JPWO2005058458A1 - Low pressure loss laminated nonwoven fabric and filter - Google Patents

Abstract

The present invention provides a nonwoven fabric having high rigidity and excellent shielding properties and filter characteristics, and a filter that is less likely to be deformed due to fluid resistance during filtration operation. In addition, the present invention provides a filter with a good performance balance that has high dust filtration and long filtration life and high filtration accuracy. A laminated nonwoven fabric in which at least one surface is a polyester nonwoven fabric. The constitution is a low-melting polyester in which the fiber diameter is between 7 to 15 μm and the basis weight is 10 to 100 g / m 2, and the sheath component has a melting point of 110 to 250 ° C. Non-woven fabric B, which is made of a core-sheath type composite fiber having a fiber diameter of 20 to 50 μm, which is a polyester having a melting point of 180 ° C. to 300 ° C., and a basis weight of 15 to 270 g / m 2, and a basis weight of 30 to 200 g. A polyester-based laminated nonwoven fabric in which polyester nonwoven fabric C of / m 2 is laminated and integrated. These are also pleated and used as a filter. When used as a filter, the filtration surface is a flame retardant nonwoven fabric.

Description

  The present invention relates to a nonwoven fabric excellent in filter properties having a low pressure loss and high shielding properties, and a filter using the same. In particular, the present invention relates to a filter that becomes a cartridge after pleating.

  Nonwoven fabrics are widely used as filter media for filter products. For example, a roll type filter that uses a non-woven fabric concentrically wound around a core member, a pleated type filter that is subjected to a folding process, and the like are used as a liquid filter and an air filter.

  These filter media are required to have a high collection performance and a long service life. Furthermore, in order to perform a fold processing, a pleated type air filter is required to have a workability and a rigidity that is not deformed by a wind pressure during use. In order to obtain high collection performance, nonwoven fabrics composed of fine fibers such as melt blown nonwoven fabrics are suitable, but these nonwoven fabrics have low rigidity and cannot satisfy all required characteristics.

  As a method for imparting rigidity to a nonwoven fabric, it is generally known that 1) the fibers are solidified with a resin, 2) the fibers are composed of thick fibers, 3) the basis weight is increased, 4) the density is increased, etc. Non-patent document 1). However, when the fibers are hardened with resin, the pores are reduced by the resin and the ventilation resistance is increased.When the fibers are made of thick fibers, the pores are large and the collection performance is low.When the basis weight is increased, the thickness is increased. As a result, the pleatability is lowered, and when the density is increased, the ventilation resistance is increased, which is not preferable as a filter medium.

Further, as a countermeasure for the long life required for the filter medium, a means of collecting particles in the depth direction of the filter medium by reducing the fiber density on the particle inflow side in a one-pass filter (for example, patent document) 1). However, the above-mentioned method is not preferable for a filter medium in which particles are shaken off by vibration or air pressure and the filter is clogged many times. Therefore, a means for smoothing the surface of the filter medium and improving the detachability of the particles is taken. For example, means such as calendering and smoothing the filter medium, or covering the filter medium surface with a polytetraethylene microporous membrane is taken. However, in the case of the calendar treatment, there is a problem that the ventilation resistance is high, and the cost is high in the case of coating the microporous film.
Textile Research Jounal, 48,309,1978 Republished patent WO 98/13123

  An object of the present invention is to provide a non-woven fabric having excellent pleatability, high rigidity, and low pressure loss, which solves the above-mentioned drawbacks of the prior art, at low cost. Another object of the present invention is to provide a long-life filter with low pressure loss while having high collection performance.

  The present invention has been achieved as a result of intensive studies to solve the above-mentioned problems, and takes the following means.

That is, the first invention is a laminated nonwoven fabric having a flexural rigidity of 0.10 to 1.50 N / 2 cm and a final pressure loss of 600 Pa or less in the following load test.
Load test method: Filtration speed: 3.0 m / min
Filtration air volume: 1.98 m ³ / min
Inlet dust concentration: 2.5 g / m ³
Filtration area: 0.66m ²
Pulse control: Time control pulse condition: Pressure 0.3 MPa, interval 2 min, injection time 0.1 s
Test powder: 10 kinds of dust for JIS test Evaluation time: 7 hr

The second invention is a polyester non-woven fabric A having a fiber diameter of 7 to 20 μm, a basis weight of 10 to 100 g / m ² , and a sheath component having a melting point between 110 ° C. and 250 ° C. Nonwoven fabric B having a basis weight of 15 to 200 g / m ² and a basis weight of 30 to 200 g / m ² containing 50% or more of a core-sheath type composite fiber having a fiber diameter of 20 to 50 μm, which is a polyester having a melting point of 185 ° C. to 300 ° C. The laminated nonwoven fabric according to the first invention, wherein the polyester nonwoven fabric C of m ² is laminated and integrated and has a total basis weight of 400 g / m ² or less.

