JP6583005B2 - Manufacturing method and manufacturing system of deinked waste paper pulp - Google Patents

Description

The present invention relates to a manufacturing method and a manufacturing system of deinked waste paper pulp for obtaining recycled pulp from used printed 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. By this method, the whiteness of the deinked pulp can be increased. In addition, the normal deinked pulp manufacturing process controls the amount of water used so as not to reduce the pulp yield as much as possible, and changes it according to the quality of the pulp to be manufactured. It is necessary to effectively use the circulating white water (filtrate generated in the washing process) in the system.

However, since around 2006, the acid newspaper, which was relatively easy to remove the ink from the pulp fiber, was replaced with the neutral newspaper, so that it was very difficult to remove the ink. Therefore, it is necessary to actively use a large amount of a surfactant or alkali for ink peeling, or strengthen ink peeling in a dispersion process. As a result, a large amount of fine ink is circulated in the white water in the waste paper pulp manufacturing process. Therefore, the whiteness of the waste paper pulp diluted with the white water is inevitably lowered.

In general, several methods have been proposed in which white water discharged from a washing machine is floated with a floatator and used as washing and dilution water for pulp (for example, Patent Documents 1 to 4). Expenses and chemical costs increase.

Japanese Patent No. 2032977 JP 2004-68175 A Japanese Patent No. 3618324 JP 2004-19025 A

An object of the present invention is to produce, at low cost, a pulp having high whiteness and little dirt from a paper to which ink is adhered.

In a series of processes for producing deinked waste paper pulp from paper with ink attached, the present inventors circulate in the deinked pulp manufacturing process after the bleaching process or after the continuous bleaching process and the dispersing process. By using non-circulating water (fresh water) other than the existing water and diluting until the pulp concentration is 10% by mass or less, it was found that the above problems can be solved, and the following inventions have been made. is there.

[1]
In the method for producing deinked pulp having at least a disaggregation step, a flotation step, a dispersion step, a bleaching step, a dehydration step, and a washing step,
After the bleaching step or after the dispersing step, use non-circulated water other than the water circulated in any step of the deinked pulp manufacturing method, and dilute until the pulp concentration becomes 10% by mass or less. Further comprising a first dilution step
A method for producing deinked waste paper pulp, wherein a flotation step is performed at least once after the first dilution step.
[2]
The method for producing deinked waste paper pulp according to [1], wherein fresh water is used as at least a part of the non-circulated water.
[3]
The method for producing deinked waste paper pulp according to either [1] or [2], wherein papermaking wastewater generated from a papermaking facility is used as at least a part of the non-circulated water.
[4]
The method for producing deinked waste paper pulp according to any one of [1] to [3], wherein fresh water or industrial water is used as at least part of the non-circulated water.
[5]
Any one of [1] to [4], further comprising a second dilution step of further diluting the pulp using white water circulating in the deinking step before performing the deinking step after the first dilution step. A method for producing deinked waste paper pulp according to 1.
[6]
In a deinked pulp manufacturing system having at least disaggregation means, flotation means, dispersion means, bleaching means, dewatering means, and washing means,
After the bleaching step by the bleaching means or after the dispersing step by the dispersing means, using non-circulated water other than the water circulating in the deinked pulp manufacturing system, the pulp concentration is 10% by mass or less. Further comprising first dilution means for diluting until
A deinked waste paper pulp production system, wherein after the dilution step by the first diluting means, the flotation means by the deinking means is performed at least once.

According to the method of the present invention, a pulp having high whiteness and less dirt can be produced at low cost from paper to which ink has adhered.

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 of the present invention includes a disaggregation process (process for disaggregating used printing paper), a flotation process (deinking process), a dispersion process (process for dispersing ink), a bleaching process, a dewatering process, and a washing process. It is a method according to a pulping process of waste paper having at least a process. And after the process of high concentration (after the bleaching process, or after the continuous bleaching process and dispersion process), use fresh water (non-circulated water other than the water circulating in the deinked pulp manufacturing process). Then, dilute until the pulp concentration is 10% by mass or less. Furthermore, after diluting until the pulp concentration becomes 10% by mass or less, it is diluted with circulating white water in the process, and a deinking process is performed in the flotation process, whereby a pulp with higher whiteness can be obtained.
More specifically, the whiteness after the bleaching step or after the continuous bleaching step and the dispersing step is significantly improved, and the removal rate of free ink in the subsequent flotation step is improved. As a result, it is possible to reduce the amount of chemicals used in the bleaching process by maintaining the whiteness of the deinked wastepaper pulp at a high level and reducing the dirt, and the method for producing the deinked wastepaper pulp at a low cost Is provided. The deinked waste paper pulp produced by the method of the present invention has a whiteness of about 50% to 85%, a dart of 15000 pieces / m ^{2 to} 25000 pieces / m ² , and a high-quality system that requires particularly high whiteness. Suitable for paper.
As described above, the present invention can provide a method for significantly reducing the manufacturing cost by efficiently improving the whiteness of the deinked waste paper pulp produced from the printed waste paper and reducing the dirt. Furthermore, the present invention can provide deinked wastepaper pulp having a quality (whiteness, dart) comparable to that of deinked wastepaper pulp produced by a general production method.

