JP2024040961A - Laminated filter media for filters - Google Patents

Abstract

[Problem] To provide a filter medium with excellent dust collection performance. [Solution] The laminated filter medium of the present invention is formed by laminating a spunbond nonwoven fabric made of fibers with an average fiber diameter of 10 to 40 μm and a meltblown nonwoven fabric made of fibers with an average fiber diameter of 1 to 6 μm. The elastic modulus ratio with the spunbond nonwoven fabric is 0.1 to 0.8, and the elongation at break ratio between the meltblown nonwoven fabric and the spunbond nonwoven fabric is 0.3 to 2.0. [Selection diagram] None

Description

TECHNICAL FIELD The present invention relates to a laminated filter medium that has excellent dust collection performance and also has excellent processability.

Conventionally, various nonwoven fabrics have been proposed as materials for air filters or liquid filters for removing dust. Particularly in recent years, thermocompression-bonded long fiber nonwoven fabrics with excellent rigidity have been suitably used as pleated filters. When a pleated filter material is used, the filtration area can be widened, so the filtration air speed can be reduced, and there are advantages in that the dust collection ability can be improved and mechanical pressure loss can be reduced.

However, in conventional thermocompression-bonded long fiber nonwoven fabrics, the fiber diameter of the constituent fibers is about 10 μm at the most, and does not have sufficient collection ability.

For example, Patent Document 1 proposes a composite long fiber nonwoven fabric for filters made of irregularly shaped fibers. According to this technology, it is possible to improve the mechanical properties and dimensional stability of the nonwoven fabric for filters, but the fiber diameter of the constituent fibers is 2 to 15 decitex, that is, about 13 μm at the thinnest, and the particle size is several μm or less. cannot collect enough dust.

Further, Patent Document 2 proposes a nonwoven fabric for filters in which a plurality of nonwoven fabrics are laminated. According to this technique, it is easy to manufacture a nonwoven fabric for filters with a high basis weight, and it is possible to obtain a nonwoven fabric for filters that has excellent air permeability. However, the nonwoven fabric proposed in this technology is one in which a nonwoven fabric with a fiber diameter of 7 to 20 μm and a nonwoven fabric with a fiber diameter of 20 to 50 μm are laminated and integrated, and like the one in Patent Document 1, the particle size is several μm. The following dust particles cannot be collected sufficiently.

Additionally, during processing, force is applied to the apex portion of the pleats, making them prone to holes or breakage. The embrittled nonwoven fabric has a reduced strength and may be physically destroyed, causing a problem as it may flow downstream as dust.

Japanese Patent Application Publication No. 2001-276529 Japanese Patent Application Publication No. 2004-124317

The present invention was made in view of the above problems, and an object of the present invention is to provide a laminated filter medium with excellent dust collection performance.

The laminated filter medium of the present invention is a filter medium in which a spunbond nonwoven fabric made of fibers with an average fiber diameter of 10 to 40 μm and a meltblown nonwoven fabric made of fibers with an average fiber diameter of 1 to 10 μm are laminated, and the meltblown nonwoven fabric and the spunbond nonwoven fabric This is a laminated filter medium for a filter, characterized in that the ratio of the elastic modulus of the polyester is 0.1 to 0.8, and the ratio of the elongation at break is 0.3 to 2.0.

According to the above configuration of the present invention, it is possible to provide a laminated filter medium that has excellent workability and excellent dust collection performance.

The laminated filter medium of this embodiment is a filter medium in which a spunbond nonwoven fabric made of fibers with an average fiber diameter of 10 to 40 μm and a meltblown nonwoven fabric made of fibers with an average fiber diameter of 1 to 6 μm are laminated, and the meltblown nonwoven fabric and the spunbond nonwoven fabric are further laminated. The ratio of elastic modulus of the nonwoven fabric is 0.1 to 0.8, and the ratio of elongation at break is 0.3 to 2.0.

The filter medium is laminated with a support layer, processed into a pleated shape, and used as a dust removal filter. In the present invention, the ratio of the elastic modulus of the melt-blown nonwoven fabric and the spunbond nonwoven fabric is 0.1 to 0.8, and the ratio of the elongation at break is 0.3 to 2.0. It is characterized by maintaining its pleated shape without reducing dust removal efficiency.

The laminated filter medium of the present invention is reinforced by laminating it with a support layer, and its workability is further improved. As the support layer, generally known nonwoven fabrics such as thermal bonded nonwoven fabrics, resin-impregnated spunbond nonwoven fabrics, and resin bonded nonwoven fabrics mainly made of polypropylene or polyester can be suitably used. As the supporting fiber layer, it is preferable to use a fiber layer having a thickness of 1.0 mm or less, a Gurley bending resistance of 1 mN or more, and a pressure loss as small as possible. Furthermore, if it is desired to impart antibacterial, antifungal, or flame retardant properties, fibers containing known additives having these functions may be mixed.

