Polypropylene resin composition, method for producing the same, and injection molded article

Abstract

The present invention provides a polypropylene resin composition that offers excellent fluidity and moldability, as well as the ability to mold products with superior impact resistance. [Solution] The polypropylene resin (A) contains a continuous phase made of a propylene polymer (a1) and a rubber phase made of an ethylene-propylene copolymer (a2), and the polypropylene resin (B) contains a continuous phase made of a propylene polymer (b1) and a rubber phase made of an ethylene-propylene copolymer (b2), wherein the mass ratio (A):(B) of the polypropylene resin (A) to the polypropylene resin (B) is 90:10 to 10:90, the total content of copolymer (a2) and copolymer (b2) is 23% by mass or more of the total mass of the polypropylene resin (A) and the polypropylene resin (B), and the MFR of the polypropylene resin composition at a temperature of 230°C and a load of 2.16 kg is 70 g / 10 min or more.

Description

[Technical Field]

[0001] This invention relates to a polypropylene resin composition, a method for producing the same, and an injection-molded article. [Background technology]

[0002] Polypropylene is widely used as a molding material for various molded products due to its excellent physical properties and balance of impact resistance, rigidity, transparency, chemical resistance, and heat resistance. For example, polypropylene is sometimes used in food containers.

[0003] In recent years, efforts have been made to reduce the use of petroleum-derived plastics by making food containers thinner. For example, to achieve thinner injection-molded containers, it is necessary to adjust the fluidity of the polypropylene raw material to match the molding method and the shape of the molded product. Conventionally, in order to improve the fluidity of polypropylene as an injection molding material, polypropylene materials with a high melt flow rate (hereinafter also called MFR), which is an indicator of fluidity during melting, have been used. However, polypropylene materials with a high MFR as described above have the problem of reduced impact resistance. In addition, although it is possible to lower the melt viscosity of polypropylene by raising the molding temperature in order to improve fluidity, raising the molding temperature can accelerate the thermal degradation of polypropylene. For this reason, raising the molding temperature not only reduces the strength of the molded product, but also causes odor and burning on the molded product, lowering the commercial value and yield rate of the molded product, and also increases manufacturing costs.

[0004] In response to the aforementioned requirements for polypropylene, such as fluidity and impact resistance, various polypropylene-based resin compositions have been proposed (Patent Documents 1-3).

[0005] For example, Patent Document 1 describes a polypropylene resin composition containing a polypropylene resin (A) comprising a continuous phase made of a propylene polymer (a1) and a rubber phase made of a copolymer (a2) of ethylene and an α-olefin having 3 to 10 carbon atoms. Furthermore, Patent Documents 2 and 3 disclose, for example, a technique for improving molding fluidity by giving polypropylene a broad molecular weight distribution. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-149485 [Patent Document 2] Japanese Patent Publication No. 2017-36356 [Patent Document 3] Special Publication No. 2011-500907 [Overview of the project] [Problems that the invention aims to solve]

[0007] The polypropylene resin composition described in Patent Document 1 contains a polypropylene resin (A) comprising a continuous phase made of a propylene polymer (a1) and a rubber phase made of a copolymer (a2) of ethylene and an α-olefin having 3 to 10 carbon atoms. It is stated that increasing the content of the copolymer (a2) in the polypropylene resin (A) (i.e., the amount of rubber) can suppress a decrease in impact resistance.

[0008] However, the polypropylene resin composition described in Patent Document 1 still had the problem of not having sufficient fluidity to be used as a molding material for thinning large injection-molded containers with long flow lengths. For example, when a large injection-molded container was manufactured using the polypropylene resin composition described in Patent Document 1, a molding defect called "sink marks," which causes indentations on the surface of the molded product, sometimes occurred at the flange portion at the end of the flow.

[0009] In addition, although a polypropylene-based resin composition having a wide molecular weight distribution in polypropylene as described in Patent Documents 2 and 3 tends to provide good moldability, there is a problem that the strength of the molded product is low and the impact resistance deteriorates. For example, when the strength of the molded product is low, there is a tendency that breakage easily occurs at the joint of the flow part of the molded product. Further, it has newly been found that when a polypropylene-based resin composition having excellent fluidity is used alone as a molding material, not only does the impact resistance of the molded product deteriorate, but also burrs are likely to occur in the obtained molded product when the fluidity during injection molding becomes excessively high.

[0010] The present invention provides a polypropylene-based resin composition and a method for producing the same, and an injection molded product, which are excellent in fluidity and moldability, and are capable of molding a molded product excellent in impact resistance, particularly a molded product excellent in the balance between rigidity and impact strength at an equivalent MFR. According to the polypropylene-based resin composition of the present invention, even a thin-walled injection molded product with a long flow length can achieve excellent impact resistance.

Means for Solving the Problems

[0011] The present invention has the following aspects. [1] A polypropylene-based resin (A) containing a continuous phase composed of a propylene polymer (a1) and a rubber phase composed of a copolymer (a2) of ethylene and propylene, and a polypropylene-based resin (B) containing a continuous phase composed of a propylene polymer (b1) and a rubber phase composed of a copolymer (b2) of ethylene and propylene, wherein the polypropylene-based resin composition contains: The mass ratio (A):(B) of the polypropylene-based resin (A) to the polypropylene-based resin (B) is 90:10 to 10:90, The total content of the copolymer (a2) and the copolymer (b2) is 23% by mass or more based on the total mass of the polypropylene-based resin (A) and the polypropylene-based resin (B), The MFR of the polypropylene-based resin composition at a temperature of 230°C and a load of 2.16 kg is 70 g / 10 minutes or more, The ratio (Mw / Mn) of the weight average molecular weight Mw to the number average molecular weight Mn of the propylene polymer (a1) is 6 to 8, The ethylene-derived unit content in the propylene polymer (a1) is 0.0 to 0.5% by mass based on the total mass of the propylene polymer (a1), The content of the copolymer (a2) is 25 to 45% by mass based on the total mass of the polypropylene resin (A), The propylene-derived unit content in the copolymer (a2) is 50 to 80% by mass based on the total mass of the copolymer (a2), The intrinsic viscosity of the xylene-soluble fraction of the polypropylene resin (A) in tetralin at 135 °C is 1.2 to 7.0 dl / g, The MFR of the polypropylene resin (A) at a temperature of 230 °C and a load of 2.16 kg is 10 to 130 g / 10 min, The ratio (Mw / Mn) of the weight average molecular weight Mw to the number average molecular weight Mn of the propylene polymer (b1) is 9 to 12, The ethylene-derived unit content in the propylene polymer (b1) is 0.0 to 0.5% by mass based on the total mass of the propylene polymer (b1), The content of the copolymer (b2) is 15 to 30% by mass based on the total mass of the polypropylene resin (B), The propylene-derived unit content in the copolymer (b2) is 50 to 80% by mass based on the total mass of the copolymer (b2), The intrinsic viscosity of the xylene-soluble fraction of the polypropylene resin (B) in tetralin at 135 °C is 1.2 to 7.0 dl / g, A polypropylene resin composition in which the MFR of the polypropylene resin (B) at a temperature of 230 °C and a load of 2.16 kg is 10 to 130 g / 10 min. [2] The polypropylene resin composition according to [1], wherein the propylene polymer (a1) and the copolymer (a2) are mixed by polymerization, and the polypropylene resin (A) is a polymerization mixture produced using a catalyst containing a phthalate compound as an electron donor. [3] The polypropylene resin composition according to [1] or [2], wherein the propylene polymer (b1) and the copolymer (b2) are mixed by polymerization, and the polypropylene resin (B) is a polymer mixture produced using a catalyst containing a succinate compound as an electron donor. [4] The polypropylene resin composition according to any one of [1] to [3], wherein the polypropylene resin (A) is a polymerization mixture produced using a catalyst containing a phthalate compound as an electron donor, and the polypropylene resin (B) is a polymerization mixture produced using a catalyst containing a succinate compound as an electron donor. [5] A polypropylene resin composition according to any one of [1] to [4], further comprising a nucleating agent (C). [6] A polypropylene resin composition according to any one of [1] to [5], used as a material for injection molding. A method for producing a polypropylene resin composition according to any one of [7][1] to [6], Step A involves polymerizing an ethylene monomer and a propylene monomer in the presence of the propylene polymer (a1) to obtain the polypropylene resin (A), Step B involves polymerizing an ethylene monomer and a propylene monomer in the presence of the propylene polymer (b1) to obtain the polypropylene resin (B), A method for producing a polypropylene resin composition, comprising step C of mixing the obtained polypropylene resin (A) and the polypropylene resin (B). [8] A method for producing a polypropylene resin composition according to [7], wherein the electron donor of the catalyst system used in step A is a phthalate compound, and the electron donor of the catalyst system used in step B is a succinate compound. An injection-molded article of a polypropylene resin composition as described in any of [9][1] to [6].

[10] The injection molded product according to [9], wherein the value obtained by dividing the length L (mm) from one end of the molded product to the other by the average wall thickness D (mm) of the molded product (L / D) is 150 to 600.

[11] An injection-molded article according to [9] or

[10] , wherein the thickness of the thinnest part is 0.6 mm or less.

[12] An injection-molded article described in any of [9] to

[11] for use as a container or packaging that comes into contact with food. [Effects of the Invention]

[0012] The polypropylene resin composition of the present invention exhibits excellent fluidity and moldability, as well as excellent impact resistance, enabling the molding of molded articles with a superior balance of rigidity and impact strength in equivalent MFR (Metal Frame Rate). The method for producing the polypropylene resin composition of the present invention allows for the simple production of the polypropylene resin composition described above. Furthermore, the polypropylene resin composition of the present invention is suitable for thin-wall injection molding. The injection-molded product of the present invention is an injection-molded product using the polypropylene resin composition of the present invention as the molding material, and even if it is a thin-walled and long-flow-length molded product, it can achieve excellent impact resistance. The injection-molded articles of the present invention are particularly suitable for food packaging applications (containers, drink cups, etc.). In addition to food packaging applications, they may also be used for other purposes such as general merchandise, daily necessities, home appliance parts, electrical and electronic components, automobile parts, housing components, toy components, furniture components, building material components, packaging components, industrial materials, logistics materials, and agricultural materials. [Modes for carrying out the invention]

[0013] ≪Polypropylene-based resin composition≫ First, a polypropylene resin composition according to the first embodiment of the present invention will be described. The polypropylene resin composition according to this embodiment contains a polypropylene resin (A) (hereinafter also referred to as component (A)) comprising a continuous phase made of a propylene polymer (a1) (hereinafter also referred to as component (a1)) and a rubber phase made of an ethylene-propylene copolymer (a2) (hereinafter also referred to as component (a2)), and a polypropylene resin (B) (hereinafter also referred to as component (B)) comprising a continuous phase made of a propylene polymer (b1) (hereinafter also referred to as component (b1)) and a rubber phase made of an ethylene-propylene copolymer (b2) (hereinafter also referred to as component (b2)).

[0014] The polypropylene resin composition of this embodiment has a mass ratio (A):(B) of polypropylene resin (A) to polypropylene resin (B) of 90:10 to 10:90. In the polypropylene resin composition of this embodiment, the content of component (A) is 10 to 90% by mass, and the content of component (B) is 10 to 90% by mass, relative to the total mass of component (A) and component (B). When the content of component (A) is 10% by mass or more (in other words, the content of component (B) is 90% by mass or less), the impact resistance of the injection molded product is increased. On the other hand, when the content of component (A) is 90% by mass or less (in other words, the content of component (B) is 10% by mass or more), the fluidity and moldability are good. In the following, the mass ratio (A):(B) of polypropylene resin (A) and polypropylene resin (B) as explained above may be referred to as "mass ratio (A):(B) of component (A) and component (B)" or simply "mass ratio (A):(B)".

[0015] The mass ratio (A):(B) of component (A) to component (B) is preferably 85:15 to 15:85, more preferably 75:25 to 25:75, and even more preferably 65:35 to 35:65. By configuring it in this way, it is possible to improve the impact resistance of injection molded products while maintaining good fluidity and moldability of the polypropylene resin composition.

[0016] Furthermore, in the polypropylene resin composition of this embodiment, the total content of copolymer (a2) and copolymer (b2) is 23% by mass or more, preferably 23-30% by mass, more preferably 23-27% by mass, and even more preferably 24-27% by mass, relative to the total mass of polypropylene resin (A) and polypropylene resin (B). By configuring it in this way, it is possible to improve the impact resistance of injection molded products while maintaining good fluidity and moldability of the polypropylene resin composition.

