JPH03234884A - Pulpification of waste heat-sensitive recording paper - Google Patents

Abstract

PURPOSE:To obtain a regenerated pulp causing little paper-breakage trouble in paper-making process and giving a paper having no black spot and few pinholes by dissociating waste heat-sensitive recording paper in an alkaline aqueous solution, adding and mixing a defoaming agent to the obtained pulp suspension and cleaning the mixture. CONSTITUTION:Waste heat-sensitive recording paper is dissociated in an alkaline aqueous solution, a defoaming agent (e.g. a mixture of polyglycol and fatty acid) is added and mixed to the obtained pulp suspension and the mixture is cleaned to obtain regenerated pulp. When the waste paper has a protective layer, it is preferable to mechanically agitate the pulp suspension at a concentration of >=15% under a compressive action prior to the cleaning treatment. When the waste paper contains color paper, the cleaned product is preferably bleached with an oxidation agent.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for obtaining recycled pulp from waste heat-sensitive recording paper (including waste paper), and in particular, a method for efficiently separating heat-sensitive recording material from pulp fibers, This invention relates to a method for processing waste paper to obtain recycled pulp with high whiteness.

[Conventional technology]

In general, heat-sensitive recording paper is composed of a base paper made of pulp fibers and a heat-sensitive recording layer made of fine particles of basic colorless dye, coloring agent, sensitizer, pigment, binder, auxiliary agent, etc. is widely known. When heat is applied to the recording layer of this thermosensitive recording paper, the sensitizer and coloring agent in that area are dissolved, and brought into contact with the basic colorless dye to obtain a colored image.

Colored images produced by thermosensitive recording paper are generally inferior in water resistance, oil resistance, plasticizer resistance, and the like. For this reason, for example, if water is added to a colored image,
If it comes into contact with oil or a plasticizer contained in the plastic film, the image density will drop significantly, and if the heat-sensitive recording layer is touched by hand during handling, it has the disadvantage of causing fingerprint-like fogging. In order to solve this problem, for example, a protective layer such as a water-based emulsion coating layer, a water-soluble polymer compound coating layer, a resin layer made of a water-soluble polymer compound cured with a curing agent, etc. is provided on the heat-sensitive recording layer. Thermosensitive recording paper has come to be widely used in fields such as labels.

As the production volume of such thermal recording paper increases, the development of a method for recycling waste thermal recording paper has become a new issue.

BACKGROUND ART Conventionally, recycled pulping of Shinkai waste paper and printed coated paper has been commonly carried out. The process of converting waste paper into recycled pulp is
Recycled pulp is produced through a disintegration process that disintegrates waste paper to obtain a pulp suspension, a rough selection and selection process that separates foreign substances from the pulp suspension, a deinking process that separates printing ink, a bleaching process that whitens the color, etc. conversion is being carried out. For example, Tokuko Sho 50-290
No. 42 proposes a waste paper recycling method consisting of disintegration and rough selection of waste printing coated paper, dehydration, bleaching, and ink separation.
A method of disintegration treatment using an alkaline solution containing a surfactant is disclosed. Furthermore, JP-A No. 63-13558
No. 5 includes a step of disintegrating waste heat-sensitive recording paper in an alkaline aqueous solution containing a surfactant and then neutralizing it, and flotation sorting of the disintegrated waste paper slurry [Problems to be Solved by the Invention] The present invention relates to a method for obtaining recycled pulp from waste heat-sensitive recording paper, in particular, it efficiently separates and removes heat-sensitive recording material from pulp fibers, obtains white recycled pulp without causing trouble in the paper-making process, and eliminates pinholes. The purpose is to provide a regenerated pulping method that generates less generation.

[Means to solve the problem]

The present invention provides a pulping method for obtaining recycled pulp from waste heat-sensitive recording paper, in which the waste paper is disintegrated with an alkaline aqueous solution,
This method of pulping waste heat-sensitive recording paper is characterized by adding and mixing an antifoaming agent to the disintegrated pulp suspension, followed by washing treatment.

