JPH0326088B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for manufacturing a filter cloth for solid-liquid separation,
More specifically, the present invention relates to a method for producing a filter cloth suitable for use in a solid-liquid separator using a running filter 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 liquid component in the solid liquid is squeezed out by the pressing section. Filter cloth running type dehydrators (belt press type dehydrators) transfer the ivy cake to a transfer drum and collect it by scraping it off 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 separation device.

Filter cloths used in the above-mentioned solid-liquid separator have conventionally been disclosed in, for example, JP-A-59-115720, JP-A-60-31811, JP-A-60-44013, and JP-A-60. −44014 Publication, JP-A-61-
164613, JP 61-171516, JP
Those described in JP-A No. 61-174912, JP-A-61-174915, JP-A-61-174916, etc. are known. This conventional filter cloth has a napped filter layer formed on the surface of a textile base material, which is made of ultrafine fibers with a thickness of 0.1 to 10 μm, which are mainly raised from the weft threads of the base material. This filter cloth has a thickness of 0.1 to 10μ
Since the filter layer is formed by the naps of microfine fibers, the gaps between the naps are very small, and even fine solid components can be blocked. In other words, the woven fabric that serves as the base material of the conventional filter cloth uses multifilament or spun yarn, which is a bundle of ultrafine fibers of 0.1 to 10 μm, as the weft, and the warp, which runs in the longitudinal direction, is made of stretchable yarn in order to sufficiently raise the weft. Uses crimped yarn with high elasticity. This is because when crimped yarn is used, the arranged warp yarns shrink in the width direction of the base material at the same time as the weft yarns are raised, making it easier to form a dense structure. Further, as the base fabric, a satin fabric is used because a structure in which the wefts are floating is easier to raise.

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

In other words, in order to increase the rejection rate of fine particles in the solid-liquid to be filtered, it is necessary to increase the thickness of the filter layer made of napped microfibers. However, if the number of naps is increased to increase the amount of naps, the width of the filter cloth will shrink as described above, the warp density will increase, and the tissue weave will become too dense and the water permeability will drop significantly. I had a problem.

The purpose of the present invention is to focus on the above-mentioned problems, and to increase the amount of raised naps without significantly shrinking the filter cloth in the width direction, and to improve the rejection rate of fine particles without reducing the amount of water permeation. It is in.

[Means for Solving the Problems] A method for manufacturing a filter cloth for solid-liquid separation according to the present invention in accordance with this purpose is a satin fabric made of synthetic fibers, in which crimped yarn is used as the warp and bundles of ultrafine fibers are used as the weft. It consists of a method in which the surface of the base material on which the wefts are floating is raised, then the raised satin fabric is impregnated and fixed with urethane, and then the raised surface is further raised.

The satin weave used as the base material has 50 to 500 denier crimped yarn as the warp, and multifilament or spun yarn made of ultrafine fibers with a thickness of 10 μm or less as the weft. 3～
It is preferable that there are 8 floating pieces. This is because if the satin weave has a loose texture, it can be sufficiently raised.

The ultrafine fibers have a thickness of 0.1 to 10 μm, and if the thickness is larger than that, a rigid and flexible filter layer cannot be formed, and the gaps between the naps are large, resulting in a poor rejection rate for fine solids. If the diameter is less than 0.1 μm, the naps will wear out so much that stable solid-liquid separation cannot be performed.

Further, as the synthetic fiber crimped yarn of the warp, anti-twisted yarn, crimped yarn of push type, conduit type, etc. can be used, and elasticity is required. Considering napping properties, false twisted yarn is most preferred. In other words, if the warp yarns are crimped yarns, they will shrink in the width direction at the same time as they are raised, making it easier to create a dense structure.

The raising is performed by directly raising the surface of the base material made of synthetic fiber satin fabric using a raising machine.
In contrast to this raised yarn, the weft yarn has a single yarn thickness of 0.1 to 10 μm.
Consists of spun yarn (double yarn or triple yarn) or multifilament of ultra-fine fibers with 200 to 50,000 single yarns.
It is preferable that the yarn is a book and has a twist of 100 to 400 times/m. However, the weft is 20 to 100
The fibers are arranged in the width direction of the filter cloth at a density of threads/cm, while the warp threads are arranged in the longitudinal direction (running direction of the filter cloth), and the warp threads are mainly raised in the longitudinal direction of the filter cloth to form a nap filter layer. Ru. As a result of the hair being raised in the longitudinal direction, the raised hair generally lies facing in that direction,
When in use, the nap is stretched so that it faces in the opposite direction to the running direction of the filter cloth. Note that the reason why the weft yarns are mainly raised is that the warp yarns are subjected to a large expansion tension during use, and if they are raised, the strength of the filter cloth will be reduced.

