the present invention, prior to the second step of digesting the fibrous plant material with an alkaline solution of hydrogen peroxide, oxalic acid or a heat treatment is optionally performed under normal pressure using an aqueous solution of hydrogen peroxide of an alkali salt of carbonic acid. By providing the first step, the fiber plant material can be digested very easily.

As a result, pulp can be produced very easily from raw materials such as flax and tropical wood mixed chips which have been conventionally difficult to digest. Further, the pulp waste liquid by-produced in the first step and the second step can be concentrated and burned in the same facility to recover alkali as ash mainly composed of carbonate.
The alkali carbonate is used as the oxalate used in the first step by adding oxalic acid, and the caustic is converted into the caustic alkali used in the second step, whereby the chemical solution can be recycled.
A method for producing pulp and a chemical solution that is closest to zero waste is provided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Pulp raw materials used in the present invention are wood and non-wood fiber raw materials. In particular, non-wood long fiber plant materials include leaf fiber materials, bast fiber materials, and seed hair fiber materials. Leaf fiber raw materials include sisal, abaca,
Examples include leaf fibers such as banana, new land flux, and pineapple. , Flax raw materials, flax,
Examples include jute, mulberry bark, mulberry (kozo), mitsumata (mitsumata), and goose (ganpi). Seeds include cotton, kapok and the like. Pulping is not easy in the conventional method, and it is also effective for pulping of mixed chips of tropical materials and raw materials of long fiber plants with a lot of lignin, which are hardly used.

[0013] Among the chemical solutions for pulping of the present invention (hereinafter also simply referred to as chemical solutions), the chemical solution used in the first step is prepared by adding a cooking aid to an aqueous solution of hydrogen peroxide, alkali carbonate and oxalate as required. The chemical used in the second step is obtained by adding a cooking aid to a caustic alkali aqueous solution of hydrogen peroxide as required, and the pulp waste liquid by-produced in the previous treatment or cooking is concentrated and burned. It can be recovered from the obtained ash mainly composed of alkali carbonate. Next, a method for producing a chemical solution used in the first step and the second step will be described in detail.

The chemical solution of the first step is based on the absolute dry matter of the fibrous plant material, and the alkali metal carbonate is 3 to _{2 in} terms of Na ₂ O.
0%, preferably 5-15%, oxalate 2-15
%, Preferably 4% to 8%, the 1-10% hydrogen peroxide or hydrogen peroxide generating agent as H ₂ O _2, preferably 2 to 5%
It is. There are various types of cooking aids, and the following ones are particularly preferable for use.

As a stabilizer for hydrogen peroxide, there is a chelating agent other than a silicate, but effective chelating agents are citric acid or a salt thereof, EDTA (ethylenediaminetetraacetic acid) or a salt thereof. And DTPA (diethylenetriaminepentaacetic acid) or a salt thereof, phosphonic acid or a salt thereof, particularly aminotriethylenephosphonic acid or a salt thereof, and in particular, a compound represented by the general formula (1) in claim 5 The use of -hydroxyalkylidene-1,1-diphosphonic acid or a salt thereof is preferred because it gives a high brightness unbleached pulp. The amount of addition is 0.05-1
%, Preferably 0.1 to 0.5%.

The magnesium compound protects cellulose and increases the pulp yield in the first and second steps of the treatment with a chemical for producing pulp containing hydrogen peroxide, and also has a high mechanical strength, especially a high tear strength. This contributes to the improvement of the bending strength. The addition amount is 0.00 as MgO.
It is 5 to 1.0%, preferably 0.1 to 0.5%.

The anthraquinone compound contains an alkyl anthraquinone in addition to anthraquinone. As the alkylanthraquinone, one having one alkyl group having 1 to 12 carbon atoms, and among them, 2 to 5 is preferable.

Anthracene compounds having a hydroxyl group at the 9,10 position include unsubstituted anthracene having a 9,10-dihydroxyl group as well as substituted anthracene,
For example, alkyl anthracene is included. 9,10
In dihydroxylalkylanthracene, the alkyl group has usually 12 or less carbon atoms, preferably 2 to 8, more preferably 2 to 6. Specific examples of the 9,10-dihydroxyl anthracene compound include:
9,10-dihydroxylethylanthracene, 9.1
0-dihydroxylpropylanthracene, 9,10-
Dihydroxylbutylanthracene, 9,10-dihydroxylamylanthracene, 9,10-dihydroxylhexylanthracene, 9,10-dihydroxyl octylundracene, 9,10-dihydroxyldecylanthracene, 9,10-dihydroxyldecylanthracene and the like Is mentioned. The amount of the anthraquinone added is 0.02 to 0.5%, preferably 0.05 to 0.3%,
The content of the alkylanthraquinone is 0.01 to 0.3%, preferably 0.02 to 0.1%.

