JP2019173241A - Digestion method of lignocellulosic material - Google Patents

Abstract

To provide a technology capable of efficiently alkali-digesting lignocellulosic materials.SOLUTION: In the method of alkali-digesting lignocellulosic material, the lignocellulosic material is efficiently digested and a pulp can be manufactured by digesting the lignocellulosic material using a cooking liquor added with nonionic surfactant and/or alkaline surfactant.SELECTED DRAWING: Figure 1

Description

  The present invention relates to cooking lignocellulosic materials.

Making a lignocellulosic material such as wood into a fiber is called cooking, and the lignin in the intercellular layer is eluted and the cellulose fibers are disaggregated by chemicals used for cooking. In the cooking of chemical pulp, bisulfite is used as a cooking chemical in the sulfite method, and alkaline chemicals such as sodium hydroxide are used in the soda method and craft method.In sulfite cooking, sulfite is combined with lignin at the beginning of cooking. Thus, lignin sulfonic acid is produced, and as the cooking proceeds, lignin sulfonic acid is hydrolyzed and sulfonated, and is eluted as a lignin sulfonate by the base cation.

  In alkaline cooking in the soda method and kraft method, alkaline chemicals such as sodium hydroxide (caustic soda) cleave the lignin phenyl ether to lower its molecular weight, and generate carboxyl groups and hydroxyl groups to become soluble and elute. Is done.

  At present, kraft pulp is the mainstream of chemical pulp, but several techniques have been proposed to improve the yield from the raw material, and for example, polysulfide method and quinone addition method are known. The polysulfide method is a technique for improving the yield by adding polysulfide to the KP cooking liquor. The quinone addition method is a technique for improving cooking efficiency using quinones such as anthraquinone as a cooking aid for KP.

  For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2010-37673) relating to a quinone addition method describes a method of cooking lignocellulose material using an alkaline cooking solution, and the lignocellulosic material as a pre-process of the lignocellulose material cooking step. It has been proposed to provide a step of heat-treating the lignocellulosic material at 80 to 120 ° C. in an alkaline solution containing an active alkali and a quinone compound with an active alkali addition rate of 1 to 5% with respect to the absolute dry weight of .

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-64888) proposes adding a nonionic surfactant to a lignocellulosic material in advance to improve cooking efficiency.

JP 2010-37673 A JP 2001-64888 A

  So far, regarding the method of cooking lignocellulosic material using alkaline cooking liquor, techniques for improving the yield have been proposed, but there is still a strong need for further yield improvement. In particular, when a quinone compound or the like is not used, it is difficult to obtain a low kappa number pulp with high efficiency.

  In view of such a situation, an object of the present invention is to provide a technology for producing a pulp of excellent quality by alkali-cooking a lignocellulosic material with high efficiency.

  As a result of intensive studies on the above problems by the present inventors, it has been found that the above problems can be solved by adding a nonionic surfactant and / or an anionic surfactant to the alkaline cooking liquid, and the present invention has been completed. I came to let you.

Although this invention is not limited to this, the following aspect is included.
(1) A method for producing pulp, comprising alkali-cooking a lignocellulosic material using a cooking solution to which a nonionic surfactant and / or an anionic surfactant is added.
(2) The method according to (1), wherein the lignocellulose material is a wood chip.
(3) The method according to (1) or (2), wherein cooking is performed without using an anthraquinone compound.
(4) The addition amount of the nonionic surfactant and / or the anionic surfactant is 0.001 to 2% by weight with respect to the lignocellulosic material, according to any one of (1) to (3). Method.

  By performing the present invention, it becomes possible to produce pulp more efficiently than conventional cooking methods. Conventionally, if a quinone compound is not added, it has been difficult to produce a low kappa number pulp in a high yield. However, according to the present invention, cooking can be efficiently performed without adding a quinone compound. That is, according to the present invention, if the kappa number and yield are made equal, the cooking temperature can be lowered, and if the cooking temperature and kappa number are equivalent, the yield can be raised, and the cooking temperature and yield are reduced. If it is the same, the copper number can be lowered.

