JPS6320958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for dispersing paper stock fibers in the headbox of a paper machine, which can disperse suspended fibers well even at high concentrations.

The headbox of a paper machine distributes the paper stock uniformly in the width direction of the paper machine and in the machine direction, and also disperses suspended fibers in the paper stock uniformly so that it is ejected onto the paper screen as a uniform stock stream. However, it is not easy to fully meet this objective. Especially when the fiber concentration in the paper stock in the head box is high (1% or more), the apparent viscosity of the paper stock increases and the strength of the fiber network structure formed in the paper stock increases significantly. , it becomes increasingly difficult to obtain a uniform stock flow as described above.

Conventionally, many methods and devices have been proposed for uniformly dispersing suspended fibers in highly concentrated paper stocks. 1 and 2 are cross-sectional explanatory views of examples of conventional dispersion devices, respectively. FIGS. 3A, 3B, and 3C are views each showing a modification of a portion of FIG. 2, and FIG. 4 is a cross-sectional explanatory view of another example of a conventional dispersion device. The device shown in FIG. 1 (Japanese Patent Application Laid-Open No. 49-20408) is a headbox equipped with an injection section, a turning section, and a delivery passage, and operates as follows. That is, the stock flowing from the injection port A passes through the injection port A1 and collides with the wall surface B of the turning section, changes its direction at right angles, passes through the narrow section C, accelerates, and then collides with the bottom surface D. By changing the direction by about 90 degrees, the fibers in the paper stock are uniformly dispersed and flowed out from the delivery passage E as a stream having a uniformly dispersed cross section. The device shown in Fig. 2
No. 83508) is an improved version of the apparatus shown in FIG. 1, in which a papermaking passage F is provided in a part of the delivery passage E.
The papermaking passage F in Fig. 2 has a structure in which the cross section of the flow passage alternately expands and contracts multiple times, but in addition to this, there are other flow paths as shown in Fig. 3 A, B, and C. A modification has also been proposed in which the cross section of the passage maintains a constant thickness and is curved or bent to change the flow direction. In the device shown in FIG. 4 (Japanese Patent Application Laid-Open No. 57-35092), a suppressed flow converges toward the slicing opening J in the slicing chamber formed by the top plate G and the bottom plate H, whose flow path cross section is gradually reduced. A flow restriction passage L is provided with a plurality of elements K, and has a smooth surface between the flow restriction elements K, in which the surfaces of adjacent flow restriction elements K approach or separate from each other (that is, the flow path repeats expansion and contraction). is formed. In other words, these conventional dispersion devices for high-concentration paper stock have a narrow section in the flow path, a turning section that changes direction, and an expansion/contraction section that repeatedly expands and contracts the cross section of the flow path, thereby dispersing the parts in the paper stock. The resulting speed difference is used to tear off the network structure of the suspended fibers and disperse them. However, since the strength of the network structure of suspended fibers in paper stocks increases exponentially with the concentration, conventional dispersion devices such as those described above cannot be used for paper stocks with high concentrations of 1% or more, especially around 3%. However, sufficient effect is not obtained.
In order to improve dispersion in a conventional dispersion device, it is difficult to increase the shearing force by reducing the cross section of the flow path as much as possible because the flow path becomes clogged with suspended fibers of the paper stock.

The present inventors conducted research aimed at providing a dispersion method and device that can sufficiently disperse fibers in highly concentrated paper stock without the above-mentioned drawbacks of the conventional methods, and as a result, they divided the flow of paper stock into two. The present invention was accomplished by discovering that the object could be achieved by dividing the flow, performing conventional dispersion in each flow path, and then colliding the two divided flows at large opposing angles.

That is, one aspect of the present invention is to divide the stock flow into two in the flow path upstream of the slice outlet in the head box to form branched flows, and to expand and contract the cross section of the branched flow in each branched flow. After repeating this several times to uniformly disperse the suspended fibers in the paper stock using shear force and micro-eddy currents, the branched flows are made to collide with each other at opposing angles of 90° to 180°. The present invention relates to a method for dispersing paper stock fibers in a paper machine headbox, which is characterized by performing secondary dispersion, and then rectifying the combined stock to flow out from a slice outlet.

