JPS6356810B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the construction of an electret filter element that can obtain a high dust removal rate with low pressure loss by converting the synthetic fiber used as the filter element's constituent material into an electret. The mainstream of conventional car filter elements is a fiber layer in which the fiber denier is varied in the thickness direction and a density gradient is imparted by varying the amount of resin deposited. This type of car filter element is due to the spinning limit when forming a web using a card machine.
Currently, it is not possible to spin fibers of less than 1 denier, so even if the upper limit of density is determined by pressing, the pore size will not fall below 50 microns at most, and the dust removal rate is inferior to that of the wet type. In addition, wet type and paper filter elements cannot make the density gradient or pores coarse, and even if the dust removal rate is good, they have the disadvantage that the dust retention capacity is significantly inferior to that of dry type nonwoven filter elements. The present invention provides a new car filter element that solves the above contradictory problems. In other words, by converting the dry non-woven car filter element, which cannot reduce the pore size formed between the fibers, to an electret, electrical cohesive force is added, and the dust removal is better than that of the conventional wet filter element or paper filter element. This is an electret filter element that improves the efficiency without increasing pressure loss. Next, to explain the electrification of the nonwoven filter element made of synthetic fibers according to the structure of the present invention, the synthetic fiber layers have a blending ratio of low melting point polyester fibers that are easily electrified from the upstream layer to the downstream layer. Or add a nonwoven fiber layer that has been mechanically bonded in advance to 150 to 180℃.
In that state, the gap is within 5 mm, and the voltage is
Process at 10KV for approximately 5 minutes. The smaller the gap, the longer the time, or the higher the humidity of the nonwoven fiber layer, the easier it is to become electret. In the case of synthetic resins and synthetic fibers, the lower the melting point, the more easily intermolecular activation occurs and the easier it is to become electret. The present invention effectively utilizes the characteristics of the synthetic fibers mentioned above,
By increasing the blending ratio of low melting point polyester fibers that are easy to electret from the upstream layer to the downstream layer, increasing the density due to the compression of the low melting point polyester fibers by heat pressurization, and reducing the gap by further reducing the fineness. It was possible to form a car filter element with a pressure loss equal to or higher than that of conventional products and a dust removal rate higher than that of wet nonwoven fabric or paper. In addition, internal combustion engines are extremely sensitive to moisture, and conventionally, filters used for such purposes have been subjected to some kind of post-treatment such as water-repellent treatment or oil-impregnating treatment because water-absorbing rayon is used in their manufacture. In the present invention, the constituent fibers are made of polyester synthetic fibers with poor hygroscopicity, and since they do not contain adhesives, the water content is extremely low, making them ideal as car filter elements that do not require water repellent treatment. Become something. Next, one embodiment of the present invention will be described in detail with reference to the drawings. High melting point polyester fiber 13de'×51mm80% with mp=250~260℃ as upper layer, mp=200~230℃
polyester fiber 23de′×51mm10%, mp=
150~180℃ low melting point polyester fiber 33de'×51
A card web with a basis weight of 80 g/m ² was formed using fibers mixed with mm10%, and mp =
250~260℃ high melting point polyester fiber 12de'×51
mm40%, mp=200~230℃ polyester fiber 2
A carded web with a basis weight of 100 g/m ² was formed using a fiber mixture of 40% of 2de'×51mm and 20% of low melting point polyester fibers of 33de'×51mm and mp=150 to 180°C.
Furthermore, as a downstream layer, high melting point polyester fiber 10.5 de' x 51 mm 10% with mp = 250 ~ 260 °C, mp = 200 ~
230℃ polyester fiber 20.5de′×51mm60%,
mp=150~180℃ low melting point polyester fiber 3
Fabric weight: 100 using mixed fiber with 3de′×51mm30%
A card web of g/m ² is formed. Figure 1 shows an enlarged view of a part of the carded web formed in this way, 1 is a high melting point polyester fiber with a melting point of 250 to 260°C, 2 is a polyester fiber with a melting point of 200 to 230°C, and 3 is a polyester fiber with a melting point of 150°C. It is a low melting point polyester fiber of ~180℃. Next, the card webs with each of the above compositions were laminated and needle punched from the downstream side at a number of punches of 40 p/cm ² and a punch depth of 12 mm. Heat treatment is performed in a dryer adjusted to a temperature of 150℃ that can control the temperature, and the MP is 150~150℃.