[Effect]

The waste thermal recording paper that is the subject of treatment in the present invention is thermal recording paper that is used for a wide range of purposes such as commercial, office, and household use in facsimiles, printers, labels, etc., and thermal recording paper is manufactured into thermal recording paper. This includes semi-finished products and waste paper generated during the process. In the waste paper processing method of the present invention, a method has been proposed in which the paper is made into recycled pulp through the above-mentioned process of aging the thermal recording paper, concentrating it with a dehydration squeezer, and disintegrating it with a high-speed disintegrator. When used thermal recording paper is recycled into pulp using the method described above, the pulp suspension after disintegrating the waste paper has a significant amount of foaming, and the foaming reduces cleaning efficiency during processes such as dehydration and concentration, washing, etc. Unfortunately, the heat-sensitive recording material remains in the pulp fibers. Incidentally, when paper is made from recycled pulp with heat-sensitive recording material remaining, there is a problem in that the heat-sensitive recording material develops color during the drying process of the paper machine, reducing the whiteness of the paper.

Furthermore, if bubbles in the pulp suspension are torn at a portion of the wire during the papermaking process, holes will form in the sheet, causing paper breakage and reducing the operating rate of the papermaking machine. In addition, although small bubbles do not cause trouble in the papermaking process, the resulting paper has numerous pinholes, making it unsuitable as a base paper for coating, high-quality paper, and base paper for information paper. There is. For these reasons, the current situation is that recycled pulp from used thermal recording paper is avoided and is treated as industrial waste.

Paper is first disintegrated with an alkaline aqueous solution using a pulper to create a pulp suspension. The aqueous alkaline solution is used to dissolve the coloring agent in the heat-sensitive recording material and to promote disintegration. Coloring agents include - phenolic compounds for boat fishing;
Organic acids such as aromatic carboxylic acids have been used, but these can be converted into salts in alkaline aqueous solutions, solubilized in water, and separated from the pulp fibers. On the other hand, basic dyes such as triallylmethane-based, phenylmethane-based, thiazine-based, and fluoran-based dyes do not dissolve in alkaline aqueous solutions, so they do not react with each other and develop color through alkali treatment.

In order to perform the above action, the pH of the pulp suspension must be adjusted.
pH of 8 or higher, and pH of 1 for better disaggregation effect.
It is preferable to set it to 0 or more. Incidentally, if J)H is less than 8, the permeability to the protective layer, heat-sensitive recording layer and base paper layer and the elution of the coloring agent component will be insufficient, and it will remain in the recycled pulp.

When this recycled pulp is used to make paper, it loses its commercial value because it develops color in the dryer of the paper machine. Alkaline agents include sodium hydroxide, sodium carbonate, calcium hydroxide, potassium hydroxide, sodium silicate, thorium phosphate, calcium carbonate, sodium hypochlorite,
Alkaline substances such as calcium hypochlorite are used as appropriate. Among them, thorium hydroxide is preferably used because it has excellent permeability.

The amount of the alkaline agent added may be appropriately adjusted so that the pH of the pulp suspension becomes 8 or more, and the amount can be adjusted by adding 0.2 to 5% based on the waste paper. In the case of this disaggregation, if the waste heat-sensitive recording paper contains pressure-sensitive adhesives, plastics, etc. (hereinafter simply referred to as foreign matter), the foreign matter will naturally be mixed into the valve suspension after disaggregation. It turns out. It is necessary to separate these foreign substances, and it is necessary to provide a screening process as a step to separate them. When disintegrating this waste paper, if these foreign substances are subjected to excessive mechanical action by an agitator, etc., they will be crushed into very small pieces and ejected from the screen opening during the selection screen process, worsening the separation effect. As a means for this, surfactants, protective colloids, etc. are used during dispersion or wet grinding. Furthermore, since binders such as PVA and latex are also used, waste heat-sensitive recording paper containing these binds air during the disintegration process, and a large amount of bubbles are present in the resulting pulp suspension.

Regarding recycled pulping technology for used paper, there is also a method called foam flotation separation, which is a waste paper processing method that actively utilizes foam. However, in the present invention, this foam impairs the cleaning efficiency in processes such as dehydration and concentration, and causes the heat-sensitive recording material to remain in the pulp fibers. When this pulp is used to make paper, as mentioned above, the whiteness of the paper decreases, and bubbles in the pulp suspension break off at some wires in the papermaking process, creating holes in the sheet and causing paper breakage, which can cause problems in the paper machine. Utilization rate decreases.

Furthermore, the resulting paper has numerous pinholes and cannot be used as a base paper for coating, high-quality paper, or base paper for information paper.

