JP6443290B2 - Method for producing deinked waste paper pulp - Google Patents

Description

The present invention relates to a method for producing deinked waste paper pulp for obtaining recycled pulp from used waste paper.

In recent years, the demand for recycled paper made from recycled paper has been growing rapidly from the viewpoint of protecting global resources. In order to meet this demand, it is an important issue to produce an excellent quality deinked pulp and to reduce the environmental load during the production. Current waste paper materials are broadly classified into newspaper waste paper, magazine waste paper, and high-quality waste paper. Old newspaper and magazine waste paper mainly consists of mechanical pulp and deinked pulp with relatively low whiteness of pulp, and also contains many waste papers that have been printed on non-coated paper. In order to produce this deinked pulp, it is necessary to process with a more appropriate production flow. Even in the use of deinked pulp based on printed high-quality waste paper, it is necessary to carry out a more appropriate treatment for the purpose of replacement with virgin pulp such as NBKP or LBKP.

In the production of deinked pulp, in order to increase the whiteness of the pulp, various deinking facilities are optimized according to the required addition of bleaching chemicals and various surfactants and the required quality of the final pulp. Is the current situation. Usually, in the deinking pulp manufacturing process, surfactants such as alkaline chemicals (caustic soda and sodium silicate), deinking agents and penetrants are used in the decontamination process, and after swelling of the pulp fibers and ink peeling. Various dispersion treatments, bleaching treatments, and deinking treatments are performed, and the whiteness of the deinked pulp can be increased by this method.

However, the normal deinked pulp manufacturing process performs disaggregation and bleaching treatment in an alkaline region (pH 10 to 13), and generates a large amount of COD components in the waste water after bleaching by using a large amount of caustic soda and sodium silicate. Let Therefore, it cannot be said that it is a method for producing recycled pulp that should be friendly to the global environment.

As a method for producing environmentally friendly deinked pulp from the viewpoint of the amount of COD generated, for example, high-whiteness wastepaper that undergoes FAS bleaching after oxidative bleaching of used paper deinked pulp obtained by deinking used printing paper A method for producing pulp has been proposed (for example, Patent Document 1). The feature of the reduction method is that, in addition to the cost, COD generation basic unit can be greatly reduced as compared with hydrogen peroxide bleaching. The reason for this is that the amount of alkali chemicals (caustic soda, sodium silicate) used as auxiliary chemicals during bleaching is small compared to the usual hydrogen peroxide bleaching. At the same time, however, the decrease in alkaline chemicals leads to an increase in the residual ink of the deinked pulp, degrading the quality of the final pulp. For this reason, a method of neutralizing waste printed paper that has been aged under alkaline conditions with acid addition, and producing a deinked pulp with less residual ink by applying a high shearing force after neutralization or simultaneously with neutralization, and deinked pulp A method for reducing the COD load discharged from the manufacturing process has been proposed (for example, Patent Document 2). However, an alkali aging tower and equipment for applying a high shear force are necessary, leading to an increase in manufacturing costs such as equipment costs and power costs.

Japanese Patent No. 3098021 Japanese Patent Laid-Open No. 11-200269

It is an object of the present invention to provide a method for greatly reducing wastewater treatment costs by enabling a significant reduction in the amount of COD in wastewater generated from the manufacturing process of deinked wastepaper pulp produced from printed wastepaper. To do. Furthermore, deinked waste paper pulp manufactured using a bleaching process in a high alkali region typified by alkaline hydrogen peroxide bleaching and deinked wastepaper pulp of inferior quality (whiteness) are manufactured at a lower cost. It is intended to provide a method that can be used.

In the series of steps for producing deinked waste paper pulp from printed waste paper, the intermediate step is a combined step in which a dispersion step and a bleaching step are continued, and the step subsequent to the intermediate step is set to a neutral pH region. It is found that the above-mentioned problems can be solved by adjusting the treatment process and circulatingly using the filtrate generated from the dehydration / washing process in the subsequent process mainly as dilution water and / or washing water in the subsequent process. The present inventors have made the following invention.

