JP2006176890A - Method for producing deinked pulp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing deinked pulp of printed wastepaper, with which the used amount of an alkaline chemical is significantly reduced, the amount of unreleased ink is small, which has low foaming properties and improved operation and improves a pulp yield. <P>SOLUTION: In the method for producing deinked pulp of printed wastepaper, a nonionic surfactant having <100 mm foam height measured at 40°C according to JIS K-3362 is added in an ink releasing process at pH 7-9 except a floatation process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing deinked pulp, and more particularly to a method for producing deinked pulp from used printed paper.

As a method for producing deinked pulp from used printing paper, generally, a method of separating pulp and ink with a floatator or the like through a disaggregation process and an alkali soaking process of used printing paper is often used. That is, in the general deinking method, the used waste paper is depulverized with a deinking agent comprising an alkaline chemical and a surfactant with a depulverizer such as a pulper, and then used as a waste paper pulp. An agent is added to perform alkali soaking (alkali soaking) to swell the pulp fiber and separate the ink.
Next, in the flotation step, the ink particles are separated from the pulp by adhering and floating the ink particles on the bubbles.

In the used paper disaggregation process, alkaline chemicals and surfactants are added for the purpose of swelling the pulp fibers and peeling the printing ink from the pulp fibers. However, by carrying out the alkali treatment, not only deinking is promoted but also fillers such as clay, talc and titanium dioxide, paper strength enhancers such as starch and polyvinyl alcohol, latex, oxidized starch, calcium carbonate and the like are applied. Not only is the work composition and fine fibers discharged by washing and dewatering, but also part of the pulp is dissolved by the swelling and dissolving action of the pulp due to alkali, so the COD (chemical oxygen demand) in this wastewater is greatly increased. To increase. Therefore, before discharging the waste water from the deinking process to the public water area, it is necessary to dilute or clarify a large amount, and there is a problem that a coagulation treatment chemical, equipment cost, and running cost are required. In order to reduce this drainage load, if the deinking process is performed under conditions of weakly alkaline to neutral range, the pulp fiber does not swell sufficiently, and the printing ink does not peel sufficiently, and this process is followed. There was a problem in quality that the printing ink was difficult to float and separated in the flotation process, and the whiteness of the deinked pulp did not increase.

In addition, in the deinking process of used printing paper containing a lot of coating components and other foaming components, the foaming process in the flotation process is higher than in the processing of used newspapers. The yield is low. Therefore, in order to suppress foaming by the flowator, a surfactant cannot be added in an ink peeling process such as a pulper, and there is a problem that peeling of printing ink becomes insufficient.

Polyethylene glycol type nonionic surfactant has long been known as a deinking agent. For example, RO- (XO) _n -H (in the formula, as a deinking agent when deinking used paper by a flotation method) R is an alkyl group having 8 to 22 carbon atoms, XO is a random addition polymer of oxyethylene and oxypropylene, containing 50 to 95% oxyethylene, and n is an integer of 8 to 100) (Patent Document 1), RO _{- (C 3 H 6 O)} m (XO) n -H ( such as an alkyl group wherein R 8 to 22 carbon atoms, m is an integer of 1 to 50, XO is a random addition polymer of oxyethylene and oxypropylene And an integer of 8 to 100) (Patent Document 2), a reaction product obtained by adding an alkylene oxide to a mixture of natural fats and oils and a polyhydric alcohol, and RO- (AO) _n- H (wherein R is an alkyl group having 12 to 18 carbon atoms, AO is an oxyalkylene group having 2 to 4 carbon atoms, and n is a number of 5 or more) at a certain ratio (Patent Document 3), RO— (PO) _X (AO) _Y (PO) _Z- H (wherein R is an alkyl group having 8 to 22 carbon atoms, AO is an oxyalkylene group, x is 1 to 20, y is 1 to 50, z is 1 to 50) (Patent Document 4), R ¹ O— (AO) _n —H (wherein R ¹ is a hydrocarbon group having 18 to 36 carbon atoms and AO is random addition of oxyethylene and oxypropylene) In the polymer, n is a number from 1 to 1000 (Patent Document 5), RO- (EO) (AO) _{× 1} (EO) -H, RO- (EO) (AO) _{× 2} (XO) -H, _{RO- (XO) (AO) ×} 3 (EO) -H, RO- (XO) (AO) × 4 (XO) a mixture of -H (wherein, R represents Such as an alkyl group of prime 8 to 36, AO is an oxyalkylene group, XO is an oxypropylene group or oxybutylene group, ×. 1 to × 4 molar number of addition of oxyalkylene group (Patent Document ^6), R 1 O- (AO ) _P- H (wherein R ¹ is an alkyl group having 10 to 14 carbon atoms, AO is an oxyalkylene group, p is an integer of 1 to 100), and R ² O— (PO) _m (EO) _n (XO _K- R ³ (wherein R ² is an alkyl group having 16 to 22 carbon atoms, R ³ is hydrogen or an acyl group having 2 to 24 carbon atoms, XO is an oxyalkylene group, m is 1 to 8, and n is 10 to 40, k is a number in which the total number of carbon atoms of the polymerized XO is 3 to 120) (Patent Document 7) etc. In any case, as a deinking agent when removing ink by flotation Because it is added, it can foam alone. It has become a mixture of foaming highly agent.