The paper used as a raw material in the present invention is paper to which ink has adhered. A suitable example of the paper to which the ink is attached is printed waste paper. Examples of used printed paper include used paper containing 7% to 40% ash, such as newspaper, finely 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 this invention. As a preferable disaggregation treatment in the disaggregation step, the raw material printed waste paper is put in diluted water so as to have a solid content concentration of 12 to 18% by mass. Furthermore, the process performed by adding alkali chemicals (sodium hydroxide etc.) 0-3.0 mass% with respect to pulp, Preferably 0.1-2.5 mass% is mentioned.
When a deinking agent is used in the disaggregation step, those having strong permeability to pulp fibers and strong ink peelability are preferred. The addition amount of the deinking agent is preferably 0.01 to 0.5% by mass, more preferably 0.03 to 0.3% by mass with respect to the pulp. The disaggregation time is preferably 10 to 30 minutes, more preferably 10 to 25 minutes, and still more preferably 10 to 18 minutes. It is preferable that disaggregation temperature is 10-50 degreeC, More preferably, it is 30-50 degreeC.

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.

The present invention may further include a screening step. 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 present invention, the dispersion step of dispersing the ink is a step of dispersing the ink using a disperser. You may arrange | position to both of a bleaching process and may arrange | position to any one before and behind a bleaching process. 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 concentration is preferably as high as (mass%), more preferably 25% to 40%. It is preferable that processing temperature is 25 to 100 degreeC, More preferably, it is 40 to 90 degreeC. In such a shaft-type disperser, the friction between the fibers is the main component, and ink separation and dirt dispersion occur. When the concentration of the pulp to be treated is 20% or more, a mechanical load is easily applied, the dispersibility of ink peeling / dirt is improved and reduced, and energy necessary for temperature rise can be saved. Moreover, it becomes easy to squeeze mechanically that the density | concentration of the pulp processed is 50% or less.

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 the present invention, the 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 preferably added in an amount of 0.1 to 5.0% by mass with respect to the pulp. Even if the amount of hydrogen peroxide added is further increased, the increase in whiteness tends to saturate.
At the time of alkaline hydrogen peroxide bleaching, it is preferable to add caustic soda to the pulp in an amount of 0.3 to 3.0% by mass and sodium silicate to the pulp in an amount of 0.3 to 3.5% by mass. Caustic soda and sodium silicate are more 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 preferably 10 minutes to 5 hours, more preferably 1.5 to 3 hours. When the bleaching time is at least the preferred lower limit, the reaction with the bleaching chemical proceeds sufficiently. When the bleaching time is less than or equal to the preferred upper limit, it is possible to prevent the yellowing of the pulp starting from the point where the bleaching chemical is exhausted. The pulp concentration (% by mass) during the bleaching treatment is preferably 15 to 35%, more preferably 25 to 30%. When the pulp concentration is 15% or more, the reactivity with bleaching chemicals is more excellent. Moreover, when the pulp concentration is 35% or less, it is possible to prevent spots from occurring in mixing with chemicals in the disperser.
The pH during the bleaching treatment is preferably 10.5 to 12.0. Within this range, the bleaching property of hydrogen peroxide is excellent. It is effective to carry out the bleaching temperature at 50 to 120 ° C.

