WO2008078858A1

WO2008078858A1 - Filter element for cleaning inlet air of internal combustion engine and process for preparing the same

Info

Publication number: WO2008078858A1
Application number: PCT/KR2007/001032
Authority: WO
Inventors: Gyu-Beom Gwag; Jae-Min Lee; Min-Hwan Chang; Jae-Jung Moon
Original assignee: Clean & Science Co Ltd
Current assignee: Clean & Science Co Ltd
Priority date: 2006-12-27
Filing date: 2007-02-28
Publication date: 2008-07-03
Anticipated expiration: 2009-06-27
Also published as: KR100952421B1; KR20080060829A

Abstract

The present invention relates to a filter material for cleaning inlet air of internal combustion engine from contaminants which can be used for a long time, and a process for preparing the same. More particularly, it relates to a dual- or multi-layer filter material with a density gradient comprising at least one spunbond non-woven fabric layer with a density gradient located on the air-inlet side and a filter paper layer or a meltblown layer as a final layer located on the air-outlet side, and a process for preparing the same. The filter material for air cleaning according to the present invention can improve the problems of low service lifetime (dust holding quantity) which was involved in the prior art filter material containing the filter paper only, and can improve the efficiency which was the drawback in the prior art non-woven fabric filter material.

Description

[DESCRIPTION] [Invention Title]

FILTER ELEMENT FOR CLEANING INLET AIR OF INTERNAL COMBUSTION ENGINE AND PROCESS FOR PREPARING THE SAME [Technical Field]

<i> The present invention relates to a filter material for cleaning inlet air of internal combustion engine from contaminants which can be used for a long time, and a process for preparing the same. More particularly, it relates to a dual- or multi-layer filter material with a density gradient comprising at least one spunbond non-woven fabric layer with a density gradient located on the air-inlet side and a filter paper layer or a meltblown layer as a final layer located on the air-outlet side, and a process for preparing the same. [Background Art]

<2> Generally, internal combustion engine is operated by supplying liquid fuel such as gasoline and diesel or gaseous fuel such as LPG with a combustion chamber, where the fuel becomes into a gas mixture with oxygen in the air and undergoes combustion/explosion. The air introduced into the engine to form the gas mixture contains impurities such as dusts which cause incomplete combustion and impeding smooth operation of vehicles or equipments. Also, the impurities may flow into the engine and be piled on the cylinder wall of the engine to deteriorate the durability of engine. In addition, the internal combustion engine which was recently developed is installed with an equipment to measure the necessary amount of air, and micro-fine carbons(soot) present in the air are contacted with the sensor of the equipment and contaminate the sensor and consequently lower output power of the engine.

<3> Conventional engines for vehicles are provided with an air filter medium in the air cleaner and an oil filter medium in the oil filter to remove impurities contained in the lubricating oil within the engine.

<4> Such a filter medium comprises various types of filter paper which are technically designed according to the size and quantity of materials to be removed. This filter medium should satisfy sufficient filtration efficiency and life span for optimizing the flow and quantity of air or lubricating oil which is needed while the engine is operated.

<5> However, in practice, when the size of pore in the filter medium is minimized in order to sufficiently hold impurities, the pore can early be clogged. That is, the filter medium with fine pores has a problem in that it cannot be used for a long period of time. On the contrary, the medium with large pores has poor filtration efficiency since fine dusts can easily escape. Therefore, it is desired to have a filter material satisfying both the filtration efficiency and the life span.

<6> Currently, filter paper and non-woven fabric are widely used as a filter material for vehicles. Filter paper is prepared by blending a natural pulp and a synthetic fiber in accordance with the final application fields and subjecting the blend to the dissociation-beating-sheet forming- impregnation-drying-winding processes. Non-woven fabric is classified into various types according to its preparation method, such as spunbond, spunlace, chemical bond, thermal bond, needle punching and meltblown. Particularly, non-woven fabric which is mainly used as a material for internal combustion engine is prepared by carding a proper combination of fibers, followed by lamination in a multi-layered structure and subjecting the laminate to subsequent processes such as needle punching, heat pressing, chemical treatment, drying and the like.

