Electret nonwoven fabric, electret filter, and method for producing nonwoven fabric

Abstract

To provide an electret nonwoven fabric which can be stably spun and has excellent thermal stability of electric charges.SOLUTION: The electret nonwoven fabric of the present invention includes constituent fibers containing a high density polyethylene resin having a high density of 0.940 to 0. 970g / cm3, a nitrogen-containing compound, and a phenol phosphorus-based compound, and has a property retention rate of 0.70 or more, the property retention rate being represented by a value obtained by dividing a filter medium quality factor (QF) value represented by the following formula after a thermal load at 100 °C is applied by a QF value before the thermal load at 100 °C is applied. QF [mmAq-1] = - [ln (1 - (particle collection efficiency (%) / 100))] / [airflow resistance (mmAq)] SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electret nonwoven fabric. [Background technology]

[0002] Materials known as electrets have been widely used. Electrets are a group of materials that can maintain and utilize electrostatic force without continuous external energy application by manipulating various dielectric materials. Electrets utilize external electrostatic force and are used in microphones, sensors, generators, and various protective and separation applications.

[0003] In addition to using films and other flat surfaces for the separation and protection applications mentioned above, methods are known for enhancing functionality by combining porous materials with their inherent separation and filtration capabilities. For example, filters made of fibrous materials are widely used due to their high porosity, long life, and low airflow resistance. These fibrous filters capture particles on the fibers through mechanical collection mechanisms such as interception, diffusion, and inertial impaction. However, in practical use, filter collection efficiency is known to be minimal when the aerodynamic equivalent diameter of the particles being captured is approximately 0.1 to 1.0 μm. To compensate for this weakness, electret filters are used, utilizing the electrostatic attraction of electrets.

[0004] It is known that, in order to improve the collection efficiency of an electret filter, it is preferable to impart an electrostatic charge to a fibrous material by a method of bringing a liquid into contact with or colliding with the fibrous material (liquid contact charging method) to form an electret. For example, as an electret that balances cost and performance, an electret is known in which an electrostatic charge is imparted to a fibrous material formed from a mixture of a resin mainly composed of a polyolefin resin and an added nitrogen-containing compound such as a hindered amine compound by bringing the fibrous material into contact with a liquid such as water.

[0005] Conventionally, polymers known as electret materials include polytetrafluoroethylene, polypropylene, and polyvinylidene fluoride. However, polyethylene is not widely used as an electret because the charge escapes when it is charged and is not retained.

[0006] In addition, polyethylene fibers are generally difficult to spin by the melt-blown method, and in order to make the fiber diameter thinner, it is necessary to raise the spinning temperature, which causes gelation due to a crosslinking reaction.

[0007] Therefore, polyethylene with a lower molecular weight than the commonly used polyethylene resin, e.g. It has been thought that fine fibers or meltblown nonwoven fabrics could be produced using only polyethylene wax. However, although these low-molecular-weight polyethylenes have good spinnability, the resulting fibers have low strength and are prone to fuzzing, making continuous web production difficult.

[0008] To solve the above problems, a method has been disclosed for providing a polyethylene nonwoven fabric obtained by molding, by a melt-blown method, a resin composition containing polyethylene (A) having a weight-average molecular weight of 21,000 to 45,000 and a melt flow rate (MFR) of 15 to 250 g / 10 min and polyethylene wax (B) having a weight-average molecular weight of 12,000 or less in a weight ratio of (A) / (B) of 70 / 30 to 30 / 70 (Patent Document 1). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 3995885 Summary of the Invention [Problem to be solved by the invention]

[0010] When a hindered amine compound was added to the raw material of Patent Document 1 to obtain an electret nonwoven fabric, spinnability was good, but the thermal stability of the charge was very low, making it difficult to use as an electret. While it was thought that adding a polyethylene wax with a low melting point could be avoided to increase the thermal stability of the charge, it was found that spinning without adding polyethylene wax caused gelation due to a crosslinking reaction, making stable spinning impossible.

[0011] As described above, when electret nonwoven fabrics are produced by known methods, the thermal stability of the charge is low, and even if the charge is applied, the charge escapes and is not retained. Furthermore, stable spinning is not possible unless polyethylene wax is added.

