阅读说明：本技术 纺粘无纺布和由纺粘无纺布构成的空气过滤器 (Spun-bonded nonwoven fabric and air filter composed of spun-bonded nonwoven fabric ) 是由 吉田润 山野浩司 中野洋平 西村诚 于 2019-07-22 设计创作，主要内容包括：本发明的目的在于,提供为低压力损失且高捕集性能、加工性优异的纺粘无纺布、和使用该纺粘无纺布的空气过滤器,提供纺粘无纺布,其由包含聚烯烃系树脂的纤维构成,其平均单纤维直径为6.5μm以上且22.0μm以下,含有0.1质量%以上且5质量%以下的受阻胺系下述通式(1)所示的化合物,前述无纺布的熔体流动速率(MFR)为32g/10分钟以上且850g/10分钟以下,该无纺布经驻极体加工。(The purpose of the present invention is to provide a spunbonded nonwoven fabric that has a low pressure loss, high trapping performance, and excellent processability, and an air filter that uses the spunbonded nonwoven fabric, wherein the spunbonded nonwoven fabric is composed of fibers that contain a polyolefin resin, has an average filament diameter of 6.5 [ mu ] m or more and 22.0 [ mu ] m or less, contains 0.1 mass% or more and 5 mass% or less of a hindered amine compound represented by the following general formula (1), has a Melt Flow Rate (MFR) of 32g/10 minutes or more and 850g/10 minutes or less, and is electret-processed.)

1. A spunbonded nonwoven fabric which comprises fibers comprising a polyolefin resin, has an average filament diameter of 6.5 to 22.0 [ mu ] m, contains 0.1 to 5 mass% of a hindered amine compound, has a Melt Flow Rate (MFR) of 32g/10 to 850g/10 min, and is electret-processed.

2. The spunbonded nonwoven fabric according to claim 1, wherein the hindered amine compound comprises a compound represented by the following general formula (1),

[ solution 1]

Herein, R is¹~R³Is hydrogen or alkyl of 1-2 carbon atoms, R⁴Is hydrogen or alkyl having 1 to 6 carbon atoms.

3. A spunbonded nonwoven fabric which is composed of fibers comprising a polyolefin resin, has an average filament diameter of 6.5 to 13.0 [ mu ] m, contains 0.1 to 5 mass% of a compound represented by the following general formula (1), has a Melt Flow Rate (MFR) of 80 to 850g/10 min, and is electret-processed.

4. The spun-bonded nonwoven fabric according to any one of claims 1 to 3, wherein the mass per unit area of the nonwoven fabric is 5g/m²Above and 60g/m²The following.

5. The spun-bonded nonwoven fabric according to any one of claims 1 to 4, wherein the thickness of the nonwoven fabric is 0.05mm or more and 1.0mm or less.

6. The spunbonded nonwoven fabric according to any one of claims 1 to 5, wherein the longitudinal tensile strength per unit mass area is 0.3(N/5 cm)/(g/m)²) The above.

7. The spunbonded nonwoven fabric according to any one of claims 1 to 6, wherein the pressure loss per unit area mass is 0.10 to 0.50 (Pa)/(g/m)²) The following.

8. The spun-bonded nonwoven fabric according to any one of claims 1 to 7, wherein the nonwoven fabric contains 0.001 mass% to 1.0 mass% of a crystal nucleating agent.

9. A filter material for an air filter, which comprises the nonwoven fabric according to any one of claims 1 to 8.

Technical Field

The present invention relates to spunbonded nonwoven fabrics. In particular, the present invention relates to a spunbonded nonwoven fabric which exhibits a low pressure loss, a high trapping performance and excellent processability when used as an air filter, and an air filter comprising the spunbonded nonwoven fabric.

Background

Conventionally, air filters have been used for removing pollen, seeds, and dusts from gases, and fibrous sheets have been often used as filter materials. The performance required for the air filter is that a large amount of fine dust can be collected (high collection performance) and that the resistance is low when gas passes through the inside of the air filter (low pressure loss characteristic).

The trapping mechanism of the air filter mainly utilizes physical actions such as brownian diffusion, blocking, inertial collision, and the like, and therefore, in order to obtain a filter material having a higher trapping performance, it is preferable that the fineness of the fiber sheet to be constituted is relatively small. On the other hand, when it is desired to obtain the same trapping performance, the fiber density in the sheet, in other words, the pore size has to be decreased, and as a result, the pressure loss becomes high.

Conversely, in order to obtain a filter material with a low pressure loss, the fineness of the fiber sheet to be formed may be relatively large, but the collection performance is lowered because the gaps between the fibers in the sheet are increased.

As described above, the trade-off between the high trapping performance and the low pressure loss characteristic is very difficult to achieve. Therefore, in general, the nonwoven sheet made of fine fibers is used for applications where high trapping performance is important, and the nonwoven sheet made of coarse fibers is used for applications where low pressure loss characteristics is important, and the applications are classified according to the fineness of the fibers.

However, a technique is known in which the fiber sheet is charged to improve the trapping performance by utilizing the electrostatic effect in addition to the physical effect. For example, a method of manufacturing an electret fibrous sheet has been proposed in which a fibrous sheet is brought into contact with a ground electrode, the ground electrode is moved together with the fibrous sheet, and a high voltage is applied to the fibrous sheet by a non-contact type application electrode to continuously electret the fibrous sheet (patent document 1). This imparts an electric charge to the fibers by causing polarization such as injection of electrons, movement of ions, and orientation of dipoles in the nonwoven fabric.

The fiber sheet described in the example of patent document 1 is a meltblown nonwoven fabric electret by applying a high voltage, and in general, a fine denier sheet such as a meltblown nonwoven fabric has a larger total surface area of fibers contained in a unit volume than a coarse denier sheet, and a larger charging effect is obtained, and therefore, the collecting performance can be further improved, and the fiber sheet can be used for applications where high collecting is more important.

On the other hand, it has been attempted to apply this charging technique to a large fineness sheet to impart high trapping performance to the original low pressure loss characteristic.

As a method for obtaining a thick fiber sheet relatively easily, there is a spunbond method, and for example, as disclosed in patent documents 2 and 3, a study has been made to charge a nonwoven fabric obtained by the spunbond method.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 61-289177

Patent document 2: japanese laid-open patent publication No. 2008-150753

Patent document 3: japanese patent laid-open publication No. 2009-275327.

Disclosure of Invention

Problems to be solved by the invention

However, the meltblown nonwoven fabric as disclosed in patent document 1 has a problem that although the collection efficiency is high, the strength is poor and cracks occur in the processing stage and the product stage. In the spunbonded nonwoven fabrics disclosed in patent documents 2 and 3, the single fiber fineness (average single fiber diameter) of the fibers used in the examples is in the conventional range, and therefore, the strength is not a problem when the spunbonded nonwoven fabrics are produced into an air filter, but the collection performance is insufficient.

