JPS61174914A - Filter cloth for solid/liquid separation - Google Patents

Abstract

PURPOSE:To obtain filter cloth realizing high percentage of transfer and having high solid/liquid separation performance by coating a water-repelling material to a pile comprising synthetic fiber and having a fixed directional property. CONSTITUTION:Piles of synthetic fibers obtd., by nap raising a basic material are laid on the surface of the basic material fabric, knitted goods, nonwoven fabric, etc., of synthetic fiber aligning the direction approximately in one direction and a filtration layer of filter cloth is formed of the piles. The pile part of the filter cloth is coated with a water repelling material. A water repelling material of silicone compd., polyethylene wax, or fluorine-contg. resin is used and the amt. of the water repelling material to be applied is 0.5-2wt% basing on the whole weight of the filter cloth. The material is applied by the foam treating method or roll treating method. In this stage, it is preferred that the pile part along is subjected to water repelling treatment.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a filter cloth for solid-liquid separation, and more particularly to a filter used when dewatering or filtration is performed while rotating an endless filter cloth carrying a solid-liquid. Regarding cloth.

[Prior art]

Conventionally, an endless filter cloth loaded with solid liquid is run through a pressing section consisting of a transfer drum and a press roll, and the pressing section squeezes out the liquid component and transfers the so-called solid components remaining on the filter cloth. A belt press type dehydrator transfers the liquid onto a drum and collects it by scraping it with a scraper, and a belt press type dehydrator uses gravity to filter the liquid component without squeezing the solid liquid on the filter cloth, and removes the remaining solid component. So-called solid-liquid separators, such as filters that collect water using water nozzles and scrapers, are used in various fields.

These solid-liquid separation devices, especially filters, are equipped with a pressure reducing section near the solid-liquid supply section and facing the back side of the filter cloth to suck out liquid components and improve separation efficiency. There is also. The filter cloth of this invention is used in such a solid-liquid bone m device.

As the filter cloth used in the solid-liquid separator as mentioned above,
Conventionally, (1) Thick short fibers with a thickness of 30 to 100 μm were flocked on the surface of a textile base material using an adhesive to form raised naps that were tilted in one direction, and (2) The base material was raised on the surface of a textile base material. It is known that there are thick piloere formations with a thickness of several tens of microns. These conventional filter cloths obtain the necessary strength as a filter cloth through the use of a textile base material, and at the same time, the naps on the surface prevent solid components from entering the cloth. In other words, the piloerection forms the seed layer. However, all such conventional filter cloths have the drawbacks of low solid-liquid separation performance and poor transferability.

In other words, in the conventional filter cloth (2) mentioned above, the naps are formed by flocking with an adhesive, and in order to prevent the holes in the base material from being buried by the adhesive, the density of the naps cannot be made very high, and the thickness of the naps cannot be made very high. Since it is very thick with a diameter of 30 to 100 μm, the gaps formed between the nape, that is, the eyes, are quite large, and fine solid components can easily pass through the gaps. Therefore, when using this conventional filter cloth ■,
It is essential to coarsen the solid component by using a flocculant,
Not only does the running cost become very high, but depending on the type of flocculant, its toxicity becomes a problem. The use of flocculants also increases the amount of solid components.

Furthermore, the conventional filter cloth (2) has very thick naps of 30 to 100 μm in thickness, so it is rigid and difficult to lie on the surface of the substrate. Therefore, the gaps formed between the raised fluffs are very deep, and if solid components get into the gaps, they will be difficult to remove and the filter cloth will become clogged. This tendency is very noticeable, partly because the piloere is rigid and easily pierced by solid components. Furthermore, the fact that the erect hairs are difficult to lie down also means that the seed layer formed by the erect hairs is bulky. Therefore, airtightness is poor when vacuum suction is performed. Further, since the gaps between the naps are deep, the surface has large irregularities, and the thickness of the solid component on the filter cloth becomes uneven, so that pressure at the pressing part is not uniformly applied.

For the reasons mentioned above, conventional filter cloth (3) has very low solid-liquid separation performance. If the solid-liquid separation performance is low, not only will the liquid component contain a large amount of solid components, but the recovered solid components will contain a large amount of water, requiring a large amount of energy for post-processing such as incineration. Become.

In addition, with the conventional filter cloth (2), as mentioned above, the solid components trapped between the naps are difficult to remove. Therefore, when the filter cloth is separated from the transfer drum, the solid components are drawn back to the filter cloth by the raised fluff, resulting in poor transferability.

On the other hand, although the conventional filter cloth (2) is not the same as the conventional filter cloth (2), the gaps between the naps are large and deep. Therefore, this conventional filter cloth (2) also has low solid-liquid separation performance and poor transferability.