[0012] In view of the above problems, the present invention has been made, and an object of the present invention is to provide an electret nonwoven fabric which can be spun stably and has excellent thermal stability of charge. [Means for solving the problem]

[0013] As a result of extensive research, the present inventors have discovered that, even when a polyethylene resin is used, gelation can be suppressed and stable meltblown spinning is possible, and an electret nonwoven fabric with excellent thermal stability of charge can be obtained by using the following constitution, and have arrived at the present invention.

[0014] 1. Density: 0.940-0.970g / cm 3 The electret nonwoven fabric has constituent fibers containing a high-density polyethylene resin, a nitrogen-containing compound, and a phenol-phosphorus compound, and the filter medium quality factor (QF) value is expressed by the following formula: The performance retention rate, which is the value obtained by dividing the QF value after applying a heat load of 100°C by the QF value before applying the heat load of 100°C, is 0.70 or more. QF[mmAq -1 ]=-[ln(1-(particle collection efficiency (%) / 100))] / [airflow resistance (mmAq)] 2. The electret nonwoven fabric according to 1 above, which is a meltblown nonwoven fabric or a spunbond nonwoven fabric. 3. The electret nonwoven fabric according to 1 or 2 above, wherein the constituent fibers further contain a thermoplastic resin different from the high-density polyethylene resin. 4. The electret nonwoven fabric according to any one of 1 to 3 above, wherein the nitrogen-containing compound and the phenol-phosphorus compound are each contained in an amount of 0.1 to 5% by mass relative to 100% by mass of the constituent fibers. 5. An electret filter using the electret nonwoven fabric according to any one of 1 to 4 above. 6.0.940~0.970g / cm 3 A method for producing a nonwoven fabric, comprising melt-mixing a high-density polyethylene resin having a density of 100 to 200°C with a nitrogen-containing compound and a phenol-phosphorus compound at 200 to 300°C, and producing the nonwoven fabric by the melt-blown method. 7. A method for producing an electret nonwoven fabric, comprising the step of converting the nonwoven fabric obtained by the production method described in 6 above into an electret. 8. The method for producing an electret nonwoven fabric according to the above item 7, wherein the electretization is carried out by a liquid contact charging method. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an electret nonwoven fabric which can be spun stably and suppresses gelation even when a polyethylene resin is used, and which has excellent thermal stability of charge. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below, but the present invention is not limited to the following and can be practiced by making appropriate modifications within the scope of the above and below described aims, and all such modifications are included in the technical scope of the present invention.

[0017] The density of the high-density polyethylene, which is an essential component of the constituent fibers of the electret nonwoven fabric of the present invention, is 0.940 to 0.970 g / cm 3 It is in the range of.

[0018] The high-density polyethylene resin in the present invention may be "derived from fossil raw materials" or "derived from plants" or a mixture of both, and an advantageous composition can be selected from the viewpoints of availability and LCA.

[0019] In the present invention, "derived from fossil raw materials" means, as in the past, that the main component is a component obtained by thermal decomposition of naphtha obtained from fossil raw materials such as petroleum, coal, and natural gas. "Plant-derived" means that carbon derived from plant raw materials is contained. In the case of a mixture of fossil and plant-derived polyethylene, the proportion of plant-derived raw materials can be calculated from the carbon ratio contained in the total polyethylene.

[0020] The melt flow rate (MFR) of the high-density polyethylene resin used in the present invention is preferably 1 to 250 g / 10 min at a temperature of 190°C under a load of 2.16 kg according to ASTM D 1238, more preferably 5 to 200 g / 10 min, and even more preferably 10 to 150 g / 10 min.

[0021] The content of the nitrogen-containing compound relative to 100% by mass of the constituent fibers of the electret nonwoven fabric is 0.1 to 5% by mass, preferably 0.5 to 3% by mass, and more preferably 0.75 to 1.5% by mass. If the content of the nitrogen-containing compound is 0.1% by mass or more, the amount of charge increases, thereby preventing a decrease in filtration properties. If the content is 5% by mass or less, the moisture absorption property decreases, thereby maintaining the stability as an electret.

