JP2010100984A - Method for deinking printed waste paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing deinked pulp from printed waste paper as a raw material, by which the microdivision of adhesive foreign matter can be prevented to lower the COD of drain water, and the deinked pulp small in residual ink content can be produced. <P>SOLUTION: The method for producing the deinked pulp of printed waste paper includes adding anhydrous crystalline laminar silicate and a deinking agent having a difference of 0 to 3.5 mN/m between a static surface tension at pH 10.5, 40°C and a concentration equal to or larger than the critical micelle concentration (CMC) and a static surface tension at pH 8.5, 40°C and a concentration equal to or larger than the critical micelle concentration (CMC), preferably in an amount of 0.1 to 1.5 mass% based on the mass of absolutely dry pulp, to the dry pulp, and peeling the ink at pH 7.0 to 9.9, in a deinking process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing deinked pulp. More specifically, in the deinking process in the production of deinked pulp, an anhydrous crystalline layered silicate and a deinking agent having a specific static surface tension are added, and the conditions from the weakly alkaline region to the neutral region are added. The present invention relates to a method for producing deinked pulp in which ink is peeled from the pulp.

  In recent years, recycling of waste paper has attracted attention from the viewpoint of resource conservation or global environmental protection, and it is extremely important for the paper industry to process waste paper at a higher level and expand the scope of recycling. It has become. As one of these directions, the printing ink of the used printing paper is deinked and removed to produce a pulp with less residual ink, and if necessary, mixed with virgin pulp to produce a new paper.

  However, in the disaggregation process and the ink peeling process in the deinking pulp production, a high shearing force is generally applied under a high alkaline condition such as a pH exceeding 10, so that the pressure-sensitive adhesive, adhesive, pressure-sensitive adhesive tape, Foreign matter such as magazine back glue and vinyl tape is becoming finer, and it is very difficult to completely remove it through subsequent selection processes such as screens and cleaners. If fine foreign matter is mixed in the deinked pulp, machine troubles such as running out of paper or paper foreign matter will be incorporated into the paper when producing paper using deinked pulp. A drop occurs. In addition, since high shear force is applied under alkaline conditions, the chemical oxygen demand (COD) of the effluent increases, and the pulp fiber hurts, resulting in a decrease in drainage and machine runnability. In addition, there is a problem that the pulp becomes less bulky and inferior in optical suitability.

  Paper 49 (1) 121-130 (Non-Patent Document 1), paper waste paper is disaggregated at low temperature and neutrality to prevent the foreign matter from being miniaturized. A method has been proposed in which the ink is removed under high alkaline conditions after removal. However, although improvement is expected with respect to foreign matters, a high shearing force is imparted to the pulp under high alkaline conditions, and no reduction in COD can be expected.

  In response to these problems, the alkaline chemicals in the production of deinked pulp (DIP) are reduced and neutralized to prevent the foreign matter mixed in the waste paper from being refined, and the waste COD There has been proposed a method for reducing the above. However, the reduction of alkaline chemicals causes a decrease in ink peelability and impairs the quality of the final pulp. For this reason, Japanese Patent Application Laid-Open No. 11-200269 (Patent Document 1) employs a method of acid-adding neutralized waste paper that has been aged under alkaline conditions, and a residual shearing ink is applied by applying a high shearing force after neutralization or simultaneously with neutralization. Has proposed a method for producing a low-DIP and reducing the COD of the effluent from the DIP production process. However, the use of acid for neutralization of alkali-aged waste paper leads to increased costs.

  Japanese Patent No. 3260211 (Patent Document 2) discloses a crystalline silicate having deinking performance. However, it has not been shown to be used under conditions where deinking is difficult, such as weakly alkaline to neutral regions.

Japanese Patent Laid-Open No. 11-200269 Japanese Patent No. 3260211

Paper pamphlet of technical cooperation Vol. 49 (1) 121-130

  The present invention, by performing the deinking process under weakly alkaline to neutral conditions, prevents the decontamination of foreign matter, reduces the COD of wastewater, and can produce a deinked pulp with a small residual ink amount, And it aims at providing the manufacturing method of the deinking pulp excellent in operativity.

  As a result of intensive investigations on a method for producing deinked pulp using printed waste paper as a raw material under conditions from a weak alkaline region to a neutral region, the present inventors have found that crystalline layered silicate anhydrides and pH of 10 in the deinking step The difference between the static surface tension at a concentration of not less than .5, 40 ° C. and a critical micelle concentration (CMC) and the static surface tension at a concentration of not less than pH 8.5, 40 ° C. and critical micelle concentration (CMC) is 0-3. It has been found that the purpose can be achieved by adding a 5 mN / m deinking agent and peeling the ink from the pulp at pH 7.0-9.9.

