JPH05148783A - Method for pulping waste paper of heat-sensitive recording chart - Google Patents

Abstract

PURPOSE:To efficiently separate a heat-sensitive recording material layer, obtain pulp of high whiteness and suppress the drain COO load to the minimum by disaggregating waste paper of a heat-sensitive recording chart and then bleaching the disintegrated waste paper with a chlorine-based and an oxygen-based bleaching agents in many stages. CONSTITUTION:Waste paper of a heat-sensitive recording chart is disaggregated and the resultant pulp suspension is then bleached with a chlorine-based bleaching agent and/or an oxygen-based bleaching agent in many stages. Chlorine, sodium hypochlorite, hypochlorous acid and chlorine dioxide are preferred as the chlorine-based bleaching agent. Hydrogen peroxide and oxygen are preferred as the oxygen-based bleaching agent. For example, the sequence of treatments with chlorine, alkali extraction, hypochlorous acid and chlorine dioxide, etc., is cited as the multistage bleaching process. Furthermore, a drum washer having relatively large outflow of ash content or microfiber is preferred as a washer used in the multistage bleaching process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining recycled pulp from waste heat-sensitive recording paper, and more particularly to a method for pulping waste paper to efficiently separate recycled heat-sensitive recording material from pulp fibers to obtain recycled pulp. Regarding

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording paper is a base paper coated with a heat-sensitive recording material layer. The heat-sensitive recording material layer is composed of a basic colorless dye in the form of fine particles, a color former, a sensitizer, a pigment, a binder and an auxiliary agent. The recorded image of this thermal recording paper has problems in water resistance, oil resistance, plasticizer resistance, etc., for example, when a color image is contacted with a water-based material, an oil-based material, or a plasticizer contained in plastic, the image density decreases. It may end up. Further, if the heat-sensitive recording layer is touched by the hand during handling, a fog-colored fingerprint may be formed.
In order to solve such a problem, for example, a heat-sensitive recording paper having a protective layer provided by coating an aqueous emulsion, a water-soluble polymer compound or the like on the heat-sensitive recording layer has been widely used.

According to the standard quality standard compiled by the Waste Paper Recycling Promotion Center (established on January 27, 1986), this thermal recording paper is classified as contraindicated product B which is not desirable to be mixed, and is treated as paper not suitable for recovery and reuse. ing. On the other hand, as the production amount of the thermal recording paper increases, the generation of waste paper and waste paper of the thermal recording paper also increases. Therefore, the development of a recycled pulping method for recovering and reusing pulp from waste thermal recording paper has become a new issue.

[0004] Conventionally, recycled newspaper and printed coated paper have been recycled pulp. The disintegration step of disintegrating the waste paper to obtain a pulp suspension, the rough selection for separating foreign matters in the pulp suspension, Recycled pulp is formed by appropriately combining a selection process, a deinking process for separating printing ink, a bleaching process for whitening, and the like.

For example, Japanese Examined Patent Publication No. 50-29042 proposes a used paper recycling method which comprises a disintegration and rough selection process for printing coated paper, a dehydration process, a bleaching process, and an ink separation process.
Japanese Unexamined Patent Publication (Kokai) No. 50802/1975 discloses a method of disaggregation treatment using an alkaline liquid containing a surfactant. Further, in Japanese Patent Laid-Open No. 63-135585, a step of disintegrating heat-sensitive recording waste paper in an alkaline aqueous solution containing a surfactant and then neutralizing it, a step of floating and sorting the disintegrated waste paper slurry, a dehydration squeezing machine There is proposed a method of regenerating through a step of concentrating at 1, a step of disintegrating with a high speed disintegrator. However, even if these methods are applied to used thermal recording paper including thermal recording paper having a protective layer having water resistance, oil resistance, plasticizer resistance, etc., the protective layer and the unseparated pieces of the thermal recording material remain. However, when a paper is made using this pulp, the heat-sensitive recording material develops color in the drying step of the paper machine, and the whiteness of the obtained paper is reduced.

Further, Japanese Patent Laid-Open No. 133688/1990 discloses a method in which a coloring agent is removed so that the amount of the coloring agent remaining in the fiber is less than the amount of the basic dye remaining, and then a kneading treatment is carried out. Is proposed. However, this method also goes to the next kneading step without sufficient disintegration of the protective layer for waste paper of thermal recording paper having a protective layer, so that the basic dye develops color in the kneading step,
High whiteness pulp cannot be obtained. in this way,
The conventional method cannot completely remove the heat-sensitive recording material, and the paper using this recycled pulp has a large decrease in whiteness.