In the present invention, in order to solve the above-mentioned unique problem caused by waste paper being a heat-sensitive recording material, there is a risk of pulping.

Furthermore, if the recycled pulp contains foreign matter, if the recycled pulp is used to make paper, the foreign matter may block the wire openings or stain the press rolls or blankets during the papermaking process.
It also causes paper breakage and significantly reduces papermaking efficiency. Further, there is also the problem that spots are formed on the paper surface, which adversely affects the paper layer formation or quality. For this reason,
The degree of disintegration in the disintegration step is preferably adjusted so that the foreign matter does not become finer than the sparks of the screening screen.

The method of adjusting the degree of disintegration is not particularly limited, and may be adjusted by adjusting the length of disintegration time, the temperature of water, the amount of alkali added, etc., if a device such as a pulper is determined.

An important feature of the present invention is that an antifoaming agent is added to the valve suspension of waste paper of thermosensitive recording paper thus obtained.

Generally, in the paint preparation stage of heat-sensitive recording materials, in order to improve the recording sensitivity, it is necessary to atomize the material in each dispersion to a particle size of several micrometers or less, and actively remove bubbles from the suspension. It is an invention aimed at erasing. In this sense, the present invention can be said to be a waste paper processing method based on a concept completely opposite to that of the conventional foam flotation separation method.

Accordingly, in the present invention, the antifoaming agent may be added at any point before the dehydration/concentration and cleaning steps.

Antifoaming agents include polyglycol/fatty acid mixtures, phosphoric acid esters, silicone emulsion systems, nonionic fatty acid mixtures, polyglycol esters, alcohol systems, vegetable oil systems, fatty acid esters, pine oil emulsions, sulfate ester systems, metal soap systems, etc. can be used. These are, of course, illustrative and not limiting.

The type of antifoaming agent and its amount to be used should be selected and added as appropriate while checking the foam generation situation depending on the water temperature, the type of alkaline agent used, the place where the antifoaming agent is added, etc., but the amount to be added should be determined based on the amount of used paper. It is effective at 0.0001 to 0.1%.

In addition, when thermosensitive 0 recording paper with a protective layer is present in the waste thermal recording paper, the base paper layer is easily disintegrated by a normal pulper, but the thermosensitive recording layer is not disintegrated and becomes small particles. Present in suspension.

The thermosensitive recording material is present in these grains and cannot be easily removed. For this reason, when a thermal recording paper having a protective layer is present, it is necessary to dehydrate and concentrate the pulp suspension disintegrated with a normal pulper to a pulp concentration of 15% or more, and then perform mechanical stirring.

This mechanical stirring causes the particles to be dispersed.

Incidentally, when the pulp concentration is 15% or less, the dispersing power is weak, so that the particles remain in the suspension. Therefore, in this case as well, it is preferable to add an antifoaming agent before dehydrating and concentrating. This mechanical stirring method is a mechanical stirring that imparts a compressive action.
- Kneader 1 twin-screw mixer, disperser, etc. used for boat fishing can be used. In the present invention, washing is required to separate and remove the thermal recording paper material from the pulp fibers. Cleaning methods include displacement cleaning, diluted dehydration cleaning,
Press cleaning etc. can be used. It is not particularly limited. Among them, diluted dehydration cleaning and press cleaning 1 have different effects, so they can be selected as appropriate while looking at the effects.

The pulp after bleaching may be used as is, or may be washed to remove residual bleaching agent. Incidentally, if there are heavy foreign substances, a cleaner treatment may be further performed.

In addition, in order to increase the strength of the paper, beating may be performed at a pulp concentration of 3 to 4%, and this can be done as appropriate depending on the quality target of the paper.

In this way, the obtained white recycled pulp can be blended with virgin pulp without causing any trouble in the paper-making process, and the paper produced has few pinholes and no spots on the paper surface, making it suitable for coated paper base paper, high-quality paper, It can also be usefully used as information paper base paper.

〔Example〕

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

Example 1 Waste heat-sensitive recording paper without a protective layer on the pulper and hydric acid 3 is preferable because coating components such as pigments and dyes can be removed well.

The pulp thus obtained has a high degree of whiteness and can be used by blending it into ordinary coated paper base paper, high-quality paper, and information paper base paper.

