JP2002363878A - Method for manufacturing pulp having high whiteness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing pulp having high whiteness, good in strength and having high quality in a closed system not only without using a chlorine bleaching agent but also without using a sulfur-based cooking chemical. SOLUTION: The method for manufacturing pulp is carried out as follows: at first, wood or a non-wood cellulose resource is treated without using sulfur in a 1 to 3 stage treatment using an alkali solution of hydrogen peroxide to obtain non-bleached pulp having high whiteness and a low kappa number, and easy in bleaching; the obtained non-bleached pulp is further treated with ozone to obtain pulp having high whiteness; and at the same time, the by-produced pulp waste liquid and/or bleaching waste liquid is condensed and burned, and energy, even alkali and water are recovered and recycled. Thus, the pulp manufacturing method friendly to the environment is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the production of high brightness pulp.

[0002]

2. Description of the Related Art It has not been easy to produce and supply high brightness pulp from wood and non-wood in large quantities with low pollution.
Conventionally, unbleached pulp has been produced in order to obtain a large amount of high-brightness pulp, and the unbleached pulp has been bleached to produce high-brightness pulp. In order to produce unbleached pulp, the current mainstream production method, KP method, uses sodium sulfide, a sulfur-based compound, as the cooking chemical, so it suffers from waste liquid and exhaust odor problems. Investment has been required. The unbleached pulp obtained has a low whiteness and a high kappa value, which is an indicator of the lignin content, and is difficult to bleach. Therefore, elemental chlorine, hypochlorite, chlorine dioxide such as chlorine dioxide, etc. Had to be multistage bleached. Therefore, high whiteness pulp could not be obtained without accompanying the generation of the organic chlorine compound.

[0003] In recent years, environmental problems have become more severe, and the generation of organochlorine compounds has become a major social problem. Therefore, pulp of high quality having high whiteness, high strength and little or no chlorine bleach is used. There has been a strong demand for a method for producing the compound by a simple method. Although ozone bleaching is chlorine-free bleaching, it has the disadvantage that pulp with high whiteness can be obtained but pulp suitable for practical use is difficult to obtain since substances other than lignin are also decomposed. The inventor used to digest non-wood and wood cellulosic raw materials by adding a cooking aid to an alkaline solution of hydrogen peroxide (PA method) and to obtain unbleached pulp of high brightness and low kappa number without using sulfur. Pulp having higher whiteness and lower kappa value was obtained by treatment with a dilute alkali solution of hydrogen peroxide, and the pulp obtained from the unbleached pulp using a very small amount of chlorine bleach was used. The bleached pulp with whiteness was successfully obtained.

[0004] However, obtaining a high whiteness pulp without using any chlorine bleaching agent is different from that obtained by the neutral hydrogen peroxide-oxalate method in the pulping of some bast cellulose raw materials. It was not common to get it. Thus, there is a need for a method of obtaining pulp with high whiteness from various raw materials.

[0005]

The problem to be solved by the present invention is that not only does chlorine bleach not be used at all, but also, in consideration of environmental problems, no sulfur-based chemical is contained in the cooking chemical. An object of the present invention is to provide a method for producing high-quality pulp having high whiteness and strength without using a simple method and using a closed system.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, first, wood and non-wood cellulose resources are reduced by one using an alkaline solution of hydrogen peroxide.
Unbleached pulp with high whiteness, low kappa number and easy bleaching is obtained by sulfur-free treatment. The unbleached pulp thus obtained is further treated with ozone to obtain a pulp of high whiteness, and the pulp waste liquid or bleached waste liquid produced as a by-product is concentrated and burned, and energy and alkali or water are removed. It is possible to provide an environment-friendly pulp production method which is closer to an ideal closed system by collecting and recycling.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a target pulp raw material, non-wood and wood cellulose raw materials can be used. That is, as the non-wood cellulose raw material, there can be used fibers of trunk stems such as bagasse (sugar mill mill cake), abaca, jute, leaf fibers, bast fibers, seed hair fibers, and the like. The raw material can be digested as it is because it can be in good contact with the cooking chemical and the chemical is well penetrated. Both hardwoods and conifers can be used for wood. However, when it is not possible to expect the contact with the cooking chemical and the penetration of the liquid, such as wood chips and sawdust, the wood is usually used for cooking in chips. The cooking chemical liquid is prepared by adding at least one or more of a chelating agent, a quinone, an oxalate, a magnesium compound, and a polar organic solvent optionally mixed with water to an alkaline solution of hydrogen peroxide as a cooking aid. If desired, oxygen can be injected.

[0008] In the digestion of the present invention, it is possible to take a wide range of liquid ratios, and in the gas phase digestion, 1 to 4.0 L / k
g, preferably 1.5 to 2.5 L / kg. In liquid phase cooking, the liquid ratio is between 4.0 and 10 L / kg. The liquid ratio varies greatly depending on the gas phase and liquid phase digestion, and the required amount of the chemical is almost determined by the absolute dry amount of the cellulose raw material.
The amount used is shown below on a dry basis.