On the other hand, the inventors of this invention previously filed a patent application filed in 1983-22.
In the No. 6384 application, a new type of filter cloth was proposed. This filter cloth has a seed layer on the surface of the base material with a thickness of 0.1-10
It is made up of microscopic raised fibers called μ.

Since the above-mentioned filter cloth has a seed layer formed of naps of ultrafine fibers having a thickness of 0.1 to 10 μm, the gaps formed between the naps are very small, and even fine solid components can be blocked.

In addition, because the raised fibers of the ultra-fine fibers are very flexible and lie easily, the gaps between the raised fibers are shallow, and solid components do not get deformed into the gaps between the fibers and become difficult to remove, making them less likely to become clogged. The fact that the raised piloes are easy to lie down also means that the seed layer formed thereby does not become bulky and the chamber filled with the piloes becomes high, so that airtightness can be maintained highly when vacuum suction is performed.

For these reasons, the filter cloth has very high solid-liquid separation efficiency.

In addition, the transferability is also high because the gaps between the raised fluffs are small, making it difficult for solid components to fit into the gaps, and because the raised fluffs are flexible and are prevented from digging into the solid components.

As described above, the filter cloth proposed in the above-mentioned application is excellent without the above-mentioned drawback of the conventional filter cloth. It may be pushed into the holes of the base material, making it difficult to stand up again.
Another problem is that the solid-liquid separation performance is unstable due to tangled naps.

Therefore, in order to improve this problem, the inventors of the present invention further proposed in Japanese Patent Application No. 58-137639 that the naps forming the wave layer of the filter cloth have directionality.
In addition, we proposed a filter cloth whose directional index is 1.2 to 10.

In the filter cloth proposed in this application, the naps forming the wave layer have directionality, and the directional index is 1.2 to 10, so the naps are pushed into the eyes of the base material during use. It is possible to prevent the raised floes from becoming difficult to stand up again or from getting entangled, and stable solid-liquid separation efficiency can be obtained.
In the case of separating solid components with small particle sizes, there is a problem that transferability is insufficient.

[Purpose of the invention]

The present invention was made in view of the above problems, and its purpose is to provide a filter cloth for solid-liquid separation that has a high transfer rate and solid-liquid separation performance, and in which the deterioration thereof is extremely small. The purpose is to improve rejection rate, water permeability, and transfer rate.

[Structure of the invention]

A filter cloth for solid-liquid separation according to the present invention that achieves the above object has naps made of synthetic fibers on at least one side, and the naps have a directionality with a directionality index of 1.2 to 10 in the length direction of the filter cloth. and the specific surface area of the erect hair is 3 x 10'cd/g or more,
Furthermore, a water-repellent substance is applied to the raised portion.

[Embodiments of the invention]

To explain one embodiment of the filter cloth of the present invention, in FIG. 1, a filter cloth 1 is sewn together along the dotted lines and processed into an endless shape. At both ends of the filter cloth 1, there are belts 2 with holes for stretching the filter cloth 1 and running it without meandering.
．． 3 are sutured. The belt 2.3 preferably has some elasticity so that it can be stretched without causing wrinkles in the filter cloth 1. Therefore, it is preferable that the belt 2.3 has a synthetic fiber fabric as a core material, and is made of a composite of the core material and rubber.

The above-mentioned filter cloth is made by laying the raised synthetic fibers obtained by raising the base material on the surface of a base material made of synthetic fiber woven fabric, knitted fabric, non-woven fabric, etc., aligned roughly in one direction, and creating waves due to the raised raised fibers. It forms a layer with a directional index of 1.2 to 10 and a specific surface area of piloerection of 3xlO'cn! /g or more, and a water-repellent substance is further applied to the raised part.

The synthetic fibers constituting the base material are preferably those with wear resistance and chemical resistance, and polyamide fibers, polyester fibers, polyvinyl alcohol fibers, polyfluoroethylene fibers, polypropylene fibers, polyacrylonitrile fibers, etc. can be used. can. The fibers are preferably non-crimped, and those with circular or deformed cross sections can be used as staples or filaments. In addition, as the fiber, a so-called multifilamentary composite fiber having different polymeric substances as sea-island components, or a splittable composite fiber obtained by laminating and spinning different polymeric substances and being splittable at the laminated part are used. It is also possible. Also, depending on the type of solid-liquid,
It is also possible to use these fibers subjected to parent wood processing or hydrophobic processing.

