JPH08226087A - Regeneration treatment of waste paper - Google Patents

Abstract

PURPOSE: To efficiently obtain regenerated pulp having a high whiteness by soaking waste paper printed with a UV-curable ink, disintegrating the soaked paper, and further controlling the average particle diameter of the ink before deinked. CONSTITUTION: This method for regenerating the waste paper printed with a UV-curable ink comprises soaking the waste paper in a solution having a pH of >=9 for 20min in order to reduce the mechanical load to a pulper before the waste paper is disintegrated with the pulper, screening off the UV light- curable ink coating film left as broken pieces in a pulp slurry after the disintegration, controlling the average particle diameter of the ink to 10-100μm, preferably 20-80μm, in a kneading process, and subsequently deinking the treated pulp by a flotation method. In the case of a deinking process consisting mainly of a washing treatment, the average particle diameter of the ink is controlled to <=10μm, preferably <=8μm, and subsequently the pulp is washed and deinked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling printed waste paper using UV curable ink.

[0002]

2. Description of the Related Art High-quality waste paper processing such as imitation waste paper and colored waste paper consists of processes such as disaggregation, rough selection, ripening, deinking, selection, and bleaching, but in reality, depending on the circumstances of each company. It is processed in various combinations. As for the method of deinking, there are a cleaning method, a flotation method, and a method that combines both methods (eclectic method). One example is shown in FIG.
In the disintegration process using a pulper, it is common to add an alkali such as caustic soda to accelerate the peeling of the ink. After rough selection, a surfactant and the like are added and uniformly mixed with a kneader, and then the fibers are swollen in an aging tower to promote peeling of the ink. The ink in the raw material adheres to the foam by flotation and floats, and is removed to the outside of the system. Then, a bleaching process is performed if necessary.

On the other hand, in the field of printing, quick drying of ink,
The use of UV curable inks is increasing due to their excellent cured film properties and energy savings. This ink contains an acrylic monomer or prepolymer as a main component, and initiates radical photopolymerization upon irradiation with ultraviolet rays, and is rapidly polymerized to cure and dry the ink. At the beginning of development, carton printing was the main focus, but recently it has been widely used for printing magazine covers, labels, stickers, stickers, and magnetic recording paper. In this way, as the fields of application of UV curable ink have expanded, and the tendency to protect nature and reuse of resources has increased, UV curable ink printed matter mixed in recovered waste paper in the form of processing scraps, magazines, or knives. The amount is increasing.

[0004]

Since the UV curable ink is strongly hydrophobic and has a hard film, it is relatively easy to peel it from the fiber, but it is difficult to subdivide it by the conventional deinking method.
It is difficult to remove by either the washing method or the flotation method, and this is the main reason why the waste printing paper using UV curable ink cannot be used as high quality recycled paper. That is, the present invention provides a processing method for recycling printed waste paper using UV curable ink as high quality recycled paper.

[0005]

[Means for solving the problems] As a result of earnest research,
To invent a method that utilizes the fact that the film of UV curable ink is hard, suppresses the mechanical action as much as possible in the first step of disaggregating used paper, and removes as much ink as possible in the screening step with large fragments I arrived. In other words, this is a method of incorporating soaking as a pretreatment for disaggregation because the original purpose of disaggregation of paper must be sufficiently performed while reducing the load on the pulper. This soaking may be performed in another facility before the raw materials are charged into the pulper, or may be performed using the pulper. In addition, soaking can be made more efficient by adding an alkali or raising the temperature. The time required for this soaking depends on pH, temperature, paper quality, printing condition, etc., but at least about 20 minutes is required.

Since hydration and swelling of the fibers are progressed by soaking, the fibers can be disintegrated to such an extent that no undisaggregated pieces of the fibers remain by a light mechanical action. On the other hand, the film of UV curable ink has strong hydrophobicity, so it does not change at all due to soaking,
Even after disaggregation, they remain as large fragments in the slurry. By performing the screening in this state, most of the UV curable ink film can be efficiently removed. Therefore, it is desirable that the screen used here has a crushing action as small as possible.

Since the UV curable ink has a very strong hydrophobicity, there is no problem with foam adhesion in flotation. Therefore, when deinking by flotation, controlling the particle size of the ink is the most important factor. Then, as a result of experimentally attempting flotation of ink having various average particle diameters, it was found that the removal rate of ink of 10 to 100 μm, and particularly 20 to 60 μm was high. Therefore, in the kneading step before flotation, the load should be adjusted so that the average particle size of the ink falls within this range. If the load cannot be adjusted by changing the tooth profile of the kneader or the clearance, a deflaker or fiber riser may be used as an auxiliary.

