JP2964751B2 - Pulping method of pressure-sensitive adhesive waste paper - Google Patents

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 used pressure-sensitive adhesive paper, and more particularly to a method for obtaining pressure-sensitive adhesive, silicone,
The present invention relates to a method for treating waste paper that improves the effect of separating plastic films and the like and efficiently obtains recycled pulp having high whiteness.

[0002]

2. Description of the Related Art At present, waste paper used as a raw material for pulp production in Japan is 50% of a raw material for paper and paperboard production.
And has already occupied the position of main raw materials. Waste paper that can be recycled and pulped is newspaper, cardboard,
Magazine, imitation, color (including art), white, card, tokushiro, white, white manila, ticket, Nakashiro antique, tea imitation paper (including western steps), mount, ground ticket, ball, etc. is there.

[0003] These methods of pulping recycled paper generally include a defibration step of disintegrating the used paper to obtain a pulp suspension, a rough-selection step for separating foreign substances in the pulp suspension, a screening step, and a printing ink. Recycling pulping is performed through a deinking process for separating, a bleaching process for whitening the color, and the like. However, waxed paper, pressure-sensitive adhesive paper, paper containing hot melt, etc.
It cannot be separated from wax, pressure-sensitive adhesive, hot melt and the like from pulp fibers, and is regarded as waste paper (contraindicated product) that cannot be recycled.

Particularly, in the case of pressure-sensitive adhesive paper, the pressure-sensitive adhesive is contained in an amount of 5 to 50%, and cannot be completely removed by a conventional screen or the like. Has a large amount of adhesive. If paper is made using the recycled pulp while the pressure-sensitive adhesive is still contained in the recycled pulp, the pressure-sensitive adhesive blocks the eyes of the wires, stains the press rolls and blankets during the papermaking process, and breaks the paper. This causes a problem that the papermaking efficiency is remarkably reduced, and a problem that a paper layer is formed or quality is adversely affected, such as formation of spots on the paper surface.

[0005] Because of these problems, the current practice is to avoid reclaiming pressure-sensitive adhesive paper from recycled pulp, and the waste paper of pressure-sensitive adhesive paper is industrial waste.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for obtaining recycled pulp from waste paper of pressure-sensitive adhesive paper, and more particularly to improving the effect of separating pressure-sensitive adhesives, release agents such as silicone resins, plastic films and the like. It is still another object of the present invention to provide a pulping method in which a recycled pulp having a high degree of whiteness is obtained even in the case where colored waste paper is contained, and operation problems do not occur in the paper making process.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a pulping method for obtaining recycled pulp from used pressure-sensitive adhesive paper.
A step of kneading a raw material slurry having a H of 6 or less at a solid content concentration of 15 to 30% by weight, a step of treating the pulp treated in the step with a screen having a slit width of 0.2 mm or less; Adding a caustic soda and a surfactant to the treated pulp, performing a kneading treatment while applying a compressive force while heating at a solid content of 30 to 40% by weight, and a flotation step thereafter. It is a pulping method of used pressure-sensitive adhesive paper.

[0008]

[Operation] The pressure-sensitive adhesive paper to be processed 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, office, and home use. In addition to the products, semi-finished products and waste paper generated in the manufacturing process are also included as targets.

The general structure of pressure-sensitive adhesive paper is a pressure-sensitive adhesive sandwiched between a surface substrate and a release substrate. As the surface substrate, 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 Copie)
r) and paper laminated with plastic,
Films, foils, etc. are used, and as a release substrate,
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 plastic, films, etc., with release agents such as silicone compounds and fluorine compounds A coated product is used. Also, as a pressure-sensitive adhesive,
Emulsion type such as rubber type, acrylic type and vinyl ether type, and solvent or non-solvent type pressure-sensitive adhesives are used.