[0017] The MFR of the polypropylene resin composition at a temperature of 230°C and a load of 2.16 kg is 70 g / 10 min or more, preferably 70 to 92 g / 10 min, more preferably 75 to 92 g / 10 min, even more preferably 80 to 92 g / 10 min, and particularly preferably 85 to 92 g / 10 min. For example, if it is above the lower limit of the above numerical range, poor filling into the mold is less likely to occur even during thin-wall injection molding, and good thin-wall injection molding can be achieved. On the other hand, if it is below the upper limit of the above numerical range, the impact resistance of the injection-molded product can be improved.

[0018] [Polypropylene resin (A)] The polypropylene resin (A) contained in the polypropylene resin composition of this embodiment is an embodiment of the impact-resistant polypropylene polymer specified in JIS K6921-1, and is composed of two or more phases, including a continuous phase of propylene polymer (component (a1)) and a rubber phase of ethylene-propylene copolymer (component (a2)) of ethylene and propylene that exists as a dispersed phase within the continuous phase. The polypropylene resin (A) may be a mixed resin in which component (a1) and component (a2) are mixed during polymerization, or it may be a mixed resin in which component (a1) and component (a2), obtained separately, are mixed by melt kneading. It is preferable that the resin is a mixture of component (a1) and component (a2) mixed during polymerization (polymerized mixture) because it is cheaper to obtain a resin with a better balance of rigidity, low-temperature impact resistance and tensile properties (hereinafter also referred to as "mechanical property balance"). For example, although not particularly limited, the polypropylene resin (A) is more preferably a polymerization mixture produced using a catalyst containing a phthalate compound as an electron donor. That is, component (a1) and component (a2) are mixed by polymerization, and the polypropylene resin (A) is more preferably a polymerization mixture produced using a catalyst containing a phthalate compound as an electron donor. In polymerization mixtures, components (a1) and (a2) can mix on a submicron scale, so polypropylene resin compositions based on polymerization mixtures exhibit an excellent balance of mechanical properties. On the other hand, if a similar uniform mixture is obtained by melt-kneading components (a1) and (a2) separately, and a superior balance of mechanical properties is to be achieved with a simple mechanical mixture, the manufacturing cost will be high due to the need for separate processes such as storage, handling, transport, weighing, mixing, and melt-kneading. This is also undesirable from the standpoint of energy costs. It is presumed that the polymerized mixture and the mechanical mixture may exhibit different physical properties because the dispersion state of component (a2) in component (a1) is different. However, there is currently no known practical means to analyze the dispersion state at the molecular level, including the state of the interface between component (a2) and component (a1). The method for producing the polypropylene resin (A) will be explained in detail later.

[0019] The ratio of weight-average molecular weight Mw to number-average molecular weight Mn (Mw / Mn), which is an indicator of the molecular weight distribution of the propylene polymer (component (a1)) constituting the polypropylene resin (A), is 6 to 8, and preferably 6 to 7. Here, the weight-average molecular weight Mw and number-average molecular weight Mn of the propylene polymer are values ​​measured by gel permeation chromatography (GPC), specifically the values ​​measured by the method described later.

[0020] The ethylene-derived unit content (hereinafter also referred to as "C2") in the propylene polymer (component (a1)) constituting the polypropylene resin (A) is 0.0 to 0.5% by mass, and preferably 0.0 to 0.3% by mass, relative to the total mass of the propylene polymer (a1). When C2 is below the upper limit, the rigidity of the injection-molded product increases. The lower limit of C2 is not particularly limited and may be 0.0 mass%, as in the range described above. The propylene polymer (component (a1)) constituting the polypropylene resin (A) in this embodiment may be a polypropylene homopolymer consisting only of propylene-derived units, or it may be a copolymer consisting of 99.5% by mass or more and less than 100% by mass of propylene-derived units and more than 0% by mass and 0.5% by mass or less of ethylene-derived units. C2 is 13 It is measured by the 1C-NMR method.

[0021] The ethylene-propylene copolymer (component (a2)) that constitutes the polypropylene resin (A) is a copolymer having ethylene-derived units and propylene-derived units. The propylene-derived unit content in component (a2) is 50 to 80% by mass, preferably 55 to 75% by mass, more preferably 60 to 75% by mass, and even more preferably 65 to 75% by mass, based on the total mass of component (a2). If the value is above the lower limit of the range described above, the impact resistance of the injection-molded product will increase. If the value is below the upper limit of the range described above, the impact resistance of injection-molded products at low temperatures will increase. The ethylene-derived unit content in component (a2) is: 13 It is measured by the 1C-NMR method.

[0022] The content of ethylene-propylene copolymer (component (a2)) relative to the total mass of polypropylene resin (A) is 25 to 45% by mass, preferably 25 to 40% by mass, more preferably 27 to 40% by mass, and even more preferably 27 to 35% by mass. If the value is above the lower limit of the range described above, the impact resistance of the injection-molded product will increase. If the value is below the upper limit of the range described above, the risk of blockage of the flow path in the production equipment due to deterioration of powder flowability during the manufacture of polypropylene resin (A) can be reduced, thereby enabling stable and continuous production of polypropylene resin (A).

[0023] The intrinsic viscosity (hereinafter also referred to as "XSIV") of the xylene-soluble component of the polypropylene resin (A) is 1.2 to 7.0 dl / g, preferably 1.2 to 5.0 dl / g, more preferably 1.2 to 3.0 dl / g, even more preferably 1.2 to 2.5 dl / g, and particularly preferably 1.5 to 2.5 dl / g. If the value is above the lower limit of the range described above, the impact resistance of the injection-molded product will increase. If the value is below the upper limit of the range described above, polypropylene resin (A) can be produced stably and continuously. Here, XSIV is the measurement value in tetrahydronaphthalene at 135°C. The xylene-soluble component is obtained by dissolving a polypropylene resin sample in o-xylene at 135°C, cooling it to 25°C, filtering the cooled solution using filter paper, and evaporating the filtrate to dryness.

[0024] The melt flow rate (MFR) of polypropylene resin (A) at a temperature of 230°C and a load of 2.16 kg is 10 to 130 g / 10 min, more preferably 10 to 100 g / 10 min, more preferably 10 to 80 g / 10 min, even more preferably 20 to 80 g / 10 min, and particularly preferably 25 to 75 g / 10 min. Here, the MFR is a value measured by the measurement method described later. If the value is above the lower limit of the range described above, poor filling of the mold is less likely to occur even during thin-wall injection molding, and it can also handle high-cycle (high-speed) molding. If the value is below the upper limit of the range described above, the impact resistance of the injection-molded product can be improved.

[0025] The ethylene-propylene copolymer (component (a2)) that constitutes the polypropylene resin (A) is a copolymer having ethylene-derived units and propylene-derived units.

[0026] [Polypropylene resin (B)] The polypropylene resin (B) contained in the polypropylene resin composition of this embodiment is, like the polypropylene resin (A) described above, an embodiment of the impact-resistant polypropylene polymer specified in JIS K6921-1. However, the polypropylene resin (B) is composed of two or more phases, including a continuous phase of propylene polymer (component (b1)) and a rubber phase of ethylene-propylene copolymer (component (b2)) of ethylene and propylene that exists as a dispersed phase within the continuous phase. The polypropylene resin (B) may be a mixed resin in which components (b1) and (b2) are mixed during polymerization, or it may be a mixed resin in which components (b1) and (b2) obtained separately are mixed by melt kneading. It is preferable that the resin is a mixture in which components (b1) and (b2) are mixed during polymerization (polymerized mixture) because it is cheaper to obtain a resin that has an excellent balance of rigidity, low-temperature impact resistance and tensile properties. For example, although not particularly limited, the polypropylene resin (B) is more preferably a polymerization mixture produced using a catalyst containing a succinate compound as an electron donor. That is, component (b1) and component (b2) are mixed by polymerization, and the polypropylene resin (B) is more preferably a polymerization mixture produced using a catalyst containing a succinate compound as an electron donor. Similar to the polypropylene resin (A) described above, polypropylene resin compositions based on polymerization mixtures exhibit an excellent balance of mechanical properties. The manufacturing method for polypropylene resin (B) will be explained in detail later.

[0027] The ratio of weight-average molecular weight Mw to number-average molecular weight Mn (Mw / Mn), which is an indicator of the molecular weight distribution of the propylene polymer (component (b1)) constituting the polypropylene resin (B), is 9 to 12, and preferably 9 to 11. Component (b1) is prepared to have a broader molecular weight distribution range compared to component (a1) described above. If the ratio of weight-average molecular weight Mw to number-average molecular weight Mn (Mw / Mn) of component (b1) is below the lower limit of the above range, the fluidity of the polypropylene resin composition decreases, and moldability deteriorates. If Mw / Mn exceeds the upper limit of the above range, the surface impact strength of the injection-molded product deteriorates. The weight-average molecular weight Mw and number-average molecular weight Mn of the propylene polymer were measured by gel permeation chromatography (GPC), specifically using the method described later.

[0028] The ethylene-derived unit content (hereinafter also referred to as "C2-b1") in the propylene polymer (component (b1)) constituting the polypropylene resin (B) is 0.0 to 0.5% by mass, and preferably 0.0 to 0.3% by mass, relative to the total mass of the propylene polymer (b1). When C2-b1 is below the upper limit, the rigidity of the injection-molded product increases. The lower limit of C2-b1 is not particularly limited and may be 0.0 mass%, as in the range described above. The propylene polymer (component (b1)) constituting the polypropylene resin (B) in this embodiment may be a polypropylene homopolymer consisting only of propylene-derived units, or it may be a copolymer consisting of 99.5% by mass or more and less than 100% by mass of propylene-derived units and more than 0% by mass and 0.5% by mass or less of ethylene-derived units. C2-b1 is, 13 It is measured by the 1C-NMR method.

[0029] The ethylene-propylene copolymer (component (b2)) that constitutes the polypropylene resin (B) is a copolymer having ethylene-derived units and propylene-derived units. The propylene-derived unit content in component (b2) is 50 to 80% by mass, preferably 55 to 75% by mass, more preferably 60 to 75% by mass, and even more preferably 65 to 75% by mass, based on the total mass of component (b2). If the value is above the lower limit of the range described above, the impact resistance of the injection-molded product will increase. If the value is below the upper limit of the range described above, the impact resistance of injection-molded products at low temperatures will increase. The propylene-derived unit content in component (b2) is: 13 It is measured by the 1C-NMR method.

[0030] The content of ethylene-propylene copolymer (component (b2)) relative to the total mass of polypropylene resin (B) is 15 to 30% by mass, preferably 20 to 30% by mass, and more preferably 20 to 28% by mass. If the value is above the lower limit of the range described above, the impact resistance of the injection-molded product will increase. If the value is below the upper limit of the range described above, the risk of blockage of the flow path in the production equipment due to deterioration of powder flowability during the production of polypropylene resin (B) can be reduced, thus enabling stable and continuous production of polypropylene resin (B).

[0031] The intrinsic viscosity (XSIV) of the xylene-soluble component of the polypropylene resin (B) is 1.2 to 7.0 dl / g, preferably 1.2 to 5.0 dl / g, more preferably 1.2 to 3.0 dl / g, even more preferably 1.2 to 2.5 dl / g, and particularly preferably 1.5 to 2.5 dl / g. If the value is above the lower limit of the range described above, the impact resistance of the injection-molded product will increase. If the value is below the upper limit of the range described above, polypropylene resin (A) can be produced stably and continuously. Here, the XSIV of the xylene-soluble component of polypropylene resin (B) was measured in tetrahydronaphthalene at 135°C, similar to the case of polypropylene resin (A). The xylene-soluble component is obtained by dissolving the polypropylene resin sample in o-xylene at 135°C, cooling it to 25°C, filtering the cooled solution using filter paper, and evaporating the filtrate to dryness.

[0032] The melt flow rate (MFR) of polypropylene resin (B) at a temperature of 230°C and a load of 2.16 kg is 10 to 130 g / 10 min, more preferably 20 to 130 g / 10 min, more preferably 20 to 120 g / 10 min, even more preferably 20 to 110 g / 10 min, and particularly preferably 30 to 110 g / 10 min. Here, the MFR is a value measured by the measurement method described later. If the value is above the lower limit of the range described above, poor filling of the mold is less likely to occur even during thin-wall injection molding, and it can also handle high-cycle (high-speed) molding. If the value is below the upper limit of the range described above, the impact resistance of the injection-molded product can be improved.

