JP2018204158A - Production method of dissolved pulp from lignocellulose-based raw material - Google Patents

Abstract

To provide a production method of a dissolved pulp from a lignocellulose, capable of increasing cellulose content with an easy method.SOLUTION: The production method of a dissolved pulp contains pre-hydrolysis treatment of a lignocellulose, followed by digestion, and is characterized by that the pulp after digestion of the lignocellulose is subjected to xylanase treatment.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a dissolving pulp from a lignocellulosic material.

  Dissolving pulp is used in various applications as a raw material for cellulose, which is a polymer. In order to produce a dissolving pulp from a lignocellulosic material, it is necessary to selectively remove hemicellulose and lignin in the lignocellulosic material to increase the cellulose purity. As an index representing cellulose purity, α-cellulose content is generally used, and the higher the value, the higher the quality of dissolved pulp. Furthermore, the pulp viscosity, which is an index of cellulose polymerization degree, and pulp whiteness, which is an index of residual lignin, are important as the quality of dissolved pulp.

  The main constituent molecules of lignocellulose are cellulose, hemicellulose, and lignin, but a higher content of cellulose in the dissolved pulp is preferable because it is suitable for producing rayon, acetate, and the like. For this reason, conventionally, as described in Non-Patent Document 1, in order to remove insoluble components of dissolved pulp after pulping, dehemicellulose treatment with an aqueous alkaline solution has been performed.

  However, when the dehemicellulose treatment step is performed, there is a problem that the number of steps increases, for example, a washing step is required after the alkali treatment.

Sulfurous pulp and dissolving pulp (Journal of Paper Pulp Technology Association) Issued November 15, 1966, pages 373-374

  The subject of this invention is providing the manufacturing method of the melt | dissolution pulp from lignocellulose which can increase content of a cellulose with a simple method.

  As a result of intensive studies to solve the above problems, the present inventors have determined that the content of cellulose in the dissolved pulp is obtained by subjecting the lignocellulosic system to a xylanase treatment after the prehydrolysis treatment and the digested pulp. And the following invention was completed.

  In order to solve the above problems, the present invention includes the following inventions.

  Item 1. A method for producing dissolved pulp by preliminarily hydrolyzing lignocellulose and producing dissolved pulp, wherein the digested pulp is treated with xylanase.

  Item 2. Item 2. The method for producing dissolved pulp according to Item 1, wherein the digested pulp is bleached and then treated with xylanase.

  Item 3. Item 3. The method for producing a dissolving pulp according to Item 1 or 2, wherein the xylanase treatment is performed at 30 ° C to 80 ° C.

  Item 4. Item 4. The dissolving pulp production method according to any one of Items 1 to 3, wherein R-10 of the dissolving pulp is 96% or more.

  Item 5. Treating the pulp with xylanase includes adding 5-500 U xylanase to 1 g (absolute dry weight) of the pulp, The dissolved pulp according to any one of claims 1 to 4 Manufacturing method.

It is a figure which shows the apparatus for enforcing the manufacturing method of the dissolving pulp from the lignocellulose of this invention.

The method for producing a dissolving pulp of the present invention is a method for producing a dissolving pulp by prehydrolyzing lignocellulose and then digesting the lignocellulose, wherein the pulp after cooking is treated with a xylanase.
<Lignocellulose raw material>
As the lignocellulosic raw material used as a raw material in the method of the present invention, as woody material, chips or bark of papermaking trees, forest land residual materials, thinned wood, sawdust or sawdust generated from lumber mills, etc., pruning roadside trees Branches and leaves, building waste, etc., and herbaceous agricultural waste such as kenaf, rice straw, straw, corn cob, bagasse, etc., and residue and waste of industrial crops such as oil crops and rubber (for example, EFB: Empty Fruit Bunch) ), Herbaceous energy crops Eliansus, Miscanthus and Napiergrass. In addition, wood-derived paper, waste paper, pulp, pulp sludge, sludge, sewage sludge, and other food wastes can be used as the lignocellulosic raw material. These lignocelluloses can be used alone or in combination. Lignocellulose can be used as a dry solid, a solid containing water, or a slurry.

  Examples of the woody lignocellulosic material include Eucalyptus genus plants, Acacia genus plants, Salix genus plants, Populus genus plants, and Cryptomeria genus plants. Eucalyptus plants, Acacia plants, and Willow plants are preferable because they can be easily collected in large quantities as raw materials. In particular, Eucalyptus globulus and Eucalyptus pelleta are used as Eucalyptus plants, Acacia mangium and Acacia auris are used as Acacia species, and Acacia mangium and Acaciaurium species are used preferable.

