JP5374887B2 - Pulp cleaning agent and pulp manufacturing method - Google Patents

Abstract

Provided are a pulp washing agent capable of extracting lignin from raw pulp sufficiently; and a process for production of pulp. A process for the production of pulp which comprises the cooking step of cooking a raw material for pulp in a cooking zone (211) to obtain pulp, the washing step of washing the pulp in a washing zone (212) or a pulp washing section (30), and the bleaching step of bleaching the washed pulp in a bleaching section, further comprising the addition step of adding a nonionic surfactant, a chelate compound, and a water-soluble polymer to the washing zone (212) or the pulp washing section (30).

Description

  The present invention relates to a pulp cleaning agent for cleaning pulp and a method for producing the cleaned pulp.

  The pulp manufacturing process includes cooking procedures for cooking wood chips to obtain pulp, a cleaning procedure for separating the pulp and black liquor containing lignin, washing the separated pulp, and bleaching the washed pulp. Bleaching procedure (see, for example, Patent Document 1). The bleached pulp produced in this way is used for papermaking and the like.

  Conventionally, in so-called delignification, in which lignin is removed from cooking liquor by a washing procedure, a technique using oxygen is frequently used from the viewpoint of environmental protection. However, this technique has a problem that when heavy metals (for example, iron, manganese) are present in the cooking liquid, active oxygen species generated by the heavy metals promote damage to the pulp.

Then, the technique of adding a predetermined | prescribed organic chelating agent to cooking liquid in order to seal a heavy metal is disclosed (refer patent document 2). According to this technique, damage to pulp can be suppressed while delignification using oxygen is performed.
Japanese Patent Publication No. 48-39963 JP-A-5-93385

  However, even with the technique disclosed in Patent Document 2, lignin may not be sufficiently extracted. Here, a technique of adding an organic chelating agent after delignification has also been proposed, but the degree of lignin extraction is still insufficient.

  It is conceivable to increase the amount of washing water used in the washing procedure in order to improve the cleanliness of the pulp. However, since the black liquor recovered as the amount of washing water increases is diluted, when black liquor is used as a sodium hydroxide source, a great deal of energy is required to concentrate the black liquor (ie, remove water by evaporation) Cost.

  Moreover, when lignin extraction becomes insufficient, it is necessary to use a large amount of bleaching agent in order to reduce coloring by lignin, which is not preferable from the viewpoint of environmental protection.

  This invention is made | formed in view of the above situation, and it aims at providing the pulp cleaning agent which can extract lignin more fully from a pulp raw material, and a pulp manufacturing method.

  The present inventor has found that the presence of calcium, an alkaline earth metal, is a major factor that inhibits lignin extraction, and has completed the present invention. Specifically, the present invention provides the following.

  (1) A pulp cleaning agent containing a nonionic surfactant, a chelating compound, and a water-soluble polymer.

  (2) The pulp detergent according to (1), wherein the ratio of the content of the nonionic surfactant to the total content of the chelating compound and the water-soluble polymer is 0.25 times or more and 4.0 times or less.

(3) The nonionic surfactant is a polyoxyalkylene represented by the general formula H— (AO) _n —O—R (wherein AO is alkylene oxide, R is alkyl, and n is an integer of 1 or more). The pulp cleaner according to (1) or (2), which contains an alkyl ether.

  (4) The pulp cleaning agent according to (3), wherein the added mole number n of oxyalkylene in the general formula is 7 or more and 15 or less.

  (5) The pulp cleaning agent according to (3) or (4), wherein the alkyl R in the general formula has 12 or more carbon atoms.

(6) Pulp production having a cooking procedure for cooking pulp material in the cooking section to obtain pulp, a washing procedure for washing the pulp in a pulp washing system, and a bleaching procedure for bleaching the washed pulp in a bleaching section A method,
The pulp manufacturing method which further has the addition procedure which adds a nonionic surfactant, a chelating compound, and a water-soluble polymer to the said pulp washing system.