  3rd invention is a laminated nonwoven fabric as described in the invention in any one of the 1st or 2nd invention, The polyester nonwoven fabric consists of polyester which copolymerized the phosphorus flame retardant.

  A fourth invention is the laminated nonwoven fabric according to any one of the first to third inventions, wherein the polyester nonwoven fabric is a polyester-based nonwoven fabric subjected to metal vapor deposition.

  5th invention is the laminated nonwoven fabric characterized by arrange | positioning the microporous film in the filtration surface of the laminated nonwoven fabric in any one of 1st thru | or 3rd invention.

  A sixth invention is a low pressure loss filter using the laminated nonwoven fabric according to any one of the first to fifth inventions.

  A seventh invention is a low pressure loss filter according to the sixth invention, which is a cartridge type low pressure loss filter incorporating a laminated nonwoven fabric subjected to pleating.

  According to the present invention, it is possible to obtain a laminated nonwoven fabric having flame retardancy, high rigidity, and excellent filter characteristics. In particular, it becomes a laminated nonwoven fabric suitable as a filter with small deformation due to fluid resistance during filtration operation. Furthermore, it can be used as a filter with good dust removal properties. In addition, it is possible to provide a high-performance filter that is pleated and used as a cartridge.

  The present invention is described in detail below. The laminated nonwoven fabric of the present invention desirably has a final pressure loss of 600 Pa or less in a load test. More desirably, it is 500 Pa or less. In the nonwoven fabric whose final pressure loss exceeds 600 Pa, there arises a problem that the life of the filter is low.

The flexural rigidity of the laminated nonwoven fabric is preferably between 0.10 and 1.50 N / 2 cm. This is because when the rigidity is less than 0.1 N / 2 cm, defects such as deformation are likely to occur when pleated and used for a filter, or when a nonwoven fabric is used as part of the structure. Even if the bending rigidity is 1.50 N / 2 cm or more, it does not cause a big problem in carrying out the present invention, but it is presumed that it is sufficient if it is within the scope of the present invention.
In order to obtain high rigidity, it is possible to take a means of laminating and bonding the nonwoven fabrics. This is because it is possible to achieve both high rigidity and extended filter life by stacking the non-woven fabrics together.

  The surface layer material of the laminated nonwoven fabric is preferably a polyester spunbond nonwoven fabric. When a short fiber nonwoven fabric is used as the surface layer material, the number of steps is higher than that of a spunbond nonwoven fabric, which is a long fiber nonwoven fabric, resulting in an increase in cost and a problem that an inexpensive nonwoven fabric cannot be provided. Even if it is a spunbonded nonwoven fabric, there is a problem in heat resistance in the polyolefin system, and there is a problem in operability in the polyamide system. In contrast, polyester spunbonded nonwoven fabrics have excellent mechanical and chemical properties and can be used in a wide range of applications.

  Since there are fields where flame retardancy is required depending on the application, it is desirable that the raw material of the nonwoven fabric A as the surface layer material is a flame retardant polyester obtained by copolymerizing a phosphorus flame retardant. By copolymerizing the flame retardant, it is easy to uniformly disperse the flame retardant component in the polymer as a raw material, and it becomes easy to uniformly control the flame retardant as a nonwoven fabric. Phosphorus flame retardants include (2-carboxyethyl) methylphosphinic acid, (2-carboxyethyl) phenylphosphinic acid, (2-methoxycarbonylethyl) phenylphosphinic acid, (2-hydroxyethoxycarbonylethyl) phenylphosphinic acid, p- (2-carboxyethyl) chlorophenylphosphinic acid, (2-phenoxycarbonylethyl) hexylphosphinic acid and the like can be mentioned. Preferred are (2-carboxyethyl) methylphosphinic acid and (2-carboxyethyl) phenylphosphinic acid. These phosphorus-based flame retardants may be added during the production of the polyester.