<7> Upon comparison of performance between the filter paper and the non- woven fabric, the filter paper prepared according to the above-described method has a thin thickness, a high density and a low air permeability and shows excellent particle holding efficiency. It has a defect that requires a large volume upon application as a filter material, but has an excellent processibi lity.

<8> Meanwhile, non-woven fabric has a great thickness, a low density and a high air permeability, and thereby, shows a long effective dust holding life. However, it has defects of a low holding efficiency of micro-particles and a poor post-processibi lity.

<9> By the meltblown process, it is possible to form an ultra-fine fiber which is widely used for various filter materials such as air purification system. However, such an ultra-fine fiber has problems in strength, fiber shedding and fiber breakage upon pleating, and therefore, it cannot be used alone.

<io> As a prior art for the filtering material for cleaning air, US Patent No. 6,315,805 discloses a filter medion for air filtration in which a filter paper and a meltblown fabric is laminated, two or more fabric layers form a density gradient from the air-inlet side to the air-outlet side, and each fabric layer is bonded by a resin binder or an ultrasonic welding. However, when this conventional meltblown fabric and filter paper are laminated, post processing is very limited since the meltblown itself has a relatively low melting point and thus has a low heat stability. In addition, the meltblown having high permeability of 5000L/rrf(at 200Pa) and relatively small mass of (10-100 g/in², generally 25g/m² or below) is weak in its strength and thus makes the lamination work difficult. Also, since the meltblown fabric represents a relatively broad range of fiber diameter, in case of the small fiber diameter, differential pressure is elevated when the quantity of air permeated increases. [Disclosure] [Technical Problem]

<ii> The present inventors have intensively conducted studies to solve the problems involved in the conventional non-woven fabric filter material and to develop a more improved filter material, and found that a dual- or multi^¬ layer filter material prepared by laminating at least one spunbond non-woven fabric with a density gradient at the air-inlet sideCouter layer) with a filter paper or a meltblown at the air-outlet side(inner layer) can solve the problems of bonding performance between fibers, permeability and carbon holding capacity at high flow rate which are involved in the prior art filter material containing the meltblown fabric as the final layer and, as well, can improve the lamination work efficiency, and bonding performance which are involved in the filter preparation process and filter efficiency, and consequently is excellent in micro-particle holding capacity and holding quantity as compared to the conventional filter material, and completed the present invention. [Technical Solution]

<i2> Therefore, it is an object of the present invention to provide an air filter material which can solve the problems of low service lifetime and low carbon holding quantity which were involved in the prior art filter material containing the filter paper, and low efficiency which was involved in the nonwoven filter material, and to provide a process for preparing the same.

<i3> It is another object of the present invention to provide an air filter material which is excellent in heat stability and permeability at high air flow rate by using as the outer layer a spun-bond nonwoven fabric which has a relatively big fiber diameter and even distribution rate and is excellent in bonding strength between fibers, and consequently is excellent in dust holding quantity which was the drawback in the prior art filter paper and in efficiency which was the drawback in the prior art non-woven fabric filter, and to provide a process for preparing the same. [Advantageous Effects]

<i4> The air filter material according to the present invention can improve the problems of low service lifetimeCdust holding quantity) which was involved in the prior art filter material containing the filter paper only, and can improve the efficiency which was the drawback in the prior art non- woven fabric filter material. In addition, the material has an excellent heat stability compared to the prior art laminated material by containing a spunbond non-woven fabric with high heat stability. Further, post processibi lity as well as lamination work efficiency and bonding performance which are involved in the filter preparation process, and filtering efficiency can be improved. Therefore, the filter material can be used as a filter medium in the field of internal combustion engine, especially hybrid vehicles since it is excellent in capturing carbons which cause malfunction of automatic circuit sensor in the internal combustion engine. [Description of Drawings]

<i5> Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

<i6> FIG. 1 is a schematic view showing an embodiment of the process for preparing air filter material according to the present invention.

