JP2000070629A - Heat resistant filter element and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Problem] It is possible to collect dust with high efficiency, and
An object of the present invention is to provide a heat-resistant filter element that can achieve both high heat resistance and rigidity, and a method for manufacturing the same. The heat-resistant filter element is used in a dust collector for separating and collecting particles from dust-containing gas, and contains a thermoplastic polyimide powder as a main component and has a bulk density of 0.55 to 0.5.
A heat-resistant filter element formed by heating and sintering at 60 g / cm ³ to form a coating layer of fluororesin particles on the surface. Each of the thermoplastic polyimide powder particles is pulverized so that a predetermined amount of whiskers are formed, and has a bulk density of 0.55 to 0.55.
It is put into a mold at about 0.60 g / cm ³ and heated and sintered to produce a heat-resistant filter element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust collector for separating and collecting dust from a dust-containing gas, for example, a dust collector for environmental protection in a factory, or a dust contained in exhaust gas from a dryer, a boiler, an incinerator or the like. The present invention relates to a filter element used for a dust collector for collecting dust or a collector for collecting a granular product.

[0002]

2. Description of the Related Art Conventionally, a filter cloth made of braided fibers is sewn in a bag shape as a means for collecting dust generated in a factory or the like or a means for collecting the product when the product is granular. A filter material, that is, a sintered filter element, which is a sintered porous resin material obtained by sintering a synthetic resin powder, that is, a sintered filter element is used.

[0003] Since this bag filter has particularly poor mechanical strength, a so-called sintered filter element in which synthetic resin powder is sintered and made porous so as to be a part of the bag filter has recently been changed. As a sintered filter element, polyethylene, polypropylene and a powder mixture thereof are sintered to form a filter element having a self-standing shape (see Japanese Patent Publication No. 1-5934).
The surface of which is coated with polytetrafluoroethylene particles together with an adhesive (see Japanese Patent Publication No. 39996/1990), and the one in which ultrahigh molecular weight polyethylene particles having a specific particle size and polyolefin-based particles are blended in a specific ratio ( Japanese Patent Publication No. Hei 7-21081) has been proposed.

[0004] However, such a sintered filter element can withstand use at around room temperature without any change in the material. However, at a temperature of 70 to 90 ° C or higher, a change in the material starts to occur. Becomes difficult. Therefore, a filter (see Japanese Patent Application Laid-Open No. 2-277520) is disclosed in which a heat-resistant synthetic resin such as polysulfone or polyethersulfone is sintered. However, also in these, the heat-resistant temperature stops at 160 ° C. Therefore, a polyimide felt having a higher heat resistance (heat resistance temperature 250
C.) and cured, and the surface thereof is coated with polytetrafluoroethylene particles to provide a self-supporting filter (see JP-A-6-285316 and JP-A-7-730). On the other hand, there is a dust collector or an electric dust collector using a ceramic sintered body having a heat resistant temperature exceeding 300 ° C.

[0005]

However, when a bag filter using a heat-resistant filter cloth made of glass fiber or heat-resistant synthetic resin fiber is used, the fold is coarse, so that there is leakage of particles. When backwashing with pulse air to extend the filtration function, there is a problem that the filter cloth is damaged due to friction between the filter cloth and an insert (retainer) for maintaining the shape of the filter cloth. is there. Further, in the heat-resistant polyimide felt filter, the rigidity of the felt itself is low. Therefore, in the case of backwashing with pulsed air as well, a holding material for suppressing the outer side of the band is required for the purpose of suppressing a large swelling and a reduction in the wiping effect. This holding material not only increases the cost, but also can add up to 50% to the weight of the filter element body, and the filter becomes substantially thicker, which is disadvantageous in terms of space in the dust collector. There is a problem that workability such as attachment / detachment of the filter element inside is poor. Further, in a dust collector or an electric dust collector using a ceramic sintered body as a filter material, there is a problem that the ceramic sintered body is originally expensive, and the equipment cost becomes large.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a heat-resistant filter element capable of collecting dust with high efficiency, and having both high heat resistance and rigidity, and a method of manufacturing the same. To provide.

