SPUNBOND NON-WOVEN FABRICS FOR FILTERS AND METHOD FOR PREPARING THE SAME

TECHNICAL FIELD

[0001]The present disclosure relates to a spunbond nonwoven fabric for filters and a method for manufacturing the same.

BACKGROUND OF ART

[0002]A filter is a material or device that separates different phases from a gas or liquid by creating a pressure difference on both sides of a partition through which the gas or liquid containing the different phases passes.

[0003]Generally, nonwoven fabrics are applied to filters. In particular, spunbond nonwoven fabrics are being applied to various industrial fields including filters due to their high productivity and good mechanical properties.

[0004]The performance of nonwoven fabrics for filters varies depending on various factors that make up the nonwoven fabrics. For example, the performance of nonwoven fabrics for filters varies depending on the thickness of the nonwoven fabric, the weight per unit area, and the fineness of the filaments constituting the nonwoven fabric.

[0005]Typically, nonwoven fabrics for filters require to have excellent filtration performance and long service life. However, when focusing on the filtration efficiency of nonwoven fabrics for filters, pressure loss tends to increase, resulting in decreased air permeability or liquid permeability, which in turn tends to shorten the service life. Conversely, when focusing on the air permeability or liquid permeability of nonwoven fabrics for filters, the service life tends to be longer, but the filtration efficiency tends to decrease.

[0006]Accordingly, there is a demand for the development of nonwoven fabrics for filters that exhibit excellent filtration performance while maintaining a long service life.

DETAILED DESCRIPTION OF THE INVENTION

Technical Problem

[0007]It is an object of the present disclosure to provide a spunbond nonwoven fabric for filters with excellent filtration performance and a long service life.

[0008]It is another object of the present disclosure to provide a method for manufacturing the spunbond nonwoven fabric for filters.

Technical Solution

[0009]According to an embodiment of the present disclosure, there is provided a spunbond nonwoven fabric for filters, comprising a fiber web in which a first polyester filament having a melting point of 250° C. or higher and a second polyester filament having a melting point of 150° C. to 220° C. are mixedly spun, wherein the first polyester filament has a fineness of 1 to 10 denier and includes hollow cross-section filaments and heteromorphic cross-section filaments, wherein the hollow cross-section filaments and the heteromorphic cross-section filaments have a fineness difference of 2 denier or more.

[0017]Now, a spunbond nonwoven fabric for filters and a method for manufacturing the same according to embodiments of the present disclosure will be described in more detail.

[0018]Unless explicitly stated herein, technical terms are intended to refer merely to specific embodiments and are not intended to limit the scope of the invention.

[0019]Singular forms used in this specification include plural forms as well, unless the context clearly dictates otherwise.

[0020]It should be understood that the terms “comprise,” “include”, “have”, etc. are used herein to specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

[0021]The terms including ordinals such as “first” and “second” in this specification are employed to distinguish one component from another and are not intended to impose any numerical limitation. For example, within the scope of the present invention, a first component may also be referred to as a second component, and similarly, a second component may be referred to as a first component.

[0022]The term “denier” used in this specification is a unit of fineness based on the mass (gram) per 9,000 meters of a single strand of fiber. For example, 1 denier corresponds to 1 g/9000 m, 0.11 mg/m, or 0.11 tex.

[0026]As a result of the inventors' research, it has been confirmed that a spunbond nonwoven fabric satisfying the configurations described in the above embodiments exhibits excellent filtration performance while maintaining appropriate air or liquid permeability, thereby providing a long service life.

[0027]In particular, since the spunbond nonwoven fabric for filters includes filaments that meet the specified configurations, the amount of particles captured by the nonwoven fabric increases, while reducing the pressure on the surface of the nonwoven fabric due to the particles, thereby ensuring a long service life.

[0028]According to one embodiment, the spunbond nonwoven fabric for filters includes a fiber web in which a first polyester filament having a melting point of 250° C. or higher and a second polyester filament having a melting point of 150° C. to 220° C. are mixedly spun.

[0029]The first polyester filament has a melting point of 250° C. or higher, or 250° C. to 265° C., or 250° C. to 260° C., or 255° C. to 260° C.

[0030]For example, the first polyester filament may include one or more first polyesters selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytetrafluoroethylene, and copolymers thereof, which satisfy the above melting point range.

