JPS62274B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an alkali sulfide pulping method, and more particularly, the present invention relates to a method for pulping lignocellulosic materials using a cooking liquor containing sodium sulfide and sodium hydroxide as main components. Alternatively, the present invention relates to a method for pulping a lignocellulosic material by adding a 9,10-dioxyhydroanthracene-based compound to a cooking liquor. Conventionally, the so-called alkali sulfide pulping method is known, in which lignocellulosic materials such as wood, straw, bagasse, etc. are cooked and pulsed in a cooking liquor containing sodium sulfide and sodium hydroxide as main components, and the alkaline sulfide pulping method, such as the Kraft method, is known. Sulfide pulping has been the main method of chemical pulping because of its superior pulp quality compared to sulfite pulping.
It has the disadvantage of low pulp yield. In order to improve this drawback, the polysulfide method,
Many methods have been tried, including the addition of sodium borohydride, hydrazine, amine compounds, aldehyde compounds, or nitrobenzene compounds, pretreatment of chips with hydrogen sulfide, and the alkafide method, but all of them have problems with equipment, manufacturing costs, operability, and With the exception of some polysulfide methods, these methods have not yet been put into practical use because they have many problems in terms of pollution prevention and are less effective on hardwood materials. Recently, Fiehn in East Germany has improved the pulp yield by adding anthraquinones during the production of alkaline pulp [Zellstoff et al.
und Papier 21. No. 1, 3-7 (1972) East German Patent No. 98549], many methods for adding quinone compounds have been filed. For example, a method of adding anthraquinone-2-monosulfonic acid (AMS) to the first stage of two-stage cooking of soda-oxygen/alkali or kraft-oxygen/alkali (JP-A-50-29801, U.S. Patent No.
3888727), a method of pretreatment with an alkaline solution containing AMS (Canadian Patent No. 986662), a method of adding quinones to alkaline cooking (Japanese Unexamined Patent Publication No. 1983-43403), oxygen-alkali A method of adding a water-soluble oxygen transfer agent such as a quinone-hydroquinone compound to cooking (Japanese Patent Application Laid-open No. 119801/1983,
West German Publication No. 2610891), a method of adding a non-sulfur cyclic keto compound to alkaline cooking (Japanese Patent Publication No. 2610891),
51-37803, U.S. Patent No. 4,012,280), a method of adding a quinone compound to sulfite cooking (Japanese Patent Application Laid-Open No. 112903/1983), etc., but all of them are This is a method of accelerating the delignification reaction and improving the pulp yield by adding the quinone compound alone or in combination with oxygen. Recently, Holton has proposed a method in which a diketohydroanthracene compound selected from unsubstituted and lower alkyl-substituted Diels-Alder adducts of naphthoquinone and benzoquinone and a nitroaromatic compound are added to soda cooking in combination (U.S. Pat. No. 4,036,680). However, this method cannot be applied to pulping under a reducing atmosphere such as the alkali sulfide pulping method. That is, nitroaromatic compounds added to the cooking liquor containing sodium sulfide and sodium hydroxide as main components are Svensk Papperstid.71 (23) 857-863
(1968), it oxidizes hydrosulfide ions derived from sodium sulfide, resulting in a decrease in the sulfidity of the cooking liquor, and has the drawback that it is itself reduced and deactivated. In addition, diketohydroanthracene compounds contain mild oxidizing agents such as nitro compounds, hydrogen peroxide, chromic acid, and air, as shown in Japanese Patent Publication No. 35-14138 (corresponding to U.S. Pat. No. 2,938,913). Since it is known that anthraquinone compounds are easily oxidized by steam, the cooking method of Holton's patent is a method in which anthraquinone compounds are added to a soda cooking chemical, or an anthraquinone compound and a nitroaromatic compound are added. This method is substantially the same as the method aiming at the combined effect of , and it can be understood that the cooking process is carried out in a fairly oxidizing atmosphere. The present inventors have studied various aspects of Holton's patent, and have found a method in which a diketohydroanthracene compound and a nitroaromatic compound are added together to a pulping chemical solution under a reducing atmosphere, such as an alkali sulfide pulping method. found that there are drawbacks that adversely affect cooking speed, pulp yield, and quality. Furthermore, Holton's method is characterized by the combination of a diketohydroanthracene compound and a nitroaromatic compound added to soda cooking, and the addition of a diketohydroanthracene compound alone is not necessarily more effective than adding anthraquinone alone. I learned that it's not that good. By the way, as a result of the multifaceted study of cooking using a cooking liquor containing a quinone compound, the present invention found that Na ₂ S or NaHS in the cooking liquor is reduced in a region where the cooking liquor is weakly alkaline or neutral. It acts as an agent to reduce quinone to hydroquinone, but it is recognized that it does not exhibit a reducing effect in the strongly alkaline region. It was learned that quinone-hydroquinone compounds lead to an increase in the amount of compounds added, and as a solution to this problem, the lignocellulose material was cooked in a cooking liquor containing sodium sulfide and sodium hydroxide as the main components. Alkaline sulfide pulp, characterized in that at least one reducing aid selected from the group consisting of quinone-hydroquinone compounds and sulfites, hydrogen sulfites, thiosulfates and formates is added to the cooking liquor. An application was filed for the Japanese Patent Application No. 52-149195. Regarding the mechanism of the alkali sulfide pulping method, the present inventors have discovered that by adding the reducing aid to the redox reaction system of the quinone compound and hydroquinone compound during cooking, the quinone compound involving carbohydrates etc. → hydroquinone compound. A reduction system separate from the reduction system of the quinone-based compounds is formed, and the quinone-based compounds are easily reduced to hydroquinone-based compounds.
Based on the prediction that this hydroquinone compound would react with radicals generated from lignin and proceed with the delignification reaction, we further investigated the combination of the redox reaction system and the reduction aid from various angles, and surprisingly found that 9,10 instead of anthraquinone compounds and anthrahydroquinone compounds