Accordingly, an object of the present invention is to provide a spunbonded nonwoven fabric having a low pressure loss, a high collection performance, and excellent processability, and an air filter using the same.

Means for solving the problems

In the spun-bonded nonwoven fabric according to the prior art, the present inventors have attempted to further improve the trapping performance by increasing the fiber amount, but the pressure loss increases as a result of the increase in the mass per unit area. Therefore, the present inventors have further studied to achieve the above object and found that a spunbond nonwoven fabric having a low pressure loss and a high collection efficiency can be obtained by setting the melt flow rate of the spunbond nonwoven fabric within a specific range and setting the average filament diameter of the fibers constituting the spunbond nonwoven fabric within a specific range.

That is, the present invention has been completed based on these findings, and the present invention provides the following inventions.

The spunbonded nonwoven fabric of the invention is composed of fibers containing polyolefin resin, has an average filament diameter of 6.5-22.0 [ mu ] m, contains 0.1-5% by mass of hindered amine compound, has a Melt Flow Rate (MFR) of 32-10 min and 850g/10 min, and is processed by electret processing.

According to a preferred embodiment of the spunbonded fabric of the invention, the hindered amine compound is a compound represented by the following general formula (1).

[ solution 1]

(Here, R is¹~R³Is hydrogen or alkyl of 1-2 carbon atoms, R⁴Is hydrogen or alkyl having 1 to 6 carbon atoms).

According to a preferred embodiment of the spunbonded nonwoven fabric of the invention, the spunbonded nonwoven fabric has a mass per unit area of 5g/m²Above and 60g/m²The following.

According to a preferred embodiment of the spunbonded nonwoven fabric of the invention, the spunbonded nonwoven fabric has a thickness of 0.05mm to 1.0 mm.

According to a preferred embodiment of the spunbonded nonwoven fabric of the invention, the longitudinal tensile strength per unit mass is 0.3(N/5 cm)/(g/m)²) The above.

In a preferred embodiment of the spunbonded nonwoven fabric according to the invention, the crystal nucleus agent is contained in an amount of 0.001 to 1.0 mass%.

The filter medium for an air filter of the present invention is obtained by using the above-described spun-bonded nonwoven fabric.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a spun-bonded nonwoven fabric having a low pressure loss, a high trapping performance, and excellent processability, and an air filter using the spun-bonded nonwoven fabric can be obtained.

Drawings

FIG. 1 is a schematic side view showing a measuring apparatus for collection efficiency and pressure loss.

Detailed Description

The spunbonded nonwoven fabric of the invention is composed of fibers containing polyolefin resin, the average filament diameter of the spunbonded nonwoven fabric is more than 6.5 μm and less than 22.0 μm, preferably the spunbonded nonwoven fabric contains more than 0.1 mass% and less than 5 mass% of a compound represented by the following general formula (1), the Melt Flow Rate (MFR) of the spunbonded nonwoven fabric is more than 32g/10 min and less than 850g/10 min, and the spunbonded nonwoven fabric is processed by electret.

[ solution 2]

(Here, R is¹~R³Is hydrogen or alkyl of 1-2 carbon atoms, R⁴Is hydrogen or alkyl having 1 to 6 carbon atoms).

The following detailed description will be given of the constituent elements, but the present invention is not limited to the scope of the following description in any way as long as the invention does not exceed the gist thereof.

[ resin ]

The fibers constituting the spunbond nonwoven fabric used in the present invention include polyolefin resins. Examples of the polyolefin resin include a polypropylene resin and a polyethylene resin. The polypropylene resin includes homopolymers of propylene and copolymers of propylene and various α -olefins, and the polyethylene resin includes homopolymers of ethylene and copolymers of ethylene and various α -olefins, and among these, polypropylene-based materials are preferable from the viewpoint of exhibiting electret properties in particular. In addition, other components may be copolymerized within a range not to impair the properties of the polymer.

The polyolefin resin used in the present invention may be a mixture of 2 or more kinds, and a resin composition containing another polyolefin resin, a thermoplastic elastomer, or the like may be used. Of course, it is also possible to blend 2 or more thermoplastic resins having different MFR at an arbitrary ratio to adjust the MFR.

The MFR of the polyolefin resin used in the present invention is measured by ASTM D1238 (method a).

According to this standard, polypropylene, for example, is specified in the following weight ratio: 2.16kg, temperature: polyethylene is specified at a weight loading, measured at 230 ℃: 2.16kg, temperature: measured at 190 ℃. When a plurality of resins are used, the measurement is performed at the highest temperature among the measurement temperatures of the polyolefin resins.

The MFR of the polyolefin-based resin is preferably 32g/10 min or more and 850g/10 min or less. The lower limit of MFR is preferably 32g/10 min or more, more preferably 60g/10 min or more, still more preferably 80g/10 min or more, particularly preferably 120g/10 min or more, and most preferably 155g/10 min or more. The upper limit is preferably 850g/10 min or less, more preferably 600g/10 min or less, and still more preferably 400g/10 min or less. By setting the lower limit or more, the thinning behavior of the fibers in spinning the fibers constituting the spunbond nonwoven fabric is stabilized, and even if the fibers are drawn at a high spinning speed to improve productivity, stable spinning can be performed. Further, by stabilizing the thinning behavior, yarn sway is suppressed, and unevenness is less likely to occur when collected in a sheet form. Further, by setting the upper limit or less, the fiber can be drawn at a stable and fast spinning speed, and therefore, oriented crystallization of the fiber proceeds, and a fiber having high mechanical strength can be produced.

The melting point of the polyolefin resin used in the present invention is preferably 80 ℃ to 200 ℃, more preferably 100 ℃ to 180 ℃. By setting the melting point to preferably 80 ℃ or higher, more preferably 100 ℃ or higher, heat resistance that can withstand practical use is easily obtained. Further, by setting the melting point to preferably 200 ℃ or lower, more preferably 180 ℃ or lower, the yarn discharged from the spinneret is easily cooled, and fusion between fibers is suppressed, and stable spinning is easily performed. The melting point referred to herein is a value measured under the condition of a temperature rise rate of 20 ℃ per minute using a differential scanning calorimeter DSC-2 manufactured by Perkinelmer.

In addition, additives such as an antioxidant, a weather resistant stabilizer, a light resistant stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a lubricant, a nucleating agent, and a pigment, which are generally used, or other polymers may be added to the polyolefin resin used in the present invention as needed, as long as the effects of the present invention are not impaired.

The spunbonded nonwoven fabric of the present invention can be added with additives such as a heat stabilizer, a weather resistant agent, and a polymerization inhibitor, and it is important that the fiber material contains a hindered amine compound, preferably a compound represented by the general formula (1) (hindered amine compound) from the viewpoint of improving the charging property and the charge retention property when the nonwoven fabric is electret treated.