[0033] [Nuclear agent (C)] The polypropylene resin composition of this embodiment may further contain a nucleating agent (C) as an optional component. The nucleating agent (C) may be a nucleating agent contained when preparing the polypropylene resin (A) (hereinafter also referred to as nucleating agent (C-1)) or a nucleating agent contained when preparing the polypropylene resin (B) (hereinafter also referred to as nucleating agent (C-2)). It is more preferable that the polypropylene resin composition of this embodiment contains both nucleating agent (C-1) and nucleating agent (C-2) as described above. By configuring it in this way, poor filling into the mold is less likely to occur even during thin-wall injection molding, and it can also be used for high-cycle (high-speed) molding.

[0034] The nucleating agent (C) is also called a crystal nucleating agent. As the nucleating agent (C), known nucleating agents that are conventionally included in polypropylene resin compositions can be used, and nucleating agents selected from nonitol-based nucleating agents, sorbitol-based nucleating agents, phosphate ester-based nucleating agents, triaminobenzene derivative nucleating agents, carboxylate metal salt nucleating agents, and xylitol-based nucleating agents are preferred. Talc can also be used as a nucleating agent. From the viewpoint of reducing the odor of injection molded products, phosphate ester-based nucleating agents are preferred. Examples of crystal nucleating agents having a nonitol-based structure include 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol, examples of crystal nucleating agents having a xylitol-based structure include bis-1,3:2,4-(5',6',7',8'-tetrahydro-2-naphthaldehyde benzylidene)1-allyl xylitol and bis-1,3:2,4-(3',4'-dimethylbenzylidene)1-propyl xylitol, and examples of crystal nucleating agents having a sorbitol-based structure include bis-1,3:2,4-(4'-ethylbenzylidene)1-allyl sorbitol, bis-1,3:2,4-(3'-methyl-4'-fluorobenzylidene)1-propyl sorbitol and bis-1,3:2,4-(3',4'-dimethylbenzylidene) Examples include bis-1,3,2,4-dibenzylidene 2',3'-dibromopropyl sorbitol, bis-1,3,2,4-dibenzylidene 2'-bromo-3'-hydroxypropyl sorbitol, bis-1,3:2,4-(3'-bromo-4'-ethylbenzylidene)-1-allyl sorbitol, mono-2,4-(3'-bromo-4'-ethylbenzylidene)-1-allyl sorbitol, bis-1,3:2,4-(4'-ethylbenzylidene)1-allyl sorbitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene)1-methyl sorbitol, bis(p-methylbenzylidene) sorbitol, and 1,3:2,4-bis-o-(4-methylbenzylidene)-D-sorbitol. Examples of commercially available nonitol-based nucleating agents include Millad NX8000 (manufactured by Milliken Japan), and examples of commercially available sorbitol-based nucleating agents include RiKAFAST R-1 (manufactured by Shin-Nippon Rika Co., Ltd.), Millad 3988 (manufactured by Milliken Japan), Gelol E-200 (manufactured by Shin-Nippon Rika Co., Ltd.), and Gelol MD (manufactured by Shin-Nippon Rika Co., Ltd.). Examples of phosphate ester-based crystal nucleating agents include sodium 2,2-methylenebis(4,6-di-tert-butylphenyl) phosphate, aluminum 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, and lithium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate. Examples of commercially available phosphate ester-based crystal nucleating agents include Adekastab NA-11 (manufactured by ADEKA Corporation), Adekastab NA-21 (manufactured by ADEKA Corporation), and Adekastab NA-71 (manufactured by ADEKA Corporation). Examples of triaminobenzene derivative nucleating agents include 1,3,5-tris(2,2-dimethylpropanamide)benzene. Examples of commercially available triaminobenzene derivative nucleating agents include IRGACLEAR XT386 (manufactured by BASF Japan) and Ricaclear PC1 (manufactured by Shin Nippon Rika Co., Ltd.). Examples of carboxylate metal salt nucleating agents include calcium 1,2-cyclohexanedicarboxylate. Examples of commercially available carboxylate metal salt nucleating agents include Hyperform HPN-20E (manufactured by Milliken Japan). These nucleating agents can be used individually or in combination of two or more.

[0035] [Other ingredients] The polypropylene resin composition of this embodiment may further contain additives other than the polypropylene resin (A), polypropylene resin (B), and nucleating agent (C) as optional components, to the extent that they do not impair the effects of the present invention. Examples of additives include antioxidants, neutralizing agents, weathering agents, pigments (organic or inorganic), internal and external lubricants, antiblocking agents, antistatic agents, chlorine absorbers, heat stabilizers, light stabilizers, UV absorbers, slip agents, antifogging agents, flame retardants, dispersants, copper damage inhibitors, plasticizers, foaming agents, anti-foaming agents, crosslinking agents, peroxides, oil spreaders, inorganic fillers, or organic fillers. These additives may be present in single or multiply form. The amount contained may be a known quantity.

[0036] ≪Method for producing polypropylene resin compositions≫ Next, a method for producing a polypropylene resin composition according to a second embodiment of the present invention will be described. The method for producing a polypropylene resin composition according to this embodiment (hereinafter also simply referred to as the "production method") is a method for producing the polypropylene resin composition according to the first embodiment described above, and comprises the following steps A, B, and C.

[0037] Step A is a step in which an ethylene monomer and a propylene monomer are polymerized in the presence of a propylene polymer (a1) to obtain a polypropylene resin (A). Step B is a process in which an ethylene monomer and a propylene monomer are polymerized in the presence of a propylene polymer (b1) to obtain a polypropylene resin (B). Step C is a step of mixing the obtained polypropylene resin (A) and polypropylene resin (B).

[0038] In step A, it is preferable to polymerize an ethylene monomer and a propylene monomer in the presence of a propylene polymer (a1) using a catalyst containing a phthalate compound as an electron donor to obtain a polypropylene resin (A). Further details regarding step A and the catalyst containing a phthalate compound as an electron donor will be described later.

[0039] Furthermore, in step B, it is preferable to polymerize an ethylene monomer and a propylene monomer in the presence of a propylene polymer (b1) using a catalyst containing a succinate compound as an electron donor to obtain a polypropylene resin (B). Details of step B and the catalyst containing a succinate compound as an electron donor will be described later.

[0040] Furthermore, it is preferable that step C further includes a step of melt-kneading the polypropylene resin (A) and polypropylene resin (B) after mixing them with other components such as a nucleating agent (C) and an antioxidant, as needed. Mixing methods include dry blending using mixers such as Henschel mixers, tumblers, and ribbon mixers. The addition of nucleating agents (C) and antioxidants may be carried out using a connected extruder after the polymerization, residual monomer removal, and drying processes of the polypropylene resin (A) and / or polypropylene resin (B). In addition, in the present invention, a so-called masterbatch, which is obtained by melt-kneading a high concentration of nucleating agent (C) with polypropylene, may be mixed into the polypropylene resin during molding. The melt-mixing method can involve mixing while melting using a mixer such as a single-screw extruder, twin-screw extruder, Banbury mixer, kneader, or roll mill. The melting temperature during melt-mixing is preferably 160-350°C, and more preferably 170-260°C. The mixture may be further pelletized after melt-mixing.

[0041] [Process A: Manufacturing of polypropylene resin (A)] The polypropylene resin (A) may be obtained by mixing a propylene polymer (a1) (component (a1)) and an ethylene-propylene copolymer (a2) (component (a2)) during polymerization, or by mixing components (a1) and (a2) that have been manufactured separately by melt kneading. The polypropylene resin (A) is preferably a polymerized mixture in which component (a1) and component (a2) are mixed during polymerization. Such polymerization mixtures are obtained by polymerizing ethylene monomers and propylene monomers in the presence of component (a1). This method offers high productivity and improves the dispersibility of component (a2) within component (a1), thereby enhancing the balance of mechanical properties of injection-molded articles obtained using this mixture.

[0042] A typical method for producing a polymerization mixture is a multi-stage polymerization method. For example, in a polymerization apparatus equipped with two polymerization reactors, a propylene monomer and, if necessary, an ethylene monomer are polymerized in the first stage polymerization reactor to obtain a propylene polymer. This propylene polymer is then supplied to the second stage polymerization reactor, where the ethylene monomer and propylene monomer are polymerized to obtain a polymerization mixture. The polymerization conditions may be the same as known polymerization conditions. For example, a slurry polymerization method is an option for the first stage, where propylene is in the liquid phase and yields high monomer density and productivity. A gas-phase polymerization method is an option for the second stage, which generally facilitates the production of copolymers with high solubility in propylene. The polymerization temperature is preferably 50 to 90°C, more preferably 60 to 90°C, and even more preferably 70 to 90°C. When the polymerization temperature is above the lower limit of the above range, productivity and the stereoregularity of the resulting polypropylene are better. The polymerization pressure is preferably 25 to 60 bar (2.5 to 6.0 MPa) and more preferably 33 to 45 bar (3.3 to 4.5 MPa) when carried out in the liquid phase. When carried out in the gas phase, the polymerization pressure is preferably 5 to 30 bar (0.5 to 3.0 MPa) and more preferably 8 to 30 bar (0.8 to 3.0 MPa). Polymerization (polymerization of propylene monomers, ethylene monomers, and propylene monomers, etc.) is usually carried out using a catalyst. During polymerization, hydrogen may be added as needed to adjust the molecular weight. By adjusting the molecular weight of propylene polymers and ethylene-propylene copolymers, the MFR of polypropylene resin (A), and consequently the MFR of polypropylene resin compositions, can be adjusted. Before polymerization in the first stage of polymerization reactor, propylene prepolymerization may be performed to form polymer chains in the solid catalyst component, which will serve as a foothold for the subsequent main polymerization. Prepolymerization is usually carried out at 40°C or below, preferably 30°C or below, and more preferably 20°C or below.

[0043] As the catalyst, known olefin polymerization catalysts can be used. As a catalyst for polymerizing the ethylene monomer and the propylene monomer in the presence of the above-mentioned propylene polymer, a stereospecific Ziegler-Natta catalyst is preferred, and a catalyst containing the following components (a), (b), and (c) (hereinafter also referred to as "catalyst (X)") is particularly preferred. (a) A solid catalyst containing magnesium, titanium, halogen, and a phthalate compound as an essential component. (i) Organoaluminum compounds. (c) Organosilicon compounds that are external electron donors.

[0044] The polypropylene resin (A) is preferably produced by a method comprising the step of polymerizing an ethylene monomer and a propylene monomer in the presence of the above-mentioned propylene polymer using a catalyst (X) to obtain a polypropylene resin. By using catalyst (X), a polypropylene resin (A) whose physical properties are within the above-mentioned range can be easily obtained. Incidentally, the molecular weight and stereoregularity distribution of the propylene polymer obtained by the catalyst used (especially the electron donor compound of component (a)) are different, and the difference affects the crystallization behavior and the like, but the details of the relationship have not been clarified. When trying to clarify this, it is necessary to analyze the molecular weight distribution and the stereoregularity distribution together as the molecular structure. However, it is complicated because components with different molecular weights and stereoregularities affect each other during the crystallization process, making it more difficult to interpret the influence of the stereoregularity distribution on the crystallization behavior. Furthermore, since actual injection molding is carried out very rapidly and in a flowing state, it is not easy to grasp the phenomenon even using advanced analysis techniques. Therefore, it is almost impossible to specify the difference in the crystallization behavior due to the stereoregularity distribution by numerical values or the like in the polypropylene-based resin composition obtained using a specific catalyst. The molecular weight distribution and the stereoregularity distribution also change due to thermal deterioration during melt-kneading, peroxide treatment, etc. in addition to the types of catalysts described above.