[0007]

According to the present invention, there is provided a heat-resistant filter element used in a dust collector for separating and collecting particles from a dust-containing gas. 0.55-0.
A heat-resistant filter element having a configuration of a communicating porous molded body formed by sintering with heating at 60 g / cm ³ and forming a coating layer of fluororesin particles on the surface. Furthermore, in order to achieve the above object, in the method for producing a heat-resistant filter element, pulverization is performed such that a predetermined amount of whiskers are formed on each powder particle of the thermoplastic polyimide, and the bulk density is 0.55 to 0.60 g. / Cm ³ , which is a method for manufacturing a heat-resistant filter element having a configuration in which it is put into a mold and heated and sintered. The pulverization of the thermoplastic polyimide is preferably performed in multiple stages.

That is, by forming a continuous porous molded body obtained by sintering a thermoplastic polyimide powder as a main component and having a bulk density of 0.55 to 0.60 g / cm ³ , a non-thermoplastic general polyimide felt can be obtained. In contrast, if the size is the same, heat resistance and service life are as good as it is, and the weight is about half, and it is extremely light and has a hard wall, so no external holding material is required, and a compact element is obtained. Space is also improved.

Then, as a method for producing the same, as described above, pulverization is performed so that a predetermined amount of whiskers are formed in each powder particle of the thermoplastic polyimide. Thereby, a moderate bulk density of 0.55 to 0.60 g / cm ³ can be obtained. The bulk density does not change before and after sintering.
When pulverizing the thermoplastic polyimide in the present invention, the thermoplastic polyimide generally supplied as pellets having a size of several mm is subjected to a pulverizer. As this crusher,
A shearing method in which the rotating blade attached to the rotor and a fixed blade arranged in the outer peripheral portion are crushed by a shearing force, a hammer method in which a hammer is hit at a high speed, or a disk which relatively rotates the material (one rotates, the other rotates) Fixed), and crushing between narrow disks, so-called mortar method. Any type of pulverizer may be used, but a mill type is preferable in terms of pulverization efficiency. Further, in order to prevent the formation of the shape of the pulverized material, particularly an excessive beard, it is desirable to pulverize in multiple stages, for example, the first stage is a shearing system and the second stage is a milling system.

The crushed material thus obtained is filled in a mold for a filter element while applying vibration, and then the mold is placed in a heating furnace and fired. Then, sufficient cooling is performed. After that, since a large number of large pores are present in the surface opening portion, if these are used as they are, especially in the case of fine dust, so-called voids occur, and do not serve as a filter. Therefore, by coating the surface of the element base material formed by sintering with fluororesin particles having a particle size smaller than the pores opened on the surface of the element base material,
The pore diameter is reduced.

The particle size of the thermoplastic polyimide powder is 50 to 5
00 μm is preferred. More preferably 100-300μ
m. When the particle size is 50 μm or less, the size of the communication hole becomes too fine, and the pressure loss increases, so that a large amount of blowing power is required to obtain a predetermined processing air volume,
Not preferred. On the other hand, if it is 500 μm or more, a large void is formed in the communication hole, so that dust passes through the filter element, that is, a so-called through hole occurs. Further, the strength of the sintered body is undesirably reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a heat resistant filter element according to an embodiment of the present invention and a method for manufacturing the same will be described in detail. FIG. 1 is a perspective view showing the structure of a heat resistant filter element according to one embodiment of the present invention. As can be seen from the cross section 8d, a hollow chamber 8a is formed. They are furthermore cylindrical with a bottom. The cross section of the dust adhering surface 8b has a corrugated or bellows shape, and is set so that the adhering surface area is as large as possible. As a material, a thermoplastic polyimide is mainly used, and the bulk density is 0.1%.
The element base material is formed by heating and sintering at 55 to 0.60 g / cm ³ , and the surface is coated with fluororesin particles having a particle size smaller than the pores opened on the surface of the element base material. .

Next, the manufacturing process will be described. Generally, the thermoplastic polyimide is supplied as pellets having a size of several mm, and the thermoplastic polyimide pellets are crushed by a pulverizer so that the average particle size becomes 150 μm. At this time, the crushing gap of the mill-type pulverizer is adjusted, and a thermoplastic polyimide having an average particle size of about 500 μm is obtained as the first-stage pulverization. At this time, the individual particles of the thermoplastic polyimide powder have a very large number of whiskers and various lengths, and in this state, the bulk density is low, and the bulk density of the filter of the present invention is 0.55 to 0.5. 60 g / cm ³ cannot be realized. Then, as the second stage of pulverization, the average particle size is 1
The crushing gap is set so as to be 50 μm to obtain a target thermoplastic polyimide powder. At this time, in the individual particles of the thermoplastic polyimide powder, the whiskers have a bulk density of 0.55 to 0.55.
0.60 g / cm ³ can be realized. Note that the number of pulverizing stages is not limited to two, and the number of stages can be appropriately set.

