JPS63171614A - Production of filter cloth for solid-liquid separation - Google Patents

Abstract

PURPOSE:To obtain a filter cloth adequate for a solid-liquid sepn. device of a traveling filter cloth type, by using felt which is subjected o a special treatment to raise extremely fine fibers on the surface. CONSTITUTION:A polymer such as PVA which has the solvent solubility different from the solvent solubility of the sea and island components of fibers having sea and island type structure is impregnated to the felt formed by interlacing said fibers to once fix the interlaced structure; thereafter, the felt is immersed in a solvent such as trichloroethylene to remove the sea component. After polyurethane of impregnated in such felt and is fixed thereto, The felt is immersed in water to solidify the polyurethane and to wash away the solvent in the polyurethane soln. The polymer for fixing the interlaced structure mentioned above is removed from the felt and after the felt is dried, the surface of the felt if raised by buffing.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a filter cloth for solid-liquid separation, and more specifically, to a method for manufacturing a filter cloth for solid-liquid separation, and more specifically, a method for manufacturing a filter cloth for solid-liquid separation. Concerning a method of manufacturing cloth.

[Prior Art] Conventionally, an endless filter cloth carrying a solid liquid is run through a pressing section consisting of a transfer drum and a pressing roll, and the pressing section squeezes out the liquid component in the solid liquid, while the remaining filter cloth is removed from the solid liquid. There are filter cloth traveling type filters (belt press type dehydrators) that transfer the cake to a transfer drum and collect it by scraping it with a scraper. Solid-liquid separators, such as filter cloth traveling type filters, which perform filtration and recover the remaining half-cake-like components from the filter cloth, are used in various fields. The filter cloth according to the present invention is used in such a solid-liquid separator.

As the filter cloth used in the solid-liquid separator as mentioned above,
Conventionally, for example, JP-A-59-115720, JP-A-60-31811, JP-A-60-44013, JP-A-60-44014, and JP-A-61-1
Publication No. 64613, Japanese Patent Application Laid-open No. 171516/1983,
JP-A-61-174912, JP-A-61-174
915, Japanese Patent Laid-Open No. 61-174916, etc. are known. This conventional filter cloth has a napped layer of ultrafine fibers with a thickness of 0.1 to 10 μm formed by raising mainly the wefts of the base material on the surface of a textile base material. This filter cloth has a thickness of 0.1~
Since the linear layer is formed by the naps of 10 μm ultra-fine fibers, the gaps between the naps are very small, and even fine solid components can be blocked.

It is also known to make paper by mixing ultrafine fibers and low-melting point fibers or fine particles, melting them together, and then raising the surface.

[Problems to be Solved by the Invention] However, the following problems remain in the conventional filter cloth as described above.

In other words, in the method of raising the surface of a woven or knitted fabric base material to form a napped layer of ultrafine fibers, the surface of the base material inevitably becomes uneven due to the woven or knitted structure, so this surface is uneven. It has been difficult to raise the nape enough to form a sufficiently thick nape-line layer without any wrinkles. Therefore, there was a limit to the ability to form a denser and thicker line layer.

In addition, in the method of raising the surface after melting and integrating,
Due to the poor flexibility of the base material, good napping cannot be achieved, and stress concentration tends to occur during running of the filter cloth, resulting in poor durability of the filter cloth.

The present invention is capable of forming a sufficiently thick and uniform ultrafine fiber napped layer, resulting in extremely excellent solid-liquid separation performance.Furthermore, the solid-liquid separation method has excellent flexibility, allows easy raising, and has sufficient durability. An object of the present invention is to provide a method for manufacturing a filter cloth for use in filters.

[Means for Solving the Problems] The method for producing the solid-liquid separation performance A of the present invention in accordance with this objective is based on a seabird method in which ultrafine fibers are used as islands and synthetic polymers having different solvent solubility from them are used as seabirds. Fibers having a cross-sectional structure of a type are intertwined and processed into felt, the felt is impregnated with a polymer having different solvent solubility from the ultrafine fibers and the synthetic polymer, and the intertwined loose weave is fixed. The felt is immersed in a solvent to remove the sea component from the fibers having the sea-island structure, and the felt from which the sea component has been removed is immersed in a polyurethane solution, and then dipped in water to remove the solvent from the polyurethane solution impregnated into the felt. This method consists of removing the polymer to coagulate the polyurethane, then removing the polymer and drying the felt in which the polyurethane has coagulated, and then buffing the surface of the felt to raise ultrafine fibers on the surface of the felt.

In the above-mentioned fiber having a seabird-shaped structure, the ultrafine fiber of the island component may be any synthetic polymer such as polyester or polyamide that can be formed into a fiber.