[0031]The second polyester filament has a melting point at least 30° C. lower than that of the first polyester filament. Preferably, the second polyester filament has a melting point of 150° C. to 220° C., or 160° C. to 220° C., or 160° C. to 210° C., or 170° C. to 210° C., or 180° C. to 210° C., or 190° C. to 210° C.

[0032]For example, the second polyester filament may include one or more second polyesters selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytetrafluoroethylene, and copolymers thereof, which satisfy the above melting point range.

[0033]The fiber web includes 70 to 95 wt % of the first polyester filament and 5 to 30 wt % of the second polyester filament. For example, the fiber web may include 75 to 95 wt % of the first polyester filament and 5 to 25 wt % of the second polyester filament. In another example, the fiber web may include 75 to 90 wt % of the first polyester filament and 10 to 25 wt % of the second polyester filament. In yet another example, the fiber web may include 75 to 85 wt % of the first polyester filament and 15 to 25 wt % of the second polyester filament.

[0034]To ensure the bonding strength of the filaments in the fiber web, it is preferable that the second polyester filament is included in an amount of 5 weight % or more, or 10 weight % or more, or 15 weight % or more.

[0035]However, if the second polyester filament is included in excessive amounts in the fiber web, the reduced content of the first polyester filament may lead to a decline in the mechanical properties of the fiber web, as well as a decrease in the workability of the spinning process and subsequent processes. Therefore, it is preferable that the second polyester filament is included in an amount of 30 wt % or less, or 25 wt % or less.

[0036]According to one embodiment, the first polyester filament includes hollow cross-section filaments and heteromorphic cross-section filaments.

[0037]The hollow cross-section filament is a filament with a void in the central portion of its cross-section. The hollow cross-section filament may have a hollow circular cross-section or a hollow heteromorphic cross-section.

[0038]Preferably, the hollow cross-section filament may have a hollowness ratio of 10% to 30%. The hollowness ratio is a percentage of an area of an inscribed circle based on an area of a circumscribed circle of the hollow cross-section.

[0039]To ensure that the hollow structure is maintained during the filament spinning process, it is preferable that the hollowness ratio of the hollow cross-section filament is at least 10%. However, if the hollowness ratio is excessive, the mechanical properties of the filament may deteriorate, and maintaining the hollow structure may become difficult. Therefore, it is preferable that the hollowness ratio of the hollow cross-section filament is 30% or less. Specifically, the hollowness ratio of the hollow cross-section filament may be 10% to 30%, or 15% to 30%, or 15% to 25%.

[0040]The heteromorphic cross-section filament is a filament having a non-circular cross-section. For example, the heteromorphic cross-section filament may have a cross-section shape of a Y-shaped, W-shaped, triangular, star-shaped, cross-shaped, flat-shaped, or multi-lobed shaped.

[0041]The hollow cross-section filament and the heteromorphic cross-section filament included in the first polyester filaments preferably have a fineness of 1 to 10 denier, respectively. To ensure that the hollow cross-section and heteromorphic cross-section shapes are maintained during the filament spinning process, it is preferable that the hollow cross-section filament and the heteromorphic cross-section filament each have a fineness of at least 1 denier. However, to prevent deterioration in spinnability and workability, such as pack leakage, it is preferable that the hollow cross-section filament and the heteromorphic cross-section filament each have a fineness of 10 denier or less.

[0042]Specifically, the hollow cross-section filament and the heteromorphic cross-section filament have a fineness difference of at least 2 denier. More specifically, the fineness difference may be at least 2 denier, or within the range of 2 to 9 denier, 3 to 9 denier, 4 to 9 denier, 5 to 9 denier, 3 to 8 denier, 4 to 8 denier, 5 to 8 denier, 3 to 7 denier, 4 to 7 denier, or 5 to 7 denier.

[0043]To achieve excellent filtration performance and extended service life in the spunbond nonwoven fabric, it is preferable for the hollow cross-section filament and the heteromorphic cross-section filament to have a fineness difference of at least 2 denier, or at least 3 denier, or at least 4 denier, or at least 5 denier.

[0044]Under these fineness conditions, the hollow cross-section filament may have a greater or smaller fineness than the heteromorphic cross-section filament.