(1) A method for producing deinked waste paper pulp according to a series of steps having at least a disaggregation process of used printing paper, a flotation process for deinking, a dispersion process for dispersing ink, a bleaching process, and a dehydration / washing process In the above, the combination process part in which the dispersion process and the bleaching process are continuous is defined as an intermediate process, and each process in a series of processes including the preceding process from the disaggregation process to the intermediate process and the intermediate process is adjusted to pH 7.0-13. A treatment step under a pH condition selected from a range of 0.0 or less, and a subsequent step following the intermediate step is deinked under a pH condition selected from a range of pH 6.0 or more and less than 9.5 In addition to a series of steps including a flotation step and a dehydration / washing step, the filtrate generated from the dehydration / washing step in the latter step is mainly used as dilution water and / or in the latter step. Characterized by using as the washing water, a manufacturing method of deinked waste paper pulp.
(2) The intermediate step is selected from a combination step that is continuous in the order of the dispersion step of performing the ink dispersion treatment-the bleaching step and a combination step that is continuous in the order of the dispersion step of the ink dispersion treatment-the bleaching step-the dispersion step of the ink dispersion treatment. The method for producing deinked pulp according to item (1), comprising any combination step.
(3) The flotation process in which deinking is performed under a pH condition selected from a range of pH 6.0 or more and less than 9.5 in the process subsequent to the intermediate process, the pH of the pulp slurry from the intermediate process is adjusted to the acid level. The method for producing deinked pulp according to item (1) or (2), wherein the method is a flotation process in which deinking treatment is performed by adjustment by addition.
(4) It is characterized by having a flotation step of deinking treatment by diluting the disaggregation treatment liquid from the disaggregation step with dilution water and a subsequent dehydration / washing step before the intermediate step (1) The method for producing deinked pulp according to any one of items (1) to (3).
(5) A flotation step of deinking treatment by diluting the disaggregation treatment liquid from the disaggregation step with dilution water and a subsequent dehydration / washing step during the step preceding the intermediate step, Any one of the items (1) to (4), wherein the filtrate in the dehydration / washing step subsequent to the flotation step is used as dilution water in the previous disaggregation step and / or the flotation step. Method for producing deinked pulp.
(6) A part of drainage from the dehydration / washing step after the flotation step in the step subsequent to the intermediate step is used as dilution water and / or washing water in each step in the preceding step. The method for producing deinked pulp according to any one of (1) to (5).
(7) A series of steps including the preceding step, the intermediate step, and the subsequent step are a disaggregation step, a preceding flotation step, a preceding dehydration / washing step, an intermediate step (dispersion step-bleaching step or dispersion step). -Bleaching step-Dispersing step), the subsequent flotation step, and the subsequent dehydration / washing step are a series of steps arranged in all steps so as to be in this order (1 The method for producing deinked pulp according to any one of items (1) to (6).
(8) The method for producing deinked waste paper pulp according to any one of (1) to (7), wherein the bleaching step in the intermediate step is an alkali hydrogen peroxide bleaching step.
(9) Any one of items (1) to (8), wherein the pH adjustment of the pulp slurry introduced into the flotation step in the subsequent step is pH adjustment by addition of sulfuric acid. A method for producing the deinked pulp according to 1.

According to the method of the present invention, the removal rate of free ink is improved in the flotation process in which the deinking process is performed after the intermediate process consisting of the combination process in which the dispersion process and the bleaching process in which the ink dispersion process is continued, and the dehydration・ The yield in the cleaning process is also improved. As a result, while maintaining the whiteness of the deinked wastepaper pulp at a high level, it is possible to reduce the amount of chemicals used in the bleaching process and reduce the amount of COD discharged from the entire process. A method for producing pulp is provided. The deinked waste paper pulp produced by the method of the present invention has a whiteness of about 50% to 85%, and is particularly suitable for high-quality paper that requires high whiteness.

Schematic which shows an example of the processing flow of the manufacturing method of the deinked waste paper pulp of this invention.