The addition of an organic solvent mixed with water at an arbitrary ratio dissolves the resin in the cellulose raw material and makes it possible to separate and remove the resin, thereby preventing resin damage in cooking and adhering the resin to product pulp. prevent. In particular, the use of normal methylpyrrolidone (NMP) is effective. The addition amount of these solvents is 0.03 to 1.0%, preferably 0.05 to 0.3%.
It is.

The chemical solution in the second step is prepared by converting an alkali metal hydroxide into Na ₂ O with respect to the absolutely dried product of the fibrous plant material.
If the required amount of hydroxide can be used, the causticization rate is as low as, for example, about 50%, and the alkali metal carbonate is converted to Na ₂ O as Na ₂ O based on the raw material. The coexistence of 35% not only does not hinder the digestion but also prevents the cellulose from being damaged by the alkali during the digestion and helps to improve the pulp yield by 1 to 3%. Therefore, the alkali to be replenished when recovering the chemical solution from the pulp waste liquid may be the carbonate, and the elimination of the need to supply caustic alkali from the outside can greatly simplify the receiving devices such as tanks, valves, pipes, and measuring instruments. It is advantageous.

The hydrogen peroxide or hydrogen peroxide generator is H 2 O
2 is used at 1 to 10%, preferably 2 to 5%.

In many cases, it is not necessary to add the cooking aid if it is sufficiently used in the first step, but the following is a standard example of adding the cooking aid. The magnesium salt was added as MgO at 0.1.
03-0.5%, preferably 0.05-0.2%, and anthraquinones 0.01-0.2%, preferably 0.0-0.
3 to 0.1%, alkyl anthraquinones are 0 to 0.1%
%, Preferably 0 to 0.03%, and NMP is 0.030 to
0.1%, preferably 0.02 to 0.05%.

The liquid ratio is 1.0 to 3.0 L / kg, preferably 1.5 to 2.5 L / kg in the gas phase throughout the first and second steps.
L / kg, 4 to 12 L / kg in the liquid phase, preferably 4.4
８8 L / kg. In the cooking method according to the present invention, various plant raw materials are put into a vessel having at least an inner surface covered with stainless steel, titanium, or the like so as to withstand contact with hydrogen peroxide, and reacted with a cooking chemical liquid.

In the first step, an NPO chemical solution (neutral hydrogen peroxide oxalate solution) is added to the cellulose raw material and the mixture is added at room temperature for 2 to 12 hours.
The treatment is carried out for 0 day at 50-100 ° C for 10-300 minutes, preferably at 80-100 ° C under normal pressure for 30-120 minutes.

[0025] Adding or mixing a part or all of the cooking chemical liquid to the plant raw material prior to cooking not only prevents spoilage, enables long-term storage for several years, but also softens the raw material. Because it is less bulky, it can be mass-transported and used on a global scale, enabling the construction and economic operation of pulp mills that are larger than wood pulp mills. In addition, since mild digestion proceeds during transportation and storage of the raw materials, it is possible to immediately raise the temperature in the second step and proceed with the reaction. In the second step, a PA cooking chemical liquid (alkali solution of hydrogen peroxide) is put into the fiber material in an earth pot or a continuous reactor, and cooked at 50 to 190 ° C for 20 to 360 minutes, preferably at 110 to 140 ° C for 60 to 240 minutes. I do.

If the infiltration and pre-cooking of the liquor have proceeded sufficiently during the mixing of the cooking liquor with the plant material and subsequent storage,
It is recommended to employ gas-phase cooking. According to the gas phase cooking, the concentration of the cooking liquid can be increased, so the cooking temperature is lowered,
Since the cooking time can be shortened and the waste pulp liquor can be recovered in high concentration and small volume, the construction cost of pulp mill waste liquor concentration equipment etc. can be reduced, greatly contributing to energy saving in pulp digestion and pulp waste liquor concentration combustion. it can.