Among the lignocellulosic raw materials derived from woody plants, it is preferable to use forest residue (including bark and leaves) and bark. For example, bark of tree species such as Eucalyptus genus or Acacia genus commonly used for papermaking raw materials can be obtained in large quantities stably from lumber mills and chip factories for papermaking raw materials. Preferably used.
<Mechanical processing>
In the present invention, it is desirable to perform mechanical treatment on the lignocellulosic raw material. The mechanical treatment is performed to make lignocellulose easy to be saccharified in the next chemical treatment step (cooking step). Examples of the mechanical treatment include any mechanical means such as cutting, cutting, crushing, and grinding. Although it does not specifically limit about the mechanical apparatus to be used, For example, a cutting device, a uniaxial crusher, a biaxial crusher, a hammer crusher, a refiner, a kneader, a ball mill etc. can be used.

  As a pre-process or post-process of the mechanical treatment, a foreign matter removing step by washing or the like for removing foreign matter (foreign matter other than lignocellulose such as stone, dust, metal, plastic) can be introduced.

  Examples of the method for washing the raw material include a method of removing water from the foreign material mixed with the raw material by spraying water on the raw material, or a method of removing the foreign material by immersing the raw material in water and sedimenting the foreign material. Moreover, the method of isolate | separating a foreign material from a raw material using apparatuses, such as a metal trap, is mentioned.

If foreign materials are included in the raw material, there is a possibility of damage to equipment parts used in mechanical processing such as refiner discs (plates), and problems such as causing troubles in the manufacturing process such as clogging of piping. Therefore, it is desirable to introduce a foreign substance removing step.
<Prehydrolysis>
In the method of the present invention, the lignocellulosic raw material is chemically treated, that is, cooked, but the lignocellulosic raw material is prehydrolyzed before the cooking treatment. By prehydrolysis, pentoses such as xylose and furfurals contained in the lignocellulosic raw material can be liberated from lignocellulose.

  In the present invention, the lignocellulosic raw material is first heated in the presence of water to perform a prehydrolysis treatment. The amount of water (liquid ratio) with respect to the lignocellulosic raw material when performing the prehydrolysis treatment is a mass ratio, preferably 1 to 10, and more preferably 1.5 to 5. By setting the liquid ratio to 1 or more, water is insufficient and hydrolysis does not proceed sufficiently, and the reaction is prevented from becoming non-uniform. By setting it to 10 or less, it is possible to prevent the amount of heat required for heating to a desired temperature from increasing, and to perform the reaction economically. The method of adding water is not particularly limited, and water may be added from the outside, water originally contained in the lignocellulosic raw material may be used, or when steam is used during heating For this, water contained in steam may be used. In addition to water, chemicals that directly or indirectly assist the hydrolysis of polysaccharides, such as alkalis, acids, and chelating agents, can also be added.

In the prehydrolysis treatment, the treatment temperature and treatment time can be set using the P factor (Pf) as an index. 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. The temperature and time from the time when the chip and water are mixed to the time when the prehydrolysis is completed. Is calculated by integrating.

(Where T is the absolute temperature (° C. + 273.5), kH ₁ (T) / k _{100 ° C.} represents the relative rate of acid hydrolysis of the glycosidic bond)
The prehydrolysis treatment in the present invention is preferably performed in a range where the P factor (Pf) is 200 to 1400.

  By setting the P factor to 200 or more, acid hydrolysis of hemicellulose can be sufficiently performed. If acid hydrolysis is insufficient, the subsequent kraft cooking is not suitable because the cellulose purity of the pulp cannot be sufficiently increased. By making P factor 1400 or less, the fall of the pulp viscosity by the acid hydrolysis of a cellulose advances is prevented. Lowering the pulp viscosity is not suitable because the pulp yield is also lowered.

  As a prehydrolysis apparatus used in the prehydrolysis, for example, as shown in FIG. 1, a raw material suspension composed of a lignocellulosic raw material and water was hydrolyzed with a supply port to which the raw material supply line 1 is connected. In the intermediate part between the discharge port to which the discharge line 4 for discharging the lignocellulosic material is connected, and the supply port for the raw material suspension and the discharge port for the hydrolysis treatment suspension, Tower-type pre-hydrolysis having an intermediate outlet G1 equipped with a solid-liquid separation device S1 capable of continuously separating and taking out a hydrolyzed liquid composed mainly of an aqueous solution mainly containing a pentose such as xylose. An example of the decomposition device PR is given.

