JPH0978480A - Production of deinked pulp of high whiteness degree - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a deinked pulp of high whiteness degree improved in the whiteness degree without deteriorating the pulp yield by treating a pulp slurry after an alkali soaking step for a printed waste paper under specific conditions. SOLUTION: This method for producing a deinked pulp of a high whiteness degree comprises an acid addition treating step (step A) for changing the pH of a pulp slurry after a soaking step following a disintegrating step for a printed waste water such as a newspaper from a weak alkaline value to a weak acidic value combined with a step (step B) for further adding an alkyl diphenyl ether disulfonate to the resultant pulp slurry and then treating the resultant mixture according to a flotation method. Furthermore, a flocculant addition treating step for adding a flocculant comprising one or more substances selected from a protein such as an enzyme, e.g. a (hemi)cellulase, an amphoteric surfactant and an amino acid (salt) is provided between both the steps A and B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing deinked pulp from printed waste paper such as newspapers and magazines, and more particularly to a method for producing high-whiteness deinked pulp.

[0002]

2. Description of the Related Art As a method for producing deinked pulp from printed waste paper, generally, a method is widely used in which pulp and ink are separated by a floatator, etc., through a disintegration step of printed waste paper and an alkali soaking step. That is, used waste paper pulp is disintegrated with a deinking agent consisting of an alkaline chemical and a surfactant with a disintegrator such as a pulper, and then made into waste paper pulp, and alkaline chemicals, hydrogen peroxide and a surfactant are further added to the pulp to perform alkaline soaking. (Alkali immersion)
Is performed, the pulp fibers are swollen, the ink is separated, the pulp slurry is diluted, and the ink is removed by a flotation method or the like. By the way, in the flotation method, a method for improving pulp whiteness by aggregating ink fine particles with a protein or the like is known, but the optimum pH of ink agglomeration by a protein or the like is generally in the vicinity of neutral, and However, it did not fit well with the pH of the flotation process (alkalineity of 9 to 10) performed, and there was a problem in terms of pH adjustment process operation and chemical cost for practical use.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a protein, an amphoteric surfactant,
Providing a method for producing deinked pulp with high whiteness, which was not possible by the conventional method, by adding a flocculant using an amino acid or an amino acid salt, and then performing a flotation process without adjusting the pH in the subsequent process. To do.

[0004]

In order to solve the above problems, the present invention adopts the following configurations. That is, the present invention
"In the deinking pulp manufacturing process that follows the disintegration process of printed waste paper and the alkaline soaking process, an acid addition treatment process (process A) that further changes the pH of the pulp slurry after the alkaline soaking process from weak alkaline to weak acid After adding the diphenyl ether disulfonate,
The method for producing a high-whiteness deinked pulp is characterized by combining a step (step B) of treating by a flotation method. "

The present inventors effectively utilize the excellent ink particle aggregating function of proteins, particularly enzyme substances, and
The present invention was completed by finding a specific surfactant that can be directly treated by the flotation method without performing pH adjustment in the subsequent step, which is a drawback of using these as an aggregating agent, and combining them. I arrived.

In the production of ordinary deinked pulp,
The pulp slurry at the outlet of the alkaline soaking step is generally considered to have a pulp concentration of 10 to 35% by weight and a pH of 9 to 11, and the pulp is diluted in the next step and then applied to a floater or the like (flotation step). A method of separating the pulp fiber and the ink is adopted. The method of the present invention comprises:
After the alkali soaking step, an acid addition treatment step and a flocculant addition treatment step with a protein, an amphoteric surfactant, an amino acid or an amino acid salt, etc. are provided.The flow of the steps in this case is a disaggregation step, an alkali soaking step, an acid The order of the addition treatment step, the coagulant addition treatment step, and the flotation step is the order.

