JPH0994418A - Filter element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the mixing property of skeleton particles with binder particles at the time of preparing raw material and to eliminate the ununiformity of mechanical strength by mixing superhigh molecular weight polyethylene particles and polyethylene-based resin particles pulverized by shearing system and sintering them by heating to form a filter element. SOLUTION: This filter element used for a dust collector for separating and collecting particles from a dust-containing gas is produced by charging a particle (skeleton particle) composed of a porous structural hardly fluidizing resin and a particle (binder particle) composed of an easily fluidizing resin for binding the skeleton particles with each other in a molding die and heating. In such a case, the superhigh molecular weight polyethylene particles and the polyethylene-based resin particle are mixed with each other and sintered by heating to form the prescribed filter element, and as the polyethylene-based resin particles, at least particles pulverized by shearing system is used. Also, a coating layer containing fluorocarbon resin particles is preferably formed on the surface of the 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 that separates and collects particles from dust-containing gas, such as a dust collector or dryer for collecting powdery or granular products in a factory and environmental protection, a boiler, an incinerator, etc. The present invention relates to a filter element used in a dust collector for collecting dust contained in exhaust gas.

[0002]

2. Description of the Related Art Conventionally, a filter cloth made of fibers is sewn into a bag shape as a means for collecting dust generated in factories or the like and a means for collecting the product when the product is a granular material. The above-mentioned bag filter and a filter material, that is, a filter element, which is made by sintering a synthetic resin powder to form a communicating porous plate, are used. However, the bag filter tends to swell the fibers due to moisture in the case of dry filtration treatment and lowers the filtration efficiency, and in order to prevent this, it is necessary to highly dry the treatment fluid, which increases the treatment cost. Also,
Backwashing with pulsed air is regularly performed to remove particles accumulated on the surface of the filter cloth, but at that time, the particles are likely to be unevenly washed off, which easily causes partial clogging and increases the pressure loss increase rate. Is early. Further filtration,
Repeated backwashing makes the filter cloth tired and easily damaged. Further, in the case of wet filtration treatment, the accumulated particles on the surface of the filter cloth are removed by a scraper, but this causes the filter cloth to be worn and cannot be used for a long period of time.

As described above, since the bag filter is particularly inferior in mechanical strength, in recent years, a so-called sintered type filter element in which synthetic resin powder is sintered to form a continuous porous structure is a part of the bag filter. Is changing for. As the sintered filter element, a filter element having a self-supporting shape is obtained by sintering polyethylene, polypropylene, or a mixed powder thereof (Japanese Patent Publication No. 1-5934).
Japanese Laid-Open Patent Publication No. HEI-2003), whose surface is coated with polytetrafluoroethylene particles together with an adhesive (Japanese Patent Publication No. 2-3).
9926), a mixture of ultra-high molecular weight polyethylene having a specific particle size and a polyolefin resin in a specific ratio (Japanese Patent Publication No. 7-21081) and the like have been proposed.

[0004]

The sintered type filter element is composed of a non-flowing resin (hereinafter
Particles composed of particles (hereinafter referred to as skeleton resin) (hereinafter referred to as skeletal particles) and particles composed of free-flowing resin (hereinafter referred to as binder resin) for binding the skeletal particles (hereinafter referred to as binder resin)
It is manufactured by filling mixed particles with a binder particle) into a molding die and heating to a melting point of both resins or higher. However, since the obtained filter element has a porous structure, its tensile strength is usually considerably lower than the original value of the skeletal resin. Therefore, in order to improve the strength, it can be dealt with by increasing the particle size of the skeleton particles and the binder particles as small as possible (for example, 500 μm or less) and increasing the packing density. On the other hand, the sintered filter element obtained is The ventilation resistance increases, the filtration efficiency decreases, and the weight increases, which is disadvantageous in terms of economy and workability at the time of mounting or replacement.