As the base material, woven fabrics, knitted fabrics, nonwoven fabrics, etc. can be used. As a textile base material, the warp is a processed synthetic fiber filament yarn, and the weft is a yarn made of non-crimped fiber.
It is preferable to raise the weft yarns. Moreover, it is also possible to use a spun yarn or a bulky textured yarn having loops or protrusions as the weft. The woven structure is preferably a satin weave so that the warp and weft have a desired density and a desired floating structure.

Further, as the textile base material, circular knitting such as rib knitting, double-sided knitting, etc., warp knitting, such as half knitting, Queen's cord knitting, etc., can be used. Among these, half-knit tricot fabrics are preferred because they are relatively easy to form naps.

Furthermore, in the case of using a non-woven fabric base material, the staples or filaments of the synthetic fibers are mixed with fibers or fine particles having a lower melting point than that, and the paper is made into paper, and the low melting point fibers or fine particles are partially melted. After integrating the synthetic fibers, the surface is puffed to raise the synthetic fibers,
Alternatively, the stable or filament may be accumulated using an air stream or a water stream, bunched to form a felt, and the surface of the felt may be raised to form a wave layer. It may be something that has been done.

Methods for forming naps on the substrate include clothing, sand paper, sand cloth, sand net, grindstone, steel brush, polishing brush, sand roll, garnet, sand honing, and the like. Among these, it is most preferable to use clothing.

Now, in this invention, it is necessary that the above-mentioned nap has directionality and the directionality index is 1.2 to 10. A preferred directionality index is 1.3-5. Here, the directional index is measured as follows.

■ Four pieces of cut pieces 25 cm long and 3 cm wide are taken in the longitudinal direction of the filter cloth to be measured, that is, in the case of a woven fabric, the warp direction, and in the case of a knitted fabric, the longitudinal direction is the wale direction. Make one. At the end of each shredded piece, mark the end that will become the leading edge when running as a filter cloth.

■Next, in order to remove the distortion of the wave layer, each of the above shredded pieces was placed on a 50 mesh wire mesh with the wave layer facing up, and submerged in water. After 24 hours, the filter cloth was pulled up along with the wire gauze, air-dried, and then left in an atmosphere at a temperature of 25±2° C. and a relative humidity of 65±5% for 24 hours to maintain constant moisture absorption.

(2) Next, a glass plate with a length of 65 cm and a width of 39 cm is prepared, and one longitudinal end of the glass plate is raised and tilted by 2.5Ω. Furthermore, place one of the shredded pieces prepared in step ① above on top of the glass plate so that its longitudinal direction is in the longitudinal direction of the glass plate, and the mark end is positioned above the slope of the glass plate. , and cover the area up to 7 cm from the top with a polyester film 7 cm long, 3 cm wide, and 75 μm thick, and then add a 35 μm long polyester film on top of that.
, place cellophane tape with a width of 2.4 cm so that both ends protrude 5 cm from the top and bottom ends of the filter cloth and touch the surface of the glass plate, and the adhesive side is on the filter cloth side. .

■ Next, outer diameter 5cfll, length 15cm, weight 2.3
A SUS steel neck with a smooth surface weighing 1.7 kg is rolled by gravity from the upper end of the cellophane tape to adhere the filter cloth and the cellophane tape. To reduce measurement errors, this rolling operation is performed twice. After adhesion, 5 cm of both ends of the cellophane tape are cut off to obtain a bonded product of the filter cloth and the cellophane tape.

(2) Next, the adhesive obtained in (1) above is subjected to a peel test between a filter cloth and cellophane tape. This test was carried out using a tensile testing machine, with the upper chuck holding the polyester film and the lower chuck holding the filter cloth, at a tensile speed of 30.
It is carried out continuously at cm/min. Then, a portion 3 am from the peeling start end is set as the starting end, and j/, +1 gravity is measured as an average value from the starting end to 9 cm. Hereinafter, the peeling force determined by this measurement will be referred to as A.

■ Next, another cut piece is subjected to exactly the same test, but this time with the other end corresponding to the above mark end being on the upper side of the slope of the glass plate. This measurement yields the peel force.

(2) Next, the third cut piece is subjected to the same tests as (1) to (3) above, but this time, a polyester film is placed on the lower end of the filter cloth.

By this measurement, the peeling force B is obtained.

(2) Next, perform the same test as (2) above on the last test piece. However, in this case as well, place the polyester film on the lower end of the filter cloth, as in the above case. By this measurement, the peeling force C is obtained.

■ Next, from the above peeling forces A, B, C, and D, (B+D)
/ (A+C) is performed. The result of this calculation is the directional index referred to in the present invention.