The hindered amine compound is contained in an amount of 0.1 to 5% by mass, and the lower limit is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more. The content is preferably 4% by mass or less, more preferably 3% by mass or less, and particularly preferably 2.5% by mass or less.

Examples of the hindered amine compound include poly [ (6- (1,1,3, 3-tetramethylbutyl) amino-1, 3, 5-triazine-2, 4-diyl) ((2,2,6, 6-tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6, 6-tetramethyl-4-piperidyl) imino) ] (manufactured by BASF seed ジャパン (strain), "chimassob" (registered trademark) 944LD), dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2, 2,6, 6-tetramethylpiperidine polycondensate (manufactured by BASF ジャパン (strain), "Tinuvin" (registered trademark) LD 622), and 2- (3, 5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid bis (1), 2,2,6, 6-pentamethyl-4-piperidyl) (BASF ジャパン (strain), "Tinuvin" (registered trademark) 144), dibutylamine seed 1,3, 5-triazine seed N, N' -bis (2,2,6, 6-tetramethyl-4-piperidyl-1, 6-hexamethylenediamine seed N- (2,2,6, 6-tetramethyl-4-piperidyl) butylamine polycondensate (BASF seed ジャパン (strain) 2020, "chimassorb" (registered trademark) FDL), and the like. Among them, from the viewpoint of charging properties and charge retention properties when electret-treated to a spunbonded nonwoven fabric, a compound represented by the above general formula (1) (hindered amine-based additive) is preferable, and specifically, a poly [ (6- (1,1,3, 3-tetramethylbutyl) amino-1, 3, 5-triazine-2, 4-diyl) ((2,2,6, 6-tetramethyl-4-piperidyl) imino) hexamethylene ((2,2,6, 6-tetramethyl-4-piperidyl) imino) ] (BASF seed ジャパン (strain), Chimasorb (registered trademark) 944LD), dibutylamine seed 1,3, 5-triazine N, N' -bis (2,2,6, 6-tetramethyl-4-piperidyl-1, polycondensates of 6-hexamethylenediamine (BASF, seed ジャパン, or "chimassorb" (registered trademark) 2020FDL) with N- (2,2,6, 6-tetramethyl-4-piperidyl) butylamine.

The hindered amine compound such as a compound having a structure represented by general formula (1) may be used in 1 kind or a mixture of plural kinds.

[ solution 3]

(Here, R is¹~R³Is hydrogen or alkyl of 1-2 carbon atoms, R⁴Is hydrogen or alkyl having 1 to 6 carbon atoms).

Since the compound is present in the spunbonded nonwoven fabric, the charge imparted by charging can be stabilized more effectively, and therefore, when the spunbonded nonwoven fabric is used for a filter material of an air filter, the collection performance is improved, and an air filter having a low pressure loss and a high collection performance can be realized.

The fibers constituting the spunbonded nonwoven fabric of the present invention may contain a crystal nucleus agent in addition to the compound represented by the general formula (1).

Examples of the crystal nucleating agent include sorbitol nucleating agents, nonitol nucleating agents, xylitol nucleating agents, phosphate nucleating agents, triaminobenzene derivative nucleating agents, and carboxylate metal salt nucleating agents.

Examples of sorbitol-based nucleating agents include dibenzylidene sorbitol (DBS), monomethyl dibenzylidene sorbitol (e.g., 1, 3: 2, 4-bis (p-methylbenzylidene) sorbitol (p-MDBS)), dimethyl dibenzylidene sorbitol (e.g., 1, 3: 2, 4-bis (3, 4-dimethylbenzylidene) sorbitol (3,4-DMDBS)), and "Millad" (registered trademark) 3988 (manufactured by "ジャパン strain" ミリケン), and "ゲルオール" (registered trademark) E-200 (manufactured by new japanese national chemical and chemical industries (strain)).

Examples of the nonitol-based nucleating agent include 1,2, 3-trideoxy-4, 6: examples of 5, 7-bis- [ (4-propylphenyl) methylene ] -nonitol include "Millad" (registered trademark) NX8000(ミリケン seed ジャパン (manufactured by nippon corporation)) and the like.

Among the xylitol-based nucleating agents, there are included, for example, bis-1, 3: 2,4- (5',6',7',8' -tetrahydro-2-naphthaldehyde benzylidene) 1-allylxylitol, and the like. Examples of the phosphoric acid-based nucleating agent include aluminum-bis (4,4',6,6' -tetra-t-butyl-2, 2' -methylenediphenyl-phosphate) -hydroxide, and "アデカスタブ" (registered trademark) NA-11 (manufactured by ADEKA corporation) and "アデカスタブ" (registered trademark) NA-21 (manufactured by ADEKA corporation) can be given.

Examples of the triaminobenzene derivative nucleating agent include 1,3, 5-tris (2, 2-dimethylpropanamide) benzene and the like, and examples thereof include "Irgaclear" (registered trademark) XT386 "(manufactured by BASF ジャパン, inc.) represented by the following general formula (2). Further, the metal carboxylate nucleating agent includes, for example, sodium benzoate, calcium 1, 2-cyclohexanedicarboxylate and the like.

[ solution 4]

(in the general formula (2), R¹、R²And R³Each independently represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 3 to 20 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, a cycloalkenyl group having 5 to 9 carbon atoms, or an aryl group having 6 to 10 carbon atoms).

The content of the crystal nucleating agent in the fibers constituting the nonwoven fabric is preferably 0.001 mass% or more and 1.0 mass% or less. When the content of the crystal nucleating agent is 0.001% by mass or more, more preferably 0.005% by mass or more, the effect of improving the dust-trapping property can be effectively obtained. Further, fusion between fibers can be suppressed, and the ventilation amount can be increased. On the other hand, when the content of the crystal nucleus agent is 1.0% by mass or less, more preferably 0.5% by mass or less, the spinnability is stable and the cost is also excellent.

The spunbonded nonwoven fabric of the present invention is composed of a polymer containing the above-mentioned compound, and the polymer may contain a stabilizer usually contained in a resin material such as an antioxidant, a light stabilizer, a heat stabilizer, and the like, in addition to the above-mentioned compound.

The contents of the compound represented by the above general formula (1) and the crystal nucleus agent in the present invention are determined as follows.