  The details of the reason why the lignocellulosic material can be effectively cooked by the present invention are not completely clear, and the present invention is not bound by the following reasoning, but the penetration of white liquor is promoted by the surfactant. It is presumed that the cooking reaction progressed uniformly, and a pulp having a low kappa number (KN) could be efficiently produced.

FIG. 1 is a graph showing the percentage (%) when the active alkali addition rate is 13% (vertical axis: percentage percentage). FIG. 2 is a graph showing the kappa number when the active alkali addition rate is 14% (vertical axis: kappa number). FIG. 3 is a graph showing the relationship between the active alkali addition rate and the total yield.

BEST MODE FOR CARRYING OUT THE INVENTION

  The present invention relates to a technique for producing pulp by digesting lignocellulosic material. As the lignocellulose material which is a raw material of the present invention, for example, woods and herbs can be suitably used, and woods which are woody materials are preferred. As the wood-based lignocellulosic material, either softwood or hardwood can be suitably used, and the tree species is not particularly limited, and may be a single type of wood or a mixture of two or more types of wood. Good.

  In the present invention, high-quality pulp can be efficiently produced even for tree species that are relatively difficult to digest and bleach, such as conifers. As a coniferous material used in the present invention, for example, larch genus or pine genus wood can be suitably used. As for the genus Larix, for example, Larix (hereinafter abbreviated as L.) leptolepis (Larix), L. laricina (Tamarack), L. occidentalis (Larix larch), L. decidua (European larch), L. gmeliniii (Guimatsu) and the like. Conifers other than the genus Larix include, for example, Pinus radiata (Pinus radiata) for Pinus genus and Pseudotsuga (hereinafter abbreviated as P.) Regarding Cryptomeria japonica, such as japonica (Togasawara).

According to the present invention, high-quality pulp can be produced even using wood chips with a low apparent density. For example, in the present invention, the apparent density of the wood chips may be as low as 500 kg / m ³ or less, 450 kg / m ³ or less, and even 400 kg / m ³ or less, without any problem. Pulp can be produced.

(Alkali cooking step) In the present invention, the lignocellulosic material is cooked using an alkaline cooking solution to which a nonionic surfactant and / or an anionic surfactant is added.
Examples of the alkali cooking method in the present invention include a cooking method using a kraft method, a soda method, a sodium carbonate method, a polysulfide method, or the like. The cooking equipment may be either a continuous type or a batch type. Furthermore, as a cooking system, it can be applied to a modified kraft cooking (MCC), isothermal cooking (ITC) or low solid (Lo-solid) cooking in addition to the conventional continuous cooking method.

  The addition amount of the surfactant is, for example, 0.001 to 2% by weight, preferably 0.005 to 1.0% by weight, and particularly preferably 0.01 to 0. 5% by weight. When the addition amount is 0.001 to 2% by weight, the pulp yield and cooking speed can be improved while being economical. When using a nonionic surfactant and an anionic surfactant together, it is preferable that the sum of both is within the above numerical range.

  The surfactant added to the alkaline cooking liquor is not particularly limited as long as it is nonionic or anionic. A nonionic surfactant is a surfactant having a hydrophilic group that does not ionize in water, is not easily affected by the hardness of water or an electrolyte, and can be suitably used because it can be used in combination with other surfactants.

  As the nonionic surfactant, any of ester type, ether type, ester / ether type and the like can be used. The ester type nonionic surfactant is also called a polyhydric alcohol type and has a structure in which a polyhydric alcohol such as glycerin, sorbitol, or sucrose and a fatty acid are ester-bonded. The ether type nonionic surfactant has a structure in which an alkylene oxide such as ethylene oxide is added to a raw material having a hydroxyl group such as a higher alcohol or an alkylphenol. Preferred examples of the ether type nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol, and the like. The ester / ether type nonionic surfactant has a structure in which an alkylene oxide such as ethylene oxide is added to an ester composed of a polyhydric alcohol such as glycerin or sorbitol and a fatty acid. The ether type and ester / ether type nonionic surfactants may be collectively referred to as a polyethylene glycol type nonionic surfactant.