Further, in the case where recycled pulp is obtained from broke or waste paper of the thermal recording paper by the above-mentioned conventional method, dyes, colorants, sensitizers, binders, etc. constituting the thermal recording layer at the time of recycling and recovering pulp. A large amount of water is required to separate water, and high COD containing a large amount of persistent substances
Drainage occurs. When this waste water is subjected to activated sludge treatment or the like, the COD load on the biological treatment becomes high, so that it is necessary to add an aeration tank or change the treatment flow rate, for example.

Under the circumstances as described above, it is the current situation that pulping of recycled thermal recording paper and recycling thereof are avoided.

[0009]

DISCLOSURE OF THE INVENTION An object of the present invention is to recycle recycled thermal recording paper, in particular, to efficiently separate a thermal recording material layer including a protective layer from pulp fiber, and to develop a color with high whiteness due to heat. It is intended to provide a pulping method capable of obtaining a bleached pulp that can be blended with a stock for high-grade paper, which is never produced, and capable of minimizing the amount of COD in wastewater.

[0010]

DISCLOSURE OF THE INVENTION The present invention is a pulping method for waste thermal recording paper, characterized in that after disintegrating waste thermal recording paper, it is bleached in multiple stages with chlorine bleach and / or oxygen bleach. Is.

[0011]

The used thermal recording paper used in the present invention is as follows:
Thermal recording paper used for a wide range of purposes such as facsimiles, printers, labels, etc. for commercial, office, household, etc., or semi-finished products and waste paper generated in the process of manufacturing and processing these thermal recording papers. included.

The present invention provides a protective layer and a dye which is a heat-sensitive recording material by multi-stage bleaching a pulp suspension after disintegrating waste heat-sensitive recording paper with a chlorine-based bleaching agent and / or an oxygen-based bleaching agent. The purpose is to decompose and separate the color former, binder, auxiliary agent and the like.

The bleaching agent has a function of efficiently decomposing a protective layer, a dye, a coloring agent, a binder, an auxiliary agent, etc. constituting the recording paper in the presence of a compound having active chlorine or / and active oxygen described later. Use what you have.

Bleaching agents applicable to the above purpose include chlorine, sodium hypochlorite, calcium hypochlorite, hypochlorous acid, chlorine dioxide and sodium chlorite as active oxygen-containing compounds. As the compound having, hydrogen peroxide, ozone, sodium peroxide, oxygen are effectively suitable for the purpose, more preferably chlorine, sodium hypochlorite, hypochlorous acid, chlorine dioxide, hydrogen peroxide, oxygen. Are better.

Binders, dyes, colorants, auxiliaries and the like, which are the protective layer and the heat-sensitive recording material in the waste paper, are high COD components, and wastewater discharged outside the bleaching process by promoting their decomposition. COD can be reduced, and COD load can be reduced under normal biological treatment operation conditions without causing an increase in COD load on biological treatment represented by activated sludge treatment.

The multi-stage bleaching process consists of various combinations such as CED, CEHD, CEHED, CEHD.
Sequences such as D, CEHDED, and CEDD, and sequences including an oxygen delignification step before these sequences can be mentioned. Also, C to C _D , E to E _o , E
There is also a sequence in which _P , E _H , E _OP, etc. are changed, and which sequence among various multi-stage bleaches may be selected according to the situation and is not particularly limited.

C = chlorine treatment, E = alkali extraction treatment, H = sodium hypochlorite treatment, D = chlorine dioxide treatment,
C _D = chlorine treatment combined with chlorine dioxide treatment, E _o = oxidative alkali extraction treatment, E _P = alkali extraction treatment combined with hydrogen peroxide treatment, E _H = alkali extraction treatment combined with sodium hypochlorite treatment , E _OP = representing a treatment in which a hydrogen peroxide treatment is used in combination with an oxidative alkali extraction treatment.

In the present invention, the pulp suspension after disintegration of waste thermal recording paper, if it has a kraft pulp bleaching process facility, is, for example, pulp after the cooking process, or after the digestion process-oxygen delignification treatment process. It is also possible to mix with pulp and perform multi-stage bleaching. The mixing ratio of the pulp suspension after the disintegration of waste thermal recording paper to the post-process pulp is not particularly limited.

The mixing of both is preferably carried out at the outlet of the washing device closest to the bleaching step. By the way, when mixing is carried out at the inlet of the washing apparatus or before the washing apparatus, the washing effluent is recovered as black liquor by the countercurrent washing adopted in the ordinary kraft pulp step through the cooking step. Then, in the process of burning the recovered black liquor into green liquor, the pigment from the waste heat-sensitive recording paper becomes a drag, which reduces the efficiency of the green liquor refining process. However, if the green liquor clarification step has a sufficient capacity, the load of the bleaching step can be reduced by mixing and washing at the inlet of the washing device or before that.