[0010] As a general method for recycling and pulping used waste paper, there is a recycled pulping method which includes a defibration step, a rough selection step, a fine selection step, a kneading step, a flotation step and a dust removal step. Also in the method of the present invention, as a pretreatment step of the kneading step, a step of disintegrating ordinary waste paper,
A step of roughly selecting and carefully selecting foreign matter is provided. In the defibration step, it is preferable to use a high-concentration pulper in order to prevent a pressure-sensitive adhesive, a plastic film, or the like (hereinafter, collectively referred to as foreign matter) from being fragmented. Disaggregation with high concentration pulper
A raw material slurry having a solid content of about 10 to 20% by weight
In a preferred embodiment, the treatment is carried out at a temperature not exceeding 0 ° C. and at a pH of 5 or less.

In the rough / fine selection process, a screen having a round hole type or a slit type screen plate is used. In order to improve the processability and separation efficiency, an apparatus having a slit type screen plate is used. Is preferred. At this time, the solid concentration of the pulp slurry was 5%.
It is preferable to adjust the following. In the method of the present invention, the slurry of pulp (accept pulp) that has undergone such a pretreatment step is dehydrated and concentrated using an appropriate combination of devices such as a thickener, an extractor, a roll press, and a screw press to obtain a solid content concentration of 15 to 15. Adjusted to 30% by weight.
The pH of the concentrated pulp slurry is adjusted to 6 or less. Then, by kneading the pulp, the foreign matter remaining without being removed in the above-mentioned selection step is changed from a film-like form into a rounded-like granular form by an appropriate shearing force. (This morphological change is hereinafter referred to as granulation.)

The solid content of the pulp at the time of the kneading treatment is important and needs to be adjusted to 15 to 30% by weight as described above. Incidentally, when the solid content concentration is lower than 15% by weight, sufficient shearing force is not given to the pulp, and it becomes difficult to effectively granulate foreign matters. However, when the raw pulp is heated with steam and kneaded at a high solid content of more than 30% by weight as in the kneading treatment which is performed by a general regenerated pulping method, the pulp is damaged. The shearing force is too large and the foreign matter is dispersed and re-adsorbed to the pulp. The pulp once the foreign matter is re-adsorbed,
Even if a screen treatment or a flotation treatment is subsequently performed, the separation efficiency of the foreign matters becomes extremely poor, and the desired effects of the present invention cannot be obtained. Therefore, in the method of the present invention, the kneading treatment is performed at a solid content concentration of 30% by weight or less.

Further, the pH condition of the pulp at the time of the kneading treatment is also important. When the pulp is treated under the condition that the pH exceeds 9, as in the kneading treatment performed in the ordinary regenerated pulping method, Again, it is difficult to granulate the foreign matter, and particularly when the adhesive foreign matter has a pH of more than 6, the pulp needs to be adjusted to a pH of 6 or less as described above, because it becomes soft and difficult to granulate. The acidic substance used for pH adjustment is not particularly limited. For example, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, sulfuric acid band, sodium hydrogen sulfate, sodium hydrogen sulfite, chlorine dioxide, etc. Examples include waste sulfuric acid and acidic sodium sulfate.

The apparatus used for the kneading process includes, for example, a kneader, a refiner, and a disperser, and a kneader and a disperser are particularly preferably used.

The raw pulp subjected to the kneading treatment is again diluted to a solid concentration of about 5% or less and sent to the screen step. In this screen process, 0.2
The foreign matter granulated by the kneading process is separated from the pulp by an apparatus equipped with a screen plate having a slit width of not more than mm. In the method of the present invention, since the foreign matter is effectively granulated, the separation efficiency is extremely good. In the case of a screen having a slit width exceeding 0.2 mm, the separation of foreign matters becomes insufficient, and the dispersion and separation cannot be sufficiently performed in the next step. The screen device itself is not particularly limited as long as it has a screen plate having a slit width of 0.2 mm or less.