Another aspect of the present invention is that a flow path dividing body is installed in a cavity in which a paper stock inlet and a secondary dispersion chamber are open to each other on both sides, and the passage divider is installed in a cavity that is connected to the inner wall of the cavity. The two branched channels from the inlet formed by the outer wall of the channel dividing body to the secondary dispersion chamber repeatedly expand and contract, and the angle at the entrance of the secondary dispersion chamber is 90°~
This invention relates to an apparatus for dispersing paper stock fibers in a paper machine headbox, characterized in that they form an opposing angle of 180°, and that a rectifying section and a slicing outlet are successively connected to the secondary dispersion chamber.

Hereinafter, the present invention will be explained in detail with reference to the drawings.
Figures 5 to 8 are longitudinal sectional views showing embodiments of the device of the present invention, Figure 9 is an explanatory diagram showing the flow state in the branched flow path, and Figure 10 is where two branched flows collide and merge. FIG. 11 is an explanatory view showing the state, and is an enlarged explanatory view of the shape of the main part of the device of the present invention.

In the method of the present invention, the stock flow is first divided into two to form two branched flows in the flow path upstream of the slice outlet in the headbox. It is preferable that the opening state of this branch is as gradual as possible and not abrupt so as not to reduce the flow velocity. Next, in each branch flow, the cross section of the branch flow path is expanded and contracted multiple times, and the suspended fibers in the paper stock are dispersed by the micro vortices generated when expanding and the shearing force when contracting. (In the present invention, the dispersion at this stage is referred to as primary dispersion). By colliding the branched flows thus primarily dispersed with opposing angles (corresponding to the angle θ in Fig. 11, which will be explained later) of 90° to 180°, shearing action is applied to the entire paper stock. This strongly promotes the subdivision and diffusion of the fiber network structure (dispersion at this stage is referred to as secondary dispersion in the present invention). The paper stocks which are thus secondary dispersed and merged at the same time are then rectified to stabilize the dispersion state of the fibers, and then flowed out from the slicing outlet and transferred to the paper making process.

An apparatus of the present invention suitable for carrying out the method of the present invention as described above will be explained.

As shown in FIGS. 5 to 8, the device of the present invention includes:
Its basic constituent members are a hollow chamber 3 in which a stock inlet 1 and a secondary dispersion chamber 2 are open on opposite sides, respectively, and a channel dividing body 4 installed in this hollow chamber 3.
and a rectifying section 5 continuous to the secondary dispersion chamber 2, and two branched channels 6 from the inlet 1 to the secondary dispersion chamber 2 are formed by the inner wall of the cavity chamber 3 and the outer wall of the channel dividing body 4. 6 is formed, and in each of the branch channels 6, 6, an enlarged section 6a in which the channel cross section gradually expands and a reduced section 6b in which the channel cross section gradually contracts are repeated multiple times, and the two branch channels 6, 6 is secondary dispersion chamber 2
Opposing angle between 90° and 180° at the entrance (angle θ shown in Figure 11)
are merging at A slicing lip 7 that forms a slicing outlet is continuous to the rectifying section 5.

If the apparatus of the present invention is positioned in the general structure of a paper machine head box, which is composed of a header section, a distribution section, a dispersion section, and a rectification section, it will be shown as shown in FIG.

Hereinafter, aspects of the device of the present invention will be explained.

In the embodiment of the device of the present invention shown in FIG. 5, both the cavity chamber 3 and the channel dividing body 4 have a substantially regular hexagonal cross section, and each vertex of one hexagon corresponds to each side of the other hexagon. Therefore, the apex of the channel dividing body 4 forms a reduced portion 6b of the branched channel 6, and the apex of the cavity 3 forms an enlarged portion 6a of the branched channel 6. .

The embodiment shown in FIG. 6 is the same as that in FIG. 5 except that both the cavity chamber 3 and the channel dividing body 4 have substantially regular octagonal cross sections. In the embodiment shown in FIG.
Each has a rectangular cross section, each vertex of the latter is opposite to every other vertex of the former, and the reduced portion 6
b, and the enlarged part 6a is formed at the other vertex of the former.
Further, as it progresses from the inlet 1 to the secondary dispersion chamber 2 in the branch channel 6, an enlarged section 6a is formed.
The distance between the reduced portion 6b and the reduced portion 6b is shortened. In the embodiment shown in FIG. 8, the cross section of the cavity 3 is hexagonal, and the cross section of the channel dividing body 4 is a star-shaped 16 sides, and the apex angle thereof is opposite to the apex angle of the cavity 3. Branch flow path 6
Therefore, the enlarged part 6a formed by the concave angle of the channel dividing body 4 with a smooth surface and the apex angle of the cavity chamber 3 is smaller than that in the case of FIG. It facilitates the generation of a wide range of micro-eddy currents. However, it is desirable to avoid a sudden enlargement of the cross section of the flow path that would cause a large vortex to be generated by making the concave portion of the flow path dividing body 4 too deep.