[0009] Hydrogen peroxide and a hydrogen peroxide generator can be used, and the amount of H2O2 used is 1 to 20% based on the raw material.
, Preferably 3-10%. As the alkali, hydroxides and carbonates of sodium or potassium can be used, and the causticization rate is 50 to 95%, preferably 65%, and the pulp yield is higher than using a chemical solution with a causticization rate of 100%. It is also preferable in constructing a closed system for recovering and recycling pulp waste liquid. The amount of alkali used is Na ₂ O
8 to 40, preferably 12 to 25%. Alkali carbonate has almost no cooking effect, but during cooking
It does not damage the pulp and contributes to the improvement of the pulp yield, but the alkali can be recovered from the pulp waste liquid after digestion and recycled.

The addition of water glass and a chelating agent as a stabilizer for hydrogen peroxide is effective, and the use of an organic chelating agent does not require the use of silica in the recovery system. It is effective when it is premised to collect The amount of water glass used is 0.5 to 5%, preferably 1 to 2%, and the amount of chelating agent used is 0.1 to 2%.
And preferably 0.2 to 1%. Anthraquinone compounds include, in addition to anthraquinone, alkylanthraquinones having an alkyl group having 1 to 12 carbon atoms as side chains, and also include reduced anthracenes thereof. The amount used is 0.02 to 2%, preferably 0.02%.
5 to 0.5%. As a magnesium compound, compounds such as magnesium oxide, magnesium hydroxide, and magnesium acetate can be widely used. In the treatment with a chemical solution for pulp production containing hydrogen peroxide, the cellulose is protected and the pulp yield is increased. It contributes to the improvement of the mechanical strength, especially the tear strength and the bending strength. Its usage is Mg
O is 0.05 to 1%, preferably 0.1 to 0.5.
%.

The addition of a polar organic solvent that is arbitrarily soluble in water 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. In particular, the use of NMP (normal methylpyrrolidone) is effective. The added amount is 0.0
It is 3 to 1%, preferably 0.05 to 0.3%. The addition of oxalate is effective not only for removing pectin in the raw material but also for improving whiteness. Usually, it is used as a sodium salt or potassium salt, and its use amount is 1 to 20%, preferably 3 to 10%. The treatment with an alkaline solution of hydrogen peroxide is performed with a kappa value of 20 or less,
By performing the first to third steps preferably to 5 or less, an unbleached pulp having high whiteness and easy bleaching which can be bleached to a Hunter-whiteness of 80% or more by ozone treatment is obtained.

When inserting oxygen, the partial pressure should be 0.2 at room temperature.
10 to 10 kg / cm2, preferably 1.0 to 5 kg / cm2
2 In the first stage cooking, the maximum temperature is 110-190
C., preferably 115-160.degree. C., the maximum temperature holding time is 10-300 minutes, and a high cooking temperature can greatly shorten the cooking time. 30 to 1
It is preferable to set the cooking temperature and the cooking time so that the cooking time of 80 minutes is sufficient. The maximum temperature in the second to third digestion is 50 to 150C, preferably 90 to 130C. The holding time at the maximum temperature is 10 to 180 minutes, preferably 30 to 90 minutes. After cooking, the digest is squeezed, washed,
Solid-liquid separation to obtain unbleached pulp and pulp waste liquor, respectively, concentrates and burns pulp waste liquor, collects energy and ash mainly composed of alkali carbonate, extracts alkali carbonate with water, and uses calcium hydroxide with calcium hydroxide. Causticizing, causticizing rate 50-95
%, Preferably 65-85% causticization rate, recover and recover alkali hydroxide and alkali carbonate solution, and add hydrogen peroxide and other digestion aids to preserve the cellulose raw material for the next digestion, or directly Used for cooking.

The unbleached pulp that has been washed after cooking with an alkaline solution of hydrogen peroxide is bleached with ozone. Ozone to be used can be generated from air or oxygen using various types of generators, but if oxygen is used, ozone can be obtained at a high concentration, so that the generator can be small in size. In pulp mills, it is better to use a pressure-swing type oxygen separator to separate high-concentration oxygen of about 90% and use it as an ozone raw material.
Greater effect is obtained than using air as it is as ozone raw material, and it is preferable to use a cryogenic separation device to separate and use high-purity oxygen from air because the structure of the device used is simpler and the operation is easier. .

Ozone bleaching is carried out if the unbleached pulp is wet, and if the bleached pulp is dry, the liquid ratio is 10 to 20.
% Corresponding to 0.03 to 0.5, preferably 0.05 to 0.2 with respect to the kappa value of the raw pulp at a liquid ratio of L / kg, preferably 1.0 to 2 oL / kg. And the mixture is treated at 0 to 35 ° C, preferably 0 to 25 ° C, for 1 to 30 minutes, preferably for 2 to 10 minutes. At this time, the presence of the diluted alkaline solution of hydrogen peroxide is effective in preventing color return of the pulp. Alternatively, contact with dilute hydrogen peroxide of 0.01 to 1.0%, preferably 0.03 to 0.5% after ozone bleaching is effective in maintaining the whiteness of the pulp.