The flotation step in the present invention is preferably performed at a pH of 6.0 to 11.0 from neutral to alkaline, and more preferably at a pH of 7.0 to 10.0. When the pH is 6.0 or more, corrosion of piping and equipment can be prevented, and equipment costs are reduced. In addition, when the pH is 11.0 or less, the ink removal property of the deinked pulp is further improved. Sulfuric acid, hydrochloric acid, organic acid, or the like can be used as an acidic drug that adjusts the treatment pH in the flotation process. Furthermore, chemicals such as alkaline caustic soda and sodium silicate may be used for pH adjustment as necessary. After the disperser treatment in the dispersion step, the pulp concentration is diluted to 10% by mass or less with fresh water, and then the concentration is adjusted with the system white water to about 0.7 to 2.0% by mass with the system white water, It is particularly efficient to remove the peeled ink by a flotation process adjusted to the pH range. 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. Not very good.
There is no restriction on the form of the flotator in the flotation process. The pulp concentration in the flotation process is preferably 0.8 to 1.5% by mass. It is preferable that the processing temperature in a flotation process is 10-55 degreeC, More preferably, it is 30-50 degreeC.

In the flotation process for performing the deinking 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.

On the other hand, as dilution water used for diluting from 20 to 35% by mass of pulp to 10% by mass or less before the treatment in the flotation process, water containing almost no fine ink, so-called new water is used. It is preferable to do. As such new water, for example, non-circulated water (for example, clear white water of a paper machine) other than water circulated in any one of clean water, industrial water, and deinked pulp manufacturing process is used. it can. Pulp concentration can be diluted with fresh water up to 10% by mass or less and about 0.7% by mass, and then to a concentration suitable for the subsequent flotator treatment in the deinking pulp process, for example, using clear white water of a washing machine Also good.

As a process after the deinking process is performed in the flotation process, a dehydration / washing process for removing fine ink that could not be removed by the floatator is arranged. After diluting 0.6 to 1.5% by mass of pulp slurry with clear water or clear white water of a paper machine, or clear white water of a deinking pulp in-process washing machine, dewatering to 15 to 35% by mass and washing. Is preferred.
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 added amount of the chemical is less than or equal to the above preferable upper limit, it is possible to prevent the ink from being adsorbed to the pulp slurry together with the ash and the fiber, and it is economically advantageous. If the chemical flows out into the wastewater without adsorbing to the pulp, the wastewater COD will rise, so it is preferable to keep the addition to the minimum necessary amount.

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, etc. is diluted in the above 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.

<Whiteness measurement method>
After the finished pulp was disaggregated, 20.0% of the dried pulp was added to the pulp slurry, and a sheet having a basis weight of 60 g / m ² was prepared 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.

<Dirt evaluation method>
The finished pulp is dispensed onto a 150 mesh wire, and the ink released from the fibers is thoroughly washed with about 20 liters of fresh filtered water per gram of pulp, and then a handsheet with a basis weight of 60 g / m ² is applied to JIS. Five sheets were produced in accordance with the method for preparing the handsheet for testing shown in P8222. The number of darts of 0.004 to 5.0 mm ² size contained in the center 10 cm × 10 cm in 5 handsheets was measured using a Dart Analyzer (DIP-200) manufactured by Oji Scientific Instruments. The measurement result was converted to the number per 1 m ^{2 of} pulp and used as the number of dirt.

Example 1
The raw material of waste paper (ash content 14.5% by mass), mainly newspaper 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 0.6% by mass. Then, a higher alcohol-based deinking agent (manufactured by Toho Chemical Co., Ltd., FT-517) was added at an addition rate of 0.1% by mass to disaggregate.
The raw material slurry (pH 11.8) after disaggregation is adjusted with dilution water so as to have a concentration of 1.1% by mass, and sent to a floatator (manufactured by Oji Engineering Co., Ltd.). It was.
The raw slurry after the flotation treatment was subjected to dehydration and washing in the previous stage with an extractor and disc thickener (washing filtrate pH 11.0), and dehydrated and concentrated to a raw material concentration of 30% 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. In the obtained dispersion treatment liquid, hydrogen peroxide addition rate (vs. pulp) 3.0 mass%, sodium hydroxide addition rate 2.0 mass%, sodium silicate addition rate (vs. pulp: sodium hydroxide conversion) 0.6 Mass% was 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 pulp after the second dispersion treatment was diluted with fresh water in an amount corresponding to a pulp concentration of 10% by mass. Then, after diluting to a concentration of 1.0% with washing machine washing white water in the dehydration / washing step, a subsequent flotation treatment was performed with a floatator (manufactured by Oji Engineering Co., Ltd.). The deinking process by the latter stage floatator was performed at the addition rate of 0.10 mass% of the special fatty acid derivative (the Kao company make, DI-1120), and the processing temperature of the floater 40 degreeC.
Subsequent dehydration and washing treatment was performed with an extractor and disc thickener, and the concentrate was concentrated to 15% by mass to obtain a finished deinked waste paper pulp.

