JPH05209383A - Method for pulping pressure-sensitive adhesive waste paper - Google Patents

Abstract

PURPOSE:To efficiently obtain regenerated pulp having high whiteness by successively subjecting a raw material slurry comprising the pressure-sensitive adhesive waste paper to the first flotation treatment, a kneading treatment, a cleaning treatment and the second flotation treatment. CONSTITUTION:The pressure-sensitive adhesive waste paper is subjected to a disaggregation treatment with a high concentration pulper and subsequently diluted to prepare a raw material slurry. The slurry is mixed with the ethylene oxide.propylene oxide adduct of a fatty acid, etc., subjected to the first flotation treatment with a floatator and subsequently dehydrated to concentrate into a slurry having a solid content concentration of 20-40wt.%. The concentrated slurry is kneaded under the feeding of steam, left for 120min, treated with a screen equipped with a screen plate having a slit width of 0.05-0.20mm, diluted, subjected to the second flotation treatment with a floatator and subsequently washed to obtain the regenerated pulp having good quality and whiteness and not causing an operation trouble on the manufacture of paper.

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 pressure-sensitive adhesive paper, and more particularly to a method for obtaining high-quality recycled pulp having a high effect of separating foreign matters.

[0002]

2. Description of the Related Art Currently, in Japan, the amount of used paper as a raw material for pulp production exceeds 50% of the raw materials for paper and paperboard production, and it has already occupied the position of the main raw material. Recycled pulp can be recycled paper, newspaper, cardboard, magazine, imitation, color (including art), fine white, card, special white, middle white, white manila, ticket, middle old cloth, tea imitation paper (Western stage) Including), mount, land ticket, ball and the like.

[0003] In general, these methods for reclaiming pulp from waste paper include a disintegration step for disintegrating waste paper to obtain a pulp suspension, a rough selection for separating foreign matters in the pulp suspension, a fine selection step, and a printing ink. Regenerated pulp is made through a deinking step of separating and a bleaching step of making the color white. However, wax-processed paper, pressure-sensitive adhesive paper, paper containing hot-melt glue, etc. cannot be separated into wax, pressure-sensitive adhesive, hot-melt glue, etc. from pulp fiber and cannot be recycled pulp. It is considered to be a waste paper (contraindicated product).

Particularly, in the case of pressure-sensitive adhesive paper, the pressure-sensitive adhesive is contained in an amount of 5 to 50% of the whole, and it is impossible to completely remove it with a conventional screen or the like. Large amounts of pressure sensitive adhesive are present in the pulp. With the pressure sensitive adhesive still contained in the recycled pulp, when using the recycled pulp to make paper, the pressure sensitive adhesive clogs the eyes of the wire or stains the press roll or blanket in the papermaking process,
There is a problem that the paper is cut and the papermaking efficiency is remarkably lowered, and spots are formed on the paper surface, which adversely affects the paper layer formation and the quality.

[0005] Due to such problems, recycled pulp of pressure-sensitive adhesive paper is currently shunned, and the actual situation is that waste of pressure-sensitive adhesive paper is industrial waste.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a method for obtaining recycled pulp from waste paper of pressure-sensitive adhesive paper, and particularly, to improve the separation effect of pressure-sensitive adhesive, release agent such as silicone resin, plastic film and the like, Furthermore, it is an object of the present invention to provide a pulping method that can obtain recycled pulp with high whiteness and does not cause operational troubles in the papermaking process even when it contains colored waste paper.

[0007]

According to the present invention, in a pulping method for obtaining recycled pulp from waste pressure-sensitive adhesive paper, a step of subjecting a raw material slurry to a primary flotation process and kneading with a solid content concentration of 20 to 40% by weight. It is a pulping method for waste paper of pressure-sensitive adhesive paper, characterized in that a step of treating, a step of treating with a screen having a slit width of 0.05 to 0.20 mm, and a step of secondary flotation treatment are sequentially carried out.

[0008]

[Operation] The pressure-sensitive adhesive paper to be treated in the present invention is
It is processed into labels, sheets, patches, etc. and is used for a wide range of purposes such as commercial use, office use, and household use. In addition to the products and the products recovered from the market, the semi-finished products and the waste paper generated in the manufacturing process are included in the target.