  (7) In the addition procedure, the ratio of the addition amount of the nonionic surfactant to the total addition amount of the chelating compound and the water-soluble polymer is 0.25 to 4.0 times (6) Pulp manufacturing method.

(8) The nonionic surfactant is a polyoxyalkylene represented by the general formula H— (AO) _n —O—R (wherein AO is alkylene oxide, R is alkyl, and n is an integer of 1 or more). The pulp production method according to (6) or (7), comprising an alkyl ether.

  (9) The pulp production method according to (8), wherein the number n of oxyalkylene additions in the general formula is 7 or more and 15 or less.

  (10) The pulp production method according to (8) or (9), wherein the alkyl R in the general formula has 12 or more carbon atoms.

  According to the present invention, since the polyoxyalkylene alkyl ether, the chelating compound, and the water-soluble polymer are added, the degree of lignin extraction is synergistically improved, and lignin can be more fully extracted from the pulp raw material.

  Hereinafter, although embodiment of this invention is described, this invention is not specifically limited to this.

<Pulp manufacturing system and pulp manufacturing method>
FIG. 1 is a block diagram showing an example of a pulp production system to which a cleaning agent according to the present invention is applied. The pulp production system 10 includes a digestion cleaning system 20, a pulp cleaning unit 30, and a bleaching unit in order from the upstream.

  The digester cleaning system 20 has a digester 21 in which the pulp material is digested and preliminarily cleaned. Specifically, in the cooking zone 211 of the digester 21, the non-fiber components in the wood chips are dissolved by mixing wood chips that are pulp materials and a solution containing sodium hydroxide or the like, and steaming under pressure. Then, preliminary cleaning is performed in the cleaning zone 212 of the digester 21. The pulp slurry obtained through the washing zone 212 and mixed with the black liquor in which the non-fiber components are dissolved and the pulp is transferred to the next pulp washing unit 30 through a blow tank (not shown). The cooking section of the present invention is constituted by the cooking zone 211, and the cooking procedure constituting the pulp manufacturing method of the present invention refers to the work up to the upstream of the washing zone 212.

  The pulp cleaning unit 30 separates and cleans the pulp from the pulp slurry. Specifically, the pulp slurry transferred from the digester 21 is introduced into the diffusion cleaning device 31, subjected to countercurrent cleaning, and then transferred to the knotter 32. The cooking liquor is subjected to replacement washing in the first pre-drum washing device 33 and the second pre-drum washing device 34 after the undistilled material remaining in the knotter 32 is removed. Thereby, the black liquor containing lignin is collect | recovered. Sodium hydroxide may be separated from the recovered black liquor and reused.

  Subsequently, the pulp after the black liquor is removed is heated to a predetermined temperature by being supplied with steam by the steam mixer 35 and then stored in a front storage tank (not shown). The pulp stored in the pre-storage tank is supplied with oxygen and then introduced into the oxygen reactor 36 where further delignification is performed. The pulp discharged from the oxygen reactor 36 is transferred to a blow tank 37 and introduced into a first rear drum cleaning device 38 and a second rear drum cleaning device 39. In the first post-drum cleaning device 38 and the second post-drum cleaning device 39, the pulp is further cleaned and lignin and the like are removed. Pulp from the second post-drum cleaning device 39 is stored in a post-storage tank (not shown) and then transferred to the bleaching section. The pulp washing system of the present invention is constituted by the washing zone 212 and the pulp washing unit 30, and the washing procedure constituting the pulp manufacturing method of the present invention refers to the operation from the washing zone 212 to the upstream of the bleaching unit.

  Subsequently, the pulp is bleached in the bleaching section to produce a high-quality pulp that is preferably used for papermaking. A bleaching part and the bleaching agent used may be a conventionally well-known thing. The above is an example of the bleaching procedure which comprises the pulp manufacturing method of this invention.

  As described above, a large amount of calcium is present in the liquid flowing through the washing zone 212 and the pulp washing unit 30, and the lignin extraction is inhibited by this calcium. The concentration corresponds to 10 to 100 times the amount of heavy metal.