  Moreover, as for the addition amount of a phosphorus flame retardant, it is desirable that phosphorus atom content in a polymer is 0.1 to 4.0 weight%. More preferably, it is 0.3 to 3.0%. If the amount of phosphorus-based flame retardant added is less than this range, sufficient flame retardancy will not be exhibited, and if it is too large, not only will the physical properties inherent in the polyester be impaired, but also the operability of nonwoven fabric production. Is also not preferable.

The nonwoven fabric as the surface layer material is desirably a polyester-based nonwoven fabric obtained by depositing or sputtering a metal on the fiber surface. As the metal deposited on the fiber surface, common metals such as aluminum, chromium, titanium, and SUS can be used. The thickness of the deposited metal is desirably 100 to 1000 mm. More desirably, the thickness is 200 to 500 mm. When the thickness of the deposited metal is less than 100 mm, sufficient flame retardancy is not exhibited, and when it is 100 mm or more, it has flame retardancy. If the thickness of the deposited metal exceeds 1000 mm, there is no great difference in performance, and only increases the price.
Furthermore, by covering the fiber surface constituting the nonwoven fabric with a metal, it is possible to suppress not only the flame retardancy but also the decrease in dust releasability due to the charging of particles.

  The nonwoven fabric A that is a constituent element of the composite nonwoven fabric used in the present invention is preferably made of fibers having a fiber diameter of 7 to 20 μm. When the fiber diameter is between 7 and 20 μm, high filtration accuracy can be achieved without setting the packing density high. If the fiber diameter is too thin, the problem arises that fluff is likely to occur due to wear or the like. Further, when the fiber diameter is increased in order to increase the rigidity, when used as a filter, the filtration accuracy cannot be set high unless the filling rate is increased, resulting in a problem that the fluid permeation resistance increases. When the composite nonwoven fabric of the present invention is used as a filter, it is considered that it is generally used as a surface filtration material having the nonwoven fabric A as a filtration surface. Therefore, the thinner the fiber diameter, the higher the filtration accuracy, and The surface is easily smoothed, and as a result, the cake peelability is improved and the filtration life can be extended. When a composite structure is not used as in the present invention, it is considered extremely difficult to obtain a nonwoven fabric having a high balance between filtration accuracy and filtration life and having high rigidity. It is particularly preferable that the non-woven fabric is a long-fiber non-woven fabric because there is no fear of fiber dropping when used as a filter or a shielding material.

The nonwoven fabric A is desirably a nonwoven fabric having a basis weight of 10 to 100 g / m ² . More desirably, it is the range of 20-80 g / m < ² >. If the basis weight is less than 10 g / m ² , the fiber gaps on the surface become large, and dust penetrates into the nonwoven fabric, and clogging is likely to occur. On the other hand, if the basis weight exceeds 100 g / m ² , there is not much difference between the fiber gaps, and it merely increases the price.

  Nonwoven fabric B, which is a component of the composite nonwoven fabric used in the present invention, is a low-melting polyester having a melting point of the sheath component between 110 ° C and 250 ° C, and a polyester having a melting point of the core component of 180 ° C to 300 ° C. A core-sheath type composite fiber is desirable. With this configuration, it is possible to provide a highly rigid nonwoven fabric and a filter using the same, which are the objects of the present invention. If the form of the nonwoven fabric is a long-fiber nonwoven fabric, it is not necessary to apply a process oil, so that foreign matters can be eliminated. In addition, long fiber nonwoven fabrics are particularly suitable for applications such as filters because they have excellent lint-free properties and do not lose fibers. Within the scope of the study by the inventors, it was possible to obtain better rigidity as the melting point of each polymer was higher.

  The polymer used for the sheath component is preferably a low-melting polyester having a melting point between 110 ° C and 250 ° C. A melting point of 110 ° C. or lower is not preferred because there is a possibility that the adhesive force may be lowered or the tackiness may be developed even at room temperature, causing problems such as blocking. On the other hand, if the melting point is higher than 250 ° C., a high bonding processing temperature is required, and if the surface temperature of the object to be bonded is low, solidification starts immediately and adhesiveness may deteriorate or operability may deteriorate. It is not preferable. Polyester resins are particularly suitable for the market for filter-related applications because they generally do not generate foreign matter. As the resin to be used, polypropylene terephthalate, polybutylene terephthalate, aliphatic polyester or block copolymer polyester, and a copolymer having one of them as a basic skeleton can be preferably used.

