JP5455519B2 - How to deink printed waste paper - Google Patents

Description

  The present invention relates to a method for producing deinked pulp. More specifically, in the deinking process in the production of deinked pulp, a deinked pulp in which a suspension of crystalline layered silicate anhydride is added and the ink is peeled off from the pulp under conditions of weakly alkaline region to neutral region It relates to the manufacturing method.

  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 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 debris from being made finer, reduces the COD of the wastewater, and can produce a deinked pulp with a small residual ink amount, In addition, an object is to provide a method for producing deinked pulp having excellent operability.

  As a result of intensive studies on a method for producing deinked pulp using waste printed paper as a raw material under conditions from a weakly alkaline region to a neutral region, the present inventors have obtained a suspension of crystalline layered silicate anhydride in the deinking step. Was added and the ink was peeled from the pulp at pH 7.0-9.9 to find that the object could be achieved.

  By adding a suspension of crystalline lamellar silicate anhydride in the deinking process, it is weakly alkaline to neutral, which is inferior in ink releasability as compared to conditions in a high alkali region where the pH usually used exceeds 10. Even if the deinking process is performed under the condition of the region, 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. Further, by using an anhydrous crystalline layered silicate as a suspension, it can be added by a pump like other chemicals, so that operability is improved.

In the present invention, in the production of deinked pulp, a deinking process is performed in which the ink is peeled from the pulp in the presence of a suspension of an anhydrous crystalline layered silicate under the condition of pH 7.0 to 9.9. .
(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)
In the present invention, it is essential to add an anhydrous suspension of crystalline layered silicate 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 may be added by any of these treatments, but is preferably added at 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 may be adjusted at any stage prior to the addition of the crystalline layered silicate anhydride suspension, but is most preferably adjusted to the above range during the disaggregation process, which is the first stage of the deinking process. .

  (Disaggregation process) 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.

  In the present invention, the crystalline layered silicate anhydride is added in suspension. By using the suspension, addition with a pump is possible as in the case of other chemicals, so that the operability is improved as compared with the case of adding the solid (powder).

  The solid content concentration of the suspension of the crystalline layered silicate anhydride is preferably 10 to 50% by mass. When the solid content concentration is 10% by mass or less, the dissolution of the crystalline layered silicate particles tends to proceed, so that the effect of promoting ink peeling tends to be reduced. Since the fluidity of the suspension tends to deteriorate, the concentration is preferably within the above range.

  The method for preparing the suspension of the crystalline layered silicate anhydride is not particularly limited, but it is prepared by adding the crystalline layered silicate anhydride to water so that the desired concentration is obtained and stirring sufficiently. be able to.

  The suspension of crystalline layered silicate anhydride is preferably used immediately after preparation. When a long time elapses after the preparation, there is a tendency that the abrasive effect of the crystalline layered silicate on the ink and the effect of promoting the ink peeling due to the local increase in pH due to the dissolution of the surface of the crystalline layered silicate particle are reduced.

  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 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.
(Flotation treatment / cleaning treatment and dust removal process)
After finishing the disaggregation process or the ink stripping process, a flotation aid such as a deinking agent, a bleaching agent, a chelating agent, a flocculant, etc. may be added as desired to perform a flotation treatment or a washing treatment. it can. 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 a suspension of crystalline layered silicate anhydride, it is possible to produce deinked pulp with little unpeeled ink even if the deinking process is performed under conditions from weakly alkaline to neutral regions. Become. The reason is presumed as follows.

  By using crystalline layered silicate anhydride, an abrasive effect on the ink can be obtained, and the surface of the crystalline layered silicate particle dissolves and the pH is locally increased, so that the ink is peeled off. It is thought. Furthermore, by adding the anhydrous crystalline layered silicate in a suspension state, it becomes possible to add it with a pump like other chemicals, so that the operability is improved as compared with the case where it is added as a solid.

  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).

<Evaluation of operability>
○: A chemical can be added by a pump. ×: A chemical cannot be added by a pump.

<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”), dried on the filter paper, and then cellulose fiber filter paper (hereinafter abbreviated as “B”) 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 apparatus (Spec Scan 2000 manufactured by Apoge Technology).

<Measurement of whiteness>
Using the obtained deinked pulp, a handsheet was prepared according to JIS P 8222, and the ISO whiteness was measured according to JIS P 8148: 2001.

<Measurement of paper thickness, basis weight, density>
The paper thickness of the handmade sheet prepared according to JIS P 8222 was measured according to JIS P 8118: 1998. In addition, the basis weight was measured according to JIS P 8124: 1998 (ISO 536: 1995). The density was calculated from the measured values of the paper thickness and basis weight of the handmade sheet.

[Example 1]
Crystalline layered silicate anhydride (trade name: Prefeed, manufactured by Tokuyama Siltec Co., Ltd.) was added to water so as to have a solid content concentration of 10%, and stirred at 60 ° C. for 3 hours. An anhydrous suspension of was prepared.

