KR20200140040A - Wet-laid nonwoven fabric for filters comprising low melting polyester fiber - Google Patents

Abstract

The present invention relates to wet non-woven fabric for filters including low melting polyester fiber to provide increased physical properties while providing increased thermal adhesion and processability. According to the present invention, the wet non-woven fabric for filters comprises first polyester fiber including a polyester resin having a melting point of 250°C or more and second polyester fiber including a low melting polyester resin having a softening point of 100 to 150°C, wherein the first polyester fiber is a modified cross-section fiber having a circularity ratio of 50 to 80% and the second polyester fiber includes a low melting polyester resin represented by chemical formula 1. A difference between melting viscosities of the low melting polyester resin at 220°C and 260°C is 600 poise or less. In chemical formula 1, m and n are mole%, m + n = 100%, and a is a polymerization degree.

Description

Wet-laid nonwoven fabric for filter paper containing low-melting polyester fiber {WET-LAID NONWOVEN FABRIC FOR FILTERS COMPRISING LOW MELTING POLYESTER FIBER}

The present invention relates to a wet nonwoven fabric for filter paper containing a low melting point polyester fiber, and more particularly, a low melting point polyester fiber having excellent filtration efficiency and improved physical properties by using a fiber containing a novel low melting point polyester resin. It relates to a wet nonwoven fabric for filter paper comprising a.

Filter paper is a means for removing or blocking various harmful dusts that are introduced together with air from machinery or indoors, and filtering methods using filter paper include a surface filtering method and a depth filtering method. The surface filtration method collects fine dust on the surface of the filter paper by binding or splashing out, and the depth filtration method prevents fine dust entering the filter paper from escaping to the outside because it cannot be filtered out by the surface filtration method. Filter.

The surface filtration method has the advantage of being able to easily remove fine dust adhering to the surface, but in order to remove the dust accumulated on the surface, it is necessary to periodically spray compressed air to remove the dust layer. Conventional air filter paper is a typical surface filtration method. Air filter filter paper mainly uses thick special paper mixed with pulp, for the above reason, it is necessary to periodically spray compressed air to remove dust layer to remove surface dust. However, the filter paper made of pulp generates shares by compressed air, and as the usage period increases, it becomes easier to penetrate the dust inside, and the usage period is shortened due to the increase in collected dust. Being exposed.

In Korea Patent Application Publication No. 2007-0067884,'Air Purification Filter Material and Its Manufacturing Method', in order to overcome the above problems, a car in which a polyurethane-based resin layer is thinly coated to form a porous film on the surface of a special paper filter paper made of pulp. Disclosed is a filter for use. The filter of the present invention can be used for a long time and has excellent filtration efficiency, but since the main substrate is paper composed of pulp, a problem occurs when spraying compressed air to remove dust accumulated on the surface after a certain period of use. There is a limit that it is difficult to fundamentally solve the problem.

As another solution, there is an attempt to manufacture filter paper using synthetic fibers for wet nonwoven instead of pulp fibers. However, unlike pulp, synthetic fibers have a problem that the filtration efficiency is lowered because the specific surface area is not large.

In order to overcome this, Korean Patent No. 1421317,'Wet Nonwoven Fabric and Filter', developed a fiber using an island component composed of a thermoplastic polymer and a sea component composed of a polymer that is easily soluble in an aqueous alkali solution, and the fineness remaining after alkali dissolution. It was intended to improve the low filtration efficiency of synthetic fiber nonwovens by using powder. However, when the filter paper is manufactured using this, there is a problem in that industrial waste containing a large amount of polyester oligomer is generated, polluting the environment, and increasing the cost for such wastewater treatment, thereby increasing the manufacturing cost.

The present invention has been invented to solve the problems of the prior art as described above, and an object of the present invention is to provide a wet nonwoven fabric for filter paper comprising a low-melting polyester fiber having improved heat adhesion, excellent processability and improved physical properties.

In addition, it is an object of the present invention to provide a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber with improved high strength and improved collection efficiency.

The present invention includes a first polyester fiber containing a polyester resin having a melting point higher than 250°C, and a second polyester fiber containing a low melting point polyester resin having a softening point of 100°C to 150°C, and the first poly The ester fiber is a deformed cross-section yarn having a roundness of 50 to 80%, and the second polyester fiber is formed by including a low melting point polyester resin of the following [Chemical Formula 1], and the low melting point polyester resin has a melting point of 220°C It provides a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that the difference between the degree and the melt viscosity of 260 ℃ is less than 600 poise (poise).