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

Embodiment 1 FIG. 1,000 kg of flax dust (water content: 15.2%) having a length of 30 to 40 mm was subjected to a cooking experiment.

Na ₂ CO ₃ 440 is used as a chemical in the first step.
a part of Na ₂ CO ₃ and Na- salts of oxalic acid was added oxalic acid 150kg in kg, and more H ₂ O ₂ 85k
g, 4.0 kg of anthraquinone, 0.4 kg of amylanthraquinone, 8 kg of 1-hydroxyalkylidene-1,1-diphosphonic acid, 7.0 kg of MgCO ₃ , NMP
Water was added to 2.0 kg to prepare a 5,000 L drug solution.
A chemical solution was added to flax dust, and the reaction was carried out with stirring at 100 ° C. for 90 minutes. After the reaction, solid-liquid separation was performed with a screw-press, half of the liquid was recovered, and chemicals were replenished and used for the next reaction. On the other hand, the treated fiber raw material was sent to the second step.

As the chemical solution in the second step, NaOH 110
kg, in addition H ₂ O ₂ 200kg, 1- hydroxy-alkylidene-1,1-diphosphonic acid 60 kg, the water 1,
A 000 L cooking liquor was prepared. To the flax processed in the first step, add the cooking chemical for the second step, mix and stir,
130 ° C in a ³ volume stainless lined earth pot
For 120 minutes. The flax digest is carefully selected and washed to yield unbleached pulp having a whiteness of 68.5%, a breaking length of 13.2 km, a specific burst strength of 6.9, a specific tear strength of 312 and a bending strength of 4,920 times. Obtained at 58.3%. The waste pulp was concentrated and burned to obtain ash having a Na ₂ CO ₃ content of 97.3%. The ash is extracted with water, a part of which is added with oxalic acid to make a chemical solution of the first step, and the remaining is causticized by adding quick lime to the aqueous solution to obtain a mixed solution of NaOH and Na ₂ CO ₃ according to a conventional method. And the auxiliaries were added to regenerate the cooking liquor used in the second step.

Embodiment 2 FIG. 100 kg of jute waste (water 15.8%) having a length of 25 to 40 mm was subjected to a cooking experiment.

K ₂ CO ₃ 25k as a chemical solution in the first step
g, oxalic acid 10 kg, H ₂ O ₂ 25 kg, tetrahydroxyl anthraquinone 0.20 kg, tert-butyl anthraquinone 0.02 kg, 1-hydroxyalkylidene-1,1-diphosphonic acid 0.4 kg, MgCO ₃
Water was added to 0.4 kg to prepare a 130 L drug solution. After adding a chemical solution to the jute waste and mixing and stirring, it is transported for 30 days,
Stored for 15 days. Meanwhile, the reaction of the first step was continued at room temperature.

The chemical in the second step is KOH 30k
g, and _{K 2 CO 3 5kg, H 2} O 2 20kg, 1- hydroxy-alkylidene-1,1-diphosphonic acid 3 kg, cooking liquor 50L water is added to the prepared. Ju treated in the first step - mixing and stirring added cooking liquid chemical for the second step in the preparative debris, 120 ° C. The mixture was placed in a stainless steel earth kettle 1 m ³ volume
For 60 minutes. The cooked product of jute waste is carefully washed to obtain unbleached pulp having a whiteness of 56.2%, a breaking length of 6.2 km, a specific burst strength of 4.8, a specific tear strength of 161, and a folding strength of 1,620 times. Obtained in a yield of 56.3%.

The pulp waste liquid was concentrated and burned to obtain ash having a K ₂ CO ₃ content of 98.1%. The ash is extracted with water, part of which is added with oxalic acid to make the chemical solution of the first step, and the rest is causticized by adding quick lime to the aqueous solution to obtain a mixed solution of KOH and K ₂ CO ₃ by a conventional method. And the auxiliaries were added to regenerate the cooking liquor used in the second step.

Embodiment 3 FIG. Mixed chips of tropical material (moisture 1
6.0%) was subjected to a digestion experiment.

Na as a chemical solution in the first step_Two CO_Three 20
0 kg, oxalic acid 50 kg, H_Two O _Two 150kg, a
2.0 kg of untraquinone, 3 kg of -diphosphonic acid,
Water was added to 3 kg of MgCO3 and 1 kg of NMP,
A 100 L drug solution was prepared. Add chemicals to mixing tip and mix
After stirring, they were transported for 25 days and stored for 25 days. in the meantime
At room temperature, the reaction and the preservation treatment of the first step were continued.