<17> FIG. 2 is a schematic view showing other embodiment of the process for preparing air filter material according to the present invention.

<i8> FIG. 3 is a schematic view showing another embodiment of the process for preparing air filter material according to the present invention.

<19> FIG. 4 is a schematic view showing another embodiment of the process for preparing air filter material according to the present invention.

<20> FIG. 5 is a schematic view showing another embodiment of the process for preparing air filter material according to the present invention. [Best Mode]

<2i> In an aspect of the present invention, there is provided a dual- or multi-layer filter material for cleaning air comprising at least one spunbond non-woven fabric layer with a density gradient located on the air-inlet side and a filter paper layer or a meltblown layer, especially a meltblown layer which comprises heterogeneous components having different melting points as a final layer located on the air-outlet side,

<22> The term "final layer" used herein refers to a layer through which air passes to the outside, where an air-inlet side layer is an outer layer or an external layer. It also can be called "fine layer" meaning that it is a layer having a very high fiber density and these two terms can be used reciprocally. Further, this layer refers to an air outlet layer or an inner layer in the art. Here, when a support layer is added to the final layer at the fluid-outlet side, as needed, it is called as a backup layer or a support layer, but is not called as a " final layer".

<23> The filter material according to the present invention can improve the drawbacks in the efficiency of the prior art filter and has a relatively big fiber diameter and even distribution rate of diameter as a laminated filter material, and is excellent in bonding strength between fibers, and consequently has advantages that are excellent in heat stability and permeability at high air flow rate, dust holding quantity and efficiency by using spunbond nonwoven fabric as the outer layer.

<24> In order to accomplish the above objects of the present invention, at least one spunbond non-woven fabric layer with a density gradient is located on the air-inlet side and a filter paper layer or a meltblown layer, especially a meltblown layer which comprises heterogeneous components having different melting points as a final layerCfine layer) is located on the air- outlet side of the dual- or multi-layer filter material for cleaning air.

<25> The filter material according to the present invention comprises at least one outer layerCor pre-layer) having a density gradient from the air inlet side. The outer layer can preferably be made of spunbond non-woven fabric.

<26> The spunbond non-woven fabric used in the pre-layer may have various properties according to the type of the non-woven fabric and desired performance. For the material for the internal combustion engine, the spunbond non-woven fabric preferably has a weight of 10 to 25Og/nf. an air permeability of 30 to 1500 cfm at 125 Pa(20 cm²), a fiber diameter in the range of 1 to 50 jm and a pore size of 10 μm or above, and preferably has at least one layer structure.

<27> The spunbond non-woven fabric which constitutes the outer layer can be prepared from the component selected from the group consisting of polyester, acryl , polyethylene, polypropylene, polybutylene, viscose rayon, polyethylene terephthalate, polybutylene terephthalate, nylon, polyphenylenesulphide, polycarbonate and polyester glycol(PETG), which can be used alone or as a mixture thereof. The material can be spun after mixing or spun in the form of bi-component(side by side, sheath/core, or spilt micro-filament yarn).

<28> The filter material according to the present invention comprises a filter paper layer or a meltblown layer, especially a meltblown layer comprising heterogeneous components having different melting points as the final layer.

<29> It is more preferred that the above outer layer non-woven fabric form a density gradient, and the non-woven fabric which can be used to provide density gradient to the spunbond can be prepared by needle punching method, chemical bonding method, thermal bonding method, spunbonding method, bulky meltblown method, and the like.

<30> Among the filter paper or the meltblown fabric which can be used in the final layer, the meltblown materiaKpreferably a meltblown material comprising heterogeneous components having different melting points) preferably constitutes 5 to 40 wt% based on the weight of the whole filter material and has preferably a pore size in the range of 20 to 150 μm, a weight in the range of 10 to 350 g/m², an air permeability in the range of 10 to 800 cfm at 125 Pa, and a fiber diameter in the range of 0.5 to 30 [M.