  On the other hand, the amount of chelate compound necessary to seal calcium is about 70 mg / L EDTA with respect to 10 mg / L calcium. Therefore, when the amount of calcium is about 20 mg / L, the amount of EDTA added becomes extremely large. Is not practical.

  The pulp production method of the present invention has the above-mentioned problems by further including an addition procedure for adding the pulp cleaning agent of the present invention to the washing zone 212 and the pulp washing section 30 in addition to the cooking procedure, the washing procedure, and the bleaching procedure. Solve. Then, the pulp cleaning agent used by this invention is demonstrated below.

<Pulp cleaning agent>
The pulp cleaning agent of the present invention contains a nonionic surfactant, a chelating compound, and a water-soluble polymer.

  Here, the content of each component is an amount that affects lignin extraction, and may be set as appropriate. Specifically, the ratio of the content of the nonionic surfactant to the total content of the chelating compound and the water-soluble polymer is from 0.25 times to 4.0 times in that the lignin extraction efficiency can be improved. preferable. On the other hand, the ratio of the content of the water-soluble polymer to the chelating compound is not particularly limited, and may be appropriately set within a normal range (for example, 0.20 to 5.0 times).

  However, the content of each component may be set according to the conditions under which the pulp cleaner is added. Specifically, the ratio of the addition amount of the water-soluble polymer to the chelating compound may be increased according to an increase in the concentration of calcium contained in the liquid at the site to be added. In general, the upstream of the washing zone 212 and the pulp washing section 30 has a higher calcium concentration than the downstream, and therefore the amount of the water-soluble polymer added to the chelating compound as it is applied upstream of the washing zone 212 and the pulp washing section 30. The ratio increases.

  Usually, the calcium concentration is 80 to 150 mg / L in the cooking liquid introduced into the diffusion cleaning device 31, and 40 to 80 mg / L in the liquid stored in the front storage tank, and is stored in the rear storage tank. 5-40 mg / L in the liquid. However, since the calcium concentration described here may vary depending on various conditions such as the temperature in the portion to which the pulp detergent is added, the addition amount may be appropriately set according to the conditions. Further, such adjustment may be performed manually, but is provided with a concentration detection means for detecting the calcium concentration and a control means for controlling the addition amount ratio based on the detection value, and these means automatically It may be controlled.

  The addition amount of the pulp cleaning agent of the present invention is usually 0.1 to 1.5 kg / pulp t (here, “pulp” refers to dry pulp). The addition amount in this range is practical in terms of cost. In addition, the pulp cleaning agent may be added to one or a plurality of locations of the cleaning zone 212 and the pulp cleaning unit 30, or may be added to the same location or a separate location for each component such as a chelating compound and a water-soluble polymer. .

  Nonionic surfactants include polyoxyalkylene ethers, polyoxyalkylene esters, polyoxyalkylene amines, polyhydric alcohol fatty acid esters, sugar fatty acid esters, alkyl polyglycosides, and the like. May be used alone or in combination.

  Nonionic surfactants based on polyoxyalkylene ether include polyoxyalkylene alkyl ether, polyoxyalkylene alkyl phenyl ether, polyoxyalkylene polyol alkyl ether, polyoxyalkylene styrenated phenol ether, polyoxyalkylene distyrenated phenol ether, Examples include polyoxyalkylene tristyrenated phenol ether. Examples of the polyol include C2-C12 polyhydric alcohols such as propylene glycol, glycerin, sorbitol, sucrose, pentaerythritol, sorbitan, and the like.

  Examples of polyoxyalkylene ester nonionic surfactants include polyoxyalkylene fatty acid esters. Examples of the polyhydric alcohol fatty acid ester nonionic surfactant include fatty acid esters of polyhydric alcohols having 2 to 12 carbon atoms or fatty acid esters of polyoxyalkylene polyhydric alcohols. Specific examples include sorbitol fatty acid esters, sorbitan fatty acid esters, fatty acid monoglycerides, fatty acid diglycerides, polyglycerin fatty acid esters, and the like. Moreover, these polyalkylene oxide adducts (for example, polyoxyalkylene sorbitan fatty acid ester, polyoxyalkylene glycerin fatty acid ester, etc.) can also be used.