  As the anionic surfactant, for example, carboxylate, sulfonate, sulfate ester salt, phosphate ester salt and the like can be preferably used. Anionic surfactants are surfactants that ionize a portion having a hydrophobic group in water into negative (negative) ions, and many types have been known for a long time. Carboxylate anionic surfactants have long been widely used as soaps. Preferred examples of the sulfonate anionic surfactant include linear alkylbenzene sulfonate, α-sulfo fatty acid methyl ester salt (MES), α-olefin sulfonate, and dialkylsulfosuccinate. Can be mentioned. Examples of the anionic surfactant for the sulfate ester salt include alkyl sulfate ester salts obtained by sulfating higher alcohols, and polyoxyethylene alkyl sulfate ester sulfates obtained by adding alkylene oxides such as ethylene oxide to higher alcohols. Etc. can be mentioned as a suitable example. Also, phosphate esters such as higher alcohols and their alkylene oxide adducts can be suitably used in the present invention.

  The nonionic surfactant of the present invention preferably has an HLB of 6 to 18, particularly preferably 10 to 16.5. When the HLB is 6 to 18, a higher penetration effect can be obtained. Here, HLB (Hydrophile-Lipophile Balance) is HLB calculated by adding up the numerical value which shows organic property and inorganic property.

The cooking liquor preferably has an active alkali addition rate (AA) per 10% dry wood chip weight of 10 to 35% by mass. If the active alkali addition rate is less than 10% by mass, the removal of lignin and hemilulose becomes insufficient, and if it exceeds 35% by mass, the yield and quality deteriorate. Here, the active alkali addition rate is obtained by converting the total addition rate of NaOH and Na ₂ S as the addition rate of Na ₂ O, and multiplying NaOH by 0.775 and Na ₂ S by 0.795. Therefore, it can be converted into the addition rate of Na ₂ O. The degree of sulfidation is preferably in the range of 20 to 35%. In the region where the sulfidity is less than 20%, the delignification property is lowered, the pulp viscosity is lowered, and the drought rate is increased.

  In the present invention, the lignocellulosic material can be cooked using a known apparatus. In the present invention, cooking can be performed by putting the lignocellulosic material into a pressure-resistant reaction vessel (a digester) together with a cooking solution (a cooking chemical). The shape and size of the container are not particularly limited and may be cooked under known conditions. For example, you may use for cooking of correction craft methods, such as MCC, EMCC, ITC, and Lo-solid. Also, there are no particular limitations on cooking types such as 1 vessel liquid phase type, 1 vessel gas phase / liquid phase type, 2 vessel liquid phase / gas phase type, and 2 vessel liquid phase type. Furthermore, the device for impregnating and holding the cooking chemical can also be provided separately from the digester.

  In the cooking step, the ratio of lignocellulosic material such as wood chips and alkaline cooking liquid (amount of cooking chemical per kg of lignocellulosic material) can be, for example, 1.0 to 5.0 L / kg. 0.5 to 4.5 L / kg is preferable, and 2.0 to 4.0 L / kg is more preferable. Moreover, it is preferable to perform cooking in the temperature range of 120-180 degreeC, and 140-170 degreeC is more preferable. If the temperature is too low, delignification (decrease in the kappa number) is insufficient, while if the temperature is too high, the degree of polymerization (viscosity) of cellulose decreases. The cooking time in the present invention is the time from when the cooking temperature reaches the maximum temperature until the temperature starts to drop, and the cooking time is preferably 60 minutes to 600 minutes, preferably 120 minutes to 360 minutes. Further preferred. If the cooking time is less than 60 minutes, pulping does not proceed, and if it exceeds 600 minutes, the pulp production efficiency deteriorates, which is not preferable.

  Moreover, the kraft cooking in this invention can set process temperature and process time by setting H factor (Hf) as a parameter | index. The H factor is a standard representing the total amount of heat given to the reaction system in the cooking process, and is represented by the following equation. The H factor is calculated by time integration from the time when chips and water are mixed until the end of cooking. The H factor is preferably 300 to 2000.