Optimal p of coagulant addition treatment using protein etc.
H is generally in the vicinity of neutrality, does not fit well with the optimum pH (alkaline) of the flotation process, and poses a problem in terms of pH adjustment process operation and chemical cost. The present inventors have conducted various studies on surfactants that can be directly processed by the flotation method without adjusting the pH in the subsequent step. As a result, good results can be obtained when the pH in the flotation processing step is performed near neutral. Found the activator.

The reason why the method according to the present invention in which a protein, an amphoteric surfactant, an amino acid or an amino acid salt, etc. acts in the post-step of the alkali soaking step gives a deinked pulp with a higher whiteness than the conventional method is described in the present invention. The people think as follows. Since the ink is peeled from the pulp, the ink agglomerates quickly. By adding a substance having an isoelectric point such as protein, amphoteric surfactant, amino acid, etc. to the pulp slurry in the vicinity of the pH corresponding to the isoelectric point, the zeta potential of the ink is lowered, which is suitable for flotation treatment. Aggregates of ink particles of moderate size are formed. There are two actions, the deinking action of the enzyme and the aggregation action of the deinking particles by the enzyme. From the above, it is speculated that the protein and the like exerted an effect on the aggregation action of the deinking particles, and the removal of the ink particles in flotation was performed extremely effectively.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The waste paper covered by the present invention includes newspapers, leaflets, magazines, books, office papers, other copiers, printing papers produced from OA equipment, and the like.

Any acid can be used for the pH adjustment in the acid addition treatment step, but sulfuric acid is considered to be the most general industrially. Then, the pH of the pulp slurry in the flotation treatment is preferably in the range of 5-8.

The surfactant used in the coagulant addition treatment step of the present invention is mainly composed of an alkyl diphenyl ether disulfonate having an alkyl group having 9 to 14 carbon atoms, and the addition rate is from 0.01 to 100% dry bone pulp. The effect is exhibited at 5% by weight, more preferably 0.02 to 2% by weight.

Examples of proteins that can be used in the coagulant addition treatment step include alkali salts (alkali metal salts, amine salts, ammonium salts, etc.) such as gelatin, soybean protein, and protein fatty acid condensate. The inventors have found that the enzyme itself also has an aggregating action on ink particles. Further, they have found that addition of a small amount of other proteins gives good results. Examples of these enzymes include cellulase, hemicellulase, pectinase, glucosidase, lipase and the like. As a result of diligent studies on the enzyme by which the present inventors can more effectively carry out the present invention,
It was found that cellulase, hemicellulase, xylanase, mannanase, amylase and the like are particularly excellent.
The rate of addition of proteins centered on these enzyme substances is 0.01 to 1% by weight, and more preferably 0.0
The effect is exhibited at 2 to 0.1% by weight.

The pulp concentration in the coagulant addition treatment step of the present invention is 1 to 10% by weight, more preferably 3 to 7% by weight. Further, the treatment temperature of the coagulant addition treatment step is 15 to 60.
C is preferred. The treatment time is 30 to 180 minutes, preferably 60 to 120 minutes.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The symbols A, B, C, and D of the types of the surfactants added after the completion of the alkali dipping step shown in the table of Examples are as follows. A-alkyldiphenyl ether disulfonate (Sanyo Chemical Co., Ltd. Sandet ALH) B-alkyldiphenyl ether disulfonate (Sanyo Chemical Co., Ltd. Sandet BL) C-alkyldiphenyl ether disulfonate (Sanyo Chemical Co., Ltd. Eleminol MON-2) D-Poly Oxyethylene nonyl phenyl ether

The symbols a, b, c, d, e and f of the types of aggregating agents shown in the tables of the examples are as follows. a-Amylase-based enzyme (NAGASE spitase LH) b-Cellulase-based enzyme (Meiji Seika Co., Ltd. Meisserase) c-xylanase-based enzyme (ALKO Eco-Pulp X
200) d-mannanase enzyme (Pigalase M manufactured by Rakuto Chemical Co., Ltd.
50) e-amphoteric surfactant (polyoctylaminoethylglycine) f-amino acid salt (L-lysine hydrochloride)

In the examples, all percentages (%) mean% by weight except for the whiteness, and the chemical addition rate was shown by weight% based on absolute dry pulp. The evaluation of the deinked pulp was performed by the pulp whiteness and the froth rate according to the hunter whiteness test method of paper and pulp of JIS P-8122. In addition, the residual carbon area ratio (%) is a value obtained by dividing the total area of the coloring matter mainly composed of the ink remaining in the obtained deinked pulp pulp sheet by the total area of the pulp sheet in%. It is displayed.