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. This processing flow is shown in FIG. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Example 2
A deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that the pulp after the second dispersion treatment was diluted with fresh water in an amount corresponding to a pulp concentration of 4% by mass. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Example 3
The same treatment as in Example 1 except that fresh water in an amount corresponding to a pulp concentration of 1% by mass is used for the pulp after the second dispersion treatment, and the washing machine washing white water in the dehydration / washing process is not used as dilution water. The deinked waste paper pulp was obtained. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Example 4
Except for the hydrogen peroxide addition rate (vs. pulp) of 2.7% by mass, the same treatment as in Example 3 was performed to obtain deinked waste paper pulp. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Example 5
A deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that the pulp after the second dispersion treatment was diluted with a paper machine clear white water in an amount corresponding to a pulp concentration of 10% by mass. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Example 6 The deinked waste paper pulp was treated in the same manner as in Example 4 except that the pulp after the second dispersion treatment was diluted with paper machine clear white water in an amount corresponding to a pulp concentration of 4% by mass. Obtained. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Example 7
Example 4 except that the paper machine clear white water in an amount corresponding to a pulp concentration of 1% by mass is used for the pulp after the second dispersion treatment, and the washing machine washing white water in the dehydration / washing process is not used as dilution water. The same treatment was performed to obtain deinked waste paper pulp. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Example 8
A deinked waste paper pulp was obtained by performing the same treatment as in Example 7 except that the hydrogen peroxide addition ratio (vs. pulp) was 2.7% by mass. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Comparative Example 1
A deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that the pulp after the second dispersion treatment was diluted with fresh water in an amount corresponding to a pulp concentration of 15% by mass. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Comparative Example 2
A deinked waste paper pulp was obtained by performing the same treatment as in Example 1 except that the pulp after the second dispersion treatment was diluted with a paper machine clear white water in an amount corresponding to a pulp concentration of 15% by mass. . Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

Comparative Example 3
The pulp after the second dispersion treatment is the same as in Example 1 except that the pulp is not diluted with fresh water and diluted with washing machine washed white water in a dehydration / washing process in an amount corresponding to a pulp concentration of 1% by mass. Processing was performed to obtain deinked waste paper pulp. Table 1 shows the whiteness and the number of darts of the obtained deinked waste paper pulp.

From the results of Examples 1 to 8 and Comparative Examples 1 to 3 in Table 1, by diluting the high-concentration pulp after the dispersion treatment with fresh water until the pulp concentration becomes 10% by mass or less, the latter stage floatator process By improving the efficiency of removing fine ink released in the dehydration / washing process, the whiteness of the deinked wastepaper pulp can be maintained at a high level, and the dirt removal effect can be greatly improved. Is clear.

According to the present invention, deinked waste paper pulp having high whiteness and little dirt can be produced at low cost from printed waste paper.

(A): Fresh water (b): Dewatering / washing process washing machine washing white water

Claims (5)

In the method for producing deinked pulp having at least a disaggregation step, a flotation step, a dispersion step, a bleaching step, a dehydration step, and a washing step,
After the bleaching step or after the dispersing step, use non-circulated water other than the water circulated in any step of the deinked pulp manufacturing method, and dilute until the pulp concentration becomes 10% by mass or less. Further comprising a first dilution step
There at least once rows flotation step after the first dilution step,
Before performing the deinking step after the first dilution step, use white water circulating in the deinking step.
Method for producing deinked waste paper pulp characterized that you have a second dilution step for diluting the pulp al. The method for producing deinked waste paper pulp according to claim 1, wherein fresh water is used as at least a part of the non-circulated water. The method for producing deinked waste paper pulp according to any one of claims 1 and 2, wherein papermaking wastewater generated from a papermaking facility is used as at least part of the non-circulated water. The method for producing deinked waste paper pulp according to any one of claims 1 to 3, wherein fresh water or industrial water is used as at least a part of the non-circulated water. In a deinked pulp manufacturing system having at least disaggregation means, flotation means, dispersion means, bleaching means, dewatering means, and washing means,
After the bleaching step by the bleaching means or after the dispersing step by the dispersing means, using non-circulated water other than the water circulating in the deinked pulp manufacturing system, the pulp concentration is 10% by mass or less. Further comprising first dilution means for diluting until
There at least once rows flotation means using the deinking means after dilution step with the first dilution means,
Before performing the deinking step after the first dilution step, use white water circulating in the deinking step.
Manufacturing system of deinked waste paper pulp characterized that you have a second dilution step for diluting the pulp al.

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