[0045] Component (a) is prepared using, for example, a titanium compound, a magnesium compound, and an electron donor compound. As the titanium compound used in component (a), a tetravalent titanium compound represented by the general formula: Ti(OR) g X 4-g (R is a hydrocarbon group, X is a halogen, 0 ≦ g ≦ 4) is suitable. Examples of the hydrocarbon group include methyl, ethyl, propyl, butyl, etc., and examples of the halogen include Cl, Br, etc. More specific titanium compounds include titanium tetrahalides such as TiCl4, TiBr4, TiI4; trihalogenated alkoxytitaniums such as Ti(OCH3)Cl3, Ti(OC2H5)Cl3, Ti(O n -C4H9)Cl3, Ti(OC2H5)Br3, Ti(O-isoC4H9)Br3; dihalogenated alkoxytitaniums such as Ti(OCH3)2Cl2, Ti(OC2H5)2Cl2, Ti(O n -C4H9)2Cl2, Ti(OC2H5)2Br2; Ti(OCH3)3Cl, Ti(OC2H5)3Cl, Ti(O n-C4H9)3Cl, Ti(OC2H5)3Br and other monohalogenated trialkoxy titanium; Ti(OCH3)4, Ti(OC2H5)4, Ti(O n Examples include tetraalkoxytitanium compounds such as -C4H9)4. These titanium compounds may be used individually or in combination of two or more. Among the above titanium compounds, halogen-containing titanium compounds are preferred, more preferably titanium tetrahalides, and particularly preferably titanium tetrachloride (TiCl4).

[0046] Examples of magnesium compounds used in component (a) include magnesium compounds having magnesium-carbon bonds or magnesium-hydrogen bonds, such as dimethylmagnesium, diethylmagnesium, dipropylmagnesium, dibutylmagnesium, diamylmagnesium, dihexylmagnesium, didecylmagnesium, ethylmagnesium chloride, propylmagnesium chloride, butylmagnesium chloride, hexylmagnesium chloride, amylmagnesium chloride, butylethoxymagnesium, ethylbutylmagnesium, and butylmagnesium hydride. These magnesium compounds can also be used in the form of complex compounds with organoaluminum, for example, and may be in liquid or solid form. Further preferred magnesium compounds include magnesium halides such as magnesium chloride, magnesium bromide, magnesium iodide, and magnesium fluoride; alkoxymagnesium halides such as magnesium methoxychloride, magnesium ethoxychloride, magnesium isopropoxychloride, magnesium butoxychloride, and magnesium octoxychloride; alyroxymagnesium halides such as magnesium phenoxychloride and magnesium methylphenoxychloride; alkoxymagnesiums such as magnesium ethoxychloride, magnesium isopropoxychloride, magnesium butoxychloride, n-octoxymagnesium, and 2-ethylhexoxymagnesium; dialkoxymagnesiums such as dimethoxymagnesium, diethoxymagnesium, dipropoxymagnesium, dibutoxymagnesium, and magnesium ethoxymethoxymagnesium; and alyroxymagnesiums such as magnesium ethoxypropoxymagnesium, magnesium butoxyethoxymagnesium, magnesium phenoxymagnesium, and magnesium dimethylphenoxymagnesium. These magnesium compounds may be used individually or in combination of two or more.

[0047] The electron donor compound used in component (a) preferably contains a phthalate compound as an essential component. When a catalyst (X) containing a phthalate compound as an electron donor is used, a polypropylene resin in which the Mw / Mn of the propylene polymer (a1) is within the above range can be easily obtained. Examples of phthalate compounds that act as electron donors include monoethyl phthalate, dimethyl phthalate, methyl ethyl phthalate, monoisobutyl phthalate, mono-n-butyl phthalate, diethyl phthalate, ethylisobutyl phthalate, ethyl-n-butyl phthalate, di-n-propyl phthalate, diisopropyl phthalate, di-n-butyl phthalate, diisobutyl phthalate, di-n-heptyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, dineopentyl phthalate, didecyl phthalate, benzyl butyl phthalate, and diphenyl phthalate. Among these, diisobutyl phthalate is particularly preferred.

[0048] Furthermore, the electron-donating compounds used in phthalate catalysts may be used individually or in combination of two or more.

[0049] Examples of halogen atoms constituting component (A) include fluorine, chlorine, bromine, iodine, or mixtures thereof, with chlorine being particularly preferred.

[0050] Examples of organoaluminum compounds in component (a) include trialkylaluminum such as triethylaluminum and tributylaluminum, trialkenylaluminum such as triisoprenylaluminum, dialkylaluminum alkoxides such as diethylaluminum ethoxide and dibutylaluminum butoxide, alkylaluminum sesquialkoxides such as ethylaluminum sesquiethoxide and butylaluminum sesquibutoxide, R 7 2.5 Al(OR 8 ) 0.5 (R 7 ,R 8These are hydrocarbon groups that may be different or the same. Examples include partially alkoxylated alkylaluminum, dialkylaluminum halogens such as diethylaluminum chloride, dibutylaluminum chloride, and diethylaluminum bromide, partially halogenated alkylaluminum such as ethylaluminum sesquichloride, butylaluminum sesquichloride, and ethylaluminum sesquibromide, partially hydrogenated alkylaluminum such as ethylaluminum dichloride, propylaluminum dichloride, and butylaluminum dibromide, partially alkoxylated and halogenated alkylaluminum such as ethylaluminum ethoxycyclolide, butylaluminum butoxycyclolide, and ethylaluminum ethoxybromide, which have an average composition represented by (a).

[0051] As the external electron donor compound for component (c), an organosilicon compound is used. Preferred organosilicon compounds include, for example, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, t-butylmethyldimethoxysilane, t-butylmethyldiethoxysilane, t-amylmethyldiethoxysilane, diphenyldimethoxysilane, phenylmethyldimethoxysilane, diphenyldiethoxysilane, bis-o-tolyldimethoxysilane, bis-m-tolyldimethoxysilane, bis-p-tolyldimethoxysilane, bis-p-tolyldiethoxysilane, bis-ethylphenyldimethoxysilane, dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylmethyldiethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, methyltrimethoxysilane, n-propyltriethoxysilane, decyltri Methoxysilane, Decyltriethoxysilane, Phenyltrimethoxysilane, γ-Chloropropyltrimethoxysilane, Methyltriethoxysilane, Vinyltriethoxysilane, t-Butyltriethoxysilane, Texyltrimethoxysilane, n-Butyltriethoxysilane, iso-Butyltriethoxysilane, Phenyltriethoxysilane, γ-Aminopropyltriethoxysilane, Chlortriethoxysilane, Ethyltriisopropoxysilane, Vinyltributoxysilane, Cyclohexyltrimethoxysilane, Cyclohexyltriethoxysilane, 2-Norbornanetrimethoxysilane, 2-Norbornanetriethoxysilane, 2-Norbornanemethyldimethoxysilane, Ethyl silicate, Butyl silicate, Trimethylphenoxysilane, Methyltrialyloxysilane, Vinyltris(β-Methoxyethoxysilane), Vinyltriacetoxysilane, Dimethyltetraethoxydisiloxane, Methyl(3,3,3-Trifluoro-n-propyl)dimethoxysilane, cyclohexylethyldimethoxysilane, cyclopentyl-t-butoxydimethoxysilane, diisobutyldimethoxysilane, isobutylisopropyldimethoxysilane, n-propyltrimethoxysilane, di-n-propyldimethoxysilane, t-butylethyldimethoxysilane, t-butylpropyldimethoxysilane, t-butyl-t-butoxydimethoxysilane, isobutyltrimethoxysilane, cyclohexylisobutyldimethoxysilane, di-sec-butyldimethoxysilane, isobutylmethyldimethoxysilane, bis(decahydroisoquinoline-2-yl)dimethoxysilane, diethyl Examples include diaminotriethoxysilane, dicyclopentyl-bis(ethylamino)silane, tetraethoxysilane, tetramethoxysilane, isobutyltriethoxysilane, t-butyltrimethoxysilane, i-butyltrimethoxysilane, i-butylsec-butyldimethoxysilane, ethyl(perhydroisoquinoline 2-yl)dimethoxysilane, tri(isopropenyloxy)phenylsilane, i-butyli-propyldimethoxysilane, cyclohexyli-butyldimethoxysilane, cyclopentyli-butyldimethoxysilane, cyclopentylisopropyldimethoxysilane, phenyltriethoxylan, and p-tolylmethyldimethoxysilane. Among these, ethyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, t-butyltriethoxysilane, t-butylmethyldimethoxysilane, t-butylmethyldiethoxysilane, t-butylethyldimethoxysilane, t-butylpropyldimethoxysilane, t-butylt-butoxydimethoxysilane, t-butyltrimethoxysilane, i-butyltrimethoxysilane, isobutylmethyldimethoxysilane, i-butylsec-butyldimethoxysilane, ethyl(perhydroisoquinoline 2-yl)dimethoxysilane, bis(decahydroisoquinoline-2-yl)dimethoxysilane, tri(isopropenyloxy)phenylsilane, texyltrimethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, vinyltributoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane Lan, i-butyl i-propyl dimethoxysilane, cyclopentyl t-butoxydimethoxysilane, dicyclopentyl dimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexyl i-butyldimethoxysilane, cyclopentyl i-butyldimethoxysilane, cyclopentyl isopropyldimethoxysilane, di-sec-butyldimethoxysilane, diethylaminotriethoxysilane, tetraethoxysilane, tetramethoxysilane, isobutyltriethoxysilane, phenylmethyldimethoxysilane, phenyltriethoxysilane, bis-p-tolyldimethoxysilane, p-tolylmethyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylethyldimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, diphenyldiethoxysilane, methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane, ethyl silicate, etc. are preferred. The above ingredient (c) may be used alone or in combination of two or more types.

[0052] Organosilicon compounds play a particularly important role in adjusting the amount of xylene-insoluble matter. While the amount of xylene-insoluble matter depends on the type and amount of organosilicon compound and the polymerization temperature, even with appropriate organosilicon compounds, it generally decreases significantly when the amount of organosilicon compound falls below a certain value, except for diether-based catalysts. Therefore, at a polymerization temperature of 75°C, the lower limit of the molar ratio of organosilicon compound to organoaluminum compound (organosilicon compound / organoaluminum) is preferably 0.015, more preferably 0.018. The upper limit of this ratio is preferably 0.30, more preferably 0.20, and even more preferably 0.10. When a phthalate compound is used as the internal electron donor compound, increasing the polymerization temperature increases the xylene-insoluble content, thus lowering the lower and upper limits of the preferred molar ratio of organosilicon compound to organoaluminum compound (organosilicon compound / organoaluminum compound). Specifically, when polymerizing at 80°C using a phthalate compound, the lower limit of the molar ratio is preferably 0.010, more preferably 0.015, and even more preferably 0.018. The upper limit of the molar ratio is preferably 0.20, more preferably 0.14, and even more preferably 0.08.

[0053] Preferably, the catalyst (X) has component (i) as a trialkylaluminum such as triethylaluminum or triisobutylaluminum, and component (iii) as an organosilicon compound such as dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, or diisopropyldimethoxysilane.

[0054] Here, the phthalate catalyst is preferably a phthalate catalyst with high porosity. Since the polymer particles are so-called replicas having a similar shape to the catalyst particles, using a phthalate catalyst with high porosity allows the average particle diameter and average pore diameter (Dn) of component (a1) of the resulting polypropylene resin (A) to be maintained within a predetermined range.

[0055] Furthermore, although not particularly limited, the component (a1) obtained in step A is preferably porous particles with an average particle size (diameter) of 1.5 to 4.0 mm and an average pore diameter (Dn) of 8 to 50 μm. Dn is the average value of the pore diameter D measured by the mercury intrusion method in accordance with JIS R1655. When Dn is within the above range, the powder flowability of the polypropylene resin (A) composed of component (a1) and component (a2) is improved, resulting in improved productivity. Although the mechanism is not clear, it is presumed that when component (a1) has a Dn within the aforementioned range, the presence of component (a2) within component (a1) allows for both a sufficient pore size and a sufficient sum of pore surface area, making it easier for component (a2) to be retained within component (a1). Therefore, even when the copolymer (a2) content relative to the total mass of the polypropylene resin (A) is high, the powder flowability of the polymer is improved. Furthermore, the average particle size (diameter) of component (a1) is the arithmetic mean of the diameters of component (a1) measured by optical microscopy as defined in JIS Z8901. In one embodiment, it can be obtained by determining the average weight per particle by measuring the number of particles per gram, determining the average volume per particle from the bulk density, and calculating the average diameter of the spherical shape from the average volume.

