Polypropylene resin composition for meltblown nonwoven fabrics, meltblown nonwoven fabric, and method for producing the same

Abstract

To provide a polypropylene-based resin composition for meltblown nonwoven fabrics that allows for easy molding of meltblown nonwoven fabrics, possesses high durability that prevents yellowing even after long-term use as meltblown nonwoven fabrics, and has sufficient heat-seal bonding properties when laminating these nonwoven fabrics. [Solution] A polypropylene resin composition for meltblown nonwoven fabrics, comprising a propylene copolymer as the main component that satisfies the following requirements (1) to (2). Requirement (1): The following equation (1) is satisfied. 0.1≦S(M≧300,000)×Wah≦3.0···(1) (In the formula, S(M≧300,000) is the fractional proportion of the total molecular weight of components with a molecular weight of 300,000 or more in the differential molecular weight distribution curve obtained by GPC measurement, and Wah is the peak width of the differential molecular weight distribution curve obtained by GPC measurement using the area-height method.) Requirement (2): MFR (230℃, 2.16kg load) is 1000g / 10min to 8000g / 10min.

Description

[Technical Field] 【0001】 The present invention relates to a polypropylene resin composition for meltblown nonwoven fabrics, a meltblown nonwoven fabric, and a method for producing the same. [Background technology] 【0002】 Patent Document 1 discloses a polypropylene random copolymer having several properties suitable for injection molding applications with a high melt flow rate (MFR) that is not screw-brakeped, as well as for melt-blown and compounding applications. However, while polypropylene random copolymers manufactured using conventional technology offered a good balance of rigidity and impact resistance when used in other similar injection-molded products such as cups, plastic tableware, or food containers, their performance as meltblown nonwoven fabrics and their secondary processing properties, such as heat-sealing properties, were not sufficient. 【0003】 Patent Document 2 discloses a composite material / article having meltblown fibers and / or meltblown webs, the main component of which is a propylene copolymer having a comonomer content of 0.5 to 7.0% by weight and a melt flow rate MFR2 (230°C) measured in accordance with ISO 1133 of at least 200 g / 10 min. In Patent Document 2, a random propylene copolymer with a high MFR is obtained by performing bis-breaking (modification with peroxides) on a random propylene copolymer with a low MFR. However, there were problems such as smoke generation and yellowing being induced during molding due to peroxides, decomposition products of peroxides, and polypropylene that had become too low in molecular weight. [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Patent No. 5584416 [Patent Document 2] Special Publication No. 2015-501889 [Overview of the project] 【Problems to be Solved by the Invention】 【0005】 In the case of laminating a melt-blown nonwoven fabric, when heat-sealing bonding is performed as a secondary process, sufficient adhesive strength cannot be obtained and it is necessary to use an adhesive resin. Further, when the melt-blown nonwoven fabric is used for a long time, there is a problem that it is yellowed due to deterioration caused by ultraviolet rays or oxidation, resulting in a poor appearance. Further, if the fluidity is inappropriate, when manufacturing the melt-blown nonwoven fabric, the fiber diameter cannot be controlled, and thus there is also a problem that the melt-blown nonwoven fabric cannot be produced in the first place. 【0006】 In view of the above problems, an object of the present invention is to provide a polypropylene-based resin composition for melt-blown nonwoven fabrics that can be easily formed into melt-blown nonwoven fabrics, has high durability and is difficult to deteriorate and yellow even when used for a long time as a melt-blown nonwoven fabric, and has sufficient heat-sealing bondability when laminating these nonwoven fabrics, a polypropylene-based nonwoven fabric using the resin composition, and a method for producing the same. 【Means for Solving the Problems】 【0007】 As a result of intensive studies, the present inventors have found that by melt-blow molding using a polypropylene-based resin composition containing a propylene-based copolymer having specific molecular weight characteristics and fluidity, it is possible to control the fiber diameter and have high durability that does not deteriorate and yellow even when used for a long time as a melt-blown nonwoven fabric, and to provide a nonwoven fabric having sufficient heat-sealing bondability when laminating these nonwoven fabrics, and thus have reached the present invention. The present invention relates to the following <1> to <8>. <1> A polypropylene-based resin composition for melt-blown nonwoven fabrics, containing a propylene-based copolymer satisfying the following requirements (1) to (2) as a main component. Requirement (1): Satisfies the following formula (1). 0.1 ≦ S(M≧300,000) × Wah ≦ 3.0 ··· (1) (In the formula, S (M≥300,000) is the fraction ratio of components with a molecular weight of 300,000 or more in the differential molecular weight distribution curve obtained by gel permeation chromatography (GPC) measurement, and Wah is the peak width by the area height method of the differential molecular weight distribution curve obtained by GPC measurement.) Requirement (2): The melt flow rate (MFR) measured at 230 °C under a load of 2.16 kg is 1000 g / 10 min to 8000 g / 10 min. <2> The propylene-based copolymer satisfies the following requirements (3) to (5), and the polypropylene-based resin composition according to <1> above. Requirement (3): It is a propylene·α-olefin random copolymer polymerized with a metallocene catalyst. Requirement (4): The ethylene content is 0.5% by mass to 6.0% by mass. Requirement (5): The melting point (Tm) measured by differential scanning calorimetry (DSC) is 110 °C to 150 °C. <3> The polypropylene-based resin composition according to <1> or <2> above, which does not contain a propylene-based copolymer modified with a peroxide. <4> The polypropylene-based resin composition according to any one of <1> to <3> above, which contains an antioxidant. <5> The polypropylene-based resin composition according to any one of <1> to <4> above, which does not contain a neutralizing agent at 0.1 mass ppm or more. <6> The propylene-based copolymer satisfies the following requirement (2’), and the polypropylene-based resin composition according to any one of <2> to <5> above. Requirement (2’): It is a propylene·α-olefin random copolymer polymerized with a metallocene catalyst supported on an ion-exchangeable layered silicate. <7> A melt-blown nonwoven fabric containing the polypropylene-based resin composition according to any one of <1> to <6> above. <8> A method for producing a melt-blown nonwoven fabric, which includes a step of melt-blowing the polypropylene-based resin composition according to any one of <1> to <6> above to form a nonwoven fabric. 【Advantages of the Invention】 【0008】 According to the present invention, a polypropylene-based resin composition for meltblown nonwoven fabrics is provided that allows for easy molding of meltblown nonwoven fabrics, has high durability that prevents deterioration and yellowing even after long-term use as meltblown nonwoven fabrics, and has sufficient heat-seal bonding properties when laminating these nonwoven fabrics, and a polypropylene-based nonwoven fabric using the resin composition is provided. The polypropylene resin composition of the present invention, when used as a meltblown nonwoven fabric, has sufficient heat-seal bonding properties when these nonwoven fabrics are laminated, thereby reducing the amount of resin adhesive used, or providing sufficient secondary processing properties even without the use of adhesive resin. [Brief explanation of the drawing] 【0009】 [Figure 1] Figure 1 shows an example of a differential molecular weight distribution curve, where S (M ≥ 300,000) is represented. [Figure 2] Figure 2 shows an example of a differential molecular weight distribution curve, illustrating the peak area A and peak height H used to determine Wah. [Modes for carrying out the invention] 【0010】 The present invention will be described in detail below. In this specification, the "~" indicating a numerical range is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. Furthermore, any combination of upper and lower limits can be used to indicate numerical ranges in this specification. In addition, any combination of preferred ranges can be used for each characteristic in this specification. 【0011】 I. Polypropylene resin compositions for meltblown nonwoven fabrics The polypropylene resin composition for meltblown nonwoven fabrics of the present invention is characterized by containing a propylene copolymer that satisfies the following requirements (1) to (2) as a main component. Requirement (1): The following equation (1) is satisfied. 0.1≦S(M≧300,000)×Wah≦3.0···(1) (In the formula, S(M≧300,000) is the fractional proportion of the total molecular weight of components with a molecular weight of 300,000 or more in the differential molecular weight distribution curve obtained by gel permeation chromatography (GPC), and Wah is the peak width obtained by the area-height method of the differential molecular weight distribution curve obtained by GPC.) Requirement (2): The melt flow rate (MFR) measured at 230°C and a 2.16 kg load is between 1000 g / 10 min and 8000 g / 10 min. 【0012】 The polypropylene resin composition of the present invention contains a propylene copolymer as its main component that satisfies formula (1) and has specific molecular weight characteristics and specific fluidity, thereby enabling the easy formation of meltblown nonwoven fabrics, providing high durability that prevents deterioration and yellowing even after long-term use of the formed meltblown nonwoven fabrics, and having sufficient heat-seal bonding properties when laminating these nonwoven fabrics. 