In the embodiment of FIG. 8, as in FIG. 7, the distance between the enlarged part 6a and the reduced part 6b becomes shorter as the flow progresses from the inlet 1 to the secondary dispersion chamber 2, and both the reduced part 6b
The micro-eddy currents that occur after passing through are subdivided. In the embodiments shown in the above figures, the cross sections of the cavity chamber 3 and the flow path dividing body 4 are both polygonal (including polygonal).
However, one of them may be a polygon and the other may be a circle or an ellipse, or a smoothly curved waveform may be used instead of a polygon. Furthermore, the channel divider 4 may be installed movably between the inlet 1 and the secondary dispersion chamber 2, and in this case, the cross section of the branch channel 6 can be adjusted depending on the type of fiber in the paper stock. to obtain an appropriate dispersed state. For example, if there are many long fibers (coniferous pulp stock fibers) among the suspended fibers in the paper stock, the fibers become entangled and become difficult to disperse. For this reason, it is possible to obtain a good and uniform dispersion state by moving the channel dividing body 4 in the direction of the secondary dispersion chamber 2 and narrowing the gaps in some of the reduced portions 6b near the outlet of the branch channel 6. can.

The two branch channels 6, 6 for causing the two branch flows to collide merge at the entrance of the secondary dispersion chamber 2, as shown in FIG. 11, and their opposing angle θ is 90° to 180°.
The secondary dispersion chamber 2 has a space large enough to prevent generation of large vortices. The rectifying section 5 needs to be long enough to eliminate the vortex state between them and stabilize the dispersion state. Gap size Te and length Le of secondary dispersion chamber 2
and the size of the flow path gap To of the rectifier 5 are To<Te
Preferably, the relationships are ≦2To and To≦Le≦5≦To. For example, paper stock concentration 1-3%, basis weight 60-
120g/m ² , slice jet speed 200-600
The apparatus of the present invention, which is suitable for paper making with a speed of 3,800 mm and a paper width of 3,800 mm, has a gap of 10 to 40 mm at the inlet 1, a channel gap To of the straightening section of 5 to 20 mm, and a reduced section 6b of the branch channel 6. Preferably, the gap is 5 to 10 mm. Note that the material of the channel dividing body 4 is preferably an Al-Mg-Si alloy.

The device of the present invention has the above configuration and operates as follows. High-density paper stocks have a stronger network structure of suspended fibers than low-density paper stocks, and are extremely difficult to disperse. Such high-concentration paper stock flows from the inlet 1 and first enters the two branch channels 6, 6. As shown in FIG. 9, while the paper stock advances in the direction of the arrow X in each branch channel 6, it is affected by the action of shearing force from the side wall when passing through the contracted section 6b, and the enlarged section of the channel after passing through. Primary dispersion is performed through repeated synergistic effects with the micro eddies generated at 6a. This primary dispersion is a dispersion performed as a preliminary step to enhance the dispersion effect due to the subsequent collision of each branch flow. The paper stocks thus primarily dispersed collide with each other at the confluence of the two branch channels 6, 6, as shown in FIG. At this time, the two branched flows just before the collision are flowing at a flow velocity V, but the opposing angle θ of the collision is
Since the angle is between 90° and 180°, the velocity V at the collision part is very large compared to the velocity component _VX in the outflow direction.
Therefore, the two branched flows collide with each other with a strong force, and unlike the case where the branched flow paths 6 are dispersed due to the shearing force which is strongly applied only near the side wall, the entire stock is uniformly subjected to the strong shearing force. At the same time, the fibers flow into the secondary dispersion chamber 2 to maintain the fine division and dispersion of the fiber network structure, thereby performing secondary dispersion. The paper stock thus secondarily dispersed then flows into the rectifying section 5 of the narrow passage, where the swirling state is eliminated and the fibers are in a stable fiber dispersion state, which is ejected from the slicing slip 7 onto the paper screen.

Examples of the method of the present invention are shown below.