  In the apparatus of FIG. 1, the lignocellulosic raw material is continuously supplied into the pressurization / heat hydrolysis apparatus PR in the form of an aqueous suspension from the supply port to which the raw material supply line 1 is connected. It moves in the apparatus while receiving the treatment, and is continuously discharged as a hydrolyzed suspension containing hydrolyzed lignocellulose from the outlet to which the other hydrolyzed suspension discharge line 4 is connected. In addition, a hydrolyzate containing a water-soluble hydrolysis product from the hydrolyzed suspension that moves through the apparatus by the solid-liquid separation apparatus S1 installed in the intermediate part of the apparatus from the supply port to the discharge port. A portion of the decomposition treatment liquid is separated and continuously taken out from the apparatus intermediate outlet G1 to the transfer line 3 while maintaining the pressure and temperature of the hydrolysis treatment.

  The intermediate outlet G1 of the prehydrolyzer PR is optional as long as it is between the supply port to which the raw material supply line 1 is connected and the discharge port to which the line 4 containing hydrolyzed lignocellulose is connected. It can be attached at the position. An aqueous solution mainly containing a pentose or the like can be taken out from an intermediate outlet G1 attached at an arbitrary position.

  In the prehydrolysis apparatus PR of FIG. 1, only one intermediate outlet G1 is provided on the side surface of the cylindrical portion of the prehydrolysis apparatus PR. However, this intermediate outlet is not limited to one place and is provided at two places. It can also be provided in the above positions. For example, it may be a hydrolysis apparatus provided with a second intermediate outlet capable of separating only the hydrolysis treatment liquid portion and taking it out of the apparatus at a position below the intermediate outlet G1. Further, for example, an aqueous liquid supply port may be provided between the first intermediate outlet and the second intermediate outlet, and the aqueous liquid may be supplied into the prehydrolyzer PR as necessary.

  As the solid-liquid separator S1, a strainer or a filter having a mesh (mesh) in the range of 10 μm to 5 cm is employed. As the strainer, a strainer in the range of 40 to 500 μm is preferably employed in order to avoid clogging troubles and avoid the entrainment of suspended substances in the separated aqueous solution as much as possible.

  As shown in FIG. 1, the cleaning liquid is supplied from the cleaning liquid supply device W1 to the bottom of the prehydrolyzer PR through the cleaning liquid supply line 2, and is moved from the intermediate outlet G1 of the prehydrolyzer PR to the bottom outlet. Counter-current contact with the hydrolyzed suspension. The cleaning liquid from the cleaning liquid supply line 2 may be supplied continuously or intermittently. As the cleaning liquid from the cleaning liquid supply line 2, it is desirable to use an aqueous solution containing water or acid, but there is no particular limitation as long as it does not adversely affect the hydrolysis treatment liquid taken out from the intermediate outlet G <b> 1 to the transfer line 3. Can be used. The cleaning liquid supplied to the bottom moves from the lower part to the upper part in the direction opposite to the moving direction of the hydrolyzate, and is mixed with the hydrolyzed liquid from the intermediate outlet G1 equipped with the solid-liquid separator S1 in the middle of the apparatus. It is taken out to the transfer line 3.

By adopting the counter-current washing operation as described above, the hydrolyzed raw material suspension moving from the upper part to the lower part can be separated into the raw material and the hydrolyzed liquid by the solid-liquid separator S1. Since saccharides mainly containing pentose saccharide during the hydrolysis treatment are transferred to the washing liquid and can be recovered as a hydrolysis treatment liquid taken out to the transfer line 3, it is accompanied by the hydrolysis-treated raw material and is prehydrolyzed. There is an advantage that the loss of the raw material discharged from the line 4 at the bottom of the apparatus PR is suppressed.
(Continuous hydrolysis conditions)
In the method of the present invention, the hydrolysis treatment in the prehydrolysis apparatus PR can be performed using a method such as hot water treatment, acid treatment, alkali treatment under pressure, and the generated pentoses and the like are efficiently used. In order to recover the target, treatment with water or an acid aqueous solution under pressure or heating is desirable. In the case of treatment with water under pressure and heating, lignocellulose is mixed with water and hydrolyzed by pressurization and heating. As a method for the acid aqueous solution treatment, lignocellulose is mixed with water containing an acid, and hydrolyzed by pressurization and heating. The acid used in the acid aqueous solution treatment is not particularly limited, and sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, oxalic acid, and the like can be used.

