JP2002143662A - Method and apparatus for storing and/or dispersing slurry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slurry which is uniform in storage and/or dispersion by ameliorating the drawbacks of a method for dispersing the slurry by using microfibril fibers. SOLUTION: In storing and/or stirring the slurry containing the microfibril fibers in a tank 1, the slurry is circulated from the lower part of the tank to the upper part of the tank, by which the slurry is completely mixed, and the occurrence of settlement and density difference is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for uniformly dispersing a slurry containing microfibril fibers and preventing sedimentation of solids during storage of the slurry. More specifically, a mixed medium of water and an organic solvent contains S
The present invention relates to a method and an apparatus for uniformly dispersing a slurry in which an AP and microfibril fibers are dispersed, and for preventing sedimentation of solids during storage of the slurry.

[0002]

2. Description of the Related Art As a method for improving the dispersibility of a slurry, a method using microfibril fibers is disclosed in Japanese Patent No. 29.
67804. Certainly, this method is effective for dispersing hard-to-disperse solids in a medium, but if solids are present, if the specific gravity of the particles is significantly different from the dispersion medium, leave the slurry in the tank for a long time. And particles and powder are separated. If the specific gravity of the particles is relatively close to the medium, separation from the medium can be prevented. However, even in this case, the slurry in the tank has a concentration difference between the upper part and the lower part of the tank. When a concentration difference occurs, stable supply of slurry cannot be performed, and the quality of the product greatly varies. For this reason, the tank for storing and / or dispersing the slurry containing the microfibril fibers must be constantly stirred.

However, since the microfibril fibers are fibrous, the fibers are likely to be arranged in the direction of the vortex generated by the stirring when ordinary stirring is performed. For this reason, even if the vortex is turbulent by a baffle plate or the like, the generation of turbulence is suppressed as compared with ordinary slurry, and the agitation in the height direction becomes insufficient. For this reason, sedimentation of the solid content easily occurs, and the dispersion cannot be uniform. In particular, when microfibril fibers are added, the liquid viscosity increases, so the above situation becomes more remarkable.

[0004] That is, although the dispersion and sedimentation prevention of the slurry using the microfibril fibers are effective to some extent, they are not perfect, but conversely, when trying to completely disperse them, due to the properties of the microfibril fibers, they are more dispersed than ordinary slurries. Becomes difficult. Further, it is difficult to prevent sedimentation of solids during storage. For this reason, it was impossible to completely disperse the slurry containing the microfibril fibers and to prevent the solid content from settling.

Also, Japanese Patent No. 3016367, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 1-106403 proposes a method of dispersing SAP and microfibril fibers in a mixed medium of water and an organic solvent. SAP has a very large specific gravity as compared with water or an organic solvent. Therefore, when dispersed in a solvent, sedimentation is very easy. Although microfibril fibers have the effect of preventing this sedimentation, they do not completely prevent sedimentation as described above. Also,
Even if agitated, turbulence does not occur for the above-mentioned reason, SAP having a large specific gravity is unevenly distributed outside the vortex, and microfibril fibers having a relatively small specific gravity are unevenly distributed at the center of the vortex. And SAP are separated and dispersed, and a sufficient effect on prevention of sedimentation of solids cannot be obtained.

[0006] As described above, the slurry containing microfibril fibers cannot exert the effect of the microfibril fibers sufficiently when the solid content is large, such as SAP, and cannot be completely dispersed. .

[0007]

As described above, the method of dispersing a slurry using microfibril fibers is effective but not perfect. An object of the present invention is to improve the disadvantages of the slurry dispersion method using microfibril fibers and to provide a uniform slurry during storage and / or dispersion.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, when storing and / or stirring a slurry containing microfibril fibers in a tank, the slurry was transferred from the lower part of the tank to the upper part of the tank. By circulating, the slurry was completely mixed, and it was found that sedimentation and occurrence of a concentration difference could be prevented, thereby completing the present invention. In particular, the present inventors have found that a slurry in which SAP and microfibril fibers are dispersed in a mixed medium of water and an organic solvent is effective in dispersing and preventing sedimentation, and completed the present invention.