In the method of the present invention, the screened pulp slurry is again dehydrated and concentrated using an appropriate combination of a thickener, an extractor, a roll press, a screw press and the like to obtain a solid content of 30 to 40% by weight.
Is adjusted to Then, caustic soda and a surfactant are added to the concentrated pulp. The addition of caustic soda is performed in order to improve the effect of the kneading treatment in the next step, and the addition rate is selected so that the pH of the pulp is in the range of about 9 to 11. The surfactant is added to enhance the efficiency of separating foreign substances in the subsequent flotation step, and the addition rate is 0.01 to 2% based on the pulp.
It is appropriately selected within the range of the degree.

In the kneading process in this step, an apparatus similar to the apparatus used in the kneading processing in the previous step can be used. Then, by performing the kneading treatment at a solid content concentration of 30% by weight or more, the foreign matter that has passed through the screen in the above-described screen step is dispersed in a minute form. When mechanical stirring is performed at a solid content concentration of 40% by weight or more, pulp is significantly damaged, and as a result, problems such as reduced drainage when used as recycled pulp occur. However, if the solid content is less than 30% by weight, the shearing force required for dispersion cannot be obtained.
The kneading treatment in this step is performed at a solid content of 30 to 40% by weight. In addition, in order to enhance the effect of dispersing foreign substances, it is preferable to introduce steam into the raw pulp to raise the temperature to 50 ° C. or higher during kneading.

As the surfactant used in the present invention, a deinking agent which is generally used when deinking printed waste paper can be used, and among them, fatty acid-based or oil-based ethylene oxide / propylene oxide can be used. When a surfactant containing fatty acid soap as a main component is used, the pressure-sensitive adhesive is efficiently adsorbed to the surface of the foam in the subsequent flotation step. Has the effect of increasing the separation efficiency.

If the waste paper contains colored waste paper,
If the recycled pulp is used as it is without bleaching, the paper obtained by making the paper is also affected by the colored pulp, and the whiteness of the paper is reduced and the commercial value is reduced. Therefore,
If the used paper contains a colored material, it is desirable to perform a bleaching treatment. The bleaching agent is preferably added to the raw material pulp where the temperature is high and the concentration is high. Therefore, it is preferable to add the bleaching agent to the subsequent kneading treatment step.

As the bleaching agent, for example, an oxidizing agent such as sodium hypochlorite, calcium hypochlorite, hydrogen peroxide and sodium peroxide and a reducing agent such as hydrosulfite and formamidine sulfinic acid can be used. In particular, sodium hypochlorite or calcium hypochlorite is preferable since the dye has a strong decomposing ability. The amount of the bleaching agent may be appropriately adjusted according to the type and amount of the dye contained in the paper. Furthermore, in order to improve the efficiency of the bleaching treatment, it is preferable to keep the pulp after the kneading treatment process in a tower or a chest.
The pulp is appropriately adjusted depending on the degree of whiteness of the pulp and the remaining amount of the bleaching agent. For example, the pulp is preferably retained for about 5 to 240 minutes.

Next, in the recycled pulping method of the present invention, the pulp that has been subjected to the above treatment is diluted so that the solid content concentration becomes about 5% or less, and is treated in a flotation step. In the flotation step, not only foreign matter minutely dispersed in the kneading process in the subsequent stage but also ink particles and the like printed on the surface of the used paper are removed. In addition, the apparatus 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 according to the state of generation of bubbles. .

At this point, the release agent such as silicone resin and the polyethylene laminate film have been almost completely removed. However, if a cleaner treatment for removing lightweight foreign matter is further performed, a small amount of foreign matter remaining is also removed, and extremely high foreign matter is removed. High quality recycled pulp can be obtained. In addition, bleaching agents, dyes, fillers, and the like may remain in the obtained pulp slurry. Therefore, if these are removed by dehydration and washing, higher-quality pulp can be obtained.

The recycled pulp thus obtained has a high whiteness, and can form a paper having an excellent formation without causing troubles in the paper making process or forming spots on the paper surface.
It is an industrially extremely useful recycled pulp.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, of course, are not intended to limit the scope of the present invention.
In addition,% in an example shows weight%.

