JP3146891B2 - Filter cloth - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter cloth comprising a base layer as a base cloth and a filter layer formed from crimped fiber bundles having a root portion in the base layer.

More specifically, a novel filter cloth which is excellent in the ability to capture fine particles, recovers from washing, retains shape, and is durable, has excellent water permeability in liquid filtration, and can be suitably used for separating suspended substances. It is about.

[0003]

2. Description of the Related Art A filter cloth made of a woven or knitted fabric using a fiber or a nonwoven fabric is widely used as a filter medium for filtering fine particles contained in a liquid such as water or a solvent or a gas such as air or gas. In particular, for filtration of suspended solids in water, a woven fabric having a lattice structure based on a so-called ternary weave of flat, twill, and satin has been used. JP-B-62-13046 and JP-B-2
JP-A-47-244 discloses a filter cloth obtained by raising a woven fabric using ultrafine fibers for the weft and forming nap of the ultrafine fibers on the surface. In addition, as a filter medium having a fiber bundle on the surface, Japanese Utility Model Publication No. 2-36568 and Japanese Utility Model Publication No.
No. 0 and Japanese Utility Model Laid-Open No. 4-14112 are known. 6-2767
No. 2, JP-B-6-30874 discloses a pile woven or knitted fabric having a pile in which a crimped yarn and a multifilament having no crimp are mixed. Also, Japanese Patent Publication No. 140136/1988 and Japanese Patent Application Laid-Open No. 58-120834 disclose a woven fabric obtained by raising a woven fabric using a false twisted yarn as a weft.

[0004]

However, a conventional filter cloth made of a woven or knitted fabric using fibers passes raw water through gaps in the lattice structure of the fibers and traps particles contained therein by the lattice. Therefore, most of the particles smaller than the size of the lattice gap pass without being captured.
Some have increased the weaving density and reduced the size of the lattice to capture particles of small particle size, but the ratio of gaps in the filter cloth has decreased, resulting in an extremely low filtration capacity and immediate clogging. And filtration becomes impossible. In addition, although some yarns and fibers that make up the woven fabric are made thinner to improve the ability to capture small particles, particles that have bite into the gap between the fibers can be easily washed away even if backwashing is performed. However, there is a problem that causes clogging at an early stage. In addition, the filter cloth had low strength and low durability because the thread and fiber were thin. On the other hand, the knitted structure had a large elongation of the knitted material and was inferior in shape retention.
In addition, the filter cloth is easily deformed, which greatly changes the gap, so that the particle size of the fine particles that can be blocked fluctuates, and there is a problem that stable filtration performance cannot be obtained. Nonwoven fabric filter cloth has a relatively thick and dense three-dimensional structure of fibers, so it has good particle capture properties but high pressure loss, and also allows particles once captured in a three-dimensional lattice to be trapped. It is difficult to remove, and it is difficult to regenerate the filter cloth and the reusability is poor. In addition, since it is easily deformed when tension is applied, it is inferior in shape retention. In addition, Tokiko Sho 62
The filter cloths described in JP-A-13046 and JP-B-2-47244 have a limit in the performance of blocking fine particles because the length of the nap on the surface is short and the amount of nap is small. In addition, since the surface layer of the ultrafine fiber bundle constituting the weft has a loop shape formed by pulling out the fibers, fine particles are easily trapped in this portion and cause clogging, and once the fine particles enter, they are removed. Difficult to
The recoverability of performance due to washing and the like was poor. Even if the number of raisings is increased, there is a limit to the increase in the naps, so that it cannot be an effective means for improving the rejection of fine particles. Conversely, with the increase in the number of times of raising, the fibers constituting the weft are cut everywhere, causing a drop in the strength of the weft. I only got a cloth. Furthermore, in the filter cloth described in Japanese Utility Model Publication No. 2-36568, when the base cloth and the pile are cured and bound with a resin, the resin easily penetrates to the upper part of the pile to cause uneven adhesion, and the resin is uniformly applied. It was difficult to control. For this reason, the part of the fiber bundle that the resin has penetrated to the upper part and cured and bound becomes a hole, and it is not possible to trap fine particles at that part, so the filter cloth is intended only for collecting particles with a large particle diameter. I had to be. Also,
Because it is targeted for air purifier filters,
It was not at all applicable to liquid filtration. Also,
The filter cloth described in Japanese Utility Model Publication No. 5-34730 is a filter cloth obtained by bending the tip of a pile and splitting the hair. However, in order to prevent the pile from settling, the filter cloth of a few tens denier having a considerably large fineness is used. Due to the necessity of use and the large gap between the piles, the dust collection efficiency of particles having a small particle diameter was low. Further, since it is a dust-collecting filter cloth for air cleaning, it is not applied at all to liquid filtration. Further, in the filter cloth described in Japanese Utility Model Laid-Open No. 4-114112, since the nap fiber is erected almost perpendicularly to the knitted fabric portion, the percentage of the fiber itself that can prevent the passage of the particles is low, and the filter cloth stands up. Particles between the fibers tended to cause clogging during the early stages of filtration. Further, when the diameter of the particles is smaller than the size of the eyes of the knitted fabric portion, the particles entering between the raised nap fibers are not caught by the lattice of the knitted fabric portion and pass through the eyes. There was a problem that the blocking performance was low. In addition, even when the nap fibers lie down during filtration, the direction of the lie varies and the knitted fabric portion is exposed everywhere, so there is a limit to the improvement of the blocking performance. The pile woven or knitted fabric described in Japanese Utility Model Publication No. Hei 6-27672 and Japanese Utility Model Publication No. Hei 6-30874 is used for clothing and upholstery with high pile quality, excellent gloss, and performance as a filter cloth. Did not hold at all.
JP-B-1-40136, JP-A-58-12083
No. 4 describes a weaving method using a weft subjected to false twisting, but the structure of the filter cloth of the present invention is completely different from that of the filter cloth of the present invention in that each nap is an independent raised woven fabric. Furthermore, this brushed fabric is used exclusively for clothing, and cannot be applied to filter cloth.