On the other hand, since the smaller the ink particle size is, the easier it is to clean, in the case of deinking equipment where cleaning is mainly performed, the kneader is strengthened, and if necessary, a deflaker or a fiber riser is used together to reduce the average particle size. 10 μm or less,
It is preferably adjusted to 8 μm or less. In the case of the eclectic method in which flotation precedes, the maximum deinking effect can be obtained by combining the respective particle size controls.

[0009]

In this way, by soaking as a pretreatment for disaggregation, allowing the fibers to swell sufficiently and then disaggregating at the lowest possible load, both disaggregation of the fibers and prevention of film destruction of the UV curable ink are achieved. Efficient deinking is possible by screening the UV curable ink film as large fragments as possible and discharging them from the system.
Furthermore, by controlling the particle size of the ink to an appropriate size in the flotation step and / or the washing step, the deinking rate is improved, and it is possible to use recycled paper in high quality systems.

[0010]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 Example 1 is an example in which soaking is performed prior to disaggregation to enhance kneading before flotation and before washing. Samples: Magnetic recording paper with stripe printing using UV-curable ink Equipment used: Lab pulper (Aikawa Tekko Co., Ltd. 30 l high-concentration pulper), screen (Kumagaya Riki Kogyo flat screen 6cut), kneading (Kumagaya Osamu) Ware industry P
FI mill), Floatator (Labo Floatator manufactured by Kyokuto Shinko Co., Ltd.), Ink particle size and number measurement (Luzex III measurement lower limit 2 μm manufactured by Nireco), Whiteness measurement (Digital Hunter Whiteness Meter manufactured by Toyo Seiki Seisakusho)

Soaking with a lab pulper (40 ° C, 30
Min, pH 10 (NaOH), pulp concentration 8%) and then 15
After disintegrating for a minute, screening was performed on a flat screen. After that, kneading (800 rotations),
Aging (40 ° C., 60 minutes) and flotation treatment were performed in this order. After the flotation, kneading (300 rotations) was performed again to thoroughly wash on a 100-mesh wire net. The sample was used as a hand sheet for measurement of residual ink and whiteness. The results are shown in Table 1 including the measurement results of the main steps.

Example 2 One kneading before cleaning (300 rotations in Example 1)
The process was performed in the same manner as in Example 1 except that the rotation was set to 00. The results are shown in Table 1 including the measurement results of the main steps.

Example 3 Kneading before flotation (80 in Example 1)
The process was performed in the same manner as in Example 1 except that (0 rotation) was changed to 500 rotations. The results are shown in Table 1 including the measurement results of the main steps.

Comparative Example A comparative example is an example in which processing is performed under the processing conditions of imitation waste paper or colored waste paper using conventional ink. Omission of soaking before disaggregation, disaggregation at room temperature for 30 minutes (pH 10, pulp concentration 1
5%), kneading before flotation was 500 rotations, and kneading before washing was 100 rotations. The other processing method is the same as that of the first embodiment.

[0016]

[Table 1]

[0017]

The mechanical load on the pulper can be reduced by soaking before defibration, so the ink particle size after defibration is about 1.7 times that of the conventional method, and the removal rate on the screen is also large. Improved. In addition, by controlling the load of the kneader and performing flotation and washing with an appropriate ink particle size, the total area of the ink will eventually become one-third or less of that of the conventional method, and the whiteness will increase by 2 points or more. I understood.

[Brief description of drawings]

FIG. 1 is an example of a flow of recycling imitation waste paper or colored waste paper.

Claims (4)

[Claims] 1. A method for recycling used paper, comprising soaking prior to the disintegration of waste paper and screening after disintegrating, in the used paper recycling process of printed matter using UV curable ink. 2. Prior to the disaggregation of waste paper, at pH 9 and above, 20
2. Soaking for more than one minute is performed.
Recycled waste paper processing method described. 3. The average particle diameter of the ink is 10 to 100 μm.
3. The method for recycling used paper according to claim 1 or 2, wherein the flotation is performed after being adjusted to a value of preferably 20 to 80 [mu] m. 4. The average particle size of the ink is 1 in the pre-cleaning step.
3. The ink is deinked in a washing step after adjusting to 0 μm or less, preferably 8 μm or less.
Alternatively, the used paper recycling method according to claim 3.