The synthetic polymer constituting the sea component may be any synthetic polymer such as polystyrene, hydrolyzable polyester, or polyamide, as long as it can be formed into fibers. Sea components can be dissolved and removed by selecting the type of solvent and hydrolysis conditions.

The ultrafine 11#1 has a thickness of 0.1 to 10 μm, and if the thickness is larger than that, a rigid and flexible line layer cannot be formed, and the gaps between the raised fluffs are large and the rejection rate of fine solids is poor.

If the diameter is less than 0.1 μm, the naps will be severely worn and stable solid-liquid separation cannot be performed.

First, felt is created by intertwining fibers having such a seabird-shaped structure. This felt is
Since the fibers are intertwined and formed into a sheet, the surface unevenness is extremely small compared to the woven or knitted structures described above, and a uniform intertwined structure can be easily obtained.
A uniform porous structure is obtained.

This felt is impregnated with a polymer having a different solvent solubility from that of the sea and island components, and this impregnation temporarily fixes the intertwined structure for the shun process.

As this polymer, for example, PVA (polyvinyl alcohol) is suitable.

The felt is then immersed in a solvent to remove sea components from the fibers, which have a sea-island structure. In other words, leave the sea. For example, trichlorethylene is used as the solvent, and the felt is immersed in a bath of trichlorethylene at an appropriate temperature range to remove the seawater. Because the polymer for fixing the interlaced tissue is not dissolved by this de-sea removal, the felt after de-sea is composed of intertwined ultrafine fibers with the entangled structure retained by the adhering polymer (for example, PVA). Become.

This felt is impregnated and fixed with polyurethane. By immersing the felt from which the sea component has been removed into a polyurethane solution, such as a DMF solution of polyurethane, the polyurethane is impregnated and the areas where the sea component was present are replaced by polyurethane. For polyurethane, a dimethylformamide solution of highly flexible polyurethane obtained from polyether, polyester, methylene diphenyl diisocyanate, or methylene bisaniline may be applied to the surface of the filter cloth using a gravure coater or as a polyurethane aqueous emulsion. .

The polyurethane is then quenched by dipping the felt in water and the solvent in the polyurethane solution is washed away. Coagulation of the polyurethane re-fixes the intertwined microfibers with the polyurethane.

The entangled tissue fixing polymer is then removed from the felt and the felt is dried. When the polymer is PVA, the PVA is simultaneously immersed in water.
is washed away, so no special solvent is required to remove it.

The dried felt is raised by buffing its surface. Buffing is preferably performed using sandpaper. It is conceivable to perform the raising using a cloth raising machine, for example, but it is not possible to raise the cloth as uniformly as with sandpaper treatment.

In this raising method, the base material is felt made of ultra-fine fibers impregnated and fixed with polyurethane, so the surface irregularities are extremely small and smooth, so even and uniform raising is possible. Compared to cloth, it is possible to form a denser piloerection structure and a thicker piloecline.

In addition, since the base material is internally fixed with polyurethane,
It has sufficient flexibility, making it extremely easy to nap, and the completed filter cloth flexibly follows a predetermined travel trajectory.
Stress concentration is less likely to occur during use, and the durability of the filter cloth is improved.

In addition, if the felt is thick after drying, cut the felt in half in the thickness direction and comb it thinly, buffing the front side and buffing the back side to mainly remove the protruding urethane. You may also do so.

Next, more specific embodiments of the present invention will be described.

(Example 1) An 18-core multicore composite fiber containing polyester as an island component and polystyrene as a sea component was processed into felt, and the shape of the felt was fixed by needle punching to obtain a felt with a thickness of 1.0 m. Next, this felt was immersed in an aqueous solution of PVA, squeezed with a mangle, dried, and then trichlorethylene was used as a solvent to remove the sea component of the polystyrene. Next, the polyurethane was immersed in a dimethylformamide (DMF) solution, squeezed with a mangle, and the polyurethane was coagulated in a water bath, at the same time PVA and DMF were removed. Roughly dried, a felt made of ultrafine fibers was obtained. Slice the felt in half in the thickness direction to form two sheets, and lightly buff one side of each half-thick sheet with sandpaper until you get enough nap for the brown side. Buffing was done.

Through the above steps, a filter cloth according to the present invention having a thickness of 0.5 #l was obtained.

Table 1 shows the range of preferable conditions in each of the above filter cloth manufacturing steps.

Table 1 Next, in order to confirm the performance of the filter cloth of the present invention in use in a solid-liquid valve Wi device, the filter cloth was cut into a width of 30 cm and a length of 2.5 m with the warp direction as the longitudinal direction. Then, the cut ends were sewn together to obtain an endless filter cloth 1 as shown in FIG. Belts 2 with holes 3 are sewn to both ends of the endless filter cloth 1 in the width direction, so that the filter cloth 1 can be driven to run or the left and right phases can be aligned during running.