The skeleton particles and binder particles used as raw materials are resin wastes (for example, processing scraps and mill ends generated at the time of molding or cutting, from the viewpoints of cost, environmental protection and resources). It is advantageous to crush and recycle existing molded products. However, this time, according to the study by the present inventors, due to the difference in the pulverization method of resin waste,
It has been found that differences occur in the mechanical strength of the resulting sintered filter elements. The reason for this is not clear, but it is thought to be due to the following. That is, FIG. 2 shows particles obtained by pulverizing by a so-called mortar method, in which a polyethylene resin is introduced between plates that rotate relatively (one is rotating and the other is fixed) and the plates are crushed between the plates with a narrow gap. Fig. 3 is an optical microscope photograph of particles obtained by crushing the same resin at high speed with a hammer, a so-called hammer method. Is rough, and many whiskers are seen on the surface. When such particles having poor surface properties are mixed with other particles, whiskers are entangled with each other and particles having poor surface properties are easily aggregated, and it is difficult to form a uniform mixture. Particularly in a sintered filter element, it is advantageous in terms of mechanical strength that binder particles are evenly distributed between skeletal particles, but when the surface properties of the binder particles are poor, the binder particles are unevenly distributed. As a result of melting, the resulting filter element has uneven mechanical strength.

The present invention was made based on the above findings, and an object of the present invention is to provide a sintered filter element having excellent mechanical strength at low cost by recycling resin waste which is advantageous in terms of cost. It is what

[0007]

The above object is a filter element of the present invention, which comprises mixing ultra-high molecular weight polyethylene particles and polyethylene resin particles and heating and sintering the mixture, wherein at least the polyethylene resin is used. Achieved by a filter element characterized in that the particles are particles ground by a shearing method. A coating layer containing fluororesin particles is provided on the surface of the filter element. A similar object is a method for producing a filter element of the present invention, which comprises mixing ultra-high molecular weight polyethylene particles and polyethylene resin particles, filling the mold, and heating and sintering the mixture, wherein at least the polyethylene resin is used. It can also be achieved by a method for producing a filter element, characterized in that the particles are particles obtained by crushing a resin block made of the polyethylene resin by a shearing method.

[0008]

The present invention is characterized in that at the time of procuring the raw material of the sintered filter element, at least the binder particles are particles crushed by the shearing method.
Particles by this shearing method are particles having excellent surface properties with few whiskers like those found in particles obtained by a mortar method or a hammer method, and therefore, the mixing property of skeleton particles and binder particles at the time of raw material preparation And the obtained filter element is also stable with no unevenness in mechanical strength.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The filter element according to the present invention will be described in detail below. The skeletal resin constituting the filter element of the present invention is ultra high molecular weight polyethylene. The molecular weight and particle size of this ultra-high molecular weight polyethylene are not particularly limited, and may be the same as the molecular weight and particle size of the ultra-high molecular weight polyethylene conventionally used in sintered filter elements. It is preferably a numerical value. Regarding the molecular weight, 135
C. Decalin has an intrinsic viscosity [η] of 5 to 50 dl /
g, preferably 8 to 40 dl / g, and converted to a viscosity average molecular weight of 500,000 to 12,000,000, preferably 9
It is from 0 to 9 million. Here, if [η] is 5 dl / g or less, a large number of clogging parts are generated in the sintered body that is the filter element, and the ventilation resistance becomes high, which is not preferable. If [η] is 50 dl / g or more, the tensile strength of the filter element is lowered, which is not preferable. The average particle size is 250 to 750 μm, preferably 300 to 70.
The range is 0 μm. If the average particle size is 750 μm or more, the tensile strength of the filter element decreases and
If it is 0 μm or less, the clogging portion increases and the ventilation resistance increases.

The above-mentioned ultra high molecular weight polyethylene is obtained by homopolymerization of ethylene using a Ziegler catalyst or the like or by copolymerizing ethylene and α-olefin, and is available as a powder from the market, but it has been used. The molded product can also be used after being crushed to have the above average particle size. In the present invention, recycled products can be preferably used from the viewpoints of cost, environmental protection, and resource saving. That is,
Processing scraps generated when forming with a processing machine such as a press machine,
Alternatively, it is possible to mechanically pulverize a scrap material generated when the molded product is cut and a so-called resin waste such as a used molded product into a predetermined particle size before use. Upon crushing, no significant difference in surface properties of particles due to difference in crushing method is observed, and any of a mortar method, a hammer method, and a shearing method described later can be adopted. However, according to the present inventor, it has been confirmed that whiskers like the shearing method, the hammer method, and the mortar method tend to easily occur as described above, and higher surface properties are required. In this case, the shearing method is suitable.