[Formula 1]

However, m and n are mol%, m+n=100%, and a is the degree of polymerization

In addition, the first polyester fiber and the second polyester fiber provides a wet nonwoven fabric for filter paper comprising a low-melting polyester fiber, characterized in that the fineness is 0.5 to 6 denier, and the fiber length is 3 to 50 mm.

In addition, the second polyester fiber provides a wet nonwoven fabric for filter paper comprising a low-melting-point polyester fiber, characterized in that the deformed sectional yarn having a roundness of 50 to 80%.

In addition, the first polyester fiber provides a wet nonwoven fabric for filter paper comprising a low-melting-point polyester fiber, characterized in that the cross-sectional shape of the three to eight leaves.

In addition, the second polyester fiber is a polyester fiber for a binder formed of a sheath portion and a core portion, and the core portion is formed of a general polyester resin, and the sheath portion is formed of a low melting point polyester resin. It provides a wet nonwoven fabric for filter paper containing polyester fibers.

In addition, the low melting point polyester resin provides a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that the number average molecular weight is 11,000 to 15,000.

In addition, the polyester resin of the sheath portion provides a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that the molecular weight distribution (Mw/Mn) is 2.0 to 4.0.

In addition, n in [Chemical Formula 1] provides a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that 20 to 50 mol%.

In addition, a in [Chemical Formula 1] provides a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that 50 to 100.

As described above, the wet nonwoven fabric for filter paper comprising the low-melting-point polyester fiber according to the present invention has an effect of improving thermal adhesion, excellent processability, and improved physical properties.

In addition, the wet nonwoven fabric for filter paper containing the low-melting-point polyester fiber of the present invention has the effect of improving high strength and collection efficiency.

Hereinafter, a preferred embodiment of the present invention will be described in detail. First, in describing the present invention, detailed descriptions of related known functions or configurations are omitted so as not to obscure the subject matter of the present invention.

The terms'about','substantially', etc. of the degree used in the present specification are used at or close to the numerical value when manufacturing and material tolerances specific to the stated meaning are presented, and are used in the sense of the present invention. To assist, accurate or absolute figures are used to prevent unfair use of the stated disclosure by unscrupulous infringers.

The present invention is a wet type for filter paper formed comprising a first polyester fiber containing a polyester resin having a melting point higher than 250°C and a second polyester fiber containing a low melting point polyester resin having a softening point of 100°C to 150°C. It relates to non-woven fabric.

The first polyester fiber may be polyethylene terephthalate (PET) formed of terephthalic acid or an ester-forming derivative thereof and ethylene glycol (EG), and may be a copolymerized polyester resin in which a functional compound is copolymerized for functionality.

The polyester resin having a melting point higher than 250° C. may be any polyester resin having a high melting point.

In addition, the first polyester fiber is a deformed sectional yarn having a roundness of 50 to 80%.

The first polyester fiber may be any type of deformed sectional yarn having a roundness of 50 to 80%, but a deformed sectional yarn having a multi-leaf cross section of 3 to 8 leaves is preferable, and 4 cross-shaped for collection and manufacturing processability. It is most preferable to have a lobe cross section, a star-shaped five or six lobe cross-section.

The second polyester fiber is a fiber comprising a low melting point polyester resin resin of the following [Chemical Formula 1].

[Formula 1]

However, m and n are mol%, m+n=100%, and a is the degree of polymerization

The second polyester fiber is formed by spinning alone with the low melting point polyester resin, or in order to improve the physical properties of the second polyester fiber, the core part is formed of a general polyester resin and the sheath part is formed of the low melting point polyester resin. It may be a sheath-core composite fiber.

When the second polyester fiber is a cis-core composite fiber, any general polyester resin forming the core part can be used, but a polyethylene terephthalate (PET) resin made of terephthalic acid and ethylene glycol is used. It is preferable that the sheath portion may be formed of the low melting point polyester resin.

The low melting point polyester resin of [Chemical Formula 1] has a methyl group formed in the main chain of the polymer to facilitate rotation, and acts as a polymer end portion to prevent the polyester resin from rapidly decreasing its melt viscosity at high temperature and improve dyeability. .

In addition, it increases the flowability of the entire molecular chain to make the polymer amorphous and improves low melting point properties and tearing properties at high temperatures.

As described above, there are too few methyl groups in the polymer main chain, and low melting point characteristics may not be expressed, and too many methyl groups may degrade polyester properties, so it is preferable that n in [Formula 1] is 20 to 50 mol%. will be.