Hf = ∫exp (43.20-16113 / T) dt
[Wherein T represents an absolute temperature at a certain point]
Moreover, in this invention, although a quinone compound may be added to an alkaline cooking liquid, it is not necessary to add it. When adding a quinone compound, you may add the alkaline cooking liquid containing 0.01-1.5 mass% quinone compound with respect to the absolute dry weight of a raw material, for example to a digester. If the addition amount of the quinone compound is less than 0.01% by mass, the addition amount is too small to reduce the kappa number of the pulp after cooking, and the relationship between the kappa number and the pulp yield is not improved. Furthermore, the reduction of wrinkles and the suppression of the decrease in viscosity are insufficient. Moreover, even if the addition amount of a quinone compound exceeds 1.5 mass%, the further reduction of the kappa number of the pulp after cooking and the improvement of the relationship between a kappa number and a pulp yield are not recognized.

  The quinone compound used is a quinone compound, hydroquinone compound or precursor thereof as a so-called known cooking aid, and at least one compound selected from these can be used. Examples of these compounds include anthraquinone, dihydroanthraquinone (for example, 1,4-dihydroanthraquinone), tetrahydroanthraquinone (for example, 1,4,4a, 9a-tetrahydroanthraquinone, 1,2,3,4-tetrahydroanthraquinone). Methyl anthraquinone (eg 1-methyl anthraquinone, 2-methyl anthraquinone), methyl dihydroanthraquinone (eg 2-methyl-1,4-dihydroanthraquinone), methyl tetrahydroanthraquinone (eg 1-methyl-1,4,4a) , 9a-tetrahydroanthraquinone, 2-methyl-1,4,4a, 9a-tetrahydroanthraquinone) and the like, anthrahydroquinone (generally 9,10-dihydroxyanthracene), Tyranthrahydroquinone (for example, 2-methylanthrahydroquinone), dihydroanthrahydroanthraquinone (for example, 1,4-dihydro-9,10-dihydroxyanthracene) or an alkali metal salt thereof (for example, disodium salt of anthrahydroquinone, 1 , 4-dihydro-9,10-dihydroxyanthracene disodium salt), and precursors such as anthrone, anthranol, methylanthrone, and methylanthranol. These precursors have the potential to convert to quinone compounds or hydroquinone compounds under cooking conditions.

  In a preferred embodiment, the unbleached pulp that has been cooked can be washed with a washing device such as a diffusion washer after discharging the cooking liquor. In the case of softwood, the copper value of unbleached pulp is preferably 8 to 22, for example, and may be 12 to 20. In the case of hardwood, for example, it is preferably 5-20, and may be 6-16.

(pre-process)
In the present invention, the lignocellulosic material can be hydrolyzed as a pretreatment before cooking (prehydrolysis). By prehydrolysis, it becomes easy to decompose and remove the hemicellulose content in the lignocellulosic material into water-soluble sugars. Pre-hydrolysis is carried out by treating the raw material with high-temperature water, but the water to be added may be in the form of hot water or steam. Since an organic acid or the like is generated by the progress of hydrolysis, the pH of the treatment liquid is generally 2 to 5.

  The prehydrolysis treatment is preferably performed in a temperature range of 150 to 180 ° C. If temperature is less than 150 degreeC, removal of hemicellulose will become inadequate, and when it exceeds 180 degreeC, hydrolysis will become excess and alpha-cellulose content will also fall. The treatment time is not particularly limited, but is preferably 30 to 400 minutes, more preferably 35 to 250 minutes, and further preferably 40 to 150 minutes. When the treatment time is too short, the removal of hemicellulose becomes insufficient, and the delignification improving effect due to the removal of hemicellulose is also reduced. On the other hand, if the treatment time is too long, hydrolysis becomes excessive and the α-cellulose content is reduced, resulting in a decrease in pulp yield, and condensing of lignin causes deterioration in digestibility in the subsequent cooking step.

