JPH0515793A - Method for opening pulp fiber - Google Patents

Abstract

PURPOSE:To easily lower an unopen rate and to rapidly perform opening treatment by arranging a screen having a large number of rectangular transmitting holes obliquely arranged thereto along the revolving zone of a rotary hammer at a specific angle with respect to the an axial line in the peripaheral direction of the hammer and having a specific opening ratio. CONSTITUTION:The opening ratio of a screen 4 is set to 20-30% and the shape of the holes of the screen is made rectangular to obliquely arrange the holes at 15-60 deg. with respect to the axial line in the rotary periapheral direction of a hammer 5 and pulp is transmitted through the screen 4 to select opened pulp. When the opening ratio is 20% or less, the transmissivity of pulp is markedly lowered but opened pulp can be smoothly discharged by the obliquely arranged state of the rectangular holes, the rotation of the hammer 5 and the meeting posture of the holes to the hammer 5. Therefore, the opening ratio of the screen is lowered and the amount of unopen pulp is reduced and, at the same time, the pulp can rapidly be treated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for defibrating pulp fibers.

[0002]

2. Description of the Related Art Asbestos fibers have hitherto been widely used as reinforcing fibers for fiber-reinforced cement products because they have not only a reinforcing effect on the products but also a shape-retaining effect on uncured molded products.
However, since asbestos fibers cause pollution, there is a strong demand for their use to be restricted or totally abolished, and various reinforcing fibers to replace them are being sought. As the asbestos-substituting fiber, pulp fiber is promising as a reinforcing fiber for cement products because it is superior to other fibers such as glass fiber and synthetic resin fiber in terms of heat resistance and alkali resistance. By the way, the pulp fiber needs to be finely defibrated with a hammer mill or the like before being added to the cement mixture, and the pulp fiber crushed with a hammer mill or the like in order to make the defibration state uniform, has a mesh structure. It is carried out through a screen to make the defibrated state uniform.

[0003]

[Problems of conventional technology] However, the amount of undefibrated pulp is 20% of the total amount of defibrated pulp by the conventional defibration means.
It is difficult to make the amount below, and for example, in the case of a screen formed by making circular holes with a hole diameter of 5 mm in a steel plate, the amount of undisentangled pulp is limited to 26%, and there is a drawback that an undisentangled ratio below this cannot be achieved. there were. Of course, the reduction of the undisentangled ratio can be achieved by reducing the pore size, but if it is too small, there is a drawback that the transmittance becomes very poor and the treatment efficiency becomes very poor.

[0004]

In view of the above problems, the present invention is a method for defibrating pulp fibers in which the defibration rate can be easily reduced when defibrating the pulp fibers and the defibration process can be performed quickly. It is made for the purpose of providing.

[0005]

That is, the method for defibrating pulp fibers of the present invention is to arrange a large number of rectangular permeation holes at an angle of 45 degrees with respect to the circumferential axis along the swirl zone of a rotary hammer. And disposing a screen having an opening ratio of 20%, supplying pulp fibers in the form of a sheet into the rotating area of the rotating hammer, and discharging the defibrated pulp from the screen. It is a thing.

[0006]

The function of the defibrated pulp can be lowered by lowering the aperture ratio of the screen as described above. However, when the aperture ratio is lowered, the transmittance of the defibrated pulp is deteriorated, and the treatment efficiency is remarkably lowered. Therefore, in the present invention, the aperture ratio of the screen is set to 20% or less, and at the same time, the holes are rectangular in shape, and the holes are arranged at an angle of 45 degrees with respect to the rotational circumferential axis of the hammer. The defibrated pulp is selected by passing through. When the aperture ratio is 20% or less, the transmittance of the valp is significantly reduced, but due to the inclined arrangement of the rectangular holes, the fibrillated fiber is discharged very smoothly by the rotation of the hammer and the attitude of the holes facing the hammer. Is possible.

[0007]

Embodiments of the present invention will be described below. As shown in FIG. 1, the steel plate 1 has a circumference 45 (arrow X) with respect to the axis 2.
The length d is 10 mm and the width b is 3 so that the posture is inclined.
mm, and rectangular holes 3 ... 3 each having a semi-circle with a radius of curvature of 1.5 mm at both ends are drilled so as to have an aperture ratio of 20%, and a screen 4 is formed. As shown in FIG. The hammer mill 5 was arranged at the discharge portion 5A. The pulp sheet P was supplied to perform defibration, and the undefibrated rate of the pulp fiber obtained through the screen 4 was measured. The rightmost column of Table 1 shows the defibration rate, and the evaluation "appropriate" indicates a speed at which there is no delay when supplied to the other cement raw material mixing process, and "improper" indicates that there is a delay when supplied to the raw material mixing process. It was a slow rate that occurred and affected productivity.

[0008]

[Table 1]

As is clear from Table 1, the defibration means according to the method of the present invention has a very low undefibration rate and can be treated at an appropriate defibration rate.

Next, using the pulp fibers obtained in Table 1, a plate-like body having a thickness of 5 mm and a width of 45 cm and a length of 90 cm was formed by a dry method, cured by an autoclave, and flexural strength and deflection were measured. The result was 2.

[0011]

[Table 2]

As is clear from Table 2, it was found that the fiber-reinforced cement board obtained in the present invention has the highest strength.

[0013]

As described above, according to the method of the present invention, it is possible to reduce the aperture ratio of the screen and reduce the amount of undisentangled pulp, and at the same time, to perform the treatment quickly. The quality can be improved without lowering the production efficiency of the fiber-reinforced cement board.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part of a screen used in the method of the present invention.

FIG. 2 is a sectional view of an essential part of a hammer mill used in the method of the present invention.

[Explanation of symbols]

 1 Steel plate 2 Circumferential axis 3 Rectangular hole 4 Screen 5 Hammer mill

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D21D 5/02 A 7199-3B

Claims (1)

Claims: 1. A large number of rectangular permeation holes are arranged at an angle of 15 to 60 ° with respect to the circumferential axis along the swirl zone of a rotary hammer, and the aperture ratio is 20 to 20. A method for defibrating pulp fibers, comprising disposing a screen of 30%, supplying sheet-shaped pulp fibers into the rotating area of the rotating hammer, and discharging the defibrated pulp from the screen.