The pressure-sensitive adhesive paper generally has a structure in which a pressure-sensitive adhesive is sandwiched between a surface base material and a release base material. As the surface substrate, for example, kraft paper,
Medium-quality paper, high-quality paper, coated paper, art paper, cast coated paper, pressure-sensitive copying paper, thermal recording paper, PPC (Plain Paper Co
pier) and paper laminated with plastic, film, foil, etc. are used. As the release substrate, for example, high-density paper such as glassine paper, kraft paper, medium-quality paper, high-quality paper, coated paper, art paper, cast-coated paper and paper laminated with them, various kinds of grades A paper, film or the like coated with a coating agent and coated with a release agent such as a silicone compound or a fluorine compound is used. As the pressure-sensitive adhesive, for example, a water-based type such as a rubber type, an acrylic type, a vinyl ether type, a solvent type, or a solventless type such as a hot melt or an electron beam curing type is used. ..

As a general method for making recycled pulp from these waste papers, there is, for example, a regenerated pulp making method which includes a disintegration step-coarse selection step-selection step-kneading step-flotation step-dust removal step. Also in the method of the present invention, as a pretreatment step of the flotation step, a step of disintegrating ordinary waste paper and a step of roughly selecting and carefully selecting foreign matter are provided. In the disaggregation step, it is preferable to use a high-concentration pulper in order to prevent the pressure-sensitive adhesive, the plastic film and the like (hereinafter collectively referred to as foreign matter) from being fragmented. For disaggregation with a high-concentration pulper, a raw material slurry having a solid content concentration of about 10 to 20% by weight is heated within a range not exceeding 50 ° C.
It is preferable to carry out the treatment under alkaline or acidic conditions.

Further, in the rough selection process and the fine selection process, a screen having a round hole type or a slit type screen plate is used, but an apparatus having a slit type screen plate is used to improve processability and separation efficiency. Preferably. The solid content concentration of the pulp slurry at this time is 5
It is preferable to adjust it to be not more than%.

In the method of the present invention, the slurry of the pulp (accepted pulp) that has undergone such a pretreatment step is diluted so that the solid content concentration becomes about 2% or less, and the surfactant is added to the pulp in an amount of 0. Add in the range of about 01 to 2%,
It is important to treat in the primary flotation process. This flotation process removes the pressure-sensitive adhesives and films that have become smaller and the dispersed ink, and prevents the fibers from being kneaded into the pulp fiber in the subsequent kneading process. By the way, if you omit the flotation process and send the pulp slurry to the kneading process, the pressure-sensitive adhesive that has become smaller and the dispersed ink will be kneaded into the pulp fiber, and the flotation process that is a post-process is sufficient. Cannot be removed.

As the surfactant, a deinking agent which is usually used in deinking printed waste paper can be used. Among them, fatty acid-based or oil-based ethylene oxide / propylene oxide adducts, or When a surfactant containing a fatty acid soap as a main component is used, the pressure-sensitive adhesive is efficiently adsorbed on the surface of the foam, so that it is floated and separated together with the foam, which has the effect of enhancing the separation efficiency of foreign substances. The device used in this step is not particularly limited as long as it is a floatator capable of introducing fine air bubbles, and a surfactant can be additionally added depending on the generation state of bubbles. ..

In the present invention, the pressure-sensitive adhesive and the ink adsorbed on the pulp fiber still remain in the slurry treated in the primary flotation step. This slurry is dehydrated and concentrated by using a combination of a thickener, an extractor, a roll press, a screw press and the like as appropriate, and a solid content concentration of 20 to 40% by weight, more preferably 25 to 35.
Adjust to wt%. Then, the kneading treatment of this pulp changes the large pressure-sensitive adhesive left unremoved in the above step from a film-like form to a rounded granular form by an appropriate shearing force. (This morphological change is referred to as granulation hereinafter) Further, the ink adsorbed on the pulp fiber is one in which the ink is separated from the pulp fiber by an appropriate shearing force and dispersed.

The solid content of the pulp during the kneading treatment is important and needs to be adjusted to 20 to 40% by weight as described above. By the way, if the solid content concentration is lower than 20% by weight, sufficient shearing force cannot be applied to the pulp, and effective granulation of the pressure-sensitive adhesive becomes difficult. Further, it becomes difficult to effectively separate and disperse the ink from the pulp fiber. When mechanical stirring is carried out at a high concentration such that the solid content concentration exceeds 40% by weight, the pulp is significantly damaged, and as a result, when used as a regenerated pulp, there is a problem that drainage is lowered. In order to effectively granulate the pressure-sensitive adhesive and effectively separate and disperse the ink from the pulp fiber, the solid content concentration during the kneading treatment of the pulp is more preferably 25 to 35% by weight.