Next, the endless filter cloth is applied to the belt press type dewatering machine 11 shown in FIG. A dehydration test was conducted with a pressing force of approximately 60 to 9 J. In the device 11 shown in the figure, the 'Ia cloth 1 is
2 and a guide roll 13, 14, 15 in a tensioned state, and moves on a fixed trajectory regulated by these rolls 12, 13, 14, 15, a squeeze roll 16, 17, 18, and a transfer drum 19. Run and circle in the direction of arrow A.

20 is a solid liquid to be treated, and a liquid component is sucked through the running filter cloth 1 by a vacuum suction tank 21, and the solid component is left on the filter cloth 1 and filtered. The solid components are squeezed onto the transfer drum 19 by squeeze rolls 16, 17, 18 and scraped off by the scraper 22.

As a solid liquid, water was used and clay with an average particle size of about 20 μm was used, and the clay was adjusted so that the 11°C of the clay was about 300 my/fl.
01/min. The particle size distribution of the clay in the solid-liquid as measured by a Coulter counter was approximately 1 to 50 μm, which was found to be distributed over a fairly wide range.

As a result of the test, the rejection rate by the filter cloth 1 was 99%, and the components recovered by scraping with the scraper 22 were about 50% solids. Further, the transfer rate to the transfer drum 19 was approximately 90%, which was extremely high. Furthermore, the particle size distribution of the clay in the solid component measured with a Coulter counter was about 1 to 5 μm, and most of the particles larger than 5 μm were removed. Further, even after approximately 500 hours of operation, the above-mentioned performance did not change at all, and no abnormality was observed in the filter cloth, indicating remarkable durability.

The filter cloth obtained by the method according to the present invention has a uniform microfiber nape cline layer with a large amount of naps, so it has high solid-liquid separation efficiency and is flexible due to urethane impregnation and fixation. It has excellent running stability and excellent operability, and the filter cloth has high durability, so the processing capacity is stable.

Therefore, it can be used for various solid-liquid separations. For example, sludge, scum, flocs, wash water, and concentrated sludge generated during wastewater treatment, such as suspended sludge discharged from activated sludge treatment equipment and so-called fixed sludge discharged from biofilm treatment equipment. It can be used for concentration, dehydration, etc. Specifically, sludge generated from water and sewage treatment, excess sludge generated from septic tanks, sludge generated from human waste treatment, scum generated from pressure flotation operations, coagulated flocs and flocculated sediment flocs generated from industrial wastewater treatment, and sand filtration equipment. This includes backwash water from various filtration devices such as @, and sludge condensed in screen devices. Furthermore, it can be used to recover solid components in various manufacturing industries, such as paper pulp manufacturing, food manufacturing, sake brewing, and miso brewing. Furthermore, it can be used to purify ponds and rivers, remove algae at water purification plants, and prevent rivers and lakes from becoming contaminated during dredging.

[Effects of the Invention] In the method according to the present invention, since the piloecline is formed by raising the felt having a smooth surface, the piloecline is easily raised and the piloecline is made of extremely dense and uniform ultra-fine fibers. In addition, it is possible to form a cline with sufficient thickness. Therefore, a filter cloth having extremely high solid-liquid separation performance with a high solid component rejection rate can be obtained.

In addition, polyurethane is impregnated and fixed in the intertwined structure of ultrafine fibers, and the filter cloth has extremely excellent flexibility and can easily follow a desired running path. Therefore, stress concentration on the filter cloth is less likely to occur, the durability of the filter cloth can be improved, stable processing performance can be maintained for a long period of time, and its lifespan can be significantly extended.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing one embodiment of a filter cloth obtained by the method of the present invention, and FIG. 2 is a schematic side view of a belt press type dehydrator using the filter cloth according to the present invention.

Claims (1)

[Claims] Fibers having a sea-island cross-sectional structure in which the microfibers are islands and the synthetic polymers having different solvent solubility are the seas are intertwined and processed into felt. is impregnated with polymers having different solvent solubility to fix the intertwined structure, and then immersing the felt in a solvent to remove the sea component from the fiber having the sea-island structure;
The felt from which the sea component has been removed is immersed in a polyurethane solution, and then immersed in water to remove the solvent from the polyurethane solution impregnated with the felt and coagulate the polyurethane.
Next, the polymer is removed and the felt in which the polyurethane has coagulated is dried, and then the surface of the felt is buffed to raise ultrafine fibers on the felt surface.