In addition, as a deinking agent that can be used in any deinking method of the flotation method, the cleaning method, and the eclectic method, RO— (AO) _n —H (wherein R is a mixture such as an alkyl group having 8 to 24 carbon atoms, AO is an oxyalkylene group having 2 to 4 carbon atoms, and n is an integer of 0 or 1 or more) (Patent Document 8). This is also a general-purpose type having flotation suitability. This is a deinking agent that is not a single type, but a mixture of several components such as highly foaming ingredients.
On the other hand, as an office waste paper treating agent, RO- (AO) _n -X (wherein R is a hydrocarbon group having 8 to 22 carbon atoms, AO is an oxyalkylene group, n is a number of 5 to 59, and X is a hydrogen atom) (Alkyl group or acyl group) (Patent Document 9) is disclosed, but the target waste paper is limited to office waste paper and also has flotation suitability, so the amount of foaming increases compared to the comparative example. In the case of processing highly foamed waste paper, there are operational problems.

Moreover, in the method of deinking used printing paper by the flotation process, a method of using a deinking agent having a higher cloud point and a lower deinking agent than the flotation processing temperature is disclosed (Patent Document 10). Again, in order to provide flotation suitability, it is essential to use a deinking agent having a high cloud point and a high foaming property.
As a deinking agent, R ¹ O— (PO) _m (EO) _n (XO) _k —R ² (wherein R ¹ is a block addition of oxyethylene and oxypropylene in this order at the end of a specific hydrophobic group) R ² is hydrogen or an acyl group having 2 to 24 carbon atoms, XO is an oxyalkylene group, m is 1 to 8, n is 10 to 40, and k is the number of carbon atoms in the polymerized XO. (Patent Document 11), a method of deinking by flotation is disclosed, but it is essential to foam with a flotator, the cloud point is low, and the processing temperature is It is difficult to use a deinking agent that does not foam.
R ₁ O— (AO) _p —H (wherein R ₁ is an alkyl group having 14 to 24 carbon atoms, AO is an oxyethylene group or an oxypropylene group, and an average added mole number of EO is 30 to 160, and EO / PO addition mole ratio _{1.5~4.5), R 2 [-COO- (} AO) m -R 3] n ( wherein n is an integer of 1 or more, _{R 2} is the n -COOH A residue obtained by removing all —COOH from a carboxylic acid having 14 to 24 carbon atoms in total, R ₃ is hydrogen or an alkyl group having 1 to 20 carbon atoms, AO is an oxyethylene group, an oxypropylene group, The ink is peeled with one or more deinking agents selected from an average addition mole number of 30 to 160 and an EO / PO addition mole ratio of 1.5 to 4.5). After flotation, warm water of 40 to 80 ° C. Although a deinking method for cleaning (Patent Document 12) is disclosed, Since this method is also assumed flotation, low cloud point, at a processing temperature is not used deinking agent does not foam, hot water washing after flotation is essential.
In any of the above methods, the surfactant is designed to maximize the effect under strong alkaline conditions, so it must be solubilized with strong alkalinity. The point is raised. Therefore, when used under conditions of weak alkalinity to neutral region, it is too soluble in water, the surface activity is lowered, and the penetrating power is reduced.