【0013】 1. Propylene copolymer The propylene copolymer used in the present invention may be a copolymer of propylene and an α-olefin other than propylene, from the viewpoint of sufficient heat-seal bonding properties. The α-olefin may be any α-olefin having 2 to 20 carbon atoms, excluding propylene, and examples include one or more selected from ethylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, etc. Of these, ethylene is the most preferred. The propylene copolymer used in the present invention may be a propylene-ethylene copolymer, or a propylene-α-olefin copolymer containing ethylene and other α-olefin comonomers. Alternatively, the propylene copolymer used in the present invention may be a propylene-α-olefin copolymer which is a copolymer of propylene and an α-olefin comonomer having 4 or more carbon atoms. When using α-olefins, the amount used may be 10.0% by mass or less, preferably 6.0% by mass or less, relative to the total monomers (the sum of propylene and α-olefins). 【0014】 1-1. Requirements (1) The propylene copolymer used in the present invention satisfies the following formula (1). 0.1≦S(M≧300,000)×Wah≦3.0···(1) (In the formula, S(M≧300,000) is the fractional proportion of the total molecular weight of components with a molecular weight of 300,000 or more in the differential molecular weight distribution curve obtained by gel permeation chromatography (GPC), and Wah is the peak width obtained by the area-height method of the differential molecular weight distribution curve obtained by GPC.) 【0015】 The fractional percentage (S(M≧300,000)) and peak width (Wah) of the component with a molecular weight of 300,000 or more are obtained from the differential molecular weight distribution curve obtained by gel permeation chromatography (GPC) measurement, and are specifically determined as follows. Measurement device: Agilent Technologies GPC (PL-GPC220) Detector: Polymer Char IR-4, IR detector (measurement wavelength: 3.42 μm) Columns: Resonaq AT-806MS (3 columns) Mobile phase solvent: o-dichlorobenzene (ODCB) Measurement temperature: 140℃ Flow rate: 1.0mL / min Injection amount: 0.3ml A 1 mg / mL solution is prepared using the sample and ODCB (containing 0.5 mg / mL of BHT), and the sample is prepared by dissolving it at 140°C for approximately 1 hour. 【0016】 The conversion from retention capacity obtained by GPC measurement to molecular weight is performed using a calibration curve prepared in advance using standard polystyrene. The standard polystyrene used is the following brand manufactured by Tosoh Corporation. Brands: F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000 Calibration curves are created by injecting 0.3 mL of a solution dissolved in ODCB (containing 0.5 mg / mL butylhydroxytoluene (BHT)) so that each component is at 0.5 mg / mL. The calibration curves are approximated using a cubic equation obtained by the least squares method. Viscosity formula used for conversion to molecular weight ([η]=K×M) α The following values ​​are used for ). (a) When creating a calibration curve using standard polystyrene PS: K = 1.38 × 10 -4 α = 0.70 (i) When measuring samples of polypropylene or propylene polymers PP:K = 1.03 × 10 -4 α = 0.78 【0017】 S(M≧300,000) is the value obtained by subtracting from 1 the integral value up to a molecular weight (M) of 300,000 in the differential molecular weight distribution curve (total integral value normalized to 1) obtained by GPC measurement as shown in Figure 1. S(M≧300,000) represents the amount of high molecular weight components with a molecular weight of 300,000 or more. S (M ≥ 300,000) may be 0.002 or higher, 0.005 or higher, while on the other hand, it may be 0.100 or lower, 0.080 or lower, 0.060 or lower, or 0.040 or lower, from the viewpoint of excellent melt-blown spinnability. S (M ≥ 300,000) can be adjusted by (i) changing the temperature and / or pressure during polymerization of the propylene copolymer and / or (ii) adding hydrogen or other chain transfer agents to the monomer during polymerization of the propylene copolymer. 【0018】 Wah is the peak width obtained by the area-height method of the differential molecular weight distribution curve obtained by GPC measurement. Wah can represent the molecular weight distribution (uniformity of molecular chain length). In the differential molecular weight distribution curve obtained by GPC measurement as shown in Figure 2, Wah can be calculated from the following equation (2), where A is the peak area (total integral value) and H is the peak top height. 【0019】 【number】 【0020】 Wah may be 56 or more, 60 or more, while Wah may be 78 or less, 74 or less, or 70 or less, from the viewpoint of obtaining a suitable fiber diameter for the nonwoven fabric. Wah can be adjusted by the catalyst and polymerization conditions (polymerization temperature, monomer concentration, polymerization time, etc.) used in the polymerization process. 【0021】 In this invention, S(M≧300,000)×Wah is between 0.1 and 3. S (M ≥ 300,000) represents the amount of high molecular weight components above a certain level, and Wah represents the molecular weight distribution (uniformity of molecular chain length). As shown in equation (1), the multiplication of the amount of high molecular weight components and the molecular weight distribution exhibits synergistic and complementary effects within a specific range. The smaller S(M≧300,000) value, the fewer defects are susceptible to oxidative degradation, and the less likely yellowing is to occur due to the formation of unsaturated bonds associated with molecular chain severance. On the other hand, if S(M≧300,000) is too small, the fibrous molten resin becomes more prone to breaking during meltblown spinning, which can cause short, thin fibers to fly up (flying), potentially negatively affecting the appearance, strength, and other qualities of the meltblown nonwoven fabric. Furthermore, a smaller Wah value indicates greater uniformity of molecular chain length, making it easier for molecular chains to align and intertwine during spinning, resulting in higher fiber strength. Consequently, when nonwoven fabrics made from these fibers are heat-sealed, the heat seal strength increases. On the other hand, if the Wah value is too small, the melt tension decreases, which can negatively affect the heat seal strength when nonwoven fabrics made from these fibers are heat-sealed. While it is preferable for both S(M≧300,000) and Wah to be small, within the range where S(M≧300,000)×Wah is 0.1 or greater, even if S(M≧300,000) is large, if Wah is sufficiently small, the uniformity of the molecules reduces oxidative degradation and suppresses yellowing. Also, even if Wah is large, if S(M≧300,000) is sufficiently small, the low molecular weight fraction melts easily, and sufficient heat-seal bonding properties can be obtained when laminating these nonwoven fabrics. On the other hand, if both S(M≧300,000) and Wah are too small, such that S(M≧300,000)×Wah is less than 0.1, the fibers of the meltblown nonwoven fabric, especially the increase in ultrafine fibers, become more prone to yellowing, and it becomes difficult to obtain sufficient heat-seal bonding properties. 【0022】 S(M≧300,000)×Wah may be 0.2 or greater, 2.8 or less, or 2.0 or less, as it is easier to obtain a meltblown nonwoven fabric with excellent heat sealability and resistance to deterioration and yellowing even after prolonged use. S(M≧300,000)×Wah can be adjusted by adjusting S(M≧300,000) and Wah individually. 【0023】 1-2. Requirements (2) The propylene copolymer used in this invention has a melt flow rate (MFR) of 1000 g / 10 min to 8000 g / 10 min, measured at 230°C and a 2.16 kg load, in terms of melt-blown moldability and the appearance of the melt-blown nonwoven fabric. The propylene copolymer used in the present invention may have an MFR of 1200 g / min or more, 1550 g / 10 min or more, 2000 g / 10 min or more, while on the other hand, it may have an MFR of 6000 g / 10 min or less, or 5000 g / 10 min or less. When the MFR of the propylene copolymer is above the lower limit, it exhibits excellent melt-blown moldability and allows for easy control of fiber diameter. Furthermore, when the MFR is below the upper limit, it results in a suitable amount of low molecular weight components, making it easier to obtain a desirable nonwoven fabric appearance with fewer foreign substances called flies and shots. 【0024】 Here, MFR is a value measured in accordance with JIS K7210-1:2014 (test temperature: 230°C, nominal load: 2.16 kg). The MFR of the aforementioned propylene copolymer can be adjusted during polymerization using a chain transfer agent such as hydrogen. 【0025】 The propylene copolymer used in the present invention may satisfy the following requirements (3) to (5) because it is easy to create a polypropylene resin composition for meltblown nonwoven fabrics that has high durability, is resistant to deterioration and yellowing even after long-term use as a meltblown nonwoven fabric, and has sufficient heat-seal bonding properties when laminating these nonwoven fabrics. Requirement (3): It is a propylene-α-olefin random copolymer polymerized with a metallocene catalyst. Requirement (4): The ethylene content is 0.5% by mass to 6.0% by mass. Requirement (5): The melting point (Tm) measured by differential scanning calorimetry (DSC) is between 110°C and 150°C. 【0026】 1-3. Requirements (3) The propylene copolymer used in the present invention may be a propylene-α-olefin random copolymer polymerized with a metallocene catalyst. The propylene copolymer used in the present invention, when polymerized with a metallocene catalyst, can achieve a higher melt flow rate (MFR) than those polymerized using conventionally known Ziegler-Natta catalysts, has a narrower molecular weight distribution, and produces less high molecular weight components, thus easily satisfying requirements (1) and (2) above, and exhibiting excellent melt-blown moldability. The propylene copolymer used in the present invention may further be a propylene-α-olefin random copolymer polymerized with a metallocene catalyst supported on an ion-exchangeable layered silicate. Polymerization using metallocene catalysts will be explained later in the section on polymerization methods for propylene copolymers. 【0027】 1-4. Requirements (4) The propylene copolymer used in the present invention may have an ethylene content of 0.5% to 6.0% by mass, in terms of excellent heat welding strength and low-temperature heat sealability. The propylene copolymer used in the present invention may have an ethylene content of 0.5% to 4.0% by mass, or 1.0% to 4.0% by mass. If the ethylene content is above the lower limit, the melting point (Tm) of the propylene copolymer decreases, resulting in superior heat welding strength and low-temperature heat sealability. Furthermore, if the ethylene content is below the upper limit, a suitable proportion of crystals is formed in the resin composition, preventing the nonwoven fabric from blocking, which is preferable from the standpoint of handling the nonwoven fabric. The propylene copolymer used in the present invention may be a propylene-ethylene copolymer, or a propylene-α-olefin copolymer containing ethylene and other α-olefin comonomers. 