An object of the present invention is to solve the above-mentioned problems of the conventional filter cloth and to provide a novel filter cloth excellent in the ability to capture fine particles, recover from washing, and have durability. To provide a novel filter cloth which can be suitably used for separating suspended substances having a high rejection rate of fine particles in liquid filtration, high water permeability and high clogging durability, and excellent form retention and long life. is there.

[0006]

This object is basically achieved by the following constitution. That is, "at least a base layer and a filter layer mainly composed of a fiber bundle having a crimp rate of 2 to 45% are crimped, and one end of the fiber bundle is integrated with the base layer as a root. A filter cloth characterized by having a structure in which a structure and / or a part of the fiber bundle is integrated with the base layer.

The fibers that can be used in the fiber bundle constituting the filtration layer of the present invention are made of a polymer substance having a fiber forming ability,
Polyamides such as nylon 6, nylon 66, nylon 12, and copolymer nylon, aromatic polyamides, polyesters such as polyethylene terephthalate, copolymer polyethylene terephthalate, polybutylene terephthalate, copolymer polybutylene terephthalate, wholly aromatic polyesters, polyethylene, polypropylene, etc. Polyolefin, polyurethane, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, vinyl polymer, polyvinylidene chloride, polyhydrosulfite, polyfluoroethylene, copolymerized polyfluoroethylene, polyoxymethylene and the like. In addition, a combination of composite fibers and fiber types such as a core-sheath structure, a multi-core-sheath structure, a sea-island structure, and a bimetal structure in which a plurality of these polymer substances are combined may be used according to the purpose. The thickness of the fiber is preferably 2 denier or less, which is relatively thin. However, in order to improve the performance of capturing fine particles, 0.001 to 1 denier is more preferable, and the performance of capturing fine particles while maintaining the durability of the fiber high. Is preferably 0.03 to 0.5 denier. The fiber bundle of the present invention is a fiber bundle in which a large number of different or similar fibers are arranged in a bundle. It is preferable that at least one end of the fiber bundle constituting the filtration layer is a free end, and the other end or a part of the fiber bundle in the middle is integrated with the base layer. The end portion of the fiber bundle or the middle portion of the fiber bundle and the base layer are integrated by entanglement with the yarn of the base layer, bonding with an adhesive, heat fusion, ultrasonic bonding, a combination thereof, and the like. Things. In the case of a filter cloth having a structure in which the base layer is a woven fabric and the root portion of the fiber bundle of the filter layer is alternately entangled with the weft and / or warp of the base layer at three or more places, the fiber bundle falls off during use. It is more preferable because it is difficult to perform. The integrated part is preferably arranged regularly on the surface of the base layer, but even if it is not regular, there is no coarse part of the fiber bundle or a part without the fiber bundle which affects the filtration performance, and the base layer It is preferable that the integrated portions are arranged evenly on the surface.