As is clear from the above definition, the directional index is the ratio of the peeling force in the direction in which the cellophane tape is easy to peel and in the direction in which it is difficult to peel, and this indicates the stability of the direction of napping. A directional index of 1.2 to 10 can be obtained by appropriately selecting the number of times and direction of napping, the type of napping machine, and the like. In the above test, the cellophane tape used has an adhesive strength specified in JIS Z1522-1982 and has a width of 24 mm.

In addition, in this invention, the specific surface area of the piloerection is 3
It is necessary that the IQ is 3cA/g or more. Here, the specific surface area is the product of the average circumference of the fiber cross section and the total fiber length per Ig, and the average circumference is the average value of several samples.

Furthermore, in this invention, it is necessary that a water-repellent substance be applied to the raised portion. In other words, it is preferable to water-repellent only the raised portion. This is because when both sides of the base material are treated to be water repellent, the amount of water permeation is extremely reduced.

Water repellents include silicone, polyethylene wax,
A commonly used water repellent such as fluororesin can be used. Methods for applying a water repellent to the raised area include the foam treatment method (adding a raising agent and running the raised area over the foam to apply the water repellent), the roller treatment method (applying the water repellent to a roller,
It is preferable to apply a water repellent agent by contacting the raised portion of the cloth with the water repellent agent, and the amount of the applied water repellent agent to the entire filter cloth is 0.
5 to 2.0% is preferred.

Figure 2 shows that the naps of synthetic fibers obtained by raising the base material are laid on the surface of a textile base material, aligned in almost one direction, the naps form a wave layer, and only the naps are repelled. This is a side view of the warp-disintegrated yarns of a water-treated filter cloth, where A is the ground texture part and B is the raised part to which the water repellent agent is attached.

When the filter cloth of the present invention is used in a belt press type dehydrator, as shown in FIG. The loaded endless filter cloth 1 is run, and the liquid components in the solid liquid 6 are squeezed out by the above-mentioned squeezing section, and the solid components remaining on the filter cloth 1 are transferred to the transfer drum 4 and scraped off with the scraper 7 to be recovered. do. In this case, the filter cloth 1 is mounted so that the surface with the nap, that is, the front surface, faces the surface of the transfer drum, and the direction of the inclination of the nap faces in the opposite direction to the running direction of the filter cloth 1. . In addition, in Figure 3,
Reference numeral 8 is a water spray nozzle for washing the filter cloth from the front and back surfaces after transfer, and 9 is a vacuum suction tank for liquid components.

The filter does not have a transfer drum as described above, and the solid components remaining on the filter cloth are collected with a scraper or a water spray nozzle.

The filter fabric of this invention can be manufactured by various methods. Next, a preferable example will be shown.

That is, the weft consists of an island component made of a polymeric material, preferably polyester, and a sea component made of a polymeric material, preferably polystyrene, and the island component is made of a polymer material, preferably polystyrene.
Multifilament yarns are also used for so-called multifilament composite fibers containing 5% or more of fibers that generate ultrafine fibers, and double or triple spun yarns of mixed spun fibers that contain 80% or more of fibers that generate ultrafine fibers, and false twisted yarns or composite yarns are used as warp yarns. Using latent crimped yarns, satin weave is carried out so that the weft and warp yarns have a desired density and a desired floating structure.

Next, the sea component of the weft yarn is removed with a suitable solvent, such as trichlorethylene, and after drying, the weft yarn is raised to form a nap, and only the raised part is treated to be water repellent.

Another method is to make a woven fabric using composite fibers obtained by pasting and spinning different polymeric substances, peeling off the pasting, and raising the nap to form a nap, and treating only the nap part to make it water repellent. . The polymer material to be bonded together is preferably polyamide and polyester copolymer. As for the peeling method, it is preferable to rub vigorously in hot water and then air dry.

The filter cloth of the present invention can stably separate extremely fine solid components, and therefore can be used for various purposes. For example, sludge, scum, etc. generated during wastewater treatment, such as so-called suspended sludge and so-called fixed sludge discharged from biofilm treatment equipment,
It can be used to concentrate and dehydrate flocs, wash water, concentrated sludge, etc. Specifically, for example, sludge generated from water and sewage treatment, excess sludge generated from septic tanks, sludge generated from human waste treatment, scum generated from pressurized flotation operations, coagulated flocs and coagulated sediment flocs generated from industrial wastewater treatment, and sand. These include backwash water from various filtration devices, sludge concentrated in screen devices, etc. Furthermore, it can be used to recover solid components in various manufacturing industries, such as the pulp manufacturing industry, the food manufacturing industry, the sake brewing industry, and the brewing industry such as miso.

Furthermore, it can also be used to purify water in ponds and rivers.