The method for producing deinked pulp according to the present invention comprises a depulling step for disaggregating used printing paper, a flotation step for deinking, a dispersion step for dispersing ink, a bleaching step, and a dewatering / washing step. It is a method according to the conversion process. And it has a process part in which a dispersion process and a bleaching process for performing an ink dispersion treatment as an intermediate process among all processes, and each process in the intermediate process and the previous process is pH 7.0 to 13.0. The treatment is performed under a pH condition selected from a neutral to alkaline pH region, and each step in the subsequent step from the intermediate step is treated under a pH condition selected from a pH region of pH 6.0 or more and less than 9.5. It is characterized by making it the process of performing. The intermediate step in the series of steps for carrying out the method of the present invention includes a case where the intermediate step is a combined step in which a dispersing step is further arranged after the bleaching step following the dispersing step.

In the method of the present invention, examples of the used printing paper used as a raw material include used paper containing 7% to 40% ash, such as newspaper, fine coated paper, high ash coated paper, and non-coated paper. The method of the present invention is also effective for the treatment of printed waste paper including some neutral newspapers having a large amount of surface treatment agent and having poor deinking properties and coated paper having a high ash content.

There is no restriction | limiting in particular about the disaggregation process in a series of processes which implement the method of this invention. As a preferable disaggregation process in the disaggregation process, raw printed paper is put in diluted water so as to have a solid content concentration of 12 to 18% by mass, and further an alkali chemical (such as sodium hydroxide) is added to 0 to 3.0% by mass of pulp, A treatment performed preferably by adding 0.1 to 2.5% by mass is mentioned.
The pH during the disaggregation treatment by adding an alkaline chemical is generally set to pH 10.0 to 13.0.
When a deinking agent is used in the disaggregation step, it is preferable that the ink has a strong permeability to pulp fibers and a strong ink peeling property, and the deinking agent is 0.01 to 0.5% by mass with respect to pulp, preferably Add 0.03-0.3 mass%. The disaggregation time is 10 to 30 minutes, preferably 10 to 25 minutes, more preferably 10 to 18 minutes, and the disaggregation temperature is 10 to 50 ° C, preferably 30 to 50 ° C.

Examples of deinking agents with strong ink peelability include higher alcohol deinking agents, amphoteric deinking agents, and hybrid types of higher alcohols and fatty acids. Examples include, but are not limited to: Is not to be done.
DI-7020, DI-7030, DI-767, DI-7282, DI-7300, DI-7250, manufactured by Kao Corporation, DIA-Z-100, DIA- manufactured by Nissin Chemical Laboratory Co., Ltd. Z-5000, Neoscore FW-780, Neoscore FW-790, Neoscore FW-795, FT-467, FT-470, FT-487, FT-511, FT-513, FT-514, manufactured by Toho Chemical Co., Ltd. , FT-515, FT-517, BB agent, Daihope 940, Daihope 960, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Lipobright DP-810, manufactured by Nikka Corporation.

A screening step can be arranged in a series of steps for carrying out the method of the present invention. There are no particular restrictions on the apparatus used in the screening process. Although it is sufficient that foreign substances in the raw material can be removed with a screen cleaner, it is preferable to use a slit screen (first stage 0.15 mm slit or less, second stage 0.15 mm slit or less). Any cleaner may be used as long as it can efficiently remove heavy foreign matter.

In the method of the present invention, the dispersing step in the intermediate step having the dispersing step of dispersing the ink and the subsequent bleaching step is a step of dispersing the ink with a disperser. As the disperser, a low speed / high concentration shaft type disperser and a disk type disperser are suitable. As the low-speed / high-concentration shaft type disperser, a uniaxial or biaxial kneader type disperser is preferable. This type of disperser has a rotary blade attached to a shaft-like rotor and a fixed blade attached to a casing, and has a processing concentration of 20% to 50% (in terms of pulp concentration) at a low speed of 50 to 300 rpm. The dispersion treatment is performed at a high concentration (mass%), preferably 25% to 40%. The processing temperature is 25 to 100 ° C, preferably 40 to 90 ° C. In such a shaft-type disperser, the friction between the fibers is the main component, and ink separation and dirt dispersion occur. If the treatment concentration is less than 20%, it is difficult to apply a mechanical load, ink dispersibility / dirt dispersibility is lowered, and energy required for temperature increase is enormous, which is not suitable. Further, when the treatment concentration exceeds 50% and the concentration is increased, it becomes difficult to squeeze mechanically.