As the chemical in the second step, NaOH 230
water, 30 kg of H ₂ O _2, 30 kg of 1-hydroxyalkylidene-1,1-diphosphonic acid,
A 700 L cooking liquor was prepared. To the mixed chips treated in the first step, add the cooking liquid for the second step and mix and stir.
Put into a 0m ³ stainless steel lined earth pot, 13
Cooking was carried out at 0 ° C. for 120 minutes. The digest of the mixed chips of tropical timber is carefully washed and washed to a brightness of 52.5% and a breaking length of 5.2.
km, specific burst strength 4.2, specific tear strength 95, bending strength 1
Twenty unbleached pulps were obtained with a yield of 48.4%.

The pulp waste liquid was concentrated and burned to obtain ash having a Na ₂ CO ₃ content of 97.3%. The ash is extracted with water, a part of which is added with oxalic acid to make a chemical solution of the first step, and the rest is causticized by adding quick lime to the aqueous solution to make NaOH and Na ₂ C
A mixed solution of O ₃ was obtained, and hydrogen peroxide and an auxiliary were added to regenerate the cooking liquor used in the second step.

[0039]

According to the present invention, prior to the cooking in the PA method, N
PO (neutral hydrogen peroxide oxalic acid method) chemicals, each of which is simply heated at normal temperature or normal temperature under normal pressure. Pulp excellent in unused resources such as long-fiber plants and mixed chips of tropical materials can be easily manufactured.

In particular, treatment at normal temperature and normal pressure enables a large amount of raw materials to be stored for an extremely long period of time, and enables the collection and utilization of raw materials that are easily perishable in a wet state. Further, the pulp waste liquids of the first step and the second step can be concentrated and burned together, and can be recovered as ash mainly composed of alkali carbonate. Furthermore, since it can be regenerated as a chemical solution in the first step and the second step, environmental measures by drainage and exhaustion, energy saving,
Labor saving has become extremely easy. In addition, long-term storage and long-distance transportation of wet wood, non-wood plant raw materials, and high-temperature and high-humidity raw materials became possible, so that unused resources could be collected on a global scale and pulped on a large scale. .

Claims (6)

[Claims] The first step is to treat the raw material of fiber plant by adding hydrogen peroxide to an alkali salt solution of oxalic acid and carbonic acid and, if desired, adding a digestion aid to form a chemical solution, and treating it under normal pressure. A method for producing a chemical pulp and a chemical solution, wherein a cooking aid is added to a caustic alkali solution of hydrogen, if desired, to prepare a cooking chemical, and cooking is performed in the second step. 2. The effluent of the first step or the effluent of the second step according to claim 1 is concentrated and burned to obtain an ash containing alkali carbonate as a main component. Oxalic acid and hydrogen peroxide are added to an aqueous solution containing alkali carbonate as a main component or an aqueous solution mainly containing caustic alkali containing alkali carbonate or an aqueous solution containing alkali carbonate obtained by causticizing an alkali carbonate aqueous solution. The agent is added and regenerated and used as a solution for the treatment in the first step,
Hydrogen peroxide is added to an aqueous solution containing caustic alkali containing alkali carbonate and a main component obtained by causticizing an aqueous alkali carbonate solution, and if necessary, a cooking aid is added to regenerate and use as a chemical solution for the second step cooking. The method of claim 1. 3. The method according to claim 1, wherein carbonate is used as an alkali to be replenished when the pulp waste liquid is concentrated and burned to recover a chemical solution from the ash. 4. An anthraquinone-based compound having a hydroxyl group at the 9,10-position, an alkylanthraquinone-based compound and / or an anthracene-based compound, an alkylanthracene-based compound, a magnesium salt, as a cooking aid used in the first step and / or the second step. 4. The process according to claim 1, wherein one or more of an organic solvent and / or a chelating agent optionally dissolving in water is added as a cooking aid. 5. A chelating agent used as a cooking aid,
5. The method according to claim 1, 2, 3 or 4, wherein -hydroxyalkylene-11-diphosphonic acid or a salt thereof is used. 6. NMP (normal methylpyrrolidone) as an organic solvent optionally dissolving in water used as a cooking aid
6. The method of claim 1, 2, 3, 4, or 5, wherein