Examples of the apparatus used for the kneading treatment include a kneader, refiner, disperser and the like, and the kneader and disperser are particularly preferably used. It should be noted that it is a preferred embodiment because the addition of a surfactant during the kneading treatment causes the ink to be more effectively released and dispersed from the pulp fiber.
Further, in the case where there is a color in the waste paper, it is a preferred embodiment to add a bleaching chemical. As this bleaching chemical,
For example, sodium hypochlorite, calcium hypochlorite,
Oxidizing agents such as hydrogen peroxide and sodium peroxide, and reducing agents such as hydrosulfite and formamidinesulfinic acid can be used. In particular, sodium hypochlorite or calcium hypochlorite is preferable because the dye decomposing power is strong.
Further, the addition amount of the bleaching agent may be appropriately adjusted depending on the kind and amount of the dye contained in the paper. Further, in order to improve the efficiency of the bleaching treatment, it is preferable to retain the pulp after the kneading treatment step in a tower or a chest, and the retention time is appropriately adjusted depending on the appearance of the whiteness of the pulp and the remaining amount of the bleaching agent. However, for example, 5 to 2
It is preferable to stay for about 40 minutes.

The raw material pulp subjected to the kneading treatment is again diluted to a solid content concentration of about 5% or less and sent to the screen step. In the present invention, the slit width of the screen plate is 0.05 to 0.
It is important that it is 20 mm. And, more preferably, the pressure-sensitive adhesive bond granulated by the kneading process is separated from the pulp by a device equipped with a screen plate having a slit width of 0.10 to 0.20 mm. In the method of the present invention, the pressure-sensitive adhesive bond is effectively granulated, so that the separation efficiency is extremely good. It should be noted that with a screen having a slit width exceeding 0.20 mm, the pressure-sensitive adhesive having a large particle size is sent to the next step, and the pressure-sensitive adhesive is sufficiently supplied in the secondary flotation step of the next step. Cannot be separated. Further, if the slit width is less than 0.05 mm, the passage of the pulp is deteriorated, which is not practical. Therefore, it is more preferable that the slit width is 0.10 to 0.20 mm. For the screen device itself,
There is no particular limitation as long as a screen plate having a slit width of 0.05 to 0.20 mm is mounted.

In the method of the present invention, it is important to process the screened pulp slurry in the secondary flotation step. In this flotation step, the small pressure sensitive adhesive and dispersed ink remaining in the screened pulp slurry are removed. When the kneading treatment is carried out, when the surfactant is not added, it is appropriately selected and added within the range of about 0.01 to 2% with respect to the pulp. As the surfactant, a commonly used deinking agent can be used. Among them, fatty acid-based or oil-based ethylene oxide / propylene oxide adducts,
Alternatively, when a surfactant containing a fatty acid soap as a main component is used, the pressure-sensitive adhesive is efficiently adsorbed on the surface of the bubbles, so that it is floated and separated together with the bubbles, which has the effect of increasing the separation efficiency of foreign substances. The device used in this step is not particularly limited as long as it is a floatator capable of introducing fine air bubbles, and a surfactant can be additionally added depending on the generation state of bubbles. ..

At this point, most of the release agent such as the silicone resin and the polyethylene laminate film have been removed. However, if a cleaner treatment for removing the lightweight foreign matter is carried out, a slight amount of the remaining foreign matter is also removed, resulting in an extremely high level. It is possible to obtain a quality recycled pulp. Further, since the bleaching agent, the dye, the filler, etc. may remain in the obtained pulp slurry, a higher quality pulp can be obtained by removing them by dehydration and washing treatment.

Thus, the obtained recycled pulp has a high degree of whiteness and can form a paper with excellent formation without causing troubles in the papermaking process or forming spots on the paper surface,
It is an industrially very useful recycled pulp.

[0021]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
In addition,% in an example shows weight%.

Example 1 A cast coated paper as a surface substrate, a cream-colored high quality paper laminated with a polyethylene film as a release substrate coated with a silicone resin as a release agent, and an acrylic emulsion as a pressure sensitive adhesive. Was used as a raw material for waste paper (printed).

With a high-concentration pulper (manufactured by Aikawa Tekko Co., Ltd .: high-concentration pulper), solid content concentration of 15% and caustic soda were added at 1% per used paper, and disintegration was carried out at a disaggregation temperature of 40 ° C. for 20 minutes. After the disintegrated raw material was diluted to a solid content concentration of 3%, it was treated with a screen for rough selection (CH screen made by Aikawa Iron Works) equipped with a screen plate having round holes with a diameter of 3 mm,
Next, the screen accept was treated with a screening screen (manufactured by Aikawa Iron Works: Fine Screen) equipped with a screen plate having a slit width of 0.25 mm.