Generally, the following are used as a uniaxial kneader. Kneading Disperser KD (trade name: IH IVOIT Paper Technology), Disperser (trade name: Aikawa Tekko), Disperser (trade name: ASEC), Disperser (trade name) : Sanei Regulator Co., Ltd.), CCE type kneading machine (trade name: Niihama Pump Manufacturing Co., Ltd.), kneader (trade name: Yamamoto Hyakuma Manufacturing Co., Ltd.). Further, as the biaxial kneader, those manufactured by Niihama Pump Manufacturing Co., Ltd., Yamamoto Hyakuma Manufacturing Co., Ltd., etc. are used. On the other hand, as a disc type disperser, Disperser HTD (trade name: manufactured by IH IFOIT Paper Technology Co., Ltd.), KRIMA hot dispersion equipment (trade name: manufactured by Cellwood), Koni Disc (trade name: Aikawa) Iron Disperser, Conical Dispersion System / HI Preheater / OptiFinner Disperser (trade name: Metso SHI) and the like are used. However, it is not limited to these models.

In a series of steps for carrying out the method of the present invention, a bleaching step in an intermediate step having a dispersing step for dispersing the ink and a subsequent bleaching step is a step of performing a bleaching treatment using a bleaching chemical for recycling used paper. Hydrogen peroxide, hydrosulfide, thiourea dioxide, hypo, etc. are used as bleaching chemicals. In the method of the present invention, alkaline hydrogen peroxide bleaching is mainly performed using hydrogen peroxide. Hydrogen peroxide is added to the pulp in an amount of 0.1 to 5.0% by mass. Even if the amount of hydrogen peroxide added is further increased, the increase in whiteness tends to saturate.
During alkaline hydrogen peroxide bleaching, 0.3 to 3.0 mass% of caustic soda and 0.3 to 3.5 mass% of sodium silicate are added to pulp. Caustic soda and sodium silicate are preferably 0.5 to 2.0% by mass because the lower the addition rate, the lower the amount of COD generated in the waste water.

The bleaching time is 10 minutes to 5 hours, preferably 1.5 to 3 hours. If the bleaching time is too short, the hydrogen peroxide will not react sufficiently, which is not preferable. Also, if the bleaching time is longer than 5 hours, the consumption of hydrogen peroxide will proceed and the yellow of the pulp will start from the point when the remaining hydrogen peroxide is exhausted. It is not appropriate because it will occur.
The pulp concentration (% by mass) during bleaching is 15 to 35%, preferably 25 to 30%. When the concentration is lower than 15%, the reactivity of hydrogen peroxide becomes worse. On the other hand, if the concentration is higher than 35%, it is not preferable because the disperser is mixed with chemicals.
Further, the pH during the bleaching treatment is preferably 10.5 to 12.0, and if it is outside this range, the bleaching property of hydrogen peroxide is inferior. It is effective to carry out the bleaching temperature at 50 to 120 ° C.

In the series of steps for carrying out the method of the present invention, the flotation step in which deinking treatment is performed in a step subsequent to the intermediate step is a step in which the flotation treatment is performed by adjusting the pH to a substantially neutral pH region. .
It is particularly efficient to remove the ink peeled by the disperser process in the separation process in the intermediate process in the flotation process adjusted to the pH range in the subsequent process. When adopting the method of removing the peeled ink in the dehydration / washing process, the ink particles may circulate in the white water together with the washing filtrate, which may adversely affect the finished whiteness of the pulp. It is not preferable.
There is no restriction on the form of the flotator in the flotation process. The treatment concentration in the flotation process is 0.7 to 1.5 mass%, and the treatment temperature is 10 to 55 ° C, preferably 30 to 50 ° C.