The laminated filter material for filters in the present invention preferably has an elastic modulus ratio of melt-blown nonwoven fabric and spunbond nonwoven fabric (elastic modulus of melt-blown nonwoven fabric/elastic modulus of spunbond nonwoven fabric) of 0.1 to 0.8. If it is larger than 0.8, stress remains at the apex during pleating and tends to cause breakage, which is not preferable. Moreover, if the ratio of elongation at break is smaller than 0.3, the protection effect of the apex may be reduced, and if it is larger than 2.0, wrinkles tend to occur during lamination, resulting in difficulty in workability.

The melt-blown nonwoven fabric in the present invention is typically produced by extruding a molten polymer from a die, stretching the molten polymer while blowing a heated high-speed gas fluid, etc., to form ultra-fine fibers, and collecting them to form a sheet. It is manufactured by the so-called melt blow method.

The average fiber diameter of the fibers constituting the melt-blown nonwoven fabric is 1 to 6 μm, and is selected depending on the required dust removal efficiency. When the average fiber diameter is smaller than 1 μm, the fibers tend to break easily when the polymer is stretched to form ultrafine fibers, and lumpy polymers may be mixed in, which is not preferable. Furthermore, the air permeability of the nonwoven fabric tends to decrease, which is not preferable. If the average fiber diameter exceeds 6 μm, the fibers become too thick, which tends to reduce dust collection performance, which is not preferable. Note that the average fiber diameter here is determined by taking 10 small samples randomly from the nonwoven fabric, taking photographs with a scanning electron microscope, etc., magnifying 500 to 3000 times, and measuring 10 fibers in total, 10 from each sample. It is calculated by measuring the diameter and rounding off the average value to the first decimal place.

Further, the melt-blown nonwoven fabric in the present invention may be made of common fibers such as polyethylene fibers, polypropylene fibers, and polyolefin fibers such as copolymerized polypropylene.

Further, to the raw material resin of the melt-blown nonwoven fabric, a crystal nucleating agent, a matting agent, a pigment, a fungicide, an antibacterial agent, a flame retardant, a hydrophilic agent, etc. may be added to the extent that the effects of the present invention are not impaired. Further, it may contain a trace amount of a copolymer component as long as the original function is not impaired.

Moreover, it is preferable that the spunbond nonwoven fabric in this invention contains polyester terephthalate. Polyester nonwoven fabrics are preferred because they have a high melting point and excellent heat resistance, and also excellent rigidity. Furthermore, it has excellent oxidation resistance and is preferable from the viewpoint of dust removal performance and shape retention. The nonwoven fabric containing polyester terephthalate is a spunbond nonwoven fabric made only of polyethylene terephthalate, or a core-sheath type fiber whose core part contains polyethylene terephthalate and whose sheath part contains a copolymerized polyester having a lower melting point than the polymer in the core part. A spunbond nonwoven fabric consisting of is a preferred form from the viewpoint of strength and rigidity of the nonwoven fabric. The copolymerized polyester preferably has a melting point lower than that of polyethylene terephthalate contained in the core by 15° C. or more. Further, the copolymerized polyester is preferably copolymerized polyethylene terephthalate, and the copolymerized component is preferably isophthalic acid or adipic acid.

The average fiber diameter of the fibers constituting the spunbond nonwoven fabric is in the range of 10 to 40 μm, preferably in the range of 12 to 35 μm. If the average fiber diameter is smaller than 10 μm, the air permeability of the nonwoven fabric tends to decrease, and the rigidity of the nonwoven fabric also tends to decrease, which is not preferable. Furthermore, during the production of spunbond nonwoven fabrics, thread breakage tends to occur, which is unfavorable from the viewpoint of production stability. If the average fiber diameter is larger than 40 μm, thread breakage is likely to occur due to insufficient cooling of the threads during production of the spunbond nonwoven fabric, which is undesirable from the viewpoint of production stability. Note that the average fiber diameter here is determined by taking 10 small samples randomly from the nonwoven fabric, taking photographs with a scanning electron microscope, etc., magnifying 500 to 3000 times, and measuring 10 fibers in total, 10 from each sample. It is calculated by measuring the diameter and rounding off the average value to the first decimal place.

Furthermore, the cross-sectional shape of the fibers constituting the spunbond nonwoven fabric is not limited in any way, but may be circular, hollow round, elliptical, flat, irregularly shaped such as X-shape or Y-shape, polygonal, or multilobed. type, etc. are preferred forms. The fiber diameter of non-circular fibers may be determined by taking the circumscribed circle and inscribed circle with respect to the fiber cross section, and taking the average value of the respective diameters as the fiber diameter.

