JPH03278810A - Cartridge filter - Google Patents

Abstract

PURPOSE:To permit a cartridge filter to be used over an extended period of time without causing clogging in separation by filtration of solid from liq. by a method wherein, in a cartridge filter consisting of a multilayer structure having a porous cylinder around which nonwoven fabric is wound, the close layers consisting of the nonwoven fabric having a specific average fiber and pore diameter and the diffusion layers having an average pore diameter larger than that of the close layer are laminated. CONSTITUTION:A cartridge filter is obtained by forming into a porous cylindrical shape a nonwoven fabric of multilayer structure wherein a plurality of close layers consisting of the nonwoven fabric having an average fiber size of 0.5-25mum in diameter and an average pore size of 10-300mum in diameter and the diffusion layers consisting of the nonwoven fabric having an average pore size larger than that of any of the nonwoven fabric composing the aforesaid close layers and not more than 500mum are laminated and wherein the diffusion layers exist between the aforesaid close layers. By the use of this filter, particles can be collected with a high degree of efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cartridge filter used for filtering solids in a liquid.

[Prior Art] Cartridge filters made of thread, string, paper, nonwoven fabric, etc. molded into a porous cylindrical shape are generally used as filters for filtering solid matter in liquids.

However, since these cartridge filters have relatively coarse meshes, when the solid matter is fine particles, they cannot be sufficiently captured.

For this reason, a cartridge filter has been proposed in which a nonwoven fabric made of fine fibers with a fiber diameter of 0.5 to 50 μm obtained by a melt blowing method or a jet spinning method is formed into a cylindrical shape (Japanese Patent Laid-Open No. 60-218818). ,
(See Japanese Patent Application Laid-Open No. 1-297113). Since these filters have a dense network structure, they can reliably capture fine particles and exhibit high collection efficiency, but on the other hand, they have the drawback of being easily clogged and having a short service life. In contrast, in conventional technology, when laminating nonwoven fabrics made of the fine fibers mentioned above, an attempt is made to prevent clogging by providing a density gradient so that the density decreases from the upstream side to the downstream side of the liquid fluid to be treated. was.

Preventing clogging using a density gradient can be somewhat effective, but in any case, since it is made of non-woven fabric made of fine fibers with a dense structure, there is a limit to how well it can eliminate clogging, and its service life is short. The problem had not been resolved. In addition, in the filter with the above-mentioned laminated structure, the processing liquid flows so as to be gradually concentrated along the flow direction, but the solids present in the processing liquid are not necessarily uniformly dispersed. Another drawback was that localized clogging was likely to occur when hot liquid flowed.

When clogging occurs locally, the clogging tends to spread around that area, accelerating clogging as a whole.

Furthermore, nonwoven fabrics obtained by melt-blowing methods generally have low fiber strength and poor impact resilience, so when a cartridge filter is manufactured by winding a nonwoven fabric around a perforated tube, for example, it is easily crushed by the winding pressure. However, the smaller the voids, the more likely they are to become clogged, which poses a problem.

[The problem that the invention seeks to solve! ] The present invention has been made to solve the above-mentioned drawbacks of the prior art, and aims to provide a cartridge filter that can collect fine particles with high collection efficiency, is free from clogging, and has a long service life. Take it as a challenge.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a cartridge filter in which a non-woven fabric is wound around a porous tube to form a multilayer structure. Pore diameter 1
A plurality of dense layers made of a nonwoven fabric with a diameter of 0 to 300 μm and a diffusion layer made of a nonwoven fabric with an average pore size larger than the average pore size of any of the nonwoven fabrics forming the dense layer and 500 μm or less are laminated, and The present invention provides a cartridge filter characterized in that the diffusion layer is present between the dense layers.

That is, the cartridge filter of the present invention has an average wA
11 From a nonwoven fabric with an average pore diameter larger than any of the nonwoven fabrics forming the IR dense layer between dense layers consisting of nonwoven fabrics with an average pore diameter of 10 to 300 μm and composed of fine fibers with a diameter of 0.5 to 25 μm. Because a diffusion layer is arranged, fine particles that are not captured in the first dense layer are captured in the next dense layer after being diffused in the diffusion layer. This diffusion occurs due to a large decrease in resistance when the liquid flow passes from the dense layer to the diffusion layer, and then a large increase in resistance when passing from the diffusion layer to the next dense layer, causing part of the liquid flow to It is reflected and promotes diffusion. Since the fine particles are diffused in the diffusion layer in this manner, high concentration of fine particles will not be concentrated in a part of the next dense layer, making clogging less likely to occur. Also,
By interposing the diffusion layer between the dense layers, the liquid passage resistance of the cartridge filter as a whole is reduced. Moreover, in the cartridge filter of the present invention, even if winding pressure is applied to the nonwoven fabric during manufacturing, the diffusion layer between the dense layers is preferentially compressed, and the compression ratio of the dense layer becomes small. The collapse of the void becomes smaller and clogging becomes less likely to occur.