In the flotation process in which the deinking process is performed in a process subsequent to the intermediate process, a process in which an ink aggregating deinking agent is added is performed. Examples of deinking agents having strong ink aggregating properties include fatty acid-based or fatty acid derivative-based deinking agents. Examples of fatty acid-based deinking agents include DI-254 (oleic acid) and DI-268 manufactured by Kao Corporation, and K-4004-D manufactured by Daiichi Kogyo Seiyaku Co., Ltd. In addition, as fatty acid derivatives, DI-1120, DI-1211, DI-1050 manufactured by Kao Corporation, DIY-23543 manufactured by Nissin Chemical Laboratory Co., Ltd., Daiichi Kogyo Seiyaku Co., Ltd. Paper Aid W made by However, it is not limited to these.

In the method of the present invention, the treatment in the flotation step subsequent to the intermediate step is suitably performed in the pH range of 6.0 to 9.5, and in the pH range of pH 7.0 to 8.5. More preferably. When the pH is lower than 6.0, the corrosion of piping and equipment becomes a problem, and the equipment cost becomes expensive. Moreover, when pH exceeds 9.5, the ink removability of a deinked pulp will deteriorate remarkably.
Although sulfuric acid is suitable as an agent for reducing the treatment pH in the flotation process, hydrochloric acid, organic acid, or the like may be used. When adjusting the pH, caustic soda, sodium silicate, or the like may be used as necessary. On the other hand, as the diluting water used in the flotation process in the subsequent process, fresh water or waste water from the dehydration / washing process in the process subsequent to the intermediate process is used. The filtrate (drainage) generated during dehydration / washing in the neutral pH region dissolves the COD component from the pulp slurry into the filtrate compared to the usual dehydration / washing filtrate in the alkaline pH region. Since the discharge is suppressed, it is particularly suitable for use as washing water or diluting water in each of the subsequent steps.

As a process after the deinking process is performed in the flotation process in the process subsequent to the intermediate process, a dehydration / washing process for removing fine ink that could not be removed by the floatator is provided. There is no particular limitation on the dehydrating / cleaning apparatus as long as it can perform the dehydrating process and the cleaning process in a pH range of pH 6.0 to 9.5. It is preferable that the pulp slurry having a concentration of 0.6 to 1.5% by mass is diluted with clean water or clear white water of a paper machine and then dehydrated to 15 to 35% by mass and washed.
Equipment used in the dehydration and washing process includes extractors, fall washers (Eiko), and double nip thickener (Ishikawajima Sangyo), but the dehydration and washing equipment gives priority to the ink content in the raw material. It is preferable that the apparatus removes the loss of fiber and ash to a minimum. Among them, a wire washer is preferable, and the eye hole can be about 20 to 200 mesh, preferably 40 to 100 mesh, more preferably 50 to 80 mesh.

You may add chemical | medical agents, such as a paper strength agent, a retention agent, and a coagulant | flocculant, to the pulp slurry immediately before the dehydration and washing | cleaning process in the said latter process. As a drug that can be added, a drug that improves the yield of ash and fiber can be preferably used. The following can be mentioned as such a chemical | medical agent.
One or more mixtures selected from drugs mainly composed of polyacrylamide, aluminum sulfate, polydadomac, polyamine, polyethyleneimine, 2- (methacryloyloxy) ethyltrimethylammonium chloride polymer, modified polyethyleneimine, etc. What consists of. A drug comprising (meth) acrylamide, a water-soluble cationic monomer, and a water-soluble anionic monomer as constituents (generally referred to as amphoteric acrylamide, for example, Hariup AC manufactured by Harima Kasei Co., Ltd.). Other commercially available drugs (for example, Polystron 372, KW-387-20 manufactured by Arakawa Chemical Co., Ltd., Acracac 208E manufactured by MT Aquapolymer Co., Accurac 100E, Fixage 621 manufactured by Kurita Kogyo Co., Ltd., Hymolock NR-70 manufactured by Hymo Co., Ltd. , Somali Realizer R500, Realizer R600, Kyowa Sangyo Keith Lock RP-532, etc.). Among them, a drug containing amphoteric acrylamide as a component is particularly effective for improving the yield.