Example 1 Cast coated paper was used as a surface substrate, cream-colored high-quality paper laminated with a polyethylene film was used as a release substrate, and a silicone resin was applied as a release agent. A pressure-sensitive adhesive paper formed by applying an acrylic emulsion as a pressure-sensitive adhesive was used as a raw paper material.

A high-concentration pulper (manufactured by Aikawa Iron Works: high-concentration pulper) was charged with the above-mentioned waste paper and water having a pH of 3.5 with sulfuric acid so as to have a solid content of 15%. Disintegrated for 20 minutes. The disintegrated raw material has a solid concentration of 3
%, And then treated with a screen for rough selection (manufactured by Aikawa Iron Works: CH screen) equipped with a screen plate having a round hole having a diameter of 3 mm, and then screen accept was provided with a screen plate having a slit width of 0.25 mm. The screen was treated with a fine selection screen (Fine Screen, manufactured by Aikawa Iron Works).

After the treatment, the accept raw material is converted to a solid concentration of 23.
% (Made by Aikawa Tekko: Inclined extractor + screw press). Since the pH of the concentrated raw material was 5.5, no particular pH adjustment was performed. Then, the concentrated material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using a disperser). The raw material temperature after the kneading treatment was 45 ° C.

After the processed raw material was diluted to a solid content of 3%, it was processed with a screening screen (fine screen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.20 mm. Then, the screen accept material was dehydrated and concentrated to a solid concentration of 33% (manufactured by Aikawa Iron Works: Inclined extractor + screw press).
Next, a 1% caustic soda (absolute dry solid content) was added to this concentrated raw material, and a surfactant comprising a fatty acid ethylene oxide / propylene oxide adduct (trade name: DI-610 /
(Manufactured by Kao Corporation) was added in an amount of 0.4% (based on absolute dry solids), and sodium hypochlorite was added as effective chlorine in an amount of 2.0% (based on absolute dry solids). And kneading treatment of the concentrated raw material while introducing steam (made by Aikawa Iron Works: using disperser)
did. 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 concentration of 0.8%, and a flotation treatment was performed with a flotator (a vertical floater manufactured by Aikawa Iron Works). Then, after the flotation treatment was repeated three times, the accepting raw material was treated with a lightweight foreign matter cleaner (manufactured by Aikawa Iron Works: Giroclean), and then washed with a drum washer to obtain recycled pulp.

The resulting recycled pulp was white with a Hunter whiteness of 76%, the content of the pressure-sensitive adhesive was only 0.01%, and no residual film was observed. The paper produced by blending the recycled pulp had an excellent texture, and did not cause any trouble of soiling the wire of the paper machine.

Example 2 Cast-coated paper was used as the surface substrate, glassine paper colored in Asagi as a release substrate coated with a silicone resin as a release agent, and was pressure-sensitively bonded to glassine paper. A pressure-sensitive adhesive paper coated with an acrylic emulsion was used as a raw paper material.

A high-concentration pulper (manufactured by Aikawa Iron Works: high-concentration pulper) was charged with the above-mentioned waste paper and water having a pH of 4.5 with a sulfuric acid band so as to have a solid concentration of 15%.
At 20 ° C. for 20 minutes. After the disintegrated raw material was diluted to a solid concentration of 2%, it was treated with a screening screen (Fine Screen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.25 mm. The treated accept material was dehydrated and concentrated to a solid content concentration of 25% (Aikawa Iron Works: Inclined Extractor + Screw Press). Since the pH of the concentrated raw material was 6.0, no particular pH adjustment was performed. Then, the concentrated material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using a disperser). The raw material temperature after the kneading treatment was 40 ° C.

After diluting the treated raw material to a solid concentration of 2%, the raw material was treated with a screening screen (fine screen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.20 mm. Then, the screen-accepting raw material was dehydrated and concentrated to a solid concentration of 32% (manufactured by Aikawa Iron Works: Inclined extractor + screw press).
Next, a 1% caustic soda (absolute dry solid content) was added to this concentrated raw material, and a surfactant comprising a fatty acid ethylene oxide / propylene oxide adduct (trade name: DI-610 /
(Manufactured by Kao Corporation) was added in an amount of 0.3% (based on absolute dry solids), and sodium hypochlorite was added as effective chlorine in an amount of 1.5% (based on absolute dry solids). And kneading treatment of the concentrated raw material while introducing steam (made by Aikawa Iron Works: using disperser)
did. The raw material temperature after the kneading treatment was 60 ° C.