  Examples of sugar fatty acid ester nonionic surfactants include sucrose, glucose, maltose, fructose, polysaccharide fatty acid esters, and the like, and these polyalkylene oxide adducts can also be used.

Among these, a polyoxyalkylene alkyl ether is preferable in that it has excellent affinity with an ether bond in the lignin molecule. Such polyoxyalkylene alkyl ether is represented by the general formula H- (AO) _n -O-R (wherein AO is alkylene oxide, R is alkyl, and n is an integer of 1 or more). Here, the number n of added moles of oxyalkylene in the general formula is not particularly limited, but is preferably 7 or more and 15 or less in that the extraction efficiency of lignin can be improved. Similarly, the alkyl R in the general formula preferably has 12 or more carbon atoms, and more preferably 18 or less carbon atoms in that the extraction efficiency of lignin can be improved. In addition, as above-mentioned, these surfactants may be used individually by 1 type and may be used together by multiple types.

  A chelating compound refers to a compound having an effect of complexing a metal. Although it does not specifically limit as a chelating compound which can be used, For example, EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), HEDTA (hydroxyethylenediaminetetraacetic acid), EDDS (ethylenediaminesuccinic acid), TTHA (triethylenetetraamine) It may be at least one selected from the group consisting of hexaacetic acid), HEDP (hydroxyethanephosphonic acid), NTMP (nitrilotrismethylenephosphonic acid), and PBTC (phosphonobutanetricarboxylic acid). That is, the chelating compound may be used alone or in combination of two or more.

  Although it does not specifically limit as a water-soluble polymer, For example, an acrylic acid type polymer and a maleic acid type polymer can be used. In addition, a water-soluble polymer may be used individually by 1 type, and may be used together with multiple types. However, the monomer ratio of acrylic acid and / or maleic acid is preferably 30% or more.

  Examples of the acrylic polymer include polyacrylic acid (AA), a copolymer of acrylic acid and 2-hydroxy-3-allyloxy-1-propanesulfonic acid (AA / HAPS), and a copolymer of acrylic acid and methyl acrylate. Examples thereof include one or more of a polymer (AA / MA), a copolymer of methyl acrylate and isobutylene (MA / IB), and a copolymer of methyl acrylate, acrylic acid, and vinyl acetate.

  As the maleic acid polymer, various conventionally known polymers can be used.

  The pulp cleaning agent of each composition was added to the shower line of the first post-drum cleaning device 38 of the pulp manufacturing system 10 described above. The composition and amount of the added pulp cleaning agent and the characteristics of the nonionic surfactant (polyoxyalkylene alkyl ether) are as shown in Tables 1 and 2, and the calcium concentration in the first post-drum cleaning device 38 is It was 50 mg / L. In addition, EDTA was used as the chelating compound, and “Aquaric DL40S” (manufactured by Nippon Shokubai Co., Ltd.) was used as the water-soluble polymer.

  Six hours after the addition, the pulp was recovered at the outlet of the first post-drum cleaning device 38. The recovered pulp was measured for kappa number (Kα) according to the method described in “JIS P 8211”. The results are also shown in Tables 1 and 2. The kappa number is an indicator of the amount of lignin in the pulp, and the smaller the kappa number, the more extracted the lignin.

  Moreover, the example which performed the pulp washing | cleaning on the conditions similar to each Example of said Table 2 except the point which changed the nonionic surfactant is shown next.

  As shown in Table 1, in Examples 4 to 6, the kappa number was greatly reduced as compared to both Comparative Examples 1 and 2. Thereby, it turned out that a lignin extraction can be improved synergistically by using together a nonionic surfactant, a chelating compound, and a water-soluble polymer.