  The core component polymer is desirably polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polylactic acid, or a copolymer partially containing any of them. These polyester resins are particularly preferable if the melting point is between 180 ° C. and 300 ° C. because they are excellent in dimensional stability at high temperatures and mechanical strength characteristics. Recently, it has become possible to obtain raw materials from natural ingredients and biotechnology, which is particularly preferable from the viewpoint of environmental conservation. In particular, when shape stability is resinized as a liquid filter or the like, the high rigidity of the polyester fiber becomes effective. The polymer of the core component is preferably at a temperature that is at least 20 ° C. higher than the melting point or softening point of the polymer of the sheath component in view of the operability of the adhesive processing. If the difference between the melting points is small, it is necessary to strictly control the processing temperature, so that an advanced temperature control facility is required, and the processing speed must be reduced.

  The weight ratio of the core component and the sheath component of the composite fiber is desirably about 20:80 to 70:30, more desirably between 30:70 and 60:40, and particularly preferably 40:60 to 55: Between 45. If the sheath component which is an adhesive component is less than 30%, it is difficult to obtain a sufficient adhesive force. On the other hand, if it exceeds 70%, it is difficult to control the temperature during the bonding process, and mechanical strength characteristics are liable to deteriorate.

  The fiber diameter of the main fibers constituting the nonwoven fabric B is desirably between 20 and 50 μm, more desirably between 25 and 50 μm, and particularly desirably between 30 and 50 μm. When the fiber diameter is smaller than 20 μm, the area of the bonded portion becomes small, and the adhesive force tends to be lowered, which is not preferable. On the other hand, when the fiber diameter is larger than 50 μm, the unevenness of the nonwoven fabric increases, which is not preferable. In addition, when the nonwoven fabric is produced by the spunbond method, thread breakage may occur during the spinning process, and problems such as fiber sticking or clogging of the fiber pulling ejector may easily occur, resulting in problems in operability. Not a few. Moreover, since the nonwoven fabric which consists of a too thick fiber has few fiber amounts, the spot of a formation is conspicuous, and it leads to the dispersion | variation in a physical property. A place where there are few fibers is not preferable because it causes insufficient rigidity of the nonwoven fabric and decreases the adhesive strength of the nonwoven fabric.

Furthermore, it is desirable that the nonwoven fabric B has a basis weight of 15 to 200 g / m ² . On the other hand, when the basis weight is larger than 200 g / m ² , when heat embossing is performed, a problem that the adhesive strength is lowered due to the problem of heat transfer in the embossing roll is likely to occur, which is not so desirable. When the nonwoven fabric of the present invention is used as a separation membrane support, the basis weight is preferably 15 to 70 g / m ² . If the basis weight is less than 15 g / m ^2, it is difficult to obtain an appropriate adhesive force for the reasons described above, and the form retainability is lowered, which is not preferable. On the other hand, even if the basis weight is greater than 70 g / m ² , it cannot be expected that the adhesive strength will be high. When used as a support for a separation membrane, the thickness and weight will increase and the handling will be reduced, or the pressure loss It is not preferable because it tends to cause a problem of large. Further, when the thickness is large, the number of weaving folds is reduced when used for a pleated filter, and as a result, the effective filtration area is reduced.

The nonwoven fabric C used in the present invention is desirably a polyester nonwoven fabric having a basis weight of 30 to 200 g / m ² . More preferably, it is 40-180 g / m < ² >, More preferably, it is 100-180 g / m < ² >. Although the manufacturing method of a nonwoven fabric is not prescribed | regulated, the polyester long fiber nonwoven fabric excellent in heat resistance and cost performance can be used. Since the nonwoven fabric C often has a higher thickness and basis weight than other nonwoven fabrics, there is a risk of poor heat transfer when the nonwoven fabrics are bonded together by thermal calendaring or the like. In order to prevent this, it is also desirable to preheat the nonwoven fabric C with an infrared heater or the like in advance.

  Since the filter using the composite nonwoven fabric of the present invention has high rigidity, it is desirable that the filter is pleated and then formed into a cartridge. It is possible to set bending rigidity high by carrying out lamination processing. In addition, since the nonwoven fabric B has a low melting point component, the pleat formability is improved, and reciprocating processing as well as conventional spunbond nonwoven fabric, which is said to be difficult to process, can be folded at high speed. .

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. The evaluation method is described below.