The washing machine used in the multi-stage bleaching process of the present invention may be, for example, a drum washer, a diffuser washer, a roll press or the like, but a drum washer having a relatively large loss of ash and fine fibers is preferably used.

The amount of each chemical added to the pulp in the multi-stage bleaching step can be appropriately changed so that the whiteness of the bleached pulp is 80% or more, and is not particularly limited. By the way, when the whiteness is less than 80%, when the bleached pulp is mixed with a stock for high-grade paper, the whiteness of the paper is lowered, and further, the whiteness of the paper after coating is lowered,
The appearance is significantly impaired. The bleached pulp can be appropriately screened depending on the state of impurities contained therein. The pulp thus obtained is a pulp with a high whiteness and a small amount of contaminants, and can be sufficiently used for high-quality paper.

When disintegrating waste thermal recording paper,
The pH, temperature, method, etc. are not particularly limited. Further, when the recycled pulp obtained by the present invention or the pulp containing the recycled pulp is used for papermaking, a known papermaking method can be applied as it is. Furthermore, the papermaking base paper is high-quality paper,
Needless to say, it can be applied to coated paper for printing, various recording papers, industrial papers, paperboards, thin papers and the like.

[0023]

EXAMPLES Examples will be described below, but it goes without saying that the present invention is not limited to these examples. In addition,
Unless otherwise specified, "%" and "parts" in the examples mean "% by weight" and "parts by weight".

Example 1 Waste paper of thermal recording paper having a protective layer on the pulper was charged with water so that the pulp concentration was 8%, and disintegrated for 30 minutes. The disintegrated pulp suspension obtained was adjusted to a concentration of 4.5% and mixed with the pulp after the oxygen delignification step to obtain a mixed pulp to be used in the next bleaching step (after oxygen delignification pulp and thermosensitive recording. Mixed ratio of waste paper = 90:10).

[Chlorine Treatment] Water was added to the above mixed pulp to prepare a pulp concentration of 3.5%, and chlorine of 3.7% to pulp was added thereto, and treated at 35 ° C. for 60 minutes. Then, it was dehydrated and washed to obtain a chlorine-treated pulp.

[Alkali Extraction Treatment] Water was added to the chlorine-treated pulp to prepare a pulp concentration of 10%, and 2.2% NaOH to pulp was added thereto, and the mixture was added at 50 ° C. for 12 hours.
After the treatment for 0 minutes, the pulp was dehydrated and washed to obtain an alkali extraction treated pulp.

[Sodium hypochlorite treatment] Water was added to the alkali extraction-treated pulp to prepare a pulp concentration of 10%, and 0.8% sodium hypochlorite to pulp was added to the pulp. The pulp was treated at 50 ° C. for 150 minutes and then dehydrated and washed to obtain sodium hypochlorite-treated pulp.

[Chlorine Dioxide Treatment] Water was added to the sodium hypochlorite treated pulp to prepare a pulp concentration of 10%, and 0.18% chlorine dioxide to pulp was added to the pulp, After being treated at 180 ° C. for 180 minutes, it was dehydrated and washed to obtain multistage bleached pulp.

Using the pulp thus obtained, 100 g / m
^Two handsheets were created. About the obtained sheet,
A quality test as described below was performed. As the COD measurement, the first dehydrated liquid was measured.

Example 2 In Example 1, after the oxygen-delivered pulp and the thermal recording paper waste paper were mixed at a mixing ratio of 70:30, a mixed pulp was obtained.
Chlorine 4.9% with chlorination, NaOH 2.9 with alkali treatment
%, Sodium hypochlorite in sodium hypochlorite treatment 1.0
% And chlorine dioxide treated with chlorine dioxide 0.2% were added to obtain a multi-stage bleached pulp in the same manner as in Example 1 and to prepare a handmade sheet in the same manner as in Example 1. A quality test was performed on the obtained sheet in the same manner as in Example 1.
As the COD measurement, the first dehydrated liquid was measured.

Example 3 In Example 1, the mixing ratio of the pulp after oxygen delignification and the used thermal recording paper was set to 50:50, and after the mixed pulp was obtained,
9.4% chlorine in chlorination, NaOH5.6 in alkali treatment
%, Sodium hypochlorite 2.5 in sodium hypochlorite treatment
%, Chlorine dioxide in the chlorine dioxide treatment was added to 0.4%, and a handmade sheet was prepared in the same manner as in Example 1, a quality test was conducted, and COD was measured.