  Crystalline layered silicate anhydrides, and static surface tension at pH 10.5, 40 ° C. and above critical micelle concentration (CMC) and pH 8.5, 40 ° C., at concentrations above critical micelle concentration (CMC) By using a deinking agent with a difference from static surface tension of 0 to 3.5 mN / m in the deinking process, the ink peelability is higher than the conditions in a highly alkaline region where the pH normally used exceeds 10. Even if the deinking process is carried out under weakly alkaline to neutral conditions, the deinked pulp with a small residual ink amount can be produced. In addition, by performing the deinking process under conditions of weak alkaline to neutral region, the adhesive foreign matter is not excessively refined, so that the adhesive foreign matter removal efficiency in the subsequent dust removing step can be improved, and the drainage COD can be reduced.

  In the present invention, in the deinking step in the production of deinked pulp, an anhydrous crystalline layered silicate and a deinking agent having a specific static surface tension are added, and the pH is 7.0 to 9.9. Under, peel the ink from the pulp.

(used paper)
The used paper used as the raw material for the deinked pulp of the present invention may be any used printed paper, and includes, for example, newspapers, flyers, magazines, books, office papers, other copiers, printing papers generated from OA equipment, and the like. . In particular, used magazine paper including pressure-sensitive adhesives, adhesives, pressure-sensitive adhesive tapes, and pressure-sensitive adhesives such as magazine back glue can also be used as a raw material for the deinked pulp of the present invention.

(Manufacture of deinked pulp)
Usually, in the production of deinked pulp, it is separated from the pulp, the disaggregation treatment that disintegrates the waste paper by adding alkaline chemicals and surfactants, the ink stripping treatment that strips the ink from the pulp under mechanical share and alkaline conditions Flotation treatment and / or washing treatment to remove the residual ink, generally after dehydrating to a pulp concentration of 10 to 35% by mass, adding alkaline chemicals, hydrogen peroxide and / or surfactant to the ink from the pulp Further, an alkali dipping treatment (also referred to as an aging treatment) for further peeling is performed, and a flotation treatment and / or a washing treatment is performed again. Thereafter, the foreign matter is removed in a dust removing step (foreign matter removing step).

(Addition of crystalline layered silicate and deinking agent)
In the present invention, the crystalline layered silicate anhydride, and the static surface tension and pH 8.5, 40 ° C., critical micelle concentration (CMC) at pH 10.5, 40 ° C. and higher than the critical micelle concentration (CMC). It is essential to add a deinking agent having a difference from the static surface tension of 0 to 3.5 mN / m in the above concentration in the deinking step. The “deinking step” in the present invention refers to a step of peeling the ink adhering to the pulp fiber by giving a mechanical share, and specifically, the above-mentioned disaggregation treatment, alkali dipping treatment ( It is also called aging treatment) and ink peeling treatment by mechanical share. The crystalline layered silicate and the deinking agent may be added by any of these treatments, but it is preferable to add them during the disaggregation treatment, which is the first stage of the deinking process.

(PH)
In the present invention, the deinking step is performed under conditions of a weak alkaline region to a neutral region of pH 7.0 to 9.9, preferably pH 7.0 to 9.5, for example, by suppressing the addition amount of alkaline chemicals. When the pH is lower than 7.0, it is not desirable because the disintegration property and ink releasability of the used paper are remarkably lowered. On the other hand, when the pH exceeds 9.9, it is not preferable because the refining of the sticking foreign matter is promoted during the disaggregation of the used paper and the ink peeling, and the COD of the drainage is remarkably increased. The pH can be adjusted at any stage prior to the addition of the crystalline layered silicate anhydride and the deinking agent, but it is most preferable to adjust the pH to the above range during the deflocculation process, which is the first stage of the deinking process. .

(Disaggregation processing)
In the disaggregation process in the present invention, any of a high concentration pulper, a low concentration pulper, and a drum pulper may be used, but it is preferable to perform the disaggregation process using a high concentration pulper. The temperature during the disaggregation treatment is preferably 60 ° C. or lower, more preferably 50 ° C. or lower, but is not limited thereto.

(Ink peeling treatment)
Any of a kneader, a disperser, and a refiner may be used in the ink stripping process based on the mechanical share.