In addition, if the degree of polymerization is too small, the polyester properties are deteriorated, and if the degree of polymerization is too large, the polymerization process may be difficult and may take a long time, and a in [Chemical Formula 1] is preferably 50 to 100.

The polyester resin of [Chemical Formula 1] is a low-melting-point polyester resin in which the difference between the melt viscosity of 220°C and the melt viscosity of 260°C is 600 poise or less and the melt viscosity does not drop sharply at high temperature.

The lower the difference between the melt viscosity at 220°C and the melt viscosity at 260°C of the low melting point polyester resin, the lower it is, the more preferable it is, and it will be more preferably 500 poise or less.

When the second polyester fiber is formed of a sheath-core composite fiber composed of a sheath part of the low melting point polyester resin, the general polyester resin of the core part has a melt viscosity of 280°C for spinning of the composite fiber in the spinning process. Is 2,000 to 4,000 poise, and the polyester resin of the sheath portion will preferably have a melt viscosity of 500 to 1,400 poise at 260°C.

If the melt viscosity of the general polyester resin of the core portion is too high, the spinning processability may be deteriorated, resulting in a thread trimming phenomenon, and if the melt viscosity of the core portion is lower than that of the polyester resin of the sheath portion, the shape stability of the composite fiber may be reduced. In other words, it is preferable that the fiber cross section of the cis-core type may not be formed, and the general polyester resin of the core portion has a melt viscosity of 2,000 to 4,000 poise at 280°C.

The melt viscosity of the polyester resin of the sheath part is too high and the shape stability of the composite fiber may be reduced, and if the melt viscosity of the sheath part is too low, cross-sectional unevenness, howitzer, and trimming may occur. The resin preferably has a melt viscosity of 500 to 1,400 poise at 260°C, and more preferably 700 poise or more at 260°C.

The general polyester forming the core part is advantageous for improving the shape stability and spinning processability of the composite fiber in that the melt viscosity of the general polyester resin forming the core part and the melt viscosity of the polyester resin forming the sheath part are different within a certain range. It is preferable that the difference between the melt viscosity of the resin at 280° C. and the melt viscosity at 260° C. of the polyester resin forming the sheath is 700 to 2,500 poise, more preferably 1,000 to 2,000 poise.

The melt viscosity of the polyester resin of the sheath part can be adjusted according to the molecular weight and molecular weight distribution (Mw/Mn). In order for the polyester resin of the sheath part according to the present invention to have a melt viscosity of 500 to 1,400 poise at 260°C It is preferable that the number average molecular weight is 11,000 to 15,000, and the molecular weight distribution (Mw/Mn) is preferably 2.0 to 4.0.

In general, the molecular weight and molecular weight distribution of a polyester resin can increase the molecular weight and molecular weight distribution by suppressing the reverse reaction in the polymerization process.In addition, an excessive amount of a diol component is added and the molecular weight is increased by controlling the pressure, temperature and polymerization time. You can get down.

In order to prepare the molecular weight distribution to be less than 2, polymerization is required for a long time at high temperature and high pressure, so the polyester resin of the sheath portion according to the present invention preferably has a molecular weight distribution (Mw/Mn) of 2.0 or more, and when the molecular weight distribution exceeds 4.0 Since the melt viscosity may drop rapidly at high temperature, it is preferable that the molecular weight distribution is 4.0 or less.

The molecular weight distribution (Mw/Mn) of the polyester resin of the sheath portion according to the present invention will most preferably be 2.5 to 3.5.

The low melting point polyester resin of the present invention formed by [Chemical Formula 1] as described above has a softening temperature of 100°C to 150°C, a glass transition temperature of 50°C to 90°C, and an intrinsic viscosity of 0.50 dl/g or more. Will have.

The second polyester fiber may also further improve the collecting property of the wet nonwoven fabric for filter paper by using a deformed sectional yarn having a roundness of 50 to 80%.

The second polyester fiber may be any type of cross-section yarn having a roundness of 50 to 80%, but it is preferable to have a cross-section of 3 to 8 leaves of a cross-section like the first polyester fiber. For manufacturing processability, it would be more preferable to have a cross-shaped four-leaf cross section, a star-shaped five-leaf or six-leaf cross-section.

The first polyester fiber and the second polyester fiber are short fibers to form a wet nonwoven fabric. The first polyester fiber and the second polyester fiber have a fineness of 0.5 to 6 denier, and a fiber length of 3 to 50 mm. It would be desirable to be.