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 preferable to use a napping machine using a cloth, and it is particularly preferable to pass through a French napping machine about 10 to 30 times. The additional raising is preferably carried out by a raising machine using a cloth, and it is particularly preferable to pass through a French raising machine about 5 to 15 times.
The reason why such a range is preferable is that even if the number of naps is increased more than this, the number of naps will not increase so much, but the wear of the weft yarns will increase, which will have a serious effect on reducing the strength of the filter cloth.

In this invention, first, the first raising is performed directly on the satin fabric base material, and when a raised layer of ultrafine fibers has been formed to some extent, urethane is impregnated and fixed,
Additional raising is then performed. It is preferable to carry out the first raising to such an extent that the ground structure of the satin weave is no longer visible due to the raised layer of ultra-fine fibers, and this first raising increases the warp density by about 10 to 20% in the width direction of the base material. Become. If the number of naps is further increased as it is, in addition to the above-mentioned problem of lowering the strength of the filter cloth, there will be a problem that the warp yarn density will become too high and the water permeability of the filter cloth will decrease significantly.

Therefore, in the present invention, after the first raising is performed an appropriate number of times, urethane is impregnated and fixed to fix the warp density, and then additional raising is performed.

For impregnation with urethane, a dimethyl formamide solution of polyurethane obtained from polyether, polyester, methylene diphenyl diisocyanate, and methylene bisaniline may be applied from the back side of the filter cloth using a gravure coater or as a polyurethane aqueous emulsion. Alternatively, the substrate may be simply immersed in an aqueous polyurethane emulsion, and after immersion, excess urethane may be removed using a squeezing roll or the like. Furthermore, a method of simply applying and impregnating urethane by spraying may be used.

The impregnated urethane is dried and fixed. Drying is carried out, for example, by passing the urethane-impregnated base material through a tenter, and if necessary, excess urethane may be blown off in a circuit after drying. In the urethane-impregnated and fixed base material thus obtained, the final amount of urethane relative to the textile base material is preferably about 2 to 10% by weight.

This urethane impregnation and fixation allows for additional raising without increasing the warp density, as described below, as well as stabilizing the structure of the filter cloth.
In a filter cloth traveling type solid-liquid separator, it is possible to stabilize the running by reducing deformation of the filter cloth dimensions.

After urethane impregnation and fixation, additional raising is performed on the satin fabric base material that has already been subjected to the first raising.

After being impregnated with urethane and fixed, the structure of the filter cloth is fixed and stable by the urethane, so when it is additionally raised using a raising machine, there is no shrinkage in the width direction, the warp density increases, the tissue weave becomes denser, and water permeability increases. When the amount decreases, the amount of piloerection increases without causing the phenomenon of itching.

This additional brushing after urethane impregnation increases the rejection rate of fine solid particles by 10% without reducing water permeation.
It can be improved by about 20%, and if the rejection rate is constant, the water permeation can be improved by about 30 to 50%.

FIG. 1 shows a comparison of the water permeability and rejection rate of the filter cloth of the present invention and the comparative filter cloth. The comparison filter fabric was simply impregnated with and fixed with urethane to stabilize the structure of the filter cloth after the base material was raised, and was not additionally raised. Here, the water permeability is the water head
It is the filtration rate per unit area of distilled water at 20℃ under a pressure difference of 500mmAq, and the rejection rate is 50% when the particle size of diatomaceous earth is 1 to 30μm and the weight average particle size is 5μm.
It is the value obtained by dividing the difference in concentration between the stock solution and the filtrate when filtered at a concentration of mg/ml by the stock solution concentration. As shown in Fig. 1, in the comparison filter cloth, when the number of times of raising is increased to increase the rejection rate, the amount of water permeation inevitably decreases, but in the filter cloth of the present invention, the amount of water permeation is significantly reduced by additional raising. It is possible to improve the rejection rate without any problems.

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

Example 1 Made by spinning 18-core multicore composite fibers with polyester as the island component and polystyrene as the sea component.
The weft is 20/2S spun yarn, and the warp is a false twisted yarn made by bundling 38 single yarns with a fineness of 5 denier.5
A sheet satin fabric was obtained.

Next, the sea component of the weft was removed using trichlorethylene as a solvent to obtain a fabric whose weft was a bundle of ultrafine fibers with a thickness of 3 μm.

Next, the above-mentioned woven fabric was passed through a French-type napping machine for clothing 16 times to mainly nap the weft yarns in the warp direction to obtain a raised fabric constituting a filter layer with a number of naps of about 1000/mm.

After soaking this in a solution containing urethane emulsion and squeezing out the excess liquid with a mangle device, it was heated to 120°C.
After drying and heating at 180° C. to react the urethane, the cloth was soaked with warm water at 20° C. in a circular device and dried to obtain a urethane-impregnated filter cloth with a 5% urethane adhesion amount.