-Diketohydroanthracene compounds and 9,10
- It was discovered that the use of dioxyhydroanthracene compounds further improves the pulp yield. The present invention was made based on this knowledge, and its purpose is to provide an alkali sulfide pulping method that provides excellent results in terms of cooking speed, pulp yield, etc. To summarize the present invention, the present invention involves cooking lignocellulosic material with a cooking liquor containing sodium sulfide and sodium hydroxide as main components.
9,10-diketohydroanthracene compounds and/or 9,10-dioxyhydroanthracene compounds, and at least one reducing agent selected from the group consisting of sulfites, bisulfites, thiosulfates, and formates. The present invention relates to an alkali sulfide pulping method characterized in that an agent is added to the cooking liquor. Examples of the 9,10-diketohydroanthracene compounds used in the present invention include 1,4
-dihydro-9,10-diketoanthracene, 1,
2,3,4-tetrahydro-9,10-diketoanthracene, 1,4,4a,9a-tetrahydro-9,
10-diketoanthracene, 2-ethyl-1,4,
4a,9a-tetrahydro-9,10-diketoanthracene, 2,3-dimethyl-1,4,4a,9a-tetrahydro-9,10-diketoanthracene, 1,3
-dimethyl-1,4,4a,9a-tetrahydro-
9,10-diketoanthracene, 1-methyl-1,
2,3,4-tetrahydro-9,10-diketoanthracene, 1,2,3,4,5,8-hexahydro-9,10-diketoanthracene, 1,4,4a,
5,8,8a,9a,10a-octahydro-9,10-
Diketoanthracene, 2,3,6,7-tetramethyl-1,4,4a,5,8,8a,9a,10a-octahydro-9,10-diketoanthracene, 1,
2,3,4,5,6,7,8-octahydro-
9,10-diketoanthracene, and 2,6- and 2,7-diethyl-1,4,4a, 5,8,8a,
A mixture of 9a,10a-octahydro-9,10-diketoanthracene, etc., preferably a compound selected from unsubstituted and lower alkyl-substituted Diels-Alder adducts of naphthoquinone and benzoquinone, and from the viewpoint of effectiveness and economy, 1, 4, 4a, 9a―
Tetrahydro-9,10-diketoanthracene and 1,4,4a,5,8,8a,9a,10a-octahydro-9,10-diketoanthracene are suitable. In addition, examples of 9,10-dioxyhydroanthracene-based compounds include 1,4-dihydro-9,10-dioxyanthracene, 1,4,5,8-tetrahydro-9,10-dioxyanthracene, 1,4, 5,
8,8a,10a-hexahydro-9,10-dioxyanthracene, etc., and 1,4-dihydro-9,
Sodium and potassium 10-dioxyanthracene can also be used. These compounds, like anthraquinone compounds, are added in an amount of about 0.01 to about 5% by weight based on the bone-dry lignocellulose material. The reduction aid is required to be a water-soluble salt that is stable at high temperatures, and quinones cannot be reduced without the combined use of Na ₂ S and NaHS. The reducing aid is preferably sodium sulfite, sodium hydrogen sulfite, sodium thiosulfate, sodium formate, which are readily available from kraft pulp mills, but other water-soluble salts, such as potassium salts or ammonium salts thereof, are preferably used. Salt etc. may also be used. Sodium sulfite and sodium hydrogen sulfite can be easily obtained not only from flue gas desulfurization at kraft pulp manufacturing plants, but also from factories that use sodium hydroxide for flue gas desulfurization from boilers that use sulfur-containing gas, heavy oil, etc. as fuel. Currently, it is difficult to dispose of and discarded. Fortunately, in kraft pulp manufacturing plants, sodium sulfite and sodium hydrogen sulfite after flue gas desulfurization can be concentrated and burned to be used as sodium sulfide for cooking, but according to the present invention, sodium sulfite and sodium hydrogen sulfite after flue gas desulfurization Sodium can be used by directly mixing it with white liquor without going through a concentration or combustion process. Furthermore, as a result of advances in flue gas desulfurization technology, kraft pulp manufacturing plants are now discharging very little sulfur to the outside of the system, and the degree of sulfidation in the cooking liquor tends to increase. Although a high sulfidity is very desirable in terms of pulp yield and pulp quality, it is very problematic in terms of odor prevention measures, and the pulp and paper industry is struggling to keep the sulfidity low. As one solution to this problem, sodium sulfide can be changed to sodium thiosulfate by oxidizing a part of the white liquor, and this and the above-mentioned hydroanthracene compound can be added in combination. Similarly, it is also possible to oxidize the black liquor to convert the sodium sulfide remaining in the black liquor into sodium thiosulfate, which is then added. Normally, even if sodium thiosulfate is present in the Kraft cooking liquor, it does not affect the cooking process in any way, but by using it in combination with the hydroanthracene compound mentioned above, in addition to promoting the delignification reaction, it can also have a secondary purpose of countering sulfidity. It is possible. The reducing aid may be any of those mentioned above, but the amount added is about 0.5 to about 5% by weight based on the bone-dry lignocellulosic material, and is added to the cooking liquor at the beginning of cooking. The sulfidity of the cooking liquor in the present invention is generally about 5 to about 50%, preferably 5 to 30%. The cooking temperature is 140-190°C, preferably 145-180°C. Next, the present invention will be explained with reference to examples, but the present invention is not limited thereto. Regarding the evaluation of pulp quality in the examples, the cut par value was determined by the Tappi test method T236m-60, and the viscosity was determined by the copper ethylenediamine solution viscosity Tappi test method T230SU.
-66, whiteness is according to JISP8123. Examples 1 to 3 and Comparative Examples 1 to 9 1700 g of beech chips (air-dried) were packed into an 8-volume autoclave, and various types of kraft cooking liquor were added to an effective alkali of 13 to 15% (relative to bone-dry chips), a sulfidity of 25%, and a liquid ratio of 4. 9,10-diketohydroanthracene-based compounds and 9,10-dioxyhydroanthracene-based compounds in an amount of 0.05 to 0.1% by weight (based on absolute dry chips), and 3% by weight (based on absolute dry chips) of Na ₂ SO ₃ as a reducing agent. dry chips)
The mixture was added and cooked at a maximum temperature of 165°C and a holding time of 70 minutes. At the same time, we conducted a comparative experiment to clarify its effects. The results are shown in Table 1. The chemicals added in Table 1 are the following compounds. A; 1,4,4a,9a-tetrahydro-9,10-diketoanthracene B; 1,4,4a,5,8,8a,9a,10a-octahydro-9,10-diketoanthracene C; 1, 4-dihydro-9,10-dioxyanthracene The same applies to each table below.