【0028】 Here, the ethylene content is determined by the proton complete decoupling method according to the following conditions 13 This value is obtained by analyzing the 1C-NMR spectrum. Equipment: JEOL Ltd. GSX-400 or equivalent device (carbon nucleus resonance frequency of 100 MHz or higher) Solvent: o-dichlorobenzene + deuterated benzene (4:1 (volume ratio)) Concentration: 100mg / mL Temperature: 130℃ Pulse angle: 90° Pulse interval: 15 seconds Total number of times: 5,000 or more The spectral assignments can be done by referring to, for example, Macromolecules, 17, 1950 (1984). The spectral assignments measured under the above conditions are shown in Table 1. In Table 1, S αα The symbols, etc., follow the notation of Carman et al. (Macromolecules, 10, 536 (1977)), where P represents methyl carbon, S represents methylene carbon, and T represents methine carbon. 【0029】 [Table 1] 【0030】 Hereinafter, when "P" represents a propylene unit in the copolymer chain and "E" represents an ethylene unit, six types of triads, PPP, PPE, EPE, PEP, PEE, and EEE, may exist in the chain. As described in Macromolecules 15, 1150 (1982) and the like, the concentration of these triads and the peak intensity of the spectrum are related by the following relational expressions (3) to (8). [PPP]=k×I(T ββ )···(3) [PPE]=k×I(T βδ )···(4) [EPE]=k×I(T δδ )···(5) [PEP]=k×I(S ββ )···(6) [PEE]=k×I(S βδ )···(7) [EEE]=k×{I(S δδ ) / 2+I(S γδ ) / 4}···(8) Here, [] indicates the fraction of the triad. For example, [PPP] is the fraction of the PPP triad in all triads. Therefore, [PPP]+[PPE]+[EPE]+[PEP]+[PEE]+[EEE]=1···(9) That is. 【0031】 Also, k is a constant, I indicates the spectral intensity. For example, I(T ββ ) means the intensity of the peak at 28.7 ppm attributed to T ββ . By using the relational expressions (3) to (9) above, the fraction of each triad can be obtained, and further, the ethylene content can be obtained by the following formula. Ethylene content (mol%) = ([PEP]+[PEE]+[EEE])×100 Furthermore, the polypropylene copolymer of the present invention contains a small amount of heteropolymer propylene bonds (2,1-bonds and / or 1,3-bonds), which results in the generation of minute peaks. 【0032】 To determine the exact ethylene content, it is necessary to include the peaks originating from these heterogeneous bonds in the calculation. However, complete separation and identification of these heterogeneous bond-derived peaks are difficult, and the amount of heterogeneous bonds is small. Therefore, in this invention, the ethylene content is determined using the relationships (3) to (9), similar to the analysis of copolymers produced with Ziegler-Natta catalysts that are substantially free of heterogeneous bonds. 【0033】 The conversion of ethylene content from molar percentage to mass percentage is performed using the following formula. Ethylene content (mass%) = (28 × X / 100) / {28 × X / 100 + 42 × (1 - X / 100)} × 100 Here, X is the ethylene content in mole percent. 【0034】 1-5. Requirements (5) The propylene copolymer used in the present invention has high durability and is resistant to yellowing, and also has good thermal fusion bonding properties when laminating nonwoven fabrics. Therefore, its melting point (Tm) measured by differential scanning calorimetry (DSC) may be 110°C to 150°C. The propylene copolymer used in the present invention may have a melting point of 120°C to 145°C, or 130°C to 145°C. If the melting point of the propylene copolymer is above the lower limit, it is less prone to yellowing and tends to have excellent durability. If the melting point is below the upper limit, it is easier to obtain a melt-blown nonwoven fabric with excellent heat-welding strength and low-temperature heat-sealing properties. 【0035】 Here, the melting point (Tm) is measured by differential scanning calorimetry (DSC). A 5.0 mg sample is taken, held at 200°C for 5 minutes, then cooled to 40°C at a rate of 10°C / min, and then heated again at a rate of 10°C / min. The peak temperature of the melting curve observed is defined as the melting point (Tm). The melting point of the propylene copolymer can be controlled by the type of supported metallocene catalyst used, as well as the type and amount of α-olefin copolymerized. 【0036】 The propylene copolymer used in the present invention may further satisfy at least one of the following requirements (6) to (9). 【0037】 1-6. Requirements (6) The propylene copolymer used in the present invention may have a weight-average molecular weight Mw of 30,000 or more and 100,000 or less, and may be 75,000 or less, or 60,000 or less, from the viewpoint of melt-blown moldability. 【0038】 1-7. Requirements (7) The propylene copolymer used in the present invention may have a molecular weight distribution (Mw / Mn) of 2.0 to 4.0, as it readily exhibits melt-blown moldability and sufficient heat-seal bonding properties when laminating nonwoven fabrics. The molecular weight distribution (Mw / Mn) of the propylene copolymer used in the present invention may be 2.2 to 4.0, or 2.5 to 3.5. If the molecular weight distribution (Mw / Mn) of the propylene copolymer is above the lower limit, the nonwoven fabric tends to have excellent heat-welding strength, and if it is below the upper limit, the melt-blown moldability tends to improve. The values ​​of Mw, Mn, and Mw / Mn are all obtained by GPC measurement. Details of the measurement method and equipment are as described in requirement (1) above. Mw, Mn, and Mw / Mn can be adjusted by the catalyst and polymerization conditions (polymerization temperature, monomer concentration, polymerization time, etc.) used in the polymerization process. 【0039】 1-8. Requirements (8) The propylene copolymer used in the present invention may be in the form of a powder or particulate matter. When the propylene copolymer of the present invention is in particulate form, its average particle size is preferably 0.5 mm to 10 mm. Having an average particle size within this range ensures sufficient particle transfer capacity in screw feeders and other equipment during molding and transport. Furthermore, it prevents the copolymer from becoming fine powder during molding, thus avoiding deterioration of the working environment, which is preferable from a safety standpoint against dust explosions. Additionally, the absence of particles larger than this range reduces the likelihood of sedimentation or classification in the polymerization reaction system, preventing the formation of lumps or blockages during transport. A more preferred range for the average particle size is 0.7 mm to 5 mm, and an even more preferred range is 1 mm to 5 mm. Furthermore, from the standpoint of suppressing blockage during pipe transfer and quantitative introduction into the molding machine during molding, a preferred particle size distribution is 4 or greater, and more preferably 6 or greater, when expressed as n-term in the Rosin-Rammler distribution. A higher n-term indicates a narrower particle size distribution, so there is no upper limit, but considering the manufacturable range, n-term should be 15 or less. The average particle size and particle size distribution will be determined using the Camsizer particle size distribution analyzer manufactured by Lechsche Technologies. Specifically, the particle width (X) which shows a high correlation with the sieving measurement results will be determined. c min The particle size is calculated using the (conversion) method to obtain the particle size distribution. The average particle size is defined as the particle size corresponding to a cumulative frequency of 50%. 【0040】 1-9. Requirements (9) When the propylene copolymer of the present invention is in powder or particulate form, its bulk density is preferably 0.30 g / cm³. 3 ~0.60g / cm 3 It may be within this range. When the bulk density is within this range, productivity improves, and clogging during transport and molding becomes less likely due to improved particle fluidity. A more preferred range for bulk density is 0.35 g / cm³. 3 ~0.60g / cm 3 A more preferable range is 0.35 g / cm³. 3 ~0.55 g / cm³ 3 These are some examples. Furthermore, the bulk density shall be determined by a method compliant with ASTM D1895-69. Bulk density can be controlled, for example, by eliminating the generation of irregularly shaped particles, aggregates, and fine powders, and by standardizing their shape. 【0041】 2. Method for producing propylene copolymers 2-1. Catalyst The method for producing the propylene copolymer used in the present invention is not particularly limited, as long as it is a method that can produce a propylene copolymer having the above-mentioned requirements that are characteristic of the present invention. The propylene copolymer used in the present invention may be a propylene copolymer polymerized with a metallocene catalyst, as it readily satisfies the above requirements (1) and (2) and exhibits excellent melt-blown moldability. When producing the propylene copolymer used in the present invention, a supported metallocene catalyst may be used. Here, the type of supported metallocene catalyst is not particularly limited as long as it can produce the propylene copolymer used in the present invention. In order for the propylene copolymer used in the present invention to satisfy the above requirements (1) and (2), it is preferable to use a metallocene catalyst consisting of, for example, component (a) and component (b) as shown below, and component (c) which may be used as needed. Component (a): At least one metallocene transition metal compound selected from transition metal compounds represented by the following general formula (I). Component (b): At least one solid component selected from (b-1) to (b-4) below. (b-1) Particulate carrier on which an organoaluminum oxy compound is supported (b-2) A particulate carrier on which an ionic compound or Lewis acid capable of reacting with component (a) to convert component (a) into a cation is supported. (b-3) Solid acid fine particles (b-4) Ion-exchange layered silicate Ingredient (c): Organoaluminum compound 【0042】 2-1-1. Ingredients (a) As component (a), at least one metallocene transition metal compound selected from the transition metal compounds represented by the following general formula (I) can be used. General formula (I): Q(C5H 4-a -aR 1 )(C5H 4-b -bR 2 )MeXY [Here, Q represents a divalent bonding group that bridges two conjugated five-membered ring ligands, Me represents a metal atom selected from titanium, zirconium, and hafnium, and X and Y independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, an alkoxy group, an amino group, a nitrogen-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, or a silicon-containing hydrocarbon group. R 1 and R 2 Each of these independently represents a hydrogen atom, a hydrocarbon group, a halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group, or a phosphorus-containing hydrocarbon group. a and b are the number of substituents. 