[0056] Furthermore, the method for obtaining a polymerization mixture by multi-stage polymerization is not limited to the method described above. A propylene polymer (a1) (component (a1)) may be polymerized in multiple polymerization reactors, or an ethylene-propylene copolymer (a2) (component (a2)) may be polymerized in multiple polymerization reactors. One method for obtaining a polymerization mixture is to use a polymerizer with gradients of monomer concentration and polymerization conditions. In such a polymerizer, for example, one in which at least two polymerization regions are joined together can be used to polymerize monomers by gas-phase polymerization. Specifically, in the presence of a catalyst, monomers are supplied and polymerized in a polymerization region consisting of an ascending tube, monomers are supplied and polymerized in a descending tube connected to the ascending tube, and the polymerization product is recovered while circulating between the ascending and descending tubes. This method includes means to prevent the gaseous mixture present in the ascending tube from entering the descending tube, either entirely or partially. In addition, a gas and / or liquid mixture having a different composition from the gaseous mixture present in the ascending tube is introduced into the descending tube. This polymerization method can be applied, for example, to the method described in Japanese Patent Publication No. 2002-520426.

[0057] [Process B: Manufacturing of polypropylene resin (B)] The polypropylene resin (B) may be obtained by mixing a propylene polymer (b1) (component (b1)) and an ethylene-propylene copolymer (b2) (component (b2)) during polymerization, or by mixing components (b1) and (b2) that have been manufactured separately by melt kneading. The polypropylene resin (B) is preferably a polymerized mixture in which component (b1) and component (b2) are mixed during polymerization. Such polymerization mixtures are obtained by polymerizing ethylene monomers and propylene monomers in the presence of component (b1). This method offers high productivity and improves the dispersibility of component (b2) within component (b1), thereby enhancing the balance of mechanical properties of injection-molded articles obtained using this mixture.

[0058] As for the method of producing the polymerization mixture, a multi-stage polymerization method is typically used, similar to step A. For example, in a polymerization apparatus equipped with two polymerization reactors, a propylene monomer and, if necessary, an ethylene monomer are polymerized in the first stage polymerization reactor to obtain a propylene polymer. The obtained propylene polymer is then supplied to the second stage polymerization reactor, where the ethylene monomer and propylene monomer are polymerized to obtain the polymerization mixture. The polymerization conditions may be the same as known polymerization conditions. For example, a slurry polymerization method is an option for the first stage, where propylene is in the liquid phase and yields high monomer density and productivity. A gas-phase polymerization method is an option for the second stage, which generally facilitates the production of copolymers with high solubility in propylene. The polymerization temperature is preferably 50 to 90°C, more preferably 60 to 90°C, and even more preferably 70 to 90°C. When the polymerization temperature is above the lower limit of the above range, productivity and the stereoregularity of the resulting polypropylene are better. The polymerization pressure is preferably 25 to 60 bar (2.5 to 6.0 MPa) and more preferably 33 to 45 bar (3.3 to 4.5 MPa) when carried out in the liquid phase. When carried out in the gas phase, the polymerization pressure is preferably 5 to 30 bar (0.5 to 3.0 MPa) and more preferably 8 to 30 bar (0.8 to 3.0 MPa). Polymerization is usually carried out using a catalyst. During polymerization, hydrogen may be added as needed to adjust the molecular weight. By adjusting the molecular weight of the propylene polymer or ethylene-propylene copolymer, the MFR of the polypropylene resin (B), and consequently the MFR of the polypropylene resin composition, can be adjusted. Before polymerization in the first stage of polymerization reactor, propylene prepolymerization may be performed to form polymer chains in the solid catalyst component, which will serve as a foothold for the subsequent main polymerization. Prepolymerization is usually carried out at 40°C or below, preferably 30°C or below, and more preferably 20°C or below.

[0059] As a catalyst, known olefin polymerization catalysts can be used, but it is preferable to use a catalyst containing a succinate compound as an electron donor (hereinafter also referred to as a "succinate catalyst"). By using a succinate catalyst, a polymerization mixture having a continuous phase consisting of a component (b1) prepared to have a broad molecular weight distribution range, such as a polypropylene resin (B), can be obtained in good condition.

[0060] Polymers polymerized using succinate-based catalysts have a broad molecular weight distribution (high Mw / Mn) and uniform dispersion of high and low molecular weight components. Molecular weight distribution is a physical quantity and can be determined by measurement. However, this measurement does not represent the degree of dispersion of high and low molecular weight components. For example, it is possible to obtain polymers that appear to have a molecular weight distribution (measured value) equivalent to those obtained by polymerization using succinate-based catalysts by melt-kneading high and low molecular weight components given in powder or pellet form using an extruder, or by performing multi-stage polymerization of components with different molecular weights using a catalyst other than succinate-based catalysts. However, the degree of dispersion of high and low molecular weight components differs between polymers obtained in this way and polymers obtained by polymerization using succinate-based catalysts, with the latter achieving a uniform degree of dispersion. This difference is significant in performance such as rigidity, impact resistance, processability, and appearance.

[0061] As a catalyst for polymerizing the ethylene monomer and the propylene monomer in the presence of the above-mentioned propylene polymer, a stereospecific Ziegler-Natta catalyst is preferred, and a catalyst containing the following components (d), (b), and (c) (hereinafter also referred to as "catalyst (Y)") is particularly preferred. (e) A solid catalyst containing magnesium, titanium, a halogen, and the succinate compound as an essential component. (i) Organoaluminum compounds. (c) Organosilicon compounds that are external electron donors.

[0062] The titanium compound, magnesium compound used in component (E), component (I), and component (U) can be the same compounds as in step A.

[0063] A succinate compound is preferred as the electron donor, and this compound refers to a diester of succinic acid or a diester of substituted succinic acid. The succinate compound will be described in detail below. The succinate compound preferably used in the present invention is represented by the following formula (I).

[0064] [ka]

[0065] In formula (I), groups R1 and R2 are either identical or different from each other, and may include heteroatoms, C1-C 20 The linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl, or alkylaryl groups; groups R3-R6 are identical or different from each other and contain hydrogen, or possibly heteroatoms, C1-C 20 The linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl, or alkylaryl groups, wherein groups R3-R6 bonded to the same or different carbon atoms may bond together to form a ring.

[0066] R1 and R2 are preferably C1-C8 alkyl, cycloalkyl, aryl, arylalkyl, and alkylaryl groups. Compounds in which R1 and R2 are selected from primary alkyls, particularly branched primary alkyls, are especially preferred. Examples of preferred R1 and R2 groups are C1-C8 alkyl groups, such as methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, and 2-ethylhexyl. Ethyl, isobutyl, and neopentyl are especially preferred.

[0067] One preferred group of compounds represented by formula (I) is one in which R3 to R5 are hydrogen atoms and R6 is a branched alkyl, cycloalkyl, aryl, arylalkyl, and alkylaryl group having 3 to 10 carbon atoms. Preferred specific examples of such monosubstituted succinate compounds include diethyl-sec-butyl succinate, diethyl texyl succinate, diethylcyclopropyl succinate, diethylnorbonyl succinate, diethylperihydrosuccinate, diethyltrimethylsilyl succinate, diethyl methoxysuccinate, diethyl-p-methoxyphenyl succinate, diethyl-p-chlorophenyl succinate, diethylphenyl succinate, diethylcyclohexyl succinate, and di Ethyl benzyl succinate, diethylcyclohexylmethyl succinate, diethyl-t-butyl succinate, diethyl isobutyl succinate, diethyl isopropyl succinate, diethyl neopentyl succinate, diethyl isopentyl succinate, diethyl (1-trifluoromethylethyl) succinate, diethylfluorenyl succinate, 1-ethoxycarbodisobutylphenyl succinate, diisobutyl-sec-butyl succinate, diisobutyltexyl succinate Diisobutyl cyclopropyl succinate, diisobutyl norbonyl succinate, diisobutyl perihydrosuccinate, diisobutyl trimethylsilyl succinate, diisobutyl methoxysuccinate, diisobutyl-p-methoxyphenyl succinate, diisobutyl-p-chlorophenyl succinate, diisobutyl cyclohexyl succinate, diisobutyl benzyl succinate, diisobutyl cyclohexyl methyl succinate, diisobutyl-t-butyl succinate Diisobutyl isobutyl succinate, diisobutyl isopropyl succinate, diisobutyl neopentyl succinate, diisobutyl isopentyl succinate, diisobutyl (1-trifluoromethylethyl) succinate, diisobutyl fluorenyl succinate, dineopentyl-sec-butyl succinate, dineopentyl texyl succinate, dineopentyl cyclopropyl succinate, dineopentyl norbonyl succinate, dineopentyl perihydrosuccinate,These are dineopentyl trimethylsilyl succinate, dineopentyl methoxysuccinate, dineopentyl-p-methoxyphenyl succinate, dineopentyl-p-chlorophenyl succinate, dineopentylphenyl succinate, dineopentyl cyclohexyl succinate, dineopentyl benzyl succinate, dineopentyl cyclohexylmethyl succinate, dineopentyl-t-butyl succinate, dineopentyl isobutyl succinate, dineopentyl isopropyl succinate, dineopentyl neopentyl succinate, dineopentyl isopentyl succinate, dineopentyl (1-trifluoromethylethyl) succinate, and dineopentyl fluorenyl succinate.

[0068] Other preferred groups of compounds within the range of formula (I) are those in which at least two groups from R3 to R6 are C1 to C, which, unlike hydrogen, may include heteroatoms. 20The groups are selected from linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl, or alkylaryl groups. Compounds in which two groups other than hydrogen are bonded to the same carbon atom are particularly preferred. Specifically, compounds in which R3 and R4 are groups other than hydrogen and R5 and R6 are hydrogen atoms. Preferred examples of such disubstituted succinates include diethyl-2,2-dimethyl succinate, diethyl-2-ethyl-2-methyl succinate, diethyl-2-benzyl-2-isopropyl succinate, diethyl-2-cyclohexylmethyl-2-isobutyl succinate, diethyl-2-cyclopentyl-2-n-butyl succinate, diethyl-2,2-diisobutyl succinate, diethyl-2-cyclohexyl-2-ethyl succinate, diethyl-2-isopropyl-2-methyl succinate, diethyl-2-tetradecyl-2-ethyl succinate, diethyl-2-isobutyl-2-ethyl succinate, diethyl-2-(1-trifluoromethylethyl)-2-methyl succinate, diethyl-2-isopentyl-2-isobutyl succinate, diethyl-2-phenyl-2-n-butyl succinate, and diisobutyl -2,2-dimethyl succinate, diisobutyl-2-ethyl-2-methyl succinate, diisobutyl-2-benzyl-2-isopropyl succinate, diisobutyl-2-cyclohexylmethyl-2-isobutyl succinate, diisobutyl-2-cyclopentyl-2-n-butyl succinate, diisobutyl-2,2-diisobutyl succinate, diisobutyl-2-cyclohexyl-2-ethyl succinate, diisobutyl-2-isopropyl-2-methyl succinate, diisobutyl-2-tetradecyl-2-ethyl succinate, diisobutyl-2-isobutyl-2-ethyl succinate, diisobutyl-2-(1-trifluoromethylethyl)-2-methyl succinate, diisobutyl-2-isopentyl-2-isobutyl succinate, diisobutyl-2-phenyl-2-n-butyl succinate, dineopentyl-2,These are 2-dimethyl succinate, dineopentyl-2-ethyl-2-methyl succinate, dineopentyl-2-benzyl-2-isopropyl succinate, dineopentyl-2-cyclohexylmethyl-2-isobutyl succinate, dineopentyl-2-cyclopentyl-2-n-butyl succinate, dineopentyl-2,2-diisobutyl succinate, dineopentyl-2-cyclohexyl-2-ethyl succinate, dineopentyl-2-isopropyl-2-methyl succinate, dineopentyl-2-tetradecyl-2-ethyl succinate, dineopentyl-2-isobutyl-2-ethyl succinate, dineopentyl-2-(1-trifluoromethylethyl)-2-methyl succinate, dineopentyl-2-isopentyl-2-isobutyl succinate, and dineopentyl-2-phenyl-2-n-butyl succinate. ,