(Anhydrous crystalline layered silicate)
The crystalline layered silicate anhydrides used in the present invention are preferably those represented by general formulas such as Na ₂ O · 2SiO ₂ , K ₂ O · 2SiO ₂ , but are not necessarily limited thereto. It is not a thing. Silicates (water glass and the like) that are usually used for peeling off ink are in an amorphous state and do not have a fixed crystal structure. On the other hand, the crystalline layered silicate anhydride used in the present invention has a structure as shown in the following [Chemical Formula 1], and the basic structure of the molecule is a silicate layer (SiO ₄ ) and its structure. It is composed of surrounding sodium ions or potassium ions, has a layered structure in which plate-like layers are stacked, and has a δ-type crystal structure. Such a crystalline layered silicate has a markedly higher metal ion trapping ability than other crystalline silicates.

  The crystalline layered silicate anhydride is preferably one having a particle size of 600 μm or less, but is not necessarily limited thereto. More preferably, those having a particle size of 60 μm or more and 100 μm or less are used. The added amount of the crystalline layered silicate anhydride used in the present invention is preferably 0.1 to 1.5% by mass, and 0.1 to 1.0% by mass with respect to the mass of the absolutely dry pulp. More preferably. By making the addition amount 0.1% by mass or more, the disaggregation property and ink releasability of the used paper can be improved. Moreover, by setting it as 1.5 mass% or less, it can prevent that pH at the time of used paper disaggregation and ink peeling becomes too high, and can suppress the refinement | miniaturization of a sticking foreign material, and the remarkable increase in COD.

The crystalline layered silicate anhydride used in the present invention is preferably added in a solid or suspension state, but is not necessarily limited thereto.
The alkaline chemical used in combination with the crystalline layered silicate anhydride may be at least one of caustic soda, potassium hydroxide, sodium silicate, and sodium carbonate.

(Deinking agent)
In the present invention, the static surface tension at a pH of 10.5, 40 ° C. and a critical micelle concentration (CMC) or higher and the static surface tension at a pH of 8.5, 40 ° C., a critical micelle concentration (CMC) or higher. Add a deinking agent with a difference of 0-3.5 mN / m. By using such a deinking agent, the effect of the deinking agent is sufficiently exerted even if the deinking process is performed under conditions of weak alkaline to neutral range. Here, the critical micelle concentration (CMC; Critical Micelle Concentration) refers to the concentration at which surfactant molecules in the deinking agent form aggregates (micelles) with lipophilic groups facing inward. The static surface tension can be measured based on the Wilhelmy method (plate method).

As such a deinking agent, one containing a higher alcohol polyoxyalkylene ether is preferable.
The static surface tension at a pH of 10.5 and 40 ° C. and a critical micelle concentration (CMC) or higher and the static surface tension at a pH of 8.5 and 40 ° C. and a critical micelle concentration (CMC) and higher used in the present invention. The addition amount of the deinking agent having a difference of 0 to 3.5 mN / m is preferably 0.01 to 0.5% by mass relative to the pulp dry mass.

  In the present invention, in addition to the deinking agent having the specific static surface tension, other known deinking agents can be used at the same time as necessary. Such other deinking agents include, for example, anionic sea surface active agents, nonionics, such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, higher alcohols, alkylphenols, alkylene oxide adducts such as fatty acids. Surfactants and cationic surfactants can be used.

(Flotation treatment / cleaning treatment and dust removal process)
After finishing the disaggregation process or the ink peeling process, a flotation process or a washing process is performed by adding an additional deinking agent, bleaching agent, chelating agent, flocculant or the like as desired. be able to. Thereafter, a dust removal step (foreign matter removal step) can be performed. In these cases, since a high shearing force is not applied to the fibers and foreign matters, the pH may remain weakly neutral or neutral, or may be alkaline. However, it is desirable that the treatment with the weak alkalinity to neutrality be performed, the time during which the pulp fibers are under alkaline conditions is shortened, so that the COD reduction effect is enhanced. You may perform a dust removal process (foreign matter removal process) after a disaggregation process and / or after an ink peeling process.

(Deinked pulp)
The deinked pulp obtained by the above method may then be subjected to bleaching such as ECF bleaching, if necessary. Since the deinked pulp produced by the method of the present invention has reduced adhesion foreign matter, when producing paper containing deinked pulp, the occurrence of defects such as paper breakage due to the sticking foreign matter is suppressed, and operational troubles are prevented. Can be reduced, and stable productivity can be secured.

(paper)
The paper containing deinked pulp produced according to the present invention has a small amount of dirt (black spots, dust, etc.) on the paper surface and has excellent quality. In the method for producing deinked pulp of the present invention, the swelling and damage of the pulp fibers are suppressed, and the freeness and strength of the fibers are not lowered. Therefore, the bulk, opacity and rigidity are good, and the printability is improved. Excellent paper can be obtained.