【0043】 More specifically, Q represents a divalent bonding group that bridges two conjugated five-membered ring ligands. Examples include a divalent hydrocarbon group, a silylene group or an oligosilylene group, a silylene group having a hydrocarbon group as a substituent, an oligosilylene group or a germylene group. Among these, the preferred ones are a divalent hydrocarbon group and a silylene group having a hydrocarbon group as a substituent. X and Y represent a hydrogen atom, a halogen atom, a hydrocarbon group, an alkoxy group, an amino group, a nitrogen-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, or a silicon-containing hydrocarbon group. Preferred examples among these include a hydrogen atom, a chlorine atom, a methyl group, an isobutyl group, a phenyl group, a dimethylamide group, and a diethylamide group. X and Y may be independent of each other, that is, they may be the same or different. R 1 and R 2This represents a hydrogen atom, a hydrocarbon group, a halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group, or a phosphorus-containing hydrocarbon group. Specific examples of hydrocarbon groups include methyl, ethyl, propyl, butyl, hexyl, octyl, phenyl, naphthyl, butenyl, and butadienyl groups. Typical examples of halogenated hydrocarbon groups, silicon-containing hydrocarbon groups, nitrogen-containing hydrocarbon groups, oxygen-containing hydrocarbon groups, boron-containing hydrocarbon groups, or phosphorus-containing hydrocarbon groups include methoxy, ethoxy, phenoxy, trimethylsilyl, diethylamino, diphenylamino, pyrazolyl, indolyl, dimethylphosphono, diphenylphosphono, diphenylboron, and dimethoxyboron groups. Among these, it is preferable that the hydrocarbon group has 1 to 20 carbon atoms, and particularly preferable that it be a methyl, ethyl, propyl, or butyl group. Also, adjacent R 1 and R 2 These may be bonded together to form a ring, and this ring may have substituents consisting of a hydrocarbon group, a halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group, or a phosphorus-containing hydrocarbon group. Me is a metal atom selected from titanium, zirconium, and hafnium, and is preferably zirconium or hafnium. 【0044】 Among the components (a) described above, those preferred for the production of propylene copolymers used in the present invention are transition metal compounds comprising ligands having hydrocarbon-substituted silylene groups, germylene groups, or alkylene groups that are crosslinked with substituted cyclopentadienyl groups, substituted indenyl groups, substituted fluorenyl groups, or substituted azlenyl groups. Particularly preferred are transition metal compounds comprising ligands having 2,4-substituted indenyl groups or 2,4-substituted azlenyl groups that are crosslinked with hydrocarbon-substituted silylene groups or germylene groups. Among these, transition metal compounds comprising ligands having 2,4-substituted azlenyl groups are even more preferred. Furthermore, the substituent at the 4-position of the 2,4-substituted indenyl group and the 2,4-substituted azlenyl group is particularly preferably a transition metal compound having a ligand having an aryl group having 6 to 20 carbon atoms, or a ligand having an aryl group having 6 to 20 carbon atoms substituted with a halogen, a silicon-containing hydrocarbon group, or a hydrocarbon group having 1 to 20 carbon atoms. Among these, a transition metal compound having a ligand in which the substituent at the 4-position is an aryl group having 6 to 20 carbon atoms substituted with a halogen, a silicon-containing hydrocarbon group, or a hydrocarbon group having 1 to 20 carbon atoms is particularly preferred, and among these, the most preferred is a transition metal compound having a ligand in which the substituent at the 4-position is an aryl group having 7 to 20 carbon atoms substituted with a halogen, a silicon-containing hydrocarbon group, or a hydrocarbon group having 1 to 20 carbon atoms. 【0045】 Suitable specific examples include (1) dichloro{1,1'-dimethylsilylenebis[2-methyl-4-(2-naphthyl)-4H-azlenyl]}hafnium, (2) dichloro{1,1'-dimethylsilylenebis[2-methyl-4-(4-t-butylphenyl)-4H-azlenyl]}hafnium, (3) dichloro{1,1'-dimethylsilylenebis[2-methyl-4-(2-fluoro-4-biphenylyl)-4H-azlenyl]}hafnium, and (4) dichloro{1,1'-dimethylsilylene (5) Dichloro{1,1'-dimethylsilylenebis[2-ethyl-4-(2-fluoro-4-biphenyl)-4H-5,6,7,8-tetrahydroazlenyl]}hafnium, (6) Dichloro{1,1'-dimethylsilylenebis[2-ethyl-4-(2-fluoro-4-biphenyl)-4H-azlenyl]}hafnium, (7) Dichloro{1,1'-di (8) Methylsilylenebis[2-ethyl-4-(3-chloro-4-t-butylphenyl)-4H-azlenyl]}hafnium, (9) Dichloro{1,1'-dimethylsilylenebis[2-ethyl-4-(3-chloro-4-trimethylsilylphenyl)-4H-azlenyl]}hafnium, (10) Dichloro[1,1'-dimethylsilylenebis[2-ethyl-4-(4-trimethylsilyl-3-methylphenyl)-4H-azlenyl]}hafnium, (10) Dichloro[1,1'-dimethyl Examples include silylenebis{2-ethyl-4-(4-trimethylsilyl-3,5-dichlorophenyl)-4H-azlenyl}]hafnium, (11)dichloro{1,1'-silafluorenylbis[2-ethyl-4-(4-trimethylsilyl-3,5-dichlorophenyl)-4H-azlenyl]}hafnium, and (12)dichloro{1,1'-silafluorenylbis[2-ethyl-4-(4-trimethylsilyl-3,5-dimethylphenyl)-4H-azlenyl]}hafnium. Compounds obtained by replacing the silylene group with a germylene group and hafnium with zirconium in these specific examples are also exemplified as suitable compounds. It should be noted that catalyst components are not essential elements of this invention, and therefore, a lengthy list has been avoided, and only representative examples have been provided. However, it is self-evident that this does not limit the effective scope of this invention. 【0046】 2-1-2. Component (b) As component (b), at least one solid component selected from components (b-1) to (b-4) described above is used. The solid component functions as a support for the metallocene catalyst component and is an important factor in determining the shape and size of the supported metallocene catalyst. In olefin polymerization catalysts, the shape and size of the catalyst are reflected in the shape and size of the polypropylene polymerization particles produced by polymerization, so it is preferable to control the shape and size of solid component (b) in order to obtain polypropylene particles with uniform properties that are easy to handle. Each of these components is publicly known and can be appropriately selected and used from publicly known technologies. Detailed examples of specific components and manufacturing methods can be found in Japanese Patent Publication No. 2002-53609, Japanese Patent Publication No. 2002-69116, Japanese Patent Publication No. 2002-284808, and Japanese Patent Publication No. 2003-105015, among others. Here, examples of particulate carriers used in components (b-1) and (b-2) include inorganic oxides such as silica, alumina, magnesia, silica-alumina, and silica-magnesia; inorganic halides such as magnesium chloride, magnesium oxychloride, aluminum chloride, and lanthanum chloride; and porous organic carriers such as polypropylene, polyethylene, polystyrene, styrene-divinylbencene copolymer, and acrylic acid copolymer. 【0047】 Non-limiting specific examples of component (b) include particulate carriers supporting methyl almoxane, isobutyl almoxane, methyl isobutyl almoxane, aluminum tetraisobutyl butylboronate, etc. as component (b-1); particulate carriers supporting triphenylborane, tris(3,5-difluorophenyl)borane, tris(pentafluorophenyl)borane, triphenylcarbonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, etc. as component (b-2); alumina, silica alumina, magnesium chloride, etc. as component (b-3); and smectite group materials such as montmorillonite, zakonite, byderite, nontronite, saponite, hectorite, stevensite, bentonite, teniolite, vermiculite group materials, mica group materials, etc. as component (b-4). These may also form a mixed layer. 【0048】 Of the above components (b), the most preferred is the ion-exchangeable layered silicate of component (b-4), and even more preferred is the ion-exchangeable layered silicate that has been subjected to chemical treatments such as acid treatment, alkali treatment, salt treatment, or organic matter treatment. Component (b) preferably uses spherical particles with an average particle size of 20 μm or more. More preferably, the average particle size is 30 μm to 500 μm, from the viewpoint of improving the fluidity and bulk density of the catalyst and polymerization particles and preventing the generation of fine or coarse powders that would hinder polymerization operation and handling. Even more preferably, it is 40 μm to 300 μm. In the metallocene catalyst of the present invention, components (b-1), (b-2), (b-3), or (b-4) can each be used individually as component (b), or these four components can be used in appropriate combinations. 【0049】 2-1-3. Ingredient (c) If necessary, at least one organoaluminum compound selected from the organoaluminum compounds represented by the following general formula (II) can be used as component (c). General formula (II): AlR a X 3-a (In the formula, R is a hydrocarbon group having 1 to 20 carbon atoms, X is a hydrogen atom, a halogen atom, an alkoxy group, and a is a number where 0 < a ≤ 3) Examples of the organoaluminum compound represented by the general formula (II) include trialkylaluminums such as trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum, or halogen- or alkoxy-containing alkylaluminums such as diethylaluminum monochloride and diethylaluminum monomethoxide. In addition, aluminoxanes such as methylaluminoxane can also be used as the organoaluminum compound used as the component (c). Among these, trialkylaluminum is particularly preferable as the component (c). 