In addition, if the content of the second polyester fiber is too small, the bonding strength between the fibers may be reduced and physical properties may be deteriorated. If the content of the second polyester fiber is too large, basic physical properties such as strength and elongation of the wet nonwoven fabric are produced. Since it may be degraded, it will be preferable that the first polyester fiber and the second polyester fiber are mixed in a weight ratio of 20:80 to 80:20.

As described above, the present invention is that the wet nonwoven for filter paper formed including the first polyester fiber and the second polyester fiber can be manufactured by a general wet process (Wet-Laid). The web is formed in water with a type paper machine, and the low melting point polyester resin of the second polyester fiber bonds the web by heat during the drying process.

As described above, the wet nonwoven fabric for filter paper of the present invention comprising the first polyester fiber having a release cross-section and the second polyester fiber having heat-sealing property increases the surface area inside the wet nonwoven fabric due to the fiber of the release cross-section. It is possible to provide a wet nonwoven fabric for filter paper with improved strength and elongation through a novel second polyester fiber having improved physical properties than a conventional heat-sealed fiber.

Hereinafter, examples of a method for manufacturing a wet nonwoven fabric for filter paper comprising a low-melting-point polyester fiber according to the present invention are shown, but the present invention is not limited to the examples.

◈ Second polyester fiber manufacturing

Preparation Examples 1 to 6

Polyethylene terephthalate having a melt viscosity of about 2,300 poise at 280°C was used as the core part, and the sheath part was made of a low-melting polyester resin, and the weight ratio of the sheath part and the core part was 50:50. To prepare a polyester fiber for a binder with improved fairness.

The cis portion of the low melting point polyester resin was polymerized to have 42 mol% of n in [Chemical Formula 1] using the following [Chemical Formula 2], [Chemical Formula 3], and [Chemical Formula 4] monomers.

The low melting point polyester resin was prepared with a low melting point polyester resin having a different molecular weight and molecular weight distribution according to the preparation example, and the intrinsic viscosity was constantly adjusted to about 0.56 dl/g as shown in Table 1 below.

[Formula 2]

[Formula 3]

[Formula 4]

division Softening point
(℃) Tg
(℃) IV
(dl/g) Mn Mw Molecular Weight
Distribution Degree of polymerization
(a) Melt viscosity 220℃ 240℃ 260℃ Manufacturing Example 1 117 60.2 0.564 11200 45900 4.10 58.3 1146 873 442 Manufacturing Example 2 121 60.8 0.561 13100 49300 3.76 68.2 1197 992 564 Manufacturing Example 3 120 60.7 0.563 13500 45200 3.35 70.3 1214 1078 826 Manufacturing Example 4 124 61.4 0.562 14200 43100 3.04 74.0 1311 1186 967 Manufacturing Example 5 124 62.9 0.563 13700 36400 2.66 71.4 1388 1192 1041 Manufacturing Example 6 123 64.5 0.562 13300 31400 2.36 69.3 1498 1331 1213

As shown in Table 1, it can be seen that the melt viscosity increases as the molecular weight distribution increases, and through Preparation Example 3, it is possible to maintain a high melt viscosity at a high temperature with a polymerization degree of 3.5 or less and a melt viscosity of 260°C to 700 poise or more. In addition, it can be seen from Preparation Examples 3 to 6 that the difference between the melt viscosity at 220°C and the melt viscosity at 260°C is 200 to 400 poise at the degree of polymerization of 3.5 or less, and the difference in melt viscosity is very small.

▶ Measurement of fiber properties in the manufacturing example

The following physical properties of the low-melting-point polyester resin and the polyester fiber for a binder prepared in Preparation Example were measured, and the results are shown in Tables 1 and 2.

(1) Softening point (or melting point) and glass transition temperature (Tg) measurement

The glass transition temperature (Tg) of the copolymerized polyester resin was measured using a differential scanning calorimeter (Perkin Elmer, DSC-7), and the softening behavior was measured in TMA mode using a dynamic mechanical analyzer (DMA-7, Perkin Elmer). I did.

(2) Intrinsic viscosity (IV) measurement

The polyester resin was dissolved in a solution in which phenol and tetrachloroethane were mixed at a ratio of 1:1 by weight at a concentration of 0.5% by weight, and the intrinsic viscosity (I.V) was measured at 35°C using an Uberod viscometer.