In order to achieve the object of the present invention, it is necessary that the filtration layer is mainly composed of a fiber bundle having a crimp rate of 2 to 45%. When the crimp rate is lower than 2%, the fibers constituting the fiber bundle tend to converge, and the surface of the filter cloth cannot be sufficiently covered with the fiber. Is not enough. Also,
Even when the crimping ratio is higher than 45%, the fibers in the fiber bundle are strongly entangled with each other to form a bundle, so that the surface of the filter cloth cannot be sufficiently covered with the fibers, and the particles are not sufficiently captured. In order to reduce the convergence and entanglement of the fibers to form an appropriate space between the fibers and further enhance the trapping of the particles, a crimp rate of 2 to 35% is preferable, and 2 to 25%
Is more preferable.

Further, it is preferable that the filtration layer is mainly composed of at least two kinds of fiber bundles having a difference of 2% or more in the crimp ratio. Examples of the form having a difference in the crimp rate include a case in which the fibers in one bundle have a difference in the crimp rate, a case in which the fiber bundle has a difference in the crimp rate, and both cases. The most suitable one is selected depending on the application to be applied and expected performance. Those that capture fine particles are suitable. When trapping relatively large particles having an average particle size exceeding 20 μm, a small particle is preferable. If the difference in the crimp rate is less than 2%, it is difficult to obtain the effect due to the difference in the crimp rate. on the other hand,
When a difference in the crimping ratio is provided by 45% or more, the entanglement of the fibers becomes too strong to form a bundle-like aggregate state, similarly to the case where a high crimp is given alone. Is formed, and the particles cannot be sufficiently captured. In order to properly balance the difference in crimp, increase the bulkiness of the filtration layer, and form fine and appropriate voids between the fibers, a difference in the crimp rate of 2 to 35% is preferable, and 3 to 20%.
% Crimp rates are more preferred. As at least two types of fiber bundles having a difference of 2% or more in the crimp rate, at least 2
It is more preferable that all of the fiber bundles of the species are crimped. However, a combination of at least one fiber bundle having no crimp can be employed depending on the purpose.

[0010] The fiber bundle of the filtration layer may have a structure in which one end is integrated with the base layer as a root portion, and / or a structure in which an intermediate portion of the fiber bundle is integrated with the base layer. is necessary. Further, in the case of a structure in which one end is integrated with the base layer as a root, the other end is a free end. In the case of a structure in which a part of the fiber bundle is integrated with the base layer, both ends are free ends. It is preferred that The free end means a state in which the tip of the fiber is released and can move freely. The fiber bundle is opened from the root to the tip,
It is preferable that the filter cloth is bent and inclined in a certain direction such as the length direction or the width direction of the filter cloth. The average length of the fiber bundle fibers from the portion where the fiber bundle is integrally fixed to the base layer, that is, the position from the outermost surface of the base layer to the free end, is L (mm), and the thickness of the filtration layer is T (mm).
It is preferable that T / L is 0.02 to 0.5. If the T / L is smaller than 0.02, it is not preferable because the trapping property of the fine particles is low and the fine particles cannot be retained in a large amount in the filtration layer, or the filtration layer is too dense and easily causes clogging. If it is larger than 0.5, the fine particles hardly enter the surface of the filtration layer without being filtered at the surface portion of the filtration layer and easily pass through without being blocked. In addition, when the thickness is larger than 0.5 and the base layer has a dense structure, the fine particles that have entered the inside are deposited and cause clogging, and even if cleaning is performed, the fine particles that have entered the inside are difficult to be washed off, and the cleaning recovery property is improved. It is not preferable because it is poor. More preferably, the value of T / L is 0.02
~ 0.46, more preferably 0.03 ~
0.4. In addition, the apparent density of the filter cloth is 0.15 to
It is preferably 0.6 gf / cm ³ . The apparent density (gf / cm ³ ) of the filter cloth is determined by the basis weight (gf / cm ³ ) of the filter cloth.
m ² ) is divided by the thickness T ₁ of the filter cloth according to the measuring method described in Note (3) of the examples described later, and the unit is determined. If the apparent density is too low, the ability to capture fine particles will not be sufficient, and if it is too high, the water permeability will be insufficient. In order to balance the ability to capture fine particles and the water permeability, the apparent density of the filter cloth is more preferably 0.2 to 0.6 gf / cm ³ . 0.25 to 0.5 gf / cm ³ is more preferable.