Example 1 A filler-free paper stock with a concentration of 3% and a water content of csf 450 c.c. was prepared by suspending fibers consisting of 80% bleached hardwood kraft pulp and 20% bleached softwood kraft pulp. The liquid was ejected from each head box equipped with a dispersion device (with a movable channel dividing body 4) shown in FIGS. 6, 7, and 8. The dimensions of each part of each dispersion device were as follows.
Gap of inflow part 1 20mm, gap of rectification part 5 To10mm,
Reduced portion 6b near the confluence of the two branch channels 6, 6
Gap 5mm, opening angle θ120°, gap between secondary dispersion chambers
Te14mm, same length Le30mm, slice lip 7
opening 3.5mm, head box flow path width 1000mm. Note that the slice jet speed was 300 m/min. In each of the above cases, the paper material ejected from the slice lip 7 had a smooth surface. Also,
A light source was placed below the jet at a point 50 mm after exiting the slice lip 7, and the transmitted light of the jet was received by a phototube placed 100 mm above the jet, and the dispersion state of the fibers in the jet was determined from the amount of variation. Dispersion was extremely good in all of the above cases. It was also confirmed by high-speed photography that the dispersion state was good.

Example 2 A filler-free paper stock with a concentration of 3% and a water content of c, s, f, and 400 c.c. was prepared by suspending long fibers of 100% bleached softwood kraft pulp. The liquid was ejected from each headbox equipped with a dispersion device shown in FIGS. 7 and 8, respectively. The same dispersing devices and headboxes as in Example 1 were used, and the stock jetting conditions (slicing jet speed) and dispersion state determination method were also conducted in the same manner as in Example 1. In each of the above cases, when the dispersion state of the stock was examined by moving the channel dividing body 4 of the dispersion device, it was found that when the gap of the reduced part 6a near the confluence of the two branch channels 6, 6 was set to 4 mm. Example 1
A good dispersion state similar to that obtained was obtained.

As described above, the method and apparatus of the present invention can achieve extremely good dispersion even when the fiber concentration of paper stock is as high as 1% or more, and even 3% or more. By making the fibers movable, the channel state can be freely changed depending on the type of fiber to achieve dispersion conditions suitable for that type.

[Brief explanation of the drawing]

1 and 2 are cross-sectional explanatory diagrams of examples of conventional dispersing devices, FIG. 3 A, B, and C are views showing modified examples of a portion of FIG. FIGS. 5 to 8 are longitudinal sectional views showing embodiments of the device of the present invention, FIG. 9 is an explanatory view showing the flow state in a branch channel, and FIG. 11 is an explanatory view showing a state in which two branched flows collide and merge, and FIG. 11 is an enlarged explanatory view of the shape of the main part of the device of the present invention. DESCRIPTION OF SYMBOLS 1... Inflow port, 2... Secondary dispersion chamber, 3... Cavity chamber, 4... Channel dividing body, 5... Rectifying section, 6... Branching channel, 6a... Enlarged section, 6b... Reduction section, 7...
...slice lip, X...arrow, A...injection part,
A1...Injection port, B...Wall surface of turning section, C...Narrow part, D...Bottom surface, E...Delivery passage, F...Paper making passage, G...Top plate, H...Bottom plate, I... Slice chamber, J...slice opening, K...suppression element, L
... Suppression passage.

Claims (1)

[Claims] 1. In the flow path upstream of the slice outlet in the head box, the flow of stock is divided into two to form branched flows, and each branched flow has a plurality of expansions and contractions in the cross section of the branched flow. The suspended fibers in the stock are firstly dispersed by shearing force and micro-eddy currents by repeating the process several times, and then the branched flows are made to collide with each other at opposing angles of 90° to 180°. A method for dispersing paper stock fibers in a paper machine headbox, which comprises performing subsequent dispersion, and then rectifying the combined paper stock to flow out from a slice outlet. 2. A channel dividing body is installed in a cavity chamber in which a paper stock inlet and a secondary dispersion chamber are open to each other on both sides, and the channel dividing body is formed by the inner wall of the cavity chamber and the outer wall of the channel dividing body. The two branched channels from the inlet to the secondary dispersion chamber repeatedly expand and contract, and form opposing angles of 90° to 180° at the entrance of the secondary dispersion chamber,
A dispersion device for paper fibers in a paper machine headbox, characterized in that a rectifying section and a slicing outlet are successively connected to the secondary dispersion chamber. 3. The paper fiber dispersion device in a paper machine headbox according to claim 2, wherein the flow path dividing body is movably installed between the inlet and the secondary dispersion chamber.