In addition, the raw material resin for the spunbond nonwoven fabric in the present invention may contain crystal nucleating agents, matting agents, pigments, antifungal agents, antibacterial agents, flame retardants, hydrophilic agents, etc., to the extent that the effects of the present invention are not impaired. May be added. Further, it may contain a trace amount of a copolymer component as long as the original function is not impaired.

In the present invention, the melt-blown nonwoven fabric and the spunbond nonwoven fabric are laminated, and further, the laminated filter medium and the support layer are bonded together by a known method to form a filter medium. Lamination methods include, for example, partial thermocompression bonding after mechanical entanglement using water jet punching or needle punching, thermal bonding using a hot embossing roll, and bonding by spraying or coating hot melt resin. can be mentioned.

Further, the method of laminating the melt-blown nonwoven fabric and the spunbond nonwoven fabric in the present invention is not limited in any way, but there is a method of laminating the melt-blown nonwoven fabric and the spunbond nonwoven fabric after each has been produced, and a method of laminating the melt-blown nonwoven fabric and the spunbond nonwoven fabric once produced, This can be carried out by a method in which yarns are sprayed and laminated using a melt-blown method, a method in which yarns are sprayed and laminated by a spunbond method on a once-produced melt-blown nonwoven fabric, or a combination thereof. It can also be carried out by a method in which a meltblown web and a spunbond web are continuously laminated and then integrated by thermocompression bonding or the like to form a nonwoven fabric.

Furthermore, the lamination form of the melt-blown nonwoven fabric (M) and the spunbond nonwoven fabric (S) in the present invention is not limited in any way, but preferred forms include SM lamination, SMS lamination, and SMMS lamination (for example, SMS Lamination refers to a laminate in which one layer of melt-blown nonwoven fabric is sandwiched between one layer of spunbond nonwoven fabric from both sides.) When laminating multiple layers of melt-blown nonwoven fabrics or spunbond nonwoven fabrics, there is no problem even if the average fiber diameters and fiber shapes of the constituent fibers are different as long as the average fiber diameters and fiber shapes are within the above-mentioned ranges.

The laminated and integrated nonwoven fabric of the present invention may be partially or entirely applied with an antifungal agent, an antibacterial agent, a flame retardant, a hydrophilic agent, a pigment, a dye, etc., to the extent that the effects of the present invention are not impaired. Good too.

Since the filter medium in which the laminated filter medium and the support layer of the present embodiment are integrated has excellent rigidity, it can be easily formed into a pleat shape and also has excellent retention of the pleat shape. Therefore, it is preferable to use it as a pleated filter.

The present invention will be specifically described below with reference to Examples. However, the present invention is not limited to the following examples, and can be modified as appropriate within the scope of the spirit described above and below. Appropriate modifications thereof are also included within the technical scope of the present invention.

First, the characteristic values and measurement methods measured in Examples and Comparative Examples are shown below.

[Measuring method]

(1) Average fiber diameter (μm)
Take 10 small samples randomly from the nonwoven fabric, take photos with a scanning electron microscope at 500 to 3000 times magnification, measure the diameter of 100 fibers (10 from each sample), and calculate the average value to the decimal place. Calculate by rounding off the first place.

(2) Area weight (g/m ² )
A 200 mm square piece of nonwoven fabric is cut out, and the weight of each sample is measured, converted to per unit area, and rounded to the first decimal place.

(3) Collection efficiency (%)
A sample was set in a 60 mm square acrylic column, air was flowed at a linear velocity of 10 cm/s, and the air on the upstream and downstream sides of the filter medium was sampled using a particle counter (KC-01 manufactured by RION). and count the number of particles of 1.0 to 5.0μ. The calculation formula for collection efficiency is determined using the following formula.
Collection efficiency (%) = [1-(D1/D2)] x 100 where D1: number of downstream particles (total of two times), D2: number of particles upstream (total of two times).
(4) Breaking elongation According to JIS L-1906, 5 samples were cut out at 5 cm in the CD direction and 20 cm in the MD direction so that they were evenly spaced in the CD direction, and tested using a tensile tester at a gripping interval of 15 cm and a tensile speed of 20 cm/min. It was measured. Samples were measured at five points in the longitudinal direction, and the measured values were averaged to calculate the elongation at break.
(5) Elasticity Modulus From the graph obtained in (4) above, the elasticity modulus was calculated from the slope, where the horizontal axis is strain [cm] and the vertical axis is tensile stress [cN].
(6) Pleating property Pleating was performed using a reciprocating folding type pleating machine at a pleat height of 60 mm, a slit width of 600 mm, and a folding speed of 20 folds/min. Pleating property is evaluated as ○ (good pleating property) when the peak height is stable and the tops of peaks and valleys are bent at acute angles, and when pleating is possible but the peak height is not stable, If tears are visually observed in the peaks and troughs, it is judged as △ (pleatability is slightly poor), and if pleats cannot be processed or large tears are visually observed in the peaks and valleys, it is judged as ×. (The pleat workability was poor) and the evaluation was made.