【0050】 2-1-4. Formation of Catalyst The component (a), the component (b), and, if necessary, the component (c) are brought into contact to form a catalyst. The contact method is not particularly limited, but they can be contacted in the following order. Also, this contact may be carried out not only during catalyst preparation but also during prepolymerization with an olefin or during polymerization of an olefin. 1) Contact the component (a) and the component (b) 2) Add the component (c) after contacting the component (a) and the component (b) 3) Add the component (b) after contacting the component (a) and the component (c) 4) Add the component (a) after contacting the component (b) and the component (c) 5) Contact the three components simultaneously The amounts of the components (a), (b), and (c) used in the present invention are arbitrary. For example, the amount of the component (a) used with respect to the component (b) is preferably in the range of 0.1 μmol to 500 μmol, particularly preferably 0.5 μmol to 100 μmol, per 1 g of the component (b).<000038The amount of component (c) used relative to component (b) is preferably in the range of 0.001 mmol to 100 mmol, and particularly preferably 0.005 mmol to 50 mmol, of aluminum element per 1 g of component (b). Therefore, the amount of component (c) relative to component (a) is such that, with the transition metal being 1, the amount of aluminum element is 0.002 to 1 × 10⁻¹⁶ in molar ratio. 6 Preferably 0.02 to 1 × 10 5 Particularly preferably 0.2 to 1 × 10 4 It is within the range. The catalyst used in this invention is preferably subjected to a prepolymerization treatment, which involves contacting an olefin and polymerizing a small amount beforehand. The olefin used is not particularly limited, but ethylene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane, styrene, etc. can be used, and propylene is particularly preferred. The method of supplying the olefin can be any method, such as supplying the olefin to the reaction vessel at a constant rate or under constant pressure, a combination thereof, or by introducing stepwise changes. The prepolymerization temperature and time are not particularly limited, but are preferably in the range of -20°C to 100°C and 5 minutes to 24 hours, respectively. The amount of prepolymerization is preferably 0.01 to 100, more preferably 0.1 to 50, of the amount of prepolymerized polymer relative to component (b). After prepolymerization is completed, the catalyst can be used as is, depending on the form of use, but drying may be performed if necessary. Furthermore, it is possible to include polymers such as polyethylene, polypropylene, and polystyrene, or inorganic oxide solids such as silica and titania, during or after contact with each of the above components. 【0051】 2-2. Polymerization method Polymerization reactions can occur in the presence or absence of solvents such as inert hydrocarbons like butane, pentane, hexane, heptane, toluene, and cyclohexane, or liquefied α-olefins. The polymerization process is carried out at a polymerization temperature of 30°C to 120°C, preferably 50°C to 90°C, and a polymerization pressure of 0.1 to 6 MPa, preferably 0.1 to 4 MPa. Polymerization can be carried out by batch, continuous, or semi-batch methods. Furthermore, the S (M ≥ 300,000) and Wah of the resulting propylene copolymer can be controlled by the supply of a molecular weight modifier, polymerization temperature, polymerization pressure, etc. Hydrogen is preferred as the molecular weight modifier. The amount of hydrogen is appropriately selected considering the desired molecular weight and MFR of the polymer to be produced, for example, a gas phase hydrogen concentration of 0.001 mol% to 20 mol% is used. In the present invention, it is preferable to continuously introduce hydrogen so that the hydrogen concentration remains constant during polymerization, so that the propylene copolymer can easily satisfy the above requirements (1) and (2). 【0052】 3. Polypropylene resin composition The polypropylene resin composition for meltblown nonwoven fabrics of the present invention mainly comprises a propylene copolymer that satisfies the above requirements (1) to (2). Here, "containing as a main component" means that the polypropylene resin composition contains 50% by mass or more of the propylene copolymer. The polypropylene resin composition of the present invention may contain 70% by mass or more of a propylene copolymer that satisfies the above requirements (1) to (2), may contain 80% by mass or more, may contain 90% by mass or more, may contain 95% by mass or more, may contain 97% by mass or more, may contain 99% by mass or more, may contain 99% by mass or more, may contain 99.5% by mass or more, may contain 99.9% by mass or more, or may contain 100% by mass. 【0053】 The polypropylene resin composition of the present invention does not need to contain a propylene copolymer modified with a peroxide. In other words, the polypropylene resin composition of the present invention does not need to contain a propylene copolymer that has been modified with a peroxide beforehand, and may be different from a polypropylene resin composition that has been modified with a peroxide. A method widely used to produce propylene polymers with high melt flow rates (MFRs) is to improve the MFR by modifying the polymer with peroxides. However, while propylene polymers modified with peroxides exhibit excellent melt-blown moldability, they are unsuitable for use in production because they cause problems such as smoke generation and yellowing during molding due to peroxides, peroxide decomposition products, and excessively low molecular weight polypropylene. The polypropylene resin composition of the present invention does not contain a propylene copolymer modified with peroxide, but contains a propylene copolymer that satisfies the specific requirements (1) to (2) above, thereby achieving excellent meltblown moldability and realizing the effects of the present invention. 【0054】 The polypropylene resin composition of the present invention may further contain additives as needed. By appropriately selecting additives, it is possible to improve the functionality of the polypropylene resin composition, for example, by enhancing the properties of the nonwoven fabric or adding other properties such as oxidation resistance. Additives may be used individually or in combination of two or more. 【0055】 3-1. Antioxidants The polypropylene resin composition of the present invention may contain an antioxidant. The polypropylene resin composition of the present invention, by containing an antioxidant, not only prevents thermal degradation during melt-blown molding but also suppresses molecular scalding caused by heat and air during raw material and product storage, thereby reducing the deterioration of physical properties and odors associated with the generation of volatile components. 【0056】 There are no particular limitations on the method for incorporating an antioxidant into the polypropylene resin composition of the present invention, but preferably at least one of the following methods (i) to (iii) is employed. (i) A method in which an antioxidant is added to the catalyst in advance before polymerization. (ii) A method of adding an antioxidant to the polymerization system. (iii) A method of adding an antioxidant to the polymerized powder after polymerization. In method (i), there are methods in which an antioxidant is mixed with the catalyst component, such as mixing component (b) with an antioxidant in advance to form a metallocene catalyst, or adding an antioxidant during the preparation of the prepolymerization catalyst. In method (ii), there are methods described in the publicly available documents Japanese Patent Publication No. 63-92613, Japanese Patent Publication No. 5-271335, and Japanese Patent Publication No. 9-12621, which can be selected and used as appropriate. For example, methods such as adding a pre-mixed catalyst and antioxidant to the polymerization system, or adding an antioxidant from a feedline separate from the catalyst, can be employed. In method (iii), impregnation spraying, powder addition, and melt spraying are performed. Specifically, these include a method of coating polymerized powder with an antioxidant attached with paraffin wax (Japanese Patent Publication No. 3-220248), a method of adding a stabilizer in liquid monomer in a step before flushing the liquid monomer (Japanese Patent Publication No. 6-179713), and a method of treating the granular polymer obtained by polymerization with water vapor and then spraying an antioxidant to blend it (Japanese Patent Publication No. 2003-231711). When antioxidants are included by the methods described in (i) and (ii) above, the antioxidant effect can be achieved with a smaller amount than the amount normally required. 【0057】 The antioxidants used in the propylene copolymer in the present invention are preferably phenolic antioxidants or sulfur-based antioxidants, and phenolic antioxidants are particularly preferred. Specific phenolic antioxidants include tris-(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], Examples include 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, and 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid. Among these, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate are more preferred from the standpoint of volatility and extraction of the drug, as they have a high molecular weight, low volatility, and excellent extractability. 【0058】 The antioxidant content may be 0.005 to 0.300 parts by mass, or 0.010 to 0.200 parts by mass, per 100 parts by mass of propylene copolymer, in order to prevent discoloration and bleeding problems in the meltblown nonwoven fabric product. 【0059】 3-2. Other additives Other additives include, for example, at least one selected from the group consisting of lubricants, antistatic agents, antistatic agents, antiblocking agents, ultraviolet absorbers, light stabilizers, and neutralizing agents. However, when the meltblown nonwoven fabric, which is the application of the polypropylene resin composition of the present invention, is used as a nonwoven fabric for high-performance filters used in ultrapure water filtration, high-purity chemical filtration, and air conditioning in semiconductor factories and clean rooms, it is preferable to minimize the addition of additional components other than the propylene copolymer. 