[0022] The nitrogen-containing compound is not particularly limited as long as it can provide the above-described desired properties. However, it is preferably a hindered amine compound containing at least one of a 2,2,6,6-tetramethylpiperidyl structure and a triazine structure, and more preferably the hindered amine compound contains a 2,2,6,6-tetramethylpiperidine structure and a triazine structure.

[0023] The hindered amine compound is not particularly limited, but examples thereof 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}] (Chimasorb (registered trademark) 944LD, manufactured by BASF Japan Ltd.), dimethyl succinate-1-(2hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate (Tinuvin (registered trademark) 622LD, manufactured by BASF Japan Ltd.), 2-[[3,5-bis(1,1-dimethylethyl)-4-hydroxy [phenyl]methyl]-2-butylpropanedioate bis[1,2,2,6,6-pentamethyl-4-piperidinyl] (Tinuvin (registered trademark) 144, manufactured by BASF Japan Ltd.), polycondensate of dibutylamine 1,3,5-triazine·N,N-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexamethylenediamine·N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine (Chimasorb (registered trademark) 2020FDL, manufactured by BASF Japan Ltd.), and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyloxy)-phenol (Tinuvin (registered trademark) 1577FF, manufactured by BASF Japan Ltd.). Among these, those containing a 2,2,6,6-tetramethylpiperidine structure and a triazine structure are preferred, and Chimassorb (registered trademark) 944LD or Chimassorb (registered trademark) 2020FD are more preferred. As the hindered amine compound, one of the above compounds may be used alone, or two or more may be used in combination.

[0024] The content of the phenol-phosphorus compound relative to 100% by mass of the constituent fibers of the electret nonwoven fabric of the present invention is 0.1 to 5% by mass, preferably 0.2 to 3% by mass, and more preferably 0.3 to 1.5% by mass. When the content of the phenol-phosphorus compound is 0.1% by mass or more, it has the effect of suppressing the crosslinking reaction and can suppress the occurrence of gelation. When it is 5% by mass or less, it can suppress the nonwoven fabric from discoloring to pink or yellow.

[0025] The phenol-phosphorus compound is a compound having a phosphorus moiety and a phenol moiety in one molecule, and is not particularly limited as long as it can provide the desired properties described above. Commercially available products include, for example, Sumilizer (registered trademark) GP (Sumitomo Chemical Co., Ltd.).

[0026] The thermoplastic resin is not particularly limited as long as it can achieve the desired properties described above. However, from the viewpoint of charge stability of the electret, a hydrophobic and highly electrically resistive polyolefin resin is preferred, and the polyolefin resin is more preferably a polypropylene resin. Examples of polyolefin resins include homopolymers of olefins such as propylene, butylene, hexene, octene, butadiene, isoprene, chloroprene, methyl-1-pentene, and cyclic olefins, and copolymers of two or more of the above olefins. The polyolefin resin may be a homopolymer, a random copolymer, or a block copolymer, or two or more of them may be used in combination. The polyolefin resin preferably contains at least one selected from polypropylene and polymethylpentene, and more preferably contains polypropylene.

[0027] The thermoplastic resin in the present invention may be "derived from fossil raw materials," "derived from plants," or a mixture of both, and an advantageous composition can be selected from the viewpoints of availability and LCA.

[0028] The average fiber diameter of the fibers constituting the electret nonwoven fabric of the present invention is preferably 0.001 to 100 μm, more preferably 0.05 to 50 μm, even more preferably 0.1 to 30 μm, particularly preferably 0.3 to 25 μm, and most preferably 0.5 to 20 μm. If the average fiber diameter of the fibers is thicker than 100 μm, it is difficult to achieve a practical collection efficiency, and the efficiency decreases significantly during charge decay. If the average fiber diameter of the fibers is thinner than 0.001 μm, it is difficult to produce an electret to which a charge has been imparted. The above fineness is calculated as the geometric mean by measuring the diameters of 100 fibers in the same field of view using a scanning electron microscope, with no overlapping fibers.

[0029] The electretization method in the present invention is not particularly limited as long as it can provide the desired properties when the electret material is used, but a method in which a liquid is brought into contact with or impinged on a nonwoven fabric (liquid contact charging method) is preferred, and an electret material with high filtration properties can be obtained by the liquid contact charging method. More specifically, a method in which a liquid is brought into contact with or impinged on a nonwoven fabric by a method such as suction, pressure, or spraying is preferred.