If the length of the fibers in the filtration layer is too short,
Since the amount of fibers that can contribute to filtration is reduced, the ability to capture particles is reduced. In addition, since the fibers are less likely to bend and the tip portions of the fibers tend to stand on the surface of the filtration layer, particles are likely to accumulate in the valleys of the standing fibers to cause clogging, and the cleaning recovery is also reduced. Conversely, if the length of the fibers in the filtration layer is too long, the ability to trap particles will be improved, but the permeability of gas and liquid will deteriorate, and the amount that can be treated will decrease. In addition, fibers tend to be entangled during filtration, so that a nep-like lump is easily generated. For these reasons, it is preferable that the fiber length of the filtration layer is 2 mm to 20 mm. 2
More preferable results are obtained when the distance is in the range of mm to 15 mm. The length of the fiber referred to here means the average length of the fiber bundle fiber from the portion where the fiber bundle is fixed integrally with the base layer, that is, from the position of the outermost surface of the base layer to the free end. In order to avoid large deformation when a strong tension is applied to the filter cloth, the elongation percentage in the length direction and the width direction is preferably 10% or less. The elongation here is a width 3c under standard conditions.
m is marked on the strip-shaped test piece at an interval of 20 cm, a load of 12 kgf is applied to the test piece in the length direction, and a load of 6 kgf is applied to the test piece in the width direction.
After 90 minutes, measure the length between the markings. At this time, the elongation is determined by the following equation.

Elongation rate = (ba) ÷ a × 100 (%) Here, “a” represents the length between markings when an initial load of 100 gf is applied to the test piece, and “b” passes for 90 minutes under a load. It represents the length between the markings under a later load. In order to prevent the scale of the base layer from expanding and the filtration performance from decreasing, the length direction is more preferably 8% or less, and 6% or less.
% Is more preferable. Although the elongation in the width direction is allowed to be a little higher than that in the warp direction, it is still more preferably 9% or less, and still more preferably 7% or less.

In order to avoid a large deformation of the filter cloth and obtain a filter cloth having excellent shape retention, the fiber of the base layer has an initial tensile resistance of 250 kgf / mm ² or more measured by the method of JIS L1013. , Preferably 300k
gf / mm ² or more, more preferably 350 kgf / m
it is recommended to use m ² or more fibers mainly. Further, as a form of the fiber of the base layer, a straight fiber is preferable to a crimped yarn such as a false twisted yarn.
Straight fibers include, of course, twisted yarns.
Further, as a filter cloth having excellent shape retention, the structure of the base layer is preferably a woven fabric. In actual filtration, it is often the case that filtration is performed by using a filter cloth alone without placing a wire mesh or perforated plate on the downstream side of the filter cloth. It is easy to stretch and deform.

[0014]

The following examples are provided to clarify the present invention, but the present invention is not limited thereto.

As the yarn (F1) of the base layer, a woven fabric is formed by using 250 denier and 48 filament yarns of polyethylene terephthalate for the warp and the weft, and 240 denier of polyethylene terephthalate as the fiber bundle (F2) for the filter layer. 576 filaments and false twisting of the yarns to give 3.2%, 19%,
False twisted yarns having crimp rates of 7%, 41% and 53% were used. For each F2 having a different crimp rate, the warp F
F2 is arranged at a fixed ratio to the number of 1
A double fabric consisting of two identical fabrics was made. This fabric is
F2 is a double woven fabric formed by repeating reciprocation between two upper and lower woven fabrics separated by a predetermined interval. F2 integrates the wefts of the upper and lower fabrics alternately with interlacing points. About the obtained integrated double fabric,
By slicing at a designated position in the thickness direction in parallel with the surface of the fabric, a fabric in which the surface of the filtration layer became the free end of the fiber bundle was obtained. Next, these woven fabrics are passed between the rotating brush roll and the back roll, and the fiber bundles are brushed according to the direction in which the fiber bundles are naturally inclined to open the fiber bundles. At the same time, the directions of the fibers were aligned. Subsequently, the surface of the opened fiber bundle was pressed against the surface of the heated metal roll with tension, and the fiber bundle was set to produce a filter cloth. The filtration performance of the filter cloth thus obtained was evaluated. As shown in Fig. 1, a rotating drum type continuous filtration machine with a mechanism for attaching a filter cloth with the filter layer inside on the circumference of the rotating drum and filtering the raw water guided inside the drum to the outside as shown in Fig. 1 This was performed using For the evaluation, wrinkle water (raw water having a concentration of suspended matter containing fine particles of about 11 mg / liter) from the secondary treatment of sewage was used. The results obtained were as shown in Table 1.

[0016]

[Table 1] Note: (1) Crimp ratio Measure according to the following procedure.

A. Under standard conditions, for the yarn to be measured,
Using a scalpel winder, make a scalpel with a circumference of 40 cm and 10 turns.

B. Put the scalpel on the hook and place it in a transparent container with water at 20 degrees Celsius. C. An initial load of 0.002 gf per denier is applied to the twentieth yarn for 20 yarns, and after 2 minutes, the length L ₀ of the two yarns is measured with a water column.