【0060】 Generally, polypropylene resins contain acidic catalyst residues, so neutralizing agents are often added to polypropylene resin compositions. Conventional polypropylene resins use Ziegler-type catalysts in their manufacture, resulting in chlorine in the catalyst residue, which necessitates the use of a neutralizing agent. Common neutralizing agents used with polypropylene resins include fatty acid metal salts such as calcium stearate and inorganic hydrotalcites. The polypropylene resin composition of the present invention may contain no neutralizing agent at a concentration of 0.1 ppm by mass or more, depending on the application of the meltblown nonwoven fabric, and may contain no neutralizing agent at all, i.e., the neutralizing agent content may be 0 ppm by mass. When a fatty acid metal salt is used as a neutralizing agent in the polypropylene resin composition of the present invention, the fatty acid metal salt may decompose into free fatty acids and metal due to the heat during spinning or heat sterilization. When the nonwoven fabric is used as a filter for ultrapure water or high-purity chemicals, these free fatty acids may dissolve into the water or chemicals and become insoluble fine particles. Furthermore, when the nonwoven fabric is used as an air conditioning filter in semiconductor factories or clean rooms, the fatty acids may turn into dust and become a factor in air pollution. Furthermore, when hydrotalcite is used as a neutralizing agent, there is a risk that these neutralizing agent particles may detach from the fibers constituting the nonwoven fabric. Therefore, if this nonwoven fabric is used as a filter for ultrapure water or high-purity chemicals, these neutralizing agent particles may dissolve into the water or chemicals and become insoluble fine particles. Also, if it is used as an air conditioning filter in semiconductor factories or clean rooms, the neutralizing agent particles may turn into dust and become a cause of air pollution. 【0061】 In the polypropylene resin composition of the present invention, the total content of additives is not particularly limited and can be appropriately selected according to the properties of the additives. In the polypropylene resin composition of the present invention, the total content of additives, per 100 parts by mass of the propylene copolymer, may have an upper limit of, for example, 10 parts by mass or less, 1,000 parts by mass or less, 0,500 parts by mass or less, 0,300 parts by mass or less, or 0,200 parts by mass or less, and a lower limit of 0 parts by mass, but may be 0.005 parts by mass or more, 0.010 parts by mass or more, or 0.100 parts by mass or more. 【0062】 The polypropylene resin composition of the present invention comprises a propylene copolymer that satisfies the above requirements (1) to (2), and other components that do not impair the effects of the present invention as needed. Two examples of methods for mixing these components include mixing with a Henschel mixer, V-blender, ribbon blender, tumbler blender, etc., and, if necessary, melt-kneading with a kneader such as a single-screw extruder, multi-screw extruder, kneader, or Banbarri mixer. In any case, the mixing method is not particularly limited as long as the effects of the present invention are not impaired. 【0063】 The polypropylene resin composition of the present invention may be in particulate form. The average particle size of the polypropylene resin composition of the present invention may preferably be 0.5 mm to 10 mm. Having an average particle size within this range ensures sufficient particle transfer capacity in screw feeders and other equipment during molding and transport. Furthermore, it prevents the particles from becoming fine powder during molding, thus avoiding deterioration of the working environment, which is preferable from a safety standpoint against dust explosions. Additionally, the absence of particles larger than this range reduces the likelihood of sedimentation or classification in the polymerization reaction system, preventing the formation of lumps or blockages during transport. A more preferred range for the average particle size is 0.7 mm to 5 mm, and an even more preferred range is 1 mm to 5 mm. Furthermore, from the standpoint of suppressing blockage during pipe transfer and quantitative introduction into the molding machine during molding, a preferred particle size distribution is 4 or greater, and more preferably 6 or greater, when expressed as n-term in the Rosin-Rammler distribution. A higher n-term indicates a narrower particle size distribution, so there is no upper limit, but considering the manufacturable range, n-term should be 15 or less. The average particle size and particle size distribution will be determined using the Camsizer particle size distribution analyzer manufactured by Retsch Technology. 【0064】 The bulk density of the particles in the polypropylene resin composition of the present invention is preferably 0.30 g / cm³. 3 ~0.60g / cm 3 It may be within this range. When the bulk density is within this range, productivity improves, and clogging during transport and molding becomes less likely due to improved particle fluidity. A more preferred range for bulk density is 0.35 g / cm³. 3 ~0.60g / cm 3 A more preferable range is 0.35 g / cm³. 3 ~0.55 g / cm³ 3 These are some examples. Furthermore, the bulk density shall be determined by a method compliant with ASTM D1895-69. Bulk density can be controlled, for example, by eliminating the generation of irregularly shaped particles, aggregates, and fine powders, and by standardizing their shape. 【0065】 3-3. Properties of Polypropylene Resin Compositions The polypropylene resin composition of the present invention may have a melt flow rate (MFR) measured at 230°C and a 2.16 kg load of 1000 g / 10 min to 8000 g / 10 min, 1200 g / 10 min or more, 1550 g / 10 min or more, 2000 g / 10 min or more, while on the other hand, it may be 6000 g / 10 min or less, or 5000 g / 10 min or less. 【0066】 In the polypropylene resin composition of the present invention, in order to have high durability that is resistant to yellowing and to have sufficient thermal fusion bonding properties when laminating nonwoven fabrics, the melting point (Tm) measured by differential scanning calorimetry (DSC) may be 110°C to 150°C, 120°C to 145°C, or 130°C to 145°C. 【0067】 4. Uses of polypropylene resin compositions The polypropylene resin composition of the present invention allows for easy molding of meltblown nonwoven fabrics, possesses high durability that prevents deterioration and yellowing even after long-term use as a meltblown nonwoven fabric, and has sufficient heat-seal bonding properties when laminating these nonwoven fabrics. This reduces the amount of resin adhesive used, or even eliminates the need for adhesive resins altogether, resulting in sufficient secondary processing properties. Therefore, it is suitably used for meltblown nonwoven fabric applications. 【0068】 II. Meltblown nonwoven fabric and method for manufacturing the same 1. Meltblown nonwoven fabric The meltblown nonwoven fabric of the present invention contains the polypropylene-based resin composition of the present invention. The meltblown nonwoven fabric of the present invention may be made of the polypropylene-based resin composition of the present invention. The meltblown nonwoven fabric of the present invention, by using the polypropylene resin composition of the present invention, has high durability that resists deterioration and yellowing even after long-term use, and also has sufficient heat-seal bonding properties when laminating these nonwoven fabrics. 【0069】 The meltblown nonwoven fabric of the present invention can be appropriately selected according to the application and is not particularly limited, but the average fiber diameter may be 0.5 μm to 10 μm, or 1 μm to 8 μm. The average fiber diameter here can be evaluated by the method described in the examples below. 【0070】 The meltblown nonwoven fabric of the present invention is not particularly limited and can be appropriately selected depending on the application, but the post-heating yellowness (YI) of the nonwoven fabric after being placed in a gear oven at 135°C for 4 hours, as determined in accordance with JIS K7373:2006, may be 2.3 or less, or 2.2 or less. 【0071】 The meltblown nonwoven fabric of the present invention has sufficient heat-sealing properties. For example, using a 10 mm x 200 mm heat seal bar, the nonwoven fabrics can be joined together at temperatures ranging from 100°C to 160°C in 10°C increments, at a pressure of 2 kg / cm². 2 Under heat sealing conditions of 1 second, the sample is sealed perpendicular to the direction of melt extrusion (MD) of melt-blown molding. A 15 mm wide sample (10 mm x 15 mm) is cut from the sealed area and pulled apart at a 180° angle using a tensile testing machine at a tensile speed of 500 mm / min. The minimum temperature at which a strength of 10 N / 15 mm or more is obtained may be less than 130°C and may be less than 124°C. Furthermore, the meltblown nonwoven fabric of the present invention can be sealed using, for example, a 10 mm x 200 mm heat seal bar, with the nonwoven fabrics sealed together at a pressure of 2 kg / cm² in 10°C increments within the range of 100°C to 160°C. 2 Under heat sealing conditions of 1 second, the sample is sealed perpendicular to the direction of melt extrusion (MD) of melt-blown molding. A 15 mm wide sample is cut from the sealed area and pulled apart at a 180° angle using a tensile testing machine at a tensile speed of 500 mm / min. The maximum value obtained is defined as the heat seal strength (unit: N / 15 mm). This heat seal strength may be 49 N / 15 mm or higher, or 77 N / 15 mm or higher. 【0072】 Because the meltblown nonwoven fabric of the present invention uses the polypropylene-based resin composition of the present invention, it does not undergo peroxide thermal attenuation and can be molded with little to no additives. Therefore, the meltblown nonwoven fabric of the present invention is an extremely clean nonwoven fabric because it has very little extractable material into solvents and chemicals, can withstand high temperatures and sterilization, and does not produce fine resin beads during fiber molding. Therefore, it is extremely useful as an ultra-high-performance filter for ultrapure water filtration and high-purity chemical filtration in biotechnology, and as a high-performance air filter used in air conditioning systems in semiconductor factories and clean rooms. 