Example 4 Waste thermal recording paper having a protective layer with a pulper was charged with water so that the pulp concentration was 8%, and disintegrated for 30 minutes. The disintegrated pulp suspension obtained was adjusted to a concentration of 3.5% and used in the next bleaching step.

In Example 1, chlorine 9.4 during chlorination
%, NaOH 5.6% by alkali treatment, sodium hypochlorite 2.5% by sodium hypochlorite treatment, chlorine dioxide 0.6% by chlorine dioxide treatment, and multi-stage bleaching in the same manner as in Example 1. The pulp was obtained. Hereinafter, the same procedure as in Example 1 was performed.

Example 5 Waste paper containing thermal recording paper having a protective layer with a pulper was charged with water so that the pulp concentration was 8%, and disintegrated for 30 minutes.

The obtained disintegrated pulp suspension was adjusted to a concentration of 4.5% and mixed with the pulp after the oxygen delignification step to obtain a mixed pulp to be used in the next bleaching step (pulp after oxygen delignification pulp. Mixing ratio of waste paper and thermal recording paper = 80:20
).

[Treatment in which chlorine dioxide treatment is used in combination with chlorine treatment] Water is added to the above mixed pulp to give a pulp concentration of 3.
It was adjusted to 5%, and 3.15% chlorine to pulp and 0.21% chlorine dioxide to pulp were added thereto, treated at 35 ° C. for 60 minutes, and then dehydrated and washed to obtain a chlorine-treated pulp.

[Oxidative Alkali Extraction Treatment] Water was added to the chlorine-treated pulp to prepare a pulp concentration of 10%, and 2.2% NaOH to pulp was added to the pulp, followed by rotation with pure oxygen gas. The mixture was sealed in a pressure cooker, treated at 60 ° C. for 2 minutes at an oxygen pressure of 2 kg / cm ² , and then dehydrated and washed to obtain alkali extraction treated pulp.

[Sodium Hypochlorite Treatment] Water was added to the alkali extraction treated pulp to prepare a pulp concentration of 10%, and 1.0% of pulp to sodium hypochlorite was added thereto. The pulp was treated at 50 ° C. for 150 minutes and then dehydrated and washed to obtain sodium hypochlorite-treated pulp.

[Chlorine Dioxide Treatment] Water was added to the sodium hypochlorite-treated pulp to prepare a pulp concentration of 10%, and 0.20% of chlorine dioxide to pulp was added to the pulp, After being treated at 180 ° C. for 180 minutes, it was dehydrated and washed to obtain multistage bleached pulp.

Using the bleached pulp thus obtained, 100
A hand-made sheet of g / m ² was prepared. A quality test was performed on the obtained sheet in the same manner as in Example 1. Note that C
As the measurement of OD, the first dehydrated liquid was measured.

Example 6 A mixed pulp used in the next bleaching step was obtained in the same manner as in Example 5.

[Treatment in which chlorine dioxide treatment is used in combination with chlorine treatment] Water is added to the above mixed pulp to give a pulp concentration of 3.
It was adjusted to 5%, and 3.15% chlorine to pulp and 0.21% chlorine dioxide to pulp were added thereto, treated at 35 ° C. for 60 minutes, and then dehydrated and washed to obtain a chlorine-treated pulp.

[Treatment Using Oxidative Alkali Extraction Treatment and Hydrogen Peroxide Treatment] Water was added to the chlorine-treated pulp to prepare a pulp concentration of 10%, and the pulp concentration was adjusted to 2.2% of NaOH. And 0.56% hydrogen peroxide against pulp were added, sealed in a rotary pressure cooker with pure oxygen gas, treated at 60 ° C. for 2 minutes at an oxygen pressure of 2 kg / cm ² and then dehydrated and washed to obtain alkali extraction treated pulp. Obtained.

[Chlorine Dioxide Treatment] Water was added to the alkali extraction treated pulp to prepare a pulp concentration of 10%, and 0.20% chlorine dioxide with respect to pulp was added to the pulp, and the mixture was heated at 70 ° C. for 180 ° C. After the treatment for a minute, it was dehydrated and washed to obtain a multi-stage bleached pulp. The bleached pulp thus obtained was used in the same manner as in Example 1 below.