The crushed material thus obtained is filled into a mold for a filter element having the shape shown in FIG. 1 while applying vibration, and then the mold is placed in a heating furnace and fired. At this time, the sintering conditions in the heating furnace are such that the melting point of the thermoplastic polyimide is around 380 ° C., so that the temperature of the heating furnace is preferably in the range of 380 to 430 ° C. The firing time is preferably in the range of 30 minutes to 3 hours after the temperature of the mold reaches 380 ° C. If the mold temperature is 380 ° C or less, or the time after the mold temperature reaches 380 ° C is 30 minutes or less, the fusion of the thermoplastic polyimide powders is insufficient, and the strength of the sintered body is reduced. Low temperature and 430 ℃
Above, or when the time after the temperature of the heating furnace reaches 380 ° C. is 3 hours or more, the particles of the thermoplastic polyimide are excessively fused together, and the size of the communication hole is reduced,
Pressure loss increases.

Further, since the crystallization speed of thermoplastic polyimide is extremely slow, crystallization does not proceed when quenched after sintering, resulting in an amorphous product. The amorphous product has an elastic modulus and chemical resistance that are lower than those of the crystalline product. It is not preferable because it is inferior. Therefore, the cooling condition of the communicating porous body is preferably gradually cooled as follows. That is, the time required for cooling to 200 ° C. is preferably in the range of 30 minutes to 2 hours. If the time is less than 30 minutes, the crystallization does not proceed, and if the time is more than 2 hours, the production efficiency decreases. When the porous compact is taken out of the mold after sintering, the temperature of the sintered compact is preferably 100 ° C. or lower.

The surface of the porous molded body as the filter element thus obtained has a diameter of 40 to 100 μm.
Larger ones have pores of 400 μm or more. Therefore, skipping occurs as it is. Therefore, by forming a surface coating layer, the size of the continuous ventilation hole is reduced. That is, by forming the coating layer, the average pore diameter is 5 to 10 μm. The coating layer is formed by spray-coating a suspension obtained by mixing polytetrafluoroethylene particles, a thermosetting resin and water as an adhesive on the surface of the molded body, and heating and curing the suspension. Low molecular weight polytetrafluoroethylene is used for the polytetrafluoroethylene particles, and the average diameter is preferably in the range of 3 to 10 μm.

FIG. 2 is a partial vertical sectional view of a dust collecting apparatus using the heat resistant filter element according to the present invention. The trapping device 1 has a sealed casing 2 having a substantially rectangular shape, and the inside thereof is divided into a trapping chamber 4 at a lower part and a clean air chamber 5 at an upper part by an upper top plate 3 which is a partition wall. . In addition, a supply port 6 for dust-containing air communicating with the lower collecting chamber 4 is provided in the middle of the casing 2. A clean air outlet 7 communicating with the clean air chamber 5 is provided at an upper portion of the casing 2.
Is provided. A plurality of hollow flat filter elements 8, which are one form of the sintered body filter of the present invention, are attached to the lower surface of the upper top plate 3 at predetermined intervals. The filter element 8 has a large-diameter portion 9 formed at the upper end, and the large-diameter portion 9 is attached to the upper top plate 3 by a fastening bolt 11.

The dust-containing air supplied from the supply port 6 into the collection chamber 4 of the casing 2 flows through the filter element 8 formed in the hollow, and flows inward. At this time, the dust adheres and accumulates on the surface of the filter element 8 and is collected, and the clean air flowing inside the filter element 8 enters the clean air chamber 5 in the upper part of the casing 2 and passes through a discharge port 7 through a predetermined outlet. Guided to the place. The injection pipe 13 is used at the time of backwashing in which an airflow opposite to a normal airflow is instantaneously injected into the filter element 8, and the dust or the like adhering and accumulating on the surface of the filter element 8 is deposited on the tray 15. It has a function to remove it.