[0030] In the liquid contact charging method, the liquid to be contacted or collided with is not particularly limited as long as it can provide the desired characteristics, but water is preferred in terms of ease of handling and performance. Instead of water, a liquid containing added subcomponents (components other than water) may be used, and the conductivity and pH of the liquid can be adjusted by the type and amount of the added subcomponents.

[0031] The liquid to be contacted or collided with in the liquid contact charging method preferably has a pH of 1 to 11, more preferably a pH of 3 to 9, and even more preferably a pH of 5 to 7. Furthermore, the liquid to be contacted or collided with in the liquid contact charging method preferably has a conductivity of 100 μS / cm or less, more preferably 10 μS / cm or less, and even more preferably 3 μS / cm or less.

[0032] Filters using the electret nonwoven fabric of the present invention are also within the scope of the present invention. When the electret nonwoven fabric of the present invention is used as a filter, the QF value described below is 0.10 mmAq-1 or more, preferably 0.11 mmAq-1 or more, more preferably 0.12 mmAq-1 or more, even more preferably 0.13 mmAq-1 or more, and most preferably 0.14 mmAq-1 or more. In particular, a filter using an electret melt-blown nonwoven fabric with an average fiber diameter of 0.5 to 5 μm preferably has a QF value exceeding the above values. If the QF value is below 0.10 mmAq-1, particles are not sufficiently captured by the electret, resulting in insufficient filter performance. The QF value herein is calculated based on the airflow resistance when air is passed through the filter thickness at a wind speed of 10 cm / s and the number of particles counted in the particle size range of 0.3 to 0.5 μm using a laser particle counter.

[0033] When the electret nonwoven fabric of the present invention is used as a filter, the particle collection efficiency at a wind speed of 10 cm / s can be adjusted in various ways depending on the required properties, but is preferably 50% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more. In this specification, the particle collection efficiency is calculated based on the number of particles in the particle size range of 0.3 to 0.5 μm measured by a laser particle counter before and after passing through the filter when air is passed through the filter in the thickness direction at a wind speed of 10 cm / s.

[0034] When the electret nonwoven fabric of the present invention is used as a filter, the airflow resistance at a wind speed of 10 cm / s is preferably in the range of 0.05 to 50 mmAq, more preferably 0.2 to 30 mmAq, and particularly preferably 0.5 to 20 mmAq. If the airflow resistance is too small, the performance as a filter becomes insufficient, and if the airflow resistance is too large, the advantages as an electret filter are lost.

[0035] The electret nonwoven fabric of the present invention may be a meltblown nonwoven fabric or a spunbonded nonwoven fabric. The electret nonwoven fabric of the present invention can be used in combination with other components as needed. That is, the electret nonwoven fabric of the present invention can be used in combination with a prefilter layer, a fiber protection layer, a reinforcing member, a functional fiber layer, etc. Furthermore, an electret filter using the electret nonwoven fabric of the present invention is also within the scope of the present invention.

[0036] The electret nonwoven fabric of the present invention can be used in a wide range of applications. In particular, it can be suitably used as a filter for protecting various devices, such as dust masks, dust clothing, various air conditioning elements, air purifiers, cabin filters, and the like, for the purposes of protection, breathability, stain resistance, waterproofing, etc.

[0037] The electret nonwoven fabric of the present invention may contain other polymers, colorants, stabilizers, nucleating agents, lubricants, and other compounding agents, as needed, within the scope of the present invention. Examples of optional components include various stabilizers such as conventionally known heat stabilizers and weather stabilizers, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, and the like.

[0038] The electret nonwoven fabric of the present invention can be obtained, for example, by melt-mixing a high-density polyethylene resin, a nitrogen-containing compound, and a phenol-phosphorus compound, producing a nonwoven fabric by a melt-blown method, and converting the nonwoven fabric into an electret.

[0039] The temperature of the molten resin in the melt-blown method is preferably 200° C. to 300° C., more preferably 240° C. to 295° C., and most preferably 260° C. to 290° C. If the spinning temperature is too low, the fibers cannot be thinned, and if it is too high, the phenol-phosphorus compound may decompose, making it impossible to obtain the effect of inhibiting gelation.