Thermal recording paper is used for commercial, office, and household purposes, and colored waste paper is often mixed in during the collection process of these waste papers. In this case, it is necessary to further bleach with a bleaching agent. Bleaching agents include sodium hypochlorite or calcium hypochlorite, hydrogen peroxide, sodium peroxide, chlorine dioxide oxidizing agents and hydrosulfides,
Formamidine sulfinic acid reducing agent can also be used, but
Pulp bleached with a reducing agent tends to change color when exposed to light, so it is preferable to bleach it with an oxidizing agent because it is more stable against light. Also, among oxidizing agents, sodium hypochlorite or calcium hypochlorite has a strong ability to decompose dyes, so
preferable.

The amount of bleach added depends on the amount of colored material mixed in and the type of dye used in the colored material.Add 2% bleaching sodium bichloride aqueous solution to the waste paper until the pulp concentration is 5%. Water was added to the mixture and disintegrated for 30 minutes.

The pH of this suspension was 11.5. This suspension was adjusted to a pulp concentration of 3.5%, and was carefully selected using a screen with a slit width of 0.5 mm (CH type mold density screen manufactured by Aiyo Tekko ■).

This accepted pulp was diluted to a pulp concentration of 1%, an antifoaming agent (manufactured by San Nopco Co., Ltd.; Nopco 1407-K) was added to the waste paper at 0.01%, mixed, and dehydrated to 10% using a desk filter. Concentrated.

Again, this 10% dehydrated and concentrated pulp was diluted with water to 1% and filtered to 10% to obtain regenerated pulp.

The obtained recycled pulp has a Hunter whiteness of 77%
A paper prepared by blending 50% of this recycled pulp with virgin pulp had fewer pinholes.

Example 2 A waste thermosensitive recording paper without a protective layer was added to the pulper, and an aqueous solution of calcium 4-hydroxide was added at 0.3% to the waste paper, water was added so that the pulp concentration was 5%, and the mixture was disintegrated for 30 minutes. .

The pH of this suspension was 8.5. This suspension was adjusted to a pulp concentration of 3.5% and was carefully selected using a screen with a slit width of 0.5 mm (CH type temperature concentration screen manufactured by Aiyo Tekko ■).

This accepted pulp was diluted to a pulp concentration of 1%, an antifoaming agent (manufactured by San Nopco; Nopco DF-122) was added to the waste paper at 0.03%, mixed, and the concentration was reduced to 10% using a desk filter. Dehydrated and concentrated.

Again, this 10% dehydrated and concentrated pulp was diluted with water to 1% and filtered to 10% to obtain regenerated pulp.

The obtained recycled pulp has a Hunter whiteness of 73% white (
A paper prepared by blending 50% of this recycled pulp with virgin pulp had fewer pinholes.

Example 3 Waste thermosensitive recording paper without a protective layer was mixed into the pulper (containing asagi-colored high-quality paper) and 2% aqueous sodium hydroxide solution was added to the waste paper, and water was added so that the pulp concentration was 5%. was prepared and disintegrated for 30 minutes.

The pH of this suspension was 11.5. This suspension was adjusted to a pulp concentration of 3.5% and was carefully selected using a screen with a slit width of 0.5 mm (CH type temperature concentration screen manufactured by Aiyo Iron Works ■).

This ACEPJ pulp was diluted to a pulp concentration of 1%, and an antifoaming agent (manufactured by Zan Nopco; Nopco 1407-K) was added.
was added at 0.01% to the waste paper, mixed, and dehydrated and concentrated to 10% using a desk filter. Again, this 10% dehydrated and concentrated pulp was diluted to 1% with water and made up to 10% with a desk filter.Next, sodium hypochlorite was added to the pulp at 3%, and the pulp was incubated at 40°C for 23 hours. After bleaching, recycled pulp was obtained.

The obtained recycled pulp was white with a Hunter whiteness of 80%, and paper prepared by blending this recycled pulp with virgin pulp at 50% had fewer pinholes.

Example 4 Waste thermal recording paper with a protective layer on the pulper, 2% sodium hydroxide aqueous solution added to the waste paper, and 0.0% antifoaming agent (manufactured by San Nopco; Nobuco 1407-K) to the waste paper.
5% was added, water was added so that the pulp concentration was 5%, and disintegrated for 30 minutes.