[0069] Furthermore, compounds in which at least two groups other than hydrogen are bonded to different carbon atoms are particularly preferred. Specifically, these are compounds in which R3 and R5 are groups other than hydrogen. In this case, R4 and R6 may be hydrogen atoms or groups other than hydrogen, but it is preferable that one of them is a hydrogen atom (trisubstituted succinate). Preferred specific examples of such compounds are diethyl-2,3-bis(trimethylsilyl)succinate, diethyl-2,2-sec-butyl-3-methylsuccinate, diethyl-2-(3,3,3-trifluoropropyl)-3-methylsuccinate, diethyl-2,3-bis(2-ethylbutyl)succinate, diethyl-2,3-diethyl-2-isopropylsuccinate, diethyl-2,3-diisopropyl-2-methylsuccinate, and diethyl-2,3 -Dicyclohexyl-2-methyldiethyl-2,3-dibenzyl succinate, diethyl-2,3-diisopropyl succinate, diethyl-2,3-bis(cyclohexylmethyl) succinate, diethyl-2,3-di-t-butyl succinate, diethyl-2,3-diisobutyl succinate, diethyl-2,3-dineopentyl succinate, diethyl-2,3-diisopentyl succinate, diethyl-2,3-(1-trifluoromethylethyl) succinate Succinate, diethyl-2,3-tetradecyl succinate, diethyl-2,3-fluorenyl succinate, diethyl-2-isopropyl-3-isobutyl succinate, diethyl-2-tert-butyl-3-isopropyl succinate, diethyl-2-isopropyl-3-cyclohexyl succinate, diethyl-2-isopentyl-3-cyclohexyl succinate, diethyl-2-tetradecyl-3-cyclohexylmethyl succinate, diethyl-2 -Cyclohexyl-3-cyclopentyl succinate, diisobutyl-2,3-diethyl-2-isopropyl succinate, diisobutyl-2,3-diisopropyl-2-methyl succinate, diisobutyl-2,3-dicyclohexyl-2-methyl succinate, diisobutyl-2,3-dibenzyl succinate, diisobutyl-2,3-diisopropyl succinate, diisobutyl-2,3-bis(cyclohexylmethyl) succinate, diisobutyl-2,3-di-t-butyl succinate, diisobutyl-2,3-diisobutyl succinate, diisobutyl-2,3-dineopentyl succinate, diisobutyl-2,3-diisopentyl succinate, diisobutyl-2,3-(1-trifluoromethylethyl) succinate, diisobutyl-2,3-tetradecyl succinate, diisobutyl-2,3-fluorenyl succinate, diisobutyl-2-isopropyl-3-isobutyl succinate, diisobutyl-2-te rt-butyl-3-isopropyl succinate, diisobutyl-2-isopropyl-3-cyclohexyl succinate, diisobutyl-2-isopentyl-3-cyclohexyl succinate, diisobutyl-2-tetradecyl-3-cyclohexylmethyl succinate, diisobutyl-2-cyclohexyl-3-cyclopentyl succinate, dineopentyl-2,3-bis(trimethylsilyl) succinate, dineopentyl-2,2-sec-butyl-3-methyl succinate Dineopentyl-2-(3,3,3-trifluoropropyl)-3-methylsuccinate, Dineopentyl-2,3-bis(2-ethylbutyl)succinate, Dineopentyl-2,3-diethyl-2-isopropylsuccinate, Dineopentyl-2,3-diisopropyl-2-methylsuccinate, Dineopentyl-2,3-dicyclohexyl-2-methylsuccinate, Dineopentyl-2,3-dibenzylsuccinate, Dineopentyl-2,3-diisopropyl Lusuccinate, Dineopentyl-2,3-bis(cyclohexylmethyl)succinate, Dineopentyl-2,3-di-t-butylsuccinate, Dineopentyl-2,3-diisobutylsuccinate, Dineopentyl-2,3-Dineopentylsuccinate, Dineopentyl-2,3-diisopentylsuccinate, Dineopentyl-2,3-(1-trifluoromethylethyl)succinate, Dineopentyl-2,3-tetradecylsuccinate, Dineopentyl-2,These are 3-fluorenyl succinate, dineopentyl-2-isopropyl-3-isobutyl succinate, dineopentyl-2-tert-butyl-3-isopropyl succinate, dineopentyl-2-isopropyl-3-cyclohexyl succinate, dineopentyl-2-isopentyl-3-cyclohexyl succinate, dineopentyl-2-tetradecyl-3-cyclohexylmethyl succinate, and dineopentyl-2-cyclohexyl-3-cyclopentyl succinate.

[0070] Furthermore, the electron-donating compounds used in succinate catalysts may be used individually or in combination of two or more.

[0071] The method for obtaining the polymerization mixture by multi-stage polymerization is not limited to the method described above. In the same manner as in step A described above, the propylene polymer (b1) (component (b1)) may be polymerized in multiple polymerization reactors, or the ethylene-propylene copolymer (b2) (component (b2)) may be polymerized in multiple polymerization reactors. One method for obtaining a polymerization mixture is to use a polymerizer with gradients of monomer concentration and polymerization conditions. In such a polymerizer, for example, one in which at least two polymerization regions are joined together can be used to polymerize monomers by gas-phase polymerization. Specifically, in the presence of a catalyst, monomers are supplied and polymerized in a polymerization region consisting of an ascending tube, monomers are supplied and polymerized in a descending tube connected to the ascending tube, and the polymerization product is recovered while circulating between the ascending and descending tubes. This method includes means to prevent the gaseous mixture present in the ascending tube from entering the descending tube, either entirely or partially. In addition, a gas and / or liquid mixture having a different composition from the gaseous mixture present in the ascending tube is introduced into the descending tube. This polymerization method can be applied, for example, to the method described in Japanese Patent Publication No. 2002-520426.

[0072] <Injection molded products> Next, an injection-molded article of a third embodiment of the present invention will be described. The injection-molded article of this embodiment is an injection-molded article obtained by injection molding the polypropylene resin composition of the first embodiment described above. As described above, the polypropylene resin composition of the first embodiment has excellent fluidity and moldability, and can produce molded articles with excellent impact resistance, making it suitable for, for example, thin-walled and long-flow-length injection-molded articles. For example, although not particularly limited, the injection-molded article of this embodiment is particularly suitable for food packaging applications (containers, drink cups, etc.). In addition to food packaging applications, it may also be used for applications such as general merchandise, daily necessities, home appliance parts, electrical and electronic components, automobile parts, housing members, toy members, furniture members, building material members, packaging members, industrial materials, logistics materials, agricultural materials, etc.

[0073] Injection molding temperatures are generally 150-350°C, preferably 170-250°C. If the molding temperature exceeds 350°C, it can lead to deterioration of the resin composition and molding defects. If it is below 150°C, fluidity decreases, resulting in insufficient filling of the mold, leading to poor appearance and molding defects. The mold temperature is preferably in the range of 10-60°C. While mold temperatures above 60°C result in superior surface finish and rigidity, the molding cycle lengthens, reducing productivity. Conversely, setting the mold temperature below 10°C leads to significant warping and shrinkage, making it difficult to obtain satisfactory molded products. Furthermore, it increases the likelihood of condensation in the mold, accelerating mold corrosion. It is also unsuitable from the perspective of energy costs associated with cooling.

[0074] The polypropylene resin composition of the first embodiment is suitable for thin-wall injection molding. For example, it can form injection-molded articles with a thickness of 0.6 mm or less, preferably 0.5 mm or less, and more preferably 0.4 mm or less at the thinnest part. The lower limit of the thickness of the thin part is approximately 0.1 mm. The thickness of the thin part is measured by observing the cross-section of the measurement site with a known means such as an optical microscope.

[0075] In this embodiment, the injection-molded product preferably has a value (L / D) of 150 to 600, more preferably 180 to 400, and even more preferably 210 to 280, obtained by dividing the length L (mm) from one end of the injection-molded product to the other by the average wall thickness D (mm) of the injection-molded product. Here, the length L (mm) from one end of the injection-molded product to the other corresponds to the length from the tip to the end of the mold. The average wall thickness D (mm) of the injection-molded product is 0.3 to 0.6 mm.

[0076] The shape of the injection-molded product in this embodiment is not particularly limited, and it is suitable for containers because it has excellent rigidity and impact resistance and can be made thin. The thickness of the side wall of the container as an injection-molded product can be, for example, 0.1 to 1 mm, preferably 0.1 to 0.7 mm, and more preferably 0.1 to 0.5 mm. The thickness of the side wall is measured by observing the cross-section of the measurement point using a known means such as a measuring microscope.

[0077] For injection-molded articles of this embodiment, the flexural modulus measured by the test method described later is preferably 1000 MPa or higher, more preferably 1100 MPa or higher, and even more preferably 1200 MPa or higher. The upper limit is approximately 2000 MPa or lower, and may also be 1800 MPa or lower. The higher the flexural modulus, the more rigid the injection-molded article is, making it suitable for containers with thin-walled sections.

[0078] For the injection-molded product according to this embodiment, the Charpy impact strength at 23°C, as measured by the test method described later, is 3.5 kJ / m². 2 The above is preferable, with a concentration of 4.0 kJ / m³. 2 The above is more preferable, 4.5 kJ / m 2 The above is even more preferable. The guideline for the upper limit is 60 kJ / m³. 2 The following is true: 50 kJ / m³ 2 The following is also acceptable: The higher the Charpy impact strength at 23°C, the better the impact resistance of the injection-molded product, making it suitable for containers with thin walls. Furthermore, for the injection-molded product according to this embodiment, the Charpy impact strength at 0°C, as measured by the test method described later, is 3.0 kJ / m 2The above is preferable, and 3.5 kJ / m³ 2 The above is more preferable, 4.0 kJ / m 2 The above is even more preferable. The guideline for the upper limit is 30 kJ / m³. 2 The following is true: 20 kJ / m³ 2 The following is also acceptable. Similar to the Charpy impact strength at 23°C, the higher the Charpy impact strength at 0°C, the better the impact resistance of the injection-molded product, making it suitable for containers with thin walls. [Examples]

[0079] Examples and comparative examples are shown below, but the present invention is not limited to these examples.

[0080] Preparation of component (A) Components (A-1) and (A-2) were prepared using the following method. In the following explanation, component (1) refers to the propylene polymer (a1) that constitutes the continuous phase in the polypropylene resin (A), which is component (A). Furthermore, component (2) is the component that corresponds to the copolymer (a2) of ethylene and propylene that constitutes the rubber phase in the polypropylene resin (A), which is component (A).

[0081] <Preparation of component (A-1)> A solid catalyst, in which TiCl4 and diisobutyl phthalate as an internal donor are supported on MgCl2, was prepared by the method described in lines 46-53 of Example 5 of European Patent No. 728769. The solid catalyst is prepared by supporting Ti and diisobutyl phthalate as an internal donor on MgCl2 using the method described in the above-mentioned patent publication. The solid catalyst was contacted with TEAL and dicyclopentyl dimethoxysilane (DCPMS) in amounts such that the weight ratio of TEAL to the solid catalyst was 20 and the weight ratio of TEAL / DCPMS was 10, at 12°C for 24 minutes. The resulting catalyst system was prepolymerized by holding it in a suspension state in liquid propylene at 20°C for 5 minutes. The obtained prepolymer was introduced into the first stage polymerization reactor of a polymerization apparatus equipped with two polymerization reactors in series, and propylene was supplied to produce a propylene homopolymer. Subsequently, the propylene homopolymer, propylene, and ethylene were supplied to the second stage polymerization reactor to produce an ethylene-propylene copolymer. During polymerization, the temperature and pressure were adjusted, and hydrogen was used as a molecular weight modifier. The polymerization temperature and reactant ratios were as follows: in the first reactor, the polymerization temperature and hydrogen concentration were 70°C and 2.88 mol%, respectively; and in the second reactor, the polymerization temperature, hydrogen concentration, and the ratio of ethylene to the total of ethylene and propylene were 80°C, 2.73 mol%, and 0.28 mol%, respectively. The polymerization times in the first and second stages were adjusted so that the content of the ethylene-propylene copolymer component was 28% by mass. By this method, the target component (A-1) was obtained.

[0082] The obtained component (A-1) was defined as component (1), and its molecular weight distribution Mw / Mn, as well as the ethylene-derived unit content in component (a1-1), are shown in Table 1. Furthermore, if component (a2-1) is a copolymer of ethylene and propylene, then "C2C3" should be written in the "Monomer composition of component (2)" column of Table 1. The propylene-derived unit content in component (a2-1) was as shown in Table 1. The content of component (a2-1) relative to the total mass of component (a1-1) and component (a2-1) is shown in the "Mass Ratio Component (2) / [Component (1) + Component (2)] (Mass %)" column of Table 1. Furthermore, the XSIV and MFR of component (A-1) are shown in Table 1.