  In the prehydrolysis treatment in the present invention, the treatment temperature and treatment time can be set using the P factor (Pf) as an index. The P-factor is a standard that represents the total amount of heat given to the reaction system in the prehydrolysis treatment, and is expressed by the following formula in the present invention, and is digested from the time when the lignocellulosic material (wood chips) and water are mixed. Calculated by time integration until the end point.

Pf = ∫ln-1 (40.48-15106 / T) dt
[Wherein T represents an absolute temperature at a certain point]
The prehydrolysis treatment in the present invention is preferably performed in a range where the P factor (Pf) is 350 to 800. If it is less than Pf350, the removal of hemicellulose will become inadequate, and the delignification improvement effect by removing hemicellulose will also decrease. On the other hand, if it exceeds Pf800, hydrolysis becomes excessive and the α-cellulose content is reduced, resulting in a decrease in pulp yield, and condensing of lignin leads to deterioration in digestibility in the subsequent kraft cooking process.

  The prehydrolysis step can be performed by putting wood chips and water in a pressure resistant container (prehydrolysis kettle), but the shape and size of the container are not particularly limited. The liquid ratio of wood chips and water in the prehydrolysis kettle can be, for example, 1.0 to 5.0 L / kg, preferably 1.5 to 4.5 L / kg, and 2.0 to 4. 0 L / kg is more preferable. If the liquid ratio is less than 1.0 L / kg, hydrolysis is insufficient because the amount of water is too small relative to the wood chips, and if the liquid ratio exceeds 5.0 L / kg, the size of the container becomes excessive. Therefore, it is not preferable. Moreover, you may add a small amount of mineral acid as needed.

  In the present invention, for example, after the prehydrolysis step, a step of washing and recovering the lignocellulose material with water may be provided. Insufficient cleaning can cause adverse effects in subsequent cooking steps. Washing and removal of the hydrolyzed liquid can be performed by using a general solid-liquid separator. For example, an extraction screen can be provided in a container used for prehydrolysis, and washing water can be introduced from the lower part of the container and extracted from the screen for countercurrent washing.

(Post-process)
In the present invention, the unbleached pulp obtained by cooking can be subjected to various treatments as necessary.

  In one preferred embodiment, oxygen delignification treatment can be performed on pulp obtained by cooking. As the oxygen delignification used in the present invention, a known medium concentration method or high concentration method can be applied as it is. In the case of the medium concentration method, the pulp concentration is preferably 8 to 15% by mass, and in the case of the high concentration method, it is preferably performed at 20 to 35% by mass. As the alkali in oxygen delignification, sodium hydroxide and potassium hydroxide can be used. As oxygen gas, oxygen from a cryogenic separation method, oxygen from PSA (Pressure Swing Adsorption), VSA (Vacuum Swing Adsorption) Oxygen etc. from) can be used.

The reaction conditions for the oxygen delignification treatment are not particularly limited, but the oxygen pressure is 3 to 9 kg / cm ² , more preferably 4 to 7 kg / cm ² , the alkali addition rate is 0.5 to 4% by mass, and the temperature is 80%. ~ 140 ° C, treatment time is 20 to 180 minutes, and other conditions can be applied. In the present invention, the oxygen delignification treatment may be performed a plurality of times.

  The pulp that has been subjected to the oxygen delignification treatment is then sent to a washing step, and after washing, it is sent to a multistage bleaching step to perform a multistage bleaching treatment. The multi-stage bleaching treatment of the present invention is not particularly limited, but acid (A), chlorine dioxide (D), alkali (E), oxygen (O), hydrogen peroxide (P), ozone (Z), It is preferable to combine a known bleaching agent such as peracid and a bleaching aid. For example, the first stage of the multistage bleaching process uses a chlorine dioxide bleaching stage (D) or an ozone bleaching stage (Z), the second stage is an alkali extraction stage (E), the hydrogen peroxide stage (P), the third stage or later. A bleaching sequence using chlorine dioxide or hydrogen peroxide is preferably used. The number of stages after the third stage is not particularly limited, but considering energy efficiency, productivity, etc., it is preferable to finish in three or four stages in total. Further, a chelating agent treatment stage with ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) or the like may be inserted during the multistage bleaching treatment.