[0015]

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, all of the following percentages are absolute dry weight percentages.
It is.

Embodiment 1 FIG. In the first step, 100 kg of bagasse (having a water content of 50.1%) is treated as gas phase PA (H ₂ O ₂ 3%, NaOH Na ₂ O 1).
6%, anthraquinone 0.08%, D as chelating agent
TPA 0.3%, MgO 0.1%, NMP 0.1
(Water ratio 1.8 L / kg), and digestion was carried out at 120 ° C. for 2 hours to obtain 23.8 kg of unbleached pulp having a kappa number of 4 and a Hunter brightness of 48.3%. In Step 2, the separated and recovered pulp waste liquid is concentrated and burned, ash mainly containing sodium carbonate is recovered, and crude sodium carbonate extracted with water is treated with calcium hydroxide until the causticization rate reaches 80%, The sodium hydroxide and sodium carbonate were regenerated and used for the next digestion. To 15.0 kg of the obtained unbleached pulp, 150 L of water containing 6 g of ozone was added, and the mixture was treated at 15 ° C. for 10 minutes. Hunter-whiteness 80.4%, breaking length 3.6 km,
A pulp having a specific burst strength of 2.4 and a specific tear strength of 56 was obtained with a yield of uncured pulp of 92.7%.

[0017] Example 2. Abaca a 1,000kg (water content 15.1%) PA (cooking chemical vapor as the processing of the first step for the H ₂ O ₂ 3%, the NaOH Na ₂ O
16% as a chelating agent, 0.3% of 1-hydroxyalkylidene-1,1-diphosphonic acid, 0.3% of alkylanthraquinone having 4 carbon atoms in the alkyl group (tert-alkylanthraquinone), Mg ( OH)
2 was made 0.1% as MgO, water was added to 0.1% NMP, and the liquid ratio was 1.8 L / kg). Further, as a second step, the digested product was treated with Pa (H ₂ O ₂ at 2%, NaOH at 2% as Na ₂ O, E
Pulp having a whiteness of 65.3% and a kappa number of 3.9 at 90 ° C. for 1 hour by adding water to 0.2% of DTA and 0.1% of MgO so that the liquid ratio becomes 10 L / kg. I got Third
To the 10.0 kg of pulp obtained in the first step, 100 L of water containing 4 g of ozone was added to 10.0 kg of the pulp and treated at 8 ° C. for 10 minutes. Hunter-whiteness: 86.4%, breaking length: 8.1 km, specific burst strength: 4 .2, a pulp having a specific tear strength of 212 was obtained at an unbleached pulp yield of 92.7%.

Example 3 As a treatment in the first step, 1,000 kg of birch chips (water content: 17.5%) were used as a gas phase PA (H 2 O: 3%, NaOH: Na ₂ O: 16).
%, Anthraquinone 0.08%, DT as a chelating agent
PA is 0.1% with 0.3% Mg (OH) ₂ as NgO.
%, NMP to 0.1% and water added to the solution, and the liquid ratio is 2.1 L / kg
The digestion was carried out at 145 ° C. for 2 hours. Pa treated with oxygen under pressure as a second step with respect to the cooking product (oxygen 2.5 kg / cm @ 2, Pa chemical liquid H2 O2 2% for O2, 2% of NaOH as Na ₂ O, and EDTA 0.2
%, MgO 0.1%, and water, and the liquid ratio is 5.2 L / kg.
) At 90 ° C for 1 hour, whiteness 55.3%,
A pulp with a kappa number of 6.3 was obtained. The first as the third step
70 kg of pulp ozone to 10.0 kg of pulp obtained in the process
100 liters of water containing 10 g of water, and treated at 8 ° C. for 10 minutes. A pulp having a Hunter whiteness of 81.4%, a breaking length of 5.8 km, a specific burst strength of 3.8 and a specific tear strength of 78 is obtained from unbleached pulp. Obtained at a rate of 92.7%.

[0019]

According to the present invention, wood and non-wood cellulos
High-brightness pulp can be obtained from raw materials without using any sulfur or chlorine chemicals. In addition, chemicals and energy can be recovered and regenerated from pulp waste liquid, and a high-level closed system can be assembled, making it easier to solve environmental problems. Not only do not use chlorine bleach at all, but also anticipate environmental issues, do not use sulfur chemicals at all in the cooking liquor, and use a simple method to produce high-quality pulp with high whiteness and strength, And a method of manufacturing by a closed system.

Claims (3)

[Claims] A first step is to inject a digestion aid and, if desired, oxygen into an alkaline solution of hydrogen peroxide to digest wood or non-wood fiber raw material in one to three stages. The second step is to separate and collect and concentrate and burn to recover energy and alkali, and the third step is to perform ozone treatment. Wood or non-wood made of a combination of the first, second, and third steps is used. A method for producing pulp with high whiteness, comprising treating. 2. The method according to claim 1, wherein an alkali metal hydroxide or carbonate is used as the alkali solution in the first step. 3. The method according to claim 1, wherein at least one of a chelating agent, anthraquinones and a magnesium salt is used as a cooking aid in the first step.