[0040] It has been found that the electret nonwoven fabric of the present invention improves its electret performance by containing a nitrogen-containing compound, and inhibits gelation by containing a phenol-phosphorus compound, thereby exhibiting high thermal stability of charge. This is believed to be because the phenol-phosphorus compound traps the radicals that cause gelation, thereby inhibiting gelation. [Example]

[0041] The embodiments of the present invention will be described below. Test methods are shown below.

[0042] (1) Airflow resistance A sample punched to 72 mm diameter was attached to an adapter with an effective ventilation diameter of 50 mm diameter, and a minute differential pressure was measured. A 50 mm diameter pipe connected to a meter was connected above and below, and air was passed through the thickness of the sample at a speed of 10 cm / s. The differential pressure above and below the sample without any restriction was measured as the airflow resistance (pressure loss).

[0043] (2) Particle collection efficiency and particle penetration rate A sample punched to 72 mm diameter was attached to an adapter with an effective ventilation diameter of 50 mm diameter, and ventilation was conducted in the thickness direction of the sample. The particle collection efficiency was measured using a light scattering particle counter KC-01E manufactured by Rion Co., Ltd. using the following method. Evaluated particles: Atmospheric dust particles Wind speed: 10cm / s Particle collection efficiency [%] = (1 - (number concentration of particles with a particle diameter of 0.3 to 0.5 μm after passing through the sample ÷ number concentration of particles with a particle diameter of 0.3 to 0.5 μm before passing through the sample)) × 100 Particle transmittance = (number concentration of particles with a particle size of 0.3 to 0.5 μm after passing through the sample ÷ number concentration of particles with a particle size of 0.3 to 0.5 μm before passing through the sample)

[0044] (3) Filter quality factor (QF) value The QF value was calculated from the following formula using the values ​​of the airflow resistance measured in (1) above and the particle permeability measured in (2) above. QF[mmAq -1]=-[ln(1-(particle collection efficiency (%) / 100))] / [airflow resistance (mmAq)]

[0045] (4) Thermal stability of charge The sample used in (2) above was wrapped in aluminum foil and then left to stand in a dryer set to 100°C for 30 minutes to apply a thermal load. The particle transmittance of the sample to which the thermal load was applied was then measured in the same manner as in (2) above, and the QF value was determined in the same manner as in (3) above. The QF value of the sample to which the thermal load was applied was then divided by the QF value of the sample before the thermal load was applied, obtained in (3) above, to determine the performance retention rate.

[0046] Example 1 Melt flow rate (MFR) 40g / 10min, density 0.960g / cm 3 98% by mass of the fossil-derived high-density polyethylene resin, 1% by mass of Chimassorb (registered trademark) 944 manufactured by BASF, which is a hindered amine compound as a nitrogen-containing compound, and 1% by mass of Sumilizer (registered trademark) GP manufactured by Sumitomo Chemical, which is a phenol-phosphorus compound, were melt-mixed and melt-spun using a melt-blowing device at a molten resin temperature of 290°C with a spinning nozzle having a diameter of 0.2 mm, to obtain a nonwoven fabric. The obtained nonwoven fabric was charged by passing water with an electrical conductivity of 0.7 μS / cm and a pH of 6.8 from the surface layer to the back side, and then air-dried at 25° C. to obtain the electret nonwoven fabric of Example 1. The thermal stability of the charge of the electret nonwoven fabric of Example 1 was 0.72.

[0047] <Example 2> Instead of the fossil-derived high-density polyethylene resin of Example 1, a polyethylene terephthalate resin with a melt flow rate (MFR) of 20 g / 10 min and a density of 0.955 g / cm 3 An electret nonwoven fabric of Example 2 was obtained in the same manner as in Example 1, except that 98 mass% of the plant-derived high-density polyethylene resin (biomass content of 90% or more) was used. The thermal stability of the charge of the electret nonwoven fabric of Example 2 was 0.70.