  The following experiment was conducted using a pulper equipped with a stirring blade that can arbitrarily change the rotation speed of a capacity of 2 L. Printed waste paper composed of 80% by weight waste newspaper and 20% by weight recycled magazine paper was placed in the pulper. Further, fresh water and chemicals were added to adjust the pulp concentration to 15% by mass. As chemicals, a suspension of crystalline layered silicate anhydride is added so that the concentration of crystalline layered silicate is 0.8% by mass (pure content) with respect to the weight of waste paper, and higher alcohol The system deinking agent was added in an amount of 0.2% by weight based on the weight of the used paper. The temperature was set to 40 to 50 ° C., and disaggregation was performed at 400 rpm for 15 minutes. Subsequently, deinked pulp was produced through a coarse selection screen, a floater, a selection screen, and a disperser. The deinked pulp thus obtained was washed with 150 mesh (φ0.1 mm) until the filtrate became clear. The remaining ink area and operability were evaluated. The results are shown in Table 1.

[Comparative Example 1]
The treatment was carried out in the same manner as in Example 1 except that 0.8% (pure content) of the crystalline layered silicate anhydride was added instead of the suspension of the crystalline layered silicate anhydride. The results are shown in Table 1.

[Comparative Example 2]
The treatment was conducted in the same manner as in Example 1 except that 0.4% of caustic soda was added instead of the suspension of the crystalline layered silicate anhydride. The results are shown in Table 1.

  As shown in Table 1, Example 1 using an anhydrous suspension of crystalline layered silicate was compared to Comparative Example 1 using an anhydrous powder of crystalline layered silicate, The remaining ink area was almost the same, and the operability was excellent. Moreover, the residual ink area was small compared with the comparative example 2 using caustic soda.

[Example 2]
Crystalline layered silicic acid anhydride (trade name: Prefeed, manufactured by Tokuyama Siltec Co., Ltd.) is added to water so that the solid content concentration becomes 10%, and stirred at room temperature for 1 hour to obtain crystalline layered silicic acid anhydride. A suspension of was prepared.

  The following experiment was conducted using a pulper equipped with a stirring blade that can arbitrarily change the rotation speed of a capacity of 2 L. Printed waste paper consisting of 100% by weight waste newspaper was placed in the pulper. Further, fresh water and chemicals were added to adjust the pulp concentration to 15% by mass. As a chemical, a suspension of an anhydrous crystalline layered silicate is added so that the concentration of the crystalline layered silicate is 1.3% (pure content) with respect to the waste paper mass. The deinking agent was added at 0.2% based on the weight of the waste paper. The temperature was 40 to 50 ° C., and disaggregation was performed for 6 minutes at 400 rpm. The pulp thus obtained was washed with 150 mesh (φ0.1 mm) until the filtrate became clear, and the remaining ink area and operability were evaluated. The results are shown in Table 2.

[Example 3]
The treatment was performed in the same manner as in Example 2 except that the solid content concentration of the suspension of the crystalline layered silicate anhydride was 25%. The results are shown in Table 2.

[Example 4]
The treatment was carried out in the same manner as in Example 2 except that the solid content concentration of the suspension of the crystalline layered silicate anhydride was 40%. The results are shown in Table 2.

[Comparative Example 3]
The treatment was performed in the same manner as in Example 2 except that 1.3% (pure content) of the crystalline layered silicate anhydride powder was added instead of the crystalline layered silicate anhydride suspension. The results are shown in Table 2.

[Comparative Example 4]
The treatment was performed in the same manner as in Example 2 except that 0.4% of caustic soda was added instead of the suspension of the crystalline layered silicate anhydride. The results are shown in Table 2.

[Comparative Example 5]
The treatment was performed in the same manner as in Example 2 except that 0.7% of caustic soda was added instead of the suspension of the crystalline layered silicate anhydride. The results are shown in Table 2.

  As shown in Table 2, all of Examples 2 to 4 using a suspension of crystalline layered silicate anhydride (concentration 10% to 40%) are crystalline powders of crystalline layered silicate anhydride. Compared with Comparative Example 3 using No. 3, the remaining ink area was almost the same, and the operability was excellent. Moreover, the residual ink area was small compared with the comparative example 4 using caustic soda. Furthermore, even when using caustic soda and comparing with Comparative Example 6 having a high pH, the residual ink area was the same.

Claims (5)

In the deinking step, an anhydrous suspension of crystalline layered silicate having a δ-type crystal structure represented by Na ₂ O · 2SiO ₂ and / or K ₂ O · 2SiO ₂ is added, and the pH is 7.0. A method for producing deinked pulp using waste printed paper as a raw material , comprising peeling ink from pulp by giving a mechanical share at ˜9.9. The method of Claim 1 that the addition amount of the anhydrous crystalline layered silicate is 0.1-1.5 mass% with respect to the absolute dry pulp mass. The method according to claim 1, wherein the used printing paper as a raw material contains an adhesive. The method according to claim 1, wherein the deinking step is at least one of a disaggregation process, an ink peeling process, and an alkali dipping process. The method according to any one of claims 1 to 4, wherein the suspension of the crystalline layered silicate anhydride has a solid content of 10 to 50% by mass.