Japanese Patent Laid-Open No. 55-51891 JP-A-55-51892 JP 631655592 JP-A-5-263379 Japanese Patent Laid-Open No. 10-72789 Japanese Patent Laid-Open No. 2001-200484 Japanese Patent No. 3225143 JP-A-5-25789 JP 2003-166186 A JP-A-6-257081 JP-A-6-257083 Japanese Patent No. 3313046

When removing high-quality pulp by removing ink from waste printed paper, it is necessary to sufficiently peel and disperse the ink from the pulp. However, in order to reduce drainage load, the deinking process is changed from weakly alkaline to neutral. When carried out under the condition of the region, the pulp fiber does not swell sufficiently, and the printing ink is insufficiently peeled, which causes a problem. Furthermore, in the deinking process of used printing paper that contains a lot of coating components and other foaming components, the floatation process is more difficult than the processing of used newspapers, so it is difficult to operate the floatator and the pulp process. Since the yield is low, the surfactant cannot be added in the ink peeling step, and there is a problem that peeling of the printing ink becomes insufficient. That is, the present invention relates to a method for producing deinked pulp of used printed paper, in which the ink is peeled off under weakly alkaline to neutral conditions, and has a low foaming property and low unpeeled ink. It is to provide.

In order to solve the above-mentioned problems, the present inventors have intensively studied a deinking treatment method under conditions of weakly alkaline to neutral regions, particularly a deinking treatment method for used paper with high foamability.
As a result, it was found that the purpose can be effectively achieved by using a surfactant having a specific structure in which the bubble height measured at 40 ° C. of JIS K-3362 is less than 100 mm.
That is, the present invention includes the following inventions.

(1) In the method for producing deinked pulp of used printing paper, a nonionic surfactant having a foam height measured at 40 ° C. of JIS K-3362 of less than 100 mm is removed as a foaming power, except for the flotation step, pH 7 The manufacturing method of the deinking pulp added in the ink peeling process performed by ~ 9.

(2) The method for producing a deinked pulp according to (1), wherein the surfactant is a polyethylene glycol type nonionic surfactant having a cloud point of 25 ° C. or lower, represented by the following general formula (I).

(3) The method for producing a deinked pulp according to (1), wherein the surfactant has a molecular weight of 2000 to 3000.

(4) The method for producing a deinked pulp according to (1), wherein the addition ratio of the surfactant is 0.01 to 2.0 mass% with respect to the absolutely dry pulp.

In the deinking treatment method under the condition of weakly alkaline to neutral region, in particular, in the deinking treatment method of waste paper with high foaming property, the method according to the present invention in which a surfactant having a specific structure is applied with a low cloud point, The present inventors consider the reason why a low-foaming and high-whiteness deinked pulp can be obtained by the conventional method as follows.
That is, when removing ink from used printed paper to obtain high-quality pulp, it is necessary to sufficiently peel and disperse the ink from the pulp. When carried out under neutral conditions, the pulp fibers are not sufficiently swollen, and the printing ink is insufficiently peeled, which is a problem. Furthermore, in the deinking process of used printing paper that contains a lot of coating components and other foaming components, the floatation process is more difficult than the processing of used newspapers, so it is difficult to operate the floatator and the pulp process. Since the yield is low, the surfactant cannot be added in the ink peeling step, and there is a problem that peeling of the printing ink becomes insufficient.

Therefore, in order to obtain a deinked pulp without foaming by a floatator process under conditions of weakly alkaline to neutral range, the binding force between the ink and the pulp or the ink and the coating layer is required. Some treatment is necessary to weaken and prevent foaming, and a chemical suitable for such purpose, that is, does not have foamability, and treatment for promoting ink peeling from the pulp and washing is essential. The present inventors have found that a surfactant having a low foaming property is very suitable as such a compound, and have completed the present invention. Further, the reason why the surfactant represented by the above general formula (I) is effective is that the surfactant having a low cloud point has strong hydrophobicity and high penetrability. It is presumed that the cleaning property is excellent. In addition, in the floatator, the hydrophobic property of the ink itself is increased by adsorbing the highly hydrophobic surfactant to the fine ink particles peeled and dispersed from the pulp. It seems that the adsorptivity to the foam is improved.
Commonly used deinking agents need to be strongly alkaline and solubilized, so when the ink stripping process is carried out under weak alkaline to pH 7-9 conditions, it dissolves in water. Too much, the surface activity decreases and the penetrating power becomes small.

Furthermore, another reason why a surfactant with low foaming property is effective is that the foaming property in the flotator is remarkably suppressed, and in the treatment of used paper with strong foaming property, the operability is remarkably improved. It is done.
On the other hand, surfactants generally known as deinking agents are considered to be effective if they have a cloud point at a temperature that is the same as or slightly lower than the processing temperature, from the viewpoint of foamability in the floatator. As the force, a bubble height measured at 40 ° C. of JIS K-3362 is generally about 100 to 300 mm, as in the present invention, the cloud point is 25 ° C. or less, and the bubble height is less than 100 mm. There is no example of using a certain surfactant alone.

  The waste paper targeted by the present invention includes newspapers, flyers, magazines, books, office paper, other copiers, printing papers generated from OA equipment, and the like.