[0045]Moreover, the first polyester filaments may include 30 to 70 wt % of the hollow cross-section filaments and 30 to 70 wt % of the heteromorphic cross-section filaments. For example, the first polyester filaments may include 35 to 70 wt % of the hollow cross-section filaments and 30 to 65 wt % of the heteromorphic cross-section filaments. In another example, the first polyester filaments may include 35 to 65 wt % of the hollow cross-section filaments and 35 to 65 wt % of the heteromorphic cross-section filaments. In yet another example, the first polyester filaments may include 40 to 65 wt % of the hollow cross-section filaments and 35 to 60 wt % of the heteromorphic cross-section filaments.

[0046]To achieve excellent filtration performance and an extended service life of the spunbond nonwoven fabric, it is preferable that the first polyester filaments include the hollow cross-section filaments and the heteromorphic cross-section filaments within the aforementioned ranges.

[0047]According to one embodiment, the second polyester filament may be a circular cross-section filament.

[0048]Preferably, the second polyester filament may be a circular cross-section filament with a fineness of 1 to 5 denier, or 1 to 4 denier, or 2 to 4 denier. To ensure the bonding strength of the filaments in the fiber web, it is desirable for the second polyester filament to have a fineness within the aforementioned range.

[0049]The weight and thickness of the spunbond nonwoven fabric for filters are not particularly limited and may be adjusted within an appropriate range depending on the application field.

[0050]Preferably, the spunbond nonwoven fabric for filters may have a basis weight of 100 g/m² to 350 g/m², or 150 g/m² to 350 g/m², or 150 g/m² to 300 g/m², or 200 g/m² to 300 g/m².

[0051]Additionally, the spunbond nonwoven fabric for filters may have a thickness of 0.1 mm to 1.0 mm, or 0.2 mm to 1.0 mm, or 0.2 mm to 0.9 mm, or 0.3 mm to 0.9 mm.

[0059]According to one embodiment, the spunbond nonwoven fabric for filters may be manufactured by melt-spinning a first polyester and a second polyester to form a fiber web in which the first polyester filament and the second polyester filament are mixed, followed by heat-treatment under pressure.

[0060]In the above manufacturing method, the characteristics of the first polyester, the first polyester filament, the second polyester, and the second polyester filament are the same as previously described.

[0061]According to one embodiment, the first polyester and the second polyester may be independently melted and spun through separate spinnerets to form the first and second polyester filaments. Alternatively, the first and second polyesters may be melted separately and spun through a single spinneret designed for composite spinning, which allows control over the number and shape of the discharge orifices for different resins, thereby forming the first and second polyester filaments.

[0062]Specifically, in the step of forming the first polyester filament, the molten first polyester may be spun through a spinneret capable of adjusting the ratio of hollow cross-section discharge orifices to heteromorphic cross-section discharge orifices, thereby obtaining the hollow cross-section filaments and the heteromorphic cross-section filaments.

[0063]In the melt-spinning process, the spinning speed and tension may be adjusted in consideration of the preferred fineness of the first and second polyester filaments.

[0064]The step of forming the first and second polyester filaments is preferably carried out at a spinning speed of 4000 m/min to 6000 m/min, or 4500 m/min to 6000 m/min, or 4500 m/min to 5500 m/min, respectively. To form filaments with an appropriate degree of crystallization, the spinning speed is preferably 4000 m/min or more or 4500 m/min or more. However, if the spinning speed is excessive, filament entanglement may occur during the spinning process, leading to a decrease in the uniformity of the nonwoven fabric. Therefore, the spinning speed is preferably 6000 m/min or less or 5500 m/min or less.

[0065]The first and second polyester filaments are blended to form the fiber web. The first and second polyester filaments, which are mixedly spun, are deposited onto a continuously moving net conveyor by conventional fiber-opening methods such as electrostatic charging, collision plate method, and airflow diffusion methods to form the fiber web. Here, the fiber web preferably comprises 70 to 95 wt % of the first polyester filament and 5 to 30 wt % of the second polyester filament.

[0066]Subsequently, the fiber web undergoes heat-treatment under pressure to form the spunbond nonwoven fabric.