The content referred to herein can be determined, for example, as follows. Subjecting non-woven fabric to Soxhlet extraction with methanol/chloroform mixed solution, and performing needle extractionThe extract was subjected to repeated HPLC separation, and the separated product was subjected to IR measurement, GC/MS measurement, MALDI-MS measurement, mass spectrometry, etc,¹H-NMR measurement and¹³the structure was confirmed by C-NMR measurement. The mass of the isolate contained in the crystal nucleus agent was summed up to obtain the ratio to the whole nonwoven fabric, and this was referred to as the content of the crystal nucleus agent. In addition, with respect to the compound represented by the above general formula (1), the mass of the isolate including the compound is also summed up, and the ratio to the whole nonwoven fabric is obtained and referred to as the content of the compound.

[ fibers ]

Further, the fibers constituting the spunbonded nonwoven fabric of the invention may be composite fibers. Examples of the composite form of the composite fiber include a concentric core-sheath type, an eccentric core-sheath type, and a sea-island type. The single component fiber, the core-sheath type, the sea-island type, and other composite component fibers are not particularly limited, and in the case of the composite component fiber, depending on the selection of the resin, there is a possibility that charge leakage occurs due to a difference in electrical resistance between the resins, and therefore the single component fiber is a preferable embodiment.

It is important that the fibers constituting the spunbonded nonwoven fabric used in the present invention have an average filament diameter of 6.5 to 22.0 μm. By setting the average single fiber diameter to preferably 6.5 μm or more, more preferably 7.5 μm or more, and further preferably 8.4 μm or more, it is possible to prevent a decrease in spinnability and stably produce a nonwoven fabric with good quality. On the other hand, by setting the average single fiber diameter to preferably 22.0 μm or less, more preferably 13.0 μm or less, further preferably 11.2 μm or less, and particularly preferably 10.0 μm or less, the spun-bonded nonwoven fabric has high denseness and uniformity and excellent processability that can withstand practical use, and when an air filter is produced using the spun-bonded nonwoven fabric, high collection efficiency can be achieved.

The cross-sectional shape of the fibers constituting the spunbonded nonwoven fabric of the present invention is not particularly limited as long as the obtained spunbonded nonwoven fabric is suitable for filter applications, and a round shape, a hollow round shape, an oval shape, a flat shape, an irregular shape such as an X-shape and a Y-shape, a polygonal shape, a multi-lobal shape, and the like are preferable. The fiber diameter of the non-circular fiber is determined by taking a circumscribed circle and an inscribed circle of the fiber cross section and taking the average value of the diameters as the fiber diameter.

[ spunbonded nonwoven Fabric ]

It is important that the MFR of the spunbonded nonwoven fabric of the invention is 32g/10 min or more and 850g/10 min or less. Preferably 32g/10 min or more, more preferably 60g/10 min or more, further preferably 80g/10 min or more, particularly preferably 120g/10 min or more, and most preferably 155g/10 min or more. This makes the nonwoven fabric thin and high in collection efficiency. On the other hand, by setting the fiber to 850g/10 min or less, preferably 600g/10 min or less, and more preferably 400g/10 min or less, the fiber thinning behavior during spinning is stable, and even if the fiber is drawn at a high spinning speed for improving productivity, stable spinning can be achieved.

The MFR of the spunbonded nonwoven fabric of the present invention is a value measured by ASTM D1238 (method a). In addition, according to this standard, for example, polypropylene is specified as a polypropylene resin having a specific weight ratio in terms of load: 2.16kg, temperature: polyethylene, measured at 230 ℃, is specified as the weight ratio: 2.16kg, temperature: measured at 190 ℃. In the case where a plurality of resins are used, such as the polyolefin resin constituting the spunbonded nonwoven fabric and the resin constituting the other nonwoven fabric, in the mode of laminating the spunbonded nonwoven fabric and the other nonwoven fabric described later, the measurement is performed at the highest temperature among the measurement temperatures of the polyolefin resin constituting the spunbonded nonwoven fabric.

Further, it is important that the spunbonded nonwoven fabric of the present invention is charged and a high trapping performance can be obtained while maintaining a low pressure loss characteristic by utilizing an electrostatic adsorption effect by forming the charged spunbonded nonwoven fabric.

Here, the pressure loss and the trapping efficiency in the present invention are measured by the following measurement methods or measurement methods that obtain results equivalent thereto. That is, 5 measurement samples of 15cm × 15cm were collected from any part of the spunbonded nonwoven fabric, and the collection efficiency and the pressure loss were measured for each sample by a collection performance measuring apparatus shown schematically in fig. 1.

The mass per unit area of the spunbonded nonwoven fabric of the invention is only requiredSuitable for filter applications, but is not particularly limited, and is preferably 5g/m²Above, more preferably 8g/m²Above, particularly preferably 10g/m²The above. In this way, the strength and rigidity of the nonwoven fabric can be improved. Further, it is preferably 60g/m²Below, more preferably 50g/m²The amount of the surfactant is preferably 40g/m or less²The following. In this way, the pressure loss can be reduced, and this is a preferable range in terms of cost.

Further, the spunbonded nonwoven fabric of the present invention may be laminated with other sheets to form a laminated fiber sheet. For example, it is preferable to laminate a spunbonded nonwoven fabric and a sheet having higher rigidity than the spunbonded nonwoven fabric to increase the strength of the product; and sheets having deodorizing, seeding, antibacterial and other functional properties.

The spunbonded nonwoven fabric of the invention preferably has a tensile strength per unit mass in the machine direction of 0.3(N/5 cm)/(g/m)²) The above. By setting the tensile strength per unit area mass in the machine direction to 0.3(N/5 cm)/(g/m)²) Above, preferably 0.5(N/5 cm)/(g/m)²) More preferably 1.0(N/5 cm)/(g/m)²) More than, particularly preferably 1.5(N/5 cm)/(g/m)²) As described above, the resin composition is not broken during processing and has excellent processability. The longitudinal tensile strength per unit mass can be adjusted by the spinning speed of the fibers constituting the spunbond nonwoven fabric layer, the average filament diameter, the thermocompression bonding conditions (the bonding ratio, the temperature, and the line pressure) of the spunbond nonwoven fabric, and the like. The longitudinal direction referred to herein means the longitudinal direction of the nonwoven fabric.

Further, the tensile elongation at the highest tensile strength of the above tensile strengths is preferably 15% or more, more preferably 20% or more, and still more preferably 30% or more, whereby the steel sheet can be processed without breaking during molding or the like, and thus can be made into a material having excellent processability.

The thickness of the spun-bonded non-woven fabric is preferably 0.05-1.0 mm. The thickness is preferably 0.05 to 1.0mm, more preferably 0.08 to 0.8mm, and further preferably 0.10 to 0.5 mm. The thickness is preferably in the above range in order to suppress an increase in pressure loss due to the pleated shape when the air filter is manufactured. If the thickness is less than the lower limit, it is not preferable because it is difficult to obtain shape retention of the filter material when handling high air volume, and if the thickness is greater than the upper limit, it is not preferable because storage property when used as an air filter is lowered.