  In normal deinked pulp production, alkaline chemicals and surfactants are added to disaggregate waste paper, the pulp is diluted and subjected to a flotation treatment and / or a washing treatment, from pulp fibers to ash, After the ink is separated and generally dehydrated to a pulp concentration of 10 to 35% by mass, alkaline soaking is performed by adding an alkaline chemical, hydrogen peroxide and a surfactant. Furthermore, in the next step, the pulp is diluted and subjected to a flotation treatment and / or a washing treatment to separate the ink. In the method of the present invention, the surfactant represented by the general formula (I) is added in the ink peeling step. The ink stripping process can be added in any process as long as it is a process that strips ink, such as a disaggregation process, an alkali soaking process, and an ink stripping process by mechanical share, but it suppresses the addition rate of alkaline chemicals. When adding for the purpose of accelerating the ink peeling as an alternative to alkaline chemicals under the conditions of weak alkaline to neutral range of pH 7-9, it is preferable to add in the disaggregation step. When the treatment pH exceeds 9, since the effect of alkaline chemicals is high as the ink peeling effect, the effect of adding the surfactant is reduced, and the effect of reducing the drainage load cannot be expected. Since solubility decreases, it is necessary to reduce hydrophobicity. On the other hand, when the pH is lower than 7, the disaggregation property and ink releasability of waste paper are remarkably lowered, which is not desirable.

As the surfactant used in the present invention, it is a surfactant that promotes ink peeling from the pulp and dispersion of the coating layer, and it is difficult to foam with a floatator, etc. A surfactant having an action not to be suppressed is preferable. In the present invention, a synthetic polymer nonionic surfactant is used.

So-called synthetic polymeric nonionic surfactants are classified into polyethylene glycol type and polyhydroxy type depending on the type of hydrophilic group. Since many polyhydroxy type nonionic surfactants do not dissolve in water and are poor in penetrability and detergency of the release ink, it is desirable to use a polyethylene glycol type nonionic surfactant in the present invention. Among the polyethylene glycol type nonionic surfactants, those having the structure of the general formula (I) are particularly preferable.

  More specifically, the polyethylene glycol type nonionic surfactant represented by the general formula (I) is an oxyalkylene group adduct of a higher alcohol. This has good ink peeling and penetrating power, and those with low cloud point have low foaming in the floatator, so the ink is peeled from neutral to weakly alkaline, low foaming and unpeeled ink It is suitable for obtaining a deinked pulp having a low content. As the foaming power, it is desirable that the foam height measured at 40 ° C. of JIS K-3362 is less than 100 mm. In addition, those having 11 or less carbon atoms in the alkyl group are generally not synthesized, and when used, the cost becomes very high. Further, when the carbon number of the alkyl group is 19 or more, or the molecular weight of the oxyalkylene group with respect to the molecular weight of the alkyl group becomes low, water solubility becomes poor, dispersibility in the reaction system deteriorates, and penetrating power is reduced. Not only does this decrease, but there will also be problems with operability. The oxyalkylene group preferably has 2 to 4 carbon atoms, is generally an oxyethylene group or an oxypropylene group, and the added mole number is adjusted so that the cloud point is 25 ° C. or lower depending on the molecular weight of the alkyl group. It is desirable to change. The number of added moles is preferably 5 or more, and preferably 35 or less.

  Further, the lower the cloud point of the surfactant represented by the general formula (I), the higher the hydrophobicity and the higher the permeability. However, since the general processing temperature is around 40 ° C., effective clouding is possible. As a point, 25 degrees C or less is preferable and 0 degreeC or more is preferable from the problem of handling.

As the molecular weight of the surfactant represented by the general formula (I), the smaller the molecular weight, the higher the permeability. However, the higher the molecular weight, the better the dispersibility and detergency. Desirably, generally a molecular weight of 2000 to 3000 is preferred. The molecular weight is measured by gel permeation chromatography (GPC) with a standard substance: polyethylene.

  The addition rate of the surfactant having the ability to promote the ink peeling and coating layer dispersion and hardly foam is 0.01 to 2% by mass with respect to the absolutely dry pulp, preferably 0.1 to 2% by mass. 1% by mass.