The pH of this suspension was 12. This suspension was adjusted to a pulp concentration of 3.5% and was carefully selected using a screen with a slit width of 0.5 mm (CH type temperature concentration screen manufactured by Aiyo Iron Works ■).

This accepted pulp was dehydrated and concentrated using a gradient extractor and a screw press to give a pulp concentration of 28%, and mechanically stirred with a kneader while applying a compression action.

After diluting this diluted pulp to a concentration of 1%,
After adding and mixing 0.005% of an antifoaming agent (manufactured by San Nopco Co., Ltd.; Nopco 1407-K) to the waste paper, the mixture was dehydrated and concentrated to 10% using a desk filter to obtain recycled pulp.

The obtained recycled pulp was white with a Hunter whiteness of 75%, and paper prepared by blending this recycled pulp with virgin pulp at 50% had fewer pinholes.

Example 5 Waste paper of thermal recording paper with a protective layer on the pulper (containing high-quality paper of Asagi color) was added with 2% sodium hydroxide aqueous solution to the waste paper so that the pulp concentration was 5%. Water was added and disintegrated for 30 minutes. The pH of this suspension is I
It was 2. This suspension was adjusted to a pulp concentration of 3.5% and carefully selected using a screen with a slit width of 0.5 mm (CH type temperature concentration screen manufactured by Aiyo Tekko ■).

To this accepted pulp, an antifoaming agent (manufactured by San Nopco; Nopco 1407-K) was added at 0.05% based on the waste paper, and after mixing, the pulp was dehydrated and concentrated using an inclined extractor and a screw press to give a pulp concentration of 23%. The mixture was mechanically stirred while applying compression using a kneader.

This diluted pulp was diluted to 1% concentration and added to an antifoaming agent (manufactured by San Nopco; Nopco 14o7-K).
Added 0.001% to the waste paper, dehydrated and concentrated it to 10% using a desk filter, then added 4% sodium hypochlorite to the pulp, bleached it at 43°C for 13 hours, and recycled. Obtained pulp.

The obtained recycled pulp was white with a Hunter whiteness of 82%, and paper prepared by blending this recycled pulp with virgin pulp at 50% had fewer pinholes.

Comparative Example 1 Sodium hydroxide and antifoaming agent used in Example 1 were not used. Other than this, the same procedure as in Example 1 was carried out. The obtained recycled pulp had a low whiteness of 60%, and paper prepared by blending 50% of this recycled pulp with virgin pulp had many pinholes.

Comparative Example 2 Addition of the antifoaming agent used in Example 1 was stopped. Other than this, the same procedure as in Example 1 was carried out. The obtained recycled pulp is
The whiteness was 70%, which was lower than the whiteness of Example 1, which was 77%. In addition, 50% of this recycled pulp is virgin pulp.
The blended and prepared paper had many pinholes.

Comparative Example 3 Addition of the antifoaming agent used in Example 5 was stopped, and furthermore, no bleaching treatment was performed. Except for this, the same procedure as in Example 5 was carried out to obtain recycled pulp. The resulting recycled pulp had a whiteness of 55%. In paper prepared by blending 50% of this recycled pulp with virgin pulp, large holes were observed, as well as many fine pinholes and black granular spots.

〔effect〕

According to the present invention, it is now possible to convert used heat-sensitive recording paper into recycled pulp, which has been avoided until now, and even if the obtained recycled pulp is blended with virgin pulp to make paper, Because there are fewer holes in the paper, there are fewer paper breaks, and the paper produced is excellent, with no black granular spots and fewer fine pinholes.

Claims (3)

[Claims] (1) In the pulping method for obtaining recycled pulp from waste heat-sensitive recording paper, the waste paper is disintegrated with an alkaline aqueous solution, and an antifoaming agent is added to and mixed with this pulp suspension, followed by washing treatment. A method for pulping waste heat-sensitive recording paper. (2) If the waste heat-sensitive recording paper is waste paper with a protective layer, 15% pulp suspension is added before washing.
The pulping method according to claim 1, characterized in that disintegration is carried out by mechanical stirring to impart a compressive action under the above concentration. (3) Claim (1) characterized in that if the waste paper contains colored substances, it is bleached with an oxidizing agent after the washing process.
and the pulping method described in (2).