  Since hemicellulose and various phenols are removed from the pulp produced by the present invention, high-quality dissolved kraft pulp can be easily produced by ordinary oxygen delignification treatment or bleaching treatment.

  Hereinafter, the present invention will be described in more detail while showing specific experiments, but the present invention is not limited to the following specific examples. In the present specification, unless otherwise specified, concentrations and the like are based on weight, and numerical ranges are described as including the end points.

KP cooking of wood chips (Example 1)
Japanese hardwood chips were sieved using a sieving machine (gyro shifter) to obtain wood chips having a size of 9.5 to 25.4 mm. Using a rotary autoclave (volume: 2.5 L), an alkaline cooking chemical solution was added to 300 g of this wood chip so that the liquid ratio was 2.5 (L / kg). 25% conditions, that is, 29.3 g of NaOH and 9.8 g of Na ₂ S (each converted to Na ₂ O), cooking time 120 minutes, cooking temperature 160 ° C., H factor (HF) 800 The alkali digestion was performed under the conditions of In this experiment, a nonionic surfactant (PENSURF 74428 manufactured by NALCO) was mixed and added to the cooking chemical solution as a cooking aid in an amount of 0.03% to chips.

(Example 2)
Digestion was performed in the same manner as in Example 1 except that the active alkali addition rate was 14%.
(Example 3)
Cooking was performed in the same manner as in Example 1 except that the cooking temperature was 158 ° C.

(Example 4)
Digestion was performed in the same manner as in Example 3 except that the active alkali addition rate was 14%.
(Example 5)
Cooking was carried out in the same manner as in Example 1 except that the nonionic surfactant was an anionic surfactant (polyoxyethylene copolymer ester, DynaSpers 40 manufactured by Plasmine Technology).

(Example 6)
Digestion was carried out in the same manner as in Example 5 except that the active alkali addition rate was 14%.
(Example 7)
Cooking was carried out in the same manner as in Example 1, except that the nonionic surfactant was changed to a nonionic surfactant (alkylphenol ethoxylate, AmiSperse AP8566 manufactured by AMAZON).

(Example 8)
Digestion was performed in the same manner as in Example 7 except that the active alkali addition rate was 14%.
(Comparative Example 1)
Cooking was performed in the same manner as in Example 1 except that the nonionic surfactant was not added to the cooking chemical as a cooking aid.

(Comparative Example 2)
Cooking was performed in the same manner as in Example 2 except that the nonionic surfactant was not added to the cooking chemical as a cooking aid.

Various analyzes and total yield (%): The yield was calculated from the absolute dry weight of wood chips before cooking and the absolute dry weight of unbleached pulp obtained after cooking.
-Fraction rate: The unbleached pulp obtained after cooking was carefully selected with a flat screen (6 cuts: 0.15 mm), and the ratio of the absolute dry weight was calculated using the residue that did not pass through the screen as the culm.
Pulp Kappa Number (KN): The pulp kappa number was measured according to JIS P 8221.

  As shown in Table 1, when compared with the case where no surfactant is used (Comparative Examples 1 and 2), when nonionic surfactant or anionic surfactant is added to the cooking chemical, It was found that the generation of soot was greatly reduced at the same active alkali addition rate, and the resulting pulp had a lower copper.

Moreover, in Examples 3-4, generation | occurrence | production of soot was suppressed by the same active alkali addition rate compared with the case where surfactant is not used, although the cooking temperature was lowered | hung, Copper numbers were comparable.

Claims (4)

  A method for producing pulp, comprising alkali-cooking a lignocellulosic material using a cooking liquid to which a nonionic surfactant and / or an anionic surfactant is added.   The method of claim 1, wherein the lignocellulosic material is wood chips.   The method according to claim 1 or 2, wherein the cooking is carried out without using an anthraquinone compound. The method in any one of Claims 1-3 whose addition amount of nonionic surfactant and / or anionic surfactant is 0.001-2 weight% with respect to a lignocellulose material.

Images