EXAMPLES Next, although this invention is demonstrated in detail based on an Example, an Example does not limit this invention at all. In this example, the percentage (%) means mass% except whiteness, and the chemical addition rate is expressed by mass% per dry pulp.
The quality of the deinked pulp was evaluated by the pulp whiteness and froth amount ratio and the residual ink area ratio according to the hunter whiteness test method of paper and pulp of JIS P-8148. Here, the floss amount ratio is a value obtained by dividing a liquid amount of a separated product (floss) mainly composed of ink separated and removed by a floatator by a floss liquid amount without addition of a surfactant in%, The remaining ink area ratio (%) is a colored product mainly composed of ink remaining in the pulp sheet of the obtained deinked pulp using an image analyzer (dot analyzer) manufactured by Oji Scientific Co., Ltd. The value obtained by dividing the total area by the total area of the pulp sheet is expressed in%.

<Example 1>
Warm water at 40 ° C. adjusted to pH 9 with caustic soda was added to the printed waste paper consisting of 100% coated waste paper, and the test pulper was separated into 5 pieces under the following conditions.
Pulp concentration 4%
Surfactant addition rate 1%
(Surfactant having a cloud point of 20 ° C. shown in Table 1 in the formula (I))
Next, warm water of 40 ° C. was added to dilute the pulp concentration to 1%, put into a laboratory flowator, and subjected to flotation at an air flow rate of 400 L / hr for 6 minutes. The pulp slurry before and after the flotation treatment is diluted to a pulp concentration of 0.5%, and a sulfuric acid band is added to the pure dry pulp by 15% (band product), and the pulp is 325 mesh wire On the top, hand-washed sheets were prepared by the TAPPI standard method and washed with air using ion-exchanged water until the components through the wire were completely removed (cleaned product). The handsheets were measured for pulp whiteness and residual ink area ratio, and as Example 1, the pulp whiteness and floss amount ratio are shown in Table 2, and the residual ink area ratio is shown in Table 3.

<Comparative Example 1>
In Example 1, it processed like Example 1 except not having added the surfactant shown by a formula (I) by immersion treatment. The results are shown in Tables 2 and 3 as Comparative Example 1.
<Comparative example 2>
All the treatments were carried out in the same manner as in Example 1 except that the formula (I) was a surfactant having a cloud point of 32 ° C. shown in Table 1. The results are shown in Tables 2 and 3 as Comparative Example 2.
<Comparative Example 3>
All the treatments were carried out in the same manner as in Example 1 except that the formula (I) was a surfactant having a cloud point of 46 ° C. shown in Table 1. The results are shown in Tables 2 and 3 as Comparative Example 3.

<Example 2>
The processing was the same as in Example 1 except that the printed paper was 25% offset offset newspaper and 75% flyer waste paper. The results are shown in Tables 4 and 5 as Example 2.
<Example 3>
In Example 2, the same treatment as in Example 2 was performed except that the surfactant addition rate represented by the formula (I) was changed to 0.5%. The results are shown in Tables 4 and 5 as Example 3.
<Example 4>
In Example 2, the same treatment as in Example 2 was performed except that the surfactant addition rate represented by the formula (I) was changed to 0.1%. The results are shown in Tables 4 and 5 as Example 4.

<Comparative example 4>
In Example 2, everything was processed in the same manner as in Example 2 except that the surfactant represented by the formula (I) was not added. The results are shown in Tables 4 and 5 as Comparative Example 4.

  The band product whiteness is used for deinking by flotation, and the washed product whiteness is used for evaluating the ink peelability. However, when the floater floss increases, not only the operability of the floatator is remarkably deteriorated, but also the yield is lowered, so there is no merit even if the whiteness is improved.

In the method for producing deinked pulp of used printing paper, as a foaming force, a nonionic surfactant having a foam height measured at 40 ° C. of JIS K-3362 of less than 100 mm is adjusted to a pH of 7 to 9, excluding the flotation step. By adding in the ink peeling step performed in this manner, it is possible to provide a method for producing a deinked pulp with little unpeeled ink while greatly reducing the amount of alkaline chemicals used. Furthermore, since it is low foaming, operation becomes easy and the effect of improving the pulp yield can be obtained.

Claims (4)

In the method for producing deinked pulp of used printed paper, a nonionic surfactant having a foam height of less than 100 mm measured at 40 ° C. according to JIS K 3362 is used at a pH of 7 to 9, excluding the flotation step. A method for producing deinked pulp, which is added in an ink peeling step. The method for producing deinked pulp according to claim 1, wherein the surfactant is a polyethylene glycol type nonionic surfactant represented by the following general formula (I) and having a cloud point of 25 ° C or lower.

The method for producing a deinked pulp according to claim 1, wherein the surfactant has a molecular weight of 2000 to 3000. The method for producing a deinked pulp according to claim 1, wherein an addition rate of the surfactant is 0.01 to 2.0 mass% with respect to the absolutely dry pulp.