[Example 1]
Synthetic rubber adhesive was sprayed in the form of a mist at 2 g/m ² onto a polyethylene terephthalate spunbond nonwoven fabric (average fiber diameter 10 μm, basis weight 20 g/m ² ), and a polypropylene melt-blown nonwoven fabric (average fiber diameter 3 μm, basis weight 30 g/m ² ) were laminated to produce the laminated filter medium of Example 1. The elastic modulus ratio between the melt blown nonwoven fabric and the spunbond nonwoven fabric (elastic modulus of the melt blown nonwoven fabric/elastic modulus of the spunbond nonwoven fabric) was 0.6, and the ratio of elongation at break was 1.5.

[Example 2]
A synthetic rubber adhesive was sprayed in the form of a mist at 2 g/m ² onto a polyethylene terephthalate spunbond nonwoven fabric (average fiber diameter 40 μm, basis weight 20 g/m ² ), and a polypropylene melt-blown nonwoven fabric (average fiber diameter 3 μm, basis weight 30 g/m ² ) were laminated to produce the laminated filter medium of Example 2. The elastic modulus ratio of the melt-blown nonwoven fabric and the spunbond nonwoven fabric was 0.38, and the ratio of elongation at break was 0.8.

[Comparative example 1]
Synthetic rubber adhesive was sprayed in the form of a mist at 2 g/m ² onto polypropylene spunbond nonwoven fabric (average fiber diameter 20 μm, basis weight 15 g/m ² ), and polypropylene melt-blown nonwoven fabric (average fiber diameter 3 μm, basis weight 30 g/m ² ) was produced. were laminated to produce a laminated filter medium of Comparative Example 1. The elastic modulus ratio of the melt-blown nonwoven fabric and the spunbond nonwoven fabric was 1.0, and the ratio of elongation at break was 2.7.

[Comparative example 2]
A synthetic rubber adhesive was sprayed in the form of a mist at 2 g/m ² onto a polypropylene spunbond nonwoven fabric (average fiber diameter 20 μm, basis weight 15 g/m ² ), and a polypropylene melt-blown nonwoven fabric (average fiber diameter 7 μm, basis weight 20 g/m ² ) was prepared. were laminated to produce a laminated filter medium of Comparative Example 2. The elastic modulus ratio of the melt-blown nonwoven fabric and the spunbond nonwoven fabric was 0.7, and the ratio of elongation at break was 0.2.

Next, the filter will be explained.
A thermally bonded nonwoven fabric made of polyethylene terephthalate (average fiber diameter 40 μm, basis weight 45 g/m ² ) was used as the support layer, and a synthetic rubber adhesive was sprayed at 2 g/m ² in the form of a mist. A filter was produced by overlapping the melt-blown nonwoven fabric side of the laminated filter media of Examples 1 and 2 and passing it through a calender roll. The collection efficiency and pleatability of the produced filter were measured. The results are shown in Table 1.

As can be seen from Table 1, the laminated filter medium of the example of the present invention has an elastic modulus ratio of 0.1 to 0.8 between the melt blown nonwoven fabric and the spunbond nonwoven fabric, and a rupture elongation of the melt blown nonwoven fabric and the spunbond nonwoven fabric. The ratio is between 0.3 and 2.0. It can be seen that the filter using the laminated filter medium of the example has higher dust removal efficiency and excellent workability than the filter using the laminated filter medium of the comparative example.

The filter medium of the present invention not only has excellent processability, but also excellent dust collection performance and good mechanical strength. Therefore, it can be suitably used as, for example, an industrial air filter or a liquid filter.

Claims (4)

A filter medium in which a spunbond nonwoven fabric made of fibers with an average fiber diameter of 10 to 40 μm and a meltblown nonwoven fabric made of fibers with an average fiber diameter of 1 to 6 μm are laminated,
The elastic modulus ratio of the melt-blown nonwoven fabric and the spunbond nonwoven fabric is 0.1 to 0.8,
A laminated filter medium characterized in that the elongation at break ratio of the melt-blown nonwoven fabric and the spunbond nonwoven fabric is 0.3 to 2.0. The laminated filter medium according to claim 1, wherein a support layer of a nonwoven fabric made of fibers having an average fiber diameter of 20 to 50 μm is laminated on the melt-blown nonwoven fabric side. The laminated filter medium according to claim 2, wherein the fibers of the support layer are made of polyethylene terephthalate. A filter using the laminated filter medium according to any one of claims 1 to 3.