D. Next, in addition to the initial load, a constant load of 0.1 gf per denier is applied to the scalpel, and after 2 minutes, the length L ¹ of the combined scalpel is measured.

E. The crimp ratio is determined by the following equation.

Crimp ratio = (L ₁ −L ₀ ) ÷ L ₁ × 100 (%) (2) Length of fiber bundle Upper end face of base layer (if the base layer is a woven fabric and the surface is uneven, the protrusion is The average length of the constituent fibers from the upper end to the free end of the fiber bundle of the filtration layer.

(3) The thickness of the filtration layer: 9 test pieces of about 3 cm × 3 cm were collected, and 3
The sheets are stacked and placed on the press table of the compression elasticity tester. 2cm
The circular probe of No. ² is allowed to stand on the test piece with a load of 6 g, and the thickness after 10 seconds is measured. 3 times by dividing this value an average value of the measured values at 3 to calculate the thickness T ₁ of the per sheet. Next, a sample of the base layer by removing the fiber bundle of the filtration layer from filter cloth, to calculate the thickness T ₂ of the per sheet in the same manner as was determined T _1. The thickness T of the filtration layer is T =
It is determined from the equation of T ₁ -T ₂ (mm).

(4) Rejection When the concentrations of suspended solids in the raw water and the filtered water are C ₁ and C ₂ , respectively, the rejection R is R = (C ₁ −C ₂ ) ÷ C ₁ × 100.
(%)

The suspended matter concentration is measured based on JIS K0102.

(5) Loss Head The difference between the raw water level and the filtered water level in the rotary drum is defined as the loss head.

Thus, the filter cloth according to the embodiment of the present invention has a high rejection rate of suspended matter in raw water and a low head loss, and the rejection rate and the water permeability are well balanced. On the other hand, Comparative Example 1 in which a fiber bundle without crimp was used for the filtration layer
In Nos. To 4, those having a high rejection rate had a low head loss and the other way around, and none of them had a balance between rejection rate and water permeability. In Comparative Example 5, the crimping ratio was too high, the entanglement of the fibers in the fiber bundle was strong, and the fiber could not be sufficiently opened.

Since a gap was left, a high rejection could not be obtained.

According to the constitution of the present invention, the ability to capture fine particles,
Excellent clogging resistance and durability.
Further, it is possible to obtain a novel filter cloth which has excellent water permeability and can be suitably used for separating suspended substances.

[Brief description of the drawings]

FIG. 1 is a side view showing a mechanism of a rotary drum type continuous filter.

[Explanation of symbols]

 1: filter cloth 2: raw water 3: filtered water 4: concentrated water 5: washing water pump 6: backwash spray 7: front wash spray 8: rotary drum 9: loss head

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-202837 (JP, A) JP-A 5-22017 (JP, U) JP-A 6-27672 (JP, Y2) (58) Field (Int. Cl. ⁷ , DB name) B01D 39/08 D03D 27/00

Claims (10)

(57) [Claims] 1. A fiber filter comprising at least a base layer and a filter layer mainly composed of a fiber bundle having a crimp rate of 2 to 45%, and one end of the fiber bundle is integrated with the base layer as a root. A filter cloth characterized in that the filter cloth has a structure in which a part of the fiber bundle and / or a part of the fiber bundle is integrated with the base layer. 2. The filter cloth according to claim 1, wherein at least one end of the fiber bundle is a free end. 3. The filter cloth according to claim 1, wherein the fibers of the fiber bundle are opened and inclined and bent in a directional manner. 4. When the length of the fibers of the fiber bundle constituting the filtration layer is L and the thickness of the filtration layer is T, T / L is 0.02 to 0.02.
2. The filter cloth according to claim 1, wherein the value is 0.5. 5. The filter cloth has an apparent density of 0.15 to 0.6 g.
2. The filter cloth according to claim 1, wherein f / cm ³ . 6. The filter cloth according to claim 1, wherein the frequency of appearance of the fiber bundle strain on the surface of the base layer is 40 to 900 strains / cm ² . 7. The fiber length of the filtration layer is 2 mm to 20 mm.
The filter cloth according to claim 1, wherein 8. The filter cloth according to claim 1, wherein the structure of the base layer is a woven fabric. 9. The filter cloth according to claim 8, wherein the fiber bundle constituting the filter layer is a woven fabric having three or more entanglement points with the weft and / or warp of the base layer at the root. 10. A base layer, and at least a filtration layer mainly composed of at least two types of fiber bundles having a difference of 2% or more in a crimp rate, wherein one end of the fiber bundle serves as a root and a base layer. A filter cloth, wherein the filter cloth has an integrated structure and / or a structure in which a part of the fiber bundle is integrated with a base layer.