  The paper containing deinked pulp produced by the present invention can be used as, for example, printing paper, newsprint paper, coated paper, information recording paper, processed paper, sanitary paper, etc. . More specifically, examples of the information recording paper include electrophotographic transfer paper, ink jet recording paper, thermal recording material, and foam paper. More specifically, examples of processed paper include release paper base paper, laminated base paper, and base paper for molding. More specifically, sanitary paper includes tissue paper, toilet paper, paper towels, and the like. Moreover, it can also be used as a paperboard such as a corrugated base paper. Furthermore, it can be used as a base paper for paper having a coating layer containing a pigment, such as coated paper, information recording paper, and processed paper.

(Function)
By adding an anhydrous crystalline layered silicate, it is possible to produce a deinked pulp with little unpeeled ink even if the deinking step is performed under conditions of weak alkaline to neutral range. The reason is considered to be the abrasive effect on the ink by using the crystalline layered silicate and the promotion of ink peeling due to local increase in pH due to dissolution of the surface of the crystalline layered silicate particle.

  Further, the difference between the static surface tension at a pH of 10.5 and 40 ° C. and a critical micelle concentration (CMC) or higher and the static surface tension at a pH of 8.5 and 40 ° C. and a critical micelle concentration (CMC) or higher is 0. By adding a deinking agent of ~ 3.5 mN / m, even if the deinking process is carried out under weak alkaline to neutral conditions, the deinking agent performance does not easily change, so the foaming power does not decrease. In addition, since sufficient foaming power is maintained in the ink removing process such as a floatator, deinked pulp with less fluctuation in operability and a small amount of residual ink can be stably produced.

  EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to such examples. The deinked pulp obtained in Examples and Comparative Examples was evaluated by measuring the following items.

<Measurement of remaining ink area>
After free ink in the pulp was washed and removed using 150 mesh (φ0.1 mm) until the filtrate became clear, a handsheet was prepared according to JIS P 8222, and a foreign matter measuring device (Apoge Technology, Inc.) The area of the ink remaining on the sheet surface was measured using a trade name: Spec Scan 2000).

<Number and area of adhesive foreign matter>
The number and area of adhesive foreign substances were measured according to the method for measuring adhesive foreign substances disclosed in Japanese Patent Application No. 2006-95937 (Japanese Patent Laid-Open No. 2007-271389) shown below.

A deinked pulp having an absolutely dry mass of 1 kg was prepared as a low-concentration slurry, and foreign matters were separated using a test flat screen having a slit width of 0.15 mm. These foreign matters are filtered using a glass fiber filter paper (hereinafter abbreviated as “A”), and after the foreign matters on the filter paper are dried, the cellulose fiber filter paper (hereinafter abbreviated as “B”) is placed so as to sandwich the foreign matters. And heated to 105 ° C. and immediately pressurized at 3.5 kg / cm ² for 5 minutes. Next, the upper and the second are peeled off from the foreign matter adhesion surface, and the adhesive foreign matter (low-adhesive foreign matter) attached to the former and the adhesive foreign matter (high-adhesive foreign matter) attached to the second are 0.01% oil blue N ethanol. The solution was used for staining. After staining, the sample was washed for 5 minutes in a mixed solution of water / ethanol = 50/50. Washing was repeated twice. After the sample was dried, the number and area of adhesive foreign matter adhering to the former and the second were measured using a foreign substance measuring device (Apoge Technology, product name: Spec Scan 2000).

<Measurement of static surface tension>
The deinking agent is diluted with distilled water to a concentration of 0.005%, and an alkali is added to adjust the pH to 10.5 or 8.5. An automatic surface tension meter (manufactured by Kyowa Interface Science Co., Ltd.) , Trade name: CBVP-Z), the static surface tension of the deinking agent aqueous solution at 40 ° C. was measured based on the Wilhelmy method (plate method) using a platinum plate.