After being left for 120 minutes after the treatment, this raw material was diluted to a solid concentration of 0.8%, and a flotation treatment was carried out with a flotator (vertical floater, manufactured by Aikawa Iron Works). After repeating the flotation treatment three times, the accept raw material is subjected to dust removal treatment with a heavy foreign matter cleaner (Aikawa Iron Works: Ramoe Low Concentration Cleaner), and then
The washed pulp was obtained by washing with a drum washer.

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

Example 3 A 1: 1 mixture of the used paper used in Example 1 and the used paper used in Example 2 was used as a used raw material, and the other conditions were the same as in Example 1. Recycled pulp was obtained.
The resulting recycled pulp 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 any troubles in soiling the paper machine wire.

Example 4 An art paper was used as a surface substrate, and a glass compound paper coated with a silicone compound was used as a release substrate, and a glass compound coated with Asahi was coated with a silicone compound. A pressure-sensitive adhesive paper formed by applying a system emulsion was used as a raw material for waste paper.

The above-mentioned pressure-sensitive adhesive paper and water adjusted to pH 5 with hydrochloric acid were charged into a pulper so that the pulp concentration was 5%, and the mixture was disintegrated for 40 minutes. Then, the disaggregated suspension was diluted to a solid content concentration of 2.5%, and coarsely and finely screened using the rough and fine screens used in Example 1. The accept pulp was dehydrated and concentrated to a solid content concentration of 20% (manufactured by Aikawa Iron Works: Inclined extractor + screw press). Since the pH of this concentrated raw material was 6.5, hydrochloric acid was added to adjust the pH to 5.5. Then, the concentrated raw material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using a disperser). The raw material temperature after the kneading treatment was 45 ° C.

After the treated raw material was diluted to a solid concentration of 2%, it was treated with a screening screen (fine screen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.20 mm. Then, the screen accept material was dehydrated and concentrated to a solid content concentration of 35% (manufactured by Aikawa Iron Works: Inclined extractor + screw press).
Next, a 1% caustic soda (absolute dry solid content) was added to this concentrated raw material, and a surfactant comprising a fatty acid ethylene oxide / propylene oxide adduct (trade name: DI-610 /
(Manufactured by Kao Corporation) was added in an amount of 0.4% (based on absolute dry solids), and calcium hypochlorite was added as effective chlorine in an amount of 2.0% (based on absolute dry solids). And kneading treatment of the concentrated raw material while introducing steam (made by Aikawa Iron Works: using disperser)
did. 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 concentration of 0.8%, and a flotation treatment was performed using a flotator (a vertical floater manufactured by Aikawa Iron Works). After repeating the flotation treatment three times, the resultant was washed with a drum washer to obtain a recycled pulp. The resulting recycled pulp has a Hunter whiteness of 80.
%, 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 any troubles in soiling the paper machine wire.

Example 5 A heat-sensitive recording paper was used as a surface base material, and a high-quality cream-colored paper laminated with polyethylene was coated with a silicon compound as a release base material. A pressure-sensitive adhesive paper formed by applying an acrylic emulsion as an agent was used as a raw material for waste paper.

The used paper and water were charged into a high-concentration pulper (manufactured by Aikawa Iron Works: high-concentration pulper) so that the solid content concentration became 15%, and the mixture was disintegrated for 20 minutes. The disintegration temperature at this time is 3
It was 0 ° C. The disaggregated raw material was diluted to a solid content concentration of 2.5%, and was coarsely selected and finely selected using the coarse selection screen and the fine selection screen used in Example 1. Then, the accept pulp was dehydrated and concentrated to a solid content concentration of 28% (manufactured by Aikawa Tekko: Inclined extractor + screw press).
Since the pH of the concentrated raw material was 7.5, the pH was adjusted to 5.0 by adding a sulfuric acid band. Then, the concentrated raw material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using a disperser). The raw material temperature after the kneading treatment was 40 ° C.

