JPS609990A - Production of mechanical pulp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing mechanical pulp by converting cellulose-containing materials such as wood chips and ribs into J-pulp using a refiner.

Mechanical pulping methods using glue refiners containing cellulose include RMP method, TMP method, C-RMP method, C-
The TMP method and the like are known. In these pulping methods, cellulose-containing materials are processed as they are, or pretreated with heat, chemicals, or both to form a finer material.
The pulp is then mechanically processed to produce pulp. However, the mechanical pulp produced by this refiner contains bound fibers. In particular, pulp obtained by pre-treating a non-wood fiber raw material such as bagasse in the presence of an alkali and then processing it in a refiner contains a large amount of these bound fibers.

If such bundled fibers are included in the final paper product, they must be removed because they have a significant negative effect on printability.

Conventionally, there has been a method of increasing the number of refining stages as a countermeasure to this problem, but since the fibers separated into single fibers are also refined excessively, problems such as a decrease in pulp strength and a decrease in reactor water resistance occur. As another countermeasure, there is a method in which the pulp is separated into coarse pulp after refining and only this coarse pulp is processed again in the refiner.

This method requires large amounts of water in the separation step (usually
It is necessary to feed the pulp to the 0-Tally screen at a pulp concentration of 1 to 2%), and since the coarse pulp from the separator usually contains a large amount of water with a pulp concentration of 1 to 3%, In order to effectively refine this, it is necessary to dehydrate the pulp until the pulp concentration is at least 20%, which complicates the process and causes large losses in heat and power.

The object of the present invention is to produce a mechanical pulp that can separate pulp containing bound fibers from a refiner into coarse pulp containing bound fibers and fine pulp not containing bound fibers without using water. The point is to provide the following.

In order to achieve the above object, the method for producing mechanical pulp according to the present invention involves dispersing water-containing pulp containing bound fibers from the outlet of a refiner into an air stream, and then classifying the water-containing pulp containing bound fibers from the outlet of a refiner into fine pulp that does not substantially contain bound fibers and producing bound fibers. The coarse pulp is separated into a coarse pulp that contains the raw materials, and the coarse pulp is processed again in a refiner.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The cellulose-containing material (1) consists of wood chips, non-wood fiber materials (banose, straw, kenaf, etc.). This cellulose-containing material (1) is refined by a ramie disk-type glue refiner (2) to form a single fiber or fibrillate into mechanical pulp. Before this refining, the cellulose-containing material (1) is pretreated with chemicals or steam, if necessary. Further, the refining concentration is desirably carried out at a moisture content of 75% or less in order to improve pulp quality and dispersion in the next step. Refining is usually done at a freeness of 15 to avoid excessive refining.
It should be about 0 to 500 TdIC5F. Furthermore, refi: Shiji is usually performed in one stage, but in some cases it may be processed in a two-stage series. As a result, a water-containing pulp (3) containing bound fibers is discharged from the outlet of the refiner (2), and this water-containing pulp "j (3) is passed through the dispersing machine (4).
) and distributed. This disperser c4) has an intake port for the water-containing pulp (3) and an air flow (air) (5) in order to disperse the water-containing pulp (3) from the refiner (2) into the air flow, and furthermore, For example, it has stirring blades (6) so as to be dispersed in the airflow. Dispersion is usually carried out in the air stream (5), but in some cases steam generated in the refiner (2) is also used alone or together with the air stream (5). Water-containing pulp dispersed in airflow (3)
is separated into a fine pulp (3A) substantially free of bound fibers and a coarse pulp (8B) containing bound fibers by air classification in a separator (7). In the example, a pressurized upward flow separator is shown as the separator (7), and according to this, the water-containing pulp (3) uniformly dispersed in the air from the disperser (4) is ), the coarse pulp (3B
) is discharged through the lower rotary pulp (9), and the thin pulp (-8A) discharged from the upper part along with the airflow is sent through the tact to the cyclone αO. The separator (7) is normally operated at a pressure somewhat higher than atmospheric pressure (caoo to 1000 mm water column), and an internal air flow rising speed of 3 to 10 m/It is suitable for classification. As the separator (7), various types of wind separators such as a gravity separation type, an inertial type, and a mechanical type are used. The coarse pulp (3B) from the separator (7) is refined again in the refiner αD. In addition, if necessary,
The coarse pulp (3B) is diluted with water before refining in order to obtain a suitable refining concentration (usually 15-40%). The thin pulp (8A) fed into the cyclone α1 is separated from the airflow (5) and discharged from the bottom.

3 and 4 show another embodiment. That is, the dispersion and separation of the water-containing pulp (3) after passing through the refiner is carried out in one device, the dispersion separator. 3) is dispersed by the stirring blade (6) that rotates at high speed, and the generated airflow causes the inner part of the cylindrical screen α, which has round holes (Fig. 4A) α or slots (Fig. 4B) Qυ, to be dispersed. While rotating and falling, the thin pulp (3A) falls through the round hole 0.
It is discharged from the pulp or slit αQ along with the airflow and separated from the coarse pulp (3B). αη indicates a fan.

According to the method for producing mechanical pulp according to the present invention described above, the following effects can be expected. In other words, the pulp containing bundled fibers from the refiner can be easily separated into fine pulp that does not contain bundled fibers and coarse pulp that contains bundled fibers by air classification, and since only the coarse pulp is refined again, excessive refining is avoided. As a result, the freeness is high and the number of bundled fibers is low.
Mechanical pulp with excellent strength properties can be obtained. Additionally, there is no need to use water to remove the bound fibers from the pulp, simplifying the process. Furthermore, heat loss is small, and refinement and Ig are performed effectively, so the power required for refining can be reduced.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is a process diagram, FIG. 2 is an explanatory diagram of the main part, and FIG. 3 is an explanatory diagram of the main part showing another embodiment, 4(A) and 4(B) are enlarged views of the main parts in FIG. 3, respectively. (1)... Cellulose-containing material, (2)... Refiner, (3)... Water-containing pulp, (3A)... Thin pulp, (3B)... Coarse pulp, (4)... ... Dispersion machine, (7) ... Separator, 00 ... Cyclone, a2
...dispersion separator

Claims (1)

[Claims] 1. Refining cellulose-containing materials using a refiner
In the manufacturing method of the machine J<ru, the water-containing pulp containing bundled fibers from the refiner outlet is dispersed in an air stream, and by air classification, a fine pulp containing substantially no bundled fibers and a coarse pulp containing bundled fibers are separated. A method for producing mechanical pulp, which comprises separating the pulp into pulp and pulp, and processing the coarse pulp again in a refiner.