The spun-bonded nonwoven fabric of the present invention preferably has a pressure loss per unit area mass of 0.10 (Pa)/(g/m)²) Above and 0.50 (Pa)/(g/m)²) The following. The lower limit of the pressure loss per unit area mass is preferably 0.10 (Pa)/(g/m)²) More preferably 0.15 (Pa)/(g/m)²) More preferably 0.20 (Pa)/(g/m) or more²) As above, the upper limit is preferably 0.50 (Pa)/(g/m)²) Hereinafter, more preferably 0.45 (Pa)/(g/m)²) Hereinafter, more preferably 0.40 (Pa)/(g/m)²) The following. By setting the lower limit or more, the number of fibers contained in the mass per unit area is large, or the total surface area is large, so that strength excellent in workability without breaking at the time of processing can be obtained. By setting the upper limit or less, the number of fibers contained in the mass per unit area or the total surface area becomes appropriate, and a low pressure loss can be obtained.

[ method for producing spunbonded nonwoven Fabric ]

Next, an example of a method for producing the spunbonded nonwoven fabric of the present invention will be described.

The spunbonded nonwoven fabric according to the present invention is produced by first spinning a molten polyolefin resin as long fibers from a spinning nozzle, drawing the spun filaments by suction with compressed air through an ejector, and collecting the fibers on a moving web.

The spinneret and the ejector may have various shapes such as a circular shape and a rectangular shape. Among them, a combination of a rectangular spinneret and a rectangular ejector is preferably used because the amount of compressed air used is small, the energy cost is excellent, the fusion and rubbing of the yarns are difficult to occur, and the opening of the yarns is also easy.

In the present invention, the polyolefin resin is melted in an extruder, metered, and supplied to a spinning spinneret, and spun as a long fiber. The spinning temperature when the polyolefin resin is melted and spun is preferably 200 ℃ or higher and 270 ℃. By setting the spinning temperature to 200 ℃ or higher, more preferably 210 ℃ or higher, and still more preferably 220 ℃ or higher, or 270 ℃ or lower, more preferably 260 ℃ or lower, and still more preferably 250 ℃ or lower, a stable molten state can be obtained, and excellent spinning stability can be obtained.

The spun sliver of filament is then cooled. Examples of a method for cooling the spun yarn include a method of forcibly blowing cold air to the yarn, a method of naturally cooling the yarn at an ambient temperature around the yarn, a method of adjusting the distance between the spinneret and the ejector, and the like, or a method of combining these methods. The cooling conditions may be appropriately adjusted in consideration of the discharge amount per one hole of the spinneret, the spinning temperature, the atmosphere temperature, and the like.

Then, the cooled and solidified sliver is drawn and stretched by the compressed air ejected from the ejector. The spinning speed is preferably 3000 m/min or more and 6500 m/min or less. By setting the spinning speed to 3000 m/min or more and 6500 m/min or less, more preferably 3500 m/min or more and 6500 m/min or less, and still more preferably 4000 m/min or more and 6500 m/min or less, high productivity is achieved, and the oriented crystallization of the fiber progresses, whereby a long fiber having high strength can be obtained. In general, if the spinning speed is increased, the spinnability deteriorates and the yarn-like material cannot be stably produced, but as described above, by using a polyolefin-based resin having an MFR within a specific range, a desired polyolefin fiber can be stably spun.

Subsequently, the long fibers obtained are collected on the moving web to produce a nonwoven web. In the present invention, it is also preferable that the nonwoven web is pre-bonded by contacting a heated flat roll from one side of the web. In this way, the surface layer of the nonwoven fabric layer is prevented from curling or blowing off the web during conveyance and the quality is prevented from deteriorating, and the conveyance property from the collection of the sliver to the thermocompression bonding can be improved.

In the present invention, it is a preferable embodiment for the use as an air filter that the intersections of the nonwoven web obtained are pre-bonded by a heated flat roll before thermal bonding.

The surface temperature of the hot flat roll in the hot pre-bonding is preferably-60 to-25 ℃ relative to the melting point of the polyolefin resin used. The lower limit of the surface temperature of the hot flat roll is preferably-60 ℃ or higher, more preferably-55 ℃ or higher, relative to the melting point of the polyolefin resin. By setting the lower limit or more, excessive thermal adhesion at the time of the thermal adhesion is suppressed, and strength and air permeability suitable for use in air filter applications can be obtained. The upper limit of the surface temperature of the hot flat roll is preferably-25 ℃ or lower, more preferably-30 ℃ or lower, with respect to the melting point of the polyolefin resin. By setting the upper limit or less, the formation of a film on the surface of the nonwoven fabric is suppressed, and appropriate air permeability can be obtained. When 2 or more kinds of polyolefin resins are blended, if two or more melting points are observed, the lowest temperature among the melting points of the respective polyolefin resins is adjusted to the above range.

Examples of the method for thermally bonding the thermally prebonded nonwoven web include a method in which thermal bonding is performed by various rolls such as a hot embossing roll having engraved marks (uneven portions) on the upper and lower roll surfaces, a hot embossing roll comprising a combination of a roll having a flat (smooth) one roll surface and a roll having engraved marks (uneven portions) on the other roll surface, and a hot calendering roll comprising a combination of a pair of upper and lower flat (smooth) rolls; ultrasonic bonding by thermal welding by ultrasonic vibration of a horn (ホーン), and the like. Among them, a heat embossing roller having excellent productivity, imparting strength to a part of the heat-adhesive portion, and maintaining the texture and the touch of the non-adhesive portion unique to the nonwoven fabric is preferably used, and a heat embossing roller having engraved marks (uneven portions) on the surfaces of the upper and lower pair of rollers, or a heat embossing roller including a combination of a roller having a flat (smooth) roller surface and a roller having engraved marks (uneven portions) on the other roller surface is preferably used.

As the surface material of the heat embossing roll, in order to obtain a sufficient thermocompression bonding effect and prevent marks (uneven portions) of the individual embossing roll from being transferred to the surface of the other roll, it is preferable to pair a metal roll and a metal roll.

The embossed bonding area ratio by such a heat embossing roll is preferably 3% or more and 30% or less. By setting the bonding area to 3% or more, more preferably 5% or more, and still more preferably 8% or more, the nonwoven fabric can have a strength that can be practically used. On the other hand, by setting the bonding area to preferably 30% or less, more preferably 25% or less, and further preferably 20% or less, appropriate air permeability suitable for use in particular in air filter applications can be ensured. In the case of using ultrasonic bonding, the bonding area ratio is also preferably in the same range.