That is, the present invention relates to a method for storing and / or dispersing a slurry containing microfibril fibers, wherein the slurry containing microfibril fibers is put into a tank and the slurry is circulated from the lower part of the tank to the upper part of the tank. And / or disperse. . Further, the present invention is the above-mentioned method for storing and / or dispersing a slurry, wherein the slurry is obtained by dispersing microfibril fibers and SAP in a mixed medium of water and an organic solvent.

The present invention also relates to a tank for storing and / or dispersing a slurry containing microfibril fibers, a tank, a slurry suction port provided at a lower portion of the tank, and a slurry discharge port provided at an upper portion of the tank. A circulation path connecting the suction port and the discharge port, and a circulation pump provided in the middle of the circulation path so that slurry can flow from the suction port to the discharge port, and the slurry in the tank is sucked by the circulation pump. An apparatus for storing and / or dispersing a slurry, characterized in that the slurry can be circulated from a mouth to a discharge port through a circulation path.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The shape and circulation structure of the tank proposed by the present invention are not particularly limited as long as the structure allows the slurry at the bottom of the tank to circulate to the top. In the present invention, the lower portion of the tank refers to a portion from the bottom of the tank to the height at which the solid content has settled when the slurry was put in the tank and left.
The height at which the solid content sediments greatly depends on the type of slurry, the addition ratio and shape of microfibril fibers (fiber length, fiber diameter), solid content concentration, time, and the like. It is necessary to check the sedimentation degree of the slurry in advance by a jar test or the like.
The slurry at the lower part of the tank circulating to the upper part of the tank is preferably at the bottom of the tank as much as possible from the viewpoint of efficiency.

The upper part of the tank referred to in the present invention refers to a portion where the solid content does not settle even when the slurry is left in the tank from the upper end of the tank. Considering efficiency, it is preferable to circulate the slurry from the lower part of the tank to the upper end part of the tank as much as possible.

As a method of circulating, a method in which a suction port is provided at a lower portion of the tank, the slurry is guided to a circulation path from the suction port, and the slurry is circulated to an upper portion of the tank by using a circulation pump can be used. Also, without providing an inlet, a circulation path is provided in the tank from the tank upper part to the tank lower part,
A method of using a circulation pump to circulate the slurry at the lower part of the tank from the circulation path to the upper part of the tank can also be used. Furthermore,
It is also possible to use a method in which a suction port is provided at the slurry outlet, and a part of the slurry to be fed is circulated to the upper portion of the tank at the same time as the slurry is fed from the tank. This method can be used particularly for tanks in which the slurry is constantly or shortly flowed. The method of circulating by providing a suction port in the flow port,
This method is advantageous in that the flow rate of the slurry flowed from the flow port is less affected by the circulation equipment and the flow rate of the slurry is less likely to fluctuate as compared with other methods.

An in-line mixer for further stirring the circulating slurry may be provided in the middle of the circulation path. The shape of the inline mixer may be a screw rotation type, a baffle plate type, or the like.

Two or more circulation paths may be provided. Also,
When two or more circulation paths are provided, the circulation means (type of pump, position of the suction port, etc.) of the plurality of circulation paths may be the same or may be circulated by different methods.

As the circulating pump, a spiral pump, a diaphragm pump, a Mohno pump, a tube pump or the like can be used. Since fine fibers are used in the present invention, there is no need to worry about flocking or kinking of the fibers, so there is no need to limit the type of pump.

The circulation of the slurry may be performed at all times, or may be performed only when necessary. A device that can measure the viscosity of the paint, the concentration distribution of the solid content, etc. in the tank may be provided, a signal from the device may be used to confirm the situation where stirring is required, and a device that automatically circulates only when necessary may be provided. good.

A filter device for removing foreign matter in the paint may be provided in the circulation path. For these filters, a processed wire mesh, a commercially available strainer, or the like can be used. By using the filter, foreign matter is removed from the slurry in the tank at the time of circulation, and it is possible to provide a slurry with less foreign matter.

The tank used in the present invention can be provided with any stirring equipment as long as circulation is not hindered. For example, a stirring blade type stirring device, a stirring device provided inside the tank, a baffle plate and the like can be used.

The present invention is not particularly limited as long as it is a slurry containing microfibril fibers, and the amount of microfibril fibers added is 0.1% by weight based on the solid content.
It is preferably about 40%. When microfibril fibers are added in an amount of 40% or more based on the solid content, the liquid viscosity becomes too high, and circulation becomes impossible. On the other hand, if the content is 0.1% or less, the effect of improving the dispersibility by the microfibril fibers becomes too small, and the solid content cannot be dispersed only by circulation.