[0083] <Preparation of component (A-2)> Except for the changes described below, component (A-2) was obtained in the same manner as component (A-1). The polymerization times of the first and second stages were changed so that the mass ratio of component (a2) / [component (a1) + component (a2)] was as shown in Table 1. In order to adjust the propylene-derived unit content and XSIV in component (a2) to the values ​​shown in Table 1, the ratio of ethylene to the total of ethylene and propylene in the second stage reactor was changed to 0.17 molars, and the hydrogen concentration in the second stage was changed to 2.09 mol%. Furthermore, in order to adjust the MFR of component (a1) + component (a2) to the value shown in Table 1, the hydrogen concentration in the first stage was changed to 2.40 mol%.

[0084] Table 1 shows the molecular weight distribution (Mw / Mn) of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio (component (2) / [component (1) + component (2)]), the propylene-derived unit content in component (2), XSIV, and MFR for the obtained component (A-2).

[0085] Preparation of component (B) Components (B-1) to (B-4) were prepared using the following method. In the following explanation, component (1) refers to the propylene polymer (b1) that constitutes the continuous phase in the polypropylene resin (B), which is component (B). Furthermore, component (2) is the component corresponding to the copolymer (b2) of ethylene and polypropylene that constitutes the rubber phase in the polypropylene resin (B), which is component (B).

[0086] <Preparation of component (B-1)> A solid catalyst was prepared according to the preparation method described in the examples of Japanese Patent Publication No. 2011-500907. The solid catalyst was prepared by supporting Ti and diethyl-2,3-(diisopropyl) succinate as an internal donor on MgCl2 in the manner described in the above-mentioned patent publication. The solid catalyst was contacted with TEAL and dicyclopentyl dimethoxysilane (DCPMS) in amounts such that the weight ratio of TEAL to the solid catalyst was 18 and the weight ratio of TEAL / DCPMS was 10, at 12°C for 24 minutes. The resulting catalyst system was prepolymerized by holding it in a suspension state in liquid propylene at 20°C for 5 minutes. The obtained prepolymer was introduced into the liquid-phase polymerization reactor of a polymerization apparatus equipped with a liquid-phase polymerization reactor and a gas-phase polymerization reactor in series. A propylene polymer was produced in the liquid phase of propylene in the first-stage polymerization reactor, and an ethylene-propylene copolymer was produced in the second-stage gas-phase polymerization reactor. During polymerization, the polymerization temperatures for the first and second stages were set to 70°C and 80°C, respectively. The polymerization pressure and the amount of catalyst added were adjusted, and the ethylene and propylene supply amounts in the second stage were adjusted so that the propylene-derived unit content of component (b2) was a predetermined amount, resulting in a ethylene-to-propylene ratio of 0.29 molars. In addition, hydrogen was used as a molecular weight modifier, and the hydrogen concentration was set to 1.38 mol% in the first stage and 3.01 mol% in the second stage so that the MFR and XSIV of component (b1) + component (b2) were predetermined values. Furthermore, the polymerization times for the first and second stages were adjusted so that the mass ratio of component (b2) / [component (b1) + component (b2)] was 22.5% by mass. By the above method, the target component (B-1) was obtained.

[0087] Table 1 shows the molecular weight distribution (Mw / Mn) of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio (component (2) / [component (1) + component (2)]), the propylene-derived unit content in component (2), XSIV, and MFR for the obtained component (B-1).

[0088] <Preparation of component (B-2)> Except for the changes described below, component (B-2) was obtained in the same manner as component (B-1). The polymerization time of the first stage was adjusted so that the mass ratio of component (b2) / [component (b1) + component (b2)] was the value shown in Table 1. In order to adjust the propylene-derived unit content and XSIV in component (b2) to the values ​​shown in Table 1, the ratio of ethylene to the total of ethylene and propylene in the second stage reactor was changed to 0.27 mol%, and the hydrogen concentration in the second stage was changed to 2.73 mol%. Furthermore, in order to adjust the MFR of component (b1) + component (b2) to the value shown in Table 1, the hydrogen concentration in the first stage was changed to 1.51 mol%.

[0089] Table 1 shows the molecular weight distribution (Mw / Mn) of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio (component (2) / [component (1) + component (2)]), the propylene-derived unit content in component (2), XSIV, and MFR for the obtained component (B-2).

[0090] <Preparation of component (B-3)> Except for the changes listed below, component (B-3) was obtained in the same manner as component (B-1). The ratio of ethylene to the total of ethylene and propylene in the second reactor was changed to 0.26 molars so that the propylene-derived unit content of component (b2) would be the ratio shown in Table 1. The hydrogen concentration in the second stage was changed to 2.73 mol% so that the XSIV would be the value shown in Table 1. Furthermore, the hydrogen concentration in the first stage was changed to 0.61 mol% to adjust the MFR of component (b1) + component (b2) to the value shown in Table 1.

[0091] Table 1 shows the molecular weight distribution (Mw / Mn) of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio (component (2) / [component (1) + component (2)]), the propylene-derived unit content in component (2), XSIV, and MFR for the obtained component (B-3).

[0092] <Preparation of component (B-4)> Component (B-4) was obtained in the same manner as for component (B-3), except that the hydrogen concentration in the second stage was changed to 2.09 mol% so that the XSIV would be the value shown in Table 1, and the hydrogen concentration in the first stage was changed to 0.91 mol% to adjust the MFR of component (b1) + component (b2) to the value shown in Table 1.

[0093] Table 1 shows the molecular weight distribution (Mw / Mn) of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio (component (2) / [component (1) + component (2)]), the propylene-derived unit content in component (2), XSIV, and MFR for the obtained component (B-4).

[0094] Preparation of component (X) Components (X-1) to (X-3) were prepared using the following method. Here, component (X) is a polypropylene resin that does not correspond to either component (A) or component (B), and includes a continuous phase consisting of a propylene polymer (x1) and a rubber phase consisting of an ethylene-propylene copolymer (x2).

[0095] <Preparation of component (X-1)> A solid catalyst, in which Ti and diisobutyl phthalate as an internal donor were supported on MgCl2, was prepared by the method described in paragraph 0032, lines 21-36 of Japanese Patent Application Publication No. 2004-27218. Next, the solid catalyst was contacted with triethylaluminum (TEAL) as an organoaluminum compound and dicyclopentyl dimethoxysilane (DCPMS) as an external electron donor compound in amounts such that the weight ratio of TEAL to the solid catalyst was 20 and the weight ratio of TEAL / DCPMS was 10, at 12°C for 24 minutes. The resulting catalyst system was prepolymerized by holding it in a suspension state in liquid propylene at 20°C for 5 minutes. The obtained preliminary polymer was introduced into the first stage polymerization reactor of a polymerization apparatus equipped with two polymerization reactors in series to produce a propylene homopolymer (component (x1-1)), and then the ethylene-propylene copolymer (component (x2-1)) was produced in the second stage polymerization reactor. During polymerization, the temperature and pressure were adjusted, and hydrogen was used as a molecular weight modifier. The polymerization temperature and reactant ratios were as follows: in the first reactor, the polymerization temperature and hydrogen concentration were 70°C and 1.90 mol%, respectively; and in the second reactor, the polymerization temperature, hydrogen concentration, and C2 / (C2+C3) ratio were 80°C, 1.93 mol%, and 0.46 mol%, respectively. The polymerization times for both the first and second stages were adjusted so that the ethylene-propylene copolymer component content was 15% by weight.

[0096] For the obtained component (X-1), the molecular weight distribution Mw / Mn of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio component (2) / [component (1) + component (2)], the propylene-derived unit content in component (2), XSIV, and MFR are shown in Table 1.

[0097] <Preparation of component (X-2)> Except for changing the hydrogen concentration in the first reactor to 1.43 mol%, the hydrogen concentration in the second reactor and the C2 / (C2+C3) ratio to 2.73 mol% and 0.41 mol%, respectively, and adjusting the polymerization times of the first and second stages so that the mass ratio of component (x2) / [component (x1)+component (x2)] was the value shown in Table 1, component (X-2) was obtained in the same manner as component (X-1).

[0098] Table 1 shows the molecular weight distribution (Mw / Mn) of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio (component (2) / [component (1) + component (2)]), the propylene-derived unit content in component (2), XSIV, and MFR for the obtained component (X-2).

[0099] <Preparation of component (X-3)> Except for changing the hydrogen concentration in the first reactor to 1.15 mol%, the hydrogen concentration in the second reactor and the C2 / (C2+C3) ratio to 2.49 mol% and 0.39 mol%, respectively, and adjusting the polymerization times of the first and second stages so that the mass ratio of component (x2) / [component (x1)+component (x2)] was the value shown in Table 1, component (X-3) was obtained in the same manner as component (X-1).

[0100] For the obtained component (X-3), the molecular weight distribution Mw / Mn of component (1), the ethylene-derived unit content in component (11), the monomer composition of component (2), the mass ratio component (2) / [component (1) + component (2)], the propylene-derived unit content in component (2), XSIV, and MFR are shown in Table 1.

[0101] [Table 1]

[0102] The measurement results in Table 1 are values ​​measured using the following measurement method.

[0103] <Component (1) Mw / Mn> A 2.5g sample of component (1) polymerized in the first reactor was used as the measurement sample. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured as follows, and the molecular weight distribution (Mw / Mn) was obtained by dividing the weight-average molecular weight (Mw) by the number-average molecular weight (Mn). A PL GPC220 from Polymer Laboratories was used as the apparatus. 1,2,4-trichlorobenzene containing an antioxidant was used as the mobile phase. A series-connected column consisting of one UT-G, one UT-807, and two UT-806M columns from Showa Denko Corporation was used, and a differential refractometer was employed as the detector. The same solvent as the mobile phase was used for the sample solution. A sample was prepared by dissolving the sample at a concentration of 1 mg / mL at 150°C for 2 hours with shaking. 500 μL of this sample solution was injected into the column, and measurements were taken at a flow rate of 1.0 mL / min, a temperature of 145°C, and a data acquisition interval of 1 second. For column calibration, polystyrene standard samples with molecular weights of 5.8 to 7.45 million (Shodex STANDARD, Showa Denko Corporation) were used, and a cubic approximation was performed. The Mark-Houwink-Sakurada coefficient for the polystyrene standard samples was K = 1.21 × 10⁻⁶. -4 For polypropylene homopolymers, propylene random copolymers, and polypropylene-based polymers, α=0.707, K=1.37×10 -4 We used α=0.75.

[0104] <Ethylene-derived unit content of component (1)> For copolymer samples dissolved in a mixed solvent of 1,2,4-trichlorobenzene / deuterated benzene / hexamethyldisiloxane = 30 / 10 / 1 (volume ratio), a Bruker AVANCE III HD400 was used. 13 Using a C resonance frequency of 100 MHz, under the following conditions: measurement temperature 120°C, flip angle 45 degrees, pulse interval 7 seconds, sample rotation speed 20 Hz, and number of integrations 6000 times. 13 The 1C-NMR spectrum was obtained. Using the spectra obtained above, the total ethylene content (mass%) of the copolymer sample was determined by the method described in the literature Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 15, 1150-1152 (1982). When component (1) is used as the sample for measurement, the total ethylene content (mass%) obtained by the above method is the ethylene-derived unit content (C2-a1) (mass%) of component (1).