Example A thermoplastic polyimide pellet (PL-450, manufactured by Mitsui Chemicals, Inc.) having an average particle size of 15
Pulverization was performed using a two-stage mortar type pulverizer so that the thickness became 0 μm. The pulverized material obtained in this manner is put into a mold (outer diameter: 1050 × 960 × 60 mm, thickness: 3 mm,
(Cross-sectional shape: corrugated) while applying vibration, then put this mold into a superheated furnace, and raise the temperature of the furnace to 395 ° C. over 1 hour.
Temperature. The same temperature was maintained for 2 hours to perform sintering. Next, with the mold in the superheater,
After cooling to 00 ° C., the mold was taken out of the furnace, and the mold was forcibly cooled with a fan. After 10 minutes, the sintered body was taken out of the mold.

Next, polytetrafluoroethylene powder 2
A suspension in which 4% by weight of a thermosetting adhesive, 3% by weight of a thermosetting adhesive, 3% by weight of methanol and 70% by weight of water are well mixed is applied to the surface of the sintered body by a spray method, and then dried at 180 ° C. for 20 minutes using a drier. Cured the coating layer. The obtained filter element has a compact shape with a total thickness of 40 mm and a very light weight of 18 kg. Attach this filter element to the load tester,
A load test was performed based on the configuration of FIG. 2 under the following acceleration conditions.

* Load test conditions: Temperature: 230 ° C. Wind speed: 1 m / min Pulse condition: pressure 4.5 kgf / cm ² , time 0.2 seconds, interval 12 seconds (normally 120 seconds, 10-fold acceleration) Powder: Tankal (325 mesh) Zentsu), concentration 5 g / m ² * continuous 1200 hours (50 days) continued after the test results: pressure loss: 180MmAq (typically filtered under equivalent) (the inlet of the filter element, measured by manometer pressure difference at the outlet) quantity of dust : 0.005 g / m ² N or less (equivalent to ordinary filtration). (Measured with a digital dust meter (manufactured by Shibata Scientific Instruments)) No damage was found on the filter element. Since the pulse interval condition is 12 seconds, which is 10 times faster than usual,
It can be confirmed that the battery has a life of 2000 hours (about 1 year and 5 months) or more.

[0022]

According to the heat-resistant filter element and the method of manufacturing the same of the present invention, there is no leakage of the filtration particles and the rigidity can be increased as in the case of a general filter element using polyimide. In this case, the holding material is not required without swelling greatly. Therefore, it is light in weight and small in size, and the workability of mounting and removing the filter element in the dust collector is improved. Therefore, dust can be collected with high efficiency, and high heat resistance and rigidity can be achieved at the same time.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of a heat resistant filter element according to an embodiment of the present invention.

FIG. 2 is a partial longitudinal sectional view of a powder separation device using the heat-resistant filter element according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Collection device 2 Casing 3 Upper top plate (partition wall) 4 Collection room 5 Clean air room 8 Sintered filter element 9 Large diameter part 13 Injection pipe 14 Injection nozzle

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4D019 AA01 BA13 BB06 BC12 BC20 BD01 BD03 BD10 CA04 CB04 CB06 CB09 4D058 JA04 JA06 JB14 JB21 JB36 KA01 KA13 KB05 MA15 MA17 MA25 RA02

Claims (4)

[Claims] 1. A heat-resistant filter element for use in a dust collector for separating and collecting particles from a dust-containing gas, comprising a thermoplastic polyimide powder as a main component and a bulk density of 0.1%.
A heat-resistant filter element, which is a continuous porous molded body formed by heating and sintering at 55 to 0.60 g / cm ³ to form a coating layer of fluororesin particles on the surface. 2. The thermoplastic polyimide powder has a particle size of 50 to 50.
The heat-resistant filter element according to claim 1, wherein the filter element has a thickness of 500 µm. 3. The method for producing a heat-resistant filter element according to claim 1, wherein each of the thermoplastic polyimide powder particles is pulverized so that a predetermined amount of whiskers is formed, and has a bulk density of 0.55 to 0. A method for producing a heat-resistant filter element, wherein the heat-resistant filter element is charged into a mold at about 60 g / cm ³ and heated and sintered. 4. The method according to claim 3, wherein the pulverization of the thermoplastic polyimide is performed in another stage.