<Example 1> Water was added to printed waste paper consisting of offset printed newspaper, letterpress printed newspaper, and flyer recycled paper, and the mixture was disintegrated with a test pulper under the following conditions and dehydrated to a concentration of 20%. Pulp concentration: 4.2% Surfactant addition rate: 0.25% (Polyoxyethylene nonylphenyl ether: ethylene oxide N = 9) Furthermore, the alkali immersion process (same meaning as the soaking process)
Was performed under the following processing conditions. Pulp concentration: 15% Treatment time: 4 hours Treatment temperature: ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 80 ℃ Caustic soda addition rate ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 2.8% Sodium silicate addition rate ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 10% (JIS No. 3) Silicic acid equivalent Same as below) Surfactant addition rate ・ ・ ・ 0.07% Hydrogen peroxide addition rate ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 2.5% (Purity equivalent same below ) After the alkaline soaking step, dilute the pulp concentration to 5%,
After disintegrating with a disintegrator for 5 minutes, the pH was adjusted to 5.0 with sulfuric acid, and spitase LH (manufactured by Nagase Co., referred to as aggregating agent a), which is an amylase-based enzyme, was used as an aggregating agent in an absolutely dry pulp 0 0.02% added,
Surfactant Sandet ALH (manufactured by Sanyo Chemical Co., Ltd., referred to as post-added surfactant A) was used in an amount of 0.
07% was added and the mixture was treated at 40 ° C. for 2 hours. Without adjusting the pH before flotation, the pulp concentration is diluted to 1%, put in a lab floater, and floated at an air flow rate of 180 l / hr for 5 minutes. After dewatering the floated pulp slurry to a pulp concentration of 10%, the pulp concentration is diluted to 0.5% to obtain 100 g / m 2 of tsubo.
Hand-cut with 2 and air dried. For the handmade sheet, the pulp whiteness and the residual carbon ink area ratio were measured, and Table 1 is shown as Example 1.
It was shown to. The pulp whiteness was measured by an Erlejo whiteness measuring device, and the residual carbon ink area ratio was measured by an image analyzer.

<Example 2> In Example 1, pH was adjusted with sulfuric acid.
The results of treating in the same manner as in Example 1 except that the value was adjusted to 6.0 are shown in Table 1 as Example 2. <Example 3> The results of treating in the same manner as in Example 1 except that the pH was adjusted to 7.0 with sulfuric acid in Example 1 are shown in Table 1 as Example 3. <Example 4> The results of treating in the same manner as in Example 1 except that the pH was adjusted to 8.0 with sulfuric acid in Example 1 are shown in Table 1 as Example 4. <Example 5> The same process as in Example 2 was repeated except that the surfactant added after the completion of the alkali dipping step was Sandet BL (manufactured by Sanyo Kasei Co., Ltd., post-added surfactant B). The results obtained are shown in Table 1 as Example 5. <Example 6> In Example 2, the surfactant added after the completion of the alkali immersion step was replaced by eleminol MON-2.
The results of treating in the same manner as in Example 2 except that (post-added surfactant C manufactured by Sanyo Kasei Co., Ltd.) was used are shown in Table 1 as Example 6.