The bonding area referred to herein means a ratio of the bonded portion to the whole spunbond nonwoven fabric. Specifically, the thermal bonding by a pair of rollers having concave and convex portions means a ratio of a portion (bonding portion) in which the convex portion of the upper roller overlaps with the convex portion of the lower roller and which is in contact with the nonwoven fabric layer to the whole spunbond nonwoven fabric. In the case of thermal bonding by a roll having irregularities and a flat roll, the ratio of the portion (bonding portion) where the irregularities of the roll having irregularities and the nonwoven fabric layer are in contact with each other is the ratio of the whole spunbond nonwoven fabric. In the case of ultrasonic bonding, the ratio of the portion thermally welded by ultrasonic processing (bonded portion) to the whole spunbond nonwoven fabric is referred to.

As the shape of the bonding portion by the heat embossing roller or the ultrasonic bonding, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, or the like can be used. The bonding portions are preferably uniformly present at regular intervals in the longitudinal direction (conveyance direction) and the width direction of the spunbond nonwoven fabric. In this way, variations in the strength of the spunbond nonwoven fabric can be reduced.

The surface temperature of the hot embossing roll during thermal bonding is preferably-50 to-15 ℃ relative to the melting point of the polyolefin resin used. By setting the surface temperature of the heat roll to preferably-50 ℃ or higher, more preferably-45 ℃ or higher, relative to the melting point of the polyolefin resin, a spunbonded nonwoven fabric having a practical strength can be obtained by appropriate thermal bonding. Further, by setting the surface temperature of the heat embossing roll to preferably-15 ℃ or lower, more preferably-20 ℃ or lower, with respect to the melting point of the polyolefin-based resin, excessive thermal bonding is suppressed, and as a spunbond nonwoven fabric, appropriate air permeability and seed processability particularly suitable for use in air filter applications can be obtained.

When 2 or more kinds of polyolefin resins are blended, if two or more melting points are observed, the lowest temperature among the melting points of the respective polyolefin resins is adjusted to the above range.

The line pressure of the heat embossing roll at the time of thermal bonding is preferably 10N/cm or more and 500N/cm or less. By setting the linear pressure of the rolls to preferably 10N/cm or more, more preferably 50N/cm or more, further preferably 100N/cm or more, and particularly preferably 150N/cm, it is possible to obtain a spunbonded nonwoven fabric having a suitable strength for practical use by appropriate thermal bonding. On the other hand, by setting the line pressure of the heat embossing roll to preferably 500N/cm or less, more preferably 400N/cm or less, and even more preferably 300N/cm or less, it is possible to obtain air permeability and seed processability particularly suitable for use in air filter applications as a spunbond nonwoven fabric.

In the present invention, before and/or after the thermal bonding by the hot embossing roll, the thermal bonding may be performed by a hot embossing roll including a pair of upper and lower flat rolls in order to adjust the thickness of the spunbonded nonwoven fabric. The pair of upper and lower flat rolls are metal rolls and elastic rolls having no irregularities on the surfaces of the rolls, and the metal rolls may be used in pairs or the metal rolls and the elastic rolls may be used in pairs.

Here, the elastic roller is a roller made of a material having elasticity as compared with a metal roller. Examples of the elastic roller include paper, so-called paper rolls such as cotton and aramid paper, and resin rollers made of urethane resin, epoxy resin, silicone resin, polyester resin, hard rubber, and a mixture thereof.

In addition, the thermal bonding method described above is also a preferable method in the method of thermally bonding the pre-bonded nonwoven web and another sheet in a laminated manner.

In the production of a spunbonded nonwoven fabric obtained by electret processing, the charging method is not particularly limited, and according to various findings of the present inventors, a corona charging method, a method of applying water to a nonwoven fabric sheet and then drying the nonwoven fabric sheet to charge the nonwoven fabric sheet (for example, methods described in japanese unexamined patent publication No. 9-501604, japanese unexamined patent publication No. 2002-249978, and the like), a thermal electret method, and the like are particularly suitable. In the case of the corona charging method, an electric field strength of preferably 15kV/cm or more, more preferably 20kV/cm or more is suitable. The charging process may be continuously performed during the production of the nonwoven fabric, or the produced nonwoven fabric may be temporarily rolled and processed in another step.

Examples

The present invention will be described in further detail below with reference to examples, but the following examples are not intended to limit the present invention, and design changes according to the gist of the present description are also included in the technical scope of the present invention.

[ measurement method ]

The measurement method is not particularly described, and the measurement is performed by the method described above.

Next, the electret fiber sheet of the present invention will be described based on examples. The characteristics and properties of the present invention are obtained by the following methods.

(1) Mass per unit area of spunbond nonwoven fabric:

the mass of the sheet with length x cross =5cm x 5cm was determined for 3 pieces for 1 sample. Converting the obtained value to 1m each²Rounding off the 1 st position after decimal point to calculate the sheet mass per unit area (g/m)²)。

(2) Average single fiber diameter:

with respect to the average single fiber diameter, 10 measurement samples of 3mm × 3mm were collected from any portion of the sheet, the magnification was adjusted to 200 to 3000 times with a scanning electron microscope, and photographs of the surface of each of 1 and 10 total fibers were taken from the collected measurement samples. The fiber diameter (filament diameter) of the fiber clearly confirmed in the photograph was measured, and the 2 nd digit after the decimal point of the average value was rounded off and referred to as the average filament diameter.

(3) Sheet thickness:

the thickness of the sheet was measured at 10 points at equal intervals in the width direction using a thickness meter (model "TECCLOCK" (registered trademark) SM-114 manufactured by テクロック Co.), and the decimal point and the 3 rd position after the decimal point were rounded off from the average value and recorded as the thickness.

(4) Trapping performance of spunbond nonwoven (trapping efficiency and pressure loss):

samples for measurement having a length of × width =15cm × 15cm were collected at 5 locations in the width direction of the sheet, and the collection efficiency was measured for each sample using the collection efficiency measurement device shown in fig. 1. In the trapping efficiency measuring apparatus of fig. 1, a dust storage box 2 is connected to an upstream side of a sample stage 1 on which a measurement sample M is mounted, and a flow meter 3, a flow rate regulating valve 4, and a blower 5 are connected to a downstream side. Further, the sample stage 1 is provided with a particle counter 6, and the number of the upstream dust and the number of the downstream dust of the measurement sample M can be measured by a switching cock 7. Further, the sample stage 1 has a pressure gauge 8 capable of reading a static pressure difference between the upstream and downstream of the measurement sample M.