The obtained filter cloth had a water permeability of 4 ml/cm ² sec and a rejection rate of fine diatomaceous earth of 40%. This filter cloth was further passed through the above-mentioned napping machine 10 times to obtain a filter cloth of the present invention. The performance of the obtained filter cloth is that the water permeability is 4
ml/cm ² sec, the inhibition rate of fine diatomaceous earth was 60%.

For comparison, a urethane-impregnated filter fabric was obtained by the method described above by first passing it through the napping machine 26 times and then immersing it in a solution containing urethane emulsion. The performance of the obtained filter cloth is that the water permeability is 2ml/cm ²
sec, the inhibition rate of fine diatomaceous earth was 60%.

That is, the filter cloth of the present invention was able to improve its rejection rate by 20% by additionally raising the cloth after impregnating it with urethane. Furthermore, when the rejection rate was the same, the water permeability could be increased by about twice as much.

Next, in order to confirm the performance of the filter cloth of the present invention in use in a solid-liquid separator, the filter cloth was cut into a width of 30 cm and a length of 2.5 m with the warp direction in the longitudinal direction, and the cut ends were sewn together. Thus, an endless filter cloth 1 as shown in FIG. 2 was obtained. 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 dehydrator 11 shown in FIG.
A dehydration test was conducted with a pressing force of approximately 60 kg against the water column and the transfer drum 19. In the device 11 shown in the figure, the filter cloth 1
The drive roll 12 and the guide rolls 13,1
These rolls 12, 13, 14, 15 and squeeze rolls 16, 1
7, 18, it travels and circles in the direction of arrow A on a fixed trajectory regulated by the transfer drum 19. 2
0 is the solid liquid to be treated, and the vacuum suction tank 21
As a result, the liquid component is sucked through the running filter cloth 1, 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 then the scraper 2
Scraped by 2.

As the solid liquid, tap water and clay with an average particle size of about 20 μm were used, and the clay concentration was adjusted to about 1000 mg/min, which was supplied at a rate of about 80 mg/min without adding a flocculant. . The particle size distribution of the clay in the above 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 95%, 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 95%, which was extremely high. Furthermore, the particle size distribution of clay in the solid component measured with a coal 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 performance did not change at all, and no abnormalities were observed in the filter cloth, indicating that it had remarkable durability.

In addition, the filter cloth obtained by the method according to the present invention has an ultrafine fiber nap filter layer with a large amount of naps without reducing the amount of water permeation due to additional naps, so it has high solid-liquid separation efficiency. And urethane impregnation,
Since the woven structure is fixed by adhesion, it has high running stability and excellent operability, and the processing capacity is stable because there is little permanent deformation of the filter cloth.
Therefore, it can be used for various solid-liquid separations. For example, sludge, scum, flocs, wash water, etc. generated by 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 to concentrate and dehydrate concentrated sludge. 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, and coagulated flocs and flocculated sediment flocs generated from industrial wastewater treatment. , backwash water from various filtration devices such as sand filters, 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, after the first raising, the urethane is impregnated and fixed, and then the raised layer of the ultrafine fibers is increased by additional raising, so that the warp density during the additional raising is increased. It is possible to increase the napped filter layer while preventing the increase, and it is possible to improve the rejection rate of fine particles without reducing the amount of water permeation, and it is possible to obtain a filter cloth with extremely high performance.

In addition, since the filter cloth is impregnated with urethane and fixed in a desired state, the filter cloth can run stably in the solid-liquid separator, and the life of the filter cloth can be maintained for a long time. Additionally, the device becomes easier to operate. Further, the treatment performance, that is, the amount of water permeation and the rejection rate of solids, do not change during operation due to permanent deformation of the filter cloth, and stable treatment performance can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram of a filter cloth obtained by the method of the present invention and a comparison filter cloth, FIG. 2 is a schematic perspective view showing an embodiment of the filter cloth obtained by the method of the present invention, and FIG. 3 is a characteristic diagram of a filter cloth obtained by the method of the present invention. 1 is a schematic side view of a belt press type dehydrator using a filter cloth according to the present invention. 1...Filter cloth, 2...Rubber belt, 11...Belt press type dehydrator, 12...Drive roll, 13,
14, 15...Guide roll, 16, 17, 18
... Press roll, 19 ... Transfer drum, 20 ...
Solid liquid, 21...reduced pressure suction tank, 22... scraper.

Claims (1)

[Claims] 1. Raise the floating side of the weft of a synthetic fiber satin fabric base material in which the crimped yarn is the warp and a bundle of ultra-fine fibers are the weft, and then the raised satin fabric is impregnated with urethane and fixed. 1. A method for producing a filter cloth for solid-liquid separation, which comprises further raising the raised surface.