  The pH of the aqueous suspension containing lignocellulose used for the prehydrolysis treatment is preferably in the range of 0.5 to 5. Although it can carry out at 120-250 degreeC as a temperature of a hydrolysis process, 140-230 degreeC is preferable and 150-190 degreeC is more preferable. By setting the prehydrolysis temperature to 120 ° C. or higher, the reaction time can be reduced to 10 hours or shorter. When the reaction time exceeds 10 hours, it is not economical because a huge reaction vessel needs to be prepared. On the other hand, if the prehydrolysis temperature is higher than 250 ° C., depending on the lignocellulosic material used, the reaction time needs to be 0.1 hour or less, which makes it difficult to control the reaction. Since the material of the device that can withstand is expensive, it is not economically suitable.

  The hydrolysis treatment pressure is preferably 0.35 MPa to 2.8 MPa. The mass ratio of the aqueous liquid to be mixed with lignocellulose and lignocellulose (the ratio of aqueous liquid / lignocellulose, also referred to as “liquid ratio”) is preferably in the range of 1 to 10, and more preferably 1.5 to 5. An aqueous suspension raw material is prepared by mixing lignocellulose and an aqueous liquid, supplied to a hydrolysis apparatus, and hydrolyzed at a predetermined temperature and pressure in the hydrolysis apparatus.

  The hydrolysis treatment time of lignocellulose can be appropriately selected according to the type of lignocellulose, the temperature in the hydrolysis apparatus PR, and the like. For example, when the hydrolysis treatment is performed at 140 to 230 ° C., the hydrolysis treatment time is appropriately selected within the range of 0.5 to 180 minutes. By the hydrolysis treatment under the above conditions, a hydrolysis treatment suspension comprising a hydrolysis treatment lignocellulose mainly composed of cellulose and a pentose, which is a hydrolysis product derived from lignocellulose, and the like. A turbid liquid is obtained.

The hydrolysis treatment liquid taken out from the intermediate outlet G1 contains components including pentose sugars, furfurals and the like. The furfurals contained in this hydrolysis treatment liquid can be purified, and ethanol can also be produced from the pentose using this hydrolysis treatment liquid as a raw material using a pentose-fermenting microorganism.
<Digestion>
The raw material that has been subjected to the prehydrolysis treatment (the raw material suspension discharged from the discharge port of the prehydrolyzer) to the discharge line 4 is then digested by the digester D.

  As the cooking used in the present invention, known cooking methods such as kraft cooking, polysulfide cooking, soda cooking, alkali sulfite cooking and the like can be used, but considering pulp quality, energy efficiency, etc., the kraft cooking method is used. Preferably used. For example, in the case of kraft cooking of wood, the sulfidity of the kraft cooking liquor is 5 to 75%, preferably 15 to 45%, and the effective alkali addition rate is 5 to 30% by weight, preferably 10 to 25, per weight of absolutely dry wood. Perform by weight percent. The cooking method may be either a continuous cooking method or a batch cooking method. When a continuous cooking kettle is used, it may be a modified cooking method in which a cooking solution is added at multiple points, and the method is not particularly limited.

  For cooking, one or more alkali chemicals selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate and sodium hydrogencarbonate, or one or more alkalis selected from sodium sulfite and the above alkaline chemicals are used. Chemicals, sodium sulfite, sodium sulfide and the like can be used, but one or more alkaline chemicals selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate and sodium hydrogen carbonate, or sodium sulfite and the alkali It is preferable to use one or more alkaline chemicals selected from chemicals.

  The amount of chemicals used in cooking can be arbitrarily adjusted according to the situation, but from the viewpoint of reducing the cost of chemicals, and also from the viewpoint of preventing yield loss due to cellulose elution and over-decomposition, lignocellulosic raw materials It is desirable that it is 50 mass parts or less with respect to 100 mass parts of absolutely dry. Although the immersion time and the processing temperature of the chemical | medical agent in digestion can be arbitrarily set with the raw material and chemical | medical agent to be used, processing time 20-300 minutes and the processing temperature 80-230 degreeC are preferable. By tightening the processing conditions, elution or excessive decomposition of cellulose in the raw material may occur, so the processing time is preferably 120 minutes or less. The treatment temperature is preferably 180 ° C. or lower.

  As shown in FIG. 1, the cooking device D has a supply port to which a discharge line 4 is connected and a discharge port to which a discharge line 7 for discharging a lignocellulosic raw material suspension subjected to cooking is connected. And a solid solution capable of continuously separating and taking out the cooking liquor (black liquor) from the cooking suspension at an intermediate portion between the raw material suspension supply port and the cooking suspension discharge port. A tower-type digester D having an intermediate outlet G2 equipped with a liquid separator S2 may be mentioned.