Example The weft is a 20/2 S spun yarn made by spinning 223-core multicore composite fiber (fineness 2.5 D') with polyester as the island component and polystyrene as the sea component.
A bundle of 48 0μ polyester fibers was warped and unwound to obtain a 5-ply satin fabric having a weft of 30/e1 and a warp of 40/e1m.

Next, the sea component of the weft was removed using trichlorethylene as a solvent to obtain a woven fabric consisting of a bundle of about 3,570 ultrafine fibers with a weft of about 0.02D in fineness.

Next, the above-mentioned fabric is put through a napping machine, and the napping operation is carried out 20 times in the warp direction, and the napping operation is further carried out 10 times in the opposite direction to mainly nap the weft yarns to form a nap, and the napping part is subjected to the following conditions. Water-repellent with foam treatment, resulting in approximately 20 pilasters
A filter cloth of the present invention was obtained which had a fiber count of 0.00 fibers/trace and a directional index of about 2.2.

<ta water processing conditions) ・Processing process Water repellent application (applied to the raised part by fluorocarbon resin, foam treatment) - Drying (110°C) - Heat treatment (180°C, 1 minute) ・Processing agent composition Water repellent ( Fluorine resin) 350g/j! Water repellent durability improver 16 Foaming agent
20 Softener 50
〃Foam stabilizer 3 〃・Amount of foam attached to processed cloth 35g/rr? Next, the above filter cloth,
The warp direction is the longitudinal direction, and the width is 30 cm and the length is 2.5 cm.
The cloth was cut into lengths of m, and the cut ends were sewn to obtain an endless filter cloth as shown in FIG.

Next, the endless filter cloth was applied to a belt press type dewatering machine shown in Fig. 3, and the running speed of the filter cloth was set to 4 m/min, the degree of vacuum in the vacuum suction tank was set to approximately 900 mm water column, and the pressing force to the transfer drum was set to approximately 900 mm. A dehydration test was conducted using a weight of 60 kg. As a solid liquid,
Tap water and clay having an average particle size of about 20 μm were used, and the concentration of the clay was adjusted to about 300 nv/liter, which was fed at a rate of about 40 liters/min without adding a flocculant. The particle size distribution of the clay in the solid-liquid as measured by a Coulter counter was approximately 1 to 50 microns, which was found to be distributed over a fairly wide range.

As a result of the test, the rejection rate by the filter cloth was 72%, and the components recovered by scraping with the scraper were about 60% solids.
It was actually about 2000 times more concentrated than the original concentration. Further, the transfer rate to the transfer drum 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 10 microns, and most of the particles larger than 10 microns were removed. Further, even after approximately 500 hours of operation, the above performance did not change at all, and no abnormality was observed in the filter cloth.

〔Effect of the invention〕

As described above, the filter cloth for solid-liquid separation of the present invention has naps made of synthetic fibers on at least one side, and the naps have a directionality of 1°2 to 10 in the longitudinal direction of the filter cloth. have,
The nape has a specific surface area of 3 x 10' cal/g or more, and the nape portion is coated with a ↑Ω aqueous substance, and the filter fabric of the present invention has a so-called wave layer. Since the pils that is formed has directionality and has a directional index of 1.2 to 10, the pils may be pushed into the holes of the base material during use, making it difficult to stand up again.
It is possible to prevent the naps from becoming entangled, and stable solid-liquid separation efficiency can be obtained. In addition, the filter cloth of the present invention has a nape specific surface area of 3 x 103 ccA/g or more,
And since a water-repellent substance is applied to the raised part,
The transfer rate can be improved without reducing the amount of water permeation, and the recovery rate of solid components is improved. Furthermore, even a cake with a high moisture content can be transferred, and even a fine solid component with a small particle size can be efficiently transferred. Furthermore, since even fine solid components can be blocked, it is not necessary to add a flocculant.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of the filter cloth of the present invention, FIG. 2 is a side view of the weft disintegration yarn of the filter cloth whose napped portion has been water-repellent, and FIG. 3 is the same as shown in FIG. 1 above. FIG. 2 is a schematic front view showing a belt press type dehydrator in operation using the filter cloth shown in FIG. DESCRIPTION OF SYMBOLS 1...Filter cloth, 2.3...Perforated belt, 4...Transfer drum, 5...Press roll, 6...[fi, 7.
...Scraper, 8...Water spray nozzle, 9...
Decompression suction tank.

Claims (1)

[Claims] At least one side has naps made of synthetic fibers, the naps have a directionality index of 1.2 to 10 in the length direction of the filter cloth, and the specific surface area of the naps is 3 x 10^3 cm^2 /g or more, and further comprising a water-repellent substance coated on the napped portion.