Melt 3 surfaces of low melting point polyester fibers at 180℃,
The constituent fibers are bonded and fixed together and pressed to a thickness of 2 mm using a punching plate. Next, an electret treatment is performed for 5 minutes at a gap of 3 mm and a voltage of 10 KV to form an electret filter element. The thickness of the electric car filter element of the present invention can be adjusted within the range of 0.5 to 3 mm. In addition, polyester synthetic fibers are used as the constituent fibers, and the blending ratio between the upstream layer, middle layer, and downstream layer of the low melting point polyester fiber B used as the electrified fiber is 1:1:
It is preferable to mix in the range of 2 to 1:8:12. Furthermore, the downstream layer can be made more electrified by increasing the blending ratio and turning it into a molten resin.
In addition, as the electrified fiber, it is also possible to use other fibers such as polypropylene, polyvinyl chloride polyethylene, etc. alone or in combination.
In addition to the cross web, a random web may be used. The present invention is constructed as described above, and in its practical test, the supplied dust is first collected by a sieving method in the upstream layer, and then is collected in the intermediate layer and the upstream layer. The fine dust that was not collected by conventional dry non-woven car filter elements is collected by the sieving method and the electretted electrostatic cohesive force in the downstream layer. Complete collection is achieved through force and densification. As mentioned above, the polyester synthetic fiber is changed physically and chemically in stages from the upstream layer to the downstream layer, and dust is collected uniformly in each layer, making it the most important property for car filters after dust removal rate. We were able to complete a revolutionary car filter element that significantly increases the dust retention capacity and is maintenance-free for 100,000 km. Next, a performance comparison test with a conventional car filter element was conducted, and the results obtained are shown in FIG. In the figure, a shows an electret car filter element according to the present invention, b shows a dry non-woven fabric car filter element, c shows a paper car filter element, and d shows a paper car filter element impregnated with a water repellent and adsorbent. It is an element. After standardizing the initial pressure loss of each of the above filter materials to around 40 mmH ₂ O at 1 m/sec (the oil-impregnated type is the one before impregnation), they were molded in a zigzag shape so that the effective overarea was 2500 cm ² . Filter surface wind speed 0.5m/sec, as dust
JIS Class 8 powder, dust concentration 300mg/ ^m2 supplied, dust
The dust removal rate after supplying 20g is the initial dust removal rate and the pressure loss is
Full life dust removal rate with increased value up to 200mmH ₂ O,
The following table shows the results of a performance comparison at three points: dust retention capacity, which is the amount of dust collected by the effective over-area section converted to m ² when the pressure drop increases to 200 mmH ₂ O.

[Table] As shown in the table above, the electrified car filter element of the present invention is particularly excellent in dust removal rate and dust retention capacity, and greatly contributes to maintenance-free internal combustion engines such as automobiles, improving the fuel ratio and reducing maintenance man-hours. This invention has excellent effects such as:

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged view of the fiber layer used in the present invention;
FIG. 2 is a performance comparison curve diagram of the electret car filter element of the present invention and the conventional car filter element. 1... High melting point polyester fiber with a melting point of 250 to 260°C, 2... Polyester fiber with a melting point of 200 to 230°C,
3...Low melting point polyester fiber with a melting point of 150 to 180°C.

Claims (1)

[Claims] 1 The upper layer, middle layer, and lower layer each have a melting point of 250~
Mainly made of polyester fiber with a high melting point of 260℃,
Consisting of a laminate of fiber layers formed using polyester fibers with a lower melting point of 200 to 230°C and mixed fibers with low melting point polyester fibers with a melting point of 150 to 180°C, and the low melting point polyester fibers between each of the above fiber layers. The blending ratio is 1: from the upstream layer to the downstream layer.
An electret car filter element characterized by having a ratio of 1:2 to 1:8:12, fixed together by heat and pressure, and subjected to electret processing.