For measurement of the trapping efficiency, a 10% solution of polystyrene (Nacalai TESSQUE, INC.) was diluted 200-fold with distilled water and filled in the dust storage box 2. Next, the measurement sample M was set on the sample stage 1, and the air flow rate was adjusted by the flow rate adjusting valve 4 so that the filter passing speed became 6.5M/min, thereby controlling the dust concentration to be 1 ten thousand/(2.83X 10)^-4m³) Above and 4 ten thousand/(2.83X 10)^-4m³) The following range (2.83X 10)^-4m³Equal to 0.01ft³) The number D of dust particles at the upstream and the number D of dust particles at the downstream of the measurement sample M were measured 3 times per 1 measurement sample by a particle counter 6 (KC-01D manufactured by リオン Co.), and the collection efficiency (%) of the particles of 0.3 μ M to 0.5 μ M was determined based on JIS K0901 (1991) "shape, size and performance test method of filter material for collecting dust sample in gas" using the following calculation formula ". The average of 3 samples measured was taken as the final capture efficiency.

Seed and seed trapping efficiency (%) = [1- (D/D) } × 100

(wherein D represents the total number of measurements of 3 downstream dusts, and D represents the total number of measurements of 3 upstream dusts).

The higher the nonwoven fabric to be collected, the lower the number of downstream dusts, and therefore the higher the collection efficiency. The pressure loss was determined by reading the difference in static pressure between the upstream and downstream of the measurement sample M at the time of measurement of the trapping efficiency by the pressure gauge 8. The average of 5 samples determined is recorded as the final pressure loss.

The QF value, which is an index of trapping performance calculated according to the following equation and having a pressure loss of 25Pa or less, was 0.13Pa^-1In the above case, it is determined as pass.

Seed (QF) value (Pa)^-1) = -ln (1-trapping efficiency (%)/100)/pressure loss (Pa)

(5) Tensile Strength (N/5 cm)/(g/m) of nonwoven Fabric per unit area weight²)；

The tensile strength in the machine direction was measured as described below according to JIS L1913 (2010) at 6.3.1.

(A) 2 test pieces 5cm × 30cm wide were collected from the laminated nonwoven fabric.

(B) The test pieces were mounted on a tensile tester at a grip interval of 20 cm.

(C) The tensile test was conducted at a tensile rate of 10 cm/min, and the strength at break of the specimen was referred to as the tensile strength (N/5cm), and the second position after the decimal point of the average of 3 points was rounded off. The tensile strength obtained here was divided by the mass per unit area measured in (1) above, and the tensile strength per mass per unit area of the nonwoven fabric was calculated. Note that 0.3(N/5 cm)/(g/m)²) In the above case, the tensile strength is referred to.

(6) Pressure loss (Pa)/(g/m) per unit area mass of nonwoven fabric²)；

The pressure loss measured in (4) above was divided by the mass per unit area measured in (1) above to calculate the pressure loss per mass per unit area of the nonwoven fabric, and the decimal point and the 3 rd position of the obtained value were rounded off. The pressure loss per unit mass of the nonwoven fabric was 0.10 (Pa)/(g/m)²) Above and 0.50 (Pa)/(g/m)²) In the following cases, the determination is passed.

(7) Density of sheet

The density of the sheet was calculated by dividing the mass per unit area measured in (1) by the thickness measured in (3). The decimal point of the obtained value was rounded off at the 4 th position, and the density (g/cm) of the sheet was calculated³)。

[ example 1]

A polyolefin resin containing 1 mass% of a hindered amine compound "Chimassrob" (registered trademark) 944LD (manufactured by BASF ジャパン Co., Ltd.) represented by Compound A in a polypropylene resin composed of a homopolymer having an MFR of 200g/10 min was melted by an extruder, spun from a rectangular spinneret having a hole diameter of 0.30mm and a hole depth of 2mm at a spinning temperature of 235 ℃ and a single-hole discharge amount of 0.32 g/min, cooled and solidified, and then drawn, stretched and collected on a collecting net by a compressed air having a jet pressure of 0.35MPa by a rectangular jet. The obtained nonwoven web was thermally pre-bonded at 120 ℃ using a flat roll, and the thermally pre-bonded nonwoven web was thermally bonded at a temperature of 130 ℃ by a linear pressure of 30N/cm using an upper roll using an embossing roll made of metal and having a bonding area ratio of points with speckles of 16% and a lower roll using a pair of upper and lower hot embossing rolls made of flat rolls made of metal to obtain a nonwoven web having a mass per unit area of 30g/m²A spunbonded nonwoven fabric. The average filament diameter of the resulting spunbonded nonwoven fabric was 10.1. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The spunbonded nonwoven fabric was allowed to travel along the water surface of a water tank supplied with pure water, and water was sucked by contacting a slit-shaped suction nozzle on the surface thereof to impregnate the entire surface of the fiber sheet with water, and then, water was removed and hot air-dried at a temperature of 100 ℃. The measured values and calculated values of the electret nonwoven fabric are shown in table 1.

[ solution 5]

。

[ example 2]

MFR is set toAn electret nonwoven fabric was obtained in the same manner as in example 1, except that the mass per hole was 800g/10 minutes and the ejection rate per hole was 0.21 g/minute. The mass per unit area of the nonwoven fabric was 30g/m²The average single fiber diameter was 7.2. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 3]

An electret nonwoven fabric was obtained in the same manner as in example 1, except that the MFR was 155g/10 min and the single-hole discharge rate was 0.24 g/min. The mass per unit area of the nonwoven fabric was 45g/m²The average single fiber diameter was 8.9. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 4]

A polyolefin resin comprising 1 mass% of a hindered amine compound A "Chimassorb" (registered trademark) 944LD (manufactured by BASF ジャパン, Ltd.) and 0.05 mass% of a crystal nucleating agent "Irgaclear" (registered trademark) XT386 (manufactured by BASF ジャパン, Ltd.) in a polypropylene resin composed of a homopolymer having an MFR of 200g/10 min was melted by an extruder, spun out from a rectangular spinneret having an aperture diameter of 0.30mm and a hole depth of 2mm at a spinning temperature of 235 ℃ and a single hole discharge amount of 0.32 g/min, and the obtained sliver was cooled and solidified, and drawn, stretched and collected on a collecting net by a rectangular ejector by compressed air having an ejector pressure of 0.35 MPa. Except for the above, an electret nonwoven fabric was obtained in the same manner as in example 1. The mass per unit area of the nonwoven fabric was 30g/m²The average single fiber diameter was 9.8. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ solution 6]

。

[ example 5]

A polyolefin resin comprising a polypropylene resin composed of a homopolymer having an MFR of 200g/10 min and 1 mass% of a hindered amine compound "Chimassrob" (registered trademark) 2020 (manufactured by BASF ジャパン, Inc.) represented by Compound C was melted by an extruder, spun from a rectangular spinneret having a hole diameter of 0.30mm and a hole depth of 2mm at a spinning temperature of 235 ℃ and a single-hole discharge amount of 0.32 g/min, cooled and solidified to obtain a yarn, and then drawn, stretched and collected on a collecting net by a compressed air jet having a jet pressure of 0.35MPa by a rectangular jet. The obtained nonwoven web was thermally pre-bonded at 145 ℃ by using a flat roll, and the obtained thermally pre-bonded nonwoven web was thermally bonded at a temperature of 145 ℃ by using an upper roll, an embossing roll made of metal and having a bonding area ratio of points with speckles of 16%, and a pair of upper and lower hot embossing rolls, each consisting of a flat roll made of metal, at a line pressure of 30N/cm and a thermal bonding temperature of 145 ℃ to obtain a nonwoven web having a mass per unit area of 60g/m²A spunbonded nonwoven fabric. The average single fiber diameter was 11.8. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