[0067]This step involves thermally bonding the filaments contained in the fiber web to obtain the spunbond nonwoven fabric. For example, by passing the fiber web through heated rolls, a spunbond nonwoven fabric with appropriate smoothness and thickness is obtained. Conventional devices such as calender rolls and embossing rolls may be used in this step. The rolls are heated to a temperature capable of melting the second polyester filament to a bondable degree.

Advantageous Effects

[0068]According to the present disclosure, there is provided a spunbond nonwoven fabric for filters having excellent filtration performance and a long service life, as well as a method for manufacturing the same.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0069]Hereinafter, preferred embodiments are provided for better understanding of the invention. However, the following embodiments are merely illustrative of the invention and do not limit the invention to these embodiments alone.

Example 1

[0070]Polyethylene terephthalate (PET; first polyester) with a melting point of 255° C. and copolyester (Co-PET; second polyester) with a melting point of 210° C. were each melted at 280° C. using a continuous extruder.

[0071]The first polyester melt was extruded through a spinning pack equipped with spinnerets having hollow cross-section discharge holes and heteromorphic cross-section discharge holes, forming hollow cross-section filaments (hollow ratio: 10%) and heteromorphic cross-section filaments (Y-shaped cross-section) with the fineness specified in Table 1 below. The extruded continuous filaments were solidified using cooling air and then drawn using a high-pressure air-drawing device to achieve a spinning speed of 5000 m/min, thereby obtaining the first polyester filaments. At this stage, the first polyester filaments were prepared to include 50 wt % of the hollow cross-section filaments and 50 wt % of the heteromorphic cross-section filaments.

[0072]The second polyester melt was extruded through a spinneret with circular cross-section discharge holes to form the second polyester filament with a fineness of 2 denier.

[0073]The first polyester filament and the second polyester filament were mixedly spun at a weight ratio of 80:20 (wt %) and then deposited onto a continuously moving net conveyor to form a fiber web.

[0074]The fiber web was passed through calender rolls and embossing rolls maintained at 200° C. and 35 N/mm to produce a spunbond nonwoven fabric with a basis weight of 270 g/m² and a thickness of 0.65 mm.

Examples 2~5 and Comparative Examples 1~4

[0075]Except for manufacturing the hollow cross-section filaments and the heteromorphic cross-section filaments to have the fineness specified in Table 1 below, the spunbond nonwoven fabric was produced in the same manner as in Example 1.

Test Example

(1) Thickness of Nonwoven Fabric

[0076]The thickness of the nonwoven fabric was measured in accordance with the Korean Standards Association KS K ISO 9073-2:2006. The distance between a reference plate, on which the nonwoven fabric specimen was placed, and a parallel presser applying the specified pressure to the nonwoven fabric was measured. For each example and comparative example, ten nonwoven fabric specimens (20 cm×20 cm) were prepared, and the average thickness values were recorded in Table 2 below. For thickness measurement, the ProGage Thickness Tester from Thwing-Albert Instrument was used.

(2) Filtration Performance of Nonwoven Fabric

[0077]The filtration performance of the nonwoven fabric was evaluated using a Filter Media Test System (AFC-131, Topas GmbH) according to the following method.

(3) Spinnability

[0087]By referring to Tables 1 and 2, the spunbond nonwoven fabrics of the examples exhibit excellent filtration performance with a collection efficiency of 81.5% or more and a DHC of 11.8 g/m² or more, while maintaining an appropriate pressure loss (ΔPa) in the range of 25 to 38, which is expected to ensure a long service life.

[0088]The spunbond nonwoven fabric of comparative example 1 demonstrated the highest collection efficiency but had the highest pressure loss (ΔPa), indicating a shorter service life. The spunbond nonwoven fabric of comparative example 2 exhibited a pressure loss (ΔPa) similar to that of the examples but showed the lowest collection efficiency. In comparative example 3, the production of the spunbond nonwoven fabric was not possible due to pack leakage during the melt-spinning process. The spunbond nonwoven fabric of comparative example 4 showed relatively low collection efficiency and high pressure loss (ΔPa).

[0089]As described above, while the present invention has been explained by reference to limited examples, it is not limited thereto. Various modifications and alterations may be made by those skilled in the art to which the present invention belongs, without departing from its technical concept and within the equivalent scope of the claims set forth below.