  The raw material that has been prehydrolyzed is continuously supplied into the digester D in the form of an aqueous suspension from the supply port to which the discharge line 4 is connected, and moves through the apparatus while undergoing digestion. It is continuously discharged as a suspension containing lignocellulose that has been digested from the discharge port to which the discharge line 7 at the bottom of the tube is connected, and is installed in the middle of the apparatus from the supply port to the discharge port. The cooking liquor (black liquor) is separated from the raw material suspension moving in the apparatus by the solid-liquid separation device S2 and is continuously fed from the intermediate outlet G2 to the transfer line 6 while maintaining the pressure and temperature of the cooking process. It is taken out.

  The intermediate outlet G2 of the cooking apparatus D is optional as long as it is between the supply port to which the discharge line 4 is connected and the discharge port to which the discharge line 7 for discharging the cooked raw material suspension is connected. It can be attached at the position. By removing the cooking liquor from the intermediate outlet G2 attached at an arbitrary position, the raw material and the cooking liquor can be efficiently separated.

  As the solid-liquid separator S2, a strainer or a filter having a mesh (mesh) in the range of 10 μm to 5 cm is employed. As the strainer, a strainer in the range of 40 to 500 μm is preferably employed in order to avoid clogging troubles and avoid the entrainment of suspended substances in the separated aqueous solution as much as possible.

  As shown in FIG. 1, the raw material suspension is supplied from the cleaning liquid supply device W2 to the bottom of the digester D through the cleaning liquid supply line 5 and moves from the intermediate outlet G2 of the digester D to the bottom outlet. It can be in countercurrent contact with the liquid. The cleaning liquid from the cleaning liquid supply line 5 may be supplied continuously or intermittently. As the cleaning liquid from the cleaning liquid supply line 5, it is desirable to use an aqueous solution containing water or acid. However, the raw material suspension moving in the digester or the steaming liquid taken out from the intermediate outlet G <b> 2 to the transfer line 6 is used. Any aqueous solution that does not have an adverse effect can be used without particular limitation. The cleaning liquid supplied to the bottom moves from the lower part to the upper part in the direction opposite to the moving direction of the raw material, and is taken out as a cooking liquid to the transfer line 6 from an intermediate outlet G2 provided with a solid-liquid separator S2 in the middle of the cooking apparatus. .

  By employing the counter-current washing operation as described above, the raw material and the cooking liquid can be separated from the cooked raw material suspension moving from the upper part to the lower part by the solid-liquid separator S2. Since the cooking liquor is transferred from the raw material being cooked into the washing liquid and can be recovered as the cooking liquid taken out to the transfer line 6, it is discharged from the discharge line 7 at the bottom of the cooking apparatus D along with the lignocellulose that has been cooked. There is a merit that the loss of the raw material is suppressed.

At least a part of the cooking liquid taken out from the intermediate outlet G2 may be circulated to the supply port of the cooking device D. By circulating, the amount of chemicals used in cooking can be reduced, so the cost is reduced. Further, at least a part of the cooking liquor can be transferred to an energy recovery device such as a boiler to recover energy from the cooking liquor.
<Oxygen delignification process>
In the present invention, the pulp after cooking can be subjected to oxygen delignification treatment. A known method can be used for the oxygen delignification treatment, and the conditions are not particularly limited. As conditions for general oxygen delignification treatment, the oxygen gas addition rate is 0.5 to 3% by mass per the dry pulp mass, the alkali addition rate is 0.5 to 4% by mass, and the reaction temperature is 80 to 120. C., the reaction time is 15 to 100 minutes, and the pulp concentration is 8 to 15% by mass.
<Bleaching process>
In order to bleach the pulp after the above digestion or oxygen delignification treatment and remove residual lignin, it is preferable to bleach the pulp after cooking. The bleaching step is composed of the reaction towers (R1, R2, R3,...) And the washing towers (C1, C2, C3...) Of FIG. As shown in FIG. 1, in a pulp manufacturing process, one reaction tower (for example, R1) and one washing tower (for example, C1) are usually connected in series, and this pair of A plurality of reaction towers and washing towers are connected in series. Any of these reaction towers and washing towers may be used in the bleaching step.

  Usually, pulp after digestion is bleached with alkali oxygen and then bleached with bleaching agents such as chlorine, hypochlorite (hypo), chlorine dioxide, oxygen, hydrogen peroxide, caustic soda, and bleaching aids. . By bleaching, it is possible to remove lignin and the like which are coloring cause substances contained in the pulp.

