JPH03234883A - Method for disintegrating waste paper - Google Patents

Abstract

PURPOSE:To dissociate waste paper in a short time under gentle mechanical agitation condition without causing the crushing of plastic foreign materials while suppressing the damage of the fiber by dissociating waste paper in water under the simultaneous application of mechanical agitation and ultrasonic vibration. CONSTITUTION:Waste paper is dissociated in water under the simultaneous application of mechanical agitation and ultrasonic vibration of preferably 10-50kHz frequency.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a dissociation process that is necessary when producing recycled paper from waste paper such as old newspapers and old magazines. It is about how to do it.

[Conventional technology]

The general processing steps when using waste paper as recycled paper are: ■ Dissociating the waste paper by stirring it in water ■
A process in which waste paper that has dissociated into fibers is separated from foreign substances by using centrifugal force or passing through a screen.■ A process in which ink is removed by adding chemicals.■ A process in which fibers are loosened using a deflaker.■ Paper is made using a paper machine. Consists of processes etc.

In the first dissociation step, if necessary, the water in which the sodium hydroxide is dissolved and the waste paper are placed in a tank with a rotary blade stirrer and agitation is carried out using a rotary blade, or the water is placed in a horizontally placed rotating drum. Mechanical agitation is performed, such as by placing waste paper in the drum and rotating a drum, and the impact causes the waste paper to dissociate.

[Problem to be solved by the invention]

However, used paper, which is a waste product, usually contains various foreign substances such as plastic film, packing tape, and string in addition to paper. When mechanical agitation is strengthened to increase the efficiency of waste paper dissociation processing, these foreign substances are crushed into small pieces together with the waste paper, making it extremely difficult to separate them from the dissociated waste paper fibers.

In view of the fact that the strength of mechanical agitation in the conventional waste paper disassembly method was limited due to the above-mentioned reasons and required a very long time for dissociation, the present invention was developed to eliminate waste paper even when waste paper containing foreign matter is processed. The purpose of this invention is to provide a dissociation method that enables selective and efficient dissociation.

[Means to solve the problem]

The waste paper disassembly method of the present invention, which has succeeded in achieving the above object, is characterized by simultaneously performing mechanical stirring and ultrasonic treatment when dissociating waste paper in water.

[Effect]

In the dissociation method of the present invention, in which mechanical stirring and ultrasonic treatment are performed simultaneously, the impact caused by mechanical stirring and the fine bubbles generated by cavitation caused by ultrasonic treatment act synergistically on the waste paper, and foreign objects such as plastic films are not crushed. Even mild mechanical agitation causes waste paper to dissociate in a short period of time.

In the dissociation method of the present invention, the ultrasonic treatment is carried out at a frequency of 1
It is preferable to use a power of about 0 to 50 KllZ and an output (normally about several hundred watts) that can sufficiently cause cavitation. As for the mechanical stirring, any stirring method employed in conventional waste paper disassembly methods can be employed, but stirring using a stirring blade is preferable.

As in the case of the conventional dissociation method, the water used to dissociate the waste paper may be made alkaline by adding an alkali such as sodium hydroxide to chemically promote dissociation.

〔Example〕

Hereinafter, the present invention will be explained with reference to Examples.

A 0.5% aqueous sodium hydroxide solution 15a is placed in a treatment tank with a capacity of 201+ equipped with a propeller-shaped three-blade stirring device, and waste paper with a low foreign matter content of 15% is added to the treatment tank to have a solid content of 5%. I put it in so that it would work. Furthermore, frequency 20KH
z, The ultrasonic vibrator part (made of stainless steel, rod-shaped) of an ultrasonic generator (US-600 manufactured by Nippon Seiki Seisakusho Co., Ltd.) with an output of 600 W was fixed in the tank, and stirring was performed while operating this ultrasonic generator. A stirring process was performed using a device.

After starting the process, collect a small amount of the material in the tank every 5 minutes.
The amount that did not pass through the screen with a mesh spacing of 5 mm was quantified.

For comparison, dissociation treatment was performed in the same manner as above except that the ultrasonic treatment was not performed.

The results are shown in Figure 1. In the comparative example without ultrasonic treatment, even after 20 minutes of treatment, nearly 40% of the material did not pass through the screen, of which 70% was paper. , by simultaneously performing ultrasonic treatment, waste paper becomes 1
Almost complete dissociation occurred in 0 minutes.

In addition, it was confirmed that the plastic foreign matter was not crushed very much in the above treatment, and the paper components were selectively dissociated.

〔Effect of the invention〕

According to the dissociation method of the present invention that simultaneously performs mechanical agitation and ultrasonic treatment, it is possible to efficiently dissociate only waste paper under weak mechanical agitation conditions that do not substantially cause fragmentation of plastic foreign matter. Since there is less damage to the fibers and foreign matter can be easily separated after the dissociation process, it is possible to produce high-quality recycled paper in a shorter time than before.

[Brief explanation of drawings]

FIG. 1 is a graph showing the results of Examples and Comparative Examples.

Claims (1)

[Claims] A method for dissociating waste paper, which is characterized by simultaneously performing mechanical stirring and ultrasonic treatment when dissociating waste paper in water.