The filter element of the present invention is constructed by binding the skeletal particles made of the above-mentioned ultra high molecular weight polyethylene with a binder resin made of a polyethylene resin. In the present invention, the resin waste made of polyethylene resin is crushed and used as the binder resin,
It is characterized in that the crushing is performed by a shearing method. The crushing by the shearing method is performed using, for example, a crusher [mesh mill manufactured by Horai Co., Ltd.] shown in FIG. The crusher 1
Fixed blades 3 symmetrically arranged on the upper inclined portion of the main body 2,
A plurality of blades 4 corresponding to the fixed blade 3 are provided on the rotor 5,
A rotary blade 6 fixed radially, and a screen 7 arranged with the fixed blade 3 at both ends so as to surround the rotary blade 6.
And the resin waste is introduced from the upper opening 11 of the main body 2. The input resin waste is finely cut by the rotary blade 6 and the fixed blade 3, and only particles having a diameter smaller than the opening hole of the screen 7 fall on the wall surface of the screen receiver 8,
It is collected in the collection container 10 through the opening 9. By selecting the diameter of the open hole of the screen 7, crushed particles having a desired particle size can be obtained. The resin particles crushed by the shearing method as described above have excellent surface properties with few whiskers and the like on the surface, as shown in an optical micrograph in FIG.

In the present invention, the raw material of the polyethylene resin is resin waste, and its resin composition and polymerization method are not particularly limited, but the following are more preferable in consideration of the characteristics of the obtained filter element. desirable. The polyethylene resin used for the sintered filter element is practically MFR (melt flow rate, ASTM
According to D1238-65T 190 ° C, 2.16kg
(Under load) 0.01 to 30 g / 10 min, preferably 0.1 to 10 g / 10 min, converted to an intrinsic viscosity [η] of 1.0 to 4 dl / g, preferably 1.2 to 3 dl
It is said that it is preferably in the range of / g, and it is more desirable that the ethylene copolymer of the present invention also satisfies these values. Regarding the resin composition, in addition to ethylene homopolymer, copolymers with ethylene and a comonomer copolymerizable with ethylene can be widely used. Suitable comonomers include C3-C8 α-olefins such as propylene, butene-1,4-methylpentene-1, hexene-
1, octene-1 and the like, and the content thereof is preferably 20 mol% or less, more preferably 15 mol% or less. Further, an ethylene-vinyl ester copolymer, an ethylene-acrylic acid ester copolymer and the like can be preferably used, and in this case, the comonomer concentration is preferably 20% by weight or less, more preferably 10% by weight or less. In any of the resins, when the comonomer concentration exceeds 20% by weight, the clogging portion increases and the ventilation resistance tends to increase. High-density polyethylene is preferable in terms of strength, but low-density polyethylene or medium-density polyethylene may be used. Further, blended polymers of these may be used. Further, it is preferable that the particle size of the pulverized ethylene copolymer is the same as the particle size of the skeleton particles made of the ultra-high molecular weight polyethylene from the viewpoint of the mixing property when the both are mixed. That is, the average particle size is 250 to 750 μm, preferably 3
The range of 00 to 700 μm is preferable. Average particle size is 25
When it is 0 μm or less, the clogging part increases and the ventilation resistance increases, and when it is 750 μm or more, the tensile strength decreases, which is not preferable.