  The amount of the drug added is preferably 1 ppm to 3000 ppm, more preferably 1000 ppm to 2000 ppm. When the amount of the added chemical is excessive, the ink is adsorbed by the pulp slurry together with the ash and fiber, resulting in a decrease in whiteness, and it is also uneconomical. If the chemical flows out into the wastewater without adsorbing to the pulp, the wastewater COD will rise, so it is necessary to keep the minimum addition.

The method of producing the deinked waste paper pulp of the present invention is a normal waste paper pulp as long as it includes the above-mentioned disintegration process of the used waste paper, the flotation process for the deinking process, the dispersion process for the ink dispersion process, the bleaching process, and the dehydration and washing process It can be carried out according to a series of steps including other processing steps employed in the manufacturing method. In general, a foreign matter removing step or a dust removing step (screening step) using a screen or a cleaner for the purpose of removing foreign matters mixed in the waste paper and brought into the manufacturing process of the deinked waste paper pulp can be employed. Waste paper contains foreign materials such as adhesives, adhesives, adhesive tapes, magazine backs, vinyl tapes, poly straps, films, etc., so foreign matter removal is limited to devices for removing specific foreign materials. In addition, a device for removing various foreign substances may be combined. In the method of the present invention, the foreign matter removing apparatus is preferably installed immediately after the disaggregation process in the preceding process, but can also be installed before the dehydration / washing process in the subsequent process, or both. It can also be installed. Further, it is preferable that the screen is a combination of a screen having a slit of 0.15 mm or less and a round hole for removing poly string, film and the like. The form of the cleaner is not limited as long as heavy foreign substances can be efficiently removed.

It is also possible to provide a pre-stage flotation process for deinking treatment after the pulp slurry that has undergone the disaggregation process, the screening process and the like is diluted in the pre-stage process. In the former flotation process, the ink can be agglomerated and separated by the deinking agent added in the disaggregation process, but when used in the flotation process in the latter process, the same ink aggregating deinking agent is used. You may add newly.

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is of course not limited to these examples. In addition, unless otherwise indicated, the addition rate of the chemical | medical agent in an Example and a comparative example shows the mass% per the absolute dry pulp mass.
Examples 1 and 7 are reference examples.

<COD measurement method>
The amount of COD in the wastewater generated from the production process was determined as described below. The COD amount is shown as a result of measuring each COD concentration according to JIS K 0102 standard 17 and then converting it to the COD amount per COD (COD kg / pulp T). Specifically, in the process shown in FIG. 1, the amount of COD in the surplus drainage that could not be used in the disaggregation process, and the COD in the floss drainage generated from the flotation drainage process and the flotation drainage process generated from the subsequent flotation process. The amounts were summed to determine the total COD amount.
The “total COD amount” here is an index indicating the total amount of COD discharged out of the deinked waste paper pulp manufacturing process system, and the smaller the total COD amount, the lower the wastewater treatment cost. means.

<Whiteness measurement method>
After the finished pulp was disaggregated, a sulfuric acid band was added to the pulp slurry in an amount of 20.0% against dry pulp, and a sheet having a basis weight of 60 g / m 2 was produced according to Tappi test method T205os-71 (JIS P 8209). Then, about the whiteness of the pulp, the whiteness of the fluorescence intensity cut was measured with a spectral whiteness colorimeter (manufactured by Suga Test Instruments). The “whiteness” here is an index indicating how much free ink that could not be removed mainly by the deinking process by flotation remains. The higher the whiteness, the less free ink remains. Means that.