(Final pressure loss)
Under the following load test conditions, the final pressure after 7 hours is obtained.
Filtration speed: 3.0 m / min
Filtration air volume: 1.98 m ³ / min
Inlet dust concentration: 2.5 g / m ³
Filtration area: 0.66m ²
Pulse control: Time control pulse condition: Pressure 0.3 MPa, interval 2 min, injection time 0.1 s
Test powder: 10 kinds of dust for JIS test Evaluation time: 7 hr

(Weight)
A sample piece having a width of 5 cm and a length of 20 cm is taken in the product width direction, and the arithmetic average value of the weight is converted per 1 m ² .

(Thickness)
Evaluation is made at a load of 20 gf / cm ² at intervals of 5 cm in the product width direction, and the arithmetic average value is defined as the thickness.

(Fiber diameter)
An enlarged photograph of the nonwoven fabric surface and fibers was taken with a scanning electron microscope (SEM), 100 or more fibers were read, and the arithmetic average value was taken as the fiber diameter. In the reading method, a diagonal line is drawn on the photograph, and the width of the fiber crossing the diagonal line is read. At this time, fibers fused to each other are excluded.

(Melting point)
A DSC7 manufactured by PERKIN-ELMER was used and evaluated at a heating rate of 20 ° C./min. The crystal melting peak value at this time is defined as the melting point.

(Bending rigidity)
A sample piece having a width of 2 cm and a length of 10 cm is set at a support interval of 5 cm, and a pressure used in the JIS-L-1096 loop compression method is used to make the stress at the time of compressive deformation bending stiffness at a deformation rate of 5 cm / min. .

Example 1
Nonwoven fabric A was a polyethylene terephthalate spunbonded nonwoven fabric (6701A manufactured by Toyobo Co., Ltd.) having a fiber diameter of about 14 μm and a basis weight of 70 g / m ² . A spunbond nonwoven fabric B comprising a core-sheath type composite fiber having a fiber diameter of about 40 μm having a copolymer component (melting point: about 130 ° C.) introduced with isophthalic acid as a sheath component and polyethylene terephthalate having a melting point of about 270 ° C. as a core component. A basis weight of 40 g / m ² ) was prepared. The core-sheath ratio was 50:50 on a weight basis. Non-woven fabric C is a polyethylene terephthalate spunbonded non-woven fabric (6A31AD manufactured by Toyobo Co., Ltd.) having a fiber diameter of 14 μm and a basis weight of 130 g / m ² , and the three non-woven fabrics are 220 ° C. with a plain calender, set linear pressure is about 25 kg / cm, speed Bonding was performed at 10 m / min. The bending rigidity of the laminated nonwoven fabric was 0.50 N / 2 cm. The final pressure loss of the laminated nonwoven fabric was 430 Pa. When the non-woven fabric A was placed on the upper surface and processed with a rotary type folding machine, it could be processed without any problems.

(Example 2)
Example except that non-woven fabric B was changed to a non-woven fabric having a basis weight of 40 g / m ² made of core-sheath short fiber (Melty 2080 (trade name) manufactured by Nihon Ester Co., Ltd., melting point of core part: about 200 ° C.) having a fiber diameter of about 35 μm. The laminated nonwoven fabric was created by the same method as 1. The bending rigidity of the laminated nonwoven fabric was 0.47 N / 2 cm. The final pressure loss of the laminated nonwoven fabric was 440 Pa. When the non-woven fabric A was placed on the upper surface and processed with a rotary type folding machine, it could be processed without any problems.

Example 3
Example except that polyethylene terephthalate spunbonded nonwoven fabric (H6701A manufactured by Toyobo Co., Ltd.) blended with 3000 ppm of a phosphorus flame retardant (2-carboxyethyl) phenylphosphinic acid having a fiber diameter of 14 μm and a basis weight of 70 g / m ² 1 was used to obtain a laminated nonwoven fabric. The bending rigidity of the laminated nonwoven fabric was 0.55 N / 2 cm. The final pressure loss of the laminated nonwoven fabric was 440 Pa. When the non-woven fabric A was placed on the upper surface and processed with a rotary type folding machine, it could be processed without any problems. In addition, self-extinguishing results were shown in the flame resistance evaluation by JIS L-1096 micro burner method.