In the filter element according to the present invention, the ultra high molecular weight polyethylene particles and the ethylene copolymer particles are mixed and filled in a mold, and heated and sintered at a temperature equal to or higher than the melting points of both polyethylene particles. Can be obtained at. The mixing ratio of both resins is preferably in the range of 25/75 to 55/45 (wt%) of the ultra high molecular weight polyethylene resin and the polyethylene resin, and more preferably 30/70 to 50/50. If the ultra high molecular weight polyethylene resin is less than 25% by weight, the filter element to be obtained is partially clogged to increase the ventilation resistance, while if the ultra high molecular weight polyethylene resin is more than 55% by weight, the tensile strength is increased. Is low,
In either case, it is not practically preferable.

At the time of production, the method of mixing both particles, the method of filling in a mold, the method of heating, and the like are not particularly limited, and are in accordance with the production conditions of a general sintered type filter element made of polyethylene resin. be able to. For example, by applying vibration to the mold when filling the mold with the mixed particles, the entire mold can be uniformly filled with a high filling rate. Regarding heating, the mold may be placed in an electric dryer, an electric heating furnace, or the like, or may be heated from the outside by circulating a heat medium between the heat source and the mold. The heating condition is a dryer. The temperature is in the range of approximately 150 to 250 ° C., and the time is in the range of 30 minutes to 4 hours, although it is not generally regulated due to differences in the heating furnace structure. Generally, if the temperature is too high or the time is too long, the clogging part increases and the ventilation resistance increases, and if the temperature is too low or the time is too short, the sintering becomes insufficient and the tensile strength tends to decrease. It is in. Further, the shape of the obtained filter element is not particularly limited, and can be a shape according to the place of use or the purpose.

The filter element according to the present invention is obtained by sintering as described above, but has relatively large pores inside. Such pores are not particularly limited to the filter element of the present invention, but are commonly found in sintered filter elements. Therefore, particles smaller than the size of the pores are filled in the filter element surface to form a coating layer. The coating layer is a slurry liquid in which fluororesin particles and an adhesive are dispersed in a solvent, is applied to the filter element surface after sintering by a coating means such as a spray or a brush so as to have a predetermined film thickness,
It is obtained by curing the adhesive. The fluororesin particles are, for example, polytetrafluoroethylene, hexafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, ethylene / tetrafluoroethylene copolymer. Average particle size 3 consisting of polymer, ethylene / chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, etc.
It is a particle of 10 μm. The adhesive is preferably an adhesive made of vinyl resin, phenol resin, melamine resin, resorcinol resin, or the like. In addition to alcohols, water can be preferably used as the solvent. Although the thickness of the coating layer is arbitrary, it is practically several tens μm to several hundreds μm,
It is preferably 50 to 150 μm.

[0016]

EXAMPLES The present invention can be clarified based on the following examples.

[Skeletal Resin Particles A to F] Block-shaped mill ends made of ultra-high molecular weight polyethylene having an intrinsic viscosity ([η] = 16) are crushed by a shearing type crusher [manufactured by Horai Co., Ltd.] and various Skeleton resin particles A to C having different average particle diameters were obtained using a size screen. The skeleton resin particles A have an average particle size of 320 μm, and the skeleton resin particles A have a particle size of
80 μm, C is 640 μm. Similarly, a block-shaped end material made of ultra-high molecular weight polyethylene having an intrinsic viscosity ([η] = 13.2) was crushed by a shearing method to obtain a skeleton resin particle D having an average particle diameter of 360 μm. In addition, a block-shaped end material made of ultra-high molecular weight polyethylene having an intrinsic viscosity ([η] = 16) was crushed by a hammer method [manufactured by Fuji Electric].
Skeletal resin particles E having an average particle diameter of 300 μm
I got Further, polymerized ultrahigh molecular weight polyethylene powder [HF1900 manufactured by Highmont Co., Ltd.] having an average particle diameter of 230 μm was used as a skeleton resin particle F.