  In any of Examples 1 to 3, the kappa number was sufficiently reduced. Thus, it has been found that such a three-component cleaning agent can sufficiently extract lignin without largely depending on the addition amount ratio of the water-soluble polymer to the chelating compound.

  As shown in Table 2, the kappa number decreased in all of Examples 2 and 7 to 10, but significantly decreased in Examples 2 and 8 to 9, in particular. Thereby, it turned out that lignin extraction can be improved more by making the addition mole number of the oxyalkylene in polyoxyalkylene alkyl ether into 7-15.

  Moreover, although the kappa number fell in any of Example 2, 11-13, it was falling large especially in Example 2, 12-13. Thereby, it turned out that lignin extraction can be improved more by making carbon number of the alkyl in a polyoxyalkylene alkyl ether into 12 or more, preferably 18 or less.

  In addition, the kappa number in Examples 7, 10 and 11 is slightly higher than Comparative Example 1 because the addition amount of the chelating compound and the water-soluble polymer in Examples 7, 10 and 11 is 40% of Comparative Example 1. This is thought to be due to the extremely low level. That is, even when a polyoxyalkylene alkyl ether having an addition mole number of oxyalkylene of less than 7 or more than 15, or an alkyl carbon number of less than 12 or more than 18, is used in combination with a chelating compound and a water-soluble polymer. The improvement effect of the lignin extraction efficiency is only weakened, and the lignin extraction efficiency is not lowered.

  Further, as shown in Table 3, it was found that not only polyoxyalkylene alkyl ether but also other nonionic surfactants can sufficiently extract lignin. Thereby, it was confirmed that lignin extraction can be efficiently performed using various nonionic surfactants.

It is a block diagram which shows an example of the pulp manufacturing system with which the cleaning agent which concerns on this invention is applied.

Explanation of symbols

10 Pulp production system 20 Cooking cleaning system 211 Cooking zone (cooking part)
212 Washing zone (pulp washing system)
30 Pulp washing section (pulp washing system)

Claims (6)

A pulp cleaning agent comprising a nonionic surfactant, a chelating compound, and a water-soluble polymer ,
The nonionic surfactant is a polyoxyalkylene alkyl ether represented by the general formula H— (AO) _n —O—R (wherein AO is alkylene oxide, R is alkyl, and n is an integer of 1 or more). Including
The added mole number n of oxyalkylene in the general formula is 7 or more and 15 or less,
The water-soluble polymer is a pulp cleaning agent containing at least one selected from the group consisting of acrylic acid-based polymers or maleic acid-based polymers .   The pulp cleaning agent according to claim 1, wherein a ratio of the content of the nonionic surfactant to the total content of the chelating compound and the water-soluble polymer is 0.25 times or more and 4.0 times or less. The pulp cleaning agent according to claim 1 or 2 , wherein the alkyl R in the general formula has 12 or more carbon atoms. A pulp production method comprising: a cooking procedure for cooking pulp material in a cooking section to obtain pulp; a washing procedure for washing the pulp in a pulp washing system; and a bleaching procedure for bleaching the washed pulp in a bleaching section. And
The pulp washing system, further possess a nonionic surfactant, a chelating compound, a water-soluble polymer, an additive procedure of adding,
The nonionic surfactant is a polyoxyalkylene alkyl ether represented by the general formula H— (AO) _n —O—R (wherein AO is alkylene oxide, R is alkyl, and n is an integer of 1 or more). Including
The added mole number n of oxyalkylene in the general formula is 7 or more and 15 or less,
The said water-soluble polymer is a pulp manufacturing method containing 1 or more types chosen from the group which consists of an acrylic acid type polymer or a maleic acid type polymer . The pulp production according to claim 4 , wherein in the addition procedure, a ratio of the addition amount of the nonionic surfactant to a total addition amount of the chelating compound and the water-soluble polymer is 0.25 times or more and 4.0 times or less. Method. The alkyl R in the said general formula is a pulp manufacturing method of Claim 4 or 5 which has 12 or more carbon number.

Images