Example 7 In Example 5, after the oxygen-delivered pulp and the thermal recording paper waste paper were mixed at a mixing ratio of 50:50 to obtain a mixed pulp,
Chlorine 8.0 in the process that combined chlorine dioxide treatment and chlorine dioxide treatment
%, Chlorine dioxide 0.54%, NaOH 5 in oxidative alkali treatment.
6%, oxygen pressure 2 kg / cm ² , 2.5% sodium hypochlorite in sodium hypochlorite treatment, chlorine dioxide in chlorine dioxide treatment
A multi-stage bleached pulp was obtained in the same manner as in Example 5 except that 0.4% was added. The bleached pulp thus obtained was used in the same manner as in Example 1 below.

Example 8 In Example 6, after the oxygen-delivered pulp and the thermal recording paper waste paper were mixed at a mixing ratio of 50:50 to obtain mixed pulp,
Chlorine 8.0 in the process that combined chlorine dioxide treatment and chlorine dioxide treatment
%, Chlorine dioxide 0.54%, NaOH 5.6% in the treatment that uses hydrogen peroxide treatment in combination with oxidative alkali treatment, hydrogen peroxide 0.84
%, Oxygen pressure 2 kg / cm ² , chlorine dioxide treated with chlorine dioxide
A multi-stage bleached pulp was obtained in the same manner as in Example 6 except that 0.6% was added. The bleached pulp thus obtained was used in the same manner as in Example 1 below.

Comparative Example 1 Waste paper for thermal recording paper having a protective layer with a pulper was charged with water so that the pulp concentration was 8%, and disintegrated for 30 minutes. The obtained pulp suspension was diluted to a pulp concentration of 3.5% and treated with a screen having a slit width of 0.2 mm (fine screen / manufactured by Aikawa Iron Works). Next, the accept was dehydrated and concentrated to a pulp concentration of 28% using a dehydration concentrator (gradient extractor, screw press / manufactured by Aikawa Iron Works). Next, this dehydrated and concentrated pulp was subjected to a strong mechanical stirring (disperser / manufactured by Aikawa Iron Works). Then, the pulp subjected to the mechanical strong stirring treatment was diluted so that the pulp concentration became 4%, and then the pulp was dispersed by a high-speed disintegrator (Top Finer / manufactured by Aikawa Iron Works) to obtain a recycled pulp. A quality test was performed in the same manner as in Example 1 below.

Comparative Example 2 To the pulp after dewatering and concentration of Comparative Example 1, 2% of hydrogen peroxide and 2% of sodium silicate based on the dry solid content of this pulp were used.
%, And a deinking agent (DI-600 R / manufactured by Kao Co., Ltd.) of 0.3%, respectively, and subjected to mechanical strong stirring (disperser / manufactured by Aikawa Iron Works).
Regenerated pulp was obtained in the same manner as in Comparative Example 1 except that the pulp was left (aged) at 100 ° C for 100 minutes. A quality test was performed in the same manner as in Example 1 below.

Comparative Example 3 80% of bleached LKP having a whiteness of 85% and 20% of the regenerated pulp obtained in Comparative Example 1 were mixed, and the obtained mixed pulp was mixed with a laboratory beater at a pulp concentration of 10% and a temperature of 20. Freeness at ℃
After beating to 500 ml, 100 g of this pulp is used.
/ M ^{2 hand-} made sheet was prepared. A quality test was performed on the obtained sheet in the same manner as in Example 1. The freeness was measured according to JIS P8121. (Unit = ml)

The results thus obtained are shown in Table 1. Each test item shown in the table was performed by the following method. Whiteness: JIS P8123 (Hunter whiteness) The higher the value, the whiter (unit =%) Thermal fading whiteness: TapiUM200 (4 Hr Hunter whiteness at 105 ° C) Drainage COD load: Measured according to JIS K0102 (100 ° C Oxygen consumption due to potassium permanganate in kg / bleached pulp t)

[0051]

[Table 1]

[0052]

As is clear from the results shown in Table 1, the pulp obtained by the method of the present invention has a high whiteness, does not develop color by heat, and has the same pulp quality as bleached kraft pulp. There was no problem even if blended in paper. And, the COD load amount of the waste water could be suppressed to the minimum.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D21C 9/153 7199-3B 9/16 7199-3B

Claims (2)

[Claims] 1. A method for obtaining recycled pulp from waste paper for thermal recording paper, comprising disintegrating the waste paper, and then using a chlorine bleach or /
And a method for pulping waste thermal recording paper, which comprises multi-stage bleaching with an oxygen-based bleaching agent. 2. A chlorine-based bleaching agent is chlorine, sodium hypochlorite,
Oxygen-based bleaching agent is selected from hydrogen peroxide, ozone, sodium peroxide and oxygen from calcium hypochlorite, hypochlorous acid, chlorine dioxide and sodium chlorite, and used alone or in mixture. The method for pulping waste heat-sensitive recording paper according to claim 1.