  In the alkaline oxygen bleaching step, a known alkaline oxygen bleaching method can be applied. In the alkaline oxygen bleaching step, caustic soda or oxidized kraft white liquor can be used as the alkali. The alkali and oxygen gas are added to the pulp slurry by a mixer and mixed sufficiently, and then sent to a reaction tower capable of holding a mixture of pulp, oxygen, and alkali for a predetermined time under pressure. Preferably, the alkali addition rate is 0.5 to 4% by weight, the oxygen gas addition rate is 0.5 to 3% by weight per the dry pulp weight, the reaction temperature is 80 to 120 ° C., and the reaction time is 15 to 100 minutes. As other conditions, known conditions can be applied.

  In one bleaching step with a bleaching agent and a bleaching assistant, the addition rate of the bleaching agent to the dry pulp is 0.1 to 5% by mass, the reaction temperature is 60 ° C to 120 ° C, and the reaction time is 15 minutes to 120 minutes. It is preferable.

  In pulp bleaching where strength is required, instead of radical one-step static bleaching to minimize the impact on carbohydrate (such as cellulose) degradation to keep the pulp fiber itself strong. In general, a multistage bleaching process (sequence) in which the bleaching agent and the bleaching conditions are gently changed is adopted. In multi-stage bleaching, usually, lignin is first chlorinated by chlorination to add solubility, and then lignin is dissolved and extracted with an alkali. Thereafter, the remaining small amount of lignin is decomposed and removed using hypochlorite, chlorine dioxide or the like to obtain bleached pulp. This bleaching sequence is expressed as (C) for chlorination, (E) for alkali treatment, (H) for hypochlorite treatment, (D) for chlorine dioxide treatment and (P) for hydrogen peroxide treatment. Multiple stages of bleaching such as C-E-H-E-D, C-E-D-E-D, C-E-H-P-D, etc., in accordance with the order of bleaching agents and / or bleaching aids used Done in stages.

In addition, in the manufacturing method of the dissolving pulp of this invention, a xylanase process can be performed in the middle of a bleaching process before a bleaching process, after a bleaching process. In one embodiment, the method for producing a dissolving pulp of the present invention does not perform a bleaching step including a multi-stage bleaching step after xylanase treatment.
<Xylanase treatment process>
The pulp after cooking is optionally further bleached and washed, and then treated with xylanase. In the xylanase treatment step of the present invention, after culturing a microorganism that produces the enzyme, the enzyme can be added in the state of a medium without separating the enzyme and the microorganism. The microorganism that produces the enzyme of the present invention is not particularly limited. For example, a microorganism that belongs to the genus Bacillus is suitably used as a microorganism that produces an enzyme having xylan-degrading activity. Of these, Bacillus SP 2113 (Department of Fertility and Industrial Technology, Institute of Industrial Technology, Ministry of International Trade and Industry, Deposit No. FERMBP-5264) or Bacillus SP 208 (Deposit No. FERMBP-5321, Institute of Biotechnology and Industrial Technology, Ministry of International Trade and Industry) Is particularly preferably used from the viewpoint of the properties and productivity of enzymes produced by these microorganisms.

  In the xylanase treatment step of the present invention, stirring is performed using a low-concentration mixer, a medium-concentration mixer, a static mixer, a high-concentration mixer, or the like so that the enzyme and the water-containing pulp are uniformly mixed. The amount of the enzyme added depends on the state of the pulp, the processing temperature, and the processing time, and is added after being adjusted so as to obtain a certain enzyme treatment. For example, the amount of addition is determined such that R-10 measured according to ISO 699 of the resulting dissolved pulp is increased by enzyme treatment as compared with the comparative example in which no xylanase is added. For example, xylanase is added so that the R-10 measured according to ISO 699 of the resulting dissolved pulp by enzyme treatment is 96% or more, preferably 97% or more.