<3i> The filter paper preferably has a pore size in the range of 3 to 80 μm, a weight in the range of 30 to 350 g/m², an air permeability in the range of 3 to 150 cfm at 125 Pa, and a fiber diameter in the range of 5 to 50 μm. This filter paper may preferably comprise, but not limited thereto, cellulose fiber alone or synthetic fiber, and the synthetic fiber includes, but not limited thereto, PET or PVA etc.

<32> The meltblown non-woven fabric as the final layer can be selected from the conventional meltblown, and especially two or more components selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, nylon, polyphenylenesulphide, polycarbonate(PC) and polyester glycol(PTEG) are spun after mixing or spun in the form of bi-component(side by side, sheath/core, or spilt micro-filament yarn) to constitute the heterogeneous fiber having different melting points, and it includes, for example, low melting point PET-high melting point PET, low melting point PET-high melting point PBT, low melting nylon-high melting nylon, PBT-nylon, etc.

<33> Each layer of the filter material can be laminated by either of an ultrasonic fusing or a heat resistant hot melt such as polyamide, polyester and polyurethane, wet curable polyurethane, etc. In addition, it is preferred that a combination of two or more methods can be used in order to improve the bonding performance.

<34> In addition, each layer of the filter material can be laminated by either of needle punching, low melting point resin or water-soluble resin, or the mixture thereof. It is also preferred that a heat treatment in the post processing may be used in order for easy bonding. Lamination process by the heat treatment can be accomplished by heat treatment of the meltblown web using fusing oven, belt press, calender or hot air, etc. at 100 ~ 300^°C , and the low melting point resin within the meltblown layer is then melted to give the lamination. As a consequence of the heat treatment, the heterogeneous polymeric fibers with different melting points are tangled and twisted by heat thereby giving effects of more improved porosity, increases in filtering efficiency and filter life span compared to the conventional filter material. Furthermore, the method according to the present invention simplifies lamination process of the respective non-woven web and can prevents the secondary problems which can occur in the lamination process. The filter material laminated by the conventional needle punching was poor in its filter performance due to the holes generated by the needles. However, the heat treatment after the needle punching by the process according to the present invention results in considerable recovery of the holes by the melted fibers which does not necessitate the additional adhesive resin during the process and the meltblown performs adhesive function. Of course, a chemical resin such as hot melt may be used, if necessary, in order to maximize the bonding strength.

<35> The filter material according to the present invention may preferably comprises a support layer in the back of the meltblown layer, as needed. The support may be formed by the conventional non-woven fabric and preferably has a weight of 5 to 60 g/m\

<36> The non-woven fabric can also be prepared according to the conventional preparation method. For example, spunbond, spunlace, needle punching, chemical bond, thermal bond, air-laid and meltblown processes, etc. can be used.

<37> The finally prepared composite filter material has preferably a total weight of 150 to 500 g/m\ a pore size of 10 ~ 100 μm, an air permeability of 10 to 150 cfm at 125 Pa.

<38> In another aspect of the present invention, there is provided a method for preparing the above-described filter material.

<39> As briefly shown in Figures 1 and 2, the method for preparing the filter material according to the present invention may be performed by combining conventional preparation methods. In embodiments for preparing the multi-layered material as set forth in Figures 3 to 5, a filter paper layer or a meltblown layer serves as the final layer to which one or more of spunbond non-woven layer and(or) a support layer may be laminated. The outer layer may comprises a single spunbond non-woven fabric or a combination of a conventional non-woven fabric and a spunbond non-woven web.