【table】

[Table] Cooking No. 1 used a normal kraft cooking liquor, and cooking No. 2 added only Na ₂ SO ₃ to the kraft cooking liquor. As is clear from this comparison, the presence of Na ₂ SO ₃ in a normal kraft cooking liquor impairs digestibility and reduces pulp yield.・For cooking Nos. 3, 5, 7, 9, and 11, only anthraquinone, anthrahydroquinone, 9,10-diketohydroanthracene-based compounds, or 9,10-dioxyhydroanthracene-based compounds were added to the Kraft cooking liquor; In cooking Nos. 4, 6, 8, 10, and 12, the above compound and Na ₂ SO ₃ were added together as a reducing agent. In normal kraft cooking liquor as mentioned above.
The presence of Na ₂ SO ₃ impairs digestibility, but when used in combination with anthraquinone compounds, anthrahydroquinone compounds, 9,10-diketohydroanthracene compounds, or 9,10-dioxyhydroanthracene compounds, Digestion progresses more than when the above-mentioned compound is added alone, and the pulp yield and pulp viscosity also improve. It can also be seen that as the cooking progresses further, the alkali addition rate can be significantly reduced. Among the above compounds, especially 9 according to the present invention,
10-diketohydroanthracene compound or 9,
The combined addition of a 10-dioxyhydroanthracene compound and a reducing aid is most effective. Examples 4 to 7 1700 g of puna chips (air-dried) were packed in an 8-volume autoclave, and 9,10-diketohydro was added to Kraft cooking liquor with an effective alkali of 13 to 14% (vs. bone dry chips), sulfidity of 25%, and liquid ratio of 4. 0.05 to 0.1% by weight of 1,4,4a,9a-tetrahydro-9,10-diketoanthracene (based on bone dry chips) is added as an anthracene compound, and 1 to 5% by weight of various reducing aids are added.
(vs. absolutely dry chips) and cooked at a maximum temperature of 165°C and a holding time of 70 minutes. The results are shown in Table 2. In addition, in order to clarify the effect, experimental examples are also listed in Table 1.