  In the xylanase treatment step of the present invention, the pulp concentration in the aqueous solution containing the pulp after cooking is 1 to 30% by mass, preferably 2 to 15% by mass. A pulp concentration of less than 1% by mass is not suitable because a large capacity of equipment is required for processing. If the pulp concentration exceeds 30% by mass, a problem arises in that the pulp and enzyme or culture are mixed uniformly, which is not suitable. The amount of xylanase added is not particularly limited, but 5-500 U xylanase is preferably added to 1 g of pulp (absolutely dry weight), more preferably 5-400 U xylanase is added, more preferably 10-300 U. More preferably, xylanase is added. By adding xylanase in the above range to the pulp, a dissolving pulp having a high cellulose content can be efficiently produced. Xylanase activity 1U indicates the amount of enzyme that produces a reducing end corresponding to 1 μmol of xylose per minute using xylan derived from pulp as a substrate. The treatment temperature is in the range of 10 to 90 ° C., preferably 30 to 80 ° C., but a treatment temperature close to the optimum temperature of the enzyme is more preferred. In the case of a general enzyme, if the treatment temperature is less than 10 ° C., the reaction becomes insufficient, and obtaining such a temperature itself is not suitable because it requires a great deal of cost. On the other hand, if the temperature exceeds 90 ° C., heat loss increases unless the treatment system is sealed, and in the case of a general enzyme, the enzyme itself is denatured and becomes inactive, which is not suitable. The solution pH during the treatment is in the range of 3 to 10, preferably 5 to 9, but a pH close to the optimum pH of the enzyme is more preferable. If pH adjustment is necessary, it can be adjusted by adding an arbitrary acidic solution or alkaline solution. The treatment time is 10 minutes or more, preferably 30 minutes to 180 minutes, but the time is not particularly limited. The pulp may be washed after the xylanase treatment step or may not be washed.

  The enzyme treatment may be performed in any one of the reaction tower R1, the washing tower C1, the reaction tower R2, or the washing tower C2 shown in FIG. 1. For example, the bleaching process is performed in the reaction tower R1, and the bleached pulp is obtained. The xylanase enzyme E may be washed in the washing tower C1 and supplied from the line 12 to the line 9 connected to the supply port of the reaction tower R2, mixed with the raw material, and treated with the xylanase in the reaction tower R2. Thus, the manufacturing method of the dissolving pulp of this invention can be performed continuously.

  The dissolving pulp obtained by the above-described dissolving pulp production method of the present invention is a pulp having a high cellulose content (α-cellulose content), and the α-cellulose content of the dissolving pulp is preferably 90% or more, More preferably, it is 92% or more. Although the dissolving pulp of this invention can be used as raw materials, such as rayon, an acetate, a cellulose derivative, a use is not specifically limited.

  Thus, according to the manufacturing method of the dissolving pulp of this invention, a high quality dissolving pulp can be obtained on the mild conditions using a xylanase enzyme.

  In addition, the manufacturing method of the dissolving pulp of this invention can also be implemented on a laboratory scale, and can also be implemented industrially on a larger scale.

EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these Examples.
Experimental example 1
Preparation of dissolving pulp <prehydrolysis treatment>
Eucalyptus / perita material chips (300 g) were collected in an absolutely dry mass and immersed in 10 liters of tap water overnight. Thereafter, the chips are taken out, emptied through a 400 mesh sieve, filtered, and then the dehydrated chips are placed in a 2.5 liter autoclave, tap water is added so that the liquid ratio becomes 3, and 165 Prehydrolysis treatment was performed at 60 ° C. for 60 minutes. The P factor at this time was 406. After pre-hydrolysis, waste gas was extracted from the deaeration cock of the autoclave, and after confirming that the pressure in the autoclave was zero, the treated chips were evacuated through a 400-mesh sieve and filtered.
<Cooking process>
200 g of the chip after filtration was collected at an absolute dry mass, and again put into a 2.5 liter autoclave. The liquid ratio was 5, the active alkali was 16% per absolute dry chip mass, the sulfidity of the cooking liquid was 28%, and the cooking temperature was 165. Kraft cooking was performed under the conditions of ℃ and cooking time of 50 minutes. After cooking, the black liquor and the pulp were separated, and the pulp was carefully selected on a flat screen equipped with an 8-cut screen plate to obtain 120.0 g of unbleached (unbleached) pulp in an absolutely dry mass.
<Oxygen delignification treatment>
70.0 g was collected at an absolute dry mass of the unbleached kraft pulp, and 2.0% caustic soda per mass of the absolute dry pulp was added, and then diluted with ion-exchanged water to adjust the pulp concentration to 10 mass%. The pulp suspension was placed in an indirect heating autoclave, 99.9% of commercially available compressed oxygen gas was injected, and oxygen delignification was performed at 100 ° C. for 60 minutes at a gauge pressure of 0.5 MPa. After the oxygen bleaching was completed, the pressure was reduced until the gauge pressure became 0.05 MPa or less, and the pulp was taken out from the autoclave, washed and dehydrated with 7 liters of ion-exchanged water.
<Bleaching treatment>
60 g of the kraft pulp after alkaline oxygen delignification was collected in an absolute dry mass, put in a plastic bag, adjusted to a pulp concentration of 10 mass% using ion-exchanged water, and then 1.0 mass% per absolute dry pulp mass. The chlorine dioxide was added and immersed in a constant temperature water bath at a temperature of 70 ° C. for 60 minutes for D0 stage treatment. The obtained pulp was diluted to 3% by mass with ion-exchanged water, and then dehydrated and washed with a Buchner funnel. The pulp after the D0 stage is put in a plastic bag, and ion-exchanged water is added to adjust the pulp concentration to 10% by mass. Then, caustic soda is 1.0% by mass and the hydrogen peroxide is 0.2% by mass per the dry pulp mass. Was added and mixed well, and then immersed in a constant temperature water bath at 70 ° C. for 90 minutes to perform E / P stage treatment. The obtained pulp was diluted to 3% with ion-exchanged water, then dehydrated and washed with a Buchner funnel.