After the raw material after the treatment was diluted to a solid concentration of 2%, it was treated with a screening screen (fine screen, manufactured by Aikawa Iron Works) equipped with a screen plate having a slit width of 0.20 mm. Then, the screen accept material was dehydrated and concentrated to a solid concentration of 33% (manufactured by Aikawa Iron Works: Inclined extractor + screw press).
Next, 1% of caustic soda (based on absolute dry solid content) was added to the concentrated raw material, and a fatty acid surfactant (trade name: DI-260 /
0.4% to absolutely dry pulp and 0.1% to the pulp a special anionic surfactant (trade name: DI-380 / Kao Corporation) Sodium chlorate was added at 2.0% (vs. absolute dry solids) as available chlorine. Then, while introducing steam, the concentrated material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using 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 concentration of 0.8%, and a flotation treatment was performed with a flotator (a vertical floater manufactured by Aikawa Iron Works). And this flotation process is 3
After repeating the process, the accept material is dust-removed with a heavy foreign matter cleaner (Aikawa Tekko: Low concentration cleaner) and a light foreign matter cleaner (Aikawa Teiko: Giroclean).
Subsequently, it was washed with a drum washer to obtain a recycled pulp.

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

Example 6 A high-concentration pulper (manufactured by Aikawa Iron Works: high-concentration pulper) using the pressure-sensitive adhesive paper used in Example 1 as a raw material for waste paper.
Was added to the waste paper and water adjusted to pH 1.5 with hydrochloric acid so that the solid content concentration was 15%, and the mixture was disintegrated for 20 minutes. The defibration temperature at this time was 30 ° C.

The defibrated raw material is diluted to a solid concentration of 3%,
Screens with slit widths of 0.5 mm and 0.2 mm were respectively incorporated into the coarsely-selected screen and the finely-selected screen used in Example 1, and were subjected to coarse-selection and fine-selection. Then, the accepted pulp was dehydrated and concentrated to a solid concentration of 23% (manufactured by Aikawa Tekko:
Inclined extractor + screw press used). Since the pH of this concentrated raw material was 4.5, no particular pH adjustment was performed. Next, the concentrated raw material was subjected to a kneading treatment (manufactured by Aikawa Iron Works: using a disperser). The raw material temperature after the kneading treatment was 40 ° C.

After diluting this raw material to a solid concentration of 1.5%, it was 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. Then, the screen accept material was dehydrated and concentrated to a solid content concentration of 35% (manufactured by Aikawa Iron Works: Inclined extractor + screw press).
Next, a 1% caustic soda (based on absolute dry solids) was added to the concentrated raw material, and a surfactant (trade name: DI-600R) composed of an adduct of oil-based ethylene oxide and propylene oxide was used.
/ Kao Corporation) was added to the absolutely dry pulp at 0.4%, and sodium hypochlorite as available chlorine at 3.0% (vs. absolutely dry solids). The concentrated raw material was subjected to a kneading treatment (manufactured by Aikawa Iron Works, using a disperser) while introducing steam during the treatment. The raw material temperature after the kneading treatment was 65 ° C.

After standing for 120 minutes after the treatment, this raw material was diluted to a solid concentration of 0.8%, and a flotation treatment was carried out with a flotator (a vertical floater manufactured by Aikawa Iron Works). After repeating the flotation process three times, the accept material is dust-removed with a heavy foreign matter cleaner (made by Aikawa Tekko: Ramo low concentration cleaner) and a lightweight foreign matter cleaner (made by Aikawa Tekko: Giroclean), and then washed with a drum washer. Recycled pulp was obtained.