[0048] Example 3 Instead of the raw materials of Example 1, a melt flow rate (MFR) of 20 g / 10 min and a density of 0.955 g / cm 3 The following materials were used: 50% by mass of plant-derived high-density polyethylene resin (biomass content of 90% or more); 45% by mass of fossil-derived polypropylene resin with a melt flow rate (MFR) of 200 g / 10 min as a thermoplastic resin different from the high-density polyethylene resin; 3% by mass of JSR Corporation's DYNARON (registered trademark) 6200P as a thermoplastic resin different from the high-density polyethylene resin; 1% by mass of BASF's Chimassorb (registered trademark) 944 as a nitrogen-containing compound, which is a hindered amine compound; and 1% by mass of Sumitomo Chemical's Sumilizer (registered trademark) GP as a phenol-phosphorus compound. The electret nonwoven fabric of Example 3 was obtained in the same manner as in Example 1, except for the raw materials. The charge thermal stability of the electret nonwoven fabric of Example 3 was 0.82.

[0049] Example 4 Instead of the raw materials of Example 1, a melt flow rate (MFR) of 20 g / 10 min and a density of 0.955 g / cm 3 The following materials were used: 50% by mass of plant-derived high-density polyethylene resin (biomass content of 90% or more); 46.5% by mass of fossil-derived polypropylene resin with a melt flow rate (MFR) of 200 g / 10 min as a thermoplastic resin different from the high-density polyethylene resin; 1.5% by mass of Kraton (registered trademark) MD1648 from Kraton Polymer Japan as a thermoplastic resin different from the high-density polyethylene resin; 1% by mass of Chimassorb (registered trademark) 944 from BASF, a hindered amine compound as a nitrogen-containing compound; and 1% by mass of Sumilizer (registered trademark) GP from Sumitomo Chemical as a phenol-phosphorus compound. The electret nonwoven fabric of Example 4 was obtained in the same manner as in Example 1, except for the raw materials. The thermal stability of the charge of the electret nonwoven fabric of Example 4 was 0.75.

[0050] <Comparative Example 1> Instead of the raw materials of Example 1, a melt flow rate (MFR) of 40 g / 10 min and a density of 0.960 g / cm 3The materials used were 98.0% by mass of the fossil-derived high-density polyethylene resin, 1.0% by mass of Sanyo Chemical Industries' Sanwax 171-P as a polyethylene wax, and 1% by mass of BASF's Chimassorb (registered trademark) 944, a hindered amine compound, as a nitrogen-containing compound. The electret nonwoven fabric of Comparative Example 1 was obtained in the same manner as in Example 1, except for the raw materials. The thermal stability of the charge of the electret nonwoven fabric of Comparative Example 1 was 0.22.

[0051] <Comparative Example 2> Instead of the fossil-derived high-density polyethylene resin of Comparative Example 1, a polyethylene terephthalate resin with a melt flow rate (MFR) of 20 g / 10 min and a density of 0.955 g / cm 3 Except for using 98 mass% of the plant-derived high-density polyethylene resin (biomass content of 90% or more), an electret nonwoven fabric of Comparative Example 2 was obtained in the same manner as in Comparative Example 1. The thermal stability of the charge of the electret nonwoven fabric of Comparative Example 2 was 0.24.

[0052] <Comparative Example 3> Melt flow rate (MFR) 40g / 10min, density 0.960g / cm 3 The materials used were 97.0% by mass of the fossil-derived high-density polyethylene resin, 1.0% by mass of Sanyo Chemical Industries' Sanwax 171-P as a polyethylene wax, 1% by mass of BASF's Chimassorb (registered trademark) 944, a hindered amine compound as a nitrogen-containing compound, and 1% by mass of Irganox (registered trademark) 1010 as a phenolic antioxidant. The electret nonwoven fabric of Comparative Example 3 was obtained in the same manner as in Example 1, except for the above. The thermal stability of the charge of the electret nonwoven fabric of Comparative Example 3 was 0.40.

[0053] <Comparative Example 4> Instead of the raw materials in Example 1, a melt flow rate (MFR) of 40 g / 10 min and a density of 0.955 g / cm 3The materials used were 97.0% by mass of the fossil-derived high-density polyethylene resin, 1.0% by mass of Sanyo Chemical Industries' Sanwax 171-P as a polyethylene wax, 1% by mass of BASF's Chimassorb (registered trademark) 944, a hindered amine compound as a nitrogen-containing compound, and 1% by mass of Irgafos (registered trademark) 168 as a phosphorus-based antioxidant. The electret nonwoven fabric of Comparative Example 4 was obtained in the same manner as in Example 1, except for the above. The thermal stability of the charge of the electret nonwoven fabric of Comparative Example 4 was 0.43.