  The pulp after the E / P stage is put in a plastic bag, and the pulp concentration is adjusted to 10% by mass using ion-exchanged water. Then, 0.3% by mass of chlorine dioxide per mass of the absolutely dry pulp is added, and the temperature is 70. It was immersed in a constant temperature water bath at 60 ° C. for 60 minutes to perform D1 stage bleaching. The obtained pulp was diluted to 3% by mass with ion-exchanged water, and then dehydrated and washed with a Buchner funnel.

The pulp after stage D1 is put into a plastic bag, and the pulp concentration is adjusted to 10% by mass using ion-exchanged water, and then 0.6% by mass of sulfuric acid and 0.3% by mass of hydrogen peroxide per mass of dry pulp. %, And immersed in a constant temperature water bath of 90 ° C. for 60 minutes to perform acidic peroxide treatment. The obtained pulp was diluted to 3% by mass with ion-exchanged water, and then dehydrated and washed with a Buchner funnel. The following tests were conducted using the pulp obtained above (hereinafter referred to as “dissolving pulp A”).
<Enzyme treatment>
Dissolve pulp A (viscosity 22.0 mPa · s, R-10 95.5%) 20 g (absolutely dry weight) is collected, put into a plastic bag, ion-exchanged water, 10 mM acetate buffer (pH 5) is added, and the concentration of the dissolved pulp is 5 After adjusting to mass% (pH 5), it was preheated in a 50 ° C. warm bath for 30 minutes.

  As the xylanase enzyme, xylanase A produced by Bacillus SP 2113 (Deposit number FERMBP-5264, Institute of Biotechnology, Institute of Industrial Science and Technology, Ministry of International Trade and Industry) was used.

20 U of xylanase A (enzyme activity values shown in Table 2) per 1 mass (absolute dry weight) of pulp is added to the solution containing the dissolved pulp, treated at 50 ° C. for 120 minutes, and then washed with ion-exchanged water. Dehydrated. The pulp viscosity, R-10, and α-cellulose content of the pulp obtained above were measured by the following methods. The results are shown in Table 1.
<Pulp viscosity>
Pulp viscosity was measured according to JAPAN TAPPI No.230.
<R-10>
The R-10 of the pulp was measured according to ISO699.
<Measurement of α-cellulose content of pulp>
It measured according to JIS P8101.

Experimental example 2
In Experimental Example 1, all tests were performed in the same manner as in Experimental Example 1 except that 40 U of xylanase A added to the pulp was added per 1 mass (absolute dry weight) of the pulp.

Experimental example 3
In Experimental Example 1, all tests were performed in the same manner as in Experimental Example 1 except that 120 U of xylanase A added to the pulp was added per 1 mass (absolute dry weight) of the pulp.

Experimental Example 4
All tests were performed in the same manner as in Experimental Example 1 except that xylanase A was not added in Experimental Example 1.

  As shown in Table 1, by allowing xylanase A to act on the pulp, it was possible to produce a dissolving pulp having a low R-10 viscosity and a high R-10 value.

  According to the present invention, it is possible to produce a dissolving pulp having a high cellulose content.

Claims (5)

  A method for producing dissolved pulp by preliminarily hydrolyzing lignocellulose and producing dissolved pulp, wherein the digested pulp is treated with xylanase.   The method for producing dissolved pulp according to claim 1, wherein the pulp after cooking is bleached and then treated with xylanase.   The method for producing a dissolving pulp according to claim 1 or 2, wherein the xylanase treatment is performed at 30 to 80 ° C.   The method for producing a dissolving pulp according to any one of claims 1 to 3, wherein R-10 of the dissolving pulp is 96% or more.   The treatment according to any one of claims 1 to 4, wherein treating the pulp with xylanase comprises adding 5 to 500 U of xylanase to 1 g (absolute dry weight) of the pulp. Pulp manufacturing method.

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