<40> More specifically, the method for preparing the filter material according to the present invention from a spunbond non-woven web and a filter paper comprises the steps of:

<4i> a) transferring at least one spunbond non-woven fabric and a filter paper from respective winding rolls;

<42> b) if necessary, applying an adhesive(hot melt or water soluble binder) to the above spunbond non-woven fabric or filter paper layer by spray or dot type application;

<43> c) laminating the above layers(i, e., the adhesive applied filter layer and the other layer) by a tension roll;

<44> d) fusing the laminated filter materials by ultrasonic fusion; and

<45> e) winding the fused filter material. <46> Also, when it is prepared from the spunbond non-woven web and meltblown(preferably a meltblown comprising heterogeneous components), the present invention provides a method for preparing a filter material for air cleaning comprising the steps of:

<47> a) transferring at least one spunbond non-woven fabric and meltblown(s) from respective winding rolls;

<48> b) if necessary, applying an adhesive(hot melt or water soluble binder) to the above spunbond non-woven fabric or meltblown layer by spray or dot type application and; laminating the above layersd, e., the adhesive applied filter layer and the other layer) by a tension roll;

<49> c) if necessary, laminating the above layersG, e., the adhesive applied filter layer and the other layer); and, bonding the resulting laminate by a plurality of needles to form a web; (needle punching non-woven web lamination method);

<50> d) fusing the laminated filter material by fusing oven, belt press, calender or hot air maintained at the range of 100 ~ 300°C ; and

<5i> e) winding the fused filter material.

<52> Lamination of layers by the conventional methods such as calender, fusing oven or belt press required a large amount of the low melting point fiber at the bonding face of the non-woven fabric and a high treatment temperature. However, if a filter material is prepared according to the present invention, lamination at a low temperature is possible as the low melting point resin in the meltblown is arranged in the form of ultra-fine fiber and, therefore, the use of the low melting point fiber in non-woven fabric can be minimized. In addition, the process provides effects in the productivity and the cost save aspects since it does not require an additional adhesive.

<53> In addition, according to the conventional needle punching, rupture of fibers occurred which is a fatal defect in the filtering efficiency. However, according to the above method of the invention, the rupture can be recovered by the use of calender, fusing oven or belt press process in the post processing after lamination of fibers, and low melting point meltblown is melted to increase the bonding strength to the non-woven web. In addition, since the filter material contains a high melting point fiber, pore closing according to the film formation of fibers can be minimized. Of course, the bonding strength and porosity can be regulated according to mixing ratio of the meltblown.

<54> The filter material according to the present invention can be pleatable. Therefore, the pleating process comprises pleating the meltblown material in accordance with a desired shape, cutting the pleated material to a desired size and curing the product at a predetermined temperature for a predetermined time. Here, the curing step can be omitted according to the used resin and process. Therefore, in an additional aspect of the present invention, there is provided a filter element prepared by pleating the filtering material. The filter element may be in a star shape or a flat panel shape.

<55> In the pleating process for shaping, the pleating machine may be a rotary, minipleat, or knife pleating machine. Among them, the knife pleating machine is preferably used. The curing temperature for fixing the pleated shape is in the range of 130 to 180°C, which is similar to the curing temperature of the non-woven fabric.

<56> The final filter material thus prepared preferably has a total weight of 150 to 500 g/nf, a pore size of 10 to 100 μm, and an air permeability of 10 to 150 cfm at 125 Pa. [Mode for Invention]

<57> The present invention will hereinafter be described in further detail by examples. However, the examples are given for illustration and the present invention is not limited thereto.

<58> The filter materials produced by different bonding methods based on the below mixing ratio of the raw material were tested for the filter performance. Dust used in the test was AC fine. The amount of flow tested was 25 mVmin, filtering area was 176.6 cπf, and dust input amount was 0.5g/2min. The test was performed until the final pressure loss is 400 mmAg.

<59> In addition, in order to measure carbon capturing capacity, the conditions of filtering area of 216 αn\ the flow amount of 1.6 mVmin, termination condition-" initial pressure + until increase up to 300 mmAq, alcohol lamp fire size of 15 cm and the distance to the alcohol lamp of 440 cm were used.