【0073】 The meltblown nonwoven fabric of the present invention has sufficient heat-seal bonding properties when the nonwoven fabric is laminated, and may have a laminated structure. Furthermore, the meltblown nonwoven fabric of the present invention may have a laminated structure with other meltblown nonwoven fabrics, provided that it includes a meltblown nonwoven fabric containing the polypropylene resin composition of the present invention. Furthermore, the meltblown nonwoven fabric of the present invention may be used as a laminated nonwoven fabric with other nonwoven fabrics. Examples of laminated nonwoven fabrics include those laminated with spunbond nonwoven fabric, and the laminated nonwoven fabric may be formed by laminating spunbond nonwoven fabric / meltblown nonwoven fabric of the present invention / spunbond nonwoven fabric in this order. 【0074】 2. Method for manufacturing meltblown nonwoven fabric The method for producing the meltblown nonwoven fabric of the present invention includes the step of forming a nonwoven fabric by meltblown molding the polypropylene resin composition of the present invention. 【0075】 Meltblown molding is a well-known method and is widely used in the production of polyolefin resin nonwoven fabrics with fine fiber diameters. The molding process is outlined below. After the raw materials are melted in an extruder, the molten strands are extruded into a heated air stream from a spinning nozzle head with pore diameters ranging from tens to hundreds of micrometers and pore counts ranging from tens to thousands. This air stream causes the molten strands to become thinner. Subsequently, they are bundled on a collection device such as a conveyor to obtain a nonwoven fabric. [Examples] 【0076】 Next, the present invention will be described in more detail by reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. In the following examples, the autoclave was thoroughly dried beforehand by heating and circulating nitrogen. Furthermore, catalyst preparation and polymerization were all carried out under inert gas conditions. 【0077】 I. Measurement and Evaluation Methods The following (1) to (4) were measured and calculated using the methods described in this specification. (1) Mw, Mw / Mn, S(M≧300,000), Wah, S(M≧300,000)×Wah (2) Melt Flow Rate (MFR) (3) 13 Ethylene content measured by 13C NMR (4) Melting point (Tm) 【0078】 (5) Average fiber diameter: Images were taken at any position on the nonwoven fabric using a scanning electron microscope (Hitachi High-Technologies Corporation field emission scanning electron microscope SU-8020) at a magnification of 1,000x. The diameter of 20 random fibers in each image was measured, and this was done for 5 images. The average fiber diameter was then calculated from the diameters of a total of 100 fibers. (6) Yellowness after heating (YI): The YI of the nonwoven fabric was determined in accordance with JIS K7373:2006 after placing the nonwoven fabric in a gear oven at 135°C for 4 hours. A smaller value indicates less yellowing and higher durability. (7) Heat sealability: Using a 10mm x 200mm heat seal bar, the nonwoven fabrics were sealed together at a temperature of 100°C and a pressure of 2kg / cm². 2The sample was sealed perpendicular to the melt-blown extrusion direction (MD) under heat-sealing conditions of 1 second. A 15 mm wide sample (10 mm x 15 mm) was cut from the sealed area and pulled apart at a 180° angle using a tensile testing machine at a tensile speed of 500 mm / min, and its strength was measured. Samples were prepared in the same manner as above, except that the heat-sealing temperature was changed from 100°C to 110°C, 120°C, 130°C, 140°C, 150°C, or 160°C, and the strength of each sample was measured. The obtained strength was plotted against the heat-sealing temperature. A straight line was drawn connecting the plot of the highest temperature at which the strength did not exceed 10 N / 15 mm and the plot of the lowest temperature at which the strength was 10 N / 15 mm or greater, and the temperature at which the strength was 10 N / 15 mm or greater along this line was defined as the lowest temperature at which the strength was 10 N / 15 mm or greater. The lower the minimum temperature at which a strength of 10N / 15mm or higher is achieved, the better the thermal fusion bonding performance is considered to be. (8) Heat seal strength (unit: N / 15mm): The highest strength value obtained when measuring (7) above was taken as the heat seal strength. A higher value indicates higher heat fusion bonding strength. 【0079】 II. Production of polypropylene resin compositions and meltblown nonwoven fabrics (Example 1) (1) Production of polypropylene resin compositions for meltblown nonwoven fabrics (i) Preparation of prepolymerization catalyst (Carrier particle size measurement) Catalyst synthesis was performed using an ion-exchangeable layered silicate (montmorillonite: Benclay SL, manufactured by Mizusawa Chemical Co., Ltd.) as a support. Prior to catalyst synthesis, the average particle size of the support was measured using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.). Ethanol was used as the dispersion medium for the measurement, and the average particle size was determined with a shape factor of 1.0. The obtained value was 50 μm. (Chemical treatment of silicates) 3.75 liters of distilled water were added to a 10-liter glass separable flask equipped with a stirring blade, followed by 2.5 kg of concentrated sulfuric acid (96%). After heating the separable flask to 50°C, 1 kg of montmorillonite (product name "Benklay SL" manufactured by Mizusawa Chemical Co., Ltd.) was dispersed in it. The temperature was then raised to 90°C and maintained at that temperature for 6.5 hours. After cooling to 50°C, the slurry was filtered under reduced pressure to recover the cake. Seven liters of distilled water were added to the cake to re-slurry it, and then filtered under reduced pressure. This process was repeated until the pH of the washing solution (filtrate) exceeded 3.5. The recovered cake was then dried overnight at 110°C under a nitrogen atmosphere. The weight after drying was 707g. The silicate thus obtained was further dried using a kiln dryer to obtain dried silicate. (Preparation of catalyst) 200 g of the dried silicate obtained above was introduced into a glass reactor with a stirring blade and an internal volume of 3 liters. 1,160 mL of mixed heptane and then 840 mL of a heptane solution of triethylaluminum (0.60 M) were added, and the mixture was stirred at room temperature. After 1 hour, the mixture was washed with mixed heptane to prepare a silicate slurry to 2.0 liters. Next, 9.6 mL of a 0.71 M solution of triisobutylaluminum in heptane was added to the prepared silicate slurry and reacted at 25°C for 1 hour. In parallel, 2,180 mg (3 mmol) of [(r)-dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-chlorophenyl)-4H-azlenyl}]zirconium] (synthesis carried out according to the examples in Japanese Patent Publication No. 10-226712) was mixed with 870 mL of heptane, to which 33.1 mL of a 0.71 M solution of triisobutylaluminum in heptane was added and reacted at room temperature for 1 hour. This mixture was added to the silicate slurry and stirred for a further 1 hour to obtain the catalyst slurry. 【0080】 (Pre-polymerization / cleaning) Next, 2.1 liters of n-heptane were introduced into a 10-liter stirred autoclave, which had been purged with nitrogen, and the temperature was maintained at 40°C. The previously prepared catalyst slurry was then introduced. Once the temperature stabilized at 40°C, propylene was supplied at a rate of 100 g / hour, and the temperature was maintained. After 4 hours, the supply of propylene was stopped, and the temperature was maintained for another 2 hours. After the preliminary polymerization was complete, the gas in the autoclave was purged, and stirring was stopped. After standing for 10 minutes, approximately 3 liters of the supernatant was decanted. Next, 9.5 mL of a heptane solution of triisobutylaluminum (0.71 M) and then 5.6 liters of mixed heptane were added, the mixture was stirred at 40°C for 30 minutes, and after standing for 10 minutes, 5.6 liters of the supernatant was removed. This procedure was repeated three more times. Component analysis of the final supernatant revealed that the concentration of organoaluminum components was 1.23 mmol / L, and the Zr concentration was 8.6 × 10⁻⁶. -6 The concentration was g / L, and the amount of Zr present in the supernatant relative to the amount of fermented material was 0.016%. Next, 170 mL of a heptane solution of triisobutylaluminum (0.71 M) was added, and the mixture was dried under reduced pressure at 45°C. This procedure yielded a prepolymerization catalyst containing 2.2 g of polypropylene per gram of catalyst. 【0081】 (ii) First polymerization step A horizontal reactor (L / D=4.3, internal volume 100 liters) equipped with stirring blades was thoroughly dried, and then the interior was placed under a nitrogen gas atmosphere. In the presence of a polypropylene powder bed, the prepolymerization catalyst prepared by the above method (as solid catalyst amount excluding prepolymerization powder) was continuously supplied to the upstream side of the reactor at a rate of 0.19 g / hr and triisobutylaluminum at a rate of 31 mmol / hr while stirring at 30 rpm. The temperature was set to 57°C on the upstream side and 58°C on the downstream side of the reactor, the pressure was maintained at 2.1 MPaG, and a monomer mixed gas was continuously circulated into the reactor to achieve an ethylene / propylene molar ratio of 0.03 and a hydrogen concentration of 0.16 mol% in the gas phase of the reactor, thereby carrying out gas-phase polymerization. The polymer powder produced by the reaction was continuously withdrawn from the downstream side of the reactor to maintain a constant amount of powder bed in the reactor. At this time, the amount of polymer powder withdrawn when the steady state was reached was 7.1 kg / hr. Analysis of the propylene-α-olefin random copolymer obtained in the first polymerization step revealed an MFR of 4,000 g / 10 min and an ethylene content of 1.1% by mass. 