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

Comparative Example 1 The pressure-sensitive adhesive paper used in Example 1 was used as a waste paper material and subjected to disintegration, rough selection and fine selection in the same manner as in Example 1. The treated accept pulp was concentrated to a solid content concentration of 32% and kneaded. The temperature after kneeling is 65 ° C
Met. A 1% caustic soda (based on absolute dry solids) is added to the kneaded raw material, and a surfactant comprising an adduct of oil-based ethylene oxide and propylene oxide (trade name: DI-600R / manufactured by Kao Corporation) Was added to 0.4% of absolutely dry pulp, and 3.0% of sodium hypochlorite as effective chlorine (based on absolutely dry solids) was added, and the mixture was allowed to stand for 120 minutes.

After diluting this raw material to a solid concentration of 0.8%, a flotation treatment was carried out using a flotator (a vertical floater manufactured by Aikawa Iron Works). Then, after the flotation treatment is repeated three times, the accept material is dust-removed with a heavy foreign matter cleaner (made by Aikawa Tekko: Ramo low concentration cleaner) and a lightweight foreign matter cleaner (made by Aikawa Tekko: Giroclean), and then washed with a drum washer. To obtain recycled pulp.

The regenerated pulp thus obtained was white with a Hunter brightness of 80%, but contained 0.2% of the pressure-sensitive adhesive. In the paper containing this pulp, the pressure-sensitive adhesive stained the wires, rolls and dryers during papermaking, and smooth operation was not possible.

COMPARATIVE EXAMPLE 2 Using the pressure-sensitive adhesive paper used in Example 1 as a waste paper material, defibration, rough selection and fine selection were carried out in the same manner as in Example 1 to obtain a solid content concentration of 32% in the former kneading step and the latter step. Reprocessed pulp was obtained by performing the same treatment as in Example 1 except that the solid content concentration in the kneading step was changed to 28%.

The obtained recycled pulp was white with a Hunter whiteness of 80% and no residual film was observed. However, it contained 0.2% of the pressure-sensitive adhesive and caused troubles that stained the wire of the paper machine. Occurred.

Comparative Example 3 Recycled pulp was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive paper of Example 1 was used as a waste paper material and the flotation step was omitted. The obtained recycled pulp was white with a Hunter whiteness of 80% and no residual film was observed, but contained 1.2% of the pressure-sensitive adhesive and caused troubles that stained the wire of the paper machine.

Comparative Example 4 Recycled pulp was processed in the same manner as in Example 1 except that the pressure-sensitive adhesive paper of Example 1 was used as a waste paper raw material and the screen step between the former kneading step and the latter kneading step was omitted. I got The resulting recycled pulp was white with a Hunter whiteness of 80% and no residual film was observed, but contained 3.5% of the pressure-sensitive adhesive, and caused troubles that stained the wire of the paper machine.

[0058]

According to the method of the present invention, it is possible to recycle pulverized pressure-sensitive adhesive paper, which has been avoided in the past, and paper produced by blending the obtained reclaimed pulp can be used. The texture was excellent, and no trouble occurred during papermaking.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) D21B 1/14 D21C 5/02

Claims (4)

(57) [Claims] In a pulping method for obtaining recycled pulp from waste pressure-sensitive adhesive paper, a kneading treatment is carried out on a raw material slurry having a pH of 6 or less at a solid content concentration of 15 to 30% by weight. Pulp treated with a slit width of 0.
A step of treating with a screen of 2 mm or less, adding caustic soda and a surfactant to the pulp treated in this step,
A method for pulping used pressure-sensitive adhesive paper, comprising: a step of kneading while applying a compressive force at a solid content concentration of 40% by weight while heating, followed by a flotation step. 2. A bleaching chemical is added to the screen-treated pulp in addition to caustic soda and a surfactant.
The pulping method as described. 3. A bleaching chemical comprising sodium hypochlorite and / or
3. The pulping method according to claim 2, wherein the pulping is calcium hypochlorite. 4. The pulping method according to claim 1, wherein the surfactant is a fatty acid-based or fat-based ethylene oxide / propylene oxide adduct or a fatty acid soap as a main component.