The dense layer of the present invention is formed of a nonwoven fabric having an average fiber diameter of 0.5 to 25 μm and an average pore diameter of 10 to 300 μm.

If the average fiber diameter of the fibers used is smaller than this, the strength of the fibers will be significantly weakened and breakage will occur easily.
On the other hand, if the average fiber diameter is larger than this, a dense structure cannot be obtained and a dense layer cannot be formed. Furthermore, if the average pore diameter is larger than 300 μm, it will not be possible to sufficiently trap fine particles, whereas if it is smaller than 10 μm, clogging will easily occur and the service life will be shortened. Such nonwoven fabrics are usually produced by melt blowing or jet spinning. In these nonwoven fabric manufacturing methods, when extruding molten resin through a nozzle, high-speed airflow is applied from around the nozzle to thin and accumulate the fibers, making it possible to produce dense nonwoven fabrics made of extremely thin fibers. can. Thermoplastic resins such as polyolefin, polyamide, and polyester can be used as the resin for forming the fibers, but polypropylene is particularly suitable because it is excellent in terms of spinning conditions, chemical resistance, bacteria resistance, etc.

Note that the thickness of the dense layer is preferably in the range of 200 to 800 μm per layer; if it is less than 200 μm, this layer mainly performs filtration, so it will not be able to capture enough fine particles, and if it exceeds 800 μm, it will cause clogging. becomes noticeable, and even if a diffusion layer is placed between the dense layers, there is no effect of preventing clogging.

In addition, two or more dense layers are laminated, and each layer becomes denser with an average pore diameter smaller as it goes downstream when viewed from the flow direction of the liquid flow, that is, as it goes inside the cartridge filter. This is desirable. this is,
This is to increase the collection efficiency by gradually capturing solids with smaller particle diameters while repeating the collection of solids in the dense layer and the diffusion in the diffusion layer, and to prevent clogging.

As the nonwoven fabric of the diffusion layer of the present invention, a nonwoven fabric having an average pore diameter larger than that of the nonwoven fabric forming any of the dense layers and 500 μm or less is used. For example, among the nonwoven fabrics constituting the dense layer, the one with the largest average pore diameter is 50
μm indicates that the average pore diameter is in the range of more than 50 μm and less than 500 μm, and if the largest average pore diameter of the nonwoven fabric constituting the dense layer is 300 μm, then 3
It shows that the average pore diameter is in the range of 0.004m8 to 0.004m8 or less.

When the average pore diameter of the diffusion layer becomes smaller than that of the dense layer, it no longer has the effect of diffusing the processing liquid, and therefore no longer has the effect of preventing clogging. On the other hand, if the average pore diameter is larger than 500 μm, relatively large particles cannot be trapped in the diffusion layer, so the effect of preventing clogging in the *W layer is also reduced.

The nonwoven fabric used for the diffusion layer is not particularly limited as long as it has the above average pore diameter, and any nonwoven fabric can be used. However, in general, nonwoven fabrics in which fibers are bonded by a binder have a risk of the binder eluting into the processing liquid and contaminating the processing liquid, so it is desirable to use a binder-free type nonwoven fabric. Examples of binder-free nonwoven fabrics include nonwoven fabrics produced by melt blowing and flash spinning, as well as spunbond nonwoven fabrics, fiber bonded nonwoven fabrics, water flow platform nonwoven fabrics, and needle punched nonwoven fabrics.

The thickness of the nonwoven fabric constituting one of the diffusion layers is 100~
It is desirable that the thickness be in the range of 500 μm. If the thickness of the diffusion layer is less than 100 μm, the effect of diffusing fine particles,
The effect of absorbing the pressure applied during winding through cushioning properties cannot be expected. On the other hand, if the thickness of the diffusion layer is greater than 500 μm, the cartridge filter will become large. Furthermore, if the size of the cartridge filter is to be kept constant, the proportion occupied by the dense layer will be relatively reduced, resulting in a decrease in collection efficiency.