After the treatment, the accept raw material has a solid content of 0.
A surfactant (trade name: DI- which is diluted to 8% and consists of an adduct of ethylene oxide / propylene oxide of fatty acid
0.4% (versus dry solid content) of 610 / (Kao Corporation) was added, and the primary flotation treatment was performed with a flotator (Aikawa Iron Works: Vertical Floater).
And after repeating the flotation process three times,
The treated accepting raw material was dehydrated and concentrated to a solid content concentration of 30% (Aikawa Iron Works: inclined extractor + screw press used).

Next, 1% of caustic soda was added to this concentrated raw material.
(Compared to absolute dry solids), a surfactant consisting of an adduct of fatty acid ethylene oxide / propylene oxide (trade name: D
I-610 / Kao Corporation) 0.2% (against dry solids), sodium hypochlorite 2.0% as effective chlorine
(Vs absolute dry solids) was added. Then, while introducing steam, the concentrated raw material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using a disperser). Raw material temperature after kneading is 6
It was 0 ° C.

After standing for 120 minutes after the treatment, this raw material was diluted to a solid content concentration of 3%, and then treated with a screening screen (Finescreen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.20 mm. did. Then, the screen accept raw material was diluted to a solid content concentration of 0.8%, and the secondary flotation treatment was performed with a floatator (Aikawa Iron Works: Vertical floater).
Then, after repeating the flotation treatment three times, the accept raw material was treated with a lightweight foreign substance cleaner (manufactured by Aikawa Iron Works: Giroclean), and then washed with a drum washer to obtain a recycled pulp.

The recycled pulp thus obtained had a whiteness of Hunter as white as 76%, and no pressure-sensitive adhesive or residual film was observed. The paper produced by blending this recycled pulp had an excellent texture and did not cause the trouble of soiling the wire of the paper machine.

Example 2 A cast-coated paper as a surface substrate, a glass-paper colored asagi as a release substrate coated with a silicone resin as a release agent, and an acrylic resin as a pressure-sensitive adhesive on the glassine paper. The pressure-sensitive adhesive paper coated with the emulsion of was used as a waste paper raw material (which had been printed).

A high-concentration pulper (manufactured by Aikawa Tekko Co., Ltd .: high-concentration pulper) was charged with water having a pH of 4.5 with the used paper and sulfuric acid band so that the solid content concentration was 15%, and the temperature was 30 ° C.
It disintegrated for 20 minutes at the disaggregation temperature of. The disaggregated raw material was diluted to a solid content concentration of 2%, and then treated with a screening screen (Aikawa Iron Works: Fine Screen) equipped with a screen plate having a slit width of 0.25 mm. After the treatment, the accepting raw material was diluted to a solid content concentration of 0.8%, and the primary flotation treatment was performed with a floatator (Aikawa Tekko KK: vertical floater). After repeating the flotation treatment three times, this accepting raw material was dehydrated and concentrated to a solid content concentration of 25% (Aikawa Iron Works: inclined extractor + screw press).

Next, 1% of caustic soda was added to this concentrated raw material.
(Compared to absolute dry solids), a surfactant consisting of an adduct of fatty acid ethylene oxide / propylene oxide (trade name: D
I-610 / Kao Corporation) 0.3% (against dry solids), sodium hypochlorite as effective chlorine 1.5%
(Vs absolute dry solids) was added. Then, while introducing steam, the concentrated raw material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using a disperser). Raw material temperature after kneading is 6
It was 0 ° C. After standing for 120 minutes after the treatment, this raw material was diluted to a solid content concentration of 2% and then treated with a screening screen (Fine Screen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.15 mm.

This raw material was diluted to a solid content concentration of 0.8%,
The secondary flotation treatment was performed with a flotator (Aikawa Iron Works: Vertical Floater). After repeating the flotation treatment three times, the accept raw material was subjected to a dust removal treatment with a heavy foreign substance cleaner (Aikawa Iron Works: Rameau low concentration cleaner), and then washed with a drum washer to obtain a regenerated pulp.

The recycled pulp thus obtained had a whiteness of Hunter of 80% and was white, and no pressure-sensitive adhesive was observed. The paper produced by blending this recycled pulp had an excellent texture and did not cause the trouble of soiling the wire of the paper machine.

Example 3 A thermal recording paper was used as the surface substrate, a cream-colored high-quality paper laminated with polyethylene was used as the release substrate, coated with a silicon compound, and an acrylic emulsion was coated as a pressure-sensitive adhesive. Pressure-sensitive adhesive paper was used as a raw material for waste paper.