Example 1
The raw material of waste paper (ash content: 13.9% by mass), mainly newspapers and leaflets, is charged to the pulper, the dilution water is adjusted to a raw material concentration of 3.5% by mass, and the caustic soda addition rate is 0.5% by mass. Then, a higher alcohol-based deinking agent (manufactured by Kao Corporation, DI-7020) was added at an addition rate of 0.1% by mass to disaggregate.
The raw slurry (pH 11.9) after disaggregation is adjusted with dilution water to a concentration of 1.1% by mass and sent to a floatator (manufactured by Oji Engineering Co., Ltd.), and the previous flotation treatment is performed at a temperature of 40 ° C. It was.
The raw slurry after the flotation treatment was subjected to the previous dehydration and washing treatment with an extractor and disc thickener (washing filtrate pH 11.2), and dehydrated and concentrated to a raw material concentration of 29% by mass with a screw press.
Subsequently, the first ink dispersion treatment was performed on the dehydrated concentrated raw material using a Disperser manufactured by Aikawa Tekko Co., Ltd., and the obtained dispersion treatment liquid was added with a hydrogen peroxide addition rate (vs. pulp) of 3.5% by mass, A sodium hydroxide addition rate of 2.0% by mass and a sodium silicate addition rate (vs. pulp: sodium hydroxide equivalent) of 0.6% by mass were added, and bleaching was performed with a bleaching time of 120 minutes. The pH immediately after the bleaching treatment was 10.9. Next, while maintaining the temperature and concentration of the bleaching solution, a second dispersion treatment was performed using the Disperser manufactured by Aikawa Tekko.

Thereafter, the treatment liquid after the second dispersion treatment was diluted with dilution water, and then the pH was adjusted to 9.0 by adding sulfuric acid, and the subsequent flotation treatment was performed with the above-mentioned floatator (manufactured by Oji Engineering Co., Ltd.). It was. The deinking process by the latter stage floatator is performed at an addition rate of 0.11% by mass of a special fatty acid derivative (manufactured by Kao Corporation, DI-1120), a process concentration of 1.1% by mass of the floatator, and a process temperature of the floatator of 40 ° C. went.
After subsequent dehydration and washing treatment with an extractor and disc thickener, it was concentrated to 15% by mass with a screw press to obtain a finished deinked waste paper pulp.

In the method of the present embodiment, the waste water (b) of the preceding dewatering / washing process shown in FIG. 1 is mainly used as the diluting water in the disaggregation process and the pre-stage flotation process. Process wastewater (a) was used. In addition, the waste water (a) from the subsequent dehydration / washing process was used as the dilution water in the subsequent flotation process after the intermediate process (first dispersion process-bleaching process-second dispersion process).
For the disaggregation treatment, flotation treatment, dehydration / washing treatment, bleaching treatment, and ink dispersion treatment described above, equipment used for the production of ordinary deinked waste paper pulp was used. The above processing flow is shown in FIG. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Example 2
In the method of Example 1, a deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that the raw material containing a floatator in the subsequent flotation step was adjusted to pH 8.0 with sulfuric acid. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Example 3
In the method of Example 1, a deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that the raw material containing a floatator in the subsequent flotation step was adjusted to pH 7.0 with sulfuric acid. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Example 4
In the method of Example 1, the raw material containing a floatator in the preceding flotation step was adjusted to 9.0 with sulfuric acid, and the raw material containing the floatator in the latter flotation step was adjusted to pH 8.0 with sulfuric acid. The same treatment as in Example 1 was performed to obtain deinked waste paper pulp. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Example 5
In the method of Example 4, a deinked waste paper pulp was obtained by performing the same treatment as in Example 4 except that the raw material containing a floatator in the previous flotation step was adjusted to 8.0 with sulfuric acid. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Example 6
In the method of Example 4, a deinked waste paper pulp was obtained by performing the same treatment as in Example 4 except that the raw material containing a floatator in the previous flotation step was adjusted to 7.0 with sulfuric acid. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Example 7
In the method of Example 1, a deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that the second dispersion treatment was not performed. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Comparative Example 1
In the method of Example 1, a deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that sulfuric acid was not added to the raw material containing the floatator in the subsequent flotation step. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Comparative Example 2
In the method of Comparative Example 1, the same treatment as in Comparative Example 1 was performed except that the sodium hydroxide addition rate was 3.0% and the sodium silicate addition rate (converted to sodium hydroxide) was 0.9% in the bleaching step. To obtain deinked waste paper pulp. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

Comparative Example 3
In the method of Example 7, a deinked waste paper pulp was obtained by performing the same treatment as in Example 7 except that sulfuric acid was not added to the raw material containing the floatator in the latter flotation step. Table 1 shows the total COD amount and the whiteness of the obtained deinked waste paper pulp.