Example 4
The same method as in Example 1 except that a polyethylene terephthalate spunbonded nonwoven fabric (H6701A manufactured by Toyobo Co., Ltd.) having a fiber diameter of 14 μm and a basis weight of 70 g / m ² was used as nonwoven fabric A, and the nonwoven fabric was vapor-deposited with a thickness of 300 mm by SUS. A laminated nonwoven fabric was obtained. The bending rigidity of the laminated nonwoven fabric was 0.49 N / 2 cm. The final pressure loss of the laminated nonwoven fabric was 400 Pa. When the non-woven fabric A was placed on the upper surface and processed with a rotary type folding machine, it could be processed without any problems. In addition, self-extinguishing results were shown in the flame resistance evaluation by JIS L-1096 micro burner method. Furthermore, the dust releasability was good.

(Example 5)
Except that polyethylene terephthalate spunbonded nonwoven fabric (H6701A manufactured by Toyobo Co., Ltd.) blended with a phosphorus-based flame retardant having a fiber diameter of 14 μm and a basis weight of 70 g / m ² was used as nonwoven fabric A, and the nonwoven fabric was deposited with a thickness of 300 mm by SUS. A laminated nonwoven fabric was obtained in the same manner as in Example 1. The bending rigidity of the laminated nonwoven fabric was 0.53 N / 2 cm. The final pressure loss of the laminated nonwoven fabric was 400 Pa. When the non-woven fabric A was placed on the upper surface and processed with a rotary type folding machine, it could be processed without any problems. In addition, self-extinguishing results were shown in the flame resistance evaluation by JIS L-1096 micro burner method. Furthermore, the dust releasability was good.

(Comparative Example 1)
A spunbonded non-woven fabric having a fiber diameter of 17 μm and a basis weight of 240 g / m ² was prepared using a copolymer polyester (melting point: about 130 ° C.) into which isophthalic acid was introduced as a sheath component and polyethylene terephthalate having a melting point of about 270 ° C. as a core component. . This nonwoven fabric was adjusted to a fiber filling rate of 30% by a plain calendar at 100 ° C., a set linear pressure of about 25 kg / cm, and a speed of 10 m / min. The bending rigidity of the nonwoven fabric was 0.3 N / 2 cm. The final pressure loss of the nonwoven fabric was 720 Pa, and the lifetime was short.

(Comparative Example 2)
A polyethylene terephthalate nonwoven fabric having a fiber diameter of 14 μm and a basis weight of 240 g / m ² was prepared. This was calendered under the same processing conditions as in Comparative Example 1. Adhesion between the fibers constituting the nonwoven fabric was weak, and when it was processed with a rotary type folding machine, delamination occurred and processing could not be performed.

  The laminated nonwoven fabric and the filter according to the present invention can obtain high rigidity and improved filter life, and can be widely used for filter applications in general and contribute to the industry.

Claims (7)

A laminated nonwoven fabric having a flexural rigidity of 0.10 to 1.50 N / 2 cm and a final pressure loss of 600 Pa or less in the following load test.
Load test method:
Filtration speed: 3.0 m / min
Filtration air volume: 1.98 m ³ / min
Inlet dust concentration: 2.5 g / m ³
Filtration area: 0.66m ²
Pulse control: Time control pulse condition: Pressure 0.3 MPa, interval 2 min, injection time 0.1 s
Test powder: 10 kinds of dust for JIS test Evaluation time: 7 hr Polyester nonwoven fabric A having a fiber diameter of 7 to 20 μm and a basis weight of 10 to 100 g / m ^2, a polyester having a sheath component having a melting point between 110 ° C. and 250 ° C., and a core component having a melting point of 185 Non-woven fabric B having a basis weight of 15 to 200 g / m ² containing 50% or more of a core-sheath type composite fiber having a fiber diameter of 20 to 50 μm, which is a polyester at ℃ to 300 ° C., and a basis weight of 30 to 200 g
^2. The laminated nonwoven fabric according to claim 1, wherein the nonwoven fabric is a laminated nonwoven fabric in which polyester nonwoven fabric C of / m ² is laminated and integrated, and has a total basis weight of 400 g / m ² or less. The laminated nonwoven fabric according to claim 1 or 2, wherein the polyester nonwoven fabric comprises a polyester obtained by copolymerizing a phosphorus flame retardant. The laminated nonwoven fabric according to any one of claims 1 to 3, wherein the polyester nonwoven fabric is a polyester nonwoven fabric subjected to metal vapor deposition. A laminated nonwoven fabric comprising a microporous membrane disposed on the filtration surface of the laminated nonwoven fabric according to any one of claims 1 to 3. A filter using the laminated nonwoven fabric according to claim 1. 7. A low pressure loss filter according to claim 6, wherein the filter is a cartridge type incorporating a laminated nonwoven fabric subjected to pleating.