Except for the above, an electret nonwoven fabric was obtained in the same manner as in example 1. The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ solution 7]

。

[ example 6]

An electret nonwoven fabric was obtained in the same manner as in example 5, except that the MFR was 155g/10 min, the single hole discharge rate was 0.37 g/min, and the ejector pressure was 0.20 MPa. The mass per unit area of the nonwoven fabric was 20g/m²The average single fiber diameter was 11.8. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 7]

An electret nonwoven fabric was obtained in the same manner as in example 2. The mass per unit area of the nonwoven fabric was 10g/m²The average single fiber diameter was 6.6. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 8]

An electret nonwoven fabric was obtained in the same manner as in example 1, except that the MFR was 39g/10 min and the single-hole discharge rate was 0.65 g/min. The mass per unit area of the nonwoven fabric was 23g/m²The average single fiber diameter was 21.5. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 9]

An electret nonwoven fabric was obtained in the same manner as in example 4, except that the addition rate of the crystal nucleating agent "Irgaclear" (registered trademark) XT386 (manufactured by BASF ジャパン corporation) shown in compound B was set to 0.005 mass%. The mass per unit area of the nonwoven fabric was 30g/m²The average single fiber diameter was 9.8. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 10]

A spunbonded nonwoven fabric was obtained in the same manner as in example 4, except that the addition rate of the crystal nucleating agent "Irgaclear" (registered trademark) XT386 (manufactured by BASF ジャパン corporation) shown in compound B was set to 0.5 mass%. The mass per unit area of the nonwoven fabric was 30g/m²The average single fiber diameter was 10.1. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 11]

MFR was 60g/10 min, the single-hole discharge rate was 0.43 g/min, and the pressure of the ejectorAn electret nonwoven fabric was obtained in the same manner as in example 1, except that the force was set to 0.15 MPa. The mass per unit area of the nonwoven fabric was 30g/m²The average single fiber diameter was 14.0. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the obtained electret nonwoven fabric are shown in table 1.

[ example 12]

The nonwoven web was thermally pre-bonded at 110 ℃ using a flat roll, the resulting thermally pre-bonded nonwoven web was thermally bonded at 120 ℃ using a pair of upper and lower thermal embossing rolls each consisting of a metal flat roll, an embossing roll having a bonding area ratio of % and having a spot pattern formed on the upper roll, and a pair of upper and lower thermal embossing rolls each consisting of a metal flat roll at a linear pressure of 10N/cm and a thermal bonding temperature, to obtain a nonwoven fabric having a mass per unit area of 200g/m²An electret nonwoven fabric was obtained in the same manner as in example 11, except for the spunbonded nonwoven fabric of (1). The average filament diameter of the resulting spunbonded nonwoven fabric was 14.0. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The measured values and calculated values of the electret nonwoven fabric are shown in table 1.

Comparative example 1

A polypropylene resin comprising a homopolymer having MFR of 800 g/min was melted by an extruder and spun through a spinneret having an orifice diameter of 0.25mm at a spinning temperature of 260 ℃ and a single-hole discharge rate of 0.10 g/min. Thereafter, air was blown to the yarn under the conditions of an air temperature of 290 ℃ and an air pressure of 0.10MPa, and the yarn was collected on the heat-fusible nonwoven fabric layer to form a melt-blown nonwoven fabric. The mass per unit area of the nonwoven fabric was 20g/m²The average fiber diameter and the average single fiber diameter were 4 μm.

The nonwoven fabric is subjected to electret treatment to obtain an electret nonwoven fabric. The measured values and calculated values of the electret nonwoven fabric are shown in table 1.

The nonwoven fabric obtained was very excellent in collection efficiency, but had poor tensile strength and high pressure loss, and could not be used in the range of applications for air filters.

Comparative example 2

A spunbond nonwoven fabric was obtained in the same manner as in example 1, except that the addition rate of the hindered amine compound a, "chimassorb" (registered trademark) 944LD (manufactured by BASF ジャパン (ltd)) was 1 mass%. The mass per unit area of the nonwoven fabric was 30g/m²The average single fiber diameter was 10.1. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The nonwoven fabric is subjected to electret treatment to obtain an electret nonwoven fabric. The measured values and calculated values of the electret nonwoven fabric are shown in table 1.

The nonwoven fabric obtained had a low collection efficiency and could not be used for air filter applications.

Comparative example 3

A spunbonded nonwoven fabric was obtained in the same manner as in example 1, except that MFR was 30g/10 min and the single-hole discharge rate was 0.70 g/min. The mass per unit area of the nonwoven fabric was 30g/m²The average single fiber diameter was 22.5. mu.m. In terms of spinnability, no yarn breakage was observed in 1 hour of spinning, and the spinning was good.

The nonwoven fabric is subjected to electret treatment to obtain an electret nonwoven fabric. The measured values and calculated values of the electret nonwoven fabric are shown in table 1.

The nonwoven fabric obtained had a low collection efficiency and could not be used for air filter applications.

The spunbonded nonwoven fabrics of examples 1 to 10, which are produced by electret processing, are formed from fibers comprising a polyolefin resin, have an average filament diameter of 6.5 to 22.0 [ mu ] m, and contain 0.1 to 5 mass% of a hindered amine compound, and have a Melt Flow Rate (MFR) of 32 to 850g/10 min, and have a high tensile strength per unit mass and high trapping performance. On the other hand, the mass per unit area of the nonwoven fabric of comparative example 1 is high, and therefore the pressure loss is high, while the tensile strength per mass per unit area of the nonwoven fabric is low because of the meltblown nonwoven fabric of comparative example 2, and the incorporation rate of the hindered amine compound a is low in comparative example 3, and therefore electret properties are insufficient, and the collection efficiency is low. Further, the average filament diameter of comparative example 4 was large, and as a result, the collection efficiency was low.

Industrial applicability

By the present invention, a high-performance spunbond showing a high trapping performance with a low pressure loss is obtained, which can be preferably used for an air filter as a filter material, but the application range thereof is not limited thereto.

Description of the marks

1: sample stage

2: dust storage box

3: flow meter

4: flow regulating valve

5: blower fan

6: particle counter

7: switching cock

8: pressure gauge

M: the samples were tested.