<60> Examples 1~5, and Comparative Examples 1 and 2:

<6i> The filter papers as described in the table 1 below and made of wood pulp which are used in the conventional vehicle were prepared by the steps of dissociation-beating-sheet forming-drying-impregnation processes according to the conventional process of preparing filter paper. Also, filtering material prepared by ultrasonic lamination of meltblown and filter paper was tested for the properties. Additionally, spunbonds with various weights and meltblowns(especially those comprising two or more components having different melting points) were tested for their properties. Needle puched filtering material was prepared in the manner of carding-needIe punching- calendering-taking-up. The products were examined for their properties, and the results thereof are set forth below.

<62> [Table 1]

<63> Properties of the filter raw materials

<64>

<66> <o5>

<67>

Each filtering material was prepared based on the raw material of Table 1 by the conventional lamination method of ultrasonic bonding, hot-melt and needle punching and the fabric was then examined for its properties and filter performance. In addition, each fabric was compared with the filter paper which did not subject to the lamination and that of the laminated composite material of the filter paper and the meltblown, and the results are set forth in the Tables 2 and 3.

<69> [Table 2] <70> Comparison of properties of the filter material containing filter paper as the final layer

<71>

<72> <76>

<m>

<73>

As can be seen from the results of the table, when the filter materials of Comparative Examples 1 and 2 are compared with that of Example 1, the filter material of Example 1 in which the same filter paper and the spunbond

2 non-woven web of 15 g/m were laminated by ultrasonic fusion resulted in equal level of performance in aspect of the dust holding efficiency, however, represented a considerable increase in aspect of the dust holding quantity, that is, life span. A little short service life in the Example 1 compared with the meltblown of Comparative Example 2 seems to be originated from the weight difference. Also, it is noted that the carbon holding quantity in aspect of the carbon holding efficiency is remarkably increased.

<78> Meantime, upon comparing the filter materials of Examples 1 to 3, the

2 filter material in which the weight of spunbond was increased from 15 g/m to

2

40 g/m was excellent in the dust and carbon holding efficiency aspects, and that of example 2 comprising two-layered spunbond with the same weight represented more excellent performance. This suggests that the spunbonded non-woven fabric can be used as the pre-filter at the outer layer of the filter paper as well as the meltblown fabric. Therefore, the filter material of the invention is considered to be excellent in the cost competitiveness, workability and post processibi lity aspects.

<79> Then, spunbond and meltblown were subjected to a needle punch-heat calender-winding process, i.e., surface treatment by heat calender after lamination by needle punching process to prepare a filter materiaKExample 4), and then, upon preparing a needle punched non-woven fabric by the order of carding-needle punching-calendering-winding, spunbond and meltblown were inserted in the front stage of the needle punching process to prepare a filter materiaKExample 5). Each filter performance was set forth in Table 3. Table 3 represents the performance comparison results of the filter material in which meltblown layer was applied as the final layer.

<80> [Table 3] <81>

<82> <86>

<83>

As can be seen from the above table 3, when the filter material of Example 4 which comprises the meltblown as the final layer is compared with that of Example 3 which comprises the filter paper as the final layer, the filter material of Example 3 with the filter paper revealed more excellent result on the filter performance for the dust and carbon. However, this result is interpreted as being originated from the weight differences between the filter paper and the meltblown used as the final layer. Upon comparison of the filter material of Example 5 into which the needle punched non-woven 2 fabric of 200 g/m was applied with that of Example 3, the material of Example

5 resulted in a very good efficiency regarding the life span for dust holding as well as carbon holding efficiency.

[Industrial Applicability]

<88> As described above, the filter material for air cleaning according to the present invention can improve the problems of low service lifetimeCdust holding quantity) which was involved in the prior art filter material containing the filter paper only, and can improve the efficiency which was the drawback in the prior art non-woven fabric filter material. In addition, the material has an excellent heat stability compared to the prior art laminated material by containing a spun-bond non-woven fabric with a high heat stabilitiy. Further, post processibility as well as lamination work efficiency and bonding performance which are involved in the filter preparation process, and filtering efficiency can be improved. Therefore, the filter material can be used as a filter medium in the field of internal combustion engine, especially hybrid vehicles since it is excellent in capturing carbons which may result in malfunction of automatic circuit sensor in the internal combustion engine.