Binder particles a to g Regenerated pellets of high density polyethylene (MFR =
0.3) was crushed by a shearing type crusher (manufactured by Horai Co., Ltd.), and binder particles a to c having different average particle sizes were obtained using screens of various sizes. The binder particles a have an average particle size of 350 μm, and the particles b have an average particle size of 470 μm.
The same c is 540 μm. Similarly, by the shearing method, MF
A waste block made of high-density polyethylene with R of 0.05 was crushed to obtain binder particles d having an average particle diameter of 340 μm.
And a waste block made of high-density polyethylene having an MFR of 0.05 was crushed to obtain binder particles e having an average particle size of 400 μm. Also, regenerated pellets (MFR = 0.08) made of high-density polyethylene were crushed by a mortar type crusher [manufactured by Turbo Kogyo] to have an average particle size of 300 μm.
Binder particles f of were obtained. Furthermore, regenerated pellets (MFR = 0.3) made of high-density polyethylene were crushed by a hammer-type crusher (manufactured by Fuji Electric Co., Ltd.) to obtain an average particle size of 4
Binder particles g of 10 μm were obtained.

The above resin particles were mixed in the proportions shown in Table 1, and then the mixture was put into a mold (outer diameter: 1050 × 960 ×).
60, thickness: 3 mm, cross-sectional shape: fir tree shape) was filled while vibrating, and this mold was placed in a heating furnace adjusted to 230 ° C. for 2.5 hours for sintering. Then, the filter element was taken out from the heating furnace, air-cooled by a fan, and then the molded filter element was taken out from the mold. Then, a suspension solution of 12 parts by weight of polytetrafluoroethylene, 1 part by weight of vinyl acetate-vinyl chloride-ethylene copolymer and 14 parts by weight of water was applied onto the surface of the obtained filter element by spraying and cured at room temperature. Let

The weight of the filter element thus obtained and the pressure loss when the wind speed was 1 m / min, and the length from the filter element was 100 mm and the width was 10
mm test pieces were cut out and the tensile strength was measured. The measurement conforms to JIS K7113, Strograph R-2
Using [Toyo Seiki Co., Ltd.], pulling speed 20 mm /
Min, and the distance between chucks was 80 mm. The measurement results are shown in Table 1.

[0021]

[Table 1]

It can be seen from Table 1 that the filter element according to the present invention has a small pressure loss as a whole and is particularly excellent in mechanical strength.

[0023]

As described above, the present invention is characterized in that at the time of procuring the raw material of the sintered type filter element, at least the particles crushed by the shearing method are used as the binder particles. Particles by this shearing method are particles having excellent surface properties with few whiskers like those found in particles obtained by a mortar method or a hammer method, and therefore, the mixing property of skeleton particles and binder particles at the time of raw material preparation And the obtained filter element is also stable with no unevenness in mechanical strength. In addition, it is significant from the viewpoint of recycling resin waste and is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a schematic view showing a shearing type crusher.

FIG. 2 is an optical micrograph (25 times) of an example of polyethylene-based resin particles (binder particles f prepared in the example) obtained by pulverizing with a mortar type pulverizer.

FIG. 3 is an optical micrograph (25 ×) of an example of the polyethylene resin (binder particles g prepared in the example) obtained by pulverizing with a hammer type pulverizer.

FIG. 4 is an optical micrograph (25 times) of an example of polyethylene-based resin particles (binder particles a prepared in the example) obtained by crushing with a shearing type crusher.

[Explanation of symbols]

 1 Crusher 2 Main body 3 Fixed blade 4 Blade 5 Rotor 6 Rotating blade 7 Screen 8 Screen receiver 9 Opening 10 Recovery container 11 Upper opening

Claims (3)

[Claims] 1. A filter element obtained by mixing ultra-high molecular weight polyethylene particles and polyethylene resin particles and heating and sintering, wherein at least the polyethylene resin particles are particles crushed by a shearing method. The characteristic filter element. 2. The filter element according to claim 1, wherein a film containing fluororesin particles is formed on the surface of the filter element. 3. A method for producing a filter element, which comprises mixing ultra-high molecular weight polyethylene particles and polyethylene resin particles, filling the mixture in a mold, and heating and sintering the mixture, wherein at least the polyethylene resin particles are mixed with polyethylene. A method for producing a filter element, which comprises crushing a resin block made of a system resin by a shearing method to obtain particles.