JPS6149436B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing alkaline pulp and neutral or alkaline sulfite pulp, in which two or more compounds having different redox potentials and capable of reversibly carrying out redox reactions are added to a normal cooking liquor. The present invention relates to a method for producing pulp, which comprises cooking the pulp by cooking. Traditional methods for producing alkaline pulp from various lignocellulosic materials such as wood include the kraft method, soda method, polysulfide method, and soda carbonate method, but compared to the sulfite method, the pulp quality is better, but the pulp yield is lower. It had the disadvantage of being low. In the neutral or alkaline sulfite method, the lignin is digested with a neutral or alkaline solution such as sodium sulfite, ammonium sulfite, or magnesium sulfite to soften or delignify it, and then mechanically defibrated if necessary. pulp is produced. This sulfite method had disadvantages in that the cooking rate was slow and the pulp quality was inferior compared to the Kraft method. In order to improve these drawbacks, Japanese Patent Publication No. 55-1398, cited in the cited document, added quinone selected from anthraquinone, naphthoquinone, benzoquinone, etc. to the normal cooking liquor in the production of alkaline pulp. In order to prevent the disintegration of cellulose and hemicellulose and to promote the disintegration of lignin, a method has been shown that can improve pulp yield and pulp quality, increase pulp production by increasing cooking speed, and save cooking chemicals and steam. ing. Mata Tokukoaki
No. 53-13002 describes a method of adding small amounts of quinone compounds during sulfite cooking, and Japanese Patent Application No. 51-148492 describes a method of adding a small amount of quinone compounds during alkaline cooking or sulfite cooking.
A cooking method with the addition of hydroxyanthracene is shown. These additives, for example, exhibit a reversible redox reaction between anthraquinone and anthrahydroquinone, and as in a reaction, they oxidize the reducing terminal groups of cellulose and hemicellulose to form aldonic acid groups, and alkali It prevents the breakdown of carbohydrates due to the peeling reaction during cooking, improving pulp yield and pulp quality. Anthraquinone is then reduced to anthrahydroquinone. Anthrahydroquinone reacts with lignin like a reaction and returns to anthraquinone, donates electrons to lignin, induces the lower molecular weight of lignin, and promotes delignification. In this reaction, the reaction is the rate-limiting step, so if the redox potential is too high, the reduction reaction of lignin will be difficult to proceed, and the reaction from anthrahydroquinone to anthraquinone will also be difficult to proceed, resulting in this reversible reaction. becomes difficult to progress. However, in order to improve the pulp yield, it is desirable that the oxidizing power of the carbohydrate is stronger, that is, the redox potential is higher. In this way, contradictory characteristics are satisfied: additives with a high redox potential are preferable to improve pulp yield and pulp quality, while compounds with a low redox potential are preferable to promote delignification. is necessary. Therefore, as shown in the cited document, there is a limit to the improvement of pulp yield and promotion of delignification with one type of additive. The present invention has conducted intensive research on how to make this contradictory reaction proceed efficiently, and has come up with the invention of dramatically making it proceed by adding two or more types of compounds with different redox potentials. That is, the present invention adds a compound that has a high redox potential and therefore tends to oxidize the reducing end groups of carbohydrates to a normal cooking liquor, suppresses the peeling reaction of carbohydrates during cooking, and improves the pulp yield. In addition to improving pulp quality, the combination of adding another compound that has a low redox potential and therefore tends to donate electrons to lignin and promotes delignification can improve pulp yield and cooking speed. At the same time, it has become possible to dramatically improve the The reaction in the present invention is estimated as follows. In the above reaction, additive A is one or more compounds capable of performing a reversible redox reaction whose redox potential is higher than that of additive B;
One or more compounds that can perform a reversible redox reaction with a lower redox potential. Examples of organic compounds that can perform reversible redox reactions and have relatively high redox potential include benzoquinone, naphthoquinone, and their sulfoxy, carboxy, amino, hydroxy, and halogen derivatives. Examples of inorganic materials include potassium ferricyanide and ferric citrate. In addition, organic compounds with relatively low redox potential include:
Anthraquinone, phenanquinone, dihydrodihydroxyanthracene, indigo, anthrone and their derivatives, maleic acid, fumaric acid,
Organic carboxylic acids such as benzoic acid, and inorganic compounds include cerium sulfate. By selecting two or more compounds with different redox potentials from among these and adding them to the ordinary cooking liquor, it is possible to improve the results by selecting two or more compounds with different redox potentials from among these and adding them to the ordinary cooking liquor. oxidizes the reducing end groups of the carbohydrates and donates electrons to lignin, resulting in
Improvements in pulp yield, cooking rate, and pulp quality are increased. The addition rate of these two or more types of compounds having different redox potentials is 0.002 to 0.5%, preferably 0.005 to 0.1%, respectively, based on the absolute dry weight of the raw material lignocellulosic material, and the addition rate is 0.002 to 0.5%, preferably 0.005 to 0.1%, respectively, and the addition rate is 0.002 to 0.5%, preferably 0.005 to 0.1%, based on the absolute dry weight of the raw material lignocellulose material. The present invention can be achieved by carrying out the following. The present invention will be explained in more detail below using examples. Example 1 600 g of coniferous wood chips were packed in a No. 4 autoclave, and kraft cooking liquor containing 17% active alkali vs. bone dry chips and 25% sulfidity was added to the autoclave, and benzoquinone (oxidation-reduction potential E ₀ = 0.70 V) was added to the autoclave. 0.012% based on dry chip weight and 1,4-dihydro-9.
10-dihydroxyanthracene (F ₀ =-
0.130V) 0.038% and cooked at 165°C for 75 minutes. On the other hand, for comparison, 1,4-dihydro-9,10
- Craft cooking with the addition of only 0.05% dihydroxyanthracene under the same conditions as above (Comparative Example 1), and no addition of benzoquinone or 1,4-dihydro-9,10-dihydroxyanthracene. We tested a product (Reference Example 1) that had been cooked using the normal Kraft method under the same conditions as above. The results of these cooking tests are shown in Table 1 below.