Claims

[CLAIMS]

[Claim 1]

<90> A dual- or multi-layer filter material for cleaning air which comprises at least one spunbond non-woven fabric layer with a density gradient located on the air-inlet side and a filter paper layer or a meltblown layer as a final layer located on the air-outlet side.

[Claim 2]

<9i> The filter material according to Claim 1, wherein the spunbond non- woven fabric has a weight of 10 to 25Og/m\ an air permeability of 30 to 1500 cfm at 125 Pa(20 cm²), a fiber diameter in the range of 1 to 50 μm and a pore size of 10 μm or above.

[Claim 3]

<92> The filter material according to Claim 1, wherein the spunbond non- woven fabric is formed by spinning two or more components selected from the group consisting of polyester, acryl , polyethylene, polypropylene, viscose rayon, polyethylene terephthalate, polybutylene terephthalate, nylon, polyphenylenesulphide, polycarbonate and polyester glycol(PTEG) after mixing or spinning in the form of bi-components.

[Claim 4]

<93> The filter material according to Claim 1, wherein said meltblown layer is formed by spinning two or more components selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, nylon, polyphenylenesulphide, polycarbonate and polyester glycol(PTEG) after mixing or spinning in the form of bi-components.

[Claim 5]

<94> The filter material according to Claim 1, in which the meltblown as the final layer has a pore size in the range of 20 to 150 μm, a weight in the range of 10 to 350 g/m², an air permeability in the range of 10 to 800 cfm at 125 Pa, and a fiber diameter in the range of 0.5 to 30 μm.

[Claim 6] <95> The filter material according to Claim 1, in which the filter paper as the final layer has a pore size in the range of 3 to 80 μm, a weight in the range of 30 to 350 g/m\ an air permeability in the range of 3 to 150 cfm at

125 Pa, and a fiber diameter in the range of 5 to 50 μm, and comprises cellulose fiber alone or synthetic fiber.

[Claim 7] <96> The filter material according to Claim 1, in which each layer, in case of the final layer of the filter paper, is laminated by ultrasonic bonding, chemical bonding, hot melt lamination by dotting or spraying or a combination of two or more thereof.

[Claim 8] <97> The filter material according to Claim 1, in which each layer, in case of the final layer of the meltblown, is laminated by needle punching, thermal bonding, chemical bonding, hot melt lamination by dotting or spraying or a combination of two or more thereof.

[Claim 9] <98> The filter material according to Claim 1, which further comprises a support layer at the backside.

[Claim 10] <99> A filter element prepared by pleating the filter material according to

Claim 1.

[Claim 11]

<ioo> A method for preparing filter material which comprises the steps of: <ioι> a) transferring at least one spunbond non-woven fabric and a filter paper from respective winding rolls! <io2> b) if necessary, applying an adhesive to the above spunbond non-woven fabric or filter paper layer by spray or dot type application; <i03> c) laminating the adhesive applied filter layer and the other layer by a tension roll ;

<!04> d) fusing the laminated filter materials by ultrasonic fusion; and <iO5> e) winding the fused filter material. [Claim 12] <iO6> A method for preparing a filter material for air cleaning which comprises the steps of: <iO7> a) transferring at least one spunbond non-woven fabric and meltblown from respective winding rolls; <iO8> b) if necessary, applying an adhesive to the above spunbond non-woven fabric or meltblown layer by spray or dot type application and; laminating the above adhesive applied filter layer and the other layer by a tension roll; <iO9> c) if necessary, laminating the above spunbond non-woven fabric and the meltblown layer; and, bonding the resulting laminate by a plurality of needles to form a web; <uo> d) fusing the laminated filter materials by fusing oven, belt press, calender or hot air maintained at the range of 100 ~ 300^°C ; and <iii> e) winding the fused filter material.