<Example 7> The result of the same treatment as in Example 2 was repeated except that the aggregating agent added in Example 2 was a cellulase-based enzyme, macerase (manufactured by Meiji Seika Co., Ltd., aggregating agent b). The results are shown in Table 2 as Example 7. <Example 8> The results obtained by treating in the same manner as in Example 2 except that the coagulant added in Example 2 was Ecopulp X200 (manufactured by ALKO Co., coagulant c) which is a xylanase enzyme, were used. 8 is shown in Table 2. <Example 9> The result of treating in the same manner as in Example 2 except that the coagulant added in Example 2 was Piglarase M50 (manufactured by Rakuto Chemical Co., Ltd., coagulant d) which is a mannanase-based enzyme, It is shown in Table 2 as Example 9. <Example 10> The result of treating in the same manner as in Example 2 except that the aggregating agent added in Example 2 was an amphoteric surfactant (polyoctylaminoethylglycine, aggregating agent e) was used. Is shown in Table 2. <Example 11> The result of treating in the same manner as in Example 2 except that the aggregating agent added in Example 2 was an amino acid salt (L-lysine hydrochloride, aggregating agent f) is shown as Example 11. Shown in 2. <Example 12> The results of the same treatment as in Example 2 except that no coagulant was added are shown in Table 2 as Example 12. <Example 13> In Example 2, the surfactant added after the completion of the alkali immersion step was polyoxyethylene nonylphenyl ether (hereinafter referred to as post-added surfactant D), and the pulp slurry before flotation was treated with caustic soda. The results of the same treatment as in Example 2 except that the pH was adjusted to 10 are shown in Table 2 as Example 13.

<Comparative Example 1> In Example 2, the acid addition treatment step and the coagulant addition treatment step after soaking were not performed,
The results of the same treatments as in Example 2 except that the flotation treatment was performed are shown in Table 3 as Comparative Example 1. <Comparative Example 2> The results of the same treatment as in Example 2 are shown in Table 3 as Comparative Example 2 except that the flocculating agent and the surfactant added after the alkali dipping step are not added. It was <Comparative Example 3> In Example 2, the flocculant and the surfactant added after the completion of the alkali dipping step were not added, and the pulp slurry before flotation was adjusted to pH with caustic soda.
The result of treating in the same manner as in Example 2 except that it was adjusted to 10 is shown in Table 3 as Comparative Example 3. <Comparative Example 4> The same treatment as in Example 2 was conducted except that polyoxyethylene nonylphenyl ether (post-added surfactant D) was used as the surfactant added after the completion of the alkali dipping step. The results are shown in Table 3 as Comparative Example 4. <Comparative Example 5> The results of treating in the same manner as in Example 1 except that the pH was adjusted to 9.0 with sulfuric acid in Example 1 are shown in Table 3 as Comparative Example 5. It was shown to.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

As described above, the present invention has been described in detail. The present invention clarifies a new deinking function of an enzyme and the possibility of further increasing the whiteness, and further, in the technical field of enzyme deinking. Practical application has become a reality.

Claims (6)

[Claims] 1. The pH of the pulp slurry after the alkali soaking step in the process of producing deinked pulp through the alkali soaking step following the disintegration step of printed waste paper.
A high whiteness removal process characterized by combining an acid addition treatment step (step A) for changing the acid from weakly alkaline to weakly acidic and a step (step B) of adding an alkyldiphenyl ether disulfonate and then treating by a flotation method. Ink pulp manufacturing method. 2. The method for producing deinked pulp according to claim 1, wherein a coagulant addition treatment step is provided between step A and step B. 3. The method for producing deinked pulp according to claim 2, wherein the flocculant is one or more substances selected from proteins, amphoteric surfactants, amino acids or amino acid salts. 4. The method for producing deinked pulp according to claim 3, wherein the protein is an enzyme. 5. The method according to claim 4, wherein the enzyme is one or more enzymes selected from cellulase, hemicellulase, xylanase, mannanase, and amylase. 6. In the step A, the acid addition treatment step after the alkali soaking step is carried out in the pH range of 5 to 8, and in the step B, the flotation method is carried out in the pulp slurry pH range of 5 to 8. It carries out, The manufacturing method of the deinking pulp in any one of Claims 1-5 characterized by the above-mentioned.