In addition, it is desirable that the porosity of the diffusion layer be in the range of 70 to 95%; if it exceeds 95%, the diffusion effect will be significantly inhibited, and if it is less than 70%, even relatively large particles will not be able to be captured by this layer. Moreover, when pressure is applied, the bulge becomes too large, making it impossible to obtain a cartridge filter with a reproducible shape.

In the present invention, as described above, the diffusion layer and the dense layer must be stacked so that the diffusion layer exists between the dense layers. However, in order to provide a density gradient and further extend the service life, a layer having an average pore diameter between the dense layer and the diffusion layer may be arranged between the dense layer and the diffusion layer.

Further, it is desirable that a diffusion layer be present in the outermost layer so that large particles in the processing liquid are first filtered through the dense layer and do not block the voids in this layer. Note that this outermost layer does not have to be the nonwoven fabric that constitutes the diffusion layer in the present invention; it may be made of any material, such as woven fabric, knitted fabric, paper, nonwoven fabric, or net, as long as it is a filter with a relatively large average pore diameter. It may be formed.

In order to manufacture the cartridge filter of the present invention, for example, the above-mentioned nonwoven fabric forming the dense layer and nonwoven fabric forming the diffusion layer may be cut to a predetermined length, and then alternately wound one layer at a time around a porous tube. . However, for more efficient production, it is preferable to use a method in which a nonwoven fabric forming a dense layer is layered on a long nonwoven fabric forming a diffusion layer, and this is wound around a porous tube. In particular, when it is desired to create a gradient in the dense layer so that the inner layer has a smaller density, the nonwoven fabric for forming the dense layer is placed at predetermined lengths on the long nonwoven fabric forming the diffusion layer. All you have to do is arrange them with different densities and wind them around a perforated cylinder. In addition, when forming a nonwoven fabric layer with an average pore size between these layers between the dense layer and the diffusion layer, the nonwoven fabric forming the intermediate layer between the nonwoven fabric forming the dense layer and the nonwoven fabric forming the diffusion layer. They may be stacked with the two layers sandwiched in between, and then wound around a porous cylinder. Furthermore, a mesh or a net made of plastic or metal may be laminated on these filters together with the above-mentioned non-woven fabric for the purpose of stabilizing the shape or the like.

In some cases, a non-woven fabric may be wound and laminated around a perforated tube. After alternately forming dense layers and diffusion layers, this may be installed in a porous mesh cylinder to form a cartridge filter.

Note that the average pore diameter of the nonwoven fabric in the present invention is determined according to JIS-B
Measured according to the test method for -83569, 10 filtration particle size. However, instead of the light oil used in the above JIS,
JIS-8839 isopropyl alcohol was used. In addition, the nonwoven fabric is measured in sheet form, so the test equipment also has a section for attaching the nonwoven fabric to the upper outlet of a cylindrical container with an air inlet and an air outlet, and isopropyl alcohol can be poured onto the nonwoven fabric. A test was conducted by dropping isopropyl alcohol onto the nonwoven fabric and storing the isopropyl alcohol in the space above the nonwoven fabric when the air flow rate was 50 cc/min. The test measures the air pressure at each air flow rate, draws a graph, and from that graph
A predetermined air pressure was determined by the method shown in IS-B-83569, 10 Test method for filtration particle size, and the average pore diameter was calculated using a calculation formula.

(Example 1) Average fiber diameter 8 μm produced by melt blowing method,
Non-woven fabric with an average pore diameter of 80 μm and a basis weight of 80 g/m2, an average fiber diameter of 15 μm, an average pore diameter of 250 μm, and a thickness of 250 μm.
, and a nonwoven fabric with a basis weight of 30 g/+" are laminated and wound around a porous cylinder made of polypropylene resin so that the latter is on the outside, and a diffusion layer and a dense layer are alternately laminated with an outer diameter of 67 I.
A cartridge filter II was produced.

The collection efficiency and filtration life of the obtained cartridge filter were measured by the following method and are shown in Table 1.

(Tllll Collection Efficiency) Water in which JIS 8 type dust was dispersed was passed through a cartridge filter as a treatment liquid, and the number of 10 μm particles before and after passing through the filter was measured using a particle counter, and the collection efficiency was determined by calculation.

(Filtration life) Pressure loss was measured through a JIS Class 8 dispersion water dispersion filter, and the differential pressure from the initial pressure loss was 1.5 kg/c.
The total amount of filtration processed up to m'' was measured, and this was taken as the filtration life.