[Table] Example 2 700 g of hardwood chips were packed in a No. 4 autoclave, containing 10% of soda carbonate and bone dry chips, and potassium ferricyanide (half-wave potential E _1/2 =
0.24V) and 1,4-naphthoquinone (E 0 = 0.47V) in an amount equivalent to 0.05% of the bone-dry chip weight and 1,4-naphthoquinone (E ₀ = 0.47V), and heated at 180℃.
Cooked for 20 minutes. The cooking chips were beaten to a freeness of 450 ml using a disk refiner and made into paper. On the other hand, for comparison, 1,4-naphthoquinone was added at a rate of 0.1% and the product was cooked in sodium carbonate under the same conditions as above (Comparative Example 3), and potassium ferricyanide, 1,
A test was carried out under the same conditions as above, except that 4-naphthoquinone was not added, and a product prepared by ordinary sodium carbonate cooking (Reference Example 3) was tested. The results of these cooking tests are shown in Table 3 below.

[Table] Example 3 Example 1 using softwood chips and changing the additives
Kraft cooking was carried out according to the following. As additives, 0.02% of 1,4-dihydro-9,10-dihydroxyanthracene (E ₀ = -0.130V) and 0.01% of sodium benzoate (E _1/2 = -1.4V) were added to the chips.
Using. Also, for comparison, 1,4-dihydro-9,10
A cooking test was also conducted on a sample to which 0.04% -dihydroxyanthracene was added (comparative example) and a sample to which nothing was added (reference example). The results are shown in the table below.

【table】

Claims (1)

[Claims] 1. Benzoquinone, naphthoquinone, and anthraquinone are added to each cooking liquor of alkaline pipes such as kraft pulp, soda pulp, polysulfide pulp, and soda carbonate pulp, and neutral sulfite pulp and alkaline sulfite pulp. , 1,4-dihydro-
9,10-dihydroxyanthracene, phenanthrenequinone, indigo, anthrone, anthrol and their derivatives; iron complex salts, citric acid 2
Two or more compounds selected from the group consisting of iron, ferric tartrate; maleic acid, fumaric acid, benzoic acid, and metal salts thereof; and ceric sulfate, and which have substantially different redox potentials A method for producing pulp, which comprises adding and digesting the compound. 2. The method for producing pulp according to claim 1, wherein the iron complex salt is potassium ferrocyanide or potassium ferrocyanide. 3. Two or more compounds having different redox potentials are combined with one or more compounds selected from the group consisting of benzoquinone, naphthoquinone, or their derivatives.
The production of pulp according to claim 1, characterized in that one or more compounds selected from the group consisting of 4-dihydro-9,10-dihydroxyanthracene and its derivatives are simultaneously added and digested. Method. 4. Two or more types of compounds having different redox potentials are one or more compounds selected from the group consisting of benzoquinone, naphthoquinone, or their derivatives, and one or more compounds selected from the group consisting of anthraquinone or its derivatives. The method for producing pulp according to claim 1, characterized in that the pulp is simultaneously added and digested. 5. Two or more compounds having different redox potentials are one or more compounds selected from the group consisting of benzoquinone, naphthoquinone, anthraquinone, 1,4-dihydro-9,10-dihydroxyarethracene, and derivatives thereof. The method for producing pulp according to claim 1, characterized in that one or more compounds selected from the group consisting of , anthrone, anthrol, and derivatives thereof are added at the same time. 6. The two or more types of compounds having different redox potentials are one or more compounds selected from the group of benzoquinone, naphthoquinone, anthraquinone, 1,4-dihydro-9,10-dihydroxyanthracene, and derivatives thereof, Iron complex salt and citric acid 2
The method for producing pulp according to claim 1, characterized in that one or more compounds selected from the group consisting of iron, ferric tartrate, and ceric sulfate are added at the same time. 7. Two or more compounds having different redox potentials are one or more compounds selected from the group consisting of benzoquinone, naphthoquinone, anthraquinone, 1,4-dihydro-9,10-dihydroxyanthracene, and derivatives thereof. The method for producing pulp according to claim 1, characterized in that one or more compounds selected from the group consisting of , fumaric acid, and benzoic acid are added at the same time. 8. The method for producing pulp according to claim 1, wherein the addition rate of two or more types of compounds having different redox potentials is in the range of 0.002 to 0.5% relative to bone dry chips.