The number average fiber length of the microfibril fibers is preferably 0.05 to 0.1 mm. When the number average fiber length of the microfibril fibers exceeds 0.1 mm, the fibers become too large with respect to the solid content, and particularly when the solid content is SAP.
In the case of, the effect of improving the dispersibility of the solid content by the microfibril fiber is too small, and the solid content is settled. Further, since the fiber length is long, the fibers are entangled with each other to form flocs. When flocs are formed, not only is the ability to disperse solids reduced, but also the solids concentration of the slurry is not uniform. When the number average fiber length of the microfibril fibers is 0.05 mm or less, the performance of dispersing the solid content of each fiber decreases, and as a result, the amount of the microfibril fibers required for dispersing the solid content increases. This is not only economically disadvantageous, but also increases the viscosity of the liquid and makes circulation impossible. In addition, when the slurry is used as a coating liquid, the viscosity is too high, and the productivity becomes very poor.

The microfibril fibers used in the slurry can be obtained by subjecting cellulose or a cellulose derivative to microfibrillation. For example, it is obtained by grinding and highly beating wood pulp. This microfibril is called MFC. Not only wood pulp but also non-wood pulp such as cotton, kenaf and bamboo, recycled pulp such as rayon, and refined pulp such as lyocell can be used.

Alternatively, the microfibril fiber can be obtained by metabolism of a microorganism. Generally Acetob
An acetic acid bacterium such as actor Xylinum or the like is stirred and cultured in a medium containing an appropriate carbon source to produce crude microfibrils, which are then purified.

[0024]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

[Brief description of the drawings]

FIG. 1 shows a suction path 2 provided in a lower part of a tank 1 and a circulation path 3
FIG. 7 is a flowchart showing an example in which is provided outside the tank. The circulation path is connected to a circulation pump P, and the slurry in the tank is sent from the suction port 2 through the circulation path 3 to the discharge port 4 in the upper part of the tank.

FIG. 2 is a flowchart showing an example in which an inline mixer 7 is provided in the middle of a circulation path 3. When the slurry passes through the circulation path 3, the slurry is stirred by the in-line mixer 7 and returned to the upper portion of the tank.

FIG. 3 is a flowchart showing an example in which a filter 5 is provided in the middle of the circulation path 3.

FIG. 4 is a flowchart showing an example in which a circulation path 3 is provided in a tank.

FIG. 5 is a flowchart showing an example in which a suction port 2 is provided in an outflow port 6;

FIG. 6 is a flowchart showing an example in which a suction port 2 is provided on a lower side surface of a tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tank 2 Inlet 3 Circulation path 4 Discharge port 5 Filter 6 Outflow port 7 In-line mixer P Circulation pump

Claims (6)

[Claims] 1. A method for storing and / or dispersing a slurry containing microfibril fibers, wherein the slurry containing microfibril fibers is put into a tank, and the slurry is circulated from the lower part of the tank to the upper part of the tank. Storage and / or dispersion method. 2. The method for storing and / or dispersing a slurry according to claim 1, wherein the slurry is obtained by dispersing microfibril fibers and SAP in a mixed medium of water and an organic solvent. 3. The method for storing and / or dispersing a slurry according to claim 1, wherein the slurry in the tank is agitated. 4. A tank for storing and / or dispersing a slurry containing microfibril fibers, comprising: a tank; a slurry inlet provided at a lower portion of the tank; a slurry outlet provided at an upper portion of the tank; A circulation path connecting the discharge port, and a circulation pump provided in the middle of the circulation path so that the slurry can flow from the suction port to the discharge port, and the slurry in the tank is circulated from the suction port by the circulation pump. An apparatus for storing and / or dispersing a slurry, wherein the apparatus can be circulated to a discharge port through a path. 5. A tank for storing and / or dispersing a slurry containing microfibril fibers, wherein a circulation path is provided in the tank, one of which has a suction port at the bottom of the tank and the other has a discharge port at the top of the tank. An apparatus for storing and / or dispersing a slurry, characterized in that the path can be sent by a circulation pump. 6. The apparatus for storing and / or dispersing a slurry according to claim 3, wherein a stirring device is provided in the tank.