(Comparative Example 1) Average fiber diameter 8 μm produced by melt blowing method,
A nonwoven fabric having an average pore diameter of 60 μm and a basis weight of 80 g/a″ was wound around a porous cylinder made of polypropylene resin to produce a cartridge filter having an outer diameter of 67 M and consisting only of a dense layer.

The collection efficiency and filtration life of the obtained cartridge filter were measured and shown in Table 1.

Table 1 Table 1 shows that although Example 1 is a cartridge filter with a diffusion layer interposed, it is superior to Comparative Example 1's cartridge filter consisting of only a wI dense layer in terms of collection efficiency for 10 μm fine particles. There is almost no difference, and it can be seen that nearly 60% more liquid can be processed than in Comparative Example 1 before the filter is replaced.

(Example 2) On a nonwoven fabric with an average fiber diameter of 15 μm, an average pore diameter of 250 μm, a thickness of 250 μm, and a basis weight of 30 g/m to form a diffusion layer, ■ an average fiber diameter of 8 μm, an average pore diameter of 60 μm, and a basis weight of 80 g/m” nonwoven fabric, ■average fiber diameter 10.5 μm,
Non-woven fabric with an average pore diameter of 78 μm and a basis weight of 80 g/m2, ■Average fiber diameter of 11.8 μm, and an average pore diameter of 90. czm, weight 8
Nonwoven fabrics of 0g/i'' are arranged at predetermined lengths and wound around a porous cylinder made of polypropylene resin, with the nonwoven fabric of ■ being the innermost layer, and diffusion layers and dense layers are alternately stacked. and an outer diameter 8 arranged so that the average pore diameter becomes smaller as the dense layer becomes closer to the inside of the cartridge filter.
A 7 m cartridge filter was produced.

The collection efficiency and filtration life of the obtained cartridge filter were measured and shown in Table 2.

(Comparative Example 2) Same as Example 2 except that a polypropylene net with a basis weight of 40 g/e" and a vertical and horizontal pitch of 1.51111 intervals was used instead of the nonwoven fabric for forming the diffusion layer of Example 2. A cartridge filter was produced in the same manner, and the collection efficiency and filtration life of the obtained cartridge filter were measured and shown in Table 2.

(Comparative Example 3) Instead of the nonwoven fabric for forming the diffusion layer of Example 2, an average fiber diameter of 10.5 μm, an average pore diameter of 85 μm, and a thickness of 300 μm were used.
A cartridge filter was produced in the same manner as in Example 2, except that a nonwoven fabric with a basis weight of 30 g/+" was used, and the collection efficiency and filtration life of the obtained cartridge filter were measured and are shown in Table 2. Ta.

Table 2 As is clear from Table 2, the cartridge filter of Example 2 has a longer filtration life even though it exhibits the same collection efficiency as the cartridge filter of Comparative Example 2.3.

[Effects of the Invention] Since the present invention has the above configuration, it has the following effects.

■By placing a diffusion layer between dense layers with high filtration performance, the collection of solids in the dense layer and the diffusion of solids in the diffusion layer are repeated, so solids in the processing liquid are can be efficiently collected down to fine particles.

■Due to the presence of a diffusion layer, liquid flow resistance is low when looking at the cartridge filter as a whole.

■ Solid matter in the processing liquid is diffused in the diffusion layer interposed between the dense layers, so clogging is less likely to occur.

■For this reason, the usable life of the cartridge filter is extended.

■During the manufacture of cartridge filters, the diffusion layer acts as a cushion layer and prevents the dense layer from collapsing.

As described above, the cartridge filter of the present invention is excellent in that it has a high collection efficiency and a long service life despite its low resistance to liquid passage.

Claims (4)

[Claims] (1) In a cartridge filter formed by winding a nonwoven fabric around a porous cylinder to form a multilayer structure, the average fiber diameter is 0.5
A plurality of dense layers made of a nonwoven fabric with an average pore size of ~25 μm and an average pore size of 10 to 300 μm, and a diffusion layer made of a nonwoven fabric whose average pore size is larger than the average pore size of any nonwoven fabric forming the dense layer and 500 μm or less are laminated. A cartridge filter characterized in that the diffusion layer is present between the dense layers. (2) The cartridge filter according to claim 1, wherein the denser layer existing inside the cartridge filter has a smaller average pore diameter. (3) The cartridge filter according to claim 1 or 2, wherein the outermost layer is a diffusion layer. (4) The cartridge filter according to any one of claims 1 to 3, further comprising an intermediate layer having an average pore diameter between the dense layer and the diffusion layer.