A high-concentration pulper (manufactured by Aikawa Tekko Co., Ltd .: a high-concentration pulper) having a solid content concentration of 15% and caustic soda of 2% per waste paper was added and disaggregated for 20 minutes. The disaggregation temperature at this time was 40 ° C. 2.5% solid content of disaggregated raw material
It was diluted to 1, and rough selection and selection were performed using the rough selection screen and the fine selection screen used in Example 1. Then, the accepting raw material was diluted to a solid content concentration of 0.8%, and a surfactant (trade name: DI-610 / manufactured by Kao Corporation) consisting of an adduct of ethylene oxide / propylene oxide of a fatty acid was added to 0.4.
% (Vs. dry solid content) was added, and the primary flotation treatment was performed with a floatator (Aikawa Iron Works: Vertical Floater). And the flotation process 3
After repeating the process once, the treated accept raw material was dehydrated and concentrated to a solid content concentration of 34% (Aikawa Tekko Co., Ltd .: inclined extractor + screw press).

Next, a fatty acid-based surfactant (trade name: DI-260 / manufactured by Kao Corporation) was added to this concentrated raw material in an amount of 0.3% with respect to the absolutely dry pulp, and a special anionic surfactant ( A brand name: DI-380 / manufactured by Kao Corporation) was added to the pulp in an amount of 0.1%, and sodium hypochlorite was added as effective chlorine in an amount of 2.0% (relative to dry solid content). Then, kneading the concentrated raw material while introducing steam (manufactured by Aikawa Iron Works:
I used a disperser). The raw material temperature after the kneading treatment was 60 ° C.

After standing for 120 minutes after the treatment, this raw material was diluted to a solid content concentration of 3%, and then treated with a screening screen (Fine Screen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.15 mm. did. Then, the screen accept raw material was diluted to a solid content concentration of 0.8%, and the secondary flotation treatment was performed with a floatator (Aikawa Iron Works: Vertical floater).
Then, after repeating the flotation treatment three times, the accept raw material was treated with a lightweight foreign substance cleaner (manufactured by Aikawa Iron Works: Giroclean), and then washed with a drum washer to obtain a recycled pulp.

The recycled pulp obtained was white with a Hunter whiteness of 78%, and no pressure-sensitive adhesive or residual film was observed. The paper produced by blending this recycled pulp had an excellent texture and did not cause the trouble of soiling the wire of the paper machine.

Comparative Example 1 The same process as in Example 1 was carried out except that the primary flotation process was not carried out. The obtained recycled pulp had a whiteness of Hunter of 80% and was white, but contained 0.1% of a pressure-sensitive adhesive. The paper containing this pulp has a pressure-sensitive adhesive for wire, roll,
The dryer was soiled, and smooth operation was not possible.

Comparative Example 2 The same process as in Example 1 was carried out except that the secondary flotation process was not performed in Example 1. The obtained recycled pulp had a whiteness of Hunter of 80%, which was white, but contained 0.3% of a pressure-sensitive adhesive. The paper containing this pulp has a pressure-sensitive adhesive for wire, roll,
The dryer was soiled, and smooth operation was not possible.

Comparative Example 3 The same treatment as in Example 1 was carried out except that the treatment concentration in the kneading treatment was changed to 15%. The obtained recycled pulp was white with a Hunter whiteness of 80%, but contained 0.5% of a pressure-sensitive adhesive. The paper containing this pulp could not be operated smoothly because the pressure-sensitive adhesive soiled the wires, rolls, and dryers during papermaking.

Comparative Example 4 The same process as in Example 1 was carried out except that the slit width of the screen after the kneading process was changed to 0.30 mm. The obtained recycled pulp was white with a Hunter whiteness of 80%, but contained 0.8% of a pressure-sensitive adhesive. The paper containing this pulp could not be operated smoothly because the pressure-sensitive adhesive soiled the wires, rolls, and dryers during papermaking.

[0042]

EFFECTS OF THE INVENTION According to the method of the present invention, it is possible to recycle used pressure-sensitive adhesive paper, which has conventionally been shunned to be recycled pulp, into recycled pulp. The texture was excellent and no troubles occurred during paper making.

Claims (1)

[Claims] 1. In a pulping method for obtaining recycled pulp from waste paper of pressure-sensitive adhesive paper, a step of primary flotation treatment of a raw material slurry, a step of kneading treatment with a solid content concentration of 20 to 40% by weight, a slit width of 0. A method for pulping waste paper of pressure-sensitive adhesive paper, which comprises sequentially performing a step of treating with a screen of 05 to 0.20 mm and a step of secondary flotation treatment.