[Example 1]
Waste paper made up of 37.5% by weight waste newspaper and 62.5% waste paper was fed into a high-concentration pulper (manufactured by Aikawa Tekko Co., Ltd.) in the deinked pulp manufacturing process at Nippon Paper Industries A Factory. A chemical was further added to the pulp so that the pulp concentration became 15% by mass, and the disaggregation treatment was performed. As the chemicals used, deinking agents containing caustic soda, sodium silicate, crystalline layered silicate anhydrides (trade name: Prefeed, manufactured by Tokuyama Siltec Co., Ltd.) and higher alcohol polyoxyalkylene ethers, respectively, with respect to the waste paper mass (Concentration 0.005%, static surface tension 34.1 mN / m at pH 10.5, 40 ° C., pH 10.5, static surface tension 33.8 mN / m at pH 8.5) 0.14% was added. Subsequently, deinked pulp was produced through a coarse screen and a floater. The pH in the flotator was adjusted to be about 10.0 or 8.5. The whiteness of the deinked pulp collected from the inlet and outlet of the floatator was measured. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, a higher alcohol deinking agent (concentration 0.005%, 40 ° C., static surface tension 36.7 mN / m at pH 10.5, static surface tension 32. 6 mN / m) was treated in the same manner as in Example 1 except that 0.14% was added to the waste paper mass. The results are shown in Table 1.

[Example 2]
Waste paper consisting of 50% by weight waste paper and 50% by weight magazine waste paper was put into a high-concentration pulper (manufactured by Aikawa Tekko Co., Ltd.) in the deinked pulp manufacturing process of Nippon Paper Industries' A factory. A chemical was further added to the pulp so that the pulp concentration became 15% by mass, and the disaggregation treatment was performed. As the chemicals used, a deinking agent (concentration 0. 1%) containing 0.1% by mass of caustic soda, 0.2% by mass of crystalline layered silicate anhydride, and higher alcohol polyoxyalkylene ether with respect to the mass of used paper. 005%, static surface tension 34.1 mN / m at 40 ° C., pH 10.5, static surface tension 33.8 mN / m at pH 8.5) was added at 0.14% by mass. Subsequently, deinked pulp was produced through a coarse screen and a floater. The whiteness of the deinked pulp collected from the inlet and outlet of the floatator and the amount of sticking foreign matter in the finished raw material were measured. The results are shown in Table 2.

[Comparative Example 2]
As chemicals used, 0.6% by mass of caustic soda, 0.5% by mass of sodium silicate, and higher alcohol deinking agent (concentration 0.005%, 40 ° C., static surface tension at pH 10.5 34.1 mN / m) And a static surface tension of 33.8 mN / m at pH 8.5) were added in the same manner as in Example 2 except that 0.14% was added to the waste paper mass. The results are shown in Table 2.

[Comparative Example 3]
Waste paper made up of 37.5% by weight waste newspaper and 62.5% waste magazine paper was fed into a high-concentration pulper (manufactured by Aikawa Tekko Co., Ltd.) in the deinked pulp manufacturing process at Nippon Paper Industries' A factory. A chemical was further added to the pulp so that the pulp concentration became 15% by mass, and the disaggregation treatment was performed. As chemicals used, 0.6% by mass of caustic soda, 0.5% by mass of sodium silicate, and higher alcohol-based deinking agents (concentration 0.005%, 40 ° C., pH 10.5, respectively) 0.14% by mass) (surface tension 36.7 mN / m, static surface tension 32.6 mN / m at pH 8.5). The whiteness of the deinked pulp collected from the inlet and outlet of the floatator and the amount of sticking foreign matter in the finished raw material were measured. The results are shown in Table 2.

[Comparative Example 4]
As chemicals used, caustic soda 0.1% by weight, crystalline layered silicate anhydride 0.4% by weight, and higher alcohol deinking agent (concentration 0.005%, 40 ° C., static surface at pH 10.5) The treatment was carried out in the same manner as in Example 2 except that 0.14% by mass (static surface tension 32.6 mN / m at a tension of 36.7 mN / m, pH 8.5) was added. The results are shown in Table 2.

Claims (5)

  A method for producing deinked pulp made from used printing paper, wherein in the deinking step, an anhydrous crystalline layered silicate and a static pH of 10.5, 40 ° C. and a critical micelle concentration (CMC) or higher A deinking agent having a difference of 0 to 3.5 mN / m in static surface tension and a static surface tension at a pH of 8.5, 40 ° C., or a critical micelle concentration (CMC) or higher, and pH 7.0 to 9. 9. A method for producing deinked pulp, wherein the ink is peeled from the pulp in step 9.   The deinking pulp manufacturing method according to claim 1, wherein the deinking agent includes a higher alcohol polyoxyalkylene ether.   The method for producing deinked pulp according to claim 1 or 2, wherein the addition amount of the crystalline layered silicate anhydride is 0.1 to 1.5 mass% with respect to the mass of the absolutely dry pulp.   Used printing paper, which is a raw material, contains adhesive foreign matter. The manufacturing method of the deinking pulp in any one of Claims 1-3.   A deinked pulp produced by the method according to claim 1.