[0054] <Comparative Example 5> Instead of the fossil-derived high-density polyethylene resin of Example 1, a polyethylene terephthalate resin with a melt flow rate (MFR) of 200 g / 10 min and a density of 0.919 / cm 3 The petrochemically derived low-density polyethylene resin was used at 98% by mass. Except for this, the electret nonwoven fabric of Comparative Example 5 was obtained in the same manner as in Example 1. The thermal stability of the charge of the electret nonwoven fabric of Comparative Example 5 was 0.16.

[0055] <Comparative Example 6> Instead of the fossil-derived high-density polyethylene resin of Example 1, a polyethylene terephthalate resin with a melt flow rate (MFR) of 100 g / 10 min and a density of 0.933 g / cm 3 The petrochemically derived linear low-density polyethylene resin was used in an amount of 98% by mass. Except for this, the electret nonwoven fabric of Comparative Example 6 was obtained in the same manner as in Example 1. The thermal stability of the charge of the electret nonwoven fabric of Comparative Example 6 was 0.18.

[0056] <Comparative Example 7> Instead of the raw materials in Example 1, a melt flow rate (MFR) of 40 g / 10 min and a density of 0.960 g / cm 3 An attempt was made to obtain a nonwoven fabric in the same manner as in Example 1 except for this, but gelation occurred and stable spinning was not possible.

[0057] <Comparative Example 8> Instead of the raw materials in Example 1, a melt flow rate (MFR) of 20 g / 10 min and a density of 0.955 g / cm 3An attempt was made to obtain a nonwoven fabric in the same manner as in Example 1 except for this, but gelation occurred and stable spinning was not possible.

[0058] From the above, it can be seen that the electret nonwoven fabrics of Examples 1 to 4 have superior charge stability compared to Comparative Examples 1 to 8. It can also be seen that even when plant-derived materials are used, the results are equal to or better than those of materials derived from fossil materials. [Industrial Applicability]

[0059] The electret nonwoven fabric of the present invention has excellent electret properties and can be suitably used, for example, as a filter for dustproof clothing, dustproof masks, air purifiers, etc., and can make a great contribution to industry.

Claims

1. Density is 0.940 to 0.970 g / cm ３ The electret nonwoven fabric has constituent fibers containing a high-density polyethylene resin, a nitrogen-containing compound, and a phenol-phosphorus compound, Regarding the filter medium quality factor (QF) value shown by the following formula, the performance maintenance rate, which is the value obtained by dividing the QF value after applying a heat load of 100 ° C. by the QF value before applying a heat load of 100 ° C., is 0.70 or more. An electret nonwoven fabric. QF [mmAq -1 ] = - [ln(1 - (particle collection efficiency (%) / 100))] / [airflow resistance (mmAq)]

2. 2. The electret nonwoven fabric according to claim 1, which is a meltblown nonwoven fabric or a spunbond nonwoven fabric.

3. The electret nonwoven fabric according to claim 1 , wherein the constituent fibers further contain a thermoplastic resin different from the high-density polyethylene resin.

4. 2. The electret nonwoven fabric according to claim 1, wherein the nitrogen-containing compound and the phenol-phosphorus compound are each contained in an amount of 0.1 to 5% by mass relative to 100% by mass of the constituent fibers.

5. An electret filter using the electret nonwoven fabric according to any one of claims 1 to 4.

6. 0.940~0.970g / cm ３ A method for producing a nonwoven fabric, comprising melt-mixing a high-density polyethylene resin having a density of 100 to 1500°C with a nitrogen-containing compound and a phenol-phosphorus compound at 200 to 300°C, and producing the nonwoven fabric by a melt-blown method.

7. A method for producing an electret nonwoven fabric, comprising the step of electretizing the nonwoven fabric obtained by the method of claim 6.

8. The method for producing an electret nonwoven fabric according to claim 7, wherein the electretization is carried out by a liquid contact charging method.