[Table] Cooking Nos. 7, 8, 13, and 14 show that increasing the addition rate of Na ₂ SO ₃ improves the digestibility and improves pulp yield and pulp quality. Cooking Nos. 15 and 16 show that Na ₂ S ₂ O ₃ and HCOONa have the same effect as Na ₂ SO ₃ as reducing aids. Examples 8-10 and Comparative Examples 10-18 1500 g of Douglas fir chips (air-dried) were packed in an 8-volume autoclave, and the effective alkali was 16-17%.
Add 0.1% by weight of various 9,10-diketohydroanthracene compounds or 9,10-dioxyhydroanthracene compounds to Kraft cooking liquor with a sulfidity of 25% and a liquid ratio of 4.5 (based on bone dry chips). bone dry chips)
Furthermore, 3% by weight of Na ₂ SO ₃ (relative to bone dry chips) was added as a reducing agent, and the maximum temperature was 170℃ and the holding time was 70~.
Cooked in 75 minutes. At the same time, a comparative experiment was conducted to clarify the effect. The results are shown in Table 3.

【table】

[Table] Cooking No. 17 used a normal kraft cooking liquor, and cooking No. 18 added Na ₂ SO ₃ to the kraft cooking liquor.
As is clear from these comparisons, the presence of Na ₂ SO ₃ has a negative effect on cooking even in conifers. Cooking
In Nos. 19, 21, 23, 25, and 27, only anthraquinone, anthrahydroquinone, 9,10-diketohydroanthracene-based compounds, or 9,10-dioxyhydroanthracene-based compounds were added to the Kraft cooking liquor; .20, 22, 24, 26, and 28 were added with the above compound and Na ₂ SO ₃ as a reduction aid. It can be seen that the combined addition of the above compound and reducing agent has the same effect on softwood as when applied to hardwood. As is clear from the above description, the present invention can be applied to other lignocellulosic materials such as coniferous or hardwood wood, as well as bamboo, hemp, straw, bagasse, etc. It has the effect of reducing the addition rate, improving pulp yield, improving pulp quality, and reducing the degree of sulfidation.

Claims (1)

[Claims] 1. When cooking lignocellulosic materials with a cooking liquor containing sodium sulfide and sodium hydroxide as main components, 9,10-diketohydroanthracene compounds and/or 9,10-dioxyhydr Anthracene compounds, sulfites, bisulfites,
A method for producing alkaline sulfide pulp, which comprises adding at least one reducing aid selected from the group consisting of thiosulfates and formates to the cooking liquor. 2 9,10-diketohydroanthracene-based compound is 1,4,4a,9a-tetrahydro-9,10-diketoanthracene or 1,4,4a,5,8,8a,
The method for pulping an alkali sulfide according to claim 1, wherein the alkali sulfide pulp is 9a,10a-octahydro-9,10-diketoanthracene. 3 9,10-dioxyhydroanthracene type compound is 1,4-dihydro-9,10-dioxyanthracene, 1,4,5,8-tetrahydro-9,10
-dioxyanthracene, 1,4,5,8,8a,
The method for pulping an alkali sulfide according to claim 1, wherein the pulp is 10a-hexahydro-9,10-dioxyanthracene or a sodium salt thereof. 4. The amount of 9,10-diketohydroanthracene compound and/or 9,10-dioxyanthracene compound is approximately
A process for pulping an alkali sulfide according to any one of claims 1 to 3, wherein the content is from 0.01 to about 5% by weight. 5. The alkali sulfide pulping method according to claim 1, wherein the reducing aid is a sodium or potassium sulfite salt, a sodium or potassium bisulfite salt, a sodium or potassium thiosulfate salt, a sodium or potassium formate salt. 6. The alkaline sulfide pulping method according to claim 1 or claim 5, wherein the amount of reducing aid is about 0.5 to about 5% by weight based on the bone-dry lignocellulosic material. 7. The alkali sulfidation pulping method according to claim 1, wherein the degree of sulfidation of the cooking liquor is about 5 to about 50%.