[0105] <Propylene-derived unit content in component (2)> The ethylene-derived unit content in component (2), determined by the method described later, was calculated using the following formula. Propylene-derived unit content in component (2) (unit: mass%) = 100 - Ethylene-derived unit content in component (2)

[0106] <Ethylene-derived unit content in component (2)> Except for using the integral intensity T'ββ obtained by the following formula instead of the integral intensity Tββ obtained when measuring the total ethylene content of the copolymer using the method described in the above-mentioned literature, the calculation was performed in the same manner as for the total ethylene content to determine the ethylene-derived unit content (mass%) of component (2). T'ββ=0.98×Sαγ×A / (1-0.98×A) Here, A = Sαγ / (Sαγ+Sαδ), which is calculated from Sαγ and Sαδ as described in the above-mentioned literature. In a copolymer consisting of component (1) and component (2), if component (1) contains ethylene units, the ethylene-derived unit content in component (2) was determined by the following formula when the mass ratio component (2) / [component (1) + component (2)] is clear from the polymerization conditions. Ethylene-derived unit content of component (a2) (unit: mass%) = [Total ethylene content of copolymer] [-Ethylene-derived unit content of component (1) × Percentage of component (1) in the copolymer] / (Percentage of component (2) in the copolymer)

[0107] <Mass ratio component (2) / [component (1) + component (2)]> It was calculated using the following formula. Component (2) / [Component (1) + Component (2)] (Unit: mass %) = Total ethylene content of copolymer / (Ethylene-derived unit content in Component (2) / 100)

[0108] <XSIV of component (1) + component (2)> The xylene-soluble component of the copolymer was obtained by the following method, and its intrinsic viscosity (XSIV) was measured. 2.5 g of the copolymer sample was placed in a flask containing 250 mL of o-xylene (solvent), and stirred for 30 minutes at 135°C using a hot plate and reflux apparatus while purging with nitrogen to completely dissolve the copolymer. The mixture was then cooled at 25°C for 1 hour. The resulting solution was filtered using filter paper. 100 mL of the filtered filtrate was taken and transferred to an aluminum cup or similar container. The solution was evaporated to dryness at 140°C while purging with nitrogen, and allowed to stand at room temperature for 30 minutes to obtain the xylene-soluble component. The intrinsic viscosity was measured in tetrahydronaphthalene at 135°C using an automatic capillary viscometer (SS-780-H1, manufactured by Shibayama Scientific Instruments Co., Ltd.).

[0109] <MFR of component (1) + component (2)> To 5 g of copolymer sample, 0.05 g of H-BHT manufactured by Honshu Chemical Industry Co., Ltd. was added, and after homogenization by dry blending, the sample was measured according to JIS K6921-2 under conditions of 230°C and 2.16 kg load.

[0110] [Examples 1-5, Comparative Examples 1-10] Components (A), (B), (X), and nucleating agent (C) were blended in the composition shown in Table 2. To 100 parts by mass of the total amount of these components, 0.2 parts by mass of BASF B225 as an antioxidant and 0.05 parts by mass of calcium stearate manufactured by Tannan Chemical Industry Co., Ltd. as a neutralizing agent were added, and the mixture was stirred and mixed in a Henschel mixer for 1 minute. The mixture was melt-kneaded and extruded using a JSW Co., Ltd. co-directional twin-screw extruder TEX-30α at a cylinder temperature of 200°C. After cooling the strands in water, they were cut with a pelletizer to obtain pellets of the polypropylene-based composition. Various physical properties of the polypropylene-based resin composition produced in this way and the injection-molded articles obtained using them were evaluated. The results are shown in Table 2.

[0111] [Table 2]

[0112] <Liquidity MFR> In accordance with JIS K7210-1, the MFR of the polypropylene resin composition was measured under conditions of 230°C and 2.16 kg load, based on JIS K6921-2.

[0113] <Stiffness, Flexural Modulus> In accordance with JIS K6921-2, a multi-purpose test specimen (Type A1) as specified in JIS K7139 was injection molded from a polypropylene resin composition using an injection molding machine (FANUC ROBOSHOT S2000i manufactured by FANUC Corporation) under the following conditions: molten resin temperature of 200°C, mold temperature of 40°C, average injection speed of 200 mm / sec, holding pressure time of 40 seconds, and total cycle time of 60 seconds, to obtain a test specimen for measurement. In accordance with JIS K7161-2, the flexural modulus was measured using a precision universal testing machine (Autograph AG-X 10kN) manufactured by Shimadzu Corporation under the following conditions: temperature of 23°C, relative humidity of 50%, and test speed of 2 mm / min.

[0114] <Impact Resistance: Charpy Impact Strength> In accordance with JIS K6921-2 and JIS K7139, a test specimen for measurement of type A1 was obtained in the same manner as described above. Furthermore, in accordance with JIS K7111-1, a test specimen for measurement of shape A was obtained by processing it to a width of 10 mm, a thickness of 4 mm, and a length of 80 mm using a notching tool A-4 manufactured by Toyo Seiki Seisakusho Co., Ltd., and then making a 2 mm notch in the width direction. A test specimen for measurement of shape A was obtained. The Charpy impact strength (edgewise impact, 1eA method) of this test specimen was measured at a temperature of 23°C and a temperature of 0°C using a fully automatic impact testing machine with a low-temperature chamber (No. 258-ZA) manufactured by Yasuda Seiki Seisakusho Co., Ltd. The measurement results at 23°C are shown in the "Impact Resistance Charpy Impact Strength @23°C (kJ / m1)" column of Table 1. The measurement results at 0°C are shown in the "Impact Resistance Charpy Impact Strength @0°C (kJ / m1)" column of Table 1.

[0115] <Temperature of deflection under load> In accordance with JIS K7191-1 and K7191-2, the load deflection temperature at 0.45 MPa was measured using an AUTO HDT.TESTER 6A-2 manufactured by Toyo Seiki Seisakusho Co., Ltd.

[0116] <Moldability of thin-walled containers> The moldability was evaluated based on the injection pressure used when injection molding thin-walled containers. Specifically, using an injection molding machine (SE230HY, manufactured by Sumitomo Heavy Industries, Ltd.), the molding temperature, injection speed, injection pressure, and holding pressure were kept constant, and a polypropylene resin composition was molded into a thin-walled container with a thickness of 0.35 mm. Molding was performed by gradually increasing the amount of material measured at regular intervals, starting from a small amount. If the filling amount is too small, shrinkage will occur. As the amount increases, the filling will become appropriate. If the amount increases further, it will exceed the appropriate amount, and burrs will start to form and the frequency of occurrence will increase. The fluidity was determined based on the following evaluation criteria, considering the weighing position where shrinkage occurs, the weighing position where the fluidity becomes appropriate, the weighing position where burrs begin to form, and the frequency of burr formation. Rating "0": No sink marks occur with small amounts of material. Also, when the amount of material is increased in stages, burr formation is less likely or the number (frequency) of burrs is low. Rating "1": While inferior to Rating "0", the range of weighing required to eliminate or partially resolve sink marks is slightly wider. Also, when increasing the weighing amount in stages, burr formation is less likely or occurs in smaller quantities (frequency). Rating "2": Sink marks are prone to occur with small amounts of material, and these are difficult to eliminate even when the amount of material is gradually increased. Also, when the amount of material is gradually increased, burrs are likely to occur or the number (frequency) of burrs is high. Rating "3": Compared to rating "2", sink marks are more likely to occur with smaller amounts of material, and even when the amount of material is increased in stages, the sink marks are difficult to eliminate, or burrs occur without the sink marks being eliminated. Also, when the amount of material is increased in stages, burrs are more likely to occur or the number (frequency) of burrs is higher than with rating "2". In evaluating the moldability of thin-walled containers, ratings "0" and "1" shown in the "Moldability of Thin-Walled Containers" column of Table 2 are considered passing grades, while ratings "2" and "3" are considered failing grades.

[0117] The polypropylene resin compositions of Examples 1 to 5 exhibited good moldability. Furthermore, the injection-molded articles obtained using the polypropylene resin compositions of Examples 1 to 5 possessed a certain level of impact resistance. Therefore, the polypropylene resin compositions of Examples 1 to 5 enable improved moldability while maintaining a certain level of impact resistance. The injection-molded articles obtained using the polypropylene resin compositions of Examples 1 to 5 also showed no problems with other properties such as flexural modulus and temperature of deflection under load. On the other hand, the polypropylene resin compositions of Comparative Examples 1, 3 to 10 failed the moldability evaluation (ratings "2" and "3"). The polypropylene resin composition of Comparative Example 2 passed the moldability evaluation (rating "0"), but had inferior impact resistance. In addition, in a comparison of the physical property balance of compositions with an MFR of around 85 g / 10 min, the polypropylene resin compositions of Examples 4 and 5 showed comparable rigidity and superior impact resistance (especially at 23°C) compared to the polypropylene resin compositions of Comparative Examples 3 and 6.

Claims

1. A polypropylene resin (A) comprising a continuous phase made of a propylene polymer (a1) and a rubber phase made of a copolymer of ethylene and propylene (a2), A polypropylene resin composition containing a polypropylene resin (B) comprising a continuous phase made of a propylene polymer (b1) and a rubber phase made of an ethylene-propylene copolymer (b2), The mass ratio (A):(B) of the polypropylene resin (A) to the polypropylene resin (B) is 90:10 to 10:

90. The total content of the copolymer (a2) and the copolymer (b2) is 23% by mass or more relative to the total mass of the polypropylene resin (A) and the polypropylene resin (B). The polypropylene resin composition has an MFR of 70 g / 10 min or more at a temperature of 230°C and a load of 2.16 kg. The ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn (Mw / Mn) of the propylene polymer (a1) is 6 to 8. The ethylene-derived unit content in the propylene polymer (a1) is 0.0 to 0.5% by mass relative to the total mass of the propylene polymer (a1). The content of the copolymer (a2) is 25 to 45% by mass relative to the total mass of the polypropylene resin (A). The propylene-derived unit content in the copolymer (a2) is 50 to 80% by mass relative to the total mass of the copolymer (a2). The intrinsic viscosity of the xylene-soluble component of the polypropylene resin (A) in tetrahydronaphthalene at 135°C is 1.2 to 7.0 dl / g. The MFR of the aforementioned polypropylene resin (A) at a temperature of 230°C and a load of 2.16 kg is 10 to 130 g / 10 min. The ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn (Mw / Mn) of the propylene polymer (b1) is 9 to 12. The ethylene-derived unit content in the propylene polymer (b1) is 0.0 to 0.5% by mass relative to the total mass of the propylene polymer (b1). The content of the copolymer (b2) is 15 to 30% by mass relative to the total mass of the polypropylene resin (B). The propylene-derived unit content in the copolymer (b2) is 50 to 80% by mass relative to the total mass of the copolymer (b2). The intrinsic viscosity of the xylene-soluble component of the polypropylene resin (B) in tetrahydronaphthalene at 135°C is 1.2 to 7.0 dl / g. A polypropylene resin composition wherein the polypropylene resin (B) has an MFR of 10 to 130 g / 10 min at a temperature of 230°C and a load of 2.16 kg.

2. The polypropylene resin composition according to claim 1, wherein the propylene polymer (a1) and the copolymer (a2) are mixed by polymerization, and the polypropylene resin (A) is a polymerized mixture produced using a catalyst containing a phthalate compound as an electron donor.

3. The polypropylene resin composition according to claim 1, wherein the propylene polymer (b1) and the copolymer (b2) are mixed by polymerization, and the polypropylene resin (B) is a polymerization mixture produced using a catalyst containing a succinate compound as an electron donor.

4. The polypropylene resin composition according to claim 1, wherein the polypropylene resin (A) is a polymerization mixture produced using a catalyst containing a phthalate compound as an electron donor, and the polypropylene resin (B) is a polymerization mixture produced using a catalyst containing a succinate compound as an electron donor.

5. A polypropylene resin composition according to any one of claims 1 to 4, further comprising a nucleating agent (C).

6. A polypropylene resin composition according to any one of claims 1 to 4, used as a material for injection molding.

7. A method for producing a polypropylene resin composition according to any one of claims 1 to 4, Step A involves polymerizing the ethylene monomer and the propylene monomer in the presence of the propylene polymer (a1) to obtain the polypropylene resin (A), Step B involves polymerizing an ethylene monomer and a propylene monomer in the presence of the propylene polymer (b1) to obtain the polypropylene resin (B), A method for producing a polypropylene resin composition, comprising step C of mixing the obtained polypropylene resin (A) and the polypropylene resin (B).

8. A method for producing a polypropylene resin composition according to claim 7, wherein the electron donor of the catalyst system used in step A is a phthalate compound, and the electron donor of the catalyst system used in step B is a succinate compound.

9. An injection-molded article of a polypropylene resin composition according to any one of claims 1 to 4.

10. The injection-molded article according to claim 9, wherein the value obtained by dividing the length L (mm) from one end of the molded article to the other by the average wall thickness D (mm) of the molded article (L / D) is 150 to 600.

11. The injection-molded article according to claim 10, wherein the thickness of the thinnest part is 0.6 mm or less.

12. An injection-molded article according to any of claim 10, for use as a container or packaging that comes into contact with food.

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