表１の実施例１〜７及び比較例１〜３の結果から、前記中間工程より後段の工程中の脱墨処理するフローテーション工程を中性領域のｐＨ値に調整して行うことが、遊離インキの除去を効率的に行うことを可能として脱墨古紙パルプの白色度を高い水準に維持することができるとともに、工程全体からのＣＯＤの排出量を少なくすることも可能とする手段であることが明らかである。

From the results of Examples 1 to 7 and Comparative Examples 1 to 3 in Table 1, adjusting the flotation process for deinking in the process subsequent to the intermediate process to a pH value in the neutral region is free. It is a means that makes it possible to efficiently remove ink and maintain the whiteness of the deinked waste paper pulp at a high level, and to reduce COD emissions from the entire process. Is clear.

According to the present invention, the amount of chemicals used in the bleaching process can be reduced while maintaining the whiteness at a high level, and the amount of COD discharged from the entire process is small. A manufacturing method is provided.

(A): Dewatering / washing process wastewater in the subsequent process (b): Dewatering / washing process wastewater in the previous process

Claims (8)

Dispersion in deinked waste paper pulp manufacturing method according to a series of steps that have at least a disaggregation process of printed waste paper, a flotation process for deinking treatment, a dispersion process for ink dispersion treatment, a bleaching process, and a dehydration / washing process A combination process part in which a process and a bleaching process are continuous is an intermediate process, the bleaching process in the intermediate process is an alkali hydrogen peroxide bleaching process, and includes the preceding process from the disaggregation process to the intermediate process and the intermediate process Each step in the series of steps is a treatment step under a pH condition selected from the range of pH 7.0 to 13.0, and subsequent steps subsequent to the intermediate step are pH 6.0 to 8.5 A series of steps including a flotation step for deinking under pH conditions selected from the range of steps, and a dehydration / washing step, and dehydration during the subsequent steps Characterized by using as dilution water and / or wash water filtrate produced from the washing step in primarily subsequent series of steps, the production method of deinked waste paper pulp. Either of the intermediate steps is selected from a combination step that is continuous in the order of a dispersion step for ink dispersion treatment-a bleaching step and a combination step that is a sequence of a dispersion step for ink dispersion treatment-a bleaching step-a dispersion step for ink dispersion treatment The method for producing deinked pulp according to claim 1, comprising a combination step. The flotation step of deinking treatment under a pH condition selected from the range of pH 6.0 or more and 8.5 or less in the step subsequent to the intermediate step is performed by adding acid to the pH value of the pulp slurry from the intermediate step. 3. The method for producing deinked pulp according to claim 1 or 2, wherein the method is a flotation step for adjusting and deinking. 4. A flotation step of deinking treatment by diluting a disaggregation treatment liquid from the disaggregation step with dilution water and a subsequent dehydration / washing step in a step preceding the intermediate step. The manufacturing method of the deinking pulp of any one of these. In the process preceding the intermediate process, the decontamination process liquid from the disaggregation process has a flotation process for deinking by diluting with dilution water and a subsequent dehydration / washing process. The method for producing deinked pulp according to any one of claims 1 to 4, wherein waste water in the washing step is used as dilution water in the disaggregation step and / or the flotation step. The part of the waste water from the dehydration / washing process after the flotation process in the process subsequent to the intermediate process is used as dilution water and / or cleaning water in the process in the previous process. The method for producing a deinked pulp according to any one of the preceding claims. A series of steps consisting of the preceding step, the intermediate step, and the latter step are a disaggregation step, a previous flotation step, a preceding dehydration / washing step, an intermediate step (dispersion step-bleaching step or dispersion step-bleaching step- The dispersion step), the subsequent flotation step, and the subsequent dehydration / washing step are a series of steps arranged in all steps so as to be in this order. The method for producing a deinked pulp according to any one of the preceding claims. The deinked pulp production according to any one of claims 1 to 7 , wherein the pH adjustment of the pulp slurry introduced into the flotation step in the subsequent step is pH adjustment by addition of sulfuric acid. Method.

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