(3) Melt viscosity measurement

After melting the polyester resin at the measurement temperature, the melt viscosity was measured using RDA-III of Rheometric Scientific. Specifically, when measured by setting from Initial Frequency = 1.0 rad/s to Final Frequency = 500.0 rad/s under Frequency Sweep condition at the set temperature, the value at 100 rad/s was calculated as the melt viscosity.

(4) Measurement of compression hardness

5 g of polyester fibers were opened, stacked at a height of 5 cm in a circular mold having a diameter of 10 cm, and then thermally bonded at a set temperature for 90 seconds to prepare a cylindrical molded article. The manufactured molded article was compressed by 75% through Instron, and the compressive hardness was measured by measuring the load applied to the compression. In this experiment, the compression hardness was measured by thermal bonding at 140°C, 150°C, and 160°C, respectively.

(5) Measurement of spinning yield (%, 24hr)

The spinning yield was calculated by the following equation by measuring the amount of the polyester resin used for 24 hours and the amount of spun fibers.

Spinning yield (%) = (Amount of spun fiber (kg) / Amount of PET resin used (kg)) * 100

(6) molecular weight measurement

The number average molecular weight (Mn) and weight average molecular weight (Mw) of the polyester resin were measured by the GPC analysis method.

* GPC (Gel permeation chromatograph) analysis instrument conditions

1) Analysis device: Tosoh EcoSEC HLC-8320 GPC

2) Detector: RI-Detector

3) Development solvent: CHCl ₃ (chloroform)

4) Column: 2 X Shodex LF-804 + Shodex KF-802.5 (7.8 x 300mm)

5) Temperature: 40℃

6) Flow rate: 1.0mL/min

7) Standard material: Polystyrene

division Compression hardness (kgf) Spinning yield
(%, 24hr) 140℃ 150℃ 160℃ Manufacturing Example 1 0.49 0.66 0.71 98.1 Manufacturing Example 2 0.52 0.79 0.84 98.3 Manufacturing Example 3 0.58 0.85 0.93 98.9 Manufacturing Example 4 0.61 0.99 1.19 98.9 Manufacturing Example 5 0.69 1.18 1.30 99.1 Manufacturing Example 6 0.79 1.24 1.36 99.7

As for the compression hardness, the higher the value, the better the thermal adhesion between the fibers of the molded article. As shown in Table 2 above, the polyester fiber for the binder of the present invention shows that the compression hardness increases as the molecular weight distribution of the low melting point polyester resin increases. It can be seen that the spinning yield is also excellent.

As described above, the molecular weight distribution of the low melting point polyester resin of the sheath part according to the present invention is closely related to the spinning processability and thermal adhesion.As the molecular weight distribution increases, the fairness and heat adhesion improve, but the molecular weight distribution is due to the polymerization process. It is difficult to manufacture less than 2, and the low melting point polyester resin according to the present invention preferably has a molecular weight distribution of 2 to 4, more preferably 2.5 to 3.5.

◈ Manufacture of wet nonwoven fabric for filtration

Example 1

The first polyester fiber was a fiber having a six-leaf cross section (68% roundness) manufactured using polyethylene terephthalate having a melting point of about 265° C., and the second polyester fiber was the low melting point polyester of Preparation Example 3. Fiber was used.

The first polyester fiber has a fineness of 1.4 denier and a fiber length of 6 mm, and the second polyester fiber is a short fiber having a fineness of 2 denier and a fiber length of 6 mm, and 60% by weight of the first polyester fiber and the second polyester fiber After mixing and stirring 40% by weight in water, paper was made in a water paper machine of 25X25cm according to the standard standard TAPPI of pulp paper, dried for 3 minutes at 130°C using a drum dryer, and a wet nonwoven fabric for filtration having a basis weight of 100gsm was prepared.

Example 2

It was prepared in the same manner as in Example 1, but as the second polyester fiber, a wet nonwoven fabric for filtration was prepared using the low melting point polyester fiber of Preparation Example 5.

Example 3

The first polyester fiber was prepared in the same manner as in Example 1, but a wet nonwoven fabric for filtration was prepared using a cross-shaped four-leaf cross-section (74% roundness ratio) of a deformed cross-section yarn.

Example 4

The first polyester fiber was prepared in the same manner as in Example 2, but a wet nonwoven fabric for filtration was prepared by using a cross-shaped deformed cross-section yarn having a four-leaf cross section (74% roundness).