【0082】 (iii) Second polymerization step A horizontal reactor (L / D=4.3, internal volume 100 liters) equipped with stirring blades was continuously supplied with propylene-α-olefin random copolymer withdrawn from the first step. While stirring at 25 rpm, the reactor temperature was maintained at 65°C and the pressure at 1.9 MPaG, and a monomer mixed gas was continuously circulated into the reactor to maintain an ethylene / propylene molar ratio of 0.03 and a hydrogen concentration of 0.16 mol% in the gas phase of the reactor, thereby carrying out gas-phase polymerization. The polymer powder produced by the reaction was continuously withdrawn from the downstream part of the reactor to maintain a constant amount of powder bed in the reactor. At this time, oxygen was supplied as an activity inhibitor to control the polymerization reaction amount in the second polymerization step so that the amount of polymer powder withdrawn was 8.9 kg / hr. The activity was 47 kg / g-catalyst. The obtained powdered PP1 (propylene-α-olefin random copolymer polymerized with a metallocene catalyst) had an MFR of 4,000 g / 10 min, an ethylene content of 1.1% by mass, and a melting point of 140°C. Table 2 shows the evaluation results of formula (1) of powdered PP1 by gel permeation chromatography (GPC). 【0083】 (iv) Production of polypropylene resin composition (granular PP1) 500 ppm of Irganox® 1076 was added to the obtained powdered PP1 as an antioxidant, and the mixture was combined in a Henschel mixer to obtain a polypropylene resin composition (granular PP1). 【0084】 (2) Manufacturing of meltblown nonwoven fabrics A polypropylene resin composition (granular PP1) was melt-blown under the following conditions, resulting in a basis weight of 20 g / m². 2 We obtained a nonwoven fabric. Nozzle (die); Die size: 225mm, Nozzle holes: 451, Nozzle diameter: 0.1mm Spinning conditions: Spinning temperature: 280°C, Air temperature: 280°C, Air flow rate: 57 Nm 3 / hr, discharge amount: 0.09g / min / hole Fiber collection conditions; Distance between ejector and conveyor: 285 mm The evaluation results of the obtained polypropylene-based nonwoven fabrics are also shown in Table 2. 【0085】 (Example 2) (1) Production of polypropylene resin compositions for meltblown nonwoven fabrics A polymer powder was obtained in the same manner as in Example 1, except that the hydrogen concentration in the first polymerization step and the second polymerization step was changed from 0.16 mol% to 0.15 mol%. The obtained powdered PP2 (propylene-α-olefin random copolymer polymerized with a metallocene catalyst) had an MFR of 2,900 g / 10 min, an ethylene content of 1.1% by mass, and a melting point of 140°C. Table 2 shows the evaluation results of formula (1) of the powdered PP2 by gel permeation chromatography (GPC). A polypropylene resin composition (granular PP2) was obtained in the same manner as in Example 1, except that powdered PP2 was used instead of powdered PP1 in the production of the polypropylene resin composition of Example 1. 【0086】 (2) Manufacturing of meltblown nonwoven fabrics In the production of the meltblown nonwoven fabric of Example 1, the nonwoven fabric was meltblown in the same manner as in Example 1, except that the polypropylene resin composition (granular PP1) was changed to a polypropylene resin composition (granular PP2). The evaluation results of the obtained polypropylene-based nonwoven fabrics are also shown in Table 2. 【0087】 (Example 3) (1) Production of polypropylene resin compositions for meltblown nonwoven fabrics A polymer powder was obtained in the same manner as in Example 1, except that the hydrogen concentration in the first polymerization step and the second polymerization step was changed from 0.16 mol% to 0.13 mol%. The obtained powdered PP3 (propylene-α-olefin random copolymer polymerized with a metallocene catalyst) had an MFR of 1,500 g / 10 min, an ethylene content of 1.1% by mass, and a melting point of 140°C. Table 2 shows the evaluation results of formula (1) of the powdered PP3 by gel permeation chromatography (GPC). A polypropylene resin composition (granular PP3) was obtained in the same manner as in Example 1, except that powdered PP3 was used instead of powdered PP1 in the production of the polypropylene resin composition of Example 1. 【0088】 (2) Manufacturing of meltblown nonwoven fabrics In the production of the meltblown nonwoven fabric of Example 1, the nonwoven fabric was meltblown in the same manner as in Example 1, except that the polypropylene resin composition (granular PP1) was changed to a polypropylene resin composition (granular PP3). The evaluation results of the obtained polypropylene-based nonwoven fabrics are also shown in Table 2. 【0089】 (Comparative Example 1) (1) Production of polypropylene resin compositions for meltblown nonwoven fabrics A polymer powder was obtained in the same manner as in Example 1, except that the hydrogen concentration in the first polymerization step and the second polymerization step was changed from 0.16 mol% to 0.11 mol%. The obtained powdered PPc1 (propylene-α-olefin random copolymer polymerized with a metallocene catalyst) had an MFR of 500 g / 10 min, an ethylene content of 1.1 mass%, and a melting point of 140°C. Table 2 shows the evaluation results of formula (1) of powdered PPc1 by gel permeation chromatography (GPC). A polypropylene resin composition (granular PPc1) was obtained in the same manner as in Example 1, except that powdered PPc1 was used instead of powdered PP1 in the production of the polypropylene resin composition of Example 1. 【0090】 (2) Manufacturing of meltblown nonwoven fabrics In the production of the meltblown nonwoven fabric of Example 1, the nonwoven fabric was meltblown in the same manner as in Example 1, except that the polypropylene resin composition (granular PP1) was changed to a polypropylene resin composition (granular PPc1). The evaluation results of the obtained polypropylene-based nonwoven fabrics are also shown in Table 2. 【0091】 (Comparative Example 2) (1) Production of polypropylene resin compositions for meltblown nonwoven fabrics A polypropylene resin composition (granular PPc2) was obtained in the same manner as in Example 1, except that powdered PPc2 (propylene homopolymer polymerized with a metallocene catalyst, manufactured by ExxonMobil Corporation, trade name Achieve PP6936G2, MFR: 1,500 g / 10 min, melting point: 153°C) was used instead of powdered PP1 in the production of the polypropylene resin composition of Example 1. Table 2 shows the evaluation results of formula (1) by gel permeation chromatography (GPC) measurement of powdered PPc2. 【0092】 (2) Manufacturing of meltblown nonwoven fabrics In the production of the meltblown nonwoven fabric of Example 1, the nonwoven fabric was meltblown in the same manner as in Example 1, except that the polypropylene resin composition (granular PP1) was changed to a polypropylene resin composition (granular PPc2). The evaluation results of the obtained polypropylene-based nonwoven fabrics are also shown in Table 2. 【0093】 [Table 2] In Comparative Example 1, the fiber diameter could not be controlled during the production of the meltblown nonwoven fabric, and the average fiber diameter was too large to form a nonwoven fabric. Therefore, post-heating YI, heat sealability, and heat seal strength were not evaluated. 【0094】 As is clear from the results in Table 2 above, the meltblown nonwoven fabrics obtained in Examples 1 to 3 using the polypropylene resin composition of the present invention, which contains a propylene copolymer satisfying formula (1) specified in this application and having specific fluidity as a main component, were shown to have high durability that is resistant to deterioration and yellowing, high heat seal strength, and excellent low-temperature heat sealability. On the other hand, among Comparative Examples 1 and 2, which used polypropylene resin compositions that did not satisfy formula (1) specified in this application, the meltblown nonwoven fabric obtained in Comparative Example 1, which lacked specific fluidity, had an average fiber diameter that was too large, resulting in a very coarse weave and making it difficult to evaluate the YI after heating, heat sealability, and heat sealability strength. Furthermore, the meltblown nonwoven fabric obtained in Comparative Example 2 had poor durability and problems with heat sealability strength and low-temperature heat sealability. [Industrial applicability] 【0095】 As described above, the polypropylene resin composition of the present invention, when used in meltblown nonwoven fabrics, can improve high heat seal strength and low-temperature heat sealability while maintaining excellent durability, making it suitable as a raw material for meltblown nonwoven fabrics, and its industrial applicability is very large.

Claims

[Claim 1] A polypropylene resin composition for meltblown nonwoven fabrics, comprising a propylene copolymer as the main component, satisfying the following requirements (1) to (2). Requirement (1): The following equation (1) must be satisfied. 0.1≦S (M≧300,000)×Wah≦3.0...(1) (In the formula, S (M ≥ 300,000) is the fractional proportion of the total molecular weight of components with a molecular weight of 300,000 or more in the differential molecular weight distribution curve obtained by gel permeation chromatography (GPC) measurement, and Wah is the peak width obtained by the area-height method of the differential molecular weight distribution curve obtained by GPC measurement.) Requirement (2): The melt flow rate (MFR) measured at 230°C and a 2.16 kg load is between 1000 g / 10 min and 8000 g / 10 min. [Claim 2] The propylene copolymer further satisfies the following requirements (3) to (5), the polypropylene resin composition according to claim 1. A resin composition. Requirement (3): It is a propylene-α-olefin random copolymer polymerized with a metallocene catalyst. Requirement (4): The ethylene content is 0.5% by mass to 6.0% by mass. Requirement (5): The melting point (Tm) measured by differential scanning calorimetry (DSC) is between 110°C and 150°C. [Claim 3] A polypropylene resin composition according to claim 1 or 2, which does not contain a propylene copolymer modified with peroxide. [Claim 4] A polypropylene resin composition according to claim 1 or 2, comprising an antioxidant. [Claim 5] A polypropylene resin composition according to claim 1 or 2, which does not contain 0.1 ppm by mass or more of a neutralizing agent. [Claim 6] The propylene copolymer satisfies the following requirement (2') and is a polypropylene resin composition according to claim 2. Requirement (2'): A propylene-α-olefin random copolymer polymerized with a metallocene catalyst supported on an ion-exchangeable layered silicate. [Claim 7] A meltblown nonwoven fabric comprising the polypropylene resin composition described in claim 1 or 2. [Claim 8] A method for producing a meltblown nonwoven fabric, comprising the step of forming a nonwoven fabric by meltblown molding a polypropylene resin composition according to claim 1 or 2.