Comparative Example 1

It was prepared in the same manner as in Example 1, but the first polyester fiber was a fiber having a circular cross-section (100% roundness), and the second polyester fiber was a sheath-core fiber, and polyethylene terephthalate was used as a core part. , Terephthalic acid (66.5 mol%) and isophthalic acid (33.5 mol%) were used as the acid component for the low melting point polyester resin of the cis part, and diethylene glycol (10.5 mol%) and ethylene glycol (89.5 mol%) were used as the diol component. Prepared using.

Comparative Example 2

The second polyester fiber was prepared in the same manner as in Example 1, but the second polyester fiber was a sheath-core fiber, and polyethylene terephthalate was used as the core part, and the low melting point polyester resin of the sheath part was terephthalic acid as an acid component, and as a diol component. It was prepared using 2-methyl-1,3-propanediol (42.5 mol%) and ethylene glycol (57.5 mol%).

▶ Measurement of properties of wet nonwoven fabrics in Examples and Comparative Examples

The following physical properties of the wet nonwoven fabric for filtration prepared in Examples and Comparative Examples were measured, and the results are shown in Table 3.

(1) Basis weight: The weight per 1m² of paper was measured.

(2) Thickness: The thickness was measured according to KS K 0506.

(3) Strength: The force tolerated when the paper is pulled, measured by KS K 0520.

(4) Roundness: The ratio of the area of the circumscribed circle to the inscribed circle of the yarn cross section

Roundness rate (%) = inscribed circle (B) area/circumscribed circle (A) area*100

# The lower the roundness, the higher the cross-sectional shape release.

(5) Filtration rate and air permeability: It was measured with a filter test device, MFP-1000 (manufacturer Palas).

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Basis weight (gsm) 50 50 50 50 50 50 Thickness(mm) 0.63 0.67 0.68 0.66 0.67 0.66 The tensile strength
(kgf) MD 6.31 6.16 6.28 6.20 5.47 5.59 CD 2.71 2.64 2.62 2.78 2.28 2.11 Filtration rate (%) 99.5 99.2 98.8 9.85 94.5 96.4 Speculation (cfm) 363 354 358 361 326 305

As shown in Table 1, Examples 1 to 4, which are wet nonwoven fabrics for filtration according to the present invention, have more improved physical properties such as strength and elongation than Comparative Example 1,2, and when using the low melting point polyester fiber according to the present invention, wet nonwoven fabrics It can be seen that the basic physical properties of are improved.

In addition, Examples 1 to 4, which are wet nonwoven fabrics for filtration according to the present invention, have improved filtration rate and air permeability than Comparative Example 1,2, and when using a back-sided yarn and using a low-melting-point polyester fiber according to the present invention It can be seen that the filter function of the nonwoven fabric is improved.

Claims (9)

A first polyester fiber containing a polyester resin having a melting point higher than 250° C. and a second polyester fiber containing a low melting point polyester resin having a softening point of 100° C. to 150° C.,
The first polyester fiber is a deformed sectional yarn having a roundness of 50 to 80%,
The second polyester fiber is formed including a low melting point polyester resin of the following [Chemical Formula 1],
The low melting point polyester resin is a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that the difference between the melt viscosity of 220 °C and the melt viscosity of 260 °C is 600 poise or less.
[Formula 1]

However, m and n are mol%, m+n=100%, and a is the degree of polymerization The method of claim 1,
The first polyester fiber and the second polyester fiber have a fineness of 0.5 to 6 denier, and a fiber length of 3 to 50 mm, characterized in that the wet non-woven fabric for filter paper comprising a low melting point polyester fiber. The method of claim 1,
The second polyester fiber is a wet nonwoven fabric for filter paper comprising a low-melting polyester fiber, characterized in that the roundness is 50 to 80% of the deformed cross-section yarn. The method of claim 1,
The first polyester fiber is a wet nonwoven fabric for filter paper comprising a low-melting polyester fiber, characterized in that the cross-section of 3 to 8 lobes. The method of claim 1,
The second polyester fiber is a polyester fiber for a binder formed of a sheath portion and a core portion, and the core portion is formed of a general polyester resin, and the sheath portion is formed of a low melting point polyester resin. Wet non-woven fabric for filter paper containing fibers. The method of claim 1,
The low melting point polyester resin is a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that the number average molecular weight of 11,000 to 15,000. The method of claim 1,
The polyester resin of the sheath portion is a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that the molecular weight distribution (Mw/Mn) is 2.0 to 4.0. The method of claim 1,
In [Chemical Formula 1] n is a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that 20 to 50 mol%. The method of claim 1,
A of [Chemical Formula 1] is a wet nonwoven fabric for filter paper comprising a low melting point polyester fiber, characterized in that 50 to 100.